bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Humic‐Based Sorption Enthalpies from Nonlinear Isotherm Temperature Dependence: Theoretical Development and Application to Substituted Phenylureas
Authors: Spurlock F. C. 
Published: July 2010

AbstractThermodynamic assessments of organic chemical‐soil interactions are important for understanding various aspects of sorption phenomena, including isotherm nonlinearity. Expressions were derived here for calculating organic carbon based Freundlich nonlinear sorbed phase partial molar enthalpies (ΔH̄1) and entropies (ΔS̄1) from isotherm temperature dependence. It was shown that, in general, any changes in nonlinearity with temperature must be evaluated when estimating enthalpy effects from isotherm temperature dependence. The results were applied to nonlinear soil sorption data of three substituted phenylurea herbicides between 281 K and 297 K. The ΔH̄1 estimated at 289 K were found to range down to approximately −50 kJ mol−1, and were associated with negative ΔS̄1. Differential heats of sorption, which also include solution phase interactions, were ≈ 10 to 15 kJ mol−1 more exothermic than ΔH̄1. The ΔH̄1 were significantly less exothermic as sorbed phase concentrations increased. For diuron (1,1‐dimethyl‐3‐(3,4‐dichlorophenyl) urea), a compound that displays comparable solubility and octanol‐water partition coefficient as naphthalene, ΔH̄1 at higher concentrations were similar to values estimated for naphthalene (approximately −4 to + 10 kJ mol−1, calculated here from literature data), a nonpolar compound without polar functional groups. The data suggest that specific interactions between the phenylureas and soil organic matter moieties are dominant at low sorbed phase concentrations, but become less important relative to nonspecific London‐van der Waals forces as sorbed phase concentration increases. The urea isotherms are therefore nonlinear, with nonlinearity fundamentally related to the nature of substituted phenylurea sorbed phase interactions.
Dissipation and Distribution of Herbicides in the Soil Profile
Authors: Weed D. A. J. , Kanwar R. S. , Stoltenberg D. E. , Pfeiffer R. L. 
Published: July 2010

AbstractThe distribution and dissipation of alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl) acetanilide], atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5 triazine), and metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one] in soil were studied in 1990, 1991, and 1992. Crop management practices included four tillage methods—chisel plow, moldboard plow, no‐till, and ridge‐till—and two crop rotations—continuous corn (Zea mays L.) and a corn‐soybean [Glycine max (L.) Merr.] rotation. All herbicides were broadcast‐spray applied with no incorporation. No‐till plots had the smallest amounts of alachlor and metribuzin, whereas ridge‐till plots had the smallest amounts of atrazine. Moldboard‐plow plots usually contained the highest amounts of all three herbicides, although ridge‐till plots had the highest metribuzin levels in 1992. These differences were seldom significant at the 0.05 level of probability, however. Throughout the growing season, 50 to 84% of the alachlor and metribuzin were retained in the top 10‐cm layer of soil, and at least 68% of the atrazine was retained in the top 20 cm. From 84 to 98% of the herbicide applied was lost each year, probably by microbial degradation and, for alachlor, by volatilization after application. First‐order half‐lives were 36 d for alachlor, 55 d for atrazine, and 32 d for metribuzin. A two‐compartment model better fitting the alachlor data returned a half‐life of 24 d for that herbicide.
Concurrent Evaluation of Agronomic, Economic, and Environmental Aspects of Trickle‐Irrigated Watermelon Production
Authors: Pier J. W. , Doerge T. A. 
Published: July 2010

AbstractReducing application rates of water and N fertilizers in irrigated cropping systems can lower the potential for N losses, but increases economic risk to producers. A data normalization method and an abstract spatial analysis procedure examined yield, net economic return and unaccounted for N from a subsurface, trickle‐irrigated watermelon [Citrullus lanatus (Thumb.) Matsum. & Nakai] cropping system in southern Arizona as a function of N and water inputs. Field research was conducted on a Casa Grande sandy loam (fine‐loamy, mixed, hyperthermic Typic Natrargid). A factorial design consisting of four levels of N (60, 216, 315, and 500 kg N ha−1) and three average soil water tensions (4, 7, and 17 kPa) resulted in a yield response surface. Watermelon marketable value and costs of water and N inputs were estimated to determine a net return response surface. A N mass balance was calculated by the difference method to estimate post harvest unaccounted for fertilizer N. Predicted maximum marketable yield was 102 Mg ha−1 at 7.2 kPa tension and 336 kg N ha−1. Predicted maximum net return was $10 819 ha−1 at 10.2 kPa tension and 256 kg applied N ha−1. Predicted maximum unaccounted for N was 300 kg N ha−1 at 4 kPa tension and 500 kg applied N ha−1. Normalization and summation of yield, net return and unaccounted for N response variables resulted in a predicted optimum response at 12.6 kPa and 178 kg N ha−1. The combined response variable was within 95% of this maximum value across the range of 10 to 16 kPa tension and 60 to 300 kg applied N ha−1. Similarly, spatial analysis of the three response variables indicated 7 to 17 kPa tension and 60 to 315 kg applied N ha−1 would result in yield and net return of >95% of the calculated maxima of marketable yield and net return, while limiting calculated NO3−‐N concentration in soil water draining below the root zone to <10 mg NO−3‐N L−1. These results suggest that data normalization and abstract spatial analysis are useful in concurrent evaluation of agronomic, economic, and environmental production criteria for subsurface trickle‐irrigated watermelon.
On‐Site Wastewater Treatment Using Unsaturated Absorbent Biofilters
Authors: Jowett E. Craig , McMaster Michaye L. 
Published: July 2010

AbstractA new type of single‐pass aerobic biofilter is being developed as an alternative to the conventional septic tile bed and for treatment of wastewater in general. The Waterloo Biofilter uses absorbent filter media that combine long retention tunes, separate flowpaths for wastewater and air, and large surface areas, thereby enabling loading rates 10 times greater than that for solid particle filter media. Although absorbent sphagnum peat and coarse sand plug readily at loading rates of 50 to 80 cm d−1, absorbent plastic particles provide consistent treatment with no plugging problems. The latest field trial removes 97.8% BOD7, 96.1% TSS, and 99.5% fecal coliform bacteria with 12 to 16°C wastewater loaded at 49 cm d−1. Surge flows up to 204 cm d−1 over several days are handled with little effect on effluent quality. In laboratory column experiments, removal of fecal coliforms averages >99.99% at 80 cm d−1 loading, and >99.999% at 10 cm d−1 after a 10‐ to 14‐d acclimatization period. Ammonium is thoroughly oxidized to NO−3 with typically <2.5 mg L−1 NH4+‐N in the effluent. Overall treatment improves with forced air flow compared with natural convection. Cold influent and plugging by freezing are the main causes of poor treatment. A typical household would likely require a biofilter with 3.3‐m2 surface area in cold climates when flow is balanced, possibly less in warmer areas. This biofilter should also find general application in renovating polluted water, including water for domestic consumption in developing regions of the world.
Nutrient‐Loss Trends for Vegetable and Citrus Fields in West‐Central Florida: II. Phosphate
Authors: Stanley C. D. , McNeal B. L. , Gilreath P. R. , Creighton J. F. , Graham W. D. , Alverio G. 
Published: July 2010

AbstractVegetable and citrus production in west‐central Florida has come under suspicion as a hazard (with respect to NO3‐N and ortho‐P) to local groundwater and surface‐water bodies, including a 33 000‐ha drinking‐water supply reservoir near Bradenton in Manatee County. Using a combination of multilevel samplers in the shallow (surficial) aquifer beneath selected vegetable fields and citrus groves, coupled with piezometric wells around each field's periphery to assess depthintegrated solute concentrations and direction and rate of groundwater flow, ortho‐P levels have been assessed at 10 sites for three vegetable‐production seasons during 1990 and 1991. Some ortho‐P movement from vegetable production beds to surface waters and shallow groundwater appears likely, but ortho‐P concentrations also are elevated at a native range site that has not received P fertilizers, and in both man‐made and natural surface‐wateretention ponds plus nearby intermittent streams throughout the area. Naturally occurring phosphatic clays appear to be introducing considerable P into local shallow groundwater and associated surface‐water bodies. Regulatory strategies requiring sizeable retention ponds for tailwater‐return flow capture may be contributing to P loadings of the surface water, whenever pond construction intercepts phosphatic clay materials.
Reduction of Phosphorus in Runoff from Field‐Applied Poultry Litter Using Chemical Amendments
Authors: Shreve B. R. , Moore P. A. , Daniel T. C. , Edwards D. R. , Miller D. M. 
Published: July 2010

AbstractField applications of poultry litter at rates to meet forage N requirements normally result in an over‐application of P. Chemical amendments have the potential to reduce the solubility of manure P through precipitation and/or adsorption reactions. This study was conducted to determine the effects of two chemical amendments, alum (Al2 (SO4)3 · 14H2O) and ferrous sulfate (FeSO4 · 7H2O), on P concentrations and load in runoff and to evaluate the effects of amended litter on forage production. Litter was broadcast applied to fescue (Festuca arundinacea Schreb.) plots at 11.2 Mg ha−1 alone and in combination with alum or ferrous sulfate (1:5 amendment/litter). Rainfall simulators were used to produce three runoff events at 2, 9, and 16 d after litter application. Alum reduced the P concentrations in runoff by 87 and 63% of that from litter alone for the first and second runoff events, respectively, whereas ferrous sulfate decreased runoff P concentration by 77 and 48%, respectively. Both chemical amendments resulted in significant reductions (P < 0.05) in total P load for the first runoff event. Litter application significantly increased fescue yields, with total forage yield having the greatest response to alum‐amended litter. Mean forage yield with alum amended litter was 2358 kg ha−1, compared with a mean yield of 1847 kg ha−1 with litter alone. This was probably due to decreased NH3 volatilization with the alum treatment. The combination of decreased P loss and increased forage yields suggest that alum‐amended litter has substantial promise for use as an environmental and economic management tool in the poultry industry.
Speciation of Cadmium and Zinc with Application to Soil Solutions
Authors: Holm P. E. , Christensen T. H. , Tjell J. C. , McGrath S. P. 
Published: July 2010

AbstractA two‐part method has been developed for determination of Cd and Zn species in 50‐mL soil solution samples containing low concentrations of Cd and Zn (1–10 μg Cd L−1 and 50–1000 μg Zn L−1). The method uses two cation exchange resins (Amberlite CG 120 and Chelex 100) in a batch‐column‐batch procedure and relies on analytical determinations of Cd and Zn by graphite furnace atomic absorption spectrophotometry. The first part (batch) of the method allows determination of free divalent Cd2+ and Zn2+. This part is experimentally sensitive to cation concentrations and ionic strength and these parameters should be controlled during the experimental procedures. However, it is shown that Cd and Zn concentrations and pH do not influence the method. Speciations performed on samples containing chloride and sulfate were in accordance with theoretical calculations. The second part (column‐batch) of the method operationally separates the complexed fraction into labile complexes, slowly labile complexes, and stable complexes. Chloro complexes were identified as labile complexes, while EDTA complexes were identified as stable complexes. The method works well with relatively small volumes of sample solutions and at low metal concentrations and may be useful in characterization of Cd and Zn in soil solutions.
Use of Calcium/Aluminum Ratios as Indicators of Stress in Forest Ecosystems
Authors: Cronan Christopher S. , Grigal David F. 
Published: July 2010

AbstractThe calcium/aluminum (Ca/Al) molar ratio of the soil solution provides a valuable measurement endpoint or ecological indicator for identification of approximate thresholds beyond which the risk of forest damage from Al stress and nutrient imbalances increases. The Ca/Al ratio can also be used as an indicator to assess forest ecosystem changes over time in response to acidic deposition, forest harvesting, or other processes contributing to acid soil infertility. Based on a critical review of literature on Al stress, we estimate that there is a 50:50 risk of adverse impacts on tree growth or nutrition when the soil solution Ca/Al ratio is as low as 1.0, a 75% risk when the soil solution ratio is as low as 0.5, and nearly a 100% risk when the soil solution Ca/Al molar ratio is as low as 0.2. The Ca/Al ratio of the soil solution can be corroborated with other complementary indices. Our analysis found that threshold conditions for potential forest impacts from Al stress are indicated by four successive measurement endpoints: (i) soil base saturation less than 15% of effective CEC; (ii) soil solution Ca/Al molar ratio ≤1.0 (for 50% risk); (iii) fine root tissue Ca/Al molar ratio ≤0.2 (for 50% risk); and (iv) a foliar tissue Ca/Al molar ratio ≤12.5 (for 50% risk). With appropriate precautions and caveats, these sequential indices based on the Ca/Al ratio provide a means of distinguishing site conditions where Al stress is likely to affect tree growth adversely.
Macroinvertebrate Communities in Headwater Streams Affected by Acidic Precipitation in the Central Appalachians
Authors: Griffith Michael B. , Perry Sue A. , Perry William B. 
Published: July 2010

AbstractWe collected quantitative macroinvertebrate samples monthly from September 1989 to October 1990 from four streams on the Allegheny Plateau of West Virginia that were characterized by different bedrock geology and streamwater pH. Mean pH was 4.3, 6.1, 6.0, and 7.5 in the four streams. We compared species and functional group composition of the benthic macroinvertebrate community in these streams to choose taxa that could be used as indicator species for differences in pH in bioassessment studies. The streams differed in species composition and abundance and several species were found that could be used as indicators for each of the levels of pH. Higher densities of Amphinemura sp., Leuctra sp., Euryophella funeralis, and Paracapnia angulata were characteristic of the stream with a pH of 4.3. Higher densities of Peltoperla arcuata and Wormaldia moesta were found in the streams with a pH of about 6.0. Gammarus minus, Baetis sp., Ephemerella dorothea, and Sweltsa sp. were found at higher densities in the stream with a pH of 7.5.
Occurrence of Pesticides in Prairie Lakes in Saskatchewan in Relation to Drought and Salinity
Authors: Donald David B. , Syrgiannis Jim 
Published: July 2010

AbstractPrairie lakes are critical breeding, staging, and feeding habitat for a variety of shorebirds and waterfowl, and lower trophic levels in these habitats could be affected by agricultural pesticides. Following the severe drought of 1988 in Saskatchewan, concentration of 11 pesticides were determined in water, sediment, and zooplankton in 10 permanent and nine semipermanent lakes (those lakes that did not have standing water in 1988). The detection frequency for lindane, α‐HCH, and 2,4‐D in water was 57, 70, and 78%, respectively, with the maximum concentration 0.011, 0.004, and 0.43 µg/L, respectively. Triallate was detected in 39% of sediment samples and 54% of zooplankton samples at a maximum concentration of 31 and 10.2 µg/kg, respectively. When the lakes were grouped by salinity, detection frequencies of these pesticides were significantly higher in brackish lakes, which tended to be semipermanent (N = 6, mean specific conductance 3100 µS/cm) than in saline lakes, which tended to be permanent (N = 6, mean specific conductance 60 900 µS/cm). Other pesticides were detected in <20% of samples (diclofop‐methyl, atrazine, MPCA, dicamba, and bromoxynil) or not at all (trifuralin and picloram). With one exception, pesticide concentrations in these lakes were below those levels that might be deleterious to aquatic life, suggesting that these pesticides have not affected the food of avifauna at these lakes.
Uranium Isotopes Distribution in Soils at the Rocky Flats Plant, Colorado
Authors: Litaor M. Iggy 
Published: July 2010

AbstractSoils east of Rocky Flats Plant (RTF) near Golden, CO, are contaminated with U as a result of past waste‐storage practices, accidental release of oils laden with U, and low‐level airborne emissions. A spatial analysis of three U isotopes was conducted to determine the concentration and distribution pattern of U contamination. Soils were sampled from 118 plots of 1.01‐ or 4.05‐ha by compositing 25 evenly spaced samples from the top 0.64 cm. Uranium‐234 activity ranged from 25.9 to 92.8 Bq kg−1, U‐235 activity ranged from 0.1 to 25.1 Bq kg−1, whereas U‐238 activity ranged from 30.7 kg−1 to 286 Bq kg−1. Geostatistical techniques were used to model the spatial dependency and construct isopleth maps showing U isotope distributions. Spatial correlation was not observed for U‐234. This implies that U‐234 is randomly distributed in the soil environment east of RFP. Uranium‐235 exhibited a spotty and localized concentration pattern with no clear relationship between known burial and spill sites, and the present distribution of U‐235 in the soils. Proposed wind‐dispersal mechanisms were not consistent with the spatial distribution of U isotopes. Most of the observed activities of U‐234 and U‐235 were well within the natural range of U isotopes in soils. The lack of similarity in spatial distribution between Pu‐239 + 240 and U isotopes probably resulted from the higher solubility and teachability of U isotopes compared with Pu‐239 + 240 in the soil system. Although U‐238 exhibited a pattern of localized spatial distribution, most of its observed activity was well within the natural range of U‐238 activity in soils.
Crop Residue Effects on the Leaching of Surface‐Applied Chemicals
Authors: Green J. D. , Horton Robert , Baker J. L. 
Published: July 2010

AbstractUnknown effects of surface crop residues on interception, subsequent wash‐off, and movement of herbicides through soil are concerns associated with no‐tillage agriculture. To address these concerns, 12 undisturbed columns of a Clarion (fine‐loamy, mixed, mesic Typic Hapudoll) soil were obtained from a no‐till corn (Zea mays L.) field following harvest. Saturated hydraulic conductivity (Ksat), Cl− breakthrough, and drainable porosity were measured and used to group the columns into three blocks (high, medium, and low Ksat values). Corn residue was placed on the surface at rates of 0, 473, 946, and 1419 kg ha−1. Atrazine [6‐choloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] and CaCl2 solutions were surface applied to the columns, and 24 h later a sprinkling device was used to apply CaSO4 at a rate of 5 cm h−1. Effluent draining from the columns was collected and analyzed for Cl− and atrazine. Greater amounts of atrazine were recovered with the first 5.0 cm of drainage in the 100%‐residue columns than with the zero‐residue columns for the high and medium‐Ksat blocks. Differences in mass of atrazine recovered were greater in high‐Ksat than in medium‐Ksat columns. A trend indicating more recovery with less drainage for the high‐residue treatment was not apparent for the low‐Ksat columns. The time to peak atrazine concentrations decreased as crop residue levels increased for the higher‐Ksat columns, but not for the low‐Ksat columns. With 100% residue cover, the medium‐ and high‐Ksat columns demonstrated two peaks in Cl− and atrazine concentrations. This may indicate two pathways for the C− and atrazine movement through these columns; perhaps indicating the surface‐applied chemical that was not intercepted by crop residue was moving more slowly through the soil matrix.
Transport of Nitrate in Soils as Affected by Earthworm Activities
Authors: Li Yimin , Ghodrati Masoud 
Published: July 2010

AbstractEarthworm (Lumbricus sp.) holes have long been recognized as an important conduit for water and solute transport in field soils. In this study we investigated preferential movement of NO3 through artificially induced earthworm holes and compared three commonly used solute transport models with respect to their ability to describe NO3 transport through the earthworm macropore system. Earthworms holes were created by introducing earthworms into uniformly packed soil columns of 20‐cm i.d. and 30‐ or 60‐cm long. After 8 wk of incubation, the columns were leached at a range of fluxes and NO3 breakthrough curves (BTCs) were determined. The columns also were traced with dyes to visualize the spatial distribution of the earthworm holes. The results showed that the earthworms completely altered the uniformity of the packed soil cores. The average saturated hydraulic conductivities of the earthworm hole columns (Ksm) increased 17.9‐ to 22.3‐folds compared with the control columns. Significant preferential movement of NO3 occurred in these columns even at relative fluxes as low as 0.014 Ksm. A nonlinear least squares program, CXTFIT, was used to fit three solute transport models to all BTCs. The physical nonequilibrium model (MIM) fitted the experimental data better than the convection‐dispersion equation (CDE) and the stochastic model (SM), while none of them was adequate to describe the data well.
Effects of Tall Fescue Endophyte Infestation on Relative Abundance of Small Mammals
Authors: Coley Alex B. , Fribourg Henry A. , Pelton Michael R. , Gwinn Kimberly D. 
Published: July 2010

AbstractSmall mammal populations were characterized nine times during six sampling periods on six plots in five different fields of tall fescue (Festuca arundinacea Schreb.) to determine differences in their abundance and species composition associated with the presence or absence of the endophytic fungus Acremonium coenophialum Morgan‐Jones & Gams. No differences were found in species richness (n = 4 for both types) between endophyte‐free (E−) plots and endophyte‐infested (E+) plots. Capture success, number of individuals, total captures, and recapture rates were more for E− plots than for E+ plots. All four species [eastern harvest mice (Reithrodontomys humulis Giglioli), short‐tailed shrews (Blarina brevicauda Gray), pine voles (Microtus pinetorum McMurtrie), and cotton rats (Sigmodon hispidus Say & Ord)] were captured more often in E− than in E+ plots. The diminished population densities of small mammals demonstrate the potential of E+ tall fescue as a permanent ground cover for waste disposal sites, orchards, tree farms, irrigation ditch banks, golf courses, and other residential, commercial, and industrial situations where burrowing activities of mammals may create human health hazards or financial burdens.