Environmental risk assessment of floating gardens in Inle Lake, Myanmar

Abstract

Inle Lake is a valuable wetland for local ecosystems and one of Myanmar's freshwater biodiversity hotspot. In this lake, poor management of floating gardens cultivation by some farmers has resulted in leaching of excess nutrients, and then water and sediment were contaminated by chemical residues. This study aims to assess the environmental risk to Lake Ecosystem by investigating the nutrient contamination of water, sediment and monitoring pesticide residues from fish, sediment along with water. Sediment and Water samples have been gathered from non-GAP and GAP floating gardens, including the central lake as a reference point, during the wet season of 2019 and dry season of 2020. Health risk linked with intake of pesticide residues in fish from floating gardens and central lake are assessed. The result showed that the pesticide and fertilizer applications were increased in non-GAP when compared with GAP method. The nutrients (nitrogen, phosphorus) contamination was higher in non-GAP than in GAP for both water and sediment. The presence of pesticide residues in surface sediment shows that the non-GAP farms had higher concentrations than the GAP farms. For the water pollution assessment, the water quality index value was higher in non-GAP than in GAP. Nutrient pollution assessment indicated that nutrient contamination threatens in floating garden sites but non-GAP has potentially influence on Lake Ecosystem. The health risk assessment model resulted that current used pesticide residues are not caused detrimental effects on human health but in long run, low doses exposure has been linked to human health. This study concludes that poor management of agricultural practices by more agrochemicals usage has had a negative effect on the surface water, ecosystem and sediment of the lake.