bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Controlled Drainage on Forest Water Quality
Authors: Amatya D. M. , Gilliam J. W. , Skaggs R. W. , Lebo M. E. , Campbell R. G.
Published: July 2010

The effects of controlled drainage (CD) on hydrology and water quality are presented for three eastern North Carolina watersheds in loblolly pine (Pinus taeda L.). Timing of CD treatments were: the spring fish recruitment period in the downstream estuary in one watershed, and the summer‐fall period to facilitate tree growth in another watershed. A third watershed was maintained under conventional drainage throughout the study. It was demonstrated that seasonal controlled drainage can reduce both the total drainage outflows and corresponding sediment and nutrient exports. For example, CD reduced drainage outflows by as much as 88% during the summer‐fall and 39% during the spring with annual average reduction of 20 to 25%. Annual average total phosphorus (TP) and ammonium‐nitrogen (NH4‐N) exports from watersheds under treatment were reduced by 7 to 72% as compared to the watershed under conventional drainage. For other nutrients and total suspended solids (TSS), concentrations were significantly different (α = 0.05) among the three watersheds during the winter when they were all under conventional drainage. This indicated characteristic differences unrelated to applied treatments. Taking these differences into account, the reductions in annual average export of TSS (up to 47%) and nitrate plus nitrite‐nitrogen (NO3+NO2‐N) (up to 16%), total Kjeldahl nitrogen (TKN) (up to 45%) and total organic carbon (TOC) (up to 33%) from watersheds under treatment were directly attributed to reduction in outflows. Even though CD appeared to have increased concentrations of some of the nutrients analyzed, except for NH4‐N, the applied treatments lowered the export of TSS and most nutrients measured. It is concluded that CD can be used to reduce TSS and nutrient exports from pine plantations, primarily through reduced drainage outflows.
Predicting Stream Pathogen Loading from Livestock using a Geographical Information System‐Based Delivery Model
Authors: Fraser Robert H. , Barten Paul K. , Pinney David A. K.
Published: July 2010

Recent cases of drinking water contamination by pathogens have underscored the importance of preventing livestock waste from entering surface waters. To this end, analytical tools are needed that can identify subwatersheds or livestock operations that contribute disproportionately to contamination. This paper presents a geographical information system (GIS)‐based transport model (SEDMOD) that provides an index of pathogen loading potential to streams by characterizing five key transport parameters: flow‐path hydraulic roughness, gradient, and slope shape, stream proximity, and a normalized soil moisture index. We applied SEDMOD to 12 subwatersheds (10 agricultural, 2 forested controls) of the Saw Kill, a tributary of the Hudson River, New York, and compared model predictions with measured fecal coliform (FC) levels. The transport model, combined with a livestock density GIS layer, could explain 50% of the variation in average FC discharge among the subwatersheds (r = 0.71, P = 0.01, n = 12). By contrast, neither total livestock FC output nor predicted FC transport were correlated with geometric mean FC concentration (P > 0.05). In a multiple regression, predicted FC transport, mean water temperature, and mean turbidity could account for 80% of the observed variation in FC discharge (r = 0.90, P = 0.001, n = 12). We conclude that, although more field work and algorithm development is needed to yield more accurate quantitative predictions, the model is useful for predicting the relative contribution of diverse livestock operations within a varied landscape. This provides watershed managers and regulators with a rating method to prioritize sites for nonpoint source pollution control.
Sulfate Reduction in Freshwater Wetland Soils and the Effects of Sulfate and Substrate Loading
Authors: Feng Jinan , Hsieh Yuch Ping
Published: July 2010

Elevated sulfate and organic C loadings in freshwater wetlands could stimulate dissimilatory sulfate reduction that oxidizes organic C, produces hydrogen sulfide and alkalinity, and sequesters trace metals. We determined the extent of sulfate reduction in two freshwater wetland soils, that is, black gum (Nyssa biflona) swamp soils and titi (Cliftonia monophylla) swamp soils, in northern Florida. We also investigated the potential of sulfate reduction in the wetland soils by adding sulfate, organic substrate, and lime. Sulfate reduction was found to be an active process in both swamp soils without any amendment, where the pore water pH was as low as 3.6 and sulfate concentration was as low as 5 mg L−1. Without amendment, 11 to 14% of organic C was oxidized through sulfate reduction in the swamp soils. Sulfate loading, liming, and substrate addition significantly increased sulfate reduction in the black gum swamp soil, but none of those treatments increase sulfate reduction in the titi swamp soil. The limiting factor for sulfate reduction in the titi swamp soil were likely texture and soil aggregate related properties. The results suggested that wastewater loading may increase sulfate reduction in some freshwater wetlands such as the black swamps while it has no stimulating effect on other wetlands such as the titi swamps.
Nutrient Retention by Multipond Systems: Mechanisms for the Control of Nonpoint Source Pollution
Authors: Yan Weijin , Yin Chengqing , Tang Hongxiao
Published: July 2010

The processes of the multipond system in an experimental agricultural watershed located in southeastern China were studied during a 2‐yr period (1994–1995), with the purpose of the research being the reduction of nonpoint nutrient pollution at its sources. The mechanisms studied included water storage capacity, sedimentation, denitrification, and removal of nutrients by the harvest of macrophytes from ponds and ditches. The results showed that the retention of both water and nutrients depended on the water storage capacity of the ponds, the total pond volume, rainfall, surface runoff, and irrigation amounts. For the years of 1994 and 1995, the water retention rate was 85.5%, while the nutrient retention rate reached 98.1 and 97.8% for total N (TN) and total P (TP), respectively. Sediment deposit was another important mechanism. The average sedimentation rate was 30.0 mm yr−1 (from 1985–1995). For the whole multipond system (35 ha), the average retention amounts reached 9800 kg of N and 2800 kg of P by sediment accumulation per year. The results demonstrated that denitrification in ponds and ditches was an important mechanism for removing N from the watershed. The highest possible rate was more than 0.17 mg N g−1 soil during the summer season. The results suggested that the multipond system, which kept water in balance, benefited the water, nutrient, and sediment recycling in the terrestrial ecosystem, as well as helped to reduce agricultural nonpoint pollution at its sources. Therefore, the multipond system, with its low cost in construction and maintenance, is recommended as a good practice both for the control of nonpoint pollution at its sources and for sustainable agricultural development.
The Impact of Pesticide Use on Groundwater in North Carolina
Authors: Wade Henry F. , York Alan C. , Morey A. Elizabeth , Padmore Joel M. , Rudo Kenneth M.
Published: July 2010

A North Carolina study revealed that certain pesticides have impacted groundwater above health‐based standards in vulnerable areas. Ninety‐seven shallow, surficial aquifer‐monitoring wells were sampled at least twice. Sites for the monitoring wells were chosen based on an evaluation with the Pesticide DRASTIC model and a known record of pesticide use. Where possible, areas of greater risk were intentionally selected. Twenty‐three pesticides or pesticide degradates were detected in 26 of the 97 wells. Nine of the pesticides or degradates are no longer registered for use; two of these chemicals, dibromochloropropane and methylene chloride, were found in excess of health‐based guidance levels (HBGL) or state groundwater quality standards (GWQS). Of the registered pesticides or their degradates, the herbicides dichlorprop and simazine and the insecticide isomers BHC‐alpha and BHC‐delta were in excess of HBGL. The herbicide atrazine was detected at 83% of its GWQS. The U.S. Environmental Protection Agency (USEPA) Pesticides and Groundwater State Management Plans will be required for atrazine and simazine to be sold and used, which will provide additional protection to public health and the environment. Pesticide DRASTIC ratings or soil‐leaching potential values and the proportion of wells were unrelated to pesticide detections.
Mercury Speciation in Floodplain Soils and Sediments along a Contaminated River Transect
Authors: Wallschläger Dirk , Desai Madhukar V. M. , Spengler Markus , Wilken Rolf‐Dieter
Published: July 2010

A novel mercury‐specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg‐contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesting low availability. However, distinct differences between Hg speciation in the floodplain soils and sediments were also discovered. Mercury deposited in the floodplains shows speciation patterns that indicate stronger fixation compared with Hg in the sediments. This difference is attributed to the association of Hg with larger quantities of OM, which presumably also has higher molecular weight (MW). By comparison, Hg in the sediments was distributed among weaker binding forms, which are more likely to liberate Hg. Particularly, sediments showed a total lack of sulfidic binding forms for Hg. Pronounced geographical trends were detected in the Hg speciation along the river transect, with a general downstream shift from weaker to stronger binding forms, probably due to increased association with OM. These studies indicate that Hg speciation in riverine ecosystems is dynamic and reflects the chemical mechanisms underlying (bio)geochemical processes like distribution and transport.
Surface Complexation Modeling of Phosphate Adsorption by Water Treatment Residual
Authors: Butkus Michael A. , Grasso Domenico , Schulthess Cristian P. , Wijnja Hotze
Published: July 2010

Use of water treatment plant residuals (WTR), as a soil amendment is a promising alternative to landfill disposal. Unfortunately, WTR has a propensity to bind with phosphate, which is an important plant nutrient. Phosphate may be added to WTR prior to soil application. This type of pretreatment may convert WTR from a phosphate consumer to a phosphate supplier. The binding of phosphate to WTR is typically attributed to surface complexation with metal oxides. However, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) data and phosphate‐WTR adsorption equilibrium data indicate that phosphate also binds to a cationic polyelectrolyte that is added during water treatment processes. Using the FITEQL optimization program, equilibrium constants and total number of surface sites were determined for the polymer. Results from the FITEQL optimization were used to model binding of phosphate by cationic polymer. Binding of phosphate by hydrous ferric oxide was modeled using a diffuse double layer model, which included surface precipitation (MICROQL). The model was validated through the use of phosphate equilibrium partitioning data at pH values of 6 and 8. The model predicted that a significant fraction of phosphate adsorbed onto WTR is associated with the cationic polymer.
Fluxes of Carbon Dioxide, Nitrous Oxide, and Methane in Grass Sod and Winter Wheat‐Fallow Tillage Management
Authors: Kessavalou Anabayan , Mosier Arvin R. , Doran John W. , Drijber Rhae A. , Lyon Drew J. , Heinemeyer O.
Published: July 2010

Cropping and tillage management can increase atmospheric CO2, N2O, and CH4 concentrations, and contribute to global warming and destruction of the ozone layer. Fluxes of these gases in vented surface chambers, and water‐filled pore space (WFPS) and temperature of survace soil were measured weekly from a long‐term winter wheat (Triticum aestivum L.)‐fallow rotation system under chemical (no‐tillage) and mechanical tillage (noninversion subtillage at 7 to 10 cm or moldboard plowing to 15 cm) follow management and compared with those from “native” grass sod at Sidney, NE, from March 1993 to July 1995. Cropping, tillage, within‐field location, time of year, soil temperature, and WFPS influenced net greenhouse gas fluxes. Mean annual interrow CO2 emissions from wheat‐fallow ranged from 6.9 to 20.1 kg C ha−1 d−1 and generally increased with intensity and degree of tillage (no‐till least and plow greatest). Nitrous oxide flux averaged <1.2 g N ha−1 d−1 for sod and 1 to 2 g N ha−1 d−1 for wheat‐fallow. Tillage during fallow increased N2O flux by almost 100%. Nitrous oxide emissions were 1.5 to 3.7 times greater from crop row than interrow locations with greatest differences occurring during periods of highest N2O emission. Mean annual N2O flux over the 3 yr of study were 1.54 and 0.76 g N ha−1 d−1 for row and interrow locations. Methane uptake ranged from 5.9 to 9.9 g C ha−1 d−1 and was not influenced by row location. Seasonal CO2 and N2O flux, and CH4 uptake ranked as spring ≥ summer > autumn > winter. Winter periods accounted for 4 to 10% and 3 to 47% of the annual CO2 and N2O flux, respectively, and 12 to 21% of the annual CH4 uptake. Fluxes of CO2 and N2O, and CH4 uptake increased linearly with soil temperature. No‐till fallow exhibited the least threat to deterioration of atmospheric or soil quality as reflected by greater CH4 uptake, decreased N2O and CO2 emissions, and less loss of soil organic C than tilled soils. However, potential for increased C sequestration in this wheat‐fallow system is limited due to reduced C input from intermittent cropping.
Ammonia Volatilization from Tall Fescue Pastures Fertilized with Broiler Litter
Authors: Marshall S. B. , Wood C. W. , Braun L. C. , Cabrera M. L. , Mullen M. D. , Guertal E. A.
Published: July 2010

Ammonia (NH3) volatilization is an important and often overlooked component of the N budget in many agricultural systems involving land application of animal wastes. We quantified the amount and rate of NH3 volatilization from broiler litter applied to established tall fescue pastures (Festuca arundinacea Schreb.). Study sites were located in the Coastal Plain (Alabama), Piedmont (Georgia), and Cumberland Plateau (Tennessee) Major Land Resource Areas (MLRA) of the southeast USA. Litter was applied to supply 70 kg of available N ha−1 based on equations developed by the U.S. Department of Agriculture (USDA) and the U.S. Environmental Protection Agency (USEPA). Measurements of NH3‐N volatilization were taken using a micrometeorological, field‐scale technique for 14 d immediately following litter application during the spring of 1995 and 1996. Ammonia flux for the study period ranged from 3.7 to 10.6 kg N ha−1 in 1995, and from 3.5 to 8.0 kg N ha−1 in 1996. A sharp increase in volatilization rate occurred 1 to 3 d after litter application at all three sites in both years. However, volatilization rates rapidly decreased to normal levels within 10 d. Volatilization rates peaked at 2.8 kg NH3‐N ha−1 d−1 in 1995 and 2.2 kg NH3‐N ha−1 d−1 in 1996. Overall, N losses due to NH3 volatilization were less than expected based on previous studies. These data suggest that for these conditions, NH3 volatilization was a relatively minor component of the N cycle and was not a major pathway for N loss.
Accumulation Dynamics of Triclopyr Ester in Aquatic Leaf Packs and Effects on Detritivorous Insects
Authors: Kreutzweiser David P. , Thompson Dean G. , Staznik Bozena , Shepherd Janelle A.
Published: July 2010

Previous field studies have demonstrated that residues of the herbicide, triclopyr butoxyethyl ester (3,5,6‐trichloro‐2‐pyridinyloxyacetic acid, butoxyethyl ester) (TBEE), can accumulate in submerged leaf material of aquatic systems at concentrations up to 20 times the maximum aqueous concentrations. Accumulated TBEE residues may pose a risk of adverse effects to detritivorous invertebrates inhabiting and using natural leaf packs. We examined the dynamics of TBEE accumulation and persistence in leaf materials of laboratory and outdoor aquatic systems, and determined the ecological significance of this in terms of effects on detritivorous insects and organic matter processing. Accumulations of TBEE in leaf packs of semi‐static laboratory microcosms were up to 80 times aqueous concentrations, and residues persisted for 4 to 5 d. Leaf material of flow‐through laboratory microcosms accumulated TBEE at much higher rates (up to 1000 times aqueous concentrations), but residues were cleared by 48 to 72 h. Accumulation and persistence in flow‐through units were dependent on water depth, velocity, and exposure duration. Accumulated TBEE residues were less in outdoor stream channels than in laboratory flow‐through units, probably because of losses through sorption to natural benthic material in the stream channels. Despite accumulations of TBEE in leaf packs at up to 90 mg kg−1 in systems treated at or near expected environmental concentrations, there was no significant mortality of detritivorous insects and no significant reductions in leaf consumption. Significant mortality and reduced feeding occurred only in systems treated at concentrations well above (up to 10 times) expected environmental concentrations.
Long‐Term Soil Redistribution in a Small French Watershed as Estimated from Cesium‐137 Data
Authors: Bernard Claude , Mabit Lionel , Wicherek Stanislas , Laverdière Marc R.
Published: July 2010

Changes initiated in the 1970s in the agricultural landscape of the north European plains have resulted in increased water erosion. The spatial redistribution of 137Cs was used to assess the magnitude of long‐term soil movements in a 180 ha watershed located in northern France. The 137Cs base level was estimated at 2000 ± 200 Bq m−2. The point data suggest annual soil movements ranging from a loss of 18 Mg ha−1 to a deposition of 19 Mg ha−1. After spatializing these data, it is concluded that 41% of the watershed area can be considered as stable. Some 45% of the watershed area suffered a net soil loss, with an average rate of 6 Mg ha−1 yr−1. Net deposition occurred over 14% of the area, with an average annual rate of 7 Mg ha−1. From these values, it was estimated that a net output of 1.9 Mg ha−1 yr−1 of eroded material would have left the watershed. This represents a sediment delivery ratio of 59%. These results are consistent with those of other European researchers under comparable environments. They also stress the point that redeposition is an important part of the global erosion process. Finally, these results highlight some of the advantages of the 137Cs technique, which makes possible the development of long‐term sediment budgets at the watershed scale.
Natural‐Gradient Transport of Bromide, Atrazine, and Alachlor in an Organic Carbon‐Rich Aquifer
Authors: Springer A. E. , Bair E. S.
Published: July 2010

In situ values of retardation factors and dispersivity were determined from a field tracer study using bromide, atrazine (2‐chloro‐4‐ethlamino‐6‐isopropylamineo‐s‐triazine), and alachlor (2‐chloro‐2′‐6′‐diethyl‐N‐(methoxymethyl)‐acetanilide). The tracers were injected at the water table in an unconfined aquifer to evaluate how these pesticides are attenuated within the groundwater flow system in a typical alluvial valley setting in the Midwest where corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are the dominant crops and atrazine and alachlor are the most commonly used pesticides. Water samples were collected for 49 d after tracer injection from 63 wells to establish the direction and magnitude of tracer movement. Following injection, no degradation products of atrazine were detected in any of the monitoring wells. Aquifer hydraulic properties were measured in the field prior to the test. Sorption on organic carbon (0.0009–0.0016 Mg/Mg) in the aquifer caused the transport of atrazine and alachlor to be retarded relative to bromide. At the scale of the field test, retardation factors of 6.1 and 7.1 were estimated for atrazine and alachlor, respectively, based on a one‐dimensional, nonlinear least squares inversion analysis. These retardation factors are two to three times larger than retardation factors measured in laboratory batch tests using the same aquifer materials, are larger than other values reported in the literature, and are due to the relatively large fraction of organic C found in the aquifer. Dispersivity was approximately 9 cm at a distance of 1 to 2 m from the injection well and approximately 140 cm at a distance of 5 m from the injection well.
Remediating RDX‐Contaminated Water and Soil Using Zero‐Valent Iron
Authors: Singh J. , Comfort S. D. , Shea P. J.
Published: July 2010

Soil and water contaminated with RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) pose a serious threat to the environment and human health. Our objective was to determine the potential for using zero‐valent iron (Fe0) to remediate RDX‐contaminated water and soil. Mixing an aqueous solution of 32 mg RDX L−1 (spiked with 14C‐labeled RDX) with 10 g Fe0 L−1 resulted in complete RDX destruction within 72 h. Nitroso derivatives of RDX accounted for approximately 26% of the RDX transformed during the first 24 h; these intermediates disappeared within 96 h and the remaining 14C products were water soluble and not strongly sorbed by iron surfaces. When RDX‐contaminated soil (30 mg RDX kg−1 spiked with 14C‐RDX) was treated with a single amendment of Fe0 (20 g kg−1 soil) in a static soil microcosm, more than 60% of the initial 14C‐RDX was recovered as 14CO2 after 112 d. Treating surface and subsurface soils containing 3600 mg RDX kg−1 with 50 g Fe0 kg−1 at a constant soil water content (0.35–0.40 kg H2O kg−1 soil) resulted in a 52% reduction in extractable RDX following 12 mo of static incubation. A second Fe0 addition at 12 mo further reduced the initial extractable RDX by 71% after 15 mo. These results support the use of zero‐valent iron for in situ remediation of RDX‐contaminated soil.
Nitrogen Leaching from Unlined Cull‐Onion Landfills
Authors: Hutchings J. J. , Hammel J. E. , Osiensky J. L.
Published: July 2010

Disposal of cull onions (Allium cepa L.) in unlined landfills in the Treasure Valley region of eastern Oregon and southwestern Idaho is a historic management practice that has been identified as potentially causing NO3‐N contamination of regional groundwater. To investigate NO3‐N generation and transport during a 6‐yr period, monitoring wells were placed in the cull onion waste inside two landfills. The soil below each landfill was instrumented with soil‐solution samplers and matric‐potential sensors. Four to 6 Mg of organic N were loaded into each landfill in the form of onion waste. Little leaching of NO3‐N was observed during the study. With the exception of a NO3‐N pulse during loading, solution NO3‐N concentrations within and beneath both landfills remained <1 mg L−1. Concurrently, NH4‐N increased to 500 mg L−1 at 0.5 m and to 7 mg L−1 at 3 m below the landfill bases. Build‐up of NH4‐N and lack of NO3‐N in the landfills are hypothesized to result from nitrification inhibition in an anaerobic environment. Hydraulic heads showed that saturated waste resided over unsaturated soil. Formation of a hydraulically restrictive layer at the interface between the landfill contents and the underlying soil probably caused these conditions. Saturated cull‐onion landfills do not appear to be a source of NO3‐N contamination. Potential groundwater contamination from nitrification upon drying of landfill contents can be mitigated by removing and land‐applying residual waste after sufficient degradation.
Boron, Zinc, Iron, and Manganese Content in Four Grassland Species
Authors: Adarve M. J. , Hernández A. J. , Gil A. , Pastor J.
Published: July 2010

A pot experiment was carried out to test the response of the B, Zn, Fe, and Mn concentration in four wild herbaceous species exposed to three landfill leachate treatments of increasing concentration of contaminants. The species tested were clustered clover (Trifolium glomeratum L.), cotton clover (T. tomentosum L.), wall barley (Hordeum murinum L.), and soft brome (Bromus hordaceus L.). The legume species accumulated more Fe and B than the grasses. The least contaminated leachate (leachate A) significantly increased the Fe and Mn content in T. glomeratum. Leachate B significantly increased the Zn content in both clover species and Fe content in T. glomeratum and H. murinum, while it significantly decreased the B content in T. glomeratum. The most contaminated leachate (leachate C) significantly increased the Zn content in T. glomeratum, while it significantly decreased the B and Fe content. In the four species the content of B, Fe, and Mn in the plants under the leachate treatments was in a normal values range, while in T. glomeratum and H. murinum the Zn content had in some cases a toxic level (>100 mg L−1). The dry weight of the four species tested diminished significantly under the most contaminated leachate. The ANOVA confirmed a major significant influence of the “species factor” on the response of the plant to leachate supply, but the treatment factor also had significant F‐values in some cases. The species tested have a potential revegetation value for some areas degraded by landfill leachates.
Comparison of Four USEPA Digestion Methods for Trace Metal Analysis Using Certified and Florida Soils
Authors: Chen Ming , Ma Lena Q.
Published: July 2010

It is critical to compare existing sample digestion methods for evaluating soil contamination and remediation. USEPA Methods 3050, 3051, 3051a, and 3052 were used to digest standard reference materials and representative Florida surface soils. Fifteen trace metals (Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, and Zn), and six macro elements (Al, Ca, Fe, K, Mg, and P) were analyzed. Precise analysis was achieved for all elements except for Cd, Mo, Se, and Sb in NIST SRMs 2704 and 2709 by USEPA Methods 3050 and 3051, and for all elements except for As, Mo, Sb, and Se in NIST SRM 2711 by USEPA Method 3052. No significant differences were observed for the three NIST SRMs between the microwave‐assisted USEPA Methods 3051 and 3051a and the conventional USEPA Method 3050 except for Hg, Sb, and Se. USEPA Method 3051a provided comparable values for NIST SRMs certified using USEPA Method 3050. However, for method correlation coefficients and elemental recoveries in 40 Florida surface soils, USEPA Method 3051a was an overall better alternative for Method 3050 than was Method 3051. Among the four digestion methods, the microwave‐assisted USEPA Method 3052 achieved satisfactory recoveries for all elements except As and Mg using NIST SRM 2711. This total‐total digestion method provided greater recoveries for 12 elements Ag, Be, Cr, Fe, K, Mn, Mo, Ni, Pb, Sb, Se, and Zn, but lower recoveries for Mg in Florida soils than did the total‐recoverable digestion methods (3050, 3051, and 3051a).
Formulation and Adjuvant Effects on Leaching of Atrazine and Metolachlor
Authors: Hall J. K. , Jones G. A. , Hickman M. V. , Amistadi M. K. , Bogus E. R. , Mumma R. O. , Hartwig N. L. , Hoffman L. D.
Published: July 2010

Atrazine (6‐chloro‐N‐ethyl‐N′‐(methyethyl)‐1,3,5‐triazine‐2,4‐diamine) and metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide) levels in pan lysimeter leachates, collected 1.2 m deep in a Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf), were used to evaluate leaching of these chemicals applied in combination (1.7 + 1.7; 3.4 + 3.4 kg a.i. ha−1) as a commercial formulation (CF) or adjuvant (polyacrylate polymer)‐amended (AA)‐CF and as a microencapsulated (ME) or starch‐encapsulated (SE) formulation in conventional tillage (CT) and no‐tillage planted corn (Zea mays L.). Atrazine leached more under NT than CT conditions. Areal losses of atrazine in 1992 from NT at the low rate were 4, 66, and 277 µg m−2 for the treatment sequence (CF, SE, and AA‐CF); at the high rate, losses were 887, 488, and 334 µg m−2. These amounts represented losses of <0.01 to 0.16% and 0.26 to 0.10%, respectively, of applied rates. In 1993, areal losses for the treatment succession (lesser rate) were 888, 253, and 497 µg m−2 of atrazine (0.52, 0.15, and 0.29%); these treatments (greater rate) yielded 5440, 1220, and 1600 µg m−2 of applied chemical (1.60, 0.36, and 0.47%). Application of ME (polyurea polymer) and AA‐metolachlor reduced mobility of this chemical at both rates in 1993, but their effect was especially exemplified at the greater rate where a loss of 2.29% (CF) was reduced to 0.83% (ME) and 0.54% (AA). Where herbicide leaching was reduced, greater concentrations, particularly atrazine, were detected in the surface 15 cm of soil in late‐season and in leachates, 6 to 12 mo following application.
Impacts of Historical Changes in Land Use and Dairy Herds on Water Quality in the Catskills Mountains
Authors: Scott C. A. , Walter M. F. , Brooks E. S. , Boll J. , Hes M. B. , Merrill M. D.
Published: July 2010

Surface water eutrophication has been linked to nonpoint sources of agricultural nutrients. Based on 1938 and 1968 aerial photos and 1993 Landsat imagery of a 31.7 km2 watershed, corn (Zea mays L.)/hay rotation, pasture, forest, and impervious/water land uses were digitized in a raster GIS. Monthly runoff volumes resulting from each year's land use were predicted using a variable source area hydrologic model. Historical data on dairy animal populations and the spatial distribution of current soil test phosphorus (STP) levels were used to derive manure loading intensities. Event‐mean SP concentration in runoff as a function of manure application intensity and soil test P was derived from field data and published sources. The maximum predicted event‐mean SP concentration in runoff was 15.8 mg L−1. Watershed average potential SP loading to perennial streams remained essentially constant at 0.14 kg ha−1 yr−1 over the period 1938 to 1993. Herd size and total manure load dropped significantly over the period 1938 to 1993; however, the P content in manure and confinement of animals increased, counteracting the hypothesized trend that SP loading would drop. The analyses indicate that, for 1993, <6% of the agricultural land accounted for 50% of the agricultural SP load, suggesting that with improved manure handling practices over a relatively small area, it may be feasible to reduce SP loads to streams.
Revegetation on a Coal Fine Ash Disposal Site in South Africa
Authors: Van Rensburg L. , De Sousa Correia R. I. , Booysen J. , Ginster M.
Published: July 2010

Eight medium amendments were conducted on top of a fine ash coal dump (i) to evaluate a few cost‐effective treatments that could determine the minimum fertility status required for the local ash to support the establishment of a viable vegetation cover, and (ii) to select suitable grass species that would establish on the ash and could serve as a foundation for long‐term rehabilitation. Degree and success of grass establishment per medium amelioration treatment is expressed in terms of total biomass, percentage basal cover, and in terms of a condition assessment model. Both the chemical and physical nature of the ash medium before and after amendment was characterized, as were the concentrations of some essential and potentially toxic elements in leaf samples. In terms of medium amelioration 5000 kg ha−1 compost, or 500 kg ha−1 kraal manure or 480 kg 2:3:2 ha−1 proved to be most effective. The grass species that occurred with the highest frequency, irrespective of treatment, were the perennials bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon], weeping lovegrass [Eragrostis curvula (Schrader) Nees], and the annual teff [Eragrostis tef (Zuccagni) Trotter]. Of the potentially toxic extractable metals monitored in the leaves of vegetation on the dump, only Se accumulated to an average level of 4.4 mg kg−1 that could be toxic to livestock.
The Effect of Acidification and Chelating Agents on the Solubilization of Uranium from Contaminated Soil
Authors: Ebbs Stephen D. , Norvell Wendell A. , Kochian Leon V.
Published: July 2010

The role of acidification and chelating agents in the solubilization of uranium (U) from contaminated soil was examined in a series of experiments. Soil acidification and the addition of chelating agents were the two methods compared initially. The results indicated that the addition of citric acid solubilized more U than acidification or the other amendments tested. This increase in U solubility was, however, transitory. A subsequent experiment indicated that citrate concentration had a more dramatic effect on U solubility than did acidification. The greatest soluble U concentration during this experiment (775 mg kg−1 soil, or ∼85% of the total U) was observed after 24 h in the presence of 20 millimoles citrate kg−1 soil at pH 5. The persistence of U solubility over the 96‐h experimental period was primarily a function of pH and citrate degradation. In a separate experiment, in which citric acid rather than citrate was added to contaminated soil, the soluble U concentrations observed were generally lower than those observed in the presence of citrate. Citric acid decreased soil pH to values ≤3.6, and solubilized higher concentrations of Al and Fe than observed in the presence of citrate. Since the maximum solubilization of U was observed at pH 5, the implication of these results is that a combined approach, using both soil acidification and citric acid addition, may be necessary to maximize the phytoextraction of U from soils with a pH > 6.0.
Particle‐Facilitated Transport of Prochloraz in Undisturbed Sandy Loam Soil Columns
Authors: de Jonge H. , Jacobsen O. H. , de Jonge L. W. , Moldrup P.
Published: July 2010

The mobility of strongly sorbing pesticides in soils may be higher than formerly assumed, due to facilitated transport along with mobilized colloids. Our objective was to verify whether facilitated transport enhances the vertical movement of prochloraz (N‐propyl‐N‐[2‐(2,4,6‐trichlorophenoxy)ethyl] imidazole‐1‐carboxamide). Experiments were carried out using 20 cm diam. by 20 cm long undisturbed soil columns taken from the topsoil (sandy loam, Typic Hapludalf) from a field under barley/grass (Hordeum vulgare L/Lolium perenne L.) cultivation near Rogen, Denmark. Prochloraz was applied to the surface as a pulse in solution. The irrigation intensity was 10 mm h−1, and the lower boundary of the columns was at atmospheric pressure. Three treatments each with four replicates were performed to study the effect of ionic strength and pH on pesticide and particle transport. Leaching of particles and pesticide was promoted by decreasing the ionic strength of the irrigation solution, and increasing pH by ammonia application. This is in line with the theory of electrostatic interactions. Preferential flow and particle transport were the two most important factors determining the amount of pesticide leached. A large variability in amount leached was observed among the replicates (standard deviations of 38–141%) mainly due to differences in water transport in the columns. Particle‐facilitated transport was significant, but did not dominate prochloraz transport. Depending on the pH and ionic strength of the applied solution, 2.5 to 13.1% of the leached pesticide was sorbed to particles with diameter d > 0.24 µm, and 3 to 9% to particles with 0.02 < d < 0.24 µm.
Denitrification from Soils of a Year‐Round Forage Production System Fertilized with Liquid Dairy Manure
Authors: Lowrance R. , Johnson J. C. , Newton G. L. , Williams R. G.
Published: July 2010

Denitrification is an important potential sink for N in liquid manure and the amount of denitrification may affect sustainability of crops grown with liquid manure as a nutrient source. This study examined gaseous N loss by denitrification and the changes in soil N pools after liquid manure application. Liquid dairy manure was applied at four N rates (246, 427, 643, and 802 kg N ha−1 yr−1) to four quadrants of a center‐pivot in a year‐round forage production system. Denitrification (using the acetylene block technique on intact cores) and soil N pools were determined before and for 2 yr after beginning liquid manure application. Nitrous oxide evolution from soil cores was compared to denitrification for a third year of the study. Denitrification rates and soil N pools increased after manure application at all rates of application. The two highest rates of manure had highest denitrification rates, although differences in soil moisture due to soil and drainage properties complicated the interpretation of manure rate effects. At the two highest rates of N application and two lowest rates of N application, the quadrant with higher soil moisture had higher denitrification. Nitrous oxide emissions accounted for about 29% of total denitrification. Denitrification ranged from 11 to 37% of total N applied in the manure. Highest rates of denitrification and highest proportions of total N denitrified were found with the second highest manure application rate because these soils were wetter. Annual denitrification totals ranged from 32 to 114% of the excess N (application‐crop uptake) available.
Lead Exposure of Waterfowl Ingesting Coeur d'Alene River Basin Sediments
Authors: Beyer W. Nelson , Audet Daniel J. , Morton Anna , Campbell Julie K. , LeCaptain Leonard
Published: July 2010

Feces from tundra swans [Cygnus columbianus (Ord)], Canada geese [Branta canadensis (L.)], and mallards [Arias platyrhynchos (L.)] were collected from the Coeur d'Alene River Basin and two reference areas in Idaho to estimate exposure to lead from mining activities and relate that exposure to the ingestion of contaminated sediments. The average acid‐insoluble ash content of the feces, a measure of sediment ingestion, was 18% for Canada geese and tundra swans, and 12% for ducks. The 18% value corresponded to an estimated 9% sediment ingestion rate (dry weight). The 90th percentile for acid‐insoluble ash in feces of tundra swans corresponded to an estimated 22% sediment in the diet. The average lead concentration (dry weight) of tundra swan feces from all Coeur d'Alene River Basin wetlands sampled was 880 mg/kg, compared to 2.1 mg kg−1 from reference areas. The 90th percentile of lead in tundra swan feces from the Coeur d'Alene River Basin sites was 2700 mg kg−1. Fecal lead concentrations of tundra swans were correlated (Spearman's rho = 0.74, P < 0.05) with the acid‐insoluble ash content of the feces. The very low lead concentrations in feces having low acid‐insoluble ash contents established that the sediment was the primary source of the lead ingested by waterfowl. Sediment lead concentrations at 11 wetland sites were closely correlated (r = 0.91, P < 0.05) with average fecal lead concentrations for all waterfowl, corrected for the average percent acid‐insoluble ash in the feces.
Water Quality in Walnut Creek Watershed: Herbicides and Nitrate in Surface Waters
Authors: Jaynes D. B. , Hatfield J. L. , Meek D. W.
Published: July 2010

There is a lack of quantitative information describing the impact of farming on water quality at the watershed scale. This study documents the surface water quality of Walnut Creek—a 5130‐ha watershed with about 86% of the land used for crop production. Starting in 1990, flow and concentrations of NO3‐N and four herbicides—atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide], metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4N)‐one], and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl) ‐ N ‐ (2 ‐methoxy ‐1‐methylethyl)acetamide]—were measured at eight locations. Nitrate‐N concentrations often exceeded 10 mg L−1 during May, June, and July. Total losses from the watershed ranged from 4 to 66 kg ha−1 yr−1 and represented 6 to 115% of the N applied as fertilizer in any year. Atrazine and metolachlor were detected at concentrations >0.2 µg L−1 in about half of all water samples, while alachlor and metribuzin were seldom detected. Median concentrations for atrazine and metolachlor were below 1 µg L−1 for all locations within the watershed. During runoff events, herbicide concentrations in the stream increased while NO3‐N concentrations decreased. Yearly losses from the watershed ranged from 0.2 to 7.5 g ha−1 for atrazine and from 03 to 6.7 g ha−1 for metolachlor. These losses represent 0.18 to 5.6% of the atrazine and 0.047 to 1.6% of the metolachlor applied in any year.
Geology, Groundwater Flow, and Water Quality in the Walnut Creek Watershed
Authors: Eidem J. M. , Simpkins W. W. , Burkart M. R.
Published: July 2010

An investigation of the Walnut Creek watershed was performed to characterize the geology, groundwater flow, and water quality in geological units impacted by agriculture. Six Quaternary lithostratigraphic units induding alluvium of the DeForest Formation, till of the Dows and Wolf Creek Formations, and loess of the Peoria, Pisgah, and Loveland Formations, along with two pedostratigraphic units, the Farmdale and Sangamon Geosols, were identified. The thickness and spatial distribution of the units were controlled by the formation of a paleo‐valley before the advance of the Des Moines Lobe, sediment movement into the paleo‐valley, and later erosion and deposition by the Des Moines Lobe. Groundwater flows toward the creek under unconfined conditions in the fractured, oxidized zone of till of the Dows Formation. Tritium data indicate that recent recharge occurs at the water table and that the 1963 bomb peak occurs near the bottom of the oxidized zone. Fifty‐five percent of groundwater samples taken in 1995 showed NO3‐N concentrations at or above the MCL of 10 mg/L; pesticides were detected in two samples. Some of the highest concentrations of NO3‐N occur in bomb peak groundwater near the base of the oxidized zone. This relationship implies that NO3‐N leaching has decreased during a period of increased N application in Iowa. It may actually reflect an increase in tile drain efficiency, decrease in groundwater recharge, and resultant isolation of NO3‐N in less‐mobile groundwater. Agricultural practices that further decrease NO3‐N leaching will be needed to improve the quality of shallow groundwater in the watershed.
Deconstruction of the Chemical Effects of Road Salt on Stream Water Chemistry
Authors: Mason Charles F. , Norton Stephen A. , Fernandez Ivan J. , Katz Lynn E.
Published: July 2010

The chemistry of a first‐order stream in Amherst, ME, with a catchment area of 103 ha has been strongly altered as a result of road salt application at a rate of approximately 4 t of NaCl per year in the lower 15% of the catchment. Downstream from the road, elevated stream Cl is accompanied by elevated Ca, K, Mg, and Na. The chemistry of the stream was deconstructed to identify the impact of the salt on total stream chemistry. Components quantified include precipitation (including dry deposition), chemical weathering, road salt, and cation exchange. Sodium from the road salt displaces Ca, K, and Mg from the soil on an equivalent basis. The displacement was at a maximum in late Fall and early Spring, indicating a long residence time for the NaCl. The exchange process was reversible. With continued loading of NaCl the water chemistry should reach a steady state such that Na and Cl move through the soil in a relatively conservative way, when the soils are at equilibrium with elevated concentrations of Na. Concentrations of Ca, K, and Mg in stream water should concurrently return to pre‐salting values under the new steady state.
Removal of Aromatic Amines from Water by Montmorillonite‐(Cerium or Zirconium) Phosphate Crosslinked Compounds
Authors: González‐Pradas E. , Villafranca‐Sánchez M. , Del Rey‐Bueno F. , García‐Rodríguez A. , Ureña‐Amate M. D.
Published: July 2010

To evaluate the potential use of two montmorillonite‐(Ce or Zr) phosphate crosslinked compounds in removing organic pollutants such as aniline, p‐toluidine, and p‐acetylaniline from water, adsorption experiments were performed under conditions of varied temperature (288 and 308 K). Adsorption on the montmorillonite‐Ce‐phosphate compound was best described by a hyperbolic (H‐type) isotherm, whereas for the montmoriilonite‐Zr‐phosphate compound, S‐type isotherms were obtained for p‐toluidine and aniline and L‐type for p‐acetylaniline. Amines adsorption increases with increasing temperature on the cerium crosslinked material, while for the zirconium‐crosslinked compound, adsorption decreases as temperature increases from 288 to 308 K, possibly due to a mainly physical process. Fourier‐transform infrared (FTIR) spectroscopy indicated that at the pH generated by the adsorbents, the protonated species of these amines plays an important role in the adsorption process. X‐ray diffraction analysis showed that the aromatic amines are intercalated into the adsorbents. For any given amine, the cerium‐montmorillonite adsorbent shows a higher capacity of adsorption compared with zirconium‐montmorillonite adsorbent, so it might be reasonably used in removing aromatic amines from water.
Isoproturon Sorption and Degradation in a Soil from Grassed Buffer Strip
Authors: Benoit P. , Barriuso E. , Vidon Ph. , Réal B.
Published: July 2010

The fate of the herbicide isoproturon [3‐(4‐isopropylphenyl)‐l,1‐dimethylurea] was investigated in soil from a grassed buffer strip. Compared to a cropped soil originating from the same experimental site (Kd = 1.8 L kg−1), sorption of isoproturon was enhanced in the grassed soil and especially in the surface layer (0‐2 cm) containing high proportion of nondecomposed plant residues (Kd = 5.0 L kg−1). Nonhumified organic fractions isolated from the surface soil layer and corresponding to above and bdow‐ground plant residues derived from the grass exhibited high sorption coefficients Kd and Koc compared to the rest of the soil. Reversibility of sorption was lower in the grassed soil than in the cropped soil and decreased rapidly with time. A rapid degradation of isoproturon was observed at different depths of the grassed soil whereas most of the herbicide remained nondegraded in the cultivated soil: half‐lives were respectively 72 d in the cultivated soil, and only 8 d in the superficial layer (0–2 cm) of the grassed soil. The highest mineralization rate of the isoproturon ring (20% after 35 d) was observed in the top layer (0–2 cm) having the highest mineralization rates of organic matter. In relation with this fast degradation, a large proportion of isoproturon residues became nonavailable to water and methanol extractions (54% of the initial applied isoproturon found as nonextractable (bound) residues). Thus the grassed strip surface soil had a high potential to dissipate isoproturon trapped from run‐off.