bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting and Measuring Environmental Concentration of Pesticides in Air after Soil Application
Authors: Ferrari Federico , Trevisan Marco , Capri Ettore
Published: June 2010

Pesticides can volatilize into the atmosphere, which affects the air quality. The ability to predict pesticide volatilization is an essential tool for human risk and environmental assessment. Even though there are several mathematical models to assess and predict the fate of pesticides in different compartments of the environment, there is no reliable model to predict volatilization. The objectives of this study were to evaluate pesticide volatilization under agricultural conditions using malathion [O,O‐dimethyl‐S‐(1,2‐dicarbethoxyethyl)‐dithiophosphate], ethoprophos (O‐ethyl S,S‐dipropylphosphorodithioate), and procymidone [N‐(3,5‐dichlorophenyl)‐1,2‐dimethylcyclopropane‐1,2‐dicarboximide] as test compounds and to evaluate the ability of the Pesticide Leaching Model (PELMO) to calculate the predicted environmental concentrations of pesticides in air under field conditions. The volatilization rate of procymidone, malathion, and ethoprophos was determined in a field study during two different periods (December 1998 and September 1999) using the Theoretical Profile Shape (TPS) method. The experiments were performed on bare silty soil in the Bologna province, Italy. Residues in the air were continuously monitored for 2 to 3 wk after the pesticide applications. The amount of pesticide volatilized was 16, 5, and 11% in December 1998 and 41, 23, and 19% in September 1999 for procymidone, malathion, and ethoprophos, respectively. In both these experiments, the PELMO simulations of the concentration of ethoprophos and procymidone were in good agreement with the measured data (factor ± 1.1 on average). The volatilization of malathion was underestimated by a factor of 30 on average. These results suggest that volatilization described by PELMO may be reliable for volatile substances, but PELMO may underpredict volatilization for less‐volatile substances.
Simple Protocols to Determine Dust Potentials from Cattle Feedlot Soil and Surface Samples
Authors: Miller Daniel N. , Woodbury Bryan L.
Published: June 2010

Cattle feedlot dust is an annoyance and may be a route for nutrient transport, odor emission, and pathogen dispersion, but important environmental factors that contribute to dust emissions are poorly characterized. A general protocol was devised to test feedlot samples for their ability to produce dust under a variety of environmental conditions. A blender was modified to produce dust from a variety of dried feedlot surface and soil samples and collect airborne particles on glass fiber filters by vacuum collection. A general blending protocol optimized for sample volume (150–175 cm3), blending time (5 min of pre‐blending), and dust collection time (15 s) provided consistent dust measurements for all samples tested. The procedure performed well on samples that varied in organic matter content, but was restricted to samples containing less than 200 to 700 g H2O kg−1 dry matter (DM). When applied to field samples, the technique demonstrated considerable spatial variability between feedlot pen sites. Mechanistically, dust potential was related to moisture and organic matter content. An alternative protocol also demonstrated differences within pen sites in maximum dust potential and dust airborne residence time. The two protocols were not intended, nor are they suitable, for predicting actual particulate matter emissions from agricultural sources. Rather, the protocols rapidly and inexpensively compared the potential for dust emission from samples of differing composition under a variety of environmental conditions.
Phenanthrene Sorption to Structurally Modified Humic Acids
Authors: Simpson Myrna J. , Chefetz Benny , Hatcher Patrick G.
Published: June 2010

Several studies emphasize the importance of soil organic matter characteristics in hydrophobic contaminant sorption and outline the strong dependence of sorption on organic matter aromaticity. In this study, the role of organic matter aromaticity in phenanthrene sorption was investigated using humic acids (HAs) from compost, peat, and soil that were structurally modified by bleaching, hydrolysis, oximation, and subcritical water extraction. The HAs were characterized with cross polarization magic angle spinning carbon‐13 nuclear magnetic resonance (CPMAS13C NMR) spectroscopy and used in batch equilibrations with phenanthrene. Bleaching substantially reduced the aromaticity of the samples whereas the other treatments increased the relative aromaticity. Phenanthrene sorption increased, even though there was a substantial reduction in sorbent aromaticity with some samples. The HAs that exhibited comparable CPMAS13C NMR spectra and aromaticity did not behave similarly with respect to phenanthrene sorption. When the sorption data (Kocvalues) were correlated to sample aromaticity, the correlation coefficients (r2) did not exceed 0.39. Comparisons with the atomic H to C ratio provided slightly betterr2values (up to 0.54). This study demonstrates that macroscopic sorbent characteristics could not explain the observed phenanthrene sorption coefficients, aliphatic structural components of HAs can contribute appreciably to phenanthrene sorption, and organic matter physical conformation may regulate access to organic matter structures. Therefore, the use of only macroscopic sorbent properties, such as aromaticity, to predict and rationalize sorption values cannot solely be used to explain the behavior of organic contaminants in soil environments.
Impact of Dissolved Organic Matter on Copper Mobility in Aquifer Material
Authors: Han Nizhou , Thompson Michael L.
Published: June 2010

Naturally occurring dissolved organic matter (DOM) and biosolids‐derived DOM have been implicated in the mobility of metals in soils and aquifer materials. To investigate the effect of DOM on copper mobility in aquifer material, DOM derived from sewage biosolids was separated into two apparent molecular‐weight (MW) fractions, 500 to 3500 Da (LMW) and >14000 Da (HMW). In each MW fraction, the DOM was further fractionated into hydrophilic, hydrophobic acid, and hydrophobic neutral compounds by an XAD‐8 chromatography technique. The mobility of these DOM components and their influences on copper transport in a sesquioxide‐coated, sandy aquifer material were examined with column transport experiments. The LMW DOM was found to be highly mobile, whereas the HMW DOM had a greater tendency to be retained by the aquifer material. Within the same MW fraction, the mobility of DOM followed the order of hydrophilic DOM > hydrophobic acid DOM > hydrophobic neutral DOM. Copper breakthrough curves in the presence of various DOM components showed that, except for the HMW hydrophilic fraction, DOM components enhanced Cu transport through the aquifer columns at early stages of transport (the first 75 pore volumes). In the later stages, however, all the DOM components substantially inhibited Cu mobility. We hypothesize that several mechanisms could account for retardation of Cu movement in the presence of the DOM fractions, including the formation of ternary complexes between the aquifer material, Cu, and DOM; changes in the electrostatic potential at the solid‐phase surface; and pH buffering by DOM.
Rainfall Timing and Frequency Influence on Leaching of Escherichia coli RS2G through Soil Following Manure Application
Authors: Saini R. , Halverson L. J. , Lorimor J. C.
Published: June 2010

The time between swine (Sus scrofa) manure application to soil as a crop fertilizer, the first rainfall event, and the frequency of rainfall events should influence leaching potential of fecal pathogens. Soil microcosms were inoculated in the lab with a swine manure isolate of Escherichia coli, strain RS2G, expressing green fluorescent protein, to examine how timing and frequency of rainfall events influences RS2G leaching and survival in soil. Liquid swine manure inoculated with RS2G was applied to intact soil cores (20 cm in diameter × 30 cm long) 4, 8, or 16 d before the first rainfall event (50.8 mm over a 4‐h period), and each core received one to three rainfall events. Manure application methods (no‐till surface‐broadcast, broadcast and incorporated, and tilled before broadcast) had no affect on leaching, although there was greater survival in soils when the manure had been incorporated. Most of the RS2G in the leachate appeared following the first rainfall event and RS2G leaching decreased with increasing time between manure application and the first rainfall, although leachates contained as much as 3.4 to 4.5 log colony forming units (CFU) 100 mL−1 of RS2G when the first rainfall occurred 16 d after manure application. With increasing frequency of rainfalls there was a decrease in subsequent concentrations of RS2G in the leachate. There was no correlation between leachate RS2G and total coliforms or fecal streptococci concentrations. Soil RS2G numbers were 1 to 10% of the inoculum regardless of the length of time between manure application and the first rainfall. RS2G leaching was mostly influenced by the time between manure application and first rainfall event, and significant leaching and survival in soil was possible even if the first rain occurred 16 d after manure application.
Bedding and Seasonal Effects on Chemical and Bacterial Properties of Feedlot Cattle Manure
Authors: Miller Jim J. , Beasley Bruce W. , Yanke L. Jay , Larney Francis J. , McAllister Tim A. , Olson Barry M. , Selinger L. Brent , Chanasyk David S. , Hasselback Paul
Published: June 2010

Nutrients, soluble salts, and pathogenic bacteria in feedlot‐pen manure have the potential to cause pollution of the environment. A three‐year study (1998–2000) was conducted at a beef cattle (Bos taurus) feedlot in southern Alberta, Canada to determine the effect of bedding material [barley (Hordeum vulgare L.) straw versus wood chips] and season on the chemical and bacterial properties of pen‐floor manure. Manure was sampled for chemical content (N, P, soluble salts, electrical conductivity, and pH) and populations of four groups of bacteria (Escherichia coli, total coliforms, and total aerobic heterotrophs at 27 and 39°C). More chemical parameters of manure were significantly (P ≤ 0.05) affected by season (SO4, Na, Mg, K, Ca, sodium adsorption ratio [SAR], total C, NO3–N, NH4–N, total P, and available P) than by bedding (K, pH, total C, C to N ratio, NH4–N, and available P). Bedding had no significant (P > 0.05) effect on the four bacterial groups whereas season affected all four groups. Numbers of E. coli and total coliforms (TC) were significantly higher by 1.72 to 2.02 log10 units in the summer than the other three seasons, which was consistent with a strong positive correlation of E. coli and TC with air temperature. The low ratio of bedding to manure in the pens was probably the major cause of the lack of significant bedding effects. Bedding material and seasonal timing of cleaning feedlot pens and land application of manure may be a potential tool to manage nutrients, soluble salts, and pathogens in manure.
Gas‐Phase Sorption–Desorption of Propargyl Bromide and 1,3‐Dichloropropene on Plastic Materials
Authors: Allaire S. E. , Yates S. R. , Ernst F. , Papiernik S. K.
Published: June 2010

The goal of this research was to provide information for choosing appropriate materials for studying gas‐phase concentrations of propargyl bromide (3BP) and 1,3‐dichloropropene (1,3‐D) in laboratory experiments. Several materials were tested and found to sorb both gas‐phase chemicals in the following order: stainless steel (SS) < Teflon polytetrafluoroethylene (PTFE‐FEP) ≈ flexible polyvinyl chloride (PVC) ≈ acrylic < low‐density polyethylene (PE) < vinyl ≈ silicone < polyurethane foam (PUF). Sorption of SS was insignificant and PUF sorbed all the fumigant that was applied. For the other materials, linear sorption coefficients (Kd) for 3BP ranged from 3.0 cm3 g−1 for PVC to 215 cm3 g−1 for silicone. Freundlich sorption coefficients for 1,3‐D ranged from 11.5 to 371 cm3 g−1 First‐order desorption rate constants in an open system ranged from 0.05 to 1.38 h−1 for 3BP and from 0.07 to 1.73 h−1 for 1,3‐D. In a closed system, less than 2% of sorbed fumigant desorbed from vinyl while up to 99% desorbed from PVC within 24 h when equilibrated at the highest headspace concentration. Sorption of both fumigants was linearly related to the square root of time except for vinyl and silicone. This may indicate non‐fickian diffusion of fumigant into the polymer matrix. Vinyl, silicone, PE, and PUF should be avoided for quantitative study of organic gases, except possibly as a trapping medium. Use of PTFE, PVC, and acrylic may require correction for sorption–desorption and diffusion.
Phosphorus Restrictions for Land Application of Biosolids
Authors: Shober Amy L. , Sims J. Thomas
Published: June 2010

The application of biosolids (sewage sludge) to agricultural soils provides P in excess of crop needs when applied to meet the N needs of most agronomic crops. These overapplications can result in the buildup of P in soils to values well above those needed for optimum crop yields and also may increase risk of P losses to surface and ground waters. Because of concerns regarding the influence of P on water quality in the USA, many state and federal agencies now recommend or require P‐based nutrient management plans for animal manures. Similar actions are now under consideration for the land application of biosolids. We reviewed the literature on this subject and conducted a national survey to determine if states had restrictions on P levels in biosolids‐amended soils. The literature review indicates that while the current N‐based approach to biosolids management does result in increases of soil P, some properties of biosolids may mitigate the environmental risk to water quality associated with land application of P in biosolids. Results of the survey showed that 24 states have regulations or guidelines that can be imposed to restrict land application of biosolids based on P. Many of these states use numerical thresholds for P in biosolids‐amended soils that are based on soil test phosphorus (STP) values that are much greater than the values considered to be agronomically beneficial. We suggest there is the need for a comprehensive environmental risk assessment of biosolids P. If risk assessment suggests the need for regulation of biosolids application, we suggest regulations be based on the P Site Index (PSI), which is the method being used by most states for animal manure management.
Spatial Variability of Nitrous Oxide Emissions and Their Soil‐Related Determining Factors in an Agricultural Field
Authors: Yanai Junta , Sawamoto Takuji , Oe Taku , Kusa Kanako , Yamakawa Keisuke , Sakamoto Kazunori , Naganawa Takahiko , Inubushi Kazuyuki , Hatano Ryusuke , Kosaki Takashi
Published: June 2010

To evaluate spatial variability of nitrous oxide (N2O) emissions and to elucidate their determining factors on a field‐scale basis, N2O fluxes and various soil properties were evaluated in a 100‐ × 100‐m onion (Allium cepa L.) field. Nitrous oxide fluxes were determined by a closed chamber method from the one‐hundred 10‐ × 10‐m plots. Physical (e.g., bulk density and water content), chemical (e.g., total N and pH), and biological (e.g., microbial biomass C and N) properties were determined from surface soil samples (0–0.1 m) of each plot. Geostatistical analysis was performed to examine spatial variability of both N2O fluxes and soil properties. Multivariate analysis was also conducted to elucidate relationships between soil properties and observed fluxes. Nitrous oxide fluxes were highly variable (average 331 μg N m−2 h−1, CV 217%) and were log–normally distributed. Log‐transformed N2O fluxes had moderate spatial dependence with a range of >75 m. High N2O fluxes were observed at sites with relatively low elevation. Multivariate analysis indicated that an organic matter factor and a pH factor of the principal component analysis were the main soil‐related determining factors of log‐transformed N2O fluxes. By combining multivariate analysis with geostatistics, a map of predicted N2O fluxes closely matched the spatial pattern of measured fluxes. The regression equation based on the soil properties explained 56% of the spatially structured variation of the log‐transformed N2O fluxes. Site‐specific management to regulate organic matter content and water status of a soil could be a promising means of reducing N2O emissions from agricultural fields.
Mineralogical Characteristics and Transformations during Long‐Term Operation of a Zerovalent Iron Reactive Barrier
Authors: Phillips D. H. , Watson D. B. , Roh Y. , Gu B.
Published: June 2010

Design and operation of Fe0 permeable reactive barriers (PRBs) can be improved by understanding the long‐term mineralogical transformations that occur within PRBs. Changes in mineral precipitates, cementation, and corrosion of Fe0 filings within an in situ pilot‐scale PRB were examined after the first 30 months of operation and compared with results of a previous study of the PRB conducted 15 months earlier using X‐ray diffraction and scanning electron microscopy employing energy dispersive X‐ray and backscatter electron analyses. Iron (oxy)hydroxides, aragonite, and maghemite and/or magnetite occurred throughout the cores collected 30 mo after installation. Goethite, lepidocrocite, mackinawite, aragonite, calcite, and siderite were associated with oxidized and cemented areas, while green rusts were detected in more reduced zones. Basic differences from our last detailed investigation include (i) mackinawite crystallized from amorphous FeS, (ii) aragonite transformed into calcite, (iii) akaganeite transformed to goethite and lepidocrocite, (iv) iron (oxy)hydroxides and calcium and iron carbonate minerals increased, (v) cementation was greater in the more recent study, and (vi) oxidation, corrosion, and disintegration of Fe0 filings were greater, especially in cemented areas, in the more recent study. If the degree of corrosion and cementation that was observed from 15 to 30 mo after installation continues, certain portions of the PRB (i.e., up‐gradient entrance of the ground water to the Fe0 section of the PRB) may last less than five more years, thus reducing the effectiveness of the PRB to mitigate contaminants.
Sorption of MS2 Bacteriophage to Layered Double Hydroxides
Authors: You Youwen , Vance George F. , Sparks Donald L. , Zhuang Jie , Jin Yan
Published: June 2010

Batch sorption and column breakthrough studies were conducted to investigate the potential of layered double hydroxides (LDHs) to remove bacteriophage MS2 from contaminated waters. All four of the LDHs evaluated in this study had very high retention capacities for MS2. Sorption results showed that MS2 could be completely removed from 5.2 × 102 plaque‐forming units (pfu)/mL solution by Mg–Al LDH 2 (i.e., 2:1 Mg to Al ratio LDH), with the highest sorption capacity observed in this study of 1.51 × 1010 pfu/g. Attachment of MS2 to LDHs was a rapid process and reached quasi‐equilibrium after a 1‐h reaction time. Within the pH range studied (pH 4–9), Mg–Al LDH 2 showed high sorption potential for MS2 at all pH values but sorption decreased slightly with increasing solution pH. Background solution anions influenced virus sorption, with SO2−4 and HPO2−4 decreasing sorption significantly whereas the presence of NO−3 had little effect on the attachment of MS2 to Mg–Al LDH 2. The addition of another virus (φX174) only caused a slight decrease in the retention of MS2 by Mg–Al LDH 2, suggesting that there was insignificant competitive sorption between MS2 and φX174 on LDH surfaces. Results from column experiments indicate that there was no MS2 breakthrough from columns packed with Mg–Al LDH 2–coated sand, suggesting complete MS2 retention at the virus concentration tested. The high mass recovery by beef extract solution revealed that the removal of viruses by the LDH was due to sorption of MS2 to LDH surfaces, rather than inactivation.
Are Methylmercury Concentrations in the Wetlands of Kejimkujik National Park, Nova Scotia, Canada, Dependent on Geology?
Authors: Siciliano Steven D. , Sangster Al , Daughney Chris J. , Loseto Lisa , Germida James J. , Rencz Andrew N. , O'Driscoll Nelson J. , Lean David R. S.
Published: June 2010

In the relatively pristine ecosystem in Kejimkujik Park, Nova Scotia, methylmercury (MeHg) concentrations in loons, Gavia immer, are among the highest recorded anywhere in the world. This study investigated the influence of bedrock lithology on MeHg concentrations in wetlands. Twenty‐five different wetland field sites were sampled over four different bedrock lithologies; Kejimkujik monzogranite, black sulfidic slate, gray slate, and greywacke. Soil samples were analyzed for ethylmercury (EtHg), MeHg, total Hg, acid‐volatile sulfides (AVS), organic matter, and water content as well as the biological parameters, mercury methyltransferase (HgMT) activity, sulfate reduction rates, fatty acid methyl ester (FAME) composition, and acidity. Methylmercury concentrations in the wetlands were highly dependent (P < 0.08) on lithology with no significant difference between bogs, fens, and swamps. Methylmercury concentrations in wetland soils developed on Kejimkujik monzogranite averaged 900 ng kg−1 compared with only 300 ng kg−1 in wetland soils developed on black sulfidic slate. Fatty acid methyl ester composition was also lithologically dependent (P < 0.001) with biomarkers for Desulfobulbus spp. discriminating between sites containing high and low MeHg concentrations. Levels of MeHg in wetlands were predicted mainly (41% of the sum of squares) by HgMT activity that differed (P < 0.009) between wetlands, with activity in bogs almost three times that present in swamps. Wetland MeHg concentrations are highly dependent on the lithology on which they have developed for largely biological reasons.
Influence of Organic Matter Decomposition on Soluble Carbon and Its Copper‐Binding Capacity
Authors: Merritt Karen A. , Erich M. Susan
Published: June 2010

Bulk and low molecular weight (LMW) (<1 kDa) water‐extractable carbon were collected from fresh and microbially degraded wheat straw (Triticum aestivum L.) and crimson clover (Trifolium incarnatum L.) residues to monitor early‐stage humification over an 8‐wk incubation. Copper complexation parameters were determined for both bulk and LMW water‐extractable C for both plant materials in a separate 1‐wk incubation. Humification progressed through increasing molar absorptivity (A285) and phenolic and total acidity (TA), and through an increase in average molecular size and degree of polymerization as determined by ultrafiltration and changes in fluorescence peak locations. Such dynamic transformations demonstrate that while humification is a bulk property, with C breakdown and stabilization occurring simultaneously and continuously in soil, its early stages can be effectively monitored for fresh plant residues. Significant changes consistently occurred during the first 7 d of the incubation and were more pronounced for LMW fractions than bulk extracts. For both residues, water‐extractable C extracted initially and following a 7‐d incubation desorbed and complexed 0.11 to 0.55 mmol resin‐bound Cu g−1 C. Low molecular weight water‐extractable C generated the higher values within this range, and values increased consistently following incubation. Potential concerns regarding LMW soluble Cu complexes include percolation through soils or runoff into adjacent water bodies as well as effects on plant root development.
Earthworm Additions Affect Leachate Production and Nitrogen Losses in Typical Midwestern Agroecosystems
Authors: Shuster William D. , Shipitalo Martin J. , Subler Scott , Aref Susanne , McCoy Edward L.
Published: June 2010

Earthworms affect soil structure and the movement of agrochemicals. Yet, there have been few field‐scale studies that quantify the effect of earthworms on dissolved nitrogen fluxes in agroecosystems. We investigated the influence of semi‐annual earthworm additions on leachate production and quality in different row crop agroecosystems. Chisel‐till corn (Zea maysL.)–soybean [Glycine max(L.) Merr.] rotation (CT) and ridge‐till corn–soybean–wheat (Triticum aestivumL.) rotation (RT) plots were arranged in a complete randomized block design (n= 3) with earthworm treatments (addition and ambient) as subplots where zero‐tension lysimeters were placed 45 cm below ground. We assessed earthworm populations semi‐annually and collected leachate biweekly over a three‐year period and determined leachate volume and concentrations of total inorganic nitrogen (TIN) and dissolved organic nitrogen (DON). Abundance of deep‐burrowing earthworms was increased in addition treatments over ambient and for both agroecosystems. Leachate loss was similar among agroecosystems, but earthworm additions increased leachate production in the range of 4.5 to 45.2% above ambient in CT cropping. Although leachate TIN and DON concentrations were generally similar between agroecosystems or earthworm treatments, transport of TIN was significantly increased in addition treatments over ambient in CT cropping due to increased leachate volume. Losses of total nitrogen in leachate loadings were up to approximately 10% of agroecosystem N inputs. The coincidence of (i) soluble N production and availability and (ii) preferential leaching pathways formed by deep‐burrowing earthworms thereby increased N losses from the CT agroecosystem at the 45‐cm depth. Processing of N compounds and transport in soil water from RT cropping were more affected by management phase and largely independent of earthworm activity.
Turfgrass Thatch Effects on Pesticide Leaching
Authors: Raturi S. , Carroll M. J. , Hill R. L.
Published: June 2010

Process‐based models are frequently used to assess the water quality impacts of turfgrass management emanating from proposed or existing golf courses. Thatch complicates the prediction of pesticide transport because surface‐applied pesticides must pass through an organic‐rich layer before entering the soil. This study was conducted to (i) compare the use of a linear equilibrium model (LEM) and two‐site nonequilibrium (2SNE) model to predict pesticide transport through soil and thatch + soil columns, and (ii) evaluate thatch effects on pesticide transport through soil columns with a volume‐averaging approach. Pesticide breakthrough curves were obtained for soil and thatch + soil columns from a 1 cm h−1 flux applied one day after applying triclopyr (3,5,6‐trichloro‐2‐pyridinyloxyacetic acid) and carbaryl (1‐napthyl‐methyl carbamate). Pesticide and bromide transport parameters indicated that nonequilibrium processes were affecting pesticide transport. Columns containing zoysiagrass (Zoysia japonica Steud.) thatch had lower triclopyr and carbaryl leaching losses than did soil‐only columns, although total reductions attributable to thatch did not exceed 15% of the applied pesticide. When laboratory‐based retardation factors were used, the 2SNE model explained 88 to 93% of the variability for triclopyr and 70 to 94% of the variability for carbaryl. Laboratory‐based retardation factors performed well in a 2SNE model to predict the peak concentration and tailing behavior of triclopyr and carbaryl with a volume‐averaging approach. These results suggest that separate representation of the thatch layer in process‐based models is not a prerequisite to obtain reasonable estimates of pesticide transport under steady state flow conditions.
Size Distribution of Organic Matter and Associated Propiconazole in Agricultural Runoff Material
Authors: Wu Qinglan , Riise Gunnhild , Kretzschmar Ruben
Published: June 2010

Sorption and desorption characteristics of propiconazole (1‐[[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1, 3‐dioxolan‐2‐yl] methyl]‐1H‐1,2,4‐triazole) to different particle/aggregate‐size fractions of agricultural runoff material were investigated. Emphasis was put on clay and colloidal size fractions to evaluate their role as potential sorbents and carriers for this pesticide. The runoff material was separated into size fractions ranging from 2 mm to ca. 15 nm by wet sieving, sedimentation, centrifugation, and membrane ultrafiltration. Each fraction was characterized by its organic C content and C/N ratio. Distinctive sorption properties of clay‐sized particles and colloids were investigated. The obtained size fractions differed significantly in their organic C concentration, C/N ratio, and sorption properties to propiconazole. Organic matter was mainly associated in aggregates >2 μm. Binding of propiconazole to this coarse fraction made up 80% of the sorbed propiconazole. The distribution coefficient between solid and aqueous phases increased with decreasing particle size. The colloidal fraction (<0.16 μm) exhibited the highest sorbtivity, with a distribution coefficient of 113 L kg−1, which was more than four times higher than that in the bulk sample (27 L kg−1). The fraction <2 μm represented 8% of the total sample weight, but contributed to 20% of the sorbed propiconazole. Strong hysteresis was observed for the sorption–desorption of propiconazole on the runoff material. Under dilution very little sorbed propiconazole will be released into the water phase. Due to its high sorbtivity and mobility and the strong sorption–desorption hysteresis, particles in the fraction <2 μm can be important carriers of propiconazole in runoff suspensions with high sediment load.
Effect of Formulation on the Behavior of 1,3‐Dichloropropene in Soil
Authors: Kim Jung‐Ho , Papiernik Sharon K. , Farmer Walter J. , Gan Jianying , Yates Scott R.
Published: June 2010

The fumigant 1,3‐dichloropropene (1,3‐D) has been identified as a partial replacement for methyl bromide (CH3Br) in soil fumigation. 1,3‐Dichloropropene is formulated for soil fumigation as Telone II (Dow AgroSciences, Indianapolis, IN) for shank application and as an emulsifiable concentrate (EC) (Telone EC or InLine; Dow AgroSciences) for drip application. This study investigated the effect of formulation on the phase partitioning, transformation rate, and volatilization of 1,3‐D isomers. Air–water partitioning coefficients (KH) were slightly higher for Telone II than for Telone EC, presumably due to the higher apparent water solubility of the EC formulation. Sorption of 1,3‐D isomers in two soils was not affected by formulation. Formulation had no significant effect on the rate of 1,3‐D transformation in water or soil. In general, differences in the rate of 1,3‐D transformation and phase partitioning due to formulation as Telone II or Telone EC were very small. Thus, the effect of formulation on 1,3‐D fate may be ignored in transformation and phase partition of 1,3‐D in water and soil. Packed soil columns without plastic tarp indicated that with relatively shallow subsurface (10 cm) drip application of Telone EC, emission of 1,3‐D isomers was more rapid and produced greater maximum instantaneous flux than deeper (30 cm) shank injection of Telone II. Both application methods resulted in the same cumulative emissions for both isomers, 45% for (E)‐1,3‐D and approximately 50% for (Z)‐1,3‐D. These results suggest that for drip application of fumigants to be effective in reducing emissions, the fumigant must be applied at sufficient depths to prevent rapid volatilization from the soil surface if the water application rate does not sufficiently restrict vapor diffusion.
Barley, a Potential Species for Initial Reclamation of Saline Composite Tailings of Oil Sands
Authors: Renault Sylvie , MacKinnon Mike , Qualizza Clara
Published: June 2010

The oil sands industry in Alberta (Canada) has developed the composite tailings (CT) process to reduce the fluid fine tails resulting from the processing of oil sands. This process uses a chemical coagulant (gypsum or alum) to produce aggregated fines (clay), so they are retained with the coarse sand fraction of the extraction tailings to form CT, from which fines‐free water is released relatively quickly compared with untreated tailings. The resulting CT and CT waters are saline‐sodic, with Na+, SO2−4, and Cl− being the dominant ions. When freshly deposited, the CT deposits are too soft for access by reclamation equipment, and the time required for these deposits to remove the water sufficiently to support traffic is uncertain. A greenhouse study was designed to determine the suitability of barley (Hordeum vulgare L.) for reclamation of fresh CT deposits and to evaluate benefits of peat amendments. This study assessed germination, early plant growth, chlorophyll content, and survival of barley growing in alum‐ and gypsum‐treated CT, with and without peat amendment. Ion and trace metal accumulation in the root and shoot tissues of barley was determined. Amendment of CT with peat improved germination, survival, and growth of barley, but did not prevent leaf injury (probably due to Na and Cl and possibly multiple nutrient deficiency). Field studies will be undertaken to validate our greenhouse results suggesting that barley could be used to improve dewatering of the freshly deposited substrates, reduce soil erosion, and facilitate leaching of ions by root penetration into the substrate.
Cesium‐134 and Strontium‐85 in Strawberry Plants following Wet Aerial Deposition
Authors: Carini F. , Brambilla M. , Mitchell N. , Ould‐Dada Z.
Published: June 2010

The understanding of the processes that control the behavior of radionuclides in crops can support policymakers to take actions to protect the environment and safeguard human health. Data concerning the behavior of radionuclides in fruits are limited. Strawberry (Fragaria × ananassa Duchesne) plants were contaminated on the aboveground part by sprinkling an aqueous solution of 134Cs and 85Sr at three growing stages: predormancy, anthesis, and beginning of ripening. Intercepted activity was more affected by the posture and physical orientation of leaves rather than by leaf area or biomass. Fruit interception ranges from 0.2 to 1.2% of the sprinkled activity. Translocation coefficients from leaf to fruit are on the order of 10−4 for 134Cs and 10−5 for 85Sr. Translocation reaches its highest intensity between anthesis and ripening. If deposition occurs when plants are bearing fruits, the fruit activity will be affected by the activity initially deposited on the fruit surfaces. This is important for 85Sr as it is not translocated in the phloem. The loss of the dead leaves at the resumption of growth causes high plant decontamination, but a fraction of both radionuclides remains in the storage organs, roots, and shoots, which is retranslocated to fruits in the following spring. The values of the environmental half‐time, tw, after deposition at predormancy are 114 d for 134Cs and 109 d for 85Sr. Cesium‐134 tends to be allocated to fruits, while 85Sr remains in leaves and crowns. Translocation of radionuclides to roots results in soil contamination.
Revisiting Nitrate Concentrations in the Des Moines River
Authors: McIsaac G. F. , Libra R. D.
Published: June 2010

Recent compilations of historical and contemporary riverine nitrate (NO3) concentrations indicate that concentrations in many rivers in the north‐central USA increased during the second half of the 20th century. The Des Moines River near Des Moines, Iowa, however, was reported to have had similar NO3 concentrations in 1945 and the 1980s, in spite of substantially greater N input to the watershed during the latter period. The objective of this study was to reconsider the comparison of historical and contemporary NO3 concentrations in the Des Moines River near Des Moines in light of the following: (i) possible errors in the historical data used, (ii) variations in methods of sample collection, (iii) variations in location of sampling, and (iv) additional data collected since 1990. We discovered that an earlier study had compared the flow‐weighted average concentration in 1945 to arithmetic annual average concentrations in the 1980s. The intertemporal comparison also appeared to be influenced by differences in sample collection methods and locations used at different times. Depending on the model used and the estimated effects of composite sample collection, the 1945 arithmetic average NO3 concentration was between 44 and 57% of the expected mean value at a similar water yield during 1976–2001. The flow‐weighted average NO3 concentration for 1945 was between 54 and 73% of the expected mean value at a similar water yield during 1976–2001. The difference between NO3 concentrations in 1945 and the contemporary period are larger than previously reported for the Des Moines River.
Intra‐Storm Study of Solute Chemical Composition of Overland Flow Water in Two Agricultural Fields
Authors: Langlois Jacques L. , Mehuys Guy R.
Published: June 2010

Few studies have assessed the transport of dissolved nutrients at the field scale under natural rainfall conditions. Hysteresis between dissolved nutrients and discharge behavior can complicate such assessments and this effect has only been examined qualitatively. In this study, we investigated factors contributing to short‐term variations of dissolved cation (Ca, Mg, Na, and K) and anion (soluble reactive phosphorus [SRP], NO3, and SO4) concentrations in runoff water and developed a quantitative method to study their hysteretic behavior. Within‐storm variations of dissolved nutrient concentrations were determined in two agricultural fields during four natural rainfall events along with discharge, sediment, antecedent soil water conditions, and nutrient contents. For each event, nutrient loads were plotted against discharge during the rising and falling limb of the runoff hydrograph. The resulting hysteresis curves were characterized by an index H, which is the ratio between the integrated areas under the rising and falling curves of the hydrograph. Results showed that nutrient concentrations increased with time during each event. Counterclockwise (H < 1) hysteresis, occurring when the falling limb had larger loads, was found when soils were initially dry whereas clockwise hysteresis (H > 1) was associated with prior wet soil conditions. Two hypotheses are suggested to explain these variations. First, suspended sediments could have acted as a sink for dissolved nutrients and the sensitivity of nutrients to hydrological conditions was determined by their preferential sorption on these sediments. Second, movement of nutrients into runoff occurred more readily as soils became wetter during an event.
Use of Alkaline Extraction to Quantify Sulfate Concentration in Oxidized Mine Tailings
Authors: Yin Guohong , Catalan Lionel J. J.
Published: June 2010

An alkaline extraction method has been developed for the determination of total sulfate in mine tailings containing secondary sulfate minerals formed by the oxidation of primary sulfides. Oxidized tailings were extracted with a 0.3 M NaOH solution at a liquid/solid ratio of 30 at room temperature for 16 h. The sulfate concentration in the extracts was determined by ion chromatography (IC). The coefficient of variation for sulfate determinations ranged from 1.9 to 3.2% for five tailings samples collected at two tailings impoundments. Mineralogical analysis of the tailings by scanning electron microscopy/X‐ray energy dispersive spectrometry (SEM/EDS) demonstrated that the extraction of sulfate was complete, with the exception of extremely insoluble barite. The proposed method is simple, yields an accurate yet rapid measurement of sulfate, and involves a safer laboratory operation than conventional methods that make use of strong HCl acid solutions. Moreover, this method allows the specific measurement of sulfate in the extract, whereas conventional methods are generally limited to the measurement of total S by inductively coupled plasma atomic emission spectrometry (ICP–AES) due to the interference of chloride with sulfate in IC.
Potential Nitrification and Denitrification on Different Surfaces in a Constructed Treatment Wetland
Authors: Bastviken Sofia Kallner , Eriksson Peder G. , Martins Irene , Neto João M. , Leonardson Lars , Tonderski Karin
Published: June 2010

Improved understanding of the importance of different surfaces in supporting attached nitrifying and denitrifying bacteria is essential if we are to optimize the N removal capacity of treatment wetlands. The aim of this study was therefore to examine the nitrifying and denitrifying capacity of different surfaces in a constructed treatment wetland and to assess the relative importance of these surfaces for overall N removal in the wetland. Intact sediment cores, old pine and spruce twigs, shoots of Eurasian watermilfoil (Myriophyllum spicatum L.), and filamentous macro‐algae were collected in July and November 1999 in two basins of the wetland system. One of the basins had been constructed on land that contained lots of wood debris, particularly twigs of coniferous trees. Potential nitrification was measured using the isotope‐dilution technique, and potential denitrification was determined using the acetylene‐inhibition technique in laboratory microcosm incubations. Nitrification rates were highest on the twigs. These rates were three and 100 times higher than in the sediment and on Eurasian watermilfoil, respectively. Potential denitrification rates were highest in the sediment. These rates were three times higher than on the twigs and 40 times higher than on Eurasian watermilfoil. The distribution of denitrifying bacteria was most likely due to the availability of organic material, with higher denitrification rates in the sediment than on surfaces in the water column. Our results indicate that denitrification, and particularly nitrification, in treatment wetlands could be significantly increased by addition of surfaces such as twigs.
Soil Microbial Communities Associated with Bt and Non‐Bt Corn in Three Soils
Authors: Blackwood Christopher B. , Buyer Jeffrey S.
Published: June 2010

The effects of expression of Cry endotoxin by Bt corn (transgenic corn engineered to express Bacillus thuringiensis toxin) on soil microbial community structure were assessed in a growth chamber experiment. Two lines of transgenic corn expressing different Cry endotoxins were compared with their respective non‐transgenic isolines in three soil types with differing textures. Phospholipid fatty acid (PLFA) profiles from bulk soil and community‐level physiological profiles (CLPP) from the rhizosphere community were used to assess community structure. Differences in PLFA profiles due to soil type were significant, accounting for 73% of the total variability in the dataset. Differences in bacterial and fungal CLPP profiles due to soil type were statistically significant, but probably not biologically important, accounting for 6.3 and 3.8% of the total variability, respectively. Neither expression of Cry endotoxin nor corn line had a significant effect on microbial profiles, except in the high‐clay soil where both factors significantly affected bacterial CLPP profiles (accounting for 6.6 and 6.1% of the variability in that soil, respectively). Expression of Cry endotoxin also significantly reduced the presence of eukaryotic PLFA biomarker in bulk soils, although it is unclear which groups of eukaryotes were affected. We conclude that the effects of transgenic Bt corn in this short‐term experiment are small, and longer‐term investigations are necessary.
Plant and Soil Responses to Biosolids Application following Forest Fire
Authors: Meyer V. F. , Redente E. F. , Barbarick K. A. , Brobst R. B. , Paschke M. W. , Miller A. L.
Published: June 2010

Soil stability and revegetation is a great concern following forest wildfires. Biosolids application might enhance revegetation efforts and enhance soil stability. In May 1997, we applied Metro Wastewater Reclamation District (Denver, CO, USA) composted biosolids at rates of 0, 5, 10, 20, 40, and 80 Mg ha−1 to a severely burned, previously forested site near Buffalo Creek, CO to improve soil C and N levels and help establish eight native, seeded grasses. The soils on the site belong to the Sphinx series (sandy‐skeletal, mixed, frigid, shallow Typic Ustorthents). Vegetation and soils data were collected for four years following treatment. During the four years following treatment, total plant biomass ranged from approximately 50 to 230 g m−2 and generally increased with increasing biosolids application. The percentage of bare ground ranged from 4 to 58% and generally decreased with increasing biosolids rate. Higher rates of biosolids application were associated with increased concentrations of N, P, and Zn in tissue of the dominant plant species, streambank wheatgrass [Elymus lanceolatus (Scribn. & J.G. Sm) Gould subsp. lanceolatus], relative to the unamended, unfertilized control. At two months following biosolids application (1997), total soil C and N at soil depths of 0 to 7.5, 7.5 to 15, and 15 to 30 cm showed significant (P < 0.05) linear increases (r2 > 0.88) as biosolids rate increased. The surface soil layer also showed this effect one year after application (1998). For Years 2 through 4 (1999–2001) following treatment, soil C and N levels declined but did not show consistent trends. The increase in productivity and cover resulting from the use of biosolids can aid in the rehabilitation of wildfire sites and reduce soil erosion in ecosystems similar to the Buffalo Creek area.
Denitrification Potential in Relation to Lithology in Five Headwater Riparian Zones
Authors: Hill Alan R. , Vidon Philippe G. F. , Langat Jackson
Published: June 2010

The influence of riparian zone lithology on nitrate dynamics is poorly understood. We investigated vertical variations in potential denitrification activity in relation to the lithology and stratigraphy of five headwater riparian zones on glacial till and outwash landscapes in southern Ontario, Canada. Conductive coarse sand and gravel layers occurred in four of the five riparian areas. These layers were thin and did not extend to the field–riparian perimeter in some riparian zones, which limited their role as conduits for ground water flow. We found widespread organic‐rich layers at depths ranging from 40 to 300 cm that resulted from natural floodplain processes and the burial of surface soils by rapid valley‐bottom sedimentation after European settlement. The organic matter content of these layers varied considerably from 2 to 5% (relic channel deposit) to 5 to 21% (buried soils) and 30 to 62% (buried peat). Denitrification potential (DNP) was measured by the acetylene block method in sediment slurries amended with nitrate. The highest DNP rates were usually found in the top 0‐ to 15‐cm surface soil layer in all riparian zones. However, a steep decline in DNP with depth was often absent and high DNP activity occurred in the deep organic‐rich layers. Water table variations in 2000–2002 indicated that ground water only interacted frequently with riparian surface soils between late March and May, whereas subsurface organic layers that sustain considerable DNP were below the water table for most of the year. These results suggest that riparian zones with organic deposits at depth may effectively remove nitrate from ground water even when the water table does not interact with organic‐rich surface soil horizons.