Journal of Environmental Quality 31:1065-1070 (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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Measuring Gas Production and Movement in Soil
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Air contaminated from VOC (volatile organic compound) and greenhouse gases are of special interest for the environment. Better instruments are needed to estimate gas movement in soil and to the air. Allaire et al. present a 2-D system for measuring VOC volatilization at the soil surface and, simultaneously, its movement in the soil profile. The importance of lateral variability, pressure distribution in the profile, and irrigation on volatilization is shown. Different uses of their measuring system are suggested.
S. Allaire (sallaire{at}sga.ulaval.ca)
A Dynamic Two-Dimensional System for Measuring Volatile Organic Compound Volatilization and Movement in Soils. J. Environ. Qual. 31:1079–1087.
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N2O Emissions from Maize–Groundnut Rotation
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Agricultural soils of the humid tropics, receiving large amounts of inorganic and organic N fertilizers, are conducive to N2O production and release. Khalil et al. report that added chicken manure showed a higher and persistent influence on N transformation and N2O release than inorganic N alone or in combination with maize and groundnut residues. The mineral N added or mineralized from organic amendments became low by 2 to 4 weeks, coinciding with the small N2O fluxes or its consumption in a few isolated instances. Direct annual emission from a maize–groundnut rotation was lower than that estimated using methodology of the Intergovernmental Panel on Climate Change. The N2O–N loss of N applied, either as inorganic N alone or in combination with organic amendment plus N-fixed, ranged from 0.49 to 0.83% from the cropping system, indicating an insignificant response from an agronomic standpoint.
M.I. Khalil
(khalil_ibrahim{at}yahoo.com)
Nitrous Oxide Emissions from an Ultisol of the Humid Tropics under Maize–Groundnut Rotation. J. Environ. Qual. 31:1071–1078.
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Atmospheric MTBE in Rural California
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Atmospheric methyl tertiary butyl ether (MTBE) was measured near the University of California–Berkeley Blodgett Forest Research Station on the western slope of the Sierra Nevada Mountains of California. Concentrations were generally lower than 0.3 ppb and the diurnal cycle reflected transport from and dilution of sources in the Central Valley. Correlations and ratios of MTBE to other anthropogenic hydrocarbons and back-trajectory analysis were used to determine an average regional hydroxyl radical concentration, and to conclude that nonequilibrium ground deposition is small compared with oxidation in the atmosphere.
G.W. Schade
(gws{at}nature.berkeley.edu)
Atmospheric Methyl Tertiary Butyl Ether (MTBE) at a Rural Mountain Site in California. J. Environ. Qual. 31:1088–1094.
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Transport of Bacteriophage in Shale Saprolite
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Tracer experiments in a column of undisturbed fractured shale saprolite collected at a depth of 1.2 to 1.4 m show that microbial contaminants, in this case the bacteriophage strains PRD-1 and MS-2, can be transported rapidly and with little attenuation in these materials. Bacteriophage retention decreased substantially as the saturated flow rate increased, suggesting microbial transport in these materials will tend to be episodic, coinciding with heavy rains and rapid flow rates.
L.D. McKay (lmckay{at}utk.edu)
Influence of Flow Rate on Transport of Bacteriophage in Shale Saprolite. J. Environ. Qual. 31:1095–1105.
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Competition for Sorption Sites on Zeolite
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Competition between cationic surfactants and metal cations for sorption onto negatively charged mineral surfaces has strong influence on the use of surfactants for environmental remediation. Sorption capacity and the affinity for Cs+, Sr2+, La3+, Pb2+, and Zn2+ of clinoptilolite decreased as surfactant loading on the zeolite increased, indicating pre-sorbed cationic surfactants block sorption sites for metal cations. On the other hand, sorption of cationic surfactants on zeolite preloaded with different metal cations and the desorption of pre-sorbed metal cations by cationic surfactants were strongly affected by chain length of the surfactant tail groups. More metal cations desorbed as the surfactant chain lengths increased, indicating cationic surfactant may be used as desorbing agents for ex situ soil decontamination.
Z. Li (li{at}uwp.edu)
Influence of Quaternary Ammonium on Sorption of Selected Metal Cations onto Clinoptilolite Zeolite. J. Environ. Qual. 31:1106–1114.
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Competitive Adsorption between Arsenic and Organic Acids
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Naturally occurring, ubiquitous organic acids such as humic (Hap), fulvic (FA), or citric acid (CA) may increase the bioavailability of arsenate [As(V)] and arsenite [As(III)] at the iron oxide–water interface. Arsenate adsorption on ferrihydrite was lowered in the presence of CA between pH 3 and 5, whereas Hap and FA had no effect on As(V) adsorption. The adsorption of As(III) on ferrihydrite was lowered by CA and FA between pH 3 and 7, but not by Hap. Results of this study stand in contrast to a previous study with goethite and show the importance of the adsorbent phase in competitive adsorption reactions of the arsenic–organic acid system. Additional research is needed examining other common mineral surfaces.
M.J. Eick (eick{at}vt.edu)
Adsorption of Arsenate and Arsenite on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon. J. Environ. Qual. 31:1115–1123.
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Fate of Dimethyldiselenide
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Behavior of dimethyldiselenide in the soil environment is important in understanding the biogeochemical cycling of selenium (Se). Zhang and Frankenberger report dimethyldiselenide is not a stable form of Se in soil. Dimethyldiselenide was highly dissolved in water and sorbed onto soil. Chemical and biological transformations of dimethyldiselenide converted a large amount of dimethyldiselenide to elemental Se and nonvolatile organic Se. Microbial conversion of dimethyldiselenide to dimethylselenide indicated dimethyldiselenide may be one of the important precursors of dimethyselenide in the soil environment.
W.T. Frankenberger, Jr.
(williamf{at}orange.ucr.edu)
Fate of Dimethyldiselenide in Soil. J. Environ. Qual. 31:1124–1128.
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Copper Adsorption–Desorption in Contaminated Soils
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Copper (Cu) concentrations have reached contaminating levels in some soils through applications of Cu-containing fungicides, stable manures (e.g., pig slurry), and liquid or solid wastes from Cu-related mining and manufacturing. Understanding adsorption–desorption behavior of Cu2+ is important for management of Cu-contaminated soils. Yu et al. show adsorption and desorption of Cu2+ at contaminated levels in two red soils could be described by the Freundlich and the simple Langmuir models. Adsorption of Cu2+ decreased with soil pH and the number of protons released per Cu2+ adsorbed increased with increasing Cu2+ concentration up to a Cu loading of 2 g kg-1 soil. The distribution coefficient (Kd) of Cu2+ in the soils decreased exponentially with increasing Cu2+ loadings. After five successive extractions with 1 mol L-1 NH4Ac (pH 5.0), 61 to 95% of the total adsorbed Cu2+ was desorbed, indicating high release potential of the adsorbed Cu2+.
Z.L. He (zhe{at}mail.ifas.ufl.edu)
Adsorption–Desorption Behavior of Copper at Contaminated Levels in Red Soils from China. J. Environ. Qual. 31:1129–1136.
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Low Levels of Lead Found in Appalachian Hardwoods
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While there have been many studies assessing the condition of the spruce–fir ecosystem in the southern Appalachian Mountains, there is scarce published data regarding northern hardwood forest health in that region. Fisher et al., using dendrochemical techniques, examined concentrations of Pb and Ca in growth rings of an important northern hardwood species, American beech, at Mount Rogers and Whitetop Mountain, Virginia. They examined the relationships between metal concentration and stem growth patterns at research plots established at two elevations (1371 and 1524 m). Decadal measurements of ring widths were inversely correlated with Pb and Ca concentrations and higher-elevation plots contained increased concentrations of Pb. Lead and calcium concentrations in rings were associated with decreased growth measurements. Although an increased trend of both Pb and Ca concentrations was observed over time, specifically during the 1860s and mid-1900s, maximum concentrations of Pb found in tree rings located on Mt. Rogers and Whitetop Mountain were considered lower than levels found in tree rings taken in other regions that are considered contaminated.
L.S. Fisher (fishers{at}ornl.gov)
Dendrochemical Analysis of Lead and Calcium in Southern Appalachian American Beech. J. Environ. Qual. 31:1137–1145.
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Selenium Sequestration Revealed by Stable Isotopes
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Selenium (Se) contamination is a pervasive concern in the western San Joaquin Valley of California, particularly in areas associated with agricultural drainage water. Selenium stable isotope ratios can be used as indicators of Se transformation processes, and are especially useful in distinguishing between (i) plant and algal uptake (assimilation) of Se oxyanions followed by deposition and mineralization of the reduced Se, and (ii) chemical or bacterial respiratory reduction of Se oxyanions to elemental Se. Herbel et al. measured 80Se/76Se ratios in macrophytes, surface and shallow ground waters, and sediment extracts of constructed flow-through wetland, agroforestry, and evaporation pond systems, which were designed to treat or impound Se-affected drainage water. Comparisons of the 80Se/76Se values indicate that assimilatory reduction, deposition, and mineralization, rather than chemical or bacterial respiration reduction, was the dominant reduction and accumulation pathway in sediments at the investigated sites. This work demonstrates the utility of Se stable isotope analyses in the first such study of San Joaquin Valley contamination.
M.J. Herbel (mjherbel{at}usgs.gov)
Selenium Stable Isotope Ratios in California Agricultural Drainage Water Management Systems. J. Environ. Qual. 31:1146–1156.
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Soil Factors Contributing to Trace Metal Mobility
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Dissolved organic matter is expected to contribute to trace metal mobility in soils of neutral to alkaline pH following amendment with biosolids. The concentrations of dissolved organic carbon (DOC) and Cu collected 10 cm below the zone of biosolids addition were increased in both an irrigated and dryland soil, resulting in a positive correlation between Cu and DOC. Zinc mobility was positively correlated with electrical conductivity, suggesting a cation exchange mechanism influenced Zn mobility.
D. Heil (dheil{at}lamar.colostate.edu)
Solution Chemistry Influence on Metal Mobility in Biosolids-Amended Soils. J. Environ. Qual. 31:1157–1165.
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Winter-Applied Manure Alters Snowmelt
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Although the practice of manure landspreading in winter is thought to lead to excessive P runoff losses, field experiments to explore the issue are extraordinarily difficult. To learn the effects of winter-applied manure on snowmelt, experiments were performed to partition the problem into tractable parts, and the phenomena was captured in a mechanistic snow ablation model. The manure–snow model simulated the observed delay in snow cover disappearance caused by manure. Model simulations showed that during intense melting events, manure reduced the energy available for melt to the underlying snow. Even relatively light applications of manure gave substantial reductions in peak melt rate. Lower peak rates beneath manure may allow greater infiltration of meltwater compared with bare snow. This enhanced infiltration and attenuated peak water outflow rate may partially mitigate the enhanced likelihood of P runoff of unincorporated winter-spread manure.
C. Kongoli (Cezar.Kongoli{at}noaa.gov)
Influence of Manure Application on Surface Energy and Snow Cover: Field Experiments. J. Environ. Qual. 31:1166–1173.
Influence of Manure Application on Surface Energy and Snow Cover: Model Development and Sensitivities. J. Environ. Qual. 31:1174–1183.
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Modeling Atmospheric N Deposition and Transport
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Atmospheric deposition of nitrate-N and ammonium-N has been identified as a major factor in the decline of water quality in the Chesapeake Bay, and may account for 25 to 80% of the total N load. Recent estimates were reassessed using a high-resolution wet deposition model, improved dry deposition and nutrient retention estimates, existing soils and land use data, and geographic information systems software. Model results for years 1984 to 1996 indicate atmospheric N deposition represents 20 to 32% of the total N load to the Chesapeake Bay. Data suggest dry N deposition is considerably less than previous estimates, and substantial inter- and intra-annual variation in N deposition rates exist that should be considered in management strategies.
S.A. Sheeder (sas371{at}psu.edu)
Modeling Atmospheric Nitrogen Deposition and Transport in the Chesapeake Bay Watershed. J. Environ. Qual. 31:1194–1206.
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Vegetation Change Linked to Nutrient Losses
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Hillslopes in central California, once covered by coastal sage scrub communities, have been largely replaced with annual grasslands. Fierer and Gabet conducted rainfall simulation experiments to determine the impact of this vegetation change on rates of C and N removal in surface runoff waters. Results from these experiments were incorporated into a numerical model to estimate hillslope scale sediment-bound nutrient losses. They found type conversion of coastal sage scrub to annual grasslands increases hillslope nutrient losses and this may have profound effects on stream water quality in the region.
N. Fierer (fierer{at}lifesci.ucsb.edu)
Carbon and Nitrogen Losses by Surface Runoff following Changes in Vegetation. J. Environ. Qual. 31:1207–1213.
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Agroforestry Reduces NPS in Water
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Agroforestry practices purport to play a significant role in nonpoint-source pollution reduction. Udawatta et al. have demonstrated that agroforestry and contour strips reduce runoff, sediment, phosphorus, and nitrate loss from agricultural watersheds in a corn–soy-bean rotation. Further, as trees grow and their root systems expand, greater impacts are expected, especially in further reducing the export of nutrients off site.
R.P. Udawatta
(udawattar{at}missouri.edu)
Agroforestry Practices, Runoff, and Nutrient Loss: A Paired Watershed Comparison. J. Environ. Qual. 31:1214–1225.
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Polymer Effects on Herbicide Sorption
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Application of polymers to soil to enhance infiltration and reduce soil erosion is a growing practice. Among the polymers, polyacrylamide is the one most frequently used. The impacts of polyacrylamide and other polymers on sorption of herbicides were assessed by the batch equilibrium method. Polyacrylamide treatment kinetically reduced the sorption rate of all herbicides. The effects of polymers on the equilibrium sorption amounts of herbicides depend on the charge and molecular characteristics of polymers and herbicides, and salt concentration in the solution. At high salt concentrations, equilibrium sorption amounts of all herbicides were essentially unaffected or slightly decreased by the polymers, while at low salt concentrations, polymers could slightly increase or decrease herbicide sorption. Electrostatic interaction and competition for sorption sites are two primary underlying mechanisms for the polymer influence.
L. Wu (laowu{at}mail.ucr.edu)
Anionic Polyacrylamide Effects on Sorption and Desorption of Metolachlor, Atrazine, 2,4-D, and Picloram. J. Environ. Qual. 31:1226–1233.
Picloram and Napropamide Sorption as Affected by Polymer Addition and Salt Concentration. J. Environ. Qual. 31:1234–1239.
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Site-Specific Fertilizer Phosphorus Application
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Site-specific management of P is done to optimize crop production and to minimize the loss of P from soils. The spatial variability of the available P before fertilizer application (P0) and the P fixation tendency of soil both need to be taken into account for variable-rate P application. Lee et al. document the spatial variability of the fertilizer P availability index (Fp), which shows the P fixation tendency, and develop a strategy that takes the spatial distribution of this index into account for site-specific P application. They used ordinary kriging in spatial interpolation of Fp and P0. The spatial distributions of both Fp and P0 were simultaneously used to make a recommendation map for variable-rate P application.
D.Y. Lee (dylee{at}ccms.ntu.edu.tw)
Site-Specific Phosphorus Application Based on the Kriging Fertilizer-Phosphorus Availability Index of Soils. J. Environ. Qual. 31:1248–1255.
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Protect Topsoil from Wind Erosion in Northwest China
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For decades, wind erosion has triggered dust/sand storms, buffeting Beijing and areas of northwest China to the point of being hazardous to human health while rapidly eroding crop and livestock productivity. The EPIC (Environmental Policy Integrated Climate) field-scale simulation model was used to assess long-term impacts of improved crop rotations and crop residue management practices on wind erosion in Inner Mongolia, China. Simulation results indicate preserving crop stalks until land is prepared by zone tillage for the next year's crop in lieu of using stalks as a source of heating fuel or livestock fodder reduces wind erosion by 60%. At the same time, grain and potato yields were maintained or improved. Reductions in erosion also resulted from delaying stalk removal until late January through late April. Altering current crop rotation systems by expanding corn, wheat, and millet, and reducing potato and pea production, reduced simulated wind erosion, thus diminishing the severity of dust/sand storms in northwestern China. Saving and protecting topsoil over time will sustain land productivity and has long-term implications for improving conditions of rural poverty in the region.
E. Wang (wang{at}tarleton.edu)
Simulated Effects of Crop Rotations and Residue Management on Wind Erosion in Wuchuan, West-Central Inner Mongolia, China. J. Environ. Qual. 31:1240–1247.
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Water Quality in Georgia Streams
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Since 1994, water-quality constituents have been measured monthly in three adjacent Coastal Plain watersheds in southwestern Georgia, and included periods of record flooding and record drought. The watersheds are human-dominated with row-crop agriculture and managed forestlands being the major land uses. Suspended particles, dissolved organic C, NH4–N, and soluble reactive P concentrations were greater during wet and flood periods compared with dry and drought periods for each stream. Regional hydrologic conditions had little effect on NO3–N or dissolved inorganic C. Although substantial human land use occurred within watersheds, water quality was generally good and can be attributed to low stream drainage density and relatively intact floodplain forests.
S. Golladay (sgollada{at}jonesctr.org)
Effects of Flooding and Drought on Water Quality in Gulf Coastal Plain Streams in Georgia. J. Environ. Qual. 31:1266–1272.
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Geographic Variability of Microbes from Farm Animals
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Some microbial source tracking methods rely on a host origin database to identify environmental isolates. It is not well understood how geographically variable (i.e., cosmopolitan or endemic) these host origin isolates are. Hartel et al. used one microbial source tracking method, ribotyping, to determine the geographic variability of the fecal coliform, Escherichia coli, from one location in Idaho and three locations in Georgia for cattle, horses, swine, and chickens. The percentage of ribotype sharing within an animal species increased with decreased distance between geographic locations for cattle and horses, but not for swine and chicken. These results suggest the ability to match environmental isolates to a host origin database might depend on environmental and host origin isolates that ideally are not geographically separated.
P.G. Hartel
(pghartel{at}arches.uga.edu)
Geographic Variability of Escherichia coli Ribotypes from Animals in Idaho and Georgia. J. Environ. Qual. 31:1273–1278.
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Predict Phosphorus Loss from Soil
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The degree of phosphorus saturation (DPS) has been used as an indicator of the amount of P likely to be mobilized from a soil. In the Netherlands, studies on acid, coarse-textured soils identified a DPS value of 25% as contributing to groundwater pollution with P. The original procedure of the Dutch calculated DPS as a percentage of oxalate-extractable P to the sum of oxalate-extractable Fe and Al. Since Mehlich 1-P is a common soil test P in the southeastern USA, we calculated DPS as a percentage of Mehlich 1-P to Mehlich 1-(Fe + Al). There was a linear relationship between the two methods of DPS calculation, and both DPS calculations were related to water-extractable P, suggesting either index predicts P loss potential.
V. Nair (vdna{at}mail.ifas.ufl.edu)
Phosphorus Saturation in Spodosols Impacted by Manure. J. Environ. Qual. 31:1279–1285.
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The Search for a Fecal Indicator Bacterium
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Regulatory agencies are interested in a fecal indicator bacterium with a host range limited to humans because human fecal contamination represents the greatest hazard to humans, yet is a relatively easy nonpoint source to remedy. Literature suggests the fecal indicator bacterium Enterococcus faecalis has a limited host range. Wheeler et al. determined the host range of the Ent. faecalis isolates was potentially limited to humans and chickens. When the Ent. faecalis isolates were ribotyped, it was possible to differentiate clearly among the isolates from humans and chickens. It may be that combining the potentially limited host range of Ent. faecalis with ribotyping is useful for prioritizing watersheds with fecal contamination.
P.G. Hartel
(pghartel{at}arches.uga.edu)
Potential of Enterococcus faecalis as a Human Fecal Indicator for Microbial Source Tracking. J. Environ. Qual. 31:1286–1293.
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Mixing Soil Aggregates Alters the Solution Phosphorus Concentration
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During erosion events, soil aggregates are separated due to differences in size and density, and when soil aggregates of different size and from various sources enter and mix in surface waters, they can affect the solution P concentration through a combination of P sorption and desorption reactions. Smaller soil aggregates tended to have greater resin-P and less water soluble P (WSP), and therefore, greater P buffer capacities (PBC = resin P/WSP) than larger aggregates. When two aggregate-size fractions were mixed, the measured WSP was always less than the average of the WSP in the individual aggregates, due to P desorbed by one aggregate being resorbed by another aggregate, with the strength of one aggregate's ability to control solution P concentration decided by its P buffering capacity. This resorption of P by aggregates with low WSP may mitigate P release by eroded aggregates high in P to some extent and lead to lower than expected P concentrations in surface waters in some situations.
R. Maguire (rmaguire{at}udel.edu)
Effect of Mixing Soil Aggregates on the Phosphorus Concentration in Surface Waters. J. Environ. Qual. 31:1294–1299.
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Soil-Bound Contaminants and Their Long-Term Behavior
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The state of soil-bound contaminants determines their bioavailability and the ability to remediate such soils. The long-term behavior of porous media contaminated by nonvolatile organic compounds was investigated in terms of specific interfacial surface area. Results indicate that for relatively simple, lab-contaminated systems, most of the surface area can be recovered without sample treatment and that heating or solvent washing were required to fully restore soil properties. For field-contaminated soils, the thermodynamics of complex PAH (polycyclic aromatic hydrocarbon) mixtures effect the results, as evidenced by the much higher temperatures required to restore these soils.
C.S. Khachikian
(ckhachi{at}calstatela.edu)
Long-Term Studies on the Effects of Nonvolatile Organic Compounds on Porous Media Surface Areas. J. Environ. Qual. 31:1309–1315.
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Manure and Fertilizer Effects on Turf Runoff
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Surface applications of manure on turfgrass enable export of excess P through sod harvests, but P on the soil surface is susceptible to transport and loss in runoff during rain events. Observations on a steep slope of bermudagrass indicated dissolved P concentrations in runoff were five times greater for inorganic fertilizer than for manure applied at equal rates shortly before an intense rainstorm. Observations over eight rain events indicated total P losses in runoff were similar between surface applications of composted manure and inorganic fertilizer. Manure rates on turf must be managed to balance the benefits of exporting excess manure through sod harvests with the environmental cost of P losses in surface runoff.
D.M. Vietor (dvietor{at}tamu.edu)
Response of Turf and Quality of Water Runoff to Manure and Fertilizer. J. Environ. Qual. 31:1316–1322.
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Compost Curing Influences Extractable Organic Carbon
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This study examined the relationship between extractable organic carbon (OC) and compost stability expressed by CO2 evolution. The extractable OC concentration decreased with compost curing. Water- and NaOH-extractable fulvic acid carbon concentration are highly correlated with compost stability and can be easily measured by a photometric method.
L. Wu (lingzheng_wu{at}hotmail.com)
Relationship between Compost Stability and Extractable Organic Carbon. J. Environ. Qual. 31:1323–1328.
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Reduce Ammonia Losses from Cattle Slurry
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Ammonia volatilization is often a major N loss process for surface-applied cattle slurry. A series of field studies, using a system of small wind tunnels, was conducted to examine the effect of management factors and slurry characteristics on ammonia loss. These studies showed slurry ammonia losses were 1.5 times greater from grass surfaces than from bare soil. Slurry dry matter (DM) content did not affect total ammonia loss, but did affect the time-course of loss. High DM slurries lost more ammonia than low DM slurries during the first 12 to 24 hours, but this effect was reversed after 1 day due to crust formation on the high DM slurries. Studies also compared the effect of immediate tillage on ammonia losses. Losses from unincorporated slurry were 45% of the applied ammonium N; losses after immediate tillage with a chisel plow were 9%, with a tandem-disk harrow were 5%, and with a moldboard plow were 1%. Immediate incorporation was an effective method to reduce ammonia loss.
J.J. Meisinger
(jmeising{at}anri.barc.usda.gov)
Management Factors Affecting Ammonia Volatilization from Land-Applied Cattle Slurry in the Mid-Atlantic USA. J. Environ. Qual. 31:1329–1338.
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Wastewater Sludge as a Carrier for Inoculants
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The efficiency of rhizobial inoculants produced in wastewater sludge used as a growth medium and as a carrier was compared with that of inoculants produced in YMB medium and by using peat as a carrier. Alfalfa plants were inoculated with solid and liquid S. meliloti inoculants and grown in pots containing two soils (a clay soil and a sandy soil). The sludge-based inoculants showed the same symbiotic efficiency (nodulation and plant yield) as YMB-based inoculants. Inoculation increased the nodulation indexes from 4–6 to 8–12, and the rhizobial number from 103 (uninoculated soils) to 106 to 107 cells/g in inoculated soils. The application of sludge as amendment enhanced the rhizobial number in soils from 103 to 104 cells/g and improved the plant growth (shoot dry weights and N contents). Compared with sludge, N fertilizer gave lower plant yields.
R.D. Tyagi
(tyagi{at}inrs-eau.uquebec.ca)
Growth of Alfalfa in Sludge-Amended Soils and Inoculated with Rhizobia Produced in Sludge. J. Environ. Qual. 31:1339–1348.
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Wastewater Treatment Process Impacts Phosphorus Pollution
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Land application of biosolids is a common agricultural practice that can improve soil fertility and recycle a potential waste product, but may also contribute to nonpoint-source phosphorus (P) pollution of surface waters. In addition, because biosolids are often treated with chemicals such as calcium oxide, aluminum sulfate, and iron chloride at wastewater treatment plants, the potential for biosolids to cause nonpoint P pollution of surface waters when land applied may vary with treatment process. Results of a rainfall simulation study conducted on biosolids-amended soils showed P concentrations in runoff varied with treatment process when equivalent rates (based on total P) of biosolids were applied to soils. Variation in P runoff concentrations due to biosolids type resulted from differences in the forms of P added with each biosolids type.
C.J. Penn (chpenn{at}vt.edu)
Phosphorus Forms in Biosolids-Amended Soils and Losses in Runoff: Effects of Wastewater Treatment Process. J. Environ. Qual. 31:1349–1361.
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Water Treatment Residuals Reduce Phosphorus Leaching
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Water treatment residuals (WTRs), produced in purification of drinking water supplies, have strong phosphorus (P)-sorbing properties and are potentially useful in reducing P losses from waste-amended soil. Elliott et al. report mixing of WTRs with biosolids before application to greenhouse soil columns dramatically reduced P in drainage water. Reduction in leachate-P depended strongly on the content of amorphous oxides of iron and aluminum in the WTRs and the potentially releasable P in the biosolids. The authors propose that the P saturation index (PSI = [POX]/[AlOX + FeOX]), based on a simple oxalate extraction of the preapplied materials, can be used to predict and alter P in drainage when biosolids are applied to low P-sorbing soils.
H.A. Elliott (hae1{at}psu.edu)
Influence of Water Treatment Residuals on Phosphorus Solubility and Leaching. J. Environ. Qual. 31:1362–1369.
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Relating Soil Test P to Runoff P
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Agricultural nonpoint sources of P may negatively impact the water quality within a watershed. Torbert et al. investigated the relationship between soil test P and depth of soil sampling with runoff losses of dissolved P in calcareous and noncalcareous soils in the Bosque River Basin of Texas. Runoff P losses as a function of the concentration of P in soil were lower in calcareous soils compared with noncalcareous soils. The 0- to 5-cm depth provided the most reliable results for predicting P losses. The results indicate a soil test for environmental P could be developed, but it would require establishing different soil test P level criteria for different soils or classes of soils.
H.A. Torbert
(atorbert{at}ars.usda.gov)
Relationship of Soil Test Phosphorus and Sampling Depth to Runoff Phosphorus in Calcareous and Noncalcareous Soils. J. Environ. Qual. 31:1380–1387.
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Ag Lands–Wetlands May Release Phosphorus into Water Column
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Constructed wetlands are now established on agricultural lands that received P fertilization for a long time. Once these lands are converted into wetlands, they can potentially release P to the water column. Pant et al. suggest manure-impacted soils may function as potential sources of P to the water column as lateral and vertical movement of P could occur through eluted E horizons of Spodosols. It is apparent that pre-establishment of vegetative communities or chemical amendments of the P-enriched soils is crucial for the efficient use of these lands for constructed wetlands.
H.K. Pant (hari{at}mail.ifas.ufl.edu)
Influence of Flooding on Phosphorus Mobility in Manure-Impacted Soil. J. Environ. Qual. 31:1399–1405.
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Measuring Gas Production and...
N2O Emissions from Maize...