Localized Profile of Arsenic in Soil and Water in the Area Around Gold Mine

Soil and water samples from the area vicinity to gold mine at Wangsaphung District, Loei province, have been collected to investigate the arsenic concentration. Five boreholes were drilled into the ground until reaching to gravel layer or bedrock, and Soil samples were collected at every 0.50 - meter depth. Four boreholes are located inside the catchment in which the gold mine situated whereas the other one was bored at the outside. In addition, 13 sets of surface water and 8 sets of groundwater were also collected. The results of concentration test indicated that soil samples within at least 3 boreholes have arsenic content enormously exceeded the maximum concentration limits (MCL) specified by the Office of National Environment Board of Thailand. Geologic condition underneath soil layer also play an important role on the concentration of arsenic. Soil column placed on the originally-deposited gravel bed can retain less concentration of arsenic, whereas soil column on bedrock can retain much more. For water samples, arsenic contents were generally less than 10 μg/l, the MCL specified by U.S.EPA, except that there is one interesting location found extremely high. That location give an useful information for further finding of arsenic pathway.