State Key Laboratory of Grassland Agro-Ecosystems, Institute of Arid Agro-Ecology, School of Life Sciences, Lanzhou University, Lanzhou 730000, China; Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou 730030, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Grassland Agro-Ecosystems, Institute of Arid Agro-Ecology, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
J Hazard Mater. 2021 Aug 15;416:125954. doi: 10.1016/j.jhazmat.2021.125954. Epub 2021 Apr 27.
Biodegradable (Bio) plastic films are widely viewed as promising alternative products of low-density polyethylene (LDPE) films to minimize plastic debris accumulation and pollution in agroecosystems. Yet, this speculation indeed lacks of sufficient evidences. We conducted a landfill investigation on the aging characteristics of Bio and LDPE plastic films in maize field, and the effects on soil aggregate composition and carbon & nitrogen stocks. The degradation rate of Bio film was up to 41.1% while that of LDPE film was zero. Scanning electron microscope (SEM) showed that the crack formation of Bio film had a pronounced domino effect, and FTIR showed that old Bio film displayed an extra wide peak threshold ranging from 3000 to 3500 cm. Particularly, the abundance of microplastics was elevated with the increased plastic residues, and the increment mostly resulted from Bio residues. Critically, plastic residues significantly lowered the soil macro-aggregates (>0.25 mm) proportion, while increasing that of micro-aggregates (0.1-0.25 mm) in LDPE, and silt/clay fraction (<0.1 mm) in Bio respectively. They significantly promoted total nitrogen content of the aggregates with the same size, but decreased the organic carbon content, dramatically lowering the C/N. Therefore, we first identified the fate of plastic film residues in agroecosystems and revealed the serious deficiencies of Bio plastic film.
可生物降解（Bio）塑料薄膜被广泛认为是低密度聚乙烯（LDPE）薄膜的有前途的替代品，可以最大限度地减少农业生态系统中塑料碎片的积累和污染。然而，这种推测确实缺乏足够的证据。我们在玉米田中对生物和 LDPE 塑料薄膜的老化特性进行了垃圾填埋场调查，并研究了它们对土壤团聚体组成和碳氮储量的影响。生物薄膜的降解率高达 41.1%，而 LDPE 薄膜的降解率为零。扫描电子显微镜（SEM）显示，生物薄膜的裂缝形成具有明显的多米诺骨牌效应，傅里叶变换红外光谱（FTIR）显示，旧的生物薄膜显示出一个额外的宽峰阈值，范围从 3000 到 3500 cm。特别是，随着塑料残留物的增加，微塑料的丰度增加，而增量主要来自生物残留物。关键的是，塑料残留物显著降低了土壤大团聚体（>0.25mm）的比例，而在 LDPE 中增加了微团聚体（0.1-0.25mm）的比例，在生物中则增加了淤泥/粘土部分（<0.1mm）。它们显著促进了相同大小的团聚体中总氮含量的增加，但降低了有机碳含量，大大降低了 C/N。因此，我们首次确定了塑料薄膜残留物在农业生态系统中的命运，并揭示了生物塑料薄膜的严重缺陷。
