聚己二酸对苯二甲酸丁二酯基生物可降解塑料在近海环境中的降解特征

Degradation characteristics of poly(butylene adipate-co-terephthalate)-based biodegradable plastics in offshore environment

认识生物可降解塑料的真实降解行为对全面评价其环境安全性至关重要。本文结合野外环境挂样和室内模拟实验,探究了聚己二酸对苯二甲酸丁二酯(PBAT)基生物可降解塑料在近海环境中的降解特征。经过在东海水域一年的暴露,3种PBAT基塑料产品仅表面出现了破损、孔洞,表面含氧基团和羟基的红外信号增强,以及热稳定性下降等理化性质的改变。可能是由于海水的低温,塑料表面附着大量藻类和矿物等杂质,3种塑料整体降解性差。而室内海水模拟降解实验发现,强紫外光辐射加速了PBAT地膜的老化,地膜的失重率和释放的微塑料数量随光照时间增加而增加,光照84 h(相当于自然光下约340 d)的失重率为44.1%±3.68%,共释放(67.1±18.8)个/mg微塑料。同时,老化过程还释放了溶解性有机物(DOM),其中荧光DOM主要为酪氨酸和类蛋白类以及芳香族蛋白类,这些物质具有光不稳定性,因而容易进一步光降解,导致PBAT释放的溶解性有机碳含量呈先上升后下降的趋势。

Understanding the real degradation of biodegradable plastics is crucial for comprehensively evaluating their environmental safety.In this study,the degradation characteristics of poly(butylene adipate-co-terephthalate)(PBAT)in offshore environment through field and laboratory researches were investigated.After one year of exposure in the East China Sea,three types of PBAT-based products showed breakage and holes on the surface,and the infrared signals of the oxygen-containing functional groups and hydroxyl groups increased,but their thermal stability decreased.There was a poor degradation of plastics possibly due to low temperature of seawater and the attachment of lots of algae and minerals to the surface.However,a degradation experiment in laboratory found that strong ultraviolet irradiation accelerated the aging of PBAT mulching films.Both the weight loss rate of plastics and the number of released microplastics increased as the irradiation period,and reached 44.1%±3.68%and 67.1±18.8 items/mg after UV radiation for 84 h(equivalent to approximately 340 days in nature),respectively.Dissolved organic matters(DOM)were also released from the films during aging and main fluorescent organic compounds included tyrosine,protein-like substances,and aromatic proteins,but photodegradation occurred due to their photo lability.Therefore,the content of dissolved organic carbon released from PBAT initially increased and then decreased.