Degradation of chlorsulfuron and triasulfuron in alkaline soils under laboratory conditions

Abstract

The degradation of chlorsulfuron and triasulfuron was investigated in alkaline soils (pH 7.1±9.4) spiked at 40 lg a.i. kg ±1 under laboratory conditions at 25°C and a moisture content corresponding to 70% ®eld capacity (±33 kPa), using high-performance liquid chromatography. Degradation data for the two herbicides did not follow ®rst-order kinetics, and observed DT 50 values in surface soils ranged from 19 to 42 days and from 3 to 24 days for chlorsulfuron and triasulfuron respectively. Disappearance of both chlorsulfuron and triasulfuron was faster in non-sterile than in sterile soil, demonstrating the importance of microbes in the breakdown process. The persistence of chlorsulfuron increased with increasing depth, which can be attributed to the decline in the microbial populations down the pro®le. The DT 50 value for chlorsulfuron at 30±40 cm depth was nearly four times higher than that in the top-soil. The results obtained show that persistence of these herbicides in alkaline surface soils at 25°C and at a moisture content of 70% ®eld capacity is similar to those reported in other European and North American soils. The study shows that if these herbicides are contained in surface soil layers, the risk of residue carry-over under southern Australian conditions is small. However, the rate of their degradation in alkaline subsoils is very slow, and under conditions conducive to leaching their prolonged persistence in the soil pro®le is possible. Materials and methods Soils and herbicidesThis study entailed three experiments. Experiment 1 consisted of chlorsulfuron and triasulfuron degradation studies in freshly collected surface soils (0±10 cm) of Avon (calcareous sandy loam), 84 A K Sarmah et al.

Comparision of HPLC and Bioassay Methods for Analysis of Sulfosulforun Residues in Wheat Field Soil

“…The halflife of herbicides in soil varies with the chemical structure and soil conditions that affect degradation. According to Sarmah et al (1999), the half-life of a sulfonylurea herbicide in soil can vary significantly depending on pH, temperature, moisture, texture and organic matter content of the soil (Blacklow and Pheloung, 1991;Sarmah et al, 1999). Sulfosulfuron, with a field half-life of 14 to 75 days, is often one of the more persistent herbicides (Vencill, 2002).…”

Application of Bioassays in Studies on Phytotoxic Herbicide Residues in the Soil Environment

“…The process of degradation and translocation of herbicide active ingredients depends on many environmental and soil factors, which determine their adsorption and absorption in the soil. Such factors include the type of soil, mechanical composition (particularly the content of clays and zeolites), temperature, moisture content, content of organic matter (humus), pH of soil as well as the content of soil entomofauna biomass Vicari et al, 1994;James et al, 1999;Sarmah et al, 1999;Sadowski & Kucharski, 2004). The sorption capacity of herbicides is defined by the index of soil sorption of the herbicide (K d ) and sorption of the herbicide to organic carbon (K oc ).…”

“…In particular cases biotests may also provide information on transport and on the situation of applied active ingredients (Günther et al, 1993;Sadowski & Kucharski, 2004). We may find numerous examples in literature concerning applications of plant biodetectors in studies on herbicide active ingredient residue (Günther et al, 1993;Stork & Hannah, 1996;Sarmah et al, 1999;Sekutowski & Sadowski 2005;2009).…”

“…herbicides) found in the soil environment. The phytotoxic effect of active ingredients originating from herbicides may be observed on the basis of the reduction of dry or fresh weight of roots or aboveground parts (stems, leaves) of test plants (Günther et al, 1993;Stork & Hannah, 1996;Sarmah et al, 1999;Sadowski et al, 2002;Demczuk et al, 2004;Sekutowski & Sadowski, 2005;2009). Thanks to the wide-scale application of the bioindication method using plants it is possible to evaluate the degree of contamination not only for the soil, but also for the entire agrophytocenosis (Dećkowska et al, 2008).…”

Calagem e o potencial de lixiviação de imazaquin em colunas de solo

“…A lixiviação de pesticidas no perfil do solo tem também implicações diretas no seu potencial de contaminação dos recursos hídricos do subsolo, já que, uma vez retirado das camadas superficiais de solo, onde há maior teor de matéria orgânica e atividade microbiana, a sua persistência pode ser prolongada (Sarmah et al, 1999;Costa et al, 2000;Prata et al, 2000;Albuquerque et al, 2001). …”