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[Occurrence and Characteristics of Macro/Micro-plastics and Phthalates in Soils Under Different Plastic Film Mulching].
Summary
Researchers assessed residual characteristics of macroplastics, microplastics, and phthalate plasticizers in agricultural soils under different plastic film mulching treatments over a three-year field experiment, comparing traditional PE film with three types of biodegradable mulch and a no-mulch control. The study examined whether biodegradable film substitution effectively reduces soil plastic and PAE residual pollution.
Biodegradable plastic film mulching （BFM） replacement is one of the effective approaches to alleviate the plastic residual pollution caused by long-term and extensive application of traditional mulching film in agriculture. However, information on their residual characteristics of plastic and PAEs in practical applications is limited. Here, we determined the residual characteristics of macroplastics and microplastics, as well as phthalates （PAEs）, in soils based on a three-year site-specific field experiment with five treatments including non-mulch film （CK）, traditional PE film （PE）, and three fully BFMs bought from the manufacturers, namely BS, HB, and SH, respectively. The results showed that the amount of macroplastics （>5 mm） in the soil ranged from （3.24±2.77） to （67.93 ±11.65） kg·hm-2, with the order of PE>BS>HB>SH. The dominant colors of macroplastics were transparent in CK, silver-black in PE, and black in the three biodegradable film mulch treatments. The abundance of microplastics in the soils ranged between （4 950±219） and （9 152±563） particles·kg-1, with an increase of 29.78%, 84.89%, 52.89%, and 51.11% for PE, BS, HB, and SH treatments compared to that in CK, respectively. The dominant shapes of microplastics were sheets and particles, and the colors were mainly transparent and black. Plastic film mulching reduced the proportion of sheet-shaped microplastics, while increasing the proportions of black microplastics and microplastics with sizes less than 20 and 20-100 μm, especially in the BMF-treated soils. Plastic film mulching also showed a non-significant increase in the total contents of five detectable priority controlled PAEs in the soil. The ecological risk grades of DBP were raised to a low and medium level by PE film mulching and BMF, respectively. Overall, our study demonstrated that plastic film is a major source of macroplastics and microplastics in soils, and continuous use of biodegradable plastic film can effectively reduce the residual amounts of macroplastics, while leading to more accumulation of microplastics with smaller particle size and increasing the ecological risks of DBP in soils.