Occurrence and spatial distribution of microplastic contaminated with heavy metals in a tropical river: Effect of land use and population density

Microplastics are of concern due to their potential environmental risks. This research aims to find the effect of land use (agriculture, urban, and aquaculture) and population density on the abundance of microplastics contaminated with heavy metals in surface water and sediment of the Chao Phraya River in Thailand. Results indicated that population density is directly correlated with increased microplastic abundance. Most microplastics were found in the urban zone (water: 80 ± 38 items/m3 and sediment: 62 ± 11 items/kg) and were small fragments (0.05 to 0.3 mm). Polymer types of polypropylene and polyethylene were commonly found. Heavy metals of Cr, Cu, Cd, Pb, Zn, Ni, and Ti were detected in microplastics in water and sediment, with Cu, Pb, and Zn being the most dominant. Heavy metals in microplastics were highest in the agriculture zone. In general, the presence of metals on microplastics may potentially impact the ecosystem and human health. [Display omitted] •MPs were found in agricultural, urban, and aquaculture zones of Chao Phraya River.•Urban zone of the river had the highest MPs, agricultural zone had the lowest.•Population density showed a direct correlation with MP abundance on the river.•Most MPs were white color, fragment shape, PP, PE types, and 0.05–0.3 mm in size.•Cr, Cu, Cd, Pb, Zn, Ni, and Ti were detected in MPs at study zones of the river.