Occurrence and distribution of plastic debris along shores sediment of Lake Hawassa, Ethiopia

Abstract

Micro-plastic particles are carriers of harmful substances including pathogenic bacteria and potentially invasive species. Their small size enables them to spread from one aquatic environment to another. Plastic pollution has been reported in sediment, surface water, and biota of freshwater systems especially in Europe, North and South America, and Asia with limited studies focusing on Ethiopia lakes. This study therefore investigated the occurrence and distribution of plastic debris along the shore sediment of Lake Hawassa. The occurrence and distribution of plastic debris along the shore sediment of Lake Hawassa was investigated at five sampling site(Tikur Wuha, Fiker haike, Amora gedel, Referral, and Loke) 1 kg of sediment was randomly collected with a stainless steel shovel from a random 1×1m at every sampling sites. Collected samples were immediately transferred to the laboratory and stored at 60°C by sealing in a perfect in Aluminum foil sack. Homogenized 50 g of each dried sediment sample was placed in a 1000 ml glass beaker, and 1.6g/ml zinc chloride in a750 ml was added. The mixture was manually stirred for 5 min, and after settlement the suspension was decanted in a beaker. The result shows that the average micro-plastics abundance in sediment samples ranged from 160 ± 2.55 to 326.67± 0.57 Items/kg. The highest abundance was found in the sediment of the Tikur wuha site about 326.67items/kg, and the lowest was at the Fiker hayik site about 160.00items/kg. MP size classes quantified between 0.25-0.5mm were the most abundant in sediment of all study sites. The most common MP particle types were fragment (41.1%), fibers (30.5%), spherical (12.2%), film (9.1%), and foam (7.1%) and also the large size shape of plastics was listed from the most dominant to smaller fragment, fibers , spherical, foam, and film . The common colors of MP identified were 49.2% white, 29.4% black, 7.6% yellow, 6.6 green, 4.6% red and 2.5 % blue. The plastic spatial distribution revealed major Plastic pollution in areas where recreational and tourism activities have been developed except Fikir Hayik site where low plastic distribution was recorded. These results demonstrated that the Tikur Wuha sites along Lake Hawassa are hotspot area for plastic pollution of the lake and should therefore be targeted for the management of plastic pollution of Lake Hawassa.