Controls on stream water dissolved mercury in three mid-Appalachian forested headwater catchments

NASA Astrophysics Data System (ADS)

Riscassi, Ami L.; Scanlon, Todd M.

2011-12-01

Determining the controls on dissolved mercury (HgD) transport is necessary to improve estimations of export from unmonitored watersheds and to forecast responses to changes in deposition and other environmental forcings. Stream water HgD and dissolved organic carbon (DOC) were evaluated over a range of discharge conditions in three streams within Shenandoah National Park, VA. Watersheds are distinguished by stream water pH (ranging from neutral to acidic) and soil size fractioning (ranging from clays to sands). At all sites, discharge was a significant but poor predictor of HgD concentrations (r2 from 0.13-0.52). HgD was strongly coupled with DOC at all sites (r2 from 0.74-0.89). UV absorbance at 254 nm (UV254), a proxy for DOC quantity and quality, slightly improved the predictions of HgD. Mean DOC quality differed between streams, with less aromatic DOC mobilized from the more acidic watershed. The site with less aromatic DOC and sandy soils mobilized more Hg to the stream for the same quantity and quality of DOC, likely due to the reduced capacity of the larger-grained soils to retain Hg, leaving a greater fraction associated with the organic matter. A similar amount of 0.54 ng HgD/mg DOC is transported at all sites, suggesting the less aromatic DOC transports less Hg per unit DOC, offsetting the effects of soil type. This research demonstrates that soil composition and DOC quality influence HgDexport. We also provide evidence that soil organic carbon is a primary control on Hg-DOC ratios (0.12-1.4 ng mg-1) observed across the U.S. and Sweden.

Effects of Land Use on Stable Carbon Isotopic Composition and Concentration of Dissolved Organic Carbon (DOC) and Dissolved Inorganic Carbon (DIC) in Southeastern US Piedmont Headwater Streams

EPA Science Inventory

Stable carbon isotopic composition (delta 13C) and concentrations of DOC and DIC were measured in stream water samples collected monthly in 15 headwater streams from an area with extensive poultry and cattle production and a rapidly growing human population. Linear regression te...

Dissolved organic carbon fluxes in the Middle Atlantic Bight: An integrated approach based on satellite data and ocean model products

NASA Astrophysics Data System (ADS)

Mannino, Antonio; Signorini, Sergio R.; Novak, Michael G.; Wilkin, John; Friedrichs, Marjorie A. M.; Najjar, Raymond G.

2016-02-01

Continental margins play an important role in global carbon cycle, accounting for 15-21% of the global marine primary production. Since carbon fluxes across continental margins from land to the open ocean are not well constrained, we undertook a study to develop satellite algorithms to retrieve dissolved organic carbon (DOC) and combined these satellite data with physical circulation model products to quantify the shelf boundary fluxes of DOC for the U.S. Middle Atlantic Bight (MAB). Satellite DOC was computed through seasonal relationships of DOC with colored dissolved organic matter absorption coefficients, which were derived from an extensive set of in situ measurements. The multiyear time series of satellite-derived DOC stocks (4.9 Teragrams C; Tg) shows that freshwater discharge influences the magnitude and seasonal variability of DOC on the continental shelf. For the 2010-2012 period studied, the average total estuarine export of DOC into the MAB shelf is 0.77 Tg C yr-1 (year). The integrated DOC tracer fluxes across the shelf boundaries are 12.1 Tg C yr-1 entering the MAB from the southwest alongshore boundary, 18.5 Tg C yr-1 entering the MAB from the northeast alongshore boundary, and 29.0 Tg C yr-1 flowing out of the MAB across the entire length of the 100 m isobath. The magnitude of the cross-shelf DOC flux is quite variable in time (monthly) and space (north to south). The highly dynamic exchange of water along the shelf boundaries regulates the DOC budget of the MAB at subseasonal time scales.

Dissolved organic carbon fluxes in the Middle Atlantic Bight: An integrated approach based on satellite data and ocean model products.

PubMed

Mannino, Antonio; Signorini, Sergio R; Novak, Michael G; Wilkin, John; Friedrichs, Marjorie A M; Najjar, Raymond G

2016-02-01

Continental margins play an important role in global carbon cycle, accounting for 15-21% of the global marine primary production. Since carbon fluxes across continental margins from land to the open ocean are not well constrained, we undertook a study to develop satellite algorithms to retrieve dissolved organic carbon (DOC) and combined these satellite data with physical circulation model products to quantify the shelf boundary fluxes of DOC for the U.S. Middle Atlantic Bight (MAB). Satellite DOC was computed through seasonal relationships of DOC with colored dissolved organic matter absorption coefficients, which were derived from an extensive set of in situ measurements. The multiyear time series of satellite-derived DOC stocks (4.9 Teragrams C; Tg) shows that freshwater discharge influences the magnitude and seasonal variability of DOC on the continental shelf. For the 2010-2012 period studied, the average total estuarine export of DOC into the MAB shelf is 0.77 Tg C yr -1 (year). The integrated DOC tracer fluxes across the shelf boundaries are 12.1 Tg C yr -1 entering the MAB from the southwest alongshore boundary, 18.5 Tg C yr -1 entering the MAB from the northeast alongshore boundary, and 29.0 Tg C yr -1 flowing out of the MAB across the entire length of the 100 m isobath. The magnitude of the cross-shelf DOC flux is quite variable in time (monthly) and space (north to south). The highly dynamic exchange of water along the shelf boundaries regulates the DOC budget of the MAB at subseasonal time scales.

Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater.

PubMed

Chapelle, Francis H; Bradley, Paul M; McMahon, Peter B; Kaiser, Karl; Benner, Ron

2012-01-01

Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA(254)) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems. Ground Water © 2011, National Ground Water Association. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

DOC and nitrate export linked to dominant rainfall-runoff processes, end-members and seasonality - a long-term high frequency measurement campaign

NASA Astrophysics Data System (ADS)

Schwab, M. P.; Klaus, J.; Pfister, L.; Weiler, M.

2016-12-01

Over the past decades, stream sampling protocols for hydro-geochemical parameters were often limited by logistical and technological constraints. While long-term monitoring protocols were typically based on weekly sampling intervals, high frequency sampling was commonly limited to a few single events. In this contribution, we combined high frequency and long-term measurements to understand DOC and nitrate dynamics in a forest headwater for different runoff events and seasons. Our study area is the forested Weierbach catchment (0.47 km2) in Luxembourg, where the fractured schist bedrock is covered by cambisol soils. The runoff response is characterized by a double peak behaviour. The first peak occurs during or right after a rainfall event triggered by fast near surface runoff generation processes, while a second delayed peak lasts several days and is generated by subsurface flow. This second peak occurs only if a distinct storage threshold of the catchment is exceeded. Our observations were carried out with a field deployable UV-Vis spectrometer measuring DOC and nitrate concentrations in-situ at 15 min intervals for more than two years. In addition, a long-term validation was carried out with data obtained from the analysis of water collected with grab samples. The long-term, high-frequency measurements allowed us to calculate a complete and detailed balance of DOC and nitrate export over two years. Transport behaviour of the DOC and nitrate showed different dynamics between the first and second hydrograph peaks. DOC is mainly exported during the first peaks, while nitrate is mostly exported during the delayed second peaks. Biweekly end-member measurement of soil and groundwater over several years enables us to link the behaviour of DOC and nitrate export to various end-members in the catchment. Altogether, the long-term and high-frequency time series provides the opportunity to study DOC and nitrate export processes without having to just rely only on either a few single event measurements or coarse measurement protocols.

On-line Eclipse Resources from the U.S. Naval Observatory: Planning Ahead for April 2024

NASA Astrophysics Data System (ADS)

Fredericks, Amy C.; Bartlett, J. L.; Bell, S.; Stapleton, J. C.

2014-01-01

On 8 April 2024, “…night from mid-day…” (Archilochus, 648 BCE) will appear to fortunate observers along a narrow band, approximately 115 mi (185 km) wide, that crosses fifteen states from Texas to Maine. In response to growing interest in the two total solar eclipses that will sweep the continental United States in the next 11 years, the U.S. Naval Observatory has developed an on-line resource center with direct links to 2024-specific services: the 2024 April 8 Total Solar Eclipse page (http://aa.usno.navy.mil/data/docs/Eclipse2024.php). The Solar Eclipse Computer (http://aa.usno.navy.mil/data/docs/SolarEclipses.php) calculates tables of local circumstances for events visible throughout the world. A similar service is available for lunar eclipses, Lunar Eclipse Computer (http://aa.usno.navy.mil/data/docs/LunarEclipse.php). The USNO Eclipse Portal (http://astro.ukho.gov.uk/eclbin/query_usno.cgi) provides diagrams and animations showing the global circumstances for events visible throughout the world and local circumstances for events visible at selected locations. The Web site, which includes both solar and lunar eclipses, is a joint effort with Her Majesty’s Nautical Almanac Office. The Eclipses of the Sun and Moon page (http://aa.usno.navy.mil/data/docs/UpcomingEclipses.php) links to electronic copies of the visibility maps from The Astronomical Almanac. The Eclipse Reference List (http://aa.usno.navy.mil/faq/docs/eclipse_ref.php) is a representative survey of the available literature for those interested in delving into these phenomena, either technically or historically. As exciting as the 2024 total solar eclipse, another spectacular event will precede it; a total solar eclipse will cross a different swath of the continent on August 21, 2017. The U.S. Naval Observatory has a resource center for that event as well (http://aa.usno.navy.mil/data/docs/Eclipse2017.php) . If your plans for 2024 are not yet made, visit the 2024 April 8 Total Solar Eclipse page to prepare for up to 4 minutes 31 seconds of “unexampled beauty, grandeur, and impressiveness” (Newcomb 1890) and of darkness.

14 CFR 45.1 - Applicability.

Code of Federal Regulations, 2011 CFR

2011-01-01

... and registration marking of U.S. registered aircraft. [Doc. No. 2047, 29 FR 3223, Mar. 11, 1964, as...) Nationality and registration marking of U.S. registered aircraft. ... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT IDENTIFICATION...

Understanding the relationship between DOC and nitrate export and dominant rainfall-runoff processes through long-term high frequency measurements

NASA Astrophysics Data System (ADS)

Schwab, Michael; Klaus, Julian; Pfister, Laurent; Weiler, Markus

2016-04-01

Over the past decades, stream sampling protocols for hydro-geochemical parameters were often limited by logistical and technological constraints. While long-term monitoring protocols were typically based on weekly sampling intervals, high frequency sampling was commonly limited to a few single events. In our study, we combined high frequency and long-term measurements to understand the DOC and nitrate behaviour and dynamics for different runoff events and seasons. Our study area is the forested Weierbach catchment (0.47 km2) in Luxembourg. The fractured schist bedrock is covered by cambisol soils. The runoff response of the catchment is characterized by a double peak behaviour. A first discharge peak occurs during or right after a rainfall event (triggered by fast near surface runoff generation processes), while a second delayed peak lasts several days (generated by subsurface flow/ shallow groundwater flow). Peaks in DOC concentrations are closely linked to the first discharge peak, whereas nitrate concentrations follow the second peak. Our observations were carried out with the field deployable instrument spectro::lyser (scan Messtechnik GmbH). This instrument relies on the principles of UV-Vis spectrometry and measures DOC and nitrate concentrations. The measurements were carried out at a high frequency of 15 minutes in situ in the Weierbach creek for more than two years. In addition, a long-term validation was carried out with data obtained from the analysis of water collected with automatic samplers. The long-term, high-frequency measurements allowed us to calculate a complete and detailed balance of DOC and nitrate export over two years. Transport behaviour of the DOC and nitrate showed different dynamics between the first and second hydrograph peaks. DOC is mainly exported during first peaks, while nitrate is mostly exported during the delayed second peaks. In combination with other measurements in the catchment, the long and detailed observations have enabled us to derive relationships between DOC and nitrate export and different catchment states: soil wetness and groundwater levels, precipitation and seasonality. Altogether, the long-term and high-frequency time series provides the opportunity to study DOC and nitrate export without having to just rely only on either a few single event measurements or coarse measurement protocols.

Studying dissolved organic carbon export from the Penobscot Watershed in to Gulf of Maine using Regional Hydro-Ecological Simulation System (RHESSys)

NASA Astrophysics Data System (ADS)

Rouhani, S. F. B. B.; Schaaf, C.; Douglas, E. M.; Choate, J. S.; Yang, Y.; Kim, J.

2014-12-01

The movement of Dissolved Organic Carbon (DOC) from terrestrial system into aquatic system plays an important role for carbon sequestration in ecosystems and affects the formation of soil organic matters.Carbon cycling, storage, and transport to marine systems have become critical issues in global-change science, especially with regard to northern latitudes (Freeman et al., 2001; Benner et al., 2004). DOC, as an important composition of the carbon cycling, leaches from the terrestrial watersheds is a large source of marine DOC. The Penobscot River basin in north-central Maine is the second largest watershed in New England, which drains in to Gulf of Maine. Approximately 89% of the watershed is forested (Griffith and Alerich, 1996).Studying temporal and spatial changes in DOC export can help us to understand terrestrial carbon cycling and to detect any shifts from carbon sink to carbon source or visa versa in northern latitude forested ecosystems.Despite for the importance of understanding carbon cycling in terrestrial and aquatic biogeochemistry, the Doc export, especially the combination of DOC production from bio-system and DOC transportation from the terrestrial in to stream has been lightly discussed in most conceptual or numerical models. The Regional Hydro-Ecological Simulation System (RHESSys), which has been successfully applied in many study sites, is a physical process based terrestrial model that has the ability to simulate both the source and transportation of DOC by combining both hydrological and ecological processes. The focus of this study is on simulating the DOC concentration and flux from the land to the water using RHESSys in the Penobscot watershed. The simulated results will be compared with field measurement of DOC from the watershed to explore the spatial and temporal DOC export pattern. This study will also enhance our knowledge to select sampling locations properly and also improve our understanding on DOC production and transportation in terrestrial forest ecosystem.

Fingerprinting Dissolved Organic Carbon (DOC) Sources with Specific UV Absorbance (SUVA) and Fluorescence

NASA Astrophysics Data System (ADS)

van Verseveld, W. J.; Lajtha, K.; McDonnell, J. J.

2007-12-01

DOC is an important water quality constituent because it is an important food source for stream biota, it plays a significant role in metal toxicity and transport, and protects aquatic organisms by absorbing visible and UV light. However, sources of stream DOC and changes in DOC quality at storm and seasonal scales remain poorly understood. We characterized DOC concentrations and SUVA (as an indicator of aromaticity) at the plot, hillslope and catchment scale during and between five storm events over the period Fall 2004 until Spring 2005, in WS10, H.J. Andrews, Oregon, USA. This study site has hillslopes that issue directly into the stream. This enabled us to compare a trenched hillslope response to the stream response without the influence of a riparian zone. The main result of this study was that SUVA in addition to DOC was needed to fingerprint sources of DOC. Stream water and lateral subsurface flow showed a clockwise DOC and SUVA hysteresis pattern. Both organic horizon water and transient groundwater were characterized by high DOC concentrations and SUVA values, while DOC concentrations and SUVA values in soil water decreased with depth in the soil profile. This indicates transient groundwater was an important contributor to high DOC concentrations and SUVA values during storm events. During the falling limb of the hydrograph deep soil water and seepage groundwater based on SUVA values contributed significantly to lateral subsurface flow and stream water. Preliminary results showed that fluorescence of stream water and lateral subsurface flow continuously measured with a fluorometer was significantly related to UV-absorbance during a December storm event. Finally, SUVA of lateral subsurface flow was lower than SUVA of stream water at the seasonal scale, indicating a difference in mixing of water sources at the hillslope and catchment scale. Overall, our results show that SUVA and fluorescence are useful tracers for fingerprinting DOC sources.

Comparing Stream DOC Fluxes from Sensor- and Sample-Based Approaches

NASA Astrophysics Data System (ADS)

Shanley, J. B.; Saraceno, J.; Aulenbach, B. T.; Mast, A.; Clow, D. W.; Hood, K.; Walker, J. F.; Murphy, S. F.; Torres-Sanchez, A.; Aiken, G.; McDowell, W. H.

2015-12-01

DOC transport by streamwater is a significant flux that does not consistently show up in ecosystem carbon budgets. In an effort to quantify stream DOC flux, we analyzed three to four years of high-frequency in situ fluorescing dissolved organic matter (FDOM) concentrations and turbidity measured by optical sensors at the five diverse forested and/or alpine headwater sites of the U.S. Geological Survey (USGS) Water, Energy, and Biogeochemical Budgets (WEBB) program. FDOM serves as a proxy for DOC. We also took discrete samples over a range of hydrologic conditions, using both manual weekly and automated event-based sampling. After compensating FDOM for temperature effects and turbidity interference - which was successful even at the high-turbidity Luquillo, PR site -- we evaluated the DOC-FDOM relation based on discrete sample DOC analyses matched to corrected FDOM at the time of sampling. FDOM was a moderately robust predictor of DOC, with r2 from 0.60 to more than 0.95 among sites. We then formed continuous DOC time series by two independent approaches: (1) DOC predicted from FDOM; and (2) the composite method, based on modeled DOC from regression on stream discharge, season, air temperature, and time, forcing the model to observations and adjusting modeled concentrations between observations by linearly-interpolated model residuals. DOC flux from each approach was then computed directly as concentration times discharge. DOC fluxes based on the sensor approach were consistently greater than the sample-based approach. At Loch Vale, CO (2.5 years) and Panola Mountain GA (1 year), the difference was 5-17%. At Sleepers River, VT (3 years), preliminary differences were greater than 20%. The difference is driven by the highest events, but we are investigating these results further. We will also present comparisons from Luquillo, PR, and Allequash Creek, WI. The higher sensor-based DOC fluxes could result from their accuracy during hysteresis, which is difficult to model. In at least one case the higher sensor-based DOC flux was linked to an unsampled event outside the range of the concentration model. Sensors require upkeep and vigilance with the data, but have the potential to yield more accurate fluxes than sample-based approaches.

Century-long increasing trend and variability of dissolved organic carbon export from the Mississippi River basin driven by natural and anthropogenic forcing

NASA Astrophysics Data System (ADS)

Ren, Wei; Tian, Hanqin; Cai, Wei-Jun; Lohrenz, Steven E.; Hopkinson, Charles S.; Huang, Wei-Jen; Yang, Jia; Tao, Bo; Pan, Shufen; He, Ruoying

2016-09-01

There has been considerable debate as to how natural forcing and anthropogenic activities alter the timing and magnitude of the delivery of dissolved organic carbon (DOC) to the coastal ocean, which has ramifications for the ocean carbon budget, land-ocean interactions, and coastal life. Here we present an analysis of DOC export from the Mississippi River to the Gulf of Mexico during 1901-2010 as influenced by changes in climate, land use and management practices, atmospheric CO2, and nitrogen deposition, through the integration of observational data with a coupled hydrologic/biogeochemical land model. Model simulations show that DOC export in the 2000s increased more than 40% since the 1900s. For the recent three decades (1981-2010), however, our simulated DOC export did not show a significant increasing trend, which is consistent with observations by U.S. Geological Survey. Our factorial analyses suggest that land use and land cover change, including land management practices (LMPs: i.e., fertilization, irrigation, tillage, etc.), were the dominant contributors to the century-scale trend of rising total riverine DOC export, followed by changes in atmospheric CO2, nitrogen deposition, and climate. Decadal and interannual variations of DOC export were largely attributed to year-to-year climatic variability and extreme flooding events, which have been exacerbated by human activity. LMPs show incremental contributions to DOC increase since the 1960s, indicating the importance of sustainable agricultural practices in coping with future environmental changes such as extreme flooding events. Compared to the observational-based estimate, the modeled DOC export was 20% higher, while DOC concentrations were slightly lower. Further refinements in model structure and input data sets should enable reductions in uncertainties in our prediction of century-long trends in DOC.

Assessing the relative bioavailability of DOC in regional groundwater systems

USGS Publications Warehouse

Chapelle, Francis H.; Bradley, Paul M.; Journey, Celeste A.; McMahon, Peter B.

2013-01-01

It has been hypothesized that the degree to which a hyperbolic relationship exists between concentrations of dissolved organic carbon (DOC) and dissolved oxygen (DO) in groundwater may indicate the relative bioavailability of DOC. This hypothesis was examined for 73 different regional aquifers of the United States using 7745 analyses of groundwater compiled by the National Water Assessment (NAWQA) program of the U.S. Geological Survey. The relative reaction quotient (RRQ), a measure of the curvature of DOC concentrations plotted versus DO concentrations and regressed to a decaying hyperbolic equation, was used to assess the relative bioavailability of DOC. For the basalt aquifer of Oahu, Hawaii, RRQ values were low (0.0013 mM−2), reflecting a nearly random relationship between DOC and DO concentrations. In contrast, on the island of Maui, treated sewage effluent injected into a portion of the basalt aquifer resulted in pronounced hyperbolic DOC-DO behavior and a higher RRQ (142 mM−2). RRQ values for the 73 aquifers correlated positively with mean concentrations of ammonia, dissolved iron, and manganese, and correlated negatively with mean pH. This indicates that greater RRQ values are associated with greater concentrations of the final products of microbial reduction reactions. RRQ values and DOC concentrations were negatively correlated with the thickness of the unsaturated zone (UNST) and depth to the top of the screened interval. Finally, RRQ values were positively correlated with mean annual precipitation (MAP), and the highest observed RRQ values were associated with aquifers receiving MAP rates ranging between 900 and 1300 mm/year. These results are uniformly consistent with the hypothesis that the hyperbolic behavior of DOC-DO plots, as quantified by the RRQ metric, can be an indicator of relative DOC bioavailability in groundwater systems.

Dissolved organic carbon fluxes in the Middle Atlantic Bight: An integrated approach based on satellite data and ocean model products

PubMed Central

Mannino, Antonio; Signorini, Sergio R.; Novak, Michael G.; Wilkin, John; Friedrichs, Marjorie A. M.; Najjar, Raymond G.

2017-01-01

Continental margins play an important role in global carbon cycle, accounting for 15–21% of the global marine primary production. Since carbon fluxes across continental margins from land to the open ocean are not well constrained, we undertook a study to develop satellite algorithms to retrieve dissolved organic carbon (DOC) and combined these satellite data with physical circulation model products to quantify the shelf boundary fluxes of DOC for the U.S. Middle Atlantic Bight (MAB). Satellite DOC was computed through seasonal relationships of DOC with colored dissolved organic matter absorption coefficients, which were derived from an extensive set of in situ measurements. The multiyear time series of satellite-derived DOC stocks (4.9 Teragrams C; Tg) shows that freshwater discharge influences the magnitude and seasonal variability of DOC on the continental shelf. For the 2010–2012 period studied, the average total estuarine export of DOC into the MAB shelf is 0.77 Tg C yr−1 (year). The integrated DOC tracer fluxes across the shelf boundaries are 12.1 Tg C yr−1 entering the MAB from the southwest alongshore boundary, 18.5 Tg C yr−1 entering the MAB from the northeast alongshore boundary, and 29.0 Tg C yr−1 flowing out of the MAB across the entire length of the 100 m isobath. The magnitude of the cross-shelf DOC flux is quite variable in time (monthly) and space (north to south). The highly dynamic exchange of water along the shelf boundaries regulates the DOC budget of the MAB at subseasonal time scales. PMID:29201582

14 CFR 45.1 - Applicability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... certificated products; and (c) Nationality and registration marking of U.S. registered aircraft. [Doc. No. 2047... articles; and (b) Nationality and registration marking of U.S. registered aircraft. ... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT IDENTIFICATION...

Designing a Dynamic Data Driven Application System for Estimating Real-Time Load of DOC in a River

NASA Astrophysics Data System (ADS)

Ouyang, Y.; None

2011-12-01

Understanding the dynamics of naturally occurring dissolved organic carbon (DOC) in a river is central to estimating surface water quality, aquatic carbon cycling, and climate change. Currently, determination of DOC in surface water is primarily accomplished by manually collecting samples for laboratory analysis, which requires at least 24 hours. In other words, no effort has been devoted to monitoring real-time variations of DOC in a river due to the lack of suitable and/or cost-effective wireless sensors. However, when considering human health, carbon footprints, and effects of urbanization, industry, and agriculture on water resource supply, timely DOC information may be critical. We have developed here a new paradigm, a dynamic data driven application system (DDDAS), for estimating the real-time load of DOC into a river. This DDDAS consisted of the following four components: (1) a Visual Basic (VB) program for downloading US Geological Survey real-time chlorophyll and discharge data; (2) a STELLA model for evaluating real-time DOC load based on the relationship between chlorophyll a, DOC, and river discharge; (3) a batch file for linking the VB program and STELLA model; and (4) a Microsoft Windows Scheduled Tasks wizard for executing the model and displaying output on a computer screen at selected times. Results show that the real-time load of DOC into the St. Johns River basin near Satsuma, Putnam County, Florida, USA varied over a range from -13,143 to 29,248 kg/h at the selected site in Florida, USA. The negative loads occurred because of the back flow in the estuarine reach of the river. The cumulative load of DOC in the river for the selected site at the end of the simulation (178 hours) was about 1.2 tons. Our results support the utility of the DDDAS developed in this study for estimating the real-time variations of DOC in river ecosystems.

Calculating Depth of Closure Using WIS Hindcast Data

DTIC Science & Technology

2016-03-01

revised the Hallermeier (1978, 1981) equations using data from the Duck , NC, U.S. Army Corps of Engineers (USACE) Field Research Facility. Many studies ... Study (WIS) hindcast stations along the United States coastlines. The results summarized in this CHETN are available in the form of a spreadsheet on...theoretical definition of DOC came from a study by Hallermeier (1978, 1981) using wave tank and field data. Initially, the DOC was related to the critical

Plant diversity induces a shift of DOC concentration over time - results from long term and large scale experiment

NASA Astrophysics Data System (ADS)

Lange, Markus; Gleixner, Gerd

2016-04-01

Plant diversity has been demonstrated as a crucial factor for soil organic carbon (SOC) storage. The horizontal SOC formation in turn is strongly impacted by the relative small but consistent flow of dissolved organic carbon (DOC) in soils. In this process, pore water leaches plant material and already stored SOC while simultaneously these leachates are transported downwards. However, there is a big uncertainty about the drivers of DOC flux; in particular about the importance of biological processes. We investigated the impact of plant diversity and other biotic drivers on DOC concentrations and total DOC fluxes (concentration × sampled water amount). In addition, we considered abiotic factors such as weather and soil conditions to assess the relative importance of biotic and abiotic drivers and how their importance changes over time. We used a comprehensive data set, gathered in the frame of the long-term biodiversity experiment "The Jena Experiment". Permanent monitoring started directly after establishment of the field site in 2002 and is still running. This enabled us to trace the impact of plant communities with their increasing establishment over the time on DOC concentration. We found the amount of sampled pore water best explained by rainfall, while it was not related to plant associated variables. Directly after establishing the experimental site, DOC concentrations were highest and then decreasing with time. In the first period of the experiment plant diversity had no or even a slightly negative impact on DOC concentrations. The direction of the plant diversity effect on DOC concentrations changed over time; namely in later phases we observed highest DOC concentrations on plots with high plant diversity. Moreover, DOC concentrations were negatively affected by increased amounts of sampled pore water indicating a dilution effect. Even though this impact was highly significant; its effect size was even less pronounced at later time points. In summary, inter annual differences of total DOC fluxes reflect patterns of sampled soil water, indicating the major driver of total DOC flux is driven by rainfall. In contrast, intra annually the DOC flux reflects the patterns of the DOC concentrations with a strengthening positive impact of plant diversity among time. Our results show that variations of the total DOC fluxes are more affected by the pore water flux than by the differences in DOC concentrations as the magnitude of the pore water flux exceeds the magnitude of concentrations by a factor of 20. This indicates that abiotic conditions set the frame in which biotic properties can drive the DOC flux. However, the biotic drivers are getting more important over time and might outperform the dominating role of the abiotic conditions on the longer term.

77 FR 44704 - Generalized System of Preferences (GSP): Notice of Initiation of the 2012 Annual GSP Product and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-30

... Sanford, Assistant U.S. Trade Representative for Small Business, Market Access & Industrial Competitiveness,Office of the U.S. Trade Representative. [FR Doc. 2012-18426 Filed 7-27-12; 8:45 am] BILLING CODE...

Summary Report of Air Quality Modeling Research Activities for 2007

EPA Science Inventory

Through a Memorandum of Understanding (MOU) and Memorandum of Agreement (MOA) between the U.S. Department of Commerce (DOC) and the U.S. Environmental Protection Agency (EPA), the Atmospheric Sciences Modeling Division (ASMD) of the National Oceanic and Atmospheric Administration...

Validation of the digital opacity compliance system under regulatory enforcement conditions.

PubMed

McFarland, Michael J; Rasmussen, Steve L; Stone, Daniel A; Palmer, Glenn R; Wander, Joseph D

2006-09-01

U.S. Environmental Protection Agency (EPA) Emission Measurement Center in conjunction with EPA Regions VI and VIII, the state of Utah, and the U.S. Department of Defense have conducted a series of long-term pilot and field tests to determine the accuracy and reliability of a visible opacity monitoring system consisting of a conventional digital camera and a separate computer software application for plume opacity determination. This technology, known as the Digital Opacity Compliance System (DOCS), has been successfully demonstrated at EPA-sponsored Method-9 "smoke schools", as well as at a number of government and commercially operated industrial facilities. Results from the current DOCS regulatory pilot study demonstrated that, under regulatory enforcement conditions, the average difference in opacity measurement between the DOCS technology and EPA Reference Method 9 (Method 9) was 1.12%. This opacity difference, which was computed from the evaluation of 241 regulated air sources, was found to be statistically significant at the 99% confidence level. In evaluating only those sources for which a nonzero visible opacity level was recorded, the

75 FR 43208 - Withdrawal of Regulatory Guide 5.17

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-23

... Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 20555.... Introduction The U.S. Nuclear Regulatory Commission (NRC) is withdrawing Regulatory Guide 5.17, ``Truck... Development Branch, Division of Engineering, Office of Nuclear Regulatory Research. [FR Doc. 2010-18077 Filed...

78 FR 14773 - U.S. Environmental Solutions Toolkit-Medical Waste

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-07

...--Medical Waste AGENCY: International Trade Administration, DOC. ACTION: Notice and Request for Comment... or services relevant to management of medical waste. The Department of Commerce continues to develop... foreign end-users of environmental technologies that will outline U.S. approaches to a series of...

75 FR 79049 - Notice of Issuance of Regulatory Guide

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-17

..., Division of Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission... INFORMATION: I. Introduction The U.S. Nuclear Regulatory Commission (NRC) is issuing a revision to an existing... Development Branch, Division of Engineering, Office of Nuclear Regulatory Research. [FR Doc. 2010-31731 Filed...

76 FR 76477 - Generalized System of Preferences (GSP): Extension of Deadlines for Filing Petitions for the 2011...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-07

... the U.S. Trade Representative. [FR Doc. 2011-31316 Filed 12-6-11; 8:45 am] BILLING CODE 3190-w2-P ... after the due date. William D. Jackson, Deputy Assistant, U.S. Trade Representative for the Generalized...

Toward a quantitative and empirical dissolved organic carbon budget for the Gulf of Maine, a semienclosed shelf sea

NASA Astrophysics Data System (ADS)

Balch, William; Huntington, Thomas; Aiken, George; Drapeau, David; Bowler, Bruce; Lubelczyk, Laura; Butler, Kenna

2016-02-01

A time series of organic carbon export from Gulf of Maine (GoM) watersheds was compared to a time series of biological, chemical, bio-optical, and hydrographic properties, measured across the GoM between Yarmouth, NS, Canada, and Portland, ME, U.S. Optical proxies were used to quantify the dissolved organic carbon (DOC) and particulate organic carbon in the GoM. The Load Estimator regression model applied to river discharge data demonstrated that riverine DOC export (and its decadal variance) has increased over the last 80 years. Several extraordinarily wet years (2006-2010) resulted in a massive pulse of chromophoric dissolved organic matter (CDOM; proxy for DOC) into the western GoM along with unidentified optically scattering material (<0.2 µm diameter). A survey of DOC in the GoM and Scotian Shelf showed the strong influence of the Gulf of Saint Lawrence on the DOC that enters the GoM. A deep plume of CDOM-rich water was observed near the coast of Maine which decreased in concentration eastward. The Forel-Ule color scale was derived and compared to the same measurements made in 1912-1913 by Henry Bigelow. Results show that the GoM has yellowed in the last century, particularly in the region of the extension of the Eastern Maine Coastal Current. Time lags between DOC discharge and its appearance in the GoM increased with distance from the river mouths. Algae were also a significant source of DOC but not CDOM. Gulf-wide algal primary production has decreased. Increases in precipitation and DOC discharge to the GoM are predicted over the next century.

Toward a quantitative and empirical dissolved organic carbon budget for the Gulf of Maine, a semienclosed shelf sea

USGS Publications Warehouse

Balch, William; Huntington, Thomas G.; Aiken, George R.; Drapeau, David; Bowler, Bruce; Lubelczyk, Laura; Butler, Kenna D.

2016-01-01

A time series of organic carbon export from Gulf of Maine (GoM) watersheds was compared to a time series of biological, chemical, bio-optical, and hydrographic properties, measured across the GoM between Yarmouth, NS, Canada, and Portland, ME, U.S. Optical proxies were used to quantify the dissolved organic carbon (DOC) and particulate organic carbon in the GoM. The Load Estimator regression model applied to river discharge data demonstrated that riverine DOC export (and its decadal variance) has increased over the last 80 years. Several extraordinarily wet years (2006–2010) resulted in a massive pulse of chromophoric dissolved organic matter (CDOM; proxy for DOC) into the western GoM along with unidentified optically scattering material (<0.2 μm diameter). A survey of DOC in the GoM and Scotian Shelf showed the strong influence of the Gulf of Saint Lawrence on the DOC that enters the GoM. A deep plume of CDOM-rich water was observed near the coast of Maine which decreased in concentration eastward. The Forel-Ule color scale was derived and compared to the same measurements made in 1912–1913 by Henry Bigelow. Results show that the GoM has yellowed in the last century, particularly in the region of the extension of the Eastern Maine Coastal Current. Time lags between DOC discharge and its appearance in the GoM increased with distance from the river mouths. Algae were also a significant source of DOC but not CDOM. Gulf-wide algal primary production has decreased. Increases in precipitation and DOC discharge to the GoM are predicted over the next century.

Regional Monitoring of Acidic Lakes and Streams

EPA Pesticide Factsheets

This asset provides data on the acid-base status of lakes and streams. Key chemical indicators measured include: sulfate, nitrate, ammonium, chloride, Acid Neutralizing Capacity (ANC), pH, base cations, dissolved organic carbon (DOC), total aluminum. TIME and LTM are part of EPA's Environmental Monitoring and Assessment Program (EMAP). Long-term monitoring of the acid-base status (pH, ANC, SO4, NO3, NH4, DOC, base cations, Al) in lakes and streams. Monitoring is conducted in acid sensitive regions of the Eastern U.S.

Appreciation and Determination of the Hydrodynamic Qualities of Seaplanes

DTIC Science & Technology

1947-05-17

satisfqctory handling on the ~ atar , — Tincyclso provida maans i’o:comperati~e evaluations “ofdifYeront seaplanes and direct correlations between model...Washington, D. C. PUBLISHED BY: (Same) SAH May 47 ABSTRACT: DOC OAM. Unclass. _yjL English _2A_ ATI- 12970 (None) TN-1290 (Same) f...MOtCT HO. TN-1290 PUBLISHED BY: (Same) ruaawtto AS1HCT KO. DATO May 󈧳 DOC OJU1. Unclass. coumar U.S. i. NOUAM English FAOB 54 numuTiOKS

Organizational Implications of the U.S. Army’s Increasing Demand for Explosive Ordnance Disposal Capabilities

DTIC Science & Technology

2008-05-22

Washington D.C: Government Printing Office, 1976), 1-1 to 1-5. 43 Ibid, 2-1 to 2-32. 16 “orchestrated ballet of farm implements.”44 The Army’s...Orchestrated Ballet of Farm Implements”, Engineer Bulletin, August 1996, http://fas.org/man/dod 101/sys/land/docs /960800-greene2.htm (accessed 5 April...An Alternative to the Orchestrated Ballet of Farm Implements” Engineer Bulletin (August 1996), http://fas.org/man/dod_101/sys/land/docs/960800

Enhancing and Managing Regionally Oriented Individuals and Organizations

DTIC Science & Technology

2014-06-30

RAF. An additional challenge with the Army’s approach to RAF is funding. According to a recent article in Military Review, “very little ‘ juice ’ comes...http://www.hqmc.marines.mil/Portals/138/Docs/PL/ PLU /2012%20USMC%20Security%20Cooperation%20Narrative.pdf. 174 H.A.S.C. 112-89, Institutionalizing...Security Cooperation. 2012. http://www.hqmc.marines.mil/Portals/138/Docs/PL/ PLU /2012%20USMC%20Secur ity%20Cooperation%20Narrative.pdf. U.S. Air Force

Life cycle cost evaluation of the digital opacity compliance system.

PubMed

McFarland, Michael J; Palmer, Glenn R; Olivas, Arthur C

2010-01-01

The US Environmental Protection Agency (EPA) has established EPA Reference Method 9 (Method 9) as the preferred enforcement approach for verifying compliance with federal visible opacity standards. While Method 9 has an extensive history of successful employment, reliance on human observers to quantify visible emissions is inherently subjective, a characteristic that exposes Method 9 results to claims of inaccuracy, bias and, in some cases, outright fraud. The Digital Opacity Compliance System (DOCS), which employs commercial-off-the-shelf digital photography coupled with simple computer processing, is a new approach for quantifying visible opacity. The DOCS technology has been previously demonstrated to meet and, in many cases, surpass the Method 9 accuracy and reliability standards (McFarland et al., 2006). Beyond its performance relative to Method 9, DOCS provides a permanent visual record of opacity, a vital feature in legal compliance challenges. In recent DOCS field testing, the opacity analysis of two hundred and forty one (241) regulated air emissions from the following industrial processes: 1) industrial scrubbers, 2) emergency generators, 3) asphalt paving, 4) steel production and 5) incineration indicated that Method 9 and DOCS were statistically equivalent at the 99% confidence level. However, a life cycle cost analysis demonstrated that implementation of DOCS could potentially save a facility $15,732 per trained opacity observer compared to utilization of Method 9. Copyright 2009 Elsevier Ltd. All rights reserved.

Career paths through the U.S. EPA

EPA Science Inventory

In a recent survey of employee satisfaction, the U.S. EPA was ranked 6th of the 30 large federal agencies that were surveyed (http://data.bestplacestowork.org). I have been working as a post doc at the EPA since receiving my Ph.D. in ecological physiology from the University of ...

78 FR 17702 - Agency Information Collection Activities: Application for Action on an Approved Application or...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-22

... DEPARTMENT OF HOMELAND SECURITY U.S. Citizenship and Immigration Services [OMB Control Number 1615... Department of Homeland Security (DHS), U.S. Citizenship and Immigration Services (USCIS) invites the general....S. Citizenship and Immigration Services, Department of Homeland Security. [FR Doc. 2013-06582 Filed...

Dissolved organic carbon export and its contribution to the carbon budget in a boreal peat landscape undergoing rapid permafrost thaw

NASA Astrophysics Data System (ADS)

Sonnentag, O.; Fouche, J.; Helbig, M.; Karoline, W.; Hould Gosselin, G.; Hanisch, J.; Quinton, W. L.; Moore, T. R.

2017-12-01

Northern permafrost soils store 1035 ± 150 Pg of organic carbon in the first 3 m. In boreal lowlands with warm and thin isolated, sporadic and discontinuous permafrost, increasing temperatures cause a thaw-induced expansion of permafrost-free wetlands at the expense of forested permafrost peat plateaus. Permafrost thaw associated with warmer soils may enhance microbial decomposition of near-surface and deeper organic matter but also increase dissolved organic carbon (DOC) export to aquatic systems. Recent studies suggest that, under a warmer climate, the current net CO2 sink strength of boreal peat landscapes may decline over the next few decades, eventually turning them into net CO2 sources. DOC export from these organic-rich landscapes undergoing rapid permafrost thaw may play a non-negligible role for the carbon budget in a warmer climate. In this study, we quantify the DOC export from a boreal peat landscape in the southern Northwest Territories (Canada). We use half-hourly discharge measurements and DOC concentrations sampled at the outlets of three small catchments ( 0.1 km2) to quantify runoff and DOC export from April to August 2014, 2015 and 2016. We estimate the DOC export contribution to the overall carbon budget using concurrent eddy covariance measurements of net CO2 and methane exchanges. The primary control of DOC export is discharge. In 2016, 70% of the DOC was exported during the two weeks of the spring freshet in early May. DOC export from the three catchments was 3g C m-2 from April to August, which accounted for 15% of the annual net ecosystem exchange. For the same period, the cumulative methane emissions were 6 g C-CH4 m-2. Our findings suggest that thawing boreal peat landscapes along the southern limit of permafrost currently act as net carbon sinks with 11 g C m-2 y-1. Investigating the optical properties of the dissolved organic matter across the different landforms (e.g., transition between forested permafrost peat plateau and permafrost-free wetland) will allow us to assess the different contributions to catchment DOC export and better forecast the changes in DOC lability with permafrost thaw and wetland expansion. Associated with a more rainfall-controlled runoff regime, changes in DOC export with warming may affect the carbon budget in the southern boundaries of the permafrost region.

The role of DOM in nitrogen processing in streams across arctic regions affected by fire

NASA Astrophysics Data System (ADS)

Rodriguez-Cardona, B.; Schade, J. D.; Holmes, R. M.; Natali, S.; Mann, P. J.; Wymore, A.; Coble, A. A.; Prokishkin, A. S.; Zito, P.; Podgorski, D. C.; Spencer, R. G.; McDowell, W. H.

2017-12-01

In stream ecosystems, inputs of dissolved organic carbon (DOC) have a strong influence on nitrogen (N) processing. Previous studies have demonstrated that increases in DOC concentrations can promote greater N removal in many stream ecosystems. Most of what we know about C and N coupling comes from studies of temperate streams; less is known about this relationship in the Arctic. Streams in Arctic ecosystems are facing rapid changes in climate and disturbance regimes, in particular increasing fire frequencies that are likely to alter biogeochemical cycles. Although fires can lead to increases in NO3 concentrations in streams, the effects of fire on DOC (concentration and composition) have been difficult to generalize. We studied the relationships between DOC and N in two locations; the Central Siberian Plateau, Russia and the Yukon-Kuskokwim (YK) River Delta, Alaska. Streams in both regions show increases in NO3 concentrations after fire, while DOC concentrations decrease in Siberia but increase in streams within the YK-Delta. These patterns in DOC and NO3 create a gradient in DOC and nutrient concentrations, allowing us to study this coupling in a wider Pan-Arctic scope. In order to assess the role of DOC in Arctic N processing, we conducted NO3 and NH4 additions to stream microcosms at the Alaskan site as well as whole-stream additions in Siberia. We hypothesized that nutrient uptake would be high in older burn sites of Siberia and recently burned sites in the YK-Delta, due to greater DOC concentrations and availability. Our results suggest that nitrogen dynamics in the Alaskan sites is strongly responsive to C availability, but is less so in Siberian sites. The potential impacts of permafrost thawing and fires on DOM and nutrient dynamics thus appear to not be consistent across the Arctic suggesting that different regions of the Arctic have unique biogeochemical controls.

Preliminary assessment of DOC and THM precursor loads from a freshwater restored wetland, an agricultural field, and a tidal wetland in the Sacramento-San Joaquin River Delta

USGS Publications Warehouse

Fujii, R.; Bergamaschi, B.A.; Ganju, N.K.; Fleck, J.A.; Burow-Fogg, K.R.; Schoellhamer, D.; Deverel, S.J.

2003-01-01

Water exported from the Sacramento-San Joaquin River Delta supplies drinking water to more than 22 million people in California. At certain times of the year, Delta waters contain relatively high concentrations of dissolved organic carbon (DOC) and bromide. During these times, chlorination of Delta water for drinking water disinfection will form disinfection byproducts, such as trihalomethanes (THMs), that can exceed the U.S. Environmental Protection Agency's maximum contaminant level for THMs of 80 mg/L. Important sources of DOC and THM precursors (types of DOC that form THMs when chlorinated) to the Delta include rivers, drainage water from peat islands, water from wetlands and areas with extensive riparian vegetation, and in-channel growth of algae and macrophytes. Due to proposed ecosystem restoration and creation of wetlands in the Delta, there is an urgent need for information on the relative loads of DOC and THM precursors produced from three different land uses: restored wetlands constructed for subsidence mitigation, tidal wetlands, and agricultural operations. We have been conducting research in the Delta to provide this information. A restored wetland and agricultural field located on Twitchell Island, and a tidal wetland on Browns Island have been monitored for flow, DOC, and THM precursors. Initial results indicate that the loads of DOC and THM precursors are similar for the restored wetland (surface water only) and the agricultural field. These land uses produce DOC loads of about 14 and 11 g C/m2/yr, respectively, and THM precursor loads of about 1.7 and 1.0 g THM/m2/yr, respectively. Estimates of DOC and THM precursor loads for the tidal wetland site on Browns Island and seepage associated with the restored wetland are being developed.

Potential vulnerability of southeast Alaskan wetland soil carbon stocks to climate warming

NASA Astrophysics Data System (ADS)

Fellman, J.; D'Amore, D. V.; Hood, E. W.

2015-12-01

Carbon cycling along the high latitude coastal margins of Alaska is poorly understood relative to boreal and arctic ecosystems. The perhumid coastal temperate rainforest (PCTR) of southeast Alaska has some of the densest carbon stocks (>300 Mg C ha-1) in the world but the fate of these stocks with continued warming will balance on the poorly constrained rates of carbon accumulation and loss. We quantified the rate of dissolved organic carbon (DOC) and carbon dioxide (CO2) production from four different wetland types (rich fen, poor fen, forested wetland and cedar wetland) using controlled laboratory incubations of surface (10 cm) and subsurface (25 cm) soils incubated at 8 ºC and 15 ºC for 37 weeks. This design allowed us to determine the potential vulnerability of wetland soil carbon stocks to climate warming and partition organic matter mineralization into DOC and CO2 fluxes and its controls (e.g., wetland type and temperature). Furthermore, we used fluorescence characterization of DOC and laboratory bioassays to assess how climate warming may impact the quality and bioavailability of DOC delivered to fluvial systems. Soil depth and temperature strongly influenced carbon loss in all four wetland types with the greatest CO2 fluxes observed in the rich fen and greatest DOC fluxes observed in the poor fen. Of the fluxes, CO2 was the most sensitive to incubation temperature but DOC showed more variation with wetland type. Fluxes of DOC and CO2 were positively correlated only during the last few months of the incubation suggesting strong biotic control of DOC production developed as soil organic matter decomposition progressed. Moreover, bioavailable DOC and protein-like fluorescence were greatest in the initial soil extractions but dramatically decreased over the length of the incubations. Our findings suggest that soil organic matter decomposition will increase as the PCTR continues to warm, but this response will also will vary with wetland type.

77 FR 15841 - Generalized System of Preferences (GSP): Change in Hearing Date for the 2011 Annual GSP Product...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-16

...-9674, and the email address is [email protected] . William D. Jackson, Deputy Assistant U.S... Trade Policy Staff Committee, Office of the U.S. Trade Representative. [FR Doc. 2012-6454 Filed 3-15-12; 8:45 am] BILLING CODE 3190-W2-P ...

77 FR 55485 - Agency Information Collection Activities: H-2 Petitioner's Employment Related or Fee Related...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-10

... DEPARTMENT OF HOMELAND SECURITY U.S. Citizenship and Immigration Services [OMB Control Number 1615...-Day notice. SUMMARY: The Department of Homeland Security (DHS), U.S. Citizenship and Immigration.... Citizenship and Immigration Services, Department of Homeland Security. [FR Doc. 2012-22137 Filed 9-7-12; 8:45...

77 FR 55486 - Agency Information Collection Activities: Employment Eligibility Verification, Form I-9, OMB...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-10

... DEPARTMENT OF HOMELAND SECURITY U.S. Citizenship and Immigration Services [OMB Control Number 1615.... On August 22, 2012 the Department of Homeland Security, U.S. Citizenship and Immigration Services.... Citizenship and Immigration Services, Department of Homeland Security. [FR Doc. 2012-22138 Filed 9-7-12; 8:45...

Using Eco-hydrologic modeling in the Penobscot River Watershed to explore the role of climate and land use change on DOC concentration and flux

NASA Astrophysics Data System (ADS)

Rouhani, S. F. B. B.; Schaaf, C.; Douglas, E. M.; Huntington, T. G.; Kim, J.

2017-12-01

Dissolved Organic Carbon leaches from the terrestrial watersheds to serve as one of the largest sources of marine DOC. Runoff, slope, soil organic matter and land cover characteristics are the primary spatial factors controlling the variability of fluvial Dissolved Organic Carbon fluxes through the catchment. In large, more heterogeneous catchments, streamflow dissolved organic carbon dynamics are regulated by the combined effect of hydrological mechanisms and the proportion of major landscape elements, such as wetland and forested areas. A number of studies have demonstrated that the amount of wetlands, especially peatlands, controls the watershed level transport of DOC in streams.The Penobscot River Watershed is located in north-central Maine and drains into the Gulf of Maine. It is the second largest watershed in New England. The Penobscot River Watershed is primarily forested but also contains extensive bogs, marshes, and wooded swamps.Studying the spatial and temporal changes in DOC export in the Penobscot River Watershed allows us to better understand and detect carbon sinks to carbon source shifts (or vice versa) in northern forested ecosystems.The Regional Hydro-Ecological Simulation System, is a physical process based terrestrial model that has the ability to simulate both the source and transportation of DOC by combining both hydrological and ecological processes. The study is focused on simulating the DOC concentration and flux with RHESSys in the Penobscot River Watershed. The simulated results are compared with field measurements of DOC from the watershed and the model results from the LOADEST and the temporal DOC export patterns are explored. Future changes in the amount of streamflow DOC will also be investigated by using projected land cover and climate change scenarios. Incremental increases in the loss of wetland areas have been implemented to explore the sensitivity of this watershed to wetland loss and progressive changes in forested land cover have been implemented to understand the role of vegetation types to the DOC flux.The simulated daily streamflow for the period of 2004-2013 corresponded well with observed daily streamflowat USGS gauge station. in addition, the simulated DOC flux and concentration values matched well with observed data and LODEST model results.

Music in Research and Rehabilitation of Disorders of Consciousness: Psychological and Neurophysiological Foundations.

PubMed

Kotchoubey, Boris; Pavlov, Yuri G; Kleber, Boris

2015-01-01

According to a prevailing view, the visual system works by dissecting stimuli into primitives, whereas the auditory system processes simple and complex stimuli with their corresponding features in parallel. This makes musical stimulation particularly suitable for patients with disorders of consciousness (DoC), because the processing pathways related to complex stimulus features can be preserved even when those related to simple features are no longer available. An additional factor speaking in favor of musical stimulation in DoC is the low efficiency of visual stimulation due to prevalent maladies of vision or gaze fixation in DoC patients. Hearing disorders, in contrast, are much less frequent in DoC, which allows us to use auditory stimulation at various levels of complexity. The current paper overviews empirical data concerning the four main domains of brain functioning in DoC patients that musical stimulation can address: perception (e.g., pitch, timbre, and harmony), cognition (e.g., musical syntax and meaning), emotions, and motor functions. Music can approach basic levels of patients' self-consciousness, which may even exist when all higher-level cognitions are lost, whereas music induced emotions and rhythmic stimulation can affect the dopaminergic reward-system and activity in the motor system respectively, thus serving as a starting point for rehabilitation.

Music in Research and Rehabilitation of Disorders of Consciousness: Psychological and Neurophysiological Foundations

PubMed Central

Kotchoubey, Boris; Pavlov, Yuri G.; Kleber, Boris

2015-01-01

According to a prevailing view, the visual system works by dissecting stimuli into primitives, whereas the auditory system processes simple and complex stimuli with their corresponding features in parallel. This makes musical stimulation particularly suitable for patients with disorders of consciousness (DoC), because the processing pathways related to complex stimulus features can be preserved even when those related to simple features are no longer available. An additional factor speaking in favor of musical stimulation in DoC is the low efficiency of visual stimulation due to prevalent maladies of vision or gaze fixation in DoC patients. Hearing disorders, in contrast, are much less frequent in DoC, which allows us to use auditory stimulation at various levels of complexity. The current paper overviews empirical data concerning the four main domains of brain functioning in DoC patients that musical stimulation can address: perception (e.g., pitch, timbre, and harmony), cognition (e.g., musical syntax and meaning), emotions, and motor functions. Music can approach basic levels of patients’ self-consciousness, which may even exist when all higher-level cognitions are lost, whereas music induced emotions and rhythmic stimulation can affect the dopaminergic reward-system and activity in the motor system respectively, thus serving as a starting point for rehabilitation. PMID:26640445

Mapping Surface Water DOC in the Northern Gulf of Mexico Using CDOM Absorption Coefficients and Remote Sensing Imagery

NASA Astrophysics Data System (ADS)

Kelly, B.; Chelsky, A.; Bulygina, E.; Roberts, B. J.

2017-12-01

Remote sensing techniques have become valuable tools to researchers, providing the capability to measure and visualize important parameters without the need for time or resource intensive sampling trips. Relationships between dissolved organic carbon (DOC), colored dissolved organic matter (CDOM) and spectral data have been used to remotely sense DOC concentrations in riverine systems, however, this approach has not been applied to the northern Gulf of Mexico (GoM) and needs to be tested to determine how accurate these relationships are in riverine-dominated shelf systems. In April, July, and October 2017 we sampled surface water from 80+ sites over an area of 100,000 km2 along the Louisiana-Texas shelf in the northern GoM. DOC concentrations were measured on filtered water samples using a Shimadzu TOC-VCSH analyzer using standard techniques. Additionally, DOC concentrations were estimated from CDOM absorption coefficients of filtered water samples on a UV-Vis spectrophotometer using a modification of the methods of Fichot and Benner (2011). These values were regressed against Landsat visible band spectral data for those same locations to establish a relationship between the spectral data, CDOM absorption coefficients. This allowed us to spatially map CDOM absorption coefficients in the Gulf of Mexico using the Landsat spectral data in GIS. We then used a multiple linear regressions model to derive DOC concentrations from the CDOM absorption coefficients and applied those to our map. This study provides an evaluation of the viability of scaling up CDOM absorption coefficient and remote-sensing derived estimates of DOC concentrations to the scale of the LA-TX shelf ecosystem.

75 FR 52801 - Membership of the Performance Review Board (PRB)

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-27

... for Administration and Director of Human Resources (202) 395-7360. Lorraine Green, Deputy Assistant U.S. Trade Representative for Administration and Director of Human Resources. [FR Doc. 2010-21371...

Anthropogenic inputs of dissolved organic matter in New York Harbor

NASA Astrophysics Data System (ADS)

Gardner, G. B.; Chen, R. F.; Olavasen, J.; Peri, F.

2016-02-01

The Hudson River flows into the Atlantic Ocean through a highly urbanized region which includes New York City to the east and Newark, New Jersey to the west. As a result, the export of Dissolved Organic Carbon (DOC) from the Hudson to the Atlantic Ocean includes a significant anthropogenic component. A series of high resolution studies of the DOC dynamics of this system were conducted between 2003 and 2010. These included both the Hudson and adjacent large waterways (East River, Newark Bay, Kill Van Kull and Arthur Kill) using coastal research vessels and smaller tributaries (Hackensack, Pasaic and Raritan rivers) using a 25' boat. In both cases measurements were made using towed instrument packages which could be cycled from near surface to near bottom depths with horizontal resolution of approximately 20 to 200 meters depending on depth and deployment strategy. Sensors on the instrument packages included a CTD to provide depth and salinity information and a chromophoric dissolved organic matter(CDOM) fluorometer to measure the fluorescent fraction of the DOC. Discrete samples allowed calibration of the fluorometer and the CDOM data to be related to DOC. The combined data set from these cruises identified multiple scales of source and transport processes for DOC within the Hudson River/New York Harbor region. The Hudson carries a substantial amount of natural DOC from its 230 km inland stretch. Additional sources exist in fringing salt marshes adjacent to the Hackensack and Raritan rivers. However the lower Hudson/New Harbor region receives a large input of DOC from multiple publically owned treatment works (POTW) discharges. The high resolution surveys allowed us to elucidate the distribution of these sources and the manner in which they are rapidly mixed to create the total export. We estimate that anthropogenic sources account for up to 2.5 times the DOC flux contributed by natural processes.

Evaluation of acute copper toxicity to juvenile freshwater mussels (fatmucket, lampsilis siliquoidea) in natural and reconstituted waters

USGS Publications Warehouse

Wang, N.; Mebane, C.A.; Kunz, J.L.; Ingersoll, C.G.; May, T.W.; Arnold, W.R.; Santore, R.C.; Augspurger, T.; Dwyer, F.J.; Barniiart, M.C.

2009-01-01

The influence of dissolved organic carbon (DOC) and water composition on the toxicity of copper to juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea) were evaluated in natural and reconstituted waters. Acute 96-h copper toxicity tests were conducted at four nominal DOC concentrations (0, 2.5, 5, and 10 mg/L as carbon [C]) in dilutions of natural waters and in American Society for Testing and Materials (ASTM) reconstituted hard water. Toxicity tests also were conducted in ASTM soft, moderately hard, hard, and very hard reconstituted waters (nominal hardness 45-300 mg/L as CaCO3). Three natural surface waters (9.5-11 mg/L DOC) were diluted to obtain a series of DOC concentrations with diluted well water, and an extract of natural organic matter and commercial humic acid was mixed with ASTM hard water to prepare a series of DOC concentrations for toxicity testing. Median effective concentrations (EC50s) for dissolved copper varied >40-fold (9.9 to >396 ??g Cu/L) over all 21 treatments in various DOC waters. Within a particular type of DOC water, EC50s increased 5- to 12-fold across DOC concentrations of 0.3 to up to 11 mg C/L. However, EC50s increased by only a factor of 1.4 (21 30 ??g Cu/L) in the four ASTM waters with wide range of water hardness (52-300 mg CaCO 3/L). Predictions from the biotic ligand model (BLM) for copper explained nearly 90% of the variability in EC50s. Nearly 70% of BLM-normalized EC50s for fatmucket tested in natural waters were below the final acute value used to derive the U.S. Environmental Protection Agency acute water quality criterion for copper, indicating that the criterion might not be protective of fatmucket and perhaps other mussel species. ?? 2009 SETAC.

77 FR 49476 - Generalized System of Preferences (GSP): Change in Hearing Date and Related Deadlines for the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-16

... is (202) 395-9674, and the email address is [email protected] . James Sanford, Assistant U.S. Trade Representative for Small Business, Market Access & Industrial Competitiveness, Office of the U.S. Trade Representative. [FR Doc. 2012-20149 Filed 8-15-12; 8:45 am] BILLING CODE 3290-W2-P ...

76 FR 14107 - Notice of Issuance of Regulatory Guide

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

... INFORMATION: I. Introduction The U.S. Nuclear Regulatory Commission (NRC or Commission) is issuing a revision... Branch, Division of Engineering, Office of Nuclear Regulatory Research. [FR Doc. 2011-5967 Filed 3-14-11...

Impact of sampling strategy on stream load estimates in till landscape of the Midwest

USGS Publications Warehouse

Vidon, P.; Hubbard, L.E.; Soyeux, E.

2009-01-01

Accurately estimating various solute loads in streams during storms is critical to accurately determine maximum daily loads for regulatory purposes. This study investigates the impact of sampling strategy on solute load estimates in streams in the US Midwest. Three different solute types (nitrate, magnesium, and dissolved organic carbon (DOC)) and three sampling strategies are assessed. Regardless of the method, the average error on nitrate loads is higher than for magnesium or DOC loads, and all three methods generally underestimate DOC loads and overestimate magnesium loads. Increasing sampling frequency only slightly improves the accuracy of solute load estimates but generally improves the precision of load calculations. This type of investigation is critical for water management and environmental assessment so error on solute load calculations can be taken into account by landscape managers, and sampling strategies optimized as a function of monitoring objectives. ?? 2008 Springer Science+Business Media B.V.

Seasonality and flux estimates of dissolved organic carbon in tidal wetlands and estuaries in the U.S. Mid- Atlantic Bight and Gulf of Mexico from ocean color

NASA Astrophysics Data System (ADS)

Cao, F.; Tzortziou, M.; Hu, C.; Najjar, R.

2016-02-01

Tidal wetlands and estuaries are dynamic features of coastal ocean and play critical roles in the global carbon cycle. Exchanges of dissolved organic carbon (DOC) between tidal wetlands and adjacent estuaries have important implications for carbon sequestration in tidal wetlands as well as biogeochemical cycling of wetlands derived material in the coastal zones. Recent studies demonstrated that the absorption coefficients of chromophoric dissolved organic matter at λ= 275 and 295 nm, which can be derived from satellite ocean color observations, can be used to accurately retrieve dissolved organic carbon (DOC) in some coastal waters. Based on a synthesis of existing field observations collected covering wide spatial and temporal variability in the Mid-Atlantic Bight and the Gulf of Mexico, here we developed and validated new empirical models to estimate coastal DOC from remotely sensed bio-optical properties of the surface water. We focused on the interfaces between tidal wetland-estuary and estuary-shelf water domains. The DOC algorithms were applied to SeaWiFs and MODIS observations to generate long-term climatological DOC distributions from 1998 to 2014. Empirical orthogonal function analysis revealed strong seasonality and spatial gradients in the satellite retrieved DOC in the tidal wetlands and estuaries. Combined with field observations and biogeochemical models, satellite retrievals can be used to scale up carbon fluxes from individual marshes and sub-estuaries to the whole estuarine system, and improve understanding of biogeochemical exchanges between terrestrial and aquatic ecosystems.

Climatic and chemical drivers of trends in DOC in northern surface waters in Europa and North America

NASA Astrophysics Data System (ADS)

de Wit, Heleen A.; Monteith, Don T.; Stoddard, John L.

2016-04-01

Concentrations of DOC in boreal surface waters have increased to levels that create challenges for water treatment plants, and that potentially impact lake habitat through increased anoxia and thermal mixing, and productivity. Aquatic transport of DOC from land to oceans is likely to increase, even if runoff patterns would remain stable. Reduced acid deposition appears to be a dominant driver behind the increase in DOC concentrations, through increasing organic matter solubility. We hypothesize that the higher solubility of organic matter makes DOC more susceptible to climate change. Here, we present trends in DOC from circa 500 lakes and streams in subarctic, boreal and temperate headwater catchments in Europe (UK, Fennoscandia, Czech Republic, Slovakia) and North America (Northeastern US, Ontario, Atlantic Canada) from 1990 until 2012; an extension of the trend analysis presented in Monteith et al. (2007). The water chemical data stem from national monitoring networks, assembled by the ICP Waters network. Sampling frequencies vary from 1 to 52 samples per year. Climate data were obtained from Climate Research Unit in the UK. Trends were calculated using the Mann-Kendall test and the Sen-slope estimator. We test 1) if DOC responds to changes in the rate of decline in acid deposition, and 2) if trends in temperature and precipitation affect trends and variability in DOC. Positive trends dominate: the median (±2.5% quartile) of the absolute and relative DOC trends is +0.06 (+0.36 to -0.02) mg C L-1 yr-1 and +1.4 (+4.7 to -0.9) % yr-1, respectively. Overall, the trends do not level off when comparing 1990-2004, and 1998-2012, except in the UK and Atlantic Canada. These two regions are strongly impacted by seasalt deposition but may also experience stronger warming than elsewhere. The response of DOC to changes in SO4 (expressed as trend ratios) is stronger in 1998-2012 than in 1990-2004. We will explore whether this changing relates to increasing dominance of drivers, such as temperature or precipitation, and will present multivariate models of DOC trends in relation to climate and deposition. References Monteith DT, Stoddard JL, Evans CD, de Wit HA, Forsius M, Hogasen T, Wilander A, Skjelkvale BL, Jeffries DS, Vuorenmaa J, Keller B, Kopacek J, Vesely J (2007) Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry. Nature 450(7169): 537-540

Exploring Collaboratively Written L2 Texts among First-Year Learners of German in Google Docs

ERIC Educational Resources Information Center

Abrams, Zsuzsanna

2016-01-01

Grounded in research on collaborative writing and computer-mediated writing the present study examines the computer-mediated collaborative writing process among first-year learners of German as a second language (L2) at a US university. The data come from 28 first-year learners of German at a US university, who wrote hypothesized endings to a…

77 FR 75188 - Certain Video Analytics Software, Systems, Components Thereof, and Products Containing Same...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-19

..., Esq., Office of the General Counsel, U.S. International Trade Commission, 500 E Street SW., Washington... 5:15 p.m.) in the Office of the Secretary, U.S. International Trade Commission, 500 E Street SW... 13, 2012. Lisa R. Barton, Acting Secretary to the Commission. [FR Doc. 2012-30488 Filed 12-18-12; 8...

78 FR 72712 - Certain Portable Electronic Communications Devices, Including Mobile Phones and Components...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-03

...: Michael Liberman, Esq., Office of the General Counsel, U.S. International Trade Commission, 500 E Street...:45 a.m. to 5:15 p.m.) in the Office of the Secretary, U.S. International Trade Commission, 500 E...: November 26, 2013. Lisa R. Barton, Acting Secretary to the Commission. [FR Doc. 2013-28794 Filed 12-2-13; 8...

77 FR 33089 - Announcement of Entry Into Force of the Defense Trade Cooperation Treaty Between the United...

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2012-06-05

... of Political-Military Affairs, U.S. Department of State, Washington, DC 20522-0112, telephone (202..., Bureau of Political-Military Affairs, U.S. Department of State. [FR Doc. 2012-13583 Filed 6-4-12; 8:45 am... 7913 ] Announcement of Entry Into Force of the Defense Trade Cooperation Treaty Between the United...

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Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-29

... Polypeptide II, a Biomarker for Use in Diagnosis of Brain Injury,'' and U.S. Patent Application Serial No. 12... and Treatment of Brain Injury,'' filed August 19, 2010. The United States Government, as represented... type of brain injury. Brenda S. Bowen, Army Federal Register Liaison Officer. [FR Doc. 2011-19205 Filed...

76 FR 5647 - Public Availability of U.S. Small Business Administration FY 2010 Service Contract Inventory

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-01

...-3499 or [email protected] . Dated: January 26, 2011. Jonathan I. Carver, Chief Financial Officer/Associate Administrator for Performance Management, Office of the Chief Financial Officer. [FR Doc. 2011...

North American Society for Pediatric Gastroenterology, Hepatology and Nutrition

MedlinePlus

North American Society for Pediatric Gastroenterology, Hepatology and Nutrition Skip to Navigation NASPGHAN Annual Meeting and Postgraduate ... transition well. Moreover, Doc4me provides information about medications, nutrition and living with IBD. Please help us promote ...

14 CFR 187.15 - Payment of fees.

Code of Federal Regulations, 2014 CFR

2014-01-01

..., or by credit card payable in U.S. currency, prior to the provision of any service under this part. (b... electronic funds transfer, check, money order, credit card, or draft. [Doc. No. 27809, 60 FR 19631, Apr. 19...

14 CFR 187.15 - Payment of fees.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., or by credit card payable in U.S. currency, prior to the provision of any service under this part. (b... electronic funds transfer, check, money order, credit card, or draft. [Doc. No. 27809, 60 FR 19631, Apr. 19...

14 CFR 187.15 - Payment of fees.

Code of Federal Regulations, 2010 CFR

2010-01-01

..., or by credit card payable in U.S. currency, prior to the provision of any service under this part. (b... electronic funds transfer, check, money order, credit card, or draft. [Doc. No. 27809, 60 FR 19631, Apr. 19...

The river as a chemostat: fresh perspectives on dissolved organic matter flowing down the river continuum

USGS Publications Warehouse

Creed, Irena F.; McKnight, Diane M.; Pellerin, Brian; Green, Mark B.; Bergamaschi, Brian; Aiken, George R.; Burns, Douglas A.; Findlay, Stuart E G; Shanley, James B.; Striegl, Robert G.; Aulenbach, Brent T.; Clow, David W.; Laudon, Hjalmar; McGlynn, Brian L.; McGuire, Kevin J.; Smith, Richard A.; Stackpoole, Sarah M.

2015-01-01

A better understanding is needed of how hydrological and biogeochemical processes control dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) composition from headwaters downstream to large rivers. We examined a large DOM dataset from the National Water Information System of the US Geological Survey, which represents approximately 100 000 measurements of DOC concentration and DOM composition at many sites along rivers across the United States. Application of quantile regression revealed a tendency towards downstream spatial and temporal homogenization of DOC concentrations and a shift from dominance of aromatic DOM in headwaters to more aliphatic DOM downstream. The DOC concentration–discharge (C-Q) relationships at each site revealed a downstream tendency towards a slope of zero. We propose that despite complexities in river networks that have driven many revisions to the River Continuum Concept, rivers show a tendency towards chemostasis (C-Q slope of zero) because of a downstream shift from a dominance of hydrologic drivers that connect terrestrial DOM sources to streams in the headwaters towards a dominance of instream and near-stream biogeochemical processes that result in preferential losses of aromatic DOM and preferential gains of aliphatic DOM.

A comparison of four porewater sampling methods for metal mixtures and dissolved organic carbon and the implications for sediment toxicity evaluations.

PubMed

Cleveland, Danielle; Brumbaugh, William G; MacDonald, Donald D

2017-11-01

Evaluations of sediment quality conditions are commonly conducted using whole-sediment chemistry analyses but can be enhanced by evaluating multiple lines of evidence, including measures of the bioavailable forms of contaminants. In particular, porewater chemistry data provide information that is directly relevant for interpreting sediment toxicity data. Various methods for sampling porewater for trace metals and dissolved organic carbon (DOC), which is an important moderator of metal bioavailability, have been employed. The present study compares the peeper, push point, centrifugation, and diffusive gradients in thin films (DGT) methods for the quantification of 6 metals and DOC. The methods were evaluated at low and high concentrations of metals in 3 sediments having different concentrations of total organic carbon and acid volatile sulfide and different particle-size distributions. At low metal concentrations, centrifugation and push point sampling resulted in up to 100 times higher concentrations of metals and DOC in porewater compared with peepers and DGTs. At elevated metal levels, the measured concentrations were in better agreement among the 4 sampling techniques. The results indicate that there can be marked differences among operationally different porewater sampling methods, and it is unclear if there is a definitive best method for sampling metals and DOC in porewater. Environ Toxicol Chem 2017;36:2906-2915. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

SUMMARY REPORT OF AIR QUALITY MODELING RESEARCH ACTIVITIES FOR 2006

EPA Science Inventory

Through a Memorandum of Understanding (MOU) and Memorandum of Agreement (MOA) between the Department of Commerce (DOC) and U.S. Environmental Protection Agency (EPA), the Atmospheric Sciences Modeling Division (ASMD) of National Oceanic and Atmospheric Administration's (NOAA's) ...

75 FR 22689 - Fiscal Service

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-29

... the U.S. Department of the Treasury, Financial Management Service, Financial Accounting and Services..., 2010. Sandra Paylor-Sanders, Acting Director, Financial Accounting and Services Division. [FR Doc. 2010... Bonding Company AGENCY: Financial Management Service, Fiscal Service, Department of the Treasury. ACTION...

78 FR 68814 - Call for Applications for the International Buyer Program Calendar Year 2015

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-15

... receive DOC assistance in the form of global promotion in foreign markets, provision of export counseling... events and provides practical, hands-on assistance such as export counseling and market analysis to U.S...

77 FR 64837 - Federal Aviation Administration

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2012-10-23

... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Fourth Meeting: RTCA Special Committee 227, Standards of Navigation Performance AGENCY: Federal Aviation Administration (FAA), U.S... Operations Group, Federal Aviation Administration. [FR Doc. 2012-26034 Filed 10-22-12; 8:45 am] BILLING CODE...

78 FR 41183 - Federal Aviation Administration

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2013-07-09

... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Meeting: RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION... Operations Group, Federal Aviation Administration. [FR Doc. 2013-16464 Filed 7-8-13; 8:45 am] BILLING CODE...

75 FR 69703 - Notice of Receipt of Complaint; Solicitation of Comments Relating to the Public Interest

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-15

.... Abbott, Secretary to the Commission, U.S. International Trade Commission, 500 E Street, SW., Washington... Commission. Issued: November 5, 2010. Marilyn R. Abbott, Secretary to the Commission. [FR Doc. 2010-28625...

76 FR 15246 - Anchorage Regulations; Narragansett Bay and Rhode Island Sound, RI

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-21

... impression that the area is reserved for a special purpose (i.e., explosives vessel anchoring) when in fact..., 2011. Daniel A. Neptun, Rear Admiral, U.S. Coast Guard, Commander, First Coast Guard District. [FR Doc...

Relationships between Δ14C and the molecular quality of dissolved organic carbon in rivers draining to the coast from the conterminous United States

USGS Publications Warehouse

Butman, David; Raymond, Peter A.; Butler, Kenna D.; Aiken, George R.

2012-01-01

Dissolved organic carbon (DOC) in natural waters possesses chemical and molecular qualities indicative of its source and age. The apportionment of DOC by age into millennial and decadal pools is necessary to understand the temporal connection between terrestrial and aquatic ecosystems in the global carbon cycle. We measured Δ14C-DOC and chemical composition indices (specific ultraviolet absorbance (SUVA254), fluorescence index (FI), hydrophobic organic acid fraction (HPOA) content) for 15 large river basins in the conterminous United States. Across all rivers the average proportion of HPOA in DOC correlated strongly with SUVA254 (r2 = 0.93 p < 0.001). Individual Δ14C-DOC ranged from a low of −92.9‰ (726 y.b.p.) in the Colorado River to 73.4‰ (>Modern) in the Altamaha River for the year 2009. When adjusted by total discharge, these U.S. Rivers export modern carbon at between 34 and 46‰, a signal dominated by the Mississippi River. The variation in Δ14C correlates to indices of the aromaticity of the DOC measured by the SUVA254 (r2 = 0.87, p < 0.001), and FI (r2 = 0.6; p < 0.001) as well as differences in annual river discharge (r2 = 0.46, p < 0.006). SUVA254 was further correlated to broad scale vegetation phenology estimated from the Enhanced Vegetation Index derived from the NASA Moderate Resolution Imaging Spectrometer (MODIS). We show that basins with high discharge, high proportions of vegetation cover, and low human population densities export DOC enriched in aromatic material that corresponds to recently fixed atmospheric CO2. Conversely old DOC is exported from low discharge watersheds draining arid regions, and watersheds more strongly impacted by humans. The potential influence from fossil carbon from human inputs to aquatic systems may be important and requires more research.

Hydro-climatic control of stream water dissolved organic carbon (DOC) across northern catchments within the North-Watch program

NASA Astrophysics Data System (ADS)

Laudon, Hjalmar; Tetzlaff, Doerthe; Seibert, Jan; Soulsby, Chris; Carey, Sean; Buttle, Jim; McDonnell, Jeff; McGuire, Kevin; Caissie, Daniel; Shanley, Jamie

2010-05-01

There has been an increasing interest in understanding the regulating mechanisms of surface water dissolved organic carbon (DOC) the last decade. A majority of this recent work has been based on individual well characterized research catchments or on regional synoptic datasets combined with readily available landscape and climatic variables. However, as the production and transport of DOC primarily is a function of hydro-climatic conditions a better description of catchment hydrological functioning across large geographic regions would be favorable for moving the mechanistic understanding forward. To do this we report from a first assessment of catchment DOC within the international inter-catchment comparison program North-Watch (http://www.abdn.ac.uk/northwatch/). North-Watch includes long-term research catchments ranging from northern temperate regions to the boreal and sub-arctic biomes with the aim to better understand the variable hydrological and biogeochemical responses in Northern catchments to climate change. The North-Watch catchments are located in Sweden (Krycklan), Scotland (Mharcaidh, Girnock and Strontian), the US (Sleepers River and HJ Andrews) and Canada (Catamaran, Dorset and Wolf Creek). The annual average DOC concentration in the nine catchments investigated were directly linked to hydro-climatic influences (e.g. temperature, water storage) and landscape configuration. In general, the DOC concentration followed a parabolic shape with temperature, where the highest concentrations were found in the boreal and near boreal sites and with the lowest concentrations in the temperate and sub-arctic catchments. The between catchment variability in DOC concentration could also be explained by catchment water storage and amount of wetlands in the catchment. Whereas there is a mechanistic link between long-term climatic conditions and the areal coverage of wetlands, the total catchment storage of water is more strongly linked to topography, parent material and soil depth. The result from this analysis will serve as a conceptual framework for understanding biogeochemical response to environmental change across northern catchments. The next step in this work will be to include more detailed comparisons of the role catchment hydrological functioning for explaining the patterns and dynamics of catchment DOC of these northern watersheds.

76 FR 35199 - Notice of Intent To Grant Partially-Exclusive Patent License; Sound Metrics Corp.

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-16

... described in U.S. Patent No. 12/806,258, Navy Case No. 100,287: Facemask Display. DATES: Anyone wishing [email protected] . Authority: 35 U.S.C. 207, 37 CFR Part 404. Dated: June 9, 2011. L.M. Senay, Lieutenant, Judge Advocate General's Corps, U.S. Navy, Federal Register Liaison Officer. [FR Doc. 2011-14930 Filed 6...

An economic and financial review of Airbus Indsutrie

DOT National Transportation Integrated Search

1990-09-04

This report was prepared for the International Trade Administration of the U.S. Department of Commerce (DOC). It examines the economics of Airbus Industre (AI) civil transport programs and the potential effects of AI's presence on both the market for...

77 FR 22831 - Public Availability of U.S. Small Business Administration FY 2010 Service Contract Inventory

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-17

[email protected] . Dared: March 7, 2012. Jonathan I. Carver, Chief Financial Officer/Associate Administrator for Performance Management, Office of the Chief Financial Officer. [FR Doc. 2012-8997 Filed 4-16-12; 8...

78 FR 16563 - Public Availability of U.S. Small Business Administration FY 2012 Service Contract Inventory

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-15

[email protected] . Dated: January 28, 2013. Jonathan I. Carver, Chief Financial Officer/Associate Administrator for Performance Management, Office of the Chief Financial Officer. [FR Doc. 2013-05957 Filed 3-14-13...

14 CFR 91.703 - Operations of civil aircraft of U.S. registry outside of the United States.

Code of Federal Regulations, 2011 CFR

2011-01-01

... International Civil Aviation Organization (Attention: Distribution Officer), P.O. Box 400, Succursale, Place de L'Aviation Internationale, 1000 Sherbrooke Street West, Montreal, Quebec, Canada H3A 2R2. [Doc. No...

75 FR 53710 - Notice of Receipt of Complaint; Solicitation of Comments Relating to the Public Interest

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-01

...: Marilyn R. Abbott, Secretary to the Commission, U.S. International Trade Commission, 500 E Street, SW... Commission. Issued: August 26, 2010. Marilyn R. Abbott, Secretary to the Commission. [FR Doc. 2010-21789...

78 FR 13393 - Mississippi Disaster Number MS-00064

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2013-02-27

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 13492 and 13493] Mississippi Disaster Number MS-00064 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an... Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc...

76 FR 58329 - Connecticut Disaster Number CT-00024

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-20

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 12797 and 12798] Connecticut Disaster Number CT-00024 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an... Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc. 2011...

77 FR 19408 - Notice of Public Meeting on FY 2013 U.S. Refugee Admissions Program

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-30

... to attend this meeting must notify the Bureau of Population, Refugees, and Migration at telephone... Population, Refugees, and Migration, Department of State. [FR Doc. 2012-7700 Filed 3-29-12; 8:45 am] BILLING...

14 CFR 45.1 - Applicability.

Code of Federal Regulations, 2013 CFR

2013-01-01

... and registration marking of U.S. registered aircraft. [Doc. No. 2047, 29 FR 3223, Mar. 11, 1964, as... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT IDENTIFICATION AND REGISTRATION MARKING General § 45.1 Applicability. This part prescribes the requirements for— (a...

14 CFR 45.1 - Applicability.

Code of Federal Regulations, 2014 CFR

2014-01-01

... and registration marking of U.S. registered aircraft. [Doc. No. 2047, 29 FR 3223, Mar. 11, 1964, as... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT IDENTIFICATION AND REGISTRATION MARKING General § 45.1 Applicability. This part prescribes the requirements for— (a...

14 CFR 45.1 - Applicability.

Code of Federal Regulations, 2012 CFR

2012-01-01

... and registration marking of U.S. registered aircraft. [Doc. No. 2047, 29 FR 3223, Mar. 11, 1964, as... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT IDENTIFICATION AND REGISTRATION MARKING General § 45.1 Applicability. This part prescribes the requirements for— (a...

Climate Prediction Center - Reanalysis: Atmospheric Data

Science.gov Websites

files; i.e., wgrib for GRIB-2 files wgrib2mv,wgrib2ms parallel processing with wgrib2 grb1to2.pl perl US government, DOC, NWS, NCEP or CPC. All spelling errors are property of the finder. comments

76 FR 79218 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-U.S. Photovoltaic...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-21

... Nanoscale Science and Engineering (``CNSE'') of the University at Albany, State University of New York.... Patricia A. Brink, Director of Civil Enforcement, Antitrust Division. [FR Doc. 2011-32709 Filed 12-20-11; 8...

78 FR 1832 - Nez Perce-Clearwater National Forests; Id; Crooked River Valley Rehabilitation Project

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-09

... the thirty-fourth through thirty-sixth lines, `` http://www.fs.fed.usinepa/fs-usda-pop.php/?project=40648 '' should read `` http://www.fs.fed.us/nepa/fs-usda-pop.php/?project=40648 ''. [FR Doc. C1-2012...

78 FR 45282 - Oklahoma Disaster Number OK-00073

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-26

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 13647 and 13648] Oklahoma Disaster Number OK-00073 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an Amendment of... Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc...

75 FR 57539 - Illinois Disaster Number IL-00025

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2010-09-21

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 12290 and 12291] Illinois Disaster Number IL-00025 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of... Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc. 2010...

76 FR 27739 - Tennessee Disaster Number TN-00051

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-12

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77 FR 61466 - Oklahoma Disaster Number OK-00063

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-09

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 13241 and 13242] Oklahoma Disaster Number OK-00063 AGENCY: U.S. Small Business Administration. ACTION: Amendment 2. SUMMARY: This is an amendment of... Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc. 2012...

76 FR 59766 - Texas Disaster Number TX-00381

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-27

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 12815 and 12816] Texas Disaster Number TX-00381 AGENCY: U.S. Small Business Administration. ACTION: Amendment 3. SUMMARY: This is an amendment of... Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc...

76 FR 31671 - Kentucky Disaster Number KY-00039

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-01

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 12566 and 12567] Kentucky Disaster Number KY-00039 AGENCY: U.S. Small Business Administration. ACTION: Amendment 3. SUMMARY: This is an amendment of... Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc...

75 FR 55619 - Nebraska Disaster Number NE-00038

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-13

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 12238 and 12239] Nebraska Disaster Number NE-00038 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of... Numbers 59002 and 59008) Roger B. Garland, Acting Associate Administrator for Disaster Assistance. [FR Doc...

76 FR 70528 - Texas Disaster Number TX-00382

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-14

... SMALL BUSINESS ADMINISTRATION [Disaster Declaration 12848 and 12849] Texas Disaster Number TX-00382 AGENCY: U.S. Small Business Administration. ACTION: Amendment 5. SUMMARY: This is an amendment of... Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. [FR Doc...

Optimized treatment conditions for textile wastewater reuse using photocatalytic processes under UV and visible light sources.

PubMed

Starling, Maria Clara V M; Castro, Luiz Augusto S; Marcelino, Rafaela B P; Leão, Mônica M D; Amorim, Camila C

2017-03-01

In this study, photo-Fenton systems using visible light sources with iron and ferrioxalate were tested for the DOC degradation and decolorization of textile wastewater. Textile wastewaters originated after the dyeing stage of dark-colored tissue in the textile industry, and the optimization of treatment processes was studied to produce water suitable for reuse. Dissolved organic carbon, absorbance, turbidity, anionic concentrations, carboxylic acids, and preliminary cost analysis were performed for the proposed treatments. Conventional photo-Fenton process achieved near 99 % DOC degradation rates and complete absorbance removal, and no carboxylic acids were found as products of degradation. Ferrioxalate photo-Fenton system achieved 82 % of DOC degradation and showed complete absorbance removal, and oxalic acid has been detected through HPLC analysis in the treated sample. In contrast, photo-peroxidation with UV light was proved effective only for absorbance removal, with DOC degradation efficiency near 50 %. Treated wastewater was compared with reclaimed water and had a similar quality, indicating that these processes can be effectively applied for textile wastewater reuse. The results of the preliminary cost analysis indicated costs of 0.91 to 1.07 US$ m -3 for the conventional and ferrioxalate photo-Fenton systems, respectively. Graphical Abstract ᅟ.

Stormflow chemistry in the Santa Ana River below Prado Dam and at the diversion downstream from Imperial Highway, southern California, 1995-98

USGS Publications Warehouse

Izbicki, John A.; Mendez, Gregory O.; Burton, Carmen A.

2000-01-01

The Santa Ana River drains about 2,670 square miles of the densely populated coastal area of southern California, near Los Angeles. Almost all the flow in the river, more than 200,000 acre-feet annually, is diverted into ponds where it infiltrates and recharges underlying aquifers. About 2 million people are dependent on these aquifers for water supply. Stormflow in the Santa Ana River is considered a source of 'high-quality' water suitable for use as a source of ground-water recharge. To test this assumption, stormflow samples were collected at two locations--below Prado Dam and at the diversion point downstream from Imperial Highway--for 12 winter storms between 1995 and 1998. Nitrate concentrations decreased during stormflow from a median concentration of 7.8 milligrams per liter in base flow to concentrations less than 1 milligram per liter in some large storms. Concentrations of chemically reduced forms of nitrogen (nitrite, ammonia, and organic nitrogen) increased during stormflow and are the predominant forms of nitrogen in large stormflows. Dissolved organic carbon (DOC) concentrations increased from a median concentration of 4.6 milligrams per liter in base flow to more than 20 milligrams per liter in some stormflows. Concentrations of DOC were especially high during the first storm of the rainy season, and large increases in DOC concentrations were measured even as a result of small early season storms that did not cause large increases in streamflow. DOC present during early season stormflow had less ultraviolet absorbance at 254 nanometers (UV254 ) per unit of carbon than did DOC from late season stormflows. DOC in water held in storage behind Prado Dam had the highest UV254 absorbance per unit of carbon. Maximum pesticide concentrations in stormflow did not exceed U.S. Environmental Protection Agency Maximum Contaminant Levels. Most pesticide concentrations were less than 1 microgram per liter and less than the detection limits obtained using standard drinking water analyses. Increases in concentrations of pesticides such as diazinon, malathion, and chlorpyrifos in stormflow result from runoff from urban areas downstream from Prado Dam. In general, large late season stormflows have the most pesticide detections of all stormflows sampled. Concentrations of methyl tert-butyl ether (MTBE), a gasoline additive, during base flow were as high as 0.9 microgram per liter and concentrations decreased during stormflow. Like pesticides, the concentrations did not exceed the U.S. Environmental Protection Agency Maximum Contaminant Levels for MTBE.

78 FR 71704 - Request for Comments on Draft SBA Strategic Plan for FY 2014-2018

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-29

... AGENCY: Office of Associate Administrator for Performance Management & Chief Financial Officer, Small.... Carver, Associate Administrator for Performance Management & Chief Financial Officer. [FR Doc. 2013-28623...-7274. Mail: U.S. Small Business Administration, Office of Performance Management & Chief Financial...

77 FR 16022 - Agency Information Collection Extension

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2012-03-19

... DEPARTMENT OF ENERGY Office of Energy Efficiency and Renewable Energy Agency Information Collection Extension AGENCY: Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy... Renewable Energy. [FR Doc. 2012-6546 Filed 3-16-12; 8:45 am] BILLING CODE 6450-01-P ...

77 FR 35855 - Safety Zone, Temporary Change for Recurring Fifth Coast Guard District Fireworks Displays...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-15

..., approximately 500 yards northwest of the waterfront at Oxford, MD. * * * * * Dated: June 4, 2012. Mark P. O'Malley, Captain, U.S. Coast Guard, Captain of the Port Baltimore. [FR Doc. 2012-14647 Filed 6-14-12; 8:45...

75 FR 37842 - Notice of Issuance of Regulatory Guide

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-30

... INFORMATION CONTACT: R. A. Jervey, Regulatory Guide Development Branch, Division of Engineering, Office of...) 251-7404 or e-mail [email protected] . SUPPLEMENTARY INFORMATION: I. Introduction The U.S. Nuclear..., Regulatory Guide Development Branch, Division of Engineering, Office of Nuclear Regulatory Research. [FR Doc...

Mercury dynamics in a coastal plain watershed: insights from multiple models and empirical data

EPA Science Inventory

Interactions among atmospherically deposited mercury, abundant wetlands, and surface waters with elevated acidity and dissolved organic carbon (DOC) often lead to widespread mercury-related fish consumption advisories in the Coastal Plain of the southeastern United States (US). H...

Chromophoric dissolved organic matter export from U.S. rivers

NASA Astrophysics Data System (ADS)

Spencer, Robert G. M.; Aiken, George R.; Dornblaser, Mark M.; Butler, Kenna D.; Holmes, R. Max; Fiske, Greg; Mann, Paul J.; Stubbins, Aron

2013-04-01

Chromophoric dissolved organic matter (CDOM) fluxes and yields from 15 major U.S. rivers draining an assortment of terrestrial biomes are presented. A robust relationship between CDOM and dissolved organic carbon (DOC) loads is established (e.g., a350 versus DOC; r2 = 0.96, p < 0.001). Calculated CDOM yields are also correlated to watershed percent wetland (e.g. a350; r2 = 0.81, p < 0.001) providing a method for the estimation of CDOM export from ungauged watersheds. A large variation in CDOM yields was found across the rivers. The two rivers in the north-eastern U.S. (Androscoggin and Penobscot), the Edisto draining into the South Atlantic Bight, and some rivers draining into the Gulf of Mexico (Atchafalaya and Mobile) exhibit the highest CDOM yields, linked to extensive wetlands in these watersheds. If the Edisto CDOM yield is representative of other rivers draining into the South Atlantic Bight, this would result in a CDOM load equivalent to that of the Mississippi from a region of approximately 10% of the Mississippi watershed, indicating the importance of certain regions with respect to the role of terrigenous CDOM in ocean color budgets.

Nitrogen speciation in wastewater treatment plant influents and effluents-the US and Polish case studies.

PubMed

Pagilla, K R; Urgun-Demirtas, M; Czerwionka, K; Makinia, J

2008-01-01

The fate of N species, particularly dissolved organic nitrogen (DON), through process trains of a wastewater treatment plant (WWTP) was investigated. In this study, three fully nitrifying plants in Illinois, USA and biological nutrient removal (BNR) plants in northern Poland were sampled for N characterization in the primary and secondary effluents as a function of the particle size distribution. The correlations between dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations were examined. The key findings are that DON becomes significant portion (about 20%) of the effluent N, reaching up to 50% of effluent total N in one of the Polish plants. The DON constituted 56-95% of total ON (TON) in the secondary effluents, whereas in the Polish plants the DON contribution was substantially lower (19-62%) and in one case (Gdansk WWTP) colloidal ON was the dominating fraction (62% of TON). The DOC to DON ratio in the US plants is significantly lower than that in the receiving waters indicating potential for deterioration of receiving water quality. In Polish plants, the influent and effluent C:N ratios are similar, but not in the US plants. IWA Publishing 2008.

Chromophoric dissolved organic matter export from U.S. rivers

USGS Publications Warehouse

Spencer, Robert G. M.; Aiken, George R.; Dornblaser, Mark M.; Butler, Kenna D.; Holmes, R. Max; Fiske, Greg; Mann, Paul J.; Stubbins, Aron

2013-01-01

Chromophoric dissolved organic matter (CDOM) fluxes and yields from 15 major U.S. rivers draining an assortment of terrestrial biomes are presented. A robust relationship between CDOM and dissolved organic carbon (DOC) loads is established (e.g., a350 versus DOC; r2 = 0.96, p < 0.001). Calculated CDOM yields are also correlated to watershed percent wetland (e.g. a350; r2 = 0.81, p < 0.001) providing a method for the estimation of CDOM export from ungauged watersheds. A large variation in CDOM yields was found across the rivers. The two rivers in the north-eastern U.S. (Androscoggin and Penobscot), the Edisto draining into the South Atlantic Bight, and some rivers draining into the Gulf of Mexico (Atchafalaya and Mobile) exhibit the highest CDOM yields, linked to extensive wetlands in these watersheds. If the Edisto CDOM yield is representative of other rivers draining into the South Atlantic Bight, this would result in a CDOM load equivalent to that of the Mississippi from a region of approximately 10% of the Mississippi watershed, indicating the importance of certain regions with respect to the role of terrigenous CDOM in ocean color budgets.

Low Cost, Low Complexity Sensor Design for Non-Cooperative Geolocation via Received Signal Strength

DTIC Science & Technology

2012-03-01

6 IOT&E Initial Operational Test and Evaluation . . . . . . . . . . 6 LBS Location - Based Services . . . . . . . . . . . . . . . . . . . 6 LOS Line-of...subscribers. Location - Based Services (LBS) are poised to become a significant growth driver for the US wireless industry. While deployments have been slow...Markets”. PELOUS Group, NJ, Tech. Rep., 2001. 9. “Wi-Fi Location - Based Services (4.1 Desing Guidie)”, May 2008. URL http: //www.cisco.com/en/US/docs

High-frequency DOC and nitrate measurements provide new insights into their export and their relationships to rainfall-runoff processes

NASA Astrophysics Data System (ADS)

Schwab, Michael; Klaus, Julian; Pfister, Laurent; Weiler, Markus

2015-04-01

Over the past decades, stream sampling protocols for environmental tracers were often limited by logistical and technological constraints. Long-term sampling programs would typically rely on weekly sampling campaigns, while high-frequency sampling would remain restricted to a few days or hours at best. We stipulate that the currently predominant sampling protocols are too coarse to capture and understand the full amplitude of rainfall-runoff processes and its relation to water quality fluctuations. Weekly sampling protocols are not suited to get insights into the hydrological system during high flow conditions. Likewise, high frequency measurements of a few isolated events do not allow grasping inter-event variability in contributions and processes. Our working hypothesis is based on the potential of a new generation of field-deployable instruments for measuring environmental tracers at high temporal frequencies over an extended period. With this new generation of instruments we expect to gain new insights into rainfall-runoff dynamics, both at intra- and inter-event scales. Here, we present the results of one year of DOC and nitrate measurements with the field deployable UV-Vis spectrometer spectro::lyser (scan Messtechnik GmbH). The instrument measures the absorption spectrum from 220 to 720 nm in situ and at high frequencies and derives DOC and nitrate concentrations. The measurements were carried out at 15 minutes intervals in the Weierbach catchment (0.47 km2) in Luxemburg. This fully forested catchment is characterized by cambisol soils and fractured schist as underlying bedrock. The time series of DOC and nitrate give insights into the high frequency dynamics of stream water. Peaks in DOC concentrations are closely linked to discharge peaks that occur during or right after a rainfall event. Those first discharge peaks can be linked to fast near surface runoff processes and are responsible for a remarkable amount of DOC export. A special characterisation of the Weierbach catchment are the delayed second peaks a few days after the rainfall event. Nitrate concentrations are following this second peak. We assume that this delayed response is going back to subsurface or upper groundwater flows, with nitrate enriched water. On an inter-event scale during low flow / base flow conditions, we observe interesting diurnal patterns of both DOC and nitrate concentrations. Overall, the long-term high-frequency measurements of DOC and nitrate provide us the opportunity to separate different rainfall-runoff processes and link the amount of DOC and nitrate export to them to quantify the overall relevance of the different processes.

String of Pearls: Meeting the Challenge of China’s Rising Power across the Asian Littoral

DTIC Science & Technology

2006-07-01

Forecasting, July 11, 2005. 62. Seth Mydans, "New Group for Asian Century Shuns U.S.," International Herald Tribune, December 12, 2005. 63. Robert G. Sutter...Glenn Kessler , "U.S. Says China Must Address Its Intentions: How Its Power Will Be Used Is of Concern," Washington Post, September 22, 2005, p. A-16...n.p. On line. Internet, November 8, 2005. Available from www.theatlantic.com/doc/prem/2005O6Aaplan. Kessler , Glenn. "U.S. Says China Must Address Its

77 FR 12796 - Commerce Business Apps Challenge

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2012-03-02

... data set, an application (Web, mobile, PC, etc.) that assists businesses and/or improves the service... use DOC and other federal data and program information to help businesses: Learn about and evaluate opportunities, both here in the U.S. and internationally; Access useful government services, data, and market...

75 FR 61246 - Surety Companies Acceptable on Federal Bonds: Darwin National Assurance Company

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-04

... the U.S. Department of the Treasury, Financial Management Service, Financial Accounting and Services..., 2010. Laura Carrico, Director, Financial Accounting and Services Division, [FR Doc. 2010-24632 Filed 10... National Assurance Company AGENCY: Financial Management Service, Fiscal Service, Department of the Treasury...

78 FR 18954 - Incentives To Adopt Improved Cybersecurity Practices

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2013-03-28

... [Docket Number 130206115-3115-01] Incentives To Adopt Improved Cybersecurity Practices AGENCY: U.S... infrastructure and other interested entities of the Cybersecurity Framework being developed by the National... on the Internet Policy Task Force Web page at http://www.ntia.doc.gov/category/cybersecurity . For...

78 FR 33072 - Recruitment of First Responder Network Authority Board of Directors

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2013-06-03

....doc.gov ; by U.S. mail or commercial delivery service to: Office of Public Safety Communications...-0016; email: [email protected] . Please direct media inquiries to NTIA's Office of Public Affairs... conflict of interest statutes and ethics regulations, including some financial disclosure requirements...

78 FR 50396 - Common Format for Federal Entity Transition Plans

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2013-08-19

..., Associate Administrator, Office of Spectrum Management. [FR Doc. 2013-20149 Filed 8-16-13; 8:45 am] BILLING..., Office of Spectrum Management. Each commenter should include the name of the person or organization... Spectrum Management, National Telecommunications and Information Administration, U.S. Department of...

Dissolved Organic Carbon in Marginal, Damaged Peatlands: Using 14C to Understand DOC Losses

NASA Astrophysics Data System (ADS)

Luscombe, D.; Grand-Clement, E.; Garnett, M.; Anderson, K.; Gatis, N.; Benaud, P.; Brazier, R.

2013-12-01

Peatlands are widely represented throughout the world and act as an important store of carbon, as well as providing society with a range of other ecosystem services, such as drinking water or the support of rare habitats. However, the combination of historical management practices, and the predicted impact of climate change means that they are now largely under threat. In the shallow peatlands of Exmoor National Park (South West UK), peat cutting and intensive drainage in the 19th and 20th century for agricultural reclamation have changed the hydrological behaviour of the peat. This damage has dried out the upper layers, causing oxidation, erosion and vegetation change. In addition, their location on the southernmost limit of peatlands geographical extent in northern Europe makes them particularly vulnerable to the predicted changes in rainfall and temperature. Recent modelling work has shown that such marginal peatlands may disappear as early as 2050. Restoration programs are currently in place, aiming to restore the hydrological functioning of the peat. However, current dissolved organic carbon (DOC) losses from damaged peatlands are especially of concern, because of the contribution of the aquatic pathways in the C flux, and because of the impact on water quality. DOC has been shown to originate from the drainage of highly-aged organic matter. In stream waters, DOC from low flow tends to contain a larger component of older C compared to that of high flow. Both the impact of extensive drainage on where DOC is originating from and the effect of peatland restoration on this process remain poorly understood. We used 14C dating of DOC from streams and pore water, as well as from damaged peat, in order to gain a better understanding of the process and origin of DOC loss in drained shallow peatlands. This will further help us understand the potential for peatland restoration. Work was carried out in a small intensively monitored catchment in Exmoor. Samples were taken in an area of shallow peat (ca. 20-30 cm depth) drained by a medium size ditch (50 x 50 cm). Samples of DOC from stream water were taken at low and high flow during 3 separate rain events in Winter- Spring 2013 using automatic pump samplers. Samples of DOC in pore water were taken 2 m away from the ditch at 5 and 15 cm depth on two occasions. Finally, matching bulk peat samples were collected at 5 and 15 cm depth. Intensive monitoring data also provides information on water table depth and level in streams. A neighbouring pristine peat area was used as a control, and DOC pore water and bulk peat soil samples were taken at 5, 15 and 45 cm depth on two occasions. Preliminary results show that DOC lost in streams at high flow contains a greater contribution of bomb-14C compared to that at low flow (107 and 101 % modern respectively). Stream water DOC at low flow had a 14C concentration lower than that in pore water at both 5 and 15 cm depth (105 and 102% modern, respectively), suggesting that low flow stream water DOC is predominantly older than that found in pore water at depth.

Detailed behavioral assessment promotes accurate diagnosis in patients with disorders of consciousness

PubMed Central

Gilutz, Yael; Lazary, Avraham; Karpin, Hana; Vatine, Jean-Jacques; Misha, Tamar; Fortinsky, Hadassah; Sharon, Haggai

2015-01-01

Introduction: Assessing the awareness level in patients with disorders of consciousness (DOC) is made on the basis of exhibited behaviors. However, since motor signs of awareness (i.e., non-reflex motor responses) can be very subtle, differentiating the vegetative from minimally conscious states (which is in itself not clear-cut) is often challenging. Even the careful clinician relying on standardized scales may arrive at a wrong diagnosis. Aim: To report our experience in tackling this problem by using two in-house use assessment procedures developed at Reuth Rehabilitation Hospital, and demonstrate their clinical significance by reviewing two cases. Methods: (1) Reuth DOC Response Assessment (RDOC-RA) –administered in addition to the standardized tools, and emphasizes the importance of assessing a wide range of motor responses. In our experience, in some patients the only evidence for awareness may be a private specific movement that is not assessed by standard assessment tools. (2) Reuth DOC Periodic Intervention Model (RDOC-PIM) – current literature regarding assessment and diagnosis in DOC refers mostly to the acute phase of up to 1 year post injury. However, we have found major changes in responsiveness occurring 1 year or more post-injury in many patients. Therefore, we conduct periodic assessments at predetermined times points to ensure patients are not misdiagnosed or neurological changes overlooked. Results: In the first case the RDOC-RA promoted a more accurate diagnosis than that based on standardized scales alone. The second case shows how the RDOC-PIM allowed us to recognize late recovery and promoted reinstatement of treatment with good results. Conclusion: Adding a detailed periodic assessment of DOC patients to existing scales can yield critical information, promoting better diagnosis, treatment, and clinical outcomes. We discuss the implications of this observation for the future development and validation of assessment tools in DOC patients. PMID:25788882

Predicting toxic effects of copper on aquatic biota in mineralized areas by using the Biotic Ligand Model

USGS Publications Warehouse

Smith, Kathleen S.; Ranville, James F.; Adams, M.; Choate, LaDonna M.; Church, Stan E.; Fey, David L.; Wanty, Richard B.; Crock, James G.

2006-01-01

The chemical speciation of metals influences their biological effects. The Biotic Ligand Model (BLM) is a computational approach to predict chemical speciation and acute toxicological effects of metals on aquatic biota. Recently, the U.S. Environmental Protection Agency incorporated the BLM into their regulatory water-quality criteria for copper. Results from three different laboratory copper toxicity tests were compared with BLM predictions for simulated test-waters. This was done to evaluate the ability of the BLM to accurately predict the effects of hardness and concentrations of dissolved organic carbon (DOC) and iron on aquatic toxicity. In addition, we evaluated whether the BLM and the three toxicity tests provide consistent results. Comparison of BLM predictions with two types of Ceriodaphnia dubia toxicity tests shows that there is fairly good agreement between predicted LC50 values computed by the BLM and LC50 values determined from the two toxicity tests. Specifically, the effect of increasing calcium concentration (and hardness) on copper toxicity appears to be minimal. Also, there is fairly good agreement between the BLM and the two toxicity tests for test solutions containing elevated DOC, for which the LC50 is 3-to-5 times greater (less toxic) than the LC50 for the lower-DOC test water. This illustrates the protective effects of DOC on copper toxicity and demonstrates the ability of the BLM to predict these protective effects. In contrast, for test solutions with added iron there is a decrease in LC50 values (increase in toxicity) in results from the two C. dubia toxicity tests, and the agreement between BLM LC50 predictions and results from these toxicity tests is poor. The inability of the BLM to account for competitive iron binding to DOC or DOC fractionation may be a significant shortcoming of the BLM for predicting site- specific water-quality criteria in streams affected by iron-rich acidic drainage in mined and mineralized areas.

Interlinkages between Carbon and Water Residence Times in Peat

NASA Astrophysics Data System (ADS)

Visser, A.; Wilson, R.; Sebestyen, S.; Griffiths, N.; Chanton, J.; Veale, N.; McFarlane, K. J.; Kolka, R. K.; Guilderson, T.

2016-12-01

Peatlands play an important role in the terrestrial carbon cycle. Understanding their response to climate change is crucial to predict their role as carbon sink or source of methane and carbon dioxide to the atmosphere. The hydrology of the peatland plays a crucial role, providing anoxic conditions for peat accumulation and advective transport of nutrients and dissolved organic carbon (DOC) to methanogens at depth. The interlinkages between the hydrology and carbon-cycling at the S1 bog at the Marcell Experimental Forest were investigated as part of the SPRUCE experiment, using a combination of isotopic techniques characterizing the carbon and water ages to assess the role of advective transport in the peat pore water. Tritium and tritiogenic helium concentrations constrain the age of the pore water to less than 10 years, although gas exchange with the atmosphere complicates direct use of 3H/3He dating methods. The pore water ages further constrain the interpretation of the peat, DOC and DIC ages. While carbon-14 values of solid peat decrease from 0‰ at the surface to -550‰ (corresponding to carbon-14 ages of 8 ka) at 2m depth, the DOC and DIC shift from +50‰ to -50‰ at depth. Knowing that the advective transport time of pore water is negligible on this time scale, the shift in carbon-14 of DOC must result from peat decomposition at depth, rather than in situ aging of DOC. Combined with the DOC concentration data, the carbon-cycling rates at the SPRUCE experiment are further constrained. The integrated application of isotopes in the carbon and water cycle emphasizes the importance of understanding peatland hydrology for understanding carbon-cycle dynamics. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675107

Israel: Background and U.S. Relations in Brief

DTIC Science & Technology

2016-09-16

above and below the $500 million mark from year to year. 32 Barbara Opall -Rome, “Israel Claims...at page 119-A, available at http://docs.house.gov/meetings/RU/RU00/20151216/104298/HMTG-114-RU00-20151216-SD004.pdf. 34 Barbara Opall -Rome, “Israel

Work with Us | Research Site Name | NREL

Science.gov Websites

ullamco laboris nisi ut aliquip ex ea commodo consequat. Hero Image - Width of 1746px - Height can vary ex ea commodo consequat. Learn about our technology partnership agreements. Use our cutting-edge commercialization programs. Join Our Team Find an opportunity: Job | Internship | Post Doc | Director's Postdoctoral

77 FR 64829 - Sunshine Act Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... (Pub. L. 94-409) (5 U.S.C. 552b) I, Isaac Fulwood, of the United States Parole Commission, was present... following Commissioners voted that the meeting be closed: Isaac Fulwood, Jr., Cranston J. Mitchell, Patricia... the public. Dated: October 16, 2012. Isaac Fulwood, Jr., Chairman, U.S. Parole Commission. [FR Doc...

75 FR 34736 - Draft FY 2011-2015 EPA Strategic Plan

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2010-06-18

... Accountability, Office of the Chief Financial Officer [email protected] . Instructions: EPA's policy is that... Chief Financial Officer, Office of the Chief Financial Officer. [FR Doc. 2010-14649 Filed 6-17-10; 8:45... Financial Officer, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave, NW., Washington, DC 20460...

76 FR 25783 - Surety Companies Acceptable on Federal Bonds; Name Change: Odyssey America Reinsurance Corporation

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2011-05-05

... directed to the U.S. Department of the Treasury, Financial Management Service, Financial Accounting and...: April 22, 2011. Laura Carrico, Director, Financial Accounting and Services Division. [FR Doc. 2011-10773... Change: Odyssey America Reinsurance Corporation AGENCY: Financial Management Service, Fiscal Service...

77 FR 74828 - Call for Applications for the International Buyer Program Calendar Years 2014 and 2015

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-18

... DEPARTMENT OF COMMERCE International Trade Administration [Docket No. 120913451-2681-02] Call for... Administration, Department of Commerce. ACTION: Notice extending application deadline. SUMMARY: The U.S. Department of Commerce (DOC) is amending the Notice and Call for Applications for the International Buyer...

78 FR 34174 - Proposed Information Collection (Pension Claim Questionnaire for Farm Income) Activity: Comment...

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2013-06-06

... to determine net income derived from farming. DATES: Written comments and recommendations on the... use of other forms of information technology. Title: Pension Claim Questionnaire for Farm Income, VA... Information Security, Office of Information and Technology, U.S. Department of Veterans Affairs. [FR Doc. 2013...

78 FR 24380 - National Sheep Industry Improvement Center: Notice of Request for Extension and Revision of a...

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2013-04-25

... Service [Doc. No. AMS-LPS-13-0020] National Sheep Industry Improvement Center: Notice of Request for... the currently approved information collection 0581-0263: National Sheep Industry Improvement Center... Division; Livestock, Poultry, and Seed Program; Agricultural Marketing Service; U.S. Department of...

Characterizing mercury concentrations and flux dynamics in a coastal plain watershed using multiple models and data

EPA Science Inventory

Mercury-related fish consumption advisories are widespread in the coastal plain of the southeastern U.S., where atmospherically deposited mercury interacts with an abundance of wetlands and high-dissolved organic carbon (DOC), acidic waters. Recent trends in decision making proce...

69. PHOTOCOPY OF RENDERING OF PROPOSED OPEN VALLEY TREATMENT OF ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

69. PHOTOCOPY OF RENDERING OF PROPOSED OPEN VALLEY TREATMENT OF P STREET BEND, FROM U.S. CONGRESS. HOUSE. REPORT OF THE ROCK CREEK AND POTOMAC PARKWAY COMMISSION, 1916. HOUSE DOC. No. 1114, 64th CONG. 1st SESS. - Rock Creek & Potomac Parkway, Washington, District of Columbia, DC

75 FR 16525 - Notice of Issuance of Regulatory Guide

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-01

... CONTACT: Mekonen M. Bayssie, Regulatory Guide Development Branch, Division of Engineering, Office of...) 251-7489 or e-mail [email protected] . SUPPLEMENTARY INFORMATION: I. Introduction The U.S..., Division of Engineering, Office of Nuclear Regulatory Research. [FR Doc. 2010-7391 Filed 3-31-10; 8:45 am...

Amphibious Operations: Ensuring Capabilities to Assure Access

DTIC Science & Technology

2011-04-05

Headquarters U.S. Marine Corps, 2008. Henriksen, Thomas H. "Security Lessons from The Israeli Trenches." Policy Review (February 2007): 17-31. Johnson...GetTRDoc? AD=ADA521772&Location= U2&doc=GetTRDoc.pdf. Lyall, Jason, and Isaiah Wilson III. "Rage against the machines: Explaining outcomes in

77 FR 2774 - Notice of Intent To Prepare a Supplemental Environmental Impact Statement: Fond du Lac...

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2012-01-19

... Fredrichs, Assistant Division Administrator, Federal Highway Administration, Madison, Wisconsin. [FR Doc... capacity improvements to Wisconsin Highway 23 from U.S. Highway 151 to County Highway P in Fond du Lac and Sheboygan Counties, Wisconsin. FOR FURTHER INFORMATION CONTACT: Bethaney Bacher-Gresock, Environmental...

75 FR 58444 - Technical Correction of the Caption for Prohibited Transaction Exemption (PTE) 2010-27, Involving...

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2010-09-24

... DEPARTMENT OF LABOR Employee Benefits Security Administration Technical Correction of the Caption... Mid-Atlantic Region (the Plan) AGENCY: Employee Benefits Security Administration, Department of Labor..., Employee Benefits Security Administration, U.S. Department of Labor. [FR Doc. 2010-23931 Filed 9-23-10; 8...

77 FR 7655 - Renewal of Discretionary Advisory Committees

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2012-02-13

... about SBA's Advisory Committees can be directed to SBA's Committee Management Officer, Dan Jones, telephone (202) 205-7583, fax (202) 481-6536, email dan[email protected] or mail, U.S. Small Business... District Advisory Council. Dated: February 7, 2012. Dan Jones, SBA Committee Management Officer. [FR Doc...

78 FR 9745 - Kewaunee Power Station; Application for Amendment to Facility Operating License

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2013-02-11

... FURTHER INFORMATION CONTACT: Karl Feintuch, Project Manager, Office of Nuclear Reactor Regulation, U.S... Licensing, Office of Nuclear Reactor Regulation. [FR Doc. 2013-03037 Filed 2-8-13; 8:45 am] BILLING CODE... NUCLEAR REGULATORY COMMISSION [Docket No. 50-305; NRC-2013-0028] Kewaunee Power Station...

Airpower in Peripheral Conflict: The French Experience in Africa

DTIC Science & Technology

1989-01-01

U.S. Air Force. The purpose of this research effort is to assist in developing a basis for enhancing the future effectiveness of U.S. Air Force air... development of air doc- trine, air operations in limited conflicts, Fren.:h policy toward Africa, and the French Ai Force. Aecesslon For GNTIS RA& DTIC TAB 5...1970s encouraged the development and provided the initial tests of the specialized equipment, organization, and operational con- cepts developed during

When Will It Be …?: U.S. Naval Observatory Religious Calendar Computers Expanded

NASA Astrophysics Data System (ADS)

Bartlett, Jennifer L.; Chizek Frouard, Malynda; Ziegler, Cross; Lesniak, Michael V.

2017-01-01

Reflecting increasing sensitivity to differing religious practices, the U.S. Naval Observatory (USNO) has expanded its on-line calendar resources to compute additional religious dates for specific years via an Application Programming Interface (API). This flexible method now identifies Christian, Islamic, and Jewish events in JavaScript Object Notation (JSON) that anyone can use.Selected Christian Observances (http://aa.usno.navy.mil/data/docs/easter.php) returns dates of eight events for years after 1582 C.E. (A.D. 1582): Ash Wednesday, Palm Sunday, Good Friday, Easter, Ascension, Whit Sunday, Trinity Sunday, and the first Sunday of Advent. The determination of Easter, a moveable feast, uses the method of western Christian churches.Selected Islamic Observances (http://aa.usno.navy.mil/data/docs/islamic.php) returns approximate Gregorian dates of three events for years after 1582 C.E. (A.H. 990) and Julian dates for 622-1582 C.E. (A.H. 1-990) along with the corresponding Islamic year (anno Hegirae). Ramadân, Shawwál, and the Islamic year begin at sunset on the preceding Gregorian or Julian date. For planning purposes, the determination of these dates uses a tabular calendar; in practice, observation of the appropriate waxing crescent Moon determines the actual date, which may vary.Selected Jewish Observances (http://aa.usno.navy.mil/data/docs/passover.php) returns Gregorian dates of six events for years after 1582 C.E. (A.M. 5342) and Julian dates for the years 360-1582 C.E. (A.M. 4120-5342) along with the corresponding Jewish year (anno Mundi). Passover, Shavuot, Rosh Hashanah, Yom Kippur, and Hanukkah begin at sunset on the preceding Gregorian or Julian date.On-line documentation for using the API-enabled calendar computers, including sample calls, is available (http://aa.usno.navy.mil/data/docs/api.php). The webpage also describes how to use the API with the Complete Sun and Moon Data for One Day, Phases of the Moon, Solar Eclipse Computer, Day and Night Across the Earth, Apparent Disk of a Solar System Object, Julian Date Conversion, and Sidereal Time services.Introduction to Calendars (http://aa.usno.navy.mil/faq/docs/calendars.php) provides an overview of the topic and links to additional resources.

When Will It Be …?: U.S. Naval Observatory Calendar Computers

NASA Astrophysics Data System (ADS)

Bartlett, Jennifer L.; Chizek Frouard, Malynda; Lesniak, Michael V.

2016-06-01

Sensitivity to religious calendars is increasingly expected when planning activities. Consequently, the U.S. Naval Observatory (USNO) has redesigned its on-line calendar resources to allow the computation of select religious dates for specific years via an application programming interface (API). This flexible interface returns dates in JavaScript Object Notation (JSON) that can be incorporated into third-party websites or applications. Currently, the services compute Christian, Islamic, and Jewish events.The “Dates of Ash Wednesday and Easter” service (http://aa.usno.navy.mil/data/docs/easter.php) returns the dates of these two events for years after 1582 C.E. (1582 A.D.) The method of the western Christian churches is used to determined when Easter, a moveable feast, occurs.The “Dates of Islamic New Year and Ramadan” service (http://aa.usno.navy.mil/data/docs/islamic.php) returns the approximate Gregorian dates of these two events for years after 1582 C.E. (990 A.H.) and Julian dates are computed for the years 622-1582 C.E. (1-990 A.H.). The appropriate year in the Islamic calendar (anno Hegira) is also provided. Each event begins at 6 P.M. or sunset on the preceding day. These events are computed using a tabular calendar for planning purposes; in practice, the actual event is determined by observation of the appropriate new Moon.The “First Day of Passover” service (http://aa.usno.navy.mil/data/docs/passover.php) returns the Gregorian date corresponding to Nisan 15 for years after 1582 C.E. (5342 A.M.) and Julian dates are computed for the years 360-1582 C.E. (4120-5342 A.M.). The appropriate year in the Jewish calendar (anno Mundi) is also provided. Passover begins at 6 P.M. or sunset on the preceding day.On-line documentation for using the API-enabled calendar computers, including sample calls, is available (http://aa.usno.navy.mil/data/docs/api.php). The same web page also describes how to reach the Complete Sun and Moon Data for One Day, Phases of the Moon, Solar Eclipse Computer, Day and Night Across the Earth, and Apparent Disk of a Solar System Object services using API calls.An “Introduction to Calendars” (http://aa.usno.navy.mil/faq/docs/calendars.php) provides an overview of the topic and links to additional resources.

Using biotic ligand models to predict metal toxicity in mineralized systems

USGS Publications Warehouse

Smith, Kathleen S.; Balistrieri, Laurie S.; Todd, Andrew S.

2015-01-01

The biotic ligand model (BLM) is a numerical approach that couples chemical speciation calculations with toxicological information to predict the toxicity of aquatic metals. This approach was proposed as an alternative to expensive toxicological testing, and the U.S. Environmental Protection Agency incorporated the BLM into the 2007 revised aquatic life ambient freshwater quality criteria for Cu. Research BLMs for Ag, Ni, Pb, and Zn are also available, and many other BLMs are under development. Current BLMs are limited to ‘one metal, one organism’ considerations. Although the BLM generally is an improvement over previous approaches to determining water quality criteria, there are several challenges in implementing the BLM, particularly at mined and mineralized sites. These challenges include: (1) historically incomplete datasets for BLM input parameters, especially dissolved organic carbon (DOC), (2) several concerns about DOC, such as DOC fractionation in Fe- and Al-rich systems and differences in DOC quality that result in variations in metal-binding affinities, (3) water-quality parameters and resulting metal-toxicity predictions that are temporally and spatially dependent, (4) additional influences on metal bioavailability, such as multiple metal toxicity, dietary metal toxicity, and competition among organisms or metals, (5) potential importance of metal interactions with solid or gas phases and/or kinetically controlled reactions, and (6) tolerance to metal toxicity observed for aquatic organisms living in areas with elevated metal concentrations.

Trihalomethanes in marine mammal aquaria: occurrences, sources, and health risks.

PubMed

Wang, Jun-Jian; Chow, Alex T; Sweeney, Joelle M; Mazet, Jonna A K

2014-08-01

Disinfecting water containing the high levels of dissolved organic carbon (DOC) commonly generated during pinniped husbandry may cause the formation of carcinogenic disinfection byproducts (DBPs). Little information is available on DBP levels, sources, and health risks in marine mammal aquaria. Using the commonly observed trihalomethanes (THMs) as a DBP indicator, we monitored concentrations for seven months at The Marine Mammal Center in Sausalito, California, one of the largest pinniped rehabilitation facilities in the world. Concentrations of THMs ranged 1.1-144.2 μg/L in pool waters and generally increased with number of animals housed (P < 0.05). To identify the sources of THM precursors in marine mammal aquaria, we intensively monitored the mass flows of potential THM precursors (i.e. food and wastes) in an isolated system with nine individual California sea lions to evaluate the sources and reactivity of dissolved organic carbon (DOC) for 2-5 weeks. The common frozen foods used in feeding pinnipeds, including herring, sardine, and squid, produced an average of 22-34 mg-DOC/g-food in water and 836-1066 μg-THM/g-food after chlorination, whereas the fecal materials, including fresh scat, decomposed scat, and urine, produced 2-16 mg-DOC/g-waste and 116-768 μg-THM/g-waste. Food not eaten by animals could cause a sharp increase of DOC and DBP production and therefore should be removed rapidly from pools. Marine mammal husbandry staff and trainers are at risk (5.16 × 10(-4) to 1.30 × 10(-3)) through exposure of THMs, exceeding the negligible risk level (10(-6)) defined by the US Environmental Protection Agency. Copyright © 2014 Elsevier Ltd. All rights reserved.

Changes in the character of DOC in streams during storms in two Midwestern watersheds with contrasting land uses

USGS Publications Warehouse

Vidon, P.; Wagner, L.E.; Soyeux, E.

2008-01-01

Dissolved organic carbon (DOC) dynamics in streams is important, yet few studies focus on DOC dynamics in Midwestern streams during storms. In this study, stream DOC dynamics during storms in two Midwestern watersheds with contrasting land uses, the change in character of stream DOC during storms, and the usability of DOC as a hydrologic tracer in artificially drained landscapes of the Midwest are investigated. Major cation/DOC concentrations, and DOC specific UV absorbance (SUVA) and fluorescence index (FI) were monitored at 2-4 h intervals during three spring storms. Although DOC is less aromatic in the mixed land use watershed than in the agricultural watershed, land use has little impact on stream DOC concentration during storms. For both watersheds, DOC concentration follows discharge, and SUVA and FI values indicate an increase in stream DOC aromaticity and lignin content during storms. The comparison of DOC/major cation flushing dynamics indicates that DOC is mainly exported via overland flow/macropore flow. In both watersheds, the increase in DOC concentration in the streams during storms corresponds to a shift in the source of DOC from DOC originating from mineral soil layers of the soil profile at baseflow, to DOC originating from surficial soil layers richer in aromatic substances and lignin during storms. Results also suggest that DOC, SUVA and FI could be used as hydrologic tracers in artificially drained landscapes of the Midwest. These results underscore the importance of sampling streams for DOC during high flow periods in order to understand the fate of DOC in streams. ?? 2008 Springer Science+Business Media B.V.

Ocean observer study: A proposed national asset to augment the future U.S. operational satellite system

USGS Publications Warehouse

Cunningham, J.D.; Chambers, D.; Davis, C.O.; Gerber, A.; Helz, R.; McGuire, J.P.; Pichel, W.

2003-01-01

The next generation of U.S. polar orbiting environmental satellites, are now under development. These satellites, jointly developed by the Department of Defense (DoD), the Department of Commerce (DOC), and the National Aeronautics and Space Administration (NASA), will be known as the National Polar-orbiting Operational Environmental Satellite System (NPOESS). It is expected that the first of these satellites will be launched in 2010. NPOESS has been designed to meet the operational needs of the U.S. civilian meteorological, environmental, climatic, and space environmental remote sensing programs, and the Global Military Space and Geophysical Environmental remote sewing programs. This system, however, did not meet all the needs of the user community interested in operational oceanography (particularly in coastal regions). Beginning in the fall of 2000, the Integrated Program Office (IPO), a joint DoD, DOC, and NASA office responsible for the NPOESS development, initiated the Ocean Observer Study (OOS). The purpose of this study was to assess and recommend how best to measure the missing or inadequately sampled ocean parameters. This paper summarizes the ocean measurement requirements documented in the OOS, describes the national need to measure these parameters, and describes the satellite instrumentation required to make those measurements.

78 FR 6804 - Codex Alimentarius Commission: Meeting of the Codex Committee on Food Labeling

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-31

...; (c) Studying specific labeling problems assigned to it by Codex; and (d) Studying problems associated... the Production, Processing, Labeling and Marketing of Organically Produced Foods. (a) Use of ethylene... Washington, DC on January 24, 2013. Mary Frances Lowe, U.S. Manager for Codex Alimentarius. [FR Doc. 2013...

Potential limitations of NRC in predicting energetic requirements of beef females within western U.S. grazing systems

USDA-ARS?s Scientific Manuscript database

Assessment of beef cow energy balance and efficiency in grazing-extensive rangelands has occurred on a nominal basis over short time intervals and has not accounted for the complexity of metabolic and digestive responses; behavioral adaptations to climatic, terrain, and vegetation variables; and doc...

75 FR 79417 - Record of Vote of Meeting Closure

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-20

...] Record of Vote of Meeting Closure I, Isaac Fulwood, of the United States Parole Commission, was present... following Commissioners voted that the meeting be closed: Isaac Fulwood, Cranston J. Mitchell and Patricia K.... Isaac Fulwood, Chairman, U.S. Parole Commission. [FR Doc. 2010-31860 Filed 12-17-10; 8:45 am] BILLING...

76 FR 55457 - Notice of Rights and Protections Available Under the Federal Antidiscrimination and Whistleblower...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-07

... Civil Rights, Office of the Secretary, U.S. Department of Transportation, 1200 New Jersey Avenue, SE..., Director, Departmental Office of Civil Rights, United States Department of Transportation. [FR Doc. 2011... DEPARTMENT OF TRANSPORTATION Office of the Secretary [DOT-OST-2011-0165] Notice of Rights and...

78 FR 79460 - Notification of GSA Strategic Plan

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-30

...] Notification of GSA Strategic Plan AGENCY: Office of the Chief Financial Officer, U.S. General Services..., Office of the Chief Financial Officer, 1800 F Street NW., Washington, DC 20405. FOR FURTHER INFORMATION... Officer, Office of the Chief Financial Officer. [FR Doc. 2013-31168 Filed 12-27-13; 8:45 am] BILLING CODE...

77 FR 4555 - Service Contract Inventory for Fiscal Year (FY) 2011

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-30

... Chief Financial Officer, U.S. Department of Education. ACTION: Notice of availability--FY 2011 Service... Appropriations Act of 2010, Pub. L. 111-117. Dated: January 26, 2012. Hugh J. Hurwitz, Deputy Chief Financial Officer. [FR Doc. 2012-2032 Filed 1-27-12; 8:45 am] BILLING CODE 4000-01-P ...

76 FR 5567 - Service Contract Inventory for Fiscal Year (FY) 2010

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-01

... DEPARTMENT OF EDUCATION Service Contract Inventory for Fiscal Year (FY) 2010 AGENCY: Office of the Chief Financial Officer, U.S. Department of Education. ACTION: Notice of availability--FY 2010 Service.... Skelly, Chief Financial Officer. [FR Doc. 2011-2236 Filed 1-28-11; 11:15 am] BILLING CODE 4000-01-P ...

78 FR 10611 - Service Contract Inventory for Fiscal Year (FY) 2012

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-14

... DEPARTMENT OF EDUCATION Service Contract Inventory for Fiscal Year (FY) 2012 AGENCY: Office of the Chief Financial Officer, U.S. Department of Education. ACTION: Notice of availability--FY 2012 service... Deputy Chief Financial Officer. [FR Doc. 2013-03441 Filed 2-13-13; 8:45 am] BILLING CODE 4000-01-P ...

U.G. Government Technology Information Locator

DTIC Science & Technology

1998-04-01

National Science Foundation (NSF); the United States Department of Agriculture (USDA); and the Department of Commerce (DOC)-plus eight other government S&T resources. It is intended as a starter set to help users locate U.S. government technology information. For convenience, it uses Internet addresses, e-mail addresses, and telephone numbers. The Appendix contains a

75 FR 74685 - Initiation of Five-Year (“Sunset”) Review

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-01

... pistachios from Iran (A-507-502) in December 2010. However, the recently enacted Comprehensive Iran Sanctions, Accountability, and Divestment Act of 2010 includes a ban on all U.S. imports from Iran, including pistachios... on raw pistachios from Iran until two months after the import ban on pistachios is lifted. DOC case...

77 FR 19012 - Environmental Financial Advisory Board; Notice of Charter Renewal

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-29

... of duties imposed on the Agency by law. Inquiries may be directed to Joseph L. Dillon, Director, Center for Environmental Finance, U.S. EPA, Ariel Rios Building, 1200 Pennsylvania Ave. NW., Washington.... Vanessa Bowie, Acting Director, Center for Environmental Finance. [FR Doc. 2012-7576 Filed 3-28-12; 8:45...

77 FR 31607 - Commission Information Collection Activities (FERC-587); Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-29

... improvement of navigation and for the development, transmission, and utilization of power across, along, from... applicable U.S. land. \\1\\ 16 U.S.C. 797d (2010). \\2\\ Public Law 99-495, 100 Stat. 1243 (1996). The... of information technology. Dated: May 21, 2012. Kimberly D. Bose, Secretary. [FR Doc. 2012-12869...

Dynamic Evaluation of CMAQ Part II: Evaluation of relative response factor metrics for ozone attainment demonstrations

EPA Science Inventory

The U.S. Environmental Protection Agency provides guidelines on the use of air quality models for projecting whether an emission reduction strategy will lead to future pollutant levels that are at or below the National Ambient Air Quality Standards (NAAQS). The EPA's guidance doc...

77 FR 58356 - Environmental Technologies Trade Advisory Committee Public Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-20

... technology sector. Background: The ETTAC is mandated by Public Law 103-392. It was created to advise the U.S... Advisory Committee Public Meeting AGENCY: International Trade Administration, DOC. ACTION: Notice of.... to 3:30 p.m. EDT. This meeting is open to the public and time will be permitted for public comment...

76 FR 30825 - Special Local Regulation; Olympia Harbor Days Tug Boat Races, Budd Inlet, WA

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-27

..., 2011. G.T. Blore, Rear Admiral, U.S. Coast Guard Commander, Thirteenth Coast Guard District. [FR Doc... standards (e.g., specifications of materials, performance, design, or operation; test methods; sampling..., paragraph (34)(g.) of the Instruction. This rule involves tug boat racing by various classes of tugboats in...

GOES Data Collection System - Home

Science.gov Websites

Contact Us Survey GOES Data Collection System GOES DCS High Data Rate Transition has ended For more ), as well as contact information for reporting trouble, and gaining personal assistance. NOAA Policy on Spring, MD 20910-3282 USA DOC logo NOAASIS Contact | Contact Webmaster weather.gov | Privacy Act

78 FR 53374 - Energy Conservation Program for Consumer Products: Test Procedures for Refrigerators...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-29

... Freezers AGENCY: Office of Energy Efficiency and Renewable Energy, Department of Energy. ACTION: Extension... INFORMATION CONTACT: Mr. Lucas Adin, U.S. Department of Energy, Office of Energy Efficiency and Renewable... Energy Efficiency, Energy Efficiency and Renewable Energy. [FR Doc. 2013-21115 Filed 8-28-13; 8:45 am...

77 FR 15719 - Public Workshop to Seek Comment on Federal Conformity Assessment Guidance

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-16

... (NIST), Department of Commerce. ACTION: Notice of Public Workshop. SUMMARY: The U.S. Department of Commerce's (DOC) National Institute of Standards and Technology (NIST) will hold a free public workshop.... Eastern Time (ET) at NIST in Gaithersburg, Maryland. The purpose of the NIST public workshop is (1) to...

75 FR 16517 - FirstEnergy Nuclear Operating Company; Environmental Assessment and Finding of No Significant Impact

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-01

... Perry. FOR FURTHER INFORMATION CONTACT: Michael Mahoney, Office of Nuclear Reactor Regulation, U.S... Nuclear Reactor Regulation. [FR Doc. 2010-7331 Filed 3-31-10; 8:45 am] BILLING CODE 7590-01-P ... NUCLEAR REGULATORY COMMISSION [Docket No. 50-440; NRC-2010-0124] FirstEnergy Nuclear Operating...

76 FR 11521 - Prairie Island Nuclear Generating Plant, Unit 1, Northern States Power Company-Minnesota; Notice...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-02

..., Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001..., Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation. [FR Doc. 2011-4557 Filed 3-1... NUCLEAR REGULATORY COMMISSION [Docket No. 50-282; NRC-2011-0040] Prairie Island Nuclear Generating...

75 FR 366 - Notice of Agreement Filed

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-05

... vessel space in the trade between the U.S. ports and ports in Malaysia, Vietnam, Japan, Korea, People's... the Commission's Web site ( http://www.fmc.gov ) or by contacting the Office of Agreements at (202... Commission. Dated: December 31, 2009. Tanga S. FitzGibbon, Assistant Secretary. [FR Doc. E9-31371 Filed 1-4...

Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analyses

NASA Astrophysics Data System (ADS)

Zigah, Prosper K.; Minor, Elizabeth C.; McNichol, Ann P.; Xu, Li; Werne, Josef P.

2017-07-01

We measured the concentrations and isotopic compositions of solid phase extracted (SPE) dissolved organic carbon (DOC) and high molecular weight (HMW) DOC and their constituent organic components in order to better constrain the sources and cycling of DOC in a large oligotrophic lacustrine system (Lake Superior, North America). SPE DOC constituted a significant proportion (41-71%) of the lake DOC relative to HMW DOC (10-13%). Substantial contribution of 14C-depleted components to both SPE DOC (Δ14C = 25-43‰) and HMW DOC (Δ14C = 22-32‰) was evident during spring mixing, and depressed their radiocarbon values relative to the lake dissolved inorganic carbon (DIC; Δ14C ∼ 59‰). There was preferential removal of 14C-depleted (older) and thermally recalcitrant components from HMW DOC and SPE DOC in the summer. Contemporary photoautotrophic addition to HMW DOC was observed during summer stratification in contrast to SPE DOC, which decreased in concentration during stratification. Serial thermal oxidation radiocarbon analysis revealed a diversity of sources (both contemporary and older) within the SPE DOC, and also showed distinct components within the HMW DOC. The thermally labile components of HMW DOC were 14C-enriched and are attributed to heteropolysaccharides (HPS), peptides/amide and amino sugars (AMS) relative to the thermally recalcitrant components reflecting the presence of older material, perhaps carboxylic-rich alicyclic molecules (CRAM). The solvent extractable lipid-like fraction of HMW DOC was very 14C-depleted (as old as 1270-2320 14C years) relative to the carbohydrate-like and protein-like substances isolated by acid hydrolysis of HMW DOC. Our data constrain relative influences of contemporary DOC and old DOC, and DOC cycling in a modern freshwater ecosystem.

How appetizing is the dissolved organic matter (DOM) trees lose during rainfall?

NASA Astrophysics Data System (ADS)

Howard, D.; Van Stan, J. T., II; Whitetree, A.; Zhu, L.; Stubbins, A.

2017-12-01

Dissolved organic carbon (DOC) is the chemical backbone of dissolved organic matter (DOM), which is important because it drives many processes in soils and waterways. Current DOC work has paid little attention to interactions between rain and plant canopies, where rainfall is partitioned into throughfall and stemflow. Even less DOC research has investigated the effect of arboreal epiphytes on throughfall and stemflow DOC. The purpose of this study is twofold: (1) assess the degree and timing of DOC consumption by microbial communities (biolability) in throughfall and stemflow, and (2) determine whether the presence of arboreal epiphytes in the canopy affect DOC biolability. Biolability of stemflow and throughfall DOC from Juniperus virginiana (cedar) was determined by incubating samples for 14 days. Throughfall and stemflow DOC was highly biolabile with DOC concentrations decreasing by 30-60%. Throughfall DOC was more biolabile than stemflow DOC. DOC in both throughfall and stemflow from epiphyte-covered cedars was less biolabile than DOC from trees without epiphytes. The high biolability of tree-derived DOC indicates that its supply provides carbon substrates to the microbial community at the forest floor, in soils and the rhizosphere. Epiphytes appear to be important in determining the biolability of DOC and therefore the size of this carbon subsidy to the soil ecosystem.

75 FR 71147 - Record of Vote of Meeting Closure

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-22

.... 94-409) (5 U.S.C. Sec. 552b) I, Isaac Fulwood, of the United States Parole Commission, was present at... following Commissioners voted that the meeting be closed: Isaac Fulwood, Cranston J. Mitchell and Patricia K..., 2010. Isaac Fuiwood, Chairman, U.S. Parole Commission. [FR Doc. 2010-29354 Filed 11-19-10; 8:45 am...

78 FR 63274 - Notice of Rights and Protections Available Under the Federal Antidiscrimination and Whistleblower...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-23

..., Departmental Office of Civil Rights, Office of the Secretary, U.S. Department of Transportation, 1200 New...(s) within your agency (e.g., EEO/civil rights offices, human resources offices, or legal offices... Office of Civil Rights, United States Department of Transportation. [FR Doc. 2013-24811 Filed 10-22-13; 8...

77 FR 74923 - Water Quality Standards for the State of Florida's Estuaries, Coastal Waters, and South Florida...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-18

... proposing numeric water quality criteria to protect ecological systems, aquatic life, and human health from... Technical Support Section. http://www.dep.state.fl.us/water/wqssp/.everglades/docs/pctsd/IIIChapter.2.pdf... Water Quality Standards for the State of Florida's Estuaries, Coastal Waters, and South Florida Inland...

77 FR 47826 - Record of Decision for F35A Training Basing Final Environmental Impact Statement

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-10

... DEPARTMENT OF DEFENSE Department of the Air Force Record of Decision for F35A Training Basing Final Environmental Impact Statement ACTION: Notice of Availability (NOA) of a Record of Decision ([email protected]us.af.mil . Henry Williams Jr., Acting Air Force Federal Register Liaison Officer. [FR Doc...

75 FR 4845 - Advice Concerning Possible Modifications to the U.S. Generalized System of Preferences, 2010...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-29

...: Information specific to this investigation may be obtained from Philip Stone, Project Leader, Office of Industries (202-205-3424 or philip.stone@usitc.gov ). For information on the legal aspects of this.... Issued: January 25, 2010. Marilyn R. Abbott, Secretary to the Commission. [FR Doc. 2010-1812 Filed 1-28...

76 FR 44324 - Environmental Laboratory Advisory Board; Notice of Charter Renewal

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-25

... imposed on the Agency by law. Inquiries may be directed to Lara P. Autry, Senior Advisor, U.S. Environmental Protection Agency, Office of the Science Advisor, 109 T W Alexander Drive (E243-05), Research... Science Advisor. [FR Doc. 2011-18709 Filed 7-22-11; 8:45 am] BILLING CODE 6560-50-P ...

76 FR 45402 - Rules of Origin

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-29

... DEPARTMENT OF HOMELAND SECURITY U.S. Customs and Border Protection 19 CFR Part 102 Rules of Origin CFR Correction In Title 19 of the Code of Federal Regulations, Parts 0 to 140, revised as of April 1, 2011, on page 578, in Sec. 102.20, in the table, the second entry for 8708.99 is removed. [FR Doc. 2011...

78 FR 20148 - Reporting Procedure for Mathematical Models Selected To Predict Heated Effluent Dispersion in...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-03

... Regulatory Research, U.S. Nuclear Regulatory Commission, Washington DC 20555-0001; telephone: 301-251-7445... relevant modeling factors to accompany descriptive material for the one or more models submitted by an..., Division of Engineering, Office of Nuclear Regulatory Research. [FR Doc. 2013-07702 Filed 4-2-13; 8:45 am...

78 FR 16709 - Certain Cold Cathode Fluorescent Lamp (“CCFL”) Inverter Circuits and Products Containing Same...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-18

.... International Trade Commission, 500 E Street SW., Washington, DC 20436, telephone (202) 205-2737. The public... the Office of the Secretary, U.S. International Trade Commission, 500 E Street SW., Washington, DC... the Commission. Lisa R. Barton, Acting Secretary to the Commission. [FR Doc. 2013-06166 Filed 3-15-13...

75 FR 5879 - Grapes Grown in a Designated Area of Southeastern California and Imported Table Grapes; Change in...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-05

... from normal marketing channels for up to 60 days after their arrival at a U.S. port. The practice of... products. Under normal marketing conditions, imported grapes move directly through distribution channels... DEPARTMENT OF AGRICULTURE Agricultural Marketing Service 7 CFR Parts 925 and 944 [Doc. No. AMS-FV...

76 FR 42036 - Determining the Amount of Taxes Paid for Purposes of the Foreign Tax Credit

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-18

.... Approved: July 11, 2011. Emily S. McMahon, Acting Assistant Secretary of the Treasury (Tax Policy). [FR Doc... of the entity's gross income, as determined under U.S. tax principles, is attributable to passive investment income and substantially all of the entity's assets are held to produce such passive investment...

77 FR 60454 - Proposed Information Collection; Declaration for Importation or Exportation of Fish or Wildlife

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-03

... country of origin of the fish or wildlife. In addition, certain information, such as the airway bill or bill of lading number, the location of the fish or wildlife for inspection, and the number of cartons.... Campbell, Chief, Division of Policy and Directives Management, U.S. Fish and Wildlife Service. [FR Doc...

78 FR 8998 - Energy Conservation Program for Consumer Products and Certain Commercial and Industrial Equipment...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-07

... and Renewable Energy, Department of Energy. ACTION: Notice of reopening of public comment period.... James Raba, U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Building... Efficiency and Renewable Energy. [FR Doc. 2013-02755 Filed 2-6-13; 8:45 am] BILLING CODE 6450-01-P ...

76 FR 64073 - Announcement of Changes to the Membership of the Performance Review Board

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-17

...: Ronda L. Holbrook, U.S. Department of Commerce, Human Resources Operations Center (DOCHROC), Office of Executive Resources Operations, 14th and Constitution Avenue, NW., Room 7419, Washington, DC 20230, at (202... Commerce Human Resources Operations Center. [FR Doc. 2011-26739 Filed 10-14-11; 8:45 am] BILLING CODE 3510...

78 FR 68025 - Membership of the Economic Development Administration Performance Review Board

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-13

... CONTACT: Ruthie B. Stewart, U.S. Department of Commerce, Office of Human Resources Management, Office of...) Edith J. McCloud, Associate Director for Management, Career SES 4. Department of Commerce, Office of the... Commerce Human Resources Operations Center. [FR Doc. 2013-27080 Filed 11-12-13; 8:45 am] BILLING CODE 3510...

78 FR 15009 - Consideration of Withdrawal From Commercial Production and Distribution of the Radioisotope...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-08

... may be addressed to: Dr. Marc Garland, Program Manager, Office of Nuclear Physics, Office of Science... Management Division, Office of Nuclear Physics, Office of Science, U.S. Department of Energy, Germantown..., Office of Nuclear Physics, Office of Science. [FR Doc. 2013-05444 Filed 3-7-13; 8:45 am] BILLING CODE...

14 CFR 158.9 - Limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... PASSENGER FACILITY CHARGES (PFC'S) General § 158.9 Limitations. (a) No public agency may impose a PFC on any... Department of Transportation for which PFC's may not be imposed under this section; (3) Who is a nonrevenue... a point or points in the U.S. to collect a PFC from a passenger. [Doc. No. 26385, 56 FR 24278, May...

14 CFR 158.9 - Limitations.

Code of Federal Regulations, 2012 CFR

2012-01-01

... PASSENGER FACILITY CHARGES (PFC'S) General § 158.9 Limitations. (a) No public agency may impose a PFC on any... Department of Transportation for which PFC's may not be imposed under this section; (3) Who is a nonrevenue... a point or points in the U.S. to collect a PFC from a passenger. [Doc. No. 26385, 56 FR 24278, May...

14 CFR 158.9 - Limitations.

Code of Federal Regulations, 2013 CFR

2013-01-01

... PASSENGER FACILITY CHARGES (PFC'S) General § 158.9 Limitations. (a) No public agency may impose a PFC on any... Department of Transportation for which PFC's may not be imposed under this section; (3) Who is a nonrevenue... a point or points in the U.S. to collect a PFC from a passenger. [Doc. No. 26385, 56 FR 24278, May...

14 CFR 158.9 - Limitations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... PASSENGER FACILITY CHARGES (PFC'S) General § 158.9 Limitations. (a) No public agency may impose a PFC on any... Department of Transportation for which PFC's may not be imposed under this section; (3) Who is a nonrevenue... a point or points in the U.S. to collect a PFC from a passenger. [Doc. No. 26385, 56 FR 24278, May...

14 CFR 158.9 - Limitations.

Code of Federal Regulations, 2014 CFR

2014-01-01

... PASSENGER FACILITY CHARGES (PFC'S) General § 158.9 Limitations. (a) No public agency may impose a PFC on any... Department of Transportation for which PFC's may not be imposed under this section; (3) Who is a nonrevenue... a point or points in the U.S. to collect a PFC from a passenger. [Doc. No. 26385, 56 FR 24278, May...

76 FR 26320 - Entergy Operations, Inc.; Biweekly Notice; Notice of Issuance of Amendment to Facility Operating...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-06

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Estimating Changes in Runoff and Carbon Exports From Northern Canadian Catchments Under a 2X CO2 Atmosphere

NASA Astrophysics Data System (ADS)

Clair, T. A.; Ehrman, J. M.

2006-12-01

The doubling of atmospheric CO2 on temperature and precipitation will change annual runoff and dissolved organic carbon (DOC) export patterns in northern Canada. Because of the physical size and the range of climatic changes of northern Canada, we found it necessary to model potential changes in river water and carbon exports in the region using a neural network approach. We developed a model for hydrology and one for DOC using as inputs, monthly General Circulation Model temperature and precipitation predictions, historical hydrology and dissolved organic carbon values, as well as catchment size and slope. Mining Environment Canada's historical hydrology and water chemistry databases allowed us to identify 20 sites suitable for our analysis. The site results were summarized within the Canadian Terrestrial Ecozone classification system. Our results show spring melts occurring one month sooner in all northern ecozones except for the Hudson Bay Plains zone, with changes in melt intensity occurring in most regions. The DOC model predicts that exports from catchments will increase by between 10 and 20% depending on the ecozone. Generally, we predict that major changes in both hydrology and carbon cycling should be expected in northern Canadian ecosystems in a warmer planet.

Diagnosis of Processes Controlling Dissolved Organic Carbon (DOC) Export in a Subarctic Region by a Dynamic Ecosystem Model

NASA Astrophysics Data System (ADS)

Tang, J.

2015-12-01

Permafrost thawing in high latitudes allows more soil organic carbon (SOC) to become hydrologically accessible. This can increase dissolved organic carbon (DOC) exports and carbon release to the atmosphere as CO2 and CH4, with a positive feedback to regional and global climate warming. However, this portion of carbon loss through DOC export is often neglected in ecosystem models. In this paper, we incorporate a set of DOC-related processes (DOC production, mineralization, diffusion, sorption-desorption and leaching) into an Arctic-enabled version of the dynamic ecosystem model LPJ-GUESS (LPJ-GUESS WHyMe) to mechanistically model the DOC export, and to link this flux to other ecosystem processes. The extended LPJ-GUESS WHyMe with these DOC processes is applied to the Stordalen catchment in northern Sweden. The relative importance of different DOC-related processes for mineral and peatland soils for this region have been explored at both monthly and annual scales based on a detailed variance-based Sobol sensitivity analysis. For mineral soils, the annual DOC export is dominated by DOC fluxes in snowmelt seasons and the peak in spring is related to the runoff passing through top organic rich layers. Two processes, DOC sorption-desorption and production, are found to contribute most to the annual variance in DOC export. For peatland soils, the DOC export during snowmelt seasons is constrained by frozen soils and the processes of DOC production and mineralization, determining the magnitudes of DOC desorption in snowmelt seasons as well as DOC sorption in the rest of months, play the most important role in annual variances of DOC export. Generally, the seasonality of DOC fluxes is closely correlated with runoff seasonality in this region. The current implementation has demonstrated that DOC-related processes in the framework of LPJ-GUESS WHyMe are at an appropriate level of complexity to represent the main mechanism of DOC dynamics in soils. The quantified contributions from different processes on DOC export dynamics could be further linked to the climate change, vegetation composition change and permafrost thawing in this region.

Dissolved organic carbon in Alaskan boreal forest: Sources, chemical characteristics, and biodegradability

USGS Publications Warehouse

Wickland, K.P.; Neff, J.C.; Aiken, G.R.

2007-01-01

The fate of terrestrially-derived dissolved organic carbon (DOC) is important to carbon (C) cycling in both terrestrial and aquatic environments, and recent evidence suggests that climate warming is influencing DOC dynamics in northern ecosystems. To understand what determines the fate of terrestrial DOC, it is essential to quantify the chemical nature and potential biodegradability of this DOC. We examined DOC chemical characteristics and biodegradability collected from soil pore waters and dominant vegetation species in four boreal black spruce forest sites in Alaska spanning a range of hydrologic regimes and permafrost extents (Well Drained, Moderately Well Drained, Poorly Drained, and Thermokarst Wetlands). DOC chemistry was characterized using fractionation, UV-Vis absorbance, and fluorescence measurements. Potential biodegradability was assessed by incubating the samples and measuring CO2 production over 1 month. Soil pore water DOC from all sites was dominated by hydrophobic acids and was highly aromatic, whereas the chemical composition of vegetation leachate DOC varied significantly with species. There was no seasonal variability in soil pore water DOC chemical characteristics or biodegradability; however, DOC collected from the Poorly Drained site was significantly less biodegradable than DOC from the other three sites (6% loss vs. 13-15% loss). The biodegradability of vegetation-derived DOC ranged from 10 to 90% loss, and was strongly correlated with hydrophilic DOC content. Vegetation such as Sphagnum moss and feathermosses yielded DOC that was quickly metabolized and respired. In contrast, the DOC leached from vegetation such as black spruce was moderately recalcitrant. Changes in DOC chemical characteristics that occurred during microbial metabolism of DOC were quantified using fractionation and fluorescence. The chemical characteristics and biodegradability of DOC in soil pore waters were most similar to the moderately recalcitrant vegetation leachates, and to the microbially altered DOC from all vegetation leachates. ?? 2007 Springer Science+Business Media, LLC.

Human Space Flight Plans Committee Report

NASA Image and Video Library

2009-10-21

NASA Public Affairs Officer Doc Mirelson, left, and Chairman of the U.S. Human Space Flight Plans Committee Norman Augustine, right, listen to reporters questions during a press conference where the committee released it's report on Thursday, Oct., 22, 2009 at the National Press Club in Washington. The Obama Administration tasked the committee to do an independent review of planned U.S. human space flight activities with the goal of ensuring that the nation is on a vigorous and sustainable path to achieving its boldest aspirations in space. Photo Credit: (NASA/Bill Ingalls)

Dissolved organic carbon and its potential predictors in eutrophic lakes.

PubMed

Toming, Kaire; Kutser, Tiit; Tuvikene, Lea; Viik, Malle; Nõges, Tiina

2016-10-01

Understanding of the true role of lakes in the global carbon cycle requires reliable estimates of dissolved organic carbon (DOC) and there is a strong need to develop remote sensing methods for mapping lake carbon content at larger regional and global scales. Part of DOC is optically inactive. Therefore, lake DOC content cannot be mapped directly. The objectives of the current study were to estimate the relationships of DOC and other water and environmental variables in order to find the best proxy for remote sensing mapping of lake DOC. The Boosted Regression Trees approach was used to clarify in which relative proportions different water and environmental variables determine DOC. In a studied large and shallow eutrophic lake the concentrations of DOC and coloured dissolved organic matter (CDOM) were rather high while the seasonal and interannual variability of DOC concentrations was small. The relationships between DOC and other water and environmental variables varied seasonally and interannually and it was challenging to find proxies for describing seasonal cycle of DOC. Chlorophyll a (Chl a), total suspended matter and Secchi depth were correlated with DOC and therefore are possible proxies for remote sensing of seasonal changes of DOC in ice free period, while for long term interannual changes transparency-related variables are relevant as DOC proxies. CDOM did not appear to be a good predictor of the seasonality of DOC concentration in Lake Võrtsjärv since the CDOM-DOC coupling varied seasonally. However, combining the data from Võrtsjärv with the published data from six other eutrophic lakes in the world showed that CDOM was the most powerful predictor of DOC and can be used in remote sensing of DOC concentrations in eutrophic lakes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Soil-solution partitioning of DOC in acid organic soils: Results from a UK field acidification and alkalization experiment

NASA Astrophysics Data System (ADS)

Oulehle, Filip; Jones, Timothy; Burden, Annette; Evans, Chris

2013-04-01

Dissolved organic carbon (DOC) is an important component of the global carbon (C) cycle and has profound impacts on water chemistry and metabolism in lakes and rivers. Reported increases of DOC concentration in surface waters across Europe and Northern America have been attributed to several drivers; from changing climate and land-use to eutrophication and declining acid deposition. The last of these suggests that acidic deposition suppressed the solubility of DOC, and that this historic suppression is now being reversed by reducing emissions of acidifying pollutants. We studied a set of four parallel acidification and alkalization experiments in organic rich soils which, after three years of manipulation, have shown clear soil solution DOC responses to acidity change. We tested whether these DOC concentration changes were related to changes in the acid/base properties of DOC. Based on laboratory determination of DOC site density (S.D. = amount of carboxylic groups per milligram DOC) and charge density (C.D. = organic acid anion concentration per milligram DOC) we found that the change in DOC soil-solution partitioning was tightly related to the change in degree of dissociation (α = C.D./S.D. ratio) of organic acids (R2=0.74, p<0.01). Carbon turnover in soil organic matter (SOM), determined by soil respiration and β-D-glucosidase enzyme activity measurements, also appears to have some impact on DOC leaching, via constraints on the actual supply of available DOC from SOM; when the turnover rate of C in SOM is low, the effect of α on DOC leaching is reduced. Thus, differences in the magnitude of DOC changes seen across different environments might be explained by interactions between physicochemical restrictions of DOC soil-solution partitioning, and SOM carbon turnover effects on DOC supply.

Effect of Photochemical Transformation on Dissolved Organic Carbon Concentration and Bioavailability from Watersheds with Varying Landcover

NASA Astrophysics Data System (ADS)

Vermilyea, A.; Sanders, A.; Vazquez, E.

2017-12-01

The transformation of freshwater dissolved organic carbon (DOC) can have important implications for water quality, aquatic ecosystem health, and our climate. DOC is an important nutrient for heterotrophic microorganisms near the base of the aquatic food chain and the extent of conversion of DOC to CO2 is a critical piece of the global carbon cycle. Photochemical pathways have the potential to transform recalcitrant DOC into more labile forms that can then be converted to smaller DOC molecules and eventually be completely mineralized to CO2. This may lead to a DOC pool with different bioavailability depending on the structural composition of the original DOC pool and the mechanistic pathways undergone during transformation. This study aimed to measure the changes in DOC concentration and bioavailability due solely to photochemical processes in three watersheds of northern Vermont, USA that have varied land cover, land use (LCLU) attributes. Our hypothesis was that photochemical transformations will lead to (1) an overall loss of DOC due to mineralization to CO2 and (2) a relative increase in the bioavailable fraction of DOC. Additionally, the influence of LCLU and base flow versus storm flow on both mineralization rates and changes in DOC bioavailability was investigated. Irradiation of filtered samples in quartz vessels under sunlight led to small changes in DOC concentration over time, but significant changes in DOC bioavailability. In general, fluorescence excitation-emission matrices (EEMs) showed a shift from an initially more humic-like DOC pool, to a more protein-like (bioavailable) DOC pool. Specific UV index (SUVA) along with bioavailable DOC (BDOC) incubations were also used to characterize DOC and its bioavailability. There were only small differences in the DOC transformation that took place among sites, possibly due to only small differences in the initial bioavailability and fluorescent properties between water samples. Photochemical transformation appears to play an important role in the transformation of a more recalcitrant (humic) pool of DOC into a more bioavailable DOC pool that can then be utilized by aquatic heterotrophs and ultimately be converted to CO2.

Understanding DOC Mobilization Dynamics Through High Frequency Measurements in a Headwater Catchment

NASA Astrophysics Data System (ADS)

Werner, B.; Musolff, A.; Lechtenfeld, O.; de Rooij, G. H.; Fleckenstein, J. H.

2017-12-01

Increasing dissolved organic carbon (DOC) exports from headwater catchments impact the quality of downstream waters and pose challenges to water supply. The importance of riparian zones for DOC export from catchments in humid, temperate climates has generally been acknowledged, but the hydrological controls and biogeochemical factors that govern mobilization of DOC from riparian zones remain elusive. By analyzing high-frequency time series of UV-VIS based water quality we therefore aim at a better understanding on temporal dynamics of DOC mobilization and exports. In a first step a one year high frequency (15 minutes) data set from a headwater catchment in the Harz Mountains (Germany) was systematically analyzed for event-based patterns in DOC concentrations. Here, a simplistic linear model was generated to explain DOC concentration level and variability in the stream. Furthermore, spectral (e.g. slopes and SUVA254) and molecular (FT-ICR-MS) characterization of DOC was used to fingerprint in-stream DOC during events. Continuous DOC concentrations were best predicted (R², NSE = 0.53) by instantaneous discharge (Q) and antecede wetness conditions of the last 30 days (AWC30 = Precip.30/PET30) as well as mean air temperature (Tmean30) and mean discharge (Qmean30) of the preceding 30 days. Analyses of 36 events revealed seasonal trends for the slope, intercept and R² of linear log(DOC)-log(Q) regressions that can be best explained by the mean air temperature of the preceding 15 days. Continuously available optical DOC quality parameters SUVA254 and spectral slope (275 nm - 295 nm) systematically changed with shifts in discharge and in DOC concentration. This is underlined by selected FT-ICR-MS measurements indicating higher DOC aromaticity and oxygen content at high flow conditions. The change of DOC quality parameters during events indicate a shift in the activated source zones: DOC with a different quality was mobilized during high flow conditions when higher groundwater levels connected formerly disconnected DOC source zones to the stream. We conclude that the high concentration variability of DOC can be explained by a few controlling variables only. These variables can be linked to event-based DOC source activation and more seasonal controls of DOC production.

Amounts, isotopic character and ages of organic and inorganic carbon exported from rivers to ocean margins: Assessment of natural and anthropogenic controls

NASA Astrophysics Data System (ADS)

Bauer, J. E.; Hossler, K.

2012-12-01

Riverine exports of carbon (C) and organic matter (OM) are regulated by a variety of natural and anthropogenic factors. Understanding the relationships between these various factors and C and OM exports can help to constrain global C budgets, as well allow assessment of current and future anthropogenic impacts on both riverine and global C cycles. We quantified the effects of multiple natural and anthropogenic controls on riverine export fluxes and compositions of particulate organic C (POC), dissolved organic C (DOC), and dissolved inorganic C (DIC) for a regional group of eight rivers in the northeastern U.S. For allochthonous and aged C contributions to POC, DOC and DIC exports, we first estimated fractional contributions from six potential sources for POC and DOC (i.e., modern C3 plant material (C3-OC), modern C4 plant material (C4-OC), modern algal material (algal OC), slow-turnover soil OC (slow SOC; turnover time 25 yr), passive-turnover soil OC (passive SOC; turnover time 5,000 yr) and fossil OC and four potential sources for DIC (i.e., modern atmospheric CO2 exchange, carbonate dissolution, POC remineralization and DOC remineralization) using a novel time-varying isotope mixing model. Using these estimated source contributions, we then estimated the allochthonous proportions of (a) the POC and DOC pools to be the C3-OC, C4-OC, slow SOC, passive SOC, and fossil OC contributions; and (b) the DIC pools to be the dissolved carbonates, remineralized allochthonous POC, and remineralized allochthonous DOC contributions. We considered aged C to be anything older than ˜ 60 yr, which included passive SOC and fossil OC for POC and DOC and dissolved carbonates and aged fractions of remineralized POC and DOC for DIC. Potential controls related to hydrogeomorphology and regional climate, soil order, soil texture, bedrock lithology, land use, and additional anthropogenic factors were analyzed collectively, individually, and at scales of both local and regional influence. Factors related either to hydrogeomorphology and climate or to anthropogenic factors exhibited the strongest impacts on riverine C exports and compositions, particularly at broader regional scales. The effect of hydrogeomorphology and climate was primarily one of size, as larger watersheds with greater discharge exported more total C and terrestrial C. Principal anthropogenic factors included impacts of wastewater treatment plants (WWTPs) and river impoundments. The presence of WWTPs as well as anthropogenic use of carbonate-based materials (e.g., limestone) may have substantially increased riverine C exports, particularly fossil C exports, in the study region. The presence of nuclear power plants in the associated watersheds is also discussed because of the potential for anthropogenic 14C inputs and subsequent biasing of aquatic C studies utilizing natural abundance 14C.

Disinfection byproduct precursor dynamics and water treatability during an extreme flooding event in a coastal blackwater river in southeastern United States.

PubMed

Ruecker, A; Uzun, H; Karanfil, T; Tsui, M T K; Chow, A T

2017-12-01

Coastal blackwater rivers, characterized by high concentrations of natural organic matter, are source water for millions of people in the southeastern US. In October 2015, large areas of coastal South Carolina were flooded by Hurricane Joaquin. This so-called "thousand-year" rainfall mobilized and flushed large amounts of terrestrial organic matter and associated pollutants (e.g. mercury) into source water, affecting water quality and safety of municipal water supply. To understand the dynamics of water quality and water treatability during this extreme flood, water samples were collected from Waccamaw River (a typical blackwater river in the southeastern US) during rising limb, peak discharge, falling limb, and base flow. Despite decreasing water flow after peak discharge, dissolved organic carbon (DOC) levels (increased by up to 125%), and formation potentials of trihalomethanes and haloacetic acids (increased by up to 150%) remained high for an extended period of time (>eight weeks after peak discharge), while variation in the N-nitrosodimethylamine (NDMA) FP was negligible. Coagulation with alum and ferric at optimal dosage significantly reduced concentrations of DOC by 51-76%, but up to 10 mg/L of DOC still remained in treated waters. For an extended period of time, elevated levels of THMs (71-448 μg/L) and HAAs (88-406 μg/L) were quantified in laboratory chlorination experiments under uniform formation conditions (UFC), exceeding the United States Environmental Protection Agency's (USEPA) maximum contaminant level of 80 and 60 μg/L, respectively. Results demonstrated that populations in coastal cities are at high risk with disinfection by-products (DBPs) under the changing climate. Copyright © 2017 Elsevier Ltd. All rights reserved.

When Will It Be ...?: U.S. Naval Observatory Sidereal Time and Julian Date Calculators

NASA Astrophysics Data System (ADS)

Chizek Frouard, Malynda R.; Lesniak, Michael V.; Bartlett, Jennifer L.

2017-01-01

Sidereal time and Julian date are two values often used in observational astronomy that can be tedious to calculate. Fortunately, the U.S. Naval Observatory (USNO) has redesigned its on-line Sidereal Time and Julian Date (JD) calculators to provide data through an Application Programming Interface (API). This flexible interface returns dates and times in JavaScript Object Notation (JSON) that can be incorporated into third-party websites or applications.Via the API, Sidereal Time can be obtained for any location on Earth for any date occurring in the current, previous, or subsequent year. Up to 9999 iterations of sidereal time data with intervals from 1 second to 1095 days can be generated, as long as the data doesn’t extend past the date limits. The API provides the Gregorian calendar date and time (in UT1), Greenwich Mean Sidereal Time, Greenwich Apparent Sidereal Time, Local Mean Sidereal Time, Local Apparent Sidereal Time, and the Equation of the Equinoxes.Julian Date can be converted to calendar date, either Julian or Gregorian as appropriate, for any date between JD 0 (January 1, 4713 BCE proleptic Julian) and JD 5373484 (December 31, 9999 CE Gregorian); the reverse calendar date to Julian Date conversion is also available. The calendar date and Julian Date are returned for all API requests; the day of the week is also returned for Julian Date to calendar date conversions.On-line documentation for using all USNO API-enabled calculators, including sample calls, is available (http://aa.usno.navy.mil/data/docs/api.php).For those who prefer using traditional data input forms, Sidereal Time can still be accessed at http://aa.usno.navy.mil/data/docs/siderealtime.php, and the Julian Date Converter at http://aa.usno.navy.mil/data/docs/JulianDate.php.

Stable and radiocarbon isotopic composition of dissolved organic matter in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Walker, B. D.; Druffel, E. R. M.; Kolasinski, J.; Roberts, B. J.; Xu, X.; Rosenheim, B. E.

2017-08-01

Dissolved organic carbon (DOC) is of primary importance to marine ecosystems and the global carbon cycle. Stable carbon (δ13C) and radiocarbon (Δ14C) isotopic measurements are powerful tools for evaluating DOC sources and cycling. However, the isotopic signature of DOC in the Gulf of Mexico (GOM) remains almost completely unknown. Here we present the first DOC Δ14C and δ13C depth profiles from the GOM. Our results suggest the Mississippi River exports large amounts of DOC with an anthropogenic "bomb" Δ14C signature. Riverine DOC is removed and recycled offshore, and some marine production of DOC is observed in the river plume. Offshore profiles show that DOC has higher Δ14C than its Caribbean feed waters, indicative of a modern deep DOC source in the GOM basin. Finally, high DOC with negative δ13C and Δ14C values were observed near the Macondo Wellhead, suggesting a transformation of Deepwater Horizon hydrocarbons into a persistent population of DOC.

Degradation potentials of dissolved organic carbon (DOC) from thawed permafrost peat

PubMed Central

Panneer Selvam, Balathandayuthabani; Lapierre, Jean-François; Guillemette, Francois; Voigt, Carolina; Lamprecht, Richard E.; Biasi, Christina; Christensen, Torben R.; Martikainen, Pertti J.; Berggren, Martin

2017-01-01

Global warming can substantially affect the export of dissolved organic carbon (DOC) from peat-permafrost to aquatic systems. The direct degradability of such peat-derived DOC, however, is poorly constrained because previous permafrost thaw studies have mainly addressed mineral soil catchments or DOC pools that have already been processed in surface waters. We incubated peat cores from a palsa mire to compare an active layer and an experimentally thawed permafrost layer with regard to DOC composition and degradation potentials of pore water DOC. Our results show that DOC from the thawed permafrost layer had high initial degradation potentials compared with DOC from the active layer. In fact, the DOC that showed the highest bio- and photo-degradability, respectively, originated in the thawed permafrost layer. Our study sheds new light on the DOC composition of peat-permafrost directly upon thaw and suggests that past estimates of carbon-dioxide emissions from thawed peat permafrost may be biased as they have overlooked the initial mineralization potential of the exported DOC. PMID:28378792

Hurricane Katrina Impact on Water Quality in the East Pearl River, Mississippi

NASA Astrophysics Data System (ADS)

Shiller, A. M.; Shim, M.; Guo, L.; Bianchi, T. S.; Smith, R. W.; Duan, S.

2010-12-01

Hurricanes and other intense storms have previously been reported to cause short term changes in surface water quality. We examined the water quality of the East Pearl River in southern Mississippi both before and after Hurricane Katrina caused extensive damage to the watershed in 2005. Our post-storm sampling began two months after the hurricane, and thus we missed any immediate short-term consequences. However, sampling over the following two years allowed us to examine whether damage to watershed resulted in significant longer term effects on water quality. Interpretation of the time series data is complicated by the natural seasonal and climatic variability of the system. Thus, we utilized property-property plots as well as empirical relationships to compare pre- and post-storm water quality. Based on the variability of our empirical relationships, we estimate that to within 20%, the hurricane-induced vegetative destruction within this river basin has not changed the concentrations of DOC, POC, SPM, pH, or dissolved Fe. Nor has the quality of the DOC, as inferred from lignin-phenol analysis and the Fe-DOC relationship, been significantly changed either. This may be partly due to the slow degradation of woody materials that occurs only over a period of a few years, even in the sub-tropical climate of this region. Also, transport of DOC material from the land, through the soils, and into the river is not always instantaneous because DOC may stay in soils for a long time. Our work can be examined in the context of other research focused on hurricane effects on different time scales. For instance, shorter term hurricane influences, such as immediate flooding, can cause concurrent, short-lived water quality changes. Likewise, if increased hurricane activity (as might result from climate change) results in permanent landscape or ecosystem changes, then significant long-term water quality changes might be expected.

76 FR 29805 - Notice of Revision of Standard Form 62

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2011-05-23

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TARDEC Annual Report 2010

DTIC Science & Technology

2011-06-15

capable of engaging threats while interacting with system operators. Through autonomous perception and navigation, intelligent tactical behavior... systems integration approach. TARDEC’s role is to assess the best way to apply the VICTORY architecture to future tactical wheeled vehicles and...Track tops Thrown Object Protection System traDoc U.S. Army Training and Doctrine Command twVs Tactical Wheeled Vehicle Survivability ugV Unmanned

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Carbon Isotope Composition as an Indicator of DOC Sources to a Stream During Events in a Temperate Forested Catchment

NASA Astrophysics Data System (ADS)

Doctor, D. H.; Sebestyen, S. D.; Aiken, G. R.; Shanley, J. B.; Kendall, C.; Boyer, E. W.

2006-12-01

Increased DOC flux in streams and rivers is commonly observed during high runoff regimes, however DOC concentrations alone do not provide information about multiple sources or pathways of DOC to streams. In an effort to gain this information, we measured DOC concentrations and stable carbon isotope composition (δ13C-DOC) on samples collected at high-frequency during events at Sleepers River Research Watershed in Vermont, USA. During snowmelt and storm events, peaks in stream DOC concentration (up to 10.5 mg/L) were coincident with peaks in flow. Stream water δ13C-DOC measurements ranged between -23.7‰ and - 28.9‰ and indicated changing sources of DOC during events; the highest δ13C-DOC values occurred consistently at the lowest flows, and the lowest δ13C-DOC values occurred with peaks in discharge. Water samples collected from shallow wells and stacked soil lysimeters showed the highest DOC concentrations in the most shallow (<0.5 m) lysimeter waters, and the lowest concentrations in the deeper (>1.5 m) well waters. Wells and lysimeters exhibited a range of δ13C-DOC values similar to those observed in the stream; however, samples collected from shallow horizons at nested wells and lysimeters consistently showed lower δ13C-DOC values than those from greater depths. Maple leaf litter collected from across the watershed provided an end-member of fresh organic material, with average δ13C composition of -31.3±0.7‰ (n=57), which is lower than the lowest measured DOC values in any of the stream, well, or lysimeter waters. A subset of stream waters were fractionated onto XAD4 and XAD8 resins; the hydrophobic acid fraction (XAD8) had consistently lower δ13C values than the transphilic acid fraction (XAD4), and both of these were lower than those of the bulk DOC. Samples with lower δ13C-DOC values also exhibited higher SUVA-254 values, i.e. greater aromaticity. Thus, lower δ13C-DOC values are interpreted as an indicator of relatively "fresh", more aromatic and more biologically labile material while higher δ13C-DOC values indicate relatively more degraded material. Since lower δ13C-DOC values were observed in the shallowest well and lysimeter waters and in stream water during periods of highest DOC flux, we surmise that fresh DOC is mobilized to the stream along relatively shallow flowpaths during high flows, and that a second source of more degraded DOC supplies background concentrations to the stream at lower flows.

The relationship between soil heterotrophic activity, soil dissolved organic carbon (DOC) leachate, and catchment-scale DOC export in headwater catchments

USGS Publications Warehouse

Brooks, P.D.; McKnight, Diane M.; Bencala, K.E.

1999-01-01

Dissolved organic carbon (DOC) from terrestrial sources forms the major component of the annual carbon budget in many headwater streams. In high-elevation catchments in the Rocky Mountains, DOC originates in the upper soil horizons and is flushed to the stream primarily during spring snowmelt. To identify controls on the size of the mobile soil DOC pool available to be transported during the annual melt event, we measured soil DOC production across a range of vegetation communities and soil types together with catchment DOC export in paired watersheds in Summit County, Colorado. Both surface water DOC concentrations and watershed DOC export were lower in areas where pyrite weathering resulted in lower soil pH. Similarly, the amount of DOC leached from organic soils was significantly smaller (p < 0.01) at sites having low soil pH. Scaling point source measurements of DOC production and leaching to the two basins and assuming only vegetated areas contribute to DOC production, we calculated that the amount of mobile DOC available to be leached to surface water during melt was 20.3 g C m−2 in the circumneutral basin and 17.8 g C m−2 in the catchment characterized by pyrite weathering. The significant (r2=0.91 and p < 0.05), linear relationship between over-winter CO2 flux and the amount of DOC leached from upper soil horizons during snowmelt suggests that the mechanism for the difference in production of mobile DOC was heterotrophic processing of soil carbon in snow-covered soil. Furthermore, this strong relationship between over-winter heterotrophic activity and the size of the mobile DOC pool present in a range of soil and vegetation types provides a likely mechanism for explaining the interannual variability of DOC export observed in high-elevation catchments.

Dissolved organic carbon in runoff and tile-drain water under corn and forage fertilized with hog manure.

PubMed

Royer, Isabelle; Angers, Denis A; Chantigny, Martin H; Simard, Régis R; Cluis, Daniel

2007-01-01

Dissolved organic carbon (DOC) export from soils can play a significant role in soil C cycling and in nutrient and pollutant transport. However, information about DOC losses from agricultural soils as influenced by management practices is scarce. We compared the effects of mineral fertilizer (MF) and liquid hog manure (LHM) applications on the concentration and molecular size of DOC released in runoff and tile-drain water under corn (Zea mays L.) and forage cropping systems. Runoff and tile-drain water samples were collected during a 2-mo period (October to December 1998) and DOC concentration was measured. Characterization of DOC was performed by tangential ultrafiltration with nominal cut-offs at 3 and 100 kDa. Mean concentration of DOC in runoff water (12.7 mg DOC L(-1)) was higher than in tile-drain water (6.5 mg DOC L(-1)). Incorporation of corn residues increased the DOC concentration by 6- to 17-fold in surface runoff, but this effect was short-lived. In runoff water, the relative size of the DOC molecules increased when corn residues and LHM were applied probably due to partial microbial breakdown of these organic materials and to a faster decomposition or preferential adsorption of the small molecules. The DOC concentration in tile-drain water was slightly higher under forage (7.5 mg DOC L(-1)) than under corn (5.4 mg DOC L(-1)) even though the application rates of LHM were higher in corn plots. We suggest that preferential flow facilitated the migration of DOC to tile drains in forage plots. In conclusion, incorporation of corn residues and LHM increased the concentration of DOC and the relative size of the molecules in surface runoff water, whereas DOC in tile-drain water was mostly influenced by the cropping system with relatively more DOC and larger molecules under forage than corn.

Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

USGS Publications Warehouse

Aravena, R.; Wassenaar, L.I.; Spiker, E. C.

2004-01-01

This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

Assessing contribution of DOC from sediments to a drinking-water reservoir using optical profiling

USGS Publications Warehouse

Downing, Bryan D.; Bergamaschi, Brian A.; Evans, David G.; Boss, Emmanuel

2008-01-01

Understanding the sources of dissolved organic carbon (DOC) in drinking-water reservoirs is an important management issue because DOC may form disinfection by-products, interfere with disinfection, or increase treatment costs. DOC may be derived from a host of sources-algal production of DOC in the reservoir, marginal production of DOC from mucks and vascular plants at the margins, and sediments in the reservoir. The purpose of this study was to assess if release of DOC from reservoir sediments containing ferric chloride coagulant was a significant source of DOC to the reservoir. We examined the source-specific contributions of DOC using a profiling system to measure the in situ distribution of optical properties of absorption and fluorescence at various locations in the reservoir. Vertical optical profiles were coupled with discrete water samples measured in the laboratory for DOC concentration and optical properties: absorption spectra and excitation emission matrix spectra (EEMs). Modeling the in situ optical data permitted estimation of the bulk DOC profile in the reservoir as well as separation into source-specific contributions. Analysis of the source-specific profiles and their associated optical characteristics indicated that the sedimentary source of DOC to the reservoir is significant and that this DOC is labile in the reservoir. We conclude that optical profiling is a useful technique for understanding complex biogeochemical processes in a reservoir.

Dissolved Organic Carbon in the Yukon, Tanana and Porcupine Rivers, Alaska

NASA Astrophysics Data System (ADS)

Aiken, G. R.; Striegl, R. G.; Wickland, K. P.; Dornblaser, M. M.; Raymond, P. A.

2006-12-01

The spatial and temporal variability of dissolved organic carbon (DOC) in the Yukon River (YR) and two major tributaries, the Porcupine River (PR), a black water river draining a watershed almost entirely underlain by permafrost, and the Tanana River (TR), a glacial dominated river, are being studied to better define processes controlling DOC in these systems. Five-year seasonal averages indicate DOC concentrations follow the discharge hydrograph, with highest daily and seasonal flux occurring during spring in YR and PR and during summer-autumn in TR. Largest DOC concentrations and specific UV absorption (SUVA) values, a measure of aromatic carbon content of the DOC and an indicator of DOC source, occurred at all locations during spring snowmelt. Lowest DOC concentration and SUVA occurred during low-flow in winter due to greatly reduced contributions of soil organic matter and to relatively greater influences of ground water. While all sites had comparable DOC concentration during winter, DOC concentration was greatest at PR during spring and summer-autumn, whereas TR had the lowest average DOC and SUVA values. Within the YR, average DOC concentration and SUVA values in spring and summer-autumn increase downriver due to contributions from organic carbon rich tributaries, such as PR, that increase in number and significance as the river flows through Alaska. Most the DOC in each system was comprised of hydrophobic organic acids (HPOA) derived from terrestrial vegetation. During winter, the hydrophilic fraction, determined to be the most biodegradable, was a larger percentage of the DOC than during spring-autumn. During spring, HPOA concentration and SUVA increased significantly at all sites, suggesting that most DOC in spring is derived from terrestrial organic matter that was frozen on the land surface over winter. During spring-autumn, PR had the largest concentration of HPOA and TR had the least. Like DOC concentration, HPOA concentration and SUVA increased down river. 14C-DOC values correspond to radiocarbon ages of modern (PR), 282 (TR), and 328 (YR) yrs B.P, indicating the presence of some aged DOC in YR and TR. Comparison of the chemical character of DOC from sites along the YR suggests that most DOC is transported from its source to the Bering Sea with little within river chemical or biological alteration, a result supported by laboratory biodegradation experiments.

Relationship between the colored dissolved organic matter and dissolved organic carbon and the application on remote sensing in East China Sea

NASA Astrophysics Data System (ADS)

Qiong, Liu; Pan, Delu; Huang, Haiqing; Lu, Jianxin; Zhu, Qiankun

2011-11-01

A cruise was conducted in the East China Sea (ECS) in autumn 2010 to collect Dissolved Organic Carbon (DOC) and Colored Dissolved Organic Matter (CDOM) samples. The distribution of DOC mainly controlled by the hydrography since the relationship between DOC and salinity was significant in both East China Sea. The biological activity had a significant influence on the concentration of DOC with a close correlation between DOC and Chl a. The absorption coefficient of CDOM (a355) decreased with the salinity increasing in the shelf of East China Sea (R2=0.9045). CDOM and DOC were significantly correlated in ECS where DOC distribution was dominated largely by the Changjiang diluted water. Based on the relationship of CDOM and DOC, we estimated the DOC concentration of the surface in ECS from satellite-derived CDOM images. Some deviations induced by the biological effect and related marine DOC accumulations were discussed.

Overview of a simple model describing variation of dissolved organic carbon in an upland catchment

USGS Publications Warehouse

Boyer, Elizabeth W.; Hornberger, George M.; Bencala, Kenneth E.; McKnight, Diane M.

1996-01-01

Hydrological mechanisms controlling the variation of dissolved organic carbon (DOC) were investigated in the Deer Creek catchment located near Montezuma, CO. Patterns of DOC in streamflow suggested that increased flows through the upper soil horizon during snowmelt are responsible for flushing this DOC-enriched interstitial water to the streams. We examined possible hydrological mechanisms to explain the observed variability of DOC in Deer Creek by first simulating the hydrological response of the catchment using TOPMODEL and then routing the predicted flows through a simple model that accounted for temporal changes in DOC. Conceptually the DOC model can be taken to represent a terrestrial (soil) reservoir in which DOC builds up during low flow periods and is flushed out when infiltrating meltwaters cause the water table to rise into this “reservoir”. Concentrations of DOC measured in the upper soil and in streamflow were compared to model simulations. The simulated DOC response provides a reasonable reproduction of the observed dynamics of DOC in the stream at Deer Creek.

Photochemical alteration of organic carbon draining permafrost soils shifts microbial metabolic pathways and stimulates respiration.

PubMed

Ward, Collin P; Nalven, Sarah G; Crump, Byron C; Kling, George W; Cory, Rose M

2017-10-03

In sunlit waters, photochemical alteration of dissolved organic carbon (DOC) impacts the microbial respiration of DOC to CO 2 . This coupled photochemical and biological degradation of DOC is especially critical for carbon budgets in the Arctic, where thawing permafrost soils increase opportunities for DOC oxidation to CO 2 in surface waters, thereby reinforcing global warming. Here we show how and why sunlight exposure impacts microbial respiration of DOC draining permafrost soils. Sunlight significantly increases or decreases microbial respiration of DOC depending on whether photo-alteration produces or removes molecules that native microbial communities used prior to light exposure. Using high-resolution chemical and microbial approaches, we show that rates of DOC processing by microbes are likely governed by a combination of the abundance and lability of DOC exported from land to water and produced by photochemical processes, and the capacity and timescale that microbial communities have to adapt to metabolize photo-altered DOC.The role of dissolved organic carbon (DOC) photo-alteration in the microbial respiration of DOC to CO 2 is unclear. Here, the authors show that the impact of this mechanism depends on whether photo-alteration of DOC produces or removes molecules used by native microbial communities prior to light exposure.

Photooxidation and Microbial Processing of Ancient and Modern Dissolved Organic Carbon in the Kolyma River, Siberia.

NASA Astrophysics Data System (ADS)

Behnke, M. I.; Mann, P. J.; Schade, J. D.; Spawn, S.; Zimov, N.

2015-12-01

Permafrost soils in northern high latitudes store large quantities of organic carbon that have remained frozen for thousands of years. As global temperatures increase, permafrost deposits have begun to thaw, releasing previously stored ancient carbon to streams and rivers in the form of dissolved organic carbon (DOC). Newly mobilized DOC is then subjected to processing by photooxidation and microbial metabolism. Permafrost-derived DOC is highly bioavailable directly upon release relative to modern DOC derived from plants and surface active layer soils. Our objectives were to assess the interaction of photodegradation and microbial processing, and to quantify any light priming effect on the microbial consumption of both ancient and modern sourced DOC pools. We exposed sterilized mixtures of ancient and modern DOC to ambient sunlight for six days, and then inoculated mixtures (0, 1, 10, 25, 50 & 100% ancient DOC) with microbes from both modern and ancient water sources. After inoculation, samples were incubated in the dark for five days. We measured biological oxygen demand, changes in absorbance, and DOC concentrations to quantify microbial consumption of DOC and identify shifts in DOC composition and biolability. We found evidence of photobleaching during irradiation (decreasing S275-295, increasing slope ratio, and decreasing SUVA254). Once inoculated, mixtures with more ancient DOC showed initially increased microbial respiration compared to mixtures with primarily modern DOC. During the first 24 hours, the light-exposed mixture with 50% ancient DOC showed 47.6% more oxygen consumption than did the dark 50% mixture, while the purely modern DOC showed 11.5% greater oxygen consumption after light exposure. After 5 days, the modern light priming was comparable to the 50% mixture (31.2% compared to 20.5%, respectively). Our results indicate that natural photoexposure of both modern and newly released DOC increases microbial processing rates over non photo-exposed DOC.

Organic solutes in ground water at the Idaho National Engineering Laboratory

USGS Publications Warehouse

Leenheer, Jerry A.; Bagby, Jefferson C.

1982-01-01

In August 1980, the U.S. Geological Survey started a reconnaissance survey of organic solutes in drinking water sources, ground-water monitoring wells, perched water table monitoring wells, and in select waste streams at the Idaho National Engineering Laboratory (INEL). The survey was to be a two-phase program. In the first phase, 77 wells and 4 potential point sources were sampled for dissolved organic carbon (DOC). Four wells and several potential point sources of insecticides and herbicides were sampled for insecticides and herbicides. Fourteen wells and four potential organic sources were sampled for volatile and semivolatile organic compounds. The results of the DOC analyses indicate no high level (>20 mg/L DOC) organic contamination of ground water. The only detectable insecticide or herbicide was a DDT concentration of 10 parts per trillion (0.01 microgram per liter) in one observation well. The volatile and semivolatile analyses do not indicate the presence of hazardous organic contaminants in significant amounts (>10 micrograms per liter) in the samples taken. Due to the lack of any significant organic ground-water contamination in this reconnaissance survey, the second phase of the study, which was to follow up the first phase by additional sampling of any contaminated wells, was canceled.

Mercury dynamics in relation to dissolved organic carbon concentration and quality during high flow events in three northeastern U.S. streams

USGS Publications Warehouse

Dittman, Jason A.; Shanley, James B.; Driscoll, Charles T.; Aiken, George R.; Chalmers, Ann T.; Towse, Janet E.; Selvendiran, Pranesh

2010-01-01

Mercury (Hg) contamination is widespread in remote areas of the northeastern United States. Forested uplands have accumulated a large reservoir of Hg in soil from decades of elevated anthropogenic deposition that can be released episodically to stream water during high flows. The objective of this study was to evaluate spatial and temporal variations in stream water Hg species and organic matter fractions over a range of hydrologic conditions in three forested upland watersheds (United States). Mercury and organic matter concentrations increased with discharge at all three sites; however, the partitioning of Hg fractions (dissolved versus particulate) differed among sites and seasons. Associated with increased discharge, flow paths shifted from mineral soil under base flow to upper soil horizons. As flow paths shifted, greater concentrations of dissolved organic carbon (DOC) richer in aromatic substances were flushed from upper soil horizons to stream water. The hydrophobic organic matter associated with humic material from upper soils appears to have had a greater capacity to bind Hg. Because of the strong correlation between Hg and DOC, we hypothesize that there was a concurrent shift in the source of Hg with DOC from lower mineral soil to upper soil horizons. Our study suggests that stream discharge is an effective predictor of dissolved total Hg flux.

Diminished Stream Nitrate Concentrations Linked to Dissolved Organic Carbon Dynamics After Leaf Fall

NASA Astrophysics Data System (ADS)

Sebestyen, S. D.; Shanley, J. B.; Boyer, E. W.; Doctor, D. H.; Kendall, C.

2004-05-01

Thermodynamic coupling of the nitrogen and carbon cycles has broad implications for controls on catchment nutrient fluxes. In the northeast US, leaf fall occurs in early October and the availability of organic carbon increases as the leaves decompose. At the Sleepers River Research Watershed in northeastern Vermont (USA), we sampled stream chemistry from seven nested catchments to determine how stream dissolved organic carbon (DOC) and nitrate vary as a function of flow conditions, land-use, and basin size in response to leaf fall. Following leaf fall, nitrate concentration patterns were quantitatively different from other times of the year. Under baseflow conditions, stream and soil water DOC concentrations were higher than normal, whereas nitrate concentrations declined sharply at the five smallest catchments and more modestly at the two largest catchments. Under high flow conditions, flushing of nitrate was observed, as is typical for stormflow response at Sleepers River. Our field data suggest that in-stream processing of nitrate is likely thermodynamically and kinetically favorable under baseflow but not at higher flow conditions when expanding variable source areas make hydrological connections between nitrate source areas and streams. We are working to evaluate this hypothesis with isotopic and other monitoring data, and to model the coupled interactions of water, DOC, and nitrate fluxes in these nested catchments.

Removal of terrestrial DOC in aquatic ecosystems of a temperate river network

USGS Publications Warehouse

Wollheim, W.M.; Stewart, R. J.; Aiken, George R.; Butler, Kenna D.; Morse, Nathaniel B.; Salisbury, J.

2015-01-01

Surface waters play a potentially important role in the global carbon balance. Dissolved organic carbon (DOC) fluxes are a major transfer of terrestrial carbon to river systems, and the fate of DOC in aquatic systems is poorly constrained. We used a unique combination of spatially distributed sampling of three DOC fractions throughout a river network and modeling to quantify the net removal of terrestrial DOC during a summer base flow period. We found that aquatic reactivity of terrestrial DOC leading to net loss is low, closer to conservative chloride than to reactive nitrogen. Net removal occurred mainly from the hydrophobic organic acid fraction, while hydrophilic and transphilic acids showed no net change, indicating that partitioning of bulk DOC into different fractions is critical for understanding terrestrial DOC removal. These findings suggest that river systems may have only a modest ability to alter the amounts of terrestrial DOC delivered to coastal zones.

Long-term decomposition of DOC from experimental diatom blooms

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

Fry, B.; Hopkinson, C.S. Jr.; Nolin, A.

1996-09-01

Decomposition of {sup 13}C-labeled dissolved organic carbon (DOC) produced in two marine diatom blooms was followed for 2.5 yr with large volume (20 liter) incubations performed in the dark. The {sup 13}C tracer was used to partition decomposition dynamics of the fresh diatom-derived DOC and the turnover of background DOC from Woods Hole Harbor. DOC from Woods Hole harbor proved largely refractory, with DOC concentrations falling from 122 to {approximately} 100 {mu}M C in 2.5 yr. DOC from the diatom blooms was more labile, but was also incompletely mineralized, with 25-35% remaining after 2.5 yr. Neither nutrients nor labile carbonmore » (dextrose) added at 1.5 yr significantly stimulated DOC mineralization. The experiments indicate that DOC produced in short-term blooms can be surprisingly resistant to microbial attack. 21 refs., 1 fig., 1 tab.« less

Acid-induced changes in DOC quality in an experimental whole-lake manipulation

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

Donahue, W.F.; Schindler, D.W.; Page, S.J.

1998-10-01

Fluorescence analyses of archived water samples were used to typify dissolved organic carbon (DOC) quality in experimentally acidified lakes and reference lakes at the Experimental Lakes Area, in northwestern Ontario. Carbon-specific DOC fluorescence (CSF) during peak acidification was 40--50% of that for a high-DOC reference lake and similar to a low-DOC reference lake. Reference lakes showed similar but smaller decreases in CSF during several years of prolonged drought in the late 1980s. During the 1990s, recovery from acidification resulted in increased CSF, whereas reference lakes remained unchanged during the same time period. In addition to causing decreased [DOC], acidification causesmore » changes in fluorescence-peak geometry that indicate a switch in DOC quality from allochthonous to autochthonous-like during acidification. The acid-induced change in DOC quality was likely due to increased chemical oxidation or precipitation of the UV-absorbent aromatic portions of allochthonous DOC molecules, leaving more UV-transparent aliphatic chains. The change in the nature of DOC following acidification and drought may have an important role in physical, biological, and chemical processes within these lakes. With recovery from acidification, DOC quality has also recovered.« less

Response Characteristics of Dissolved Organic Carbon Flushing in a Subarctic Alpine Catchment

NASA Astrophysics Data System (ADS)

Carey, S. K.

2002-12-01

Dissolved organic carbon (DOC) is an important part of ecosystem-scale carbon balances and in the transport of contaminants as it interacts with other dissolved substances including trace metals. It also can be used as a surrogate hydrological tracer in permafrost regions as near-surface waters are often DOC enriched due to the presence of thick organic soils. In a small subarctic alpine catchment within the Wolf Creek Research Basin, Yukon, Canada, DOC was studied in the summer of 2001 and spring of 2002 to determine the role frost (both permanent and seasonal), snowmelt and summer storms on DOC flushing. Peak DOC concentrations occurred during the snowmelt period, approximately one week prior to peak discharge. However, peak discharge took place several weeks after snow on south facing exposures had melted. Within the hillslopes, DOC concentrations were three to five times greater in wells underlain with permafrost compared with seasonal frost. Groundwater DOC concentrations declined during snowmelt, yet remained at levels above the streamflow. After peaking, streamflow DOC concentrations declined exponentially suggesting a simple flushing mechanism, however there did not appear to be a relation between DOC and topographic position. Following melt, permafrost underlain slopes had near-surface water tables and retained elevated levels of DOC, whereas slopes without permafrost had rapidly declining water tables at upslope locations with low DOC concentrations at all positions except near-stream riparian zones. The influence of summer rainstorms on DOC was monitored on three occasions. In each case DOC peaked on the ascending limb of the runoff hydrograph and declined exponentially on the receding limb and hysteretic behavior occurred between discharge and DOC during all events. Patterns of DOC within the hillslopes and streams suggest that runoff from permafrost-underlain slopes control DOC flushing within the stream during both snowmelt and summer periods. This flushing mechanism conforms with conceptual models of runoff generation in discontinuous permafrost catchments whereby water tables within permafrost-underlain slopes rise into porous organic-layers, whereupon DOC is leached into the water and rapidly conveyed to the stream.

Does wildfire cause cascading effects on aquatic C cycling? A study of soil, well and lake DOC composition and bio/photolability

NASA Astrophysics Data System (ADS)

Olefeldt, D.; Turetsky, M. R.; Devito, K. J.; Blodau, C.

2012-12-01

In May 2011 a wildfire broke out north of Utikuma Lake in central Alberta, Canada, which eventually burned an area of ~880 km2. Wildfire alters soil properties, potentially altering the chemical composition of terrestrial DOC that reaches downstream aquatic environments. In order to study the potential effects of wildfire on lake carbon cycling, we sampled and incubated DOC from soil samples (n=52), wells (n=35) and lakes (n=32) from within and outside the recent fire perimeter. We incubated the DOC samples under both dark and UV conditions to assess both bio- and photolability, and followed DOC composition throughout the incubations by measuring DOC absorbing and fluorescing properties. A strong effect of wildfire was found among DOC samples leached from surface peatland and upland soils - with fire yielding increased DOC aromaticity associated with decreased biodegradability but also increased photolability. Parallel factor analysis of fluorescence matrices revealed distinct regions that were associated with DOC leached from charred soils, potentially linked to their lower biodegradability. Dark and UV conditions gave rise to very different trajectories of changes to DOC composition throughout incubations, with preferential losses of non-aromatic DOC under dark conditions and aromatic DOC under UV conditions. The DOC composition index that was found to best predict both DOC bio- and photolability was specific UV absorbance, which is also a very simple and quick index to measure. For lakes, we found that the primary influences on DOC composition and bio-/photolability was linked to lake size and hydrogeological setting (whether located on a lacustrine clay plain or in a moraine/outwash region) that controls groundwater influence and the hydrological connectivity to adjacent peatlands. Further analysis of well and lake water incubations will be used to detect whether wildfire can be detected to have a subtle secondary effect on DOC composition and lability or if the potential for cascading effects on lake C cycling due to altered soil DOC sources remain unrealized in the study region.

Nonlocal Effects of Crack Curving.

DTIC Science & Technology

1982-07-01

Structures Research Division Marine Corps Development Langley Research Center and Education Comand Langley Station Quantice , Virginia 22134i~l EaptOn, Vtiina...Advanced lomn 3C128 Research and Technology The Pentagon Washington. D.C. 2054 Washington, D.C* 20301 Air Force Dr. G Sans National Science Foundation... Science and Technology Division (FIS) Washingtono DOC* 20540 AM (XIM)Director Chief Applied Mechanics Group Defense Nuclear Agency U.S.. Air Force

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DTIC Science & Technology

2007-07-01

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The role of hillslope hydrology in controlling nutrient loss

Treesearch

Willem J. van Verseveld; Jeffrey J. McDonnell; Kate Lajtha

2009-01-01

Hydrological controls on DOC and N transport at the catchment scale were studied for five storm events from the fall of 2004 through the spring of 2005 in WS10, H,J, Andrews Experimental Forest in the western Cascade Mountains of Oregon, This catchment is devoid of any riparian zone and characterized by hillslopes that issue directly into the stream. This enabled us to...

Dams impact carbon dynamics in U.S. rivers

NASA Astrophysics Data System (ADS)

Bhattacharya, Atreyee

2012-09-01

Dissolved organic carbon (DOC)—which leaches into freshwater systems from plants, soils, and sediments, and from other detritus present in the water itself—is the major food supplement for microorganisms and plays an important role in several environmental processes and in the global carbon cycle. In some aquatic systems such as estuaries, the optically measurable colored component of dissolved organic matter (CDOM) is often proportional to the concentration of DOC. CDOM forms when light-absorbing compounds are released into the water by decaying organic material and through photochemical degradation of certain organic compounds. Hence, CDOM reflects not just the environment and ecosystem, which is the source of the detritus, but also the processes that deliver the organic matter into aquatic systems. Human activities, such as logging, agriculture, and waste water treatment, also affect CDOM levels in aquatic systems. It is relatively easy and inexpensive to measure the CDOM content in small volumes of water.

Particle Dynamics in Linear Resonance Accelerators,

DTIC Science & Technology

1982-11-08

function, which describes the defocusing action of accelerating field eS ’ dE1 Q. (,) _ as, -. .(). (2.57) Before passing to the analysis of equations (2.53...no focusing fields; therefore, according to expressions (2.55), (2.57), DOC - 82105202 PAGE|I eS dE, Q (T) 2 0y- * -N (T). Let us replace derivative of...d2.vS OU Y,-- 1 + Q X (T) X + g0- - -j = 0; d2u _ 2_d_a~g , eS ’ aU’ Let us assume that there is such-stationary distribution of phase density

NASA/DOD Aerospace Knowledge Diffusion Research Project. A Comparison of the Technical Communication Practices of Aerospace Engineers and Scientists in India and the United States

DTIC Science & Technology

1993-09-01

Indiana University Bloomington, Indiana doc~𔃻 ~ e-an aPP’oveThi %o u E -l:•-,•d sale; its II September 1993 iot public te, an .. itS S =- National...Amount of Time Spent Communicating Technical Information by India and 11 S . Aerospace Engineers and Scientists India U.S. Change % (n) % (n) Increased 83...respondents and 76% of the U.S. respondents indicated that they had taken a course( s ) in technical communications/writing. (Approximately 75% of the India

2014-2015 Offshore Wind Technologies Market Report

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

Smith, Aaron; Stehly, Tyler; Musial, Walter

2015-09-01

This report provides data and analysis to assess the status of the U.S. offshore wind industry through June 30, 2015. It builds on the foundation laid by the Navigant Consortium, which produced three market reports between 2012 and 2014. The report summarizes domestic and global market developments, technology trends, and economic data to help U.S. offshore wind industry stakeholders, including policymakers, regulators, developers, financiers, and supply chain participants, to identify barriers and opportunities. Title page contains link to associated data tables posted at http://www.nrel.gov/docs/fy15osti/64283_data_tables.xlsx.

Dynamics, chemical properties and bioavailability of DOC in an early successional catchment

NASA Astrophysics Data System (ADS)

Risse-Buhl, U.; Hagedorn, F.; Dümig, A.; Gessner, M. O.; Schaaf, W.; Nii-Annang, S.; Gerull, L.; Mutz, M.

2013-07-01

The dynamics of dissolved organic carbon (DOC) have been intensively studied in mature ecosystems, but little is known about DOC dynamics and the significance of DOC as a substrate for microbial activity in early-successional catchments. We determined the concentration, chemical composition, source, radiocarbon age, and bioavailability of DOC along the hydrological flow path from soil solution to a downstream pond in a recently constructed catchment (Chicken Creek Catchment, Germany). Soil solution, upwelling ground water, stream water, subsurface water in an alluvial fan, and pond water all had high DOC concentrations (averages: 6.0-11.6 mg DOC L-1), despite small carbon stocks in both vegetation and soil of the catchment. Solid-state CPMAS 13C NMR of DOC in upwelling ground water revealed a higher proportion of aromatic compounds (32%) and a lower proportion of carbohydrates (33%) than in pond water (18% and 45%, respectively). The average 14C age of DOC in upwelling ground water was 2600 to 2900 yr, while organic matter of the Quaternary substrate of the catchment had a 14C age of 3000 to 16 000 yr. Both the 14C age data and 13C NMR spectra suggest that DOC partly derived from organic matter of the Quaternary substrate (about 40 to 90% of the C in the DOC), indicating that both recent and old C of the DOC can support microbial activity during early ecosystem succession. However, in a 70 day incubation experiment, only about 11% of the total DOC was found to be bioavailable. This proportion was irrespective of the water type. Origin of the microbial communities within the catchment (enriched from soil, stream sediment or pond water) also had only a marginal effect on overall DOC utilization.

Drivers of inverse DOC-nitrate loss patterns in forest soils and streams

NASA Astrophysics Data System (ADS)

Goodale, C. L.

2013-12-01

Nitrate loss from forested catchments varies greatly across sites and over time, with few reliable correlates. One of the few recurring patterns, however, is the negative nonlinear relationship that occurs regularly between surface water nitrate and dissolved organic carbon (DOC) concentrations: that is, nitrate declines sharply as DOC concentrations increase, and high nitrate levels occur only at low DOC concentrations. Several hypotheses have been proposed to explain this pattern, but its cause has remained speculative. It is likely to be driven by C- or N-limitation of biological processes such as assimilation or denitrification, but the identity of which biological process or the main landscape position of their activity are not known. We examined whether DOC and nitrate are both driven by soil C content, at scales of both soil blocks and across catchments, by measuring soil, soil extract, and surface water chemistry across nine catchments selected from long-term monitoring networks in the Catskill and Adirondack Mountains. We measured soil C and N status and solution nitrate, DOC, bioavailable DOC (bDOC), and isotopic composition (13C-DOC, 15N- and 18O-NO3) to examine whether variation in stocks of soil C partly controls DOC and nitrate loss from forested catchments in New York State. These measurements showed that surface soil C and C:N ratio together determine soil production of DOC and nitrate, reflecting assimilative demand for N by heterotrophic microbes. Yet, they also show that these processes do not produce the inverse DOC-NO3 curve observed at the catchment scale. Rather, catchment-scale DOC-nitrate patterns are more likely to be governed by the balance between excess nitrate production and its bDOC-mediated loss to denitrification.

Diel fluctuations of viscosity-driven riparian inflow affect streamflow DOC concentration

NASA Astrophysics Data System (ADS)

Schwab, Michael P.; Klaus, Julian; Pfister, Laurent; Weiler, Markus

2018-04-01

Diel fluctuations of stream water DOC concentrations are generally explained by a complex interplay of different instream processes. We measured the light absorption spectrum of water and DOC concentrations in situ and with high frequency by means of a UV-Vis spectrometer during 18 months at the outlet of a forested headwater catchment in Luxembourg (0.45 km2). We generally observed diel DOC fluctuations with a maximum in the afternoon during days that were not affected by rainfall-runoff events. We identified an increased inflow of terrestrial DOC to the stream in the afternoon, causing the DOC maxima in the stream. The terrestrial origin of the DOC was derived from the SUVA-254 (specific UV absorbance at 254 nm) index, which is a good indicator for the aromaticity of DOC. In the studied catchment, the most likely process that can explain the diel DOC input variations towards the stream is the so-called viscosity effect. The water temperature in the upper parts of the saturated riparian zone is increasing during the day, leading to a lower viscosity and therefore a higher hydraulic conductivity. Consequently, more water from areas that are rich in terrestrial DOC passes through the saturated riparian zone and contributes to streamflow in the afternoon. We believe that not only diel instream processes, but also viscosity-driven diel fluctuations of terrestrial DOC input should be considered to explain diel DOC patterns in streams.

Organic Carbon Mobilisation Mechanisms: Evidence from Globally Distributed Stalagmite Records

NASA Astrophysics Data System (ADS)

Baldini, J. U. L.; Fairchild, I. J.; Wynn, P.; Bourdin, C.; Muller, W.; Hartland, A.; Perrette, Y.; Worrall, F.; Bartlett, R.

2017-12-01

Identifying the cause of widespread increases in surface water dissolved organic carbon (DOC) concentrations in recent years is the subject of a contentious debate. Although DOC trends may partially reflect climate change, in many catchments they may also result from increased soil carbon solubility associated with decreases in acid rain due to lower atmospheric sulphur emissions. However, the lack of long-term DOC records hampers constraining climate's role in modulating DOC trends versus that of recovery from acidification. Here we help clarify the causes of recent DOC increases by using a combination of laboratory soil experiments and new stalagmite geochemical data. Laboratory experiments with soils sampled from above several key caves simulate the effect of acidity, temperature, and soil microbial processes on DOC release. These experiments are used to inform records of DOC encoded within several stalagmites from currently acidified, previously acidified, and unacidified sites, and which collectively yield insights into the timing of DOC change in the past. These records of stalagmite DOC concentration and composition are discussed within the context of the ongoing debate regarding the mechanism responsible for DOC release.

Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain, northeast China.

PubMed

Xi, Min; Lu, Xian-Guo; Li, Yue; Kong, Fan-Long

2007-01-01

Overwhelming evidence reveals that concentrations of dissolved organic carbon (DOC) have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soil-water solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland (R2 = 0.3122 and R2 = 0.443). The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon (TOC), total carbon (TC) and Fe(II), DOC mobility and continuous vertical and lateral flow affected the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe(II) were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

Process Inference from High Frequency Temporal Variations in Dissolved Organic Carbon (DOC) Dynamics Across Nested Spatial Scales

NASA Astrophysics Data System (ADS)

Tunaley, C.; Tetzlaff, D.; Lessels, J. S.; Soulsby, C.

2014-12-01

In order to understand aquatic ecosystem functioning it is critical to understand the processes that control the spatial and temporal variations in DOC. DOC concentrations are highly dynamic, however, our understanding at short, high frequency timescales is still limited. Optical sensors which act as a proxy for DOC provide the opportunity to investigate near-continuous DOC variations in order to understand the hydrological and biogeochemical processes that control concentrations at short temporal scales. Here we present inferred 15 minute stream water DOC data for a 12 month period at three nested scales (1km2, 3km2 and 31km2) for the Bruntland Burn, a headwater catchment in NE Scotland. High frequency data were measured using FDOM and CDOM probes which work by measuring the fluorescent component and coloured component, respectively, of DOC when exposed to ultraviolet light. Both FDOM and CDOM were strongly correlated (r2 >0.8) with DOC allowing high frequency estimations. Results show the close coupling of DOC with discharge throughout the sampling period at all three spatial scales. However, analysis at the event scale highlights anticlockwise hysteresis relationships between DOC and discharge due to the delay in DOC being flushed from the increasingly large areas of peaty soils as saturation zones expand and increase hydrological connectivity. Lag times vary between events dependent on antecedent conditions. During a 10 year drought period in late summer 2013 it was apparent that very small changes in discharge on a 15 minute timescale result in high increases in DOC. This suggests transport limitation during this period where DOC builds up in the soil and is not flushed regularly, therefore any subsequent increase in discharge results in large DOC peaks. The high frequency sensors also reveal diurnal variability during summer months related to the photo-oxidation, evaporative and biological influences of DOC during the day. This relationship is less significant during the winter months.

Dynamics, chemical properties and bioavailability of DOC in an early successional catchment

NASA Astrophysics Data System (ADS)

Risse-Buhl, U.; Hagedorn, F.; Dümig, A.; Gessner, M. O.; Schaaf, W.; Nii-Annang, S.; Gerull, L.; Mutz, M.

2013-01-01

The dynamics of dissolved organic carbon (DOC) have been intensively studied in mature ecosystems, but little is known about DOC dynamics and the significance of DOC as a substrate for microbial activity in early-successional catchments. We determined the concentration, chemical composition, source, radiocarbon age, and bioavailability of DOC along the hydrological flow path from soil solution to a downstream pond in a recently constructed catchment (Chicken Creek Catchment, Germany). Soil solution, upwelling ground water, subsurface water in an alluvial fan, and pond water all had high DOC concentrations (averages of 6.0-11.6 mg DOC L-1), despite small carbon stocks in either vegetation or soil of the early-successional catchment. The mean 14C age of DOC in upwelling ground water was 2600 to 2800 yr. Solid-state CPMAS 13C NMR revealed a higher proportion of aromatic compounds (32%) and a lower proportion of carbohydrates (33%) in upwelling ground water than in pond water (18% and 45%, respectively). The 14C age and 13C NMR spectra suggest that DOC was partly mobilized from charred organic matter of the Quaternary substrate. In an experimental 70-days incubation experiment, 20% of the total DOC was found to be bioavailable, irrespective of the water type. Origin of microbial communities (enriched from soil, stream sediment or pond water) had only marginal effects on overall DOC utilization. Overall, these data suggest that the old DOC can support microbial activity during early ecosystem succession to some extent, although the largest fraction is recalcitrant DOC that is exported from the catchment once it has been mobilized.

[Response of mineralization of dissolved organic carbon to soil moisture in paddy and upland soils in hilly red soil region].

PubMed

Chen, Xiang-Bi; Wang, Ai-Hua; Hu, Le-Ning; Huang, Yuan; Li, Yang; He, Xun-Yang; Su, Yi-Rong

2014-03-01

Typical paddy and upland soils were collected from a hilly subtropical red-soil region. 14C-labeled dissolved organic carbon (14C-DOC) was extracted from the paddy and upland soils incorporated with 14C-labeled straw after a 30-day (d) incubation period under simulated field conditions. A 100-d incubation experiment (25 degrees C) with the addition of 14C-DOC to paddy and upland soils was conducted to monitor the dynamics of 14C-DOC mineralization under different soil moisture conditions [45%, 60%, 75%, 90%, and 105% of the field water holding capacity (WHC)]. The results showed that after 100 days, 28.7%-61.4% of the labeled DOC in the two types of soils was mineralized to CO2. The mineralization rates of DOC in the paddy soils were significantly higher than in the upland soils under all soil moisture conditions, owing to the less complex composition of DOC in the paddy soils. The aerobic condition was beneficial for DOC mineralization in both soils, and the anaerobic condition was beneficial for DOC accumulation. The biodegradability and the proportion of the labile fraction of the added DOC increased with the increase of soil moisture (45% -90% WHC). Within 100 days, the labile DOC fraction accounted for 80.5%-91.1% (paddy soil) and 66.3%-72.4% (upland soil) of the cumulative mineralization of DOC, implying that the biodegradation rate of DOC was controlled by the percentage of labile DOC fraction.

Benthic fluxes of dissolved organic carbon from gas hydrate sediments in the northern South China Sea

PubMed Central

Hung, Chia-Wei; Huang, Kuo-Hao; Shih, Yung-Yen; Lin, Yu-Shih; Chen, Hsin-Hung; Wang, Chau-Chang; Ho, Chuang-Yi; Hung, Chin-Chang; Burdige, David J.

2016-01-01

Hydrocarbon vents have recently been reported to contribute considerable amounts of dissolved organic carbon (DOC) to the oceans. Many such hydrocarbon vents widely exist in the northern South China Sea (NSCS). To investigate if these hydrocarbon vent sites release DOC, we used a real-time video multiple-corer to collect bottom seawater and surface sediments at vent sites. We analyzed concentrations of DOC in these samples and estimated DOC fluxes. Elevated DOC concentrations in the porewaters were found at some sites suggesting that DOC may come from these hydrocarbon vents. Benthic fluxes of DOC from these sediments were 28 to 1264 μmol m−2 d−1 (on average ~321 μmol m−2 d−1) which are several times higher than most DOC fluxes in coastal and continental margin sediments. The results demonstrate that the real-time video multiple-corer can precisely collect samples at vent sites. The estimated benthic DOC flux from the methane venting sites (8.6 × 106 mol y−1), is 24% of the DOC discharge from the Pearl River to the South China Sea, indicating that these sediments make an important contribution to the DOC in deep waters. PMID:27432631

Web-based Loansome Doc, librarians, and end users: results from a survey of the Southeast Region.

PubMed

Paden, S L; Batson, A L; Wallace, R L

2001-07-01

The study examines how Loansome Doc services are implemented and used by libraries in the Southeast Region and describe end users' experiences with and attitudes toward Loansome Doc. 251 active DOCLINE libraries and 867 Loansome Doc users were surveyed. Roughly one half of the libraries offered Loansome Doc services. Of those that did not, most indicated no plans to offer it in the future. The majority had a small number of end users and experienced minimal increases in interlibrary loan activity. Problems were relatively rare. Satisfaction with Loansome Doc was high among all types of libraries. End users were usually physicians or other health care professionals who requested articles for research and patient care. Most learned about Loansome Doc through PubMed or Internet Grateful Med. End users appeared to be largely self-taught or received informal instruction in Loansome Doc. Loansome Doc filled document requests in a timely manner, and end users reported being satisfied with the service. Greater promotion of what Loansome Doc is and how it can benefit libraries can increase the number of participating libraries. While satisfaction of Loansome Doc end users is high, satisfaction could be increased with more help on the PubMed screen, more library training, and faster delivery methods.

Inverse coupling of DOC and nitrate export from soils and streams

NASA Astrophysics Data System (ADS)

Goodale, Christine

2013-04-01

Over the last two decades, nitrate concentrations in surface waters have decreased across the Northeastern United States and parts of northern Europe. Many hypotheses have been proposed to explain this decrease, but the cause remains unclear. One control may be associated with increasing abundance of dissolved organic carbon (DOC), which in turn may be a result of soil recovery from acidification. Compared across catchments, surface water NO3- decreases sharply with increasing DOC concentration. Here, we used measurements of soil and solution nitrate, DOC, and their isotopic composition (13C-DOC, 15N- and 18O-NO3) to test several related hypotheses that changing acidification affects the release of DOC and bio-available DOC (bDOC) from soil, and that variation in stocks of soil C and release of bDOC partly control NO3- export from forested catchments in New York State, USA. We examined whether DOC and NO3- are both driven by soil C processes that produce inverse coupling at the scale of soil cores as well as across catchments, through comparison of soil and surface water chemistry across nine catchments selected from long-term monitoring networks in the Catskill and Adirondack Mountains. In addition, we conducted a series of soil core leaching experiments to examine the role of acidification and recovery in driving the net production of DOC and NO3- from soils. Over 8 months, soil cores were leached biweekly with simulated rainfall solutions of varying pH (3.6 to 7.0) from additions of H2SO4, CaCO3 and NaOH. These experiments did not yield a pH-induced change in DOC quantity, but did show a change in DOC quality, in that acidified cores released more bio-available DOC with less depleted 13C-DOC than cores with experimentally increased pH. All cores leached substantial amounts of nitrate. Together, these lab- and field comparisons are being used to identify the role of soil production and consumption processes in driving cross-watershed differences in DOC and NO3- loss, or whether other factors (e.g., riparian, in-stream or hydrologic processes) likely explain this relationship.

An investigation of size-fractionated organic matter from Lake Superior and a tributary stream using radiocarbon, stable isotopes and NMR

NASA Astrophysics Data System (ADS)

Zigah, Prosper K.; Minor, Elizabeth C.; Abdulla, Hussain A. N.; Werne, Josef P.; Hatcher, Patrick G.

2014-02-01

This study investigated the concentration and isotopic composition of different size fractions of organic matter (OM) in Lake Superior and in one of its many tributary streams and rivers (Amity Creek, Duluth, Minnesota, USA). Structural compositional drivers of the Δ14C of high molecular weight (HMW, >1 kDa) dissolved organic carbon (DOC) in the lake were also evaluated. Low molecular weight (LMW, <1 kDa) DOC was the fraction containing the largest proportion (68-88%) of organic carbon (OC) in the lake. Particulate organic carbon (POC, >0.7 μm) was generally 13C-depleted (-29 ± 1.2‰) relative to “bulk” (<0.7 μm) DOC (-26.4 ± 0.7‰), “init” (<0.2 μm) DOC (-26.6 ± 0.8‰), HMW DOC (-26.9 ± 0.3‰) and LMW DOC (-26.5 ± 0.9‰), and had more variable 14C content (Δ14C of -94‰ to 53‰; 735 years BP to modern) than the other size fractions. Init DOC (Δ14C of 17-59‰), HMW DOC (Δ14C of 23-64‰) and LMW DOC (Δ14C of 16-62‰) all reflected contemporary (modern) radiocarbon signatures. Bulk DOC (Δ14C of -19‰ to 57‰; 90 years BP to modern) had modern radiocarbon values in the offshore sites (Δ14C of 2-57‰) with pre-aged samples (Δ14C of -8‰ to -19‰) seen at the nearshore site. HMW DOM was relatively N-poor (C:N of 12-19) compared to particulate organic matter (POM, C:N of 8-10) revealing either a more diagenetically altered state or contrasting sources. 13C NMR data showed that biochemical composition of HMW DOC in Lake Superior was dominated by carbohydrates (53-65%) with only trace aromatic components (2-4%). Structurally complex components such as heteropolysaccharides (HPS), amide/peptides and amino sugars (AMS) constitute 75-84% of HMW DOC whereas carboxylic-rich alicyclic molecules (CRAM) made up 16-25% of HMW DOC in the lake. Combined HPS and AMS, O-alkyl carbohydrate carbon, and total carbohydrate carbon contents were significantly positively correlated to the Δ14C of HMW DOC suggesting they contribute a contemporary 14C-enriched component to the HMW DOC in the lake. In contrast, CRAM and aliphatic carbons were significantly inversely correlated with Δ14C of HMW DOC implying that these represent 14C-depleted (older) components of HMW DOC in the lake. At Amity Creek, storm events led to larger loads of bulk DOC and POC, which were both 14C-enriched (modern). However, in baseflow conditions 14C-depleted bulk DOC and POC were exported. LMW DOC from the creek was considerably 14C-depleted compared to concurrent HMW DOC.

There's An App For That: Planning Ahead for the Solar Eclipse in August 2017

NASA Astrophysics Data System (ADS)

Chizek Frouard, Malynda R.; Lesniak, Michael V.; Bell, Steve

2017-01-01

With the total solar eclipse of 2017 August 21 over the continental United States approaching, the U.S. Naval Observatory (USNO) on-line Solar Eclipse Computer can now be accessed via an Android application, available on Google Play.Over the course of the eclipse, as viewed from a specific site, several events may be visible: the beginning and ending of the eclipse (first and fourth contacts), the beginning and ending of totality (second and third contacts), the moment of maximum eclipse, sunrise, or sunset. For each of these events, the USNO Solar Eclipse 2017 Android application reports the time, Sun's altitude and azimuth, and the event's position and vertex angles. The app also lists the duration of the total phase, the duration of the eclipse, the magnitude of the eclipse, and the percent of the Sun obscured for a particular eclipse site.All of the data available in the app comes from the flexible USNO Solar Eclipse Computer Application Programming Interface (API), which produces JavaScript Object Notation (JSON) that can be incorporated into third-party Web sites or custom applications. Additional information is available in the on-line documentation (http://aa.usno.navy.mil/data/docs/api.php).For those who prefer using a traditional data input form, the local circumstances can still be requested at http://aa.usno.navy.mil/data/docs/SolarEclipses.php.In addition the 2017 August 21 Solar Eclipse Resource page (http://aa.usno.navy.mil/data/docs/Eclipse2017.php) consolidates all of the USNO resources for this event, including a Google Map view of the eclipse track designed by Her Majesty's Nautical Almanac Office (HMNAO).Looking further ahead, a 2024 April 8 Solar Eclipse Resource page (http://aa.usno.navy.mil/data/docs/Eclipse2024.php) is also available.

Transformation of molecular weight distributions of dissolved organic carbon and UV-absorbing compounds at full-scale wastewater-treatment plants.

PubMed

Esparza-Soto, Mario; Fox, Peter; Westerhoff, Paul

2006-03-01

The molecular-weight distribution (MWD) of wastewater dissolved-organic carbon (DOC) was determined in samples from seven full-scale wastewater-treatment plants (WWTPs) that use different biological treatments (air activated sludge [air-AS], pure-oxygen AS [O2-AS], and trickling filters). The research objective was to determine how different biological treatments influenced the MWD of wastewater DOC. Primary sedimentation effluent DOC from most of the WWTPs exhibited a skewed distribution toward the low-molecular-weight fraction (MWF) (40 to 50%, < 0.5 K Daltons [KDa]). The Air-AS effluent DOC exhibited a centrally clustered distribution, with the majority of DOC in the intermediate MWF (0.5 to 3 KDa). The O2-AS effluent DOC exhibited a skewed distribution toward the high MWF (> 3 KDa). The removal of DOC by air- and O2-AS bacteria followed trends predicted by a macromolecule degradation model. Trickling-filter effluent DOC exhibited a skewed distribution toward the high MWF (50% DOC, > 3 KDa).

Humic substances-part 7: the biogeochemistry of dissolved organic carbon and its interactions with climate change.

PubMed

Porcal, Petr; Koprivnjak, Jean-François; Molot, Lewis A; Dillon, Peter J

2009-09-01

Dissolved organic matter, measured as dissolved organic carbon (DOC), is an important component of aquatic ecosystems and of the global carbon cycle. It is known that changes in DOC quality and quantity are likely to have ecological repercussions. This review has four goals: (1) to discuss potential mechanisms responsible for recent changes in aquatic DOC concentrations; (2) to provide a comprehensive overview of the interactions between DOC, nutrients, and trace metals in mainly boreal environments; (3) to explore the impact of climate change on DOC and the subsequent effects on nutrients and trace metals; and (4) to explore the potential impact of DOC cycling on climate change. We review recent research on the mechanisms responsible for recent changes in aquatic DOC concentrations, DOC interactions with trace metals, N, and P, and on the possible impacts of climate change on DOC in mainly boreal lakes. We then speculate on how climate change may affect DOC export and in-lake processing and how these changes might alter nutrient and metal export and processing. Furthermore, the potential impacts of changing DOC cycling patterns on climate change are examined. It has been noted that DOC concentrations in lake and stream waters have increased during the last 30 years across much of Europe and North America. The potential reasons for this increase include increasing atmospheric CO(2) concentration, climate warming, continued N deposition, decreased sulfate deposition, and hydrological changes due to increased precipitation, droughts, and land use changes. Any change in DOC concentrations and properties in lakes and streams will also impact the acid-base chemistry of these waters and, presumably, the biological, chemical, and photochemical reactions taking place. For example, the interaction of trace metals with DOC may be significantly altered by climate change as organically complexed metals such as Cu, Fe, and Al are released during photo-oxidation of DOC. The production and loss of DOC as CO(2) from boreal lakes may also be affected by changing climate. Climate change is unlikely to be uniform spatially with some regions becoming wetter while others become drier. As a result, rates of change in DOC export and concentrations will vary regionally and the changes may be non-linear. Climate change models predict that higher temperatures are likely to occur over most of the boreal forests in North America, Europe, and Asia over the next century. Climate change is also expected to affect the severity and frequency of storm and drought events. Two general climate scenarios emerge with which to examine possible DOC trends: warmer and wetter or warmer and drier. Increasing temperature and hydrological changes (specifically, runoff) are likely to lead to changes in the quality and quantity of DOC export from terrestrial sources to rivers and lakes as well as changes in DOC processing rates in lakes. This will alter the quality and concentrations of DOC and its constituents as well as its interactions with trace metals and the availability of nutrients. In addition, export rates of nutrients and metals will also change in response to changing runoff. Processing of DOC within lakes may impact climate depending on the extent to which DOC is mineralized to dissolved inorganic carbon (DIC) and evaded to the atmosphere or settles as particulate organic carbon (POC) to bottom sediments and thereby remaining in the lake. The partitioning of DOC between sediments and the atmosphere is a function of pH. Decreased DOC concentrations may also limit the burial of sulfate, as FeS, in lake sediments, thereby contributing acidity to the water by increasing the formation of H(2)S. Under a warmer and drier scenario, if lake water levels fall, previously stored organic sediments may be exposed to greater aeration which would lead to greater CO(2) evasion to the atmosphere. The interaction of trace metals with DOC may be significantly altered by climate change. Iron enhances the formation of POC during irradiation of lake water with UV light and therefore may be an important pathway for transfer of allochthonous DOC to the sediments. Therefore, changing Fe/DOC ratios could affect POC formation rates. If climate change results in altered DOC chemistry (e.g., fewer and/or weaker binding sites) more trace metals could be present in their toxic and bioavailable forms. The availability of nutrients may be significantly altered by climate change. Decreased DOC concentrations in lakes may result in increased Fe colloid formation and co-incident loss of adsorbable P from the water column. Climate change expressed as changes in runoff and temperature will likely result in changes in aquatic DOC quality and concentration with concomitant effects on trace metals and nutrients. Changes in the quality and concentration of DOC have implications for acid-base chemistry and for the speciation and bioavailability of certain trace metals and nutrients. Moreover, changes in DOC, metals, and nutrients are likely to drive changes in rates of C evasion and storage in lake sediments. The key controls on allochthonous DOC quality, quantity, and catchment export in response to climate change are still not fully understood. More detailed knowledge of these processes is required so that changes in DOC and its interactions with nutrients and trace metals can be better predicted based on changes caused by changing climate. More studies are needed concerning the effects of trace metals on DOC, the effects of changing DOC quality and quantity on trace metals and nutrients, and how runoff and temperature-related changes in DOC export affect metal and nutrient export to rivers and lakes.

Biogeochemistry of forested watersheds in the Southeastern U.S. prior to conversion to short-rotation pine for bioenergy

NASA Astrophysics Data System (ADS)

Griffiths, N. A.; Mulholland, P. J.; Jackson, C. R.; McDonnell, J. J.; Blake, J. I.; Du, E.; Klaus, J.; Langholtz, M.

2012-12-01

In the southeastern U.S., intensively-managed pine plantations are projected to be a significant source of feedstocks for bioenergy, and the environmental sustainability (water quality, quantity) of this practice needs to be addressed at the watershed scale. In the Upper Coastal Plain of South Carolina, we are examining water quality in 3 forested watersheds (1 reference [R], 2 treatment watersheds [B, C]) before and after the conversion to loblolly pine for bioenergy. We collected pre-treatment water quality data (nitrogen, phosphorus, dissolved organic carbon [DOC], herbicides) from all watersheds for two years (2009-2011) to determine baseline conditions. In May 2012, 40% of the extant forest in the two treatment watersheds was harvested and planting of loblolly pine will begin in early 2013. We will discuss our pre-treatment water quality results from the 3 study watersheds in context with our watershed-scale experiment. Baseline stream chemistry differed among the three watersheds, with higher mean concentrations of ammonium (59 μg/L) and DOC (8.1 mg/L) in Watershed R than in Watersheds B (ammonium = 17 μg/L, DOC = 6.9 μg/L) and C (ammonium = 17 μg/L, DOC = 6.1 μg/L), suggesting that anaerobic conditions in Watershed R may influence stream chemistry. Stream nitrate concentrations were higher in Watershed B (111 μg/L) than in Watersheds R (29 μg/L) and C (30 μg/L), suggesting that shallower flowpaths may be contributing to stream water chemistry. Dual isotope analysis of nitrate (15N, 18O) suggests that riparian groundwater is the source of nitrate in streams. However, nitrate in precipitation can be an important source to these watersheds during storms, as nitrate in flowing soil water had similar δ18O-NO3 values to precipitation. Nitrate may travel more conservatively in these watersheds than ammonium or phosphorus, as an irrigation experiment which simulated nutrient deposition from rainwater showed that the majority of added ammonium and phosphorus is removed (via uptake and/or sorption) compared to nitrate. Overall, quantifying baseline water chemistry among the three watersheds prior to the establishment of loblolly pine is necessary in order to determine any potential effects that short-rotation pine management may have on water quality.

Time scales of change in chemical and biological parameters after engineered levee breaches adjacent to Upper Klamath and Agency Lakes, Oregon

USGS Publications Warehouse

Kuwabara, James S.; Topping, Brent R.; Carter, James L.; Wood, Tamara M.; Parcheso, Francis; Cameron, Jason M.; Asbill, Jessica R.; Carlson, Rick A.; Fend, Steven V.

2012-01-01

Eight sampling trips were coordinated after engineered levee breaches hydrologically reconnected both Upper Klamath Lake and Agency Lake, Oregon, to adjacent wetlands. The reconnection, by a series of explosive blasts, was coordinated by The Nature Conservancy to reclaim wetlands that had for approximately seven decades been leveed for crop production. Sets of nonmetallic porewater profilers (U.S. Patent 8,051,727 B1; November 8, 2011; http://www.uspto.gov/web/patents/patog/ week45/OG/html/1372-2/US08051727-20111108.html.) were deployed during these trips in November 2007, June 2008, May 2009, July 2009, May 2010, August 2010, June 2011, and July 2011 (table 1). Deployments temporally spanned the annual cyanophyte bloom of Aphanizomenon flos-aquae and spatially involved three lake and four wetland sites. Spatial and temporal variation in solute benthic flux was determined by the field team, using the profilers, over an approximately 4-year period beginning 3 days after the levee breaches. The highest flux to the water column of dissolved organic carbon (DOC) was detected in the newly flooded wetland, contrasting negative or insignificant DOC fluxes at adjacent lake sites. Over the multiyear study, DOC benthic fluxes dissipated in the reconnected wetlands, converging to values similar to those for established wetlands and to the adjacent lake (table 2). In contrast to DOC, benthic sources of soluble reactive phosphorus, ammonium, dissolved iron and manganese from within the reconnected wetlands were consistently elevated (that is, significant in magnitude relative to riverine and established-wetland sources) indicating a multi-year time scale for certain chemical changes after the levee breaches (table 2). Colonization of the reconnected wetlands by aquatic benthic invertebrates during the study trended toward the assemblages in established wetlands, providing further evidence of a multiyear transition of this area to permanent aquatic habitat (table 3). Both the lake and wetland benthic environments substantively contribute to macro- and micronutrients in the water column. Wetland areas undergoing restoration, and those being used for water storage, function very differently relatively to the established wetland within the Upper Klamath Lake National Wildlife Refuge, adjacent Upper Klamath Lake. Developing long-term management strategies for water quality in the Upper Klamath Basin requires recognition of the multi-year time scales associated with restoring wetlands that provide natural, seasonal ecosystem function and services.

Dissolved Organic Carbon 14C in Southern Nevada Groundwater and Implications for Groundwater Travel Times

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

Hershey, Ronald L.; Fereday, Wyall; Thomas, James M

Dissolved inorganic carbon (DIC) carbon-14 ( 14C) ages must be corrected for complex chemical and physical reactions and processes that change the amount of 14C in groundwater as it flows from recharge to downgradient areas. Because of these reactions, DIC 14C can produce unrealistically old ages and long groundwater travel times that may, or may not, agree with travel times estimated by other methods. Dissolved organic carbon (DOC) 14C ages are often younger than DIC 14C ages because there are few chemical reactions or physical processes that change the amount of DOC 14C in groundwater. However, there are several issuesmore » that create uncertainty in DOC 14C groundwater ages including limited knowledge of the initial (A 0) DOC 14C in groundwater recharge and potential changes in DOC composition as water moves through an aquifer. This study examines these issues by quantifying A 0 DOC 14C in recharge areas of southern Nevada groundwater flow systems and by evaluating changes in DOC composition as water flows from recharge areas to downgradient areas. The effect of these processes on DOC 14C groundwater ages is evaluated and DOC and DIC 14C ages are then compared along several southern Nevada groundwater flow paths. Twenty-seven groundwater samples were collected from springs and wells in southern Nevada in upgradient, midgradient, and downgradient locations. DOC 14C for upgradient samples ranged from 96 to 120 percent modern carbon (pmc) with an average of 106 pmc, verifying modern DOC 14C ages in recharge areas, which decreases uncertainty in DOC 14C A 0 values, groundwater ages, and travel times. The HPLC spectra of groundwater along a flow path in the Spring Mountains show the same general pattern indicating that the DOC compound composition does not change along this flow path. Although DOC concentration decreases from recharge-area to downgradient groundwater, the organic compounds are similar, indicating that DOC 14C is unaffected by other processes such as microbial degradation. A small amount of organic carbon was leached from crushed volcanic and carbonate aquifer outcrop rock in rock-leaching experiments. The leached DOC was high in 14C (75 pmc carbonate rocks, 91 pmc volcanic) suggesting that the leached DOC likely came from microbes in the rock samples. The small amount of DOC and high 14C indicates that the amount of old organic carbon in these rocks is low so there should be minimal impact on groundwater DOC 14C ages. Based on the results from this study, DOC 14C ages do not require additional corrections. Several correction models were applied to DIC 14C ages to correct for water-rock reactions along two carbonate and two volcanic flow paths and the corresponding travel times were compare to DOC 14C travel times. The DOC 14C travel times were hundreds to thousands of years shorter than uncorrected and corrected DIC 14C travel times except for the upper section of one carbonate flow path. DOC 14C travel times ranged from 400 to 5,400 years as compared to DIC 14C that ranged from modern to 20,900 years. The DIC 14C ages are greatly influenced by carbonate mineral and gas reactions and other processes such as matrix diffusion, isotope exchange, or adsorption, which are not always adequately accounted for in DIC 14C groundwater age correction models.« less

Variable flushing mechanisms and landscape structure control stream DOC export during snowmelt in a set of nested catchments

Treesearch

Vincent J. Pacific; Kelsey G. Jencso; Brian L. McGlynn

2010-01-01

Stream DOC dynamics during snowmelt have been the focus of much research, and numerous DOC mobilization and delivery mechanisms from riparian and upland areas have been proposed. However, landscape structure controls on DOC export from riparian and upland landscape elements remains poorly understood. We investigated stream and groundwater DOC dynamics across three...

Dissolved Organic Carbon along the Louisiana coast from MODIS and MERIS satellite data

NASA Astrophysics Data System (ADS)

Chaichi Tehrani, N.; D'Sa, E. J.

2012-12-01

Dissolved organic carbon (DOC) plays a critical role in the coastal and ocean carbon cycle. Hence, it is important to monitor and investigate its the distribution and fate in coastal waters. Since DOC cannot be measured directly through satellite remote sensors, chromophoric dissolved organic matter (CDOM) as an optically active fraction of DOC can be used as an alternative proxy to trace DOC concentrations. Here, satellite ocean color data from MODIS, MERIS, and field measurements of CDOM and DOC were used to develop and assess CDOM and DOC ocean color algorithms for coastal waters. To develop a CDOM retrieval algorithm, empirical relationships between CDOM absorption coefficient at 412 nm (aCDOM(412)) and reflectance ratios Rrs(488)/Rrs(555) for MODIS and Rrs(510)/Rrs(560) for MERIS were established. The performance of two CDOM empirical algorithms were evaluated for retrieval of (aCDOM(412)) from MODIS and MERIS in the northern Gulf of Mexico. Further, empirical algorithms were developed to estimate DOC concentration using the relationship between in situ aCDOM(412) and DOC, as well as using the newly developed CDOM empirical algorithms. Accordingly, our results revealed that DOC concentration was strongly correlated to aCDOM (412) for summer and spring-winter periods (r2 = 0.9 for both periods). Then, using the aCDOM(412)-Rrs and the aCDOM(412)-DOC relationships derived from field measurements, a relationship between DOC-Rrs was established for MODIS and MERIS data. The DOC empirical algorithms performed well as indicated by match-up comparisons between satellite estimates and field data (R2=0.52 and 0.58 for MODIS and MERIS for summer period, respectively). These algorithms were then used to examine DOC distribution along the Louisiana coast.

Hydrological controls on DOC  :  nitrate resource stoichiometry in a lowland, agricultural catchment, southern UK

NASA Astrophysics Data System (ADS)

Heppell, Catherine M.; Binley, Andrew; Trimmer, Mark; Darch, Tegan; Jones, Ashley; Malone, Ed; Collins, Adrian L.; Johnes, Penny J.; Freer, Jim E.; Lloyd, Charlotte E. M.

2017-09-01

The role that hydrology plays in governing the interactions between dissolved organic carbon (DOC) and nitrogen in rivers draining lowland, agricultural landscapes is currently poorly understood. In light of the potential changes to the production and delivery of DOC and nitrate to rivers arising from climate change and land use management, there is a pressing need to improve our understanding of hydrological controls on DOC and nitrate dynamics in such catchments. We measured DOC and nitrate concentrations in river water of six reaches of the lowland river Hampshire Avon (Wiltshire, southern UK) in order to quantify the relationship between BFI (BFI) and DOC : nitrate molar ratios across contrasting geologies (Chalk, Greensand, and clay). We found a significant positive relationship between nitrate and BFI (p < 0. 0001), and a significant negative relationship between DOC and BFI (p < 0. 0001), resulting in a non-linear negative correlation between DOC : nitrate molar ratio and BFI. In the Hampshire Avon, headwater reaches which are underlain by clay and characterized by a more flashy hydrological regime are associated with DOC : nitrate ratios > 5 throughout the year, whilst groundwater-dominated reaches underlain by Chalk, with a high BFI have DOC : nitrate ratios in surface waters that are an order of magnitude lower (< 0.5). Our analysis also reveals significant seasonal variations in DOC : nitrate transport and highlights critical periods of nitrate export (e.g. winter in sub-catchments underlain by Chalk and Greensand, and autumn in drained, clay sub-catchments) when DOC : nitrate molar ratios are low, suggesting low potential for in-stream uptake of inorganic forms of nitrogen. Consequently, our study emphasizes the tight relationship between DOC and nitrate availability in agricultural catchments, and further reveals that this relationship is controlled to a great extent by the hydrological setting.

A U.S. Carbon Cycle Science Plan

NASA Astrophysics Data System (ADS)

Michalak, Anna M.; Jackson, Rob; Marland, Gregg; Sabine, Christopher

2009-03-01

First Meeting of the Carbon Cycle Science Working Group; Washington, D. C., 17-18 November 2008; The report “A U.S. carbon cycle science plan” (J. L. Sarmiento and S. C. Wofsy, U.S. Global Change Res. Program, Washington, D. C., 1999) outlined research priorities and promoted coordinated carbon cycle research across federal agencies for nearly a decade. Building on this framework and subsequent reports (available at http://www.carboncyclescience.gov/docs.php), the Carbon Cycle Science Working Group (CCSWG) was formed in 2008 to develop an updated strategy for the next decade. The recommendations of the CCSWG will go to agency managers who have collective responsibility for setting national carbon cycle science priorities and for sponsoring much of the carbon cycle research in the United States.

76 FR 81980 - Sunshine Act Meeting; Record of Vote of Meeting Closure (Pub. L. 94-409) (5 U.S.C. 552b)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-29

... (Pub. L. 94-409) (5 U.S.C. 552b) I, Isaac Fulwood, of the United States Parole Commission, was present... following Commissioners voted that the meeting be closed: Isaac Fulwood, Cranston J. Mitchell, Patricia..., 2011. Isaac Fulwood, Chairman, U.S. Parole Commission. [FR Doc. 2011-33524 Filed 12-27-11; 4:15 pm...

Physical Model Study of Cross Vanes and Ice

DTIC Science & Technology

2009-08-01

spacing since, in the pre-scour state, experiments and the HEC - RAS hydraulic model (USACE 2002b) found that water surface ele- vation merged with the...docs/eng-manuals/em1110- 2-1612/toc.htm. USACE (2002b) HEC - RAS , Hydraulic Reference Manual. US Army Corps of Engineers Hydrologic Engineering Center...Currently little design guidance is available for constructing these structures on ice-affected rivers . This study used physical and numerical

Semiconductor Technology and U.S. National Security

DTIC Science & Technology

2010-04-21

control regime as hindrances to compete in the global market.45 Interestingly, DOD’s Defense Technology Security Administration ( DTSA ) reviews export...licenses and only advises DOS or DOC.46 DTSA has neither compliance nor enforcement authority. There is no lead organization or a centralized...which lists several semiconductor technologies, is out of date and not used, even by DOD’s DTSA .51 In order to remove certain export controls on

Velocity: Speed with Direction. The Professional Career of Gen Jerome F. O’Malley

DTIC Science & Technology

2007-09-01

per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing...other US government agency. Cleared for public release: distribution unlimited. Muir S. Fairchild Research Information Center Cataloging Data Casey...www.west-point.org/users/ usma1983/40768/docs/taylor.html (accessed 24 April 2007). 16. Officer Effectiveness Report, unpublished data , 2 January 1956. 17

78 FR 50143 - Agency Information Collection (Application for CHAMPVA Benefits) Activities Under OMB Review

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-16

...,402 hours. c. VA Form 10-7959c--6,728 hours. d. VA Form 10-7959d--467 hours. e. VA Form 10-7959e--1500...,000. Dated: August 13, 2013. By direction of the Secretary. Crystal Rennie, VA Clearance Officer, U.S. Department of Veterans Affairs. [FR Doc. 2013-19914 Filed 8-15-13; 8:45 am] BILLING CODE 8320-01-P ...

75 FR 10687 - Regulated Navigation Areas; Bars Along the Coasts of Oregon and Washington; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-09

..., 3306, 3703; 50 U.S.C. 191, 195; 33 CFR 1.05-1(g), 6.04-1, 6.04-6, and 160.5; Pub. L. 107-295, 116 Stat... 22A prior to crossing the bar between sunset and sunrise. * * * * * * * * Dated: February 17, 2010. G.T. Blore, Rear Admiral, U.S. Coast Guard, Commander, Thirteenth Coast Guard District. [FR Doc. 2010...

The Age of Terrestrial Carbon Export and Rainfall Intensity in a Temperate River Headwater System

NASA Astrophysics Data System (ADS)

Tittel, J.; Büttner, O.; Freier, K.; Heiser, A.; Sudbrack, R.; Ollesch, G.

2013-12-01

Riverine dissolved organic carbon (DOC) supports the production of estuaries and coastal ecosystems, constituting one of the most actively recycled pools of the global carbon cycle. A substantial proportion of DOC entering oceans is highly aged, but its origins remain unclear. Significant fluxes of old DOC have never been observed in temperate headwaters where terrestrial imports take place. Here, we studied the radiocarbon age of DOC in three streams draining forested headwater catchments of the river Mulde (Ore Mountains, Germany). We found modern DOC at moderately dry and moderately wet conditions as well as at high discharges during snowmelt. Old groundwater carbon contributed to stream DOC during the summer drought, although the yield was negligible. However, in a four-week summer precipitation event DOC aged at between 160 and 270 years was delivered into the watershed. In one stream, the DOC was modern but depleted in radiocarbon compared to other hydrological conditions. The yield was substantial and corresponded to 20 to 52% of the annual DOC yields in wet and dry years, respectively. Time-integrating samples of a downstream reservoir also revealed modern DOC ages under moderate conditions and old DOC from the rainfall event. Earlier studies suggested that increasing precipitation escalates the contribution of modern DOC from topsoil layers to surface runoff. Our results demonstrate a step change occurring if rainfall intensities increase and become extreme; then the consequences lead to the mobilization of old carbon in exceptionally high concentrations. The runoff/precipitation ratios of rainfall events indicated that during extreme events upland areas of the catchments were hydrologically connected to the stream and upland DOC was activated. Furthermore, the analysis of long-term data suggested that the DOC export in extreme precipitation events added to the annual yield and was not compensated for by lower exports in remaining periods. We conclude that climate change, along with additional processes associated with human activities, channels old soil carbon into more rapidly cycled carbon pools of the hydrosphere.

The influence of dissolved organic carbon on bacterial phosphorus uptake and bacteria-phytoplankton dynamics in two Minnesota lakes

USGS Publications Warehouse

Stets, E.G.; Cotner, J.B.

2008-01-01

The balance of production in any ecosystem is dependent on the flow of limiting nutrients into either the autotrophic or heterotrophic components of the food web. To understand one of the important controls on the flow of inorganic nutrients between phytoplankton and bacterioplankton in lakes, we manipulated dissolved organic carbon (DOC) in two lakes of different trophic status. We hypothesized that labile DOC additions would increase bacterial phosphorus (P) uptake and decrease the response of phytoplankton to nutrient additions. Supplemental nutrients and carbon (C), nitrogen (N, 1.6 ??mol NH4Cl L-1 d-1), P (0.1 ??mol KH 2PO4 L-1 d-1), and DOC (glucose, 15 ??mol C L-1 d-1) were added twice daily to 8-liter experimental units. We tested the effect of added DOC on chlorophyll concentration, bacterial production, biomass, and P uptake using size-fractionated 33P-PO4 uptake. In the oligotrophic lake, DOC additions stimulated bacterial production and increased bacterial biomass-specific P uptake. Bacteria consumed added DOC, and chlorophyll concentrations were significantly lower in carboys receiving DOC additions. In the eutrophic lake, DOC additions had less of a stimulatory effect on bacterial production and biomass-specific P uptake. DOC accumulated over the time period, and there was little evidence for a DOC-induced decrease in phytoplankton biomass. Bacterial growth approached the calculated ??max and yet did not accumulate biomass, indicating significant biomass losses, which may have constrained bacterial DOC consumption. Excess bacterial DOC consumption in oligotrophic lakes may result in greater bacterial P affinity and enhanced nutrient uptake by the heterotrophic compartment of the food web. On the other hand, constraints on bacterial biomass accumulation in eutrophic lakes, from either viral lysis or bacterial grazing, can allow labile DOC to accumulate, thereby negating the effect of excess DOC on the planktonic food web. ?? 2008, by the American Society of Limnology and Oceanography, Inc.

Modeling the Dynamics and Export of Dissolved Organic Matter in the Northeastern U.S. Continental Shelf

NASA Technical Reports Server (NTRS)

Druon, J.N.; Mannino, A.; Signorini, Sergio R.; McClain, Charles R.; Friedrichs, M.; Wilkin, J.; Fennel, K.

2009-01-01

Continental shelves are believed to play a major role in carbon cycling due to their high productivity. Particulate organic carbon (POC) burial has been included in models as a carbon sink, but we show here that seasonally produced dissolved organic carbon (DOC) on the shelf can be exported to the open ocean by horizontal transport at similar rates (1-2 mol C/sq m/yr) in the southern U.S. Mid-Atlantic Bight (MAB). The dissolved organic matter (DOM) model imbedded in a coupled circulation-biogeochemical model reveals a double dynamics: the progressive release of dissolved organic nitrogen (DON) in the upper layer during summer increases the regenerated primary production by 30 to 300%, which, in turns ; enhances the DOC production mainly from phytoplankton exudation in the upper layer and solubilization of particulate organic matter (POM) deeper in the water column. This analysis suggests that DOM is a key element for better representing the ecosystem functioning and organic fluxes in models because DOM (1) is a major organic pool directly related to primary production, (2) decouples partially the carbon and nitrogen cycles (through carbon excess uptake, POM solubilization and DOM mineralization) and (3) is intimately linked to the residence time of water masses for its distribution and export.

Impact of wetland decline on decreasing dissolved organic carbon concentrations along the Mississippi River continuum

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

Duan, Shuiwang; He, Yuxiang; Kaushal, Sujay S.

Prior to discharging to the ocean, large rivers constantly receive inputs of dissolved organic carbon (DOC) from tributaries or fringing floodplains and lose DOC via continuous in situ processing along distances that span thousands of kilometers. Current concepts predicting longitudinal changes in DOC mainly focus on in situ processing or exchange with fringing floodplain wetlands, while effects of heterogeneous watershed characteristics are generally ignored. We analyzed results from a 17-year time-series of DOC measurements made at seven sites and three expeditions along the entire Mississippi River main channel with DOC measurements made every 17 km. The results show a clearmore » downstream decrease in DOC concentrations that was consistent throughout the entire study period. Downstream DOC decreases were primarily (~63–71%) a result of constant dilutions by low-DOC tributary water controlled by watershed wetland distribution, while in situ processing played a secondary role. We estimate that from 1780 to 1980 wetland loss due to land-use alterations caused a ca. 58% decrease in in DOC concentrations in the tributaries of the Mississippi River. DOC reductions caused by watershed wetland loss likely impacted the capacity for the river to effectively remove nitrogen via denitrification, which can further exacerbate coastal hypoxia. Lastly, these findings highlight the importance of watershed wetlands in regulating DOC longitudinally along the headland to ocean continuum of major rivers.« less

Impact of wetland decline on decreasing dissolved organic carbon concentrations along the Mississippi River continuum

DOE PAGES

Duan, Shuiwang; He, Yuxiang; Kaushal, Sujay S.; ...

2017-01-09

Prior to discharging to the ocean, large rivers constantly receive inputs of dissolved organic carbon (DOC) from tributaries or fringing floodplains and lose DOC via continuous in situ processing along distances that span thousands of kilometers. Current concepts predicting longitudinal changes in DOC mainly focus on in situ processing or exchange with fringing floodplain wetlands, while effects of heterogeneous watershed characteristics are generally ignored. We analyzed results from a 17-year time-series of DOC measurements made at seven sites and three expeditions along the entire Mississippi River main channel with DOC measurements made every 17 km. The results show a clearmore » downstream decrease in DOC concentrations that was consistent throughout the entire study period. Downstream DOC decreases were primarily (~63–71%) a result of constant dilutions by low-DOC tributary water controlled by watershed wetland distribution, while in situ processing played a secondary role. We estimate that from 1780 to 1980 wetland loss due to land-use alterations caused a ca. 58% decrease in in DOC concentrations in the tributaries of the Mississippi River. DOC reductions caused by watershed wetland loss likely impacted the capacity for the river to effectively remove nitrogen via denitrification, which can further exacerbate coastal hypoxia. Lastly, these findings highlight the importance of watershed wetlands in regulating DOC longitudinally along the headland to ocean continuum of major rivers.« less

Determination of an organic-acid analog of DOC for use in copper toxicity studies on salmonids

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

MacRae, R.K.; Meyer, J.S.; Hansen, J.A.

1995-12-31

Concentrations of dissolved copper in streams draining mine sites often exceed concentrations shown to cause acute and chronic mortality in salmonids. However, toxicity and impaired behaviors may be modified by dissolved organic carbon (DOC) and other inorganic components present in the site water. The effects of DOC on copper speciation, and thus bioavailability and toxicity, were determined by titrating stream waters with copper, using a cupric ion-specific electrode to detect free copper concentrations. Effects of various competing cations (e.g., Ca{sup +2}, Co{sup +2}) on copper-DOC binding were also evaluated. Titration results were evaluated using Scatchard and non-linear regression analyses tomore » quantify the strength and capacity of copper-DOC binding. Inorganic speciation was determined using the geochemical model MINEQL{sup +}. Results of these titrations indicated the presence of two or three distinct copper binding components in site water DOC. Three commercially available organic acids where then chosen to mimic the binding characteristics of natural DOC. This DOC-analog was used successfully in fish toxicity studies to evaluate the influence of DOC on copper bioavailability. Geochemical models were developed to predict copper speciation in both laboratory test waters and site waters, for any typical combination of water chemistry parameters (pH, alkalinity, [DOC], etc.). A combined interpretation of fish toxicity and modeling results indicate that some DOC-bound copper was bioavailable.« less

Transformations and Fates of Terrigenous Dissolved Organic Matter in River-influenced Ocean Margins

NASA Astrophysics Data System (ADS)

Fichot, Cedric G.

Rivers contribute about 0.25 Pg of terrigenous dissolved organic carbon (tDOC) to the ocean each year. The fate and transformations of this material have important ramifications for the metabolic state of the ocean, air-sea CO2 exchange, and the global carbon cycle. Stable isotopic compositions and terrestrial biomarkers suggest tDOC must be efficiently mineralized in ocean margins. Nonetheless, the extent of tDOC mineralization in these environments remains unknown, as no quantitative estimate is available. The complex interplay of biogeochemical and physical processes in these systems compounded by the limited practicality of chemical proxies (organic biomarkers, isotopic compositions) make the quantification of tDOC mineralization in these dynamic systems particularly challenging. In this dissertation, new optical proxies were developed (Chapters 1 and 2) and facilitated the first quantitative assessment of tDOC mineralization in a dynamic river-influenced ocean margin (Chapter 3) and the monitoring of continental runoff distributions in the coastal ocean using remote sensing (Chapter 4). The optical properties of chromophoric dissolved organic matter (CDOM) were used as optical proxies for dissolved organic carbon concentration ([DOC]) and %tDOC. In both proxies, the CDOM spectral slope coefficient ( S275-295) was exploited for its informative properties on the chemical nature and composition of dissolved organic matter. In the first proxy, a strong relationship between S275-295 and the ratio of CDOM absorption to [DOC] facilitated accurate retrieval (+/- 4%) of [DOC] from CDOM. In the second proxy, the existence of a strong relationship between S275-295 and the DOC-normalized lignin yield facilitated the estimation of the %tDOC from S 275-295. Using the proxies, the tDOC concentration can be retrieved solely from CDOM absorption coefficients (lambda = 275-295 nm) in river-influenced ocean margins. The practicality of optical proxies facilitated the calculation of tDOC mineralization rates on the Louisiana shelf. Seasonal tDOC mass balances for the shelf revealed that between 26% (winter) and 71% (summer) of the mixed layer tDOC is mineralized during its residence on the shelf. Independent approaches further indicated biomineralization accounts for 60% of the tDOC mineralization whereas photomineralization contributes only 8%. The remaining 32% was attributed to the coupled photo-biomineralization. On an annual basis, our results indicated ˜40% of the tDOC discharged by the Mississippi and Atchafalaya rivers to the Louisiana shelf (˜1 Tg tDOC) is mineralized within 2 to 3 months. This extensive mineralization on the shelf is direct evidence ocean margins act as efficient filters of tDOC between the land and ocean. Finally, the amenability of S275-295 to ocean color remote sensing was demonstrated, and facilitates the real-time, synoptic monitoring of tDOC and freshwater runoff in coastal waters. Implementation of this approach provided the first pan-Arctic distributions of tDOC and continental runoff in surface polar waters, and will help understand the manifestations of climate change in this remote region.

Concentrations and characteristics of organic carbon in surface water in Arizona: Influence of urbanization

USGS Publications Warehouse

Westerhoff, P.; Anning, D.

2000-01-01

Dissolved (DOC) and total (TOC) organic carbon concentrations and compositions were studied for several river systems in Arizona, USA. DOC composition was characterized by ultraviolet and visible absorption and fluorescence emission (excitation wavelength of 370 nm) spectra characteristics. Ephemeral sites had the highest DOC concentrations, and unregulated perennial sites had lower concentrations than unregulated intermittent sites, regulated sites, and sites downstream from wastewater-treatment plants (p < 0.05). Reservoir outflows and wastewater-treatment plant effluent were higher in DOC concentration (p < 0.05) and exhibited less variability in concentration than inflows to the reservoirs. Specific ultraviolet absorbance values at 254 nm were typically less than 2 m-1(milligram DOC per liter)-1 and lower than values found in most temperate-region rivers, but specific ultraviolet absorbance values increased during runoff events. Fluorescence measurements indicated that DOC in desert streams typically exhibit characteristics of autochthonous sources; however, DOC in unregulated upland rivers and desert streams experienced sudden shifts from autochthonous to allochthonous sources during runoff events. The urban water system (reservoir systems and wastewater-treatment plants) was found to affect temporal variability in DOC concentration and composition. (C) 2000 Elsevier Science B.V.Dissolved (DOC) and total (TOC) organic carbon concentrations and compositions were studied for several river systems in Arizona, USA. DOC composition was characterized by ultraviolet and visible absorption and fluorescence emission (excitation wavelength of 370 nm) spectra characteristics. Ephemeral sites had the highest DOC concentrations, and unregulated perennial sites had lower concentrations than unregulated intermittent sites, regulated sites, and sites downstream from wastewater-treatment plants (p<0.05). Reservoir outflows and wastewater-treatment plant effluent were higher in DOC concentration (p<0.05) and exhibited less variability in concentration than inflows to the reservoirs. Specific ultraviolet absorbance values at 254 nm were typically less than 2 m-1(milligram DOC per liter)-1 and lower than values found in most temperate-region rivers, but specific ultraviolet absorbance values increased during runoff events. Fluorescence measurements indicated that DOC in desert streams typically exhibit characteristics of autochthonous sources; however, DOC in unregulated upland rivers and desert streams experienced sudden shifts from autochthonous to allochthonous sources during runoff events. The urban water system (reservoir systems and wastewater-treatment plants) was found to affect temporal variability in DOC concentration and composition.The influence of urbanization, becoming increasingly common in arid regions, on dissolved organic carbon (DOC) concentrations in surface water resources was studied. DOC concentration and composition, seasonal watershed runoff events, streamflow variations, water management practices, and urban infrastructure in several Arizona watersheds were monitored. Ephemeral sites had the highest DOC levels, and unregulated perennial sites and lower concentrations than unregulated intermittent sites, regulated sites, and sites downstream from wastewater treatment plants. Reservoir outflows and wastewater treatment plant effluent had higher and less variable DOC concentrations than inflows to reservoirs. UV absorbance values, fluorescence measurements, and other indicators suggest that urban water systems (reservoirs and wastewater treatment plants) affect temporal variability in DOC concentration and composition.

Long-term trends in dissolved iron and DOC concentration linked to nitrate depletion in riparian soils

NASA Astrophysics Data System (ADS)

Musolff, Andreas; Selle, Benny; Fleckenstein, Jan H.; Oosterwoud, Marieke R.; Tittel, Jörg

2016-04-01

The instream concentrations of dissolved organic carbon (DOC) are rising in many catchments of the northern hemisphere. Elevated concentrations of DOC, mainly in the form of colored humic components, increase efforts and costs of drinking water purification. In this study, we evaluated a long-term dataset of 110 catchments draining into German drinking water reservoirs in order to assess sources of DOC and drivers of a potential long-term change. The average DOC concentrations across the wide range of different catchments were found to be well explained by the catchment's topographic wetness index. Higher wetness indices were connected to higher average DOC concentrations, which implies that catchments with shallow topography and pronounced riparian wetlands mobilize more DOC. Overall, 37% of the investigated catchments showed a significant long-term increase in DOC concentrations, while 22% exhibited significant negative trends. Moreover, we found that increasing trends in DOC were positively correlated to trends in dissolved iron concentrations at pH≤6 due to remobilization of DOC previously sorbed to iron minerals. Both, increasing trends in DOC and dissolve iron were found to be connected to decreasing trends and low concentrations of nitrate (below ~6 mg/L). This was especially observed in forested catchments where atmospheric N-depositions were the major source for nitrate availability. In these catchments, we also found long-term increases of phosphate concentrations. Therefore, we argue that dissolved iron, DOC and phosphate were jointly released under iron-reducing conditions when nitrate as a competing electron acceptor was too low in concentrations to prevent the microbial iron reduction. In contrast, we could not explain the observed increasing trends in DOC, iron and phosphate concentrations by the long-term trends of pH, sulfate or precipitation. Altogether this study gives strong evidence that both, source and long-term increases in DOC are primarily controlled by riparian wetland soils within the catchments. Here, the achievement of a long-term reduction in nitrogen deposition may in turn lead to a more pronounced iron reduction and a subsequent release of DOC and other iron-bound substances such as phosphate.

Seasonal variations in production and consumption rates of dissolved organic carbon in an organic-rich coastal sediment

NASA Astrophysics Data System (ADS)

Alperin, M. J.; Albert, D. B.; Martens, C. S.

1994-11-01

Dissolved organic carbon (DOC) concentrations in anoxic marine sediments are controlled by at least three processes: (1) production of nonvolatile dissolved compounds, such as peptides and amino acids, soluble saccharides and fatty acids, via hydrolysis of particulate organic carbon (POC). (2) conversion of these compounds to volatile fatty acids and alcohols by fermentative bacteria. (3) consumption of volatile fatty acids and alcohols by terminal bacteria, such as sulfate reducers and methanogens. We monitored seasonal changes in concentration profiles of total DOC, nonacid-volatile (NAV) DOC and acid-volatile (AV) DOC in anoxic sediment from Cape Lookout Bight, North Carolina, USA, in order to investigate the factors that control seasonal variations in rates of hydrolysis, fermentation, and terminal metabolism. During the winter months, DOC concentrations increased continuously from 0.2 mM in the bottomwater to ~4 mM at a depth of 36 cm in the sediment column. During the summer, a large DOC maximum developed between 5 and 20 cm, with peak concentrations approaching 10 mM. The mid-depth summertime maximum was driven by increases in both NAV- and AV-DOC concentrations. Net NAV-DOC reaction rates were estimated by a diagenetic model applied to NAV-DOC concentration profiles. Depth-integrated production rates of NAV-DOC increased from February through July, suggesting that net rates of POC hydrolysis during this period are controlled by temperature. Net consumption of NAV-DOC during the late summer and early fall suggests reduced gross NAV-DOC production rates, presumably due to a decline in the availability of labile POC. A distinct subsurface peak in AV-DOC concentration developed during the late spring, when the sulfate depletion depth shoaled from 25 to 10 cm. We hypothesize that the AV-DOC maximum results from a decline in consumption by sulfate-reducing bacteria (due to sulfate limitation) and a lag in the development of an active population of methanogenic bacteria. A diagenetic model that incorporates a lag period in the sulfate reducer-methanogen transition successfully simulates the timing, magnitude, depth and shape of the AV-DOC peak.

Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America

USGS Publications Warehouse

Hanley, Kevin W.; Wollheim, Wilfred M.; Salisbury, Joseph; Huntington, Thomas G.; Aiken, George R.

2013-01-01

Understanding the processes controlling the transfer and chemical composition of dissolved organic carbon (DOC) in freshwater systems is crucial to understanding the carbon cycle and the effects of DOC on water quality. Previous studies have identified watershed-scale controls on bulk DOC flux and concentration among small basins but fewer studies have explored controls among large basins or simultaneously considered the chemical composition of DOC. Because the chemical character of DOC drives riverine biogeochemical processes such as metabolism and photodegradation, accounting for chemical character in watershed-scale studies will improve the way bulk DOC variability in rivers is interpreted. We analyzed DOC quantity and chemical character near the mouths of 17 large North American rivers, primarily between 2008 and 2010, and identified watershed characteristics that controlled variability. We quantified DOC chemical character using both specific ultraviolet absorbance at 254 nm (SUVA254) and XAD-resin fractionation. Mean DOC concentration ranged from 2.1 to 47 mg C L−1 and mean SUVA254 ranged from 1.3 to 4.7 L mg C−1 m−1. We found a significant positive correlation between basin wetland cover and both bulk DOC concentration (R2 = 0.78; p < 0.0001) and SUVA254 (R2 = 0.91; p < 0.0001), while other land use characteristics were not correlated. The strong wetland relationship with bulk DOC concentration is similar to that found by others in small headwater catchments. However, two watersheds with extremely long surface water residence times, the Colorado and St. Lawrence, diverged from this wetland relationship. These results suggest that the role of riverine processes in altering the terrestrial DOC signal at the annual scale was minimal except in river systems with long surface water residence times. However, synoptic DOC sampling of both quantity and character throughout river networks will be needed to more rigorously test this finding. The inclusion of DOC chemical character will be vital to achieving a more complete understanding of bulk DOC dynamics in large river systems.

Absorption features of chromophoric dissolved organic matter (CDOM) and tracing implication for dissolved organic carbon (DOC) in Changjiang Estuary, China

NASA Astrophysics Data System (ADS)

Zhang, X. Y.; Chen, X.; Deng, H.; Du, Y.; Jin, H. Y.

2013-07-01

Chromophoric dissolved organic matter (CDOM) represents the light absorbing fraction of dissolved organic carbon (DOC). Studies have shown that the optical properties of CDOM can be used to infer the distribution and diffusion characteristics of DOC in the estuary and coastal zone. The inversion of DOC concentrations from remote sensing has been implemented in certain regions. In this study we investigate the potential of tracing DOC from CDOM by the measurement of DOC, absorption spectrum of CDOM, Chla concentration, suspended sediment (SS), and salinity from cruises in different seasons around the Changjiang estuary. Our results show that around the Changjiang estuary the absorption coefficients of CDOM in general have the similar spatial and temporal characteristics as that of DOC, but the strength of the correlation between CDOM and DOC varies locally and seasonally. The input of pollutants from outside the estuary, the bloom of phytoplankton in spring, re-suspension of deposited sediment, and light bleaching all contribute to the local and seasonal variation of the correlation between DOC and CDOM. An inversion model for the determination of DOC from CDOM is established, but the stability of model parameters and its application in different environments need further study. We find that relative to the absorption coefficient of CDOM, the fitted parameters of the absorption spectrum of DOM are better indictors for the composition of DOC. In addition, it is found that the terrestrial input of DOC to Changjiang estuary is a typical two-stage dilution process instead of a linear diffusion process.

Modeling the production, decomposition, and transport of dissolved organic carbon in boreal soils

USGS Publications Warehouse

Fan, Zhaosheng; Neff, Jason C.; Wickland, Kimberly P.

2010-01-01

The movement of dissolved organic carbon (DOC) through boreal ecosystems has drawn increased attention because of its potential impact on the feedback of OC stocks to global environmental change in this region. Few models of boreal DOC exist. Here we present a one-dimensional model with simultaneous production, decomposition, sorption/desorption, and transport of DOC to describe the behavior of DOC in the OC layers above the mineral soils. The field-observed concentration profiles of DOC in two moderately well-drained black spruce forest sites (one with permafrost and one without permafrost), coupled with hourly measured soil temperature and moisture, were used to inversely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model, along with the estimated parameters, reasonably reproduces the concentration profiles of DOC and highlights some important potential controls over DOC production and cycling in boreal settings. The values of estimated parameters suggest that humic OC has a larger potential production capacity for DOC than fine OC, and most of the DOC produced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC was associated with time-dependent sorption/desorption. The simulated DOC efflux at the bottom of soil OC layers was highly dependent on the component and structure of the OC layers. The DOC efflux was controlled by advection at the site with no humic OC and moist conditions and controlled by diffusion at the site with the presence of humic OC and dry conditions.

Hydrologic and forest management controls on DOC dynamics in the small watersheds of the H.J. Andrews Experimental Forest, OR

NASA Astrophysics Data System (ADS)

Lajtha, K.; Jones, J. A.

2016-12-01

Dissolved organic carbon (DOC) export from hillslopes to streams is an important component of the carbon cycle of a catchment and may be a critical source of energy for the aquatic food web in receiving waters. Using a long-term record of DOC and other dissolved nutrients and elements from paired watersheds from the H.J. Andrews Experimental Forest in Oregon, we explored hydrologic, climatic, and land-use controls on seasonal and inter-annual patterns of DOC flux in a seasonally dry ecosystem. Seasonal patterns of DOC flux demonstrated source limitations to DOC export, with DOC concentrations highest immediately following the first rains after a dry summer, and lowest after winter rains. In contrast, more geochemically-controlled elements showed simple dilution-concentration patterns with no seasonal hysteresis. Inter-annual patterns of DOC flux, however, did not provide evidence of source limitation, with DOC flux within a watershed tightly correlated to total discharge but not temperature. Among watersheds, forest harvest, even over 50 years ago, significantly reduced DOC flux but not fluxes of other elements including N; this response was linked to the loading of coarse woody debris to the forest floor. Chemical fingerprinting of DOC revealed that old-growth watersheds had higher fluxes of DOC characteristic of forest floor organic materials, likely delivered to streams through more surficial preferential flow pathways not subject to microbial alteration, respiration, or sorption losses. Taken together these results suggest that the biogeochemical composition of forested streams reflects both current hydrologic patterns and also processes that occurred many decades ago within the catchment.

Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

NASA Astrophysics Data System (ADS)

Guo, Yuedong; Song, Changchun; Tan, Wenwen; Wang, Xianwei; Lu, Yongzheng

2018-02-01

Permafrost thawing in peatlands has the potential to alter the catchment export of dissolved organic carbon (DOC), thus influencing the carbon balance and cycling in linked aquatic and ocean ecosystems. Peatlands along the southern margins of the Eurasian permafrost are relatively underexplored despite the considerable risks associated with permafrost degradation due to climate warming. This study examined dynamics of DOC export from a permafrost peatland catchment located in northeastern China during the 2012 to 2014 growing seasons. The estimated annual DOC loads varied greatly between 3211 and 19 022 kg yr-1, with a mean DOC yield of 4.7 g m-2 yr-1. Although the estimated DOC yield was in the lower range compared with other permafrost regions, it was still significant for the net carbon balance in the studied catchment. There were strong linkages between daily discharge and DOC concentrations in both wet and dry years, suggesting a transport-limited process of DOC delivery from the catchment. Discharge explained the majority of both seasonal and interannual variations of DOC concentrations, which made annual discharge a good indicator of total DOC load from the catchment. As indicated by three fluorescence indices, DOC source and chemical characteristics tracked the shift of flow paths during runoff processes closely. Interactions between the flow path and DOC chemical characteristics were greatly influenced by the seasonal thawing of the soil active layer. The deepening of the active layer due to climate warming likely increases the proportion of microbial-originated DOC in baseflow discharge.

On the Use of Ocean Color Remote Sensing to Measure the Transport of Dissolved Organic Carbon by the Mississippi River Plume

NASA Technical Reports Server (NTRS)

DelCastillo, Carlos E.; Miller, Richard L.

2007-01-01

We investigated the use of ocean color remote sensing to measure transport of dissolved organic carbon (DOC) by the Mississippi River to the Gulf of Mexico. From 2000 to 2005 we recorded surface measurements of DOC, colored dissolved organic matter (CDOM), salinity, and water-leaving radiances during five cruises to the Mississippi River Plume. These measurements were used to develop empirical relationships to derive CDOM, DOC, and salinity from monthly composites of SeaWiFS imagery collected from 1998 through 2005. We used river flow data and a two-end-member mixing model to derive DOC concentrations in the river end-member, river flow, and DOC transport using remote sensing data. We compared our remote sensing estimates of river flow and DOC transport with data collected by the United States Geological Survey (USGS) from 1998 through 2005. Our remote sensing estimates of river flow and DOC transport correlated well (r2 0.70) with the USGS data. Our remote sensing estimates and USGS field data showed low variability in DOC concentrations in the river end-member (7-11%), and high seasonal variability in river flow (50%). Therefore, changes in river flow control the variability in DOC transport, indicating that the remote sensing estimate of river flow is the most critical element of our DOC transport measurement. We concluded that it is possible to use this method to estimate DOC transport by other large rivers if there are data on the relationship between CDOM, DOC, and salinity in the river plume.

Direct observation and determination of the mechanisms governing mobility of asbestos in porous media

NASA Astrophysics Data System (ADS)

Seiphoori, A.; Ortiz, C. P.; Jerolmack, D. J.

2017-12-01

Transport of asbestos through soil by groundwater is typically considered to be negligible. There are indications, however, that under some conditions of pore-water/soil chemistry asbestos may become mobile, implying that buried contaminants could migrate from a disposal site and surface elsewhere. Shape, size and surface charge may influence the physical and chemical interactions of colloids with the soil matrix, and asbestos consists of elongated particles with different size and unique surface charge properties. Although chemical factors such as pH and ionic strength of pore water may affect the transport properties, the presence of dissolved organic carbon (DOC) has been identified to remarkably enhance the mobility of colloids including asbestos. To date, there is no explanation for how the presence of DOC may facilitate the mobilization of asbestos in soil - mainly because the soil medium has been treated as a black box without the possibility of observing particles within the matrix. Here, we investigated the mobility of chrysotile asbestos particles ( 10 um long) in porous media by developing a flow cell with an optically-transparent porous medium composed of granules of a refractive-index matched material. This enabled us to observe and track the particles within the water-saturated porous medium using in situ microscopy. The aqueous suspension of asbestos fibers was passed through this artificial soil, while the physical and chemical interaction of asbestos particles with the medium and their pore-scale distribution were analyzed. We studied the effects of changing solution chemistry (e.g., ionic strength, pH, and DOC content) on transport, attachment and aggregation of chrysotile particles. Experiments revealed a novel mechanism where the DOC-associated nanoparticles attach to chrysotile fibers by an electrostatic attraction, which facilitates their mobilization through the porous medium while modulating aggregation among fibers. Although pH and ionic strength also influenced aggregation and the attachment rate of particles to the substrate, the effect of DOC was more pronounced. This work may lead to enhanced predictions for the fate and transport of asbestos (as well as other contaminants) in the environment, and has implications for the mobility of asbestos particles in the human body.

Similarities and differences in dissolved organic matter response in two headwater streams under contrasted hydro-climatic regimes

NASA Astrophysics Data System (ADS)

Butturini, Andrea; Guarch, Alba; Battin, Tom

2017-04-01

Dissolved organic matter (DOM) concentration and properties in headwater streams are strongly shaped by hydrology. Besides the direct relationship with storms and high flows, seasonal variability of base flow also influences DOM variability. This study focuses on identifying the singularities and similarities in DOM - discharge relationships between an intermittent Mediterranean stream (Fuirosos) and a perennial Alpine stream (Oberer Seebach). Oberer Seebach had a higher discharge mean, but Fuirosos had a higher variability in flow and in magnitude of storm events. During three years we performed an intensive sampling that allows us to satisfactorily capture abrupt and extreme storms. We analysed dissolved organic carbon concentration (DOC) and optical properties of DOM and we calculated the specific ultraviolet absorbance (SUVA), the spectral slopes ratio (SR), the fluorescence index (FI), the biological index (BIX) and the humification index (HIX). DOM in Fuirosos was significantly more concentrated than in Oberer Seebach, and more terrigenous (lower FI), more degraded (lower BIX), more aromatic (higher SUVA) and more humificated (higher HIX). Most of the DOM properties showed a clear relationship with discharge and the sign of the global response was identical in both streams. However, discharge was a more robust predictor of DOM variability in Oberer Seebach than in Fuirosos. In fact, low flow and rewetting periods in Fuirosos introduced considerable dispersion in the relationship. During snowmelt in Oberer Seebach the sensitivity to discharge also decreased (DOC and BIX) or disappeared (SR, FI and HIX). The magnitude of the storm events (DQ) in Fuirosos significantly drove the changes in DOC, FI, BIX and SUVA. This suggests that the flushing/dilution patterns were essentially associated to the occurrence of storm episodes in Fuirosos. In contrast, in Oberer Seebach all DOM qualitative properties were unrelated to DQ and it significantly explained only the change in DOC. While the storms were behind the DOC oscillations, DOM quality change in Oberer Seebach was more coupled to basal flow conditions. Finally, the biogeochemical analysis of two hydrologically different headwaters motivates to speculate about the impact of the hydrological regime alteration forced by atmospheric drivers on DOM quantity and properties.

Use of the 9-item Shared Decision Making Questionnaire (SDM-Q-9 and SDM-Q-Doc) in intervention studies-A systematic review.

PubMed

Doherr, Hanna; Christalle, Eva; Kriston, Levente; Härter, Martin; Scholl, Isabelle

2017-01-01

The Shared Decision Making Questionnaire (SDM-Q-9 and SDM-Q-Doc) is a 9-item measure of the decisional process in medical encounters from both patients' and physicians' perspectives. It has good acceptance, feasibility, and reliability. This systematic review aimed to 1) evaluate the use of the SDM-Q-9 and SDM-Q-Doc in intervention studies on shared decision making (SDM) in clinical settings, 2) describe how the SDM-Q-9 and SDM-Q-Doc performed regarding sensitivity to change, and 3) assess the methodological quality of studies and study protocols that use the measure. We conducted a systematic review of studies published between 2010 and October 2015 that evaluated interventions to facilitate SDM. The search strategy comprised three databases (EMBASE, PsycINFO, and Medline), reference tracking, citation tracking, and personal knowledge. Two independent reviewers screened titles and abstracts as well as full texts of potentially relevant records. We extracted the data using a pilot tested sheet, and we assessed the methodological quality of included studies using the Quality Assessment Tools from the U.S. National Institute of Health (NIH). Five completed studies and six study protocols fulfilled the inclusion criteria. The measure was used in a variety of health care settings, mainly in Europe, to evaluate several types of interventions. The reported mean sum scores ranged from 42 to 75 on a scale from 0 to 100. In four studies no significant change was detected in the mean-differences between main groups. In the fifth study the difference was small. Quality assessment revealed a high risk of bias in four of the five completed studies, while the study protocols received moderate quality ratings. We found a wide range of areas in which the SDM-Q-9 and SDM-Q-Doc were applied. In the future this review may help researchers decide whether the measure fits their purposes. Furthermore, the review revealed risk of bias in previous trials that used the measure, and may help future trials decrease this risk. More research on the measure's sensitivity to change is strongly suggested.

Where does boreal stream DOC come from? - Quantifying the contribution from different landscape compartments using stable C isotope ratios.

NASA Astrophysics Data System (ADS)

Brink Bylund, J.; Bastviken, D.; Morth, C.; Laudon, H.; Giesler, R.; Buffam, I.

2007-12-01

Stable carbon isotope (δ13C) ratios are frequently used as a source tracer of e.g. organic matter (OM) produced in terrestrial versus aquatic environments. To our knowledge there has been no previous attempt to quantify the relative contribution of dissolved organic carbon (DOC) from various landscape compartments in catchments of different sizes. Here, we test to what extent δ13C values can be used also to quantify the relative contribution of DOC from wetlands/riparian zones along streams, and off stream forest habitats, respectively. We present data on spatial and temporal variability of DOC concentrations and δ13C-DOC values, during the year of 2005 in Krycklan catchment, a boreal stream network in northern Sweden. Ten stream sites, ranging from order 1 to 4, were monitored in sub catchments with different wetland coverage. Spatial variation of DOC concentration showed a weak but statistically significant relationship with wetland area, with higher concentration with increasing percent of wetland in the drainage area. During base flow the difference in δ13C-DOC values was significantly different between forest (-27.5‰) and wetland (-28.1‰). This spatial pattern disappears during spring peak flow when higher discharge flushing upper soil layer and the riparian zone on DOC in the catchments. A simple mixing model using DOC and δ13C-DOC showed that stream water DOC could be describe as a mixture of DOC coming from forest (deep) groundwater and wetland/riparian zone water. The result indicates that during spring peak flow almost all stream DOC (84-100%) is derived from wetlands and riparian zones. The wetland/riparian water dominates the stream DOC flux at all hydrological events, except for two sites, one forest dominated and one mixed catchment, where the forest groundwater dominated the DOC transport during base flow. Although the total wetland area in Krycklan catchment only represent 8.3%, it contributed, together with riparian zones, to as much as 83% of the yearly DOC transport. This study shows that there is a great potential in using stable carbon isotopes to quantify the relative contribution of DOC from various landscape compartments in catchments. Quantitative patterns are crucial for several reasons. It is for example necessary in predicting the response to global warming which will result in a changed hydrology and shifts in the relative area of the landscape compartments in boreal environments. KEY WORDS carbon isotopes; dissolved organic carbon; streams; boreal; landscape compartments; wetland; groundwater

Direct analysis of δ13C and concentration of dissolved organic carbon (DOC) in environmental samples by TOC-IRMS

NASA Astrophysics Data System (ADS)

Kirkels, Frédérique; Cerli, Chiara; Federherr, Eugen; Kalbitz, Karsten

2014-05-01

Dissolved organic carbon (DOC) plays an important role in carbon cycling in terrestrial and aquatic systems. Stable isotope analysis (delta 13C) of DOC could provide valuable insights in its origin, fluxes and environmental fate. Precise and routine analysis of delta 13C and DOC concentration are therefore highly desirable. A promising, new system has been developed for this purpose, linking a high-temperature combustion TOC analyzer trough an interface with a continuous flow isotope ratio mass spectrometer (Elementar group, Hanau, Germany). This TOC-IRMS system enables simultaneous stable isotope (bulk delta 13C) and concentration analysis of DOC, with high oxidation efficiency by high-temperature combustion for complex mixtures as natural DOC. To give delta 13C analysis by TOC-IRMS the necessary impulse for broad-scale application, we present a detailed evaluation of its analytical performance for realistic and challenging conditions inclusive low DOC concentrations and environmental samples. High precision (standard deviation, SD predominantly < 0.15 permil) and accuracy (R2 = 0.9997, i.e. comparison TOC-IRMS and conventional EA-IRMS) were achieved by TOC-IRMS for a broad diversity of DOC solutions. This precision is comparable or even slightly better than that typically reported for EA-IRMS systems, and improves previous techniques for δ13C analysis of DOC. Simultaneously, very good precision was obtained for DOC concentration measurements. Assessment of natural abundance and slightly 13C enriched DOC, a wide range of concentrations (0.2-150 mgC/L) and injection volumes (0.05-3 ml), demonstrated good analytical performance with negligible memory effects, no concentration/volume effects and a wide linearity. Low DOC concentrations (< 2 mgC/L), were correctly analyzed without any pre-concentration. Moreover, TOC-IRMS was successfully applied to analyze DOC from diverse terrestrial, freshwater and marine environments (SD < 0.23 permil). In summary, the TOC-IRMS performs fast and reliable analysis of DOC concentration and δ13C in aqueous samples, without any pre-concentration/freeze-drying. Flexible usage is highlighted by automated, online analysis, a variable injection volume, high throughput and no extensive maintenance. Sample analysis is simple, using small aliquots and with minimal sample preparation. Further investigations should focus on complex, saline matrices and very low DOC concentrations, to achieve a potential lower limit of 0.2 mgC/L. High-resolution, routine delta 13C analysis of DOC by TOC-IRMS offers opportunities for wide-scale application in terrestrial, freshwater and marine research to elucidate the role of DOC in biogeochemical processes and ecosystem functioning.

Earth System Documentation (ES-DOC) Preparation for CMIP6

NASA Astrophysics Data System (ADS)

Denvil, S.; Murphy, S.; Greenslade, M. A.; Lawrence, B.; Guilyardi, E.; Pascoe, C.; Treshanksy, A.; Elkington, M.; Hibling, E.; Hassell, D.

2015-12-01

During the course of 2015 the Earth System Documentation (ES-DOC) project began its preparations for CMIP6 (Coupled Model Inter-comparison Project 6) by further extending the ES-DOC tooling ecosystem in support of Earth System Model (ESM) documentation creation, search, viewing & comparison. The ES-DOC online questionnaire, the ES-DOC desktop notebook, and the ES-DOC python toolkit will serve as multiple complementary pathways to generating CMIP6 documentation. It is envisaged that institutes will leverage these tools at different points of the CMIP6 lifecycle. Institutes will be particularly interested to know that the documentation burden will be either streamlined or completely automated.As all the tools are tightly integrated with the ES-DOC web-service, institutes can be confident that the latency between documentation creation & publishing will be reduced to a minimum. Published documents will be viewable with the online ES-DOC Viewer (accessible via citable URL's). Model inter-comparison scenarios will be supported using the ES-DOC online Comparator tool. The Comparator is being extended to:• Support comparison of both Model descriptions & Simulation runs;• Greatly streamline the effort involved in compiling official tables.The entire ES-DOC ecosystem is open source and built upon open standards such as the Common Information Model (CIM) (versions 1 and 2).

Hidden cycle of dissolved organic carbon in the deep ocean.

PubMed

Follett, Christopher L; Repeta, Daniel J; Rothman, Daniel H; Xu, Li; Santinelli, Chiara

2014-11-25

Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ(13)C and age via Δ(14)C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle.

Hidden cycle of dissolved organic carbon in the deep ocean

PubMed Central

Follett, Christopher L.; Repeta, Daniel J.; Rothman, Daniel H.; Xu, Li; Santinelli, Chiara

2014-01-01

Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ13C and age via Δ14C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle. PMID:25385632

Support for U.S. Participants at the 15th International Congress on Catalysis

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

Wachs, Israel E.

2013-08-05

The grant was used to partially assist the travel expenses of U.S. academic scientists to attend the 15th International Congress on Catalysis. The conference was held in Munich, Germany from July 1-6, 2012. The importance of the International Congress was to bring together the international community of faculty members who participate in catalysis research, and to share information that would lead to further developments and directions in the field of study. Graduate students and Post Docs were invited to apply for travel assistance based on criteria established by the North American Catalysis Society (NACS) and the local Catalysis Clubs.

Development of a combined isotopic and mass-balance approach to determine dissolved organic carbon sources in eutrophic reservoirs.

PubMed

Pierson-Wickmann, Anne-Catherine; Gruau, Gérard; Jardé, Emilie; Gaury, Nicolas; Brient, Luc; Lengronne, Marion; Crocq, André; Helle, Daniel; Lambert, Thibault

2011-04-01

A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9mgL(-1)) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ(13)C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ(13)C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ(13)C values of the DOC recovered in the reservoir (-28.5±0.2‰; n=22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ(13)C in algae=-30.1±0.3‰; n=2) being indistinguishable from the δ(13)C values of allochthonous DOC from inflowing rivers (-28.6±0.1‰; n=8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs. Copyright © 2010 Elsevier Ltd. All rights reserved.

The influence of reservoirs, climate, land use and hydrologic conditions on loads and chemical quality of dissolved organic carbon in the Colorado River

USGS Publications Warehouse

Miller, Matthew P.

2012-01-01

Longitudinal patterns in dissolved organic carbon (DOC) loads and chemical quality were identified in the Colorado River from the headwaters in the Rocky Mountains to the United States-Mexico border from 1994 to 2011. Watershed- and reach-scale climate, land use, river discharge and hydrologic modification conditions that contribute to patterns in DOC were also identified. Principal components analysis (PCA) identified site-specific precipitation and reach-scale discharge as being correlated with sites in the upper basin, where there were increases in DOC load from the upstream to downstream direction. In the lower basin, where DOC load decreased from upstream to downstream, sites were correlated with site-specific temperature and reach-scale population, urban land use and hydrologic modification. In the reaches containing Lakes Powell and Mead, the two largest reservoirs in the United States, DOC quantity decreased, terrestrially derived aromatic DOC was degraded and/or autochthonous less aromatic DOC was produced. Taken together, these results suggest that longitudinal patterns in the relatively unregulated upper basin are influenced by watershed inputs of water and DOC, whereas DOC patterns in the lower basin are reflective of a balance between watershed contribution of water and DOC to the river and loss of water and DOC due to hydrologic modification and/or biogeochemical processes. These findings suggest that alteration of constituent fluxes in rivers that are highly regulated may overshadow watershed processes that would control fluxes in comparable unregulated rivers. Further, these results provide a foundation for detailed assessments of factors controlling the transport and chemical quality of DOC in the Colorado River.

Insights and issues with simulating terrestrial DOC loading of Arctic river networks

USGS Publications Warehouse

Kicklighter, David W.; Hayes, Daniel J.; McClelland, James W.; Peterson, Bruce J.; McGuire, A. David; Melillo, Jerry M.

2013-01-01

Terrestrial carbon dynamics influence the contribution of dissolved organic carbon (DOC) to river networks in addition to hydrology. In this study, we use a biogeochemical process model to simulate the lateral transfer of DOC from land to the Arctic Ocean via riverine transport. We estimate that, over the 20th century, the pan-Arctic watershed has contributed, on average, 32 Tg C/yr of DOC to river networks emptying into the Arctic Ocean with most of the DOC coming from the extensive area of boreal deciduous needle-leaved forests and forested wetlands in Eurasian watersheds. We also estimate that the rate of terrestrial DOC loading has been increasing by 0.037 Tg C/yr2 over the 20th century primarily as a result of climate-induced increases in water yield. These increases have been offset by decreases in terrestrial DOC loading caused by wildfires. Other environmental factors (CO2 fertilization, ozone pollution, atmospheric nitrogen deposition, timber harvest, agriculture) are estimated to have relatively small effects on terrestrial DOC loading to Arctic rivers. The effects of the various environmental factors on terrestrial carbon dynamics have both offset and enhanced concurrent effects on hydrology to influence terrestrial DOC loading and may be changing the relative importance of terrestrial carbon dynamics on this carbon flux. Improvements in simulating terrestrial DOC loading to pan-Arctic rivers in the future will require better information on the production and consumption of DOC within the soil profile, the transfer of DOC from land to headwater streams, the spatial distribution of precipitation and its temporal trends, carbon dynamics of larch-dominated ecosystems in eastern Siberia, and the role of industrial organic effluents on carbon budgets of rivers in western Russia.

Carbonaceous composition changes of heavy-duty diesel engine particles in relation to biodiesels, aftertreatments and engine loads.

PubMed

Cheng, Man-Ting; Chen, Hsun-Jung; Young, Li-Hao; Yang, Hsi-Hsien; Tsai, Ying I; Wang, Lin-Chi; Lu, Jau-Huai; Chen, Chung-Bang

2015-10-30

Three biodiesels and two aftertreatments were tested on a heavy-duty diesel engine under the US FTP transient cycle and additional four steady engine loads. The objective was to examine their effects on the gaseous and particulate emissions, with emphasis given to the organic and elemental carbon (OC and EC) in the total particulate matter. Negligible differences were observed between the low-sulfur (B1S50) and ultralow-sulfur (B1S10) biodiesels, whereas small reductions of OC were identified with the 10% biodiesel blend (B10). The use of diesel oxidation catalyst (DOC1) showed moderate reductions of EC and particularly OC, resulting in the OC/EC ratio well below unity. The use of DOC plus diesel particulate filter (DOC2+DPF) yielded substantial reductions of OC and particularly EC, resulting in the OC/EC ratio well above unity. The OC/EC ratios were substantially above unity at idle and low load, whereas below unity at medium and high load. The above changes in particulate OC and EC are discussed with respect to the fuel content, pollutant removal mechanisms and engine combustion conditions. Overall, the present study shows that the carbonaceous composition of PM could change drastically with engine load and aftertreatments, and to a lesser extent with the biodiesels under study. Copyright © 2015 Elsevier B.V. All rights reserved.

A Comparison of Dissolved and Particulate Organic Material in Two Southwestern Desert River Systems

NASA Astrophysics Data System (ADS)

Haas, P. A.; Brooks, P.

2001-12-01

Desert river systems of the southwestern U.S. acquire a substantial fraction of their dissolved organic matter (DOM) from the terrestrial environment during episodic rain events. This DOM provides carbon for stream metabolism and nitrogen, which is limiting in lower order streams in this environment. The San Pedro and Rio Grande Rivers represent two endpoints of catchment scale, discharge, and land use in the southwest. The San Pedro is a protected riparian corridor (San Pedro Riparian National Conservation Area), while the middle Rio Grande is a large river with extensive agriculture, irrigation, and reservoirs. Relative abundance and spectral properties of fulvic acids isolated from filtered samples were used to determine the source of dissolved organic carbon (DOC). Total DOC and particulate organic carbon (POC) changes with respect to episodic flooding events were compared for the two river systems. The San Pedro River DOC concentrations remain low approximately 2.2 to 3.3 ppm unless a relatively large storm event occurs when concentrations may go above 5.5 ppm (1000cfs flow). In contrast typical concentrations for the Rio Grande were approximately 5 ppm during the monsoon season. Particulate organic matter (POM) appears to be a more significant source of organic matter to the San Pedro than DOM. The relative importance of terrestrial vs. aquatic and dissolved vs. particulate organic matter with respect to aquatic ecosystems will be discussed.

Long-Term Experimental Acidification Drives Watershed Scale Shift in Dissolved Organic Matter Composition and Flux.

PubMed

SanClements, Michael D; Fernandez, Ivan J; Lee, Robert H; Roberti, Joshua A; Adams, Mary Beth; Rue, Garret A; McKnight, Diane M

2018-03-06

Over the last several decades dissolved organic carbon concentrations (DOC) in surface waters have increased throughout much of the northern hemisphere. Several hypotheses have been proposed regarding the drivers of this phenomenon including decreased sulfur (S) deposition working via an acidity- change mechanism. Using fluorescence spectroscopy and data from two long-term (24+ years at completion of this study) whole watershed acidification experiments, that is, the Bear Brook Watershed in Maine (BBWM) and Fernow Experimental Forest in West Virginia (FEF) allowed us to control for factors other than the acidity-change mechanism (e.g., differing vegetation, shifting climate), resulting in the first study we are aware of where the acidity change mechanism could be experimentally isolated at the whole ecosystem and decadal scales as the driver of shifts in DOM dynamics. The multidecadal record of stream chemistry at BBWM demonstrates a significantly lower DOC concentration in the treated compared to the reference watershed. Additionally, at both BBWM and FEF we found significant and sustained differences in stream fluorescence index (FI) between the treated and reference watersheds, with the reference watersheds demonstrating a stronger terrestrial DOM signature. These data, coupled with evidence of pH shifts in upper soil horizons support the hypotheses that declines in S deposition are driving changes in the solubility of soil organic matter and increased flux of terrestrial DOC to water bodies.

Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

NASA Astrophysics Data System (ADS)

Lawson, E. C.; Wadham, J. L.; Lis, G. P.; Tranter, M.; Pickard, A. E.; Stibal, M.; Dewsbury, P.; Fitzsimons, S.

2015-08-01

Glacial runoff is an important source of dissolved organic carbon (DOC) for downstream heterotrophic activity, despite the low overall DOC concentrations. This is because of the abundance of bioavailable, low molecular weight (LMW) DOC species. However, the provenance and character of LMW-DOC is not fully understood. We investigated the abundance and composition of DOC in subglacial environments via a molecular level DOC analysis of basal ice, which forms by water/sediment freeze-on to the glacier sole. Spectrofluorometry and a novel ion chromatographic method, which has been little utilised in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates and carboxylic acids) in basal ice from four glaciers, each with a different basal debris type. Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse FAA pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn, was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard) and Engabreen (Norway) were low (0-417 nM C), attributed to the relatively refractory nature of the OC in the overridden paleosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (>17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet sediments in current subglacial environments.

Partial coupling and differential regulation of biologically and photo-chemically labile dissolved organic carbon across boreal aquatic networks

NASA Astrophysics Data System (ADS)

Lapierre, J.-F.; del Giorgio, P. A.

2014-05-01

Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC in aquatic environments, little is known on the large-scale patterns in biologically and photo-chemically degradable DOC (Bd-DOC and Pd-DOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explore the patterns of Bd- and Pd-DOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophy and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of Bd- and Pd-DOC co-varied across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM, identified by fluorescence analyses) in ambient waters. A combination of nutrients and protein-like DOM explained nearly half of the variation in Bd-DOC, whereas Pd-DOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific fluorescent DOM (FDOM) pools that we experimentally determined. The concentrations of colored DOM (CDOM), a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both Bd- and Pd-DOC. The concentrations of CDOM and of the putative bio-labile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in browner streams and wetlands. This suggests a baseline autochthonous Bd-DOC pool fuelled by internal production that is gradually overwhelmed by land-derived Bd-DOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photo-chemically degradable DOC for continental watersheds resulted in a partial coupling of those carbon pools in natural freshwaters, despite fundamental contrasts in terms of their composition and regulation.

Characterization of Greenbeard Genes Involved in Long-Distance Kind Discrimination in a Microbial Eukaryote

PubMed Central

Heller, Jens; Zhao, Jiuhai; Rosenfield, Gabriel; Kowbel, David J.; Gladieux, Pierre; Glass, N. Louise

2016-01-01

Microorganisms are capable of communication and cooperation to perform social activities. Cooperation can be enforced using kind discrimination mechanisms in which individuals preferentially help or punish others, depending on genetic relatedness only at certain loci. In the filamentous fungus Neurospora crassa, genetically identical asexual spores (germlings) communicate and fuse in a highly regulated process, which is associated with fitness benefits during colony establishment. Recognition and chemotropic interactions between isogenic germlings requires oscillation of the mitogen-activated protein kinase (MAPK) signal transduction protein complex (NRC-1, MEK-2, MAK-2, and the scaffold protein HAM-5) to specialized cell fusion structures termed conidial anastomosis tubes. Using a population of 110 wild N. crassa isolates, we investigated germling fusion between genetically unrelated individuals and discovered that chemotropic interactions are regulated by kind discrimination. Distinct communication groups were identified, in which germlings within one communication group interacted at high frequency, while germlings from different communication groups avoided each other. Bulk segregant analysis followed by whole genome resequencing identified three linked genes (doc-1, doc-2, and doc-3), which were associated with communication group phenotype. Alleles at doc-1, doc-2, and doc-3 fell into five haplotypes that showed transspecies polymorphism. Swapping doc-1 and doc-2 alleles from different communication group strains was necessary and sufficient to confer communication group affiliation. During chemotropic interactions, DOC-1 oscillated with MAK-2 to the tips of conidial anastomosis tubes, while DOC-2 was statically localized to the plasma membrane. Our data indicate that doc-1, doc-2, and doc-3 function as “greenbeard” genes, involved in mediating long-distance kind recognition that involves actively searching for one’s own type, resulting in cooperation between non-genealogical relatives. Our findings serve as a basis for investigations into the mechanisms associated with attraction, fusion, and kind recognition in other eukaryotic species. PMID:27077707

Permafrost conditions in peatlands regulate magnitude, timing, and chemical composition of catchment dissolved organic carbon export.

PubMed

Olefeldt, David; Roulet, Nigel T

2014-10-01

Permafrost thaw in peatlands has the potential to alter catchment export of dissolved organic carbon (DOC) and thus influence downstream aquatic C cycling. Subarctic peatlands are often mosaics of different peatland types, where permafrost conditions regulate the hydrological setting of each type. We show that hydrological setting is key to observed differences in magnitude, timing, and chemical composition of DOC export between permafrost and nonpermafrost peatland types, and that these differences influence the export of DOC of larger catchments even when peatlands are minor catchment components. In many aspects, DOC export from a studied peatland permafrost plateau was similar to that of a forested upland catchment. Similarities included low annual export (2-3 g C m(-2) ) dominated by the snow melt period (~70%), and how substantial DOC export following storms required wet antecedent conditions. Conversely, nonpermafrost fens had higher DOC export (7 g C m(-2) ), resulting from sustained hydrological connectivity during summer. Chemical composition of catchment DOC export arose from the mixing of highly aromatic DOC from organic soils from permafrost plateau soil water and upland forest surface horizons with nonaromatic DOC from mineral soil groundwater, but was further modulated by fens. Increasing aromaticity from fen inflow to outlet was substantial and depended on both water residence time and water temperature. The role of fens as catchment biogeochemical hotspots was further emphasized by their capacity for sulfate retention. As a result of fen characteristics, a 4% fen cover in a mixed catchment was responsible for 34% higher DOC export, 50% higher DOC concentrations and ~10% higher DOC aromaticity at the catchment outlet during summer compared to a nonpeatland upland catchment. Expansion of fens due to thaw thus has potential to influence landscape C cycling by increasing fen capacity to act as biogeochemical hotspots, amplifying aquatic C cycling, and increasing catchment DOC export. © 2014 John Wiley & Sons Ltd.

Role of Fire and Landscape Position on Dissolved Organic Carbon Composition and Reactivity in the Yukon-Kuskokwim Delta, Alaska

NASA Astrophysics Data System (ADS)

Bristol, E. M.; Dabrowski, J. S.; Jimmie, J. A.; Peter, D. L.; Holmes, R. M.; Mann, P. J.; Natali, S.; Schade, J. D.

2017-12-01

The Yukon-Kuskokwim Delta in southwest, Alaska is characterized by discontinuous permafrost, which is vulnerable to thaw induced by climate change. Recent fires in the delta have caused dramatic changes in the landscape, likely changing carbon dynamics, and potentially altering dissolved organic carbon (DOC) composition and DOC concentrations in aquatic ecosystems. These changes, in turn, likely affect microbial respiration and hydrologic C export from watersheds in the delta. In this study, we investigated how landscape position and fire history drive changes in DOC composition and reactivity in aquatic ecosystems. We surveyed soil pore waters, ponds, fens, and streams at varying landscape positions in burned and unburned landscapes. We also conducted a laboratory experiment to compare the role of photooxidation, photodegradation, and microbial respiration in altering DOC composition and concentration. Surface waters in burned regions were higher in temperature and inorganic nitrogen concentrations. Higher conductivity in burned areas suggests that fire is deepening the water table, causing water to flow through a more mineral soil horizon. While DOC concentrations did not vary significantly by landscape position or fire history, optical properties of DOC suggest that DOC molecular weight is lower in burned regions and decreases along flow paths. Similarly, our incubation experiment indicated that changes in DOC composition are driven by exposure to light more than bacterial respiration, and that photochemical reactivity declines along flow paths. Percent DOC loss was greatest in waters exposed to both light and bacterial, and percent DOC loss from burned watershed waters was correlated with optical properties. Based on our findings, we predict that the combination of increased surface water temperatures, increased inorganic nitrogen concentrations, and lower molecular weight DOC will increase bacterial respiration of DOC in watersheds burned by wildfire. Further research is needed to better understand the changing hydrology in burned tundra, and the relationship between photooxidation and biological mineralization of DOC.

Temporal changes in photoreactivity of dissolved organic carbon and implications for aquatic carbon fluxes from peatlands

NASA Astrophysics Data System (ADS)

Pickard, Amy E.; Heal, Kate V.; McLeod, Andrew R.; Dinsmore, Kerry J.

2017-04-01

Aquatic systems draining peatland catchments receive a high loading of dissolved organic carbon (DOC) from the surrounding terrestrial environment. Whilst photo-processing is known to be an important process in the transformation of aquatic DOC, the drivers of temporal variability in this pathway are less well understood. In this study, 8 h laboratory irradiation experiments were conducted on water samples collected from two contrasting peatland aquatic systems in Scotland: a peatland stream and a reservoir in a catchment with high percentage peat cover. Samples were collected monthly at both sites from May 2014 to May 2015 and from the stream system during two rainfall events. DOC concentrations, absorbance properties and fluorescence characteristics were measured to investigate characteristics of the photochemically labile fraction of DOC. CO2 and CO produced by irradiation were also measured to determine gaseous photoproduction and intrinsic sample photoreactivity. Significant variation was seen in the photoreactivity of DOC between the two systems, with total irradiation-induced changes typically 2 orders of magnitude greater at the high-DOC stream site. This is attributed to longer water residence times in the reservoir rendering a higher proportion of the DOC recalcitrant to photo-processing. During the experimental irradiation, 7 % of DOC in the stream water samples was photochemically reactive and direct conversion to CO2 accounted for 46 % of the measured DOC loss. Rainfall events were identified as important in replenishing photoreactive material in the stream, with lignin phenol data indicating mobilisation of fresh DOC derived from woody vegetation in the upper catchment. This study shows that peatland catchments produce significant volumes of aromatic DOC and that photoreactivity of this DOC is greatest in headwater streams; however, an improved understanding of water residence times and DOC input-output along the source to sea aquatic pathway is required to determine the fate of peatland carbon.

The Universe Adventure - Teachers

Science.gov Websites

Go Teachers The Universe Adventure provides a variety of supplementary resources to bring cosmology Bangs Activity .doc .rtf List of Relevant California Science Standards .doc .rtf Class Discussion Calendar" Activity .doc .rtf Practice with Orders of Magnitude Activity .doc .rtf Ordering the Events

Influences of organic carbon speciation on hyporheic corridor biogeochemistry and microbial ecology.

PubMed

Stegen, James C; Johnson, Tim; Fredrickson, James K; Wilkins, Michael J; Konopka, Allan E; Nelson, William C; Arntzen, Evan V; Chrisler, William B; Chu, Rosalie K; Fansler, Sarah J; Graham, Emily B; Kennedy, David W; Resch, Charles T; Tfaily, Malak; Zachara, John

2018-02-08

The hyporheic corridor (HC) encompasses the river-groundwater continuum, where the mixing of groundwater (GW) with river water (RW) in the HC can stimulate biogeochemical activity. Here we propose a novel thermodynamic mechanism underlying this phenomenon and reveal broader impacts on dissolved organic carbon (DOC) and microbial ecology. We show that thermodynamically favorable DOC accumulates in GW despite lower DOC concentration, and that RW contains thermodynamically less-favorable DOC, but at higher concentrations. This indicates that GW DOC is protected from microbial oxidation by low total energy within the DOC pool, whereas RW DOC is protected by lower thermodynamic favorability of carbon species. We propose that GW-RW mixing overcomes these protections and stimulates respiration. Mixing models coupled with geophysical and molecular analyses further reveal tipping points in spatiotemporal dynamics of DOC and indicate important hydrology-biochemistry-microbial feedbacks. Previously unrecognized thermodynamic mechanisms regulated by GW-RW mixing may therefore strongly influence biogeochemical and microbial dynamics in riverine ecosystems.

Factors affecting the movement and persistence of nitrate and pesticides in the surficial and upper Floridan aquifers in two agricultural areas in the southeastern United States

USGS Publications Warehouse

Katz, B.G.; Berndt, M.P.; Crandall, C.A.

2014-01-01

Differences in the degree of confinement, redox conditions, and dissolved organic carbon (DOC) are the main factors that control the persistence of nitrate and pesticides in the Upper Floridan aquifer (UFA) and overlying surficial aquifer beneath two agricultural areas in the southeastern US. Groundwater samples were collected multiple times from 66 wells during 1993–2007 in a study area in southwestern Georgia (ACFB) and from 48 wells in 1997–98 and 2007–08 in a study area in South Carolina (SANT) as part of the US Geological Survey National Water-Quality Assessment Program. In the ACFB study area, where karst features are prevalent, elevated nitrate-N concentrations in the oxic unconfined UFA (median 2.5 mg/L) were significantly (p = 0.03) higher than those in the overlying oxic surficial aquifer (median 1.5 mg/L). Concentrations of atrazine and deethylatrazine (DEA; the most frequently detected pesticide and degradate) were higher in more recent groundwater samples from the ACFB study area than in samples collected prior to 2000. Conversely, in the SANT study area, nitrate-N concentrations in the UFA were mostly <0.06 mg/L, resulting from anoxic conditions and elevated DOC concentrations that favored denitrification. Although most parts of the partially confined UFA in the SANT study area were anoxic or had mixed redox conditions, water from 28 % of the sampled wells was oxic and had low DOC concentrations. Based on the groundwater age information, nitrate concentrations reflect historic fertilizer N usage in both the study areas, but with a lag time of about 15–20 years. Simulated responses to future management scenarios of fertilizer N inputs indicated that elevated nitrate-N concentrations would likely persist in oxic parts of the surficial aquifer and UFA for decades even with substantial decreases in fertilizer N inputs over the next 40 years.

Fluvial dissolved organic carbon composition varies spatially and seasonally in a small catchment draining a wind farm and felled forestry.

PubMed

Zheng, Ying; Waldron, Susan; Flowers, Hugh

2018-06-01

Assessing whether land use, from activities such as wind farm construction and tree-felling, impacts on terrestrial C delivery to rivers has focused on quantifying the loss of dissolved organic carbon (DOC), and not the composition changes. Here we explore how land use influences DOC composition by considering fluvial DOC concentration, [DOC], and spectrophotometric composition of a river draining a peat-rich catchment. We find that in this 5.7km 2 catchment differences occur in both the concentration and composition of the DOC in its sub-catchments. This is attributed to differences in how land was used: one tributary (D-WF) drains an area with wind farm construction and forestry in the headwaters, and one tributary (D-FF) drains an area with felled plantation trees. Generally, [DOC] in both streams showed similar seasonal variation, and autumn maxima. However, the felled catchment had greater mean [DOC] than the wind farm catchment. The SUVA 254 and E 4 /E 6 indicated DOC in both streams had similar aromaticity and fulvic:humic acid for most of the time, but SUVA 410 and E 2 /E 4 indicated less DOC humification in the felled catchment. This may be due to young DOC from the breakdown of residual branches and roots, or more humification in soils in the wind farm area. During the dry months, DOC composition showed more spatial variation: the D-WF DOC had smaller SUVA 254 (less total aromatic material) and SUVA 410 (fewer humic substances). The decreased E 2 /E 4 in both streams indicated the total aromatic carbon decreased more than humic substances content. Moreover, the larger E 4 /E 6 for D-WF in summer indicated that the humic substances were richer in fulvic acids than humic acids. Soil disturbance associated with forestry-felling likely contributed to the higher [DOC] and release of less-humified material in D-FF. This research indicates drivers of different DOC concentration and composition can exist even in small catchments. Copyright © 2018 Elsevier B.V. All rights reserved.

Modelling impacts of temperature, and acidifying and eutrophying deposition on DOC trends

NASA Astrophysics Data System (ADS)

Sawicka, Kasia; Rowe, Ed; Evans, Chris; Monteith, Don; Vanguelova, Elena; Wade, Andrew; Clark, Joanna

2017-04-01

Surface water dissolved organic carbon (DOC) concentrations in large parts of the northern hemisphere have risen over the past three decades, raising concern about enhanced contributions of carbon to the atmosphere and seas and oceans. The effect of declining acid deposition has been identified as a key control on DOC trends in soil and surface waters, since pH and ionic strength affect sorption and desorption of DOC. However, since DOC is derived mainly from recently-fixed carbon, and organic matter decomposition rates are considered sensitive to temperature, uncertainty persists regarding the extent to the relative importance of different drivers that affect these upward trends. We ran the dynamic model MADOC (Model of Acidity and Soil Organic Carbon) for a range of UK soils (podzols, gleysols and peatland), for which the time-series were available, to consider the likely relative importance of decreased deposition of sulphate and chloride, accumulation of reactive N, and higher temperatures, on DOC production in different soils. Modelled patterns of DOC change generally agreed favourably with measurements collated over 10-20 years, but differed markedly between sites. While the acidifying effect of sulphur deposition appeared to be the predominant control on the observed soil water DOC trends in all the soils considered other than a blanket peat, the model suggested that over the long term, the effects of nitrogen deposition on N-limited soils may have been sufficient to elevate the DOC recovery trajectory significantly. The second most influential cause of rising DOC in the model simulations was N deposition in ecosystems that are N-limited and respond with stimulated plant growth. Although non-marine chloride deposition made some contribution to acidification and recovery, it was not amongst the main drivers of DOC change. Warming had almost no effect on modelled historic DOC trends, but may prove to be a significant driver of DOC in future via its influence on nutrient availability and productivity. This suggests that current and future DOC concentrations could also exceed preindustrial levels due to the increased productivity of N enriched ecosystems, having important implications for drinking water catchment management and the setting and pursuit of appropriate restoration targets.

Catchment-Scale Sampling Reveals the Consistent Function of the Sediment-Water Interface to Remove Landscape Scale Dissolved Organic Carbon Properties

NASA Astrophysics Data System (ADS)

Lee-Cullin, J. A.; Zarnetske, J. P.; Wiewiora, E.; Ruhala, S.; Hampton, T. B.

2016-12-01

Dissolved organic carbon (DOC) is a critical component to biogeochemical cycling and water quality in surface waters. As DOC moves through stream networks, from headwaters to higher order streams, the sediment-water interface (SWI), where streams and groundwater readily interact, exerts a strong influence on DOC concentrations and compositional characteristics (i.e., molecular properties). Few studies examine SWI patterns at larger spatial scales, instead focusing primarily on site-level studies because sampling in the SWI is methodologically time and labor intensive. It is presently unknown how land use and landcover influence the fate of DOC in the SWI and therefore the function of the SWI on catchment-scale DOC conditions. Here, we performed a catchment-scale, high spatial-resolution SWI sampling campaign to test how landscape pattern DOC signatures are propagated into the stream and groundwater, and to assess the fate of these signatures when DOC travels through the SWI. We sampled across 39 sites composed of first-, second-, and third-order locations in a lowland, third-order catchment composed of diverse landscape units and properties, including wetland, upland forest, and agriculture. At each of these locations, surface water, groundwater, and SWI water were collected, including six discrete depths across the SWI. The major land use and landcover properties were also determined for each of these locations. We developed two simple generalized linear models to identify the landscape properties with greatest explanatory power for DOC conditions - one for stream water and one for groundwater. The correlation between landscape properties and surface water DOC characteristics was stronger than between landscape properties and groundwater DOC characteristics. To test if the DOC properties from surface and groundwater were preserved or removed by the SWI, the resulting best-fit models for each water source were used to predict the DOC conditions across the SWI. The models were unable to predict SWI DOC conditions, indicating that the landscape signature present in both the surface water and groundwater is removed by processes occurring in the SWI. Overall, this suggests that the SWI functions as and effective zone for processing the landscape-derived DOC signatures.

Catchment-Scale Sampling Reveals the Consistent Function of the Sediment-Water Interface to Remove Landscape Scale Dissolved Organic Carbon Properties

NASA Astrophysics Data System (ADS)

Lee-Cullin, J. A.; Zarnetske, J. P.; Wiewiora, E.; Ruhala, S.; Hampton, T. B.

2017-12-01

Dissolved organic carbon (DOC) is a critical component to biogeochemical cycling and water quality in surface waters. As DOC moves through stream networks, from headwaters to higher order streams, the sediment-water interface (SWI), where streams and groundwater readily interact, exerts a strong influence on DOC concentrations and compositional characteristics (i.e., molecular properties). Few studies examine SWI patterns at larger spatial scales, instead focusing primarily on site-level studies because sampling in the SWI is methodologically time and labor intensive. It is presently unknown how land use and landcover influence the fate of DOC in the SWI and therefore the function of the SWI on catchment-scale DOC conditions. Here, we performed a catchment-scale, high spatial-resolution SWI sampling campaign to test how landscape pattern DOC signatures are propagated into the stream and groundwater, and to assess the fate of these signatures when DOC travels through the SWI. We sampled across 39 sites composed of first-, second-, and third-order locations in a lowland, third-order catchment composed of diverse landscape units and properties, including wetland, upland forest, and agriculture. At each of these locations, surface water, groundwater, and SWI water were collected, including six discrete depths across the SWI. The major land use and landcover properties were also determined for each of these locations. We developed two simple generalized linear models to identify the landscape properties with greatest explanatory power for DOC conditions - one for stream water and one for groundwater. The correlation between landscape properties and surface water DOC characteristics was stronger than between landscape properties and groundwater DOC characteristics. To test if the DOC properties from surface and groundwater were preserved or removed by the SWI, the resulting best-fit models for each water source were used to predict the DOC conditions across the SWI. The models were unable to predict SWI DOC conditions, indicating that the landscape signature present in both the surface water and groundwater is removed by processes occurring in the SWI. Overall, this suggests that the SWI functions as and effective zone for processing the landscape-derived DOC signatures.

Deoxycholate-Enhanced Shigella Virulence Is Regulated by a Rare π-Helix in the Type Three Secretion System Tip Protein IpaD.

PubMed

Bernard, Abram R; Jessop, T Carson; Kumar, Prashant; Dickenson, Nicholas E

2017-12-12

Type three secretion systems (T3SS) are specialized nanomachines that support infection by injecting bacterial proteins directly into host cells. The Shigella T3SS has uniquely evolved to sense environmental levels of the bile salt deoxycholate (DOC) and upregulate virulence in response to DOC. In this study, we describe a rare i + 5 hydrogen bonding secondary structure element (π-helix) within the type three secretion system tip protein IpaD that plays a critical role in DOC-enhanced virulence. Specifically, engineered mutations within the π-helix altered the pathogen's response to DOC, with one mutant construct in particular exhibiting an unprecedented reduction in virulence following DOC exposure. Fluorescence polarization binding assays showed that these altered DOC responses are not the result of differences in affinity between IpaD and DOC, but rather differences in the DOC-dependent T3SS tip maturation resulting from binding of IpaD to translocator/effector protein IpaB. Together, these findings begin to uncover the complex mechanism of DOC-enhanced Shigella virulence while identifying an uncommon structural element that may provide a much needed target for non-antibiotic treatment of Shigella infection.

Character, quality and bioavailability of Dissolved Organic Carbon (DOC) in a boreal stream network (Invited)

NASA Astrophysics Data System (ADS)

Laudon, H.; Berggren, M.; Agren, A.; Jansson, M.

2010-12-01

The conceptual understanding of the role of terrestrially derived dissolved organic carbon (DOC) in freshwaters has been changing rapidly. While it was once considered mainly a pool of recalcitrant compounds, DOC is now better known for its interactivity and ability to affect both the biogeochemistry and ecology of streams, rivers and lakes. Here we summarize the recent work from the multi-investigatory project conducted in the Krycklan Catchment Study in Sweden with an emphasis on the spatial and temporal variability of the character and bioavailability of DOC. In total, 15 streams and their adjacent soils have been investigated. The streams cover a forest-wetland gradient, spanning from 0% to 69% wetland coverage (hence with a 100% to 31% forest cover). Lower values of the ratio between absorbance measured at 254 nm and 365 nm (A254/A365), in both soil plots and streams, indicated that wetland-derived DOC has a higher average molecular weight than forest DOC. Higher SUVA254 (DOC specific ultraviolet absorption at 254 nm) in wetland runoff indicated more aromatic DOC from wetlands than forests. In accordance, low molecular weight non-aromatic compounds such as free organic acids (OA), amino acids (AA) and carbohydrates (CH) had higher quantities in the forested streams. We have shown that a variety of the OA, AA and CH compounds can be significantly assimilated by bacteria, meeting 15-100% of the bacterial carbon demand and explaining most of the observed variance in bacterial growth efficiency. We can now also show that in small homogenous catchments, the hydrological functioning provides a first order control on the temporal variability of stream water DOC and its quality. As a consequence, streams with heterogeneous catchments undergo a temporal switch in the DOC source. In a typical boreal catchment of 10-20% wetlands, DOC originates predominantly from wetland sources during low flow conditions whereas the major source of DOC originates from forested areas of the catchment during high flow resulting in dramatic shifts in the character and bioavailability of DOC during different flow conditions. By connecting knowledge about the sources and quality of DOC with detailed hydrological process understanding, an improved representation of stream water DOC regulation can be provided. This work also illustrates that the sensitivity of stream water DOC in the boreal landscape ultimately depends on how individual landscape elements are affected, the proportion of these landscape elements and how these changes are propagated downstream.

You have been Friended by the U.S. Military; Using Social Networking Services for IO Messaging

DTIC Science & Technology

2010-12-01

Performance NEFA Nine Eleven Finding Answers OPSEC Operations Security PA Public Affairs PEO C3T Program Executive Office Command Control and...Foundation. “Anwar al Awlaki: Pro al-Qaida Ideologue with Influence In the West,” NEFA Foundation, (2009), http://www.nefafoundation.org/miscellaneous...With Influence In the West,” NEFA Foundation, (2009), http://www.nefafoundation.org/miscellaneous/FeaturedDocs/nefabackgrounder_al awlaki.pdf (accessed

CTC Sentinel. Volume 2, Issue 8, August 2009

DTIC Science & Technology

2009-08-01

Ul-Islami As-Sahih Tutorial Protocol for Prisoners,” NEFA Foundation, December 14, 2007. 9 Shaykh Jamaal al-Din Zarabozo’s “He Came to Teach You...Prison,” U.S. Department of Justice, Central District of California, March 6, 2009. 17 See Kevin James, “Blue Print 2005,” available at nefa ...International Airport, the Israeli 22 Kevin James, “Notoriety Moves,” available at nefa - foundation.org/miscellaneous/FeaturedDocs/U.S._v_

76 FR 60938 - Advisory Committee on the Medical Uses of Isotopes; Meeting Notice

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-30

...The U.S. Nuclear Regulatory Commission (NRC) will convene a teleconference meeting of the Advisory Committee on the Medical Uses of Isotopes (ACMUI) on October 18, 2011, to discuss the ACMUI Permanent Implant Brachytherapy Subcommittee Report. A copy of the agenda for the meeting will be available at http://www.nrc.gov/reading-rm/doc- collections/acmui/agenda or by contacting Ms. Ashley Cockerham using the information below.

78 FR 34709 - Proposed Information Collection (Application for CHAMPVA Benefits); Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-10

...-5870 or Fax (202) 495-5397. SUPPLEMENTARY INFORMATION: Under the PRA of 1995 (Pub. L. 104-13; 44 U.S.C...,402 hours. c. VA Form 10-7959c--6,728 hours. d. VA Form 10-7959d--467 hours. e. VA Form 10-7959e--1500... Technology, U.S. Department of Veterans Affairs. [FR Doc. 2013-13693 Filed 6-7-13; 8:45 am] BILLING CODE 8320...

Defense: FY2014 Authorization and Appropriations

DTIC Science & Technology

2013-12-16

Remarks on the U.S;- India Defense Partnership at the Center for American Progress,” September 30, 2013, accessed at http://www.cq.com/doc...en bloc 1) Move $10 million to increase funding for research on prostate cancer agreed to voice vote Jackson Lee H.Amdt. 351 Move $500,000...to increase funding for PTSD treatment agreed to voice vote Jackson Lee H.Amdt. 354 Move $10 million to increase funding for research on breast

76 FR 69318 - Generalized System of Preferences (GSP): Initiation of a Review: Designation of the Republic of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-08

... the U.S. Trade Representative. [FR Doc. 2011-28826 Filed 11-7-11; 8:45 am] BILLING CODE 3190-W2-P ... sections 502(b)(2) and 502(c) of the Trade Act of 1974, as amended (19 U.S.C. 2462(b)(2), 2462(c)) (``the Act''), including definitions found in section 507 of the Act (19 U.S.C. 2467). When determining...

Influences of organic carbon speciation on hyporheic corridor biogeochemistry and microbial ecology

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

Stegen, James C.; Johnson, Tim; Fredrickson, James K.

The hyporheic corridor (HC) is a critical component of riverine ecosystems that encompasses the river-11 groundwater continuum. The mixing of groundwater (GW) with river water (RW) in the HC can 12 stimulate biogeochemical activity, and here we (i) propose a novel thermodynamic mechanism 13 underlying this phenomenon, and (ii) reveal broader impacts on dissolved organic carbon (DOC) 14 biogeochemistry and microbial ecology. We show that thermodynamically-favorable DOC 15 accumulates in GW despite decreases in DOC concentration along subsurface flow paths, and that RW 16 contains less thermodynamically-favorable DOC, but at higher concentrations. This indicates that DOC 17 in GW ismore » protected from microbial oxidation by low total energy contained within the DOC pool, while 18 RW DOC is protected by lower thermodynamic favorability of carbon species. We propose that GW-19 RW mixing overcomes these protection mechanisms and stimulates respiration. Mixing models 20 coupled with time-lapse electrical resistance tomography revealed that stimulated respiration leads 21 to tipping points in spatiotemporal dynamics of DOC across the HC. Further, shifts in DOC speciation 22 and biochemical pathways were associated with shifts in microbiome composition, highlighting 23 feedbacks among hydrology, DOC biochemistry, and microbial ecology. These results reveal that 24 previously unrecognized thermodynamic-based mechanisms regulated by GW-RW mixing can strongly 25 influence biogeochemical and microbial dynamics in riverine ecosystems.« less

Influences of organic carbon speciation on hyporheic corridor biogeochemistry and microbial ecology

DOE PAGES

Stegen, James C.; Johnson, Tim; Fredrickson, James K.; ...

2018-02-08

The hyporheic corridor (HC) is a critical component of riverine ecosystems that encompasses the river-11 groundwater continuum. The mixing of groundwater (GW) with river water (RW) in the HC can 12 stimulate biogeochemical activity, and here we (i) propose a novel thermodynamic mechanism 13 underlying this phenomenon, and (ii) reveal broader impacts on dissolved organic carbon (DOC) 14 biogeochemistry and microbial ecology. We show that thermodynamically-favorable DOC 15 accumulates in GW despite decreases in DOC concentration along subsurface flow paths, and that RW 16 contains less thermodynamically-favorable DOC, but at higher concentrations. This indicates that DOC 17 in GW ismore » protected from microbial oxidation by low total energy contained within the DOC pool, while 18 RW DOC is protected by lower thermodynamic favorability of carbon species. We propose that GW-19 RW mixing overcomes these protection mechanisms and stimulates respiration. Mixing models 20 coupled with time-lapse electrical resistance tomography revealed that stimulated respiration leads 21 to tipping points in spatiotemporal dynamics of DOC across the HC. Further, shifts in DOC speciation 22 and biochemical pathways were associated with shifts in microbiome composition, highlighting 23 feedbacks among hydrology, DOC biochemistry, and microbial ecology. These results reveal that 24 previously unrecognized thermodynamic-based mechanisms regulated by GW-RW mixing can strongly 25 influence biogeochemical and microbial dynamics in riverine ecosystems.« less

Ursodeoxycholic and deoxycholic acids: Differential effects on intestinal Ca(2+) uptake, apoptosis and autophagy of rat intestine.

PubMed

Rodríguez, Valeria A; Rivoira, María A; Pérez, Adriana del V; Marchionatti, Ana M; Tolosa de Talamoni, Nori G

2016-02-01

The aim of this work was to study the effect of sodium deoxycholate (NaDOC) and ursodeoxycholic acid (UDCA) on Ca(2+) uptake by enterocytes and the underlying mechanisms. Rats were divided into four groups: a) controls, b) treated with NaDOC, c) treated with UDCA d) treated with NaDOC and UDCA. Ca(2+) uptake was studied in enterocytes with different degrees of maturation. Apoptosis, autophagy and NO content and iNOS protein expression were evaluated. NaDOC decreased and UDCA increased Ca(2+) uptake only in mature enterocytes. The enhancement of protein expression of Fas, FasL, caspase-8 and caspase-3 activity by NaDOC indicates triggering of the apoptotic extrinsic pathway, which was blocked by UDCA. NO content and iNOS protein expression were enhanced by NaDOC, and avoided by UDCA. The increment of acidic vesicular organelles and LC3 II produced by NaDOC was also prevented by UDCA. In conclusion, the inhibitory effects of NaDOC on intestinal Ca(2+) absorption occur by decreasing the Ca(2+) uptake by mature enterocytes. NaDOC triggers apoptosis and autophagy, in part as a result of nitrosative stress. In contrast, UDCA increases the Ca(2+) uptake by mature enterocytes, and in combination with NaDOC acts as an antiapoptotic and antiautophagic agent normalizing the transcellular Ca(2+) pathway. Copyright © 2015 Elsevier Inc. All rights reserved.

Mineralocorticoid receptor blockade but not steroid withdrawal reverses renal fibrosis in deoxycorticosterone/salt rats.

PubMed

Lam, Emily Y M; Funder, John W; Nikolic-Paterson, David J; Fuller, Peter J; Young, Morag J

2006-07-01

The pathophysiologic effects of nonepithelial mineralocorticoid receptor (MR) activation include vascular inflammation followed by renal and cardiac remodeling in experimental animals. We have recently shown that MR blockade can reverse established cardiac fibrosis and vascular inflammation; the present study explores whether a similar protection is seen in renal tissue. Rats were uninephrectomized and maintained on 0.9% NaCl solution to drink and treated as follows: control, vehicle; deoxycorticosterone (DOC), 20 mg/wk sc for 4 wk and then killed; DOC for 8 wk; DOC for 4 wk and no steroid for wk 5-8; DOC for 8 wk and eplerenone 100 mg/kg.d in the food for wk 5-8. DOC increased renal collagen at 4 and 8 wk; rats given DOC for 4 wk and killed at 8 wk showed levels of fibrosis identical with those killed at 4 wk, whereas rats given DOC for 8 wk plus eplerenone for wk 5-8 were indistinguishable from control. The inflammatory markers ED-1, osteopontin, and cyclooxygenase-2 remained significantly elevated despite the withdrawal of DOC (DOC404), whereas eplerenone restored cyclooxygenase-2 expression (but not that of ED-1 or osteopontin) to control levels. In addition, markers of oxidative stress and TGFbeta were determined. We hypothesize that continuing tubular inflammation and fibrosis despite DOC withdrawal indicates that the renal tissue may reflect MR activation in the context of tissue damage.

Regulation of stream water dissolved organic carbon concentrations ([DOC]) during snowmelt in forest streams; the role of discharge, winter climate and memory effects

NASA Astrophysics Data System (ADS)

Ågren, A.; Haei, M.; Öquist, M.; Buffam, I.; Ottosson-Löfvenius, M.; Kohler, S.; Bishop, K.; Blomkvist, P.; Laudon, H.

2011-12-01

Using 15 year stream records from two forested northern boreal catchments, coupled with soil frost experiments in the riparian zone, we demonstrate the complex inter-annual control on [DOC] and export during snowmelt. Stream [DOC] varied by a factor of 2 during those 15 years with no consistent trend. Based on our long-term analysis, we demonstrate, for the first time, that stream water [DOC] is strongly linked to the climatic conditions during the preceding winter, but that there is also a long-term memory effect in the catchment soils, related to the extent of the previous export from the catchment. Hydrology had a first order control on the inter-annual variation in concentrations, and the length of the winter was more important than the memory effect. By removing the effect of discharge on [DOC], using a conceptual hydrological model, we could detect processes that would otherwise have been overshadowed. A short and intense snowmelt gave higher [DOC] in the stream. During a prolonged snowmelt, one soil layer at the time might have been "flushed" from easily exported DOC, resulting in slightly lower stream [DOC] during such years. We found that longer and colder winters resulted in higher [DOC] during the subsequent snowmelt. A soil frost manipulation experiment in the riparian soils of the study catchment showed that the DOC concentrations in the soil water increased with the duration of the soil frost. A high antecedent DOC export during the preceding summer and autumn resulted in lower concentrations during the following spring, indicating a long-term "memory effect" of the catchment soils. In a nearby stream draining mire, we found a different response to hydrology but similar response to climate and memory effect. The inter-annual variation in snowmelt DOC exports was mostly controlled by the amount of runoff, but the variability in [DOC] also exerted a significant control on the exports, accounting for 15% of the variance in exports. We conclude that winter climatic conditions can play a substantial role in controlling stream [DOC] in ways not previously understood. These findings are especially important for northern latitude regions expected to be most affected by climate change. It's difficult to directly translate this to a future climate change prediction. If warmer winters with less insulating snow cover increase the soil frost, the results from the soil frost manipulation experiment then suggest increasing [DOC] in a future climate. At the same time the statistical analysis of the stream records suggest that a shorter and warmer winter would decrease the [DOC]. Our results do, however, highlight the role of winter climate for regulating DOC in areas with seasonally frozen soils which should be considered when resolving the sensitivity of stream [DOC] to global environmental change.

Impact of hurricanes on the flux of rainwater and Cape Fear River water dissolved organic carbon to Long Bay, southeastern United States

NASA Astrophysics Data System (ADS)

Avery, G. Brooks; Kieber, Robert J.; Willey, Joan D.; Shank, G. Christopher; Whitehead, Robert F.

2004-09-01

The hurricane flux of rain and river water dissolved organic carbon (DOC) to Long Bay located on the southeastern coast of the United States was determined for four hurricanes that made landfall in the Cape Fear region of North Carolina. Riverine flux of DOC following hurricanes Fran (1996) and Floyd (1999) represented one third and one half of the entire annual river flux of DOC to Long Bay, respectively. The majority of this DOC was recalcitrant and not available for biological consumption. The high flux of DOC from hurricane Floyd resulted from extremely high precipitation amounts (in excess of 50 cm) associated with the hurricane and subsequent flooding. High riverine DOC fluxes were observed following hurricane Fran but not hurricanes Bertha (1996) and Bonnie (1998). The westerly path of Fran deposited rain inland along the Cape Fear River watershed, causing high river flow conditions, while Bonnie and Bertha took an eastern path, resulting in a minimal effect to the Cape Fear River flow rates. The rainwater flux of total DOC to Long Bay from the four hurricanes was not as dramatic as that observed for riverine fluxes. However, unlike river water DOC that is refractory, rainwater DOC is highly labile. Rainwater from the four hurricanes in this study deposited 2-5 times the DOC deposited in an average storm. This represented a flux of 3-9% of the entire annual budget of bioavailable DOC to Long Bay being deposited over a 1 or 2 day period, likely spurring short-term secondary productivity following the hurricanes.

Sources, bioavailability, and photoreactivity of dissolved organic carbon in the Sacramento-San Joaquin River Delta

USGS Publications Warehouse

Stepanauskas, R.; Moran, M.A.; Bergamaschi, B.A.; Hollibaugh, J.T.

2005-01-01

We analyzed bioavailability, photoreactivity, fluorescence, and isotopic composition of dissolved organic carbon (DOC) collected at 13 stations in the Sacramento-San Joaquin River Delta during various seasons to estimate the persistence of DOC from diverse shallow water habitat sources. Prospective large-scale wetland restorations in the Delta may change the amount of DOC available to the food web as well as change the quality of Delta water exported for municipal use. Our study indicates that DOC contributed by Delta sources is relatively refractory and likely mostly the dissolved remnants of vascular plant material from degrading soils and tidal marshes rather than phytoplankton production. Therefore, the prospective conversion of agricultural land into submerged, phytoplankton-dominated habitats may reduce the undesired export of DOC from the Delta to municipal users. A median of 10% of Delta DOC was rapidly utilizable by bacterioplankton. A moderate dose of simulated solar radiation (286 W m-2 for 4 h) decreased the DOC bioavailability by an average of 40%, with a larger relative decrease in samples with higher initial DOC bioavailability. Potentially, a DOC-based microbial food web could support ???0.6 ?? 109 g C of protist production in the Delta annually, compared to ???17 ?? 109 g C phytoplankton primary production. Thus, DOC utilization via the microbial food web is unlikely to play an important role in the nutrition of Delta zooplankton and fish, and the possible decrease in DOC concentration due to wetland restoration is unlikely to have a direct effect on Delta fish productivity. ?? Springer 2005.

Intrinsic Controls of Groundwater-Surface Water Dissolved Organic Carbon Quality and Quantity on Hyporheic Carbon Oxidation.

NASA Astrophysics Data System (ADS)

Garayburu-Caruso, V. A.; Stegen, J.; Graham, E.

2017-12-01

Inputs of dissolved organic carbon (DOC) and nutrients from groundwater (GW) and surface water (SW) to the hyporheic zone strongly influence biogeochemical processes. Despite increased research efforts, we still lack a mechanistic understanding of the conditions driving elevated hyporheic metabolism. This work explores hyporheic carbon oxidation from a thermodynamic perspective by evaluating changes in metabolic rates within hyporheic zone sediments in response to changes on DOC concentration and thermodynamic profiles that are characteristic of GW and SW sources. We hypothesize that GW DOC is protected from microbial oxidation due to low concentration and that SW DOC is protected due low thermodynamic favorability. Further, we propose that GW-SW mixing can simultaneously overcome both limitations and stimulate carbon oxidation. Hyporheic sediments from the Hanford site in Richland, WA were exposed to ambient, 2-,5- and 10-fold concentrations of natural DOC from SW and GW sources, separately, and incubated at in-situ temperature. The two DOC sources supply contrasting thermodynamic profiles, with GW providing lower concentration but more thermodynamically favorable DOC and SW higher concentration, more recalcitrant DOC. Across DOC treatments we characterized time series of oxygen concentration, DOC concentration, and pH as well as endpoint measurements of DOC thermodynamics using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Our results suggest that hyporheic metabolism of distinct carbon pools (GW or SW) can be limited by concentration or thermodynamic favorability. Our work provides an experimental approach to contribute to mechanistic understanding of freshwater carbon oxidation, and a process-based foundation for the development of watershed-scale hydrobiogeochemical models.

Modeling nonlinear responses of DOC transport in boreal catchments in Sweden

NASA Astrophysics Data System (ADS)

Kasurinen, Ville; Alfredsen, Knut; Ojala, Anne; Pumpanen, Jukka; Weyhenmeyer, Gesa A.; Futter, Martyn N.; Laudon, Hjalmar; Berninger, Frank

2016-07-01

Stream water dissolved organic carbon (DOC) concentrations display high spatial and temporal variation in boreal catchments. Understanding and predicting these patterns is a challenge with great implications for water quality projections and carbon balance estimates. Although several biogeochemical models have been used to estimate stream water DOC dynamics, model biases common during both rain and snow melt-driven events. The parsimonious DOC-model, K-DOC, with 10 calibrated parameters, uses a nonlinear discharge and catchment water storage relationship including soil temperature dependencies of DOC release and consumption. K-DOC was used to estimate the stream water DOC concentrations over 5 years for eighteen nested boreal catchments having total area of 68 km2 (varying from 0.04 to 67.9 km2). The model successfully simulated DOC concentrations during base flow conditions, as well as, hydrological events in catchments dominated by organic and mineral soils reaching NSEs from 0.46 to 0.76. Our semimechanistic model was parsimonious enough to have all parameters estimated using statistical methods. We did not find any clear differences between forest and mire-dominated catchments that could be explained by soil type or tree species composition. However, parameters controlling slow release and consumption of DOC from soil water behaved differently for small headwater catchments (less than 2 km2) than for those that integrate larger areas of different ecosystem types (10-68 km2). Our results emphasize that it is important to account for nonlinear dependencies of both, soil temperature, and catchment water storage, when simulating DOC dynamics of boreal catchments.

Influence of dissolved organic carbon on toxicity of copper to a unionid mussel (Villosa iris) and a cladoceran (Ceriodaphnia dubia) in acute and chronic water exposures

USGS Publications Warehouse

Wang, Ning; Mebane, Christopher A.; Kunz, James L.; Ingersoll, Christopher G.; Brumbaugh, William G.; Santore, Robert C.; Gorsuch, Joseph W.; Arnold, W. Ray

2011-01-01

Acute and chronic toxicity of copper (Cu) to a unionid mussel (Villosa iris) and a cladoceran (Ceriodaphnia dubia) were determined in water exposures at four concentrations of dissolved organic carbon (DOC; nominally 0.5, 2.5, 5, and 10 mg/L as carbon [C]). Test waters with DOC concentrations of 2.5 to 10 mg C/L were prepared by mixing a concentrate of natural organic matter (Suwannee River, GA, USA) in diluted well water (hardness 100 mg/L as CaCO3, pH 8.3, DOC 0.5 mg C/L). Acute median effect concentrations (EC50s) for dissolved Cu increased approximately fivefold (15–72 μg Cu/L) for mussel survival in 4-d exposures and increased about 11-fold (25–267 μg Cu/L) for cladoceran survival in 2-d exposures across DOC concentrations from 0.5 to 10 mg C/L. Similarly, chronic 20% effect concentrations (EC20s) for the mussel in 28-d exposures increased about fivefold (13–61 μg Cu/L for survival; 8.8–38 μg Cu/L for biomass), and the EC20s for the cladoceran in 7-d exposures increased approximately 17-fold (13–215 μg Cu/L) for survival or approximately fourfold (12–42 μg Cu/L) for reproduction across DOC concentrations from 0.5 to 10 mg C/L. The acute and chronic values for the mussel were less than or approximately equal to the values for the cladoceran. Predictions from the biotic ligand model (BLM) used to derive the U.S. Environmental Protection Agency's ambient water quality criteria (AWQC) for Cu explained more than 90% of the variation in the acute and chronic endpoints for the two species, with the exception of the EC20 for cladoceran reproduction (only 46% of variation explained). The BLM-normalized acute EC50s and chronic EC20s for the mussel and BLM-normalized chronic EC20s for the cladoceran in waters with DOC concentrations of 2.5 to 10 mg C/L were equal to or less than the final acute value and final chronic value in the BLM-based AWQC for Cu, respectively, indicating that the Cu AWQC might not adequately protect the mussel from acute and chronic exposure, and the cladoceran from chronic exposure.

Close-Out Report: North Area, Revision 0, LCP Chemicals-Georgia, Brunswick, Georgia

EPA Pesticide Factsheets

December 1997 removal close-out report to document response activities in areas north of B-Street at the LCP Chemicals Superfund Site, GA. Region ID: 04 DocID: 10879193, DocDate: 12-01-1997 Region ID: 04 DocID: 10879193, DocDate: 12-01-1997

Effect of diesel oxidation catalysts on the diesel particulate filter regeneration process.

PubMed

Lizarraga, Leonardo; Souentie, Stamatios; Boreave, Antoinette; George, Christian; D'Anna, Barbara; Vernoux, Philippe

2011-12-15

A Diesel Particulate Filter (DPF) regeneration process was investigated during aftertreatment exhaust of a simulated diesel engine under the influence of a Diesel Oxidation Catalyst (DOC). Aerosol mass spectrometry analysis showed that the presence of the DOC decreases the Organic Carbon (OC) fraction adsorbed to soot particles. The activation energy values determined for soot nanoparticles oxidation were 97 ± 5 and 101 ± 8 kJ mol(-1) with and without the DOC, respectively; suggesting that the DOC does not facilitate elementary carbon oxidation. The minimum temperature necessary for DPF regeneration was strongly affected by the presence of the DOC in the aftertreatment. The conversion of NO to NO(2) inside the DOC induced the DPF regeneration process at a lower temperature than O(2) (ΔT = 30 K). Also, it was verified that the OC fraction, which decreases in the presence of the DOC, plays an important role to ignite soot combustion.

CDOM fluorescence as a proxy of DOC concentration in natural waters: a comparison of four contrasting tropical systems.

PubMed

Rochelle-Newall, E; Hulot, F D; Janeau, J L; Merroune, A

2014-01-01

Chromophoric dissolved organic matter (CDOM) fluorescence or absorption is often proposed as a rapid alternative to chemical methods for the estimation of bulk dissolved organic carbon (DOC) concentration in natural waters. However, the robustness of this method across a wide range of systems remains to be shown. We measured CDOM fluorescence and DOC concentration in four tropical freshwater and coastal environments (estuary and coastal, tropical shallow lakes, water from the freshwater lens of two small islands, and soil leachates). We found that although this method can provide an estimation of DOC concentration in sites with low variability in DOC and CDOM sources in systems where the variability of DOC and CDOM sources are high, this method should not be used as it will lead to errors in the estimation of the bulk DOC concentration.

Google Docs in an Out-of-Class Collaborative Writing Activity

ERIC Educational Resources Information Center

Zhou, Wenyi; Simpson, Elizabeth; Domizi, Denise Pinette

2012-01-01

Google Docs, an online word processing application, is a promising tool for collaborative learning. However, many college instructors and students lack knowledge to effectively use Google Docs to enhance teaching and learning. Goals of this study include (1) assessing the effectiveness of using Google Docs in an out-of-class collaborative writing…

49 CFR 22.57 - Loan reporting requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

....dot.gov/financial/docs/Loan_Activation_DOT_F_2303-1.pdf. The Participating Lender must also provide....osdbu.dot.gov/financial/docs/Loan_Close-Out_DOT_F_2304-1.pdf. To fulfill this requirement, the....dot.gov/financial/docs/Pending_Loan_DOT_F_2306-1.xls and http://www.osdbu.dot.gov/financial/docs...

49 CFR 22.57 - Loan reporting requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

....dot.gov/financial/docs/Loan_Activation_DOT_F_2303-1.pdf. The Participating Lender must also provide....osdbu.dot.gov/financial/docs/Loan_Close-Out_DOT_F_2304-1.pdf. To fulfill this requirement, the....dot.gov/financial/docs/Pending_Loan_DOT_F_2306-1.xls and http://www.osdbu.dot.gov/financial/docs...

49 CFR 22.57 - Loan reporting requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

....dot.gov/financial/docs/Loan_Activation_DOT_F_2303-1.pdf. The Participating Lender must also provide....osdbu.dot.gov/financial/docs/Loan_Close-Out_DOT_F_2304-1.pdf. To fulfill this requirement, the....dot.gov/financial/docs/Pending_Loan_DOT_F_2306-1.xls and http://www.osdbu.dot.gov/financial/docs...

Light absorption properties of colored dissolved organic matter (CDOM) in adjacent waters of the Changjiang Estuary during a flood season: implication for DOC estimation

NASA Astrophysics Data System (ADS)

Liu, Yangyang; Shen, Fang; Li, Xiuzhen

2014-11-01

Light absorption properties of colored dissolved organic matter (CDOM) in adjacent waters of the Changjiang Estuary were investigated during the summer of 2013. CDOM absorption showed a substantial portion of the total absorption and clearly dominant among most investigation stations. It generally decreased from the northwest to the southeast, which controlled by physical mixing of fresh water and seawater as was indicated by a conservative behaviour of CDOM. CDOM absorption sharply increased during phytoplankton blooms. Similarly, dissolved organic carbon (DOC) also peaked during blooms period. However, DOC exhibited a more complex behavior relative to a simple conservative mixing, possibly attributed to multiple origins of DOC. CDOM absorption and DOC co-varied to some degree, implying a potential way of DOC estimation from CDOM absorption. However, more detailed information such as CDOM and DOC composition and more validation data were required to obtain a stable CDOM - DOC pattern. Lastly, empirical algorithms with limited data were developed to retrieve CDOM absorption. Further validation of the algorithms were needed when they were to be commonly applied.

Dissolved organic carbon in the carbon cycle of the Indian Ocean

NASA Astrophysics Data System (ADS)

Hansell, Dennis A.

Dissolved organic carbon (DOC) is one of the least quantified and least understood bioreactive pools of carbon in the Indian Ocean. Data gaps are large, with much of the central Indian Ocean not yet sampled. Here model results depict the surface distribution of DOC, which is interpreted in terms of anticipated net DOC production (13-26 Tmol C a-1), advective transport, and export to the subsurface with overturning circulation. These interpretations are tested against DOC measurements made on sections in the Arabian Sea, across the Agulhas Current, in the central Indian Ocean, and into the Bay of Bengal. The seasonality of net DOC production and consumption is evaluated in the Arabian Sea, where data density is relatively rich. DOC stocks in the upper 150 m of the western Arabian Sea increased by >1.5 mol C m-2 during the NE monsoon and disappeared rapidly during the SW monsoon. Rapid DOC removal may result in part from aggregation of dust and biogenic particles along with stripping of trace metals and DOC, perhaps as transparent exopolymer particles, from the surrounding waters.

Hyperactive external awareness against hypoactive internal awareness in disorders of consciousness using resting-state functional MRI: highlighting the involvement of visuo-motor modulation.

PubMed

He, Jiang-Hong; Yang, Yi; Zhang, Yi; Qiu, Si-You; Zhou, Zhen-Yu; Dang, Yuan-Yuan; Dai, Yi-Wu; Liu, Yi-Jun; Xu, Ru-Xiang

2014-08-01

Resting-state functional MRI (fMRI) has emerged as a valuable tool to characterize the complex states encompassing disorders of consciousness (DOC). Awareness appears to comprise two coexistent, anticorrelated components named the external and internal awareness networks. The present study hypothesizes that DOC interrupts the balance between the internal and external awareness networks. To gain more understanding of this phenomenon, the present study analyzed resting-state fMRI data from 12 patients with DOC versus 12 healthy age-matched controls. The data were explored using independent component analysis and amplitude of low-frequency fluctuation (ALFF) analysis. The results indicated that DOC deactivated midline areas associated with internal awareness. In addition, external awareness was strengthened in DOC because of increased activation in the insula, lingual gyrus, paracentral and supplementary motor area. The activity patterns suggested strengthened external awareness against weakened internal awareness in DOC. In particular, increased activity found in the insula, lingual gyrus, paracentral and supplementary motor area of patients with DOC implied possible involvement of augmented visuo-motor modulation in these patients. DOC is probably related to hyperactive external awareness opposing hypoactive internal awareness. This unique pattern of brain activity may potentially be a prognostic marker for DOC. Copyright © 2014 John Wiley & Sons, Ltd.

Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater

USGS Publications Warehouse

Chapelle, Francis H.; Bradley, Paul M.; McMahon, Peter B.; Kaiser, Karl; Benner, Ron

2012-01-01

Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA254) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems.

The diabetes online community: Older adults supporting self-care through peer health.

PubMed

Litchman, Michelle L; Rothwell, Erin; Edelman, Linda S

2018-03-01

The use of the diabetes online community (DOC) is growing across all age groups. The aim of this exploratory study was to describe why older adults participated in the DOC, and how DOC users interacted with their healthcare providers. Telephone interviews (N=20) were conducted with older adult DOC users (born between 1946 and 1964) living in the United States. Interviews were analyzed using qualitative content analysis adhering to rigor and reproducibility standards. Themes that emerged from the data related to DOC participation included: information to improve self-care, emotional support, belonging to a community, validation of information, cause for concern and interaction with healthcare providers. Participants used the DOC for day to day diabetes management advice and healthcare providers for medical information and care. Participants highly valued the DOC and regarded their participation as a way to increase knowledge to improve self-care and reciprocate emotional support with others for diabetes management. The DOC filled gaps in knowledge and support participants were not able to get elsewhere. The DOC serves as an important source of information and support for individuals with diabetes and may be a cost-effective strategy to augment standard diabetes care. Copyright © 2017 Elsevier B.V. All rights reserved.

Temporal Variability of Stemflow Dissolved Organic Carbon (DOC) Concentrations and Quality from Morphologically Contrasting Deciduous Canopies

NASA Astrophysics Data System (ADS)

van Stan, J. T.; Levia, D. F.; Inamdar, S. P.; Mitchell, M. J.; Mage, S. M.

2010-12-01

Dissolved organic carbon (DOC) inputs from canopy-derived hydrologic fluxes play a significant role in the terrestrial carbon budgets of forested ecosystems. However, no studies known to the authors have examined the variability of both DOC concentrations and quality for stemflow across time scales, nor has any study to date evaluated the effects of canopy structure on stemflow DOC characteristics. This investigation seeks to rectify this knowledge gap by examining the variability of stemflow DOC concentrations and quality across contrasting canopy morphologies and time scales (seasonal, storm and intrastorm). Bulk and intrastorm stemflow samples from a less dense, rough-barked, more plagiophile (Liriodendron tulipifera L. (tulip poplar)) and a denser, thin-barked, more erectophile (Fagus grandifolia Ehrh. (American beech)) canopy were collected and analyzed for DOC quality using metrics derived from UV-vis spectroscopy (E2:E3 ratio, SUVA254, select spectral slope (S), and spectral slope ratios (SR)). Our results suggest that stemflow DOC concentrations and quality change as crown architectural traits enhance or diminish hydrologic retention time within the canopy. The architecture of L. tulipifera canopies likely retards the flow of intercepted water, increasing chemical exchange with bark and foliar surfaces. UV-vis metrics indicated that this increased chemical exchange, particularly with bark surfaces, generally enhanced aromatic hydrocarbon content and increased molecular weight. Because leaf presence influenced DOC quality, stemflow DOC characteristics also varied seasonally in response to canopy condition. At the inter- and intrastorm scale, stemflow DOC concentration and quality varied with meteorological and antecedent canopy conditions. Since recent studies have linked stemflow production to preferential subsurface transport of dissolved chemistries, trends in DOC speciation and fluxes described in this study may impact soil environments within wooded ecosystems.

Geochemistry and Flux of Terrigenous Dissolved Organic Matter to the Arctic Ocean

NASA Astrophysics Data System (ADS)

Spencer, R. G.; Mann, P. J.; Hernes, P. J.; Tank, S. E.; Striegl, R. G.; Dyda, R. Y.; Peterson, B. J.; McClelland, J. W.; Holmes, R. M.

2011-12-01

Rivers draining into the Arctic Ocean exhibit high concentrations of terrigenous dissolved organic carbon (DOC) and recent studies indicate that DOC export is changing due to climatic warming and alteration in permafrost condition. The fate of exported DOC in the Arctic Ocean is of key importance for understanding the regional carbon cycle and remains a point of discussion in the literature. As part of the Arctic Great Rivers Observatory (Arctic-GRO) project, samples were collected for DOC, chromophoric dissolved organic matter (CDOM) and lignin phenols from the Ob', Yenisey, Lena, Kolyma, Mackenzie and Yukon rivers in 2009 - 2010. DOC and lignin concentrations were elevated during the spring freshet and measurements related to DOC composition indicated an increasing contribution from terrestrial vascular plant sources at this time of year (e.g. lignin carbon-normalized yield, CDOM spectral slope, SUVA254, humic-like fluorescence). CDOM absorption was found to correlate strongly with both DOC (r2=0.83) and lignin concentration (r2=0.92) across the major arctic rivers. Utilizing these relationships we modeled loads for DOC and lignin export from high-resolution CDOM measurements (daily across the freshet) to derive improved flux estimates, particularly from the dynamic spring discharge maxima period when the majority of DOC and lignin export occurs. The new load estimates for DOC and lignin are higher than previous evaluations, emphasizing that if these are more representative of current arctic riverine export, terrigenous DOC is transiting through the Arctic Ocean at a faster rate than previously thought. It is apparent that higher resolution sampling of arctic rivers is exceptionally valuable with respect to deriving accurate fluxes and we highlight the potential of CDOM in this role for future studies and the applicability of in-situ CDOM sensors.

Spatial and temporal variability in the amount and source of dissolved organic carbon: Implications for ultraviolet exposure in amphibian habitats

USGS Publications Warehouse

Brooks, P.D.; O'Reilly, C. M.; Diamond, S.A.; Campbell, D.H.; Knapp, R.; Bradford, D.; Corn, P.S.; Hossack, B.; Tonnessen, K.

2005-01-01

The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1–2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain (R2 = 0.39, F = 25.71, P < 0.0001) and across all parks in 2000 (R2 = 0.44, F = 38.25, P < 0.0001). The relatively low R2 values, however, reflect significant temporal and spatial variability in the specific attenuation per unit DOC. Fluorescence analysis of the fulvic acid DOC fraction (roughly 600–2,000 Daltons) indicated that the source of DOC significantly affected the attenuation of UV-B. Sites in Sequoia–Kings Canyon were characterized by DOC derived primarily from algal sources and showed much deeper UV-B penetration, whereas sites in Glacier and Rocky Mountain contained a mix of algal and terrestrial DOC-dominated sites, with more terrestrially dominated sites characterized by greater UV-B attenuation per unit DOC. In general, site characteristics that promoted the accumulation of terrestrially derived DOC showed greater attenuation of UV-B per unit DOC; however, catchment vegetation and soil characteristics, precipitation, and local hydrology interacted to make it difficult to predict potential exposure from DOC concentrations.

The role of irrigation runoff and winter rainfall on dissolved organic carbon loads in an agricultural watershed

USGS Publications Warehouse

Oh, Neung-Hwan; Pellerin, Brian A.; Bachand, Philip A.M.; Hernes, Peter J.; Bachand, Sandra M.; Ohara, Noriaki; Kavvas, M. Levent; Bergamaschi, Brian A.; Horwath, William R.

2013-01-01

We investigated the role of land use/land cover and agriculture practices on stream dissolved organic carbon (DOC) dynamics in the Willow Slough watershed (WSW) from 2006 to 2008. The 415 km2watershed in the northern Central Valley, California is covered by 31% of native vegetation and the remaining 69% of agricultural fields (primarily alfalfa, tomatoes, and rice). Stream discharge and weekly DOC concentrations were measured at eight nested subwatersheds to estimate the DOC loads and yields (loads/area) using the USGS developed stream load estimation model, LOADEST. Stream DOC concentrations peaked at 18.9 mg L−1 during summer irrigation in the subwatershed with the highest percentage of agricultural land use, demonstrating the strong influence of agricultural activities on summer DOC dynamics. These high concentrations contributed to DOC yields increasing up to 1.29 g m−2 during the 6 month period of intensive agricultural activity. The high DOC yields from the most agricultural subwatershed during the summer irrigation period was similar throughout the study, suggesting that summer DOC loads from irrigation runoff would not change significantly in the absence of major changes in crops or irrigation practices. In contrast, annual DOC yields varied from 0.89 to 1.68 g m−2 yr−1 for the most agricultural watershed due to differences in winter precipitation. This suggests that variability in the annual DOC yields will be largely determined by the winter precipitation, which can vary significantly from year to year. Changes in precipitation patterns and intensities as well as agricultural practices have potential to considerably alter the DOC dynamics.

Impact of catchment geophysical characteristics and climate on the regional variability of dissolved organic carbon (DOC) in surface water.

PubMed

Cool, Geneviève; Lebel, Alexandre; Sadiq, Rehan; Rodriguez, Manuel J

2014-08-15

Dissolved organic carbon (DOC) is a recognized indicator of natural organic matter (NOM) in surface waters. The aim of this paper is twofold: to evaluate the impact of geophysical characteristics, climate and ecological zones on DOC concentrations in surface waters and, to develop a statistical model to estimate the regional variability of these concentrations. In this study, multilevel statistical analysis was used to achieve three specific objectives: (1) evaluate the influence of climate and geophysical characteristics on DOC concentrations in surface waters; (2) compare the influence of geophysical characteristics and ecological zones on DOC concentrations in surface waters; and (3) develop a model to estimate the most accurate DOC concentrations in surface waters. The case study involved 115 catchments from surface waters in the Province of Quebec, Canada. Results showed that mean temperatures recorded 60 days prior to sampling, total precipitation 10 days prior to sampling and percentages of wetlands, coniferous forests and mixed forests have a significant positive influence on DOC concentrations in surface waters. The catchment mean slope had a significant negative influence on DOC concentrations in surface waters. Water type (lake or river) and deciduous forest variables were not significant. The ecological zones had a significant influence on DOC concentrations. However, geophysical characteristics (wetlands, forests and slope) estimated DOC concentrations more accurately. A model describing the variability of DOC concentrations was developed and can be used, in future research, for estimating DBPs in drinking water as well evaluating the impact of climate change on the quality of surface waters and drinking water. Copyright © 2014 Elsevier B.V. All rights reserved.

Hydrologically transported dissolved organic carbon influences soil respiration in a tropical rainforest

NASA Astrophysics Data System (ADS)

Zhou, Wen-Jun; Lu, Hua-Zheng; Zhang, Yi-Ping; Sha, Li-Qing; Schaefer, Douglas Allen; Song, Qing-Hai; Deng, Yun; Deng, Xiao-Bao

2016-10-01

To better understand the effect of dissolved organic carbon (DOC) transported by hydrological processes (rainfall, throughfall, litter leachate, and surface soil water; 0-20 cm) on soil respiration in tropical rainforests, we detected the DOC flux in rainfall, throughfall, litter leachate, and surface soil water (0-20 cm), compared the seasonality of δ13CDOC in each hydrological process, and δ13C in leaves, litter, and surface soil, and analysed the throughfall, litter leachate, and surface soil water (0-20 cm) effect on soil respiration in a tropical rainforest in Xishuangbanna, south-west China. Results showed that the surface soil intercepted 94.4 ± 1.2 % of the annual litter leachate DOC flux and is a sink for DOC. The throughfall and litter leachate DOC fluxes amounted to 6.81 and 7.23 % of the net ecosystem exchange respectively, indicating that the DOC flux through hydrological processes is an important component of the carbon budget, and may be an important link between hydrological processes and soil respiration in a tropical rainforest. Even the variability in soil respiration is more dependent on the hydrologically transported water than DOC flux insignificantly, soil temperature, and soil-water content (at 0-20 cm). The difference in δ13C between the soil, soil water (at 0-20 cm), throughfall, and litter leachate indicated that DOC is transformed in the surface soil and decreased the sensitivity indices of soil respiration of DOC flux to water flux, which suggests that soil respiration is more sensitive to the DOC flux in hydrological processes, especially the soil-water DOC flux, than to soil temperature or soil moisture.

[Characteristics of dissolved organic carbon release under inundation from typical grass plants in the water-level fluctuation zone of the Three Gorges Reservoir area].

PubMed

Tan, Qiu-Xia; Zhu, Boi; Hua, Ke-Ke

2013-08-01

The water-level fluctuation zone of the Three Gorges Reservoir (TGR) exposes in spring and summer, then, green plants especially herbaceous plants grow vigorously. In the late of September, water-level fluctuation zone of TGR goes to inundation. Meanwhile, annually accumulated biomass of plant will be submerged for decaying, resulting in organism decomposition and release a large amount of dissolved organic carbon (DOC). This may lead to negative impacts on water environment of TGR. The typical herbaceous plants from water-level fluctuation zone were collected and inundated in the laboratory for dynamic measurements of DOC concentration of overlying water. According to the determination, the DOC release rates and fluxes have been calculated. Results showed that the release process of DOC variation fitted in a parabolic curve. The peak DOC concentrations emerge averagely in the 15th day of inundation, indicating that DOC released quickly with organism decay of herbaceous plant. The release process of DOC could be described by the logarithm equation. There are significant differences between the concentration of DOC (the maximum DOC concentration is 486.88 mg x L(-1) +/- 35.97 mg x L(-1) for Centaurea picris, the minimum is 4.18 mg x L(-1) +/- 1.07 mg x L(-1) for Echinochloacrus galli) and the release amount of DOC (the maximum is 50.54 mg x g(-1) for Centaurea picris, the minimum is 6.51 mg x g(-1) for Polygonum hydropiper) due to different characteristics of plants, especially, the values of C/N of herbaceous plants. The cumulative DOC release quantities during the whole inundation period were significantly correlated with plants' C/N values in linear equations.

Physiological protective action of dissolved organic carbon on ion regulation and nitrogenous waste excretion of zebrafish (Danio rerio) exposed to low pH in ion-poor water.

PubMed

Duarte, Rafael M; Wood, Chris M; Val, Adalberto L; Smith, D Scott

2018-06-11

Dissolved organic carbon (DOC) represents a heterogeneous group of naturally-occurring molecules in aquatic environments, and recent studies have evidenced that optically dark DOCs can exert some positive effects on ionoregulatory homeostasis of aquatic organisms in acidic waters. We investigated the effects of Luther Marsh DOC, a dark allochthonous DOC, on ion regulation and N-waste excretion of zebrafish acutely exposed to either neutral or low pH in ion-poor water. In the first experiment, simultaneous exposure to pH 4.0 and DOC greatly attenuated the stimulation of Na + diffusive losses (J out Na ), and prevented the blockade of Na + uptake (J in Na ) seen in zebrafish exposed to pH 4.0 alone, resulting in much smaller disturbances in Na + net losses (J net Na ). DOC also attenuated the stimulation of net Cl - losses (J net Cl ) and ammonia excretion (J net Amm ) during acidic challenge. In the second experiment, zebrafish acclimated to DOC displayed similar regulation of J in Na and J out Na , and, therefore, reduced J net Na at pH 4.0, effects which persisted even when DOC was no longer present. Protective effects of prior acclimation to DOC on J net Cl and J net Amm at pH 4.0 also occurred, but were less marked than those on Na + balance. Urea fluxes were unaffected by the experimental treatments. Overall, these effects were clearly beneficial to the ionoregulatory homeostasis of zebrafish at low pH, and were quite similar to those seen in a recent parallel study using darker DOC from the upper Rio Negro. This suggests that dark allochthonous DOCs share some chemical properties that render fish tolerant to ionoregulatory disturbances during acidic challenge.

Feasibility of the music therapy assessment tool for awareness in disorders of consciousness (MATADOC) for use with pediatric populations.

PubMed

Magee, Wendy L; Ghetti, Claire M; Moyer, Alvin

2015-01-01

Measuring responsiveness to gain accurate diagnosis in populations with disorders of consciousness (DOC) is of central concern because these patients have such complex clinical presentations. Due to the uncertainty of accuracy for both behavioral and neurophysiological measures in DOC, combined assessment approaches are recommended. A number of standardized behavioral measures can be used with adults with DOC with minor to moderate reservations relating to the measures' psychometric properties and clinical applicability. However, no measures have been standardized for use with pediatric DOC populations. When adapting adult measures for children, confounding factors include developmental considerations for language-based items included in all DOC measures. Given the lack of pediatric DOC measures, there is a pressing need for measures that are sensitive to the complex clinical presentations typical of DOC and that can accommodate the developmental levels of pediatric populations. The music therapy assessment tool for awareness in disorders of consciousness (MATADOC) is a music-based measure that has been standardized for adults with DOC. Given its emphasis on non-language based sensory stimuli, it is well-suited to pediatric populations spanning developmental stages. In a pre-pilot exploratory study, we examined the clinical utility of this measure and explored trends for test-retest and inter-rater agreement as well as its performance against external reference standards. In several cases, MATADOC items in the visual and auditory domains produced outcomes suggestive of higher level functioning when compared to outcomes provided by other DOC measures. Preliminary findings suggest that the MATADOC provides a useful protocol and measure for behavioral assessment and clinical treatment planning with pediatric DOC. Further research with a larger sample is warranted to test a version of the MATADOC that is refined to meet developmental needs of pediatric DOC populations.

Does Litter Impart A Detectable Chemical Signal on Soil DOC? DOC Fluorescence Signatures in Soils Undergoing Long-Term Litter Manipulations

NASA Astrophysics Data System (ADS)

Lajtha, K.; Strid, A.; Lee, B. S.

2015-12-01

Soil dissolved organic carbon (DOC) is a small but crucial part of the forest carbon cycle. Characterizing the relationship between organic matter inputs to soil and DOC chemistry is crucial to understanding the ultimate fate of root carbon, fallen wood and needles. Chemical differences in the DOC pool may help to explain whether fractions are sorbed to mineral surfaces and contribute to accumulation of soil organic carbon, respired as CO2, or exported. Soil solution DOC was sampled from the detrital input and removal treatment (DIRT) plots located in the H.J. Andrews Experimental Forest, OR to determine whether detrital inputs impart a detectable signal on DOC in mineral soil. Multiple types of fresh litter extracts, along with lysimeter and soil extracts from DIRT treatment plots were characterized using UV-Vis and fluorescence spectroscopy coupled with the Cory and McKnight (2005) parallel factor analysis (PARAFAC) model. Principal component analysis of 13 unique fluorophores distinguished using PARAFAC show that litter and soil extracts (needles, wood of decomposition Class 1, Class 3 and Class 5, O-horizon, and A-horizon) each have distinct fluorescence signatures. However, while litter-leached DOC chemistry varies by litter type, neither lysimeter-collected DOC or soil extracts show statistically significant differences in fluorescence signatures among treatments, even after 17 years of litter manipulations. The lack of observed differences among DIRT treatments suggests a "Soil Blender" hypothesis whereby both abiotic and biotic mechanisms effectively homogenize organic carbon constituents within the dissolved pool. The results of this work emphasize the ability of sorption and biodegradation to homogenize soil DOC and demonstrate that fluorescence can be an effective fingerprinting technique for soil DOC composition.

Partitioning of fluorotelomer alcohols to octanol and different sources of dissolved organic carbon.

PubMed

Carmosini, Nadia; Lee, Linda S

2008-09-01

Interest in the environmental fate of fluorotelomer alcohols (FTOHs) has spurred efforts to understand their equilibrium partitioning behavior. Experimentally determined partition coefficients for FTOHs between soil/water and air/water have been reported, but direct measurements of partition coefficients for dissolved organic carbon (DOC)/water (K(doc)) and octanol/ water(K(ow)) have been lacking. Here we measured the partitioning of 8:2 and 6:2 FTOH between one or more types of DOC and water using enhanced solubility or dialysis bag techniques, and also quantified K(ow) values for 4:2 to 8:2 FTOH using a batch equilibration method. The range in measured log K(doc) values for 8:2 FTOH using the enhanced solubility technique with DOC derived from two soils, two biosolids, and three reference humic acids is 2.00-3.97 with the lowest values obtained for the biosolids and an average across all other DOC sources (biosolid DOC excluded) of 3.54 +/- 0.29. For 6:2 FTOH and Aldrich humic acid, a log K(doc) value of 1.96 +/- 0.45 was measured using the dialysis technique. These average values are approximately 1 to 2 log units lower than previously indirectly estimated K(doc) values. Overall, the affinity for DOC tends to be slightly lower than that for particulate soil organic carbon. Measured log K(ow) values for 4:2 (3.30 +/- 0.04), 6:2 (4.54 +/- 0.01), and 8:2 FTOH (5.58 +/- 0.06) were in good agreement with previously reported estimates. Using relationships between experimentally measured partition coefficients and C-atom chain length, we estimated K(doc) and K(ow) values for shorter and longer chain FTOHs, respectively, that we were unable to measure experimentally.

Feasibility of the music therapy assessment tool for awareness in disorders of consciousness (MATADOC) for use with pediatric populations

PubMed Central

Magee, Wendy L.; Ghetti, Claire M.; Moyer, Alvin

2015-01-01

Measuring responsiveness to gain accurate diagnosis in populations with disorders of consciousness (DOC) is of central concern because these patients have such complex clinical presentations. Due to the uncertainty of accuracy for both behavioral and neurophysiological measures in DOC, combined assessment approaches are recommended. A number of standardized behavioral measures can be used with adults with DOC with minor to moderate reservations relating to the measures’ psychometric properties and clinical applicability. However, no measures have been standardized for use with pediatric DOC populations. When adapting adult measures for children, confounding factors include developmental considerations for language-based items included in all DOC measures. Given the lack of pediatric DOC measures, there is a pressing need for measures that are sensitive to the complex clinical presentations typical of DOC and that can accommodate the developmental levels of pediatric populations. The music therapy assessment tool for awareness in disorders of consciousness (MATADOC) is a music-based measure that has been standardized for adults with DOC. Given its emphasis on non-language based sensory stimuli, it is well-suited to pediatric populations spanning developmental stages. In a pre-pilot exploratory study, we examined the clinical utility of this measure and explored trends for test-retest and inter-rater agreement as well as its performance against external reference standards. In several cases, MATADOC items in the visual and auditory domains produced outcomes suggestive of higher level functioning when compared to outcomes provided by other DOC measures. Preliminary findings suggest that the MATADOC provides a useful protocol and measure for behavioral assessment and clinical treatment planning with pediatric DOC. Further research with a larger sample is warranted to test a version of the MATADOC that is refined to meet developmental needs of pediatric DOC populations. PMID:26074850

Nonlinear and threshold-dominated runoff generation controls DOC export in a small peat catchment

NASA Astrophysics Data System (ADS)

Birkel, C.; Broder, T.; Biester, H.

2017-03-01

We used a relatively simple two-layer, coupled hydrology-biogeochemistry model to simultaneously simulate streamflow and stream dissolved organic carbon (DOC) concentrations in a small lead and arsenic contaminated upland peat catchment in northwestern Germany. The model procedure was informed by an initial data mining analysis, in combination with regression relationships of discharge, DOC, and element export. We assessed the internal model DOC processing based on stream DOC hysteresis patterns and 3-hourly time step groundwater level and soil DOC data for two consecutive summer periods in 2013 and 2014. The parsimonious model (i.e., few calibrated parameters) showed the importance of nonlinear and rapid near-surface runoff generation mechanisms that caused around 60% of simulated DOC load. The total load was high even though these pathways were only activated during storm events on average 30% of the monitoring time—as also shown by the experimental data. Overall, the drier period 2013 resulted in increased nonlinearity but exported less DOC (115 kg C ha-1 yr-1 ± 11 kg C ha-1 yr-1) compared to the equivalent but wetter period in 2014 (189 kg C ha-1 yr-1 ± 38 kg C ha-1 yr-1). The exceedance of a critical water table threshold (-10 cm) triggered a rapid near-surface runoff response with associated higher DOC transport connecting all available DOC pools and subsequent dilution. We conclude that the combination of detailed experimental work with relatively simple, coupled hydrology-biogeochemistry models not only allowed the model to be internally constrained but also provided important insight into how DOC and tightly coupled pollutants or trace elements are mobilized.

Seasonal Dynamics of Dissolved Organic Carbon Under Complex Circulation Schemes on a Large Continental Shelf: The Northern South China Sea

NASA Astrophysics Data System (ADS)

Meng, Feifei; Dai, Minhan; Cao, Zhimian; Wu, Kai; Zhao, Xiaozheng; Li, Xiaolin; Chen, Junhui; Gan, Jianping

2017-12-01

We examined the distribution and seasonality of dissolved organic carbon (DOC) based on a large data set collected from the northern South China Sea (NSCS) shelf under complex circulation schemes influenced by river plume, coastal upwelling, and downwelling. The highest surface values of ˜117 μmol L-1 were observed nearshore in summer suggesting high DOC supplies from the river inputs, whereas the lowest surface values of ˜62 μmol L-1 were on the outer shelf in winter due to entrainment of DOC-poor subsurface water under strengthened vertical mixing. While the summer coastal upwelling brought lower DOC from offshore depth to the nearshore surface, the winter coastal downwelling delivered higher surface DOC to the midshelf deep waters from the inner shelf fueled by the China Coastal Current (CCC) transporting relatively high DOC from the East China Sea to the NSCS. The intensified winter downwelling generated a cross-shelf DOC transport of 3.1 × 1012 g C over a large shelf area, which induced a significant depression of the NSCS DOC inventory in winter relative to in autumn. In addition to the variable physical controls, net biological production of DOC was semiquantified in both the river plume (2.8 ± 3.0 μmol L-1) and coastal upwelling (3.1 ± 1.3 μmol L-1) in summer. We demonstrated that the NSCS shelf had various origins of DOC including riverine inputs, inter-shelf transport and in situ production. Via cross-shelf transport, the accumulated DOC would be exported to and stored in the deep ocean, suggesting that continental shelves are a potentially effective carbon sink.

Effect of past peat cultivation practices on present dynamics of dissolved organic carbon.

PubMed

Frank, S; Tiemeyer, B; Bechtold, M; Lücke, A; Bol, R

2017-01-01

Peatlands are a major source of dissolved organic carbon (DOC) for aquatic ecosystems. Naturally high DOC concentrations in peatlands may be increased further by drainage. For agricultural purposes, peat has frequently been mixed with sand, but the effect of this measure on the release and cycling of DOC has rarely been investigated. This study examined the effects of (i) mixing peat with sand and (ii) water table depth (WTD) on DOC concentrations at three grassland sites on shallow organic soils. The soil solution was sampled bi-weekly for two years with suction plates at 15, 30 and 60cm depth. Selected samples were analysed for dissolved organic nitrogen (DON), δ 13 C DOM and δ 15 N DOM . Average DOC concentrations were surprisingly high, ranging from 161 to 192mgl -1 . There was no significant impact of soil organic carbon (SOC) content or WTD on mean DOC concentrations. At all sites, DOC concentrations were highest at the boundary between the SOC-rich horizon and the mineral subsoil. In contrast to the mean concentrations, the temporal patterns of DOC concentrations, their drivers and the properties of dissolved organic matter (DOM) differed between peat-sand mixtures and peat. DOC concentrations responded to changes in environmental conditions, but only after a lag period of a few weeks. At the sites with a peat-sand mixture, temperature and therefore probably biological activity determined the DOC concentrations. At the peat site, the contribution of vegetation-derived DOM was higher. The highest concentrations occurred during long, cool periods of waterlogging, suggesting a stronger physicochemical-based DOC mobilisation. Overall, these results indicate that mixing peat with sand does not improve water quality and may result in DOC losses of around 200kg DOCha -1 a -1 . Copyright © 2016 Office national des forêts. Published by Elsevier B.V. All rights reserved.

ORCHIDEE-SOM: modeling soil organic carbon (SOC) and dissolved organic carbon (DOC) dynamics along vertical soil profiles in Europe

NASA Astrophysics Data System (ADS)

Camino-Serrano, Marta; Guenet, Bertrand; Luyssaert, Sebastiaan; Ciais, Philippe; Bastrikov, Vladislav; De Vos, Bruno; Gielen, Bert; Gleixner, Gerd; Jornet-Puig, Albert; Kaiser, Klaus; Kothawala, Dolly; Lauerwald, Ronny; Peñuelas, Josep; Schrumpf, Marion; Vicca, Sara; Vuichard, Nicolas; Walmsley, David; Janssens, Ivan A.

2018-03-01

Current land surface models (LSMs) typically represent soils in a very simplistic way, assuming soil organic carbon (SOC) as a bulk, and thus impeding a correct representation of deep soil carbon dynamics. Moreover, LSMs generally neglect the production and export of dissolved organic carbon (DOC) from soils to rivers, leading to overestimations of the potential carbon sequestration on land. This common oversimplified processing of SOC in LSMs is partly responsible for the large uncertainty in the predictions of the soil carbon response to climate change. In this study, we present a new soil carbon module called ORCHIDEE-SOM, embedded within the land surface model ORCHIDEE, which is able to reproduce the DOC and SOC dynamics in a vertically discretized soil to 2 m. The model includes processes of biological production and consumption of SOC and DOC, DOC adsorption on and desorption from soil minerals, diffusion of SOC and DOC, and DOC transport with water through and out of the soils to rivers. We evaluated ORCHIDEE-SOM against observations of DOC concentrations and SOC stocks from four European sites with different vegetation covers: a coniferous forest, a deciduous forest, a grassland, and a cropland. The model was able to reproduce the SOC stocks along their vertical profiles at the four sites and the DOC concentrations within the range of measurements, with the exception of the DOC concentrations in the upper soil horizon at the coniferous forest. However, the model was not able to fully capture the temporal dynamics of DOC concentrations. Further model improvements should focus on a plant- and depth-dependent parameterization of the new input model parameters, such as the turnover times of DOC and the microbial carbon use efficiency. We suggest that this new soil module, when parameterized for global simulations, will improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future SOC response to global warming.

Nutrient dynamics across a dissolved organic carbon and burn gradient in central Siberia

NASA Astrophysics Data System (ADS)

Rodriguez-Cardona, B.; Coble, A. A.; Prokishkin, A. S.; Kolosov, R.; Spencer, R. G.; Wymore, A.; McDowell, W. H.

2016-12-01

In stream ecosystems, dissolved organic carbon (DOC) and nitrogen (N) processing are tightly linked. In temperate streams, greater DOC concentrations and higher DOC:NO3- ratios promote the greatest nitrate (NO3-) uptake. However, less is known about this relationship in other biomes including the arctic which is undergoing changes due to climate change contributing to thawing of permafrost and alterations in biogeochemical cycles in soils and streams. Headwater streams draining into the N. Tunguska River in the central Siberian plateau are affected by forest fires but little is known about the aquatic biogeochemical implications in both a thawing and burning landscape. There are clear patterns between carbon concentration and fire history where generally DOC concentration in streams decrease after fires and older burn sites have shown greater DOC concentrations and more bioavailable DOC that could promote greater heterotrophic uptake of NO3-. However, the relationship between nutrient dynamics, organic matter composition, and fire history in streams is not very clear. In order to assess the influence of organic matter composition and DOC concentration on nutrient uptake in arctic streams, we conducted a series of short-term nutrient addition experiments following the tracer addition for spiraling curve characterization (TASCC) method, consisting of NO3- and NH4++PO43- additions, across 4 streams that comprise a fire gradient that spans 3- >100 years since the last burn with DOC concentrations ranging between 12-23 mg C/L. We hypothesized that nutrient uptake would be greatest in older burn sites due to greater DOC concentrations and availability. We will specifically examine how nutrient uptake relates to DOC concentration and OM composition (analyzed via FTICR-MS) across the burn gradient. Across the four sites DOC concentration and DOC:NO3- ratios decreased from old burn sites to recently burned sites. Results presented here can elucidate on the potential impacts of permafrost thawing and forest fires on nutrient dynamics in arctic streams.

Evaluating the impacts of landscape positions and nitrogen fertilizer rates on dissolved organic carbon on switchgrass land seeded on marginally yielding cropland.

PubMed

Lai, Liming; Kumar, Sandeep; Mbonimpa, Eric G; Hong, Chang Oh; Owens, Vance N; Neupane, Ram P

2016-04-15

Dissolved organic carbon (DOC) through leaching into the soils is another mechanism of net C loss. It plays an important role in impacting the environment and impacted by soil and crop management practices. However, little is known about the impacts of landscape positions and nitrogen (N) fertilizer rates on DOC leaching in switchgrass (Panicum virgatum L.). This experimental design included three N fertilizer rates [0 (low); 56 (medium); 112 (high) kg N ha(-1)] and three landscape positions (shoulder, backslope and footslope). Daily average DOC contents at backslope were significantly lower than that at shoulder and footslope. The DOC contents from the plots that received medium N rate were also significantly lower than the plots that received low N rates. The interactions of landscape and N rates on DOC contents were different in every year from 2009 to 2014, however, no significant consistent trend of DOC contents was observed over time. Annual average DOC contents from the plots managed with low N rate were higher than those with high N rate. These contents at the footslope were higher than that at the shoulder position. Data show that there is a moderate positive relationship between the total average DOC contents and the total average switchgrass biomass yields. Overall, the DOC contents from leachate in the switchgrass land were significantly influenced by landscape positions and N rates. The N fertilization reduced DOC leaching contents in switchgrass field. The switchgrass could retain soil and environment sustainability to some extent. These findings will assist in understanding the mechanism of changes in DOC contents with various parameters in the natural environment and crop management systems. However, use of long-term data might help to better assess the effects of above factors on DOC leaching contents and loss in the switchgrass field in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Relationship Between DOC Partition Coefficient and Mineral Soil C:N Ratio

NASA Astrophysics Data System (ADS)

Aitkenhead-Peterson, J. A.; McDowell, W. H.

2001-12-01

Since our recent publication showing that soil C:N predicts DOC flux at local and global scales, an effort has been made to understand mechanisms controlling the relationship between the two variables. We have approached this at multiple scales, using soil batch experiments, soil column experiments, and long-term field manipulations. We present here the results from our batch adsorption experiment. Mineral soils from tropical (wet and moist) and temperate (coniferous and hardwood) forests were used to assess DOC adsorption by the initial mass isotherm approach. We found that the DOC partition co-efficient (m) which represents a soil's tendency to adsorb DOC is strongly and inversely related to mineral soil C:N ratio (R2 = 0.99 n = 10 p < 0.001). The intercept of the mass isotherm, or the desorption term, was positively related to mineral soil C:N ratio (R2 = 0.80 n = 10 p < 0.01), but we found that desorption of DOC was more closely correlated with equilibrium DOC concentration (R2 = 0.97 n = 10 p < 0.001) than with mineral soil C:N. The mass isotherm approach is also useful in calculating the reactive soil pool (RSP), the fraction of the soil pool of organic carbon that may be lost to leaching. The RSP was not significantly related to mineral soil C:N, but tropical soils tended to have a larger RSP than temperate soils. Although some of the tropical soils came from areas where the natural forest had been cleared, used for plantations and then abandoned, the relationship between DOC adsorption and mineral soil C:N was not compromised. Watershed soil C:N ratio is an excellent predictor of DOC export because soil C:N is related to physiochemical adsorption processes in mineral soils and biotic production of DOC in organic soil horizons. It appears that soil C:N is a relatively robust predictor of soil solution DOC concentration and surface water DOC export for ecosystems undergoing environmental stress.

Drivers of dissolved organic carbon export in a subarctic catchment: Importance of microbial decomposition, sorption-desorption, peatland and lateral flow.

PubMed

Tang, Jing; Yurova, Alla Y; Schurgers, Guy; Miller, Paul A; Olin, Stefan; Smith, Benjamin; Siewert, Matthias B; Olefeldt, David; Pilesjö, Petter; Poska, Anneli

2018-05-01

Tundra soils account for 50% of global stocks of soil organic carbon (SOC), and it is expected that the amplified climate warming in high latitude could cause loss of this SOC through decomposition. Decomposed SOC could become hydrologically accessible, which increase downstream dissolved organic carbon (DOC) export and subsequent carbon release to the atmosphere, constituting a positive feedback to climate warming. However, DOC export is often neglected in ecosystem models. In this paper, we incorporate processes related to DOC production, mineralization, diffusion, sorption-desorption, and leaching into a customized arctic version of the dynamic ecosystem model LPJ-GUESS in order to mechanistically model catchment DOC export, and to link this flux to other ecosystem processes. The extended LPJ-GUESS is compared to observed DOC export at Stordalen catchment in northern Sweden. Vegetation communities include flood-tolerant graminoids (Eriophorum) and Sphagnum moss, birch forest and dwarf shrub communities. The processes, sorption-desorption and microbial decomposition (DOC production and mineralization) are found to contribute most to the variance in DOC export based on a detailed variance-based Sobol sensitivity analysis (SA) at grid cell-level. Catchment-level SA shows that the highest mean DOC exports come from the Eriophorum peatland (fen). A comparison with observations shows that the model captures the seasonality of DOC fluxes. Two catchment simulations, one without water lateral routing and one without peatland processes, were compared with the catchment simulations with all processes. The comparison showed that the current implementation of catchment lateral flow and peatland processes in LPJ-GUESS are essential to capture catchment-level DOC dynamics and indicate the model is at an appropriate level of complexity to represent the main mechanism of DOC dynamics in soils. The extended model provides a new tool to investigate potential interactions among climate change, vegetation dynamics, soil hydrology and DOC dynamics at both stand-alone to catchment scales. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparing Stream Discharge, Dissolved Organic Carbon, and Selected MODIS Indices in Freshwater Basins

NASA Astrophysics Data System (ADS)

Shaver, W. T.; Wollheim, W. M.

2009-12-01

In a preliminary study of the Ipswich Basin in Massachusetts, a good correlation was found to exist between the MODIS (Moderate Resolution Imaging Spectroradiometer) Enhanced Vegetation Index and stream dissolved organic carbon (DOC). Further study was warranted to determine the utility of MODIS indices in predicting temporal stream DOC. Stream discharge rates and DOC data were obtained from the USGS National Water Quality Assessment Program (NAWQA) database. Twelve NAWQA monitoring sites were selected for evaluation based on the criteria of having drainage basin sizes less than 600 km2 with relatively continuous, long-term DOC and discharge data. MODIS indices were selected based on their connections with terrestrial DOC and were obtained for each site's catchment area. These included the Normalized Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI), the Daily Photosynthesis (PSN) and the Leaf Area Index (LAI). Regression analysis was used to evaluate the relationships between DOC, discharge and MODIS products. Data analysis revealed several important trends. Sites with strong positive correlation coefficients (r values ranging from 0.462 to 0.831) between DOC and discharge displayed weak correlations with all of the MODIS indices (r values ranging from 0 to 0.322). For sites where the DOC/discharge correlation was weak or negative, MODIS indices were moderately correlated, with r values ranging from 0.35 to 0.647, all of which were significant at less than 1 percent. Some sites that had weak positive correlations with MODIS indices displayed a lag time, that is, the MODIS index rose and fell shortly before the DOC concentration rose and fell. Shifting the MODIS data forward in time by roughly one month significantly increased the DOC/MODIS r values by about 10%. NDVI and EVI displayed the strongest correlations with temporal DOC variability (r values ranging from 0.471 to 0.647), and therefore these indices are the most promising for being incorporated into a model for remotely sensing terrestrial DOC.

Dilute Oxygen Combustion Phase IV Final Report

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

Riley, M.F.

2003-04-30

Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five DOC-based designs and three conventional air5-fired designs using a 10-year net present value calculation. A furnace direct completely with DOC burners offers low capital cost, low fuel rate, and minimal NOx emissions. However, these benefits do not offset the costmore » of oxygen and a full DOC-fired furnace is projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The incremental cost of the improved NOx performance is roughly $6/lb NOx, compared with an estimated $3/lb. NOx for equ8pping a conventional furnace with selective catalytic reduction (SCCR) technology. A furnace fired with DOC burners in the heating zone and ambient temperature (cold) air-fired burners in the soak zone offers low capital cost with less oxygen consumption. However, the improvement in fuel rate is not as great as the full DOC-fired design, and the DOC-cold soak design is also projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The NOx improvement with the DOC-cold soak design is also not as great as the full DOC fired design, and the incremental cost of the improved NOx performance is nearly $9/lb NOx. These results indicate that a DOC-based furnace design will not be generally competitive with conventional technology for new furnace construction under current market conditions. Fuel prices of $7/MMBtu or oxygen prices of $23/ton are needed to make the DOC furnace economics favorable. Niche applications may exist, particularly where access to capital is limited or floor space limitations are critical. DOC technology will continue to have a highly competitive role in retrofit applications requiring increases in furnace productivity.« less

Concentration, UV-spectroscopic characteristics and fractionation of DOC in stormflow from an urban stream, Southern California, USA

USGS Publications Warehouse

Izbicki, J.A.; Pimentel, I.M.; Johnson, Russell; Aiken, G.R.; Leenheer, J.

2007-01-01

The composition of dissolved organic carbon (DOC) in stormflow from urban areas has been greatly altered, both directly and indirectly, by human activities and there is concern that there may be public health issues associated with DOC, which has unknown composition from different sources within urban watersheds. This study evaluated changes in the concentration and composition of DOC in stormflow in the Santa Ana River and its tributaries between 1995 and 2004 using a simplified approach based on the differences in the optical properties of DOC and using operationally defined differences in molecular weight and solubility. The data show changes in the composition of DOC in stormflow during the rainy season and differences associated with runoff from different parts of the basin, including extensive upland areas burned prior to the 2004 rainy season.Samples were collected from the Santa Ana River, which drains ~6950 km2 of the densely populated coastal area of southern California, during 23 stormflows between 1995 and 2004. Dissolved organic carbon (DOC) concentrations during the first stormflows of the ‘winter’ (November to March) rainy season increased rapidly with streamflow and were positively correlated with increased faecal indicator bacteria concentrations. DOC concentrations were not correlated with streamflow or with other constituents during stormflows later in the rainy season and DOC had increasing UV absorbance per unit carbon as the rainy season progressed. DOC concentrations in stormflow from an urban drain tributary to the river also increased during stormflow and were greater than concentrations in the river. DOC concentrations in stormflow from a tributary stream, draining urban and agricultural land that contained more than 320 000 animals, mostly dairy cows, were higher than concentrations in stormflow from the river and from the urban drain. Fires that burned large areas of the basin before the 2004 rainy season did not increase DOC concentrations in the river during stormflow after the fires – possibly because the large watershed of the river damped the effect of the fires. However, the fires increased the hydrophobic neutral organic carbon fraction of DOC in stormflow from the urban drain and the tributary stream.

Non-linear, connectivity and threshold-dominated runoff-generation controls DOC and heavy metal export in a small peat catchment

NASA Astrophysics Data System (ADS)

Birkel, Christian; Broder, Tanja; Biester, Harald

2017-04-01

Peat soils act as important carbon sinks, but they also release large amounts of dissolved organic carbon (DOC) to the aquatic system. The DOC export is strongly tied to the export of soluble heavy metals. The accumulation of potentially toxic substances due to anthropogenic activities, and their natural export from peat soils to the aquatic system is an important health and environmental issue. However, limited knowledge exists as to how much of these substances are mobilized, how they are mobilized in terms of flow pathways and under which hydrometeorological conditions. In this study, we report from a combined experimental and modelling effort to provide greater process understanding from a small, lead (Pb) and arsenic (As) contaminated upland peat catchment in northwestern Germany. We developed a minimally parameterized, but process-based, coupled hydrology-biogeochemistry model applied to simulate detailed hydrometric and biogeochemical data. The model was based on an initial data mining analysis, in combination with regression relationships of discharge, DOC and element export. We assessed the internal model DOC-processing based on stream-DOC hysteresis patterns and 3-hourly time step groundwater level and soil DOC data (not used for calibration as an independent model test) for two consecutive summer periods in 2013 and 2014. We found that Pb and As mobilization can be efficiently predicted from DOC transport alone, but Pb showed a significant non-linear relationship with DOC, while As was linearly related to DOC. The relatively parsimonious model (nine calibrated parameters in total) showed the importance of non-linear and rapid near-surface runoff-generation mechanisms that caused around 60% of simulated DOC load. The total load was high even though these pathways were only activated during storm events on average 30% of the monitoring time - as also shown by the experimental data. Overall, the drier period 2013 resulted in increased nonlinearity, but exported less DOC (115 kg C ha-1 yr-1 ± 11 kg C ha-1 yr-1) compared to the equivalent but wetter period in 2014 (189 kg C ha-1 yr-1 ± 38 kg C ha-1 yr-1). The exceedance of a critical water table threshold (-10 cm) triggered a rapid near-surface runoff response with associated higher DOC transport connecting all available DOC pools, and with subsequent dilution. We conclude that the combination of detailed experimental work with relatively simple, coupled hydrology-biogeochemistry models allowed not only the model to be internally constrained, but also provided important insight into how DOC and tightly coupled heavy metals are mobilized.

Temperature sensitivity of DOC production and transformation in organic soils of the Yukon River Basin, Alaska

NASA Astrophysics Data System (ADS)

O'Donnell, J.; Butler, K. D.; Aiken, G.

2012-12-01

The flux of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems represents a critical component of the high-latitude carbon balance. In the Yukon River basin (YRB), DOC fluxes have declined in recent decades, likely in response to regional permafrost thaw and increased groundwater discharge to river flow. Despite improved flux estimates for many arctic rivers, considerable uncertainty exists regarding the potential response of DOC fluxes to projected warming. To improve estimates of future DOC dynamics, it is important to develop a process-based approach whereby empirical constraints are placed on source and sink terms in both soil and river systems. Here, we examine variability in DOC production and microbially mediated transformations as a function of both temperature and organic matter (OM) composition in soils of the YRB. We conducted "tea" experiments by incubating three organic-soil types that vary with depth and decomposition extent (live/dead moss, fibric OM and humic OM) at two temperatures (4 vs. 20 °C). Leachate samples were collected periodically over a 30-day incubation and characterized for DOC concentration, optical properties (specific UV absorbance at 254 nm or SUVA254, fluorescence), and major chemical fractions using XAD8/XAD4 resins. We observed a non-linear increase in DOC production over time, characterized by a rapid initial release of DOC from soils followed by a slower rise in DOC concentration in subsequent weeks. Mean DOC concentration was described by a significant interaction between organic-soil type and temperature, indicating a strong relationship between temperature sensitivity of net DOC production and the decomposition extent of soil OM. On average across all sampling dates, DOC concentrations were highest in leachate from fibric OM (13.4 to 17.8 mgC L-1), and lowest in leachate from humic OM (3.5 to 8.5 mgC L-1). However, the temperature sensitivity of net DOC production was highest in the humic OM treatment, with mean DOC concentrations increasing by 145% between the 4 and 20°C temperature treatments, whereas DOC concentrations in leachate from fibric OM only increased by 33%. We also observed compositional differences in dissolved organic matter (DOM) across experimental treatments and over time, as reflected by UV absorbance and fluorescence measurements. For instance, mean SUVA254 values increased from near-surface soil (live/dead moss = 2.28 ± 0.27 L mgC m-1) to deeper organic horizons (humic OM = 3.86 ± 0.60 L mgC m-1). SUVA254 also increased over time, suggesting selective mineralization of low-molecular weight compounds and enrichment of the aromatic DOM pool. Together, these data help to distinguish vertical differences in DOM origin and composition through soil profiles, and can be used to track the fate of terrestrial DOC under future warming at high latitudes.

Influence of adsorption versus coprecipitation on the retention of rice straw-derived dissolved organic carbon and subsequent reducibility of Fe-DOC systems

NASA Astrophysics Data System (ADS)

Sodano, Marcella; Lerda, Cristina; Martin, Maria; Celi, Luisella; Said-Pullicino, Daniel

2016-04-01

The dissimilatory reduction of Fe oxides is the main organic C-consuming process in paddy soils under anoxic conditions. The contribution of Fe(III) reduction to anaerobic C mineralization depends on many factors, but most importantly on the bioavailability of labile organic matter and a reducible Fe pool as electron donors and acceptors, respectively. On the other hand, the strong affinity of these minerals for organic matter and their capability of protecting it against microbial decomposition is well known. Natural Fe oxides in these soils may therefore play a key role in determining the C source/sink functions of these agro-ecosystems. Apart from contributing to C stabilization, the interaction between Fe oxides and dissolved organic C (DOC) may influence the structure and reactivity of these natural oxides, and selectively influence the chemical properties of DOC. Indeed, Fe-DOC associations may not only reduce the availability of DOC, but may also limit the microbial reduction of Fe oxides under anoxic conditions. In fact, the accessibility of these minerals to microorganisms, extracellular enzymes, redox active shuttling compound or reducing agents may be impeded by the presence of sorbed organic matter. In soils that are regularly subjected to fluctuations in redox conditions the interaction between DOC and Fe oxides may not only involve organic coatings on mineral surfaces, but also Fe-DOC coprecipitates that form during the rapid oxidation of soil solutions containing important amounts of DOC and Fe(II). However, little is known on how these processes influence DOC retention, and the structure and subsequent reducibility of these Fe-DOC associations. We hypothesized that the nature and extent of the interaction between DOC and Fe oxides may influence the accessibility of the bioavailable Fe pool and consequently its reducibility. We tested this hypothesis by synthesizing a series of Fe-DOC systems with increasing C:Fe ratios prepared by either surface adsorption or coprecipitation, DOC was obtained by incubating a suspension of rice straw in water (straw-solution ratio of 1:30) under oxic conditions at 25° C for 30 days to simulate the decomposition of rice straw in the field. Increasing amounts of DOC were equilibrated (pH = 6) with a known mass of ferrihydrite (initial molar C:Fe ratios of 1, 5 and 10) to obtain surface coated Fe-DOC systems with increasing C loading. On the other hand, coprecipitates with similar initial C:Fe ratios were obtained by oxidation of a Fe(II) solution in the presence of increasing amounts of DOC at pH = 6. A natural Fe-DOC coprecipitate was also obtained by in situ sampling of a paddy soil solution from the topsoil during a cropping season, and subsequent oxidation in the laboratory. The surface and chemical properties of all substrates were subsequently evaluated and compared. We hereby present the first results of the influence of adsorption vs coprecipitation on the selective retention of DOC, structure and surface charge, as well as their susceptibility to chemical reduction with ascorbic acid.

Data Report: Results of the July 2011 Sampling in the Former Brunswick-Altamaha Canal, South of the LCP Chemicals Site, Brunswick, Georgia

EPA Pesticide Factsheets

October 11, 2011 report, prepared for LCP site steering Committee by EPS, presents results of sediment and fish tissue samples. Region ID: 04 DocID: 10839615, DocDate: 10-11-2011. Region ID: 04 DocID: 10839615, DocDate: 10-11-2011

Setting the Conditions for the Rule of Law During Military Interventions

DTIC Science & Technology

2008-05-27

Transition and Reconstruction Operations Joint Operating Concept, ver. 2.0 (Washington, DC: DoD, December 2006), 9. iv Milan N. Vego, Joint...prosecutors, judges and corrections personnel within the U.S. Dep’t of State). iii GEN Maxwell Thurman, quoted in Richard H. Schultz , In the Aftermath of...U.N. Doc. S/RES/1483 (2003). lviii Ricks, 179. lix Schultz , 16. lx Ibid., 17. lxi SSTR JOC, 30. lxii Kelly, 407; Hague Regulations

Status of Research in Underwater Physiology

DTIC Science & Technology

1956-03-01

Qc ýLEVELSý A 0 ~STAT US O F RESEARCH IN ~ UNDERWATER PHYSIOLOGY MARCH 1958I 0 79 0 .15 U This doc-iment was prapartd Ly the Physiology Grouo of the...under- water breathing patterns, are vitally necessary to determine whether or not rad- ical deviations from the present design of self-contained...certain SCUBA operations. In single mul- tilevel dives no known tables could apply without a rigid control of the depth-time factors, and even under

Special Operations Forces and Conventional Forces: Integration, Interoperability, and Interdependence

DTIC Science & Technology

2016-12-07

Phasing Model8 WESBROCK, HARNED, AND PLOUS 88 | FEATURES PRISM 6, no. 3 views on how to design, plan, and execute operat ions and campaigns. The...population-centric” operational environment. SOF views campaign design dif- ferently from the six-phase model in joint doc- trine depicted above.9...U.S. interests. This difference between SOF and CF views of cam- paigning can hamper integration from the start of an operation if components of the

The Influence of Submarine Groundwater Discharge on Nearshore Marine Dissolved Organic Carbon Reactivity, Concentration Dynamics, and Offshore Export

NASA Astrophysics Data System (ADS)

Goodridge, B.

2017-12-01

Dissolved organic carbon (DOC) is the largest pool of reduced carbon in the oceans, with a reservoir equivalent to atmospheric CO2. In nearshore marine regions, DOC sources include primary production, terrestrial DOC delivered by river discharge, and/or terrestrial and marine DOC delivered via submarine groundwater discharge (SGD). While the importance of SGD to coastal carbon cycling has been implicated, the actual influence of this process on nearshore carbon dynamics and offshore export has not been explicitly identified. This study, conducted at a predominantly marine-influenced intertidal beach-nearshore ocean system along the Santa Barbara, California coastline, aimed to address this knowledge gap. I coupled dark, temperature-controlled laboratory incubations, radioisotopic (Rn-222) SGD estimates, and a DOC box model to identify the influence of pore water mixing with seawater on nearshore DOC reactivity, concentration dynamics, and offshore export. Even with a relatively low volumetric contribution, SGD pore water mixing altered nearshore DOC reactivity, and elevated the nearshore DOC concentration by 0.9 to 5.6 µmol L-1 over nearshore seawater residence times ranging from 1 to 6 days. These elevated DOC concentrations were equivalent to 1.2 to 7.5% of the mean offshore DOC concentration taken during the summer months in the Santa Barbara Channel, when the coastal water column is highly thermally stratified. Despite the challenge of assessing carbon dynamics in physically and biogeochemically complex nearshore marine regions, this study demonstrates the need for future investigations to assess and account for SGD as a non-trivial component of coastal marine carbon cycles.

Climate change and dissolved organic carbon export to the Gulf of Maine

USGS Publications Warehouse

Huntington, Thomas G.; Balch, William M.; Aiken, George R.; Sheffield, Justin; Luo, Lifeng; Roesler, Collin S.; Camill, Philip

2016-01-01

Ongoing climate change is affecting the concentration, export (flux), and timing of dissolved organic carbon (DOC) exported to the Gulf of Maine (GoM) through changes in hydrologic regime. DOC export was calculated for water years 1950 through 2013 for 20 rivers and for water years 1930 through 2013 for 14 rivers draining to the GoM. DOC export was also estimated for the 21st century based on climate and hydrologic modeling in a previously published study. DOC export was calculated by using the regression model LOADEST to fit seasonally adjusted concentration discharge (C-Q) relations. Our results are an analysis of the sensitivity of DOC export to changes in hydrologic conditions over time since land cover and vegetation were held constant over time. Despite large interannual variability, all rivers had increasing DOC export during winter and these trends were significant (p < 0.05) in 10 out of 20 rivers for 1950 to 2013 and in 13 out of 14 rivers for 1930 to 2013. All rivers also had increasing annual export of DOC although fewer trends were statistically significant than for winter export. Projections for DOC export during the 21st century were variable depending on the climate model and greenhouse gas emission scenario that affected future river discharge through effects on precipitation and evapotranspiration. The most consistent result was a significant increase in DOC export in winter in all model-by-emission scenarios. DOC export was projected to decrease during the summer in all model-by-emission scenarios, with statistically significant decreases in half of the scenarios.

High light intensity mediates a shift from allochthonous to autochthonous carbon use in phototrophic stream biofilms

NASA Astrophysics Data System (ADS)

Wagner, Karoline; Bengtsson, Mia M.; Findlay, Robert H.; Battin, Tom J.; Ulseth, Amber J.

2017-07-01

Changes in the riparian vegetation along stream channels, diurnal light availability, and longitudinal fluctuations in the local light regime in streams influence primary production and carbon (C) cycling in benthic stream biofilms. To investigate the influence of light availability on the uptake dynamics of autochthonous and allochthonous dissolved organic carbon (DOC) in benthic biofilms, we experimentally added 13C-labeled allochthonous DOC to biofilms grown under light intensities ranging from 5 to 152 μmol photons m-2 s-1. We calculated the net C flux, which showed that benthic biofilms released autochthonous DOC across the entire light gradient. Light availability and diurnal light patterns influenced C uptake by benthic biofilms. More allochthonous DOC was respired under low light availability and at night, whereas under high light availability and during the day mainly autochthonous C was respired by the benthic biofilm community. Furthermore, phenol oxidase activity (indicative of allochthonous DOC uptake) was more elevated under low light availability, whereas beta-glucosidase activity (indicative of autochthonous DOC use) increased with light intensity. Collectively, our results suggest that biofilms exposed to high light inputs preferentially used autochthonous DOC, whereas biofilms incubated at attenuated levels showed greater use of allochthonous DOC. This has implications for the spatial dynamics of DOC uptake in streams and speaks against the occurrence of priming effects in algal-dominated stream biofilms.

Influence of land cover on riverine dissolved organic carbon concentrations and export in the Three Rivers Headwater Region of the Qinghai-Tibetan Plateau.

PubMed

Ma, Xiaoliang; Liu, Guimin; Wu, Xiaodong; Smoak, Joseph M; Ye, Linlin; Xu, Haiyan; Zhao, Lin; Ding, Yongjian

2018-07-15

The Qinghai-Tibetan plateau (QTP) stores a large amount of soil organic carbon and is the headwater region for several large rivers in Asia. Therefore, it is important to understand the influence of environmental factors on river water quality and the dissolved organic carbon (DOC) export in this region. We examined the water physico-chemical characteristics, DOC concentrations and export rates of 7 rivers under typical land cover types in the Three Rivers Headwater Region during August 2016. The results showed that the highest DOC concentrations were recorded in the rivers within the catchment of alpine wet meadow and meadow. These same rivers had the lowest total suspended solids (TSS) concentrations. The rivers within steppe and desert had the lowest DOC concentrations and highest TSS concentrations. The discharge rates and catchment areas were negatively correlated with DOC concentrations. The SUVA 254 values were significantly negatively correlated with DOC concentrations. The results suggest that the vegetation degradation, which may represent permafrost degradation, can lead to a decrease in DOC concentration, but increasing DOC export and soil erosion. In addition, some of the exported DOC will rapidly decompose in the river, and therefore affect the regional carbon cycle, as well as the water quality in the source water of many large Asian rivers. Copyright © 2018 Elsevier B.V. All rights reserved.

Enhanced antitumor effects by docetaxel/LL37-loaded thermosensitive hydrogel nanoparticles in peritoneal carcinomatosis of colorectal cancer

PubMed Central

Fan, Rangrang; Tong, Aiping; Li, Xiaoling; Gao, Xiang; Mei, Lan; Zhou, Liangxue; Zhang, Xiaoning; You, Chao; Guo, Gang

2015-01-01

Intraperitoneal chemotherapy was explored in clinical trials as a promising strategy to improve the therapeutic effects of chemotherapy. In this work, we developed a biodegradable and injectable drug-delivery system by coencapsulation of docetaxel (Doc) and LL37 peptide polymeric nanoparticles (Doc+LL37 NPs) in a thermosensitive hydrogel system for colorectal peritoneal carcinoma therapy. Firstly, polylactic acid (PLA)-Pluronic L35-PLA (PLA-L35-PLA) was explored to prepare the biodegradable Doc+LL37 NPs using a water-in-oil-in-water double-emulsion solvent-evaporation method. Then, biodegradable and injectable thermosensitive PLA-L64-PLA hydrogel with lower sol–gel transition temperature at around body temperature was also prepared. Transmission electron microscopy revealed that the Doc+LL37 NPs formed with the PLA-L35-PLA copolymer were spherical. Fourier-transform infrared spectra certified that Doc and LL37 were encapsulated successfully. X-ray diffraction diagrams indicated that Doc was encapsulated amorphously. Intraperitoneal administration of Doc+LL37 NPs–hydrogel significantly suppressed the growth of HCT116 peritoneal carcinomatosis in vivo and prolonged the survival of tumor-bearing mice. Our results suggested that Doc+LL37 NPs–hydrogel may have potential clinical applications. PMID:26664119

Effect of wildfires on physicochemical changes of watershed dissolved organic matter.

PubMed

Revchuk, Alex D; Suffet, I H

2014-04-01

Physicochemical characterization of dissolved organic carbon (DOC) provides essential data to describe watershed characteristics after drastic changes caused by wildfires. Post-fire watershed behavior is important for water source selection, management, and drinking water treatment optimization. Using ash and other burned vegetation fragments, a leaching procedure was implemented to describe physicochemical changes to watershed DOC caused by wildfires. Samples were collected after the 2007 and 2009 wildfires near Santa Barbara, California. Substantial differences in size distribution (measured by ultrafiltration), polarity (measured by polarity rapid assessment method), and the origin of leached DOC (measured by fluorescence) were observed between burned and unburned sites. Recently burned ash had 10 times the DOC leaching potential, and was dominated by large size fragments, compared to weathered 2-year-old ash. Charged DOC fractions were found to positively correlate with DOC size, whereas hydrophobic and hydrophilic DOC fractions were not. Proteins were only observed in recently burned ash and were indicative of recent post-fire biological activity.

Simulating dissolved organic carbon dynamics at the swedish integrated monitoring sites with the integrated catchments model for carbon, INCA-C.

PubMed

Futter, M N; Löfgren, S; Köhler, S J; Lundin, L; Moldan, F; Bringmark, L

2011-12-01

Surface water concentrations of dissolved organic carbon ([DOC]) are changing throughout the northern hemisphere due to changes in climate, land use and acid deposition. However, the relative importance of these drivers is unclear. Here, we use the Integrated Catchments model for Carbon (INCA-C) to simulate long-term (1996-2008) streamwater [DOC] at the four Swedish integrated monitoring (IM) sites. These are unmanaged headwater catchments with old-growth forests and no major changes in land use. Daily, seasonal and long-term variations in streamwater [DOC] driven by runoff, seasonal temperature and atmospheric sulfate (SO₄(2-)) deposition were observed at all sites. Using INCA-C, it was possible to reproduce observed patterns of variability in streamwater [DOC] at the four IM sites. Runoff was found to be the main short-term control on [DOC]. Seasonal patterns in [DOC] were controlled primarily by soil temperature. Measured SO₄(2-) deposition explained some of the long-term [DOC] variability at all sites.

The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer

PubMed Central

Tanaka, Kazuki; Takesue, Nobuyuki; Nishioka, Jun; Kondo, Yoshiko; Ooki, Atsushi; Kuma, Kenshi; Hirawake, Toru; Yamashita, Youhei

2016-01-01

The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation. PMID:27658444

Performance evaluation of a biodiesel fuelled transportation engine retrofitted with a non-noble metal catalysed diesel oxidation catalyst for controlling unregulated emissions.

PubMed

Shukla, Pravesh Chandra; Gupta, Tarun; Agarwal, Avinash Kumar

2018-02-15

In present study, engine exhaust was sampled for measurement and analysis of unregulated emissions from a four cylinder transportation diesel engine using a state-of-the-art FTIR (Fourier transform infrared spectroscopy) emission analyzer. Test fuels used were Karanja biodiesel blend (B20) and baseline mineral diesel. Real-time emission measurements were performed for raw exhaust as well as exhaust sampled downstream of the two in-house prepared non-noble metal based diesel oxidation catalysts (DOCs) and a baseline commercial DOC based on noble metals. Two prepared non-noble metal based DOCs were based on Co-Ce mixed oxide and Lanthanum based perovskite catalysts. Perovskite based DOC performed superior compared to Co-Ce mixed oxide catalyst based DOC. Commercial noble metal based DOC was found to be the most effective in reducing unregulated hydrocarbon emissions in the engine exhaust, followed by the two in-house prepared non-noble metal based DOCs. Copyright © 2017 Elsevier B.V. All rights reserved.

Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation.

PubMed

Fontela, Marcos; García-Ibáñez, Maribel I; Hansell, Dennis A; Mercier, Herlé; Pérez, Fiz F

2016-05-31

The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr(-1)). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr(-1)) is considerable and represents almost a third of the atmospheric CO2 uptake in the region.

Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation

PubMed Central

Fontela, Marcos; García-Ibáñez, Maribel I.; Hansell, Dennis A.; Mercier, Herlé; Pérez, Fiz F.

2016-01-01

The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr−1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr−1) is considerable and represents almost a third of the atmospheric CO2 uptake in the region. PMID:27240625

Prevalence of Circulating Tumor Cells After Adjuvant Chemotherapy With or Without Anthracyclines in Patients With HER2-negative, Hormone Receptor-positive Early Breast Cancer.

PubMed

Schramm, Amelie; Schochter, Fabienne; Friedl, Thomas W P; de Gregorio, Nikolaus; Andergassen, Ulrich; Alunni-Fabbroni, Marianna; Trapp, Elisabeth; Jaeger, Bernadette; Heinrich, Georg; Camara, Oumar; Decker, Thomas; Ober, Angelika; Mahner, Sven; Fehm, Tanja N; Pantel, Klaus; Fasching, Peter A; Schneeweiss, Andreas; Janni, Wolfgang; Rack, Brigitte K

2017-07-01

Use of anthracycline-based chemotherapy in patients with early breast cancer (EBC) has been well-established but is often associated with cardiotoxicity. Based on data suggesting a limited benefit of anthracyclines in human epidermal growth factor receptor 2 (HER2)-negative patients, the Simultaneous Study of Docetaxel Based Anthracycline Free Adjuvant Treatment Evaluation, as well as Life Style Intervention Strategies (SUCCESS) C study randomized patients to either anthracycline-containing or anthracycline-free chemotherapy. Given the proven prognostic value of circulating tumor cells (CTCs) in EBC, we compared the prevalence of CTCs after chemotherapy between both treatment arms for a preliminary efficacy assessment. The SUCCESS C trial (NCT00847444) is an open-label, phase III study randomizing 3547 patients with HER2-negative EBC to either 3 cycles of epirubicin, 5-fluorouracil, and cyclophosphamide followed by 3 cycles of docetaxel (FEC-DOC) or 6 cycles of docetaxel and cyclophosphamide (DOC-C). CTC status was prospectively evaluated in hormone receptor-positive patients at the time of last chemotherapy cycle using the US Food and Drug Administration-approved CellSearch System (Janssen Diagnostics). Data on CTC status were available for 1766 patients. Overall, CTCs were found in 221 (12.5%) patients. Univariate analyses revealed that presence of CTCs at time of last chemotherapy cycle was not significantly associated with tumor or patient characteristics (all P > .1). There was no significant difference with respect to presence of CTCs between patients randomized to FEC-DOC or DOC-C (11.5% vs. 13.6%; P = .18). The comparable prevalence of CTCs at the time of last chemotherapy cycle may indicate that anthracycline-free chemotherapy is equally effective to anthracycline-containing chemotherapy in HER2-negative, hormone receptor-positive EBC. However, efficacy data from the final survival analysis of SUCCESS C have to be awaited to confirm these preliminary findings. Copyright © 2017 Elsevier Inc. All rights reserved.

High-resolution chemical and hydrologic records identify environmental factors that control coastal anchialine cave ecosystem function

NASA Astrophysics Data System (ADS)

Brankovits, D.; Pohlman, J.; Lapham, L.; Casso, M.; Roth, E.; Lowell, N. S.; Iliffe, T. M.

2015-12-01

Anchialine caves host a coastal aquifer ecosystem occupied by cave-adapted crustaceans that reside within distinct fresh, brackish and marine waters. Our initial investigation of this subsurface ecotone in the Yucatan Peninsula (Mexico) provides stable isotope-based evidence that methane and dissolved organic carbon (DOC) are the primary sources of energy and carbon for the food web. However, the frequency of observations is sparse, leaving us 'in the dark' with respect to the temporal dynamics of the ecosystem function. In this study, we obtained undisturbed vertical profiles of methane, DOC and DIC concentration and isotopic composition with the 'Octopipi' water sampler from an anchialine cave located ~8 km from the coastline. To document the temporal variability of methane availability in the cave, we deployed an osmotically-driven pump (OsmoSampler). Data loggers recorded dissolved oxygen (DO), salinity, temperature and current velocities, and a rain gauge recorded precipitation. A high-methane water mass near the ceiling (up to 7795 nM) contained elevated concentration (900 µM), 13C-depleted (-27.8 to -28.2 ‰) DOC, suggesting terrestrial organic matter input from the overlying soils. Low-methane saline water (36 to 84 nM) had lower concentration DOC (15 to 97 µM) with a similar δ13C (-25.9 to -27.2 ‰), suggesting significant terrestrial organic matter consumption or removal with increasing depth, from fresh to saline water, within the water column. Our 6-month water chemistry record reveals high concentrations of methane in the wet season, especially following rainfall events, and relatively lower methane concentrations in the dry season. These observations suggest rain flushes methane generated in overlying anoxic soils into the cave. DO, water level, and groundwater flow patterns were also linked to the precipitation record. These data provide novel insight into the interconnections between external climate forcing and subterranean anchialine ecosystems within coastal aquifers.

The significance of GW-SW interactions for biogeochemical processes in sandy streambeds

NASA Astrophysics Data System (ADS)

Arnon, Shai; De Falco, Natalie; Fox, Aryeh; Laube, Gerrit; Schmidt, Christian; Fleckenstein, Jan; Boano, Fulvio

2015-04-01

Stream-groundwater interactions have a major impact on hyporheic exchange fluxes in sandy streambeds. However, the physical complexity of natural streams has limited our ability to study these types of interactions systematically, and to evaluate their importance to biogeochemical processes and nutrient cycling. In this work we were able to quantify the effect of losing and gaining fluxes on hyporheic exchange and nutrient cycling in homogeneous and heterogeneous streambeds by combining experiments in laboratory flumes and modeling. Tracer experiments for measuring hyporheic exchange were done using dyes and NaCl under various combinations of overlying water velocity and losing or gaining fluxes. Nutrient cycling experiments were conducted after growing a benthic biofilm by spiking with Sodium Benzoate (as a source of labile dissolved organic carbon, DOC) and measuring DOC and oxygen dynamics. The combination of experimental observations and modeling revealed that interfacial transport increases with the streambed hydraulic conductivity and proportional to the square of the overlying water velocity. Hyporheic exchange fluxes under losing and gaining flow conditions were similar, and became smaller when the losing or gaining flux increases. Increasing in streambed hydraulic conductivity led to higher hyporheic fluxes and reduction in the effects of losing and gaining flow conditions to constrain exchange. Despite the evident effect of flow conditions on hyporheic exchange, labile DOC uptake was positively linked to increasing overlying water velocity but was not affected by losing and gaining fluxes. This is because microbial aerobic activity was taking place at the upper few millimeters of the streambed as shown by local oxygen consumption rates, which was measured using microelectrodes. Based on modeling work, it is expected that GW-SW interaction will be more significant for less labile DOC and anaerobic processes. Our results enable us to study systematically the coupling between flow conditions and biogeochemical processes under highly controlled physical and chemical conditions and are expected to improve our understanding of nutrient cycling in streams.

Hydrological Controls on Dissolved Organic Matter Quality and Export in a Coastal River System in Southeastern USA

NASA Astrophysics Data System (ADS)

Bhattacharya, R.; Osburn, C. L.

2017-12-01

Dissolved organic matter (DOM) exported from river catchments can influence the biogeochemical processes in coastal environments with implications for water quality and carbon budget. High flow conditions are responsible for most DOM export ("pulses") from watersheds, and these events reduce DOM transformation and production by "shunting" DOM from river networks into coastal waters: the Pulse-Shunt Concept (PSC). Subsequently, the source and quality of DOM is also expected to change as a function of river flow. Here, we used stream dissolved organic carbon concentrations ([DOC]) along with DOM optical properties, such as absorbance at 350 nm (a350) and fluorescence excitation and emission matrices modeled by parallel factor analysis (PARAFAC), to characterize DOM source, quality and fluxes under variable flow conditions for the Neuse River, a coastal river system in the southeastern US. Observations were made at a flow gauged station above head of tide periodically between Aug 2011 and Feb 2013, which captured low flow periods in summer and several high flow events including Hurricane Irene. [DOC] and a350 were correlated and varied positively with river flow, implying that a large portion of the DOM was colored, humic and flow-mobilized. During high flow conditions, PARAFAC results demonstrated the higher influx of terrestrial humic DOM, and lower in-stream phytoplankton production or microbial degradation. However, during low flow, DOM transformation and production increased in response to higher residence times and elevated productivity. Further, 70% of the DOC was exported by above average flows, where 3-4 fold increases in DOC fluxes were observed during episodic events, consistent with PSC. These results imply that storms dramatically affects DOM export to coastal waters, whereby high river flow caused by episodic events primarily shunt terrestrial DOM to coastal waters, whereas low flow promotes in-stream DOM transformation and amendment with microbial DOM.

Investigating Forest Harvest Effects on DOC Concentration and Quality: An In Situ, High Resolution Approach to Quantifying DOC Export Dynamics

NASA Astrophysics Data System (ADS)

Jollymore, A. J.; Johnson, M. S.; Hawthorne, I.

2013-12-01

Justification: Forest harvest effects on water quality can signal alterations in hydrologic and ecologic processes incurred as a result of forest harvest activities. Organic matter (OM), specifically dissolved organic carbon (DOC), plays a number of important roles mediating UV-light penetration, redox reactivity and microbial activity within aquatic ecosystems. Quantification of DOC is typically pursued via grab sampling followed by chemical or spectrophotometric analysis, limiting the temporal resolution obtained as well as the accuracy of export calculations. The advent of field-deployable sensors capable of measuring DOC concentration and certain quality characteristics in situ provides the ability to observe dynamics at temporal scales necessary for accurate calculation of DOC flux, as well as the observation of dynamic changes in DOC quality on timescales impossible to observe through grab sampling. Methods: This study utilizes a field deployable UV-Vis spectrophotometer (spectro::lyzer, s::can, Austria) to investigate how forest harvest affects DOC export. The sensor was installed at an existing hydrologic monitoring site at the outlet of a headwater stream draining a small (91 hectare) second growth Douglasfir-dominated catchment near Campbell River on Vancouver Island, British Columbia. Measurement began late in 2009, prior to forest harvest and associated activities such as road building (which commenced in October 2010 and ended in early 2011), and continues to present. During this time - encompassing the pre, during and post-harvest conditions - the absorbance spectrum of stream water from 200 to 750 nm was measured. DOC concentration and spectroscopic indices related to DOC quality (including SUVA, which relates to the concentration of aromatic carbon, and spectral slope) were subsequently calculated for each spectra obtained at 30-minute intervals. Results and conclusions: High frequency measurements of DOC show that overall export of OM increased in the months following harvest. A major advantage of this study is the use of in situ measurements, allowing for high temporal resolution of DOC dynamics occurring within specific hydrologic events. For example, concentration-discharge relationships for both the pre- and post-logging periods demonstrate similar clockwise hysteresis during individual storm events, while the magnitude of change dramatically increased during the post-logging period. However, in situ measurements of SUVA over this period suggest that DOC quality may be less affected by forest harvest than overall DOC concentration, where high frequency data also allows for the observation of SUVA and spectral slope responses to specific hydrologic events during the pre- and post- harvest period.

Water-quality changes and organic-carbon characterization during recharge with recycled water at a research basin in Montebello Forebay, Los Angeles County, California, 1991-1996

USGS Publications Warehouse

Schroeder, Roy A.

2003-01-01

During the early 1990s, the U.S. Geological Survey (USGS) investigated water-quality changes that occur in treated municipal wastewater (recycled water) at a small research basin constructed in the Montebello Forebay of the Central Ground-Water Basin in south-central Los Angeles County. The instrumented research basin is located on a 1/2-acre site at the upgradient end of the San Gabriel River Coastal Spreading Grounds where recharge has been augmented using recycled water since 1961. The facility was used to measure attenuation in selected constituents as recycled water delivered to the basin percolates downward and moves laterally beneath the basin. Attenuation in aqueous concentration was found to range from 20 to 60 percent for total dissolved nitrogen and was about one-third for dissolved organic carbon (DOC). Isotopic data confirmed permanent loss of nitrogen by denitrification. Detailed investigations showed that there were no large differences in the loss of various components of the DOC at the structural or compound level, although surfactants and their metabolites were abundant and did persist in the subsurface. The DOC of wastewater origin was found to have a lower trihalomethane (THM) formation potential upon chlorination than does organic matter of natural origin from most surface-water sources. The organization of this report into 12 topical chapters, and the report's relation to additional USGS publications from this study, is noted in a preface.

Local and regional scale exchanges of dissolved organic carbon (DOC) between tidal wetlands and their adjacent coastal waters

NASA Astrophysics Data System (ADS)

Osburn, C. L.; Joshi, I.; Lebrasse, M. C.; Oviedo-Vargas, D.; Bianchi, T. S.; Bohnenstiehl, D. R.; D'Sa, E. J.; He, R.; Ko, D.; Arellano, A.; Ward, N. D.

2017-12-01

The contribution of blue carbon from tidal wetlands to the coastal ocean in the form of dissolved organic carbon (DOC) represents a terrestrial-aquatic linkage of increasing importance. DOC flux results will be presented from local (tidal creek) and regional (bays) scale studies in which various combinations of field observations, ocean-color satellite observations, and the outputs of high-resolution hydrodynamic models were used to estimate DOC export. The first project was located in Bald Head Creek, a tributary to the Cape Fear River estuary in eastern North Carolina (NC). DOC fluxes were computed using a bathymetric data collected via unmanned surface vehicle (USV) and a numerical hydrodynamic model (SCHISM) based on the relationships between colored dissolved organic matter (CDOM) absorption, DOC concentration, and salinity taken from field observations. Model predictions estimated an annual net export of DOC at 54 g C m-2 yr-1 from the tidal creek to the adjacent estuary. Carbon stable isotope (δ13C) values were used to estimate the contribution of wetland carbon to this export. In the second project, DOC fluxes from the Apalachicola Bay, FL, Barataria Bay, LA, were based on the development of algorithms between DOC and CDOM absorption derived from the VIIRS ocean color sensor. The Navy Coastal Ocean Model (NCOM) was used to compute salt flux estimates from each bay to the Louisiana-Texas shelf. The relationship between salinity and CDOM was used to estimate net annual DOC exports of 8.35 x 106 g C m-2 y-1 (Apalachicola Bay) and 7.14 x 106 g C m-2 yr-1 (Barataria Bay). These values approximate 13% and 9% of the annual loads of DOC from the Mississippi River to the Gulf of Mexico, respectively. CDOM and lignin were used in a mixing model to estimate wetland-derived DOC were 2% for Apalachicola Bay and 13% for Barataria Bay, the latter having one of the highest rates of relative sea level rise in North America. Results from our project demonstrated the utility of CDOM, amenable to high resolution observations from multiple platforms, as a basis for constraining the heterogeneity of DOC exports from tidal wetlands to estuaries and coastal waters using numerical models at local and regional scales.

Flux of carbon from 14C-enriched leaf litter throughout a forest soil mesocosm

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

Froberg, Mats J.; Hanson, Paul J; Trumbore, Susan E.

2009-01-01

The role of DOC for the build-up of soil organic carbon pools is still not well known, but it is thought to play a role in the transport of carbon to a greater depth where it becomes more stable. The aim of this study was to elucidate within-year dynamics of carbon transport from litter to the O (Oe and Oa) and A horizons. Mesocosms with constructed soil profiles were used to study dynamics of C transport from 14C-enriched (about 1000 ) leaf litter to the Oe/Oa and A horizons as well as the mineralization of leaf litter. The mesocosms weremore » placed in the field for 17 months during which time fluxes and 14C content of DOC and CO2 were measured. Changes in 14C in leaf litter and bulk soil C pools were also recorded. Significant simultaneous release and immobilization of DOC occurring in both the O and A horizons was hypothesized. Contrary to our hypothesis, DOC released from the labeled Oi horizon was not retained within the Oe/Oa layer. DOC originating in the unlabeled Oe/Oa layer was also released for transport. Extensive retention of DOC occurred in the A horizon. DOC leaching from A horizon consisted of a mix of DOC from different sources, with a main fraction originating in the A horizon and a smaller fraction leached from the overlaying horizons. The C and 14C budget for the litter layer also indicated a surprisingly large amount of carbon with ambient Δ14C-signature to be respired from this layer. Data for this site also suggested significant contributions from throughfall to dissolved organic carbon (DOC) transport into and respiration from the litter layer. The results from this study showed that DOC retentionwas low in the O horizon and therefore not important for the O horizon carbon budget. In the A horizon DOC retention was extensive, but annual DOC input was small compared to C stocks and therefore not important for changes in soil C on an annual timescale.« less

Identification and analysis of low-molecular-weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

NASA Astrophysics Data System (ADS)

O'Donnell, Emily C.; Wadham, Jemma L.; Lis, Grzegorz P.; Tranter, Martyn; Pickard, Amy E.; Stibal, Marek; Dewsbury, Paul; Fitzsimons, Sean

2016-07-01

Determining the concentration and composition of dissolved organic carbon (DOC) in glacial ecosystems is important for assessments of in situ microbial activity and contributions to wider biogeochemical cycles. Nonetheless, there is limited knowledge of the abundance and character of DOC in basal ice and the subglacial environment and a lack of quantitative data on low-molecular-weight (LMW) DOC components, which are believed to be highly bioavailable to microorganisms. We investigated the abundance and composition of DOC in basal ice via a molecular-level DOC analysis. Spectrofluorometry and a novel ion chromatographic method, which has been little utilized in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates, and carboxylic acids) in basal ice from four glaciers, each with a different type of overridden material (i.e. the pre-entrainment sedimentary type such as lacustrine material or palaeosols). Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse free amino acid (FAA) pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard), and Engabreen (Norway) were low (0-417 nM C), attributed to the relatively refractory nature of the OC in the overridden palaeosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (> 17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet subglacial sediments.

The effectiveness of arbuscular-mycorrhizal fungi and Aspergillus niger or Phanerochaete chrysosporium treated organic amendments from olive residues upon plant growth in a semi-arid degraded soil.

PubMed

Medina, A; Roldán, A; Azcón, R

2010-12-01

Arbuscular mycorrhizal (AM) fungi and a residue from dry olive cake (DOC) supplemented with rock phosphate (RP) and treated with either Aspergillus niger (DOC-A) or Phanerochaete chrysosporium (DOC-P), were assayed in a natural, semi-arid soil using Trifolium repens or Dorycnium pentaphyllum plants. The effects of the AM fungi and/or DOC-A were compared with P-fertilisation (P) over eleven successive harvests to evaluate the persistence of the effectiveness of the treatments. The biomass of dually-treated plants after four successive harvests was greater than that obtained for non-treated plants or those receiving the AM inoculum or DOC-A treatments after eleven yields. The AM inoculation was critical for obtaining plant growth benefit from the application of fermented DOC-A residue. The abilities of the treatments to prevent plant drought stress were also assayed. Drought-alleviating effects were evaluated in terms of plant growth, proline and total sugars concentration under alternative drought and re-watering conditions (8th and 9th harvests). The concentrations of both compounds in plant biomass increased under drought when DOC-A amendment and AM inoculation were employed together: they reinforced the plant drought-avoidance capabilities and anti-oxidative defence. Water stress was less compensated in P-fertilised than in DOC-A-treated plants. DOC-P increased D. pentaphyllum biomass, shoot P content, nodule number and AM colonisation, indicating the greater DOC-transforming ability of P. chrysosporium compared to A. niger. The lack of AM colonisation and nodulation in this soil was compensated by the application of DOC-P, particularly with AM inoculum. The management of natural resources (organic amendments and soil microorganisms) represents an important strategy that assured the growth, nutrition and plant establishment in arid, degraded soils, preventing the damage that arises from limited water and nutrient supply. Copyright © 2010 Elsevier Ltd. All rights reserved.

Relative importance of multiple factors on terrestrial loading of DOC to Arctic river networks

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

Kicklighter, David W.; Hayes, Daniel J; Mcclelland, James W

2014-01-01

Terrestrial carbon dynamics influence the contribution of dissolved organic carbon (DOC) to river networks in addition to controlling carbon fluxes between the land surface and the atmosphere. In this study, we use a biogeochemical process model to simulate the lateral transfer of DOC from land to the Arctic Ocean via riverine transport. We estimate that the pan-arctic watershed has contributed, on average, 32 Tg C/yr of DOC to the Arctic Ocean over the 20th century with most coming from the extensive area of boreal deciduous needle-leaved forests and forested wetlands in Eurasian watersheds. We also estimate that the rate ofmore » terrestrial DOC loading has been increasing by 0.037 Tg C/yr2 over the 20th century primarily as a result of increases in air temperatures and precipitation. These increases have been partially compensated by decreases in terrestrial DOC loading caused by wildfires. Other environmental factors (CO2 fertilization, ozone pollution, atmospheric nitrogen deposition, timber harvest, agriculture) are estimated to have relatively small effects on terrestrial DOC loading to arctic rivers. The effects of the various environmental factors on terrestrial carbon dynamics have both compensated and enhanced concurrent effects on hydrology to influence terrestrial DOC loading. Future increases in riverine DOC concentrations and export may occur from warming-induced increases in terrestrial DOC production associated with enhanced microbial metabolism and the exposure of additional organic matter from permafrost degradation along with decreases in water yield associated with warming-induced increases in evapotranspiration. Improvements in simulating terrestrial DOC loading to pan-arctic rivers in the future will require better information on the spatial distribution of precipitation and its temporal trends, carbon dynamics of larch-dominated ecosystems in eastern Siberia, and the role of industrial organic effluents on carbon budgets of rivers in western Russia.« less

Dissolved Organic Matter Land-Ocean Linkages in the Arctic

NASA Astrophysics Data System (ADS)

Mann, P. J.; Spencer, R. M.; Hernes, P. J.; Tank, S. E.; Striegl, R.; Dyda, R. Y.; Peterson, B. J.; McClelland, J. W.; Holmes, R. M.

2012-04-01

Rivers draining into the Arctic Ocean exhibit high concentrations of terrigenous dissolved organic carbon (DOC), and recent studies indicate that DOC export is changing due to climatic warming and alteration in permafrost condition. The fate of exported DOC in the Arctic Ocean is important for understanding the regional carbon cycle and remains a point of discussion in the literature. As part of the NSF funded Arctic Great Rivers Observatory (Arctic-GRO) project, samples were collected for DOC, chromophoric and fluorescent dissolved organic matter (CDOM & FDOM) and lignin phenols from the Ob', Yenisey, Lena, Kolyma, Mackenzie and Yukon rivers in 2009 - 2010. DOC and lignin concentrations were elevated during the spring freshet and measurements related to DOC composition indicated an increasing contribution from terrestrial vascular plant sources at this time of year (e.g. lignin carbon-normalized yield, CDOM spectral slope, SUVA254, humic-like fluorescence). CDOM absorption was found to correlate strongly with both DOC (r2=0.83) and lignin concentration (r2=0.92) across the major arctic rivers. Lignin composition was also successfully modeled using FDOM measurements decomposed using PARAFAC analysis. Utilizing these relationships we modeled loads for DOC and lignin export from high-resolution CDOM measurements (daily across the freshet) to derive improved flux estimates, particularly from the dynamic spring discharge maxima period when the majority of DOC and lignin export occurs. The new load estimates for DOC and lignin are higher than previous evaluations, emphasizing that if these are more representative of current arctic riverine export, terrigenous DOC is transiting through the Arctic Ocean at a faster rate than previously thought. It is apparent that higher resolution sampling of arctic rivers is exceptionally valuable with respect to deriving accurate fluxes and we highlight the potential of CDOM in this role for future studies and the applicability of in-situ CDOM sensors.

Multi-site Field Verification of Laboratory Derived FDOM Sensor Corrections: The Good, the Bad and the Ugly

NASA Astrophysics Data System (ADS)

Saraceno, J.; Shanley, J. B.; Aulenbach, B. T.

2014-12-01

Fluorescent dissolved organic matter (FDOM) is an excellent proxy for dissolved organic carbon (DOC) in natural waters. Through this relationship, in situ FDOM can be utilized to capture both high frequency time series and long term fluxes of DOC in small streams. However, in order to calculate accurate DOC fluxes for comparison across sites, in situ FDOM data must be compensated for matrix effects. Key matrix effects, include temperature, turbidity and the inner filter effect due to color. These interferences must be compensated for to develop a reasonable relationship between FDOM and DOC. In this study, we applied laboratory-derived correction factors to real time data from the five USGS WEBB headwater streams in order to gauge their effectiveness across a range of matrix effects. The good news is that laboratory derived correction factors improved the predicative relationship (higher r2) between DOC and FDOM when compared to uncorrected data. The relative importance of each matrix effect (i.e. temperature) varied by site and by time, implying that each and every matrix effect should be compensated for when available. In general, temperature effects were more important on longer time scales, while corrections for turbidity and DOC inner filter effects were most prevalent during hydrologic events, when the highest instantaneous flux of DOC occurred. Unfortunately, even when corrected for matrix effects, in situ FDOM is a weaker predictor of DOC than A254, a common surrogate for DOC, implying that either DOC fluoresces at varying degrees (but should average out over time), that some matrix effects (e.g. pH) are either unaccounted for or laboratory-derived correction factors do not encompass the site variability of particles and organics. The least impressive finding is that the inherent dependence on three variables in the FDOM correction algorithm increases the likelihood of record data gaps which increases the uncertainty in calculated DOC flux values.

Dynamics of dissolved organic carbon (DOC) through stormwater basins designed for groundwater recharge in urban area: Assessment of retention efficiency.

PubMed

Mermillod-Blondin, Florian; Simon, Laurent; Maazouzi, Chafik; Foulquier, Arnaud; Delolme, Cécile; Marmonier, Pierre

2015-09-15

Managed aquifer recharge (MAR) has been developed in many countries to limit the risk of urban flooding and compensate for reduced groundwater recharge in urban areas. The environmental performances of MAR systems like infiltration basins depend on the efficiency of soil and vadose zone to retain stormwater-derived contaminants. However, these performances need to be finely evaluated for stormwater-derived dissolved organic matter (DOM) that can affect groundwater quality. Therefore, this study examined the performance of MAR systems to process DOM during its transfer from infiltration basins to an urban aquifer. DOM characteristics (fluorescent spectroscopic properties, biodegradable and refractory fractions of dissolved organic carbon -DOC-, consumption by micro-organisms during incubation in slow filtration sediment columns) were measured in stormwater during its transfer through three infiltration basins during a stormwater event. DOC concentrations sharply decreased from surface to the aquifer for the three MAR sites. This pattern was largely due to the retention of biodegradable DOC which was more than 75% for the three MAR sites, whereas the retention of refractory DOC was more variable and globally less important (from 18% to 61% depending on MAR site). Slow filtration column experiments also showed that DOC retention during stormwater infiltration through soil and vadose zone was mainly due to aerobic microbial consumption of the biodegradable fraction of DOC. In parallel, measurements of DOM characteristics from groundwaters influenced or not by MAR demonstrated that stormwater infiltration increased DOC quantity without affecting its quality (% of biodegradable DOC and relative aromatic carbon content -estimated by SUVA254-). The present study demonstrated that processes occurring in soil and vadose zone of MAR sites were enough efficient to limit DOC fluxes to the aquifer. Nevertheless, the enrichments of DOC concentrations measured in groundwater below infiltration basins need to be considered in future studies to especially assess their impact on groundwater quality. Copyright © 2015 Elsevier Ltd. All rights reserved.

Online stable isotope analysis of dissolved organic carbon size classes using size exclusion chromatography coupled to an isotope ratio mass spectrometer.

PubMed

Malik, Ashish; Scheibe, Andrea; LokaBharathi, P A; Gleixner, Gerd

2012-09-18

Stable isotopic content of dissolved organic carbon (δ(13)C-DOC) provides valuable information on its origin and fate. In an attempt to get additional insights into DOC cycling, we developed a method for δ(13)C measurement of DOC size classes by coupling high-performance liquid chromatography (HPLC)-size exclusion chromatography (SEC) to online isotope ratio mass spectrometry (IRMS). This represents a significant methodological contribution to DOC research. The interface was evaluated using various organic compounds, thoroughly tested with soil-water from a C3-C4 vegetation change experiment, and also applied to riverine and marine DOC. δ(13)C analysis of standard compounds resulted in excellent analytical precision (≤0.3‰). Chromatography resolved soil DOC into 3 fractions: high molecular weight (HMW; 0.4-10 kDa), low molecular weight (LMW; 50-400 Da), and retained (R) fraction. Sample reproducibility for measurement of δ(13)C-DOC size classes was ±0.25‰ for HMW fraction, ± 0.54‰ for LMW fraction, and ±1.3‰ for R fraction. The greater variance in δ(13)C values of the latter fractions was due to their lower concentrations. The limit of quantification (SD ≤0.6‰) for each size fraction measured as a peak is 200 ng C (2 mg C/L). δ(13)C-DOC values obtained in SEC mode correlated significantly with those obtained without column in the μEA mode (p < 0.001, intercept 0.17‰), which rules out SEC-associated isotopic effects or DOC loss. In the vegetation change experiment, fractions revealed a clear trend in plant contribution to DOC; those in deeper soils and smaller size fractions had less plant material. It was also demonstrated that the technique can be successfully applied to marine and riverine DOC without further sample pretreatment.

The Spatial and Temporal Distribution of Dissolved Organic Carbon Exported from Three Chinese Rivers to the China Sea

PubMed Central

Shi, Guohua; Peng, Changhui; Wang, Meng; Shi, Shengwei; Yang, Yanzheng; Chu, Junyao; Zhang, Junjun; Lin, Guanghui; Shen, Yan; Zhu, Qiuan

2016-01-01

The lateral transport of dissolved organic carbon (DOC) plays an important role in linking the carbon cycles of terrestrial and aquatic ecosystems. Neglecting the lateral flow of dissolved organic carbon can lead to an underestimation of the organic carbon budget of terrestrial ecosystems. It is thus necessary to integrate DOC concentrations and flux into carbon cycle models, particularly with regard to the development of models that are intended to directly link terrestrial and ocean carbon cycles. However, to achieve this goal, more accurate information is needed to better understand and predict DOC dynamics. In this study, we compiled an inclusive database of available data collected from the Yangtze River, Yellow River and Pearl River in China. The database is collected based on online literature survey and analysed by statistic method. Overall, our results revealed a positive correlation between DOC flux and discharge in all three rivers, whereas the DOC concentration was more strongly correlated with the regional net primary productivity (NPP). We estimated the total DOC flux exported by the three rivers into the China Sea to be approximately 2.73 Tg yr-1. Specifically, the annual flux of DOC from the Yangtze River, Yellow River and Pearl River was estimated to be 1.85 Tg yr-1, 0.06 Tg yr-1 and 0.82 Tg yr-1, respectively, and the average annual DOC concentrations were estimated to be 2.24 ± 0.53 mg L-1, 2.70 ± 0.38 mg L-1 and 1.51 ± 0.09 mg L-1, respectively. Seasonal variations in DOC concentrations are greatly influenced by the interaction between temperature and precipitation. NPP is significantly and positively related to the DOC concentration in the Yangtze River and the Pearl River. In addition, differences in climate and the productivity of the vegetation may influence both the flux and concentrations of DOC transported by the rivers and thus potentially affect estuarine geochemistry. PMID:27755581

Sedimentary sources of old high molecular weight dissolved organic carbon from the ocean margin benthic nepheloid layer

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

Guo, L. Santschi, P.H.

2000-02-01

Average {sup 14}C ages of dissolved organic carbon (DOC) in the ocean are 3--6,000 years, and are influenced by old DOC from continental margins. However, sources of DOC from terrestrial, autochthonous, and sedimentary organic carbon seem to be too young to be responsible for the old DOC observed in the ocean. Since colloidal organic carbon (COC, i.e., high molecular weight DOC), which is chemically very similar to that of bulk DOC, can be effectively isolated from seawater using cross-flow ultrafiltration, it can hold clues to sources and pathways of DOC turnover in the ocean. Radiocarbon measurements on COC in themore » water column and benthic nepheloid layer (BNL) from two continental margin areas (the Middle Atlantic Bight and the Gulf of Mexico) and controlled laboratory experiments were carried out to study sources of old DOC in the ocean margin areas. Vertical distributions of suspended particulate matter (SPM), particulate organic carbon (POC), nitrogen (PON), and DOC in the water column and bottom waters near the sediment-water interface all demonstrate a well developed benthic nepheloid layer in both ocean margin areas. COC from the BNL was much older than COC from the overlying water column. These results, together with strong concentration gradients of SPM, POC, PON, and DOC, suggest a sedimentary source for organic carbon species and possibly for old COC as well in BNL waters. This is confirmed by the results from controlled laboratory experiments. The heterogeneity of {Delta}{sup 14}C signatures in bulk SOC thus points to a preferential release of old organic components from sediment resuspension, which can be the transport mechanism of the old benthic COC observed in ocean margin areas. Old COC from continental margin nepheloid layers may thus be a potential source of old DOC to the deep ocean.« less

Decreasing DOC trends in soil solution along the hillslopes at two IM sites in southern Sweden--geochemical modeling of organic matter solubility during acidification recovery.

PubMed

Löfgren, Stefan; Gustafsson, Jon Petter; Bringmark, Lage

2010-12-01

Numerous studies report increased concentrations of dissolved organic carbon (DOC) during the last two decades in boreal lakes and streams in Europe and North America. Recently, a hypothesis was presented on how various spatial and temporal factors affect the DOC dynamics. It was concluded that declining sulphur deposition and thereby increased DOC solubility, is the most important driver for the long-term DOC concentration trends in surface waters. If this recovery hypothesis is correct, the DOC levels should increase both in the soil solution as well as in the surrounding surface waters as soil pH rises and the ionic strength declines due to the reduced input of SO(4)(2-) ions. In this project a geochemical model was set up to calculate the net humic charge and DOC solubility trends in soils during the period 1996-2007 at two integrated monitoring sites in southern Sweden, showing clear signs of acidification recovery. The Stockholm Humic Model was used to investigate whether the observed DOC solubility is related to the humic charge and to examine how pH and ionic strength influence it. Soil water data from recharge and discharge areas, covering both podzols and riparian soils, were used. The model exercise showed that the increased net charge following the pH increase was in many cases counteracted by a decreased ionic strength, which acted to decrease the net charge and hence the DOC solubility. Thus, the recovery from acidification does not necessarily have to generate increasing DOC trends in soil solution. Depending on changes in pH, ionic strength and soil Al pools, the trends might be positive, negative or indifferent. Due to the high hydraulic connectivity with the streams, the explanations to the DOC trends in surface waters should be searched for in discharge areas and peat lands. Copyright © 2010 Elsevier B.V. All rights reserved.

Monitoring Carbon Fluxes from Shallow Surface Soils in the Critical Zone

NASA Astrophysics Data System (ADS)

Stielstra, C. M.; Brooks, P. D.; Chorover, J.

2011-12-01

The critical zone (CZ) is the earth's porous near-surface layer, characterized by the integrated processes that occur between the bedrock and the atmospheric boundary layer. Within this area water, atmosphere, ecosystems, and soils interact on a geomorphic and geologic template. We hypothesize that CZ systems organize and evolve in response to open system fluxes of energy and mass, including meteoric inputs of radiation, water, and carbon, which can be quantified at point to watershed scales. The goal of this study is to link above-ground and below-ground carbon processes by quantifying carbon pools and fluxes from near surface soils. Soil CO2 efflux and dissolved organic carbon (DOC) are monitored over a two year period across bedrock type and vegetation type at two seasonally snow covered subalpine catchments in Arizona and New Mexico. We measure the amount of DOC present in surface soils, and install ion exchange resins at the A/B soil horizon interface to capture DOC leachate mobilized during snowmelt and summer rainfall. Throughout the summer rain and spring snowmelt seasons we monitor soil respiration of CO2. Preliminary results show that rates of gaseous carbon flux are significantly higher (p<0.05) from soils with schist bedrock (2.5 ± 0.2 gC/m2/d )than from granite bedrock (1.3 ± 0.1 gC/m2/d), and higher from healthy mixed conifer forests (1.9 ± 0.3 gC/m2/d) than from mixed conifer forests impacted by spruce budworm (1.4 ± 0.1 gC/m2/d). DOC leached from soil samples does not vary significantly with bedrock type; however, spruce budworm impacted forests have significantly higher levels of leachable DOC in surface soils (22.8 ± 4.5 gC/m2) than are found in the soils of healthy forests (10.0 ± 1.5 gC/m2) or subalpine meadows (9.1 ± 0.5 gC/m2). The results of this study will allow us to evaluate the variability of carbon fluxes with vegetation and soil type within a shallow soil carbon pool and help constrain the contributions of soil organic carbon to net carbon balance in CZO catchments with seasonal precipitation regimes.

The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources

NASA Astrophysics Data System (ADS)

Ritson, Jonathan P.; Brazier, Richard E.; Graham, Nigel J. D.; Freeman, Chris; Templeton, Michael R.; Clark, Joanna M.

2017-06-01

Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought-tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6 % increase in DOC production from peat and that peat DOC that had been exposed to oxygen was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on the amount of DOC production from vegetation litters; however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought-tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter layer effects. Long-term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas pulses related to drought may be observed in peat soils and are likely to become more common in the future. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch blocking to raise water tables.

Sunlight Controls Water Column Processing of Carbon in Arctic Freshwaters

NASA Astrophysics Data System (ADS)

Cory, R. M.; Ward, C. P.; Crump, B. C.; Kling, G. W.

2014-12-01

Carbon (C) in thawing permafrost soils may have global impacts on climate change, yet controls on its processing and fate are poorly understood. The dominant fate of dissolved organic C (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Both processes are most often attributed to bacterial respiration, but we recently showed that photochemical oxidation exceeds rates of respiration and accounts for 70-95% of total DOC processed in the water column of arctic lakes and rivers. While the overall dominance of photochemical processing in streams and lakes remained, the fate of DOC varied consistently by water type. In small streams DOC was mainly mineralized by sunlight to CO2, while in lakes the main fate of DOC was partial photo-oxidation. Large rivers were intermediate between these end members, and photo-mineralization to CO2 was about equal to or less than partial photo-oxidation. We suggest this pattern is a result of light-exposure history, where DOC leached from soils into headwater streams has little prior light exposure and is labile to complete photo-oxidation, but as light exposure increases moving downstream and into lakes with longer residence times the DOC photo-lability declines. Thus as easily photo-mineralized moieties are removed, DOC fate shifts toward partial photo-oxidation and downstream export in rivers and lakes. At the basin scale, photochemical processing of DOC is about one third of the total CO2 released from surface waters, and is thus an important, newly measured component of the Arctic C budget. We also suggest that these photochemical transformations of DOC will occur in any shallow surface water, and could be important for better understanding inland water carbon cycling.

Drought causes step-changes in catchment-scale carbon export from peatland catchments

NASA Astrophysics Data System (ADS)

Howden, Nicholas; Worrall, Fred; Burt, Tim

2015-04-01

Increases in fluvial DOC concentrations in world rivers, particularly those that drain areas of peatland, have been observed for some years, suggesting an increase in carbon loss from the terrestrial biosphere. But it has not been straightforward to identify what causes these increases due to a lack of long-term time series to characterise both observed DOC concentrations and potential drivers. The York Waterworks Company (York, UK) abstracted drinking water from the Yorkshire Ouse just upstream of the city from the late 1800s until 2002. During the period August 1945 to December 2002, records of monthly-average DOC concentrations were kept (using water colour as a surrogate). From January 2003 onwards, the Environment Agency of England and Wales (EA) continued the monitoring, thus providing a 68-year record of monthly-average DOC concentrations in the Yorkshire Ouse, which is the longest DOC time series ever reported for a catchment with significant peat cover. We use the Yorkshire Ouse DOC record to develop a new method that shows how changes in DOC concentration and river flow have influenced carbon fluxes in the Ouse for the latter half of the 20th century and show that the only major changes in DOC flux are caused by step-increases in concentration following severe drought. We then use this method to identify a similar effect in other DOC records for UK rivers. The results suggest that increases in DOC export are due more to discrete events than to the impact of continuous drivers (such as increasing temperatures or changing atmospheric deposition), and also show these increases not to be reversed for at least four decades.

Greenland Ice Sheet exports labile organic carbon to the Arctic oceans

NASA Astrophysics Data System (ADS)

Lawson, E. C.; Wadham, J. L.; Tranter, M.; Stibal, M.; Lis, G. P.; Butler, C. E. H.; Laybourn-Parry, J.; Nienow, P.; Chandler, D.; Dewsbury, P.

2013-12-01

Runoff from small glacier systems contains dissolved organic carbon (DOC), rich in protein-like, low molecular weight (LMW) compounds, designating glaciers as an important source of bioavailable carbon for downstream heterotrophic activity. Fluxes of DOC and particulate organic carbon (POC) exported from large Greenland catchments, however, remain unquantified, despite the Greenland Ice Sheet (GrIS) being the largest source of global glacial runoff (ca. 400 km3 yr-1). We report high and episodic fluxes of POC and DOC from a large (1200 km2) GrIS catchment during contrasting melt seasons. POC dominates organic carbon (OC) export (70-89% on average), is sourced from the ice sheet bed and contains a significant bioreactive component (9% carbohydrates). A major source for the "bioavailable" (free carbohydrates) LMW-DOC fraction is microbial activity on the ice sheet surface, with some further addition of LMW-DOC to meltwaters by biogeochemical processes at the ice sheet bed. The bioavailability of the exported DOC (30-58%) to downstream marine microorganisms is similar to that reported from other glacial watersheds. Annual fluxes of DOC and free carbohydrates during two melt seasons were similar, despite the ~ 2 fold difference in runoff fluxes, suggesting production-limited DOC sources. POC fluxes were also insensitive to an increase in seasonal runoff volumes, indicating supply-limitation of suspended sediment in runoff. Scaled to the GrIS, the combined DOC and POC fluxes (0.13-0.17 Tg C yr-1 DOC, 0.36-1.52 Tg C yr-1 mean POC) are of a similar order of magnitude to a large Arctic river system, and hence represent an important OC source to the North Atlantic, Greenland and Labrador Seas.

Conformational Changes in IpaD from Shigella flexneri Upon Binding Bile Salts Provide Insight into the Second Step of Type III Secretion†

PubMed Central

Dickenson, Nicholas E.; Zhang, Lingling; Epler, Chelsea R.; Adam, Philip R.; Picking, Wendy L.; Picking, William D.

2011-01-01

Shigella flexneri uses its type III secretion apparatus (TTSA) to inject host-altering proteins into targeted eukaryotic cells. The TTSA is composed of a basal body and an exposed needle with invasion plasmid antigen D (IpaD) forming a tip complex that controls secretion. The bile salt deoxycholate (DOC) stimulates recruitment of the translocator protein IpaB into the maturing TTSA needle tip complex. This process appears to be triggered by a direct interaction between DOC and IpaD. Fluorescence spectroscopy and NMR spectroscopy are used here to confirm the DOC-IpaD interaction and to reveal that IpaD conformational changes upon DOC binding trigger the appearance of IpaB at the needle tip. Förster resonance energy transfer between specific sites on IpaD was used here to identify changes in distances between IpaD domains as a result of DOC binding. To further explore the effects of DOC binding on IpaD structure, NMR chemical shift mapping was employed. The environments of residues within the proposed DOC binding site and additional residues within the “distal” globular domain were perturbed upon DOC binding, further indicating that conformational changes occur within IpaD upon DOC binding. These events are proposed to be responsible for the recruitment of IpaB at the TTSA needle tip. Mutation analyses combined with additional spectroscopic analyses confirms that conformational changes in IpaD induced by DOC binding contribute to the recruitment of IpaB to the S. flexneri TTSA needle tip. These findings lay the foundation for determining how environmental factors promote TTSA needle tip maturation prior to host cell contact. PMID:21126091

Abundance, stable isotopic composition, and export fluxes of DOC, POC, and DIC from the Lower Mississippi River during 2006–2008

USGS Publications Warehouse

Cai, Yihua; Guo, Laodong; Wang, Xuri; Aiken, George R.

2015-01-01

Sources, abundance, isotopic compositions, and export fluxes of dissolved inorganic carbon (DIC), dissolved and colloidal organic carbon (DOC and COC), and particulate organic carbon (POC), and their response to hydrologic regimes were examined through monthly sampling from the Lower Mississippi River during 2006–2008. DIC was the most abundant carbon species, followed by POC and DOC. Concentration and δ13C of DIC decreased with increasing river discharge, while those of DOC remained fairly stable. COC comprised 61 ± 3% of the bulk DOC with similar δ13C abundances but higher percentages of hydrophobic organic acids than DOC, suggesting its aromatic and diagenetically younger status. POC showed peak concentrations during medium flooding events and at the rising limb of large flooding events. While δ13C-POC increased, δ15N of particulate nitrogen decreased with increasing discharge. Overall, the differences in δ13C between DOC or DIC and POC show an inverse correlation with river discharge. The higher input of soil organic matter and respired CO2 during wet seasons was likely the main driver for the convergence of δ13C between DIC and DOC or POC, whereas enhanced in situ primary production and respiration during dry seasons might be responsible for their isotopic divergence. Carbon export fluxes from the Mississippi River were estimated to be 13.6 Tg C yr−1 for DIC, 1.88 Tg C yr−1 for DOC, and 2.30 Tg C yr−1 for POC during 2006–2008. The discharge-normalized DIC yield decreased during wet seasons, while those of POC and DOC increased and remained constant, respectively, implying variable responses in carbon export to the increasing discharge.

Mercury and methylmercury dynamics in the hyporheic zone of an Oregon stream

USGS Publications Warehouse

Hinkle, Stephen R.; Bencala, Kenneth E.; Wentz, Dennis A.; Krabbenhoft, David P.

2014-01-01

The role of the hyporheic zone in mercury (Hg) cycling has received limited attention despite the biogeochemically active nature of this zone and, thus, its potential to influence Hg behavior in streams. An assessment of Hg geochemistry in the hyporheic zone of a coarse-grained island in the Coast Fork Willamette River in Oregon, USA, illustrates the spatially dynamic nature of this region of the stream channel for Hg mobilization and attenuation. Hyporheic flow through the island was evident from the water-table geometry and supported by hyporheic-zone chemistry distinct from that of the bounding groundwater system. Redox-indicator species changed abruptly along a transect through the hyporheic zone, indicating a biogeochemically reactive stream/hyporheic-zone continuum. Dissolved organic carbon (DOC), total Hg, and methylmercury (MeHg) concentrations increased in the upgradient portion of the hyporheic zone and decreased in the downgradient region. Total Hg (collected in 2002 and 2003) and MeHg (collected in 2003) were correlated with DOC in hyporheic-zone samples: r2=0.63 (total Hg-DOC, 2002), 0.73 (total Hg-DOC, 2003), and 0.94 (MeHg-DOC, 2003). Weaker Hg/DOC association in late summer 2002 than in early summer 2003 may reflect seasonal differences in DOC reactivity. Observed correlations between DOC and both total Hg and MeHg reflect the importance of DOC for Hg mobilization, transport, and fate in this hyporheic zone. Correlations with DOC provide a framework for conceptualizing and quantifying Hg and MeHg dynamics in this region of the stream channel, and provide a refined conceptual model of the role hyporheic zones may play in aquatic ecosystems.

A Global Assessment of Rain-Dissolved Organic Carbon

NASA Astrophysics Data System (ADS)

Safieddine, S.; Heald, C. L.

2017-12-01

Precipitation is the largest physical removal pathway of atmospheric organic carbon from the atmosphere. The removed carbon is transferred to the land and ocean in the form of dissolved organic carbon (DOC). Limited measurements have hindered efforts to characterize global DOC. In this poster presentation, we show the first simulated global DOC distribution based on a GEOS-Chem model simulation of the atmospheric reactive carbon budget. Over the ocean, simulated DOC concentrations are between 0.1 to 1 mgCL-1 with a total of 85 TgCyr-1 deposited. DOC concentrations are higher inland, ranging between 1 and 10 mgCL-1, producing a total of 188 TgCyr-1 terrestrial organic wet deposition. We compare the 2010 simulated DOC to a 30-year synthesis of available DOC measurements over different environments. Despite imperfect matching of observational and simulated time intervals, the model is able to reproduce much of the spatial variability of DOC (r= 0.63), with a low bias of 35%. We compare the global average carbon oxidation state (OSc) of both atmospheric and dissolved organic carbon, as a simple metric for describing the chemical composition of organics. In the global atmosphere reactive organic carbon (ROC) is dominated by hydrocarbons and ketones, and OSc, ranges from -1.8 to -0.6. In the dissolved form, formaldehyde, formic acid, primary and secondary semi-volatiles organic aerosol dominate the DOC concentrations. The increase in solubility upon oxidation leads to a global increase in OSc in rainwater with -0.6<=OSc <=0. This simulation provides new insight into the current model representation of the flow of atmospheric and rain-dissolved organic carbon, and new opportunities to use observations and simulations to understand the DOC reaching land and ocean.

Wetlands receiving water treated with coagulants improve water quality by removing dissolved organic carbon and disinfection byproduct precursors.

PubMed

Hansen, Angela M; Kraus, Tamara E C; Bachand, Sandra M; Horwath, William R; Bachand, Philip A M

2018-05-01

Constructed wetlands are used worldwide to improve water quality while also providing critical wetland habitat. However, wetlands have the potential to negatively impact drinking water quality by exporting dissolved organic carbon (DOC) that upon disinfection can form disinfection byproducts (DBPs) like trihalomethanes (THMs) and haloacetic acids (HAAs). We used a replicated field-scale study located on organic rich soils in California's Sacramento-San Joaquin Delta to test whether constructed flow-through wetlands which receive water high in DOC that is treated with either iron- or aluminum-based coagulants can improve water quality with respect to DBP formation. Coagulation alone removed DOC (66-77%) and THM (67-70%) precursors, and was even more effective at removing HAA precursors (77-90%). Passage of water through the wetlands increased DOC concentrations (1.5-7.5mgL -1 ), particularly during the warmer summer months, thereby reversing some of the benefits from coagulant addition. Despite this addition, water exiting the wetlands treated with coagulants had lower DOC and DBP precursor concentrations relative to untreated source water. Benefits of the coagulation-wetland systems were greatest during the winter months (approx. 50-70% reduction in DOC and DBP precursor concentrations) when inflow water DOC concentrations were higher and wetland DOC production was lower. Optical properties suggest DOC in this system is predominantly comprised of high molecular weight, aromatic compounds, likely derived from degraded peat soils. Published by Elsevier B.V.

Experimental whole-lake increase of dissolved organic carbon concentration produces unexpected increase in crustacean zooplankton density

USGS Publications Warehouse

Kelly, Patrick T.; Craig, Nicola; Solomon, Christopher T.; Weidel, Brian C.; Zwart, Jacob A.; Jones, Stuart E.

2016-01-01

The observed pattern of lake browning, or increased terrestrial dissolved organic carbon (DOC) concentration, across the northern hemisphere has amplified the importance of understanding how consumer productivity varies with DOC concentration. Results from comparative studies suggest these increased DOC concentrations may reduce crustacean zooplankton productivity due to reductions in resource quality and volume of suitable habitat. Although these spatial comparisons provide an expectation for the response of zooplankton productivity as DOC concentration increases, we still have an incomplete understanding of how zooplankton respond to temporal increases in DOC concentration within a single system. As such, we used a whole-lake manipulation, in which DOC concentration was increased from 8 to 11 mg L−1 in one basin of a manipulated lake, to test the hypothesis that crustacean zooplankton production should subsequently decrease. In contrast to the spatially derived expectation of sharp DOC-mediated decline, we observed a small increase in zooplankton densities in response to our experimental increase in DOC concentration of the treatment basin. This was due to significant increases in gross primary production and resource quality (lower seston carbon-to-phosphorus ratio; C:P). These results demonstrate that temporal changes in lake characteristics due to increased DOC may impact zooplankton in ways that differ from those observed in spatial surveys. We also identified significant interannual variability across our study region, which highlights potential difficulty in detecting temporal responses of organism abundances to gradual environmental change (e.g., browning).

Biochar feedstock and pyrolysis temperature effects on leachate: DOC characteristics and nitrate losses from a Brazilian Cerrado Arenosol mixed with agricultural waste biochars.

PubMed

Speratti, Alicia B; Johnson, Mark S; Sousa, Heiriane Martins; Dalmagro, Higo J; Couto, Eduardo Guimarães

2018-04-01

Dissolved organic carbon (DOC) leached from Brazilian Cerrado Arenosols can lead to carbon (C) losses and lower soil fertility, while excessive nutrient, e.g. nitrate (NO 3 - ), leaching can potentially cause water contamination. As biochar has been shown to stabilize C and retain soil nutrients, a greenhouse experiment was conducted to test different biochars' contributions to DOC and NO 3 - leaching from a sandy soil. Biochars were made from four local agricultural waste feedstocks (cotton residue, swine manure, eucalyptus sawmill residue, sugarcane filtercake) pyrolysed at 400, 500 and 600 °C. Biochar was mixed with soil at 5% weight in pots and maize seeds planted. Leachate was collected weekly for six weeks and analyzed for DOC and NO 3 - concentrations, while fluorescence spectroscopy with parallel factor analysis (PARAFAC) was used to interpret DOC characteristics. Cotton and swine manure biochar treatments had higher DOC and NO 3 - losses than eucalyptus biochar, filtercake biochar, and control treatments. Cotton and swine manure biochar treatments at high temperatures lost mostly terrestrial, humified DOC, while swine manure, filtercake, and eucalyptus biochars at low temperatures lost mostly labile, microbially-derived DOC. Through the practical use of fluorescence spectroscopy, our study identified filtercake and eucalyptus biochars as most promising for retaining DOC and NO 3 - in a Cerrado Arenosol, potentially reducing stable C and nutrient losses. Copyright © 2018 Elsevier Ltd. All rights reserved.

Improved automation of dissolved organic carbon sampling for organic-rich surface waters.

PubMed

Grayson, Richard P; Holden, Joseph

2016-02-01

In-situ UV-Vis spectrophotometers offer the potential for improved estimates of dissolved organic carbon (DOC) fluxes for organic-rich systems such as peatlands because they are able to sample and log DOC proxies automatically through time at low cost. In turn, this could enable improved total carbon budget estimates for peatlands. The ability of such instruments to accurately measure DOC depends on a number of factors, not least of which is how absorbance measurements relate to DOC and the environmental conditions. Here we test the ability of a S::can Spectro::lyser™ for measuring DOC in peatland streams with routinely high DOC concentrations. Through analysis of the spectral response data collected by the instrument we have been able to accurately measure DOC up to 66 mg L(-1), which is more than double the original upper calibration limit for this particular instrument. A linear regression modelling approach resulted in an accuracy >95%. The greatest accuracy was achieved when absorbance values for several different wavelengths were used at the same time in the model. However, an accuracy >90% was achieved using absorbance values for a single wavelength to predict DOC concentration. Our calculations indicated that, for organic-rich systems, in-situ measurement with a scanning spectrophotometer can improve fluvial DOC flux estimates by 6 to 8% compared with traditional sampling methods. Thus, our techniques pave the way for improved long-term carbon budget calculations from organic-rich systems such as peatlands. Copyright © 2015 Elsevier B.V. All rights reserved.

Linking pulses of atmospheric deposition to DOC release in an upland peat-covered catchment

NASA Astrophysics Data System (ADS)

Worrall, F.; Burt, T. P.; Adamson, J. K.

2008-12-01

Changes in atmospheric deposition have been proposed as one possible explanation of the widespread increase in DOC concentration observed in many Northern Hemisphere catchments. This study uses detailed, long-term, monthly monitoring records of pH, conductivity SO4, and DOC in precipitation, soil water, and runoff chemistry from an upland peat-covered catchment in northern England. By deriving impulse transfer functions this study explores whether changes in deposition lead to significant changes in the occurrence of each component in the soil and runoff water; especially significant changes in DOC. The study shows that (1) impulses in the deposition of acidity have no significant effect upon pH or DOC in soil water or runoff. (2) DOC in soil water and runoff is responsive to impulses in SO4 and conductivity, but only when those impulses are changes in soil water chemistry and not when they are in atmospheric deposition. (3) The effects of changes in SO4 and/or conductivity can easily be overemphasized if memory effects are not accounted for, and their effect is limited to only 1 or 2 months after a severe drought. This study can support the view that changes in ionic strength can result in changes in DOC concentration in soil water or runoff, but the system studied is unresponsive to changes in atmospheric deposition. Impulses in soil water SO4 do not lead to increases in DOC concentrations, and so this mechanism does not provide an explanation for DOC increases.

Towards a universal microbial inoculum for dissolved organic carbon degradation experiments

NASA Astrophysics Data System (ADS)

Pastor, Ada; Catalán, Núria; Gutiérrez, Carmen; Nagar, Nupur; Casas-Ruiz, Joan P.; Obrador, Biel; von Schiller, Daniel; Sabater, Sergi; Petrovic, Mira; Borrego, Carles M.; Marcé, Rafael

2017-04-01

Dissolved organic carbon (DOC) is the largest biologically available pool of organic carbon in aquatic ecosystems and its degradation along the land-to-ocean continuum has implications for carbon cycling from local to global scales. DOC biodegradability is usually assessed by incubating filtered water inoculated with native microbial assemblages in the laboratory. However, the use of a native inoculum from several freshwaters, without having a microbial-tailored design, hampers our ability to tease apart the relative contribution of the factors driving DOC degradation from the effects of local microbial communities. The use of a standard microbial inoculum would allow researchers to disentangle the drivers of DOC degradation from the metabolic capabilities of microbial communities operating in situ. With this purpose, we designed a bacterial inoculum to be used in experiments of DOC degradation in freshwater habitats. The inoculum is composed of six bacterial strains that easily grow under laboratory conditions, possess a versatile metabolism and are able to grow under both aerobic and anaerobic conditions. The mixed inoculum showed higher DOC degradation rates than those from their isolated bacterial components and the consumption of organic substrates was consistently replicated. Moreover, DOC degradation rates obtained using the designed inoculum were responsive across a wide range of natural water types differing in DOC concentration and composition. Overall, our results show the potential of the designed inoculum as a tool to discriminate between the effects of environmental drivers and intrinsic properties of DOC on degradation dynamics.

Multi-facetted Metadata - Describing datasets with different metadata schemas at the same time

NASA Astrophysics Data System (ADS)

Ulbricht, Damian; Klump, Jens; Bertelmann, Roland

2013-04-01

Inspired by the wish to re-use research data a lot of work is done to bring data systems of the earth sciences together. Discovery metadata is disseminated to data portals to allow building of customized indexes of catalogued dataset items. Data that were once acquired in the context of a scientific project are open for reappraisal and can now be used by scientists that were not part of the original research team. To make data re-use easier, measurement methods and measurement parameters must be documented in an application metadata schema and described in a written publication. Linking datasets to publications - as DataCite [1] does - requires again a specific metadata schema and every new use context of the measured data may require yet another metadata schema sharing only a subset of information with the meta information already present. To cope with the problem of metadata schema diversity in our common data repository at GFZ Potsdam we established a solution to store file-based research data and describe these with an arbitrary number of metadata schemas. Core component of the data repository is an eSciDoc infrastructure that provides versioned container objects, called eSciDoc [2] "items". The eSciDoc content model allows assigning files to "items" and adding any number of metadata records to these "items". The eSciDoc items can be submitted, revised, and finally published, which makes the data and metadata available through the internet worldwide. GFZ Potsdam uses eSciDoc to support its scientific publishing workflow, including mechanisms for data review in peer review processes by providing temporary web links for external reviewers that do not have credentials to access the data. Based on the eSciDoc API, panMetaDocs [3] provides a web portal for data management in research projects. PanMetaDocs, which is based on panMetaWorks [4], is a PHP based web application that allows to describe data with any XML-based schema. It uses the eSciDoc infrastructures REST-interface to store versioned dataset files and metadata in a XML-format. The software is able to administrate more than one eSciDoc metadata record per item and thus allows the description of a dataset according to its context. The metadata fields can be filled with static or dynamic content to reduce the number of fields that require manual entries to a minimum and, at the same time, make use of contextual information available in a project setting. Access rights can be adjusted to set visibility of datasets to the required degree of openness. Metadata from separate instances of panMetaDocs can be syndicated to portals through RSS and OAI-PMH interfaces. The application architecture presented here allows storing file-based datasets and describe these datasets with any number of metadata schemas, depending on the intended use case. Data and metadata are stored in the same entity (eSciDoc items) and are managed by a software tool through the eSciDoc REST interface - in this case the application is panMetaDocs. Other software may re-use the produced items and modify the appropriate metadata records by accessing the web API of the eSciDoc data infrastructure. For presentation of the datasets in a web browser we are not bound to panMetaDocs. This is done by stylesheet transformation of the eSciDoc-item. [1] http://www.datacite.org [2] http://www.escidoc.org , eSciDoc, FIZ Karlruhe, Germany [3] http://panmetadocs.sf.net , panMetaDocs, GFZ Potsdam, Germany [4] http://metaworks.pangaea.de , panMetaWorks, Dr. R. Huber, MARUM, Univ. Bremen, Germany

ISER - Electric Disturbance Events (OE-417)

Science.gov Websites

Training. (PDF 1.1 MB) (DOC 1 MB) OE-417 Form and Instructions Survey Form (PDF 136 KB) ( DOC 104 KB) Form Instructions (PDF 383 KB) (DOC 104 KB) Annual Summaries Current Year Summary (PDF 71 KB) (XLS 43 KB) Archives -417 Survey Form E-Filing System Training. (PDF 1.1 MB) (DOC 1 MB) OE-417 FORM AND INSTRUCTIONS Survey

France: Factors Shaping Foreign Policy, and Issues in U.S.-French Relations

DTIC Science & Technology

2006-01-03

national governments to expend public funds on enhancing the competitiveness of key companies. See Bennhold, Katrin , “ Sarkozy Urges Europe to Forge...consternés par la fragilité de leur puissance,” Le Monde, Sept. 3, 2005, p. 3; “ Hurricane Katrina: French Assistance,” doc. supplied by French embassy, Sept...the United States as having feet of clay. Hurricane Katrina fueled this sentiment. The French media was both puzzled by and critical of the U.S

Blades of Glory: An Energy.gov Mini-Doc – The 2016 Collegiate Wind Competition

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

Zayas, Jose; Newcomb, Charles

2016-06-06

In this short documentary, we follow three collegiate teams who are participating in this year’s U.S. Department of Energy Collegiate Wind Competition in New Orleans. Learn about their experiences and why the competition is important for America’s clean energy future. The competition provides undergraduates with real-world skills they need to enter tomorrow’s clean energy workforce by challenging them to develop and deliver a business plan, establish a deployment strategy, and build and test a wind turbine.

Emerging Powers and Future Threats: Implications for the U.S. and Global Defense Industry

DTIC Science & Technology

2017-01-01

unctad.org/sections/dite_dir/docs/wir2016/wir16_fs_ tr_en.pdf. 67 75. “Erdogan: Ankara bombing ‘collective terrorist act’,” Deutsche Welle, October 22...2015, available from www.dw.com/en/ erdogan-ankara- bombing -collective-terrorist-act/a-18799878. 76. Cenk Sidar and Emre Tuncalp, “Who’s Going to Save...1432640795; Staff Writer, “Uncovering SA em - ployment by race,” Business Tech, September 18, 2014, available from businesstech.co.za/news/general/68842

Develop, Build, and Test a Virtual Lab to Support a Vulnerability Training System

DTIC Science & Technology

2004-09-01

docs.us.dell.com/support/edocs/systems/pe1650/ en /it/index.htm> (20 August 2004) “HOWTO: Installing Web Services with Linux /Tomcat/Apache/Struts...configured as host machines with VMware and VNC running on a Linux RedHat 9 Kernel. An Apache-Tomcat web server was configured as the external interface to...1650, dual processor, blade servers were configured as host machines with VMware and VNC running on a Linux RedHat 9 Kernel. An Apache-Tomcat web

Break the Kill Chain, not the Budget: How to Avoid U.S. Strategic Retrenchment

DTIC Science & Technology

2016-06-10

annihilation: Sun Tzu wisely stated: “Know the enemy and know yourself; in a hundred battles you will never be in peril.”18 This wise edict espoused by...sites/default/files/docs/2015_national_security_strategy.pdf (accessed October 3, 2015). 18 Sun Tzu , The Art of War (London: Oxford University Press...80-90. http://search.proquest.com.nduezproxy.idm.oclc.org/docview/211508216?accountid= 12686 (accessed September 21, 2015). Tzu , Sun . The Art of

Break the Kill Chain, Not the Budget: How to Avoid U.S. Strategic Retrenchment

DTIC Science & Technology

2016-06-10

annihilation: Sun Tzu wisely stated: “Know the enemy and know yourself; in a hundred battles you will never be in peril.”18 This wise edict espoused by...sites/default/files/docs/2015_national_security_strategy.pdf (accessed October 3, 2015). 18 Sun Tzu , The Art of War (London: Oxford University Press...80-90. http://search.proquest.com.nduezproxy.idm.oclc.org/docview/211508216?accountid= 12686 (accessed September 21, 2015). Tzu , Sun . The Art of

Estimating grassland curing with remotely sensed data

NASA Astrophysics Data System (ADS)

Chaivaranont, Wasin; Evans, Jason P.; Liu, Yi Y.; Sharples, Jason J.

2018-06-01

Wildfire can become a catastrophic natural hazard, especially during dry summer seasons in Australia. Severity is influenced by various meteorological, geographical, and fuel characteristics. Modified Mark 4 McArthur's Grassland Fire Danger Index (GFDI) is a commonly used approach to determine the fire danger level in grassland ecosystems. The degree of curing (DOC, i.e. proportion of dead material) of the grass is one key ingredient in determining the fire danger. It is difficult to collect accurate DOC information in the field, and therefore ground-observed measurements are rather limited. In this study, we explore the possibility of whether adding satellite-observed data responding to vegetation water content (vegetation optical depth, VOD) will improve DOC prediction when compared with the existing satellite-observed data responding to DOC prediction models based on vegetation greenness (normalised difference vegetation index, NDVI). First, statistically significant relationships are established between selected ground-observed DOC and satellite-observed vegetation datasets (NDVI and VOD) with an r2 up to 0.67. DOC levels estimated using satellite observations were then evaluated using field measurements with an r2 of 0.44 to 0.55. Results suggest that VOD-based DOC estimation can reasonably reproduce ground-based observations in space and time and is comparable to the existing NDVI-based DOC estimation models.

Isolation, purification and analysis of dissolved organic carbon from Gohagoda uncontrolled open dumpsite leachate, Sri Lanka.

PubMed

Vithanage, Meththika; Wijesekara, Hasintha; Mayakaduwa, S S

2017-07-01

Extract and analysis of the Dissolved Organic Carbon (DOC) fractions were analyzed from the leachate of an uncontrolled dumpsite at Gohagoda, Sri Lanka. DOC fractions, humic acid (HA), fulvic acid (FA) and the hydrophilic (Hyd) fractions were isolated and purified with the resin techniques. Spectroscopic techniques and elemental analysis were performed to characterize DOCs. Maximum TOC and DOC values recorded were 56,955 and 28,493 mg/L, respectively. Based on the total amount of DOC fractionation, Hyd dominated accounting for ∼60%, and HA and FA constituted ∼22% and ∼17%, respectively, exhibiting the mature phase of the dumpsite. The elemental analysis of DOCs revealed carbon variation following HA > FA > Hyd, while hydrogen and nitrogen were similar in each fraction. The N/C ratio for HA was recorded as 0.18, following a similar trend in old dumpsite leachate elsewhere. The O/C ratios for HA and FA were recorded higher as much as 1.0 and 9.3, respectively, indicating high degree of carbon mineralization in the leachates. High content of carboxylic, phenolic and lactone groups in all DOCs was observed disclosing their potential for toxic substances transportation. The results strongly suggest the risk associated with DOCs in dumpsite leachate to the aquatic and terrestrial environment.

Concentration, sources, and flux of dissolved organic carbon of precipitation at Lhasa city, the Tibetan Plateau.

PubMed

Li, Chaoliu; Yan, Fangping; Kang, Shichang; Chen, Pengfei; Qu, Bin; Hu, Zhaofu; Sillanpää, Mika

2016-07-01

Dissolved organic carbon (DOC) plays an important role in the climate system, but few data are available on the Tibetan Plateau (TP). In this study, 89 precipitation samples were collected at Lhasa, the largest city of southern Tibet, from March to December 2013. The average concentration and wet deposition flux of DOC was 1.10 mg C L(-1) and 0.63 g C m(-2) year(-1), respectively. Seasonally, low DOC concentration and high flux appeared during the monsoon period, which were in line with heavy precipitation amount, reflecting dilution effect of precipitation for the DOC. Compared to other regions, the values of Lhasa were lower than those of large cities (e.g., Beijing and Seoul) mainly because of less air pollution of Lhasa. The principal component analysis (PCA) of DOC and ions (Ca(2+), Mg(2+), Na(+), K(+), NH4 (+), Cl(-), NO3 (-), and SO4 (2-)) showed that DOC of Lhasa was derived mainly from the natural sources, followed by anthropogenic burning activities. Furthermore, △(14)C value of DOC indicated that fossil fuel combustion contributed around 28 % of the rainwater DOC of Lhasa, indicating that the atmosphere of Lhasa has been influenced by emission from fossil fuel combustion or high-temperature industrial processes.

ISACS-DOC: Monitoring and Diagnostic System for AKARI and HINODE

NASA Astrophysics Data System (ADS)

Mizutani, Mitsue; Hirose, Toshinori; Takaki, Ryoji; Honda, Hideyuki

ISACS-DOC (Intelligent Satellite Control Software-DOCtor), which is an automatic monitoring and diagnostic system for scientific satellites or spacecraft, aims to rapidly and accurately capture important changes and sign of anomaly during daily satellite operations. After three systems for deep space missions, the new generation of ISACS-DOC with a higher speed processing performance had been developed for the satellites in earth orbit, AKARI and HINODE. This paper reports on the newest ISACS-DOC about enhanced functions, operating status, and an approach to create standards to build and keep up the knowledge data base. Continuous enhancements through the actual operations are the advantage of ISACS-DOC.

The first insight into the metabolite profiling of grapes from three Vitis vinifera L. cultivars of two controlled appellation (DOC) regions.

PubMed

Teixeira, António; Martins, Viviana; Noronha, Henrique; Eiras-Dias, José; Gerós, Hernâni

2014-03-10

The characterization of the metabolites accumulated in the grapes of specific cultivars grown in different climates is of particular importance for viticulturists and enologists. In the present study, the metabolite profiling of grapes from the cultivars, Alvarinho, Arinto and Padeiro de Basto, of two Portuguese Controlled Denomination of Origin (DOC) regions (Vinho Verde and Lisboa) was investigated by gas chromatography-coupled time-of-flight mass spectrometry (GC-TOF-MS) and an amino acid analyzer. Primary metabolites, including sugars, organic acids and amino acids, and some secondary metabolites were identified. Tartaric and malic acids and free amino acids accumulated more in grapes from vines of the DOC region of Vinho Verde than DOC Lisboa, but a principal component analysis (PCA) plot showed that besides the DOC region, the grape cultivar also accounted for the variance in the relative abundance of metabolites. Grapes from the cultivar, Alvarinho, were particularly rich in malic acid and tartaric acids in both DOC regions, but sucrose accumulated more in the DOC region of Vinho Verde.

The First Insight into the Metabolite Profiling of Grapes from Three Vitis vinifera L. Cultivars of Two Controlled Appellation (DOC) Regions

PubMed Central

Teixeira, António; Martins, Viviana; Noronha, Henrique; Eiras-Dias, José; Gerós, Hernâni

2014-01-01

The characterization of the metabolites accumulated in the grapes of specific cultivars grown in different climates is of particular importance for viticulturists and enologists. In the present study, the metabolite profiling of grapes from the cultivars, Alvarinho, Arinto and Padeiro de Basto, of two Portuguese Controlled Denomination of Origin (DOC) regions (Vinho Verde and Lisboa) was investigated by gas chromatography-coupled time-of-flight mass spectrometry (GC-TOF-MS) and an amino acid analyzer. Primary metabolites, including sugars, organic acids and amino acids, and some secondary metabolites were identified. Tartaric and malic acids and free amino acids accumulated more in grapes from vines of the DOC region of Vinho Verde than DOC Lisboa, but a principal component analysis (PCA) plot showed that besides the DOC region, the grape cultivar also accounted for the variance in the relative abundance of metabolites. Grapes from the cultivar, Alvarinho, were particularly rich in malic acid and tartaric acids in both DOC regions, but sucrose accumulated more in the DOC region of Vinho Verde. PMID:24619195

DOC quantity and quality in northeastern USA catchments

NASA Astrophysics Data System (ADS)

Shanley, J. B.; Sebestyen, S. D.; Aiken, G.; Pellerin, B. A.

2011-12-01

At the Sleepers River Research Watershed in Vermont we have studied interactions of dissolved organic carbon (DOC) cycling and hydrological processes for nearly 20 years to determine how and when DOC is transported through the landscape. Stream DOC concentration in this cool temperate forested catchment varies from ~1 to ~15 mg L-1 and is transport-limited; concentrations increase with increasing flow, even under the wettest conditions, suggesting shifting but non-depletable sources. Specific UV absorbance (SUVA) also increases consistently with flow. Source strength does vary seasonally, however, evidenced by higher DOC for a given flow during autumn leaf fall relative to spring snowmelt. Recent high-frequency optical sensor measurements have revealed fine-scale structure in the temporal DOC pattern not possible from discrete sampling. We observe a consistent counterclockwise hysteresis and diurnal cycles with seasonally variable amplitude. In this presentation we infer DOC sources and processes through analysis of antecedent moisture conditions and concurrent variations in nitrate, dissolved organic nitrogen, and SUVA. With sensors and sampling in place at several other research catchments, we are investigating the similarity of patterns across the northeastern USA.

Sustainable brooder for supporting local chicken in North Sumatera Province, Indonesia

NASA Astrophysics Data System (ADS)

Ginting, N.; Hidayat, R.

2018-02-01

Demand for local chicken has lasted for ages in Sumatera Utara Province, Indonesia. Demand is higher than supply because local chicken has low productivity which caused by several factors, for example heater or brooder for day old chicken (DOC). People who live in villages where mostly local chicken are raised have difficulty in serving brooder as electricity is expensive. In Biological Laboratory, Animal Production Programme Study, University of Sumatera Utara, a study has been conducted from August until November 2016. The objective of this study is to investigate sustainable brooder for local chicken. A study of 300 local DOC with designs: T1) local DOC + electric lamp brooder, T2) local DOC + biogas lamp brooder, T3) local DOC + propane lamp brooder has conducted. The key parameters measured were temperature stability, DOC spread, body weight gain, and mortality. Designs T1, T2 and T3 were almost equal in temperature stability, DOC spread, body weight gain and mortality while T2 was superior as it was environmentally friendly. A recommendation for local people to use biogas brooder instead of electric or LPG brooder.

Secondary Psychometric Examination of the Dimensional Obsessive-Compulsive Scale: Classical Testing, Item Response Theory, and Differential Item Functioning.

PubMed

Thibodeau, Michel A; Leonard, Rachel C; Abramowitz, Jonathan S; Riemann, Bradley C

2015-12-01

The Dimensional Obsessive-Compulsive Scale (DOCS) is a promising measure of obsessive-compulsive disorder (OCD) symptoms but has received minimal psychometric attention. We evaluated the utility and reliability of DOCS scores. The study included 832 students and 300 patients with OCD. Confirmatory factor analysis supported the originally proposed four-factor structure. DOCS total and subscale scores exhibited good to excellent internal consistency in both samples (α = .82 to α = .96). Patient DOCS total scores reduced substantially during treatment (t = 16.01, d = 1.02). DOCS total scores discriminated between students and patients (sensitivity = 0.76, 1 - specificity = 0.23). The measure did not exhibit gender-based differential item functioning as tested by Mantel-Haenszel chi-square tests. Expected response options for each item were plotted as a function of item response theory and demonstrated that DOCS scores incrementally discriminate OCD symptoms ranging from low to extremely high severity. Incremental differences in DOCS scores appear to represent unbiased and reliable differences in true OCD symptom severity. © The Author(s) 2014.

The sensitivity of peat soil and peatland vegetation to drought: release of dissolved organic carbon (DOC) on rewetting

NASA Astrophysics Data System (ADS)

Ritson, Jonathan; Graham, Nigel; Templeton, Michael; Freeman, Christopher; Clark, Joanna

2015-04-01

Organic rich peat soils are a major store of carbon worldwide. Their existence is predicated on high year-round water tables which create an anoxic environment, thus limiting decay, and also to the recalcitrance of plant litter (dead plant material) commonly found in peatland areas. Climate change threatens the stability of peat soils by altering the biogeochemical cycles which control plant decay, lowering water tables so that oxic degradation can occur and by changing habitat niches such that less recalcitrant species can thrive in peatlands. One of the major fluxes of carbon from peatlands is through dissolved organic carbon (DOC) in surface waters. As peatland areas in the UK are often used as source waters for drinking water supply this presents a problem to water utilities as DOC must be effectively removed to limit colour, odour and the formation of potentially carcinogenic by-products on disinfection. Changes in catchment vegetation may occur due to climate change, nutrient deposition and changing bioclimatic envelopes. How different peatland vegetation contribute to DOC flux and how this may change in the future is therefore of interest. A six week laboratory simulation was performed on typical peatland litter (Sphagnum spp., Calluna vulgaris, Molinea caerulea, Juncus effusus) and a peat soil collected from Exmoor National Park, UK. The simulation monitored DOC flux from the decaying litter/soil and considered the impact of different drought severities using the 50th, 25th, 10th and 5th percentiles of the mean July/August monthly rainfall for Exmoor. On rewetting following the drought, all sources produced significantly different amounts of DOC (Tukey HSD p<0.05) in the order Molinia>Juncus>Calluna>Sphagnum>peat. The source also had a significant (ANOVA p<0.001) effect on coagulation removal efficiency, a typical method of removing DOC during drinking water treatment, with Juncus DOC proving the easiest to remove whilst Sphagnum DOC was the most difficult. Sphagnum DOC had the lowest ratio of humic-like to protein-like fluorescence, which is indicative of DOC which is poorly removed by coagulation. An interactive effect was noted between DOC source and the drought treatment which was explored further using a one-way ANOVA with a Holm-Šidák correction. This suggested peat will produce significantly more DOC when affected by drought (p=0.010), possibly explained by increased oxygenation engaging the 'enzymatic latch' mechanism. A similar analysis was performed on the interaction between drought and DOC source for the specific UV absorbance at 254nm (SUVA) value (a measure of aromaticity). This suggested that Molinea caerulea produces DOC of significantly (p=0.001) higher aromaticity following periods of drought. Comparisons between drought and DOC source factors suggest the source in more important than climatic conditions of decay which is consistent with our previously published findings. These results have implications for marginal peatlands which may be at risk from increased water table drawdown in the future as climate changes and where Molinea caerulea, typically a fen species, is encroaching on bog communities.

Data-based mechanistic modeling of dissolved organic carbon load through storms using continuous 15-minute resolution observations within UK upland watersheds

NASA Astrophysics Data System (ADS)

Jones, T.; Chappell, N. A.

2013-12-01

Few watershed modeling studies have addressed DOC dynamics through storm hydrographs (notable exceptions include Boyer et al., 1997 Hydrol Process; Jutras et al., 2011 Ecol Model; Xu et al., 2012 Water Resour Res). In part this has been a consequence of an incomplete understanding of the biogeochemical processes leading to DOC export to streams (Neff & Asner, 2001, Ecosystems) & an insufficient frequency of DOC monitoring to capture sometimes complex time-varying relationships between DOC & storm hydrographs (Kirchner et al., 2004, Hydrol Process). We present the results of a new & ongoing UK study that integrates two components - 1/ New observations of DOC concentrations (& derived load) continuously monitored at 15 minute intervals through multiple seasons for replicated watersheds; & 2/ A dynamic modeling technique that is able to quantify storage-decay effects, plus hysteretic, nonlinear, lagged & non-stationary relationships between DOC & controlling variables (including rainfall, streamflow, temperature & specific biogeochemical variables e.g., pH, nitrate). DOC concentration is being monitored continuously using the latest generation of UV spectrophotometers (i.e. S::CAN spectro::lysers) with in situ calibrations to laboratory analyzed DOC. The controlling variables are recorded simultaneously at the same stream stations. The watersheds selected for study are among the most intensively studied basins in the UK uplands, namely the Plynlimon & Llyn Brianne experimental basins. All contain areas of organic soils, with three having improved grasslands & three conifer afforested. The dynamic response characteristics (DRCs) that describe detailed DOC behaviour through sequences of storms are simulated using the latest identification routines for continuous time transfer function (CT-TF) models within the Matlab-based CAPTAIN toolbox (some incorporating nonlinear components). To our knowledge this is the first application of CT-TFs to modelling DOC processes. Furthermore this allows a data-based mechanistic (DBM) modelling philosophy to be followed where no assumptions about processes are defined a priori (given that dominant processes are often not known before analysis) & where the information contained in the time-series is used to identify multiple structures of models that are statistically robust. Within the final stage of DBM, biogeochemical & hydrological processes are interpreted from those models that are observable from the available stream time-series. We show that this approach can simulate the key features of DOC dynamics within & between storms & that some of the resultant response characteristics change with varying DOC processes in different seasons. Through the use of MISO (multiple-input single-output) models we demonstrate the relative importance of different variables (e.g., rainfall, temperature) in controlling DOC responses. The contrasting behaviour of the six experimental catchments is also reflected in differing response characteristics. These characteristics are shown to contribute to understanding of basin-integrated DOC export processes & to the ecosystem service impacts of DOC & color on commercial water treatment within the surrounding water supply basins.

Re-evaluation of colorimetric Cl- data from natural waters with DOC

USGS Publications Warehouse

Norton, S.A.; Handlet, M.J.; Kahl, J.S.; Peters, N.E.

1996-01-01

Colorimetric Cl- data from natural solutions that contain dissolved organic carbon (DOC) may be biased high. We evaluated aquatic Cl- concentrations in ecosystem compartments at the Bear Brook Watershed, Maine, and from lakes in Maine, using ion chromatography and colorimetry. DOC imparts a positive interference on colorimetric Cl- results proportional to DOC concentrations at approximately 0.8 ??eq Cl-/L per mg DOC/L. The interference is not a function of Cl- concentration. The resulting bias in concentrations of Cl- may be 50% or more of typical environmental values for Cl- in areas remote from atmospheric deposition of marine aerosols. Such biased data in the literature appear to have led to spurious conclusions about recycling of Cl- by forests, the usefulness of Cl- as a conservative tracer in watershed studies, and calculations of elemental budgets, ion balance, charge density of DOC, and dry deposition factors.

Modelling hydrological processes and dissolved organic carbon dynamics in a rehabilitated Sphagnum-dominated peatland

NASA Astrophysics Data System (ADS)

Bernard-Jannin, Léonard; Binet, Stéphane; Gogo, Sébastien; Leroy, Fabien; Perdereau, Laurent; Laggoun-Défarge, Fatima

2017-04-01

Sphagnum-dominated peatlands represent a global major stock of carbon (C). Dissolved organic carbon (DOC) exports through runoff and leaching could reduce their potential C sink function and impact downstream water quality. DOC production in peatlands is strongly controlled by the hydrology, especially water table depth (WTD). Therefore, disturbances such as drainage can lead to increase DOC exports by lowering the WTD. Hydrological restoration (e.g. rewetting) can be undertaken to restore peatland functioning with an impact on DOC exports. The objective of this study is to assess the impact of drainage and rewetting on hydrological processes and their interactions with DOC dynamics in a Sphagnum dominated peatland. A hydrological model has been applied to a drained peatland (La Guette, France) which experienced a rewetting action on February 2014 and where WTD has been recorded in four piezometers at a 15 min time step since 2009. In addition, DOC concentrations in the peatland have been measured 6 times a year since 2014. The hydrological model is a WTD dependent reservoir model composed by two reservoirs representing the micro and macro porosity of the peatland (Binet et al., 2013). A DOC production module in both reservoirs was implemented based on temperature and WTD. The model was calibrated against WTD and DOC concentrations for each piezometer. The results show that the WTD in the study area is strongly affected by local meteorological conditions that could hide the effect of the rewetting action. The preliminary results evidenced that an additional source of water, identified as groundwater supply originating from the surrounding sandy layer aquifer, is necessary to maintain the water balance, especially during wet years (NS>0.8). Finally, the DOC module was able to describe DOC concentrations measured in the peatland and could be used to assess the impact of rewetting on DOC dynamics at different locations and to identify the factors of control of DOC exports at the peatland scale before and after the restoration. This simple conceptual model requires few data to operate. Its application on different sites with contrasted settings (hydrological and climatic conditions) could provide insight on the dominant hydrological processes and their impact on DOC dynamics in peatlands. Binet S., Gogo S., Laggoun-Défarge F., A water-table dependent reservoir model to investigate the effect of drought and vascular plant invasion on peatland hydrology, Journal of Hydrology, Volume 499, 30 August 2013, Pages 132-139, ISSN 0022-1694, http://dx.doi.org/10.1016/j.jhydrol.2013.06.035.

Concentration and age of DOC transported from thawing permafrost soils into Arctic headwater streams

NASA Astrophysics Data System (ADS)

Romano, E. L.; Wickland, K.; Ebert, C.; Schuur, E.

2017-12-01

As Arctic permafrost stability decreases due to global climate change, hydrologic dynamics in catchments underlain by permafrost are expected to shift. The thickness of seasonally thawed surface soils is an important driver of the extent to which carbon (C) that was previously stored as frozen soil organic carbon (SOC) will be transported laterally as dissolved organic carbon (DOC). The concentration and radiocarbon (14C) age of newly thawed DOC that moves downslope through tundra soils and is delivered to headwater streams is an important indicator of changing C dynamics. Understanding the timing and quantity of C loss in this form is imperative for greenhouse gas emission and soil C stock estimates, as well as predicting the impact of permafrost thaw on aquatic ecosystems. In this study we examined the relationship between DOC concentrations, 14C-DOC, and active layer thickness (ALT) in thawing soils over time. Water samples were collected once in July 2016 and weekly in 2017 from late May to late August from wells within a long-term tundra soil warming experiment (n=36), located in a discontinuous permafrost zone in Interior Alaska. Preliminary data from 2016 shows average maximum ALT at wells within the warming treatment of 68.9 cm, while wells from control averaged 86.6 cm. 2016 water sample data from wells within the warming treatment showed higher mean DOC concentrations (103.1 ± 32.5 mg/L) and older 14C-DOC values (-28.7 ± 21.1 ‰) than samples from the control (44.5 ± 3.0 mg/L and 11.3 ± 8.6 ‰). To assess inter-annual changes in DOC delivery to local headwater streams, DOC concentration and 14C-DOC were also measured on water samples taken in late summer of 2007, 2008, and 2016 from streams within the watershed surrounding the experimental sites. Weekly sampling in 2017 allowed analysis of seasonal patterns of DOC concentration for that year. Values increased slightly over time at some stream sites (ranging from 4-33 mg/L in 2012 to 2-80 mg/L in 2016). Seasonal and inter-annual permafrost thaw appears to drive the release of previously stored old C in the form of DOC, which increases downslope mobility. In-situ terrestrial greenhouse gas emission estimates may therefore underestimate C losses, especially when precipitation is high or early in the season when spring snowmelt and shallow ALT promote lateral transport of DOC.

Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes

NASA Astrophysics Data System (ADS)

Berggren, Martin; Klaus, Marcus; Panneer Selvam, Balathandayuthabani; Ström, Lena; Laudon, Hjalmar; Jansson, Mats; Karlsson, Jan

2018-01-01

Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in changes in DOC composition and pigmentation (color). However, the process-based understanding of these changes is incomplete, especially for headwater lakes. We hypothesized that because heterotrophic bacteria preferentially consume noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend on the relative importance of these two processes, accordingly. To test this hypothesis we combined laboratory experiments with field studies in nine boreal lakes, assessing both the relative importance of different DOC decay processes (biological or photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net losses of colored DOC. However, in highly pigmented brown-water lakes (absorbance at 420 nm > 7 m-1) biological processes dominated, and there was no systematic relationship between color loss and WTT. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes.

Source water controls on the character and origin of dissolved organic matter in streams of the Yukon River basin, Alaska

USGS Publications Warehouse

O'Donnell, Jonathan A.; Aiken, George R.; Kane, Evan S.; Jones, Jeremy B.

2010-01-01

Climate warming and permafrost degradation at high latitudes will likely impact watershed hydrology, and consequently, alter the concentration and character of dissolved organic carbon (DOC) in northern rivers. We examined seasonal variation of DOC chemistry in 16 streams of the Yukon River basin, Alaska. Our primary objective was to evaluate the relationship between source water (shallow versus deep groundwater flow paths) and DOC chemical composition. Using base cation chemistry and principal component analysis, we observed high contributions of deep groundwater to glacial and clearwater streams, whereas blackwater streams received larger contributions from shallow groundwater sources. DOC concentration and specific ultraviolet absorbance peaked during spring snowmelt in all streams, and were consistently higher in blackwater streams than in glacial and clearwater streams. The hydrophobic acid fraction of DOC dominated across all streams and seasons, comprising between 35% and 56% of total DOC. The hydrophilic acid fraction of DOC was more prominent in glacial (23% ± 3%) and clearwater streams (19% ± 1%) than in blackwater streams (16% ± 1%), and was enriched during winter base flow (29% ± 1%) relative to snowmelt and summer base flow. We observed that an increase in the contribution of deep groundwater to streamflow resulted in decreased DOC concentration, aromaticity, and DOC-to-dissolved organic nitrogen ratio, and an increase in the proportion of hydrophilic acids relative to hydrophobic acids. Our findings suggest that future permafrost degradation and higher contributions of groundwater to streamflow may result in a higher fraction of labile DOM in streams of the Yukon basin.

Long-term environmental drivers of DOC fluxes: Linkages between management, hydrology and climate in a subtropical coastal estuary

NASA Astrophysics Data System (ADS)

Regier, Peter; Briceño, Henry; Jaffé, Rudolf

2016-12-01

Urban and agricultural development of the South Florida peninsula has disrupted historic freshwater flow in the Everglades, a hydrologically connected ecosystem stretching from central Florida to the Gulf of Mexico, USA. Current system-scale restoration efforts aim to restore natural hydrologic regimes to reestablish pre-drainage ecosystem functioning through increased water availability, quality and timing. Aquatic transport of carbon in this ecosystem, primarily as dissolved organic carbon (DOC), plays a critical role in biogeochemical cycling and food-web dynamics, and will be affected both by water management policies and climate change. To better understand DOC dynamics in South Florida estuaries and how hydrology, climate and water management may affect them, 14 years of monthly data collected in the Shark River estuary were used to examine DOC flux dynamics in a broader environmental context. Multivariate statistical methods were applied to long-term datasets for hydrology, water quality and climate to untangle the interconnected environmental drivers that control DOC export at monthly and annual scales. DOC fluxes were determined to be primarily controlled by hydrology but also by seasonality and long-term climate patterns and episodic weather events. A four-component model (salinity, rainfall, inflow, Atlantic Multidecadal Oscillation) capable of predicting DOC fluxes (R2 = 0.84, p < 0.0001, n = 155) was established and applied to potential climate change scenarios for the Everglades to assess DOC flux response to climate and restoration variables. The majority of scenario runs indicated that DOC export from the Everglades is expected to decrease due to future changes in rainfall, water management and salinity.

Seasonal Changes of DOC Composition of Rivers in Temperate Monsoon Climates

NASA Astrophysics Data System (ADS)

Oh, N. H.; Shin, Y.; Lee, E. J.; Hur, J.

2014-12-01

The spatial and seasonal dynamics of dissolved organic carbon (DOC) composition and biodegradability were investigated for the five largest rivers in the Republic of Korea during the years 2012 - 2013 using dark incubation experiments and spectroscopic measurements, including parallel factor analysis (PARAFAC). The DOC concentrations of the rivers in relatively steep and forest-dominated basins were <~2 mg L-1, and remained relatively constant over the seasons. In contrast, those of the rivers influenced by urban and agricultural activities rose up to 5.4 mg L-1, which was decreased to ~2 mg L-1 during the summer monsoon period, indicating that increased precipitation had the effect of dilution. Among the fluorescence components, terrestrial humic-like components were dominant in all the rivers except for one, where tyrosine- or tryptophan-like compounds were the major component. However, terrestrial humic-like components became dominant in all five of the rivers after high precipitation which occurred during the monsoon season, during which ~76% of the annual precipitation was received. Considering that 64% of South Korea is forested, our results suggest that the forests could be a large source of riverine DOC, elevating the DOC loads during monsoon rainfall. Although more DOC could be degraded when DOC input increased, regardless of its sources, the percent biodegradability was reduced with increased proportions of terrestrially derived and aromatic compounds. These results suggest that the relatively stable and terrestrial humic-like compounds released during the monsoon rainfall could reduce the potential of microbial respiration of riverine DOC and evasion of river CO2 to the atmosphere, despite of the increase in the DOC load.

Dissolved organic carbon fluxes from soils in the Alaskan coastal temperate rainforest

NASA Astrophysics Data System (ADS)

D'Amore, D. V.; Edwards, R.; Hood, E. W.; Herendeen, P. A.; Valentine, D.

2011-12-01

Soil saturation and temperature are the primary factors that influence soil carbon cycling. Interactions between these factors vary by soil type, climate, and landscape position, causing uncertainty in predicting soil carbon flux from. The soils of the North American perhumid coastal temperate rainforest (NCTR) store massive amounts of carbon, yet there is no estimate of dissolved organic carbon (DOC) export from different soil types in the region. There are also no working models that describe the influence of soil saturation and temperature on the export of DOC from soils. To address this key information gap, we measured soil water table elevation, soil temperature, and soil and stream DOC concentrations to calculate DOC flux across a soil hydrologic gradient that included upland soils, forested wetland soils, and sloping bog soils in the NCTR of southeast Alaska. We found that increased soil temperature and frequent fluctuations of soil water tables promoted the export of large quantities of DOC from wetland soils and relatively high amounts of DOC from mineral soils. Average area-weighted DOC flux ranged from 7.7 to 33.0 g C m-2 y-1 across a gradient of hydropedologic soil types. The total area specific export of carbon as DOC for upland, forested wetland and sloping bog catchments was 77, 306, and 329 Kg C ha-1 y-1 respectively. The annual rate of carbon export from wetland soils in this region is among the highest reported in the literature. These findings highlight the importance of terrestrial-aquatic fluxes of DOC as a pathway for carbon loss in the NCTR.

The fate of terrigenous dissolved organic carbon on the Eurasian shelves and export to the North Atlantic

NASA Astrophysics Data System (ADS)

Kaiser, K.; Benner, R.; Amon, R. M. W.

2017-01-01

Dissolved lignin phenols, chromophoric dissolved organic matter (CDOM) absorption, and fluorescence were analyzed along cross-slope mooring locations in the Barents, Laptev, and East Siberian Seas to gain a better understanding of terrigenous dissolved organic carbon (tDOC) dynamics in Arctic shelf seas and the Arctic Ocean. A gradient of river water and tDOC was observed along the continental shelf eastward into the East Siberian Sea. Correlations of carbon-normalized yields of lignin-derived phenols supplied by Siberian rivers with river water fractions and known water residence times yielded in situ decay constants of 0.18-0.58 yr-1. Calculations showed ˜50% of annual tDOC discharged by Siberian rivers was mineralized in estuaries and on Eurasian shelves per year indicating extensive removal of tDOC. Bioassay experiments and in situ decay constants indicated a reactivity continuum for tDOC. CDOM parameters and acid/aldehyde ratios of vanillyl (V) and syringyl (S) lignin phenols showed biomineralization was the dominant mechanism for the removal of tDOC. Characteristic ratios of p-hydroxy (P), S, and V phenols (P/V, S/V) also identified shelf regions in the Kara Sea and regions along the Western Laptev Sea shelf where formation of Low Salinity Halocline Waters (LSHW) and Lower Halocline Water (LHW) occurred. The efficient removal of tDOC demonstrates the importance of Eurasian margins as sinks of tDOC derived from the large Siberian Rivers and confirms tDOC mineralization has a major impact on nutrients budgets, air-sea CO2 exchange, and acidification in the Siberian Shelf Seas.

The fate of terrigenous dissolved organic carbon on the Eurasian shelves and export to the North Atlantic

NASA Astrophysics Data System (ADS)

Kaiser, Karl; Amon, Rainer; Benner, Ronald

2017-04-01

Dissolved lignin phenols, chromophoric dissolved organic matter (CDOM) absorption, and fluorescence were analyzed along cross-slope mooring locations in the Barents, Laptev, and East Siberian Seas to gain a better understanding of terrigenous dissolved organic carbon (tDOC) dynamics in Arctic shelf seas and the Arctic Ocean. A gradient of river water and tDOC was observed along the continental shelf eastward into the East Siberian Sea. Correlations of carbon-normalized yields of lignin-derived phenols supplied by Siberian rivers with river water fractions and known water residence times yielded in situ decay constants of 0.18-0.58 per year. Calculations showed about 50% of annual tDOC discharged by Siberian rivers was mineralized in estuaries and on the Eurasian shelves per year indicating extensive removal of tDOC. Bioassay experiments and in situ decay constants indicated a reactivity continuum for tDOC. CDOM parameters and acid/aldehyde ratios of vanillyl (V) and syringyl (S) lignin phenols showed biomineralization was the dominant mechanism for the removal of tDOC. Characteristic ratios of p-hydroxy (P), S, and V phenols (P/V, S/V) also identified shelf regions in the Kara Sea and regions along the Western Laptev Sea shelf where formation of Low Salinity Halocline Waters (LSHW) and Lower Halocline Water (LHW) occurred. The efficient removal of tDOC demonstrates the importance of Eurasian margins as sinks of tDOC derived from the large Siberian Rivers and confirms tDOC mineralization has a major impact on nutrients budgets, air-sea CO2 exchange, and acidification in the Siberian Shelf Seas.

Variation of the isotopic composition of dissolved organic carbon during the runoff cycle in the Amazon River and the floodplains

NASA Astrophysics Data System (ADS)

Albéric, Patrick; Pérez, Marcela A. P.; Moreira-Turcq, Patricia; Benedetti, Marc F.; Bouillon, Steven; Abril, Gwenaël

2018-01-01

Given the relative scarcity of stable isotope data on dissolved organic carbon (DOC) in the Amazon Basin, we hypothesized that the variability in DOC sources may be underestimated in such major river basins. To explore the links between the mainstem and tributaries and the floodplain, particular efforts were made during five distinct cruises at different stages of the hydrograph between October 2008 and January 2011, to document the spatial and temporal variation of DOC concentrations and δ13C-DOC in the central Amazon River system (Brazil). Based on more than 200 data, the spatial and temporal variability of δ13C-DOC values was found to be larger than previously reported in the same area. Although a small range of variation was observed throughout the hydrological cycle in the upper reach of the studied section (-29.2 to -29.5‰ in the Rio Negro and -28.7 to -29.0‰ in the Rio Solimões), a much larger one (-28.0 to -34.6‰) was found in the lower reach of the river, as the proportion of open lakes increased downstream in the floodplains. The low variability in the upper reaches suggests constant and homogeneous DOC sources from upland soils and flooded forest, while lower δ13C-DOC values recorded in the lower reach mainstem at high and falling waters can be attributed to a greater export of plankton-derived 13C-depleted DOC from flooded lakes. Noteworthy are the higher δ13C-DOC values measured in the Rio Madeira and the associated flooded lakes (-26.5 to -28.8‰), which may reflect the imprint from upland headwaters and a weaker density of flooded forest in the watershed. The higher δ13C-DOC values observed in the lower reach during low waters are still not fully understood. Floating meadows principally consisting of C4 macrophytes were found to increase δ13C-DOC values by ∼1.5‰ in their vicinity, but this impact was no longer noticeable at distances of ∼10 m from the plant rafts. This rather modest 13C-enrichment suggests rapid decomposition and/or dilution of this wetland-derived DOC.

Identifying dissolved organic carbon sources at a gaged headwater catchment using FDOM sensors

NASA Astrophysics Data System (ADS)

Malzone, J. M.; Shanley, J. B.

2014-12-01

The United States Geological Survey's (USGS) W-9 gage at the headwaters of Sleepers River, Vermont has been monitored for dissolved organic carbon (DOC) concentration for more than 20 years. However, the sources of this DOC during base flow and hydrologic events remain unclear. The major objectives of this research were to identify sources of DOC during storm events and to explain the observed DOC-streamflow counterclockwise hysteresis during hydrologic events. Two main hypotheses to explain hysteresis during hydrologic events were tested: (1) distant headwater wetlands are the major DOC source, which lags behind peak flow due to travel time; and (2) the entire watershed contributes to the DOC at the gage, but the response of DOC lags behind the period when groundwater contributes most to streamflow. Sources of DOC were tracked using fluorescent dissolved organic matter (FDOM) sensors in surface water and groundwater wells. Wells were installed at four depths, 0.3, 0.6, 0.9, and 1.2 m, at four sites: a peaty low-gradient riparian area near the headwaters; a mid-hillslope area on a long hillslope mid-watershed; a near-stream area on a long hillslope mid-watershed; and a low-gradient tributary confluence area just above the gage. During storm events, FDOM and hydraulic head were measured at the nested groundwater wells. Samples for DOC analysis were also taken to determine the relationship between FDOM and DOC. Results suggest that both distant sources and the greater watershed played a role in the transport of DOC to the W-9 gage. Distant peaty sources dominated during large storms and contributed the highest surface water FDOM measurements. The peak FDOM at the gage was therefore best described as a result of transport. However, export from these distant sources terminated rapidly and did not explain continued elevated FDOM at the gage. Groundwater across the watershed exhibited hysteresis analogous to that in the stream itself, with FDOM peaking as head receded. As groundwater is recharged, the water table intersects more carbon rich soil layers. Pre-event water is flushed out first before event water mobilizes DOC, causing the groundwater hysteresis. High FDOM groundwater discharging to the stream likely sustained elevated FDOM at the gage. The gage hysteresis, therefore, seems to be a result of both hypotheses tested.

Impact of managed moorland burning on DOC concentrations in soil solutions and stream waters

NASA Astrophysics Data System (ADS)

Palmer, Sheila; Wearing, Catherine; Johnson, Kerrylyn; Holden, Joseph; Brown, Lee

2013-04-01

In the UK uplands, prescribed burning of moorland vegetation is a common practice to maintain suitable habitats for game birds. Many of these landscapes are in catchments covered by significant deposits of blanket peat (typically one metre or more in depth). There is growing interest in the effect of land management on the stability of these peatland carbon stores, and their contribution to dissolved and particulate organic carbon in surface waters (DOC and POC, respectively) and subsequent effects on stream biogeochemistry and ecology. Yet there are surprisingly few published catchment-scale studies on the effect of moorland burning on DOC and POC. As part of the EMBER project, stream chemistry data were collected approximately monthly in ten upland blanket peat catchments in the UK, five of which acted as controls and were not subject to burning. The other five catchments were subject to a history of prescribed burning, typically in small patches (300-900 m2) in rotations of 8-25 years. Soil solution DOC was also monitored at four depths at two intensively studied sites (one regularly burned and one control). At the two intensive sites, soil solution DOC was considerably higher at the burned site, particularly in surface solutions where concentrations in excess of 100 mg/L were recorded on several occasions (median 37 mg/L over 18 months). The high soil solution DOC concentrations at the burned site occurred in the most recently burned plots (less than 2 years prior to start of sampling) and the lowest DOC concentrations were observed in plots burned 15-25 years previously. On average, median stream DOC and POC concentrations were approximately 43% and 35% higher respectively in burned catchments relative to control catchments. All streams exhibited peak DOC in late summer/early autumn with higher peak DOC concentrations in burned catchments (20-66 mg/L) compared to control catchments (18-54 mg/L). During winter months, DOC concentrations were low in control catchments (typically less than 15 mg/L) but were highly variable in burned catchments (9-40 mg/L), implying some instability of peat carbon stores and/or fluctuation in source. The results offer strong evidence for an impact of burning on the delivery of DOC to streams, possibly through increased surface run-off from bare or partially vegetated patches.

Dissolved organic carbon and nitrogen release from Holocene permafrost and seasonally frozen soils

NASA Astrophysics Data System (ADS)

Wickland, K.; Waldrop, M. P.; Koch, J. C.; Jorgenson, T.; Striegl, R. G.

2017-12-01

Permafrost (perennially frozen) soils store vast amounts of carbon (C) and nitrogen (N) that are vulnerable to mobilization to the atmosphere as greenhouse gases and to terrestrial and aquatic ecosystems as dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) upon thaw. Such releases will affect the biogeochemistry of arctic and boreal regions, yet little is known about active layer (seasonally frozen) and permafrost source variability that determines DOC and TDN mobilization. We quantified DOC and TDN leachate yields from a range of active layer and permafrost soils in Alaska varying in age and C and N content to determine potential release upon thaw. Soil cores from the upper 1 meter were collected in late winter, when soils were frozen, from three locations representing a range in geographic position, landscape setting, permafrost depth, and soil types across interior Alaska. Two 15 cm-thick segments were extracted from each core: a deep active-layer horizon and a shallow permafrost horizon. Soils were thawed and leached for DOC and TDN yields, dissolved organic matter optical properties, and DOC biodegradability; soils were analyzed for C and N content, and radiocarbon content. Soils had wide-ranging C and N content (<1-44% C, <0.1-2.3% N), and varied in radiocarbon age from 450-9200 years before present - thus capturing typical ranges of boreal and arctic soils. Soil DOC and TDN yields increased linearly with soil C and N content, and decreased with increasing radiocarbon age. However, across all sites DOC and TDN yields were significantly greater from permafrost soils (0.387 ± 0.324 mg DOC g-1 soil; 0.271 ± 0.0271 mg N g-1 soil) than from active layer soils (0.210 ± 0.192 mg DOC g-1 soil; 0.00716 ± 0.00569 mg N g-1 soil). DOC biodegradability increased with increasing radiocarbon age, and was statistically similar for active layer and permafrost soils. Our findings suggest that the continuously frozen state of permafrost soils has preserved higher relative potential DOC and TDN yields compared to seasonally thawed soils exposed to annual leaching and decomposition, and that frozen soils undergo microbial processes that produce labile DOC over time.

Advances in the Control System for a High Precision Dissolved Organic Carbon Analyzer

NASA Astrophysics Data System (ADS)

Liao, M.; Stubbins, A.; Haidekker, M.

2017-12-01

Dissolved organic carbon (DOC) is a master variable in aquatic ecosystems. DOC in the ocean is one of the largest carbon stores on earth. Studies of the dynamics of DOC in the ocean and other low DOC systems (e.g. groundwater) are hindered by the lack of high precision (sub-micromolar) analytical techniques. Results are presented from efforts to construct and optimize a flow-through, wet chemical DOC analyzer. This study focused on the design, integration and optimization of high precision components and control systems required for such a system (mass flow controller, syringe pumps, gas extraction, reactor chamber with controlled UV and temperature). Results of the approaches developed are presented.

Sources and characteristics of organic matter in the Clackamas River, Oregon, related to the formation of disinfection by-products in treated drinking water

USGS Publications Warehouse

Carpenter, Kurt D.; Kraus, Tamara E.C.; Goldman, Jami H.; Saraceno, John Franco; Downing, Bryan D.; Bergamaschi, Brian A.; McGhee, Gordon; Triplett, Tracy

2013-01-01

This study characterized the amount and quality of organic matter in the Clackamas River, Oregon, to gain an understanding of sources that contribute to the formation of chlorinated and brominated disinfection by-products (DBPs), focusing on regulated DBPs in treated drinking water from two direct-filtration treatment plants that together serve approximately 100,000 customers. The central hypothesis guiding this study was that natural organic matter leaching out of the forested watershed, in-stream growth of benthic algae, and phytoplankton blooms in the reservoirs contribute different and varying proportions of organic carbon to the river. Differences in the amount and composition of carbon derived from each source affects the types and concentrations of DBP precursors entering the treatment plants and, as a result, yield varying DBP concentrations and species in finished water. The two classes of DBPs analyzed in this study-trihalomethanes (THMs) and haloacetic acids (HAAs)-form from precursors within the dissolved and particulate pools of organic matter present in source water. The five principal objectives of the study were to (1) describe the seasonal quantity and character of organic matter in the Clackamas River; (2) relate the amount and composition of organic matter to the formation of DBPs; (3) evaluate sources of DBP precursors in the watershed; (4) assess the use of optical measurements, including in-situ fluorescence, for estimating dissolved organic carbon (DOC) concentrations and DBP formation; and (5) assess the removal of DBP precursors during treatment by conducting treatability "jar-test" experiments at one of the treatment plants. Data collection consisted of (1) monthly sampling of source and finished water at two drinking-water treatment plants; (2) event-based sampling in the mainstem, tributaries, and North Fork Reservoir; and (3) in-situ continuous monitoring of fluorescent dissolved organic matter (FDOM), turbidity, chlorophyll-a, and other constituents to continuously track source-water conditions in near real-time. Treatability tests were conducted during the four event-based surveys to determine the effectiveness of coagulant and powdered activated carbon (PAC) on the removal of DBP precursors. Sample analyses included DOC, total particulate carbon (TPC), total and dissolved nutrients, absorbance and fluorescence spectroscopy, and, for regulated DBPs, concentrations of THMs and HAAs in finished water and laboratory-based THM and HAA formation potentials (THMFP and HAAFP, respectively) for source water and selected locations throughout the watershed. The results of this study may not be typical given the record and near record amounts of precipitation that occurred during spring that produced streamflow much higher than average in 2010-11. Although there were algal blooms, lower concentrations of chlorophyll-a were observed in the water column during the study period compared to historical data. Concentrations of DBPs in finished (treated) water averaged 0.024 milligrams per liter (mg/L) for THMs and 0.022 mg/L for HAAs; maximum values were about 0.040 mg/L for both classes of DBPs. Although DBP concentrations were somewhat higher within the distribution system, none of the samples collected for this study or for the quarterly compliance monitoring by the water utilities exceeded levels permissible under existing U.S. Environmental Protection Agency (USEPA) regulations: 0.080 mg/L for THMs and 0.060 mg/L for HAAs. DOC concentrations were generally low in the Clackamas River, typically about 1.0-1.5 mg/L. Concentrations in the mainstem occasionally increased to nearly 2.5 mg/L during storms; DOC concentrations in tributaries were sometimes much higher (up to 7.8 mg/L). The continuous in-situ FDOM measurements indicated sharp rises in DOC concentrations in the mainstem following rainfall events; concentrations were relatively stable during summer base flow. Even though the first autumn storm mobilized appreciable quantities of carbon, higher concentrations of DBPs in finished water were observed 3-weeks later, after the ground was saturated from additional rainfall. The majority of the DOC in the lower Clackamas River appears to originate from the upper basin, suggesting terrestrial carbon was commonly the dominant source. Lower-basin tributaries typically contained the highest concentrations of DOC and DBP precursors and contributed substantially to the overall loads in the mainstem during storms. During low-flow periods, tributaries were not major sources of DOC or DBP precursors to the Clackamas River. Although the dissolved fraction of organic carbon contributed the majority of DBP precursors, at times the particulate fraction (inorganic sediment and organic particles including detritus and algal material) contributed a substantial fraction of DBP precursors. Considering just the main-stem sites, on average, 10 percent of THMFP and 32 percent of HAAFP were attributed to particulate carbon. This finding suggests water-treatment methods that remove particles prior to chlorination would reduce finished-water DBP concentrations to some degree. Overall, concentrations of THM and HAA precursors were closely linked to DOC concentrations; laboratory DBP formation potentials (DBPFPs) clearly showed that THMFP and HAAFP were greatest in the downstream tributaries that contained elevated carbon concentrations. However, carbon-normalized "specific" formation potentials for THMs and HAAs (STHMFP and SHAAFP, respectively) revealed changes in carbon character over time that affected the two types of DBP classes differently. HAA precursors were elevated in waters containing aromatic-rich soil-derived material arising from forested areas. In contrast, THM precursors were associated with carbon having a lower aromatic content; highest STHMFP occurred in autumn 2011 in the mainstem from North Fork Reservoir downstream to LO DWTP. This pattern suggests the potential for a link between THM precursors and algal-derived carbon. The highest STHMFP value was measured within North Fork Reservoir, indicating reservoir derived carbon may be important for this class of DBPs. Weak correlations between STHMFP and SHAAFP emphasize that precursor sources for these types of DBPs may be different. This highlights not only that different locations within the watershed produce carbon with different reactivity (specific DBPFP), but also that different management approaches for each class of DBP precursors could be required for control. Treatability tests conducted on source water during four basin-wide surveys demonstrated that an average of about 40 percent of DOC can be removed by coagulation. While the decrease in THMFP following coagulation was similar to DOC, the decrease in HAAFP was much greater (approximately 70 percent), indicating coagulation is particularly effective at removing HAA precursors'likely because of the aromatic nature of the carbon associated with HAA precursors. Several findings from this study have direct implications for managing drinking-water resources and for providing useful information that may help improve treatment-plant operations. For example, the use of in-situ fluorometers that measure FDOM provided an excellent proxy for DOC concentration in this system and revealed short-term, rapid changes in DOC concentration during storm events. In addition, the strong correlation between FDOM values measured in-situ and HAA5 concentrations in finished water may permit estimation of continuous HAA concentrations, as was done here. As part of this study, multiple in-situ FDOM sensors were deployed continuously and in real-time to characterize the composition of dissolved organic matter. Although the initial results were promising, additional research and engineering developments will be needed to demonstrate the full utility of these sensors for this purpose. In conclusion, although DBPFPs were strongly correlated to DOC concentration, some DBPs formed from particulate carbon, including terrestrial leaf material and algal material such as planktonic species of blue-green algae and sloughed filaments, stalks, and cells of benthic algae. Different precursor sources in the watershed were evident from the data, suggesting specific actions may be available to address some of these sources. In-situ measurements of FDOM proved to be an excellent proxy for DOC concentration as well as HAA formation during treatment, which suggests further development and refinement of these sensors have the potential to provide real-time information about complex watershed processes to operators at the drinking-water treatment plants. Follow-up studies could examine the relative roles that terrestrial and algal sources have on the DBP precursor pool to better understand how watershed-management activities may be affecting the transport of these compounds to Clackamas River drinking-water intakes. Given the low concentrations of algae in the water column during this study, additional surveys during more typical river conditions could provide a more complete understanding of how algae contribute DBP precursors. Further development of FDOM-sensor technology can improve our understanding of carbon dynamics in the river and how concentrations may be trending over time. This study was conducted in collaboration with Clackamas River Water and the City of Lake Oswego water utilities. Other research partners included Oregon Health and Science University in Hillsboro, Oregon, Alexin Laboratory in Tigard, Oregon, U.S. Geological Survey National Research Program Laboratory in Denver, Colorado, and the U.S. Geological Survey Water Science Centers in Portland, Oregon, and Sacramento, California. This project was supported with funding from Clackamas River Water, City of Lake Oswego, the U.S. Geological Survey, and the Water Research Foundation.

Influences of glacial melt and permafrost thaw on the age of dissolved organic carbon in the Yukon River basin

USGS Publications Warehouse

Aiken, George R.; Spencer, Robert G.M.; Striegl, Robert G.; Schuster, Paul F.; Raymond, Peter A.

2014-01-01

Responses of near-surface permafrost and glacial ice to climate change are of particular significance for understanding long-term effects on global carbon cycling and carbon export by high-latitude northern rivers. Here we report Δ14C-dissolved organic carbon (DOC) values and dissolved organic matter optical data for the Yukon River, 15 tributaries of the Yukon River, glacial meltwater, and groundwater and soil water end-member sources draining to the Yukon River, with the goal of assessing mobilization of aged DOC within the watershed. Ancient DOC was associated with glacial meltwater and groundwater sources. In contrast, DOC from watersheds dominated by peat soils and underlain by permafrost was typically enriched in Δ14C indicating that degradation of ancient carbon stores is currently not occurring at large enough scales to quantitatively influence bulk DOC exports from those landscapes. On an annual basis, DOC exported was predominantly modern during the spring period throughout the Yukon River basin and became older through summer-fall and winter periods, suggesting that contributions of older DOC from soils, glacial meltwaters, and groundwater are significant during these months. Our data indicate that rapidly receding glaciers and increasing groundwater inputs will likely result in greater contributions of older DOC in the Yukon River and its tributaries in coming decades.

36 year trends in dissolved organic carbon export from Finnish rivers to the Baltic Sea.

PubMed

Räike, Antti; Kortelainen, Pirkko; Mattsson, Tuija; Thomas, David N

2012-10-01

Increasing dissolved organic carbon (DOC) concentrations in lakes, rivers and streams in northern mid latitudes have been widely reported during the last two decades, but relatively few studies have dealt with trends in DOC export. We studied the export of DOC from Finnish rivers to the Baltic Sea between 1975 and 2010, and estimated trends in DOC fluxes (both flow normalised and non-normalised). The study encompassed the whole Finnish Baltic Sea catchment area (301,000 km(2)) covering major land use patterns in the boreal zone. Finnish rivers exported annually over 900,000 t DOC to the Baltic Sea, and the mean area specific export was 3.5 t km(-2). The highest export (7.3t km(-2)) was measured in peat dominated catchments, whereas catchments rich in lakes had the lowest export (2.2 t km(-2)). Inter-annual variation in DOC export was high and controlled mainly by hydrology. There was no overall trend in the annual water flow, although winter flow increased in northern Finland over 36 years. Despite the numerous studies showing increases in DOC concentrations in streams and rivers in the northern hemisphere, we could not find any evidence of increases in DOC export to the northern Baltic Sea from Finnish catchments since 1975. Copyright © 2012 Elsevier B.V. All rights reserved.

Organic Matter in Rivers: The Crossroads between Climate and Water Quality

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

Davisson, M L

2001-04-27

All surface waters in the world contain dissolved organic matter and its concentration depends on climate and vegetation. Dissolved organic carbon (DOC) is ten times higher in wetlands and swamps than in surface water of arctic, alpine, or arid climate. Climates of high ecosystem productivity (i.e., tropics) typically have soils with low organic carbon storage, but drain high dissolved organic loads to rivers. Regions with lower productivity (e.g. grasslands) typically have high soil carbon storage while adjacent rivers have high DOC contents. Most DOC in a free-flowing river is derived from leaching vegetation and soil organic matter, whereas in dammedmore » rivers algae may comprise a significant portion. Water chemistry and oxygen-18 abundance of river water, along with radiocarbon and carbon-13 isotope abundance measurements of DOC were used to distinguish water and water quality sources in the Missouri River watershed. Drinking water for the City of St. Louis incorporates these different sources, and its water quality depends mostly on whether runoff is derived from the upper or the lower watershed, with the lower watershed contributing water with the highest DOC. During drinking water chlorination, DOC forms carcinogenic by-products in proportion to the amount of DOC present. This has recently led the USEPA to propose federal regulation standards. Restoration of natural riparian habitat such as wetlands will likely increase DOC concentrations in river water.« less

Variation of dissolved organic carbon transported by two Chinese rivers: The Changjiang River and Yellow River.

PubMed

Liu, Dong; Pan, Delu; Bai, Yan; He, Xianqiang; Wang, Difeng; Zhang, Lin

2015-11-15

Real-time monitoring of riverine dissolved organic carbon (DOC) and the associated controlling factors is essential to coastal ocean management. This study was the first to simulate the monthly DOC concentrations at the Datong Hydrometric Station for the Changjiang River and at the Lijin Hydrometric Station for the Yellow River from 2000 to 2013 using a multilayer back-propagation neural network (MBPNN), along with basin remote-sensing products and river in situ data. The average absolute error between the modeled values and in situ values was 9.98% for the Changjiang River and 10.84% for the Yellow River. As an effect of water dilution, the variations of DOC concentrations in the two rivers were significantly negatively affected by discharge, with lower values reported during the wet season. Moreover, vegetation growth status and agricultural activities, represented by the gross primary product (GPP) and cropland area percent (CropPer) in the river basin, respectively, also significantly affected the DOC concentration in the Changjiang River, but not the Yellow River. The monthly riverine DOC flux was calculated using modeled DOC concentrations. In particular, the riverine DOC fluxes were affected by discharge, with 71.06% being reported for the Changjiang River and 90.71% for the Yellow River. Over the past decade, both DOC concentration and flux in the two rivers have not shown significant changes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dissolved organic carbon from the upper Rio Negro protects zebrafish (Danio rerio) against ionoregulatory disturbances caused by low pH exposure

PubMed Central

Duarte, Rafael M.; Smith, D. Scott; Val, Adalberto L.; Wood, Chris M.

2016-01-01

The so-called “blackwaters” of the Amazonian Rio Negro are rich in highly coloured dissolved organic carbon (DOC), but ion-poor and very acidic, conditions that would cause fatal ionoregulatory failure in most fish. However these blackwaters support 8% of the world’s ichthyofauna. We tested the hypothesis that native DOC provides protection against ionoregulatory dysfunction in this extreme environment. DOCs were isolated by reverse-osmosis from two Rio Negro sites. Physico-chemical characterization clearly indicated a terrigenous origin, with a high proportion of hydroxyl and phenolic sites, high chemical reactivity to protons, and unusual proteinaceous fluorescence. When tested using zebrafish (a model organism), Rio Negro DOC provided almost perfect protection against ionoregulatory disturbances associated with acute exposure to pH 4.0 in ion-poor water. DOC reduced diffusive losses of Na+ and Cl−, and promoted a remarkable stimulation of Na+ uptake that otherwise would have been completely inhibited. Additionally, prior acclimation to DOC at neutral pH reduced rates of branchial Na+ turnover, and provided similar protection against acid-induced ionoregulatory disturbances, even if the DOC was no longer present. These results reinforce the important roles that DOC molecules can play in the regulation of gill functions in freshwater fish, particularly in ion-poor, acidic blackwaters. PMID:26853589

Spatiotemporal Variation of Dissolved Carbon in Semi-humid/arid Inland Waters: A Case Study from Songnen Plain, China

NASA Astrophysics Data System (ADS)

Song, K.; Li, L.; Zang, S.; Zhao, Y.

2012-12-01

Spatial and seasonal variations of dissolved organic carbon (DOC) and inorganic carbon (DIC) in 34 waters across the semi-humid/arid Songnen Plain, China were examined with 320 samples collected in 2011-2012. Large variations in both the concentration and quality of DOC are revealed, ranging from 0.47 mgL-1 to 720 mgL-1, which is mainly caused by the hydro-climatic condition in the plain. Large variations of DOC and DIC concentrations are observed between open (mean ± sd: 5.6 ± 2.4 mgL-1, 57.4 ± 34.7 mgL-1) and closed lakes (43.3 ± 7.9 mgL-1, 172.9 ± 113.3 mgL-1). Temporally, higher DOC and DIC concentrations are measured for ice-underlying water in winter than ice-free seasons. Colored dissolved organic matter (CDOM) and DOC concentrations are higher after high discharge events with terrigenous sources of CDOM/DOC dominated, while autochthonous sources also contributed to CDOM/DOC concentrations during algal bloom seasons. An interesting result of this study is that the non-outflow conditions for various water catchments had condensed effects on the dissolved carbon, resulting in close relationships between salinity and dissolved carbon parameters, e.g. salinity vs DOC (R2 = 0.83, p < 0.001), DIC (R2 = 0.96, p < 0.0001) using data set collected in 2011. Independent data set collected in May 2012 also confirmed this finding, yielding high correlation for salinity vs DOC (R2 = 0.79, p < 0.001), salinity vs DIC (R2 = 0.91, p < 0.0001), highlighting the potential of quantifying DOC/DIC from salinity measurements for thousand of waters dispersed in the semi-arid Songnen Plain. Indices based on CDOM absorption spectra, e.g. E250:365, DOC specific CDOM absorption (SUVA254) and spectral slope ratio (Sr, S275-295/S350-400), were applied to characterize DOM components and sources. Our results indicate high molecular weight CDOM fractions are more abundant in open waters than closed waters.

Temporal-spatial variation of DOC concentration, UV absorbance and the flux estimation in the Lower Dagu River, China

NASA Astrophysics Data System (ADS)

Xi, Min; Kong, Fanlong; Li, Yue; Kong, Fanting

2017-12-01

Dissolved organic carbon (DOC) is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transport processes. To better understand the temporal and spatial variation of DOC, 7 sites along the Lower Dagu River were chosen to conduct a comprehensive measurement from March 2013 to February 2014. Specifically, water samples were collected from the Lower Dagu River between the 26th and 29th of every month during the experimental period. The DOC concentration (CDOC) and UV absorbance were analyzed using a total organic carbon analyzer and the ultraviolet-visible absorption spectrum, and the DOC export flux was estimated with a simple empirical model. The results showed that the CDOC of the Lower Dagu River varied from 1.32 to 12.56 mg/L, consistent with global rivers. The CDOC and UV absorbance showed significant spatial variation in the Dagu River during the experiential period because of the upstream natural processes and human activities in the watershed. The spatial variation is mainly due to dam or reservoir constructions, riverside ecological environment changes, and non-point source or wastewater discharge. The seasonal variation of CDOC was mainly related to the source of water DOC, river runoff, and temperature, and the UV absorbance and humification degree of DOC had no obvious differences among months ( P<0.05). UV absorbance was applied to test the CDOC in Lower Dagu River using wave lengths of 254 and 280 nm. The results revealed that the annual DOC export flux varied from 1.6 to 3.76 × 105 g C/km2/yr in a complete hydrological year, significantly lower than the global average. It is worth mentioning that the DOC export flux was mainly concentrated in summer (˜90% of all-year flux in July and August), since the runoff in the Dagu River took place frequently in summer. These observations implied environment change could bring the temporal-spatial variation of DOC and the exports, which would further affect the land-ocean interactions in the Lower Dagu River and the global carbon cycle.

Winter Ground Temperatures Control Snowmelt DOC Export From a Discontinuous Permafrost Watershed: A Multi-Year Perspective

NASA Astrophysics Data System (ADS)

Carey, S. K.

2006-12-01

For discontinuous and continuous permafrost watersheds, the largest mass flux of dissolved organic carbon (DOC) occurs during the snowmelt period. During this time, available allochtonous organic carbon that has accumulated over the winter in frozen organic soils is rapidly flushed to the basin outlet. While this process has been observed now in many river systems of different size and location, there have been few inter-annual reports on the mass of DOC loss and the factors controlling its variability during freshet. Hydrological and DOC fluxes were recorded for the 2002, 2003 and 2006 snowmelt season with supplementary over-winter data for an 8 square kilometer sub-basin (Granger Basin) of the Wolf Creek Research Basin, Yukon Territory, Canada. Granger Basin is an alpine catchment above treeline underlain with discontinuous permafrost (approximately 70 %) and has widespread surface organic soils up to 0.4 m in thickness. Pre-melt snow water equivalent varied widely throughout the basin, yet was greatest in 2006, followed by 2002 and 2003. Ground temperatures were notably colder throughout the 2003 winter compared with 2006 and 2002. For all years, discharge began in mid-May, and was a continuous event in 2002 and 2006. In 2003 four distinct melt-periods were observed due to rising and falling temperatures. During freshet, stream DOC concentration increased rapidly from < 2 mg C/L to > 15 mg C/L on the first ascending limb of the hydrograph in each year. In 2003, DOC was largely flushed from the catchment several weeks prior to peak freshet. DOC concentration in wells and piezometers followed a similar pattern to streamflow DOC, with 2003 groundwater DOC concentrations less than 2002 and 2006. The total mass flux of DOC during freshet was 0.85, 0.45 and 1.01 g C/m2 for 2002, 2003 and 2006 respectively. Despite differences in pre-melt snow accumulation, the timing of melt and the volume of discharge, it appears that spring DOC export is largely controlled by over-winter ground temperatures. This has important implications for carbon mass balances as warming temperatures in the pan-arctic are largely occurring during the winter months.

Deep nitrogen acquisition in warming permafrost soils: Contributions of belowground plant traits and fungal symbioses in the permafrost carbon feedback to climate

NASA Astrophysics Data System (ADS)

Hartnett, H. E.; Palta, M. M.; Grimm, N. B.; Ruhi, A.; van Shaijik, M.

2016-12-01

Tempe Town Lake (TTL) is a hydrologically-regulated reservoir in Tempe, Arizona. The lake has high primary production and receives dissolved organic carbon (DOC) from rainfall, storm flow, and upstream river discharge. We applied an ARIMA time-series model to a three-year period for which we have high-frequency chemistry, meteorology, and streamflow data and analyzed external (rainfall, stream flow) and internal (dissolved O2) drivers of DOC content and composition. DOC composition was represented by fluorescence-based indices (fluorescence index, humification index, freshness) related to DOC source (microbially- vs. terrestrially-derived) and reactivity DOC. Patterns in DOC concentration and composition suggest carbon cycling in the lake responds to both meteorological events and to anthropogenic activity. The fluorescence-derived DOC composition is consistent with seasonally-distinct inputs of algal- and terrestrially-derived carbon. For example, Tempe Town Lake is supersaturated in O2 over 70% of the time, suggesting the system is autotrophic and primary productivity (i.e., O2 saturation state) was the strongest driver of DOC concentration. In contrast, external drivers (rainfall pattern, streamflow) were the strongest determinants of DOC composition. Biological processes (e.g., algal growth) generate carbon in the lake during spring and summer, and high Fluorescence Index and Freshness values at this time are indicative of algal-derived material; these parameters generally decrease with rain or flow suggesting algal-derived carbon is diluted by external water inputs. During dry periods, carbon builds up on the land surface and subsequent rainfall events deliver terrestrial carbon to the lake. Further evidence that rain and streamflow deliver land-derived material are increases in the Humification Index (an indicator of terrestrial material) following rain/flow events. Our results indicate that Tempe Town Lake generates autochthonous carbon and has the capacity to process allochthonous carbon from the urban environment. Ongoing work is comparing these results to other periods in the 10-year time series to test if the driver-DOC relationships are robust over longer time-scales and evaluating how changes in lake management and climate have altered DOC over time.

Temporal Patterns in Dissolved Organic Carbon Composition in an Urban Lake

NASA Astrophysics Data System (ADS)

Hartnett, H. E.; Palta, M. M.; Grimm, N. B.; Ruhi, A.; van Shaijik, M.

2017-12-01

Tempe Town Lake (TTL) is a hydrologically-regulated reservoir in Tempe, Arizona. The lake has high primary production and receives dissolved organic carbon (DOC) from rainfall, storm flow, and upstream river discharge. We applied an ARIMA time-series model to a three-year period for which we have high-frequency chemistry, meteorology, and streamflow data and analyzed external (rainfall, stream flow) and internal (dissolved O2) drivers of DOC content and composition. DOC composition was represented by fluorescence-based indices (fluorescence index, humification index, freshness) related to DOC source (microbially- vs. terrestrially-derived) and reactivity DOC. Patterns in DOC concentration and composition suggest carbon cycling in the lake responds to both meteorological events and to anthropogenic activity. The fluorescence-derived DOC composition is consistent with seasonally-distinct inputs of algal- and terrestrially-derived carbon. For example, Tempe Town Lake is supersaturated in O2 over 70% of the time, suggesting the system is autotrophic and primary productivity (i.e., O2 saturation state) was the strongest driver of DOC concentration. In contrast, external drivers (rainfall pattern, streamflow) were the strongest determinants of DOC composition. Biological processes (e.g., algal growth) generate carbon in the lake during spring and summer, and high Fluorescence Index and Freshness values at this time are indicative of algal-derived material; these parameters generally decrease with rain or flow suggesting algal-derived carbon is diluted by external water inputs. During dry periods, carbon builds up on the land surface and subsequent rainfall events deliver terrestrial carbon to the lake. Further evidence that rain and streamflow deliver land-derived material are increases in the Humification Index (an indicator of terrestrial material) following rain/flow events. Our results indicate that Tempe Town Lake generates autochthonous carbon and has the capacity to process allochthonous carbon from the urban environment. Ongoing work is comparing these results to other periods in the 10-year time series to test if the driver-DOC relationships are robust over longer time-scales and evaluating how changes in lake management and climate have altered DOC over time.

Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils

USGS Publications Warehouse

Neff, J.C.; Hooper, D.U.

2002-01-01

Climatic change may influence decomposition dynamics in arctic and boreal ecosystems, affecting both atmospheric CO2 levels, and the flux of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) to aquatic systems. In this study, we investigated landscape-scale controls on potential production of these compounds using a one-year laboratory incubation at two temperatures (10?? and 30??C). We measured the release of CO2, DOC and DON from tundra soils collected from a variety of vegetation types and climatic regimes: tussock tundra at four sites along a latitudinal gradient from the interior to the north slope of Alaska, and soils from additional vegetation types at two of those sites (upland spruce at Fairbanks, and wet sedge and shrub tundra at Toolik Lake in northern Alaska). Vegetation type strongly influenced carbon fluxes. The highest CO2 and DOC release at the high incubation temperature occurred in the soils of shrub tundra communities. Tussock tundra soils exhibited the next highest DOC fluxes followed by spruce and wet sedge tundra soils, respectively. Of the fluxes, CO2 showed the greatest sensitivity to incubation temperatures and vegetation type, followed by DOC. DON fluxes were less variable. Total CO2 and total DOC release were positively correlated, with DOC fluxes approximately 10% of total CO2 fluxes. The ratio of CO2 production to DOC release varied significantly across vegetation types with Tussock soils producing an average of four times as much CO2 per unit DOC released compared to Spruce soils from the Fairbanks site. Sites in this study released 80-370 mg CO2-C g soil C-1 and 5-46 mg DOC g soil C-1 at high temperatures. The magnitude of these fluxes indicates that arctic carbon pools contain a large proportion of labile carbon that could be easily decomposed given optimal conditions. The size of this labile pool ranged between 9 and 41% of soil carbon on a g soil C basis, with most variation related to vegetation type rather than climate.

Across the consciousness continuum—from unresponsive wakefulness to sleep

PubMed Central

Blume, Christine; del Giudice, Renata; Wislowska, Malgorzata; Lechinger, Julia; Schabus, Manuel

2015-01-01

Advances in the development of new paradigms as well as in neuroimaging techniques nowadays enable us to make inferences about the level of consciousness patients with disorders of consciousness (DOC) retain. They, moreover, allow to predict their probable development. Today, we know that certain brain responses (e.g., event-related potentials or oscillatory changes) to stimulation, circadian rhythmicity, the presence or absence of sleep patterns as well as measures of resting state brain activity can serve the diagnostic and prognostic evaluation process. Still, the paradigms we are using nowadays do not allow to disentangle VS/UWS and minimally conscious state (MCS) patients with the desired reliability and validity. Furthermore, even rather well-established methods have, unfortunately, not found their way into clinical routine yet. We here review current literature as well as recent findings from our group and discuss how neuroimaging methods (fMRI, PET) and particularly electroencephalography (EEG) can be used to investigate cognition in DOC or even to assess the degree of residual awareness. We, moreover, propose that circadian rhythmicity and sleep in brain-injured patients are promising fields of research in this context. PMID:25805982

Spatial and temporal patterns of dissolved organic matter quantity and quality in the Mississippi River Basin, 1997–2013

USGS Publications Warehouse

Stackpoole, Sarah M.; Stets, Edward G.; Clow, David W.; Burns, Douglas A.; Aiken, George R.; Aulenbach, Brent T.; Creed, Irena F.; Hirsch, Robert M.; Laudon, Hjalmar; Pellerin, Brian; Striegl, Robert G.

2017-01-01

Recent studies have found insignificant or decreasing trends in time-series dissolved organic carbon (DOC) datasets, questioning the assumption that long-term DOC concentrations in surface waters are increasing in response to anthropogenic forcing, including climate change, land use, and atmospheric acid deposition. We used the weighted regressions on time, discharge, and season (WRTDS) model to estimate annual flow-normalized concentrations and fluxes to determine if changes in DOC quantity and quality signal anthropogenic forcing at 10 locations in the Mississippi River Basin. Despite increases in agriculture and urban development throughout the basin, net increases in DOC concentration and flux were significant at only 3 of 10 sites from 1997 to 2013 and ranged between −3.5% to +18% and −0.1 to 19%, respectively. Positive shifts in DOC quality, characterized by increasing specific ultraviolet absorbance at 254 nm, ranged between +8% and +45%, but only occurred at one of the sites with significant DOC quantity increases. Basinwide reductions in atmospheric sulfate deposition did not result in large increases in DOC either, likely because of the high buffering capacity of the soil. Hydroclimatic factors including annual discharge, precipitation, and temperature did not significantly change during the 17-year timespan of this study, which contrasts with results from previous studies showing significant increases in precipitation and discharge over a century time scale. Our study also contrasts with those from smaller catchments, which have shown stronger DOC responses to climate, land use, and acidic deposition. This temporal and spatial analysis indicated that there was a potential change in DOC sources in the Mississippi River Basin between 1997 and 2013. However, the overall magnitude of DOC trends was not large, and the pattern in quantity and quality increases for the 10 study sites was not consistent throughout the basin.

Dissolved organic carbon content and characteristics in relation to carbon dioxide partial pressure across Poyang Lake wetlands and adjacent aquatic systems in the Changjiang basin.

PubMed

Wang, Huaxin; Jiao, Ruyuan; Wang, Fang; Zhang, Lu; Yan, Weijin

2016-12-01

Dissolved organic carbon (DOC) plays diverse roles in carbon biogeochemical cycles. Here, we explored the link between DOC and pCO 2 using high-performance size-exclusion chromatography (HPSEC) with UV 254 detection and excitation emission matrix (EEM) fluorescence spectroscopy to determine the molecular weight distribution (MW) and the spectral characteristics of DOC, respectively. The relationship between DOC and pCO 2 was investigated in the Poyang Lake wetlands and their adjacent aquatic systems. The results indicated significant spatial variation in the DOC concentrations, MW distributions, and pCO 2 . The DOC concentration was higher in the wetlands than in the rivers and lakes. pCO 2 was high in wetlands in which the dominant vegetation was Phragmites australis, whereas it was low in wetlands in which Carex tristachya was the dominant species. DOC was divided into five fractions according to MW, as follows: super-low MW (SLMW, <1 kDa); low MW (LMW, 1-2.5 kDa); intermediate MW (IMW, 2.5-3.5 kDa); high MW (HMW, 3.5-6 kDa); and super-high MW (SMW, > 40 kDa). Rivers contained high proportions of HMW and extremely low amounts of SLMW, whereas wetlands had relatively high proportions of SLMW. The proportion of SMW (SMW p ) was particularly high in wetlands. We found that pCO 2 significantly positively correlated with the proportion of IMW, and significantly negatively correlated with SMW p . These data improve our understanding of the MW of bioavailable DOC and its conversion to CO 2 . The present results demonstrate that both the content and characteristics of DOC significantly affect pCO 2 . pCO 2 and DOC must be studied further to help understanding the role of the wetland on the regional CO 2 budget. Copyright © 2016 Elsevier Ltd. All rights reserved.

Carbon and nitrogen stoichiometry across stream ecosystems

NASA Astrophysics Data System (ADS)

Wymore, A.; Kaushal, S.; McDowell, W. H.; Kortelainen, P.; Bernhardt, E. S.; Johnes, P.; Dodds, W. K.; Johnson, S.; Brookshire, J.; Spencer, R.; Rodriguez-Cardona, B.; Helton, A. M.; Barnes, R.; Argerich, A.; Haq, S.; Sullivan, P. L.; López-Lloreda, C.; Coble, A. A.; Daley, M.

2017-12-01

Anthropogenic activities are altering carbon and nitrogen concentrations in surface waters globally. The stoichiometry of carbon and nitrogen regulates important watershed biogeochemical cycles; however, controls on carbon and nitrogen ratios in aquatic environments are poorly understood. Here we use a multi-biome and global dataset (tropics to Arctic) of stream water chemistry to assess relationships between dissolved organic carbon (DOC) and nitrate, ammonium and dissolved organic nitrogen (DON), providing a new conceptual framework to consider interactions between DOC and the multiple forms of dissolved nitrogen. We found that across streams the total dissolved nitrogen (TDN) pool is comprised of very little ammonium and as DOC concentrations increase the TDN pool shifts from nitrate to DON dominated. This suggests that in high DOC systems, DON serves as the primary source of nitrogen. At the global scale, DOC and DON are positively correlated (r2 = 0.67) and the average C: N ratio of dissolved organic matter (molar ratio of DOC: DON) across our data set is approximately 31. At the biome and smaller regional scale the relationship between DOC and DON is highly variable (r2 = 0.07 - 0.56) with the strongest relationships found in streams draining the mixed temperate forests of the northeastern United States. DOC: DON relationships also display spatial and temporal variability including latitudinal and seasonal trends, and interactions with land-use. DOC: DON ratios correlated positively with gradients of energy versus nutrient limitation pointing to the ecological role (energy source versus nutrient source) that DON plays with stream ecosystems. Contrary to previous findings we found consistently weak relationships between DON and nitrate which may reflect DON's duality as an energy or nutrient source. Collectively these analyses demonstrate how gradients of DOC drive compositional changes in the TDN pool and reveal a high degree of variability in the C: N ratio (3-100) of stream water dissolved organic matter.

Distinct expression of alkaline phosphatase activity in epilimnetic bacteria: Implication for persistent DOC consumption in a P-limited reservoir

NASA Astrophysics Data System (ADS)

Tseng, Y.; Kao, S.; Shiah, F.

2013-12-01

In a P-deficient system, P availability usually controls the microbial activity and thus the ecosystem function. Thingstad et al. (1997) first addressed a 'Malfunctioning Microbial-loop' theory, which stated that low bacterial production (BP) caused by insufficient nutrient supply would result in DOC accumulation in an oligotrophic ecosystem. In this study we re-examined the theory by conducting seasonal patterns and correlations among soluble reactive phosphate (SRP) and DOC, microbial abundances (picocyanobacteria, bacteria, and heterotrophic nanoflagellate; HNF) and activities (primary production, bacterial production, and alkaline phosphatase activity; APA) coupled with enzyme-labeled fluorescence (ELF) assays on bacterioplankton in a subtropical reservoir sharing the common features, nitrate-replete and P-deficient, with most natural freshwater system during Oct 2007-Oct 2008. Persistently high APA was recorded during most of time, implying that the system was P-deficient. Size fractionated APA and ELF assay revealed that bacteria were the major APA contributor. However, significantly low epilimnion DOC was recorded during the stratified summer season accompanying with high BP and APA as well as high PP, implying that heterotrophic bacteria can well sustain in P-deficient system by utilizing DOP to rapidly lower down DOC under relatively high PP. Such findings oppose the 'Malfunctioning Microbial-loop' theory. On the other hand, strong epilimnetic DOC accumulation occurred in Oct 2007 under low light and low PP condition accompanying with high abundance of HNF, implying that HNF grazing may contribute to a certain degree of DOC accumulation. Correlation matrix supported our suggestions. This study testified the DOC dynamics in P-deficient ecosystem are tightly coupled with the source (PP and grazing) and sink (BP). We also suggested that in SRP-limited freshwater systems bacteria are capable of breaking down autochthonous DOC to reduce the chance of DOC accumulation during transport even dam construction continues to increase.

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

NASA Astrophysics Data System (ADS)

Oliver, Allison A.; Tank, Suzanne E.; Giesbrecht, Ian; Korver, Maartje C.; Floyd, William C.; Sanborn, Paul; Bulmer, Chuck; Lertzman, Ken P.

2017-08-01

The perhumid region of the coastal temperate rainforest (CTR) of Pacific North America is one of the wettest places on Earth and contains numerous small catchments that discharge freshwater and high concentrations of dissolved organic carbon (DOC) directly to the coastal ocean. However, empirical data on the flux and composition of DOC exported from these watersheds are scarce. We established monitoring stations at the outlets of seven catchments on Calvert and Hecate islands, British Columbia, which represent the rain-dominated hypermaritime region of the perhumid CTR. Over several years, we measured stream discharge, stream water DOC concentration, and stream water dissolved organic-matter (DOM) composition. Discharge and DOC concentrations were used to calculate DOC fluxes and yields, and DOM composition was characterized using absorbance and fluorescence spectroscopy with parallel factor analysis (PARAFAC). The areal estimate of annual DOC yield in water year 2015 was 33.3 Mg C km-2 yr-1, with individual watersheds ranging from an average of 24.1 to 37.7 Mg C km-2 yr-1. This represents some of the highest DOC yields to be measured at the coastal margin. We observed seasonality in the quantity and composition of exports, with the majority of DOC export occurring during the extended wet period (September-April). Stream flow from catchments reacted quickly to rain inputs, resulting in rapid export of relatively fresh, highly terrestrial-like DOM. DOC concentration and measures of DOM composition were related to stream discharge and stream temperature and correlated with watershed attributes, including the extent of lakes and wetlands, and the thickness of organic and mineral soil horizons. Our discovery of high DOC yields from these small catchments in the CTR is especially compelling as they deliver relatively fresh, highly terrestrial organic matter directly to the coastal ocean. Hypermaritime landscapes are common on the British Columbia coast, suggesting that this coastal margin may play an important role in the regional processing of carbon and in linking terrestrial carbon to marine ecosystems.

Assessing Environmental Drivers of DOC Fluxes in the Shark River Estuary: Modeling the Effects of Climate, Hydrology and Water Management

NASA Astrophysics Data System (ADS)

Regier, P.; Briceno, H.; Jaffe, R.

2016-02-01

Urban and agricultural development of the South Florida peninsula has disrupted freshwater flow in the Everglades, a hydrologically connected ecosystem stretching from central Florida to the Gulf of Mexico. Current system-scale restoration efforts aim to restore natural hydrologic regimes to reestablish pre-drainage ecosystem functioning through increased water availability, quality and timing. However, it is uncertain how hydrologic restoration combined with climate change will affect the downstream section of the system, including the mangrove estuaries of Everglades National Park. Aquatic transport of carbon, primarily as dissolved organic carbon (DOC), plays a critical role in biogeochemical cycling and food-web dynamics, and will be affected both by water management policies and climate change. To better understand DOC dynamics in these estuaries and how hydrology, climate and water management may affect them, 14 years of monthly data collected in the Shark River estuary were used to build a DOC flux model. Multi-variate methods were applied to long-term data-sets for hydrology, water quality and climate to untangle the interconnected environmental drivers that control DOC export at intra and inter-annual scales. DOC fluxes were determined to be primarily controlled by hydrology but also by seasonality and long-term climate patterns. Next, a 4-component model (salinity, inflow, rainfall, Atlantic Multidecadal Oscillation) capable of predicting DOC fluxes (R2=0.78, p<0.0001, n=161) was established. Finally, potential climate change scenarios for the Everglades were applied to this model to assess DOC flux variations in response to climate and restoration variables. Although global predictions anticipate that DOC export will generally increase in the future, the majority of scenario runs indicated that DOC export from the Everglades is expected to decrease due to changes in rainfall, evapotranspiration, inflows and sea-level rise.

Dissolved organic carbon and nitrogen release from boreal Holocene permafrost and seasonally frozen soils of Alaska

NASA Astrophysics Data System (ADS)

Wickland, Kimberly P.; Waldrop, Mark P.; Aiken, George R.; Koch, Joshua C.; Torre Jorgenson, M.; Striegl, Robert G.

2018-06-01

Permafrost (perennially frozen) soils store vast amounts of organic carbon (C) and nitrogen (N) that are vulnerable to mobilization as dissolved organic carbon (DOC) and dissolved organic and inorganic nitrogen (DON, DIN) upon thaw. Such releases will affect the biogeochemistry of permafrost regions, yet little is known about the chemical composition and source variability of active-layer (seasonally frozen) and permafrost soil DOC, DON and DIN. We quantified DOC, total dissolved N (TDN), DON, and DIN leachate yields from deep active-layer and near-surface boreal Holocene permafrost soils in interior Alaska varying in soil C and N content and radiocarbon age to determine potential release upon thaw. Soil cores were collected at three sites distributed across the Alaska boreal region in late winter, cut in 15 cm thick sections, and deep active-layer and shallow permafrost sections were thawed and leached. Leachates were analyzed for DOC, TDN, nitrate (NO3 ‑), and ammonium (NH4 +) concentrations, dissolved organic matter optical properties, and DOC biodegradability. Soils were analyzed for C, N, and radiocarbon (14C) content. Soil DOC, TDN, DON, and DIN yields increased linearly with soil C and N content, and decreased with increasing radiocarbon age. These relationships were significantly different for active-layer and permafrost soils such that for a given soil C or N content, or radiocarbon age, permafrost soils released more DOC and TDN (mostly as DON) per gram soil than active-layer soils. Permafrost soil DOC biodegradability was significantly correlated with soil Δ14C and DOM optical properties. Our results demonstrate that near-surface Holocene permafrost soils preserve greater relative potential DOC and TDN yields than overlying seasonally frozen soils that are exposed to annual leaching and decomposition. While many factors control the fate of DOC and TDN, the greater relative yields from newly thawed Holocene permafrost soils will have the largest potential impact in areas dominated by organic-rich soils.

A study of dissolved organic carbon and nitrate export in Catskill Mountain watersheds

NASA Astrophysics Data System (ADS)

Son, K.; Moore, K. E.; Lin, L.; Schneiderman, E. M.; Band, L. E.

2016-12-01

Watersheds in the Catskill Mountain region of New York State have historically experienced soil and stream acidification due to deposition of acidic compounds created from atmospheric SO2 and NOx. Recent studies in this region, and elsewhere in North America and Europe, have shown increases in dissolved organic carbon (DOC) in streams and lakes. Watersheds in the Catskills are the major source of drinking water for New York City and other communities in the region. Due to use of chlorine for disinfection, there is potential for the increase in DOC to lead to increased levels of disinfection byproducts in treated drinking water. Therefore, developing an improved understanding of the sources, fate and transport mechanisms, and export patterns for nitrate and DOC is important for informing watershed and water supply management. In this study, we analyzed the relationships between watershed characteristics, nitrate, and DOC for 12 gauged streams in the Neversink River watershed. Watershed characteristics included topography (elevation, slope, topographic wetness index), vegetation (leaf area index, species composition), soil (soil hydraulic parameters, soil carbon, wetland soil), atmospheric deposition (SO2, NOx), and climate (precipitation, temperature). Our preliminary analysis showed that both watershed slope and baseflow ratio are negatively correlated with annual median DOC concentration. At Biscuit Brook in the Neversink watershed, annual precipitation explained about 25% of annual DOC median concentration. DOC concentration was highly correlated with storm runoff in spring, summer, and fall, but stream nitrate concentration was weakly correlated with storm runoff in most seasons except summer when it was highly correlated with baseflow. We also applied a process-based ecohydrologic model (Regional Hydrologic Ecologic System Simulation, RHESSys) to the Biscuit Brook watershed to explore sources of nitrate and DOC and their movement within the watershed. We expect that this study will increase our understanding of how, when, and where DOC and nitrate are stored and transported to streams, as well as give insights into the key controls on nitrate and DOC processes in Catskill Mountain watersheds.