Plastic film residue concentrations in Chinese croplands

Agricultural plastic mulch films are a major source of plastic pollution
of croplands. In China, which uses about 68% of the plastic mulch film
produced globally (ca. 1.4 million tonnes y-1), soils have been heavily
contaminated with mulch fragments. Here, we collected a national dataset
of macroplastic residues (> 5 mm) in soil, including 3145 sampling
sites, and provincial plastic film usage from 1992 to 2019 in China, and
we established a linear model between the residue amount and historical
cumulative usage within each province. We quantified the amount of plastic
mulch residues in Chinese croplands on a national scale during the past 30
years and predicted plastic pollution until 2050. Our results reveal the
total national amount of plastic mulch residue in 2020 to be 2.07 million
tonnes with a 95% CI of [1.67, 2.58]. This accumulated amount of plastic
in Chinese soils roughly equals the annual amount of plastic films used
globally (2.08 million tonnes in 2018), which is about 8% of the national
historical used plastic mulch film (27.3 million tonnes) remains in soil
as legacy plastic. Plastic concentrations in Chinese croplands range from
7.7 kg ha-1 in Anhui to 399 kg ha-1 in Xinjiang, with an average value of
119 kg ha-1 (equivalent to 0.03 g kg-1 soil). We predict that the total
amount and average concentration of plastic residues in Chinese croplands
will reach 6.24 million tonnes and 357 kg ha-1 (equivalent to 0.1 g kg-1
soil) in 2050 under current plastic usage. There is an urgent need for
regulatory actions to control plastic pollution in Chinese agriculture.