Contamination of Vinyl Chloride in Shallow Urban Rivers in Osaka, Japan

Vinyl chloride (VC) contamination had taken place in heavily polluted shallow rivers (Taishogawa and lower Hiranogawa Rivers) in Osaka, Japan. VC concentrations ranged from below detection limit to 55.6 μg l−1 (mean: 3.35 μgl−1, standard deviation: 5.96 μg l−1). Of 55 volatile organic compounds (VOCs) analyzed, concentrations of cis-1,2-dichloroethene (c-DCE), tetrachloroethene (PCE) and trichloroethene (TCE) were significantly correlated to VC concentrations in the rivers, indicating that they share common sources. The four VOCs were invariably present at approximate relative ratios of about 1 : 2.7 : 1.5 : 0.31 (VC: c-DCE: PCE: TCE). The similarity between sampling dates in the distribution pattern of the four VOCs concentrations were observed, but their concentrations were different between the dates. The concentrations of the four VOCs decreased with distance down the river. A sample from the upper Taishogawa River in July 1997 had 55.6 μg l−1 of VC, 152 μg l−1 of c-DCE, 86.2 μg l−1 of PCE and 18.4 μg l−1 of TCE, respectively. These values are about an order of magnitude higher than the other sites over the study period and are likely indicative of point source inputs.