bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACTDesign 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

ABSTRACTBatch 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

ABSTRACTIn 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

ABSTRACTBulk 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

ABSTRACTEarthworms 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

ABSTRACTProcess‐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

ABSTRACTSorption 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTRecent 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

ABSTRACTFew 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

ABSTRACTAn 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.