Environmental Dissipation of Fungicide Triphenyltin Acetate and Its Potential as a Groundwater Contaminant

Jui-Hung Yen, Chia-Chun Tsai, Cheng-Chang Su, and Yei-Shung Wang¹

Department of Agricultural Chemistry, National Taiwan University, Taipei 10617, Taiwan

        The effects of various factors on fungicide triphenyltin acetate dissipation in selected soil types were studied; temperature is clearly the more important factor of these.  Residues of this fungicide in Fangtzupo clay loam and Lanyang loam incubated at 30℃ for 32 days (water content 100, 70 or 40% of field capacity) were 25% of the original amounts.  In soil samples incubated at 10, 30 or 40℃ with 100% field capacity water content, residues were 80, 26 and 5.5% for Fangtzupo soil, respectively, and 83, 26 and 7.0% for Lanyang soil, respectively.  No significant difference in dissipation rate was found between sterilized and unsterilized soil, suggesting that microbial degradation is not an important factor in this process.  Rapid degradation rates were observed--- half-lives of 8.3 to 19.4 days in Fangtzupo clay loam and 8.0 to 16.3 days in Lanyang loam at temperatures ranging from 30 to 40℃ (soil water content of 100, 70 and 40% of field capacity).  Significant increases in half-life (approximately 150 days) occurred at lower temperatures (10℃) in both soil types.  The potential of triphenyltin acetate to contaminate groundwater was tested using the behavior assessment (BAM) and groundwater pollution-potential (GWP) models.  Results indicate that the leaching rate of the fungicide is very slow (1.0 cm day^-1) under normal conditions.