Are microplastics correlated to phthalates in facility agriculture soil?

Intensive use of plastic films can induce contamination of microplastics (MPs) and phthalate esters (PAEs), but data on their relationship in agricultural soil has been scarce. This study investigated the occurrence of MPs and PAEs in Shouguang (SG) and Xuzhou (XZ), two typical facility agriculture areas in China with years of history of vegetable greenhouse plantation. Thirty-four soil samples covering greenhouse and non-greenhouse soils were collected. MPs were quantified using the laser direct infrared (LDIR) method to realize IR analysis for all the collected particles. The total MP and PAE was 380-3786 pieces/kg and 0.30-1.58 mg/kg, respectively. The MP content in greenhouse soil was significantly higher than that in non-greenhouse soil in both areas. However, this trend for PAEs was only found in XZ, but not in SG. A positive correlation was observed between MPs and PAEs in XZ but not in SG. Our results suggested that MP concentrations mainly depend on input, while the residue of PAEs in soil was a consequence of both input and removal. Even in the facility soil, MPs and PAEs may not always possess a definitive relationship, and other environmental factors must be considered to elucidate the relationship between them.