bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nutrients in a Playa Wetland Receiving Wastewater
Authors: Pezzolesi T. P. , Zartman R. E. , Fish E. B. , Hickey M. G. 
Published: July 2010

AbstractWe determined nutrient sequestration differences in soil and vegetation within two regions of a playa wetland that receives agricultural runoff and secondarily treated wastewater. Playas are small, topographically closed, ephemeral wetlands that serve as catchments for surface runoff in the Southern High Plains of the USA. The wetland studied received natural runoff and secondarily treated wastewater from the U.S. Department of Energy, Pantex facility near Amarillo, TX. Soil and aboveground biomass N, P, Cu, and Fe and water N and P were evaluated seven times during a 2‐yr period in cattail (Typha domingensis Pers.) and pink smartweed [Persicaria pensylvanica (Raf.) Nieuw.] dominated regions of the playa. Spatial and temporal variabilities were observed in water, vegetation, and soil‐nutrient concentrations. These variabilities were likely due to fluctuation of water depth and quality in the playa. Water was deeper (P < 0.05) in the cattail region compared with the smartweed region. Water quality [Total Kjeldahl N (TKN) and total P (TP)] was not effected (P > 0.05) by vegetation type. Soil concentrations of TKN, TP, Cu, and Fe were not significantly different (P > 0.05) between cattail and smartweed vegetative types. Cattail had significantly greater (P < 0.05) levels of TKN, TP, Cu, and Fe than did smartweed. Aboveground biomass was greatest in August. Based on nutrient sequestration this playa wetland functioned quite well as a receptor for added nutrients from runoff and the wastewater treatment facility.
In‐Stream Nonpoint Source Nutrient Prediction with Land‐Use Proximity and Seasonality
Authors: Tufford Daniel L. , McKellar Hank N. , Hussey James R. 
Published: July 2010

AbstractThis research developed multiple regression models relating land use to in‐stream concentrations of total nitrogen (TOTN) and total phosphorus (TOTP) in eight, low‐order watersheds on the coastal plain of South Carolina. The study area (4860 km2) included dominant land‐use categories of agriculture, forest, urban, and wetland comprising the lower portion of the Lake Marion drainage. Land‐use data were obtained from a pre‐existing GIS database derived by classification of satellite images. The models partitioned land‐use categories according to distance from stream channels using a series of buffer zones around each stream. Effects of point source contributions were removed from observed in‐stream concentrations so that nonpoint source effects could be more clearly delineated. All models except two were significant at P < 0.05. The models for TOTN (r2 from 0.25–0.63) explained more variability of stream nutrient concentrations than those for TOTP (r2 from 0.16–0.39). Greater predictive strength for TOTN than TOTP likely reflects differing pathways from terrestrial to aquatic systems. Land close to the stream channel (<150 m) was better predictor of nutrient concentrations than land away from the channel (>150 m). Land‐use change scenarios (converting forest and wetland to agriculture) support the conclusion that management of stream water quality will be most effective with emphasis on riparian and adjacent lands. Seasonal models were generally significant (P < 0.05) and demonstrate that the seasonal profile of stream nutrient concentrations is dependent on the mosaic of land uses in a specific subbasin.
Sediment Enrichment Mechanisms of Organic Carbon and Phosphorus in a Well‐Aggregated Oxisol
Authors: Wan Y. , El‐Swaify S. A. 
Published: July 2010

AbstractMechanisms of organic carbon (OC) and P enrichment in sediment eroded from well‐aggregated soils are not well understood. This study was conducted to examine why OC and extractable P (ext‐P) were enriched in sediment with a well‐aggregated Oxisol. Soil samples presented four field treatments: no fertilization (NF), short‐term P fertilization (STP), long‐term P fertilization (LTP), and organic waste fertilization (OW). Organic C in dry‐sieved aggregates increased with decreasing aggregate size for all treatments, suggesting that OC is preferentially retained in small aggregates and, perhaps, protected from microbial attack. Extractable P concentration changed little with aggregate size for the NF treatment, but increased significantly with decreasing aggregate size for the STP and OW treatments and for liquid‐P incubated NF soil. This difference was attributed to the blockage of interior sorption sites within large aggregates. Breakdown of dry STP and OW aggregates by simulated storms produced fine aggregates that were richer in OC and ext‐P than the original larger ones. Most of the fine aggregates were created in the early phase of rainfall by slaking dry aggregates, and further breakdown by stripping water‐stable aggregates was more difficult and slow. Sediment enrichment observed in eroded sediment was caused by selective transport of P and OC‐rich fine aggregates induced by the effects of aggregation blockage and aggregate breakdown by slaking and stripping. For the LTP treatment, however, ext‐P concentration was independent of aggregate size, indicating that a uniform P distribution in aggregates can be reached given sufficiently long equilibration time.
Patchiness in Groundwater Nitrate Removal in a Riparian Forest
Authors: Gold A. J. , Jacinthe P. A. , Groffman P. M. , Wright W. R. , Puffer R. H. 
Published: July 2010

AbstractOur ability to identify and manage riparian sites for groundwater nitrate (NO−3) removal is limited by uncertainty surrounding the relative importance of plant uptake vs. microbially mediated removal processes. Microcosm studies often demonstrate negligible transformation rates in the subsoil of riparian forests, even in situations where groundwater well networks showed substantial groundwater NO−3 removal during the winter and a decline in dissolved oxygen (DO) in ambient groundwater moving through the site. We hypothesize that microcosm studies may miss groundwater transformations that occur within microsites, that is, “hotspots” of riparian subsoils. We created mesocosms of large (15 cm diam. × 40 cm length), undisturbed cores from the seasonally saturated zone of poorly drained (PD) and moderately well drained (MWD) sandy soils from a forested riparian area in southern New England. We dosed the mesocosms for 130 d with ambient groundwater amended with NO−3‐N and Br−. Changes in the NO−3‐N/Br− ratios were used to calculate groundwater NO−3‐N removal rates. The PD treatment demonstrated substantial groundwater NO−3‐N removal rates. The PD mesocosms contained patches of dark‐stained material that often surrounded roots in various stages of decay. The dry mass of patches in the PD treatment ranged from 0.07 to 1.4% of the mesocosms. The MWD treatment contained no patches and exhibited no groundwater NO−3‐N removal. Further investigations on the relationships between the extent of subsurface patchiness, water table dynamics and plant characteristics might yield fruitful insights into the management of vegetated riparian zones for groundwater NO−3‐N removal.
Greenhouse Evaluation of Agronomic and Crude Oil‐Phytoremediation Potential among Alfalfa Genotypes
Authors: Wiltse C. C. , Rooney W. L. , Chen Z. , Schwab A. P. , Banks M. K. 
Published: July 2010

AbstractPhytoremediation is an effective, non‐intrusive, and inexpensive means of remediating soils contaminated with organic chemicals. Different plant species have different remediation capabilities, so intraspecies variation may also exist. If intraspecific variation exists and is heritable, population improvement for performance in and phytoremediation of contaminated soils should be possible. The objectives of this study were (i) to determine if variability exists among alfalfa (Medicago sativa L.) genotypes for agronomic performance in and phytoremediation of crude oil‐contaminated soil and (ii) to determine the effect of contaminated soil on the agronomic performance of alfalfa. In one greenhouse experiment, 20 genotypic clones were transplanted into 20 g kg−1 crude oil‐contaminated soil. After 1 yr, differences existed among genotypes for total forage yield (P < 0.05), maturity at harvest (P < 0.001), plant height (P < 0.01), and phytoremediation potential (P < 0.001). Degradation rates ranged from 33 to 56% among genotypes with 46% for the unvegetated control. Two genotypes had significantly greater degradation rates than that of the unvegetated control. In a second greenhouse experiment, eight genotypes from the previous experiment were compared with their clones in uncontaminated soil. After 1 yr, mean total forage yield in contaminated soil was 32% of the yield of the same clones in uncontaminated soil. Plants in contaminated soil also matured later and were shorter. Genotype variability was present for all traits but not on all evaluation dates. The results indicate that overall agronomic performance is reduced in contaminated soil, but variability exists among genotypes for growth in and phytoremediation of contaminated soils.
Agricultural Phosphorus and Water Quality: A U.S. Environmental Protection Agency Perspective
Authors: Parry Roberta 
Published: July 2010

AbstractPollution of lakes, rivers, and estuaries from agricultural sources of P is a major water quality problem in the USA. This paper explains the regulatory and nonregulatory programs developed by the U.S. Environmental Protection Agency (USEPA) to implement its legal mandate to control water pollution from these sources. The Clean Water Act defines concentrated animal feeding operations as point sources of pollution that are required to obtain permits to discharge into waters of the USA. All other agricultural sources are considered nonpoint and are not regulated under federal law. The USEPA prorides grant money to the states to develop and implement nonpoint source programs. The Coastal Zone Act Reauthorization Amendments of 1990 requires coastal states to adopt nonpoint management measures that are backed by enforceable policies and mechanisms. For water bodies that continue to be impaired despite the basic implementation of these laws and other programs, states are required to develop a total maximum daily load (TMDL). The TMDL process is the quantitative basis for reaching water quality standards. The USEPA is putting a new emphasis on controlling nutrient pollution sources to meet the goal of the Clean Water Act.
Modeling Phosphorus Dynamics in Ecosystems: Mass Balance and Dynamic Simulation Approaches
Authors: Cassell E. A. , Dorioz J. M. , Kort R. L. , Hoffmann J. P. , Meals D. W. , Kirschtel D. , Braun D. C. 
Published: July 2010

AbstractPhosphorus (P) export from agriculture is a major cause of eutrophication in many lake ecosystems. Human activity, hydrology, and physicochemical and biological processes that store, transform, and transport P, define P export patterns over time and space. We suggest that an ecosystem paradigm is useful to holistically view P dynamics within complex watersheds. An ecosystem model of a dairy agricultural system was created within a hierarchical compartment‐flux structure of a conceptual watershed ecosystem. Mass balance calculations with our Agriculture Ecosystem model (AEP model) describe P dynamics for the farm system, which are driven by the amount of P stored in agricultural soils and system management practices. Longterm P dynamics respond predominately to human interventions in watersheds and define conditions for future generations. Model simulations suggest that long‐term environmental protection programs should incorporate the notions of P sustainability into management decisions. Dynamic simulation modeling is a valuable paradigm for understanding how complex watersheds process P and for developing management perspectives and public policy to achieve goals of environmental quality as well as economic and resource sustainability.
Plant Genetic Approaches to Phosphorus Management in Agricultural Production
Authors: Ertl D. S. , Young K. A. , Raboy V. 
Published: July 2010

AbstractMuch of the P in corn (Zea mays L.) grain is present in the form of phytic acid. Phytic acid P is unavailable to monogastric animals with most being excreted in the waste. As a result, the substantial P stores in grain are essentially wasted and may contribute to water pollution rather than animal productivity. The initial goal of this research was to isolate chemically induced mutants with reduced levels of phytic acid P in corn. Such mutants, referred to as low phytic acid or Ipa, were isolated and were found to have little or no other effect on kernel composition including no effect on total grain P content. The first mutant characterized, Ipal‐1, a 65% reduction in phytic acid and is accompanied by a molar‐equivalent increase in inorganic P. This mutant was backcrossed into elite corn inbred lines and resulting hybrids were evaluated for yield and other important agronomic traits. Preliminary field trials indicated germination, stalk strength, grain moisture at harvest, and flowering date were not affected by Ipal‐1. Some, but not all, Ipal‐1 hybrids had yield reductions. In a preliminary chick feeding trial, the low phytic acid grain resulted in greater P availability and reduced P content in the waste. Altering the phytic acid content genetically in corn is possible and may have the potential to improve feeding efficiencies and reduce P released to the environment.
Seasonal and Spatial Patterns of Nitrate and Silica Concentrations in Canajoharie Creek, New York
Authors: Wall G. R. , Phillips P. J. , Riva‐Murray K. 
Published: July 2010

AbstractThe impact of nonpoint‐source pollution on surface waters in agricultural watersheds is an emerging environmental issue. As part of the U.S. Geological Survey National Water Quality Assessment program in the Hudson River Basin, Canajoharie Creek was monitored for seasonal and spatial patterns of nutrient chemistry from March 1993 to January 1996. Nitrate and silica concentrations in Canajoharie Creek suggest that seasonal and spatial variations of these nutrients are dominated by biological processes, particularly uptake by phytoplankton. Observed concentration patterns were more typical of those observed in much larger, low‐gradient streams. The median nitrate and silica concentrations in Canajoharie Creek were significantly lower from April through November than during winter. Concentrations of both constituents declined downstream from the headwaters during base‐flow conditions in June 1995. Groundwater and surface water chemistry data support biological causes for downstream decreases in silica. The strong correlation between nitrate and silica in samples collected along the mainstem suggests that most of the nitrate decrease is due to uptake by diatoms. Downstream patterns of chlorophyll‐a in phytoplankton strongly suggest the conversion of in‐stream nutrients to algal biomass. Data collected from Canajoharie Creek outlet during the northeast drought of 1995 indicate that silica concentrations in May had possibly declined to a level that adversely affected the diatom community. This decline in the diatom population and subsequent resurgence is inferred from a sharp rise in silica concentrations between May and July and a reversal of this trend from mid‐July through October without associated changes in hydrology.
Phosphorus Sorption Capacities of Wetland Soils and Stream Sediments Impacted by Dairy Effluent
Authors: Reddy K. R. , O Connor G. A. , Gale P. M. 
Published: July 2010

AbstractThe ability of stream sediments and adjacent wetlands to retain added P depends on the P sorption capacity and physico‐chemical properties of sediments or wetland soils. The objectives of this study were to: (i) determine the potential P sorption capacities of wetland soils and stream sediments in systems with distinctly different P loadings, and (ii) establish the relationship between P sorption capacity and selected physico‐chemical properties. Batch sorption isotherms were measured under aerobic and anaerobic conditions for sediments and wetland soils along a stream‐wetland‐upland continuum at two sites in the Lower Kissimmee River Basin and Taylor Creek/Nubbin slough of the Okeechobee Basin, Florida. Soluble P and equilibrium P concentrations (EPC) of stream sediments generally decreased along the wetland‐upland continuum. The EPC values were about twofold greater under anaerobic conditions than aerobic conditions; however, P sorption capacities decreased by about 35% under anaerobic conditions compared with aerobic conditions. The P sorption maxima, estimated by a single point isotherm measured at an added P level of 1000 mg P kg−1. correlated well with Langmuir adsorptive maxima. Phosphorus retention by stream sediments and wetland soils was strongly correlated with contents of amorphous and poorly crystalline forms of Fe and Al, which explained 87% of the variability in P retention maximum. Addition of total organic C to predictive equations improved the predictability by only 5%.
Preferential Transport of Phosphorus in Drained Grassland Soils
Authors: Stamm C. , Flühler H. , Gächter R. , Leuenberger J. , Wunderli H. 
Published: July 2010

AbstractPhosphorus is the limiting factor for primary production in most freshwater ecosystems. In many areas, diffuse P losses from intensively cultivated land cause severe eutrophication of surface waters. We investigated the P export from two drainage systems under intensively used grassland in a catchment of the Swiss Plateau. Flow rate and nutrient concentrations were measured with a high temporal resolution during discharge events. During most flow peaks, P concentrations strongly increased with increasing flow rates. Concentrations of soluble‐reactive P (SRP) reached up to 155 µmol L−1. Phosphorus was mainly transported as soluble‐reactive and particulate P. Organic P compounds, as well as P associated with colloids between 0.05 and 0.45 µm in effective diameter, were of minor importance. Estimated P loads from the drainage systems were 227 g SRP ha−1 within a period of 2.5 mo at site I and 1290 g ha−1 during 6 mo at site II. Estimation uncertainty was large (±21 and ±36% for the two sites, respectively) due to the weak correlation between discharge and concentration for all data from a given site. Water‐extractable P in the soil was concentrated in the uppermost layer of the profiles or, for short periods after spreading of manure, deposited on the vegetation. The discharge‐concentration relationship indicated that P was transported through preferential flow paths extending from close to the surface to the drains. Sprinkling experiments with a blue dye confirmed this conclusion. At one site, we observed preferential flow in a downhill direction within the saturated zone.
Transport and Persistence of Pesticides in Alluvial Soils: II. Carbofuran
Authors: Cogger C. G. , Stark J. D. , Bristow P. R. , Getzin L. W. , Montgomery M. 
Published: July 2010

AbstractCarbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate), a soil‐applied insecticide, is a potential leaching risk when applied to permeable soils overlying shallow, unconfined aquifers. We conducted this project to evaluate the long‐term movement, persistence, and leaching risk of carbofuran applied to perennial small fruit crops grown on alluvial soils with shallow (<3 m deep) groundwater. Carbofuran was applied to strawberry (Fragaria × ananassa Duch.) and red raspberry (Rubus idaeus L.) in paired plots at two sites in western Washington. Strawberry received carbofuran at 2.2 kg ha−1 in a 30‐cm wide band each August, and raspberry received 3.1 kg ha−1 in a 90‐cm band each November. We applied carbofuran yearly from 1986 to 1989, and sampled soil (to 180 cm) and shallow groundwater monthly until April 1991, and at one site again in March 1994. Carbofuran was initially mobile, and significantly more carbofuran moved below 60 cm in raspberry than in strawberry. Differences in carbofuran leaching between sites corresponded to differences in soil‐binding constants. The disappearance half‐life of carbofuran decreased from 110–221 d in 1986–1987 to 69–100 d in 1989–1990, evidence of enhanced degradation. Enhanced degradation appeared to affect freshly added carbofuran, but not residual carbofuran that had become more tightly bound to the soil over time. Carbofuran was found in shallow groundwater beneath both crops and sites the first winter. The leaching risk declined after the first winter, which is probably a result of enhanced degradation and nonequilibrium binding.
Low Molecular Weight Aliphatic Acid Contents of Composted Manures
Authors: Baziramakenga R. , Simard R. R. 
Published: July 2010

AbstractComposted organic wastes improve nutrient availability by releasing organic compounds, particularly low molecular weight organic acids, which may affect nutrients availability in soils. In this study, composts were collected from different farms and industries across the Quebec Province (Canada). Low molecular weight aliphatic acids (LMWA) were extracted with water or Ca(OH)2, and analyzed by ion chromatography. The main LMWA were acetic, formic, and oxalic acids. Small amounts of lactic, propionic, malic, citric, and aconitic acids were also found. The total amount of water‐soluble LMWA ranged from 5.88 to 69.17 mmol g−1. Compared with fresh manure, the quantities of LMWA decreased with composting time. The volatile aliphatic acids (VAA) accumulated in the early stage of composting while larger amounts of the nonvolatile aliphatic acids (NVAA) were found in the later stages. Turned and uncovered composts contained small amounts of LMWA. High amounts of LMWA were found in compost made with straw or wood residues. Land application of compost may introduce large amounts of LMWA to soils and strongly affect nutrient mobility and plant availability.
Biointrusion of Protective Barriers at Hazardous Waste Sites
Authors: Bowerman Andrew G. , Redent Edward F. 
Published: July 2010

AbstractAt locations throughout the world, hazardous wastes have been buried in an attempt to ensure the health and safety of the environment. The ability of simple and complex barriers to protect against biotic intrusion in the short‐ and long‐term is questionable. Little research has been conducted to assess the risk that biota may pose to barrier integrity. Evidence of documented and potential cases of biointrusion of protective barriers by various species of plants, burrowing mammals, and invertebrates at various hazardous waste sites throughout the USA is examined to assess whether biointrusion has occurred. Studies documenting plant root intrusion were examined to assess their ability to affect barrier integrity. Various plant species, including kochia [Kochia scoparia (L.) Schrader], crested wheatgrass (Agropyron cristatum L.), big sagebrush (Artemisia tridentata ssp. wyomingensis Nutt.), and salt cedar (Tamarix ramosissima Ledeb.) were found to have penetrated into protective barriers in mesic and arid environments. There is also evidence of biointrusion by harvester ants (Pogonomymrmex owyheii) through rock barriers. Mice (Perognathus parvus, Peromyscus maniculatus), kangaroo rats (Dipodyms ordii), pocket gophers (Thomomys bottae), ground squirrels (Spermophilus elegans, S. townsendii), and prairie dogs (Cynomyous leucurus) are also a threat to the integrity of protective barriers. These results indicate that plants, invertebrates, and burrowing mammals pose a threat to barrier integrity and waste isolation. Engineered protective caps have been designed without the consideration of ecological principles and processes. The incorporation of these components into barrier designs may be crucial to their performance.