Release of Additives from Agricultural Plastic Films in Water: Experiment and Modeling

Globally, more than 6 million metric tons of agricultural
plastic
films are used to increase crop yields and reduce the use of water
and herbicides, resulting in the contamination of soil and water by
plastic debris and additives. However, knowledge of the occurrence
and release of additives from agricultural films is limited. In this
study, suspect screening with high-resolution mass spectrometry, one-dimensional
Fickian diffusion models, and linear free energy relationships (LFERs)
were used to determine the occurrence and mass transfer of various
additives from agricultural plastic films. A total of 89 additives
were tentatively identified in 40 films, and 62 of them were further
validated and quantified. The aqueous concentrations of 26 released
additives reached mg L–1 after a 28 day incubation
at 25 °C. Diffusion models and LFERs demonstrated that the film–water
partition coefficient and the diffusivity in the polymer, the two
critical parameters controlling the mass transfer, could be predicted
using Abraham descriptors. The findings of this study highlighted
the need for future research on the environmental fate and risk assessment
of previously neglected additives in agricultural plastic films and
other similar products.

全球范围内，农用塑料薄膜的年使用量超600万吨，其虽可提升作物产量、减少灌溉用水与除草剂的施用，却会因塑料碎屑与添加剂的释放造成土壤与水体污染。然而，当前学界对于农用塑料薄膜中添加剂的赋存状态与释放行为的认知仍较为有限。本研究采用高分辨质谱（high-resolution mass spectrometry）可疑筛查法、一维菲克扩散模型（one-dimensional Fickian diffusion models）以及线性自由能关系（linear free energy relationships, LFERs），对农用塑料薄膜中各类添加剂的赋存状态与传质过程展开分析。研究人员从40份薄膜样品中初步鉴定出89种添加剂，其中62种得到进一步验证与定量分析。在25℃条件下孵育28天后，26种已释放添加剂的水相浓度可达毫克每升级别。扩散模型与线性自由能关系研究表明，控制传质过程的两个关键参数——薄膜-水分配系数与聚合物内扩散系数——可通过阿布拉罕描述符（Abraham descriptors）进行预测。本研究结果凸显出，未来需针对农用塑料薄膜及其他同类产品中此前被忽视的添加剂开展环境归趋与风险评估相关研究。