Pollution Characteristics and Ecological Risk Assessment of Microplastics and Six Phthalate Esters in Farmland of Shanghai Suburb

Microplastics (MPs) and phthalate esters (PAEs) pollution in farmland soil have received great attention in recent years. Used and discarded plastic products of agricultural production process is probably important source of MPs and PAEs, as a typical plasticizer, in environment. In this study, pollution characteristics of MPs and PAEs in agricultural soil from greenhouse and filed in Shanghai suburb were investigated. The ecological risk assessment of PAEs was also performed. The results show that abundance of MPs in greenhouse and field soil were (1.47±0.54)×10⁵ and (2.06±1.10)×10⁵ items·kg^-1, respectively. The proportions of polyvinyl chloride and polyethylene terephthalate in greenhouse soil were relatively high, while in field soil polyethylene contributed the most. In greenhouse soil, the average proportions of pellet, film and fiber MPs were 77.1%, 21.3% and 1.6%, respectively, of which the pellets and films MPs mainly composed of polyvinyl chloride, polyethylene terephthalate and nylon. In the field soil, the average proportions of pellet, film and fiber MPs were 45.5%, 54.0% and 0.5% respectively, of which the pellet and film MPs mainly composed of polyethylene, nylon and polypropylene. The concentration of PAEs in greenhouse soil and field soil ranges from 151.3 to 2 026.3 μg·kg^-1 and from 186.3 to 503.4 μg·kg^-1, respectively. Bis (2-ethylhexyl) phthalate and dibutyl phthalate were dominant in soil samples, with an average concentration of 402.5 and 128.2 μg·kg^-1, respectively, which were one to two orders of magnitude higher than the other four PAEs. Overall, the ecological risk of PAEs in farmland in the suburbs of Shanghai is at low to medium level. The results of this study indicate that greenhouse plastic film and agricultural plastic film have a significant impact on the content and composition of MPs and PAEs in soil. Subsequent research should be conducted on the environmental fate of plastic residues during agricultural production in order to develop pollution prevention and control strategies for MPs and PAEs in farmland soil.