bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Variability of Soil Carbon in Forested and Cultivated Sites
Authors: Conant Richard T. , Smith Gordon R. , Paustian Keith
Published: August 2012

The potential to sequester atmospheric carbon in agricultural and forest soils to offset greenhouse gas emissions has generated interest in measuring changes in soil carbon resulting from changes in land management. However, inherent spatial variability of soil carbon limits the precision of measurement of changes in soil carbon and hence, the ability to detect changes. We analyzed variability of soil carbon by intensively sampling sites under different land management as a step toward developing efficient soil sampling designs. Sites were tilled cropland and a mixed deciduous forest in Tennessee, and old‐growth and second‐growth coniferous forest in western Washington, USA. Six soil cores within each of three microplots were taken as an initial sample and an additional six cores were taken to simulate resampling. Soil C variability was greater in Washington than in Tennessee, and greater in less disturbed than in more disturbed sites. Using this protocol, our data suggest that differences on the order of 2.0 Mg C ha−1 could be detected by collection and analysis of cores from at least five (tilled) or two (forest) microplots in Tennessee. More spatial variability in the forested sites in Washington increased the minimum detectable difference, but these systems, consisting of low C content sandy soil with irregularly distributed pockets of organic C in buried logs, are likely to rank among the most spatially heterogeneous of systems. Our results clearly indicate that consistent intramicroplot differences at all sites will enable detection of much more modest changes if the same microplots are resampled.
Wet Chemical and Phosphorus‐31 Nuclear Magnetic Resonance Analysis of Phosphorus Speciation in a Sandy Soil Receiving Long‐Term Fertilizer or Animal Manure Applications
Authors: Koopmans G. F. , Chardon W. J. , Dolfing J. , Oenema O. , van der Meer P. , van Riemsdijk W. H.
Published: August 2012

In areas under intensive livestock farming and with high application rates of animal manure, inorganic and organic phosphorus (P) may be leached from soils. Since the contribution of these P compounds to P leaching may differ, it is important to determine the speciation of P in these soils. We determined the effect of various fertilization regimes on the P speciation in NaOH–Na2EDTA (ethylenediaminetetraacetic acid) and water extracts of acidic sandy soil samples from the top 5 cm of grassland with wet chemical analysis and 31P nuclear magnetic resonance (NMR) spectroscopy. These soils had been treated for a period of 11 years with no fertilizer (control), N (no P application), N–P–K, or different animal manures. Inorganic P was highly elevated in the NaOH–Na2EDTA extracts of the soils amended with N–P–K or animal manures, while organic P increased only in the soil treated with pig slurry. Water‐extractable P showed a similar trend. As indicated by 31P NMR, orthophosphate monoesters were the main organic P compounds in all soils. Our results suggest that long‐term applications of large amounts of P fertilizer and animal manures caused an accumulation of inorganic P, resulting in an increase of the potential risk related to mobilization of inorganic P in the top 5 cm of these soils.
Microbial Reduction of Hexavalent Chromium under Vadose Zone Conditions
Authors: Oliver Douglas S. , Brockman Fred J. , Bowman Robert S. , Kieft Thomas L.
Published: August 2012

Hexavalent chromium [Cr(VI)] is a common contaminant associated with nuclear reactors and fuel processing. Improper disposal at facilities in arid and semiarid regions has contaminated underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those in the vadose zone, and to evaluate the potential for enhancing biological Cr(VI) reduction through nutrient addition. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO−3) and organic C (molasses). Nutrient amendments resulted in up to 87% reduction of the initial 67 mg L−1 Cr(VI) in an unsaturated batch experiment. Molasses and nitrate additions to 15 cm long unsaturated flow columns receiving 65 mg L−1 Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45‐d experiment. All of the immobilized Cr was in the form of Cr(III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy, and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.
Stable Sulfur Isotope Ratio Indicates Long‐Term Changes in Sulfur Deposition in the Broadbalk Experiment since 1845
Authors: Zhao F. J. , Knights J. S. , Hu Z. Y. , McGrath S. P.
Published: August 2012

Archived wheat (Triticum aestivum L.) grain and straw, and soil samples from the control plot of the Rothamsted Broadbalk Experiment, located in southeastern England and established in 1843, were used to investigate the effects of dramatically changing SO2 pollution inputs on the concentrations and stable isotope ratios (δ34S) of S in the samples. Representative coal samples from UK major coal fields were also determined for δ34S. Concentrations of S showed no clear trends in either grain or straw over the 155 years from 1845 to 1999. However, grain and straw δ34S decreased rapidly from 6 to 7‰ in 1845 to −2 to −5‰ in the early 1970s, and since then have increased to 0.5 to 2‰ in the late 1990s. This pattern mirrored the trend of UK SO2 emissions over the 155 years. Both grain and straw δ34S correlated strongly and negatively with UK SO2 emissions (R2 > 0.89), but the relationships were different for the pre‐ and post‐1970 data sets. Soil δ34S also decreased considerably, from 8.2‰ in 1865 to 3.7 to 4.5‰ during 1965–1999. A negative δ34S value was inferred for the anthropogenic S deposited at the experimental site before 1970, and further confirmed by negative δ34S values (−6 to −10‰) found in the coal samples from southeastern England and southern Wales. Based on the S isotope ratios, we estimated that anthropogenic S contributed 62 to 78% of the S uptake by wheat at the peak of SO2 emissions, and accounted for 28 to 37% of the topsoil S in 1965.
Decadal Change in Vegetation and Soil Phosphorus Pattern across the Everglades Landscape
Authors: Childers Daniel L. , Doren Robert F. , Jones Ronald , Noe Gregory B. , Rugge Michael , Scinto Leonard J.
Published: August 2012

Wetlands respond to nutrient enrichment with characteristic increases in soil nutrients and shifts in plant community composition. These responses to eutrophication tend to be more rapid and longer lasting in oligotrophic systems. In this study, we documented changes associated with water quality from 1989 to 1999 in oligotrophic Everglades wetlands. We accomplished this by resampling soils and macrophytes along four transects in 1999 that were originally sampled in 1989. In addition to documenting soil phosphorus (P) levels and decadal changes in plant species composition at the same sites, we report macrophyte tissue nutrient and biomass data from 1999 for future temporal comparisons. Water quality improved throughout much of the Everglades in the 1990s. In spite of this improvement, though, we found that water quality impacts worsened during this time in areas of the northern Everglades (western Loxahatchee National Wildlife Refuge [NWR] and Water Conservation Area [WCA] 2A). Zones of high soil P (exceeding 700 mg P kg−1 dry wt. soil) increased to more than 1 km from the western margin canal into the Loxahatchee NWR and more than 4 km from northern boundary canal into WCA‐2A. This doubling of the high soil P zones since 1989 was paralleled with an expansion of cattail (Typha spp.)‐dominated marsh in both regions. Macrophyte species richness declined in both areas from 1989 to 1999 (27% in the Loxahatchee NWR and 33% in WCA‐2A). In contrast, areas well south of the Everglades Agricultural Area, including WCA‐3A and Everglades National Park (ENP), did not decline during this time. We found no significant decadal change in plant community patterns from 1989 and 1999 along transects in southern WCA‐3A or Shark River Slough (ENP). Our 1999 sampling also included a new transect in Taylor Slough (ENP), which will allow change analysis here in the future. Regular sampling of these transects, to verify decadal‐scale environmental impacts or improvements, will continue to be an important tool for long‐term management and restoration of the Everglades.
Mercury Sequestration in Forests and Peatlands
Authors: Grigal D. F.
Published: August 2012

Nearly all Hg in vegetation is derived directly from the atmosphere. Mass of Hg in forest vegetation (roughly 0.1 mg m−2) is about an order of magnitude smaller than that in the forest floor (1 mg m−2) and two orders of magnitude smaller than that in the mineral soil (10 mg m−2). Mass of Hg in peat (20 mg m−2) is greater than the sum of that in mineral soil and the forest floor; wetlands usually sequester more Hg than associated uplands. The strong relationship of Hg to organic matter, associated with binding by reduced S groups, is fundamental to understanding Hg distribution and behavior in terrestrial systems. The stoichiometry of the Hg–C relationship varies; Hg–S relationships, though less variable, are not constant. Because of the Hg–organic matter link, landscape conditions that lead to differential soil organic matter accumulation are likely to lead to differential Hg accumulation. The ratio of methylmercury (MeHg) to total Hg is generally low in both vegetation (near 1.5%) and soil (<1%), but areas of poorly drained soils and wetlands are sites of MeHg production. The annual emission of anthropic Hg from the 48 contiguous states of the USA (144 Mg) is two orders of magnitude less than the pool of Hg in forests of those states (30 300 Mg). Peatlands, less than 2% of total land area, sequester more than 20 times annual emissions (2930 Mg). If global climate change affects C storage it will indirectly affect Hg storage, having a major effect on the balance between emissions and sequestration and on the global Hg cycle.
Environmental Fate and Impacts of Sulfometuron on Watersheds in the Southern United States
Authors: Michael J. L.
Published: August 2012

Dissipation of sulfometuron (SM), methyl 2‐[[[[(4,6‐dimethyl‐2‐pyrimidinyl)amino]carbonyl]amino]sulfonyl] benzoate, in streamflow, sediment, plant tissue, litter, and soil following operational forestry applications at the target rate of 0.42 kg a.i. ha−1 was monitored. Streamflow samples were collected at a weir on the perimeter and 30, 60, and 150 m downstream from the perimeter of the application site. Sulfometuron was detected in streamflow at low levels up to 29 days after treatment (DAT) on the watershed treated with the 75% dispersible granule formulation (Oust; DuPont Chemical Company, Wilmington, DE) and less than 53 DAT on the watershed treated with the experimental formulation (1% pellet). Twenty‐four‐hour average SM concentration in water ranged from not detected to a maximum of 49.3 μg L−1 Sulfometuron was not detected at quantifiable levels (1 μg L−1) 150 m downstream. Stream sediment, vegetation, litter, and soil were sampled periodically up to 180 DAT. All samples were analyzed for SM by high performance liquid chromatography. Sulfometuron dissipated from these watersheds with half‐lives that ranged from 4 d in plant tissues to 33 d in soil. Acidic soil solution on these treated watersheds contributed to their rapid dissipation. Environmental impacts are discussed for these watersheds in the context of available toxicological data.
Surface and Subsurface Geologic Risk Factors to Ground Water Affecting Brownfield Redevelopment Potential
Authors: Kaufman Martin M. , Murray Kent S. , Rogers Daniel T.
Published: August 2012

A model is created for assessing the redevelopment potential of brownfields. The model is derived from a space and time conceptual framework that identifies and measures the surface and subsurface risk factors present at brownfield sites. The model then combines these factors with a contamination extent multiplier at each site to create an index of redevelopment potential. Results from the application of the model within an urbanized watershed demonstrate clear differences between the redevelopment potential present within five different near‐surface geologic units, with those units containing clay being less vulnerable to subsurface contamination. With and without the extent multiplier, the total risk present at the brownfield sites within all the geologic units is also strongly correlated to the actual costs of remediation. Thus, computing the total surface and subsurface risk within a watershed can help guide the remediation efforts at broad geographic scales, and prioritize the locations for redevelopment.
Occurrence of Metals in Soil and Ground Water Near Chromated Copper Arsenate–Treated Utility Poles
Authors: Zagury Gérald J. , Samson Réjean , Deschênes Louise
Published: August 2012

To thoroughly investigate the metal contamination around chromated copper arsenate (CCA)/polyethylene glycol (PEG)–treated utility poles, a total of 189 soil samples obtained from different depths and distances near six treated poles in the Montreal area (Canada) were analyzed for Cu, Cr, and As content. Various soil physicochemical properties were also determined. Ground water samples collected below the poles were analyzed for metals and bioassays with Daphnia magna were conducted. Generally, sandy soils had lower contaminant levels than clayey and organic soils. Copper concentrations in soil were highest followed by As and Cr. The highest Cu (1460 ± 677 mg kg−1), As (410 ± 150 mg kg−1), and Cr (287 ± 32 mg kg−1) concentrations were found at the ground line and immediately adjacent to the pole. Contaminant levels then decreased with distance, approaching background levels within 0.1 m from the pole for Cr and 0.5 m for Cu and As. Chromium and Cu levels generally approached background levels at a depth of 0.5 m. Average As content near the pole on all study sites was three to eight times higher than Quebec's Level C criterion (50 mg kg−1), although it dropped to 31 mg kg−1 at 0.1 m. Results also showed that As persisted up to 1 m in soil depth (17–54 mg kg−1). Copper and Cr concentrations in ground water samples were always <1.000 mg L−1 and <0.05 mg L−1, respectively and Cr(VI) was <0.02 mg L−1 One sample contained an As concentration > 0.025 mg L−1 but bioassays showed that, overall, ground water had a low ecotoxic potential.
Weathering of Lead Bullets and Their Environmental Effects at Outdoor Shooting Ranges
Authors: Cao Xinde , Ma Lena Q. , Chen Ming , Hardison Donald W. , Harris Willie G.
Published: August 2012

Lead contamination at shooting range soils is of great environmental concern. This study focused on weathering of lead bullets and its effect on the environment at five outdoor shooting ranges in Florida, USA. Soil, plant, and water samples were collected from the ranges and analyzed for total Pb and/or toxicity characteristic leaching procedure (TCLP) Pb. Selected bullet and berm soil samples were mineralogically analyzed with X‐ray diffraction and scanning electron microscopy. Hydrocerussite [Pb3(CO3)2(OH)2] was found in both the weathered crusts and berm soils in the shooting ranges with alkaline soil pH. For those shooting ranges with acidic soil pH, hydrocerussite, cerussite (PbCO3), and small amount of massicot (PbO) were predominantly present in the weathered crusts, but no lead carbonate mineral was found in the soils. However, hydroxypyromorphite [(Pb10(PO4)6(OH)2] was formed in a P‐rich acidic soil, indicating that hydroxypyromorphite can be a stable mineral in P‐rich shooting range soil. Total Pb and TCLP Pb in the soils from all five shooting ranges were significantly elevated with the highest total Pb concentration of 1.27 to 4.84% (w/w) in berm soils. Lead concentrations in most sampled soils exceeded the USEPA's critical level of 400 mg Pb kg−1 soil. Lead was not detected in subsurface soils in most ranges except for one, where elevated Pb up to 522 mg kg−1 was observed in the subsurface, possibly due to enhanced solubilization of organic Pb complexes at alkaline soil pH. Elevated total Pb concentrations in bermudagrass [Cynodon dactylon (L.) Pers.] (up to 806 mg kg−1 in the aboveground parts) and in surface water (up to 289 μg L−1) were observed in some ranges. Ranges with high P content or high cation exchange capacity showed lower Pb mobility. Our research clearly demonstrates the importance of properly managing shooting ranges to minimize adverse effects of Pb on the environment.
Managing Material Transfer and Nutrient Flow in an Agricultural Watershed
Authors: Nord E. A. , Lanyon L. E.
Published: August 2012

Place‐based resource management, such as watershed or ecosystem management, is being promoted to replace the media‐focused approach for achieving water quality protection. We monitored the agricultural area of a 740‐ha watershed to determine the nature and scale of farm material transfers, N and P balances, and farmer decisions that influenced them. Using field data and farmer interviews we found that 3 of 15 farms, emphasizing hog, dairy, or cash crops with poultry production, accounted for more than 80% of the inputs and outputs of N and P for the 362‐ha agricultural area (332 ha of managed cropland and animal facilities). Feed for hogs (38% each of total N and P) and manure applied to fields as part of the cash crop and poultry operation (28 and 38% of total N and P, respectively) were the dominant inputs. No crops grown in the watershed were fed to animals in the watershed and more manure nutrients were applied from animals outside than from those in the watershed. A strategic decision by the hog farmer to begin marketing finished hogs changed the material transfers and nutrient balances more than tactical decisions by other farmers in allocating manure to cropland. Since the components of agricultural production were not all interconnected, the fundamental assumption of place‐based management programs is not well‐suited to this situation. Alternative approaches to managing the effect of agriculture on water quality should consider the organization of agricultural production and the role of strategic decisions in controlling farm nutrient balances.
Water Quality Changes in a Polluted Stream over a Twenty‐Five‐Year Period
Authors: Stewart Jason , Skousen Jeff
Published: August 2012

The Deckers Creek watershed in northern West Virginia (USA), containing a land area of 166 km2 (63 mi2), has a long history of industrial development and attendant environmental abuses from both land and water pollution practices. The water in Deckers Creek was sampled in 1974 at 29 locations along the main stem and resampled in 1999–2000 to determine water quality changes over this 25‐year period. Water samples were analyzed for pH, acidity, alkalinity, iron, and calcium at both times, while aluminum, manganese, zinc, and fecal coliform (FC) bacteria densities were added in 1999–2000. Water at almost all sampling points showed lower acidity and metal contents in 1999–2000 compared with 1974. Water pH increased at the mouth from 5.4 in 1974 to 6.0 in 1999–2000. Acidity and iron concentrations were decreased an average of 70% in the upper stretches of the creek. However, one major untreated point source of water from an abandoned underground mining complex continues to degrade the quality of the creek in its lower stretches. In the upper section, the water quality in Deckers Creek has improved due to decreased surface and underground coal mining activities, reclamation of abandoned and recently permitted surface mined lands, and natural healing of past land use scars from timbering and mining over time. The decrease in mineral extraction activities and the reclamation of disturbed lands has occurred due to the passage and enforcement of water quality and land reclamation laws and regulations. More time and additional reclamation projects will continue to enhance the water quality in the creek. Improved water chemistry in the majority of the creek, however, shows the previously unnoticeable biological contamination from sewage inputs.
Evaluation of an Acid Ammonium Oxalate Extraction to Determine Fluoride Resident Concentrations in Soils
Authors: Bégin Louis , Fortin Josée
Published: August 2012

Fluoride depositions near aluminum smelters and other fluoride‐emitting plants can lead to fluoride accumulation in soils, which constitutes a risk for ground water contamination. This study was conducted to investigate the capacity of a 0.2 M acid ammonium oxalate solution to selectively and quantitatively extract fluoride accumulated in soils. The recovery of fluoride added to three soils was evaluated following 7‐ to 28‐d incubations. Oxalate extraction was also compared with a total fluoride extraction method, using oxalate‐extractable fluoride (Fox) and total fluoride (Ftot) accumulation profiles derived from column percolation experiments. To determine low‐level fluoride concentrations without interference from high Al and Fe concentrations, an adapted ion chromatography method was used. Following soil incubations, oxalate extracted 42 to 86% of added fluoride. Recovery varied between soils and, in one soil, increased with added fluoride concentration. Recovery was unaffected by incubation time. Maximum recovery was obtained in a soil high in amorphous Fe and Al, low in clay, and free of carbonate. Lower recoveries were obtained in soils with higher clay or carbonate contents. Only 4 to 8% of Ftot was extracted in untreated samples using Fox, which suggests a high selectivity of this method for added fluoride. In percolation experiments, the use of Fox reduced considerably the background noise associated with Ftot for the evaluation of fluoride accumulation profiles. Because of its high selectivity and despite incomplete fluoride recovery, the use of Fox to determine fluoride resident concentrations in soils may improve environmental monitoring of fluoride accumulation and movement in contaminated soils.
Polyacrylamide Distribution in Columns of Organic Matter–Removed Soils following Surface Application
Authors: Lu Jianhang , Wu Laosheng
Published: August 2012

Knowledge of how polyacrylamide (PAM) penetrates and distributes in a soil profile after application in irrigation water is important for understanding PAM conditioning depth and evaluating its environmental effects. Little is known, however, about PAM distribution in soil because of the difficulty in quantifying PAM content in natural soils. By using a recently modified substrate‐borne PAM quantification method, PAM distribution in columns of organic matter–removed soils was determined. Results showed that penetration of PAM into the soil was affected by salt level of irrigation water, soil texture, initial soil water content, water application method, and other factors. Polyacrylamide penetration depth was about one‐eighth to one‐half of the water penetration depth, with a particularly high PAM retention in the top few centimeters of the soil. Under different experimental conditions, the PAM retained in the top 0 to 2 cm of soil ranged from 16 to 95% of the total applied amount. More favorable solution–soil contact conditions, longer solution–soil contact time, and lower initial soil moisture caused much more PAM retention in the top few centimeters of the soil. High sorptive affinity of PAM on soil is the main reason for its low penetration into the soil. Although these results were not obtained from natural soils, they are still helpful in improving our understanding of PAM transport behavior in soils.
Swine Effluent Irrigation Rate and Timing Effects on Bermudagrass Growth, Nitrogen and Phosphorus Utilization, and Residual Soil Nitrogen
Authors: Adeli A. , Varco J. J. , Rowe D. E.
Published: August 2012

Maximizing utilization of effluent nutrients by forage grasses requires a better understanding of irrigation rate and timing effects. This study was conducted in 1998 and 1999 on a Vaiden silty clay (very‐fine, smectitic, thermic Aquic Dystrudert) soil to determine the effects of swine lagoon effluent irrigation rate and timing on bermudagrass [Cynodon dactylon (L.) Pers.] growth, nitrogen (N) and phosphorus (P) recovery, and postseason soil profile NO−3–N. Treatments consisted of swine effluent irrigation at the rates of 0, 5, 10, 15, and 20 ha‐cm. Two additional treatments included 2.5 ha‐cm applied on 1 September and 1 October in addition to a base summer rate of 10 ha‐cm. In both years for early to mid‐season irrigation, bermudagrass dry matter yield quadratically increased with increasing swine effluent irrigation rates. Averaged across years, effluent irrigation in October resulted in 30% less dry matter than in September. For late‐season irrigation, apparent N recovery averaged 59% less and P recovery averaged 46% less with a delay in irrigation from 1 September to 1 October. The greatest quantity of soil NO−3–N was associated with both the greatest effluent rate and October irrigation treatments. Minimal yield benefit was obtained when effluent was applied at rates greater than 10 ha‐cm during the summer months. Late‐season irrigation, especially after 1 October for areas with similar climatic conditions, should be avoided to maximize synchronization of nutrient availability with maximum growth rates to minimize potential offsite movement of residual soil N and P.
Properties of Several Fly Ash Materials in Relation to Use as Soil Amendments
Authors: Pathan S. M. , Aylmore L. A. G. , Colmer T. D.
Published: August 2012

Fly ash samples from five power stations in Western Australia and Queensland, and two soils used for horticulture in Western Australia, were evaluated for a series of physical and chemical properties. Soils were comprised primarily of coarse sand‐sized particles, whereas most of the fly ashes were primarily fine sand‐ and silt‐sized particles. Hydraulic conductivities in the fly ashes were 105‐ to 248‐fold slower than in the soils. The water‐holding capacities of fly ashes at “field capacity” were three times higher than those of the soils. Extractable P in the fly ashes (except Tarong and Callide) were 20‐ to 88‐fold higher than in the soils. The pH showed considerable variation among the different sources of fly ash, with samples from Muja being the most acidic (pH = 3.8; 1:5 in CaCl2 extract) and from Gladstone the most alkaline (pH = 9.9). The toxicity characteristic leaching procedure (TCLP) values indicate that the potential for release of trace elements from the fly ashes was well below regulatory levels. When applied at sufficient rates (e.g., to achieve 10% w/w in surface layers) to sandy soils, fly ash altered texture and increased water‐holding capacity. Depending on the source of fly ash used, such amendments could also provide P and aid nutrient retention by increasing the phosphorus retention index (PRI) and/or cation exchange capacity (CEC). The considerable variability in physical and chemical properties among the fly ash samples evaluated in the present study supports the notion that field trials are essential to the future development of soil amendment strategies making use of any particular source of fly ash.
Nutrient and Hydrology Effects on Soil Respiration in a Northern Everglades Marsh
Authors: DeBusk W. F. , Reddy K. R.
Published: August 2012

Microbial respiration in peat and overlying plant litter, as influenced by water level and phosphorus enrichment, was evaluated for an Everglades (Florida, USA) marsh ecosystem by measuring CO2and CH4release from soil–water microcosms. Intact cores of peat, overlying plant litter, and surface water were collected at seven locations in cattail (Typha domingensisPers.) and sawgrass (Cladium jamaicenseCrantz) stands along a phosphorus (P) enrichment gradient in Water Conservation Area 2A (WCA‐2A). Each soil–water microcosm was outfitted with a controlled air circulation system whereby outflow gas from the headspace could be analyzed for CO2and CH4to determine flux of C from the soil–water column to the atmosphere. Gaseous C flux was determined for flooded conditions (10‐cm water depth) and for water levels of 0, 5, 10, and 15 cm below the peat surface. Overall, decreasing water level resulted in significantly increased C flux, although rates were significantly higher under flooded conditions than under nonflooded, saturated‐soil conditions, presumably due to O2availability associated with algal photosynthesis within the litter layer in the water column. Carbon flux decreased significantly for sites increasingly distant from the primary hydrologic and nutrient inflows to WCA‐2A. The microcosm study demonstrated that the C turnover rate was significantly increased by accelerated nutrient loading to the marsh, and was further enhanced by decreasing water level under drained conditions. Our results also demonstrated that photosynthesis within the water column is a potentially important regulator of C mineralization rate in the litter layer of the marsh system.
Antimony Impurity in Lead Arsenate Insecticide Enhances the Antimony Content of Old Orchard Soils
Authors: Wagner Sandra E. , Peryea Frank J. , Filby Royston A.
Published: August 2012

Lead arsenate was a commonly used insecticide during the first half of the 20th century, particularly in deciduous tree fruit orchards. Antimony is cotransported with As during the ore refining process and could occur as an impurity in commercial lead arsenate products. The total concentrations of As and Sb in eight soil samples collected from eight orchards located throughout central Washington State were analyzed by neutron activation analysis. Total soil Sb concentrations ranged between 0.4 and 1.5 mg kg−1, while total soil As concentration ranged from 1 to 170 mg kg−1 Total soil Sb and As concentrations were positively related. Total Pb and As concentrations in four of the soils were substantially higher than natural background, while the Sb to As concentration ratios in these soils were consistent with values measured in three lead arsenate insecticide products. These results confirm that Sb impurity is present in lead arsenate insecticide and has contributed to Sb enrichment of soils on which lead arsenate–treated plants were grown. Although higher than in uncontaminated soils from the same region, the Sb concentrations in the affected soils fall within the normal range observed worldwide and are substantially lower than values associated with impaired human or environmental health.
Leaching Characteristics of Heavy Metals from Sewage Sludge by Acidithiobacillus thiooxidans MET
Authors: Ryu H. W. , Moon H. S. , Lee E. Y. , Cho K. S. , Choi H.
Published: August 2012

An acidophilic, sulfur‐oxidizing Acidithiobacillus thiooxidans MET bacterium was isolated from anaerobically digested, dewatered sewage sludge. This bacterium showed sulfur‐oxidizing ability at both acidic and neutral conditions, and allowed metal leaching even at a high (130 g L−1) sludge solids concentration. We found that low metal leaching efficiency at high solids concentration was mainly due to an increase in buffering capacity resulting in retardation of pH reduction. Therefore, metal leaching was mainly influenced not by sludge solids concentration, but by the pH (or sulfate concentration per unit sludge mass) of the sludge solutions. The relationship between the pH of the sludge solution and the efficiency of metal leaching was obtained by quantitatively investigating the effect of pH reduction or the amount of sulfate produced per unit sludge mass on leaching of each metal. Furthermore, the relationship between total metal content in the sludge and metal leached to the solution was obtained for each metal. Such a relationship allowed estimation of leachable metal at various amounts of total metal content in sludge.
Reduction of Arsenic Uptake by Lettuce with Ferrous Sulfate Applied to Contaminated Soil
Authors: Warren G. P. , Alloway B. J.
Published: August 2012

Soil contamination by arsenic (As) presents a hazard in many countries and there is a need for techniques to minimize As uptake by plants. A proposed in situ remediation method was tested by growing lettuce (Lactuca sativa L. cv. Kermit) in a greenhouse pot experiment on soil that contained 577 mg As kg−1, taken from a former As smelter site. All combinations of iron (Fe) oxides, at concentrations of 0.00, 0.22, 0.54, and 1.09% (w/w), and lime, at concentrations of 0.00, 0.27, 0.68, and 1.36% (w/w), were tested in a factorial design. To create the treatments, field‐moist soil, commercial‐grade FeSO4, and ground agricultural lime were mixed and stored for one week, allowing Fe oxides to precipitate. Iron oxides gave highly significant (P < 0.001) reductions in lettuce As concentrations, down to 11% of the lettuce As concentration for untreated soil. For the Fe oxides and lime treatment combinations where soil pH was maintained nearly constant, the lettuce As concentration declined in an exponential relationship with increasing FeSO4 application rate and lettuce yield was almost unchanged. Iron oxides applied at a concentration of 1.09% did not give significantly lower lettuce As concentrations than the 0.54% treatment. Simultaneous addition of lime with FeSO4 was essential. Ferrous sulfate with insufficient lime lowered soil pH and caused mobilization of Al, Ba, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn. At the highest Fe oxide to lime ratios, Mn toxicity caused severe yield loss.
Nitrate Distributions and Source Identification in the Abbotsford–Sumas Aquifer, Northwestern Washington State
Authors: Mitchell Robert J. , Babcock R. Scott , Gelinas Sharon , Nanus Leora , Stasney David E.
Published: August 2012

The Abbotsford–Sumas Aquifer is a shallow, predominantly unconfined aquifer that spans regions in southwestern British Columbia, Canada and northwestern Washington, USA. The aquifer is prone to nitrate contamination because of extensive regional agricultural practices. A 22‐month ground water nitrate assessment was performed in a 10‐km2 study area adjacent to the international boundary in northwestern Washington to examine nitrate concentrations and nitrogen isotope ratios to characterize local source contributions from up‐gradient sources in Canada. Nitrate concentrations in excess of 10 mg nitrate as nitrogen per liter (mg N L−1) were observed in ground water from most of the 26 domestic wells sampled in the study area, and in a creek that dissects the study area. The nitrate distribution was characteristic of nonpoint agricultural sources and consistent with the historical documentation of agriculturally related nitrate contamination in many parts of the aquifer. Hydrogeologic information, nitrogen isotope values, and statistical analyses indicated a nitrate concentration stratification in the study area. The highest concentrations (>20 mg N L−1) occurred in shallow regions of the aquifer and were linked to local agricultural practices in northwestern Washington. Nitrate concentrations in excess of 10 mg N L−1 deeper in the aquifer (>10 m) were related to agricultural sources in Canada. The identification of two possible sources of ground water nitrate in northwestern Washington adds to the difficulty in assessing and implementing local nutrient management plans for protecting drinking water in the region.
Use of Mini‐Sprinklers to Strip Trichloroethylene and Tetrachloroethylene from Contaminated Ground Water
Authors: Berisford Yvette C. , Bush Parshall B. , Blake John I. , Bayer Cassandra L.
Published: August 2012

Three low‐volume mini‐sprinklers were tested for their efficacy to strip trichloroethylene (TCE) and tetrachloroethylene (PCE) from water. Deionized water spiked with TCE and PCE was pumped for approximately 1 h at 0.19 to 0.21 MPa (28 to 30 lb in−2) through a mini‐sprinkler supported on top of a 1.8‐m‐tall riser. Water was collected in collection vessels at 0.61 and 1.22 m above the ground on support columns that were spaced at 0.61‐m intervals from the riser base, and samples were composited per height and distance from the riser. Overall, air‐stripping reduced dissolved concentrations of TCE and PCE by 99.1 to 100 and 96.9 to 100%, respectively, from mean influent dissolved concentrations of 466 to 1675 μg L−1 TCE and 206 to 940 μg L−1 PCE. In terms of mass removed, the mini‐sprinklers removed TCE and PCE at a rate of approximately 1400 to 1700 and 700 to 900 μg L−1, respectively, over a 1‐h test period. Mini‐sprinklers offer the advantages of (i) easy setup in series that can be used on practically any terrain; (ii) operation over a long period of time that does not threaten aquifer depletion; (iii) use in small or confined aquifers in which the capacity is too low to support large irrigation or purging systems; and (iv) use in forests in which the small, low‐impact droplets of the mini‐sprinklers do not damage bark and in which trees can help manage (via evapotranspiration) excess waste water.
Metal Bioavailability and Speciation in a Wetland Tailings Repository Amended with Biosolids Compost, Wood Ash, and Sulfate
Authors: DeVolder Pam S. , Brown Sally L. , Hesterberg Dean , Pandya Kumi
Published: August 2012

Lead poisoning of waterfowl from direct ingestion of wetland mine tailings has been reported at the Coeur d'Alene River basin in Idaho. A greenhouse study was conducted to evaluate the effects of surface applications of amendments on lead bioavailability in the tailings. Treatments included sediment only, and sediment with three different surface amendments: (i) biosolids compost plus wood ash, (ii) compost + wood ash + a low SO2−4 addition as K2SO4, and (iii) compost + wood ash + a high SO2−4 addition. Measured variables included growth and tissue Pb, Zn, and Cd concentration of arrowhead (Sagittaria latifolia Willd.) and cattail (Typha latifolia L.) and soil pH, redox potential (Eh), pore water Pb, Pb speciation by X‐ray absorption spectroscopy, and in vitro Pb bioavailability. The compost + ash amendment alleviated phytotoxicity for both plant species. Bioavailability of Pb as measured by a rapid in vitro extract decreased by 24 to 34% (over control) in the tailings directly below the amendment layer in the compost + SO4 treatments. The ratio of acid volatile sulfide (AVS) to simultaneously extracted metals (SEM) also indicated a reduction in Pb bioavailability (1:40 control, 1:20 compost, 1:8 compost + low SO4, and 1:3 compost + high SO4). Extended X‐ray adsorption fine structure (EXAFS) and X‐ray absorption near edge structure (XANES) spectroscopy data indicated that lead sulfide was greater after 99 d in the treatments that included additions of sulfate. These results indicated that, under reducing conditions, surface amendments of compost + wood ash (with or without sulfate) decreased the bioavailability of Pb in metal‐contaminated mine tailings.
Heavy Metal Release from Contaminated Soils
Authors: Voegelin Andreas , Barmettler Kurt , Kretzschmar Ruben
Published: August 2012

Heavy metals in soils may adversely affect environmental quality. In this study, we investigated the release of Zn, Cd, Pb, and Cu from four contaminated soils by column leaching and single and sequential batch extractions. Homogeneously packed soil columns were leached with 67 mL/g 10−2 M CaCl2 to investigate the exchangeable metal pool and subsequently with 1400 mL/g 10−2 M CaCl2 adjusted to pH 3 to study the potential of metal release in response to soil acidification. In two noncalcareous soils (pH 5.7 and 5.1), exchange by Ca resulted in pronounced release peaks for Zn and Cd that were coupled to the exchange of Mg by Ca, and 40 to 70% of total Zn and Cd contents were rapidly mobilized. These amounts compared well with exchangeable pools determined in single and sequential batch extractions. In two soils with near‐neutral pH, the effluent concentrations of Zn and Cd were several orders of magnitude lower and no pronounced elution peaks were observed. This behavior was also observed for Cu and Pb in all four soils. When the soils were leached at pH 3, the column effluent patterns reflected the coupling of CaCO3 dissolution (if present) and other proton buffering reactions, proton‐induced metal release, and metal‐specific readsorption within the soil column. Varying the flow rate by a factor of five had only minor effects on the release patterns. Overall, Ca exchange and subsequent acidification to pH 3 removed between 65 and 90% of total Zn, Cd, Pb, and Cu from the four contaminated soils.
Chemical Extraction Methods to Assess Bioavailable Arsenic in Soil and Solid Media
Authors: Rodriguez R. R. , Basta N. T. , Casteel S. W. , Armstrong F. P. , Ward D. C.
Published: August 2012

Soil ingestion by children is an important pathway in assessing public health risks associated with exposure to arsenic‐contaminated soils. Soil chemical methods are available to extract various pools of soil arsenic, but their ability to measure bioavailable arsenic from soil ingestion is unknown. Arsenic extracted by five commonly used soil extractants was compared with bioavailable arsenic measured in vivo by immature swine (Sus scrofa) dosing trials. Fifteen contaminated soils that contained 233 to 17 500 mg kg−1 arsenic were studied. Soil extractants were selected to dissolve surficially adsorbed and/or readily soluble arsenic (water, 1 M sodium acetate, 0.1 M Na2HPO4/0.1 M NaH2PO4) and arsenic in Fe and Mn oxide minerals (hydroxylamine hydrochloride, ammonium oxalate). The mean percent of total arsenic extracted was: ammonium oxalate (53.6%) ≥ hydroxylamine hydrochloride (51.7%) > phosphate (10.5%), acetate (7.16%) > water (0.15%). The strongest relationship between arsenic determined by soil chemical extraction and in vivo bioavailable arsenic was found for hydroxylamine hydrochloride extractant (r = 0.88, significant at the 0.01 probability level). Comparison of the amount of arsenic extracted by soil methods with bioavailable arsenic showed the following trend: ammonium oxalate, hydroxylamine hydrochloride > in vivo > phosphate, acetate > water. The amount of arsenic dissolved in the stomach (potentially bioavailable) is between surficially adsorbed (extracted by phosphate or acetate) and surficially adsorbed + nonsurficial forms in Fe and Mn oxides (extracted by hydroxylamine hydrochloride or ammonium oxalate). Soil extraction methods that dissolve some of the amorphous Fe, such as hydroxylamine hydrochloride, can be designed to provide closer estimates of bioavailable arsenic.
Herbicides in Ground Water beneath Nebraska's Management Systems Evaluation Area
Authors: Spalding Roy F. , Exner Mary E. , Snow Daniel D. , Cassada David A. , Burbach Mark E. , Monson Stephen J.
Published: August 2012

Profiles of ground water pesticide concentrations beneath the Nebraska Management Systems Evaluation Area (MSEA) describe the effect of 20 yr of pesticide usage on ground water in the central Platte Valley of Nebraska. During the 6‐yr (1991–1996) study, 14 pesticides and their transformation products were detected in 7848 ground water samples from the unconfined water table aquifer. Triazine and acetamide herbicides applied on the site and their transformation products had the highest frequencies of detection. Atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4,‐diamine] concentrations decreased with depth and ground water age determined with 3H/3He dating techniques. Assuming equivalent atrazine input during the past 20 yr, the measured average changes in concentration with depth (age) suggest an estimated half‐life of >10 yr. Hydrolysis of atrazine and deethylatrazine (DEA; 2‐chloro‐4‐amino‐6‐isopropylamino‐s‐triazine) to hydroxyatrazine [6‐hydroxy‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] appeared to be the major degradation route. Aqueous hydroxyatrazine concentrations are governed by sorption on the saturated sediments. Atrazine was detected in the confined Ogallala aquifer in ultra‐trace concentrations (0.003 μg L−1); however, the possibility of introduction during reverse circulation drilling of these deep wells cannot be eliminated. In fall 1997 sampling, metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] was detected in 57% of the 230 samples. Metolachlor oxanilic acid [(2‐ethyl‐6‐methylphenyl)(2‐methoxy‐1‐methylethyl)amino]oxo‐acetic acid] was detected in most samples. In ground water profiles, concentrations of metolachlor ethane sulfonic acid [2‐[(ethyl‐6‐methylphenyl)(2‐methoxy‐1‐methylethyl)amino]‐2‐oxo‐ethanesulfonic acid] exceeded those of deethylatrazine. Alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] was detected in <1% of the samples; however, alachlor ethane sulfonic acid [2‐[(2,6‐diethylphenyl)(methoxymethyl)amino]‐2‐oxoethanesulfonic acid] was present in most samples (63%) and was an indicator of past alachlor use.
Uptake and Release of Phosphorus from Overland Flow in a Stream Environment
Authors: McDowell R. W. , Sharpley A. N.
Published: August 2012

Phosphorus runoff from agricultural fields has been linked to freshwater eutrophication. However, edge‐of‐field P losses can be modified by benthic sediments during stream flow by physiochemical processes associated with Al, Fe, and Ca, and by biological assimilation. We investigated fluvial P when exposed to stream‐bed sediments (top 3 cm) collected from seven sites representing forested and agricultural areas (pasture and cultivated), in a mixed‐land‐use watershed. Sediment was placed in a 10‐m‐long, 0.2‐m‐wide fluvarium to a 3‐cm depth and water was recirculated over the sediment at 2 L s−1 and 5% slope. When overland flow (4 mg dissolved reactive phosphorus [DRP] and 9 mg total phosphorus [TP] L−1) from manured soils was first recirculated, P uptake was associated with Al and Fe hydrous oxides for sediments from forested areas (pH 5.2–5.4) and by Ca for sediments from agricultural areas (pH 6.5–7.2). A large increase (up to 200%) in readily available P NH4Cl fraction was noted. After 24 h, DRP concentration in channel flow was related to sediment solution P concentration at which no net sorption or desorption of P occurs (EPC0) (r2 = 0.77), indicating quasi‐equilibrium. When fresh water (approximately 0.005 mg P L−1; mean base flow DRP at seven sites) was recirculated over the sediments for 24 h, P release kinetics followed an exponential function. Microbial biomass P accounted for 34 to 43% of sediment P uptake from manure‐rich overland flow. Although abiotic sediment processes played a dominant role in determining P uptake, biotic process are clearly important and both should be considered along with the location and management of landscape inputs for remedial strategies to be effective.