抄録
Benthiocarb was detected in raw water but not in processed tap water. This was attributed to chlorination in the filtration process at water purification plants. A study was conducted to identify the degradation products and to elucidate the degradation characteristics. Concentrations of the degradation products in tap water were also determined.
The degradation products identified in the regions of differents pH values, i.e. acidic, neutral and basic, were p-chlorotoluene, p-chlorobenzaldehyde, p-chlorobenzyl chloride, p-ethyl chlorobenzoate, p-chlorobenzyl acetate, p-chlorobenzyl alcohol, p-chlorobenzoic acid and three other products. The difference in the amount of products was large when compared among the regions of different pH values. A small quantity of benthiocarb remained intact in the basic region when compared to the acidic or neutral region.
The total amount of identified degradation products was about 3% at the acidic region, but the amount gradually increased with the rise of pH value, amounting to about 20% at the basic region. The products other than those identified were assumed to be aliphatic fatty acids, carbon dioxide, water and cyclic molecular sulfur. The more acidic region of pH value became, the more degradation to carbon dioxide, water and cyclic molecular sulfur proceeded. Chlorination for benthiocarb included mainly oxidization reaction and partly chlorine addition reaction, chlorine substitution reaction and reaction with fellow degradation products.
Among the identified degradation products, p-chlorotoluene, p-chlorobenzaldehyde, p-chlorobenzyl chloride, p-chlorobenzyl alcohol, p-chlorobenzoic acid were detected in the tap water at our research laboratories. p-Chlorobenzaldehyde, p-chlorobenzyl chloride, p-chlorobenzyl alcohol in the order of ng·l-1 were detected in the tap water during the months when benthiocarb was being used. Among degradation products, p-chlorobenzyl chloride in the tap water was derived from benthiocarb chlorination.
