Agricultural films are the fourth largest agricultural production material after seeds, fertilizers, and pesticides, and are widely used in China. Plasticizer is an important agricultural film additive that can be released in the environment and pollute the environment.

    Recently, Qianqin Zhang, associate researcher of Professor Guangguo Ying team in SCNU Environmental Research Institute of South China Normal University. comprehensively described the amount of agricultural films used in China and the environmental residues of its plastic debris and assessed the release and environmental fate of phthalate esters (plasticizers) in the whole life cycle of agricultural film use. The study was published in Environmental Science and Technology.

China's annual agricultural film recycling rate is less than 2/3

     Agricultural films, which mainly consist of ground and shed films, greatly improve the efficiency of agricultural production, but also cause pollution from plastic debris and related chemicals. After use, less than 2/3 of agricultural films are recycled annually in China.

     Plastic films that are not easily degradable remain and accumulate in the soil, causing "white pollution". The main plasticizers in agricultural films will continue to be released into the environment during the use cycle and after disposal, causing environmental pollution.

 "The amount of plastic used, the amount of residue and the emission of major toxic and hazardous pollutants in its use cycle are important basic data for quantitatively assessing the pollution of agricultural films, no study has been reported yet." Guangguo Ying told China Science Daily.

     Guangguo Ying said that the paper estimated the residual amount, erosion amount and the release of plasticizer in the whole life cycle of agricultural films in each province of China, and constructed the environmental multi-media model of ground film and shed film based on the fugitive method, simulated the environmental attribution of plasticizers, and provided the data basis and technical support for the management of environmental pollution of agricultural films in China.

Annual growth of 6.5% and 5.9% for ground and shed films.

    The team analyzed the use of agricultural films (ground and trellis films) in China from 1997 to 2017 based on a combination of big data collection, laboratory testing, and model simulation, and assessed the amount of plastic debris remaining and migrating from agricultural films after use and partial recycling.

 "We collected the use of ground and shed films and the area covered by films in China during the past 20 years as the basic data of plastic pollution from agricultural films. Data analysis found that the annual growth rate of ground film and shed film was 6.5% and 5.9%, respectively, and the area of mulching film peaked in 2011 and then fell slightly, and since then the annual growth rate has remained at ±1%, entering a period of stabilization." Guangguo Ying said.

     The estimation results show that 18.6% of agricultural films are left in farmland in China every year and there is a correlation between the amount of agricultural film residues in each province and the accumulated residues of agricultural films in the Second National Census of Pollution Source in all the years, and the correlation coefficient is 0.95.

    The results showed that in 2017, China's agricultural plastic film use was 2,528,600 tons; after the agricultural film recycling and soil erosion process, the agricultural plastic residue amounted to 465,016 tons, while 4,329 tons of plastic debris into the aquatic environment and discharged into the oceans in soil erosion process.

Construct two models.

    "Based on the fugacity approach, we constructed a ground-film cover model and a shed-film semi-elliptical plastic tunnel model to simulate the multi-media environmental levels of dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) in each province, as well as transport fluxes between each environmental medium. The predicted concentrations of the target plasticizers in agricultural fields were slightly lower than the published concentrations in various provinces, suggesting the contribution of other sources of plasticizers in the agricultural environment." Guangguo Ying said.

    Flux analyses showed that the main output fluxes of DBP and DEHP from ground films are degradation. For shed films, 60.9% of the released DBP would be degraded, while 96.3% of DEHP would accumulate in vegetables. However, the assessment showed that the consumption risk of plasticizers in greenhouse vegetables is low.

    According to the report, in 2017, 18.8 tons of DBP and 42.2 tons of DEHP were released from the ground film in China. Among them, 7.53 tons and 16.9 tons entered the atmospheric environment, respectively, and the rest entered the soil environment. The releases of the two typical plasticizers showed significant regional characteristics.

    The provinces and regions with the largest releases are Xinjiang, Gansu, Shandong, Inner Mongolia and Yunnan, whose total releases can reach more than 50% of the national emissions. The amount of plasticizer release is the lowest in Tibet.

    In 2017, 5.94 tons of DBP and 24.5 tons of DEHP were released from shed films.

    Among them, 50~51.6% were released inside the greenhouses and enriched in the vegetables and soil, and the rest released into the external environment. The influence of temperature on the release of plasticizers was significant, as evidenced by the ratio of the release of plasticizers inside and outside the greenhouses in the northeastern and northwestern provinces and regions being 1.06:1, while that in the warm and humid southern China region was 1.009:1.

Article reprinted from WeChat's China Science Daily, by Zhu Hanbin