Estimation of Sorption Coefficients for Fungicides in Soil and Turfgrass Thatch

Abstract

Environmental fates of turf‐applied fungicides are not well understood. The role of thatch as a sorptive surface for fungicides has not been evaluated. Thatch may decrease mobility of fungicides and decrease their potential to be transported off‐site. Batch type sorption studies were conducted to determine sorption coefficients (Kf) for the fungicides triadimefon, [1‐(4‐chlorophenoxy)‐3,3‐dimethyl 1‐1‐(1H‐1,2,4‐triazol‐1‐g‐1) butanone], vinclozolin [3‐(3,5‐dichlorophenyl)‐5‐methyl‐5‐vinyl‐1,3‐oxazolidine‐2,4‐dione], and chloroneb (1,4‐dichloro‐2,5‐dimethoxybenzone) in thatch and in the underlying soil. The Kf values also were derived from octanol/water partitioning coefficients (Kow) for these and five other compounds. All Kow values were determined with reverse‐phase high pressure liquid chromatography (HPLC) and calculated from physical properties of the fungicides. The Kf values [µmol(l‐n) Ln kg−1] determined from isotherm data for thatch and soil (respectively) were 90 and 10 for triadimefon, 163 and 21 for chloroneb, and 431 and 47 for vinclozolin. When Kf values were adjusted for organic C content of the sample, the resulting Kow values were similar for thatch and soil. The Koc values estimated from HPLC‐derived Kow values were consistently less than those obtained using batch isotherm methods. The Kow values calculated from physical properties of the fungicides were poorly correlated with measured values. The HPLC method appears to be useful for determining sorption coefficients. Results indicate that thatch substantially increases fungicide sorption, which, in turn, decreases the potential for these compounds to migrate off site.

Pesticide transport with runoff from creeping bentgrass turf: Relationship of pesticide properties to mass transport

“…Therefore, the pesticides were primarily on the leaf tissues rather than in the underlying thatch or soil at the onset of precipitation. Others have shown that pesticide residues can be found in thatch where they may be sorbed [34][35][36], resulting in reduced mobility to underlying soil [37,38]. It is important to point out that numerous environmental and management factors contribute to the availability of pesticides for movement with overland flow.…”

Atrazine and Metolachlor Sorption to Switchgrass Residues

“…Other studies have shown greater pesticide adsorption capacities on thatch or dry straw than on soil for fungicides (Dell et al 1994) and herbicides (Reddy et al 1995;Rautri et al 1997). High organic matter soils have much higher atrazine and metolachlor K d values (i.e., 40 and 66 L kg 21 , respectively) than low organic matter mineral soils Seybold and Mersie 1996).…”

Spatial and Temporal Distribution of Fungicides Applied to Creeping Bentgrass

“…The presence of turfgrass cover drastically reduced the movement of fungicide residues into the soil. Dell et al (1994) conducted sorption studies for triadimefon, vinclozolin, and chloroneb in thatch and soil. They were able to show that thatch drastically increased the sorption of fungicides.…”

“…Horst et al (1996) monitored the vertical movement and dissipation of pendimethalin, chlorpyrifos, isazofos, and metalaxyl. Sorption studies were conducted for the fungicides triadimefon, vinclozolin, and chloroneb in thatch and soil (Dell et al, 1994). Frederick et al (1994) observed the degradation of chloroneb, triadimefon, and vinclozolin in soil, thatch, and grass clippings under laboratory conditions.…”