bluuebunny/crossref_metadata_2025 huggingface dataset:
Degradation of 2,4‐D, 2,4‐Dichlorophenol, and 4‐Chlorophenol in Soil after Sorption on Humified and Nonhumified Organic Matter
Authors: Benoit P. , Barriuso E. , Soulas G.
Published: July 2010

Soil organic matter (SOM) primarily governs sorption processes and therefore affects the availability of organic chemicals to degrading microorganisms. Transformations of 14C‐ring‐labeled 2,4‐dichlorophenoxyacetic acid (2,4‐D); 2,4‐dichlorophenol (2,4‐DCP); and 4‐chlorophenol (4‐CP) sorbed on organic materials with increasing degrees of humification (wood, fresh straw, composted straw, lignin, and humic acid) and on a reference mineral sorbent (Al‐oxide) were studied during soil incubation experiments. Chemicals previously sorbed on the different sorbents were applied to the soil. Mineralization kinetics, analysis of water and methanol extracts and measurements of the nonextractable radioactivity before and after soil incubation were done to characterize changes in the availability of sorbed 14C chemicals. Mineralization of 2,4‐D was higher than mineralization of 2,4‐DCP and 4‐CP: depending on the nature of the sorbent, 47 to 87% of 2,4‐D, 10 to 68% of sorbed 2,4‐DCP and 12 to 65% of sorbed 4‐CP were mineralized. Specific metabolic transformations and formation of bound residues occurred principally with the less humified organic sorbents. The formation of bound residues from the three chemicals was high after sorption on composted straw, where bound residues accounted for 20, 23, and 78% of applied 2,4‐D; 2,4‐DCP; and 4‐CP, respectively. This was attributed partially to the initial sorption‐desorption characteristics but was also explained by transformations that had occurred on this decomposing organic material. Our results showed that protection of chemicals against biodegradation by sorption processes can not be generalized since in most of the cases studied sorption induced an increase of mineralization rate.
Tillage Effects on Persistence and Distribution of Trifluralin in Soil
Authors: Berger Bernhard M. , Dühlmeier Detlef , Siebert Christina F.
Published: July 2010

The aim of this study was to investigate the effects of the substitution of plowing with harrowing—twice in a 3‐yr crop rotation—on persistence and distribution of a persistent herbicide such as trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) to rate these two tillage systems for their environmental impact (e.g., regarding potential ground water contamination with pesticides). Therefore, studies have been performed in Germany at two sites, a clayey silt in Reinshof and a loamy sand in Eickhorst. The herbicide was applied to oilseed rape (Brassica napus L. var. napus), followed in consecutive years by applications to wheat (Triticum aestivum L.) or to wheat followed by rye (Secale cereale L.). The disappearance time of 50% of the initial concentration (DT‐50 value) decreased from >300 d after preplant incorporation of trifluralin to <150 d after pre‐emergence treatment, losses being greater due to volatilization resulting from the lack of soil incorporation. No influence of different tillage systems on trifluralin persistence could be observed. Distribution of the herbicide in the top 30 cm of the soils, however, was significantly influenced by the soil cultivation systems. Reduced tillage (harrowing) in two consecutive years resulted in trifluralin concentrations in the soil layers 10 to 20 cm and 20 to 30 cm under the limit of determination (0.005 mg kg−1). In contrast, plowing led to trifluralin residues of up to 0.019 mg kg−1 in these soil layers. Although no trifluralin residues could be found in the 30‐ to 45‐cm and 45‐ to 60‐cm soil layers under either soil cultivation system, our results imply an increased risk of ground water contamination after plowing.
Phosphorus and Nitrogen in Runoff following Beef Cattle Manure or Compost Application
Authors: Eghball Bahman , Gilley John E.
Published: July 2010

Manure or compost from beef cattie feediots can be an excellent sources of nutrients and organic matter when added to soils, but they can also pollute runoff. We determined the effects of simulated rainfall on runoff losses of P and N, and EC and pH following application of manure and compost to a Sharpsburg silty clay loam (fine smectitic, mesic Typic Argiudoll) soil having grain sorghum [Sorghum bicolor (L.) Moench] and winter wheat (Triticum aestivum L.) residues. Manure, compost, and fertilizer were applied to no‐till fields at rates required to meet N or P requirements for corn (Zea mays L.) production and were either left on the soil surface or disked to 8 cm. There were also untreated checks. Runoff concentrations of dissolved P (DP), bioavailable P (BAP), and NH4‐N were significantly greater when the soil was not disked. Total and particulate P concentrations in runoff were generally less under wheat than sorghum residue and were less for the no‐till than the disked condition. In the disked system, N or P‐based manure or compost application resulted in DP concentration <1 mg L−1. Manure and compost application resulted in greater runoff EC values than fertilizer application. Phosphorus concentration of runoff receiving P fertilizer or N‐based manure and compost application can be an environmental concern when these sources are applied under no‐till conditions without incorporation.
Spatial—Temporal Variability of Preferential Flow in a Clay Soil under No‐Till and Plow‐Till
Authors: Ogden C. B. , van Es H. M. , Wagenet R. J. , Steenhuis T. S.
Published: July 2010

Tillage most affects the large pore spaces, including macropores, which dominate percolation through field soils. Rain events are expected to promote post‐tillage changes in pore geometry. Pore‐geometric influences on macropore transport were examined under multiple rains, in a Kingsbury clay soil under no‐till (NT) and plow‐till (PT). Four replicate pairs of large undisturbed sample columns were installed on grid wick iysimeters comprising 5 × 5 grids of 36‐cm2 cells. Five simulated rains having mean depths and intensifies of 40 mm and 38 mm h−1, respectively, were applied, separated by intervals of 4, 8, 9, and 50 d, using a constant‐head drop‐forming rainfall simulator. Atrazine [6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine] and a Br− tracer were applied 24 and 1 h, respectively, before the first rain. Persistence of spatial percolation patterns was quantified by inter‐event correlation coefficients of the cell‐scale water outflows. Outflow was significantly greater in NT than in PT, averaging 75 and 54% of applied rain, respectively, but Br− export did not differ significantly between them. Spatial outflow patterns changed between events in both tillage treatments and were more variable in NT. Distributions of cell‐scale cumulative change in outflow proportion were unimodal and symmetric. Percolation in NT occurred as bypass flow through direct pathways, relative to PT pathways characterized by mixing. Transport variability due to temporal variability of functional macropore flowpaths may account for some solute tailing in field soils.
Global Sensitivity Analyses of Three Pesticide Leaching Models Using a Monte‐Carlo Approach
Authors: Soutter Marc , Musy André
Published: July 2010

The modeling of large natural systems requires a lot of data, carries a considerable amount of uncertainties and involves a significant computational effort. A global parameter sensitivity analysis, accounting for simultaneous parameter variations over their entire admissible ranges, is therefore potentially useful at all stages of the modeling process. The sensitivity analysis presented in this paper were carried out within the frame of a regional vulnerability assessment regarding ground water contamination by pesticides. The three selected pesticide leaching models include an analytical solution of the convection‐dispersion equation (attenuation factor, AF), a tipping bucket model (LEACHA), and a numerical solution of the convection‐dispersion equation (LEACHM). Sensitivity analysis was performed with a Monte‐Carlo based technique involving Latin hypercube sampling along with multiple regression. The results show that the parameters controlling degradation and sorption processes are far more important than those accounting for the transport process. Actually, pesticide properties (degradation rate and partition coefficient), organic C content and water table depth are the most predominant variables regarding cumulated (10 yr) pesticide fluxes to the ground water. Unexpectedly, variables such as soil hydrodynamic properties, dispersivity, or pesticide solubility did not have a significant effect on the magnitude of cumulated pesticide fluxes. As a consequence, in a stochastic approach to regional‐scale ground water vulnerability assessments, the probability density functions of those variables may be chosen empirically or according to a classification of soils combined with pedotransfer functions, without affecting significantly the resulting assessment maps and their uncertainties.
Effects of Soil Moisture, Depth, and Organic Amendments on Selenium Volatilization
Authors: Zhang YiQiang , Frankenberger William T.
Published: July 2010

Effects of soil moisture, depth, and organic amendments on selenium (Se) volatilization in a Se‐contaminated soil were studied in three different experiments. Results showed that the volatilization rate of Se as dimethylselenide (DMSe) was increased during a transition from air‐dry soil (<2 µg/m2 per day) to a wetted soil (185 µg/m2 per day), and was also much higher after rewetting an air‐dried soil than keeping the soil continuously moist. Although more DMSe was produced with increasing soil mass, DMSe was trapped in the subsoil layers. DMSe emission to the air was related to the moisture content. After 10 d, 96 and 14% of injected DMSe was volatilized to the air from an air‐dried soil and a water‐saturated soil, respectively. Both insoluble (casein) and soluble (Casamino acids) organic amendments enhanced DMSe production and removal from soil through volatilization. This study suggests that organic amendments and frequent tillage are needed to increase Se volatilization from soil by enhancing production of DMSe and increasing soil porosity in facilitating the diffusion of trapped DMSe to the atmosphere.
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

Effects 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

Macrophyte 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

Crop 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

Enzymes 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

Alachlor [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

Organic 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

Interest 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

Frequent 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

Filter 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

The 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

Principal 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

A 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

Emissions 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

The 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

Nitrous 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%.
Tropospheric Carbon Dioxide or Ozone Enrichments and Moisture Effects on Soil Organic Carbon Quality
Authors: Islam K. R. , Mulchi C. L. , Ali A. A.
Published: July 2010

Carbon, as an active component of organic matter, has considerable effects on soil quality and productivity. The objective of this study was to examine the effect of climate change variables on soil organic C (CT) quality in an agroecosystem. Wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr] plants were grown in 3 m in diam. open‐top field chambers and exposed to charcoal‐filtered (CF) air at 350 µL CO2 L−1; CF air + 150 µL CO2 L−1; nonfiltered (NF) air + 35 nL O3 L−1; and NF air + 35 nL O3 L−1 + 150 µL CO2 L−1 at two soil moisture levels from 1994 to 1996. The 150 µL CO2 L−1 addition was 18 h d−1 and the 35 nL O3 L−1 was 7 h d−1 from April until late October. In response to treatments, the Cr contents did not change significantly; however, participate, oxidizable, dissolved, humic (CHA) and fulvic (CFA) acid, and carbohydrate C pools increased in soils under CO2 enrichment and well‐watered conditions but decreased under O3 stress compared with soils under CF ambient air quality. Tropospheric CO2 enrichment and well‐watered condition increased, and O3 stress decreased the log optical density slope for both CHA and CFA fractions more than CF ambient air and restricted moisture treatment. Also, the E465/E665 ratios of both CHA and CFA fractions were higher for the CO2 enrichment and smaller for the O3 stress compared with CF ambient air quality. Results suggest that tropospheric CO2 enrichment and well‐watered conditions may favor an accumulation of low molecular weight and more aliphatic quality of C and O3 stress favor high molecular weight and more aromatic quality of C.
Soil Hydraulic Conductivity Changes Caused by Irrigation with Reclaimed Waste Water
Authors: Levy G. J. , Rosenthal A. , Tarchitzky J. , Shainberg I. , Chen Y.
Published: July 2010

Use of reclaimed waste water (RWW) in arid and semiarid regions may alleviate problems of fresh water shortage; however, it also involves some potential risks among which are degradation of soil hydraulic properties. The objectives of the current study were to study the effects of organic matter (OM) loads found in RWW obtained from a secondary treatment plant in Tel Aviv, Israel, and different size fractions of the suspended solids in the RWW on the hydraulic conductivity (HC) of three Israeli soils. The hydraulic conductivity of a clayey grumusol (Typic Chromoxerert), a typic loamy loess (Calcic Haploxeralf), and a sandy loam hamra (Typic Rhodexeralf) was determined in the laboratory using soil columns, by leaching with RWW containing zero, low, or high OM load, followed by leaching with distilled water (DW). The effects of suspended solids' size fraction on the HC was determined by filtering RWW. Leaching with high OM load RWW caused the relative HC of the grumusol, loess and hamra to drop to final values of 13.9, 24.2, and 58.8%, respectively. Filtering out suspended solids >1.2 µ in this water improved the HC of the hamra, but did not significantly affect the final relative HC of the grumusol and loess. Leaching with low OM load RWW did not significantly decrease the HC beyond the decrease attributed to the effects of the concentration and composition of the electrolytes present in the zero OM load RWW. Subsequent leaching with DW caused an additional decrease in HC, whose magnitude for a given soil did not depend on the quality of the RWW previously used. The presence of OM in the irrigation water did not seem to have significant residual effects on soil HC. Evidently, in high OM load RWW the OM fraction determines the soils' HC, whereas in low OM load RWW, it is the electrolyte concentration and composition in the water, that seem to pose the hazard to soil hydraulic properties, especially during subsequent leaching with DW.
Purification of Fuel and Nitrate Contaminated Ground Water Using a Free Water Surface Constructed Wetland Plant
Authors: Machate Thomas , Heuermann Elisabeth , Schramm Karl‐Werner , Kettrup Antonius
Published: July 2010

Contaminated ground water from a former coke plant site was purified in a free water surface (FWS) constructed wetland plant during a 3‐mo short‐term experiment. The pilot plant (total surface area 27 m2) was filled with a 1 m thick lava‐gravel substrate planted with cattail (Typha spp.) and bulrush (Scirpus lacustris). Major contaminants were low to moderate concentrations of polycyclic aromatic hydrocarbons (PAH 50–9000 µg L−1 according to USEPA, 1‐methylnaphthalene 2–1900 µg L−1, 2‐methylnaphthalene 3–4300 µg L−1), BTEX (10–450 µg L−1), nitrate (60 mg L−1 as N), and nitrite (7 mg L−1 as N). The wetland was dosed at hydraulic loading rates of qA = 4.8 and 9.6 cm d−1 with a hydraulic residence time (HRT) of 13.7 and 6.8 d. The surface removal rates of PAH were between 98.8 and 1914 mg m−2 d−1. Efficiency was always >99%. Extraction of lava gravel showed that approx. 0.4% of the applied PAH were retained on the substratum. The ratio of ∑2,3‐ring PAH and ∑4,5,6‐ring PAH showed a shift from 1:0.11 in water (influent) to 1:2.5 in lava (Tank 1). The removal of BTEX was >99%, but might be in part due to volatilization. The efficiency in the removal of nitrate was 91% (2.47–3.34 g m−2 d−1) and of nitrite was 97% (0.034–0.036 g m−2 d−1). Purification performance was not influenced by hydraulic loading rates or after die‐back of the macrophytes.
Effects of Silvicultural Activities on Wetland Biogeochemistry
Authors: Lockaby B. G. , Trettin C. C. , Schoenholtz S. H.
Published: July 2010

The unique biogeochemistry of wetlands either causes or influences many landscape functions that are valued by society. Because of their critical ecological role and the importance of wetlands to commodity and noncommodity values, we have reviewed the current state of knowledge regarding influences of silviculture on nutrient circulation, transformation, and retention in forested wetlands. Our approach was to contrast riverine and depressional systems. Globally, there are few generalizations that can be made regarding the effects of silvicultural disturbance. This conclusion is primarily a result of too few studies on the mechanisms and processes controlling ecosystem responses. Most work to date has focused solely on characterizing responses of state variables, and therefore a basis for integration is often lacking. While studies do show that water quality functions are not degraded as a result of harvesting, many other aspects of ecosystem functionality are not clarified. As examples, there are significant gaps in our understanding of biogeochemical controls on net primary productivity, organic matter turnover, and hydrologic interactions. Considerable research is warranted to provide information for effective resource management and conservation.
Lead Migration in Some Acid Forest Soils under Beech in Greece
Authors: Michopoulos P.
Published: July 2010

The ratio of Pb concentrations in A and H horizons (relative migration ratio or RMR) of acid forest soils under beech in Greece was determined and assumed as an index of potential Pb migration. The pH of the A horizon was the only factor studied that significantly and negatively correlated with RMR. Decreasing solubility of organic matter in the A horizon is a possible cause for this correlation. The E4/E6 ratio (absorbance at 465 nm/absorbance at 665 nm) in water extracts from H horizon did not affect RMR, suggesting that soluble organic matter of low molecular weight derived from humic layers could not significantly cause Pb leaching from the A horizon.
Chemistry of Arsenic in Soils: I. Sorption of Arsenate and Arsenite by Four Australian Soils
Authors: Smith E. , Naidu R. , Alston A. M.
Published: July 2010

Ten soils varying widely in chemistry and mineralogy were used to examine the physical and chemical properties that influence As sorption processes in soils. The sorption of As was measured using a batch technique with Asv and AsIII concentrations added in background solutions of NaNO3 (0.003–0.3 mol L−1) and a range of pH values (2.0–8.5). The soils generally sorbed more Asv than AsIII at equivalent As concentrations. In general, highly oxidic soils sorbed three times more Asv than soils containing small amounts of oxidic minerals. The effect of pH on As sorption varied considerably among the soils. In soils with low concentrations of oxidic minerals, increasing pH had little affect on the amount of Asv sorbed while in highly oxidic soils, sorption of Asv decreased with increasing pH. This decrease was attributed to two interacting factors, the increasing negative surface potential on the plane of sorption and increasing amount of negatively charged Asv species present in soil solution. In contrast to Asv, sorption of AsIII increased with increasing pH. The effect of ionic strength on As sorption varied between the As species. In general, there was a pH (∼3) below which Asv sorption decreased with increasing ionic strength and above which the reverse occurred. For AsIII species, increasing ionic strength had little effect on the amount of As sorbed.
Flue Gas Desulfurization By‐Product Weathering by Acidic Mine Drainage
Authors: Laperche Valérie , Traina Samuel J.
Published: July 2010

We examined the suitability using a flue gas desulfurization grout (FGDG) for the attenuation and abatement of acidic mine drainage (AMD). The FGDG used was a mixture of fly ash (FA) and filter cake (FC) with a FA/FC ratio of 1:1 to improve handling. Five percent of lime (CaO) was added to improve strength development and allow the use of this FGDG as a hydrologic seal for underground mines. Acidic mine drainage solutions collect from wells located within mine voids were reacted with samples of FGDG for up to 168 d, to evaluate the potential for grout dissolution subsequent to subterranean implacement. Shortly upon reaction with AMD, FGDG released a number of ions into solution (As, B, Ca, K, Na, Se, SO4), concomitant with a rapid increase in solution pH (8.5), causing decreases in the solubility of most cations (AI, Fe, Mn, Zn). Significant increases in dissolved As and B concentrations were noted. Both elements were present in solution at levels below respective regulatory limits for drinking water. Of the original quantities of As and B present in FGDG, 1.3 and 45.6%, respectively, were released to solution over a 168‐d reaction period. Concomitant with changes in solution composition, reaction of FGDG with AMD resulted in a loss of ettringite and hannebachgite and a growth of gypsum. Additional changes in mineralogy were observed as FGDG equilibrated with AMD solutions. From these reactions, the long‐term stability of FGDG in underground acidic mine environments is questionable and warrants study in situ.
Mobility of Cadmium‐109 and Zinc‐65 in Soil Influenced by Equilibration Time, Temperature, and Organic Matter
Authors: Almås Å. , Singh B. R. , Salbu B.
Published: July 2010

Partitioning of 109Cd and 65Zn fractions in an alum shale soil as affected by time, temperature, and organic matter was investigated. The soil was extracted sequentially by H20 (F1), 1 M NH4OAc at pH 7 (F2), 1 M NH4OAc at pH 5 (F3), 0.04 M NH2OH HCl (F4), 30% H2O2 (F5), and finally by 7 M HNO3 (F6). Sequential extraction of metals was performed on soil samples collected at time intervals ranging from 0.5 to 8760 h (1 yr) after spiking the soil with 109Cd and 65Zn. The soil was placed incipiently in temperature controlled climate chambers at 9, 15, and 21°C. Before spiking, the soil was treated with 0 or 4% organic matter. Adsorption of 109Cd and 65Zn was rapid, but a subsequent slow diffusion of the metals toward chemisorbed fractions was also evident since the 109Cd and 65Zn concentrations decreased in the three mobile fractions (F1–F3) and increased in the inert fractions (F4, F5, F6 and F7) with time. Temperature elevation resulted in decreased concentrations of 109Cd and 65Zn in the F2 and F3 fractions, whereas the concentrations of these metals increased in the inert fractions. In the organic matter‐treated soil, 109Cd and 65Zn were increased significantly in the mobile fractions, with a corresponding reduction of 109Cd and 65Zn in the inert fractions. The effect of organic matter was more pronounced at 9°C than at 21°C. The results thus indicate that increasing time and temperature reduce the organic matter‐induced mobilization of 109Cd and 65Zn in soil.
Occurrence and Transport of Acetochlor in Streams of the Mississippi River Basin
Authors: Clark G. M. , Goolsby D. A.
Published: July 2010

The herbicide acetochlor [2‐chloro‐N‐(ethoxymethyl)‐N‐(2‐ethyl‐6‐methylphenyl) acetamide] was first used on corn (Zea mays L.) in the USA during the growing season of 1994. By 1996, it was the third most heavily used corn herbicide in the midwestern USA. During the growing season of 1997, 78% of 375 samples collected at 32 stream sites in the Mississippi River Basin contained detectable concentrations of acetochlor. However, concentrations in only 2% of the samples exceeded 2/µg/L, the maximum annual average concentration allowable in public water supplies derived primarily from surface water. The largest acetochlor concentrations were detected in streams draining basins in parts of Illinois, Indiana, and Iowa. The median concentration of acetochlor in streams was about 10% that of atrazine (6‐chloro‐N‐ethyl‐N‐isopropyl‐1,3,5‐triazine‐2,4‐diamine), about 25% that of metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide], about 50% that of cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐l,3,5‐triazin‐2‐yl]amino]‐2‐methylpropionitrile], and about threefold that of alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl) acetanilide]. Load estimates indicate that, during the growing season of 1997, agricultural subbasins draining areas of Illinois, Indiana, and Iowa contributed about 37 000 kg, or 74%, of the 50 000 kg of acetochlor measured in streams of the Mississippi River Basin.