HEAVY METALS IN SURFACE SEDIMENTS FROM LAKE BATUR, BALI, INDONESIA: SPATIAL DISTRIBUTION, RISK ASSESSMENT, AND SOURCE APPORTIONMENT

This study aims to assess the environmental conditions of Lake Batur, Indonesia, a closed alkaline lake. In this study, the identification of heavy metals was carried out using 27 sediment and 13 water samples. The methods used in the study include magnetic susceptibility, geochemical, and multivariate analysis. The concentration of heavy metals in sediment samples follows the order Fe > Ti > Mn > V > Cu > Cr (wt%). The results of the pollution assessment (EF, Igeo, CF, and PLI) in sediment indicate that the lake sediment is currently polluted. The PLI shows that the Lake Batur sediment is in the high contamination category at all sample sites, especially because of the high enrichment of Cu and Cr. The use of metal (kepeng) in religious activities in temples near Lake Batur is believed to be the source of the Cu enrichment. The results of multivariate analysis and magnetic susceptibility reveal three groups of heavy metals in Lake Batur sediment based on their main sources: 1) Fe and Ti are dominated by lithogenic factors, 2) Cu and Cr are dominated by anthropogenic factors, and 3) Mn and V are influenced by a combination of lithogenic and anthropogenic factors. The heavy metal concentrations in water samples are as follows: Zn > Fe > Mn > As > Cu > Cr > Pb > Cd (ppb). Water samples show that heavy metal concentrations are still below the WHO's minimum drinking water threshold.