Abstract
Very high concentration of Cr6+ was detected from leachate on a street pavement in March 2011, in Komatsugawa, Edogawa-ku, Tokyo. This study has aimed to monitor Cr6+ leaching on a long-term basis, and therefore retaining water in drainages has been collected every month since January 2013. More than several dozen mg/L of Cr6+ was regularly observed in the water samples and their pH exceeded 10. The high pH value was corresponding with that reported for the Cr6+ sludge, suggesting a strong influence from dumped sludge. The trend of contamination could be associated with a few-meter-scale-distribution of sludge because concentration of Cr6+ and its monthly change differed intricately by the drainages. High level of Cu, Zn, Cd, Pb and other heavy metals as well as Cr6+ were detected from the leachate collected in March 2011, and electric conductivity and Cr6+ concentration were proportionally increased each other in the retaining water samples collected in and after January 2013. These facts indicate sludge has been an emission source of various hazardous elements. There remain many tasks including pinpointing the source of the leachate, elucidating chemical mechanism of leakage, investigating actual situation of release of Cr6+ through the combined sewage collection system and so on. We need to keep monitoring the latest status of pollution and resolve the issue by collaborating with public and local organizations concerned.
