Cyanide potential pollution in ricefields as affected by traditional gold mine process using the Tong technique

Abstract Tong technique is one of gold processing methods employed by traditional gold mines in Indonesia. This technique involves cyanide compounds along with other substances to extract the gold from the ores, which could cause pollution of cyanide to the environment. This study was aimed to investigate potential cyanide pollution on a ricefield irrigated using water mixed with water wastes from a gold-mine process using a Tong technique. The study was conducted in North Lebong District, Lebong Regency, Bengkulu Province, Indonesia. The study involved collections of four water & sediment samples from Racun River and three water & soil samples from a ricefield irrigated using water from Racun River. All collected water, sediments, and soils samples were analyzed for hydrogen cyanide (HCN) in the Laboratory. Data showed HCN was found 0.59-0.96 ppm in the water of the river and 0.45-0.75 ppm in streambed sediments of the river, while 0.14-0.23 ppm in soils of the ricefields. Most HCN concentration in water & sediment were above the tresholds, except those in the soil. The implication of these findings is that the discharged wastes from the Tong technique had potential to cause cyanide pollution to the environments, particularly the river and surrounding ricefields.