Der Einfluß des Wassergehaltes auf den Atrazin-Abbau im Boden

The influence of water-content on atrazine degradation in soil In samples of the standard soil 2.2 (loamy sand, 3 % C, pH 7,0) and of a Luvisol (Ap-horizon, loam 1,4 % C, pH 5,2), the degradation of [ethyl-1-¹⁴C]atrazine was investigated in dependence of the soil water content. The experimental conditions were choosen in accordance with the methods proposed by the Biologische Bundesanstalt to study the degradation of pesticides in the soil. The soil water content was varied to simulate the moisture conditions observed in a soil during plant growth. Therefore, besides a steady water content of 20, 40, 60, and 80 % of the maximum water holding capacity of the soils, the soil water contents were fluctuated by 20 to 60 % of the maximum water holding capacity by passing dry air through the soil. At a concentration of 10mg atrazin/kg of soil between 4 and 6 % of the ethyl-1-carbonatom of the atrazine molecule was mineralized to CO₂ within 71 days at a constant soil temperature of 22°C. In the standard soil 2.2 the mineralization in total was reduced to 2/3 compared to the degradation in the Luvisol. With decreasing water content increasing hydroxilated metabolites were formed. About 30–40 % of the applied radioactivity was determined as non-extractable residue in the soil. In general the degradation processes were more enhanced and more intense in the Luvisol as compared to the Standard soil 2.2 which again unterlines that for this type of experiments a fresh soil should be used. In conclusion, the variation of the soil water content did not have a pronounced influence on the mineralization rates of atrazine, but did influence the metabolism and the formation of certain metabolite fractions.