bluuebunny/crossref_metadata_2025_split huggingface dataset:
Binding of Mercury(II) to Reduced Sulfur in Soil Organic Matter along Upland‐Peat Soil Transects
Authors: Skyllberg Ulf , Xia Kang , Bloom Paul R. , Nater Edward A. , Bleam William F. 
Published: July 2010

AbstractThe binding of Hg2+ in organic matter of soils and waters controls the transport and transformations of Hg in terrestrial and aquatic ecosystems. We developed a competitive complexation method using the strong complexation of Hg2+ by Br− for determining the Hg2+ binding strength in organic soils at native and elevated Hg concentrations. The distribution coefficients determined in KBr suspensions for sorption of native Hg2+ to soil organic carbon (SOC) (KSOC) are in the range of 1022 to 1023. The KSOC significantly decreased with increased additions of Hg2+ and with decreasing pH. Using data for reduced organic S concentrations determined by x‐ray absorption near‐edge structure spectroscopy (XANES), we calculated surface complex formation constants on the order of 1032 for a model site having acidity constants of mercaptoacetic acid. This value is in fair agreement with the tabulated value of 10345 for Hg2+ binding in mercaptoacetic acid. At native Hg concentrations, formation constants and KSOC values were similar for different types of soil organic matter along transects from uplands into wetlands, despite varying concentrations of Hg and reduced organic S. Our adsorption data are consistent with the conclusions from our previous extended x‐ray absorption fine structure spectroscopy (EXAFS) study that in a humic acid and soil, Hg2+ ions bond in two‐fold coordination involving one reduced S and one O or N.
Long‐Term Changes in the Extractability and Bioavailability of Zinc and Cadmium after Sludge Application
Authors: McGrath S. P. , Zhao F. J. , Dunham S. J. , Crosland A. R. , Coleman K. 
Published: July 2010

AbstractChanges in the extractability and uptake by crops of sludge metals in a long‐term field experiment, started in 1942, were measured to assess whether Zn and Cd are either fixed by the sludge/soil constituents or are released as the sludge organic matter (OM) decomposes. Total and 0.1 M CaCl2‐extractable concentrations of Zn and Cd in soil and total concentrations in crops were measured on archived crop and soil samples. Extractability of Zn as a proportion of the total ranged from 0.5 to 3% and that of Cd from 4 to 18%, and were higher in sludge‐amended than farmyard manure or fertilizer‐amended soils. Over a 23‐yr period after 1961, when sludge was last applied, the extractability of both metals fluctuated, but neither decreased or increased consistently. The relationships between total soil and crop metal concentrations were linear, with no evidence of a plateau across the range of soil metal concentrations achieved. The slopes of the soil‐plant relationships depended on the type of crop or crop part examined, but were generally in the order red beet (Beta vulgaris L.) > sugar beet (Beta vulgaris L.) > carrot (Daucus carota L.) > barley (Hordeum vulgare L.). However, there also were large seasonal differences in metal concentrations in the crops. It is concluded from the available evidence that up to 23 yr after sludge applications cease, Zn and Cd extractability and bioavailability do not decrease.
Duplicate Sampling of Surface Films and Associated Pond Water for Herbicides
Authors: Waite D. T. , Cessna A. J. , Grover R. , Woodsworth E. J. 
Published: July 2010

AbstractThis paper describes the variability of herbicide concentrations in the surface film and subsurface water of small, artificial prairie ponds (dugouts) as determined by comparing duplicate samples. Duplicate surface film samples were collected using a horizontally held glass plate and washed into a collection bottle with dichloromethane. Subsurface water samples were collected by plunging bottles into the pond to a depth of approximately 0.25 m. The samples were collected weekly from two dugouts in 1989 and from one dugout in 1990. Samples were analyzed for 2,4‐D, dicamba, bromoxynil, MCPA, triallate, trifluralin, and diclofop using a gas chromatograph interfaced with a mass selective detector. The average variability of the surface film samples was ±40% of the average of the pair with a confidence interval of 97% (p = 0.05). The average variability of the subsurface water samples was ±25% of the average of the pair with a confidence interval of 71% (p = 0.05). Possible reasons for the variability, including the nonhomogeneity of the surface film, are discussed.
Salinity, Boron, and Irrigated Pecan Productivity along New Mexico's Rio Grande Basin
Authors: Picchioni G. A. , Karaca H. , Boyse L. G. , McCaslin B. D. , Herrera E. A. 
Published: July 2010

AbstractWe surveyed 15 commercial irrigated orchards of ‘Western’ pecan [Carya illinoinensis (Wangenh.) K. Koch] along a 120‐km stretch of the middle Rio Grande basin in southern New Mexico. Our intent was to determine if high salinity and boron (B) broadly threaten pecan cultivation in this region. Ten of the fifteen sites were found to be on soils considered too saline for pecan trees (>2–3 dS m−1 in the soil saturation extract of the upper 0–60 cm of soil depth). Of these 10 sites, 4 had saturation extract Na concentration exceeding 20 mM, which is at or about the concentration corresponding to pecan seedling rootstock growth suppression. A laboratory study showed that cell membranes of excised, subapical seedling root segments from ‘Riverside’ pecan were damaged by about twice the salinity of the saturation extract at the highest salinity sites (9 dS m−1). At all sites, midsummer leaflet B concentration surpassed the published accepted range for pecan of about 50 to 100 mg B kg−1 dry weight, especially at the sites with higher soil salinity. Evaluation of two nearby sites (low salinity and B and high salinity and B orchards) showed that the higher salinity and B were associated with 25% lower yield efficiency, 3% lower percentage kernel, 13% lower mass per nut, and a 9 to 16% reduction in the tree's capacity to recycle N and P into perennial storage organs. The findings bring attention to the sustainability of current irrigation and soil management practices in much of this concentrated pecan producing region.
Nutrient and Fecal Coliform Discharge from Coastal North Carolina Golf Courses
Authors: Mallin Michael A. , Wheeler Tracey L. 
Published: July 2010

AbstractWater quality investigations were conducted at five golf courses in southeastern North Carolina to determine levels of pollutants contributed by the courses to adjacent coastal streams. In general, nitrate levels were greater in streams leaving the courses compared with streams entering the courses, but concentrations varied considerably among courses. Ammonium concentrations increased in passage through most of the courses. Orthophosphate concentrations were elevated on midcourse sites on two courses, but were low in the outflow water except at one course. The golf courses studied were not significant sources of fecal coliform bacteria to nearby waterways; in fact, passage through some courses served to reduce coliform loads entering from upstream suburbs. Recent rainfall and fertilization application influenced outfall nitrate concentrations only at some courses. Landscape management practices appeared to play a critical role in determining nutrient concentrations in the outfall and at midcourse sites. Nutrient addition bioassay experiments conducted in one of the coastal creeks receiving golf course effluent demonstrated that nutrient concentrations as low as 50 to 100 µg nitrate N L−1 were capable of causing significant phytoplankton biomass increases. Nitrate levels in the outflow streams were at or above concentrations causing significant increases in phytoplankton biomass in our bioassay experiments. These coastal creeks host spring and summer algal blooms; thus, some golf course discharge nutrient concentrations are at levels great enough to contribute to eutrophication problems in estuarine waters. Vegetated buffer zones, wet detention ponds, and wooded wetland areas led to considerably lower nutrient output than sites lacking such management practices and should be used whenever possible to protect nutrient‐sensitive receiving waters.
Herbicide Application Method Effects on Napropamide Complexation with Dissolved Organic Matter
Authors: Nelson S. D. , Letey J. , Farmer W. J. , Williams C. F. , Ben‐Hur M. 
Published: July 2010

AbstractNapropamide [2‐(α‐naphthoxy)‐N,N‐diethyl propionamide] has been shown to form soluble complexes with dissolved organic matter (DOM). Batch equilibrium and soil column leaching studies were performed to evaluate the effect of a drying event following herbicide application on napropamide‐DOM complex formation. Napropamide was applied directly to the soil and allowed to dry and compared with studies where the herbicide was not allowed to dry. In batch studies the presence of napropamide‐DOM complexes was inferred from reduced sorption coefficients measured on extracts of treated soils as compared with those from aqueous solutions. In column studies, drying was shown to induce herbicide movement with the wetting front even when preferential flow pathways were eliminated. The formation of napropamide‐DOM complexes was verified by dialysis tubing techniques. Increased napropamide movement through soil was the result of stable napropamide‐DOM complexes that lacked an adsorption affinity. Although less than 6% of the total herbicide applied moved by facilitated transport, this amount of rapidly mobile pesticide could significantly increase the potential for ground water contamination. Results suggest that preventing the applied herbicide solution from drying before irrigation could reduce or eliminate the threat of facilitated transport of napropamide by DOM. We suggest that a short irrigation period after herbicide application could allow for herbicide movement beyond the soil surface to deter drying while preventing deep movement of pesticide with the water front.
Water Dynamics and Nutrient Leaching through a Cropped Ferralsol in the Loyalty Islands (New Caledonia)
Authors: Duwig Céline , Becquer Thierry , Vogeler Iris , Vauclin Michel , Clothier Brent E. 
Published: July 2010

AbstractOn the South Pacific islands, the change from traditional to more intensive agricultural practices is leading to more fertilizer use, both extensively and intensively. Nutrient leaching should be minimized to avoid plant deficiencies and ground water pollution. The fate of nitrate and potassium under corn (Lea mays L.) and perennial grass (Rhodes grass, Chloris gayana Kunth.) was monitored during three wet seasons on a Ferralsol soil from Mare in the Loyalty Islands. In 1995,130 and 41% of the applied NO−3 and K+, respectively, leached beyond the root zone. Split application of the fertilizers in 1996 decreased the amounts leached to 48 and 11%, respectively. This reduction occurred even though the rainfall nearly doubled from 1995 to 1996. Nitrate and potassium transport, however, can be decreased due to their retention by this Ferralsol. Nitrate can be adsorbed on the positively charged surface of aluminum and ferric oxides. Due to the rapid drainage under tropical rainfall, however, this phenomenon is not very effective. Potassium is usually tightly fixed on 2:1 clay minerals, but these are nonexistent in our soil. Potassium also is bound to humic substances and the organic matter reaches 15% in the subsoil of this Ferralsol. Leaching of K+ was retarded compared with NO−3, but was still quite high compared with others studies on tropical soils.
Characterizing Kinetics of Sequential Selenium Transformation in Soil
Authors: Guo Lei , Jury William A. , Frankenberger William T. , Zhang YiQiang 
Published: July 2010

AbstractThe speciation of selenium (Se) in a Hanford sandy loam was measured as a function of time at two soil water contents under aerobic and anaerobic conditions to evaluate the kinetics of selenium transformation. The stepwise reaction coefficients describing sequential selenium transformation were determined using an inverse method based on a five‐compartment model that included selenate, selenite, elemental Se, organic Se, and gaseous Se as the major Se species (or fractions). Transformation of Se was less affected by soil water content at ≥21.5%, but was distinctively faster under anaerobic conditions where O2 was displaced with N2 gas. During the incubation period of 49 to 52 d, between 27.9 and 74.9% of the total selenium, initially present as selenate, was reduced to elemental or organic Se species. Although volatilization of Se required a reduced precursor, the rate of volatilization was not correlated to the rate of reduction. No volatilization of Se was detected under anaerobic conditions, suggesting that O2 was a critical factor controlling the methylation of Se, the reaction that converts nonvolatile Se species into gaseous forms.
Selenium Volatilization from a Soil—Plant System for the Remediation of Contaminated Water and Soil in the San Joaquin Valley
Authors: Lin Z.‐Q. , Schemenauer R. S. , Cervinka V. , Zayed A. , Lee A. , Terry N. 
Published: July 2010

AbstractSelenium (Se) contamination of agricultural drainage water is a major environmental problem facing California agriculture. To demonstrate the potential effectiveness of biological volatilization in removing Se from contaminated water and soil, Se volatilization was determined under field conditions from a soil—plant (Salicornia bigelovii Torr.) treatment system in the San Joaquin Valley, California. Volatile Se was collected using an open‐flow sampling chamber system, biweekly during the S. bigelovii growing season from February to September 1997, and monthly from September 1997 to January 1998. The rate of Se volatilization fluctuated under different field conditions during the study year, with an overall mean of 155 ± 25 µg Se m−2 d−1. Biological volatilization removed 62 mg Se m−2 yr−1, which accounted for 6.5% of the annual total Se input (958 mg Se m−2 yr−1) to the S. bigelovii field. Forward trajectory analysis showed that the air mass that passed through the research area generally moved quickly out of the San Joaquin Valley within the first 24 h, probably transporting airborne Se from the research site toward the eastern Sierra Nevada in spring and fall, the southern mountainous areas in summer, and the Coast Mountain region in winter. This study suggests that biovolatilization represents an environmentally sound technology for managing Se‐contaminated soil and agricultural drainage water. Future research will focus on establishing new means for enhancing Se volatilization in the field.
Movement of Bromide, Nitrogen‐15, and Atrazine through Flooded Soils
Authors: Kelly Walton R. , Wilson Steven D. 
Published: July 2010

AbstractIn order to study the movement of agrichemicals in a flooded system under controlled conditions, we performed two tracer tests on a 3‐ by 8‐m plot that was deliberately flooded twice during the study: once in fall 1996 and again in fall 1997. Each test was monitored through the summer following flooding. Hydraulic head data continuously collected while the site was flooded indicate that a downward vertical hydraulic gradient predominated throughout the entire depth monitored (4.5 m), although there was also a horizontal gradient. Atrazine, bromide, and nitrate enriched in 15N were sprayed at the surface in the center of the plot prior to each flooding. Water samples were taken from multi‐level samplers to depths up to 4.6 m for tracer analysis seven times throughout the flooding cycle. The atrazine, bromide, and 15N moved rapidly after flooding, in a nearly vertical direction, greater than 4.5 m in less than 24 h. After 24 h, concentrations of the three applied chemicals decreased with time, 15N most rapidly and atrazine least rapidly. Most of the atrazine (65%) remained bound in the top 50 cm of soil, but the rapid movement of the dissolved atrazine indicates the potential for ground water contamination when flood events coincide with atrazine presence in soils. The presence of dissolved sulfide indicated suboxic conditions in the submerged soil, which were conducive to denitrification reactions, thus nitrate appears to be of less concern than atrazine.
Virus Transport through Saturated Sand Columns as Affected by Different Buffer Solutions
Authors: Chu Yanjie , Jin Yan , Yates Marylynn V. 
Published: July 2010

AbstractTo accurately examine the mechanisms that control virus retention and transport in porous media, it is essential to perform experiments under environmentally relevant conditions. Laboratory studies of virus transport are generally conducted using buffered solutions. However, there are no standards for the concentration and composition of the solution, making comparisons between different studies difficult. Our objective was to systematically investigate the effects of the ionic strength and composition of buffer solutions on adsorption of viruses during transport through saturated sand columns. Two phosphate buffered saline solutions (PBS and PBS2) and one artificial ground water (AGW) were used and experiments were conducted under saturated, steady state flow conditions. Bromide tracer and bacteriophages φX174 and MS‐2 were introduced into saturated sand columns as step inputs and their concentrations in the outflow samples were determined. Change in ionic strength did not affect the behavior of φX174, whereas MS‐2 was largely removed in the high ionic strength PBS buffer (0.16 M) but moved through the columns in the low ionic strength PBS2 and AGW buffers (0.002 2M). An additional experiment conducted under an ionic strength gradient (from 0.002 to 0.2 M) using PBS indicated that the outflow concentration of MS‐2 decreased slowly from an ionic strength of ∼0.03 M, reached a minimum at an apparent critical value of ∼0.1 M, and then increased gradually. This study also suggests that metals or metal oxides on sand surfaces can cause significant virus removal under high ionic strength conditions.
Watershed‐Level Uncertainties: Implications for Phosphorus Management and Eutrophication
Authors: Hession W. C. , Storm D. E. 
Published: July 2010

AbstractEutrophication is often the critical problem associated with surface waters having impaired water quality. Managing eutrophication in lakes and reservoirs typically involves the control of phosphorus inputs since it is often the limiting nutrient and because nitrogen and carbon are difficult to control. Management activities to address water quality impairment require a watershed‐level approach. However, uncertainty and stochasticity are ubiquitous in watershed‐level assessment and management. We describe and demonstrate a method for incorporating uncertainty analyses in watershed‐level modeling using Wister Lake in Oklahoma as an example. Natural stochasticity, parameter error, and error due to aggregation of data are quantified separately to allow for a comparison of the various sources of uncertainty in modeling activities. Parameter error was found to be the greatest contributor to overall output uncertainty. Several example management scenarios are presented to illustrate the utility and flexibility of including uncertainty quantification in watershed‐level management and decision making.
Fecal Bacteria in the Waters of an Upland Area in Derbyshire, England: The Influence of Agricultural Land Use
Authors: Hunter Colin , Perkins Joy , Tranter Jamie , Hardwick Paul 
Published: July 2010

AbstractLong‐term data on the dynamics of sanitary indicator bacteria in fresh waters is limited. This paper provides a data record of fluctuations in fecal bacterial concentrations in the waters of an upland area of northern England that can be examined in relation to agricultural land use practices and standards for contact recreation. Concentrations of fecal coliforms (FCs) were monitored in the waters of semi‐improved sheep pasture on the edge of a limestone karst system in north Derbyshire, England for a 21‐mo period. Data were obtained for three small streams and six water inflows to streams, comprising the end points of shallow subsurface tile drainage networks and natural, semi‐permanent, channelized overland flows. All sites showed significant contamination by fecal indicator bacteria. A consistent pattern of seasonal FC concentration change was observed at all sites, with concentrations generally highest during the summer and lowest during the winter. This may be explained by land use factors, including higher summer sheep stocking densities and the application of farmyard manure and sewage sludge. Correlations between changes in bacterial concentration at inflow sites and downstream changes in streamwater concentration were generally highly significant, providing strong empirical evidence for the assumed causal relationship between inflow and streamwater quality. The degree of fecal bacterial contamination of the streams, particularly during summer months, may constitute a real health risk to recreational cavers using parts of the limestone karst system into which the streams drain.
Modeling of Sulfate Adsorption on Andisols for Implementation in the SAFE Model
Authors: Fumoto Tamon , Sverdrup Harald 
Published: July 2010

AbstractSulfate adsorption models were investigated in this study to simulate the pH dependence of SO2−4 and H+ adsorption on Andisols and thereby show the effects on acidification and recovery processes of Andisols. An extended constant capacitance model (ECCM), which assumed protonation of surface ‐OH groups and outer‐sphere complexation of SO2−4, proved valid to simulate SO2−4 and H+ adsorption on Andisols when evaluated using batch experiment data of SO2−4 and base cation adsorption at pH 4 to 5 and low ionic strengths. According to the ECCM calculation, SO2−4 adsorption was reproduced by an empirical equation using SO2−4 and H+ concentrations and H+ adsorption was approximated by another empirical equation using pH and SO2−4 adsorption. Since these two empirical equations are quite simple, they will be an efficient SO2−4 adsorption submodel in SAFE, the dynamic soil chemistry model to simulate the soil acidification and recovery processes.
Asymmetrical Distribution and Dissipation of Band‐Applied Atrazine in Soil
Authors: Dowdy R. H. , Dolan M. S. , Lamb J. A. , Koskinen W. C. 
Published: July 2010

AbstractMovement of herbicides, particularly atrazine [2‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], is of great interest, as farming systems are designed to protect water quality. The effects of time and precipitation on the distribution of atrazine banded over corn (Zea mays L.) rows were measured for 2 yr in a ridge‐tillage corn‐soybean [Glycine max (L.) Merr.] rotation. The soil was a Zimmerman fine sand (mixed, frigid Lamellic Udipsamment). During the growing season, soil atrazine was determined at 0.1‐m horizontal intervals perpendicular to the row to a depth of 0.3 m. Within the first 22 days after treatment (DAT), atrazine concentrations decreased 65% in the application zone and had not leached below 0.075 m. A 60‐mm rain between 22 and 29 DAT first moved atrazine into the 0.075‐ to 0.15‐m depth increment. By 60 DAT and 240 mm of accumulated rain, atrazine concentrations had decreased by an estimated 90% in the zone of application. Atrazine movement appeared to be greater on the windward side of the row. An estimated 98% of applied atrazine was dissipated by the end of the first growing season and by the end of the second year, detections of residual atrazine were very limited and confined to the zone directly below the treated area. Significant horizontal movement of atrazine was never observed. Atrazine was not detected in soil samples below 0.6 m to a depth of 2.4 m.