Relevance of Hexavalent Chromium Seepage to Rainfall at Chromium Slag Dumping Site in Tokyo

Abstract

High Cr(VI) contaminants have often been detected in groundwater and soils around chromium slag dumping site in Tokyo. The actual status of Cr(VI) seepage in Ojima-Komatsugawa Park was surveyed from January to December 2016, followed with examination of its causes. Firstly, quite heavily concentrated Cr(VI) was detected in seepage water from permeable pipe at the Wansaka Field in the Park. The 50 mm of total rainfall was found to be the trigger for Cr(VI) to leach and spread to the sidewalk. Secondly, Cr(VI) exceeding the standard value concentration flows out into the sewage at the catch basin in Komatsugawa area during rainfall. Leakage at the both points could not be directly related to groundwater level. Results indicated that rainfall causes seepage of Cr(VI), which results in the ongoing pollution in these areas. There had been some attempts to remediate the pollution by applying iron sulfate, however, the investigation revealed significance of further development for fundamental solution.