Abstract
In the present study, the metabolism of [$^{14}C$]butachlor was investigated in rice plant according to the OECD test guideline No. 501. [$^{14}C$]Butachlor was treated as granule to paddy water by application of 1.5 kg ingredient (a.i.)/ha at the 3~4 leave stage of rice plant. At 85 days after treatment (DAT), samples of panicle, foliage, and roots were taken for radioactivity analysis. Upon harvest at 126 DAT, rice plants were separated into brown rice, husk, straw, and root parts. Amounts of total radioactivity absorbed by rice plant ranged from 8.6 to 9.8% of applied radioactivity (AR). Total radioactive residues (TRRs) of rice plant at 126 DAT was the highest as 4.0421 mg/kg (7.3% AR) in the straw followed by 1.4595 mg/kg (2.4% AR) in the root, 0.7257 mg/kg (0.1% AR) in the husk. The lowest level recording 0.1020 mg/kg (0.1% AR) was found in brown rice. Each part was extracted with various solvents and solvent/water mixtures. Greater than 70% of TRRs was readily extractable from foliage, panicle, husk and straw. Only 34.0% of the brown rice and 43% of root based on TRRs were extractable showing that the residues were completely assimilated in the plant tissue. The level of non-extractable radioactivity was ranged from 26.2 to 66.0% of TRRs. From this study, five tentative major metabolites (M1, M2, M3, M4 and M5) were observed in rice extracts. Among the metabolites, 2,6-diethylaniline assigned as M4 was identified in rice plant by comparing to retention time of reference standard. Un-metabolized butachlor was not detected in any fractions. In soil extracts, N-(butoxymethyl)-N-(2,6-diethyl phenyl)acetamide, 2,6-diethylaniline, M2, M3 and M5 were observed. And the concentration of butachlor was low level (ca. 0.03 mg/kg).
OECD Test guideline 501에 따라, 벼에서의 [$^{14}C$]butachlor의 식물대사 시험을 실시하였다. 시험토양은 국내 논토양의 대표적인 토성인 양토였으며, 사용지침서상의 사용법에 준하여 이앙 6일 후 [$^{14}C$]butachlor를 입제로 조제하여 1.5 kg/ha 수준으로 토양 수면에 처리하였다. 시료는 시험물질 처리 후 85일과 126일에 채취하였다. 85일 시료는 이삭, 벼 잎, 뿌리로 126일 후 시료는 현미, 왕겨, 볏짚, 뿌리로 분리하였다. 모든 식물 부위의 총 방사성 잔류량은 0.01 mg/kg 이상이었다. 그 후, 대사산물과 모화합물를 확인하기 위하여 극성이 다른 유기용매와 물 혼합용액을 이용하여 시료를 추출 후 Radio-HPLC로 분석하였다. 벼 추출액 중 butachlor는 검출되지 않았고, 5개의 잠정적 주요 대사산물(M1, M2, M3, M4 그리고 M5)이 검출되었으며, 대사산물 중 M4는 2,6-diethylanline로 동정되었다. 토양 추출액에서 N-(butoxymethyl)-N-(2,6-diethyl phenyl)acetamide, 2,6-diethylaniline, M2, M3 그리고 M5가 검출되었으며 butachlor의 농도는 낮은 수준 (약 0.03 mg/kg)으로 검출되었다.
