Portal de Periódicos da CAPES

Remobilization by a major earthquake of DiPhenylArsinic Acid (DPAA) pollution at a site in Kamisu City, Japan

2017; International Union of Geological Sciences; Volume: 40; Issue: 1 Linguagem: Inglês

10.18814/epiiugs/2017/v40i1/017005

2586-1298

Tomoyo Hiyama, Hisashi Nirei, Jonas Satkunas, Kunio Furuno, Kazuya Kimura,

Pesticide and Herbicide Environmental Studies

Japan has a limited amount of readily developable land.Sites are used and reused with alternating phases of excavation and deposition of man-made strata (MMS).The Great East Japan earthquake of 11 th March 2011 caused widespread damage due to ground waves and associated liquefaction-fluidization of MMS.A site at Kamisu City, Ibaraki Prefecture, was significantly affected.There, a gravel pit had been filled, partly excavated and then refilled.In 2003 it was found that a nearby drinking water well was seriously contaminated with arsenic.The site was sampled using a grid of boreholes and then excavated within a sheet pile enclosure at the source of the arsenic.The pollution came from large blocks that had been made by mixing cement with DiPhenylArsinic Acid powder and wastes that had been illegally dumped during refilling.The blocks were excavated and removed.Contaminated groundwater was pumped out and purified and the excavation was filled.The site was thought to be decontaminated, but the earthquake caused liquefaction-fluidization. Sand and water contaminated with arsenic were extruded onto the land surface through sand boils.After careful investigation of the site history and the depositional stages of the MMS it was found that arsenic had not been fully removed from MMS beneath the level containing the blocks because remediation works had been designed on the basis of grid sampling rather than an understanding the stratigraphy of, and discontinuities within and beneath, the MMS.The mechanism of DiPhenylArsinic Acid (DPAA) geopollution had not been properly understood.It is important to take history and stratigraphy of MMS into account when designing surveys and works.