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(19-28) Effect of chemicals on nitrogen transformation in soil. Roberts, Gary*,1, Penwell, Alison1, Peurou, Fabrice1, 1 AstraZeneca Global Safety, Health & Environment, Brixham, UK ABSTRACT- The OECD guideline 216, adopted on 21st January 2000, describes a laboratory test method to investigate the long-term adverse effects of a substance on nitrogen transformation activity of soil microorganisms. In the assessment and evaluation of toxic characteristics of test substances, determination of effects on soil microbial activity may be required. Therefore, a 28-day nitrogen transformation test was successfully developed according to the above guideline. Sieved soil was amended with powdered plant meal and either treated with the test substance or left untreated. In this investigation, the soil was exposed to 1.0, 3.2, 10, 32 and 100 mg of 2-Chloro-6-(trichloromethyl)-pyridine kg-1 dry weight. On day 0 and 28 of incubation, treated and control soils were extracted with 0.1M potassium chloride and the extracts were filtered. Following reduction of nitrate to nitrite and a diazonium reaction, the resulting diazo compound was coupled with N-(1-naphthyl)-ethylene diamine under acidic condition, to form a reddish dye. The quantities of nitrate were then determined by colorimetry at 545nm. Nitrate formed in treated samples was statistically analysed for a significant difference compared to the control. A dose-response curve was produced and the EC50 (± 95% C.I.) of 2-Chloro-6-(trichloromethyl)-pyridine was found to be 3.081 (1.894-4.267) mg kg-1 dry soil. Key words: nitrogen, nitrapyrin, pesticide, soil |
