bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupling Vadose Zone Models with GIS: Emerging Trends and Potential Bottlenecks
Authors: Tim U. Sunday 
Published: July 2010

AbstractThe capabilities of geographic information systems (GIS) to capture, edit, manipulate, analyze, and display spatial and nonspatial data have long been recognized. Since its initial development in the 1960s, GIS technology has been used extensively to generate and spatially organize large volumes of data to support modeling of contaminant transport in the vadose zone. In the literature, however, two constantly recurring themes have been, on one hand, the opportunities that GIS provide for sophisticated analysis and visualization of spatial data, and on the other hand, their inadequacy for research and application in many disciplines, including environmental modeling. In vadose zone modeling, the gap between user demands and the functional capabilities of GIS have become something of a cliché. An intensive research effort will be needed to couple vadose zone models with GIS. The extent to which such research is advantageous depends upon the benefits to be derived and the potential problems that can be encountered. This paper examines broad issues concerning the coupling of vadose zone models with GIS and emphasizes the emerging trends and potential bottlenecks. Application examples involving the coupling of some vadose zone models of nonpoint source pollution with GIS are described. The issues addressed will help to explain how to loosely, closely, or tightly couple models with GIS, and to hopefully stimulate more discussions and future research activities.
Movement of Nitrate Fertilizer to Glacial Till and Runoff from a Claypan Soil
Authors: Blevins D. W. , Wilkison D. H. , Kelly B. P. , Silva S. R. 
Published: July 2010

AbstractAlthough water from 20 to 25% of shallow farmstead wells in northern Missouri has concentrations of nitrate (NO−3) exceeding 10 mg L−1 as nitrogen (N), many potential sources for this NO−3 are usually present. A field experiment was designed to trace and isolate the amount of a single application of N fertilizer lost to a glacial‐till aquifer and runoffrom a 400 m2 corn (Zea mays L.) plot with bromide (Br−) and isotopically labeled (15N) fertilizer. Soil at the plot is a Albaquic Hapludalf of the Adco Series containing a 61 cm claypan beneath 41 to 43 cm of topsoil. Groundwater levels ranged from 0.38 to 2.40 m below the land surface. Transport of water and NO−3 to the saturated zone was not substantially retarded by the claypan. Labeled‐N fertilizer accounted for as much as 8.6 mg L−1 of the NO−3 (as N) in groundwater, but only in the top 1 to 2 m of the saturated zone. After two growing seasons (16 mo), <2% of the labeled‐N fertilizer was lost to runoff, about 30% was in the saturated zone, 27.3% was removed with the grain, and about 5% remained in the unsaturated zone. A large part of the remaining labeled N may have been lost in gaseous N forms. The presence of labeled NO−3 only in the top 2 m of the aquifer, slow horizontal transport, and winter recharge indicate grass crops such as wheat (Triticum aestivum L.) or rye (Secale cereale L.) might be used to extract near‐surface N during the winter recharge period. Also, fall fertilizations can be expected to readily leach. Because groundwater concentrations of labeled NO−3 were still increasing after two growing seasons, rotation of crops requiring small N inputs could be expected to limit the cumulative effect of large annual fertilizer applications on groundwater.
Vapor‐Phase and Particulate‐Associated Pesticides and PCB Concentrations in Eastern North Dakota Air Samples
Authors: Hawthorne Steven B. , Miller David J. , Louie Peter K. K. , Butler Raymond D. , Mayer Gale G. 
Published: July 2010

AbstractVapor‐phase and suspended particulate (<50 µm) samples were collected on polyurethane foam (PUF) and quartz fiber filters in rural North Dakota to determine the air concentrations of pesticides in an area where agriculture is a primary source of semivolatile pollutants. Samples were collected at two sites from 1992 to 1994 that were at least 0.4 km from the nearest farmed fields and known application of pesticides, and analyzed for 22 different organochlorine, triazine, and acid herbicide pesticides. Fourteen pesticides were found above the detection limits (typically <1 pg/m3). The most prevalent species found in the PUF extracts were endosulfan I and II (6,7,8,9,10,10‐hexachloro‐1,5,5a,6,9,9a‐hexahydro‐6,9‐methano‐2,4,3‐benzodioxathiepin 3‐oxide, exo‐ and endo‐isomers, respectively) at <1 to 2200 pg/m3 and <1 to 500 pg/m3, respectively, trifluralin (2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline) at 3 to 700 pg/m3, and 4,4′‐DDE (1,1‐dichloro‐2,2‐bis‐(4‐(chlorophenyl)ethylene) at 6 to 200 pg/m3. The most prevalent pesticides in filter extracts included carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate) at <0.5 to 470 pg/m3, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐l,3,5‐triazine) at <0.4 to 46 pg/m3, 2,4‐D ((2,4‐dichlorophenoxy)acetic acid) at <0.4 to 1800 pg/m3, and chlorothalonil (2,4,5,6‐tetrachloro‐1,3‐benzenedicarbonitrile) at <13 to 7800 pg/m3. Concentrations of polychlorinated biphenyl (PCB) congeners were much lower (<50 pg/m3 in all cases) than many of the pesticides. These results demonstrate that pesticides are among the most prevalent chlorinated semivolatile pollutants present in rural North Dakota, that significant transport of pesticides occurs both in the vapor‐phase and on suspended particulate matter, and that blown soil may be a significant mechanism for introducing pesticides into surface and ground waters.
Observed and Simulated Solute Transport Under Varying Water Regimes: II. 2,6‐Difluorobenzoic Acid and Dicamba
Authors: Pearson R. J. , Inskeep W. P. , Wraith J. M. , Gaber H. M. , Comfort S. D. 
Published: July 2010

AbstractSignificant interest in the fate of agrichemicals in soils has prompted the development of several transport simulation models. Our primary objective was to evaluate the simulation model LEACHM for predicting the fate of dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) and a nonreactive tracer, 2,6‐difluorobenzoic acid (2,6‐DFBA) in fallow and cropped (barley, Hordeum vulgare L.) systems under different water application levels. A field study (1992) was conducted using in situ soil columns on a Borollic Calciorthid (Brocko silt loam, Gallatin Co., MT). Dicamba (14C‐labeled) and 2,6‐DFBA were surface applied at rates of 0.26 and 112 kg ha−1, respectively. Solute concentrations were measured at three depths (0.36, 0.66, and 0.96 m) using porous cup lysimeters for 70 d following chemical application. Time‐moment analysis of observed solute breakthrough curves (BTCs) generally showed increasing travel times with increasing soil depth and decreasing water application. Dicamba transport was similar to 2,6‐DFBA, with the exception that 40 to 60% of applied dicamba was degraded during transport. The distribution of 14C remaining in the soil columns showed that the primary degradate of dicamba, 3,6‐dichlorosalicylic acid (DCSA), was confined primarily to surface samples (0–0.2 while dicamba was found only at lower depths. This is consistent with a much higher sorption coefficient (Koc) determined for DCSA relative to dicamba. Comparison of observed and predicted (LEACHM) solute BTCs suggested that preferential solute transport occurred especially under high and medium water regimes. Finally, data from three field seasons at the same site suggest that the timing of chemical application relative to initial soil water content and plant stage, the presence of root channels, and temporal changes in soil hydraulic properties in the absence of tillage may significantly affect the degree of preferential flow and subsequent agreement between predicted and observed BTCs.
Growth Response of Barley on Unweathered Fly Ash‐Amended Soil
Authors: Salé L. Y. , Naeth M. A. , Chanasyk D. S. 
Published: July 2010

AbstractA clay loam topsoil that tends to form surface crusts was mixed with unweathered fly ash from a western Canada power plant in mixtures ranging from 0 to 100% fly ash (v/v). Barley (Hordeum vulgare L. var. Leduc) was grown on the mixtures in a greenhouse to examine the potential for phytotoxicity caused by trace elements in the fly ash. Plant emergence was delayed when ≥6.25% fly ash was added to the soil, however, it was not reduced unless ≥25% fly ash was added. The addition of 6.25 and 12.5% fly ash increased both plant height and grain yield while 25% fly ash produced similar plant heights and grain yields as the 0% fly ash treatment. Boron toxicity symptoms were evident in treatments with ≥6.25% fly ash and B accumulated in silage and straw to levels in excess of amounts considered adequate for most plant species. There was no reduction in yield, however, unless ≥50% fly ash was added to the soil. Adding ≤25% fly ash increased Se concentrations favorably in the grain, straw, and silage. Fly ash increased plant Mo concentrations to alter Cu/Mo such that it could be a concern for ruminant diets.
Response of European Chestnut to Varying Calcium/Aluminum Ratios
Authors: Zysset M. , Brunner I. , Frey B. , Blaser P. 
Published: July 2010

AbstractThe response of European chestnut (Castanea sativa Mill.) to varying Ca/Al ratios of 10, 1, 0.1, and control (no Al added) in nutrient solutions with constant concentrations of 1 mmol L−1 Ca was investigated in a greenhouse experiment. The various Ca/Al ratios did not cause a significant effect on biomasses of roots, stems, shoots, and total plants. At a Ca/Al ratio of 0.1, however, a lower number of leaves with lengths >15 cm, a decreased biomass of leaves, an increased root/shoot ratio, and a decreased fine root ratio (roots with diameters <1 mm/root with diameters 1–2 mm) were observed. Elemental analyses of Al and base nutrient cations in roots and leaves revealed that increased Al concentrations reduced the uptake of Ca and Mg, but not the uptake of K. Aluminum concentrations were much higher in fine roots than in leaves, clearly indicating that only a minor amount of root Al was transported into leaves. This finding was supported by EDX analyses and microscopic data, where Al in fine roots was mainly detected in epidermal and cortical cells, but to a lesser extent in cells of the stele. The comparison of the results from the greenhouse experiment with field data from southern Switzerland suggests that there is no current risk originating from low Ca/Al ratio in the soil solution for European chestnut at the field site.
Elevated Atmospheric Carbon Dioxide in Agroecosystems Affects Groundwater Quality
Authors: Torbert H. A. , Prior S. A. , Rogers H. H. , Schlesinger W. H. , Mullins G. L. , Runion G. B. 
Published: July 2010

AbstractIncreasing atmospheric carbon dioxide (CO2) concentration has led to concerns about global changes to the environment. One area of global change that has not been addressed is the effect of elevated atmospheric CO2 on groundwater quality below agroecosystems. Elevated CO2 concentration alterations of plant growth and C/N ratios may modify C and N cycling in soil and affect nitrate (NO3−) leaching to groundwater. This study was conducted to examine the effects of a legume [soybean [Glycine max (L.) Merr.]] and a nonlegume [grain sorghum [Sorghum bicolor (L.) Moench]] CO2‐enriched agroecosystems on NO3− movement below the root zone in a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study was a split‐plot design replicated three times with plant species (soybean and grain sorghum) as the main plots and CO2 concentration (∼360 and ∼720 µL L−1 CO2) as subplots using open‐top field chambers. Fertilizer application was made with 15N‐depleted NH4NO3 to act as a fertilizer tracer. Soil solution samples were collected weekly at 90‐cm depth for a 2‐yr period and monitored for NO3−‐N concentrations. Isotope analysis of soil solution indicated that the decomposition of organic matter was the primary source of NO3−‐N in soil solution below the root zone through most of the monitoring period. Significant differences were observed for NO3−‐N concentrations between soybean and grain sorghum, with soybean having the higher NO3−‐N concentrations. Elevated CO2 increased total dry weight, total N content, and C/N ratio of residue returned to soil in both years. Elevated CO2 significantly decreased NO3−‐N concentrations below the root zone in both soybean and grain sorghum. The results of this study indicate that retention of N in organic pools because of elevated atmospheric CO2 could reduce the nitrate concentration in groundwater beneath agroecosystems as indicated by NO3− movement.
Nitrate Removal in Stream Riparian Zones
Authors: Hill Alan R. 
Published: July 2010

AbstractThis review considers the role of stream riparian zones in regulating the transport of nitrate (NO−3) in groundwater flow from uplands to streams. The current consensus is that most riparian zones effectively remove NO−3 from subsurface water. However, research has not focused on the relationship between hydrology and chemistry within the context of the riparian zone hydrogeologic setting. Most riparian zones that remove NO−3 occur in landscapes with impermeable layers near the ground surface. In this setting, small amounts of groundwater follow shallow horizontal flow paths that increase water residence time and contact with vegetation roots and organic‐rich riparian soils. Limited research suggests that riparian zones have less effect on NO−3 transport in hydrogeologic settings where groundwater has little interaction with vegetation and sediments because flow occurs mainly across the surface, or at depth beneath the riparian zone before discharging to the stream. Considerable uncertainty surrounds the relative importance of vegetation uptake and microbial denitrification in NO−3 removal from subsurface water in riparian zones. Plant NO−3 uptake requires the presence of the root zone below the water table. Information is lacking on the vertical distribution and seasonal dynamics of fine root biomass in relation to water table fluctuations. High denitrification rates have been reported in 0 to 10 cm surface soils of riparian zones in the USA, France, and New Zealand. However, rapid NO−3 removal from groundwater also occurs in riparian locations where the water table is always >0.5 m below the surface. Denitrification at depth within the saturated zone has been studied to a limited extent and has been found not to occur at some sites. An interdisciplinary approach in which patterns of NO−3 depletion and the role of NO−3 removal processes are related to groundwater flow paths is needed to provide a better understanding of NO−3 regulation in riparian zones.
Chemical and Biological Characterization of Organic Matter during Composting of Municipal Solid Waste
Authors: Chefetz Benny , Hatcher Patrick G. , Hadar Yitzhak , Chen Yona 
Published: July 2010

AbstractComposting of municipal solid waste (MSW) was studied in an attempt to elaborate transformations of organic matter (OM) during the process and define parameters for the degree of maturity of the product. Composting was performed in 1‐m3 plastic boxes and the following parameters were measured in 13 samples during 132 d of composting: temperature, C/N ratio, ash content, humic substance contents, and fractions (humic acid, fulvic acid, and nonhumic fraction‐HA, FA, and NHF, respectively). Spectroscopic methods (CPMAS 13C‐NMR, DRIFT) were used to study the chemical composition of the OM. A bioassay based on growth of cucumber (Cucumis sativus L. cv. Dlila) plants was correlated to other parameters. The C/N ratio and ash content showed a typical high rate of change during the first 60 d and reached a plateau thereafter. The HA content increased to a maximum at 112 d, corresponding to the highest plant dry weight and highest 1650/1560 (cm−1/cm−1) peak ratios calculated from DRIFT spectra. 13C‐NMR and DRIFT spectra of samples taken from the composting MSW during the process showed that the residual OM contained an increasing level of aromatic structures. Plant‐growth bioassay, HA content, and the DRIFT spectra indicated that MSW compost described in this study, stabilized and achieved maturity after about 110 d.
Long‐Term Fate of Nitrogen from Annual Feedlot Manure Applications
Authors: Chang C. , Janzen H. H. 
Published: July 2010

AbstractAnimal wastes are a valuable soil amendment, but when rates of application exceed crop nitrogen (N) requirements, N can leach into groundwater or be lost to the atmosphere. The prediction of optimum manure application rates, however, is complicated by the mineralization of organic N that accumulates with repeated manure applications over many years. The objective of this study was to determine the N balance in soils receiving long‐term, repeated manure applications, as influenced by application rate and moisture regime. A N balance was constructed for a site at Lethbridge, AB, in which various rates of 1‐ to 2‐yr‐old manure (up to 180 Mg ha−1 yr−1) have been applied annually to irrigated and nonirrigated Chernozemic (Typic Haploboroll) clay loam since 1973. Under nonirrigated conditions, all of the N applied in manure was accounted for by crop uptake, soil organic N (Kjeldahl N), and soil NO3‐N. Losses of N via leaching or volatilization were small. Under irrigation, however, particularly at higher rates of manure application, appreciable amounts of N were lost by leaching and volatilization. The proportion of manure N mineralized was independent of application rate and irrigation regime. During a period of almost 20 yr, about 56% of the N applied in manure was mineralized. This estimate permits more quantitative estimation of manure application rates that exploit the agronomic value of manure without risk of adverse environmental effects under similar climatic conditions.
Nitrous Oxide and Carbon Dioxide Fluxes from a Bare Soil Using a Micrometeorological Approach
Authors: Wagner‐Riddle C. , Thurtell G. W. , King K. M. , Kidd G. E. , Beauchamp E. G. 
Published: July 2010

AbstractIncreasing atmospheric carbon dioxide (CO2) and nitrous oxide (N2O) levels have prompted research on management of the soil C and N pools. The impact of C and N fertilizer addition on N2O and CO2 field emissions is not clear. We determined N2O and CO2 fluxes from a 1‐ha bare soil plot using micrometeorological methods with the objective of evaluating the effect of management practices (cultivation, irrigation, fertilizer, and sucrose applications) on the relative importance of both trace gases. Research was conducted at the Elora Research Station (Typic Hapludalf) in Ontario, Canada, over 7 mo. The N2O concentration gradients were measured using a Tunable Diode Laser Trace Gas Analyzer and the CO2 gradients using an Infra‐Red Gas Analyzer. The transport coefficients were calculated using a Bowen Ratio Energy Balance and two wind profile approaches. These three approaches resulted in similar hourly fluxes. Daily N2O fluxes for nonevent periods were 12 ng m−2 s−1 in 1991, and 2 ng m−2 s−1 in the summer of 1992, while CO2 fluxes before treatments in 1991 were 0.18 mg m−2 s−1. Sucrose addition (420 kg C ha−1) resulted in the highest N2O and CO2 daily emissions measured during the experiment at 3100 ng m−2 s−1 and 0.5 mg m−2 s−1, respectively. Peak emissions of 250 ng N2O m−2 s−1 were measured after wetting of dry soil (WFP < 0.4) through irrigation in 1991, and rain in 1992. Application of ammonium sulfate (100 kg N ha−1) and irrigation increased N2O emissions to 75 ng m−2 s−1, with a smaller effect caused by two subsequent irrigations on wet soil (WFP > 0.6). Carbon dioxide fluxes varied between 0.01 and 0.5 mg m−2 s−1 being the predominant gas contributing to an equivalent CO2 global‐warming potential, but addition of sucrose increased the contribution of N2O to twice the contribution of CO2. The combined effect of C and N additions (e.g. manure and legume) on the N2O emissions in irrigated or high rainfall areas should be considered in the efforts of atmospheric C sequestering.
Estimating Polyacrylamide Concentration in Irrigation Water
Authors: Lentz R. D. , Sojka R. E. , Foerster J. A. 
Published: July 2010

AbstractOne practice used to control irrigation‐induced erosion amends irrigation furrow inflows with water‐soluble, anionic polyacrylamide (PAM) at low concentrations (0.25–10 mg L−1). Researchers wish to determine the fate of PAM, once added to furrow water streams. We developed and tested an instrumented flocculation test for quantifying PAM concentration in irrigation water. A kaolinite mineral standard is mixed with a PAM‐amended water sample, agitated, then placed in a spectrophotometer. The PAM concentration in the suspension was correlated with settling‐related transmittance changes. One highly correlated (r = 0.91–0.98) parameter, the time needed to initiate suspension clearing (clarity‐shift inflection, CSI), was used as the procedure endpoint. The procedure was sensitive to variations in the amount of kaolinite added, and sample volume, water salinity, and original sediment content. A 10% change in these factors altered measured CSIs by 10 to 50%. The sediment affected CSI by increasing the sample's dissolved organic C concentration. The procedure detected as little as 0.1 mg L−1 PAM dissolved in irrigation water; in samples containing >4 mL settled sediment per liter, the PAM detection limit was approximately 0.25 mg L−1. Precision ranged from ±0.06 to 0.11 mg L−1 for 0 to 2.5 mg L−1 PAM and ±0.39 to 0.86 mg L−1 for 2.5 to 10.0 mg L−1 PAM. The PAM concentration in runoff from irrigated furrows equaled that of the inflow stream after 3 h continuous treatment at 10 mg L−1. The CSI test provides a simple and accurate method of determining polyacrylamide in surface waters.
Transient Multicomponent Gas‐Phase Transport of Volatile Organic Chemicals in Porous Media
Authors: Amali S. , Rolston D. E. , Yamaguchi T. 
Published: July 2010

AbstractLiquid mixtures of volatile organic chemicals (VOCs) contaminating many soil and groundwater sites give rise to multicomponent mixtures of their vapors. Column studies were conducted to characterize multicomponent diffusive transport of TCE and benzene vapors through air‐dry sand. The vapors diffused from their liquid mixture source at one end of the column to the other end where their concentration was maintained at zero by flowing clean air across the column. Simulations based on Stefan‐Maxwell equations of vapor diffusion predicted that the TCE and benzene multicomponent steady‐state flux densities should be 6.7 and 5.5% higher than the predictions based on Fick's law, respectively. The measured steady‐state multicomponent mass flux densities were higher than Fick's law estimates by 4.5 to 10.6 and 3.9 to 10.0% for TCE and benzene, respectively. These results show that multicomponent equations should be used to predict the steady‐state flux densities in a multicomponent VOC vapor mixture. During the transient phase of the experiments, use of Fick's law led to adequate predictions of flux density and concentration. A transient transport model based on Fick's law and a multicomponent, nonlinear adsorption model predicted measured TCE and benzene concentrations along the column in both experiments more accurately than a model based on a single‐species linear isotherm, which underpredicted vapor concentrations for both species. The magnitude of the underestimation was less for benzene, which is less strongly adsorbed at low concentrations than TCE. The linear adsorption isotherm adequately predicted concentrations at the early stages of the experiment when low concentrations were predominant.