bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating the Fate of a Volatile Pesticide in Unsaturated Soil: A Case Study with DBCP
Authors: Wagenet R. J. , Hutson J. L. , Biggar J. W.
Published: July 2010

A field experiment that measured DBCP (1,2‐dibromo‐3‐chloropropane) distribution during leaching through unsaturated soil was interpreted with the aid of a numerical model designed to describe the movement of a volatile pesticide under field conditions. Field‐measured relationships between hydraulic conductivity, water content, and matric potential were used as model input. Simulated matric potential and water flux compared well with values measured in the field plots. The accuracy of simulated water flow inferred accurate solute description, particularly considering good agreement of the model with a published analytical solution and other reported field tests of the model. Simulated and measured DBCP solution concentrations were different, probably due to the use of a vacuum extraction apparatus to obtain soil solution samples. It was hypothesized that substantial quantities of DBCP were lost in the gaseous form during the extraction process, minimizing the usefulness of the data for the purpose of estimating DBCP fate under field conditions. Given these facts, the numerical model provided estimates of DBCP fate in field soils that were perhaps more reliable and accurate than could be obtained for this volatile chemical by standard field sampling techniques.
Land‐Use and Water Quality in Tributary Streams of Lake Tahoe, California‐Nevada
Authors: Byron Earl R. , Goldman Charles R.
Published: July 2010

We examined land‐use and water quality monitoring data for 10 watersheds of tributary streams to Lake Tahoe, California‐Nevada, to describe relationships between watershed disturbance and water quality degradation from nonpoint sources. Discharge‐weighted annual average concentrations of nitrate (as NO3‐N), soluble P, total P and suspended sediment were plotted against the proportion of each watershed represented as disturbed and imperviously covered land of various land‐use classes. Comparisons between land‐use and runoff water quality demonstrated significant relationships between increased coverage and disturbance in the watersheds and decreased water quality. The concentrations of NO3‐N, total P, and suspended sediment in the streams increased significantly with the disturbance of high hazard lands (erodible soils, steep slopes, stream environment zones). Increased disturbance of lower hazard lands (less erodible soils) resulted in increases in the concentrations of soluble and total P. The patterns of significance and slopes of the relationships demonstrated increased nonpoint source water quality degradation with increased land disturbance in these Sierra Nevada watersheds.
Mineralization and Leaching of Phosphorus from Soil Incubated with Surface‐Applied and Incorporated Crop Residue
Authors: Sharpley A. N. , Smith S. J.
Published: July 2010

With the increasing use of conservation tillage, consideration of crop residue as a potential source of plant‐available P and mobility of this P in soil will be important from both agronomic and environmental standpoints. The effect of placement (surface or incorporation) of residue of six crop types (alfalfa, Medicago sativa L.; corn, Zea mays L.; oat, Avena sativa L.; peanut, Arachis hypogaea L.; soybean, Glycine max (L) Merr.; wheat, Triticum aestivum L.) on the mineralization and leaching of P from eight soils was investigated. Significantly greater (1.0% level) amounts of inorganic P were leached from surface‐applied compared to incorporated residues during the 84‐d incubation at 35°C, with the maximum amount leached after 28 d. The opposite was true for organic P, with greater amounts leached from incorporated residue than from surface‐applied residue. These amounts steadily decreased during the 84‐d incubation. Apparently, mineralization of residue P and movement within the soil was greater for surface‐applied compared to incorporated residue and was a positive linear function of available soil P content (r2 = 0.69–0.81). Any increase in soil P solubility caused by residue leachate would be expected to occur to a greater extent with an increase in available soil P. Leaching of mineralized P may be an important source of available P during initial crop growth.
Dissipation of Bentazon in Flooded Rice Fields
Authors: Ross L. J. , Powell S. , Fleck J. E. , Buechler B.
Published: July 2010

The dissipation of bentazon (3‐isopropyl‐1H‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide) in water, soil and vegetation from three flooded rice (Oryza sativa L.) fields was investigated in California. Regression analyses were used to describe dissipation and to determine half‐lives. Maximum bentazon concentrations in water, soil and vegetation were 2100 µg/L, 960 µg/kg and 23,000 µg/kg, respectively. Concentrations in water showed a gradient from the upper to lower end of the fields over time and were related to movement of bentazon downfield in flood water. Bentazon mass recovered in water samples was not linear over time but was related to degradation, dilution, application rate and mass flow within a field. In water, the time estimated for a 50% reduction in initial bentazon mass ranged between 11 and 32 d after application for the three fields. Bentazon mass in soil declined exponentially over time and the dissipation half‐life was calculated to be 5 d. Bentazon mass recovered from vegetation samples was not linear over time but was related to degradation and wash‐off from plant surfaces. The time estimated for a 50% reduction in initial bentazon mass in and/or on vegetation was between 2 and 3 d after application. Dissipation rates determined in this study were different than published results from small field plots and from laboratory data, indicating the need for field measurements in the development of regulatory strategies.
Comparison of Lumped and Distributed Models for Chemical Transport by Surface Runoff
Authors: Emmerich W. E. , Woolhiser D. A. , Shirley E. D.
Published: July 2010

A simple, complete mixing model is used to evaluate the degree of distortion involved in modeling chemical exchange and transport at the soil surface as a lumped rather than a distributed process. A complete mixing model was coupled to the kinematic cascade model, KINEROS, to provide a distributed representation of chemical exchange and transport. A lumped model was developed by ignoring spatial variations of chemical concentration in overland flow and in the mixing zone. Chemical concentration and transport predicted by the alternative approaches were evaluated for total transport, arrival time, peak concentration time, and peak concentration. Total chemical transport was virtually unaffected by model form. However, significant differences were found in arrival and peak concentration times as well as peak concentrations when chemical was placed only in the upper plane of a two plane cascade. The lumped model predicted significantly lower peak chemical concentrations and arrival times that were too short. A lumped model provides a good approximation for transport from a single plane, but caution should be used when a lumped model is used to describe chemical exchange and transport on a cascade of planes.
Chemistry of Rainwater and Cloud Water at Remote Sites in Alaska and Oregon
Authors: Bormann B. T. , Tarrant R. F. , McClellan M. H. , Savage T.
Published: July 2010

Cloud water and rainwater were examined at remote sites in southeastern Alaska and coastal Oregon using standardized collection and analytical techniques. Cloud water and rainwater were characterized by extremely low concentrations of most ions except SO2−4, Na+, and Cl−. Acidity was greater than expected because of organic acids from unknown sources. Concentrations of NO−3 and NH+4 were extremely low, especially compared to samples collected similarly in the eastern USA. Rainwater did not differ between Alaska and Oregon except in concentrations of Ca2+, Mg2+, K+, Na+, and Cl−. Cloud water generally had higher concentrations of ions than rainwater, especially in NO−3, NH+4, and SO2−4. Ion concentrations were highly variable and non‐normally distributed. Sample sizes in future studies should be large (>40). Cloud water deposition may be very important in terms of potential pollution effects and nutrient cycling in ecosystems with frequent cloud cover.
Reasons for the Acclimation for 2,4‐D Biodegradation in Lake Water
Authors: Chen Shaojin , Alexander Martin
Published: July 2010

A study was undertaken to determine reasons for the occurrence of an acclimation period for the biodegradation of 2,4‐dichlorophenoxyacetate (2,4‐D) in lake water. The length of the acclimation period was not affected by removal of larger protozoa from the water or the presence of cycloheximide and nystatin. The population of 2,4‐D‐degrading bacteria increased long before 2,4‐D loss was detected, and herbicide loss was evident only when the population size was large. The acclimation phase was virtually eliminated if a culture of 2,4‐D‐utilizing bacteria was added to lake water. A culture of glucose‐grown 2,4‐D‐degrading bacteria metabolized the herbicide in a time interval far shorter than the acclimation phase. The time for acclimation was identical in 14 replicate samples of the same lake water. These data suggest that the length of the acclimation phase is not mainly a result of the time for reduction of grazing pressure on 2,4‐D‐degrading bacteria, the destruction of antimicrobial compounds, the decomposition of alternative C sources used preferentially to the herbicide, induction of the requisite enzymes, or the appearance of a mutant able to utilize the pesticide. The acclimation for 2,4‐D degradation in lake water appears chiefly to reflect the time for a small population of bacteria able to use the compound to become sufficiently large to cause a detectable loss of the chemical.
Application of Sewage Sludge and Other Amendments to Coal Refuse Material: I. Effects on Chemical Composition
Authors: Pietz R. I. , Carlson C. R. , Peterson J. R. , Zenz D. R. , Lue‐Hing C.
Published: July 2010

The effects of sewage sludge, lime, and gypsum on the chemical composition of coal refuse material were examined at a Fulton County, IL, land reclamation site. Treatments consisted of a control, 542 dry Mg ha−1 anaerobically digested sewage sludge, 89.6 Mg ha−1 lime, 112 Mg ha−1 gypsum, and combinations of these amendments. Analysis of coal refuse material (0–15 cm) from 1976 to 1981 showed that the sewage sludge + lime treatment was the most effective in maintaining the refuse pH, and in reducing water‐soluble Al and Fe, KCl extractable Al, and total acidity. Gypsum applications decreased the refuse pH and increased water‐soluble Al and Fe, KCl extractable Al, and total acidity. The effectiveness of treatments in reducing total acidity was sewage sludge + lime > gypsum + sewage sludge + lime > sewage sludge > lime > gypsum + sewage sludge > control > gypsum + lime > gypsum. Concentrations of water‐soluble Ca, Mg, and Na reflected the additions of these cations made by various treatments and the contribution of these cations to refuse electrical conductivity (EC). Profile sampling (0–100 cm) in 1976 and 1981 showed a decline in pH, and an increase in water‐soluble Al and Fe and total acidity in 1981 samples from the sewage sludge and gypsum treatments. The changes in the sludge treatment indicate there was a solubilization of metals from the refuse material and sewage sludge with time, as the surface pH (0–15 cm) declined, and a subsequent increase in the total acidity from metals and acidic by‐products leached to the 15‐ to 100‐cm depths of the coal refuse material. In the gypsum treatment, the changes observed in the 1981 profile samples reflected the leaching of H3O+, metals, and acidic by‐products of pyrite oxidation produced by exchange with Ca from the gypsum amendment.
Effects of Ozone and Water Stress, Separately and in Combination, on Soybean Yield
Authors: Miller Joseph E. , Heagle Allen S. , Vozzo Steven F. , Philbeck Robert B. , Heck Walter W.
Published: July 2010

A primary concern in applying existing 03‐effects data on crop production is the relatively unknown influence of soil moisture, which may modify plant response to 03. One deficiency in field experiments that have tested the influence of soil moisture on crop response to 03 has been lack of control of soil moisture conditions in open‐top chamber plots. Most experiments have relied on the occurrence of normal drought periods during the growing season and use of irrigation to adjust soil moisture conditions. This has not allowed the control of the water stress cycles that is desirable. In 1986 a field experiment was performed with soybean [Glycine max. (L.) Merr. cv. Young] to test the influence of periodic water stress on the yield response to O3. Open‐top field chambers were used to expose plants to a range of O3 concentrations, and rain exclusion caps were used on individual chambers to help regulate soil moisture levels. Three soil moisture treatments were used [well‐watered (WW), waterstressed (WS), and well‐watered with permanent rain exclusion caps that were in place from 35 d after planting until physiological maturity (WW‐C)]. In the WW and WS treatments, the rain caps were put in place only during an exceptionally wet period from mid‐August to mid‐September. The WW and WW‐C treatments had approximately the same yield and response to O3, indicating that the presence of the caps for most of the growing season had little effect on growth or sensitivity to O3. The WS plots yielded approximately 10% less on the average than the WW and WW‐C plots, but water stress did not change the response to O3 (i.e., no significant O3 × water interaction). Based on a Weibull dose‐response model, O3 reduced yield of ‘Young’ soybean 13% at a concentration of 0.05 µL L−1 (12 h d−1 seasonal mean) compared to a hypothetical background of 0.02 µL L−1.
Measurement of the Deposition and Fate of Sulfur‐Dioxide‐35 in a Pine Plantation
Authors: Gay D. W. , Murphy Charles E.
Published: July 2010

An experiment was carried out to determine the uptake rate and fate of SO2 absorbed by the forest canopy. The radioactive tracer, 35S was used. Branches of loblolly pine were exposed to 35SO2 in the field with a portable chamber. The exposed branches were excised and a sample of needles was immediately washed with distilled water. The needles and water collected in the field were analyzed for 35S content. The results indicated that a portion of the 35S could be washed from the needles and another portion was not removed with a water rinse. The portion that could not be removed by rinsing was absorbed at a rate and followed patterns of absorption, which suggested that absorption was controlled by stomatal diffusion, and thus was internal. The 35S that could be removed by rinsing appeared to be surface absorption. The average deposition velocity for the entire leaf surface of the pine plantation was 0.0041 m/s. The distribution of 35S was investigated by serial extractions. The fresh whole needles were rinsed in distilled water. Following rinsing, the dried and crushed leaf material was extracted with acetone, and then extracted with hexane. About 50% of the 35S activity was removed by the water rinse. About one‐third, 30 to 38%, of the 35S activity remaining after washing was found in each of the two extracts and about one‐third in the residual material left after extraction.
Design and Performance of a Large, Field Exposure Chamber to Measure Effects of Air Quality on Plants
Authors: Heagle Allen S. , Philbeck Robert B. , Ferrell Ronald E. , Heck Walter W.
Published: July 2010

A 4.66‐m diam., 3.6 m tall, cylindrical open‐top field chamber was designed, constructed, and tested as a tool to measure the effects of air quality on plant function and yield. It is a larger version of the 3‐m diam. chamber that has been used to measure the effects of gaseous pollutants on crop plants. The new chamber has an aluminum‐channel frame covered with clear polyvinyl chloride plastic film. It is equipped with a frustum (truncated cone) that decreases ambient air ingress and can be fitted with a device to exclude rain (rain cap) for studies with simulated rain pH. During the daylight hours, the mean air temperature within the chamber was 0.6 °C greater than ambient on cloudy, cold days, 2.2 °C greater than ambient on partly cloudy, cool days, and 2.8 °C greater than ambient on sunny, warm days. The mean dew point temperature for a wide range of conditions was 0.7 ° greater inside than outside. Mean solar radiation in the chamber, with new plastic panels, was 15% less than ambient with a rain cap and 12% less with no rain cap. Charcoal filtration removed 78% of the O3 in ambient air; long‐term measurements during charcoal filtration showed that the mean O3 concentration in the chamber (all positions and heights) was 77% less than ambient suggesting little or no long‐term ingress through the top. Short‐term gradients in O3 concentrations existed (mostly near the top of the chamber) during infrequent periods of strong winds. During addition of approximately 0.09 µL L−1 of O3 to nonfiltered air, the mean (14‐d) O3 concentrations across all positions and heights varied by less than 0.005 µL L−1 of the overall mean.
Spatial Patterns in Elemental Concentrations of the Forest Floor across the North Central USA
Authors: Grigal D. F. , Ohmann L. F.
Published: July 2010

Forest floor material was sampled in 171 forest stands, representing five forest types, across the states of Minnesota, Wisconsin, and Michigan. Elemental concentrations of forest floor material were related to forest type, and for most elements, concentrations were also related to location defined by five sampling zones along a northwest‐southeast geographic gradient. Calcium, Mg, K, Na, and P decreased in concentration from west to east; Pb and Cd increased; Cu and Zn did not differ among zones, and although Ni differed, there was no pattern to those differences. The trends are consistent with atmospheric deposition of Ca, Mg, K, Na, and P from westerly soil‐derived sources and deposition of Pb and Cd from eastern anthropogenic sources.
Sources of Error in Analysis of Municipal Sludges and Sludge‐Amended Soils for Di(2‐ethylhexyl) Phthalate
Authors: Eiceman G. A. , Gardea‐Torresdey J. L. , O'Connor G. A. , Urquhart N. S.
Published: July 2010

Rapid quantitative determination of di‐(2‐ethylhexyl) phthalate (DEHP) in municipal sludge is described for capillary gas chromatography/mass spectrometry (GC/MS) using selected ion monitoring with isotope dilution techniques. Propagation of error through a four‐step technique is measured as an increase in variance with each additional step. Stepwise accumulated variation (as a percentage of total error) was GC/MS analysis with data reduction, 3%; analyst (sample preparation), 8%; heterogeneity of sludge, 30%; heterogeneity in sludge‐amended soil, 77%; and errors between planters, 100%. The relative standard deviation (RSD) associated with analysis of sludge alone was 16% at 51 mg kg−1 DEHP. Analysis precision was dependent on sample size and DEHP concentration. The RSD for a 13 mg kg−1 DEHP loading in soil/sludge mixtures for a greenhouse study was 26.5%. Detection limits for DEHP in sludges with rapid screening procedures were fixed by interfering extractable matrices.
Long‐Term Relationships between Molybdenum and Sulfur Concentrations in Redcedar Tree Rings
Authors: Guyette Richard P. , Cutter Bruce E. , Henderson Gray S.
Published: July 2010

Molybdenum and S concentrations were determined in growth increments of 13 eastern redcedar (Juniperus virginana L.) trees from the Ozark region of Missouri. Chonologies were constructed, which dated from 1280 to 1960 for Mo, and from 1580 to 1960 for S. A 45% increase in Mo concentrations occurred between 1720 and 1860 when compared with the previous 440 yr. A decline in heartwood Mo concentration, beginning in 1860, is hypothesized to be due to increasing soil sulfate from the atmospheric deposition of S compounds. There was a 65% reduction in Mo concentration concomitant with a 44% increase in S concentration in redcedar heartwood formed after 1860. Sulfur and Mo concentrations were found to be negatively correlated in serial heartwood increments. Competition between sulfate and molybdate ions in soil solutions are thought to have decreased Mo in recent heartwood growth increments.
The Environmental Microbiology of Chlorinated Aromatic Decomposition
Authors: Boyle Michael
Published: July 2010

The difficulty in predicting the microbial degradation rates of such xenobiotic chemicals as chlorinated aromatic hydrocarbons necessitates that empirical data on decomposition be collected to model the environmental fate and transport of these recalcitrant compounds. A partial list of microorganisms reported to degrade chlorinated aromatic hydrocarbons is provided. The processes of degradation, including dehalogenation, cometabolism, and synergistic mineralization, are discussed as they pertain to these halogenated compounds. Adaptation through genetic exchange within a microbial community is addressed through a brief review of the physical‐chemical factors required for plasmid transfer in the laboratory. The ecological significance of gene recruitment in response to xenobiotic stress is also considered. Because chlorinated aromatic hydrocarbons were rare in the environment until a few decades ago, they provide a unique opportunity to study the evolution of multistep catabolic pathways for the degradation of compounds with novel chemical structures.
Herbicide Leaching and Distribution in Tilled and Untilled Soil
Authors: Hall J. K. , Murray M. R. , Hartwig N. L.
Published: July 2010

Leaching and distribution of several pesticides, applied at recommended rates, were evaluated in a Hagerstown silty clay loam (Typic Hapludalf) by analyzing soil fractions and pan lysimeter percolates (PLP) collected at a soil depth of 122 cm under conventional tillage (CT) and no‐tillage (NT) corn (Zea mays L.) management. In general, maximum herbicide concentrations detected and mean total amounts in PLP were higher in 1985 than 1984 for both CT and NT, and were greater under NT conditions where more leachate was collected each year than in CT. Concentrations and amounts of simazine (6‐chloro‐N, N′‐diethyl‐1, 3,5‐triazine‐2, 4‐diamine) and atrazine (6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) were generally more substantial in PLP than cyanazine (2‐[[4‐chloro‐6‐(ethylamino)‐1, 3,5‐triazin‐2yl] amino]‐2‐methylpropanenitrile), and metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide, particularly under NT conditions. In 1984, mean areal leaching losses (NT) were 0.6% (simazine, atrazine) and 0.15% (cyanazine, metolachlor) of applied rates (1.7 and 2.2 kg ha−1, respectively). In 1985, mean areal losses (NT) were 3.4% (simazine, atrazine) and 1.6% (cyanazine, metolachlor). Respective CT losses were <0.1% (1984) and ranged from 0.4 to 1.0% (1985). Where worst‐case conditions were considered (1985), mean leaching losses (simazine, atrazine) were 0.15 kg ha−1, therefore, at least 91% (1.55 kg ha−1) was retained and/or degraded within the soil profile or in the corn tissue after absorption. Soil core analysis corroborated PLP results revealing that simazine and atrazine were the most persistent and mobile herbicides, and were consistently detected at all soil depths to 122 cm. Differences in the yearly extent and magnitude of leaching losses were related strongly to rainfall distribution and number of leaching events proximal to the herbicide spray date.
Infiltration of Wastewater in a Newly Started Pilot Sand‐Filter System: I. Reduction of Organic Matter and Phosphorus
Authors: Pell Mikael , Nyberg Fred
Published: July 2010

The objective of the study was to monitor variables on P and organic matter reduction related to the wastewater purification process in a sand‐filter system constructed according to the directives issued by the National Swedish Environment Protection Board. Monitoring was conducted from start‐up until a steady state was reached. The system consists of a three‐chambered septic tank, a pilot sand‐filter, corresponding to the demand for one person, and eight sand‐filter columns. It was loaded with 67 L m−2 d−1 of an artificial wastewater. The effluent from the septic tank reached a steady state with respect to the chemical oxygen demand (COD) and P levels after 3 wk. By Day 78 the cumulative load of COD and P had been reduced by 37 and 48%, respectively. In the sand filter the reduction in COD started immediately and concentrations in the effluent remained low and steady from Day 18 until Day 78 when the last sampling was made. The total reduction in COD amounted to 91%. Effluent concentrations of P were initially low but increased as the experimental period progressed. The total decrease in P in the sand filter was 83%. The reduction in COD was highest in the upper 1.5 cm of the sand profile and was almost complete after 15 cm of infiltration; in contrast, P levels showed an overall decrease throughout the sand profile. The columns were less efficient at reducing COD but more efficient at decreasing P compared with the sand filter. The results from the columns suggest that anaerobic conditions had developed.
Self‐Diffusion of Selenate and Selenite in Overburden
Authors: Ahlrichs J. S. , Hossner L. R.
Published: July 2010

Self‐diffusion coefficients (D) for selenate (SeO2−4) and selenite (HSeO−3) were evaluated as a function of overburden pH (2, 3, 5, 7, 9) and volumetric water content (Θv = 0.22, 0.28, 0.34). Selenate self‐diffusion coefficients were least (D = 0.23 × 10−6 cm2 s−1 in overburden adjusted to pH 3 and Θv = 0.22 and greatest (D = 1.8 × 10−6 cm2 s−1 and 1.7 × 10−6 cm2 s−1) in overburden adjusted to pH 9 and Θv = 0.28 and 0.34. Self‐diffusion coefficients for HSeO−3 were 2 to 3 orders of magnitude slower than for SeO2−4. The most rapid HSeO−3 diffusion was observed at pH 2 and Θv = 0.34 (D = 53.2 × 10−9 cm2 s−1). The slowest was at pH 3 and Θv = 0.22 (D = 0.2 × 10−9 cm2 s−1). For both SeO2−4 and HSeO−3 the self‐diffusion coefficients increased with increasing water content and were related to adsorption characteristics of the soil and the Se species present at each soil pH.
Interactions of Hydrazine with Clays and Soils
Authors: Moliner Ana M. , Street J. J.
Published: July 2010

The nature and extent of hydrazine adsorption by clays and soils was found to be highly dependent on the suspension pH and on the types of surface functional groups. Under acidic conditions, replacement of Na+ by N2H+5 was the primary mechanism for hydrazine retention by every system studied. Most of the hydrazinium ion was readily desorbed by K+ from the surfaces of reference clays under acidic conditions, but remained absorbed on the surfaces of the Arredondo soil (Grossarenic Paleudults) horizons investigated. Under alkaline conditions, ion exchange was the predominant mechanism for hydrazine retention only in the case of montmorillonitic smectite. Kaolinite and two of the upper horizons of Arredondo soil adsorbed hydrazine via a different mechanism. Hydrazine retained on exchange sites was readily desorbed by K+.
Growth, Photosynthesis, and Chlorophyll Concentrations of Red Spruce Seedlings Treated with Mist Containing Hydrogen Peroxide
Authors: Hanson P. J. , McLaughlin S. B.
Published: July 2010

The effects of controlled exposures of mist (50–90 µm drop size) containing hydrogen peroxide (H2O2) on greenhouse‐grown red spruce (Picea rubens Sarg.) were studied for 16 wk coincident with the 1987 growing season. One‐year‐old seedlings were treated with simulated mist containing 0, 15, 59, or 235 µM H2O2 three times each week from 2400 to 0930 h. Height, diameter, net photosynthesis, respiration, chlorophyll, and dry weight measurements were made. After 16 wk of H2O2 exposures, no visible symptoms of foliar injury were evident. Similarly, no differences in net photosynthesis, respiration, or needle pigment concentrations were observed. Analysis of covariance of the dry weight data showed significantly greater dry matter in seedlings exposed to 235 µM H2O2 treatment vs. those treatments representing a range of ambient conditions (0, 15, and 59 µM). Mean relative growth rates were also the greatest for seedlings of the 235 µM treatment. Given these controlled exposure studies, it is hypothesized that concentrations of wet‐deposited H2O2 of up to twice current ambient maximums are unlikely to reduce red spruce seedling growth through direct impairment of leaf function.
Fate of Contaminants during Utilization of Peat Materials
Authors: Sheppard S. C. , Gibb C. L. , Hawkins J. L.
Published: July 2010

Since peat soils are used for a variety of industrial purposes, the fate of contaminants in peat is of interest for environmental impact studies. Peat soils effectively retain many contaminants and can receive contaminants from both the atmosphere and groundwater. We investigated the fate of I, Se, Cs, U, and Pb in peats subjected to treatments simulating commercial processes. The soils were contaminated with three concentrations of the study elements and incubated for 3 yr. Subsamples were subjected to static pyrolysis, extraction with base, acid hydrolysis, and extraction with chelates to represent burning of peat, humic and fulvic acid extraction as industrial materials, carbohydrate extraction for single‐cell protein production, and application of chelate‐based fertilizers. The results are presented as product concentration ratios and percent recoveries. In several cases, the contaminants were markedly concentrated. As an example, food products produced from fungal culture in peat hydrolysates may contain 50‐fold higher U concentrations, on a dry wt. basis, than the original peat. Thus, contaminants are transferred to these products and this should be considered for environmental and human safety.
Hexazinone Persistence and Mobility of a Steep Forested Watershed
Authors: Lavy T. L. , Mattice J. D. , Kochenderfer J. N.
Published: July 2010

The mobility and persistence of hexazinone, 3‐cyclohexyl‐6‐(dimethylamino)‐1‐methyl‐1,3,5‐triazine‐2,4‐(1H,3H)‐dione, applied to a forest floor with a spot‐gun applicator was monitored for 43 months. A 15‐m buffer zone separated the steeply sloping (40%) treated area from a continuously flowing stream directly below. Automated in‐stream samplers revealed that the highest hexazinone concentrations in water routinely occurred during storm events, even when stream flow increased tenfold. More hexazinone ran off the treated watershed during winter months after tree leaves had fallen. During the first 24 months after treatment, 4.7% of total applied was detected in the stream sampled. Initially, forest litter was highly effective in adsorbing surface applications of hexazinone; however, after 5 months less than 0.2% of the original amount was retained in the litter. Over 99% of the hexazinone had dissipated from the top 30 cm of soil within 18 months after application. After 36 months, trace levels of hexazinone were detected in water samples collected soon after storms. However, no hexazinone was present in samples collected 43 months after application. Distribution coefficients for hexazinone adsorption revealed that this compound was retained most readily by the litter layer and decreasing adsorption was shown for soil deeper in the profile. Mean concentrations of hexazinone in green leaves of trees in the treated area ranged from 0.5 to 1.0 kg−1. Rapid dissipation of hexazinone in leaves lying on the floor suggested the possibility of recycling into existing vegetation.
Cadmium Distribution in Field‐Grown Fruit Trees
Authors: Korcak R. F.
Published: July 2010

The effect of soil applied Cd on Cd distribution in and growth of five species of fruit trees was investigated. Cadmium was applied at three rates (0, 5, and 10 mg kg−1 soil) as CdSO4 to orchard plots established at two pH levels, low (5.5) and high (6.5). Five fruit tree types were planted: ‘Gala’ apple (Malus domestica Borkh.) budded on M.26 (dwarfing) or MM.111 (semistandard) rootstocks, ‘Redskin’ peach (Prunus persica L.) on Lovell rootstock, ‘Stanley’ plum (Prunus domestica L.) on Myrobalon rootstock, and ‘Seckel’ pear (Pyrus communis L.) on seedling rootstock. The trees were grown for 6 yr, 7 yr in the case of pear, and leaf, bark, wood, fruit, and root Cd concentrations were monitored. Gala apple on both rootstocks accumulated very small concentrations of Cd, usually 0.1 mg kg−1 dry wt. in all tissues tested. Peach and plum were intermediate in Cd accumulation, but both still relatively low. Seckel pear had high Cd concentrations in all tissues including fruit flesh and peel. Pear leaf Cd concentrations were 2.0 mg kg−1 from the 10 mg kg−1 soil Cd application after 5 yr. Pear fruit peel and flesh showed elevated, although nonsignificant, Cd concentrations with increased Cd applied. There was little difference between bark and wood tissue Cd concentrations independent of tree type. Root Cd concentrations were highest for pear followed by peach and plum, and lowest in apple.
Selenium in the Southern Coast Range of California: Well Waters, Mapped Geological Units, and Related Elements
Authors: Tracy J. E. , Oster J. D. , Beaver R. J.
Published: July 2010

A reconnaissance survey of 151 irrigation and stock wells was conducted in the southern coast range of California bounded by Alameda and San Joaquin counties in the north (37°45′N) and Ventura and Santa Barbara counties in the south (34°15′N). Selenium concentrations in 11 wells exceeded 20 µg/L, the recommended water quality guideline for irrigation water. Wells with Se concentrations >2 µg/L were associated with nearby surface Pliocene and Miocene (P < 0.001) marine rocks based on Pearson's chi‐square analysis. Selenium was linearly related (P < 0.001) to electrical conductivity (EC), SO4, and P concentrations. Improved regression fits resulted from stratification by Pliocene and Miocene marine surface rocks; stratification also improved the regression fit (P < 0.001) between Se and Cl. The multiple linear regression equation relating Se to EC and P within 2.5 km of Pliocene surface rocks produced an R2 of 0.74 and a standard error of estimate of 11 µg Se/L. We conclude that either both Pliocene and Miocence rocks are Se sources, or that Pliocene rocks are positional markers locating recently uplifted, Sebearing Miocene rocks. Also, surface rock geology and well water composition (EC, P) would be useful information to locate wells that are likely to contain high levels of Se.
Sulfur, Nitrogen, and pH Levels in Wisconsin Precipitation
Authors: Andraski T. W. , Bundy L. G.
Published: July 2010

Precipitation is an important source of S and to a lesser extent N for agricultural crops and natural ecosystems. Reductions in S and N emissions have occurred and additional revisions in air quality standards will be expected to further reduce the amounts of nutrients such as S and N in precipitation. This study was conducted to determine current nutrient deposition rates and precipitation pH levels at 10 sites in important agricultural areas of Wisconsin. Bulk precipitation samples were collected at 10‐d intervals for a 2‐yr period from Nov. 1985 to Oct. 1987. Average annual SO4‐S deposition was 11 kg S ha−1 in northwestern Wisconsin and 23 kg S ha−1 in the south. These S deposition rates are approximately 42% less than the amounts found in a Wisconsin study conducted from 1969 to 1971. Despite this apparent decrease in S deposition, most of the S requirement for crop production is still likely to be provided by S in precipitation in most areas of the state. Annual average NO3‐N deposition also differed geographically with 4.2 kg N ha−1 deposited in the northwest and 8.4 kg N ha−1 in the south. Average annual NH4‐N deposition was 8.7 kg N ha−1 but showed no geographical trend, and variations among sites were probably influenced by point sources. For most sites, annual deposition amounts of nutrients were similar both years, although concentrations were lower during a year with above‐normal precipitation. The annual volume‐weighted mean pH ranged from 5.1 to 5.9 in a year with above‐normal precipitation and from 3.4 to 4.5 in a year with slightly below‐normal precipitation.
Pine Growth Variation Associated with Overburden Rock Type on a Reclaimed Surface Mine in Virginia
Authors: Torbert J. L. , Burger J. A. , Daniels W. L.
Published: July 2010

This study was designed to compare the effects of two overburden spoil types and various mixtures of the two spoils on the performance of pitch × loblolly hybrid pine (Pinus × rigitaeda). Sandstone and siltstone overburden were used to create five rock mix treatments: pure sandstone (SS), pure siltstone (SiS), a 2:1 SS/SiS mix, a 1:1 SS/SiS mix, and a 1:2 SS/SiS mix. Tree survival was not affected by rock mix, but growth was greatly affected. The greatest growth response occurred on the SS treatment and decreased as the amount of siltstone increased in the rock mix. The average stem volume of trees on the SS treatment was nearly five times greater than trees on the SiS treatment. The coarse fragment content of the SS (52%) was much lower than the SiS (72%), thus providing a greater volume of fine earth (<2 mm) for water retention and root exploitation. The pH of the SS was much lower than SiS (5.7 vs. 7.1), and available Mn was higher in the SS than in the SiS (540 vs. 160 mg kg−1 foliar Mn). The results of this study demonstrate the need to consider the effects of various overburden types on tree growth when forest land is the designated post‐mining land use.
Nutrient Cycling in Forests of Walker Branch Watershed, Tennessee: Roles of Uptake and Leaching in Causing Soil Changes
Authors: Johnson D. W. , Todd D. E.
Published: July 2010

Previous studies showed that subsoil exchangeable Ca2+ and Mg2+ decreased over the period 1971 to 1982 in several plots on Walker Branch Watershed. It was hypothesized that wood accumulation (i.e., uptake and sequestering in both living and dead tree biomass) was the dominant cause of the exchangeable Ca2+ decreases, whereas atmospheric deposition‐induced leaching was the dominant cause of the exchangeable Mg2+ decreases. As hypothesized, wood accumulation far exceeded leaching of Ca2+ in those plots where soil exchangeable Ca2+ decreased. The hypothesis regarding causes of exchangeable Mg2+ decrease was neither accepted nor rejected from the data on hand. Leaching exceeded wood accumulation of Mg2+ in three of the four plots studied (pine, Pinus; yellow‐poplar, Liriodendron tulipifera; and chestnut oak Quercus prinus). Cation leaching in these three plots was balanced by SO2−4, and input‐output balances indicated that soil solution SO2−4 originated primarily from atmospheric deposition. Thus, the trends toward decreased subsoil exchangeable Mg2+ in those particular plots (while not all statistically significant at the 95% level), are attributable primarily to atmospheric S deposition. However, leaching was minimal in the fourth plot (oak hickory, Quercus‐Carya spp.) due to very low soil solution SO2−4 concentrations, yet subsoil Mg2+ decreases were significant at the 95% level. In the latter case, wood uptake was the dominant mechanism of Mg2+ removal from the soil. The importance of slope position in determining nutrient cycling patterns and the long‐term changes in nutrient status is also discussed.
Runoff of Sulfometuron‐Methyl and Cyanazine from Small Plots: Effects of Formulation and Grass Cover
Authors: Wauchope R. Don , Williams Randall G. , Marti Luz. R.
Published: July 2010

To determine the effects of application rates, grass cover, and formulation type on herbicide losses in runoff, we applied 4.5 kg/ha cyanazine (2‐[(4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl)] amino]‐2‐methylpropanenitrile) with 0.4 kg/ha sulfometuron‐methyl (methyl‐2[[[[(4,6‐dimethyl‐2‐pyrimidinyl)amino] carbonyl] amino] sulfonyl] benzoate) to 1.2 by 2.4 m plots, using suspension concentrate (SC) and dispersible granule (DG) formulations of cyanazine, and SC and emulsifiable concentrate (EC) formulations of sulfometuron‐methyl. The plots were established on a Tifton loamy sand soil (fine‐loamy, siliceous, thermic Plinthic Paleudults) and had 3% slope. The plots were bare or covered with a mixed stand of common Bermudagrass [Cynodon dactylon (L.) Pers.] and Bahiagrass (Paspalum notatum Flugge var. suarae Parodi). On the day after the herbicides were applied, we simulated rainfall events of 69 mm/h intensity until 2 mm of runoff occurred. The runoff was analyzed for sediment and herbicides. The bare plots required one‐third less rain to produce the same amount of runoff and yielded twice as much sediment as the grassy plots. However, losses of all formulations were 1 to 2% of the amounts applied regardless of grass cover and even though cyanazine rates were 11 times that of sulfometuronmethyl. Total losses of all formulations were sensitive to the length of time between rainfall initiation and runoff initiation, indicating that leaching made herbicide unavailable for runoff. These results suggest that, for these formulations under conditions of similar runoff volumes, losses of pesticides are a fairly constant fraction of the amounts applied, with or without grass cover. For intense storms where the amount of rainfall is similar, chemical runoff from the grassed plots was predicted by computer simulation to be less than half of that from bare soil.
Nitrate‐Nitrogen Concentrations in Percolate from Lysimeters Planted to a Legume‐Grass Mixture
Authors: Owens L. B.
Published: July 2010

Growing concern that N from agricultural sources is a major pollutant of groundwater has stimulated research on NO3‐N concentrations in groundwater under crops receiving N fertilizer. Knowledge of the effects of legumes on groundwater quality and their potential for reducing NO3‐N concentrations is limited. Three Coshocton monolith lysimeters (Y‐102A, B, and C) containing a well‐drained silt loam soil on a 13% slope, and four lysimeters (Y103A, B, C, and D) containing a moderately well‐drained silt loam soil on a 6% slope were used to study the effects of a legume‐grass mixture on groundwater quality. Between experiments with corn (Zea mays L.), an alfalfa‐orchard grass mix (70% Medicago sativa L. + 30% Dactylis glomerata L.), was grown for 2 yr and 3 yr on the Y102 and Y103 lysimeters respectively. The corn, some of which received high rates of N fertilizer, produced NO3‐N concentrations in percolate ranging from 15 to 40 mg/L. Under alfalfa, NO3‐N concentrations in leachate often were less than 5 mg/L, especially on the moderately well‐drained lysimeters. The highest NO3‐N percolate concentrations under all treatments occurred during the winter/early spring months.
Oxygen Transport through Aquatic Macrophytes: The Role in Wastewater Treatment
Authors: Reddy K. R. , D'Angelo E. M. , DeBusk T. A.
Published: July 2010

Laboratory experiments were conducted to determine the effectiveness of three floating and six emergent aquatic macrophytes in improving domestic wastewater quality, based on their capacities for O2 transport into the effluent. Oxygen transport into the rooting zone of the plants created an oxidized microenvironment, thereby stimulating C and N transformations critical to wastewater treatment. Plants were cultured in flasks containing deoxygenated primary and secondary sewage effluent for an 8‐d period. Oxygen transport by the plants was measured in terms of both O2 consumed by the effluent (biological O2 demand reduction—BOD5) and increased effluent dissolved O2. Two floating plants, pennywort (Hydrocotyle umbellata L.) and waterhyacinth [Eichhornia crassipes (Mart.) Solms], and the emergent plants pickerelweed (Pontederia cordata L.) and common arrowhead (Sagittaria latifolia L.), were superior in improving primary sewage effluent quality, by reducing BOD5 up to 88%, NH4‐N up to 77%, and increasing dissolved O2 up to 6.1 mg L−1. Nitrification rates in pennywort‐ and water hyacinth‐based water treatment systems were calculated to be in the range of 12 to 47 kg NH4‐N ha−1 d−1. Oxygen transport through plants accounted for up to 90% of the total O2 transported into the effluent. In separate batch experiments, the effectiveness of diffuse mechanical aeration (5 and 50 mL air min−1) and of biological aeration (O2 transport by selected plants including pennywort, waterhyacinth, pickerelweed, and common arrowhead) on the rate of contaminant removal from deoxygenated primary sewage effluent were compared for a 26‐d period. Biological and mechanical aeration effected similar BOD5 removal. First‐order reaction rate constants for BOD5 removal were from 0.0066 to 0.0079 h−1 and from 0.0041 to 0.0051 h−1 for biological and mechanical aeration, respectively. Rate constants for NH4‐N removal were from 0.0024 to 0.0107 h−1 for the plant treatments. Virtually complete BOD5 removal occurred in biological and mechanical aeration treatments within 20 d. Complete nitrification of NH4‐N had occurred within 12 d after mechanical aeration was initiated, but subsequent N‐loss by denitrification was inhibited. In the biological aeration treatments, negligible effluent (NO3 + NO2)‐N levels were measured, but 65 to 100% NH4‐N loss occurred both by plant assimilation and by sequential nitrification‐denitrification reactions.
Processes of Iron and Manganese Retention in Laboratory Peat Microcosms Subjected to Acid Mine Drainage
Authors: Henrot Jacqueline , Wieder R. Kelman
Published: July 2010

Despite increasing use of constructed wetlands for treatment of metal‐enriched acid coal mine drainage (AMD), the biotic and abiotic mechanisms of metal retention in such wetlands are poorly understood. The present study was conducted to evaluate the processes responsible for Fe and Mn retention in peat and the effects of microbial activity, pH, temperature, and metal concentration in AMD on these processes. Experimental units consisted in 30 g (wet wt.) of fresh Sphagnum peat, which was repeatedly flushed with synthetic AMD at pH 3.5. Of the four major processes of metal cation retention in peat (cation exchange, complexation with peat organics, precipitation as oxides, and precipitation as sulfides), Fe oxidation and Fe binding on peat organics were predominant, with Fe oxides and organically bound Fe making up, respectively, 62 and 22% of the total Fe in the peat at the end of the experiment. Whereas Fe complexation was a finite process, reaching saturation at 12 mg Fe g−1 dry peat, Fe‐oxide concentration in peat increased steadily throughout the experiment. At pH 3.5, Fe‐oxide precipitation was depressed by the addition of an antiseptic (formaldehyde) to AMD, suggesting that the process was microbially mediated. Iron oxide precipitation was higher at pH 5.5 than 3.5 and less depressed at pH 5.5 than 3.5 by the presence of formaldehyde in AMD. The efficiency of peat to remove Fe from AMD was diminished at low temperature (<15°C) and high Fe concentration in AMD (>100 mg L−1). Manganese retention in peat was small compared with that of Fe, and Mn was retained in peat almost exclusively as exchangeable Mn2+. Retention of Fe2+ in peat was not affected by the presence of Mn2+ in AMD. Iron oxides that had accumulated in peat subjected to AMD were not readily resolubilized by any of three processes investigated: photoreduction, microbial Fe(III) reduction under reducing conditions, and exposure to simulated acid precipitation. These findings suggest that constructed wetlands may be an appropriate technology to remove Fe from AMD with low soluble Fe concentration, but are inadequate for treating drainage waters rich in soluble Mn.