THYMOL AS A BIOCIDE IN JAPANESE RAINWATER

Rainwater samples (wet-only; event samples) collected in Niigata in la te autumn 1996 and springtime 1997 were used to assess the effectivene ss of thymol as a biocide in Japanese rainwater. Upon collection each rainwater sample was divided into sub-samples, with thymol added to on e sub-sample. Sub-samples with and without thymol were shipped to CSIR O, Australia, for chemical analysis. Comparison of analytical results for each pair of sub-samples proved the effectiveness of thymol in pre venting biological action in this region where effects of rainwater mi croflaura and fauna on rainwater composition have not before been stud ied. Sub-samples without thymol exhibited lowered electrical conductiv ity, loss of the cations H+ and NH4+, and loss of the anions HCOO-, CH 3COO-, C2O42-, CH3SO3- and PO43-. Nitrate showed no change in all but one of the samples, indicating that ammonia was the preferred source o f nitrogen for the biological processes that consumed the rainwater or ganic acids and phosphate. These results suggest that thymol is a suit able rainwater biocide for use under Japanese conditions.