bluuebunny/crossref_metadata_2025 huggingface dataset:
Drinking Water from Agriculturally Contaminated Groundwater
Authors: Goodrich James A. , Lykins Benjamin W. , Clark Robert M.
Published: July 2010

Sharp increases in fertilizer and pesticide use throughout the 1960s and 1970s along with generally less attachment to soil particles may result in more widespread contamination of drinking water supplies. The purpose of this study was to highlight the use of agricultural chemicals and their occurrence in groundwater while focusing on the engineering processes available for removing them to acceptable limits for consumers. Through various case studies and field‐scale research projects, several different drinking water treatment technologies have been evaluated for their capability removing various groundwater contaminants. Both central treatment and individual household point of entry devices were studied. Treatment options vary depending on the types of contaminants to be removed. Best available technology consists of ion exchange or reverse osmosis for removing nitrates, granular activated C for removing non‐volatile synthetic organics, and air stripping for volatile synthetic organics. Since there is no single treatment for all contaminants, a homeowner or individual community will have to evaluate their particular situation and possibly select a treatment scheme or combination of technologies to provide the best cost‐effective solution.
Assessing the Spatial Distribution of Evapotranspiration Using Remotely Sensed Inputs
Authors: Moran M. Susan , Jackson Ray D.
Published: July 2010

The evaporation of water from soil and plant surfaces is of vital environmental interest. The importance of this process becomes apparent when one considers that the scales involved range from water loss from leaf stomata to the circulation of the planetary atmosphere. Since the launch of the first earth observing satellite in 1972, the idea of using remotely sensed data to evaluate the spatial distribution of evaporation has moved from the conceptual to the developmental phase. Problems that currently impede the development of operational systems include spatial resolution, atmospheric interference, estimation of aerodynamic resistance, spatial extrapolation of ground‐based meteorological data, partial vegetation cover, and the extension of instantaneous values to daily totals. In this review, efforts to evaluate evaporation using remotely sensed data on both local and regional scales are reviewed, and some impediments that must be resolved before an operational system can be developed are discussed.
Evaluation of Methods for Characterizing Carbofuran Hydrolysis in Soil
Authors: Parkin T. B. , Shelton D. R. , Robinson J. A.
Published: July 2010

The objective of this study was to develop a method that could be applied to investigations of soil/environmental factors influencing the spatial and temporal variability of carbofuran hydrolysis in field soils. Two factors were considered: (i) soil handling and pesticide application, and (ii) the method of data summarization. Three soil handling/pesticide treatments were evaluated: (i) sieved soil/sprayed pesticide application, (ii) injected pesticide application/sieved soil, and (iii) injected pesticide application/intact core incubation. This last method was developed to mimic field conditions where high localized concentrations of carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate) occur as a result of banded application of granular carbofuran at planting time. For all three treatments sigmoidal 14CO2 production kinetics were observed. Several mathematical models for describing sigmoidal product appearance data were evaluated and a general saturation model was found to yield the best fit. Using parameter estimates obtained from this model in statistical tests, we found that the intact core soil treatment yielded significantly longer half lives for carbofuran degradation. Additional experimental evidence suggests that soil structure of the intact cores retarded diffusion of the 14CO2 produced from carbofuran degradation and influenced the kinetic pattern observed.
Hydrolysis and Free Radial Mediated Degradation of Phosphonates
Authors: Schowanek Diederik , Verstraete Willy
Published: July 2010

While studying the biodegradation and environmental fate of phosphonates, two almost undocumented nonbiological degradation processes acting on the stable C‐P bond were observed. Under test conditions comparable to the environmental situation, phosphonates in solution are prone to a slow light‐independent hydrolytic cleavage of the C‐P bond(s). The process requires divalent cations, aerobic conditions, and is particularly active on N‐containing phosphonates. Highest hydrolysis rates, up to 1% phosphonate‐P converted to inorganic phosphate per day, were measured with the polyphosphonates. Second, C‐P bonds in all phosphonates can efficiently be cleaved, also with release of orthophosphate, by means of physicochemically generated free radicals. The riboflavin/light and Cu2+/H2O2 systems were more efficient than the Fenton reagent (Fe2+/H2O2) in this respect. Both processes are likely to contribute to the removal of xenobiotic phosphonates in the environment, particularly in the absence of photo‐ and biodegradation.
Selenium Mobility in Irrigated Soil Columns as Affected by Organic Carbon Amendment
Authors: Neal Rosemary H. , Sposito Garrison
Published: July 2010

Samples of two agricultural soil profiles were collected from the western San Joaquin Valley, CA, and packed into 1.5‐m columns. The soils were leached sporadically over 9 wk with an aqueous solution containing selenate and subjected to two different chemical environments in order to investigate the effects of an added C source and intermittent irrigation on the fate of applied Se. Evaluation of the soluble Se present in the soil columns at the end of the leaching experiments showed the movement of Se to be retarded with respect to that of the leaching solution, and this was attributed to the effect of intermittent irrigation on the behavior of Se in the soil columns. Under control conditions, soluble Se was predominantly in the selenate form, whereas the inclusion of a C amendment resulted in reduced total soluble Se in the upper portions of the columns and transformation to organically associated Se. Elevated concentrations of soluble Mn were found where selenate had transformed to selenite and organically associated Se, indicating the possibility of localized reduction processes.
Exposing Loblolly Pine Seedlings to Acid Precipitation and Ozone: Effects on Soil Rhizosphere Chemistry
Authors: Ruark G. A. , Thornton F. C. , Tiarks A. E. , Lockaby B. G. , Chappelka A. H. , Meldahl R. S.
Published: July 2010

Rhizosphere and nonrhizosphere soils were sampled in association with the roots of field‐grown, 1‐year‐old loblolly pine (Pinus taeda L.) that had been exposed to simulated acidic precipitation and O3 treatments. Soil samples adjacent to roots and from the bulk soil were analyzed separately for H, Al3, Ca2, and Mg2 concentrations. For the acid precipitation treatment, H levels were significantly greater in the rhizophere compared with the bulk soil, but no clear trend could be attributed to acidic precipitation levels. Hydrogen ion concentrations associated with the O3 levels, at times, differed significantly by treatment, butnot between rhizosphere and bulk soil. Rain pH and 3 level produced no statistically significant distinction between rhizosphere and nonrhizosphere soil for Al3, Ca2, or Mg2. However, after combining rhizosphere and nonrhizosphere soil samples, Al3 concentrations were found to generally increase as rain pH decreased, whereas Ca2 and Mg2 followed the opposite pattern. No such pattern for O3 level was apparent. Significant interactions between acid precipitation and O3 treatments were not detected.
Seasonal Variation of Selenium in Outdoor Experimental Stream‐Wetland Systems
Authors: Allen Kathleen N.
Published: July 2010

Two outdoor experimental stream‐wetland systems were exposed continuously to 10 µg/L Se(IV) over a 2‐yr period. A seasonal variation in the water column Se concentration was found in wetlands; a comparable variation was not observed in the stream segments. Water column Se was never reduced by more than 20% in the streams, but was reduced by greater than 90% in midsummer in the wetlands. Accumulation of Se in plants was much higher in the wetlands than in the streams, particularly in duckweed (Lerana minor). The deposition of Se in sediments was extremely variable within the wetlands.
Wind Flow within Open‐Top Growth Chambers and the Gas Exchange Implications
Authors: Flesch T.K. , Grant R.H.
Published: July 2010

Field studies of atmospheric pollutant effects on plants commonly use an open‐top plant growth chamber (OTC). Altered wind flow characteristics within an OTC may create aerodynamic and boundary layer transport resistances (ra and rb) which differ from field values, complicating the extension of OTC results to field conditions. An OTC was placed in an enclosed area and the wind velocity was measured at five heights at nine locations using a triple hot‐film sensor. Measurements were made in an empty OTC and at two different surface roughnesses. The flow was turbulent, highly variable with location, and had well‐defined vertical and horizontal circulation patterns. Average wind speed in empty OTC ranged from 0.28 to 1.33 m s−1. Increased roughness decreased the mean flow speed but had little effect on the turbulence level or the circulation pattern. The flow within the OTC was used to estimate the ra and rb for O3 uptake in a hypothetical soybean [Glycine max (L.) Merr.] plant canopy, a representative low stomatal resistance species. Results showed that the variable flow in the OTC results in widely varying rb values within the OTC itself, depending on actual physical location within the chamber. In addition, the OTC ra and rb would differ from field values under typical meteorological conditions. For plants with low stomatal resistance this could create significant differences in gaseous uptake for individual plants within the OTC as well as for the average plant in the OTC vs. that in the field.
Effects of Acidity of Simulated Rain on the Fruiting of ‘Summerred’ Apple Trees
Authors: Rinallo C.
Published: July 2010

The effects of rain acidity on field‐grown ‘Summerred’ apple trees (Malus domestica Borkh) under natural conditions were investigated. One group of four trees was exposed to ambient rainfall. Four other groups were covered with rainshields and received water, pH 5.6, 4, and 3, respectively, as simulated rain. Simulated acid rain, particularly at pH 3, adversely affected fruit production in terms of individual fruit weight, fruit set, fruit appearance (necrosis and russetting of the peel) and dry weight. Ambient rain was not found to cause significant reductions in apple fruit production in this study.
Ion Enrichment of Snowmelt Water by Processes within a Podzolic Soil
Authors: Hazlett P.W. , English M.C. , Foster N.W.
Published: July 2010

Ion concentrations in snowmelt runoff, forest‐floor percolate and mineral‐soil percolate collected in a tolerant hardwood forest at the Turkey Lakes Watershed, ON, were determined during the spring snowmelt of 1986. The results were examined to assess the modification of snowmelt water after contact with the forest soil. Concentrations of NO3− increased from 17 to 201 µmolc L−1 and SO42− increased from 25 to 107 µmolc L−1 as meltwater passed through the organic layers and the upper mineral‐soil horizons. Mineralization of organic N and S, and desorption of SO42− from the soil, provide sources of these ions for leaching during the snowmelt period. Ion‐exchange reactions in the forest floor and upper mineral soil resulted in a decrease in H+ and an increase in Ca2+ concentration in solution. In the steep topography of this forested basin, the altered snowmelt solutions are rapidly transported downslope towards the aquatic system by lateral flow. Processes within the forest soil may therefore play an important role in determining the effects of snowmelt water on surface water chemistry in the spring.
Herbicide and Tracer Movement in Soil Columns Containing an Artificial Macropore
Authors: Czapar G.F. , Horton R. , Fawcett R.S.
Published: July 2010

Preferential flow has been shown to be an important mechanism affecting water and solute movement in some soils. The movement of agricultural chemicals to groundwater is of special concern. Soil columns containing an artificial macropore were used to study alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide], cyanazine [2‐{[4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl]amino}‐2‐methyl‐propanenitrile], pendimethalin [N‐(1‐ethylpropyl)‐3,4 dimethyl‐2,6 dinitrobenzenamine], and chloride movement. Packed columns were modified by removing a 6‐mm diam. core from the center. Herbicides and chloride were applied to the soil surface and columns were irrigated with 63 mm of a 0.0075 M calcium sulfate solution. Initial chloride breakthrough occurred much sooner in columns with a continuous macropore than in columns with either a partial or no macropore. Total chloride loss in column drainage, however, was less in columns containing a continuous macropore than in those without a continuous macropore. In contrast, alachlor, cyanazine, and pendimethalin were only detected in drainage from columns with a continuous macropore. Because herbicides were not detected in column drainage unless a continuous macropore was present, leaching studies using packed soil columns may significantly underestimate the extent of herbicide movement through a structured soil. Pesticide leaching experiments using soil columns with an artificial macropore may provide estimates that are more representative of field behavior and could be used to supplement current pesticide mobility studies required by the USEPA to support product registration.
Effects of Open‐Top Chambers on ‘Valencia’ Orange Trees
Authors: Olszyk D.M. , Takemoto B.K. , Kats G. , Dawson P.J. , Morrison C.L. , Preston J. Wolf , Thompson C.R.
Published: July 2010

Open‐top field chambers are the most widely used technology for evaluating the impacts of air pollutants on vegetation. This study was conducted to evaluate the long‐term effects of chambers on Valencia orange trees (Citrus sinensis [L.] Osbeck). The trees were exposed to ambient ozone (O3) for 51 months in large (4.3‐m diam. by 2.9‐m high) nonfiltered open‐top chambers (NF) and in ambient air without chambers (AA). During this period, the 12‐h daytime (M12) average O3 concentration was approximately 8% lower, and the cumulative O3 exposure for hourly average concentrations >0.1 µL L−1 (SUM10) was 29% lower than for NF than for AA trees. By December 1984 (after eight months in chambers), canopy volume for NF trees was 67% greater than for AA trees; and by March 1988 canopy volume for NF trees was 104% greater than for AA trees (P < 0.001). Specific leaf areas (cm2 g−1) were larger for NF than AA trees (P < 0.05). Total harvestable fruit weight combined for years 1986, 1987 and 1988 was 98% higher for NF than for AA trees (P < 0.01). The higher yield for NF trees was associated with lower immature fruit drop, especially during the growing seasons prior to the 1986 and 1987 harvests (P < 0.01). Warm season (April–October) rates of stomatal conductance and transpiration were 14 and 12% lower, respectively, for NF than AA trees; which coincided with 29% more negative leaf water potentials for NF than AA trees (P < 0.05) . In contrast, cool season net photosynthetic rates were 18% lower for NF than for AA trees, and starch concentrations were 31% higher in leaves from NF compared to AA trees in February 1988 (P < 0.05). Overall, the yield increases for NF compared to AA trees could, in part, be accounted for by decreased flux of O3 into leaves (based on decreased O3 exposure and leaf conductance). However, other factors, i.e., increased tree growth, altered leaf C allocation, and lack of wind stress occurring only in chambers, likely contributed to higher NF tree yields.
Selective‐Placement Burial of Drilling Fluids: I. Effects on Soil Chemical Properties
Authors: McFarland Mark L. , Ueckert Darrell N. , Hons Frank M. , Hartmann Steve
Published: July 2010

Burial of spent drilling fluids used in petroleum and natural gas exploration was evaluated for reducing soil contamination caused by conventional, surface disposal of these wastes on arid and semiarid rangelands. Simulated reserve pits at two locations provided burial depths of 30, 90 (with and without a 30‐cm capillary barrier of coarse limestone), and 150 cm below the surface, with sequential replacement of stockpiled subsoil and topsoil. The drilling fluids contained extremely high concentrations of soluble salts [electrical conductivities (EC) = 155–185 dS m−1], with Na and Cl being the dominant soluble ions. Upward migration of contaminants was evaluated over a 20‐month period. Soluble salts migrated upward 15 to 30 cm into the overlying soil, and salt movement appeared to be governed to a greater extent by diffusive rather than convective flow mechanisms. Capillary barriers of coarse limestone effectively reduced salt movement at one of the two sites. Sodium, Ca, and Cl were the dominant mobile ions. Exchangeable Na percentages did not increase in soil increments > 15 cm above buried drilling wastes. Barium, Cr, Cu, Ni, and Zn in drilling fluids did not migrate into overlying soil. Movement of contaminants was similar where fourwing saltbush [Atriplex canescens (Pursh) Nutt.], a deep‐rooted shrub, and buffalograss [Buchloe dactyloides (Nutt.) Engelm], a hallow‐rooted grass, were used for revegetation. Selective‐placement burial of drilling fluids offers an effective and environmentally sound alternative to conventional surface disposal. The probability of upward movement of excessive soluble salts into the plant root zone appears greater for 30‐cm burial, compared to 90‐ or 150‐cm burial, because of greater soil water contents at the soil/waste interface and greater upward water potential gradients in the surface 30 cm.
Biotechnology and Hazardous Waste Treatment
Authors: Stroo Hans F.
Published: July 2010

Despite considerable speculation and research on the potential for biotechnology to improve the treatment of hazardous wastes, little progress has been made to date in developing commercially available products and processes. This paper examines the current state of the art and the progress to date, as well as the barriers to biotechnological advances in hazardous waste treatment. The potential applications of biotechnology are also discussed, in terms of the contaminated matrix, the type of reactor technology used and the types of compounds present. The most promising areas for technology development efforts are identified, as well as the critical issues which must be addressed in moving from laboratory‐scale testing to the development of commercially‐viable technologies.
Cadmium Availability and Extractability from Sewage Sludge as Affected by Waste Phosphatic Clay
Authors: Gonzalez R.X. , Sartain J.B. , Miller W.L.
Published: July 2010

Disposal of sewage sludge containing high levels of heavy metals invokes environmental concerns. Due to previous phosphate rock mining, large reserves of waste phosphatic clay exists in Florida. The objective of this study was to determine the feasibility of disposing contaminated sewage sludge in waste phosphatic clay ponds. In this study, sewage sludge containing 550 mg Cd/kg was utilized as a soil amendment. Application rates corresponding to 0, 6.25, 12.5, 25.0, 50.0, 75.0 and 100 kg Cd/ha were used on two soils in a glasshouse experiment to determine the influence of waste phosphatic clay (SCM) on the uptake and extractability of Cd. The soils were sand tailings and a 4:1 mixture of tailings and waste phosphatic clay (SCM). Alfalfa (Medicago sativa) was grown for 155 d and dry matter clippings were taken three times. The DTPA‐extractable Cd was determined and single degree of contrasts was used to compare treatment means, sludge application rates, and plant tissue Cd concentrations. Results indicated that Cd uptake by alfalfa grown on sludge‐amended soils was suppressed by the presence of waste phosphatic clay. Extractable levels of Cd decreased with time on sludge‐amended SCM while remaining relatively the same on sludge‐amended tailings. Waste phosphatic clay suppressed the uptake of Cd added as sewage sludge. Land application of sewage sludges at waste clay disposal sites could improve soil conditions and help solve the problem of sludge disposal in an environmentally sound manner.
The Rhode River Watershed: Phosphorus Distribution and Export in Forest and Agricultural Soils
Authors: Vaithiyanathan P. , Correll David L.
Published: July 2010

To evaluate the effects of land use on P transport and transformation in the Atlantic coastal plain, we examined the distribution and fractionation of P in forested and agricultural soils of the Rhode River watershed and their export rates. Nearly 70% of P in forest soils was bound in organic forms. Fractionation studies reveal that cultivation and fertilizer P application increased total and inorganic P content and decreased organic P content of the soils. About half of the increase in the inorganic P content of the agricultural soils is due to the mineralization of organic P during cultivation and the rest is probably due to fertilizer P application. The inorganic phosphates in the forest and agricultural soils are chiefly associated with Fe either as iron phosphates or as phosphates adsorbed on the iron oxide surfaces. The agricultural watershed had a higher P export (46.3 g P ha−1 wk−1) compared to the forested watershed (5.96 g P ha−1 wk−1). Particulate P dominated the P export from both watersheds. Variations in the P flux from the watersheds was correlated to changes in water discharge. The discharge pattern of organic and inorganic P forms from the watersheds are highly related to their soil P composition.
Effects of Fluidized Bed Combustion Residue on the Health and Performance of Sheep Grazing Hill Pastures
Authors: Vona L.C. , Meredith C. , Reid R.L. , Hern J.L. , Perry H.D. , Bennett O.L.
Published: July 2010

The effect of application of fluidized bed combustion residue (FBCR), a product resulting from the removal of S from high‐S coals, was compared with application of dolomitic limestone, or no treatment, on the performance of ewes (Ovis aries) grazing hill pastures over a 3‐yr period. Pastures were treated with FBCR and limestone twice per annum and ewes with their lambs grazed at two stocking rates from late April to October. Herbage analysis showed increases in Ca concentration in FBCR and lime‐treated pasture vs. control, a higher level of S in FBCR vs. lime‐treated herbage, but no differences in microelement concentrations due to treatment. There were no differences in weight gains of either ewes or lambs within years due to treatment, and no effect of treatment on blood hematocrit levels. Ewes were killed before and after the 3‐yr trials, and lambs were sacrificed before and after each grazing season, to determine the effect of FBCR application on mineral accumulation in the carcass or organs of the animals. There were either no differences or small differences in the concentrations of macro‐ and microelements in the carcass, liver, and kidney of ewes and lambs associated with treatment, and tissue concentrations of elements were within normal ranges. The results confirm studies with rats (Rattus rattus), hamsters (Mesocricetus auratus), and pigs (Sus scrofa) showing that treatment of agricultural soils with high levels of FBCR as a liming or fertilizing agent causes no adverse effects on composition of food crops or herbage, or on the health and productivity of animals consuming diets produced on such soils.
Rates of Selenium Volatilization among Crop Species
Authors: Terry Norman , Carlson C. , Raab T.K. , Zayed Adel M.
Published: July 2010

The rate of Se volatilization per plant was measured for 15 crop species grown hydroponically (for 18–48 d depending on the species) in growth chambers. Selenium was supplied as 20 micromolar sodium selenate in 0.25 strength Hoagland's solution. Selenium volatilization was determined by enclosing plants in a Plexiglas plant chamber and trapping the volatile Se emissions in alkaline peroxide traps. The results show that rice (Oryza sativa L.), broccoli (Brassica oleracea botrytis L.), and cabbage (Brassica oleracea capitata L.) volatilized Se at the fastest rates, i.e., 200 to 350 µg Se per m2 leaf area per day (1500–2500 µg Se kg−1 plant dry wt. d−1). Carrot (Daucus carota L.), barley (Hordeum vulgare L.), alfalfa (Medicago sativa L.), tomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativus L.), cotton (Gossypium hirsutum L.), eggplant (Solanum melongena L.), and maize (Zea mays L.) had intermediate rates of 30 to 100 µg Se m−2 d−1 (300–750 µg Se kg−1 d−1). Sugarbeet (Beta vulgaris L.), bean (Phaseolus vulgaris spp.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.) had the lowest rates, i.e., less than 15 µg Se m−2 d−1 (<250 µg Se kg−1 d−1). Comparing all plant species, Se volatilization rate was found to be highly correlated with Se concentration in plant tissues; we suggest that the ability of plants to absorb Se may be an important factor contributing to high rates of Se volatilization.
Lime Effects on Pine Forest Floor Leachate Chemistry and Element Fluxes
Authors: Marschner Bernd , Stahr Karl , Renger Manfred
Published: July 2010

In a 30‐mo field study, element inputs with throughfall and litter and leachate outputs from forest floor lysimeters were monitored in a control and a limed + K/Mg‐fertilized plot in a 40‐yr‐old pine plantation on a Cambic Arenosol. In the control, input‐output budgets show the retention of most elements, which probably is a natural phenomenon in this young ecosystem and not caused by inhibitory effects of anthropogenic inputs on decomposition processes. Despite the high Ca status of the forest floor, the H+ inputs of 70 to 90 mmolc m−2 yr−1 are buffered only to a small degree (0–30%). Internal H+ production from dissociation of organic acids and N transformations contributes up to 130 mmolc m−2 yr−1 to the acid load in the leachates. As a result, Zn and Cd are mobilized from the forest floor. In the limed plot, the applied K and Mg sulfates were washed out quantitatively within 1 yr. Due to the high solubility of the chalk‐lime, leachate Ca concentrations rose sharply and pH increased from 4.0 in the control to over 6, showing that acid from inputs and from internal production was almost completely neutralized. After a partial N immobilization in the 1st yr, total mineral N outputs were similar in both treatments. But in the limed lysimeters, the degree of nitrification in the leachates reached 85 to 95% compared to 30 to 55% in the control, which has consequences for N availability and for N leaching in the mineral soil. The retention of Cd and Zn was greatly increased by the treatment and reached 60 and 30% of total inputs, respectively.
Competitive Adsorption of Para‐Xylene and Water Vapors on Calcium, Sodium, and Lithium‐Saturated Kaolinite
Authors: Pennell K.D. , Rhue R.D. , Hornsby A.G.
Published: July 2010

Vapor‐phase adsorption of volatile organic chemicals (VOC) on soils and clay minerals has been shown to be greatly reduced in the presence of water. Exchangeable metal cations are known to interact strongly with water, and thus may influence the competitive adsorption of water and organic vapors. Flow‐equilibration experiments were conducted to measure the concentration of water and p‐xylene vapors adsorbed on oven‐dried Ca‐, Na‐, and Li‐saturated kaolinite from single and binary vapor systems. Li‐saturated kaolinite adsorbed significantly less water than Ca‐ and Na‐kaolinite. This was attributed to a 50% reduction in cation exchange capacity (CEC) of Li‐kaolinite following heating at 110°C. The adsorption of p‐xylene vapors on Ca‐, Na‐, and Li‐kaolinite at 0% relative humidity (RH) was also related to the CEC and exchangeable cation species, which suggests that specific interactions occurred between exchangeable cations and p‐xylene molecules. When the RH was increased to 10 and 20%, p‐xylene adsorption decreased in small, but successive, increments. The competitive adsorption of both water and p‐xylene on Ca‐, Na‐ and Li‐kaolinite was underestimated by two‐component adsorption equations based on the Brunauer, Emmett, and Teller (BET) model. At low RH's, water adsorption on kaolinite was hypothesized to occur primarily at cation exchange sites, allowing for the continued adsorption of p‐xylene on exposed mineral surfaces. Thus, the assumption of complete monolayer coverage prior to the onset of multilayer formation, upon which the BET model is based, may limit the ability of these equations to accurately predict the competitive adsorption of polar and nonpolar vapors.
Modeling Soil Sulfate Sorption Characteristics
Authors: Comfort S.D. , Dick R.P. , Baham J.
Published: July 2010

Knowledge of soil SO4 adsorption characteristics is required for predicting the fate of atmospheric S depositions on terrestrial ecosystems. This study developed two models for predicting the SO4 sorption characteristics of field moist soils from routinely measured soil physical and chemical properties. Sixty‐two soil samples from the U.S. Northeastern (NE) and Southern Blue Ridge Province (SBRP) regions were used in model development. The first modeling approach used stepwise multiple regression to identify which combinations of soil properties best predicted each Langmuir constant. The Langmuir constant regression equations were then substituted back into the Langmuir model and used to predict SO4 sorption for each equilibrium SO4 concentration. This approach described SO4 sorption reasonably well for both regions (R2 of 0.57–0.89). In the second approach, a better fit of SO4 sorption was achieved (R2 of 0.81–0.92) using fewer soil properties by expressing the Langmuir constants as linear functions of selected soil properties and directly estimating the soil property coefficients by nonlinear regression. Soil properties used in the second model included: dithionite‐citrate‐extractable Al (Ald), total organic C (TOC), and extractable SO4 for the NE region; and Ald, TOC, clay content, pH, and CEC for the SBRP region. These results indicated that regional soil SO4 sorption characteristics could be predicted for field moist soils with the knowledge of only a few routinely measured soil properties.
Sorption‐Desorption Kinetics of Alachlor in Surface Soil from Two Soybean Tillage Systems
Authors: Locke Martin A.
Published: July 2010

Alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide] sorption patterns were evaluated in surface (0–5 cm) Dundee silt loam (fine‐silty, mixed, thermic Aeric Ochraqualf) soil collected from long‐term conventional tillage (CT) and no‐tillage (NT) soybean [Glycine max (L.) Merr.] plots. Three concentrations of [14C] alachlor (0.58, 2.44, and 18.1 µmol L−1) in 0.01 M CaCl2 were added to soil (3 g/18 mL) and samples were shaken for time periods ranging from 1 min to 96 h. The difference between initial and final alachlor concentration was attributed to sorption. Desorption (0.01 M CaCl2) was measured for samples initially sorbed for 1, 24, or 96 h. Desorbed soils were extracted with methanol and then combusted. Freundlich parameters (Kf [1/n]) were calculated for alachlor sorption and desorption using nonlinear regression. Sorption Kf values for soil from both tillage systems increased as sorption shaking time increased. Desorption was hysteretic, and length of sorption shaking increased non‐singularity. Sorption Kf values measured for NT were greater than CT for each of the 1, 24, and 96 h sorption shaking times. Similarly, desorption Kf values for NT were greater than for CT. Kinetics were evaluated using a three‐site model. Sorption patterns indicated rapid initial sorption up to approximately 3 h followed by slower sorption. No change in solution alachlor was observed after 48 h for either tillage treatment. Labile and restricted fractions increased with time, especially for NT. The increased rate and overall quantity of alachlor sorption in NT was attributed to higher soil organic residues.
Water Quality Impacts Associated with Pre‐ and Postemergence Applications of Atrazine in Maize
Authors: Pantone D.J. , Young R.A. , Buhler D.D. , Eberlein C.V. , Koskinen W.C. , Forcella F.
Published: July 2010

Herbicide contamination in surface runoff varies greatly depending on the herbicide management alternatives used. This study was conducted to determine if herbicide runoff is influenced by the timing of herbicide application with respect to maize (Zea mays L.) emergence. Preemergence (PRE) and postemergence (POST) applications of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] were compared during 1988 and 1989 on a field with no prior history of atrazine use on a Barnes loam (fine‐loamy, mixed Udic Haploboroll) soil at the Swan Lake Research Farm near Morris, MN. A rainfall simulator applied precipitation events of 50 min with an intensity of 64 mm h−1 on Days 1,7, and 30 after PRE or POST applications of atrazine. Rainfall 1 d after application resulted in 32 g ha−1 of atrazine (less than 2% of the amount applied) in the runoff water and sediment for PRE treatments compared with 16 g ha−1 (less than 1% of the atrazine applied) for POST treatments. Similarly, 7 d after the herbicide applications, 20 g ha−1 was lost with PRE treatments and 1 g ha−1 for POST treatments. At 30 d, PRE treatments resulted in 8 g ha−1 being transported in the water and sediment compared with 1 g ha−1 for POST treatments. The rate of surface runoff, rather than the concentration of herbicide in the runoff, was the critical factor responsible for the reduction of the quantity of atrazine in the surface runoff with the POST treatments as compared with the PRE treatments.
Coupling Groundwater Contamination with Economic Returns When Applying Farm Pesticides
Authors: Hoag Dana L. , Hornsby Arthur G.
Published: July 2010

A methodology is presented that permits simultaneous consideration of the economics of production and groundwater contamination hazard of pesticide use. An example is constructed for weed control in soybean (Glycine max L.) production at Clayton, NC. A cost/groundwater hazard frontier is developed that can be used to identify and illustrate the cost tradeoffs of selecting alternative weed control strategies that reduce the risk of adverse health effects from drinking contaminated groundwater. The methodology relies on models to estimate costs, crop yields, pest competition, and leaching of pesticides; thus, its applicability depends on availability of local data and appropriately validated models for the site considered. The cost/groundwater hazard frontier provides a useful decision aid to assist pesticide users in making cost‐effective and environmentally favorable production decisions. It is also useful in evaluating policy or the value of new pest control technologies, as it indicates a farmer's ability to substitute alternatives for currently used practices.
Nitrogen Outputs from a Field‐Size Agricultural Watershed
Authors: Lowrance Richard
Published: July 2010

Nitrogen outputs from a 0.34‐ha field were measured for 1984 through 1987. The field consisted of Cowarts loamy sand (fine‐loamy, siliceous, thermic Typic Hapludult) managed in a summer row crop‐winter cover crop sequence. Outputs measured were subsurface flow, surface runoff, and denitrification. Monthly sampling of denitrification rates showed a high degree of temporal and spatial variability. Rates significantly increased with soil moisture and depth. Denitrification also increased after irrigation events. Nitrogen movement in subsurface flow was 97% NO3‐N and was about 10 times that in surface runoff. Most subsurface flow and movement of N (77 kg NO3‐N ha−1) occurred in December 1986 through February 1987 when 62 cm of precipitation fell in a 12‐wk period (December 1986–February 1987) following fertilizer application. This period accounted for one‐half the total subsurface nitrate movement for the 4‐yr study. Even though no crop was harvested in 1985, subsurface outputs of N were low in winter of 1985–1986. Soil NH4‐N levels were significantly higher after the year without a harvest, indicating that more of the N in crop residue was found in the soil pool.
Nitrate Dynamics in Riparian Forests: Microbial Studies
Authors: Groffman Peter M. , Gold Arthur J. , Simmons Robert C.
Published: July 2010

While riparian forests have a demonstrated ability to remove nitrate (NO−3) moving from uplands before it enters streams, there is considerable uncertainty as to the mechanisms of NO−3 removal in these areas. We characterized spatial and temporal variation in denitrification enzyme activity (DEA), microbial biomass C and N content, soil respiration and potential net N mineralization and nitrification in three riparian forest sites consisting of soil catenas containing moderately well, somewhat poorly, poorly, and very poorly drained soils (inceptisols and entisols). These measurements were made in conjunction with studies of NO−3 removal from groundwater during growing and dormant seasons that are reported in a companion paper. Two of the sites were on stratified glacial drift, one with an undeveloped upland and one with an upland with high density unsewered residential development that produced groundwater at the edge of the riparian zone with NO−3‐N concentrations between 8 and 12 mg/L The third site was on unstratified glacial drift with an undeveloped upland. Hydric surface (0–15 cm) soils (poorly and very poorly drained) consistently had higher DEA than upland‐wetland transition zone (moderately well and somewhat poorly drained) surface soils. Spatial patterns of microbial biomass C and N content were more variable but showed the same general pattern as DEA. Levels of DEA and microbial biomass were consistently low or undetectable at and below the seasonal high water table. Surface soil DEA and microbial biomass were correlated with NO−3 removal from groundwater during the growing season. Low levels of DEA and microbial biomass in the subsurface however, suggested that plant uptake was the dominant groundwater NO−3 sink during the growing season. During the dormant season, water table levels were higher and groundwater‐borne NO−3 was able to interact with near surface soil and be removed by denitrification and/or microbial immobilization. Potential net N mineralization was quite variable both within and between sites, while potential net nitrification was very low at most sites. A notable exception was in the transition‐zone soils at the stratified drift site with a densely developed upland, which had relatively high rates of net NO−3 production. The high nitrification rates observed at this site may suggest that the long‐term buffering potential of this site is limited.
Spatial and Temporal Variability of Carbofuran Degradation in Soil
Authors: Parkin T.B. , Shelton D.R.
Published: July 2010

Loss of pesticide efficacy resulting from enhanced rates of microbial degradation has been observed with several pesticides including the insecticide carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate). Soils in which this phenomenon occurs are often referred to as “problem soils.” Several previous studies have documented the temporal aspects of the conversion of a nonproblem soil to a problem soil, and have compared carbofuran degradation rates in problem vs. nonproblem soils. There have been few studies of the spatial or temporal variability of pesticide degradation, and no studies of the variability of carbofuran degradation, however. Our study was designed to evaluate the spatial variability of carbofuran degradation activity in a conventional‐till and a no‐till corn (Zea mays L.) field, and to assess temporal variations of carbofuran degradation activity. Soil samples were collected at two positional locations in each field (in‐row and between‐row) at three times during the growing season. Within the planting furrow, maximum rates of carbofuran degradation were higher and resulting half‐lives of carbofuran (DT‐50%) were lower than in samples collected between corn rows. Interactive effects of both microbial biomass and soil water content appeared to contribute to the observed differences in carbofuran degradation kinetics as well as to the positional differences observed. Temporal variations in carbofuran degradation appeared to be dominated by soil water content. At this time it remains unknown whether the observed increase in carbofuran degradation activity, in the row, occurred in response to the banded application of carbofuran, or to increased C availability in the rhizosphere.
Effect of pH on Sorption and Desorption of Imazaquin and Imazethapyr on Clays and Humic Acid
Authors: Che M. , Loux M. M. , Traina S. J. , Logan T. J.
Published: July 2010

The interaction of imazaquin (2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐3‐quinolinecarboxylic acd) and imazethapyr ((±)‐2‐4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid) with clay suspensions and humic acid was studied using a batch equilibrium method and by fluorescence emission spectroscopy. The objectives of this study were to: (i) determine the effect of different sorbents and pH on the sorption of imazaquin and imazethapyr, and the hysteresis in adsorption‐desorption isotherms, and ii) evaluate the effect of pH on the mechanisms of imidazolinone herbicide sorption by specimen hectorite. Sorption of both herbicides increased as pH decreased, but the increased sorption was most evident as soil pH decreased from 5 to 3. Illite and kaolinite, which exhibit more pH‐dependent charge characteristics and less total surface area than hectorite, can impart important adsorptive character to soil, especially with regard to imazethapyr. Humic acid had much greater affinity for both herbicides than clay did, indicating that organic matter content could be a major factor controlling the sorption of these herbicides in soils. The rate of desorption varied among absorbents and between herbicides; imazethapyr desorbed more readily than imazaquin from most adsorbents. The results of fluorescence emission spectroscopy indicated that imazaquin and imazethapyr molecules were protonated and sorbed on the clay surface under acidic conditions. The extent of protonation was greater in the clay suspensions than in clay‐free solutions.
Organic and Inorganic Amendments to Reduce Ammonia Losses from Liquid Hog Manure
Authors: Al‐Kanani T. , Akochi E. , MacKenzie A. F. , Alli I. , Barrington S.
Published: July 2010

Liquid hog manure (Sus scrofa domesticus) is in common use as a fertilizer or a soil conditioner in agricultural production. Liquid hog manure (LHM) suffers from N loss through volatilization of ammonia (NH3), however. Reduction of NH3 loss from 4% total solids LHM was studied using added Sphagnum peat moss (Sphagnum fuscum peat), sulfuric acid, phosphoric acid, monocalcium phosphate monohydrate (MCPM), elemental S, and calcium carbonate. Cumulative losses of NH3‐N ranged between 0 and 711 mg N kg−1 LHM applied. Elemental Sulfur and calcium carbonate (CaCO3) treatments induced greater NH3 losses compared with the nonamended LHM, whereas acidic treatments including Sphagnum peat moss (SM) reduced NH3 losses by at least 74.6%. Volatilization of NH3 from LHM increased as the pH of amended LHM treatment increased. The relationships between cumulative (15 d) NH3 volatilized and initial pH of amended LHM varied, depending on the amendment. The nutrient values of amended LHM stored for 25 d under continuous aeration were assessed on two soils mapped as Chicot (fine loamy, mixed, nonacid, mesic Typic Hapludoll) and Uplands (coarse loamy, mixed, nonacid, Typic Haplorthod) from eastern Canada. Treatment of LHM with SM at greater than 1% (w/w) reduced NH3 volatilization. Added CaCO3 increased NH3 loss. In general, amendments did not reduce effectiveness of LHM‐N for barley (Hordeum vulgare L.) growth. An exception was the 1% SM + 2% CaCO3 amendment that reduced plant growth.
Wastewater Renovation in Buried and Recirculating Sand Filters
Authors: Gold A.J. , Lamb B.E. , Loomis G.W. , Boyd J.R. , Cabelli V.J. , McKiel C.G.
Published: July 2010

A replicated, multiyear field study was conducted to assess the reduction of N, P and microbial indicators by a recirculating sand filter (RSF) and buried multilayer sand filter patterned after the RUCK filter. The RSF's received 38 L m−1 d−1 of septic tank effluent, while the buried sand filters were loaded at 76 L m−2 d−1. The RSF's had significantly greater reductions of N and P (21 and 31%, respectively) than the buried filters (8 and 1%, respectively); however, reduction was not significantly different per unit area. The lower daily loading rate and even distribution of effluent on the recirculating filters may have contributed to the elevated P reductions noted. Total Kjeldahl N (TKN) reductions in the RSF's were markedly lower during the cold season (≤ 10 °C) than the warm season. In contrast, TKN reductions in the buried sand filters were relatively constant, except during the coldest periods of winter. Substantial TKN reductions occurred under acidic conditions. During warm weather sampling, both types of filters dramatically reduced levels of fecal coliform, enterococci, and F male‐specific bacteriophage. During cold conditions, the buried sand filters produced greater reductions of fecal coliforms and enterococci levels, while neither filter consistently reduced the levels of Clostridium perfringens or F phage. Increased reductions in fecal coliform, enterococci and F phage were associated with lower effluent pH for both sand filters.
The Dust Bowl of the 1930s: Analog of Greenhouse Effect in the Great Plains?
Authors: Rosenzweig Cynthia , Hillel Daniel
Published: July 2010

For nine sites in the southern Great Plains, the decade of the Dust Bowl was consistently warmer than the 1951 to 1980 “normal.” It also tended to be drier, but less consistently so. At four of the nine sites, the combination of consistently higher temperature and mostly lower precipitation had a cumulative effect over the 1930s, making the entire decade a period of agricultural drought as characterized by the Palmer Drought Severity Index (PDSI). Episodes of extreme drought occurred at many sites, particularly in 1934 in Nebraska. Temperature and precipitation changes predicted by two general circulation models (GCMs) at the upper range of current climate model predictions for doubled concentrations of CO2 (+4.2 °C and +4.0 °C mean global surface air temperature warming) suggest drought conditions as defined by the PDSI that are worse than those for the 1930s for all stations. Droughtiness is projected to increase overall, even when the GCM climate change scenarios produce little change or even increases in precipitation. In most instances, the mean GCM‐predicted drought conditions equal or exceed the extreme drought years of the decade. When dynamic crop growth models were run in combination with the GCM‐predicted climates, simulated wheat (Triticum aestivum L.) and corn (Zea mays L.) yields were obtained that were generally lower (∼30%) than those of simulations for the actual climate of the 1930s. The crop model simulations indicated that the predicted climate change is likely to be less detrimental to a crop such as wheat, whose main growing period is in the spring, than to a typical summer crop such as corn. The overall results of this study suggest that the Dust Bowl experience of the 1930s may be characterized as a preliminary analog of possible future climate conditions for the southern Great Plains, with the importance difference that the higher projections of GCM warming produce more severe climatic consequences than the Dust Bowl.