bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial Reduction of Structural Iron in Clays—A Renewable Source of Reduction Capacity
Authors: Ernstsen Vibeke , Gates Will P. , Stucki Joseph W. 
Published: July 2010

AbstractThe ability of microorganisms to reduce structural Fe in minerals has become recognized as an important mechanism in the oxidation of pollutants in soils and sediments. To better understand the factors controlling the concentration of Fe(II) in natural deposits, samples of clayey till from sites near Havrebjerg and Sparresholm, Denmark, were incubated for up to 160 d with a combination of Pseudomonas bacteria strains. These strains were previously shown to reduce structural Fe(III) to Fe(II) in smectites. According to Eh, pH, microbial activity, and structural Fe(II) content, the incubation could be separated into four phases of which the second phase (from 4 to 10 d after inoculation) generated the most structural Fe(II). Microbial activity increased the structural Fe(II) content from approximately 10% to 20–34% of total clay Fe, a lower level than that obtained for chemically reduced subsamples (76–79%), but more similar to values typical of unweathered tills of Denmark (about 50%). In addition to microbial activity, the particle size (fine or coarse clay) and the Fe(II) content of the clay minerals prior to incubation were very important factors affecting the extent of Fe reduction. The results indicate that structural Fe in clay minerals of clayey till is very reactive and can undergo extensive in situ redox cycling. Electron transfer to structural Fe(III) of the weathered, oxidized clay minerals may renew natural redox barriers in imperfectly drained soils and sediments and thereby control geochemical processes.
Enhanced Sorption of Organic Contaminants by Smectitic Soils Modified with a Cationic Surfactant
Authors: Sheng Guangyao , Wang Xiaorong , Wu Shunnian , Boyd Stephen A. 
Published: July 2010

AbstractSoils, subsoils, and aquifer materials can be modified with hydrophobic cationic surfactants to increase their sorptive capabilities for organic contaminants. In this study, we evaluated the adsorption/desorption of hexadecyltrimethylammonium (HDTMA) by smectitic soils, and the sorptive characteristics of the resultant organo‐modified soils for trichloroethylene and chlorobenzene. Adsorption of HDTMA with loading levels up to 70% of the cation exchange capacity (0.70 CEC) was nearly quantitative and resulted in an equivalent release of Ca2+ from the soils, indicating ion exchange as the sole mechanism over this range. At higher loadings, HDTMA is adsorbed by both ion exchange and hydrophobic bonding. The selectivity coefficients for HDTMA replacing Ca2+ were very high (109 −107 between 0.1 and 0.8 CEC), indicating the high chemical stability of HDTMA‐soil complexes at these loadings. Desorption is more significant for HDTMA adsorbed via hydrophobic bonding than via ion exchange. Sorption coefficients for trichloroethylene and chlorobenzene on HDTMA‐modified soils (0.7 CEC) were 20 to 60 and 100 to 350 times higher, respectively, than those on the corresponding unmodified soils. The HDTMA derived phase was 10 to 30 and 80 to 160 times more effective than natural soil organic matter (on a unit mass basis) as a sorptive phase for trichloroethylene and chlorobenzene, respectively. A synergistic effect on sorption of trichloroethylene and chlorobenzene in binary solute systems was observed. The sorptive characteristics of HDTMA modified smectitic soils for organic contaminants are similar to those of pure HDTMA‐smectites.
Quantification and Remediation of Pesticides in Runoff Water from Containerized Plant Production
Authors: Briggs J. A. , Riley M. B. , Whitwell T. 
Published: July 2010

AbstractDuring containerized plant production pesticides may move from application site in runoff water created by overhead irrigation systems. In this study, four pesticides, isoxaben {N‐[3‐(1‐ethyl‐1‐methylpropyl)‐5‐isoxazolyl]‐2,6‐dimethoxybenzamide}, trifluralin {(2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline}, chlorpyrifos {O,O‐diethyl O‐3,5,6‐trichloro‐2‐pyridyl phosphorothioate) and thiophanate‐methyl {dimethyl 4,4−‐o‐phenylene bis(3‐thioallophanate), were applied at a commercial plant nursery. Overhead irrigation after application generated runoff water which was channeled into waterways of clay/gravel or hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy]. Isoxaben was detected in runoff water through 4 d after application (DAA). Other pesticides were detected primarily on the day of application (DOA). Thirteen percent of applied thiophanate‐methyl was recovered from the clay/gravel waterway and 11% from the grass waterway. Total amounts of isoxaben lost were 23% of total applied in both treatments. Less than 0.01% of applied chlorpyrifos and trifluralin were detected. Isoxaben amounts recovered from the grassed waterway on the DOA were 16% lower than from the clay/gravel treatment. Thiophanate‐methyl amounts were 18% lower from the grassed treatment on the DOA. The results suggest that vegetated waterways can reduce pesticide losses from application site in runoff water.
Heavy Metal Balances of an Italian Soil as Affected by Sewage Sludge and Bordeaux Mixture Applications
Authors: Moolenaar S.W. , Beltrami P. 
Published: July 2010

AbstractApplications of sewage sludge and Bordeaux mixture (Bm) (a mixture of copper sulfate and lime) add heavy metals to the soil. At an experimental farm in the Cremona district (Italy), we measured current heavy metal contents in soil and their removal via harvested products. We also measured heavy metal adsorption by soil from this farm. With these data, projections were made of the long‐term development of heavy metal (Cd, Cu, and Zn) contents in soil, crop removal, and leaching at different application rates of sewage sludge and Bm. These projections were compared with existing quality standards of the European Union (EU) and Italy with regard to soil and groundwater. The calculations reveal that the permitted annual application rates of sewage sludge and Bm are likely to result in exceedance of groundwater and soil standards. Sewage sludge applications, complying with the Italian (I) legal limits, may pose problems for Cd, Cu, and Zn within 30, 70, and 100 yr, respectively. Furthermore, severe Cu pollution of integrated (mildew controlled by Bm and organopesticides) and especially organic (Bm only) vineyards is unavoidable with the currently allowed application rates of Bm. The results suggest that the current I soil protection policy as well as the EU policy are not conducive of a sustainable heavy metal management in agroecosystems.
Microbial Oxidation and Solubilization of Precipitated Elemental Selenium in Soil
Authors: Losi M. E. , Frankenberger W. T. 
Published: July 2010

AbstractOxidation of elemental selenium (Se0) leads to increased solubilizalion and enhanced bioavailability. In this work, laboratory microcosm experiments were conducted to study oxidation of Se0 in soil and liquid cultures. Major objectives were to examine the oxidation rates of four San Joaquin Valley, California soils, and to assess the contribution of biological vs. chemical processes. For these experiments, red, crystalline Se0 was prepared by both chemical and biological synthesis, and its presence was confirmed by synchrotron‐based x‐ray absorption spectroscopy. The amount of Se0 oxidized over 125 d was from 1 to 10% of Se0 in soils spiked to 250 mg Se0 kg−1 and approximately half that in soils spiked to 100 mg Se0 kg−1. First order rate constants for oxidation of Se0 were from 0.05 to 0.32 yr−1 and 0.04 to 0.39 yr−1 at 250 and 100 mg Se0 kg−1 soil, respectively. The amount of Se0 oxidized was generally correlated with prior exposure of the soil lo Se. Products included either selenite (SeO2−3), or both SeO2−3 and selenate (SeO2−4). Biotic processes were shown to be of major importance. Both heterotrophic and autotrophic oxidation were observed, and an inorganic C source (NaHCO3) was favored relative to glucose. This study demonstrates that Se0 oxidation in soils is largely biotic in nature, occurs at relatively slow rates and yields both SeO2−3 and SeO2−4.
Transport of Agrichemicals to Ground and Surface Water in a Small Central Indiana Watershed
Authors: Fenelon J. M. , Moore R. C. 
Published: July 2010

AbstractThe occurrence, distribution, concentrations, and pathways of agrichemicals in water were investigated in the Sugar Creek watershed, a poorly drained agricultural watershed typical of many watersheds in the midwestern USA. Water samples from Sugar Creek, two tile drains, and 11 wells along a groundwater flowpath to Sugar Creek were collected between May 1992 and August 1996 and analyzed for N and pesticide compounds. Nitrate was the principal N species and pesticides were common in alluvial water‐bearing units in the Sugar Creek floodplain. In the confined stratified drift aquifers, ammonia was the principal N species and pesticides were rare. Tile drains directly affected the water quality in Sugar Creek by transporting soil pore water and shallow groundwater containing high concentrations of nitrate (NO3) and pesticides to the creek. When tile drains were flowing (typically December through July), elevated NO3 concentrations (2–10 mg/L NO3N) in the creek correlated with high NO3 concentrations (2–23 mg/L NO3N) in tile drains discharging to the creek. Likewise, with concentrations of atrazine and atrazine metabolites, seasonal trends in the tile‐drain effluent were similar to seasonal trends in Sugar Creek. When tile drains went dry, NO3 concentrations in the creek were low, indicating most groundwater discharge to the creek consisted of old or denitrified water. Trace levels of pesticides in the creek at low flow probably were the result of seepage from alluvial water‐bearing units.
Impact of Nitrogen Management Practices on Nutritional Status and Yield of Valencia Orange Trees and Groundwater Nitrate
Authors: Alva A.K. , Paramasivam S. , Graham W.D. 
Published: July 2010

AbstractA field experiment was conducted using 36‐yr‐old Valencia orange trees (Citrus sinensis) planted in an Astatula fine sand (hyperthermic, uncoated, Typic Quartzipsamments) to evaluate the effects of two different N management practices on the mineral nutrition status of the trees, fruit yield and quality, and nitrate (NO−3) loading into groundwater. The N treatments included 180 kg ha−1 yr−1 as either (i) three broadcast applications per year of a combination of dry soluble form (DSF; 135 kg N ha−1 yr−1) and controlled‐release form (CRF; 45 kg ha−1 yr−1); or (ii) fertigation in 18 equally divided applications per year. Nitrate‐N was measured in groundwater sampled at 3‐wk intervals using four monitoring wells in each of the two blocks over 2 yr. Fruit yield was greater by 2.7 to 8.2 Mg ha−1 in the fertigation compared to that in the DSF/CRF broadcast treatment. Leaf nutrient concentrations or fruit quality parameters were not significantly influenced by the different N management treatments. Most of the leaf nutrients were within the recommended optimal ranges. Mean groundwater NO3‐N concentrations for the DSF/CRF treatment ranged from 6.5 to 16.5, and 9.4 to 14.1 mg L−1 during 1995 and 1996, respectively. The corresponding values for the fertigation treatment ranged from 7.0 to 14.6 and 1.4 to 6.9 mg L−1. Fertigation with 18 applications per year decreased NO3‐N loading into groundwater as compared to three broadcast applications of the same rate of N using DSF/CRF granular blend.
Effects of Controlled Drainage on Forest Water Quality
Authors: Amatya D. M. , Gilliam J. W. , Skaggs R. W. , Lebo M. E. , Campbell R. G. 
Published: July 2010

AbstractThe effects of controlled drainage (CD) on hydrology and water quality are presented for three eastern North Carolina watersheds in loblolly pine (Pinus taeda L.). Timing of CD treatments were: the spring fish recruitment period in the downstream estuary in one watershed, and the summer‐fall period to facilitate tree growth in another watershed. A third watershed was maintained under conventional drainage throughout the study. It was demonstrated that seasonal controlled drainage can reduce both the total drainage outflows and corresponding sediment and nutrient exports. For example, CD reduced drainage outflows by as much as 88% during the summer‐fall and 39% during the spring with annual average reduction of 20 to 25%. Annual average total phosphorus (TP) and ammonium‐nitrogen (NH4‐N) exports from watersheds under treatment were reduced by 7 to 72% as compared to the watershed under conventional drainage. For other nutrients and total suspended solids (TSS), concentrations were significantly different (α = 0.05) among the three watersheds during the winter when they were all under conventional drainage. This indicated characteristic differences unrelated to applied treatments. Taking these differences into account, the reductions in annual average export of TSS (up to 47%) and nitrate plus nitrite‐nitrogen (NO3+NO2‐N) (up to 16%), total Kjeldahl nitrogen (TKN) (up to 45%) and total organic carbon (TOC) (up to 33%) from watersheds under treatment were directly attributed to reduction in outflows. Even though CD appeared to have increased concentrations of some of the nutrients analyzed, except for NH4‐N, the applied treatments lowered the export of TSS and most nutrients measured. It is concluded that CD can be used to reduce TSS and nutrient exports from pine plantations, primarily through reduced drainage outflows.
Predicting Stream Pathogen Loading from Livestock using a Geographical Information System‐Based Delivery Model
Authors: Fraser Robert H. , Barten Paul K. , Pinney David A. K. 
Published: July 2010

AbstractRecent cases of drinking water contamination by pathogens have underscored the importance of preventing livestock waste from entering surface waters. To this end, analytical tools are needed that can identify subwatersheds or livestock operations that contribute disproportionately to contamination. This paper presents a geographical information system (GIS)‐based transport model (SEDMOD) that provides an index of pathogen loading potential to streams by characterizing five key transport parameters: flow‐path hydraulic roughness, gradient, and slope shape, stream proximity, and a normalized soil moisture index. We applied SEDMOD to 12 subwatersheds (10 agricultural, 2 forested controls) of the Saw Kill, a tributary of the Hudson River, New York, and compared model predictions with measured fecal coliform (FC) levels. The transport model, combined with a livestock density GIS layer, could explain 50% of the variation in average FC discharge among the subwatersheds (r = 0.71, P = 0.01, n = 12). By contrast, neither total livestock FC output nor predicted FC transport were correlated with geometric mean FC concentration (P > 0.05). In a multiple regression, predicted FC transport, mean water temperature, and mean turbidity could account for 80% of the observed variation in FC discharge (r = 0.90, P = 0.001, n = 12). We conclude that, although more field work and algorithm development is needed to yield more accurate quantitative predictions, the model is useful for predicting the relative contribution of diverse livestock operations within a varied landscape. This provides watershed managers and regulators with a rating method to prioritize sites for nonpoint source pollution control.
Sulfate Reduction in Freshwater Wetland Soils and the Effects of Sulfate and Substrate Loading
Authors: Feng Jinan , Hsieh Yuch Ping 
Published: July 2010

AbstractElevated sulfate and organic C loadings in freshwater wetlands could stimulate dissimilatory sulfate reduction that oxidizes organic C, produces hydrogen sulfide and alkalinity, and sequesters trace metals. We determined the extent of sulfate reduction in two freshwater wetland soils, that is, black gum (Nyssa biflona) swamp soils and titi (Cliftonia monophylla) swamp soils, in northern Florida. We also investigated the potential of sulfate reduction in the wetland soils by adding sulfate, organic substrate, and lime. Sulfate reduction was found to be an active process in both swamp soils without any amendment, where the pore water pH was as low as 3.6 and sulfate concentration was as low as 5 mg L−1. Without amendment, 11 to 14% of organic C was oxidized through sulfate reduction in the swamp soils. Sulfate loading, liming, and substrate addition significantly increased sulfate reduction in the black gum swamp soil, but none of those treatments increase sulfate reduction in the titi swamp soil. The limiting factor for sulfate reduction in the titi swamp soil were likely texture and soil aggregate related properties. The results suggested that wastewater loading may increase sulfate reduction in some freshwater wetlands such as the black swamps while it has no stimulating effect on other wetlands such as the titi swamps.
Nutrient Retention by Multipond Systems: Mechanisms for the Control of Nonpoint Source Pollution
Authors: Yan Weijin , Yin Chengqing , Tang Hongxiao 
Published: July 2010

AbstractThe processes of the multipond system in an experimental agricultural watershed located in southeastern China were studied during a 2‐yr period (1994–1995), with the purpose of the research being the reduction of nonpoint nutrient pollution at its sources. The mechanisms studied included water storage capacity, sedimentation, denitrification, and removal of nutrients by the harvest of macrophytes from ponds and ditches. The results showed that the retention of both water and nutrients depended on the water storage capacity of the ponds, the total pond volume, rainfall, surface runoff, and irrigation amounts. For the years of 1994 and 1995, the water retention rate was 85.5%, while the nutrient retention rate reached 98.1 and 97.8% for total N (TN) and total P (TP), respectively. Sediment deposit was another important mechanism. The average sedimentation rate was 30.0 mm yr−1 (from 1985–1995). For the whole multipond system (35 ha), the average retention amounts reached 9800 kg of N and 2800 kg of P by sediment accumulation per year. The results demonstrated that denitrification in ponds and ditches was an important mechanism for removing N from the watershed. The highest possible rate was more than 0.17 mg N g−1 soil during the summer season. The results suggested that the multipond system, which kept water in balance, benefited the water, nutrient, and sediment recycling in the terrestrial ecosystem, as well as helped to reduce agricultural nonpoint pollution at its sources. Therefore, the multipond system, with its low cost in construction and maintenance, is recommended as a good practice both for the control of nonpoint pollution at its sources and for sustainable agricultural development.
The Impact of Pesticide Use on Groundwater in North Carolina
Authors: Wade Henry F. , York Alan C. , Morey A. Elizabeth , Padmore Joel M. , Rudo Kenneth M. 
Published: July 2010

AbstractA North Carolina study revealed that certain pesticides have impacted groundwater above health‐based standards in vulnerable areas. Ninety‐seven shallow, surficial aquifer‐monitoring wells were sampled at least twice. Sites for the monitoring wells were chosen based on an evaluation with the Pesticide DRASTIC model and a known record of pesticide use. Where possible, areas of greater risk were intentionally selected. Twenty‐three pesticides or pesticide degradates were detected in 26 of the 97 wells. Nine of the pesticides or degradates are no longer registered for use; two of these chemicals, dibromochloropropane and methylene chloride, were found in excess of health‐based guidance levels (HBGL) or state groundwater quality standards (GWQS). Of the registered pesticides or their degradates, the herbicides dichlorprop and simazine and the insecticide isomers BHC‐alpha and BHC‐delta were in excess of HBGL. The herbicide atrazine was detected at 83% of its GWQS. The U.S. Environmental Protection Agency (USEPA) Pesticides and Groundwater State Management Plans will be required for atrazine and simazine to be sold and used, which will provide additional protection to public health and the environment. Pesticide DRASTIC ratings or soil‐leaching potential values and the proportion of wells were unrelated to pesticide detections.
Mercury Speciation in Floodplain Soils and Sediments along a Contaminated River Transect
Authors: Wallschläger Dirk , Desai Madhukar V. M. , Spengler Markus , Wilken Rolf‐Dieter 
Published: July 2010

AbstractA novel mercury‐specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg‐contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesting low availability. However, distinct differences between Hg speciation in the floodplain soils and sediments were also discovered. Mercury deposited in the floodplains shows speciation patterns that indicate stronger fixation compared with Hg in the sediments. This difference is attributed to the association of Hg with larger quantities of OM, which presumably also has higher molecular weight (MW). By comparison, Hg in the sediments was distributed among weaker binding forms, which are more likely to liberate Hg. Particularly, sediments showed a total lack of sulfidic binding forms for Hg. Pronounced geographical trends were detected in the Hg speciation along the river transect, with a general downstream shift from weaker to stronger binding forms, probably due to increased association with OM. These studies indicate that Hg speciation in riverine ecosystems is dynamic and reflects the chemical mechanisms underlying (bio)geochemical processes like distribution and transport.
Surface Complexation Modeling of Phosphate Adsorption by Water Treatment Residual
Authors: Butkus Michael A. , Grasso Domenico , Schulthess Cristian P. , Wijnja Hotze 
Published: July 2010

AbstractUse of water treatment plant residuals (WTR), as a soil amendment is a promising alternative to landfill disposal. Unfortunately, WTR has a propensity to bind with phosphate, which is an important plant nutrient. Phosphate may be added to WTR prior to soil application. This type of pretreatment may convert WTR from a phosphate consumer to a phosphate supplier. The binding of phosphate to WTR is typically attributed to surface complexation with metal oxides. However, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) data and phosphate‐WTR adsorption equilibrium data indicate that phosphate also binds to a cationic polyelectrolyte that is added during water treatment processes. Using the FITEQL optimization program, equilibrium constants and total number of surface sites were determined for the polymer. Results from the FITEQL optimization were used to model binding of phosphate by cationic polymer. Binding of phosphate by hydrous ferric oxide was modeled using a diffuse double layer model, which included surface precipitation (MICROQL). The model was validated through the use of phosphate equilibrium partitioning data at pH values of 6 and 8. The model predicted that a significant fraction of phosphate adsorbed onto WTR is associated with the cationic polymer.