bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil‐to‐Root Transfer and Translocation of Polycyclic Aromatic Hydrocarbons by Vegetables Grown on Industrial Contaminated Soils
Authors: Fismes Joëlle , Perrin‐Ganier Corinne , Empereur‐Bissonnet Pascal , Morel Jean Louis
Published: June 2010

Polycyclic aromatic hydrocarbons (PAHs) are possible contaminants in some former industrial sites, representing a potential risk to human health if these sites are converted to residential areas. This work was conducted to determine whether PAHs present in contaminated soils are transferred to edible parts of selected vegetables. Soils were sampled from a former gasworks and a private garden, exhibiting a range of PAH concentrations (4 to 53 to 172 to 1263 and 2526 mg PAHs kg−1 of dry soil), and pot experiments were conducted in a greenhouse with lettuce (Lactuca sativa L. var. Reine de Mai), potato (Solanum tuberosum L. var. Belle de Fontenay), and carrot (Daucus carota L. var. Nantaise). At harvest, above‐ and belowground biomass were determined and the PAH concentrations in soil were measured. In parallel, plates were placed in the greenhouse to estimate the average PAH‐dust deposition. Results showed that the presence of PAHs in soils had no detrimental effect on plant growth. Polycyclic aromatic hydrocarbons were detected in all plants grown in contaminated soils. However, their concentration was low compared with the initial soil concentration, and the bioconcentration factors were low (i.e., ranging from 13.4 × 10−4 in potato and carrot pulp to 2 × 10−2 in potato and carrot leaves). Except in peeled potatoes, the PAH concentration in vegetables increased with the PAH concentration in soils. The PAH distribution profiles in plant tissues and in soils suggested that root uptake was the main pathway for high molecular weight PAHs. On the opposite, lower molecular weight PAHs were probably taken up from the atmosphere through the leaves as well as by roots.
Arsenic Accumulation in the Hyperaccumulator Chinese Brake and Its Utilization Potential for Phytoremediation
Authors: Tu Cong , Ma Lena Q. , Bondada Bhaskar
Published: June 2010

The unique property of arsenic hyperaccumulation by the newly discovered Chinese brake (Pteris vittata L.) fern is of great significance in the phytoremediation of arsenic‐contaminated soils. The objectives of this study were to (i) examine arsenic accumulation characterized by its distribution pattern in Chinese brake, and (ii) assess the phytoextraction potential of the plant. Young ferns with five or six fronds were transferred to an arsenic‐contaminated soil containing 98 mg As kg−1 and grown for 20 wk in a greenhouse. At harvest, the Chinese brake produced a total dry biomass of 18 g plant−1 Arsenic concentration in the fronds was 6000 mg kg−1 dry mass after 8 wk of transplanting, and it increased to 7230 mg kg−1 after 20 wk with a bioconcentration factor (ratio of plant arsenic concentration to water‐soluble arsenic in soil) of 1450 and a translocation factor (ratio of arsenic concentration in shoot to that in root) of 24. The arsenic concentrations increased as the fronds aged, with the old fronds accumulating as much as 13 800 mg As kg−1 Most (approximately 90%) of the arsenic taken up by the Chinese brake was transported to the fronds, with the lowest arsenic concentrations in roots. About 26% of the initial soil arsenic was removed by the plant after 20 wk of transplanting. Our data suggest that the arsenic hyperaccumulating property of the Chinese brake could be exploited on a large scale to remediate arsenic contaminated soils.
Export of Manure Phosphorus and Nitrogen in Turfgrass Sod
Authors: Vietor D. M. , Griffith E. N. , White R. H. , Provin T. L. , Muir J. P. , Read J. C.
Published: June 2010

Regulatory mandates have increased demand for best management practices (BMPs) that will reduce nutrient loading on watersheds impaired by excess manure P and N. Export of manure P and N in turfgrass sod harvests is one BMP under consideration. This study quantified amounts and percentages of P and N removed in a sod harvest for different rates of manure and inorganic P and N. Six treatments comprised an unfertilized control, two manure rates with and without supplemental inorganic N, and inorganic P and N only. The treatments were applied to ‘Tifway’ bermudagrass (Cynodon dactylonL. ×C. transvaalensisBurtt‐Davey), ‘609’ buffalograss [Buchloe dactyloides(Nutt.) Engelm.], and ‘Reveille’ bluegrass (Poa arachniferaTorr. ×P. pratensisL.) under field conditions. Comparisons among treatments revealed small variations of P and N content in clippings and the plant component of sod, but large variations in the soil component of sod for each turf species. In addition, 2 to 10 times more P and 1.3 to 5 times more N was removed in soil than in plant components of sod for the two manure rates with and without added inorganic N. Percentages of applied P and N in harvested sod were similar for the two manure rates with and without added N for each species, but differed among turf species for each P (46 to 77%) and N (36 to 47%). The large amounts and percentages of manure P and N removed by sod harvest support the feasibility of this BMP in efforts to reduce nutrient loads on watersheds.
Environmental and Agronomic Implications of Water Table and Nitrogen Fertilization Management
Authors: Elmi Abdirashid A. , Madramootoo Chandra , Egeh Mohamud , Liu Aiguo , Hamel Chantal
Published: June 2010

Nitrate (NO−3) pollution of surface and subsurface waters has become a major problem in agricultural ecosystems. Field trials were conducted from 1996 to 1998 at St‐Emmanuel, Quebec, Canada, to investigate the combined effects of water table management (WTM) and nitrogen (N) fertilization on soil NO−3 level, denitrification rate, and corn (Zea mays L.) grain yield. Treatments consisted of a combination of two water table treatments: free drainage (FD) with open drains at a 1.0‐m depth from the soil surface and subirrigation (SI) with a design water table of 0.6 m below the soil surface, and two N fertilizer (ammonium nitrate) rates: 120 kg N ha−1 (N120) and 200 kg N ha−1 (N200). Compared with FD, SI reduced NO−3–N concentrations in the soil profile by 37% in spring 1997 and 2% in spring 1998; and by 45% in fall 1997 and 19% in fall 1998 (1 mg NO−3–N L−1 equals approximately 4.43 mg NO−3 L−1). The higher rate of N fertilization resulted in greater levels of NO−3–N in the soil solution. Denitrification rates were higher in SI than in FD plots, but were unaffected by N rate. The N200 rate produced higher yields than N120 in 1996 and 1997, but not 1998. Corn yields in SI plots were 7% higher than FD plots in 1996 and 3% higher in 1997, but 25% lower in 1998 because the SI system was unable to drain the unusually heavy June rains, resulting in waterlogging. These findings suggest that SI can be used as an economical means of reducing NO−3 pollution without compromising crop yields during normal growing seasons.
Lead Phytoextraction from Contaminated Soil with High‐Biomass Plant Species
Authors: Shen Zhen‐Guo , Li Xiang‐Dong , Wang Chun‐Chun , Chen Huai‐Man , Chua Hong
Published: June 2010

In this study, cabbage [Brassica rapa L. subsp. chinensis (L.) Hanelt cv. Xinza No 1], mung bean [Vigna radiata (L.) R. Wilczek var. radiata cv. VC‐3762], and wheat (Triticum aestivum L. cv. Altas 66) were grown in Pb‐contaminated soils. Application of ethylenediaminetetraacetic acid (EDTA) (3.0 mmol of EDTA/kg soil) to the soil significantly increased the concentrations of Pb in the shoots and roots of all the plants. Lead concentrations in the cabbage shoots reached 5010 and 4620 mg/kg dry matter on Days 7 and 14 after EDTA application, respectively. EDTA was the best in solubilizing soil‐bound Pb and enhancing Pb accumulation in the cabbage shoots among various chelates (EDTA, diethylenetriaminepentaacetic acid [DTPA], hydroxyethylenediaminetriacetic acid [HEDTA], nitrilotriacetic acid [NTA], and citric acid). Results of the sequential chemical extraction of soil samples showed that the Pb concentrations in the carbonate–specifically adsorbed and Fe–Mn oxide phases were significantly decreased after EDTA treatment. The results indicated that EDTA solubilized Pb mainly from these two phases in the soil. The relative efficiency of EDTA enhancing Pb accumulation in shoots (defined as the ratio of shoot Pb concentration to EDTA concentration applied) was highest when 1.5 or 3.0 mmol EDTA/kg soil was used. Application of EDTA in three separate doses was most effective in enhancing the accumulation of Pb in cabbage shoots and decreased mobility of Pb in soil compared with one‐ and two‐dose application methods. This approach could help to minimize the amount of chelate applied in the field and to reduce the potential risk of soluble Pb movement into ground water.
Impacts of Golf Courses on Macroinvertebrate Community Structure in Precambrian Shield Streams
Authors: Winter Jennifer G. , Somers Keith M. , Dillon Peter J. , Paterson Carolyn , Reid Ron A.
Published: June 2010

The influence of golf course operation on benthic macroinvertebrate communities in Precambrian Shield streams was evaluated using rapid bioassessment and the reference condition approach. Streams were sampled for water chemistry and invertebrates in 1999 and 2000, six on operational golf courses, and seven in forested reference locations. Correspondence analysis (CA) was used to determine the major patterns in the macroinvertebrate taxa, and canonical correspondence analysis (CCA) was used to evaluate relationships with environmental variables. The reference streams were used to define the normal range of variation for a variety of summary indices to evaluate the golf course streams. In all cases, golf course streams were higher in nutrients and dissolved ions and more alkaline than the forested reference streams. There was considerable variability in the macroinvertebrate fauna from the golf course streams, which was related to differences in golf course land management practices and to the potential influence of highway runoff. Of the management practices evaluated, fertilizer application rates in particular were important, as was the presence of ponds upstream on the course. Invertebrate taxa with higher abundances in golf course streams included Turbellaria, Isopoda, Amphipoda, Zygoptera, and Trombidiformes. Taxa more common in the reference streams included Ephemeroptera, Megaloptera, Culicidae, and Plecoptera. There were marked differences in the overall benthic macroinvertebrate community in three of the six golf course streams studied relative to the forested reference streams, suggesting that golf course land management on the Precambrian Shield can be associated with significant differences in macroinvertebrate community structure.
Effects of Prolonged Irrigation with Treated Municipal Effluent on Runoff Rate
Authors: Agassi M. , Tarchitzky J. , Keren R. , Chen Y. , Goldstein D. , Fizik E.
Published: June 2010

The use of domestic effluents for the irrigation of crops has been widespread in Israel for the past 30 years. The sodium adsorption ratio (SAR) of the standardized domestic effluents ranges between 4 and 6. According to the literature, when soils with SAR levels of 4 to 6 are exposed to direct raindrop impact they are subjected to enhanced aggregate disintegration, leading to sealing processes of the soil surface and subsequent increased runoff and soil erosion. However, these phenomena were not observed in the laboratory and field experiments of this study. On the other hand, a rapid decrease of the soil SAR to its initial values was observed, in laboratory and fieldwork, once the soil was subjected to a simulated rainstorm of distilled water (laboratory) or natural rainstorms (field plots). We can conclude that the process of SAR increase during irrigation with standardized effluent water is reversible. Further investigation in this direction can lead to recommendations regarding the necessary levels of domestic sewage water purification in correlation with soil types, climatic conditions, and hazards to tap water aquifers.
Denitrification Potential in Urban Riparian Zones
Authors: Groffman Peter M. , Crawford Marshall Kamau
Published: June 2010

Denitrification, the anaerobic microbial conversion of nitrate NO−3to nitrogen (N) gases, is an important process contributing to the ability of riparian zones to function as “sinks” for NO−3in watersheds. There has been little analysis of riparian zones in urban watersheds despite concerns about high NO−3concentrations in many urban streams. Vegetation and soils in urban ecosystems are often highly disturbed, and few studies have examined microbial processes like denitrification in these ecosystems. In this study, we measured denitrification potential and a suite of related microbial parameters (microbial biomass carbon [C] and N content, potential net N mineralization and nitrification, soil inorganic N pools) in four rural and four urban riparian zones in the Baltimore, MD metropolitan area. Two of the riparian zones were forested and two had herbaceous vegetation in each land use context. There were few differences between urban and rural and herbaceous and forest riparian zones, but variability was much higher in urban than rural sites. There were strong positive relationships between soil moisture and organic matter content and denitrification potential. Given the importance of surface runoff in urban watersheds, the high denitrification potential of the surface soils that we observed suggests that if surface runoff can be channeled through areas with high denitrification potential (e.g., stormwater detention basins with wetland vegetation), these areas could function as important NO−3sinks in urban watersheds.
Nitrous Oxide Emission and Denitrification in Chronically Nitrate‐Loaded Riparian Buffer Zones
Authors: Hefting Mariet M. , Bobbink Roland , de Caluwe Hannie
Published: June 2010

Riparian buffer zones are known to reduce diffuse N pollution of streams by removing and modifying N from agricultural runoff. Denitrification, often identified as the key N removal process, is also considered as a major source of the greenhouse gas nitrous oxide (N2O). The risks of high N2O emissions during nitrate mitigation and the environmental controls of emissions have been examined in relatively few riparian zones and the interactions between controls and emissions are still poorly understood. Our objectives were to assess the rates of N2O emission from riparian buffer zones that receive large loads of nitrate, and to evaluate various factors that are purported to control N emissions. Denitrification, nitrification, and N2O emissions were measured seasonally in grassland and forested buffer zones along first‐order streams in the Netherlands. Lateral nitrate loading rates were high, up to 470 g N m−2 yr−1 Nitrogen process rates were determined using flux chamber measurements and incubation experiments. Nitrous oxide emissions were found to be significantly higher in the forested (20 kg N ha−1 yr−1) compared with the grassland buffer zone (2–4 kg N ha−1 yr−1), whereas denitrification rates were not significantly different. Higher rates of N2O emissions in the forested buffer zone were associated with higher nitrate concentrations in the ground water. We conclude that N transformation by nitrate‐loaded buffer zones results in a significant increase of greenhouse gas emission. Considerable N2O fluxes measured in this study indicate that Intergovernmental Panel on Climate Change methodologies for quantifying indirect N2O emissions have to distinguish between agricultural uplands and riparian buffer zones in landscapes receiving large N inputs.
Chromate Reduction by Chromium‐Resistant Bacteria Isolated from Soils Contaminated with Dichromate
Authors: Camargo F. A. O. , Bento F. M. , Okeke B. C. , Frankenberger W. T.
Published: June 2010

Extensive use of hexavalent chromium [Cr(VI)] in various industrial applications has caused substantial environmental contamination. Chromium‐resistant bacteria isolated from soils can be used to remove toxic Cr(VI) from contaminated environments. This study was conducted to isolate chromium‐resistant bacteria from soils contaminated with dichromate and describes the effects of some environmental factors such as pH, temperature, and time on Cr(VI) reduction and resistance. We found that chromium‐resistant bacteria can tolerate 2500 mg L−1 Cr(VI), but most of the isolates tolerated and reduced Cr(VI) at concentrations lower than 1500 mg L−1 Chromate reduction activity of whole cells was detected in five isolates. Most of these isolates belong to the genus Bacillus as identified by the 16S rRNA gene sequencing. Maximal Cr(VI) reduction was observed at the optimum pH (7.0–9.0) and temperature (30°C) of growth. One bacterial isolate (Bacillus sp. ES 29) was able to aerobically reduce 90% of Cr(VI) in six hours. The Cr(VI) reduction activity of the whole cells of five isolates had a KM of 0.271 (2.61 mM) to 1.51 mg L−1 (14.50 mM) and a Vmax of 88.4 (14.17 nmol min−1) to 489 mg L−1 h−1 (78.36 nmol min−1). Our consortia and monocultures of these isolates can be useful for Cr(VI) detoxification at low and high concentrations in Cr(VI)‐contaminated environments and under a wide range of environmental conditions.
Soil Mixing to Decrease Surface Stratification of Phosphorus in Manured Soils
Authors: Sharpley Andrew N.
Published: June 2010

Continual applications of fertilizer and manure to permanent grassland or no‐till soils can lead to an accumulation of P at the surface, which in turn increases the potential for P loss in overland flow. To investigate the feasibility of redistributing surface stratified P within the soil profile by plowing, Mehlich‐3 P rich surface soils (128–961 mg kg−1in 0–5 cm) were incubated with lower‐P subsoil (16–119 mg kg−1in 5–20 cm) for 18 manured soils from Oklahoma and Pennsylvania that had received long‐term manure applications (60–150 kg P ha−1yr−1as dairy, poultry, or swine manure for up to 20 yr). After incubating a mixture of 5 g surface soil (0‐ to 5‐cm depth) and 15 g subsoil (5‐ to 20‐cm depth) for 28 d, Mehlich‐3 P decreased 66 to 90% as a function of the weighted mean Mehlich‐3 P of surface and subsoil (i.e., 1:3 ratio) (r2= 0.87). At Klingerstown, Northumberland County, south central Pennsylvania, a P‐stratified Berks soil (Typic Dystrochrept) (495 mg kg−1Mehlich‐3 P in 0‐ to 5‐cm depth) was chisel plowed to about 25 cm and orchardgrass (Dactylis glomerataL.) planted. Once grass was established and erosion minimized (about 20 wk after plowing and planting), total P concentration in overland flow during a 30‐min rainfall (6.5 cm h−1) was 1.79 mg L−1compared with 3.4 mg L−1before plowing, with dissolved P reduced from 2.9 to 0.3 mg L−1Plowing P‐stratified soils has the potential to decrease P loss in overland flow, as long as plowing‐induced erosion is minimized.
Phosphorus Runoff
Authors: Daverede I. C. , Kravchenko A. N. , Hoeft R. G. , Nafziger E. D. , Bullock D. G. , Warren J. J. , Gonzini L. C.
Published: June 2010

Continued inputs of fertilizer and manure in excess of crop requirements have led to a build‐up of soil phosphorus (P) levels and increased P runoff from agricultural soils. The objectives of this study were to determine the effects of two tillage practices (no‐till and chisel plow) and a range of soil P levels on the concentration and loads of dissolved reactive phosphorus (DRP), algal‐available phosphorus (AAP), and total phosphorus (TP) losses in runoff, and to evaluate the P loss immediately following tillage in the fall, and after six months, in the spring. Rain simulations were conducted on a Typic Argiudoll under a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation. Elapsed time after tillage (fall vs. spring) was not related to any form of P in runoff. No‐till runoff averaged 0.40 mg L−1 and 0.05 kg ha−1 DRP and chisel‐plow plots averaged 0.24 mg L−1 and 0.02 kg ha−1 DRP concentration and loads, respectively. The relationship between DRP and Bray P1 extraction values was approximated by a logistic function (S‐shaped curve) for no‐till plots and by a linear function for tilled plots. No significant differences were observed between tillage systems for TP and AAP in runoff. Bray P1 soil extraction values and sediment concentration in runoff were significantly related to the concentrations and amounts of AAP and TP in runoff. These results suggest that soil Bray P1 extraction values and runoff sediment concentration are two easily measured variables for adequate prediction of P runoff from agricultural fields.
Predicting Nitrate Leaching under Potato Crops Using Transfer Functions
Authors: Gasser M. O. , Caron J. , Lagacé R. , Laverdière M. R.
Published: June 2010

Nitrate leaching is a major issue in many cultivated soils. Models that predict the major processes involved at the field scale could be used to test and improve management practices. This study aims to evaluate a simple transfer function approach to predict nitrate leaching in sandy soils. A convective lognormal transfer (CLT) function is convoluted with functional equations simulating N mineralization, plant N uptake, N fertilizer dissolution, and nitrification at the soil surface to predict solute concentrations under potato (Solanum tuberosumL.) and barley (Hordeum vulgareL.) fields as a function of drainage water. Using this approach, nitrate flux concentrations measured in drainable lysimeters (1‐m soil depth) were reasonably predicted from 29 Apr. 1996 to 3 Dec. 1996. With average application rates of 16.9 g m−2of N fertilizer in potato crops, mean nitrate‐leaching losses measured under potato were 8.5 g N m−2Tuber N uptake averaged 9.7 g N m−2and soil mineral N at start (spring) and end (fall) of N mass balance averaged 1.7 and 4.5 g N m−2, respectively. Soil N mineralization was estimated by difference (4.3 g N m−2on average) and was small compared with N fertilization. Small nitrate flux concentrations at the beginning of the cropping season (May) resulted mainly from initial soil nitrate concentrations. Measured and predicted nitrate flux concentrations significantly increased at mid‐season (July–August) following important drainage events coupled with complete dissolution and nitrification of N fertilizers, and declining N uptake by potato plants. Decreases in nitrate concentrations before the end of year (November–December) underlined the predominant effect of N fertilizers applied for the most part at planting acting as a pulse input of solute.
Potential Environmental Benefits of Ionophores in Ruminant Diets
Authors: Tedeschi Luis Orlindo , Fox Danny Gene , Tylutki Thomas Paul
Published: June 2010

A concern of the USEPA is the volatilization of NH3 from animal manure and CH4 produced from ruminal fermentation. Excess N in the environment has been associated with adverse effects on human health, and CH4 and N2O emissions are sources of greenhouse gases. The objectives of this paper are to summarize and quantify the benefits of ionophores, principally monensin, in decreasing NH3 and CH4 emissions to the environment and reducing resource utilization in cattle (Bos spp.) production. The data indicate that monensin in the diets of ruminants may decrease protein degradation in the rumen and may increase feed protein utilization by an average of 3.5 percentage units. These changes would have an effect in reducing N losses and decreasing fecal N and the amount of protein that must be fed to meet animal requirements. Additionally, CH4 is produced by enteric fermentation in ruminants, which is responsible for about 33 to 39% of CH4 emissions from agriculture. Ionophores can reduce CH4 production by 25% and decrease feed intake by 4% without affecting animal performance. The inclusion of monensin in beef and dairy cattle diets may benefit air quality by reducing CH4 and N emissions and water quality by reducing N in manure, which can potentially leave the farm through leaching into ground water and through runoff into surface water.
In Situ Reduction of Chromium(VI) in Heavily Contaminated Soils through Organic Carbon Amendment
Authors: Tokunaga Tetsu K. , Wan Jiamin , Firestone Mary K. , Hazen Terry C. , Olson Keith R. , Herman Donald J. , Sutton Stephen R. , Lanzirotti Antonio
Published: June 2010

Chromium has become an important soil contaminant at many sites, and facilitating in situ reduction of toxic Cr(VI) to nontoxic Cr(III) is becoming an attractive remediation strategy. Acceleration of Cr(VI) reduction in soils by addition of organic carbon was tested in columns pretreated with solutions containing 1000 and 10 000 mg L−1Cr(VI) to evaluate potential in situ remediation of highly contaminated soils. Solutions containing 0, 800, or 4000 mg L−1organic carbon in the form of tryptic soy broth or lactate were diffused into the Cr(VI)‐contaminated soils. Changes in Cr oxidation state were monitored through periodic micro‐XANES analyses of soil columns. Effective first‐order reduction rate constants ranged from 1.4 × 10−8to 1.5 × 10−7s−1, with higher values obtained for lower levels of initial Cr(VI) and higher levels of organic carbon. Comparisons with sterile soils showed that microbially dependent processes were largely responsible for Cr(VI) reduction, except in the soils initially exposed to 10 000 mg L−1Cr(VI) solutions that receive little (800 mg L−1) or no organic carbon. However, the microbial populations (≤2.1 × 105g−1) in the viable soils are probably too low for direct enzymatic Cr(VI) reduction to be important. Thus, synergistic effects sustained in whole soil systems may have accounted for most of the observed reduction. These results show that acceleration of in situ Cr(VI) reduction with addition of organic carbon is possible in even heavily contaminated soils and suggest that microbially dependent reduction pathways can be dominant.
Evaluation of Water Treatment Sludge for Ameliorating Acid Mine Waste
Authors: Van Rensburg L. , Morgenthal T. L.
Published: June 2010

This study investigated the liming effect of water treatment sludge on acid mine spoils. The study was conducted with sludge from a water purification plant along the Vaal River catchments in South Africa. The optimum application rate for liming acid spoils and the speed and depth with which the sludge reacted with the mine waste were investigated. Chemical analysis indicated that the sludge is suitable as a liming agent because of its alkaline pH (8.08), high bicarbonate concentration (183.03 mg L−1), and low salinity (electrical conductivity = 76 mS m−1). The high cation exchange capacity of 15.47 cmolckg−1and elevated nitrate concentration (73.16 mg L−1) also increase its value as an ameliorative material. The soluble concentrations for manganese, aluminum, lead, and selenium were high at a pH of 5 although only selenium (0.83 mg L−1) warranted some concern. According to experimental results, the application of 10 Mg ha−1of sludge to acid gold tailings increased the leach water pH from 4.5 to more than 7.5 and also increased the medium pH from 2.4 to 7.5. The addition of sludge further reduced the solubility of iron, manganese, copper, and zinc in the ameliorated gold tailings, but increased the electrical conductivity. The liming tempo was highest in the coal discard profile that had a coarse particle size distribution and took the longest to move through the gold tailings that had a fine particle size distribution. Results from this study indicate that the water treatment sludge investigated is suitable as a liming agent for rehabilitation of acid mine waste.
Effect of Soil Properties on Saturated and Unsaturated Virus Transport through Columns
Authors: Chu Yanjie , Jin Yan , Baumann Thomas , Yates Marylynn V.
Published: June 2010

Viruses from contaminant sources can be transported through porous media to drinking water wells. The objective of this study was to investigate inactivation and sorption of viruses during saturated and unsaturated transport in different soils. Bacteriophages φX174 and MS‐2, and Br− tracer in a phosphate‐buffered saline solution were introduced into saturated and unsaturated soil columns as a step function under constant flow rate and hydraulic conditions. Results showed that significantly greater virus removal occurred in the unsaturated columns than in the saturated columns in the two soils containing high metal oxides content. However, the increase in virus retention under unsaturated conditions was not significant in two other soils having high phosphorus and calcium contents and high pH, and in another soil with high organic matter content. The results imply that the extent of water content effect on inactivation and sorption of viruses can range from significant to minimal depending on the properties of the transport medium. We found that the presence of in situ metal oxides was a significant factor responsible for virus sorption and inactivation. Therefore, soils with high metal oxides content may have the potential to be used as hydrological barriers in preventing microbial contamination in the subsurface environments. We also found that the water content effect on virus removal and inactivation strongly depended on solid properties of the testing medium.
Modeling of Sorption and Biodegradation of Parathion and Its Metabolite Paraoxon in Soil
Authors: Saffih‐Hdadi K. , Bruckler L. , Barriuso E.
Published: June 2010

To investigate the distribution of parathion [O,O‐diethyl O‐(4‐nitrophenyl) phosphorothioate] and its highly toxic metabolite paraoxon [O,O‐diethyl O‐(4‐nitrophenyl)phosphate] between the soluble and sorbed pools in the soil, batch experiments were conducted to evaluate the rate of adsorption and desorption of 14C‐labeled parathion and paraoxon in soil. The mineralization and degradation of these products were also investigated during a 56‐d experiment under controlled laboratory conditions. Adsorption patterns indicated initial fast adsorption reactions occurring within 4 h for both parathion and paraoxon. We also observed the formation of nonextractable residues. The paraoxon was more intensively degraded than the parathion, and production of p‐nitrophenol and other metabolites was observed. A kinetic model was developed to describe the sorption and biodegradation rates of parathion, taking into account the production, retention, and biodegradation of paraoxon, the main metabolite of parathion. After fitting the parameters of the model we made a simulation of the kinetics of the appearance and disappearance of paraoxon. From the simulation we predicted a quantity of metabolite in the liquid phase amounting to 1% of the quantity of parathion initially applied. This is in agreement with the experimental data.
Targeted Sampling Protocol as Prelude to Bacterial Source Tracking with Enterococcus faecalis
Authors: Kuntz Robin L. , Hartel Peter G. , Godfrey Dominique G. , McDonald Jennifer L. , Gates Keith W. , Segars William I.
Published: June 2010

Recent studies suggest that host origin databases for bacterial source tracking (BST) must contain a large number of isolates because bacterial subspecies change with geography and time. A new targeted sampling protocol was developed as a prelude to BST to minimize these changes. The research was conducted on the Sapelo River, a tidal river on the Georgia coast. A general sampling of the river showed fecal enterococcal numbers ranging from <10 (below the limit of detection) to 990 colony‐forming units (CFU) per 100 mL. Locations with high enterococcal numbers were combined with local knowledge to determine targeted sampling sites. Fecal enterococcal numbers around one site ranged from <10 to 24000 CFU per 100 mL. Bacterial source tracking was conducted to determine if a wastewater treatment facility at the site was responsible for this contamination. The fecal indicator bacterium was Enterococcus faecalis Ribotyping, automated with a RiboPrinter (DuPont Qualicon, Wilmington, DE), was the BST method. Thirty‐seven ribotypes were observed among 83 Ent. faecalis isolates obtained from the Sapelo River and the wastewater lagoon. Sixteen ribotypes were associated with either the river or the lagoon, and only five ribotypes (14%) were shared. Nevertheless, these five ribotypes represented 39 of the 83 Ent. faecalis isolates, almost a majority (47%). These results suggest that the fecal contamination in the river came from the wastewater treatment facility. As a prelude to BST, targeted sampling minimized subspecies changes with geography and time, and eliminated the need for a permanent host origin database by restricting BST to a small geographic area and requiring sampling to be completed in one day.
Sorption of Arsenic from Soil‐Washing Leachate by Surfactant‐Modified Zeolite
Authors: Sullivan Enid J. , Bowman Robert S. , Legiec Irene A.
Published: June 2010

Post‐treatment of leachate from soil‐washing remedial actions may be necessary depending on the amounts of dissolved contaminants present. Uptake of arsenic species by surfactant‐modified zeolite (SMZ) from a synthetic soil leachate (pH of approximately 12 [NaOH]) was measured as a test of SMZ as a post‐treatment sorbent. Batch sorption isotherms were prepared using leachate to SMZ ratios from 40:1 to 4:1, and temperatures of 25 and 15°C. Equilibrium levels of dissolved and total solution arsenic were similar. At each temperature, sorption appeared to reach a plateau or maximum, then decreased at the highest solution concentration, corresponding to the lowest amount of zeolite added (2.5 g). A maximum sorption value of 72.0 mmol of arsenic per kg of SMZ (5400 mg/kg) was observed at 25°C, and 42.1 mmol/kg (3150 mg/kg) at 15°C. Total arsenic recoveries varied from 74 to 125%. Surfactant‐modified zeolite removed up to 97% of dissolved organic carbon and decolorized the leachate solutions. Excluding the points for the highest arsenic to SMZ ratio, the sorption isotherms were well described by the linearized form of the Langmuir equation, with coefficients of determination greater than 0.90 at both temperatures. Sorption of arsenic by SMZ is attributed to anion exchange with counterions on the surfactant head groups, and/or partitioning of organic carbon–complexed arsenic into the surfactant bilayer.
Redistribution of Slurry Components as Influenced by Injection Method, Soil, and Slurry Properties
Authors: Petersen S⊘ren O. , Nissen Henrik H. , Lund Ivar , Ambus Per
Published: June 2010

The distribution of moisture, degradable C, and N after direct injection of slurry can affect the turnover and plant availability of slurry N. This study examined effects of injection method, soil conditions, and slurry properties on the infiltration of several slurry components under practical conditions. The water retention capacity of 22 pig and cattle slurries was quantified by dialysis at −0.016, −0.047, and −0.100 MPa. All slurries followed the relationship: relative water loss = 1/(1 +aVS[volatile solids]), indicating that retention of liquids in the slurry injection zone can be predicted from slurry VS and soil water potential. Two‐disc injection and harrow tine injection were simulated (no slurry applied) in five trials. Two trials indicated that disc injection resulted in higher permeability compared with harrow tine injection. In a separate experiment, soil moisture and dissolved ions were monitored in and around injection slits amended with pig or cattle slurry. Moisture gradients, which were recorded with small printed‐circuit‐board (PCB) time‐domain‐reflectometry (TDR) probes, were temporally stable and reestablished following rainfall. Slit sections with pig and cattle slurry containing13C‐acetate and15N‐ammonium showed a shift in the13C to15N ratio of the injection zone within 24 h, which was explained by removal of dissolved C and/or retention of NH+4Cattle slurry was more concentrated around the injection slit than pig slurry, and greater contact between slurry and soil was obtained with harrow tine injection. The heterogeneity of slurry C and N distribution after direct injection should be accounted for in models describing slurry N turnover.
Effect of Cry3Bb Transgenic Corn and Tefluthrin on the Soil Microbial Community: Biomass, Activity, and Diversity
Authors: Devare M. H. , Jones C. M. , Thies J. E.
Published: June 2010

Transgenic Bt corn expressing the Cry3Bb insecticidal protein active against corn rootworm (CRW) (Diabroticaspp.; Coleoptera: Chrysomelidae) was released for commercial use in 2003 and is expected to be widely adopted. Yet, the direct and indirect risks to soil microorganisms of growing this CRW‐resistant Bt corn versus applying insecticides to control the rootworm have not been assessed under field conditions. The effects of CRW Bt corn and the insecticide tefluthrin [2,3,5,6‐tetrafluoro‐4‐methylbenzyl (Z)‐(1RS)‐cis‐3‐(2‐chloro‐3,3,3‐trifluoroprop‐1‐enyl)‐2,2‐dimethylcyclopropanecarboxylate] on soil microbial biomass, activity (N mineralization potential, short‐term nitrification rate, and soil respiration), and bacterial community structure as determined by terminal restriction fragment length polymorphism (T‐RFLP) analysis were assessed over two seasons in a field experiment. Bt corn had no deleterious effects on microbial activity or bacterial community measures compared with the non‐transgenic isoline. The T‐RFLP analysis indicated that amplifiable bacterial species composition and relative abundance differed substantially between years, but did not differ between rhizosphere and bulk soils. The application of tefluthrin also had no effect on any microbial measure except decreased soil respiration observed in tefluthrin‐treated plots compared with Bt and non‐transgenic isoline (NoBt) plots in 2002. Our results indicate that the release of CRW Bt corn poses little threat to the ecology of the soil microbial community based on parameters measured in this study.
Dissolution of Trace Element Contaminants from Two Coastal Plain Soils as Affected by pH
Authors: Bang JiSu , Hesterberg Dean
Published: June 2010

Trace element mobility in soils depends on contaminant concentration, chemical speciation, water movement, and soil matrix properties such as mineralogy, pH, and redox potential. Our objective was to characterize trace element dissolution in response to acidification of soil samples from two abandoned incinerators in the North Carolina Coastal Plain. Trace element concentrations in 11 soil samples from both sites ranged from 2 to 46 mg Cu kg−1, 3 to 105 mg Pb kg−1, 1 to 102 mg Zn kg−1, 3 to 11 mg Cr kg−1, <0.1 to 10 mg As kg−1, and <0.01 to 0.9 mg Cd kg−1 Acidified CaCl2 solutions were passed through soil columns to bring the effluent solution to approximately pH 4 during a 280‐h flow period. Maximum concentrations of dissolved Cu, Pb, and Zn at the lowest pH of an experiment (pH 3.8–4.1) were 0.32 mg Cu L−1, 0.11 mg Pb L−1, and 1.3 mg Zn L−1 for samples from the site with well‐drained soils, and 0.25 mg Cu L−1, 1.2 mg Pb L−1, and 1.4 mg Zn L−1 for samples from the site with more poorly drained soils. Dissolved Cu concentration at pH 4 increased linearly with increasing soil Cu concentration, but no such relationship was found for Zn. Dissolved concentrations of other trace elements were below our analytical detection limits. Synchrotron X‐ray absorption near edge structure (XANES) spectroscopy showed that Cr and As were in their less mobile Cr(III) and As(V) oxidation states. XANES analysis of Cu and Zn on selected samples indicated an association of Cu(II) with soil organic matter and Zn(II) with Al‐ and Fe‐oxides or franklinite.
Assessment of the Use of Industrial By‐Products to Remediate a Copper‐ and Arsenic‐Contaminated Soil
Authors: Lombi Enzo , Hamon Rebecca E. , Wieshammer Gerlinde , McLaughlin Mike J. , McGrath Steve P.
Published: June 2010

Two water treatment sludges (WTS‐A, WTS‐B), two red muds (RM), and red gypsum (RG), all rich in iron oxy‐hydroxides, were added to a soil highly polluted with As and Cu at 2% (w/w) to reduce metal bioavailability. Because the amendments increased soil pH to approximately 6, a lime treatment to the same pH and an unamended treatment were included for comparison. All the amendments had significant positive effects on the soil microbial biomass and growth of ryegrass (Lolium multiflorum Lam. cv. Avance), but only WTS‐A improved lettuce (Lactuca sativa L. cv. Tom Thumb) growth. The mineralization of added ammonium nitrogen was not significantly affected by the treatments, while a physiologically based extraction test (PBET) showed that bioaccessibility of As was low (<5%) and decreased only in the WTS‐A treatment. Concentrations of As in soil pore water and extractable As only decreased in the WTS and RG treatments. In contrast, Cu concentrations in soil pore water and extractable Cu decreased in all treatments, by more than 84% in the WTS, RM, and RG treatments. Non‐isotopically exchangeable As and Cu were present in colloids in the soil pore water. Untreated soil had <4% isotopically exchangeable As and this decreased by approximately 50%, with WTS, RM, and RG. The labile Cu pool represented a large proportion (34%) of the total Cu pool, and the isotopically exchangeable and soluble Cu were strongly correlated with soil pH. Acidification of the treated soils showed that the labile As and Cu both increased in the treated soils compared with untreated soils. The significance of the treatment effects on soil fertility and potential off‐site transport of As and Cu to ground water are discussed.
Field Dissipation of Acetochlor in Two New Zealand Soils at Two Application Rates
Authors: Ma Qingli , Rahman Anis , Holland Patrick T. , James Trevor K. , McNaughton Don E.
Published: June 2010

The persistence of pesticides in soils has both economic and environmental significance and is often used as a key parameter in pesticide risk assessment. Persistence of acetochlor [2′‐ethyl‐6′‐methyl‐N‐(ethoxymethyl)‐2‐chloroacetylanilide] in two New Zealand field soils was measured over two years and the data were used to identify models that adequately describe acetochlor persistence in the field. Acetochlor was sprayed onto six fallow plots (3 × 9 m each) at each site at the recommended rate (2.5 kg a.i. ha−1) and at twice that rate. Acetochlor concentrations were measured in soil cores. Simple first‐order kinetics (Model 1) adequately described acetochlor persistence in Hamilton clay loam soil (Humic Hapludull, Illuvial Spadic) at the high application rate, but overestimated it at the low application rate. A quadratic model (Model 2), a first‐order double‐exponential model (Model 3), a first‐order biphasic model (Model 4), or a two‐compartment model (Model 5) better described acetochlor persistence at the low application rate. The time for 50% (DT50) and 90% (DT90) of initial acetochlor loss was approximately 9 and 56 d, and 18 and 63 d at low and high application rates, respectively. The more complex Models 2 through 5 also better described the biphasic dissipation of acetochlor in Horotiu sandy loam soil (Typic Orthic Allophanic) than Model 1, with Model 1 significantly underestimating acetochlor concentrations on the day of application at both application rates. The DT50and DT90values were 5 and 29 d and 7 and 31 d at low and high application rates, respectively. Overall, application rate significantly affected the DT50and DT90values in the Hamilton soil, but not in the Horotiu soil. Faster acetochlor loss in the Horotiu soil possibly resulted from the higher soil organic carbon content that retained more acetochlor near the soil surface where higher temperature and photolysis accelerated the loss.
Reduction of Nitrate Leaching with Haying or Grazing and Omission of Nitrogen Fertilizer
Authors: Owens L. B. , Bonta J. V.
Published: June 2010

In some high‐fertility, high‐stocking‐density grazing systems, nitrate (NO3) leaching can be great, and ground water NO3–N concentrations can exceed maximum contaminant levels. To reduce high N leaching losses and concentrations, alternative management practices need to be used. At the North Appalachian Experimental Watershed near Coshocton, OH, two management practices were studied with regard to reducing NO3–N concentrations in ground water. This was following a fertilized, rotational grazing management practice from which ground water NO3–N concentrations exceeded maximum contaminant levels. Using four small watersheds (each approximately 1 ha), rotational grazing of a grass forage without N fertilizer being applied and unfertilized grass forage removed as hay were used as alternative management practices to the previous fertilized pastures. Ground water was sampled at spring developments, which drained the watershed areas, over a 7‐yr period. Peak ground water NO3–N concentrations before the 7‐yr study period ranged from 13 to 25.5 mg L−1 Ground water NO3–N concentrations progressively decreased under each watershed and both management practices. Following five years of the alternative management practices, ground water NO3–N concentrations ranged from 2.1 to 3.9 mg L−1 Both grazing and haying, without N fertilizer being applied to the forage, were similarly effective in reducing the NO3–N levels in ground water. This research shows two management practices that can be effective in reducing high NO3–N concentrations resulting from high‐fertility, high‐stocking‐density grazing systems, including an option to continue grazing.
Cation–π Bonding: A New Perspective on the Sorption of Polycyclic Aromatic Hydrocarbons to Mineral Surfaces
Authors: Zhu Dongqiang , Herbert Bruce E. , Schlautman Mark A. , Carraway Elizabeth R. , Hur Jin
Published: June 2010

Recent molecular modeling and spectroscopic studies have suggested that relatively strong interactions can occur between aromatic π donors and metal cations in aqueous solutions. The objective of this study was to characterize potential cation–π interactions between π donors and exchangeable cations accumulated at mineral surfaces via both spectroscopic and batch sorption methods. Quadrupolar splitting in deuterium nuclear magnetic resonance (2H NMR) spectroscopy for d2–dichloromethane, d6–benzene, and d8–toluene (C6D5– moiety) in aqueous suspensions of a Na‐saturated reference montmorillonite unambiguously indicated the ordering of solute molecules with respect to the clay surface. The half line broadening (Δν1/2) of 2H NMR of d6–benzene in montmorillonite suspensions showed that soft exchangeable cations generally resulted in more benzene sorption compared with harder cations (e.g., Ag+ > Cs+ > Na+ > Mg2+, Ba2+). In batch sorption experiments, saturating minerals (e.g., porous silica gels, kaolinite, vermiculite, montmorillonite) with a soft transition metal or softer base cations generally increased the polycyclic aromatic hydrocarbon (PAH) sorption relative to harder cations (e.g., Ag+ >> Cs+ > K+ > Na+; Ba2+ > Mg2+). Sorption of phenanthrene to Ag+–saturated montmorillonite was much stronger compared with 1,2,4,5‐tetrachlorobenzene, a coplanar non‐π donor having slightly higher hydrophobicity. In addition, a strong positive correlation was found between the cation‐dependent sorption and surface charge density of the minerals (e.g., vermiculite, montmorillonite >> silica gels, kaolinite). These results, coupled with the observations in 2H NMR experiments with montmorillonite, strongly suggest that cation–π bonding forms between PAHs and exchangeable cations at mineral surfaces and affects PAH sorption to hydrated mineral surfaces.