Abstract:

With the increasing problem of “white pollution” caused by traditional plastic products, biodegradable plastics have emerged and given rise to new biodegradable microplastic (MPs) pollution. The toxic effects of biodegradable MPs on soil ecosystems and crop growth are poorly understood. In this study, biodegradable polybutylene terephthalate-adipate microplastics (PBAT-MPs) were used as the research object, and the non-degradable polypropylene MPs (PP-MPs) were used as control. Pot experiments were conducted to investigate the morphological changes of MPs before and after landfill, meanwhile, the effects of MPs on soil physicochemical properties and physiological indexes of Brassica chinensis L. were evaluated. The results showed that PBAT-MPs degraded in the soil, but the surface morphology of PP-MPs hardly changed. The addition of PP-MPs decreased TN content in the soil, and the TP content first decreased and then increased. The PBAT-MPs addition increased the TN content in soil, and the TP content first decreased and then recovered. The addition of the two types of MPs increased the content of water-stable aggregates and affected particle size distribution of the aggregates in soil. The effects of MPs on Brassica chinensis L. were weakened with the self-regulation of plants, and this influence on plant physiological indexes was dynamic. Correlation analysis showed that TP of soil treated with PBAT-MPs was positively correlated with plant germination rate, root activity, root length and stem length, while the MDA content was negatively correlated with germination rate, root activity and stem length. Compared with non-degradable PP-MPs, biodegradable PBAT-MPs didn't have significant adverse effects on soil and Brassica chinensis L. due to their self- degradation. It is promising to replace traditional non-degradable films in agricultural production to reduce white pollution. The results of this study are of great significance for evaluating the toxic effects of biodegradable MPs on soil-plant system.

Key words: polybutylene terephthalate-adipate, microplastics, soil, biodegradation, physical and chemical properties of soil, seed germination, seedling growth

摘要：

伴随着传统塑料制品引发的“白色污染”问题日益严重，可生物降解塑料应运而生，同时引发了新的可生物降解微塑料污染，但有关可生物降解微塑料对土壤生态系统以及农作物生长的毒性效应尚未完全明确。该研究以可生物降解材料聚对苯二甲酸-己二酸丁二醇酯微塑料（PBAT-MPs）为研究对象，同时以不可降解聚丙烯微塑料（PP-MPs）为对照，通过发芽试验和盆栽试验探究了微塑料填埋前后的形态变化、对土壤理化性质及上海青（Brassica chinensis L.）生长过程中生理指标的影响。结果表明，PBAT-MPs在土壤中发生了降解，而PP-MPs表面形态几乎未发生变化；PP-MPs的添加会导致土壤中TN含量的下降，TP含量先降低后升高，而PBAT-MPs会增加土壤TN含量，TP含量先降低而后恢复；两种微塑料的添加整体会增加土壤中水稳性团聚体含量，影响团聚体粒径分布；MPs对上海青产生的影响会随着植物的自身调节作用减弱，对植物生理指标的影响呈动态变化；相关性分析结果表明，PBAT-MPs处理土壤总磷与植物发芽率、根系活力、根长和茎长呈现正相关，植物丙二醛含量与发芽率、根系活力和茎长呈现负相关。与不可降解微塑料相比，可生物降解微塑料PBAT未因其自身降解而对土壤、上海青产生显著的不良效应，有希望在农业生产中代替传统不可降解农膜以减轻白色污染问题。本研究结果对评价可生物降解微塑料对土壤-植物系统的毒性效应具有重要意义。

关键词: 聚对苯二甲酸-己二酸丁二醇酯, 微塑料, 土壤, 生物降解, 植种子发芽, 幼苗生长