bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monitoring for Selected Degradation Products following a Spill of VAPAM into the Sacramento River
Authors: del Rosario Aurora , Remoy John , Soliman Violeta , Dhaliwal Joginder , Dhoot Jagdev , Perera Kusum 
Published: July 2010

AbstractFollowing a rail accident that spilled the soil fumigant VAPAM into the Sacramento River on 14 July 1991, a special study was carried out to assess the extent of contamination in Lake Shasta. A total of 32 river water samples collected on 18 July and another 316 samples collected from 22 July through 30 August were analyzed. Data obtained clearly showed the presence of the degradation products of Metham, namely, methyl isothiocyanate, carbonyl sulfide, methyl sulfide, and traces of methylamine. However, due to the emergency nature of the incident that required quick analytical turnaround times, as well as the unavailability of a satisfactory analytical method, the presence of Metham could not be demonstrated with certainty initially. Nonetheless, the laboratory's timely response to the crisis assisted public health officials in assessing the extent of the contamination and assuring the community‐at‐large that their drinking water was safe to consume. None of the degradation products analyzed were detected 1 wk after the spill.
Effect of Formulation and Tillage Practice on Volatilization of Atrazine and Alachlor
Authors: Wienhold Brian J. , Gish Timothy J. 
Published: July 2010

AbstractConservation tillage practices are being implemented by many farmers to conserve water and soil resources. These practices may modify the soil surface in ways that differentially effect dissipation of pesticide when compared to conventionally tilled fields. We measured volatilization of atrazine [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine] and alachlor [2‐chloro‐2′‐6′‐diethyl‐n‐(methoxymethyl) acetanilide] applied as either an experimental starch‐encapsulated formulation or as a commercial formulation, containing atrazine as a wettable powder and microencapsulated alachlor, to adjacent no‐till and conventionally tilled corn fields in Maryland. Both formulations were applied at the same rate; 1.7 kg ha−1 for atrazine and 2.8 kg ha−1 for alachlor. After 35 d, cumulative volatilization of alachlor from conventionally tilled fields was 14% of that applied for both formulations. Cumulative volatilization of alachlor was less from no‐till fields with 9% of the commercial formulation and 4% of the starch‐encapsulated formulation being lost. After 35 d, cumulative volatilization of the commercial formulation of atrazine from the conventionally tilled field was 9% of that applied compared with 4% of that applied to the no‐till field. Starch encapsulation reduced volatilization losses of atrazine to <2% of that applied for both tillage practices. Starch encapsulation appears to be a viable formulation modification for reducing volatilization losses of herbicides, especially from no‐till fields.
Comparing Microbial Parameters in Natural and Constructed Wetlands
Authors: Duncan Colin P. , Groffman Peter M. 
Published: July 2010

AbstractMicrobial biomass C, soil respiration, denitrification enzyme activity (DEA), and potential net N mineralization and nitrification were compared in two constructed and three natural wetlands in Massachusetts and Rhode Island. The constructed wetlands studied had marsh and wet meadow vegetation and received storm water discharge directly from a large shopping mall and its associated parking lots. The natural sites encompassed three soil drainage classes (moderately well drained, poorly drained, and very poorly drained) across an upland to wetland transition zone with red maple (Acer rubrum L.) swamps and mixed oak (Quercus sp.) forests in the transition zone. Our objective was to determine if microbial biomass and activity were similar in the constructed wetlands and the most common type of natural wetland in our area. Microbial biomass C, DEA, and potential net N mineralization and nitrification were similar among the constructed and natural wetland sites. In all cases, levels of these parameters in the constructed wetlands fell within the range of variability observed in the natural wetlands. Denitrification enzyme activity was higher (p < 0.05) in the constructed wetlands than in the moderately well drained soils at the natural sites. Soil respiration was generally lower (p < 0.05) in the constructed wetlands than in the natural wetlands. The results suggest that the constructed wetlands have a significant and active microbial community that facilitates nutrient cycling and water quality maintenance functions similar to natural wetlands. The successful development of the microbial community in these wetlands was likely due to the use of organic substrates and aggressive establishment of the plant community during wetland construction.
Fertilizer Management Effects on Leaching of Labeled Nitrogen for No‐Till Corn in Field Lysimeters
Authors: Baker J. L. , Timmons D. R. 
Published: July 2010

AbstractThe fate of labeled N fertilizer applied to no‐till corn (Zea mays L.) grown in nonweighing lysimeters was determined for 3 yr after application to evaluate NO3‐N leaching losses from point‐injection and conventional N management systems. In 1984, 15N‐enriched double‐labeled urea‐ammonium nitrate solution (UAN) at 200 kg N ha−1 was either surface‐banded or knifed‐in at the VI growth state. It was also point‐injected at either 200 or 125 kg N ha−1 in split applications at the V1, V5, and V9 growth stages. Labeled N as NO3‐N was detected in drainage from the bottom of the lysimeters (1.37 m deep) with the first significant rain (54 mm) 7 d after application for all treatments. Greatest labeled NO3‐N concentrations, however, occurred with drainage in the fall after harvest and in the spring of 1985, the year after application. In 1985, when unlabeled N was applied using the same four systems, average labeled NO3‐N concentrations and annual losses were the greatest and ranged from 1.0 to 5.1 mg L−1 and from 1.7 to 6.8 kg ha−1, respectively; the ratio of labeled NO3‐N to total NO3‐N ranged from 0.08 to 0.25. Labeled NO3‐N concentrations, losses, and ratios were smallest for the 125 kg ha−1 point injected‐split system for each of 3 yr. For all systems, about one‐fourth of the applied labeled N remained in the soil profile at the end of the study. Total recovery (77%) and recovery in grain (48% in 1984) were also greatest for the 125 kg ha−1 point‐injected system and least for the surface‐banded system (64 and 30%, respectively). Unrecovered N was believed lost through denitrification and ammonia volatilization from soil or aboveground vegetation.
Characterizing Chemical Transport Variability Due to Natural Weather Sequences
Authors: Haan C. T. , Nofziger D. L. , Ahmed F. K. 
Published: July 2010

AbstractA chemical transport model, CMLS, and a weather simulation modal, WGEN, were coupled to investigate the impact of possible and equally likely weather sequences on the travel time and relative amount of various chemicals penetrating given depths into the soil profile. Several combinations of geographical locations and soil chemical properties were investigated. Considerable variability in travel time from one weather sequence to another resulted. This variability is expressed in the form of probability distributions. Implications of this variability in terms of monitoring programs, the interpretation of model studies, and regulations on agricultural chemicals are discussed.
Field‐Scale Mobility and Persistence of Commercial and Starch‐Encapsulated Atrazine and Alachlor
Authors: Gish T. G. , Shirmohammadi A. , Wienhold B. J. 
Published: July 2010

AbstractRecent laboratory studies have shown that starch‐encapsulation (SE) may reduce leachate losses of certain pesticides. This study compares field‐scale mobility and persistence of SE‐atrazine [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine] and alachlor [2‐chloro‐N(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] to that of a commercial formulation (CF) of atrazine and alachlor. The research site consisted of four (0.25 ha) fields. Two fields were under no‐tillage management (NT) and two were under conventional tillage (CT). One field in each tillage system received SE‐formulated atrazine and alachlor, while the others received CF‐atrazine and alachlor. Chemical movement and persistence was determined by analysis of surface samples (≈3 cm) taken immediately after application and 1.1‐m soil cores collected seven times over 2 yr. No significant difference in herbicide residue levels was observed between NT and CT, but there was a herbicide formulation effect. Soil residue analysis suggests that SE‐atrazine was more persistent and less mobile than CF‐atrazine. Starch‐encapsulated‐alachlor was slightly more persistent than CF‐alachlor, but no differences in mobility between formulations was observed. The differential field behavior between SE‐herbicides is attributed to the faster release of alachlor from the starch granules. Increased atrazine persistence was attributed to the reduction of leachate losses. The reduction in atrazine leaching is likely due to the slow release from the starch granules and subsequent diffusion into the soil matrix where it is less subject to preferential flow processes.
Detoxificant Enzymes in Pumpkin Grown in Polluted Ambient Air
Authors: Ranieri Annamaria , Schenone Giorgio , Lencioni Livio , Soldatini Gian Franco 
Published: July 2010

AbstractPumpkin [Cucurbita pepo (L.) cv. Ambassador] plants were grown under either nonfiltered or filtered ambient air in open‐top field chambers (OTCs) near the urban area of Milan, Northern Italy. The effects of ambient air pollution on the enzymatic detoxification system of the leaves, both in terms of activity and isoform pattern were investigated. The data on air quality showed that ozone was the main phytotoxic pollutant present in ambient air, reaching a 7 h mean of 63 nL L−1 and a maximum hourly peak of 104 nL L−1. The peroxidase and catalase activities increased fourfold and twofold, respectively in the nonfiltered air plants in comparison to the filtered air ones. The peroxidase patterns were very modified in the polluted plants. In contrast no significant changes were found in the activity and isoenzyme pottern of superoxide dismutase. The data reported here suggest that in field‐grown pumpkin plants exposed to ambient levels of photooxidants, a stimulation of the peroxidase‐catalase detoxification system takes place.
Ferric Complexes as Catalysts for “Fenton” Degradation of 2,4‐D and Metolachlor in Soil
Authors: Pignatello Joseph J. , Baehr Katharina 
Published: July 2010

AbstractFenton‐type reactions of hydrogen peroxide with Fe compounds generate hydroxyl radical (OH‐) or other reactive species and are potentially useful for degrading organic contaminants in soil. The use of simple Fe salts is limited, however. This study investigated certain pH 6‐soluble Fe(III) complexes (Fe‐L, where L is an organic ligand) as catalysts for degradation of herbicides 2,4‐dichlorophenoxyacetic acid (2,4‐D) and metolachor (2‐chloro‐N‐[2‐ethyl‐6‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl]acetamide). Reactions were carried out in 1:1 aqueous suspensions of a topsoil (15.7 g kg−1 organic C) at the natural pH of 5.7 with herbicides at concentrations representative of a spill (2–3 g kg−1, about 0.01 mol kg−1). The two herbicides had contrasting sorption behavior in that 2,4‐D was mostly in solution, whereas metolachlor was mostly sorbed. The best results were obtained using Fe‐nitrilotriacetate (NTA) or Fehydroxyethyleniminodiacetate (HEIDA) at 0.01 mol kg−1 and [H2O2] ≥ 0.5 mol kg−1. The gallic acid complex was less effective. In 3 h, 14C‐labeled 2,4‐D was quantitatively dechlorinated and partially (15–30%) converted to 14CO2: metolachlor was 93% transformed and 29% dechlorinated. Controls using free ligand plus peroxide or peroxide alone gave little or no reaction. Fe‐L + H2O2 was superior to the Fenton reagent itself (Fe2+ + H2O2). The results of this study demonstrate that relatively mild chemical oxidation can be effective for remediation of certain contaminants in soil.
Soil Degassing of Carbon‐14 Dioxide: Rates and Factors
Authors: Sheppard Marsha I. , Ewing L. L. , Hawkins J. L. 
Published: July 2010

AbstractSoil air normally contains elevated levels of CO2 relative to the atmosphere. The primary source of soil C is plant‐root and microbial respiration. The exchange of soil and atmospheric CO2 is important to many environmental concerns, such as acid rain, global warming and waste management. Proposed disposal of high‐level nuclear wastes containing primarily inorganic 14C may provide a source of 14CO2 to the atmosphere. Field and laboratory experiments show that 14CO2 soil degassing rate constants, the flux density (Bq·m2·s−1) divided by soil inventory (Bq·m−2), range from −10−7 to −10−2 s−1, and that the loss of inorganic 14C is driven primarily by gaseous diffusion. These constants are affected by soil pH and porosity, with smaller influences of soil temperature, moisture and organic matter content. Degassing rate constants derived through mass balance calculations to estimate loss differ only by 20% from direct trapping methods. Frozen soil degassing rate constants were up to 25 times smaller than lab values, indicating that annual 14C loss rates in northern climates would be lower because of reduced gaseous diffusion during the winter months. Using our field data, we recommend an annual 14C soil degassing rate constant of −1 × 10−6 s−1 for acidic soils and a value of −5 × 10−7 s−1 for calcareous soils. For probabilistic assessment modelling, we recommend a geometric mean degassing constant of −4.3 × 10−7 s−1 with a geometric standard deviation of 3.26 for three different soils. This indicates the median half‐life of 14C in surface soils is 18 d, with a 99% confidence interval of 13 h and 640 d.
A Two‐Region Model of Preferential Flow of Chemicals Using a Transfer Function Approach
Authors: Grochulska J. , Kladivko E. J. 
Published: July 2010

AbstractPreferential flow processes are often used to explain rapid leaching of chemicals through intact soils. In this study we postulate a physical model within the framework of transfer function modeling, to describe the multiple chemical mass peaks in leachate from multiple rainstorms after a one‐tune chemical application. Two flow regions are assumed, the fast flow zone (preferential flow region) and a slow flow zone. The fast flow zone is completely leached of chemicals during each rainstorm event and subsequently replenished by the slow zone during periods between storms. Using the model equations, the chemical masses are calculated and fitted to the observed values of bromide, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐S‐triazine) and alachlor [2‐chloro‐2′‐6′‐diethyl‐N‐(methoxymethyl)‐acetanilide] and several parameters characterizing the flow are found. These parameters are: cross‐sectional areas occupied by the fast and slow flow zones, mean chemical travel time, coefficient of variation (CV) characterizing the spread of the travel times, mixing time describing the rate of the chemical mixing with the pure water, and the coefficient of the effective mass transport between the slow and fast zones. The fitted parameters are examined to see whether they are attributable to any physical or chemical explanation, and if they indicate that the model assumptions are reasonable. The mean chemical travel times and the CV of travel times are similar for all three chemicals, suggesting that sorption is negligible during flow through the fast flow zone. The rate of chemical mixing with the new rainwater, as well as the rate of mass transport from the slow zone to the fast zone between storms, is related to the sorption properties of the chemicals. The model shows promise in describing preferential flow of pesticides under multiple rainstorms from data on bromide under the same water flow conditions.
Changes of Soil Nitrate‐Nitrogen and Denitrification as Affected by Nitrogen Fertilizer on Two Quebec Soils
Authors: Liang B. C. , MacKenzie A. F. 
Published: July 2010

AbstractCorn (Zea mays L.) production may result in NO−3‐N accumulation in soils because of high N fertilizer applications. Nitrate‐N in soil may be lost by denitrification and leaching. Prediction of the amount lost would be helpful in minimizing these losses. Field experiments were conducted to investigate the effects of N fertilizer rates on soil NO−3‐N under corn on two soils of contrasting texture from 1988 to 1991 in southwestern Quebec. Denitrification as affected by previous N fertilizer rates was estimated for the nongrowing season of 1990–1991. Soil NO−3‐N levels in the fall increased linearly with increasing N fertilizer rates above the normal N rate both on clay and sandy clay loam soils. However, NO−3‐N could have been leached out of the rooting zone on the coarser Chicot soil (fine‐loamy, mixed, frigid Typic Hapludalf) in the late growing season, depending on rainfall. The changes in soil NO−3‐N over winter were a function of both soil NO−3‐N levels the previous fall and over‐winter precipitation. Denitrification losses varied from 7 to 24 kg ha−1 during the nongrowing season, increasing with N fertilizer rates only on the Ste. Rosalie clay soil (fine, mixed, frigid Typic Humaquept). In comparison with total NO−3‐N disappearance over the same period, losses of NO−3‐N due to denitrification were relatively small. Thus, significant portions of NO−3‐N losses were probably due to leaching both on clay and sandy clay loam soils.
Contaminant Enrichment and Properties of Soil Adhering to Skin
Authors: Sheppard S. C. , Evenden W. G. 
Published: July 2010

AbstractThe adhesion of contaminated soil to skin has potentially important health implications, because the contaminants may ultimately be ingested or absorbed through the skin. Previous studies indicated that the adhering soil is enriched in contaminant concentration relative to the original soil because of the selective adhesion of finer particles. This study investigated this enrichment using 11 markedly different soils. Two sandy soils consistently gave very high contaminant enrichment ratios, with a mean enrichment of 10‐fold. The other soils all had enrichment ratios above unity. Scanning electron microscopy illustrated the potential for strong adhesion of very fine clay particles. The contaminant enrichment ratios were positively correlated to enrichments in specific surface area, organic matter content, and extractable Fe content. Correlations to soil textural properties and detailed particle‐size analysis of the adhering soil indicated that 50 to 100 µm may be a critical particle size: larger grains and aggregates do not adhere readily to skin. Because of this, enrichment ratios will vary positively with the proportion of particles in the whole soil that are greater than 50 µm. A simple model is provided to predict enrichments using information from routine soil particle‐size analysis.
Radionuclides in Milk of Dairy Heifers Raised on Forages Harvested from Phosphatic Clay Soils on Reclaimed Mined Land
Authors: Staples C. R. , Umana R. , Stricker J. A. , Shibles D. , Hayen M. J. , Hissem C. D. , Lough D. S. , Demorest D. L. 
Published: July 2010

AbstractAlfalfa (AR; Medicago sativa L.) and corn (CSR; Zea mays L.) were grown in phosphatic clay soils on phosphate‐mined reclaimed land in central Florida. Corn (CSC) also was grown on unmined land and served as a control forage. Upon harvesting, plants were chopped and ensiled. Concentrations of 226Ra averaged 2.44, 0.26, and 0.15; 210Pb averaged 1.04, 0.63, and 0.52; and 210Po averaged 1.59, 0.59, and 1.26 Bq kg−1 DM for AR, CSR, and CSC, respectively. These forages were fed separately to Holstein dairy replacement heifers (Bos taurus) (n = 15 per forage) from approximately 9 to 25 mo of age. Heifers gave birth to calves at approximately 24 mo of age. Samples of milk were collected on d 1, 15, and 30 of lactation and analyzed for radionuclides. Averaged across sampling days, heifers fed AR had greater milk concentrations of 226Ra compared with those fed CSR (0.27 vs. 0.22 Bq kg−1 DM; P<0.10), which, in turn, had greater milk concentrations compared with heifers fed CSC (0.22 vs. 0.13 Bq kg−1 DM; P<0.05). Heifers fed AR also had greater milk concentrations of 210Po compared with heifers fed CSR (0.58 vs. 0.30 Bq kg−1 DM; P<0.10), but values of CSR‐fed heifers were not different from CSC‐fed heifers (0.45 Bq kg−1 DM). Lead‐210 was greater in milk from heifers fed CSR compared with those fed AR or CSC (1.38 vs. 0.94 and 0.92 Bq kg−1 DM; P<0.13), respectively. Plasma S and Cu concentrations suggested subclinical molybdenosis in heifers fed AR. However, all heifers grew at an acceptable rate, conceived normally, had normal gestation periods, gave high quality colostrum at calving, and produced similar amounts of milk.
Naturally Occurring Radionuclides in Tissue from Beef Fed Phosphatic Clay‐Grown Forages
Authors: Stricker J. A. , Hanlon E. A. , West R. L. , Shibles D. B. , Sumner S. L. , Umana R. 
Published: July 2010

AbstractThis study was designed to determine if beef animals (Bos taurus) fed forages grown on reclaimed phosphate land accumulated selected radionuclides in muscle, kidney, or bone tissues. Sixty (60) beef steers (average weight 194.5 kg) were randomly assigned to one of four treatment groups: unmined pasture (control), reclaimed pasture, full feed of alfalfa (Medicago sativa L.) hay, or full feed of corn (Zea mays L.) silage both grown on reclaimed phosphatic clay. Animals remained on the study for approximately 14 mo and were then slaughtered. Radium226 in muscle tissue from the reclaimed pasture treatment was 0.081 Bq kg−1 and higher (P<0.05) than in muscle tissue from the other three treatments. Radium226 levels in kidney tissue from the unmined and reclaimed pasture treatments were higher (P<0.05) than from both corn silage and alfalfa hay treatments. Bone 226Ra levels were higher than both muscle and kidney tissue (P<0.05), but no statistically significant differences were observed in bone samples among the four treatment groups. Results of this study indicate no food safety problems from consuming products from beef animals fed forages grown on reclaimed phosphate land.
Atrazine and Metolachlor Dissipation in Soils Incubated in Undisturbed Cores, Repacked Cores, and Flasks
Authors: Topp Edward , Smith Ward N. , Reynolds W. Daniel , Khan Shahamat U. 
Published: July 2010

AbstractThis study compared three different laboratory methods for determining soil pesticide dissipation kinetics and pathways. The dissipation kinetics of the herbicides atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and metolachlor (2‐chloro‐6′‐ethyl‐N‐(2‐methoxy‐1‐methylethyl)acet‐o‐toluidine) were examined in three soils (sandy loam, loam, clay loam) incubated for 63 d in flasks or intact cores (20 by 20 cm) under controlled moisture (field capacity) and temperature (25°C) conditions in the laboratory. The dissipation of metolachlor and atrazine were also examined in repacked cores of the loam soil adjusted to the field bulk density. The rates of atrazine or of metolachlor dissipation in soils incubated in flasks or in intact cores were indistinguishable (P<0.05). The rate of net accumulation of extractable transformation products from radiolabeled atrazine and the rate of nonextractable residue formation in soils incubated in flasks and intact cores were likewise the same. However, the rate of dissipation of metolachlor, the rate of accumulation of atrazine transformation products, and the rate of formation of nonextractable atrazine residues were all significantly slower in repacked cores of the loam soil. These results indicate that, under controlled laboratory conditions, atrazine and metolachior dissipation occured at the same rate in undisturbed soil cores and in flask incubations with soil that had been disrupted by previous air‐drying and sieving. We conclude that, at least in some soils, structure need not necessarily be maintained in laboratory soil pesticide dissipation experiments.