Current situation and control strategies of residual film pollution in Xinjiang

Abstract: Plastic pollution has become a global environmental concern and residual plastic films resulted from agricultural production played a significant part in it. Xinjiang in China is a region of 160 million hectares and its agricultural production is mainly in the proximal areas of the Taklamakan desert - the second largest desert in the world. Rainfall in Xinjiang is scanty but sunshine is abundant. For reducing evaporation, therefore, approximately 3.478 million hm2 of croplands in Xinjiang is mulched annually by over 200,000 tons of plastic films, making Xinjiang the most contaminated region by residual plastic films in China. In this paper, we analyzed the distribution of residual plastic films in croplands in Xinjiang based on literature review, consulting and field surveys. The results showed that the residual plastic films in soil were found mainly in three layers: soil surface, 0-12 cm and 12-30 cm layers, among which 6%-8.33% was on the soil surface, 53.99%-68% in 0-12 cm layer and 26%-37.68% in 12-30 cm layer. We also analyzed the reasons behind residual film pollution, including costs of the mulch film, its mechanical properties and factors affecting its recovery. Comprehensive technologies for alleviating residual film pollution in Xinjiang were evaluated, which include improving agronomic control, using degradable films and improving film recycling. We also discussed the difficulties faced by implementation of these technologies, especially in integrating agricultural machinery and agronomical technology, mechanical recovery of the films, and systems to monitor and evaluate the residual film pollution. To ameliorate the film contamination, legal regulation for improving treatment of residual film pollution should be mandatory and new technique of integrating agricultural machinery-agronomy-agricultural film should be developed. In addition to these, methods such as boosting residual film degradation in soil, developing new plastic film, and innovating strategies to prevent and control residual film pollution, should be sought. Currently, PE mulch is still the main application in agricultural production and future research should focus on developing new degradable mulch to replace the PE mulch. In summary, mitigating residual film pollution in croplands in Xinjiang should follow 1) "restraining the increase in film production, and reducing the film stock", 2) increasing mechanical recovery, standardizing film, optimizing cropping systems, and establishing recycling systems.