bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Transfers in a Rapidly Eroding Agroecosystem:Loess Plateau, China
Authors: Hamilton Hugh , Luk Shiu‐hung 
Published: July 2010

AbstractA study was initiated to assess the influence of high erosion rates and sediment hyperconcentrations on patterns of N loss in China's Loess Plateau region. The study was conducted in a 12.6‐ha subbasin where the upper slopes are terraced and cultivated, and the lower slopes are grazed by sheep. Seventeen rainstorms were monitored over 2 yr at a flume located in the ephemeral channel at the basin outlet. Runoff events were characterized by large sediment concentrations (mean 508 kg m−3), dilution of dissolved NO3 + NO2‐N concentrations during periods of peak flow, and high sediment‐associated Kjeldahl N concentrations near the end of events when larger‐sized particles are deposited. Hyperconcentrated flow ensured that most entrained sediment and N was exported. Annual soil losses equaled 203.4 Mg ha−1 and 176.9 Mg ha−1 in 1987 and 1988. Total N losses equaled 76.4 kg ha−1 and 44.1 kg ha−1. In each year, one or two large events contributed the bulk of soil and N losses. About 98% of the N losses were sediment associated, with low‐intensity events having the highest soluble proportion. A simple N mass balance shows that erosion losses of N are serious, and that most of the N removed from both cultivated and grazed areas is exported. Results indicate that N cycling in this semiarid area is strongly influenced not only by the amount of rainfall, but also by the timing and intensity of the storms.
Effect of Starch Encapsulation and Temperature on Volatilization of Atrazine and Alachlor
Authors: Wienhold Brian J. , Sadeghi Ali M. , Gish Timothy J. 
Published: July 2010

AbstractVolatilization of agricultural chemicals is one process whereby chemicals may enter into parts of the environment where they were not intended. Starch encapsulation of pesticides has been proposed as a way of modifying pesticide behavior in the soil environment. This study was conducted to assess how starch encapsulation and temperature affect volatilization of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] and alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide]. Volatilization was measured using agroecosystem chambers as model systems. Herbicides were applied at rates of 1.7 kg ha−1 for atrazine and 2.8 kg ha−1 for alachlor, as either a commercial formulation or a starch encapsulated formulation, to the surface of moist soils maintained at temperatures of 15, 25 and 35°C. Air was drawn through the chambers (2.5 m3 min−1) and herbicide in the vapor phase was trapped in polyurethane foam plugs. Volatilization of both herbicides increased as temperature increased. Volatilization of atrazine was less when applied as starch‐encapsulated formulation than the commercial formulation. After 35 d cumulative volatilization of atrazine ranged from <1% of that applied as starch‐encapsulated formulation at 15°C, to 14% of that applied as the commercial formulation at 35°C. Cumulative volatilization of alachlor was greater when applied as starch‐encapsulated formulation than as the commercial formulation. After 35 d, cumulative volatilization of alachlor ranged from >2% of that applied as either formulation at 15°C to 32% of that applied as starch encapsulated formulation at 35°C. Differences in volatilization behavior between these herbicides are likely to be due to differences in chemical properties of these herbicides.
Characteristics of Earthworm Burrow Lining Affecting Atrazine Sorption
Authors: Stehouwer R. C. , Dick W. A. , Traina S. J. 
Published: July 2010

AbstractVertically oriented earthworm burrows exist in many agricultural sites, especially in no‐tillage soils where the burrows are left intact from year to year. Earthworm burrows can function as preferential flow conduits and may enhance downward transport of surface‐applied pesticides. Earthworm activity induces changes in the soil characteristics of the burrow walls that may affect pesticide sorption and transport. Little information is available describing the properties of the lining material. Earthworm (Lumbricus terrestris L.) burrow lining and bulk soil at seven depth intervals from 0 to 50 cm were characterized with respect to pH, clay content, total organic C (TOC), water‐soluble organic C (WSOC), and alkaline phosphatase (AP) activity. Atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] sorption‐desorption isotherms were conducted on the same materials. Burrow linings were found to have a narrower range of pH and clay content than the bulk soil within the 0‐ to 50‐cm depth. Levels of TOC and WSOC in burrow linings were two to three times higher than in the bulk soil at the profile surface. This difference increased to eight times at the 35‐cm depth although concentrations were lower than at the profile surface. Activity of AP in burrow lining from 0 to 20 cm was three times greater than in the surface bulk soil, and at depths of 20 to 40 cm AP activity in burrow lining was similar to that of the surface bulk soil. Freundlich Kf values for atrazine sorption and desorption were higher for burrow lining than bulk soil at almost every depth. The largest differences (1.5‐ to 3‐fold) occurred in the 15‐ to 30‐cm depth range. Multivariate regression analysis of atrazine sorption‐desorption indicated that of the parameters measured, TOC could account for most of the variability in atrazine sorption‐desorption.
Des Moines River Nitrate in Relation to Watershed Agricultural Practices: 1945 Versus 1980s
Authors: Keeney D. R. , DeLuca T. H. 
Published: July 2010

AbstractConcern for nitrate (NO3‐N) contamination of surface waters in Iowa has brought much speculation with regard to the source of NO3‐N. It is frequently assumed that the large percentage increase in fertilizer N use over the last 50 yr is the primary cause of high concentrations of NO3‐N in surface waters of central Iowa. We performed an analysis of data relating flow and NO3‐N concentration for the Des Moines River to identify the effect of agricultural practices on NO3‐N in the river. Annual and weekly stream flow values for the 1980‐1990 period at a site just below the city of Des Moines were positively related to the NO3‐N concentration in the river water for the 11‐yr period (r2 = 0.60, P < 0.01). From 1980 to 1991 the average annual NO3‐N concentration ranged from 2.0 mg L−1 in the low flow year of 1989 to 9.1 mg L−1 in 1982. Over the 11 yr, the river averaged 5.6 mg L−1 NO3‐N and had an average flow of 733 580 m3 h−1. In 1945, the average flow was 723 710 m3 h−1 and NO3‐N concentrations were 5.0 mg L−1. These values were similar to the 11‐yr average data obtained 35 to 45 yr later. We infer from the data that the intensive agricultural activities in 1945 and 1980 to 1990 are the major source of the NO3‐N to the river rather than solely N fertilizer. Changes in land management, cropping patterns, and land use are therefore required to markedly lower the NO3‐N levels of surface water in this basin.
Aerobic Degradation of Calcium Magnesium Acetate in Roadside Soils: Field Simulations from Soil Microcosms
Authors: Ostendorf D. W. , Pollock S. J. , De Cheke M. E. , Palaia T. A. 
Published: July 2010

AbstractAseptic soil samples from the 0.2‐m loamy sand cover and underlying sand fill of a state highway shoulder in southeastern Massachusetts were placed in sterile serum bottles at 5 °C, forming a series of aerobic soil microcosms. The sand fill belonged to the Carver coarse sand series (Mesic, uncoated Typic Quartzisamment), while the loamy sand was of unknown origin. The samples were dosed with reagent grade glacial acetic acid and commercially available calcium magnesium acetate [(CMA; Ca0.3Mg0.7(C2H3O2)2] solutions without acclimation, then sampled at various time intervals and analyzed by gas chromatography in a laboratory determination of the microbial degradation kinetics. The aerobic reaction rate varied strongly and directly with depth but was uniform with distance along and normal to the highway. A simple steady state transport simulation model balancing infiltration and degradation was derived and run with the observed microcosm kinetics for a range of assumed snowmelt rates. The resulting simulated profiles suggested that the loamy sand cover bad the potential to reduce O2 demand by CMA on groundwater for slow (10−7 m/s−1 snowmelt rates at 5 °C under aerobic conditions. Shoulders with more rapid infiltration, colder temperatures, and thinner loamy sand covers would pass more CMA to the underlying aquifer.
Small‐Scale Spatial Patterns of Bulk Atmospheric Deposition
Authors: Berndtsson Ronny 
Published: July 2010

AbstractIn total 14 bulk atmospheric deposition collectors were distributed over the city of Lund (about 20 km2) in the south of Sweden during September 1980 to June 1981. The observations were made to investigate small‐scale spatial variability of atmospheric deposition. Monthly bulk deposition samples were analyzed for Cl, Ptot, Zn, Cu, and Pb. Correlation analysis shows that the spatial scale for the variation pattern is of the order > 10 km for precipitation and Cl, and about 2 km for Ptot and metals. This indicates that remote sources with a general large‐scale deposition pattern are dominating for Cl deposition and that local sources dominate for Ptot, Zn, Cu, and Pb. The total atmospheric deposition in the investigated urban area is assumed to be superposed by three components: (i) regional background, (ii) urban background, and (iii) urban point deposition. The urban background deposition may be considerable in relation to regional background deposition. The urban point sources may represent deposition rates of twice or more of the total deposition.
Effects of Poultry Litter Application Rate and Rainfall Intensity on Quality of Runoff from Fescuegrass Plots
Authors: Edwards D.R. , Daniel T.C. 
Published: July 2010

AbstractA 4 × 2 factorial experiment with three replications was conducted to determine how quality of runoff from grassed areas treated with poultry (Gallus gallus domesticus) litter is impacted by litter application rate and rainfall intensity for storms occurring 1 d after application. Poultry litter was applied at 0, 218, 435, and 870 kg N ha−1 to plots established with fescuegrass (Festuca arundinacea Schreb.) on a Captina silt loam soil (fine‐silty, mixed, mesic Typic Fragiudult). Simulated rainfall was applied 24 h after litter application at 5 and 10 cm h−1 until runoff had occurred for a duration of 0.5 h. Flow‐weighed composite samples were collected and analyzed for total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3‐N), nitrate nitrogen (NO3‐N), total phosphorus (TP), dissolved reactive phosphorus (DP), chemical oxygen demand (COD), total suspended solids, and electrical conductivity. Increasing the litter application rate significantly increased runoff concentrations of all litter constituents investigated. Concentrations of TKN, TP, DP, and COD significantly decreased with increasing rainfall intensity because of more runoff and the associated dilution. Masses of litter constituents transported off the plots via runoff significantly increased with both litter application rate and rainfall intensity. For a given rainfall intensity, the proportions of applied litter constituents lost in runoff were generally indendent of application rate with the exception of total N at the high rainfall intensity.
Evaluation of Solid‐State Fermentation Techniques to Dispose of Atrazine and Carbofuran
Authors: Berry Duane F. , Tomkinson Richard A. , Hetzel Glen H. , Mullins Donald E. , Young Roderick W. 
Published: July 2010

AbstractMethods to dispose of unused concentrated and dilute formulated pesticide suspensions or solutions such as rinsate are urgently needed by small‐scale farm operators and applicators. The suitability of solid‐state fermentation (SSF) techniques to dispose of atrazine (2‐chloro‐4‐[ethylamino]‐6‐[isopropylamino]‐1,3,5‐triazine, purity 99.0%) and carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate, purity 99.0%) formulations was evaluated. Pesticides were added to bioreactors containing either sphagnum peat moss or steam‐exploded wood (SEW) and monitored periodically for disappearance. Soil column leaching studies and the USEPA standard toxicity characteristic leaching procedure were used to assess the potential environmental hazard of land application of spent lignocellulosic matrix materials. Pesticide bioavailability was determined with plant or animal bioassay indicators. In peat‐filled bioreactors containing atrazine at loading rates of 1.4, 2.0, and 7.2 g kg−1 (dry wt. basis), solvent extractable atrazine decreased to less than 0.2% of starting levels within 480 d. For the SEW‐filled bioreactors containing atrazine at a loading rate of 2.0 g kg−1, solvent extractability decreased to 20% of starting levels within 320 d. Extractable carbofuran in peat‐filled (initial loading rates 0.7, 1.8, and 5.0 g kg−1) and SEW‐filled (initial loading rate 5.0 g kg−1) bioreactors decreased to less than 0.05% of starting levels within 480 d. Both leachability and bioavailability of pesticides were dramatically reduced during the process of SSF. The amount of leachable pesticide remaining in peat sorbent following bioreactor start‐up was dependent on the initial pesticide loading rate and the length of bioreactor operation time. The use of SSF techniques to dispose of pesticide waste may prove a viable alternative to other disposal methods that are either too expensive or technically sophisticated.
Lake Water Quality Modeling for Projected Future Climate Scenarios
Authors: Stefan H. G. , Hondzo M. , Fang X. 
Published: July 2010

AbstractA deterministic, one‐dimensional numerical simulation model for water temperature and dissolved oxygen (DO) in lakes of different size, depth, and trophic status has been formulated, validated, and applied to lakes in the north central USA. The standard error of predictions is on the order of 1 °C for temperature and 1.5 mg L−1 for DO. The model is driven by weather measurements at off‐lake weather stations. Simulations can be made for the open water season at daily timesteps and for as many years as weather data are available without any parameter adjustments. The model has been used to simulate the effect of climate change due to a doubling of atmospheric CO2 on water temperatures and DO in 27 lake classes in Minnesota. The lakes have been differentiated by surface area, maximum depth, and trophic status. Maximum water temperature near the surface is projected to increase by no more than 2 °C in midsummer, and DO will drop by less than 2 mg L−1 in the surface waters but will remain above 7 mg L−1. In contrast, hypolimnetic water temperature in mid‐summer may rise by as much as 4 °C or may become colder by as much as 4 °C. Hypolimnetic DO will be lower by as much as 8 mg L−1 in midsummer and DO depletion is projected to occur for a longer period of time in midsummer in lakes with seasonal summer stratification. Changes will be largest in spring and fall because the summer stratification season will lengthen by 20 to 90 d for different lake types.
Simulating Funnel‐Type Preferential Flow and Overall Flow Property Induced by Multiple Soil Layers
Authors: Ju S.‐H. , Kung K.‐J. S. 
Published: July 2010

AbstractFunnel‐type preferential flow was observed in Plainfield sand (sandy, mixed, mesic Typic Udipsamment) of central Wisconsin. The objective of this paper was (i) to develop a numerical model based on the Richards equation and finite element scheme to simulate this preferential flow in a soil profile with inclined layers, and (ii) to determine flow properties in a soil with funnel‐type preferential paths. The model was first validated by testing against two‐dimensional (2‐D) laboratory results and then used to simulate water flow patterns in hypothetical 2D soil profiles made of medium sand with multiple randomly distributed, inclined coarse layers. The following results were found from the numerical experiments; (i) funnel‐type preferential flow paths could be deterministically simulated if soil layering structure, hydraulic conductivity of the overall profile, and threshold potential of the embedded coarse layers were known; (ii) distribution of the vertical component of flux was determined by the funneling effect along the upper coarse sand lenses. The lenses located in deeper parts of the profile would only influence macrotortuosity of the preferential flow paths; (iii) funnel‐type preferential flow paths were determined not only by soil structures and textures but also by water application rate; and (iv) although funnel‐type preferential paths were very complex, the vertical component of flux could be very simply described by two stochastic parameters—the mean and standard deviation of a log‐normal distribution after the flow paths became stationary.
Factors Affecting Preferential Flow of Water and Atrazine through Earthworm Burrows under Continuous No‐Till Corn
Authors: Edwards W. M. , Shipitalo M. J. , Owens L. B. , Dick W. A. 
Published: July 2010

AbstractWatershed studies have documented that summer storms produce less runoff from fields farmed with continuous no‐tillage corn (Zea mays L.) than from the same soils when corn is produced with conventional tillage practices. The lack of tillage favors a continuous surface cover of crop residue and the persistence of earthworm burrows, which have been shown to be preferential flow paths for water and chemicals, especially during intense summer storms. We investigated factors affecting preferential water and chemical transport in burrows formed by the earthworm Lumbricus terrestris (L.) in the field using individual burrow samplers and in the laboratory using blocks of undisturbed soil subjected to simulated rainfall. Rainfall amount and intensity and antecedent soil moisture content affected the amount of water transmitted in earthworm burrows, with high intensity storms on relatively dry no‐till soils producing the greatest amounts of preferential flow. Atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) transport was affected by the factors influencing the amount of preferential flow and by the time of storms relative to the time of herbicide application. Atrazine movement in earthworm burrows was greatest when high‐intensity rainfall occurred shortly after application. Atrazine transport was reduced by a delay in rainfall and by low‐intensity events prior to high intensity, percolate‐producing events.
Nutrient Interception by a Riparian Forest Receiving Inputs from Adjacent Cropland
Authors: Jordan Thomas E. , Correll David L. , Weller Donald E. 
Published: July 2010

AbstractTo investigate the ability of riparian forest to intercept nutrients leaving adjacent cropland, we examined changes in the chemistry of groundwater flowing from a corn (Zea mays L.) field through a riparian forest. This study provided a comparison to previous studies of a different forest. We sampled groundwater from a transect of wells, and used a Br− tracer to confirm that groundwater moved laterally along the transect through the forest. As groundwater flowed through the forest, NO−3 concentrations decreased from about 8 mg/L at the edge of the corn field to <0.4 mg/L halfway through the forest. Dissolved organic N and NH+4 increased by less than 0.1 mg/L, and dissolved organic C did not change with distance. Sulfate remained constant with distance until midway through the forest, where it began to increase. Chloride concentration rose until midway through the forest, then fell. Values of pH increased from under 5 at the edge of the corn field to over 7 at the stream bank, perhaps as a result of the NO−3 consumption. Most of the change in NO−3 occurred abruptly at the edge of a floodplain within the forest. There the water table was closest to the surface and soil Eh below the water table was less than −90 mV. Such strongly reducing conditions may have promoted denitrification in the floodplain. In contrast, soil Eh on the adjacent hill slope was above 500 mV, too high to support denitrification. There were only slight seasonal changes in groundwater chemistry. We also studied the net annual accretion of sediment in the riparian forest by measuring changes in the elevation of the soil surface. There was little or no accretion in the forest, but along a path of overland storm flow there was net erosion. Thus, nutrient retention by this forest, in contrast with the forest we previously studied, was entirely a below ground process. Functional differences within sections of this forest and among different riparian forests suggest a need for research on the factors that control nutrient retention.
Determining Off‐Site Concentrations of Volatile Pesticides Using the Trajectory‐Simulation Model
Authors: Yates S. R. 
Published: July 2010

AbstractAn environmental transport model is described and illustrated that will enable the prediction of the mass and/or concentration of volatile pesticides at any depth in the soil profile and at any height in the atmosphere relatively far distanced downwind from agricultural fields. The theoretical profile shape model is used to determine transport in the atmosphere and is coupled to the behavior assessment model (BAM) to describe transport in soils. The model outputs include the soil‐water concentrations, the surface volatilization rate, the concentration of pesticides in the atmosphere above the field, and the atmospheric concentration at specified distances downwind from the field. The results from this approach can be used in exposure assessment studies to determine the risk for individuals living near agricultural fields.
Sorption of Cadmium and Lead by Clays from Municipal Incinerator Ash—Water Suspensions
Authors: Roy W. R. , Krapac I. G. , Steele J. D. 
Published: July 2010

AbstractThe effect of Cl complexation in extracts of a flue gas‐scrubber incinerator fly ash sample on the sorption of Cd and Pb by kaolinite and illite was investigated using batch‐sorption methods. In the pH range of 5 to 9, Cl complexation may reduce sorption and thus increase the mobility of these metals. When an ash—water suspension was acidified to pH 6.85, the dissolution of Cl and Ca essentially eliminated Cd sorption because of complexation and cationic competition. Cadmium would be considered as either mobile or very mobile under these conditions. Lead was not soluble in the pH‐6.85 suspension. At pH 12, the approximate pH of water in contact with flue gas‐scrubber fly ash, Cd was essentially insoluble and Pb occurred as anionic Pb hydroxide. Anionic Pb was sorbed by the two clays, and the extent of sorption was not influenced by Cl or carbonate complexation. Sorption constants, derived from isotherms, suggested that Pb would be relatively immobile in saturated soil—water systems. The recent concern that highly alkaline, flue gas‐scrubber fly ash may release environmentally significant concentrations of mobile Pb when placed in an ash‐disposal site with a soil liner should be reevaluated in light of this study.