Heavy Metal Contents in Surficial Sediment of Banjir Kanal Barat and Babon Rivers, Semarang, Central Java, Indonesia

Abstract

Bottom sediment (0 -5 cm) along the Banjir Kanal Barat (Garang River) and Babon Rivers which are situated in Semarang, Central Java, Indonesia were analyzed for their trace/heavy metals content Eight elements namely Nickel (Ni), Copper (Cu), Lead (Pb ), Chromium (Cr), Cadmium (Cd), Zinc (Zn), Iron (Fe), and Manganese (Mn) were investigated. Their concentrations provide information related to the industrial and municipal discharge. There are serious concerns about the contamination in the study area, and previous studies found some elevated concentration of several metals (trace elements). Total metal analyses of the fine (< 63 μm) sediment fraction by Atomic Absorption Spectrophotometer using strong acid digestion indicated high (Ni, Cu, Zn, and Mn) metal contamination. Weak acid digestion of total sediments (whole fraction) showed relatively low Cd to moderately (Cu, Cr, and Pb) levels. High Iron concentration was detected using X-RF Fluorescence. The result of trace/heavy metal and sediment characteristic analyses were statistically processed by Spearman's Rank Correlation analyses. In the Babon River, weak acid digestion results found a strong correlation between organic carbon and Chromium. Sediment characteristics, particularly in terms of organic carbon, appeared to be the primary factor controlling metal concentration. In Babon River, strong acid digestion showed that most metals were highly correlated with Mn (𝘱 < 0.05) , except Zn. In Banjir Kanal Barat River, weak acid digestion results show that Copper (Cu) was highly correlated with organic carbon. From strong acid digestion results significant relationship was found between Zn and Mn (𝘱 < 0.05) . Analyses of surficial sediment in Banjir Kanal Barat River demonstrate very little significant correlation between metals and sediment characteristics. This condition probably reflected the diverse nature of metal input into the system, either originated from point or non-point sources. However, statistical (t-test) analyses suggested that there were contamination of Ni, Cu, and Zn in both rivers. Most of these values exceeded the Canadian Standard/Guidelines for contaminated soils and sediments. In addition, t-test result also showed different levels of contamination between Banjir Kanal Barat and Babon Rivers. Mean values indicated higher contamination in Banjir Kanal Barat River compared to Babon river.