bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Numerical Model to Estimate Sediment Oxygen Levels and Demand
Authors: Park Seok Soon , Jaffé Peter R. 
Published: July 2010

AbstractA numerical model that simulates sediment oxygen levels and demand (SOLD) was developed and tested against field data. The model accounts for changes in sediments due to advection, diffusion, chemically and biologically mediated redox reactions, and other chemical transformations. The microbial degradation of organic matter and the interactions of the subsequent chemical constituents are described using appropriate stoichiometric relationships. Sediment oxygen demand (SOD) is computed from fluxes of oxygen and reduced compounds across the sediment‐water interface. To test the the model, simulations were compared against published data obtained from lake sediments. The model results displayed reasonable agreement with the measurements. The model was used to examine some of the major factors that affect the sediment oxygen demand. Results show that although fluxes of methane and ammonia increase with an increasing C rain rate, the oxygen flux remains almost constant for the simulations conducted. For an increase in bloturbation anti,or temperature, however, all fluxes increase significantly. The oxygen concentration at the sediment/water interface also affects the SOD significantly, especially the fraction of the total SOD that is due to the flux of oxygen into the sediments. The fraction of the SOD that is due to the oxidation of ammonia increases with increasing oxygen concentration at the sediment/water interface, while the fraction associated to the methane release and its oxidation decreases slightly because more organic C is oxidized aerobically. The contribution of reduced manganese, iron, and sulfide to the SOD are relatively low, due to their precipitation with other chemical species.
Mycobacteria in Runoff Waters from Natural and Drained Peatlands
Authors: Iivanainen Eila , Sallantaus Tapani , Katila Marja‐Leena , Martikainen Pertti J. 
Published: July 2010

AbstractTo assess the effect of peatland type and of forest‐drainage performed 30 yr earlier on the occurrence of mycobacteria in runoff‐waters, the counts of culturable mycobacteria were followed during a snow‐free season. Runoff‐waters were from a natural and a drained peatland and each had a different nutrient status. Samples were collected in May, June, August, and October of 1992. Mycobacteria were isolated from all waters. The highest culturable counts were detected in August (up to 7.3 × 103 CFU/L). The runoff‐waters from the two natural peatlands had similar median counts, whereas lowering of the water table by drainage slightly increased the mycobacterial counts in most cases. Changes in vegetation, such as a decrease in the coverage of Sphagnum species, or soil characteristics following drainage had little effect on the occurrence of mycobacteria in the runoff‐waters, even though Sphagnum vegetation has been regarded as important for the growth of these bacteria. The counts of mycobacteria in the runoff‐waters correlated with precipitation but not with air temperature. This indicates that the mycobacterial growth took place mainly in vegetation and soil, not in the runoff‐waters. When total runoff during May to October was taken into account, the leaching rates of mycobacteria from all catchments were about 4 to 5 × 1011 CPU km−2. Thus drainage had a negligible effect on the leaching of mycobacteria from peatlands.
Invasive Plant Species and Microbial Processes in a Tidal Freshwater Marsh
Authors: Otto Sibylle , Groffman Peter M. , Findlay Stuart E. G. , Arreola Anna E. 
Published: July 2010

AbstractVegetation has a strong influence on N retention in wetlands via direct uptake and by indirect effects on microbial N uptake and denitrificafion. Vegetation change in freshwater tidal marshes is dynamic due to both natural and anthropogenic factors and these changes may influence the water quality maintenance value (i.e., the ability to absorb exogenous N) of these marshes. We measured sediment microbial biomass and activity and plant N content and height in stands of Lythrum salicaria (L.), Phragmites australis [(Cav.) Trin. Ex Steud], and Typha angustifolia (L.) in 1995 and 1996 in Tivoli North Bay, a tidal freshwater marsh along the Hudson River in Dutchess County, New York. Lythrum and Phragmites are invasive plants that have displaced Typha in significant areas of this marsh over the past few decades. A fertilizer (two 5 g N m−2 additions of urea) response study was conducted in 1996. There were few differences in microbial biomass and activity and response to N addition between the different plants despite marked differences in plant biomass and N content and significant annual variation in several variables. Although plant change has been dramatic in this marsh, and the new plants appear to cycle N differently than the native plant, microbially‐based water quality functions may not have been affected by this change.
A Dual‐Porosity Model to Quantify Macropore Flow Effects on Nitrate Leaching
Authors: Larsson Martin H. , Jarvis Nicholas J. 
Published: July 2010

AbstractThe dual‐porosity model MACRO was coupled with the N turnover and leaching model SOILN to quantify macropore flow effects on nitrate (NO3) leaching from structured soils. This was done by comparing model simulations performed with and without macropore flow with measurements of tile drain flow, NO3 contents in the soil profile, NO3 concentrations in drain discharge, and N in harvested grain made in an 8‐yr field experiment on a day soil. Macropore flow had only small effects on the soil hydrology, so that the MACRO model could give good predictions of the accumulated tile drain discharge for simulations both with and without macropore flow. By taking macropore flow into account, the SOILN model could satisfactorily depict the NO3 amounts in the soil and harvested grain and the leaching pattern, while simulations without macropore flow could not match all measured components of the N mass balance. In simulations with macropore flow, 62% of the simulated NO3‐N concentrations in drain flow were within a factor of 1.5 of measured values, while simulating without macropore flow resulted in only 35% of concentrations within a factor of 1.5 of the measured values. A comparison of simulations with and without macropore flow showed that macropore flow reduced NO3‐N leaching by 28% from June 1990 to July 1995, but with large variations found between different years (from 3–45%). However, for shorter periods, macropore flow increased leaching. The results demonstrate the importance of macropore flow for NO3 transport in structured soils.
Arsenic Solubility and Attenuation in Soils of the Madison River Basin, Montana: Impacts of Long‐Term Irrigation
Authors: Jones C. A. , Inskeep W. P. , Bauder J. W. , Keith K. E. 
Published: July 2010

AbstractArsenic concentrations in 8S0 km of the Madison and Upper Missouri Rivers exceed the Montana State human health standard (0.24 µM). In addition, ground water As concentrations in the northern portion of the Lower Madison River Valley are above the federal drinking water standard (0.67 µM) and correlate with high soluble As levels in overlying soils. The objectives of this study were to determine processes affecting As solubility in soils of the Madison and Upper Missouri River Basins and assess potential impacts of long‐term irrigation with As‐rich river water on As mobility. Sixteen irrigated (>20 yr of irrigation) and nonirrigated (never irrigated) soils were sampled in four major regions adjacent to the Madison and Upper Missouri Rivers. There were no significant differences (α = 0.05) in total or soluble As levels between irrigated and nonirrigatcd soils within any of the four regions. In addition, sorption coefficients (Kd values) in six paired soils selected for additional chemical characterization were not significantly different (α = 0.05) between irrigated and nonirrigated soils. Ammonium oxalate extractable Fe and Mn concentrations were found to be positively correlated with Kd, and Olsen P concentration was found to be negatively correlated with Kd based on a multiple linear regression (r2 = 0.92). Sequential extractions performed for a subset of soils showed that labile As concentrations were similar between irrigated and nonirrigated soils. Soils that had been irrigated for >100 yr had additional As sorption capacities of at least 3 mg kg−1 in saturated column studies following 30 yr of simulated irrigation. Based on this suite of data, it was determined that irrigation history has not significantly affected As solubility or attenuation capacities in soils of the study area.
Determining Travel Time and Stream Mixing using Tracers and Empirical Equations
Authors: Verstraeten I. M. , Soenksen P. J. , Engel G. B. , Miller L. D. 
Published: July 2010

AbstractWater‐supply managers need adequate warning to protect water supplies if a contaminant is spilled in an upgradient tributary. The city of Lincoln draws water from alluvium associated with the Platte River near Ashland, eastern Nebraska. Using constant‐rate injection methods and a conservative tracer, travel time and degree of mixing of contaminants in the Elkhorn and Platte Rivers were evaluated in 1995 and 1996. The results indicate that, for flows of 584 to 162 m3/s in the Platte River at Ashland with 13 to 28% of its flow contributed by the Elkhorn River, 8.2 to 13.2 h are required for the leading edge of a chemical plume to travel from the Elkhorn River at Waterloo to the Platte River at Ashland. The peak concentration of a chemical spilled as a slug in the Elkhorn River near Waterloo would pass the well field after 11.3 to 16.1 h. Existing empirical equations for calculation of travel time were shown to apply to reaches of streams studied, but underestimated the leading edge up to 14% and overestimated the plateau concentration up to 11% at Site 5. However, time of travel may be influenced by the relative contribution of a tributary. The plateau concentration of the chemical in the Platte River at Ashland was 45 to 60% of its concentration in the Elkhorn River. The degree of mixing of the tracer in the Platte River at Ashland increased from 53 to 65% as the relative contribution of the Elkhorn River increased.
Surface Water‐Ground Water Interaction: Herbicide Transport into Municipal Collector Wells
Authors: Verstraeten I. M. , Carr J. D. , Steele G. V. , Thurman E. M. , Bastian K. C. , Dormedy D. F. 
Published: July 2010

AbstractDuring spring runoff events, herbicides in the Platte River are transported through an alluvial aquifer into collector wells located on an island in the river in 6 to 7 d. During two spring runoff events in 1995 and 1996, atrazine [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine] concentrations in water from these wells reached approximately 7 µg/L, 70 times more than the background concentration in ground water. Concentrations of herbicides and metabolites in the collector wells generally were one‐half to one‐fifth the concentrations of herbicides in the river for atrazine, alachlor [2‐chloro‐2′‐6′‐diethyl‐N‐(methoxymethyl)‐acetanilide], alachlor ethane‐sulfonic acid (ESA) [2‐((2,6‐diethylphenyl) (methoxymethyl)amino)‐2‐oxoethane‐sulfonic acid], metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide], cyanazine [2‐((4‐chloro‐6‐(ethylamino)‐1,3,5 triazin‐2‐yl)‐amino)‐2‐methylpropionitrile], and acetochlor [2‐chloro‐N‐(ethoxymethyl)‐N‐(2‐ethyl‐6methyl‐phenyl) acetamide], suggesting that 20 to 50% river water could be present in the water from the collector wells, assuming no degradation. The effect of the river on the quality of water from the collector wells can be reduced through selective management of horizontal laterals of the collector wells. The quality of the water from the collector wells is dependent on the (i) selection of the collector well used, (ii) number and selection of laterals used, (iii) chemical characteristics of the contaminant, and (iv) relative mixing of the Platte River and a major upstream tributary.
A Unified Sorption Variable for Environmental Applications of the Freundlich Equation
Authors: Chen Z. , Xing B. , McGill W. B. 
Published: July 2010

AbstractThe Freundlich equation (x/m = Kf C1/ne) has been used widely in sorption studies in chemistry and environmental research. Two problems arise in comparing sorbate‐sorbent systems if Ce ≠ 1 or if 1/n values differ. First, it is often not possible to compare Kf values from the literature if they were derived from different units of x/m and Ce. Second, the exponent 1/n, determines the interpretation of Kf. Consequently, comparing values of Kf or Koc—f is problematic. We propose a way to characterize sorption dynamics in systems that follow the Freundlich isotherm that avoids problems caused by comparing Kf values. We show that: (i) The units of Kf are: mmol1‐1/n kg−1 L1/n, or mg1‐1/n kg−1 L1/n, etc. depending on the units of x/m and Cc. Therefore, Kf parameters cannot be compared among samples whenever the 1/n parameters are different; (ii) For Kf values that are associated with different units, the units‐conversion factor for Kf is also a function of 1/n. It has the form of: A1‐1/n, where A is the units‐conversion factor if 1/n = 1; (iii) We propose a new variable, Ku, to unify the units of Kf and to conduct sensitivity analyses of Kf and 1/n. Numerically Ku is the slope, (x/m)/Ce, of the sorption isotherm at any value of Ce or x/m and has units of L kg−1.
Determination of Suspended Sediment Concentrations and Particle Size Distributions Using Pressure Measurements
Authors: Lewis Alan J. , Rasmussen Todd C. 
Published: July 2010

AbstractWe present an automated, in‐situ technique for measuring suspended‐sediment concentrations and particle‐size distributions. The technique uses pressure transducers to continuously monitor the fluid density, which is shown to be directly related to the mass of sediments suspended in the water column. We estimate the depth‐integrated mass of 5 g of suspended sediments with an accuracy of 3%, corresponding to a suspended sediment concentration of 542 ± 14 mg L−1. Particle‐size distributions of the sediments were estimated from the rate of change of the suspended‐sediment concentrations coupled with Stokes' Law. We evaluated the accuracy using three size classes of precision glass microspheres. Good agreement between observed and calculated fall times was only found for the smallest size fraction (106 to 150 µm). Larger particles (180 to 250 µm and 300 to 425 µm) fell slower than predicted by Stokes' Law, presumably due to the onset of turbulent flow around the particles. Also, equal masses of two different sizes of microspheres did not fall independently of each other. The larger microspheres were slowed by the presence of the smaller particles while the smaller microspheres were accelerated, presumably due to entrainment of smaller particles in the wake of the larger particles. Application to laboratory characterization of soil sedimentation processes, as well as field applications for automated suspended sediment monitoring, provides the ability for real‐time determination of depth‐integrated sediment characteristics.
Co‐Application Effects of Water Treatment Residuals and Biosolids on Two Range Grasses
Authors: Ippolito J. A. , Barbarick K. A. , Redente E. F. 
Published: July 2010

AbstractAlum [Al2(SO4)314H2O] is commonly used in the municipal water treatment process to destabilize colloids for subsequent flocculation and water clarification. Water treatment residuals (WTR) can be classified as a waste material from these treatment plants. Concerns over land application of WTR are due to its postulated reduction of plant available P and potential plant Al toxicity with increasing WTR rates. Co‐application of WTR with biosolids may benefit municipalities with biosolids inherently high in P concentrations and in terms of a cost savings by landfill avoidance. In a greenhouse study, we investigated the efficacy of co‐application of WTR and biosolids to the native shortgrass prairie species blue grama (Bouteloua gracilis H.B.K. Lag) and western wheatgrass [Pascopyrum smithii (Rydb.) A. Love]. Our objectives were to quantify co‐application effects on plant P and Al concentrations and uptake, biomass production, and WTR P adsorbing capacity. With blue grama, we observed a positive linear relationship between increasing WTR rate and yield and a negative linear relationship with increasing WTR rate and shoot P and Al concentration (P < 0.10). With western wheatgrass, increasing WTR rate produced a negative quadratic effect on shoot Al concentration (P < 0.10). Some investigators have observed P deficiency symptoms associated with WTR application; however, we did not. Our adsorption study indicated that co‐mixing of the City of Fort Collins, CO, WTR and biosolids at ratios of 8:1 will adsorb all soluble biosolids P. Beyond this ratio the WTR could adsorb all biosolids available P and possibly some soil‐borne P.
Chelate‐Assisted Phytoextraction of Lead from Contaminated Soils
Authors: Cooper E. M. , Sims J. T. , Cunningham S. D. , Huang J. W. , Berti W. R. 
Published: July 2010

AbstractPhytoextraction, a remediation strategy for lead (Pb)‐contaminated soils that removes soil Pb through plant uptake and harvest, may be enhanced by use of synthetic chelates. We evaluated Pb desorption from four contaminated soils (total Pb 1278‐14 349 mg kg −1) by seven chelates (CDTA, DTPA, EDDHA, EGTA, HEDTA, HEIDA, and NTA) at three rates (0.2, 2.0, and 20 mmol chelate kg soil−1) . The three most effective chelates (CDTA, DTPA, and HEDTA) were used in greenhouse studies with an uncontaminated soil and a Pb‐contaminated soil (total Pb = 3212 mg kg−1) to determine the effect of chelate type and rate on growth, Pb uptake, and plant elemental composition. Lead desorption varied with chelate and soil and increased with chelate rate, averaging 948 mg Pb kg−1 at the 20 mmol kg−1 rate vs. 28 mg Pb kg−1 by the control. The general ranking of chelate effectiveness, based on total Pb desorbed, was HEDTA > CDTA > DTPA > EGTA > HEIDA > EDDHA ~ NTA. Plant uptake of Pb from the contaminated soil was enhanced by CDTA, DTPA, and HEDTA, but with even the most effective treatment (corn, high CDTA rate), the amount of Pb extracted by plants was rather low (0.4 kg Pb ha−1). Lead extractable by the Toxicity Characteristic Leaching Procedure) (TCLP) was increased from 9 L−1 in the control to from 47 to 174 mg L−1 in soils treated with 20 mmol kg−1 CDTA or DTPA and chelates generally caused a shift in Pb from resistant to more soluble chemical fractions.
Heavy Metal Leaching from Mine Tailings as Affected by Plants
Authors: Zhu D. , Schwab A. P. , Banks M. K. 
Published: July 2010

AbstractA column experiment was conducted to determine the impact of soil cover and plants on heavy metal leaching from mine tailings and heavy metal contaminated soil. Columns made of PVC were constructed with 30 cm subsoil covered by 30 cm of mine tailings followed by 0, 30, or 60 cm of clean topsoil. Two grasses, tall fescue (Festuca arundinacea Schreb.) and big bluestem (Andropogon gerardii), were grown in the columns. The columns were leached at a slow rate for 1 yr with a 0.001 M CaCl2 solution under unsaturated conditions. The presence of both tall fescue and big bluestem increased Zn and Cd concentrations in the leachate. Lead concentrations in leachates were not affected by the presence of plants. Although plants generally reduced the total amount of water leached, total mass of Zn and Cd leached generally was not impacted by plants. Total mass of Pb leached was positively correlated (r = 0.9) with total leachate collected from each column. Covering the mine tailings with 60 cm of topsoil (with or without vegetation) increased the mass of Zn and Cd leached relative to no topsoil. When the subsoil was absent, Zn and Cd leaching increased by as much as 20‐fold, verifying the ability of soil to act as a sink for metals. Mine tailing remediation by establishing vegetation can reduce Pb movement but may enhance short‐term Cd and Zn leaching. However, the changes were relatively small and do not outweigh the benefits of using vegetation in mine tailings reclamation.
Phosphate Leaching Responses from Unperturbed, Anaerobic, or Cattle Manured Mesotrophic Sandy Loam Soils
Authors: Magid Jakob , Jensen Marina Bergen , Mueller Torsten , Hansen Hans Christian Bruun 
Published: July 2010

AbstractControl of P from sewage outlets has not led to expected improvement of Danish freshwater quality, calling the diffuse P losses especially from drained agricultural land into question. We studied some mechanisms for P loss from the fertilized topsoil from selected catchments that have been monitored for P losses: (i) losses due to desorption of P from A horizons enriched throughout the last decades by fertilization, (ii) losses of P associated with temporarily reducing conditions imposed on A horizons, and (iii) losses associated with application of fresh cattle manure to the soil surface or by mixing into the soil matrix. The effluent concentrations of P from 15 intact topsoil samples were 10 to 40 times lower than what could be expected from batch studies, presumably due to nonhomogeneous flow conditions. Addition of solid cattle feces by incorporation or directly on the surface had markedly differing effects on P leaching. While incorporation did result in a 10‐ to 20‐fold increase in effluent P concentration, surface application resulted in a further 10‐ to 20‐fold higher effluent concentration of molybdate‐reactive P. These results indicate that while desorption from the soil matrix is likely to be much less than expected from batch chemical considerations, special attention should be given to drained pastures, where the important P source may not be the soil matrix per se, but fecal remnants on the surface, that may be transported directly to the drains through macropores. Furthermore, reductive dissolution of Fe associated P may be of some importance.
The Pre‐Sidedress Soil Nitrate Test and Nitrate Leaching from Corn
Authors: Guillard Karl , Morris Thomas F. , Kopp Kelly L. 
Published: July 2010

AbstractThe pre‐sidedress soil nitrate test (PSNT) is recommended in many states as a best management practice (BMP) for corn (Zea mays L.). A 2‐yr study was conducted in Connecticut on a Woodbridge fine sandy loam soil (coarse loamy, mixed, mesic Aquic Dystrochrept) to determine NO3‐N concentrations and losses in soil water from corn managed with three different N fertilization regimes: (i) PRE, 196 kg N ha−1 applied preplant; (ii) PSNT‐1, 90 kg N ha−1 applied at preplant and any remaining N needs estimated by the PSNT (0 kg ha−1 in 1995 and 45 kg ha−1 in 1996); and (iii) PSNT‐2, no preplant N and all N needs estimated by the PSNT (34 kg ha−1 in 1995 and 123 kg ha−1 in 1996). Percolate was collected with zero‐tension pan lysimeters. Flow‐weighted NO3‐N concentrations from the PRE treatment were 22.3 mg L−1 in 1995 and 17.4 mg L−1 in 1996; the PSNT treatments were <8.0 mg L−1. Losses of NO3‐N as a percent of N applied in 1995 were 20%, 10%, and 12% for PRE, PSNT‐1, and PSNT‐2, respectively, and 31%, 21%, and 21%, respectively, in 1996. Greatest leaching losses occurred after corn harvest. Corn yields were not significantly (P > 0.05) different among N treatments. These findings suggest that a well calibrated soil N test can reduce excess fertilization and the potential for NO3 contamination of ground water.