bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil and Phosphorus Loss from Conservation and Conventional Tillage in Corn Production
Authors: Gaynor J. D. , Findlay W. I.
Published: July 2010

Conservation tillage is encouraged in southwestern Ontario by concern for soil erosion and compaction. The contribution of agriculture to eutrophication of the Great Lakes by P is also at issue. Soil loss and ortho‐P transport were measured from a conventional and two conservation tillage treatments (zero and ridge tillage) from January 1988 to 30 Sept. 1990 to evaluate their impact on meeting Great Lakes water quality objectives for P. Sediment concentration from the poorly drained, Brookston clay loam (clayey, mixed, mesic Typic Haplaquolls), cropped to corn (Zea mays L.) was 2.1 times larger in surface runoff than tile discharge (0.20 g L−1) but tile discharge contributed 44 to 65% of the soil loss probably from preferential flow. Conservation tillage reduced average soil loss 49% from conventional tillage (899 kg ha−1). Conservation tillage increased ortho‐P concentrations in runoff 2.2 times from conventional tillage (0.25 mg L−1). Orthophosphate transport decreased in the order zero>ridge>conventional tillage. Average ortho‐P loss was 1.7 to 2.7 times greater from conservation than conventional tillage (559 g ha−1 yr−1). Subsurface drainage accounted for 55 to 68% of the ortho‐P transported. Transport of total soluble P and total P (sum of sediment‐attached P and soluble P, only measured in 1990) increased 2.2 and 2.0 times, respectively, with conservation than conventional tillage. Dissolved P accounted for 84 to 93% of the P transported from the three tillage treatments. Sediment‐attached P constituted 7 to 16% of total P loss. Conservation tillage effectively reduced soil erosion but increased P loss.
Device for Sampling Unconsolidated Soft‐Bottom Sediments in Moderately Deep Waters
Authors: Doyle E. F. , van Dokkum H. P. , Vermulst C. J. W. , Anderson D. L. , Mossa J.
Published: July 2010

Sampling unconsolidated soft‐bottom sediments in shallow to moderately deep canals is difficult. A sediment core sampler was constructed from commercially available parts, utilizing a readily removable plastic liner. The removable prefit liner facilitates easy removal, transport, and storage of the core, and reduces the likelihood of core contamination from sample to sample. The device also consists of a transparent polycarbonate tube with a removable stainless‐steel cutting head. Soft‐bottom core samples up to 30‐cm in length were taken in water as deep as 8 m. The device is relatively lightweight and can be used from a small boat.
Sorption of Manganese, Uranium, and Radium by Highly Weathered Soils
Authors: Willett I. R. , Bond W. J.
Published: July 2010

Large concentrations of Mn, 238U, and 226Ra are present in U mine waste waters in comparison with those in surrounding natural waters. Excess mine waste water is being disposed by irrigation of bushland near Ranger Uranium Mine, Northern Territory, Australia. We report the sorption properties of highly weathered and sandy soils (Utric Acruustox, Grossameric Kandiustalf, and Typic Fragiumbrept), near the mine for Mn, U, and 226Ra as determined by batch sorption experiments, and competitive sorption between U and Mn. Manganese sorption was small in comparison with loads expected to be applied to the soils, and Mn was expected to be mobile within the soils. In contrast with Mn, U sorption by the soils was very much greater than the amount that may be applied. Simultaneous additions of U and Mn reduced sorption of both, but the effect of U on Mn sorption was far greater than that of Mn on U. Uranium also caused the displacement of Mn from the soil in the absence of added Mn. The U additions favored the mobility of Mn. Radium−226 at trace levels was strongly sorbed by the soil and <1% of the sorbed 226Ra was displaced during the desorption step. Uranium and 226Ra applied as mine waste water will be retained in surface soil, but Mn was expected to be relatively mobile, particularly in the sandiest soils and when applied in waters that also contain U.
Siderite Weathering in Acidic Solutions under Carbon Dioxide, Air, and Oxygen
Authors: Frisbee N. M. , Hossner L. R.
Published: July 2010

Siderite (FeCO3) is found in coal overburden, and is commonly subjected to acidic environments in reclaimed minelands. Manganese commonly substitutes for Fe, and can be present in significant concentrations in the mineral. Siderite was incubated in a solution of either potassium hydrogen phthalate (KHP) or sulfuric acid with an initial pH of 3.0 in environments of CO2, air, or O2. Iron and Mn release from siderite under varying gaseous environments decreased in the following order: CO2 > air > O2. Weathering zones developed that were from 0.39 to 0.85 mm thick. Iron oxides precipitated in the weathering zone and slowed iron release from siderite samples incubated in H2SO4 under all three gaseous atmospheres. Iron oxides did not precipitate in the weathering zone for samples reacted in KHP solution. The release of Fe and Mn to solution followed a zero order reaction rate.
Uptake of a Hydrologic Tracer (Bromide) by Ryegrass from Well and Poorly‐Drained Soils
Authors: Schnabel R. R. , Stout W. L. , Shaffer J. A.
Published: July 2010

Ryegrass (Lolium perenne L.) accumulated an average 32% of applied bromide (Br−) in aboveground biomass. Bromide uptake was greater on a well‐drained soil (38%) than a poorly drained soil (27%). Uptake was also affected by an interaction between season and N fertility. Bromide concentration of ryegrass was affected by interactions between soil drainage and season, and between soil drainage and N fertility. The magnitude of uptake shows Br− to be quite biologically reactive in the soil root zone. The impact of interactions between common experimental variables on Br− uptake makes it difficult to select settings where Br− uptake will be low. Consequently, the amount and pattern of uptake among common experimental variables greatly restricts the settings in which Br− is an appropriate hydrologic tracer.
Identifying Sites Vulnerable to Phosphorus Loss in Agricultural Runoff
Authors: Sharpley Andrew
Published: July 2010

The continual application of more phosphorus (P) in fertilizer and manure to agricultural systems than removed in harvested crops can lead to surface soil accumulation of P. As a result, soil P has become of environmental rather than agronomic concern in areas of intensive crop and livestock production where P enrichment of runoff can promote eutrophication. To target cost‐effective remedial measures, sites vulnerable to P loss in runoff must be identified. Site identification by traditional field trials and computer simulations can be time consuming, costly, and data intensive. The Lemunyon and Gilbert field index was used to rank the vulnerability for P loss from 30 unfertilized and P‐fertilized, grassed, and cropped watersheds in the Southern Plains. Watershed vulnerability to P loss in runoff was closely related (r2 = 0.70**) to actual losses measured over the last 16 yr (0.1–5 kg P ha−1 yr−1). Vulnerability to P loss decreased in the order: conventionally tilled wheat (Triticum aestivum L.); no‐till wheat; native grass; and set‐aside grass. Also, erosive gully remediation by shaping, sprigging with Midland bermudagrass [Cynodon dactylon (L.) Pers.] reduced vulnerability from medium to low. The P index is a valuable tool to identify P sources within a watershed that will require more intensive management to minimize P loss in runoff while maintaining crop productivity.
Nitrous Oxide Loss from Poultry Manure‐Amended Soil after Rain
Authors: Coyne M. S. , Villalba A. , Blevins R. L.
Published: July 2010

Land application of poultry wastes in Kentucky will increase as the broiler industry grows. If poultry manure stimulates N2O loss from soil it will reduce the fertilizer N value of this waste. In contrast, stimulated N2O loss in grass filter strips receiving the runoff from manured fields could help reduce contamination of surface water by NO−3. Our objectives were to determine (i) if poultry manure stimulated N2O loss in soil after rainfall and (ii) if there was an edge‐of‐field effect on N2O loss in grass filters intercepting runoff from amended soil. Soil covers were used to measure N2O loss from a well‐drained, poultry manure‐amended, silt loam soil immediately after simulated rainfall and were also used to measure N2O loss from grass filters intercepting their surface runoff. Nitrous oxide loss from manure‐amended soil was greater than from unamended controls and ranged from 5 to 13 mg N2O‐N m−2 h−1. The maximum N2O loss was equivalent to 3.2 kg N2O‐N ha−1 d−1. Nitrous oxide loss from grass filters intercepting runoff ranged from 0.1 to 1.4 mg N2O‐N m−2 h−1 and was significantly greater than portions of the grass filters that did not intercept runoff. Nitrous oxide loss from poultry manure‐amended soils was greater than N2O loss typically measured from waste‐amended agricultural soils. However, it only represented up to 0.7% of the total N in the applied manure.
Effects of Liming on Soils and Streamwaters in a Deciduous Forest: Comparison of Field Results and Simulations
Authors: Johnson Dale W. , Swank Wayne T. , Vose James M.
Published: July 2010

Soil and stream chemical responses to liming in a deciduous forest watershed at Coweeta, NC, are compared with simulation results using the Nutrient Cycling Model (NuCM). Field comparisons of limed and unlimed soils after 23 yr indicated substantial net retention of applied Ca2+ and Mg2+ in upper soil horizons, even in black locust (Robinia pseudoacacia L.) sites where NO−3 leaching was elevated. We hypothesized that NuCM simulations would also show that (i) retention of most applied Ca2+ and Mg2+ in the upper horizons and (ii) increased Ca2+ and Mg2+ retention with increased cation exchange capacity (CEC) and exchangeable H+ (simulating pH‐dependent CEC). Both hypotheses were supported by simulation results for Ca2+, but not for Mg2+. Most applied Mg2+ in the simulations was retained in the BC horizon, where the largest pool of exchangeable Mg2+ was initially located. Increasing CEC and exchangeable H+ did result in increased retention of applied Ca2+ and Mg2+ in surface horizons. However, increasing CEC caused lower Mg2+ retention in the BC horizon, which offset the surface horizon increases and resulted in lower total retention of applied Mg2+. Simulated BC horizon soil solution concentrations mimicked the general patterns in streamwater NO−3, Mg2+, Na+, Cl−, SO2−4, and K+ between 1971 (12 yr after liming) and 1979. NuCM simulations did not, nor was it possible to simulate the observed effects of an insect outbreak on streamwater NO−3.
Assessing Colloidal Forms of Phosphorus and Iron in the Tualatin River Basin
Authors: Mayer T. D. , Jarrell W. M.
Published: July 2010

Although colloids can affect the transport and chemistry of trace constituents in some aquatic systems, there are few estimates of the mass of given constituents in colloidal forms. The existence, variability, and origin of colloidal Fe oxide, and its effect on P chemistry, was evaluated in the Tualatin River Basin of northwestern Oregon. Watershed streams were regularly sampled during 1992 and 1993. The concentrations of P and Fe in the colloidal size class (0.05–1.0 µm) were determined by filtration. Elemental composition of the suspended material was assessed using scanning electron microscopy/energy‐dispersive spectroscopy (SEM/EDS). Colloidal P and Fe ranged from 0 to 48% and 2 to 77% of the total P and total Fe, respectively. Since filtration underestimates colloidal concentrations, these are conservative estimates. Concentrations of P and Fe in colloidal form were correlated (r2 = 0.83; P < 0.001) but total P, total Fe, and total suspended sediments were not correlated. SEM/EDS analysis showed that, in addition to P and Fe, the colloids contained Si, Al, and Ca. The colloids were enriched with P and Fe relative to Al and Si. Evidence suggests that the colloidal P and Fe particles form as groundwater‐ or sediment‐released Fe(II) is oxidized to Fe(III), which associates with P, either as coatings on the surface of colloidal clays and organics or as homogeneous particles.
Influence of Organic Amendments on Biodegradation of Atrazine as a Nitrogen Source
Authors: Alvey S. , Crowley D. E.
Published: July 2010

Carbon and N dynamics may be particularly important for selective enrichment of microorganisms that are capable of using xenobiotics as sources of N for growth. To investigate this hypothesis in relation to s‐triazines, a soil microcosm study was performed to determine the effect of organic amendments differing in complexity and C/N ratio, and the effects of inorganic N addition on atrazine mineralization in a soil having a 15‐yr history of prior exposure to this herbicide. When the soil was spiked with 100 mg/kg of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) in the absence of organic amendments, 73% of the atrazine was mineralized after 11 wk. Soils amended with rice hulls, starch, and compost yielded mineralization rates of 88, 75, and 59% in the same period, respectively. In contrast, <10% of the atrazine was mineralized in soils amended with glucose, Sudan hay, or sodium citrate. All treatments receiving supplemental inorganic N had a considerably lower rate of atrazine mineralization than corresponding treatments without N addition. However, the different effects of the organic matter supplements suggested there was no relationship between the C/N ratio of the soil and atrazine mineralization. An atrazine‐degrading consortium was subsequently isolated for further characterization. The results demonstrate that while atrazine mineralization is suppressed under high N conditions in this soil, the mineralization rate also is influenced by poorly understood population dynamics related to the nutrient composition and complexity of specific organic amendments.
Effect of Concentration on Persistence of Alachlor in Soil
Authors: Gan J. , Koskinen W. C. , Becker R. L. , Buhler D. D.
Published: July 2010

To determine the behavior of alachlor [2‐chloro‐N‐(methoxymethyl)‐N‐(2,6‐diethylphenyl)‐acetamide] at concentrations common with spill and waste disposal sites, alachlor degradation was determined over a concentration range of 10 to 10 000 mg kg−1 in a Webster clay loam (fine loamy, mixed, mesic Typic Haplaquoll) and an Estherville sandy loam (sandy, mixed, mesic Typic Hapludoll) in laboratory incubation experiments. Effect of concentration on the overall behavior of alachlor was similar in both soils. Based on percent of applied chemical, persistence of alachlor increased with increasing concentration. Mineralization and formation of degradation products and bound residues decreased at higher concentrations. At 10 000 mg kg−1, alachlor was extremely persistent, with estimated 50% dissipation times (DT50) of 12.6 and 13.5 yr in the Webster and Estherville soil, respectively. Although the DT50 increased with increasing concentration, significant amounts of alachlor, in absolute mass, degraded at higher concentration. However, mineralization at 1000 and 10 000 mg kg−1 was similar to that at 100 mg kg−1. Specific alachlor biodegradation mechanisms, limited water solubility, and kinetics of dissolution of precipitated alachlor and alachlor desorption are postulated as the rate‐limiting factors for the degradation of alachlor at elevated levels. A field experiment also indicated alachlor dissipation at high concentration was extremely slow over the first 6 mo after application. Degradation and leaching increased by the following spring. It would appear that an effective remediation means to detoxify alachlor‐contaminated soil would be to land‐spread the soil, thereby diluting the concentration of alachlor in the soil to <100 mg kg−1.
TNT Transport and Fate in Contaminated Soil
Authors: Comfort S. D. , Shea P. J. , Hundal L. S. , Li Z. , Woodbury B. L. , Martin J. L. , Powers W. L.
Published: July 2010

Past disposal practices at munitions production plants have contaminated terrestrial and aquatic ecosystems with 2,4,6‐trinitrotoluene (TNT). We determined TNT transport, degradation, and long‐term sorption characteristics in soil. Transport experiments were conducted with repacked, unsaturated soil columns containing uncontaminated soil or layers of contaminated and uncontaminated soil. Uncontaminated soil columns received multiple pore volumes (22–50) of a TNT‐3H2O pulse, containing 70 or 6.3 mg TNT L−1 at a constant pore water velocity. TNT breakthrough curves (BTCs) never reached initial solute pulse concentrations. Apex concentrations (C/Co) were between 0.6 and 0.8 for an initial pulse of 70 mg TNT L−1 and 0.2 to 0.3 for the 6.3 mg TNT L−1 pulse. Earlier TNT breakthrough was observed at the higher pulse concentration. This mobility difference was predicted from the nonlinear adsorption isotherm determined for TNT sorption. In all experiments, a significant fraction of added TNT was recovered as amino degradates of TNT. Mass balance estimates indicated 81% of the added TNT was recovered (as TNT and amino degradates) from columns receiving the 70 mg TNT L−1 pulse compared to 35% from columns receiving the 6.3 mg TNT L−1 pulse. Most of the unaccountable TNT was hypothesized to be unextractable. This was supported by a 168‐d sorption experiment, which found that within 14 d, 80% of 14C activity (added as 14C‐TNT) was adsorbed and roughly 40% unextractable. Our observations illustrate that TNT sorption and degradation are concentration‐dependent and the assumptions of linear adsorption and adsorption‐desorption singularity commonly used in transport modeling, may not be valid for predicting TNT transport in munitions‐contaminated soils.
Nitrogen Loss from a Soil Restored after Surface Mining
Authors: Davies R. , Hodgkinson R. , Younger A. , Chapman R.
Published: July 2010

Anaerobic conditions develop below about 1‐m depth in soil stockpiles and this can lead to an accumulation of ammonium (NH+4) and transformations of a normally relatively inert organic‐N pool within the soil. After reinstatement of the soil from the stockpile, the NH+4 may rapidly be transformed to nitrate (NO−3) and lost from the soil with the labile organic‐N. These losses may lead to a pollution risk in addition to the loss of a resource. The magnitude of N losses were measured from a soil that had been reinstated for agricultural use after being stored in a stockpile for 12 yr. Nitrogen movement in the soil profile and losses into the water‐course were monitored for 2 yr beginning immediately after reinstatement. Relatively large movements of N were detected within the soil profile and large losses to the atmosphere and/or water‐courses were estimated. Over the 2‐yr monitoring period, 2449 kg ha−1 of N was lost from the soil profile; 90% of this was not accounted for either in the soil or in the runoff or drainage water as mineral‐N and was presumed to have entered either the atmosphere or aquatic environment as organic‐N. To aid remedial measures, the proportion entering the atmosphere as nitrogen and nitrous oxides or the aquatic environment as organic‐N, needs further investigation.
Experimental Evidence of Transport of Pesticides through Field Soils—A Review
Authors: Flury Markus
Published: July 2010

Much information is available in the literature about pesticide transport through soils at the field scale. The purpose of this study is to review the literature with a focus on pesticide leaching to groundwater. The literature was compiled and discussed with respect to different factors that influence pesticide leaching. Pesticide leaching below the root zone has been demonstrated in sandy as well as in loamy soils. Particularly in loamy soils, there is evidence that even strongly adsorbing chemicals can move along preferential flow pathways and that the travel times of pesticides are comparable to those of conservative solutes. The amounts of pesticides leached below the root zone by worst case rainfall events depend on the chemical properties and can reach up to 5% of the applied mass. When there is no heavy rainfall shortly following application of chemicals, the mass annually leached below the root zone is in the range of <0.1 to 1%, occasionally it can reach up to 4%. Although a direct comparison cannot be made, the mass lost by leaching seems generally to be smaller than that lost by runoff, depending of course on the slope of the fields. Several factors that affect pesticide leaching, such as surface preparation, soil structure, soil water content, type of irrigation, pesticide formulation, time of application and rainfall events, are discussed with support of experimental evidence. While some factors showed inconsistent effects, others show promise in controlling leaching mechanisms. These latter factors include initial water content, surface preparation, and time of pesticide application. Based on the reviewed literature, recommendations were made for future research activities.
Phosphorus Losses in Irrigation Runoff from Fertilized Pasture
Authors: Austin Nick R. , Prendergast J. Bernard , Collins Matthew D.
Published: July 2010

Runoff from flood‐irrigated perennial pastures contains significant loads of P. Factors affecting the P load in runoff are unknown, and there are no guidelines currently available for management of phosphatic fertilizers to reduce runoff P loads. This study was conducted to determine the relationship between single superphosphate application rate and runoff P concentration. Four rates of single superphosphate (250, 500, 750, and 1000 kg/ha) were applied to 12 30 by 8‐m flood irrigated bays in a randomized design, on a Lemnos loam (Natric Xeralf), in the Shepparton Irrigation Region, Victoria, Australia. In runoff, total P (TP), filtrable reactive P (FRP) concentrations and EC increased linearly with application rate, with initial concentrations (5 min) being significantly higher than those later in a runoff event (P < 0.025). In the irrigation directly following fertilizer application the depth of irrigation water that infiltrated (calculated from volume balance) was in direct proportion to single superphosphate application rate (P = 0.03). Normalized runoff losses of single superphosphate in consecutive irrigations followed a single exponential decay. The primary loss mechanism for P following single superphosphate application was through dissolution, rather than sediment transport.
Forms of Cadmium, Lead, and Zinc in Contaminated Soils from Southwest Poland
Authors: Chlopecka Anna , Bacon J. R. , Wilson M. J. , Kay J.
Published: July 2010

The metals Cd, Pb, and Zn occurring in Haplorthods and Haplumbrepts of both sandy and loamy textures in the vicinity of Tarnowskie Gory in southwest Poland, an area that has been subjected to severe metal contamination, were studied according to a procedure based on sequential extraction analysis. Concentrations of the metals ranged from background levels to levels well in excess of the maximum tolerable limits in agricultural soils. Thus, Cd, Pb, and Zn ranged from 0.2 to 103, 14 to 7100 and 20 to 10 000 mg kg−1 soil, respectively. Soil type, texture, organic matter, and cation exchange capacity (CEC) did not influence the relative proportions of heavy metal forms in any consistent manner. However, the influence of soil pH was clear. Soil samples of pH < 5.6 contained relatively more of all metals in the exchangeable form than in samples where pH was >5.6. The most consistent distribution patterns were found when the soil samples were grouped according to their total metal contents. The inferred relative mobility of the metals and their redistribution among the different fractions are generally consistent with the findings of previous studies of contaminated soils and support the view that metals from anthropogenic sources are more mobile than those from soil parent materials.
Nitrate Leaching Losses Under Repeated Cattle Feedlot Manure Applications in Southern Alberta
Authors: Chang C. , Entz T.
Published: July 2010

An experiment was conducted at Lethbridge, Alberta, to determine the long‐term effects of annual applications of cattle manure on nitrate (NO3)‐N accumulation and movement, and to assess the environmental impact of such a practice. Manure was applied annually at 0, 30, 60, and 90 Mg ha−1 (wet wt. basis) and 0, 60, 120, and 180 Mg ha−1 (zero, one, two, and three times the maximum recommended annual application rate, respectively), to nonirrigated and irrigated Dark Brown Chernozemic (Typic Haploboroll) clay loam soils from 1973 to 1992. All plots were planted to barley (Hordeum vulgare L. cv. Galt) in spring each year. In the fall, duplicate soil cores were taken to a depth of 1.5 m. Water content (gravimetric), chloride, ammonium‐ and NO3‐N concentration of soil and manure samples were determined to estimate leaching and deep percolation loss of water and solutes. Level of manure and moisture regime affected the extent of NO3‐N increases. Under nonirrigated conditions, manure applied at one to three times the recommended rate resulted in a significant accumulation of NO3‐N in the root zone. However, minimal leaching loss was observed below 1.5 m except for a year with unusually high precipitation. On irrigated soils, contamination of soil and groundwater from repeated applications at or greater than the recommended rate of 60 Mg ha−1 was significant and annual losses may reach 93 to 341 kg N ha−1. Therefore, long‐term annual application of manure at the maximum recommended level is not advised because of potential soil and water contamination problems.
Volatilization of EPTC: Simulation and Measurement
Authors: Baker J. M. , Koskinen W. C. , Dowdy R. H.
Published: July 2010

Many of the organic chemicals used in agricultural production are susceptible to loss from the soil surface to the atmosphere by volatilization. Adequate prediction of the impact of these chemicals on the environment thus requires consideration of both downward movement through the soil to groundwater and upward movement in the gas phase to the atmosphere. We developed a method to mechanistically simulate volatilization within the framework of a conventionally formulated solute transport model and used it to simulate the gas‐phase losses of EPTC, a commonly used volatile herbicide. The model considers efflux of a trace gas at the soil surface to be a process of unsteady diffusion, interrupted intermittently by dispersive events that can be thought of as eddies at the innermost scale. Model results were compared to measurements of volatilization during the first 7 d following application of EPTC, conducted with a Bowen ratio system in a 17‐ha field at Rosemount, MN. The measurements indicated a relatively large initial flux (ca. 150 g ha−1 h−1) that rapidly decreased to negligible levels within a day following application. The model agreed reasonably well on the first day, if a measured value for Henry's constant was used rather than a value estimated from the saturation vapor pressure and the solubility. However, on subsequent days the model considerably overestimated volatilization, regardless of the Henry's constant that was used. It is likely that hysteresis in sorption/desorption, particularly as surface soil dries following herbicide incorporation, may be the primary reason why volatile losses are lower than might be predicted on the basis of equilibrium partitioning theory.
Methyl Bromide Emissions from a Covered Field: I. Experimental Conditions and Degradation in Soil
Authors: Yates S. R. , Gan J. , Ernst F. F. , Mutziger A. , Yates M. V.
Published: July 2010

An experiment is described to investigate the environmental fate and transport of methyl bromide in agricultural systems. The experiment was designed to determine the dynamics of methyl bromide movement through soil, degradation, and total emissions to the atmosphere. This is of particular interest because it will allow an assessment of the environmental impacts (i.e., stratospheric ozone depletion) resulting from the agricultural use of methyl bromide. Methyl bromide was applied at a rate of 843 kg in a 3.5‐ha (i.e., 240 kg/ha) field at a depth of 0.25 m and covered with a sheet of 1‐mil polyethylene plastic. The maximum methyl bromide concentration in the atmosphere occurred at night between 0200 and 0600 h. During the first 3 d of the experiment, the maximum daily concentrations at 0.2 m above the soil surface were 30, 5, and 1 mg/(m3 of air), respectively. The trend of reduced emissions with time continued until the plastic was removed, when a momentary increase in the methyl bromide emissions occurred. The maximum soil gas concentration 24 h after injection was 30 g/m3 located at a 0.25‐m depth. When the plastic was removed from the field (at 5.6 d), the maximum soil gas concentration was approximately 2 g/m3 at a 0.5‐m depth. A mass‐difference method for estimating the total methyl bromide emissions from the soil, based on degradation of methyl bromide to Br−, indicates that approximately 39% or 325 kg (± 164 kg) of the applied methyl bromide was converted to Br− and, therefore, 61% or 518 kg (±164 kg) was lost via volatilization.
Methyl Bromide Emissions from a Covered Field: II. Volatilization
Authors: Yates S. R. , Ernst F. F. , Gan J. , Gao F. , Yates M. V.
Published: July 2010

An experiment to investigate the environmental fate and transport of methyl bromide in agricultural fields is described. The methyl bromide volatilization rate was determined as a function of time for conditions where methyl bromide was applied at a rate of 843 kg in a 3.5‐ha (i.e., 240 kg/ha) field covered with plastic at a depth of 25 cm. Three methods were used to estimate the methyl bromide volatilization rate, including: the aerodynamic, theoretical profile shape and integrated horizontal flux methods. The highest methyl bromide volatilization rates were at the beginning of the experiment. Within the first 24 h, approximately 36% of the applied methyl bromide mass was lost. Diurnally, the largest volatilization rates occurred during the day when temperatures were high and the atmosphere was unstable. Cooler temperatures, light winds, and neutral to stable atmospheric conditions were present at night, reducing the flux. The total emission calculated using these methods was found to be approximately 64% (±10%)of the applied mass. A mass balance was calculated using each flux estimation technique and several methods for analyzing the data. The average mass recovery using all the flux methods was 867 kg (±83 kg), which was 102.8% (±9.8%) of the applied mass (i.e., 843 kg). The range in the mass balance percent (i.e., percent of applied mass that is measured) is from 88 to 112%. The averaged mass balance percent for the aerodynamic method, which involved using the measured data directly, was approximately 100.8%. The total emission calculated using the aerodynamic method was found to be approximately 62% (± 11%) of the applied mass.
Influence of Controlled Drainage‐Subirrigation on Surface and Tile Drainage Nitrate Loss
Authors: Drury C. F. , Tan C. S. , Gaynor J. D. , Oloya T. O. , Welacky T. W.
Published: July 2010

Controlled drainage‐subirrigation (CDS), conservation tillage, and corn (Zea mays L.) production practices were evaluated as methods of reducing NO−3 loss through tile drainage. Controlled drainage‐subirrigation was used to manage water from precipitation and subirrigation. Samples of tile drainage (5801) and surface runoff (3274) water were collected with autosamplers during each runoff event over a 3‐yr period. Annual tile drainage volumes were reduced 24% with CDS compared with the drainage (DR) treatments. Flow weighted mean NO−3 concentration of tile drainage water was reduced 25% from 10.6 mg N L−1 for the DR treatments to 7.9 mg N L−1 for the CDS treatments. The average annual NO−3 loss was reduced 43% from 25.8 kg N ha−1 for the DR treatment to 14.6 kg N ha−1 for the CDS treatments. Eighty‐eight to 95% of the NO−3 losses from all treatments occurred in the noncrop period (1 Nov.–31 Apr.). Conservation tillage in combination with CDS reduced annual NO−3 losses 49% (11.6 kg N ha−1) when compared with the conventional moldboard plow tillage and DR treatment. Annual NO−3 loss through surface runoff was increased to 1.9 kg N ha−1 with the CDS treatments compared with 1.4 kg N ha−1 with the DR treatment, this loss was minor compared with losses incurred through tile drainage. Controlled drainage‐subirrigation is a technological advancement in soil and water management as it enables farmers to minimize the effect of dry summers on crop growth and reduce NO−3 contamination of drainage water.
Laboratory Scale In‐Vessel Composter Designed for Volatile Emissions Analysis
Authors: Spongberg A. L. , Thomas J. C. , Brown K. W.
Published: July 2010

Airtight laboratory scale in‐vessel composters equipped to capture gaseous emissions were constructed from modified portable cement mixers. Any compounds that are volatilized during composting can be collected from the exiting air stream and quantified using gas chromatography. Measurements of the amount of each compound vaporized and its residual concentration can be used to determine air quality impacts and degradation rates.
Applications of GIS to the Modeling of NonPoint Source Pollutants in the Vadose Zone: A Conference Overview
Authors: Corwin D. L. , Wagenet R. J.
Published: July 2010

Because of their ubiquitous nature and potential chronic health effects, nonpoint source (NPS) pollutants have become a focal point of attention by the general public, particularly regarding pollution of surface and subsurface drinking water sources. The NPS pollutants pose a technical problem because of the areal extent of their contamination that increases the complexity and sheer volume of data far beyond that of point‐source pollutants. The spatial nature of the NPS pollution problem necessitates the use of a geographic information system (GIS) to manipulate, retrieve, and display the large volumes of spatial data. This overview provides a brief introduction and review of the modeling of NPS pollutants with GIS and a brief discussion of some of the papers presented at the ASA‐CSSA‐SSSA 1995 Bouyoucos Conference entitled Applications of GIS to the Modeling of Nonpoint Source Pollutants in the Vadose Zone.
Determination of Nonpoint‐Source Pollution Using GIS and Numerical Models
Authors: Zhang R. , Hamerlinck J. D. , Gloss S. P. , Munn L.
Published: July 2010

A geographic information system (GIS) was utilized to apply a modified DRASTIC method to the assessment of ground water contamination sensitivity in Goshen County, Wyoming. Several basic environmental characteristics, identified as influencing contaminant transport through the vadose zone to groundwater systems, were mapped, automated, and analyzed. These characteristics include: depth to groundwater, net recharge, hydrogeologic setting, vadose zone soil properties, land surface slope, and saturated hydraulic conductivity. Sensitivity ratings were developed for each parameter based on a combination of mathematical functions and the inherent capacity of each characteristic to influence transport of contaminants. A raster‐based overlay analysis was performed to derive a map that portrays cumulative aquifer sensitivity ratings across the county, providing a relative indication of groundwater vulnerability to contamination. A process‐based numerical model was used to simulate water flow and solute transport in the vadose zone and groundwater systems. The model incorporated soil and hydraulic properties produced with the GIS into the simulations. Numerical simulations described the time and spatial distributions of contaminants. Chemical mass stored in the soil and leaching out from the vadose zone were computed to characterize groundwater contamination. Groundwater sensitivity indexes, which were developed based on the numerical modeling results, were compared with the GIS sensitivity map and used to verify the reliability of the map.
Use of Logistic Regression and GIS Modeling to Predict Groundwater Vulnerability to Pesticides
Authors: Teso Roberto R. , Poe Minn P. , Younglove Theodore , McCool Patrick M.
Published: July 2010

Soils are considered important components of many pesticide contamination models and are frequently the direct or indirect targets of pesticides applied during agricultural activities. Soil texture is commonly referenced on pesticide labels as an important factor in the selection and application of pesticides and in identifying target areas that are vulnerable to leaching. In general, no guidelines exist for the common interpretation of generic soil texture terms found on pesticide labels, for example, coarse or coarse‐textured soils. In the present study, a significant logistic regression model (P = 0.017) was developed that is based on the soil particle‐size class composition of sections containing wells sampled for DBCP (1,3‐dibromochloropropane). Particle‐size class is a concept used in Soil Taxonomy to describe soil family texture and is a component of soil family names. The model contains terms for the sandy and fine particle‐size classes. The model was validated using data obtained from sources independent of those used to develop the model. Records in the California Soils Map Unit Inventory database that describes the soil map unit composition of >65 000 sections (1600 m2 or 1 mi2) were used to generate probability scores for >15 000 sections located in the San Joaquin Valley, CA. A geographic information system, an information management technique that is becoming an accepted tool for a wide range of regulatory agencies, was used to generate visual images of the probability scores. A map was developed that depicts four distinct probability classes of the DBCP‐contamination status of section‐sized areas and their distribution within the study area.
Use of Soil Survey Information to Assess Regional Salinization Risk Using Geographical Information Systems
Authors: Bui Elisabeth N. , Smettem Keith R. J. , Moran Chris J. , Williams John
Published: July 2010

Previous experience in southern and western Australia has shown that tree clearing alters the water balance in a landscape, leading to increased deep drainage and consequent rises in phreatic water tables. Assessment of the risk of regional salinization involves integration of hydrology, hydrogeology, soil and land management issues. An example of the use of soil survey data, integrated with water resources and digital elevation data in a GIS, to estimate the risk of salinization after tree clearing is illustrated for the upper Burdekin river basin in the wet/dry tropics of North Queensland. Soil map unit descriptions include information on soil‐landform relations, parent material, soil thickness, depth to bedrock and dominant and subdominant soil types. Such information can be used to qualitatively estimate permeability and drainage classes (high, medium, or low) and to determine likely recharge and discharge areas in the landscape. Analysis of the spatial association between surveyed electrical conductivity measurements and estimated recharge and discharge areas was used to cross‐check this qualitative classification. The distributions of saline soils and shallow water tables are used to assess the salinity hazard of the region. Where % total soluble salts (TSS) are >0.25% and water table >6 m deep, a salinity hazard is present. This hazard can translate into a salinity problem if the hydrologic balance is altered so that the salt is remobilized and redeposited in the landscape. An estimate of the likelihood and amount of increased recharge to groundwater after tree clearing was obtained using water balance models with soil physical parameters measured at key sites. Where physical data were not available, surrogate physical properties were estimated from the soil survey data. Results suggest that tree clearing may increase deep drainage by up to 10 times and that in watersheds where shallow unconfined aquifers are present and where %TSS > 0.25%, recharge areas should not be cleared.
GIS Modeling of Recharge on a Watershed
Authors: Rogowski A. S.
Published: July 2010

The study describes a model developed to delineate primary recharge contributing areas on a large watershed based on the field‐measured parameters. The procedure uses measured values of soil water content, bulk density, hydraulic conductivity, and depth to water at 31 locations, to generate kriged overlays of input in a Geographic Information Systems (GIS) framework. The number of locations was a compromise between sampling efficiency and requirements of the geostatistical analysis. Mathematical operations on the overlays are carried out on a pixel‐by‐pixel basis to predict distributions of water flux from below the root zone, travel time to the groundwater, and recharge flux pulse at the water table. Comparison with field data suggests that flow may occur through ouly a portion of total pore space. Field application is illustrated on a 123 km2 catchment in Pennsylvania.
Uncertainty of Groundwater Vulnerability Assessments for Agricultural Regions in Hawaii: Review
Authors: Loague Keith , Bernknopf R. L. , Green R. E. , Giambelluca T. W.
Published: July 2010

There are important challenges associated with assessing potential groundwater vulnerability hazards that may result from regional scale applications of agrochemicals. The increasing availability of Geographic Information System (GIS) software to those involved in assisting with landuse decisions has resulted in the widespread production of multicolored risk management maps for many environmentally sensitive issues. Soil‐based GIS's have recently been coupled to various solute‐leaching models to make near‐surface groundwater vulnerability assessments for guidance in pesticide regulation in several states. In general, these assessments rest on soil, climatic, and chemical data that are extremely sparse and contain considerable uncertainty. It is also important to acknowledge the uncertainty associated with the transport/fate processes that are not accounted for by the modeling approach used to make the assessment. In this paper, we review the results from a series of papers that have focused on characterization of uncertainty in pesticide mobility estimates, using the attenuation and retardation indices (AF and RF), for the Pearl Harbor Basin on the Hawaiian island of Oahu. Relative to data error uncertainties, we discuss the impacts of: (i) soil, climatic, and chemical data base uncertainties, (ii) reductions in data base uncertainties, (iii) extrapolation of soil data base information based on soil taxonomy and soil survey, and (iv) importing information from outside the region of interest. Relative to model error uncertainties, we compare pesticide leaching estimates from the simple AF and RF mobility indices with simulations from the EPA's Pesticide Root Zone Model (PRZM) and field observations. Finally, we outline a Regional Integrated Risk Assessment approach for characterizing regional scale groundwater vulnerability for near‐surface nonpoint sources.

“Hey farmer farmer put away that DDT” Joni Mitchell, “Big Yellow Taxi”
Use of Soil Survey Data for Modeling Solute Transport in the Vadose Zone
Authors: Bouma J. , Booltink H. W. G. , Finke P. A.
Published: July 2010

Soil surveys have now been completed in many countries and qualitative interpretations in terms of soil suitability for different forms of land use, which are part of most soil survey reports, are being used widely. These interpretations are, however, essentially based on expert judgement and they are inadequate to answer many modern questions about ecological and environmental aspects of alternative forms of land use. Simulation modeling of solute transport and plant growth has become an operational tool in land use studies and soil survey databases can be an important source of basic soil and landscape information to be used in modeling. Still, many data are not in a form that can be used directly and an effort has to be made to transform soil survey data into a usable format, by developing pedotransfer functions. In discussing soil survey data, a distinction can be made between point‐ and area data. Case studies for leaching of nitrates (NO−3) and growth of potato (Solanum tuberosum L.) in a loamy and clayey soil, illustrate use of different types of class‐pedotransfer functions for functional soil horizons. Monte Carlo techniques are used to illustrate the effect of variability of hydraulic basic data on results obtained. Soil surveys define soil data and interpretations for areas of land by considering “representative” soil profiles for delineated areas on the map. Internal variation is expressed only in qualitative terms. Geostatistical techniques can be used to interpolate point data to areas of land, allowing quantitative expressions including error statements. The effects of upscaling of point data to cells of different sizes on leaching of NO−3 and growth of potato are illustrated for data derived from a Dutch field. All illustrations demonstrate the crucial role of Geographic Information Systems (GIS) in storing and manipulating basic soil and landscape data.
Treatment of Fish Farm Wastewater Using Sand Filtration
Authors: Kristiansen Rolv , Cripps Simon J.
Published: July 2010

The treatment of aquaculture wastewaters typically consists of screening suspended particles from the primary flow, producing a sludge that must be disposed of. Two experiments were conducted to determine the feasibility of using sand to renovate, stabilize, and dry salmon farm sludge. Data from a preliminary laboratory experiment were used to quantify and design a pilot‐scale study facility linked to a salmon farm. The pilot study comprised coarse sand‐filled infiltration beds loaded with either an artificial fish farm wastewater (AFW), backwash water from a microsieve (BW), or sedimented microsieve backwash water (SBW) collected daily from a settling chamber. A large reduction in hydraulic capacity was caused by the establishment of a clogging mat on the sand filter surface. About 60% of the sludge total organic C was removed by the filters. Nitrogen in the effluent from the SBW loaded filters was predominately organic, and nitrate concentrations were insignificant (<0.03 mg NO3‐N L−1). Effluent ammonium concentration decreased from 97% of the effluent total nitrogen (TN) after 1 mo of loading, to 10% after 2 to 3 mo, with an attendant increase in nitrate to about 65% of the TN. The P binding capacity of the test sand volume was exceeded after 1 to 2 mo of SBW loading. This capacity was not exceeded during the experiment, using the two other effluent types (BW and AFW). Filter effluent P concentrations were about 1.4 mg L−1. At a SBW loading of 1 cm d−1, to a coarse sand, with a hydraulic head of >10 cm, it is expected that 2 to 3 mo loading can be conducted before maintenance or change of filter surface sand is required, as a result of hydraulic malfunction. The use of sand infiltration for treating salmon farm sludge was therefore shown to be feasible.
Application of a Lumped, Nonlinear Kinetics Model to Metal Sorption on Humic Substances
Authors: Yu Y. Shane , Bailey George W. , Xianchan Jin
Published: July 2010

Exposure assessment models are needed to predict the sorption behavior of metal ions with humic substances. To address this need, a lumped parameter nonlinear kinetics model based on the Langmuir‐Hinshelwood kinetic model—dC/dt = k1C/(1 + k0C)—is introduced and evaluated. The model was applied to a mixture of seven metal ions— Cr(III), Pb(II), Cu(II), Cd(II), Co(II), Ag(I), and Li(I)—reacted with three individual humic substances. The lumped parameter model employs a dimensional analysis technique (i.e., uses dimensionless parameters), Laplace transforms, gamma functions, and gamma distributions to produce analytical solutions for the kinetic equation of metal ion sorption to humic substances. During the initial reaction period, the most reactive species—Cr(III) and Pb(II)—dominated the lump parameter value, and the mixture behaved like a first‐order reaction. At longer periods, the lump followed a second‐order decay if there were less reactive species involved. The lumped parameter model provides valuable information about the overall kinetics behavior of metal ion mixtures with humic substances and could serve as a simulation tool to investigate the transport of metal ions in and out of landfill sites and the transport/retardation of metals in contaminated soils and aquifers.