bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractionation of Arsenic in Soil by a Continuous‐Flow Sequential Extraction Method
Authors: Shiowatana J. , McLaren R. G. , Chanmekha N. , Samphao A. 
Published: June 2010

ABSTRACTBatch sequential extraction techniques for fractionating metals or metalloids in soils are time consuming and subject to several potential errors. The development of a continuous‐flow sequential extraction method for soil As is described and assessed, having the benefits of simplicity, rapidity, less risk of contamination, and less vulnerability to changes in extraction conditions compared with traditional batch methods. The validated method was used to fractionate soil As using water, NaHCO3, NaOH, and HCl, followed by digestion of the residue with HNO3 and HF acids. The extracts and digests were analyzed for As by graphite furnace atomic absorption spectrometry. Good recoveries of total soil As (97–115%) were obtained and fractionation data generally comparable with those obtained using conventional batch techniques. Soils from a tin‐mining area in Thailand and soils from As‐contaminated cattle (Bos taurus) dip sites in Australia were used to test the applicability of the method, and to demonstrate the usefulness of the extractogram obtained. The ability to produce detailed extractograms for As and other elements (Al, Fe, and Ca) enabled an examination of elemental associations in individual fractions. With the exception of As extracted with HCl, the extractograms generally support previous suggestions of the likely forms or associations of As present in the different soil fractions.
Heavy Metal Interactions with Phosphatic Clay: Sorption and Desorption Behavior
Authors: Singh S. P. , Ma L. Q. , Harris W. G. 
Published: June 2010

ABSTRACTHeavy metals produced and released during agricultural and industrial activities may pose a serious threat to the environment. This study investigated the effectiveness of phosphatic clay, a by‐product of the phosphate mining industry, for immobilizing heavy metals (Pb+2, Cd+2, and Zn+2) from aqueous solutions. A batch equilibrium technique was adopted to evaluate metal sorption in the presence of 0.05MKNO3background electrolyte solution. The amounts of metals sorbed onto phosphatic clay decreased in the order Pb+2> Cd+2> Zn+2Desorption data suggest that a large fraction of metals sorbed onto phosphatic clay stayed intact under a wide variation in extracting solution pH (ranging from 3 to 10). Desorption rates were slowest for Pb followed by Cd and Zn. Only 8.1 to 23.1% of Pb, 8.4 to 45% of Cd, and 21.9 to 73.9% of Zn sorbed on phosphatic clay was mobilized by USEPA toxicity characteristic leaching procedure (TCLP) solutions at pH 2.93 ± 0.05 and 4.93 ± 0.05, respectively. Formation of fluoropyromorphite [Pb10(PO4)6(F2)], confirmed by scanning electron microscopy (SEM) and X‐ray diffraction (XRD), after reaction of aqueous Pb with phosphatic clay suggested that precipitation remained the dominant mechanism for Pb removal from aqueous solution. In the case of aqueous Cd and Zn interaction with phosphatic clay, we are not able to confirm the formation of a new amorphous and/or crystalline phase on the basis of available information. Other possible sorption mechanisms for Cd and Zn may include sorption and coprecipitation. Thus, phosphatic clay may be an effective amendment for in situ immobilization of heavy metals in contaminated soils and sediments.
Irrigation with Effluents: Effects of Prewetting Rate and Clay Content on Runoff and Soil Loss
Authors: Mamedov A.I. , Shainberg I. , Levy G.J. 
Published: June 2010

ABSTRACTStability of soil surface aggregates and irrigation water quality significantly affect runoff and soil erosion. Slow wetting of aggregates prevents slaking. We hypothesized that wetting rate will affect a soil's susceptibility to seal formation and soil erosion, and that this susceptibility will differ between effluent‐ and fresh water (FW)–irrigated soils. Effects of prewetting rate (2, 4, 8, and 64 mm h−1) on runoff and interrill erosion from five Israeli soils exposed to 60 mm of simulated rain were studied in the laboratory. Soils were taken from fields irrigated with FW or effluents for >15 yr. In general, for effluent‐ and FW‐irrigated samples, runoff and soil loss were greatest for the soil with 22.5% clay; at lower or higher clay contents, less runoff and soil losses were noted. Runoff and soil loss decreased with decreasing prewetting rate (PWR) mainly in soils with clay content ≥38%. Total runoff and soil loss were higher in effluent‐irrigated soils than in FW‐irrigated ones in the loamy sand (8% clay) only. Greater soil losses occurred from effluent‐irrigated soils exposed to fast PWR (64 m h−1) compared with FW‐irrigated soils. In general, PWR had similar effects on total runoff and soil loss for effluent‐ and FW‐irrigated soils. Use of wetting rates ≤8 mm h−1 to prevent aggregate slaking decreased runoff and soil loss from loam and clayey soils exposed to simulated rainfall of high kinetic energy (15.9 kJ m−3). Long term irrigation with effluents in soils containing >20% clay did not seem to adversely affect soil susceptibility to runoff and soil loss in soils exposed to simulated rainfall, beyond that observed in FW‐irrigated soils.
Seven Years of Biosolids versus Inorganic Nitrogen Applications to Tall Fescue
Authors: Cogger Craig G. , Bary Andy I. , Fransen Steven C. , Sullivan Dan M. 
Published: June 2010

ABSTRACTRepeated applications of municipal wastewater biosolids is cost effective for biosolids managers, but may lead to undesirable accumulations of nutrients or contaminants. We evaluated the effects of seven years of biosolids applications on tall fescue (Festuca arundinacea Schreb.) production and nutrient availability. We compared two types of Class A biosolids applied to tall fescue on a sandy loam in western Washington. Mean annual biosolids rates of 290, 580, and 870 kg total N ha−1 yr−1 were compared with inorganic N and zero‐N controls using a randomized complete block design. We measured yield and N uptake for each forage harvest, plant tissue metals at selected harvests, soil nitrate each fall, diethylenetriaminepentaacetic acid (DTPA)‐extractable metals after five years of applications, and soil pH, available P, and organic C after seven years. Forage yields increased with biosolids rate. Apparent nitrogen recovery (ANR) for biosolids averaged 18% in 1993 (Year 1), 35% in 1994, and 46% in 1999. The ANR for inorganic N averaged 62% from 1994–1999. Residual soil nitrate was less than 25 kg ha−1 for all treatments through 1995, but increased beginning in 1996 for the high biosolids rate. Biosolids increased soil organic C levels by 2 to 5 g kg−1 and Bray‐1 P levels by 300 to 600 mg kg−1 (0–15 cm depth). Plant tissue Zn increased from 24 to 66 mg kg−1 at the highest application rate. Nearly all of the DTPA‐extractable metals remained in the 0‐ to 8‐cm soil depth.
Rapid, Sensitive, Microscale Determination of Phosphate in Water and Soil
Authors: D'Angelo Elisa , Crutchfield J. , Vandiviere M. 
Published: June 2010

ABSTRACTA rapid and sensitive analysis of inorganic and organic phosphorus (P) is needed to analyze water and soil extracts at submicromolar concentrations. The proposed method, based on the complexation of malachite green with phosphomolybdate under acidic conditions, was adapted to a 96‐well microtiter plate format, and was tested for matrix interferences using 15 soils and some common extractants, including water, KCl, CaCl2, NaOH, and HCl. The accuracy of P determination was affected when CaCl2 and HCl concentrations were greater than 0.1 M and when NaOH concentration exceeded 0.4 M Potassium chloride concentration up to 1 M did not interfere with P determination. The molar absorptivity was 46841 M−1 cm−1 and the reagent blank absorbance was 0.071 ± 0.003 (n = 10). At the 99% confidence limit, the method detection limit was calculated to be 0.006 mg P L−1 Recovery of added inorganic P in different types of soils and extracts ranged between 95 and 112% with an average of 102%. The proposed microplate method allows P to be determined rapidly in a wide range of soil types and extracts and requires limited volume (20–200 μL). The procedure uses limited quantities (40 μL) of two stable reagents (>1 yr), and generates low amounts of hazardous waste.
The Relationship between Microbial Carbon and the Resource Quality of Soil Carbon
Authors: Webster E.A. , Hopkins D.W. , Chudek J.A. , Haslam S.F.I. , Šimek M. , Pîcek T. 
Published: June 2010

ABSTRACTThe biological health of soil is an important aspect of soil quality because of the many critical functions performed by organisms in soil. Various indicators of soil quality have been proposed, but measurements of microbial biomass are most commonly used. During decomposition of plant residues in soil the relative intensities of the O‐alkyl‐C signal decreases and the alkyl‐C signal increases in nuclear magnetic resonance (NMR) spectra. This leads to the suggestion that the alkyl‐C to O‐alkyl‐C ratio of a soil may indicate the degree of decomposition. Consequently, the overall resource quality of soil C as a substrate for heterotrophic microorganisms may be inversely related to the alkyl‐C to O‐alkyl‐C ratio. Our hypothesis is that a relationship exists between the size of the soil microbial community (microbial biomass) and the quality of soil carbon as a resource for microorganisms. New data have been combined with previously published data to show that there was a significant, negative correlation between the biomass C to total C (Cmic to Corg) ratio and the alkyl‐C to O‐alkyl‐C ratio (p < 0.01), which supports our hypothesis.
Potential Mineralization of Four Herbicides in a Ground Water–Fed Wetland Area
Authors: Larsen Lise , Jørgensen Claus , Aamand Jens 
Published: June 2010

ABSTRACTHerbicides may leach from agricultural fields into ground water feeding adjacent wetlands. However, only little is known of the fate of herbicides in wetland areas. The purpose of the study was to examine the potential of a riparian fen to mineralize herbicides that could leach from an adjacent catchment area. Slurries were prepared from sediment and ground water collected from different parts of a wetland representing different redox conditions. The slurries were amended with O2, NO−3, SO2−4, and CO2, or CO2alone as electron acceptors to simulate the in situ conditions and their ability to mineralize the herbicides mecoprop, metsulfuron‐methyl, isoproturon and atrazine. In addition, the abundance of bacteria able to utilize O2, NO−3, SO2−4+ CO2, and CO2as electron acceptors was investigated along with the O2–reducing and methanogenic potential of the sediment. The recalcitrance to bacterial degradation depended on both the type of herbicide and the redox conditions pertaining. Mecoprop was the most readily degraded herbicide, with 36% of [ring‐U‐14C]mecoprop being mineralized to14CO2under aerobic conditions after 473 d. In comparison, approximately 29% of [phenyl‐U‐14C]metsulfuron‐methyl and 16% of [ring‐U‐14C]isoproturon mineralized in aerobic slurries during the same period. Surprisingly, 8 to 13% of mecoprop also mineralized under anaerobic conditions. Neither metsulfuron‐methyl nor isoproturon were mineralized under anaerobic conditions and atrazine was not mineralized under any of the redox conditions examined. The present study is the first to report mineralization of mecoprop in ground water in a wetland area, and the first to report mineralization of a phenoxyalcanoic acid herbicide under both aerobic and anaerobic conditions.
Nitrogen and Carbon Leaching in Agroecosystems and Their Role in Denitrification Potential
Authors: Brye K.R. , Norman J.M. , Bundy L.G. , Gower S.T. 
Published: June 2010

ABSTRACTThe drainage of water and leaching of dissolved constituents represent major components of agroecosystem mass budgets that have been exceedingly difficult to measure. Equilibrium‐tension lysimeters (ETLs) were used to monitor drainage, nitrogen (N), and carbon (C) leaching through Plano silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudoll) for a 4‐yr period in a restored prairie and N‐fertilized no‐tillage and chisel‐plowed maize (Zea mays L.) agroecosystems. Mean drainage recorded during 4 yr for the prairie, no‐tillage, and chisel‐plowed ecosystems totaled 461, 1116, and 1575 mm and represented 16, 33, and 47% of precipitation plus melting of drifted snow received, respectively. Total inorganic N leaching losses during the 4‐yr period for the prairie, no‐tillage, and chisel‐plowed ecosystems were 0.6, 201, and 179 kg N ha−1, respectively. Inorganic N leaching represented 26 and 24% of applied fertilizer N additions to the no‐tillage and chisel‐plowed agroecosystems. Total dissolved C leaching losses were 119, 435, and 502 kg C ha−1 for the prairie, no‐tillage, and chisel‐plowed ecosystems, respectively. Sufficient dissolved organic carbon (DOC) and nitrate N (NO−3–N) existed in the prairie and agroecosystems to support subsoil denitrification. Potential denitrification, however, was limited by insufficient lengths of saturated soil conditions in all three ecosystems, the supply of DOC in the agroecosystems, and the supply of nitrate N in the prairie. Based on available DOC and nitrate N, the maximum contribution of denitrification below the root zone in the agroecosystems was less than 25% of the total amount of leached nitrate N and the probable contribution of denitrification was much less.
Oxygen‐Deficient Waters along the Japanese Coast and Their Effects upon the Estuarine Ecosystem
Authors: Suzuki Teruaki 
Published: June 2010

ABSTRACTDevelopment of hypoxia in Japan has been confirmed in the inner part of almost every major bay of Japan on the Pacific Coast from Tokyo southward. This paper presents multiple aspects (present condition, hydraulic mechanism, effect upon fisheries, historical progress and nutrient budget between sediment and water) using Mikawa Bay, where Japan's most serious hypoxia occurs, as an example. Although hypoxia basically results from the increase of nutrient load input from domestic and livestock sources, the intense reclamation of shallows (including tidal flats) and the large reduction in river flow due to farmland irrigation drastically accelerated dissolved oxygen deficiency. Oxygen‐deficient waters in Mikawa Bay are large enough to strip the water purification capacity of the remaining shallows. Unfortunately, the shallows have turned from a purifier to a source of nutrient load. These conditions are more or less common in all bays where the dissolved oxygen–deficient waters have been reported. To break this cycle, dissolved oxygen deficiency must be contained to the extent that the purification capacity of the shallows can be restored to an efficient level. For this purpose, the first thing to do is to restore tidal flats over an extensive area and to recover sufficient water flow, which may be a more urgent imperative than reducing the nutrient load input.
Chesapeake Bay Eutrophication: Scientific Understanding, Ecosystem Restoration, and Challenges for Agriculture
Authors: Boesch Donald F. , Brinsfield Russell B. , Magnien Robert E. 
Published: June 2010

ABSTRACTChesapeake 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

ABSTRACTSeasonally 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTIn 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.