Heavy metal pollution and mobility of sediment in Tajum River caused by artisanal gold mining in Banyumas, Central Java']Java, Indonesia

The heavy metals Cu, Pb, Zn, and Cd in the stream sediment of the Tajum River were studied based on 12 sediment samples obtained from upstream to downstream. The artisanal mining activities in the study area generated mining processing waste (tailing) and are the primary source of heavy metal pollution. The samples were analyzed for metal concentration as well as metal mobility based on sequential extraction analysis. Heavy metal analysis for the concentration of the metals showed that the value of Cu, Pb, Zn, and Cd in sediment samples transcends the mean crust. The change of the heavy metal concentrations in stream sediment between the upstream and downstream areas showed that higher levels were located near mining activities in upstream and that these decreased with distance to downstream. The result of the sequential extraction study revealed that Cu and Pb were more found in the exchangeable and carbonate fraction of about 26% and 24%. Meanwhile, Zn and Cd were present in the Fe-Mn oxide, an organic and residual fraction of about 90% and 85%, respectively. The mobility factor assessment revealed that the heavy metals investigated had an average mobility factor of 25.89%, 23.9%, 14.4 %, and 9.24% for Cu, Pb, Zn, and Cd, respectively. Overall, Zn and Cd in sediment in the study area were less mobile compared with Cu and Pb.