Ecological risk, seasonal and depth variations of toxic elements in a closed landfill in Vietnamese Mekong Delta province

Abstract

The study was carried out to assess ecological risks at the closed landfill in Cai Dau town, Chau Phu district, An Giang province. Soil samples were collected at six locations (S1-S6) at depths of 0-20 cm and 60-80 cm in the rainy season (November 2020) and dry season (March 2021). The soil quality was evaluated using eight heavy metals (Mn, Fe, Cu, Zn, Ni, Pb, Cr and As). The results showed that most monitoring sites had heavy metal contents within the allowable limits for agricultural land of QCVN 03-MT:2015/BTNMT. Some heavy metals have been found to migrate to the soil layer of 60-80 cm. The heavy metals accumulation (I geo ) in the two soil layers did not differ; Ni, Cr, Pb and As accumulated at non-polluting levels -moderate to high in the rainy season, while Cr and As only accumulated in the dry season. The composite pollution index (PLI) indicated that the locations around the landfill were polluted; however, the ecological risk ranged from low to moderate (potential ecological risk index (PERI) = 102-195) in the rainy season. Only about 50% of study sites during the dry season were contaminated and the risk was low (PERI = 44-68). However, the area around the landfill always poses potential risks due to the presence of heavy metals, including Ni, Cr, As and Pb. Monitoring the heavy metals in the surrounding landfill for the potential risks to human health and environment is needed.