Where did all the Nitrogen go? Use of Watershed-Scale Budgets to Quantify Nitrogen Inputs, Storages, and Losses.

NASA Astrophysics Data System (ADS)

Boyer, E. W.; Goodale, C. L.; Howarth, R. W.; VanBreemen, N.

2001-12-01

Inputs of nitrogen (N) to aquatic and terrestrial ecosystems have increased during recent decades, primarily from the production and use of fertilizers, the planting of N-fixing crops, and the combustion of fossil fuels. We present mass-balanced budgets of N for 16 catchments along a latitudinal profile from Maine to Virginia, which encompass a range of climatic variability and are major drainages to the coast of the North Atlantic Ocean. We quantify inputs of N to each catchment from atmospheric deposition, application of nitrogenous fertilizers, biological nitrogen fixation by crops and trees, and import of N in agricultural products (food and feed). We relate these input terms to losses of N (total, organic, and nitrate) in streamflow. The importance of the relative N sources to N exports varies widely by watershed and is related to land use. Atmospheric deposition was the largest source of N to the forested catchments of northern New England (e.g., Penobscot and Kennebec); import of N in food was the largest source of N to the more populated regions of southern New England (e.g., Charles and Blackstone); and agricultural inputs were the dominant N sources in the Mid-Atlantic region (e.g., Schuylkill and Potomac). In all catchments, N inputs greatly exceed outputs, implying additional loss terms (e.g., denitrification or volatilization and transport of animal wastes), or changes in internal N stores (e.g, accumulation of N in vegetation, soil, or groundwater). We use our N budgets and several modeling approaches to constrain estimates about the fate of this excess N, including estimates of N storage in accumulating woody biomass, N losses due to in-stream denitrification, and more. This work is an effort of the SCOPE Nitrogen Project.

Eutrophication and Hypoxia Degrade Ecosystem Functions and Services of Narragansett Bay Benthic Communities

EPA Science Inventory

Excessive input of nitrogen to estuaries and coastal waters leads to eutrophication; the resulting organic matter over-enrichment of the sediments and seasonal hypoxia of the bottom water have well-known deleterious effects on benthic community biodiversity, abundance, and biomas...

Effect of Organic Enrichment and Hypoxia on the Biodiversity of Benthic Communities in Narragansett Bay

EPA Science Inventory

Excessive input of nitrogen to coastal waters leads to eutrophication and hypoxia that reduce biodiversity and impair key ecosystem services provided by benthic communities; for example, fish and shellfish production, bioturbation, nutrient cycling, and water filtration. Hypoxia ...

Eutrophication and Hypoxia Diminish Ecosystem Functions of Benthic Communities in a New England Estuary

EPA Science Inventory

Excessive input of nitrogen to estuaries and coastal waters leads to eutrophication; the resulting organic matter over-enrichment of sediments and seasonal hypoxia of bottom water have significant deleterious effects on benthic community biodiversity, abundance, and biomass. Our ...

Use of pharmaceuticals and pesticides to constrain nutrient sources in coastal groundwater of northwestern Long Island, New York, USA

USGS Publications Warehouse

Zhao, S.; Zhang, P.; Crusius, John; Kroeger, K.D.; Bratton, J.F.

2011-01-01

In developed, non-agricultural, unsewered areas, septic systems and fertilizer application to lawns and gardens represent two major sources of nitrogen to coastal groundwater, in addition to atmospheric input. This study was designed to distinguish between these two possible nitrogen sources by analyzing groundwater samples for pharmaceutical residuals, because fertilizers do not contain any of these pharmaceuticals, but domestic wastewater commonly does. In addition, several herbicides and insecticides used in lawn treatment were analyzed as indicators of nitrogen delivery to groundwater from fertilizers. Groundwater samples were taken through piezometres at shoreline sites in unsewered areas surrounding Northport Harbor and in sewered areas adjacent to Manhasset Bay (hereafter referred to as "Northport" and "Manhasset", respectively), both in northwestern Long Island, USA. Excessive nitrogen loading has led to reduced dissolved oxygen concentrations in Long Island Sound, and the groundwater contribution to the nitrogen budget is poorly constrained. The frequent detection of the anticonvulsant compound carbamazepine in groundwater samples of the Northport Harbor area (unsewered), together with the fact that few pesticides associated with lawn applications were detected, suggests that wastewater input and atmospheric input are the likely sources of nitrogen in the Northport groundwater. High concentrations of nitrogen were also detected in the Manhasset (sewered) groundwater. The low detection frequency and concentration of carbamazepine, however, suggest that the sewer system effectively intercepts nitrogen from wastewater there. The likely sources of nitrogen in the Manhasset groundwater are atmospheric deposition and lawn fertilizers, as this area is densely populated.

Seasonal and spatial patterns in coupled nitrification-denitrification rates in a large Great Lakes coastal system: The St. Louis River Estuary

EPA Science Inventory

Anthropogenic inputs of excess nitrogen (N) to aquatic systems are detrimental, but aquatic plants and sediments have the potential to mitigate N-loading. Sediment processes are driven by microbially mediated N-cycling. Coastal embayments purportedly play a significant role in N-...

Chesapeake Bay nitrogen fluxes derived from a land-estuarine ocean biogeochemical modeling system: Model description, evaluation, and nitrogen budgets.

PubMed

Feng, Yang; Friedrichs, Marjorie A M; Wilkin, John; Tian, Hanqin; Yang, Qichun; Hofmann, Eileen E; Wiggert, Jerry D; Hood, Raleigh R

2015-08-01

The Chesapeake Bay plays an important role in transforming riverine nutrients before they are exported to the adjacent continental shelf. Although the mean nitrogen budget of the Chesapeake Bay has been previously estimated from observations, uncertainties associated with interannually varying hydrological conditions remain. In this study, a land-estuarine-ocean biogeochemical modeling system is developed to quantify Chesapeake riverine nitrogen inputs, within-estuary nitrogen transformation processes and the ultimate export of nitrogen to the coastal ocean. Model skill was evaluated using extensive in situ and satellite-derived data, and a simulation using environmental conditions for 2001-2005 was conducted to quantify the Chesapeake Bay nitrogen budget. The 5 year simulation was characterized by large riverine inputs of nitrogen (154 × 10 9  g N yr -1 ) split roughly 60:40 between inorganic:organic components. Much of this was denitrified (34 × 10 9  g N yr -1 ) and buried (46 × 10 9  g N yr -1 ) within the estuarine system. A positive net annual ecosystem production for the bay further contributed to a large advective export of organic nitrogen to the shelf (91 × 10 9  g N yr -1 ) and negligible inorganic nitrogen export. Interannual variability was strong, particularly for the riverine nitrogen fluxes. In years with higher than average riverine nitrogen inputs, most of this excess nitrogen (50-60%) was exported from the bay as organic nitrogen, with the remaining split between burial, denitrification, and inorganic export to the coastal ocean. In comparison to previous simulations using generic shelf biogeochemical model formulations inside the estuary, the estuarine biogeochemical model described here produced more realistic and significantly greater exports of organic nitrogen and lower exports of inorganic nitrogen to the shelf.

Chesapeake Bay nitrogen fluxes derived from a land‐estuarine ocean biogeochemical modeling system: Model description, evaluation, and nitrogen budgets

PubMed Central

Friedrichs, Marjorie A. M.; Wilkin, John; Tian, Hanqin; Yang, Qichun; Hofmann, Eileen E.; Wiggert, Jerry D.; Hood, Raleigh R.

2015-01-01

Abstract The Chesapeake Bay plays an important role in transforming riverine nutrients before they are exported to the adjacent continental shelf. Although the mean nitrogen budget of the Chesapeake Bay has been previously estimated from observations, uncertainties associated with interannually varying hydrological conditions remain. In this study, a land‐estuarine‐ocean biogeochemical modeling system is developed to quantify Chesapeake riverine nitrogen inputs, within‐estuary nitrogen transformation processes and the ultimate export of nitrogen to the coastal ocean. Model skill was evaluated using extensive in situ and satellite‐derived data, and a simulation using environmental conditions for 2001–2005 was conducted to quantify the Chesapeake Bay nitrogen budget. The 5 year simulation was characterized by large riverine inputs of nitrogen (154 × 109 g N yr−1) split roughly 60:40 between inorganic:organic components. Much of this was denitrified (34 × 109 g N yr−1) and buried (46 × 109 g N yr−1) within the estuarine system. A positive net annual ecosystem production for the bay further contributed to a large advective export of organic nitrogen to the shelf (91 × 109 g N yr−1) and negligible inorganic nitrogen export. Interannual variability was strong, particularly for the riverine nitrogen fluxes. In years with higher than average riverine nitrogen inputs, most of this excess nitrogen (50–60%) was exported from the bay as organic nitrogen, with the remaining split between burial, denitrification, and inorganic export to the coastal ocean. In comparison to previous simulations using generic shelf biogeochemical model formulations inside the estuary, the estuarine biogeochemical model described here produced more realistic and significantly greater exports of organic nitrogen and lower exports of inorganic nitrogen to the shelf. PMID:27668137

County-level estimates of nitrogen and phosphorus from commercial fertilizer for the Conterminous United States, 1987–2006

USGS Publications Warehouse

Gronberg, Jo Ann M.; Spahr, Norman E.

2012-01-01

The U.S. Geological Survey’s National Water-Quality Assessment program requires nutrient input for analysis of the national and regional assessment of water quality. Detailed information on nutrient inputs to the environment are needed to understand and address the many serious problems that arise from excess nutrients in the streams and groundwater of the Nation. This report updates estimated county-level farm and nonfarm nitrogen and phosphorus input from commercial fertilizer sales for the conterminous United States for 1987 through 2006. Estimates were calculated from the Association of American Plant Food Control Officials fertilizer sales data, Census of Agriculture fertilizer expenditures, and U.S. Census Bureau county population. A previous national approach for deriving farm and nonfarm fertilizer nutrient estimates was evaluated, and a revised method for selecting representative states to calculate national farm and nonfarm proportions was developed. A national approach was used to estimate farm and nonfarm fertilizer inputs because not all states distinguish between farm and nonfarm use, and the quality of fertilizer reporting varies from year to year. For states that distinguish between farm and nonfarm use, the spatial distribution of the ratios of nonfarm-to-total fertilizer estimates for nitrogen and phosphorus calculated using the national-based farm and nonfarm proportions were similar to the spatial distribution of the ratios generated using state-based farm and nonfarm proportions. In addition, the relative highs and lows in the temporal distribution of farm and nonfarm nitrogen and phosphorus input at the state level were maintained—the periods of high and low usage coincide between national- and state-based values. With a few exceptions, nonfarm nitrogen estimates were found to be reasonable when compared to the amounts that would result if the lawn application rates recommended by state and university agricultural agencies were used. Also, states with higher nonfarm-to-total fertilizer ratios for nitrogen and phosphorus tended to have higher urban land-use percentages.

Nitrogen attenuation in the Connecticut River, northeastern USA; a comparison of mass balance and N2 production modeling approaches

USGS Publications Warehouse

Smith, T.E.; Laursen, A.E.; Deacon, J.R.

2008-01-01

Two methods were used to measure in-stream nitrogen loss in the Connecticut River during studies conducted in April and August 2005. A mass balance on nitrogen inputs and output for two study reaches (55 and 66 km), at spring high flow and at summer low flow, was computed on the basis of total nitrogen concentrations and measured river discharges in the Connecticut River and its tributaries. In a 10.3 km subreach of the northern 66 km reach, concentrations of dissolved N2 were also measured during summer low flow and compared to modeled N2 concentrations (based on temperature and atmospheric gas exchange rates) to determine the measured "excess" N2 that indicates denitrification. Mass balance results showed no in-stream nitrogen loss in either reach during April 2005, and no nitrogen loss in the southern 55 km study reach during August 2005. In the northern 66 km reach during August 2005, however, nitrogen output was 18% less than the total nitrogen inputs to the reach. N2 sampling results gave an estimated rate of N2 production that would remove 3.3% of the nitrogen load in the river over the 10.3 km northern sub-reach. The nitrogen losses measured in the northern reach in August 2005 may represent an approximate upper limit for nitrogen attenuation in the Connecticut River because denitrification processes are most active during warm summer temperatures and because the study was performed during the annual low-flow period when total nitrogen loads are small. ?? 2008 Springer Science+Business Media B.V.

What does atmospheric nitrogen contribute to the Gulf of Mexico area of oxygen depletion?

NASA Astrophysics Data System (ADS)

Rabalais, N. N.

2017-12-01

The northern Gulf of Mexico influenced by the freshwater discharge and nutrient loads of the Mississippi River watershed is the location of the world's second largest human-caused area of coastal hypoxia. Over 500 more anthropogenic `dead zones' exist in coastal waters. The point source inputs within the Mississippi River watershed account for about ten per cent of the total nitrogen inputs to the Mississippi River, with the remaining being nonpoint source. Atmospheric nitrogen makes up about sixteen per cent of the nonpoint source input of nitrogen. Most of the NOx is generated within the Ohio River watershed from the burning of fossil fuels. Some remains to be deposited into the same watershed, but the airshed deposits much of the NOx along the U.S. eastern seaboard, including Chesapeake Bay, which also has a hypoxia problem. Most of the volatilized ammonia is produced from fertilizers or manure within the upper Mississippi River watershed, is deposited within a localized airshed, and is not airborne long distances like the NOx. The atmospheric nitrogen input to the coastal waters affected by hypoxia is considered to be minimal. In the last half century, the nitrogen load from the Mississippi River to the Gulf of Mexico has increased 300 percent. During this period, low oxygen bottom-waters have developed in the coastal waters and worsened coincident with the increase in the nitrogen load. The 31-yr average size of the bottom-water hypoxia area in the Gulf of Mexico is 13,800 square kilometers, well over the 5,000 square kilometers goal of the Mississippi River Nutrient/Gulf of Mexico Hypoxia Task Force. Knowing the amounts and sources of excess nutrients to watersheds with adjacent coastal waters experiencing eutrophication and hypoxia is important in the management strategies to reduce those nutrients and improve water quality.

Denitrification rates and excess nitrogen gas concentrations in the Arabian Sea oxygen deficient zone

NASA Astrophysics Data System (ADS)

Devol, A. H.; Uhlenhopp, A. G.; Naqvi, S. W. A.; Brandes, J. A.; Jayakumar, D. A.; Naik, H.; Gaurin, S.; Codispoti, L. A.; Yoshinari, T.

2006-09-01

Rates of canonical, i.e. heterotrophic, water-column denitrification were measured by 15N incubation techniques at a number of coastal and open ocean stations in the Arabian Sea. Measurements of N 2:Ar gas ratios were also made to obtain independent estimates of N 2 excess resulting from denitrification. Measured denitrification rates ( 15NO 3-→15-14N 2) at open ocean stations averaged 9.1±1.0 nmol N l -1 d -1 ( n=15), and coastal rates averaged 33.2±12.4 nmol N l -1 d -1 ( n=18). When extrapolated to the entire Arabian Sea, deep measurements within the offshore perennial suboxic zone indicate an overall denitrification rate of 41 Tg N a -1±18 Tg N a -1, which is within the range (10-44 Tg N a -1) of previous estimates for canonical denitrification in the region based on stoichiometric calculations and electron transport system activity. Nitrogen excess gas measurements predict a larger nitrogen anomaly than estimated by classical stoichiometric methods (maximum anomaly=23 μg at N l -1 vs. 13 μg at N l -1, respectively). This mismatch may result from incorrect assumptions of Redfield stoichiometry inherent in the nitrate deficit calculation, inputs of new nitrogen through N-fixation, N 2 contributions from sedimentary denitrification along continental margins, the anammox reaction, and metal catalyzed denitrification reactions. Nevertheless, if denitrification is defined as the conversion of combined nitrogen to a gaseous end product, then the data suggest that denitrification in the Arabian Sea may have been underestimated so far.

Tracing the Fate of Atmospheric Nitrate in a Subalpine Watershed Using Δ17O.

PubMed

Bourgeois, Ilann; Savarino, Joël; Caillon, Nicolas; Angot, Hélène; Barbero, Albane; Delbart, Franck; Voisin, Didier; Clément, Jean-Christophe

2018-05-15

Nitrogen is an essential nutrient for life on Earth, but in excess, it can lead to environmental issues (e.g., N saturation, loss of biodiversity, acidification of lakes, etc.). Understanding the nitrogen budget (i.e., inputs and outputs) is essential to evaluate the prospective decay of the ecosystem services (e.g., freshwater quality, erosion control, loss of high patrimonial-value plant species, etc.) that subalpine headwater catchments provide, especially as these ecosystems experience high atmospheric nitrogen deposition. Here, we use a multi-isotopic tracer (Δ 17 O, δ 15 N and δ 18 O) of nitrate in aerosols, snow, and streams to assess the fate of atmospherically deposited nitrate in the subalpine watershed of the Lautaret Pass (French Alps). We show that atmospheric N deposition contributes significantly to stream nitrate pool year-round, either by direct inputs (up to 35%) or by in situ nitrification of atmospheric ammonium (up to 35%). Snowmelt in particular leads to high exports of atmospheric nitrate, most likely fast enough to impede assimilation by surrounding ecosystems. Yet, in a context of climate change, with shorter snow seasons, and increasing nitrogen emissions, our results hint at possibly stronger ecological consequences of nitrogen atmospheric deposition in the close future.

Toward a nitrogen footprint calculator for Tanzania

NASA Astrophysics Data System (ADS)

Hutton, Mary Olivia; Leach, Allison M.; Leip, Adrian; Galloway, James N.; Bekunda, Mateete; Sullivan, Clare; Lesschen, Jan Peter

2017-03-01

We present the first nitrogen footprint model for a developing country: Tanzania. Nitrogen (N) is a crucial element for agriculture and human nutrition, but in excess it can cause serious environmental damage. The Sub-Saharan African nation of Tanzania faces a two-sided nitrogen problem: while there is not enough soil nitrogen to produce adequate food, excess nitrogen that escapes into the environment causes a cascade of ecological and human health problems. To identify, quantify, and contribute to solving these problems, this paper presents a nitrogen footprint tool for Tanzania. This nitrogen footprint tool is a concept originally designed for the United States of America (USA) and other developed countries. It uses personal resource consumption data to calculate a per-capita nitrogen footprint. The Tanzania N footprint tool is a version adapted to reflect the low-input, integrated agricultural system of Tanzania. This is reflected by calculating two sets of virtual N factors to describe N losses during food production: one for fertilized farms and one for unfertilized farms. Soil mining factors are also calculated for the first time to address the amount of N removed from the soil to produce food. The average per-capita nitrogen footprint of Tanzania is 10 kg N yr-1. 88% of this footprint is due to food consumption and production, while only 12% of the footprint is due to energy use. Although 91% of farms in Tanzania are unfertilized, the large contribution of fertilized farms to N losses causes unfertilized farms to make up just 83% of the food production N footprint. In a developing country like Tanzania, the main audiences for the N footprint tool are community leaders, planners, and developers who can impact decision-making and use the calculator to plan positive changes for nitrogen sustainability in the developing world.

Contrasting nitrogen and phosphorus budgets in urban watersheds and implications for managing urban water pollution

PubMed Central

Janke, Benjamin D.; Nidzgorski, Daniel A.; Millet, Dylan B.; Baker, Lawrence A.

2017-01-01

Managing excess nutrients remains a major obstacle to improving ecosystem service benefits of urban waters. To inform more ecologically based landscape nutrient management, we compared watershed inputs, outputs, and retention for nitrogen (N) and phosphorus (P) in seven subwatersheds of the Mississippi River in St. Paul, Minnesota. Lawn fertilizer and pet waste dominated N and P inputs, respectively, underscoring the importance of household actions in influencing urban watershed nutrient budgets. Watersheds retained only 22% of net P inputs versus 80% of net N inputs (watershed area-weighted averages, where net inputs equal inputs minus biomass removal) despite relatively low P inputs. In contrast to many nonurban watersheds that exhibit high P retention, these urban watersheds have high street density that enhanced transport of P-rich materials from landscapes to stormwater. High P exports in storm drainage networks and yard waste resulted in net P losses in some watersheds. Comparisons of the N/P stoichiometry of net inputs versus storm drain exports implicated denitrification or leaching to groundwater as a likely fate for retained N. Thus, these urban watersheds exported high quantities of N and P, but via contrasting pathways: P was exported primarily via stormwater runoff, contributing to surface water degradation, whereas N losses additionally contribute to groundwater pollution. Consequently, N management and P management require different strategies, with N management focusing on reducing watershed inputs and P management also focusing on reducing P movement from vegetated landscapes to streets and storm drains. PMID:28373560

TOND1 confers tolerance to nitrogen deficiency in rice

PubMed Central

Zhang, Yangjun; Tan, Lubin; Zhu, Zuofeng; Yuan, Lixing; Xie, Daoxin; Sun, Chuanqing

2015-01-01

Nitrogen (N), the most important mineral nutrient for plants, is critical to agricultural production systems. N deficiency severely affects rice growth and decreases rice yields. However, excessive use of N fertilizer has caused severe pollution to agricultural and ecological environments. The necessity of breeding of crops that require lower input of N fertilizer has been recognized. Here we identified a major quantitative trait locus on chromosome 12, Tolerance Of Nitrogen Deficiency 1 (TOND1), that confers tolerance to N deficiency in the indica cultivar Teqing. Sequence verification of 75 indica and 75 japonica cultivars from 18 countries and regions demonstrated that only 27.3% of cultivars (41 indica cultivars) contain TOND1, whereas 72.7% of cultivars, including the remaining 34 indica cultivars and all 75 japonica cultivars, do not harbor the TOND1 allele. Over-expression of TOND1 increased the tolerance to N deficiency in the TOND1-deficient rice cultivars. The identification of TOND1 provides a molecular basis for breeding rice varieties with improved grain yield despite decreased input of N fertilizers. PMID:25439309

QTL and QTL x environment effects on agronomic and nitrogen acquisition traits in rice.

PubMed

Senthilvel, Senapathy; Vinod, Kunnummal Kurungara; Malarvizhi, Palaniappan; Maheswaran, Marappa

2008-09-01

Agricultural environments deteriorate due to excess nitrogen application. Breeding for low nitrogen responsive genotypes can reduce soil nitrogen input. Rice genotypes respond variably to soil available nitrogen. The present study attempted quantification of genotype x nitrogen level interaction and mapping of quantitative trait loci (QTLs) associated with nitrogen use efficiency (NUE) and other associated agronomic traits. Twelve parameters were observed across a set of 82 double haploid (DH) lines derived from IR64/Azucena. Three nitrogen regimes namely, native (0 kg/ha; no nitrogen applied), optimum (100 kg/ha) and high (200 kg/ha) replicated thrice were the environments. The parents and DH lines were significantly varying for all traits under different nitrogen regimes. All traits except plant height recorded significant genotype x environment interaction. Individual plant yield was positively correlated with nitrogen use efficiency and nitrogen uptake. Sixteen QTLs were detected by composite interval mapping. Eleven QTLs showed significant QTL x environment interactions. On chromosome 3, seven QTLs were detected associated with nitrogen use, plant yield and associated traits. A QTL region between markers RZ678, RZ574 and RZ284 was associated with nitrogen use and yield. This chromosomal region was enriched with expressed gene sequences of known key nitrogen assimilation genes.

Urban rivers as hotspots of regional nitrogen pollution.

PubMed

Zhang, Xiaohong; Wu, Yiyun; Gu, Baojing

2015-10-01

Excess nitrogen inputs to terrestrial ecosystems via human activities have deteriorated water qualities on regional scales. Urban areas as settlements of over half global population, however, were usually not considered in the analysis of regional water pollution. Here, we used a 72-month monitoring data of water qualities in Hangzhou, China to test the role of urban rives in regional nitrogen pollution and how they response to the changes of human activities. Concentrations of ammonium nitrogen in urban rivers were 3-5 times higher than that in regional rivers. Urban rivers have become pools of reactive nitrogen and hotspots of regional pollution. Moreover, this river pollution is not being measured by current surface water monitoring networks that are designed to measure broader regional patterns, resulting in an underestimation of regional pollution. This is crucial to urban environment not only in China, but also in other countries, where urban rivers are seriously polluted. Copyright © 2015 Elsevier Ltd. All rights reserved.

Using Bayesian Belief Networks to Explore the Effects of Nitrogen Inputs on Wetland Ecosystem Services

NASA Astrophysics Data System (ADS)

Spence, P. L.; Jordan, S. J.

2011-12-01

Increased reactive nitrogen (Nr) inputs to freshwater wetlands resulting from infrastructure development due to population growth along with intensive agricultural practices associated with food production can threaten regulating (i.e. climate change, water purification, and waste treatment) and supporting (i.e. nutrient cycling) ecosystem services. Wetlands generally respond both by sequestering Nr (i.e. soil accumulation and biomass assimilation) and converting Nr into inert gaseous forms via biogeochemical processes. It is important for wetlands to be efficient in removing excessive Nr inputs from polluted waters to reduce eutrophication in downstream receiving water bodies while producing negligible amounts of nitrous oxide (N2O), a potent greenhouse gas, which results from incomplete denitrification. Wetlands receiving excessive Nr lose their ability to provide a constant balance between regulating water quality and mitigating climate change. The purpose of this study is to explore the effects of Nr inputs on ecosystem services provided by wetlands using a Bayesian Belief Network (BBN). The network was developed from established relationships between a variety of wetland function indicators and biogeochemical process associated with Nr removal. Empirical data for 34 freshwater wetlands were gathered from a comprehensive review of published peer-reviewed and gray literature. The BBN was trained using 30 wetlands (88% of the freshwater wetland case file) and tested using 4 wetlands (12% of the freshwater wetland case file). Sensitivity analysis suggested that Nr removal, water quality, soil Nr accumulation and N2O emissions had the greatest influence on ecosystem service tradeoffs. The magnitude of Nr inputs did not affect ecosystem services. The network implies that Nr removal efficiency has a greater influence on final ecosystem services associated with water quality impairment and atmospheric pollution. A very low error rate, which was based on 4 wetland cases, indicated that a larger dataset is required to provide robust predictions. These findings are considered preliminary and could change as the model is updated.

Nitrogen excess in North American ecosystems: Predisposing factors, ecosystem responses, and management strategies

USGS Publications Warehouse

Fenn, M.E.; Poth, M.A.; Aber, J.D.; Baron, Jill S.; Bormann, B.T.; Johnson, D.W.; Lemly, A.D.; McNulty, S.G.; Ryan, D.F.; Stottlemyer, R.

1998-01-01

Most forests in North America remain nitrogen limited, although recent studies have identified forested areas that exhibit symptoms of N excess, analogous to overfertilization of arable land. Nitrogen excess in watersheds is detrimental because of disruptions in plant/soil nutrient relations, increased soil acidification and aluminum mobility, increased emissions of nitrogenous greenhouse gases from soil, reduced methane consumption in soil, decreased water quality, toxic effects on freshwater biota, and eutrophication of coastal marine waters. Elevated nitrate (NO3/-) loss to groundwater or surface waters is the primary symptom of N excess. Additional symptoms include increasing N concentrations and higher N:nutrient ratios in foliage (i.e., N:Mg, N:P), foliar accumulation of amino acids or NO3/-, and low soil C:N ratios. Recent nitrogen-fertilization studies in New England and Europe provide preliminary evidence that some forests receiving chronic N inputs may decline in productivity and experience greater mortality. Long-term fertilization at Mount Ascutney, Vermont, suggests that declining and slow N-cycling coniferous stands may be replaced by fast-growing and fast N-cycling deciduous forests. Symptoms of N saturation are particularly severe in high-elevation, nonaggrading spruce-fir ecosystems in the Appalachian Mountains and in eastern hardwood watersheds at the Fernow Experimental Forest near Parsons, West Virginia. In the Los Angeles Air Basin, mixed conifer forests and chaparral watersheds with high smog exposure are N saturated and exhibit the highest streamwater NO3/- concentrations for wildlands in North America. High-elevation alpine watersheds in the Colorado Front Range and a deciduous forest in Ontario, Canada, are N saturated, although N deposition is moderate (~8 kg??ha-1??yr-1). In contrast, the Harvard Forest hardwood stand in Massachusetts has absorbed >900 kg N/ha during 8 yr of N amendment studies without significant NO3/- leaching, illustrating that ecosystems vary widely in the capacity to retain N inputs. Overly mature forests with high N deposition, high soil N stores, and low soil C:N ratios are prone to N saturation and NO3/- leaching. Additional characteristics favoring low N retention capacity include a short growing season (reduced plant N demand) and reduced contact time between drainage water and soil (i.e., porous coarse-textured soils, exposed bedrock or talus). Temporal patterns of hydrologic fluxes interact with biotic uptake and internal cycling patterns in determining ecosystem N retention. Soils are the largest storage pool for N inputs, although vegetation uptake is also important. Recent studies indicate that nitrification may be widespread in undisturbed ecosystems, and that microbial assimilation of NO3/- may be a significant N retention mechanism, contrary to previous assumptions. Further studies are needed to elucidate the sites, forms, and mechanisms of N retention and incorporation into soil organic matter, and to test potential management options for mitigating N losses from forests. Implementation of intensive management practices in N-saturated ecosystems may only be feasible in high-priority areas and on a limited scale. Reduction of N emissions would be a preferable solution, although major reductions in the near future are unlikely in many areas due to economic, energy-use, policy, and demographic considerations.

Element budgets of two contrasting catchments in the Black Forest (Federal Republic of Germany)

NASA Astrophysics Data System (ADS)

Feger, K. H.; Brahmer, G.; Zöttl, H. W.

1990-08-01

Rainfall and throughfall inputs of all major cations and anions, via open-field bulk precipitation and canopy throughfall, are compared with streamwater outputs in two forested catchments at higher altitudes of the Black Forest. The sites differ considerably in terms of bedrock geology, soil type, soilwater characteristics, topography, and forest management history. Deposition at both sites is almost equal and, in contrast to other forest areas in Central Europe, of a low-to-moderate level. Dry deposition does not seem to play an important role. Distinct differences in the elemental output emerge owing to the differing site conditions. At Villingen, deposited nitrogen is almost totally retained, whereas at Schluchsee, nitrogen output and input are of the same order of magnitude. This is consistent with the different nitrogen nutrition level of the stands, microbial turnover in the soil, and former management practices (change of tree species, excessive nutrient export). Sulphur is not retained in either of the catchments. At Schluchsee, sulphur export exceeds input from canopy throughfall by a factor of 2.5. The higher output rates, both of nitrogen and sulphur at Schluchsee, are due to the much higher microbial mineralization of organic matter as shown by previous incubation tests. Differences in cation and proton export are mainly caused by a different drainage pattern. In contrast to the Schluchsee catchment, where vertical water pathways prevail, the streamwater solute output at Villingen is dominated by a shallow subsurface runoff. Atmospheric deposition is a contributing, but not the dominant, factor in the biogeochemical cycling at these sites. Hence, a generally applicable quantitative definition of 'critical loads', especially for nitrogen, is illusory and the use of such numbers will be misleading.

RESTORED STREAMS ENHANCE ABILITY TO REMOVE EXCESS NITROGEN

EPA Science Inventory

Issue: Excess nitrogen from fertilizer, septic tanks, animal feedlots, and runoff from pavement can threaten human and aquatic ecosystem health. Furthermore, degraded ecosystems like those impacted by urbanization have reduced ability to process and remove excess nitrogen from t...

Exploring the nutrient inputs and cycles in Tampa Bay and coastal watersheds using MODIS images and data mining

NASA Astrophysics Data System (ADS)

Chang, Ni-Bin; Xuan, Zhemin

2011-09-01

Excessive nutrients, which may be represented as Total Nitrogen (TN) and Total Phosphorus (TP) levels, in natural water systems have proven to cause high levels of algae production. The process of phytoplankton growth which consumes the excess TN and TP in a water body can also be related to the changing water quality levels, such as Dissolved Oxygen (DO), chlorophyll-a, and turbidity, associated with their changes in absorbance of natural radiation. This paper explores spatiotemporal nutrient patterns in Tampa Bay, Florida with the aid of Moderate Resolution Imaging Spectroradiometer or MODIS images and Genetic Programming (GP) models that are deigned to link those relevant water quality parameters in aquatic environments.

Impact of anthropogenic atmospheric nitrogen and sulfur deposition on ocean acidification and the inorganic carbon system.

PubMed

Doney, Scott C; Mahowald, Natalie; Lima, Ivan; Feely, Richard A; Mackenzie, Fred T; Lamarque, Jean-Francois; Rasch, Phil J

2007-09-11

Fossil fuel combustion and agriculture result in atmospheric deposition of 0.8 Tmol/yr reactive sulfur and 2.7 Tmol/yr nitrogen to the coastal and open ocean near major source regions in North America, Europe, and South and East Asia. Atmospheric inputs of dissociation products of strong acids (HNO(3) and H2SO(4)) and bases (NH(3)) alter surface seawater alkalinity, pH, and inorganic carbon storage. We quantify the biogeochemical impacts by using atmosphere and ocean models. The direct acid/base flux to the ocean is predominately acidic (reducing total alkalinity) in the temperate Northern Hemisphere and alkaline in the tropics because of ammonia inputs. However, because most of the excess ammonia is nitrified to nitrate (NO(3)(-)) in the upper ocean, the effective net atmospheric input is acidic almost everywhere. The decrease in surface alkalinity drives a net air-sea efflux of CO(2), reducing surface dissolved inorganic carbon (DIC); the alkalinity and DIC changes mostly offset each other, and the decline in surface pH is small. Additional impacts arise from nitrogen fertilization, leading to elevated primary production and biological DIC drawdown that reverses in some places the sign of the surface pH and air-sea CO(2) flux perturbations. On a global scale, the alterations in surface water chemistry from anthropogenic nitrogen and sulfur deposition are a few percent of the acidification and DIC increases due to the oceanic uptake of anthropogenic CO(2). However, the impacts are more substantial in coastal waters, where the ecosystem responses to ocean acidification could have the most severe implications for mankind.

Is groundwater discharge the dominant source of nutrients to Alabama estuaries and will it keep impacting these waters for the foreseeable future?

NASA Astrophysics Data System (ADS)

Mortazavi, B.; Domangue, R.; Kleinhuizen, A.; Tatariw, C.

2017-12-01

Land use change and population growth are dominant factors impacting coastal waters. Populations in Alabama coastal counties have increased by several folds since the 1950s and a large fraction of the farmed land are now being used for growing sod requiring large amounts of fertilizers. Concurrent with these changes, marshes bordering Mobile Bay have been disappearing such that they now only cover 50% of their areal extent compared to the 1780s. These changes in land use and coastal geomorphology, as well as the population growth ultimately result in larger delivery of nutrients either through runoff or groundwater discharge to the coastal waters. The Mobile Bay estuary in Alabama is bordered with several subestuaries and a coastal lagoon. Our investigations suggest that the large inputs of nutrients through river discharge in Weeks Bay (140 g N m-2 yr-1) and groundwater discharge in Little Lagoon (300 g N m-2 yr-1) by far dominate inputs of N to the water column and exceed N input, for example, from benthic regeneration, by an order of magnitude. Furthermore, the capacity for N removal through denitrification in these systems is low and instead nitrogen is retained through dissimilatory nitrate reduction to ammonium at a rate that exceed denitrification by an order of magnitude. Our measurements also suggest that once marshes are transformed to subtidal unvegetated sediments rates of nitrogen removal by denitrification decline four folds. Excessive inputs of nitrogen and the high efficiency with which nitrogen is retained in these systems is impacting the foodweb and harmful algal blooms and fish kills are reoccurring events. While changes in agricultural practices and reconstruction of marshes can potentially reduce the delivery of N or enhance N removal by denitrification, nutrient inputs through groundwater discharge are going to impact these estuaries for the foreseeable future. Our capacity to construct nutrient budgets and to predict the trajectory of ecosystem changes will therefore depend greatly on accurate knowledge of groundwater discharge to these systems. Quantifying the magnitudes of groundwater derived nutrients and the fate of these nutrients in nearshore systems requires concerted efforts amongst hydrologists, biogeochemists, and ecologists.

Controls on nitrogen flux in alpine/subalpine watersheds of Colorado

USGS Publications Warehouse

Campbell, Donald H.; Baron, Jill S.; Tonnessen, Kathy A.; Brooks, Paul D.; Schuster, Paul F.

2000-01-01

High‐altitude watersheds in the Front Range of Colorado show symptoms of advanced stages of nitrogen excess, despite having less nitrogen in atmospheric deposition than other regions where watersheds retain nitrogen. In two alpine/subalpine subbasins of the Loch Vale watershed, atmospheric deposition of NO3− plus NH4+ was 3.2–5.5 kg N ha−1, and watershed export was 1.8–3.9 kg N ha−1 for water years 1992–1997. Annual N export increased in years with greater input of N, but most of the additional N was retained in the watershed, indicating that parts of the ecosystem are nitrogen‐limited. Dissolved inorganic nitrogen (DIN) concentrations were greatest in subsurface water of talus landscapes, where mineralization and nitrification augment high rates of atmospheric deposition of N. Tundra landscapes had moderately high DIN concentrations, whereas forest and wetland landscapes had low concentrations, indicating little export of nitrogen from these landscapes. Between the two subbasins the catchment of Icy Brook had greater retention of nitrogen than that of Andrews Creek because of landscape and hydrologic characteristics that favor greater N assimilation in both the terrestrial and aquatic ecosystems. These results suggest that export of N from alpine/subalpine watersheds is caused by a combination of direct flushing of N from atmospheric deposition and release of N from ecosystem biogeochemical processes (N cycling). Sensitivity of alpine ecosystems in the western United States to atmospheric deposition of N is a function of landscape heterogeneity, hydrologic flow paths, and climatic extremes that limit primary productivity and microbial activity, which, in turn, control retention and release of nitrogen. Conceptual and mechanistic models of N excess that have been developed for forested ecosystems need to be modified in order to predict the response of alpine ecosystems to future changes in climate and atmospheric deposition of N.

Assessing variable rate nitrogen fertilizer strategies within an extensively instrument field site using the MicroBasin model

NASA Astrophysics Data System (ADS)

Ward, N. K.; Maureira, F.; Yourek, M. A.; Brooks, E. S.; Stockle, C. O.

2014-12-01

The current use of synthetic nitrogen fertilizers in agriculture has many negative environmental and economic costs, necessitating improved nitrogen management. In the highly heterogeneous landscape of the Palouse region in eastern Washington and northern Idaho, crop nitrogen needs vary widely within a field. Site-specific nitrogen management is a promising strategy to reduce excess nitrogen lost to the environment while maintaining current yields by matching crop needs with inputs. This study used in-situ hydrologic, nutrient, and crop yield data from a heavily instrumented field site in the high precipitation zone of the wheat-producing Palouse region to assess the performance of the MicroBasin model. MicroBasin is a high-resolution watershed-scale ecohydrologic model with nutrient cycling and cropping algorithms based on the CropSyst model. Detailed soil mapping conducted at the site was used to parameterize the model and the model outputs were evaluated with observed measurements. The calibrated MicroBasin model was then used to evaluate the impact of various nitrogen management strategies on crop yield and nitrate losses. The strategies include uniform application as well as delineating the field into multiple zones of varying nitrogen fertilizer rates to optimize nitrogen use efficiency. We present how coupled modeling and in-situ data sets can inform agricultural management and policy to encourage improved nitrogen management.

Nitrogen excess in North American ecosystems: predisposing factors, ecosystem responses, and management strategies

Treesearch

Mark E. Fenn; Mark A. Poth; John D. Aber; Jill S. Baron; Bernard T. Bormann; Dale W. Johnson; A. Dennis Lemly; Steven G. McNulty; Douglas F. Ryan; Robert Stottlemyer

1998-01-01

Most forests in North America remain nitrogen limited, although recent studies have identified forested areas that exhibit symptoms of N excess, analogous to overfertilization of arable land. Nitrogen excess in watersheds is detrimental because of disruptions in plantlsoil nutrient relations, increased soil acidification and aluminum mobility, increased emissions of...

Nitrogen Excess in North American Ecosystems: Predisposing Factors, Ecosystem Responses, and Management Strategies

Treesearch

Mark E. Fenn; Mark A. Poth; John D. Aber; Jill S. Baron; Bernard T. Bormann; Dale W. Johnson; A. Dennis Lemly; Steven G. McNulty; Douglas F. Ryan; Robert Stottlemyer

1998-01-01

Most forests in North America remain nitrogen limited, although recent studies have identified forested areas that exhibit symptoms of N excess, analogous to overfertilization of arable land. Nitrogen excess in watersheds is detrimental because of disruptions in plant/soil nutrient relations, increased soil acidification and aluminum mobility, increased emissions of...

40 CFR 77.6 - Penalties for excess emissions of sulfur dioxide and nitrogen oxides.

Code of Federal Regulations, 2010 CFR

2010-07-01

... sulfur dioxide and nitrogen oxides. 77.6 Section 77.6 Protection of Environment ENVIRONMENTAL PROTECTION... sulfur dioxide and nitrogen oxides. (a)(1) If excess emissions of sulfur dioxide occur at the affected... under paragraph (a)(1) of this section for any increase in excess emissions of sulfur dioxide determined...

40 CFR 77.6 - Penalties for excess emissions of sulfur dioxide and nitrogen oxides.

Code of Federal Regulations, 2011 CFR

2011-07-01

... sulfur dioxide and nitrogen oxides. 77.6 Section 77.6 Protection of Environment ENVIRONMENTAL PROTECTION... sulfur dioxide and nitrogen oxides. (a)(1) If excess emissions of sulfur dioxide occur at the affected... under paragraph (a)(1) of this section for any increase in excess emissions of sulfur dioxide determined...

40 CFR 77.6 - Penalties for excess emissions of sulfur dioxide and nitrogen oxides.

Code of Federal Regulations, 2014 CFR

2014-07-01

... sulfur dioxide and nitrogen oxides. 77.6 Section 77.6 Protection of Environment ENVIRONMENTAL PROTECTION... sulfur dioxide and nitrogen oxides. (a)(1) If excess emissions of sulfur dioxide occur at the affected... under paragraph (a)(1) of this section for any increase in excess emissions of sulfur dioxide determined...

40 CFR 77.6 - Penalties for excess emissions of sulfur dioxide and nitrogen oxides.

Code of Federal Regulations, 2012 CFR

2012-07-01

... sulfur dioxide and nitrogen oxides. 77.6 Section 77.6 Protection of Environment ENVIRONMENTAL PROTECTION... sulfur dioxide and nitrogen oxides. (a)(1) If excess emissions of sulfur dioxide occur at the affected... under paragraph (a)(1) of this section for any increase in excess emissions of sulfur dioxide determined...

Nitrogen Deposition: A Component of Global Change Analyses

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

Norby, Richard J.

1997-12-31

The global cycles of carbon and nitrogen are being perturbed by human activities that increase the transfer from large pools of nonreactive forms of the elements to reactive forms that are essential to the functioning of the terrestrial biosphere. The cycles are closely linked at all scales, and global change analyses must consider carbon and nitrogen cycles together. The increasing amount of nitrogen originating from fossil fuel combustion and deposited to terrestrial ecosystems as nitrogen oxides could increase the capacity of ecosystems to sequester carbon thereby removing some of the excess carbon dioxide from the atmosphere and slowing the developmentmore » of greenhouse warming. Several global and ecosystem models have calculated the amount of carbon sequestration that can be attributed to nitrogen deposition based on assumptions about the allocation of nitrogen among ecosystem components with different carbon-nitrogen ratios. They support the premise that nitrogen deposition is responsible for a an increasing terrestrial carbon sink since industrialization began, but there are large uncertainties related to the continued capacity of ecosystems to retain exogenous nitrogen. Whether terrestrial ecosystems continue to sequester additional carbon will depend in part on their response to increasing atmospheric carbon dioxide concentrations, which is widely thought to be constrained by limited nitrogen availability. Ecosystem models generally support the conclusion that the responses of ecosystems to increasing concentrations of carbon dioxide will be larger, and the range of possible responses will be wider, in ecosystems with increased nitrogen inputs originating as atmospheric deposition.« less

Numerical model simulations of nitrate concentrations in groundwater using various nitrogen input scenarios, mid-Snake region, south-central Idaho

USGS Publications Warehouse

Skinner, Kenneth D.; Rupert, Michael G.

2012-01-01

As part of the U.S. Geological Survey’s National Water Quality Assessment (NAWQA) program nitrate transport in groundwater was modeled in the mid-Snake River region in south-central Idaho to project future concentrations of nitrate. Model simulation results indicated that nitrate concentrations would continue to increase over time, eventually exceeding the U.S. Environmental Protection Agency maximum contaminant level for drinking water of 10 milligrams per liter in some areas. A subregional groundwater model simulated the change of nitrate concentrations in groundwater over time in response to three nitrogen input scenarios: (1) nitrogen input fixed at 2008 levels; (2) nitrogen input increased from 2008 to 2028 using the same rate of increase as the average rate of increase during the previous 10 years (1998 through 2008); after 2028, nitrogen input is fixed at 2028 levels; and (3) nitrogen input related to agriculture completely halted, with only nitrogen input from precipitation remaining. Scenarios 1 and 2 project that nitrate concentrations in groundwater continue to increase from 10 to 50 years beyond the year nitrogen input is fixed, depending on the location in the model area. Projected nitrate concentrations in groundwater increase by as much as 2–4 milligrams per liter in many areas, with nitrate concentrations in some areas reaching 10 milligrams per liter. Scenario 3, although unrealistic, estimates how long (20–50 years) it would take nitrate in groundwater to return to background concentrations—the “flushing time” of the system. The amount of nitrate concentration increase cannot be explained solely by differences in nitrogen input; in fact, some areas with the highest amount of nitrogen input have the lowest increase in nitrate concentration. The geometry of the aquifer and the pattern of regional groundwater flow through the aquifer greatly influence nitrate concentrations. The aquifer thins toward discharge areas along the Snake River which forces upward convergence of good-quality regional groundwater that mixes with the nitrate-laden groundwater in the uppermost parts of the aquifer, which results in lowered nitrate concentrations. A new method of inputting nitrogen to the subregional groundwater model was used that prorates nitrogen input by the probability of detecting nitrate concentrations greater than 2 mg/L. The probability map is based on correlations with physical factors, and prorates an existing nitrogen input dataset providing an estimate of nitrogen flux to the water table that accounts for new factors such as soil properties. The effectiveness of this updated nitrogen input method was evaluated using the software UCODE_2005.

Nitrous oxide emissions could reduce the blue carbon value of marshes on eutrophic estuaries

NASA Astrophysics Data System (ADS)

Roughan, Brittney L.; Kellman, Lisa; Smith, Erin; Chmura, Gail L.

2018-04-01

The supply of nitrogen to ecosystems has surpassed the Earth’s Planetary Boundary and its input to the marine environment has caused estuarine waters to become eutrophic. Excessive supply of nitrogen to salt marshes has been associated with shifts in species’ distribution and production, as well as marsh degradation and loss. Our study of salt marshes in agriculturally intensive watersheds shows that coastal eutrophication can have an additional impact. We measured gas fluxes from marsh soils and verified emissions of nitrous oxide (N2O) in nitrogen-loaded marshes while the reference marsh was a sink for this gas. Salt marsh soils are extremely efficient carbon sinks, but emissions of N2O, a greenhouse gas 298 times more potent than CO2, reduces the value of the carbon sink, and in some marshes, may counterbalance any value of stored carbon towards mitigation of climate change. Although more research is merited on the nitrogen transformations and carbon storage in eutrophic marshes, the possibility of significant N2O emissions should be considered when evaluating the market value of carbon in salt marshes subject to high levels of nitrogen loading.

Effects of nitrogen fertilization on the acidity and salinity of greenhouse soils.

PubMed

Han, Jiangpei; Shi, Jiachun; Zeng, Lingzao; Xu, Jianming; Wu, Laosheng

2015-02-01

A greenhouse pot experiment was conducted to study the effects of conventional nitrogen fertilization on soil acidity and salinity. Three N rates (urea; N0, 0 kg N ha(-1); N1, 600 kg N ha(-1); and N2, 1,200 kg N ha(-1)) were applied in five soils with different greenhouse cultivation years to evaluate soil acidification and salinization rate induced by nitrogen fertilizer in lettuce production. Both soil acidity and salinity increased significantly as N input increased after one season, with pH decrease ranging from 0.45 to 1.06 units and electrolytic conductivity increase from 0.24 to 0.68 mS cm(-1). An estimated 0.92 mol H(+) was produced for 1 mol (NO2 (-) + NO3 (-))-N accumulation in soil. The proton loading from nitrification was 14.3-27.3 and 12.1-58.2 kmol H(+) ha(-1) in the center of Shandong Province under N1 and N2 rate, respectively. However, the proton loading from the uptake of excess bases by lettuces was only 0.3-4.5 % of that from nitrification. Moreover, the release of protons induced the direct release of base cations and accelerated soil salinization. The increase of soil acidity and salinity was attributed to the nitrification of excess N fertilizer. Compared to the proton loading by lettuce, nitrification contributed more to soil acidification in greenhouse soils.

Tracking historical increases in nitrogen-driven crop production possibilities

NASA Astrophysics Data System (ADS)

Mueller, N. D.; Lassaletta, L.; Billen, G.; Garnier, J.; Gerber, J. S.

2015-12-01

The environmental costs of nitrogen use have prompted a focus on improving the efficiency of nitrogen use in the global food system, the primary source of nitrogen pollution. Typical approaches to improving agricultural nitrogen use efficiency include more targeted field-level use (timing, placement, and rate) and modification of the crop mix. However, global efficiency gains can also be achieved by improving the spatial allocation of nitrogen between regions or countries, due to consistent diminishing returns at high nitrogen use. This concept is examined by constructing a tradeoff frontier (or production possibilities frontier) describing global crop protein yield as a function of applied nitrogen from all sources, given optimal spatial allocation. Yearly variation in country-level input-output nitrogen budgets are utilized to parameterize country-specific hyperbolic yield-response models. Response functions are further characterized for three ~15-year eras beginning in 1961, and series of calculations uses these curves to simulate optimal spatial allocation in each era and determine the frontier. The analyses reveal that excess nitrogen (in recent years) could be reduced by ~40% given optimal spatial allocation. Over time, we find that gains in yield potential and in-country nitrogen use efficiency have led to increases in the global nitrogen production possibilities frontier. However, this promising shift has been accompanied by an actual spatial distribution of nitrogen use that has become less optimal, in an absolute sense, relative to the frontier. We conclude that examination of global production possibilities is a promising approach to understanding production constraints and efficiency opportunities in the global food system.

Leaf Stable Isotope and Nutrient Status of Temperate Mangroves As Ecological Indicators to Assess Anthropogenic Activity and Recovery from Eutrophication

PubMed Central

Gritcan, Iana; Duxbury, Mark; Leuzinger, Sebastian; Alfaro, Andrea C.

2016-01-01

We measured nitrogen stable isotope values (δ15N), and total phosphorus (%P) and total nitrogen (%N) contents in leaves of the temperate mangrove (Avicennia marina sp. australasica) from three coastal ecosystems exposed to various levels of human impact (Manukau, high; Mangawhai, low; and Waitemata, intermediate) in northern New Zealand. We measured δ15N values around 10‰ in environments where the major terrestrial water inputs are sewage. The highest average total nitrogen contents and δ15N values were found in the Auckland city region (Manukau Harbour) at 2.2%N and 9.9‰, respectively. The lowest values were found in Mangawhai Harbour, situated about 80 km north of Auckland city, at 2.0%N and 5.2‰, respectively. In the Waitemata Harbour, also located in Auckland city but with less exposure to human derived sewage inputs, both parameters were intermediate, at 2.1%N and 6.4‰. Total phosphorus contents did not vary significantly. Additionally, analysis of historical mangrove leaf herbarium samples obtained from the Auckland War Memorial Museum indicated that a reduction in both leaf total nitrogen and δ15N content has occurred over the past 100 years in Auckland’s harbors. Collectively, these results suggest that anthropogenically derived nitrogen has had a significant impact on mangrove nutrient status in Auckland harbors over the last 100 years. The observed decrease in nitrogenous nutrients probably occurred due to sewage system improvements. We suggest that mangrove plant physiological response to nutrient excess could be used as an indicator of long-term eutrophication trends. Monitoring leaf nutrient status in mangroves can be used to assess environmental stress (sewage, eutrophication) on coastal ecosystems heavily impacted by human activities. Moreover, nitrogen and phosphorus leaf contents can be used to assess levels of available nutrients in the surrounding environments. PMID:28066477

40 CFR 77.6 - Penalties for excess emissions of sulfur dioxide and nitrogen oxides.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Penalties for excess emissions of sulfur dioxide and nitrogen oxides. 77.6 Section 77.6 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) EXCESS EMISSIONS § 77.6 Penalties for excess emissions of...

Effects of increased deposition of atmospheric nitrogen on an upland moor: leaching of N species and soil solution chemistry.

PubMed

Pilkington, M G; Caporn, S J M; Carroll, J A; Cresswell, N; Lee, J A; Ashenden, T W; Brittain, S A; Reynolds, B; Emmett, B A

2005-05-01

This study was designed to investigate the leaching response of an upland moorland to long-term (10 yr) ammonium nitrate additions of 40, 80 and 120 kg N ha(-1) yr(-1) and to relate this response to other indications of potential system damage, such as acidification and cation displacement. Results showed increases in nitrate leaching only in response to high rates of N input, in excess of 96 and 136 kg total N input ha(-1) yr(-1) for the organic Oh horizon and mineral Eag horizon, respectively. Individual N additions did not alter ammonium leaching from either horizon and ammonium was completely retained by the mineral horizon. Leaching of dissolved organic nitrogen (DON) from the Oh horizon was increased by the addition of 40 kg N ha(-1) yr(-1), but in spite of increases, retention of total dissolved nitrogen reached a maximum of 92% and 95% of 80 kg added N ha(-1) yr(-1) in the Oh and Eag horizons, respectively. Calcium concentrations and calcium/aluminium ratios were decreased in the Eag horizon solution with significant acidification mainly in the Oh horizon leachate. Nitrate leaching is currently regarded as an early indication of N saturation in forest systems. Litter C:N ratios were significantly lowered but values remained above a threshold predicted to increase leaching of N in forests.

Fish track wastewater pollution to estuaries.

PubMed

Schlacher, Thomas A; Liddell, Ben; Gaston, Troy F; Schlacher-Hoenlinger, Monika

2005-08-01

Excess nitrogen is a forceful agent of ecological change in coastal waters, and wastewater is a prominent source of nitrogen. In catchments where multiple sources of nitrogen pollution co-exist, biological indicators are needed to gauge the degree to which wastewater-N can propagate through the receiving food webs. The purpose of this study was to test whether estuarine fish are suitable as indicators of sewage-N pollution. Fish were analysed from three estuaries within a 100-km strip on the Australian East Coast. The estuaries differ substantially in wastewater loading: (1) the Maroochy Estuary receives a large fraction of the local shire's treated sewage, (2) the Mooloolah Estuary has no licensed treated wastewater outfalls but marinas/harbours and storm-water may contribute nitrogen, and (3) the Noosa Estuary which neither receives licensed discharges nor has suspected wastewater loads. Sampling for fish included both high rainfall ('wet' season) and low rainfall ('dry' season) periods. Muscle-delta15N was the variable predicted to respond to treated wastewater loading, reflecting the relative enrichment in 15N resulting from the treatment process and distinguishing it from alternative N sources such as fertiliser and natural nitrogen inputs (both 15N-depleted). Of the 19 fish species occurring in all three estuaries, those from the Maroochy Estuary had significantly elevated delta15N values (up to 9.9 per thousand), and inter-estuarine differences in fish-delta15N were consistent across seasons. Furthermore, not only did all fish from the estuary receiving treated wastewater carry a very distinctive sewage-N tissue signal, but enriched muscle-delta15N was also evident in all species sampled from the one estuary in which sewage contamination was previously only suspected (i.e. the Mooloolah Estuary: 0.2-4.8 per thousand enrichment over fish from reference system). Thus, fish-delta15N is a suitable indicator of wastewater-N not only in systems that receive large loads, but also for the detection of more subtle nitrogen inputs. Arguably, fish may be preferred indicators of sewage-N contamination because they: (1) integrate nitrogen inputs over long time periods, (2) have an element of 'ecological relevance' because fish muscle-delta15N reflect movement of sewage-N through the food chain, and (3) pollution assessments can usually be based on evidence from multiple species.

Environmental effect of constructed wetland as biofuel production system

NASA Astrophysics Data System (ADS)

Liu, Dong

2017-04-01

Being as a renewable energy, biofuel has attracted worldwide attention. Clean biofuel production is an effective way to mitigate global climate change and energy crisis. Biofuel may offer a promising alternative to fossil fuels, but serious concerns arise about the adverse greenhouse gas consequences from using nitrogen fertilizers. Waste-nitrogen recycling is an attractive idea. Here we advocate a win-win approach to biofuel production which takes advantage of excessive nitrogen in domestic wastewater treated via constructed wetland (CW) in China. This study will carry on environmental effect analysis of CW as a biomass generation system through field surveys and controllable simulated experiments. This study intends to evaluate net energy balance, net greenhouse effect potential and ecosystem service of CW as biomass generation system, and make comparation with traditional wastewater treatment plant and other biofuel production systems. This study can provide a innovation mode in order to solve the dilemma between energy crops competed crops on production land and excessive nitrogen fertilizer of our traditional energy plant production. Data both from our experimental CWs in China and other researches on comparable CWs worldwide showed that the biomass energy yield of CWs can reach 182.3 GJ ha-1 yr-1, which was two to eight times higher than current biofuel-production systems. Energy output from CW was ˜137% greater than energy input for biofuel production. If CWs are designed with specific goal of biofuel production, biofuel production can be greatly enhanced through the optimization of N supply, hydraulic structures, and species selection in CWs. Assuming that 2.0 Tg (1 Tg = 1012 g) waste nitrogen contained in domestic wastewater is treated by CWs, biofuel production can account for 1.2% of national gasoline consumption in China. The proportion would increase to 6.7% if extra nitrogen (9.5 Tg) from industrial wastewater and agricultural runoff was included. This approach is also suitable for use in other countries, and can help promote sustainable development for energy and environment.

Impact of aircraft emissions on reactive nitrogen over the North Atlantic Flight Corridor region

NASA Astrophysics Data System (ADS)

Koike, M.; Kondo, Y.; Ikeda, H.; Gregory, G. L.; Anderson, B. E.; Sachse, G. W.; Blake, D. R.; Liu, S. C.; Singh, H. B.; Thompson, A. M.; Kita, K.; Zhao, Y.; Sugita, T.; Shetter, R. E.; Toriyama, N.

2000-02-01

The impact of aircraft emissions on reactive nitrogen in the upper troposphere (UT) and lowermost stratosphere (LS) was estimated using the NOy-O3 correlation obtained during the Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX) carried out over the U.S. continent and North Atlantic Flight Corridor (NAFC) region in October and November 1997. To evaluate the large-scale impact, we made a reference NOy-O3 relationship in air masses, upon which aircraft emissions were considered to have little impact. For this purpose, the integrated input of NOx from aircraft into an air mass along a 10-day back trajectory (ΔNOy) was calculated based on the Abatement of Nuisance Caused by Air Traffic/European Commission (ANCAT/EC2) emission inventory. The excess NOy (dNOy) was calculated from the observed NOy and the reference NOy-O3 relationship. As a result, a weak positive correlation was found between the dNOy and ΔNOy, and dNOy and NOx/NOy values, while no positive correlation between the dNOy and CO values was found, suggesting that dNOy values can be used as a measure of the NOx input from aircraft emissions. The excess NOy values calculated from another NOy-O3 reference relationship made using in situ condensation nuclei data also agreed with these dNOy values, within the uncertainties. At the NAFC region (45°N-60°N) the median value of dNOy in the troposphere increased with altitude above 9 km and reached 70 parts per trillion by volume (pptv) (20% of NOy) at 11 km. The excess NOx was estimated to be about half of the dNOy values, corresponding to 30% of the observed NOx level. Higher dNOy values were generally found in air masses where O3 = 75-125 ppbv, suggesting a more pronounced effect around the tropopause. The median value of dNOy in the stratosphere at the NAFC region at 8.5-11.5 km was about 120 pptv. The higher dNOy values in the LS were probably due to the accumulated effect of aircraft emissions, given the long residence time of affected air in the LS. Similar dNOy values were also obtained in air masses sampled over the U.S. continent.

Nitrogen and phosphorus removed from a subsurface flow multi-stage filtration system purifying agricultural runoff.

PubMed

Zhao, Yaqi; Huang, Lei; Chen, Yucheng

2018-07-01

Agricultural nonpoint source pollution has been increasingly serious in China since the 1990s. The main causes were excessive inputs of nitrogen fertilizer and pesticides. A multi-stage filtration system was built to test the purification efficiencies and removal characteristics of nitrogen and phosphorus when treating agricultural runoff. Simulated runoff pollution was prepared by using river water as source water based on the monitoring of local agricultural runoff. Experimental study had been performed from September to November 2013, adopting 12 h for flooding and 12 h for drying. The results showed that the system was made adaptive to variation of inflow quality and quantity, and had good removal for dissolved total nitrogen, total nitrogen, dissolved total phosphorus (DTP), and total phosphorus, and the average removal rate was 27%, 36%, 32%, and 48%, respectively. Except nitrate ([Formula: see text]), other forms of nitrogen and phosphorus all decreased with the increase of stages. Nitrogen was removed mainly in particle form the first stage, and mostly removed in dissolved form the second and third stage. Phosphorus was removed mainly in particulate during the first two stages, but the removal of particulate phosphorus and DTP were almost the same in the last stage. An approximate logarithmic relationship between removal loading and influent loading to nitrogen and phosphorus was noted in the experimental system, and the correlation coefficient was 0.78-0.94. [Formula: see text]: ammonium; [Formula: see text]: nitrite; [Formula: see text]: nitrate; DTN: dissolved total nitrogen; TN: total nitrogen; DTP: dissolved total phosphorus; TP: total phosphorus; PN: particulate nitrogen; PP: particulate phosphorus.

Toward an inventory of nitrogen input to the United States

EPA Science Inventory

Accurate accounting of nitrogen inputs is increasingly necessary for policy decisions related to aquatic nutrient pollution. Here we synthesize available data to provide the first integrated estimates of the amount and uncertainty of nitrogen inputs to the United States. Abou...

MEAD Marine Effects of Atmospheric Deposition

NASA Astrophysics Data System (ADS)

Jickells, T.; Spokes, L.

2003-04-01

The coastal seas are one of the most valuable resources on the planet but they are threatened by human activity. We rely on the coastal area for mineral resources, waste disposal, fisheries and recreation. In Europe, high population densities and high levels of industrial activity mean that the pressures arising from these activities are particularly acute. One of the main problems concerning coastal seas is the rapid increase in the amounts of nitrogen-based pollutants entering the water. They come from many sources, the most important ones being traffic, industry and agriculture. These pollutants can be used by algae as nutrients. The increasing concentrations of these nutrients have led to excessive growth of algae, some of which are harmful. When algae die and decay, oxygen in the water is used up and the resulting lower levels of oxygen may lead to fish kills. Human activity has probably doubled the amount of chemically and biologically reactive nitrogen present globally. In Europe the increases have been greater than this, leading to real concern over the health of coastal waters. Rivers have, until recently, been thought to be the most important source of reactive nitrogen to the coastal seas but we now know that inputs from the atmosphere are large and can equal, or exceed, those from the rivers. Our initial hypothesis was that atmospheric inputs are important and potentially different in their effect on coastal ecosystems to riverine inputs and hence require different management strategies. However, we had almost no information on the direct effects of atmospheric deposition on marine ecosystems, though clearly such a large external nitrogen input should lead to enhanced phytoplankton growth The aim of this European Union funded MEAD project has been to determine how inputs of nitrogen from the atmosphere affect the chemistry and biology of coastal waters. To try to answer this, we have conducted field experiments in the Kattegat, an area where we know atmospheric deposition to be an important source of nitrogen and where various eutrophication problems are evident. Fieldwork has involved atmospheric and water column measurements using ships, automated buoys and coastal stations. The results obtained have then been used in computer models which allow us to determine how atmospheric pollutants are transported in the atmosphere, deposited to the ocean and how this affects the growth of algae. These models have then been used to predict whether changing the amounts and types of pollutants entering the atmosphere will affect algal growth in coastal waters. We have also used existing monitoring data on phytoplankton abundance in the Kattegat in a retrospective analysis to identify incidences of blooms and test for any relation between these and atmospheric deposition. The final product of the MEAD project has been an improved scientific understanding of the transport and deposition of nitrogen in coastal waters and the effect of such deposition on phytoplankton ecosystems. These results will, we hope, allow policy makers to make rational decisions as to whether increased regulation of atmospheric nitrogen emissions are necessary.

Effects of different N sources on riverine DIN export and retention in subtropical high-standing island, Taiwan

NASA Astrophysics Data System (ADS)

Huang, J.-C.; Lee, T.-Y.; Lin, T.-C.; Hein, T.; Lee, L.-C.; Shih, Y.-T.; Kao, S.-J.; Shiah, F.-K.; Lin, N.-H.

2015-10-01

Increases in nitrogen (N) availability and mobility resulting from anthropogenic activities has substantially altered N cycle both locally and globally. Taiwan characterized by the subtropical montane landscape with abundant rainfall, downwind to the most rapidly industrializing east coast of China can be a demonstration site for extreme high N input and riverine DIN (dissolved inorganic N) export. We used 49 watersheds classified into low-, moderate-, and highly-disturbed categories based on population density to illustrate their differences in nitrogen inputs through atmospheric N deposition, synthetic fertilizers and human emission and DIN export ratios. Our results showed that the island-wide average riverine DIN export is ~ 3800 kg N km-2 yr-1, approximately 18-fold higher than the global average mostly due to the large input of synthetic fertilizers. The average riverine DIN export ratio is 0.30-0.51, which is much higher than the average of 0.20-0.25 of large rivers around the world indicating excessive N input relative to ecosystem demand or retention capacity. The low-disturbed watersheds, despite of high N input, only export 0.06-0.18 of the input so were well buffered to changes in input quantity suggesting high efficiency of nitrogen usage or high N retention capacity of the less disturbed watersheds. The high retention capacity probably is due to the effective uptake by secondary forests in the watersheds. The moderate-disturbed watersheds show a linear increase of output with increases in total N inputs and a mean DIN export ratio of 0.20 to 0.31. The main difference in land use between low and moderately disturbed watershed is the relative proportions of agricultural land and forests, not the built-up lands. Thus, their greater DIN export quantity could be attributed to N fertilizers used in the agricultural lands. The greater export ratios also imply that agricultural lands have lower proportional N retention capacity and that reforestation could be an effective land management practice to reduce riverine DIN export. The export ratio of the highly-disturbed watersheds is 0.42-0.53, which is very high and suggests that much of the N input is transported downstream and the need of improvement in wastewater treatment capacity or sewerage systems. The increases in riverine DIN export ratio along with the gradient of human disturbance indicates a gradient in N saturation in subtropical Taiwan. Our results help to understand factors controlling riverine DIN export and provide a sound basis for N emissions/pollution control.

Nitrogen Balance and Use Efficiency in the Calapooia River ...

EPA Pesticide Factsheets

Reducing nitrogen (N) release into the environment through greater N use efficiencies (NUE) is a current challenge in watershed management. Examining N sources and sinks at local scales allows for better watershed-scale N use, for example when considering the tradeoffs between the uses of animal waste from Concentrated Animal Feeding Operations (CAFOs) as a resource compared with the use of synthetic fertilizers. We use data on land-use, CAFOs, N deposition, stream chemistry, and crop-level and county-level fertilizer use to assess the N inputs, exports and retention in the Calapooia River Watershed (CRW). The CRW is influenced by intensive agricultural activities, mostly in grass seed crops. We determined that at the CRW scale, annual TN export is 25% of the inputs. Nearly 48% of the total area has a net TN input of 100-200 kg N ha-1 yr-1, dominated by agricultural land. About 41% has an input of 200 kg N ha-1 yr-1. Almost 50% of the annual hydrologic N yield occurs during wet winter and reaches 50 kg ha-1. The minimum TN yield as low as <1 kg ha-1 happens in dry summer. The effect of crop type on NUE is estimated based on N retention calculation and land use data. A manure-distribution model will be built to help improve manure NUE and prevent excess fertilizer application. Information on N balances will also be combined with local groundwater and drinking water nitrate level to assess the implications of N release for water quality an

Impact of nutrient imbalance on wine alcoholic fermentations: nitrogen excess enhances yeast cell death in lipid-limited must.

PubMed

Tesnière, Catherine; Delobel, Pierre; Pradal, Martine; Blondin, Bruno

2013-01-01

We evaluated the consequences of nutritional imbalances, particularly lipid/nitrogen imbalances, on wine yeast survival during alcoholic fermentation. We report that lipid limitation (ergosterol limitation in our model) led to a rapid loss of viability during the stationary phase of fermentation and that the cell death rate is strongly modulated by nitrogen availability and nature. Yeast survival was reduced in the presence of excess nitrogen in lipid-limited fermentations. The rapidly dying yeast cells in fermentations in high nitrogen and lipid-limited conditions displayed a lower storage of the carbohydrates trehalose and glycogen than observed in nitrogen-limited cells. We studied the cell stress response using HSP12 promoter-driven GFP expression as a marker, and found that lipid limitation triggered a weaker stress response than nitrogen limitation. We used a SCH9-deleted strain to assess the involvement of nitrogen signalling pathways in the triggering of cell death. Deletion of SCH9 increased yeast viability in the presence of excess nitrogen, indicating that a signalling pathway acting through Sch9p is involved in this nitrogen-triggered cell death. We also show that various nitrogen sources, but not histidine or proline, provoked cell death. Our various findings indicate that lipid limitation does not elicit a transcriptional programme that leads to a stress response protecting yeast cells and that nitrogen excess triggers cell death by modulating this stress response, but not through HSP12. These results reveal a possibly negative role of nitrogen in fermentation, with reported effects referring to ergosterol limitation conditions. These effects should be taken into account in the management of alcoholic fermentations.

Impact of Nutrient Imbalance on Wine Alcoholic Fermentations: Nitrogen Excess Enhances Yeast Cell Death in Lipid-Limited Must

PubMed Central

Tesnière, Catherine; Delobel, Pierre; Pradal, Martine; Blondin, Bruno

2013-01-01

We evaluated the consequences of nutritional imbalances, particularly lipid/nitrogen imbalances, on wine yeast survival during alcoholic fermentation. We report that lipid limitation (ergosterol limitation in our model) led to a rapid loss of viability during the stationary phase of fermentation and that the cell death rate is strongly modulated by nitrogen availability and nature. Yeast survival was reduced in the presence of excess nitrogen in lipid-limited fermentations. The rapidly dying yeast cells in fermentations in high nitrogen and lipid-limited conditions displayed a lower storage of the carbohydrates trehalose and glycogen than observed in nitrogen-limited cells. We studied the cell stress response using HSP12 promoter-driven GFP expression as a marker, and found that lipid limitation triggered a weaker stress response than nitrogen limitation. We used a SCH9-deleted strain to assess the involvement of nitrogen signalling pathways in the triggering of cell death. Deletion of SCH9 increased yeast viability in the presence of excess nitrogen, indicating that a signalling pathway acting through Sch9p is involved in this nitrogen-triggered cell death. We also show that various nitrogen sources, but not histidine or proline, provoked cell death. Our various findings indicate that lipid limitation does not elicit a transcriptional programme that leads to a stress response protecting yeast cells and that nitrogen excess triggers cell death by modulating this stress response, but not through HSP12. These results reveal a possibly negative role of nitrogen in fermentation, with reported effects referring to ergosterol limitation conditions. These effects should be taken into account in the management of alcoholic fermentations. PMID:23658613

Participatory Systems Modeling to Explore Sustainable ...

EPA Pesticide Factsheets

Decision makers often need assistance in understanding dynamic interactions and linkages among economic, environmental and social systems in coastal watersheds. They also need scientific input to better evaluate potential costs and benefits of alternative policy interventions. The US EPA is applying sustainability science to address these needs. Triple Value (3V) Scoping and Modeling projects bring a systems approach to understand complex environmental problems, incorporate local knowledge, and allow decision-makers to explore policy scenarios. This leads to better understanding of feedbacks and outcomes to both human and environmental systems. The Suffolk County, NY (eastern Long Island) 3V Case uses SES interconnections to explore possible policy options and scenarios for intervention to mitigate the effects of excess nitrogen (N) loading to ground, surface, and estuarine waters. Many of the environmental impacts of N pollution negatively affect social and economic well-being and productivity. Key are loss of enjoyment and recreational use of local beach environments and loss of income and revenues from tourism and local fisheries. Stakeholders generated this Problem Statement: Suffolk County is experiencing widespread degradation to groundwater and the coastal marine environment caused by excess nitrogen. How can local stakeholders and decision makers in Suffolk County arrest and reverse this degradation, restore conditions to support a healthy thriving ecos

Special Report on the Data Collection Programs for the Ground Based Nitrogen Washout Experiment. Volume 2 - Detailed Program Descriptions, Listings, Examples and Hardware Specifications

NASA Technical Reports Server (NTRS)

1982-01-01

Personal data input, decompression data, nitrogen washout, nitrogen data, and update computer programs are described. Input data and formats; program output, reports, and data; program flowcharts; program listings; sample runs with input and output pages; hardware operation; and engineering data are provided.

Anthropogenic modification of the nitrogen cycling within the Greater Hangzhou Area system, China.

PubMed

Gu, Baojing; Chang, Jie; Ge, Ying; Ge, Hanliang; Yuan, Chi; Peng, Changhui; Jiang, Hong

2009-06-01

Based on the mass balance approach, a detailed quantification of nitrogen (N) cycling was constructed for an urban-rural complex system, named the Greater Hangzhou Area (GHA) system, for this paper. The GHA is located in the humid climatic region on the southeastern coast of China, one of the earliest regions in the Yangtze Delta to experience economic development. Total N input into the GHA was calculated at 274.66 Gg/yr (1 Gg = 10(9) g), and total output was calculated at 227.33 Gg/yr, while N accumulation was assessed at 47.33 Gg/yr (17.2% of the total N input). Human activity resulted in 73%of N input by means of synthetic fertilizers, human food, animal feed, imported N containing chemicals, fossil fuel combustion, and other items. More than 69.3% of N was released into the atmosphere, and riverine N export accounted for 22.2% of total N output. N input and output to and from the GHA in 1980 were estimated at 119.53 Gg/yr and 98.30 Gg/yr, respectively, with an increase of 130% and 131%, respectively, during a 24-year period (from 1980 to 2004). The N input increase was influenced by synthetic fertilizers (138%), animal feed (225%), N-containing chemicals (371%), riverine input (311%), and N deposition (441%). Compared to the N balance seen in the arid Central Arizona-Phoenix (CAP) system in the United States, the proportion of N transferred to water bodies in the humid GHA system was found to be 36 times higher than the CAP system. Anthropogenic activity, as it typically does, enhanced the flux of N biogeochemistry in the GHA; however, a lack of an N remover (N pollutant treatment facilities) causes excess reactive N (Nr; such as NH3, N2O, NOx), polluting water bodies and the atmosphere within the GHA. Therefore many challenges remain ahead in order to achieve sustainable development in the rapidly developing GHA system.

Relating net nitrogen input in the Mississippi River Basin to nitrate flux in the Lower Mississippi River--A comparison of approaches

USGS Publications Warehouse

McIsaac, Gregory F.; David, Mark B.; Gertner, George Z.; Goolsby, Donald A.

2002-01-01

A quantitative understanding of the relationship between terrestrial N inputs and riverine N flux can help guide conservation, policy, and adaptive management efforts aimed at preserving or restoring water quality. The objective of this study was to compare recently published approaches for relating terrestrial N inputs to the Mississippi River basin (MRB) with measured nitrate flux in the lower Mississippi River. Nitrogen inputs to and outputs from the MRB (1951 to 1996) were estimated from state-level annual agricultural production statistics and NO y (inorganic oxides of N) deposition estimates for 20 states that comprise 90% of the MRB. A model with water yield and gross N inputs accounted for 85% of the variation in observed annual nitrate flux in the lower Mississippi River, from 1960 to 1998, but tended to underestimate high nitrate flux and overestimate low nitrate flux. A model that used water yield and net anthropogenic nitrogen inputs (NANI) accounted for 95% of the variation in riverine N flux. The NANI approach accounted for N harvested in crops and assumed that crop harvest in excess of the nutritional needs of the humans and livestock in the basin would be exported from the basin. The U.S. White House Committee on Natural Resources and Environment (CENR) developed a more comprehensive N budget that included estimates of ammonia volatilization, denitrification, and exchanges with soil organic matter. The residual N in the CENR budget was weakly and negatively correlated with observed riverine nitrate flux. The CENR estimates of soil N mineralization and immobilization suggested that there were large (2000 kg N ha−1) net losses of soil organic N between 1951 and 1996. When the CENR N budget was modified by assuming that soil organic N levels have been relatively constant after 1950, and ammonia volatilization losses are redeposited within the basin, the trend of residual N closely matched temporal variation in NANI and was positively correlated with riverine nitrate flux in the lower Mississippi River. Based on results from applying these three modeling approaches, we conclude that although the NANI approach does not address several processes that influence the N cycle, it appears to focus on the terms that can be estimated with reasonable certainty and that are correlated with riverine N flux.

Engineering crop nutrient efficiency for sustainable agriculture.

PubMed

Chen, Liyu; Liao, Hong

2017-10-01

Increasing crop yields can provide food, animal feed, bioenergy feedstocks and biomaterials to meet increasing global demand; however, the methods used to increase yield can negatively affect sustainability. For example, application of excess fertilizer can generate and maintain high yields but also increases input costs and contributes to environmental damage through eutrophication, soil acidification and air pollution. Improving crop nutrient efficiency can improve agricultural sustainability by increasing yield while decreasing input costs and harmful environmental effects. Here, we review the mechanisms of nutrient efficiency (primarily for nitrogen, phosphorus, potassium and iron) and breeding strategies for improving this trait, along with the role of regulation of gene expression in enhancing crop nutrient efficiency to increase yields. We focus on the importance of root system architecture to improve nutrient acquisition efficiency, as well as the contributions of mineral translocation, remobilization and metabolic efficiency to nutrient utilization efficiency. © 2017 Institute of Botany, Chinese Academy of Sciences.

Spatial variability in groundwater N2 and N2O in the San Joaquin River

NASA Astrophysics Data System (ADS)

Hinshaw, S.; Dahlgren, R. A.

2010-12-01

The San Joaquin River is surrounded by nearly 2 million acres of irrigated agricultural land. Groundwater inputs from agricultural areas can have severe negative effects on water quality with high nitrate concentrations being a major concern. Riparian zones are important ecological habitats that mitigate nitrogen loading from groundwater discharging into rivers primarily by denitrification. Denitrification is a permanent removal of nitrate by anaerobic microbial communities via the reduction to NO, N2O and N2. However, previous studies have shown that these areas can be source of N2O emissions. Although removal of nitrate through denitrification is advantageous from a water quality perspective, N2O is a harmful greenhouse gas. This study aimed to investigate nitrogen dynamics and dissolved N gases in surface and groundwater of the riparian zones of the San Joaquin River. Excess N2 and N2O concentrations were measured in surface and groundwater at 4 locations along a 33 km reach of the river. Samples were collected within bank sediments and 5 transect points across the river at depth intervals between 2-3 cm and 150 cm. Dissolved N2 and Ar were measured by membrane inlet mass spectrometry and used to estimate excess dissolved N2 concentrations. Dissolved N2O concentrations were measured using the headspace equilibrium technique and analyzed with a gas chromatograph. Both N2 uptake and excess N2 were present, ranging from -3.40 to 8.65 N2 mg/L with a median concentration of 1.20 N2 mg/L. Significantly lower concentrations of N2O were present ranging from 0.0 to 0.12 N2O mg/L. Deeper groundwater sites had significantly higher N2 and N2O concentrations coinciding with decreased O2. The presence of excess N2 and low N2O concentrations documents the importance of denitrification in removing nitrate from groundwater. Further investigation will examine N2O emissions from riparian soils and benthic sediments using static chambers and focus on nitrogen pathways that contribute to high ammonium concentrations with increasing depth.

Estimated anthropogenic nitrogen and phosphorus inputs to the land surface of the conterminous United States--1992, 1997, and 2002

USGS Publications Warehouse

Sprague, Lori A.; Gronberg, Jo Ann M.

2013-01-01

Anthropogenic inputs of nitrogen and phosphorus to each county in the conterminous United States and to the watersheds of 495 surface-water sites studied as part of the U.S. Geological Survey National Water-Quality Assessment Program were quantified for the years 1992, 1997, and 2002. Estimates of inputs of nitrogen and phosphorus from biological fixation by crops (for nitrogen only), human consumption, crop production for human consumption, animal production for human consumption, animal consumption, and crop production for animal consumption for each county are provided in a tabular dataset. These county-level estimates were allocated to the watersheds of the surface-water sites to estimate watershed-level inputs from the same sources; these estimates also are provided in a tabular dataset, together with calculated estimates of net import of food and net import of feed and previously published estimates of inputs from atmospheric deposition, fertilizer, and recoverable manure. The previously published inputs are provided for each watershed so that final estimates of total anthropogenic nutrient inputs could be calculated. Estimates of total anthropogenic inputs are presented together with previously published estimates of riverine loads of total nitrogen and total phosphorus for reference.

Modeling nitrate leaching and optimizing water and nitrogen management under irrigated maize in desert oases in Northwestern China.

PubMed

Hu, Kelin; Li, Yong; Chen, Weiping; Chen, Deli; Wei, Yongping; Edis, Robert; Li, Baoguo; Huang, Yuanfang; Zhang, Yuanpei

2010-01-01

Understanding water and N transport through the soil profile is important for efficient irrigation and nutrient management to minimize nitrate leaching to the groundwater, and to promote agricultural sustainable development in desert oases. In this study, a process-based water and nitrogen management model (WNMM) was used to simulate soil water movement, nitrate transport, and crop growth (maize [Zea mays L.]) under desert oasis conditions in northwestern China. The model was calibrated and validated with a field experiment. The model simulation results showed that about 35% of total water input and 58% of the total N input were leached to <1.8 m depth under traditional management practice. Excessive irrigation and N fertilizer application, high nitrate concentration in the irrigation water, together with the sandy soil texture, resulted in large nitrate leaching. Nitrate leaching was significantly reduced under the improved management practice suggested by farm extension personnel; however, the water and nitrate inputs still far exceeded the crop requirements. More than 1700 scenarios combining various types of irrigation and fertilizer practices were simulated. Quantitative analysis was conducted to obtain the best management practices (BMPs) with simultaneous consideration of crop yield, water use efficiency, fertilizer N use efficiency, and nitrate leaching. The results indicated that the BMPs under the specific desert oasis conditions are to irrigate the maize with 600 mm of water in eight times with a single fertilizer application at a rate of 75 kg N ha(-1).

Predicting Nitrogen in Streams: A Comparison of Two Estimates of Fertilizer Application

NASA Astrophysics Data System (ADS)

Mehaffey, M.; Neale, A.

2011-12-01

Decision makers frequently rely on water and air quality models to develop nutrient management strategies. Obviously, the results of these models (e.g., SWAT, SPARROW, CMAQ) are only as good as the nutrient source input data and recently the Nutrient Innovations Task Group has called for a better accounting of nonpoint nutrient sources. Currently, modelers frequently rely on county level fertilizer sales records combined with acreage of crops to estimate nitrogen sources from fertilizer for counties or watersheds. However, since fertilizer sales data are based on reported amounts they do not necessarily reflect actual use on the fields. In addition the reported sales data quality varies by state resulting in differing accuracy between states. In this study we examine an alternative method potentially providing a more uniform, spatially explicit, estimate of fertilizer use. Our nitrogen application data is estimated at a 30m pixel resolution which allows for scalable inputs for use in water and air quality models. To develop this dataset we combined raster data from the National Cropland data layer (CDL) data with the National Land Cover Data (NLCD). This process expanded the NLCD's 'cultivated crops' classes to included major grains, cover crops, and vegetable and fruits. The Agriculture Resource Management Survey chemical fertilizer application rate data were summarized by crop type and year for each state, encompassing the corn, soybean, spring wheat, and winter wheat crop types (ARMS, 2002-2005). The chemical fertilizer application rate data were then used to estimate annual application parameters for nitrogen, phosphate, potash, herbicide, pesticide, and total pesticide, all expressed on a mass-per-unit-crop-area basis for each state for each crop type. By linking crop types to nitrogen application rates, we can better estimate where applied fertilizer would likely be in excess of the amounts used by crops or where conservation practices may improve retention and uptake helping offset the impacts to water. To test the accuracy of our finer resolution nitrogen application data, we compare its ability to predict nitrogen concentrations in streams with the ability of the county sales data to do the same.

USING MUSSEL ISTOPE RATIOS TO ASSESS ANTHROPOGENIC NITROGEN INPUTS TO FRESHWATER ECOSYSTEMS

EPA Science Inventory

Stable nitrogen isotope ratios ( 15N) of freshwater mussels from a series of lakes and ponds were related to watershed land use characteristics to assess their utility in determining the source of nitrogen inputs to inland water bodies. Nitrogen isotope ratios measured in freshwa...

USING MUSSEL ISOTOPE RATIOS TO ASSESS ANTHROPOGEN NITROGEN INPUTS TO COASTAL ECOSYSTEMS

EPA Science Inventory

The stable nitrogen isotope ratio in ribbed mussel (Geukensia demissus) tissue was investigated as an indicator of the source of nitrogen inputs to coastal salt marshes. Mussels fed a diet of 15N enriched algae in the laboratory showed an increase in tissue nitrogen isotope rati...

The anthropogenic perturbation of the marine nitrogen cycle by atmospheric deposition: Nitrogen cycle feedbacks and the 15N Haber-Bosch effect

NASA Astrophysics Data System (ADS)

Yang, Simon; Gruber, Nicolas

2016-10-01

Over the last 100 years, anthropogenic emissions have led to a strong increase of atmospheric nitrogen deposition over the ocean, yet the resulting impacts and feedbacks are neither well understood nor quantified. To this end, we run a suite of simulations with the ocean component of the Community Earth System Model v1.2 forced with five scenarios of nitrogen deposition over the period from 1850 through 2100, while keeping all other forcings unchanged. Even though global oceanic net primary production increases little in response to this fertilization, the higher export and the resulting expansion of the oxygen minimum zones cause an increase in pelagic and benthic denitrification and burial by about 5%. In addition, the enhanced availability of fixed nitrogen in the surface ocean reduces global ocean N2 fixation by more than 10%. Despite the compensating effects through these negative feedbacks that eliminate by the year 2000 about 60% of the deposited nitrogen, the anthropogenic nitrogen input forced the upper ocean N budget into an imbalance of between 9 and 22 Tg N yr-1 depending on the deposition scenario. The excess nitrogen accumulates to highly detectable levels and causes in most areas a distinct negative trend in the δ15N of the oceanic fixed nitrogen pools—a trend we refer to as the 15N Haber-Bosch effect. Changes in surface nitrate utilization and the nitrogen feedbacks induce further changes in the δ15N of NO3-, making it a good but complex recorder of the overall impact of the changes in atmospheric deposition.

Nitrogen removal in shallow groundwater below three arable land systems in a high nitrogen loading region

NASA Astrophysics Data System (ADS)

Yan, X.; Zhou, W.

2017-12-01

The Taihu Lake region (TLR) is one of the most intensive agricultural regions with high nitrogen (N) loading in eastern China. Large inputs of synthetic N fertilizer have led to a series of environmental problems including eutrophication of surface waters, nitrate (NO3-) pollution of groundwater. To fully evaluate the risk of NO3- on groundwater environments, it is necessary to know the natural NO3- removal ability. In this study, denitrification capacity was assessed for two years through measuring the concentration of different N species (NO3-, NH4+, TN, excess N2 and dissolved N2O) in groundwater below three typical agricultural land-use types in the TLR. The results suggested that the conversion of paddy field (PF) to vineyard (VY) and vegetable (VF) significantly increased the groundwater NO3-N concentration, but denitrification consumed 76%, 83% and 65% of the groundwater NO3-N in VY, VF and PF, respectively. Because of the low O2 and high DOC concentrations in groundwater, denitrification activity was high in the study sites, resulting in high excess N2 accumulation in groundwater, and the concentration even exceeded the total active N in the deep layer. The large amounts of excess N2 observed in the VY and VF over all the sample times indicated that considerable N was stored as gaseous N2 in groundwater and should not be ignored in balancing N budgets in aquifers where denitrification is high. Our results also demonstrated that the indirect N2O emission factor (EF5-g) in VY (0.0052)and VF (0.0057)was significantly higher than PF (0.0011)as well as higher than the IPCC default values (0.0025. In view of the increasing trend of paddy fields being converted to uplands combined with the low GWT in the TLR, we thus concluded that the risk of NO3- contamination in groundwater and indirect N2O emission will intensify below arable land.

Trends in nitrogen isotope ratios of juvenile winter flounder reflect changing nitrogen inputs to Rhode Island, USA estuarine systems

EPA Science Inventory

Nitrogen isotope ratios (d 15N) in juvenile winter flounder, Pseudopleuronectes americanus, were used to examine changes in nitrogen inputs to several Rhode Island, USA estuarine systems. Fish were collected over two three-year periods with a ten-year interval between sampling pe...

Determination of nitrogen balance in agroecosystems

USDA-ARS?s Scientific Manuscript database

Nitrogen balance in agroecosystems provides a quantitative framework of N inputs and outputs and retention in the soil that examine sustainability of agricultural productivity and soil and environmental quality. Nitrogen inputs include N additions from manures and fertilizers, atmospheric deposition...

Novel insight of carotenoid and lipid biosynthesis and their roles in storage carbon metabolism in Chlamydomonas reinhardtii.

PubMed

Sun, Han; Mao, Xuemei; Wu, Tao; Ren, Yuanyuan; Chen, Feng; Liu, Bin

2018-05-10

Revenues of carotenoid and lipid biosynthesis under excess light and nitrogen starvation were firstly analyzed for the increased biomass value through carbon metabolism analysis. The results suggested excess light and nitrogen starvation resulted in carbon partitioning among protein, starch, lipid and carotenoid. Nitrogen starvation promoted more cellular lipid content than excess light, while excess light promoted carotenoid and polyunsaturated fatty acid accumulation. In the molecular level, the stresses redirected carbon skeletons into the central metabolite of pyruvate and oriented into starch and lipid as the primary and secondary carbon storage, respectively. Economic estimation revealed nitrogen starvation potentially increased 14.76 × 10 -6 and 72.11 × 10 -6  $/g revenues of biofuel production at per batch and cell weight scales, respectively. Excess light could increase 63.90 × 10 -6 and 19.21 × 10 -6  $/g at per cell weight scale of lipid and carotenoid, respectively. In combination with metabolism analysis, conversion procedure of process-compatible products was divided into four phases. Copyright © 2018 Elsevier Ltd. All rights reserved.

A Network Flow Analysis of the Nitrogen Metabolism in Beijing, China.

PubMed

Zhang, Yan; Lu, Hanjing; Fath, Brian D; Zheng, Hongmei; Sun, Xiaoxi; Li, Yanxian

2016-08-16

Rapid urbanization results in high nitrogen flows and subsequent environmental consequences. In this study, we identified the main metabolic components (nitrogen inputs, flows, and outputs) and used ecological network analysis to track the direct and integral (direct + indirect) metabolic flows of nitrogen in Beijing, China, from 1996 to 2012 and to quantify the structure of Beijing's nitrogen metabolic processes. We found that Beijing's input of new reactive nitrogen (Q, which represents nitrogen obtained from the atmosphere or nitrogen-containing materials used in production and consumption to support human activities) increased from 431 Gg in 1996 to 507 Gg in 2012. Flows to the industry, atmosphere, and household, and components of the system were clearly largest, with total integrated inputs plus outputs from these nodes accounting for 31, 29, and 15%, respectively, of the total integral flows for all paths. The flows through the sewage treatment and transportation components showed marked growth, with total integrated inputs plus outputs increasing to 3.7 and 5.2 times their 1996 values, respectively. Our results can help policymakers to locate the key nodes and pathways in an urban nitrogen metabolic system so they can monitor and manage these components of the system.

Response of Benthic Microalgae to Phosphorus Inputs in Grand Bay National Estuarine Research Reserve

NASA Astrophysics Data System (ADS)

Sleek, J.; Caffrey, J. M.; Baine, G. C., II; Capps, R.

2016-12-01

Benthic microalgae are an important, but often understudied component of shallow, photic estuaries in the Gulf of Mexico. Grand Bay National Estuarine Research Reserve (GBNERR) is located in a small and relatively pristine estuary in the northern Gulf of Mexico. Freshwater input into the estuary is primarily local runoff from bayous and tidal creeks, including Bayou Cumbest, Bayou Heron, and Bangs Lake. Nutrient loading to Grand Bay is relatively small, with ambient nutrient concentrations often below detection. However, several events in 2005, 2012, 2013, and 2014 due to breaches in a containment levee from a gypsum stack have led to high phosphate levels near Bangs Lake. GBNERR staff assembled a phosphate working group to investigate scientific questions related to these phosphate loadings. This working group includes members from GBNERR, regional universities, marine labs, and Mississippi Department of Environmental Quality. In marine ecosystems, nitrogen availability normally limits growth of phytoplankton and previous research has shown this to be the case in Grand Bay. However, little is known about benthic microalgae in Grand Bay and what their response is to these phosphorus inputs. Between 2013 and 2015, summer concentrations of water column and benthic chlorophyll a were positively correlated, with the highest concentrations occurring in Bangs Lake. Benthic chlorophyll was also positively correlated with the percent surface irradiance reaching the bottom. Bottom light levels range from 3 to 36% surface irradiance. This along with experiments that showed no enhancement of growth of benthic microalgae following addition of nutrients (ammonium, phosphate or both) suggest that benthic microalgae are predominantly light limited rather than nutrient limited. Preliminary nitrogen fixation measurements suggest that nitrogen fixation was positively correlated with extractable phosphate concentrations. Thus, enhanced sediment nitrogen fixation and excess phosphate from the fertilizer plant runoff in this high light environment may enhance benthic microalgal production. The results of this research are part of the larger effort by the phosphate working group to understand the impact of repeated phosphate impacts. These results will provide information needed to help manage the reserve.

Response of Benthic Microalgae to Phosphorus Inputs in Grand Bay National Estuarine Research Reserve

NASA Astrophysics Data System (ADS)

Sleek, J.; Caffrey, J. M.; Baine, G. C., II; Capps, R.

2016-02-01

Benthic microalgae are an important, but often understudied component of shallow, photic estuaries in the Gulf of Mexico. Grand Bay National Estuarine Research Reserve (GBNERR) is located in a small and relatively pristine estuary in the northern Gulf of Mexico. Freshwater input into the estuary is primarily local runoff from bayous and tidal creeks, including Bayou Cumbest, Bayou Heron, and Bangs Lake. Nutrient loading to Grand Bay is relatively small, with ambient nutrient concentrations often below detection. However, several events in 2005, 2012, 2013, and 2014 due to breaches in a containment levee from a gypsum stack have led to high phosphate levels near Bangs Lake. GBNERR staff assembled a phosphate working group to investigate scientific questions related to these phosphate loadings. This working group includes members from GBNERR, regional universities, marine labs, and Mississippi Department of Environmental Quality. In marine ecosystems, nitrogen availability normally limits growth of phytoplankton and previous research has shown this to be the case in Grand Bay. However, little is known about benthic microalgae in Grand Bay and what their response is to these phosphorus inputs. Between 2013 and 2015, summer concentrations of water column and benthic chlorophyll a were positively correlated, with the highest concentrations occurring in Bangs Lake. Benthic chlorophyll was also positively correlated with the percent surface irradiance reaching the bottom. Bottom light levels range from 3 to 36% surface irradiance. This along with experiments that showed no enhancement of growth of benthic microalgae following addition of nutrients (ammonium, phosphate or both) suggest that benthic microalgae are predominantly light limited rather than nutrient limited. Preliminary nitrogen fixation measurements suggest that nitrogen fixation was positively correlated with extractable phosphate concentrations. Thus, enhanced sediment nitrogen fixation and excess phosphate from the fertilizer plant runoff in this high light environment may enhance benthic microalgal production. The results of this research are part of the larger effort by the phosphate working group to understand the impact of repeated phosphate impacts. These results will provide information needed to help manage the reserve.

Excess nitrogen in selected thermal and mineral springs of the Cascade Range in northern California, Oregon, and Washington: Sedimentary or volcanic in origin?

USGS Publications Warehouse

Mariner, R.H.; Evans, William C.; Presser, T.S.; White, L.D.

2003-01-01

Anomalous N2/Ar values occur in many thermal springs and mineral springs, some volcanic fumaroles, and at least one acid-sulfate spring of the Cascade Range. Our data show that N2/Ar values are as high as 300 in gas from some of the hot springs, as high as 1650 in gas from some of the mineral springs, and as high as 2400 in gas from the acid-sulfate spring on Mt. Shasta. In contrast, gas discharging from hot springs that contain nitrogen and argon solely of atmospheric origin typically exhibits N2/Ar values of 40-80, depending on the spring temperature. If the excess nitrogen in the thermal and mineral springs is of sedimentary origin then the geothermal potential of the area must be small, but if the nitrogen is of volcanic origin then the geothermal potential must be very large. End-member excess nitrogen (??15N) is +5.3% for the thermal waters of the Oregon Cascades but is only about +1% for fumaroles on Mt. Hood and the acid-sulfate spring on Mt. Shasta. Dissolved nitrogen concentrations are highest for thermal springs associated with aquifers between 120 and 140??C. Chloride is the major anion in most of the nitrogen-rich springs of the Cascade Range, and N2/Ar values generally increase as chloride concentrations increase. Chloride and excess nitrogen in the thermal waters of the Oregon Cascades probably originate in an early Tertiary marine formation that has been buried by the late Tertiary and Quaternary lava flows of the High Cascades. The widespread distribution of excess nitrogen that has been generated in low to moderate-temperature sedimentary environments is further proof of the restricted geothermal potential of the Cascade Range. ?? 2002 Elsevier Science B.V. All rights reserved.

Excess nitrogen in selected thermal and mineral springs of the Cascade Range in northern California, Oregon, and Washington: sedimentary or volcanic in origin?

NASA Astrophysics Data System (ADS)

Mariner, R. H.; Evans, W. C.; Presser, T. S.; White, L. D.

2003-02-01

Anomalous N 2/Ar values occur in many thermal springs and mineral springs, some volcanic fumaroles, and at least one acid-sulfate spring of the Cascade Range. Our data show that N 2/Ar values are as high as 300 in gas from some of the hot springs, as high as 1650 in gas from some of the mineral springs, and as high as 2400 in gas from the acid-sulfate spring on Mt. Shasta. In contrast, gas discharging from hot springs that contain nitrogen and argon solely of atmospheric origin typically exhibits N 2/Ar values of 40-80, depending on the spring temperature. If the excess nitrogen in the thermal and mineral springs is of sedimentary origin then the geothermal potential of the area must be small, but if the nitrogen is of volcanic origin then the geothermal potential must be very large. End-member excess nitrogen (δ 15N) is +5.3‰ for the thermal waters of the Oregon Cascades but is only about +1‰ for fumaroles on Mt. Hood and the acid-sulfate spring on Mt. Shasta. Dissolved nitrogen concentrations are highest for thermal springs associated with aquifers between 120 and 140°C. Chloride is the major anion in most of the nitrogen-rich springs of the Cascade Range, and N 2/Ar values generally increase as chloride concentrations increase. Chloride and excess nitrogen in the thermal waters of the Oregon Cascades probably originate in an early Tertiary marine formation that has been buried by the late Tertiary and Quaternary lava flows of the High Cascades. The widespread distribution of excess nitrogen that has been generated in low to moderate-temperature sedimentary environments is further proof of the restricted geothermal potential of the Cascade Range.

Nitrogen retention across a gradient of 15N additions to an unpolluted temperate forest soil in Chile

USGS Publications Warehouse

Perakis, Steven S.; Compton, J.E.; Hedin, L.O.

2005-01-01

Accelerated nitrogen (N) inputs can drive nonlinear changes in N cycling, retention, and loss in forest ecosystems. Nitrogen processing in soils is critical to understanding these changes, since soils typically are the largest N sink in forests. To elucidate soil mechanisms that underlie shifts in N cycling across a wide gradient of N supply, we added 15NH415NO3 at nine treatment levels ranging in geometric sequence from 0.2 kg to 640 kg NA? ha-1A? yr-1 to an unpolluted old-growth temperate forest in southern Chile. We recovered roughly half of tracers in 0-25 cm of soil, primarily in the surface 10 cm. Low to moderate rates of N supply failed to stimulate N leaching, which suggests that most unrecovered 15N was transferred from soils to unmeasured sinks above ground. However, soil solution losses of nitrate increased sharply at inputs > 160 kg NA? ha-1A? yr-1, corresponding to a threshold of elevated soil N availability and declining 15N retention in soil. Soil organic matter (15N in soils at the highest N inputs and may explain a substantial fraction of the 'missing N' often reported in studies of fates of N inputs to forests. Contrary to expectations, N additions did not stimulate gross N cycling, potential nitrification, or ammonium oxidizer populations. Our results indicate that the nonlinearity in N retention and loss resulted directly from excessive N supply relative to sinks, independent of plant-soil-microbial feedbacks. However, N additions did induce a sharp decrease in microbial biomass C:N that is predicted by N saturation theory, and which could increase long-term N storage in soil organic matter by lowering the critical C:N ratio for net N mineralization. All measured sinks accumulated 15N tracers across the full gradient of N supply, suggesting that short-term nonlinearity in N retention resulted from saturation of uptake kinetics, not uptake capacity, in plant, soil, and microbial pools.

Effects of Atmospheric Nitrate on an Upland Stream of the Northeastern USA

NASA Astrophysics Data System (ADS)

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

2009-05-01

Excess nitrogen cascades through terrestrial biogeochemical cycles and affects stream nitrate concentrations in upland forests where atmospheric deposition is an important source of anthropogenic nitrogen. We will discuss approaches including high-frequency sampling, isotopic tracers, and end-member mixing analysis that can be used to decipher the sources, transformations, and hydrological processes that affect nitrate transport through forested upland catchments to streams. We present results of studies at the Sleepers River Research Watershed in Vermont, USA, a site where we have intensively measured stream nitrate concentrations during baseflow and stormflow. Stream nitrate concentrations are typically low and nearly 75% of annual inorganic N inputs from atmospheric deposition are retained within the catchment. However, high concentrations and stream loadings of nitrate occur during storm events due to source variation and hydrological flushing of nitrate from catchment soils. Using isotopic tracers and end-member mixing analysis, we have quantified source inputs of unprocessed atmospheric nitrate and show that this stream is directly affected by nitrogen pollution. Using a long-term record of stream hydrochemistry and our findings on event- scale nitrate flushing dynamics, we then explore how stream nitrate loading may respond to anthropogenic climate forcing during the next century. Results suggest that stream runoff and nitrate loadings will change during future emission scenarios (i.e. longer growing seasons and higher winter precipitation rates). Understanding the timing and magnitude of hydrological and hydrochemical responses is important because climate change effects on catchment hydrology may alter how nitrate is retained, produced, and hydrologically flushed in headwater ecosystems with implications for aquatic metabolism, nutrient export from catchments, and downstream eutrophication.

Least-cost input mixtures of water and nitrogen for photosynthesis.

PubMed

Wright, Ian J; Reich, Peter B; Westoby, Mark

2003-01-01

In microeconomics, a standard framework is used for determining the optimal input mix for a two-input production process. Here we adapt this framework for understanding the way plants use water and nitrogen (N) in photosynthesis. The least-cost input mixture for generating a given output depends on the relative cost of procuring and using nitrogen versus water. This way of considering the issue integrates concepts such as water-use efficiency and photosynthetic nitrogen-use efficiency into the more inclusive objective of optimizing the input mix for a given situation. We explore the implications of deploying alternative combinations of leaf nitrogen concentration and stomatal conductance to water, focusing on comparing hypothetical species occurring in low- versus high-humidity habitats. We then present data from sites in both the United States and Australia and show that low-rainfall species operate with substantially higher leaf N concentration per unit leaf area. The extra protein reflected in higher leaf N concentration is associated with a greater drawdown of internal CO2, such that low-rainfall species achieve higher photosynthetic rates at a given stomatal conductance. This restraint of transpirational water use apparently counterbalances the multiple costs of deploying high-nitrogen leaves.

Utilizing Physical Input-Output Model to Inform Nitrogen related Ecosystem Services

EPA Science Inventory

Here we describe the development of nitrogen PIOTs for the midwestern US state of Illinois with large inputs of nitrogen from agriculture and industry. The PIOTs are used to analyze the relationship between regional economic activities and ecosystem services in order to identify...

Effects of Nitrogen Inputs and Watershed Characteristics on Summer Stream Nitrogen Concentrations: A National-Scale Analysis

EPA Science Inventory

Nitrogen (N) inputs to the landscape have been linked previously to N loads exported from watersheds at the national scale; however, stream N concentration is arguably more relevant than N load for drinking water quality, freshwater biological responses and establishment of nutri...

The long-term impact of urbanization on nitrogen patterns and dynamics in Shanghai, China.

PubMed

Gu, Baojing; Dong, Xiaoli; Peng, Changhui; Luo, Weidong; Chang, Jie; Ge, Ying

2012-12-01

Urbanization is an important process that alters the regional and global nitrogen biogeochemistry. In this study, we test how long-term urbanization (1952-2004) affects the nitrogen flows, emissions and drivers in the Greater Shanghai Area (GSA) based on the coupled human and natural systems (CHANS) approach. Results show that: (1) total nitrogen input to the GSA increased from 57.7 to 587.9 Gg N yr(-1) during the period 1952-2004, mainly attributing to fossil fuel combustion (43%), Haber-Bosch nitrogen fixation (31%), and food/feed import (26%); (2) per capita nitrogen input increased from 13.5 to 45.7 kg N yr(-1), while per gross domestic product (GDP) nitrogen input reduced from 22.2 to 0.9 g N per Chinese Yuan, decoupling of nitrogen with GDP; (3) emissions of reactive nitrogen to the environment transformed from agriculture dominated to industry and human living dominated, especially for air pollution. This study provides decision-makers a novel view of nitrogen management. Copyright © 2012 Elsevier Ltd. All rights reserved.

RESEARCH FOR NUTRIENT SOLUTIONS ON CAPE COD SERIES

EPA Science Inventory

Excess nitrogen causes the quality of estuary waters to decrease and impacts the ability of people to use those waters. Because of a lawsuit, towns on Cape Cod are required to address the excess nitrogen that flows into the Cape’s estuaries. These towns are examining both t...

Ecological Engineering Practices for the Reduction of Excess Nitrogen in Human-Influenced Landscapes: A Guide for Watershed Managers

EPA Science Inventory

Excess nitrogen (N) in freshwater systems, estuaries, and coastal areas has well-documented deleterious effects on ecosystems. Ecological engineering practices (EEPs) may be effective at decreasing nonpoint source N leaching to surface and groundwater. However, few studies have s...

Linking annual N2O emission in organic soils to mineral nitrogen input as estimated by heterotrophic respiration and soil C/N ratio.

PubMed

Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti

2014-01-01

Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted.

Watershed nitrogen and phosphorus balance: The upper Potomac River basin

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

Jaworski, N.A.; Groffman, P.M.; Keller, A.A.

1992-01-01

Nitrogen and phosphorus mass balances were estimated for the portion of the Potomac River basin watershed located above Washington, D.C. The total nitrogen (N) balance included seven input source terms, six sinks, and one 'change-in-storage' term, but was simplified to five input terms and three output terms. The phosphorus (P) baance had four input and three output terms. The estimated balances are based on watershed data from seven information sources. Major sources of nitrogen are animal waste and atmospheric deposition. The major sources of phosphorus are animal waste and fertilizer. The major sink for nitrogen is combined denitrification, volatilization, andmore » change-in-storage. The major sink for phosphorus is change-in-storage. River exports of N and P were 17% and 8%, respectively, of the total N and P inputs. Over 60% of the N and P were volatilized or stored. The major input and output terms on the budget are estimated from direct measurements, but the change-in-storage term is calculated by difference. The factors regulating retention and storage processes are discussed and research needs are identified.« less

Biotic Nitrogen Enrichment Regulates Calcium Sources to Forests

NASA Astrophysics Data System (ADS)

Pett-Ridge, J. C.; Perakis, S. S.; Hynicka, J. D.

2015-12-01

Calcium is an essential nutrient in forest ecosystems that is susceptible to leaching loss and depletion. Calcium depletion can affect plant and animal productivity, soil acid buffering capacity, and fluxes of carbon and water. Excess nitrogen supply and associated soil acidification are often implicated in short-term calcium loss from soils, but the long-term role of nitrogen enrichment on calcium sources and resupply is unknown. Here we use strontium isotopes (87Sr/86Sr) as a proxy for calcium to investigate how soil nitrogen enrichment from biological nitrogen fixation interacts with bedrock calcium to regulate both short-term available supplies and the long-term sources of calcium in montane conifer forests. Our study examines 22 sites in western Oregon, spanning a 20-fold range of bedrock calcium on sedimentary and basaltic lithologies. In contrast to previous studies emphasizing abiotic control of weathering as a determinant of long-term ecosystem calcium dynamics and sources (via bedrock fertility, climate, or topographic/tectonic controls) we find instead that that biotic nitrogen enrichment of soil can strongly regulate calcium sources and supplies in forest ecosystems. For forests on calcium-rich basaltic bedrock, increasing nitrogen enrichment causes calcium sources to shift from rock-weathering to atmospheric dominance, with minimal influence from other major soil forming factors, despite regionally high rates of tectonic uplift and erosion that can rejuvenate weathering supply of soil minerals. For forests on calcium-poor sedimentary bedrock, we find that atmospheric inputs dominate regardless of degree of nitrogen enrichment. Short-term measures of soil and ecosystem calcium fertility are decoupled from calcium source sustainability, with fundamental implications for understanding nitrogen impacts, both in natural ecosystems and in the context of global change. Our finding that long-term nitrogen enrichment increases forest reliance on atmospheric calcium helps explain reports of greater ecological calcium limitation in an increasingly nitrogen-rich world.

Atmospheric Nitrogen Deposition in the Western United States: Sources, Sinks and Changes over Time

NASA Astrophysics Data System (ADS)

Anderson, Sarah Marie

Anthropogenic activities have greatly modified the way nitrogen moves through the atmosphere and terrestrial and aquatic environments. Excess reactive nitrogen generated through fossil fuel combustion, industrial fixation, and intensification of agriculture is not confined to anthropogenic systems but leaks into natural ecosystems with consequences including acidification, eutrophication, and biodiversity loss. A better understanding of where excess nitrogen originates and how that changes over time is crucial to identifying when, where, and to what degree environmental impacts occur. A major route into ecosystems for excess nitrogen is through atmospheric deposition. Excess nitrogen is emitted to the atmosphere where it can be transported great distances before being deposited back to the Earth's surface. Analyzing the composition of atmospheric nitrogen deposition and biological indicators that reflect deposition can provide insight into the emission sources as well as processes and atmospheric chemistry that occur during transport and what drives variation in these sources and processes. Chapter 1 provides a review and proof of concept of lichens to act as biological indicators and how their elemental and stable isotope composition can elucidate variation in amounts and emission sources of nitrogen over space and time. Information on amounts and emission sources of nitrogen deposition helps inform natural resources and land management decisions by helping to identify potentially impacted areas and causes of those impacts. Chapter 2 demonstrates that herbaria lichen specimens and field lichen samples reflect historical changes in atmospheric nitrogen deposition from urban and agricultural sources across the western United States. Nitrogen deposition increases throughout most of the 20 th century because of multiple types of emission sources until the implementation of the Clean Air Act Amendments of 1990 eventually decrease nitrogen deposition around the turn of the 21st century. Chapter 3 focuses on how nitrogen emissions and subsequent deposition are affected by processes and chemistry during atmospheric transport through analysis of the oxygen isotope composition of nitrate in wet deposition. Local emission sources drive spatial variation, changes in solar radiation drive seasonal variation, and variability in atmospheric conditions and transport drive interannual variation in the processes and chemistry occurring during atmospheric transport of reactive nitrogen.

Variation in watershed nitrogen input and export across the Willamette River Basin

EPA Science Inventory

Nitrogen (N) export from watersheds is influenced by hydrology, land use/cover, and the timing and spatial arrangement of N inputs and removal within basins. We examined the relationship between N input and watershed N export for 25 monitoring stations between 1996 and 2006 with...

Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large-scale field sampling: Fixed nitrogen and dry deposition of phosphorus

NASA Astrophysics Data System (ADS)

Baker, A. R.; Lesworth, T.; Adams, C.; Jickells, T. D.; Ganzeveld, L.

2010-09-01

Atmospheric nitrogen inputs to the ocean are estimated to have increased by up to a factor of three as a result of increased anthropogenic emissions over the last 150 years, with further increases expected in the short- to mid-term at least. Such estimates are largely based on emissions and atmospheric transport modeling, because, apart from a few island sites, there is very little observational data available for atmospheric nitrogen concentrations over the remote ocean. Here we use samples of rainwater and aerosol we obtained during 12 long-transect cruises across the Atlantic Ocean between 50°N and 50°S as the basis for a climatological estimate of nitrogen inputs to the basin. The climatology is for the 5 years 2001-2005, during which almost all of the cruises took place, and includes dry and wet deposition of nitrate and ammonium explicitly, together with a more uncertain estimate of soluble organic nitrogen deposition. Our results indicate that nitrogen inputs into the region were ˜850-1420 Gmol (12-20 Tg) N yr-1, with ˜78-85% of this in the form of wet deposition. Inputs were greater in the Northern Hemisphere and in wet regions, and wet regions had a greater proportion of input via wet deposition. The largest uncertainty in our estimate of dry inputs is associated with variability in deposition velocities, while the largest uncertainty in our wet nitrogen input estimate is due to the limited amount and uneven geographic distribution of observational data. We also estimate a lower limit of dry deposition of phosphate to be ˜0.19 Gmol P yr-1, using data from the same cruises. We compare our results to several recent estimates of N and P deposition to the Atlantic and discuss the likely sources of uncertainty, such as the potential seasonal bias introduced by our sampling, on our climatology.

Microbial nitrogen sinks in the water column of a large coastal hypoxic area, the Gulf of Mexico "Dead Zone"

NASA Astrophysics Data System (ADS)

Rogener, M. K.; Roberts, B. J.; Rabalais, N. N.; Stewart, F. J.; Joye, S. B.

2016-02-01

Excess nitrogen in coastal environments leads to eutrophication, harmful algal blooms, habitat loss, oxygen depletion and reductions in biodiversity. As such, biological nitrogen (N) removal through the microbially-mediated process of denitrification is a critical ecosystem function that can mitigate the negative consequences of excess nitrogen loading. However, denitrification can produce nitrous oxide, a potent greenhouse gas, as a byproduct under some environmental conditions. To understand how excess nitrogen loading impacts denitrification, we measured rates of this process in the water column of the Gulf of Mexico "Dead Zone" three times over the summer of 2015. The Dead Zone is generated by excessive nitrogen loading from the Mississippi River co-occurring with strong water column stratification, which leads to a large summer-time hypoxic/anoxic area at the mouth of the river and along the coast of Louisiana. Rates of denitrification ranged from 31 to 153 nmol L-1 d-1. Dead Zone waters are also enriched in methane and aerobic methane oxidation rates ranged from 0.1 to 4.3 nmol L-1 d-1. Maximal denitrification rates were observed at stations with the lowest oxygen concentrations and highest methane oxidation rates, suggesting a potential coupling between nitrate reduction and methane oxidation which both scrubs reactive N and methane from the system, thus performing a duel ecosystem service.

Ecosystem Services in Lakes of the Northeastern United States: Upstream Benefits from Estuarine Nitrogen Reduction Scenarios

EPA Science Inventory

Reduction of nitrogen inputs to estuaries can be achieved by the control of agricultural, atmospheric, and urban sources. We use the USGS MRB1 SPARROW model to estimate reductions necessary to reduce nitrogen loads to estuaries by 10%. If only agricultural inputs are reduced, ...

A LANDSCAPE MODEL TO PREDICT TOTAL NITROGEN LEVELS IN SURFACE WATERS OF THE WILLAMETTE AND CENTRAL VALLEYS ECOREGION OF THE WESTERN UNITED STATES

EPA Science Inventory

Excess nutrients are a leading cause of impairment to streams, rivers, lakes and the coastal ecosystems. Excessive nutrient loadings result in increased primary productivity of plant and algal communities leading to eutrophication and other impacts to aquatic resources. Nitrogen ...

Nutrient Mass Balance for the Mobile River Basin in Alabama, Georgia, and Mississippi

NASA Astrophysics Data System (ADS)

Harned, D. A.; Harvill, J. S.; McMahon, G.

2001-12-01

The source and fate of nutrients in the Mobile River drainage basin are important water-quality concerns in Alabama, Georgia, and Mississippi. Land cover in the basin is 74 percent forested, 16 percent agricultural, 2.5 percent developed, and 4 percent wetland. A nutrient mass balance calculated for 18 watersheds in the Mobile River Basin indicates that agricultural non-point nitrogen and phosphorus sources and urban non-point nitrogen sources are the most important factors associated with nutrients in the streams. Nitrogen and phosphorus inputs from atmospheric deposition, crop fertilizer, biological nitrogen fixation, animal waste, and point sources were estimated for each of the 18 drainage basins. Total basin nitrogen inputs ranged from 27 to 93 percent from atmospheric deposition (56 percent mean), 4 to 45 percent from crop fertilizer (25 percent mean), <0.01 to 31 percent from biological nitrogen fixation (8 percent mean), 2 to 14 percent from animal waste (8 percent mean), and 0.2 to 11 percent from point sources (3 percent mean). Total basin phosphorus inputs ranged from 10 to 39 percent from atmospheric deposition (26 percent mean), 7 to 51 percent from crop fertilizer (28 percent mean), 20 to 64 percent from animal waste (41 percent mean), and 0.2 to 11 percent from point sources (3 percent mean). Nutrient outputs for the watersheds were estimated by calculating instream loads and estimating nutrient uptake, or withdrawal, by crops. The difference between the total basin inputs and outputs represents nutrients that are retained or processed within the basin while moving from the point of use to the stream, or in the stream. Nitrogen output, as a percentage of the total basin nitrogen inputs, ranged from 19 to 79 percent for instream loads (35 percent mean) and from 0.01 to 32 percent for crop harvest (10 percent mean). From 53 to 87 percent (75 percent mean) of nitrogen inputs were retained within the 18 basins. Phosphorus output ranged from 9 to 29 percent for instream loads (18 percent mean) and from 0.01 to 23 percent for crop harvest (7 percent mean). The basins retained from 60 to 87 percent (74 percent mean) of phosphorous inputs. Correlation of basin nutrient output loads and concentrations with the basin inputs and correlation of output loads and concentrations with basin land use were tested using the Spearman rank test. The correlation analysis indicated that higher nitrogen concentrations in the streams are associated with urban areas and higher loads are associated with agriculture; high phosphorus output loads and concentrations are associated with agriculture. Higher nutrient loads in agricultural basins are partly an effect of basin size-- larger basins generate larger nutrient loads. Nutrient loads and concentrations showed no significant correlation to point-source inputs. Nitrogen loads were significantly (p<0.05, correlation coefficient >0.5) higher in basins with greater cropland areas. Nitrogen concentrations also increased as residential, commercial, and total urban areas increased. Phosphorus loads were positively correlated with animal-waste inputs, pasture, and total agricultural land. Phosphorus concentrations were highest in basins with the greatest amounts of row-crop agriculture.

Improvements to the Characterization of Organic Nitrogen Chemistry

EPA Science Inventory

Excess atmospheric nitrogen deposition can cause significant harmful effects to ecosystems. Organic nitrogen deposition can be an important contributor to the total nitrogen budget, contributing 10-30%, however there are large uncertainties in the chemistry and deposition of thes...

Piling up reactive nitrogen and declining nitrogen use efficiency in Pakistan: a challenge not challenged (1961-2013)

NASA Astrophysics Data System (ADS)

Raza, Sajjad; Zhou, Jianbin; Aziz, Tariq; Rahil Afzal, Muhammad; Ahmed, Muneer; Javaid, Shahbaz; Chen, Zhujun

2018-03-01

Excessive nitrogen (N) application and reduced nitrogen use efficiency (NUE) are the key reasons behind N notoriety worldwide, including in Pakistan. We estimated the changes in NUE of Pakistan by calculating the N budget of Pakistan’s agriculture during the last 53 years (1961-2013). A more than ten-fold increase in N input (including N fertilizer, biological N fixation, manure, and atmospheric deposition) from 408 GgNyr-1 (1961-1965) to 4636 GgNyr-1 (2009-2013) highlights the fact that Pakistan is experiencing a massive expansion of N consumption. Significantly declining NUE (from 58% to 23%) and sharply increasing surplus N (171 GgNyr-1 to 3581 GgNyr-1) may cause N-related environment problems in the future if not handled immediately. Escalating gaseous N emissions of NH3, N2O, and NO (70, 10, and 1 GgNyr-1 to 1023, 155, and 46 GgNyr-1, respectively) is already posing a serious threat in terms of impaired air quality. There is a dire need to devise/adapt strategies and consistent policies for improving NUE, using proper management approaches at the grass root level and applying appropriate legislative measures for judicious N use as per crops requirements. Moreover, promotion of a balanced use of fertilizers would help in improving NUE in agriculture.

Linking Annual N2O Emission in Organic Soils to Mineral Nitrogen Input as Estimated by Heterotrophic Respiration and Soil C/N Ratio

PubMed Central

Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti

2014-01-01

Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted. PMID:24798347

The Paradox of Excess Nitrogen in Boreal Peatlands: Biogeochemical Gaps in Nitrogen Cycling Revealed

NASA Astrophysics Data System (ADS)

Vile, M. A.; Prsa, T.; Wieder, R.; Lamers, L. P.

2011-12-01

Globally, peatlands cover 3-4 % of the Earth's land surface (over 4 million km 2, yet they store 25-30 % of the world's soil carbon (C) and 9-16% of the world's soil nitrogen (N, 8-15 Pg) in peat. As in other terrestrial ecosystems, the cycling of C and N is closely linked, especially for ombrotrophic bogs. Bogs receive nutrient and water exclusively from the atmosphere, which ensures an N-limited, nutrient-poor habitat. In Alberta, NW Canada, peatlands have received exceptionally low atmospheric inputs of N (< 1 7 kg/ha/yr) from their first introduction on the landscape ~ 7000 yrs bp, up to the present time. Paradoxically, despite these low inputs of atmospheric N deposition, bases on 210-fixation Pb dating of peat cores, we have shown that over the past 50 years these bogs have accumulated approximately 11-21 times more N in peat than can be explained by inputs of atmospheric N. A likely missing input is N2-fixation from cyanobacteria associated with Sphagnum mosses, however this process has been largely overlooked in boreal peatlands. Here we demonstrate the importance of N2-fixation in explaining the high accumulation rates of N found in unpolluted, boreal bogs of western Canada. Calibrated (using theoretical ratio of 1.5-3:1) rates of N2-fixation for 4 bogs in northern Alberta ranged from 1.6 to 8.0 ± 0.7 kg/ha/yr, indicating that 42-58 % of the N accumulated over in peat, can be attributed to biological N2-fixation. Although most of northern Alberta's peatlands continue to receive exceptionally low atmospheric N deposition rates, over the last 3 decades, rapid development and industrial expansion of Alberta's Oil Sands Mining (OSM) potentially threaten the pristine nature of peatlands through regionally elevated deposition of N-compounds (NOx). Prior to OSM, N inputs to bogs were limited exclusively to (1) biological N fixation, and (2) bulk background deposition. We examined the response of peatlands located in the OSM area to enhanced N deposition. Despite the large accumulation rates of N in peat, mean N:P ratios in Sphagnum moss capitula (11.0 ± 3.4; mean ± stdev) suggest that peat of boreal western Canada is still severely N limited and not limited by phosphorus. Collectively, these data underscore the severity of N-limitation in pristine bogs and their potential sensitivity to increased N inputs from oils sands mining. Additionally, because the majority of the data generated for N stress in peatlands is from eastern Canada and western Europe, we stress the need to encompass the response of bogs to N deposition within the bounds of the low N deposition gradient. We postulate the loss of symbiosis between Sphagnum and N-fixing microorganisms (cyanobacteria, bacteria) in nitrogen-polluted areas, and indicate its consequences at the species level (trade-off) and ecosystem level (including C sequestration).

Nitrogen excess in slowly-rotating β Cephei stars: deep mixing or diffusion?

NASA Astrophysics Data System (ADS)

Morel, T.; Butler, K.; Aerts, C.; Neiner, C.; Briquet, M.

2007-06-01

We present the results of an NLTE abundance study of a small sample of β Cephei stars, which point to the existence of a population of slowly-rotating B-type pulsators exhibiting a significant amount of nitrogen-enriched material at their surface. Although the origin of this nitrogen excess remains unclear, an overabundance preferentially occurring in stars with a detected magnetic field seems to emerge at this stage. Full details can be found in Morel et al. (2006).

Biofiltration of air contaminated by styrene: Effect of nitrogen supply, gas flow rate, and inlet concentration

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

Jorio, H.; Bibeau, L.; Heitz, M.

2000-05-01

The biofiltration process is a promising technology for the treatment of dilute styrene emissions in air. The efficiency of this process is however strongly dependent upon various operational parameters such as the filter bed characteristics, nutrient supplies, input contaminant concentrations, and gas flow rates. The biofiltration of air containing styrene vapors was therefore investigated, employing a novel biomass filter material, in two identical but separate laboratory scale biofiltration units (units 1 and 2), both biofilters being initially inoculated with a microbial consortium. Each biofilter was irrigated with a nutrient solution supplying nitrogen in one of two forms; i.e., mainly asmore » ammonia for unit 1 and exclusively as nitrate for unit 2. The experimental results have revealed that greater styrene elimination rates are achieved in the biofilter supplied with ammonia as the major nitrogen source in comparison to the lesser elimination performance obtained with the nitrate provided biofilter. However, in achieving the high styrene removal rates in the ammonia supplied biofilter, the excess of biomass accumulates on the filtering pellets and causes progressive clogging of the filter media. Furthermore, the effectiveness of nitrate supply as the sole nitrogen nutrient form, on reducing or controlling the biomass accumulation in the filter media in comparison to ammonia, could not be satisfactorily demonstrated because the two biofilters operated with very different styrene elimination capacities. The monitoring of the carbon dioxide concentration profile through both biofilters revealed that the ratio of carbon dioxide produced to the styrene removed was approximately 3/1, which confirms the complete biodegradation of removed styrene, given that some of the organic carbon consumed is also used for the microbial growth. The effects of the most important design parameters, namely styrene input concentrations and gas flow rates, were investigated for each nutrient solution.« less

Interactions between reactive nitrogen and the Canadian landscape: A budget approach

NASA Astrophysics Data System (ADS)

Clair, Thomas A.; Pelletier, Nathan; Bittman, Shabtai; Leip, Adrian; Arp, Paul; Moran, Michael D.; Dennis, Ian; Niemi, David; Sterling, Shannon; Drury, Craig F.; Yang, Jingyi

2014-11-01

The movement of excess reactive nitrogen (Nr) from anthropogenic activities to natural ecosystems has been described as one of the most serious environmental threats facing modern society. One of the approaches for tracking this movement is the use of budgets that quantify fluxes. We constructed an Nr budget for Canada using measured and modeled values from the scientific literature, government databases, and data from new agri-environmental indicators, in order to produce information for policy makers and scientists to understand the major flows of nitrogen to allow a better assessment of risks to the Canadian environment. We divided the Canadian territory south of 60°N into areas dominated by natural ecosystems, as well as by agricultural and urban/industrial activities to evaluate Nr flows within, between, and out of these units. We show that Canada is a major exporter of Nr due to the availability of inexpensive commercial fertilizers. The large land area suitable for agriculture makes Canada a significant agricultural Nr exporter of both grain crops and livestock. Finally, Canada exports petroleum N mainly to the United States. Because of its location and prevailing atmospheric transport patterns, Canada is a net receptor of Nr air pollution from the United States, receiving approximately 20% of the Nr leaving the U.S. airshed. We found that overall, terrestrial natural ecosystems as well as the atmosphere are in balance between Nr inputs and outputs when all N reactive and nonreactive fluxes are included. However, when only reactive forms are considered, almost 50% of N entering the Canadian atmosphere cannot be accounted for and is assumed to be lost to the Atlantic and Arctic oceans or to unmeasured dry deposition. However, agricultural and freshwater landscapes are showing large differences between measured inputs and outputs of N as our data suggest that denitrification in soils and aquatic systems is larger than what models predict. Our work also shows that Canada is a major contributor to the global flow of nitrogen through commercial exports.

Nitrogen mass balance in the Brazilian Amazon: an update.

PubMed

Martinelli, L A; Pinto, A S; Nardoto, G B; Ometto, J P H B; Filoso, S; Coletta, L D; Ravagnani, E C

2012-08-01

The main purpose of this study is to perform a nitrogen budget survey for the entire Brazilian Amazon region. The main inputs of nitrogen to the region are biological nitrogen fixation occurring in tropical forests (7.7 Tg.yr(-1)), and biological nitrogen fixation in agricultural lands mainly due to the cultivation of a large area with soybean, which is an important nitrogen-fixing crop (1.68 Tg.yr(-1)). The input due to the use of N fertilizers (0.48 Tg.yr(-1)) is still incipient compared to the other two inputs mentioned above. The major output flux is the riverine flux, equal to 2.80 Tg.yr(-1) and export related to foodstuff, mainly the transport of soybean and beef to other parts of the country. The continuous population growth and high rate of urbanization may pose new threats to the nitrogen cycle of the region through the burning of fossil fuel and dumping of raw domestic sewage in rivers and streams of the region.

Historical trend of nitrogen and phosphorus loads from the upper Yangtze River basin and their responses to the Three Gorges Dam.

PubMed

Sun, Chengchun; Shen, Zhenyao; Liu, Ruimin; Xiong, Ming; Ma, Fangbing; Zhang, Ouyang; Li, Yangyang; Chen, Lei

2013-12-01

Excessive inputs of nitrogen and phosphorus (N and P) degrade surface water quality worldwide. Impoundment of reservoirs alters the N and P balance of a basin. In this study, riverine nutrient loads from the upper Yangtze River basin (YRB) at the Yichang station were estimated using Load Estimator (LOADEST). Long-term load trends and monthly variabilities during three sub-periods based on the construction phases of the Three Gorges Dam (TGD) were analyzed statistically. The dissolved inorganic nitrogen (DIN) loads from the upper YRB for the period from 1990 to 2009 ranged from 30.47 × 10(4) to 78.14 × 10(4) t, while the total phosphorus (TP) loads ranged from 2.54 × 10(4) to 7.85 × 10(4) t. DIN increased rapidly from 1995 to 2002 mainly as a result of increased fertilizer use. Statistics of fertilizer use in the upper YRB agreed on this point. However, the trend of the TP loads reflected the combined effect of removal by sedimentation in reservoirs and increased anthropogenic inputs. After the TGD impoundment in 2003, decreasing trends in both DIN and TP loads were found. The reduction in DIN was mainly caused by ammonium consumption and transference. From an analysis of monthly loads, it was found that DIN had a high correlation to discharges. For TP loads, an average decrease of 4.91 % in October was found when the TGD impoundment occurred, but an increase of 4.23 % also occurred in July, corresponding to the washout from sediment deposited in the reservoir before July. Results of this study revealed the TGD had affected nutrient loads in the basin, and it had played a role in nutrient reduction after its operation.

Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers.

PubMed

Cocking, Edward C; Stone, Philip J; Davey, Michael R

2005-12-01

It has been forecast that the challenge of meeting increased food demand and protecting environmental quality will be won or lost in maize, rice and wheat cropping systems, and that the problem of environmental nitrogen enrichment is most likely to be solved by substituting synthetic nitrogen fertilizers by the creation of cereal crops that are able to fix nitrogen symbiotically as legumes do. In legumes, rhizobia present intracellularly in membrane-bound vesicular compartments in the cytoplasm of nodule cells fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound vesicular compartments, rhizobia are supplied with energy derived from plant photosynthates and in return supply the plant with biologically fixed nitrogen, usually as ammonia. This minimizes or eliminates the need for inputs of synthetic nitrogen fertilizers. Recently we have demonstrated, using novel inoculation conditions with very low numbers of bacteria, that cells of root meristems of maize, rice, wheat and other major non-legume crops, such as oilseed rape and tomato, can be intracellularly colonized by the non-rhizobial, non-nodulating, nitrogen fixing bacterium, Gluconacetobacter diazotrophicus that naturally occurs in sugarcane. G. diazotrophicus expressing nitrogen fixing (nifH) genes is present in symbiosome-like compartments in the cytoplasm of cells of the root meristems of the target cereals and non-legume crop species, somewhat similar to the intracellular symbiosome colonization of legume nodule cells by rhizobia. To obtain an indication of the likelihood of adequate growth and yield, of maize for example, with reduced inputs of synthetic nitrogen fertilizers, we are currently determining the extent to which nitrogen fixation, as assessed using various methods, is correlated with the extent of systemic intracellular colonization by G. diazotrophicus, with minimal or zero inputs.

Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers.

PubMed

Cocking, Edward C; Stone, Philip J; Davey, Michael R

2005-09-01

It has been forecast that the challenge of meeting increased food demand and protecting environmental quality will be won or lost in maize, rice and wheat cropping systems, and that the problem of environmental nitrogen enrichment is most likely to be solved by substituting synthetic nitrogen fertilizers by the creation of cereal crops that are able to fix nitrogen symbiotically as legumes do. In legumes, rhizobia present intracellularly in membrane-bound vesicular compartments in the cytoplasm of nodule cells fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound vesicular compartments, rhizobia are supplied with energy derived from plant photosynthates and in return supply the plant with biologically fixed nitrogen, usually as ammonia. This minimizes or eliminates the need for inputs of synthetic nitrogen fertilizers. Recently we have demonstrated, using novel inoculation conditions with very low numbers of bacteria, that cells of root meristems of maize, rice, wheat and other major non-legume crops, such as oilseed rape and tomato, can be intracellularly colonized by the non-rhizobial, non-nodulating, nitrogen fixing bacterium,Gluconacetobacter diazotrophicus that naturally occurs in sugarcane.G. diazotrophicus expressing nitrogen fixing (nifH) genes is present in symbiosome-like compartments in the cytoplasm of cells of the root meristems of the target cereals and non-legume crop species, somewhat similar to the intracellular symbiosome colonization of legume nodule cells by rhizobia. To obtain an indication of the likelihood of adequate growth and yield, of maize for example, with reduced inputs of synthetic nitrogen fertilizers, we are currently determining the extent to which nitrogen fixation, as assessed using various methods, is correlated with the extent of systemic intracellular colonization byG. diazotrophicus, with minimal or zero inputs.

Improvements to the treatment of organic nitrogen chemistry & deposition in CMAQ

EPA Science Inventory

Excess atmospheric nitrogen deposition can cause significant harmful effects to ecosystems. Organic nitrogen deposition can be an important contributor to the total nitrogen budget, contributing 10-30%, however there are large uncertainties in the chemistry and deposition of thes...

Improvements to the characterization of organic nitrogen chemistry and deposition in CMAQ

EPA Science Inventory

Excess atmospheric nitrogen deposition can cause significant harmful effects to ecosystems. Organic nitrogen deposition can be an important contributor to the total nitrogen budget, contributing 10-30%, however there are large uncertainties in the chemistry and deposition of thes...

Impact of Aircraft Emissions on Reactive Nitrogen over the North Atlantic Flight Corridor Region

NASA Technical Reports Server (NTRS)

Koike, M.; Kondo, Y.; Ikeda, H.; Gregory, G. L.; Anderson, B. E.; Sachse, G. W.; Blake, D.; Liu, S. C.; Singh, H. B.; Thompson, A.

1999-01-01

The impact of aircraft emissions on reactive nitrogen in the upper troposphere (UT) and lowermost stratosphere (LS) was estimated using the NO(y)-O3 correlation obtained during the SASS Ozone and NO(x) Experiment (SONEX) carried out over the US continent and North Atlantic Flight Corridor (NAFC) region in October and November 1997. To evaluate the large scale impact, we made a reference NO(y)-O3 relationship in air masses, upon which aircraft emissions were considered to have little impact. For this purpose, the integrated input of NO(x) from aircraft into an air mass along a 10-d back trajectory (DELTA-NO(y)) was calculated based on the ANCAT/EC2 emission inventory. The excess NO(y) (dNO(y)) was calculated from the observed NO(y) and the reference NO(y)-O3 relationship. As a result, a weak positive correlation was found between the dNO(y) and DELTA-NO(y), and dNO(y) and NO(x)/NO(y) values, while no positive correlation between the dNO(y) and CO values was found, suggesting that dNO(y) values can be used as a measure of the NO(x) input from aircraft emissions. The excess NO(y) values calculated from another NO(y)-O3 reference relationship made using in-situ CN data also agreed with these dNO(y) values, within the uncertainties. At the NAFC region (45 N - 60 N), the median value of dNO(y) in the troposphere increased with altitude above 9 km and reached 70 pptv (20% of NO(y)) at 11 km. The excess NO(x) was estimated to be about half of the dNO(y) values, corresponding to 30% of the observed NO(x) level. Higher dNO(y) values were generally found in air masses where O3 = 75 - 125 ppbv, suggesting a more pronounced effect around the tropopause. The median value of dNO(y) in the stratosphere at the NAFC region at 8.5 - 11.5 km was about 120 pptv. The higher dNO(y) values in the LS were probably due to the accumulated effect of aircraft emissions, given the long residence time of affected air in the LS. Similar dNO(y) values were also obtained in air masses sampled over the US continent.

The Growing Human Footprint on Coastal and Open-Ocean Biogeochemistry

NASA Astrophysics Data System (ADS)

Doney, Scott C.

2010-06-01

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources.

The growing human footprint on coastal and open-ocean biogeochemistry.

PubMed

Doney, Scott C

2010-06-18

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources.

Early results from an effort to downscale a global dissolved inorganic nitrogen model to achieve a regional assessment of nitrogen dynamics in the Columbia River Basin

NASA Astrophysics Data System (ADS)

Miller, C. C.; Harrison, J.

2013-12-01

Excessive nitrogen (N) export to coastal systems has increased dramatically since the early 20th century. The increase in N has been linked to significant environmental impacts such as eutrophication, fish kills, and harmful algal blooms and is caused in part by the increasing use and quantity of synthetic fertilizer on farmland. Significant portions of both the Willamette River Valley in Oregon and the Palouse region of eastern Washington are agricultural land, approximately 20% and 57% respectively. Nitrogen in the form of dissolved inorganic nitrogen (DIN) can leach from farms and pasture land into ground and surface water systems. This leaching, combined with DIN in runoff, contributes to the environmental degradation of both waterways (i.e. streams, rivers) and coastal estuaries. Because of this it is important to understand what effects changes in DIN application will have on water quality and DIN export to the coast. DIN export data, retrieved from the U.S. Geological Survey National Water Information System, was analyzed for 23 major subbasins in the Columbia River Basin (CRB) and estimates DIN export (per area yield) ranging from 5.0 to 883.1 kg N km-2 yr-1. Here we present early results from our effort to downscale the Global Nutrient Export from WaterSheds (Global NEWS) DIN model for application within the Columbia River Basin (CRB). This first attempt at downscaling Global NEWS is missing some key higher-resolution N inputs for the model as well as accurate dam retention and runoff factors which could account for the low correlation between model output and observed data (R2 = 0.21).Our regional model predicts DIN yields ranging from 7.9 to 1146.6 kg N km-2 yr-1. Both the model output and observed data predict the highest per area DIN yields occurring in the Willamette river subbasin. Total DIN export to the coast was modeled as 0.06 Tg N yr-1 compared to 0.07 Tg N yr-1 calculated from the measured data. Based on current model inputs biological N2 fixation is the dominant source of DIN in 15 of the 23 subbasins, including the CRB as a whole. N fertilizer is the dominant source of anthropogenic DIN export among the rest of the subbasins. With improvements to the model inputs we expect to see a higher correlation between the measured data and the model output.

Study on Release Characteristics and Recovery of Nitrogen and Phosphorus during the Anaerobic Fermentation of Excess Sludge

NASA Astrophysics Data System (ADS)

Qin, Yuqian; Hu, Shulong

2018-01-01

Ammonia nitrogen and phosphate are produced from activated excess sludge under anaerobic conditions,and will cause eutrophication upon release to the environment. A study of sludge from a eutrophication was carried out, to obtain knowledge of the nitrogen and phosphorus release patterns of the excess sludge during anaerobic fermentation and the recycling efficiency of both nitrogen and phosphorus, by adding magnesium salt and alkali solution to the supernatant liquors. The results showed that the concentration of ammonia nitrogen and phosphate of the supernatant liquors continued to increase during the process of anaerobic digestion, and both reached a maximum in 12 days, at 41.56mg / L and 47.02 mg / L respectively. By adding magnesium salt to the supernatant with c(Mg): c(P) = 1.1:1, adjusting pH value to 9.0 ∼ 9.5, phosphorus recovery rate reached up to 95.0%, while the recovery rate of ammonia was 47.4%, resulting in the formation of a sediment of magnesium ammonium phosphate, or MAP, which may he used as a high-quality fertilizer.

Inputs and internal cycling of nitrogen to a causeway influenced, hypersaline lake, Great Salt Lake, Utah, USA

USGS Publications Warehouse

Naftz, David L.

2017-01-01

Nitrogen inputs to Great Salt Lake (GSL), located in the western USA, were quantified relative to the resident nitrogen mass in order to better determine numeric nutrient criteria that may be considered at some point in the future. Total dissolved nitrogen inputs from four surface-water sources entering GSL were modeled during the 5-year study period (2010–2014) and ranged from 1.90 × 106 to 5.56 × 106 kg/year. The railroad causeway breach was a significant conduit for the export of dissolved nitrogen from Gilbert to Gunnison Bay, and in 2011 and 2012, net losses of total nitrogen mass from Gilbert Bay via the Causeway breach were 9.59 × 105 and 1.51 × 106 kg. Atmospheric deposition (wet + dry) was a significant source of nitrogen to Gilbert Bay, exceeding the dissolved nitrogen load contributed via the Farmington Bay causeway surface-water input by >100,000 kg during 2 years of the study. Closure of two railroad causeway culverts in 2012 and 2013 likely initiated a decreasing trend in the volume of the higher density Deep Brine Layer and associated declines in total dissolved nitrogen mass contained in this layer. The large dissolved nitrogen pool in Gilbert Bay relative to the amount of nitrogen contributed by surface-water inflow sources is consistent with the terminal nature of GSL and the predominance of internal nutrient cycling. The opening of the new railroad causeway breach in 2016 will likely facilitate more efficient bidirectional flow between Gilbert and Gunnison Bays, resulting in potentially substantial changes in nutrient pools within GSL.

Monitoring plant tissue nitrogen isotopes to assess nearshore inputs of nitrogen to Lake Crescent, Olympic National Park, Washington

USGS Publications Warehouse

Cox, Stephen E.; Moran, Patrick W.; Huffman, Raegan L.; Fradkin, Steven C.

2016-05-31

Mats of filamentous-periphytic algae present in some nearshore areas of Lake Crescent, Olympic National Park, Washington, may indicate early stages of eutrophication from nutrient enrichment of an otherwise highly oligotrophic lake. Natural abundance ratios of stable isotopes of nitrogen (δ15N) measured in plant tissue growing in nearshore areas of the lake indicate that the major source of nitrogen used by these primary producing plants is derived mainly from atmospherically fixed nitrogen in an undeveloped forested ecosystem. Exceptions to this pattern occurred in the Barnes Point area where elevated δ15N ratios indicate that effluent from septic systems also contribute nitrogen to filamentous-periphytic algae growing in the littoral zone of that area. Near the Lyre River outlet of Lake Crescent, the δ15N of filamentous-periphytic algae growing in close proximity to the spawning areas of a unique species of trout show little evidence of elevated δ15N indicating that nitrogen from on-site septic systems is not a substantial source of nitrogen for these plants. The δ15N data corroborate estimates that nitrogen input to Lake Crescent from septic sources is comparatively small relative to input from motor vehicle exhaust and vegetative sources in undeveloped forests, including litterfall, pollen, and symbiotic nitrogen fixation. The seasonal timing of blooms of filamentous-periphytic algal near the lake shoreline is also consistent with nitrogen exported from stands of red alder trees (Alnus rubra). Isotope biomonitoring of filamentous-periphytic algae may be an effective approach to monitoring the littoral zone for nutrient input to Lake Crescent from septic sources.

Improvements to the characterization of organic nitrogen chemistry and deposition in CMAQ (CMAS Presentation)

EPA Science Inventory

Excess atmospheric nitrogen deposition can cause significant harmful effects to ecosystems. Organic nitrogen deposition can be an important contributor to the total nitrogen budget, contributing 10-30%, however there are large uncertainties in the chemistry and deposition of thes...

Growth response of Douglas-fir seedlings to nitrogen fertilization: importance of Rubisco activation state and respiration rates.

Treesearch

Daniel K. Manter; Kathleen L. Kavanagh; Cathy L. Rose

2005-01-01

High foliar nitrogen concentration ([N]) is associated with high rates of photosynthesis and thus high tree productivity; however, at excessive [N], tree productivity is reduced. Reports of excessive [N] in the Douglas-fir forests of the Oregon Coast Range prompted this investigation of growth and needle physiological responses to increasing foliar N concentrations in...

Reversible control of biofilm formation by Cellulomonas spp. in response to nitrogen availability.

PubMed

Young, Jenna M; Leschine, Susan B; Reguera, Gemma

2012-03-01

The microbial degradation of cellulose contributes greatly to the cycling of carbon in terrestrial environments and feedbacks to the atmosphere, a process that is highly responsive to nitrogen inputs. Yet how key groups of cellulolytic microorganisms adaptively respond to the global conditions of nitrogen limitation and/or anthropogenic or climate nitrogen inputs is poorly understood. The actinobacterial genus Cellulomonas is of special interest because it incorporates the only species known to degrade cellulose aerobically and anaerobically. Furthermore, despite their inability to fix nitrogen, they are active decomposers in nitrogen-limited environments. Here we show that nitrogen limitation induced biofilm formation in Cellulomonas spp., a process that was coupled to carbon sequestration and storage in a curdlan-type biofilm matrix. The response was reversible and the curdlan matrix was solubilized and used as a carbon and energy source for biofilm dispersal once nitrogen sources became available. The biofilms attached strongly to cellulosic surfaces and, despite the growth limitation, produced cellulases and degraded cellulose more efficiently. The results show that biofilm formation is a competitive strategy for carbon and nitrogen acquisition and provide valuable insights linking nitrogen inputs to carbon sequestration and remobilization in terrestrial environments. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Assessment of nitrogen and phosphate balance and the roles of bacteria and viruses at the water-sediment interface in the Allal El Fassi reservoir (Morocco).

PubMed

Alaoui-Mhamdi, Mohamed; Dhib, Amel; Bouhaddioui, Abderrahim; Ziadi, Boutheina; Turki, Souad; Aleya, Lotfi

2014-09-01

Balances of nitrogen and phosphate were studied in the Allal El Fassi reservoir (Morocco); the results showing that nitrogen input (296 mg m(-2) d(-1)) was 161% higher than output (183 mg m(-2) d(-1)). Phosphate input (35.65 mg m(-2) d(-1)) was 865% higher than output (4.12 mg m(-2) d(-1)), causing a progressive increase in the internal phosphate stock. Sedimentation flux was equally high (53.80 and 18 mg m(-2) d(-1)) for both nitrogen and phosphate input, mainly from the Sebou River and in particulate form which immediately settles upon arrival in the reservoir. The release of nitrogen and phosphate from the sediment (5.40 and 1.15 mg m(-2) d(-1), respectively) depended on physicochemical and biological (bacteria and viruses) variability and the calcareous nature of the catchment basin. Calcium-bound phosphate prevailed in the reservoir. Drastic control of phosphate input is suggested to avoid accumulation of calcium-bound phosphate which may dissociate and thereby contribute to eutrophication.

County-level estimates of nitrogen and phosphorus from animal manure for the conterminous United States, 2007 and 2012

USGS Publications Warehouse

Gronberg, JoAnn M.; Arnold, Terri L.

2017-03-24

County-level estimates of nitrogen and phosphorus inputs from animal manure for the conterminous United States were calculated from animal population inventories in the 2007 and 2012 Census of Agriculture, using previously published methods. These estimates of non-point nitrogen and phosphorus inputs from animal manure were compiled in support of the U.S. Geological Survey’s National Water-Quality Assessment Project of the National Water Quality Program and are needed to support national-scale investigations of stream and groundwater water quality. The estimates published in this report are comparable with older estimates which can be compared to show changes in nitrogen and phosphorus inputs from manure over time.

Controls on Nitrogen Retention and Loss in Urban and Rural Forest Ecosystems.

NASA Astrophysics Data System (ADS)

Templer, P. H.

2011-12-01

Human activities, such as the burning of fossil fuels and production of fertilizer, have increased the amount of nitrogen deposited onto terrestrial ecosystems. In addition to changes in atmospheric deposition of nitrogen, other human-induced disturbances have led to dramatic shifts in forest composition of the United States over the last 100 years. Tree species composition of many forests is changing in response to introduced pests and pathogens, competition with introduced plant species and changes in climate. Understanding the combined effects of increased nitrogen inputs and changes in plant species composition on forest nitrogen cycling is critical to our understanding of forest biogeochemistry and nutrient budgets. Despite several decades of research on the effects of atmospheric nitrogen deposition, there is still significant uncertainty about the factors that regulate nitrogen retention and loss in forest ecosystems. The use of natural abundance stable isotopes of nitrogen and oxygen has proven to be a powerful tool for tracing the sources of nitrate in water, from inputs to leaching, as it moves through an ecosystem. The evaluation of natural abundance nitrogen values in atmospheric deposition has been used to partition sources of nitrogen, such as coal-fired power plants vs. tailpipe exhaust, since each of their isotopic signatures is distinct. Similarly, natural abundance oxygen values of nitrate in atmospheric inputs and soil leachate have been used as a tool to partition sources of nitrate between precipitation and nitrate produced microbially during nitrification. We measured the natural abundance isotopic composition of nitrate to quantify rates of nitrogen inputs to the forest and to determine rates of nitrogen losses from healthy, declining and preemptively cut eastern hemlock (Tsuga canadensis) stands in both an urban forest at the Arnold Arboretum in Boston, MA, and a rural forest at Harvard Forest in Petersham, MA. The hemlock woolly adelgid (Adelges tsugae Annand), an introduced aphid-like insect from Japan, threatens hemlock stands throughout the eastern United States. The hemlock woolly adelgid was first reported in forests of the eastern United States in the early 1950s and is currently leading to mortality of eastern hemlock trees from Georgia to Massachusetts. We found that rates of nitrogen inputs to the forest floor were 4-5 times greater, and rates of nitrogen losses via leachate were more than ten times greater, at the Arnold Arboretum compared to Harvard Forest. Our results also show that current management regimes used to control the hemlock woolly adelgid, such as salvage cutting, may be reducing nitrogen losses in urban areas due to rapid regrowth of vegetation and the associated uptake of nitrogen by those plants. In contrast, cutting of trees in rural areas may be leading to proportionately greater losses of nitrogen in those sites, though the total magnitude of nitrogen lost is still smaller than in urban sites. Results of this study suggest that the combination of the hemlock woolly adelgid, atmospheric nitrogen inputs and management practices lead to changes in the nitrogen cycle within eastern hemlock forest ecosystems.

Analysis of nitrogen saturation potential in Rocky Mountain tundra and forest: implications for aquatic systems

USGS Publications Warehouse

Baron, Jill S.; Ojima, Dennis S.; Holland, Elisabeth A.; Parton, William J.

1994-01-01

We employed grass and forest versions of the CENTURY model under a range of N deposition values (0.02–1.60 g N m−2 y−1) to explore the possibility that high observed lake and stream N was due to terrestrial N saturation of alpine tundra and subalpine forest in Loch Vale Watershed, Rocky Mountain National Park, Colorado. Model results suggest that N is limiting to subalpine forest productivity, but that excess leachate from alpine tundra is sufficient to account for the current observed stream N. Tundra leachate, combined with N leached from exposed rock surfaces, produce high N loads in aquatic ecosystems above treeline in the Colorado Front Range. A combination of terrestrial leaching, large N inputs from snowmelt, high watershed gradients, rapid hydrologic flushing and lake turnover times, and possibly other nutrient limitations of aquatic organisms constrain high elevation lakes and streams from assimilating even small increases in atmospheric N. CENTURY model simulations further suggest that, while increased N deposition will worsen the situation, nitrogen saturation is an ongoing phenomenon.

Using Bayesian Belief Networks to Explore the Effects of Nitrogen Inputs on Wetland Ecosystem Services

EPA Science Inventory

Increased reactive nitrogen (Nr) inputs to freshwater wetlands resulting from infrastructure development due to population growth along with intensive agricultural practices associated with food production can threaten regulating (i.e. climate change, water purification, and wast...

Design of long-term sludge-loading rates for forests under uncertainty

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

Crohn, D.M.

1995-09-01

A simple time series describing nitrate-nitrogen concentrations percolating form a sludge-amended forest is presented for the case where applications are made at several-year intervals. The time series converges to a quasi-steady-state solution that can be solved for an application rate limited by percolating nitrate-nitrogen concentrations. Excess nitrogen is commonly converted to nitrate, a form that leaches readily to pollute ground water. A chance constraint incorporates uncertainty associated with precipitation and evapotranspiration, the most important factors in determining the excess of water available for leaching. Design loading rates for eight New York state forest regions are discussed. If applications occur atmore » 3-year intervals, rates range form 0.2 to 5.3 Mg/ha dry weight depending on the design confidence level, local excess water patterns, forest nitrogen uptake, sludge type, and atmospheric nitrogen deposition rates. Results are compared to predictions made with FORSENTO, a comprehensive model for simulating sludge applications to northern hardwood forests. FORSENTO simulations suggest that mature hardwoods need only 12 kg/ha to support annually perennial material growth and that atmospheric nitrogen deposition may eventually meet or exceed needs of trees so that landspreading may not be sustainable indefinitely in some areas.« less

Bioremediation using Gracilaria lemaneiformis to manage the nitrogen and phosphorous balance in an integrated multi-trophic aquaculture system in Yantian Bay, China.

PubMed

Wei, Zhangliang; You, Jiaguo; Wu, Hailong; Yang, Fangfang; Long, Lijuan; Liu, Qiao; Huo, Yuanzi; He, Peimin

2017-08-15

To reduce negative environmental impacts from human aquaculture activities, the red alga Gracilaria lemaneiformis was co-cultured with the fish Pseudosciaena crocea in an integrated multi-trophic aquaculture (IMTA) system for 35d in Yantian Bay. The eutrophication index value decreased from 14.5 to 8.4 after seaweeds were co-cultured in cage farming areas, which indicated that the eutrophic water column in Yantian Bay could be mediated by IMTA. Total DIN and DIP of the tidal input and output were 9.23kg, 0.19kg and 11.08kg, and 0.27kg, respectively. Total 5.24kg of dissolved N and 0.81kg of dissolved P were released from IMTA system. These results indicate that G. lemaneiformis co-cultured in IMTA system could not completely remove all excess nutrients. In theory, at least 324.48kg of seaweed seedlings would be required to balance excess nutrients generated from fish cages. Copyright © 2017. Published by Elsevier Ltd.

Robust regulation of hepatic pericentral amination by glutamate dehydrogenase kinetics.

PubMed

Bera, Soumen; Lamba, Sanjay; Rashid, Mubasher; Sharma, Anuj K; Medvinsky, Alexander B; Acquisti, Claudia; Chakraborty, Amit; Li, Bai-Lian

2016-11-07

Impaired glutamate dehydrogenase (GDH) sensitivity to its inhibitors causes excessive insulin secretion by pancreatic beta-cells and defective ammonia metabolism in the liver. These symptoms are commonly associated with hyperinsulinism/hyperammonemia syndrome (HI/HA), which causes recurrent hypoglycaemia in early infancy. Hepatic localization of GDH amination and deamination activities linked with the urea cycle is known to be involved in ammonia metabolism and detoxification. Although deamination activities of hepatic GDH in the periportal zones of liver lobules and its connection to the urea cycle have been exhaustively investigated, physiological roles of GDH amination activity observed at pericentral zones have often been overlooked. Using kinetic modelling approaches, here we report a new role for hepatic GDH amination kinetics in maintaining ammonia homeostasis under an excess intrahepatocyte input of ammonium. We have shown that α-ketoglutarate substrate inhibition kinetics of GDH, which include both random and obligatory ordered association/dissociation reactions, robustly control the ratio between glutamate and ammonium under a wide range of intracellular substrate variation. Dysregulation of this activity under pericentral nitrogen insufficiency contributes to the breaking down of ammonia homeostasis and thereby can significantly affect HI/HA syndrome.

Reducing fertilizer-nitrogen losses from rowcrop landscapes: Insights and implications from a spatially explicit watershed model

USGS Publications Warehouse

McLellan, Eileen; Schilling, Keith; Robertson, Dale M.

2015-01-01

We present conceptual and quantitative models that predict changes in fertilizer-derived nitrogen delivery from rowcrop landscapes caused by agricultural conservation efforts implemented to reduce nutrient inputs and transport and increase nutrient retention in the landscape. To evaluate the relative importance of changes in the sources, transport, and sinks of fertilizer-derived nitrogen across a region, we use the spatially explicit SPAtially Referenced Regression On Watershed attributes watershed model to map the distribution, at the small watershed scale within the Upper Mississippi-Ohio River Basin (UMORB), of: (1) fertilizer inputs; (2) nutrient attenuation during delivery of those inputs to the UMORB outlet; and (3) nitrogen export from the UMORB outlet. Comparing these spatial distributions suggests that the amount of fertilizer input and degree of nutrient attenuation are both important in determining the extent of nitrogen export. From a management perspective, this means that agricultural conservation efforts to reduce nitrogen export would benefit by: (1) expanding their focus to include activities that restore and enhance nutrient processing in these highly altered landscapes; and (2) targeting specific types of best management practices to watersheds where they will be most valuable. Doing so successfully may result in a shift in current approaches to conservation planning, outreach, and funding.

Nitrogen isotopes as indicators of NOx source contributions to atmospheric nitrate deposition across the midwestern and northeastern United States

USGS Publications Warehouse

Elliott, E.M.; Kendall, C.; Wankel, Scott D.; Burns, Douglas A.; Boyer, E.W.; Harlin, K.; Bain, D.J.; Butler, T.J.

2007-01-01

Global inputs of NOx are dominated by fossil fuel combustion from both stationary and vehicular sources and far exceed natural NOx sources. However, elucidating NOx sources to any given location remains a difficult challenge, despite the need for this information to develop sound regulatory and mitigation strategies. We present results from a regional-scale study of nitrogen isotopes (??15N) in wet nitrate deposition across 33 sites in the midwestern and northeastern U.S. We demonstrate that spatial variations in ??15N are strongly correlated with NOx emissions from surrounding stationary sources and additionally that ??15N is more strongly correlated with surrounding stationary source NOx emissions than pH, SO 42-, or NO3- concentrations. Although emission inventories indicate that vehicle emissions are the dominant NOx source in the eastern U.S., our results suggest that wet NO 3- deposition at sites in this study is strongly associated with NOx emissions from stationary sources. This suggests that large areas of the landscape potentially receive atmospheric NOy deposition inputs in excess of what one would infer from existing monitoring data alone. Moreover, we determined that spatial patterns in ??15N values are a robust indicator of stationary NOx contributions to wet NO3- deposition and hence a valuable complement to existing tools for assessing relationships between NO 3- deposition, regional emission inventories, and for evaluating progress toward NOx reduction goals. ?? 2007 American Chemical Society.

Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer

USGS Publications Warehouse

Heffernan, J.B.; Albertin, A.R.; Fork, M.L.; Katz, B.G.; Cohen, M.J.

2011-01-01

Aquifer denitrification is among the most poorly constrained fluxes in global and regional nitrogen budgets. The few direct measurements of denitrification in groundwaters provide limited information about its spatial and temporal variability, particularly at the scale of whole aquifers. Uncertainty in estimates of denitrification may also lead to underestimates of its effect on isotopic signatures of inorganic N, and thereby confound the inference of N source from these data. In this study, our objectives are to quantify the magnitude and variability of denitrification in the Upper Floridan Aquifer (UFA) and evaluate its effect on N isotopic signatures at the regional scale. Using dual noble gas tracers (Ne, Ar) to generate physical predictions of N2 gas concentrations for 112 observations from 61 UFA springs, we show that excess (i.e. denitrification-derived) N2 is highly variable in space and inversely correlated with dissolved oxygen (O2). Negative relationship between O2 and ??15NNO 3 across a larger dataset of 113 springs, well-constrained isotopic fractionation coefficients, and strong 15N: 18O covariation further support inferences of denitrification in this uniquely organic-matter-poor system. Despite relatively low average rates, denitrification accounted for 32% of estimated aquifer N inputs across all sampled UFA springs. Back-calculations of source ??15NNO 3 based on denitrification progression suggest that isotopically-enriched nitrate (NO3-) in many springs of the UFA reflects groundwater denitrification rather than urban- or animal-derived inputs. ?? Author(s) 2011.

Atmospheric nitrogen deposition influences denitrification and nitrous oxide production in lakes.

PubMed

McCrackin, Michelle L; Elser, James J

2010-02-01

Microbially mediated denitrification is an important process that may ameliorate the effects of nitrogen (N) loading by permanently removing excess N inputs. In this study, we measured the rate of denitrification and nitrous oxide (N2O) production during denitrification in sediments from 32 Norwegian lakes at the high and low ends of a gradient of atmospheric N deposition. Denitrification and N2O production rates averaged 41.7 and 1.1 micromol N x m(-2) x h(-1), respectively, for high-deposition lakes. There was no detectable denitrification or N2O production in low-deposition lakes. Epilimnetic nitrate concentration was strongly correlated with denitrification rate (r2 = 0.67). We also measured the denitrification rate in response to experimental additions of organic carbon, nitrate, and phosphorus. Experimental nitrate additions stimulated denitrification in sediments of all lakes, regardless of N deposition level. In fact, the rate of denitrification in nitrate-amended treatments was the same magnitude for lakes in both deposition areas. These findings suggest that lake sediments possess considerable capacity to remove nitrate and that this capacity has not been saturated under conditions of chronic N loading. Further, nitrous oxide was nearly 3% of the total gaseous product during denitrification in high-deposition lakes, a fraction that is comparable to polluted marine sediments. Our findings suggest that, while lakes play an important role in N removal in the landscape, they may be a source of N2O emissions, especially in areas subject to elevated N inputs.

Changes in nitrogen budget and potential risk to the environment over 20years (1990-2010) in the agroecosystems of the Haihe Basin, China.

PubMed

Zheng, Mengmeng; Zheng, Hua; Wu, Yingxia; Xiao, Yi; Du, Yihua; Xu, Weihua; Lu, Fei; Wang, Xiaoke; Ouyang, Zhiyun

2015-02-01

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output, surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from 1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields. Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by 16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010, partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk, decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields. Copyright © 2014. Published by Elsevier B.V.

Denitrification Rates in a Lake Superior Coastal Wetland

EPA Science Inventory

Inputs of anthropogenic nitrogen to the Nation’s aquatic ecosystems have increased substantially over the past several decades. Nitrogen inputs to Lake Superior since about 1900 have increased at a rate of about 2% per year, doubling about every 35 years (Bennett, 1986), althoug...

Spatial and Temporal Variations of Crop Fertilization and Soil Fertility in the Loess Plateau in China from the 1970s to the 2000s

PubMed Central

Wang, Xiaoying; Tong, Yanan; Gao, Yimin; Gao, Pengcheng; Liu, Fen; Zhao, Zuoping; Pang, Yan

2014-01-01

Increased fertilizer input in agricultural systems during the last few decades has resulted in large yield increases, but also in environmental problems. We used data from published papers and a soil testing and fertilization project in Shaanxi province during the years 2005 to 2009 to analyze chemical fertilizer inputs and yields of wheat (Triticum aestivum L.) and maize (Zea mays L.) on the farmers' level, and soil fertility change from the 1970s to the 2000s in the Loess Plateau in China. The results showed that in different regions of the province, chemical fertilizer NPK inputs and yields of wheat and maize increased. With regard to soil nutrient balance, N and P gradually changed from deficit to surplus levels, while K deficiency became more severe. In addition, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium increased during the same period. The PFP of N, NP and NPK on wheat and maize all decreased from the 1970s to the 2000s as a whole. With the increase in N fertilizer inputs, both soil total nitrogen and alkali-hydrolysis nitrogen increased; P fertilizer increased soil available phosphorus and K fertilizer increased soil available potassium. At the same time, soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium all had positive impacts on crop yields. In order to promote food safety and environmental protection, fertilizer requirements should be assessed at the farmers' level. In many cases, farmers should be encouraged to reduce nitrogen and phosphate fertilizer inputs significantly, but increase potassium fertilizer and organic manure on cereal crops as a whole. PMID:25380401

Increasing importance of deposition of reduced nitrogen in the United States

Treesearch

Yi Li; Bret A. Schichtel; John T. Walker; Donna B. Schwede; Xi Chen; Christopher M. B. Lehmann; Melissa A. Puchalski; David A. Gay; Jeffrey L. Collett

2016-01-01

Rapid development of agriculture and fossil fuel combustion greatly increased US reactive nitrogen emissions to the atmosphere in the second half of the 20th century, resulting in excess nitrogen deposition to natural ecosystems. Recent efforts to lower nitrogen oxides emissions have substantially decreased nitrate wet deposition. Levels of wet ammonium...

Nitrogen Bsalance for a Plantation Forest Drainage Canal on the North Carolina Coastal Plain

USDA-ARS?s Scientific Manuscript database

Human alteration of the nitrogen cycle has led to increased riverine nitrogen loads, contributing to the eutrophication of lakes, streams, estuaries, and near-coastal oceans. These riverine nitrogen loads are usually less than the total nitrogen inputs to the system, indicating nitrogen removal duri...

Estimated nitrogen and phosphorus inputs to the Fish Creek watershed, Teton County, Wyoming, 2009–15

USGS Publications Warehouse

Eddy-Miller, Cheryl A.; Sando, Roy; MacDonald, Michael J.; Girard, Carlin E.

2016-12-15

Nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of bioavailable nitrogen and phosphorus in water can cause adverse health and ecological effects. It is generally accepted that increased primary production of surface-water bodies because of high inputs of nutrients is now the most important polluting effect in surface water in the developed world.

Genomic regions associated with the nitrogen limitation response revealed in a global wheat core collection.

PubMed

Bordes, Jacques; Ravel, C; Jaubertie, J P; Duperrier, B; Gardet, O; Heumez, E; Pissavy, A L; Charmet, G; Le Gouis, J; Balfourier, F

2013-03-01

Modern wheat (Triticum aestivum L.) varieties in Western Europe have mainly been bred, and selected in conditions where high levels of nitrogen-rich fertilizer are applied. However, high input crop management has greatly increased the risk of nitrates leaching into groundwater with negative impacts on the environment. To investigate wheat nitrogen tolerance characteristics that could be adapted to low input crop management, we supplied 196 accessions of a wheat core collection of old and modern cultivars with high or moderate amounts of nitrogen fertilizer in an experimental network consisting of three sites and 2 years. The main breeding traits were assessed including grain yield and grain protein content. The response to nitrogen level was estimated for grain yield and grain number per m(2) using both the difference and the ratio between performance at the two input levels and the slope of joint regression. A large variability was observed for all the traits studied and the response to nitrogen level. Whole genome association mapping was carried out using 899 molecular markers taking into account the five ancestral group structure of the collection. We identified 54 main regions involving almost all chromosomes that influence yield and its components, plant height, heading date and grain protein concentration. Twenty-three regions, including several genes, spread over 16 chromosomes were involved in the response to nitrogen level. These chromosomal regions may be good candidates to be used in breeding programs to improve the performance of wheat varieties at moderate nitrogen input levels.

A Review and Evaluation of the Phase Equilibria, Liquid-Phase Heats of Mixing and Excess Volumes, and Gas-Phase PVT Measurements for Nitrogen+Methane

NASA Astrophysics Data System (ADS)

Kidnay, A. J.; Miller, R. C.; Sloan, E. D.; Hiza, M. J.

1985-07-01

The available experimental data for vapor-liquid equilibria, heat of mixing, change in volume on mixing for liquid mixtures, and gas-phase PVT measurements for nitrogen+methane have been reviewed and where possible evaluated for consistency. The derived properties chosen for analysis and correlation were liquid mixture excess Gibbs free energies, and Henry's constants.

Water fluxes and diffuse nitrate pollution at river basin scale: coupling of agro-economic models and hydrological approaches.

PubMed

Wendland, F; Kunkel, R; Bogena, H; Gömann, H; Kreins, P

2007-01-01

An integrated model system has been developed to estimate the impact of nitrogen reduction measures on the nitrogen load in groundwater and in river catchment areas. The focus lies on an area-wide, regionally differentiated, consistent link-up between the indicator "nitrogen balance surplus" and nitrogen charges into surface waters. As a starting point of the analysis actual nitrogen surpluses in the soil were quantified using the agro-economic RAUMIS-model, which considers the most important N-inputs to the soil and N-removals from the soil through crop harvest. The most important pathways for diffuse nitrogen inputs into river systems are modelled with the water balance model GROWA. Additionally, the time-dependent nitrogen degradation along the nitrogen pathways in soil and groundwater are modelled using the WEKU-model. The two selected river basins in Germany cover a variety of landscape units with different hydrological, hydrogeological and socio-economic characteristics. The results indicate a wide range of annual nitrogen surpluses for the rural areas between than 10 kg N ha(-1) x a(-1) and 200 kg N ha(-1) x a(-1) or more, depending on the type and intensity of farming. The level of nitrogen inputs into the surface waters is reduced because of degradation processes during transport in soil and groundwater. Policy impact analyses for a nitrogen tax and a limitation of the livestock density stress the importance of regionally adjusted measures.

Trends in nitrogen isotope ratios of juvenile winter flounder reflect changing nitrogen inputs to Rhode Island, USA estuarine systems.

PubMed

Pruell, Richard J; Taplin, Bryan K; Miller, Kenneth M

2017-05-15

Nitrogen isotope ratios (δ 15 N) in juvenile winter flounder, Pseudopleuronectes americanus, were used to examine changes in nitrogen inputs to several Rhode Island, USA estuarine systems. Fish were collected over two three-year periods with a ten-year interval between sampling periods (2002-2004 and 2012-2014). During that interval numerous changes to nutrient management practices were initiated in the watersheds of these estuarine systems including the upgrade of several major wastewater treatment facilities that discharge to Narragansett Bay, which significantly reduced nitrogen inputs. Following these reductions, the δ 15 N values of flounder in several of the systems decreased as expected; however, isotope ratios in fish from upper Narragansett Bay significantly increased. We believe that low δ 15 N values measured in 2002-2004 were related to concentration-dependent fractionation at this location. Increased δ 15 N values measured between 2012 and 2014 may indicate reduced fractionation or that changes in wastewater treatment processes altered the nitrogen isotopic ratios of the effluents. Published by Elsevier Ltd.

Human Powered Centrifuge

NASA Technical Reports Server (NTRS)

Mulenburg, Gerald M. (Inventor); Vernikos, Joan (Inventor)

1997-01-01

A human powered centrifuge has independently established turntable angular velocity and human power input. A control system allows excess input power to be stored as electric energy in a battery or dissipated as heat through a resistors. In a mechanical embodiment, the excess power is dissipated in a friction brake.

COUPLING BETWEEN THE COASTAL OCEAN AND YAQUINA BAY, OREGON: THE IMPORTANCE OF OCEANIC INPUTS RELATIVE TO OTHER NITROGEN SOURCES

EPA Science Inventory

Understanding of the role of oceanic input in nutrient loadings is important for understanding nutrient and phytoplankton dynamics in estuaries adjacent to coastal upwelling regions as well as determining the natural background conditions. We examined the nitrogen sources to Yaqu...

Performance of low-input turfgrass species as affected by mowing and nitrogen fertilization in Minnesota

USDA-ARS?s Scientific Manuscript database

In Minnesota, most lawns and higher cut turfgrass areas consist primarily of species such as Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) that require significant management inputs such as frequent mowing and nitrogen fertility. Several studies have shown that oth...

INPUT-OUTPUT BUDGETS OF INORGANIC NITROGEN FOR 24 FOREST WATERSHEDS IN THE NORTHEASTERN UNITED STATES: A REVIEW

EPA Science Inventory

Input-output budgets for dissolved inorganic nitrogen (DIN) are summarized for 24 small watersheds at 15 locations in the northeasternUnited States. The study watersheds are completely forested, free of recent physical disturbances, and span a geographical region bounded by West ...

Spatial Variability of Nitrogen Isotope Ratios of Particulate Material from Northwest Atlantic Continental Shelf Waters

EPA Science Inventory

Human encroachment on the coastal zone has led to a rise in the delivery of nitrogen (N) to estuarine and near-shore waters. Potential routes of anthropogenic N inputs include export from estuaries, atmospheric deposition, and dissolved N inputs from groundwater outflow. Stable...

International food trade reduces environmental effects of nitrogen pollution in China.

PubMed

Shi, Yaxing; Wu, Shaohua; Zhou, Shenglu; Wang, Chunhui; Chen, Hao

2016-09-01

The globalization of agricultural trade has dramatically altered global nitrogen flows by changing the spatial pattern of nitrogen utilization and emissions at a global scale. As a major trading country, China uses a large amount of nitrogen, which has a profound impact on global nitrogen flows. Using data on food production and trade between China and 26 other countries and regions, we calculated nitrogen inputs and outputs in food production ecosystem in each country. We estimated nitrogen flows in international food trade and analyzed their impact on nitrogen pollution in China. We divided nitrogen flows into embodied and virtual nitrogen flows. Embodied nitrogen is taken up by the plant and incorporated into the final food product, whereas virtual nitrogen is lost to the environment throughout the food production process and is not contained in the final food product. Our results show that China mainly imports food products from America and Asia, accounting for 95 % of all imported food. Asia (mainly Japan) and Europe are the main exporters of food from China, with Japan and the EU accounting for 17 and 10 % of all exported food, respectively. Total nitrogen inputs and outputs in food production in China were 55,400 and 61,000 Gg respectively, which were much higher than in other countries. About 1440 and 950 Gg of embodied and virtual nitrogen respectively flow into China through the food trade, mainly from food-exporting countries such as the USA, Argentina, and Brazil. Meanwhile, 177 and 160 Gg of embodied and virtual nitrogen respectively flow out of China from the export of food products, mainly to Japan. China's net food imports have reduced 720 and 458 Gg for nitrogen utilization and outputs, respectively, which accounted for 1.3 and 0.78 % of total nitrogen inputs and outputs in China. These results suggest that food trade in China has a profound effect on nitrogen flows and has greatly reduced environmental impacts on nitrogen pollution in China.

A comparison of drainage basin nutrient inputs with instream nutrient loads for seven rivers in Georgia and Florida, 1986-90

USGS Publications Warehouse

Asbury, C.E.; Oaksford, E.T.

1997-01-01

Instream nutrient loads of the Altamaha, Suwannee, St. Johns, Satilla, Ogeechee, Withlacoochee, and Ochlockonee River Basins were computed and compared with nutrient inputs for each basin for the period 1986-90. Nutrient constituents that were considered included nitrate, ammonia, organic nitrogen, and total phosphorus. Sources of nutrients considered for this analysis included atmospheric deposition, fertilizer, animal waste, wastewater-treatment plant discharge, and septic discharge. The mean nitrogen input ranged from 2,400 kilograms per year per square kilometer (kg/yr)km2 in the Withlacoochee River Basin to 5,470 (kg/yr)km2 in the Altamaha River Basin. The Satilla and Ochlockonee River Basins also had large amounts of nitrogen input per unit area, totaling 5,430 and 4,920 (kg/yr)km2, respectively.Fertilizer or animal waste, as sources of nitrogen, predominated in all basins. Atmospheric deposition contributed less than one-fourth of the mean total nitrogen input to all basins and was consistently the third largest input in all but the Ogeechee River Basin, where it was the second largest.The mean total phosphorus input ranged from 331 (kg/yr)km2 in the Withlacoochee River Basin to 1,380 (kg/yr)km2 in both the Altamaha and Satilla River Basins. The Ochlockonee River Basin had a phosphorus input of 1,140 (kg/yr)km2.Per unit area, the Suwannee River discharged the highest instream mean total nitrogen and phosphorus loads and also discharged higher instream nitrate loads per unit area than the other six rivers. Phosphorus loads in stream discharge were highest in the Suwannee and Ochlockonee Rivers.The ratio of nutrient outputs to inputs for the seven studied rivers ranged from 4.2 to 14.9 percent, with the St. Johns (14.9 percent) and Suwannee (12.1 percent) Rivers having significantly higher percentages than those from the other basins. The output/input percentages for mean total phosphorus ranged from 1.0 to 7.0 percent, with the St. Johns (6.2 percent) and Suwannee (7.0 percent) Rivers exporting the highest percentage of phosphorus.Although instream nutrient loads constitute only one of the various pathways nutrients may take in leaving a river basin, only a relatively small part of nutrient input to the basin leaves the basin in stream discharge for the major coastal rivers examined in this study. The actual amount of nutrient transported in a river basin depends on the ways in which nutrients are physically handled, geographically distributed, and chemically assimilated within a river basin.

Economic Analysis of Nitrate Source Reductions in California Agriculture

NASA Astrophysics Data System (ADS)

Medellin-Azuara, J.; Howitt, R.; Rosenstock, T.; Harter, T.; Pettygrove, S. G.; Dzurella, K.; Lund, J. R.

2011-12-01

We present an analytical approach to assess the economic impact of improving nitrogen management practices in California agriculture. We employ positive mathematical programming to calibrate crop production to base input information. The production function representation is a nested constant elasticity of substitution with two nests: one for applied water and one for applied nitrogen. The first nest accounts for the tradeoffs between irrigation efficiency and capital investments in irrigation technology. The second nest represents the tradeoffs between nitrogen application efficiency and the marginal costs of improving nitrogen efficiency. In the production function nest, low elasticities of substitution and water and nitrogen stress constraints keep agricultural crop yields constant despite changes in nitrogen management practices. We use the Tulare Basin, and the Salinas Valley in California's Central Valley and Central Coast respectively as our case studies. Preliminary results show that initial reductions of 25% in nitrogen loads to groundwater may not impose large costs to agricultural crop production as substitution of management inputs results in only small declines in net revenue from farming and total land use. Larger reductions in the nitrogen load to groundwater of 50% imposes larger marginal costs for better nitrogen management inputs and reductions in the area of lower valued crops grown in the study areas. Despite the shortage of data on quantitative effects of improved nitrogen efficiency; our results demonstrate the potential of combining economic and agronomic data into a model that can reflect differences in cost and substitutabilty in nitrogen application methods, that can be used to reduce the quantity of nitrogen leaching into groundwater.

System and method for controlling ammonia levels in a selective catalytic reduction catalyst using a nitrogen oxide sensor

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

None

A system according to the principles of the present disclosure includes an air/fuel ratio determination module and an emission level determination module. The air/fuel ratio determination module determines an air/fuel ratio based on input from an air/fuel ratio sensor positioned downstream from a three-way catalyst that is positioned upstream from a selective catalytic reduction (SCR) catalyst. The emission level determination module selects one of a predetermined value and an input based on the air/fuel ratio. The input is received from a nitrogen oxide sensor positioned downstream from the three-way catalyst. The emission level determination module determines an ammonia level basedmore » on the one of the predetermined value and the input received from the nitrogen oxide sensor.« less

Undercover isotopes: tracking the fate of nitrogen in streams

Treesearch

Rhonda Mazza; Sherri Johnson

2009-01-01

Excess nitrogen stemming from human activities is a common water pollutant. Fertilizer runoff, sewage, and fossil fuel emission all contain nitrogen that often ends in streams, rivers, and ultimately the ocean. Research has found that more nitrogen enters a river system than can be accounted for at its mouth, indicating that instream processing is occurring. A team of...

40 CFR 60.55a - Standard for nitrogen oxides.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 7 2013-07-01 2013-07-01 false Standard for nitrogen oxides. 60.55a... § 60.55a Standard for nitrogen oxides. On and after the date on which the initial compliance test is... gases that contain nitrogen oxides in excess of 180 parts per million by volume, corrected to 7 percent...

40 CFR 60.55a - Standard for nitrogen oxides.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Standard for nitrogen oxides. 60.55a... § 60.55a Standard for nitrogen oxides. On and after the date on which the initial compliance test is... gases that contain nitrogen oxides in excess of 180 parts per million by volume, corrected to 7 percent...

40 CFR 60.55a - Standard for nitrogen oxides.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 7 2012-07-01 2012-07-01 false Standard for nitrogen oxides. 60.55a... § 60.55a Standard for nitrogen oxides. On and after the date on which the initial compliance test is... gases that contain nitrogen oxides in excess of 180 parts per million by volume, corrected to 7 percent...

40 CFR 60.55a - Standard for nitrogen oxides.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 7 2014-07-01 2014-07-01 false Standard for nitrogen oxides. 60.55a... § 60.55a Standard for nitrogen oxides. On and after the date on which the initial compliance test is... gases that contain nitrogen oxides in excess of 180 parts per million by volume, corrected to 7 percent...

Regional nitrogen budgets and riverine N & P fluxes for the drainages to the North Atlantic Ocean: Natural and human influences

USGS Publications Warehouse

Howarth, R.W.; Billen, G.; Swaney, D.; Townsend, A.; Jaworski, N.; Lajtha, K.; Downing, J.A.; Elmgren, Ragnar; Caraco, N.; Jordan, T.; Berendse, F.; Freney, J.; Kudeyarov, V.; Murdoch, P.; Zhu, Z.-L.

1996-01-01

We present estimates of total nitrogen and total phosphorus fluxes in rivers to the North Atlantic Ocean from 14 regions in North America, South America, Europe, and Africa which collectively comprise the drainage basins to the North Atlantic. The Amazon basin dominates the overall phosphorus flux and has the highest phosphorus flux per area. The total nitrogen flux from the Amazon is also large, contributing 3.3 Tg yr-1 out of a total for the entire North Atlantic region of 13.1 Tg yr-1. On a per area basis, however, the largest nitrogen fluxes are found in the highly disturbed watersheds around the North Sea, in northwestern Europe, and in the northeastern U.S., all of which have riverine nitrogen fluxes greater than 1,000 kg N km-2 yr-1. Non-point sources of nitrogen dominate riverine fluxes to the coast in all regions. River fluxes of total nitrogen from the temperate regions of the North Atlantic basin are correlated with population density, as has been observed previously for fluxes of nitrate in the world's major rivers. However, more striking is a strong linear correlation between river fluxes of total nitrogen and the sum of anthropogenically-derived nitrogen inputs to the temperate regions (fertilizer application, human-induced increases in atmospheric deposition of oxidized forms of nitrogen, fixation by leguminous crops, and the import/export of nitrogen in agricultural products). On average, regional nitrogen fluxes in rivers are only 25% of these anthropogenically derived nitrogen inputs. Denitrification in wetlands and aquatic ecosystems is probably the dominant sink, with storage in forests perhaps also of importance. Storage of nitrogen in groundwater, although of importance in some localities, is a very small sink for nitrogen inputs in all regions. Agricultural sources of nitrogen dominate inputs in many regions, particularly the Mississippi basin and the North Sea drainages. Deposition of oxidized nitrogen, primarily of industrial origin, is the major control over river nitrogen export in some regions such as the northeastern U.S. Using data from relatively pristine areas as an index of change, we estimate that riverine nitrogen fluxes in many of the temperate regions have increased from pre-industrial times by 2 to 20 fold, although some regions such as northern Canada are relatively unchanged. Fluxes from the most disturbed region, the North Sea drainages, have increased by 6 to 20 fold. Fluxes from the Amazon basin are also at least 2 to 5 fold greater than estimated fluxes from undisturbed temperate-zone regions, despite low population density and low inputs of anthropogenic nitrogen to the region. This suggests that natural riverine nitrogen fluxes in the tropics may be significantly greater than in the temperate zone. However, deforestation may be contributing to the tropical fluxes. In either case, projected increases in fertilizer use and atmospheric deposition in the coming decades are likely to cause dramatic increases in nitrogen loading to many tropical river systems. ?? 1996 Kluwer Academic Publishers.

DENITRIFICATION AND NITROGEN DYNAMICS IN SEDIMENTS OF A MID-ATLANTIC INCISED STREAM DEPOSITED WITH DEEP LEGACY SEDIMENTS.

EPA Science Inventory

Excess legacy sediments deposited in former impounded streams frequently bury Holocene pre-settlement wetlands, decrease in-situ nitrogen removal, and increase nitrogen transport downstream, particularly where deep incised channels limit sediment-water interactions. This has prom...

Geohydrology and limnology of Walden Pond, Concord, Massachusetts

USGS Publications Warehouse

Colman, John A.; Friesz, Paul J.

2001-01-01

The trophic ecology and ground-water contributing area of Walden Pond, in Concord and Lincoln, Mass., were investigated by the U.S. Geological Survey in cooperation with the Massachusetts Department of Environmental Management from April 1997 to July 2000. Bathymetric investigation indicated that Walden Pond (24.88 hectares), a glacial kettle-hole lake with no surface inlet or outlet, has three deep areas. The maximum depth (30.5 meters) essentially was unchanged from measurements made by Henry David Thoreau in 1846. The groundwater contributing area (621,000 square meters) to Walden Pond was determined from water-table contours in areas of stratified glacial deposits and from land-surface contours in areas of bedrock highs. Walden Pond is a flow-through lake: Walden Pond gains water from the aquifer along its eastern perimeter and loses water to the aquifer along its western perimeter. Walden Pond contributing area also includes Goose Pond and its contributing area. A water budget calculated for Walden Pond, expressed as depth of water over the lake surface, indicated that 45 percent of the inflow to the lake was from precipitation (1.215 meters per year) and 55 percent from ground water (1.47 meters per year). The groundwater inflow estimate was based on the average of two different approaches including an isotope mass-balance approach. Evaporation accounted for 26 percent of the outflow from the lake (0.71 meters per year) whereas lake-water seepage to the groundwater system contributed 74 percent of the outflow (1.97 meters per year). The water-residence time of Walden Pond is approximately 5 years. Potential point sources of nutrients to ground water, the Concord municipal landfill and a trailer park, were determined to be outside the Walden Pond groundwater contributing area. A third source, the septic leach field for the Walden Pond State Reservation facilities, was within the groundwater contributing area. Nutrient budgets for the lake indicated that nitrogen inputs (858 kilograms per year) were dominated (30 percent) by plume water from the septic leach field and, possibly, by swimmers (34 percent). Phosphorus inputs (32 kilograms per year) were dominated by atmospheric dry deposition, background ground water, and estimated swimmer inputs. Swimmer inputs may represent more than 50 percent of the phosphorus load during the summer. The septic-system plume did not contribute phosphorus, but increased the nitrogen to phosphorus ratio for inputs from 41 to 59, on an atom-to-atom basis. The ratio of nitrogen to phosphorus in input loads and within the lake indicated algal growth would be strongly phosphorus limited. Nitrogen supply in excess of plant requirements may mitigate against nitrogen fixing organisms including undesirable blooms of cyanobacteria. Based on areal nutrient loading, Walden Pond is a mesotrophic lake. Hypolimnetic oxygen demand of Walden Pond has increased since a profile was measured in 1939. Currently (1999), the entire hypolimnion of Walden Pond becomes devoid of dissolved oxygen before fall turnover in late November; whereas historical data indicated dissolved oxygen likely remained in the hypolimnion during 1939. The complete depletion of dissolved oxygen likely causes release of phosphorus from the sediments. Walden Pond contains a large population of the deep-growing benthic macro alga Nitella, which has been hypothesized to promote water clarity in other clear-water lakes by sequestering nutrients and keeping large areas of the sediment surface oxygenated. Loss of Nitella populations in other lakes has correlated with a decline in water quality. Although the Nitella standing crop is large in Walden Pond, Nitella still appears to be controlled by nutrient availability. Decreasing phosphorus inputs to Walden Pond, by amounts under anthropogenic control would likely contribute to the stability of the Nitella population in the metalimnion, may reverse oxygen depletion in the hypolimnion, and decreas

40 CFR 76.13 - Compliance and excess emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 16 2011-07-01 2011-07-01 false Compliance and excess emissions. 76.13 Section 76.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.13 Compliance and excess emissions...

40 CFR 76.13 - Compliance and excess emissions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 17 2012-07-01 2012-07-01 false Compliance and excess emissions. 76.13 Section 76.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.13 Compliance and excess emissions...

40 CFR 76.13 - Compliance and excess emissions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Compliance and excess emissions. 76.13 Section 76.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.13 Compliance and excess emissions...

40 CFR 76.13 - Compliance and excess emissions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Compliance and excess emissions. 76.13 Section 76.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.13 Compliance and excess emissions...

40 CFR 76.13 - Compliance and excess emissions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Compliance and excess emissions. 76.13 Section 76.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.13 Compliance and excess emissions...

New, national bottom-up estimate for tree-based biological nitrogen fixation in the US

EPA Science Inventory

Nitrogen is a limiting nutrient in many ecosystems, but is also a chief pollutant from human activity. Quantifying human impacts on the nitrogen cycle and investigating natural ecosystem nitrogen cycling both require an understanding of the magnitude of nitrogen inputs from biolo...

Ecological Engineering Practices for the Reduction of Excess Nitrogen in Human-Influenced Landscapes: A Guide for Watershed Managers

NASA Astrophysics Data System (ADS)

Passeport, Elodie; Vidon, Philippe; Forshay, Kenneth J.; Harris, Lora; Kaushal, Sujay S.; Kellogg, Dorothy Q.; Lazar, Julia; Mayer, Paul; Stander, Emilie K.

2013-02-01

Excess nitrogen (N) in freshwater systems, estuaries, and coastal areas has well-documented deleterious effects on ecosystems. Ecological engineering practices (EEPs) may be effective at decreasing nonpoint source N leaching to surface and groundwater. However, few studies have synthesized current knowledge about the functioning principles, performance, and cost of common EEPs used to mitigate N pollution at the watershed scale. Our review describes seven EEPs known to decrease N to help watershed managers select the most effective techniques from among the following approaches: advanced-treatment septic systems, low-impact development (LID) structures, permeable reactive barriers, treatment wetlands, riparian buffers, artificial lakes and reservoirs, and stream restoration. Our results show a broad range of N-removal effectiveness but suggest that all techniques could be optimized for N removal by promoting and sustaining conditions conducive to biological transformations (e.g., denitrification). Generally, N-removal efficiency is particularly affected by hydraulic residence time, organic carbon availability, and establishment of anaerobic conditions. There remains a critical need for systematic empirical studies documenting N-removal efficiency among EEPs and potential environmental and economic tradeoffs associated with the widespread use of these techniques. Under current trajectories of N inputs, land use, and climate change, ecological engineering alone may be insufficient to manage N in many watersheds, suggesting that N-pollution source prevention remains a critical need. Improved understanding of N-removal effectiveness and modeling efforts will be critical in building decision support tools to help guide the selection and application of best EEPs for N management.

Nitrogen balance in response to dryland crop rotations and cultural practices

USDA-ARS?s Scientific Manuscript database

Nitrogen balance provides a measure of agroecosystem performance and environmental sustainability by taking into accounts of N inputs and outputs and N retention in the soil. The objective of this study was to evaluate N balance based on N inputs and outputs and soil N sequestration after 7 yr in re...

Reactive nitrogen inputs to US lands and waterways: how certain are we about sources and fluxes?

EPA Science Inventory

An overabundance of reactive nitrogen (N) as a result of anthropogenic activities has led to multiple human health and environmental concerns. Efforts to address these concerns require an accurate accounting of N inputs. Here, we present a novel synthesis of data describing N inp...

Modeling the Air-Vegetation-Soil Exchange of Reactive Nitrogen

EPA Science Inventory

Nitrogen is an essential building block of all proteins and thus an essential nutrient for all life. However, in excess reactive nitrogen can lead to poor air or water quality, loss of biodiversity, and impact respiratory and cardiac health. Human activity has perturbed this cycl...

SOIL NITRATE AND AMMONIUM THROUGH 2 YEARS OF SELECTIVE HERBIVORY AND CHRONIC NITROGEN ENRICHMENT

EPA Science Inventory

-The effects of increased amounts and flux of bioavailable nitrogenous compounds in the ecosystem is of great interest to ecological researchers and longstanding concern to land-managers. Excess nitrogen in the environment is associated with many large-scale environmental concer...

Source, movement, and effects of nitrogen and phosphorus in three ponds in the headwaters of Hop Brook, Marlborough, Massachusetts

USGS Publications Warehouse

Briggs, John C.; Silvey, William D.

1984-01-01

The headwaters of Hop Brook near Marlborough, Massachusetts, contain a series of three in-line ponds--Hager Pond, Brist Millpond, and Carding Millpond--which receive over half of their surface-water inflow as effluent from the Marlborough Easterly Wastewater Treatment Plant. These ponds have a history of summer algal blooms and fish kills. Water entering these ponds contains quantities of nitrogen and phosphorus far higher than the levels known to promote excessive growth of aquatic vegetation. As the water moves through the three ponds, nitrogen levels decrease. Although some nitrogen is lost to the atmosphere by denitrification, the bulk of the nitrogen probably is retained in the pond sediments. There is a net decrease in phosphorus in the water leaving Carding Millpond compared to the water entering Hager Pond. However, during most sampling periods, the phosphorus concentration of water leaving Carding Millpond is still above the level known to cause excessive growth of aquatic vegetation in lakes. During certain summer periods, there appears to be release of some phosphorus from the sediments in Carding and Grist Millponds. No improvement in water quality of the three ponds can be expected until the concentrations of nutrients entering Hager Pond are reduced to levels that will not support excessive growth of aquatic vegetation. (USGS)

Water organic pollution and eutrophication influence soil microbial processes, increasing soil respiration of estuarine wetlands: site study in jiuduansha wetland.

PubMed

Zhang, Yue; Wang, Lei; Hu, Yu; Xi, Xuefei; Tang, Yushu; Chen, Jinhai; Fu, Xiaohua; Sun, Ying

2015-01-01

Undisturbed natural wetlands are important carbon sinks due to their low soil respiration. When compared with inland alpine wetlands, estuarine wetlands in densely populated areas are subjected to great pressure associated with environmental pollution. However, the effects of water pollution and eutrophication on soil respiration of estuarine and their mechanism have still not been thoroughly investigated. In this study, two representative zones of a tidal wetland located in the upstream and downstream were investigated to determine the effects of water organic pollution and eutrophication on soil respiration of estuarine wetlands and its mechanism. The results showed that eutrophication, which is a result of there being an excess of nutrients including nitrogen and phosphorus, and organic pollutants in the water near Shang shoal located upstream were higher than in downstream Xia shoal. Due to the absorption and interception function of shoals, there to be more nitrogen, phosphorus and organic matter in Shang shoal soil than in Xia shoal. Abundant nitrogen, phosphorus and organic carbon input to soil of Shang shoal promoted reproduction and growth of some highly heterotrophic metabolic microorganisms such as β-Proteobacteria, γ-Proteobacteria and Acidobacteria which is not conducive to carbon sequestration. These results imply that the performance of pollutant interception and purification function of estuarine wetlands may weaken their carbon sequestration function to some extent.

Water Organic Pollution and Eutrophication Influence Soil Microbial Processes, Increasing Soil Respiration of Estuarine Wetlands: Site Study in Jiuduansha Wetland

PubMed Central

Zhang, Yue; Wang, Lei; Hu, Yu; Xi, Xuefei; Tang, Yushu; Chen, Jinhai; Fu, Xiaohua; Sun, Ying

2015-01-01

Undisturbed natural wetlands are important carbon sinks due to their low soil respiration. When compared with inland alpine wetlands, estuarine wetlands in densely populated areas are subjected to great pressure associated with environmental pollution. However, the effects of water pollution and eutrophication on soil respiration of estuarine and their mechanism have still not been thoroughly investigated. In this study, two representative zones of a tidal wetland located in the upstream and downstream were investigated to determine the effects of water organic pollution and eutrophication on soil respiration of estuarine wetlands and its mechanism. The results showed that eutrophication, which is a result of there being an excess of nutrients including nitrogen and phosphorus, and organic pollutants in the water near Shang shoal located upstream were higher than in downstream Xia shoal. Due to the absorption and interception function of shoals, there to be more nitrogen, phosphorus and organic matter in Shang shoal soil than in Xia shoal. Abundant nitrogen, phosphorus and organic carbon input to soil of Shang shoal promoted reproduction and growth of some highly heterotrophic metabolic microorganisms such as β-Proteobacteria, γ-Proteobacteria and Acidobacteria which is not conducive to carbon sequestration. These results imply that the performance of pollutant interception and purification function of estuarine wetlands may weaken their carbon sequestration function to some extent. PMID:25993326

Nitrogen use efficiency and crop production: Patterns of regional variation in the United States, 1987-2012.

PubMed

Swaney, Dennis P; Howarth, Robert W; Hong, Bongghi

2018-04-17

National-level summaries of crop production and nutrient use efficiency, important for international comparisons, only partially elucidate agricultural dynamics within a country. Agricultural production and associated environmental impacts in large countries vary significantly because of regional differences in crops, climate, resource use and production practices. Here, we review patterns of regional crop production, nitrogen use efficiency (NUE), and major inputs of nitrogen to US crops over 1987-2012, based on the Farm Resource Regions developed by the Economic Research Service (USDA-ERS). Across the US, NUE generally decreased over time over the period studied, mainly due to increased use in mineral N fertilizer above crop N requirements. The Heartland region dominates production of major crops and thus tends to drive national patterns, showing linear response of crop production to nitrogen inputs broadly consistent with an earlier analysis of global patterns of country-scale data by Lassaletta et al. (2014). Most other regions show similar responses, but the Eastern Uplands region shows a negative response to nitrogen inputs, and the Southern Seaboard shows no significant relationship. The regional differences appear as two branches in the response of aggregate production to N inputs on a cropland area basis, but not on a total area basis, suggesting that the type of scaling used is critical under changing cropland area. Nitrogen use efficiency (NUE) is positively associated with fertilizer as a percentage of N inputs in four regions, and all regions considered together. NUE is positively associated with crop N fixation in all regions except Northern Great Plains. It is negatively associated with manure (livestock excretion); in the US, manure is still treated largely as a waste to be managed rather than a nutrient resource. This significant regional variation in patterns of crop production and NUE vs N inputs, has implications for environmental quality and food security. Copyright © 2018 Elsevier B.V. All rights reserved.

40 CFR 60.72 - Standard for nitrogen oxides.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Standard for nitrogen oxides. 60.72... Plants § 60.72 Standard for nitrogen oxides. (a) On and after the date on which the performance test...) Contain nitrogen oxides, expressed as NO2, in excess of 1.5 kg per metric ton of acid produced (3.0 lb per...

40 CFR 60.72 - Standard for nitrogen oxides.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Standard for nitrogen oxides. 60.72... Plants § 60.72 Standard for nitrogen oxides. (a) On and after the date on which the performance test...) Contain nitrogen oxides, expressed as NO2, in excess of 1.5 kg per metric ton of acid produced (3.0 lb per...

40 CFR 60.72 - Standard for nitrogen oxides.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 7 2012-07-01 2012-07-01 false Standard for nitrogen oxides. 60.72... Plants § 60.72 Standard for nitrogen oxides. (a) On and after the date on which the performance test...) Contain nitrogen oxides, expressed as NO2, in excess of 1.5 kg per metric ton of acid produced (3.0 lb per...

40 CFR 60.72 - Standard for nitrogen oxides.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 7 2013-07-01 2013-07-01 false Standard for nitrogen oxides. 60.72... Plants § 60.72 Standard for nitrogen oxides. (a) On and after the date on which the performance test...) Contain nitrogen oxides, expressed as NO2, in excess of 1.5 kg per metric ton of acid produced (3.0 lb per...

Sulphur and nitrogen fluxes and budgets in the Bohemian Forest and Tatra Mountains during the Industrial Revolution (1850-2000)

NASA Astrophysics Data System (ADS)

Kopcek, J.; Vesel, J.; Stuchlk, E.

Major fluxes of sulphur and dissolved inorganic nitrogen were estimated in Central European mountain ecosystems of the Bohemian Forest (forest lakes) and Tatra Mountains (alpine lakes) over the industrial period. Sulphur outputs from these ecosystems were comparable to inputs during a period of relatively stable atmospheric deposition (10-35 mmol m-2 yr-1) around the 1930s. Atmospheric inputs of sulphur increased by three- to four-fold between the 1950s and 1980s to ~140 and ~60 mmol mm-2 yr-1 in the Bohemian Forest and Tatra Mountains, respectively. Sulphur outputs were lower than inputs due to accumulation in soils, which was higher in forest soils than in the sparser alpine soils and represented 0.8-1.6 and 0.2-0.3 mol m-2, respectively, for the whole 1930-2000 period. In the 1990s, atmospheric inputs of sulphur decreased 80% and 50% in the Bohemian Forest and Tatra Mountains, respectively, and sulphur outputs exceeded inputs. Catchment soils became pronounced sources of sulphur with output fluxes averaging between 15 and 31 mmol m-2 yr-1. Higher sulphur accumulation in the forest soils has delayed (by several decades) recovery of forest lakes from acidification compared to alpine lakes. Estimated deposition of dissolved inorganic nitrogen was 53-75 mmol m-2 yr-1 in the Bohemian Forest and 35-45 mmol m-2 yr-1 in the Tatra Mountains in the 1880- 1950 period, i.e. below the empirically derived threshold of ~70 mmol m-2 yr-1, above which nitrogen leaching often occurs. Dissolved inorganic nitrogen was efficiently retained in the ecosystems and nitrate export was negligible (0-7 mmol m-2 yr-1). By the 1980s, nitrogen deposition increased to ~160 and ~80 mmol m-2 yr-1 in the Bohemian Forest and Tatra Mountains, respectively, and nitrogen output increased to 120 and 60 mmol m-2 yr-1. Moreover, assimilation of nitrogen in soils declined from ~40 to 10-20 mmol m-2 yr-1 in the alpine soils and even more in the Bohemian Forest, where one of the catchments has even become a net source of nitrogen. In the 1990s, nitrogen deposition decreased by ~30% and DIN output decreased to < 70 and 35 mmol m-2 yr-1 in the Bohemian Forest and Tatra Mountains, respectively. New steady-state conditions, with negligible nitrogen export, could be reached in future but at lower nitrogen depositions than in the 1930s.

Increasing anthropogenic nitrogen inputs and riverine DIN exports from the Changjiang River basin under changing human pressures

NASA Astrophysics Data System (ADS)

Yan, Weijin; Mayorga, Emilio; Li, Xinyan; Seitzinger, Sybil P.; Bouwman, A. F.

2010-12-01

In this paper, we estimate the inputs of nitrogen (N) and exports of dissolved inorganic nitrogen (DIN) from the Changjiang River to the estuary for the period 1970-2003, by using the global NEWS-DIN model. Modeled DIN yields range from 260 kg N km-2 yr-1 in 1970 to 895 kg N km-2 yr-1 in 2003, with an increasing trend. The study demonstrated a varied contribution of different N inputs to river DIN yields during the period 1970-2003. Chemical fertilizer and manure together contributed about half of the river DIN yields, while atmospheric N deposition contributed an average of 21% of DIN yields in the period 1970-2003. Biological N fixation contributed 40% of DIN yields in 1970, but substantially decreased to 13% in 2003. Point sewage N input also showed a decreasing trend in contribution to DIN yields, with an average of 8% over the whole period. We also discuss possible future trajectories of DIN export based on the Global NEWS implementation of the Millennium Ecosystem Assessment scenarios. Our result indicates that anthropogenically enhanced N inputs dominate and will continue to dominate river DIN yields under changing human pressures in the basin. Therefore, nitrogen pollution is and will continue to be a great challenge to China.

Chain Reaction: A Detailed look at Reactive Nitrogen and Possible Management Approaches

EPA Science Inventory

Nitrogen is one of the building blocks of life, yet excessive amounts in the environment can cause problems in various ecosystems. Abundant in the atmosphere as dinitrogen (N₂), nitrogen needs to be combined with other elements such as hydrogen or oxygen to...

The Increasing Importance of Deposition of Reduced Nitrogen in the United States

EPA Science Inventory

Rapid development of agricultural activities and fossil fuel combustion in the United States has led to a great increase in reactive nitrogen (Nr) emissions in the second half of the twentieth century. These emissions have been linked to excess nitrogen (N) deposition (i.e. depos...

Modeling Historical and Projected Future Atmospheric Nitrogen Loading to the Chesapeake Bay Watershed

EPA Science Inventory

Land use and climate change are expected to alter key processes in the Chesapeake Bay watershed and can potentially exacerbate the impact of excess nitrogen. Atmospheric sources are one of the largest loadings of nitrogen to the Chesapeake Bay watershed. In this study, we explore...

Linking Agricultural Crop Management and Air Quality Models for Regional to National-Scale Nitrogen Assessments

EPA Science Inventory

While nitrogen (N) is an essential element for life, human population growth and demands for energy, transportation and food can lead to excess nitrogen in the environment. A modeling framework is described and implemented to promote a more integrated, process-based and system le...

Dynamic SPARROW Modeling of Nitrogen Flux with Climate and MODIS Vegetation Indices as Drivers

NASA Astrophysics Data System (ADS)

Smith, R. A.; Brakebill, J.; Schwarz, G.; Alexander, R. B.; Hirsch, R. M.; Nolin, A. W.; Macauley, M.; Zhang, Q.; Shih, J.; Wang, W.; Sproles, E.

2011-12-01

SPARROW models are widely used to identify and quantify the sources of contaminants in watersheds and to predict their flux and concentration at specified locations downstream. Conventional SPARROW models are statistically calibrated and describe the average relationship between sources and stream conditions based on long-term water quality monitoring data and spatially-referenced explanatory information. But many watershed management issues stem from intra- and inter-annual changes in contaminant sources, hydrologic forcing, or other environmental conditions which cause a temporary imbalance between inputs and stream water quality. Dynamic behavior of the system relating to changes in watershed storage and processing then becomes important. In this study, we describe a dynamically calibrated SPARROW model of total nitrogen flux in the Potomac River Basin based on seasonal water quality and watershed input data for 80 monitoring stations over the period 2000 to 2008. One challenge in dynamic modeling of reactive nitrogen is obtaining frequently-reported, spatially-detailed input data on the phenology of agricultural production and terrestrial vegetation. In this NASA-funded research, we use the Enhanced Vegetation Index (EVI) and gross primary productivity data from the Terra Satellite-borne MODIS sensor to parameterize seasonal uptake and release of nitrogen. The spatial reference frame of the model is a 16,000-reach, 1:100,000-scale stream network, and the computational time step is seasonal. Precipitation and temperature data are from PRISM. The model formulation allows for separate storage compartments for nonpoint sources including fertilized cropland, pasture, urban land, and atmospheric deposition. Removal of nitrogen from watershed storage to stream channels and to "permanent" sinks (deep groundwater and the atmosphere) occur as parallel first-order processes. We use the model to explore an important issue in nutrient management in the Potomac and other basins: the long-term response of total nitrogen flux to changing climate. We model the nitrogen flux response to projected seasonal and inter-annual changes in temperature and precipitation, but under current seasonal nitrogen inputs, as indicated by MODIS measures of productivity. Under these constant inter-annual inputs, changing temperature and precipitation is predicted to lead to flux changes as temporary basin stores of nitrogen either grow or shrink due to changing relative rates of nitrogen removal to the atmosphere and release to streams.

SENSITIVITY OF NITROGEN CONCENTRATIONS IN ESTUARIES TO LOADING AND WATER RESIDENCE TIME: APPLICATION TO THE POTOMAC ESTUARY

EPA Science Inventory

We use a simple nitrogen budget model to analyze concentrations of total nitrogen (TN) in estuaries for which both nitrogen inputs and water residence time are correlated with freshwater inflow rates. While the nitrogen concentration of an estuary varies linearly with TN loading ...

Genetics Home Reference: arginase deficiency

MedlinePlus

... occurs in liver cells. This cycle processes excess nitrogen, generated when protein is used by the body, ... the urea cycle, which produces urea by removing nitrogen from arginine. In people with arginase deficiency , arginase ...

Effects of reduced nitrogen inputs on crop yield and nitrogen use efficiency in a long-term maize-soybean relay strip intercropping system.

PubMed

Chen, Ping; Du, Qing; Liu, Xiaoming; Zhou, Li; Hussain, Sajad; Lei, Lu; Song, Chun; Wang, Xiaochun; Liu, Weiguo; Yang, Feng; Shu, Kai; Liu, Jiang; Du, Junbo; Yang, Wenyu; Yong, Taiwen

2017-01-01

The blind pursuit of high yields via increased fertilizer inputs increases the environmental costs. Relay intercropping has advantages for yield, but a strategy for N management is urgently required to decrease N inputs without yield loss in maize-soybean relay intercropping systems (IMS). Experiments were conducted with three levels of N and three planting patterns, and dry matter accumulation, nitrogen uptake, nitrogen use efficiency (NUE), competition ratio (CR), system productivity index (SPI), land equivalent ratio (LER), and crop root distribution were investigated. Our results showed that the CR of soybean was greater than 1, and that the change in root distribution in space and time resulted in an interspecific facilitation in IMS. The maximum yield of maize under monoculture maize (MM) occurred with conventional nitrogen (CN), whereas under IMS, the maximum yield occurred with reduced nitrogen (RN). The yield of monoculture soybean (MS) and of soybean in IMS both reached a maximum under RN. The LER of IMS varied from 1.85 to 2.36, and the SPI peaked under RN. Additionally, the NUE of IMS increased by 103.7% under RN compared with that under CN. In conclusion, the separation of the root ecological niche contributed to a positive interspecific facilitation, which increased the land productivity. Thus, maize-soybean relay intercropping with reduced N input provides a very useful approach to increase land productivity and avert environmental pollution.

Modeling Nitrogen Processing in Northeast US River Networks

NASA Astrophysics Data System (ADS)

Whittinghill, K. A.; Stewart, R.; Mineau, M.; Wollheim, W. M.; Lammers, R. B.

2013-12-01

Due to increased nitrogen (N) pollution from anthropogenic sources, the need for aquatic ecosystem services such as N removal has also increased. River networks provide a buffering mechanism that retains or removes anthropogenic N inputs. However, the effectiveness of N removal in rivers may decline with increased loading and, consequently, excess N is eventually delivered to estuaries. We used a spatially distributed river network N removal model developed within the Framework for Aquatic Modeling in the Earth System (FrAMES) to examine the geography of N removal capacity of Northeast river systems under various land use and climate conditions. FrAMES accounts for accumulation and routing of runoff, water temperatures, and serial biogeochemical processing using reactivity derived from the Lotic Intersite Nitrogen Experiment (LINX2). Nonpoint N loading is driven by empirical relationships with land cover developed from previous research in Northeast watersheds. Point source N loading from wastewater treatment plants is estimated as a function of the population served and the volume of water discharged. We tested model results using historical USGS discharge data and N data from historical grab samples and recently initiated continuous measurements from in-situ aquatic sensors. Model results for major Northeast watersheds illustrate hot spots of ecosystem service activity (i.e. N removal) using high-resolution maps and basin profiles. As expected, N loading increases with increasing suburban or agricultural land use area. Network scale N removal is highest during summer and autumn when discharge is low and river temperatures are high. N removal as the % of N loading increases with catchment size and decreases with increasing N loading, suburban land use, or agricultural land use. Catchments experiencing the highest network scale N removal generally have N inputs (both point and non-point sources) located in lower order streams. Model results can be used to better predict nutrient loading to the coastal ocean across a broad range of current and future climate variability.

Leaf-litter inputs from an invasive nitrogen-fixing tree influence organic-matter dynamics and nitrogen inputs in a Hawaiian river

Treesearch

Richard A. MacKenzie; Tracy N. Wiegner; Frances Kinslow; Nicole Cormier; Ayron M. Strauch

2013-01-01

Abstract. We examined how invasion of tropical riparian forests by an exotic N-fixing tree (Falcataria moluccana) affects organic-matter dynamics in a Hawaiian river by comparing early stages of leaf-litter breakdown between the exotic F. moluccana and native Metrosideros polymorpha trees. We examined early...

Impact of glacial/interglacial sea level change on the ocean nitrogen cycle.

PubMed

Ren, Haojia; Sigman, Daniel M; Martínez-García, Alfredo; Anderson, Robert F; Chen, Min-Te; Ravelo, Ana Christina; Straub, Marietta; Wong, George T F; Haug, Gerald H

2017-08-15

The continental shelves are the most biologically dynamic regions of the ocean, and they are extensive worldwide, especially in the western North Pacific. Their area has varied dramatically over the glacial/interglacial cycles of the last million years, but the effects of this variation on ocean biological and chemical processes remain poorly understood. Conversion of nitrate to N 2 by denitrification in sediments accounts for half or more of the removal of biologically available nitrogen ("fixed N") from the ocean. The emergence of continental shelves during ice ages and their flooding during interglacials have been hypothesized to drive changes in sedimentary denitrification. Denitrification leads to the occurrence of phosphorus-bearing, N-depleted surface waters, which encourages N 2 fixation, the dominant N input to the ocean. An 860,000-y record of foraminifera shell-bound N isotopes from the South China Sea indicates that N 2 fixation covaried with sea level. The N 2 fixation changes are best explained as a response to changes in regional excess phosphorus supply due to sea level-driven variations in shallow sediment denitrification associated with the cyclic drowning and emergence of the continental shelves. This hypothesis is consistent with a glacial ocean that hosted globally lower rates of fixed N input and loss and a longer residence time for oceanic fixed N-a "sluggish" ocean N budget during ice ages. In addition, this work provides a clear sign of sea level-driven glacial/interglacial oscillations in biogeochemical fluxes at and near the ocean margins, with implications for coastal organisms and ecosystems.

Impact of glacial/interglacial sea level change on the ocean nitrogen cycle

NASA Astrophysics Data System (ADS)

Ren, Haojia; Sigman, Daniel M.; Martínez-García, Alfredo; Anderson, Robert F.; Chen, Min-Te; Ravelo, Ana Christina; Straub, Marietta; Wong, George T. F.; Haug, Gerald H.

2017-08-01

The continental shelves are the most biologically dynamic regions of the ocean, and they are extensive worldwide, especially in the western North Pacific. Their area has varied dramatically over the glacial/interglacial cycles of the last million years, but the effects of this variation on ocean biological and chemical processes remain poorly understood. Conversion of nitrate to N2 by denitrification in sediments accounts for half or more of the removal of biologically available nitrogen (“fixed N”) from the ocean. The emergence of continental shelves during ice ages and their flooding during interglacials have been hypothesized to drive changes in sedimentary denitrification. Denitrification leads to the occurrence of phosphorus-bearing, N-depleted surface waters, which encourages N2 fixation, the dominant N input to the ocean. An 860,000-y record of foraminifera shell-bound N isotopes from the South China Sea indicates that N2 fixation covaried with sea level. The N2 fixation changes are best explained as a response to changes in regional excess phosphorus supply due to sea level-driven variations in shallow sediment denitrification associated with the cyclic drowning and emergence of the continental shelves. This hypothesis is consistent with a glacial ocean that hosted globally lower rates of fixed N input and loss and a longer residence time for oceanic fixed N—a “sluggish” ocean N budget during ice ages. In addition, this work provides a clear sign of sea level-driven glacial/interglacial oscillations in biogeochemical fluxes at and near the ocean margins, with implications for coastal organisms and ecosystems.

Impact of glacial/interglacial sea level change on the ocean nitrogen cycle

PubMed Central

Ren, Haojia; Sigman, Daniel M.; Martínez-García, Alfredo; Anderson, Robert F.; Chen, Min-Te; Ravelo, Ana Christina; Straub, Marietta; Wong, George T. F.; Haug, Gerald H.

2017-01-01

The continental shelves are the most biologically dynamic regions of the ocean, and they are extensive worldwide, especially in the western North Pacific. Their area has varied dramatically over the glacial/interglacial cycles of the last million years, but the effects of this variation on ocean biological and chemical processes remain poorly understood. Conversion of nitrate to N2 by denitrification in sediments accounts for half or more of the removal of biologically available nitrogen (“fixed N”) from the ocean. The emergence of continental shelves during ice ages and their flooding during interglacials have been hypothesized to drive changes in sedimentary denitrification. Denitrification leads to the occurrence of phosphorus-bearing, N-depleted surface waters, which encourages N2 fixation, the dominant N input to the ocean. An 860,000-y record of foraminifera shell-bound N isotopes from the South China Sea indicates that N2 fixation covaried with sea level. The N2 fixation changes are best explained as a response to changes in regional excess phosphorus supply due to sea level-driven variations in shallow sediment denitrification associated with the cyclic drowning and emergence of the continental shelves. This hypothesis is consistent with a glacial ocean that hosted globally lower rates of fixed N input and loss and a longer residence time for oceanic fixed N—a “sluggish” ocean N budget during ice ages. In addition, this work provides a clear sign of sea level-driven glacial/interglacial oscillations in biogeochemical fluxes at and near the ocean margins, with implications for coastal organisms and ecosystems. PMID:28760968

A 25-Year Retrospective Analysis of River Nitrogen Fluxes in the Atchafalaya

NASA Astrophysics Data System (ADS)

Xu, Y.

2005-05-01

Nitrogen enrichment from the upper Mississippi River Basin has been attributed to be the major cause for the hypoxia in the Northern Gulf of Mexico. The hypoxia threatens not only the aquatic ecosystem health but Louisiana's fishery industry directly among other problems. Although fresh water diversion from the lower Mississippi River into the region's wetlands has been considered an alternative means for reducing nitrogen loading, it is largely uncertain how much nitrogen can actually be retained from the overflowing waters in these natural wetlands. Generally, there is a knowledge gap in what tools are available for accurate assessment of nitrogen inflow, outflow and removal potential for the complex and diverse coastal floodplain systems. This study is to seek answers to three critical questions: (1) Does the Atchafalaya River Swamp remove a significant amount of nitrogen from the overflowing water or release more nitrogen into the Gulf than removing it? (2) How seasonally and annually do the nitrogen removal or release rates fluctuate? (3) What are the relationships between the nitrogen removal capacity and the basin's hydrologic conditions such as river stage and discharge? By utilizing river's long-term discharge and water quality data (1978-2002), monthly and annual nitrogen fluxes were quantified, and their relationships with the basin's hydrologic conditions were investigated. A total Kjeldahl nitrogen (TKN) mass input-output balance between the upstream (Simmesport) and downstream (Morgan City and Wax Lake Outlet) locations was established to examine the organic nitrogen removal potential for this largest freshwater swamp basin in North America. The results showed that on average, TKN input into the Atchafalaya was 200,323 Mg yr-1 and TKN output leaving the basin was 145,917 Mg yr-1, resulting in a 27% removal rate of nitrogen. Monthly nitrogen input and output in the basin were highest from March to June (input vs. output: 25,000 vs. 18,000 Mg mon-1) and lowest from August to November (8,000 vs. 6,000 Mg mon-1). There was a large variation in both annual and inter-annual nitrogen removals, and the variability was positively correlated with the amount of inflow water at Simmesport. However, no close relationship between the river inflow and percentage nitrogen removal rate was found. The results gained from this study suggest that regulating the river's inflow will help reduce nitrogen loading of the Mississippi River to the Gulf of Mexico. The in-stream loss of nitrogen indicates that previous studies may have overestimated nitrogen discharge from the Mississippi-Atchafalaya River system. Furthermore, the study found that knowledge on spatial hydrological conditions in the basin is needed to understand nitrogen dynamics in the Atchafalaya River Swamp.

Nitrogen removal from natural gas using two types of membranes

DOEpatents

Baker, Richard W.; Lokhandwala, Kaaeid A.; Wijmans, Johannes G.; Da Costa, Andre R.

2003-10-07

A process for treating natural gas or other methane-rich gas to remove excess nitrogen. The invention relies on two-stage membrane separation, using methane-selective membranes for the first stage and nitrogen-selective membranes for the second stage. The process enables the nitrogen content of the gas to be substantially reduced, without requiring the membranes to be operated at very low temperatures.

Constraint-Based Modeling Highlights Cell Energy, Redox Status and α-Ketoglutarate Availability as Metabolic Drivers for Anthocyanin Accumulation in Grape Cells Under Nitrogen Limitation

PubMed Central

Soubeyrand, Eric; Colombié, Sophie; Beauvoit, Bertrand; Dai, Zhanwu; Cluzet, Stéphanie; Hilbert, Ghislaine; Renaud, Christel; Maneta-Peyret, Lilly; Dieuaide-Noubhani, Martine; Mérillon, Jean-Michel; Gibon, Yves; Delrot, Serge; Gomès, Eric

2018-01-01

Anthocyanin biosynthesis is regulated by environmental factors (such as light, temperature, and water availability) and nutrient status (such as carbon, nitrogen, and phosphate nutrition). Previous reports show that low nitrogen availability strongly enhances anthocyanin accumulation in non carbon-limited plant organs or cell suspensions. It has been hypothesized that high carbon-to-nitrogen ratio would lead to an energy excess in plant cells, and that an increase in flavonoid pathway metabolic fluxes would act as an “energy escape valve,” helping plant cells to cope with energy and carbon excess. However, this hypothesis has never been tested directly. To this end, we used the grapevine Vitis vinifera L. cultivar Gamay Teinturier (syn. Gamay Freaux or Freaux Tintorier, VIVC #4382) cell suspension line as a model system to study the regulation of anthocyanin accumulation in response to nitrogen supply. The cells were sub-cultured in the presence of either control (25 mM) or low (5 mM) nitrate concentration. Targeted metabolomics and enzyme activity determinations were used to parametrize a constraint-based model describing both the central carbon and nitrogen metabolisms and the flavonoid (phenylpropanoid) pathway connected by the energy (ATP) and reducing power equivalents (NADPH and NADH) cofactors. The flux analysis (2 flux maps generated, for control and low nitrogen in culture medium) clearly showed that in low nitrogen-fed cells all the metabolic fluxes of central metabolism were decreased, whereas fluxes that consume energy and reducing power, were either increased (upper part of glycolysis, shikimate, and flavonoid pathway) or maintained (pentose phosphate pathway). Also, fluxes of flavanone 3β-hydroxylase, flavonol synthase, and anthocyanidin synthase were strongly increased, advocating for a regulation of the flavonoid pathway by alpha-ketoglutarate levels. These results strongly support the hypothesis of anthocyanin biosynthesis acting as an energy escape valve in plant cells, and they open new possibilities to manipulate flavonoid production in plant cells. They do not, however, support a role of anthocyanins as an effective mechanism for coping with carbon excess in high carbon to nitrogen ratio situations in grape cells. Instead, constraint-based modeling output and biomass analysis indicate that carbon excess is dealt with by vacuolar storage of soluble sugars. PMID:29868039

Constraint-Based Modeling Highlights Cell Energy, Redox Status and α-Ketoglutarate Availability as Metabolic Drivers for Anthocyanin Accumulation in Grape Cells Under Nitrogen Limitation.

PubMed

Soubeyrand, Eric; Colombié, Sophie; Beauvoit, Bertrand; Dai, Zhanwu; Cluzet, Stéphanie; Hilbert, Ghislaine; Renaud, Christel; Maneta-Peyret, Lilly; Dieuaide-Noubhani, Martine; Mérillon, Jean-Michel; Gibon, Yves; Delrot, Serge; Gomès, Eric

2018-01-01

Anthocyanin biosynthesis is regulated by environmental factors (such as light, temperature, and water availability) and nutrient status (such as carbon, nitrogen, and phosphate nutrition). Previous reports show that low nitrogen availability strongly enhances anthocyanin accumulation in non carbon-limited plant organs or cell suspensions. It has been hypothesized that high carbon-to-nitrogen ratio would lead to an energy excess in plant cells, and that an increase in flavonoid pathway metabolic fluxes would act as an "energy escape valve," helping plant cells to cope with energy and carbon excess. However, this hypothesis has never been tested directly. To this end, we used the grapevine Vitis vinifera L. cultivar Gamay Teinturier (syn. Gamay Freaux or Freaux Tintorier, VIVC #4382) cell suspension line as a model system to study the regulation of anthocyanin accumulation in response to nitrogen supply. The cells were sub-cultured in the presence of either control (25 mM) or low (5 mM) nitrate concentration. Targeted metabolomics and enzyme activity determinations were used to parametrize a constraint-based model describing both the central carbon and nitrogen metabolisms and the flavonoid (phenylpropanoid) pathway connected by the energy (ATP) and reducing power equivalents (NADPH and NADH) cofactors. The flux analysis (2 flux maps generated, for control and low nitrogen in culture medium) clearly showed that in low nitrogen-fed cells all the metabolic fluxes of central metabolism were decreased, whereas fluxes that consume energy and reducing power, were either increased (upper part of glycolysis, shikimate, and flavonoid pathway) or maintained (pentose phosphate pathway). Also, fluxes of flavanone 3β-hydroxylase, flavonol synthase, and anthocyanidin synthase were strongly increased, advocating for a regulation of the flavonoid pathway by alpha-ketoglutarate levels. These results strongly support the hypothesis of anthocyanin biosynthesis acting as an energy escape valve in plant cells, and they open new possibilities to manipulate flavonoid production in plant cells. They do not, however, support a role of anthocyanins as an effective mechanism for coping with carbon excess in high carbon to nitrogen ratio situations in grape cells. Instead, constraint-based modeling output and biomass analysis indicate that carbon excess is dealt with by vacuolar storage of soluble sugars.

Nitrogen enrichment and speciation in a coral reef lagoon driven by groundwater inputs of bird guano

NASA Astrophysics Data System (ADS)

McMahon, Ashly; Santos, Isaac R.

2017-09-01

While the influence of river inputs on coral reef biogeochemistry has been investigated, there is limited information on nutrient fluxes related to submarine groundwater discharge (SGD). Here, we investigate whether significant saline groundwater-derived nutrient inputs from bird guano drive coral reef photosynthesis and calcification off Heron Island (Great Barrier Reef, Australia). We used multiple experimental approaches including groundwater sampling, beach face transects, and detailed time series observations to assess the dynamics and speciation of groundwater nutrients as they travel across the island and discharge into the coral reef lagoon. Nitrogen speciation shifted from nitrate-dominated groundwater (>90% of total dissolved nitrogen) to a coral reef lagoon dominated by dissolved organic nitrogen (DON; ˜86%). There was a minimum input of nitrate of 2.1 mmol m-2 d-1 into the lagoon from tidally driven submarine groundwater discharge estimated from a radon mass balance model. An independent approach based on the enrichment of dissolved nutrients during isolation at low tide implied nitrate fluxes of 5.4 mmol m-2 d-1. A correlation was observed between nitrate and daytime net ecosystem production and calcification. We suggest that groundwater nutrients derived from bird guano may offer a significant addition to oligotrophic coral reef lagoons and fuel ecosystem productivity and the coastal carbon cycle near Heron Island. The large input of groundwater nutrients in Heron Island may serve as a natural ecological analogue to other coral reefs subject to large nutrient inputs from anthropogenic sources.

Ambient and potential denitrification rates in marsh soils of Northeast Creek and Bass Harbor Marsh watersheds, Mount Desert Island, Maine

USGS Publications Warehouse

Huntington, Thomas G.; Culbertson, Charles W.; Duff, John H.

2012-01-01

Nutrient enrichment from atmospheric deposition, agricultural activities, wildlife, and domestic sources is a concern at Acadia National Park on Mount Desert Island, Maine, because of the potential problems of degradation of water quality and eutrophication in estuaries. Degradation of water quality has been observed at Bass Harbor Marsh estuary in the park but only minimally in Northeast Creek estuary. Previous studies at Acadia National Park have estimated nutrient inputs to estuaries from atmospheric deposition and surface-water runoff, and have identified shallow groundwater as an additional potential source of nutrients. Previous studies at Acadia National Park have assumed that a certain fraction of the nitrogen input was removed through microbial denitrification, but rates of denitrification (natural or maximum potential) in marsh soils have not been determined. The U.S. Geological Survey, in cooperation with Acadia National Park, measured in-place denitrification rates in marsh soils in Northeast Creek and in Bass Harbor Marsh watersheds during summer 2008 and summer 2009. Denitrification was measured under ambient conditions as well as after additions of inorganic nitrogen and glucose. In-place denitrification rates under ambient conditions were similar to those reported for other coastal wetlands, although they were generally lower than those reported for salt marshes having high ambient concentrations of nitrate (NO3). Denitrification rates generally increased by at least an order of magnitude following NO3 additions, with or without glucose (as the carbohydrate) additions, compared with the ambient treatments that received no nutrient additions. The treatment that added both glucose and NO3 resulted in a variety of denitrification responses when compared with the addition of NO3 alone. In most cases, the addition of glucose to a given rate of NO3 addition resulted in higher rates of denitrification. These variable responses indicate that the amount of labile carbohydrates can limit denitrification even if NO3 is present. For most sites in both watersheds, the maximum denitrification rates ranged from of 150 to 900 micromoles of nitrous oxide per square meter per hour. These rates were equivalent to the release of 37 to 221 grams of nitrogen per square meter per year. Weak positive correlations were observed for soil temperature and for measured ammonium concentration in groundwater. Weak negative correlations were observed between denitrification rate and water level and specific conductance. The rates of denitrification in Bass Harbor Marsh and Northeast Creek under ambient conditions, both of which were relatively low, indicate that NO3 availability is low in both systems. It is evident from the addition of combined treatments of NO3 and glucose that these marsh soils are capable of comparatively high rates of denitrification, therefore, estuarine eutrophication is not a result of nitrogen inputs to marsh soils that are in excess of the denitrification capacity in these systems. If terrestrial inputs to the estuary are the cause of the observed eutrophic condition in Bass Harbor Marsh, then these inputs to the estuary must bypass the marsh in channelized surface flow, or perhaps they circumvent the marsh in shallow groundwater seepage along subsurface pathways that enter the estuary directly.

40 CFR 60.332 - Standard for nitrogen oxides.

Code of Federal Regulations, 2012 CFR

2012-07-01

... from paragraph (a) of this section. (f) Stationary gas turbines using water or steam injection for... Turbines § 60.332 Standard for nitrogen oxides. (a) On and after the date on which the performance test... stationary gas turbine, any gases which contain nitrogen oxides in excess of: EC16NO91.020 where: STD...

40 CFR 60.332 - Standard for nitrogen oxides.

Code of Federal Regulations, 2014 CFR

2014-07-01

... from paragraph (a) of this section. (f) Stationary gas turbines using water or steam injection for... Turbines § 60.332 Standard for nitrogen oxides. (a) On and after the date on which the performance test... stationary gas turbine, any gases which contain nitrogen oxides in excess of: EC16NO91.020 where: STD...

40 CFR 60.332 - Standard for nitrogen oxides.

Code of Federal Regulations, 2011 CFR

2011-07-01

... from paragraph (a) of this section. (f) Stationary gas turbines using water or steam injection for... Turbines § 60.332 Standard for nitrogen oxides. (a) On and after the date on which the performance test... stationary gas turbine, any gases which contain nitrogen oxides in excess of: EC16NO91.020 where: STD...

40 CFR 60.332 - Standard for nitrogen oxides.

Code of Federal Regulations, 2010 CFR

2010-07-01

... from paragraph (a) of this section. (f) Stationary gas turbines using water or steam injection for... Turbines § 60.332 Standard for nitrogen oxides. (a) On and after the date on which the performance test... stationary gas turbine, any gases which contain nitrogen oxides in excess of: EC16NO91.020 where: STD...

40 CFR 60.332 - Standard for nitrogen oxides.

Code of Federal Regulations, 2013 CFR

2013-07-01

... from paragraph (a) of this section. (f) Stationary gas turbines using water or steam injection for... Turbines § 60.332 Standard for nitrogen oxides. (a) On and after the date on which the performance test... stationary gas turbine, any gases which contain nitrogen oxides in excess of: EC16NO91.020 where: STD...

Coupled nitrogen and calcium cycles in forests of the Oregon Coast Range

USGS Publications Warehouse

Perakis, S.S.; Maguire, D.A.; Bullen, T.D.; Cromack, K.; Waring, R.H.; Boyle, J.R.

2006-01-01

Nitrogen (N) is a critical limiting nutrient that regulates plant productivity and the cycling of other essential elements in forests. We measured foliar and soil nutrients in 22 young Douglas-fir stands in the Oregon Coast Range to examine patterns of nutrient availability across a gradient of N-poor to N-rich soils. N in surface mineral soil ranged from 0.15 to 1.05% N, and was positively related to a doubling of foliar N across sites. Foliar N in half of the sites exceeded 1.4% N, which is considered above the threshold of N-limitation in coastal Oregon Douglas-fir. Available nitrate increased five-fold across this gradient, whereas exchangeable magnesium (Mg) and calcium (Ca) in soils declined, suggesting that nitrate leaching influences base cation availability more than soil parent material across our sites. Natural abundance strontium isotopes (87Sr/86Sr) of a single site indicated that 97% of available base cations can originate from atmospheric inputs of marine aerosols, with negligible contributions from weathering. Low annual inputs of Ca relative to Douglas-fir growth requirements may explain why foliar Ca concentrations are highly sensitive to variations in soil Ca across our sites. Natural abundance calcium isotopes (??44Ca) in exchangeable and acid leachable pools of surface soil measured at a single site showed 1 per mil depletion relative to deep soil, suggesting strong Ca recycling to meet tree demands. Overall, the biogeochemical response of these Douglas-fir forests to gradients in soil N is similar to changes associated with chronic N deposition in more polluted temperate regions, and raises the possibility that Ca may be deficient on excessively N-rich sites. We conclude that wide gradients in soil N can drive non-linear changes in base-cation biogeochemistry, particularly as forests cross a threshold from N-limitation to N-saturation. The most acute changes may occur in forests where base cations are derived principally from atmospheric inputs. ?? 2006 Springer Science+Business Media, Inc.

Performance assessment of nitrate leaching models for highly vulnerable soils used in low-input farming based on lysimeter data.

PubMed

Groenendijk, Piet; Heinen, Marius; Klammler, Gernot; Fank, Johann; Kupfersberger, Hans; Pisinaras, Vassilios; Gemitzi, Alexandra; Peña-Haro, Salvador; García-Prats, Alberto; Pulido-Velazquez, Manuel; Perego, Alessia; Acutis, Marco; Trevisan, Marco

2014-11-15

The agricultural sector faces the challenge of ensuring food security without an excessive burden on the environment. Simulation models provide excellent instruments for researchers to gain more insight into relevant processes and best agricultural practices and provide tools for planners for decision making support. The extent to which models are capable of reliable extrapolation and prediction is important for exploring new farming systems or assessing the impacts of future land and climate changes. A performance assessment was conducted by testing six detailed state-of-the-art models for simulation of nitrate leaching (ARMOSA, COUPMODEL, DAISY, EPIC, SIMWASER/STOTRASIM, SWAP/ANIMO) for lysimeter data of the Wagna experimental field station in Eastern Austria, where the soil is highly vulnerable to nitrate leaching. Three consecutive phases were distinguished to gain insight in the predictive power of the models: 1) a blind test for 2005-2008 in which only soil hydraulic characteristics, meteorological data and information about the agricultural management were accessible; 2) a calibration for the same period in which essential information on field observations was additionally available to the modellers; and 3) a validation for 2009-2011 with the corresponding type of data available as for the blind test. A set of statistical metrics (mean absolute error, root mean squared error, index of agreement, model efficiency, root relative squared error, Pearson's linear correlation coefficient) was applied for testing the results and comparing the models. None of the models performed good for all of the statistical metrics. Models designed for nitrate leaching in high-input farming systems had difficulties in accurately predicting leaching in low-input farming systems that are strongly influenced by the retention of nitrogen in catch crops and nitrogen fixation by legumes. An accurate calibration does not guarantee a good predictive power of the model. Nevertheless all models were able to identify years and crops with high- and low-leaching rates. Copyright © 2014 Elsevier B.V. All rights reserved.

A role for shellfish aquaculture in coastal nitrogen management.

PubMed

Rose, Julie M; Bricker, Suzanne B; Tedesco, Mark A; Wikfors, Gary H

2014-01-01

Excess nutrients in the coastal environment have been linked to a host of environmental problems, and nitrogen reduction efforts have been a top priority of resource managers for decades. The use of shellfish for coastal nitrogen remediation has been proposed, but formal incorporation into nitrogen management programs is lagging. Including shellfish aquaculture in existing nitrogen management programs makes sense from environmental, economic, and social perspectives, but challenges must be overcome for large-scale implementation to be possible.

RIBBED MUSSEL NITROGEN ISOTOPE SIGNATURES REFLECT NITROGEN SOURCES IN COASTAL MARSHES

EPA Science Inventory

The stable nitrogen isotope ratio in tissue of the ribbed mussel (Geukensia demissa) was investigated as an indicator of the source of nitrogen inputs to coastal salt marshes. Initially, mussels were fed a diet of 15N-enriched algae in the laboratory to determine how the tissue n...

Metabolism of organic acids, nitrogen and amino acids in chlorotic leaves of 'Honeycrisp' apple (Malus domestica Borkh) with excessive accumulation of carbohydrates.

PubMed

Wang, Huicong; Ma, Fangfang; Cheng, Lailiang

2010-07-01

Metabolite profiles and activities of key enzymes in the metabolism of organic acids, nitrogen and amino acids were compared between chlorotic leaves and normal leaves of 'Honeycrisp' apple to understand how accumulation of non-structural carbohydrates affects the metabolism of organic acids, nitrogen and amino acids. Excessive accumulation of non-structural carbohydrates and much lower CO(2) assimilation were found in chlorotic leaves than in normal leaves, confirming feedback inhibition of photosynthesis in chlorotic leaves. Dark respiration and activities of several key enzymes in glycolysis and tricarboxylic acid (TCA) cycle, ATP-phosphofructokinase, pyruvate kinase, citrate synthase, aconitase and isocitrate dehydrogenase were significantly higher in chlorotic leaves than in normal leaves. However, concentrations of most organic acids including phosphoenolpyruvate (PEP), pyruvate, oxaloacetate, 2-oxoglutarate, malate and fumarate, and activities of key enzymes involved in the anapleurotic pathway including PEP carboxylase, NAD-malate dehydrogenase and NAD-malic enzyme were significantly lower in chlorotic leaves than in normal leaves. Concentrations of soluble proteins and most free amino acids were significantly lower in chlorotic leaves than in normal leaves. Activities of key enzymes in nitrogen assimilation and amino acid synthesis, including nitrate reductase, glutamine synthetase, ferredoxin and NADH-dependent glutamate synthase, and glutamate pyruvate transaminase were significantly lower in chlorotic leaves than in normal leaves. It was concluded that, in response to excessive accumulation of non-structural carbohydrates, glycolysis and TCA cycle were up-regulated to "consume" the excess carbon available, whereas the anapleurotic pathway, nitrogen assimilation and amino acid synthesis were down-regulated to reduce the overall rate of amino acid and protein synthesis.

Mining Environmental Data from a Coupled Modelling System to Examine the Impact of Agricultural Management Practices on Groundwater and Air Quality

NASA Astrophysics Data System (ADS)

Garcia, V.; Cooter, E. J.; Hayes, B.; Murphy, M. S.; Bash, J. O.

2014-12-01

Excess nitrogen (N) resulting from current agricultural management practices can leach into sources of drinking water as nitrate, increasing human health risks of 'blue baby syndrome', hypertension, and some cancers and birth defects. Nitrogen also enters the atmosphere from land surfaces forming air pollution increasing human health risks of pulmonary and cardio-vascular disease. Characterizing and attributing nitrogen from agricultural management practices is difficult due to the complex and inter-related chemical and biological reactions associated with the nitrogen cascade. Coupled physical process-based models, however, present new opportunities to investigate relationships among environmental variables on new scales; particularly because they link emission sources with meteorology and the pollutant concentration ultimately found in the environment. In this study, we applied a coupled meteorology (NOAA-WRF), agricultural (USDA-EPIC) and air quality modelling system (EPA-CMAQ) to examine the impact of nitrogen inputs from corn production on ecosystem and human health and wellbeing. The coupled system accounts for the nitrogen flux between the land surface and air, and the soil surface and groundwater, providing a unique opportunity to examine the effect of management practices such as type and timing of fertilization, tilling and irrigation on both groundwater and air quality across the conterminous US. In conducting the study, we first determined expected relationships based on literature searches and then identified model variables as direct or surrogate variables. We performed extensive and methodical multi-variate regression modelling and variable selection to examine associations between agricultural management practices and environmental condition. We then applied the regression model to predict and contrast pollution levels between two corn production scenarios (Figure 1). Finally, we applied published health functions (e.g., spina bifida and cardio-vascular mortality rates) and economic impact functions (e.g., loss of work/school days, decontamination of drinking water wells). The results of this analysis will be presented at the conference.

Nitrogen input from residential lawn care practices in suburban watersheds in Baltimore county, MD

Treesearch

Neely L. Law; Lawrence E. Band; J. Morgan Grove

2004-01-01

A residential lawn care survey was conducted as part of the Baltimore Ecosystem Study, a Long-term Ecological Research project funded by the National Science Foundation and collaborating agencies, to estimate the nitrogen input to urban watersheds from lawn care practices. The variability in the fertilizer N application rates and the factors affecting the application...

Net anthropogenic nitrogen inputs and nitrogen fluxes from Indian watersheds: An initial assessment

NASA Astrophysics Data System (ADS)

Swaney, D. P.; Hong, B.; Paneer Selvam, A.; Howarth, R. W.; Ramesh, R.; Purvaja, R.

2015-01-01

In this paper, we apply an established methodology for estimating Net Anthropogenic Nitrogen Inputs (NANI) to India and its major watersheds. Our primary goal here is to provide initial estimates of major nitrogen inputs of NANI for India, at the country level and for major Indian watersheds, including data sources and parameter estimates, making some assumptions as needed in areas of limited data availability. Despite data limitations, we believe that it is clear that the main anthropogenic N source is agricultural fertilizer, which is being produced and applied at a growing rate, followed by N fixation associated with rice, leguminous crops, and sugar cane. While India appears to be a net exporter of N in food/feed as reported elsewhere (Lassaletta et al., 2013b), the balance of N associated with exports and imports of protein in food and feedstuffs is sensitive to protein content and somewhat uncertain. While correlating watershed N inputs with riverine N fluxes is problematic due in part to limited available riverine data, we have assembled some data for comparative purposes. We also suggest possible improvements in methods for future studies, and the potential for estimating riverine N fluxes to coastal waters.

Effects of agricultural intensification on ability of natural enemies to control aphids

PubMed Central

Zhao, Zi-Hua; Hui, Cang; He, Da-Han; Li, Bai-Lian

2015-01-01

Agricultural intensification through increasing fertilization input and cropland expansion has caused rapid loss of semi-natural habitats and the subsequent loss of natural enemies of agricultural pests. It is however extremely difficult to disentangle the effects of agricultural intensification on arthropod communities at multiple spatial scales. Based on a two-year study of seventeen 1500 m-radius sites, we analyzed the relative importance of nitrogen input and cropland expansion on cereal aphids and their natural enemies. Both the input of nitrogen fertilizer and cropland expansion benefited cereal aphids more than primary parasitoids and leaf-dwelling predators, while suppressing ground-dwelling predators, leading to an disturbance of the interspecific relationship. The responses of natural enemies to cropland expansion were asymmetric and species-specific, with an increase of primary parasitism but a decline of predator/pest ratio with the increasing nitrogen input. As such, agricultural intensification (increasing nitrogen fertilizer and cropland expansion) can destabilize the interspecific relationship and lead to biodiversity loss. To this end, sustainable pest management needs to balance the benefit and cost of agricultural intensification and restore biocontrol service through proliferating the role of natural enemies at multiple scales. PMID:25620737

Determination of nitrogen balance in agroecosystems.

PubMed

Sainju, Upendra M

2017-01-01

Nitrogen balance in agroecosystems provides a quantitative framework of N inputs and outputs and retention in the soil that examines the sustainability of agricultural productivity and soil and environmental quality. Nitrogen inputs include N additions from manures and fertilizers, atmospheric depositions including wet and dry depositions, irrigation water, and biological N fixation. Nitrogen outputs include N removal in crop grain and biomass and N losses through leaching, denitrification, volatilization, surface runoff, erosion, gas emissions, and plant senescence. Nitrogen balance, which is the difference between N inputs and outputs, can be reflected in changes in soil total (organic + inorganic) N during the course of the experiment duration due to N immobilization and mineralization. While increased soil N retention and mineralization can enhance crop yields and decrease N fertilization rate, reduced N losses through N leaching and gas emissions (primarily NH 4 and NO x emissions, out of which N 2 O is a potent greenhouse gas) can improve water and air quality. •This paper discusses measurements and estimations (for non-measurable parameters due to complexity) of all inputs and outputs of N as well as changes in soil N storage during the course of the experiment to calculate N balance.•The method shows N flows, retention in the soil, and losses to the environment from agroecosystems.•The method can be used to measure agroecosystem performance and soil and environmental quality from agricultural practices.

Atmospheric nitrogen deposition budget in a subtropical hydroelectric reservoir (Nam Theun II case study, Lao PDR)

NASA Astrophysics Data System (ADS)

Adon, Marcellin; Galy-Lacaux, Corinne; Serça, Dominique; Guerin, Frederic; Guedant, Pierre; Vonghamsao, Axay; Rode, Wanidaporn

2016-04-01

With 490 km² at full level of operation, Nam Theun 2 (NT2) is one of the largest hydro-reservoir in South East Asia. NT2 is a trans-basin hydropower project that diverts water from the Nam Theun river (a Mekong tributary) to the Xe Ban Fai river (another Mekong tributary). Atmospheric deposition is an important source of nitrogen (N), and it has been shown that excessive fluxes of N from the atmosphere has resulted in eutrophication of many coastal waters. A large fraction of atmospheric N input is in the form of inorganic N. This study presents an estimation of the atmospheric inorganic nitrogen budget into the NT2 hydroelectric reservoir based on a two-year monitoring (July 2010 to July 2012) including gas concentrations and precipitation. Dry deposition fluxes are calculated from monthly mean surface measurements of NH3, HNO3 and NO2 concentrations (passive samplers) together with simulated deposition velocities, and wet deposition fluxes from NH4+ and NO3- concentrations in single event rain samples (automated rain sampler). Annual rainfall amount was 2500 and 3160 mm for the two years. The average nitrogen deposition flux is estimated at 1.13 kgN.ha-1.yr-1 from dry processes and 5.52 kgN.ha-1.yr-1 from wet ones, i.e., an average annual total nitrogen flux of 6.6 kgN.ha-1.yr-1 deposited into the NT2 reservoir. The wet deposition contributes to 83% of the total N deposition. The nitrogen deposition budget has been also calculated over the rain tropical forest surrounding the reservoir. Due to higher dry deposition velocities above forested ecosystems, gaseous dry deposition flux is estimated at 4.0 kgN.ha-1.yr-1 leading to a total nitrogen deposition about 9.5 kgN.ha-1.yr-1. This result will be compared to nitrogen deposition in the African equatorial forested ecosystems in the framework of the IDAF program (IGAC-DEBITS-AFrica).

Organic and nitrogen removal from landfill leachate in aerobic granular sludge sequencing batch reactors

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

Wei Yanjie; Key Laboratory of Environmental Protection in Water Transport Engineering Ministry of Communications, Tianjin Research Institute of Water Transport Engineering, Tianjin 300456; Ji Min, E-mail: jmtju@yahoo.cn

2012-03-15

Highlights: Black-Right-Pointing-Pointer Aerobic granular sludge SBR was used to treat real landfill leachate. Black-Right-Pointing-Pointer COD removal was analyzed kinetically using a modified model. Black-Right-Pointing-Pointer Characteristics of nitrogen removal at different ammonium inputs were explored. Black-Right-Pointing-Pointer DO variations were consistent with the GSBR performances at low ammonium inputs. - Abstract: Granule sequencing batch reactors (GSBR) were established for landfill leachate treatment, and the COD removal was analyzed kinetically using a modified model. Results showed that COD removal rate decreased as influent ammonium concentration increasing. Characteristics of nitrogen removal at different influent ammonium levels were also studied. When the ammonium concentration inmore » the landfill leachate was 366 mg L{sup -1}, the dominant nitrogen removal process in the GSBR was simultaneous nitrification and denitrification (SND). Under the ammonium concentration of 788 mg L{sup -1}, nitrite accumulation occurred and the accumulated nitrite was reduced to nitrogen gas by the shortcut denitrification process. When the influent ammonium increased to a higher level of 1105 mg L{sup -1}, accumulation of nitrite and nitrate lasted in the whole cycle, and the removal efficiencies of total nitrogen and ammonium decreased to only 35.0% and 39.3%, respectively. Results also showed that DO was a useful process controlling parameter for the organics and nitrogen removal at low ammonium input.« less

The effect of nitrogen rate on vine kill, tuber skinning injury, tuber yield and size distribution, and tuber nutrients and phytonutrients in two potato cultivars grown for early potato production

USDA-ARS?s Scientific Manuscript database

Early potatoes are typically produced using less nitrogen than a full season potato crop as high rates of nitrogen may delay tuber set and lead to excessive vine growth that is difficult to terminate prior to harvest. Bintje and Ciklamen potato cultivars were grown with preplant soil nitrogen levels...

Reactive Nitrogen in Atmospheric Emission Inventories

EPA Science Inventory

Excess reactive Nitrogen (NT) has become one of the most pressing environmental problems leading to air pollution, acidification and eutrophication of ecosystems, biodiversity impacts, leaching of nitrates into groundwater and global warming. This paper investigates how current i...

Genetics Home Reference: gyrate atrophy of the choroid and retina

MedlinePlus

... disorder. Occasionally, newborns with gyrate atrophy develop excess ammonia in the blood (hyperammonemia), which may lead to ... which processes excess nitrogen (in the form of ammonia) that is generated when protein is broken down ...

The stream subsurface: nitrogen cycling and the cleansing function of hyporheic zones

Treesearch

Rhonda Mazza; Steve Wondzell; Jay Zarnetske

2014-01-01

Nitrogen is an element essential to plant growth and ecosystem productivity. Excess nitrogen, however, is a common water pollutant. It can lead to algal blooms that deplete the water's dissolved oxygen, creating "dead zones" devoid of fish and aquatic insects.Previous research showed that the subsurface area of a stream, known as the hyporheic...

Evaluation of a single-stage carbon oxidation-nitrification process for treating high TAN effluent from anaerobic digestion of poultry rendering wastewater

USDA-ARS?s Scientific Manuscript database

Nitrogen is an essential nutrient for plants and animals. However, an excess amount of nitrogen in waterways may lead to anoxic condition and negatively alter various aquatic lifeforms due to their toxicity. Main sources of nitrogen in the environment include the discharge from wastewater treatment ...

Linking Landscape Characteristics and High Stream Nitrogen in the Oregon Coast Range: Red Alder Complicates Use of Nutrient Criteria

EPA Science Inventory

Red alder (a nitrogen-fixing tree) and sea salt inputs can strongly influence stream nitrogen concentrations in western Oregon and Washington. We compiled a database of stream nitrogen and landscape characteristics in the Oregon Coast Range. Basal area of alder, expressed as a ...

Effect of management on nitrogen budgets and implications for air, soil, and water quality

USDA-ARS?s Scientific Manuscript database

Nitrogen is a key nutrient for both national and global food security, and nitrogen inputs from organic and/or inorganic sources are essential to maintain sustainable and economically viable agricultural systems. The challenge with nitrogen is that it is very dynamic and mobile, and some forms are s...

OPPORTUNITIES IN NITROGEN MANAGEMENT RESEARCH; IMPROVING APPLICATIONS FOR PROVEN TECHNOLOGIES AND IDENTIFYING NEW TOOLS FOR MANAGING NITROGEN FLUX AND INPUT IN ECOSYSTEMS

EPA Science Inventory

The presence and distribution of undesirable quantities of bioavailable nitrogenous compounds in the environment are issues of long-standing concern. Importantly for us today, deleterious effects associated with high levels of nitrogen in the ecosystem are becoming everyday news...

[Effects of invasive Cenchrus spinifex on nitrogen pools in sandy grassland].

PubMed

Zhang, Ting; Fu, Wei Dong; Zhang, Rui Hai; Song, Zhen; Bai, Chao; Huang, Cheng Cheng; Zhang, Guo Liang

2017-05-18

Cenchrus spinifex is an invasive plant found in large areas of northern China. In this study, we focused on analysis of the effects of C. spinifex on soil nitrogen and plant nitrogen pools in Horqin sandy grassland. In addition, a pot experiment with 15 N tracing techniques was designed to study the biological nitrogen fixation ability of C. spinifex, compared with two native grasses, Elymus dahuricus and Agropyron cristatum. The total soil nitrogen pool in C. spinifex invaded-area increased significantly by 47.5% and 20.8%, and the soil ammonium nitrogen pool decreased significantly by 25.6% and 25.2%, compared with those in bare and native plant Roegneria kamoji areas, respectively. The plant shoot nitrogen pool decreased significantly by 18.7% in C. spinifex compared with native plant R. kamoji. Atom% 15 N, atom% 15 N excess and atom% 15 N weighting excess of C. spinifex were all significantly lower than those of E. dahuricus and A. cristatum. The nitrogen use efficiencies of C. spinifex and E. dahuricus were 48.5% and 47.0%, respectively, and no significant difference was observed. Ndfa of C. spinifex accounted for 60.2%, when growing together with E. dahuricus. These results suggested that the characteristics on the high efficient use for nitrogen of this invasive weed might an ecological adaptation mechanism, leading to successful colonization and spread in Horqin Steppe.

Oxidized Nitrogen in Precipitation, Throughfall, and Streamfall from a Forested Watershed in Oklahoma

USGS Publications Warehouse

Lawrence, Stephen J.; Wigington, Parker J.

1987-01-01

Oxidized nitrogen (nitrite plus nitrate N) concentrations were measured from bulk precipitation, bulk throughfall, and screamflow in a 7. 86 hectare forested watershed in southeastern Oklahoma during the wet season from March through June 1983. Oxidized nitrogen inputs comparable to results of other studies were recorded during the 19 rainstorms sampled. Oxidized nitrogen concentrations appeared to increase after rainfall interacted with the pine and hardwood canopies and were inversely related to both rainfall and throughfall depth. Oxidized N concentrations in streamflow were greatest during the rising limb of storm flow with subsequent decreases during the falling limb of storm hydrographs and lowest during base flow. The oxidized N inputs from bulk precipitation were considerably greater than outputs from streamflow resulting in a net retention of oxidized nitrogen within the watershed during the study period.

Nitrogen addition affects leaf nutrition and photosynthesis in sugar maple in a nutrient-poor northern Vermont forest

Treesearch

David S. Ellsworth

1999-01-01

Sugar maple-dominated forest ecosystems in the northeastern U.S. have been receiving precipitation nitrogen (N) inputs of 15 -20 kg N ha1 year1 since at least the mid 1980s sustained chronic N inputs of this magnitude into nutrient-poor forest ecosystems may cause eutrophication and affect ecosystem functioning as well as...

The relative importance of oceanic nutrient inputs for Bass Harbor Marsh Estuary at Acadia National Park, Maine

USGS Publications Warehouse

Huntington, Thomas G.; Culbertson, Charles W.; Fuller, Christopher; Glibert, Patricia; Sturtevant, Luke

2014-01-01

The U.S. Geological Survey and Acadia National Park (ANP) collaborated on a study of nutrient inputs into Bass Harbor Marsh Estuary on Mount Desert Island, Maine, to better understand ongoing eutrophication, oceanic nutrient inputs, and potential management solutions. This report includes the estimation of loads of nitrate, ammonia, total dissolved nitrogen, and total dissolved phosphorus to the estuary derived from runoff within the watershed and oceanic inputs during summers 2011 and 2012. Nutrient outputs from the estuary were also monitored, and nutrient inputs in direct precipitation to the estuary were calculated. Specific conductance, water temperature, and turbidity were monitored at the estuary outlet. This report presents a first-order analysis of the potential effects of projected sea-level rise on the inundated area and estuary volume. Historical aerial photographs were used to investigate the possibility of widening of the estuary channel over time. The scope of this report also includes analysis of sediment cores collected from the estuary and fringing marsh surfaces to assess the sediment mass accumulation rate. Median concentrations of nitrate, ammonium, and total dissolved phosphorus on the flood tide were approximately 25 percent higher than on the ebb tide during the 2011 and 2012 summer seasons. Higher concentrations on the flood tide suggest net assimilation of these nutrients in biota within the estuary. The dissolved organic nitrogen fraction dominated the dissolved nitrogen fraction in all tributaries. The median concentration of dissolved organic nitrogen was about twice as high on the on the ebb tide than the flood tide, indicating net export of dissolved organic nitrogen from the estuary. The weekly total oceanic inputs of nitrate, ammonium, and total dissolved phosphorus to the estuary were usually much larger than inputs from runoff or direct precipitation. The estuary was a net sink for nitrate and ammonium in most weeks during both years. Oceanic inputs of nitrate and ammonium were an important source of inorganic nitrogen to the estuary in both years. In both years, the total seasonal inputs of ammonium to the estuary in flood tides were much larger than the inputs from watershed runoff or direct precipitation. In 2011, the total seasonal input of nitrate from flood tides to the estuary was more than twice as large the inputs from watershed runoff and precipitation, but in 2012, the inputs from flood tides were only marginally larger than the inputs from watershed runoff and precipitation. Turbidity was measured intermittently in 2012, and the pattern that emerged from the measurements indicated that the estuary was a source of particulate matter to the ocean rather than the ocean being a source to the estuary. From the nutrient budgets determined for the estuary it is evident that oceanic sources of nitrate and ammonium are an important part of the supply of nutrients that are contributing to the growth of macroalgae in the estuary. The relative importance of these oceanic nutrients compared with sources within the watershed typically increases as the summer progresses and runoff decreases. It is likely that rising sea levels, estimated by the National Oceanic and Atmospheric Administration to be 11 centimeters from 1950 through 2006 in nearby Bar Harbor, have resulted in an increase in oceanic inputs (tidal volume and nutrients derived from oceanic sources).

Effects of different N sources on riverine DIN export and retention in a subtropical high-standing island, Taiwan

PubMed Central

Huang, Jr-Chuan; Lee, Tsung-Yu; Lin, Teng-Chiu; Hein, Thomas; Lee, Li-Chin; Shih, Yu-Ting; Kao, Shuh-Ji; Shiah, Fuh-Kwo; Lin, Neng-Huei

2016-01-01

Increases in nitrogen (N) availability and mobility resulting from anthropogenic activities have substantially altered the N cycle, both locally and globally. Taiwan characterized by the subtropical montane landscape with abundant rainfall, downwind of the most rapidly industrializing eastern coast of China, can be a demonstration site for extremely high N input and riverine DIN (dissolved inorganic N) export. We used 49 watersheds with similar climatic and landscape settings but classified into low, moderate, and highly disturbed categories based on population density to illustrate their differences in nitrogen inputs (through atmospheric N deposition, synthetic fertilizers, and human emission) and DIN export ratios. Our results showed that the island-wide average riverine DIN export is ~ 3800 kg N km−2 yr−1, approximately 18 times the global average. The average riverine DIN export ratios are 0.30−0.51, which are much higher than the averages of 0.20−0.25 of large rivers around the world, indicating excessive N input relative to ecosystem demand or retention capacity. The low disturbed watersheds have a high N retention capacity and DIN export ratios of 0.06−0.18 in spite of the high N input (~ 4900 kg N km−2 yr−1). The high retention capacity is likely due to effective uptake by secondary forests in the watersheds. The moderately disturbed watersheds show a linear increase in DIN export with increases in total N inputs and mean DIN export ratios of 0.20 to 0.31. The main difference in land use between low and moderately disturbed watersheds is the greater proportion of agricultural land cover in the moderately disturbed watersheds. Thus, their greater DIN export could be attributed to N fertilizers used in the agricultural lands. The greater export ratios also imply that agricultural lands have a lower proportional N retention capacity and that reforestation could be an effective land management practice to reduce riverine DIN export. The export ratios of the highly disturbed watersheds are very high, 0.42–0.53, suggesting that much of the N input is transported downstream directly, and urges the need to increase the proportion of households connected to a sewage system and improve the effectiveness of wastewater treatment systems. The increases in the riverine DIN export ratio along the gradient of human disturbance also suggest a gradient in N saturation in subtropical Taiwan. Our results help to improve our understanding of factors controlling riverine DIN export and provide empirical evidence that calls for sound N emission/pollution control measures. PMID:27212969

Effects of different N sources on riverine DIN export and retention in a subtropical high-standing island, Taiwan.

PubMed

Huang, Jr-Chuan; Lee, Tsung-Yu; Lin, Teng-Chiu; Hein, Thomas; Lee, Li-Chin; Shih, Yu-Ting; Kao, Shuh-Ji; Shiah, Fuh-Kwo; Lin, Neng-Huei

Increases in nitrogen (N) availability and mobility resulting from anthropogenic activities have substantially altered the N cycle, both locally and globally. Taiwan characterized by the subtropical montane landscape with abundant rainfall, downwind of the most rapidly industrializing eastern coast of China, can be a demonstration site for extremely high N input and riverine DIN (dissolved inorganic N) export. We used 49 watersheds with similar climatic and landscape settings but classified into low, moderate, and highly disturbed categories based on population density to illustrate their differences in nitrogen inputs (through atmospheric N deposition, synthetic fertilizers, and human emission) and DIN export ratios. Our results showed that the island-wide average riverine DIN export is ~ 3800 kg N km -2 yr -1 , approximately 18 times the global average. The average riverine DIN export ratios are 0.30-0.51, which are much higher than the averages of 0.20-0.25 of large rivers around the world, indicating excessive N input relative to ecosystem demand or retention capacity. The low disturbed watersheds have a high N retention capacity and DIN export ratios of 0.06-0.18 in spite of the high N input (~ 4900 kg N km -2 yr -1 ). The high retention capacity is likely due to effective uptake by secondary forests in the watersheds. The moderately disturbed watersheds show a linear increase in DIN export with increases in total N inputs and mean DIN export ratios of 0.20 to 0.31. The main difference in land use between low and moderately disturbed watersheds is the greater proportion of agricultural land cover in the moderately disturbed watersheds. Thus, their greater DIN export could be attributed to N fertilizers used in the agricultural lands. The greater export ratios also imply that agricultural lands have a lower proportional N retention capacity and that reforestation could be an effective land management practice to reduce riverine DIN export. The export ratios of the highly disturbed watersheds are very high, 0.42-0.53, suggesting that much of the N input is transported downstream directly, and urges the need to increase the proportion of households connected to a sewage system and improve the effectiveness of wastewater treatment systems. The increases in the riverine DIN export ratio along the gradient of human disturbance also suggest a gradient in N saturation in subtropical Taiwan. Our results help to improve our understanding of factors controlling riverine DIN export and provide empirical evidence that calls for sound N emission/pollution control measures.

Effects of different N sources on riverine DIN export and retention in a subtropical high-standing island, Taiwan

NASA Astrophysics Data System (ADS)

Huang-Chuan, Jr.; Lee, Tsung-Yu; Lin, Teng-Chiu; Hein, Thomas; Lee, Li-Chin; Shih, Yu-Ting; Kao, Shuh-Ji; Shiah, Fuh-Kwo; Lin, Neng-Huei

2016-03-01

Increases in nitrogen (N) availability and mobility resulting from anthropogenic activities have substantially altered the N cycle, both locally and globally. Taiwan characterized by the subtropical montane landscape with abundant rainfall, downwind of the most rapidly industrializing eastern coast of China, can be a demonstration site for extremely high N input and riverine DIN (dissolved inorganic N) export. We used 49 watersheds with similar climatic and landscape settings but classified into low, moderate, and highly disturbed categories based on population density to illustrate their differences in nitrogen inputs (through atmospheric N deposition, synthetic fertilizers, and human emission) and DIN export ratios. Our results showed that the island-wide average riverine DIN export is ˜ 3800 kg N km-2 yr-1, approximately 18 times the global average. The average riverine DIN export ratios are 0.30-0.51, which are much higher than the averages of 0.20-0.25 of large rivers around the world, indicating excessive N input relative to ecosystem demand or retention capacity. The low disturbed watersheds have a high N retention capacity and DIN export ratios of 0.06-0.18 in spite of the high N input (˜ 4900 kg N km-2 yr-1). The high retention capacity is likely due to effective uptake by secondary forests in the watersheds. The moderately disturbed watersheds show a linear increase in DIN export with increases in total N inputs and mean DIN export ratios of 0.20 to 0.31. The main difference in land use between low and moderately disturbed watersheds is the greater proportion of agricultural land cover in the moderately disturbed watersheds. Thus, their greater DIN export could be attributed to N fertilizers used in the agricultural lands. The greater export ratios also imply that agricultural lands have a lower proportional N retention capacity and that reforestation could be an effective land management practice to reduce riverine DIN export. The export ratios of the highly disturbed watersheds are very high, 0.42-0.53, suggesting that much of the N input is transported downstream directly, and urges the need to increase the proportion of households connected to a sewage system and improve the effectiveness of wastewater treatment systems. The increases in the riverine DIN export ratio along the gradient of human disturbance also suggest a gradient in N saturation in subtropical Taiwan. Our results help to improve our understanding of factors controlling riverine DIN export and provide empirical evidence that calls for sound N emission/pollution control measures.

A Novel Hybrid Approach for Estimating Total Deposition in the United States

EPA Science Inventory

Atmospheric deposition of nitrogen and sulfur causes many deleterious effects on ecosystems including acidification and excess eutrophication. Assessments to support development of strategies to mitigate these effects require spatially and temporally continuous values of nitrogen...

A Hybrid Approach for Estimating Total Deposition in the United States

EPA Science Inventory

Atmospheric deposition of nitrogen and sulfur causes many deleterious effects on ecosystems including acidification and excess eutrophication. Assessments to support development of strategies to mitigate these effects require spatially and temporally continuous values of nitrogen...

RESEARCH SHOWS IMPORTANCE OF RIPARIAN BUFFERS FOR AQUATIC HEALTH

EPA Science Inventory

Issue: Excess nitrogen from fertilizer, septic tanks, animal feedlots, and runoff from pavement can threaten aquatic ecosystem health. Riparian buffers -- the vegetated region adjacent to streams and wetlands -- are thought to be effective at intercepting and controlling excess ...

DEVELOPING INDICATORS OF NITROGEN SOURCE IN COASTAL ECOSYSTEMS

EPA Science Inventory

Several studies have linked stable isotope ratios of biota to nitrogen source. In particular, ribbed mussels show promise as sensitive indicators of the origins of nitrogen inputs to coastal ecosystems. Here we expand on previous work which demonstrated that mussel isotope ratios...

Watershed delineation and nitrogen source analysis for Bayou Chico, an urban watershed in northwest Florida

EPA Science Inventory

Nutrient pollution in stormwater runoff from urbanized areas contributes to water quality degradation in streams and receiving waterbodies. Agriculture, population growth, and industrial activities are significant sources of nitrogen inputs for surface waters. Increased nitrogen ...

THE EFFECTS OF NITROGEN LOADING AND FRESHWATER RESIDENCE TIME ON THE ESTUARINE ECOSYSTEM

EPA Science Inventory

A simple mechanistic model, designed to predict annual average concentrations of total nitrogen (TN) concentrations from nitrogen inputs and freshwater residence time in estuaries, was applied to data for several North American estuaries from previously published literature. The ...

Groundwater Discharge of Legacy Nitrogen to River Networks: Linking Regional Groundwater Models to Streambed Groundwater-Surface Water Exchange and Nitrogen Processing

NASA Astrophysics Data System (ADS)

Barclay, J. R.; Helton, A. M.; Briggs, M. A.; Starn, J. J.; Hunt, A.

2017-12-01

Despite years of management, excess nitrogen (N) is a pervasive problem in many aquatic ecosystems. More than half of surface water in the United States is derived from groundwater, and widespread N contamination in aquifers from decades of watershed N inputs suggest legacy N discharging from groundwater may contribute to contemporary N pollution problems in surface waters. Legacy N loads to streams and rivers are controlled by both regional scale flow paths and fine-scale processes that drive N transformations, such as groundwater-surface water exchange across steep redox gradients that occur at stream bed interfaces. Adequately incorporating these disparate scales is a challenge, but it is essential to understanding legacy N transport and making informed management decisions. We developed a regional groundwater flow model for the Farmington River, a HUC-8 basin that drains to the Long Island Sound, a coastal estuary that suffers from elevated N loads despite decades of management, to understand broad patterns of regional transport. To evaluate and refine the regional model, we used thermal infrared imagery paired with vertical temperature profiling to estimate groundwater discharge at the streambed interface. We also analyzed discharging groundwater for multiple N species to quantify fine scale patterns of N loading and transformation via denitrification at the streambed interface. Integrating regional and local estimates of groundwater discharge of legacy N to river networks should improve our ability to predict spatiotemporal patterns of legacy N loading to and transformation within surface waters.

Atmospheric nutrient inputs to the northern levantine basin from a long-term observation: sources and comparison with riverine inputs

NASA Astrophysics Data System (ADS)

Koçak, M.; Kubilay, N.; Tuğrul, S.; Mihalopoulos, N.

2010-12-01

Aerosol and rainwater samples have been collected at a rural site located on the coastline of the Eastern Mediterranean, Erdemli, Turkey between January 1999 and December 2007. Riverine sampling was carried out at five Rivers (Ceyhan, Seyhan, Göksu, Berdan and Lamas) draining into the Northeastern Levantine Basin (NLB) between March 2002 and July 2007. Samples have been analyzed for macronutrients of phosphate, silicate, nitrate and ammonium (PO43-, Sidiss, NO3- and NH4+). Phosphate and silicate in aerosol and rainwater showed higher and larger variations during the transitional period when air flows predominantly originate from North Africa and Middle East/Arabian Peninsula. Deficiency of alkaline material have been found to be the main reason of the acidic rain events whilst high pH values (>7) have been associated with high Sidiss concentrations due to sporadic dust events. In general, lowest nitrate and ammonium concentrations in aerosol and rainwater have been associated with air flow from the Mediterranean Sea. Comparison of atmospheric with riverine fluxes demonstrated that DIN and PO43- fluxes to NLB have been dominated by atmosphere (~90% and ~60% respectively) whereas the input of Si was mainly derived from riverine runoff (~90%). N/P ratios in the atmospheric deposition (233); riverine discharge (28) revealed that NLB receives excessive amounts of DIN and this unbalanced P and N inputs may provoke even more phosphorus deficiency. Observed molar Si/N ratio suggested Si limitation relative to nitrogen might cause a switch from diatom dominated communities to non-siliceous populations particularly at coastal NLB.

Benthic biogeochemical cycling, nutrient stoichiometry, and carbon and nitrogen mass balances in a eutrophic freshwater bay

USGS Publications Warehouse

Klump, J.V.; Fitzgerald, S.A.; Waplesa, J.T.

2009-01-01

Green Bay, while representing only ,7% of the surface area and ??1.4% of the volume of Lake Michigan, contains one-third of the watershed of the lake, and receives approximately one-third of the total nutrient loading to the Lake Michigan basin, largely from the Fox River at the southern end of the bay. With a history of eutrophic conditions dating back nearly a century, the southern portion of the bay behaves as an efficient nutrient and sediment trap, sequestering much of the annual carbon and nitrogen input within sediments accumulating at up to 1 cm per year. Depositional fluxes of organic matter varied from ??0.1 mol C m-2 yr-1 to >10 mol C m-2 yr-1 and were both fairly uniform in stoichiometric composition and relatively labile. Estimates of benthic recycling derived from pore-water concentration gradients, whole-sediment incubation experiments, and deposition-burial models of early diagenesis yielded an estimated 40% of the carbon and 50% of the nitrogen recycled back into the overlying water. Remineralization was relatively rapid with ??50% of the carbon remineralized within <15 yr of deposition, and a mean residence time for metabolizable carbon and nitrogen in the sediments of 20 yr. On average, organic carbon regeneration occurred as 75% CO2, 15% CH4, and 10% dissolved organic carbon (DOC). Carbon and nitrogen budgets for the southern bay were based upon direct measurements of inputs and burial and upon estimates of export and production derived stoichiometrically from a coupled phosphorus budget. Loadings of organic carbon from rivers were ??3.7 mol m-2 yr-1, 80% in the form of DOC and 20% as particulate organic carbon. These inputs were lost through export to northern Green Bay and Lake Michigan (39%), through sediment burial (26%), and net CO2 release to the atmosphere (35%). Total carbon input, including new production, was 4.54 mol m-2 C yr-1, equivalent to ??10% of the gross annual primary production. Nitrogen budget terms were less well quantified, with nitrogen export ??54% of total inputs and burial ??24%, leaving an unquantified residual loss term in the nitrogen budget of ??22%. ?? 2009.

Hypochlorite-induced damage to proteins: formation of nitrogen-centred radicals from lysine residues and their role in protein fragmentation.

PubMed Central

Hawkins, C L; Davies, M J

1998-01-01

Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl damages proteins by reaction with amino acid side-chains or backbone cleavage. Little information is available about the mechanisms and intermediates involved in these reactions. EPR spin trapping has been employed to identify radicals on proteins, peptides and amino acids after treatment with HOCl. Reaction with HOCl gives both high- and low-molecular-mass nitrogen-centred, protein-derived radicals; the yield of the latter increases with both higher HOCl:protein ratios and enzymic digestion. These radicals, which arise from lysine side-chain amino groups, react with ascorbate, glutathione and Trolox. Reaction of HOCl-treated proteins with excess methionine eliminates radical formation, which is consistent with lysine-derived chloramines (via homolysis of N-Cl bonds) being the radical source. Incubation of HOCl-treated proteins, after removal of excess oxidant, gives rise to both nitrogen-centred radicals, over a period of hours, and time-dependent fragmentation of the protein. Treatment with excess methionine or antioxidants (Trolox, ascorbate, glutathione) protects against fragmentation; urate and bilirubin do not. Chloramine formation and nitrogen-centred radicals are therefore key species in HOCl-induced protein fragmentation. PMID:9620862

Land Application of Wastes: An Educational Program. Nitrogen Considerations - Module 15, Objectives, Script and Booklet.

ERIC Educational Resources Information Center

Clarkson, W. W.; And Others

This module expands on the introductory discussion of nitrogen in other modules. The various chemical forms of nitrogen found in land treatment systems are defined. Inputs from waste application as well as natural sources are quantified for typical situations. A discussion of nitrogen transformations in the soil includes mineralization and…

Input-output budgets of inorganic nitrogen for 24 forest watersheds in the northeastern United States: a review

Treesearch

John L. Campbell; James W. Hornbeck; Myron J. Mitchell; Mary Beth Adams; Mark S. Castro; Charles T. Driscoll; Jeffrey S. Kahl; James N. Kochenderfer; Gene E. Likens; James A. Lynch; Peter S. Murdoch; Sarah J. Nelson; James B. Shanley

2004-01-01

Input-output budgets for dissolved inorganic nitrogen (DIN) are summarized for 24 small watersheds at 15 locations in the northeastern United States. The study watersheds are completely forested, free of recent physical disturbances, and span a geographical region bounded by West Virginia on the south and west, and Maine on the north and east. Total N budgets are not...

Carbon source recovery from excess sludge by mechanical disintegration for biological denitrification.

PubMed

Zubrowska-Sudol, M

2018-04-01

The goal of the study was to evaluate the possibility of carbon source recovery from excess sludge by mechanical disintegration for biological denitrification. The total efficiency of denitrification, unit demand for organic compounds for denitrification, unit volume of disintegrated sludge and unit cost of nitrogen removal as a function of energy density used for excess sludge disintegration (70, 140 and 210 kJ/L) were analyzed. In the study a full-scale disc disintegrator was used (motor power: 30 kWh, motor speed: 2,950 rpm). It was shown that the amounts of organic compounds released from the activated sludge flocs at all tested levels of energy density are high enough to be used to intensify the removal of nitrogen compounds from wastewater. It was also documented that the energy density provided during process of disintegration was an important factor determining the characteristics of organic compounds obtained under the disintegration for their use in order to intensify the process of denitrification. The highest value of total efficiency of denitrification (50.5 ± 3.1 mg N/L) was obtained for carbon source recovery from excess sludge at 70 kJ/L, but the lowest unit cost of nitrogen removal occurred for 140 kJ/L (0.0019 ± 0.0011 EUR/g N).

Nitrogen in agricultural systems: Implications for conservation policy

USDA-ARS?s Scientific Manuscript database

Nitrogen is an important agricultural input that is critical for providing food to feed a growing world population. However, the introduction of large amount of reactive nitrogen into the environment has a number of undesirable impacts on water, terrestrial, and atmospheric resources. Careful manage...

Nitrogen management and the future of food: Lessons from the management of energy and carbon

PubMed Central

Socolow, Robert H.

1999-01-01

The food system dominates anthropogenic disruption of the nitrogen cycle by generating excess fixed nitrogen. Excess fixed nitrogen, in various guises, augments the greenhouse effect, diminishes stratospheric ozone, promotes smog, contaminates drinking water, acidifies rain, eutrophies bays and estuaries, and stresses ecosystems. Yet, to date, regulatory efforts to limit these disruptions largely ignore the food system. There are many parallels between food and energy. Food is to nitrogen as energy is to carbon. Nitrogen fertilizer is analogous to fossil fuel. Organic agriculture and agricultural biotechnology play roles analogous to renewable energy and nuclear power in political discourse. Nutrition research resembles energy end-use analysis. Meat is the electricity of food. As the agriculture and food system evolves to contain its impacts on the nitrogen cycle, several lessons can be extracted from energy and carbon: (i) set the goal of ecosystem stabilization; (ii) search the entire production and consumption system (grain, livestock, food distribution, and diet) for opportunities to improve efficiency; (iii) implement cap-and-trade systems for fixed nitrogen; (iv) expand research at the intersection of agriculture and ecology, and (v) focus on the food choices of the prosperous. There are important nitrogen-carbon links. The global increase in fixed nitrogen may be fertilizing the Earth, transferring significant amounts of carbon from the atmosphere to the biosphere, and mitigating global warming. A modern biofuels industry someday may produce biofuels from crop residues or dedicated energy crops, reducing the rate of fossil fuel use, while losses of nitrogen and other nutrients are minimized. PMID:10339531

Application of a Two-Dimensional Reservoir Water-Quality Model of Beaver Lake, Arkansas, for the Evaluation of Simulated Changes in Input Water Quality, 2001-2003

USGS Publications Warehouse

Galloway, Joel M.; Green, W. Reed

2007-01-01

Beaver Lake is considered a primary watershed of concern in the State of Arkansas. As such, information is needed to assess water quality, especially nutrient enrichment, nutrient-algal relations, turbidity, and sediment issues within the system. A previously calibrated two-dimensional, laterally averaged model of hydrodynamics and water quality was used for the evaluation of changes in input nutrient and sediment concentrations on the water quality of the reservoir for the period of April 2001 to April 2003. Nitrogen and phosphorus concentrations were increased and decreased and tested independently and simultaneously to examine the nutrient concentrations and algal response in the reservoir. Suspended-solids concentrations were increased and decreased to identify how solids are distributed in the reservoir, which can contribute to decreased water clarity. The Beaver Lake model also was evaluated using a conservative tracer. A conservative tracer was applied at various locations in the reservoir model to observe the fate and transport and how the reservoir might react to the introduction of a conservative substance, or a worst-case spill scenario. In particular, tracer concentrations were evaluated at the locations of the four public water-supply intakes in Beaver Lake. Nutrient concentrations in Beaver Lake increased proportionally with increases in loads from the three main tributaries. An increase of 10 times the calibrated daily input nitrogen and phosphorus in the three main tributaries resulted in daily mean total nitrogen concentrations in the epilimnion that were nearly 4 times greater than the calibration concentrations at site L2 and more than 2 times greater than the calibrated concentrations at site L5. Increases in daily input nitrogen in the three main tributaries independently did not correspond in substantial increases in concentrations of nitrogen in Beaver Lake. The greatest proportional increase in phosphorus occurred in the epilimnion at sites L3 and L4 and the least increase occurred at sites L2 and L5 when calibrated daily input phosphorus concentrations were increased. When orthophosphorus was increased in all three tributaries simultaneously by a factor of 10, daily mean orthophosphorus concentrations in the epilimnion of the reservoir were almost 11 times greater than the calibrated concentrations at sites L2 and L5, and 15 times greater in the epilimnion of the reservoir at sites L3 and L4. Phosphorus concentrations in Beaver Lake increased less when nitrogen and phosphorus were increased simultaneously than when phosphorus was increased independently. The greatest simulated increase in algal biomass (represented as chlorophyll a) occurred when nitrogen and phosphorus were increased simultaneously in the three main tributaries. On average, the chlorophyll a values only increased less than 1 microgram per liter when concentrations of nitrogen or phosphorous were increased independently by a factor of 10 at all three tributaries. In comparison, when nitrogen and phosphorus were increased simultaneously by a factor of 10 for all three tributaries, the chlorophyll a concentration increased by about 10 micrograms per liter on average, with a maximum increase of about 57 micrograms per liter in the epilimnion at site L3 in Beaver Lake. Changes in algal biomass with changes in input nitrogen and phosphorus were variable through time in the Beaver Lake model from April 2001 to April 2003. When calibrated daily input nitrogen and phosphorus concentrations were increased simultaneously for the three main tributaries, the increase in chlorophyll a concentration was the greatest in late spring and summer of 2002. Changes in calibrated daily input inorganic suspended solids concentrations were examined because of the effect they may have on water clarity in Beaver Lake. The increase in total suspended solids was greatest in the hypolimnion at the upstream end of Beaver Lake, and negligible changes

High frequency measurements of reach scale nitrogen uptake in a fourth order river with contrasting hydromorphology and variable water chemistry (Weiße Elster, Germany)

NASA Astrophysics Data System (ADS)

Kunz, Julia Vanessa; Hensley, Robert; Brase, Lisa; Borchardt, Dietrich; Rode, Michael

2017-01-01

River networks exhibit a globally important capacity to retain and process nitrogen. However direct measurement of in-stream removal in higher order streams and rivers has been extremely limited. The recent advent of automated sensors has allowed high frequency measurements, and the development of new passive methods of quantifying nitrogen uptake which are scalable across river size. Here we extend these methods to higher order streams with anthropogenically elevated nitrogen levels, substantial tributaries, complex input signals, and multiple N species. We use a combination of two station time-series and longitudinal profiling of nitrate to assess differences in nitrogen processing dynamics in a natural versus a channelized impounded reach with WWTP effluent impacted water chemistry. Our results suggest that net mass removal rates of nitrate were markedly higher in the unmodified reach. Additionally, seasonal variations in temperature and insolation affected the relative contribution of assimilatory versus dissimilatory uptake processes, with the latter exhibiting a stronger positive dependence on temperature. From a methodological perspective, we demonstrate that a mass balance approach based on high frequency data can be useful in deriving quantitative uptake estimates, even under dynamic inputs and lateral tributary inflow. However, uncertainty in diffuse groundwater inputs and more importantly the effects of alternative nitrogen species, in this case ammonium, pose considerable challenges to this method.

Modeling of the mesoscale structure of coupled upwelling/downwelling events and the related input of nutrients to the upper mixed layer in the Gulf of Finland, Baltic Sea

NASA Astrophysics Data System (ADS)

Zhurbas, Victor; Laanemets, Jaan; Vahtera, Emil

2008-05-01

A high resolution numerical study is undertaken to simulate an upwelling event along the northern coast of the Gulf of Finland, 21-29 July 1999, which was documented well by in situ and remote measurements. The simulated sequence of SST maps shows a reasonably good resemblance to that of satellite infrared imagery, including both mesoscale coherent structures (filaments or squirts) and the whole process of post-upwelling relaxation of the temperature field. Upwelling along the northern coast of the Gulf is accompanied by downwelling along the southern coast so that two longshore baroclinic jets and related fronts are developed simultaneously. When the strong westerly winds producing the upwelling/downwelling weaken, the longshore jets become unstable and produce transverse jets, cold/warm water squirts. Using pseudo-random simulated fields of temperature and velocity of currents, the apparent lateral diffusivity due to squirts is directly estimated at 500 m2 s-1. The model is also applied to estimate nutrient transport. Simulated phosphate concentration in the surface layer at the cold side of upwelling front is found to be about 0.3 mmol m-3 which is consistent with observations. The total content of phosphorus and nitrogen in the upper 10 m layer of the Gulf introduced by the upwelling event is estimated to be 387 and 36 tons, respectively. It follows, that the upwelling event transports nutrients into the upper layer with clear excess of phosphorus (N:P = 36:387 = 0.093) compared to the Redfield ratio of 7.2. Therefore phosphorus input caused by upwelling during summer most likely promotes nitrogen-fixing cyanobacteria blooms.

Nitrogen dynamics in an Alaskan salt marsh following spring use by geese

USGS Publications Warehouse

Zacheis, Amy B.; Ruess, Roger W.; Hupp, Jerry W.

2002-01-01

Lesser snow geese (Anser caerulescens caerulescens) and Canada geese (Branta canadensis) use several salt marshes in Cook Inlet, Alaska, as stopover areas for brief periods during spring migration. We investigated the effects of geese on nitrogen cycling processes in Susitna Flats, one of the marshes. We compared net nitrogen mineralization, organic nitrogen pools and production in buried bags, nitrogen fixation by cyanobacteria, and soil and litter characteristics on grazed plots versus paired plots that had been exclosed from grazing for 3 years. Grazed areas had higher rates of net nitrogen mineralization in the spring and there was no effect of grazing on organic nitrogen availability. The increased mineralization rates in grazed plots could not be accounted for by alteration of litter quality, litter quantity, microclimate, or root biomass, which were not different between grazed and exclosed plots. In addition, fecal input was very slight in the year that we studied nitrogen cycling. We propose that trampling had two effects that could account for greater nitrogen availability in grazed areas: litter incorporation into soil, resulting in increased rates of decomposition and mineralization of litter material, and greater rates of nitrogen fixation by cyanobacteria on bare, trampled soils. A path analysis indicated that litter incorporation by trampling played a primary role in the nitrogen dynamics of the system, with nitrogen fixation secondary, and that fecal input was of little importance.

Watershed delineation and nitrogen source analysis for Bayou ...

EPA Pesticide Factsheets

Nutrient pollution in stormwater runoff from urbanized areas contributes to water quality degradation in streams and receiving waterbodies. Agriculture, population growth, and industrial activities are significant sources of nitrogen inputs for surface waters. Increased nitrogen loading stimulates eutrophication through algal blooms, which leads to an overall decrease in drinking water and aquatic habitat quality. Bayou Chico, a highly urbanized watershed in the Pensacola Bay system in northwest Florida, is a nutrient-impaired waterbody under management to reduce bacteria and nutrient loadings, in accordance with the Florida Department of Environmental Protection’s (FDEP) Basin Management Action Plan. Best management practices and green infrastructure (GI) throughout Bayou Chico help reduce nitrogen inputs by retaining and filtering water. GI can function as a nitrogen sink by sorption or infiltration into soils, sequestration into plant material, and denitrification through microbial processes. However, a better understanding of the efficiency of these systems is needed to better inform management practices on future nitrogen reduction. This project will address two issues relating to the presence of nitrogen in the Bayou Chico watershed: 1) the identification of specific nitrogen sources within urbanized areas, and 2) the potential rates of nitrogen removal and sequestration from GI and nitrogen transport throughout the bayou. To accomplish these goals, nitr

Using Remote Sensing Data to Update a Dynamic Regional-Scale Water Quality Model

NASA Astrophysics Data System (ADS)

Smith, R. A.; Nolin, A.; Brakebill, J.; Sproles, E.; Macauley, M.

2012-04-01

Regional scale SPARROW models, used by the US Geological Survey, relate watershed characteristics to in stream water quality. SPARROW models are widely used to identify and quantify the sources of contaminants in watersheds and to predict their flux and concentration at specified locations downstream. Conventional SPARROW models are steady-state models and describe the average relationship between sources and stream conditions based on long-term water quality monitoring data and spatially referenced explanatory information. However, many watershed management issues stem from intra- and inter-annual changes in contaminant sources, hydrologic forcing, or other environmental conditions, which cause a temporary imbalance between inputs and stream water quality. Dynamic behavior of the system relating to changes in watershed storage and processing then becomes important. Here, we describe a dynamically calibrated SPARROW model of total nitrogen flux in the Potomac River Basin based on seasonal water quality and watershed input data for 80 monitoring stations over the period 2000 to 2008. One challenge in dynamic modeling of reactive nitrogen is obtaining spatially detailed and sufficiently frequent input data on the phenology of agricultural production and terrestrial vegetation. We use the Enhanced Vegetation Index (EVI) and gross primary productivity data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) Terra satellite to parameterize seasonal uptake and release of nitrogen. The spatial reference frame of the model is a 16,000-reach, 1:100,000-scale stream network, and the computational time step is seasonal. Precipitation and temperature data are from the PRISM gridded data set, augmented with snow frequency derived from MODIS. The model formulation allows for separate storage compartments for nonpoint sources including fertilized cropland, pasture, urban land, and atmospheric deposition. Removal of nitrogen from watershed storage to stream channels and to "permanent" sinks (deep groundwater and the atmosphere) occur as parallel first-order processes. We use the model to explore an important issue in nutrient management in the Potomac and other basins: the long-term response of total nitrogen flux to changing climate. We model the nitrogen flux response to projected seasonal and inter-annual changes in temperature and precipitation, but under current seasonal nitrogen inputs, as indicated by MODIS measures of productivity. Under these constant inter-annual inputs, changing temperature and precipitation are predicted to lead to flux changes as temporary basin stores of nitrogen either grow or shrink due to changing relative rates of nitrogen removal to the atmosphere and release to streams.

Fertilizing Nature: A Tragedy of Excess in the Commons

PubMed Central

Good, Allen G.; Beatty, Perrin H.

2011-01-01

Globally, we are applying excessive nitrogen (N) fertilizers to our agricultural crops, which ultimately causes nitrogen pollution to our ecosphere. The atmosphere is polluted by N2O and NOx gases that directly and indirectly increase atmospheric warming and climate change. Nitrogen is also leached from agricultural lands as the water-soluble form NO3 −, which increases nutrient overload in rivers, lakes, and oceans, causing “dead zones”, reducing property values and the diversity of aquatic life, and damaging our drinking water and aquatic-associated industries such as fishing and tourism. Why do some countries show reductions in fertilizer use while others show increasing use? What N fertilizer application reductions could occur, without compromising crop yields? And what are the economic and environmental benefits of using directed nutrient management strategies? PMID:21857803

Atmospheric Nitrogen Inputs to the Ocean and their Impact

NASA Astrophysics Data System (ADS)

Jickells, Tim D.

2016-04-01

Atmospheric Nitrogen Inputs to the Ocean and their Impact T Jickells (1), K. Altieri (2), D. Capone (3), E. Buitenhuis (1), R. Duce (4), F. Dentener (5), K. Fennel (6), J. Galloway (7), M. Kanakidou (8), J. LaRoche (9), K. Lee (10), P. Liss (1), J. Middleburg (11), K. Moore (12), S. Nickovic (13), G. Okin (14), A. Oschilies (15), J. Prospero (16), M. Sarin (17), S. Seitzinger (18), J. Scharples (19), P. Suntharalingram (1), M. Uematsu (20), L. Zamora (21) Atmospheric nitrogen inputs to the ocean have been identified as an important source of nitrogen to the oceans which has increased greatly as a result of human activity. The significance of atmospheric inputs for ocean biogeochemistry were evaluated in a seminal paper by Duce et al., 2008 (Science 320, 893-7). In this presentation we will update the Duce et al 2008 study estimating the impact of atmospheric deposition on the oceans. We will summarise the latest model estimates of total atmospheric nitrogen deposition to the ocean, their chemical form (nitrate, ammonium and organic nitrogen) and spatial distribution from the TM4 model. The model estimates are somewhat smaller than the Duce et al estimate, but with similar spatial distributions. We will compare these flux estimates with a new estimate of the impact of fluvial nitrogen inputs on the open ocean (Sharples submitted) which estimates some transfer of fluvial nitrogen to the open ocean, particularly at low latitudes, compared to the complete trapping of fluvial inputs on the continental shelf assumed by Duce et al. We will then estimate the impact of atmospheric deposition on ocean primary productivity and N2O emissions from the oceans using the PlankTOM10 model. The impacts of atmospheric deposition we estimate on ocean productivity here are smaller than those predicted by Duce et al impacts, consistent with the smaller atmospheric deposition estimates. However, the atmospheric input is still larger than the estimated fluvial inputs to the open ocean, even with the increased transport across shelf to the open ocean from low latitude fluvial systems identified. 1. School of Environmental Science University of East Anglia UK 2. Energy Research Centre University of Cape Town SA 3. Department of Biological Sciences University of S California USA 4. Departments of Oceanography and Atmospheric Sciences Texas A&M University USA 5. JRC Ispra Italy 6. Department of Oceanography Dalhousie University Canada 7. Department of Environmental Sciences U. Virginia USA 8. Department of Chemistry, University of Crete, Greece 9. Department of Biology Dalhousie University, Canada 10. School of Environmental Science and Engineering Pohang University S Korea. 11. Faculty of Geosciences University of Utrecht Netherlands 12. Department of Earth System Science University of California at Irvine USA 13. WMO Geneva 14. Department of Geography University of California USA 15. GEOMAR Keil Germany 16. Department of Atmospheric Sciences, University of Miami, USA 17. Geosciences Division at Physical Research Laboratory, Ahmedabad, India 18. Department of Environmental Studies, University of Victoria, Canada 19. School of Environmentak Sciences, U Liverpool UK 20. Center for International Collaboration, Atmosphere and Ocean Research Institute, The University of Tokyo Japan 21. Oak Ridge Associated Universities USA

The role of oyster restoration and aquaculture in nitrogen removal within a Rhode Island estuary

EPA Science Inventory

Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster aquaculture and restoration are hypothesized to mitigate excessive nitrogen (N) loads via assimilation, burial, or benthic denitrification. Stu...

STREAM RESTORATION STRATEGIES FOR REDUCING RIVER NITROGEN LOADS

EPA Science Inventory

Despite decades of work implementing agricultural and urban best management practices to reduce the movement of excess nitrogen (N) from the land to aquatic ecosystems, the amount of N moving down streams and rivers remains unacceptably high in many watersheds. During this same ...

Ecosystem responses to reduced and oxidised nitrogen inputs in European terrestrial habitats.

PubMed

Stevens, Carly J; Manning, Pete; van den Berg, Leon J L; de Graaf, Maaike C C; Wamelink, G W Wieger; Boxman, Andries W; Bleeker, Albert; Vergeer, Philippine; Arroniz-Crespo, Maria; Limpens, Juul; Lamers, Leon P M; Bobbink, Roland; Dorland, Edu

2011-03-01

While it is well established that ecosystems display strong responses to elevated nitrogen deposition, the importance of the ratio between the dominant forms of deposited nitrogen (NH(x) and NO(y)) in determining ecosystem response is poorly understood. As large changes in the ratio of oxidised and reduced nitrogen inputs are occurring, this oversight requires attention. One reason for this knowledge gap is that plants experience a different NH(x):NO(y) ratio in soil to that seen in atmospheric deposits because atmospheric inputs are modified by soil transformations, mediated by soil pH. Consequently species of neutral and alkaline habitats are less likely to encounter high NH(4)(+) concentrations than species from acid soils. We suggest that the response of vascular plant species to changing ratios of NH(x):NO(y) deposits will be driven primarily by a combination of soil pH and nitrification rates. Testing this hypothesis requires a combination of experimental and survey work in a range of systems. Copyright © 2010 Elsevier Ltd. All rights reserved.

Identification and characterization of finger millet OPAQUE2 transcription factor gene under different nitrogen inputs for understanding their role during accumulation of prolamin seed storage protein.

PubMed

Gaur, Vikram Singh; Kumar, Lallan; Gupta, Supriya; Jaiswal, J P; Pandey, Dinesh; Kumar, Anil

2018-03-01

In this study, we report the isolation and characterization of the mRNA encoding OPAQUE2 (O2) like TF of finger millet (FM) ( Eleusine coracana) ( EcO2 ). Full-length EcO2 mRNA was isolated using conserved primers designed by aligning O2 mRNAs of different cereals followed by 3' and 5' RACE (Rapid Amplification of cDNA Ends). The assembled full-length EcO2 mRNA was found to contain an ORF of 1248-nt coding the 416 amino acids O2 protein. Domain analysis revealed the presence of the BLZ and bZIP-C domains which is a characteristic feature of O2 proteins. Phylogenetic analysis of EcO2 protein with other bZIP proteins identified using finger millet transcriptome data and O2 proteins of other cereals showed that EcO2 shared high sequence similarity with barley BLZ1 protein. Transcripts of EcO2 were detected in root, stem, leaves, and seed development stages. Furthermore, to investigate nitrogen responsiveness and the role of EcO2 in regulating seed storage protein gene expression, the expression profiles of EcO2 along with an α-prolamin gene were studied during the seed development stages of two FM genotypes (GE-3885 and GE-1437) differing in grain protein content (13.8 and 6.2%, respectively) grown under increasing nitrogen inputs. Compared to GE-1437, the EcO2 was relatively highly expressed during the S2 stage of seed development which further increased as nitrogen input was increased. The Ecα - prolamin gene was strongly induced in the high protein genotype (GE-3885) at all nitrogen inputs. These results indicate the presence of nitrogen responsiveness regulatory elements which might play an important role in accumulating protein in FM genotypes through modulating EcO2 expression by sensing plant nitrogen status.

Evaluation of pollution levels due to the use of consumer fertilizers under Florida conditions : summary.

DOT National Transportation Integrated Search

2010-01-01

Many surface waters in Florida are polluted with excessive nitrogen and phosphorus. Applied as fertilizer to turf and landscape plants, excess nutrients are deposited into rivers, lakes, and other surface waters through stormwater runoff. These nutri...

Nutrient additions in pristine Patagonian Sphagnum bog vegetation: can phosphorus addition alleviate (the effects of) increased nitrogen loads.

PubMed

Fritz, C; van Dijk, G; Smolders, A J P; Pancotto, V A; Elzenga, T J T M; Roelofs, J G M; Grootjans, A P

2012-05-01

Sphagnum-bog ecosystems have a limited capability to retain carbon and nutrients when subjected to increased nitrogen (N) deposition. Although it has been proposed that phosphorus (P) can dilute negative effects of nitrogen by increasing biomass production of Sphagnum mosses, it is still unclear whether P-addition can alleviate physiological N-stress in Sphagnum plants. A 3-year fertilisation experiment was conducted in lawns of a pristine Sphagnum magellanicum bog in Patagonia, where competing vascular plants were practically absent. Background wet deposition of nitrogen was low (≈ 0.1-0.2 g · N · m(-2) · year(-1)). Nitrogen (4 g · N · m(-2) · year(-1)) and phosphorus (1 g · P · m(-2) · year(-1)) were applied, separately and in combination, six times during the growing season. P-addition substantially increased biomass production of Sphagnum. Nitrogen and phosphorus changed the morphology of Sphagnum mosses by enhancing height increment, but lowering moss stem density. In contrast to expectations, phosphorus failed to alleviate physiological stress imposed by excess nitrogen (e.g. amino acid accumulation, N-saturation and decline in photosynthetic rates). We conclude that despite improving growth conditions by P-addition, Sphagnum-bog ecosystems remain highly susceptible to nitrogen additions. Increased susceptibility to desiccation by nutrients may even worsen the negative effects of excess nitrogen especially in windy climates like in Patagonia. © 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.

The Autophagic Degradation of Chloroplasts via Rubisco-Containing Bodies Is Specifically Linked to Leaf Carbon Status But Not Nitrogen Status in Arabidopsis1[W][OA

PubMed Central

Izumi, Masanori; Wada, Shinya; Makino, Amane; Ishida, Hiroyuki

2010-01-01

Autophagy is an intracellular process facilitating the vacuolar degradation of cytoplasmic components and is important for nutrient recycling during starvation. We previously demonstrated that chloroplasts can be partially mobilized to the vacuole by autophagy via spherical bodies named Rubisco-containing bodies (RCBs). Although chloroplasts contain approximately 80% of total leaf nitrogen and represent a major carbon and nitrogen source for new growth, the relationship between leaf nutrient status and RCB production remains unclear. We examined the effects of nutrient factors on the appearance of RCBs in leaves of transgenic Arabidopsis (Arabidopsis thaliana) expressing stroma-targeted fluorescent proteins. In excised leaves, the appearance of RCBs was suppressed by the presence of metabolic sugars, which were added externally or were produced during photosynthesis in the light. The light-mediated suppression was relieved by the inhibition of photosynthesis. During a diurnal cycle, RCB production was suppressed in leaves excised at the end of the day with high starch content. Starchless mutants phosphoglucomutase and ADP-Glc pyrophosphorylase1 produced a large number of RCBs, while starch-excess mutants starch-excess1 and maltose-excess1 produced fewer RCBs. In nitrogen-limited plants, as leaf carbohydrates were accumulated, RCB production was suppressed. We propose that there exists a close relationship between the degradation of chloroplast proteins via RCBs and leaf carbon but not nitrogen status in autophagy. We also found that the appearance of non-RCB-type autophagic bodies was not suppressed in the light and somewhat responded to nitrogen in excised leaves, unlike RCBs. These results imply that the degradation of chloroplast proteins via RCBs is specifically controlled in autophagy. PMID:20807997

Anthropogenic Impacts on Biological Carbon Sequestration in the Coastal Waters

NASA Astrophysics Data System (ADS)

Jiao, N.

2016-02-01

The well-known biological mechanism for carbon sequestration in the ocean is the biological pump (BP) which is driven by primary production initially in the surface water and then dependent on particulate organic carbon sinking process in the water column. In contrast microbial carbon pump (MCP) depends on microbial transformation of dissolved organic carbon (DOC) to refractory DOC (RDOC).Although the BP and the MCP are distinct mechanisms, they are intertwined. Both mechanisms should be considered regarding maximum sequestration of carbon in the ocean. Recent studies have showed that excess nutrients could facilitate the uptake of DOC and enhance both bacterial production and respiration. Bacterial growth efficiency increases with increasing nitrogen concentration to certain levels and then decreases thereafter, while the remaining DOC in the water usually decreases with increasing nitrogen concentration, suggesting that excess nitrogen could simulate uptake of DOC in the environment and thus have negative impacts on the ocean DOC storage.This is somehow against the case of the BP which is known to increase with increasing availability of nutrients. Another responsible factor is the nature of algal products. If it is labile, the organic carbon cannot be preserved in the environment.On top of that, labile organic carbon has priming effects for river discharged semi-labile DOC for bacterial respiration.That is, labile organic matter will become the incubator for bacteria. While bacteria respire DOC into CO2, they consume oxygen, and finally result in hypoxia. Under anoxic condition, anaerobic bacteria successively work on the rest of the organic carbon and produce harmful gasses such as methane and H2S. Such story did have happened during geological events in the history of the earth. The above processes not only result in ecological disasters but also reduce the capacity of carbon sequestration in the ocean. To achieve maximum carbon sinks, both BP and MCP should be considered in management, especially in the coastal waters where eutrophication and hypoxia are severe. Currently, farm over-fertilization is found world widely to be responsible for coastal water eutrophication. Therefore nutrients input must be under control for optimum outputs of the sum of BP and MCP towards sustainable coastal ecosystems.

Risk of wine-distillery waste compost application in vulnerable zones: nitrogen balance

NASA Astrophysics Data System (ADS)

Requejo, M. I.; Villena, R.; Ventas, L.; Ribas, F.; Castellanos, M. T.; Cabello, M. J.; Arce, A.; Cartagena, M. C.

2012-04-01

Nitrogen (N) is the nutrient with the greatest impact on yield of horticultural crops. It is extremely dynamic in soil and undergoes changes that include processes of gains, losses and transformations. The melon crop area at Ciudad Real adds the 29% of the national production in Spain. The common agronomic management is representative of semiarid cropped zones of Spain where environmental degradation of water supplies with high N loads is observed. The site of this work is located near of Mancha Occidental aquifer (U.H.04.04, 6.953 km2) and Campo de Montiel aquifer (U.H. 04.06, 3.192 km2) with high contamination problems. The efficient use of fertilizers and irrigation is especially important in these areas designated vulnerables to nitrate pollution from agricultural sources. The aim of this study was to assess N losses when applying exhausted grape marc compost to a melon crop as source of nutrients in a vulnerable area. The doses are often excessive because are normally based on the input of organic matter rather than on the potentially mineralizable nitrogen. This N is not only released during the growing season but also in the intercropping period. In this experiment a nitrogen balance was carried out with three different doses of compost: 0 (D0), 6.7 (D1), 13.3 (D2) and 20 T compost ha-1 (D3). The soil was a shallow sandy-loam (Alfisol Xeralf Petrocalcic Palexeralfs), with a depth of 0.6 m and a discontinuous petrocalcic horizon between 0.6 and 0.7 m. Nitrogen plant absorption and nitrate losses were measured weekly, controlling at the same time N mineralized in soil. Simultaneously, a mineralization experiment was carried out without crop (either in laboratory and field conditions) to compare it with the results obtained with melon crop. Acknowledgements This project has been supported by INIA-RTA2010-00110-C03-01.

Nitrogen dynamics in northern peatland ecosystems

EPA Science Inventory

Nitrogen pollution has become a global issue over the last century due to increased fertilizer use and burning of fossil fuels. Excess N has been responsible for algal blooms, hypoxic zones, climate change, and human health issues. Extent of peatlands in the Great Lakes basin is ...

Directly measured denitrification reveals oyster aquaculture and restored oyster reefs remove nitrogen at comparable high rates

EPA Science Inventory

Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster restoration and aquaculture are both hypothesized to mitigate excessive nitrogen (N) loads via benthic denitrification (DNF). However, this has...

Towards an integrated nitrogen and phosphorus footprint tool for consumers in the United States

EPA Science Inventory

Background/Question/Methods: Human activity has fundamentally altered the global nitrogen (N) and phosphorus (P) cycles—even more profoundly than the carbon cycle—leading to massive environmental consequences. Although P is necessary for food production, excess P lea...

Accounting for the biogeochemical cycle of nitrogen in input-output life cycle assessment.

PubMed

Singh, Shweta; Bakshi, Bhavik R

2013-08-20

Nitrogen is indispensable for sustaining human activities through its role in the production of food, animal feed, and synthetic chemicals. This has encouraged significant anthropogenic mobilization of reactive nitrogen and its emissions into the environment resulting in severe disruption of the nitrogen cycle. This paper incorporates the biogeochemical cycle of nitrogen into the 2002 input-output model of the U.S. economy. Due to the complexity of this cycle, this work proposes a unique classification of nitrogen flows to facilitate understanding of the interaction between economic activities and various flows in the nitrogen cycle. The classification scheme distinguishes between the mobilization of inert nitrogen into its reactive form, use of nitrogen in various products, and nitrogen losses to the environment. The resulting inventory and model of the US economy can help quantify the direct and indirect impacts or dependence of economic sectors on the nitrogen cycle. This paper emphasizes the need for methods to manage the N cycle that focus not just on N losses, which has been the norm until now, but also include other N flows for a more comprehensive view and balanced decisions. Insight into the N profile of various sectors of the 2002 U.S. economy is presented, and the inventory can also be used for LCA or Hybrid LCA of various products. The resulting model is incorporated in the approach of Ecologically-Based LCA and available online.

Ra and Rn isotopes as natural tracers of submarine groundwater discharge in Tampa Bay, Florida

USGS Publications Warehouse

Swarzenski, P.W.; Reich, C.; Kroeger, K.D.; Baskaran, M.

2007-01-01

A suite of naturally occurring radionuclides in the U/Th decay series (222Rn, 223,224,226,228Ra) were studied during wet and dry conditions in Tampa Bay, Florida, to evaluate their utility as groundwater discharge tracers, both within the bay proper and within the Alafia River/estuary — a prominent free-flowing river that empties into the bay. In Tampa Bay, almost 30% of the combined riverine inputs still remain ungauged. Consequently, groundwater/surface water (hyporheic) exchange in the discharging coastal rivers, as well as submarine groundwater discharge (SGD) within the bay, are still unresolved components of this system's water and material budgets. Based on known inputs and sinks, there exists an excess of 226Ra in the water column of Tampa Bay, which can be evaluated in terms of a submarine groundwater contribution to the bay proper. Submarine groundwater discharge rates calculated using a mass balance of excess 226Ra ranged from 2.2 to 14.5 L m− 2 day− 1, depending on whether the estuarine residence time was calculated using 224Ra/xs228Ra isotope ratios, or whether a long term, averaged model-derived estuarine residence time was used. When extrapolated to the total shoreline length of the bay, such SGD rates ranged from 1.6 to 10.3 m3 m− 1 day− 1. Activities of 222Rn were also elevated in surface water and shallow groundwater of the bay, as well as in the Alafia River estuary, where upstream activities as high as 250 dpm L− 1 indicate enhanced groundwater/surface water exchange, facilitated by an active spring vent. From average nutrient concentrations of 39 shallow, brackish, groundwater samples, rates of nutrient loading into Tampa Bay by SGD rates were estimated, and these ranged from 0.2 to 1.4 × 105 mol day− 1 (PO43−), 0.9–6.2 × 105 mol day− 1 (SiO4−), 0.7–5.0 × 105 mol day− 1 (dissolved organic nitrogen, DON), and 0.2–1.4 × 106 mol day− 1 (total dissolved nitrogen, TDN). Such nutrient loading estimates, when compared to average river discharge estimates (e.g., TDN = 6.9 × 105 mol day− 1), suggest that SGD-derived nutrient fluxes to Tampa Bay are indeed important components to the overall nutrient economy of these coastal waters.

Nitrogen Isotope Ratios of Juvenile Winter Flounder as an Indicator of Anthropogenic Nitrogen Inputs to Estuarine Systems

EPA Science Inventory

Nitrogen isotope ratios (15N) were measured in muscle tissue of juvenile winter flounder, Pseudopleuronectes americanus, collected from several estuarine systems (lagoons, river, bay) along the coast of Rhode Island, USA over a three-year period. Significant differences i...

Partitioning of applied nitrogen in corn and switchgrass in soils of variable depths in Central Missouri, USA

USDA-ARS?s Scientific Manuscript database

Deployment of biomass feedstock production systems in marginal lands with minimal external inputs is being recommended for sustainable feedstock supply. While nitrogen is critical for plant growth, injudicious application of fertilizer nitrogen in such marginal lands could magnify the existing non-p...

Linking landscape characteristics and stream nitrogen in the Oregon Coast Range: Empirical modeling of water quality monitoring data

EPA Science Inventory

Background sources of nitrogen (N) provide a challenge for setting stream nutrient criteria in the Pacific Northwest US. Red alder (Alnus rubra), an early successional nitrogen fixing tree, and sea salt inputs can strongly influence stream N concentrations observed in individual...

Nitrogen Fertilizer Dependency and Its Contradictions: A Theoretical Exploration of Social-Ecological Metabolism

ERIC Educational Resources Information Center

Mancus, Philip

2007-01-01

The global agro-food system relies heavily on inorganic nitrogenous fertilizers. In addition to consuming enormous amounts of energy, this manufactured input contributes to the accumulation of reactive nitrogen in the biosphere and undermines the biological basis of agricultural production itself. While technological inefficiency and population…

Cover crop, N-rate impacts on corn yield and soil N

USDA-ARS?s Scientific Manuscript database

Nitrogen fertilizer is a significant input expense for producers, as conversion of stable nitrogen into plant available reactive forms such as NH4 or NO3 is energy intensive and costly. These reactive forms of nitrogen (Nr), critical for crop production, can escape from agricultural systems into sur...

Regional and national significance of biological nitrogen fixation by crops in the United States

EPA Science Inventory

Background/Questions/Methods Biological nitrogen fixation by crops (C-BNF) represents one of the largest anthropogenic inputs of reactive nitrogen (N) to land surfaces around the world. In the United States (US), existing estimates of C-BNF are uncertain because of incomplete o...

Nitrogen inputs accelerate phosphorus cycling rates across a wide variety of terrestrial ecosystems.

PubMed

Marklein, Alison R; Houlton, Benjamin Z

2012-02-01

• Biologically essential elements--especially nitrogen (N) and phosphorus (P)--constrain plant growth and microbial functioning; however, human activities are drastically altering the magnitude and pattern of such nutrient limitations on land. Here we examine interactions between N and P cycles of P mineralizing enzyme activities (phosphatase enzymes) across a wide variety of terrestrial biomes. • We synthesized results from 34 separate studies and used meta-analysis to evaluate phosphatase activity with N, P, or N×P fertilization. • Our results show that N fertilization enhances phosphatase activity, from the tropics to the extra-tropics, both on plant roots and in bulk soils. By contrast, P fertilization strongly suppresses rates of phosphatase activity. • These results imply that phosphatase enzymes are strongly responsive to changes in local nutrient cycle conditions. We also show that plant phosphatases respond more strongly to fertilization than soil phosphatases. The tight coupling between N and P provides a mechanism for recent observations of N and P co-limitation on land. Moreover, our results suggest that terrestrial plants and microbes can allocate excess N to phosphatase enzymes, thus delaying the onset of single P limitation to plant productivity as can occur via human modifications to the global N cycle. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Recovery of nitrogen stable isotope signatures in the food web of an intermittently open estuary following removal of wastewater loads

NASA Astrophysics Data System (ADS)

Smith, Phoebe E.; Oakes, Joanne M.; Eyre, Bradley D.

2016-12-01

Nitrogen (N) stable isotope values (δ15N) were used to assess the removal of wastewater N from the food web within Tallow Creek, a small intermittently closed/open lake/lagoon (ICOLL) on the east coast of Australia, following the cessation of wastewater inputs in 2005. Current (2013) δ15N values of sediment organic carbon, plants, and animals within Tallow Creek were compared to values obtained before wastewater inputs ceased, and to values within a nearby near-pristine ICOLL (Jerusalem Creek). Most biota had significantly depleted δ15N values compared to conspecifics collected before wastewater inputs ceased (mean reduction of 6.0‰; 38% of impacted enrichment), indicating substantial loss of wastewater N since inputs ceased. However, δ15N values remained enriched compared to the near-pristine ICOLL for some components (mean enrichment of 3.3‰ or 38%), suggesting that some wastewater N remains. The δ15N recovery rate (decrease in δ15N as a percentage of the impacted enrichment) for Tallow Creek biota was slow compared to that of biota in more open systems. This slow recovery rate and the persistence of some wastewater N, even after 8 years without new inputs, reflects differences in hydrology and nitrogen cycling between permanently open and intermittently open estuarine systems and highlights the likely lower resilience of ICOLLs to anthropogenic N inputs.

Environmental Nitrogen Losses from Commercial Crop Production Systems in the Suwannee River Basin of Florida.

PubMed

Prasad, Rishi; Hochmuth, George J

2016-01-01

The springs and the Suwannee river of northern Florida in Middle Suwanee River Basin (MSRB) are among several examples in this planet that have shown a temporal trend of increasing nitrate concentration primarily due to the impacts of non-point sources such as agriculture. The rate of nitrate increase in the river as documented by Ham and Hatzell (1996) was 0.02 mg N L-1 y-1. Best management practices (BMPs) for nutrients were adopted by the commercial farms in the MSRB region to reduce the amounts of pollutants entering the water bodies, however the effectiveness of BMPs remains a topic of interest and discussion among the researchers, environmental administrators and policy makers about the loads of nitrogen entering into groundwater and river systems. Through this study, an initiative was taken to estimate nitrogen losses into the environment from commercial production systems of row and vegetable crops that had adopted BMPs and were under a presumption of compliance with state water quality standards. Nitrogen mass budget was constructed by quantifying the N sources and sinks for three crops (potato (Solanum tuberosum L.), sweet corn (Zea mays L.) and silage corn (Zea mays L.)) over a four year period (2010-2013) on a large representative commercial farm in northern Florida. Fertilizer N was found to be the primary N input and represented 98.0 ± 1.4, 91.0 ± 13.9, 78.0 ± 17.3% of the total N input for potato, sweet corn, and silage corn, respectively. Average crop N uptake represented 55.5%, 60.5%, and 65.2% of the mean total input N whereas average mineral N left in top 0.3 m soil layer at harvest represented 9.1%, 4.5%, and 2.6% of the mean total input N. Mean environmental N losses represented 35.3%, 34.3%, and 32.7% of the mean total input N for potato, sweet corn, and silage corn, respectively. Nitrogen losses showed a linear trend with increase in N inputs. Although, there is no quick fix for controlling N losses from crop production in MSRB, the strategies to reduce N losses must focus on managing the crop residues, using recommended fertilizer rates, and avoiding late-season application of nitrogen.

Environmental Nitrogen Losses from Commercial Crop Production Systems in the Suwannee River Basin of Florida

PubMed Central

Prasad, Rishi; Hochmuth, George J.

2016-01-01

The springs and the Suwannee river of northern Florida in Middle Suwanee River Basin (MSRB) are among several examples in this planet that have shown a temporal trend of increasing nitrate concentration primarily due to the impacts of non-point sources such as agriculture. The rate of nitrate increase in the river as documented by Ham and Hatzell (1996) was 0.02 mg N L-1 y-1. Best management practices (BMPs) for nutrients were adopted by the commercial farms in the MSRB region to reduce the amounts of pollutants entering the water bodies, however the effectiveness of BMPs remains a topic of interest and discussion among the researchers, environmental administrators and policy makers about the loads of nitrogen entering into groundwater and river systems. Through this study, an initiative was taken to estimate nitrogen losses into the environment from commercial production systems of row and vegetable crops that had adopted BMPs and were under a presumption of compliance with state water quality standards. Nitrogen mass budget was constructed by quantifying the N sources and sinks for three crops (potato (Solanum tuberosum L.), sweet corn (Zea mays L.) and silage corn (Zea mays L.)) over a four year period (2010–2013) on a large representative commercial farm in northern Florida. Fertilizer N was found to be the primary N input and represented 98.0 ± 1.4, 91.0 ± 13.9, 78.0 ± 17.3% of the total N input for potato, sweet corn, and silage corn, respectively. Average crop N uptake represented 55.5%, 60.5%, and 65.2% of the mean total input N whereas average mineral N left in top 0.3 m soil layer at harvest represented 9.1%, 4.5%, and 2.6% of the mean total input N. Mean environmental N losses represented 35.3%, 34.3%, and 32.7% of the mean total input N for potato, sweet corn, and silage corn, respectively. Nitrogen losses showed a linear trend with increase in N inputs. Although, there is no quick fix for controlling N losses from crop production in MSRB, the strategies to reduce N losses must focus on managing the crop residues, using recommended fertilizer rates, and avoiding late-season application of nitrogen. PMID:27907130

Agricultural Nutrient Cycling at the Strawberry Creek Watershed: Insights Into Processes Using Stable Isotope Analysis

NASA Astrophysics Data System (ADS)

Thuss, E.; English, M. C.; Spoelstra, J.

2009-05-01

When nitrogen availability exceeds biological demand, excess nitrogen, especially nitrate, may subsequently pollute ground and surface water. Agricultural practices in Southern Ontario typically supplement soils with organic and inorganic nutrients to aid in crop development, and employ various management techniques to limit nutrient loss. Excess nitrogen has several potential fates, which are controlled by the net effects of numerous nitrogen cycling reactions in the soil that are often difficult to measure directly. Nitrogen cycling in soils is controlled in large part by soil moisture, as it affects microbial activity and soil redox conditions. Stable isotope geochemistry is a powerful tool that provides information on nitrogen sources and processes. This study uses crop nitrogen and carbon isotope ratios to provide insights into the net effects of soil nitrogen cycling and nitrogen fate. This research was conducted at the Strawberry Creek Watershed (SCW), an agricultural research watershed located between Kitchener-Waterloo and Guelph, Ontario. The SCW exhibits elevated nitrate concentrations in groundwater, tile discharge, and the stream itself. Previous isotopic work revealed that this nitrate is largely derived from chemical fertilizer and manure applications. Field-scale hydrological processes lead to areas where the fate of applied nitrogen differs, which has an isotopic effect on the residual nitrogen that is available to plants. Results of this study indicate significant patterns in the isotopic signature of plant tissue, in both temporal and spatial scales. At the plot-scale where soil conditions are similar, there is little to no variation in foliar isotope values, but at the field-scale there appears to be a significant amount of variability related to soil moisture and nitrogen loss. This relationship can potentially provide insight into ideal conditions for nitrogen uptake efficiency. Reducing agricultural nitrogen leaching to ground and surface water requires a better understanding of nitrogen fate in the soil zone, and will result in more effective agricultural nutrient management.

AEROBIC DENITRIFICATION: IMPLICATIONS FOR THE MOM RIVER BASIN

EPA Science Inventory

Each year about 1.6 million metric tons of nitrogen, mostly from agriculture, is discharged from the lower Mississippi/Atchafalaya River Basin into the Gulf of Mexico, and each spring this excess nitrogen fuels the formation of a huge hypoxic zone in the Gulf. In the Mississippi...

Climate Strategy Impact on Nitrogen Deposition in the USA

EPA Science Inventory

Nitrogen (N) leakage to the environment in the United States costs an estimated $210 billion per year, equivalent to 1-3% of the national GDP, in part due to atmospheric N pollution. Excess N deteriorates ecosystems via eutrophication in water bodies, causing fish kills and addi...

Macrophyte Community Response to Nitrogen Loading and Thermal Stressors in Rapidly Flushed Mesocosm Systems

EPA Science Inventory

Increased nitrogen loading has been directly linked to the proliferation of planktonic and macroalgal blooms at a global scale with negative impacts on estuarine ecology and human health. Under excessive anthropogenic nutrient loads, seagrass systems can be replaced by either ma...

Evaluating the Ability of Oysters (Crassostrea virginica) to Mitigate Coastal Nitrogen Over-Enrichment

EPA Science Inventory

Human actions have resulted in a doubling of the rate of bio-available nitrogen production in the biosphere, leading to over-fertilization of coastal ecosystems worldwide. Such over-fertilization has numerous negative consequences for coastal ecosystems, such as excessive algal g...

An Isotopic view of water and nitrogen transport through the ...

EPA Pesticide Factsheets

Groundwater nitrate contamination affects thousands of households in Oregon’s southern Willamette Valley and many more across the Pacific Northwest. The southern Willamette Valley Groundwater Management Area (SWV GWMA) was established in 2004 due to nitrate levels in the groundwater exceeding the human health standard of 10 mg nitrate-N L-1. Much of the nitrogen inputs to the GWMA comes from agricultural nitrogen use, and thus efforts to reduce N inputs to groundwater are focused upon improving N management. However, the effectiveness of these improvements on groundwater quality is unclear because of the complexity of nutrient transport through the vadose zone and long groundwater residence times. Our objective was to focus on vadose zone transport and understand the dynamics and timing of N and water movement below the rooting zone in relation to N management and water inputs. Stable isotopes are a powerful tool for tracking water movement, and understanding nitrogen transformations within the vadose zone. In partnership with local farmers, and state agencies, we established lysimeters and groundwater wells in multiple agricultural fields in the GWMA, and have monitored nitrate, nitrate isotopes, and water isotopes weekly for multiple years. Our results indicate that vadose zone transport is highly complex, and the residence time of water collected in lysimeters was much longer than expected. While input precipitation water isotopes were highly variab

An Isotopic view of water and nitrogen transport through the ...

EPA Pesticide Factsheets

Background/Question/MethodsGroundwater nitrate contamination affects thousands of households in Oregon's southern Willamette Valley and many more across the Pacific Northwest. The southern Willamette Valley Groundwater Management Area (SWV GWMA) was established in 2004 due to nitrate levels in the groundwater exceeding the human health standard of 10 mg nitrate-N L-1. Much of the nitrogen inputs to the GWMA comes from agricultural nitrogen use, and thus efforts to reduce N inputs to groundwater are focused upon improving N management. However, the effectiveness of these improvements on groundwater quality is unclear because of the complexity of nutrient transport through the vadose zone and long groundwater residence times. Our objective was to focus on vadose zone transport and understand the dynamics and timing of N and water movement below the rooting zone in relation to N management and water inputs. Stable isotopes are a powerful tool for tracking water movement, and understanding nitrogen transformations within the vadose zone. In partnership with local farmers, and state agencies, we established lysimeters and groundwater wells in multiple agricultural fields in the GWMA, and have monitored nitrate, nitrate isotopes, and water isotopes weekly for multiple years Results/ConclusionsOur results indicate that vadose zone transport is highly complex, and the residence time of water collected in lysimeters was much longer than expected. While input precipitatio

Impacts of prescribed fire on ecosystem C and N cycles at Fort Benning Installation, Georgia

NASA Astrophysics Data System (ADS)

Zhao, S.; Liu, S.; Tieszen, L.

2007-12-01

A critical challenge for the land managers at military installation is to maintain the ecological sustainability of natural resources while meeting the needs of military training. Prescribed ground fire as a land management practice has been used to remove the ground layer plants at Fort Benning for two purposes: to facilitate access for military training, and to maintain and restore fire-adapted longleaf pine communities that are critical habitat for the federally endangered red-cockaded woodpecker (Picoides borealis). Nevertheless, the impacts of prescribed fire on ecosystem processes and health are not well-understood and quantified at the plot to regional scales. Frequent fire may result in ecosystem nitrogen (N) deficiency due to repeated N loss through combustion, volatilization, and leaching, threatening ecosystem sustainability at Fort Benning. On the other hand, N loss may be offset by enhanced symbiotic N2 fixation since fire favors herbaceous legumes by scarifying legume seeds and stimulating germination. Quantifying the impacts of prescribed fire on ecosystem carbon (C) and N cycles is further complicated by interactions and feedbacks among burning, nitrogen inputs, other land use practices (e.g. tree thinning or clear-cutting), and soil properties. In this study, we used the Erosion-Deposition-Carbon Model (EDCM), a process-based biogeochemical model, to simulate C and N dynamic at Fort Benning under different combinations of fire frequency, fire intensity, nitrogen deposition, legume nitrogen input, forest harvesting, and soil sand content. Model simulations indicated that prescribed fire led to nitrogen losses from ecosystems at Fort Benning, especially with high intensity and high frequency fires. Forest harvesting further intensified ecosystem nitrogen limitation, leading to reduced biophysical potential of C sequestration. The adverse impacts of prescribed fire and forest harvesting on C and N cycles were much higher in more sandy soil than in less sandy soil. N inputs from nitrogen deposition and legume N fixation helped replenish N losses to some extent. However, N losses due to fire and harvesting were not balanced or exceeded under current atmospheric N deposition and legume N input rates, suggesting additional N input (e.g., fertilization) may be needed to maintain the sustainability of current ecosystem states and management practices at Fort Benning.

Ecosystem processes and nitrogen export in northern U.S. watersheds.

USGS Publications Warehouse

Stottlemyer, R.

2001-01-01

There is much interest in the relationship of atmospheric nitrogen (N) inputs to ecosystem outputs as an indicator of possible "nitrogen saturation" by human activity. Longer-term, ecosystem-level mass balance studies suggest that the relationship is not clear and that other ecosystem processes may dominate variation in N outputs. We have been studying small, forested watershed ecosystems in five northern watersheds for periods up to 35 years. Here I summarize the research on ecosystem processes and the N budget. During the past 2 decades, average wet-precipitation N inputs ranged from about 0.1 to 6 kg N ha(-1) year(-1) among sites. In general, sites with the lowest N inputs had the highest output-to-input ratios. In the Alaska watersheds, streamwater N output exceeded inputs by 70 to 250%. The ratio of mean monthly headwater nitrate (NO3-) concentration to precipitation NO3- concentration declined with increased precipitation concentration. A series of ecosystem processes have been studied and related to N outputs. The most important appear to be seasonal change in hydrologic flowpath, soil freezing, seasonal forest-floor inorganic N pools resulting from over-winter mineralization beneath the snowpack, spatial variation in watershed forest-floor inorganic N pools, the degree to which snowmelt percolates soils, and gross soil N mineralization rates.

Nitrogen availability regulates proline and ethylene production and alleviates salinity stress in mustard (Brassica juncea).

PubMed

Iqbal, Noushina; Umar, Shahid; Khan, Nafees A

2015-04-15

Proline content and ethylene production have been shown to be involved in salt tolerance mechanisms in plants. To assess the role of nitrogen (N) in the protection of photosynthesis under salt stress, the effect of N (0, 5, 10, 20 mM) on proline and ethylene was studied in mustard (Brassica juncea). Sufficient N (10 mM) optimized proline production under non-saline conditions through an increase in proline-metabolizing enzymes, leading to osmotic balance and protection of photosynthesis through optimal ethylene production. Excess N (20 mM), in the absence of salt stress, inhibited photosynthesis and caused higher ethylene evolution but lower proline production compared to sufficient N. In contrast, under salt stress with an increased demand for N, excess N optimized ethylene production, which regulates the proline content resulting in recovered photosynthesis. The effect of excess N on photosynthesis under salt stress was further substantiated by the application of the ethylene biosynthesis inhibitor, 1-aminoethoxy vinylglycine (AVG), which inhibited proline production and photosynthesis. Without salt stress, AVG promoted photosynthesis in plants receiving excess N by inhibiting stress ethylene production. The results suggest that a regulatory interaction exists between ethylene, proline and N for salt tolerance. Nitrogen differentially regulates proline production and ethylene formation to alleviate the adverse effect of salinity on photosynthesis in mustard. Copyright © 2015 Elsevier GmbH. All rights reserved.

Responses of tree and insect herbivores to elevated nitrogen inputs: A meta-analysis

NASA Astrophysics Data System (ADS)

Li, Furong; Dudley, Tom L.; Chen, Baoming; Chang, Xiaoyu; Liang, Liyin; Peng, Shaolin

2016-11-01

Increasing atmospheric nitrogen (N) inputs have the potential to alter terrestrial ecosystem function through impacts on plant-herbivore interactions. The goal of our study is to search for a general pattern in responses of tree characteristics important for herbivores and insect herbivorous performance to elevated N inputs. We conducted a meta-analysis based on 109 papers describing impacts of nitrogen inputs on tree characteristics and 16 papers on insect performance. The differences in plant characteristics and insect performance between broadleaves and conifers were also explored. Tree aboveground biomass, leaf biomass and leaf N concentration significantly increased under elevated N inputs. Elevated N inputs had no significantly overall effect on concentrations of phenolic compounds and lignin but adversely affected tannin, as defensive chemicals for insect herbivores. Additionally, the overall effect of insect herbivore performance (including development time, insect biomass, relative growth rate, and so on) was significantly increased by elevated N inputs. According to the inconsistent responses between broadleaves and conifers, broadleaves would be more likely to increase growth by light interception and photosynthesis rather than producing more defensive chemicals to elevated N inputs by comparison with conifers. Moreover, the overall carbohydrate concentration was significantly reduced by 13.12% in broadleaves while increased slightly in conifers. The overall tannin concentration decreased significantly by 39.21% in broadleaves but a 5.8% decrease in conifers was not significant. The results of the analysis indicated that elevated N inputs would provide more food sources and ameliorate tree palatability for insects, while the resistance of trees against their insect herbivores was weakened, especially for broadleaves. Thus, global forest insect pest problems would be aggravated by elevated N inputs. As N inputs continue to rise in the future, forest ecosystem management should pay more attention to insect pest, especially in the regions dominated by broadleaves.

Nitrogen input inventory in the Nooksack-Abbotsford-Sumas Transboundary Region: Key component of an international nitrogen management study

EPA Science Inventory

Nitrogen (N) is an essential biological element, so optimizing N use for food production while minimizing the release of N and co-pollutants to the environment is an important challenge. The Nooksack-Abbotsford-Sumas Transboundary (NAS) Region, spanning a portion of the western...

Nitrogen input inventory in the Nooksack-Abbotsford-Sumas Transboundary Region: Key component of an international nitrogen management study.

EPA Science Inventory

Background/Question/Methods: Nitrogen (N) is an essential biological element, so optimizing N use for food production while minimizing the release of N and co-pollutants to the environment is an important challenge. The Nooksack-lower Fraser Valley, spanning a portion of the w...

Seasonal and annual watershed nitrogen export within the Willamette River Basin (Water in Columia conference)

EPA Science Inventory

Anthropogenic nitrogen (N) enrichment is recognized as one of the leading threats to aquatic ecosystems and water quality. In order to manage this threat, we need to understand patterns of N input to the landscape and export from watersheds. Nitrogen export from watersheds is i...

Diversity and antifungal activity of endophytic diazotrophic bacteria colonizing sugarcane in Egypt

USDA-ARS?s Scientific Manuscript database

The price of nitrogen continues to increase and is a major input in sugarcane production. Sugarcane grown in Egypt was screened for the presence of nitrogen-fixing bacteria. Nitrogen-free medium LGI-P was used to isolate bacteria from cane stalks. Among the 52 isolates subjected to acetylene redu...

EFFECT OF RESIDENCE TIME ON ANNUAL EXPORT AND DENITRIFICATION OF NITROGEN IN ESTUARIES: A MODEL ANALYSIS

EPA Science Inventory

A simple model of annual average response of an estuary to mean nitrogen loading rate and freshwater residence time was developed and tested. It uses nitrogen inputs from land, deposition from the atmosphere, and first-order calculations of internal loss rate and export to perfor...

Influence of forest disturbance on stable nitrogen isotope ratios in soil and vegetation profiles

Treesearch

Jennifer D. Knoepp; Scott R. Taylor; Lindsay R. Boring; Chelcy F. Miniat

2015-01-01

Soil and plant stable nitrogen isotope ratios (15 N) are influenced by atmospheric nitrogen (N) inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting 15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems; longleaf pine wiregrass (...

Dietary nitrogen alters codon bias and genome composition in parasitic microorganisms.

PubMed

Seward, Emily A; Kelly, Steven

2016-11-15

Genomes are composed of long strings of nucleotide monomers (A, C, G and T) that are either scavenged from the organism's environment or built from metabolic precursors. The biosynthesis of each nucleotide differs in atomic requirements with different nucleotides requiring different quantities of nitrogen atoms. However, the impact of the relative availability of dietary nitrogen on genome composition and codon bias is poorly understood. Here we show that differential nitrogen availability, due to differences in environment and dietary inputs, is a major determinant of genome nucleotide composition and synonymous codon use in both bacterial and eukaryotic microorganisms. Specifically, low nitrogen availability species use nucleotides that require fewer nitrogen atoms to encode the same genes compared to high nitrogen availability species. Furthermore, we provide a novel selection-mutation framework for the evaluation of the impact of metabolism on gene sequence evolution and show that it is possible to predict the metabolic inputs of related organisms from an analysis of the raw nucleotide sequence of their genes. Taken together, these results reveal a previously hidden relationship between cellular metabolism and genome evolution and provide new insight into how genome sequence evolution can be influenced by adaptation to different diets and environments.

Modeling the long-term deposition trends in US over 1990-2010 and impacts on the ecosystem assessment

EPA Science Inventory

Reactive nitrogen (Nr) is very important pollutant which at the same time plays a very important role on air and water quality, human health and biological diversity. The atmospheric nitrogen deposition can cause acidification and excess eutrophication, which brings damages to th...

Ecosystem services altered by human changes in the nitrogen cycle: A new perspective for assessment

EPA Science Inventory

Human alteration of the nitrogen (N) cycle has produced benefits for health and well-being, but excess N has altered many ecosystems and degraded air and water quality. US regulations mandate protection of the environment in terms that directly connect to ecosystem services. Here...

Reactive nitrogen in the United States: How certain are we about sources and fluxes?

EPA Science Inventory

Human alteration of the nitrogen (N) cycle has produced benefits for health and well-being, but excess N has altered many ecosystems and degraded air and water quality. US regulations mandate protection of the environment in terms that directly connect to ecosystem services. Here...

Future riverine nitrogen export to US coastal regions: Prospects for improving water quality amid population growth.

EPA Science Inventory

Excess nitrogen (N) in the environment degrades ecosystems and adversely affects human health. Here we examine predictions of contemporary (2000) and future (2030) coastal N loading in the continental US by the Nutrient Export from WaterSheds (NEWS) model. Future scenarios were b...

Sensitivity Analysis of SWAT Nitrogen Simulations with and without In-Stream Processes

EPA Science Inventory

Nitrogen (N) losses to surface waters are of great concern on both national and regional scales. Scientists have concluded that large areas of hypoxia in the northern Gulf of Mexico are due to excessive nutrients derived primarily from agricultural runoff via the Mississippi Rive...

Proteomic comparison of Gibberella moniliformis in limited-nitrogen (fumonisin-inducing) and excess-nitrogen (fumonisin-repressing) conditions

USDA-ARS?s Scientific Manuscript database

The maize pathogen Gibberella moniliformis produces fumonisins, a group of mycotoxins associated with several disorders in animals and humans including cancer. The current focus of our research is to understand the regulatory mechanisms involved in fumonisin biosynthesis. In this study, we employed ...

Long-term atmospheric nutrient inputs to the Eastern Mediterranean: sources, solubility and comparison with riverine inputs

NASA Astrophysics Data System (ADS)

Koçak, M.; Kubilay, N.; Tuǧrul, S.; Mihalopoulos, N.

2010-07-01

Aerosol and rain samples were collected at a rural site located on the coastline of the Eastern Mediterranean, Erdemli, Turkey between January 1999 and December 2007. Riverine sampling was carried out at five Rivers (Ceyhan, Seyhan, Göksu, Berdan and Lamas) draining into the Northeastern Levantine Basin (NLB) between March 2002 and July 2007. Samples were analyzed for macronutrients of phosphate, silicate, nitrate and ammonium (PO43-, Sidiss, NO3- and NH4+). Phosphate and silicate in aerosol and rainwater showed higher and larger variation during the transitional period (March-May, September) when air flows predominantly originate from North Africa and Middle East/Arabian Peninsula. Deficiency of alkaline material were found to be the main reason of the acidic rain events whilst high pH values (>7) were associated with high Sidiss concentrations due to sporadic dust events. In general, lowest nitrate and ammonium concentrations in aerosol and rainwater were associated with air flow from the Mediterranean Sea. Unlike NO3- and NH4+ (Dissolved Inorganic Nitrogen, DIN), there were statistical differences for PO43- and Sidiss solubilities in sea-water and pure-water. Solubilities of PO43- and Sidiss were found to be related with air mass back trajectories and pH. Comparison of atmospheric with riverine fluxes demonstrated that DIN and PO43- fluxes to NLB were dominated by atmosphere (~90% and ~60% respectively) whereas the input of Si was mainly derived from riverine runoff (~90%). N/P ratios (atmosphere ~233; riverine ~28) revealed that NLB receives excessive amounts of DIN and this unbalanced P and N inputs may provoke even more phosphorus deficiency. Molar Si/N ratios (atmosphere + riverine) suggested Si limitation which might cause a switch from diatom dominated phytoplankton communities to non-siliceous populations in NLB.

Nutrient delivery to Lake Winnipeg from the Red-Assiniboine River Basin – A binational application of the SPARROW model

USGS Publications Warehouse

Benoy, Glenn A.; Jenkinson, R. Wayne; Robertson, Dale M.; Saad, David A.

2016-01-01

Excessive phosphorus (TP) and nitrogen (TN) inputs from the Red–Assiniboine River Basin (RARB) have been linked to eutrophication of Lake Winnipeg; therefore, it is important for the management of water resources to understand where and from what sources these nutrients originate. The RARB straddles the Canada–United States border and includes portions of two provinces and three states. This study represents the first binationally focused application of SPAtially Referenced Regressions on Watershed attributes (SPARROW) models to estimate loads and sources of TP and TN by jurisdiction and basin at multiple spatial scales. Major hurdles overcome to develop these models included: (1) harmonization of geospatial data sets, particularly construction of a contiguous stream network; and (2) use of novel calibration steps to accommodate limitations in spatial variability across the model extent and in the number of calibration sites. Using nutrient inputs for a 2002 base year, a RARB TP SPARROW model was calibrated that included inputs from agriculture, forests and wetlands, wastewater treatment plants (WWTPs) and stream channels, and a TN model was calibrated that included inputs from agriculture, WWTPs and atmospheric deposition. At the RARB outlet, downstream from Winnipeg, Manitoba, the majority of the delivered TP and TN came from the Red River Basin (90%), followed by the Upper Assiniboine River and Souris River basins. Agriculture was the single most important TP and TN source for each major basin, province and state. In general, stream channels (historically deposited nutrients and from bank erosion) were the second most important source of TP. Performance metrics for the RARB SPARROW model are similarly robust compared to other, larger US SPARROW models making it a potentially useful tool to address questions of where nutrients originate and their relative contributions to loads delivered to Lake Winnipeg.

Effects of agricultural nutrient management on nitrogen fate and transport in Lancaster County, Pennsylvania

USGS Publications Warehouse

Hall, D.W.; Risser, D.W.

1993-01-01

Nitrogen inputs to, and outputs from, a 55-acre site in Lancaster County, Pennsylvania, were estimated to determine the pathways and relative magnitude of loads of nitrogen entering and leaving the site, and to compare the loads of nitrogen before and after the implementation of nutrient management. Inputs of nitrogen to the site were manure fertilizer, commercial fertilizer, nitrogen in precipitation, and nitrogen in ground-water inflow; and these sources averaged 93, 4, 2, and 1 percent of average annual nitrogen additions, respectively. Outputs of nitrogen from the site were nitrogen in harvested crops, loads of nitrogen in surface runoff, volatilization of nitrogen, and loads of nitrogen in ground-water discharge, which averaged 37, less than 1,25, and 38 percent of average annual nitrogen removals from the site, respectively. Virtually all of the nitrogen leaving the site that was not removed in harvested crops or by volatilization was discharged in the ground water. Applications of manure and fertilizer nitrogen to 47.5 acres of cropped fields decreased about 33 percent, from an average of 22,700 pounds per year (480 pounds per acre per year) before nutrient management to 15,175 pounds of nitrogen per year (320 pounds per acre per year) after the implementation of nutrient management practices. Nitrogen loads in ground-water discharged from the site decreased about 30 percent, from an average of 292 pounds of nitrogen per million gallons of ground water before nutrient management to an average of 203 pounds of nitrogen per million gallons as a result of the decreased manure and commercial fertilizer applications. Reductions in manure and commercial fertilizer applications caused a reduction of approximately 11,000 pounds (3,760 pounds per year, 70 pounds per acre per year) in the load of nitrogen discharged in ground water from the 55-acre site during the three-year period 1987-1990.

The USA Nr Inventory: Dominant Sources and Primary Transport Pathways

NASA Astrophysics Data System (ADS)

Sabo, R. D.; Clark, C.; Sobota, D. J.; Compton, J.; Cooter, E. J.; Schwede, D. B.; Bash, J. O.; Rea, A.; Dobrowolski, J. P.

2016-12-01

Efforts to mitigate the deleterious effects of excess reactive nitrogen (Nr) on human health and ecosystem goods and service while ensuring food, biofuel, and fiber availability, is one of the most pressing environmental management challenges of this century. Effective management of Nr requires up to date inventories that quantitatively characterize the sources, transport, and transformation of Nr through the environment. The inherent complexity of the nitrogen cycle, however, through multiple exchange points across air, water, and terrestrial media, renders such inventories difficult to compile and manage. Previous Nr Inventories are for 2002 and 2007, and used data sources that have since been improved. Thus, this recent inventory will substantially advance the methodology across many sectors of the inventory (e.g. deposition and biological fixation in crops and natural systems) and create a recent snapshot that is sorely needed for policy planning and trends analysis. Here we use a simple mass balance approach to estimate the input-output budgets for all United States Geologic Survey Hydrologic Unit Code-8 watersheds. We focus on a recent year (i.e. 2012) to update the Nr Inventory, but apply the analytical approach for multiple years where possible to assess trends through time. We also compare various sector estimates using multiple methodologies. Assembling datasets that account for new Nr inputs into watersheds (e.g., atmospheric NOy deposition, food imports, biologic N fixation) and internal fluxes of recycled Nr (e.g., manure, Nr emmissions/volatilization) provide an unprecedented, data driven computation of N flux. Input-output budgets will offer insight into 1) the dominant sources of Nr in a watershed (e.g., food imports, atmospheric N deposition, or fertilizer), 2) the primary loss pathways for Nr (e.g., crop N harvest, volatilization/emissions), and 3) what watersheds are net sources versus sinks of Nr. These insights will provide needed clarity for managers looking to minimize the loss of Nr to atmospheric and aquatic compartments, while also providing a foundational database for researchers assessing the dominant controls of N retention and loss in natural and anthropogenically dominated ecosystems. Disclaimer: Views expressed are the authors' and not views or polices of the U.S.EPA.

Prioritizing Crop Management to Increase Nitrogen Use Efficiency in Australian Sugarcane Crops.

PubMed

Thorburn, Peter J; Biggs, Jody S; Palmer, Jeda; Meier, Elizabeth A; Verburg, Kirsten; Skocaj, Danielle M

2017-01-01

Sugarcane production relies on the application of large amounts of nitrogen (N) fertilizer. However, application of N in excess of crop needs can lead to loss of N to the environment, which can negatively impact ecosystems. This is of particular concern in Australia where the majority of sugarcane is grown within catchments that drain directly into the World Heritage listed Great Barrier Reef Marine Park. Multiple factors that impact crop yield and N inputs of sugarcane production systems can affect N use efficiency (NUE), yet the efficacy many of these factors have not been examined in detail. We undertook an extensive simulation analysis of NUE in Australian sugarcane production systems to investigate (1) the impacts of climate on factors determining NUE, (2) the range and drivers of NUE, and (3) regional variation in sugarcane N requirements. We found that the interactions between climate, soils, and management produced a wide range of simulated NUE, ranging from ∼0.3 Mg cane (kg N) -1 , where yields were low (i.e., <50 Mg ha -1 ) and N inputs were high, to >5 Mg cane (kg N) -1 in plant crops where yields were high and N inputs low. Of the management practices simulated (N fertilizer rate, timing, and splitting; fallow management; tillage intensity; and in-field traffic management), the only practice that significantly influenced NUE in ratoon crops was N fertilizer application rate. N rate also influenced NUE in plant crops together with the management of the preceding fallow. In addition, there is regional variation in N fertilizer requirement that could make N fertilizer recommendations more specific. While our results show that complex interrelationships exist between climate, crop growth, N fertilizer rates and N losses to the environment, they highlight the priority that should be placed on optimizing N application rate and fallow management to improve NUE in Australian sugarcane production systems. New initiatives in seasonal climate forecasting, decisions support systems and enhanced efficiency fertilizers have potential for making N fertilizer management more site specific, an action that should facilitate increased NUE.

Prioritizing Crop Management to Increase Nitrogen Use Efficiency in Australian Sugarcane Crops

PubMed Central

Thorburn, Peter J.; Biggs, Jody S.; Palmer, Jeda; Meier, Elizabeth A.; Verburg, Kirsten; Skocaj, Danielle M.

2017-01-01

Sugarcane production relies on the application of large amounts of nitrogen (N) fertilizer. However, application of N in excess of crop needs can lead to loss of N to the environment, which can negatively impact ecosystems. This is of particular concern in Australia where the majority of sugarcane is grown within catchments that drain directly into the World Heritage listed Great Barrier Reef Marine Park. Multiple factors that impact crop yield and N inputs of sugarcane production systems can affect N use efficiency (NUE), yet the efficacy many of these factors have not been examined in detail. We undertook an extensive simulation analysis of NUE in Australian sugarcane production systems to investigate (1) the impacts of climate on factors determining NUE, (2) the range and drivers of NUE, and (3) regional variation in sugarcane N requirements. We found that the interactions between climate, soils, and management produced a wide range of simulated NUE, ranging from ∼0.3 Mg cane (kg N)-1, where yields were low (i.e., <50 Mg ha-1) and N inputs were high, to >5 Mg cane (kg N)-1 in plant crops where yields were high and N inputs low. Of the management practices simulated (N fertilizer rate, timing, and splitting; fallow management; tillage intensity; and in-field traffic management), the only practice that significantly influenced NUE in ratoon crops was N fertilizer application rate. N rate also influenced NUE in plant crops together with the management of the preceding fallow. In addition, there is regional variation in N fertilizer requirement that could make N fertilizer recommendations more specific. While our results show that complex interrelationships exist between climate, crop growth, N fertilizer rates and N losses to the environment, they highlight the priority that should be placed on optimizing N application rate and fallow management to improve NUE in Australian sugarcane production systems. New initiatives in seasonal climate forecasting, decisions support systems and enhanced efficiency fertilizers have potential for making N fertilizer management more site specific, an action that should facilitate increased NUE. PMID:28928756

Benchmarking carbon-nitrogen interactions in Earth System Models to observations: An inter-comparison of nitrogen limitation in global land surface models with carbon and nitrogen cycles (CLM-CN and O-CN)

NASA Astrophysics Data System (ADS)

Thomas, R. Q.; Zaehle, S.; Templer, P. H.; Goodale, C. L.

2011-12-01

Predictions of climate change depend on accurately modeling the feedbacks among the carbon cycle, nitrogen cycle, and climate system. Several global land surface models have shown that nitrogen limitation determines how land carbon fluxes respond to rising CO2, nitrogen deposition, and climate change, thereby influencing predictions of climate change. However, the magnitude of the carbon-nitrogen-climate feedbacks varies considerably by model, leading to critical and timely questions of why they differ and how they compare to field observations. To address these questions, we initiated a model inter-comparison of spatial patterns and drivers of nitrogen limitation. The experiment assessed the regional consequences of sustained nitrogen additions in a set of 25-year global nitrogen fertilization simulations. The model experiments were designed to cover effects from small changes in nitrogen inputs associated with plausible increases in nitrogen deposition to large changes associated with field-based nitrogen fertilization experiments. The analyses of model simulations included assessing the geographically varying degree of nitrogen limitation on plant and soil carbon cycling and the mechanisms underlying model differences. Here, we present results from two global land-surface models (CLM-CN and O-CN) with differing approaches to modeling carbon-nitrogen interactions. The predictions from each model were compared to a set of globally distributed observational data that includes nitrogen fertilization experiments, 15N tracer studies, small catchment nitrogen input-output studies, and syntheses across nitrogen deposition gradients. Together these datasets test many aspects of carbon-nitrogen coupling and are able to differentiate between the two models. Overall, this study is the first to explicitly benchmark carbon and nitrogen interactions in Earth System Models using a range of observations and is a foundation for future inter-comparisons.

Nitrogen Inputs via Nitrogen Fixation in Northern Plants and Soils

NASA Astrophysics Data System (ADS)

Thorp, N. R.; Wieder, R. K.; Vile, M. A.

2015-12-01

Dominated by cold and often acidic water logged environments, mineralization of organic matter is slow in the majority of northern ecosystems. Measures of extractable ammonium and nitrate are generally low and can be undetectable in peat pore waters. Despite this apparent nitrogen limitation, many of these environments produce deep deposits of soil organic matter. Biological nitrogen fixation carried out by autotrophic and heterotrophic diazotrophs associated with cryptograms provides the majority of known nitrogen inputs in these northern ecosystems. Nitrogen fixation was assessed in a variety of northern soils within rhizospheres of dominant plant communities. We investigated the availability of this newly fixed nitrogen to the vascular plant community in nitrogen limited northern plant communities. We tracked nitrogen flow from 15N2 gas fixed in Sphagnum mosses into tissues of two native vascular plant species, boreal cranberry (Vaccinium oxycoccus) and black spruce (Picea mariana). 15N-labeled Sphagnum microcosms were grown within variable mesh size exclusion/inclusion fabrics in a nitrogen addition experiment in situ in order to investigate the role of mycorrhizal fungi in the uptake of newly fixed nitrogen. Up to 24% of daily fixed 15N label was transferred to vascular plant tissues during 2 months. Nitrogen addition resulted in decreased N2 fixation rates; however, with higher nitrogen availability there was a higher rate of 15N label uptake into the vascular plants, likely the result of increased production of dissolved organic nitrogen. Reliance on mycorrhizal networks for nitrogen acquisition was indicated by nitrogen isotope fractionation patterns. Moreover, N2 fixation activities in mosses were stimulated when vascular plants were grown in moss microcosms versus "moss only" treatments. Results indicate that bog vascular plants may derive considerable nitrogen from atmospheric N2 biologically fixed within Sphagnum mosses. This work demonstrates that diazotroph-mediated 15N labeling is a viable technique for tracking nitrogen flow without altering form and concentration of native nitrogen pools in a nitrogen limited ecosystem.

Atmospheric dry deposition of sulfur and nitrogen in the Athabasca Oil Sands Region, Alberta, Canada

Treesearch

Yu-Mei Hsu; Andrzej Bytnerowicz; Mark E. Fenn; Kevin E. Percy

2016-01-01

Due to the potential ecological effects on terrestrial and aquatic ecosystems from atmospheric deposition in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, this study was implemented to estimate atmospheric nitrogen (N) and sulfur (S) inputs. Passive samplers were used to measure ambient concentrations of ammonia (NH3), nitrogen dioxide...

Impact of bioenergy on regionalized nitrogen balances

NASA Astrophysics Data System (ADS)

Häußermann, Uwe; Klement, Laura; Bach, Martin

2017-04-01

Results of regionalized and overall net-N-balances are used to fulfil different reporting obligations, as well as input data for nitrate leaching modelling (Bach et al. 2014). For Germany, these regionalized net-N-balances are calculated for 402 administrative units on the NUTS-III-level (Landkreise and kreisfreie Städte in Germany), 16 administrative units on the NUTS-I-level (Bundesländer in Germany) and the whole country for every year from 1995 to 2015. The so far existing net-N-balancing method includes nitrogen inputs and outputs of crop production and animal husbandry, however, not the utilization of crops and farmyard manure for energy production (Bach et al. 2014). Due to the introduction of guaranteed feed in tariffs for electricity production from biomass by the German renewable energy law in 2000 and the introduction of more favourable conditions for electricity production from biogas in 2004 (EEG 2000, EEG 2004) in the frame of the German policy of energy transition towards renewable energies („Energiewende"), the electric capacity of biogas plants had a steep increase in the years afterwards, the installed electric capacity increased from 149 MW in 2004 to 5080 MW in 2015 (BMWi and AGEE Stat 2016). The cropping area for the production of energy cops for biogas production increased as well from 0.4 Mio ha in 2007 to 1.393 Mio ha in 2015 (Statista 2017). We introduced a method to calculate the nitrogen input via energy crops, farmyard manure and organic waste, output via biogas digestates and gaseous nitrogen losses via NH3, N2O, NOx and N2 during the anaerobic digestion, digestate storage and spreading on the field, the emission factors for these nitrogen species are obtained from the report on methods and data for the agricultural part of the German national greenhouse gas inventory and informative inventory report (Haenel et al. 2016). To obtain highly resolved information on the distribution and capacity of biogas plants on NUTS-III-level, we use a dataset which is kept and regularly updated by the Germany Federal Network Agency („Bundesnetzagentur") (Bundesnetzagentur 2016). These dataset does not include information about substrate input and therefore need to be intersect with regionalized substrate input data (DBFZ 2012), and to obtain nitrogen input quantities with the nitrogen content of these substrates (KTBL 2016). Without including bioenergy production, the linear trend of the net-N-surplus in 2003 to 2014 for Germany is -1.66x + 71.25 kg N (ha LF a)-1? , therefore, an overall decrease of the net-N-surplus of 18.3 kg N ha LF-1 within 11 years was calculated. No such decrease was calculated, when biogas production was included into the net-N-balance.

Corn nitrogen fertilization rate tools compared over eight midwest states

USDA-ARS?s Scientific Manuscript database

Publicly-available nitrogen (N) rate recommendation tools are utilized to help maximize yield in corn production. These tools often fail both when N is over-applied and result in excess N being lost to the environment, or when N is under-applied and the result in decreased yield and economic returns...

Future riverine nitrogen export to US coastal regions: Prospects for improving water quality considering population growth

EPA Science Inventory

Excess nitrogen (N) in the environment degrades ecosystems and adversely affects human health. Here we examine predictions of contemporary (2000) and future (2030) coastal N loading in the continental US by the Nutrient Export from WaterSheds (NEWS) model. Future output is from s...

Excess nitrogen in the U.S. environment: Trends, risks, and solutions

USDA-ARS?s Scientific Manuscript database

It is not surprising that humans have profoundly altered the global nitrogen (N) cycle in an effort to feed nearly 7 billion people, because N is an essential plant and animal nutrient. Food and energy production from agriculture, combined with industrial and energy sources, have more than doubled t...

REMOTE SENSING AND SPATIALLY EXPLICIT LANDSCAPE-BASED NITROGEN MODELING METHODS DEVELOPMENT IN THE NEUSE RIVER BASIN, NC

EPA Science Inventory

The objective of this research was to model and map the spatial patterns of excess nitrogen (N) sources across the landscape within the Neuse River Basin (NRB) of North
Carolina. The process included an initial land cover characterization effort to map landscape "patches" at ...

Assessment of microbial biomass carbon and nitrogen of native and non-native perennial pasture soils using hyperspectral data

USDA-ARS?s Scientific Manuscript database

Soil microbial biomass carbon (MBC) and nitrogen (MBN) are integral parts to soil organic matter. Increased production costs and chemical runoff can result from excessive application of fertilizer if these measurements are not used in total nutrient calculations. More timely and cost-effective me...

Digital data used to relate nutrient inputs to water quality in the Chesapeake Bay watershed

USGS Publications Warehouse

Brakebill, John W.; Preston, Stephen D.

1999-01-01

Digital data sets were compiled by the U. S. Geological Survey (USGS) and used as input for a collection of Spatially Referenced Regressions On Watershed attributes for the Chesapeake Bay region. These regressions relate streamwater loads to nutrient sources and the factors that affect the transport of these nutrients throughout the watershed. A digital segmented network based on watershed boundaries serves as the primary foundation for spatially referencing total nitrogen and total phosphorus source and land-surface characteristic data sets within a Geographic Information System. Digital data sets of atmospheric wet deposition of nitrate, point-source discharge locations, land cover, and agricultural sources such as fertilizer and manure were created and compiled from numerous sources and represent nitrogen and phosphorus inputs. Some land-surface characteristics representing factors that affect the transport of nutrients include land use, land cover, average annual precipitation and temperature, slope, and soil permeability. Nutrient input and land-surface characteristic data sets merged with the segmented watershed network provide the spatial detail by watershed segment required by the models. Nutrient stream loads were estimated for total nitrogen, total phosphorus, nitrate/nitrite, amonium, phosphate, and total suspended soilds at as many as 109 sites within the Chesapeake Bay watershed. The total nitrogen and total phosphorus load estimates are the dependent variables for the regressions and were used for model calibration. Other nutrient-load estimates may be used for calibration in future applications of the models.

Numerical research of reburning-process of burning of coal-dust torch

NASA Astrophysics Data System (ADS)

Trinchenko, Alexey; Paramonov, Aleksandr; Kadyrov, Marsel; Koryabkin, Aleksey

2017-10-01

This work is dedicated to numerical research of ecological indicators of technological method of decrease in emissions of nitrogen oxides at combustion of solid fuel in coal-dust torch to improve the energy efficiency of steam boilers. The technology of step burning with additional input in zone of the maximum concentration of pollutant of strongly crushed fuel for formation of molecular nitrogen on surface of the burning carbon particles is considered. Results of modeling and numerical researches of technology, their analysis and comparison with the experimental data of the reconstructed boiler are given. Results of work show that input of secondary fuel allows to reduce emissions of nitrogen oxides by boiler installation without prejudice to its economic indicators.

Estimating the energetic cost of feeding excess dietary nitrogen to dairy cows

USDA-ARS?s Scientific Manuscript database

Feeding N in excess of requirements could require the use of additional energy to synthesize and excrete urea, however, the amount energy required is unclear. Little progress has been made on this topic in recent decades so an extension of work published in 1970 was conducted to quantify the effect ...

Exploring spatiotemporal patterns of phosphorus concentrations in a coastal bay with MODIS images and machine learning models

EPA Science Inventory

Excessive nutrients, which may be represented as Total Nitrogen (TN) and Total Phosphorus (TP) levels, in natural water systems have proven to cause high levels of algae production. The process of phytoplankton growth which consumes the excess nutrients in a water body can also b...

Reduction of excess sludge production using mechanical disintegration devices.

PubMed

Strünkmann, G W; Müller, J A; Albert, F; Schwedes, J

2006-01-01

The usability of mechanical disintegration techniques for the reduction of excess sludge production in the activated sludge process was investigated. Using three different disintegration devices (ultrasonic homogeniser, stirred media mill, high pressure homogeniser) and different operational parameters of the disintegration, the effect of mechanical disintegration on the excess sludge production and on the effluent quality was studied within a continuously operated, laboratory scale wastewater treatment system with pre-denitrification. Depending on the operational conditions and the disintegration device used, a reduction of excess sludge production of up to 70% was achieved. A combination of mechanical disintegration with a membrane bioreactor process with high sludge age is more energy effective concerning reduction of sludge production than with a conventional activated sludge process at lower sludge ages. Depending on the disintegration parameters, the disintegration has no, or only minor, negative effect on the soluble effluent COD and on the COD-removal capacity of the activated sludge process. Nitrogen-removal was slightly deteriorated by the disintegration, whereas the system used was not optimised for nitrogen removal before disintegration was implemented.

Effects of melatonin on seedling growth, mineral nutrition, and nitrogen metabolism in cucumber under nitrate stress.

PubMed

Zhang, Ruimin; Sun, Yunkuo; Liu, Zeyu; Jin, Wen; Sun, Yan

2017-05-01

In China, excessive use of nitrogen fertilizers in glasshouses leads to nitrate accumulations in soil and plants, which then limits productivity. Melatonin, an evolutionarily highly conserved molecule, has a wide range of functions in plants. We analyzed the effects of melatonin pretreatment on the growth, mineral nutrition, and nitrogen metabolism in cucumber (Cucumis sativus L. "Jin You No. 1") when seedlings were exposed to nitrate stress. An application of 0.1 mmol/L melatonin significantly improved the growth of plants and reduced their susceptibility to damage due to high nitrate levels (0.6 mol/L) during the ensuing period of stress treatment. Although excess nitrate led to an increase in the concentrations of nitrogen, potassium, and calcium, as well as a decrease in levels of phosphorus and magnesium, exogenous melatonin generally had the opposite effect except for a further rise in calcium concentrations. Pretreatment also significantly reduced the accumulations of nitrate nitrogen and ammonium nitrogen and enhanced the activities of enzymes involved in nitrogen metabolism. Expression of Cs-NR and Cs-GOGAT, two genes that function in that metabolism, was greatly down-regulated when plants were exposed to 0.6 mol/L nitrate, but was up-regulated in plants that had received the 0.1 mmol/L melatonin pretreatment. Our results are the first evidence that melatonin has an important role in modulating the composition of mineral elements and nitrogen metabolism, thereby alleviating the inhibitory effect on growth normally associated with nitrate stress. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

UNCERTAINTIES IN NITROGEN MASS LOADINGS IN COASTAL WATERSHEDS

EPA Science Inventory

With the increasing reduction of nutrients for coastal eutrophication control, the importance of well defined nitrogen mass balance becomes paramount. imited number of attempts have been made to quantify inputs and outputs within major coastal ecosystems including its watersheds....

75 FR 62358 - Stakeholder Input on Stormwater Rulemaking Related to the Chesapeake Bay; Notice of Public Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-08

... including, but not limited to, nitrogen, phosphorus, and sediment in the Chesapeake Bay Watershed; requiring... specificity of the minimum control measures could include considerations for nitrogen, phosphorus and sediment...

Nutrient and organic matter inputs to Hawaiian anchialine ponds: influences of n-fixing and non-n-fixing trees

Treesearch

Kehauwealani K. Nelson-Kaula; Rebecca Ostertag; R. Flint Hughes; Bruce D. Dudley

2016-01-01

Invasive nitrogen-fixing plants often increase energy and nutrient inputs to both terrestrial and aquatic ecosystems via litterfall, and these effects may be more pronounced in areas lacking native N2-fixers. We examined organic matter and nutrient inputs to and around anchialine ponds...

Understanding nutrients in the Chesapeake Bay watershed and implications for management and restoration: the Eastern Shore

USGS Publications Warehouse

Ator, Scott W.; Denver, Judith M.

2015-03-12

The Eastern Shore includes only a small part of the Chesapeake Bay watershed, but contributes disproportionately large loads of the excess nitrogen and phosphorus that have contributed to ecological and economic degradation of the bay in recent decades. Chesapeake Bay is the largest estuary in the United States and a vital ecological and economic resource. The bay and its tributaries have been degraded in recent decades by excessive nitrogen and phosphorus in the water column, however, which cause harmful algal blooms and decreased water clarity, submerged aquatic vegetation, and dissolved oxygen. The disproportionately large nitrogen and phosphorus yields from the Eastern Shore to Chesapeake Bay are attributable to human land-use practices as well as natural hydrogeologic and soil conditions. Applications of nitrogen and phosphorus compounds to the Eastern Shore from human activities are intensive. More than 90 percent of nitrogen and phosphorus reaching the land in the Eastern Shore is applied as part of inorganic fertilizers or manure, or (for nitrogen) fixed directly from the atmosphere in cropland. Also, hydrogeologic and soil conditions promote the movement of these compounds from application areas on the landscape to groundwater and (or) surface waters, and the proximity of much of the Eastern Shore to tidal waters limits opportunities for natural removal of these compounds in the landscape. The Eastern Shore only includes 7 percent of the Chesapeake Bay watershed, but receives nearly twice as much nitrogen and phosphorus applications (per area) as the remainder of the watershed and yields greater nitrogen and phosphorus, on average, to the bay. Nitrogen and phosphorus commonly occur in streams at concentrations that may adversely affect aquatic ecosystems and have increased in recent decades.

Integrated modelling of nitrogen transport and turnover in lowland catchements of northern Germany

NASA Astrophysics Data System (ADS)

Wriedt, G.

2003-04-01

Nitrogen loads in surface water often do not reflect the actual input situation. This retention of nitrogen can be explained by chemical transformations in the soil and groundwater (e.g. denitrification) and hydrological factors (e.g. transition time, mixing) in soil and groundwater and depends strongly on the geological and chemical patterns within the catchment areas (e.g. reactive substances, conductivities). In order to facilitate modelling studies on the relation between nitrogen transport and catchment characteristics we developed a modelling approach, that allows simulation of the complete nitrogen transport path from the soil input until the exfiltration into the surface water system. This approach is based on the loose coupling of a soil water model and an analytical soil nitrogen model (mRISK-N) with a groundwater flow model (MODFLOW) and a multi-species reactive transport model (RT3D). Groundwater nitrogen turnover is represented by a closed reaction scheme that explicitly includes oxidation of organic matter and pyrite oxidation by several electron acceptors as the main reactive pathways, in order to link nitrogen turnover directly to the availability of the substances involved in the chemical reactions. This reaction module has been implemented into the modelling system as a user defined reaction module within the RT3D-environment. The soil submodel was tested against lysimeter data. It was found, that soil water balance was represented quite well. Nitrogen leaching rates however, can only be interpreted for larger time scales, whereas considerable deviations from measured values do occur in single years. Nevertheless, model performance is comparable to other, more complex soil water and nitrogen models currently available. It was found, that the high uncertainty of model parameters and input data as well as limited knowledge on processes limit the accuracy of soil nitrogen models in general. The next step of the project is the model application in the study area “Schaugraben catchment”. The study area is located near Osterburg/Altmark in the north of Sachsen-Anhalt, its size is about 25 km2. The geology is determined by pleistocene deposits, mainly glacial till in the plateau areas and glaciofluvial sandy deposits in the valleys. A dense drainage network, a high groundwater table and intensive agricultural use provide a high risk for both, groundwater and surface water quality. Model application focuses on the analysis of the interactions between catchment characteristics (hydrological and geological), spatial input patterns and the fate of nitrogen within the catchment. This is done by applying sensitivity analysis, uncertainty analysis and scenario simulation. A three dimensional groundwater flow model for the Schaugraben area has been set up and calibrated in order to analyse the regional flow paths, transition times and groundwater catchments. More detailed modelling studies including the reactive groundwater transport are performed on selected cutouts and transects, defining specific hydrogeological settings, e.g. riparian areas, buffer stripes, hydrological windows etc. Under special consideration is also the influence of spatial input patterns of nitrate and organic matter leaching to the groundwater. Results of the modelling studies are expect until March ‘03. The modelling approach developed here is a tool for the assessment of transport-turnover interaction and may help to improve experimental studies and measurement strategies and to provide useful information for managing purposes.

Trends in nitrogen isotope ratios of juvenile winter flounder ...

EPA Pesticide Factsheets

Nitrogen isotope ratios (d 15N) in juvenile winter flounder, Pseudopleuronectes americanus, were used to examine changes in nitrogen inputs to several Rhode Island, USA estuarine systems. Fish were collected over two three-year periods with a ten-year interval between sampling periods (2002-2004 and 2012-2014). During that interval numerous changes to nutrient management practices were initiated in the watersheds of these estuarine systems including the upgrade of several major wastewater treatment facilities that discharge to Narragansett Bay, which significantly reduced nitrogen inputs. Following these reductions, the d 15N values of flounder in several of the systems decreased as expected; however, isotope ratios in fish from upper Narragansett Bay significantly increased. We believe that low d 15N values measured in 2002-2004 were related to concentration-dependant fractionation at this location. Increased d 15N values measured between 2012 and 2014 may indicate reduced fractionation or that changes in wastewater treatment processes altered the nitrogen isotopic ratios of the effluents. This manuscript advances the development of methodology to assess the influence of anthropogenic nitrogen in estuarine systems. Juvenile winter flounder were collected from several estuarine systems along the coast of Rhode Island over two three-year periods and nitrogen isotopes were measured in the muscle tissues of the flounder. The results showed that there was a good cor

Effects of silvicultural practices on soil carbon and nitrogen in a nitrogen saturated central Appalachian (USA) hardwood forest ecosystem

Treesearch

Frank S. Gilliam; David A. Dick; Michelle L. Kerr; Mary Beth Adams

2004-01-01

Silvicultural treatments represent disturbances to forest ecosystems often resulting in transient increases in net nitrification and leaching of nitrate and base cations from the soil. Response of soil carbon (C) is more complex, decreasing from enhanced soil respiration and increasing from enhanced postharvest inputs of detritus. Because nitrogen (N) saturation can...

Changes in biogeochemical cycling following forest defoliation by pine wilt disease in Kiryu experimental catchment in Japan

NASA Astrophysics Data System (ADS)

Tokuchi, Naoko; Ohte, Nobuhito; Hobara, Satoru; Kim, Su-Jin; Masanori, Katsuyama

2004-10-01

Changes in nutrient budgets and hydrological processes due to the natural disturbance of pine wilt disease (PWD) were monitored in a small, forested watershed in Japan. The disturbance caused changes in soil nitrogen transformations. Pre-disturbance, mineralized nitrogen remained in the form of NH4+, whereas in disturbed areas most mineralized nitrogen was nitrified. Stream NO3- concentrations increased following PWD. There was a delay between time of disturbance and the increase of NO3- in ground and stream waters. Stream concentrations of NO3- and cations (Ca2+ + Mg2+) were significantly correlated from 1994 to 1996, whereas the correlation among NO3-, H+, and SO42- was significant only in 1995. Although both cation exchange and SO42- adsorption buffered protons, cation exchange was the dominant and continuous mechanism for acid buffering. SO42- adsorption was variable and highly pH dependent. The disturbance also resulted in slight delayed changes of input-output nutrient balances. The nitrogen contribution to PWD litter inputs was 7.39 kmol ha-1, and nitrogen loss from streamwater was less than 0.5 kmol ha-1 year-1 throughout the observation period. This large discrepancy suggested substantial nitrogen immobilization.

Simple additive simulation overestimates real influence: altered nitrogen and rainfall modulate the effect of warming on soil carbon fluxes.

PubMed

Ni, Xiangyin; Yang, Wanqin; Qi, Zemin; Liao, Shu; Xu, Zhenfeng; Tan, Bo; Wang, Bin; Wu, Qinggui; Fu, Changkun; You, Chengming; Wu, Fuzhong

2017-08-01

Experiments and models have led to a consensus that there is positive feedback between carbon (C) fluxes and climate warming. However, the effect of warming may be altered by regional and global changes in nitrogen (N) and rainfall levels, but the current understanding is limited. Through synthesizing global data on soil C pool, input and loss from experiments simulating N deposition, drought and increased precipitation, we quantified the responses of soil C fluxes and equilibrium to the three single factors and their interactions with warming. We found that warming slightly increased the soil C input and loss by 5% and 9%, respectively, but had no significant effect on the soil C pool. Nitrogen deposition alone increased the soil C input (+20%), but the interaction of warming and N deposition greatly increased the soil C input by 49%. Drought alone decreased the soil C input by 17%, while the interaction of warming and drought decreased the soil C input to a greater extent (-22%). Increased precipitation stimulated the soil C input by 15%, but the interaction of warming and increased precipitation had no significant effect on the soil C input. However, the soil C loss was not significantly affected by any of the interactions, although it was constrained by drought (-18%). These results implied that the positive C fluxes-climate warming feedback was modulated by the changing N and rainfall regimes. Further, we found that the additive effects of [warming × N deposition] and [warming × drought] on the soil C input and of [warming × increased precipitation] on the soil C loss were greater than their interactions, suggesting that simple additive simulation using single-factor manipulations may overestimate the effects on soil C fluxes in the real world. Therefore, we propose that more multifactorial experiments should be considered in studying Earth systems. © 2016 John Wiley & Sons Ltd.

Effects of Anthropogenic Nitrogen Loading on Riverine Nitrogen Export in the Northeastern USA

NASA Astrophysics Data System (ADS)

Boyer, E. W.; Goodale, C. L.; Howarth, R. W.

2001-05-01

Human activities have greatly altered the nitrogen (N) cycle, accelerating the rate of N fixation in landscapes and delivery of N to water bodies. To examine the effects of anthropogenic N inputs on riverine N export, we quantified N inputs and riverine N loss for 16 catchments along a latitudinal profile from Maine to Virginia, which encompass a range of climatic variability and are major drainages to the coast of the North Atlantic Ocean. We quantified inputs of N to each catchment: atmospheric deposition, fertilizer application, agricultural and forest biological N fixation, and the net import of N in food and feed. We compared these inputs with N losses from the system in riverine export. The importance of the relative sources varies widely by watershed and is related to land use. Atmospheric deposition was the largest source (>60%) to the forested catchments of northern New England (e.g., Penobscot and Kennebec); import of N in food was the largest source of N to the more populated regions of southern New England (e.g., Charles and Blackstone); and agricultural inputs were the dominant N sources in the Mid-Atlantic region (e.g., Schuylkill and Potomac). Total N inputs to each catchment increased with percent cover in agriculture and urban land, and decreased with percent forest. Over the combined area of the catchments, net atmospheric deposition was the largest single source input (34%), followed by imports of N in food and feed (24%), fixation in agricultural lands (21%), fertilizer use (15%), and fixation in forests (6%). Riverine export of N is well correlated with N inputs, but it accounts for only a fraction (28%) of the total N inputs. This work provides an understanding of the sources of N in landscapes, and highlights how human activities impact N cycling in the northeast region.

Convergent responses of nitrogen and phosphorus resorption to nitrogen inputs in a semiarid grassland

USGS Publications Warehouse

Lü, Xiao-Tao; Reed, Sasha; Yu, Qiang; He, Nian-Peng; Wang, Zheng-Wen; Han, Xing-Guo

2013-01-01

Human activities have significantly altered nitrogen (N) availability in most terrestrial ecosystems, with consequences for community composition and ecosystem functioning. Although studies of how changes in N availability affect biodiversity and community composition are relatively common, much less remains known about the effects of N inputs on the coupled biogeochemical cycling of N and phosphorus (P), and still fewer data exist regarding how increased N inputs affect the internal cycling of these two elements in plants. Nutrient resorption is an important driver of plant nutrient economies and of the quality of litter plants produce. Accordingly, resorption patterns have marked ecological implications for plant population and community fitness, as well as for ecosystem nutrient cycling. In a semiarid grassland in northern China, we studied the effects of a wide range of N inputs on foliar nutrient resorption of two dominant grasses, Leymus chinensis and Stipa grandis. After 4 years of treatments, N and P availability in soil and N and P concentrations in green and senesced grass leaves increased with increasing rates of N addition. Foliar N and P resorption significantly decreased along the N addition gradient, implying a resorption-mediated, positive plant–soil feedback induced by N inputs. Furthermore, N : P resorption ratios were negatively correlated with the rates of N addition, indicating the sensitivity of plant N and P stoichiometry to N inputs. Taken together, the results demonstrate that N additions accelerate ecosystem uptake and turnover of both N and P in the temperate steppe and that N and P cycles are coupled in dynamic ways. The convergence of N and P resorption in response to N inputs emphasizes the importance of nutrient resorption as a pathway by which plants and ecosystems adjust in the face of increasing N availability.

Nutrient co-limited Trichodesmium as nitrogen source or sink in a future ocean.

PubMed

Walworth, Nathan G; Fu, Fei-Xue; Lee, Michael D; Cai, Xiaoni; Saito, Mak A; Webb, Eric A; Hutchins, David A

2017-11-27

Nitrogen-fixing (N 2 ) cyanobacteria provide bioavailable nitrogen to vast ocean regions but are in turn limited by iron (Fe) and/or phosphorus (P), which may force them to employ alternative nitrogen acquisition strategies. The adaptive responses of nitrogen-fixers to global-change drivers under nutrient-limited conditions could profoundly alter the current ocean nitrogen and carbon cycles. Here, we show that the globally-important N 2 -fixer Trichodesmium fundamentally shifts nitrogen metabolism towards organic-nitrogen scavenging following long-term high-CO 2 adaptation under iron and/or phosphorus (co)-limitation. Global shifts in transcripts and proteins under high CO 2 /Fe-limited and/or P-limited conditions include decreases in the N 2 -fixing nitrogenase enzyme, coupled with major increases in enzymes that oxidize trimethylamine (TMA). TMA is an abundant, biogeochemically-important organic nitrogen compound that supports rapid Trichodesmium growth while inhibiting N 2 fixation. In a future high-CO 2 ocean, this whole-cell energetic reallocation towards organic nitrogen scavenging and away from N 2 -fixation may reduce new-nitrogen inputs by Trichodesmium , while simultaneously depleting the scarce fixed-nitrogen supplies of nitrogen-limited open ocean ecosystems. Importance Trichodesmium is among the most biogeochemically-significant microorganisms in the ocean, since it supplies up to 50% of the new nitrogen supporting open ocean food webs. We used Trichodesmium cultures adapted to high CO 2 for 7 years followed by additional exposure to iron and/or phosphorus (co)-limitation. We show that 'future ocean' conditions of high CO 2 and concurrent nutrient limitation(s) fundamentally shift nitrogen metabolism away from nitrogen fixation, and instead towards upregulation of organic-nitrogen scavenging pathways. We show that Trichodesmium's responses to projected future ocean conditions include decreases in the nitrogen-fixing nitrogenase enzymes, coupled with major increases in enzymes that oxidize the abundant organic nitrogen source trimethylamine (TMA). Such a shift towards organic nitrogen uptake and away from nitrogen fixation may substantially reduce new-nitrogen inputs by Trichodesmium to the rest of the microbial community in the future high-CO 2 ocean, with potential global implications for ocean carbon and nitrogen cycling. Copyright © 2017 American Society for Microbiology.

Isotopic evidence for nitrogen mobility in peat bogs

NASA Astrophysics Data System (ADS)

Novak, Martin; Stepanova, Marketa; Jackova, Ivana; Vile, Melanie A.; Wieder, R. Kelman; Buzek, Frantisek; Adamova, Marie; Erbanova, Lucie; Fottova, Daniela; Komarek, Arnost

2014-05-01

Elevated nitrogen (N) input may reduce carbon (C) storage in peat. Under low atmospheric deposition, most N is bound in the moss layer. Under high N inputs, Sphagnum is not able to prevent penetration of dissolved N to deeper peat. Nitrogen may become available to the roots of invading vascular plants. The concurrent oxygenation of deeper peat layers, along with higher supply of labile organic C, may enhance microbial decomposition and lead to peat thinning. The resulting higher emissions of greenhouse gases may accelerate global warming. Seepage of N to deeper peat has never been quantified. Here we present evidence for post-depositional mobility of atmogenic N in peat, based on natural-abundance N isotope ratios. We conducted a reciprocal peat transplant experiment between two Sphagnum-dominated peat bogs in the Czech Republic (Central Europe), differing in anthropogenic N inputs. The northern site VJ received as much as 33 kg N ha-1 yr-1 via spruce canopy throughfall. The southern site was less polluted (17.6 kg N ha-1 yr-1). Isotope signatures of living moss differed between the two sites (δ15N of -3‰ and -7‰ at VJ and CB, respectively). After 18 months, an isotope mass balance was constructed. In the CB-to-VJ transplant, a significant portion of original CB nitrogen (98-31%) was removed and replaced by nitrogen of the host site throughout the top 10 cm of the profile. Nitrogen, deposited at VJ, was immobilized in imported CB peat that was up to 20 years old. Additionally, we compared N concentration and N accumulation rates in 210Pb-dated peat profiles with well-constrained data on historical atmospheric N pollution. Nationwide N emissions peaked in 1990, while VJ exhibited the highest N content in peat that formed in 1930. This de-coupling of N inputs and N retention in peat might be interpreted as a result of translocation of dissolved pollutant N downcore, corroborating our δ15N results at VJ and CB. Data from a variety of peat bogs along pollution and climatic gradients would be needed to test to what extent the record of atmospheric N inputs in peat is overprinted by variable, locally-controlled decomposition rates.

Altered nitrogen balance and decreased urea excretion in male rats fed cafeteria diet are related to arginine availability.

PubMed

Sabater, David; Agnelli, Silvia; Arriarán, Sofía; Fernández-López, José-Antonio; Romero, María del Mar; Alemany, Marià; Remesar, Xavier

2014-01-01

Hyperlipidic diets limit glucose oxidation and favor amino acid preservation, hampering the elimination of excess dietary nitrogen and the catabolic utilization of amino acids. We analyzed whether reduced urea excretion was a consequence of higher NO x ; (nitrite, nitrate, and other derivatives) availability caused by increased nitric oxide production in metabolic syndrome. Rats fed a cafeteria diet for 30 days had a higher intake and accumulation of amino acid nitrogen and lower urea excretion. There were no differences in plasma nitrate or nitrite. NO(x) and creatinine excretion accounted for only a small part of total nitrogen excretion. Rats fed a cafeteria diet had higher plasma levels of glutamine, serine, threonine, glycine, and ornithine when compared with controls, whereas arginine was lower. Liver carbamoyl-phosphate synthetase I activity was higher in cafeteria diet-fed rats, but arginase I was lower. The high carbamoyl-phosphate synthetase activity and ornithine levels suggest activation of the urea cycle in cafeteria diet-fed rats, but low arginine levels point to a block in the urea cycle between ornithine and arginine, thereby preventing the elimination of excess nitrogen as urea. The ultimate consequence of this paradoxical block in the urea cycle seems to be the limitation of arginine production and/or availability.

Altered Nitrogen Balance and Decreased Urea Excretion in Male Rats Fed Cafeteria Diet Are Related to Arginine Availability

PubMed Central

Sabater, David; Arriarán, Sofía; Fernández-López, José-Antonio; Romero, María del Mar; Remesar, Xavier

2014-01-01

Hyperlipidic diets limit glucose oxidation and favor amino acid preservation, hampering the elimination of excess dietary nitrogen and the catabolic utilization of amino acids. We analyzed whether reduced urea excretion was a consequence of higher NOx; (nitrite, nitrate, and other derivatives) availability caused by increased nitric oxide production in metabolic syndrome. Rats fed a cafeteria diet for 30 days had a higher intake and accumulation of amino acid nitrogen and lower urea excretion. There were no differences in plasma nitrate or nitrite. NOx and creatinine excretion accounted for only a small part of total nitrogen excretion. Rats fed a cafeteria diet had higher plasma levels of glutamine, serine, threonine, glycine, and ornithine when compared with controls, whereas arginine was lower. Liver carbamoyl-phosphate synthetase I activity was higher in cafeteria diet-fed rats, but arginase I was lower. The high carbamoyl-phosphate synthetase activity and ornithine levels suggest activation of the urea cycle in cafeteria diet-fed rats, but low arginine levels point to a block in the urea cycle between ornithine and arginine, thereby preventing the elimination of excess nitrogen as urea. The ultimate consequence of this paradoxical block in the urea cycle seems to be the limitation of arginine production and/or availability. PMID:24707502

Bioremediation using Gracilaria chouae co-cultured with Sparus macrocephalus to manage the nitrogen and phosphorous balance in an IMTA system in Xiangshan Bay, China.

PubMed

Wu, Hailong; Huo, Yuanzi; Han, Fang; Liu, Yuanyuan; He, Peimin

2015-02-15

A cage experiment using the red alga Gracilaria chouae co-cultured with the black seabream Sparus macrocephalus in Xiangshan Bay, China was conducted to measure the nutrient flux of the integrated multi-trophic aquaculture (IMTA) system. Results showed that trash fish were the main nutrient input contributor and adult fish were the main nutrient output contributor in the system. Contents of N and P in adult fish accounted for 54.45% and 59.48% of N and P in trash fish and fry, which suggests that 45.55% of N and 40.52% of P generated by fish farming were released into to the water. G. chouae proved to be an efficient bioremediation species in this IMTA system. To balance the excess nutrients generated by the system, 231.09 kg of seedlings should be cultured and 5315.07 kg of adult seaweed should be harvested. Copyright © 2014 Elsevier Ltd. All rights reserved.

Nutrient input from the Loxahatchee River Environmental Control District sewage-treatment plant to the Loxahatchee River Estuary, southeastern Florida

USGS Publications Warehouse

Sonntag, W.H.; McPherson, B.F.

1984-01-01

Two test discharges of treated-sewage effluent were made to the Loxahatchee River in February and September 1981 from the ENCON sewage-treatment plant to document nutrient loading and downstream transport of the effluent to the estuary under maximum daily discharge allowable by law (4 million gallons per day). Concentrations of total nitrogen in the effluent exceeded background concentrations by as much as 7 times during the February test, while concentrations of total phosphorus exceeded background concentrations by as much as 112 times during the September test. The effluent was transported downstream to the estuary in less than 24 hours. Discharge of treated sewage effluent to the river-estuary system in the 1981 water year accounted for less than 0.5 percent of the total nitrogen and 8 percent of the total phosphorus discharged from the major tributaries to the estuary. If maximum discharges of effluent (4 million gallons per day) were sustained throughout the year, annual nitrogen loading from the effluent would account for 5 to 18 percent of the total nitrogen input by the major tributaries to the estuary. With maximum discharges of effluent, annual phosphorus loading would exceed the amount of phosphorus input by the major tributaries to the estuary by 54 to 167 percent. (USGS)

Nutrient mass balance and trends, Mobile River Basin, Alabama, Georgia, and Mississippi

USGS Publications Warehouse

Harned, D.A.; Atkins, J.B.; Harvill, J.S.

2004-01-01

A nutrient mass balance - accounting for nutrient inputs from atmospheric deposition, fertilizer, crop nitrogen fixation, and point source effluents; and nutrient outputs, including crop harvest and storage - was calculated for 18 subbasins in the Mobile River Basin, and trends (1970 to 1997) were evaluated as part of the U.S. Geological Survey National Water Quality Assessment (NAWQA) Program. Agricultural nonpoint nitrogen and phosphorus sources and urban nonpoint nitrogen sources are the most important factors associated with nutrients in this system. More than 30 percent of nitrogen yield in two basins and phosphorus yield in eight basins can be attributed to urban point source nutrient inputs. The total nitrogen yield (1.3 tons per square mile per year) for the Tombigbee River, which drains a greater percentage of agricultural (row crop) land use, was larger than the total nitrogen yield (0.99 tons per square mile per year) for the Alabama River. Decreasing trends of total nitrogen concentrations in the Tombigbee and Alabama Rivers indicate that a reduction occurred from 1975 to 1997 in the nitrogen contributions to Mobile Bay from the Mobile River. Nitrogen concentrations also decreased (1980 to 1995) in the Black Warrior River, one of the major tributaries to the Tombigbee River. Total phosphorus concentrations increased from 1970 to 1996 at three urban influenced sites on the Etowah River in Georgia. Multiple regression analysis indicates a distinct association between water quality in the streams of the Mobile River drainage basin and agricultural activities in the basin.

The best and worst of corn nitrogen rate recommendation tools used in the Midwest

USDA-ARS?s Scientific Manuscript database

Publicly-available nitrogen (N) rate recommendation tools are utilized to help maximize yield in corn production. These tools often fail when N is over-applied and results in excess N being lost to the environment, or when N is under-applied and results in decreased yield and economic returns. The p...

Using epiphytic macrolichen communities for biomonitoring ammonia in forests of the greater Sierra Nevada, California

Treesearch

Sarah Jovan; Bruce Mccune

2006-01-01

Chronic, excessive nitrogen deposition is potentially an important ecological threat to forests of the greater Sierra Nevada in California. We developed a model for ammonia bioindication, a major nitrogen pollutant in the region, using epiphytic macrolichens. We used non-metric multidimensional scaling to extract gradients in lichen community composition from surveys...

Growth, gas exchange, foliar nitrogen content, and water use of subirrigated and overhead irrigated Populus tremuloides Michx. seedlings

Treesearch

Anthony S. Davis; Matthew M. Aghai; Jeremiah R. Pinto; Kent G. Apostal

2011-01-01

Because limitations on water used by container nurseries has become commonplace, nursery growers will have to improve irrigation management. Subirrigation systems may provide an alternative to overhead irrigation systems by mitigating groundwater pollution and excessive water consumption. Seedling growth, gas exchange, leaf nitrogen (N) content, and water use were...

Nitrogen balance of a boreal Scots pine forest

NASA Astrophysics Data System (ADS)

Korhonen, J. F. J.; Pihlatie, M.; Pumpanen, J.; Aaltonen, H.; Hari, P.; Levula, J.; Kieloaho, A.-J.; Nikinmaa, E.; Vesala, T.; Ilvesniemi, H.

2013-02-01

The productivity of boreal forests is considered to be limited by low nitrogen (N) availability. Increased atmospheric N deposition has altered the functioning and N cycling of these N-sensitive ecosystems by increasing the availability of reactive nitrogen. The most important components of N pools and fluxes were measured in a boreal Scots pine stand in Hyytiälä, Southern Finland. The measurements at the site allowed direct estimations of nutrient pools in the soil and biomass, inputs from the atmosphere and outputs as drainage flow and gaseous losses from two micro-catchments. N was accumulating in the system, mainly in woody biomass, at a rate of 7 kg N ha-1 yr-1. Nitrogen input as atmospheric deposition was 7.4 kg N ha-1 yr-1. Dry deposition and organic N in wet deposition contributed over half of the inputs in deposition. Total outputs were 0.4 kg N ha-1 yr-1, the most important outputs being N2O emission to the atmosphere and organic N flux in drainage flow. Nitrogen uptake and retranslocation were equally important sources of N for plant growth. Most of the assimilated N originated from decomposition of organic matter, and the fraction of N that could originate directly from deposition was about 30%. In conclusion, atmospheric N deposition fertilizes the site considerably, but there are no signs of N saturation. Further research is needed to estimate soil N2 fluxes (emission and fixation), which may amount up to several kg N ha-1 yr-1.

Unusually high (210)Po activities in the surface water of the Zhubi Coral Reef Lagoon in the South China Sea.

PubMed

Yang, Weifeng; Huang, Yipu; Chen, Min; Qiu, Yusheng; Li, Hongbin; Zhang, Lei

2011-10-01

Recent researches revealed the exciting application of (210)Po in tracing carbon and nitrogen cycling in the coral reef system. In order to quantify the recycling of particulate organic nitrogen (PON), both (210)Po and (210)Pb were examined at both high and low tides in the Zhubi Coral Reef lagoon, the South China Sea. Unusually, much higher (210)Po activities and (210)Po/(210)Pb ratios, in comparison with those found in the open seawater and the lagoon subsurface water, showed additional input of (210)Po besides production from in situ(210)Pb in the lagoon surface water. Statistical analysis identified that the reef flat seawater was the additional (210)Po source. Based on a mass balance model, the input rates of (210)Po varied from 0.04 Bq m(-3)year(-1) to 8.41 Bq m(-3)year(-1). On average, the additional (210)Po contributed more than 60% of the total (210)Po. The particulate (210)Po significantly correlated with the concentrations of PON, indicating that diffusion of (210)Po from sediment could be used to quantify the recycling of nitrogen. The average input rate of nitrogen was 16 mmol m(-3)year(-1), which can support up to 11% of the primary production rate. These results suggested that the unusual behavior of (210)Po could provide new insight into the nitrogen recycling in the coral reef system. Copyright © 2011 Elsevier B.V. All rights reserved.

[Spatio-temporal changes of nitrogen balance in 1980-2005 for agricultural land in Three Gorges Reservoir Area].

PubMed

Xu, Xi-bao; Yang, Gui-shan; Li, Heng-peng

2009-08-15

Based on the long-term agricultural statistics data at the county scale, the estimation of nitrogen balance from 1980 to 2005 for agricultural land in Three Gorges Reservoir Area was made by the OECD soil surface nitrogen balance model with some suitable modification. The spatio-temporal changes of nitrogen balance and its drivers were analyzed. The results showed that the total inputs and total surplus of nitrogen from 1980 to 2005 presented increasing trends continuously, from 23.4 x 10(4) t and 14.4 x 104 t to 45.6 x 10(4) t and 30 x 10(4) t respectively. The total output of nitrogen in 1980-1995 was at the increasing trend, from 9.0 x 10(4) t to 16.7 x 10(4) t, while that of 1996-2005 was keeping steady. The average unit surplus of nitrogen in 1980-1998 was also at the increasing trend, from 133.4 kg/hm2 to 310.3 kg/hm(2); and the trend inclined to be steady after 1998, while the spatial differential pattern toned up. The great spatial changes for nitrogen surplus from 1980 to 2005, mainly centralized at the head and the middle of the Three Gorges Reservoir Area, similar to the spatial distribution of the resettlement. Fertilizer, manure and biological fixation were the main contributors of nitrogen input sources, accumulatively totaled for above 90%. Nitrogen balance changes were mainly influenced by the macro-environment of fertilizer utilization before 1995, while which were influenced by the large amounts of the resettlement for Three Gorges Project after 1995. However, how much the effects of the resettlement on nitrogen balance need to be further explored. Developing sideline, agricultural structure transition or ecological resettlement should be considered to control nitrogen emission.

Nitrogen Limitation of Pond Ecosystems on the Plains of Eastern Colorado

PubMed Central

Mischler, John A.; Taylor, Philip G.; Townsend, Alan R.

2014-01-01

Primary production in freshwater ecosystems is often limited by the availability of phosphorus (P), nitrogen (N), or a combination of both (NP co-limitation). While N fixation via heterocystous cyanobacteria can supply additional N, no comparable mechanism for P exists; hence P is commonly considered to be the predominant and ultimate limiting nutrient in freshwater ecosystems. However, N limitation can be maintained if P is supplied in stoichiometric excess of N (including N fixation). The main objective of this study was to examine patterns in nutrient limitation across a series of 21 vernal ponds in Eastern Colorado where high P fluxes are common. Across all ponds, water column dissolved inorganic N steadily decreased throughout the growth season due to biological demand while total dissolved P remained stable. The water column dissolved inorganic N to total dissolved P ratios suggested a transition from NP co-limitation to N limitation across the growth season. Periphyton and phytoplankton %C was strongly correlated with %N while %P was assimilated in excess of %N and %C in many ponds. Similarly, in nutrient addition bottle assays algae responded more strongly to N additions (11 out of 18 water bodies) than P additions (2 out of 18 water bodies) and responded most strongly when N and P were added in concert (12 out of 18 water bodies). Of the ponds that responded to nutrient addition, 92% exhibited some sort of N limitation while less than 8% were limited by P alone. Despite multiple lines of evidence for N limitation or NP co-limitation, N fixation rates were uniformly low across most ponds, most likely due to inhibition by water column nitrate. Within this set of 18 water bodies, N limitation or NP co-limitation is widespread due to the combination high anthropogenic P inputs and constrained N fixation rates. PMID:24824838

Duelling 'CyanoHABs': unravelling the environmental drivers controlling dominance and succession among diazotrophic and non-N2 -fixing harmful cyanobacteria.

PubMed

Paerl, Hans W; Otten, Timothy G

2016-02-01

Eutrophication often manifests itself by increased frequencies and magnitudes of cyanobacterial harmful algal blooms (CyanoHABs) in freshwater systems. It is generally assumed that nitrogen-fixing cyanobacteria will dominate when nitrogen (N) is limiting and non-N2 fixers dominate when N is present in excess. However, this is rarely observed in temperate lakes, where N2 fixers often bloom when N is replete, and non-fixers (e.g. Microcystis) dominate when N concentrations are lowest. This review integrates observations from previous studies with insights into the environmental factors that select for CyanoHAB groups. This information may be used to predict how nutrient reduction strategies targeting N, phosphorus (P) or both N and P may alter cyanobacterial community composition. One underexplored concern is that as N inputs are reduced, CyanoHABs may switch from non-N2 fixing to diazotrophic taxa, with no net improvement in water quality. However, monitoring and experimental observations indicate that in eutrophic systems, minimizing both N and P loading will lead to the most significant reductions in total phytoplankton biomass without this shift occurring, because successional patterns appear to be strongly driven by physical factors, including temperature, irradiance and hydrology. Notably, water temperature is a primary driver of cyanobacterial community succession, with warming favouring non-diazotrophic taxa. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Convergent evidence for widespread rock nitrogen sources in Earth’s surface environment

NASA Astrophysics Data System (ADS)

Houlton, B. Z.; Morford, S. L.; Dahlgren, R. A.

2018-04-01

Nitrogen availability is a pivotal control on terrestrial carbon sequestration and global climate change. Historical and contemporary views assume that nitrogen enters Earth’s land-surface ecosystems from the atmosphere. Here we demonstrate that bedrock is a nitrogen source that rivals atmospheric nitrogen inputs across major sectors of the global terrestrial environment. Evidence drawn from the planet’s nitrogen balance, geochemical proxies, and our spatial weathering model reveal that ~19 to 31 teragrams of nitrogen are mobilized from near-surface rocks annually. About 11 to 18 teragrams of this nitrogen are chemically weathered in situ, thereby increasing the unmanaged (preindustrial) terrestrial nitrogen balance from 8 to 26%. These findings provide a global perspective to reconcile Earth’s nitrogen budget, with implications for nutrient-driven controls over the terrestrial carbon sink.

Nitrogen and harvest impact on warm-season grasses biomass yield

USDA-ARS?s Scientific Manuscript database

Perennial warm-season grasses have drawn interest as bioenergy feedstocks due to their high productivity with minimal amounts of inputs while producing multiple environmental benefits. Nitrogen (N) fertility and harvest timing are critical management practices when optimizing biomass yield of these ...

BELOWGROUND NITROGEN UPTAKE AND ALLOCATION BY SPARTINA ALTERNIFLORA AND DISTICHLIS SPICATA

EPA Science Inventory

Anthropogenic nitrogen inputs coupled with rising sea level complicate predictions of marsh stability. As marsh stability is a function of its vegetation, it is important to understand the mechanisms that drive community dynamics. Many studies have examined aboveground dynamics a...

EFFECTS OF SUCCESSION ON NITROGEN EXPORT IN THE WEST-CENTRAL CASCADES, OREGON

EPA Science Inventory

Conceptual models predict that unpolluted, aggrading forest ecosystems tightly retain available nitrogen (N) until declining productivity by mature trees and storage in detritus reduces the demand for essential nutrients, and N export increases to equal input. Short-term nitrate ...

Modelling Nitrogen Cycling in a Mariculture Ecosystem as a Tool to Evaluate its Outflow

NASA Astrophysics Data System (ADS)

Lefebvre, S.; Bacher, C.; Meuret, A.; Hussenot, J.

2001-03-01

A model was constructed to describe an intensive mariculture ecosystem growing sea bass ( Dicentrarchus labrax), located in the salt marshes of the Fiers d'Ars Bay on the French Atlantic coast, in order to assess nitrogen cycling within the system and nitrogen outflow from the system. The land-based system was separated into three main compartments: a seawater reservoir, fish ponds and a lagoon (sedimentation pond). Three submodels were built for simulation purposes: (1) a hydrological submodel which simulated water exchange; (2) a fish growth and excretion bioenergetic submodel; and (3) a nitrogen compound transformation and loss submodel (i.e. ammonification, nitrification and assimilation processes). A two-year sampling period of nitrogen water quality concentrations and fish growth was used to validate the model. The model fitted the observations of dissolved nitrogen components, fish growth and water fluxes on a daily basis in all the compartments. The dissolved inorganic nitrogen ranged widely and over time from 0·5 to 9 g N m -3within the system, depending on seawater supply and water temperature, without affecting fish growth. Fish feed was the most important input of nitrogen into the system. The mean average input of nitrogen in the feed was 205 kg N day -1, of which 19% was retained by fish, 4% accumulated in the sediment and 61% flowed from the system as dissolved components. The farm represented about 25% of the total dissolved nitrogen export from the bay, although the farm surface area was 100 times smaller than that of the bay.

Declining spatial efficiency of global cropland nitrogen allocation

NASA Astrophysics Data System (ADS)

Mueller, Nathaniel D.; Lassaletta, Luis; Runck, Bryan C.; Billen, Gilles; Garnier, Josette; Gerber, James S.

2017-02-01

Efficiently allocating nitrogen (N) across space maximizes crop productivity for a given amount of N input and reduces N losses to the environment. Here we quantify changes in the global spatial efficiency of cropland N use by calculating historical trade-off frontiers relating N inputs to possible N yield assuming efficient allocation. Time series cropland N budgets from 1961 to 2009 characterize the evolution of N input-yield response functions across 12 regions and are the basis for constructing trade-off frontiers. Improvements in agronomic technology have substantially increased cropping system yield potentials and expanded N-driven crop production possibilities. However, we find that these gains are compromised by the declining spatial efficiency of N use across regions. Since the start of the Green Revolution, N inputs and yields have moved farther from the optimal frontier over time; in recent years (1994-2009), global N surplus has grown to a value that is 69% greater than what is possible with efficient N allocation between regions. To reflect regional pollution and agricultural development goals, we construct scenarios that restrict reallocation, finding that these changes only slightly decrease potential gains in nitrogen use efficiency. Our results are inherently conservative due to the regional unit of analysis, meaning a larger potential exists than is quantified here for cross-scale policies to promote spatially efficient N use.

Mycorrhizal fungal community relationship to root nitrogen concentration over a regional atmospheric nitrogen deposition gradient in the northeastern USA

Treesearch

Erik A. Lilleskov; Philip M. Wargo; Kristiina A. Vogt; Daniel J. Vogt

2008-01-01

Increased nitrogen (N) input has been found to alter ectomycorrhizal fungal communities over short deposition gradients and in fertilization experiments; however, its effects over larger spatial scales have not been determined. To address this gap, we reanalyzed data from a study originally designed to examine the effects of soil aluminum/calcium (Al/Ca) ratios on the...

Use of MODIS Vegetation Data in Dynamic SPARROW Modeling of Reactive Nitrogen Flux

NASA Astrophysics Data System (ADS)

Smith, R. A.; Brakebill, J.; Schwarz, G. E.; Nolin, A. W.; Shih, J.; Blomquist, J.; Alexander, R. B.; Macauley, M.

2012-12-01

SPARROW models are widely used to identify and quantify the sources of contaminants in watersheds and to predict their flux and concentration at specified locations downstream. Conventional SPARROW models are steady-state in form, and describe the average relationship between sources and stream conditions based on non-linear regression of long-term water quality monitoring data on spatially-referenced explanatory information. But many watershed management issues involve intra- and inter-annual changes in contaminant sources, hydrologic forcing, or other environmental conditions which cause a temporary imbalance between watershed inputs and outputs. Dynamic behavior of the system relating to changes in watershed storage and processing then becomes important. We describe the results of dynamic statistical calibration of a SPARROW model of total reactive nitrogen flux in the Potomac River Basin based on seasonal water quality and watershed explanatory data for 80 monitoring stations over the period 2000 to 2008. One challenge in dynamic modeling of reactive nitrogen is obtaining frequently-reported, spatially-detailed input data on the phenology of agricultural production and growth of other terrestrial vegetation. In this NASA-funded research, we use the Enhanced Vegetation Index (EVI) and gross primary productivity (GPP) data from the Terra Satellite-borne MODIS sensor to parameterize seasonal uptake and release of nitrogen. The spatial reference frame of the model is a 16,000-reach, 1:100,000-scale stream network, and the computational time step is seasonal. Precipitation and temperature data are from PRISM. The model describes transient storage and transport of nitrogen from multiple nonpoint sources including fertilized cropland, pasture, urban/suburban land, and atmospheric deposition. Removal of nitrogen from watershed storage to stream channels and to "permanent" sinks (deep groundwater and the atmosphere) occurs as parallel first-order processes. Point sources of nitrogen bypass storage and flow directly to stream channels. Model results indicate that, on average, a little more than half of the reactive nitrogen flux comes from transient storage; but in some sub-watersheds a large majority of the flux comes from stored nitrogen input to the watershed in previous seasons and years.

Plasma-chemical processes accompanying discharge in air excited by a microwave beam

NASA Astrophysics Data System (ADS)

Askar'ian, G. A.; Batanov, G. M.; Gritsinin, S. I.; Kossyi, I. A.; Kostinskii, A. Iu.

1990-11-01

Experimental results are presented on plasma-chemical processes of nitrogen oxidation and ozone production accompanying microwave discharge in dry air and in nitrogen-oxygen mixtures. The degree of nitrogen oxidation and the energy expenditure toward the formation of oxides as a function of discharge conditions are established. The experimental results can be explained by assuming oxidation reactions of electron-excited metastable nitrogen molecules by oxygen atoms. Low ozone concentrations in the discharge indicate a significant energy input into the gas.

Effect of different cover crops on C and N cycling in sorghum NT systems.

PubMed

Frasier, Ileana; Quiroga, Alberto; Noellemeyer, Elke

2016-08-15

In many no-till (NT) systems, residue input is low and fallow periods excessive, for which reasons soil degradation occurs. Cover crops could improve organic matter, biological activity, and soil structure. In order to study changes in soil carbon, nitrogen and microbial biomass a field experiment (2010-2012) was set up with sorghum (Sorghum bicolor Moench.) monoculture and with cover crops. Treatments were control (NT with bare fallow), rye (Secale cereale L.) (R), rye with nitrogen fertilization (R+N), vetch (Vicia villosa Roth.) (V), and rye-vetch mixture (VR) cover crops. A completely randomized block design with 4 replicates was used. Soil was sampled once a year at 0.06 and 0.12m depth for total C, microbial biomass carbon (MBC) and-nitrogen (MBN) determinations. Shoot and root biomass of sorghum and cover crops, litter biomass, and their respective carbon and nitrogen contents were determined. Soil temperatures at 0.06 and 0.12m depth, volumetric water contents and nitrate concentrations were determined at sowing, and harvest of each crop, and during sorghum's vegetative phase. NT led to a small increase in MBC and MBN, despite low litter and root biomass residue. Cover crops increased litter, root biomass, total C, MBC, and MBN. Relationships between MBC, MBN, and root-C and -N adjusted to logistic models (R(2)=0.61 and 0.43 for C and N respectively). Litter cover improved soil moisture to 45-50% water filled pore space and soil temperatures not exceeding 25°C during the warmest month. Microbial biomass stabilized at 20.1gCm(-2) and 1.9gNm(-2) in the upper 0.06m. Soil litter disappearance was a good indicator of mineral N availability. These findings support the view that cover crops, specifically legumes in NT systems can increase soil ecosystem services related to water and carbon storage, habitat for biodiversity, and nutrient availability. Copyright © 2016 Elsevier B.V. All rights reserved.

Nutrients discharged to the Mississippi River from eastern Iowa watersheds, 1996-1997

USGS Publications Warehouse

Becher, Kent D.; Schnoebelen, Douglas J.; Akers, Kimberlee K.

2000-01-01

The introduction of nutrients from chemical fertilizer, animal manure, wastewater, and atmospheric deposition to the eastern Iowa environment creates a large potential for nutrient transport in watersheds. Agriculture constitutes 93 percent of all land use in eastern Iowa. As part of the U.S. Geological Survey National Water Quality Assessment Program, water samples were collected (typically monthly) from six small and six large watersheds in eastern Iowa between March 1996 and September 1997. A Geographic Information System (GIS) was used to determine land use and quantify inputs of nitrogen and phosphorus within the study area. Streamliow from the watersheds is to the Mississippi River. Chemical fertilizer and animal manure account for 92 percent of the estimated total nitrogen and 99.9 percent of the estimated total phosphorus input in the study area. Total nitrogen and total phosphorus loads for 1996 were estimated for nine of the 12 rivers and creeks using a minimum variance unbiased estimator model. A seasonal pattern of concentrations and loads was observed. The greatest concentrations and loads occur in the late spring to early summer in conjunction with row-crop fertilizer applications and spring nmoff and again in the late fall to early winter as vegetation goes into dormancy and additional fertilizer is applied to row-crop fields. The three largest rivers in eastern Iowa transported an estimated total of 79,000 metric tons of total nitrogen and 6,800 metric tons of total phosphorus to the Mississippi River in 1996. The estimated mass of total nitrogen and total phosphorus transported to the Mississippi River represents about 19 percent of all estimated nitrogen and 9 percent of all estimated phosphorus input to the study area.

Changes in Chesapeake Bay Hypoxia over the Past Century

NASA Astrophysics Data System (ADS)

Friedrichs, M. A.; Kaufman, D. E.; Najjar, R.; Tian, H.; Zhang, B.; Yao, Y.

2016-02-01

The Chesapeake Bay, one of the world's largest estuaries, is among the many coastal systems where hypoxia is a major concern and where dissolved oxygen thus represents a critical factor in determining the health of the Bay's ecosystem. Over the past century, the population of the Chesapeake Bay region has almost quadrupled, greatly modifying land cover and management practices within the watershed. Simultaneously, the Chesapeake Bay has been experiencing a high degree of climate change, including increases in temperature, precipitation, and precipitation intensity. Together, these changes have resulted in significantly increased riverine nutrient inputs to the Bay. In order to examine how interdecadal changes in riverine nitrogen input affects biogeochemical cycling and dissolved oxygen concentrations in Chesapeake Bay, a land-estuarine-ocean biogeochemical modeling system has been developed for this region. Riverine inputs of nitrogen to the Bay are computed from a terrestrial ecosystem model (the Dynamic Land Ecosystem Model; DLEM) that resolves riverine discharge variability on scales of days to years. This temporally varying discharge is then used as input to the estuarine-carbon-biogeochemical model embedded in the Regional Modeling System (ROMS), which provides estimates of the oxygen concentrations and nitrogen fluxes within the Bay as well as advective exports from the Bay to the adjacent Mid-Atlantic Bight shelf. Simulation results from this linked modeling system for the present (early 2000s) have been extensively evaluated with in situ and remotely sensed data. Longer-term simulations are used to isolate the effect of increased riverine nitrogen loading on dissolved oxygen concentrations and biogeochemical cycling within the Chesapeake Bay.

A nitrogen mass balance for California

NASA Astrophysics Data System (ADS)

Liptzin, D.; Dahlgren, R. A.

2010-12-01

Human activities have greatly altered the global nitrogen cycle and these changes are apparent in water quality, air quality, ecosystem and human health. However, the relative magnitude of the sources of new reactive nitrogen and the fate of this nitrogen is not well established. Further, the biogeochemical aspects of the nitrogen cycle are often studied in isolation from the economic and social implications of all the transformations of nitrogen. The California Nitrogen Assessment is an interdisciplinary project whose aim is evaluating the current state of nitrogen science, practice, and policy in the state of California. Because of the close proximity of large population centers, highly productive and diverse agricultural lands and significant acreage of undeveloped land, California is a particularly interesting place for this analysis. One component of this assessment is developing a mass balance of nitrogen as well as identifying gaps in knowledge and quantifying uncertainty. The main inputs of new reactive nitrogen to the state are 1) synthetic nitrogen fertilizer, 2) biological nitrogen fixation, and 3) atmospheric nitrogen deposition. Permanent losses of nitrogen include 1) gaseous losses (N2, N2O, NHx, NOy), 2) riverine discharge, 3) wastewater discharge to the ocean, and 4) net groundwater recharge. A final term is the balance of food, feed, and fiber to support the human and animal populations. The largest input of new reactive nitrogen to California is nitrogen fertilizer, but both nitrogen fixation and atmospheric deposition contribute significantly. Non-fertilizer uses, such as the production of nylon and polyurethane, constitutes about 5% of the synthetic N synthesized production. The total nitrogen fixation in California is roughly equivalent on the 400,000 ha of alfalfa and the approximately 40 million ha of natural lands. In addition, even with highly productive agricultural lands, the large population of livestock, in particular dairy cows, requires a net influx of N in feed to the state. In terms of exports, the riverine N loads are smaller than many more mesic climates. Because many of the large population centers are on the coast, N discharged directly from wastewater treatment plants into the ocean is almost four times greater than the N discharge of all of the watersheds in the state combined. Gas losses are estimated through a combination of bottom up approaches using field data, emissions inventories, and numerical models. The largest uncertainties are in emissions of N2 and NH3. Calculated by difference, groundwater N loading represents the largest loss term in the mass balance. Contamination of groundwater with nitrates is a serious concern in many areas of the state. Given the long residence time of groundwater in many aquifers like the Central Valley the current and past N inputs to groundwater pose a hazard to drinking water supplies for decades to come. These calculations along with the analysis of management and policy tools will help elucidate the spatial location or activities that would be best to target to reduce the negative consequences of human alteration of the nitrogen cycle.

N-ViroTech--a novel process for the treatment of nutrient limited wastewaters.

PubMed

Slade, A H; Gapes, D J; Stuthridge, T R; Anderson, S M; Dare, P H; Pearson, H G W; Dennis, M

2004-01-01

As pulp and paper wastewaters are mostly deficient in nitrogen and phosphorus, historical practice has dictated that they cannot be effectively treated using microbiological processes without the addition of supplementary nutrients, such as urea and phosphoric acid. Supplementation is a difficult step to manage efficiently, requiring extensive post-treatment monitoring and some degree of overdosing to ensure sufficient nutrient availability under all conditions. As a result, treated wastewaters usually contain excess amounts of both nutrients, leading to potential impacts on the receiving waters such as eutrophication. N-ViroTech is a highly effective alternative treatment technology which overcomes this nutrient deficiency/excess paradox. The process relies on communities of nitrogen-fixing bacteria, which are able to directly fix nitrogen from the atmosphere, thus satisfying their cellular nitrogen requirements. The process relies on manipulation of growth conditions within the biological system to maintain a nitrogen-fixing population whilst achieving target wastewater treatment performance. The technology has significant advantages over conventional activated sludge operation, including: Improved environmental performance. Nutrient loadings in the final treated effluent for selected nitrogen and phosphorus species (particularly ammonium and orthophosphate) may be reduced by over 90% compared to conventional systems; Elimination of nitrogen supplementation, and minimisation of phosphorus supplementation, thus achieving significant chemical savings and resulting in between 25% and 35% savings in operational costs for a typical system; Self-regulation of nutrient requirements, as the bacteria only use as much nitrogen as they require, allowing for substantially less operator intervention and monitoring. This paper will summarise critical performance outcomes of the N-ViroTech process utilising results from laboratory-, pilot-scale and recent alpha-adopter, full-scale trials.

Nitrogen deposition and its contribution to nutrient inputs to intensively managed agricultural ecosystems.

PubMed

He, Chun-E; Wang, Xin; Liu, Xuejun; Fangmeier, Andreas; Christie, Peter; Zhang, Fusuo

2010-01-01

Interest in nitrogen inputs via atmospheric deposition to agricultural ecosystems has increased recently, especially on the North China Plain because of extremely intensive agricultural systems and rapid urbanization in this region. Nitrogen deposition may make a significant contribution to crop N requirements but may also impose a considerable nutrient burden on the environment in general. We quantified total N deposition at two locations, Dongbeiwang near Beijing and Quzhou in Hebei province, over a two-year period from 2005 to 2007 using an 15N tracer method, the integrated total N input (ITNI) system. Total airborne N inputs to a maize wheat rotation system at both locations ranged from 99 to 117 kg N x ha(-1) x yr(-1), with higher N deposition during the maize season (57-66 kg N/ha) than the wheat season (42-51 kg N/ha). Plant available N from deposition for maize and wheat was about 52 kg N x ha(-1) x yr(-1), accounting for 50% of the total N deposition or 31% of total N uptake by the two crop species. In addition, a correction factor was derived for the maize season to adjust values obtained from small pots (0.057 m2) compared with field trays (0.98 m2) because of higher plant density in the pots. The results indicate that atmospheric N deposition is a very important N input and must be taken into account when calculating nutrient budgets in very intensively managed agricultural ecosystems.

Soil C storage and greenhouse gas emission perennial grasses managed for bio energy feedstock

USDA-ARS?s Scientific Manuscript database

Perennial grasses like switchgrass or big bluestem when managed as bioenergy feedstock require nitrogenous inputs. Nitrogen fertilizer frequently cause nitrous oxide emission. Therefore, managing grasses as feedstock may reduce the greenhouse gas (GHG) mitigation potential expected from perennial. ...

How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input

EPA Science Inventory

We conducted a meta-analysis of 103 nitrification inhibitor (NI) studies, and evaluated how NI application affects crop productivity and other ecosystem services in agricultural systems. Our results showed that, compared to conventional fertilizer practice, applications of NI alo...

Changes in nitrogen isotope ratios in estuarine biota following nutrient reductions to Narragansett Bay

EPA Science Inventory

Increased nutrient inputs globally have resulted in widespread eutrophication to many coastal water bodies including Narragansett Bay. Efforts to reduce point source nitrogen load¬ings from waste water treatment facilities (WWTFs) and combined sewer overflows (CSOs) started i...

A Nitrogen Physical Input-Output Table (PIOT) Model for Illinois

EPA Science Inventory

Nitrogen (N) presents an important challenge for sustainability due to its role in providing goods and services to society, since release of N beyond its intended use has many negative consequences. Several systems modeling approaches have been developed to understand the tradeof...

NITROGEN FLUX FROM WEST CASCADE RANGE HEADWATER STREAMS DRAINING FORESTS ALONG A SUCCESSIONAL GRADIENT

EPA Science Inventory

Conceptual models predict that unpolluted, aggrading forest ecosystems tightly retain available nitrogen (N) until declining productivity by mature trees reduces the demand for essential nutrients and export increases to equal N inputs. Short-term nitrate loss following disturban...

COMPARISON OF GENKENSIA DEMISSA (DILLWYN) POPULATIONS IN RHODE ISLAND FRINGE MARSHES WITH VARYING NITROGEN LOADS

EPA Science Inventory

Increased residential development in coastal watersheds has led to increases in anthropogenic nitrogen inputs into estuaries. Sessile bivalves are good candidate organisms to examine animal condition in nutrient-enriched areas because they contribute significantly to energy flow...

The Arabidopsis halophytic relative Thellungiella halophila tolerates nitrogen-limiting conditions by maintaining growth, nitrogen uptake, and assimilation.

PubMed

Kant, Surya; Bi, Yong-Mei; Weretilnyk, Elizabeth; Barak, Simon; Rothstein, Steven J

2008-07-01

A comprehensive knowledge of mechanisms regulating nitrogen (N) use efficiency is required to reduce excessive input of N fertilizers while maintaining acceptable crop yields under limited N supply. Studying plant species that are naturally adapted to low N conditions could facilitate the identification of novel regulatory genes conferring better N use efficiency. Here, we show that Thellungiella halophila, a halophytic relative of Arabidopsis (Arabidopsis thaliana), grows better than Arabidopsis under moderate (1 mm nitrate) and severe (0.4 mm nitrate) N-limiting conditions. Thellungiella exhibited a lower carbon to N ratio than Arabidopsis under N limitation, which was due to Thellungiella plants possessing higher N content, total amino acids, total soluble protein, and lower starch content compared with Arabidopsis. Furthermore, Thellungiella had higher amounts of several metabolites, such as soluble sugars and organic acids, under N-sufficient conditions (4 mm nitrate). Nitrate reductase activity and NR2 gene expression in Thellungiella displayed less of a reduction in response to N limitation than in Arabidopsis. Thellungiella shoot GS1 expression was more induced by low N than in Arabidopsis, while in roots, Thellungiella GS2 expression was maintained under N limitation but was decreased in Arabidopsis. Up-regulation of NRT2.1 and NRT3.1 expression was higher and repression of NRT1.1 was lower in Thellungiella roots under N-limiting conditions compared with Arabidopsis. Differential transporter gene expression was correlated with higher nitrate influx in Thellungiella at low (15)NO(3)(-) supply. Taken together, our results suggest that Thellungiella is tolerant to N-limited conditions and could act as a model system to unravel the mechanisms for low N tolerance.

The Arabidopsis Halophytic Relative Thellungiella halophila Tolerates Nitrogen-Limiting Conditions by Maintaining Growth, Nitrogen Uptake, and Assimilation1[W][OA

PubMed Central

Kant, Surya; Bi, Yong-Mei; Weretilnyk, Elizabeth; Barak, Simon; Rothstein, Steven J.

2008-01-01

A comprehensive knowledge of mechanisms regulating nitrogen (N) use efficiency is required to reduce excessive input of N fertilizers while maintaining acceptable crop yields under limited N supply. Studying plant species that are naturally adapted to low N conditions could facilitate the identification of novel regulatory genes conferring better N use efficiency. Here, we show that Thellungiella halophila, a halophytic relative of Arabidopsis (Arabidopsis thaliana), grows better than Arabidopsis under moderate (1 mm nitrate) and severe (0.4 mm nitrate) N-limiting conditions. Thellungiella exhibited a lower carbon to N ratio than Arabidopsis under N limitation, which was due to Thellungiella plants possessing higher N content, total amino acids, total soluble protein, and lower starch content compared with Arabidopsis. Furthermore, Thellungiella had higher amounts of several metabolites, such as soluble sugars and organic acids, under N-sufficient conditions (4 mm nitrate). Nitrate reductase activity and NR2 gene expression in Thellungiella displayed less of a reduction in response to N limitation than in Arabidopsis. Thellungiella shoot GS1 expression was more induced by low N than in Arabidopsis, while in roots, Thellungiella GS2 expression was maintained under N limitation but was decreased in Arabidopsis. Up-regulation of NRT2.1 and NRT3.1 expression was higher and repression of NRT1.1 was lower in Thellungiella roots under N-limiting conditions compared with Arabidopsis. Differential transporter gene expression was correlated with higher nitrate influx in Thellungiella at low 15NO3− supply. Taken together, our results suggest that Thellungiella is tolerant to N-limited conditions and could act as a model system to unravel the mechanisms for low N tolerance. PMID:18467466

Evaluation of Nitrate Sources and Nitrate Management Strategies in California Suburban Growth Areas

NASA Astrophysics Data System (ADS)

Singleton, M. J.; Moran, J. E.; Esser, B. K.; Leif, R. N.; McNab, W. W.; Carle, S. F.; Moore, K. B.

2005-12-01

Population growth in California has pushed the boundaries of suburban communities into formerly agricultural areas. As a result there is considerable uncertainty as to whether nitrate contamination in groundwater wells results from current sources or is a legacy of agriculture. Fertilizer application for historical agriculture is frequently assumed to be a major source, but septic system leachate, other animal waste, and residential fertilizer application may also contribute. Potential remediation strategies may include improved fertilizer management and/or conversion from septic tanks to sewer systems, but the sources of nitrate and pathways to groundwater must first be identified in order to develop a plan of action. We combine the detection of trace organic compounds that are specific to domestic waste with isotopic compositions of nitrogen and oxygen in nitrate in order to determine nitrate sources. Under anaerobic conditions and in the presence of an electron donor such as organic carbon, microbially mediated denitrification may transform nitrate to harmless nitrogen gas, and fractionate the isotopologues of any residual nitrate. The occurrence of saturated zone denitrification is detected by measuring excess dissolved nitrogen gas with a field-portable membrane inlet mass spectrometer system. Groundwater age dating using the 3H/3He method provides a means of tracking the history of nitrate inputs to groundwater, including changes in nitrate flux after implementation of a remediation program. Groundwater that pre-dates agricultural or suburban activity is used to define natural background levels of nitrate. Study areas in California include Chico, Livermore, and Gilroy. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Biological nitrogen fixation and biomass accumulation within poplar clones as a result of inoculations with diazotrophic endophyte consortia.

PubMed

Knoth, Jenny L; Kim, Soo-Hyung; Ettl, Gregory J; Doty, Sharon L

2014-01-01

Sustainable production of biomass for bioenergy relies on low-input crop production. Inoculation of bioenergy crops with plant growth-promoting endophytes has the potential to reduce fertilizer inputs through the enhancement of biological nitrogen fixation (BNF). Endophytes isolated from native poplar growing in nutrient-poor conditions were selected for a series of glasshouse and field trials designed to test the overall hypothesis that naturally occurring diazotrophic endophytes impart growth promotion of the host plants. Endophyte inoculations contributed to increased biomass over uninoculated control plants. This growth promotion was more pronounced with multi-strain consortia than with single-strain inocula. Biological nitrogen fixation was estimated through (15)N isotope dilution to be 65% nitrogen derived from air (Ndfa). Phenotypic plasticity in biomass allocation and branch production observed as a result of endophyte inoculations may be useful in bioenergy crop breeding and engineering programs. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

40 CFR 60.42c - Standard for sulfur dioxide (SO2).

Code of Federal Regulations, 2010 CFR

2010-07-01

....2 lb/MMBtu) heat input. If coal is combusted with other fuels, the affected facility shall neither... excess of 520 ng/J (1.2 lb/MMBtu) heat input. If coal is fired with coal refuse, the affected facility.../MMBtu) heat input. If coal is combusted with other fuels, the affected facility is subject to the 50...

Informing Policy and Management in New Zealand Agricultural Regions Using Nitrogen and Oxygen Isotopes to Quantify Hot Spots and Hot Moments of Nitrate Loss

NASA Astrophysics Data System (ADS)

Baisden, W. T.; Rissman, C.; Ellis, T.; Rayner, S.; Clough, T. J.; Moore, C.; Killick, M.; Rodway, E.; Horton, T. W.; Clark, M.; Matthews, A.; Roygard, J.

2016-12-01

Nitrate losses from agriculture have significant impacts on freshwater, and occur when runoff generation coincides with nitrogen excess in soil. Analysis of δ15N and δ18O in NO3 is well suited to characterize hot spots and hot moments when NO3 losses occur, by working back from impacted water to soil sources. New Zealand's lack of high δ18O atmospheric and fertilizer NO3 sources and the nation's intensive pastoral agriculture enable δ15N and δ18O in NO3 to differentiate soil and effluent sources, as well as processes linked to flow in different soil physiographic zones. This presentation reviews δ15N-NO3 and δ18O-NO3 results gathered across multiple catchments in three regions (Manawatu, Wairarapa, and Southland) with at least 100 measurements per region. River monitoring sites provide an integrated measure of sources, while fractionation associated with removal processes such as denitrification is largely lost. Within rivers, predominantly pastoral regions show a tight pattern along a 1:1 line where δ15N ranges between 4 and 8 ‰ and δ18O ranges between 0 and 4 ‰, in proportion to agricultural intensity. The δ15N of NO3 appears linked to the δ15N of soil organic matter. Exploration of catchments with higher proportions of crop-based agricultural land use, as well as highly intensive grazing with a decreased reliance on pastoral cover, show migration to lower δ15N values with no change in δ18O. This result was in contrast to expectations of greater evidence for effluents and denitrification, and is interpreted as breakthrough of urea fertilizer or animal urine inputs which have δ15N values close to 0 ‰. Drilling into the landscape using springs, drains and groundwater wells shows greater variability both in space and time. These data provide evidence for a range of sources, including urine, fertilizer and effluents, which breakthrough according to soil and physiographic attributes of landscapes that explain the magnitude and timing of processes controlling the coincidence of nitrogen excess and runoff generation. There appears to be considerable potential for dual-isotope NO3 measurements to be used in conjunction with a simplified classification of landscape physiographic units to support environmental policy and agricultural management.

Effect of nitrogen source on curdlan production by Alcaligenes faecalis ATCC 31749.

PubMed

Jiang, Longfa

2013-01-01

This study aims to investigate the effect of nitrogen source on curdlan production by Alcaligenes faecalis ATCC 31749. Curdlan production fell when excess nitrogen source was present, while biomass accumulation increased as the level of nitrogen source raised. Curdlan production and biomass accumulation were greater with urea compared with those with other nitrogen sources. The highest production of curdlan and biomass accumulation by A. faecalis ATCC 31749 was 28.16 g L(-1) and 9.58 g L(-1), respectively, with urea, whereas those with NH(4)Cl were 15.17 g L(-1) and 6.25 g L(-1), respectively. The optimum fermentation time for curdlan production was also affected by the nitrogen source in the medium. Copyright © 2012 Elsevier B.V. All rights reserved.

Use of MODIS Data in Dynamic SPARROW Analysis of Watershed Loading Reductions

NASA Astrophysics Data System (ADS)

Smith, R. A.; Schwarz, G. E.; Brakebill, J. W.; Hoos, A.; Moore, R. B.; Nolin, A. W.; Shih, J. S.; Journey, C. A.; Macauley, M.

2014-12-01

Predicting the temporal response of stream water quality to a proposed reduction in contaminant loading is a major watershed management problem due to temporary storage of contaminants in groundwater, vegetation, snowpack, etc. We describe the response of dynamically calibrated SPARROW models of total nitrogen (TN) flux to hypothetical reductions in reactive nitrogen inputs in three sub-regional watersheds: Potomac River Basin (Chesapeake Bay drainage), Long Island Sound drainage, and South Carolina coastal drainage. The models are based on seasonal water quality and watershed input data from 170 monitoring stations for the period 2002 to 2008.The spatial reference frames of the three models are stream networks containing an average 38,000 catchments and the time step is seasonal. We use MODIS Enhanced Vegetation Index (EVI) and snow/ice cover data to parameterize seasonal uptake and release of nitrogen from vegetation and snowpack. The model accounts for storage of total nitrogen inputs from fertilized cropland, pasture, urban land, and atmospheric deposition. Model calibration is by non-linear regression. Model source terms based on previous season export allow for recursive simulation of stream flux and can be used to estimate the approximate residence times of TN in the watersheds. Catchment residence times in the Long Island Sound Basin are shorter (typically < 1 year) than in the Potomac or South Carolina Basins (typically > 1 year), in part, because a significant fraction of nitrogen flux derives from snowmelt and occurs within one season of snowfall. We use the calibrated models to examine the response of TN flux to hypothetical step reductions in source inputs at the beginning of the 2002-2008 period and the influence of observed fluctuations in precipitation, temperature, vegetation growth and snow melt over the period. Following non-point source reductions of up to 100%, stream flux was found to continue to vary greatly for several years as a function of seasonal conditions, with high values in both winter (January, February, March) and spring due to high precipitation and snow melt, but much lower summer yields due to low precipitation and nitrogen retention in growing vegetation (EVI). Temporal variations in stream flux are large enough to potentially mask water quality improvements for several years.

Removal of Nutrients from Septic Effluent with Re-circulated Hybrid Tidal Flow Constructed Wetland

Treesearch

Lihua Cui; Jigkun Feng; Ying Ouyang; Peiwen Deng

2012-01-01

Hybrid tidal flow constructed wetland (CW) with recirculation is an improved biological and engineering technique for removal of excess nutrients and certain pollutants from wastewater. This study investigated the removal efficiency of total phosphorus (TP), ammonia-nitrogen (NH3-N), and total nitrogen (TN) from septic tank effluent with the hybrid tidal flow CW system...

Nitrogen saturation in a high elevation New England spruce-fir stand

Treesearch

Steven G. McNulty; John D. Aber; Steven D. Newman

1994-01-01

High rates of nitrogen (N) deposition were first postulated as a cause of N saturation (i.e. the availability of NH-N and NO3-N in excess of total combined plant and microbial nutritional demand) and spruce mortality during the1980s. To test this hypothesis, N addition plots were established in 1988, in a high elevation...

Twenty-five-year response of the herbaceous layer of a temperate hardwood forest to elevated nitrogen deposition

Treesearch

Frank S. Gilliam; Nicole Turrill Welch; Anne Hockenberry Phillips; Jake H. Billmyer; William T. Peterjohn; Zachariah K. Fowler; Christopher A. Walter; Mark B. Burnham; Jeffrey D. May; Mary Beth Adams; D. P. C. Peters

2016-01-01

Increasing rates of atmospheric deposition of nitrogen (N) present a novel threat to the biodiversity of terrestrial ecosystems. Many forests are particularly susceptible to excess N given their proximity to sources of anthropogenic N emissions. This study summarizes results of a 25-yr treatment of an entire central Appalachian hardwood forest watershed via aerial...

Seasonal relationships between precipitation, forest floor, and streamwater nitrogen, Isle Royale, Michigan

USGS Publications Warehouse

Stottlemyer, R.; Toczydlowski, D.

1999-01-01

The Upper Great Lakes receive large amounts of precipitation-NH4/+ and moderate NO3/- inputs. Increased atmospheric inorganic N input has led to concern about ecosystem capacity to utilize excess N. This paper summarizes a 5-yr study of seasonal N content and flux in precipitation, snowpack, forest floor, and streamwater in order to assess the source of inorganic N outputs in streamflow from a small boreal watershed. Average precipitation N input was 3 kg ha-1 yr-1. The peak snowpack N content averaged 0.55 kg ha-1. The forest floor inorganic N pool was ???2 kg ha-1, eight times larger than monthly precipitation N input. The inorganic N pool size peaked in spring and early summer. Ninety percent of the forest floor inorganic N pool was made up of NH4/+-N. Forest floor inorganic N pools generally increased with temperature. Net N mineralization was 15 kg ha-1 yr-1, and monthly rates peaked in early summer. During winter, the mean monthly net N mineralization rate was twice the peak snowpack N content. Streamwater NO3/- concentration peaked in winter, and inorganic N output peaked in late fall. Beneath the dominant boreal forest species, net N mineralization rates were positively correlated (P < 0.05) with streamwater NO3/- concentrations. Forest floor NO3/- pools beneath alder [Alnus rugosa (Du Roi) Spreng] were positively correlated (P < 0.01) to streamwater NO3/- output. At the watershed mouth, streamwater NO3/- concentrations were positively correlated (P < 0.05) with precipitation NO3/- input and precipitation amount. The relatively small snowpack N content and seasonal precipitation N input compared to forest floor inorganic N pools and net N mineralization rates, the strong ecosystem retention of precipitation N inputs, and the seasonal streamwater NO3/- concentration and output pattern all indicated that little streamwater NO3/- came directly from precipitation or snowmelt.The Upper Great Lakes receive large amounts of precipitation-NH4+ and moderate NO3- inputs. Increased atmospheric inorganic N input has led to concern about ecosystem capacity to utilize excess N. This paper summarizes a 5-yr study of seasonal N content and flux in precipitation, snowpack, forest floor, and streamwater in order to assess the source of inorganic N outputs in streamflow from a small boreal watershed. Average precipitation N input was 3 kg ha-1 yr-1. The peak snowpack N content averaged 0.55 kg ha-1. The forest floor inorganic N pool was ??? 2 kg ha-1, eight times larger than monthly precipitation N input. The inorganic N pool size peaked in spring and early summer. Ninety percent of the forest floor inorganic N pool was made up of NH4+-N. Forest floor inorganic N pools generally increased with temperature. Net N mineralization was 15 kg ha-1 yr-1, and monthly rates peaked in early summer. During winter, the mean monthly net N mineralization rate was twice the peak snowpack N content. Streamwater NO3- concentration peaked in winter, and inorganic N output peaked in late fall. Beneath the dominant boreal forest species, net N mineralization rates were positively correlated (P < 0.05) with streamwater NO3- concentrations. Forest floor NO3- pools beneath alder [Alnus rugosa (Du Roi) Spreng] were positively correlated (P<0.01) to streamwater NO3- output. At the watershed mouth, streamwater NO3- concentrations were positively correlated (P < 0.05) with precipitation NO3- input and precipitation amount. The relatively small snowpack N content and seasonal precipitation N input compared to forest floor inorganic N pools and net N mineralization rates, the strong ecosystem retention of precipitation N inputs, and the seasonal streamwater NO3- concentration and output pattern all indicated that little streamwater NO3- came directly from precipitation or snowmelt.

Estimating nitrogen loading to ground water and assessing vulnerability to nitrate contamination in a large karstic springs Basin, Florida

USGS Publications Warehouse

Katz, B.G.; Sepulveda, A.A.; Verdi, R.J.

2009-01-01

A nitrogen (N) mass-balance budget was developed to assess the sources of N affecting increasing ground-water nitrate concentrations in the 960-km 2 karstic Ichetucknee Springs basin. This budget included direct measurements of N species in rainfall, ground water, and spring waters, along with estimates of N loading from fertilizers, septic tanks, animal wastes, and the land application of treated municipal wastewater and residual solids. Based on a range of N leaching estimates, N loads to ground water ranged from 262,000 to 1.3 million kg/year; and were similar to N export from the basin in spring waters (266,000 kg/year) when 80-90% N losses were assumed. Fertilizers applied to cropland, lawns, and pine stands contributed about 51% of the estimated total annual N load to ground water in the basin. Other sources contributed the following percentages of total N load to ground water: animal wastes, 27%; septic tanks, 12%; atmospheric deposition, 8%; and the land application of treated wastewater and biosolids, 2%. Due to below normal rainfall (97.3 cm) during the 12-month rainfall collection period, N inputs from rainfall likely were about 30% lower than estimates for normal annual rainfall (136 cm). Low N-isotope values for six spring waters (??15N-NO3 = 3.3 to 6.3???) and elevated potassium concentrations in ground water and spring waters were consistent with the large N contribution from fertilizers. Given ground-water residence times on the order of decades for spring waters, possible sinks for excess N inputs to the basin include N storage in the unsaturated zone and parts of the aquifer with relatively sluggish ground-water movement and denitrification. A geographical-based model of spatial loading from fertilizers indicated that areas most vulnerable to nitrate contamination were located in closed depressions containing sinkholes and other dissolution features in the southern half of the basin. ?? 2009 American Water Resources Association.

Water-quality assessment of the Lower Grand River Basin, Missouri and Iowa, USA, in support of integrated conservation practices

USGS Publications Warehouse

Wilkison, Donald H.; Armstrong, Daniel J.

2016-01-01

The effectiveness of agricultural conservation programmes to adequately reduce nutrient exports to receiving streams and to help limit downstream hypoxia issues remains a concern. Quantifying programme success can be difficult given that short-term basin changes may be masked by long-term water-quality shifts. We evaluated nutrient export at stream sites in the 44 months that followed a period of increased, integrated conservation implementation within the Lower Grand River Basin. These short-term responses were then compared with export that occurred in the main stem and adjacent rivers in northern Missouri over a 22-year period to better contextualize any recent changes. Results indicate that short-term (October 2010 through May 2014) total nitrogen (TN) concentrations in the Grand River were 20% less than the long-term average, and total phosphorus (TP) concentrations were 23% less. Nutrient reductions in the short term were primarily the result of the less-than-average precipitation and, consequently, streamflow that was 36% below normal. Therefore, nutrient concentrations measured in tributary streams were likely less than normal during the implementation period. Northern Missouri streamflow-normalized TN concentrations remained relatively flat or declined over the period 1991 through 2013 likely because available sources of nitrogen, determined as the sum of commercial fertilizers, available animal manures and atmospheric inputs, were typically less than crop requirement for much of that time frame. Conversely, flow-normalized stream TP concentrations increased over the past 22 years in northern Missouri streams, likely in response to many years of phosphorus inputs in excess of crop requirements. Stream nutrient changes were most pronounced during periods that coincided with the major tillage, planting and growth phases of row crops and increased streamflow. Nutrient reduction strategies targeted at the period February through June would likely have the greatest impact on reducing nutrient export from the basin. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Integrated tool for risk assessment in agricultural management of soil erosion and losses of phosphorus and nitrogen.

PubMed

Bechmann, Marianne; Stålnacke, Per; Kvaernø, Sigurn; Eggestad, Hans Olav; Oygarden, Lillian

2009-01-01

In recent years, increased attention has been focused on models for risk assessment of source areas in agricultural landscapes. Among the simplest of such models are index tools, which have been developed particularly for phosphorus (P) and to some extent nitrogen (N). However, only a few studies have considered the development of an integrated management strategy that includes erosion and losses of both P and N. Accordingly, the major objective of this study was to initiate the development of an integrated risk assessment tool, consisting of indices for erosion, P and N. The strategy used to create the integrated tool was based on the assumption that all input data at field scale should be readily available either from ordinary agricultural statistics or from the farmer. The results from using the indices in a pilot case study catchment illustrated that losses of P and N had often different critical source areas. The P index was highest for fields with manure application and/or high soil P status or with autumn ploughing, and the N index was highest for fields with excessive N application. The integrated risk was greatest for areas with manure application and some areas with a high erosion risk in combination with high nutrient application rate. Additionally, four different management options were assessed: (1) reduced fertilisation, (2) catch crops, (3) autumn ploughing, and (4) no autumn ploughing. The results verified that reduced nutrient application and stubble during autumn and winter led to the largest decrease in index values, and it was also apparent that management changes in high-risk areas had the greatest impact on the indices. Overall, our findings indicate that the present integrated risk assessment tool with readily available input data can be used to rank farm fields according to risk of soil erosion and losses of P and N.

Rates of nitrification and nitrate assimilation in the Changjiang River estuary and adjacent waters based on the nitrogen isotope dilution method

NASA Astrophysics Data System (ADS)

Wang, Wentao; Yu, Zhiming; Wu, Zaixing; Song, Shuqun; Song, Xiuxian; Yuan, Yongquan; Cao, Xihua

2018-07-01

Being supplied from both terrestrial inputs and internal regeneration, nitrate is usually in excess in the Changjiang River estuary (CRE) and adjacent waters (CREAW). As significant reactions in the nitrogen cycle, nitrate assimilation and nitrification rates were calculated by field incubation experiments following the isotope dilution method during June and November 2014. Besides this, distribution of other field parameters in the CREAW were also investigated. The results showed that the nitrate assimilation rates were higher in nearshore areas and lower in offshore areas. The nitrate assimilation rates were also higher during June, at 0.3-11.9 μmol L-1 d-1, whereas the rates were 0-3.2 μmol L-1 d-1 in November. The highest rate was observed in the surface water of the estuary, where the chlorophyll-a (chl-a) concentration reached 11.02 μg L-1. In addition, the phytoplankton community structure affected the nitrate assimilation rates, and dinoflagellates presented weaker nitrate assimilation abilities than those of diatoms. By contrast, the nitrification rates were higher in nearshore areas in June but higher in offshore areas in November. The nitrification rates were 0-4.1 μmol L-1 d-1 and 0-3.6 μmol L-1 d-1 in June and November, respectively. At most sites, the nitrification rates were positively correlated with the ammonium concentrations and were higher in November, which might be attributable to the higher temperature. Moreover, a theoretical calculation was used to study the regional nitrate flux throughout the vertical water column. The results showed that a gradual supplement from nitrification might replenish the nitrate consumed by assimilation far from the CRE. The overall result was that terrestrial input remained the primary source of estuarine nitrate; however, the role of internal nitrate regeneration, which would be effective for primary production in the CREAW, should also be highlighted as a source of nitrate, especially in offshore areas.

A wheat CCAAT box-binding transcription factor increases the grain yield of wheat with less fertilizer input.

PubMed

Qu, Baoyuan; He, Xue; Wang, Jing; Zhao, Yanyan; Teng, Wan; Shao, An; Zhao, Xueqiang; Ma, Wenying; Wang, Junyi; Li, Bin; Li, Zhensheng; Tong, Yiping

2015-02-01

Increasing fertilizer consumption has led to low fertilizer use efficiency and environmental problems. Identifying nutrient-efficient genes will facilitate the breeding of crops with improved fertilizer use efficiency. This research performed a genome-wide sequence analysis of the A (NFYA), B (NFYB), and C (NFYC) subunits of Nuclear Factor Y (NF-Y) in wheat (Triticum aestivum) and further investigated their responses to nitrogen and phosphorus availability in wheat seedlings. Sequence mining together with gene cloning identified 18 NFYAs, 34 NFYBs, and 28 NFYCs. The expression of most NFYAs positively responded to low nitrogen and phosphorus availability. In contrast, microRNA169 negatively responded to low nitrogen and phosphorus availability and degraded NFYAs. Overexpressing TaNFYA-B1, a low-nitrogen- and low-phosphorus-inducible NFYA transcript factor on chromosome 6B, significantly increased both nitrogen and phosphorus uptake and grain yield under differing nitrogen and phosphorus supply levels in a field experiment. The increased nitrogen and phosphorus uptake may have resulted from the fact that that overexpressing TaNFYA-B1 stimulated root development and up-regulated the expression of both nitrate and phosphate transporters in roots. Our results suggest that TaNFYA-B1 plays essential roles in root development and in nitrogen and phosphorus usage in wheat. Furthermore, our results provide new knowledge and valuable gene resources that should be useful in efforts to breed crops targeting high yield with less fertilizer input. © 2015 American Society of Plant Biologists. All Rights Reserved.

A Wheat CCAAT Box-Binding Transcription Factor Increases the Grain Yield of Wheat with Less Fertilizer Input1

PubMed Central

Qu, Baoyuan; He, Xue; Wang, Jing; Zhao, Yanyan; Teng, Wan; Shao, An; Zhao, Xueqiang; Ma, Wenying; Wang, Junyi; Li, Bin; Li, Zhensheng; Tong, Yiping

2015-01-01

Increasing fertilizer consumption has led to low fertilizer use efficiency and environmental problems. Identifying nutrient-efficient genes will facilitate the breeding of crops with improved fertilizer use efficiency. This research performed a genome-wide sequence analysis of the A (NFYA), B (NFYB), and C (NFYC) subunits of Nuclear Factor Y (NF-Y) in wheat (Triticum aestivum) and further investigated their responses to nitrogen and phosphorus availability in wheat seedlings. Sequence mining together with gene cloning identified 18 NFYAs, 34 NFYBs, and 28 NFYCs. The expression of most NFYAs positively responded to low nitrogen and phosphorus availability. In contrast, microRNA169 negatively responded to low nitrogen and phosphorus availability and degraded NFYAs. Overexpressing TaNFYA-B1, a low-nitrogen- and low-phosphorus-inducible NFYA transcript factor on chromosome 6B, significantly increased both nitrogen and phosphorus uptake and grain yield under differing nitrogen and phosphorus supply levels in a field experiment. The increased nitrogen and phosphorus uptake may have resulted from the fact that that overexpressing TaNFYA-B1 stimulated root development and up-regulated the expression of both nitrate and phosphate transporters in roots. Our results suggest that TaNFYA-B1 plays essential roles in root development and in nitrogen and phosphorus usage in wheat. Furthermore, our results provide new knowledge and valuable gene resources that should be useful in efforts to breed crops targeting high yield with less fertilizer input. PMID:25489021

Net anthropogenic nitrogen accumulation in the Beijing metropolitan region.

PubMed

Han, Yuguo; Li, Xuyong; Nan, Zhe

2011-03-01

A rapid increase in anthropogenic nitrogen inputs has a strong impact on terrestrial and aquatic ecosystems. We have estimated net anthropogenic nitrogen accumulation (NANA) as an index of nitrogen (N) pollution potential in the Beijing metropolitan region, China. Our research provides a basis for understanding the potential impact of anthropogenic N inputs on environmental problems, such as nation-wide water quality degradation under the current rapid urban expansion in modern China. The NANA estimation is based on an inventory of atmospheric N deposition, N fertilizer use, consumption of human food and animal feed, N fixation, and riverine N import and export. We calculated N accumulation values for the years 1991, 1997, 2003, and 2007. The average NANA values for the urban and suburban areas from 1991 to 2007 were 24,038 and 13,090 kg N km(-2) year(-1), respectively. NANA is higher in eastern and southern areas than in northern and western areas, and higher in the urban area than in the suburban area. The overall average NANA in Beijing has a downward trend from 15,187 kg N km(-2) year(-1) in 1991 to 11,606 kg N km(-2) year(-1) in 2007, but is still two to five times as that of developed countries. N input from nitrogenous fertilizer is the largest source of NANA, accounting for 44.4% (6,764 kg N km(-2) year(-1)) of the total N input, followed by atmospheric N deposition and N in human food and animal feed. NANA is closely related to land use, on average 23,140 kg N km(-2) year(-1) in densely populated developed land, 17,904 kg N km(-2) year(-1) in agricultural land, and 10,445 kg N km(-2) year(-1) in forest land. Human population density is the best single predictor of NANA.

Identifying sources of nitrogen to Hanalei Bay, Kauai, utilizing the nitrogen isotope signature of macroalgae

USGS Publications Warehouse

Derse, E.; Knee, K.L.; Wankel, Scott D.; Kendall, C.; Berg, C.J.; Paytan, A.

2007-01-01

Sewage effluent, storm runoff, discharge from polluted rivers, and inputs of groundwater have all been suggested as potential sources of land derived nutrients into Hanalei Bay, Kauai. We determined the nitrogen isotopic signatures (??15N) of different nitrate sources to Hanalei Bay along with the isotopic signature recorded by 11 species of macroalgal collected in the Bay. The macroalgae integrate the isotopic signatures of the nitrate sources over time, thus these data along with the nitrate to dissolved inorganic phosphate molar ratios (N:P) of the macroalgae were used to determine the major nitrate source to the bay ecosystem and which of the macro-nutrients is limiting algae growth, respectively. Relatively low ??15N values (average -0.5???) were observed in all algae collected throughout the Bay; implicating fertilizer, rather than domestic sewage, as an important external source of nitrogen to the coastal water around Hanalei. The N:P ratio in the algae compared to the ratio in the Bay waters imply that the Hanalei Bay coastal ecosystem is nitrogen limited and thus, increased nitrogen input may potentially impactthis coastal ecosystem and specifically the coral reefs in the Bay. Identifying the major source of nutrient loading to the Bay is important for risk assessment and potential remediation plans. ?? 2007 American Chemical Society.

Cost-effective control of nitrogen loadings in Long Island Sound

NASA Astrophysics Data System (ADS)

Bennett, Lynne L.; Thorpe, Steven G.; Guse, A. Joseph

2000-12-01

Long Island Sound is plagued by conditions of severe hypoxia (low levels of dissolved oxygen) during the summer months because of the existence of excessive amounts of nitrogen. A new proposal that would allow sewage treatment plants to buy or sell nitrogen discharge credits is currently being evaluated by the states of Connecticut and New York. Existing theory suggests that a trading program for nitrogen emissions would be a cost-effective means of addressing the problem. We estimate the costs associated with several trading scenarios and find that the potential for cost savings is substantial and that cost savings rise as the scope of trading expands.

QUANTIFYING SEASONAL SHIFTS IN NITROGEN SOURCES TO OREGON ESTUARIES: PART II: TRANSPORT MODELING

EPA Science Inventory

Identifying the sources of dissolved inorganic nitrogen (DIN) in estuaries is complicated by the multiple sources, temporal variability in inputs, and variations in transport. We used a hydrodynamic model to simulate the transport and uptake of three sources of DIN (oceanic, riv...

Effects of Nitrogen Inputs on Freshwater Wetland Ecosystem Services–A Bayesian Network Analysis

EPA Science Inventory

Wetlands can provide a balance between regulating water quality and one aspect of mitigating climate change, by reducing the quantity of reactive nitrogen (Nr) reaching downstream receiving water bodies, while emitting negligible amounts of nitrous oxide (N2O) during incomplete d...

Nitrogen input inventory in the Nooksack-Fraser Transboundary Region: Key component of an international nitrogen management study

EPA Science Inventory

The Nooksack-Abbotsford-Sumas (NAS) Transboundary Watershed, spanning which spans a portion of the western interface of British Columbia, Washington State, and the Lummi Nation and the Nooksack Tribal lands , supports agriculture, estuarine fisheries, diverse wildlife, and urban ...

Emerging and established technologies to increase nitrogen use efficiency of cereals

USDA-ARS?s Scientific Manuscript database

Nitrogen (N) fertilizers are expensive inputs; additionally, loss of N increases costs, contributes to soil acidification, and causes off-site pollution of air, groundwater and waterways. This study reviews current knowledge about technologies for N fertilization with potential to increase N use eff...

Modeling pathways of riverine nitrogen and phosphorus in the Baltic Sea

NASA Astrophysics Data System (ADS)

Radtke, H.; Neumann, T.; Voss, M.; Fennel, W.

2012-09-01

A better understanding of the fate of nutrients entering the Baltic Sea ecosystem is an important issue with implications for environmental management. There are two sources of nitrogen and phosphorus: riverine input and atmospheric deposition. In the case of nitrogen, the fixation of dinitrogen by diazotrophic bacteria represents a third source. From an analysis of stable nitrogen isotope ratios it was suggested that most of the riverine nitrogen is sequestered in the coastal rim, specifically along the southern Baltic Sea coast with its coarse sediments, whereas nitrogen from fixation dominates the central basins. However, pathways of nutrients and timescales between the input of the nutrients and their arrival in different basins are difficult to obtain from direct measurements. To elucidate this problem, we use a source attribution technique in a three-dimensional ecosystem model, ERGOM, to track nutrients originating from various rivers. An “age” variable is attributed to the marked elements to indicate their propagation speeds and residence times. In this paper, we specifically investigate the spreading of nitrogen and phosphorus from the riverine discharges of the Oder, Vistula, Neman and Daugava. We demonstrate which regions they are transported to and for how long they remain in the ecosystem. The model results show good agreement with source estimations from observed δ15N values in sediments. The model results suggest that 95% of nitrogen is lost by denitrification in sediments, after an average time of 1.4 years for riverine nitrogen. The residence time of riverine phosphorus is much longer and exceeds our simulated period of 35 years.

A Nitrogen Inventory of Major Water Regions Across the USA as a Benchmark for Future Progress in Mitigating Nitrogen Pollution

NASA Astrophysics Data System (ADS)

Boyer, E. W.; Galloway, J. N.; Alexander, R. B.

2012-12-01

We present a contemporary inventory of reactive nitrogen (Nr) inputs and, air, and surface waters throughout major water regions in the United States. Inputs of Nr to the nation and the world have been increasing, largely due to human activities associated with food production and energy consumption via the combustion of fossil fuels and biofuels. Despite the obvious essential benefits of a plentiful supply of food and energy, the adverse consequences associated with the accumulation of Nr in the environment are large. Most of the Nr created by anthropogenic activities is released to the environment, often with unintended negative consequences. The greater the inputs of Nr to the landscape, the greater the potential for negative effects, caused by greenhouse gas production, ground level ozone, acid deposition, and Nr overload that can contribute to climate change, degradation of soils and vegetation, acidification of surface waters, coastal eutrophication, hypoxia and habitat loss. Here, we present a consistent accounting method for quantifying Nr sources and transport that was used in our inventory, and discuss associated data needs for tallying Nr inputs at regional scales. The inventory is a necessary tool for exploring the role of Nr contributed to the environment from various sources (e.g., from fertilizers, manure, biological fixation, human waste, atmospheric deposition) and from various industrial sectors (e.g., from agriculture, transportation, electricity generation). Agriculture and use of fertilizers to produce food, feed, and fiber (including bioenergy and biological nitrogen fixation) and combustion of fossil fuels are the largest sources of Nr released into the environment in the USA. Our inventory can be used as a benchmark of the current Nr situation against which future progress can be assessed in varying regions of the country, amidst changing Nr inputs and implementation of policy and management strategies to mitigate Nr pollution.

A contemporary national nitrogen inventory as a benchmark for future progress in mitigating nitrogen pollution in the USA

NASA Astrophysics Data System (ADS)

Boyer, E. W.; Galloway, J. N.; Theis, T.; Alexander, R. B.

2011-12-01

We present a contemporary inventory of reactive nitrogen (Nr) inputs to land, air, and water in the United States. Inputs of Nr to the nation and the world have been increasing, largely due to human activities associated with food production and energy consumption via the combustion of fossil fuels and biofuels. Despite the obvious essential benefits of a plentiful supply of food and energy, the adverse consequences associated with the accumulation of Nr in the environment are large. Most of the Nr created by anthropogenic activities is released to the environment, often with unintended negative consequences. The greater the inputs of Nr to the landscape, the greater the potential for negative effects, caused by greenhouse gas production, ground level ozone, acid deposition, and Nr overload that can contribute to climate change, degradation of soils and vegetation, acidification of surface waters, coastal eutrophication, hypoxia and habitat loss. Here, we present a consistent accounting method for quantifying Nr sources and transport that was used in our inventory, and discuss associated data needs for tallying Nr inputs at regional scales. The inventory is a necessary tool for exploring the role of Nr contributed to the environment from various sources (e.g., from fertilizers, manure, biological fixation, human waste, atmospheric deposition) and from various industrial sectors (e.g., from agriculture, transportation, electricity generation). Agriculture and use of fertilizers to produce food, feed, and fiber (including bioenergy and biological nitrogen fixation) and combustion of fossil fuels are the largest sources of Nr released into the environment in the USA. Our inventory is currently being used by the U.S. Environmental Protection Agency as a benchmark of the current Nr situation against which future progress can be assessed -- amidst changing Nr inputs and implementation of policy and management strategies to mitigate Nr pollution.

Management of Excess Reactive Nitrogen in the Environment

NASA Astrophysics Data System (ADS)

Galloway, J. N.; Theis, T.; Doering, O.

2011-12-01

Managing the impacts of excessive reactive nitrogen (Nr) in the environment is a complex problem that begins with the recognition of the obligate dietary need for Nr by all living populations. The human solution to this need has been to devise ways to bring Nr into the biosphere (via the Haber-Bosch process) to grow food. Other Nr is created as a by-product of fossil-fuel combustion. The net result is the introduction of more than five times the Nr created by natural processes in the U.S., only a fraction of which is converted back to diatomic nitrogen through denitrification. This presentation summarizes findings and recommendations of the newly-released US EPA Science Advisory Board's Integrated Nitrogen Committee report, "Reactive Nitrogen in the United States: An Analysis of Flows, Consequences, and Management Options", that deal specifically with approaches for solving the excess Nr problem. These can be grouped into four general areas: (1) Recognition of the Problem. Until there is recognition that excess Nr is a serious problem with economic, health, and societal consequences, there will be little willingness to expend resources on this issue. Education, communication and outreach are critically important to engender in regulators, and the public at large, sufficient will to undertake the large scale effort needed to reduce Nr in the environment. (2) Development of Integrated Regulatory Approaches. Given what is known about the way Nr behaves, efforts to deal with excess Nr must be organized in a way that reflects the nature of the problem. Unfortunately, most approaches tend to conceive of Nr issues within a narrowly focused disciplinary model, and our policy and regulatory institutions are often bound by enabling legislation that stresses source-by-source, chemical-by-chemical, and media-by-media. The resulting regulatory structure that has evolved for problems such as Nr that affect human health and the environment is apt to miss the complex nature of the problem. Such silos have to be broken down if the excess Nr problem is to be dealt with holistically. (3) Essential Monitoring and Research. The Committee recommends improved monitoring and research to enhance our understanding of Nr in the environment. In some cases our knowledge has such wide margins of error that we cannot identify or quantify important concentrations or flows sufficiently for necessary decisions. In other cases there is incomplete knowledge about the indirect impacts of Nr, while in still others there is a need for much better understanding of the efficacy of actions that might be taken to control Nr. (4) Setting Goals for Action. In spite of knowledge gaps identified by the Committee, there is sufficient understanding of the Nr problem to enable the responsible regulatory agencies to begin to decrease excess Nr entering the environment. The Committee suggests actions that might be taken by EPA or other management authorities using current technologies and regulatory authority to decrease Nr in the environment by 25% over the near (10-20 year) term, without negatively impacting dietary needs or economic trends.

Discrimination factors of carbon and nitrogen stable isotopes in meerkat feces

PubMed Central

2017-01-01

Stable isotope analysis of feces can provide a non-invasive method for tracking the dietary habits of nearly any mammalian species. While fecal samples are often collected for macroscopic and genetic study, stable isotope analysis can also be applied to expand the knowledge of species-specific dietary ecology. It is somewhat unclear how digestion changes the isotope ratios of animals’ diets, so more controlled diet studies are needed. To date, most diet-to-feces controlled stable isotope experiments have been performed on herbivores, so in this study I analyzed the carbon and nitrogen stable isotope ratios in the diet and feces of the meerkat (Suricata suricatta), a small omnivorous mammal. The carbon trophic discrimination factor between diet and feces (Δ13Cfeces) is calculated to be 0.1 ± 1.5‰, which is not significantly different from zero, and in turn, not different than the dietary input. On the other hand, the nitrogen trophic discrimination factor (Δ15Nfeces) is 1.5 ± 1.1‰, which is significantly different from zero, meaning it is different than the average dietary input. Based on data generated in this experiment and a review of the published literature, carbon isotopes of feces characterize diet, while nitrogen isotope ratios of feces are consistently higher than dietary inputs, meaning a discrimination factor needs to be taken into account. The carbon and nitrogen stable isotope values of feces are an excellent snapshot of diet that can be used in concert with other analytical methods to better understand ecology, diets, and habitat use of mammals. PMID:28626611

Nitrogen deposition in precipitation to a monsoon-affected eutrophic embayment: Fluxes, sources, and processes

NASA Astrophysics Data System (ADS)

Wu, Yunchao; Zhang, Jingping; Liu, Songlin; Jiang, Zhijian; Arbi, Iman; Huang, Xiaoping; Macreadie, Peter Ian

2018-06-01

Daya Bay in the South China Sea (SCS) has experienced rapid nitrogen pollution and intensified eutrophication in the past decade due to economic development. Here, we estimated the deposition fluxes of nitrogenous species, clarified the contribution of nitrogen from precipitation and measured ions and isotopic composition (δ15N and δ18O) of nitrate in precipitation in one year period to trace its sources and formation processes among different seasons. We found that the deposition fluxes of total dissolved nitrogen (TDN), NO3-, NH4+, NO2-, and dissolved organic nitrogen (DON) to Daya Bay were 132.5, 64.4 17.5, 1.0, 49.6 mmol m-2•yr-1, respectively. DON was a significant contributor to nitrogen deposition (37% of TDN), and NO3- accounted for 78% of the DIN in precipitation. The nitrogen deposition fluxes were higher in spring and summer, and lower in winter. Nitrogen from precipitation contributed nearly 38% of the total input of nitrogen (point sources input and dry and wet deposition) in Daya Bay. The δ15N-NO3- abundance, ion compositions, and air mass backward trajectories implicated that coal combustion, vehicle exhausts, and dust from mainland China delivered by northeast monsoon were the main sources in winter, while fossil fuel combustion (coal combustion and vehicle exhausts) and dust from PRD and southeast Asia transported by southwest monsoon were the main sources in spring; marine sources, vehicle exhausts and lightning could be the potential sources in summer. δ18O results showed that OH pathway was dominant in the chemical formation process of nitrate in summer, while N2O5+ DMS/HC pathways in winter and spring.

Nitrogen modulation of legume root architecture signaling pathways involves phytohormones and small regulatory molecules.

PubMed

Mohd-Radzman, Nadiatul A; Djordjevic, Michael A; Imin, Nijat

2013-10-01

Nitrogen, particularly nitrate is an important yield determinant for crops. However, current agricultural practice with excessive fertilizer usage has detrimental effects on the environment. Therefore, legumes have been suggested as a sustainable alternative for replenishing soil nitrogen. Legumes can uniquely form nitrogen-fixing nodules through symbiotic interaction with specialized soil bacteria. Legumes possess a highly plastic root system which modulates its architecture according to the nitrogen availability in the soil. Understanding how legumes regulate root development in response to nitrogen availability is an important step to improving root architecture. The nitrogen-mediated root development pathway starts with sensing soil nitrogen level followed by subsequent signal transduction pathways involving phytohormones, microRNAs and regulatory peptides that collectively modulate the growth and shape of the root system. This review focuses on the current understanding of nitrogen-mediated legume root architecture including local and systemic regulations by different N-sources and the modulations by phytohormones and small regulatory molecules.

Relevance of ammonium oxidation within biological soil crust communities

USGS Publications Warehouse

Johnson, S.L.; Budinoff, C.R.; Belnap, J.; Garcia-Pichel, F.

2005-01-01

Thin, vertically structured topsoil communities that become ecologically important in arid regions (biological soil crusts or BSCs) are responsible for much of the nitrogen inputs into pristine arid lands. We studied N2 fixation and ammonium oxidation (AO) at subcentimetre resolution within BSCs from the Colorado Plateau. Pools of dissolved porewater nitrate/ nitrite, ammonium and organic nitrogen in wetted BSCs were high in comparison with those typical of aridosoils. They remained stable during incubations, indicating that input and output processes were of similar magnitude. Areal N2 fixation rates (6.5-48 ??mol C2H2 m-2 h -1) were high, the vertical distribution of N2 fixation peaking close to the surface if populations of heterocystous cyanobacteria were present, but in the subsurface if they were absent. Areal AO rates (19-46 ??mol N m-2 h-1) were commensurate with N2 fixation inputs. When considering oxygen availability, AO activity invariably peaked 2-3 mm deep and was limited by oxygen (not ammonium) supply. Most probable number (MPN)-enumerated ammonia-oxidizing bacteria (6.7-7.9 ?? 103 cells g-1 on average) clearly peaked at 2-3 mm depth. Thus, AO (hence nitrification) is a spatially restricted but important process in the nitrogen cycling of BSC, turning much of the biologically fixed nitrogen into oxidized forms, the fate of which remains to be determined.

Nitrogen emissions from broilers measured by mass balance over eighteen consecutive flocks.

PubMed

Coufal, C D; Chavez, C; Niemeyer, P R; Carey, J B

2006-03-01

Emission of nitrogen in the form of ammonia from poultry rearing facilities has been an important topic for the poultry industry because of concerns regarding the effects of ammonia on the environment. Sound scientific data is needed to accurately estimate air emissions from poultry operations. Many factors, such as season of the year, ambient temperature and humidity, bird health, and management practices can influence ammonia volatilization from broiler rearing facilities. Precise results are often difficult to attain from commercial facilities, particularly over long periods of time. Therefore, an experiment was conducted to determine nitrogen loss from broilers in a research facility under conditions simulating commercial production for 18 consecutive flocks. Broilers were reared to 40 to 42 d of age and fed diets obtained from a commercial broiler integrator. New rice hulls were used for litter for the first flock, and the same litter was recycled for all subsequent flocks with caked litter removed between flocks. All birds, feeds, and litter materials entering and leaving the facility were quantified, sampled, and analyzed for total nitrogen content. Nitrogen loss was calculated by the mass balance method in which loss was equal to the difference between the nitrogen inputs and the nitrogen outputs. Nitrogen partitioning as a percentage of inputs averaged 15.29, 6.84, 55.52, 1.27, and 21.08% for litter, caked litter, broiler carcasses, mortalities, and nitrogen loss, respectively, over all eighteen flocks. During the production of 18 flocks of broilers on the same recycled litter, the average nitrogen emission rate was calculated to range from 4.13 to 19.74 g of N/ kg of marketed broiler (grams of nitrogen per kilogram) and averaged 11.07 g of N/kg. Nitrogen loss was significantly (P < 0.05) greater for flocks reared in summer vs. winter. Results of this experiment have demonstrated that the rate of nitrogen volatilization from broiler grow-out facilities varies significantly on a flock-to-flock basis.

40 CFR 60.43Da - Standard for sulfur dioxide (SO2).

Code of Federal Regulations, 2010 CFR

2010-07-01

..., and that burns 75 percent or more (by heat input) coal refuse on a 12-month rolling average basis...) of this section, any gases that contain SO2 in excess of: (1) 520 ng/J (1.20 lb/MMBtu) heat input and.../MMBtu) heat input. (b) On and after the date on which the initial performance test is completed or...

Atmospheric Inputs of Nitrogen, Carbon, and Phosphorus across an Urban Area: Unaccounted Fluxes and Canopy Influences

NASA Astrophysics Data System (ADS)

Decina, Stephen M.; Templer, Pamela H.; Hutyra, Lucy R.

2018-02-01

Rates of atmospheric deposition are declining across the United States, yet urban areas remain hotspots of atmospheric deposition. While past studies show elevated rates of inorganic nitrogen (N) deposition in cities, less is known about atmospheric inputs of organic N, organic carbon (C), and organic and inorganic phosphorus (P), all of which can affect ecosystem processes, water quality, and air quality. Further, the effect of the tree canopy on amounts and forms of nutrients reaching urban ground surfaces is not well-characterized. We measured growing season rates of total N, organic C, and total P in bulk atmospheric inputs, throughfall, and soil solution around the greater Boston area. We found that organic N constitutes a third of total N inputs, organic C inputs are comparable to rural inputs, and inorganic P inputs are 1.2 times higher than those in sewage effluent. Atmospheric inputs are enhanced two-to-eight times in late spring and are elevated beneath tree canopies, suggesting that trees augment atmospheric inputs to ground surfaces. Additionally, throughfall inputs may directly enter runoff when trees extend above impervious surfaces, as is the case with 26.1% of Boston's tree canopy. Our results indicate that the urban atmosphere is a significant source of elemental inputs that may impact urban ecosystems and efforts to improve water quality, particularly in terms of P. Further, as cities create policies encouraging tree planting to provide ecosystem services, locating trees above permeable surfaces to reduce runoff nutrient loads may be essential to managing urban biogeochemical cycling and water quality.

Quantifying seasonal shifts in nitrogen sources to Oregon estuaries using a transport model combined with stable isotopes

EPA Science Inventory

Identifying the sources of dissolved inorganic nitrogen (DIN) in estuaries is complicated by the multiple sources, temporal variability in inputs, and variations in transport. We used a hydrodynamic model to simulate the transport and uptake of three sources of DIN (oceanic, riv...

76 FR 3060 - Call for Information: Information Related to the Development of Emission-Estimating Methodologies...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-19

... approach that incorporates ``mass balance'' constraints to determine emissions from AFOs. Unfortunately... ventilation rate of the monitored confinement structure. Nitrogen content of process inputs and outputs (e.g., feed, water, bedding, eggs, milk). Nitrogen content of manure excreted. Description of any control...

Influences of climate and land use on contemporary anthropogenic watershed phosphorus input and riverine export across the United States

EPA Science Inventory

Human beings have greatly accelerated nitrogen and phosphorus flows from land to aquatic ecosystems, often resulting in eutrophication, harmful algal blooms, and hypoxia in lakes and coastal waters. Although differences in nitrogen export from watersheds have been clearly linked ...

A Precision Nitrogen Management Approach to Minimize Impacts

USDA-ARS?s Scientific Manuscript database

Nitrogen fertilizer is a crucial input for crop production but contributes to agriculture’s environmental footprint via CO2 emissions, N2O emissions, and eutrophication of coastal waters. The low-cost way to minimize this impact is to eliminate over-application of N. This is more difficult than it s...

Carbon and nitrogen isotope ratios of juvenile winter flounder as indicators of inputs to estuarine systems

EPA Science Inventory

Stable carbon and nitrogen isotope ratios were measured in the muscle tissues of young-of-the-year (YOY) winter flounder, Pseudopleuronectes americanus, collected from several estuarine systems along the coast of Rhode Island, USA. These systems included three coastal lagoons (Ni...

Nitrogen management to reduce nitrous oxide emissions

USDA-ARS?s Scientific Manuscript database

Nitrous oxide (N2O) emissions from agricultural soils represent a complex interaction between the inputs of nitrogen into the soil and the soil environment. Mitigating these emissions will have a positive impact on greenhouse gases. Agriculture is the primary source of N2O emissions and must develop...

Nitrogen source and application method impact on corn yield and nutrient uptake

USDA-ARS?s Scientific Manuscript database

Farmers are looking for better management practices to enhance production and reduce negative environmental impact from nitrogen (N) fertilizer application since N is one of the most important and costly nutrient inputs for crop production. In this field experiment pre-plant swine effluent applicati...

Water deficit and nitrogen fertility effects on NDVI of 'Tifton 85' bermudagrass during regrowth

USDA-ARS?s Scientific Manuscript database

A better understanding of how bermudagrass (Cynodon spp.) regrowth is influenced by production inputs will aid in advancing precision management in the southeast US. The objective of this two-yr study was to evaluate how irrigation and nitrogen influence bermudagrass regrowth. Normalized difference ...

Capturing sediment and nutrients in irrigated terraced landscapes

NASA Astrophysics Data System (ADS)

Slaets, Johanna; Schmitter, Petra; Hilger, Thomas; Piepho, Hans-Peter; Dercon, Gerd; Cadisch, Georg

2016-04-01

Terraces are often promoted as green filters in landscapes, buffering discharge and constituent peaks. For irrigated rice terraces, however, this mitigating potential has not been assessed at the landscape level. Additionally, sediment and nutrient inputs potentially affect soil fertility in agricultural terraces and therefore yield - the extent of the impact depending on the quality and quantity of the captured material. Quantifying such upland-lowland linkages is particularly important in intensely cultivated landscapes, as declining upland soil fertility could alter beneficial hydrological connectivity between terraces and surrounding landscapes. In this study, we therefore quantified the sediment, sediment-associated organic carbon and nitrogen inputs and losses for a 13 ha paddy rice area, surrounded by upland maize cultivation in Northwest Vietnam in 2010 and 2011. Turbidity sensors were used in combination with a linear mixed model in order to obtain continuous predictions of the constituent concentrations. Sediment texture was determined using mid-infrared spectroscopy. Uncertainty on annual load estimates was quantified by calculating 95% confidence intervals with a bootstrap approach. Sediment inputs from irrigation water to the rice area amounted to 48 Mg ha-1 a-1 and runoff during rainfall events contributed an additional 16 Mg ha-1 a-1. Export from the rice terraces equalled 63 Mg ha-1 a-1 of sediments, resulting in a net balance of 28 Mg ha-1 a-1 or a trapping of almost half of the annual sediment inputs. Runoff contributed one third of the sand inputs, while irrigated sediments were predominantly silty. As paddy outflow contained almost exclusively silt- and clay-sized material, 24 Mg ha-1 a-1 of captured sediments consisted of sand. The sediment-associated organic carbon resulted in a deposit of 1.09 Mg ha-1 a-1. For sediment-associated nitrogen, 0.68 Mg ha-1 a-1 was trapped in the terraces. Combining both sediment-associated and dissolved nitrogen, irrigation water provided a total input of 1.11 Mg ha-1 a-1, of which 54% was in the plant-available forms of ammonium and nitrate - an input larger than the recommended application of chemical fertilizer. Rice terraces were net traps for sediment and protected downstream areas by filtering coarse sediments. Combined with the importance of irrigation water as a source of organic carbon and nitrogen for the rice, this connectivity underscores the vulnerability of agricultural terraces to changes in surrounding land use.

Pre-development conditions to assess the impact of growth in an urbanizing watershed in Northern Virginia

NASA Astrophysics Data System (ADS)

Kumar, Saurav; Godrej, Adil N.; Grizzard, Thomas J.

2016-09-01

Pre-development conditions are an easily understood state to which watershed nonpoint nutrient reduction targets may be referenced. Using the pre-development baseline, a "developed-excess" measure may be computed for changes due to anthropogenic development. Developed-excess is independent of many geographical, physical, and hydrological characteristics of the region and after normalization by area may be used for comparison among various sub-sets of the watershed, such as jurisdictions or land use types. We have demonstrated this method by computing pre-development nitrogen and phosphorus loads entering the Occoquan Reservoir from its tributary watershed in Northern Virginia. The pre-development loads in this study were computed using the calibrated water quality models for the period 2002-2007. Current forest land was used as a surrogate for pre-development land use conditions for the watershed and developed-excess was estimated for fluvial loads of Total Inorganic Nitrogen (TIN) and Orthophosphate-Phosphorus (OP) by subtracting simulated predevelopment loads from observed loads. It was observed that within the study period (2002-2007), the average annual developed-excess represented about 30% of the TIN and OP average annual loads exported to the reservoir. Comparison of the two disturbed land use types, urban and agricultural, showed that urban land uses exported significantly more excess nonpoint nutrient load per unit area than agricultural land uses.

Harmful Algal Bloom Webinar

EPA Pesticide Factsheets

The problem is complex. Excessive nitrogen and phosphorous levels can cause harmful algal blooms. Different algal/cyanobacteria strains bloom under different conditions. Different strains produce different toxins at varying amounts.

Curing preceramic polymers by exposure to nitrogen dioxide

NASA Technical Reports Server (NTRS)

Rabe, James A. (Inventor); Lipowitz, Jonathan (Inventor); Lu, Paul P. (Inventor)

1991-01-01

A rapid method of infusibilizing (curing) preceramic polymers comprising treatment said polymers with gaseous nitrogen dioxide. The infusibilized polymers may be pyrolyzed to temperatures in excess of about 800.degree. C. to yield ceramic materials with low oxygen content and, thus, good thermal stability. The methods are especially useful for the production of ceramic fibers and, more specifically, to the on-line production of ceramic fibers.

Climate change decreases nitrogen pools and mineralization rates in northern hardwood forests

Treesearch

Jorge Durán; Jennifer L. Morse; Peter M. Groffman; John L. Campbell; Lynn M. Christenson; Charles T. Driscoll; Timothy J. Fahey; Melany C. Fisk; Gene E. Likens; Jerry M. Melillo; Myron J. Mitchell; Pamela H. Templer; Matthew A. Vadeboncoeur; D. P. C. Peters

2016-01-01

Nitrogen (N) supply often limits the productivity of temperate forests and is regulated by a complex mix of biological and climatic drivers. In excess, N is linked to a variety of soil, water, and air pollution issues. Here, we use results from an elevation gradient study and historical data from the long-term Hubbard Brook Ecosystem Study (New Hampshire, USA) to...

The Nitrogen Balancing Act: Tracking the Environmental Performance of Food Production

PubMed Central

McLellan, Eileen L; Cassman, Kenneth G; Eagle, Alison J; Woodbury, Peter B; Sela, Shai; Tonitto, Christina; Marjerison, Rebecca D; van Es, Harold M

2018-01-01

Abstract Farmers, food supply-chain entities, and policymakers need a simple but robust indicator to demonstrate progress toward reducing nitrogen pollution associated with food production. We show that nitrogen balance—the difference between nitrogen inputs and nitrogen outputs in an agricultural production system—is a robust measure of nitrogen losses that is simple to calculate, easily understood, and based on readily available farm data. Nitrogen balance provides farmers with a means of demonstrating to an increasingly concerned public that they are succeeding in reducing nitrogen losses while also improving the overall sustainability of their farming operation. Likewise, supply-chain companies and policymakers can use nitrogen balance to track progress toward sustainability goals. We describe the value of nitrogen balance in translating environmental targets into actionable goals for farmers and illustrate the potential roles of science, policy, and agricultural support networks in helping farmers achieve them. PMID:29662247

Convergent evidence for widespread rock nitrogen sources in Earth's surface environment.

PubMed

Houlton, B Z; Morford, S L; Dahlgren, R A

2018-04-06

Nitrogen availability is a pivotal control on terrestrial carbon sequestration and global climate change. Historical and contemporary views assume that nitrogen enters Earth's land-surface ecosystems from the atmosphere. Here we demonstrate that bedrock is a nitrogen source that rivals atmospheric nitrogen inputs across major sectors of the global terrestrial environment. Evidence drawn from the planet's nitrogen balance, geochemical proxies, and our spatial weathering model reveal that ~19 to 31 teragrams of nitrogen are mobilized from near-surface rocks annually. About 11 to 18 teragrams of this nitrogen are chemically weathered in situ, thereby increasing the unmanaged (preindustrial) terrestrial nitrogen balance from 8 to 26%. These findings provide a global perspective to reconcile Earth's nitrogen budget, with implications for nutrient-driven controls over the terrestrial carbon sink. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Effects of Nitrogen Inputs and Watershed Characteristics on ...

EPA Pesticide Factsheets

Nitrogen (N) inputs to the landscape have been linked previously to N loads exported from watersheds at the national scale; however, stream N concentration is arguably more relevant than N load for drinking water quality, freshwater biological responses and establishment of nutrient criteria. In this study, we combine national-scale anthropogenic N input data, including synthetic fertilizer, crop biological N fixation, manure applied to farmland, atmospheric N deposition, and point source inputs, with data from the 2008-09 National Rivers and Streams Assessment to quantify the relationship between N inputs and in-stream concentrations of total N (TN), dissolved inorganic N (DIN), and total organic N (TON) (calculated as TN – DIN). In conjunction with simple linear regression, we use multiple regression to understand how watershed and stream reach attributes modify the effect of N inputs on N concentrations. Median TN was 0.50 mg N L-1 with a maximum of 25.8 mg N L-1. Total N inputs to the watershed ranged from less than 1 to 196 kg N ha-1 y-1, with a median of 14.4 kg N ha-1 y-1. Atmospheric N deposition was the single largest anthropogenic N source in the majority of sites, but, agricultural sources generally dominate total N inputs in sites with elevated N concentrations. The sum of all N inputs were positively correlated with concentrations of all forms of N [r2 = 0.44, 0.43, and 0.18 for TN, DIN, and TON, respectively (all log-transformed), n = 1112], indi

County-level estimates of nitrogen and phosphorus from animal manure for the conterminous United States, 2002

USGS Publications Warehouse

Mueller, David K.; Gronberg, Jo Ann M.

2013-01-01

County-level nitrogen and phosphorus inputs from animal manure for the conterminous United States for 2002 were estimated from animal populations from the 2002 Census of Agriculture by using methods described in U.S. Geological Survey Scientific Investigations Report 2006–5012. These estimates of nitrogen and phosphorus from animal manure were compiled in support of the U.S. Geological Survey’s National Water-Quality Assessment Program.

Marine west coast forests: Chapter 9

USGS Publications Warehouse

Perakis, Steven S.; Geiser, Linda H.; Lilleskov, Erik A.; Pardo, Linda H.; Robin-Abbott, Molly J.; Driscoll, Charles T.

2011-01-01

Human activities have greatly increased nitrogen emissions and deposition across large areas of Earth. Although nitrogen is an essential nutrient for plant growth, too much nitrogen in excess of critical loads leads to losses of biodiversity, soil and stream acidification, nutrient imbalances, and other deleterious effects. In a new report quantifying critical loads of nitrogen deposition across the United States, USGS scientist Steve Perakis and co-authors provided a chapter about responses of marine west coast forests. Much of this region is understudied with respect to nitrogen deposition, and in this chapter the authors identify known adverse effects and estimate critical loads of nitrogen deposition for western Oregon and Washington and southeast Alaska forests. Perakis also contributed to the synthesis chapter, which includes background, objectives, advantages and uncertainties of critical loads, an overview of critical loads across U.S. ecoregions, and other topics.

A 100-year sedimentary record of natural and anthropogenic impacts on a shallow eutrophic lake, Lake Chaohu, China.

PubMed

Zan, Fengyu; Huo, Shouliang; Xi, Beidou; Zhu, Chaowei; Liao, Haiqing; Zhang, Jingtian; Yeager, Kevin M

2012-03-01

In this study, the sediment profiles of total organic carbon, total nitrogen, C/N ratios, total phosphorus, N/P ratios, C/P ratios, particle sizes, and stable carbon and nitrogen isotopes (δ(13)C and δ(15)N) were used to investigate natural and anthropogenic impacts on Lake Chaohu over the past 100 years. Before 1960, Lake Chaohu experienced low productivity and a relatively steady and low nutrient input. The increasing concentration and fluxes of total organic carbon, total nitrogen, total phosphorus, together with changes in the δ(13)C and δ(15)N of organic material in the sediment cores, suggested that the anthropogenic effects on trophic status first started because of an increase in nutrient input caused by a population increase in the drainage area. With the construction of the Chaohu Dam, an increase in the utilization of fertilizer and the population growth which occurred since 1960, stable depositional conditions and increasing nutrient input resulted in a dominantly algae-derived organic matter source and high productivity. Nutrient input increased most significantly around 1980 following the rapidly growing population, with concomitant urbanization, industrial and agricultural development. This study also revealed that the concentration and distribution of nutrients varied between different areas of sediment within Lake Chaohu because of the influence of different drainage basins and pollution sources. This journal is © The Royal Society of Chemistry 2012

Master Amino acid Pattern as sole and total substitute for dietary proteins during a weight-loss diet to achieve the body's nitrogen balance equilibrium.

PubMed

Lucà-Moretti, M; Grandi, A; Lucà, E; Muratori, G; Nofroni, M G; Mucci, M P; Gambetta, P; Stimolo, R; Drago, P; Giudice, G; Tamburlin, N; Karbalai, M; Valente, C; Moras, G

2003-01-01

Results of this multicentric study have shown that by giving Master Amino acid Pattern (MAP) as a sole and total substitute of dietary proteins to 500 overweight participants undergoing the American Nutrition Clinics/Overweight Management Program (ANC/OMP), the participants' body nitrogen balance could be maintained in equilibrium with essentially no calories (MAP 1 g=0.04 kcal), thereby preserving the body's structural and functional proteins, eliminating excessive water retention from the interstitial compartment, and preventing the sudden weight increase after study conclusion commonly known as the yo-yo effect. Study results have shown that the use of MAP, in conjunction with the ANC/OMP regimen, has proven to be safe and effective by preventing those adverse effects associated with a negative nitrogen balance, such as oversized or flabby tissue, stretch marks, the sagging of breast tissue, increased hair loss, faded hair color, and fragile or brittle nails. Also prevented were those anomalies commonly associated with weight-loss diets, such as hunger, weakness, headache caused by ketosis, constipation, and decreased libido. The use of MAP in conjunction with the ANC/OMP also allowed for mean weight loss of 2.5 kg (5.5 lb) per week, achieved through reduction of excessive fat tissue and elimination of excessive water retention from the interstitial compartment.

Nitrogen Starvation and TorC1 Inhibition Differentially Affect Nuclear Localization of the Gln3 and Gat1 Transcription Factors Through the Rare Glutamine tRNACUG in Saccharomyces cerevisiae

PubMed Central

Tate, Jennifer J.; Rai, Rajendra; Cooper, Terrance G.

2015-01-01

A leucine, leucyl-tRNA synthetase–dependent pathway activates TorC1 kinase and its downstream stimulation of protein synthesis, a major nitrogen consumer. We previously demonstrated, however, that control of Gln3, a transcription activator of catabolic genes whose products generate the nitrogenous precursors for protein synthesis, is not subject to leucine-dependent TorC1 activation. This led us to conclude that excess nitrogen-dependent down-regulation of Gln3 occurs via a second mechanism that is independent of leucine-dependent TorC1 activation. A major site of Gln3 and Gat1 (another GATA-binding transcription activator) control occurs at their access to the nucleus. In excess nitrogen, Gln3 and Gat1 are sequestered in the cytoplasm in a Ure2-dependent manner. They become nuclear and activate transcription when nitrogen becomes limiting. Long-term nitrogen starvation and treatment of cells with the glutamine synthetase inhibitor methionine sulfoximine (Msx) also elicit nuclear Gln3 localization. The sensitivity of Gln3 localization to glutamine and inhibition of glutamine synthesis prompted us to investigate the effects of a glutamine tRNA mutation (sup70-65) on nitrogen-responsive control of Gln3 and Gat1. We found that nuclear Gln3 localization elicited by short- and long-term nitrogen starvation; growth in a poor, derepressive medium; Msx or rapamycin treatment; or ure2Δ mutation is abolished in a sup70-65 mutant. However, nuclear Gat1 localization, which also exhibits a glutamine tRNACUG requirement for its response to short-term nitrogen starvation or growth in proline medium or a ure2Δ mutation, does not require tRNACUG for its response to rapamycin. Also, in contrast with Gln3, Gat1 localization does not respond to long-term nitrogen starvation. These observations demonstrate the existence of a specific nitrogen-responsive component participating in the control of Gln3 and Gat1 localization and their downstream production of nitrogenous precursors. This component is highly sensitive to the function of the rare glutamine tRNACUG, which cannot be replaced by the predominant glutamine tRNACAA. Our observations also demonstrate distinct mechanistic differences between the responses of Gln3 and Gat1 to rapamycin inhibition of TorC1 and nitrogen starvation. PMID:25527290

A synthesis of regional inputs and damage costs of reactive nitrogen in the United States

EPA Science Inventory

We estimated the fate of N in crops and in the environment (air, land, freshwater, groundwater, and coastal zones) with published coefficients describing nutrient uptake efficiency, gaseous emissions, and leaching losses. Benefits and damage costs of anthropogenic N inputs were ...

Tracing the source and fate of nitrate in contemporary mixed land-use surface water systems

NASA Astrophysics Data System (ADS)

Stewart, S. D.; Young, M. B.; Horton, T. W.; Harding, J. S.

2011-12-01

Nitrogenous fertilizers increase agricultural productivity, ultimately feeding the planet. Yet, it is possible to have too much of a good thing, and nitrogen is no exception. When in excess nitrogen has been shown to accelerate eutrophication of water bodies, and act as a chronic toxin (e.g. methemoglobinemia). As land-use intensity continues to rise in response to increases in agricultural productivity, the risk of adverse effects of nitrogen loading on surface water bodies will also increase. Stable isotope proxies are potential tracers of nitrate, the most common nitrogenous phase in surface waters. Applying stable isotope proxies therefore presents an opportunity to identify and manage sources of excess nitrogen before aquatic systems are severely degraded. However, the heterogeneous nature of potential pollution sources themselves, and their distribution with a modified catchment network, make understanding this issue highly complex. The Banks Peninsula, an eroded late tertiary volcanic complex located on the east coast of the South Island New Zealand, presents a unique opportunity to study and understand the sources and fates of nitrate within streams in a contemporary mixed land-use setting. Within this small geographic area there a variety of agricultural activities are practiced, including: heavily fertilized golf courses; stands of regenerating native forest; and areas of fallow gorse (Ulex europaeus; a invasive N-fixing shrub). Each of these landuse classes has its own unique nitrogen budget. Multivariate analysis was used on stream nitrate concentrations to reveal that stream reaches dominated by gorse had significantly higher nitrate concentrations than other land-use classes. Nitrate δ15N & δ18O data from these sites show strong covariance, plotting along a distinct fractionation line (r2 = 0.96). This finding facilitates interpretation of what processes are controlling nitrate concentration within these systems. Further, complementary aquatic foodweb δ15N δ13C analyses of multiple species in various trophic positions allow for a unique, holistic insight in to the fate of gorse-derived nitrate at an ecosystem level. We present here physicochemical and stable isotopic data from a variety of aqueous and aquatic foodweb components. Data is generated using emerging and established analytical techniques, in order to explore links between foodweb ecology, ecosystem function, and fate and transport of excess nitrate along longitudinal gradients of mixed land-use catchments.

GATA Factor Regulation in Excess Nitrogen Occurs Independently of Gtr-Ego Complex-Dependent TorC1 Activation.

PubMed

Tate, Jennifer J; Georis, Isabelle; Rai, Rajendra; Vierendeels, Fabienne; Dubois, Evelyne; Cooper, Terrance G

2015-05-29

The TorC1 protein kinase complex is a central component in a eukaryotic cell's response to varying nitrogen availability, with kinase activity being stimulated in nitrogen excess by increased intracellular leucine. This leucine-dependent TorC1 activation requires functional Gtr1/2 and Ego1/3 complexes. Rapamycin inhibition of TorC1 elicits nuclear localization of Gln3, a GATA-family transcription activator responsible for the expression of genes encoding proteins required to transport and degrade poor nitrogen sources, e.g., proline. In nitrogen-replete conditions, Gln3 is cytoplasmic and Gln3-mediated transcription minimal, whereas in nitrogen limiting or starvation conditions, or after rapamycin treatment, Gln3 is nuclear and transcription greatly increased. Increasing evidence supports the idea that TorC1 activation may not be as central to nitrogen-responsive intracellular Gln3 localization as envisioned previously. To test this idea directly, we determined whether Gtr1/2- and Ego1/3-dependent TorC1 activation also was required for cytoplasmic Gln3 sequestration and repressed GATA factor-mediated transcription by abolishing the Gtr-Ego complex proteins. We show that Gln3 is sequestered in the cytoplasm of gtr1Δ, gtr2Δ, ego1Δ, and ego3Δ strains either long term in logarithmically glutamine-grown cells or short term after refeeding glutamine to nitrogen-limited or -starved cells; GATA factor-dependent transcription also was minimal. However, in all but a gtr1Δ, nuclear Gln3 localization in response to nitrogen limitation or starvation was adversely affected. Our data demonstrate: (i) Gtr-Ego-dependent TorC1 activation is not required for cytoplasmic Gln3 sequestration in nitrogen-rich conditions; (ii) a novel Gtr-Ego-TorC1 activation-independent mechanism sequesters Gln3 in the cytoplasm; (iii) Gtr and Ego complex proteins participate in nuclear Gln3-Myc(13) localization, heretofore unrecognized functions for these proteins; and (iv) the importance of searching for new mechanisms associated with TorC1 activation and/or the regulation of Gln3 localization/function in response to changes in the cells' nitrogen environment. Copyright © 2015 Tate et al.

GATA Factor Regulation in Excess Nitrogen Occurs Independently of Gtr-Ego Complex-Dependent TorC1 Activation

PubMed Central

Tate, Jennifer J.; Georis, Isabelle; Rai, Rajendra; Vierendeels, Fabienne; Dubois, Evelyne; Cooper, Terrance G.

2015-01-01

The TorC1 protein kinase complex is a central component in a eukaryotic cell’s response to varying nitrogen availability, with kinase activity being stimulated in nitrogen excess by increased intracellular leucine. This leucine-dependent TorC1 activation requires functional Gtr1/2 and Ego1/3 complexes. Rapamycin inhibition of TorC1 elicits nuclear localization of Gln3, a GATA-family transcription activator responsible for the expression of genes encoding proteins required to transport and degrade poor nitrogen sources, e.g., proline. In nitrogen-replete conditions, Gln3 is cytoplasmic and Gln3-mediated transcription minimal, whereas in nitrogen limiting or starvation conditions, or after rapamycin treatment, Gln3 is nuclear and transcription greatly increased. Increasing evidence supports the idea that TorC1 activation may not be as central to nitrogen-responsive intracellular Gln3 localization as envisioned previously. To test this idea directly, we determined whether Gtr1/2- and Ego1/3-dependent TorC1 activation also was required for cytoplasmic Gln3 sequestration and repressed GATA factor-mediated transcription by abolishing the Gtr-Ego complex proteins. We show that Gln3 is sequestered in the cytoplasm of gtr1Δ, gtr2Δ, ego1Δ, and ego3Δ strains either long term in logarithmically glutamine-grown cells or short term after refeeding glutamine to nitrogen-limited or -starved cells; GATA factor−dependent transcription also was minimal. However, in all but a gtr1Δ, nuclear Gln3 localization in response to nitrogen limitation or starvation was adversely affected. Our data demonstrate: (i) Gtr-Ego-dependent TorC1 activation is not required for cytoplasmic Gln3 sequestration in nitrogen-rich conditions; (ii) a novel Gtr-Ego-TorC1 activation-independent mechanism sequesters Gln3 in the cytoplasm; (iii) Gtr and Ego complex proteins participate in nuclear Gln3-Myc13 localization, heretofore unrecognized functions for these proteins; and (iv) the importance of searching for new mechanisms associated with TorC1 activation and/or the regulation of Gln3 localization/function in response to changes in the cells’ nitrogen environment. PMID:26024867

Reactive Oxygen Species, Mitochondria, and Endothelial Cell Death during In Vitro Simulated Dives.

PubMed

Wang, Qiong; Guerrero, François; Mazur, Aleksandra; Lambrechts, Kate; Buzzacott, Peter; Belhomme, Marac; Theron, Michaël

2015-07-01

Excessive reactive oxygen species (ROS) is considered a consequence of hyperoxia and a major contributor to diving-derived vascular endothelial damage and decompression sickness. The aims of this work were: 1) to directly observe endothelial ROS production during simulated air dives as well as its relation with both mitochondrial activity and cell survival; and 2) to determine which ambient factor during air diving (hydrostatic pressure or oxygen and/or nitrogen partial pressure) is responsible for the observed modifications. In vitro diving simulation was performed with bovine arterial endothelial cells under real-time observation. The effects of air diving, hydrostatic, oxygen and nitrogen pressures, and N-acetylcysteine (NAC) treatment on mitochondrial ROS generation, mitochondrial membrane potential and cellular survival during simulation were investigated. Vascular endothelial cells performing air diving simulation suffered excessive mitochondrial ROS, mitochondrial depolarization, and cell death. These effects were prevented by NAC: after NAC treatment, the cells presented no difference in damage from nondiving cells. Oxygen diving showed a higher effect on ROS generation but lower impacts on mitochondrial depolarization and cell death than hydrostatic or nitrogen diving. Nitrogen diving had no effect on the inductions of ROS, mito-depolarization, or cell death. This study is the first direct observation of mitochondrial ROS production, mitochondrial membrane potential and cell survival during diving. Simulated air SCUBA diving induces excessive ROS production, which leads to mitochondrial depolarization and endothelial cell death. Oxygen partial pressure plays a crucial role in the production of ROS. Deleterious effects of hyperoxia-induced ROS are potentiated by hydrostatic pressure. These findings hold new implications for the pathogenesis of diving-derived endothelial dysfunction.

Contribution Of Spray Irrigation Of Wastewater To Groundwater Contamination In The Karst Of Southeastern Minnesota, USA

NASA Astrophysics Data System (ADS)

Mooers, H. D.; Alexander, E. C., Jr.

1994-01-01

A vegetable- and meat-canning facility located in the karst of southeastern Minnesota disposes ≈2.85×105 m3 yr-1 of wastewater by spray irrigation of an 83.7-ha field located atop the local groundwater divide. Cannery effluent contains high levels of chloride and nitrogen (organic and ammonia), in excess of 7000 mg/l and 400 mg/l, respectively. Nitrate-nitrogen concentrations are generally < 5 mg/l. Agricultural, domestic, and municipal sources of chloride and nitrate are common in the region, and water supplies frequently exceed the drinking-water limit for nitrate-nitrogen of 10 mg/l. Fifty-two area wells and thirteen surface-water locations were sampled and analyzed for five ionic species, including: chloride (Cl), nitrate-nitrogen (NO3-N), sulfate (SO4), nitrite-nitrogen (NO2-N), and phosphate (PO4). Two distinct chloride plumes flowing outward from the groundwater divide were identified, and 65% of the wells sampled had nitrate-nitrogen concentrations in excess of 10 mg/l. The data were divided into two groups: one group of samples from wells located near the canning facility and another group from outside that area. A correlation coefficient of R2= 0.004 for Cl vs. NO3-N in the vicinity of the irrigation fields indicates essentially no relationship between the source of Cl and NO3. In areas of agricultural and domestic activities located away from the cannery, an R2 of 0.54 suggests that Cl and NO3 have common sources in these areas.

Management options to limit nitrate leaching from grassland

NASA Astrophysics Data System (ADS)

Cuttle, S. P.; Scholefield, D.

1995-12-01

Nitrate leaching can be reduced by the adoption of less intensive grassland systems which, though requiring a greater land area to achieve the same agricultural output, result in less nitrate leaching per unit of production than do intensively managed grasslands. The economic penalties associated with reductions in output can be partly offset by greater reliance on symbiotic nitrogen fixation and the use of clover-based swards in place of synthetic N fertilisers. Alternatively, specific measures can be adopted to improve the efficiency of nitrogen use in intensively managed systems in order to maintain high outputs but with reduced losses. Controls should take account of other forms of loss and flows of nitrogen between grassland and other components of the whole-farm system and, in most instances, should result in an overall reduction in nitrogen inputs. Removing stock from the fields earlier in the grazing season will reduce the accumulation of high concentrations of potentially leachable nitrate in the soil of grazed pastures but will increase the quantity of manure produced by housed animals and the need to recycle this effectively. Supplementing grass diets with low-nitrogen forages such as maize silage will reduce the quantity of nitrogen excreted by livestock but may increase the potential for nitrate leaching elsewhere on the farm if changes to cropping patterns involve more frequent cultivation of grassland. Improved utilisation by the sward of nitrogen in animal excreta and manures and released by mineralisation of soil organic matter will permit equivalent reductions to be made in fertiliser inputs, provided that adequate information is available about the supply of nitrogen from these non-fertiliser sources.

Ocean N2O Emissions : Recent Global Estimates and Anthropogenically Influenced Changes

NASA Astrophysics Data System (ADS)

Suntharalingam, P.; Buithenuis, E.; Andrews, O.; Le Quere, C.

2016-12-01

Oceanic N2O is produced by microbial activity during organic matter cycling in the subsurface ocean; its production mechanisms display sensitivity to ambient oxygen level. In the oxic ocean, N2O is produced as a byproduct during the oxidation of ammonia to nitrate, mediated by ammonia oxidizing bacteria and archea. N2O is also produced and consumed in sub-oxic and anoxic waters through the action of marine denitrifiers during the multi-step reduction of nitrate to gaseous nitrogen. The oceanic N2O distribution therefore displays significant heterogeneity with background levels of 10-20 nmol/l in the well-oxygenated ocean basins, high concentrations (> 40 nmol/l) in hypoxic waters, and N2O depletion in the core of ocean oxygen minimum zones (OMZs). Oceanic N2O emissions are estimated to account for up to a third of the pre-industrial N2O fluxes to the atmosphere, however the natural cycle of ocean N2O has been perturbed in recent decades by inputs of anthropogenically derived nutrient, and by the impacts of climate change. Anthropogenic nitrogen inputs (e.g., NOx and NHy from fossil fuel combustion and agricultural fertilizer) enter the ocean via atmospheric deposition and riverine fluxes, influencing oceanic N2O production via their impact on the marine organic matter cycle. In addition, climate variations associated with surface ocean warming affect oceanic circulation and nutrient transport pathways, influencing marine productivity and the ventilation of oxygen minimum zones. Recent studies have suggested that possible expansion of oceanic OMZs in a warming climate could lead to significant changes in N2O production and fluxes from these regions. We will summarise the current state of knowledge on the ocean N2O budget and net flux to the atmosphere. Recently reported estimates have been based on (i) empirical relationships derived from ocean tracer data (e.g., involving excess N2O and Apparent Oxygen Utilization (AOU) correlations), (ii) ocean biogeochemical models, and (iii) air-sea flux calculations which combine surface ocean N2O measurements with gas-exchange relationships. We will also present results from ongoing ocean biogeochemistry model analyses evaluating the separate influences of climate variation and anthropogenic nutrient inputs on ocean N2O emissions for recent decades.

Increasing water productivity, nitrogen economy, and grain yield of rice by water saving irrigation and fertilizer-N management.

PubMed

Aziz, Omar; Hussain, Saddam; Rizwan, Muhammad; Riaz, Muhammad; Bashir, Saqib; Lin, Lirong; Mehmood, Sajid; Imran, Muhammad; Yaseen, Rizwan; Lu, Guoan

2018-06-01

The looming water resources worldwide necessitate the development of water-saving technologies in rice production. An open greenhouse experiment was conducted on rice during the summer season of 2016 at Huazhong Agricultural University, Wuhan, China, in order to study the influence of irrigation methods and nitrogen (N) inputs on water productivity, N economy, and grain yield of rice. Two irrigation methods, viz. conventional irrigation (CI) and "thin-shallow-moist-dry" irrigation (TSMDI), and three levels of nitrogen, viz. 0 kg N ha -1 (N 0 ), 90 kg N ha -1 (N 1 ), and 180 kg N ha -1 (N 2 ), were examined with three replications. Study data indicated that no significant water by nitrogen interaction on grain yield, biomass, water productivity, N uptake, NUE, and fertilizer N balance was observed. Results revealed that TSMDI method showed significantly higher water productivity and irrigation water applications were reduced by 17.49% in TSMDI compared to CI. Thus, TSMDI enhanced root growth and offered significantly greater water saving along with getting more grain yield compared to CI. Nitrogen tracer ( 15 N) technique accurately assessed the absorption and distribution of added N in the soil crop environment and divulge higher nitrogen use efficiency (NUE) influenced by TSMDI. At the same N inputs, the TSMDI was the optimal method to minimize nitrogen leaching loss by decreasing water leakage about 18.63%, which are beneficial for the ecological environment.

Development and Application of Regression Models for Estimating Nutrient Concentrations in Streams of the Conterminous United States, 1992-2001

USGS Publications Warehouse

Spahr, Norman E.; Mueller, David K.; Wolock, David M.; Hitt, Kerie J.; Gronberg, JoAnn M.

2010-01-01

Data collected for the U.S. Geological Survey National Water-Quality Assessment program from 1992-2001 were used to investigate the relations between nutrient concentrations and nutrient sources, hydrology, and basin characteristics. Regression models were developed to estimate annual flow-weighted concentrations of total nitrogen and total phosphorus using explanatory variables derived from currently available national ancillary data. Different total-nitrogen regression models were used for agricultural (25 percent or more of basin area classified as agricultural land use) and nonagricultural basins. Atmospheric, fertilizer, and manure inputs of nitrogen, percent sand in soil, subsurface drainage, overland flow, mean annual precipitation, and percent undeveloped area were significant variables in the agricultural basin total nitrogen model. Significant explanatory variables in the nonagricultural total nitrogen model were total nonpoint-source nitrogen input (sum of nitrogen from manure, fertilizer, and atmospheric deposition), population density, mean annual runoff, and percent base flow. The concentrations of nutrients derived from regression (CONDOR) models were applied to drainage basins associated with the U.S. Environmental Protection Agency (USEPA) River Reach File (RF1) to predict flow-weighted mean annual total nitrogen concentrations for the conterminous United States. The majority of stream miles in the Nation have predicted concentrations less than 5 milligrams per liter. Concentrations greater than 5 milligrams per liter were predicted for a broad area extending from Ohio to eastern Nebraska, areas spatially associated with greater application of fertilizer and manure. Probabilities that mean annual total-nitrogen concentrations exceed the USEPA regional nutrient criteria were determined by incorporating model prediction uncertainty. In all nutrient regions where criteria have been established, there is at least a 50 percent probability of exceeding the criteria in more than half of the stream miles. Dividing calibration sites into agricultural and nonagricultural groups did not improve the explanatory capability for total phosphorus models. The group of explanatory variables that yielded the lowest model error for mean annual total phosphorus concentrations includes phosphorus input from manure, population density, amounts of range land and forest land, percent sand in soil, and percent base flow. However, the large unexplained variability and associated model error precluded the use of the total phosphorus model for nationwide extrapolations.

Episodic inputs of atmospheric nitrogen to the Sargasso Sea: Contributions to new production and phytoplankton blooms

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

Michaels, A.F.; Johnson, R.J.; Siegel, D.A.

1993-06-01

This paper compares a recent atmospheric wet deposition record (including all measurable daily rainfall events between October 1988 and June 1991) with concurrent measurements of nitrogen cycling and biomass at the U.S. Joint Global Ocean Flux Study Bermuda Atlantic Time Series Study station. The two data sets, among the most complete synoptic records of atmospheric nitrogen deposition and ocean nitrogen cycling, provide an opportunity to directly assess the importance of nitrogen deposition in the ocean. The results indicate that individual nitrogen wet deposition events are usually small compared to the ambient nitrogen cycle and that only under sustained calm conditionsmore » following large deposition events will nitrogen deposition processes be an important signal for the understanding of ocean biochemistry. 46 refs., 7 figs.« less

Effects of anthropogenic nitrogen input on the aquatic food webs of river ecosystem in central Japan

NASA Astrophysics Data System (ADS)

Ohte, N.; Togashi, H.; Tokuchi, N.; Yoshimura, M.; Kato, Y.; Ishikawa, N. F.; Osaka, K.; Kondo, M.; Tayasu, I.

2014-12-01

To evaluate the impact of the anthropogenic nitrogen input to the river ecosystem, we conducted the monitoring on nutrient status of river waters and food web structures of aquatic organisms. Especially, changes of sources and concentration of nitrate (NO3-) in river water were focused to evaluate the impact of anthropogenic nitrogen loadings from agricultural and residential areas. Stable nitrogen isotope ratio (δ15N) of aquatic organisms has also intensively been monitored not only to describe their food web structure, but also to detect the influences of extraneous nitrogen inputs. Field samplings an observation campaigns were conducted in the Arida river watershed located in central part of Japan at four different seasons from September 2011 to October 2012. Five observation points were set from headwaters to the point just above the brackish waters starts. Water samples for chemical analysis were taken at the observation points for each campaign. Organisms including leaf litters, benthic algae, aquatic insects, crustacean, and fishes were sampled at each point quantitatively. Results of the riverine survey utilizing 5 regular sampling points showed that δ15N of nitrate (NO3-) increased from forested upstream (˜2 ‰) to the downstream (˜7 ‰) due to the sewage loads and fertilizer effluents from agricultural area. Correspondingly the δ15N of benthic algae and aquatic insects increased toward the downstream. This indicates that primary producers of each reach strongly relied on the local N sources and it was utilized effectively in their food web. Simulation using a GIS based mixing model considering the spatial distributions of human population density and fertilizer effluents revealed that strongest impacts of N inputs was originated from organic fertilizers applied to orchards in the middle to lower parts of catchment. Differences in δ15N between primary producers and predators were 6-7 ‰ similarly at all sampling points. Food web structural analysis using food network unfolding technique based on observed δ15N suggested that the structure of nutrient pyramid did not differ significantly along the riverine positions, while the members of species in each trophic revel changed and the impact of anthropogenic N input was visible along the river.

Hindcasting of nutrient loadings from its catchment on a highly valuable coastal lagoon: the example of the Fleet, Dorset, UK, 1866–2004

PubMed Central

Weber, Geraint J; O'Sullivan, Patrick E; Brassley, Paul

2006-01-01

Background Nutrient loadings from its catchment upon The Fleet, a highly valuable coastal lagoon in Southern England, were hindcast for the period AD 1866–2004, using a catchment model, export coefficients, and historical data on land use changes, livestock numbers, and human population. Agriculture was the main nutrient source throughout, other inputs representing minor contributions. Permanent pasture was historically the main land use, with temporary grassland and cereals increasing during the mid-20th century. Sheep, the main 19th century livestock, were replaced by cattle during the 1930s. Results Total nitrogen loadings rose from ca 41 t yr-1 during the late 19th century to 49–54 t yr-1 for the mid-20th, increasing to 98 t yr-1 by 1986. Current values are ca 77 t yr-1. Total phosphorus loads increased from ca 0.75 t yr-1 for the late 19th century to ca 1.6 t yr-1 for the mid-20th, reached ca 2.2 t yr-1 in 1986, and are now ca 1.5 t yr-1. Loadings rose most rapidly between 1946 and 1988, owing to increased use of inorganic fertilisers, and rising sheep and cattle numbers. Livestock were the main nutrient source throughout, but inputs from inorganic fertilisers increased after 1946, peaking in 1986. Sewage treatment works and other sources contribute little nitrogen, but ca 35% of total phosphorus. Abbotsbury Swannery, an ancient Mute Swan community, provides ca 0.5% of total nitrogen, and ca 5% of total phosphorus inputs. Conclusion The Fleet has been grossly overloaded with nitrogen since 1866, climaxing during the 1980s. Total phosphorus inputs lay below 'permissible' limits until the 1980s, exceeding them in inner, less tidal parts of the lagoon, during the 1940s. Loadings on Abbotsbury Bay exceeded 'permissible' limits by the 1860s, becoming 'dangerous' during the mid-20th century. Phosphorus stripping at point sources will not significantly reduce loadings to all parts of the lagoon. Installation of 5 m buffer strips throughout the catchment and shoreline will marginally affect nitrogen loadings, but will reduce phosphorus inputs to the West Fleet below 'permissible' limits. Only a combination of measures will significantly affect Abbotsbury Bay, where, without effluent diversion, loadings will remain beyond 'permissible'. PMID:17196108

Nitrogen extraction potential of wild and cultured bivalves harvested from nearshore waters of Cape Cod, USA.

PubMed

Reitsma, Joshua; Murphy, Diane C; Archer, Abigail F; York, Richard H

2017-03-15

As nitrogen entering coastal waters continues to be an issue, much attention has been generated to identify potential options that may help alleviate this stressor to estuaries, including the propagation of bivalves to remove excess nitrogen. Oysters (Crassostrea virginica) and quahogs (Mercenaria mercenaria) from numerous Cape Cod, MA, (USA) sources were analyzed for nitrogen content stored in tissues that would represent a net removal of nitrogen from a water body if harvested. Results showed local oysters average 0.69% nitrogen by total dry weight (mean 0.28gN/animal) and quahogs average 0.67% nitrogen by total dry weight (mean 0.22gN/animal); however, these values did vary by season and to a lesser extent by location or grow-out method. The differences in nitrogen content were largely related to the mass of shell or soft tissue. Nitrogen isotope data indicate shellfish from certain water bodies in the region are incorporating significant amounts of nitrogen from anthropogenic sources. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Tracking Urban Air Deterioration in San Francisco: Carbon and Nitrogen Isotope Study of Weedy Plants.

NASA Astrophysics Data System (ADS)

Colman, A. S.; Wessells, A.; Swaine, M. E.; Fogel, M. L.

2003-12-01

Stable isotopes of carbon and nitrogen have long been used as indicators of ecosystem structure and nutrient cycling in natural and anthropogenically disturbed terrestrial ecosytems. However, relatively few of these studies have targeted urban environments, where nitrogen and CO2 emissions dramatically impact atmospheric composition. Here we present the results of carbon and nitrogen isotope analyses of herbaceous plants growing in and around San Francisco. These plants were collected mainly as part of a public outreach walking tour of San Francisco ("The Weed Walk - Concrete Jungle") sponsored by the San Francisco Exploratorium. In all cases, the plants were sampled in areas with negligible forest canopy. A consortium of species was collected at each of several distinct sites to examine the localized and regional impact of automobile traffic and proximity to the ocean on isotopic compositions of carbon and nitrogen. δ 13C measurements trend towards relatively light values in the range of --26 to --36 permil. In comparison, the leaves from similar types of herbaceous species in relatively unpolluted and unforested environments typically have δ 13C values in the range of --22 to --28 permil. The observed light carbon isotopic compositions potentially reflect input of isotopically light CO2 emissions from fossil fuel burning, boosting atmospheric CO2 concentrations to >10 % above background. δ 15N values range from +4 to +9 permil. This is substantially offset from the --4 to +1 permil values that typify vegetation in regions where nitrogen oxides from fossil fuel combustion dominate the nitrogen inputs. The nitrogen isotope compositions might suggest nitrogen contributions from a marine source (typically +6 permil).

Nitrogen cycle and ecosystem services in the Brazilian La Plata Basin: anthropogenic influence and climate change.

PubMed

Watanabe, M; Ortega, E; Bergier, I; Silva, J S V

2012-08-01

The increasing human demand for food, raw material and energy has radically modified both the landscape and biogeochemical cycles in many river basins in the world. The interference of human activities on the Biosphere is so significant that it has doubled the amount of reactive nitrogen due to industrial fertiliser production (Haber-Bosch), fossil fuel burning and land-use change over the last century. In this context, the Brazilian La Plata Basin contributes to the alteration of the nitrogen cycle in South America because of its huge agricultural and grazing area that meets the demands of its large urban centres - Sao Paulo, for instance - and also external markets abroad. In this paper, we estimate the current inputs and outputs of anthropogenic nitrogen (in kg N.km(-2).yr(-1)) in the basin. In the results, we observe that soybean plays a very important role in the Brazilian La Plata, since it contributes with an annual entrance of about 1.8 TgN due to biological nitrogen fixation. Moreover, our estimate indicates that the export of soybean products accounts for roughly 1.0 TgN which is greater than the annual nitrogen riverine exports from Brazilian Parana, Paraguay and Uruguay rivers together. Complimentarily, we built future scenarios representing changes in the nitrogen cycle profile considering two scenarios of climate change for 2070-2100 (based on IPCC's A2 and B2) that will affect land-use, nitrogen inputs, and loss of such nutrients in the basin. Finally, we discuss how both scenarios will affect human well-being since there is a connection between nitrogen cycle and ecosystem services that affect local and global populations, such as food and fibre production and climate regulation.

Correlation of seasonal variations in phosphorous and nitrogen species in upper Black Warrior River with duckweed

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

Gabrielson, F.C. Jr.; Malatino, A.M.; Santa Cruz, G.J.

1980-10-01

Water samples taken throughout the year from a drainage system that had supported giant duckweed blooms were analyzed for nitrogen and phosphorus. Although seasonal separation of the data indicates possible differences within an imppoundment (Bayview Lake), extreme variations make meaningful conclusions difficult. Daily discharge from a large number of points may have masked seasonal differences. Extensive plant mats were present at minimal levels of nitrogen and phosphorus. The growth rate seemed to be governed more by climate than nutrient conditions. Laboratory investigations indicate that giant duckweed can grow under a wide range of nutrient conditions including high heavy metal concentrations.more » Growth rate data show that without a continual input of nutrients, maximum growth rates do not usually continue beyond 14 to 20 days regardless of the initial single element concentration. With a continuous nutrient input, growth would probably only be inhibited by extreme climate conditions.« less

The whale pump: marine mammals enhance primary productivity in a coastal basin.

PubMed

Roman, Joe; McCarthy, James J

2010-10-11

It is well known that microbes, zooplankton, and fish are important sources of recycled nitrogen in coastal waters, yet marine mammals have largely been ignored or dismissed in this cycle. Using field measurements and population data, we find that marine mammals can enhance primary productivity in their feeding areas by concentrating nitrogen near the surface through the release of flocculent fecal plumes. Whales and seals may be responsible for replenishing 2.3×10(4) metric tons of N per year in the Gulf of Maine's euphotic zone, more than the input of all rivers combined. This upward "whale pump" played a much larger role before commercial harvest, when marine mammal recycling of nitrogen was likely more than three times atmospheric N input. Even with reduced populations, marine mammals provide an important ecosystem service by sustaining productivity in regions where they occur in high densities.

The Whale Pump: Marine Mammals Enhance Primary Productivity in a Coastal Basin

PubMed Central

Roman, Joe; McCarthy, James J.

2010-01-01

It is well known that microbes, zooplankton, and fish are important sources of recycled nitrogen in coastal waters, yet marine mammals have largely been ignored or dismissed in this cycle. Using field measurements and population data, we find that marine mammals can enhance primary productivity in their feeding areas by concentrating nitrogen near the surface through the release of flocculent fecal plumes. Whales and seals may be responsible for replenishing 2.3×104 metric tons of N per year in the Gulf of Maine's euphotic zone, more than the input of all rivers combined. This upward “whale pump” played a much larger role before commercial harvest, when marine mammal recycling of nitrogen was likely more than three times atmospheric N input. Even with reduced populations, marine mammals provide an important ecosystem service by sustaining productivity in regions where they occur in high densities. PMID:20949007

[Inventory of regional surface nutrient balance and policy recommendations in China].

PubMed

Chen, Min-Peng; Chen, Ji-Ning

2007-06-01

By applying OECD surface soil nitrogen balance methodology, the framework, methodology and database for nutrient balance budget in China are established to evaluate the impact of nutrient balance on agricultural production and water environment. Results show that nitrogen and phosphorus surplus in China are 640 x 10(4) t and 98 x 10(4) t respectively, and nitrogen and phosphorus surplus intensity in China are 16.56 kg/hm2 and 2.53 kg/hm2 respectively. Because of striking spatial difference of nutrient balance across the country, China is seeing a dual-challenge of nutrient surplus management as well as nutrient deficit management. Chemical fertilizer and livestock manure are best targets to perform nutrient surplus management due to their marked contributions to nutrient input. However, it is not cost-effective to implement a uniform management for all regions since nutrient input structures of them vary considerably.

Explanatory characteristics for nutrient concentrations and loads in the Sava River Catchment and cross-regionally

NASA Astrophysics Data System (ADS)

Levi, L.; Cvetkovic, V.; Destouni, G.

2015-12-01

This study compiles estimates of waterborne nutrient concentrations and loads in the Sava River Catchment (SRC). Based on this compilation, we investigate hotspots of nutrient inputs and retention along the river, as well as concentration and load correlations with river discharge and various human drivers of excess nutrient inputs to the SRC. For cross-regional assessment and possible generalization, we also compare corresponding results between the SRC and the Baltic Sea Drainage Basin (BSDB). In the SRC, one small incremental subcatchment, which is located just downstream of Zagreb and has the highest population density among the SRC subcatchments, is identified as a major hotspot for net loading (input minus retention) of both total nitrogen (TN) and total phosphorus (TP) to the river and through it to downstream areas of the SRC. The other SRC subcatchments exhibit relatively similar characteristics with smaller net nutrient loading. The annual loads of both TN and TP along the Sava River exhibit dominant temporal variability with considerably higher correlation with annual river discharge (R2 = 0.51 and 0.28, respectively) than that of annual average nutrient concentrations (R2 = 0.0 versus discharge for both TN and TP). Nutrient concentrations exhibit instead dominant spatial variability with relatively high correlation with population density among the SRC subcatchments (R2=0.43-0.64). These SRC correlation characteristics compare well with corresponding ones for the BSDB, even though the two regions are quite different in their hydroclimatic, agricultural and wastewater treatment conditions. Such cross-regional consistency in dominant variability type and explanatory catchment characteristics may be a useful generalization basis, worthy of further investigation, for at least first-order estimation of nutrient concentration and load conditions in less data-rich regions.

African N Assessment

NASA Astrophysics Data System (ADS)

Bekunda, M.; Galford, G. L.; Hickman, J. E.; Palm, C.

2011-12-01

Africa's smallholder agricultural systems face unique challenges in planning for reducing poverty, concurrent with adaptation and mitigation to climate change. At continental level, policy seeks to promote a uniquely African Green Revolution to increase crop yields and food production, and improve local livelihoods. However, the consequences on the environment and climate are not clear; these pro-economic development measures should be linked to climate change adaptation and mitigation measures, and research is required to help achieve these policy proposals by identifying options, and testing impacts. In particular, increased nitrogen (N) inputs are essential for increasing food production in Africa, but are accompanied by inevitable increases in losses to the environment. These losses appear to be low at input levels promoted in agricultural development programs, while the increased N inputs both increase current food production and appear to reduce the vulnerability of food production to changes in climate. We present field and remote sensing evidence from Malawi that subsidizing improved seed and fertilizers increases resilience to drought without adding excess N to the environment. In Kenya, field research identified thresholds in N2O losses, where emissions are very low at fertilization rates of less than 200 kg ha-1. Village-scale models have identified potential inefficiencies in the food production process where the largest losses of reactive N occur, and which could be targeted to reduce the amount of N released to the environment. We further review some on-going research activities and progress in Africa that compare different methods of managing resources that target resilience in food production and adaptation to climate change, using nutrient N as an indicator, while evaluating the effects of these resource management practices on ecosystems and the environment.

Global sensitivity and uncertainty analysis of the nitrate leaching and crop yield simulation under different water and nitrogen management practices

USDA-ARS?s Scientific Manuscript database

Agricultural system models have become important tools in studying water and nitrogen (N) dynamics, as well as crop growth, under different management practices. Complexity in input parameters often leads to significant uncertainty when simulating dynamic processes such as nitrate leaching or crop y...

δ 15 N constraints on long-term nitrogen balances in temperate forests

EPA Science Inventory

Natural abundance δ15N of ecosystems integrates nitrogen (N) inputs and losses, and thus reflects factors that control the long-term development of ecosystem N balances. We here report N and carbon (C) content of forest vegetation and soils, and associated δ15N, across nine Doug...

Mechanisms of nitrogen deposition effects on temperate forest lichens and trees

Treesearch

Therese S. Carter; Christopher M. Clark; Mark E. Fenn; Sarah Jovan; Steven S. Perakis; Jennifer Riddell; Paul G. Schaberg; Tara L. Greaver; Meredith G. Hastings

2017-01-01

We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus on trees and lichens. Elevated anthropogenic N deposition to forests has varied effects on individual organisms depending on characteristics both of the N inputs (form, timing, amount) and of the organisms (ecology, physiology) involved. Improved...

NON-LINEAR NITROGEN RETENTION IN AN UNPOLLUTED OLD-GROWTH TEMPERATE FOREST RECEIVING A GEOMETRIC RANGE OF EXPERIMENTAL 15N ADDITIONS

EPA Science Inventory

Over the past century, human activities have increased the rate and extent of atmospheric nitrogen (N) deposition over large regions of Earth. These novel N inputs have driven many previously N-limited temperate forests towards a condition of "N saturation," characterized by poo...

Sinks for nitrogen inputs in terrestrial ecosystems: A meta-analysis of 15N tracer field studies

EPA Science Inventory

Anthropogenic nitrogen (N) deposition can have a range of effects on terrestrial ecosystems, but these effects depend in part on the fate of this deposited N, particularly in the amount retained or lost from the system, and in the partitioning of retained N between plants and soi...

NITROGEN CONCENTRATIONS IN LOADING SOURCES FOR THREE COASTAL LAGOONS FROM ATMOSPHERIC AND WATERSHED SOURCES, ADJACENT COASTAL MARSHES, TIDAL EXCHANGES

EPA Science Inventory

Abstract and Oral Presentation Gulf Estuarine Research Society.

Standing stocks and inputs of total dissolved nitrogen (TDN) to three coastal lagoons, hereafter referred to as Kee's Bayou, Gongora, and State Park, with varying adjacent land-use, geomorphology, and water re...

A public-industry partnership for enhancing corn nitrogen research and datasets: project description, methodology, and outcomes

USDA-ARS?s Scientific Manuscript database

Due to economic and environmental consequences of nitrogen (N) lost from fertilizer applications in corn (Zea mays L.), considerable public and industry attention has been devoted to development of N decision tools. Now a wide variety of tools are available to farmers for managing N inputs. However,...

Overview of a public-industry partnership for enhancing corn nitrogen research and datasets

USDA-ARS?s Scientific Manuscript database

Due to economic and environmental consequences of nitrogen (N) lost from fertilizer applications in corn (Zea mays L.), considerable public and industry attention has been devoted to development of N decision tools. Now a wide variety of tools are available to farmers for managing N inputs. However,...

Seasonal patterns of climate controls over nitrogen fixation by Alnus viridis subsp

Treesearch

Jennifer S. Mitchell; Roger W. Ruess

2009-01-01

Patterns of and controls over N2 fixation by green alder were studied in post-fire, mid-succession, and white spruce upland forests in interior Alaska, focusing on the hypothesis that ecosystem-level nitrogen (N) inputs decrease with successional development. N2-fixation rates tracked plant phenology during the 1997 (...

Predicting Ecosystem Services in Northeastern Lakes From Monitoring Data and USGS SPARROW Nutrient Load Estimates

EPA Science Inventory

Reduction of nitrogen inputs to estuaries can be achieved by the control of agricultural, atmospheric, and urban sources. We use the USGS MRB1 SPARROW model to estimate reductions necessary to decrease nitrogen loads to estuaries by 10%. As a first approximation we looked at s...

Runoff Water Quality During Drought in a Zero-Order Georgia Piedmont Pasture: Nitrogen and Total Organic Carbon

EPA Science Inventory

Approximately 11% of the Southern Piedmont (1.8 million ha) is used for pasture and hay production, mostly under low-input management. Few studies have investigated in the region long-term nitrogen and carbon losses in surface runoff, which can be significant. We present 1999 to ...

CULTURAL EUTROPHICATION IN THE CHOPTANK AND PATUXENT ESTUARIES OF CHESAPEAKE BAY

EPA Science Inventory

The Choptank and Patuxent tributaries of Chesapeake Bay have become eutrophic over the last 50-100 years. Systematic monitoring of nutrient inputs began in ~1970, and there have been 2-5-fold increases in nitrogen (N) and phosphorus (P) inputs during 1970-2004 due to sewage disch...

Nitrogen and phosphorus fluxes from watersheds of the northeast U.S. from 1930 to 2000: Role of anthropogenic nutrient inputs, infrastructure, and runoff

NASA Astrophysics Data System (ADS)

Hale, Rebecca L.; Grimm, Nancy B.; Vörösmarty, Charles J.; Fekete, Balazs

2015-03-01

An ongoing challenge for society is to harness the benefits of nutrients, nitrogen (N) and phosphorus (P), while minimizing their negative effects on ecosystems. While there is a good understanding of the mechanisms of nutrient delivery at small scales, it is unknown how nutrient transport and processing scale up to larger watersheds and whole regions over long time periods. We used a model that incorporates nutrient inputs to watersheds, hydrology, and infrastructure (sewers, wastewater treatment plants, and reservoirs) to reconstruct historic nutrient yields for the northeastern U.S. from 1930 to 2002. Over the study period, yields of nutrients increased significantly from some watersheds and decreased in others. As a result, at the regional scale, the total yield of N and P from the region did not change significantly. Temporal variation in regional N and P yields was correlated with runoff coefficient, but not with nutrient inputs. Spatial patterns of N and P yields were best predicted by nutrient inputs, but the correlation between inputs and yields across watersheds decreased over the study period. The effect of infrastructure on yields was minimal relative to the importance of soils and rivers. However, infrastructure appeared to alter the relationships between inputs and yields. The role of infrastructure changed over time and was important in creating spatial and temporal heterogeneity in nutrient input-yield relationships.

Artificial intelligence models for predicting the performance of biological wastewater treatment plant in the removal of Kjeldahl Nitrogen from wastewater

NASA Astrophysics Data System (ADS)

Manu, D. S.; Thalla, Arun Kumar

2017-11-01

The current work demonstrates the support vector machine (SVM) and adaptive neuro-fuzzy inference system (ANFIS) modeling to assess the removal efficiency of Kjeldahl Nitrogen of a full-scale aerobic biological wastewater treatment plant. The influent variables such as pH, chemical oxygen demand, total solids (TS), free ammonia, ammonia nitrogen and Kjeldahl Nitrogen are used as input variables during modeling. Model development focused on postulating an adaptive, functional, real-time and alternative approach for modeling the removal efficiency of Kjeldahl Nitrogen. The input variables used for modeling were daily time series data recorded at wastewater treatment plant (WWTP) located in Mangalore during the period June 2014-September 2014. The performance of ANFIS model developed using Gbell and trapezoidal membership functions (MFs) and SVM are assessed using different statistical indices like root mean square error, correlation coefficients (CC) and Nash Sutcliff error (NSE). The errors related to the prediction of effluent Kjeldahl Nitrogen concentration by the SVM modeling appeared to be reasonable when compared to that of ANFIS models with Gbell and trapezoidal MF. From the performance evaluation of the developed SVM model, it is observed that the approach is capable to define the inter-relationship between various wastewater quality variables and thus SVM can be potentially applied for evaluating the efficiency of aerobic biological processes in WWTP.

Effects of nitrogen fertilization strategies on nitrogen use efficiency in physiology, recovery, and agronomy and redistribution of dry matter accumulation and nitrogen accumulation in two typical rice cultivars in Zhejiang, China.

PubMed

Xie, Wen-xia; Wang, Guang-huo; Zhang, Qi-chun; Guo, Hai-chao

2007-03-01

Field experiments were conducted in farmers' rice fields in 2001 and 2002 to study the effects of nitrogen (N) management strategies on N use efficiency in recovery (RE), agronomy (AE) and physiology (PE) and redistribution of dry matter accumulation (DMA) and nitrogen accumulation (NA) in two typical rice cultivars in Jinhua, Zhejiang Province. This study aimed mainly at identifying the possible causes of poor fertilizer N use efficiency (NUE) of rice in Zhejiang by comparing farmers' fertilizer practice (FFP) with advanced site-specific nutrient management (SSNM) and real-time N management (RTNM). The results showed that compared to FFP, SSNM and RTNM reduced DMA and NA before panicle initiation and increased DMA and NA at post-flowering. There is no significant difference between SSNM and FFP in post-flowering dry matter redistribution (post-DMR) and post-flowering nitrogen redistribution (post-NR). These results suggest that high input rate of fertilizer N and improper fertilizer N timing are the main factors causing low NUE of irrigated rice in the farmer's routine practice of Zhejiang. With SSNM, about 15% of the current total N input in direct-seeding early rice and 45% in single rice could be reduced without yield loss in Zhejiang, China.

Influence of Dynamic Hydraulic Conditions on Nitrogen Cycling in Column Experiments

NASA Astrophysics Data System (ADS)

Gassen, Niklas; von Netzer, Frederick; Ryabenko, Evgenia; Lüders, Tillmann; Stumpp, Christine

2015-04-01

In order to improve management strategies of agricultural nitrogen input, it is of major importance to further understand which factors influence turnover processes within the nitrogen cycle. Many studies have focused on the fate of nitrate in hydrological systems, but up to date only little is known about the influence of dynamic hydraulic conditions on the fate of nitrate at the soil-groundwater interface. We conducted column experiments with natural sediment and compared a system with a fluctuating water table to systems with different water content and static conditions under the constant input of ammonia into the system. We used hydrochemical methods in order to trace nitrogen species, 15N isotope methods to get information about dominating turnover processes and microbial community analysis in order to connect hydrochemical and microbial information. We found that added ammonia was removed more effectively under dynamic hydraulic conditions than under static conditions. Furthermore, denitrification is the dominant process under saturated, static conditions, while nitrification is more important under unsaturated, static conditions. We conclude that a fluctuating water table creates hot spots where both nitrification and denitrification processes can occur spatially close to each other and therefore remove nitrogen more effectively from the system. Furthermore, the fluctuating water table enhances the exchange of solutes and triggers hot moments of solute turnover. Therefore we conclude that a fluctuating water table can amplify hot spots and trigger hot moments of nitrogen cycling.

Investigation of the Explosive Potential of the Hybrid Propellant Combinations N2O4/PBAN and CTF/PBAN

DTIC Science & Technology

1967-03-01

nitrogen tetroxide (N„0 ) and polybutadyne-aluminum (PBAN), and chlorine trifluoride (CTF) and PBAN. This program consisted of a series of eight...explosive potential of two hybrid propellant combinations; nitrogen tetroxide QLOL) and polybutadyne - aluminum (PBAN) and chlorine triflouride (CTF...or positive-phase impulse yield. FREE AIR OVERPRESSURE: (OR FREE FIELD OVERPRESSURE): The unreflected pressure, in excess of the ambient atmospheric

Limitation of Bacterial Growth by Dissolved Organic Matter and Iron in the Southern Ocean†

PubMed Central

Church, Matthew J.; Hutchins, David A.; Ducklow, Hugh W.

2000-01-01

The importance of resource limitation in controlling bacterial growth in the high-nutrient, low-chlorophyll (HNLC) region of the Southern Ocean was experimentally determined during February and March 1998. Organic- and inorganic-nutrient enrichment experiments were performed between 42°S and 55°S along 141°E. Bacterial abundance, mean cell volume, and [3H]thymidine and [3H]leucine incorporation were measured during 4- to 5-day incubations. Bacterial biomass, production, and rates of growth all responded to organic enrichments in three of the four experiments. These results indicate that bacterial growth was constrained primarily by the availability of dissolved organic matter. Bacterial growth in the subtropical front, subantarctic zone, and subantarctic front responded most favorably to additions of dissolved free amino acids or glucose plus ammonium. Bacterial growth in these regions may be limited by input of both organic matter and reduced nitrogen. Unlike similar experimental results in other HNLC regions (subarctic and equatorial Pacific), growth stimulation of bacteria in the Southern Ocean resulted in significant biomass accumulation, apparently by stimulating bacterial growth in excess of removal processes. Bacterial growth was relatively unchanged by additions of iron alone; however, additions of glucose plus iron resulted in substantial increases in rates of bacterial growth and biomass accumulation. These results imply that bacterial growth efficiency and nitrogen utilization may be partly constrained by iron availability in the HNLC Southern Ocean. PMID:10653704

Nitrogen balance dynamics during 2000-2010 in the Yangtze River Basin croplands, with special reference to the relative contributions of cropland area and synthetic fertilizer N application rate changes

PubMed Central

Wang, Lijuan; Zhao, He; Robinson, Brian E.

2017-01-01

With the increases of cropland area and fertilizer nitrogen (N) application rate, general N balance characteristics in regional agroecosystems have been widely documented. However, few studies have quantitatively analyzed the drivers of spatial changes in the N budget. We constructed a mass balance model of the N budget at the soil surface using a database of county-level agricultural statistics to analyze N input, output, and proportional contribution of various factors to the overall N input changes in croplands during 2000–2010 in the Yangtze River Basin, the largest basin and the main agricultural production region in China. Over the period investigated, N input increased by 9%. Of this 87% was from fertilizer N input. In the upper and middle reaches of the basin, the increased synthetic fertilizer N application rate accounted for 84% and 76% of the N input increase, respectively, mainly due to increased N input in the cropland that previously had low synthetic fertilizer N application rate. In lower reaches of the basin, mainly due to urbanization, the decrease in cropland area and synthetic fertilizer N application rate nearly equally contributed to decreases in N input. Quantifying spatial N inputs can provide critical managerial information needed to optimize synthetic fertilizer N application rate and monitor the impacts of urbanization on agricultural production, helping to decrease agricultural environment risk and maintain sustainable agricultural production in different areas. PMID:28678841

Nitrogen balance dynamics during 2000-2010 in the Yangtze River Basin croplands, with special reference to the relative contributions of cropland area and synthetic fertilizer N application rate changes.

PubMed

Wang, Lijuan; Zheng, Hua; Zhao, He; Robinson, Brian E

2017-01-01

With the increases of cropland area and fertilizer nitrogen (N) application rate, general N balance characteristics in regional agroecosystems have been widely documented. However, few studies have quantitatively analyzed the drivers of spatial changes in the N budget. We constructed a mass balance model of the N budget at the soil surface using a database of county-level agricultural statistics to analyze N input, output, and proportional contribution of various factors to the overall N input changes in croplands during 2000-2010 in the Yangtze River Basin, the largest basin and the main agricultural production region in China. Over the period investigated, N input increased by 9%. Of this 87% was from fertilizer N input. In the upper and middle reaches of the basin, the increased synthetic fertilizer N application rate accounted for 84% and 76% of the N input increase, respectively, mainly due to increased N input in the cropland that previously had low synthetic fertilizer N application rate. In lower reaches of the basin, mainly due to urbanization, the decrease in cropland area and synthetic fertilizer N application rate nearly equally contributed to decreases in N input. Quantifying spatial N inputs can provide critical managerial information needed to optimize synthetic fertilizer N application rate and monitor the impacts of urbanization on agricultural production, helping to decrease agricultural environment risk and maintain sustainable agricultural production in different areas.

County-level estimates of nutrient inputs to the landsurface of the conterminous United States, 1982-2001

USGS Publications Warehouse

Ruddy, Barbara C.; Lorenz, David L.; Mueller, David K.

2006-01-01

Nutrient input data for fertilizer use, livestock manure, and atmospheric deposition from various sources were estimated and allocated to counties in the conterminous United States for the years 1982 through 2001. These nationally consistent nutrient input data are needed by the National Water-Quality Assessment Program for investigations of stream- and ground-water quality. For nitrogen, the largest source was farm fertilizer; for phosphorus, the largest sources were farm fertilizer and livestock manure. Nutrient inputs from fertilizer use in nonfarm areas, while locally important, were an order of magnitude smaller than inputs from other sources. Nutrient inputs from all sources increased between 1987 and 1997, but the relative proportions of nutrients from each source were constant. Farm-fertilizer inputs were highest in the upper Midwest, along eastern coastal areas, and in irrigated areas of the West. Nonfarm-fertilizer use was similar in major metropolitan areas throughout the Nation, but was more extensive in the more populated Eastern and Central States and in California. Areas of greater manure inputs were located throughout the South-central and Southeastern States and in scattered areas of the West. Nitrogen deposition from the atmosphere generally increased from west to east and is related to the location of major sources and the effects of precipitation and prevailing winds. These nutrient-loading data at the county level are expected to be the fundamental basis for national and regional assessments of water quality for the National Water-Quality Assessment Program and other large-scale programs.

Peatlands in a eutrophic world - assessing the state of a poor fen-bog transition in southern Ontario, Canada, after long term nutrient input and altered hydrological conditions

NASA Astrophysics Data System (ADS)

Berger, Sina; Gebauer, Gerhard; Blodau, Christian; Knorr, Klaus-Holger

2017-04-01

Peatlands are of vital importance for global carbon (C) cycling as they sequester and store enormous amounts of C. Major threats to peatlands are excessive supply of nutrients from the atmosphere as well as from surface water and groundwater. Up to this date our knowledge of long-term consequences of such excessive nutrient supply is limited. We are unsure about how long peatlands can maintain their functioning under such circumstances. We conducted a detailed study in a once ombrotrophic bog ecosystem (Wylde Lake peatland, Ontario, Canada), which is since the 19th century embedded in a eutrophic environment with intensive agriculture. Moreover, since AD 1954 the peatland borders a water reservoir which is strongly enriched with nutrients. Our objective was to elucidate to which extent the infiltration of nutrient from the peatland periphery can be buffered and whether the inner parts can maintain typical characteristics of a pristine bog. To achieve this goal, along a transect of study sites, we Pb-210- and Cs-137-dated peat cores and determined elements of peat using x-ray fluorescence (XRF). To calculate N input, nitrogen enrichment factors in the vegetation and abundances of stable N isotopes in the peat were determined through isotope ratio mass spectrometry (IRMS). Furthermore, we re-investigated the vascular plant species composition 31 years after a previous investigation and lastly, we sporadically measured greenhouse gas fluxes with chamber techniques. In the central part of the peatland we found great N input rates of 4.28±0.75 and 4.35±0.30 g N m-2 y-1, but even greater rates were found in the peatland fringe area (5.90±0.10 g N m-2 y-1). Also, all elements essential for plant growth were abundant in increased concentrations along all peat cores, especially near the bordering reservoir, presumably due to supply by the reservoir water. A more graminoid dominated vegetation in the wetter areas (near the reservoir) and a rapid increase of tree cover in drier areas (further away from the reservoir), both over a healthy Sphagnum carpet, as well as altered fluxes of CO2, CH4 and N2O indicate a transformation of the once ombrotrophic bog into a poor fen. Very much to our surprise the peatland did not seem to decay after long-term excessive nutrient load, instead it tremendously accelerated peat accumulation which led to maximum growth rates of up to 500 g C m-2 y-1. Peatland functioning in terms of carbon storage appeared to be maintained. Our study, which combines a great variety of methods and which provides detailed insights into various processes along peat profiles and vegetation cover, therefore contradicts numerous previous studies in which it was stated that long-term excessive supply of nutrients to peatlands would cause dying of Sphagnum mosses and hence, a decay and increased peat loss of the affected site already after one decade.

Overexpression of Arabidopsis NLP7 improves plant growth under both nitrogen-limiting and -sufficient conditions by enhancing nitrogen and carbon assimilation.

PubMed

Yu, Lin-Hui; Wu, Jie; Tang, Hui; Yuan, Yang; Wang, Shi-Mei; Wang, Yu-Ping; Zhu, Qi-Sheng; Li, Shi-Gui; Xiang, Cheng-Bin

2016-06-13

Nitrogen is essential for plant survival and growth. Excessive application of nitrogenous fertilizer has generated serious environment pollution and increased production cost in agriculture. To deal with this problem, tremendous efforts have been invested worldwide to increase the nitrogen use ability of crops. However, only limited success has been achieved to date. Here we report that NLP7 (NIN-LIKE PROTEIN 7) is a potential candidate to improve plant nitrogen use ability. When overexpressed in Arabidopsis, NLP7 increases plant biomass under both nitrogen-poor and -rich conditions with better-developed root system and reduced shoot/root ratio. NLP7-overexpressing plants show a significant increase in key nitrogen metabolites, nitrogen uptake, total nitrogen content, and expression levels of genes involved in nitrogen assimilation and signalling. More importantly, overexpression of NLP7 also enhances photosynthesis rate and carbon assimilation, whereas knockout of NLP7 impaired both nitrogen and carbon assimilation. In addition, NLP7 improves plant growth and nitrogen use in transgenic tobacco (Nicotiana tabacum). Our results demonstrate that NLP7 significantly improves plant growth under both nitrogen-poor and -rich conditions by coordinately enhancing nitrogen and carbon assimilation and sheds light on crop improvement.

Changing ecosystem response to nitrogen load into Buzzards Bay, MA

NASA Astrophysics Data System (ADS)

Williamson, S.; Rheuban, J. E.; Costa, J. E.; Glover, D. M.; Doney, S. C.

2016-02-01

Nitrogen (N) and chlorophyll-a (Chla) concentration in estuarine systems often correlate positively with increased N inputs. Evaluation of a long-term water quality data set (1992 -2013) for Buzzards Bay, MA, however reveals that ecosystem response to N inputs may be changing over time, as represented by increased yield of Chla per unit total nitrogen (TN) from 1992-2013. To determine if this change is caused by changes in nitrogen sources, we estimate nitrogen input from 28 watersheds. Combining parcel specific waste water disposal, land use, and atmospheric deposition data, we estimated N loads into Buzzards Bay from 1985-2013 using a previously verified Nitrogen Loading Model. Of the 28 watersheds analyzed, the six largest watersheds released the largest absolute N loads into receiving estuaries ranging from approximately 50,000-220,000 kg N yr-1. Normalizing N loads by watershed and estuarine areas revealed that smaller watersheds release some of the greatest relative loads into estuaries making these watersheds more vulnerable to increases in N load. A linear regression analysis of N load through time revealed decreasing N loads for most watersheds on the western side of Buzzards Bay which we believe is reflecting decreased atmospheric N from 1985-2013. Out of the ten sub-watersheds on the eastern side, increases in human waste, driven primarily by increased parcels on septic have resulted in overall N load increases for 9 watersheds. Comparison of in situ TN and Chla concentrations with N load estimates for several watersheds and adjoining estuaries suggest that varied ecosystem responses to N load may be reflecting differences in physical stressors such as estuarine morphology, residence time, and climate change. Results of this study also reveal the importance of watershed specific mitigation efforts to best accommodate dominant N sources which may be influenced regionally (atmospheric N) and locally (fertilizer and human waste).

Spatio-temporal variability of dissolved organic nitrogen (DON), carbon (DOC), and nutrients in the Nile River, Egypt.

PubMed

Badr, El-Sayed A

2016-10-01

Increases in human activity have resulted in enhanced anthropogenic inputs of nitrogen (N) and carbon (C) into the Nile River. The Damietta Branch of the Nile is subject to inputs from industrial, agricultural, and domestic wastewater. This study investigated the distribution and seasonality of dissolved organic nitrogen (DON), dissolved organic carbon (DOC), and nutrients in the Nile Damietta Branch. Water samples were collected from 24 sites between May 2009 and February 2010. Dissolved organic nitrogen concentrations averaged 251 ± 115 μg/l, with a range of 90.2-671 μg/l, and contributed 40.8 ± 17.7 % to the total dissolved nitrogen (TDN) pool. Relative to autumn and winter, DON was a larger fraction of the TDN pool during spring and summer indicating the influence of bacterioplankton on the nitrogen cycle. Concentrations of DOC ranged from 2.23 to 11.3 mg/l with an average of 5.15 ± 2.36 mg/l, reflecting a high organic matter load from anthropogenic sources within the study area, and were highest during autumn. Higher values of biochemical oxygen demand (BOD), chemical oxygen demand (COD), DON, nitrate, and phosphate occurred downstream of the Damietta Branch and were probably due to anthropogenic inputs to the Nile from the Damietta district. A bacterial incubation experiment indicated that 52.1-95.0 % of DON was utilized by bacteria within 21 days. The decrease in DON concentration was accompanied by an increase in nitrate concentration of 54.8-87.3 %, presumably through DON mineralization. Based on these results, we recommend that water quality assessments consider DON and DOC, as their omission may result in an underestimation of the total organic matter load and impact.

Effects of nitrogen fertilizers on the growth and nitrate content of lettuce (Lactuca sativa L.).

PubMed

Liu, Cheng-Wei; Sung, Yu; Chen, Bo-Ching; Lai, Hung-Yu

2014-04-22

Nitrogen is an essential element for plant growth and development; however, due to environmental pollution, high nitrate concentrations accumulate in the edible parts of these leafy vegetables, particularly if excessive nitrogen fertilizer has been applied. Consuming these crops can harm human health; thus, developing a suitable strategy for the agricultural application of nitrogen fertilizer is important. Organic, inorganic, and liquid fertilizers were utilized in this study to investigate their effect on nitrate concentrations and lettuce growth. The results of this pot experiment show that the total nitrogen concentration in soil and the nitrate concentration in lettuce increased as the amount of nitrogen fertilizer increased. If the recommended amount of inorganic fertilizer (200 kg·N·ha⁻¹) is used as a standard of comparison, lettuce augmented with organic fertilizers (200 kg·N·ha⁻¹) have significantly longer and wider leaves, higher shoot, and lower concentrations of nitrate.

Effects of Nitrogen Fertilizers on the Growth and Nitrate Content of Lettuce (Lactuca sativa L.)

PubMed Central

Liu, Cheng-Wei; Sung, Yu; Chen, Bo-Ching; Lai, Hung-Yu

2014-01-01

Nitrogen is an essential element for plant growth and development; however, due to environmental pollution, high nitrate concentrations accumulate in the edible parts of these leafy vegetables, particularly if excessive nitrogen fertilizer has been applied. Consuming these crops can harm human health; thus, developing a suitable strategy for the agricultural application of nitrogen fertilizer is important. Organic, inorganic, and liquid fertilizers were utilized in this study to investigate their effect on nitrate concentrations and lettuce growth. The results of this pot experiment show that the total nitrogen concentration in soil and the nitrate concentration in lettuce increased as the amount of nitrogen fertilizer increased. If the recommended amount of inorganic fertilizer (200 kg·N·ha−1) is used as a standard of comparison, lettuce augmented with organic fertilizers (200 kg·N·ha−1) have significantly longer and wider leaves, higher shoot, and lower concentrations of nitrate. PMID:24758896

The cyanobacterial ornithine-ammonia cycle involves an arginine dihydrolase.

PubMed

Zhang, Hao; Liu, Yujie; Nie, Xiaoqun; Liu, Lixia; Hua, Qiang; Zhao, Guo-Ping; Yang, Chen

2018-06-01

Living organisms have evolved mechanisms for adjusting their metabolism to adapt to environmental nutrient availability. Terrestrial animals utilize the ornithine-urea cycle to dispose of excess nitrogen derived from dietary protein. Here, we identified an active ornithine-ammonia cycle (OAC) in cyanobacteria through an approach combining dynamic 15 N and 13 C tracers, metabolomics, and mathematical modeling. The pathway starts with carbamoyl phosphate synthesis by the bacterial- and plant-type glutamine-dependent enzyme and ends with conversion of arginine to ornithine and ammonia by a novel arginine dihydrolase. An arginine dihydrolase-deficient mutant showed disruption of OAC and severely impaired cell growth when nitrogen availability oscillated. We demonstrated that the OAC allows for rapid remobilization of nitrogen reserves under starvation and a high rate of nitrogen assimilation and storage after the nutrient becomes available. Thus, the OAC serves as a conduit in the nitrogen storage-and-remobilization machinery in cyanobacteria and enables cellular adaptation to nitrogen fluctuations.

Watershed Analysis of Nitrate Transport as a Result of Agricultural Inputs for Varying Land Use/Land Cover and Soil Type

NASA Astrophysics Data System (ADS)

Scott, M. E.; Sykes, J. F.

2006-12-01

The Grand River Watershed is one of the largest watersheds in southwestern Ontario with an area of approximately 7000 square kilometers. Ninety percent of the watershed is classified as rural, and 80 percent of the watershed population relies on groundwater as their source of drinking water. Management of the watershed requires the determination of the effect of agricultural practices on long-term groundwater quality and to identify locations within the watershed that are at a higher risk of contamination. The study focuses on the transport of nitrate through the root zone as a result of agricultural inputs with attenuation due to biodegradation. The driving force for transport is spatially and temporally varying groundwater recharge that is a function of land use/land cover, soil and meteorological inputs that yields 47,229 unique soil columns within the watershed. Fertilizer sources are determined from Statistics Canada's Agricultural Census and include livestock manure and a popular commercial fertilizer, urea. Accounting for different application rates yields 60,066 unique land parcels of which 22,809 are classified as croplands where manure and inorganic fertilizes are directly applied. The transport for the croplands is simulated over a 14-year period to investigate the impact of seasonal applications of nitrate fertilizers on the concentration leaching from the root zone to the water table. Based on land use/land cover maps, ArcView GIS is used to define the location of fertilizer applications within the watershed and to spatially visualize data and analyze results. The large quantity of input data is stored and managed using MS-Access and a relational database management system. Nitrogen transformations and ammonium and nitrate uptake by plants and transport through the soil column are simulated on a daily basis using Visual Basic for Applications (VBA) within MS-Access modules. Nitrogen transformations within the soil column were simplified using parameters that were obtained from literature or could be calculated from readily available soil information for the Grand River Watershed. Spatially and seasonally averaged results for the 14 year period indicate that nitrate leaching through the root zone does not exceed the maximum contaminant level (MCL) of 10 mg/l nitrate. However, in 1992, over 12 percent of the watershed area in crops exceeded the MCL during the winter season. The characteristically well drained soils of the central region of the watershed are more susceptible to groundwater contamination following autumn manure-N applications, as no crop-growth is present to remove excess nitrogen from the system. Therefore, farm best management practices do not ensure that groundwater contamination will not occur. This research is an important first step in developing agricultural contaminant loadings for a watershed scale surface water and groundwater model. Municipalities can utilize this model as a management tool to determine the extent of contamination and delineate site sensitive locations, such as well-head protection zones. Other applications of this model include risk assessments of contaminant migration due to climate change predictions, varying fertilizer application practices, modifications in crop management and changes in land use. The impact of climate change on recharge has been investigated.

Century-scale perspective on water quality in selected river basins of the conterminous United States

USGS Publications Warehouse

Stets, Edward G.; Kelly, Valerie J.; Broussard, Whitney P.; Smith, Thor E.; Crawford, Charles G.

2012-01-01

Nutrient pollution in the form of excess nitrogen and phosphorus inputs is a well-known cause of water-quality degradation that has affected water bodies across the Nation throughout the 20th century. The recognition of excess nutrients as pollution developed later than the recognition of other water-quality problems, such as waterborne illness, industrial pollution, and organic wastes. Nevertheless, long-term analysis of nutrient pollution is fundamental to our understanding of the current magnitude of the problem, as well the origins and the effects. This report describes the century-scale changes in water quality across a range streams in order to place current water-quality concerns in historical context and presents this history on a national scale as well as for selected river reaches. The primary focus is on nutrient pollution, but the development and societal responses to other water-quality problems also are considered. Land use and agriculture in the selected river reaches also are analyzed to consider how these factors may relate to nutrient pollution. Finally, the availability of relevant nutrient and inorganic carbon data are presented for the selected river reaches. Sources of these data included Federal agencies, State-level reports, municipal public works facilities, public health surveys, and sanitary surveys. The availability of these data extends back more than a century for most of the selected river reaches and suggests that there is a tremendous opportunity to document the development of nutrient pollution in these river reaches.

Long-term nitrogen addition causes the evolution of less-cooperative mutualists.

PubMed

Weese, Dylan J; Heath, Katy D; Dentinger, Bryn T M; Lau, Jennifer A

2015-03-01

Human activities have altered the global nitrogen (N) cycle, and as a result, elevated N inputs are causing profound ecological changes in diverse ecosystems. The evolutionary consequences of this global change have been largely ignored even though elevated N inputs are predicted to cause mutualism breakdown and the evolution of decreased cooperation between resource mutualists. Using a long-term (22 years) N-addition experiment, we find that elevated N inputs have altered the legume-rhizobium mutualism (where rhizobial bacteria trade N in exchange for photosynthates from legumes), causing the evolution of less-mutualistic rhizobia. Plants inoculated with rhizobium strains isolated from N-fertilized treatments produced 17-30% less biomass and had reduced chlorophyll content compared to plants inoculated with strains from unfertilized control plots. Because the legume-rhizobium mutualism is the major contributor of naturally fixed N to terrestrial ecosystems, the evolution of less-cooperative rhizobia may have important environmental consequences. © 2015 The Author(s).

21st Century Rise in Anthropogenic Nitrogen Deposition on a Remote Coral Reef

NASA Astrophysics Data System (ADS)

Ren, H. A.; Chen, Y. C.; Wang, X. T.; Wong, G. T. F.; Cohen, A. L.; DeCarlo, T. M.; Weigand, M. A.; Mii, H. S.; Sigman, D. M.

2017-12-01

With the rapid rise in pollution-associated nitrogen inputs to the western Pacific, it has been suggested that even the open ocean has been impacted through atmospheric deposition. In a coral core from Dongsha Atoll, a coral reef ecosystem 340 km from the nearest continent, we observe a decline in the 15N/14N of coral skeleton-bound organic matter, signaling increased deposition of anthropogenic atmospheric N on the open ocean and its incorporation into plankton and in turn the corals living on the atoll. The decrease began just several years before 2000 CE, decades later than predicted by other work, and the amplitude of decline suggests that anthropogenic atmospheric N input is now 20±5% of the annual N input to the surface ocean in this region, less than two-thirds of that estimated by models and analyses of nutrient ratio changes.

Nitrogen use efficiency in grain production and the estimated nitrogen input/output balance in China agriculture.

PubMed

Li, Shutian; He, Ping; Jin, Jiyun

2013-03-30

Understanding the nitrogen (N) use efficiency and N input/output balance in the agricultural system is crucial for best management of N fertilisers in China. In the last 60 years, N fertiliser consumption correlated positively with grain production. During that period the partial factor productivity of N (PFPN ) declined greatly from more than 1000 kg grain kg⁻¹ N in the 1950s to nearly 30 kg grain kg⁻¹ N in 2008. This change in PFPN could be largely explained by the increase in N rate. The average agronomic efficiency of fertiliser N (AEN ) for rice, wheat and maize during 2000-2010 was 12.6, 8.3 and 11.5 kg kg⁻¹ respectively, which was similar to that in the early 1980s but lower than that in the early 1960s. Estimation based on statistical data showed that a total of 49.16 × 10⁶ t of N was input into Chinese agriculture, of which chemical N, organic fertiliser N, biological fixed N and other sources accounted for 58.2, 24.3, 10.5 and 7.0% respectively. Nitrogen was surplus in all regions, the total N surplus being 10.6 × 10⁶ t (60.6 kg ha⁻¹). The great challenge is to balance the use of current N fertilisers between regions and crops to improve N use efficiency while maintaining or increasing crop production under the high-intensity agricultural system of China. © 2012 Society of Chemical Industry.

Production of polyhydroxyalkanoates (PHA) by bacterial consortium from excess sludge fermentation liquid at laboratory and pilot scales.

PubMed

Jia, Qianqian; Xiong, Huilei; Wang, Hui; Shi, Hanchang; Sheng, Xinying; Sun, Run; Chen, Guoqiang

2014-11-01

The generation of polyhydroxyalkanoates (PHA) from excess sludge fermentation liquid (SFL) was studied at lab and pilot scale. A PHA-accumulated bacterial consortium (S-150) was isolated from activated sludge using simulated SFL (S-SFL) contained high concentration volatile fatty acids (VFA) and nitrogen. The maximal PHA content accounted for 59.18% in S-SFL and dropped to 23.47% in actual SFL (L-SFL) of the dry cell weight (DCW) at lab scale. The pilot-scale integrated system comprised an anaerobic fermentation reactor (AFR), a ceramic membrane system (CMS) and a PHA production bio-reactor (PHAR). The PHA content from pilot-scale SFL (P-SFL) finally reached to 59.47% DCW with the maximal PHA yield coefficient (YP/S) of 0.17 g PHA/g COD. The results indicated that VFA-containing SFL was suitable for PHA production. The adverse impact of excess nitrogen and non-VFAs in SFL might be eliminated by pilot-scale domestication, which might resulted in community structure optimization and substrate selective ability improvement of S-150. Copyright © 2014 Elsevier Ltd. All rights reserved.

Nitrogen fluxes in a high elevation Colorado Rocky Mountain basin

USGS Publications Warehouse

Baron, Jill S.; Campbell, D.H.

1997-01-01

Measured, calculated and simulated values were combined to develop an annual nitrogen budget for Loch Vale Watershed (LVWS) in the Colorado Front Range. Nine-year average wet nitrogen deposition values were 1??6 (s = 0??36) kg NO3-N ha-1, and 1??0 (s = 0??3) kg NH4-N ha-1. Assuming dry nitrogen deposition to be half that of measured wet deposition, this high elevation watershed receives 3??9 kg N ha-1. Although deposition values fluctuated with precipitation, measured stream nitrogen outputs were less variable. Of the total N input to the watershed (3??9 kg N ha-1 wet plus dry deposition), 49% of the total N input was immobilized. Stream losses were 2??0 kg N ha-1 (1125 kg measured dissolved inorganic N in 1992, 1-2 kg calculated dissolved organic N, plus an average of 203 kg algal N from the entire 660 ha watershed). Tundra and aquatic algae were the largest reservoirs for incoming N, at approximately 18% and 15% of the total 2574 kg N deposition, respectively. Rocky areas and forest stored the remaining 11% and 5%, respectively. Fully 80% of N losses from the watershed came from the 68% of LVWS that is alpine. ?? 1997 by John Wiley & Sons, Ltd.

Seasonally-Dynamic SPARROW Modeling of Nitrogen Flux Using Earth Observation Data

NASA Astrophysics Data System (ADS)

Smith, R. A.; Schwarz, G. E.; Brakebill, J. W.; Hoos, A. B.; Moore, R. B.; Shih, J.; Nolin, A. W.; Macauley, M.; Alexander, R. B.

2013-12-01

SPARROW models are widely used to identify and quantify the sources of contaminants in watersheds and to predict their flux and concentration at specified locations downstream. Conventional SPARROW models describe the average relationship between sources and stream conditions based on long-term water quality monitoring data and spatially-referenced explanatory information. But many watershed management issues stem from intra- and inter-annual changes in contaminant sources, hydrologic forcing, or other environmental conditions which cause a temporary imbalance between inputs and stream water quality. Dynamic behavior of the system relating to changes in watershed storage and processing then becomes important. In this study, we describe dynamically calibrated SPARROW models of total nitrogen flux in three sub-regional watersheds: the Potomac River Basin, Long Island Sound drainage, and coastal South Carolina drainage. The models are based on seasonal water quality and watershed input data for a total 170 monitoring stations for the period 2001 to 2008. Frequently-reported, spatially-detailed input data on the phenology of agricultural production, terrestrial vegetation growth, and snow melt are often challenging requirements of seasonal modeling of reactive nitrogen. In this NASA-funded research, we use Enhanced Vegetation Index (EVI), gross primary production and snow/ice cover data from MODIS to parameterize seasonal uptake and release of nitrogen from vegetation and snowpack. The spatial reference frames of the models are 1:100,000-scale stream networks, and the computational time steps are 0.25-year seasons. Precipitation and temperature data are from PRISM. The model formulation accounts for storage of nitrogen from nonpoint sources including fertilized cropland, pasture, urban land, and atmospheric deposition. Model calibration is by non-linear regression. Once calibrated, model source terms based on previous season export allow for recursive dynamic simulation of stream flux: gradual increases or decreases in export occur as source supply rates and hydrologic forcing change. Based on an assumption that removal of nitrogen from watershed storage to stream channels and to 'permanent' sinks (e.g. the atmosphere and deep groundwater) occur as parallel first-order processes, the models can be used to estimate the approximate residence times of nonpoint source nitrogen in the watersheds.

[Nitrogen input altered testate amoebae community in peatland of Sanjiang Plain, Northeast China].

PubMed

Song, Li-hong; Yan, Xiu-min; Wang, Ke-hong; Zhu, Xiao-yan; Wu, Dong-hu

2015-02-01

In the present study, an in situ control experiment was carried out to explore the response of testate amoebae to exogenous nitrogen addition in peatland of Sanjiang Plain. The results showed that nitrogen addition increased the biomass of testate amoebae at lower levels (6 g N · m(-2)), while decreased it at higher levels (> 12 g N · m(-2)). At genus level, nitrogen addition significantly increased the biomass of Arcella and Phryganella, decreased the biomass of Euglypha. Only lower nitrogen addition significantly increased the biomass of Centropyxis. At species level, nitrogen addition significantly decreased the biomass of Euglypha rotunda, while the biomass of either Centropyxis cassis or Phryganella acropodia was increased by a lower nitrogen addition treatment. This study suggested that the response of peatland testate amoebae to nitrogen addition was species specific, which could potentially be used as an indicator for the environment of peatlands.

UF.sub.6 -Recovery process utilizing desublimation

DOEpatents

Eby, Robert S.; Stephenson, Michael J.; Andrews, Deborah H.; Hamilton, Thomas H.

1985-01-01

The invention is a UF.sub.6 -recovery process of the kind in which a stream of substantially pure gaseous UF.sub.6 is directed through an externally chilled desublimer to convert the UF.sub.6 directly to an annular solid ring adhering to the interior wall of the desublimer. After accumulation of a desired amount of solid UF.sub.6, the desublimer is heated to liquefy the solid. Subsequently, the liquid is recovered from the desublimer. It has been found that during the heating operation the desublimer is subjected to excessive mechanical stresses. In addition, it has been found that the incorporation of a very small percentage of relatively noncondensable, nonreactive gas (e.g., nitrogen) in the UF.sub.6 input to the desublimer effects significant decreases in the stresses generated during the subsequent melting operation. This modification to the process provides valuable advantages in terms of reduced hazard, lower operating costs for the desublimer, and increased service life for the desublimer and its auxiliaries. The new process is especially suitable for the recovery of enriched UF.sub.6 from high-speed UF.sub.6 gas-centrifuge cascades.