Degradation of chlorpyrifos in soil: effect of concentration, soil moisture, and temperature

The dissipation of the organophosphorus insecticide chlorpyrifos was investigated in field and laboratory samples. Six field locations were selected within the United States, and included the states of Arizona, Florida, Hawaii, Iowa, Mississippi, and Texas. Five of the six locations were selected based on their suspected aggressive degradative capabilities towards this chemical;In the field study, chlorpyrifos was applied to surficial trenches prepared on the north and south side of each building and parallel to the foundation. In the soil samples from Florida, Hawaii, and Texas, concentrations decreased by more than 50% of the initial concentration within 3 mo of application. Arizona, Iowa, and Mississippi soil samples showed a 50% decrease within 12 mo of application. At the end of 24 mo environmental exposure, no statistically significant differences were detected between the concentrations of chlorpyrifos remaining in the soil. However, there may be biological differences. After 24 mo, only the Iowa field location would have a sufficient concentration of chlorpyrifos remaining to prevent termite penetration through the soil-chemical barrier. A single linear or exponential regression equation did not adequately describe the degradation kinetics. Two separate first-order reactions were observed, which proceed in two distinct phases. Using both degradation rates can aid in predicting the concentration of chlorpyrifos remaining in the soil at any time after application;In the laboratory experiment, soil samples from an urban Iowa soil were treated with 0.5 [mu] Ci [[superscript]14C]chlorpyrifos; 10, 500, or 1,000 [mu]g/g formulated Dursban TC; and sufficient water to establish moisture tensions of 0.03, 0.30, and 3.00 bar. Replicate samples were divided between two incubation chambers maintained at either 20° or 27°C. Concentration and moisture significantly affect the degradation of chlorpyrifos. Only in the samples treated with 10 [mu]g/g chlorpyrifos were there significant differences between soil moisture tensions. Concentration was most important in affecting the rate of chlorpyrifos degradation in soil samples treated with either 500 or 1,000 [mu]g/g. Incubation temperature did not significantly affect the degradation of the parent compound chlorpyrifos or soil bound residues. However, temperature did significantly interact with concentration and moisture tension in the mineralization of 3,5,6-trichloro-2-pyridinol (TCP)

Interaction of Two Sulfonylurea Herbicides with Selected Insecticides on Wheat

Agronom

Fate of Methyl Bromide in Fumigated Soils

Recent controversy over the potential role of methyl bromide (MeBr) in damaging the ozone layer has spurred interest in increasing our understanding of the transformation and movement of this fumigant after it is applied to soil. Our research indicates MeBr is rapidly volatilized from fumigated soil (within the first 24 hours) and volatility significantly increases with temperature (35° C \u3e 25° C = 15° C) and moisture (0.03 bar \u3e 0.3 bar \u3e 1 bar \u3e 3 bar). Degradation of MeBr, measured by production of bromide ion (Br-), was also directly related to temperature and moisture. Undisturbed soil column studies indicated that MeBr rapidly volatilized (\u3e 50% of the MeBr flux occurred in 48 h) but did not leach into subsurface soil. Residual MeBr was degraded in the soil column, evident by the high concentrations of Br- in the leachate water. In field studies, MeBr also volatilized rapidly from soil, but a significant portion of the MeBr was degraded (30% after 2 d). These studies provide pertinent information for assessing the fate of MeBr in soil, which should lead to more informed decisions regulating its use

Variable gravity research facility

Spin and despin requirements; sequence of activities required to assemble the Variable Gravity Research Facility (VGRF); power systems technology; life support; thermal control systems; emergencies; communication systems; space station applications; experimental activities; computer modeling and simulation of tether vibration; cost analysis; configuration of the crew compartments; and tether lengths and rotation speeds are discussed

Homeowner pest management: a guide for garden center sales personnel

1 online resource (PDF, 20 pages)Includes Understanding pesticide toxicity, AGFS 3947 (1990)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Degradation of chlorpyrifos in soil: effect of concentration, soil moisture, and temperature

The dissipation of the organophosphorus insecticide chlorpyrifos was investigated in field and laboratory samples. Six field locations were selected within the United States, and included the states of Arizona, Florida, Hawaii, Iowa, Mississippi, and Texas. Five of the six locations were selected based on their suspected aggressive degradative capabilities towards this chemical;In the field study, chlorpyrifos was applied to surficial trenches prepared on the north and south side of each building and parallel to the foundation. In the soil samples from Florida, Hawaii, and Texas, concentrations decreased by more than 50% of the initial concentration within 3 mo of application. Arizona, Iowa, and Mississippi soil samples showed a 50% decrease within 12 mo of application. At the end of 24 mo environmental exposure, no statistically significant differences were detected between the concentrations of chlorpyrifos remaining in the soil. However, there may be biological differences. After 24 mo, only the Iowa field location would have a sufficient concentration of chlorpyrifos remaining to prevent termite penetration through the soil-chemical barrier. A single linear or exponential regression equation did not adequately describe the degradation kinetics. Two separate first-order reactions were observed, which proceed in two distinct phases. Using both degradation rates can aid in predicting the concentration of chlorpyrifos remaining in the soil at any time after application;In the laboratory experiment, soil samples from an urban Iowa soil were treated with 0.5 [mu] Ci [[superscript]14C]chlorpyrifos; 10, 500, or 1,000 [mu]g/g formulated Dursban TC; and sufficient water to establish moisture tensions of 0.03, 0.30, and 3.00 bar. Replicate samples were divided between two incubation chambers maintained at either 20° or 27°C. Concentration and moisture significantly affect the degradation of chlorpyrifos. Only in the samples treated with 10 [mu]g/g chlorpyrifos were there significant differences between soil moisture tensions. Concentration was most important in affecting the rate of chlorpyrifos degradation in soil samples treated with either 500 or 1,000 [mu]g/g. Incubation temperature did not significantly affect the degradation of the parent compound chlorpyrifos or soil bound residues. However, temperature did significantly interact with concentration and moisture tension in the mineralization of 3,5,6-trichloro-2-pyridinol (TCP).</p

Fate of Methyl Bromide in Fumigated Soils

Recent controversy over the potential role of methyl bromide (MeBr) in damaging the ozone layer has spurred interest in increasing our understanding of the transformation and movement of this fumigant after it is applied to soil. Our research indicates MeBr is rapidly volatilized from fumigated soil (within the first 24 hours) and volatility significantly increases with temperature (35° C > 25° C = 15° C) and moisture (0.03 bar > 0.3 bar > 1 bar > 3 bar). Degradation of MeBr, measured by production of bromide ion (Br-), was also directly related to temperature and moisture. Undisturbed soil column studies indicated that MeBr rapidly volatilized (> 50% of the MeBr flux occurred in 48 h) but did not leach into subsurface soil. Residual MeBr was degraded in the soil column, evident by the high concentrations of Br- in the leachate water. In field studies, MeBr also volatilized rapidly from soil, but a significant portion of the MeBr was degraded (30% after 2 d). These studies provide pertinent information for assessing the fate of MeBr in soil, which should lead to more informed decisions regulating its use.Reprinted (adapted) with permission from Fumigants, 652(5); 42-52. Doi: 10.1021/bk-1997-0652.ch005. 1997 American Chemical Society.</p

Short-term Effects of Burning and Disking on Songbird Use of Floodplain Conservation Easements

Extensive conversion of Midwestern riparian areas for agricultural production has had many consequences including reduced habitat for nesting birds. However, more than 120,000 ha of riparian habitat have been restored in this region through USDA conservation programs. In 2001 and 2002, we assessed songbird responses to burning and disking for management of conservation easements in east-central Iowa. We randomly assigned herbaceous riparian fields to burning and disking treatments and collected data on density and species richness of songbirds in these habitats. Total density of grassland and wetland species and red-winged blackbirds (Agelaius phoeniceus) were reduced by burning in the first and second breeding seasons after burning; common yellowthroat (Geothlypis trichas) density decreased with burning only in the first season. Disking led to increased density of grassland and wetland birds and greater overall avian conservation value on treated relative to untreated fields in the year after treatment. Changes associated with burning and disking treatments were likely related to changes in both vegetation structure and abundance of arthropod food resources. Despite decreased bird densities with burning, fire is a necessary management tool to control woody vegetation. Overall, both burning and disking appear to be effective management practices for maintaining herbaceous riparian habitats for grassland birds.This article is from American Midland Naturalis 165 (2011): 257, doi:10.1674/0003-0031-165.2.257.</p