Assessment of heavy metal contamination in the sediments of Meda - Ela canal near Karadiyana semi-controlled dumpsite, Sri Lanka

The pollution of natural waterbodies with landfill leachate from dumpsites is a severe environmental issue all over the world. Karadiyana semi-controlled dumpsite in the Western province of Sri Lanka is one of the largest dumpsites in the country. The leachate generated in the dumpsite directly flows into Meda Ela canal which is a tributary of Bolgoda Lake Weras Ganga system causing a significant pollution threat on aquatic life. The current study assesses the contamination level of selected heavy metals in the sediments of Meda-Ela close to the dumpsite. The study was carried out for a period of one year from January - December 2018. The sediment samples were characterized with an alkaline pH ranging from 8.40 to 8.70. The electrical conductivity of the sediment was recorded with a mean value of 139.93 ± 26.7 µS/cm. The mean concentration of Cu in sediment was of 73.53± 2.52 mg/Kg and it falls into the EPA guideline for heavily polluted sediments. Total Cu concentration exceeds the threshold effect concentration but falls below the probable effect concentration. The total Fe concentration was relatively high (110.83 ±1.96 mg/Kg) among the measured metal species. The other metals, Cd, Cr and Zn was recorded with mean concentrations of 0.38 ± 0.03,103 ± 41.62, 94.4 ± 2.08 mg/Kg respectively. Pollution Load Index of the sediment was 0.87 and therefore it comes under no pollution category. This suggests that there is no appreciable input from anthropogenic sources. Based on geo- accumulation index, sediments are moderately polluted with respect to Cu and Cd.