bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Hydride Generation Atomic Absorption Technique for Arsenic Speciation
Authors: Masscheleyn P. H. , Delaune R. D. , Patrick W. H. 
Published: July 2010

AbstractBased on an investigation of hydride generation responses in solutions of various acidities containing nanogram quantities of arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) a sensitive analytical method for the accurate determination of inorganic and organic As species in aqueous solutions was developed. After a pH‐selective reduction, the arsenic species were condensed in a U‐tube filled with a gas chromatographic packing immersed in liquid N2. The species were then separated by slow warming of the trap and measured with an atomic absorption spectrophotometer. The arsines from inorganic As (III) were selectively generated from a solution buffered at a pH of 6.0. The solution of then further acidified to a pH corresponding to 2 M HCl and analyzed for As(V). A second sample aliquot, buffered at pH 1.5 with oxalic acid, was used for the quantitative determination of [As(III) + As(V)], MMAA and DMAA.
Influence of Fertilizer, Irrigation, and Non‐Growing Season Precipitation on Soil Nitrate‐Nitrogen under Corn
Authors: Liang B.C. , Remillard M. , MacKenzie A.F. 
Published: July 2010

AbstractCorn (Zea mays L.) production requires large amounts of N fertilizer, which may be lost due to leaching or denitrification. Prediction of the amount lost would be helpful in minimizing these losses. A field experiment was conducted to investigate the effects of fertilization, irrigation, and non‐growing season precipitation on soil NO3‐N under corn in southwestern Quebec from 1984 to 1987. The high rate of fertilization (400 kg N ha−1, 300 kg P25 ha−1, 400 kg K2O ha−1) over the normal rate (170 kg N ha−1, 100 kg P25 ha−1, 170 kg K2O ha−1) significantly increased soil NO3‐N during the growing season, and a residual effect of fertilizer rate on soil NO3‐N levels was noted in 2 of 3 yr during the non‐growing season. The high rate of fertilization, however, did not increase NO3‐N accumulation in the soil profile over the normal rate of fertilization in successive years. Irrigation significantly decreased soil NO3‐N during the growing season. At the normal rate of fertilization, gains of soil NO3‐N over winter were found with lower winter precipitation. At the high rate of fertilization, however, losses of soil NO3‐N over winter occurred in 2 of the 3 yr. The changes in NO3‐N in the rooting zone over winter depended upon the precipitation received during the preceding winter and the amount of NO3‐N in the soil the previous fall.
Accumulation and Interactions of Arsenic, Selenium, Molybdenum and Phosphorus in Alfalfa
Authors: Khattak Riaz A. , Page A. L. , Parker D. R. , Bakhtar Dariush 
Published: July 2010

AbstractArsenic (As), selenium (Se), and molybdenum (Mo) have become increasingly important in the terrestrial and agrobiological environment in some parts of the western USA. A four factorial [3 As × 3 Se × 2 Mo × 2 P concentrations] completely randomized glasshouse study was conducted to evaluate the competitive interactions between As(V), Se(VI), Mo(VI) and P using nutrient solution concentrations representative of soil solutions and agricultural drainage waters. Alfalfa [Medicago sativa L., Germain WL 512] was grown in sand culture and irrigated five times per day with half‐strength Hoagland's solution containing 0 (background), 0.05 and 0.10 mg L−1 As as Na2HAsO4; 0, 0.05, and 0.10 mg L−1 Se as Na2SeO4; and 0.01 (background) and 1.0 mg L−1 Mo as Na2MoO4. Instead of 16 mg L−1 P and 16 mg L−1 S commonly used in the half‐strength Hoagland solution, 1.0 or 4.0 mg L−1 P added as KH2PO4 and one somewhat lower level (8.0 mg L−1) S added as MgSO4 were used. The results indicated no adverse effect of As and Se on shoot yield. Selenium and P strongly depressed shoot As concentrations, and their combined effects were multiplicative rather than additive (significant Se × P interaction). Uptake of Se was decreased by increasing P, but was stimulated by increasing As, and the combined effects of P and As were approximately additive (non‐significant As × P interaction). Tissue concentrations of Mo and P were less dramatically influenced by solution concentrations of the other elements.
Sorptive Reversibility of Atrazine and Metolachlor Residues in Field Soil Samples
Authors: Pignatello Joseph J. , Huang Lee Q. 
Published: July 2010

AbstractPredictions of the fate and transport of organic compounds in soils depend on sound sorption models. The impacts of slowly reversible (nonequilibrium) sorption on compound fate are not well quantified. Soil samples containing residues of the herbicides atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl‐1,3,5‐triazine) and metolachlor (2‐chloro‐N‐[2‐ethyl‐5‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl]‐acetamide) were collected from fields 2 to 15 mo after their last application to assess the sorptive reversibility of these residues. The apparent sorption constant of the native herbicide, Kapp, was determined from the sorbed and solution concentrations after suspension of the sample in water for 24 h. The “equilibrium” sorption constant, Kd, was determined in the same samples from 24 h sorption isotherms of freshly added herbicide, taking into account the fraction of labile native herbicide (fL). The ratio Kapp/Kd varied from 2.3 to 42 and was directly related to the “age” of the residue (i.e., time between sampling and last application). The value of fL ranged from 0.056 to 0.60 and was inversely related to the age of the residue. The results indicate that contaminated samples collected from the field can contain a large fraction of contaminant in a slowly reversible sorbed state, and that this fraction increases with time.
Long‐Term Ionic Increases from a Central Appalachian Forested Watershed
Authors: Edwards Pamela J. , Helvey J. David 
Published: July 2010

AbstractThe electrical conductivity of stream water draining from an unmanaged and undisturbed control watershed has been increasing rather steadily, about 0.03 mS m−1 yr−1, since 1971. During this period, NO−3 and Ca2+ concentrations increased and were shown to mathematically account for the ionic contribution to conductivity; therefore, they are believed to be primarily responsible for the increase. However, the percentage of conductivity explained by the two ions was different over time. The percentage of conductivity attributable to NO−3 increased in a pattern very similar to concentration. In contrast, the percentage of conductivity attributable to Ca2+ decreased slightly over time. The Ca2+ is believed to be pairing with the NO−3 as the NO−3 ions leach through the soil. While nitrification in mature stands can be strongly inhibited, limited nitrification, especially in forest gaps, and high anthropogenic inputs of NO−3 probably were primary sources of the leached NO−3. Preferential adsorption of SO2−4, rather than NO−3, on soil colloids is given as an explanation for the lack of retention of NO−3 in the soil system and subsequent leaching to the stream.
Pesticide and Nutrient Movement into Subsurface Tile Drains on a Silt Loam Soil in Indiana
Authors: Kladivko E. J. , Van Scoyoc G. E. , Monke E. J. , Oates K. M. , Pask W. 
Published: July 2010

AbstractThe objectives of this study were to determine field‐scale pesticide and nutrient losses to subsurface tile drains over a 3‐yr period on a low organic matter and poorly structured silt loam soil under typical agricultural management practices. A subsurface drain spacing study was instrumented to measure drain discharge rates and to collect drainflow samples continuously on a flow‐proportional basis. Two replicates of three drain spacings (5, 10, and 20 m) were included in the study. Water samples were analyzed for all applied pesticides (atrazine, cyanazine, alachlor, carbofuran, terbufos, and chlorpyrifos)1 as well as major nutrients (N, P, K) and sediment. Small amounts of carbofuran, atrazine, cyanazine, and alachlor were detected in subsurface drainflow within 3 wk of pesticide application and after less than 2 cm net subsurface drainflow from the soil. This early arrival of pesticides at the drain is consistent with preferential flow concepts. Annual carbofuran losses in subsurface drainflow ranged from 0.8 to 14.1 g ha−1, or 0.05 to 0.94% of the amount applied to the soil. Losses of all other pesticides were ≤0.06% of the amount applied. The rank‐order of pesticide mass losses corresponded with the rank‐order of sorption coefficients of the pesticides. Total mass of pesticides, nutrients, sediment, and water removed by subsurface drains on a per‐area basis was greatest for the 5 m spacing and least for the 20‐m spacing. Annual nitrate‐N losses to subsurface drainflow ranged from 18 to 70 kg ha−1 and averaged 41.7 kg ha−1. Annual average ammonium‐N, soluble P, and K losses were 0.5, 0.04, and 2.6 kg ha−1, respectively.
Transport and Food Chain Modeling and Its Role in Assessing Human Exposure to Organic Chemicals
Authors: Jones K. C. , Keating T. , Diage P. , Chang A. C. 
Published: July 2010

AbstractThis paper reviews the underlying assumptions behind environmental transport and food chain modeling of organic chemicals, and highlights the uncertainties affecting model applicability to exposure assessment. Limitations in: (i) our knowledge of fundamental transport and transfer mechanisms, (ii) parameter quantification, and (iii) model validation currently restrict most assessment applications of models to screening calculations. Simple multimedia partitioning and screening models identify major pathways of exposure or principal environmental sinks. Their use, however, is currently limited by a lack of accurate physicochemical data for the test chemicals.Exposure assessments for specific sources (e.g., landfill sites, incinerators, factory discharges) must evaluate the fluxes of emissions from the source to the receptor population via air, soil, surface and groundwaters, and the food chain. Current organic chemical transport models introduce many uncertainties to the exposure evaluation. This may be because the models are inherently unsatisfactory, inadequately describing the fundamental transport mechanisms likely operating in the field. Further limitations arise because some of the parameters are difficult to quantify accurately, because the environmental behavior of the test chemical is poorly understood, or because of temporal and spatial variabilities in field conditions. Until these processes are more fully understood, the usefulness of detailed simulation models for human exposure evaluations will be limited. Some media‐specific models, notably of air and surface water transport, are mechanistically sound and considerably more sophisticated than the available input data. Emphasis should therefore be placed on field calibration and validation. Even a validated model, however, can not be routinely applied to other chemicals and/or at other locations.
Can Planted Forests Counteract Increasing Atmospheric Carbon Dioxide?
Authors: Vitousek Peter M. 
Published: July 2010

AbstractEstablishing new forests has been widely suggested as a means to prevent, reduce, or delay fossil fuel‐driven increases in CO2 concentrations in the atmosphere. This analysis examines the potential magnitude of C storage in biomass, emphasizing the amount of land area that could be planted to trees, the rates of C storage in developing forest plantations, and the fate of material harvested from forests. I conclude that while converting old‐growth forests to plantations is a losing proposition, there may be sufficient formerly forested land and the possibility of sufficiently high rates of C storage in young tree plantations that reforestation could remove substantial quantifies of C from the atmosphere (≥1 Pg yr−1). However, rapid net C storage is a short‐lived phenomenon, and it is unlikely that a substantial fraction of material harvested from plantations can go into long‐term storage on land. Therefore, new tree plantations designed to store C can at best cause a brief delay in the accumulation of CO2 in the atmosphere. Forest plantations designed to produce energy from biomass would represent a longer‐term contribution to reducing rates of CO2 accumulation—as long as they replaced fossil fuel‐derived energy.
Effects of Foliar and Soil Acidity on the Rhizosphere pH of Alfalfa, Corn, and Soybean
Authors: Conkling B. L. , Blanchar R. W. , Niblack T. L. 
Published: July 2010

AbstractThe acidity of ambient rainfall and its effect on soil and plants is a growing concern. Glass microelectrodes were constructed and used to investigate the effect of soil pH and foliar application of acid rain on the rhizosphere pH of alfalfa (Medicago sativa L. cv. Arrow), corn (Zea mays L. cv. B73 × MO17), and soybean [Glycine max (L.) Merr. cv. Williams 82]. Plant roots were grown in minirhizotrons containing a reformed sample of Seymour (fine, montmorillonitic, mesic Aquic Argiudoll) silt loam A horizon over a silty clay loam Bt horizon. Low and high pH levels of 4.9 and 6.2 in the A horizon and 4.0 and 5.7 in the Bt horizon were established using dilute sulfuric acid or calcium oxide, respectively. Plants received daily applications of simulated rain, which was either acid (pH 3.1) or nonacid (pH 5.6). After 5, 6, or 15 d of foliar applications to corn, soybean, or alfalfa, respectively, the rhizosphere pH was measured using a glass microelectrode. The pH values for corn and soybean increased with distance from the root while the pH values for alfalfa decreased with distance. As the soil pH increased from 4 to near 6, the difference between the pH at the root surface and the bulk soil increased from 0 to near 1. A trend for lateral root pH values at all distances to be slightly higher than main roots was observed. Increasing the pH of the A horizon had no significant effect on the rhizosphere pH of corn roots growing into the Bt horizon, but significantly increased soybean rhizosphere pH in the Bt horizon. Acid rain applications caused foliar damage, and tended to decrease rhizosphere pH, but few effects were significant. The data emphasize the effect of roots on the heterogeneity of soil pH and show that reliable rhizosphere pH measurements of in situ roots can be made using glass microelectrodes.
Chemical Fractionation and Plant Uptake of Heavy Metals in Soils Amended with Co‐Composted Sewage Sludge
Authors: Sims J. T. , Kline J. S. 
Published: July 2010

AbstractA sequential extraction method (KNO3, H2O, NaOH, Na2‐EDTA, HNO3) was used to determine the soil fractions and plant availability of Cd, Cr, Cu, Ni, Pb, and Zn in three Atlantic coastal plain soils amended with four rates of Co‐composted sewage sludge (CCSS:0, 11, 22, and 44 Mg/ha), limed to four pH values (pH 5.3–7.2) used to grow wheat (Triticum aestivum L.) and soybean (Glycine max L.) under greenhouse conditions. The average (across soils) increases in total soil Cd, Cr, Cu, Ni, Pb, and Zn, at the highest rate of CCSS were 0.1, 2, 7, 5, 14, and 14 mg/kg, respectively. Distribution of all metals, except Cd, differed in CCSS‐amended soils, with greater percentages found in the NaOH and EDTA fractions and less in the HNO3 form than in unamended soils. The more labile fractions (KNO3, H2O) of Cu, Ni, Pb, and Zn, but not Cd and Cr, increased slightly (<1 mg/kg) when CCSS was added. Liming usually resulted in minor (<5%) changes in the distribution of Cd, Cr, Ni, and Pb among soil fractions. However, liming consistently decreased NaOH extractable Cu and (KNO3 + H2O) extractable Zn, and increased the percentage of these metals in the EDTA and HNO3 fractions. Amendment with CCSS reduced wheat dry matter production in all soils, probably from decreased N availability caused by the high C/N ratio (52:1) of the compost, and slightly increased soybean growth (6–12%). The CCSS had little effect on concentrations of Cd, Cr, or Pb in either crop, but consistently increased Cu, Ni, and Zn in vegetative tissues of wheat and soybean, and Ni and Zn in soybean grain. Liming decreased Mn and Zn in wheat and soybean, and Ni in soybean grain, but rarely affected plant Cd, Cr, Cu, or Pb. With the exception of Zn, consistent correlations between total soil metal content or individual metal fractions and plant metal concentrations or uptake were not observed. However, significant multiple regression models between soil metal fractions and pH and metal concentrations in wheat and soybean were obtained for Ni (R2 = 0.42***–0.86***), Cu (R2 = 0.37**–0.57***), and Zn (R2 = 0.62***–0.82***) with all three soils.
Phosphorus Loads from Selected Watersheds in the Drainage Area of the Northern Adriatic Sea
Authors: Vighi M. , Soprani S. , Puzzarini P. , Menghi G. 
Published: July 2010

AbstractThe Po Valley is one of the most productive agricultural areas in Europe and P losses from fertilizers are often accused of being among the main factors responsible for eutrophication of the Northern Adriatic Sea. To quantify nonpoint phosphorus loads in this area, 15 small watersheds were studied. Thirteen watersheds were in the intensive agricultural area near the coast and two watersheds were in the forested mountains. Land use in the watersheds was carefully examined and P loads from various sources were theoretically evaluated and experimentally measured. The results indicate fertilization does not increase the losses of P through leaching from the coastal soils, where the measured release were in the range 0.03 to 0.21 kg P/ha per year with a mean value of about 0.1 kg P/ha per year. There is, however, a greater loss of P through soil erosion from the mountain watersheds (0.6 kg/ha per year). It can be concluded that the control of point sources must take priority over nonpoint sources in efforts to reduce accelerated eutrophication of the Northern Adriatic Sea.
Reduction of Dissolved Oxygen Concentration in Wisconsin Streams during Summer Runoff
Authors: Graczyk David J. , Sonzogni William C. 
Published: July 2010

AbstractIt is commonly believed that runoff from heavy rainfall is not detrimental to the O content of rural streams free from industrial and municipal discharges. However, evidence is presented of low dissolved O (DO) concentrations during high flows (caused by agricultural runoff during summer rainstorms) in southern Wisconsin streams. Continuous monitoring of streams with in situ oxygen meters indicated a rapid decrease in dissolved oxygen with a rise in the hydrograph. The cause of the oxygen reduction may be due to one or more factors such as (i) inflow of large volumes of runoff with low DO concentrations, (ii) the influx or resuspension of O demanding materials as a result of the storm water input, (iii) decreased O solubility caused by increased water temperature, and (iv) possible reduced photosynthetic productivity. Loss of DO is important because it appears to be associated with fish kills and declining sport fish populations in streams in the region.
Spatial Variations of Sapwood Chemistry with Soil Acidity in Appalachian Forests
Authors: DeWalle David R. , Swistock Bryan R. , Sayre Roger G. , Sharpe William E. 
Published: July 2010

AbstractStudies were conducted at five Appalachian sites to determine if chemical element concentrations in sapwood tree rings from six tree species varied with soil and soil leachate acidity. The most recent 5‐yr‐growth increment was extracted from 10 tree boles of each species at each site and analyzed for chemical content using plasma emission spectroscopy. Sapwood tree rings generally showed higher concentrations of Mn and lower concentrations of Sr at sites with lower soil pH. Differences in tree‐ring concentrations for Ca and Mn among sites were also found in soil water samples at these sites. Significant differences in soil leachate Al between sites were not duplicated in tree rings. Sapwood tree‐ring chemistry in red oak (Quercus rubra L.), black cherry (Prunus serotina Ehrh.), eastern white pine (Pinus strobus L.) and eastern hemlock (Tsuga canadensis [L.] Carr.) was generally responsive to differences in soil chemistry between sites. Chestnut oak (Q. prinus L.) and pignut hickory (Carya glabra [Mill.] Sweet) were the least responsive species tested. Overall, results show that several common tree species and selected elements are potentially useful for studying historic soil acidification trends at these study sites.
Trace Element Contamination of Soils in the Indiana Dunes
Authors: Esser K. B. , Helmke P. A. , Bockheim J. G. 
Published: July 2010

AbstractPotential soil contamination by aerosol fallout and rainout and subsequent surface accumulation of trace elements in four soils in the Indiana Dunes have been evaluated based on chemical analyses using XRF and NAA and data from the literature. Among the studied elements, Se, Sb, Zn, and As show highest concentrations in aerosols relative to the soils. The surface accumulation of trace elements in the soil is a function of the proximity to the pollution sources, vegetation, and the organic matter content of the surface horizon. In the studied soils, presence of humus is essential for the retention of trace elements added by aerosols. Enrichment in the Ah horizon compared to the B horizon is, in decreasing order, evident for Mn, Sb, Zn, As, Cs, Se, Cr, Fe, and Co. Contaminant Mn, Sb, As, Se, and possibly Zn have migrated into the E horizon. Bioaccumulation of trace elements has been insignificant in view of apparent input of the elements by deposition, possibly with the exception of Se.
The Mobile Anion Concept—Time for a Reappraisal?
Authors: Hendershot W. H. , Warfvinge P. , Courchesne F. , Sverdrup H.U. 
Published: July 2010

AbstractThe mobile anion concept has been used to support the argument that acid precipitation, containing elevated concentrations of nitrate and sulfate, is acidifying soils and surface waters. We believe that so much attention has been focused on the behavior of the strong acid anions that the effect of other important processes has, in some cases, been obscured. The emphasis, we believe, should be placed on processes that regulate H+ in solution. Thus, we propose that the mobile anion concept (as an explanation of how acid precipitation degrades soils and surface waters) be replaced with descriptions of the mechanisms believed to control the movement of both anions and cations through ecosystems.
Transformation and Sorption of 1,2‐Dibromo‐3‐Chloropropane in Subsurface Samples Collected at Fresno, California
Authors: Deeley George M. , Reinhard Martin , Stearns Stephen M. 
Published: July 2010

AbstractThe transformation rate of 1,2‐dibromo‐3‐chloropropane (DBCP) was determined in phosphate buffer solution, in groundwater, and in groundwater/aquifer solid slurries from ambient temperatures to 72 °C. From the disappearance data, the apparent Arrhenius constants for DBCP transformation were calculated and found to decrease in Ea with temperature from 19.2 (±2.4) kcal mol−1 in the 55 to 72 °C range to 12.5 (±1.8) kcal mol−1 in the 21 to 55 °C range. Low sorption values were an indication that sorption does not play a major role in the aquifer being studied. No significant difference in the disappearance rates was observed in the buffer solution (corrected for buffer effects) and in groundwater with and without solids added. However, in the phosphate buffer solution, dehydrohalogenation appeared to be the favored transformation process in contrast to the groundwater systems where hydrolysis seemed to predominate. This apparent influence of dissolved constituents or temperature on transformation mechanism or rate may restrain the use of direct extrapolation of data between systems. Applying the transformation data from this study to median field parameters, a DBCP half‐life of 6.1 yr was calculated for typical groundwater conditions in California (pH 7.8 and 21.1 °C).