Heavy metal concentrations in Rupat Strait Riau province of Indonesia

The Rupat Strait is a strait dense with anthropogenic activities as it borders the city of Dumai and Rupat Island, serving as a connecting route between Indonesia and the Strait of Malacca. This makes the Rupat Strait a main route for national and international shipping. The Rupat Strait is also dense with industrial activities, settlements, and domestic life. Anthropogenic activities around the Rupat Strait are estimated to impact the waters of the Rupat Strait. Heavy metals are one of the wastes that can potentially enter the Rupat Strait. Heavy metals have a significant potential to degrade the quality and health of the Rupat Strait environment. In addition to anthropogenic activities, the Rupat Strait also plays a crucial role in providing livelihoods and food for the surrounding communities. Fish are marine catches with significant advantages for communities around the Rupat Strait. The quality of fish caught from the Rupat Strait plays a major role in the health quality of the people in the Rupat Strait. This research aims to assess water quality, particularly metal contamination in the Rupat Strait, and its risks to public health. The sampling method used in this study is purposive sampling for the components of water, sediment, and fish. Water components were taken during the dry and rainy seasons. Measurements were conducted in situ and analysed using Atomic Absorption Spectrophotometry. The parameters measured include the physicochemical characteristics of water and sediment and the concentration of metals in water, sediment, and fish. The average pH value of the water obtained is 1.624, Salinity 0.067 ppt, TDS 5314.101 ppm, TSS 10.902 mg/l. The results revealed a significant difference between the dry and rainy seasons with p < 0.05. Water pollution status in the Rupat Strait is from unpolluted to lightly polluted, with a Pollution Load Index ranging from 0.00 to 0.621. The concentration of metals in the sediment is as follows: Cd at 0.13 mg/kg, Cu at 0.70 mg/kg, Fe at 995.62 mg/kg, Pb at 3.76 mg/kg, and Zn at 32.70 mg/kg, all of which are below the quality standards. The order of the highest values for total metal concentration in sediments is Fe > Zn > Pb > Cu > Cd, with the average percentage of the most abundant fraction being Reducible > Residual > Oxidizable > Exchangeable. The metal pollution status in the Rupat Strait ranged from unpolluted to lightly polluted, with a metal pollution index value between 0.0688 and 0.7586. The THQ and HI values for the metals Cd, Cu, Fe, Pb, and Zn in fish and shrimp from the Rupat Strait were less than 1, which means that the fish and shrimp do not pose a significant health risk. The TR values for the metals Cd and Pb in fish and shrimp are< 10-6 and less than <10-4 , indicating that the fish and shrimp in the Rupat Strait are not at carcinogenic risk.