Simulating the Effects of Drainage and Agriculture on Hydrology and Sediment in the Minnesota River Basin

NASA Astrophysics Data System (ADS)

Downer, C. W.; Pradhan, N. R.; Skahill, B. E.; Banitt, A. M.; Eggers, G.; Pickett, R. E.

2014-12-01

Throughout the Midwest region of the United States, slopes are relatively flat, soils tend to have low permeability, and local water tables are high. In order to make the region suitable for agriculture, farmers have installed extensive networks of ditches to drain off excess surface water and subsurface tiles to lower the water table and remove excess soil water in the root zone that can stress common row crops, such as corn and soybeans. The combination of tiles, ditches, and intensive agricultural land practices radically alters the landscape and hydrology. Within the watershed, tiles have outlets to both the ditch/stream network as well as overland locations, where the tile discharge appears to initiate gullies and exacerbate overland erosion. As part of the Minnesota River Basin Integrated Study we are explicitly simulating the tile and drainage systems in the watershed at multiple scales using the physics-based watershed model GSSHA (Gridded Surface Subsurface Hydrologic Analysis). The tile drainage system is simulated as a network of pipes that collect water from the local water table. Within the watershed, testing of the methods on smaller basins shows the ability of the model to simulate tile flow, however, application at the larger scale is hampered by the computational burden of simulating the flow in the complex tile drain networks that drain the agricultural fields. Modeling indicates the subsurface drains account for approximately 40% of the stream flow in the Seven Mile Creek sub-basin account in the late spring and early summer when the tile is flowing. Preliminary results indicate that agricultural tile drains increase overland erosion in the Seven Mile Creek watershed.

Spatial and temporal patterns of pesticide losses in a small Swedish agricultural catchment

NASA Astrophysics Data System (ADS)

Sandin, Maria; Piikki, Kristin; Jarvis, Nicholas; Larsbo, Mats; Bishop, Kevin; Kreuger, Jenny

2017-04-01

Research at catchment and regional scales shows that losses of pesticides to surface water often originate from a relatively small fraction of the agricultural landscape. These 'hydrologic source areas' represent areas of land that are highly susceptible to fast transport processes, primarily surface runoff or rapid subsurface flows through soil macropores, either to subsurface field drainage systems or as shallow interflow on more strongly sloping land. A good understanding of the nature of transport pathways for pesticides to surface water in agricultural landscapes is essential for cost-effective identification and implementation of mitigation measures. However, the relative importance of surface and subsurface flows for transport of pesticides to surface waters in Sweden remains largely unknown, since very few studies have been performed under Swedish agro-environmental conditions. We conducted a monitoring study in a small sub-surface drained agricultural catchment in one of the main crop production regions in Sweden. Three small sub-catchments were selected for water sampling based on a high-resolution soil map developed from proximal sensing data; one sub-catchment was dominated by clay soils, another by coarse sandy soils while the third comprised a mix of soil types. Samples were collected from the stream, from field drains discharging into the stream and from within-field surface runoff during spring and early summer in three consecutive years. LC-MS/MS analyses of more than 100 compounds, covering the majority of the polar and semi-polar pesticides most frequently used in Swedish agriculture, were performed on all samples using accredited methods. Information on pesticide applications (products, doses and timing) was obtained from annual interviews with the farmers. There were clear and consistent differences in pesticide losses between the three sub-catchments, with the largest losses occurring in the area with clay soils, and negligible losses from the sandy sub-catchment. This suggests that transport of pesticides to the stream is almost entirely occurring along fast flow paths such as macropore flow to drains or surface runoff. Only a very small proportion of fields are directly connected to the stream by overland pathways, which suggests that macropore flow to drains was the dominant loss pathway in the studied area. Data on pesticide use patterns revealed that compounds were detected in drainage and stream water samples that had not been applied for several years. This suggests that despite the predominant role of fast flow paths in determining losses to the stream, long-term storage along the transport pathways also occurs, presumably in subsoil where degradation is slow.

Are isolated wetlands groundwater recharge hotspots?

NASA Astrophysics Data System (ADS)

Webb, A.; Wicks, C. M.; Brantley, S. T.; Golladay, S. W.

2017-12-01

Geographically isolated wetlands (GIWs) are a common landscape feature in the mantled karst terrain of the Dougherty Plain physiographic district in Southwestern Georgia. These wetlands support a high diversity of obligate/facultative wetland flora and fauna, including several endangered species. While the ecological value of these wetlands is well documented, the hydrologic effects of GIWs on larger watershed processes, such as water storage and aquifer recharge, are less clear. Our project seeks to understand the spatial and temporal variation in recharge across GIWs on this mantled karst landscape. In particular, our first step is to understand the role of isolated wetlands (presumed sinkholes) in delivering water into the underlying aquifer. Our hypothesis is that many GIWs are actually water-filled sinkholes and are locations of focused recharge feeding either the underlying upper Floridan aquifer or the nearby creeks. If we are correct, then these sinkholes should exhibit "drains", i.e., conduits into the limestone bedrock. Thus, the purposes of our initial study are to image the soil-limestone contact (the buried epikarstic surface) and determine if possible subsurface drains exist. Our field work was conducted at the Joseph W Jones Ecological Research Center. During the dry season, we conducted ground penetrating radar (GPR) surveys as grids and lines across a large wetland and across a field with no surface expression of a wetland or sinkhole. We used GPR (200 MHz antenna) with 1-m spacing between antenna and a ping rate of 1 ping per 40 centimeters. Our results show that the epikarstic surface exhibits a drain underneath the wetland (sinkhole) and that no similar feature was seen under the field, even though the survey grid and spacing were similar. As our project progresses, we will survey additional wetlands occurring across varying soil types to determine the spatial distribution between surface wetlands and subsurface drains.

Effects of tillage and application rate on atrazine transport to subsurface drainage: Evaluation of RZWQM using a six-year field study

USGS Publications Warehouse

Malone, Robert W.; Nolan, Bernard T.; Ma, Liwang; Kanwar, Rameshwar S.; Pederson, Carl H.; Heilman, Philip

2014-01-01

Well tested agricultural system models can improve our understanding of the water quality effects of management practices under different conditions. The Root Zone Water Quality Model (RZWQM) has been tested under a variety of conditions. However, the current model's ability to simulate pesticide transport to subsurface drain flow over a long term period under different tillage systems and application rates is not clear. Therefore, we calibrated and tested RZWQM using six years of data from Nashua, Iowa. In this experiment, atrazine was spring applied at 2.8 (1990–1992) and 0.6 kg/ha/yr (1993–1995) to two 0.4 ha plots with different tillage (till and no-till). The observed and simulated average annual flow weighted atrazine concentrations (FWAC) in subsurface drain flow from the no-till plot were 3.7 and 3.2 μg/L, respectively for the period with high atrazine application rates, and 0.8 and 0.9 μg/L, respectively for the period with low application rates. The 1990–1992 observed average annual FWAC difference between the no-till and tilled plot was 2.4 μg/L while the simulated difference was 2.1 μg/L. These observed and simulated differences for 1993–1995 were 0.1 and 0.1 μg/L, respectively. The Nash–Sutcliffe model performance statistic (EF) for cumulative atrazine flux to subsurface drain flow was 0.93 for the no-till plot testing years (1993–1995), which is comparable to other recent model tests. The value of EF is 1.0 when simulated data perfectly match observed data. The order of selected parameter sensitivity for RZWQM simulated FWAC was atrazine partition coefficient > number of macropores > atrazine half life in soil > soil hydraulic conductivity. Simulations from 1990 to 1995 with four different atrazine application rates applied at a constant rate throughout the simulation period showed concentrations in drain flow for the no-till plot to be twice those of the tilled plot. The differences were more pronounced in the early simulation period (1990–1992), partly because of the characteristics of macropore flow during large storms. The results suggest that RZWQM is a promising tool to study pesticide transport to subsurface drain flow under different tillage systems and application rates over several years, the concentrations of atrazine in drain flow can be higher with no-till than tilled soil over a range of atrazine application rates, and atrazine concentrations in drain flow are sensitive to the macropore flow characteristics under different tillage systems and rainfall timing and intensity.

Corn stover harvest increases herbicide movement to subsurface drains – Root Zone Water Quality Model simulations

USDA-ARS?s Scientific Manuscript database

BACKGROUND: Removal of crop residues for bioenergy production can alter soil hydrologic properties, but there is little information on its impact on transport of herbicides and their degradation products to subsurface drains. The Root Zone Water Quality Model, previously calibrated using measured fl...

Corn yield under subirrigation and future climate scenarios in the Maumee river basin

USDA-ARS?s Scientific Manuscript database

Subirrigation has been proposed as a water table management practice to maintain appropriate soil water content during periods of high crop water demand on subsurface drained croplands in the Corn Belt. Subirrigation takes advantage of the subsurface drainage systems already installed on drained agr...

Neotectonic Activity from the Upper Reaches of the Arabian Gulf and Possibilities of New Oil Fields

NASA Astrophysics Data System (ADS)

Sissakian, V. K.; Abdul Ahad, A. D.; Al-Ansari, N.; Knutsson, S.

2018-03-01

Upper reaches of the Arabian Gulf consist of different types of fine sediments including the vast Mesopotamia Plain sediments, tidal flat sediments and estuarine sabkha sediments. The height of the plain starts from zero meter and increases northwards to three meters with extremely gentle gradient. The vast plain to the north of the Arabian Gulf is drained by Shat Al-Arab (Shat means river in Iraqi slang language) and Khor Al-Zubair (Khor means estuary). The former drains the extreme eastern part of the plain; whereas, the latter drains the western part. Shat Al-Arab is the resultant of confluence of the Tigris and Euphrates rivers near Al-Qurna town; about 160 km north of the Arabian Gulf mouth at Al-Fao town; whereas, the length of Khor Al-Zubair is about 50 km; as measured from Um Qasir Harbor. The drainage system around Khor Al-Zubair is extremely fine dendritic; whereas around Shat Al-Arab is almost parallel running from both sides of the river towards the river; almost perpendicularly. The fine dendritic drainage around Khor Al-Zubair shows clear recent erosional activity, beside water divides, abandoned irrigation channels and dislocated irrigational channels and estuarine distributaries; all are good indication for a Neotectonic activity in the region. These may indicate the presence of subsurface anticlines, which may represent oil fields; since tens of subsurface anticlines occur in near surroundings, which are oil fields.

Subsurface irrigation of potato crop (Solanum tuberosum ssp. Andigena) in Suka Kollus with different drainage systems

NASA Astrophysics Data System (ADS)

Serrano-Coronel, Genaro; Chipana-Rivera, René; Fátima Moreno-Pérez, María; Roldán-Cañas, José

2016-04-01

Among the most important hydraulic structures of pre-Hispanic ancestral technology developed in the Andean region, we find the suka kollus, aymara word, called also waru waru, en quechua or raised fields, in English. They are raised platforms surrounded by water canals that irrigate subsurface, but also have the function of draining, to deal with floods because they are surrounding Lake Titicaca. They also have the property of generating a thermoregulatory effect to crops, depending on the configuration of the channels and platforms. Such agro-ecosystems are being abandoned, however, if properly addressed crop management and some drainage canals are replaced by underground drains for increased crop area could be very useful in enabling marginal soils affected by salts and / or excess water. For these reasons, the objective of this study was to evaluate the subsurface irrigation in the potato crop in suka kollus under a system of surface drainage, and mixed drainage (surface and subsurface). The study was conducted in marginal soils of Kallutaca area, located 30 km from the city of La Paz, Bolivia, at a height of 3892 m.a.s.l. The cultivation of the potato (Solanum tuberosum ssp. Andigena) was used. Four treatments were tested with different widths of the platforms: T1 (Control) with drainage through channels; T2 (replacing a channel by a drain); T3 (replacing two channels by two drains); T4 (replacing three channels by three drains). The flow of water into the soil from the water table was predominantly upward, except during periods of high rainfall. In terms of treatments, the flow in T1 was higher, mainly at weeks 8 to 11 after seedling emergence, coinciding with the phenological phases of flowering and at the beginning of the tuber ripening. It was followed by T3, T2 and T4 treatments, respectively. Tuber yield, if one considers that the channels detract arable land, was higher in the T3 treatment,16.4 Mg / ha, followed by T2 treatment, 15.2 Mg / ha, T1 treatment (Control) 7.3 Mg / ha and T4 treatment with 7.1 Mg / ha. Therefore, in the mixed system with two drains the best results were obtained.

Impacts of drainage water management on subsurface drain flow, nitrate concentration, and nitrate loads in Indiana

EPA Science Inventory

Drainage water management is a conservation practice that has the potential to reduce drainage outflow and nitrate (NO3) loss from agricultural fields while maintaining or improving crop yields. The goal of this study was to quantify the impact of drainage water management on dra...

Corn stover harvest increases herbicide movement to subsurface drains: RZWQM simulations

USGS Publications Warehouse

Shipitalo, Martin J.; Malone, Robert W.; Ma, Liwang; Nolan, Bernard T.; Kanwar, Rameshwar S.; Shaner, Dale L.; Pederson, Carl H.

2016-01-01

BACKGROUND Crop residue removal for bioenergy production can alter soil hydrologic properties and the movement of agrochemicals to subsurface drains. The Root Zone Water Quality Model (RZWQM), previously calibrated using measured flow and atrazine concentrations in drainage from a 0.4 ha chisel-tilled plot, was used to investigate effects of 50 and 100% corn (Zea mays L.) stover harvest and the accompanying reductions in soil crust hydraulic conductivity and total macroporosity on transport of atrazine, metolachlor, and metolachlor oxanilic acid (OXA). RESULTS The model accurately simulated field-measured metolachlor transport in drainage. A 3-yr simulation indicated that 50% residue removal decreased subsurface drainage by 31% and increased atrazine and metolachlor transport in drainage 4 to 5-fold when surface crust conductivity and macroporosity were reduced by 25%. Based on its measured sorption coefficient, ~ 2-fold reductions in OXA losses were simulated with residue removal. CONCLUSION RZWQM indicated that if corn stover harvest reduces crust conductivity and soil macroporosity, losses of atrazine and metolachlor in subsurface drainage will increase due to reduced sorption related to more water moving through fewer macropores. Losses of the metolachlor degradation product OXA will decrease due to the more rapid movement of the parent compound into the soil.

Targeting sediment management strategies using sediment quantification and fingerprinting methods

NASA Astrophysics Data System (ADS)

Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

2016-04-01

Cost-effective sediment management is required to reduce excessive delivery of fine sediment due to intensive land uses such as agriculture, resulting in the degradation of aquatic ecosystems. Prioritising measures to mitigate dominant sediment sources is, however, challenging, as sediment loss risk is spatially and temporally variable between and within catchments. Fluctuations in sediment supply from potential sources result from variations in land uses resulting in increased erodibility where ground cover is low (e.g., cultivated, poached and compacted soils), and physical catchment characteristics controlling hydrological connectivity and transport pathways (surface and/or sub-surface). Sediment fingerprinting is an evidence-based management tool to identify sources of in-stream sediments at the catchment scale. Potential sediment sources are related to a river sediment sample, comprising a mixture of source sediments, using natural physico-chemical characteristics (or 'tracers'), and contributions are statistically un-mixed. Suspended sediment data were collected over two years at the outlet of three intensive agricultural catchments (approximately 10 km2) in Ireland. Dominant catchment characteristics were grassland on poorly-drained soils, arable on well-drained soils and arable on moderately-drained soils. High-resolution (10-min) calibrated turbidity-based suspended sediment and discharge data were combined to quantify yield. In-stream sediment samples (for fingerprinting analysis) were collected at six to twelve week intervals, using time-integrated sediment samplers. Potential sources, including stream channel banks, ditches, arable and grassland field topsoils, damaged road verges and tracks were sampled, oven-dried (<40oC) and sieved (125 microns). Soil and sediment samples were analysed for mineral magnetics, geochemistry and radionuclide tracers, particle size distribution and soil organic carbon. Tracer data were corrected to account for particle size and organic matter selectivity processes. Contributions from potential sources type groups (channel - ditches and stream banks, roads - road verges and tracks, fields - grassland and arable topsoils) were statistically un-mixed using FR2000, an uncertainty-inclusive algorithm, and combined with sediment yield data. Results showed sediment contributions from channel, field and road groups were 70%, 25% and 5% in the poorly-drained catchment, 59%, 22% and 19% in the well-drained catchment, and 17%, 74% and 9% in the moderately-drained catchment. Higher channel contributions in the poorly-drained catchment were attributed to bank erosion accelerated by the rapid diversion of surface runoff into channels, facilitated by surface and sub-surface artificial drainage networks, and bank seepage from lateral pressure gradients due to confined groundwater. Despite the greatest proportion of arable soils in the well-drained catchment, this source was frequently hydrologically disconnected as well-drained soils largely infiltrated rainfall and prevented surface soil erosion. Periods of high and intense rainfall were associated with greater proportions of field losses in the well-drained catchment likely due to infiltration exceeding the saturated hydraulic conductivity of soils and establishment of surface hydrological connectivity. Losses from field topsoils dominated in the moderately-drained catchment as antecedent soil wetness maintained surface flow pathways and coincided with low groundcover on arable soils. For cost-effective management of sediment pressures to aquatic ecosystems, catchment specific variations in sediment sources must be considered.

Dynamics of nitrate and chloride during storm events in agricultural catchments with different subsurface drainage intensity (Indiana, USA)

USDA-ARS?s Scientific Manuscript database

Grids of perforated pipe buried beneath many poorly drained agricultural fields in the Midwestern U.S. are believed to “short circuit” pools of nitrate-laden soil water and shallow groundwater directly into streams that eventually discharge to the Mississippi River. Although much is known about the ...

Location and assessment of drainage pipes beneath farm fields and golf course greens using ground penetrating radar: A research summary

USDA-ARS?s Scientific Manuscript database

Enhancing the efficiency of soil water removal, and in turn crop productivity, on farmland already containing a subsurface drainage system, typically involves installing new drain lines between the old ones. However, before this approach can be attempted, the older drainage pipes need to be located...

Nitrate concentration-drainage flow (C-Q) relationship for a drained agricultural field in Eastern North Carolina Plain

NASA Astrophysics Data System (ADS)

Liu, W.; Youssef, M.; Birgand, F.; Chescheir, G. M.; Maxwell, B.; Tian, S.

2017-12-01

Agricultural drainage is a practice used to artificially enhance drainage characteristics of naturally poorly drained soils via subsurface drain tubing or open-ditch systems. Approximately 25% of the U.S. agricultural land requires improved drainage for economic crop production. However, drainage increases the transport of dissolved agricultural chemicals, particularly nitrates to downstream surface waters. Nutrient export from artificially drained agricultural landscapes has been identified as the leading source of elevated nutrient levels in major surface water bodies in the U.S. Controlled drainage has long been practiced to reduce nitrogen export from agricultural fields to downstream receiving waters. It has been hypothesized that controlled drainage reduces nitrogen losses by promoting denitrification, reducing drainage outflow from the field, and increasing plant uptake. The documented performance of the practice was widely variable as it depends on several site-specific factors. The goal of this research was to utilize high frequency measurements to investigate the effect of agricultural drainage and related management practices on nitrate fate and transport for an artificially drained agricultural field in eastern North Carolina. We deployed a field spectrophotometer to measure nitrate concentration every 45 minutes and measured drainage flow rate using a V-notch weir every 15 minutes. Furthermore, we measured groundwater level, precipitation, irrigation amount, temperature to characterize antecedent conditions for each event. Nitrate concentration-drainage flow (C-Q) relationships generated from the high frequency measurements illustrated anti-clockwise hysteresis loops and nitrate flushing mechanism in response to most precipitation and irrigation events. Statistical evaluation will be carried out for the C-Q relationships. The results of our analysis, combined with numerical modeling, will provide a better understanding of hydrological and biogeochemical processes controlling the fate and transport of nitrate in drained agricultural landscapes.

Characterizing phosphorus dynamics in tile-drained agricultural fields of eastern Wisconsin

NASA Astrophysics Data System (ADS)

Madison, Allison M.; Ruark, Matthew D.; Stuntebeck, Todd D.; Komiskey, Matthew J.; Good, Lara W.; Drummy, Nancy; Cooley, Eric T.

2014-11-01

Artificial subsurface drainage provides an avenue for the rapid transfer of phosphorus (P) from agricultural fields to surface waters. This is of particular interest in eastern Wisconsin, where there is a concentrated population of dairy farms and high clay content soils prone to macropore development. Through collaboration with private landowners, surface and tile drainage was measured and analyzed for dissolved reactive P (DRP) and total P (TP) losses at four field sites in eastern Wisconsin between 2005 and 2009. These sites, which received frequent manure applications, represent a range of crop management practices which include: two chisel plowed corn fields (CP1, CP2), a no-till corn-soybean field (NT), and a grazed pasture (GP). Subsurface drainage was the dominant pathway of water loss at each site accounting for 66-96% of total water discharge. Average annual flow-weighted (FW) TP concentrations were 0.88, 0.57, 0.21, and 1.32 mg L-1 for sites CP1, CP2, NT, and GP, respectively. Low TP concentrations at the NT site were due to tile drain interception of groundwater flow where large volumes of tile drainage water diluted the FW-TP concentrations. Subsurface pathways contributed between 17% and 41% of the TP loss across sites. On a drainage event basis, total drainage explained between 36% and 72% of the event DRP loads across CP1, CP2, and GP; there was no relationship between event drainflow and event DRP load at the NT site. Manure applications did not consistently increase P concentrations in drainflow, but annual FW-P concentrations were greater in years receiving manure applications compared to years without manure application. Based on these field measures, P losses from tile drainage must be integrated into field level P budgets and P loss calculations on heavily manured soils, while also acknowledging the unique drainage patterns observed in eastern Wisconsin.

Experimental utilization of tire shreds to enhance highway drainage.

DOT National Transportation Integrated Search

2001-03-01

This project investigates the practical benefits of using shredded tires as a free draining material : in a subsurface French drain to enhance drainage along a section of highway. French drains are : below-grade structures designed to re-direct groun...

Characterizing phosphorus dynamics in tile-drained agricultural fieldsof eastern Wisconsin

USGS Publications Warehouse

Madison, Allison; Ruark, Matthew; Stuntebeck, Todd D.; Komiskey, Matthew J.; Good, Laura W.; Drummy, Nancy; Cooley, Eric

2014-01-01

Artificial subsurface drainage provides an avenue for the rapid transfer of phosphorus (P) from agricultural fields to surface waters. This is of particular interest in eastern Wisconsin, where there is a concentrated population of dairy farms and high clay content soils prone to macropore development. Through collaboration with private landowners, surface and tile drainage was measured and analyzed for dissolved reactive P (DRP) and total P (TP) losses at four field sites in eastern Wisconsin between 2005 and 2009. These sites, which received frequent manure applications, represent a range of crop management practices which include: two chisel plowed corn fields (CP1, CP2), a no-till corn–soybean field (NT), and a grazed pasture (GP). Subsurface drainage was the dominant pathway of water loss at each site accounting for 66–96% of total water discharge. Average annual flow-weighted (FW) TP concentrations were 0.88, 0.57, 0.21, and 1.32 mg L−1 for sites CP1, CP2, NT, and GP, respectively. Low TP concentrations at the NT site were due to tile drain interception of groundwater flow where large volumes of tile drainage water diluted the FW-TP concentrations. Subsurface pathways contributed between 17% and 41% of the TP loss across sites. On a drainage event basis, total drainage explained between 36% and 72% of the event DRP loads across CP1, CP2, and GP; there was no relationship between event drainflow and event DRP load at the NT site. Manure applications did not consistently increase P concentrations in drainflow, but annual FW-P concentrations were greater in years receiving manure applications compared to years without manure application. Based on these field measures, P losses from tile drainage must be integrated into field level P budgets and P loss calculations on heavily manured soils, while also acknowledging the unique drainage patterns observed in eastern Wisconsin.

Test of a simplified modeling approach for nitrogen transfer in agricultural subsurface-drained catchments

NASA Astrophysics Data System (ADS)

Henine, Hocine; Julien, Tournebize; Jaan, Pärn; Ülo, Mander

2017-04-01

In agricultural areas, nitrogen (N) pollution load to surface waters depends on land use, agricultural practices, harvested N output, as well as the hydrology and climate of the catchment. Most of N transfer models need to use large complex data sets, which are generally difficult to collect at larger scale (>km2). The main objective of this study is to carry out a hydrological and a geochemistry modeling by using a simplified data set (land use/crop, fertilizer input, N losses from plots). The modelling approach was tested in the subsurface-drained Orgeval catchment (Paris Basin, France) based on following assumptions: Subsurface tile drains are considered as a giant lysimeter system. N concentration in drain outlets is representative for agricultural practices upstream. Analysis of observed N load (90% of total N) shows 62% of export during the winter. We considered prewinter nitrate (NO3) pool (PWNP) in soils at the beginning of hydrological drainage season as a driving factor for N losses. PWNP results from the part of NO3 not used by crops or the mineralization part of organic matter during the preceding summer and autumn. Considering these assumptions, we used PWNP as simplified input data for the modelling of N transport. Thus, NO3 losses are mainly influenced by the denitrification capacity of soils and stream water. The well-known HYPE model was used to perform water and N losses modelling. The hydrological simulation was calibrated with the observation data at different sub-catchments. We performed a hydrograph separation validated on the thermal and isotopic tracer studies and the general knowledge of the behavior of Orgeval catchment. Our results show a good correlation between the model and the observations (a Nash-Sutcliffe coefficient of 0.75 for water discharge and 0.7 for N flux). Likewise, comparison of calibrated PWNP values with the results from a field survey (annual PWNP campaign) showed significant positive correlation. One can conclude that the simplified modeling approach using PWNP as a driving factor for the evaluation of N losses from drained agricultural catchments gave satisfactory results and we can propose this approach for a wider use.

Corn stover harvest increases herbicide movement to subsurface drains - Root Zone Water Quality Model simulations.

PubMed

Shipitalo, Martin J; Malone, Robert W; Ma, Liwang; Nolan, Bernard T; Kanwar, Rameshwar S; Shaner, Dale L; Pederson, Carl H

2016-06-01

Crop residue removal for bioenergy production can alter soil hydrologic properties and the movement of agrochemicals to subsurface drains. The Root Zone Water Quality Model (RZWQM), previously calibrated using measured flow and atrazine concentrations in drainage from a 0.4 ha chisel-tilled plot, was used to investigate effects of 50 and 100% corn (Zea mays L.) stover harvest and the accompanying reductions in soil crust hydraulic conductivity and total macroporosity on transport of atrazine, metolachlor and metolachlor oxanilic acid (OXA). The model accurately simulated field-measured metolachlor transport in drainage. A 3 year simulation indicated that 50% residue removal reduced subsurface drainage by 31% and increased atrazine and metolachlor transport in drainage 4-5-fold when surface crust conductivity and macroporosity were reduced by 25%. Based on its measured sorption coefficient, approximately twofold reductions in OXA losses were simulated with residue removal. The RZWQM indicated that, if corn stover harvest reduces crust conductivity and soil macroporosity, losses of atrazine and metolachlor in subsurface drainage will increase owing to reduced sorption related to more water moving through fewer macropores. Losses of the metolachlor degradation product OXA will decrease as a result of the more rapid movement of the parent compound into the soil. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Ionic composition and nitrate in drainage water from fields fertilized with different nitrogen sources, middle swamp watershed, North Carolina, August 2000-August 2001

USGS Publications Warehouse

Harden, Stephen L.; Spruill, Timothy B.

2004-01-01

A study was conducted from August 2000 to August 2001 to characterize the influence of fertilizer use from different nitrogen sources on the quality of drainage water from 11 subsurface tile drains and 7 surface field ditches in a North Carolina Coastal Plain watershed. Agricultural fields receiving commercial fertilizer (conventional sites), swine lagoon effluent (spray sites), and wastewater-treatment plant sludge (sludge site) in the Middle Swamp watershed were investigated. The ionic composition of drainage water in tile drains and ditches varied depending on fertilizer source type. The dominant ions identified in water samples from tile drains and ditches include calcium, magnesium, sodium, chloride, nitrate, and sulfate, with tile drains generally having lower pH, low or no bicarbonates, and higher nitrate and chloride concentrations. Based on fertilizer source type, median nitrate-nitrogen concentrations were significantly higher at spray sites (32.0 milligrams per liter for tiles and 8.2 milligrams per liter for ditches) relative to conventional sites (6.8 milligrams per liter for tiles and 2.7 milligrams per liter for ditches). The median instantaneous nitrate-nitrogen yields also were significantly higher at spray sites (420 grams of nitrogen per hectare per day for tile drains and 15.6 grams of nitrogen per hectare per day for ditches) relative to conventional sites (25 grams of nitrogen per hectare per day for tile drains and 8.1 grams of nitrogen per hectare per day for ditches). The tile drain site where sludge is applied had a median nitrate-nitrogen concentration of 10.5 milligrams per liter and a median instantaneous nitrate-nitrogen yield of 93 grams of nitrogen per hectare per day, which were intermediate to those of the conventional and spray tile drain sites. Results from this study indicate that nitrogen loadings and subsequent edge-of-field nitrate-nitrogen yields through tile drains and ditches were significantly higher at sites receiving applications of swine lagoon effluent compared to sites receiving commercial fertilizer.

High-frequency monitoring of water fluxes and nutrient loads to assess the effects of controlled drainage on water storage and nutrient transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rozemeijer, J. C.; Visser, A.; Borren, W.

High nitrogen (N) and phosphorus (P) fluxes from upstream agriculture threaten aquatic ecosystems in surface waters and estuaries, especially in areas characterized by high agricultural N and P inputs and densely drained catchments like the Netherlands. Controlled drainage has been recognized as an effective option to optimize soil moisture conditions for agriculture and to reduce unnecessary losses of fresh water and nutrients. This is achieved by introducing control structures with adjustable overflow levels into subsurface tube drain systems. A small-scale (1 ha) field experiment was designed to investigate the hydrological and chemical changes after introducing controlled drainage. Precipitation rates andmore » the response of water tables and drain fluxes were measured in the periods before the introduction of controlled drainage (2007–2008) and after (2009–2011). For the N and P concentration measurements, auto-analyzers for continuous records were combined with passive samplers for time-averaged concentrations at individual drain outlets. The experimental setup enabled the quantification of changes in the water and solute balance after introducing controlled drainage. The results showed that introducing controlled drainage reduced the drain discharge and increased the groundwater storage in the field. To achieve this, the overflow levels have to be elevated in early spring, before the drain discharge stops due to dryer conditions and falling groundwater levels. The groundwater storage in the field would have been larger if the water levels in the adjacent ditch were controlled as well by an adjustable weir. The N concentrations and loads increased, which was largely related to elevated concentrations in one of the three monitored tube drains. The P loads via the tube drains reduced due to the reduction in discharge after introducing controlled drainage. Furthermore, this may be counteracted by the higher groundwater levels and the larger contribution of N- and P-rich shallow groundwater and overland flow to the surface water.« less

High-frequency monitoring of water fluxes and nutrient loads to assess the effects of controlled drainage on water storage and nutrient transport

DOE PAGES

Rozemeijer, J. C.; Visser, A.; Borren, W.; ...

2016-01-19

High nitrogen (N) and phosphorus (P) fluxes from upstream agriculture threaten aquatic ecosystems in surface waters and estuaries, especially in areas characterized by high agricultural N and P inputs and densely drained catchments like the Netherlands. Controlled drainage has been recognized as an effective option to optimize soil moisture conditions for agriculture and to reduce unnecessary losses of fresh water and nutrients. This is achieved by introducing control structures with adjustable overflow levels into subsurface tube drain systems. A small-scale (1 ha) field experiment was designed to investigate the hydrological and chemical changes after introducing controlled drainage. Precipitation rates andmore » the response of water tables and drain fluxes were measured in the periods before the introduction of controlled drainage (2007–2008) and after (2009–2011). For the N and P concentration measurements, auto-analyzers for continuous records were combined with passive samplers for time-averaged concentrations at individual drain outlets. The experimental setup enabled the quantification of changes in the water and solute balance after introducing controlled drainage. The results showed that introducing controlled drainage reduced the drain discharge and increased the groundwater storage in the field. To achieve this, the overflow levels have to be elevated in early spring, before the drain discharge stops due to dryer conditions and falling groundwater levels. The groundwater storage in the field would have been larger if the water levels in the adjacent ditch were controlled as well by an adjustable weir. The N concentrations and loads increased, which was largely related to elevated concentrations in one of the three monitored tube drains. The P loads via the tube drains reduced due to the reduction in discharge after introducing controlled drainage. Furthermore, this may be counteracted by the higher groundwater levels and the larger contribution of N- and P-rich shallow groundwater and overland flow to the surface water.« less

High-frequency monitoring of water fluxes and nutrient loads to assess the effects of controlled drainage on water storage and nutrient transport

NASA Astrophysics Data System (ADS)

Rozemeijer, J. C.; Visser, A.; Borren, W.; Winegram, M.; van der Velde, Y.; Klein, J.; Broers, H. P.

2016-01-01

High nitrogen (N) and phosphorus (P) fluxes from upstream agriculture threaten aquatic ecosystems in surface waters and estuaries, especially in areas characterized by high agricultural N and P inputs and densely drained catchments like the Netherlands. Controlled drainage has been recognized as an effective option to optimize soil moisture conditions for agriculture and to reduce unnecessary losses of fresh water and nutrients. This is achieved by introducing control structures with adjustable overflow levels into subsurface tube drain systems. A small-scale (1 ha) field experiment was designed to investigate the hydrological and chemical changes after introducing controlled drainage. Precipitation rates and the response of water tables and drain fluxes were measured in the periods before the introduction of controlled drainage (2007-2008) and after (2009-2011). For the N and P concentration measurements, auto-analyzers for continuous records were combined with passive samplers for time-averaged concentrations at individual drain outlets. The experimental setup enabled the quantification of changes in the water and solute balance after introducing controlled drainage. The results showed that introducing controlled drainage reduced the drain discharge and increased the groundwater storage in the field. To achieve this, the overflow levels have to be elevated in early spring, before the drain discharge stops due to dryer conditions and falling groundwater levels. The groundwater storage in the field would have been larger if the water levels in the adjacent ditch were controlled as well by an adjustable weir. The N concentrations and loads increased, which was largely related to elevated concentrations in one of the three monitored tube drains. The P loads via the tube drains reduced due to the reduction in discharge after introducing controlled drainage. However, this may be counteracted by the higher groundwater levels and the larger contribution of N- and P-rich shallow groundwater and overland flow to the surface water.

Geochemical and isotopic tracing of water in nested southern Minnesota corn-belt watersheds.

PubMed

Magner, J A; Alexander, S C

2002-01-01

Land-use changes over the last century in southern Minnesota have influenced riverine water chemistry. A nested watershed approach was used to examine hydrologic pathways of water movement in this now agriculturally intensive region. From field scale subsurface tile-drains of the Beauford ditch to the respective outlets of the Cobb River and Blue Earth River, more than 125 samples were collected for major dissolved ions and isotopes between March 1994 and June 1996 over a range of climatic conditions that included snowmelt and storm-flows. Results indicate that riverine water chemistry is dominated by subsurface tile-drained row crop agriculture. In the mid-1990s, regional ground water discharge into the Cobb and Blue Earth Rivers comprised less than 10% of the total flow based on ionic mixing calculations. Ammonia, present in manure or as anhydrous, is readily exchanged in the soil. This ion exchange releases increasing ratios of magnesium, sodium and strontium relative to calcium, the dominant cation. Soil thaw and snowmelt recharge influenced March-April tile-drain and ditch water isotopic values. Light deltaD values increased as spring infiltration-derived water was displaced from the soil zone by heavier summer precipitation. Delta15N followed a similar but opposite pattern with relatively heavy March-April tile-drain and ditch values trending to lighter delta15N through the growing season. The future of southern Minnesota riverine water quality is closely linked to the management of the landscape. To improve the riverine environment, land owners and managers will need to address cropping systems, fertilization practices and drainage.

Leaching of the Neonicotinoids Thiamethoxam and Imidacloprid from Sugar Beet Seed Dressings to Subsurface Tile Drains.

PubMed

Wettstein, Felix E; Kasteel, Roy; Garcia Delgado, Maria F; Hanke, Irene; Huntscha, Sebastian; Balmer, Marianne E; Poiger, Thomas; Bucheli, Thomas D

2016-08-24

Pesticide transport from seed dressings toward subsurface tile drains is still poorly understood. We monitored the neonicotinoid insecticides imidacloprid and thiamethoxam from sugar beet seed dressings in flow-proportional drainage water samples, together with spray applications of bromide and the herbicide S-metolachlor in spring and the fungicides epoxiconazole and kresoxim-methyl in summer. Event-driven, high first concentration maxima up to 2830 and 1290 ng/L for thiamethoxam and imidacloprid, respectively, were followed by an extended period of tailing and suggested preferential flow. Nevertheless, mass recoveries declined in agreement with the degradation and sorption properties collated in the groundwater ubiquity score, following the order bromide (4.9%), thiamethoxam (1.2%), imidacloprid (0.48%), kresoxim-methyl acid (0.17%), S-metolachlor (0.032%), epoxiconazole (0.013%), and kresoxim-methyl (0.003%), and indicated increased leaching from seed dressings compared to spray applications. Measured concentrations and mass recoveries indicate that subsurface tile drains contribute to surface water contamination with neonicotinoids from seed dressings.

Lateral and subsurface flows impact arctic coastal plain lake water budgets

USGS Publications Warehouse

Koch, Joshua C.

2016-01-01

Arctic thaw lakes are an important source of water for aquatic ecosystems, wildlife, and humans. Many recent studies have observed changes in Arctic surface waters related to climate warming and permafrost thaw; however, explaining the trends and predicting future responses to warming is difficult without a stronger fundamental understanding of Arctic lake water budgets. By measuring and simulating surface and subsurface hydrologic fluxes, this work quantified the water budgets of three lakes with varying levels of seasonal drainage, and tested the hypothesis that lateral and subsurface flows are a major component of the post-snowmelt water budgets. A water budget focused only on post-snowmelt surface water fluxes (stream discharge, precipitation, and evaporation) could not close the budget for two of three lakes, even when uncertainty in input parameters was rigorously considered using a Monte Carlo approach. The water budgets indicated large, positive residuals, consistent with up to 70% of mid-summer inflows entering lakes from lateral fluxes. Lateral inflows and outflows were simulated based on three processes; supra-permafrost subsurface inflows from basin-edge polygonal ground, and exchange between seasonally drained lakes and their drained margins through runoff and evapotranspiration. Measurements and simulations indicate that rapid subsurface flow through highly conductive flowpaths in the polygonal ground can explain the majority of the inflow. Drained lakes were hydrologically connected to marshy areas on the lake margins, receiving water from runoff following precipitation and losing up to 38% of lake efflux to drained margin evapotranspiration. Lateral fluxes can be a major part of Arctic thaw lake water budgets and a major control on summertime lake water levels. Incorporating these dynamics into models will improve our ability to predict lake volume changes, solute fluxes, and habitat availability in the changing Arctic.

Estimating drain flow from measured water table depth in layered soils under free and controlled drainage

NASA Astrophysics Data System (ADS)

Saadat, Samaneh; Bowling, Laura; Frankenberger, Jane; Kladivko, Eileen

2018-01-01

Long records of continuous drain flow are important for quantifying annual and seasonal changes in the subsurface drainage flow from drained agricultural land. Missing data due to equipment malfunction and other challenges have limited conclusions that can be made about annual flow and thus nutrient loads from field studies, including assessments of the effect of controlled drainage. Water table depth data may be available during gaps in flow data, providing a basis for filling missing drain flow data; therefore, the overall goal of this study was to examine the potential to estimate drain flow using water table observations. The objectives were to evaluate how the shape of the relationship between drain flow and water table height above drain varies depending on the soil hydraulic conductivity profile, to quantify how well the Hooghoudt equation represented the water table-drain flow relationship in five years of measured data at the Davis Purdue Agricultural Center (DPAC), and to determine the impact of controlled drainage on drain flow using the filled dataset. The shape of the drain flow-water table height relationship was found to depend on the selected hydraulic conductivity profile. Estimated drain flow using the Hooghoudt equation with measured water table height for both free draining and controlled periods compared well to observed flow with Nash-Sutcliffe Efficiency values above 0.7 and 0.8 for calibration and validation periods, respectively. Using this method, together with linear regression for the remaining gaps, a long-term drain flow record for a controlled drainage experiment at the DPAC was used to evaluate the impacts of controlled drainage on drain flow. In the controlled drainage sites, annual flow was 14-49% lower than free drainage.

Improved simulation of poorly drained forests using Biome-BGC.

PubMed

Bond-Lamberty, Ben; Gower, Stith T; Ahl, Douglas E

2007-05-01

Forested wetlands and peatlands are important in boreal and terrestrial biogeochemical cycling, but most general-purpose forest process models are designed and parameterized for upland systems. We describe changes made to Biome-BGC, an ecophysiological process model, that improve its ability to simulate poorly drained forests. Model changes allowed for: (1) lateral water inflow from a surrounding watershed, and variable surface and subsurface drainage; (2) adverse effects of anoxic soil on decomposition and nutrient mineralization; (3) closure of leaf stomata in flooded soils; and (4) growth of nonvascular plants (i.e., bryophytes). Bryophytes were treated as ectohydric broadleaf evergreen plants with zero stomatal conductance, whose cuticular conductance to CO(2) was dependent on plant water content. Individual model changes were parameterized with published data, and ecosystem-level model performance was assessed by comparing simulated output to field data from the northern BOREAS site in Manitoba, Canada. The simulation of the poorly drained forest model exhibited reduced decomposition and vascular plant growth (-90%) compared with that of the well-drained forest model; the integrated bryophyte photosynthetic response accorded well with published data. Simulated net primary production, biomass and soil carbon accumulation broadly agreed with field measurements, although simulated net primary production was higher than observed data in well-drained stands. Simulated net primary production in the poorly drained forest was most sensitive to oxygen restriction on soil processes, and secondarily to stomatal closure in flooded conditions. The modified Biome-BGC remains unable to simulate true wetlands that are subject to prolonged flooding, because it does not track organic soil formation, water table changes, soil redox potential or anaerobic processes.

An overview of impact of subsurface drainage project studies on salinity management in developing countries

NASA Astrophysics Data System (ADS)

Tiwari, Priyanka; Goel, Arun

2017-05-01

Subsurface drainage has been used for more than a century to keep water table at a desired level of salinity and waterlogging control. This paper has been focused on the impact assessment of pilot studies in India and some other countries from 1969 to 2014 . This review article may prove quite useful in deciding the installation of subsurface drainage project depending on main design parameters, such as drain depth and drain spacing, installation area and type of used outlet. A number of pilot studies have been taken up in past to solve the problems of soil salinity and waterlogging in India. The general guidelines that arise on the behalf of this review paper are to adapt drain depth >1.2 m and spacing depending on soil texture classification, i.e., 100-150 m for light-textured soils, 50-100 m for medium-textured soils and 30-50 m heavy-textured soils, for better result obtained from the problem areas in Indian soil and climatic conditions. An attempt has been made in the manner of literature survey to highlight the salient features of these studies, and it is hopeful to go a long way in selecting design parameters for subsurface drainage problems in the future with similar soil, water table and climatic conditions.

Water quality in organic systems

USDA-ARS?s Scientific Manuscript database

Non-point source contamination is a major water quality concern in the upper Midwestern USA, where plant nutrients, especially NO3-N, are susceptible to leaching due to extensive subsurface draining of the highly productive, but poorly drained, soils found in this region. Environmental impacts assoc...

Guidelines for the design of subsurface drainage systems for highway structural sections

DOT National Transportation Integrated Search

1972-06-01

Design criteria and a design method for pavement subsurface drainage systems include inflow-outflow method of analysis, open graded drainage layers, collector drains, pipe outlets and markers. Design examples are given for embankment sections, cut se...

Shallow Groundwater Discharge into Urban Drains: Identifying the Missing Link to Define Urban Typologies for Impact Assessment of Urbanization on Water and Nutrient Balances

NASA Astrophysics Data System (ADS)

Ocampo, C. J.; Oldham, C. E.

2015-12-01

Groundwater and surface water (GW-SW) interaction in drains of many sandy coastal plain areas displays an ephemeral hydrological regime, as often shifts occur in their hydraulic functioning from a losing to a gaining water conditions upon the position of the surrounding shallow water table (SWT). Urbanization in such areas and stormwater management strategies enhancing infiltration have the potential to alter the infiltration rates and the subsurface water storage dynamics with consequences for the residence time of the water and nutrient transformations prior their discharge into receiving SW drains. Identifying first order control on the above processes will assist the improvement of assessment tools for better urban development. This work presents findings on the hydrodynamics of the GW-SW water exchange in two drains of the Perth Coastal Plain area (Western Australia, Australia) impacted by a SWT developing on a layered variable texture soil: a peri-urban drain and a restored living stream drain in urban residential area. A multi-technique approach was used to investigate water mass balance and fluxes over a reach scale and involved continuous records of hydrometric data for GW-SW interactions, passive tracers for water pathway identification, pore water temperature for vertical water exchange, and differential SW discharge using an Acoustic Doppler Current Profiler. Results highlighted differences in the GW-SW interactions between both drains under stormflow and baseflow conditions. A substantial increase of GW discharge into the drain coincided with the full development of a SWT over a seasonal scale at the peri-urban drain, which suggests a more natural water infiltration and redistribution in the subsurface. In contrast, a large volume of infiltrated rain water was discharged into the living stream over a period of few weeks regardless of the development of the surrounding SWT, which suggests the influence of underground pipe system in water redistribution. The results contributed to identify key physical parameters to define urban typologies, quantify the subsurface storage discharge and residence time, and finally assess the transport and transformations of nutrients using a generalised Damköhler number. Future work will populate the framework with other study cases.

Concentrations and loads of suspended sediment and nutrients in surface water of the Yakima River basin, Washington, 1999-2000 [electronic resource] : with an analysis of trends in concentrations

USGS Publications Warehouse

Ebbert, James C.; Embrey, Sandra S.; Kelley, Janet A.

2003-01-01

Spatial and temporal variations in concentrations and loads of suspended sediment and nutrients in surface water of the Yakima River Basin were assessed using data collected during 1999?2000 as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Samples were collected at 34 sites located throughout the Basin in August 1999 using a Lagrangian sampling design, and also were collected weekly and monthly from May 1999 through January 2000 at three of the sites. Nutrient and sediment data collected at various time intervals from 1973 through 2001 by the USGS, Bureau of Reclamation, Washington State Department of Ecology, and Roza-Sunnyside Board of Joint Control were used to assess trends in concentrations. During irrigation season (mid-March to mid-October), concentrations of suspended sediment and nutrients in the Yakima River increase as relatively pristine water from the forested headwaters moves downstream and mixes with discharges from streams, agricultural drains, and wastewater treatment plants. Concentrations of nutrients also depend partly on the proportions of mixing between river water and discharges: in years of ample water supply in headwater reservoirs, more water is released during irrigation season and there is more dilution of nutrients discharged to the river downstream. For example, streamflow from river mile (RM) 103.7 to RM 72 in August 1999 exceeded streamflow in July 1988 by a factor of almost 2.5, but loads of total nitrogen and phosphorus discharged to the reach from streams, drains, and wastewater treatment plants were only 1.2 and 1.1 times larger. In years of ample water supply, canal water, which is diverted from either the Yakima or Naches River, makes up more of the flow in drains and streams carrying agricultural return flows. The canal water dilutes nutrients (especially nitrate) transported to the drains and streams in runoff from fields and in discharges from subsurface field drains and the shallow ground-water system. The average concentration of total nitrogen in drains and streams discharging to the Yakima River from RM 103.7 to RM 72 in August 1999 was 2.63 mg/L, and in July 1988 was 3.16 mg/L; average concentrations of total phosphorus were 0.20 and 0.26 mg/L. After irrigation season, streamflow in agricultural drains decreases because irrigation water is no longer diverted from the Yakima and Naches Rivers. As a result, concentrations of total nitrogen in drains increase because nitrate, which constitutes much of total nitrogen, continues to enter the drains from subsurface drains and shallow ground water. Concentrations of total phosphorus and suspended sediment often decrease, because they are transported to the drains in runoff of irrigation water from fields. In Granger Drain, concentrations of total nitrogen ranged from 2-4 mg/L during irrigation season and increased to about 6 mg/L after irrigation season, and concentrations of total phosphorus, as high as 1 mg/L, decreased to about 0.2 mg/L. In calendar year 1999, Moxee Drain transported an average of 28,000 lb/d (pounds per day) of suspended sediment, 380 lb/d of total nitrogen, and 46 lb/d of total phosphorus to the Yakima River. These loads were about half the average loads transported by Granger Drain during the same period. Average streamflows were similar for the two drains, so the difference in loads was due to differences in constituent concentrations: those in Moxee Drain were about 40-60 percent less than those in Granger Drain. Loads of suspended sediment and total phosphorus in Moxee and Granger Drains were nearly four times higher during irrigation season than during the non-irrigation season because with increased flow during irrigation season, concentrations of suspended sediment and total phosphorus are usually higher. Loads of nitrate in the drains were about the same in both seasons because nitrate concentrations are higher during the non-irrigation season.

Preferential transport of isoproturon at a plot scale and a field scale tile-drained site

NASA Astrophysics Data System (ADS)

Zehe, Erwin; Flühler, Hannes

2001-06-01

Irrigation experiments using the tracers Brilliant Blue (BB) and Bromide (Br) were conducted on three plots of 1.4×1.4 m 2 (plot scale) and a field scale subsurface drained test site (900 m 2) to clarify mechanisms causing rapid transport of surface applied Isoproturon (IPU) during preferential flow events. One of the small plots (site 10) and the field scale test site are located on the same field. One day after irrigation of the plot scale sites the Br and IPU concentration in two vertical soil profiles as well as the macroporousity on separate profiles and hydraulic properties of single macropores were determined. During irrigation of the field scale test site discharge, soil moisture as well as the concentration of IPU and Br in the drainage outlet were measured. Preferential flow in deep penetrating earthworm burrows caused a fast breakthrough of IPU and Br into the tile drain (1.2 m depth) at the field scale site as well as leaching of IPU into the subsoil (>0.8 m) at site 10. The results suggest a hierarchy of preconditions for the occurrence of preferential flow events of which a sufficient number of deep penetrating macropores interconnected to the soil surface seems to be the most important one. Moreover there is evidence that facilitated transport of IPU attached to mobile soil particles occurred during the preferential flow events at the field scale site and site 10. The susceptibility for preferential flow as well as the susceptibility for facilitated transport appear to be intrinsic properties of the investigated soil.

Assessing coastal plain risk indices for subsurface phosphorus loss

USDA-ARS?s Scientific Manuscript database

Phosphorus (P) Indices are important tools for nutrient management planning in the U.S. whose evaluation often has been deemphasized in favor of research and development. Assessing P Indices in artificially drained agroecosystems is especially important, as subsurface flow is the predominant mode of...

Continuous Passive Sampling of Solutes from Agricultural Subsurface Drainage Tubes

NASA Astrophysics Data System (ADS)

Lindblad Vendelboe, Anders; de Jonge, Hubert; Rozemeijer, Joachim; Wollesen de Jonge, Lis

2015-04-01

Agricultural subsurface tube drain systems play an important role in water and solute transport. One study, focusing on lowland agricultural catchments, showed that subsurface tube drainage contributed up to 80% of the annual discharge and 90% of the annual NO3 load from agricultural fields to the receiving water bodies. Knowledge of e.g. nutrient loads and drainage volumes, based on measurements and modelling, are important for adequate water quality management. Despite the importance of tube drain transport of solutes, monitoring data are scarce. This scarcity is a result of the existing monitoring techniques for flow and contaminant load from tube drains being expensive and labor-extensive. The study presented here aimed at developing a cheap, simple, and robust method to monitor solute loads from tube drains. The method is based on the newly developed Flowcap, which can be attached to existing tube drain outlets and can measure total flow, contaminant load and flow-averaged concentrations of solutes in the drainage. The Flowcap builds on the existing Sorbicell principle, a passive sampling system that measures average concentrations over longer periods of time (days to months) for various compounds. The Sorbicell consists of two compartments permeable to water. One compartment contains an adsorbent and one contains a tracer. When water passes through the Sorbicell the compound of interest is absorbed while a tracer is released. Using the tracer loss to calculate the volume of water that has passed the Sorbicell it is possible to calculate the average concentration of the compound. When mounting Sorbicells in the Flowcap, a flow-proportional part of the drainage is sampled from the main stream. To accommodate the wide range of drainage flow rates two Flowcaps with different capacities were tested in the laboratory: one with a capacity of 25 L min-1 (Q25) and one with a capacity of 256 L min-1 (Q256). In addition, Sorbicells with two different hydraulic resistances were tested, again to accommodate a large range of potential drainage flows rates. The experiment was continued until the Sorbicell's capacity was exhausted, which gave experimentation times from 6 to 34 days, while continuously changing the drainage flow rate to simulate field drainage conditions, and to test the range of the Flowcap. The laboratory testing yielded a very good linear correlation between drainage flow rates and Sorbicell sampling rates, giving r = 0.99 for both the Q25 and the Q256 Flowcap. The Sorbicells in this experiment were designed to measure NO3, but the Flowcap can be used with any Sorbicell and thus be used to measure any compound of interest. The Flowcap does not need housing, electricity, or maintenance and continuously register drainage volumes and contaminant loads for periods up to one month. This, in addition to the low cost of the monitoring system, enables large-scale monitoring of contaminant loads via tube drains, giving valuable data for the improvement of contaminant transport models. Further, these data will help select and evaluate the different mitigation option to improve water quality.

Using Smoke Injection in Drains to Identify Potential Preferential Pathways in a Drained Arable Field

NASA Astrophysics Data System (ADS)

Nielsen, M. H.; Petersen, C. T.; Hansen, S.

2014-12-01

Macropores forming a continuous pathway between the soil surface and subsurface drains favour the transport of many contaminants from agricultural fields to surface waters. The smoke injection method presented by Shipitalo and Gibbs (2000) used for demonstrating and quantifying such pathways has been further developed and used on a drained Danish sandy loam. In order to identify the preferential pathways to drains, smoke was injected in three 1.15 m deep tile drains (total drain length 93 m), and smoke emitting macropores (SEMP) at the soil surface were counted and characterized as producing either strong or weak plumes compared to reference plumes from 3 and 6 mm wide tubes. In the two situations investigated in the present study - an early spring and an autumn situation, smoke only penetrated the soil surface layer via earthworm burrows located in a 1.0 m wide belt directly above the drain lines. However, it is known from previous studies that desiccation fractures in a dry summer situation also can contribute to the smoke pattern. The distance between SEMP measured along the drain lines was on average 0.46 m whereas the average spacing between SEMP with strong plumes was 2.3 m. Ponded water was applied in 6 cm wide rings placed above 52 burrows including 17 reference burrows which did not emit smoke. Thirteen pathways in the soil were examined using dye tracer and profile excavation. SEMP with strong plumes marked the entrance of highly efficient transport pathways conducting surface applied water and dye tracer into the drain. However, no single burrow was traced all the way from the surface into the drain, the dye patterns branched off in a network of other macropores. Water infiltration rates were significantly higher (P < 0.05) in SEMP with strong plumes (average rate: 247 mL min-1 n = 19) compared to SEMP with weak plumes (average rate: 87 mL min-1 n = 16) and no plumes (average rate: 56 mL min-1 n = 17). The results suggest that the smoke injection method is useful for identification of potentially efficient pathways for surface applied contaminants to drains and surface waters, pathways being associated primarily with unevenly distributed SEMP producing strong smoke plumes.

Field experiments to evaluate nitrate-leaching from drained agriculturally used areas

NASA Astrophysics Data System (ADS)

Bednorz, Denise; Tauchnitz, Nadine; Christen, Olaf; Rupp, Holger; Meissner, Ralph

2016-04-01

Agricultural land use is one of the main sources for diffuse nitrogen (N) inputs into surface- and groundwater. To fulfill the objectives of the European water protection policy it is mandatory to optimize agricultural management and to adopt it to site specific conditions. N present in soil is dominated by organic N, and after mineralization inorganic plant available N, obtaining the components ammonia and nitrate (NO3-N). In the environment, NO3-N occurs as the negatively charged ion NO3- which is generally solved. Thus, NO3-N is the major N-species in waters, whereas its transport is directly influenced by the flow regime. In dependence of soil type and meteorological conditions, subsurface drainage was often installed to prevent water logged zones as a requirement for agricultural use. But drainage systems were often discussed as one of the main sources for NO3-N inputs into surface water due to temporary high discharge rates and short residence time of soil water resulting in limited conditions for NO3-N degradation via denitrification. In the study presented herein, two adjacent tile-drained agriculturally used areas with adjusted agronomic conditions but different soil properties were investigated regarding their flow regime and their N-kinetic from 11/1/2013 until 10/31/2015. Both fields obtained the same size and drainage network (drain depth 0.8 m, gab distance 10 m). Field I was influenced by confined groundwater conditions due to an alternating strata of sandy and loamy layers. Field II was impermeable from a depth of one meter, showing a backwater influenced flow regime. The temporal course of soil moisture (35, 60 and 85 cm depth), drain rate as well as ground- and backwater head was registered continuously at both sites. Furthermore NH4-N- and NO3-N-concentrations (cNO3-N) in each compartment were measured. The experimental results showed that field I revealed significantly lower discharged drain rates and NO3-N-loads (17.1 mm and 2.5 kg N/ha) compared to field II (150.1 mm and 40.3 kg N/ha) within the observation period. As expected the amount of discharged NO3-N increased with increasing drain rate. But a significant feature was the temporal course of registered cNO3-N at both fields. Mean cNO3-N in drain water of field II, was generally high during the whole observation period (mean: 22.8 mgN/l), corresponding to registered cNO3-N in backwater with 23.2 mgN/l. At field I, however, mean cNO3-N in drain water was only 4.5 mgN/l, whereas only a peak wise arise in concentration could be measured after rain events corresponding to higher discharge rates. Additionally, groundwater showed low NO3-N concentrations of only 1.1 mgN/l. These differences resulted mainly due to different soil hydraulic properties. At field II drain water consisted only of percolating seepage water whereas a small denitrification potential could be assumed. At field I however, drain water was a combination of groundwater, obtaining a higher denitrification potential, and after rain events seepage water, which was generally enriched with NO3-N. The investigations showed the need to consider small scale soil heterogeneity due to the fact that not only the flow regime but also the N-kinetic was influenced significantly.

Effect of tillage on macropore flow and phosphorus transport to tile drains

USDA-ARS?s Scientific Manuscript database

Elevated phosphorus (P) concentrations in subsurface drainage water are thought to be the result of P bypassing the soil matrix via macropore flow. The objectives of this study were to quantify event water delivery to tile drains via macropore flow paths during storm events and to determine the effe...

Modeling and analysis of sub-surface leakage current in nano-MOSFET under cutoff regime

NASA Astrophysics Data System (ADS)

Swami, Yashu; Rai, Sanjeev

2017-02-01

The high leakage current in nano-meter regimes is becoming a significant portion of power dissipation in nano-MOSFET circuits as threshold voltage, channel length, and gate oxide thickness are scaled down to nano-meter range. Precise leakage current valuation and meticulous modeling of the same at nano-meter technology scale is an increasingly a critical work in designing the low power nano-MOSFET circuits. We present a specific compact model for sub-threshold regime leakage current in bulk driven nano-MOSFETs. The proposed logical model is instigated and executed into the latest updated PTM bulk nano-MOSFET model and is found to be in decent accord with technology-CAD simulation data. This paper also reviews various transistor intrinsic leakage mechanisms for nano-MOSFET exclusively in weak inversion, like drain-induced barricade lowering (DIBL), gate-induced drain leakage (GIDL), gate oxide tunneling (GOT) leakage etc. The root cause of the sub-surface leakage current is mainly due to the nano-scale short channel length causing source-drain coupling even in sub-threshold domain. Consequences leading to carriers triumphing the barricade between the source and drain. The enhanced model effectively considers the following parameter dependence in the account for better-quality value-added results like drain-to-source bias (VDS), gate-to-source bias (VGS), channel length (LG), source/drain junction depth (Xj), bulk doping concentration (NBULK), and operating temperature (Top).

Reducing phosphorus loss in tile water with managed drainage in a claypan soil.

PubMed

Nash, Patrick R; Nelson, Kelly A; Motavalli, Peter P; Nathan, Manjula; Dudenhoeffer, Chris

2015-03-01

Installing subsurface tile drain systems in poorly drained claypan soils to improve corn ( L.) yields could potentially increase environmental phosphorus (P) loss through the tile drainage system. The objectives of the study were to quantify the average concentration and loss of ortho-P in tile drain water from a claypan soil and to determine whether managed subsurface drainage (MD) could reduce ortho-P loss in tile water compared with free subsurface drainage (FD). Flow-weighted ortho-P concentration in the tile water was significantly lower with MD (0.09 mg L) compared with that of FD (0.15 mg L). Ortho-P loss in the tile water of this study was reduced with MD (36 g ha) by 80% compared with FD (180 g ha). Contrary to previous research, reduced ortho-P loss observed over the 4-yr study was not solely due to the reduced amount of water drained annually (63%) with MD compared with FD. During the spring period, when flow was similar between MD and FD, the concentration of ortho-P in the tile water generally was lower with MD compared with FD, which resulted in significantly less ortho-P loss with MD. We speculate that MD's ability to conserve water during the dry summer months increased corn's uptake of water and P, which reduced the amount of P available for leaching loss in the subsequent springs. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Effects of manure-application practices on curli production by Escherichia coli transported through soil

NASA Astrophysics Data System (ADS)

Truhlar, A. M.; Salvucci, A. E.; Siler, J. D.; Richards, B. K.; Geohring, L.; Walter, M. T.; Hay, A. G.

2014-12-01

The release of Escherichia coli into the environment from untreated manure can pose a threat to human health. Environmental survival of E. coli has been linked to extracellular fibers called curli. We investigated the effect of manure management (surface application followed by incorporation versus immediate incorporation) on the relative abundance of curli-producing E. coli in subsurface drainage effluent. Samples were collected from three dairy farms. The proportion of curli-producing E. coli in the manure storage facilities was uniform across the farms. However, the abundance of curli-producing E. coli was much greater (P < 0.05) in the tile drains of farms performing surface application of manure than in the tile drain of the farm that incorporated manure. This field result was corroborated by controlled soil column experiments; the abundance of curli-producing E. coli in soil column effluents was greater (P < 0.05) when manure was surface-applied than when it was incorporated. Our findings suggest selection pressures resulting from the different manure application methods affected curli production by E. coli isolates transported through soil. Given the importance of curli production in pathogenesis, this work highlights the effect that manure management strategies may have on pathogenesis-associated phenotypes of bacteria in agricultural subsurface runoff.

Isotopic mixing model for quantifying contributions of soil water and groundwater in subsurface ('tile') drainage

NASA Astrophysics Data System (ADS)

Kennedy, C. D.; Gall, H.; Jafvert, C. T.; Bowen, G. J.

2010-12-01

Subsurface (‘tile’) drainage, consisting of buried grids of perforated pipe, has provided a means of converting millions of acres of poorly drained soils in the Midwestern U.S. into fertile cropland. However, by altering pathways and rates of soil water and groundwater movement through agricultural lands, this practice may accelerate the loss of nitrate and other agrochemicals. To better understand the hydrological controls on nitrogen dynamics in artificially drained agricultural watersheds, a field sampling program has been established at the Animal Science Research and Education Center (ASREC) at Purdue University (West Lafayette, Indiana) to (1) measure precipitation amount, tile flow, and water-table elevation, and (2) collect water samples for analysis of nitrate, major ions, and oxygen isotope ratios in precipitation, tile drainage, shallow (1 m) and deep (3 m) groundwater, and soil water during storm events. Preliminary physical, chemical, and isotopic data collected at the ASREC show a coincident timing of peak storm ‘event water’ and peak nitrate flux in tile drainage, suggesting significant routing of infiltrating event water. In this work, we aim to refine our understanding of tile drainage at the ASREC by developing a mixing model for partitioning contributions of soil water and groundwater in tile drainage during several storm runoff events ranging in precipitation intensity and coinciding with varying antecedent soil moisture conditions. The results of our model will describe tile drainage in terms of its hydrological components, soil water and groundwater, which in turn will provide a means of incorporating the effects of tile drainage in surface/subsurface hydrological transport models.

The Revival of a Failed Constructed Wetland Treating of a High Fe Load AMD

Treesearch

A.D. Karathanasis; C.D. Barton

1999-01-01

Acid mine drainage (AMD) from abandoned mines has significantly impaired water quality in eastern Kentucky. A small surface flow wetland constructed in 1989 to reduce AMD effects and subsequently failed after six months of operation was renovated by incorporating anoxic limestone drains (ALDs) and anaerobic subsurface drains promoting vertical flow through successive...

Anthropogenic modifications to drainage conditions on streamflow variability in the Wabash River basin, Indiana

NASA Astrophysics Data System (ADS)

Chiu, C.; Bowling, L. C.

2011-12-01

The Wabash River watershed is the largest watershed in Indiana and includes the longest undammed river reach east of the Mississippi River. The land use of the Wabash River basin began to significantly change from mixed woodland dominated by small lakes and wetlands to agriculture in the mid-1800s and agriculture is now the predominant land use. Over 80% of natural wetland areas were drained to facilitate better crop production through both surface and subsurface drainage applications. Quantifying the change in hydrologic response in this intensively managed landscape requires a hydrologic model that can represent wetlands, crop growth, and impervious area as well as subsurface and surface drainage enhancements, coupled with high resolution soil and topographic inputs. The Variable Infiltration Capacity (VIC) model wetland algorithm has been previously modified to incorporate spatially-varying estimates of water table distribution using a topographic index approach, as well as a simple urban representation. Now, the soil water characteristics curve and a derived drained to equilibrium moisture profile are used to improve the model's estimation of the water table. In order to represent subsurface (tile) drainage, the tile drainage component of subsurface flow is calculated when the simulated water table rises above a specified drain depth. A map of the current estimated extent of subsurface tile drainage for the Wabash River based on a decision tree classifier of soil drainage class, soil slope and agricultural land use is used to activate the new tile drainage feature in the VIC model, while wetland depressional storage capacity is extracted from digital elevation and soil information. This modified VIC model is used to evaluate the performance of model physical variations in the intensively managed hydrologic regime of the Wabash River system and to understand the role of surface and subsurface storage, and land use and land cover change on hydrologic change.

Modified APEX model for Simulating Macropore Phosphorus Contributions to Tile Drains.

PubMed

Ford, William I; King, Kevin W; Williams, Mark R; Confesor, Remegio B

2017-11-01

The contribution of macropore flow to phosphorus (P) loadings in tile-drained agricultural landscapes remains poorly understood at the field scale, despite the recognized deleterious impacts of contaminant transport via macropore pathways. A new subroutine that couples existing matrix-excess and matrix-desiccation macropore flow theory and a modified P routine is implemented in the Agricultural Policy Environmental eXtender (APEX) model. The original and modified formulation were applied and evaluated for a case study in a poorly drained field in Western Ohio with 31 months of surface and subsurface monitoring data. Results highlighted that a macropore subroutine in APEX improved edge-of-field discharge calibration and validation for both tile and total discharge from satisfactory and good, respectively, to very good and improved dissolved reactive P load calibration and validation statistics for tile P loads from unsatisfactory to very good. Output from the calibrated macropore simulations suggested median annual matrix-desiccation macropore flow contributions of 48% and P load contributions of 43%, with the majority of loading occurring in winter and spring. While somewhat counterintuitive, the prominence of matrix-desiccation macropore flow during seasons with less cracking reflects the importance of coupled development of macropore pathways and adequate supply of the macropore flow source. The innovative features of the model allow for assessments of annual macropore P contributions to tile drainage and has the potential to inform P site assessment tools. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

A Physical Model for Shallow Groundwater Studies and the Simulation of Land Drain Performance.

ERIC Educational Resources Information Center

Parkinson, Robert; Reid, Ian

1987-01-01

Describes a two-dimensional sand-tank model that illustrates the influence of ground slope on tile drain discharge and the movement of groundwater in general. The model can be used to demonstrate the effect of topography on sub-surface water movement in agricultural catchments, thus it is a useful hydrological teaching aid. (Author/BSR)

Landscape hydrology and scaling of nitrate 15N and 18O isotope composition in a semi-arid agroecosystem

NASA Astrophysics Data System (ADS)

Kelley, C. J.; Martin, R. A.; Keller, C. K.; Orr, C. H.; Huggins, D. R.; Evans, R. D.

2014-12-01

Understanding how pore- to hillslope-scale processes combine to control nutrient export at larger scales is a fundamental challenge in today's agroecosystems as the carbon and contamination footprints of production agriculture come under increasing scrutiny. At the Cook Agronomy Farm (CAF) Long-Term Agricultural Research (LTAR) station near Pullman, WA we are using in-field observations to track how local-scale hydrological routing and biogeochemical processing interact to control landscape-scale water and nutrient exports. Previous research at the CAF has shown that conservative tracers and reactive nutrient quantities (NO3-,and DOC concentrations, DOM quality) in landscape-scale drainage can be explained by straightforward mixing of waters from variably contributing areas. Nitrate stable isotope composition in subsurface drain effluent indicate that most leached nitrate originates from reduced nitrogen fertilizer applied to the CAF in the autumn, which undergoes nitrification and subsequent leaching. This occurs over a timespan of weeks to months. However, water samples from contributing areas exhibit nitrate d15N and d18O significantly greater than subsurface drain effluent at all locations, and time-series consistent with the occurrence of denitrification at some locations. Possible explanations include pore-scale processing of nitrogen that does not affect the other tracers (like EC, DOM quality, and DOC concentration), and landscape-scale transport pathways that bypass our field instruments. Through this work we are contributing to a broader understand of how global change and local factors and management practices interact to affect the fate of fertilizer N, which is a cross-cutting research theme of the national LTAR network.

User-inspired Research Quantifies How Floodplain Restoration Paired With Cover Crops Reduces Nutrient Export From an Agricultural Catchment Translating to Conservation Success in the Midwestern Cornbelt.

NASA Astrophysics Data System (ADS)

Tank, J. L.; Hanrahan, B.; Christopher, S. F.; Mahl, U. H.; Royer, T. V.

2017-12-01

The Midwestern US has undergone extensive land use change as forest, wetlands, and prairies have been converted to agroecosystems. Today, excess fertilizer nutrients from farm fields enter agricultural streams, which degrades both local and downstream water quality. We are quantifying the nutrient reduction benefits of two conservation practices implemented at the catchment scale. In partnership with The Nature Conservancy, in a small Indiana catchment, we have quantified how 600m of floodplain restoration (i.e., a two-stage ditch) increased nitrate-N removal via denitrification and reduced sediment export, but impacts on stream nutrient concentrations were negligible due to very high catchment loading relative to the short implementation reach. Requests from state and federal partners led to development and parameterization of a new two-stage ditch module in the SWAT model to determine the potential catchment-scale benefits when implementation lengths were extended. More recently, in partnership with state SWCD managers, we have added a landscape practice to quantify how winter cover crops reduce nutrient loss from fields, sampling year-round nutrient fluxes from multiple subsurface tile drains and longitudinally along the stream channel. Nitrate-N and dissolved P fluxes were significantly lower in tiles draining fields with cover crops compared to those without. At the urging of farmers and federal NRCS partners, we also linked tile drain nutrient reductions to changes in soil chemistry. Both soil nitrate-N and dissolved P were lower in cover cropped fields, and we found significant correlations between soil and tile drain nutrients, which may encourage future adoption of the conservation practice as soil health benefits appeal to farmers. As biogeochemists, this research has provided valuable insights on how floodplains and land cover change can alter patterns of catchment-scale nutrient export. The translation of successful soil and water quality outcomes through this significant regional demonstration project make it a potentially powerful agent of change for advancing conservation success.

A two-dimensional transient analytical solution for a ponded ditch drainage system under the influence of source/sink

NASA Astrophysics Data System (ADS)

Sarmah, Ratan; Tiwari, Shubham

2018-03-01

An analytical solution is developed for predicting two-dimensional transient seepage into ditch drainage network receiving water from a non-uniform steady ponding field from the surface of the soil under the influence of source/sink in the flow domain. The flow domain is assumed to be saturated, homogeneous and anisotropic in nature and have finite extends in horizontal and vertical directions. The drains are assumed to be standing vertical and penetrating up to impervious layer. The water levels in the drains are unequal and invariant with time. The flow field is also assumed to be under the continuous influence of time-space dependent arbitrary source/sink term. The correctness of the proposed model is checked by developing a numerical code and also with the existing analytical solution for the simplified case. The study highlights the significance of source/sink influence in the subsurface flow. With the imposition of the source and sink term in the flow domain, the pathline and travel time of water particles started deviating from their original position and above that the side and top discharge to the drains were also observed to have a strong influence of the source/sink terms. The travel time and pathline of water particles are also observed to have a dependency on the height of water in the ditches and on the location of source/sink activation area.

Simulation of ground-water flow near the nuclear-fuel reprocessing facility at the Western New York Nuclear Service Center, Cattaraugus County, New York

USGS Publications Warehouse

Yager, R.M.

1987-01-01

A two-dimensional finite-difference model was developed to simulate groundwater flow in a surficial sand and gravel deposit underlying the nuclear fuel reprocessing facility at Western New York Nuclear Service Center near West Valley, N.Y. The sand and gravel deposit overlies a till plateau that abuts an upland area of siltstone and shale on its west side, and is bounded on the other three sides by deeply incised stream channels that drain to Buttermilk Creek, a tributary to Cattaraugus Creek. Radioactive materials are stored within the reprocessing plant and are also buried within a till deposit at the facility. Tritiated water is stored in a lagoon system near the plant and released under permit to Franks Creek, a tributary to Buttermilk Creek. Groundwater levels predicted by steady-state simulations closely matched those measured in 23 observation wells, with an average error of 0.5 meter. Simulated groundwater discharges to two stream channels and a subsurface drain were within 5% of recorded values. Steady-state simulations used an average annual recharge rate of 46 cm/yr; predicted evapotranspiration loss from the ground was 20 cm/yr. The lateral range in hydraulic conductivity obtained through model calibration was 0.6 to 10 m/day. Model simulations indicated that 33% of the groundwater discharged from the sand and gravel unit (2.6 L/sec) is lost by evapotranspiration, 3% (3.0 L/sec) flows to seepage faces at the periphery of the plateau, 20% (1.6 L/sec) discharges to stream channels that drain a large wetland area near the center of the plateau, and the remaining 8% (0.6 L/sec) discharges to a subsurface french drain and to a wastewater treatment system. Groundwater levels computed by a transient-state simulation of an annual climatic cycle, including seasonal variation in recharge and evapotranspiration, closely matched water levels measured in eight observation wells. The model predicted that the subsurface drain and the stream channel that drains the wetland would intercept most of the recharge originating near the reprocessing plant. (Lantz-PTT)

Evaluation of SCS-CN method using a fully distributed physically based coupled surface-subsurface flow model

NASA Astrophysics Data System (ADS)

Shokri, Ali

2017-04-01

The hydrological cycle contains a wide range of linked surface and subsurface flow processes. In spite of natural connections between surface water and groundwater, historically, these processes have been studied separately. The current trend in hydrological distributed physically based model development is to combine distributed surface water models with distributed subsurface flow models. This combination results in a better estimation of the temporal and spatial variability of the interaction between surface and subsurface flow. On the other hand, simple lumped models such as the Soil Conservation Service Curve Number (SCS-CN) are still quite common because of their simplicity. In spite of the popularity of the SCS-CN method, there have always been concerns about the ambiguity of the SCS-CN method in explaining physical mechanism of rainfall-runoff processes. The aim of this study is to minimize these ambiguity by establishing a method to find an equivalence of the SCS-CN solution to the DrainFlow model, which is a fully distributed physically based coupled surface-subsurface flow model. In this paper, two hypothetical v-catchment tests are designed and the direct runoff from a storm event are calculated by both SCS-CN and DrainFlow models. To find a comparable solution to runoff prediction through the SCS-CN and DrainFlow, the variance between runoff predictions by the two models are minimized by changing Curve Number (CN) and initial abstraction (Ia) values. Results of this study have led to a set of lumped model parameters (CN and Ia) for each catchment that is comparable to a set of physically based parameters including hydraulic conductivity, Manning roughness coefficient, ground surface slope, and specific storage. Considering the lack of physical interpretation in CN and Ia is often argued as a weakness of SCS-CN method, the novel method in this paper gives a physical explanation to CN and Ia.

Spatial variation in herbicide leaching from a marine clay soil via subsurface drains

PubMed Central

Ulén, Barbro M; Larsbo, Mats; Kreuger, Jenny K; Svanbäck, Annika

2013-01-01

Background Subsurface transport via tile drains can significantly contribute to pesticide contamination of surface waters. The spatial variation in subsurface leaching of normally applied herbicides was examined together with phosphorus losses in 24 experimental plots with water sampled flow-proportionally. The study site was a flat, tile-drained area with 60% marine clay in the topsoil in southeast Sweden. The objectives were to quantify the leaching of frequently used herbicides from a tile drained cracking clay soil and to evaluate the variation in leaching within the experimental area and relate this to topsoil management practices (tillage method and structure liming). Results In summer 2009, 0.14, 0.22 and 1.62%, respectively, of simultaneously applied amounts of MCPA, fluroxypyr and clopyralid were leached by heavy rain five days after spraying. In summer 2011, on average 0.70% of applied bentazone was leached by short bursts of intensive rain 12 days after application. Peak flow concentrations for 50% of the treated area for MCPA and 33% for bentazone exceeded the Swedish no-effect guideline values for aquatic ecosystems. Approximately 0.08% of the glyphosate applied was leached in dissolved form in the winters of 2008/2009 and 2010/2011. Based on measurements of glyphosate in particulate form, total glyphosate losses were twice as high (0.16%) in the second winter. The spatial inter-plot variation was large (72–115%) for all five herbicides studied, despite small variations (25%) in water discharge. Conclusions The study shows the importance of local scale soil transport properties for herbicide leaching in cracking clay soils. © 2013 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. PMID:23658148

Relative importance of impervious area, drainage density, width function, and subsurface storm drainage on flood runoff from an urbanized catchment

NASA Astrophysics Data System (ADS)

Ogden, Fred L.; Raj Pradhan, Nawa; Downer, Charles W.; Zahner, Jon A.

2011-12-01

The literature contains contradictory conclusions regarding the relative effects of urbanization on peak flood flows due to increases in impervious area, drainage density and width function, and the addition of subsurface storm drains. We used data from an urbanized catchment, the 14.3 km2 Dead Run watershed near Baltimore, Maryland, USA, and the physics-based gridded surface/subsurface hydrologic analysis (GSSHA) model to examine the relative effect of each of these factors on flood peaks, runoff volumes, and runoff production efficiencies. GSSHA was used because the model explicitly includes the spatial variability of land-surface and hydrodynamic parameters, including subsurface storm drains. Results indicate that increases in drainage density, particularly increases in density from low values, produce significant increases in the flood peaks. For a fixed land-use and rainfall input, the flood magnitude approaches an upper limit regardless of the increase in the channel drainage density. Changes in imperviousness can have a significant effect on flood peaks for both moderately extreme and extreme storms. For an extreme rainfall event with a recurrence interval in excess of 100 years, imperviousness is relatively unimportant in terms of runoff efficiency and volume, but can affect the peak flow depending on rainfall rate. Changes to the width function affect flood peaks much more than runoff efficiency, primarily in the case of lower density drainage networks with less impermeable area. Storm drains increase flood peaks, but are overwhelmed during extreme rainfall events when they have a negligible effect. Runoff in urbanized watersheds with considerable impervious area shows a marked sensitivity to rainfall rate. This sensitivity explains some of the contradictory findings in the literature.

Ground-water, surface-water, and bottom-sediment contamination in the O-field area, Aberdeen Proving Ground, Maryland, and the possible effects of selected remedial actions on ground water

USGS Publications Warehouse

Vroblesky, Don A.; Lorah, Michelle M.; Oliveros, James P.

1995-01-01

Disposal of munitions and chemical-warfare substances has introduced inorganic and organic contaminants to the ground water, surface water, and bottom sediment at O-Field, in the Edgewood area of Aberdeen Proving Ground, Maryland. Contaminants include chloride, arsenic, transition metals, chlorinated aliphatic hydrocarbons, aromatic compounds, and organosulfur and organophosphorus compounds. The hydrologic effects of several remedial actions were estimated by use of a ground-water-flow model. The remedial actions examined were an impermeable covering, encapsulation, subsurface barriers, a ground-water drain, pumping of wells to manage water levels or to remove contaminated ground water for treatment, and no action.

Rye cover crop and gamagrass strip effects on NO3 concentration and load in tile drainage.

PubMed

Kaspar, T C; Jaynes, D B; Parkin, T B; Moorman, T B

2007-01-01

A significant portion of the NO3 from agricultural fields that contaminates surface waters in the Midwest Corn Belt is transported to streams or rivers by subsurface drainage systems or "tiles." Previous research has shown that N fertilizer management alone is not sufficient for reducing NO3 concentrations in subsurface drainage to acceptable levels; therefore, additional approaches need to be devised. We compared two cropping system modifications for NO3 concentration and load in subsurface drainage water for a no-till corn (Zea mays L.)-soybean (Glycine max [L.] Merr.) management system. In one treatment, eastern gamagrass (Tripsacum dactyloides L.) was grown in permanent 3.05-m-wide strips above the tiles. For the second treatment, a rye (Secale cereale L.) winter cover crop was seeded over the entire plot area each year near harvest and chemically killed before planting the following spring. Twelve 30.5x42.7-m subsurface-drained field plots were established in 1999 with an automated system for measuring tile flow and collecting flow-weighted samples. Both treatments and a control were initiated in 2000 and replicated four times. Full establishment of both treatments did not occur until fall 2001 because of dry conditions. Treatment comparisons were conducted from 2002 through 2005. The rye cover crop treatment significantly reduced subsurface drainage water flow-weighted NO3 concentrations and NO3 loads in all 4 yr. The rye cover crop treatment did not significantly reduce cumulative annual drainage. Averaged over 4 yr, the rye cover crop reduced flow-weighted NO3 concentrations by 59% and loads by 61%. The gamagrass strips did not significantly reduce cumulative drainage, the average annual flow-weighted NO3 concentrations, or cumulative NO3 loads averaged over the 4 yr. Rye winter cover crops grown after corn and soybean have the potential to reduce the NO3 concentrations and loads delivered to surface waters by subsurface drainage systems.

Assessment of Nitrate-N Load in Subsurface Drainage Water from the Agricultural Fields in the Fergana Valley, Uzbekistan

NASA Astrophysics Data System (ADS)

Kenjabaev, S.; Forkutsa, I.; Dukhovny, V.; Frede, H. G.

2012-04-01

Leaching of nitrate-N (NO3-) from irrigated agricultural land and water contamination have become a worldwide concern. This study was conducted to investigate amount of nitrate-N leached to groundwater and surface water from irrigated cotton, winter wheat and maize fields in the Fergana Valley (Uzbekistan). Therefore at two sites ("Akbarabad" and "Azizbek") equipped with closed horizontal drainage system during 2010-2011 vegetation seasons we monitored water flow, nutrient concentrations and salinity at surface and subsurface drains, at irrigation canals and groundwater. We also applied stable isotopes (δ2H and δ18O) method in order to investigate the source of drainage water runoff. Discussed are results of 2010. Farmers fertilized cotton fields with ammonium nitrate of 350-450 kg ha-1 in "Akbarabad" and 700 kg ha-1 in "Azizbek" sites. In winter wheat and maize fields (in "Akbarabad") about 500 kg ha-1 of ammonium nitrate were applied. Cotton fields were irrigated with 2700 m3 ha-1 ("Akbarabad") and 3500 m3 ha-1 ("Azizbek"). In winter wheat and maize fields applied irrigation water amounted to 3900 m3 ha-1 and 723 m3 ha-1, respectively. Frequent groundwater and subsurface drainage water sampling revealed that nitrate leaching occurred mostly during and right after the irrigation events. The estimated average nitrate-N concentration in subsurface drainage water in "Akbarabad" was slightly higher (9 mg l-1) than in "Azizbek" (8 mg l-1). During July-November (2010), in average, nitrate-N losses through subsurface drainage amounted to 24 kg ha-1 in "Akbarabad" and 18 kg ha-1 in "Azizbek". The salinity of drainage water at both sites was similar and varied between 2.3-2.7 dS m-1. Preliminary results of isotope signals of studied water (precipitation, drainage, irrigation and ground water) indicate that the source of drainage water runoff comes from the irrigation water, while the contribution of rainfall is negligible. It is planned to run simulations with DRAINMOD model for further investigation of water and N balances of the selected sites. Developed recommendations for farmers on optimum irrigation water amounts and N fertilization will allow reducing environmental risks in agricultural lands of the Fergana Valley.

Preferential flow estimates to an agricultural tile drain with implications for glyphosate transport

USGS Publications Warehouse

Stone, W.W.; Wilson, J.T.

2006-01-01

Agricultural subsurface drains, commonly referred to as tile drains, are potentially significant pathways for the movement of fertilizers and pesticides to streams and ditches in much of the Midwest. Preferential flow in the unsaturated zone provides a route for water and solutes to bypass the soil matrix and reach tile drains faster than predicted by traditional displacement theory. This paper uses chloride concentrations to estimate preferential flow contributions to a tile drain during two storms in May 2004. Chloride, a conservative anion, was selected as the tracer because of differences in chloride concentrations between the two sources of water to the tile drain, preferential and matrix flow. A strong correlation between specific conductance and chloride concentration provided a mechanism to estimate chloride concentrations in the tile drain throughout the storm hydrographs. A simple mixing analysis was used to identify the preferential flow component of the storm hydrograph. During two storms, preferential flow contributed 11 and 51% of total storm tile drain flow; the peak contributions, 40 and 81%, coincided with the peak tile drain flow. Positive relations between glyphosate [N-(phosphonomethyl)glycine] concentrations and preferential flow for the two storms suggest that preferential flow is an important transport pathway to the tile drain. ?? ASA, CSSA, SSSA.

Illinois drainage water management demonstration project

USGS Publications Warehouse

Pitts, D.J.; Cooke, R.; Terrio, P.J.; ,

2004-01-01

Due to naturally high water tables and flat topography, there are approximately 4 million ha (10 million ac) of farmland artificially drained with subsurface (tile) systems in Illinois. Subsurface drainage is practiced to insure trafficable field conditions for farm equipment and to reduce crop stress from excess water within the root zone. Although drainage is essential for economic crop production, there have been some significant environmental costs. Tile drainage systems tend to intercept nutrient (nitrate) rich soil-water and shunt it to surface water. Data from numerous monitoring studies have shown that a significant amount of the total nitrate load in Illinois is being delivered to surface water from tile drainage systems. In Illinois, these drainage systems are typically installed without control mechanisms and allow the soil to drain whenever the water table is above the elevation of the tile outlet. An assessment of water quality in the tile drained areas of Illinois showed that approximately 50 percent of the nitrate load was being delivered through the tile systems during the fallow period when there was no production need for drainage to occur. In 1998, a demonstration project to introduce drainage water management to producers in Illinois was initiated by NRCS4 An initial aspect of the project was to identify producers that were willing to manage their drainage system to create a raised water table during the fallow (November-March) period. Financial assistance from two federal programs was used to assist producers in retrofitting the existing drainage systems with control structures. Growers were also provided guidance on the management of the structures for both water quality and production benefits. Some of the retrofitted systems were monitored to determine the effect of the practice on water quality. This paper provides background on the water quality impacts of tile drainage in Illinois, the status of the demonstration project, preliminary monitoring results, and other observations.

An analytical solution for predicting the transient seepage from a subsurface drainage system

NASA Astrophysics Data System (ADS)

Xin, Pei; Dan, Han-Cheng; Zhou, Tingzhang; Lu, Chunhui; Kong, Jun; Li, Ling

2016-05-01

Subsurface drainage systems have been widely used to deal with soil salinization and waterlogging problems around the world. In this paper, a mathematical model was introduced to quantify the transient behavior of the groundwater table and the seepage from a subsurface drainage system. Based on the assumption of a hydrostatic pressure distribution, the model considered the pore-water flow in both the phreatic and vadose soil zones. An approximate analytical solution for the model was derived to quantify the drainage of soils which were initially water-saturated. The analytical solution was validated against laboratory experiments and a 2-D Richards equation-based model, and found to predict well the transient water seepage from the subsurface drainage system. A saturated flow-based model was also tested and found to over-predict the time required for drainage and the total water seepage by nearly one order of magnitude, in comparison with the experimental results and the present analytical solution. During drainage, a vadose zone with a significant water storage capacity developed above the phreatic surface. A considerable amount of water still remained in the vadose zone at the steady state with the water table situated at the drain bottom. Sensitivity analyses demonstrated that effects of the vadose zone were intensified with an increased thickness of capillary fringe, capillary rise and/or burying depth of drains, in terms of the required drainage time and total water seepage. The analytical solution provides guidance for assessing the capillary effects on the effectiveness and efficiency of subsurface drainage systems for combating soil salinization and waterlogging problems.

Nutrient transport through a Vegetative Filter Strip with subsurface drainage.

PubMed

Bhattarai, Rabin; Kalita, Prasanta Kumar; Patel, Mita Kanu

2009-04-01

The transport of nutrients and soil sediments in runoff has been recognized as a noteworthy environmental issue. Vegetative Filter Strips (VFS) have been used as one of the best management practices (BMPs) for retaining nutrients and sediments from surface runoff, thus preventing the pollutants from reaching receiving waters. However, the effectiveness of a VFS when combined with a subsurface drainage system has not been investigated previously. This study was undertaken to monitor the retention and transport of nutrients within a VFS that had a subsurface drainage system installed at a depth of 1.2 m below the soil surface. Nutrient concentrations of NO(3)-N (Nitrate Nitrogen), PO(-)(4) (Orthophosphorus), and TP (Total Phosphorus) were measured in surface water samples (entering and leaving the VFS), and subsurface outflow. Soil samples were collected and analyzed for plant available Phosphorus (Bray P1) and NO(3)-N concentrations. Results showed that PO(-)(4), NO(3)-N, and TP concentrations decreased in surface flow through the VFS. Many surface outflow water samples from the VFS showed concentration reductions of as much as 75% for PO(-)(4) and 70% for TP. For subsurface outflow water samples through the drainage system, concentrations of PO(-)(4) and TP decreased but NO(3)-N concentrations increased in comparison to concentrations in surface inflow samples. Soil samples that were collected from various depths in the VFS showed a minimal buildup of nutrients in the top soil profile but indicated a gradual buildup of nutrients at the depth of the subsurface drain. Results demonstrate that although a VFS can be very effective in reducing runoff and nutrients from surface flow, the presence of a subsurface drain underneath the VFS may not be environmentally beneficial. Such a combination may increase NO(3)-N transport from the VFS, thus invalidating the purpose of the BMP.

Shallow Subsurface Structures of Volcanic Fissures

NASA Astrophysics Data System (ADS)

Parcheta, C. E.; Nash, J.; Mitchell, K. L.; Parness, A.

2015-12-01

Volcanic fissure vents are a difficult geologic feature to quantify. They are often too thin to document in detail with seismology or remote geophysical methods. Additionally, lava flows, lava drain back, or collapsed rampart blocks typically conceal a fissure's surface expression. For exposed fissures, quantifying the surface (let along sub0surface) geometric expression can become an overwhelming and time-consuming task given the non-uniform distribution of wall irregularities, drain back textures, and the larger scale sinuosity of the whole fissure system. We developed (and previously presented) VolcanoBot to acquire robust characteristic data of fissure geometries by going inside accessible fissures after an eruption ends and the fissure cools off to <50 C. Data from VolcanoBot documents the fissure conduit geometry with a near-IR structured light sensor, and reproduces the 3d structures to cm-scale accuracy. Here we present a comparison of shallow subsurface structures (<30 m depth) within the Mauna Ulu fissure system and their counterpart features at the vent-to-ground-surface interface. While we have not mapped enough length of the fissure to document sinuosity at depth, we see a self-similar pattern of irregularities on the fissure walls throughout the entire shallow subsurface, implying a fracture mechanical origin similar to faults. These irregularities are, on average, 1 m across and protrude 30 cm into the drained fissure. This is significantly larger than the 10% wall roughness addressed in the engineering literature on fluid dynamics, and implies that magma fluid dynamics during fissure eruptions are probably not as passive nor as simple as previously thought. In some locations, it is possible to match piercing points across the fissure walls, where the dike broke the wall rock in order to propagate upwards, yet in other locations there are erosional cavities, again, implying complex fluid dynamics in the shallow sub-surface during fissure eruptions.

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Artificial Drainage (1992) and Irrigation (1997)

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the estimated area of artifical drainage for the year 1992 and irrigation types for the year 1997 compiled for every MRB_E2RF1 catchment of Major River Basins (MRBs, Crawford and others, 2006). The source data sets were derived from tabular National Resource Inventory (NRI) data sets created by the National Resources Conservation Service (NRCS, U.S. Department of Agriculture, 1995, 2000). Artificial drainage is defined as subsurface drains and ditches. Irrigation types are defined as gravity and pressure. Subsurface drains are described as conduits, such as corrugated plastic tubing, tile, or pipe, installed beneath the ground surface to collect and/or convey drainage. Surface drainage field ditches are described as graded ditches for collecting excess water. Gravity irrigation source is described as irrigation delivered to the farm and/or field by canals or pipelines open to the atmosphere; and water is distributed by the force of gravity down the field by: (1) A surface irrigation system (border, basin, furrow, corrugation, wild flooding, etc.) or (2) Sub-surface irrigation pipelines or ditches. Pressure irrigation source is described as irrigation delivered to the farm and/or field in pump or elevation-induced pressure pipelines, and water is distributed across the field by: (1) Sprinkle irrigation (center pivot, linear move, traveling gun, side roll, hand move, big gun, or fixed set sprinklers), or (2) Micro irrigation (drip emitters, continuous tube bubblers, micro spray or micro sprinklers). NRI data do not include Federal lands and are thus excluded from this dataset. The tabular data for drainage were spatially apportioned to the National Land Cover Dataset (NLCD, Kerie Hitt, U.S. Geological Survey, written commun., 2005) and the tabular data for irrigation were spatially apportioned to an enhanced version of the National Land Cover Dataset (NLCDe, Nakagaki and others, 2007). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Regional Big Injun (Price/Pocono) subsurface stratigraphy of West Virginia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donaldson, A.C.; Zou, Xiangdong

1992-01-01

The lower Big Injun (Lower Mississippian) is the oil reservoir of the Granny Creek and Rock Creek fields and consists of multiple sandstones that were deposited in different fluvial-deltaic depositional environments. These multiple sandstones became amalgamated and now appear as a widespread blanket sandstone as a result of ancient cut and fill processes associated with river-channel sedimentation. The regional study of this Price Formation subsurface equivalent considers the continuity and thickness variations of the composite sandstones of the Big Injun mainly within western West Virginia. The major fluvial drainage system apparently flowed southward through Ohio (much of it later erodedmore » by the pre-Pottsville unconformity) during Big Injun time (and earlier) and part of the system was diverted into southwestern West Virginia as vertically stacked channel and river-mouth bar deposits (Rock Creek field). This ancient Ontario River system apparently drained a huge area including the northern craton as well as the orogenic belt. The emerging West Virginia Dome probably sourced the sediment transported by small rivers developing southwestward prograding deltas across Clay County (Granny Creek field). Sedimentation was affected by differential subsidence in the basin. Paleovalley fill was considered for areas with vertically stacked sandstones, but evidence for their origin is not convincing. Oil-reservoir sandstones are classified as dip-trending river channel (D1) and deltaic shoreline (D2) deposits.« less

Contributions of systematic tile drainage to watershed-scale phosphorus transport.

PubMed

King, Kevin W; Williams, Mark R; Fausey, Norman R

2015-03-01

Phosphorus (P) transport from agricultural fields continues to be a focal point for addressing harmful algal blooms and nuisance algae in freshwater systems throughout the world. In humid, poorly drained regions, attention has turned to P delivery through subsurface tile drainage. However, research on the contributions of tile drainage to watershed-scale P losses is limited. The objective of this study was to evaluate long-term P movement through tile drainage and its manifestation at the watershed outlet. Discharge data and associated P concentrations were collected for 8 yr (2005-2012) from six tile drains and from the watershed outlet of a headwater watershed within the Upper Big Walnut Creek watershed in central Ohio. Results showed that tile drainage accounted for 47% of the discharge, 48% of the dissolved P, and 40% of the total P exported from the watershed. Average annual total P loss from the watershed was 0.98 kg ha, and annual total P loss from the six tile drains was 0.48 kg ha. Phosphorus loads in tile and watershed discharge tended to be greater in the winter, spring, and fall, whereas P concentrations were greatest in the summer. Over the 8-yr study, P transported in tile drains represented <2% of typical application rates in this watershed, but >90% of all measured concentrations exceeded recommended levels (0.03 mg L) for minimizing harmful algal blooms and nuisance algae. Thus, the results of this study show that in systematically tile-drained headwater watersheds, the amount of P delivered to surface waters via tile drains cannot be dismissed. Given the amount of P loss relative to typical application rates, development and implementation of best management practices (BMPs) must jointly consider economic and environmental benefits. Specifically, implementation of BMPs should focus on late fall, winter, and early spring seasons when most P loading occurs. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Large drainages from short-lived glacial lakes in the Teskey Range, Tien Shan Mountains, Central Asia

NASA Astrophysics Data System (ADS)

Narama, Chiyuki; Daiyrov, Mirlan; Duishonakunov, Murataly; Tadono, Takeo; Sato, Hayato; Kääb, Andreas; Ukita, Jinro; Abdrakhmatov, Kanatbek

2018-04-01

Four large drainages from glacial lakes occurred during 2006-2014 in the western Teskey Range, Kyrgyzstan. These floods caused extensive damage, killing people and livestock as well as destroying property and crops. Using satellite data analysis and field surveys of this area, we find that the water volume that drained at Kashkasuu glacial lake in 2006 was 194 000 m3, at western Zyndan lake in 2008 was 437 000 m3, at Jeruy lake in 2013 was 182 000 m3, and at Karateke lake in 2014 was 123 000 m3. Due to their subsurface outlet, we refer to these short-lived glacial lakes as the tunnel-type, a type that drastically grows and drains over a few months. From spring to early summer, these lakes either appear, or in some cases, significantly expand from an existing lake (but non-stationary), and then drain during summer. Our field surveys show that the short-lived lakes form when an ice tunnel through a debris landform gets blocked. The blocking is caused either by the freezing of stored water inside the tunnel during winter or by the collapse of ice and debris around the ice tunnel. The draining then occurs through an opened ice tunnel during summer. The growth-drain cycle can repeat when the ice-tunnel closure behaves like that of typical supraglacial lakes on debris-covered glaciers. We argue here that the geomorphological characteristics under which such short-lived glacial lakes appear are (i) a debris landform containing ice (ice-cored moraine complex), (ii) a depression with water supply on a debris landform as a potential lake basin, and (iii) no visible surface outflow channel from the depression, indicating the existence of an ice tunnel. Applying these characteristics, we examine 60 depressions (> 0.01 km2) in the study region and identify here 53 of them that may become short-lived glacial lakes, with 34 of these having a potential drainage exceeding 10 m3 s-1 at peak discharge.

Evidence for a climate-induced ecohydrological state shift in wetland ecosystems of the southern Prairie Pothole Region

USGS Publications Warehouse

McKenna, Owen; Mushet, David M.; Rosenberry, Donald O.; LaBaugh, James W.

2017-01-01

Changing magnitude, frequency, and timing of precipitation can influence aquatic-system hydrological, geochemical, and biological processes, in some cases resulting in system-wide shifts to an alternate state. Since the early 1990s, the southern Prairie Pothole Region has been subjected to an extended period of increased wetness resulting in marked changes to aquatic systems defining this region. We explored numerous lines of evidence to identify: (1) how the recent wet period compared to historical variability, (2) hydrological, geochemical, and biological responses, and (3) how these responses might represent a state shift in the region’s wetland ecosystems. We analyzed long-term climate records and compared how different hydrological variables responded in this wet period compared to decades before the observed shift. Additionally, we used multi-decadal records of waterfowl population and subsurface tile drain records to explore wildlife and human responses to a shifting climate. Since 1993, a novel precipitation regime corresponded with increased pond numbers, ponded-water depths, lake levels, stream flows, groundwater heights, soil-moisture, waterfowl populations, and installation of subsurface tile drains in agricultural fields. These observed changes reflect an alteration in water storage and movement across the landscape that in turn has altered solute sources and concentrations of prairie-pothole wetlands and has increased pond permanence. Combined, these changes represent significant evidence for a state shift in the ecohydrological functioning of the region’s wetland ecosystems, a shift that may require a significant refinement of the previously developed “wetland continuum” concept.

Denitrifying bioreactors for nitrate removal from tile drained cropland

USDA-ARS?s Scientific Manuscript database

Denitrification bioreactors are a promising technology for mitigation of nitrate-nitrogen (NO3-N) losses in subsurface drainage water. Bioreactors are constructed with carbon substrates, typically wood chips, to provide a substrate for denitrifying microorganisms. Researchers in Iowa found that for ...

Hydrologic control of dissolved organic matter concentration and quality in a semiarid artificially drained agricultural catchment

NASA Astrophysics Data System (ADS)

Bellmore, Rebecca A.; Harrison, John A.; Needoba, Joseph A.; Brooks, Erin S.; Kent Keller, C.

2015-10-01

Agricultural practices have altered watershed-scale dissolved organic matter (DOM) dynamics, including in-stream concentration, biodegradability, and total catchment export. However, mechanisms responsible for these changes are not clear, and field-scale processes are rarely directly linked to the magnitude and quality of DOM that is transported to surface water. In a small (12 ha) agricultural catchment in eastern Washington State, we tested the hypothesis that hydrologic connectivity in a catchment is the dominant control over the concentration and quality of DOM exported to surface water via artificial subsurface drainage. Concentrations of dissolved organic carbon (DOC) and humic-like components of DOM decreased while the Fluorescence Index and Freshness Index increased with depth through the soil profile. In drain discharge, these characteristics were significantly correlated with drain flow across seasons and years, with drain DOM resembling deep sources during low-flow and shallow sources during high flow, suggesting that DOM from shallow sources bypasses removal processes when hydrologic connectivity in the catchment is greatest. Assuming changes in streamflow projected for the Palouse River (which contains the study catchment) under the A1B climate scenario (rapid growth, dependence on fossil fuel, and renewable energy sources) apply to the study catchment, we project greater interannual variability in annual DOC export in the future, with significant increases in the driest years. This study highlights the variability in DOM inputs from agricultural soil to surface water on daily to interannual time scales, pointing to the need for a more nuanced understanding of agricultural impacts on DOM dynamics in surface water.

E. coli transport through surface-connected biopores identified from smoke injection tests

USDA-ARS?s Scientific Manuscript database

Macropores are the primary mechanism by which fecal bacteria from surface-applied manure can be transported into subsurface drains or shallow groundwater bypassing the soil matrix. Limited research has been performed investigating fecal bacteria transport through specific macropores identified in th...

Continuous gravity measurements reveal a low-density lava lake at Kīlauea Volcano, Hawai‘i

USGS Publications Warehouse

Carbone, Daniele; Poland, Michael P.; Patrick, Matthew R.; Orr, Tim R.

2013-01-01

On 5 March 2011, the lava lake within the summit eruptive vent at Kīlauea Volcano, Hawai‘i, began to drain as magma withdrew to feed a dike intrusion and fissure eruption on the volcanoʼs east rift zone. The draining was monitored by a variety of continuous geological and geophysical measurements, including deformation, thermal and visual imagery, and gravity. Over the first ∼14 hours of the draining, the ground near the eruptive vent subsided by about 0.15 m, gravity dropped by more than 100 μGal, and the lava lake retreated by over 120 m. We used GPS data to correct the gravity signal for the effects of subsurface mass loss and vertical deformation in order to isolate the change in gravity due to draining of the lava lake alone. Using a model of the eruptive vent geometry based on visual observations and the lava level over time determined from thermal camera data, we calculated the best-fit lava density to the observed gravity decrease — to our knowledge, the first geophysical determination of the density of a lava lake anywhere in the world. Our result, 950 +/- 300 kg m-3, suggests a lava density less than that of water and indicates that Kīlaueaʼs lava lake is gas-rich, which can explain why rockfalls that impact the lake trigger small explosions. Knowledge of such a fundamental material property as density is also critical to investigations of lava-lake convection and degassing and can inform calculations of pressure change in the subsurface magma plumbing system.

Linking selenium sources to ecosystems: San Francisco Bay-Delta Model

USGS Publications Warehouse

Presser, Theresa S.; Luoma, Samuel N.

2004-01-01

Marine sedimentary rocks of the Coast Ranges contribute selenium to soil, surface water, and ground water in the western San Joaquin Valley, California. Irrigation funnels selenium into a network of subsurface drains and canals. Proposals to build a master drain (i.e., San Luis Drain) to discharge into the San Francisco Bay-Delta Estuary remain as controversial today as they were in the 1950s, when drainage outside the San Joaquin Valley was first considered. An existing 85-mile portion of the San Luis Drain was closed in 1986 after fish mortality and deformities in ducks, grebes and coots were discovered at Kesterson National Wildlife Refuge, the temporary terminus of the drain. A 28-mile portion of the drain now conveys drainage from 100,000 acres into the San Joaquin River and eventually into the Bay-Delta. If the San Luis Drain is extended directly to the Bay-Delta, as is now being proposed as an alternative to sustain agriculture, it could receive drainage from an estimated one-million acres of farmland affected by rising water tables and increasing salinity. In addition to agricultural sources, oil refineries also discharge selenium to the Bay-Delta, although those discharges have declined in recent years. To understand the effects of changing selenium inputs, scientists have developed the Bay-Delta Selenium Model.

Self-accelerated development of salt karst during flash floods along the Dead Sea Coast, Israel

NASA Astrophysics Data System (ADS)

Avni, Yoav; Lensky, Nadav; Dente, Elad; Shviro, Maayan; Arav, Reuma; Gavrieli, Ittai; Yechieli, Yoseph; Abelson, Meir; Lutzky, Hallel; Filin, Sagi; Haviv, Itai; Baer, Gidon

2016-01-01

We document and analyze the rapid development of a real-time karst system within the subsurface salt layers of the Ze'elim Fan, Dead Sea, Israel by a multidisciplinary study that combines interferometric synthetic aperture radar and light detection and ranging measurements, sinkhole mapping, time-lapse camera monitoring, groundwater level measurements and chemical and isotopic analyses of surface runoff and groundwater. The >1 m/yr drop of Dead Sea water level and the subsequent change in the adjacent groundwater system since the 1960s resulted in flushing of the coastal aquifer by fresh groundwater, subsurface salt dissolution, gradual land subsidence and formation of sinkholes. Since 2010 this process accelerated dramatically as flash floods at the Ze'elim Fan were drained by newly formed sinkholes. During and immediately after these flood events the dissolution rates of the subsurface salt layer increased dramatically, the overlying ground surface subsided, a large number of sinkholes developed over short time periods (hours to days), and salt-saturated water resurged downstream. Groundwater flow velocities increased by more than 2 orders of magnitudes compared to previously measured velocities along the Dead Sea. The process is self-accelerating as salt dissolution enhances subsidence and sinkhole formation, which in turn increase the ponding areas of flood water and generate additional draining conduits to the subsurface. The rapid terrain response is predominantly due to the highly soluble salt. It is enhanced by the shallow depth of the salt layer, the low competence of the newly exposed unconsolidated overburden and the moderate topographic gradients of the Ze'elim Fan.

40 CFR Appendix D to Part 300 - Appropriate Actions and Methods of Remedying Releases

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Neutralization. (D) Equalization. (E) Chemical oxidation. (iii) Physical methods, including the following: (A... treatment. (F) Wet air oxidation. (G) Solidification. (H) Encapsulation. (I) Soil washing or flushing. (J... containment. (iv) Leachate control, including the following: (A) Subsurface drains. (B) Drainage ditches. (C...

40 CFR Appendix D to Part 300 - Appropriate Actions and Methods of Remedying Releases

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Neutralization. (D) Equalization. (E) Chemical oxidation. (iii) Physical methods, including the following: (A... treatment. (F) Wet air oxidation. (G) Solidification. (H) Encapsulation. (I) Soil washing or flushing. (J... containment. (iv) Leachate control, including the following: (A) Subsurface drains. (B) Drainage ditches. (C...

40 CFR Appendix D to Part 300 - Appropriate Actions and Methods of Remedying Releases

Code of Federal Regulations, 2012 CFR

2012-07-01

...) Neutralization. (D) Equalization. (E) Chemical oxidation. (iii) Physical methods, including the following: (A... treatment. (F) Wet air oxidation. (G) Solidification. (H) Encapsulation. (I) Soil washing or flushing. (J... containment. (iv) Leachate control, including the following: (A) Subsurface drains. (B) Drainage ditches. (C...

Effectiveness of conservation practices within watersheds: Case study in tile-drained systems

USDA-ARS?s Scientific Manuscript database

The effectiveness of conservation practices are governed in part by the spatial and temporal patterns of water flow as runoff and subsurface (tile) drainage. The variability in patterns of nitrate loss were examined using data from different sized catchments with four CEAP watersheds located in cent...

Comparison of contaminant transport in agricultural drainage water and urban stormwater runoff

USDA-ARS?s Scientific Manuscript database

Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts including hypoxia and harmful algal blooms. The main objective of this long-term study was to quantify and compare contaminant transport from a subsurface-drain...

Travel time analysis for a subsurface drained sub-watershed in Upper Big Walnut Creek Watershed, Ohio

USDA-ARS?s Scientific Manuscript database

Runoff travel time, which is a function of watershed and storm characteristics, is an important parameter affecting the prediction accuracy of hydrologic models. Although, time of concentration (tc) is a most widely used time parameter, it has multiple conceptual and computational definitions. Most ...

Ty Lepionka Uses Disposal System Model to Communicate With Public

ERIC Educational Resources Information Center

Vassey, Emuel E., III

1976-01-01

A sanitarian uses a model to demonstrate installation and operation of a subsurface disposal system. The model contains a septic tank, inlet and outlet T's, distribution box, and drain lines in various stages of construction. The model is used to inform mobile home owners about environmental health practices. (MR)

Fertilizer placement to maximize nitrogen use by fescue

USDA-ARS?s Scientific Manuscript database

The method of fertilizer nitrogen(N) application can affect N uptake in tall fescue and therefore its yield and quality. Subsurface-banding (knife) of fertilizer maximizes fescue N uptake in the poorly-drained clay–pan soils of southeastern Kansas. This study was conducted to determine if knifed N r...

Modeling nutrient removal using watershed-scale implementation of the two-stage ditch

USDA-ARS?s Scientific Manuscript database

Western Lake Erie Basin (WLEB) is the most intensively farmed region of the Great Lakes. Because of the flat topography and poorly-drained soils many farmers rely on drainage management practices (e.g., subsurface tile drainage, ditch channelization) to maintain productive agriculture. However, th...

40 CFR 146.3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... point before the waste fluids drain into the underlying soils. For a dry well, it is likely to be the.... Stratum (plural strata) means a single sedimentary bed or layer, regardless of thickness, that consists of... (Hydrocompaction); oxidation of organic matter in soils; or added load on the land surface. Subsurface fluid...

40 CFR 146.3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... point before the waste fluids drain into the underlying soils. For a dry well, it is likely to be the.... Stratum (plural strata) means a single sedimentary bed or layer, regardless of thickness, that consists of... (Hydrocompaction); oxidation of organic matter in soils; or added load on the land surface. Subsurface fluid...

Assessing impacts of land-applied manure from concentrated animal feeding operations on fish populations and communities

EPA Science Inventory

Concentrated animal feeding operation (CAFO) waste is a cost effective fertilizer. In the Midwest, networks of subsurface tile-drains expedite transport of animal hormones and nutrients from land-applied CAFO waste to adjacent waterways. The objective of this study was to evaluat...

Control of groundwater in surface mining

NASA Astrophysics Data System (ADS)

Brawner, C. O.

1982-03-01

The presence of groundwater in surface mining operations often creates serious problems. The most important is generally a reduction in stability of the pit slopes. This is caused by pore water pressures and hydrodynamic shock due to blasting which reduce the shear strength and seepage pressures, water in tension cracks and increased unit weight which increase the shear stress. Groundwater and seepage also increase the cost of pit drainage, shipping, drilling and blasting, tyre wear and equipment maintenance. Surface erosion may also be increased and, in northern climates, ice flows on the slopes may occur. Procedures have been developed in the field of soil mechanics and engineering of dams to obtain quantitative data on pore water pressures and rock permeability, to evaluate the influence of pore water and seepage pressures on stability and to estimate the magnitude of ground-water flow. Based on field investigations, a design can be prepared for the control of groundwater in the slope and in the pit. Methods of control include the use of horizontal drains, blasted toe drains, construction of adits or drainage tunnels and pumping from wells in or outside of the pit. Recent research indicates that subsurface drainage can be augmented by applying a vacuum or by selective blasting. Instrumentation should be installed to monitor the groundwater changes created by drainage. Typical case histories are described that indicate the approach used to evaluate groundwater conditions.

Evaluation of the hooghoudt and kirkham tile drain equations in the soil and water assessment tool to simulate tile flow and nitrate-nitrogen.

PubMed

Moriasi, Daniel N; Gowda, Prasanna H; Arnold, Jeffrey G; Mulla, David J; Ale, Srinivasulu; Steiner, Jean L; Tomer, Mark D

2013-11-01

Subsurface tile drains in agricultural systems of the midwestern United States are a major contributor of nitrate-N (NO-N) loadings to hypoxic conditions in the Gulf of Mexico. Hydrologic and water quality models, such as the Soil and Water Assessment Tool, are widely used to simulate tile drainage systems. The Hooghoudt and Kirkham tile drain equations in the Soil and Water Assessment Tool have not been rigorously tested for predicting tile flow and the corresponding NO-N losses. In this study, long-term (1983-1996) monitoring plot data from southern Minnesota were used to evaluate the SWAT version 2009 revision 531 (hereafter referred to as SWAT) model for accurately estimating subsurface tile drain flows and associated NO-N losses. A retention parameter adjustment factor was incorporated to account for the effects of tile drainage and slope changes on the computation of surface runoff using the curve number method (hereafter referred to as Revised SWAT). The SWAT and Revised SWAT models were calibrated and validated for tile flow and associated NO-N losses. Results indicated that, on average, Revised SWAT predicted monthly tile flow and associated NO-N losses better than SWAT by 48 and 28%, respectively. For the calibration period, the Revised SWAT model simulated tile flow and NO-N losses within 4 and 1% of the observed data, respectively. For the validation period, it simulated tile flow and NO-N losses within 8 and 2%, respectively, of the observed values. Therefore, the Revised SWAT model is expected to provide more accurate simulation of the effectiveness of tile drainage and NO-N management practices. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Spatial heterogeneity of mobilization processes and input pathways of herbicides into a brook in a small agricultural catchment

NASA Astrophysics Data System (ADS)

Doppler, Tobias; Lück, Alfred; Popow, Gabriel; Strahm, Ivo; Winiger, Luca; Gaj, Marcel; Singer, Heinz; Stamm, Christian

2010-05-01

Soil applied herbicides can be transported from their point of application (agricultural field) to surface waters during rain events. There they can have harmful effects on aquatic species. Since the spatial distribution of mobilization and transport processes is very heterogeneous, the contributions of different fields to the total load in a surface water body may differ considerably. The localization of especially critical areas (contributing areas) can help to efficiently minimize herbicide inputs to surface waters. An agricultural field becomes a contributing area when three conditions are met: 1) herbicides are applied, 2) herbicides are mobilized on the field and 3) the mobilized herbicides are transported rapidly to the surface water. In spring 2009, a controlled herbicide application was performed on corn fields in a small (ca 1 km2) catchment with intensive crop production in the Swiss plateau. Subsequently water samples were taken at different locations in the catchment with a high temporal resolution during rain events. We observed both saturation excess and hortonian overland flow during the field campaign. Both can be important mobilization processes depending on the intensity and quantity of the rain. This can lead to different contributing areas during different types of rain events. We will show data on the spatial distribution of herbicide loads during different types of rain events. Also the connectivity of the fields with the brook is spatially heterogeneous. Most of the fields are disconnected from the brook by internal sinks in the catchment, which prevents surface runoff from entering the brook directly. Surface runoff from these disconnected areas can only enter the brook rapidly via macropore-flow into tile drains beneath the internal sinks or via direct shortcuts to the drainage system (maintenance manholes, farmyard or road drains). We will show spatially distributed data on herbicide concentration in purely subsurface systems which shows how important such input pathways can be.

Effect of variable annual precipitation and nutrient input on nitrogen and phosphorus transport from two Midwestern agricultural watersheds

USDA-ARS?s Scientific Manuscript database

Precipitation patterns and nutrient inputs impact transport of nitrate (NO3-N) and phosphorus (TP) from Midwest watersheds. Nutrient concentrations and yields from two subsurface-drained watersheds, the Little Cobb River (LCR) in southern Minnesota and the South Fork Iowa River (SFIR) in northern Io...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramachandran, N.

New technologies were used to cost-effectively remediate several hundred feet of radioactively contaminated subsurface drain pipes at the General Motors site in Adrian, Michigan, and to conduct post-remedial verification surveys. Supplemental cleanup criteria were applied to inaccessible areas of the project, and inexpensive treatment technology was used to treat wastewater generated. Application of these methods resulted in substantial cost savings.

Comparison of performance of tile drainage routines in SWAT 2009 and 2012 in an extensively tile-drained watershed in Midwest

USDA-ARS?s Scientific Manuscript database

Subsurface tile drainage systems are widely used in agricultural watersheds in the Midwestern U.S. Tile drainage systems enable the Midwest area to become highly productive agricultural lands, but can also create environmental problems, for example nitrate-N contamination associated with drainage w...

Using a Process Based Model to Simulate the Effects of Drainage and Land Use Change on Hydrology, and Sediment and Nutrient Transport in the Midwestern United States

NASA Astrophysics Data System (ADS)

Downer, C. W.; Pradhan, N. R.; Skahill, B. E.; Wahl, M.; Turnbull, S. J.

2015-12-01

Historically the Midwestern United State was a region dominated by prairie grasses and wetlands. To make use of the rich soils underlying these fertile environments, farmers converted the land to agriculture and currently the Midwest is a region of intensive agricultural production, with agriculture being a predominant land use. The Midwest is a region of gentle slopes, tight soils, and high water tables, and in order to make the lands suitable for agriculture, farmers have installed extensive networks of ditches to drain off excess surface water and subsurface tiles to lower the water table and remove excess soil water in the root zone that can stress common row crops, such as corn and soybeans. The combination of tiles, ditches, and intensive agricultural land practices radically alters the landscape and hydrology. As part of the Minnesota River Basin Integrated Study we are simulating nested watersheds in a sub-basin of the Minnesota River Basin, Seven Mile Creek, using the physics-based watershed model GSSHA (Gridded Surface Subsurface Hydrologic Analysis) to simulate water, sediment, and nutrients. Representative of the larger basin, more than 80% of the land in the watershed is dedicated to agricultural practices. From a process perspective, the hydrology is complicated, with snow accumulation and melt, frozen soil, and tile drains all being important processes within the watershed. In this study we attempt to explicitly simulate these processes, including the tile drains, which are simulated as a network of subsurface pipes that collect water from the local water table. Within the watershed, tiles discharge to both the ditch/stream network as well as overland locations, where the tile discharge appears to initiate gullies and exacerbate overland erosion. Testing of the methods on smaller basins demonstrates the ability of the model to simulate measured tile flow. At the larger scale, the model demonstrates ability to simulate flow and sediments. Sparse nutrient data limit the assessment of nutrient simulations. The models are being used to asses an array of potential future land use scenarios, including predevelopment and increased agricultural use. Results from these simulations will be presented. Preliminary results indicate that tile drains increase discharge and erosion in the watershed.

Streamflow characteristics of a naturally drained forested watershed in southeast Atlantic coastal plain

Treesearch

Devendra M. Amatya; Carl C. Trettin

2010-01-01

Information about streamflow characteristics e.g. runoff-rainfall (R/O) ratio, rate and timing of flow, surface and subsurface drainage (SSD), and response time to rainfall events is necessary to accurately simulate fluxes and for designing best management practices (BMPs). Unfortunately, those data are scarce in the southeastern Atlantic coastal plain, a highly...

Atrazine sorption by biochar, tire chips, and steel slag as media for blind inlets: A kinetic and isotherm sorption approach

USDA-ARS?s Scientific Manuscript database

Surface inlets are installed in subsurface drainage systems to reduce ponding duration and surface runoff, but can contribute to water quality concerns by allowing water to directly enter buried drains. Blind inlets, consist of perforated pipes covered with gravel and are separated from an overlying...

Investigating summer flow paths in a Dutch agricultural field using high frequency direct measurements

NASA Astrophysics Data System (ADS)

Delsman, J. R.; Waterloo, M. J.; Groen, M. M. A.; Groen, J.; Stuyfzand, P. J.

2014-11-01

The search for management strategies to cope with projected water scarcity and water quality deterioration calls for a better understanding of the complex interaction between groundwater and surface water in agricultural catchments. We separately measured flow routes to tile drains and an agricultural ditch in a deep polder in the coastal region of the Netherlands, characterized by exfiltration of brackish regional groundwater flow and intake of diverted river water for irrigation and water quality improvement purposes. We simultaneously measured discharge, electrical conductivity and temperature of these separate flow routes at hourly frequencies, disclosing the complex and time-varying patterns and origins of tile drain and ditch exfiltration. Tile drainage could be characterized as a shallow flow system, showing a non-linear response to groundwater level changes. Tile drainage was fed primarily by meteoric water, but still transported the majority (80%) of groundwater-derived salt to surface water. In contrast, deep brackish groundwater exfiltrating directly in the ditch responded linearly to groundwater level variations and is part of a regional groundwater flow system. We could explain the observed salinity of exfiltrating drain and ditch water from the interaction between the fast-responding pressure distribution in the subsurface that determined groundwater flow paths (wave celerity), and the slow-responding groundwater salinity distribution (water velocity). We found water demand for maintaining water levels and diluting salinity through flushing to greatly exceed the actual sprinkling demand. Counterintuitively, flushing demand was found to be largest during precipitation events, suggesting the possibility of water savings by operational flushing control.

Environmental Assessment for the Replacement of Water Reservoirs

DTIC Science & Technology

2005-03-25

Intensive extraction of groundwater does not occur at Travis because of poor water- bearing subsurface geology. Intensive extraction SECTION 3.0...largest contiguous estuarine marsh and the largest wetland in the continental United States (CH2M HILL, 2001). Suisun Marsh drains into Grizzly and...and other support facilities. • Community (Commercial) – Uses include the exchange, commissary, banking, dining facilities, eating

Constraints on the age of the Great Sand Dunes, Colorado, from subsurface stratigraphy and OSL dates

USGS Publications Warehouse

Madole, Richard F.; Mahan, Shannon; Romig, Joseph H.; Havens, Jeremy C.

2013-01-01

The age of the Great Sand Dunes has been debated for nearly 150 yr. Seven ages ranging from Miocene to late Holocene have been proposed for them. This paper presents new information—chiefly subsurface stratigraphic data, OSL dates, and geomorphic evidence—that indicates that the Great Sand Dunes began to form in the latter part of the middle Pleistocene. The dunes overlie a thick wedge of piedmont-slope deposits, which in turn overlies sediment of Lake Alamosa, a paleolake that began to drain about 440 ka. The wedge of piedmont-slope deposits extends westward for at least 23 km and is as much as 60 m thick at a distance of 10 km from the Sangre de Cristo Range. Ostracodes from one well indicate that the eastern shoreline of Lake Alamosa extended to within 4.3 km of where the Great Sand Dunes eventually formed. The time represented by the wedge of piedmont-slope deposits is not known exactly, but the wedge post-dates 440 ka and was in place prior to 130 ka because by then the dunes overlying it were sufficiently close and tall enough to obstruct streams draining from the Sangre de Cristo Range.

N Channel JFET Based Digital Logic Gate Structure

NASA Technical Reports Server (NTRS)

Krasowski, Michael J (Inventor)

2013-01-01

An apparatus is provided that includes a first field effect transistor with a source tied to zero volts and a drain tied to voltage drain drain (Vdd) through a first resistor. The apparatus also includes a first node configured to tie a second resistor to a third resistor and connect to an input of a gate of the first field effect transistor in order for the first field effect transistor to receive a signal. The apparatus also includes a second field effect transistor configured as a unity gain buffer having a drain tied to Vdd and an uncommitted source.

Dissolved constituents including selenium in waters in the vicinity of Kesterson National Wildlife Refuge and the west grassland, Fresno and Merced Counties, California

USGS Publications Warehouse

Presser, T.S.; Barnes, Ivan

1985-01-01

Analyses were made for dissolved constituents including selenium (Se) in waters associated with subsurface agricultural drainage from the western San Joaquin Valley of California. In the vicinity of Kesterson National Wildlife Refuge and the Grassland wetlands area Se was found to be mobilized in water. As a consequence of this mobility and bioaccumulation in the aquatic food chain, Se occurred in waterfowl at levels toxic enough to cause deformities and deaths. Se concentrations in sumps that collect subsurface agricultural drainage water and inflows to drains sampled, ultimately leading into Kesterson National Wildlife Refuge and the Grassland, ranged from 84 to 4200 microgram/L (ug/L) Se. Levels of Se were reduced in the San Luis Drain flowing into Kesterson National Wildlife Refute to approximately 300 ug/L Se and in three of the drains sampled flowing into the Grassland to approximately 50 ug/L Se. Serious effects on water fowl habitat were caused by both these levels. Se contents of algal mats and salt crusts from evaporation ponds of the San Luis Drain contained up to parts per million Se. Total ecosystem assessment of Se may be necessary for the evaluation of the toxicity of Se to the environment. No other trace element reported exceeded the various criteria for water at the level of magnitude of Se. Other dissolved constituents and the isotopic ratios of oxygen and hydrogen were analyzed to elucidate water types, reaction states of the aqueous solution with respect to minerals, and the origin of mixed waters. These data will be used later to evaluate the geologic source of Se. Methods used for collection and analysis are described and documented. Hydrologic effects were found to be complex. Preliminary indications from wells are also given. A historical sequence is adhered to and other data from the study area which serve as a guide to the toxicity of Se are included. (Author 's abstract)

Field Investigation of Surface-Lake Processes on Ice Shelves: Results of the 2015/16 Field Campaign on McMurdo Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

MacAyeal, Doug; Banwell, Alison; Willis, Ian; Macdonald, Grant

2016-04-01

Ice-shelf instability and breakup of the style exhibited by Larsen B Ice Shelf in 2002 remains the most difficult glaciological process of consequence to observe in detail. It is, however, vital to do so because ice-shelf breakup has the potential to influence the buttressing controls on inland ice discharge, and thus to affect sea level. Several mechanisms enabling Larsen B style breakup have been proposed, including the ability of surface lakes to introduce ice-shelf fractures when they fill and drain, thereby changing the surface loads the ice-shelf must adjust to. Our model suggest that these fractures resulted in a chain-reaction style drainage of >2750 surface lakes on the Larsen B in the days prior to its demise. To validate this and other models, we began a field project on the McMurdo Ice Shelf (MIS) during the 2015/16 austral summer. Advantages of the MIS study site are: there is considerable surface melting during 3-6 weeks of the summer season, the ice is sufficiently thin (< 30 m in places) to allow observable viscoelastic responses to relatively small loads, and it is close to a center of logistical support (McMurdo Station). Here we show initial results from the field campaign, including GPS and water-depth observations of a lake that has filled and drained over multiple week timescales in previous austral summers. We also report on the analysis of high-resolution WorldView satellite imagery from several summers that reveals the complexity of surface meltwater movement in channels and subsurface void spaces. Initial reconnaissance of the largest surface-lake features reveal that they have a central circular depression surrounded by an uplifted ring, which supports one of the central tenets of our ice-shelf flexure theory. A second field season is anticipated for the 2016/17 austral summer.

Drain Current Modulation of a Single Drain MOSFET by Lorentz Force for Magnetic Sensing Application.

PubMed

Chatterjee, Prasenjit; Chow, Hwang-Cherng; Feng, Wu-Shiung

2016-08-30

This paper reports a detailed analysis of the drain current modulation of a single-drain normal-gate n channel metal-oxide semiconductor field effect transistor (n-MOSFET) under an on-chip magnetic field. A single-drain n-MOSFET has been fabricated and placed in the center of a square-shaped metal loop which generates the on-chip magnetic field. The proposed device designed is much smaller in size with respect to the metal loop, which ensures that the generated magnetic field is approximately uniform. The change of drain current and change of bulk current per micron device width has been measured. The result shows that the difference drain current is about 145 µA for the maximum applied magnetic field. Such changes occur from the applied Lorentz force to push out the carriers from the channel. Based on the drain current difference, the change in effective mobility has been detected up to 4.227%. Furthermore, a detailed investigation reveals that the device behavior is quite different in subthreshold and saturation region. A change of 50.24 µA bulk current has also been measured. Finally, the device has been verified for use as a magnetic sensor with sensitivity 4.084% (29.6 T(-1)), which is very effective as compared to other previously reported works for a single device.

Multiyear nutrient removal performance of three constructed wetlands intercepting tile drain flows from grazed pastures.

PubMed

Tanner, Chris C; Sukias, James P S

2011-01-01

Subsurface tile drain flows can be a major s ource of nurient loss from agricultural landscapes. This study quantifies flows and nitrogen and phosphorus yields from tile drains at three intensively grazed dairy pasture sites over 3- to 5-yr periods and evaluates the capacity of constructed wetlands occupying 0.66 to 1.6% of the drained catchments too reduce nutrient loads. Continuous flow records are combined with automated flow-proportional sampling of nutrient concentrations to calculate tile drain nutrient yields and wetland mass removal rates. Annual drainage water yields rangedfrom 193 to 564 mm (16-51% of rainfall) at two rain-fed sites and from 827 to 853 mm (43-51% of rainfall + irrigation) at an irrigated site. Annually, the tile drains exported 14 to 109 kg ha(-1) of total N (TN), of which 58 to 90% was nitrate-N. Constructed wetlands intercepting these flows removed 30 to 369 gTN m(-2) (7-63%) of influent loadings annually. Seasonal percentage nitrate-N and TN removal were negatively associated with wetland N mass loadings. Wetland P removal was poor in all wetlands, with 12 to 115% more total P exported annually overall than received. Annually, the tile drains exported 0.12 to 1.38 kg ha of total P, of which 15 to 93% was dissolved reactive P. Additional measures are required to reduce these losses or provide supplementary P removal. Wetland N removal performance could be improved by modifying drainage systems to release flows more gradually and improving irrigation practices to reduce drainage losses.

A theoretical approach to study the optical sensitivity of a MESFET

NASA Astrophysics Data System (ADS)

Dutta, Sutanu

2018-05-01

A theoretical model to study the optical sensitivity of a metal-semiconductor field effect transistor has been proposed for a relatively high drain field. An analytical expression of drain current of the device has been derived for a MESFET under optical illumination considering field dependent mobility of electrons across the channel. The variation of drain current with and without optical illumination has been studied with drain and gate voltages. The optical sensitivity of the drain current has been studied for different biasing conditions and gate lengths. In addition, the shift in threshold voltage of a MESFET under optical illumination is determined and optical sensitivity of the device in terms of its threshold voltage has been studied.

Modeling the long-term effect of winter cover crops on nitrate transport in artificially drained fields across the Midwest U.S.

USDA-ARS?s Scientific Manuscript database

A fall-planted cover crop is a management practice with multiple benefits including reducing nitrate losses from artificially drained fields. We used the Root Zone Water Quality Model (RZWQM) to simulate the impact of a cereal rye cover crop on reducing nitrate losses from drained fields across five...

Winter Cover Crop Effects on Nitrate Leaching in Subsurface Drainage as Simulated by RZWQM-DSSAT

NASA Astrophysics Data System (ADS)

Malone, R. W.; Chu, X.; Ma, L.; Li, L.; Kaspar, T.; Jaynes, D.; Saseendran, S. A.; Thorp, K.; Yu, Q.

2007-12-01

Planting winter cover crops such as winter rye (Secale cereale L.) after corn and soybean harvest is one of the more promising practices to reduce nitrate loss to streams from tile drainage systems without negatively affecting production. Because availability of replicated tile-drained field data is limited and because use of cover crops to reduce nitrate loss has only been tested over a few years with limited environmental and management conditions, estimating the impacts of cover crops under the range of expected conditions is difficult. If properly tested against observed data, models can objectively estimate the relative effects of different weather conditions and agronomic practices (e.g., various N fertilizer application rates in conjunction with winter cover crops). In this study, an optimized winter wheat cover crop growth component was integrated into the calibrated RZWQM-DSSAT hybrid model and then we compare the observed and simulated effects of a winter cover crop on nitrate leaching losses in subsurface drainage water for a corn-soybean rotation with N fertilizer application rates over 225 kg N ha-1 in corn years. Annual observed and simulated flow-weighted average nitrate concentration (FWANC) in drainage from 2002 to 2005 for the cover crop treatments (CC) were 8.7 and 9.3 mg L-1 compared to 21.3 and 18.2 mg L-1 for no cover crop (CON). The resulting observed and simulated FWANC reductions due to CC were 59% and 49%. Simulations with the optimized model at various N fertilizer rates resulted in average annual drainage N loss differences between CC and CON to increase exponentially from 12 to 34 kg N ha-1 for rates of 11 to 261 kg N ha-1. The results suggest that RZWQM-DSSAT is a promising tool to estimate the relative effects of a winter crop under different conditions on nitrate loss in tile drains and that a winter cover crop can effectively reduce nitrate losses over a range of N fertilizer levels.

Opportunities for Reducing Nitrate Export from Drainage Systems through In-field Nitrogen Management, Cropping Practices, and Drainage Design and Management

NASA Astrophysics Data System (ADS)

Helmers, M.; Zhou, X.; Qi, Z.; Christianson, R.; Pederson, C.

2011-12-01

Subsurface drainage systems are widely used throughout the upper Midwest corn-belt. While the use of these drainage systems has greatly increased crop production, they have also increased nitrate-nitrogen export to downstream waterbodies. As a result, there is a need to evaluate and implement management practices that have potential to reduce nitrate-nitrogen loss. A twenty year study in Iowa has shown that major factors in nitrate-nitrogen loss are land use and hydrology. Studies from north-central Iowa have also indicated that nitrogen application rate and to a lesser degree timing of nitrogen application important factors for nitrate-nitrogen loss. A four-year (2007-2010) drainage management study in southeast Iowa indicates that shallow and controlled drainage systems have potential to decrease subsurface drainage and thereby reduce nitrate-N loss from drain water but the level of implementation of controlled drainage may be limited by topography. Cropping practices through cover crops or perennial biomass crops have also been documented to have potential to reduce downstream nitrate-nitrogen export but the level of implementation may be limited by management and economic considerations. To achieve reduction goals for protection of local and regional water quality will require a combination of these practices at the landscape scale.

Nature and extent of macropores in forest soils and their influence on subsurface water movement

Treesearch

Gerald M. Aubertin; Gerald M. Aubertin

1971-01-01

Rain, falling on a sloping forested soil, may enter the soil quickly and move considerable distances through the soil by way of macropores. A macropore is a large pore, cavity, passageway, channel, tunnel, or void in the soil, through which water usually drains by gravity. Large quantities of water can move through the soil by way of these macropores-without...

Nitrate-Nitrogen Leaching and Modeling in Intensive Agriculture Farmland in China

PubMed Central

Xu, Ligang; Xu, Jin

2013-01-01

Protecting water resources from nitrate-nitrogen (NO3-N) contamination is an important public health concern and a major national environmental issue in China. Loss of NO3-N in soils due to leaching is not only one of the most important problems in agriculture farming, but is also the main factor causing nitrogen pollution in aquatic environments. Three typical intensive agriculture farmlands in Jiangyin City in China are selected as a case study for NO3-N leaching and modeling in the soil profile. In this study, the transport and fate of NO3-N within the soil profile and nitrate leaching to drains were analyzed by comparing field data with the simulation results of the LEACHM model. Comparisons between measured and simulated data indicated that the NO3-N concentrations in the soil and nitrate leaching to drains are controlled by the fertilizer practice, the initial conditions and the rainfall depth and distribution. Moreover, the study reveals that the LEACHM model gives a fair description of the NO3-N dynamics in the soil and subsurface drainage at the field scale. It can also be concluded that the model after calibration is a useful tool to optimize as a function of the combination “climate-crop-soil-bottom boundary condition” the nitrogen application strategy resulting for the environment in an acceptable level of nitrate leaching. The findings in this paper help to demonstrate the distribution and migration of nitrogen in intensive agriculture farmlands, as well as to explore the mechanism of groundwater contamination resulting from agricultural activities. PMID:23983629

Application of nonlinear-regression methods to a ground-water flow model of the Albuquerque Basin, New Mexico

USGS Publications Warehouse

Tiedeman, C.R.; Kernodle, J.M.; McAda, D.P.

1998-01-01

This report documents the application of nonlinear-regression methods to a numerical model of ground-water flow in the Albuquerque Basin, New Mexico. In the Albuquerque Basin, ground water is the primary source for most water uses. Ground-water withdrawal has steadily increased since the 1940's, resulting in large declines in water levels in the Albuquerque area. A ground-water flow model was developed in 1994 and revised and updated in 1995 for the purpose of managing basin ground- water resources. In the work presented here, nonlinear-regression methods were applied to a modified version of the previous flow model. Goals of this work were to use regression methods to calibrate the model with each of six different configurations of the basin subsurface and to assess and compare optimal parameter estimates, model fit, and model error among the resulting calibrations. The Albuquerque Basin is one in a series of north trending structural basins within the Rio Grande Rift, a region of Cenozoic crustal extension. Mountains, uplifts, and fault zones bound the basin, and rock units within the basin include pre-Santa Fe Group deposits, Tertiary Santa Fe Group basin fill, and post-Santa Fe Group volcanics and sediments. The Santa Fe Group is greater than 14,000 feet (ft) thick in the central part of the basin. During deposition of the Santa Fe Group, crustal extension resulted in development of north trending normal faults with vertical displacements of as much as 30,000 ft. Ground-water flow in the Albuquerque Basin occurs primarily in the Santa Fe Group and post-Santa Fe Group deposits. Water flows between the ground-water system and surface-water bodies in the inner valley of the basin, where the Rio Grande, a network of interconnected canals and drains, and Cochiti Reservoir are located. Recharge to the ground-water flow system occurs as infiltration of precipitation along mountain fronts and infiltration of stream water along tributaries to the Rio Grande; subsurface flow from adjacent regions; irrigation and septic field seepage; and leakage through the Rio Grande, canal, and Cochiti Reservoir beds. Ground water is discharged from the basin by withdrawal; evapotranspiration; subsurface flow; and flow to the Rio Grande, canals, and drains. The transient, three-dimensional numerical model of ground-water flow to which nonlinear-regression methods were applied simulates flow in the Albuquerque Basin from 1900 to March 1995. Six different basin subsurface configurations are considered in the model. These configurations are designed to test the effects of (1) varying the simulated basin thickness, (2) including a hypothesized hydrogeologic unit with large hydraulic conductivity in the western part of the basin (the west basin high-K zone), and (3) substantially lowering the simulated hydraulic conductivity of a fault in the western part of the basin (the low-K fault zone). The model with each of the subsurface configurations was calibrated using a nonlinear least- squares regression technique. The calibration data set includes 802 hydraulic-head measurements that provide broad spatial and temporal coverage of basin conditions, and one measurement of net flow from the Rio Grande and drains to the ground-water system in the Albuquerque area. Data are weighted on the basis of estimates of the standard deviations of measurement errors. The 10 to 12 parameters to which the calibration data as a whole are generally most sensitive were estimated by nonlinear regression, whereas the remaining model parameter values were specified. Results of model calibration indicate that the optimal parameter estimates as a whole are most reasonable in calibrations of the model with with configurations 3 (which contains 1,600-ft-thick basin deposits and the west basin high-K zone), 4 (which contains 5,000-ft-thick basin de

Watershed-Scale Cover Crops Reduce Nutrient Export From Agricultural Landscapes.

NASA Astrophysics Data System (ADS)

Tank, J. L.; Hanrahan, B.; Christopher, S. F.; Trentman, M. T.; Royer, T. V.; Prior, K.

2016-12-01

The Midwestern US has undergone extensive land use change as forest, wetlands, and prairies have been converted to agroecosystems. Today, excess fertilizer nutrients from farm fields enter Midwestern agricultural streams, which degrades both local and downstream water quality, resulting in algal blooms and subsequent hypoxic "dead zones" far from the nutrient source. We are quantifying the benefits of watershed-scale conservation practices that may reduce nutrient runoff from adjacent farm fields. Specifically, research is lacking on whether the planting of winter cover crops in watersheds currently dominated by row-crop agriculture can significantly reduce nutrient inputs to adjacent streams. Since 2013, farmers have planted cover crops on 70% of croppable acres in the Shatto Ditch Watershed (IN), and "saturation level" implementation of this conservation practice has been sustained for 3 years. Every 14 days, we have quantified nutrient loss from fields by sampling nutrient fluxes from multiple subsurface tile drains and longitudinally along the stream channel throughout the watershed. Cover crops improved stream water quality by reducing dissolved inorganic nutrients exported downstream; nitrate-N and DRP concentrations and fluxes were significantly lower in tiles draining fields with cover crops compared to those without. Annual watershed nutrient export also decreased, and reductions in N and P loss ( 30-40%) exceeded what we expected based on only a 6-10% reduction in runoff due to increased watershed water holding capacity. We are also exploring the processes responsible for increased nutrient retention, where they are occurring (terrestrial vs. aquatic) and when (baseflow vs. storms). For example, whole-stream metabolism also responded to cover crop planting, showing reduced variation in primary production and respiration in years after watershed-scale planting of cover crops. In summary, widespread land cover change, through cover crop planting, can significantly reduce annual watershed-scale nutrient export. Moreover, successful outcomes highlighted through demonstration projects may facilitate widespread adoption, making them powerful agents of change for advancing conservation success.

Tile drainage as karst: Conduit flow and diffuse flow in a tile-drained watershed

USGS Publications Warehouse

Schilling, K.E.; Helmers, M.

2008-01-01

The similarity of tiled-drained watersheds to karst drainage basins can be used to improve understanding of watershed-scale nutrient losses from subsurface tile drainage networks. In this study, short-term variations in discharge and chemistry were examined from a tile outlet collecting subsurface tile flow from a 963 ha agricultural watershed. Study objectives were to apply analytical techniques from karst springs to tile discharge to evaluate water sources and estimate the loads of agricultural pollutants discharged from the tile with conduit, intermediate and diffuse flow regimes. A two-member mixing model using nitrate, chloride and specific conductance was used to distinguish rainwater versus groundwater inputs. Results indicated that groundwater comprised 75% of the discharge for a three-day storm period and rainwater was primarily concentrated during the hydrograph peak. A contrasting pattern of solute concentrations and export loads was observed in tile flow. During base flow periods, tile flow consisted of diffuse flow from groundwater sources and contained elevated levels of nitrate, chloride and specific conductance. During storm events, suspended solids and pollutants adhered to soil surfaces (phosphorus, ammonium and organic nitrogen) were concentrated and discharged during the rapid, conduit flow portion of the hydrograph. During a three-day period, conduit flow occurred for 5.6% of the time but accounted for 16.5% of the total flow. Nitrate and chloride were delivered primarily with diffuse flow (more than 70%), whereas 80-94% of total suspended sediment, phosphorus and ammonium were exported with conduit and intermediate flow regimes. Understanding the water sources contributing to tile drainage and the manner by which pollutant discharge occurs from these systems (conduit, intermediate or diffuse flow) may be useful for designing, implementing and evaluating non-point source reduction strategies in tile-drained landscapes. ?? 2007 Elsevier B.V. All rights reserved.

Statistical variability study of random dopant fluctuation on gate-all-around inversion-mode silicon nanowire field-effect transistors

NASA Astrophysics Data System (ADS)

Yoon, Jun-Sik; Rim, Taiuk; Kim, Jungsik; Kim, Kihyun; Baek, Chang-Ki; Jeong, Yoon-Ha

2015-03-01

Random dopant fluctuation effects of gate-all-around inversion-mode silicon nanowire field-effect transistors (FETs) with different diameters and extension lengths are investigated. The nanowire FETs with smaller diameter and longer extension length reduce average values and variations of subthreshold swing and drain-induced barrier lowering, thus improving short channel immunity. Relative variations of the drain currents increase as the diameter decreases because of decreased current drivability from narrower channel cross-sections. Absolute variations of the drain currents decrease critically as the extension length increases due to decreasing the number of arsenic dopants penetrating into the channel region. To understand variability origins of the drain currents, variations of source/drain series resistance and low-field mobility are investigated. All these two parameters affect the variations of the drain currents concurrently. The nanowire FETs having extension lengths sufficient to prevent dopant penetration into the channel regions and maintaining relatively large cross-sections are suggested to achieve suitable short channel immunity and small variations of the drain currents.

Energetics of eddy-mean flow interactions in the Brazil current between 20°S and 36°S

NASA Astrophysics Data System (ADS)

Magalhães, F. C.; Azevedo, J. L. L.; Oliveira, L. R.

2017-08-01

The energetics of eddy-mean flow interactions in the Brazil Current (BC) between 20°S and 36°S are investigated in 19 transects perpendicular to the 200 m isobath. Ten years (2000-2009) of output data from the Hybrid Coordinate Ocean Model (HYCOM) NCODA reanalysis, with a spatial resolution of 1/12.5° and 5 day averages, are used. The mean kinetic energy (MKE) and eddy kinetic energy (EKE) fields presented the same subsurface spatial pattern but with reduced values. The EKE increases southward, with high values along the BC path and the offshore portion of the jet. The values of the barotropic conversion term (BTC) are highest in the surface layers and decreased with depth, whereas the values of the baroclinic conversion term (BCC) and the vertical eddy heat flux (VEHF) are highest in the subsurface. Despite the vertical thickening of the BC, the highest energy conversion rates are confined to the upper 700 m of the water column. The energetic analysis showed that the current features mixed instability processes. The vertical weighted mean of the BTC and BCC presented an oscillatory pattern related to the bathymetry. The eddy field accelerates the time-mean flow upstream and downstream of bathymetric features and drains energy from the time-mean flow over the features. The BC is baroclinically unstable south of 28°S, and the highest energy conversion rates occur in Cabo de São Tomé, Cabo Frio, and the Cone do Rio Grande.

Imaging of Subsurface Corrosion Using Gradient-Field Pulsed Eddy Current Probes with Uniform Field Excitation

PubMed Central

Ren, Shuting; Yan, Bei; Zainal Abidin, Ilham Mukriz; Wang, Yi

2017-01-01

A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size. PMID:28758985

Imaging of Subsurface Corrosion Using Gradient-Field Pulsed Eddy Current Probes with Uniform Field Excitation.

PubMed

Li, Yong; Ren, Shuting; Yan, Bei; Zainal Abidin, Ilham Mukriz; Wang, Yi

2017-07-31

A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size.

A novel thin-film transistor with step gate-overlapped lightly doped drain and raised source/drain design

NASA Astrophysics Data System (ADS)

Chien, Feng-Tso; Chen, Jian-Liang; Chen, Chien-Ming; Chen, Chii-Wen; Cheng, Ching-Hwa; Chiu, Hsien-Chin

2017-11-01

In this paper, a novel step gate-overlapped lightly doped drain (GOLDD) with raised source/drain (RSD) structure (SGORSD) is proposed for TFT electronic device application. The new SGORSD structure could obtain a low electric field at channel near the drain side owing to a step GOLDD design. Compared to the conventional device, the SGORSD TFT exhibits a better kink effect and higher breakdown performance due to the reduced drain electric field (D-EF). In addition, the leakage current also can be suppressed. Moreover, the device stability, such as the threshold voltage shift and drain current degradation under a high gate bias, is improved by the design of SGORSD structure. Therefore, this novel step GOLDD structure can be a promising design to be used in active-matrix flat panel electronics.

Assessment of the use of selected chemical and microbiological constituents as indicators of wastewater in curtain drains from home sewage-treatment systems in Medina County, Ohio

USGS Publications Warehouse

Dumouchelle, Denise H.

2006-01-01

Many home sewage-treatment systems (HSTS) in Ohio use curtain or perimeter drains to depress the level of the subsurface water in and around the systems. These drains could possibly intercept partially untreated wastewater and release potential pathogens to ground-water and surface-water bodies. The quality of water in curtain drains from two different HSTS designs in Medina County, Ohio, was investigated using several methods. Six evaporation-transpiration-absorption (ETA) and five leach-line (LL) systems were investigated by determining nutrient concentrations, chloride/bromide ratios (Cl/Br), Escherichia coli (E. coli ) concentrations, coliphage genotyping, and genetic fingerprinting of E. coli. Water samples were collected at 11 sites and included samples from curtain drains, septic tanks, and residential water wells. Nitrate concentrations in the curtain drains ranged from 0.03 to 3.53 mg/L (milligrams per liter), as N. Concentrations of chloride in 10 of the 11 curtain drains ranged from 5.5 to 21 mg/L; the chloride concentration in the eleventh curtain drain was 340 mg/L. Bromide concentrations in 11 curtain drains ranged from 0.01 to 0.22 mg/L. Cl/Br ratios ranged from 86 to 2,000. F-specific coliphage were not found in any curtain-drain samples. Concentrations of E. coli in the curtain drains ranged from 1 to 760 colonies per 100 milliliters. The curtain-drain water-quality data were evaluated to determine whether HSTS-derived water was present in the curtain drains. Nutrient concentrations were too low to be of use in the determination. The Cl/Br ratios appear promising. Coliphage was not detected in the curtain drains, so genotyping could not be attempted. E. coli concentrations in the curtain drains were all less than those from the corresponding HSTS; only one sample exceeded the Ohio secondary-contact water-quality standard. The genetic fingerprinting data were inconclusive because multiple links between unrelated sites were found. Although the curtain-drain samples from the ETA systems showed somewhat more evidence of the presence of HSTS water than did the LL systems, most of the approaches were inconclusive by themselves. The best evidence of HSTS water, from the Cl/Br ratios, indicates that the water in 10 of the 11 curtain drains, at both HSTS types, was a mixture of dilute ground water and HSTS-derived water; the 11th drain also show some effects of the HSTS, although road salt-affected water may be present. Therefore, it appears that there is no difference between the ETA and LL systems with respect to the water quality in curtain drains.

Multitracer Study of Flow to Tile Drains in Irrigated Macroporous Soil

NASA Astrophysics Data System (ADS)

Bishop, J. M.; Callaghan, M. V.; Cey, E.; Bentley, L. R.

2010-12-01

Multiple tracer experiments have been conducted to test the effectiveness of using irrigation along with a tile drain system for salt remediation in west central Alberta, Canada. The experiments were designed to characterize the shallow flow system as part of a salt flushing pilot study and to determine the role of macroporosity in groundwater flow and transport. Soils at the site are primarily silty glaciolacustrine material underlain by a relatively impermeable till layer at approximately 2.5 m below ground surface. A 20 m by 20 m infiltration test plot is underlain by two tile drains at 2 m depth that are separated by 10 m. The test plot contains a drip irrigation system and has been irrigated regularly in the summer months over the past three seasons (2008-2010). Two reportedly conservative tracers, 2,6-difluorobenzoic acid [2,6-DFBA] and pentafluorobenzoic acid [PFBA], have been used on the plot and the pre-existing soil salinity was also used as a tracer. In August of 2009 a 2,6-DFBA solution (865g/L) was applied to the surface of the plot. Irrigation of the study plot continued after tracer application on a schedule that averaged roughly 12mm/day, applied 3 days a week. During the 2010 field season, a PFBA solution (at 4.2 g/L) was injected into two separate monitoring wells. One monitoring well is situated 0.5 m directly above the north tile drain (in which samples were collected regularly). The other well is situated at 2 m depth in the center of the study plot and samples were collected from a down gradient well. Tracer concentrations in the subsurface were monitored through sampling of tile drain effluent and monitoring wells in and around the plot, in addition to soil core extractions taken at several locations within the test plot at the end of the 2009 field season. Initial breakthrough of the DFBA in the tile drains occurred 24 hours after application and remained in all subsequent water samples at concentrations of 2 to 6 mg/L. Results from the DFBA analysis showed that the tiles are highly affected by the lateral and vertical contributions to the drains. Distribution of the DFBA in the soil showed that 82% of the tracer remained in the top 75 cm of the soil profile at the end of the 2009 season. This indicates that macropore flow is occurring, but has a minor influence on the movement of the salt mass. This result is important because it illustrates that although the salt mass has migrated slowly, macroporosity can transport contaminants quickly enough to exceeded drinking water quality guidelines. Breakthrough of the PFBA occurred in the north tile drain 13 hrs after application and peaked at a concentration of 10 mg/L, followed by a sharp decrease and stabilization to concentrations of 1.0 mg/L. This shows that macropore flow is occurring at depth in addition to the surface and that contaminant transport can occur rapidly in soils with lower hydraulic conductivity. Salt concentrations in the effluent were measured at high concentrations, showing that effective salt flushing of the matrix is still occurring.

Unsteady seepage flow over sloping beds in response to multiple localized recharge

NASA Astrophysics Data System (ADS)

Bansal, Rajeev K.

2017-05-01

New generalized solutions of linearized Boussinesq equation are derived to approximate the dynamic behavior of subsurface seepage flow induced by multiple localized time-varying recharges over sloping ditch-drain aquifer system. The mathematical model is based on extended Dupuit-Forchheimer assumption and treats the spatial location of recharge basins as additional parameter. Closed form analytic expressions for spatio-temporal variations in water head distribution and discharge rate into the drains are obtained by solving the governing flow equation using eigenvalue-eigenfunction method. Downward and zero-sloping aquifers are treated as special cases of main results. A numerical example is used for illustration of combined effects of various parameters such as spatial coordinates of the recharge basin, aquifer's bed slope, and recharge rate on the dynamic profiles of phreatic surface.

Geophysical Investigations at Hidden Dam, Raymond, California: Summary of Fieldwork and Data Analysis

USGS Publications Warehouse

Minsley, Burke J.; Burton, Bethany L.; Ikard, Scott; Powers, Michael H.

2010-01-01

Geophysical field investigations have been carried out at the Hidden Dam in Raymond, California for the purpose of better understanding the hydrogeology and seepage-related conditions at the site. Known seepage areas on the northwest right abutment area of the downstream side of the dam are documented by Cedergren. Subsequent to the 1980 seepage study, a drainage blanket with a subdrain system was installed to mitigate downstream seepage. Flow net analysis provided by Cedergren suggests that the primary seepage mechanism involves flow through the dam foundation due to normal reservoir pool elevations, which results in upflow that intersects the ground surface in several areas on the downstream side of the dam. In addition to the reservoir pool elevations and downstream surface topography, flow is also controlled by the existing foundation geology as well as the presence or absence of a horizontal drain within the downstream portion of the dam. The purpose of the current geophysical work is to (1) identify present-day seepage areas that may not be evident due to the effectiveness of the drainage blanket in redirecting seepage water, and (2) provide information about subsurface geologic structures that may control subsurface flow and seepage. These tasks are accomplished through the use of two complementary electrical geophysical methods, self-potentials (SP) and direct-current (DC) electrical resistivity, which have been commonly utilized in dam-seepage studies. SP is a passive method that is primarily sensitive to active subsurface groundwater flow and seepage, whereas DC resistivity is an active-source method that is sensitive to changes in subsurface lithology and groundwater saturation. The focus of this field campaign was on the downstream area on the right abutment, or northwest side of the dam, as this is the main area of interest regarding seepage. Two exploratory self-potential lines were also collected on the downstream left abutment of the dam to identify potential seepage in that area. This report is primarily a summary of the field geophysical data acquisition, with some preliminary results and interpretation. Further work will involve a more rigorous analysis of the geophysical datasets and an examination of a large dataset of historical observations of water levels in a number of observation wells and piezometers compared with reservoir elevation. In addition, a partially saturated flow model will be developed to better understand seepage patterns given the available information about dam construction, geophysical results, and data from installed observation wells and piezometers.

Potential influence of sugarcane cultivation on estuarine water quality of Louisiana's gulf coast.

PubMed

Southwick, Lloyd M; Grigg, Brandon C; Kornecki, Ted S; Fouss, James L

2002-07-17

Sugarcane is cultivated on some 170000 ha of land in south central and southwestern Louisiana. This acreage drains into bayous and rivers that empty into Louisiana's coastal bays and estuaries. For a number of years the state's Department of Agriculture and Forestry and Department of Environmental Quality have collected water quality data from this sugarcane area. Study of these data shows that approximately one in five detections of atrazine is above the maximum contaminant level (MCL) for drinking water. Currently there is no U.S. atrazine standard for protection of aquatic life. February and October detections of this herbicide are probably due to sugarcane cultivation. Nitrate levels have remained below the MCL for drinking water, but nitrate and phosphorus concentrations may pose a potential for eutrophication problems. The contribution of sugarcane production to the nutrient status of Louisiana's coastal water bodies is difficult to assess because there are other sources of nutrients in the area and native soil phosphorus levels are high. Cultural practices such as subsurface drains, open drainage ditches, and postharvest residue management have potential through enhancement of soil infiltration for decreasing sugarcane's contribution to water quality problems in southern and coastal Louisiana. A new field project is being installed at the Louisiana State University Agricultural Experiment Station's Sugarcane Research Station at St. Gabriel to assess the water quality benefits of these practices with respect to sugarcane cultivation.

Interactions among hydraulic conductivity distributions, subsurface topography, and transport thresholds revealed by a multitracer hillslope irrigation experiment

DOE PAGES

Jackson, C. Rhett; Du, Enhao; Klaus, Julian; ...

2016-08-12

Interactions among hydraulic conductivity distributions, subsurface topography, and lateral flow are poorly understood. We applied 407 mm of water and a suite of tracers over 51 h to a 12 by 16.5 m forested hillslope segment to determine interflow thresholds, preferential pathway pore velocities, large-scale conductivities, the time series of event water fractions, and the fate of dissolved nutrients. The 12% hillslope featured loamy sand A and E horizons overlying a sandy clay loam Bt at 1.25 m average depth. Interflow measured from two drains within an interception trench commenced after 131 and 208 mm of irrigation. Cumulative interflow equaledmore » 49% of applied water. Conservative tracer differences between the collection drains indicated differences in flow paths and storages within the plot. Event water fractions rose steadily throughout irrigation, peaking at 50% sixteen h after irrigation ceased. Data implied that tightly held water exchanged with event water throughout the experiment and a substantial portion of preevent water was released from the argillic layer. Surface-applied dye tracers bypassed the matrix, with peak concentrations measured shortly after flow commencement, indicating preferential network conductivities of 864–2240 mm/h, yet no macropore flow was observed. Near steady-state flow conditions indicated average conductivities of 460 mm/h and 2.5 mm/h for topsoils and the Bt horizon, respectively. Low ammonium and phosphorus concentrations in the interflow suggested rapid uptake or sorption, while higher nitrate concentrations suggested more conservative transport. Lastly, these results reveal how hydraulic conductivity variation and subsurface topographic complexity explain otherwise paradoxical solute and flow behaviors.« less

Water-balance and groundwater-flow estimation for an arid environment: San Diego region, California

NASA Astrophysics Data System (ADS)

Flint, L. E.; Flint, A. L.; Stolp, B. J.; Danskin, W. R.

2012-03-01

The coastal-plain aquifer that underlies the San Diego City metropolitan area in southern California is a groundwater resource. The understanding of the region-wide water balance and the recharge of water from the high elevation mountains to the east needs to be improved to quantify the subsurface inflows to the coastal plain in order to develop the groundwater as a long term resource. This study is intended to enhance the conceptual understanding of the water balance and related recharge processes in this arid environment by developing a regional model of the San Diego region and all watersheds adjacent or draining to the coastal plain, including the Tijuana River basin. This model was used to quantify the various components of the water balance, including semi-quantitative estimates of subsurface groundwater flow to the coastal plain. Other approaches relying on independent data were used to test or constrain the scoping estimates of recharge and runoff, including a reconnaissance-level groundwater model of the San Diego River basin, one of three main rivers draining to the coastal plain. Estimates of subsurface flow delivered to the coastal plain from the river basins ranged from 12.3 to 28.8 million m3 yr-1 from the San Diego River basin for the calibration period (1982-2009) to 48.8 million m3 yr-1 from all major river basins for the entire coastal plain for the long-term period 1940-2009. This range of scoping estimates represents the impact of climatic variability and realistically bounds the likely groundwater availability, while falling well within the variable estimates of regional recharge. However, the scarcity of physical and hydrologic data in this region hinders the exercise to narrow the range and reduce the uncertainty.

Theory of Maxwell's fish eye with mutually interacting sources and drains

NASA Astrophysics Data System (ADS)

Leonhardt, Ulf; Sahebdivan, Sahar

2015-11-01

Maxwell's fish eye is predicted to image with a resolution not limited by the wavelength of light. However, interactions between sources and drains may ruin the subwavelength imaging capabilities of this and similar absolute optical instruments. Nevertheless, as we show in this paper, at resonance frequencies of the device, an array of drains may resolve a single source, or alternatively, a single drain may scan an array of sources, no matter how narrowly spaced they are. It seems that near-field information can be obtained from far-field distances.

Enhancement of capacitance benefit by drain offset structure in tunnel field-effect transistor circuit speed associated with tunneling probability increase

NASA Astrophysics Data System (ADS)

Asai, Hidehiro; Mori, Takahiro; Matsukawa, Takashi; Hattori, Junichi; Endo, Kazuhiko; Fukuda, Koichi

2018-04-01

The effect of a drain offset structure on the operation speed of a tunnel field-effect transistor (TFET) ring oscillator is investigated by technology computer-aided design (TCAD) simulation. We demonstrate that the reduction of gate-drain capacitance by the drain offset structure dramatically increases the operation speed of the ring oscillators. Interestingly, we find that this capacitance benefit to operation speed is enhanced by the increase in band-to-band tunneling probability. The “synergistic” speed enhancement by the drain offset structure and the tunneling rate increase will have promising application to the significant improvement of the operation speed of TFET circuits.

The fabrication of carbon nanotube field-effect transistors with semiconductors as the source and drain contact materials.

PubMed

Xiao, Z; Camino, F E

2009-04-01

Sb(2)Te(3) and Bi(2)Te(2)Se semiconductor materials were used as the source and drain contact materials in the fabrication of carbon nanotube field-effect transistors (CNTFETs). Ultra-purified single-walled carbon nanotubes (SWCNTs) were ultrasonically dispersed in N-methyl pyrrolidone solvent. Dielectrophoresis was used to deposit and align SWCNTs for fabrication of CNTFETs. The Sb(2)Te(3)- and Bi(2)Te(2)Se-based CNTFETs demonstrate p-type metal-oxide-silicon-like I-V curves with high on/off drain-source current ratio at large drain-source voltages and good saturation of drain-source current with increasing drain-source voltage. The fabrication process developed is novel and has general meaning, and could be used for the fabrication of SWCNT-based integrated devices and systems with semiconductor contact materials.

Effects of drain bias on the statistical variation of double-gate tunnel field-effect transistors

NASA Astrophysics Data System (ADS)

Choi, Woo Young

2017-04-01

The effects of drain bias on the statistical variation of double-gate (DG) tunnel field-effect transistors (TFETs) are discussed in comparison with DG metal-oxide-semiconductor FETs (MOSFETs). Statistical variation corresponds to the variation of threshold voltage (V th), subthreshold swing (SS), and drain-induced barrier thinning (DIBT). The unique statistical variation characteristics of DG TFETs and DG MOSFETs with the variation of drain bias are analyzed by using full three-dimensional technology computer-aided design (TCAD) simulation in terms of the three dominant variation sources: line-edge roughness (LER), random dopant fluctuation (RDF) and workfunction variation (WFV). It is observed than DG TFETs suffer from less severe statistical variation as drain voltage increases unlike DG MOSFETs.

Measuring bi-directional current through a field-effect transistor by virtue of drain-to-source voltage measurement

DOEpatents

Turner, Steven Richard

2006-12-26

A method and apparatus for measuring current, and particularly bi-directional current, in a field-effect transistor (FET) using drain-to-source voltage measurements. The drain-to-source voltage of the FET is measured and amplified. This signal is then compensated for variations in the temperature of the FET, which affects the impedance of the FET when it is switched on. The output is a signal representative of the direction of the flow of current through the field-effect transistor and the level of the current through the field-effect transistor. Preferably, the measurement only occurs when the FET is switched on.

Modelling rapid flow response of a tile drained hillslope with explicit representation of preferential flow paths and consideration of equifinal model structures

NASA Astrophysics Data System (ADS)

Klaus, Julian; Zehe, Erwin

2010-05-01

Rapid water flow along spatially connected - often biologically mediated - flow paths of minimum flow resistance is widely acknowledged to play a key role in runoff generation at the hillslope and small catchment scales but also in the transport of solutes like agro chemicals and nutrients in cohesive soils. Especially at tile drained fields site connected vertical flow structures such as worm burrows, roots or shrinkage cracks act as short cuts allowing water flow to bypass the soil matrix. In the present study we propose a spatially explicit approach to represent worm burrows as connected structures of high conductivity and low retention capacity in a 2D physically model. With this approach tile drain discharge and preferential flow patterns in soil observed during the irrigation of a tile drained hillslope in the Weiherbach catchment were modelled. The model parameters derived from measurements and are considered to be uncertain. Given this uncertainty of key factors that organise flow and transport at tile drained sites the main objectives of the present studies are to shed light on the following three questions: 1. Does a simplified approach that explicitly represents worm burrows as continuous flow paths of small flow resistance and low retention properties in a 2D physically model allow successful reproduction of event flow response at a tile drained field site in the Weiherbach catchment? 2. Does the above described uncertainty in key factors cause equifinality i.e. are there several model structural setups that reproduce event flow response in an acceptable manner without compromising our physical understanding of the system? 3. If so, what are the key factors that have to be known at high accuracy to reduce the equifinality of model structures? The issue of equifinality is usually discussed in catchment modelling to indicate that often a large set of conceptual model parameter sets allows acceptable reproduction of the behaviour of the system of interest - in many cases catchment stream flow response. Beven and Binley (1992) suggest that these model structures should be considered to be equally likely to account for predictive uncertainty. In this study we show that the above outline approach allows successful prediction of the tile drain discharge and preferential flow patterns in soil observed during the irrigation of a tile drained hillslope in the Weiherbach catchment flow event. Strikingly we a found a considerable equifinality in the model structural setup, when key parameters such as the area density of worm burrows, their hydraulic conductivity and the conductivity of the tile drains were varied within the ranges of either our measurements or measurements reported in the literature. Thirteen different model setups yielded a normalised time-shifted Nash-Sutcliffe of more than 0.9, which means that more than 90% of the flow variability is explained by the model. Also the flow volumes were in good accordance and timing errors were less or equal than 20 min (which corresponds to two simulation output time steps). It is elaborated that this uncertainty/equifinality could be reduced when more precise data on initial states of the subsurface and on the drainage area of a single drainage tube could be made available. However, such data are currently most difficult to assess even at very well investigated site as the one that is dealt with here. We thus suggest non uniqueness of process based model structures seems thus to be an important factor causing predictive uncertainty at many sites where preferential flow dominates systems response. References Beven, K.J. and Binley, A.M., 1992. The future of distributed models: model calibration and uncertainty prediction, Hydrological Processes, 6, p.279-298.

Dual drain MOSFET detector for crosstie memory systems

NASA Astrophysics Data System (ADS)

Bluzer, N.

1985-03-01

This patent application, which discloses a circuit for detecting binary information in crosstie memory systems includes a dual drain MOSFET device having a single channel with a common source and an integrated, thin-film strip of magnetic material suitable for the storage and propagation of Bloch line-crosstie pairs acting as both a shift register and the device's gate. Current flowing through the device, in the absence of a magnetic field, is equally distributed to each drain; however, changing magnetic fields, normal to the plane of the device and generated by Bloch line-crosstie pairs in the strip, interact with the current such that a distribution imbalance exists and one drain or the other receives a disproportionate fraction of the current depending upon the direction of the magnetic field.

Delineation of a collapse feature in a noisy environment using a multichannel surface wave technique

USGS Publications Warehouse

Xia, J.; Chen, C.; Li, P.H.; Lewis, M.J.

2004-01-01

A collapse developed at Calvert Cliffs Nuclear Power Plant, Maryland, in early 2001. The location of the collapse was over a groundwater drainage system pipe buried at an elevation of +0??9 m (reference is to Chesapeake Bay level). The cause of the collapse was a subsurface drain pipe that collapsed because of saltwater corrosion of the corrugated metal pipe. The inflow/outflow of sea water and groundwater flow caused soil to be removed from the area where the pipe collapsed. To prevent damage to nearby structures, the collapse was quickly filled with uncompacted sand and gravel (???36000 kg). However, the plant had an immediate need to determine whether more underground voids existed. A high-frequency multichannel surface-wave survey technique was conducted to define the zone affected by the collapse. Although the surface-wave survey at Calvert Cliffs Nuclear Power Plant was conducted at a noise level 50-100 times higher than the normal environment for a shallow seismic survey, the shear (S)-wave velocity field calculated from surface-wave data delineated a possible zone affected by the collapse. The S-wave velocity field showed chimney-shaped low-velocity anomalies that were directly related to the collapse. Based on S-wave velocity field maps, a potential zone affected by the collapse was tentatively defined.

Chlorinated organic compounds in ground water at Roosevelt Field, Nassau County, Long Island, New York

USGS Publications Warehouse

Eckhardt, D.A.; Pearsall, K.A.

1989-01-01

Trichloroethylene (TCE), 1,2-dichloroethylene (DCE), and tetrachloroethylene (PCE) have been detected in water from five public-supply wells and six cooling-water wells that tap the Magothy aquifer at Roosevelt Field, a 200-acre area that is now a large shopping mall and office-building complex. The cooling water is discharged after use to the water table (upper glacial) aquifer through a nearby recharge basin and a subsurface drain field. Three plumes of TCE in groundwater have been delineated--the source plume, which has penetrated both aquifers , and two more recent plumes emanating from the two discharge sites in the water-table aquifer. Concentrations of inorganic constituents in the three plumes are the same as those in ambient water in the area. The two secondary plumes discharged cooling water extended at least 1,000 ft south-southeastward in the direction of regional groundwater flow. Pumping at wells screened in the middle and basal sections of the Magothy aquifers, where clay layers are absent and sandy zones provide good vertical hydraulic connection within the aquifer system, has increased the rate of downward contaminant advection. The transient increases in downward movement are cumulative over time and have brought TCE to the bottom of the Magothy aquifer, 500 ft below land surface. (USGS)

Socially optimal drainage system and agricultural biodiversity: a case study for Finnish landscape.

PubMed

Saikkonen, Liisa; Herzon, Irina; Ollikainen, Markku; Lankoski, Jussi

2014-12-15

This paper examines the socially optimal drainage choice (surface/subsurface) for agricultural crop cultivation in a landscape with different land qualities (fertilities) when private profits and nutrient runoff damages are taken into account. We also study the measurable social costs to increase biodiversity by surface drainage when the locations of the surface-drained areas in a landscape affect the provided biodiversity. We develop a general theoretical model and apply it to empirical data from Finnish agriculture. We find that for low land qualities the measurable social returns are higher to surface drainage than to subsurface drainage, and that the profitability of subsurface drainage increases along with land quality. The measurable social costs to increase biodiversity by surface drainage under low land qualities are negative. For higher land qualities, these costs depend on the land quality and on the biodiversity impacts. Biodiversity conservation plans for agricultural landscapes should focus on supporting surface drainage systems in areas where the measurable social costs to increase biodiversity are negative or lowest. Copyright © 2014 Elsevier Ltd. All rights reserved.

Improvement in the performance of graphene nanoribbon p-i-n tunneling field effect transistors by applying lightly doped profile on drain region

NASA Astrophysics Data System (ADS)

Naderi, Ali

2017-12-01

In this paper, an efficient structure with lightly doped drain region is proposed for p-i-n graphene nanoribbon field effect transistors (LD-PIN-GNRFET). Self-consistent solution of Poisson and Schrödinger equation within Nonequilibrium Green’s function (NEGF) formalism has been employed to simulate the quantum transport of the devices. In proposed structure, source region is doped by constant doping density, channel is an intrinsic GNR, and drain region contains two parts with lightly and heavily doped doping distributions. The important challenge in tunneling devices is obtaining higher current ratio. Our simulations demonstrate that LD-PIN-GNRFET is a steep slope device which not only reduces the leakage current and current ratio but also enhances delay, power delay product, and cutoff frequency in comparison with conventional PIN GNRFETs with uniform distribution of impurity and with linear doping profile in drain region. Also, the device is able to operate in higher drain-source voltages due to the effectively reduced electric field at drain side. Briefly, the proposed structure can be considered as a more reliable device for low standby-power logic applications operating at higher voltages and upper cutoff frequencies.

Reduction in wick drain effectiveness with spacing for Utah silts and clays.

DOT National Transportation Integrated Search

2012-04-01

Although decreasing the spacing of vertical drains usually decreases the time for consolidation, previous field tests have shown that there is a critical drain spacing for which tighter spacing does not decrease the time for consolidation. This...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckhardt, D.A.V.; Pearsall, K.A.

Trichloroethylene (TCE), 1,2-dichloroethylene (DCE), and tetrachloroethylene (PCE) have been detected in water from five public-supply wells and six cooling-water wells that tap the Magothy aquifer at Roosevelt Field. The cooling water is discharged after use to the water table aquifer through a nearby recharge basin and a subsurface drain field. Three plumes of TCE in groundwater have been delineated - the source plume, which has penetrated both aquifers, and two more recent plumes emanating from the two discharge sites in the water-table aquifer. Concentrations of inorganic constituents in the three plumes are the same as those in ambient water inmore » the area. The two secondary plumes discharged cooling water extended at least 1,000 ft south-southeastward in the direction of regional groundwater flow. Pumping at wells screened in the middle and basal sections of the Magothy aquifers, where clay layers are absent and sandy zones provide good vertical hydraulic connection within the aquifer system, has increased the rate of downward contaminant advection. The transient increases in downward movement are cumulative over time and have brought TCE to the bottom of the Magothy aquifer, 500 ft below land surface. 38 refs., 11 figs., 8 tabs.« less

Monte Carlo simulations of spin transport in a strained nanoscale InGaAs field effect transistor

NASA Astrophysics Data System (ADS)

Thorpe, B.; Kalna, K.; Langbein, F. C.; Schirmer, S.

2017-12-01

Spin-based logic devices could operate at a very high speed with a very low energy consumption and hold significant promise for quantum information processing and metrology. We develop a spintronic device simulator by combining an in-house developed, experimentally verified, ensemble self-consistent Monte Carlo device simulator with spin transport based on a Bloch equation model and a spin-orbit interaction Hamiltonian accounting for Dresselhaus and Rashba couplings. It is employed to simulate a spin field effect transistor operating under externally applied voltages on a gate and a drain. In particular, we simulate electron spin transport in a 25 nm gate length In0.7Ga0.3As metal-oxide-semiconductor field-effect transistor with a CMOS compatible architecture. We observe a non-uniform decay of the net magnetization between the source and the gate and a magnetization recovery effect due to spin refocusing induced by a high electric field between the gate and the drain. We demonstrate a coherent control of the polarization vector of the drain current via the source-drain and gate voltages, and show that the magnetization of the drain current can be increased twofold by the strain induced into the channel.

Electrical characteristics of tunneling field-effect transistors with asymmetric channel thickness

NASA Astrophysics Data System (ADS)

Kim, Jungsik; Oh, Hyeongwan; Kim, Jiwon; Meyyappan, M.; Lee, Jeong-Soo

2017-02-01

Effects of using asymmetric channel thickness in tunneling field-effect transistors (TFET) are investigated in sub-50 nm channel regime using two-dimensional (2D) simulations. As the thickness of the source side becomes narrower in narrow-source wide-drain (NSWD) TFETs, the threshold voltage (V th) and the subthreshold swing (SS) decrease due to enhanced gate controllability of the source side. The narrow source thickness can make the band-to-band tunneling (BTBT) distance shorter and induce much higher electric field near the source junction at the on-state condition. In contrast, in a TFET with wide-source narrow-drain (WSND), the SS shows almost constant values and the V th slightly increases with narrowing thickness of the drain side. In addition, the ambipolar current can rapidly become larger with smaller thickness on the drain side because of the shorter BTBT distance and the higher electric-field at the drain junction. The on-current of the asymmetric channel TFET is lower than that of conventional TFETs due to the volume limitation of the NSWD TFET and high series resistance of the WSND TFET. The on-current is almost determined by the channel thickness of the source side.

Modeling Subsurface Storm and Tile Drain Systems in GSSHA with SUPERLINK

DTIC Science & Technology

2014-09-01

side is computed as . ( )e Kq d m m L   2 0 01 2 (7) de is defined as ( van der Molen and Wesseling (1991)) ERDC/CHL TR-14-11 15...Conservation Service. Van der Molen , W.H., and J. Wesseling. 1991. A solution in closed form and a series solution to replace the tables for thickness of...effective lateral hydraulic conductivity (cm hr-1) C = 1 in the present version. Hooghoudt ( van Schilfgaarde 1974) characterized flow to cylindrical

Photocurrent microscopy of contact resistance and charge carrier traps in organic field-effect transistors

NASA Astrophysics Data System (ADS)

Liewald, C.; Reiser, D.; Westermeier, C.; Nickel, B.

2016-08-01

We use a pentacene transistor with asymmetric source drain contacts to test the sensitivity of scanning photocurrent microscopy (SPCM) for contact resistance and charge traps. The drain current of the device strongly depends on the choice of the drain electrode. In one case, more than 94% of the source drain voltage is lost due to contact resistance. Here, SPCM maps show an enhanced photocurrent signal at the hole-injecting contact. For the other bias condition, i.e., for ohmic contacts, the SPCM signal peaks heterogeneously along the channel. We argue from basic transport models that bright areas in SPCM maps indicate areas of large voltage gradients or high electric field strength caused by injection barriers or traps. Thus, SPCM allows us to identify and image the dominant voltage loss mechanism in organic field-effect transistors.

Distribution of selenium in soils of agricultural fields, western San Joaquin Valley, California

USGS Publications Warehouse

Fujii, Roger; Deverel, S.J.; Hatfield, D.B.

1987-01-01

Soils from three agricultural fields in the western San Joaquin Valley were analyzed for soluble, adsorbed, and total concentrations of selenium (Se) to assess the distribution and forms of Se, and the relation of the distribution and forms of Se to the leaching of Se from soils. Soil samples were collected in three fields with drainage systems of different ages (6, 15, 1.5 yr) and different Se concentrations in drain water (58, 430, 3700 micrograms/L respectively). Preliminary methods to determine total Se and estimate adsorbed Se were developed. Of the three fields, concentrations of soluble Se and salinity were highest in soils from the field drained for 1.5 yr and lowest in the field drained for 6 yr. The field drained for 1.5 yr also had the highest concentration of total Se in soil; a median of 1.2 microgram/gm. Of the total concentration of Se in soil from all three fields, the proportion of adsorbed Se and soluble Se ranged from 1 to 11% and < 1 to 63%, respectively. Most of the variance in soluble Se is explained by salinity ( r sq > 0.68) in saturation extracts of soils sampled from below the water table, reflecting evaporative concentration of Se and salinity. In contrast, most soluble salts and Se apparently have been leached from the unsaturated soils in the fields drained for 6 and 15 yr; therefore, the correlation was lower between Se and salinity in saturation extracts of those soils (r sq < 0.33). Among soils from all three fields, the ratio of Se to salinity in saturation extracts increased with increasing salinity. (Author 's abstract)

Comparison of Contaminant Transport in Agricultural Drainage Water and Urban Stormwater Runoff

PubMed Central

Ranaivoson, Andry Z.; Feyereisen, Gary W.; Rosen, Carl J.; Moncrief, John F.

2016-01-01

Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts. The main objective of this long-term study was to quantify and compare contaminant transport in agricultural drainage water and urban stormwater runoff. We measured flow rate and contaminant concentration in stormwater runoff from Willmar, Minnesota, USA, and in drainage water from subsurface-drained fields with surface inlets, namely, Unfertilized and Fertilized Fields. Commercial fertilizer and turkey litter manure were applied to the Fertilized Field based on agronomic requirements. Results showed that the City Stormwater transported significantly higher loads per unit area of ammonium, total suspended solids (TSS), and total phosphorus (TP) than the Fertilized Field, but nitrate load was significantly lower. Nitrate load transport in drainage water from the Unfertilized Field was 58% of that from the Fertilized Field. Linear regression analysis indicated that a 1% increase in flow depth resulted in a 1.05% increase of TSS load from the City Stormwater, a 1.07% increase in nitrate load from the Fertilized Field, and a 1.11% increase in TP load from the Fertilized Field. This indicates an increase in concentration with a rise in flow depth, revealing that concentration variation was a significant factor influencing the dynamics of load transport. Further regression analysis showed the importance of targeting high flows to reduce contaminant transport. In conclusion, for watersheds similar to this one, management practices should be directed to load reduction of ammonium and TSS from urban areas, and nitrate from cropland while TP should be a target for both. PMID:27930684

Comparison of Contaminant Transport in Agricultural Drainage Water and Urban Stormwater Runoff.

PubMed

Ghane, Ehsan; Ranaivoson, Andry Z; Feyereisen, Gary W; Rosen, Carl J; Moncrief, John F

2016-01-01

Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts. The main objective of this long-term study was to quantify and compare contaminant transport in agricultural drainage water and urban stormwater runoff. We measured flow rate and contaminant concentration in stormwater runoff from Willmar, Minnesota, USA, and in drainage water from subsurface-drained fields with surface inlets, namely, Unfertilized and Fertilized Fields. Commercial fertilizer and turkey litter manure were applied to the Fertilized Field based on agronomic requirements. Results showed that the City Stormwater transported significantly higher loads per unit area of ammonium, total suspended solids (TSS), and total phosphorus (TP) than the Fertilized Field, but nitrate load was significantly lower. Nitrate load transport in drainage water from the Unfertilized Field was 58% of that from the Fertilized Field. Linear regression analysis indicated that a 1% increase in flow depth resulted in a 1.05% increase of TSS load from the City Stormwater, a 1.07% increase in nitrate load from the Fertilized Field, and a 1.11% increase in TP load from the Fertilized Field. This indicates an increase in concentration with a rise in flow depth, revealing that concentration variation was a significant factor influencing the dynamics of load transport. Further regression analysis showed the importance of targeting high flows to reduce contaminant transport. In conclusion, for watersheds similar to this one, management practices should be directed to load reduction of ammonium and TSS from urban areas, and nitrate from cropland while TP should be a target for both.

The complex filling of alae crater, Kilauea Volcano, Hawaii

USGS Publications Warehouse

Swanson, D.A.; Duffield, W.A.; Jackson, D.B.; Peterson, D.W.

1972-01-01

Since February 1969 Alae Crater, a 165-m-deep pit crater on the east rift of Kilauea Volcano, has been completely filled with about 18 million m3 of lava. The filling was episodic and complex. It involved 13 major periods of addition of lava to the crater, including spectacular lava falls as high as 100 m, and three major periods of draining of lava from the crater. Alae was nearly filled by August 3, 1969, largely drained during a violent ground-cracking event on August 4, 1969, and then filled to the low point on its rim on October 10, 1969. From August 1970 to May 1971, the crater acted as a reservoir for lava that entered through subsurface tubes leading from the vent fissure 150 m away. Another tube system drained the crater and carried lava as far as the sea, 11 km to the south. Much of the lava entered Alae by invading the lava lake beneath its crust and buoying the crust upward. This process, together with the overall complexity of the filling, results in a highly complicated lava lake that would doubtless be misinterpreted if found in the fossil record. ?? 1972 Stabilimento Tipografico Francesco Giannini & Figli.

Subsurface waste disposal by means of wells - A selective annotated bibliography

USGS Publications Warehouse

Rima, Donald Robert; Chase, Edith B.; Myers, Beverly M.

1971-01-01

Subsurface waste disposal by means of wells is the practice of using drilled wells to inject unwanted substances into underground rock formations. The use of wells for this purpose is not a new idea. As long ago as the end of the last century, it was common practice to drill wells for the express purpose of draining swamps and small lakes to reclaim the land for agricultural purposes. A few decades later in the 1920's and 1930's many oil companies began using injection wells to dispose of oil-field brines and to repressurize oil reservoirs. During World War II, the Atomic Energy Commission began using injection wells to dispose of certain types of radioactive wastes. More recently, injection wells have been drilled to dispose of a variety of byproducts of industrial processes. The number of such wells has increased rapidly since Congress passed the Clean Streams Act of 1966, which restricted the discharge of waste into surface waters.Many scientists and public officials question the propriety of using the term "disposal" when referring to the underground injection of wastes. Their reasons are that underground injection is not, as many advocates claim, "a complete and final answer" to the waste-disposal problem. Rather, it is merely a process wherein the injected wastes are committed to the subsurface with uncertainty as to their ultimate fate or limits of confinement. In effect, the wastes, undiminished and unchanged, are removed from the custody of man and placed in the custody of nature.Although the concept of waste-injection wells is relatively simple, the effects of waste injection can be very complex, particularly when dealing with the exotic and complex components of some industrial wastes. Besides the physical forces of injection, there are many varied interactions between the injected wastes and the materials within the injection zone. Because these changes occur out of sight in the subsurface, they are difficult to assess and not generally understood. In addition, the various aspects of the problem involve a wide spectrum of science and engineering. Hence, articles published on the subject are widely dispersed in the technical and scientific literature. 

Using Chemical Tracers to Estimate Pesticide Mass Discharge in an Agricultural Watershed

NASA Astrophysics Data System (ADS)

Simmons, A. N.; Allen-King, R. M.; Van Biersel, T. P.; Keller, C. K.; Smith, J. L.

2001-12-01

The goal of this research is to use environmental tracers to quantify the contributions of subsurface and surface runoff to predict the mass discharge of non-point source agricultural pollutants to rivers at multiple scales of study. Easily measured chemical tracers, such as electrical conductivity (EC), are used to distinguish ground and surface water contributions to the river system. The study area is the Missouri Flat Creek watershed, a 14,400 ha semi-arid dryland agricultural setting located near Pullman, WA. Ground and surface water samples are collected at approximately two-week intervals from an ephemeral stream and a tile drain located in actively farmed and topographically constrained fields ( ~20 ha), and from seven stream-gaging stations. Surface water discharge is monitored continuously. Samples are routinely analyzed for two pesticides (the insecticide lindane or gamma-hexachlorocyclohexane (HCH) and the herbicide triallate, S-(2,3,3-trichloroallyl) diisopropylthiocarbamate), a nutrient (nitrate), and the tracers EC and silica. Lindane is applied as a seed coating on most spring and fall crops in the region. Observed lindane concentrations in the different hydrologic reservoirs ranged over approximately two orders of magnitude, from typically less than the detection limit ( ~0.005 μ g/L) in most soil pore water and groundwater samples to a weighted mean of 0.25 μ g/L in field (ephemeral stream) surface runoff. A two-component, ground and surface water, hydrograph separation was performed using tile drain and ephemeral stream tracer concentrations from field plots to represent groundwater and surface runoff end-members. The hydrograph separation was used to predict lindane discharge. Reasonable agreement between model and observed lindane discharge timing and trend supports the hypothesis that in-stream pesticide is derived from annual surface runoff. During the high flow winter months, the model predictions are two to five times greater than observed. The differences between the model and observed mass discharges are likely attributable to dilution (from fields to which the chemical was not applied) or attenuation by biological processes. These are the subjects of continued work.

Impact of Tile Drainage on the Distribution of Concentration and Age of Inorganic Soil Nitrogen.

NASA Astrophysics Data System (ADS)

Woo, D.; Kumar, P.

2017-12-01

Extensive network of tile drainage network across the Midwestern United States, northern Europe and other regions of the world have enhanced agricultural productivity. Because of its impact on sub-surface flow patterns and moisture and temperature dynamics, it controls the nitrogen cycle in agricultural systems, and its influence on nitrogen dynamics plays a key role in determining the short- and long-term evolution of soil inorganic nitrogen concentration and age. The spatial mapping of nitrogen concentration and age under tile-drained fields has, therefore, the potential to open up novel solution to the vexing challenge of reducing environmental impacts while at the same time maintaining agricultural productivity. The objective of this study is to explore the impacts of tile drains on the age dynamics of nitrate, immobile ammonium, mobile ammonia/um, and non-reactive tracer (such as chloride) by implementing two mobile interacting pore domains to capture matrix and preferential flow paths in a coupled ecohydrology and biogeochemistry model, Dhara. We applied this model to an agricultural farm supporting a corn-soybean rotation in the Midwestern United States. It should be expected that the installation of tile drains decrease the age of soil nutrient due to nutrient losses through tile drainage. However, an increase in the age of mobile ammonia/um is observed in contrast to the cases for nitrate, immobile ammonium, and non-reactive tracer. These results arise because the depletion of mobile ammonia/um due to tile drainage causes a high mobility flux from immobile ammonium to mobile ammonia/um, which also carries a considerable amount of relatively old age of immobile ammonium to mobile ammonia/um. In addition, the ages of nitrate and mobile ammonia/um in tile drainage range from 1 to 3 years, and less than a year, respectively, implying that not considering age transformations between nitrogen species would result in substantial underestimation of nitrogen ages, possibly leading to an erroneous conclusion.

Evaluation of a “Field Cage” for Electric Field Control in GaN-Based HEMTs That Extends the Scalability of Breakdown Into the kV Regime

DOE PAGES

Tierney, Brian D.; Choi, Sukwon; DasGupta, Sandeepan; ...

2017-08-16

A distributed impedance “field cage” structure is proposed and evaluated for electric field control in GaN-based, lateral high electron mobility transistors (HEMTs) operating as kilovolt-range power devices. In this structure, a resistive voltage divider is used to control the electric field throughout the active region. The structure complements earlier proposals utilizing floating field plates that did not employ resistively connected elements. Transient results, not previously reported for field plate schemes using either floating or resistively connected field plates, are presented for ramps of dV ds /dt = 100 V/ns. For both DC and transient results, the voltage between the gatemore » and drain is laterally distributed, ensuring the electric field profile between the gate and drain remains below the critical breakdown field as the source-to-drain voltage is increased. Our scheme indicates promise for achieving breakdown voltage scalability to a few kV.« less

Evaluation of a “Field Cage” for Electric Field Control in GaN-Based HEMTs That Extends the Scalability of Breakdown Into the kV Regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tierney, Brian D.; Choi, Sukwon; DasGupta, Sandeepan

A distributed impedance “field cage” structure is proposed and evaluated for electric field control in GaN-based, lateral high electron mobility transistors (HEMTs) operating as kilovolt-range power devices. In this structure, a resistive voltage divider is used to control the electric field throughout the active region. The structure complements earlier proposals utilizing floating field plates that did not employ resistively connected elements. Transient results, not previously reported for field plate schemes using either floating or resistively connected field plates, are presented for ramps of dV ds /dt = 100 V/ns. For both DC and transient results, the voltage between the gatemore » and drain is laterally distributed, ensuring the electric field profile between the gate and drain remains below the critical breakdown field as the source-to-drain voltage is increased. Our scheme indicates promise for achieving breakdown voltage scalability to a few kV.« less

Poly(3,3‴-didodecylquarterthiophene) field effect transistors with single-walled carbon nanotube based source and drain electrodes

NASA Astrophysics Data System (ADS)

Zhang, Yuan Yuan; Shi, Yumeng; Chen, Fuming; Mhaisalkar, S. G.; Li, Lain-Jong; Ong, Beng S.; Wu, Yiliang

2007-11-01

A solution processable method for employing single-walled carbon nanotubes (SWCNTs) as bottom contact source/drain electrodes for a significant reduction of contact resistance in poly(3,3‴-didodecylquarterthiophene) based organic field effect transistors (OFETs) is proposed. A two order of magnitude reduction in contact resistance and up to a threefold improvement in field effect mobilities were observed in SWCNT contacted OFETs as opposed to similar devices with gold source/drain electrodes. Based on Kelvin probe measurements, this improvement was attributed to a reduction in the Schottky barrier for hole injection into organic semiconductor.

Models of second-order effects in metal-oxide-semiconductor field-effect transistors for computer applications

NASA Technical Reports Server (NTRS)

Benumof, Reuben; Zoutendyk, John; Coss, James

1988-01-01

Second-order effects in metal-oxide-semiconductor field-effect transistors (MOSFETs) are important for devices with dimensions of 2 microns or less. The short and narrow channel effects and drain-induced barrier lowering primarily affect threshold voltage, but formulas for drain current must also take these effects into account. In addition, the drain current is sensitive to channel length modulation due to pinch-off or velocity saturation and is diminished by electron mobility degradation due to normal and lateral electric fields in the channel. A model of a MOSFET including these considerations and emphasizing charge conservation is discussed.

Old Hickory Lake Appendix M To Park Management Shoreline Management Plan

DTIC Science & Technology

2014-07-01

The Division of Water Resources of the Tennessee Department of Environment and Conservation regulates septic tanks , drain fields, and other...sanitary facilities on adjoining private property. The construction or installation of a new privately owned septic tank , drain field, or holding tank on

Tylosin-resistant Enterococci, erm genes, and tylosin in drained fields receiving swine manure

USDA-ARS?s Scientific Manuscript database

The use of tylosin at subtherapeutic levels by the swine industry provides selective pressure for the development of antibiotic resistance in gastrointestinal bacteria. The land application of swine manure to drained agricultural fields might introduce elevated levels of total and tylosin-resistant ...

Subsurface evaluation of the west parking lot and landfill 3 areas of Air Force Plant 4, Fort Worth, Texas, using two-dimensional direct-current resistivity profiling

USGS Publications Warehouse

Braun, Christopher L.; Jones, Sonya A.

2002-01-01

During September 1999, the U.S. Geological Survey made 10 two-dimensional direct-current resistivity profile surveys in the west parking lot and landfill 3 areas of Air Force Plant 4, Fort Worth, Texas, to identify subsurface areas of anomalously high or low resistivity that could indicate potential contamination, contaminant pathways, or anthropogenic structures. Six of the 10 surveys (transects) were in the west parking lot. Each of the inverted sections of these transects had anomalously high resistivities in the terrace alluvium/fill (the surficial subsurface layer) that probably were caused by highly resistive fill material. In addition, each of these transects had anomalously low resistivities in the Walnut Formation (a bedrock layer immediately beneath the alluvium/fill) that could have been caused by saturation of fractures within the Walnut Formation. A high-resistivity anomaly in the central part of the study area probably is associated with pea gravel fill used in construction of a French drain. Another high resistivity anomaly in the west parking lot, slightly southeast of the French drain, could be caused by dense nonaqueous-phase liquid in the Walnut Formation. The inverted sections of the four transects in the landfill 3 area tended to have slightly higher resistivities in both the alluvium/fill and the Walnut Formation than the transects in the west parking lot. The higher resistivities in the alluvium/fill could have been caused by drier conditions in grassy areas relative to conditions in the west parking lot. Higher resistivities in parts of the Walnut Formation also could be a function of drier conditions or variations in the lithology of the Walnut Formation. In addition to the 10 vertical sections, four horizontal sections at 2-meteraltitude intervals show generally increasing resistivity with decreasing altitude that most likely results from the increased influence of the Walnut Formation, which has a higher resistivity than the terrace alluvium/fill.

Applying linear discriminant analysis to predict groundwater redox conditions conducive to denitrification

NASA Astrophysics Data System (ADS)

Wilson, S. R.; Close, M. E.; Abraham, P.

2018-01-01

Diffuse nitrate losses from agricultural land pollute groundwater resources worldwide, but can be attenuated under reducing subsurface conditions. In New Zealand, the ability to predict where groundwater denitrification occurs is important for understanding the linkage between land use and discharges of nitrate-bearing groundwater to streams. This study assesses the application of linear discriminant analysis (LDA) for predicting groundwater redox status for Southland, a major dairy farming region in New Zealand. Data cases were developed by assigning a redox status to samples derived from a regional groundwater quality database. Pre-existing regional-scale geospatial databases were used as training variables for the discriminant functions. The predictive accuracy of the discriminant functions was slightly improved by optimising the thresholds between sample depth classes. The models predict 23% of the region as being reducing at shallow depths (<15 m), and 37% at medium depths (15-75 m). Predictions were made at a sub-regional level to determine whether improvements could be made with discriminant functions trained by local data. The results indicated that any gains in predictive success were offset by loss of confidence in the predictions due to the reduction in the number of samples used. The regional scale model predictions indicate that subsurface reducing conditions predominate at low elevations on the coastal plains where poorly drained soils are widespread. Additional indicators for subsurface denitrification are a high carbon content of the soil, a shallow water table, and low-permeability clastic sediments. The coastal plains are an area of widespread groundwater discharge, and the soil and hydrology characteristics require the land to be artificially drained to render the land suitable for farming. For the improvement of water quality in coastal areas, it is therefore important that land and water management efforts focus on understanding hydrological bypassing that may occur via artificial drainage systems.

Short-Channel Tunneling Field-Effect Transistor with Drain-Overlap and Dual-Metal Gate Structure for Low-Power and High-Speed Operations.

PubMed

Yoon, Young Jun; Eun, Hye Rim; Seo, Jae Hwa; Kang, Hee-Sung; Lee, Seong Min; Lee, Jeongmin; Cho, Seongjae; Tae, Heung-Sik; Lee, Jung-Hee; Kang, In Man

2015-10-01

We have investigated and proposed a highly scaled tunneling field-effect transistor (TFET) based on Ge/GaAs heterojunction with a drain overlap to suppress drain-induced barrier thinning (DIBT) and improve low-power (LP) performance. The highly scaled TFET with a drain overlap achieves lower leakage tunneling current because of the decrease in tunneling events between the source and drain, whereas a typical short-channel TFET suffers from a great deal of tunneling leakage current due to the DIBT at the off-state. However, the drain overlap inevitably increases the gate-to-drain capacitance (Cgd) because of the increase in the overlap capacitance (Cov) and inversion capacitance (Cinv). Thus, in this work, a dual-metal gate structure is additionally applied along with the drain overlap. The current performance and the total gate capacitance (Cgg) of the device with a dual-metal gate can be possibly controlled by adjusting the metal gate workfunction (φgate) and φoverlap-gate in the overlapping regions. As a result, the intrinsic delay time (τ) is greatly reduced by obtaining lower Cgg divided by the on-state current (Ion), i.e., Cgg/Ion. We have successfully demonstrated excellent LP and high-speed performance of a highly scaled TFET by adopting both drain overlap and dual-metal gate with DIBT minimization.

Analytical solutions for flow fields near drain-and-gate reactive barriers.

PubMed

Klammler, Harald; Hatfield, Kirk; Kacimov, Anvar

2010-01-01

Permeable reactive barriers (PRBs) are a popular technology for passive contaminant remediation in aquifers through installation of reactive materials in the pathway of a plume. Of fundamental importance are the degree of remediation inside the reactor (residence time) and the portion of groundwater intercepted by a PRB (capture width). Based on a two-dimensional conformal mapping approach (previously used in related work), the latter is studied in the present work for drain-and-gate (DG) PRBs, which may possess a collector and a distributor drain ("full" configuration) or a collector drain only ("simple" configuration). Inherent assumptions are a homogeneous unbounded aquifer with a uniform far field, in which highly permeable drains establish constant head boundaries. Solutions for aquifer flow fields in terms of the complex potential are derived, illustrated, and analyzed for doubly symmetric DG configurations and arbitrary reactor hydraulic resistance as well as ambient groundwater flow direction. A series of practitioner-friendly charts for capture width is given to assist in PRB design and optimization without requiring complex mathematics. DG PRBs are identified as more susceptible to flow divergence around the reactor than configurations using impermeable side structures (e.g., funnel-and-gate), and deployment of impermeable walls on drains is seen to mitigate this problem under certain circumstances.

Carbon Dioxide Flux from Rice Paddy Soils in Central China: Effects of Intermittent Flooding and Draining Cycles

PubMed Central

Liu, Yi; Wan, Kai-yuan; Tao, Yong; Li, Zhi-guo; Zhang, Guo-shi; Li, Shuang-lai; Chen, Fang

2013-01-01

A field experiment was conducted to (i) examine the diurnal and seasonal soil carbon dioxide (CO2) fluxes pattern in rice paddy fields in central China and (ii) assess the role of floodwater in controlling the emissions of CO2 from soil and floodwater in intermittently draining rice paddy soil. The soil CO2 flux rates ranged from −0.45 to 8.62 µmol.m−2.s−1 during the rice-growing season. The net effluxes of CO2 from the paddy soil were lower when the paddy was flooded than when it was drained. The CO2 emissions for the drained conditions showed distinct diurnal variation with a maximum efflux observed in the afternoon. When the paddy was flooded, daytime soil CO2 fluxes reversed with a peak negative efflux just after midday. In draining/flooding alternating periods, a sudden pulse-like event of rapidly increasing CO2 efflux occured in response to re-flooding after draining. Correlation analysis showed a negative relation between soil CO2 flux and temperature under flooded conditions, but a positive relation was found under drained conditions. The results showed that draining and flooding cycles play a vital role in controlling CO2 emissions from paddy soils. PMID:23437170

Treatment of phosphorus transported from tile and ditch-drained agricultural fields using sorption materials

USDA-ARS?s Scientific Manuscript database

Many flat, poorly drained soils, such as the Delmarva Peninsula, the upper Midwest, and certain areas of Europe such as Denmark and Netherlands, have been extensively drained through the construction of artificial drainage ditches and tiles to allow agriculture and other human activities. In additi...

Attributes for NHDPlus Catchments (Version 1.1) in the Conterminous United States: Artificial Drainage (1992) and Irrigation Types (1997)

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular dataset represents the estimated area of artificial drainage for the year 1992 and irrigation types for the year 1997 compiled for every catchment of NHDPlus for the conterminous United States. The source datasets were derived from tabular National Resource Inventory (NRI) datasets created by the National Resources Conservation Service (NRCS, U.S. Department of Agriculture, 1995, 1997). Artificial drainage is defined as subsurface drains and ditches. Irrigation types are defined as gravity and pressure. Subsurface drains are described as conduits, such as corrugated plastic tubing, tile, or pipe, installed beneath the ground surface to collect and/or convey drainage. Surface drainage field ditches are described as graded ditches for collecting excess water. Gravity irrigation source is described as irrigation delivered to the farm and/or field by canals or pipelines open to the atmosphere; and water is distributed by the force of gravity down the field by: (1) A surface irrigation system (border, basin, furrow, corrugation, wild flooding, etc.) or (2) Sub-surface irrigation pipelines or ditches. Pressure irrigation source is described as irrigation delivered to the farm and/or field in pump or elevation-induced pressure pipelines, and water is distributed across the field by: (1) Sprinkle irrigation (center pivot, linear move, traveling gun, side roll, hand move, big gun, or fixed set sprinklers), or (2) Micro irrigation (drip emitters, continuous tube bubblers, micro spray or micro sprinklers). NRI data do not include Federal lands and are thus excluded from this dataset. The tabular data for drainage were spatially apportioned to the National Land Cover Dataset (NLCD, Kerie Hitt, written commun., 2005) and the tabular data for irrigation were spatially apportioned to an enhanced version of the National Land Cover Dataset (NLCDe, Nakagaki and others 2007) The NHDPlus Version 1.1 is an integrated suite of application-ready geospatial datasets that incorporates many of the best features of the National Hydrography Dataset (NHD) and the National Elevation Dataset (NED). The NHDPlus includes a stream network (based on the 1:100,00-scale NHD), improved networking, naming, and value-added attributes (VAAs). NHDPlus also includes elevation-derived catchments (drainage areas) produced using a drainage enforcement technique first widely used in New England, and thus referred to as "the New England Method." This technique involves "burning in" the 1:100,000-scale NHD and when available building "walls" using the National Watershed Boundary Dataset (WBD). The resulting modified digital elevation model (HydroDEM) is used to produce hydrologic derivatives that agree with the NHD and WBD. Over the past two years, an interdisciplinary team from the U.S. Geological Survey (USGS), and the U.S. Environmental Protection Agency (USEPA), and contractors, found that this method produces the best quality NHD catchments using an automated process (USEPA, 2007). The NHDPlus dataset is organized by 18 Production Units that cover the conterminous United States. The NHDPlus version 1.1 data are grouped by the U.S. Geological Survey's Major River Basins (MRBs, Crawford and others, 2006). MRB1, covering the New England and Mid-Atlantic River basins, contains NHDPlus Production Units 1 and 2. MRB2, covering the South Atlantic-Gulf and Tennessee River basins, contains NHDPlus Production Units 3 and 6. MRB3, covering the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins, contains NHDPlus Production Units 4, 5, 7 and 9. MRB4, covering the Missouri River basins, contains NHDPlus Production Units 10-lower and 10-upper. MRB5, covering the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins, contains NHDPlus Production Units 8, 11 and 12. MRB6, covering the Rio Grande, Colorado and Great Basin River basins, contains NHDPlus Production Units 13, 14, 15 and 16. MRB7, covering the Pacific Northwest River basins, contains NHDPlus Production Unit 17. MRB8, covering California River basins, contains NHDPlus Production Unit 18.

Fate and transport of antibiotic resistant bacteria and resistance genes in artificially drained agricultural fields receiving swine manure application

USDA-ARS?s Scientific Manuscript database

While previous studies have examined the occurrence of antibiotic resistant bacteria and antibiotic resistant genes around confined swine feeding operations, little information is known about their release and transport from artificially drained fields receiving swine manure application. Much of the...

Occurrence and movement of antibiotic resistant bacxteria, in tile-drained agricultural fields receiving swine manure

USDA-ARS?s Scientific Manuscript database

The use of tylosin at subtherapeutic levels by the swine industry provides selective pressure for the development of antibiotic resistance in gastrointestinal bacteria. The land application of swine manure to drained agricultural fields might accelerate the transport of pathogen indicators such as e...

Distribution of selenium in soils of agricultural fields, western San Joaquin Valley, California

USGS Publications Warehouse

Fujii, Roger; Deverel, S.J.; Hatfield, D.B.

1988-01-01

Soils from three agricultural fields in the Panoche Creek alluvial fan area in the western San Joaquin Valley, California, were analyzed for soluble, adsorbed, and total concentrations of selenium (Se) to assess the distribution and forms of Se in relation to the leaching of Se from soils. This assessment is needed to evaluate the importance of soil Se in affecting ground water concentrations. Soil samples were collected from three fields with drainage systems of different ages (6, 15, 1.5 yr) and different Se concentrations in drain water (58, 430, 3700 µg L−1, respectively). Concentrations of soluble Se and salinity were highest in soils from the field drained for 1.5 yr and lowest in the field drained for 6 yr. Of the total concentration of soil Se from all three fields, the proportion of adsorbed and soluble Se ranged from 1 to 11% and 2 > 0.68) in saturation extracts of soils sampled from below the water table. In contrast, most soluble salts and Se apparently have been leached from the unsaturated soils in the fields drained for 6 and 15 yr. For the leached soils, dissolution and precipitation of evaporite minerals containing Se may no longer control concentrations of soluble Se.

A novel gate and drain engineered charge plasma tunnel field-effect transistor for low sub-threshold swing and ambipolar nature

NASA Astrophysics Data System (ADS)

Yadav, Dharmendra Singh; Raad, Bhagwan Ram; Sharma, Dheeraj

2016-12-01

In this paper, we focus on the improvement of figures of merit for charge plasma based tunnel field-effect transistor (TFET) in terms of ON-state current, threshold voltage, sub-threshold swing, ambipolar nature, and gate to drain capacitance which provides better channel controlling of the device with improved high frequency response at ultra-low supply voltages. Regarding this, we simultaneously employ work function engineering on the drain and gate electrode of the charge plasma TFET. The use of gate work function engineering modulates the barrier on the source/channel interface leads to improvement in the ON-state current, threshold voltage, and sub-threshold swing. Apart from this, for the first time use of work function engineering on the drain electrode increases the tunneling barrier for the flow of holes on the drain/channel interface, it results into suppression of ambipolar behavior. The lowering of gate to drain capacitance therefore enhanced high frequency parameters. Whereas, the presence of dual work functionality at the gate electrode and over the drain region improves the overall performance of the charge plasma based TFET.

Simulation study of short-channel effects of tunnel field-effect transistors

NASA Astrophysics Data System (ADS)

Fukuda, Koichi; Asai, Hidehiro; Hattori, Junichi; Mori, Takahiro; Morita, Yukinori; Mizubayashi, Wataru; Masahara, Meishoku; Migita, Shinji; Ota, Hiroyuki; Endo, Kazuhiro; Matsukawa, Takashi

2018-04-01

Short-channel effects of tunnel field-effect transistors (FETs) are investigated in detail using simulations of a nonlocal band-to-band tunneling model. Discussion is limited to silicon. Several simulation scenarios were considered to address different effects, such as source overlap and drain offset effects. Adopting the drain offset to suppress the drain leakage current suppressed the short channel effects. The physical mechanism underlying the short-channel behavior of the tunnel FETs (TFETs) was very different from that of metal-oxide-semiconductor FETs (MOSFETs). The minimal gate lengths that do not lose on-state current by one order are shown to be 3 nm for single-gate structures and 2 nm for double gate structures, as determined from the drain offset structure.

Field Evaluation of Advanced Methods of Subsurface Exploration for Transit Tunneling

DOT National Transportation Integrated Search

1980-06-01

This report presents the results of a field evaluation of advanced methods of subsurface exploration on an ongoing urban rapid transit tunneling project. The objective of this study is to evaluate, through a field demonstration project, the feasibili...

Three-dimensional numerical model of ground-water flow in northern Utah Valley, Utah County, Utah

USGS Publications Warehouse

Gardner, Philip M.

2009-01-01

A three-dimensional, finite-difference, numerical model was developed to simulate ground-water flow in northern Utah Valley, Utah. The model includes expanded areal boundaries as compared to a previous ground-water flow model of the valley and incorporates more than 20 years of additional hydrologic data. The model boundary was generally expanded to include the bedrock in the surrounding mountain block as far as the surface-water divide. New wells have been drilled in basin-fill deposits near the consolidated-rock boundary. Simulating the hydrologic conditions within the bedrock allows for improved simulation of the effect of withdrawal from these wells. The inclusion of bedrock also allowed for the use of a recharge model that provided an alternative method for spatially distributing areal recharge over the mountains.The model was calibrated to steady- and transient-state conditions. The steady-state simulation was developed and calibrated by using hydrologic data that represented average conditions for 1947. The transient-state simulation was developed and calibrated by using hydrologic data collected from 1947 to 2004. Areally, the model grid is 79 rows by 70 columns, with variable cell size. Cells throughout most of the model domain represent 0.3 mile on each side. The largest cells are rectangular with dimensions of about 0.3 by 0.6 mile. The largest cells represent the mountain block on the eastern edge of the model domain where the least hydrologic data are available. Vertically, the aquifer system is divided into 4 layers which incorporate 11 hydrogeologic units. The model simulates recharge to the ground-water flow system as (1) infiltration of precipitation over the mountain block, (2) infiltration of precipitation over the valley floor, (3) infiltration of unconsumed irrigation water from fields, lawns, and gardens, (4) seepage from streams and canals, and (5) subsurface inflow from Cedar Valley. Discharge of ground water is simulated by the model to (1) flowing and pumping wells, (2) drains and springs, (3) evapotranspiration, (4) Utah Lake, (5) the Jordan River and mountain streams, and (6) Salt Lake Valley by subsurface outflow through the Jordan Narrows.During steady-state calibration, variables were adjusted within probable ranges to minimize differences between model-computed and measured water levels as well as between model-computed and independently estimated flows that include: recharge by seepage from individual streams and canals, discharge by seepage to individual streams and the Jordan River, discharge to Utah Lake, discharge to drains and springs, discharge by evapotranspiration, and subsurface flows into and out of northern Utah Valley from Cedar Valley and to Salt Lake Valley, respectively. The transient-state simulation was calibrated to measured water levels and water-level changes with consideration given to annual changes in the flows listed above.

Drainage effects on the transient, near-surface hydrologic response of a steep hillslope to rainfall: Implications for slope stability, Edmonds, Washington, USA

USGS Publications Warehouse

Biavati, G.; Godt, J.W.; McKenna, J.P.

2006-01-01

Shallow landslides on steep (>25??) hillsides along Puget Sound have resulted in occasional loss of life and costly damage to property during intense or prolonged rainfall. As part of a larger project to assess landslide hazards in the Seattle area, the U.S. Geological Survey instrumented two coastal bluff sites in 2001 to observe the subsurface hydrologic response to rainfall. The instrumentation at one of these sites, near Edmonds, Washington, consists of two rain gauges, two water-content probes that measure volumetric water content at eight depths between 0.2 and 2.0 m, and two tensiometer nests that measure soil-water suction at six depths ranging from 0.2 to 1.5m. Measurements from these instruments are used to test one- and two-dimensional numerical models of infiltration and groundwater flow. Capillary-rise tests, performed in the laboratory on soil sample from the Edmonds site, are used to define the soil hydraulic properties for the wetting process. The field observations of water content and suction show an apparent effect of porosity variation with depth on the hydraulic response to rainfall. Using a range of physical properties consistent with our laboratory and field measurements, we perform sensitivity analyses to investigate the effects of variation in physical and hydraulic properties of the soil on rainfall infiltration, pore-pressure response, and, hence, slope stability. For a two-layer-system in which the hydraulic conductivity of the upper layer is at least 10 times greater than the conductivity of the lower layer, and the infiltration rate is greater than the conductivity of the lower layer, a perched water table forms above the layer boundary potentially destabilizing the upper layer of soil. Two-dimensional modeling results indicate that the addition of a simple trench drain to the same two-layer slope has differing effects on the hydraulic response depending on the initial pressure head conditions. For slope-parallel flow conditions, pressure head is significantly reduced near the drain; however, for transient, vertical infiltration in a partially saturated soil, conditions consistent with those observed during monitoring at the Edmonds site, the drain decreases the thickness of a perched water table by a small amount.

Water movement and isoproturon behaviour in a drained heavy clay soil: 1. Preferential flow processes

NASA Astrophysics Data System (ADS)

Haria, A. H.; Johnson, A. C.; Bell, J. P.; Batchelor, C. H.

1994-12-01

The processes and mechanisms that control pesticide transport from drained heavy clay catchments are being studied at Wytham Farm (Oxford University) in southern England. In the first field season field-drain water contained high concentrations of pesticide. Soil studies demonstrated that the main mechanism for pesticide translocation was by preferential flow processes, both over the soil surface and through the soil profile via a macropore system that effectively by-passed the soil matrix. This macropore system included worm holes, shrinkage cracks and cracks resulting from ploughing. Rainfall events in early winter rapidly created a layer of saturation in the A horizon perched above a B horizon of very low hydraulic conductivity. Drain flow was initiated when the saturated layer in the A horizon extended into the upper 0.06m of the soil profile; thereafter water moved down slope via horizontal macropores possibly through a band of incorporated straw residues. These horizontal pathways for water movement connected with the fracture system of the mole drains, thus feeding the drains. Overland flow occurred infrequently during the season.

Ground Penetrating Radar Investigation of Sinter Deposits at Old Faithful Geyser and Immediately Adjacent Hydrothermal Features, Yellowstone National Park, Wyoming, USA

NASA Astrophysics Data System (ADS)

Foley, D.; Lynne, B. Y.; Jaworowski, C.; Heasler, H.; Smith, G.; Smith, I.

2015-12-01

Ground Penetrating Radar (GPR) was used to evaluate the characteristics of the shallow subsurface siliceous sinter deposits around Old Faithful Geyser. Zones of fractures, areas of subsurface alteration and pre-eruption hydrologic changes at Old Faithful Geyser and surrounding hydrothermal mounds were observed. Despite being viewed directly by about 3,000,000 people a year, shallow subsurface geologic and hydrologic conditions on and near Old Faithful Geyser are poorly characterized. GPR transects of 5754 ft (1754m) show strong horizontal to sub-horizontal reflections, which are interpreted as 2.5 to 4.5 meters of sinter. Some discontinuities in reflections are interpreted as fractures in the sinter, some of which line up with known hydrothermal features and some of which have little to no surface expression. Zones with moderate and weak amplitude reflections are interpreted as sinter that has been hydrothermally altered. Temporal changes from stronger to weaker reflections are correlated with the eruption cycle of Old Faithful Geyser, and are interpreted as post-eruption draining of shallow fractures, followed by pre-eruption fracture filling with liquid or vapor thermal fluids.

Subsurface transport of orthophosphate in five agricultural watersheds, USA

USGS Publications Warehouse

Domagalski, Joseph L.; Johnson, Henry M.

2011-01-01

Concentrations of dissolved orthophosphate (ortho P) in the unsaturated zone, groundwater, tile drains, and groundwater/stream water interfaces were assessed in five agricultural watersheds to determine the potential for subsurface transport. Concentrations of iron oxides were measured in the aquifer material and adsorption of ortho P on oxide surfaces was assessed by geochemical modeling. Attenuation of ortho P in these aquifers was attributed primarily to sorption onto iron oxides, and in one location onto clay minerals. Only one location showed a clear indication of phosphorus transport to a stream from groundwater discharge, although groundwater did contribute to the stream load elsewhere. Subsurface ortho P movement at a site in California resulted in a plume down gradient from orchards, which was attenuated by a 200 m thick riparian zone with natural vegetation. Iron oxides had an effect on phosphorus movement and concentrations at all locations, and groundwater chemistry, especially pH, exerted a major control on the amount of phosphorus adsorbed. Groundwater pH at a site in Maryland was below 5 and that resulted in complete sequestration of phosphorus and no movement toward the stream. Geochemical modeling indicated that as the surfaces approached saturation, groundwater concentrations of ortho P rise rapidly.

Evaluation on the Efficiency of Subsurface Drainage in Chiu-Fen Landslide at Northern Taiwan

NASA Astrophysics Data System (ADS)

Ying, L. Y.; Lin, D. G.

2015-12-01

For administrative district, the Chiu-Fen landslide is situated at northern Taiwan and comes within the jurisdiction of Ruei-Fang district, New Taipei City Government. Chiu-Fen village is a famous spot for sightseeing and tourism in Southeast Asia. In the last decade, for economic purpose, a vast area of slope land in Chiu-Fen area was reclaimed into business and commercial districts. However, due to the complicated geological and hydrological conditions, improper reclamation, and lack of appropriate soil and water conservation facilities, large scale landslides are frequently triggered by typhoon rainfall and causes damages to the transportation and residential building in the community. As a consequence, the government initiated a comprehensive field investigations and remediation plans to stabilize the landslide from 1997 and the remediation works were concentrated on subsurface drainages, namely the application of drainage well (a vertical shaft with multi-level horizontal drainage boreholes). To investigate the efficiency of drainage wells on the landslide, the A1-profile in the landslide which covers the drainage wells W2 and W4 was selected for a series of rainfall seepage and slope stability analyses. In addition, a 48-hrs design rainfall with return period of 25, 50 and 100 years based on the local meteorological data bank was adopted for the analyses. The numerical results indicate the factor safety FS of the three potential sliding surfaces within A1-profile are constantly keeping greater than one (FS > 1.0) and without decreasing with the elapsed time during rainfall. This implies that the subsurface drainage works can drain off the infiltrated rainwater from a high intensity and long duration rainfall and preserve the slope stability of landslides from deterioration. Finally, the efficiency of the drainage wells can be evaluated quantitatively in terms of the time-dependent factor of safety and the pore water pressure distribution on several potential sliding surfaces.

Development and validation of a runoff and erosion model for lowland drained catchments

NASA Astrophysics Data System (ADS)

Grangeon, Thomas; Cerdan, Olivier; Vandromme, Rosalie; Landemaine, Valentin; Manière, Louis; Salvador-Blanes, Sébastien; Foucher, Anthony; Evrard, Olivier

2017-04-01

Modelling water and sediment transfer in lowland catchments is complex as both hortonian and saturation excess-flow occur in these environments. Moreover, their dynamics was complexified by the installation of tile drainage networks or stream redesign. To the best of our knowledge, few models are able to simulate saturation runoff as well as hortonian runoff in tile-drained catchments. Most of the time, they are used for small scale applications due to their high degree of complexity. In this context, a model of intermediate complexity was developed to simulate the hydrological and erosion processes at the catchment scale in lowland environments. This GIS-based, spatially distributed and lumped model at the event scale uses a theoretical hydrograph to approximate within-event temporal variations. It comprises two layers used to represent surface and subsurface transfers. Observations of soil surface characteristics (i.e. vegetation density, soil crusting and roughness) were used to document spatial variations of physical soil characteristics (e.g. infiltration capacity). Flow was routed depending on the local slope, using LIDAR elevation data. Both the diffuse and the gully erosion are explicitly described. The model ability to simulate water and sediment dynamics at the catchment scale was evaluated using the monitoring of a selection of flood events in a small, extensively cultivated catchment (the Louroux catchment, Loire River basin, central France; 25 km2). In this catchment, five monitoring stations were equipped with water level sensors, turbidity probes, and automatic samplers. Discharge and suspended sediment concentration were deduced from field measurements. One station was installed at the outlet of a tile drain and was used to parameterize fluxes supplied by the drainage network. The selected floods were representative of various rainfall and soil surface conditions (e.g. low-intensity rainfall occurring on saturated soils as well as intense rainfall occurring on dry soils in spring). The model was able to reproduce the runoff volumes for these different situations, and performed well, especially in winter (the relationship between observed and modeled values has R2=0.72) when most of the sediment are transferred. Therefore, future work will evaluate the model ability to reproduce the erosion and sediment dynamics in this catchment in order to provide a tool for sediment management in these lowland environments draining agricultural land where river siltation is problematic.

A Combined Study of Photospheric Magnetic and Current Helicities and Subsurface Kinetic Helicities of Solar Active Regions during 2006-2013

NASA Astrophysics Data System (ADS)

Seligman, D.; Petrie, G. J. D.; Komm, R.

2014-11-01

We compare the average photospheric current helicity Hc , photospheric twist parameter α (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity Hk for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetograms, and the corresponding subsurface fluid velocity data derived from GONG (2006-2012) and Helioseismic and Magnetic Imager (2010-2013) dopplergrams. We find a significant hemispheric bias in all three parameters. The subsurface kinetic helicity is preferentially positive in the southern hemisphere and negative in the northern hemisphere. The photospheric current helicity and the α parameter have the same bias for strong fields (|B| > 1000 G) and no significant bias for weak fields (100 G <|B| < 500 G). We find no significant region-by-region correlation between the subsurface kinetic helicity and either the strong-field current helicity or α. Subsurface fluid motions of a given handedness correspond to photospheric helicities of both signs in approximately equal numbers. However, common variations appear in annual averages of these quantities over all regions. Furthermore, in a subset of 77 regions, we find significant correlations between the temporal profiles of the subsurface and photospheric helicities. In these cases, the sign of the linear correlation coefficient matches the sign relationship between the helicities, indicating that the photospheric magnetic field twist is sensitive to the twisting motions below the surface.

Importance of solar subsurface heating in ocean general circulation models

NASA Astrophysics Data System (ADS)

Rochford, Peter A.; Kara, A. Birol; Wallcraft, Alan J.; Arnone, Robert A.

2001-12-01

The importance of subsurface heating on surface mixed layer properties in an ocean general circulation model (OGCM) is examined using attenuation of solar irradiance with depth below the ocean surface. The depth-dependent attenuation of subsurface heating is given by global monthly mean fields for the attenuation of photosynthetically available radiation (PAR), kPAR. These global fields of kPAR are derived from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data on the spectral diffuse attenuation coefficient at 490 nm (k490), and have been processed to have the smoothly varying and continuous coverage necessary for use in OGCM applications. These monthly fields provide the first complete global data sets of subsurface optical fields that can be used for OGCM applications of subsurface heating and bio-optical processes. The effect on global OGCM prediction of sea surface temperature (SST) and surface mixed layer depth (MLD) is examined when solar heating, as given by monthly mean kPAR and PAR fields, is included in the model. It is found that subsurface heating yields a marked increase in the SST predictive skill of the OGCM at low latitudes. No significant improvement in MLD predictive skill is obtained when including subsurface heating. Use of the monthly mean kPAR produces an SST decrease of up to 0.8°C and a MLD increase of up to only 4-5 m for climatological surface forcing, with this primarily confined to the equatorial regions. Remarkably, a constant kPAR value of 0.06 m-1, which is indicative of optically clear open ocean conditions, is found to serve very well for OGCM prediction of SST and MLD over most of the global ocean.

Remaining Sites Verification Package for the 331 Life Sciences Laboratory Drain Field Septic System, Waste Site Reclassification Form 2008-020

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. M. Capron

2008-10-16

The 331 Life Sciences Laboratory Drain Field (LSLDF) septic system waste site consists of a diversion chamber, two septic tanks, a distribution box, and a drain field. This septic system was designed to receive sanitary waste water, from animal studies conducted in the 331-A and 331-B Buildings, for discharge into the soil column. However, field observations and testing suggest the 331 LSLDF septic system did not receive any discharges. In accordance with this evaluation, the confirmatory sampling results support a reclassification of the 331 LSLDF waste site to No Action. This site does not have a deep zone or othermore » condition that would warrant an institutional control in accordance with the 300-FF-2 ROD under the industrial land use scenario.« less

Development and testing of watershed-scale models for poorly drained soils

Treesearch

Glenn P. Fernandez; George M. Chescheir; R. Wayne Skaggs; Devendra M. Amatya

2005-01-01

Watershed-scale hydrology and water quality models were used to evaluate the crrmulative impacts of land use and management practices on dowrzstream hydrology and nitrogen loading of poorly drained watersheds. Field-scale hydrology and nutrient dyyrutmics are predicted by DRAINMOD in both models. In the first model (DRAINMOD-DUFLOW), field-scale predictions are coupled...

Isotopic evidence of nitrate sources and denitrification in the Mississippi River, Illinois

USGS Publications Warehouse

Panno, S.V.; Hackley, Keith C.; Kelly, W.R.; Hwang, H.-H.

2006-01-01

Anthropogenic nitrate (NO3-) within the Mississippi-Atchafalaya River basin and discharge to the Gulf of Mexico has been linked to serious environmental problems. The sources of this NO 3- have been estimated by others using mass balance methods; however, there is considerable uncertainty in these estimates. Part of the uncertainty is the degree of denitrification that the NO3- has undergone. The isotopic composition of NO3- in the Mississippi River adjacent to Illinois and tile drain (subsurface drain) discharge in agricultural areas of east-central Illinois was examined using N and O isotopes to help identify the major sources of NO 3- and assess the degree of denitrification in the samples. The isotopic evidence suggests that most of the NO3- in the river is primarily derived from synthetic fertilizers and soil organic N, which is consistent with published estimates of N inputs to the Mississippi River. The 1:2 relationship between ??18O and ??15N also indicate that, depending on sample location and season, NO3- in the river and tile drains lias undergone significant denitrification, ranging from about 0 to 55%. The majority of the denitrification appears to have occurred before discharge into the Mississippi River. ?? ASA, CSSA, SSSA.

Potential for Nitrogen Fixation and Nitrification in the Granite-Hosted Subsurface at Henderson Mine, CO

PubMed Central

Swanner, Elizabeth D.; Templeton, Alexis S.

2011-01-01

The existence of life in the deep terrestrial subsurface is established, yet few studies have investigated the origin of nitrogen that supports deep life. Previously, 16S rRNA gene surveys cataloged a diverse microbial community in subsurface fluids draining from boreholes 3000 feet deep at Henderson Mine, CO, USA (Sahl et al., 2008). The prior characterization of the fluid chemistry and microbial community forms the basis for the further investigation here of the source of NH4+. The reported fluid chemistry included N2, NH4+ (5–112 μM), NO2− (27–48 μM), and NO3− (17–72 μM). In this study, the correlation between low NH4+ concentrations in dominantly meteoric fluids and higher NH4+ in rock-reacted fluids is used to hypothesize that NH4+ is sourced from NH4+-bearing biotite. However, biotite samples from the host rocks and ore-body minerals were analyzed by Fourier transform infrared (FTIR) microscopy and none-contained NH4+. However, the nitrogenase-encoding gene nifH was successfully amplified from DNA of the fluid sample with high NH4+, suggesting that subsurface microbes have the capability to fix N2. If so, unregulated nitrogen fixation may account for the relatively high NH4+ concentrations in the fluids. Additionally, the amoA and nxrB genes for archaeal ammonium monooxygenase and nitrite oxidoreductase, respectively, were amplified from the high NH4+ fluid DNA, while bacterial amoA genes were not. Putative nitrifying organisms are closely related to ammonium-oxidizing Crenarchaeota and nitrite-oxidizing Nitrospira detected in other subsurface sites based upon 16S rRNA sequence analysis. Thermodynamic calculations underscore the importance of NH4+ as an energy source in a subsurface nitrification pathway. These results suggest that the subsurface microbial community at Henderson is adapted to the low nutrient and energy environment by their capability of fixing nitrogen, and that fixed nitrogen may support subsurface biomass via nitrification. PMID:22190904

Controlling the ambipolarity and improvement of RF performance using Gaussian Drain Doped TFET

NASA Astrophysics Data System (ADS)

Nigam, Kaushal; Gupta, Sarthak; Pandey, Sunil; Kondekar, P. N.; Sharma, Dheeraj

2018-05-01

Ambipolar conduction in tunnel field-effect transistors (TFETs) has been occurred as an inherent issue due to drain-channel tunneling. It makes TFET less efficient and restricts its application in complementary digital circuits. Therefore, this manuscript reports the application of Gaussian doping profile on nanometer regime silicon channel TFETs to completely eliminate the ambipolarity. For this, Gaussian doping is used in the drain region of conventional gate-drain overlap TFET to control the tunneling of electrons from the valence band of channel to the conduction band of drain. As a result, barrier width at the drain/channel junction increases significantly leading to the suppression of an ambipolar current even when higher doping concentration (1 ? 10 ? cm ?) is considered in the drain region. However, significant improvement in terms of RF figure-of-merits such as cut-off frequency (f ?), gain bandwidth product (GBW), and gate-to-drain capacitance (C ?) is achieved with Gaussian doped gate on drain overlap TFET as compared to its counterpart TFET.

Gummel Symmetry Test on charge based drain current expression using modified first-order hyperbolic velocity-field expression

NASA Astrophysics Data System (ADS)

Singh, Kirmender; Bhattacharyya, A. B.

2017-03-01

Gummel Symmetry Test (GST) has been a benchmark industry standard for MOSFET models and is considered as one of important tests by the modeling community. BSIM4 MOSFET model fails to pass GST as the drain current equation is not symmetrical because drain and source potentials are not referenced to bulk. BSIM6 MOSFET model overcomes this limitation by taking all terminal biases with reference to bulk and using proper velocity saturation (v -E) model. The drain current equation in BSIM6 is charge based and continuous in all regions of operation. It, however, adopts a complicated method to compute source and drain charges. In this work we propose to use conventional charge based method formulated by Enz for obtaining simpler analytical drain current expression that passes GST. For this purpose we adopt two steps: (i) In the first step we use a modified first-order hyperbolic v -E model with adjustable coefficients which is integrable, simple and accurate, and (ii) In the second we use a multiplying factor in the modified first-order hyperbolic v -E expression to obtain correct monotonic asymptotic behavior around the origin of lateral electric field. This factor is of empirical form, which is a function of drain voltage (vd) and source voltage (vs) . After considering both the above steps we obtain drain current expression whose accuracy is similar to that obtained from second-order hyperbolic v -E model. In modified first-order hyperbolic v -E expression if vd and vs is replaced by smoothing functions for the effective drain voltage (vdeff) and effective source voltage (vseff), it will as well take care of discontinuity between linear to saturation regions of operation. The condition of symmetry is shown to be satisfied by drain current and its higher order derivatives, as both of them are odd functions and their even order derivatives smoothly pass through the origin. In strong inversion region and technology node of 22 nm the GST is shown to pass till sixth-order derivative and for weak inversion it is shown till fifth-order derivative. In the expression of drain current major short channel phenomena like vertical field mobility reduction, velocity saturation and velocity overshoot have been taken into consideration.

Near-Field Resonance Microwave Tomography and Holography

NASA Astrophysics Data System (ADS)

Gaikovich, K. P.; Smirnov, A. I.; Yanin, D. V.

2018-02-01

We develop the methods of electromagnetic computer near-field microwave tomography of distributed subsurface inhomogeneities of complex dielectric permittivity and of holography (shape retrieval) of internally homogeneous subsurface objects. The methods are based on the solution of the near-field inverse scattering problem from measurements of the resonance-parameter variations of microwave probes above the medium surface. The capabilities of the proposed diagnostic technique are demonstrated in the numerical simulation for sensors with a cylindrical capacitor as a probe element, the edge capacitance of which is sensitive to subsurface inhomogeneities.

Simulating Sustainable P Management Practices in Tile-Drained Landscapes of Central Ohio Using the Agricultural Policy Environmental Extender (APEX)

NASA Astrophysics Data System (ADS)

Ford, W. I., III; King, K.; Williams, M.

2014-12-01

Despite extensive application of conservation practices to minimize sediment P delivery to streams, hypoxic conditions and harmful algal blooms persist in receiving water bodies. Tile-drainage networks are a focal point for reducing soluble P in the food-producing Midwestern United States in that they promote higher connectivity between upland soils and stream channels which decreases soil contact time, and biogeochemical alterations. A critical next step to reduce the environmental impact and maintain sustainable agriculture is to implement best management practices (BMPs) under a holistic framework that considers adverse effects to water resources and crop production, while maintaining economic feasibility. The objective of this study was to apply a robust numerical model, the Agricultural Policy Environmental Extender (APEX), in a tile-drained landscape in Central Ohio in order to evaluate the effectiveness of a suite of BMPs on soluble and particulate P delivery to stream channels. The model was applied and evaluated at two adjacent edge-of-field sites with similar soil, topographic and management characteristics (except for tillage and tile installation on the south field in 2012, preceded by more than 20 years of no-till operations). Three years of daily discharge, total suspended solids, soluble P, soluble N (NO3 and NH4), total P, total N, and crop yields were utilized to verify the model performance. Prevalent BMPs simulated within the modeling framework included drainage water management, tillage and crop rotations, the 4Rs framework (right fertilizer source, rate, time, and placement), and bioreactors. Results of the study quantify the ability of the numerical model to simulate hydrology and P transport for surface runoff and subsurface tile drainage and highlight modifications that improve model performance. Further, results highlight BMPs that effectively reduce P loads to streams while maintaining crop yields, which can later be used to inform BMPs implemented at edge-of-field sites in Ohio. While beyond the scope of this study, future work aims to investigate the sustainability of BMPs under dynamic climate conditions and across watershed gradients.

Capacitorless one-transistor dynamic random-access memory based on asymmetric double-gate Ge/GaAs-heterojunction tunneling field-effect transistor with n-doped boosting layer and drain-underlap structure

NASA Astrophysics Data System (ADS)

Yoon, Young Jun; Seo, Jae Hwa; Kang, In Man

2018-04-01

In this work, we present a capacitorless one-transistor dynamic random-access memory (1T-DRAM) based on an asymmetric double-gate Ge/GaAs-heterojunction tunneling field-effect transistor (TFET) for DRAM applications. The n-doped boosting layer and gate2 drain-underlap structure is employed in the device to obtain an excellent 1T-DRAM performance. The n-doped layer inserted between the source and channel regions improves the sensing margin because of a high rate of increase in the band-to-band tunneling (BTBT) probability. Furthermore, because the gate2 drain-underlap structure reduces the recombination rate that occurs between the gate2 and drain regions, a device with a gate2 drain-underlap length (L G2_D-underlap) of 10 nm exhibited a longer retention performance. As a result, by applying the n-doped layer and gate2 drain-underlap structure, the proposed device exhibited not only a high sensing margin of 1.11 µA/µm but also a long retention time of greater than 100 ms at a temperature of 358 K (85 °C).

Hydrogeologic controls on nitrate transport in a small agricultural catchment, Iowa

USGS Publications Warehouse

Schilling, K.E.; Tomer, M.D.; Zhang, Y.-K.; Weisbrod, T.; Jacobson, P.; Cambardella, C.A.

2007-01-01

Effects of subsurface deposits on nitrate loss in stream riparian zones are recognized, but little attention has been focused on similar processes occurring in upland agricultural settings. In this paper, we evaluated hydrogeologic controls on nitrate transport processes occurring in a small 7.6 ha Iowa catchment. Subsurface deposits in the catchment consisted of upland areas of loess overlying weathered pre-Illinoian till, drained by two ephemeral drainageways that consisted of Holocene-age silty and organic rich alluvium. Water tables in upland areas fluctuated more than 4 m per year compared to less than 0.3 m in the drainageway. Water quality patterns showed a distinct spatial pattern, with groundwater in the drainageways having lower nitrate concentrations (10 mg L-1) as wells as lower pH, dissolved oxygen and redox, and higher ammonium and dissolved organic carbon levels. Several lines of evidence suggested that conditions are conducive for denitrification of groundwater flowing from uplands through the drainageways. Field-measured nitrate decay rates in the drainageways (???0.02 day-1) were consistent with other laboratory studies and regional patterns. Results from MODFLOW and MT3DMS simulations indicated that soils in the ephemeral drainageways could process all upland groundwater nitrate flowing through them. However, model-simulated tile drainage increased both water flux and nitrate loss from the upland catchment. Study results suggest that ephemeral drainageways can provide a natural nitrate treatment system in our upland glaciated catchments, offering management opportunities to reduce nitrate delivery to streams. Copyright 2007 by the American Geophysical Union.

Inferring changes in water cycle dynamics of intensively managed landscapes via the theory of time-variant travel time distributions

NASA Astrophysics Data System (ADS)

Danesh-Yazdi, Mohammad; Foufoula-Georgiou, Efi; Karwan, Diana L.; Botter, Gianluca

2016-10-01

Climatic trends and anthropogenic changes in land cover and land use are impacting the hydrology and water quality of streams at the field, watershed, and regional scales in complex ways. In poorly drained agricultural landscapes, subsurface drainage systems have been successful in increasing crop productivity by removing excess soil moisture. However, their hydroecological consequences are still debated in view of the observed increased concentrations of nitrate, phosphorus, and pesticides in many streams, as well as altered runoff volumes and timing. In this study, we employ the recently developed theory of time-variant travel time distributions within the StorAge Selection function framework to quantify changes in water cycle dynamics resulting from the combined climate and land use changes. Our results from analysis of a subbasin in the Minnesota River Basin indicate a significant decrease in the mean travel time of water in the shallow subsurface layer during the growing season under current conditions compared to the pre-1970s conditions. We also find highly damped year-to-year fluctuations in the mean travel time, which we attribute to the "homogenization" of the hydrologic response due to artificial drainage. The dependence of the mean travel time on the spatial heterogeneity of some soil characteristics as well as on the basin scale is further explored via numerical experiments. Simulations indicate that the mean travel time is independent of scale for spatial scales larger than approximately 200 km2, suggesting that hydrologic data from larger basins may be used to infer the average of smaller-scale-driven changes in water cycle dynamics.

Modeling of Metal-Ferroelectric-Semiconductor Field Effect Transistors

NASA Technical Reports Server (NTRS)

Duen Ho, Fat; Macleod, Todd C.

1998-01-01

The characteristics for a MFSFET (metal-ferroelectric-semiconductor field effect transistor) is very different than a conventional MOSFET and must be modeled differently. The drain current has a hysteresis shape with respect to the gate voltage. The position along the hysteresis curve is dependent on the last positive or negative polling of the ferroelectric material. The drain current also has a logarithmic decay after the last polling. A model has been developed to describe the MFSFET drain current for both gate voltage on and gate voltage off conditions. This model takes into account the hysteresis nature of the MFSFET and the time dependent decay. The model is based on the shape of the Fermi-Dirac function which has been modified to describe the MFSFET's drain current. This is different from the model proposed by Chen et. al. and that by Wu.

Ensemble Monte Carlo particle investigation of hot electron induced source-drain burnout characteristics of GaAs field-effect transistors

NASA Astrophysics Data System (ADS)

Moglestue, C.; Buot, F. A.; Anderson, W. T.

1995-08-01

The lattice heating rate has been calculated for GaAs field-effect transistors of different source-drain channel design by means of the ensemble Monte Carlo particle model. Transport of carriers in the substrate and the presence of free surface charges are also included in our simulation. The actual heat generation was obtained by accounting for the energy exchanged with the lattice of the semiconductor during phonon scattering. It was found that the maximum heating rate takes place below the surface near the drain end of the gate. The results correlate well with a previous hydrodynamic energy transport estimate of the electronic energy density, but shifted slightly more towards the drain. These results further emphasize the adverse effects of hot electrons on the Ohmic contacts.

Watershed Models for Predicting Nitrogen Loads from Artificially Drained Lands

Treesearch

R. Wayne Skaggs; George M. Chescheir; Glenn Fernandez; Devendra M. Amatya

2003-01-01

Non-point sources of pollutants originate at the field scale but water quality problems usually occur at the watershed or basin scale. This paper describes a series of models developed for poorly drained watersheds. The models use DRAINMOD to predict hydrology at the field scale and a range of methods to predict channel hydraulics and nitrogen transport. In-stream...

A combined study of photospheric magnetic and current helicities and subsurface kinetic helicities of solar active regions during 2006-2013

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seligman, D.; Petrie, G. J. D.; Komm, R.

2014-11-10

We compare the average photospheric current helicity H{sub c} , photospheric twist parameter α (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity H{sub k} for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetograms, and the corresponding subsurface fluid velocity data derived from GONG (2006-2012) and Helioseismic and Magnetic Imager (2010-2013) dopplergrams. We find a significant hemispheric bias in all three parameters. The subsurface kinetic helicity is preferentially positive in the southern hemisphere and negative in the northern hemisphere. The photospheric current helicity and the α parameter have the same biasmore » for strong fields (|B| > 1000 G) and no significant bias for weak fields (100 G <|B| < 500 G). We find no significant region-by-region correlation between the subsurface kinetic helicity and either the strong-field current helicity or α. Subsurface fluid motions of a given handedness correspond to photospheric helicities of both signs in approximately equal numbers. However, common variations appear in annual averages of these quantities over all regions. Furthermore, in a subset of 77 regions, we find significant correlations between the temporal profiles of the subsurface and photospheric helicities. In these cases, the sign of the linear correlation coefficient matches the sign relationship between the helicities, indicating that the photospheric magnetic field twist is sensitive to the twisting motions below the surface.« less

Current conduction in junction gate field effect transistors. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Kim, C.

1970-01-01

The internal physical mechanism that governs the current conduction in junction-gate field effect transistors is studied. A numerical method of analyzing the devices with different length-to-width ratios and doping profiles is developed. This method takes into account the two dimensional character of the electric field and the field dependent mobility. Application of the method to various device models shows that the channel width and the carrier concentration in the conductive channel decrease with increasing drain-to-source voltage for conventional devices. It also shows larger differential drain conductances for shorter devices when the drift velocity is not saturated. The interaction of the source and the drain gives the carrier accumulation in the channel which leads to the space-charge-limited current flow. The important parameters for the space-charge-limited current flow are found to be the L/L sub DE ratio and the crossover voltage.

Impact of source height on the characteristic of U-shaped channel tunnel field-effect transistor

NASA Astrophysics Data System (ADS)

Yang, Zhaonian; Zhang, Yue; Yang, Yuan; Yu, Ningmei

2017-11-01

Tunnel field-effect transistor (TFET) is very attractive in replacing a MOSFET, particularly for low-power nanoelectronic circuits. The U-shaped channel TFET (U-TFET) was proposed to improve the drain-source current with a reduced footprint. In this work, the impact of the source height (HS) on the characteristic of the U-shaped channel tunnel field-effect transistor (U-TFET) is investigated by using TCAD simulation. It is found that with a fixed gate height (HG) the drain-source current has a negative correlation with HS. This is because when the gate region is deeper than the source region, the electric field near the corner of the tunneling junction can be enhanced and the tunneling rate is increased. When HS becomes very thin, the drain-source current is limited by the source region volume. The U-TFET with an n+ pocket is also studied and the same trend is observed.

Denitrification in the shallow ground water of a tile-drained, agricultural watershed

USGS Publications Warehouse

Mehnert, E.; Hwang, H.-H.; Johnson, T.M.; Sanford, R.A.; Beaumont, W.C.; Holm, T.R.

2007-01-01

Nonpoint-source pollution of surface water by N is considered a major cause of hypoxia. Because Corn Belt watersheds have been identified as major sources of N in the Mississippi River basin, the fate and transport of N from midwestern agricultural watersheds have received considerable interest. The fate and transport of N in the shallow ground water of these watersheds still needs additional research. Our purpose was to estimate denitrification in the shallow ground water of a tile-drained, Corn Belt watershed with fine-grained soils. Over a 3-yr period, N was monitored in the surface and ground water of an agricultural watershed in central Illinois. A significant amount of N was transported past the tile drains and into shallow ground water. The ground water nitrate was isotopically heavier than tile drain nitrate, which can be explained by denitrification in the subsurface. Denitrifying bacteria were found at depths to 10 m throughout the watershed. Laboratory and push-pull tests showed that a significant fraction of nitrate could be denitrified rapidly. We estimated that the N denitrified in shallow ground water was equivalent to 0.3 to 6.4% of the applied N or 9 to 27% of N exported via surface water. These estimates varied by water year and peaked in a year of normal precipitation after 2 yr of below average precipitation. Three years of monitoring data indicate that shallow ground water in watersheds with fine-grained soils may be a significant N sink compared with N exported via surface water. ?? ASA, CSSA, SSSA.

A method for subsurface-banding poultry litter in plots not accessible with conventional field equipment

USDA-ARS?s Scientific Manuscript database

Subsurface band application of poultry litter has been shown to be effective in reducing nutrients in runoff and leachate, relative to surface broadcast application of litter. Some field plot arrangements, such as plots having adjacent pits in the soil, prevent the use of conventional field equipme...

Structural tuning of nanogaps using electromigration induced by field emission current with bipolar biasing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagi, Mamiko; Ito, Mitsuki; Shirakashi, Jun-ichi, E-mail: shrakash@cc.tuat.ac.jp

We report a new method for fabrication of Ni nanogaps based on electromigration induced by a field emission current. This method is called “activation” and is demonstrated here using a current source with alternately reversing polarities. The activation procedure with alternating current bias, in which the current source polarity alternates between positive and negative bias conditions, is performed with planar Ni nanogaps defined on SiO{sub 2}/Si substrates at room temperature. During negative biasing, a Fowler-Nordheim field emission current flows from the source (cathode) to the drain (anode) electrode. The Ni atoms at the tip of the drain electrode are thusmore » activated and then migrate across the gap from the drain to the source electrode. In contrast, in the positive bias case, the field emission current moves the activated atoms from the source to the drain electrode. These two procedures are repeated until the tunnel resistance of the nanogaps is successively reduced from 100 TΩ to 48 kΩ. Scanning electron microscopy and atomic force microscopy studies showed that the gap separation narrowed from approximately 95 nm to less than 10 nm because of the Ni atoms that accumulated at the tips of both the source and drain electrodes. These results show that the alternately biased activation process, which is a newly proposed atom transfer technique, can successfully control the tunnel resistance of the Ni nanogaps and is a suitable method for formation of ultrasmall nanogap structures.« less

Active Region Formation and Subsurface Structure

NASA Astrophysics Data System (ADS)

Stein, F.; Nordlund, Robert A.

2016-10-01

We present results from emerging magnetic flux simulations showing how several different active regions form and their very different subsurface structures. The simulations assumed an infinite sheet of uniform, untwisted, horizontal field advected into the computational domain by inflows at a depth of 20 Mm. Results from two different horizontal field strengths, 1 and 5 kG, will be presented. Convective up and down flows buckle the horizontal field into Omega and U loops. Upflows and magnetic buoyancy carry the field toward the surface, while fast downflows pin down the field. Small (granular) convective motions, near the surface, shred the emerging field into fine filaments that emerge as the observed "pepper and salt" pattern. The large (supergranular) motions, at depth, keep the overall loop structure intact, so that as the overall omega-loop emerges through the surface the opposite polarity fields counter-stream into large unipolar flux concentrations producing first pores which then coalesce into spots. These tend to be located over the supergranular downflow lanes near the bottom of the domain. The pores and spots exhibit a great variety of subsurface field structures - from monolithic but twisted bundles to intertwined separate spaghetti sturctures. We will show movies of the surface evolution of the field and emergent continuum intensity and of the subsurface evolution of the magnetic field lines.

The impact of urbanization on subsurface flow paths - A paired-catchment isotopic study

NASA Astrophysics Data System (ADS)

Bonneau, Jeremie; Burns, Matthew J.; Fletcher, Tim D.; Witt, Roman; Drysdale, Russell N.; Costelloe, Justin F.

2018-06-01

Urbanization disturbs groundwater flow through the sealing of native soils with impervious surfaces and through modifications to the subsoil by constructed drainage and other infrastructure (trenches and excavations, e.g. water supply). The impact of these disturbances on groundwater contributions to urban streams (i.e. baseflow) is poorly understood. While high flows caused by impervious runoff to streams are a common focus of urban studies, the route taken by groundwater to become streamflow in urban landscapes is not generally considered. To assess the impact of urbanization on groundwater sources to streams, both rainfall and baseflow were sampled weekly for stable isotopes of water in two nearby streams-one draining a peri-urban catchment and the other draining a forested, natural catchment. In addition, to study the rate of groundwater discharge to the stream, monthly baseflow recession behavior was investigated. We found that baseflow in the forested catchment was constant in stable isotope values (δ18O = -5.73‰ ± 0.14‰) throughout the year. Monthly baseflow recession constants were close to 1 and had little variation (ranging 0.951-0.992), indicating a well-mixed groundwater store and long residence times. In contrast, the urban baseflow isotopic composition featured distinct seasonal variations (δ18O = -3.35‰ ± 1.20‰ from October to March and δ18O = -4.54‰ ± 0.43‰ from April to September) and high week-to-week variability in summer, reflecting a contribution of recent rainfall to baseflow. Recession constants were lower (ranging 0.727-0.955) with pronounced seasonal variations, suggesting shorter residence times and the likely presence of a variety of stores and pathways. These results provide evidence that the urban catchment has diversified groundwater pathways, and its groundwater storage is drained faster than that of the forested catchment. It highlights some of the subsurface hydrological consequences of urbanization. Restoring low-flow aspects of the flow regime through nature-mimicking stormwater management requires careful consideration of how the behavior of natural groundwater pathways can be restored or replicated using innovative stormwater control measures.

Effect of defect creation and migration on hump characteristics of a-InGaZnO thin film transistors under long-term drain bias stress with light illumination

NASA Astrophysics Data System (ADS)

Cho, Yong-Jung; Kim, Woo-Sic; Lee, Yeol-Hyeong; Park, Jeong Ki; Kim, Geon Tae; Kim, Ohyun

2018-06-01

We investigated the mechanism of formation of the hump that occurs in the current-voltage I-V characteristics of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) that are exposed to long-term drain bias stress under illumination. Transfer characteristics showed two-stage degradation under the stress. At the beginning of the stress, the I-V characteristics shifted in the negative direction with a degradation of subthreshold slope, but the hump phenomenon developed over time in the I-V characteristics. The development of the hump was related to creation of defects, especially ionized oxygen vacancies which act as shallow donor-like states near the conduction-band minimum in a-IGZO. To further investigate the hump phenomenon we measured a capacitance-voltage C-V curve and performed two-dimensional device simulation. Stretched-out C-V for the gate-to-drain capacitance and simulated electric field distribution which exhibited large electric field near the drain side of TFT indicated that VO2+ were generated near the drain side of TFT, but the hump was not induced when VO2+ only existed near the drain side. Therefore, the degradation behavior under DBITS occurred because VO2+ were created near the drain side, then were migrated to the source side of the TFT.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Dong-Suk; Kang, Yu-Jin; Park, Jae-Hyung

Highlights: • We developed and investigated source/drain electrodes in oxide TFTs. • The Mo S/D electrodes showed good output characteristics. • Intrinsic TFT parameters were calculated by the transmission line method. - Abstract: This paper investigates the feasibility of a low-resistivity electrode material (Mo) for source/drain (S/D) electrodes in thin film transistors (TFTs). The effective resistances between Mo source/drain electrodes and amorphous zinc–tin-oxide (a-ZTO) thin film transistors were studied. Intrinsic TFT parameters were calculated by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low source/drain voltage. The TFTs fabricated with Momore » source/drain electrodes showed good transfer characteristics with a field-effect mobility of 10.23 cm{sup 2}/V s. In spite of slight current crowding effects, the Mo source/drain electrodes showed good output characteristics with a steep rise in the low drain-to-source voltage (V{sub DS}) region.« less

Hot-Electron-Induced Device Degradation during Gate-Induced Drain Leakage Stress

NASA Astrophysics Data System (ADS)

Kim, Kwang-Soo; Han, Chang-Hoon; Lee, Jun-Ki; Kim, Dong-Soo; Kim, Hyong-Joon; Shin, Joong-Shik; Lee, Hea-Beoum; Choi, Byoung-Deog

2012-11-01

We studied the interface state generation and electron trapping by hot electrons under gate-induced drain leakage (GIDL) stress in p-type metal oxide semiconductor field-effect transistors (P-MOSFETs), which are used as the high-voltage core circuit of flash memory devices. When negative voltage was applied to a drain in the off-state, a GIDL current was generated, but when high voltage was applied to the drain, electrons had a high energy. The hot electrons produced the interface state and electron trapping. As a result, the threshold voltage shifted and the off-state leakage current (trap-assisted drain junction leakage current) increased. On the other hand, electron trapping mitigated the energy band bending near the drain and thus suppressed the GIDL current generation.

Short-term effects of salinity reduction and drainage on salt-marsh biogeochemical cycling and Spartina (Cordgrass) production

USGS Publications Warehouse

Portnoy, J.W.; Valiela, I.

1997-01-01

To assess the biogeochemical effects of tidal restrictions on salt-marsh sulfur cycling and plant growth, cores of short-form Spartina alterniflora peat were desalinated and kept either waterlogged or drained in greenhouse microcosms. Changes in net Spartina production, and porewater and solid phase chemistry of treated cores were compared to natural conditions in the field collection site over a 21-mo period. Net production among treatments increased significantly in drained and waterlogged peat compared to field conditions during the first growing season. Constantly high sulfide in waterlogged cores accompanied reduced plant growth. Aeration invigorated growth in drained cores but led to oxidization of sulfide minerals and to lowered pH. During the second growing season, growth declined in the drained treatment, probably because of acidification and decreased dissolved inorganic nitrogen. Results are pertinent to the success of current wetland protection and restoration activities in the coastal zone.

Effect of feeding strategies on pharmaceutical removal by subsurface flow constructed wetlands.

PubMed

Zhang, Dong Qing; Gersberg, Richard M; Hua, Tao; Zhu, Junfei; Nguyen, Anh Tuan; Law, Wing-Keung; Ng, Wun Jern; Tan, Soon Keat

2012-01-01

This study presents findings on an assessment of the effect of continuous and batch feeding strategies on the removal of selected pharmaceuticals from synthetic wastewater. Six mesocosm-scale constructed wetlands, including three horizontal subsurface flow constructed wetlands and three sand filters, were set up at the campus of Nanyang Technological University, Singapore. The findings showed that ibuprofen and diclofenac removal in the wetlands was significantly ( < 0.05) enhanced in the batch versus continuous mode. In contrast, naproxen and carbamazepine showed no significant differences ( > 0.05) in elimination under either feeding strategy. Our results also clearly showed that the presence of plants exerts a stimulatory effect on pharmaceutical removal for ibuprofen, diclofenac, and naproxen in batch and continuous mode. Estimation of the quantitative role of this stimulatory effect on pharmaceutical elimination of batch operation as compared with the effect of the presence of the higher plant alone showed that batch operation may account for 40 to 87% of the contribution conferred by the aquatic plant. The findings of this study imply that where maximal removal of pharmaceutical compounds is desired, periodic draining and filling might be the preferred operational strategy for full-scale, subsurface flow constructed wetlands. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Hydrology of Northern Utah Valley, Utah County, Utah, 1975-2005

USGS Publications Warehouse

Cederberg, Jay R.; Gardner, Philip M.; Thiros, Susan A.

2009-01-01

The ground-water resources of northern Utah Valley, Utah, were assessed during 2003-05 to describe and quantify components of the hydrologic system, determine a hydrologic budget for the basin-fill aquifer, and evaluate changes to the system relative to previous studies. Northern Utah Valley is a horst and graben structure with ground water occurring in both the mountain-block uplands surrounding the valley and in the unconsolidated basin-fill sediments. The principal aquifer in northern Utah Valley occurs in the unconsolidated basin-fill deposits where a deeper unconfined aquifer occurs near the mountain front and laterally grades into multiple confined aquifers near the center of the valley. Sources of water to the basin-fill aquifers occur predominantly as either infiltration of streamflow at or near the interface of the mountain front and valley or as subsurface inflow from the adjacent mountain blocks. Sources of water to the basin-fill aquifers were estimated to average 153,000 (+/- 31,500) acre-feet annually during 1975-2004 with subsurface inflow and infiltration of streamflow being the predominant sources. Discharge from the basin-fill aquifers occurs in the valley lowlands as flow to waterways, drains, ditches, springs, as diffuse seepage, and as discharge from flowing and pumping wells. Ground-water discharge from the basin-fill aquifers during 1975-2004 was estimated to average 166,700 (+/- 25,900) acre-feet/year where discharge to wells for consumptive use and discharge to waterways, drains, ditches, and springs were the principal sources. Measured water levels in wells in northern Utah Valley declined an average of 22 feet from 1981 to 2004. Water-level declines are consistent with a severe regional drought beginning in 1999 and continuing through 2004. Water samples were collected from 36 wells and springs throughout the study area along expected flowpaths. Water samples collected from 34 wells were analyzed for dissolved major ions, nutrients, and stable isotopes of hydrogen and oxygen. Water samples from all 36 wells were analyzed for dissolved-gas concentration including noble gases and tritium/helium-3. Within the basin fill, dissolved-solids concentration generally increases with distance along flowpaths from recharge areas, and shallower flowpaths tend to have higher concentrations than deeper flowpaths. Nitrate concentrations generally are at or below natural background levels. Dissolved-gas recharge temperature data support the conceptual model of the basin-fill aquifers and highlight complexities of recharge patterns in different parts of the valley. Dissolved-gas data indicate that the highest elevation recharge sources for the basin-fill aquifer are subsurface inflow derived from recharge in the adjacent mountain block between the mouths of American Fork and Provo Canyons. Apparent ground-water ages in the basin-fill aquifer, as calculated using tritium/helium-3 data, range from 2 to more than 50 years. The youngest waters in the valley occur near the mountain fronts with apparent ages generally increasing near the valley lowlands and discharge area around Utah Lake. Flowpaths are controlled by aquifer properties and the location of the predominant recharge sources, including subsurface inflow and recharge along the mountain front. Subsurface inflow is distributed over a larger area across the interface of the subsurface mountain block and basin-fill deposits. Subsurface inflow occurs at a depth deeper than that at which mountain-front recharge occurs. Recharge along the mountain front is often localized and focused over areas where streams and creeks enter the valley, and recharge is enhanced by the associated irrigation canals.

DESIGN OF A SURFACTANT REMEDIATION FIELD DEMONSTRATION BASED ON LABORATORY AND MODELINE STUDIES

EPA Science Inventory

Surfactant-enhanced subsurface remediation is being evaluated as an innovative technology for expediting ground-water remediation. This paper reports on laboratory and modeling studies conducted in preparation for a pilot-scale field test of surfactant-enhanced subsurface remedia...

Subsurface Pressure-Temperature Conditions and H2(aq) Generation at the Piccard Hydro-Thermal Field, Mid-Cayman Rise

NASA Astrophysics Data System (ADS)

Scheuermann, P. P.; Seyfried, W. E.

2018-05-01

The subsurface pressure-temperature conditions at the Piccard hydrothermal field are constrained using the Si-Cl geothermobarometer. Ol-Mgt and Opx-Mgt are proposed as assemblages that buffer H2(aq) at Piccard.

Organic Field Effect Transistors for Large Format Electronics

DTIC Science & Technology

2003-06-19

calculated output characteristics for a p-channel substrate insulator Organic layer Source Drain Gate 6 pentacene OFET with 2µm source to drain spacing...conventional transistors. Figure 3. Calculated output characteristics of a pentacene OFET with image charge induced contact barrier...Cross section view of a part of an OFET in the vicinity of a source or drain contact. local ordering due to surface energy effects. The development of

Nature of magnetization and lateral spin-orbit interaction in gated semiconductor nanowires.

PubMed

Karlsson, H; Yakimenko, I I; Berggren, K-F

2018-05-31

Semiconductor nanowires are interesting candidates for realization of spintronics devices. In this paper we study electronic states and effects of lateral spin-orbit coupling (LSOC) in a one-dimensional asymmetrically biased nanowire using the Hartree-Fock method with Dirac interaction. We have shown that spin polarization can be triggered by LSOC at finite source-drain bias,as a result of numerical noise representing a random magnetic field due to wiring or a random background magnetic field by Earth magnetic field, for instance. The electrons spontaneously arrange into spin rows in the wire due to electron interactions leading to a finite spin polarization. The direction of polarization is, however, random at zero source-drain bias. We have found that LSOC has an effect on orientation of spin rows only in the case when source-drain bias is applied.

Nature of magnetization and lateral spin–orbit interaction in gated semiconductor nanowires

NASA Astrophysics Data System (ADS)

Karlsson, H.; Yakimenko, I. I.; Berggren, K.-F.

2018-05-01

Semiconductor nanowires are interesting candidates for realization of spintronics devices. In this paper we study electronic states and effects of lateral spin–orbit coupling (LSOC) in a one-dimensional asymmetrically biased nanowire using the Hartree–Fock method with Dirac interaction. We have shown that spin polarization can be triggered by LSOC at finite source-drain bias,as a result of numerical noise representing a random magnetic field due to wiring or a random background magnetic field by Earth magnetic field, for instance. The electrons spontaneously arrange into spin rows in the wire due to electron interactions leading to a finite spin polarization. The direction of polarization is, however, random at zero source-drain bias. We have found that LSOC has an effect on orientation of spin rows only in the case when source-drain bias is applied.

The Effect of Projectile Density and Disruption on the Crater Excavation Flow-Field

NASA Technical Reports Server (NTRS)

Anderson, Jennifer L. B.; Schultz, P. H.

2005-01-01

The ejection parameters of material excavated by a growing crater directly relate to the subsurface excavation flow-field. The ejection angles and speeds define the end of subsurface material streamlines at the target surface. Differences in the subsurface flow-fields can be inferred by comparing observed ejection parameters of various impacts obtained using three-dimensional particle image velocimetry (3D PIV). The work presented here investigates the observed ejection speeds and angles of material ejected during vertical (90 impact angle) experimental impacts for a range of different projectile types. The subsurface flow-fields produced during vertical impacts are simple when compared with that of oblique impacts, affected primarily by the depth of the energy and momentum deposition of the projectile. This depth is highly controlled by the projectile/target density ratio and the disruption of the projectile (brittle vs. ductile deformation). Previous studies indicated that cratering efficiency and the crater diameter/depth ratio were affected by projectile disruption, velocity, and the projectile/target density ratio. The effect of these projectile properties on the excavation flow-field are examined by comparing different projectile materials.

Two dimensional hydrological simulation in elastic swelling/shrinking peat soils

NASA Astrophysics Data System (ADS)

Camporese, M.; Ferraris, S.; Paniconi, C.; Putti, M.; Salandin, P.; Teatini, P.

2005-12-01

Peatlands respond to natural hydrologic cycles of precipitation and evapotranspiration with reversible deformations due to variations of water content in both the unsaturated and saturated zone. This phenomenon results in short-term vertical displacements of the soil surface that superimpose to the irreversible long-term subsidence naturally occurring in drained cropped peatlands because of bio-oxidation of the organic matter. The yearly sinking rates due to the irreversible process are usually comparable with the short-term deformation (swelling/shrinkage) and the latter must be evaluated to achieve a thorough understanding of the whole phenomenon. A mathematical model describing swelling/shrinkage dynamics in peat soils under unsaturated conditions has been derived from simple physical considerations, and validated by comparison with laboratory shrinkage data. The two-parameter model relates together the void and moisture ratios of the soil. This approach is implemented in a subsurface flow model describing variably saturated porous media flow (Richards' equation), by means of an appropriate modification of the general storage term. The contribution of the saturated zone to total deformation is considered by using information from the elastic storage coefficient. Simulations have been carried out for a drained cropped peatland south of the Venice Lagoon (Italy), for which a large data set of hydrological and deformation measurements has been collected since the end of 2001. The considered domain is representative of a field section bounded by ditches, subject to rainfall and evapotranspiration. The comparison between simulated and measured quantities demonstrates the capability of the model to accurately reproduce both the hydrological and deformation dynamics of peat, with values of the relevant parameters that are in good agreement with the literature.

Calibration of an agricultural-hydrological model (RZWQM2) using surrogate global optimization

DOE PAGES

Xi, Maolong; Lu, Dan; Gui, Dongwei; ...

2016-11-27

Robust calibration of an agricultural-hydrological model is critical for simulating crop yield and water quality and making reasonable agricultural management. However, calibration of the agricultural-hydrological system models is challenging because of model complexity, the existence of strong parameter correlation, and significant computational requirements. Therefore, only a limited number of simulations can be allowed in any attempt to find a near-optimal solution within an affordable time, which greatly restricts the successful application of the model. The goal of this study is to locate the optimal solution of the Root Zone Water Quality Model (RZWQM2) given a limited simulation time, so asmore » to improve the model simulation and help make rational and effective agricultural-hydrological decisions. To this end, we propose a computationally efficient global optimization procedure using sparse-grid based surrogates. We first used advanced sparse grid (SG) interpolation to construct a surrogate system of the actual RZWQM2, and then we calibrate the surrogate model using the global optimization algorithm, Quantum-behaved Particle Swarm Optimization (QPSO). As the surrogate model is a polynomial with fast evaluation, it can be efficiently evaluated with a sufficiently large number of times during the optimization, which facilitates the global search. We calibrate seven model parameters against five years of yield, drain flow, and NO 3-N loss data from a subsurface-drained corn-soybean field in Iowa. Results indicate that an accurate surrogate model can be created for the RZWQM2 with a relatively small number of SG points (i.e., RZWQM2 runs). Compared to the conventional QPSO algorithm, our surrogate-based optimization method can achieve a smaller objective function value and better calibration performance using a fewer number of expensive RZWQM2 executions, which greatly improves computational efficiency.« less

Calibration of an agricultural-hydrological model (RZWQM2) using surrogate global optimization

NASA Astrophysics Data System (ADS)

Xi, Maolong; Lu, Dan; Gui, Dongwei; Qi, Zhiming; Zhang, Guannan

2017-01-01

Robust calibration of an agricultural-hydrological model is critical for simulating crop yield and water quality and making reasonable agricultural management. However, calibration of the agricultural-hydrological system models is challenging because of model complexity, the existence of strong parameter correlation, and significant computational requirements. Therefore, only a limited number of simulations can be allowed in any attempt to find a near-optimal solution within an affordable time, which greatly restricts the successful application of the model. The goal of this study is to locate the optimal solution of the Root Zone Water Quality Model (RZWQM2) given a limited simulation time, so as to improve the model simulation and help make rational and effective agricultural-hydrological decisions. To this end, we propose a computationally efficient global optimization procedure using sparse-grid based surrogates. We first used advanced sparse grid (SG) interpolation to construct a surrogate system of the actual RZWQM2, and then we calibrate the surrogate model using the global optimization algorithm, Quantum-behaved Particle Swarm Optimization (QPSO). As the surrogate model is a polynomial with fast evaluation, it can be efficiently evaluated with a sufficiently large number of times during the optimization, which facilitates the global search. We calibrate seven model parameters against five years of yield, drain flow, and NO3-N loss data from a subsurface-drained corn-soybean field in Iowa. Results indicate that an accurate surrogate model can be created for the RZWQM2 with a relatively small number of SG points (i.e., RZWQM2 runs). Compared to the conventional QPSO algorithm, our surrogate-based optimization method can achieve a smaller objective function value and better calibration performance using a fewer number of expensive RZWQM2 executions, which greatly improves computational efficiency.

Calibration of an agricultural-hydrological model (RZWQM2) using surrogate global optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xi, Maolong; Lu, Dan; Gui, Dongwei

Robust calibration of an agricultural-hydrological model is critical for simulating crop yield and water quality and making reasonable agricultural management. However, calibration of the agricultural-hydrological system models is challenging because of model complexity, the existence of strong parameter correlation, and significant computational requirements. Therefore, only a limited number of simulations can be allowed in any attempt to find a near-optimal solution within an affordable time, which greatly restricts the successful application of the model. The goal of this study is to locate the optimal solution of the Root Zone Water Quality Model (RZWQM2) given a limited simulation time, so asmore » to improve the model simulation and help make rational and effective agricultural-hydrological decisions. To this end, we propose a computationally efficient global optimization procedure using sparse-grid based surrogates. We first used advanced sparse grid (SG) interpolation to construct a surrogate system of the actual RZWQM2, and then we calibrate the surrogate model using the global optimization algorithm, Quantum-behaved Particle Swarm Optimization (QPSO). As the surrogate model is a polynomial with fast evaluation, it can be efficiently evaluated with a sufficiently large number of times during the optimization, which facilitates the global search. We calibrate seven model parameters against five years of yield, drain flow, and NO 3-N loss data from a subsurface-drained corn-soybean field in Iowa. Results indicate that an accurate surrogate model can be created for the RZWQM2 with a relatively small number of SG points (i.e., RZWQM2 runs). Compared to the conventional QPSO algorithm, our surrogate-based optimization method can achieve a smaller objective function value and better calibration performance using a fewer number of expensive RZWQM2 executions, which greatly improves computational efficiency.« less

Verifiable metamodels for nitrate losses to drains and groundwater in the Corn Belt, USA

USGS Publications Warehouse

Nolan, Bernard T.; Malone, Robert W.; Gronberg, Jo Ann M.; Thorp, K.R.; Ma, Liwang

2012-01-01

Nitrate leaching in the unsaturated zone poses a risk to groundwater, whereas nitrate in tile drainage is conveyed directly to streams. We developed metamodels (MMs) consisting of artificial neural networks to simplify and upscale mechanistic fate and transport models for prediction of nitrate losses by drains and leaching in the Corn Belt, USA. The two final MMs predicted nitrate concentration and flux, respectively, in the shallow subsurface. Because each MM considered both tile drainage and leaching, they represent an integrated approach to vulnerability assessment. The MMs used readily available data comprising farm fertilizer nitrogen (N), weather data, and soil properties as inputs; therefore, they were well suited for regional extrapolation. The MMs effectively related the outputs of the underlying mechanistic model (Root Zone Water Quality Model) to the inputs (R2 = 0.986 for the nitrate concentration MM). Predicted nitrate concentration was compared with measured nitrate in 38 samples of recently recharged groundwater, yielding a Pearson’s r of 0.466 (p = 0.003). Predicted nitrate generally was higher than that measured in groundwater, possibly as a result of the time-lag for modern recharge to reach well screens, denitrification in groundwater, or interception of recharge by tile drains. In a qualitative comparison, predicted nitrate concentration also compared favorably with results from a previous regression model that predicted total N in streams.

Debates - Stochastic subsurface hydrology from theory to practice: Introduction

NASA Astrophysics Data System (ADS)

Rajaram, Harihar

2016-12-01

This paper introduces the papers in the "Debates - Stochastic Subsurface Hydrology from Theory to Practice" series. Beginning in the 1970s, the field of stochastic subsurface hydrology has been an active field of research, with over 3500 journal publications, of which over 850 have appeared in Water Resources Research. We are fortunate to have insightful contributions from four groups of distinguished authors who discuss the reasons why the advanced research framework established in stochastic subsurface hydrology has not impacted the practice of groundwater flow and transport modeling and design significantly. There is reasonable consensus that a community effort aimed at developing "toolboxes" for applications of stochastic methods will make them more accessible and encourage practical applications.

Structure and function of subsurface microbial communities affecting radionuclide transport and bioimmobilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostka, Joel E.; Prakash, Om; Green, Stefan J.

2012-05-01

Our objectives were to: 1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), 2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and 3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations. Field sampling was conducted at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee. Themore » ORFRC subsurface is exposed to mixed contamination predominated by uranium and nitrate. In short, we effectively addressed all 3 stated objectives of the project. In particular, we isolated and characterized a large number of novel anaerobes with a high bioremediation potential that can be used as model organisms, and we are now able to quantify the function of subsurface sedimentary microbial communities in situ using state-of-the-art gene expression methods (molecular proxies).« less

β-Ga2O3 on insulator field-effect transistors with drain currents exceeding 1.5 A/mm and their self-heating effect

NASA Astrophysics Data System (ADS)

Zhou, Hong; Maize, Kerry; Qiu, Gang; Shakouri, Ali; Ye, Peide D.

2017-08-01

We have demonstrated that depletion/enhancement-mode β-Ga2O3 on insulator field-effect transistors can achieve a record high drain current density of 1.5/1.0 A/mm by utilizing a highly doped β-Ga2O3 nano-membrane as the channel. β-Ga2O3 on insulator field-effect transistor (GOOI FET) shows a high on/off ratio of 1010 and low subthreshold slope of 150 mV/dec even with 300 nm thick SiO2. The enhancement-mode GOOI FET is achieved through surface depletion. An ultra-fast, high resolution thermo-reflectance imaging technique is applied to study the self-heating effect by directly measuring the local surface temperature. High drain current, low Rc, and wide bandgap make the β-Ga2O3 on insulator field-effect transistor a promising candidate for future power electronics applications.

Source-drain burnout mechanism of GaAs power MESFETS: Three terminal effects

NASA Astrophysics Data System (ADS)

Takamiya, Saburo; Sonoda, Takuji; Yamanouchi, Masahide; Fujioka, Takashi; Kohno, Masaki

1997-03-01

Theoretical expressions for thermal and electrical feedback effects are derived. These limit the power capability of a power FET and lead a device to catastrophic breakdown (source-drain burnout) when the loop gain of the former reaches unity. Field emission of thermally excited electrons at the Schottky gate plays the key role in thermal feedback, while holes being impact ionized by the drain current play a similar role in the electrical feedback. Thermal feedback is dominant in a high temperature and low drain voltage area. Electrical feedback is dominant in a high drain voltage and low temperature area. In the first area, a high junction temperature is the main factor causing the thermal runaway of the device. In the second area, the electrcal feedback increases the drain current and the temperature and gives a trigger to the thermal feedback so that it reaches unity more easily. Both effects become significant in proportion to transconductance and gate bias resistance, and cause simultaneous runaway of the gate and drain currents. The expressions of the loop gains clearly indicate the safe operating conditions for a power FET. C-band 4 W (1 chip) and 16 W (4 chip) GaAs MESFETs were used as the experimental samples. With these devices the simultaneous runaway of the gate and the drain currents, apparent dependence of the three teminal breakdown voltage on the gate bias resistance in the region dominated by electrical feedback, the rapid increase of the field emitted current at the critical temperature and clear coincidence between the measured and calculated three terminal gate currents both in the thermal feedback dominant region, etc. are demonstrated. The theory explains the experimental results well.

Numerical simulation of offset-drain amorphous oxide-based thin-film transistors

NASA Astrophysics Data System (ADS)

Jeong, Jaewook

2016-11-01

In this study, we analyzed the electrical characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with an offset-drain structure by technology computer aided design (TCAD) simulation. When operating in a linear region, an enhancement-type TFT shows poor field-effect mobility because most conduction electrons are trapped in acceptor-like defects in an offset region when the offset length (L off) exceeds 0.5 µm, whereas a depletion-type TFT shows superior field-effect mobility owing to the high free electron density in the offset region compared with the trapped electron density. When operating in the saturation region, both types of TFTs show good field-effect mobility comparable to that of a reference TFT with a large gate overlap. The underlying physics of the depletion and enhancement types of offset-drain TFTs are systematically analyzed.

Aptamer-Based Carboxyl-Terminated Nanocrystalline Diamond Sensing Arrays for Adenosine Triphosphate Detection

PubMed Central

Suaebah, Evi; Naramura, Takuro; Myodo, Miho; Hasegawa, Masataka; Shoji, Shuichi; Buendia, Jorge J.; Kawarada, Hiroshi

2017-01-01

Here, we propose simple diamond functionalization by carboxyl termination for adenosine triphosphate (ATP) detection by an aptamer. The high-sensitivity label-free aptamer sensor for ATP detection was fabricated on nanocrystalline diamond (NCD). Carboxyl termination of the NCD surface by vacuum ultraviolet excimer laser and fluorine termination of the background region as a passivated layer were investigated by X-ray photoelectron spectroscopy. Single strand DNA (amide modification) was used as the supporting biomolecule to immobilize into the diamond surface via carboxyl termination and become a double strand with aptamer. ATP detection by aptamer was observed as a 66% fluorescence signal intensity decrease of the hybridization intensity signal. The sensor operation was also investigated by the field-effect characteristics. The shift of the drain current–drain voltage characteristics was used as the indicator for detection of ATP. From the field-effect characteristics, the shift of the drain current–drain voltage was observed in the negative direction. The negative charge direction shows that the aptamer is capable of detecting ATP. The ability of the sensor to detect ATP was investigated by fabricating a field-effect transistor on the modified NCD surface. PMID:28753998

Aptamer-Based Carboxyl-Terminated Nanocrystalline Diamond Sensing Arrays for Adenosine Triphosphate Detection.

PubMed

Suaebah, Evi; Naramura, Takuro; Myodo, Miho; Hasegawa, Masataka; Shoji, Shuichi; Buendia, Jorge J; Kawarada, Hiroshi

2017-07-21

Here, we propose simple diamond functionalization by carboxyl termination for adenosine triphosphate (ATP) detection by an aptamer. The high-sensitivity label-free aptamer sensor for ATP detection was fabricated on nanocrystalline diamond (NCD). Carboxyl termination of the NCD surface by vacuum ultraviolet excimer laser and fluorine termination of the background region as a passivated layer were investigated by X-ray photoelectron spectroscopy. Single strand DNA (amide modification) was used as the supporting biomolecule to immobilize into the diamond surface via carboxyl termination and become a double strand with aptamer. ATP detection by aptamer was observed as a 66% fluorescence signal intensity decrease of the hybridization intensity signal. The sensor operation was also investigated by the field-effect characteristics. The shift of the drain current-drain voltage characteristics was used as the indicator for detection of ATP. From the field-effect characteristics, the shift of the drain current-drain voltage was observed in the negative direction. The negative charge direction shows that the aptamer is capable of detecting ATP. The ability of the sensor to detect ATP was investigated by fabricating a field-effect transistor on the modified NCD surface.

The Addition of SPECT/CT Lymphoscintigraphy to Breast Cancer Radiation Planning Spares Lymph Nodes Critical for Arm Drainage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheville, Andrea L., E-mail: Cheville.andrea@mayo.edu; Brinkmann, Debra H.; Ward, Shelly B.

2013-03-15

Background: This prospective cohort study was designed to determine whether the amount of radiation delivered to the nonpathological lymph nodes (LNs) that drain the arm can be significantly reduced by integrating single-photon emission computed tomography (SPECT)/computed tomography (CT) scans into radiation treatment planning. Methods: SPECT-CT scans were acquired for the 28 patients with stage I or II breast cancer and fused with the routinely obtained radiation oncology planning CT scans. Arm-draining LNs were contoured with 0.5-cm margins automatically using a threshold of 50% maximum intensity. Two treatment plans were generated: 1 per routine clinical practice (standard; STD) and the secondmore » (modified; MOD) with treatment fields modified to minimize dose to the arm-draining LNs visible on SPECT/CT images without interfering with the dosage delivered to target tissues. Participants were treated per the MOD plans. Arm volumes were measured prior to radiation and thereafter at least three subsequent 6-month intervals. Results: Sixty-eight level I-III arm-draining LNs were identified, 57% of which were inside the STD plan fields but could be blocked in the MOD plan fields. Sixty-five percent of arm-draining LNs in the STD versus 16% in the MOD plans received a mean of ≥10 Gy, and 26% in the STD versus 4% in the MOD plans received a mean of ≥40 Gy. Mean LN radiation exposure was 23.6 Gy (standard deviation 18.2) with the STD and 7.7 Gy (standard deviation 11.3) with the MOD plans (P<.001). No participant developed lymphedema. Conclusions: The integration of SPECT/CT scans into breast cancer radiation treatment planning reduces unnecessary arm-draining LN radiation exposure and may lessen the risk of lymphedema.« less

The addition of SPECT/CT lymphoscintigraphy to breast cancer radiation planning spares lymph nodes critical for arm drainage.

PubMed

Cheville, Andrea L; Brinkmann, Debra H; Ward, Shelly B; Durski, Jolanta; Laack, Nadia N; Yan, Elizabeth; Schomberg, Paula J; Garces, Yolanda I; Suman, Vera J; Petersen, Ivy A

2013-03-15

This prospective cohort study was designed to determine whether the amount of radiation delivered to the nonpathological lymph nodes (LNs) that drain the arm can be significantly reduced by integrating single-photon emission computed tomography (SPECT)/computed tomography (CT) scans into radiation treatment planning. SPECT-CT scans were acquired for the 28 patients with stage I or II breast cancer and fused with the routinely obtained radiation oncology planning CT scans. Arm-draining LNs were contoured with 0.5-cm margins automatically using a threshold of 50% maximum intensity. Two treatment plans were generated: 1 per routine clinical practice (standard; STD) and the second (modified; MOD) with treatment fields modified to minimize dose to the arm-draining LNs visible on SPECT/CT images without interfering with the dosage delivered to target tissues. Participants were treated per the MOD plans. Arm volumes were measured prior to radiation and thereafter at least three subsequent 6-month intervals. Sixty-eight level I-III arm-draining LNs were identified, 57% of which were inside the STD plan fields but could be blocked in the MOD plan fields. Sixty-five percent of arm-draining LNs in the STD versus 16% in the MOD plans received a mean of ≥10 Gy, and 26% in the STD versus 4% in the MOD plans received a mean of ≥40 Gy. Mean LN radiation exposure was 23.6 Gy (standard deviation 18.2) with the STD and 7.7 Gy (standard deviation 11.3) with the MOD plans (P<.001). No participant developed lymphedema. The integration of SPECT/CT scans into breast cancer radiation treatment planning reduces unnecessary arm-draining LN radiation exposure and may lessen the risk of lymphedema. Copyright © 2013 Elsevier Inc. All rights reserved.

Detecting peatland drains with Object Based Image Analysis and Geoeye-1 imagery.

PubMed

Connolly, J; Holden, N M

2017-12-01

Peatlands play an important role in the global carbon cycle. They provide important ecosystem services including carbon sequestration and storage. Drainage disturbs peatland ecosystem services. Mapping drains is difficult and expensive and their spatial extent is, in many cases, unknown. An object based image analysis (OBIA) was performed on a very high resolution satellite image (Geoeye-1) to extract information about drain location and extent on a blanket peatland in Ireland. Two accuracy assessment methods: Error matrix and the completeness, correctness and quality (CCQ) were used to assess the extracted data across the peatland and at several sub sites. The cost of the OBIA method was compared with manual digitisation and field survey. The drain maps were also used to assess the costs relating to blocking drains vs. a business-as-usual scenario and estimating the impact of each on carbon fluxes at the study site. The OBIA method performed well at almost all sites. Almost 500 km of drains were detected within the peatland. In the error matrix method, overall accuracy (OA) of detecting the drains was 94% and the kappa statistic was 0.66. The OA for all sub-areas, except one, was 95-97%. The CCQ was 85%, 85% and 71% respectively. The OBIA method was the most cost effective way to map peatland drains and was at least 55% cheaper than either field survey or manual digitisation, respectively. The extracted drain maps were used constrain the study area CO 2 flux which was 19% smaller than the prescribed Peatland Code value for drained peatlands. The OBIA method used in this study showed that it is possible to accurately extract maps of fine scale peatland drains over large areas in a cost effective manner. The development of methods to map the spatial extent of drains is important as they play a critical role in peatland carbon dynamics. The objective of this study was to extract data on the spatial extent of drains on a blanket bog in the west of Ireland. The results show that information on drain extent and location can be extracted from high resolution imagery and mapped with a high degree of accuracy. Under Article 3.4 of the Kyoto Protocol Annex 1 parties can account for greenhouse gas emission by sources and removals by sinks resulting from "wetlands drainage and rewetting". The ability to map the spatial extent, density and location of peatlands drains means that Annex 1 parties can develop strategies for drain blocking to aid reduction of CO 2 emissions, DOC runoff and water discoloration. This paper highlights some uncertainty around using one-size-fits-all emission factors for GHG in drained peatlands and re-wetting scenarios. However, the OBIA method is robust and accurate and could be used to assess the extent of drains in peatlands across the globe aiding the refinement of peatland carbon dynamics .

Detecting peatland drains with Object Based Image Analysis and Geoeye-1 imagery.

PubMed

Connolly, J; Holden, N M

2017-12-01

Peatlands play an important role in the global carbon cycle. They provide important ecosystem services including carbon sequestration and storage. Drainage disturbs peatland ecosystem services. Mapping drains is difficult and expensive and their spatial extent is, in many cases, unknown. An object based image analysis (OBIA) was performed on a very high resolution satellite image (Geoeye-1) to extract information about drain location and extent on a blanket peatland in Ireland. Two accuracy assessment methods: Error matrix and the completeness, correctness and quality ( CCQ ) were used to assess the extracted data across the peatland and at several sub sites. The cost of the OBIA method was compared with manual digitisation and field survey. The drain maps were also used to assess the costs relating to blocking drains vs. a business-as-usual scenario and estimating the impact of each on carbon fluxes at the study site. The OBIA method performed well at almost all sites. Almost 500 km of drains were detected within the peatland. In the error matrix method, overall accuracy (OA) of detecting the drains was 94% and the kappa statistic was 0.66. The OA for all sub-areas, except one, was 95-97%. The CCQ was 85%, 85% and 71% respectively. The OBIA method was the most cost effective way to map peatland drains and was at least 55% cheaper than either field survey or manual digitisation, respectively. The extracted drain maps were used constrain the study area CO 2 flux which was 19% smaller than the prescribed Peatland Code value for drained peatlands. The OBIA method used in this study showed that it is possible to accurately extract maps of fine scale peatland drains over large areas in a cost effective manner. The development of methods to map the spatial extent of drains is important as they play a critical role in peatland carbon dynamics. The objective of this study was to extract data on the spatial extent of drains on a blanket bog in the west of Ireland. The results show that information on drain extent and location can be extracted from high resolution imagery and mapped with a high degree of accuracy. Under Article 3.4 of the Kyoto Protocol Annex 1 parties can account for greenhouse gas emission by sources and removals by sinks resulting from "wetlands drainage and rewetting". The ability to map the spatial extent, density and location of peatlands drains means that Annex 1 parties can develop strategies for drain blocking to aid reduction of CO 2 emissions, DOC runoff and water discoloration. This paper highlights some uncertainty around using one-size-fits-all emission factors for GHG in drained peatlands and re-wetting scenarios. However, the OBIA method is robust and accurate and could be used to assess the extent of drains in peatlands across the globe aiding the refinement of peatland carbon dynamics .

Complete genome sequence of Anaeromyxobacter sp. Fw109-5, an Anaerobic, Metal-Reducing Bacterium Isolated from a Contaminated Subsurface Environment

DOE PAGES

Hwang, C.; Copeland, A.; Lucas, Susan; ...

2015-01-22

We report the genome sequence of Anaeromyxobacter sp. Fw109-5, isolated from nitrate- and uranium-contaminated subsurface sediment of the Oak Ridge Integrated Field-Scale Subsurface Research Challenge (IFC) site, Oak Ridge Reservation, TN. The bacterium’s genome sequence will elucidate its physiological potential in subsurface sediments undergoing in situ uranium bioremediation and natural attenuation.

Nutrient loss in leachate and surface runoff from surface-broadcast and subsurface-banded broiler litter

USDA-ARS?s Scientific Manuscript database

Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff, compared to the conventional surface broadcast application. Little in situ research has been conducted to determine effects of surface broadcast application and subsurfac...

Surface stoichiometry modification and improved DC/RF characteristics by plasma treated and annealed AlGaN/GaN HEMTs

NASA Astrophysics Data System (ADS)

Upadhyay, Bhanu B.; Takhar, Kuldeep; Jha, Jaya; Ganguly, Swaroop; Saha, Dipankar

2018-03-01

We demonstrate that N2 and O2 plasma treatment followed by rapid thermal annealing leads to surface stoichiometry modification in a AlGaN/GaN high electron mobility transistor. Both the source/drain access and gate regions respond positively improving the transistor characteristics albeit to different extents. Characterizations indicate that the surface show the characteristics of that of a higher band-gap material like AlxOy and GaxOy along with N-vacancy in the sub-surface region. The N-vacancy leads to an increased two-dimensional electron gas density. The formation of oxides lead to a reduced gate leakage current and surface passivation. The DC characteristics show increased transconductance, saturation drain current, ON/OFF current ratio, sub-threshold swing and lower ON resistance by a factor of 2.9, 2.0, 103.3 , 2.3, and 2.1, respectively. The RF characteristics show an increase in unity current gain frequency by a factor of 1.7 for a 500 nm channel length device.

Nutrient concentrations and fluxes in tributaries to the Swan-Canning estuary, Western Australia

USGS Publications Warehouse

Peters, N.E.; Donohue, R.

1999-01-01

In Western Australia, catchment nutrient availability on an areal basis is primarily controlled by the disposal of animal waste and the type and rate of fertilizer application, particularly in coastal areas. The coastal areas receive notably higher rainfall and have more intense horticulture and animal production than inland areas, and are undergoing rapid urbanization, particularly adjacent to the estuary. Also, the surficial aquifers on the coastal plain are generally sandy having a low nutrient retention capacity and rapidly transmit soluble and colloidal material through the subsurface. In the Swan-Canning basin, high air and soil temperatures and seasonally arid conditions cause rapid mineralization of nitrogen and phosphorus. The nutrients are subsequently available for transport during the onset of seasonal wet weather, which typically begins during the period from late April to June. In addition to the rapid mobility of nutrients in streamwater from agricultural areas during the wet season, drains in urban areas, which typically have high nutrient concentrations, also are an important source of nutrients as the drains flow directly to the estuary throughout the year.

Sinkhole risk assessment by ERT: The case study of Sirino Lake (Basilicata, Italy)

NASA Astrophysics Data System (ADS)

Giampaolo, V.; Capozzoli, L.; Grimaldi, S.; Rizzo, E.

2016-01-01

The presence of natural or artificial lakes and reservoirs that can drain because of natural phenomena can generate catastrophic events affecting urban and agricultural areas next to the source area. Therefore, geophysical prospecting techniques have been applied in the study of Sirino Lake, which, during the last century, was affected by the sudden opening of small sinkholes, resulting in the almost total draining of the lake and in the sudden increase of water flow rates of distal springs. Two electrical resistivity tomographies (ERTs) were carried out across the lake, using electrode arrays located on land and across the water body. Self-potential (SP) data were acquired around the lake shore and the surrounding area. The geophysical prospecting contributed significant data toward explaining the unique hydrogeological characteristics of the lake. Integration of geophysical, geological, hydrogeological, and geomorphological data allowed us to estimate the thickness of the lacustrine deposits beneath the lake, to describe the main patterns of the subsurface fluid flows in the area, and to identify possible water escape routes causing the piping phenomena.

The hydrology of a drained topographical depression within an agricutlural field in north-central Iowa

USGS Publications Warehouse

Roth, Jason L.; Capel, Paul D.

2012-01-01

North-central Iowa is an agriculturally intensive area comprising the southeastern portion of the Prairie Pothole Region, a landscape containing a high density of enclosed topographical depressions. Artificial drainage practices have been implemented throughout the area to facilitate agricultural production. Vertical surface drains are utilized to drain the topographical depressions that accumulate water. This study focuses on the hydrology of a drained topographical depression located in a 39.5 ha agricultural field. To assess the hydrology of the drained depression, a water balance was constructed for 11 ponding events during the 2008 growing season. Continuous pond and groundwater level data were obtained with pressure transducers. Flows into the vertical surface drain were calculated based on pond depth. Precipitation inflows and evaporative outflows of the ponds were calculated using climatic data. Groundwater levels were used to assess groundwater/pond interactions. Results of the water balances show distinct differences between the inflows to and outflows from the depression based on antecedent conditions. In wet conditions, groundwater inflow sustained the ponds. The ponds receded only after the groundwater level declined to below the land surface. In drier conditions, groundwater was not a source of water to the depression. During these drier conditions, infiltration comprised 30% of the outflows from the depression during declining pond stages. Over the entire study period, the surface drain, delivering water to the stream, was the largest outflow from the pond, accounting for 97% of the outflow, while evapotranspiration was just 2%. Precipitation onto the pond surface proved to be a minor component, accounting for 4% of the total inflows.

Robotic Range Clearance Competition (R2C2)

DTIC Science & Technology

2011-10-01

unexploded ordnance (UXO). A large part of the debris field consists of ferrous metal objects that magnetic 39 Distribution A: Approved for public...was set at 7 degrees above horizontal based on terrain around the Base station. We used the BSUBR file for all fields except the Subsurface...and subsurface clearance test areas had numerous pieces of simulated unexploded ordinance (SUXO) buried at random locations around the field . These

Effectiveness of submerged drains in reducing subsidence of peat soils in agricultural use, and their effects on water management and nutrient loading of surface water: modelling of a case study in the western peat soil area of The Netherlands

NASA Astrophysics Data System (ADS)

Hendriks, Rob F. A.; van den Akker, Jan J. A.

2017-04-01

Effectiveness of submerged drains in reducing subsidence of peat soils in agricultural use, and their effects on water management and nutrient loading of surface water: modelling of a case study in the western peat soil area of The Netherlands In the Netherlands, about 8% of the area is covered by peat soils. Most of these soils are in use for dairy farming and, consequently, are drained. Drainage causes decomposition of peat by oxidation and accordingly leads to surface subsidence and greenhouse gas emission. Submerged drains that enhance submerged infiltration of water from ditches during the dry and warm summer half year were, and are still, studied in The Netherlands as a promising tool for reducing peat decomposition by raising groundwater levels. For this purpose, several pilot field studies in the Western part of the Dutch peat area were conducted. Besides the effectiveness of submerged drains in reducing peat decomposition and subsidence by raising groundwater tables, some other relevant or expected effects of these drains were studied. Most important of these are water management and loading of surface water with nutrients nitrogen, phosphorus and sulphate. Because most of these parameters are not easy to assess and all of them are strongly depending on the meteorological conditions during the field studies some of these studies were modelled. The SWAP model was used for evaluating the hydrological results on groundwater table and water discharge and recharge. Effects of submerged drains were assessed by comparing the results of fields with and without drains. An empirical relation between deepest groundwater table and subsidence was used to convert effects on groundwater table to effects on subsidence. With the SWAP-ANIMO model nutrient loading of surface water was modelled on the basis of field results on nutrient concentrations . Calibrated models were used to assess effects in the present situation, as thirty-year averages, under extreme weather conditions and for two extreme climate scenarios of the Royal Netherlands Meteorological Institute. In this study the model results of one of the pilot studies are presented. The case study 'de Krimpenerwaard' is situated in the peat area in the "Green Heart" between the major cities of Amsterdam, The Hague, Rotterdam and Utrecht. Model results show a halving of soil subsidence, a strong increase of water recharge but a lower increase of water discharge, and generally small to moderate effects on nutrient loading , all depending (strongly) on meteorological conditions.

Geo-spatial analysis of land-water resource degradation in two economically contrasting agricultural regions adjoining national capital territory (Delhi).

PubMed

Kaur, Ravinder; Minhas, P S; Jain, P C; Singh, P; Dubey, D S

2009-07-01

The present study was aimed at characterizing the soil-water resource degradation in the rural areas of Gurgaon and Mewat districts, the two economically contrasting areas in policy zones-II and III of the National Capital Region (NCR), and assessing the impact of the study area's local conditions on the type and extent of resource degradation. This involved generation of detailed spatial information on the land use, cropping pattern, farming practices, soils and surface/ground waters of Gurgaon and Mewat districts through actual resource surveys, standard laboratory methods and GIS/remote sensing techniques. The study showed that in contrast to just 2.54% (in rabi season) to 4.87% (in kharif season) of agricultural lands in Gurgaon district, about 11.77% (in rabi season) to 24.23% (in kharif season) of agricultural lands in Mewat district were irrigated with saline to marginally saline canal water. Further, about 10.69% of agricultural lands in the Gurgaon district and 42.15% of agricultural lands in the Mewat district were drain water irrigated. A large part of this surface water irrigated area, particularly in Nuh (48.7%), Nagina (33.5%), and Punhana (24.1%) blocks of Mewat district, was either waterlogged (7.4% area with 0.05 ppm). In fact, sub-surface drinking waters of some areas around battery and automobile manufacturing units in Gurgaon and Pataudi blocks were associated with exceptionally high (>0.1 ppm) Ni concentrations. In general, the ground waters of waterlogged or potentially waterlogged areas in the rural areas of Mewat were more contaminated than the ground waters in the rural areas of Gurgaon district with deeper (>5 m) water depths.Though Cr concentrations in the surface and sub-surface irrigation waters of both Gurgaon and Mewat districts were far above the maximum permissible limit of 1 ppm, their bio-available soil-Cr concentrations were well within permissible limit. Even bio-available Ni concentrations in agricultural lands of Gurgaon district associated with Ni contaminated sub-surface irrigations were well within desirable limit of 0.20 ppm. This was primarily attributed to the calcareous nature of the soils of the study area. About 35% of Gurgaon district and 59% of Mewat district irrigated with poor quality waters were salt-affected. These waterlogged/potentially waterlogged calcareous-salt affected soils of Mewat district were having acute zinc (Zn) deficiency (<0.6 ppm). Some areas with extremely high iron (Fe: 20-25 ppm) and Mn (10-25 ppm) concentrations were also noticed in the Gurgaon, Nuh and Punhana blocks. Generation of reduced conditions owing to paddy cultivation in areas with 3-3.5 m water depths appeared to be the main cause of such point contaminations. Extensive cadmium (Cd) contamination was also noticed in the waterlogged sodic agricultural lands of Nagina village in Mewat district associated with a large scale scrap automobile and battery business. The study could document the processes and provide spatially accurate information to the managers (e.g., National Capital Region Planning Board) and the concerned citizen groups. It could, in fact, clearly point out that dumping of industrial and domestic wastewaters especially from NCT-Delhi into river Yamuna and, to some extent, from NCT-Delhi re-located hazardous industrial units into Najafgarh drain tributaries at Delhi-Gurgaon boundary, and poor "off-farm" water management practices were the main reasons for extensive (point/non-point source) land-water degradation in Gurgaon and Mewat districts of NCR.

Results from Field Testing the RIMFAX GPR on Svalbard.

NASA Astrophysics Data System (ADS)

Hamran, S. E.; Amundsen, H. E. F.; Berger, T.; Carter, L. M.; Dypvik, H.; Ghent, R. R.; Kohler, J.; Mellon, M. T.; Nunes, D. C.; Paige, D. A.; Plettemeier, D.; Russell, P.

2017-12-01

The Radar Imager for Mars' Subsurface Experiment - RIMFAX is a Ground Penetrating Radar being developed for NASÁs MARS 2020 rover mission. The principal goals of the RIMFAX investigation are to image subsurface structures, provide context for sample sites, derive information regarding subsurface composition, and search for ice or brines. In meeting these goals, RIMFAX will provide a view of the stratigraphic section and a window into the geological and environmental history of Mars. To verify the design an Engineering Model (EM) of the radar was tested in the field in the spring 2017. Different sounding modes on the EM were tested in different types of subsurface geology on Svalbard. Deep soundings were performed on polythermal glaciers down to a couple of hundred meters. Shallow soundings were used to map a ground water table in the firn area of a glacier. A combination of deep and shallow soundings was used to image buried ice under a sedimentary layer of a couple of meters. Subsurface sedimentary layers were imaged down to more than 20 meters in sand stone permafrost. This presentation will give an overview of the RIMFAX investigation, describe the development of the radar system, and show results from field tests of the radar.

Matching agricultural freshwater supply and demand: using industrial and domestic treated wastewater for sub-irrigation purposes

NASA Astrophysics Data System (ADS)

Bartholomeus, Ruud; van den Eertwegh, Gé; Worm, Bas; Cirkel, Gijsbert; van Loon, Arnaut; Raat, Klaasjan

2017-04-01

Agricultural crop yields depend largely on soil moisture conditions in the root zone. Climate change leads to more prolonged drought periods that alternate with more intensive rainfall events. With unaltered water management practices, reduced crop yield due to drought stress will increase. Therefore, both farmers and water management authorities search for opportunities to manage risks of decreasing crop yields. Available groundwater sources for irrigation purposes are increasingly under pressure due to the regional coexistence of land use functions that are critical to groundwater levels or compete for available water. At the same time, treated wastewater from industries and domestic wastewater treatment plants are quickly discharged via surface waters towards sea. Exploitation of these freshwater sources may be an effective strategy to balance regional water supply and agricultural water demand. We present results of two pilot studies in drought sensitive regions in the Netherlands, concerning agricultural water supply through reuse of industrial and domestic treated wastewater. In these pilots, excess wastewater is delivered to the plant root zone through sub-irrigation by drainage systems. Sub-irrigation is a subsurface irrigation method that can be more efficient than classical, aboveground irrigation methods using sprinkler installations. Domestic wastewater treatment plants in the Netherlands produce annually 40-50mm freshwater. A pilot project has been setup in the eastern part of the Netherlands, in which treated wastewater is applied to a corn field by sub-irrigation during the growing seasons of 2015 and 2016, using a climate adaptive drainage system. The chemical composition of treated domestic wastewater is different from infiltrating excess rainfall water and natural groundwater. In the pilot project, the bromide-chloride ratio and traces of pharmaceuticals in the treated wastewater are used as a tracer to describe water and solute transport in the soil system. Focus of this pilot study is on quantifying potential contamination of both the root zone and the deeper groundwater with pharmaceutical residues. We have installed a field monitoring network at several locations in the vadose zone and the local groundwater system, which enables us to measure vertical solute profiles in the soil water by taking samples. Based on field data obtained during the experiments, combined with SWAP (1D) and Hydrus (2D) model simulations, flow and transport of the sub-irrigated treated wastewater are quantified. In the south of The Netherlands, the Bavaria Beer Brewery abstracts a large volume of groundwater and discharges treated wastewater to local surface water which transports the water rapidly out of the region. At the same time, neighboring farmers invest in sprinkler irrigation systems to maintain their crop production during drought periods. In this region, increasing pressure is put on the regional groundwater and surface water availability. Within a pilot study, a sub-irrigation system has been installed, by using subsurface drains, interconnected through a collector drain, and connected to an inlet control basin for the treated wastewater to enter the drainage system. We combine both process-based modeling of the soil-plant-atmosphere system and field experiments to i) investigate the amount of water that needs to be and that can be sub-irrigated, and ii) quantify the effect on soil moisture availability and herewith reduced needs for aboveground irrigation.

Si1-yGey or Ge1-zSnz Source/Drain Stressors on Strained Si1-xGex-Channel P-Type Field-Effect Transistors: A Technology Computer-Aided Design Study

NASA Astrophysics Data System (ADS)

Eneman, Geert; De Keersgieter, An; Witters, Liesbeth; Mitard, Jerome; Vincent, Benjamin; Hikavyy, Andriy; Loo, Roger; Horiguchi, Naoto; Collaert, Nadine; Thean, Aaron

2013-04-01

The interaction between two stress techniques, strain-relaxed buffers (SRBs) and epitaxial source/drain stressors, is studied on short, Si1-xGex- and Ge-channel planar transistors. This work focuses on the longitudinal channel stress generated by these two techniques. Unlike for unstrained silicon-channel transistors, for strained channels on top of a strain-relaxed buffer a source/drain stressor without recess generates similar longitudinal channel stress than source/drain stressors with a deep recess. The least efficient stress transfer is obtained for source/drain stressors with a small recess that removes only the strained channel, not the substrate underneath. These trends are explained by a trade-off between elastic relaxation of the strained-channel during source/drain recess and the increased stress generation of thicker source/drain stressors. For Ge-channel pFETs, GeSn source/drains and Si1-xGex strain-relaxed buffers are efficient stressors for mobility enhancement. The former is more efficient for gate-last schemes than for gate-first, while the stress generated by the SRB is found to be independent of the gate-scheme.

Fate and transport of tylosin and macrolide-resistance genes following manure applications in tile-drained landscapes

USDA-ARS?s Scientific Manuscript database

The use of antibiotics in swine production leads to antibiotic-resistance in gastrointestinal bacteria. Application of swine manure to drained agricultural fields introduces elevated levels of antibiotic-resistant bacteria and residual antibiotics. The persistence and transport of these agents are g...

The Mojave Subsurface Bio-Geochemistry Explorer (MOSBE)

NASA Technical Reports Server (NTRS)

Guerrero, J.; Beegle, L.; Abbey, W.; Bhartia, R.; Kounaves, S.; Russell, M.; Towles, D.

2012-01-01

The MOSBE Team has developed a terrestrial field campaign to explore two subsurface biological habitats under the Mojave Desert. This field campaign will not only help us understand terrestrial desert biology, but also will develop methodologies and strategies for potential future Mars missions that would seek to explore the Martian subsurface. We have proposed to the ASTEP program to integrate a suite of field demonstrated instruments with a 20 m subsurface drill as a coherent unit, the Mojave Subsurface Bio-geochemistry Explorer. The ATK Space Modular Planetary Drill System (MPDS) requires no drilling fluid, which allows aseptic sampling, can penetrate lithic ground up to 20 meters of depth, and utilizes less than 100 Watts throughout the entire depth. The drill has been developed and demonstrated in field testing to a depth of 10 meters in Arizona, December 2002. In addition to caching a continuous core throughout the drilling depth, it also generates and caches cuttings and fines that are strata-graphically correlated with the core. As a core segment is brought to the surface, it will be analyzed for texture and structure by a color microscopic imager and for relevant chemistry and mineralogy with a UV fluorescence/Raman spectrometer. Organic and soluble ionic species will be identified through two instruments -- a microcapillary electrophoresis, and an ion trap mass spectrometer that have been developed under PIDDP, ASTID and MIDP funding.

The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

DOE PAGES

Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A.; ...

2015-06-15

Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigativemore » techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot-scale” experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. In conclusion, geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.« less

The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Binley, Andrew; Hubbard, Susan S.; Huisman, Johan A.

Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field-based investigativemore » techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time-lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot-scale” experiments. More recently, however, the translation to larger-scale characterization has been the focus of a number of studies. In conclusion, geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services.« less

Preliminary Study of 2-D Time Domain Electromagnetic (TDEM) Modeling to Analyze Subsurface Resistivity Distribution and its Application to the Geothermal Systems

NASA Astrophysics Data System (ADS)

Aji Hapsoro, Cahyo; Purqon, Acep; Srigutomo, Wahyu

2017-07-01

2-D Time Domain Electromagnetic (TDEM) has been successfully conducted to illustrate the value of Electric field distribution under the Earth surface. Electric field compared by magnetic field is used to analyze resistivity and resistivity is one of physical properties which very important to determine the reservoir potential area of geothermal systems as one of renewable energy. In this modeling we used Time Domain Electromagnetic method because it can solve EM field interaction problem with complex geometry and to analyze transient problems. TDEM methods used to model the value of electric and magnetic fields as a function of the time combined with the function of distance and depth. The result of this modeling is Electric field intensity value which is capable to describe the structure of the Earth’s subsurface. The result of this modeling can be applied to describe the Earths subsurface resistivity values to determine the reservoir potential of geothermal systems.

Washington Geothermal Play Fairway Analysis Data From Potential Field Studies

DOE Data Explorer

Anderson, Megan; Ritzinger, Brent; Glen, Jonathan; Schermerhorn, William

2017-12-20

A recent study which adapts play fairway analysis (PFA) methodology to assess geothermal potential was conducted at three locations (Mount Baker, Mount St. Helens seismic zone, and Wind River valley) along the Washington Cascade Range (Forson et al. 2017). Potential field (gravity and magnetic) methods which can detect subsurface contrasts in physical properties, provides a means for mapping and modeling subsurface geology and structure. As part of the WA-Cascade PFA project, we performed potential field studies by collecting high-resolution gravity and ground-magnetic data, and rock property measurements to (1) identify and constrain fault geometries (2) constrain subsurface lithologic distribution (3) study fault interactions (4) identify areas favorable to hydrothermal flow, and ultimately (5) guide future geothermal exploration at each location.

Geophysical framework of the southwestern Nevada volcanic field and hydrogeologic implications

USGS Publications Warehouse

Grauch, V.J.; Sawyer, David A.; Fridrich, Chris J.; Hudson, Mark R.

1999-01-01

Gravity and magnetic data, when integrated with other geophysical, geological, and rock-property data, provide a regional framework to view the subsurface geology in the southwestern Nevada volcanic field. The region has been loosely divided into six domains based on structural style and overall geophysical character. For each domain, the subsurface tectonic and magmatic features that have been inferred or interpreted from previous geophysical work has been reviewed. Where possible, abrupt changes in geophysical fields as evidence for potential structural lithologic control on ground-water flow has been noted. Inferred lithology is used to suggest associated hydrogeologic units in the subsurface. The resulting framework provides a basis for investigators to develop hypotheses from regional ground-water pathways where no drill-hole information exists.

A two dimensional analytical modeling of surface potential in triple metal gate (TMG) fully-depleted Recessed-Source/Drain (Re-S/D) SOI MOSFET

NASA Astrophysics Data System (ADS)

Priya, Anjali; Mishra, Ram Awadh

2016-04-01

In this paper, analytical modeling of surface potential is proposed for new Triple Metal Gate (TMG) fully depleted Recessed-Source/Dain Silicon On Insulator (SOI) Metal Oxide Semiconductor Field Effect Transistor (MOSFET). The metal with the highest work function is arranged near the source region and the lowest one near the drain. Since Recessed-Source/Drain SOI MOSFET has higher drain current as compared to conventional SOI MOSFET due to large source and drain region. The surface potential model developed by 2D Poisson's equation is verified by comparison to the simulation result of 2-dimensional ATLAS simulator. The model is compared with DMG and SMG devices and analysed for different device parameters. The ratio of metal gate length is varied to optimize the result.

Frequency dependence and passive drains in fish-eye lenses

NASA Astrophysics Data System (ADS)

Quevedo-Teruel, O.; Mitchell-Thomas, R. C.; Hao, Y.

2012-11-01

The Maxwell fish eye lens has previously been reported as being capable of the much sought after phenomenon of subwavelength imaging. The inclusion of a drain in this system is considered crucial to the imaging ability, although its role is the topic of much debate. This paper provides a numerical investigation into a practical implementation of a drain in such systems, and analyzes the strong frequency dependence of both the Maxwell fish eye lens and an alternative, the Miñano lens. The imaging capability of these types of lens is questioned, and it is supported by simulations involving various configurations of drain arrays. Finally, a discussion of the near-field and evanescent wave contribution is given.

Abnormal threshold voltage shift under hot carrier stress in Ti1-xNx/HfO2 p-channel metal-oxide-semiconductor field-effect transistors

NASA Astrophysics Data System (ADS)

Tsai, Jyun-Yu; Chang, Ting-Chang; Lo, Wen-Hung; Ho, Szu-Han; Chen, Ching-En; Chen, Hua-Mao; Tseng, Tseung-Yuen; Tai, Ya-Hsiang; Cheng, Osbert; Huang, Cheng-Tung

2013-09-01

This work investigates the channel hot carrier (CHC) effect in HfO2/Ti1-xNx p-channel metal oxide semiconductor field effect transistors (p-MOSFETs). Generally, the subthreshold swing (S.S.) should increase during CHC stress (CHCS), since interface states will be generated near the drain side under high electric field due to drain voltage (Vd). However, our experimental data indicate that S.S. has no evident change under CHCS, but threshold voltage (Vth) shifts positively. This result can be attributed to hot carrier injected into high-k dielectric near the drain side. Meanwhile, it is surprising that such Vth degradation is not observed in the saturation region during stress. Therefore, drain-induced-barrier-lowering (DIBL) as a result of CHC-induced electron trapping is proposed to explain the different Vth behaviors in the linear and saturation regions. Additionally, the influence of different nitrogen concentrations in HfO2/Ti1-xNx p-MOSFETs on CHCS is also investigated in this work. Since nitrogen diffuses to SiO2/Si interface induced pre-Nit occurring to degrades channel mobility during the annealing process, a device with more nitrogen shows slightly less impact ionization, leading to insignificant charge trapping-induced DIBL behavior.

Using MODFLOW drains to simulate groundwater flow in a karst environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quinn, J.; Tomasko, D.; Glennon, M.A.

1998-07-01

Modeling groundwater flow in a karst environment is both numerically challenging and highly uncertain because of potentially complex flowpaths and a lack of site-specific information. This study presents the results of MODFLOW numerical modeling in which drain cells in a finite-difference model are used as analogs for preferential flowpaths or conduits in karst environments. In this study, conduits in mixed-flow systems are simulated by assigning connected pathways of drain cells from the locations of tracer releases, sinkholes, or other karst features to outlet springs along inferred flowpaths. These paths are determined by the locations of losing stream segments, ephemeral streammore » beds, geophysical surveys, fracture lineaments, or other surficial characteristics, combined with the results of dye traces. The elevations of the drains at the discharge ends of the inferred flowpaths are estimated from field data and are adjusted when necessary during model calibration. To simulate flow in a free-flowing conduit, a high conductance is assigned to each drain to eliminate the need for drain-specific information that would be very difficult to obtain. Calculations were performed for a site near Hohenfels, Germany. The potentiometric surface produced by the simulations agreed well with field data. The head contours in the vicinity of the karst features behaved in a manner consistent with a flow system having both diffuse and conduit components, and the sum of the volumetric flow out of the drain cells agreed closely with spring discharges and stream flows. Because of the success of this approach, it is recommended for regional studies in which little site-specific information (e.g., location, number, size, and conductivity of fractures and conduits) is available, and general flow characteristics are desired.« less

Cover cropping to reduce nitrate loss through subsurface drainage in the northern U.S. corn belt.

PubMed

Strock, J S; Porter, P M; Russelle, M P

2004-01-01

Despite the use of best management practices for nitrogen (N) application rate and timing, significant losses of nitrate nitrogen (NO3(-)-N) in drainage discharge continue to occur from row crop cropping systems. Our objective was to determine whether a autumn-seeded winter rye (Secale cereale L.) cover crop following corn (Zea mays L.) would reduce NO3(-)-N losses through subsurface tile drainage in a corn-soybean [Glycine mar (L.) Merr.] cropping system in the northern Corn Belt (USA) in a moderately well-drained soil. Both phases of the corn-soybean rotation, with and without the winter rye cover crop following corn, were established in 1998 in a Normania clay loam (fine-loamy, mixed, mesic Aquic Haplustoll) soil at Lamberton, MN. Cover cropping did not affect subsequent soybean yield, but reduced drainage discharge, flow-weighted mean nitrate concentration (FWMNC), and NO3(-)-N loss relative to winter fallow, although the magnitude of the effect varied considerably with annual precipitation. Three-year average drainage discharge was lower with a winter rye cover crop than without (p = 0.06). Over three years, subsurface tile-drainage discharge was reduced 11% and NO3(-)-N loss was reduced 13% for a corn-soybean cropping system with a rye cover crop following corn than with no rye cover crop. We estimate that establishment of a winter rye cover crop after corn will be successful in one of four years in southwestern Minnesota. Cover cropping with rye has the potential to be an effective management tool for reducing NO3(-)-N loss from subsurface drainage discharge despite challenges to establishment and spring growth in the north-central USA.

Subsurface recharge to the Tesuque aquifer system from selected drainage basins along the western side of the Sangre de Cristo Mountains near Santa Fe, New Mexico

USGS Publications Warehouse

Wasiolek, Maryann

1995-01-01

Water budgets developed for basins of five streams draining the western side of the Sangre de Cristo Mountains in northern New Mexico indicate that subsurface inflow along the mountain front is recharging the Tesuque aquifer system of the Espanola Basin. Approximately 14,700 acre-feet of water per year, or 12.7 percent of average annual precipitation over the mountains, is calculated to leave the mountain block and enter the basin as subsurface recharge from the drainage basins of the Rio Nambe, Rio en Medio, Tesuque Creek, Little Tesuque Creek, and Santa Fe River. About 5,520 acre- feet per year, or about 12 percent of average annual precipitation, is calculated to enter from the Rio Nambe drainage basin; about 1,710 acre- feet per year, or about 15 percent of average annual precipitation, is calculated to enter from the Rio en Medio drainage basin; about 1,530 acre- feet, or about 10 percent of average annual precipi- tation, is calculated to enter from the Tesuque Creek drainage basin; about 1,790 acre-feet, or about 19 percent of average annual precipitation, is calculated to enter from the Little Tesuque Creek drainage basin; and about 4,170 acre-feet per year, or about 12 percent average annual precipitation, is calculated to enter from the Santa Fe River drainage basin. Calculated subsurface recharge values were used to define maximum fluxes permitted along the specified-flux boundary defining the mountain front of the Sangre De Cristo Mountains in a numerical computer model of the Tesuque aquifer system near Santa Fe, New Mexico.

Extending RTM Imaging With a Focus on Head Waves

NASA Astrophysics Data System (ADS)

Holicki, Max; Drijkoningen, Guy

2016-04-01

Conventional industry seismic imaging predominantly focuses on pre-critical reflections, muting post-critical arrivals in the process. This standard approach neglects a lot of information present in the recorded wave field. This negligence has been partially remedied with the inclusion of head waves in more advanced imaging techniques, like Full Waveform Inversion (FWI). We would like to see post-critical information leave the realm of labour-intensive travel-time picking and tomographic inversion towards full migration to improve subsurface imaging and parameter estimation. We present a novel seismic imaging approach aimed at exploiting post-critical information, using the constant travel path for head-waves between shots. To this end, we propose to generalize conventional Reverse Time Migration (RTM) to scenarios where the sources for the forward and backward propagated wave-fields are not coinciding. RTM functions on the principle that backward propagated receiver data, due to a source at some locations, must overlap with the forward propagated source wave field, from the same source location, at subsurface scatterers. Where the wave-fields overlap in the subsurface there is a peak at the zero-lag cross-correlation, and this peak is used for the imaging. For the inclusion of head waves, we propose to relax the condition of coincident sources. This means that wave-fields, from non-coincident-sources, will not overlap properly in the subsurface anymore. We can make the wave-fields overlap in the subsurface again, by time shifting either the forward or backward propagated wave-fields until the wave-fields overlap. This is the same as imaging at non-zero cross-correlation lags, where the lag is the travel time difference between the two wave-fields for a given event. This allows us to steer which arrivals we would like to use for imaging. In the simplest case we could use Eikonal travel-times to generate our migration image, or we exclusively image the subsurface with the head wave from the nth-layer. To illustrate the method we apply it to a layered Earth model with five layers and compare it to conventional RTM. We will show that conventional RTM highlights interfaces, while our head-wave based images highlight layers, producing fundamentally different images. We also demonstrate that our proposed imaging scheme is more sensitive to the velocity model than conventional RTM, which is important for improved velocity model building in the future.

Integrating Partial Polarization into a Metal-Ferroelectric-Semiconductor Field Effect Transistor Model

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Ho, Fat Duen

1999-01-01

The ferroelectric channel in a Metal-Ferroelectric-Semiconductor Field Effect Transistor (MFSFET) can partially change its polarization when the gate voltage near the polarization threshold voltage. This causes the MFSFET Drain current to change with repeated pulses of the same gate voltage near the polarization threshold voltage. A previously developed model [11, based on the Fermi-Dirac function, assumed that for a given gate voltage and channel polarization, a sin-le Drain current value would be generated. A study has been done to characterize the effects of partial polarization on the Drain current of a MFSFET. These effects have been described mathematically and these equations have been incorporated into a more comprehensive mathematical model of the MFSFET. The model takes into account the hysteresis nature of the MFSFET and the time dependent decay as well as the effects of partial polarization. This model defines the Drain current based on calculating the degree of polarization from previous gate pulses, the present Gate voltage, and the amount of time since the last Gate volta-e pulse.

Numerical simulation of low gravity draining. [computerized simulation of liquid sloshing in cylindrical tanks, and boundary value problems

NASA Technical Reports Server (NTRS)

Bizzell, G. D.; Crane, G. E.

1976-01-01

A boundary value problem was solved numerically for a liquid that is assumed to be inviscid and incompressible, having a motion that is irrotational and axisymmetric, and having a constant (5 degrees) solid-liquid contact angle. The avoidance of excessive mesh distortion, encountered with strictly Lagrangian or Eulerian kinematics, was achieved by introducing an auxiliary kinematic velocity field along the free surface in order to vary the trajectories used in integrating the ordinary differential equations simulating the moving boundary. The computation of the velocity potential was based upon a nonuniform triangular mesh which was automatically revised to varying depths to accommodate the motion of the free surface. These methods permitted calculation of draining induced axisymmetric slosh through the many (or fractional) finite amplitude oscillations that can occur depending upon the balance of draining, gravitational, and surface tension forces. Velocity fields, evolution of the free surface with time, and liquid residual volumes were computed for three and one half decades of Weber number and for two Bond numbers, tank fill levels, and drain radii. Comparisons with experimental data are very satisfactory.

A new solar cycle model including meridional circulation

NASA Technical Reports Server (NTRS)

Wang, Y.-M.; Sheeley, N. R., Jr.; Nash, A. G.

1991-01-01

A kinematic model is presented for the solar cycle which includes not only the transport of magnetic flux by supergranular diffusion and a poleward bulk flow at the sun's surface, but also the effects of turbulent diffusion and an equatorward 'return flow' beneath the surface. As in the earlier models of Babcock and Leighton, the rotational shearing of a subsurface poloidal field generates toroidal flux that erupts at the surface in the form of bipolar magnetic regions. However, such eruptions do not result in any net loss of toroidal flux from the sun (as assumed by Babcock and Leighton); instead, the large-scale toroidal field is destroyed both by 'unwinding' as the local poloidal field reverses its polarity, and by diffusion as the toroidal flux is transported equatorward by the subsurface flow and merged with its opposite hemisphere counterpart. The inclusion of meridional circulation allows stable oscillations of the magnetic field, accompanied by the equatorward progression of flux eruptions, to be achieved even in the absence of a radial gradient in the angular velocity. An illustrative case in which a subsurface flow speed of order 1 m/s and subsurface diffusion rate of order 10 sq km/s yield 22-yr oscillations in qualitative agreement with observations.

Performance of Subsurface Tube Drainage System in Saline Soils: A Case Study

NASA Astrophysics Data System (ADS)

Pali, A. K.

2015-06-01

In order to improve the saline and water logged soils caused due to groundwater table rise, installation of subsurface drainage system is considered as one of the best remedies. However, the design of the drainage system has to be accurate so that the field performance results conform to the designed results. In this investigation, the field performance of subsurface tube drainage system installed at the study area was evaluated. The performance was evaluated on the basis of comparison of the designed value of water table drop as 30 cm after 2 days of drainage and predicted and field measured hydraulic heads for a consecutive drainage period of 14 days. The investigation revealed that the actual drop of water table after 2 days of drainage was 25 cm, about 17 % less than the designed value of 30 cm after 2 days of drainage. The comparison of hydraulic heads predicted by Van Schilfgaarde equation of unsteady drainage with the field-measured hydraulic heads showed that the deviation of predicted hydraulic heads varied within a range of ±8 % indicating high acceptability of Van Schlifgaarde equation for designing subsurface drainage system in saline and water logged soils resembling to that of the study area.

Investigation of the novel attributes in double recessed gate SiC MESFETs at drain side

NASA Astrophysics Data System (ADS)

Orouji, Ali A.; Razavi, S. M.; Ebrahim Hosseini, Seyed; Amini Moghadam, Hamid

2011-11-01

In this paper, the potential impact of drain side-double recessed gate (DS-DRG) on silicon carbide (SiC)-based metal semiconductor field effect transistors (MESFETs) is studied. We investigate the device performance focusing on breakdown voltage, threshold voltage, drain current and dc output conductance with two-dimensional and two-carrier device simulation. Our simulation results demonstrate that the channel thickness under the gate in the drain side is an important factor in the breakdown voltage. Also, the positive shift in the threshold voltage for the DS-DRG structure is larger in comparison with that for the source side-double recessed gate (SS-DRG) SiC MESFET. The saturated drain current for the DS-DRG structure is larger compared to that for the SS-DRG structure. The maximum dc output conductance in the DS-DRG structure is smaller than that in the SS-DRG structure.

Design of double gate vertical tunnel field effect transistor using HDB and its performance estimation

NASA Astrophysics Data System (ADS)

Seema; Chauhan, Sudakar Singh

2018-05-01

In this paper, we demonstrate the double gate vertical tunnel field-effect transistor using homo/hetero dielectric buried oxide (HDB) to obtain the optimized device characteristics. In this concern, the existence of double gate, HDB and electrode work-function engineering enhances DC performance and Analog/RF performance. The use of electrostatic doping helps to achieve higher on-current owing to occurrence of higher tunneling generation rate of charge carriers at the source/epitaxial interface. Further, lightly doped drain region and high- k dielectric below channel and drain region are responsible to suppress the ambipolar current. Simulated results clarifies that proposed device have achieved the tremendous performance in terms of driving current capability, steeper subthreshold slope (SS), drain induced barrier lowering (DIBL), hot carrier effects (HCEs) and high frequency parameters for better device reliability.

Field-induced strain degradation of AlGaN/GaN high electron mobility transistors on a nanometer scale

NASA Astrophysics Data System (ADS)

Lin, Chung-Han; Doutt, D. R.; Mishra, U. K.; Merz, T. A.; Brillson, L. J.

2010-11-01

Nanoscale Kelvin probe force microscopy and depth-resolved cathodoluminescence spectroscopy reveal an electronic defect evolution inside operating AlGaN/GaN high electron mobility transistors with degradation under electric-field-induced stress. Off-state electrical stress results in micron-scale areas within the extrinsic drain expanding and decreasing in electric potential, midgap defects increasing by orders-of-magnitude at the AlGaN layer, and local Fermi levels lowering as gate-drain voltages increase above a characteristic stress threshold. The pronounced onset of defect formation, Fermi level movement, and transistor degradation at the threshold gate-drain voltage of J. A. del Alamo and J. Joh [Microelectron. Reliab. 49, 1200 (2009)] is consistent with crystal deformation and supports the inverse piezoelectric model of high electron mobility transistor degradation.

Perspective analysis of tri gate germanium tunneling field-effect transistor with dopant segregation region at source/drain

NASA Astrophysics Data System (ADS)

Liu, Liang-kui; Shi, Cheng; Zhang, Yi-bo; Sun, Lei

2017-04-01

A tri gate Ge-based tunneling field-effect transistor (TFET) has been numerically studied with technology computer aided design (TCAD) tools. Dopant segregated Schottky source/drain is applied to the device structure design (DS-TFET). The characteristics of the DS-TFET are compared and analyzed comprehensively. It is found that the performance of n-channel tri gate DS-TFET with a positive bias is insensitive to the dopant concentration and barrier height at n-type drain, and that the dopant concentration and barrier height at a p-type source considerably affect the device performance. The domination of electron current in the entire BTBT current of this device accounts for this phenomenon and the tri-gate DS-TFET is proved to have a higher performance than its dual-gate counterpart.

Removal of microbial pathogens in a sandy gravel aquifer under forced-gradient subsurface flow conditions

NASA Astrophysics Data System (ADS)

Oudega, Thomas James; Derx, Julia; van Driezum, Inge; Cisneros, Anibal; Sommer, Regina; Kirschner, Alexander; Farnleitner, Andreas; Blaschke, Alfred Paul

2017-04-01

Subsurface media are being used around the world as a means to mitigate microbial contamination, but vary widely in their ability to remove pathogens. To help to provide accurate risk assessments of microbial contamination of groundwaters, and establish safe setback distances between receiving waters and disposal fields, this study aims to use aquifer tracer tests to evaluate the ability of subsurface media to attenuate these pathogens. The novelty of this work is the use of a variety of different tracer substances (e.g. phages, spores, microspheres, conservative tracers) together in field experiments. This will be done by means of injecting these substances under a forced gradient in a sandy gravel aquifer in Lobau, Austria. The extraction of the tracers will be monitored in a pumping well at a distrance of 50m downgradient. This will be able to provide us with insight to the characteristics of microbial transport and how the microorganisms react to the subsurface in the study site. Subsequent numerical modelling of the experiments can tell us more about quantification of subsurface processes such as attachment/detachment, inactivation and die-off of these substances. The first field experiment with conservative tracers (NaCl) has been carried out in December 2016, and subsequent tests are being planned for the next months.

Measuring fallout radionuclides to constrain the origin and the dynamics of suspended sediment in an agricultural drained catchment (Loire River basin, France)

NASA Astrophysics Data System (ADS)

Le Gall, Marion; Evrard, Olivier; Foucher, Anthony; Laceby, J. Patrick; Salvador-Blanes, Sébastien; Lefèvre, Irène; Cerdan, Olivier; Ayrault, Sophie

2015-04-01

Soil erosion reaches problematic levels in agricultural areas of Northwestern Europe where tile drains may accelerate sediment transfer to rivers. This supply of large quantities of fine sediment to the river network leads to the degradation of water quality by increasing water turbidity, filling reservoirs and transporting contaminants. Agricultural patterns and landscapes features have been largely modified by human activities during the last century. To investigate erosion and sediment transport in lowland drained areas, a small catchment, the Louroux (24 km²), located in the French Loire River basin was selected. In this catchment, channels have been reshaped and more than 220 tile drains outlets have been installed after World War II. As a result, soil erosion and sediment fluxes strongly increased. Sediment supply needs to be better understood by quantifying the contribution of sources and the residence times of particles within the catchment. To this end, a network of river monitoring stations was installed, and fallout radionuclides (Cs-137, excess Pb-210 and Be-7) were measured in rainwater (n=3), drain tile outlets (n=4), suspended sediment (n=15), soil surface (n=30) and channel bank samples (n=15) between January 2013 and February 2014. Cs-137 concentrations were used to quantify the contribution of surface vs. subsurface sources of sediment. Results show a clear dominance of particles originating from surface sources (99 ± 1%). Be-7 and excess Pb-210 concentrations and calculation of Be-7/excess Pb-210 ratios in rainfall and suspended sediment samples were used to estimate percentages of recently eroded sediment in rivers. The first erosive winter storm mainly exported sediment depleted in Be-7 that likely deposited on the riverbed during the previous months. Then, during the subsequent floods, sediment was directly eroded and exported to the catchment outlet. Our results show the added value of combining spatial and temporal tracers to characterize and quantify sources of sediment and particle transport processes within an agricultural catchment.

Top-Contact Pentacene-Based Organic Thin Film Transistor (OTFT) with N, N'-Bis(3-Methyl Phenyl)- N, N'-Diphenyl Benzidine (TPD)/Au Bilayer Source-Drain Electrode

NASA Astrophysics Data System (ADS)

Borthakur, Tribeni; Sarma, Ranjit

2018-01-01

A top-contact Pentacene-based organic thin film transistor (OTFT) with N, N'-Bis (3-methyl phenyl)- N, N'-diphenyl benzidine (TPD)/Au bilayer source-drain electrode is reported. The devices with TPD/Au bilayer source-drain (S-D) electrodes show better performance than the single layer S-D electrode OTFT devices. The field-effect mobility of 4.13 cm2 v-1 s-1, the on-off ratio of 1.86 × 107, the threshold voltage of -4 v and the subthreshold slope of .27 v/decade, respectively, are obtained from the device with a TPD/Au bilayer source-drain electrode.

Field evaluations of a forestry version of DRAINMOD-NII model

Treesearch

S. Tian; M. A. Youssef; R.W. Skaggs; D.M. Amatya; G.M. Chescheir

2010-01-01

This study evaluated the performance of the newly developed forestry version of DRAINMOD-NII model using a long term (21-year) data set collected from an artificially drained loblolly pine (Pinus taeda L.) plantation in eastern North Carolina, U.S.A. The model simulates the main hydrological and biogeochemical processes in drained forested lands. The...

Breakthrough of two pesticides into tile drain and shallow groundwater: comparison of tile drain reaction and soil profiles within a field scale irrigation experiment

NASA Astrophysics Data System (ADS)

Klaus, Julian; Zehe, Erwin; Elsner, Martin; Palm, Juliane; Schneider, Dorothee; Schröder, Boris; Steinbeiss, Sibylle; West, Stephanie

2010-05-01

Preferential flow in macropores is a key process which strongly affects infiltration and may cause rapid transport of pesticides into depths of 80 to 150 cm. At these depths they experience a much slower degradation, may leach into shallow groundwater or enter a tile-drain and are transported into surface water bodies. Therefore, preferential transport might be an environmental problem, if the topsoil is bypassed, which has been originally thought to act as a filter to protect the subsoil and shallow groundwater. To investigate the behaviour of two pesticides with different chemical characteristics and to compare their transport behaviour in soil and into the tile drain an irrigation experiment was performed on a 400 m² field site. The experimental plot is located in the Weiherbach valley, south-west Germany, which basic geology consists of Loess and Keuper layers, the soil at the test site is a gleyic Colluvisol. The distance of the irrigation site to the Weiherbach brook is approximately 12 m, the field is drained with a tile-drain in about 1.2 m depth and shows discharge over the entire year. Three hours before the irrigation started, the farmer applied a pesticide solution consisting of Isoproturon (80 g) and Flufenacet (20 g) (IPU and FLU) according to conventional agricultural practice on the field plot. The irrigation took place in three time blocks (80 min, 60 min, 80 min) with in total 33.6 mm of precipitation. During the first block 1600 g of Bromide were mixed in the irrigation water. The drainage outlet was instrumented with a pressure probe. About 50 water samples ware taken during the experimental day, and several samples more the days after the experiment. They were analysed for the pesticides, bromide and water isotopes. In the two days after the experiment three soil profiles were excavated and soil samples were taken on a 10x10 cm² scheme. One week after the experiment two additional profiles were excavated. The soil was analysed for IPU, FLU and bromide. The tile drain water showed traces of bromide and both pesticides within a few minutes. IPU showed highest concentration before the hydrograph started to increase, while bromide and FLU are strongly correlated to the hydrograph. Although IPU is less sorptive than FLU the concentrations and total transported mass of FLU were significantly higher then for IPU. The hydrograph reacted with two peaks on the three block irrigation; the two peaks can be attributed to the second and third irrigation block. Analysis of the water isotopes showed that during the experiment the event water mainly consisted of soil water. While the tile drain showed significant reaction in pesticides transport the picture deriving from soil profiles were different. Especially FLU was found mainly in the upper soil parts, so the bypassing might occurred so fast that it was only marginally absorbed in deeper soil party, but transported to the drain or shallow groundwater. As preferential flow paths earthworm burrows of different species could be identified, although the area density and species number of anecic earthworms was quite low compared to other field sites.

Subsurface application enhances benefits of manure redistribution

USDA-ARS?s Scientific Manuscript database

Sustainable nutrient management requires redistribution of livestock manure from nutrient-excess areas to nutrient-deficit areas. Field experiments were conducted to assess agronomic and environmental effects of different poultry litter application methods (surface vs. subsurface) and timings (fall ...

Using SWAT-MODFLOW to simulate groundwater flow and groundwater-surface water interactions in an intensively irrigated stream-aquifer system

NASA Astrophysics Data System (ADS)

Wei, X.; Bailey, R. T.

2017-12-01

Agricultural irrigated watersheds in semi-arid regions face challenges such as waterlogging, high soil salinity, reduced crop yield, and leaching of chemical species due to extreme shallow water tables resulting from long-term intensive irrigation. Hydrologic models can be used to evaluate the impact of land management practices on water yields and groundwater-surface water interactions in such regions. In this study, the newly developed SWAT-MODFLOW, a coupled surface/subsurface hydrologic model, is applied to a 950 km2 watershed in the Lower Arkansas River Valley (southeastern Colorado). The model accounts for the influence of canal diversions, irrigation applications, groundwater pumping, and earth canal seepage losses. The model provides a detailed description of surface and subsurface flow processes, thereby enabling detailed description of watershed processes such as runoff, infiltration, in-streamflow, three-dimensional groundwater flow in a heterogeneous aquifer system with sources and sinks (e.g. pumping, seepage to subsurface drains), and spatially-variable surface and groundwater exchange. The model was calibrated and tested against stream discharge from 5 stream gauges in the Arkansas River and its tributaries, groundwater levels from 70 observation wells, and evapotranspiration (ET) data estimated from satellite (ReSET) data during the 1999 to 2007 period. Since the water-use patterns within the study area are typical of many other irrigated river valleys in the United States and elsewhere, this modeling approach is transferable to other regions.

Controls on denitrification in riparian soils in headwater catchments of a hardwood forest in the Catskill Mountains, U.S.A.

USGS Publications Warehouse

Ashby, J.A.; Bowden, W.B.; Murdoch, Peter S.

1998-01-01

Denitrification in riparian soils is thought to be an important factor that reduces hydrologic export of nitrate from forested and agricultural catchments. A 2-y study to identify the soil factors most closely associated with denitrification in riparian soils in headwater catchments within the Catskill Mountains of New York, included field surveys of surface and subsurface denitrification rates, and an amendment experiment to assess the relative effects of increases in available carbon and substrate NO-/3 on denitrification rates. Denitrification rates were measured by acetylene inhibition during incubation of intact soil cores from eight soil types representing a range of drainage classes. Soil cores were analyzed for organic matter, total P, extractable NO-/3-N and NH+/4-N, organic N, pH, moisture, porosity, and water-filled pore space, to determine which of these factors were most closely associated with denitrification. The distribution of denitrification rates found during the field surveys was highly skewed, with many low or zero values and few high values. Denitrification rates were positively associated with high soil organic matter, total P, and water-filled pore space, and were highest in seep (poorly-drained) soils, toeslope (seasonally-drained) soils, and stream-edge (poorly- to moderately well-drained) soils in which these three soil characteristics were typically high. Denitrification rates in these wet locations were also positively associated with soil NH+/4-N concentration and pH, but not with NO-/3-N concentration, suggesting that the rate of NO-/3 supply (via nitrification or hydrologic transport) was more important than the instantaneous concentration of NO-/3-N in the soils. The amendment experiment indicated that denitrification in soil types studied was most responsive to added glucose alone or with NO-/3. Thus, in these soils, a combination of slow rates of NO-/3 supply and low available carbon appears to limit denitrification. Annual denitrification rates in spring-fed soils (0.74 to 1.43 kg N ha-1 y-1) were up to 5 times greater than in other surface soils, yet these soils accounted for only 1.8% of the catchment's N loss through denitrification because they represent less than 3% of the catchment area. Dry upland soils constituted 71% of the catchment area and accounted for 91% of the catchment's N loss through denitrification. Annual denitrification in the catchment equaled about 65% of stream NO-/3-N and NH+/4-N export and 14% of precipitation NO-/3-N and NH+/4-N inputs. Denitrification appears to be important relative to N input and export in these Catskill catchments.

Nutrient loss in leachate and surface runoff from surface-broadcast and subsurface-banded broiler litter.

PubMed

Lamba, Jasmeet; Srivastava, Puneet; Way, Thomas R; Sen, Sumit; Wood, C Wesley; Yoo, Kyung H

2013-09-01

Subsurface band application of poultry litter has been shown to reduce the transport of nutrients from fields in surface runoff compared with conventional surface broadcast application. Little research has been conducted to determine the effects of surface broadcast application and subsurface banding of litter on nutrients in leachate. Therefore, a field experiment was conducted to determine the effects of subsurface band application and surface broadcast application of poultry litter on nutrient losses in leachate. Zero-tension pan and passive capillary fiberglass wick lysimeters were installed in situ 50 cm beneath the soil surface of an established tall fescue ( Schreb.) pasture on a sandy loam soil. The treatments were surface broadcast and subsurface-banded poultry litter at 5 Mg ha and an unfertilized control. Results of the rainfall simulations showed that the concentrations of PO-P and total phosphorus (TP) in leachate were reduced by 96 and 37%, respectively, in subsurface-banded litter treatment compared with the surface-applied litter treatment. There was no significant difference in PO-P concentration between control and subsurface-banded litter treatment in leachate. The trend in the loading of nutrients in leachate was similar to the trend in concentration. Concentration and loading of the nutrients (TP, PO-P, NH-N, and NO-N) in runoff from the subsurface-banded treatment were significantly less than for the surface-applied treatment and were similar to those from control plots. These results show that, compared with conventional surface broadcast application of litter, subsurface band application of litter can greatly reduce loss of P in surface runoff and leachate. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Canine scent detection and microbial source tracking of human waste contamination in storm drains.

PubMed

Van De Werfhorst, Laurie C; Murray, Jill L S; Reynolds, Scott; Reynolds, Karen; Holden, Patricia A

2014-06-01

Human fecal contamination of surface waters and drains is difficult to diagnose. DNA-based and chemical analyses of water samples can be used to specifically quantify human waste contamination, but their expense precludes routine use. We evaluated canine scent tracking, using two dogs trained to respond to the scent of municipal wastewater, as a field approach for surveying human fecal contamination. Fecal indicator bacteria, as well as DNA-based and chemical markers of human waste, were analyzed in waters sampled from canine scent-evaluated sites (urban storm drains and creeks). In the field, the dogs responded positively (70% and 100%) at sites for which sampled waters were then confirmed as contaminated with human waste. When both dogs indicated a negative response, human waste markers were absent. Overall, canine scent tracking appears useful for prioritizing sampling sites for which DNA-based and similarly expensive assays can confirm and quantify human waste contamination.

A pH sensor based on electric properties of nanotubes on a glass substrate

PubMed Central

Nakamura, Motonori; Ishii, Atsushi; Subagyo, Agus; Hosoi, Hirotaka; Sueoka, Kazuhisa; Mukasa, Koichi

2007-01-01

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of ann-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that thep-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface. PMID:21806848

Multiple-channel detection of cellular activities by ion-sensitive transistors

NASA Astrophysics Data System (ADS)

Machida, Satoru; Shimada, Hideto; Motoyama, Yumi

2018-04-01

An ion-sensitive field-effect transistor to record cellular activities was demonstrated. This field-effect transistor (bio transistor) includes cultured cells on the gate insulator instead of gate electrode. The bio transistor converts a change in potential underneath the cells into variation of the drain current when ion channels open. The bio transistor has high detection sensitivity to even minute variations in potential utilizing a subthreshold swing region. To open ion channels, a reagent solution (acetylcholine) was added to a human-originating cell cultured on the bio transistor. The drain current was successfully decreased with the addition of acetylcholine. Moreover, we attempted to detect the opening of ion channels using a multiple-channel measurement circuit containing several bio transistors. As a consequence, the drain current distinctly decreased only after the addition of acetylcholine. We confirmed that this measurement system including bio transistors enables to observation of cellular activities sensitively and simultaneously.

Soft-type trap-induced degradation of MoS2 field effect transistors.

PubMed

Cho, Young-Hoon; Ryu, Min-Yeul; Lee, Kook Jin; Park, So Jeong; Choi, Jun Hee; Lee, Byung-Chul; Kim, Wungyeon; Kim, Gyu-Tae

2018-06-01

The practical applicability of electronic devices is largely determined by the reliability of field effect transistors (FETs), necessitating constant searches for new and better-performing semiconductors. We investigated the stress-induced degradation of MoS 2 multilayer FETs, revealing a steady decrease of drain current by 56% from the initial value after 30 min. The drain current recovers to the initial state when the transistor is completely turned off, indicating the roles of soft-traps in the apparent degradation. The noise current power spectrum follows the model of carrier number fluctuation-correlated mobility fluctuation (CNF-CMF) regardless of stress time. However, the reduction of the drain current was well fitted to the increase of the trap density based on the CNF-CMF model, attributing the presence of the soft-type traps of dielectric oxides to the degradation of the MoS 2 FETs.

Soft-type trap-induced degradation of MoS2 field effect transistors

NASA Astrophysics Data System (ADS)

Cho, Young-Hoon; Ryu, Min-Yeul; Lee, Kook Jin; Park, So Jeong; Choi, Jun Hee; Lee, Byung-Chul; Kim, Wungyeon; Kim, Gyu-Tae

2018-06-01

The practical applicability of electronic devices is largely determined by the reliability of field effect transistors (FETs), necessitating constant searches for new and better-performing semiconductors. We investigated the stress-induced degradation of MoS2 multilayer FETs, revealing a steady decrease of drain current by 56% from the initial value after 30 min. The drain current recovers to the initial state when the transistor is completely turned off, indicating the roles of soft-traps in the apparent degradation. The noise current power spectrum follows the model of carrier number fluctuation–correlated mobility fluctuation (CNF–CMF) regardless of stress time. However, the reduction of the drain current was well fitted to the increase of the trap density based on the CNF–CMF model, attributing the presence of the soft-type traps of dielectric oxides to the degradation of the MoS2 FETs.

Velocity overshoot decay mechanisms in compound semiconductor field-effect transistors with a submicron characteristic length

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jyegal, Jang, E-mail: jjyegal@inu.ac.kr

Velocity overshoot is a critically important nonstationary effect utilized for the enhanced performance of submicron field-effect devices fabricated with high-electron-mobility compound semiconductors. However, the physical mechanisms of velocity overshoot decay dynamics in the devices are not known in detail. Therefore, a numerical analysis is conducted typically for a submicron GaAs metal-semiconductor field-effect transistor in order to elucidate the physical mechanisms. It is found that there exist three different mechanisms, depending on device bias conditions. Specifically, at large drain biases corresponding to the saturation drain current (dc) region, the velocity overshoot suddenly begins to drop very sensitively due to the onsetmore » of a rapid decrease of the momentum relaxation time, not the mobility, arising from the effect of velocity-randomizing intervalley scattering. It then continues to drop rapidly and decays completely by severe mobility reduction due to intervalley scattering. On the other hand, at small drain biases corresponding to the linear dc region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid increase of thermal energy diffusion by electrons in the channel of the gate. It then continues to drop rapidly for a certain channel distance due to the increasing thermal energy diffusion effect, and later completely decays by a sharply decreasing electric field. Moreover, at drain biases close to a dc saturation voltage, the mechanism is a mixture of the above two bias conditions. It is suggested that a large secondary-valley energy separation is essential to increase the performance of submicron devices.« less

Analytical results from an environmental investigation of six sites on Kirtland Air Force Base, New Mexico, 1993-94

USGS Publications Warehouse

Wilcox, Ralph

1995-01-01

The six sites investigated include silver recovery units; a buried caustic drain line; a neutralization pit; an evaporation/infiltration pond; the Manzano fire training area; and a waste oil underground storage tank. Environmental samples of soil, pond sediment, soil gas, and water and gas in floor drains were collected and analyzed. Field quality-control samples were also collected and analyzed in association with the environmental samples. The six sites were investigated because past or current activities could have resulted in contamination of soil, pond sediment, or water and sediment in drains.

Suppression of ambipolar current in tunnel FETs using drain-pocket: Proposal and analysis

NASA Astrophysics Data System (ADS)

Garg, Shelly; Saurabh, Sneh

2018-01-01

In this paper, we investigate the impact of a drain-pocket (DP) adjacent to the drain region in Tunnel Field-Effect Transistors (TFETs) to effectively suppress the ambipolar current. Using calibrated two-dimensional device simulation, we examine the impact of DP in Double Gate TFET (DGTFET). We demonstrate the superiority of the DP technique over the existing techniques in controlling the ambipolar current. In particular, the addition of DP to a TFET is able to fully suppress the ambipolar current even when TFET is biased at high negative gate voltages and drain doping is kept as high as the source doping. Moreover, adding DP is complementary to the well-known technique of employ-ing source-pocket (SP) in a TFET since both need similar doping type and doping concentration.

Effects of pond draining on biodiversity and water quality of farm ponds.

PubMed

Usio, Nisikawa; Imada, Miho; Nakagawa, Megumi; Akasaka, Munemitsu; Takamura, Noriko

2013-12-01

Farm ponds have high conservation value because they contribute significantly to regional biodiversity and ecosystem services. In Japan pond draining is a traditional management method that is widely believed to improve water quality and eradicate invasive fish. In addition, fishing by means of pond draining has significant cultural value for local people, serving as a social event. However, there is a widespread belief that pond draining reduces freshwater biodiversity through the extirpation of aquatic animals, but scientific evaluation of the effectiveness of pond draining is lacking. We conducted a large-scale field study to evaluate the effects of pond draining on invasive animal control, water quality, and aquatic biodiversity relative to different pond-management practices, pond physicochemistry, and surrounding land use. The results of boosted regression-tree models and analyses of similarity showed that pond draining had little effect on invasive fish control, water quality, or aquatic biodiversity. Draining even facilitated the colonization of farm ponds by invasive red swamp crayfish (Procambarus clarkii), which in turn may have detrimental effects on the biodiversity and water quality of farm ponds. Our results highlight the need for reconsidering current pond management and developing management plans with respect to multifunctionality of such ponds. Efectos del Drenado de Estanques sobre la Biodiversidad y la Calidad del Agua en Estanques de Cultivo. © 2013 Society for Conservation Biology.

Field evaluations of "ShapeAccelArray" in-place MEMS inclinometer strings for subsurface deformation monitoring.

DOT National Transportation Integrated Search

2012-03-01

Continuous monitoring of subsurface ground movements is accomplished with in-place instruments utilizing automated data acquisition methods. These typically include TDR (Time Domain Reflectometry) or assemblies of several servo-accelerometer-based, e...

OVERVIEW -- SUBSURFACE PROTECTION AND REMEDIATION DIVISION

EPA Science Inventory

NRMRL's Subsurface Protection and Remediation Division located in Ada, Oklahoma, conducts EPA-investigator led laboratory and field research to provide the scientific basis to support the development of strategies and technologies to protect and restore ground and surface water q...

Electroluminescence and other diagnostic techniques for the study of hot-electron effects in compound semiconductor devices

NASA Astrophysics Data System (ADS)

Zanoni, Enrico; Meneghesso, Gaudenzio; Menozzi, Roberto

2000-03-01

Hot electron in III-V FETs can be indirectly monitored by measuring the current coming out from the gate when the device is biased at high electric fields. This negative current is due to the collection of holes generated by impact ionization in the gate-to drain region. Electroluminescence represents a powerful tool in order to characterize not only hot electrons but also material properties. By using spatially resolved emission microscopy it is possible to show that the light due to cold electron/hole recombination is emitted between the gate and the source (low electric field region), while the contribution due to hot electrons is emitted between the gate and the drain (high electric field region). Deep-traps created in the device by hot carriers can be analysed by means of drain current deep level transient spectroscopy and by transconductance frequency dispersion. Cathodoluminescence, optical beam induced current, X-ray spectroscopy, electron energy loss spectroscopy in combination with a transmission electron microscopy are powerful tools in order to identify and localize surface modification following hot-electron stress tests.

Modeling hydrology and in-stream transport on drained forested lands in coastal Carolinas, U.S.A.

Treesearch

Devendra Amatya

2005-01-01

This study summarizes the successional development and testing of forest hydrologic models based on DRAINMOD that predicts the hydrology of low-gradient poorly drained watersheds as affected by land management and climatic variation. The field scale (DRAINLOB) and watershed-scale in-stream routing (DRAINWAT) models were successfully tested with water table and outflow...

Hydrology of Poorly Drained Coastal Watersheds in Eastern North Carolina

Treesearch

Devendra M. Amatya; George M. Chescheir; R. Wayne Skaggs; Glenn P. Fernandez

2002-01-01

A 10,000 ha lower coastal plain land near Plymouth in eastern North Carolina has been intensively monitored since 1996 to measure hydro-meteorological parameters including outflows and quality of water drained from fields and subwatersheds with varying land management practices. This study summarized the data for a six-year period (1996-2001) for a 2950 ha forested, a...

Particle sensor array

NASA Technical Reports Server (NTRS)

Buehler, Martin G. (Inventor); Blaes, Brent R. (Inventor); Lieneweg, Udo (Inventor)

1994-01-01

A particle sensor array which in a preferred embodiment comprises a static random access memory having a plurality of ion-sensitive memory cells, each such cell comprising at least one pull-down field effect transistor having a sensitive drain surface area (such as by bloating) and at least one pull-up field effect transistor having a source connected to an offset voltage. The sensitive drain surface area and the offset voltage are selected for memory cell upset by incident ions such as alpha-particles. The static random access memory of the present invention provides a means for selectively biasing the memory cells into the same state in which each of the sensitive drain surface areas is reverse biased and then selectively reducing the reversed bias on these sensitive drain surface areas for increasing the upset sensitivity of the cells to ions. The resulting selectively sensitive memory cells can be used in a number of applications. By way of example, the present invention can be used for measuring the linear energy transfer of ion particles, as well as a device for assessing the resistance of CMOS latches to Cosmic Ray induced single event upsets. The sensor of the present invention can also be used to determine the uniformity of an ion beam.

Radio Sounding Techniques for the Galilean Icy Moons and their Jovian Magnetospheric Environment

NASA Technical Reports Server (NTRS)

Green, James L.; Markus, Thursten; Fung, Shing F.; Benson, Robert F.; Reinich, Bodo W.; Song, Paul; Gogineni, S. Prasad; Cooper, John F.; Taylor, William W. L.; Garcia, Leonard

2004-01-01

Radio sounding of the Earth's topside ionosphere and magnetosphere is a proven technique from geospace missions such as the International Satellites for Ionospheric Studies (ISIS) and the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE). Application of this technique to Jupiter's icy moons and the surrounding Jovian magnetosphere will provide unique remote sensing observations of the plasma and magnetic field environments and the subsurface conductivities, of Europa, Ganymede, and Callisto. Spatial structures of ionospheric plasma above the surfaces of the moons vary in response to magnetic-field perturbations from (1) magnetospheric plasma flows, (2) ionospheric currents from ionization of sputtered surface material, and (3) induced electric currents in salty subsurface oceans and from the plasma flows and ionospheric currents themselves. Radio sounding from 3 kHz to 10 MHz can provide the global electron densities necessary for the extraction of the oceanic current signals and supplements in-situ plasma and magnetic field measurements. While radio sounding requires high transmitter power for subsurface sounding, little power is needed to probe the electron density and magnetic field intensity near the spacecraft. For subsurface sounding, reflections occur at changes in the dielectric index, e.g., at the interfaces between two different phases of water or between water and soil. Variations in sub-surface conductivity of the icy moons can be investigated by radio sounding in the frequency range from 10 MHz to 50 MHz, allowing the determination of the presence of density and solid-liquid phase boundaries associated with oceans and related structures in overlying ice crusts. The detection of subsurface oceans underneath the icy crusts of the Jovian moons is one of the primary objectives of the Jupiter Icy Moons Orbiter (JIMO) mission. Preliminary modeling results show that return signals are clearly distinguishable be&een an ice crust with a thickness of 7 km on 1) an ocean and 2) a layer of bedrock. Knowledge of the ionospheric contributions to the time delay of the low-frequency subsurface radar is shown to be important in obtaining accurate depth information.

Controls of event-based nutrient transport within nested headwater agricultural watersheds of the western Lake Erie basin

NASA Astrophysics Data System (ADS)

Williams, Mark R.; Livingston, Stanley J.; Penn, Chad J.; Smith, Douglas R.; King, Kevin W.; Huang, Chi-hua

2018-04-01

Understanding the processes controlling nutrient delivery in headwater agricultural watersheds is essential for predicting and mitigating eutrophication and harmful algal blooms in receiving surface waters. The objective of this study was to elucidate nutrient transport pathways and examine key components driving nutrient delivery processes during storm events in four nested agricultural watersheds (298-19,341 ha) in the western Lake Erie basin with poorly drained soils and an extensive artificial drainage network typical of the Midwestern U.S. Concentration-discharge hysteresis patterns of nitrate-nitrogen (NO3-N), dissolved reactive phosphorus (DRP), and particulate phosphorus (PP) occurring during 47 storm events over a 6 year period (2004-2009) were evaluated. An assessment of the factors producing nutrient hysteresis was completed following a factor analysis on a suite of measured environmental variables representing the fluvial and wider watershed conditions prior to, and during the monitored storm events. Results showed the artificial drainage network (i.e., surface tile inlets and subsurface tile drains) in these watersheds was the primary flow pathway for nutrient delivery to streams, but nutrient behavior and export during storm events was regulated by the flow paths to and the intensity of the drainage network, the availability of nutrients, and the relative contributions of upland and in-stream nutrient sources. Potential sources and flow pathways for transport varied among NO3-N, PP, and DRP with results underscoring the challenge of mitigating nutrient loss in these watersheds. Conservation practices addressing both nutrient management and hydrologic connectivity will likely be required to decrease nutrient loss in artificially drained landscapes.

Establishment and application of the estimation model for pollutant concentrfation in agriculture drain

NASA Astrophysics Data System (ADS)

Li, Qiangkun; Hu, Yawei; Jia, Qian; Song, Changji

2018-02-01

It is the key point of quantitative research on agricultural non-point source pollution load, the estimation of pollutant concentration in agricultural drain. In the guidance of uncertainty theory, the synthesis of fertilization and irrigation is used as an impulse input to the farmland, meanwhile, the pollutant concentration in agricultural drain is looked as the response process corresponding to the impulse input. The migration and transformation of pollutant in soil is expressed by Inverse Gaussian Probability Density Function. The law of pollutants migration and transformation in soil at crop different growth periods is reflected by adjusting parameters of Inverse Gaussian Distribution. Based on above, the estimation model for pollutant concentration in agricultural drain at field scale was constructed. Taking the of Qing Tong Xia Irrigation District in Ningxia as an example, the concentration of nitrate nitrogen and total phosphorus in agricultural drain was simulated by this model. The results show that the simulated results accorded with measured data approximately and Nash-Sutcliffe coefficients were 0.972 and 0.964, respectively.

Mars' Magnetic Atmosphere: Ionospheric Currents, Lightning (or Not), E and M Subsurface Sounding, and Future Missions

NASA Technical Reports Server (NTRS)

Espley, J. R.; Connerney, J. E. P.

2014-01-01

Mars' ionosphere has no obvious magnetic signs of large-scale, dustproduced lightning. However, there are numerous interesting ionospheric currents (some associated with crustal magnetic fields) which would allow for E&M subsurface sounding.

PREDICTING SUBSURFACE CONTAMINANT TRANSPORT AND TRANSFORMATION: CONSIDERATIONS FOR MODEL SELECTION AND FIELD VALIDATION

EPA Science Inventory

Predicting subsurface contaminant transport and transformation requires mathematical models based on a variety of physical, chemical, and biological processes. The mathematical model is an attempt to quantitatively describe observed processes in order to permit systematic forecas...

Nutrient Removal Benefits of Two-Stage Ditches

NASA Astrophysics Data System (ADS)

Liu, X.; Ward, A.

2016-12-01

Annually, about one-third of the corn and soybeans in the world is grown in the North Central Region of the United States. Water quality problems associated with these production systems are caused by: (1) discharges of dissolved reactive phosphorus into the Great Lakes and inland water bodies; and (2) discharges of nitrogen into the Gulf of Mexico. These discharges have caused large blue-green algal blooms in freshwater systems and hypoxia particularly in the Gulf of Mexico. Much of the region has poorly drained soils that necessitate the use of subsurface drainage system to make the fields farmable. These drains discharge into agricultural ditches that are usually 2-5 m deep and 10 to 20 m wide. These oversized ditches often form small grassed benches in their lower third. A common maintenance practice is to periodically cleanout these deposits. However, in the last 15 years a new practice has been developed by one of the co-authors. This practice does not disturb the lower portion of the ditch but widens the top portion to make the benches larger. This floodplain development practice is known as the two-stage ditch concept. The approach results in the ditches acting as intermittent linear wetlands. The practice is eligible for cost-sharing funding as a water quality Best Management Practice in Indiana and Ohio. This presentation will provide a summary of the research that has been conducted on two-stage ditches and in particular their nutrient removal potential. In addition, results of a new controlled study on the nitrogen and phosphorus removal performance of a two-stage ditch will be presented. This study introduced water with fixed concentrations of each nutrient into a two-stage ditch. Measurements were made of: (1) the retention time in the system; (2) changes in the surface water quality; (3) and changes in the water quality and water level elevations in nested piezometers and monitoring wells located in the benches and banks of the two-stage ditch.

Innovative Technique for the Placement of the Drainage Tube for Microendoscopic Spinal Decompression.

PubMed

Mizuno, Kentaro; Mikami, Yasuo; Hase, Hitoshi; Ikeda, Takumi; Nagae, Masateru; Tonomura, Hitoshi; Shirai, Toshiharu; Fujiwara, Hiroyoshi; Kubo, Toshikazu

2017-02-01

A technical note and retrospective study. The objectives were to describe a new method of drainage tube placement during microendoscopic spinal decompression, and compare the positioning and fluid discharge obtained with this method and the conventional method. To prevent postoperative epidural hematoma after microendoscopic decompression, a drainage tube must be placed in a suitable location. However, the narrow operative field makes precise control of the position of the tube technically difficult. We developed a method to reliably place the tube in the desired location. We use a Deschamps aneurysm needle with a slightly curved tip, which we call a drain passer. With the microendoscope in position, the drain passer, with a silk thread passed through the eye at the needle tip, is inserted percutaneously into the endoscopic field of view. The drainage tube is passed through the loop of silk thread protruding from the inside of the tubular retractor, and the thread is pulled to the outside, guiding the end of the drainage tube into the wound. This method was used in 23 cases at 44 intervertebral levels (drain passer group), and the conventional method in 20 cases at 32 intervertebral levels (conventional group). Postoperative plain radiographs were taken, and the amount of fluid discharge at postoperative hour 24 was measured. Drainage tube positioning was favorable at 43 intervertebral levels (97.7%) in the drain passer group and 26 intervertebral levels (81.3%) in the conventional group. Mean fluid discharge was 58.4±32.2 g in the drain passer group and 38.4±23.0 g in the conventional group. Positioning was significantly better and fluid discharge was significantly greater in the drain passer group. The results indicate that this method is a useful drainage tube placement technique for preventing postoperative epidural hematoma.

Pits in Polar Cap

NASA Technical Reports Server (NTRS)

2006-01-01

This full-frame image from the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter shows faults and pits in Mars' north polar residual cap that have not been previously recognized.

The faults and depressions between them are similar to features seen on Earth where the crust is being pulled apart. Such tectonic extension must have occurred very recently because the north polar residual cap is very young, as indicated by the paucity of impact craters on its surface. Alternatively, the faults and pits may be caused by collapse due to removal of material beneath the surface. The pits are aligned along the faults, either because material has drained into the subsurface along the faults or because gas has escaped from the subsurface through them.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.

REE in the Great Whale River estuary, northwest Quebec

NASA Technical Reports Server (NTRS)

Goldstein, Steven J.; Jacobsen, Stein B.

1988-01-01

A report on REE concentrations within the estuary of the Great Whale River in northwest Quebec and in Hudson Bay is given, showing concentrations which are less than those predicted by conservative mixing of seawater and river water, indicating removal of REE from solution. REE removal is rapid, occurring primarily at salinities less than 2 percent and ranges from about 70 percent for light REE to no more than 40 percent for heavy REE. At low salinity, Fe removal is essentially complete. The shape of Fe and REE vs. salinity profiles is not consistent with a simple model of destabilization and coagulation of Fe and REE-bearing colloidal material. A linear relationship between the activity of free ion REE(3+) and pH is consistent with a simple ion-exchange model for REE removal. Surface and subsurface samples of Hudson Bay seawater show high REE and La/Yb concentrations relative to average seawater, with the subsurface sample having a Nd concentration of 100 pmol/kg and an epsilon(Nd) of -29.3; characteristics consistent with river inputs of Hudson Bay. This indicates that rivers draining the Canadian Shield are a major source of nonradiogenic Nd and REE to the Atlantic Ocean.

A design study for a medium-scale field demonstration of the viscous barrier technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moridis, G.; Yen, P.; Persoff, P.

1996-09-01

This report is the design study for a medium-scale field demonstration of Lawrence Berkeley National Laboratory`s new subsurface containment technology for waste isolation using a new generation of barrier liquids. The test site is located in central California in a quarry owned by the Los Banos Gravel Company in Los Banos, California, in heterogeneous unsaturated deposits of sand, silt, and -ravel typical of many of the and DOE cleanup sites and particularly analogous to the Hanford site. The coals of the field demonstration are (a) to demonstrate the ability to create a continuous subsurface barrier isolating a medium-scale volume (30more » ft long by 30 ft wide by 20 ft deep, i.e. 1/10th to 1/8th the size of a buried tank at the Hanford Reservation) in the subsurface, and (b) to demonstrate the continuity, performance, and integrity of the barrier.« less

Herbicides and transformation products in surface waters of the Midwestern United States

USGS Publications Warehouse

Battaglin, W.A.; Thurman, E.M.; Kalkhoff, S.J.; Porter, S.D.

2003-01-01

Most herbicides applied to crops are adsorbed by plants or transformed (degraded) in the soil, but small fractions are lost from fields and either move to streams in overland runoff, near surface flow, or subsurface drains, or they infiltrate slowly to ground water. Herbicide transformation products (TPs) can be more or less mobile and more or less toxic in the environment than their source herbicides. To obtain information on the concentrations of selected herbicides and TPs in surface waters of the Midwestern United States, 151 water samples were collected from 71 streams and five reservoir outflows in 1998. These samples were analyzed for 13 herbicides and 10 herbicide TPs. Herbicide TPs were found to occur as frequently or more frequently than source herbicides and at concentrations that were often larger than their source herbicides. Most samples contained a mixture of more than 10 different herbicides or TPs. The ratios of TPs to herbicide concentrations can be used to determine the source of herbicides in streams. Results of a two-component mixing model suggest that on average 90 percent or more of the herbicide mass in Midwestern streams during early summer runoff events originates from the runoff and 10 percent or less comes from increased ground water discharge.

Influence of Assimilation of Subsurface Temperature Measurements on Simulations of Equatorial Undercurrent and South Equatorial Current Along the Pacific Equator

NASA Technical Reports Server (NTRS)

Halpern, David; Leetmaan, Ants; Reynolds, Richard W.; Ji, Ming

1997-01-01

Equatorial Pacific current and temperature fields were simulated with and without assimilation of subsurface temperature measurements for April 1992 - March 1995, and compared with moored bouy and research vessel current measurements.

Time series analysis of contaminant transport in the subsurface: applications to conservative tracer and engineered nanomaterials.

PubMed

Bai, Chunmei; Li, Yusong

2014-08-01

Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Time series analysis of contaminant transport in the subsurface: Applications to conservative tracer and engineered nanomaterials

NASA Astrophysics Data System (ADS)

Bai, Chunmei; Li, Yusong

2014-08-01

Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed.

Use of Large-Scale Multi-Configuration EMI Measurements to Characterize Subsurface Structures of the Vadose Zone.

NASA Astrophysics Data System (ADS)

Huisman, J. A.; Brogi, C.; Pätzold, S.; Weihermueller, L.; von Hebel, C.; Van Der Kruk, J.; Vereecken, H.

2017-12-01

Subsurface structures of the vadose zone can play a key role in crop yield potential, especially during water stress periods. Geophysical techniques like electromagnetic induction EMI can provide information about dominant shallow subsurface features. However, previous studies with EMI have typically not reached beyond the field scale. We used high-resolution large-scale multi-configuration EMI measurements to characterize patterns of soil structural organization (layering and texture) and their impact on crop productivity at the km2 scale. We collected EMI data on an agricultural area of 1 km2 (102 ha) near Selhausen (NRW, Germany). The area consists of 51 agricultural fields cropped in rotation. Therefore, measurements were collected between April and December 2016, preferably within few days after the harvest. EMI data were automatically filtered, temperature corrected, and interpolated onto a common grid of 1 m resolution. Inspecting the ECa maps, we identified three main sub-areas with different subsurface heterogeneity. We also identified small-scale geomorphological structures as well as anthropogenic activities such as soil management and buried drainage networks. To identify areas with similar subsurface structures, we applied image classification techniques. We fused ECa maps obtained with different coil distances in a multiband image and applied supervised and unsupervised classification methodologies. Both showed good results in reconstructing observed patterns in plant productivity and the subsurface structures associated with them. However, the supervised methodology proved more efficient in classifying the whole study area. In a second step, we selected hundred locations within the study area and obtained a soil profile description with type, depth, and thickness of the soil horizons. Using this ground truth data it was possible to assign a typical soil profile to each of the main classes obtained from the classification. The proposed methodology was effective in producing a high resolution subsurface model in a large and complex study area that extends well beyond the field scale.

A novel double gate MOSFET by symmetrical insulator packets with improved short channel effects

NASA Astrophysics Data System (ADS)

Ramezani, Zeinab; Orouji, Ali A.

2018-03-01

In this article, we study a novel double-gate SOI MOSFET structure incorporating insulator packets (IPs) at the junction between channel and source/drain (S/D) ends. The proposed MOSFET has great strength in inhibiting short channel effects and OFF-state current that are the main problems compared with conventional one due to the significant suppressed penetrations of both the lateral electric field and the carrier diffusion from the S/D into the channel. Improvement of the hot electron reliability, the ON to OFF drain current ratio, drain-induced barrier lowering, gate-induced drain leakage and threshold voltage over conventional double-gate SOI MOSFETs, i.e. without IPs, is displayed with the simulation results. This study is believed to improve the CMOS device reliability and is suitable for the low-power very-large-scale integration circuits.

Thin-film transistors with a graphene oxide nanocomposite channel.

PubMed

Jilani, S Mahaboob; Gamot, Tanesh D; Banerji, P

2012-12-04

Graphene oxide (GO) and graphene oxide-zinc oxide nanocomposites (GO-ZnO) were used as channel materials on SiO(2)/Si to fabricate thin-film transistors (TFT) with an aluminum source and drain. Pure GO-based TFT showed poor field-effect characteristics. However, GO-ZnO-nanocomposite-based TFT showed better field-effect performance because of the anchoring of ZnO nanostructures in the GO matrix, which causes a partial reduction in GO as is found from X-ray photoelectron spectroscopic data. The field-effect mobility of charge carriers at a drain voltage of 1 V was found to be 1.94 cm(2)/(V s). The transport of charge carriers in GO-ZnO was explained by a fluctuation-induced tunneling mechanism.

Water balance of drained plantation watersheds in North Carolina

Treesearch

Johnny M. Grace; R. W. Skaggs

2006-01-01

A 3-year study to evaluate the effect of thinning on the hydrology of a drained loblolly pine (Pinus taeda L.) plantation was conducted in eastern North Carolina. The study utilized a paired watershed design with a 40-ha thinned watershed (WS5) and a 16-ha control watershed (WS2). Data from the field experiment conducted from 1999-2002 was used to...

Calibration and Validation of the Precision Nitrogen Management Tool for Artificially Drained Fields Under Maize

NASA Astrophysics Data System (ADS)

Marjerison, R.; Hutson, J.; Melkonian, J.; van Es, H.; Sela, S.

2015-12-01

Organic and inorganic fertilizer additions to agricultural fields can lead to soil nitrogen (N) levels in excess of those required for optimal crop growth. The primary loss pathways for this excess N are leaching and denitrification. Nitrate leaching from agricultural sources contributes to the formation of hypoxic zones in critical estuarine systems including the Chesapeake Bay and Gulf of Mexico. Denitrification can lead to the production of nitrous oxide (N2O), a potent greenhouse gas. Agricultural practices such as controlling the timing and location of fertilizer application can help reduce these losses. The Precision Nitrogen Management (PNM) model was developed to simulate water transport, nitrogen transformations and transport, and crop growth and nutrient uptake from agricultural fields. The PNM model allows for the prediction of N losses under a variety of crop and management scenarios. Recent improvements to the model include the option to simulate artificially drained fields. The model performs well in simulating drainage and nitrate leaching when compared to measured data from field studies in artificially drained soils in New York and Minnesota. A simulated N budget was compared to available data. The improved model will be used to assess different management options for reducing N losses in maize production under different climate projections for key maize production locations/systems in the U.S.

Hydrosalinity studies of the Virgin River, Dixie Hot Springs, and Littlefield Springs, Utah, Arizona, and Nevada

USGS Publications Warehouse

Gerner, Steven J.; Thiros, Susan A.; Gerner, Steven J.; Thiros, Susan A.

2014-01-01

The Virgin River contributes a substantial amount of dissolved solids (salt) to the Colorado River at Lake Mead in the lower Colorado River Basin. Degradation of Colorado River water by the addition of dissolved solids from the Virgin River affects the suitability of the water for municipal, industrial, and agricultural use within the basin. Dixie Hot Springs in Utah are a major localized source of dissolved solids discharging to the Virgin River. The average measured discharge from Dixie Hot Springs during 2009–10 was 11.0 cubic feet per second (ft3/s), and the average dissolved-solids concentration was 9,220 milligrams per liter (mg/L). The average dissolved-solids load—a measurement that describes the mass of salt that is transported per unit of time—from Dixie Hot Springs during this period was 96,200 tons per year (ton/yr). Annual dissolved-solids loads were estimated at 13 monitoring sites in the Virgin River Basin from streamflow data and discrete measurements of dissolved-solids concentrations and (or) specific conductance. Eight of the sites had the data needed to estimate annual dissolved-solids loads for water years (WYs) 1999 through 2010. During 1999–2010, the smallest dissolved-solids loads in the Virgin River were upstream of Dixie Hot Springs (59,900 ton/yr, on average) and the largest loads were downstream of Littlefield Springs (298,200 ton/yr, on average). Annual dissolved-solids loads were smallest during 2002–03, which was a period of below normal precipitation. Annual dissolved-solids loads were largest during 2005—a year that included a winter rain storm that resulted in flooding throughout much of the Virgin River Basin. An average seepage loss of 26.7 ft3/s was calculated from analysis of monthly average streamflow from July 1998 to September 2010 in the Virgin River for the reach that extends from just upstream of the Utah/Arizona State line to just above the Virgin River Gorge Narrows. Seepage losses from three river reaches in the Virgin River Gorge containing known fault zones accounted for about 48 percent of this total seepage loss. An additional seepage loss of 6.7 ft3/s was calculated for the reach of the Virgin River between Bloomington, Utah, and the Utah/Arizona State line. This loss in flow is small compared to total flow in the river and is comparable to the rated error in streamflow measurements in this reach; consequently, it should be used with caution. Littlefield Springs were studied to determine the fraction of its discharge that originates as upstream seepage from the Virgin River and residence time of this water in the subsurface. Geochemical and environmental tracer data from groundwater and surface-water sites in the Virgin River Gorge area suggest that discharge from Littlefield Springs is a mixture of modern (post-1950s) seepage from the Virgin River upstream of the springs and older groundwater from a regional carbonate aquifer. Concentrations of the chlorofluorocarbons (CFCs) CFC-12 and CFC-113, chloride/fluoride and chloride/bromide ratios, and the stable isotope deuterium indicate that water discharging from Littlefield Springs is about 60 percent seepage from the Virgin River and about 40 percent discharge from the regional carbonate aquifer. The river seepage component was determined to have an average subsurface traveltime of about 26 ±1.6 years before discharging at Littlefield Springs. Radiocarbon data for Littlefield Springs suggest groundwater ages from 1,000 to 9,000 years. Because these are mixed waters, the component of discharge from the carbonate aquifer is likely much older than the groundwater ages suggested by the Littlefield Springs samples. If the dissolved-solids load from Dixie Hot Springs to the Virgin River were reduced, the irrigation water subsequently applied to agricultural fields in the St. George and Washington areas, which originates as water from the Virgin River downstream of Dixie Hot Springs, would have a lower dissolved-solids concentration. Dissolved-solids concentrations in excess irrigation water draining from the agricultural fields are about 1,700 mg/L higher than the concentrations in the Virgin River water that is currently (2014) used for irrigation that contains inflow from Dixie Hot Springs; this increase results from evaporative concentration and dissolution of mineral salts in the irrigated agricultural fields. The water samples collected from drains downgradient from the irrigated areas are assumed to include the dissolution of all available minerals precipitated in the soil during the previous irrigation season. Based on this assumption, a change to more dilute irrigation water will not dissolve additional minerals and increase the dissolved-solids load in the drain discharge. Following the hypothetical reduction of salts from Dixie Hot Springs, which would result in more dilute Virgin River irrigation water than is currently used, the dissolution of minerals left in the soil from the previous irrigation season would result in a net increase in dissolved-solids concentrations in the drain discharge, but this increase should only last one irrigation season. After one (or several) seasons of irrigating with more dilute irrigation water, mineral precipitation and subsequent re-dissolution beneath the agricultural fields should be greatly reduced, leading to a reduction in dissolved-solids load to the Virgin River below the agricultural drains. A mass-balance model was used to predict changes in the dissolved-solids load in the Virgin River if the salt discharging from Dixie Hot Springs were reduced or removed. Assuming that 33.4 or 26.7 ft3/s of water seeps from the Virgin River to the groundwater system upstream of the Virgin River Gorge Narrows, the immediate hypothetical reduction in dissolved-solids load in the Virgin River at Littlefield, Arizona is estimated to be 67,700 or 71,500 ton/yr, respectively. The decrease in dissolved-solids load in seepage from the Virgin River to the groundwater system is expected to reduce the load discharging from Littlefield Springs in approximately 26 years, the estimated time lag between seepage from the river and discharge of the seepage water, after subsurface transport, from Littlefield Springs. At that time, the entire reduction in dissolved solids seeping from the Virgin River is expected to be realized as a reduction in dissolved solids discharging from Littlefield Springs, resulting in an additional reduction of 24,700 ton/yr (based on 33.4 ft3/s of seepage loss) or 21,000 ton/yr (based on 26.7 ft3/s of seepage loss) in the river’s dissolved-solids load at Littlefield.

Tillage impact on herbicide loss by surface runoff and lateral subsurface flow

USDA-ARS?s Scientific Manuscript database

There is worldwide interest in conservation tillage practices because they can reduce surface runoff, agrichemical, and sediment loss from farm fields. Since these practices typically increase infiltration, their use may increase subsurface transport of water-soluble contaminants. Thus, to assess lo...

A field evaluation of subsurface and surface runoff. II. Runoff processes

USGS Publications Warehouse

Pilgrim, D.H.; Huff, D.D.; Steele, T.D.

1978-01-01

Combined use of radioisotope tracer, flow rate, specific conductance and suspended-sediment measurements on a large field plot near Stanford, California, has provided more detailed information on surface and subsurface storm runoff processes than would be possible from any single approach used in isolation. Although the plot was surficially uniform, the runoff processes were shown to be grossly nonuniform, both spatially over the plot, and laterally and vertically within the soil. The three types of processes that have been suggested as sources of storm runoff (Horton-type surface runoff, saturated overland flow, and rapid subsurface throughflow) all occurred on the plot. The nonuniformity of the processes supports the partial- and variable-source area concepts. Subsurface storm runoff occurred in a saturated layer above the subsoil horizon, and short travel times resulted from flow through macropores rather than the soil matrix. Consideration of these observations would be necessary for physically realistic modeling of the storm runoff process. ?? 1978.

An Experimental Investigation of Infiltration in a Shallow Karst System

NASA Astrophysics Data System (ADS)

Bellin, A.; Becker, M. W.; Borsato, A.

2008-12-01

We present preliminary results of a field investigation of infiltration in a karst terrain in the Dolomiti del Brenta ridge, North-East Italy. A sub-horizontal cave 40 m deep drains a small catchment of about 6,000 m2 at the elevation of 2,600 m a.s.l. in a fractured triassic dolomite formation. The surface is characterized by a thin soil cover, vertical fractures, and karst collapse features (dolines). Water infiltrates through the dolines and vertical shafts which are connected to an unsaturated cave system. Within the cave, water discharge, temperature, and electric conductivity are recorded. Meterological conditions were measured at a weather station installed within the cave contributing area. Furthermore, in order to study residence time distribution in the summer 2007 we conducted a tracer experiment by injecting fluorescein in one of the dolines and recording its concentration within the cave. The recorded time series are statistically non-stationary with a wavelet spectrum strongly variable in time. However, a closer inspection of the water discharge wavelet spectrum reveals three periods in which the local power spectrum is nearly time invariant: November-April, April -July and August-October. In the first period we observe a slow exponential decline of the water discharge. The season is dominated by release of water from subsurface storage, in absence of surface input. In the second period, the system is dominated by snowmelt with a time lag that reduces from 9 hours to 1 hour through the melting season. The variation in time apparently corresponds with reduction in snowpack thickness. In the final period, the system is dominated by rainfall. The lag time in this period is on the order of 1 hour or less. These results suggest that in this hydrologic system the distribution of the residence time, and thus the transfer function relating input to output signals, is not state invariant, as typically assumed in applications. Rather, hydraulic residence time is seasonally variable and linked to both surface and subsurface hydrologic conditions.

Radiochemically-Supported Microbial Communities: A Potential Mechanism for Biocolloid Production of Importance to Actinide Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moser, Duane P.; Hamilton-Brehm, Scott D.; Fisher, Jenny C.

Due to the legacy of Cold War nuclear weapons testing, the Nevada National Security Site (NNSS, formerly known as the Nevada Test Site (NTS)) contains millions of Curies of radioactive contamination. Presented here is a summary of the results of the first comprehensive study of subsurface microbial communities of radioactive and nonradioactive aquifers at this site. To achieve the objectives of this project, cooperative actions between the Desert Research Institute (DRI), the Nevada Field Office of the National Nuclear Security Administration (NNSA), the Underground Test Area Activity (UGTA), and contractors such as Navarro-Interra (NI), were required. Ultimately, fluids from 17more » boreholes and two water-filled tunnels were sampled (sometimes on multiple occasions and from multiple depths) from the NNSS, the adjacent Nevada Test and Training Range (NTTR), and a reference hole in the Amargosa Valley near Death Valley. The sites sampled ranged from highly-radioactive nuclear device test cavities to uncontaminated perched and regional aquifers. Specific areas sampled included recharge, intermediate, and discharge zones of a 100,000-km2 internally-draining province, known as the Death Valley Regional Flow System (DVRFS), which encompasses the entirety of the NNSS/NTTR and surrounding areas. Specific geological features sampled included: West Pahute and Ranier Mesas (recharge zone), Yucca and Frenchman Flats (transitional zone), and the Western edge of the Amargosa Valley near Death Valley (discharge zone). The original overarching question underlying the proposal supporting this work was stated as: Can radiochemically-produced substrates support indigenous microbial communities and subsequently stimulate biocolloid formation that can affect radionuclides in NNSS subsurface nuclear test/detonation sites? Radioactive and non-radioactive groundwater samples were thus characterized for physical parameters, aqueous geochemistry, and microbial communities using both DNA- and cultivation-based tools in an effort to understand the drivers of microbial community structure (including radioactivity) and microbial interactions with select radionuclides and other factors across the range of habitats surveyed.« less

Optimization of limestone drains for long- term treatment of acidic mine drainage, Swatara Creek Basin, Schuylkill County, PA

USGS Publications Warehouse

Cravotta, Charles A.; Ward, S.J.; Koury, Daniel J.; Koch, R.D.

2004-01-01

Limestone drains were constructed in 1995, 1997, and 2000 to treat acidic mine drainage (AMD) from the Orchard, Buck Mtn., and Hegins discharges, respectively, in the Swatara Creek Basin, Southern Anthracite Coalfield, east-central Pennsylvania. This report summarizes the construction characteristics and performance of each of the limestone drains on the basis of influent and effluent quality and laboratory tests of variables affecting limestone dissolution rates. Data for influent and effluent indicate substantial alkalinity production by the Orchard and Buck Mtn. limestone drains and only marginal benefits from the Hegins drain. Nevertheless, the annual alkalinity loading rates have progressively declined with age of all three systems. Collapsible-container (cubitainer) testing was conducted to evaluate current scenarios and possible options for reconstruction and maintenance of the limestone drains to optimize their long-term performance. The cubitainer tests indicated dissolution rates for the current configurations that were in agreement with field flux data (net loading) for alkalinity and dissolved calcium. The dissolution rates in cubitainers were larger for closed conditions than open conditions, but the rates were comparable for coated and uncoated limestone for a given condition. Models developed on the basis of the cubitainer testing indicate (1) exponential declines in limestone mass and corresponding alkalinity loading rates with increased age of limestone drains and (2) potential for improved performance with enlargement, complete burial, and/or regular flushing of the systems.

The emergence of hydrogeophysics for improved understanding of subsurface processes over multiple scales

PubMed Central

Hubbard, Susan S.; Huisman, Johan A.; Revil, André; Robinson, David A.; Singha, Kamini; Slater, Lee D.

2015-01-01

Abstract Geophysics provides a multidimensional suite of investigative methods that are transforming our ability to see into the very fabric of the subsurface environment, and monitor the dynamics of its fluids and the biogeochemical reactions that occur within it. Here we document how geophysical methods have emerged as valuable tools for investigating shallow subsurface processes over the past two decades and offer a vision for future developments relevant to hydrology and also ecosystem science. The field of “hydrogeophysics” arose in the late 1990s, prompted, in part, by the wealth of studies on stochastic subsurface hydrology that argued for better field‐based investigative techniques. These new hydrogeophysical approaches benefited from the emergence of practical and robust data inversion techniques, in many cases with a view to quantify shallow subsurface heterogeneity and the associated dynamics of subsurface fluids. Furthermore, the need for quantitative characterization stimulated a wealth of new investigations into petrophysical relationships that link hydrologically relevant properties to measurable geophysical parameters. Development of time‐lapse approaches provided a new suite of tools for hydrological investigation, enhanced further with the realization that some geophysical properties may be sensitive to biogeochemical transformations in the subsurface environment, thus opening up the new field of “biogeophysics.” Early hydrogeophysical studies often concentrated on relatively small “plot‐scale” experiments. More recently, however, the translation to larger‐scale characterization has been the focus of a number of studies. Geophysical technologies continue to develop, driven, in part, by the increasing need to understand and quantify key processes controlling sustainable water resources and ecosystem services. PMID:26900183

Anthropogenic and geogenic Cd, Hg, Pb and Se sources of contamination in a brackish aquifer below agricultural fields

NASA Astrophysics Data System (ADS)

Mastrocicco, Micòl; Colombani, Nicolò; Di Giuseppe, Dario; Faccini, Barbara; Ferretti, Giacomo; Coltorti, Massimo

2015-04-01

Groundwater quality is often threatened by industrial, agricultural and land use practices (anthropogenic input). In deltaic areas is however difficult to distinguish between geogenic and anthropogenic inorganic contaminants pollution, since these phenomena can influence each other and often display a seasonal cycling. The effect of geogenic groundwater ionic strength (>10 g/l) on the mobility of trace elements like Cd, Hg, Pb and Se was studied in combination with the anthropogenic sources of these elements (fertilizers) in a shallow aquifer. The site is located in the Po river plain (Northern Italy) in an agricultural field belonging to a reclaimed deltaic environment, near Codigoro town. It is 6 ha wide and is drained by a subsurface drainage system made of PVC tile drains with a slope of 3‰, which provides gravity drainage towards two ditches that in turn discharge in a main channel. The whole area has been intensively cultivated with cereal rotation since 1960, mainly using synthetic urea as nitrogen fertilizer at an average rate of 180 kg-N/ha/y and pig slurry at an average rate of 60 kg-N/ha/y. The sediments were analyzed for major and trace elements via XRF, while major ions in groundwater were analyzed via IC and trace elements via ICP-MS. Three monitoring wells, with an inner diameter of 2 cm and screened down to 4 m below ground level, were set up in the field and sampled every four month from 2012 to 2014. The use of intensive depth profiles with resolution of 0.5 m in three different locations, gave insights into groundwater and sediment matrix interactions. To characterize the anthropogenic inputs synthetic urea and pig slurry were analyzed for trace elements via ICP-MS. The synthetic urea is a weak source of Cd and Hg (~1 ppb), while Se and Pb are found below detection limits. The pig slurry is a much stronger source of Se (~19 ppb) and Pb (~23 ppb) and a weak source of Cd (~3 ppb) and Hg (~2 ppb). Although, the mass loading rate pig slurry is three times lower than the synthetic urea on yearly basis. In general Cd, Hg, Pb and Se concentrations were found lower in sandy sediments, since usually these elements concentrate in the clay fraction. Hg, Pb and Se groundwater concentrations generally increased with the ionic strength of the solution witnessing a geogenic origin, while Cd groundwater concentrations were not clearly related to saline groundwater. Most probably, the latter was released both by fertilizers and by sediments during shifts between oxic and reducing conditions. In addition, the elevated soil organic carbon induced reducing conditions throughout the saturated aquifer profile (usually below the tile drains), which further promoted Hg, Pb and Se dissolution. The combined use of high-resolution sediment profiles, seasonal groundwater sampling and end-member analyses seems to be a promising procedure to distinguish between anthropogenic inorganic contaminants input and geogenic contribution in reclaimed deltaic environments.

Transducer Design Experiments for Ground-Penetrating Acoustic Systems

DTIC Science & Technology

1996-03-19

subsurface imaging experiments have utilized a source (Tx) and receiver (Rx) configuration in which signals produced by a transmitter at the soil surface...development in the field of acoustic subsurface imaging are as follows. First, a transmitter designed to minimize the emission of surface waves, while

Investigation of defect-induced abnormal body current in fin field-effect-transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Kuan-Ju; Tsai, Jyun-Yu; Lu, Ying-Hsin

2015-08-24

This letter investigates the mechanism of abnormal body current at the linear region in n-channel high-k/metal gate stack fin field effect transistors. Unlike body current, which is generated by impact ionization at high drain voltages, abnormal body current was found to increase with decreasing drain voltages. Notably, the unusual body leakage only occurs in three-dimensional structure devices. Based on measurements under different operation conditions, the abnormal body current can be attributed to fin surface defect-induced leakage current, and the mechanism is electron tunneling to the fin via the defects, resulting in holes left at the body terminal.

An underlap field-effect transistor for electrical detection of influenza

NASA Astrophysics Data System (ADS)

Lee, Kwang-Won; Choi, Sung-Jin; Ahn, Jae-Hyuk; Moon, Dong-Il; Park, Tae Jung; Lee, Sang Yup; Choi, Yang-Kyu

2010-01-01

An underlap channel-embedded field-effect transistor (FET) is proposed for label-free biomolecule detection. Specifically, silica binding protein fused with avian influenza (AI) surface antigen and avian influenza antibody (anti-AI) were designed as a receptor molecule and a target material, respectively. The drain current was significantly decreased after the binding of negatively charged anti-AI on the underlap channel. A set of control experiments supports that only the biomolecules on the underlap channel effectively modulate the drain current. With the merits of a simple fabrication process, complementary metal-oxide-semiconductor compatibility, and enhanced sensitivity, the underlap FET could be a promising candidate for a chip-based biosensor.

Performance and Design Considerations of a Novel Dual-Material Gate Carbon Nanotube Field-Effect Transistors: Nonequilibrium Green's Function Approach

NASA Astrophysics Data System (ADS)

Arefinia, Zahra; Orouji, Ali A.

2009-02-01

The concept of dual-material gate (DMG) is applied to the carbon nanotube field-effect transistor (CNTFET) with doped source and drain extensions, and the features exhibited by the resulting new structure, i.e., the DMG-CNTFET structure, have been examined for the first time by developing a two-dimensional (2D) full quantum simulation. The simulations have been done by the self-consistent solution of 2D Poisson-Schrödinger equations, within the nonequilibrium Green's function (NEGF) formalism. The results show DMG-CNTFET decreases significantly leakage current and drain conductance and increases on-off current ratio and voltage gain as compared to the single material gate counterparts CNTFET. It is seen that short channel effects in this structure are suppressed because of the perceivable step in the surface potential profile, which screens the drain potential. Moreover, these unique features can be controlled by engineering the workfunction and length of the gate metals. Therefore, this work provides an incentive for further experimental exploration.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors.

PubMed

Giusi, G; Giordano, O; Scandurra, G; Rapisarda, M; Calvi, S; Ciofi, C

2016-04-01

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz(1/2), while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.

Two-dimensional analytical model for dual-material control-gate tunnel FETs

NASA Astrophysics Data System (ADS)

Xu, Hui Fang; Dai, Yue Hua; Gui Guan, Bang; Zhang, Yong Feng

2016-09-01

An analytical model for a dual-material control-gate (DMCG) tunnel field effect transistor (TFET) is presented for the first time in this paper, and the influence of the mobile charges on the potential profile is taken into account. On the basis of the potential profile, the lateral electric field is derived and the expression for the drain current is obtained by integrating the band-to-band tunneling (BTBT) generation rate applicable to low-bandgap and high-bandgap materials over the tunneling region. The model also predicts the impacts of the control-gate work function on the potential and drain current. The advantage of this work is that it not only offers physical insight into device physics but also provides the basic designing guideline for DMCG TFETs, enabling the designer to optimize the device in terms of the on-state current, the on-off current ratio, and suppressed ambipolar behavior. Very good agreements for both the potential and drain current are observed between the model calculations and the simulated results.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giusi, G.; Giordano, O.; Scandurra, G.

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz{sup 1/2}, while DC performances are limited only bymore » the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

As part of the Hanford Federal Facility Agreement and Consent Order negotiations (Ecology et al. 1994), the US Department of Energy, Richland Operations Office, the US Environmental Protection Agency, and the Washington State Department of Ecology agreed that liquid effluent discharges to the ground on the Hanford Site which affect groundwater or have the potential to affect ground would be subject to permitting under the structure of Chapter 173-216 (or 173-218 where applicable) of the Washington Administrative Code, the State Waste Discharge Permit Program. As a result of this decision, the Washington State Department of Ecology and the US Departmentmore » of Energy, Richland Operations Office entered into Consent Order No. DE 91NM-177, (Ecology and DOE-RL 1991). The Consent Order No. DE 91NM-177 requires a series of permitting activities for liquid effluent discharges. This document presents the State Waste Discharge Permit (SWDP) application for the 200-E Chemical Drain Field. Waste water from the 272-E Building enters the process sewer line directly through a floor drain, while waste water from the 2703-E Building is collected in two floor drains, (north and south) that act as sumps and are discharged periodically. The 272-E and 2703-E Buildings constitute the only discharges to the process sewer line and the 200-E Chemical Drain Field.« less

Thermal observations of gas pistoning at Kilauea Volcano

USGS Publications Warehouse

Johnson, J.B.; Harris, A.J.L.; Hoblitt, R.P.

2005-01-01

Data acquired by three continuously recording thermal infrared thermometers situated on the north rim of Pu'u'O' o Crater at Kilauea Volcano during 2002 revealed episodes of periodic thermal pulses originating from a degassing vent on the crater floor. These thermal pulses are interpreted as gas release (jetting events) associated with gas pistoning, a mechanism observed previously at both Mauna Ulu and Pu'u'O' o. During a 35-day-long period spanning June and July 2002, gas pistoning was frequently the dominant mode of gas release, with as many as several hundred pulses occurring in uninterrupted series. On other days, degassing alternated between periods of quasi-continuous gas jetting and intervals of gas pistoning that contained a few to a few dozen pulses. Characteristic time intervals between pistoning events ranged from 2 up to 7 min. We identify three types of pistoning. Type 1 involves emission of lava, followed by gas jetting and drain back; type 2 is the same but the elevated position of the vent does not allow postjet drain back; and type 3 involves gas jetting only with no precursory lava flow. To explain gas pistoning, we apply a model whereby a stagnant cap of degassed magma develops in the conduit below the vent. Gas bubbles rise through the magma column and collect under the cap. The collective buoyancy of these bubbles pushes the cap upward. When the cap reaches the surface, it erupts from the vent as a lava flow. Unloading of the conduit magma in this way results in an abrupt pressure drop (i.e., the overburden felt by the bubbles is reduced), causing explosive gas expansion in the form of gas jetting from the vent. This terminates the event and lava drains back into the conduit to start the cycle anew. In the case where there is no surface lava emission or drain back, the cap instead pushes into and spreads out within a subsurface cavity. Again, this unloads the conduit magma and terminates in explosive gas release. Once gas is expelled, lava in the cavity is free to drain back. We hypothesize that pistoning is a stable mode of degassing for low-viscosity basaltic magmas with appropriate conduit geometries and volatile supply rates. Copyright 2005 by the American Geophysical Union.

Back bias induced dynamic and steep subthreshold swing in junctionless transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parihar, Mukta Singh; Kranti, Abhinav, E-mail: akranti@iiti.ac.in

In this work, we analyze back bias induced steep and dynamic subthreshold swing in junctionless double gate transistors operated in the asymmetric mode. This impact ionization induced dynamic subthreshold swing is explained in terms of the ratio between minimum hole concentration and peak electron concentration, and the dynamic change in the location of the conduction channel with applied front gate voltage. The reason for the occurrence of impact ionization at sub-bandgap drain voltages in silicon junctionless transistors is also accounted for. The optimum junctionless transistor operating at a back gate bias of −0.9 V, achieves over 5 orders of change inmore » drain current at a gate overdrive of 200 mV and drain bias of 1 V. These results for junctionless transistors are significantly better than those exhibited by silicon tunnel field effect transistors operating at the same drain bias.« less

Bottom-gate poly-Si thin-film transistors by nickel silicide seed-induced lateral crystallization with self-aligned lightly doped layer

NASA Astrophysics Data System (ADS)

Lee, Sol Kyu; Seok, Ki Hwan; Chae, Hee Jae; Lee, Yong Hee; Han, Ji Su; Jo, Hyeon Ah; Joo, Seung Ki

2017-03-01

We report a novel method to reduce source and drain (S/D) resistances, and to form a lightly doped layer (LDL) of bottom-gate polycrystalline silicon (poly-Si) thin-film transistors (TFTs). For application in driving TFTs, which operate under high drain voltage condition, poly-Si TFTs are needed in order to attain reliability against hot-carriers as well as high field-effect mobility (μFE). With an additional doping on the p+ Si layer, sheet resistance on S/D was reduced by 37.5% and an LDL was introduced between the channel and drain. These results contributed to not only a lower leakage current and gate-induced drain leakage, but also high immunity of kink-effect and hot-carrier stress. Furthermore, the measured electrical characteristics exhibited a steep subthreshold slope of 190 mV/dec and high μFE of 263 cm2/Vs.

Remote sensing of subsurface water temperature by Raman scattering.

PubMed

Leonard, D A; Caputo, B; Hoge, F E

1979-06-01

The application of Raman scattering to remote sensing of subsurface water temperature and salinity is considered, and both theoretical and experimental aspects of the technique are discussed. Recent experimental field measurements obtained in coastal waters and on a trans-Atlantic/Mediterranean research cruise are correlated with theoretical expectations. It is concluded that the Raman technique for remote sensing of subsurface water temperature has been brought from theoretical and laboratory stages to the point where practical utilization can now be developed.

Field Simulation of a Drilling Mission to Mars to Search for Subsurface Life

NASA Technical Reports Server (NTRS)

Stoker, C. R.; Lemke, L. G.; Cannon, H.; Glass, B.; Dunagan, S.; Zavaleta, J.; Miller, D.; Gomez-Elvira, J.

2005-01-01

The discovery of near surface ground ice by the Mars Odyssey mission and the abundant evidence for recent Gulley features observed by the Mars Global Surveyor mission support longstanding theoretical arguments for subsurface liquid water on Mars. Thus, implementing the Mars program goal to search for life points to drilling on Mars to reach liquid water, collecting samples and analyzing them with instrumentation to detect in situ organisms and biomarker compounds. Searching for life in the subsurface of Mars will require drilling, sample extraction and handling, and new technologies to find and identify biomarker compounds and search for living organisms. In spite of its obvious advantages, robotic drilling for Mars exploration is in its technological infancy and has yet to be demonstrated in even a terrestrial field environment.

Cost-Effective and High-Resolution Subsurface Characterization Using Hydraulic Tomography

DTIC Science & Technology

2017-08-28

implementation and compare costs associated with HT and conventional methods. TECHNOLOGY DESCRIPTION The HT concept is analogous to the Computerized...develop guidance for HT field implementation and compare costs associated with HT and conventional methods. 15. SUBJECT TERMS Subsurface...3  2.1  TECHNOLOGY DESCRIPTION

Yield response and economics of shallow subsurface drip irrigation systems

USDA-ARS?s Scientific Manuscript database

Field tests were conducted using shallow subsurface drip irrigation (S3DI) on cotton (Gossypium hirsutum, L.), corn (Zea mays, L.), and peanut (Arachis hypogeae, L.) in rotation to investigate yield potential and economic sustainability of this irrigation system technique over a six year period. Dri...

A novel high-performance high-frequency SOI MESFET by the damped electric field

NASA Astrophysics Data System (ADS)

Orouji, Ali A.; Khayatian, Ahmad; Keshavarzi, Parviz

2016-06-01

In this paper, we introduce a novel silicon-on-insulator (SOI) metal-semiconductor field-effect-transistor (MESFET) using the damped electric field (DEF). The proposed structure is geometrically symmetric and compatible with common SOI CMOS fabrication processes. It has two additional oxide regions under the side gates in order to improve DC and RF characteristics of the DEF structure due to changes in the electrical potential, the electrical field distributions, and rearrangement of the charge carriers. Improvement of device performance is investigated by two-dimensional and two-carrier simulation of fundamental parameters such as breakdown voltage (VBR), drain current (ID), output power density (Pmax), transconductance (gm), gate-drain and gate-source capacitances, cut-off frequency (fT), unilateral power gain (U), current gain (h21), maximum available gain (MAG), and minimum noise figure (Fmin). The results show that proposed structure operates with higher performances in comparison with the similar conventional SOI structure.

Exploring Agricultural Drainage's Influence on Wetland and ...

EPA Pesticide Factsheets

Artificial agricultural drainage (i.e. surface ditches or subsurface tile) is an important agricultural management tool. Artificial drainage allows for timely fieldwork and adequate root aeration, resulting in greater crop yields for farmers. This practice is widespread throughout many regions of the United States and the network of artificial drainage is especially extensive in flat, poorly-drained regions like the glaciated Midwest. While beneficial for crop yields, agricultural drains often empty into streams within the natural drainage system. The increased network connectivity may lead to greater contributing area for watersheds, altered hydrology and increased conveyance of pollutants into natural water bodies. While studies and models at broader scales have implicated artificial drainage as an important driver of hydrological shifts and eutrophication, the actual spatial extent of artificial drainage is poorly known. Consequently, metrics of wetland and watershed connectivity within agricultural regions often fail to explicitly include artificial drainage. We use recent agricultural census data, soil drainage data, and land cover data to create estimates of potential agricultural drainage across the United States. We estimate that agricultural drainage in the US is greater than 31 million hectares and is concentrated in the upper Midwest Corn Belt, covering greater than 50% of available land for 114 counties. Estimated drainage values for numerous countie

The nitrate response of a lowland catchment and groundwater travel times

NASA Astrophysics Data System (ADS)

van der Velde, Ype; Rozemeijer, Joachim; de Rooij, Gerrit; van Geer, Frans

2010-05-01

Intensive agriculture in lowland catchments causes eutrophication of downstream waters. To determine effective measures to reduce the nutrient loads from upstream lowland catchments, we need to understand the origin of long-term and daily variations in surface water nutrient concentrations. Surface water concentrations are often linked to travel time distributions of water passing through the saturated and unsaturated soil of the contributing catchment. This distribution represents the contact time over which sorption, desorption and degradation takes place. However, travel time distributions are strongly influenced by processes like tube drain flow, overland flow and the dynamics of draining ditches and streams and therefore exhibit strong daily and seasonal variations. The study we will present is situated in the 6.6 km2 Hupsel brook catchment in The Netherlands. In this catchment nitrate and chloride concentrations have been intensively monitored for the past 26 years under steadily decreasing agricultural inputs. We described the complicated dynamics of subsurface water fluxes as streams, ditches and tube drains locally switch between active or passive depending on the ambient groundwater level by a groundwater model with high spatial and temporal resolutions. A transient particle tracking approach is used to derive a unique catchment-scale travel time distribution for each day during the 26 year model period. These transient travel time distributions are not smooth distributions, but distributions that are strongly spiked reflecting the contribution of past rainfall events to the current discharge. We will show that a catchment-scale mass response function approach that only describes catchment-scale mixing and degradation suffices to accurately reproduce observed chloride and nitrate surface water concentrations as long as the mass response functions include the dynamics of travel time distributions caused by the highly variable connectivity of the surface water network.

Homogenization of Electromagnetic and Seismic Wavefields for Joint Inverse Modeling

NASA Astrophysics Data System (ADS)

Newman, G. A.; Commer, M.; Petrov, P.; Um, E. S.

2011-12-01

A significant obstacle in developing a robust joint imaging technology exploiting seismic and electromagnetic (EM) wave fields is the resolution at which these different geophysical measurements sense the subsurface. Imaging of seismic reflection data is an order of magnitude finer in resolution and scale compared to images produced with EM data. A consistent joint image of the subsurface geophysical attributes (velocity, electrical conductivity) requires/demands the different geophysical data types be similar in their resolution of the subsurface. The superior resolution of seismic data results from the fact that the energy propagates as a wave, while propagation of EM energy is diffusive and attenuates with distance. On the other hand, the complexity of the seismic wave field can be a significant problem due to high reflectivity of the subsurface and the generation of multiple scattering events. While seismic wave fields have been very useful in mapping the subsurface for energy resources, too much scattering and too many reflections can lead to difficulties in imaging and interpreting seismic data. To overcome these obstacles a formulation for joint imaging of seismic and EM wave fields is introduced, where each data type is matched in resolution. In order to accomplish this, seismic data are first transformed into the Laplace-Fourier Domain, which changes the modeling of the seismic wave field from wave propagation to diffusion. Though high frequency information (reflectivity) is lost with this transformation, several benefits follow: (1) seismic and EM data can be easily matched in resolution, governed by the same physics of diffusion, (2) standard least squares inversion works well with diffusive type problems including both transformed seismic and EM, (3) joint imaging of seismic and EM data may produce better starting velocity models critical for successful reverse time migration or full waveform imaging of seismic data (non transformed) and (4) possibilities to image across multiple scale lengths, incorporating different types of geophysical data and attributes in the process. Important numerical details of 3D seismic wave field simulation in the Laplace-Fourier domain for both acoustic and elastic cases will also be discussed.

Monitoring microbial growth and activity using spectral induced polarization and low-field nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Zhang, Chi; Keating, Kristina; Revil, Andre

2015-04-01

Microbes and microbial activities in the Earth's subsurface play a significant role in shaping subsurface environments and are involved in environmental applications such as remediation of contaminants in groundwater and oil fields biodegradation. Stimulated microbial growth in such applications could cause wide variety of changes of physical/chemical properties in the subsurface. It is critical to monitor and determine the fate and transportation of microorganisms in the subsurface during such applications. Recent geophysical studies demonstrate the potential of two innovative techniques, spectral induced polarization (SIP) and low-field nuclear magnetic resonance (NMR), for monitoring microbial growth and activities in porous media. The SIP measures complex dielectric properties of porous media at low frequencies of exciting electric field, and NMR studies the porous structure of geologic media and characterizes fluids subsurface. In this laboratory study, we examined both SIP and NMR responses from bacterial growth suspension as well as suspension mixed with silica sands. We focus on the direct contribution of microbes to the SIP and NMR signals in the absence of biofilm formation or biomineralization. We used Zymomonas mobilis and Shewanella oneidensis (MR-1) for SIP and NMR measurements, respectively. The SIP measurements were collected over the frequency range of 0.1 - 1 kHz on Z. mobilis growth suspension and suspension saturated sands at different cell densities. SIP data show two distinct peaks in imaginary conductivity spectra, and both imaginary and real conductivities increased as microbial density increased. NMR data were collected using both CPMG pulse sequence and D-T2 mapping to determine the T2-distribution and diffusion properties on S. oneidensis suspension, pellets (live and dead), and suspension mixed with silica sands. NMR data show a decrease in the T2-distribution in S. oneidensis suspension saturated sands as microbial density increase. A clear distinction in the T2-distribution and D-T2 plots between live and dead cell pellets was also observed. These results will provide a basis for understanding the effect of microbes within geologic media on SIP and low-field NMR measurements. This research suggests that both SIP and NMR have the potential to monitor microbial growth and activities in the subsurface and could provide spatiotemporal variations in bacterial abundance in porous media.

Imaging lateral groundwater flow in the shallow subsurface using stochastic temperature fields

NASA Astrophysics Data System (ADS)

Fairley, Jerry P.; Nicholson, Kirsten N.

2006-04-01

Although temperature has often been used as an indication of vertical groundwater movement, its usefulness for identifying horizontal fluid flow has been limited by the difficulty of obtaining sufficient data to draw defensible conclusions. Here we use stochastic simulation to develop a high-resolution image of fluid temperatures in the shallow subsurface at Borax Lake, Oregon. The temperature field inferred from the geostatistical simulations clearly shows geothermal fluids discharging from a group of fault-controlled hydrothermal springs, moving laterally through the subsurface, and mixing with shallow subsurface flow originating from nearby Borax Lake. This interpretation of the data is supported by independent geochemical and isotopic evidence, which show a simple mixing trend between Borax Lake water and discharge from the thermal springs. It is generally agreed that stochastic simulation can be a useful tool for extracting information from complex and/or noisy data and, although not appropriate in all situations, geostatistical analysis may provide good definition of flow paths in the shallow subsurface. Although stochastic imaging techniques are well known in problems involving transport of species, e.g. delineation of contaminant plumes from soil gas survey data, we are unaware of previous applications to the transport of thermal energy for the purpose of inferring shallow groundwater flow.

Modeling Phosphorus Losses through Surface Runoff and Subsurface Drainage Using ICECREAM.

PubMed

Qi, Hongkai; Qi, Zhiming; Zhang, T Q; Tan, C S; Sadhukhan, Debasis

2018-03-01

Modeling soil phosphorus (P) losses by surface and subsurface flow pathways is essential in developing successful strategies for P pollution control. We used the ICECREAM model to simultaneously simulate P losses in surface and subsurface flow, as well as to assess effectiveness of field practices in reducing P losses. Monitoring data from a mineral-P-fertilized clay loam field in southwestern Ontario, Canada, were used for calibration and validation. After careful adjustment of model parameters, ICECREAM was shown to satisfactorily simulate all major processes of surface and subsurface P losses. When the calibrated model was used to assess tillage and fertilizer management scenarios, results point to a 10% reduction in total P losses by shifting autumn tillage to spring, and a 25.4% reduction in total P losses by injecting fertilizer rather than broadcasting. Although the ICECREAM model was effective in simulating surface and subsurface P losses when thoroughly calibrated, further testing is needed to confirm these results with manure P application. As illustrated here, successful use of simulation models requires careful verification of model routines and comprehensive calibration to ensure that site-specific processes are accurately represented. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Hydrogeological and geophysical investigations to evaluate groundwater influences on GHG emissions at the national research site Skogaryd

NASA Astrophysics Data System (ADS)

Banzhaf, Stefan; Klemedtsson, Leif; Sturkell, Erik; Nyström, Elin; Barthel, Roland

2015-04-01

The overall objective of the presented study is to explore the impact of groundwater fluctuations on greenhouse gas (GHG) emissions from peatlands and in particular from drained organic soils. The hypothesis is that drained organic soils react sensitively to changing water content, i.e. that frequent changes of groundwater level enhance the emissions of GHG from these soils and thus contribute significantly to global warming. The area under investigation is based at the Skogaryd Research Catchment (within Swedish Infrastructure for Ecosystem Sciences, SITES) in western Sweden (Meyer, et al., 2013), which was recently assigned the status of a national research site by the Swedish research council (www.vr.se). Skogaryd is a unique place in Sweden for doing research on organic soils as the area was simultaneously afforested in the 1960s and the drained fertile soils have a different land-use history. The ditching for drainage purposes throughout the entire area has had and still has a huge influence on groundwater level, which in turn is assumed to trigger GHG emissions from the organic soils at Skogaryd. To address the influence of groundwater dynamics on GHG emissions in this system, a characterisation of the subsurface using electrical resistivity and Ground Penetrating Radar (GPR) measurements was carried out. These geophysical measurements were combined with drilling along them to allow for ground truthing. An average peat thickness of around 3 m was estimated for the field site. Below the peat follows a fine sand layer, which reaches a maximum thickness of around 1.0 m right at the valley borders and thins out significantly towards the middle of the valley. Below the fine sand layer follows a layer of marine clay, which extends down to the bedrock at depths between 12 and 15 m below ground surface. The results show that the peat layer in Skogaryd forms an isolated hydraulic system without interaction with deeper or regional groundwater systems. The continuously extending clay layer hinders water moving downward or upward crossing the border of peat and clay. The peat layer is a fast reacting hydraulic system that shows immediate reaction to precipitation or drought and is independent from regional groundwater levels. The study of groundwater controls on the GHG from the drained organic soils at Skogaryd can thus focus on the fast reacting peat layer. Future investigations will show if this conclusion can be generalized for similar situations in Sweden. Geophysical measurements have proved to be a valuable method for estimating the peat thickness over a large area. Meyer A, Tarvainen L, Nousratpour A, Björk RG, Ernfors M, Grelle A, Kasimir Klemedtsson Å, Lindroth A, Räntfors M, Rütting T, Wallin G, Weslien P, Klemedtsson L (2013) A fertile peatland forest does not constitute a major greenhouse gas sink. Biogeosciences 10: 7739-7758 DOI 10.5194/bg-10-7739-2013

Changes in soybean phytate content as a result of field growing conditions and influence on tofu texture.

PubMed

Ishiguro, Takahiro; Ono, Tomotada; Wada, Takahiro; Tsukamoto, Chigen; Kono, Yuhi

2006-04-01

It is known that tofu quality tends to vary among soybeans even of the same variety. Cultivation environments can affect the contents of the soybeans. Twenty-seven soybean varieties were grown in a drained paddy field and an upland field, and then their protein and phytate contents were determined using the Fourier transfer infrared spectroscopy (FT-IR) method. The phytate contents of 12 varieties were higher in the drained paddy field than in the upland field. On the other hand, the environmental factor had little effect on the protein contents. In order to determine whether the difference in phytate content affected tofu texture, the hardness of the tofu made from phytate-added soymilk was measured. The tofu texture having more phytate became softer in the range of the common coagulant concentration. We concluded that the difference in the phytate content of the soybeans among the environmental conditions is a factor that causes fluctuation in tofu quality.

Enhancement of AlGaN/GaN high-electron mobility transistor off-state drain breakdown voltage via backside proton irradiation

NASA Astrophysics Data System (ADS)

Ren, F.; Hwang, Y.-H.; Pearton, S. J.; Patrick, Erin; Law, Mark E.

2015-03-01

Proton irradiation from the backside of the samples were employed to enhance off-state drain breakdown voltage of AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates. Via holes were fabricated directly under the active area of the HEMTs by etching through the Si substrate for subsequent backside proton irradiation. By taking the advantage of the steep drop at the end of proton energy loss profile, the defects created by the proton irradiation from the backside of the sample could be precisely placed at specific locations inside the AlGaN/GaN HEMT structure. There were no degradation of drain current nor enhancement of off-state drain voltage breakdown voltage observed for the irradiated AlGaN/GaN HEMTs with the proton energy of 225 or 275 keV, for which the defects created by the proton irradiations were intentionally placed in the GaN buffer. HEMTs with defects placed in the 2 dimensional electron gas (2DEG) channel region and AlGaN barrier using 330 or 340 keV protons not only showed degradation of drain current, but also exhibited improvement of the off-state drain breakdown voltage. FLOODS TCAD finite-element simulations were performed to confirm the hypothesis of a virtual gate formed around the 2DEG region to reduce the peak electric field around the gate edges and increase the off-state drain breakdown voltage.

Antibiotic resistance genes persist longer in soils with subsurface banded poultry litter

USDA-ARS?s Scientific Manuscript database

The objective of this study was to determine the concentration of AR genes for sulfonamide (sulI), tetracycline (tetW), streptomycin (strpB) and for the class one integrase (intI1) gene in soils with subsurface banded PL. Field scale plots were established with triplicate treatments of either no fer...

SUBSURFACE CHARACTERIZATION AND MONITORING TECHNIQUES: A DESK REFERENCE GUIDE - VOLUME II: THE VADOSE ZONE, FIELD SCREENING AND ANALYTICAL METHODS - APPENDICES C AND D

EPA Science Inventory

Many EPA programs, including those under the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Response, Compensation, and Liability Act (CERCLA), require subsurface characterization and monitoring to detect ground-water contamination and provide data to deve...

Influence Of pH On The Transport Of Nanoscale Zinc Oxide In Saturated Porous Media

EPA Science Inventory

Widespread use of nanoscale zinc oxide (nZnO) in various fields causes subsurface environment contamination. Even though the transport of dissolved zinc ions in subsurface environments such as soils and sediments has been widely studied, the transport mechanism of nZnO in such e...

Modeling Subsurface Behavior at the System Level: Considerations and a Path Forward

NASA Astrophysics Data System (ADS)

Geesey, G.

2005-12-01

The subsurface is an obscure but essential resource to life on Earth. It is an important region for carbon production and sequestration, a source and reservoir for energy, minerals and metals and potable water. There is a growing need to better understand subsurface possesses that control the exploitation and security of these resources. Our best models often fail to predict these processes at the field scale because of limited understanding of 1) the processes and the controlling parameters, 2) how processes are coupled at the field scale 3) geological heterogeneities that control hydrological, geochemical and microbiological processes at the field scale and 4) lack of data sets to calibrate and validate numerical models. There is a need for experimental data obtained at scales larger than those obtained at the laboratory bench that take into account the influence of hydrodynamics, geochemical reactions including complexation and chelation/adsorption/precipitation/ion exchange/oxidation-reduction/colloid formation and dissolution, and reactions of microbial origin. Furthermore, the coupling of each of these processes and reactions needs to be evaluated experimentally at a scale that produces data that can be used to calibrate numerical models so that they accurately describe field scale system behavior. Establishing the relevant experimental scale for collection of data from coupled processes remains a challenge and will likely be process-dependent and involve iterations of experimentation and data collection at different intermediate scales until the models calibrated with the appropriate date sets achieve an acceptable level of performance. Assuming that the geophysicists will soon develop technologies to define geological heterogeneities over a wide range of scales in the subsurface, geochemists need to continue to develop techniques to remotely measure abiotic reactions, while geomicrobiologists need to continue their development of complementary technologies to remotely measure microbial community parameters that define their key functions at a scale that accurately reflects their role in large scale subsurface system behavior. The practical questions that geomicrobiologist must answer in the short term are: 1) What is known about the activities of the dominant microbial populations or those of their closest relatives? 2) Which of these activities is likely to dominate under in situ conditions? In the process of answering these questions, researchers will obtain answers to questions of a more fundamental nature such as 1) How deep does "active" life extend below the surface of the seafloor and terrestrial subsurface? 2) How are electrons exchanged between microbial cells and solid phase minerals? 3) What is the metabolic state and mechanism of survival of "inactive" life forms in the subsurface? 4) What can genomes of life forms trapped in geological material tell us about evolution of life that current methods cannot? The subsurface environment represents a challenging environment to understand and model. As the need to understand subsurface processes increases and the technologies to characterize them become available, modeling subsurface behavior will approach the level of sophistication of models used today to predict behavior of other large scale systems such as the oceans.

Drilling Automation Demonstrations in Subsurface Exploration for Astrobiology

NASA Technical Reports Server (NTRS)

Glass, Brian; Cannon, H.; Lee, P.; Hanagud, S.; Davis, K.

2006-01-01

This project proposes to study subsurface permafrost microbial habitats at a relevant Arctic Mars-analog site (Haughton Crater, Devon Island, Canada) while developing and maturing the subsurface drilling and drilling automation technologies that will be required by post-2010 missions. It builds on earlier drilling technology projects to add permafrost and ice-drilling capabilities to 5m with a lightweight drill that will be automatically monitored and controlled in-situ. Frozen cores obtained with this drill under sterilized protocols will be used in testing three hypotheses pertaining to near-surface physical geology and ground H2O ice distribution, viewed as a habitat for microbial life in subsurface ice and ice-consolidated sediments. Automation technologies employed will demonstrate hands-off diagnostics and drill control, using novel vibrational dynamical analysis methods and model-based reasoning to monitor and identify drilling fault states before and during faults. Three field deployments, to a Mars-analog site with frozen impact crater fallback breccia, will support science goals, provide a rigorous test of drilling automation and lightweight permafrost drilling, and leverage past experience with the field site s particular logistics.

AlN metal-semiconductor field-effect transistors using Si-ion implantation

NASA Astrophysics Data System (ADS)

Okumura, Hironori; Suihkonen, Sami; Lemettinen, Jori; Uedono, Akira; Zhang, Yuhao; Piedra, Daniel; Palacios, Tomás

2018-04-01

We report on the electrical characterization of Si-ion implanted AlN layers and the first demonstration of metal-semiconductor field-effect transistors (MESFETs) with an ion-implanted AlN channel. The ion-implanted AlN layers with Si dose of 5 × 1014 cm-2 exhibit n-type characteristics after thermal annealing at 1230 °C. The ion-implanted AlN MESFETs provide good drain current saturation and stable pinch-off operation even at 250 °C. The off-state breakdown voltage is 2370 V for drain-to-gate spacing of 25 µm. These results show the great potential of AlN-channel transistors for high-temperature and high-power applications.

Subsurface Microbes Expanding the Tree of Life

ScienceCinema

Banfield, Jillian

2018-02-14

Jillian Banfield, Ph.D., UC Berkeley Professor and Berkeley Lab Earth Sciences Division staff scientist and long-time user of the DOE Joint Genome Institute’s resources shares her perspective on how the DOE JGI helps advance her research addressing knowledge gaps related to the roles of subsurface microbial communities in biogeochemical cycling. The video was filmed near the town of Rifle, Colorado at the primary field site for Phase I of the Subsurface Systems Scientific Focus Area 2.0 sponsored by the DOE Office of Biological and Environmental Research.

Advancing Knowledge on Fugitive Natural Gas from Energy Resource Development at a Controlled Release Field Observatory

NASA Astrophysics Data System (ADS)

Cahill, A. G.; Chao, J.; Forde, O.; Prystupa, E.; Mayer, K. U.; Black, T. A.; Tannant, D. D.; Crowe, S.; Hallam, S.; Mayer, B.; Lauer, R. M.; van Geloven, C.; Welch, L. A.; Salas, C.; Levson, V.; Risk, D. A.; Beckie, R. D.

2017-12-01

Fugitive gas, comprised primarily of methane, can be unintentionally released from upstream oil and gas development either at surface from leaky infrastructure or in the subsurface through failure of energy well bore integrity. For the latter, defective cement seals around energy well casings may permit buoyant flow of natural gas from the deeper subsurface towards shallow aquifers, the ground surface and potentially into the atmosphere. Concerns associated with fugitive gas release at surface and in the subsurface include contributions to greenhouse gas emissions, subsurface migration leading to accumulation in nearby infrastructure and impacts to groundwater quality. Current knowledge of the extent of fugitive gas leakage including how to best detect and monitor over time, and particularly its migration and fate in the subsurface, is incomplete. We have established an experimental field observatory for evaluating fugitive gas leakage in an area of historic and ongoing hydrocarbon resource development within the Montney Resource Play of the Western Canadian Sedimentary Basin, British Columbia, Canada. Natural gas will be intentionally released at surface and up to 25 m below surface at various rates and durations. Resulting migration patterns and impacts will be evaluated through examination of the geology, hydrogeology, hydro-geochemistry, isotope geochemistry, hydro-geophysics, vadose zone and soil gas processes, microbiology, and atmospheric conditions. The use of unmanned aerial vehicles and remote sensors for monitoring and detection of methane will also be assessed for suitability as environmental monitoring tools. Here we outline the experimental design and describe initial research conducted to develop a detailed site conceptual model of the field observatory. Subsequently, results attained from pilot surface and sub-surface controlled natural gas releases conducted in late summer 2017 will be presented as well as results of numerical modelling conducted to plan methane release experiments in 2018 and onwards. This research will create knowledge which informs strategies to detect and monitor fugitive gas fluxes at the surface and in groundwater; as well as guide associated regulatory and technical policies.

Influence of the gate position on source-to-drain resistance in AlGaN/AlN/GaN heterostructure field-effect transistors

NASA Astrophysics Data System (ADS)

Liu, Yan; Lin, Zhaojun; Cui, Peng; Zhao, Jingtao; Fu, Chen; Yang, Ming; Lv, Yuanjie

2017-08-01

Using a suitable dual-gate structure, the source-to-drain resistance (RSD) of AlGaN/AlN/GaN heterostructure field-effect transistor (HFET) with varying gate position has been studied at room temperature. The theoretical and experimental results have revealed a dependence of RSD on the gate position. The variation of RSD with the gate position is found to stem from the polarization Coulomb field (PCF) scattering. This finding is of great benefit to the optimization of the performance of AlGaN/AlN/GaN HFET. Especially, when the AlGaN/AlN/GaN HFET works as a microwave device, it is beneficial to achieve the impedance matching by designing the appropriate gate position based on PCF scattering.

Using constructed wetlands to treat subsurface drainage from intensively grazed dairy pastures in New Zealand.

PubMed

Tanner, C C; Nguyen, M Long; Sukias, J P S

2003-01-01

Performance data, during the start-up period, are presented for constructed wetlands treating subsurface drainage from dairy pastures in Waikato (rain-fed) and Northland (irrigated), North Island, New Zealand. The wetlands comprised an estimated 1 and 2% of the drained catchment areas, respectively. Nitrate concentrations were high in the drainage inflows at both sites (medians 10 g m(-3) at Waikato and 6.5 g m(-3) at Northland), but organic N was also an important form of N at Waikato (37% of TN). Comparison of wetland inflow and outflow nutrient concentrations showed overall nutrient reductions during passage through the wetlands for NO3-N (34 and 94% for medians, respectively), TN (56 and 33%, respectively), and DRP (80%, Northland only). Median NH4-N (both sites) and DRP (Waikato) concentrations showed apparent increases between the wetland inlets and outlets. However, a mass balance calculated for the 3 month preliminary monitoring periods showed substantial mass removal of DRP (80%) and all measured forms of N (NO3-N 78%, NH4-N 41%, Org-N 99.8% and TN 96%) in the Waikato wetland. Monitoring of these systems needs to be continued through a range of seasons and years to fully assess their long-term performance.

Sequestration of arsenic in ombrotrophic peatlands

NASA Astrophysics Data System (ADS)

Rothwell, James; Hudson-Edwards, Karen; Taylor, Kevin; Polya, David; Evans, Martin; Allott, Tim

2014-05-01

Peatlands can be important stores of arsenic but we are lacking spectroscopic evidence of the sequestration pathways of this toxic metalloid in peatland environments. This study reports on the solid-phase speciation of anthropogenically-derived arsenic in atmospherically contaminated peat from the Peak District National Park (UK). Surface and sub-surface peat samples were analysed by synchrotron X-ray absorption spectroscopy on B18 beamline at Diamond Light Source (UK). The results suggest that there are contrasting arsenic sequestration mechanisms in the peat. The bulk arsenic speciation results, in combination with strong arsenic-iron correlations at the surface, suggest that iron (hydr)oxides are key phases for the immobilisation of arsenic at the peat surface. In contrast, the deeper peat samples are dominated by arsenic sulphides (arsenopyrite, realgar and orpiment). Given that these peats receive inputs solely from the atmosphere, the presence of these sulphide phases suggests an in-situ authigenic formation. Redox oscillations in the peat due to a fluctuating water table and an abundant store of legacy sulphur from historic acid rain inputs may favour the precipitation of arsenic sequestering sulphides in sub-surface horizons. Oxidation-induced loss of these arsenic sequestering sulphur species by water table drawdown has important implications for the mobility of arsenic and the quality of waters draining peatlands.

Topographic effects on denitrification in drained agricultural fields

USDA-ARS?s Scientific Manuscript database

Denitrification is affected by soil moisture, while soil moisture can be affected by topography. Therefore, denitrification can be spatially correlated to topographic gradients. Three prior converted fields on the Delmarva Peninsula were sampled spatially for denitrification enzyme activity. The up...

Estimates of water and solute release from a coal waste rock dump in the Elk Valley, British Columbia, Canada.

PubMed

Villeneuve, S A; Barbour, S L; Hendry, M J; Carey, S K

2017-12-01

Long term (1999 to 2014) flow and water quality data from a rock drain located at the base of a coal waste rock dump constructed in the Elk Valley, British Columbia was used to characterize the release of three solutes (NO 3 - , Cl - and SO 4 2- ) from the dump and obtain whole dump estimates of net percolation (NP). The concentrations of dump derived solutes in the rock drain water were diluted by snowmelt waters from the adjacent natural watershed during the spring freshet and reached a maximum concentration during the winter baseflow period. Historical peak baseflow concentrations of conservative ions (NO 3 - and Cl - ) increased until 2006/07 after which they decreased. This decrease was attributed to completion of the flushing of the first pore volume of water stored within the dump. The baseflow SO 4 2- concentrations increased proportionally with NO 3 - and Cl - to 2007, but then continued to slowly increase as NO 3 - and Cl - concentrations decreased. This was attributed to ongoing production of SO 4 2- due to oxidation of sulfide minerals within the dump. Based on partitioning of the annual volume of water discharged from the rock drain to waste rock effluent (NP) and water entering the rock drain laterally from the natural watershed, the mean NP values were estimated to be 446±50mm/a (area normalized net percolation/year) for the dump and 172±71mm/a for the natural watershed. The difference was attributed to greater rates of recharge in the dump from summer precipitation compared to the natural watershed where rainfall interception and enhanced evapotranspiration will increase water losses. These estimates included water moving through subsurface pathways. However, given the limitations in quantifying these flows the estimated NP rates for both the natural watershed and the waste rock dump are considered to be low, and could be much higher (e.g. ~450mm/a and ~800mm/a). Copyright © 2017 Elsevier B.V. All rights reserved.

Antimony retention and release from drained and waterlogged shooting range soil under field conditions.

PubMed

Hockmann, Kerstin; Tandy, Susan; Lenz, Markus; Reiser, René; Conesa, Héctor M; Keller, Martin; Studer, Björn; Schulin, Rainer

2015-09-01

Many soils polluted by antimony (Sb) are subject to fluctuating waterlogging conditions; yet, little is known about how these affect the mobility of this toxic element under field conditions. Here, we compared Sb leaching from a calcareous shooting range soil under drained and waterlogged conditions using four large outdoor lysimeters. After monitoring the leachate samples taken at bi-weekly intervals for >1.5 years under drained conditions, two of the lysimeters were subjected to waterlogging with a water table fluctuating according to natural rainfall water infiltration. Antimony leachate concentrations under drained conditions showed a strong seasonal fluctuation between 110 μg L(-1) in summer and <40 μg L(-1) in winter, which closely correlated with fluctuations in dissolved organic carbon (DOC) concentrations. With the development of anaerobic conditions upon waterlogging, Sb in leachate decreased to 2-5 μg L(-1) Sb and remained stable at this level. Antimony speciation measurements in soil solution indicated that this decrease in Sb(V) concentrations was attributable to the reduction of Sb(V) to Sb(III) and the stronger sorption affinity of the latter to iron (Fe) (hydr)oxide phases. Our results demonstrate the importance of considering seasonal and waterlogging effects in the assessment of the risks from Sb-contaminated sites. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evaluation of a genome-scale in silico metabolic model for Geobacter metallireducens by using proteomic data from a field biostimulation experiment.

PubMed

Fang, Yilin; Wilkins, Michael J; Yabusaki, Steven B; Lipton, Mary S; Long, Philip E

2012-12-01

Accurately predicting the interactions between microbial metabolism and the physical subsurface environment is necessary to enhance subsurface energy development, soil and groundwater cleanup, and carbon management. This study was an initial attempt to confirm the metabolic functional roles within an in silico model using environmental proteomic data collected during field experiments. Shotgun global proteomics data collected during a subsurface biostimulation experiment were used to validate a genome-scale metabolic model of Geobacter metallireducens-specifically, the ability of the metabolic model to predict metal reduction, biomass yield, and growth rate under dynamic field conditions. The constraint-based in silico model of G. metallireducens relates an annotated genome sequence to the physiological functions with 697 reactions controlled by 747 enzyme-coding genes. Proteomic analysis showed that 180 of the 637 G. metallireducens proteins detected during the 2008 experiment were associated with specific metabolic reactions in the in silico model. When the field-calibrated Fe(III) terminal electron acceptor process reaction in a reactive transport model for the field experiments was replaced with the genome-scale model, the model predicted that the largest metabolic fluxes through the in silico model reactions generally correspond to the highest abundances of proteins that catalyze those reactions. Central metabolism predicted by the model agrees well with protein abundance profiles inferred from proteomic analysis. Model discrepancies with the proteomic data, such as the relatively low abundances of proteins associated with amino acid transport and metabolism, revealed pathways or flux constraints in the in silico model that could be updated to more accurately predict metabolic processes that occur in the subsurface environment.

All-ion-implanted planar-gate current aperture vertical Ga2O3 MOSFETs with Mg-doped blocking layer

NASA Astrophysics Data System (ADS)

Wong, Man Hoi; Goto, Ken; Morikawa, Yoji; Kuramata, Akito; Yamakoshi, Shigenobu; Murakami, Hisashi; Kumagai, Yoshinao; Higashiwaki, Masataka

2018-06-01

A vertical β-Ga2O3 metal–oxide–semiconductor field-effect transistor featuring a planar-gate architecture is presented. The device was fabricated by an all-ion-implanted process without requiring trench etching or epitaxial regrowth. A Mg-ion-implanted current blocking layer (CBL) provided electrical isolation between the source and the drain except at an aperture opening through which drain current was conducted. Successful transistor action was realized by gating a Si-ion-implanted channel above the CBL. Thermal diffusion of Mg induced a large source–drain leakage current through the CBL, which resulted in compromised off-state device characteristics as well as a reduced peak extrinsic transconductance compared with the results of simulations.

The Direct Effect of Toroidal Magnetic Fields on Stellar Oscillations: An Analytical Expression for the General Matrix Element

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiefer, René; Schad, Ariane; Roth, Markus

2017-09-10

Where is the solar dynamo located and what is its modus operandi? These are still open questions in solar physics. Helio- and asteroseismology can help answer them by enabling us to study solar and stellar internal structures through global oscillations. The properties of solar and stellar acoustic modes are changing with the level of magnetic activity. However, until now, the inference on subsurface magnetic fields with seismic measures has been very limited. The aim of this paper is to develop a formalism to calculate the effect of large-scale toroidal magnetic fields on solar and stellar global oscillation eigenfunctions and eigenfrequencies.more » If the Lorentz force is added to the equilibrium equation of motion, stellar eigenmodes can couple. In quasi-degenerate perturbation theory, this coupling, also known as the direct effect, can be quantified by the general matrix element. We present the analytical expression of the matrix element for a superposition of subsurface zonal toroidal magnetic field configurations. The matrix element is important for forward calculations of perturbed solar and stellar eigenfunctions and frequency perturbations. The results presented here will help to ascertain solar and stellar large-scale subsurface magnetic fields, and their geometric configuration, strength, and change over the course of activity cycles.« less

Surface manifestations of internal waves investigated by a subsurface buoyant jet: 3. Surface manifestations of internal waves

NASA Astrophysics Data System (ADS)

Bondur, V. G.; Grebenyuk, Yu. V.; Ezhova, E. V.; Kazakov, V. I.; Sergeev, D. A.; Soustova, I. A.; Troitskaya, Yu. I.

2010-08-01

In a large test reservoir at the Institute of Applied Physics, Russian Academy of Sciences, a series of experiments were performed to investigate the surface manifestations of internal waves radiated by a subsurface buoyant jet. The field of currents on the water surface of the reservoir was studied through the distribution of temperature with shallow thermocline. Using Particle Tracking Velocimetry (PTV), the velocity field of surface currents was measured. A theoretical model was developed to calculate the rates of disturbances on the surface. A comparison with experimental data indicated that the calculated data of the surface rate value are overestimated. This discrepancy was explained by the presence of a film of surface-active substances (SASs) with experimentally obtained parameters. Using scale modeling coefficients, we estimated the parameters of internal waves radiated by the subsurface wastewater system and the values of their surface manifestations in field conditions. We estimated the hydrodynamic contrasts in the field of surface waves, which can be caused by these inhomogeneous currents on the surface. For a wind velocity of 5 m/s, the magnitude of the contrast in the field of short waves can reach up to 10-25%, which is detected with confidence by remote-sensing methods.

The Direct Effect of Toroidal Magnetic Fields on Stellar Oscillations: An Analytical Expression for the General Matrix Element

NASA Astrophysics Data System (ADS)

Kiefer, René; Schad, Ariane; Roth, Markus

2017-09-01

Where is the solar dynamo located and what is its modus operandi? These are still open questions in solar physics. Helio- and asteroseismology can help answer them by enabling us to study solar and stellar internal structures through global oscillations. The properties of solar and stellar acoustic modes are changing with the level of magnetic activity. However, until now, the inference on subsurface magnetic fields with seismic measures has been very limited. The aim of this paper is to develop a formalism to calculate the effect of large-scale toroidal magnetic fields on solar and stellar global oscillation eigenfunctions and eigenfrequencies. If the Lorentz force is added to the equilibrium equation of motion, stellar eigenmodes can couple. In quasi-degenerate perturbation theory, this coupling, also known as the direct effect, can be quantified by the general matrix element. We present the analytical expression of the matrix element for a superposition of subsurface zonal toroidal magnetic field configurations. The matrix element is important for forward calculations of perturbed solar and stellar eigenfunctions and frequency perturbations. The results presented here will help to ascertain solar and stellar large-scale subsurface magnetic fields, and their geometric configuration, strength, and change over the course of activity cycles.

A unified analytical drain current model for Double-Gate Junctionless Field-Effect Transistors including short channel effects

NASA Astrophysics Data System (ADS)

Raksharam; Dutta, Aloke K.

2017-04-01

In this paper, a unified analytical model for the drain current of a symmetric Double-Gate Junctionless Field-Effect Transistor (DG-JLFET) is presented. The operation of the device has been classified into four modes: subthreshold, semi-depleted, accumulation, and hybrid; with the main focus of this work being on the accumulation mode, which has not been dealt with in detail so far in the literature. A physics-based model, using a simplified one-dimensional approach, has been developed for this mode, and it has been successfully integrated with the model for the hybrid mode. It also includes the effect of carrier mobility degradation due to the transverse electric field, which was hitherto missing in the earlier models reported in the literature. The piece-wise models have been unified using suitable interpolation functions. In addition, the model includes two most important short-channel effects pertaining to DG-JLFETs, namely the Drain Induced Barrier Lowering (DIBL) and the Subthreshold Swing (SS) degradation. The model is completely analytical, and is thus computationally highly efficient. The results of our model have shown an excellent match with those obtained from TCAD simulations for both long- and short-channel devices, as well as with the experimental data reported in the literature.

Wastewater collection and treatment technologies for semi-urban areas of India: a case study.

PubMed

Sundaravadivel, M; Vigneswaran, S

2001-01-01

Sanitation and wastewater management problems in small and medium towns in India (referred to as "semi-urban areas"--SUAs) are distinctly different from those of large cities or rural villages. There is an apparent lack of choices of appropriate sanitation options for these semi-urban areas, leading them to adopt on-site sanitation technologies. A field study of four such small towns in India was conducted to evaluate the suitability of available low-cost wastewater collection and treatment technologies, in light of their current practice. Based on the field study, this paper suggests a system comprising "combined surface sewers" and "reed-bed channel" for collection and treatment of wastewater for semi-urban areas, that can utilize all the existing infrastructure to effect better sanitation at lower costs. The suggested system involves converting the existing open wastewater collection drains on the road sides, as "decentralized" networks of covered drains with simple structural modifications to collect both wastewater and stormwater; and, converting the large open drains on the outskirts of SUAs that carry wastewater to agricultural fields, as gravel media filled beds planted with local reeds. Cost estimates for the towns studied indicate this system to be over 70% cheaper compared to conventional collection and treatment systems.

A field study of colloid transport in surface and subsurface flows

NASA Astrophysics Data System (ADS)

Zhang, Wei; Tang, Xiang-Yu; Xian, Qing-Song; Weisbrod, Noam; Yang, Jae E.; Wang, Hong-Lan

2016-11-01

Colloids have been recognized to enhance the migration of strongly-sorbing contaminants. However, few field investigations have examined combined colloid transport via surface runoff and subsurface flows. In a headwater catchment of the upper Yangtze River, a 6 m (L) by 4 m (W) sloping (6°) farmland plot was built by cement walls to form no-flow side boundaries. The plot was monitored in the summer of 2014 for the release and transport of natural colloids via surface runoff and subsurface flows (i.e., the interflow from the soil-mudrock interface and fracture flow from the mudrock-sandstone interface) in response to rain events. The water sources of the subsurface flows were apportioned to individual rain events using a two end-member model (i.e., mobile pre-event soil water extracted by a suction-cup sampler vs. rainwater (event water)) based on δ18O measurements. For rain events with high preceding soil moisture, mobile pre-event soil water was the main contributor (generally >60%) to the fracture flow. The colloid concentration in the surface runoff was 1-2 orders of magnitude higher than that in the subsurface flows. The lowest colloid concentration was found in the subsurface interflow, which was probably the result of pore-scale colloid straining mechanisms. The rainfall intensity and its temporal variation govern the dynamics of the colloid concentrations in both surface runoff and subsurface flows. The duration of the antecedent dry period affected not only the relative contributions of the rainwater and the mobile pre-event soil water to the subsurface flows but also the peak colloid concentration, particularly in the fracture flow. The <10 μm fine colloid size fraction accounted for more than 80% of the total suspended particles in the surface runoff, while the colloid size distributions of both the interflow and the fracture flow shifted towards larger diameters. These results highlight the need to avoid the application of strongly-sorbing agrochemicals (e.g., pesticides, phosphorus fertilizers) immediately before rainfall following a long no-rain period because their transport in association with colloids may occur rapidly over long distances via both surface runoff and subsurface flows with rainfall.

SFDBSI_GLS v. 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poppeliers, Christian

Matlab code for inversion of frequency domain, electrostatic geophysical data in terms of scalar scattering amplitudes in the subsurface. The data is assumed to be the difference between two measurements: electric field measurements prior to the injection of an electrically conductive proppant, and the electric field measurements after proppant injection. The proppant is injected into the subsurface via a well, and its purpose is to prop open fractures created by hydraulic fracturing. In both cases the illuminating electric field is assumed to be a vertically incident plane wave. The inversion strategy is to solve a set of linear system ofmore » equations, where each equation defines the amplitude of a candidate scattering volume. The model space is defined by M potential scattering locations and the frequency domain (of which there are k frequencies) data are recorded on N receivers. The solution thus solves a kN x M system of linear equations for M scalar amplitudes within the user-defined solution space. Practical Application: Oilfield environments where observed electrostatic geophysical data can reasonably be assumed to be scattered by subsurface proppant volumes. No field validation examples have so far been provided.« less

Understanding heterogeneity and data assimilation in karst groundwater surface water interactions: The role of geophysics and hydrologic models in a semi-confined aquifer

NASA Astrophysics Data System (ADS)

Meyerhoff, Steven B.

Groundwater and surface water historically have been treated as different entities. Due to this, planning and development of groundwater and surface water resources, both quantity and quality are often also treated separately. Recently, there has been work to characterize groundwater and surface water as a single system. Karstic systems are widely influenced by these interactions due to varying permeability, fracture geometry and porosity. Here, three different approaches are used to characterize groundwater surface water interactions in karstic environments. 1) A hydrologic model, ParFlow, is conditioned with known subsurface data to determine whether a reduction in subsurface uncertainty will enhance the prediction of surface water variables. A reduction in subsurface uncertainty resulted in substantial reductions in uncertainty in Hortonian runoff and less reductions in Dunne runoff. 2) Geophysical data is collected at a field site in O'leno State Park, Florida to visualize groundwater and surface water interactions in karstic environments. Significant changes in resistivity are seen through time at two locations. It is hypothesized that these changes are related to changing fluid source waters (e.g groundwater or surface water). 3). To confirm these observations an ensemble of synthetic forward models are simulated, inverted and compared directly with field observations and End-Member-Mixing-Analysis (EMMA). Field observations and synthetic models have comparable resistivity anomalies patterns and mixing fractions. This allows us to characterize and quantify subsurface mixing of groundwater and surface in karst environments. These three approaches (hydrologic models, field data and forward model experiments), (1) show the complexity and dynamics of groundwater and surface mixing in karstic environments in varying flow conditions, (2) showcase a novel geophysical technique to visualize groundwater and surface water interactions and (3) confirm hypothesis of flow and mixing in subsurface karst environments.

Field study and simulation of diurnal temperature effects on infiltration and variably saturated flow beneath an ephemeral stream

USGS Publications Warehouse

Dudek Ronan, Anne; Prudic, David E.; Thodal, Carl E.; Constantz, Jim

1998-01-01

Two experiments were performed to investigate flow beneath an ephemeral stream and to estimate streambed infiltration rates. Discharge and stream-area measurements were used to determine infiltration rates. Stream and subsurface temperatures were used to interpret subsurface flow through variably saturated sediments beneath the stream. Spatial variations in subsurface temperatures suggest that flow beneath the streambed is dependent on the orientation of the stream in the canyon and the layering of the sediments. Streamflow and infiltration rates vary diurnally: Streamflow is lowest in late afternoon when stream temperature is greatest and highest in early morning when stream temperature is least. The lower afternoon Streamflow is attributed to increased infiltration rates; evapotranspiration is insufficient to account for the decreased Streamflow. The increased infiltration rates are attributed to viscosity effects on hydraulic conductivity from increased stream temperatures. The first set of field data was used to calibrate a two-dimensional variably saturated flow model that includes heat transport. The model was calibrated to (1) temperature fluctuations in the subsurface and (2) infiltration rates determined from measured Streamflow losses. The second set of field data was to evaluate the ability to predict infiltration rates on the basis of temperature measurements alone. Results indicate that the variably saturated subsurface flow depends on downcanyon layering of the sediments. They also support the field observations in indicating that diurnal changes in infiltration can be explained by temperature dependence of hydraulic conductivity. Over the range of temperatures and flows monitored, diurnal stream temperature changes can be used to estimate streambed infiltration rates. It is often impractical to maintain equipment for determining infiltration rates by traditional means; however, once a model is calibrated using both infiltration and temperature data, only relatively inexpensive temperature monitoring can later yield infiltration rates that are within the correct order of magnitude.

Subsurface microbial habitats on Mars

NASA Technical Reports Server (NTRS)

Boston, P. J.; Mckay, C. P.

1991-01-01

We developed scenarios for shallow and deep subsurface cryptic niches for microbial life on Mars. Such habitats could have considerably prolonged the persistence of life on Mars as surface conditions became increasingly inhospitable. The scenarios rely on geothermal hot spots existing below the near or deep subsurface of Mars. Recent advances in the comparatively new field of deep subsurface microbiology have revealed previously unsuspected rich aerobic and anaerobic microbal communities far below the surface of the Earth. Such habitats, protected from the grim surface conditions on Mars, could receive warmth from below and maintain water in its liquid state. In addition, geothermally or volcanically reduced gases percolating from below through a microbiologically active zone could provide the reducing power needed for a closed or semi-closed microbial ecosystem to thrive.

Bacterial communities associated with subsurface geochemical processes in continental serpentinite springs.

PubMed

Brazelton, William J; Morrill, Penny L; Szponar, Natalie; Schrenk, Matthew O

2013-07-01

Reactions associated with the geochemical process of serpentinization can generate copious quantities of hydrogen and low-molecular-weight organic carbon compounds, which may provide energy and nutrients to sustain subsurface microbial communities independently of the photosynthetically supported surface biosphere. Previous microbial ecology studies have tested this hypothesis in deep sea hydrothermal vents, such as the Lost City hydrothermal field. This study applied similar methods, including molecular fingerprinting and tag sequencing of the 16S rRNA gene, to ultrabasic continental springs emanating from serpentinizing ultramafic rocks. These molecular surveys were linked with geochemical measurements of the fluids in an interdisciplinary approach designed to distinguish potential subsurface organisms from those derived from surface habitats. The betaproteobacterial genus Hydrogenophaga was identified as a likely inhabitant of transition zones where hydrogen-enriched subsurface fluids mix with oxygenated surface water. The Firmicutes genus Erysipelothrix was most strongly correlated with geochemical factors indicative of subsurface fluids and was identified as the most likely inhabitant of a serpentinization-powered subsurface biosphere. Both of these taxa have been identified in multiple hydrogen-enriched subsurface habitats worldwide, and the results of this study contribute to an emerging biogeographic pattern in which Betaproteobacteria occur in near-surface mixing zones and Firmicutes are present in deeper, anoxic subsurface habitats.

Bacterial Communities Associated with Subsurface Geochemical Processes in Continental Serpentinite Springs

PubMed Central

Morrill, Penny L.; Szponar, Natalie; Schrenk, Matthew O.

2013-01-01

Reactions associated with the geochemical process of serpentinization can generate copious quantities of hydrogen and low-molecular-weight organic carbon compounds, which may provide energy and nutrients to sustain subsurface microbial communities independently of the photosynthetically supported surface biosphere. Previous microbial ecology studies have tested this hypothesis in deep sea hydrothermal vents, such as the Lost City hydrothermal field. This study applied similar methods, including molecular fingerprinting and tag sequencing of the 16S rRNA gene, to ultrabasic continental springs emanating from serpentinizing ultramafic rocks. These molecular surveys were linked with geochemical measurements of the fluids in an interdisciplinary approach designed to distinguish potential subsurface organisms from those derived from surface habitats. The betaproteobacterial genus Hydrogenophaga was identified as a likely inhabitant of transition zones where hydrogen-enriched subsurface fluids mix with oxygenated surface water. The Firmicutes genus Erysipelothrix was most strongly correlated with geochemical factors indicative of subsurface fluids and was identified as the most likely inhabitant of a serpentinization-powered subsurface biosphere. Both of these taxa have been identified in multiple hydrogen-enriched subsurface habitats worldwide, and the results of this study contribute to an emerging biogeographic pattern in which Betaproteobacteria occur in near-surface mixing zones and Firmicutes are present in deeper, anoxic subsurface habitats. PMID:23584766

Fabrication and Characteristics of Pentacene/Vanadium Pentoxide Field-Effect Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minagawa, M.; Nakai, K.; Baba, A.

2011-12-23

Organic field-effect transistors (OFETs) were fabricated using pentacene thin layer, and the effects of inserted Lewis-acid thin layers on electrical properties were investigated. The OFETs have active layers of pentacene and vanadium pentoxide (V{sub 2}O{sub 5}) as a Lewis-acid layer. Typical source-drain current (I{sub DS}) vs. source-drain voltage (V{sub DS}) curves were observed under negative gate voltages (V{sub G}S) application, and the shift of the threshold voltage for FET driving (V{sub t}) to positive side was also observed by V{sub 2}O{sub 5} layer insertion, that is, -2.5 V for device with V{sub 2}O{sub 5} layer and -5.7 V for devicemore » without V{sub 2}O{sub 5} layer. It was thought that charge transfer (CT) complexes which were formed at the interface between pentacene and V{sub 2}O{sub 5} layer were dissociated by the applied gate voltage, and the generated holes seem to contribute to drain current and the apparent V{sub t} improvement.« less

Study of novel junctionless Ge n-Tunneling Field-Effect Transistors with lightly doped drain (LDD) region

NASA Astrophysics Data System (ADS)

Liu, Xiangyu; Hu, Huiyong; Wang, Bin; Wang, Meng; Han, Genquan; Cui, Shimin; Zhang, Heming

2017-02-01

In this paper, a novel junctionless Ge n-Tunneling Field-Effect Transistors (TFET) structure is proposed. The simulation results show that Ion = 5.5 × 10-5A/μm is achieved. The junctionless device structure enhances Ion effectively and increases the region where significant BTBT occurs, comparing with the normal Ge-nTEFT. The impact of the lightly doped drain (LDD) region is investigated. A comparison of Ion and Ioff of the junctionless Ge n-TFET with different channel doping concentration ND and LDD doping concentration NLDD is studied. Ioff is reduced 1 order of magnitude with the optimized ND and NLDD are 1 × 1018cm-3 and 1 × 1017 cm-3, respectively. To reduce the gate induced drain leakage (GIDL) current, the impact of the sloped gate oxide structure is also studied. By employing the sloped gate oxide structure, the below 60 mV/decade subthreshold swing S = 46.2 mV/decade is achieved at Ion = 4.05 × 10-5A/μm and Ion/Ioff = 5.7 × 106.

Carbon nanotube feedback-gate field-effect transistor: suppressing current leakage and increasing on/off ratio.

PubMed

Qiu, Chenguang; Zhang, Zhiyong; Zhong, Donglai; Si, Jia; Yang, Yingjun; Peng, Lian-Mao

2015-01-27

Field-effect transistors (FETs) based on moderate or large diameter carbon nanotubes (CNTs) usually suffer from ambipolar behavior, large off-state current and small current on/off ratio, which are highly undesirable for digital electronics. To overcome these problems, a feedback-gate (FBG) FET structure is designed and tested. This FBG FET differs from normal top-gate FET by an extra feedback-gate, which is connected directly to the drain electrode of the FET. It is demonstrated that a FBG FET based on a semiconducting CNT with a diameter of 1.5 nm may exhibit low off-state current of about 1 × 10(-13) A, high current on/off ratio of larger than 1 × 10(8), negligible drain-induced off-state leakage current, and good subthreshold swing of 75 mV/DEC even at large source-drain bias and room temperature. The FBG structure is promising for CNT FETs to meet the standard for low-static-power logic electronics applications, and could also be utilized for building FETs using other small band gap semiconductors to suppress leakage current.

Evaluating permafrost thaw vulnerabilities and hydrologic impacts in boreal Alaska (USA) watersheds using field data and cryohydrogeologic modeling

NASA Astrophysics Data System (ADS)

Walvoord, M. A.; Voss, C.; Ebel, B. A.; Minsley, B. J.

2017-12-01

Permafrost environments undergo changes in hydraulic, thermal, chemical, and mechanical subsurface properties upon thaw. These property changes must be considered in addition to alterations in hydrologic, thermal, and topographic boundary conditions when evaluating shifts in the movement and storage of water in arctic and sub-arctic boreal regions. Advances have been made in the last several years with respect to multiscale geophysical characterization of the subsurface and coupled fluid and energy transport modeling of permafrost systems. Ongoing efforts are presented that integrate field data with cryohydrogeologic modeling to better understand and anticipate changes in subsurface water resources, fluxes, and flowpaths caused by climate warming and permafrost thawing. Analyses are based on field data from several sites in interior Alaska (USA) that span a broad north-south transition from continuous to discontinuous permafrost. These data include soil hydraulic and thermal properties and shallow permafrost distribution. The data guide coupled fluid and energy flow simulations that incorporate porewater liquid/ice phase change and the accompanying modifications in hydraulic and thermal subsurface properties. Simulations are designed to assess conditions conducive to active layer thickening and talik development, both of which are expected to affect groundwater storage and flow. Model results provide a framework for identifying factors that control the rates of permafrost thaw and associated hydrologic responses, which in turn influence the fate and transport of carbon.

Enhancing management of fall-applied poultry litter with cover crop and subsurface band placement in no-till cotton

USDA-ARS?s Scientific Manuscript database

Whether yield reduction risk of cotton fertilized with fall-applied poultry litter in regions with warm fall or winter months can be minimized by applying the litter in subsurface bands in conjunction with winter cover crop is unknown. A field study was conducted in Mississippi to test whether litte...

Subsurface Optical Microscopy of Coarse Grain Spinels. Phase 1

DTIC Science & Technology

2013-12-01

A 456 nm LED line bar illuminated in figure 15 and a Xenon fiber optic bar illuminator is shown for figure 16. The optical in situ or subsurface ... imaging of coarse grain spinels and AlONs is optically more complex than expected. An overhead view of the side illumination field is shown in figure 20

Magnetic perturbation inspection of inner bearing races

NASA Technical Reports Server (NTRS)

Barton, J. R.; Lankford, J.

1972-01-01

Approximately 100 inner race bearings were inspected nondestructively prior to endurance testing. Two of the bearings which failed during testing spalled at the sites of subsurface inclusions previously detected by using magnetic field perturbation. At other sites initially judged to be suspect, subsurface inclusion-nucleated cracking was observed. Inspection records and metallurgical sectioning results are presented and discussed.

Passively operated spool valve for drain-down freeze protection of thermosyphon water heaters. Final technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1982-04-30

The work done to extend the existing drain-down valve technology to provide passive drain-down freeze protection for thermosyphon-based solar water heaters is described. The basic design of the existing valve model is that of a spool valve, employing a cylindrical spool which moves axially in a mating cartridge to open and close o-rings at the two operating extremes (drain and operate) to perform the valving function. Three passive actuators to drive the basic valving mechanism were designed, fabricated, and tested. Two piping configurations used to integrate the spool valve with the thermosyphon system are described, as are the passive actuators.more » The three actuator designs are: photovoltaic driven, refrigerant-based bellows, and heat motor cable-drive designs. Costs are compared for the alternative actuator designs, and operating characteristics were examined for the thermosyphon system, including field tests. The market for the valve for thermosyphon systems is then assessed. (LEW)« less

Regenerative switching CMOS system

DOEpatents

Welch, James D.

1998-01-01

Complementary Metal Oxide Semiconductor (CMOS) Schottky barrier Field Effect Transistor systems, which are a seriesed combination of N and P-Channel MOSFETS, in which Source Schottky barrier junctions of the N and P-Channel Schottky barrier MOSFETS are electically interconnected, (rather than the Drains as in conventional diffused junction CMOS), which Schottky barrier MOSFET system demonstrates Regenerative Inverting Switching Characteristics in use are disclosed. Both the N and P-Channel Schottky barrier MOSFET devices are unique in that they provide operational Drain Current vs. Drain to Source voltage as a function of Gate voltage only where the polarities of the Drain voltage and Gate voltage are opposite, referenced to the Source as a common terminal, and where the polarity of the voltage applied to the Gate is appropriate to cause Channel inversion. Experimentally derived results which demonstrate and verify the operation of N and P-Channel Schottky barrier MOSFETS actually fabricated on P and N-type Silicon respectively, by a common procedure using vacuum deposited Chromium as a Schottky barrier forming metal, are also provided.

Regenerative switching CMOS system

DOEpatents

Welch, J.D.

1998-06-02

Complementary Metal Oxide Semiconductor (CMOS) Schottky barrier Field Effect Transistor systems, which are a series combination of N and P-Channel MOSFETS, in which Source Schottky barrier junctions of the N and P-Channel Schottky barrier MOSFETS are electrically interconnected, (rather than the Drains as in conventional diffused junction CMOS), which Schottky barrier MOSFET system demonstrates Regenerative Inverting Switching Characteristics in use are disclosed. Both the N and P-Channel Schottky barrier MOSFET devices are unique in that they provide operational Drain Current vs. Drain to Source voltage as a function of Gate voltage only where the polarities of the Drain voltage and Gate voltage are opposite, referenced to the Source as a common terminal, and where the polarity of the voltage applied to the Gate is appropriate to cause Channel inversion. Experimentally derived results which demonstrate and verify the operation of N and P-Channel Schottky barrier MOSFETS actually fabricated on P and N-type Silicon respectively, by a common procedure using vacuum deposited Chromium as a Schottky barrier forming metal, are also provided. 14 figs.

Comparative investigation of novel hetero gate dielectric and drain engineered charge plasma TFET for improved DC and RF performance

NASA Astrophysics Data System (ADS)

Yadav, Dharmendra Singh; Verma, Abhishek; Sharma, Dheeraj; Tirkey, Sukeshni; Raad, Bhagwan Ram

2017-11-01

Tunnel-field-effect-transistor (TFET) has emerged as one of the most prominent devices to replace conventional MOSFET due to its ability to provide sub-threshold slope below 60 mV/decade (SS ≤ 60 mV/decade) and low leakage current. Despite this, TFETs suffer from ambipolar behavior, lower ON-state current, and poor RF performance. To address these issues, we have introduced drain and gate work function engineering with hetero gate dielectric for the first time in charge plasma based doping-less TFET (DL TFET). In this, the usage of dual work functionality over the drain region significantly reduces the ambipolar behavior of the device by varying the energy barrier at drain/channel interface. Whereas, the presence of dual work function at the gate terminal increases the ON-state current (ION). The combined effect of dual work function at the gate and drain electrode results in the increment of ON-state current (ION) and decrement of ambipolar conduction (Iambi) respectively. Furthermore, the incorporation of hetero gate dielectric along with dual work functionality at the drain and gate electrode provides an overall improvement in the performance of the device in terms of reduction in ambipolarity, threshold voltage and sub-threshold slope along with improved ON-state current and high frequency figures of merit.

Sources and fates of heavy metals in a mining-impacted stream: Temporal variability and the role of iron oxides

PubMed Central

Schaider, Laurel A.; Senn, David B.; Estes, Emily R.; Brabander, Daniel J.; Shine, James P.

2014-01-01

Heavy metal contamination of surface waters at mining sites often involves complex interactions of multiple sources and varying biogeochemical conditions. We compared surface and subsurface metal loading from mine waste pile runoff and mine drainage discharge and characterized the influence of iron oxides on metal fate along a 0.9-km stretch of Tar Creek (Oklahoma, USA), which drains an abandoned Zn/Pb mining area. The importance of each source varied by metal: mine waste pile runoff contributed 70% of Cd, while mine drainage contributed 90% of Pb, and both sources contributed similarly to Zn loading. Subsurface inputs accounted for 40% of flow and 40-70% of metal loading along this stretch. Streambed iron oxide aggregate material contained highly elevated Zn (up to 27,000 μg g−1), Pb (up to 550 μg g−1) and Cd (up to 200 μg g−1) and was characterized as a heterogeneous mixture of iron oxides, fine-grain mine waste, and organic material. Sequential extractions confirmed preferential sequestration of Pb by iron oxides, as well as substantial concentrations of Zn and Cd in iron oxide fractions, with additional accumulation of Zn, Pb, and Cd during downstream transport. Comparisons with historical data show that while metal concentrations in mine drainage have decreased by more than an order of magnitude in recent decades, the chemical composition of mine waste pile runoff has remained relatively constant, indicating less attenuation and increased relative importance of pile runoff. These results highlight the importance of monitoring temporal changes at contaminated sites associated with evolving speciation and simultaneously addressing surface and subsurface contamination from both mine waste piles and mine drainage. PMID:24867708

Stable, geochemically mediated biospheres in the Deep Mine Microbial Observatory, SD, USA

NASA Astrophysics Data System (ADS)

Osburn, M. R.; Casar, C. P.; Kruger, B.; Flynn, T. M.

2017-12-01

The terrestrial subsurface is a vast reservoir of life, hosting diverse microbial ecosystems with varying levels of connectivity to surface inputs. Understanding long term ecosystem dynamics within the subsurface biosphere is very challenging due to limitations in accessibility, sample availability, and slow microbial growth rates. The establishment of the Deep Mine Microbial Observatory (DeMMO) at the Sanford Underground Research Facility, SD, USA has allowed for bimonthly sampling for nearly two years at six sites spanning 250 to 1500 m below the surface. Here we present a time-resolved analysis of the geomicrobiology of the six DeMMO sites, which have been created from legacy mine boreholes modified to allow for controlled sampling. Our interdisciplinary approach includes analysis of passively draining fracture fluid for aqueous and gas geochemistry, DNA sequencing, microscopy, and isotopic measurements of organic and inorganic substrates. Fluid geochemistry varies significantly between sites, but is relatively stable over time for a given site, even through significant external perturbations such as drilling and installation of permanent sampling devices into the boreholes. The fluid-hosted microbial diversity follows these trends, with consistent populations present at each site through time, even through drilling events. For instance, the shallowest site (DeMMO 1) consistently hosts >30% uncharacterized phyla and >25% Omnitrophica whereas the deepest site (DeMMO 6) is dominated by Firmicutes and Bacterioidetes. Microbial diversity appears to respond to the availability of energy sources such as organic carbon, sulfate, sulfide, hydrogen, and iron. Carbon isotopic measurements reveal closed system behavior with significant recycling of organic carbon into the DIC pool. Together these observations suggest DeMMO hosts isolated subsurface microbial populations adapted to local geochemistry that are stable on yearlong timescales.

Occurrence, leaching, and degradation of Cry1Ab protein from transgenic maize detritus in agricultural streams

DOE PAGES

Griffiths, Natalie A.; Tank, Jennifer L.; Royer, Todd V.; ...

2017-03-15

The insecticidal Cry1Ab protein expressed by transgenic (Bt) maize can enter adjacent water bodies via multiple pathways, but its fate in stream ecosystems is not as well studied as in terrestrial systems. In this study, we used a combination of field sampling and laboratory experiments to examine the occurrence, leaching, and degradation of soluble Cry1Ab protein derived from Bt maize in agricultural streams. We surveyed 11 agricultural streams in northwestern Indiana, USA, on 6 dates that encompassed the growing season, crop harvest, and snowmelt/spring flooding, and detected Cry1Ab protein in the water column and in flowing subsurface tile drains atmore » concentrations of 3–60 ng/L. In a series of laboratory experiments, submerged Bt maize leaves leached Cry1Ab into stream water with 1% of the protein remaining in leaves after 70 d. Laboratory experiments suggested that dissolved Cry1Ab protein degraded rapidly in microcosms containing water-column microorganisms, and light did not enhance breakdown by stimulating assimilatory uptake of the protein by autotrophs. Here, the common detection of Cry1Ab protein in streams sampled across an agricultural landscape, combined with laboratory studies showing rapid leaching and degradation, suggests that Cry1Ab may be pseudo-persistent at the watershed scale due to the multiple input pathways from the surrounding terrestrial environment.« less

Occurrence, leaching, and degradation of Cry1Ab protein from transgenic maize detritus in agricultural streams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffiths, Natalie A.; Tank, Jennifer L.; Royer, Todd V.

The insecticidal Cry1Ab protein expressed by transgenic (Bt) maize can enter adjacent water bodies via multiple pathways, but its fate in stream ecosystems is not as well studied as in terrestrial systems. In this study, we used a combination of field sampling and laboratory experiments to examine the occurrence, leaching, and degradation of soluble Cry1Ab protein derived from Bt maize in agricultural streams. We surveyed 11 agricultural streams in northwestern Indiana, USA, on 6 dates that encompassed the growing season, crop harvest, and snowmelt/spring flooding, and detected Cry1Ab protein in the water column and in flowing subsurface tile drains atmore » concentrations of 3–60 ng/L. In a series of laboratory experiments, submerged Bt maize leaves leached Cry1Ab into stream water with 1% of the protein remaining in leaves after 70 d. Laboratory experiments suggested that dissolved Cry1Ab protein degraded rapidly in microcosms containing water-column microorganisms, and light did not enhance breakdown by stimulating assimilatory uptake of the protein by autotrophs. Here, the common detection of Cry1Ab protein in streams sampled across an agricultural landscape, combined with laboratory studies showing rapid leaching and degradation, suggests that Cry1Ab may be pseudo-persistent at the watershed scale due to the multiple input pathways from the surrounding terrestrial environment.« less

Fluvial sandstone reservoirs of Travis Peak (Hosston) Formation, east Texas basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tye, R.S.

1989-03-01

Gas production (7.2 billion ft/sup 3/) from low-permeability sandstones in the Travis Peak Formation, North Appleby field, Nacogdoches County, Texas, is enhanced through massive hydraulic fracturing of stacked sandstones that occur at depths between 8000 and 10,000 ft. stratigraphic reservoirs were formed in multilateral tabular sandstones owing to impermeable mudstone interbeds that encase blocky to upward-fining sandstones. Pervasive quartz cement in the sandstones decreases porosity and permeability and augments the reservoir seal. Subsurface data indicate that much of this 2000-ft thick section represents aggradation of alluvial-valley deposits. Multiple channel belts form a network of overlapping, broad, tabular sandstones having thickness-to-widthmore » ratios of 1:850 (8-44 ft thick; widths exceed 4-5 mi). Six to eight channel belts, each containing 80-90% medium to fine-grained sandstone, can occupy a 200-ft thick interval. In a vertical sequence through one channel belt sandstone, basal planar cross-bedding grades upward into thinly interbedded sets of planar cross-beds and ripple cross-lamination. Clay-clast conglomerates line scoured channel bases. Adjacent to the channels, interbedded mudstones accumulated in well-drained swamps and lakes. Poorly sorted sandstones represent overbank deposition (crevasse splays and lacustrine deltas). During Travis Peak deposition, fluvial styles evolved from dominantly braided systems near the base of the formation to more mud-rich, meandering systems at the top.« less

Field drains as a route of rapid nutrient export from agricultural land receiving biosolids.

PubMed

Heathwaite, A L; Burke, S P; Bolton, L

2006-07-15

We report research on the environmental risk of incidental nutrient transfers from land to water for biosolids amended soils. We show that subsurface (drainflow) pathways of P transport may result in significant concentrations, up to 10 mg total P l(-1), in the drainage network of an arable catchment when a P source (recent biosolids application) coincides with a significant and active transport pathway (rainfall event). However, the high P concentrations were short-lived, with drainage ditch total P concentrations returning to pre-storm concentrations within a few days of the storm event. In the case of the drainflow concentrations reported here, the results are unusual in that they describe an 'incidental event' for a groundwater catchment where such events might normally be expected to be rare owing to the capacity of the hydrological system to attenuate nutrient fluxes for highly adsorbed elements such as P. Consequently, there is a potential risk of P transfers to shallow groundwater systems. We suggest that the findings are not specific to biosolids-alone, which is a highly regulated industry, but that similar results may be anticipated had livestock waste or mineral fertilizer been applied, although the magnitude of losses may differ. The risk appears to be more one of timing and the availability of a rapid transport pathway than of P source.

Estimation of the Potential for Atrazine Transport in a Silt Loam Soil

USGS Publications Warehouse

Eckhardt, D.A.V.; Wagenet, R.J.

1996-01-01

The transport potential of the herbicide atrazine (2-chloro-4-ethyl-6-isopropyl-s-triazine) through a 1-meter-thick root zone of corn (Zea mays L.) in a silty-loam soil in Kansas was estimated for a 22-year period (1972-93) using the one-dimensional water-flow and solute-transport model LEACHM. Results demonstrate that, for this soil, atrazine transport is directly related to the amount and timing of rain that follows spring applications of atrazine. Two other critical transport factors were important in wet years - [1] variability in atrazine application rate, and [2] atrazine degradation rates below the root zone. Results demonstrate that the coincidence of heavy rain soon after atrazine application can cause herbicide to move below the rooting zone into depths at which biodegradation rates are assumed to be low but are often unknown. Atrazine that reaches below the rooting zone and persists in the underlying soil can subsequently be transported into ground water as soil water drains, typically after the growing season. A frequency analysis of atrazine concentrations in subsurface drainage, combined with field data, demonstrates the relative importance of critical transport factors and confirms a need for definitive estimates of atrazine-degradation rates below the root zone. The analysis indicates that periodic leaching of atrazine can be expected for this soil when rainfall that exceeds 20 cm/mo coincides with atrazine presence in soil.

Nitrous Oxide Emissions From Northern Forested and Harvested Ecosystems

NASA Astrophysics Data System (ADS)

Kavanaugh, K. M.; Kellman, L. M.

2005-12-01

Very little is known about how deforestation alters the soil subsurface production and surface emissions of N2O from northern forest soils. Soil N2O surface fluxes and subsurface concentrations from two 3 year old harvested and intact forest pairs of contrasting soil texture were monitored during the 2004 and 2005 growing seasons in the Acadian forest of Atlantic Canada in order to: 1) quantify N2O emissions associated with each land-use type, 2) examine spatial and temporal variations in subsurface concentrations and surface fluxes at each site, and 3) determine the suitability of a photoacoustic gas monitor (PGM) for in- situ field measurements vs. field sample collection and laboratory analysis on a gas chromatograph. Each site was instrumented with 11 permanent collars for surface flux measurements designed to capture the microsite variability at the sites. Subsurface soil gas samplers, designed to identify the important zones of N2O production in the vertical profile were installed at depths of 0, 10, 20 and 35 cm below the organic-mineral soil interface. Surface fluxes were measured with non-steady-state vented surface flux chambers with measurements of all surface flux and subsurface data made on a bi-weekly basis. Results suggest that spatial and temporal variability in surface emissions are very high and routinely close to zero. Subsurface profile concentration data shows vertical concentration profiles at intact forest sites with concentrations close to atmospheric, while harvested sites show a pattern of increasing N2O concentration with depth, reaching a maximum of approximately 27000ppb at 35cm.

Subsurface soil carbon losses offset surface carbon accumulation in abandoned agricultural fields

NASA Astrophysics Data System (ADS)

Yang, Y.; Knops, J. M. H.

2017-12-01

Soil carbon is widely understood to accumulate after agricultural abandonment. However, most of the studies have been focused on shallow depths (10 to 30 cm), and there is a lack of deeper soil carbon data. It was reported that in temperate grasslands, 58% of the soil organic carbon in the first meter was stored between 20 and 100 cm, and organic matter in deeper soil might also be susceptible to agricultural disturbance. We used repeated sampling in 2001 and 2014 to directly measure rates of soil carbon change in both surface and subsurface soil in 21 abandoned agricultural fields at Cedar Creek Ecosystem Science Reserve, MN. Congruent with many other studies, we found carbon accumulated 384.2 C g/m2 in surface soil (0 - 20 cm) over the 13 years. However, we also found carbon pool declined 688.1 C g/m2 in the subsurface soil (40-100 cm), which resulted in a net total loss of soil carbon. We investigated the ecosystem carbon pools and fluxes to explore the mechanisms of the observed soil carbon changes. We found root carbon was not significantly correlated with soil carbon in any of the depth. In situ soil incubation showed nitrogen mineralization rates in subsurface soil are lower than that of surface soil. However, the estimated nitrogen and carbon output through decomposition is higher than inputs from roots, therefore leading to carbon loss in subsurface soil. These results suggest that the decomposition of soil organic matter by microorganisms in subsurface soil is significant, and should be incorporated in ecosystem carbon budget models.

Impact of Subsurface Heterogeneities on nano-Scale Zero Valent Iron Transport

NASA Astrophysics Data System (ADS)

Krol, M. M.; Sleep, B. E.; O'Carroll, D. M.

2011-12-01

Nano-scale zero valent iron (nZVI) has been applied as a remediation technology at sites contaminated with chlorinated compounds and heavy metals. Although laboratory studies have demonstrated high reactivity for the degradation of target contaminants, the success of nZVI in the field has been limited due to poor subsurface mobility. When injected into the subsurface, nZVI tends to aggregate and be retained by subsurface soils. As such nZVI suspensions need to be stabilized for increased mobility. However, even with stabilization, soil heterogeneities can still lead to non-uniform nZVI transport, resulting in poor distribution and consequently decreased degradation of target compounds. Understanding how nZVI transport can be affected by subsurface heterogeneities can aid in improving the technology. This can be done with the use of a numerical model which can simulate nZVI transport. In this study CompSim, a finite difference groundwater model, is used to simulate the movement of nZVI in a two-dimensional domain. CompSim has been shown in previous studies to accurately predict nZVI movement in the subsurface, and is used in this study to examine the impact of soil heterogeneity on nZVI transport. This work also explores the impact of different viscosities of the injected nZVI suspensions (corresponding to different stabilizing polymers) and injection rates on nZVI mobility. Analysis metrics include travel time, travel distance, and average nZVI concentrations. Improving our understanding of the influence of soil heterogeneity on nZVI transport will lead to improved field scale implementation and, potentially, to more effective remediation of contaminated sites.

Denitrifying Bacteria from the Genus Rhodanobacter Dominate Bacterial Communities in the Highly Contaminated Subsurface of a Nuclear Legacy Waste Site

PubMed Central

Green, Stefan J.; Prakash, Om; Jasrotia, Puja; Overholt, Will A.; Cardenas, Erick; Hubbard, Daniela; Tiedje, James M.; Watson, David B.; Schadt, Christopher W.; Brooks, Scott C.

2012-01-01

The effect of long-term mixed-waste contamination, particularly uranium and nitrate, on the microbial community in the terrestrial subsurface was investigated at the field scale at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site in Oak Ridge, TN. The abundance, community composition, and distribution of groundwater microorganisms were examined across the site during two seasonal sampling events. At representative locations, subsurface sediment was also examined from two boreholes, one sampled from the most heavily contaminated area of the site and another from an area with low contamination. A suite of DNA- and RNA-based molecular tools were employed for community characterization, including quantitative PCR of rRNA and nitrite reductase genes, community composition fingerprinting analysis, and high-throughput pyrotag sequencing of rRNA genes. The results demonstrate that pH is a major driver of the subsurface microbial community structure and that denitrifying bacteria from the genus Rhodanobacter (class Gammaproteobacteria) dominate at low pH. The relative abundance of bacteria from this genus was positively correlated with lower-pH conditions, and these bacteria were abundant and active in the most highly contaminated areas. Other factors, such as the concentration of nitrogen species, oxygen level, and sampling season, did not appear to strongly influence the distribution of Rhodanobacter bacteria. The results indicate that these organisms are acid-tolerant denitrifiers, well suited to the acidic, nitrate-rich subsurface conditions, and pH is confirmed as a dominant driver of bacterial community structure in this contaminated subsurface environment. PMID:22179233

Determining the 3D Subsurface Density Structure of Taurus Littrow Valley Using Apollo 17 Gravity Data

NASA Technical Reports Server (NTRS)

Urbancic, N.; Ghent, R.; Stanley, S,; Johnson, C. L.; Carroll, K. A.; Hatch, D.; Williamson, M. C.; Garry, W. B.; Talwani, M.

2016-01-01

Surface gravity surveys can detect subsurface density variations that can reveal subsurface geologic features. In 1972, the Apollo 17 (A17) mission conducted the Traverse Gravimeter Experiment (TGE) using a gravimeter that measured the local gravity field near Taurus Littrow Valley (TLV), located on the south-eastern rim of the Serenitatis basin. TLV is hypothesized to be a basaltfilled radial graben resulting from the impact that formed Mare Serenitatis. It is bounded by both the North and South Massifs (NM and SM) as well as other smaller mountains to the East that are thought to be mainly composed of brecciated highland material. The TGE is the first and only successful gravity survey on the surface of the Moon. Other more recent satellite surveys, such as NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission (2011- 2012), have produced the best global gravity field to date (approx. 13km resolution). However, these satellite surveys are not sensitive enough to detect fine-scale (<1km) lunar subsurface structures. This underscores the value of the data collected at the surface by A17. In the original analysis of the data a 2D forward-modelling approach was used to derive a thickness of the subsurface basalt layer of 1.0 km by assuming a simple flat-faced rectangular geometry and using densities derived from Apollo lunar samples. We are investigating whether modern 3D modelling techniques in combination with high-resolution topographical and image datasets can reveal additional fine-scale subsurface structure in TLV.

Simulating oil droplet dispersal from the Deepwater Horizon spill with a Lagrangian approach

USGS Publications Warehouse

North, Elizabeth W.; Schlag, Zachary; Adams, E. Eric; Sherwood, Christopher R.; He, Ruoying; Hyun, Hoon; Socolofsky, Scott A.

2011-01-01

An analytical multiphase plume model, combined with time-varying flow and hydrographic fields generated by the 3-D South Atlantic Bight and Gulf of Mexico model (SABGOM) hydrodynamic model, were used as input to a Lagrangian transport model (LTRANS), to simulate transport of oil droplets dispersed at depth from the recent Deepwater Horizon MC 252 oil spill. The plume model predicts a stratification-dominated near field, in which small oil droplets detrain from the central plume containing faster rising large oil droplets and gas bubbles and become trapped by density stratification. Simulated intrusion (trap) heights of ∼ 310–370 m agree well with the midrange of conductivity-temperature-depth observations, though the simulated variation in trap height was lower than observed, presumably in part due to unresolved variability in source composition (percentage oil versus gas) and location (multiple leaks during first half of spill). Simulated droplet trajectories by the SABGOM-LTRANS modeling system showed that droplets with diameters between 10 and 50 μm formed a distinct subsurface plume, which was transported horizontally and remained in the subsurface for >1 month. In contrast, droplets with diameters ≥90 μm rose rapidly to the surface. Simulated trajectories of droplets ≤50 μm in diameter were found to be consistent with field observations of a southwest-tending subsurface plume in late June 2010 reported by Camilli et al. [2010]. Model results suggest that the subsurface plume looped around to the east, with potential subsurface oil transport to the northeast and southeast. Ongoing work is focusing on adding degradation processes to the model to constrain droplet dispersal.

The Design and Implementation of Instruments for Low-Frequency Electromagnetic Sounding of the Martian Subsurface

NASA Technical Reports Server (NTRS)

Delory, G. T.; Grimm, R. E.

2003-01-01

Low-frequency electromagnetic soundings of the subsurface can identify liquid water at depths ranging from hundreds of meters to approx. 10 km in an environment such as Mars. Among the tools necessary to perform these soundings are low-frequency electric and magnetic field sensors capable of being deployed from a lander or rover such that horizontal and vertical components of the fields can be measured free of structural or electrical interference. Under a NASA Planetary Instrument Definition and Development Program (PIDDP), we are currently engaged in the prototype stages of low frequency sensor implementations that will enable this technique to be performed autonomously within the constraints of a lander platform. Once developed, this technique will represent both a complementary and alternative method to orbital radar sounding investigations, as the latter may not be able to identify subsurface water without significant ambiguities. Low frequency EM methods can play a crucial role as a ground truth measurement, performing deep soundings at sites identified as high priority areas by orbital radars. Alternatively, the penetration depth and conductivity discrimination of low-frequency methods may enable detection of subsurface water in areas that render radar methods ineffective. In either case, the sensitivity and depth of penetration inherent in low frequency EM exploration makes this tool a compelling candidate method to identify subsurface liquid water from a landed platform on Mars or other targets of interest.

Understanding Subsurface Flow Mechanisms by Studying Recession Flow Curves

NASA Astrophysics Data System (ADS)

patnaik, S.; Biswal, B.; D, N.

2013-12-01

The recession flows offer valuable information on the subsurface systems of the drainage which cannot be observed due to technological limitations. Many analytical frameworks have been proposed in the past to analyze recession flow curves assess. Among them the most widely used one is Brutsaert-Neiber method of expressing negative time derivative of Q (discharge at the basin outlet at time t), -dQ/dt, as a function of Q itself, which eliminates the need of finding a reference time. Typically, basins across geographical regions display a power law relationship of the type: -dQ/dt = kQ^α. For a particular basin, the exponent α remains fairly constant recession events while the coefficient k varies greatly from one recession event to another, indicating the dynamic nature -dQ/dt-Q relationship. Recent observations show that subsurface storage in a basin mainly controls the dynamic parameter k. As subsurface water takes long time to fully drain, k of a recession event can also be influenced by the storage that occurred during the past rainfall events. We indirectly analyze the effect of past storage on recession flow by considering past streamflow as a proxy of past storage. A stronger relationship implies that the basin is able to store water for longer duration, and vice versa. In this study, we used streamflow data from 388 USGS basins that are relatively unaffected by human activities to find out the factors that affect the relationship between the power law correlation (R^2_PN) between past discharge and k, where the subscript N is the number of days of past streamflow observations considered for the recession event. For most of the basins R^2_PN decreases with N. We then selected 18 physical and climatological parameters for each study basin and investigated how they influence the value of R^2_PN for each N. We followed multiple linear regression method and found that R^2_PN is strongly influenced by the selected parameters (R^2 = 0.58) for N =30 days. We also employed principal component analysis to identify influence of individual parameters on R^2_PN. Our findings strongly indicate the possibility of understanding subsurface flow mechanism by merely analyzing recession flow curves.

Dissolved-solids contribution to the Colorado River from public lands in southeastern Nevada, through September 1993

USGS Publications Warehouse

Westenburg, C.L.

1995-01-01

The Bureau of Land Management administers about 9,300 square miles of public lands in southeastern Nevada that are part of the Colorado River Basin. The U.S. Geological Survey, in cooperation with the Bureau of Land Management, began a 5-year program in October 1988 to assess the contribution of dissolved solids to the fiver from those lands. About 6,200 square miles of public lands are in the Muddy River subbasin in Nevada. The estimated average dissolved-solids load contributed to the Colorado River from those lands was 28,000 tons per year from October 1988 through September 1993. Subsurface flow contributed about 86 percent (24,000 tons per year) of that load. About 730 square miles of public lands in the Las Vegas Wash subbasin contribute dissolved-solids load to the Colorado River. (About 120 square miles of public lands do not contribute to the river.) The estimated average dissolved-solids load contributed to the river from those lands was about 1,300 tons per year from October 1988 through September 1993. Subsurface flow contributed almost all of that load. About 1,100 square miles of public lands are in the Virgin River subbasin in Nevada. The estimated average dissolved- solids load contributed to the Colorado River from Nevada public lands in the subbasin was 8,700 tons per year. Subsurface flow contributed almost the entire load. About 1,200 square miles of Nevada public lands are in ephemeral tributaries that drain direcfly to the Colorado River or its impoundments (Lake Mead and Lake Mobave). The estimated average dissolved-solids load contributed to the river from those lands was 50 tons per year from surface runoff; however, the dissolved-solids load contributed by subsurface flow was not estimated. From October 1992 to September 1993, the Colorado River carried about 6,600,000 tons of dissolved solids past a streamflow gaging station 0.3 mile downstream from Hoover Dam. In contrast, surface runoff and subsurface flow contribute an estimated average dissolved-solids load of 38,000 tons per year from public lands in southeastern Nevada to the Colorado River. Land-management practices probably would not substantially reduce this contribution.

Quantifying the sources and the transit times of sediment using fallout radionuclides (7Be, 137Cs, 210Pbxs) in contrasted cultivated catchments across the world

NASA Astrophysics Data System (ADS)

Evrard, O.; Le Gall, M.; Laceby, J. P.; Foucher, A.; Lefèvre, I.; Salvador-Blanes, S.; Morera, S.; Ribolzi, O.

2017-12-01

Soil erosion and fine sediment supply to rivers are exacerbated in intensively cultivated catchments. Information on the sediment sources and transit times in rivers is required to improve our understanding of these processes and to guide the implementation of effective conservation measures. Accordingly, natural (7Be, 210Pb) and artificial (137Cs) fallout radionuclide concentrations were measured in overland flow and suspended sediment collected during the erosive season in contrasted cultivated catchments. In Laos, samples were collected in a steep catchment (Houay Pano, 12 km²) covered with cropland and teak plantations during the first flood of the monsoon in 2014. Cropland surface sources dominated the supply of sediment at the upstream sampling location (55%), whereas subsurface sources (channel, landslides) contributed the majority of material at the outlet (60%). Furthermore, the material exported from the catchment mainly consisted of re-suspended sediment. In Central France, the study was conducted in a flat and drained cultivated catchment (Louroux, 25 km²) during a sequence of winter events in 2013-2014 and 2016. Only surface material enriched in 137Cs was found to transit through the river during floods. The results demonstrated the initial re-suspension of material accumulated in the river channel during the first winter flood before the direct supply of sediment recently eroded from the hillslopes during the next events. In Peru, sediment was collected during a series of summer flood events (2017) in a river draining páramos (Ronquillo, 42 km²) that were recently put in cultivation. Preliminary results show that subsurface re-suspended material dominates the exports from this catchment. These results confirmed the utility of coupling continuous river monitoring and fallout radionuclide measurements on sediment collected in both tropical and temperate rivers to better understand sediment dynamics in these endangered habitats. The main challenges for the future application of this technique are related to the availability of detectors to analyze a large set of samples rapidly after collection, as well as the access to ultra-low background gamma spectrometry facilities.

A novel explicit approach to model bromide and pesticide transport in connected soil structures

NASA Astrophysics Data System (ADS)

Klaus, J.; Zehe, E.

2011-07-01

The present study tests whether an explicit treatment of worm burrows and tile drains as connected structures is feasible for simulating water flow, bromide and pesticide transport in structured heterogeneous soils at hillslope scale. The essence is to represent worm burrows as morphologically connected paths of low flow resistance in a hillslope model. A recent Monte Carlo study (Klaus and Zehe, 2010, Hydrological Processes, 24, p. 1595-1609) revealed that this approach allowed successful reproduction of tile drain event discharge recorded during an irrigation experiment at a tile drained field site. However, several "hillslope architectures" that were all consistent with the available extensive data base allowed a good reproduction of tile drain flow response. Our second objective was thus to find out whether this "equifinality" in spatial model setups may be reduced when including bromide tracer data in the model falsification process. We thus simulated transport of bromide for the 13 spatial model setups that performed best with respect to reproduce tile drain event discharge, without any further calibration. All model setups allowed a very good prediction of the temporal dynamics of cumulated bromide leaching into the tile drain, while only four of them matched the accumulated water balance and accumulated bromide loss into the tile drain. The number of behavioural model architectures could thus be reduced to four. One of those setups was used for simulating transport of Isoproturon, using different parameter combinations to characterise adsorption according to the Footprint data base. Simulations could, however, only reproduce the observed leaching behaviour, when we allowed for retardation coefficients that were very close to one.

Feasibility study of a swept frequency electromagnetic probe (SWEEP) using inductive coupling for the determination of subsurface conductivity of the earth and water prospecting in arid regions

NASA Technical Reports Server (NTRS)

Latorraca, G. A.; Bannister, L. H.

1974-01-01

Techniques developed for electromagnetic probing of the lunar interior, and techniques developed for the generation of high power audio frequencies were combined to make practical a magnetic inductive coupling system for the rapid measurement of ground conductivity profiles which are helpful when prospecting for the presence and quality of subsurface water. A system which involves the measurement of the direction, intensity, and time phase of the magnetic field observed near the surface of the earth at a distance from a horizontal coil energized so as to create a field that penetrates the earth was designed and studied to deduce the conductivity and stratification of the subsurface. Theoretical studies and a rudimentary experiment in an arid region showed that the approach is conceptually valid and that this geophysical prospecting technique can be developed for the economical exploration of subterranean water resources.

Modeling flow and solute transport at a tile drain field site by explicit representation of preferential flow structures: Equifinality and uncertainty

NASA Astrophysics Data System (ADS)

Zehe, E.; Klaus, J.

2011-12-01

Rapid flow in connected preferential flow paths is crucial for fast transport of water and solutes through soils, especially at tile drained field sites. The present study tests whether an explicit treatment of worm burrows is feasible for modeling water flow, bromide and pesticide transport in structured heterogeneous soils with a 2-dimensional Richards based model. The essence is to represent worm burrows as morphologically connected paths of low flow resistance and low retention capacity in the spatially highly resolved model domain. The underlying extensive database to test this approach was collected during an irrigation experiment, which investigated transport of bromide and the herbicide Isoproturon at a 900 sqm tile drained field site. In a first step we investigated whether the inherent uncertainty in key data causes equifinality i.e. whether there are several spatial model setups that reproduce tile drain event discharge in an acceptable manner. We found a considerable equifinality in the spatial setup of the model, when key parameters such as the area density of worm burrows and the maximum volumetric water flows inside these macropores were varied within the ranges of either our measurement errors or measurements reported in the literature. Thirteen model runs yielded a Nash-Sutcliffe coefficient of more than 0.9. Also, the flow volumes were in good accordance and peak timing errors where less than or equal to 20 min. In the second step we investigated thus whether this "equifinality" in spatial model setups may be reduced when including the bromide tracer data into the model falsification process. We simulated transport of bromide for the 13 spatial model setups, which performed best with respect to reproduce tile drain event discharge, without any further calibration. Four of this 13 model setups allowed to model bromide transport within fixed limits of acceptability. Parameter uncertainty and equifinality could thus be reduced. Thirdly, we selected one of those four setups for simulating transport of Isoproturon, which was applied the day before the irrigation experiment, and tested different parameter combinations to characterise adsorption according to the footprint data base. Simulations could, however, only reproduce the observed event based leaching behaviour, when we allowed for retardation coefficients that were very close to one. This finding is consistent with observations various field observations. We conclude: a) A realistic representation of dominating structures and their topology is of key importance for predicting preferential water and mass flows at tile drained hillslopes. b) Parameter uncertainty and equifinality could be reduced, but a system inherent equifinality in a 2-dimensional Richards based model has to be accepted.

Effect of electrode design on crosstalk between neighboring organic field-effect transistors based on one single crystal

NASA Astrophysics Data System (ADS)

Li, Mengjie; Tang, Qingxin; Tong, Yanhong; Zhao, Xiaoli; Zhou, Shujun; Liu, Yichun

2018-03-01

The design of high-integration organic circuits must be such that the interference between neighboring devices is eliminated. Here, rubrene crystals were used to study the effect of the electrode design on crosstalk between neighboring organic field-effect transistors (OFETs). Results show that a decreased source/drain interval and gate electrode width can decrease the diffraction distance of the current, and therefore can weaken the crosstalk. In addition, the inherent low carrier concentration in organic semiconductors can create a high-resistance barrier at the space between gate electrodes of neighboring devices, limiting or even eliminating the crosstalk as a result of the gate electrode width being smaller than the source/drain electrode width.

Modeling of asymmetric degradation based on a non-uniform electric field and temperature in amorphous In-Ga-Zn-O thin film transistors

NASA Astrophysics Data System (ADS)

In Kim, Jong; Jeong, Chan-Yong; Kwon, Hyuck-In; Jung, Keum Dong; Park, Mun Soo; Kim, Ki Hwan; Seo, Mi Seon; Lee, Jong-Ho

2017-03-01

We propose a new local degradation model based on a non-uniform increase in donor-like traps (DLTs) determined by distributions of an electric field and measured device temperature in amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs). A systematic investigation of the degradation model reveals that vertical field-dependent DLTs are essential for modeling of measured asymmetric electrical characteristics between the source and drain after positive gate and drain bias stressing. An increased temperature due to self-heating is found to play a role in intensifying the asymmetric degradation. From the individual simulation of measured transfer curves at different stress times, the model parameters and an asymmetry index as a function of stress time are extracted. It is expected that this novel methodology will provide new insight into asymmetric degradation and be utilized to predict the influence of electric field and heat on degradation under various bias-stress conditions in a-IGZO TFTs.

Dual metal gate tunneling field effect transistors based on MOSFETs: A 2-D analytical approach

NASA Astrophysics Data System (ADS)

Ramezani, Zeinab; Orouji, Ali A.

2018-01-01

A novel 2-D analytical drain current model of novel Dual Metal Gate Tunnel Field Effect Transistors Based on MOSFETs (DMG-TFET) is presented in this paper. The proposed Tunneling FET is extracted from a MOSFET structure by employing an additional electrode in the source region with an appropriate work function to induce holes in the N+ source region and hence makes it as a P+ source region. The electric field is derived which is utilized to extract the expression of the drain current by analytically integrating the band to band tunneling generation rate in the tunneling region based on the potential profile by solving the Poisson's equation. Through this model, the effects of the thin film thickness and gate voltage on the potential, the electric field, and the effects of the thin film thickness on the tunneling current can be studied. To validate our present model we use SILVACO ATLAS device simulator and the analytical results have been compared with it and found a good agreement.

I-V Characteristics of a Ferroelectric Field Effect Transistor

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Ho, Fat Duen

1999-01-01

There are many possible uses for ferroelectric field effect transistors.To understand their application, a fundamental knowledge of their basic characteristics must first be found. In this research, the current and voltage characteristics of a field effect transistor are described. The effective gate capacitance and charge are derived from experimental data on an actual FFET. The general equation for a MOSFET is used to derive the internal characteristics of the transistor: This equation is modified slightly to describe the FFET characteristics. Experimental data derived from a Radiant Technologies FFET is used to calculate the internal transistor characteristics using fundamental MOSFET equations. The drain current was measured under several different gate and drain voltages and with different initial polarizations on the ferroelectric material in the transistor. Two different polarization conditions were used. One with the gate ferroelectric material polarized with a +9.0 volt write pulse and one with a -9.0 volt pulse.

Chemical potential shift in organic field-effect transistors identified by soft X-ray operando nano-spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagamura, Naoka, E-mail: NAGAMURA.Naoka@nims.go.jp; Kitada, Yuta; Honma, Itaru

2015-06-22

A chemical potential shift in an organic field effect transistor (OFET) during operation has been revealed by soft X-ray operando nano-spectroscopy analysis performed using a three-dimensional nanoscale electron-spectroscopy chemical analysis system. OFETs were fabricated using ultrathin (3 ML or 12 nm) single-crystalline C10-DNBDT-NW films on SiO{sub 2} (200 nm)/Si substrates with a backgate electrode and top source/drain Au electrodes, and C 1s line profiles under biasing at the backgate and drain electrodes were measured. When applying −30 V to the backgate, there is C 1s core level shift of 0.1 eV; this shift can be attributed to a chemical potential shift correspondingmore » to band bending by the field effect, resulting in p-type doping.« less

Effect of subsurface heterogeneity on free-product recovery from unconfined aquifers

NASA Astrophysics Data System (ADS)

Kaluarachchi, Jagath J.

1996-03-01

Free-product record system designs for light-hydrocarbon-contaminated sites were investigated to evaluate the effects of subsurface heterogeneity using a vertically integrated three-phase flow model. The input stochastic variable of the areal flow analysis was the log-intrinsic permeability and it was generated using the Turning Band method. The results of a series of hypothetical field-scale simulations showed that subsurface heterogeneity has a substantial effect on free-product recovery predictions. As the heterogeneity increased, the recoverable oil volume decreased and the residual trapped oil volume increased. As the subsurface anisotropy increased, these effects together with free- and total-oil contaminated areas were further enhanced. The use of multiple-stage water pumping was found to be insignificant compared to steady uniform pumping due to reduced recovery efficiency and increased residual oil volume. This observation was opposite to that produced under homogeneous scenarios. The effect of subsurface heterogeneity was enhanced at relatively low water pumping rates. The difference in results produced by homogeneous and heterogeneous simulations was substantial, indicating greater attention should be paid in modeling free-product recovery systems with appropriate subsurface heterogeneity.

Mars Analog Research and Technology Experiment (MARTE): A Simulated Mars Drilling Mission to Search for Subsurface Life at the Rio Tinto, Spain

NASA Technical Reports Server (NTRS)

Stoker, Carol; Lemke, Larry; Mandell, Humboldt; McKay, David; George, Jeffrey; Gomez-Alvera, Javier; Amils, Ricardo; Stevens, Todd; Miller, David

2003-01-01

The MARTE (Mars Astrobiology Research and Technology Experiment) project was selected by the new NASA ASTEP program, which supports field experiments having an equal emphasis on Astrobiology science and technology development relevant to future Astrobiology missions. MARTE will search for a hypothesized subsurface anaerobic chemoautotrophic biosphere in the region of the Tinto River in southwestern Spain while also demonstrating technology needed to search for a subsurface biosphere on Mars. The experiment is informed by the strategy for searching for life on Mars.

Surface and subsurface sensor performance in acoustically detecting western drywood termites in naturally infested boards.

Treesearch

V.R. Lewis; A.B. Power; M.I. Haverty

2004-01-01

Field-collected boards showing visual signs of damage by the western drywood termite, Incisitermes minor, were searched with a portable acoustic emission (AE) device. Depending on cross-sectional size, boards were either searched with a flat sensor that was hot-melt-glued to the wood surface or a subsurface sensor that wasthreaded 20 mm into the...

Concentrations of selected metals in Quaternary-age fluvial deposits along the lower Cheyenne and middle Belle Fourche Rivers, western South Dakota, 2009-10

USGS Publications Warehouse

Stamm, John F.; Hoogestraat, Galen K.

2012-01-01

The headwaters of the Cheyenne and Belle Fourche Rivers drain the Black Hills of South Dakota and Wyoming, an area that has been affected by mining and ore-milling operations since the discovery of gold in 1875. A tributary to the Belle Fourche River is Whitewood Creek, which drains the area of the Homestake Mine, a gold mine that operated from 1876 to 2001. Tailings discharged into Whitewood Creek contained arsenopyrite, an arsenic-rich variety of pyrite associated with gold ore, and mercury used as an amalgam during the gold-extraction process. Approximately 18 percent of the tailings that were discharged remain in fluvial deposits on the flood plain along Whitewood Creek, and approximately 25 percent remain in fluvial deposits on the flood plain along the Belle Fourche River, downstream from Whitewood Creek. In 1983, a 29-kilometer (18-mile) reach of Whitewood Creek and the adjacent flood plain was included in the U.S. Environmental Protection Agency's National Priority List of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, commonly referred to as a "Superfund site." Listing of this reach of Whitewood Creek was primarily in response to arsenic toxicity of fluvial deposits on the flood plain. Lands along the lower Cheyenne River were transferred to adjoining States and Tribes in response to the Water Resources Development Act (WRDA) of 1999. An amendment in 2000 to WRDA required a study of sediment contamination of the Cheyenne River. In response to the WRDA amendment, the U.S. Geological Survey completed field sampling of reference sites (not affected by mine-tailing disposal) along the lower Belle Fourche and lower Cheyenne Rivers. Reference sites were located on stream terraces that were elevated well above historical stream stages to ensure no contamination from historical mining activity. Sampling of potentially contaminated sites was performed on transects of the active flood plain and adjacent terraces that could potentially be inundated during high-flow events. Sampling began in 2009 and was completed in 2010. A total of 74 geochemical samples were collected from fluvial deposits at reference sites, and 473 samples were collected from potentially contaminated sites. Sediment samples collected were analyzed for 23 metals, including arsenic and mercury. Sequential replicate, split duplicate, and field quality-control samples were analyzed for quality assurance of data-collection methods. The metal concentrations in sediment samples and location information are presented in this report in electronic format (Microsoft Excel), along with non-parametric summary statistics of those data. Cross-sectional topography is graphed with arsenic and mercury concentrations on transects at the potentially contaminated sites. The mean arsenic concentration in reference sediment samples was 8 milligrams per kilogram (mg/kg), compared to 250, 650, and 76 mg/kg for potentially contaminated sediment samples at the surface of the middle Belle Fourche River site, the subsurface of the middle Belle Fourche River site, and the surface of the lower Cheyenne River site, respectively. The mean mercury concentration in reference sediment samples was 16 micrograms per kilogram (μg/kg), compared to 130, 370, and 71 μg/kg for potentially contaminated sediment samples at the surface of the middle Belle Fourche River site, the subsurface of the middle Belle Fourche River site, and the surface of the lower Cheyenne River site, respectively.

3D numerical modeling of hyporheic exchange processes in fractal riverbed

NASA Astrophysics Data System (ADS)

Lee, A.; Aubeneau, A.

2017-12-01

The subsurface region receiving stream water is known as the hyporheic zone and the flow of water in and out of this zone is called hyporheic exchange. The hyporheic zone is populated by biofilms and is a hotspot for nutrient uptake and contaminant transformation. Traditionally, pumping models predicting the head distribution over the riverbed boundary are used to obtain the velocity field in the subsurface. However, past research has largely overlooked the nonlinearity of the turbulent flow above the bumpy riverbed. The main objective of this research is to investigate the effect of spatial and temporal heterogeneity created by turbulent flow on hyporheic exchange and residence time distribution in fractal channel beds. The 3-D fractal riverbed is created from the power spectrum. Large-Eddy Simulation is used to provide the pressure field over the benthic boundary. Finally, Darcian fluxes in the sub-surface are calculated and hyporheic travel times computed using random walks. Surface and subsurface transport processes are represented explicitly and can be studied in detail. Our results suggest that (1) Eddies and wakes around the dunes force the exchange (2) The bigger the dunes, the greater the influence of turbulence (3) Turbulence induces more exchange than pumping predicts.

Subsurface Environment Sampler for Improved In Situ Characterization of Subsurface Microbial Communities

NASA Astrophysics Data System (ADS)

Barnhart, E. P.; Ruppert, L. F.; Orem, W. H.; McIntosh, J. C.; Cunningham, A. B.; Fields, M. W.; Hiebert, R.; Hyatt, R.

2016-12-01

There is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by the extraction and transport of fossil fuels. This threat increases the need for improved groundwater monitoring and the ability to predict the extent to which microbial activity may remediate such contamination. The characterization of subsurface microbial communities could provide an ideal biomonitoring tool for the assessment of subsurface contamination due to prokaryotes environmental ubiquity, rapidity of response to environmental perturbation and the important role they play in hydrocarbon degradation and bioremediation. New DNA sequencing technologies provide the opportunity to cost-effectively identify the vast subsurface microbial ecosystem, but use of this new technology is restricted due to issues with sampling. Prior subsurface microbiology studies have relied on core samples that are expensive to obtain hard to collect aseptically and/or ground water samples that do not reflect in situ microbial densities or activities. The development of down-well incubation of sterile sediment with a Diffusive Microbial Sampler (DMS) has emerged as an alternative method to sample subsurface microbial communities that minimizes cost and contamination issues associated with traditional methods. We have designed a Subsurface Environment Sampler with a DMS module that could enable the anaerobic transport of the in situ microbial community from the field for laboratory bioremediation studies. This sampler could provide an inexpensive and standard method for subsurface microbial sampling which would make this tool useful for Federal, State, private and local agencies interested in monitoring contamination or the effectiveness of bioremediation activities in subsurface aquifers.

Environmental Assessment for Selection and Operation of the Proposed Field Research Centers for the Natural and Accelerated Bioremediation Research (NABIR) Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

N /A

2000-04-18

The US Department of Energy (DOE) Office of Biological and Environmental Research (OBER), within the Office of Science (SC), proposes to add a Field Research Center (FRC) component to the existing Natural and Accelerated Bioremediation Research (NABIR) Program. The NABIR Program is a ten-year fundamental research program designed to increase the understanding of fundamental biogeochemical processes that would allow the use of bioremediation approaches for cleaning up DOE's contaminated legacy waste sites. An FRC would be integrated with the existing and future laboratory and field research and would provide a means of examining the fundamental biogeochemical processes that influence bioremediationmore » under controlled small-scale field conditions. The NABIR Program would continue to perform fundamental research that might lead to promising bioremediation technologies that could be demonstrated by other means in the future. For over 50 years, DOE and its predecessor agencies have been responsible for the research, design, and production of nuclear weapons, as well as other energy-related research and development efforts. DOE's weapons production and research activities generated hazardous, mixed, and radioactive waste products. Past disposal practices have led to the contamination of soils, sediments, and groundwater with complex and exotic mixtures of compounds. This contamination and its associated costs and risks represents a major concern to DOE and the public. The high costs, long duration, and technical challenges associated with remediating the subsurface contamination at DOE sites present a significant need for fundamental research in the biological, chemical, and physical sciences that will contribute to new and cost-effective solutions. One possible low-cost approach for remediating the subsurface contamination of DOE sites is through the use of a technology known as bioremediation. Bioremediation has been defined as the use of microorganisms to biodegrade or biotransform hazardous organic contaminants to environmentally safe levels in soils, subsurface materials, water, sludges, and residues.. While bioremediation technology is promising, DOE managers and non-DOE scientists have recognized that the fundamental scientific information needed to develop effective bioremediation technologies for cleanup of the legacy waste sites is lacking in many cases. DOE believes that field-based research is needed to realize the full potential of bioremediation. The Department of Energy faces a unique set of challenges associated with cleaning up waste at its former weapons production and research sites. These sites contain complex mixtures of contaminants in the subsurface, including radioactive compounds. In many cases, the fundamental field-based scientific information needed to develop safe and effective remediation and cleanup technologies is lacking. DOE needs fundamental research on the use of microorganisms and their products to assist DOE in the decontamination and cleanup of its legacy waste sites. The existing NABIR program to-date has focused on fundamental scientific research in the laboratory. Because subsurface hydrologic and geologic conditions at contaminated DOE sites cannot easily be duplicated in a laboratory, however, the DOE needs a field component to permit existing and future laboratory research results to be field-tested on a small scale in a controlled outdoor setting. Such field-testing needs to be conducted under actual legacy waste field conditions representative of those that DOE is most in need of remediating. Ideally, these field conditions should be as representative as practicable of the types of subsurface contamination conditions that resulted from legacy wastes from the nuclear weapons program activities. They should also be representative of the types of hydrologic and geologic conditions that exist across the DOE complex.« less

Induction signals from Callisto's ionosphere and their implications on a possible subsurface ocean

NASA Astrophysics Data System (ADS)

Hartkorn, Oliver; Saur, Joachim

2017-11-01

We investigate whether induction within Callisto's electrically conductive ionosphere can explain observed magnetic fields which have previously been interpreted as evidence of induction in a saline, electrically conductive subsurface ocean. Callisto's ionosphere is subject to the flow of time-periodic magnetized plasma of Jupiter's magnetosphere, which induces electric fields and electric currents in Callisto's electrically conductive ionosphere. We develop a simple analytic model for a first quantitative understanding of the effects of induction in Callisto's ionosphere caused by the interaction with a time-variable magnetic field environment. With this model, we also investigate how the associated ionospheric currents close in the ambient magnetospheric plasma. Based on our model, we find that the anisotropic nature of Callisto's ionospheric conductivity generates an enhancement effect on ionospheric loop currents which are driven by the time-variable magnetic field. This effect is similar to the Cowling channel effect known from Earth's ionosphere. Subsequently, we numerically calculate the expected induced magnetic fields due to Jupiter's time-variable magnetic field in an anisotropic conductive ionosphere and compare our results with the Galileo C-3 and C-9 flybys. We find that induction within Callisto's ionosphere is responsible for a significant part of the observed magnetic fields. Ionospheric induction creates induced magnetic fields to some extent similar as expected from a subsurface water ocean. Depending on currently unknown properties such as Callisto's nightside ionosphere, the existence of layers of "dirty ice" and the details of the plasma interaction, a water ocean might be located much deeper than previously thought or might not exist at all.

Identification and characterization of natural pipe systems in forested tropical soils

NASA Astrophysics Data System (ADS)

Bovi, Renata Cristina; Moreira, Cesar Augusto; Stucchi Boschi, Raquel; Cooper, Miguel

2017-04-01

Erosive processes on soil surface have been well studied and comprehended by several researchers, however little is known about subsurface erosive processes (piping). Piping is a type of subsurface erosion caused by water flowing in the subsurface and is still considered one of the most difficult erosive processes to be studied. Several processes have been considered as resposible for subsurface erosion and their interaction is complex and difficult to be studied separately. Surface investigations on their own may underestimate the erosion processes, due to the possible occurrence of subsurface processes that are not yet exposed on the surface. The network of subsurface processes should also be understood to better control erosion. Conservation practices that focus on water runoff control may be inefficient if the subsurface flow is not considered. In this study, we aimed to identify and characterize subsurface cavities in the field, as well as understand the network of these cavities, by using geophysical methods (electrical tomography). The study area is situated at the Experimental Station of Tupi, state of São Paulo, Brazil. The soil of the area was classified as Hapludults. The area presents several erosive features, ranging from laminar to permanent gullies and subsurface erosions. The geophysical equipment used was the Terrameter LS resistivity meter, manufactured by ABEM Instruments. The method of electrical tomography was efficient to detect collapsed and non-collapsed pipes. The results presented valuable information to detect areas of risk.

Reducing nutrient movement in manure-treated, tile-drained fields

USDA-ARS?s Scientific Manuscript database

Loss of nutrients from cropped soil represents an economic loss to producers and a threat to environmental quality. In this study, we monitored water, nutrient, and sediment in tile drainage from agricultural fields treated with manure in western Minnesota. Phosphorus results will be presented here....

Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos

NASA Astrophysics Data System (ADS)

Gourdin, E.; Huon, S.; Evrard, O.; Ribolzi, O.; Bariac, T.; Sengtaheuanghoung, O.; Ayrault, S.

2014-06-01

Tropical rivers of Southeast Asia are characterized by high specific carbon yields and supplies to the ocean. The origin and dynamics of particulate organic matter were studied in the Houay Xon River catchment located in northern Laos during the first erosive flood of the rainy season in May 2012. The partly cultivated catchment is equipped with three successive gauging stations draining areas ranging between 0.2 and 11.6 km2 on the main stem of the permanent stream, and two additional stations draining 0.6 ha hillslopes. In addition, the sequential monitoring of rainwater, overland flow and suspended organic matter compositions was realized at 1 m2 plot scale during a single storm. The composition of particulate organic matter (total organic carbon, total nitrogen, δ13C and δ15N) was determined for suspended sediment, soil surface and subsurface samples collected in the catchment (n = 57, 65 and 11 respectively). Hydrograph separation of event water was conducted using water electric conductivity and δ18O data measured for rainfall, overland flow and river water base flow (n = 9, 30 and 57, respectively). The composition of particulate organic matter indicates that upstream suspended sediments were mainly derived from cultivated soils labelled by their C3 vegetation cover (upland rice, fallow vegetation and teak plantations) but that collapsed riverbanks, characterized by C4 vegetation occurrence (Napier grass), significantly contributed to sediment yields during water level rise and at the downstream station. The highest runoff coefficient (11.7%), sediment specific yield (433 kg ha-1), total organic carbon specific yield (8.3 kg C ha-1) and overland flow contribution (78-100%) were found for the reforested areas covered by teak plantations. Total organic carbon specific yields were up to 2.6-fold higher (at downstream station) than the annual ones calculated 10 years earlier, before the expansion of teak plantations in the catchment. They may be attributed both to the sampling period at the onset of the rainy season (following field clearing by slash and burn) and to the impact of land use change during the past decade.

The Treatment Train approach to reducing non-point source pollution from agriculture

NASA Astrophysics Data System (ADS)

Barber, N.; Reaney, S. M.; Barker, P. A.; Benskin, C.; Burke, S.; Cleasby, W.; Haygarth, P.; Jonczyk, J. C.; Owen, G. J.; Snell, M. A.; Surridge, B.; Quinn, P. F.

2016-12-01

An experimental approach has been applied to an agricultural catchment in NW England, where non-point pollution adversely affects freshwater ecology. The aim of the work (as part of the River Eden Demonstration Test Catchment project) is to develop techniques to manage agricultural runoff whilst maintaining food production. The approach used is the Treatment Train (TT), which applies multiple connected mitigation options that control nutrient and fine sediment pollution at source, and address polluted runoff pathways at increasing spatial scale. The principal agricultural practices in the study sub-catchment (1.5 km2) are dairy and stock production. Farm yards can act as significant pollution sources by housing large numbers of animals; these areas are addressed initially with infrastructure improvements e.g. clean/dirty water separation and upgraded waste storage. In-stream high resolution monitoring of hydrology and water quality parameters showed high-discharge events to account for the majority of pollutant exports ( 80% total phosphorus; 95% fine sediment), and primary transfer routes to be surface and shallow sub-surface flow pathways, including drains. To manage these pathways and reduce hydrological connectivity, a series of mitigation features were constructed to intercept and temporarily store runoff. Farm tracks, field drains, first order ditches and overland flow pathways were all targeted. The efficacy of the mitigation features has been monitored at event and annual scale, using inflow-outflow sampling and sediment/nutrient accumulation measurements, respectively. Data presented here show varied but positive results in terms of reducing acute and chronic sediment and nutrient losses. An aerial fly-through of the catchment is used to demonstrate how the TT has been applied to a fully-functioning agricultural landscape. The elevated perspective provides a better understanding of the spatial arrangement of mitigation features, and how they can be implemented without impacting on the farm's primary function. The TT has the potential to yield benefits beyond those associated with water quality. Increasing catchment resilience through the use of landscape interventions can provide multiple benefits by mitigating for floods and droughts and creating ecological habitat.

A seismic search for the paleoshorelines of Lake Otero beneath White Sands Dune Field, New Mexico

NASA Astrophysics Data System (ADS)

Wagner, P. F.; Reece, R.; Ewing, R. C.

2014-12-01

The Tularosa Basin, which now houses White Sands Dune Field, was once occupied by Pleistocene Lake Otero. Several paleoshorelines of Lake Otero have been identified throughout the basin by field surveys and remote sensing using digital elevation models. Up to four shorelines may be buried beneath White Sands Dune Field and it has been posited that the current upwind margin of White Sands coincides with a one of these shorelines. Here we employ a novel geophysical instrument and method to image the subsurface: the seismic land streamer. The land streamer utilizes weighted base plates and one-component vertical geophones in a towed array. With a seisgun acoustic source, we imaged in the Alkali Flats area near the upwind margin, one potential location of paleoshorelines, as well as the Film Lot closer to the center of the dune field. Surfaces in both locations are indurated gypsum playa, which made seismic imaging possible and successful. We collected one SW-NE trending seismic line at each location, which matches the dominant wind and dune migration directions. Based on initial data analysis we find some subsurface structure that may coincide with the paleo lake bed of Lake Otero. The successful demonstration of this new method provides the foundation for an expanded regional subsurface study to image the strata and structure of the Tularosa Basin.

Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts

NASA Technical Reports Server (NTRS)

Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda

2004-01-01

Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves considerable post-processing work. For these reasons it is very advantageous to develop analytical solution schemes for subsurface stresses, whenever possible.

C-H surface diamond field effect transistors for high temperature (400 °C) and high voltage (500 V) operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawarada, H., E-mail: kawarada@waseda.jp; Institute of Nano-Science and Nano-Engineering, Waseda University, Shinjuku, Tokyo 169-8555; Kagami Memorial Laboratory for Material Science and Technology, Waseda University, Shinjuku, Tokyo 169-0051

2014-07-07

By forming a highly stable Al{sub 2}O{sub 3} gate oxide on a C-H bonded channel of diamond, high-temperature, and high-voltage metal-oxide-semiconductor field-effect transistor (MOSFET) has been realized. From room temperature to 400 °C (673 K), the variation of maximum drain-current is within 30% at a given gate bias. The maximum breakdown voltage (V{sub B}) of the MOSFET without a field plate is 600 V at a gate-drain distance (L{sub GD}) of 7 μm. We fabricated some MOSFETs for which V{sub B}/L{sub GD} > 100 V/μm. These values are comparable to those of lateral SiC or GaN FETs. The Al{sub 2}O{sub 3} was deposited on the C-Hmore » surface by atomic layer deposition (ALD) at 450 °C using H{sub 2}O as an oxidant. The ALD at relatively high temperature results in stable p-type conduction and FET operation at 400 °C in vacuum. The drain current density and transconductance normalized by the gate width are almost constant from room temperature to 400 °C in vacuum and are about 10 times higher than those of boron-doped diamond FETs.« less

Azolla pinnata growth performance in different water sources.

PubMed

Nordiah, B; Harah, Z Muta; Sidik, B Japar; Hazma, W N Wan

2012-07-01

Azolla pinnata R.Br. growth performance experiments in different water sources were conducted from May until July 2011 at Aquaculture Research Station, Puchong, Malaysia. Four types of water sources (waste water, drain water, paddy field water and distilled water) each with different nutrient contents were used to grow and evaluate the growth performance of A. pinnata. Four water sources with different nutrient contents; waste, drain, paddy and distilled water as control were used to evaluate the growth performance of A. pinnata. Generally, irrespective of the types of water sources there were increased in plant biomass from the initial biomass (e.g., after the first week; lowest 25.2% in distilled water to highest 133.3% in drain water) and the corresponding daily growth rate (3.61% in distilled water to 19.04% in drain water). The increased in biomass although fluctuated with time was consistently higher in drain water compared to increased in biomass for other water sources. Of the four water sources, drain water with relatively higher nitrate concentration (0.035 +/- 0.003 mg L(-l)) and nitrite (0.044 +/- 0.005 mg L(-1)) and with the available phosphate (0.032 +/- 0.006 mg L(-1)) initially provided the most favourable conditions for Azolla growth and propagation. Based on BVSTEP analysis (PRIMER v5), the results indicated that a combination of more than one nutrient or multiple nutrient contents explained the observed increased in biomass of A. pinnata grown in the different water sources.

Investigation and statistical modeling of InAs-based double gate tunnel FETs for RF performance enhancement

NASA Astrophysics Data System (ADS)

Poorvasha, S.; Lakshmi, B.

2018-05-01

In this paper, RF performance analysis of InAs-based double gate (DG) tunnel field effect transistors (TFETs) is investigated in both qualitative and quantitative fashion. This investigation is carried out by varying the geometrical and doping parameters of TFETs to extract various RF parameters, unity gain cut-off frequency (f t), maximum oscillation frequency (f max), intrinsic gain and admittance (Y) parameters. An asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs. Higher ON-current (I ON) of about 0.2 mA and less leakage current (I OFF) of 29 fA is achieved for DG TFET with gate-drain overlap. Due to increase in transconductance (g m), higher f t and intrinsic gain is attained for DG TFET with gate-drain overlap. Higher f max of 985 GHz is obtained for drain doping of 5 × 1017 cm‑3 because of the reduced gate-drain capacitance (C gd) with DG TFET with gate-drain overlap. In terms of Y-parameters, gate oxide thickness variation offers better performance due to the reduced values of C gd. A second order numerical polynomial model is generated for all the RF responses as a function of geometrical and doping parameters. The simulation results are compared with this numerical model where the predicted values match with the simulated values. Project supported by the Department of Science and Technology, Government of India under SERB Scheme (No. SERB/F/2660).

Evaluating Riparian and Agricultural Systems as Sinks for Surface Water Nutrients in the Upper Rio Grande

NASA Astrophysics Data System (ADS)

Oelsner, G. P.; Brooks, P. D.; Hogan, J. F.; Phillips, F. M.; Villinski, J. E.

2005-12-01

We have performed five years of biannual synoptic sampling along a 1200km reach of the Rio Grande to develop relationships between discharge, land use, and major water quality parameters. Both total dissolved nitrogen (TDN) and dissolved organic carbon (DOC) concentrations gradually increase with distance downstream, however for TDN and phosphate this trend is punctuated by large, localized inputs primarily from urban wastewater. Somewhat surprisingly, surface water draining from areas of intensive, irrigated agriculture during the growing season often had lower nutrient and DOC concentrations than the river. To better quantify the effects of urban and agricultural systems on water quality we conducted three years of higher spatial resolution sampling of a 250km reach (between Cochiti Dam and Elephant Butte Reservoir) that contains both major agricultural and urban water users. During the higher flow years of 2001 and 2005 TDN concentrations in the river were higher (x = 1.19mg/L, SD = 0.21) than in the drier years 2002-2004 (x = 0.52mg/L, SD = 0.42). TDN concentrations decreased from 1.97mg/L to 0.78 mg/L in a 5km reach below the Albuquerque wastewater treatment plant during the low discharge year of 2004, but there was little to no decrease in TDN concentrations over the 180km below the wastewater treatment plant in years with higher river discharge. In contrast, water diverted to agricultural fields and returned to the river in drains experienced a 60% reduction in TDN concentrations in dry years and a 30% reduction in wet years compared to initial river water. During the dry years, water in the conveyance channel appears to be a mixture of river and drain water whereas in wetter years the conveyance channel has a lower average TDN concentration than either the river or the drains. These data suggest that the river-riparian-hyporheic system of the Rio Grande can serve at best as a weak N sink, while the combination of agricultural fields and drains serve as a strong nutrient sink. Ongoing research is quantifying the locations and potential rates of N transformation in both the river and agricultural drain systems.

Target-oriented retrieval of subsurface wave fields - Pushing the resolution limits in seismic imaging

NASA Astrophysics Data System (ADS)

Vasconcelos, Ivan; Ozmen, Neslihan; van der Neut, Joost; Cui, Tianci

2017-04-01

Travelling wide-bandwidth seismic waves have long been used as a primary tool in exploration seismology because they can probe the subsurface over large distances, while retaining relatively high spatial resolution. The well-known Born resolution limit often seems to be the lower bound on spatial imaging resolution in real life examples. In practice, data acquisition cost, time constraints and other factors can worsen the resolution achieved by wavefield imaging. Could we obtain images whose resolution beats the Born limits? Would it be practical to achieve it, and what are we missing today to achieve this? In this talk, we will cover aspects of linear and nonlinear seismic imaging to understand elements that play a role in obtaining "super-resolved" seismic images. New redatuming techniques, such as the Marchenko method, enable the retrieval of subsurface fields that include multiple scattering interactions, while requiring relatively little knowledge of model parameters. Together with new concepts in imaging, such as Target-Enclosing Extended Images, these new redatuming methods enable new targeted imaging frameworks. We will make a case as to why target-oriented approaches to reconstructing subsurface-domain wavefields from surface data may help in increasing the resolving power of seismic imaging, and in pushing the limits on parameter estimation. We will illustrate this using a field data example. Finally, we will draw connections between seismic and other imaging modalities, and discuss how this framework could be put to use in other applications

Discriminative Random Field Models for Subsurface Contamination Uncertainty Quantification

NASA Astrophysics Data System (ADS)

Arshadi, M.; Abriola, L. M.; Miller, E. L.; De Paolis Kaluza, C.

2017-12-01

Application of flow and transport simulators for prediction of the release, entrapment, and persistence of dense non-aqueous phase liquids (DNAPLs) and associated contaminant plumes is a computationally intensive process that requires specification of a large number of material properties and hydrologic/chemical parameters. Given its computational burden, this direct simulation approach is particularly ill-suited for quantifying both the expected performance and uncertainty associated with candidate remediation strategies under real field conditions. Prediction uncertainties primarily arise from limited information about contaminant mass distributions, as well as the spatial distribution of subsurface hydrologic properties. Application of direct simulation to quantify uncertainty would, thus, typically require simulating multiphase flow and transport for a large number of permeability and release scenarios to collect statistics associated with remedial effectiveness, a computationally prohibitive process. The primary objective of this work is to develop and demonstrate a methodology that employs measured field data to produce equi-probable stochastic representations of a subsurface source zone that capture the spatial distribution and uncertainty associated with key features that control remediation performance (i.e., permeability and contamination mass). Here we employ probabilistic models known as discriminative random fields (DRFs) to synthesize stochastic realizations of initial mass distributions consistent with known, and typically limited, site characterization data. Using a limited number of full scale simulations as training data, a statistical model is developed for predicting the distribution of contaminant mass (e.g., DNAPL saturation and aqueous concentration) across a heterogeneous domain. Monte-Carlo sampling methods are then employed, in conjunction with the trained statistical model, to generate realizations conditioned on measured borehole data. Performance of the statistical model is illustrated through comparisons of generated realizations with the `true' numerical simulations. Finally, we demonstrate how these realizations can be used to determine statistically optimal locations for further interrogation of the subsurface.

Phosphorus export from artificially drained fields across the Eastern corn belt

USDA-ARS?s Scientific Manuscript database

Field observations that quantify agricultural phosphorus (P) losses are critical for the development of P reduction strategies across the Eastern Corn Belt region of North America. Within this region, surface water bodies including Lake Erie are sensitive to non-point P loadings. It is therefore imp...

Effect of tile effluent on nutrient concentration and retention efficiency in agricultural drainage ditches

USDA-ARS?s Scientific Manuscript database

Tile drainage is a common water management practice in many agricultural landscapes in the Midwestern United States. Drainage ditches regularly receive water from agricultural fields through these tile drains. This field-scale study was conducted to determine the impact of tile discharge on ambient ...

Sampling surface and subsurface particle-size distributions in wadable gravel-and cobble-bed streams for analyses in sediment transport, hydraulics, and streambed monitoring

Treesearch

Kristin Bunte; Steven R. Abt

2001-01-01

This document provides guidance for sampling surface and subsurface sediment from wadable gravel-and cobble-bed streams. After a short introduction to streams types and classifications in gravel-bed rivers, the document explains the field and laboratory measurement of particle sizes and the statistical analysis of particle-size distributions. Analysis of particle...

Subsurface Thermal Energy Storage for Improved Heating and Air Conditioning Efficiency

DTIC Science & Technology

2016-11-21

This project involved a field demonstration of subsurface thermal energy storage for improving the geothermal heat pump air conditioning efficiency... geothermal heat pump systems, undesirable heating of the ground may occur. This demonstration was performed at the MCAS, Beaufort, SC, where several...buildings with geothermal heat pump systems were exhibiting excessively high ground loop temperatures. These buildings were retrofitted with dry fluid

Long-term electrical resistivity monitoring of recharge-induced contaminant plume behavior.

PubMed

Gasperikova, Erika; Hubbard, Susan S; Watson, David B; Baker, Gregory S; Peterson, John E; Kowalsky, Michael B; Smith, Meagan; Brooks, Scott

2012-11-01

Geophysical measurements, and electrical resistivity tomography (ERT) data in particular, are sensitive to properties that are related (directly or indirectly) to hydrological processes. The challenge is in extracting information from geophysical data at a relevant scale that can be used to gain insight about subsurface behavior and to parameterize or validate flow and transport models. Here, we consider the use of ERT data for examining the impact of recharge on subsurface contamination at the S-3 ponds of the Oak Ridge Integrated Field Research Challenge (IFRC) site in Tennessee. A large dataset of time-lapse cross-well and surface ERT data, collected at the site over a period of 12 months, is used to study time variations in resistivity due to changes in total dissolved solids (primarily nitrate). The electrical resistivity distributions recovered from cross-well and surface ERT data agrees well, and both of these datasets can be used to interpret spatiotemporal variations in subsurface nitrate concentrations due to rainfall, although the sensitivity of the electrical resistivity response to dilution varies with nitrate concentration. Using the time-lapse surface ERT data interpreted in terms of nitrate concentrations, we find that the subsurface nitrate concentration at this site varies as a function of spatial position, episodic heavy rainstorms (versus seasonal and annual fluctuations), and antecedent rainfall history. These results suggest that the surface ERT monitoring approach is potentially useful for examining subsurface plume responses to recharge over field-relevant scales. Published by Elsevier B.V.

Subsurface Hydrologic Processes Revealed by Time-lapse GPR in Two Contrasting Soils in the Shale Hills CZO

NASA Astrophysics Data System (ADS)

Guo, L.; Lin, H.; Nyquist, J.; Toran, L.; Mount, G.

2017-12-01

Linking subsurface structures to their functions in determining hydrologic processes, such as soil moisture dynamics, subsurface flow patterns, and discharge behaviours, is a key to understanding and modelling hydrological systems. Geophysical techniques provide a non-invasive approach to investigate this form-function dualism of subsurface hydrology at the field scale, because they are effective in visualizing subsurface structure and monitoring the distribution of water. In this study, we used time-lapse ground-penetrating radar (GPR) to compare the hydrologic responses of two contrasting soils in the Shale Hills Critical Zone Observatory. By integrating time-lapse GPR with artificial water injection, we observed distinct flow patterns in the two soils: 1) in the deep Rushtown soil (over 1.5 m depth to bedrock) located in a concave hillslope, a lateral preferential flow network extending as far as 2 m downslope was identified above a less permeable layer and via a series of connected macropores; whereas 2) in the shallow Weikert soil ( 0.3 m depth to saprock) located in a planar hillslope, vertical infiltration into the permeable fractured shale dominated the flow field, while the development of lateral preferential flow along the hillslope was restrained. At the Weikert soil site, the addition of brilliant blue dye to the water injection followed by in situ excavation supported GPR interpretation that only limited lateral preferential flow formed along the soil-saprock interface. Moreover, seasonally repeated GPR surveys indicated different patterns of profile moisture distribution in the two soils that in comparison with the dry season, a dense layer within the BC horizon in the deep Rushtown soil prevented vertical infiltration in the wet season, leading to the accumulation of soil moisture above this layer; whereas, in the shallow Weikert soil, water infiltrated into saprock in wet seasons, building up water storage within the fractured bedrock (i.e., the rock moisture). Results of this study demonstrated the strong interplay between soil structures and subsurface hydrologic behaviors, and time-lapse GPR is an effective method to establish such a relationship under the field conditions.

Forward modeling to investigate inversion artifacts resulting from time-lapse electrical resistivity tomography during rainfall simulations

NASA Astrophysics Data System (ADS)

Carey, Austin M.; Paige, Ginger B.; Carr, Bradley J.; Dogan, Mine

2017-10-01

Time-lapse electrical resistivity tomography (ERT) is commonly used as a minimally invasive tool to study infiltration processes. In 2014, we conducted field studies coupling variable intensity rainfall simulation with high-resolution ERT to study the real-time partitioning of rainfall into surface and subsurface response. The significant contrast in resistivity in the subsurface from large changes in subsurface moisture resulted in artifacts during the inversion process of the time-lapse ERT data collected using a dipole-dipole electrode array. These artifacts, which are not representative of real subsurface moisture dynamics, have been shown to arise during time-lapse inversion of ERT data and may be subject to misinterpretation. Forward modeling of the infiltration process post field experiments using a two-layer system (saprolite overlain by a soil layer) was used to generate synthetic datasets. The synthetic data were used to investigate the influence of both changes in volumetric moisture content and electrode configuration on the development of the artifacts identified in the field datasets. For the dipole-dipole array, we found that a decrease in the resistivity of the bottom layer by 67% resulted in a 50% reduction in artifact development. Artifacts for the seven additional array configurations tested, ranged from a 19% increase in artifact development (using an extended dipole-dipole array) to as much as a 96% decrease in artifact development (using a wenner-alpha array), compared to that of the dipole-dipole array. Moreover, these arrays varied in their ability to accurately delineate the infiltration front. Model results showed that the modified pole-dipole array was able to accurately image the infiltration zone and presented fewer artifacts for our experiments. In this study, we identify an optimal array type for imaging rainfall-infiltration dynamics that reduces artifacts. The influence of moisture contrast between the infiltrating water and the bulk subsurface material was characterized and shown to be a major factor in contributing to artifact development. Through forward modeling, this study highlights the importance of considering array type and subsurface moisture conditions when using time-lapse resistivity to obtain reliable estimates of vadose zone flow processes during rainfall-infiltration events.

Design and performance of limestone drains to increase pH and remove metals from acidic mine drainage, Chapter 2

USGS Publications Warehouse

Cravotta,, Charles A.; Watzlaf, George R.

2002-01-01

Data on the construction characteristics and the composition of influent and effluent at 13 underground, limestone-filled drains in Pennsylvania and Maryland are reported to evaluate the design and performance of limestone drains for the attenuation of acidity and dissolved metals in acidic mine drainage. On the basis of the initial mass of limestone, dimensions of the drains, and average flow rates, the initial porosity and average detention time for each drain were computed. Calculated porosity ranged from 0.12 to 0.50 with corresponding detention times at average flow from 1.3 to 33 h. The effectiveness of treatment was dependent on influent chemistry, detention time, and limestone purity. At two sites where influent contained elevated dissolved Al (>5 mg/liter), drain performance declined rapidly; elsewhere the drains consistently produced near-neutral effluent, even when influent contained small concentrations of dissolved Fe^+ (<5 mg/liter). Rates of limestone dissolution computed on the basis of average long-term Ca ion flux normalized by initial mass and purity of limestone at each of the drains ranged from 0.008 to 0.079 year-1. Data for alkalinity concentration and flux during 11-day closed-container tests using an initial mass of 4kg crushed limestone and a solution volume of 2.3 liter yielded dissolution rate constants that were comparable to these long-term field rates. An analytical method is proposed using closed-container test data to evaluate long-term performance (longevity) or to estimate the mass of limestone needed for a limestone treatment. This method condisers flow rate, influent alkalinity, steady-state alkalinity of effluent, and desired effluent alkalinity or detention time at a future time(s) and aplies first-order rate laws for limestone dissolution (continuous) and production of alkalinity (bounded).

Fringing field effects in negative capacitance field-effect transistors with a ferroelectric gate insulator

NASA Astrophysics Data System (ADS)

Hattori, Junichi; Fukuda, Koichi; Ikegami, Tsutomu; Ota, Hiroyuki; Migita, Shinji; Asai, Hidehiro; Toriumi, Akira

2018-04-01

We study the effects of fringing electric fields on the behavior of negative-capacitance (NC) field-effect transistors (FETs) with a silicon-on-insulator body and a gate stack consisting of an oxide film, an internal metal film, a ferroelectric film, and a gate electrode using our own device simulator that can properly handle the complicated relationship between the polarization and the electric field in ferroelectric materials. The behaviors of such NC FETs and the corresponding metal-oxide-semiconductor (MOS) FETs are simulated and compared with each other to evaluate the effects of the NC of the ferroelectric film. Then, the fringing field effects are evaluated by comparing the NC effects in NC FETs with and without gate spacers. The fringing field between the gate stack, especially the internal metal film, and the source/drain region induces more charges at the interface of the film with the ferroelectric film. Accordingly, the function of the NC to modulate the gate voltage and the resulting function to improve the subthreshold swing are enhanced. We also investigate the relationships of these fringing field effects to the drain voltage and four design parameters of NC FETs, i.e., gate length, gate spacer permittivity, internal metal film thickness, and oxide film thickness.

Shuttle-promoted nano-mechanical current switch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Taegeun, E-mail: tsong@ictp.it; Kiselev, Mikhail N.; Gorelik, Leonid Y.

2015-09-21

We investigate electron shuttling in three-terminal nanoelectromechanical device built on a movable metallic rod oscillating between two drains. The device shows a double-well shaped electromechanical potential tunable by a source-drain bias voltage. Four stationary regimes controllable by the bias are found for this device: (i) single stable fixed point, (ii) two stable fixed points, (iii) two limit cycles, and (iv) single limit cycle. In the presence of perpendicular magnetic field, the Lorentz force makes possible switching from one electromechanical state to another. The mechanism of tunable transitions between various stable regimes based on the interplay between voltage controlled electromechanical instabilitymore » and magnetically controlled switching is suggested. The switching phenomenon is implemented for achieving both a reliable active current switch and sensoring of small variations of magnetic field.« less

Reducing the contact resistance in bottom-contact-type organic field-effect transitors using an AgO x interface layer

NASA Astrophysics Data System (ADS)

Minagawa, Masahiro; Kim, Yeongin; Claus, Martin; Bao, Zhenan

2017-09-01

Bottom-contact organic field-effect transistors (OFETs) are prepared by inserting an AgO x layer between a pentacene layer and the source-drain electrodes. The contact resistance in the device is ˜8.1 kΩ·cm with an AgO x layer oxidized for 60 s but reaches 116.9 kΩ·cm with a non-oxidized Ag electrode. The drain current and mobility in the OFETs with the AgO x layer increase with the oxidization time and then gradually plateau, and this trend strongly depends on the work function of the Ag surface. Further, the hole injection is enhanced by the presence of Ag2O but inhibited by the presence of AgO.

H-terminated diamond field effect transistor with ferroelectric gate insulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karaya, Ryota; Furuichi, Hiroki; Nakajima, Takashi

2016-06-13

An H-terminated diamond field-effect-transistor (FET) with a ferroelectric vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer gate insulator was fabricated. The VDF-TrFE film was deposited on the H-terminated diamond by the spin-coating method and low-temperature annealing was performed to suppress processing damage to the H-terminated diamond surface channel layer. The fabricated FET structure showed the typical properties of depletion-type p-channel FET and showed clear saturation of the drain current with a maximum value of 50 mA/mm. The drain current versus gate voltage curves of the proposed FET showed clockwise hysteresis loops due to the ferroelectricity of the VDF-TrFE gate insulator, and the memory windowmore » width was 19 V, when the gate voltage was swept from 20 to −20 V. The maximum on/off current ratio and the linear mobility were 10{sup 8} and 398 cm{sup 2}/V s, respectively. In addition, we modulated the drain current of the fabricated FET structure via the remnant polarization of the VDF-TrFE gate and obtained an on/off current ratio of 10{sup 3} without applying a DC gate voltage.« less

Inkjet printed graphene-based field-effect transistors on flexible substrate

NASA Astrophysics Data System (ADS)

Monne, Mahmuda Akter; Enuka, Evarestus; Wang, Zhuo; Chen, Maggie Yihong

2017-08-01

This paper presents the design and fabrication of inkjet printed graphene field-effect transistors (GFETs). The inkjet printed GFET is fabricated on a DuPont Kapton FPC Polyimide film with a thickness of 5 mill and dielectric constant of 3.9 by using a Fujifilm Dimatix DMP-2831 materials deposition system. A layer by layer 3D printing technique is deployed with an initial printing of source and drain by silver nanoparticle ink. Then graphene active layer doped with molybdenum disulfide (MoS2) monolayer/multilayer dispersion, is printed onto the surface of substrate covering the source and drain electrodes. High capacitance ion gel is adopted as the dielectric material due to the high dielectric constant. Then the dielectric layer is then covered with silver nanoparticle gate electrode. Characterization of GFET has been done at room temperature (25°C) using HP-4145B semiconductor parameter analyzer (Hewlett-Packard). The characterization result shows for a voltage sweep from -2 volts to 2 volts, the drain current changes from 949 nA to 32.3 μA and the GFET achieved an on/off ratio of 38:1, which is a milestone for inkjet printed flexible graphene transistor.

Impact of device engineering on analog/RF performances of tunnel field effect transistors

NASA Astrophysics Data System (ADS)

Vijayvargiya, V.; Reniwal, B. S.; Singh, P.; Vishvakarma, S. K.

2017-06-01

The tunnel field effect transistor (TFET) and its analog/RF performance is being aggressively studied at device architecture level for low power SoC design. Therefore, in this paper we have investigated the influence of the gate-drain underlap (UL) and different dielectric materials for the spacer and gate oxide on DG-TFET (double gate TFET) and its analog/RF performance for low power applications. Here, it is found that the drive current behavior in DG-TFET with a UL feature while implementing dielectric material for the spacer is different in comparison to that of DG-FET. Further, hetero gate dielectric-based DG-TFET (HGDG-TFET) is more resistive against drain-induced barrier lowering (DIBL) as compared to DG-TFET with high-k (HK) gate dielectric. Along with that, as compared to DG-FET, this paper also analyses the attributes of UL and dielectric material on analog/RF performance of DG-TFET in terms of transconductance (gm ), transconductance generation factor (TGF), capacitance, intrinsic resistance (Rdcr), cut-off frequency (F T), and maximum oscillation frequency (F max). The LK spacer-based HGDG-TFET with a gate-drain UL has the potential to improve the RF performance of device.

DC and analog/RF performance optimisation of source pocket dual work function TFET

NASA Astrophysics Data System (ADS)

Raad, Bhagwan Ram; Sharma, Dheeraj; Kondekar, Pravin; Nigam, Kaushal; Baronia, Sagar

2017-12-01

We investigate a systematic study of source pocket tunnel field-effect transistor (SP TFET) with dual work function of single gate material by using uniform and Gaussian doping profile in the drain region for ultra-low power high frequency high speed applications. For this, a n+ doped region is created near the source/channel junction to decrease the depletion width results in improvement of ON-state current. However, the dual work function of the double gate is used for enhancement of the device performance in terms of DC and analog/RF parameters. Further, to improve the high frequency performance of the device, Gaussian doping profile is considered in the drain region with different characteristic lengths which decreases the gate to drain capacitance and leads to drastic improvement in analog/RF figures of merit. Furthermore, the optimisation is performed with different concentrations for uniform and Gaussian drain doping profile and for various sectional length of lower work function of the gate electrode. Finally, the effect of temperature variation on the device performance is demonstrated.

Subsurface Hydrology: Data Integration for Properties and Processes

NASA Astrophysics Data System (ADS)

Hyndman, David W.; Day-Lewis, Frederick D.; Singha, Kamini

Groundwater is a critical resource and the PrinciPal source of drinking water for over 1.5 billion people. In 2001, the National Research Council cited as a "grand challenge" our need to understand the processes that control water movement in the subsurface. This volume faces that challenge in terms of data integration between complex, multi-scale hydrologie processes, and their links to other physical, chemical, and biological processes at multiple scales. Subsurface Hydrology: Data Integration for Properties and Processes presents the current state of the science in four aspects: • Approaches to hydrologie data integration • Data integration for characterization of hydrologie properties • Data integration for understanding hydrologie processes • Meta-analysis of current interpretations Scientists and researchers in the field, the laboratory, and the classroom will find this work an important resource in advancing our understanding of subsurface water movement.

Total Ionizing Dose Effects on Ge Channel $p$FETs with Raised $${\\rm Si}_{0.55}{\\rm Ge}_{0.45}$$ Source/Drain

DOE PAGES

Wang, Liang; Zhang, En Xia; Schrimpf, Ronald D.; ...

2015-12-17

Here, the total ionizing dose response of Ge channel pFETs with raised Si 0.55Ge 0.45 source/drain is investigated under different radiation bias conditions. Threshold-voltage shifts and transconductance degradation are noticeable only for negative-bias (on state) irradiation, and are mainly due to negative bias-temperature instability (NBTI). Nonmonotonic leakage changes during irradiation are observed, which are attributed to the competition of radiation-induced field transistor leakage and S/D junction leakage.

Study to Investigate the Effects of Skin Friction on the Performance of Drilled Shafts in Cohesive Soils. Volumes I, II, III.

DTIC Science & Technology

1982-03-01

2) after Marsland and Randolph (1977) represents the peak un- drained shear strength. Torvane tests were also run in the field on Shelby tube ...The laboratory test results were characterized in terms of: 4 a. stratigraphy; b. stress state; c. undrained, drained and residual shear strengths; d...in Figure 3 as P- 1. A Shelby tube could not be retrieved at 14-ft depth in Boring B-2. A new boring (Boring B-2A) was made 6 in. further away from

Assessment of Drywells as Effective Tools for Stormwater Management and Aquifer Recharge: Results of a Two-Year Field and Numerical Modeling Study

NASA Astrophysics Data System (ADS)

Edwards, E.; Washburn, B.; Harter, T.; Fogg, G. E.; Nelson, C.; Lock, B.; Li, X.

2016-12-01

Drywells are gravity-fed, excavated pits with perforated casings used to facilitate stormwater infiltration and groundwater recharge in areas with low permeability soils or cover. Stormwater runoff that would otherwise be routed to streams or drains in urban areas can be used as a source of aquifer recharge, potentially mitigating the effects of drought and harm to natural water bodies. However, the potential for groundwater contamination caused by urban runoff bypassing surface soil and near surface sediment attenuation processes has prevented more widespread use of drywells as a recharge mechanism. A field study was conducted in Elk Grove, CA, to determine the effects of drywell-induced stormwater infiltration on the local hydrogeologic system. Two drywells 13.5 meters in depth were constructed for the project: one in a preexisting drainage basin fed by residential lots, and one at an industrial site. Both sites were outfitted with vegetated pretreatments, and upgradient and downgradient groundwater monitoring wells. Site stormwater and groundwater were sampled between November, 2014, and May, 2016, and analyzed for contaminants. Results of water quality sampling have been statistically analyzed for trends and used to determine the contaminants of interest and the concentrations of these contaminants in influent stormwater. The fate and transport of these contaminants have been simulated using a 1D variably saturated flow and transport model and site specific parameters to predict long-term effects of stormwater infiltration on the surrounding hydrogeologic system. The potential for remobilization of geogenic heavy metals from changes in subsurface hydrochemistry caused by drywell infiltration have also been assessed. The results of the field study and numerical modeling assessment indicate that the study's drywells do not pose a long-term threat to groundwater quality and may be an effective source of aquifer recharge and tool for urban stormwater management.

Impact of SiNx capping on the formation of source/drain contact for In-Ga-Zn-O thin film transistor with self-aligned gate

NASA Astrophysics Data System (ADS)

Oh, Himchan; Pi, Jae-Eun; Hwang, Chi-Sun; Kwon, Oh-Sang

2017-12-01

Self-aligned gate structures are preferred for faster operation and scaling down of thin film transistors by reducing the overlapped region between source/drain and gate electrodes. Doping on source/drain regions is essential to fabricate such a self-aligned gate thin film transistor. For oxide semiconductors such as In-Ga-Zn-O, SiNx capping readily increases their carrier concentration. We report that the SiNx deposition temperature and thickness significantly affect the device properties, including threshold voltage, field effect mobility, and contact resistance. The reason for these variations in device characteristics mainly comes from the extension of the doped region to the gated area after the SiNx capping step. Analyses on capacitance-voltage and transfer length characteristics support this idea.

An improved model to predict bandwidth enhancement in an inductively tuned common source amplifier.

PubMed

Reza, Ashif; Misra, Anuraag; Das, Parnika

2016-05-01

This paper presents an improved model for the prediction of bandwidth enhancement factor (BWEF) in an inductively tuned common source amplifier. In this model, we have included the effect of drain-source channel resistance of field effect transistor along with load inductance and output capacitance on BWEF of the amplifier. A frequency domain analysis of the model is performed and a closed-form expression is derived for BWEF of the amplifier. A prototype common source amplifier is designed and tested. The BWEF of amplifier is obtained from the measured frequency response as a function of drain current and load inductance. In the present work, we have clearly demonstrated that inclusion of drain-source channel resistance in the proposed model helps to estimate the BWEF, which is accurate to less than 5% as compared to the measured results.

Two-Dimensional Quantum Model of a Nanotransistor

NASA Technical Reports Server (NTRS)

Govindan, T. R.; Biegel, B.; Svizhenko, A.; Anantram, M. P.

2009-01-01

A mathematical model, and software to implement the model, have been devised to enable numerical simulation of the transport of electric charge in, and the resulting electrical performance characteristics of, a nanotransistor [in particular, a metal oxide/semiconductor field-effect transistor (MOSFET) having a channel length of the order of tens of nanometers] in which the overall device geometry, including the doping profiles and the injection of charge from the source, gate, and drain contacts, are approximated as being two-dimensional. The model and software constitute a computational framework for quantitatively exploring such device-physics issues as those of source-drain and gate leakage currents, drain-induced barrier lowering, and threshold voltage shift due to quantization. The model and software can also be used as means of studying the accuracy of quantum corrections to other semiclassical models.

Random Telegraph Signal-Like Fluctuation Created by Fowler-Nordheim Stress in Gate Induced Drain Leakage Current of the Saddle Type Dynamic Random Access Memory Cell Transistor

NASA Astrophysics Data System (ADS)

Kim, Heesang; Oh, Byoungchan; Kim, Kyungdo; Cha, Seon-Yong; Jeong, Jae-Goan; Hong, Sung-Joo; Lee, Jong-Ho; Park, Byung-Gook; Shin, Hyungcheol

2010-09-01

We generated traps inside gate oxide in gate-drain overlap region of recess channel type dynamic random access memory (DRAM) cell transistor through Fowler-Nordheim (FN) stress, and observed gate induced drain leakage (GIDL) current both in time domain and in frequency domain. It was found that the trap inside gate oxide could generate random telegraph signal (RTS)-like fluctuation in GIDL current. The characteristics of that fluctuation were similar to those of RTS-like fluctuation in GIDL current observed in the non-stressed device. This result shows the possibility that the trap causing variable retention time (VRT) in DRAM data retention time can be located inside gate oxide like channel RTS of metal-oxide-semiconductor field-effect transistors (MOSFETs).

Corrective Action Investigation Plan for Corrective Action Unit 562: Waste Systems Nevada Test Site, Nevada, Revision 0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alfred Wickline

2009-04-01

Corrective Action Unit 562 is located in Areas 2, 23, and 25 of the Nevada Test Site, which is approximately 65 miles northwest of Las Vegas, Nevada. Corrective Action Unit 562 is comprised of the 13 corrective action sites (CASs) listed below: • 02-26-11, Lead Shot • 02-44-02, Paint Spills and French Drain • 02-59-01, Septic System • 02-60-01, Concrete Drain • 02-60-02, French Drain • 02-60-03, Steam Cleaning Drain • 02-60-04, French Drain • 02-60-05, French Drain • 02-60-06, French Drain • 02-60-07, French Drain • 23-60-01, Mud Trap Drain and Outfall • 23-99-06, Grease Trap • 25-60-04, Buildingmore » 3123 Outfalls These sites are being investigated because existing information on the nature and extent of potential contamination is insufficient to evaluate and recommend corrective action alternatives. Additional information will be obtained by conducting a corrective action investigation before evaluating corrective action alternatives and selecting the appropriate corrective action for each CAS. The results of the field investigation will support a defensible evaluation of viable corrective action alternatives that will be presented in the Corrective Action Decision Document. The sites will be investigated based on the data quality objectives (DQOs) developed on December 11, 2008, by representatives of the Nevada Division of Environmental Protection; U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office; Stoller-Navarro Joint Venture; and National Security Technologies, LLC. The DQO process was used to identify and define the type, amount, and quality of data needed to develop and evaluate appropriate corrective actions for CAU 562. Appendix A provides a detailed discussion of the DQO methodology and the DQOs specific to each CAS. The scope of the corrective action investigation for CAU 562 includes the following activities: • Move surface debris and/or materials, as needed, to facilitate sampling. • Conduct radiological surveys. • Perform field screening. • Collect and submit environmental samples for laboratory analysis to determine the nature and extent of any contamination released by each CAS. • Collect samples of source material to determine the potential for a release. • Collect samples of potential remediation wastes. • Collect quality control samples. This Corrective Action Investigation Plan has been developed in accordance with the Federal Facility Agreement and Consent Order that was agreed to by the State of Nevada; DOE, Environmental Management; U.S. Department of Defense; and DOE, Legacy Management (FFACO, 1996; as amended February 2008). Under the Federal Facility Agreement and Consent Order, this Corrective Action Investigation Plan will be submitted to the Nevada Division of Environmental Protection for approval. Fieldwork will be conducted following approval of the plan.« less

The Correlation between Radon Emission Concentration and Subsurface Geological Condition

NASA Astrophysics Data System (ADS)

Kuntoro, Yudi; Setiawan, Herru L.; Wijayanti, Teni; Haerudin, Nandi

2018-03-01

Exploration activities with standard methods have already encountered many obstacles in the field. Geological survey is often difficult to find outcrop because they are covered by vegetation, alluvial layer or as a result of urban development and housing. Seismic method requires a large expense and licensing in the use of dynamite is complicated. Method of gravity requires the operator to go back (looping) to the starting point. Given some of these constraints, therefore it needs a solution in the form of new method that can work more efficiently with less cost. Several studies in various countries have shown a correlation between the presence of hydrocarbons and Radon gas concentration in the earth surface. By utilizing the properties of Radon that can migrate to the surface, the value of Radon concentration in the surface is suggested to provide information about the subsurface structure condition. Radon is the only radioactive substance that gas-phased at atmospheric temperature. It is very abundant in the earth mantle. The vast differences of temperatures and pressures between the mantle and the earth crust cause the convection flow toward earth surface. Radon in gas phase will be carried by convection flow to the surface. The quantity of convection currents depend on the porosity and permeability of rocks where Radon travels within, so that Radon concentration in the earth surface delineates the porosity and permeability of subsurface rock layers. Some measurements were carried out at several locations with various subsurface geological conditions, including proven oil fields, proven geothermal field, and frontier area as a comparison. These measurements show that the average and the background concentration threshold in the proven oil field (11,200 Bq/m3) and proven geothermal field (7,820 Bq/m3) is much higher than the quantity in frontier area (329 and 1,620 Bq/m3). Radon concentration in the earth surface is correlated with the presence of geological faults. Peak concentrations of Radon takes place along the fault.

Heat pulse probe measurements of soil water evaporation in a corn field

USDA-ARS?s Scientific Manuscript database

Latent heat fluxes from cropped fields consist of soil water evaporation and plant transpiration. It is difficult to accurately separate evapotranspiration into evaporation and transpiration. Heat pulse probes have been used to measure bare field subsurface soil water evaporation, however, the appl...

Enhancement of subsurface geologic structure model based on gravity, magnetotelluric, and well log data in Kamojang geothermal field

NASA Astrophysics Data System (ADS)

Yustin Kamah, Muhammad; Armando, Adilla; Larasati Rahmani, Dinda; Paramitha, Shabrina

2017-12-01

Geophysical methods such as gravity and magnetotelluric methods commonly used in conventional and unconventional energy exploration, notably for exploring geothermal prospect. They used to identify the subsurface geology structures which is estimated as a path of fluid flow. This study was conducted in Kamojang Geothermal Field with the aim of highlighting the volcanic lineament in West Java, precisely in Guntur-Papandayan chain where there are three geothermal systems. Kendang Fault has predominant direction NE-SW, identified by magnetotelluric techniques and gravity data processing techniques. Gravity techniques such as spectral analysis, derivative solutions, and Euler deconvolution indicate the type and geometry of anomaly. Magnetotelluric techniques such as inverse modeling and polar diagram are required to know subsurface resistivity charactersitics and major orientation. Furthermore, the result from those methods will be compared to geology information and some section of well data, which is sufficiently suitable. This research is very useful to trace out another potential development area.

Remote sensing capacity of Raman spectroscopy in identification of mineral and organic constituents

NASA Astrophysics Data System (ADS)

Chen, Bin; Stoker, Carol; Cabrol, Nathalie; McKay, Christopher P.

2007-09-01

We present design, integration and test results for a field Raman spectrometer science payload, integrated into the Mars Analog Research and Technology (MARTE) drilling platform. During the drilling operation, the subsurface Raman spectroscopy inspection system has obtained signatures of organic and mineral compositions. We also performed ground truth studies using both this field unit and a laboratory micro Raman spectrometer equipped with multiple laser excitation wavelengths on series of field samples including Mojave rocks, Laguna Verde salty sediment and Rio Tinto topsoil. We have evaluated laser excitation conditions and optical probe designs for further improvement. We have demonstrated promising potential for Raman spectroscopy as a non-destructive in situ, high throughput, subsurface detection technique, as well as a desirable active remote sensing tool for future planetary and space missions.

Ranging methods for developing wellbores in subsurface formations

DOEpatents

MacDonald, Duncan [Houston, TX

2011-09-06

A method for forming two or more wellbores in a subsurface formation includes forming a first wellbore in the formation. A second wellbore is directionally drilled in a selected relationship relative to the first wellbore. At least one magnetic field is provided in the second wellbore using one or more magnets in the second wellbore located on a drilling string used to drill the second wellbore. At least one magnetic field is sensed in the first wellbore using at least two sensors in the first wellbore as the magnetic field passes by the at least two sensors while the second wellbore is being drilled. A position of the second wellbore is continuously assessed relative to the first wellbore using the sensed magnetic field. The direction of drilling of the second wellbore is adjusted so that the second wellbore remains in the selected relationship relative to the first wellbore.

Method of Mapping Anomalies in Homogenous Material

NASA Technical Reports Server (NTRS)

Taylor, Bryant D. (Inventor); Woodard, Stanley E. (Inventor)

2016-01-01

An electrical conductor and antenna are positioned in a fixed relationship to one another. Relative lateral movement is generated between the electrical conductor and a homogenous material while maintaining the electrical conductor at a fixed distance from the homogenous material. The antenna supplies a time-varying magnetic field that causes the electrical conductor to resonate and generate harmonic electric and magnetic field responses. Disruptions in at least one of the electric and magnetic field responses during this lateral movement are indicative of a lateral location of a subsurface anomaly. Next, relative out-of-plane movement is generated between the electrical conductor and the homogenous material in the vicinity of the anomaly's lateral location. Disruptions in at least one of the electric and magnetic field responses during this out-of-plane movement are indicative of a depth location of the subsurface anomaly. A recording of the disruptions provides a mapping of the anomaly.

WISDOM GPR investigations in a Mars-analog environment during the SAFER rover operation simulation

NASA Astrophysics Data System (ADS)

Dorizon, S.; Ciarletti, V.; Plettemeier, D.; Vieau, A.-J.; Benedix, W.-S.; Mütze, M.; Hassen-Kodja, R.; Humeau, O.

2014-04-01

The WISDOM (Water Ice Subsurface Deposits Observations on Mars) Ground Penetrating Radar has been selected to be onboard the ExoMars 2018 rover mission [1]. This instrument will investigate the Martian shallow subsurface and provide the geological context of the mission, by characterizing the subsurface in terms of structure, stratigraphy and potential buried objects. It will also quantify the geoelectrical properties of the medium, which are directly related to its nature, its water or salts content and its hardness [2]. WISDOM data will provide important clues to guide the drilling operations to location of potential exobiological interest. A prototype available in LATMOS, France, is currently tested in a wide range of natural environments. In this context, the WISDOM team participated in the SAFER (Sample Acquisition Field Experiment with a Rover) field trial that occurred from 7th to 13th October 2013 in the Atacama Desert, Chile. Designed to gather together scientists and engineers in a context of a real Martian mission with a rover, the SAFER trial was the opportunity to use three onboard ExoMars instruments, namely CLUPI (Close- UP Imager), PANCAM (Panoramic Camera) and WISDOM, to investigate the chosen area. We present the results derived from WISDOM data acquired over the SAFER trial site to characterize the shallow subsurface of the area.

Determination of field-effective soil properties in the tidewater region of North Carolina

Treesearch

J. McFero Grace; R.W. Skaggs

2013-01-01

Soils vary spatially in texture, structure, depth of horizons, and macropores, which can lead to a large variation in soil physical properties. In particular, saturated hydraulic conductivity (Ksat) and drainable porosity are critical properties required to model field hydrology in poorly drained lands. These soil-property values can be measured...

Organic [6,6]-phenyl-C61-butyric-acid-methyl-ester field effect transistors: Analysis of the contact properties by combined photoemission spectroscopy and electrical measurements

NASA Astrophysics Data System (ADS)

Scheinert, S.; Grobosch, M.; Sprogies, J.; Hörselmann, I.; Knupfer, M.; Paasch, G.

2013-05-01

Carrier injection barriers determined by photoemission spectroscopy for organic/metal interfaces are widely accepted to determine the performance of organic field-effect transistors (OFET), which strongly depends on this interface at the source/drain contacts. This assumption is checked here in detail, and a more sophisticated connection is presented. According to the preparation process described in our recently published article [S. Scheinert, J. Appl. Phys. 111, 064502 (2012)], we prepared PCBM/Au and PCBM/Al samples to characterize the interface by photoemission and electrical measurements of PCBM based OFETs with bottom and top (TOC) contacts, respectively. The larger drain currents for TOC OFETs indicate the presence of Schottky contacts at source/drain for both metals. The hole injection barrier as determined by photoemission is 1.8 eV for both Al and Au. Therefore, the electron injection barriers are also the same. In contrast, the drain currents are orders of magnitude larger for the transistors with the Al contacts than for those with the Au contacts. We show that indeed the injection is determined by two other properties measured also by photoemission, the (reduced) work functions, and the interface dipoles, which have different sign for each contact material. In addition, we demonstrate by core-level and valence band photoemission that the deposition of gold as top contact onto PCBM results in the growth of small gold clusters. With increasing gold coverage, the clusters grow inside and begin to form a metallic, but not uniform, closed film onto PCBM.

A novel explicit approach to model bromide and pesticide transport in soils containing macropores

NASA Astrophysics Data System (ADS)

Klaus, J.; Zehe, E.

2011-01-01

The present study tests whether an explicit treatment of worm burrows is feasible for simulating water flow, bromide and pesticide transport in structured heterogeneous soils. The essence is to represent worm burrows as morphologically connected paths of low flow resistance in the spatially highly resolved model domain. A recent Monte Carlo study (Klaus and Zehe, 2010) revealed that this approach allowed successful reproduction of tile drain event discharge recorded during an irrigation experiment at a tile drained field site. However, several "hillslope architectures" that were all consistent with the available extensive data base allowed a good reproduction of tile drain flow response. Our second objective was thus to find out whether this "equifinality" in spatial model setups may be reduced when including bromide tracer data in the model falsification process. We thus simulated transport of bromide and Isoproturon (IPU) for the 13 spatial model setups, which performed best with respect to reproduce tile drain event discharge, without any further calibration. All model setups allowed a very good prediction of the temporal dynamics of cumulated bromide leaching into the tile drain, while only four of them matched the accumulated water balance and accumulated bromide loss into the tile drain. The number of behavioural model architectures could thus be reduced to four. One of those setups was used for simulating transport of IPU, using different parameter combinations to characterise adsorption according to the Footprint data base. Simulations could, however, only reproduce the observed leaching behaviour, when we allowed for retardation coefficients that were very close to one.

Spatial variability of herbicide mobilisation and transport at catchment scale: insights from a field experiment

NASA Astrophysics Data System (ADS)

Doppler, T.; Camenzuli, L.; Hirzel, G.; Krauss, M.; Lück, A.; Stamm, C.

2012-07-01

During rain events, herbicides can be transported from their point of application to surface waters, where they may harm aquatic organisms. Since the spatial pattern of mobilisation and transport is heterogeneous, the contributions of different fields to the herbicide load in the stream may vary considerably within one catchment. Therefore, the prediction of contributing areas could help to target mitigation measures efficiently to those locations where they reduce herbicide pollution the most. Such spatial predictions require sufficient insight into the underlying transport processes. To improve the understanding of the process chain of herbicide mobilisation on the field and the subsequent transport through the catchment to the stream, we performed a controlled herbicide application on corn fields in a small agricultural catchment (ca. 1 km2) with intensive crop production in the Swiss Plateau. Water samples were collected at different locations in the catchment (overland flow, tile drains and open channel) for two months after application in 2009, with a high temporal resolution during rain events. We also analysed soil samples from the experimental fields and measured discharge, groundwater level, soil moisture and the occurrence of overland flow at several locations. Several rain events with varying intensities and magnitudes occurred during the study period. Overland flow and erosion were frequently observed in the entire catchment. Infiltration excess and saturation excess overland flow were both observed. However, the main herbicide loss event was dominated by infiltration excess. Despite the frequent and wide-spread occurrence of overland flow, most of this water did not reach the channel directly, but was retained in small depressions in the catchment. From there, it reached the stream via macropores and tile drains. Manholes of the drainage system and storm drains for road and farmyard runoff acted as additional shortcuts to the stream. Although fast flow processes such as overland and macropore flow reduce the influence of the herbicide's chemical properties on transport due to short travel times, sorption properties influenced the herbicide transfer from ponding overland flow to tile drains (macropore flow). However, no influence of sorption was observed during the mobilisation of the herbicides from soil to overland flow. These observations on the role of herbicide properties contradict previous findings to some degree. Furthermore, they demonstrate that valuable insight can be gained by making spatially detailed observations along the flow paths.

Influence of gate recess on the electronic characteristics of β-Ga2O3 MOSFETs

NASA Astrophysics Data System (ADS)

Lv, Yuanjie; Mo, Jianghui; Song, Xubo; He, Zezhao; Wang, Yuangang; Tan, Xin; Zhou, Xingye; Gu, Guodong; Guo, Hongyu; Feng, Zhihong

2018-05-01

Gallium oxide (Ga2O3) metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated with gate recess depths of 110 nm and 220 nm, respectively. The gate recess was formed by dry plasma etching with Cr metal as the mask. The fabricated devices with a 25-nm HfO2 gate dielectric both showed a low off-state drain current of about 1.8 × 10-10 A/mm. The effects of recess depth on the electronic characteristics of Ga2O3 MOSFETs were investigated. Upon increasing the recess depth from 110 nm to 220 nm, the saturated drain current decreased from 20.7 mA/mm to 2.6 mA/mm, while the threshold voltage moved increased to +3 V. Moreover, the breakdown voltage increased from 122 V to 190 V. This is mainly because the inverted-trapezoidal gate played the role of a gate-field plate, which suppressed the peak electric field close to the gate.

Metolachlor and its metabolites in tile drain and stream runoff in the canajoharie creek watershed

USGS Publications Warehouse

Phillips, P.J.; Wall, G.R.; Thurman, E.M.; Eckhardt, D.A.; Vanhoesen, J.

1999-01-01

Water samples collected during April-November 1997 from tile drains beneath cultivated fields in central New York indicate that two metabolites of the herbicide metolachlor-metolachlor ESA (ethanesulfonic acid) and OA (oxanilic acid) can persist in agricultural soils for 4 or more years after application and that fine-grained soils favor the transport of metolachlor ESA over metolachlor and metolachlor OA. Concentrations of metolachlor ESA from the tile drains ranged from 3.27 to 23.4 ??g/L (200 1800 times higher than those of metolachlor), metolachlor OA concentrations ranged from 1.14 to 13.5 ??g/L, and metolachlor concentrations ranged from less than 0.01 to 0.1 ??g/L. In the receiving stream, concentrations of metolachlor ESA were always below 0.6 ??g/L except during a November storm, when concentrations reached 0.85 ??g/L. Concentrations of metolachlor ESA in the stream were 2 45 times higher than those of metolachlor, reflecting the greater relative concentrations of metolachlor in surface water runoff than in tile drain runoff. These results are consistent with findings in other studies that acetanilide herbicide degredates are found in much higher concentrations than parent compounds in both surface water and groundwater.Water samples collected during April-November 1997 from tile drains beneath cultivated fields in central New York indicate that two metabolites of the herbicide metolachlor-metolachlor ESA (ethanesulfonic acid) and OA (oxanilic acid)-can persist in agricultural soils for 4 or more years after application and that fine-grained soils favor the transport of metolachlor ESA over metolachlor and metolachlor OA. Concentrations of metolachlor ESA from the tile drains ranged from 3.27 to 23.4 ??g/L (200-1800 times higher than those of metolachlor), metolachlor OA concentrations ranged from 1.14 to 13.5 ??g/L, and metolachlor concentrations ranged from less than 0.01 to 0.1 ??g/L. In the receiving stream, concentrations of metolachlor ESA were always below 0.6 ??g/L except during a November storm, when concentrations reached 0.85 ??g/L. Concentrations of metolachlor ESA in the stream were 2-45 times higher than those of metolachlor, reflecting the greater relative concentrations of metolachlor in surface water runoff than in tile drain runoff. These results are consistent with findings in other studies that acetanilide herbicide degredates are found in much higher concentrations than parent compounds in both surface water and groundwater.

Subsurface geology and oil and gas resources of Osage County, Oklahoma. Part 2, Townships 22 and 23 north, ranges 8 and 9 east

USGS Publications Warehouse

Kirk, C.T.; Jenkins, H.D.; Leatherock, Otto; Dillard, W.R.; Kennedy, L.E.; Bass, N.W.

1939-01-01

This report on the subsurface geology of Osage County, Okla., describes the structural features, the character of the oil- and gas-producing beds, and the localities where additional oil and gas may be found. It embodies a part of the results of a subsurface geologic investigation of the Osage Indian Reservation, which coincides in area with Osage County. The investigation was conducted by a field party of the Geological Survey of the United States Department of the Interior from 1934 to 1937 and involved the study of the records of about 17,000 wells that have been drilled in Osage County. Funds for the investigation were allotted to the Geological Survey by the Public Works Administration. The primary purpose of the examination was to obtain geologic data for use in the administration of the Indian lands. The results of the inquiry have shown that many localities in Osage County outside the present producing oil fields are worthy of prospecting for oil and gas and that additional oil and gas can be found also by exploring deeply buried beds in old producing fields.All townships in Osage County that contain many wells are described; the information furnished by such townships is ample for drawing detailed subsurface structure-contour maps. The descriptions of several contiguous townships are combined in separate reports, which are issued as parts of a single bulletin. No edition of the consolidated volume will be published, but the several parts can be bound together if desired.

Trends in maar crater size and shape using the global Maar Volcano Location and Shape (MaarVLS) database

NASA Astrophysics Data System (ADS)

Graettinger, A. H.

2018-05-01

A maar crater is the top of a much larger subsurface diatreme structure produced by phreatomagmatic explosions and the size and shape of the crater reflects the growth history of that structure during an eruption. Recent experimental and geophysical research has shown that crater complexity can reflect subsurface complexity. Morphometry provides a means of characterizing a global population of maar craters in order to establish the typical size and shape of features. A global database of Quaternary maar crater planform morphometry indicates that maar craters are typically not circular and frequently have compound shapes resembling overlapping circles. Maar craters occur in volcanic fields that contain both small volume and complex volcanoes. The global perspective provided by the database shows that maars are common in many volcanic and tectonic settings producing a similar diversity of size and shape within and between volcanic fields. A few exceptional populations of maars were revealed by the database, highlighting directions of future research to improve our understanding on the geometry and spacing of subsurface explosions that produce maars. These outlying populations, such as anomalously large craters (>3000 m), chains of maars, and volcanic fields composed of mostly maar craters each represent a small portion of the database, but provide opportunities to reinvestigate fundamental questions on maar formation. Maar crater morphometry can be integrated with structural, hydrological studies to investigate lateral migration of phreatomagmatic explosion location in the subsurface. A comprehensive database of intact maar morphometry is also beneficial for the hunt for maar-diatremes on other planets.

Two-dimensional resistivity investigation of the North Cavalcade Street site, Houston, Texas, August 2003

USGS Publications Warehouse

Kress, Wade H.; Teeple, Andrew

2005-01-01

Forward modeling was used as an interpretative tool to relate the subsurface distribution of resistivity from four DC resistivity lines to known, assumed, and hypothetical information on subsurface lithologies. The final forward models were used as an estimate of the true resistivity structure for the field data. The forward models and the inversion results of the forward models show the depth, thickness, and extent of strata as well as the resistive anomalies occurring along the four lines and the displacement of strata resulting from the Pecore Fault along two of the four DC resistivity lines. Ten additional DC resistivity lines show similarly distributed shallow subsurface lithologies of silty sand and clay strata. Eight priority areas of resistive anomalies were identified for evaluation in future studies. The interpreted DC resistivity data allowed subsurface stratigraphy to be extrapolated between existing boreholes resulting in an improved understanding of lithologies that can influence contaminant migration.

STRUCTURE AND FUNCTION OF SUBSURFACE MICROBIAL COMMUNITIES AFFECTING RADIONUCLIDE TRANSPORT AND BIOIMMOBILIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joel E. Kostka; Lee Kerkhof; Kuk-Jeong Chin

2011-06-15

The objectives of this project were to: (1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), (2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and (3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee, where themore » subsurface is exposed to mixed contamination predominated by uranium and nitrate. A total of 20 publications (16 published or 'in press' and 4 in review), 10 invited talks, and 43 contributed seminars/ meeting presentations were completed during the past four years of the project. PI Kostka served on one proposal review panel each year for the U.S. DOE Office of Science during the four year project period. The PI leveraged funds from the state of Florida to purchase new instrumentation that aided the project. Support was also leveraged by the PI from the Joint Genome Institute in the form of two successful proposals for genome sequencing. Draft genomes are now available for two novel species isolated during our studies and 5 more genomes are in the pipeline. We effectively addressed each of the three project objectives and research highlights are provided. Task I - Isolation and characterization of novel anaerobes: (1) A wide range of pure cultures of metal-reducing bacteria, sulfate-reducing bacteria, and denitrifying bacteria (32 strains) were isolated from subsurface sediments of the Oak Ridge Field Research Center (ORFRC), where the subsurface is exposed to mixed contamination of uranium and nitrate. These isolates which are new to science all show high sequence identity to sequences retrieved from ORFRC subsurface. (2) Based on physiological and phylogenetic characterization, two new species of subsurface bacteria were described: the metal-reducer Geobacter daltonii, and the denitrifier Rhodanobacter denitrificans. (3) Strains isolated from the ORFRC show that Rhodanobacter species are well adapted to the contaminated subsurface. Strains 2APBS1 and 116-2 grow at high salt (3% NaCl), low pH (3.5) and tolerate high concentrations of nitrate (400mM) and nitrite (100mM). Strain 2APBS1 was demonstrated to grow at in situ acidic pHs down to 2.5. (4) R. denitrificans strain 2APBS1 is the first described Rhodanobacter species shown to denitrify. Nitrate is almost entirely converted to N2O, which may account for the large accumulation of N2O in the ORFRC subsurface. (5) G. daltonii, isolated from uranium- and hydrocarbon-contaminated subsurface sediments of the ORFRC, is the first organism from the subsurface clade of the genus Geobacter that is capable of growth on aromatic hydrocarbons. (6) High quality draft genome sequences and a complete eco-physiological description are completed for R. denitrificans strain 2APBS1 and G. daltonii strain FRC-32. (7) Given their demonstrated relevance to DOE remediation efforts and the availability of detailed genotypic/phenotypic characterization, Rhodanobacter denitrificans strain 2APBS1 and Geobacter daltonii strain FRC-32 represent ideal model organisms to provide a predictive understanding of subsurface microbial activity through metabolic modeling. Tasks II and III-Diversity and distribution of active anaerobes and Mechanisms linking electron transport and the fate of radionuclides: (1) Our study showed that members of genus Rhodanobacter and Geobacter are abundant and active in the uranium and nitrate contaminated subsurface. In the contaminant source zone of the Oak Ridge site, Rhodanobacter spp. are the predominant, active organisms detected (comprising 50% to 100% of rRNA detected). (2) We demonstrated for the first time that the function of microbial communities can be quantified in subsurface sediments using messenger RNA assays (molecular proxies) under in situ conditions. (3) Active Geobacteraceae were identified and phylogenetically characterized from the cDNA of messenger RNA extracted from ORFRC subsurface sediment cores. Multiple clone sequences were retrieved from G. uraniireducens, G. daltonii, and G. metallireducens. (4) Results show that Geobacter strain FRC-32 is capable of growth on benzoate, toluene and benzene as the electron donor, thereby providing evidence that this strain is physiologically distinct from other described members of the subsurface Geobacter clade. (5) Fe(III)-reducing bacteria transform structural Fe in clay minerals from their layer edges rather than from their basal surfaces.« less

FIELD TRAPPING OF SUBSURFACE VAPOR PHASE PETROLEUM HYDROCARBONS

EPA Science Inventory

Soil gas samples from intact soil cores were collected on adsorbents at a field site, then thermally desorbed and analyzed by laboratory gas chromatography (GC). ertical concentration profiles of predominant vapor phase petroleum hydrocarbons under ambient conditions were obtaine...

FIELD-DRIVEN APPROACHES TO SUBSURFACE CONTAMINANT TRANSPORT MODELING.

EPA Science Inventory

Observations from field sites provide a means for prioritizing research activities. In the case of petroleum releases, observations may include spiking of concentration distributions that may be related to water table fluctuation, co-location of contaminant plumes with geochemi...

Global estimations of the inventory and mitigation potential of methane emissions from rice cultivation conducted using the 2006 Intergovernmental Panel on Climate Change Guidelines

NASA Astrophysics Data System (ADS)

Yan, Xiaoyuan; Akiyama, Hiroko; Yagi, Kazuyuki; Akimoto, Hajime

2009-06-01

The Intergovernmental Panel on Climate Change (IPCC) regularly publishes guidelines for national greenhouse gas inventories and methane emission (CH4) from rice paddies has been an important component of these guidelines. While there have been many estimates of global CH4 emissions from rice fields, none of them have been obtained using the IPCC guidelines. Therefore, we used the Tier 1 method described in the 2006 IPCC guidelines to estimate the global CH4 emissions from rice fields. To accomplish this, we used country-specific statistical data regarding rice harvest areas and expert estimates of relevant agricultural activities. The estimated global emission for 2000 was 25.6 Tg a-1, which is at the lower end of earlier estimates and close to the total emission summarized by individual national communications. Monte Carlo simulation revealed a 95% uncertainty range of 14.8-41.7 Tg a-1; however, the estimation uncertainty was found to depend on the reliability of the information available regarding the amount of organic amendments and the area of rice fields that were under continuous flooding. We estimated that if all of the continuously flooded rice fields were drained at least once during the growing season, the CH4 emissions would be reduced by 4.1 Tg a-1. Furthermore, we estimated that applying rice straw off season wherever and whenever possible would result in a further reduction in emissions of 4.1 Tg a-1 globally. Finally, if both of these mitigation options were adopted, the global CH4 emission from rice paddies could be reduced by 7.6 Tg a-1. Although draining continuously flooded rice fields may lead to an increase in nitrous oxide (N2O) emission, the global warming potential resulting from this increase is negligible when compared to the reduction in global warming potential that would result from the CH4 reduction associated with draining the fields.

Demonstration of β-(AlxGa1-x)2O3/Ga2O3 double heterostructure field effect transistors

NASA Astrophysics Data System (ADS)

Zhang, Yuewei; Joishi, Chandan; Xia, Zhanbo; Brenner, Mark; Lodha, Saurabh; Rajan, Siddharth

2018-06-01

In this work, we demonstrate modulation-doped β-(AlxGa1-x)2O3/Ga2O3 double heterostructure field effect transistors. The maximum sheet carrier density for a two-dimensional electron gas (2DEG) in a β-(AlxGa1-x)2O3/Ga2O3 heterostructure is limited by the conduction band offset and parasitic channel formation in the barrier layer. We demonstrate a double heterostructure to realize a β-(AlxGa1-x)2O3/Ga2O3/(AlxGa1-x)2O3 quantum well, where electrons can be transferred from below and above the β-Ga2O3 quantum well. The confined 2DEG charge density of 3.85 × 1012 cm-2 was estimated from the low-temperature Hall measurement, which is higher than that achievable in a single heterostructure. Hall mobilities of 1775 cm2/V.s at 40 K and 123 cm2/V.s at room temperature were measured. Modulation-doped double heterostructure field effect transistors showed a maximum drain current of IDS = 257 mA/mm, a peak transconductance (gm) of 39 mS/mm, and a pinch-off voltage of -7.0 V at room temperature. The three-terminal off-state breakdown measurement on the device with a gate-drain spacing (LGD) of 1.55 μm showed a breakdown voltage of 428 V, corresponding to an average breakdown field of 2.8 MV/cm. The breakdown measurement on the device with a scaled gate-drain spacing of 196 nm indicated an average breakdown field of 3.2 MV/cm. The demonstrated modulation-doped β-(AlxGa1-x)2O3/Ga2O3 double heterostructure field effect transistor could act as a promising candidate for high power and high frequency device applications.

Integrating aeromagnetic and Landsat™ 8 data into subsurface structural mapping of Precambrian basement complex

NASA Astrophysics Data System (ADS)

Kayode, John Stephen; Nawawi, M. N. M.; Abdullah, Khiruddin B.; Khalil, Amin E.

2017-01-01

The integration of Aeromagnetic data and remotely sensed imagery with the intents of mapping the subsurface geological structures in part of the South-western basement complex of Nigeria was developed using the PCI Geomatica Software. 2013. The data obtained from the Nigerian Geological Survey Agency; was corrected using Regional Residual Separation of the Total Magnetic field anomalies enhanced, and International Geomagnetic Reference Field removed. The principal objective of this study is, therefore, to introduce a rapid and efficient method of subsurface structural depth estimate and structural index evaluation through the incorporation of the Euler Deconvolution technique into PCI Geomatica 2013 to prospect for subsurface geological structures. The shape and depth of burial helped to define these structures from the regional aeromagnetic map. The method enabled various structural indices to be automatically delineated for an index of between 0.5 SI and 3.0 SI at a maximum depth of 1.1 km that clearly showed the best depths estimate for all the structural indices. The results delineate two major magnetic belts in the area; the first belt shows an elongated ridge-like structure trending mostly along the NorthNortheast-SouthSouthwest and the other anomalies trends primarily in the Northeast, Northwest, Northeast-Southwest parts of the study area that could be attributed to basement complex granitic intrusions from the tectonic history of the area. The majority of the second structures showed various linear structures different from the first structure. Basically, a significant offset was delineated at the core segment of the study area, suggesting a major subsurface geological feature that controls mineralisation in this area.

The distribution of lingering subsurface oil from the Exxon Valdez oil spill

USGS Publications Warehouse

Michel, Jacqueline; Nixon, Zachary; Hayes, Miles O.; Irvine, Gail V.; Short, Jeffrey W.

2011-01-01

This study used field data and a suite of geospatial models to identify areas where subsurface oil is likely to still be present on the shorelines of Prince William Sound (PWS) and the Gulf of Alaska (GOA) affected by the Exxon Valdez oil spill, as well as the factors related to continued presence of such oil. The goal was to identify factors and accompanying models that could serve as screening tools to prioritize shorelines for different remediation methods. The models were based on data collected at 314 shoreline segments surveyed between 2001 and 2007. These field data allowed us to identify a number of geomorphologic and hydrologic factors that have contributed to the persistence of subsurface oil within PWS and GOA two decades after the spill. Because synoptic data layers for describing each of these factors at all locations were not available, the models developed used existing data sets as surrogates to represent these factors, such as distance to a stream mouth or shoreline convexity. While the linkages between the data used and the physical phenomena that drive persistence are not clearly understood in all cases, the performance of these models was remarkably good. The models simultaneously evaluate all identified variables to predict the presence of different types of subsurface oiling in a rigorous, unbiased manner. The refined model results suggest there are a limited but significant number of as-yet unsurveyed locations in the study area that are likely to contain subsurface oil. Furthermore, the model results may be used to quantitatively prioritize shoreline for investigation with known uncertainty.

Method of doping organic semiconductors

DOEpatents

Kloc,; Christian Leo; Ramirez; Arthur Penn; So, Woo-Young

2010-10-26

An apparatus has a crystalline organic semiconducting region that includes polyaromatic molecules. A source electrode and a drain electrode of a field-effect transistor are both in contact with the crystalline organic semiconducting region. A gate electrode of the field-effect transistor is located to affect the conductivity of the crystalline organic semiconducting region between the source and drain electrodes. A dielectric layer of a first dielectric that is substantially impermeable to oxygen is in contact with the crystalline organic semiconducting region. The crystalline organic semiconducting region is located between the dielectric layer and a substrate. The gate electrode is located on the dielectric layer. A portion of the crystalline organic semiconducting region is in contact with a second dielectric via an opening in the dielectric layer. A physical interface is located between the second dielectric and the first dielectric.

Whole-stream metabolism of a perennial spring-fed aufeis field in Alaska, with coincident surface and subsurface flow

NASA Astrophysics Data System (ADS)

Hendrickson, P. J.; Gooseff, M. N.; Huryn, A. D.

2017-12-01

Aufeis (icings or naleds) are seasonal arctic and sub-arctic features that accumulate through repeated overflow and freeze events of river or spring discharge. Aufeis fields, defined as the substrate on which aufeis form and the overlaying ice, have been studied to mitigate impacts on engineering structures; however, ecological characteristics and functions of aufeis fields are poorly understood. The perennial springs that supply warm water to aufeis fields create unique fluvial habitats, and are thought to act as winter and summer oases for biota. To investigate ecosystem function, we measured whole-stream metabolism at the Kuparuk River Aufeis (North Slope, AK), a large ( 5 km2) field composed of cobble substrate and predominately subsurface flow dynamics. The single-station open channel diel oxygen method was utilized at several dissolved oxygen (DO) stations located within and downstream of the aufeis field. DO loggers were installed in August 2016, and data downloaded summer 2017. Daily ecosystem respiration (ER), gross primary production (GPP) and reaeration rates were modeled using BASE, a package freely available in the open-source software R. Preliminary results support net heterotrophy during a two-week period of DO measurements in the fall season when minimum ice extent is observed. GPP, ER, and net metabolism are greater at the upstream reach near the spring source (P/R = 0.53), and decrease as flow moves downstream. As flow exits the aufeis field, surface and subsurface flow are incorporated into the metabolism model, and indicate the stream system becomes dependent on autochthonous production (P/R = 0.91). Current work is directed towards spring and summer discharge and metabolic parameter estimation, which is associated with maximum ice extent and rapid melting of the aufeis feature.

Performance evaluation of parallel electric field tunnel field-effect transistor by a distributed-element circuit model

NASA Astrophysics Data System (ADS)

Morita, Yukinori; Mori, Takahiro; Migita, Shinji; Mizubayashi, Wataru; Tanabe, Akihito; Fukuda, Koichi; Matsukawa, Takashi; Endo, Kazuhiko; O'uchi, Shin-ichi; Liu, Yongxun; Masahara, Meishoku; Ota, Hiroyuki

2014-12-01

The performance of parallel electric field tunnel field-effect transistors (TFETs), in which band-to-band tunneling (BTBT) was initiated in-line to the gate electric field was evaluated. The TFET was fabricated by inserting an epitaxially-grown parallel-plate tunnel capacitor between heavily doped source wells and gate insulators. Analysis using a distributed-element circuit model indicated there should be a limit of the drain current caused by the self-voltage-drop effect in the ultrathin channel layer.

Early Forest Soils and Their Role in Devonian Global Change

PubMed

Retallack

1997-04-25

A paleosol in the Middle Devonian Aztec Siltstone of Victoria Land, Antarctica, is the most ancient known soil of well-drained forest ecosystems. Clay enrichment and chemical weathering of subsurface horizons in this and other Devonian forested paleosols culminate a long-term increase initiated during the Silurian. From Silurian into Devonian time, red clayey calcareous paleosols show a greater volume of roots and a concomitant decline in the density of animal burrows. These trends parallel the decline in atmospheric carbon dioxide determined from isotopic records of pedogenic carbonate in these same paleosols. The drawdown of carbon dioxide began well before the Devonian appearance of coals, large logs, and diverse terrestrial plants and animals, and it did not correlate with temporal variation in volcanic or metamorphic activity. The early Paleozoic greenhouse may have been curbed by the evolution of rhizospheres with an increased ratio of primary to secondary production and by more effective silicate weathering during Silurian time.

Preliminary assessment of the effects of selenium in agricultural drainage on fish in the San Joaquin Valley

USGS Publications Warehouse

Saiki, M.K.; Jennings, M.R.; Hamilton, S.J.; Dinar, A.; Zilberman, D.

1991-01-01

Concentrations of total selenium were measured in whole-body samples of seven fishes from the Sacramento and San Joaquin River systems and the San Francisco Bay complex. Concentrations of selenium (up to 11 µg/g dry weight in whole-body composite samples) were highest in fish from canals and sloughs in the Grassland Water District (Grasslands) that received large inflows of subsurface agricultural drainage water. Slightly lower selenium concentrations occurred in fish from the San Joaquin River immediately downstream from tributaries draining the Grasslands. Although circumstantial evidence suggests that selenium-sensitive species such as bluegills and largemouth bass are being excluded from the Grasslands, conclusive evidence of selenium toxicity is still lacking. In response to earlier reports of high concentrations of selenium in several species collected from the Grasslands, the California Department of Health Services has urged people to limit consumption of fish from this region.

Rapid laccolith intrusion driven by explosive volcanic eruption

NASA Astrophysics Data System (ADS)

Castro, Jonathan M.; Cordonnier, Benoit; Schipper, C. Ian; Tuffen, Hugh; Baumann, Tobias S.; Feisel, Yves

2016-11-01

Magmatic intrusions and volcanic eruptions are intimately related phenomena. Shallow magma intrusion builds subsurface reservoirs that are drained by volcanic eruptions. Thus, the long-held view is that intrusions must precede and feed eruptions. Here we show that explosive eruptions can also cause magma intrusion. We provide an account of a rapidly emplaced laccolith during the 2011 rhyolite eruption of Cordón Caulle, Chile. Remote sensing indicates that an intrusion began after eruption onset and caused severe (>200 m) uplift over 1 month. Digital terrain models resolve a laccolith-shaped body ~0.8 km3. Deformation and conduit flow models indicate laccolith depths of only ~20-200 m and overpressures (~1-10 MPa) that likely stemmed from conduit blockage. Our results show that explosive eruptions may rapidly force significant quantities of magma in the crust to build laccoliths. These iconic intrusions can thus be interpreted as eruptive features that pose unique and previously unrecognized volcanic hazards.

Life and Death on Mars and Earth

NASA Technical Reports Server (NTRS)

Zahnle, K. J.; Sleep, N. H.

1999-01-01

Failure to discover life on Mars has led a great many experts to conclude that it must be hiding. Where? The likeliest hiding places are deep beneath the surface, where geothermal heat could permit liquid water. In this the search for life on Mars parallels the search for water on Mars. Liquid water has been, at least on occasion, a geologically significant presence on the surface. Channels were cut and plains dissected. This water is now hidden, in all likelihood having drained to the base of the porous regolith, where it fills possibly frozen aquifers. Presumably any surviving biota has followed the water from the surface to its hiding places in the deep. Accordingly, we have extended our environmental impact assessment of the environmental hazards posed by large asteroid and comet impacts to Mars, and compare its case to Earth's. In particular, we address the continuous habitability of surface and subsurface environments.

The impact of glacier geometry on meltwater plume structure and submarine melt in Greenland fjords

NASA Astrophysics Data System (ADS)

Carroll, D.; Sutherland, D. A.; Hudson, B.; Moon, T.; Catania, G. A.; Shroyer, E. L.; Nash, J. D.; Bartholomaus, T. C.; Felikson, D.; Stearns, L. A.; Noël, B. P. Y.; Broeke, M. R.

2016-09-01

Meltwater from the Greenland Ice Sheet often drains subglacially into fjords, driving upwelling plumes at glacier termini. Ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting, leading to calving and potential glacier destabilization. Here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge, glacier depth, and ocean stratification from 12 Greenland fjords. Our results show that grounding line depth is a strong control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-trapped plumes that can overcut termini. Due to sustained upwelling velocities, plumes in cold, shallow fjords can induce equivalent depth-averaged melt rates compared to warm, deep fjords. These results detail a direct ocean-ice feedback that can affect the Greenland Ice Sheet.

Magma degassing triggered by static decompression at Kīlauea Volcano, Hawai‘i

USGS Publications Warehouse

Poland, Michael P.; Jeff, Sutton A.; Gerlach, Terrence M.

2009-01-01

During mid-June 2007, the summit of Kīlauea Volcano, Hawai‘i, deflated rapidly as magma drained from the subsurface to feed an east rift zone intrusion and eruption. Coincident with the deflation, summit SO2 emission rates rose by a factor of four before decaying to background levels over several weeks. We propose that SO2 release was triggered by static decompression caused by magma withdrawal from Kīlauea's shallow summit reservoir. Models of the deflation suggest a pressure drop of 0.5–3 MPa, which is sufficient to trigger exsolution of the observed excess SO2 from a relatively small volume of magma at the modeled source depth beneath Kīlauea's summit. Static decompression may also explain other episodes of deflation accompanied by heightened gas emission, including the precursory phases of Kīlauea's 2008 summit eruption. Hazards associated with unexpected volcanic gas emission argue for increased awareness of magma reservoir pressure fluctuations.

Trace elements and pesticides in Salton Sea area, California

USGS Publications Warehouse

Schroeder, Roy A.; Setmire, James G.; Wolfe, John C.

1988-01-01

Concentrations of numerous potentially toxic trace elements and pesticides were determined in water, sediment, and biota from the Salton Sea area in southestern California. Comparison of results with data from other studies in this area and from other areas, and with various water-quality standards or criteria, indicate that selenium probably is the principal contaminant of concern in the Salton Sea basin and that it probably is related to agricultural practices. Selenium is mobilized in the subsurface drainwater produced by agricultural irrigation and transported in ditches and rivers, some of which pass through or near the Salton Sea National Wildlife Refuge before entering the Salton Sea. Some selenium apparently is incorporated into the food chain. In response to the finding of elevated selenium residues in fish from the area by State agencies, the Imperial County Health Department has issued a health advisory restricting or prohibiting human consumption of fish from the Salton Sea and drains.

Assessing impacts of land-applied manure from concentrated animal feeding operations on fish populations and communities.

PubMed

Leet, Jessica K; Lee, Linda S; Gall, Heather E; Goforth, Reuben R; Sassman, Stephen; Gordon, Denise A; Lazorchak, James M; Smith, Mark E; Jafvert, Chad T; Javfert, Chad T; Sepúlveda, Maria S

2012-12-18

Concentrated animal feeding operation (CAFO) manure is a cost-effective fertilizer. In the Midwest, networks of subsurface tile-drains expedite transport of animal hormones and nutrients from land-applied CAFO manure to adjacent waterways. The objective of this study was to evaluate impacts of land-applied CAFO manure on fish populations and communities. Water chemistry including hormone, pesticide, and nutrient concentrations was characterized from study sites along with fish assemblage structure, growth, and endocrine disruption assessed in selected fish species. Although most CAFO water samples had hormone concentrations <1 ng/L, equivalent concentrations for 17β-E2 and 17α-TB peaked at >30 ng/L each during the period of spawning, hatching, and development for resident fishes. CAFO sites had lower fish species richness, and fishes exhibited faster somatic growth and lower reproductive condition compared to individuals from the reference site. Fathead minnows (Pimephales promelas) exposed to CAFO ditchwater during early developmental stages exhibited significantly skewed sex ratios toward males. Maximum observed hormone concentrations were well above the lowest observable effect concentrations for these hormones; however, complexities at the field scale make it difficult to directly relate hormone concentration and impacts on fish. Complicating factors include the consistent presence of pesticides and nutrients, and the difference in temperature and stream architecture of the CAFO-impacted ditches compared to the reference site (e.g., channelization, bottom substrate, shallow pools, and riparian cover).

Characterization of fly ash ceramic pellet for phosphorus removal.

PubMed

Li, Shiyang; Cooke, Richard A; Wang, Li; Ma, Fang; Bhattarai, Rabin

2017-03-15

Phosphorus has been recognized as a leading pollutant for surface water quality deterioration. In the Midwestern USA, subsurface drainage not only provides a pathway for excess water to leave the field but it also drains out nutrients like nitrogen (N) and phosphorus (P). Fly ash has been identified as one of the viable materials for phosphorus removal from contaminated waters. In this study, a ceramic pellet was manufactured using fly ash for P absorption. Three types of pellet with varying lime and clay proportions by weight (type 1: 10% lime + 30% clay, type 2: 20% lime + 20% clay, and type 3: 30% lime + 10% clay) were characterized and evaluated for absorption efficiency. The result showed that type 3 pellet (60% fly ash with 30% lime and 10% clay) had the highest porosity (14%) and absorption efficiency and saturated absorption capacity (1.98 mg P/g pellet) compared to type 1 and 2 pellets. The heavy metal leaching was the least (30 μg/L of chromium after 5 h) for type 3 pellet compared to other two. The microcosmic structure of pellet from scanning electron microscope showed the type 3 pellet had the better distribution of aluminum and iron oxide on the surface compared other two pellets. This result indicates that addition of lime and clay can improve P absorption capacity of fly ash while reducing the potential to reduce chromium leaching. Copyright © 2016 Elsevier Ltd. All rights reserved.

Study on effective MOSFET channel length extracted from gate capacitance

NASA Astrophysics Data System (ADS)

Tsuji, Katsuhiro; Terada, Kazuo; Fujisaka, Hisato

2018-01-01

The effective channel length (L GCM) of metal-oxide-semiconductor field-effect transistors (MOSFETs) is extracted from the gate capacitances of actual-size MOSFETs, which are measured by charge-injection-induced-error-free charge-based capacitance measurement (CIEF CBCM). To accurately evaluate the capacitances between the gate and the channel of test MOSFETs, the parasitic capacitances are removed by using test MOSFETs having various channel sizes and a source/drain reference device. A strong linear relationship between the gate-channel capacitance and the design channel length is obtained, from which L GCM is extracted. It is found that L GCM is slightly less than the effective channel length (L CRM) extracted from the measured MOSFET drain current. The reason for this is discussed, and it is found that the capacitance between the gate electrode and the source and drain regions affects this extraction.

Impact of random discrete dopant in extension induced fluctuation in gate-source/drain underlap FinFET

NASA Astrophysics Data System (ADS)

Wang, Yijiao; Huang, Peng; Xin, Zheng; Zeng, Lang; Liu, Xiaoyan; Du, Gang; Kang, Jinfeng

2014-01-01

In this work, three dimensional technology computer-aided design (TCAD) simulations are performed to investigate the impact of random discrete dopant (RDD) including extension induced fluctuation in 14 nm silicon-on-insulator (SOI) gate-source/drain (G-S/D) underlap fin field effect transistor (FinFET). To fully understand the RDD impact in extension, RDD effect is evaluated in channel and extension separately and together. The statistical variability of FinFET performance parameters including threshold voltage (Vth), subthreshold slope (SS), drain induced barrier lowering (DIBL), drive current (Ion), and leakage current (Ioff) are analyzed. The results indicate that RDD in extension can lead to substantial variability, especially for SS, DIBL, and Ion and should be taken into account together with that in channel to get an accurate estimation on RDF. Meanwhile, higher doping concentration of extension region is suggested from the perspective of overall variability control.