bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilization of Lead in Acidic Mine Filtercake by Addition of Alkaline Tailings
Authors: Davis Andy , Link Timothy E. , Baugh Kim , Witham Richard 
Published: July 2010

AbstractThe potential for disposal of acidic Pb‐bearing process waste in an alkaline tailings pond was assessed to ascertain if Pb would become stabilized as opposed to diluted during mixing. This study demonstrated that codisposal of the filtercake residue, consisting of ferrihydroxide, lead sulfate and lead oxide phases (pH = 6.2, Pb = 43 000 mg/kg), with tailings containing abundant calcium and strontium carbonate (pH = 9.8, Pb = 2400 mg/kg) would result in Pb stabilization. The leachable Pb was greater (p < 0.05%) for a sand‐filtercake mixture compared with the tailings‐filtercake at analogous ratios, demonstrating reactivity between filter cake and tailings. Stabilization occurs because abundant remnant calcite in the tailings neutralizes the acidic filtercake, facilitating sorption of Pb to ferrihydroxide at the pH of the filtercake/tailings mix and a >98.5% decrease in Pb solubility. Sorption (KdPb = 28 600 at pH 7.7) and possible precipitation of Ce‐Pb and Ln‐Pb oxides limit Pb solubility. These data suggest that disposal of acidic filtercake in an alkaline tailings pond would reduce Pb solubility to levels below relevant environmental standards.
Decomposition of Biosolids in a Disposal Site Soil
Authors: Gilmour John T. , Roman Fernando , Clark Mark D. 
Published: July 2010

AbstractThe objectives of this study were to determine if residual biosolids in a disposal site soil altered fresh biosolid decomposition and characterize the decomposition behavior of the residual biosolids in that soil. This information is requisite to predicting the impact of residual biosolids on release of N via net N mineralization from fresh and residual biosolids at the disposal site. Aerobically digested municipal sewage sludge from Laredo, TX, was incubated in LaGloria silty clay loam soil (coarse‐silty, mixed, hyperthermic fluventic Ustochrepts) from three locations within the disposal area. Sites 1 and 2 had been amended with biosolids at disposal rates of 647 and 418 Mg ha−1, respectively, over a 7‐yr period while Site 3 was the control. Carbon dioxide evolution was monitored for 62 d and decomposition of fresh biosolid was evaluated using first‐order kinetics for simultaneous and sequential decomposition models. Decomposition of the “active” and “total” residual biomass pools was also assessed. Decomposition of the fresh biosolid was characterized as a two phase (rapid and slow fractions) process. The rate constants for these phases and percentages of biosolid in the rapid fraction were independent of previous additions for this biosolid/soil combination. The active pool or the residual biosolid that was most labile was from 6 to 10% of the total residual biosolid C pool. First‐order rate constants for the total pool of residual biosolids approached those that have been used for more labile portions of soil organic matter.
Retention of Zero‐Valent Iron Colloids by Sand Columns: Application to Chemical Barrier Formation
Authors: Kaplan Daniel I. , Cantrell Kirk J. , Wietsma Thomas W. , Potter Margaret A. 
Published: July 2010

AbstractChemical barriers are an emerging technology used for the in situ remediation of groundwater. They are placed in the subsurface environment perpendicular to groundwater flow where they selectively remove targeted groundwater contaminants while permitting water and other nontargeted constituents to pass through freely. A novel approach to emplacing chemical barriers is by the injection of zero‐valent iron (Fe0) colloids into the subsurface. The objective of this study was to determine the effect of influent Fe0 colloid concentration and injection rate on colloid retention by columns of sand. Suspensions of Fe0 colloids (2 ± 1 µm) were injected into coarse‐grain sand that simulated a simplified aquifer matrix. Influent colloid injection rate (P ≤ 0.01) and concentration (P ≤ 0.05) had a significant effect on colloid retention by the sand. Efficiency of the column to retain colloids decreased as the concentration of retained colloids increased. Colloids were uniformly distributed throughout 1‐m long columns at concentrations >3 g kg−1. Based on filtration theory, gravitational settling was clearly the primary mechanism controlling colloid retention; diffusion, electrostatic attraction, and interception were less important mechanisms. These results were rationalized as follows: the high density of the colloids (7.6 g cm−3) enhanced gravitational settling, the fast experimental flow rates minimized diffusion, the weak surface charge of the colloids and sediments minimized electrostatic attraction, and the small size of the colloids relative to the sand particles (640 µm) minimized interception.
Stream Channel Changes Associated with Mining and Grazing in the Great Basin
Authors: Sidle Roy C. , Sharma Ashish 
Published: July 2010

AbstractCharacteristics of channel morphology and streambed sediment were sampled at 5‐ and 10‐m intervals, respectively, along a 6.4‐km reach of Birch Creek in 1989 and 1992. In this case study we evaluate changes in these channel features using kernel regression analysis. The watershed is located high in the Toiyabe Mountains of central Nevada and has experienced historical grazing and more recent (1986–1989) mining for gold. Exclusion of grazing in the incised lower 1 km of the channel since 1990 did not lead to substantial geomorphic recovery by 1992. The bankfull width did decrease a bit in the grazing exclosure, but baseflow width increased. In both years, bankfull width was about 4 m greater in the exclosure compared with the upstream reaches, reflecting the long‐term grazing influences. The shift of grazing pressure into wet riparian areas upstream apparently caused decreases in thalweg depth, increases in fine sediment deposition in the channel, and loss of pool volume in these upstream areas. Some of these changes in substrate sediment could be attributed to inputs from the mine dumps; however, since either fine sediment did not increase or D50 did not decrease in the vicinity of the mines, the changes appear to be more related to recent changes in grazing patterns. Increased fine deposition also occurred in reaches with high volumes of large woody debris. Because of the episodic nature of peakflows that occur in the Great Basin, it may take many years for the full impacts of mining and grazing to be assimilated by the fluvial and riparian systems.
Retention of Inorganic Carbon‐14 by Isotopic Exchange in Soils
Authors: Sheppard S. C. , Evenden W. G. 
Published: July 2010

AbstractCarbon‐14 is present naturally and is a waste product of the nuclear industry. It is readily incorporated into biological materials and potential impacts have to be considered carefully. From underground waste repositories, much of any 14C released will be inorganic and will pass rapidly through most terrestrial environments because of gaseous transfer. However, there will be some 14C retained in soils, in both organic and inorganic forms. This study addresses retention of inorganic 14C through isotopic exchange with soil carbonates. An outdoor study with incubations lasting up to 24 mo was conducted. A carbonated sandy soil was used unamended, amended with additional carbonate, or amended with ground alfalfa (Medicago sativa L.). One set of soil containers was left open and another set gamma‐sterilized and sealed. Volatilization of some of the 14C happened within minutes, with 98% lost in the alfalfa‐amended soils and 56% lost in the carbonate‐amended soil. However, the fractions remaining in all the soils had residence half‐times of over 1000 d. Much of this retained 14C was still inorganic and had undergone isotopic exchange with the solid 12C minerals in the soil. A progressive extraction method was used to monitor the degree of isotopic exchange, and in certain treatments the exchange process was still measurably progressing after 12 mo of incubation. Clearly, assessments of the impacts of 14C releases to the terrestrial environment must account for these long‐term reactions and retention of 14C in soils.
Assessing Soil Quality for Environmental Purposes: Roles and Challenges for Soil Scientists
Authors: Sims J. T. , Cunningham S. D. , Sumner M. E. 
Published: July 2010

AbstractSoil quality is emerging as an issue of vital importance to the use and management of land, water, and air. Clearly, we must maintain soils in a clean state that is suitable for agriculture, that minimizes the pollution of water and air, and that allows for the safe and productive use of wastes and by‐products as soil amendments. We must also remediate many unclean soils that have been severely impacted by anthropogenic activities. It can be argued that to sensibly approach these complex tasks we must first begin to develop a consensus on the proper means to assess soil quality from an environmental perspective. In doing so we must recognize that conceptual and mechanistic interpretations of soil quality will vary with the intended use of the land and will not always be the same for nonagricultural and agricultural systems. Measures of soil quality important for environmentally sound agronomic crop production will not always be the most appropriate for contaminated soils where cost‐effective remediation is often the primary objective. This paper raises some fundamental questions about the changing role of soil scientists who now must contribute more than ever to the research, technology transfer, and public policy critical to soil and environmental quality. The need for soil scientists to take a proactive role in framing, from all perspectives, the debate on soil quality and environmental issues is emphasized, as is the need for new approaches to quantify the environmental risks posed by soils in agricultural and nonagricultural settings.
Heavy Metal Displacement in a Sandy Soil at the Field Scale: II. Modeling
Authors: Streck Thilo , Richter Jörg 
Published: July 2010

AbstractAlthough several studies have tested leaching models on field‐scale data, a comparable case study on heavy metal transport has not yet been undertaken. Data concerning heavy metal displacement after 29 yr of controlled wastewater irrigation were used to compare several simple modeling approaches to predict total and solution phase concentration profiles in the soil. Approaches employed comprise parallel soil column (PSC) models and the application of the convection dispersion equation at the field scale (CD). The PSC simulations were either realized by one‐dimensional (ID) simulations at points in the field where soil properties had been determined experimentally (grid model; GM) or by the Monte‐Carlo (MC) method. Sorption was described with an extended Freundlich equation as a function of the spatially variable soil properties organic C content and pH. The CD simulations were based on conventional sorption isotherms of mixed samples determined in laboratory batch experiments. Cadmium profiles predicted by the PSC models agree very well with measured profiles, while leaching of Zn was somewhat underestimated. Grid model and MC simulations yielded largely similar results if correlation of random variables was considered in the MC simulations. In the PSC simulations no parameters were fitted to the measured concentration profiles. Agreement between CD simulations and measured data could only be achieved by adjusting the dispersion length to a value in the upper range of values found in the literature.
Heat and Water Transfer in Compacted and Layered Soils
Authors: Nassar I. N. , Horton Robert 
Published: July 2010

AbstractClay material is frequently used to cover landfills or to line hazardous waste disposal landfills. The cover of a landfill is usually exposed to solar radiation, which can cause desiccation and shrinkage of the landfill cover. This study presents two nonisothermal conditions (small and large surface temperature amplitudes) to evaluate heat and water transfer in closed soil columns. The small surface temperature amplitude ranged from 1.0 to 11.0°C, and the large surface temperature amplitude ranged from 15.0 to 16.0°C. Both uniformly compacted and layered soil columns were exposed to small temperature amplitudes, but large temperature amplitudes were used only with uniformly compacted soil columns. Clarinda clay (fine, montmorillonitic, mesic Vertic Argiaquoll) and Fayette silty clay loam (fine‐silty, mixed, mesic Typic Hapludalf) soils were moistened to initial gravimetric water contents of 0.281 and 0.187 kg kg−1, respectively. The moistened soil was packed into polyvinyl chloride columns (0.75 m in diameter and 0.30 m long). For uniform compacted soil columns, the bulk densities were 1.45 and 1.67 Mg m−3 for Clarinda and Fayette soils, respectively. In the layered soil columns, the bulk densities of the upper layers (0.05 m thick) were similar to the densities in uniform compacted soil. The bulk density of the lower layers (0.25 m thick) was 1.0 Mg m−3. A numerical model of coupled heat and water transfer predicted soil temperature and water distributions well in comparison with the measured distributions for all of the conditions. Predicted net water transfer in layered soil revealed that thermal water transfer is significant in comparison with isothermal water transfer.
Nitrate Leaching from Soil Core Lysimeters Treated with Urine or Feces under Orchardgrass: Measurement and Simulation
Authors: Jabro J. D. , Fales S. L. , Fox R. H. , Stout W. L. 
Published: July 2010

AbstractThe ability of the N submodel, LEACHN, of the Leaching Estimation And CHemical Model (LEACHM model) to simulate nitrate‐nitrogen (NO3‐N) leaching from orchardgrass (Dactylis glomerata L.) pasture was evaluated using field data from a 2‐yr experiment. Leaching data were collected from an experiment conducted in central Pennsylvania on Hagerstown silt loam soil (fine, mixed, mesic, Typic Hapludalf). Nitrate losses below the 1‐m depth from N‐fertilized orchardgrass sod were measured with intact soil core lysimeters (0.6‐m diam. by 1‐m long). Five N fertilizer treatments consisted of a control, urine application in the spring, urine application in the summer, urine application in the fall, and feces application in the summer. Calibration N transformation rate constants from previous work with inorganic fertilizer and manure treatments under corn were used to evaluate the LEACHN model under pasture conditions. Statistical analysis indicated that the model accurately predicted annual NO3‐N leaching below the 1‐m depth for three to five of the five treatments in each year. The model failed to produce accurate predictions for the control and feces treatments in 1993 to 1994. The simulation error in these two treatments appeared to be related to soil N transformation rate constants in the model. Other reasons for discrepancies between measured and simulated NO3‐N leaching for some months may have been due to restricted water flow associated with frozen soil or a heavy snowpack during winter. Results demonstrate the potential of the LEACHN model to predict NO3‐N leaching under pasture conditions using N transformation rate constants determined through the calibration process from corn (Zea mays L.) fields on similar soils.
The Sorption of Pyrene and Anthracene to Humic Acid‐Mineral Complexes: Effect of Fractional Organic Carbon Content
Authors: Onken B. M. , Traina S. J. 
Published: July 2010

AbstractCarbon‐normalized distribution coefficients (Koc) of organic solutes appear to increase as the amount of organic C in a system decreases. This study was conducted to determine the effect of fractional organic C content (foc) on the sorption of anthracene and pyrene. Batch‐sorption experiments were conducted on reagent CaCO3, a geologic calcite, and a montmorillonite to measure anthracene and pyrene sorption. An organic C‐free mineral surface and two surface loadings of humic acid (HA) were evaluated. The Koc of anthracene and pyrene varied with foc as well as with the underlying mineral surface. The sorption of anthracene and pyrene to all HA‐mineral complexes increased with increases in foc, while Koc for the compounds decreased. In higher foc systems (>3 × 10−5), isotherms were C‐type curves indicative of partitioning. In lower foc systems (<3 × 10−5), isotherms were commonly L and S‐type curves indicative of adsorption and condensation. Sources of potential experimental artifact examined were loss of HA from the mineral surface to solution, dissolution of CaCO3 during the experiment, and loss of NOS to experimental glassware or volatilization. None were found to contribute to the observations made. Our results suggest that adsorption‐condensation of pyrene and anthracene created more surface excess than predicted by partitioning alone as evidenced by the large experimental Koc values obtained.
Modification of AGNPS for Agricultural Land and Climate Conditions in Central Germany
Authors: Rode M. , Frede H.‐G. 
Published: July 2010

AbstractUntil recently, no suitable computer model was available to quantify P and N yields of nonpoint sources into surface water in central German watersheds. The event‐based erosion and nutrient transport model AGNPS (Version 3.65), developed in the USA, was adapted to central German landscape conditions and linked to a GIS. Drawing on a 2‐yr program of water quality measurements and on hydrologic data collected during 33 yr, this modified model was tested in two medium‐sized agricultural watersheds in the state of Hesse, Germany. With deviations of 1.7 and 3.8%, runoff volumes for all observed and simulated flood events showed a high level of agreement in both watersheds. Peak flows showed larger errors averaging 14.8 and 24%. Only for one of the two watersheds were sediment and total P yield computed satisfactorily, with average errors of 5% (sediment) and 6% (total P). Deviations for the second watershed were considerably greater. The same is true for the dissolved P and N yields. In the case of small events, AGNPS consistently overestimated the particulate P yield in both watersheds. However, the model correctly registered the overall dynamics of the system as well as the differences of sediment and total P yield between the two watersheds. The modified AGNPS model can thus be employed by environmental agencies as a useful planning tool.
Thermotolerant Clostridia as an Airborne Pathogen Indicator during Land Application of Biosolids
Authors: Dowd Scot E. , Widmer Kenneth W. , Pillai Suresh D. 
Published: July 2010

AbstractSince biosolids could harbor a variety of potentially infectious microorganisms, there are concerns of human exposure to these microbial pathogens in population centers surrounding sites where biosolids are land applied. A field study was conducted at a large commercial biosolid application site to determine if thermotolerant clostridia could be employed as a microbial indicator in determining the presence of such fecal contamination in aerosols. Even though the applied biosolids harbored as much as 107 MPN fecal and total coliforms per gram wet weight, these traditional indicators were undetectable at locations having the greatest potential for aerosolization. Thermotolerant clostridia and bacteriophages, however, were detectable in 73% and 53% of the samples, respectively. Hydrogen sulfide producing bacteria as a group, were detected in 93% of the samples. Even at sites directly in the vicinity of the biosolid application, thermotolerant clostridia were detected in 26% of the samples, as compared with the fecal and total coliforms which were detected in only 1 out of 15 (6.6%) samples. Since municipal sewage sludges usually undergo anaerobic digestion before land disposal, it would favor the selection of thermotolerant clostridia within these biosolids. Moreover, clostridla also could be ribotyped using the 16S–23S interspacer region length polymorphism to identify the origins or sources of aerosol contamination. Thermotolerant clostridia could thus serve as a reliable indicator to determine the presence of microbial pathogens and biosolid derived microbial populations in aerosols being generated from biosolid application programs.
Cloudwater and Precipitation Chemistry at Popocatepetl Volcano: A High Elevation Site
Authors: Baez A. P. , Belmont R.D. , Azpra E. , Torres M. B. , Padilla H. G. 
Published: July 2010

AbstractCloud and rain water were collected at Tlamacas (3900 m above sea level), a site on the northern flanks of Popocatepetl volcano, 70 km southeast of Mexico City. Ten cloud events were sampled in September 1992 (five from 9–11 September, five from 29–30 September), eight from 19–21 July (1994) and three from 25–26 July (1995). During 9 to 11 September, cloud production was orographic, while during 29 to 30 September cloud production was associated with a cold front. On 19 to 21 July 1994 and 25 to 26 July 1995, cloud production was orographic. The results showed that cloudwater had a higher ionic concentration than rainwater, with two exceptions, in agreement with previous studies.The ionic concentrations in cloud and rain water seem to indicate a clear dependency on air mass origin and trajectories. Clouds in which back trajectories show passage over zones with little or no pollution produced cloudwater with low ionic concentrations (29 and 30 September).On 10 Sept. 1992, the winds had a strong easterly component, eliminating significant contamination from crater fumaroles. This meteorological situation yielded extremely clean rainwater.
Changes in Microbial Activity after Abandonment of Cultivation in a Semiarid Mediterranean Environment
Authors: Garcia C. , Roldan A. , Hernandez T. 
Published: July 2010

AbstractSeveral organic matter fractions together with biological and biochemical parameters that might serve as markers of microbial activity were determined in an area previously dedicated to agriculture but where the soils had been abandoned for different lenghts of time (3 to 45 yr). Recently abandoned agricultural soils showed lower organic matter levels than soils not exposed to anthropic activity (natural soils). During the years immediately following abandonment the soils show lower levels of total organic C, humic substances and labile fractions of organic matter than natural soils. Soils abandoned for longer than 15 yr begin to recover their organic fractions after the appearance of spontaneous vegetation. The lower slopes appear to accumulate a greater quantity of total organic C and some labile fractions of C, such as water soluble C. Soil abandonment has a negative influence on soil microbial activity, biomass C and oxidoreductases such as dehydrogenase and catalase, although these values begin to rise again after several years. Soils abandoned for long periods of time and in the process of recovery show higher oxidoreductase values than natural soils. The activity of hydrolases belonging to the N, C, and P cycles (ureases and proteases, β‐glucosidase, and phosphatase) point to the negative influence of the agricultural practices, indicating that human activity does not favor adequate establishment of the cycles of these important nutrients. The cessation of agricultural activity leads to the recovery of soil hydrolase activities. Except in isolated cases, the hydrolase activities values determined did not appear to be affected by the position on the slope of the plot from which the samples were taken.