bluuebunny/crossref_metadata_2025 huggingface dataset:
Aquifer Denitrification as Interpreted from In Situ Microcosm Experiments
Authors: Bates H. K. , Spalding R. F.
Published: July 2010

Denitrification of 40 mg L−1 NO3‐N groundwater in the vicinity of Central City, NE was stimulated with ethanol in in situ microcosms that were vibrated into the aquifer sediment and, thus, filled with a relatively undisturbed, saturated sand and gravel matrix. In microcosms receiving the 1.25 C/N ratio, nitrate disappeared within 40 h; however, NO2‐N accumulated and persisted after NO3‐N was depleted. Nitrite has been documented in groundwater redoxclines and is expected to be reported more frequently with increased use of ion chromatography and dense sampling networks. Dissolved oxygen was consumed to <2.0 mg L−1 within 15 h, and stoichiometric production of HCO−3 occurred. Average denitrification rate decreased from 28.5 to 19.3 and to 16 mg N L−1 d−1 for C/N ratios of 1.25, 2.5, and 5.0 mg L−1. Kinetic N‐isotope effects resulted in the δ15N enrichment of residual nitrate as denitrification progressed, thus, causing the initial δ15N value of ∼+6‰ to increase to > +20‰. The data support measuring additional parameters to prevent misinterpretations when using δ15N values in NO−3 source identification investigations. Apparent isotope‐enrichment factors, ε value, were derived from δ15N increases vs. NO−3 and NO3 plus NO−2 reduction. They ranged from −11 to −16‰ for δ15N vs. residual NO−3 plus NO−2 and from −2.5 to −9‰ for δ15N vs. NO−3 alone. Since NO−3 could not be resolved from NO−2 in the δ15N analysis, a δ15N depleted NO2 phase was not identified. Nevertheless, isotopically light enrichment factors are consistent with the presence of NO−2.
Minesoil and Site Properties Associated with Early Height Growth of Eastern White Pine
Authors: Andrews Jeffrey A. , Johnson James E. , Torbert John L. , Burger James A. , Kelting Daniel L.
Published: July 2010

A study was established to investigate soil and site variables associated with early growth of eastern white pine (Pinus strobus L.) on reclaimed strip mines in southern West Virginia and Virginia. A total of 78 plantations were studied on 14 different mines, 5 to 9 yr following planting. Two‐year terminal height growth at ages 4 and 5 was selected as the growth variable in a multiple linear regression equation developed to show the relationship between tree growth and soil and site variables. Many soil/site variables were tested, but rooting depth, electrical conductivity, surface soil P and Mn, and slope were the dominant independent variables, accounting for 48% of the variability in growth. Soil depth had a standardized regression coefficient of 0.35, and was the most significant variable. Through proper reclamation, it is possible to establish a site that will not only provide for adequate early height growth to facilitate bond release, but also provide for future long‐term productivity of surface‐mined lands.
Geophysical Electromagnetic Survey Methods Applied to Agricultural Waste Sites
Authors: Eigenberg R. A. , Korthals R. L. , Nienaber J. A.
Published: July 2010

This paper reports the use of electromagnetic (EM) instrumentation for surveying agronomic and waste treatment sites at locations previously profiled by soil coring for evaluation of nutrients in the soil profile. Surveys were made using a geophysical EM instrument capable of measuring conductivity 3 to 6 m below the surface of the ground with horizontal or vertical polarization. Two specific sites were analyzed to evaluate the effects of management practices: (i) An animal waste composting site with one section in use since 1985 and with expanded operation to another section in 1989 and (ii) A waste storage pond (operational in 1973) holding precipitation runoff from a cattle feedlot. Correlation analysis between the EM conductivity measurements and chemical analysis at both sites (concentrations of NH+4, NO−3, CL−, and P) show significant (P < 0.05) correlations for the ions while P did not show a significant correlation. The EM measures were able to distinguish the 6‐yr‐old site from the 10‐yr‐old site (P < 0.05). The results indicate that EM methods provide useful information for shallow subsurface surveys of livestock waste management facilities.
Adsorption of Naphthalene onto Plant Roots
Authors: Schwab A. P. , Al‐Assi A. A. , Banks M. K.
Published: July 2010

Higher plants are being used to enhance the remediation of soils contaminated with recalcitrant organic compounds, but the mechanisms of dissipation have not been established. One possible step in the phytoremediation process is adsorption of the organic contaminant onto the surface of the roots and subsequent uptake and/or degradation. To determine the affinity of plant roots for naphthalene, a polycyclic aromatic hydrocarbon, adsorption was quantified for tall fescue (Festuca arundinacea Schreber) and alfalfa (Medicago sativa Equilibrium adsorption for naphthalene was determined for fresh roots of each species at three growth stages. For both fescue and alfalfa, adsorption was described by the Freundlich isotherm. Adsorption increased by as much as a factor of four with later growth stage of the plants. Alfalfa roots had approximately twice the affinity for naphthalene than fescue roots, despite a greater surface area per unit mass of root for fescue. Alfalfa also had a greater lipid content than fescue (10 g lipid/kg dry root vs. 4.5 g/kg), indicating that lipid content is a controlling factor in adsorption of naphthalene onto plant roots.
Comparison of Closed‐Chamber and Bowen‐Ratio Methods for Determining Methane Flux from Peatland Surfaces
Authors: Chan A. S. K. , Prueger J. H. , Parkin T. B.
Published: July 2010

Methane (CH4) is an important greenhouse gas, and it has been estimated that 50% of annual CH4 comes from terrestrial systems. Better and more accurate methods are needed to quantify CH4 flux from terrestrial environments. Two general methods commonly applied to measure trace gas fluxes are soil cover (chamber) techniques, and micrometeorology methods. Both of these methods has advantages and disadvantages, yet little information is available concerning the relative performance of the techniques. This study was conducted to compare CH4 flux measurements obtained by using a closed‐chamber soil cover technique and a micrometeorological method (Bowen‐ratio Energy Balance [BREB]). Methane flux rates obtained by both methods were compared using nine time points over 3 d at a peatland site in north central Minnesota. Mean CH4 fluxes obtained by both methods were of the same magnitude (2.43–5.88 mg CH4 m−2 h−1); however, differences were observed in the magnitudes of temporal variability as well as the detection sensitivities (minimum detectable flux). The minimum detectable flux for the closed‐chamber method was 9.32 × 10−2 mg CH4 m−2 h−1, while the minimum detectable flux for the BREB method ranged from 2.16 to 25.5 mg CH4 m−2 h−1. Due to analytical uncertainties associated with gas chromatographic determination of CH4 gradients, the BREB is not recommended.
Method for Estimating Bulk Density of Soft‐Bottom Sediment Cores
Authors: van Dokkum H. P. , van Leerdam M. E. , Anderson D. L. , Aalderink R. H. , Vermulst C. J. W. , Abbink Spaink A. P.
Published: July 2010

Soft‐bottom highly porous sediment samples can be frozen to facilitate handling, preservation, and especially separation of sediment layers before laboratory analysis. Due to core expansion upon freezing, bulk density measurements are biased (underestimation of up to 8.9% for pure water), but bulk density in separate sediment layers can only be measured after freezing. Therefore, the objective of this study was to develop a methodology that allows the actual field bulk density to be estimated from measurements on frozen cores in the laboratory. Homogeneous soft‐bottom undisturbed sediment cores (single layer) were sampled with a transparent cylindrical device in the Everglades Agricultural Area. The bulk density of the undisturbed, unfrozen sediment cores (field bulk density) was calculated by measurement of the volume and weight of sediment cores. After freezing, the solids fraction and frozen bulk density on a wet‐basis were determined. From the collected data, the field (i.e., before freezing) bulk density could adequately be predicted from the frozen bulk density and the solids fraction. The method described in this paper allows field bulk density of separate sediment layers to be estimated from parameters easily measured on frozen sediment cores, and is therefore useful when different sediment layers require delineation.
The Role of Phosphorus in the Eutrophication of Receiving Waters: A Review
Authors: Correll David L.
Published: July 2010

Phosphorus (P) is an essential element for all life forms. It is a mineral nutrient. Orthophosphate is the only form of P that autotrophs can assimilate. Extracellular enzymes hydrolyze organic forms of P to phosphate. Eutrophication is the overenrichment of receiving waters with mineral nutrients. The results are excessive production of autotrophs, especially algae and cyanobacteria. This high productivity leads to high bacterial populations and high respiration rates, leading to hypoxia or anoxia in poorly mixed bottom waters and at night in surface waters during calm, warm conditions. Low dissolved oxygen causes the loss of aquatic animals and release of many materials normally bound to bottom sediments including various forms of P. This release of P reinforces the eutrophication. Excessive concentrations of P is the most common cause of eutrophication in freshwater lakes, reservoirs, streams, and headwaters of estuarine systems. In the ocean, N becomes the key mineral nutrient controlling primary production. Estuaries and continental shelf waters are a transition zone, where excessive P and N create problems. It is best to measure and regulate total P inputs to whole aquatic ecosystems, but for an easy assay it is best to measure total P concentrations, including paniculate P, in surface waters or N/P atomic ratios in phytoplankton.
Organic Compound Sorption Enthalpy and Sorption Mechanisms in Soil Organic Matter
Authors: Borisover Mikhail D. , Graber Ellen R.
Published: July 2010

Small exothermic or even endothermic heats of sorption for organic compounds in soil organic matter (SOM) have been traditionally considered evidence for a partitioning mechanism into the bulk of SOM. This derives from considerations of solute transfer enthalpy (ΔHtr) from aqueous solution to organic solvent and partial molar enthalpies of solution in organic solvent (ΔHssol) and aqueous (−ΔHwsol) phases, where ΔHtr = ΔHssol − ΔHwsol. The dissolution of many solutes in organic solvents is accompanied by positive solution enthalpies and conforms to the condition ΔHtr > −ΔHwsol. It was suggested by analogy of SOM to organic solvents, that solute sorption enthalpies (ΔHi) in SOM that conform to the analogous condition (i.e., ΔHi > ΔHwsol) are consistent with partitioning into SOM. Systems that do not conform to this condition (i.e., ΔHi < ΔHwsol) were considered to be consistent with adsorption. The purpose of this analysis is to point out the fallacies associated with this reasoning and to demonstrate that sorption enthalpy cannot be used in this way as evidence for a particular sorption mechanism. It is shown that for partitioning of numerous organic solutes into different organic solvents, ΔHssol < 0, such that ΔHtr < −ΔHwsol. If SOM is considered the solvent phase, it is clear that ΔHi < −ΔHwsol cannot be taken to indicate surface adsorption. This is particularly true for systems that provide an opportunity for strong force specific interactions inside of SOM. Similarly, it is shown that systems involving adsorption of nonpolar organic compounds at mineral surfaces often conform to the condition suggested as evidence for partitioning.
Behavior of Sequential Extraction of Lead from Thermally Treated Lead(II)‐Doped Alumina
Authors: Wei Yu‐Ling , Huang Yu‐Ling
Published: July 2010

There are environmental concerns about emission of heavy metals in flue gases during incineration of hazardous wastes. Low temperature injection of sorbents has been suggested as a way to reduce the heavy metal content of the emitted gases. We investigated the extractive behavior of Pb in thermally treated Pb2+‐doped alumina using the USEPA toxicity characteristics leachability procedure (TCLP) and a sequential extraction method to obtain information on the Pb‐alumina reaction. Thermal treatment of Pb2+‐doped alumina was in the 100 to 900°C range for 10 to 60 min. Results indicated that the Pb2+‐doped alumina treated at higher temperature for longer duration was resistant to the TCLP and to the sequential extraction for the first four fractions, but not for the residual fraction (Fraction 5). The relationship between total extracted Pb of the first four fractions and the TCLP concentration was strong (r = 0.993 for the 100°C and r = 0.996 for the 500°C treatments). Almost all of the doped Pb was distributed between conceptual fractions that were either bound to carbonates or were residual that was extracted with 10% HF and H2O2. The shift in distribution of Pb that was carbonate‐bound to that bound in the residual fraction as treatment temperature increased from 100 to 500°C was more than that which shifted from 500 to 900°C. After treatment at 900°C most of the Pb was associated with the residual fraction (indicating a strong sorption between Pb and alumina) and the TCLP concentration dropped to nondetectable levels.
Fractionation and Distribution of Arsenic in Soils Contaminated by Cattle Dip
Authors: McLaren R. G. , Naidu R. , Smith J. , Tiller K. G.
Published: July 2010

Soils surrounding cattle dips in Australia are known to be highly contaminated with As and are potentially of major concern to the environment and human health. A study of 11 dip sites in northern New South Wales (NSW) has revealed considerable surface soil (0–10 cm) contamination with As (37–3542 mg As kg−1 soil). In addition it was shown that considerable movement of As down through the soils had occurred with concentrations at 20 to 40 cm ranging from 57 to 2282 mg As kg−1 soil. At one particular site, an As concentration of above 14 000 mg As kg−1 soil was determined at a depth of 40 to 45 cm. A sequential fractionation scheme, based on a soil P fractionation, was developed to assess the chemical nature, and thus the potential bioavailability and mobility of As, at the sites. Soil As is separated into six fractions with (i) anion exchange resin, (ii) NaHCO3, (iii) NaOH, (iv) NaOH following sonication, (v) HCl, and (vi) HCl/HNO3. Although substantial differences between sites and soil depths were present, some general trends were apparent. Most sites contained substantial concentrations of As in the two most labile fractions, indicating high potential for phytotoxicity and leaching. The bulk of the contaminant As at the sites seemed to be associated with soil amorphous Fe and Al minerals.
Fate of Pig Sludge Liquid Fraction in Calcareous Soil: Agricultural and Environmental Implications
Authors: Giusquiani P. L. , Concezzi L. , Businelli M. , Macchioni A.
Published: July 2010

The characterization of pig sludge liquid fraction (PSLF) was conducted to achieve a better understanding of its chemical and physical chemical characteristics. Total dissolved organic carbon (TDOC) from pig sludge was separated into two fractions: acid insoluble dissolved organic carbon (AIDOC) and acid soluble dissolved organic carbon (ASDOC). Elemental analysis, acidic functional group determination, E4/E6 ratio, Gel‐Filtration Cromatography and FTIR Spectroscopy of ASDOC and AIDOC showed a similarity with humic and fulvic acids, isolated from soils and organic wastes. Phosphorus‐31 Nuclear Magnetic Resonance spectra demonstrated that the organic P in PSLF was present as P‐monoester. The complexing capacity of DOC vs. trace metals was demonstrated by Gel Filtration Chromatography and FTIR Spectroscopy. The interactions of DOC, Cu, and Zn, present in PSLF, with a calcareous soil were evaluated by adsorption isotherms that indicated that Zn was completely adsorbed by the soil, while Cu followed the same behavior as DOC, with only partial adsorption. Therefore, both Cu and DOC should be taken into consideration as a possible groundwater pollution hazard after pig sludge application to calcareous soil.
Relation between Irrigation Method, Sediment Yields, and Losses of Pesticides and Nitrogen
Authors: Ebbert James C. , Kim Moon H.
Published: July 2010

Yields of suspended sediment from watersheds in the Quincy and Pasco Basins of Washington State have been reduced by the use of sprinkler irrigation on cropland previously in furrow irrigation. Mean daily yields of suspended sediment from nine watersheds sampled during April and May 1994 ranged from 0.4 kg/ha of irrigated cropland in a watershed with no furrow irrigation to 19 kg/ha in a watershed where 58% of irrigated cropland was in furrow irrigation. About 67% of the variation in the yields can be attributed to irrigation method. Temporal trends also indicated that use of sprinkler irrigation reduced sediment yields. Mean daily yields of suspended solids from one of the watersheds decreased from 0.3 kg/ha in 1975 to <0.2 kg/ha in 1988, corresponding with a decrease from about 65% to <50% in the use of furrow irrigation. Sampling in two watersheds suggests that the use of sprinkler irrigation reduces runoff losses of pesticides and N. For 10 of 13 pesticides and N, runoff losses from a watershed with mostly furrow irrigation exceeded runoff losses from a watershed with mostly sprinkler irrigation.
Evaluation of NCSWAP Model Using Nitrate‐Leaching Data from Soil Core Lysimeters
Authors: Jabro J. D. , Stout W. L. , Fales S. L. , Fox R. H.
Published: July 2010

The accuracy of the Ṉitrogen and C̱arbon cycling in S̱oil, W̱ater A̱nd P̱lant (NCSWAP) model to simulate (nitrate‐nitrogen) NO3‐N leaching from orchardgrass (Dactylis glomerata L.) pasture was evaluated using data collected from a 3‐yr leaching experiment conducted in central Pennsylvania on Hagerstown silt loam soil (fine, mixed, mesic, Typic Hapludalf). Nitrate leaching losses below the 1‐m depth from N‐fertilized orchardgrass sod were measured with intact soil core lysimeters (0.6‐m diam. by 1‐m long). Five N‐fertilizer treatments consisted of a control, urine application in the spring, urine application in the summer, urine application in the fall, and feces application in the summer were used to test the model. The model was calibrated using the data from 1993 to 1994 and then was validated using 1994 to 1995 and 1995 to 1996 water flow and NO3‐N leaching data. Statistical analysis indicated a good fit between field measured and predicted NO3‐N leaching for most treatments in each year. The model simulations of water flow and NO3‐N leaching losses below the 1‐m depth were compared with the meau of measured field data for these 3 yr. The results of this study showed that the NCSWAP model performed well and accurately simulated water flow and total annual NO3‐N loss through leaching below the 1‐m depth under orchardgrass pasture. However, the model failed to produce accurate simulations for the feces treatment in 1994 to 1995. The simulation error in the feces treatment seemed to be related to N mineralization process in the model. Generally, the results of this study suggest that the NCSWAP model can be used for predicting NO3‐N leached annually from pastured orchardgrass.
Decomposition of Land Applied Oily Food Waste and Associated Changes in Soil Aggregate Stability
Authors: Plante Alain F. , Voroney R. Paul
Published: July 2010

Since traditional methods of disposing of oily food wastes have recently lost favor, there is a current search for alternatives. Field‐and laboratory‐scale experiments examined the decomposition of oily food wastes applied to agricultural lands to examine this disposal option and potential agronomic benefits. Treatment rates of oily food waste equivalent to 3 to 11.3 g of C kg−1 increased soil microbial biomass C in the field by up to five times control levels. Wet aggregate stability also increased with waste addition and was maintained over the course of the growing season. Laboratory incubation studies examining the biodegradation of canola oil and oily food waste showed that the oily fraction of the waste was not rate limiting, and that both substrates degraded rapidly with initial decomposition half‐lives of 40 to 45 h and 70 to 94 h for canola oil and waste treatments, respectively. The extents of mineralization over 4 wk were up to 84 and 40% for canola oil and oily food waste, respectively. Similar to the field, increases in aggregate stability were measured in the canola oil incubation. Examination of the biodegradation data indicates two substrate pools are being sequentially decomposed, and that the added substrate is not directly responsible for improved structural properties. The longer lasting binding abilities of microbial products and bodies are the major contributing factors for the increased soil aggregation. It is concluded that the land application of oily food waste is agronomically beneficial by increasing soil microbial activity, and in turn improving soil structure through increased aggregate stability.
Effect of Soil Solution Chloride on Cadmium Availability to Swiss Chard
Authors: Smolders E. , Lambregts R. M. , McLaughlin M. J. , Tiller K. G.
Published: July 2010

Potted soil experiments were conducted to analyze how higher Cl concentrations in soil enhance Cd uptake by plants. Two soils (W,L) were moistened with complete nutrient solution containing either NaCl or NaNO3 at concentrations ranging from 0 to 120 mmol L−1. Swiss chard (Beta vulgaris L., cv. Fordhook Giant) was grown in the soils until the 4th leaf appeared (15 d on soil W, 20 d on soil L). Plant dry weights generally decreased with increasing salt concentration, but were not significantly affected by the type of Na salt. For both soils, shoot Cd concentrations in the 120 mmol L−1 NaCl treatment almost doubled those in the zero salt treatments. In contrast, increasing NaNO3 concentrations either reduced shoot Cd concentration (soil L) or had no effect (soil W). Increasing concentrations of NaCl in the soil solution significantly increased the Cd concentration in solution from 65 to 400 nmol L−1 (soil W) and from 64 to 300 nmol L−1 (soil L). Increasing concentrations of NaNO3 in solution had no effect on Cd concentrations in solution. Speciation calculations predicted that the solution concentration of the free metal ion Cd2+ was not significantly affected by the NaCl (both soils) or NaNO3 (soil L) treatments. In soil W, the predicted Cd2+ concentrations in soil solution slightly decreased with increasing NaNO3 rate. It is concluded that the enhancing effect of NaCl on Cd uptake is due to chloride complexation of Cd.
Relationships between Loading Rates and Pollutant Removal during Maturation of Gravel‐Bed Constructed Wetlands
Authors: Tanner Chris C. , Sukias James P. S. , Upsdell Martin P.
Published: July 2010

Relationships between pollutant mass loading and removal are reported for a series of five pilot‐scale constructed wetlands in their 4th and 5th years of operation. The wetlands received different hydraulic loadings ranging between ∼15 and 70 mm d−1 (9.5‐2 d theoretical retention, respectively). Effluent concentrations of 5‐d carbonaceous biochemical oxygen demand (CBOD), total nitrogen (TN), ammonium N (NH4‐N), and fecal coliforms (FC) broadly followed seasonal patterns in influent wastewater strength. Mean annual mass removals of 58 to 78% suspended solids (SS), 73 to 91% CBOD, 48 to 65% TN, 34 to 60% NH4‐N, 15 to 38% total phosphorus (TP), and 93 to 99.6% of FC were recorded, with removal efficiencies inversely related to loadings. Mass removal rates were monotonically related to loading rates, and could be modeled using a simple plug‐flow, first‐order approach accounting for removal down to nonzero background concentrations. Comparisons with treatment performance recorded for the wetlands soon after commissioning showed relatively constant relationships between mass loading and removal of CBOD, TN, and FC. In contrast, SS and TP removal declined significantly over the same period. Reduced SS removal efficiency appeared to result from clogging of the gravel substratum by refractory organic solids, and reduced TP removal from saturation of substratum sorption capacity and filling of plant storage pools. To improve N removal predictions for wetlands treating ammonium‐rich wastewaters, the use of a combined carbonaceous and nitrogenous BOD term is proposed, which addresses the oxygen dependence of microbial nitrification, the principal rate‐controlling process.
Dairy Manure Influences on Phosphorus Retention Capacity of Spodosols
Authors: Nair V. D. , Graetz D. A. , Reddy K. R.
Published: July 2010

Land areas used for dairy farming can result in accumulation of manure on soils that could produce nutrient‐rich surface and subsurface runoff and cause accelerated lake eutrophication. This research was conducted on Spodosols that were differentially impacted by manure; the study included sites with different levels of total P (TP), from 2300 mg kg−1 in the soil highly impacted by intensive dairy farming to 18 mg kg−1 in an unimpacted area. The P retention characteristics of these soils were determined by using both single‐point (1000 mg P kg−1 or 100 mg P L1) and traditional Langmuir isotherms. Phosphorus sorption values using a single high P solution had approximately a 1:1 relationship with values obtained for the maximum retention capacity, Smax, obtained from Langmuir isotherms (r2 = 0.98). The surface A and E horizons of manure‐impacted soils had essentially no sorbing capacity while the Bh (spodic) and Bw horizons had mean Smax values 430 and 385 mg kg−1, respectively. The P sorbing capacity of the Bh and Bw horizons were attributed to high Al concentrations in these horizons. Higher P concentrations in the surface A horizon resulted in greater P concentrations in solutions equilibrated with the Bh‐ and Bw‐ horizon materials, which suggests a potential for vertical P movement through the soil profile. The spodic horizon of the less‐impacted soils may not have been exposed to sufficiently high solution P concentrations to accumulate significant P in the soluble fraction.
Leaching Potentials of Four Pesticides Used for Bananas in the Canary Islands
Authors: Diaz‐Diaz Ricardo , Garcia‐Hernandez Jose Enrique , Loague Keith
Published: July 2010

Nonpoint source (NPS) groundwater contamination, that is related to the regional‐scale use of agrochemicals, is a major environmental problem. This paper reports preliminary assessments of groundwater vulnerability due to pesticide leaching for areas of banana (Musa balbisiana) silviculture for the Canary Island of Tenerife using simple indices. Estimates of contamination potential were made for the four most commonly used pesticides using the retardation factor (RF) and the attenuation factor (AF). Soil, crop, and recharge maps for Tenerife were overlaid using a geographic information system (GIS) approach. Soil depth, the type of irrigation, soil‐pH dependent chemical halflives, and the method of landcover characterization were each assessed relative to their individual and cumulative impacts on assessing regional‐scale NPS groundwater vulnerability. The order of leaching potential, in terms of greatest mobility, for the four chemicals was found to be: (i) carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofluranyl‐n‐methylcarbamate), (ii) ethoprophos (O‐ethyl‐S,S‐di‐n‐propylphosphorodithioate), (iii) fenamiphos (ethyl 3‐methyl‐4‐(methylthio)‐phenyl1‐methylethylphosphoramidate), and (iv) oxamyl (methyl 2‐(dimethylamino)‐N‐[[(methylamino)carbony]oxy]‐2‐oxoethanimidothioate). The worst‐case scenario for groundwater contamination in Tenerife, related to banana silviculture, was found to be carbofuran with furrow irrigation. The best pesticide and irrigation combination to minimize potential groundwater contamination, related to the cultivation of bananas in Tenerife, was oxamyl and drip irrigation. The regional‐scale NPS groundwater vulnerability assessments presented here for Tenerife are the first to be made for the island and will be useful for future chemical regulation decisions and for targeting critical areas that may require remediation.
Trace Metal Speciation in Three Unbuffered Salt Solutions Used to Assess their Bioavailability in Soil
Authors: Lebourg A. , Sterckeman T. , Ciesielski H. , Proix N.
Published: July 2010

Three unbuffered salt solutions used to estimate soil trace metal bioavailability were compared. The objective was to evaluate chemical speciation of Cd, Cu, Pb, and Zn in 0.01 M CaCl2, 0.1 M NaNO3, and 1 M NH4NO3 extracts. The metal in each extract were speciated with a model that was optimized experimentally using an exchange resin. In NH4NO3, Cd, Cu, and Zn were completely complexed by NH3. In extracts of pH lower than 6.5, Pb was essentially present as free Pb2+ and metal‐organic complexes. In extracts of higher pH, PbCO3 and free Pb2+ were dominant. In CaCl2, Cu and Zn were mainly present as organic complexes and free Zn2+, respectively. In all extracts, 50% of Cd was free Cd2+ and 50% CdCl+. As pH increased, the proportions of free Pb2+ and organic complexes decreased while those of inorganic complexes increased. In NaNO3, Cd, Cu, and Zn were, respectively, mainly present as free Cd2+, organic complexes and free Zn2+. Speciation of Pb changed with pH as in NH4NO3. Similarities were expected between the qualitative composition of the extracts and the soil solution, justifying the use of unbuffered salt solutions, particularly NaNO3 and CaCl2, in the evaluation of soil trace metal availability.
Vegetative Growth and Trace Metal Accumulation on Metalliferous Wastes
Authors: Pichtel J. , Salt Carol A.
Published: July 2010

A greenhouse study was conducted to investigate the growth of the grass cover crops Agrostis capillaris, Festuca ovina, F. rubra, Lolium perenne, and Phleum pratense and their accumulation of Cu, Pb, Zn, Ni, and Cr in three metal‐contaminated wastes arising from a steelworks, a lead mine, and a chemical works. Soil metals were extracted by five reagents (Mehlich 1, 0.1 M HCl, 0.005 M DTPA, 0.005 M EDTA, 0.005 M NTA) and values were correlated with plant tissue accumulation of metals. Agrostis capillaris accumulated the greatest concentration of metals from each waste material. Dry matter production for all grasses decreased on contaminated substrates compared to the control; however, overall ground cover was satisfactory except for A. capillaris on the chemical works waste. Lolium perenne and P. pratense consistently produced the highest dry matter yields. All grasses accumulated excessive amounts of Cr on the chemical waste and Pb on the mine waste, presumably from reservoirs in the readily extractable and soluble forms. The extractability of most metals was generally 0.1 M HCl > Mehlich 1 > DTPA = EDTA = NTA. Mehlich 1 did not appreciably extract Pb from two wastes. No extractant was able to represent metal uptake by a particular grass in a linear fashion.
Mechanical Advancing Handle that Simplifies Minirhizotron Camera Registration and Image Collection
Authors: Johnson M. G. , Meyer P. F.
Published: July 2010

Minirhizotrons in conjunction with a minirhizotron video camera system are becoming widely used tools for investigating root production and survival in a variety of ecosystems. Image collection with a minirhizotron camera can be time consuming and tedious particularly when hundreds or thousands of images are collected routinely. To help us with image collection in our minirhizotron studies we developed a mechanical handle that simplifies minirhizotron camera registration and image collection. The handle is attached to the minirhizotron camera and fits inside 5 cm, internal diameter, minirhizotron tubes. The handle couples a ratchet advancing mechanism with another mechanism that locks the handle to the minirhizotron tube, ensuring proper camera and tube registration. The ratchet mechanism advances the camera one camera field of view (frame) at a time. While the handle can be used to rapidly advance the camera, it is best to pause 2 to 3 s after each advance, to allow sufficient time for the image to be recorded on video tape. At this rate, 20 to 30 frames can be recorded each minute. The camera, with handle attached, is easily moved from one minirhizotron tube to another. We conducted a simple study of handle performance and estimate that camera registration precision (a measure of relocating the camera in the same position) is >99%.
Forms and Concentration of Phosphorus in Drainage Water of Twenty‐Seven Tile‐Drained Soils
Authors: Beauchemin Suzanne , Simard R. R. , Cluis D.
Published: July 2010

In most mineral soils, P leaching is rarely viewed as an important environmental issue. However, P accumulation and decreased P sorption capacities in surface horizons of long‐term fertilized soils may increase downward P movement. The objective of this study was to measure the concentration and characterize the P forms in drainage waters from nine soil series widely differing in clay content. Twenty‐seven sites were sampled in 1994 and 1995 from an intensively cropped area of the province of Quebec, Canada. Drainage waters were characterized for their total P (TP), dissolved reactive P (DRP), dissolved organic P (DOP), and total particulate P (TPP) contents. The Quebec surface water quality standard of 0.03 mg TP L1 was exceeded in 14 out of 27 sites in 1994 but only in 6 out of 25 sites in 1995. Of the 14 sites exceeding 0.03 mg TP L−1 in 1994, 10 were clayey soils. Under these circumstances, more than 50% of the TP was as TPP whereas DOP forms represented <30%. In 1995, TPP forms accounted for, on average, <50% of TP and DOP accounted for more than 40% of the TP concentrations. This study suggests that flat clayey soils of medium to rich P status may be particularly at risk of exceeding water quality standards in subsurface runoff. Phosphorus losses in particulate form may be important in subsurface runoff from clayey soils when weather conditions favor rapid flow through cracks or macropores.
Unwanted Agricultural Pesticides: State Disposal Programs
Authors: Centner Terence J.
Published: July 2010

Millions of pounds of unwanted pesticides have accumulated in storage barns throughout our country. The potential environmental and health risks posed by this situation have garnered public attention and governmental action. While the possession of unwanted pesticides generally is not illegal, agricultural producers need to follow requisite legal requirements and dispose of pesticides properly to avoid legal infractions. The federal government has published the Universal Waste Rule so that it is easier to dispose of unwanted pesticides through waste pesticide collection programs. Nearly every state has initiated efforts to collect and dispose of accumulated pesticides in a safe manner, but many programs only address a part of the problem. For many states, the lack of implementation of funding or a permanent mechanism for the collection of unwanted pesticides means that pesticides will continue to present risks to our society.
Microbial Reduction of Structural Iron in Clays—A Renewable Source of Reduction Capacity
Authors: Ernstsen Vibeke , Gates Will P. , Stucki Joseph W.
Published: July 2010

The ability of microorganisms to reduce structural Fe in minerals has become recognized as an important mechanism in the oxidation of pollutants in soils and sediments. To better understand the factors controlling the concentration of Fe(II) in natural deposits, samples of clayey till from sites near Havrebjerg and Sparresholm, Denmark, were incubated for up to 160 d with a combination of Pseudomonas bacteria strains. These strains were previously shown to reduce structural Fe(III) to Fe(II) in smectites. According to Eh, pH, microbial activity, and structural Fe(II) content, the incubation could be separated into four phases of which the second phase (from 4 to 10 d after inoculation) generated the most structural Fe(II). Microbial activity increased the structural Fe(II) content from approximately 10% to 20–34% of total clay Fe, a lower level than that obtained for chemically reduced subsamples (76–79%), but more similar to values typical of unweathered tills of Denmark (about 50%). In addition to microbial activity, the particle size (fine or coarse clay) and the Fe(II) content of the clay minerals prior to incubation were very important factors affecting the extent of Fe reduction. The results indicate that structural Fe in clay minerals of clayey till is very reactive and can undergo extensive in situ redox cycling. Electron transfer to structural Fe(III) of the weathered, oxidized clay minerals may renew natural redox barriers in imperfectly drained soils and sediments and thereby control geochemical processes.
Enhanced Sorption of Organic Contaminants by Smectitic Soils Modified with a Cationic Surfactant
Authors: Sheng Guangyao , Wang Xiaorong , Wu Shunnian , Boyd Stephen A.
Published: July 2010

Soils, subsoils, and aquifer materials can be modified with hydrophobic cationic surfactants to increase their sorptive capabilities for organic contaminants. In this study, we evaluated the adsorption/desorption of hexadecyltrimethylammonium (HDTMA) by smectitic soils, and the sorptive characteristics of the resultant organo‐modified soils for trichloroethylene and chlorobenzene. Adsorption of HDTMA with loading levels up to 70% of the cation exchange capacity (0.70 CEC) was nearly quantitative and resulted in an equivalent release of Ca2+ from the soils, indicating ion exchange as the sole mechanism over this range. At higher loadings, HDTMA is adsorbed by both ion exchange and hydrophobic bonding. The selectivity coefficients for HDTMA replacing Ca2+ were very high (109 −107 between 0.1 and 0.8 CEC), indicating the high chemical stability of HDTMA‐soil complexes at these loadings. Desorption is more significant for HDTMA adsorbed via hydrophobic bonding than via ion exchange. Sorption coefficients for trichloroethylene and chlorobenzene on HDTMA‐modified soils (0.7 CEC) were 20 to 60 and 100 to 350 times higher, respectively, than those on the corresponding unmodified soils. The HDTMA derived phase was 10 to 30 and 80 to 160 times more effective than natural soil organic matter (on a unit mass basis) as a sorptive phase for trichloroethylene and chlorobenzene, respectively. A synergistic effect on sorption of trichloroethylene and chlorobenzene in binary solute systems was observed. The sorptive characteristics of HDTMA modified smectitic soils for organic contaminants are similar to those of pure HDTMA‐smectites.
Quantification and Remediation of Pesticides in Runoff Water from Containerized Plant Production
Authors: Briggs J. A. , Riley M. B. , Whitwell T.
Published: July 2010

During containerized plant production pesticides may move from application site in runoff water created by overhead irrigation systems. In this study, four pesticides, isoxaben {N‐[3‐(1‐ethyl‐1‐methylpropyl)‐5‐isoxazolyl]‐2,6‐dimethoxybenzamide}, trifluralin {(2,6‐dinitro‐N,N‐dipropyl‐4‐trifluoromethylaniline}, chlorpyrifos {O,O‐diethyl O‐3,5,6‐trichloro‐2‐pyridyl phosphorothioate) and thiophanate‐methyl {dimethyl 4,4−‐o‐phenylene bis(3‐thioallophanate), were applied at a commercial plant nursery. Overhead irrigation after application generated runoff water which was channeled into waterways of clay/gravel or hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy]. Isoxaben was detected in runoff water through 4 d after application (DAA). Other pesticides were detected primarily on the day of application (DOA). Thirteen percent of applied thiophanate‐methyl was recovered from the clay/gravel waterway and 11% from the grass waterway. Total amounts of isoxaben lost were 23% of total applied in both treatments. Less than 0.01% of applied chlorpyrifos and trifluralin were detected. Isoxaben amounts recovered from the grassed waterway on the DOA were 16% lower than from the clay/gravel treatment. Thiophanate‐methyl amounts were 18% lower from the grassed treatment on the DOA. The results suggest that vegetated waterways can reduce pesticide losses from application site in runoff water.
Heavy Metal Balances of an Italian Soil as Affected by Sewage Sludge and Bordeaux Mixture Applications
Authors: Moolenaar S.W. , Beltrami P.
Published: July 2010

Applications of sewage sludge and Bordeaux mixture (Bm) (a mixture of copper sulfate and lime) add heavy metals to the soil. At an experimental farm in the Cremona district (Italy), we measured current heavy metal contents in soil and their removal via harvested products. We also measured heavy metal adsorption by soil from this farm. With these data, projections were made of the long‐term development of heavy metal (Cd, Cu, and Zn) contents in soil, crop removal, and leaching at different application rates of sewage sludge and Bm. These projections were compared with existing quality standards of the European Union (EU) and Italy with regard to soil and groundwater. The calculations reveal that the permitted annual application rates of sewage sludge and Bm are likely to result in exceedance of groundwater and soil standards. Sewage sludge applications, complying with the Italian (I) legal limits, may pose problems for Cd, Cu, and Zn within 30, 70, and 100 yr, respectively. Furthermore, severe Cu pollution of integrated (mildew controlled by Bm and organopesticides) and especially organic (Bm only) vineyards is unavoidable with the currently allowed application rates of Bm. The results suggest that the current I soil protection policy as well as the EU policy are not conducive of a sustainable heavy metal management in agroecosystems.
Microbial Oxidation and Solubilization of Precipitated Elemental Selenium in Soil
Authors: Losi M. E. , Frankenberger W. T.
Published: July 2010

Oxidation of elemental selenium (Se0) leads to increased solubilizalion and enhanced bioavailability. In this work, laboratory microcosm experiments were conducted to study oxidation of Se0 in soil and liquid cultures. Major objectives were to examine the oxidation rates of four San Joaquin Valley, California soils, and to assess the contribution of biological vs. chemical processes. For these experiments, red, crystalline Se0 was prepared by both chemical and biological synthesis, and its presence was confirmed by synchrotron‐based x‐ray absorption spectroscopy. The amount of Se0 oxidized over 125 d was from 1 to 10% of Se0 in soils spiked to 250 mg Se0 kg−1 and approximately half that in soils spiked to 100 mg Se0 kg−1. First order rate constants for oxidation of Se0 were from 0.05 to 0.32 yr−1 and 0.04 to 0.39 yr−1 at 250 and 100 mg Se0 kg−1 soil, respectively. The amount of Se0 oxidized was generally correlated with prior exposure of the soil lo Se. Products included either selenite (SeO2−3), or both SeO2−3 and selenate (SeO2−4). Biotic processes were shown to be of major importance. Both heterotrophic and autotrophic oxidation were observed, and an inorganic C source (NaHCO3) was favored relative to glucose. This study demonstrates that Se0 oxidation in soils is largely biotic in nature, occurs at relatively slow rates and yields both SeO2−3 and SeO2−4.
Transport of Agrichemicals to Ground and Surface Water in a Small Central Indiana Watershed
Authors: Fenelon J. M. , Moore R. C.
Published: July 2010

The occurrence, distribution, concentrations, and pathways of agrichemicals in water were investigated in the Sugar Creek watershed, a poorly drained agricultural watershed typical of many watersheds in the midwestern USA. Water samples from Sugar Creek, two tile drains, and 11 wells along a groundwater flowpath to Sugar Creek were collected between May 1992 and August 1996 and analyzed for N and pesticide compounds. Nitrate was the principal N species and pesticides were common in alluvial water‐bearing units in the Sugar Creek floodplain. In the confined stratified drift aquifers, ammonia was the principal N species and pesticides were rare. Tile drains directly affected the water quality in Sugar Creek by transporting soil pore water and shallow groundwater containing high concentrations of nitrate (NO3) and pesticides to the creek. When tile drains were flowing (typically December through July), elevated NO3 concentrations (2–10 mg/L NO3N) in the creek correlated with high NO3 concentrations (2–23 mg/L NO3N) in tile drains discharging to the creek. Likewise, with concentrations of atrazine and atrazine metabolites, seasonal trends in the tile‐drain effluent were similar to seasonal trends in Sugar Creek. When tile drains went dry, NO3 concentrations in the creek were low, indicating most groundwater discharge to the creek consisted of old or denitrified water. Trace levels of pesticides in the creek at low flow probably were the result of seepage from alluvial water‐bearing units.
Impact of Nitrogen Management Practices on Nutritional Status and Yield of Valencia Orange Trees and Groundwater Nitrate
Authors: Alva A.K. , Paramasivam S. , Graham W.D.
Published: July 2010

A field experiment was conducted using 36‐yr‐old Valencia orange trees (Citrus sinensis) planted in an Astatula fine sand (hyperthermic, uncoated, Typic Quartzipsamments) to evaluate the effects of two different N management practices on the mineral nutrition status of the trees, fruit yield and quality, and nitrate (NO−3) loading into groundwater. The N treatments included 180 kg ha−1 yr−1 as either (i) three broadcast applications per year of a combination of dry soluble form (DSF; 135 kg N ha−1 yr−1) and controlled‐release form (CRF; 45 kg ha−1 yr−1); or (ii) fertigation in 18 equally divided applications per year. Nitrate‐N was measured in groundwater sampled at 3‐wk intervals using four monitoring wells in each of the two blocks over 2 yr. Fruit yield was greater by 2.7 to 8.2 Mg ha−1 in the fertigation compared to that in the DSF/CRF broadcast treatment. Leaf nutrient concentrations or fruit quality parameters were not significantly influenced by the different N management treatments. Most of the leaf nutrients were within the recommended optimal ranges. Mean groundwater NO3‐N concentrations for the DSF/CRF treatment ranged from 6.5 to 16.5, and 9.4 to 14.1 mg L−1 during 1995 and 1996, respectively. The corresponding values for the fertigation treatment ranged from 7.0 to 14.6 and 1.4 to 6.9 mg L−1. Fertigation with 18 applications per year decreased NO3‐N loading into groundwater as compared to three broadcast applications of the same rate of N using DSF/CRF granular blend.