共混塑料在海水中的光降解及海洋环境风险

共混塑料因其用途广泛且价格低廉，生产和使用量逐渐增加，然而共混塑料在海水中光降解及其海洋环境风险尚不明确.选取聚丙烯/热塑性淀粉共混塑料（PP/TPS）和聚乳酸/对苯二甲酸-己二酸丁二醇酯/热塑性淀粉共混塑料（PLA/PBAT/TPS）为研究对象，单一聚合物塑料聚丙烯（PP）和聚乳酸（PLA）作为对照，探究共混塑料在海水中光降解后微塑料（MPs）的形成和物理化学性质的变化.MPs的粒径分布显示，与PP和PLA相比，PP/TPS和PLA/PBAT/TPS光降解后容易产生尺寸更小的颗粒，主要原因是共混塑料机械性能和抗紫外线能力较差.共混塑料光降解后表面出现更多裂纹和褶皱，表面形貌发生明显变化，而PP和PLA变化不明显.ATR-FTIR光谱显示PP/TPS和PLA/PBAT/TPS光降解后热塑性淀粉（TPS）的特征峰减小，表明共混塑料的淀粉组分降解.C 1s光谱表明，老化共混塑料含有更少的—OH，进一步证实了TPS的光降解.以上结果表明PP/TPS和PLA/PBAT/TPS比PP和PLA光降解程度更高，从而产生更多小粒径MPs.综上所述，共混塑料可能比单一聚合物塑料对海洋环境风险更高，对共混塑料的生产和使用应谨慎.

Photodegradation of Plastic Blends in Seawater and Its Risk to the Marine Environment

The production and use of plastic blends have been gradually increasing owing to their versatility and low cost. However, the photodegradation of plastic blends in seawater and the potential risk to the marine environment are still not well understood. In this study, plastic blends including polypropylene/thermoplastic starch blends(PP/TPS) and polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch blends(PLA/PBAT/TPS) were investigated. The corresponding neat polymers, namely polypropylene(PP) and polylactic acid(PLA), were set as control groups. We investigated the formation of MPs and the changes in the physicochemical properties of plastic blends after photodegradation in seawater. The size distribution of MPs indicated that PP/TPS and PLA/PBAT/TPS were more likely to produce small-sized particles after photodegradation than PP and PLA owing to their poorer mechanical properties and lower resistance to UV irradiation. Noticeable surface morphology alterations, including cracks and wrinkles, were observed for plastic blends following photodegradation, whereas PP and PLA were relatively resistant. After photodegradation, the ATR-FTIR spectrum of PP/TPS and PLA/PBAT/TPS showed a significant decrease in the characteristic bands of thermoplastic starch(TPS), indicating the degradation of their starch fractions. The C 1s spectra demonstrated that aged plastic blends contained fewer -OH groups than the pristine MPs did, further confirming the photodegradation of TPS. These results indicate that PP/TPS and PLA/PBAT/TPS had a higher degree of photodegradation than PP and PLA and thereby generated more small-sized MPs. In summary, plastic blends may pose a higher risk to the marine environment than neat polymers, and caution should be taken in the production and use of plastic blends.