In Vietnam, the Co Dinh mine is the largest chromite mine in the country. Mining, ore dressing
and disposal of the tailings provide obvious sources of heavy metal contamination in the mine area. The
present study examined the influence of chromite mining activities on the adjacent lowland paddy field by
investigating heavy metal and As levels in the mine tailings, sediments, paddy soils and water. At paddy
fields located near the mine tailings, the total contents of Cr, Co and Ni were 5,750, 375 and 5,590 mg kg-1,
and the contents of their water-extractable form were 12.7, 1.16 and 32.3 mg kg-1, respectively. These
results revealed severe contamination of lowland paddy soils with Cr, Co and Ni as a result of mining
activity, suggesting serious health hazards through agricultural products, including livestock in this area. The
principal source of the pollution was sediment inflow owing to the collapse of the dike, which was poorly
constructed by heaping up soil. Moreover, water flowing out from the mining area was also polluted with Cr
and Ni (15.0-41.0 and 20.0-135 ?g L-1, respectively). This might raise another problem of heavy metal
pollution of watercourses in the area, indicating the need for further investigation and monitoring of
fluctuations of water quality with seasonal changes. ?? 2010 Japanese Society of Soil Science and Plant
Nutrition.
