bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution Behavior of Pyrene to Adsorbed Humic Acids on Kaolin
Authors: Terashima Motoki , Tanaka Shunitz , Fukushima Masami 
Published: August 2012

ABSTRACTThe distribution behavior of pyrene on humic acid (HA)–kaolin complexes, prepared by adsorbing HA on kaolin, was investigated by batch experiments. The distribution coefficient (Kd) of pyrene on the HA–kaolin complex increased with the fraction (foc) of organic carbon adsorbed to the surface of the kaolin. This can be attributed to hydrophobic interactions between pyrene and the adsorbed HAs. The effects of adsorbed HAs were quantitatively evaluated by calculating the distribution coefficient (Koc) and affinity constant (Kadsoc) for pyrene to the adsorbed HAs. A fluorescence quenching method was employed to determine the affinity constant (Kaqoc) of pyrene to HAs dissolved in an aqueous solution. When the Koc values were compared with the Kaqoc values, the Koc values were found to be 4 to 11 times larger than the Kaqoc values. On the other hand, the Kadsoc values were 4 to 9 times larger than the Kaqoc values. These indicate that the affinity for pyrene is enhanced by the adsorption of HAs to kaolin. In addition, the Koc values increased with increasing average molecular weights of the HAs. These results demonstrate that HAs, when they are adsorbed to clay minerals, play an important role in the deposition of polycyclic aromatic hydrocarbons (PAHs) in a soil environment.
Fertilizer Use Efficiency and Nitrate Leaching in a Tropical Sandy Soil
Authors: Nyamangara J. , Bergström L. F. , Piha M. I. , Giller K. E. 
Published: August 2012

ABSTRACTMaize (Zea mays L.) production in the smallholder farming areas of Zimbabwe is based on both organic and mineral nutrient sources. A study was conducted to determine the effect of composted cattle manure, mineral N fertilizer, and their combinations on NO3 concentrations in leachate leaving the root zone and to establish N fertilization rates that minimize leaching. Maize was grown for three seasons (1996–1997, 1997–1998, and 1998–1999) in field lysimeters repacked with a coarse‐grained sandy soil (Typic Kandiustalf). Leachate volumes ranged from 480 to 509 mm yr−1 (1395 mm rainfall) in 1996–1997, 296 to 335 mm yr−1 (840 mm rainfall) in 1997–1998, and 606 to 635 mm yr−1 (1387 mm rainfall) in 1998–1999. Mineral N fertilizer, especially the high rate (120 kg N ha−1), and manure plus mineral N fertilizer combinations resulted in high NO3 leachate concentrations (up to 34 mg N L−1) and NO3 losses (up to 56 kg N ha−1 yr−1) in 1996–1997, which represent both environmental and economic concerns. Although the leaching losses were relatively small in the other seasons, they are still of great significance in African smallholder farming where fertilizer is unaffordable for most farmers. Nitrate leaching from sole manure treatments was relatively low (average of less than 20 kg N ha−1 yr−1), whereas the crop uptake efficiency of mineral N fertilizer was enhanced by up to 26% when manure and mineral N fertilizer were applied in combination. The low manure (12.5 Mg ha−1) plus 60 kg N ha−1 fertilizer treatment was best in terms of maintaining dry matter yield and minimizing N leaching losses.
Residual Soil Nitrate after Potato Harvest
Authors: Bélanger Gilles , Ziadi Noura , Walsh John R. , Richards John E. , Milburn Paul H. 
Published: August 2012

ABSTRACTNitrogen loss by leaching is a major problem, particularly with crops requiring large amounts of N fertilizer. We evaluated the effect of N fertilization and irrigation on residual soil nitrate following potato (Solanum tuberosum L.) harvests in the upper St‐John River valley of New Brunswick, Canada. Soil nitrate contents were measured to a 0.90‐m depth in three treatments of N fertilization (0, 100, and 250 kg N ha−1) at two on‐farm sites in 1995, and in four treatments of N fertilization (0, 50, 100, and 250 kg N ha−1) at four sites for each of two years (1996 and 1997) with and without supplemental irrigation. Residual soil NO3–N content increased from 33 kg NO3–N ha−1 in the unfertilized check plots to 160 kg NO3–N ha−1 when 250 kg N ha−1 was applied. Across N treatments, residual soil NO3–N contents ranged from 30 to 105 kg NO3–N ha−1 with irrigation and from 30 to 202 kg NO3–N ha−1 without irrigation. Residual soil NO3–N content within the surface 0.30 m was related (R2 = 0.94) to the NO3–N content to a 0.90‐m depth. Estimates of residual soil NO3–N content at the economically optimum nitrogen fertilizer application (Nop) ranged from 46 to 99 kg NO3–N ha−1 under irrigated conditions and from 62 to 260 kg NO3–N ha−1 under nonirrigated conditions, and were lower than the soil NO3–N content measured with 250 kg N ha−1 We conclude that residual soil NO3–N after harvest can be maintained at a reasonable level (<70 kg NO3–N ha−1) when N fertilization is based on the economically optimum N application.
Phosphorus Removal in Vegetated Filter Strips
Authors: Abu‐Zreig Majed , Rudra Ramesh P. , Whiteley Hugh R. , Lalonde Manon N. , Kaushik Narinder K. 
Published: August 2012

ABSTRACTVegetated filter strips (VFS) are used recently for removal, at or near the source, of sediment and sediment‐bound chemicals from cropland runoff. Vegetation within the flowpath increases water infiltration and decreases water turbulence, thus enhancing pollutant removal by sedimentation within filter media and infiltration through the filter surface. Field experiments have been conducted to examine the efficiency of vegetated filter strips for phosphorus removal from cropland runoff with 20 filters with varying length (2 to 15 m), slope (2.3 and 5%), and vegetated cover, including bare‐soil plots as control. Artificial runoff used in this study had an average phosphorus concentration of 2.37 mg L−1 and a sediment concentration of 2700 mg L−1 The average phosphorus trapping efficiency of all vegetated filters was 61% and ranged from 31% in a 2‐m filter to 89% in a 15‐m filter. Filter length has been found to be the predominant factor affecting P trapping in VFS. The rate of inflow, type of vegetation, and density of vegetation coverage had secondary influences on P removal. Short filters (2 and 5 m), which are somewhat effective in sediment removal, are much less effective in P removal. Increasing the filter length beyond 15 m is ineffective in enhancing sediment removal but is expected to further enhance P removal. Sediment deposition, infiltration, and plant adsorption are the primary mechanisms for phosphorus trapping in VFS.
A Two‐Dimensional Model for Simulating the Transport and Fate of Toxic Chemicals in a Stratified Reservoir
Authors: Gu Roy R. , Chung Se‐Woong 
Published: August 2012

ABSTRACTA two‐dimensional reservoir toxics model is essential to establishing effective water resources management and protection. In a reservoir, the fate of a toxic chemical is closely connected with flow regimes and circulation patterns. To better understand the kinetic processes and persistence and predict the dissipation of toxic contaminants in the reservoir during a spill or storm runoff event, a toxics submodel was developed and incorporated into an existing laterally integrated hydrodynamics and transport model. The toxics submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. The two‐dimensional toxicant simulation model was applied to Shasta Reservoir in California to simulate the physico–chemical processes and fate of a volatile toxic compound, methyl isothiocyanate (MITC), during a chemical spill into the Sacramento River in 1991. The predicted MITC concentrations were compared with those observed. The effect of reservoir flow regimes on the transport and fate of the toxic substance was investigated. The results suggested that the persistence of MITC is significantly influenced by different flow regimes. Methyl isothiocyanate is more persistent in the reservoir under an interflow condition due to reduced volatilization from deep layers than under an overflow condition. In the overflow situation, the plume moved more slowly toward the dam and experienced greater dissipation. This analysis can assist in toxic spill control and reservoir management, including field sampling and closure of water intakes.
Enzymatic Oxidative Transformation of Chlorophenol Mixtures
Authors: Bollag J.‐M. , Chu Horng‐Lun , Rao M. A. , Gianfreda L. 
Published: August 2012

ABSTRACTChlorinated phenols are major industrial and agricultural xenobiotics that pollute soil and ground water. It has been shown that laccases catalyze the oxidative coupling of phenolic compounds. Therefore, the transformation of one or a mixture of several chlorinated phenols by a laccase from the fungus Trametes villosa was studied. Generally, if more than one phenol was added, the transformation of chlorinated phenols decreased, and if the concentration of the laccase was increased, the transformation of the phenols was enhanced. There were exceptions to these observations: for instance, the transformation of 0.1 mM 4‐chlorophenol incubated with 1 mM 2,4‐dichlorophenol in buffered salt solutions was not enhanced if the concentration of the laccase was increased from 2 to 20 DMP units/mL. The reason for the reduced transformation of chlorinated phenols in the presence of additional phenols is still unknown. However, in spite of some limitations, the application of laccase to decontaminate wastewater polluted with chlorinated phenols appears feasible.
Evaluation of Nitrate Nitrogen Fluxes from a Tile‐Drained Watershed in Central Iowa
Authors: Tomer M. D. , Meek D. W. , Jaynes D. B. , Hatfield J. L. 
Published: August 2012

ABSTRACTNitrate N fluxes from tile‐drained watersheds have been implicated in water quality studies of the Mississippi River basin, but actual NO3–N loads from small watersheds during long periods are poorly documented. We evaluated discharge and NO3–N fluxes passing the outlet of an Iowa watershed (5134 ha) and two of its tile‐drained subbasins (493 and 863 ha) from mid‐1992 through 2000. The cumulative NO3–N load from the catchment was 168 kg ha−1, and 176 and 229 kg ha−1 from the subbasins. The outlet had greater total discharge (1831 mm) and smaller flow‐weighted mean NO3–N concentration (9.2 mg L−1) than the subbasins, while the larger subbasin had greater discharge (1712 vs. 1559 mm) and mean NO3–N concentration (13.4 vs. 11.3 mg L−1) than the smaller subbasin. Concentrations exceeding 10 mg L−1 were common, but least frequent at the outlet. Nitrate N was generally not diluted by large flows, except during 1993 flooding. The outlet showed smaller NO3–N concentrations at low flows. Relationships between discharge and NO3–N flux showed log–log slopes near 1.0 for the subbasins, and 1.2 for the outlet, considering autocorrelation and measurement‐error effects. We estimated denitrification of subbasin NO3–N fluxes in a hypothetical wetland using published data. Assuming that temperature and NO3–N supply could limit denitrification, then about 20% of the NO3–N would have been denitrified by a wetland constructed to meet USDA‐approved criteria. The low efficiency results from the seasonal timing and NO3–N content of large flows. Therefore, agricultural and wetland best management practices (BMPs) are needed to achieve water quality goals in tile‐drained watersheds.
Polyvalent Cation Effects on myo‐Inositol Hexakis Dihydrogenphosphate Enzymatic Dephosphorylation in Dairy Wastewater
Authors: Dao Thanh H. 
Published: August 2012

ABSTRACTInformation is needed on organic polyphosphates such as myo‐inositol 1,2,3,5/4,6‐hexakis dihydrogenphosphate or phytate (IP6) contribution to the sources and sinks of dissolved phosphorus (PO4–P) in the soil–manure–water system. Effects of Na+, Ca2+, Al3+, and Fe3+ and cation to IP6‐P mole ratios on the enzymatic dephosphorylation of IP6 were studied to determine controlling mechanisms of dephosphorylation and persistence in manure. Phytate‐ and PO4–P were analyzed by high‐performance liquid chromatography. Phytate dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 decreases by 50 ± 3.6 and 40 ± 4% at pH 4.5 and 6, respectively, as Ca2+ concentrations increase and cation to IP6‐P mole ratios reach 6:6. Polyanionic IP6 has a high affinity for Al3+ and Fe3+ and reductions in dephosphorylation average 27 and 32% at a cation to IP6‐P mole ratio of 1:6 for Al3+ and Fe3+, respectively, while reaching more than 99% at a mole ratio of 6:6. A phytase‐hydrolyzable phosphorus (PHP) fraction is native to ruminant animal manure and is proportional to total solids (TS) concentration in 1 to 100 g L−1 suspensions. Added phytase, in effect, increases water‐extractable P content of manure and the risk of environmental P dispersion. As the bioavailability and ecological effect of IP6‐P appear to be regulated not only by pH‐controlled enzyme activity but also by the associated counterions, the differential protective effects of cations influence the accuracy of manure PHP fraction estimates and increase phytate resistance to enzymatic dephosphorylation that may lead to its persistence in manure.
Determination of Redox‐Sensitive Phosphorus in Field Runoff without Sediment Preconcentration
Authors: Uusitalo Risto , Turtola Eila 
Published: August 2012

ABSTRACTReduction‐induced phosphorus (P) release from particles transported by field runoff has been poorly studied for want of a method that could be used for large surveys. To rectify this shortcoming, we modified the bicarbonate–dithionite (BD) extraction step of a sediment P speciation scheme for analyzing redox‐sensitive P in runoff without sample preconcentration. The extraction comprised the addition of bicarbonate (pH buffer) and dithionite (reducing agent) into a runoff sample, 15 min of gentle shaking, filtration, and sample digestion. The samples were greatly reduced (Eh < −200 mV), and Fe and P were solubilized, but Al solubility was not increased. Phosphorus release from rock phosphates (calcium phosphates) was greater in the BD extraction than in water or bicarbonate solution, although no more than 0.2% of the total P was released. For runoff from a very fine Typic Cryaquept, the particulate phosphorus (PP) versus BD‐PP relationship was linear up to a PP concentration of about 1.0 mg L−1, but over the whole PP range studied (up to 2.6 mg L−1) somewhat better described by an exponential equation (BD‐PP = 0.297 × PP0.766; r2 = 0.91, n = 79). The minimum detectable value given by the method was relatively low, 0.023 mg L−1, but reproducibility varied, with the coefficient of variation for 10 samples analyzed with 5 replicates ranging from 1.8 to 28.5%. Considering the variable reproducibility of the results and the lack of suitable reference material, the method needs further refinement and testing if it is to be used for quantitative determination of redox‐sensitive P in runoff.
Nutrient Transport in a Restored Riparian Wetland
Authors: Vellidis G. , Lowrance R. , Gay P. , Hubbard R. K. 
Published: August 2012

ABSTRACTWe determined the water quality effect of a restored forested riparian wetland adjacent to a manure application area and a heavily fertilized pasture in the Georgia Coastal Plain. The buffer system was managed based on USDA recommendations and averaged 38 m in width. Water quality and hydrology data were collected from 1991–1999. A nitrate plume in shallow ground water with concentrations exceeding 10 mg NO3–N L−1 moved into the restored forested riparian wetland. Along most of the plume front, concentrations were less than 4 mg NO3–N L−1 within 25 m. Two preferential flow paths associated with past hydrologic modifications to the site allowed the nitrate plume to progress further into the restored forested riparian wetland. Surface runoff total N, dissolved reactive phosphorus (DRP), and total P concentrations averaged 8.63 mg N L−1, 1.37 mg P L−1, and 1.48 mg P L−1, respectively, at the field edge and were reduced to 4.18 mg N L−1, 0.31 mg P L−1, and 0.36 mg P L−1, respectively, at the restored forested riparian wetland outlet. Water and nutrient mass balance showed that retention and removal rates for nitrogen species ranged from a high of 78% for nitrate to a low of 52% for ammonium. Retention rates for both DRP and total P were 66%. Most of the N retention and removal was accounted for by denitrification. Mean annual concentrations of total N and total P leaving the restored forested riparian wetland were 1.98 mg N L−1 and 0.24 mg P L−1, respectively.
Denitrification in Constructed Wetlands Used for Treatment of Swine Wastewater
Authors: Hunt Patrick G. , Matheny Terry A. , Szögi Ariel A. 
Published: August 2012

ABSTRACTConstructed wetland treatment of swine wastewater probably involves substantial denitrification. Our objective was to assess denitrification and denitrification enzyme activity (DEA) in such wetlands in relation to plant communities, N loading, carbon or nitrogen limitations, and water depth. Two wetland cells each 3.6 m wide and 33.5 m long were connected in series. One set of cells was planted with rushes and bulrushes, including soft rush (Juncus effusus L.), softstem bulrush [Schoenoplectus tabernaemontani (K.C. Gmel.) Palla], American bulrush [Schoenoplectus americanus (Pers.) Volkart ex Schinz & R. Keller], and woolgrass bulrush [Scirpus cyperinus (L.) Kunth]. Another set was planted with bur‐reeds and cattails, including American bur‐reed (Sparganium americanum Nutt.), broadleaf cattail (Typha latifolia L.), and narrowleaf cattail (Typha angustifolia L.). The sets will be referred to herein as bulrush and cattail wetlands, respectively. Denitrification and DEA were measured via the acetylene inhibition method in intact soil cores and disturbed soil samples that were taken during four years (1994–1997). Although DEA in the disturbed samples was greater than denitrification in the core samples, the measurements were highly correlated (r2 ≥ 0.82). The DEA was greater in the bulrush wetlands than the cattail wetlands, 0.516 and 0.210 mg N kg−1 soil h−1, respectively; and it increased with the cumulative applied N. The DEA mean was equivalent to 9.55 kg N ha−1 d−1 in the bulrush wetlands. We hypothesized and confirmed that DEA was generally limited by nitrate rather than carbon. Moreover, we determined that one of the most influential factors in DEA was wetland water depth. In bulrush wetlands, the slope and r2 values of the control treatment were −0.013 mg N kg−1 soil h−1 mm−1 depth and r2 = 0.89, respectively. Results of this investigation indicate that DEA can be very significant in constructed wetlands used to treat swine wastewater.
Iron Sulfide Oxidation as Influenced by Calcium Carbonate Application
Authors: Hossner L. R. , Doolittle J. J. 
Published: August 2012

ABSTRACTTwo overburden materials, with different FeS2contents (1.9 and 4.1%) and low acid neutralization potential, were limed with CaCO3at rates of 0, 25, 50, 75, 100, and 125% based on the amount of CaCO3needed to provide an acid–base account deficit (A/Ba) of zero (A/Ba= neutralization potential − potential acidity − exchangeable acidity). The limed overburden materials were inoculated withThiobacillus ferrooxidansand leached weekly with deionized water. Residual FeS2and CaCO3were determined in samples over a 378‐d period. Oxidation followed zero‐order kinetics with respect to FeS2concentration at pH values greater than 4 and first‐order kinetics at pH values less than 4. Zero‐order oxidation rates ranged from 0.0l to 0.46 μmol g−1d−1in the overburden with 1.9% FeS2and from 0.01 to 0.22 μmol g−1d−1in the overburden with 4.1% FeS2Oxidation following the first‐order rate law had a first‐order rate constant of 0.03 d−1in the 1.9% FeS2overburden and 0.01 d−1in the 4.1% FeS2overburden. The calculated half‐life was 23 d for the 1.9% FeS2overburden and 69 d for the 4.1% FeS2overburden. Additions of CaCO3affected FeS2oxidation by controlling the pH of the system. Liming to greater than 50% of the acid–base account deficit did not significantly affect the zero‐order oxidation rate. Dissolution of the applied CaCO3was found to be faster than the oxidation of FeS2at pH values greater than 4. It was projected that at lime rates up to 125%, the CaCO3would dissolve and leach out of the system before all the FeS2oxidized, leaving the potential for acid minesoil formation.
Compost and Calcium Surface Treatment Effects on Subsoil Chemistry in Acidic Minespoil Columns
Authors: von Willert Frank J. , Stehouwer Richard C. 
Published: August 2012

ABSTRACTSurface incorporation of a liming agent in combination with compost or biosolids is a proven way to revegetate acidic minespoils, but little is known about the effect of the surface amendments on subsoil chemistry. We conducted a greenhouse column experiment to investigate how different surface amendments affected plant growth and subsoil chemistry in highly acidic minespoil material. Columns were filled with shale minespoil material (pH ≈ 2.5), amended with CaCO3, CaSO4·2H2O (gypsum), and two rates of compost, and seeded with birdsfoot trefoil (Lotus corniculatus L.) and ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.). We measured leachate and plant growth over a 170‐d period with extensive irrigation. Without CaCO3, plants could only grow at the high compost rate (68.8 g kg−1), even though the soil pH in those treatments was below 3.5, indicating the capability of natural organic matter to detoxify Al3+ by forming Al–organic matter complexes. Compost had no effect on the subsoil. When CaCO3 or gypsum was added to the surface, extractable Ca increased in the subsoil, but there was no relevant increase in subsoil pH. Even in the first 5 cm of subsoil material, extractable Al did not decrease very much, possibly because a jurbanite‐like solid phase controlled subsoil Al3+ activities. During the reclamation of highly acidic minespoil material one should therefore not expect significant effects of the surface treatment on the untreated subsoil. A sufficient root zone would have to be achieved by incorporating the liming agent down to the desired rooting depth.
Laboratory‐Scale Measurement of Trace Gas Fluxes from Landfarm Soils
Authors: Ausma Sandra , Edwards Grant C. , Gillespie Terry J. 
Published: August 2012

ABSTRACTTrace gas emissions from refinery and bioremediation landfarms were investigated in a mesocosm‐scale simulator facility. Five simulators were constructed and integrated with a data acquisition system and trace gas analyzers, allowing automated real‐time sampling and calculation of total hydrocarbon (THC), CO2, and water vapor fluxes. Experiments evaluating the influence of simulated cultivation and rainfall on trace gas fluxes from the soil surfaces were conducted. Results were compared with published field results. Results showed that cultivating dry or moderately wet soil resulted in brief enhancements of THC fluxes, up to a factor of 10, followed by a sharp decline. Cultivating dry soil did not enhance respiration. Cultivating wet soil did result in sustained elevated levels of respiration. Total hydrocarbon emissions were also briefly enhanced in wet soils, but to a lesser magnitude than in dry soil. Hydrocarbon fluxes from refinery landfarm soil were very low for the duration of the experiments. This lead to the conclusion that elevated THC fluxes would only be expected during waste application. An evaluation of the influence of simultaneous water vapor fluxes on other trace gas fluxes highlighted the importance in lab‐scale experiments of correcting trace gas fluxes from soils. The results from this research can be used to guide management practices at landfarms and to provide data to aid in assessing the effect of landfarms.