Journal of Environmental Quality 31:705-710 (2002)
© 2002 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
EXECUTIVE SUMMARIES
This Issue in Journal of Environmental Quality
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Moisture and Land Use Influence Denitrification End-Products
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When soil is wet, microbes known as denitrifiers can convert soil nitrate to the gases N2, the major constituent of Earth's atmosphere, and N2O, a trace gas that contributes to global warming. Bergsma et al. created laboratory precipitation events to discover whether short-term moisture history interacts with long-term land use history to influence the relative amount of N2O produced by denitrifiers. Nitrous oxide (N2O) was one-third of the N gas produced by soil from an 11-year-old successional system, regardless of moisture history. For soil from a continuously cropped system, however, the N2O component was one-third if the soil had been wet for 2 days, but soared to nine-tenths of total N gas if the soil had been wet for only a few hours. Taking the interaction of land use and soil moisture history into consideration could lead to more accurate models of N2O flux and global warming.
T.T. Bergsma
(tbergsma{at}kbs.msu.edu)
Influence of Soil Moisture and Land Use History on Denitrification End-Products. J. Environ. Qual. 31:
711–717.
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Pesticide Volatilization Model for Turfgrass
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Chemicals used for control of turfgrass pests may volatilize, resulting in potential health hazards for turf users. Field measurements of pesticide volatilization are time-consuming, expensive, and impractical for the full range of chemicals, weather, and site conditions encountered in practice. Environmental and health assessments of pesticide volatilization must generally be based on mathematical modeling. This research has shown pesticide volatilization from turf can be reasonably predicted by a model based on estimates of turf evapotranspiration, adjusted to chemical vaporization using ratios of saturated vapor pressure and latent heat of vaporization. Testing results showed the model to be a relatively conservative approach for predicting pesticide volatilization. Predicted mean losses exceeded observations by 20%, and the model explained 67% of the observed variation in volatilization fluxes. The model was most accurate for those chemicals that exhibited the largest volatilization losses.
D.A. Haith (dah13{at}cornell.edu)
Modeling Pesticide Volatilization from Turf. J. Environ. Qual. 31:
724–729
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Roundup Ultra Enhances Soil Microbial Activity
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The objective of this study was to determine the impact of Roundup Ultra on soil microbial biomass and activity across a range of soils (9) varying in fertility. Soil microbial biomass (SMB) C was highly correlated to SMB N with and without Roundup Ultra (RU) addition. Carbon and N mineralized were also highly correlated. The slopes (C/N ratio) of the regression for both C and N mineralization decreased threefold with the addition of RU and was attributed to the 3:1 ratio of C/N by the glyphosate contained in RU. Roundup Ultra appeared to be rapidly degraded by soil microbes regardless of soil texture or organic matter content. Also, soil microbial activity appeared to be enhanced with increasing additions of RU.
S. Senseman (s-senseman{at}tamu.edu)
Effect of Roundup Ultra on Microbial Activity and Biomass from Selected Soils. J. Environ. Qual. 31:
730–735.
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Using Chemistry and Biology to Remediate TNT
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Wastes generated from the manufacture or decommissioning of munitions currently contaminate both soil and ground water at many sites around the world. Previous methods for the remediation of these wastes have been based solely on either chemical or biological means. A newly developed process that couples both chemical and biological degradation has been shown by Hess and Schrader to be more effective than either technology alone and may produce almost 80% destruction of TNT in aqueous solution. This combined abiotic and biotic process may also be useful for the remediation of munitions-contaminated soils.
T.F. Hess (tfhess{at}uidaho.edu)
Coupled Abiotic–Biotic Mineralization of 2,4,6-Trinitrotoluene (TNT). J. Environ. Qual. 31:
736–744.
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Factors Affect Nitrogen Uptake Efficiency in Citrus
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Applying N more frequently and increasing its residence time in the root zone from 2 to 8 hours increased N uptake efficiency (NUE) of young citrus seedlings from 17 to 82%. A simple conceptual model was developed for describing the potential risk of N leaching under field conditions as a function of root density, soil N concentration, and soil temperature. Using this model, it is concluded that low NUE values associated with the use of high application rates of reclaimed water for citrus irrigation appeared to be related to N displacement below the root zone prior to complete N uptake.
J.M. Scholberg
(jmscholberg{at}mail.ifas.ufl.edu)
Soil Temperature, Nitrogen Concentration, and Residence Time Affect Nitrogen Uptake Efficiency in Citrus. J. Environ. Qual. 31:
759–768.
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Sorption of Ferricyanide and Ferrocyanide Differs
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Along with large amounts of sulfate, the iron–cyanide complexes ferricyanide [Fe(CN)6]3- and ferrocyanide [Fe(CN)6]4- are present in soil on sites of former manufactured gas plants. Rennert and Mansfeldt show the presence of sulfate decreases ferricyanide sorption on goethite, but not that of ferrocyanide. Chloride and phosphate desorb ferricyanide from goethite, where phosphate does not desorb ferrocyanide at pH 3.5. The results were obtained in batch experiments with goethite suspensions, ferri- and ferrocyanide as the sorptives, sulfate as the competitive sorptive, and phosphate and chloride as desorbing agents. The study confirms that iron–cyanide complexes are sorbed on goethite by different mechanisms.
T. Mansfeldt
(tim.mansfeldt{at}ruhr-uni-bochum.de)
Sorption of Iron–Cyanide Complexes on Goethite in the Presence of Sulfate and Desorption with Phosphate and Chloride. J. Environ. Qual. 31:
745–751.
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Tillage and Irrigation Affect Environmental Quality
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It is widely recognized that long histories of frequent plowing and irrigation can result in deteriorated soil quality. However, little is known about the short-term effects of common agricultural practices such as tillage and irrigation on soil and environmental quality. Calderon and Jackson find that tillage followed by irrigation results in increased CO2 efflux from soil to the atmosphere, as well as net accumulation of nitrate in soil within a matter of days. Tillage tends to favor a physical release of soil dissolved CO2, whereas irrigation increases soil respiration and results in a CO2 efflux of biological origin. These results are based on a field experiment on a silt loam soil in the Central Valley of California. These findings underscore the importance of understanding the effect of agronomic disturbances because of the close relationship between agricultural practices and the condition of our environment and soils.
F. Calderón (fjcgztsp{at}yahoo.com)
Rototillage, Disking, and Subsequent Irrigation: Effects on Soil Nitrogen Dynamics, Microbial Biomass, and Carbon Dioxide Efflux. J. Environ. Qual. 31:
752–758.
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Phosphorus Leaches from Prairie and Corn Agroecosystems
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Most studies of P movement in soil have based conclusions on patterns of extractable soil P as a function of depth, which led to the assumption of no substantial leaching because of high P fixation capacity in mineral soils. Recent studies have indicated soil solution concentrations and subsurface P leaching are larger than once thought. Brye et al. show leachate-P concentrations from natural and managed agroecosystems exceeded 0.01 mL P L-1, and leaching was more from N-fertilized corn, regardless of tillage, than from prairie or N-unfertilized corn from which leachate-P concentrations and loads were similar. Drainage and solute leaching measurements were conducted using equilibrium-tension lysimeters. Results indicate dissolved-P concentrations in excess of acceptable critical limits can leach below the root zone of corn grown with conventional N rates and that of natural ecosystems more than 20 years after being restored from cultivated agriculture. Results also indicate N fertilization increases mobile-P concentrations in leachate solution.
K.R. Brye (kbrye{at}uark.edu)
Phosphorus Leaching under a Restored Tallgrass Prairie and Corn Agroecosystems. J. Environ. Qual. 31:
769–781.
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Precision Management of Pesticide Leaching?
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Legislation and farm management are constantly struggling with the environmental impacts of pesticide use. Van Alphen and Stoorvogel present a step-wise evaluation of the effects of soil variability and weather conditions on pesticide leaching. Leaching was strongly affected by soil variability at the within-field, field, and farm levels. Opportunities for precision management were apparent, but depended on the scale level at which environmental thresholds were implemented. When legislation is formulated in this issue, the presented step-wise evaluation can serve as a basis for identification and precision management of high-risk pesticides.
J.J. Stoorvogel
(jetse.stoorvogel{at}bodlan.beng.wau.nl)
Effects of Soil Variability and Weather Conditions on Pesticide Leaching—A Farm-Level Evaluation. J. Environ. Qual. 31:
797–805.
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Sediment Resuspension Changes Arsenic Partitioning
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Although occurring regularly in shallow lakes, the role of oxic resuspension as a mechanism for contaminant remobilization remains ill defined. Using a sequential extraction scheme, Linge and Oldham show how resuspension changes As partitioning in contaminated sediments from a shallow wetland. The sediment's inherent buffering capacity limits effect of pH variation on As remobilization or partitioning but the changes in contaminant sediment partitioning measured reflect the mechanisms controlling remobilization.
K.L. Linge (linge{at}cwr.uwa.edu.au)
Arsenic Remobilization in a Shallow Lake: The Role of Sediment Resuspension. J. Environ. Qual. 31:
822–828.
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Trace Element Migration from Pyrite Tailings
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Under toxic tailings from a pyrite mine in southern Spain, an Fe-rich layer formed in the carbonate soils, immediately underneath the tailings, when sulfides oxidized to sulfates, acidifying and polluting the soils with Zn, Cu, As, Pb, Co, Cd, Sb, Bi, Tl, and In. Less mobile elements (As, Bi, In, Pb, Sb, and Tl) concentrated toward the top of the layer, more mobile elements (Co, Cd, Zn, and Cu) precipitating where pH was basic. Concentrations, greatest in the upper 6 mm of soil, became negligible below 15 mm. Acidity degraded clay minerals while gypsum formed autigenically, as did complex salts, sulfates, jarosite, and Fe oxihydroxides.
C. Dorronsoro
(cfdorron{at}goliat.ugr.es)
Migration of Trace Elements from Pyrite Tailings in Carbonate Soils. J. Environ. Qual. 31:
829–835.
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Landscape Metrics and Estuarine Sediment Contamination
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Quantitative relationships were developed between landscape metrics and sediment contamination for 75 small estuarine systems across the mid-Atlantic and southern New England regions of the USA. Variation in sediment contamination levels across small estuarine systems was related to the surrounding land cover composition and point source discharges of pollutants. The influence of these variables was mitigated by sediment characteristics and estuarine dynamics. The landscape metrics important for explaining variation in sediment metals levels were the percent area of nonforested wetlands (negative contribution), percent area of urban land, and point source effluent volume and metals input (positive contributions). The metrics important for sediment organic levels and total polycyclic aromatic hydrocarbons were percent area of urban land (positive contribution) and percent area of nonforested wetlands (negative contribution).
J.F. Paul
(Paul.John{at}epamail.epa.gov)
Landscape Metrics and Estuarine Sediment Contamination in the Mid-Atlantic and Southern New England Regions. J. Environ. Qual. 31:
836–845.
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Landscape–Stream Water Quality Relationships
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Traditionally, the relationships between terrestrial systems and lotic systems have been studied by classifying aerial photography or satellite imagery into discrete land use–land cover (LULC) classes. Griffith et al. examined, in addition to LULC, the relationship between a satellite-derived vegetation index and landscape pattern metrics with six stream water quality parameters: P, N, conductivity, turbidity, the index of biotic integrity, and a habitat index. The results for a study region of more than 250 watersheds in Nebraska, Kansas, and Missouri revealed that, in most cases, the satellite-derived vegetation index was as highly correlated or more strongly correlated to the water quality parameters than were LULC, landscape pattern metrics, or a combination of the latter two. This study makes a new contribution to landscape–water quality studies by being among the first to examine empirical relationships between landscape pattern metrics and vegetation indices to water quality on a multistate scale. The findings underscore the usefulness of the satellite-derived normalized difference vegetation index as a potential broad-scale screening indicator of the status and condition of midwestern stream watersheds.
J. Griffith (Griffith{at}usgs.gov)
Preliminary Comparison of Landscape Pattern–Normalized Difference Vegetation Index (NDVI) Relationships to Central Plains Stream Conditions. J. Environ. Qual. 31:
846–859.
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Modeling of Microbial Contaminants on Grazing Farmlands
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Pastoral grazing practices, which create a diffuse source and disposal of animal waste, significantly contribute to the fecal contamination of catchments. The public health risk from agricultural pollution has substantial implications for farming practices and international image, both for trade and tourism. However, population distribution, transport process, and fate of fecal materials are difficult to explain using only monitored information due to the complexity of temporal and spatial variation. Tian et al. introduced an integrated and process-based modeling approach for characterizing the movement of fecal materials from land to streams and instream mobilization through interactions among processes on fecal pools in land surfaces and stream segments. The validation result showed the method is appropriate for modeling pathogenic contaminations originating from farmlands.
Y.Q. Tian
(tian{at}nature.berkeley.edu)
Spatial and Temporal Modeling of Microbial Contaminants on Grazing Farmlands. J. Environ. Qual. 31:
860–869.
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Assessing Regional Scale Nutrient Delivery
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As soil erosion and sediment delivery vary through space, nutrient delivery also varies as nutrients are often fixed to soil particles. Through the analysis of sediment deposits in flood control ponds, the regional scale variability of nutrient delivery from agricultural watersheds was determined for the Loess Belt in Belgium. Besides spatial variability in sediment dynamics, regional variations in nutrient application rates are also important in explaining nutrient delivery variability. A recent policy that redistributes surplus manure may increase total nutrient delivery in the future.
G. Verstraeten
(gert.verstraeten{at}geo.kuleuven.ac.be)
Regional Scale Variability in Sediment and Nutrient Delivery from Small Agricultural Watersheds. J. Environ. Qual. 31:
870–879.
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Sorption and Mobility of Imidacloprid in Soil
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The effect of dissolved organic carbon (DOC) on sorption and mobility of imidacloprid in a calcareous soil from southeastern Spain was evaluated. A commercial peat (DOC-PE) and high-purity tannic acid (DOC-TA) were used as sources of DOC. Results show DOC reduces imidacloprid sorption by competing with the pesticide molecules for sorption sites on the soil surface, thereby allowing an enhanced leaching process for imidacloprid and an increased ground water potential contaminant.
E. González-Pradas
(egonzale{at}ual.es)
Effects of Dissolved Organic Carbon on Sorption and Mobility of Imidacloprid in Soil. J. Environ. Qual. 31:
880–888.
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Insecticide Partitioning in a Golf Putting Green
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Research on the fate of pesticides in turf ecosystems is important for a better understanding of the potential impact of pesticide use on the environment and human health. Wu et al. investigated the environmental fate of two commonly used insecticides, trichlorfon (Dylox) and chlorpyrifos (Dursban), in a putting green under customary field management practices at the University of California-Riverside. Volatilization, clipping removal, and soil residues of the two insecticides were quantified and leaching was monitored. Results showed the fraction of applied insecticides leaving the turf putting greens was minimal.
L. Wu (Laowu{at}mail.ucr.edu)
Partitioning and Persistence of Trichlorfon and Chlorpyrifos in a Creeping Bentgrass Putting Green. J. Environ. Qual. 31:
889–895.
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Fate Modeling of Benzo[a]- pyrene in Tianjin, China
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