Occurrence, source, and ecological risk of quaternary ammonium compounds in streams near industrial zones: a different pattern of pollution from other Japanese watersheds.

Quaternary ammonium compounds (QACs)-biocides used in households, agriculture, and industry-have been increasingly detected in aquatic environments. However, the occurrence of QACs attributed to manufacturing is not well documented. We therefore monitored 14 QACs (benzalkonium chloride-C8, C10, C12, C14, C16, C18; dialkyldimethylammonium chloride-C8, C10, C12; alkyltrimethylammonium chloride-C8, C10, C12; benzethonium chloride; and cetylpyridinium chloride), a disinfectant (chlorhexidine), and 17 human and veterinary drugs seasonally in 15 streams near industrial zones in Japan. The concentrations of four QACs exceeded the ranges reported in surface waters and treated effluent worldwide. Concentration ratios (ΣDrugs ÷ ΣQACs) at most sites were much lower than those reported in Japanese municipal sewage treatment plants and watersheds receiving wastewaters from unsewered households and swine farms, indicating QACs in the study area are mainly not attributable to domestic and livestock wastewaters, which largely contain pharmaceuticals. Given that most sites of ΣQACs >1000 ng/L, where ΣQACs were relatively stable throughout the year, largely receive textile wastewater (>1000 m3/day), main source of QACs here could be the textile industry. Though catchment-average concentrations of QACs reported in the above-mentioned watersheds were correlated with their mean raw sewage concentrations, those in the study area were linked with their emissions from the textile industry reported by a Japanese ministry, supporting the dominant impact of the textile industry here. Ecological risk quotients of several QACs were >1 at several sites. Our findings on pollution hotspots of QACs attributable to the textile industry could provide a new perspective on their management.