bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulated Effects of Reduced Sulfur, Nitrogen, and Base Cation Deposition on Soils and Solutions in Southern Appalachian Forests
Authors: Johnson D. W. , Susfalk R. B. , Brewer P. F. , Swank W. T. 
Published: July 2010

AbstractEffects of reduced deposition of N, S, and CB on nutrient pools, fluxes, soil, and soil solution chemistry were simulated for two Appalachian forest ecosystems using the nutrient cycling model. In the extremely acidic, N‐ and S‐saturated red spruce [Picea rubens (Sarg.)] forest (Nolan Divide), reducing CB deposition by 50% reduced CB leaching by ∼40% during the 24‐yr simulation period. This was due solely to the effects of CB deposition on the soil exchanger rather than effects on soil solution. Reducing S and N by 50% caused immediate reductions in total anion and cation leaching at Nolan Divide, but the effects on soil solution CB diminished and CB leaching was reduced by only 17% over the simulation period. Reducing S and N deposition had a greater effect on soil solution aluminum (Al) and molar Ca/Al ratio than reducing base cation deposition at Nolan Divide. In the moderately acidic, N‐ and S‐accumulating mixed deciduous forest at Coweeta, reduced CB deposition by 50% caused a very slight (<4%) reduction in CB leaching as a result of slightly reduced base saturation and increased soil sulfate adsorption. The effects on reducing S and N deposition by 50% on CB leaching (16% over the simulation period) were greater than those of reduced CB deposition. The system continued to accumulate both S and N even at reduced deposition at Coweeta, although growth and vegetation uptake were slightly reduced (−5%) because of increased N deficiency. Base saturation remained well above the Al buffering range at all times at Coweeta and Al was an unimportant component of soil solutions in all scenarios.
Macrophyte Species Changes in the Everglades: Examination along a Eutrophication Gradient
Authors: Vaithiyanathan P. , Richardson C. J. 
Published: July 2010

AbstractMacrophyte species distribution in the marsh and slough areas of the northern Everglades were examined along a surface water and soil P gradient to characterize the effects of nutrient enrichment on the macrophyte community changes in the Everglades ecosystem. Macrophyte species distribution and frequency examined at 51 sites located in the Water Conservation Area (WCA‐2A) revealed distinct trends in species changes with P enrichment. Marshes in the unenriched and enriched areas were dominated by Cladium jamaicense and Typha domingensis, respectively. Open water areas were characterized by Eleocharis sp., Utricularia sp., Chara zeylanica, and Nymphaea odorata in the unenriched areas and by floating plants and Polygonum sp. in the enriched areas. We compared the macrophyte species distribution with the soil P contour map of WCA‐2A and derived six major categories of P enrichment (labeled 0–5) that may be used to adequately describe macrophyte species distribution in the WCA‐2A. Soil and surface water P values that correspond to the different P‐enrichment categories and the number of macrophyte species in each category have been estimated. Examination of the relative abundance of the macrophyte species in the six P‐enrichment categories showed a decline in characteristic slough macrophyte species with P enrichment. Increase in P status of the system was also accompanied by the advent and gradual establishment of macrophytes such as Mikania scandens, Sarcostemma clausum, Polygonum sp., Acrostichum danaeifolium, and a variety of floating plants. Characteristic slough macrophyte species such as Utricularia purpurea, Eleocharis elongata, and Eleocharis cellulosa serve as indicators of the unenriched P conditions.
Rapid Screening of Plants Promoting Phenanthrene Degradation
Authors: Liste Hans‐Holger , Alexander Martin 
Published: July 2010

AbstractCrop plants were tested for their capacity to bring about phenanthrene degradation in solution. A simple colorimetric method was used to quantify phenols formed from phenanthrene in 1 h. In the presence of sunflower (Helianthus annuus L.) and pea (Pisum sativum L.) roots, >50% of the phenanthrene was metabolized and converted to phenols. In the presence of roots of other plant species, phenanthrene disappeared rapidly, but little phenols accumulated. We suggest that this is a rapid, simple assay to screen plant species for use in phytoremediation.
Simultaneous Analysis of Multiple Enzymes in Environmental Samples Using Methylumbelliferyl Substrates and HPLC
Authors: Freeman C. , Nevison G. B. 
Published: July 2010

AbstractEnzymes are considered to represent valuable biological indicators of ecosystem health. This study evaluates the potential for simultaneous measurement of the activity of multiple enzymes in a single sample. The rate of degradation of a suite of artificial methylumbelliferyl substrates was monitored in a wetland soil sample following separation of the individual components using high pressure liquid chromatography (HPLC). The method allowed effective separation and quantitative monitoring of the hydrolysis of substrates for the enzymes sulfatase, β‐glucosidase, xylosidase, and esterase. The proposed method appeared simple to perform, and offered considerable time‐savings over conventional techniques.
A Simple Model of Alachlor Dissipation
Authors: Weed D. A. J. , Kanwar R. S. , Salvador R. J. 
Published: July 2010

AbstractAlachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide] dissipation in the field shows two characteristics: (i) rapid, initial loss followed by slower degradation and (ii) sensitivity to environmental conditions including precipitation patterns, soil temperature, and soil‐water content. Empirical models, such as a first‐order equation, are simple and easy to use, but they do not accurately predict alachlor dissipation in the field. Complex mechanistic models provide theoretical mechanisms for dissipation, but their usefulness can be limited because they typically require data that is difficult to acquire under field conditions. We developed a hybrid model (M2CM) for alachlor dissipation based on a two‐compartment model (2CM). Our model requires only easily‐collected weather, soil, and pesticide information. It predicts the daily amount of alachlor in the soil and calculates times for 50 and 90% dissipation. We calibrated it with data from 30‐cm‐deep field‐soil samples and weather records from the 1993 growing season. Using 1992 and 1994 environmental data, the model calculated dissipation values that fit field‐sample data accurately (0.95 ≤ r2 ≤ 0.99). Results from the 2CM were not as consistently satisfactory (0.64 ≤ r2 ≤ 0.97). According to the M2CM, the alachlor half‐life (time to 50% dissipation) was 1 d for all 3 yr. Time to 90% dissipation was 18 d for 1992, 23 d for 1993, and 15 d for 1994.
Molecular Weight of Dissolved Organic Matter‐Napropamide Complex as Affected by Napropamide‐Soil Application Methods
Authors: Williams C. F. , Farmer W. J. , Letey J. , Nelson S. D. 
Published: July 2010

AbstractOrganic matter amendments to soil are usually thought to improve soil quality. Increased soil organic matter can lead to increased concentrations of dissolved organic matter (DOM). Complexation of DOM with pesticides can lead to increased aqueous phase concentration and therefore enhanced movement through the soil profile. Dissolved organic matter has been shown to form a stable complex with napropamide [2(α‐naphthoxy)‐N,N‐diethyl propionamide] and facilitate its transport through soil columns. Equilibrium dialysis is a common method to determine napropamide DOM complexation. Napropamide was applied to a silt loam soil with (SS) and without (NoSS) sewage sludge application. Solutions from batch equilibrium experiments were analyzed using equilibrium dialysis with various molecular weight cutoffs to determine napropamide DOM complexation. A maximum of 16% of solution phase napropamide was found to be associated with a DOM complex having a molecular weight >500 Daltons. The maximum complex size had a molecular weight <25 000 Daltons. More napropamide was complexed from the SS soil treatments than from the NoSS soil treatments. The presence of a drying event following napropamide application also was found to increase the amount of napropamide complexed in both the SS and NoSS soils. Results show that the amount and molecular weight of napropamide‐DOM complexes is affected by organic matter type and application method.
Phytoaccumulation of Trace Elements by Wetland Plants: III. Uptake and Accumulation of Ten Trace Elements by Twelve Plant Species
Authors: Qian Jin‐Hong , Zayed Adel , Zhu Yong‐Liang , Yu Mei , Terry Norman 
Published: July 2010

AbstractInterest is increasing in using wetland plants in constructed wetlands to remove toxic elements from polluted wastewater. To identify those wetland plants that hyperaccumulate trace elements, 12 plant species were tested for their efficiency to bioconcentrate 10 potentially toxic trace elements including As, B, Cd, Cr, Cu, Pb, Mn, Hg, Ni, and Se. Individual plants were grown under carefully controlled conditions and supplied with 1 mg L−1 of each trace element individually for 10 d. Except B, all elements accumulated to much higher concentrations in roots than in shoots. Highest shoot tissue concentrations (mg kg−1 DW) of the various trace elements were attained by the following species: umbrella plant (Cyperus alternifolius L.) for Mn (198) and Cr (44); water zinnia (Wedelia trilobata Hitchc.) for Cd (148) and Ni (80); smartweed (Polygonum hydropiperoides Michx.) for Cu (95) and Pb (64); water lettuce (Pistia stratiotes L.) for Hg (92), As (34), and Se (39); and mare's tail (Hippuris vulgaris L.) for B (1132). Whereas, the following species attained the highest root tissue concentrations (mg kg−1 DW): stripped rush (Baumia rubiginosa) for Mn (1683); parrot's feather (Myriophyllum brasiliense Camb.) for Cd (1426) and Ni (1077); water lettuce for Cu (1038), Hg (1217), and As (177); smartweed for Cr (2980) and Pb (1882); mare's tail B (1277); and monkey flower (Mimulus guttatus Fisch.) for Se (384). From a phytoremediation perspective, smartweed was probably the best plant species for trace element removal from wastewater due to its faster growth and higher plant density.
Water Runoff and Pesticide Transport from a Golf Course Fairway: Observations vs. Opus Model Simulations
Authors: Ma Q. L. , Smith A. E. , Hook J. E. , Smith R. E. , Bridges D. C. 
Published: July 2010

AbstractFrequent pesticide applications to golf courses causes concern that surface water may become contaminated. We hypothesized that runoff potential of these pesticides could be predicted by the recently developed Opus model. We conducted a 3‐yr field study measuring surface runoff of water and dimethylamine salts of 2,4‐D [(2,4‐dichlorophenoxy) acetic acid], dicamba (3,6‐dichloro‐2‐methylphenoxy‐benzoic acid), and mecoprop [(±)‐2‐(4‐chloro‐2‐methylphenoxy)‐propanoic acid]. Twelve 7.4 m by 3.7 m plots of ‘Tifway 419’ bermudagrass (Cynodon dactylon (L.) Pers.× C. transvaalensis Burtt Davy) were managed as a golf course fairway. Simulated rainfall was applied at an average intensity of 29 mm h−1 1 d before and 1,2,4, and 8 d after pesticide application for 0.92, 1.75, 1.75, 0.92, and 0.92 h, respectively. Average annual runoff loss was 9.13, 15.41, and 10.82% of applied 2,4‐D, dicamba, and mecoprop, respectively. Both mass and concentration of pesticide runoff decreased rapidly, with the first posttreatment event runoff averaging 74.5, 71.7, and 73.0% of the total runoff of 2,4‐D, dicamba, and mecoprop, respectively. The Opus model adequately simulated runoff [R2 = 0.897 and normalized root mean square error (NRMSE) = 24.6%]. The 2,4‐D in runoff was better simulated by complete‐kinetic sorption (R2 = 0.876, NRMSE = 60.2%) than by equilibrium sorption (R2 = 0.848, NRMSE = 68.2%). Opus did not accurately simulate 2,4‐D over all runoff events, but simulated 2,4‐D in the first posttreatment runoff within a factor of 2 of those measured.
Filter Strip Performance and Processes for Different Vegetation, Widths, and Contaminants
Authors: Schmitt T. J. , Dosskey M. G. , Hoagland K. D. 
Published: July 2010

AbstractFilter strips are widely prescribed to reduce contaminants in surface runoff from agricultural fields. This study compared performance of different filter strip designs on several contaminants and evaluated the contributing processes. Different vegetation types and widths were investigated using simulated runoff event on large plots (3 m × 7.5 or 15 m) having fine‐textured soil and a 6 to 7% slope. Filter strips 7.5 and 15 m wide downslope greatly reduced concentrations of sediment in runoff (76–93%) and contaminants strongly associated with sediment (total P, 55–79%; permethrin, 27–83% [(3‐phenoxyphenyl) methyl (±)‐cis, trans‐3‐(2,2‐dichloroethenyl)‐2,2‐dimethyicyclopropanecarboxylate]). They had less effect on concentrations of primarily dissolved contaminants [atrazine, −5–43% (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine); alachlor, 10–61% [2‐chloro‐2′6′‐diethyl‐N‐(methoxymethyl) acetanilide]; nitrate, 24–48%; dissolved P, 19–43%; bromide, 13–31%]. Dilution of runoff by rainfall accounted for most of the reduction of concentration of dissolved contaminants. Infiltration (36–82% of runoff volume) substantially reduced the mass of contaminants exiting the filter strips. Doubling filter strip width from 7.5 to 15 m doubled infiltration and dilution, but did not improve sediment settling. Young trees and shrubs planted in the lower one‐half of otherwise grass strips had no impact on filter performance. Compared with cultivated sorghum [Sorghum bicolor (L.) Moench] grass clearly reduced concentrations of sediment and associated contaminants in runoff, but not volume of runoff and concentration of dissolved contaminants. Settling, infiltration, and dilution processes can explain performance differences among pollutant types and filter strip designs.
Preconcentration and Separation of Trace Phosphorus Compounds in Soil Leachate
Authors: Espinosa Miguel , Turner Benjamin L. , Haygarth Philip M. 
Published: July 2010

AbstractThe speciafion of P in soil solutions and runoff waters presents an analytical challenge that must be overcome before P transfer processes can be fully understood. We describe a method employing strong anion exchange (SAX) resins for the concentration and speciation of trace amounts of P compounds in soil waters. Concentration of P was achieved by passing filtered samples through SAX cartridges and eluting the retained negatively charged species with a solution of 0.75 M NaCl and 0.5 mM EDTA. Separation was achieved by the application of strong anion exchange HPLC with a linear ionic gradient varying between 0.11 to 0.75 M NaCl and a constant concentration of 0.5 mM Na4EDTA. Total P detection was carried out by discrete fraction collection and manual analysis using a sulphuric acid‐persulphate digest followed by reaction with molybdate. We detected a range of P species in soil leachate water, which included orthophosphate, inositol hexaphosphate, glucose‐6‐phosphate, adenosine 5′‐triphosphate, phosphonates and other as yet unidentified forms of P. With refinements, this method has the potential to significantly enhance our understanding of the P forms in soil waters and the processes controlling P transfer from the land.
Nitrate Behavior in Ground Waters of the Southeastern USA
Authors: Nolan Bernard T. 
Published: July 2010

AbstractPrincipal components analysis (PCA) was performed with water‐quality data from studies conducted during 1993 to 1995 to explore potential nitrate‐attenuation processes in ground waters of the south‐eastern USA. Nitrate reduction is an important attenuation process in selected areas of the Southeast. A nitrate‐reduction component explains 23% of the total variance in the data and indicates that nitrate and dissolved oxygen (DO) are inversely related to ammonium, iron, manganese, and dissolved organic carbon (DOC). Additional components extracted by PCA include calcite dissolution (18% of variance explained) and phosphate dissolution (9% of variance explained). Reducing conditions in ground waters of the region influence nitrate behavior through bacterially mediated reduction in the presence of organic matter, and by inhibition of nitrate formation in anoxic ground water beneath forested areas. Component scores are consistent with observed water‐quality conditions in the region. For example, median nitrate concentration in ground‐water samples from the Albemarle‐Pamlico Drainage Basin (ALBE) Coastal Plain is <0.05 mg L−1, median DOC concentration is 4.2 mg L−1, and median DO concentration is 2.1 mg L−1, consistent with denitrification. Nitrate reduction does not occur uniformly throughout the Southeast. Median DO concentrations in ground‐water samples from the Apalachicola‐Chattahoochee‐Flint River Basin (ACFB) are 6.2 to 7.1 mg L−1, and median nitrate concentrations are 0.61 to 2.2 mg L−1, inconsistent with denitrification. Similarly, median DO concentration in samples from the Georgia‐Florida Coastal Plain (GAFL) is 6.0 mg L−1 and median nitrate concentration is 5.8 mg L−1.
Observations on Preferential Flow and Horizontal Transport of Nitrogen Fertilizer in the Unsaturated Zone
Authors: Wilkison Donald H. , Blevins Dale W. 
Published: July 2010

AbstractA study site underlain by a claypan soil was instrumented to examine the transport of fertilizer nitrogen (N) under corn (Zea mays L.) cultivation. The study was designed to examine N transport within the unsaturated zone and in intedlow (the saturated flow of water on top of the claypan). A 15N‐labeled fertilizer (labeled N), bromide (Br), and chloride (Cl) were used as field tracers. Rapid or prolonged infiltration events allowed water and dissolved solutes to perch on the claypan for brief periods. However, a well‐developed network of preferential flow paths quickly diverted water and solutes through the claypan and into the underlying glacial till aquifer. Excess fertilizer N in the unsaturated zone supplied a continuous, but declining input of N to ground water for a period of 15 mo after a single fertilizer application. Calculated solute velocities through the claypan matrix (6.4 × 10−6 cm s−1) were similar to horizontal transport rates along the claypan (3.5 to 7.3 × 10−6 cm s−1) but much slower than infiltration rates determined for preferential flow paths (1.67 × 10−3 cm s−1). These flow paths accounted for 35% of the transport. A seasonally variable, dual mode of transport (matrix and preferential flow) prevented the daypan from being an effective barrier to vertical transport. Simulations of selected field observations, conducted using the variably saturated two‐dimensional flow and transport model, VS2DT, confirmed the presence of a dual flow regime in the claypan.
Nitrogen Deposition In and Around an Intensive Agricultural District in Central New York
Authors: Fahey Timothy J. , Williams Christopher J. , Rooney‐Varga Juliette N. , Cleveland Cory C. , Postek Kimberley M. , Smith Stephen D. , Bouldin David R. 
Published: July 2010

AbstractEmissions of NH3 from intensive agriculture may perturb natural ecosystems by increasing atmospheric N deposition. This study was undertaken to quantify patterns of atmospheric chemistry and N deposition in and around a highly intensive agricultural district and thereby to improve understanding of the fate of NH3 emissions and possible effects on regional forests. Atmospheric chemistry, wet and bulk deposition, canopy throughfall, and soil and vegetation N status were measured at a suite of sites in and around the agricultural district centered in southern Cayuga County, New York. Concentrations of NH+4 and acidic gases and particulates were slightly elevated compared with regional background values. Temporal variations in these species were consistent throughout the district and surrounding areas, suggesting wide dispersion. In contrast, NH3 concentrations were greatly elevated within the district (often >1 µg m−3), comparable to values in southeastern Netherlands, but declined to moderate values in outlying areas (0.2 µg m−3). Bulk deposition of NH+4 near large farms (7–8 kg NH4‐N ha−1 yr−1) was over twice as high as the regional background, declining to levels about 50% above background throughout the district but more than 2 km away from large farms (4–5 kg NH4‐N ha−1 yr−1). These values must be regarded as tentative estimates because of probable high seasonal and annual variation and the limited intervals of sampling in the current study. Also, gaseous deposition of NH3 to forests in the district probably contributes significantly to total deposition, but its magnitude remains uncertain.
Impact of Organic Production Practices on Soil Quality Indicators
Authors: Liebig M. A. , Doran J. W. 
Published: July 2010

AbstractThe impact of organic production practices on soil quality indicators, for selected farms in Nebraska and North Dakota, were evaluated to better understand their effects on soil quality and sustainability. Conventional production practices were the standard to which the effects of organic production were compared. Five organic and conventional farms, matched by soil type, were chosen for the study. Soil properties recognized as basic soil quality indicators were measured on each farm at depths of 0 to 7.6 and 0 to 30.5 cm. Averaged across locations, there was 22% more organic C (12 571 kg ha−1) and 20% more total N (970 kg ha−1) on organic farms than conventional farms in the surface 30.5 cm. At four of five locations, organic farms had soil pH closer to neutral, lower bulk density, and higher available‐water holding capacity, microbial biomass C and N, and soil respiration as compared with conventional farms. Nutrient levels above crop needs were observed in both organic and conventional farms indicating the potential for negative environmental impacts. Despite this, organic farms often had more potentially mineralizable N (anaerobic incubation) relative to NO3‐N in the surface 30.5 cm. For conditions of this study, the capacity of organic production practices to improve soil quality was mainly due to use of more diverse crop sequences, application of organic amendments, and less frequent tillage.
Nitrous Oxide Emissions from Manure and Inorganic Fertilizers Applied to Spring Barley
Authors: Petersen S. O. 
Published: July 2010

AbstractNitrous oxide emissions from soil amended with untreated liquid manure (slurry), anaerobically digested slurry, or inorganic fertilizers (calcium ammonium nitrate or urea) were quantified in a field study covering two growth seasons of spring barley (Hordeum vulgare L.). In the first year incorporation before seeding was compared with trail hose application 5 wk after seeding. In the second year all fertilizers were applied before seeding, while soil moisture and initial NO−3 availability was varied. Accumulated N2O losses between the time of fertilization and ca. 1 July represented 0.14 to 0.35% of total N in 1996 and 0.34 to 0.64% in 1997. In both years the highest N2O emissions were observed with untreated slurry, whereas digested slurry and inorganic fertilizers were at a similar level. Increasing the soil moisture content or NO−3 availability had no significant effect on accumulated N2O losses. Although metabolizable C may thus have stimulated N2O emissions via denitrification from untreated slurry, the largest contribution to N2O fluxes probably came from nitrification with all fertilizer types. Using the IPCC guidelines it was estimated that anaerobic digestion of slurry per se could potentially reduce N2O emissions from Danish agriculture by 1.2 to 2.5%.