Abstract
Standing water was collected on September 17th and 20th, 2016 from the underground space of the planned new food market facility in Toyosu, Koto-ku, Tokyo where there is a big concern on soil and ground water pollution for food safety. Hydrogen ion concentration index （pH） and element concentration of the dissolved and suspended fractions of the water samples were determined. The measurements have shown strong alkaline condition （pH 11.5） for the standing water. Molybdenum concentration was 190 and 170 µg/L on 17th and 20th respectively, largely exceeding the guideline value （70 µg/L） of the items to be monitored. Compared with non-contaminated level in ground water, the concentration factors in the standing water ranged from several hundred to thousand times higher for molybdenum, several hundred times for vanadium, gallium and tin and several dozen times for nickel and antimony. These elements are also found in coal fly ash in high concentration relative to natural soil. This study made it clear that the contamination involves various harmful elements in addition to arsenic, mercury, hexavalent chromium, benzene and cyanide which have been subjected for many media reports. The high concentration and composition of unreported harmful elements confirmed that the contamination in the standing water is mainly due to the legacy pollution of soil and ground water caused by the previous gas production from coal. The over-guideline value of molybdenum concentration indicates a necessity of further monitoring of the pollution and investigation on adverse effects to environment and food safety. In the current situation, more precise and accurate re-examination should be made with larger number of samples in the long-term basis for the risk assessment, pollution control and decontamination based on precautionary and the polluter-pays principles.
