bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of Arsenic and Phosphorus in Ditch Flow from Litter‐amended Soils and Barn Areas
Authors: Church Clinton D. , Kleinman Peter J. A. , Bryant Ray B. , Saporito Lou S. , Allen Arthur L.
Published: October 2010

Little is known about the fate of arsenic (As) in land‐applied litter from chickens that have been fed roxarsone, an organic feed additive containing As. This study seeks to elucidate the transfer of As in runoff from ditch‐drained soils of the poultry‐producing region of the Delmarva Peninsula by tracking As and phosphorus (P) export from seven drainage ditches over two water‐years (1 July 2005 to 30 June 2007). Annual losses of As from ditches ranged from 0.004 to 0.071 kg ha−1 while P losses ranged from 0.33 to 18.56 kg ha−1, with the largest loads associated with a litter storage shed that served as a point source. Event‐based As and P losses in ditch flow fluctuated by a factor of 162 and 1882, respectively. The two elements were correlated in flow from the ditch draining a litter storage shed (r = 0.99), and in sediment extracts in soils near the litter shed (r = 0.73), pointing to similar behavior under point source conditions. Indeed, As and P exhibited similar behavior within storms for all ditches, characterized by relatively high initial concentrations subject to rapid concentration declines before peak flow, consistent with dilution of a finite source. However, As and P concentrations varied significantly between ditches and showed considerable temporal variability within ditches, with no clear seasonal trends or associations with current management strategies. The results suggest that similar management strategies might be effective for As and P point sources, but that field management practices geared toward controlling nonpoint source P losses may not readily transfer to the control of As losses.
The Release of Nanosilver from Consumer Products Used in the Home
Authors: Benn Troy , Cavanagh Bridget , Hristovski Kiril , Posner Jonathan D. , Westerhoff Paul
Published: October 2010

Nanosilver has become one of the most widely used nanomaterials in consumer products because of its antimicrobial properties. Public concern over the potential adverse effects of nanosilver's environmental release has prompted discussion of federal regulation. In this paper, we assess several classes of consumer products for their silver content and potential to release nanosilver into water, air, or soil. Silver was quantified in a shirt, a medical mask and cloth, toothpaste, shampoo, detergent, a towel, a toy teddy bear, and two humidifiers. Silver concentrations ranged from 1.4 to 270,000 μg Ag g product−1 Products were washed in 500 mL of tap water to assess the potential release of silver into aqueous environmental matrices (wastewater, surface water, saliva, etc.). Silver was released in quantities up to 45 μg Ag g product−1, and size fractions were both larger and smaller than 100 nm. Scanning electron microscopy confirmed the presence of nanoparticle silver in most products as well as in the wash water samples. Four products were subjected to a toxicity characterization leaching procedure to assess the release of silver in a landfill. The medical cloth released an amount of silver comparable to the toxicity characterization limit. This paper presents methodologies that can be used to quantify and characterize silver and other nanomaterials in consumer products. The quantities of silver in consumer products can in turn be used to estimate real‐world human and environmental exposure levels.
Selenium Stable Isotope Investigation into Selenium Biogeochemical Cycling in a Lacustrine Environment: Sweitzer Lake, Colorado
Authors: Clark Scott K. , Johnson Thomas M.
Published: October 2010

We present a comprehensive set of Se concentration and isotope ratio data collected over a 3‐yr period from dissolved, sediment‐hosted, and organically bound Se in a Se‐contaminated lake and littoral wetland. Median isotope ratios of these various pools of Se spanned a narrow isotopic range (δ80/76SeSRM‐3149 = 1.14–2.40‰). Selenium (VI) reduction in the sediments is an important process in this system, but its isotopic impact is muted by the lack of direct contact between surface waters and reduction sites within sediments. This indicates that using Se isotope data as an indicator of microbial or abiotic Se oxyanion reduction is not effective in this or other similar systems. Isotopic data suggest that most Se(IV) in the lake originates from oxidation of organically bound Se rather than directly through Se(VI) reduction. Mobilization of Se(VI) from bedrock involves only a slight isotopic shift. Temporally constant isotopic differences observed in Se(VI) from two catchment areas suggest the potential for tracing Se(VI) from different source areas. Phytoplankton isotope ratios are close to those of the water, with a small depletion in heavy isotopes (0.56‰). Fish tissues nearly match the phytoplankton, being only slightly depleted in the heavier isotopes. This suggests the potential for Se isotopes as migration indicators. Volatile, presumably methylated Se was isotopically very close to median values for phytoplankton and macrophytes, indicating a lack of isotopic fractionation during methylation.
Effects of Particle Size on Chemical Speciation and Bioavailability of Copper to Earthworms (Eisenia fetida) Exposed to Copper Nanoparticles
Authors: Unrine Jason M. , Tsyusko Olga V. , Hunyadi Simona E. , Judy Jonathan D. , Bertsch Paul M.
Published: October 2010

To investigate the role of particle size on the oxidation, bioavailability, and adverse effects of manufactured Cu nanoparticles (NPs) in soils, we exposed the earthworm Eisenia fetida to a series of concentrations of commercially produced NPs labeled as 20‐ to 40‐nm or <100‐nm Cu in artificial soil media. Effects on growth, mortality, reproduction, and expression of a variety of genes associated with metal homeostasis, general stress, and oxidative stress were measured. We also used X‐ray absorption spectroscopy and scanning X‐ray fluorescence microscopy to characterize changes in chemical speciation and spatial distribution of the NPs in soil media and earthworm tissues. Exposure concentrations of Cu NPs up to 65 mg kg−1 caused no adverse effects on ecologically relevant endpoints. Increases in metallothionein expression occurred at concentrations exceeding 20 mg kg−1 of Cu NPs and concentrations exceeding 10 mg kg−1 of CuSO4 Based on the relationship of Cu tissue concentration to metallothionein expression level and the spatial distribution and chemical speciation of Cu in the tissues, we conclude that Cu ions and oxidized Cu NPs were taken up by the earthworms. This study suggests that oxidized Cu NPs may enter food chains from soil but that adverse effects in earthworms are likely to occur only at relatively high concentrations (>65 mg Cu kg−1 soil).
Transport of Sulfadiazine in Undisturbed Soil Columns: Effects of Flow Rate, Input Concentration and Pulse Duration
Authors: Unold M. , Kasteel R. , Groeneweg J. , Vereecken H.
Published: October 2010

Antibiotics reach soils via spreading of manure or sewage sludge. Knowledge on the transport behavior of antibiotics in soils is needed to assess their environmental fate. The effect of flow rate and applied mass, i.e., input concentration and pulse duration, on the transport of 14C‐sulfadiazine (SDZ; 4‐amino‐N‐pyrimidin‐2‐yl‐benzenesulfonamide) was investigated with soil column experiments and numerical studies. Sulfadiazine was applied in pulses (6.8, 68 or 306 h) under steady‐state (0.051 and 0.21 cm h−1) and intermittent flow conditions and at two input concentrations (0.57 and 5.7 mg L−1). Breakthrough curves (BTCs) of 14C were measured and for one experiment concentrations of SDZ, and its transformation products 4‐(2‐iminopyrimidin‐1(2H)‐yl)aniline (An‐SDZ) and N1‐2‐(4‐hydroxypyrimidinyl)benzenesulfanilamide (4‐OH‐SDZ) were determined. After finalizing the leaching experiments, 14C was quantified in different slices of the columns. A lower flow rate led to remarkably lower eluted masses compared with the higher flow rates. All BTCs could be described well using a three‐site attachment–detachment model for which a common set of parameters was determined. However, the BTC obtained with the high input concentration was slightly better described with a two‐site isotherm‐based model. The prediction of the concentration profiles was good with both model concepts. The fitted sorption capacities decreased in the order SDZ > 4‐OH‐SDZ > An‐SDZ. Overall, the experiments reveal the presence of similar mechanisms characterizing SDZ transport. The dependence of model performance on concentration implies that although the three‐site attachment–detachment model is appropriate to predict the transport of SDZ in soil columns, not all relevant processes are adequately captured.
Determining Sources of Dissolved Organic Carbon and Disinfection Byproduct Precursors to the McKenzie River, Oregon
Authors: Kraus Tamara E. C. , Anderson Chauncey A. , Morgenstern Karl , Downing Bryan D. , Pellerin Brian A. , Bergamaschi Brian A.
Published: October 2010

This study was conducted to determine the main sources of dissolved organic carbon (DOC) and disinfection byproduct (DBP) precursors to the McKenzie River, Oregon (USA). Water samples collected from the mainstem, tributaries, and reservoir outflows were analyzed for DOC concentration and DBP formation potentials (trihalomethanes [THMFPs] and haloacetic acids [HAAFPs]). In addition, optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) were measured to provide insight into DOM composition and assess whether optical properties are useful proxies for DOC and DBP precursor concentrations. Optical properties indicative of composition suggest that DOM in the McKenzie River mainstem was primarily allochthonous—derived from soils and plant material in the upstream watershed. Downstream tributaries had higher DOC concentrations than mainstem sites (1.6 ± 0.4 vs. 0.7 ± 0.3 mg L−1) but comprised <5% of mainstem flows and had minimal effect on overall DBP precursor loads. Water exiting two large upstream reservoirs also had higher DOC concentrations than the mainstem site upstream of the reservoirs, but optical data did not support in situ algal production as a source of the added DOC during the study. Results suggest that the first major rain event in the fall contributes DOM with high DBP precursor content. Although there was interference in the absorbance spectra in downstream tributary samples, fluorescence data were strongly correlated to DOC concentration (R2 = 0.98), THMFP (R2 = 0.98), and HAAFP (R2 = 0.96). These results highlight the value of using optical measurements for identifying the concentration and sources of DBP precursors in watersheds, which will help drinking water utilities improve source water monitoring and management programs.
Pathogens and Indicators in United States Class B Biosolids: National and Historic Distributions
Authors: Pepper Ian L. , Brooks John P. , Sinclair Ryan G. , Gurian Patrick L. , Gerba Charles P.
Published: October 2010

This paper reports on a major study of the incidence of indicator organisms and pathogens found within Class B biosolids within 21 samplings from 18 wastewater treatment plants across the United States. This is the first major study of its kind since the promulgation of the USEPA Part 503 Rule in 1993, and includes samples before and after the Part 503 Rule was promulgated. National distributions collected between 2005 and 2008 show that the incidence of bacterial and viral pathogens in Class B mesophilic, anaerobically digested biosolids were generally low with the exception of adenoviruses, which were more prevalent than enteric viruses. No Ascaris ova were detected in any sample. In contrast, indicator organism numbers were uniformly high, regardless of whether they were bacteria (fecal coliforms) or viruses (phage). Indicators were not correlated with pathogen loads. Historic distributions were collected between 1988 and 2006 at one location in Tucson, AZ. By comparing data collected before and after 1993, the influence of the USEPA Part 503 Rule on indicator and pathogen levels within Class B biosolids can be inferred. In general, the bacterial indicators total and fecal coliforms decreased from the 1980s to present. Enteric virus concentrations after 1993 are much lower than those reported in other studies in the 1980s, although our values from 1988 to 1993 are not significantly different from our values obtained from 1994 to 2006. Presumably this is due to better and more consistent treatment of the wastewater, illustrating that the Part 503 Rule has been effective in reducing public exposure to pathogens relative to 17 yr ago. The percent reduction of both indicators and pathogens during anaerobic mesophilic digestion was between 94 and 99% for all organisms, illustrating that such treatment is effective in reducing pathogen loads.
Risk Assessment of Aquifer Storage Transfer and Recovery with Urban Stormwater for Producing Water of a Potable Quality
Authors: Page Declan , Dillon Peter , Vanderzalm Joanne , Toze Simon , Sidhu Jatinder , Barry Karen , Levett Kerry , Kremer Sarah , Regel Rudi
Published: October 2010

The objective of the Parafield Aquifer Storage Transfer and Recovery research project in South Australia is to determine whether stormwater from an urban catchment that is treated in a constructed wetland and stored in an initially brackish aquifer before recovery can meet potable water standards. The water produced by the stormwater harvesting system, which included a constructed wetland, was found to be near potable quality. Parameters exceeding the drinking water guidelines before recharge included small numbers of fecal indicator bacteria and elevated iron concentrations and associated color. This is the first reported study of a managed aquifer recharge (MAR) scheme to be assessed following the Australian guidelines for MAR. A comprehensive staged approach to assess the risks to human health and the environment of this project has been undertaken, with 12 hazards being assessed. A quantitative microbial risk assessment undertaken on the water recovered from the aquifer indicated that the residual risks posed by the pathogenic hazards were acceptable if further supplementary treatment was included. Residual risks from organic chemicals were also assessed to be low based on an intensive monitoring program. Elevated iron concentrations in the recovered water exceeded the potable water guidelines. Iron concentrations increased after underground storage but would be acceptable after postrecovery aeration treatment. Arsenic concentrations in the recovered water continuously met the guideline concentrations acceptable for potable water supplies. However, the elevated concentration of arsenic in native groundwater and its presence in aquifer minerals suggest that the continuing acceptable residual risk from arsenic requires further evaluation.
Precipitation Changes Impact Stream Discharge, Nitrate–Nitrogen Load More Than Agricultural Management Changes
Authors: Nangia V. , Mulla D. J. , Gowda P. H.
Published: October 2010

Nitrate–N losses to surface waters in the Upper Midwest of the Untied States have increased in recent decades, contributing to hypoxia in the Gulf of Mexico. This paper investigates whether increasing nitrate–N export from cropland in the Upper Midwest since the late 1960s results from changes in land use or climate. The Agricultural Drainage and Pesticide Transport (ADAPT) Model simulated current and historical agricultural systems under past and recent wet climate for Seven Mile Creek in Minnesota. Simulations were run with management and climate for three distinctly different periods—namely, 1965 to 1969, 1976 to 1980, and 1999 to 2003 (wettest period). Results showed discharge and nitrate–N losses responded more to changes in climate than management. The wetter period (1999–2003) caused a simulated 70% increase in discharge under 1960s‐era management compared with that period's observed climate and a simulated 51% increase in discharge under 1970s‐era management compared with the 1976 to 1980 climate. The recent, wetter climate also produced a 62% increase in nitrate–N losses for 1960s‐era management compared with the actual climate and a 137% increase in nitrate–N losses for 1978 management conditions compared with actual 1970s climate. Had recent climate been in place and stable since 1965, agricultural changes would have decreased discharge by 6.4% through the late 1970s and then by another 21.1% under modern management but would have increased nitrate–N losses by 184% through the late 1970s and then decreased nitrate–N losses by 13.5% between 1978 and 2001. Management changes that were important drivers included increasing N‐fertilizer rates, increases in corn acreage, and increases in crop yield. But the most important factor driving increased nitrate–N losses from agriculture since the 1970s was an increasingly wetter climate.
Phosphorus Speciation in Sequentially Extracted Agro‐Industrial By‐Products: Evidence from X‐ray Absorption Near Edge Structure Spectroscopy
Authors: Kruse Jens , Negassa Wakene , Appathurai Narayana , Zuin Lucia , Leinweber Peter
Published: October 2010

The phosphorus (P) in agro‐industrial by‐products—a potential source of freshwater eutrophication but also a valuable fertilizer—needs to be speciated to evaluate its fate in the environment. We investigated to what extent X‐ray absorption near edge structure (XANES) spectroscopy at the P K‐ and L2,3‐edges reflected differences in sequentially extracted filter cakes from sugarcane (Saccharum officinarum L.) (FIC) and niger seed (Guizotia abyssinica Cass.; NIC) processing industry in Ethiopia. The P fractionation removed more labile (54%) and H2SO4–P (28%) from FIC than from NIC (18% labile, 12% H2SO4–P). For the FIC residues after each extraction step, linear combination (LC) fitting of P K‐edge spectra provided evidence for the enrichment of Ca‐P after the NaOH‐extraction and its almost complete removal after the H2SO4–treatment. The LC‐fitting was unsuccessful for the NIC samples, likely because of the predominance of organic P compounds. The different proportions of Ca‐P compounds between FIC (large) and NIC (small) were more distinctive in L2,3‐ than in the K‐edge XANES spectra. In conclusion, the added value of complementary P K‐ and L2,3‐edge XANES was clearly demonstrated, and the P fractionation and speciation results together justify using FIC and NIC as soil amendments in the tropics.
Perennial Filter Strips Reduce Nitrate Levels in Soil and Shallow Groundwater after Grassland‐to‐Cropland Conversion
Authors: Zhou Xiaobo , Helmers Matthew J. , Asbjornsen Heidi , Kolka Randy , Tomer Mark D.
Published: October 2010

Many croplands planted to perennial grasses under the Conservation Reserve Program are being returned to crop production, and with potential consequences for water quality. The objective of this study was to quantify the impact of grassland‐to‐cropland conversion on nitrate‐nitrogen (NO3–N) concentrations in soil and shallow groundwater and to assess the potential for perennial filter strips (PFS) to mitigate increases in NO3–N levels. The study, conducted at the Neal Smith National Wildlife Refuge (NSNWR) in central Iowa, consisted of a balanced incomplete block design with 12 watersheds and four watershed‐scale treatments having different proportions and topographic positions of PFS planted in native prairie grasses: 100% rowcrop, 10% PFS (toeslope position), 10% PFS (distributed on toe and as contour strips), and 20% PFS (distributed on toe and as contour strips). All treatments were established in fall 2006 on watersheds that were under bromegrass (BromusL.) cover for at least 10 yr. Nonperennial areas were maintained under a no‐till 2‐yr corn (Zea maysL.)–soybean [Glycine max(L.) Merr.] rotation since spring 2007. Suction lysimeter and shallow groundwater wells located at upslope and toeslope positions were sampled monthly during the growing season to determine NO3–N concentration from 2005 to 2008. The results indicated significant increases in NO3–N concentration in soil and groundwater following grassland‐to‐cropland conversion. Nitrate‐nitrogen levels in the vadose zone and groundwater under PFS were lower compared with 100% cropland, with the most significant differences occurring at the toeslope position. During the years following conversion, PFS mitigated increases in subsurface nitrate, but long‐term monitoring is needed to observe and understand the full response to land‐use conversion.
Implications of Cation Exchange on Clay Release and Colloid‐Facilitated Transport in Porous Media
Authors: Bradford Scott A. , Kim Hyunjung
Published: October 2010

Column experiments were conducted to study chemical factors that influence the release of clay (kaolinite and quartz minerals) from saturated Ottawa sand of different sizes (710, 360, and 240 μm). A relatively minor enhancement of clay release occurred when the pH was increased (5.8 to 10) or the ionic strength (IS) was decreased to deionized (DI) water. In contrast, clay release was dramatically enhanced when monovalent Na+ was exchanged for multivalent cations (e.g., Ca2+ and Mg2+) on the clay and sand and then the solution IS was reduced to DI water. This solution chemistry sequence decreased the adhesive force acting on the clay as a result of an increase in the magnitude of the clay and sand zeta potential with cation exchange, and expansion of the double layer thickness with a decrease in IS to DI water. The amount of clay release was directly dependent on the Na+ concentration of the exchanging solution and on the initial clay content of the sand (0.026–0.054% of the total mass). These results clearly demonstrated the importance of the order and magnitude of the solution chemistry sequence on clay release. Column results and scanning electron microscope (SEM) images also indicated that the clay was reversibly retained on the sand, despite predictions of irreversible interaction in the primary minimum. One plausible explanation is that adsorbed cations increased the separation distance between the clay–solid interfaces as a result of repulsive hydration forces. A cleaning procedure was subsequently developed to remove clay via cation exchange and IS reduction; SEM images demonstrated the effectiveness of this approach. The transport of Cu2+ was then shown to be dramatically enhanced by an order of magnitude in peak concentration by adsorption on clays that were released following cation exchange and IS reduction.
The Effect of Biofuel Production on Swine Farm Methane and Ammonia Emissions
Authors: Harper Lowry A. , Flesch Thomas K. , Weaver Kim H. , Wilson John D.
Published: October 2010

Methane (CH4) and ammonia (NH3) are emitted to the atmosphere during anaerobic processing of organic matter, and both gases have detrimental environmental effects. Methane conversion to biofuel production has been suggested to reduce CH4 emissions from animal manure processing systems. The purpose of this research is to evaluate the change in CH4 and NH3 emissions in an animal feeding operation due to biofuel production from the animal manure. Gas emissions were measured from swine farms differing only in their manure‐management treatment systems (conventional vs. biofuel). By removing organic matter (i.e., carbon) from the biofuel farms' manure‐processing lagoons, average annual CH4 emissions were decreased by 47% compared with the conventional farm. This represents a net 44% decrease in global warming potential (CO2 equivalent) by gases emitted from the biofuel farms compared with conventional farms. However, because of the reduction of methanogenesis and its reduced effect on the chemical conversion of ammonium (NH4+) to dinitrogen (N2) gas, NH3 emissions in the biofuel farms increased by 46% over the conventional farms. These studies show that what is considered an environmentally friendly technology had mixed results and that all components of a system should be studied when making changes to existing systems.
Evaluation of PCR‐based Quantification Techniques to Estimate the Abundance of Atrazine Chlorohydrolase Gene atzA in Rhizosphere Soils
Authors: Thompson Brian M. , Lin Chung‐Ho , Hsieh Hsin‐Yeh , Kremer Robert J. , Lerch Robert N. , Garrett Harold E.
Published: October 2010

There are many challenges in the accurate quantification of bacterial genes, such as the atrazine‐degrading enzyme atzA from Pseudomonas sp. strain ADP, from soil samples. We compared four quantitative methods for enumeration of atrazine‐degrading bacteria in rhizosphere environments and utilized the optimal probe‐based real‐time polymerase chain reaction (PCR)–based method in an ongoing bioremediation experiment to monitor atzA copy number over time. We compared three quantitative PCR (qPCR) based methods—quantitative competitive PCR and two real‐time qPCR methods—to traditional dilution‐plate counting techniques. The optimal real‐time qPCR assay was then used to monitor atzA copy number over time in the robust atrazine‐degrading Pseudomonas sp. strain ADP–spiked rhizosphere environment. The use of sensitive and reliable probe‐based real‐time qPCRs for the enumeration of bacterial catabolic genes allows for their detection from soil samples and monitoring of potential degradative populations over time. The addition of atrazine‐biodegrading bacteria into atrazine‐contaminated sites to remove entrapped atrazine is a promising approach for mitigating atrazine pollution and its metabolites. The methodology contained herein will allow for optimal monitoring of atzA in rhizosphere soil with or without the addition of biodegradative Pseudomonas sp. strain ADP of bacteria.
Effects of Wood Bark and Fertilizer Amendment on Trace Element Mobility in Mine Soils, Broken Hill, Australia: Implications for Mined Land Reclamation
Authors: Munksgaard N. C. , Lottermoser B.G.
Published: October 2010

Soil amendments can immobilize metals in soils, reducing the risks of metal exposure and associated impacts to flora, fauna and human health. In this study, soil amendments were compared, based on “closed system” water extracts, for reducing metal mobility in metal‐contaminated soil from the Broken Hill mining center, Australia. Phosphate fertilizer (bovine bone meal, superphosphate, triple superphosphate, potassium orthophosphate) and pine bark (Pinus radiata) were applied to two soils (BH1, BH2) contaminated with mining waste. Both soils had near neutral to alkaline pH values, were sulfide‐ or sulfate‐rich, and contained metal and metalloid at concentrations that pose high environmental risks (e.g., Pb = 1.25 wt% and 0.55 wt%, Zn = 0.71 wt% and 0.47 wt% for BH1 and BH2, respectively). The addition of fertilizers and/or pine bark to both soil types increased water extractable metals and metalloids concentrations (As, Cd, Cu, Fe, Mn, Pb, Sb, Zn) compared with nonamended soils. One or more of the elements As, Cd, Cu, Mn, Pb, and Zn increased significantly in extracts of a range of different soil+pine bark and soil+fertilizer+pine bark tests in response to increased pine bark doses. By contrast, Fe and Sb concentrations in extracts did not change significantly with pine bark addition. Solution pH was decreased by phosphate fertilizers (except for bovine bone meal) and pine bark, and pine bark enhanced dissolved organic carbon. At least in the short term, the application of phosphate fertilizers and pine bark proved to be an ineffective method for controlling metal and metalloid mobility in soils that contain admixtures of polymetallic, polymineralic mine wastes.
Effect of Varying the Phosphorus Content of Dairy Cow Diets on Losses of Phosphorus in Overland Flow Following Surface Applications of Manure
Authors: O'Rourke S. M. , Foy R. H. , Watson C. J. , Ferris C. P. , Gordon A.
Published: October 2010

The increasing use of concentrate feedstuffs within Northern Ireland dairy systems has resulted in significant farm gate phosphorus (P) surpluses, and these have contributed to increased soil P levels and risk of P loss to overland flow. However, the P content of feed concentrates can be lowered without compromising animal performance. This study focuses on P losses from grassland and evaluates how adjusting the P content of manure impacts on the P composition and concentration in overland flow. Dairy cows were offered diets containing 5.3 to 3.0 g P kg−1 dry matter (DM) and produced manures with a range of P contents. Manure was applied at a rate of 50 m3 ha−1 to 0.5‐m2 grassland plots, and simulated rainfall (40 mm h−1) was applied repeatedly 2, 9, 28, and 49 d after during the summer, winter, and spring. Decreasing the P content in the diet, from the highest to the lowest P treatment (43%), produced a proportionately greater reduction in manure TP content (63%), but reductions were not exclusively in the water‐soluble fraction. Following surface applications of manure, P concentrations in overland flow increased in all seasons (P ≤ 0.001), while the greatest impact of varying the manure P content was most evident during the first simulated overland flow event. When diet P content was reduced from 5.4 to 3.0 g P kg−1 DM, a statistically significant reduction in runoff P concentration was observed in all seasons. Elevated P concentrations in overland flow were observed for 28 d in spring and 9 d in summer and winter. The large drop in P concentrations between simulated rainfall events on Day 2 and Day 9 suggests that increasing the time interval between manure application and the generation of overland flow has a greater impact on P losses than does varying the dietary P content.
Broad‐Host‐Range Plasmids in Treated Wastewater Effluent and Receiving Streams
Authors: Akiyama Tatsuya , Asfahl Kyle L. , Savin Mary C.
Published: October 2010

The occurrence of broad‐host‐range (BHR) plasmid amplicons belonging to incompatibility (Inc) groups IncA/C, IncN, IncP, and IncW in two wastewater treatment plant (WWTP) effluents and effluent‐receiving streams in Northwest Arkansas, Mud Creek and Spring Creek, was determined. Community DNA captured on filter membranes and plasmid DNA extracted from antibiotic‐resistant Escherichia coli isolated from Mud Creek was used for polymerase chain reaction amplification of partial gene sequences specific to BHR plasmids. IncP plasmid amplicons were detected in effluent and downstream sites in both streams, while IncN and IncW plasmid amplicons were detected in Spring Creek in effluent and downstream but not upstream. IncA/C plasmid amplicons, in contrast, were detected at all sites, including upstream in most samples in Spring Creek and in one sample from Mud Creek. One IncP and two IncN were the only BHR plasmid amplicons found in 85 screened antibiotic‐resistant E. coli isolates, and were detected only in isolates from effluent and downstream samples. Broad‐host‐range plasmids frequently carry antibiotic‐resistance genes and can facilitate horizontal transfer of those genes. While BHR plasmids have been detected in WWTPs, WWTPs do not target these genetic elements for destruction. This study indicates that BHR plasmids are in WWTP effluent and are introducing BHR plasmids into streams. Additionally, species other than E. coli may be better targets as indicator bacteria for future studies of the impact of treated effluent on environmental dissemination of BHR plasmids.
Assessment of a Reclamation Cover System for Phosphogypsum Stacks in Central Alberta, Canada
Authors: Hallin Ingrid L. , Naeth M. Anne , Chanasyk David S. , Nichol Connie K.
Published: October 2010

Phosphogypsum (PG), a byproduct of the phosphate fertilizer industry, was produced and stockpiled at the Agrium Fort Saskatchewan facility from 1965 to 1991. Upon decommissioning, the outer slopes of the PG stacks were reclaimed by applying 15 cm of topsoil and planting a non‐native seed mix. Physical, chemical, and hydrologic evaluations of the cover system confirmed that plants were successfully growing in various soil capping depths and were often rooting more than 200 mm into the PG. Percolation past the substrate into PG during a typical storm event was low (<10 mm), and runoff from the stacks was negligible. Runoff quality met most guidelines, but some parameters, including fluoride, were up to 18 times higher than provincial or federal guidelines for soil and water quality. However, the cover system, when applied appropriately, does meet basic reclamation objectives. The exceedances are found in areas where the cover system has been compromised by erosion or mixing or in areas where the cover system has not been fully applied, such as roads or the inner basin. In areas where the cover system has been applied successfully, basic reclamation requirements are met.
Primary and Residual Effects of Abrams Tank Traffic on Prairie Soil Properties
Authors: Althoff Peggy S. , Thien Stephen J. , Todd Timothy C.
Published: October 2010

Mechanized maneuver training can impact soil quality in many ways, most notably through soil displacement and compaction. To identify indicator variables for inclusion in monitoring programs on military lands, a replicated small‐plot study of tracked vehicle disturbance effects on tallgrass prairie soil properties was initiated on Fort Riley, KS, in 2003. A range of disturbances encompassing soil surface texture, environmental conditions, and traffic intensity were evaluated. Soil physical (rutting and compaction) and chemical (soil organic matter and nutrients) properties were monitored annually on curve and straightaway track areas through 2007. Rut depth remained significant (P≤ 0.05) for curves of inside and outside tracks in both soil surface textures throughout the study and was more severe for repeated vs. single traffic events. Bulk density increased with disturbance under wet soil conditions, repeated traffic, and on curve areas but recovered to undisturbed levels within 1 to 3 yr. Soil compaction as measured by penetrometer resistance was more severe for traffic under wet soil conditions and remained significant (P≤ 0.05) at depths of 5 to 10 cm in both soil surface textures throughout the study. Residual effects of tank traffic on soil chemical properties were generally mild, but soil C was reduced following disturbance under wet soil conditions, repeated traffic, and on curve areas and required 3 to 4 yr to recover to undisturbed levels. The results of this study emphasize the importance of suitable impact management to maintain the sustainability of tallgrass prairie for military training activities.
Variability of the Illinois Soil Nitrogen Test across Time and Sampling Depth
Authors: Wall David P. , Weisz Randy , Crozier Carl R. , Heiniger Ronnie W. , White Jeffrey G.
Published: October 2010

There is potential for using the Illinois soil nitrogen test (ISNT) to improve N fertilizer recommendations for crops in the southeastern United States. The ISNT has been previously calibrated to predict N rates for corn (Zea mays L.) in North Carolina. This study evaluated the effects of sampling time, sampling depth, crop rotation, and fertilizer application on soil ISNT‐N during a 2‐yr period in the humid Coastal Plain and Piedmont regions of North Carolina. Ten sites were repeatedly sampled at 0‐ to 10‐, 10‐ to 20‐, and 20‐ to 30‐cm depths in fall, mid‐winter, and spring between October 2006 and May 2007. Illinois soil nitrogen test N, KCl‐extractable soil NO3–N and NH4–N, and soil organic matter (SOM) derived by loss‐on‐ignition (LOI) were evaluated at each sampling. Temporal changes in these soil parameters were evaluated for various crop rotations and N fertilizer applications. Soil ISNT‐N decreased with depth and showed significant variation with time at all three depths at all sites. Soil ISNT‐N was influenced by crop rotation and tillage but was not significantly affected by N fertilizer applications. Considering all sites together, ISNT‐N was well correlated with LOI; however, ISNT‐N was not correlated with LOI across time within sites. This suggests that the ISNT measured a fraction of SOM that behaved somewhat independently with time.
Optimizing Soil Hydraulic Parameters in RZWQM2 under Fallow Conditions
Authors: Fang Quan-Xiao , Green Timothy R. , Ma Liwang , Erskine Robert H. , Malone Robert W. , Ahuja Lajpat R.
Published: October 2010

Robust estimation of soil hydraulic parameters is essential for predicting soil water dynamics and related biogeochemical processes; however, uncertainties in estimated parameter values limit a model's ability for prediction and application. In this study, methods of global analysis (Latin hypercube sampling, LHS) and gradient‐based optimization (PEST, parameter estimation software) were explored to calibrate soil hydraulic parameters in the Root Zone Water Quality Model (RZWQM2). Six methods of estimating Brooks–Corey parameters of the soil water retention curve and saturated hydraulic conductivity were evaluated to simulate daily soil water dynamics under fallow conditions in eastern Colorado. The calibrated soil hydraulic parameters showed similar trends with soil depth for the different estimation methods in RZWQM2 but resulted in large differences between simulated and observed soil water contents. The PEST optimization based on soil type values as initial estimates gave reasonable soil water responses but with some unrealistic soil hydraulic parameters and soil evaporation. Overall, errors in simulated soil water contents were reduced by using LHS to initialize and constrain the PEST parameter space, which also stabilized the cross‐validation results. Calibration results using water content measurements at four depths (30, 60, 90, and 150 cm) were similar to results using 10 depths (30, 40, 50, 60, 70, 80, 90, 120, 150, and 170 cm). Calibrating soil hydraulic parameters remains challenging, but the combined calibration procedures (LHS + PEST) with cross‐validation can reduce parameter uncertainties and improve model performance.
Toward Landscape‐Scale Modeling of Soil Organic Matter Dynamics in Agroecosystems
Authors: Viaud Valérie , Angers Denis A. , Walter Christian
Published: October 2010

Because of its role in soil functioning, our ability to predict soil organic matter (SOM) dynamics, as influenced by natural and anthropogenic processes, is essential to mitigating soil degradation, ensuring food security, and improving the global environment. Numerous mathematical models have been developed to predict the response of SOM to agricultural practices at the soil‐profile or small‐plot scales. The same models, coupled with spatial databases, have been applied to larger spatial extents, especially in response to the demand for national inventories of soil C sequestration potential. Modeling SOM dynamics must also be developed at an intermediate integrative level to better investigate the relative importance of transfer and transformation processes in SOM dynamics in agricultural landscapes. Predictive models at the landscape scale will facilitate the assessment of the impact of SOM dynamics on the environment and provide management guidelines at the farm and watershed levels. We review the existing approaches and outline the various needs toward an integrated modeling of SOM at the landscape scale. Landscape‐scale modeling involves specific land area representation and model requirements, which include: modeling SOM dynamics in the uncultivated elements of a landscape; simulating SOM distribution and differential dynamics along the soil profile; modeling SOM vertical and lateral fluxes linked to erosion, dissolved organic matter fluxes, and litter transfer; and modeling the spatial distribution of organic matter input and management practices. Even though progress is being made toward all of these aspects, a fully integrated framework for SOM modeling at the landscape level has still to be developed. This will only be possible with the design of a flexible, three‐dimensional, spatially explicit representation of the landscape system and with the integration of functional interactions and organic matter transfer functions into the classical SOM modeling frameworks.
Available Organic Soil Phosphorus Has an Important Influence on Microbial Community Composition
Authors: DeForest Jared L. , Scott Lindsay G.
Published: October 2010

Soil acidity can have a potent influence on soil microbial composition and function, but it remains unclear if this influence is a direct response to the concentration of H+or an indirect response caused by the influence of pH on other soil chemical properties. We hypothesized that the composition and function of soil microorganisms would shift in response to decreases in the availability of inorganic P caused by mobilized Al. We tested this hypothesis at Dysart Woods, a mosaic of old growth and second growth mixed, mesophytic forest in eastern Ohio. We evaluated microbial community composition (phospholipid fatty acid [PLFA] analysis) and function (extracellular enzyme activity) in the context of P availability and common metrics of soil fertility. We observed a threshold response where available organic P (Po, i.e., bicarbonate‐extracted, molybdate‐unreactive P) dominated (∼80%) the availability of total available P when mobilized Al was present (>0.1 cmolckg−1), but when Al was immobilized, available inorganic P (Pi, i.e., bicarbonate‐extracted, molybdate‐reactive P) content was significantly greater (∼50%). Available Posignificantly correlated (r= 0.54) with acid phosphatase activity. Using nonmetric multidimensional scaling, we observed that PLFA composition ordination was significant along a gradient of soil pH and available PoBecause the composition and function of the microbial community changes due to available Po, results suggest that microbial communities in acidic forest soils are functionally P limited. The availability of Podid not influence the microbial biomass, however, indicating that the microbial community compensates for the apparent P limitation by altering its composition.
Application of Bio‐Organic Fertilizer Significantly Affected Fungal Diversity of Soils
Authors: Luo Jia , Ran Wei , Hu Jiang , Yang Xingming , Xu Yangchun , Shen Qirong
Published: October 2010

Cotton verticillium wilt (Verticillium dahliae Kleb.) is a very destructive disease. In this study, we evaluated a Bacillus subtilis enhanced bio‐organic fertilizer (BOF) for control of the disease and for its effect on rhizosphere microbiota. Greenhouse pot experiments were conducted during three cotton (Gossypium hirsutum L.) growing seasons with serial treatments of BOF or unenhanced organic fertilizer (OF). Consistent control of cotton verticillium wilt was obtained in the three trials. The complete BOF treatment, in which both nursery cups with healthy soils and transplanted pots with diseased soils were amended with BOF, was the most effective in reducing the counts of pathogenic V. dahliae and of total fungi in the cotton rhizosphere. The complete BOF treatment was also the most effective in reducing disease incidence. Rhizosphere soil DNA was extracted at harvest and the 5′ end (370 base pairs) of the fungal 18S rRNA gene was amplified by using the primer pair NS1 and GCFung (fungus specific). Seventy‐one bands were recognized in denaturing gradient gel electrophoresis (DGGE) gels and excised for sequencing, but only 35 bands were successfully sequenced during the study. Nonmetric multidimensional scaling analysis of DGGE patterns showed that the complete BOF treatments were not close to any other treatment. Ribotypes related to four Ascomycota and two Basidiomycota fungi were detected in the untreated but not in the BOF‐amended soil. The results suggest that the complete BOF treatment could effectively control cotton verticillium wilt by significantly improving fungal structure in rhizosphere soils.
Steady Infiltration from Point Sources and Water Uptake in Confined Cylindrical Domains
Authors: Communar Gregory , Friedman Shmulik P.
Published: October 2010

This article addresses the problem of steady water flow from point sources located in the center of a confined cylindrical domain. A linearized form of the water flow equation is used to analyze soil–water regimes, assuming exponential dependence of hydraulic conductivity on the matric head. Derived exact and approximate solutions are applicable to infiltration from a continuous point source into a cylindrical lysimeter and to water extraction by a subsurface point sink coupled to a surface source. Philip's superposition theorem, developed initially for a domain that is unconfined in the radial direction is shown to hold also for a cylindrically confined domain. An approximate, tractable expression keeping the first two terms of the full solution can satisfactorily replace the full accurate solution. Solutions for buried, surface, and subsurface point sources in a confined cylinder are expressed in terms of the dimensionless matric flux potential (MFP) and the dimensionless Stokes stream function. In the presence of an impermeable cylindrical boundary, the MFP decreases toward a constant value with increasing distance from the source, and the streamlines become more vertical at these distances. The smaller the cylinder radius or the soil sorptive number, the faster the MFP approaches constancy and the faster three‐dimensional flow converges to one‐dimensional flow below the source. Explicit expressions for the MFP and for the stream functions corresponding to a coupled surface point source and subsurface point sink in a semi‐infinite cylindrical domain are presented and used to simulate root water uptake rates in lysimeters. Water extraction rates produced by a coupled source/sink in the cylindrical domain are shown to be larger than those obtained in an unconfined domain and comparable with those computed for equivalent square‐arrays of coupled sources/sinks in open fields.
Soybean Response to Fluid Fertilizers Placed Near the Seed at Planting
Authors: Rehm George W. , Lamb John
Published: October 2010

As soybean [Glycine max (L.) Merr.] producers strive to improve profitability, placement of fertilizer either in contact with or near the seed should be given serious consideration. This study was conducted for the purpose of evaluating the impact of three fluid fertilizers applied at two rates near the seed at planting on soybean emergence, early growth, P uptake, and yield. All combinations of three factors (fertilizer grade, rate of application, and placement) were combined in a complete factorial in fields of cooperating soybean producers. The use of 10–15–0 (N–P–K) at 56 L ha−1 produced substantial reductions in emergence at sites where the soil had a silt loam texture. High rates of 4–4.4–8.3 and 3–8–15 fertilizer applied in contact with the seed also reduced emergence. When compared with the control, fertilizer placed near the seed increased whole plant weight, P concentration in the plant, and P uptake. Even though some treatments produced a substantial reduction in emergence, there was no significant negative effect on yield. The soybean crop growing on soils with very high levels of soil test P and K was apparently able to compensate for the reduced emergence. The data from this study lead to the conclusion that placement of fertilizer near the seed at planting should not be a suggested management practice.