Microplastics in arid soils: Impact of different cropping systems (Altay, Xinjiang)

Hao Liu; Xiyuan Wang; Qingdong Shi; Yuying Liu; Haifeng Lei; Yutong Chen

doi:10.1016/j.envpol.2022.119162

Microplastics in arid soils: Impact of different cropping systems (Altay, Xinjiang)

Environ Pollut. 2022 Jun 15:303:119162. doi: 10.1016/j.envpol.2022.119162. Epub 2022 Mar 17.

Authors

Hao Liu¹, Xiyuan Wang², Qingdong Shi³, Yuying Liu³, Haifeng Lei³, Yutong Chen³

Affiliations

¹ College of Resources and Environmental Sciences, Xinjiang University, Urumqi, 830046, China; Institute of Arid Ecology and Environment, Xinjiang University, Urumqi, 830046, China. Electronic address: liuhaolh1994@outlook.com.
² College of Resources and Environmental Sciences, Xinjiang University, Urumqi, 830046, China; Institute of Arid Ecology and Environment, Xinjiang University, Urumqi, 830046, China. Electronic address: wangxy@xju.edu.cn.
³ College of Resources and Environmental Sciences, Xinjiang University, Urumqi, 830046, China; Institute of Arid Ecology and Environment, Xinjiang University, Urumqi, 830046, China.

PMID: 35307499
DOI: 10.1016/j.envpol.2022.119162

Abstract

Although microplastic pollution in the soil environment is currently an important research topic, few studies have focused on farmland soil in arid regions. This study investigated the abundances, sizes, polymer compositions, and forms of microplastics across nine agricultural plots cultivated with maize, sunflower, and potato (three of each crop) plants to determine the influences of different cropping characteristics and agricultural practices. The study area was within the arid region of the Ulungur River basin in Qinghe County, Altay, Xinjiang, China. The main forms of microplastics were fragments and fibers, and polyethylene was the dominant polymer (91.6%). The microplastic abundance ranged from 11 347 items/kg_dw to 78 061 items/kg_dw (mean of 52 081.7 items/kg_dw). The abundance and proportion of microplastics with a diameter of <0.2 mm were significantly higher in the sunflower and maize plots (i.e., tall crops) than in the potato plots (i.e., short crops) (p < 0.05). This is due to straw residues affecting the migration and recovery of the mulch. The abundance and fragmentation of microplastics were significantly higher in the sunflower and maize plots where plastic mulch was extensively used because these tall crops anchored the mulch near their stem-root systems. The mulch was then slowly aged (e.g., via wind erosion) before being fragmented due to agricultural practices (e.g., mechanical plowing and residue retention). Although microplastics sourced from mulch are probably immobilized by straw residues in the short term, fragile and easily broken pieces of mulch are eventually released into the soil due to agricultural practices. The findings suggest that different cropping characteristics can affect the abundance and fragmentation of microplastics in agricultural soils, even within the same region, and thus the level and type of microplastic pollution. Traditional plastic mulch should be replaced with biodegradable mulch to reduce microplastic pollution in agricultural fields.

Keywords: Agricultural soil; Arid terrestrial ecosystems; Cropping characteristics; Microplastics; Residue retention.

MeSH terms

Agriculture
China
Crops, Agricultural
Farms
Microplastics*
Plastics
Soil*

Substances

Microplastics
Plastics
Soil