bluuebunny/crossref_metadata_2025 huggingface dataset:
Chesapeake Bay Eutrophication: Scientific Understanding, Ecosystem Restoration, and Challenges for Agriculture
Authors: Boesch Donald F. , Brinsfield Russell B. , Magnien Robert E.
Published: June 2010

Chesapeake Bay has been the subject of intensive research on cultural eutrophication and extensive efforts to reduce nutrient inputs. In 1987 a commitment was made to reduce controllable sources of nitrogen (N) and phosphorous (P) by 40% by the year 2000, although the causes and effects of eutrophication were incompletely known. Subsequent research, modeling, and monitoring have shown that: (i) the estuarine ecosystem had been substantially altered by increased loadings of N and P of approximately 7‐ and 18‐fold, respectively; (ii) hypoxia substantially increased since the 1950s; (iii) eutrophication was the major cause of reductions in submerged vegetation; and (iv) reducing nutrient sources by 40% would improve water quality, but less than originally thought. Strong public support and political commitment have allowed the Chesapeake Bay Program to reduce nutrient inputs, particularly from point sources, by 58% for P and 28% for N. However, reductions of nonpoint sources of P and N were projected by models to reach only 19% and 15%, respectively, of controllable loadings. The lack of reductions in nutrient concentrations in some streams and tidal waters and field research suggest that soil conservation–based management strategies are less effective than assumed. In 1997, isolated outbreaks of the toxic dinoflagellate Pfiesteria piscicida brought attention to the land application of poultry manure as a contributing factor to elevated soil P and ground water N concentrations. In addition to developing more effective agricultural practices, emerging issues include linking eutrophication and living resources, reducing atmospheric sources of N, enhancing nutrient sinks, controlling sprawling suburban development, and predicting and preventing harmful algal blooms.
Hypoxia in the Gulf of Mexico
Authors: Rabalais Nancy N. , Turner R.Eugene , Wiseman William J.
Published: June 2010

Seasonally severe and persistent hypoxia, or low dissolved oxygen concentration, occurs on the inner‐ to mid‐Louisiana continental shelf to the west of the Mississippi River and Atchafalaya River deltas. The estimated areal extent of bottom dissolved oxygen concentration less than 2 mg L−1 during mid‐summer surveys of 1993–2000 reached as high as 16000 to 20000 km2 The distribution for a similar mapping grid for 1985 to 1992 averaged 8000 to 9000 km2 Hypoxia occurs below the pycnocline from as early as late February through early October, but is most widespread, persistent, and severe in June, July, and August. Spatial and temporal variability in the distribution of hypoxia exists and is, at least partially, related to the amplitude and phasing of the Mississippi and Atchafalaya discharges and their nutrient flux. Mississippi River nutrient concentrations and loadings to the adjacent continental shelf have changed dramatically this century, with an acceleration of these changes since the 1950s to 1960s. An analysis of diatoms, foraminiferans, and carbon accumulation in the sedimentary record provides evidence of increased eutrophication and hypoxia in the Mississippi River delta bight coincident with changes in nitrogen loading.
Stability Constants for the Complexation of Various Metals with a Rhamnolipid Biosurfactant
Authors: Ochoa‐Loza Francisco J. , Artiola Janick F. , Maier Raina M.
Published: June 2010

The presence of toxic metals in natural environments presents a potential health hazard for humans. Metal contaminants in these environments are usually tightly bound to colloidal particles and organic matter. This represents a major constraint to their removal using currently available in situ remediation technologies. One technique that has shown potential for facilitated metal removal from soil is treatment with an anionic microbial surfactant, rhamnolipid. Successful application of rhamnolipid in metal removal requires knowledge of the rhamnolipid–metal complexation reaction. Therefore, our objective was to evaluate the biosurfactant complexation affinity for the most common natural soil and water cations and for various metal contaminants. The conditional stability constant (logK) for each of these metals was determined using an ion‐exchange resin technique. Results show the measured stability constants follow the order (from strongest to weakest): Al3+> Cu2+> Pb2+> Cd2+> Zn2+> Fe3+> Hg2+> Ca2+> Co2+> Ni2+> Mn2+>Mg2+> K+These data indicate that rhamnolipid will preferentially complex metal contaminants such as lead, cadmium, and mercury in the presence of common soil or water cations. The measured rhamnolipid–metal stability constants were found in most cases to be similar or higher than conditional stability constants reported in the literature for metal complexation with acetic acid, oxalic acid, citric acid, and fulvic acids. These results help delineate the conditions under which rhamnolipid may be successfully applied as a remediation agent in the removal of metal contaminants from soil, as well as surface waters, ground water, and wastestreams.
Fly Ash and Lime‐Stabilized Biosolid Mixtures in Mine Spoil Reclamation: Simulated Weathering
Authors: Abbott D.E. , Essington M.E. , Mullen M.D. , Ammons J.T.
Published: June 2010

The use of large quantities of neutral coal fly ash (NFA) may be facilitated by co‐application with a lime‐stabilized biosolid (LSB) for the reclamation of acid mine spoil (AMS). Although NFA may not aid in the mitigation of acid drainage, questions concerning the leachability and mineralogy of native and NFA‐ and LSB‐born metals must be addressed. In this study, the potential long‐term influence of LSB and NFA on AMS leachate chemistry and trace element mineralogy was evaluated using laboratory weathering and selective dissolution techniques. The application of LSB at a rate sufficient to neutralize the potential acidity of the AMS increased leachate pH from approximately 3 to 7.5 for the duration of the study. Fly ash rates (1×, 1.5×, and 2× LSB rate) did not affect leachate pH. The dominant electrolytes in all leachates were Ca and SO4, the concentrations of which were mirrored by solution electrical conductivity (EC). Leachate concentrations of Al, Fe, Mn, K, Cu, Ni, and Zn were significantly reduced by LSB application, whereas concentrations of Ca, SO4, Mg, Cl, F, B, and P were increased. Nitrate concentrations were not affected by LSB. With the exception of leachate B, which increased with increasing NFA rate and was regenerated during the weathering study, NFA did not affect leachate composition. Sequential selective dissolution indicated a transformation of Co, Cr, Cu, Ni, Pb, and Zn into less labile mineral pools with weathering. The results of these evaluations suggest that the application of NFA during AMS reclamation would have little effect on leachate chemistry or the mineralogy of trace elements. Thus, the high‐volume application of NFA to AMS during reclamation may offer an additional opportunity for the use of this combustion by‐product.
Denitrification from a Swine Lagoon Overland Flow Treatment System at a Pasture–Riparian Zone Interface
Authors: Lowrance Richard , Hubbard Robert K.
Published: June 2010

In manure disposal systems, denitrification is a major pathway for N loss and to reduce N transport to surface and ground water. We measured denitrification and the changes in soil N pools in a liquid manure disposal system at the interface of a pasture and a riparian forest. Liquid swine manure was applied weekly at two rates (approximately 800 and 1600 kg N ha−1yr−1) to triplicate plots of overland flow treatment systems with three different vegetation treatments. Denitrification (acetylene block technique on intact cores) and soil N pools were determined bimonthly for 3 yr. The higher rate of manure application had higher denitrification rates and higher soil nitrate. Depth 1 soil (0–6 cm) had higher denitrification, nitrate, and ammonium than depth 2 soil (6–12 cm). The vegetation treatment consisting of 20 m of grass and 10 m of forest had lower denitrification. Denitrification did not vary significantly with position in the plot (7, 14, 21, and 28 m downslope), but nitrate decreased in the downslope direction while ammonium increased downslope. Denitrification ranged from 4 to 12% of total N applied in the manure. Denitrification rates were similar to those from a nearby dairy manure irrigation site, but were generally a lower percent of N applied, especially at the high swine effluent rate. Denitrification rates for these soils range from 40 to 200 kg N ha−1yr−1for the top 12 cm of soil treated with typical liquid manure that is high in ammonium and low in nitrate.
Spray Drift of Pesticides Arising from Aerial Application in Cotton
Authors: Woods Nicholas , Craig Ian P. , Dorr Gary , Young Brian
Published: June 2010

This paper presents results from field studies carried out during the 1993–1998 Australian cotton (Gossypium hirsutum L.) seasons to monitor off‐target droplet movement of endosulfan (6,7,8,9,10,10‐hexachloro‐1,5,5a,6,9,9a‐hexahydro‐6,9‐methano‐2,4,3‐benzodioxathiepin 3‐oxide) insecticide applied to a commercial cotton crop. Averaged over a wide range of conditions, off‐target deposition 500 m downwind of the field boundary was approximately 2% of the field‐applied rate with oil‐based applications and 1% with water‐based applications. Mean airborne drift values recorded 100 m downwind of a single flight line were a third as much with water‐based application compared with oil‐based application. Calculations using a Gaussian diffusion model and the U.S. Spray Drift Task Force AgDRIFT model produced downwind drift profiles that compared favorably with experimental data. Both models and data indicate that by adopting large droplet placement (LDP) application methods and incorporating crop buffer distances, spray drift can be effectively managed.
Endosulfan Transport: I. Integrative Assessment of Airborne and Waterborne Pathways
Authors: Raupach M.R. , Briggs P.R. , Ford P.W. , Leys J.F. , Muschal M. , Cooper B. , Edge V.E.
Published: June 2010

To reduce endosulfan (C9H6O3Cl6S; 6,7,8,9,10,10‐hexachloro‐1,5,5a,6,9,9a‐hexahydro‐6,9‐methano‐2,4,3‐benzodioxathiepin 3‐oxide) contamination in rivers and waterways, it is important to know the relative significances of airborne transport pathways (including spray drift, vapor transport, and dust transport) and waterborne transport pathways (including overland and stream runoff). This work uses an integrated modeling approach to assess the absolute and relative contributions of these pathways to riverine endosulfan concentrations. The modeling framework involves two parts: a set of simple models for each transport pathway, and a model for the physical and chemical processes acting on endosulfan in river water. An averaging process is used to calculate the effects of transport pathways at the regional scale. The results show that spray drift, vapor transport, and runoff are all significant pathways. Dust transport is found to be insignificant. Spray drift and vapor transport both contribute low‐level but nearly continuous inputs to the riverine endosulfan load during spraying season in a large cotton (Gossypium hirsutum L.)‐growing area, whereas runoff provides occasional but higher inputs. These findings are supported by broad agreement between model predictions and observed typical riverine endosulfan concentrations in two rivers.
Olfactory Response to Mushroom Composting Emissions as a Function of Chemical Concentration
Authors: Noble R. , Hobbs P.J. , Dobrovin‐Pennington A. , Misselbrook T.H. , Mead A.
Published: June 2010

Odor pollution is a major problem facing mushroom [Agaricus bisporus(Lange) Imbach] compost production. Techniques for quantifying mushroom composting odors are needed to assess the effectiveness of odor control measures. Odor samples were obtained in nalophane bags from 11 mushroom composting sites. Samples were collected 0.2 m downwind from the pre‐wetting heaps (aerated or unaerated) of raw composting ingredients (wheat straw, poultry and horse manures, and gypsum) and subsequent Phase I composting windrows or aerated tunnels. The odor concentrations (OCs) of the samples were assessed using serial dilution olfactometry and the chemical composition of the samples was determined using gas chromatography–mass spectrometry (GC–MS), both 24 h after sampling. Gas detector tubes were used for on‐site measurement of gaseous compounds. Odorants that exceeded their published olfactory detection thresholds by the greatest order of magnitude, in decreasing order, were: H2S, dimethyl sulfide (DMS), butanoic acid, methanethiol, and trimethylamine. Concentrations of NH3were not significantly correlated with OC, and they were not significantly affected by the use of aeration. Aeration reduced the OC and the combined H2S + DMS concentrations by 87 and 92%, respectively. There was a very close correlation (r= 0.948,P< 0.001) between the OC of bag samples and the combined H2S + DMS concentrations, measured on‐site with detector tubes. This relationship was unaffected by the NH3concentration or the type of compost: aerated or unaerated, pre‐wet or Phase I, poultry manure–based or horse and poultry manure–based compost. Prediction of the OC will enable rapid and low‐cost identification of odor sources on mushroom composting sites.
Adsorption of Pesticides onto Quartz, Calcite, Kaolinite, and α‐Alumina
Authors: Clausen L. , Fabricius I. , Madsen L.
Published: June 2010

The fate of pesticides in aquifers is influenced by the small but not insignificant adsorption of pesticides to mineral surfaces. Batch experiments with five pesticides and four minerals were conducted to quantify the contributions to adsorption from different mineral surfaces and compare adsorption characteristics of selected pesticides. Investigated mineral phases included quartz, calcite, kaolinite, and α‐alumina. Selected pesticides comprised atrazine (6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine), isoproturon [3‐(4‐isopropylphenyl)‐1,1‐dimethylurea)], mecoprop [(RS)‐2‐(4‐chloro‐2‐methylphenoxy)propionic acid], 2,4‐D (2,4‐dichlorophenoxyacetic acid), and bentazone [3‐isopropyl‐1H‐2,1,3‐benzothiadiazin‐4‐(3H)‐one 2,2‐dioxide]. Specific surface area and mineral surface charge proved to be important for the adsorption of these pesticides. Detectable adsorption of the anionic pesticides (mecoprop, 2,4‐D, and bentazone) was only measured when positive sites were present on the mineral surface. However, when CaCl2 was added as an electrolyte, a detectable adsorption of mecoprop and 2,4‐D was also measured on kaolinite (which exhibits a negative surface charge), probably due to formation of Ca–pesticide–surface complexes. Adsorption of the uncharged pesticides (atrazine and isoproturon) was detected only on kaolinite. The lack of adsorption on α‐alumina indicates that the uncharged pesticides have a greater affinity for the silanol surface sites (=SiOH) than for the aluminol surface sites (=AlOH) in kaolinite. No measurable effect of ionic strength was found for the uncharged pesticides. The results indicate that quartz and calcite play a smaller role than clay minerals.
Plant Uptake of Cadmium‐109 and Zinc‐65 at Different Temperature and Organic Matter Levels
Authors: Almås Å.R. , Singh B.R.
Published: June 2010

The uptake of 109Cd and 65Zn and their stable isotopes by ryegrass (Lolium multiflorum Lam.), grown on two different soil types, was investigated in climatically controlled growth chambers at 9 and 21°C. The soils were treated with 0 and 4% organic matter (pig [Sus scrofa] manure) and spiked with 109Cd and 65Zn before sowing. The organic matter addition resulted in increased uptake of the 109Cd, Cd, and Zn by ryegrass, but the uptake of 65Zn was decreased. The latter effect was ascribed to isotopic dilution of 65Zn as the amount of stable Zn in the plant tissues increased with the organic matter addition. The effect of temperature was more pronounced than that of organic matter addition, and the uptake of both 109Cd and 65Zn and their stable isotopes was higher in ryegrass grown at 21°C than that grown at 9°C. Results from fractionation and speciation analysis of soil cadmium and zinc were correlated with plant uptake, and there was a good consistency between observed plant uptake and the physico–chemical forms of cadmium and zinc in soil and soil solution presumed to be plant available.
Copper and Calcium Transport through an Unsaturated Soil Column
Authors: Vogeler Iris
Published: June 2010

To determine the relative importance of the physical and chemical factors that influence the movement of heavy metals through soils, leaching experiments were carried out under conditions of constant molarity during unsaturated steady‐state water flow through a Manawatu fine sandy loam (a Dystric Fluventic Eutochrept). The movement and exchange of copper was studied in a binary Cu–Ca system. The movement of the associated anions, namely chloride and sulfate, was also monitored. The measurements were compared with predictions from the convection–dispersion equation (CDE), linked with cation exchange theory. The agreement between the measured and predicted breakthrough of sulfate and copper was good. This indicates that copper retardation in the Manawatu soil is closely related to the cation exchange capacity, and that exchange between Ca and Cu is the main process of Cu retardation in the Manawatu soil. However, copper appeared slightly later in the effluent than predicted, indicating that non‐exchange processes are also involved in copper transport. Measurements of suction cups could also be used to obtain the parameters for the CDE to describe sulfate movement through the soil. Time domain reflectometry (TDR) measurements of the bulk‐soil electrical conductivity could be used to monitor the movement of both sulfate and copper. This indicates that TDR can also be used to monitor cation transport and exchange through the soil, provided the percolating solution causes a sufficient change in the electrical conductivity.
In Situ Bioremediation through Mulching of Soil Polluted by a Copper–Nickel Smelter
Authors: Kiikkilä Oili , Perkiömäki Jonna , Barnette Matthew , Derome John , Pennanen Taina , Tulisalo Esa , Fritze Hannu
Published: June 2010

Bioremediation of a heavy metal–polluted soil was investigated in a 3‐yr field experiment by adding mulch to a polluted forest floor. The mulch consisted of a mixture of compost and woodchips. The remediation treatment decreased the toxicity of the soil solution to bacteria as determined by the [3H]‐thymidine incorporation technique, that is, by measuring the growth rate of soil bacteria extracted from unpolluted humus after exposing them to soil solution containing heavy metals from the experimental plots. Canonical correlation analysis was performed in order to identify the chemical and microbiological changes in the soil. The pH of the mulched organic layer increased by one unit. The concentration of complexed Cu increased and that of free Cu2+ decreased in the soil solution from the mulch treatment. According to basal respiration and litter decomposition, microbial activity increased during the 3 yr following the remediation treatment. The [3H]‐thymidine incorporation technique was also used to study the growth rate and tolerance of bacteria to Cu. The bacterial growth rate increased and the Cu tolerance decreased on the treated plots. The structure of the microbial community, as determined by phospholipid fatty acid (PLFA) analysis, remained unchanged. The results indicate that remediation of the polluted soil had occurred, and that adding a mulch to the forest floor is a suitable method for remediating heavy metal–polluted soil.
Controlling Nitrate Leaching in Irrigated Agriculture
Authors: Spalding Roy F. , Watts Darrell G. , Schepers James S. , Burbach Mark E. , Exner Mary E. , Poreda Robert J. , Martin Glen E.
Published: June 2010

The impact of improved irrigation and nutrient practices on ground water quality was assessed at the Nebraska Management System Evaluation Area using ground water quality data collected from 16 depths at 31 strategically located multilevel samplers three times annually from 1991 to 1996. The site was sectioned into four 13.4‐ha management fields: (i) a conventional furrow‐irrigated corn (Zea maysL.) field; (ii) a surge‐irrigated corn field, which received 60% less water and 31% less N fertilizer than the conventional field; (iii) a center pivot‐irrigated corn field, which received 66% less water and 37% less N fertilizer than the conventional field; and (iv) a center pivot‐irrigated alfalfa (Medicago sativaL.) field. Dating (3H/3He) indicated that the uppermost ground water was <1 to 2 yr old and that the aquifer water was stratified with the deepest water ∼20 yr old. Recharge during the wet growing season in 1993 reduced the average NO3–N concentration in the top 3 m 20 mg L−1, effectively diluting and replacing the NO3‐contaminated water. Nitrate concentrations in the shallow zone of the aquifer increased with depth to water. Beneath the conventional and surge‐irrigated fields, shallow ground water concentrations returned to the initial 30 mg NO3–N L−1level by fall 1995; however, beneath the center pivot‐irrigated corn field, concentrations remained at ∼13 mg NO3–N L−1until fall 1996. A combination of sprinkler irrigation and N fertigation significantly reduced N leaching with only minor reductions (6%) in crop yield.
A Novel Continuous‐Flow Sequential Extraction Procedure for Metal Speciation in Solids
Authors: Shiowatana J. , Tantidanai N. , Nookabkaew S. , Nacapricha D.
Published: June 2010

A continuous‐flow extraction system was developed to speed up, facilitate, and improve the accuracy of the chemical fractionation of metals in solid materials. A three‐step sequential extraction scheme was used to evaluate the novel system by analyzing calcium (Ca), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in a soil certified reference material (National Institute of Standards and Technology [NIST] SRM 2710). In the proposed system, extraction occurred in a closed chamber through which extractants were passed sequentially. The extracts were collected in a number of subfractions for subsequent flame atomic absorption analysis. Apart from the advantages of simplicity, speed, and less risk of the contamination that flow analysis systems usually possess, the continuous‐flow system can improve the accuracy of chemical fractionation of metals by sequential extraction. The system ensures that extraction is performed at designated pH values without any need of adjustment. Variation of sample weight to chamber volume ratios from 1:12 to 1:40 had no effect on the extractability of the metals studied. In the extraction of the acid soluble fraction, concentrations of acetic acid in the range 0.11 to 0.5 mol L−1 had no significant effect on the amounts of metals extracted, except Fe. Increasing the concentration of hydroxylamine in the reducible fraction step from 0.04 to 0.5 mol L−1 affected the extraction efficiency for Fe, Mn, and Zn. The extraction profile, rather than a single value of extracted concentration, of each element offers additional information about the kinetics of leaching processes and chemical associations between elements in the solid materials.
Evaluation of Leachates from Coal Refuse Blended with Fly Ash at Different Rates
Authors: Stewart B.R. , Daniels W.L. , Zelazny L.W. , Jackson M.L.
Published: June 2010

There is great interest in returning coal combustion products to mining sites for beneficial reuse as liming agents. A column study examined the effects of blending two coal fly ashes with an acid‐forming coal refuse (4% pyritic S). Both fly ashes were net alkaline, but had relatively low neutralizing capacities. One ash with moderate alkalinity (CRF) was bulk blended with coal refuse at 0, 20, and 33% (w/w), while another lower alkalinity ash (WVF) was blended at 0, 5, 10, 20, and 33% (w/w). The columns were leached (unsaturated) weekly with 2.5 cm of simulated precipitation for >150 wk. Where high amounts of ash alkalinity (>20% w/w) were mixed with the coal refuse, pyrite oxidation was controlled and leachate pH was >7.0 with low metal levels throughout the study. At lower rates of alkalinity loading, trace metals were sequentially released from the WVF ash as the 5, 10, and 20% treatments acidified due to pyrite oxidation. Lechate metals increased in proportion to the total amounts applied in the ash. In this strongly acidic environment, metals such as Mn, Fe, and Cu were dissolved and leached from the ash matrix in large quantities. If ash is to be beneficially reused in the reclamation of acid‐producing coal refuse, the alkalinity and potential acidity of the materials must be balanced through the appropriate addition of lime or other alkaline materials to the blend. Highly potentially acidic refuse material, such as that used here, may not be suitable for ash/refuse codisposal scenarios.
Denitrification at a Long‐Term Forested Land Treatment System in the Piedmont of Georgia
Authors: Meding S.Mercer , Morris Lawrence A. , Hoover Coeli M. , Nutter Wade L. , Cabrera Miguel L.
Published: June 2010

Spray irrigation of forested land can provide an effective system for nutrient removal and treatment of municipal wastewater. Evolution of N2+ N2O from denitrifying activity is an important renovation pathway for N applied to forested land treatment systems. Federal and state guidance documents for design of forested land treatment systems indicate the expected range for denitrification to be up to 25% of applied N, and most forest land treatment systems are designed using values from 15 to 20% of applied N. However, few measurements of denitrification following long‐term wastewater applications at forested land treatment sites exist. In this study, soil N2+ N2O–N evolution was directly measured at four different landscape positions (hilltop, midslope, toe‐slope, and riparian zone) in a forested land treatment facility in the Georgia Piedmont that has been operating for more than 13 yr. Denitrification rates within effluent‐irrigated areas were significantly greater than rates in adjacent nonirrigated buffer zones. Rates of N2+ N2O–N evolved from soil in irrigated forests ranged from 5 to 10 kg ha−1yr−1N on the three upland landscape positions and averaged 38 kg ha−1yr−1N within the riparian zone. The relationship between measured riparian zone denitrification rates and soil physical and chemical properties was poor. The best relationship was with soil temperature, with anr2of 0.18. Overall, on a landscape position weighted basis, only 2.4% of the wastewater‐applied N was lost through denitrification.
Acidification–Neutralization Processes in a Lignite Mine Spoil Amended with Fly Ash or Limestone
Authors: Seoane S. , Leirós M.C.
Published: June 2010

A laboratory experiment was conducted to investigate the long‐term effects of amending sulfide‐rich lignite mine spoil with fly ash (originating from a coal‐fired power station and largely comprised of aluminosilicates) and/or agricultural limestone. The experiment was carried out with soil moisture maintained at field capacity or alternate cycles of wetting and drying. Results obtained suggest that the principal acidification processes were oxidation of sulfide and formation of hydroxysulfate (FeOHSO4), whereas the main neutralization processes were weathering of aluminosilicates in fly ash–treated samples and dissolution of calcium carbonate in limestone‐treated samples. The highest dose of limestone rapidly raised the pH of the spoil, but this increase was not maintained throughout the one‐year experiment. In contrast, fly ash–treated samples showed a more sustained increase in pH, attributable to the gradual weathering of aluminosilicates. The best results (i.e., good short‐ and long‐term neutralization) were obtained in samples treated with both fly ash and limestone. The low liming capacity of the fly ash (47.85 cmol kg−1) means that it must be used in large quantities, an advantage in achieving the further aim of disposing of the fly ash.
Mechanisms of Nutrient Attenuation in a Subsurface Flow Riparian Wetland
Authors: Casey Ryan E. , Taylor M. D. , Klaine Stephen J.
Published: June 2010

Riparian wetlands are transition zones between terrestrial and aquatic environments that have the potential to serve as nutrient filters for surface and ground water due to their topographic location. We investigated a riparian wetland that had been receiving intermittent inputs of NO−3 and PO3−4 during storm runoff events to determine the mechanisms of nutrient attenuation in the wetland soils. Few studies have shown whether infrequent pulses of NO−3 are sufficient to maintain substantial denitrifying communities. Denitrification rates were highest at the upstream side of the wetland where nutrient‐rich runoff first enters the wetland (17–58 μg N2O–N kg soil−1 h−1) and decreased further into the wetland. Carbon limitation for denitrification was minor in the wetland soils. Samples not amended with dextrose had 75% of the denitrification rate of samples with excess dextrose C. Phosphate sorption isotherms suggested that the wetland soils had a high capacity for P retention. The calculated soil PO3−4 concentration that would yield an equilibrium aqueous PO3−4 concentration of 0.05 mg P L−1 was found to be 100 times greater than the soil PO3−4 concentration at the time of sampling. This indicated that the wetland could retain a large additional mass of PO3−4 without increasing the dissolved PO3−4 concentrations above USEPA recommended levels for lentic waters. These results demonstrated that denitrification can be substantial in systems receiving pulsed NO−3 inputs and that sorption could account for extensive PO3−4 attenuation observed at this site.
Aluminum Output Fluxes from Forest Ecosystems in Europe: A Regional Assessment
Authors: Dise N. B. , Matzner E. , Armbruster M. , MacDonald J.
Published: June 2010

Data from 89 forested catchments and plots across Europe were used to define empirical relationships between aluminum leaching and input fluxes of major ions, output fluxes of major ions, ecosystem parameters such as soil pH, and combinations of these. Forests that release dissolved Al to seepage or surface waters are located primarily in areas receiving the highest loading of acid rain, and the output flux of Al shows the highest correlations to the throughfall flux of inorganic nitrogen, the output fluxes of NO−3, H+, and SO2−4, and the mineral soil pH. If the speciation of Al is taken to be Al3+ (an overestimate), Al is released in a nearly 1:1 molar charge ratio with the sum of NO−3 and SO2−4 in runoff or seepage water over a wide range of base‐poor bedrock types and acid deposition across Europe. The empirical data point to a threshold range of N deposition of 80 to 150 mmolc N m−2 yr−1 and a (less clearly defined) range of S deposition of 100 to 200 mmolc SO2−4 m−2 yr−1 above which Al released from forests exceeds 100 mmolc Al m−2 yr−1 Within this threshold range, the sites that release little or no dissolved Al are those that continue to assimilate input N and/or have high soil pH (>4.5).
Phosphorus and Ammonium Concentrations in Surface Runoff from Grasslands Fertilized with Broiler Litter
Authors: Pierson S. T. , Cabrera M. L. , Evanylo G. K. , Kuykendall H. A. , Hoveland C. S. , McCann M. A. , West L. T.
Published: June 2010

Application of broiler (Gallus gallus domesticus) litter to grasslands can increase ammonium (NH4–N) and dissolved reactive phosphorus (DRP) concentrations in surface runoff, but it is not known for how long after a broiler litter application that these concentrations remain elevated. This long‐term study was conducted to measure NH4–N and DRP in surface runoff from grasslands fertilized with broiler litter. Six 0.75‐ha, fescue (Festuca arundinaceaSchreb.)–bermudagrass [Cynodon dactylon(L.) Pers.] paddocks received broiler litter applications in the spring and fall of 1995–1996 and only inorganic fertilizer N in the spring of 1997–1998. Surface runoff from each paddock was measured and analyzed for NH4–N and DRP. Broiler litter increased flow‐weighted NH4–N and DRP concentrations from background values of 0.5 and 0.4 mg L−1, respectively, to values > 18 mg L−1in a runoff event that took place immediately after the third application. Ammonium concentrations decreased rapidly after an application and were not strongly related to time after application or runoff volume. In contrast, DRP concentrations tended to decrease more slowly, reaching values near 1 mg L−1by 19 mo after the last application. Dissolved reactive P concentrations decreased linearly with the natural logarithm of days after application (p< 0.03), and increased linearly with the natural logarithm of runoff volume (p< 0.0001).
Pesticide Applications of Copper on Perennial Crops in California, 1993 to 1998
Authors: Epstein L. , Bassein S.
Published: June 2010

Inorganic copper is used as a broad‐spectrum fungicide and bacteriocide on a variety of agricultural crops. After application, the copper residue typically accumulates in the upper 15 cm of soil. Data from the California Pesticide Use Reports were used to estimate the augmentation of copper in the soil that resulted from pesticide applications for the six years from 1993 to 1998 on 12 crops that are grown without rotation. The estimated mean mg Cu kg−1soil added to the upper 15 cm during the six years was the following: walnut (Juglans regiaL.), 28; peach [Prunus persica(L.) Batsch var.persica], 22; nectarine [Prunus persica(L.) Batsch var.nucipersica(Suckow) C.K. Schneid], 19; cherry (Pseudolmedia oxyphyllariaDonn. Sm.), 18; rice (Oryza sativaL.), 16; apricot (Prunus armeniacaL.), 11; orange [Citrus sinensis(L.) Osbeck] and plum (Prunus domesticaL. subsp.domestica), 9; lemon [Citrus limon(L.) Burm. f.] and almond [Prunus dulcis(Mill.) D.A. Webb], 6; pear (Pyrus communisL.), 4; and grape (Vitis viniferaL.), 3. In addition, for the first five of these crops, we estimated the area that was treated with each level of kg Cu ha−1For example, for walnut orchards, we estimated that 12500 ha, or 17% of the planted area, was treated with a quantity of Cu that would increase the total concentration of Cu in the upper 15 cm of soil by at least 50 mg Cu kg−1soil. A comparison of the amount of Cu per unit planted area that was applied in the first and second half of the study indicated that the intensity of copper use is either relatively constant or increasing, depending on the crop. The findings are discussed in relation to the potential effect of continued long‐term use of Cu pesticides on soil sustainability.
Zinc Accumulation by the Slime Mold Fuligo septica (L.) Wiggers in the Former Soviet Union and North Korea
Authors: Zhulidov Daniel A. , Robarts Richard D. , Zhulidov Alexander V. , Zhulidova Olga V. , Markelov Danila A. , Rusanov Viktor A. , Headley John V.
Published: June 2010

Samples of the slime mold Fuligo septica (L.) Wiggers were collected from an ecologically diverse selection of sites across the former USSR and in North Korea to determine their Zn concentrations. Plasmodia were collected from trees, rocks, soils, the walls of buildings and a variety of other materials and structures from 1990 to 1996. The biomass collected ranged from 305 to 968 mg, whereas Zn concentrations in plasmodia of F. septica ranged from 8400 to 23000 mg kg−1 dry wt. (mean and standard error = 14200 ± 860 mg kg−1 dry wt.). No clear trend as to which areas produced F. septica with the highest Zn concentrations was discernable. Nor was it possible to identify any particular substrate on which F. septica grew that produced noticeably high Zn concentrations. For example, forest litter on which F. septica was found had Zn concentrations of only 25 to 130 mg kg−1 dry wt. Our data confirm the only other study showing hyperaccumulation of Zn in F. septica, which was carried out in Finland. This ability seems to be unique to this species, but how or why it does this, or why such high Zn concentrations are not toxic to F. septica, are questions requiring future research.
Nitrous Oxide Emissions from an Ultisol of the Humid Tropics under Maize–Groundnut Rotation
Authors: Khalil M.I. , Rosenani A.B. , Van Cleemput O. , Fauziah C.I. , Shamshuddin J.
Published: June 2010

Nitrous oxide (N2O) contributes to global climate change and agricultural soils seem to be the major source. Lack of information led to this study on the influence of different amounts and sources of nitrogen on N2O emission from a maize (Zea maysL.)–groundnut (Arachis hypogaeL.) crop rotation in an Ultisol of the humid tropics. The treatments were: inorganic N + crop residues (NC), inorganic N only (RN), and half of inorganic N + crop residues + chicken manure (NCM). The corresponding amount of N applied was 322, 180, and 400 kg ha−1yr−1, respectively. The N2O emissions depended on the amounts and types of N. A maximum peak (9889 ± 2106 μg N2O‐N m−2d−1) was detected at 2 wk before maize sowing amended with chicken manure, showing a persistent influence on N transformations and N2O release. The mineral N from either applied source became low by 2 to 4 wk, coinciding with the small N2O fluxes or its consumption to a few isolated instances. The N2O flux significantly correlated with the mineral N and water‐filled pore spaces. The direct annual N2O emission was 3.94 ± 0.23, 1.90 ± 0.08, and 1.41 ± 0.07 kg N2O‐N ha−1from the NCM, NC, and RN treatments, respectively. The corresponding N2O‐N loss of the applied N plus N fixed by groundnut was 0.83, 0.49, and 0.59%. Overestimations of direct annual N2O emission using the Intergovernmental Panel on Climate Change (IPCC) methodology suggest a location‐specific emission factor for variable N sources to be considered.
Site‐Specific Phosphorus Application Based on the Kriging Fertilizer‐Phosphorus Availability Index of Soils
Authors: Juang Kai‐Wei , Liou Day‐Chyng , Lee Dar‐Yuan
Published: June 2010

Site‐specific phosphorus management is done to optimize crop production and minimize P loss from soils. The spatial variability of the available P prior to fertilizer application and the P‐fixation tendency of soil both need to be taken into account for variable‐rate P application. The objectives of this research were to document the spatial variability of the fertilizer‐P availability index, which shows the P‐fixation tendency, and to develop a strategy that takes the spatial distribution of this index into account for site‐specific phosphorus application. In this study, the spatial patterns of the fertilizer‐P availability index were characterized by using geostatistics. The ordinary kriging was used for spatial interpolation of the fertilizer‐P availability index. Because the fertilizer‐P availability index of soil is related to oxalate‐extractable Fe and Al and because measuring oxalate‐extractable Fe and Al is much easier than directly determining the fertilizer‐P availability index, the spatial distribution of the fertilizer‐P availability index can be obtained using the oxalate‐extractable Fe and Al data. The spatial distribution of Olsen‐extractable P, which was used to measure the available‐P status prior to fertilizer‐P application, was also estimated by using ordinary kriging. The required fertilizer‐P amounts were then determined using the kriging estimates of the fertilizer‐P availability index and Olsen‐extractable P. A fertilizer‐P recommendation map for the 430‐ha study site in Changhua county, Taiwan was generated by using this approach for illustration. The proposed method for generating fertilizer‐P recommendation maps can be used for variable‐rate application to maintain an adequate P status for crop production and to potentially reduce the P loss from soils.
Effect of Mixing Soil Aggregates on the Phosphorus Concentration in Surface Waters
Authors: Maguire R.O. , Edwards A.C. , Sims J.T. , Kleinman P.J.A. , Sharpley A.N.
Published: June 2010

At any time, the phosphorus (P) concentration in surface waters is determined by a complex interaction of inputs of soluble P and sorption–desorption reactions of P with sediments. This study investigated what factors control P in solution when various soil aggregates were mixed, seen as being analogous to selective soil erosion events, transport, and mixing within river systems. Fifteen soils with widely differing properties were each separated into three aggregate size fractions (2–52 μm, 53–150 μm, and 151–2000 μm). Resin P, water‐soluble phosphorus (WSP), and the phosphorus buffer capacity (PBC = resin P/WSP) were measured for each aggregate size fraction and WSP was also measured for 11 mixes of the aggregate fractions. The smallest aggregates tended to be enriched with resin P relative to the larger aggregates and the whole soils, while the opposite was true for WSP. As the PBC was a function of resin P and WSP, the PBC was greatest in the 2‐ to 52‐μm aggregate size fraction in most cases. When two aggregate size fractions were mixed, the measured WSP was always lower than the predicted WSP (i.e., the average of the WSP in the two individual aggregates), indicating that WSP released by one aggregate fraction could be resorbed by another aggregate fraction. This resorption of P may result in lower than expected solution P concentration in some surface waters. The strength with which an eroded aggregate can release or resorb P to or from solution is in part determined by that aggregate's PBC.
Evaluation of Leachate Recirculation on Nitrous Oxide Production in the Likang Landfill, China
Authors: Lee Chun Man , Lin Xue Rui , Lan Chong Yu , Lo Samuel Chun Lap , Chan Gilbert Yuk Sing
Published: June 2010

Landfill leachate recirculation is efficient in reducing the leachate quantity handled by a leachate treatment plant. However, after land application of leachate, nitrification and denitrification of the ammoniacal N becomes possible and the greenhouse gas nitrous oxide (N2O) is produced. Lack of information on the effects of leachate recirculation on N2O production led to a field study being conducted in the Likang Landfill (Guangzhou, China) where leachate recirculation had been practiced for 8 yr. Monthly productions and fluxes of N2O from leachate and soil were studied from June to November 2000. Environmental and chemical factors regulating N2O production were also accessed. An impermeable top liner was not used at this site; municipal solid waste was simply covered by inert soil and compacted by bulldozers. A high N2O emission rate (113 mg m−2h−1) was detected from a leachate pond purposely formed on topsoil within the landfill boundary after leachate irrigation. A high N2O level (1.09 μg L−1) was detected in a gas sample emitted from topsoil 1 m from the leachate pond. Nitrous oxide production from denitrification in leachate‐contaminated soil was at least 20 times higher than that from nitrification based on laboratory incubation studies. The N2O levels emitted from leachate ponds were compared with figures reported for different ecosystems and showed that the results of the present study were 68.7 to 88.6 times higher. Leachate recirculation can be a cost‐effective operation in reducing the volume of leachate to be treated in landfill. However, to reduce N2O flux, leachate should be applied to underground soil rather than being irrigated and allowed to flow on topsoil.
Soil and Plant Selenium at a Reclaimed Uranium Mine
Authors: Sharmasarkar Shankar , Vance George F.
Published: June 2010

Selenium (Se) associated with reclaimed uranium (U) mine lands may result in increased food chain transfer and water contamination. To assess post‐reclamation bioavailability of Se at a U mine site in southeastern Wyoming, we studied soil Se distribution, dissolution, speciation, and sorption characteristics and plant Se accumulation. Phosphate‐extractable soil Se exceeded the critical limit of 0.5 mg/kg in all the samples, whereas total soil Se ranged from a low (0.6 mg/kg) to an extremely high (26 mg/kg) value. Selenite was the dominant species in phosphate and ammonium bicarbonate‐diethylenetriamine pentaacetic acid (AB‐DTPA) extracts, whereas selenate was the major Se species in hot water extracts. Extractable soil Se concentrations were in the order of KH2PO4 > AB‐DTPA > hot water > saturated paste. The soils were undersaturated with respect to various Se solid phases, albeit with high levels of extractable Se surpassing the critical limit. Calcium and Mg minerals were the potential primary solids controlling Se dissolution, with dissolved organic carbon in the equilibrium solutions resulting in enhanced Se availability. Adsorption was a significant (r2 = 0.76–0.99 at P < 0.05) mechanism governing Se availability and was best described by the initial mass isotherm model, which predicted a maximum reserve Se pool corresponding to 87% of the phosphate‐extractable Se concentrations. Grasses, forbs, and shrubs accumulated 11 to 1800 mg Se/kg dry weight. While elevated levels of bioavailable Se may be potentially toxic, the plants accumulating high Se may be used for phytoremediation, or the palatable forage species may be used as animal feed supplements in Se‐deficient areas.
Relationships between Bacterial Tolerance Levels and Forms of Copper and Zinc in Soils
Authors: Saeki K. , Kunito T. , Oyaizu H. , Matsumoto S.
Published: June 2010

The effects of various fractions of copper (Cu) and zinc (Zn) on soil bacteria were evaluated by the heavy metal tolerance level of the bacterial community (IC50) in soil samples collected near a mine. The IC50values had no relationship with the total concentrations of Zn and Cu in the soils, but were weakly correlated with the 0.05MCaCl2–extractable form of each metal in the soils (Cu:R2= 0.670,p< 0.01; Zn:R2= 0.453,p< 0.05). It was found that the IC50correlated strongly with the total concentration of each metal in the extracts from water‐saturated soil samples, described below as “soil solution” (Cu:R2= 0.789,p< 0.01; Zn:R2= 0.617,p< 0.01). The speciation of these metals in the soil solutions was estimated using an equilibrium thermodynamic computer model, SOILCHEM. Simulated free Cu ion ranged from 18 to 98% of total Cu, and organic complexes of Cu ranged from <1 to 56%. In all samples, Zn existing as the free ion was estimated to be more than 80% of total Zn in the soil solutions. The IC50values were also correlated with the estimated free metal ion activities, but with slightly lower correlation coefficients than found for total concentration in the soil solutions (Cu:R2= 0.735,p< 0.01; Zn:R2= 0.610,p< 0.01). The results suggest that not only high metal ion activities, but also total dissolved metal concentrations in soil solutions may affect the bacterial community.
Soil Testing to Predict Phosphorus Leaching
Authors: Maguire Rory O. , Sims J. Thomas
Published: June 2010

Subsurface pathways can play an important role in agricultural phosphorus (P) losses that can decrease surface water quality. This study evaluated agronomic and environmental soil tests for predicting P losses in water leaching from undisturbed soils. Intact soil columns were collected for five soil types that had a wide range in soil test P. The columns were leached with deionized water, the leachate analyzed for dissolved reactive phosphorus (DRP), and the soils analyzed for water‐soluble phosphorus (WSP), 0.01 M CaCl2 P (CaCl2–P), iron‐strip phosphorus (FeO‐P), and Mehlich‐1 and Mehlich‐3 extractable P, Al, and Fe. The Mehlich‐3 P saturation ratio (M3‐PSR) was calculated as the molar ratio of Mehlich‐3 extractable P/[Al + Fe]. Leachate DRP was frequently above concentrations associated with eutrophication. For the relationship between DRP in leachate and all of the soil tests used, a change point was determined, below which leachate DRP increased slowly per unit increase in soil test P, and above which leachate DRP increased rapidly. Environmental soil tests (WSP, CaCl2–P, and FeO‐P) were slightly better at predicting leachate DRP than agronomic soil tests (Mehlich‐1 P, Mehlich‐3 P, and the M3‐PSR), although the M3‐PSR was as good as the environmental soil tests if two outliers were omitted. Our results support the development of Mehlich‐3 P and M3‐PSR categories for profitable agriculture and environmental protection; however, to most accurately characterize the risk of P loss from soil to water by leaching, soil P testing must be fully integrated with other site properties and P management practices.