Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States.
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Environ Sci Technol. 2022 Oct 4;56(19):13810-13819. doi: 10.1021/acs.est.2c04348. Epub 2022 Sep 14.
Sunlight chemically transforms marine plastics into a suite of products, with formulation─the specific mixture of polymers and additives─driving rates and products. However, the effect of light-driven transformations on subsequent microbial lability is poorly understood. Here, we examined the interplay between photochemical and biological degradation of fabrics made from cellulose diacetate (CDA), a biobased polymer used commonly in consumer products. We also examined the influence of ∼1% titanium dioxide (TiO), a common pigment and photocatalyst. We sequentially exposed CDA to simulated sunlight and native marine microbes to understand how photodegradation influences metabolic rates and pathways. Nuclear magnetic resonance spectroscopy revealed that sunlight initiated chain scission reactions, reducing CDA's average molecular weight. Natural abundance carbon isotope measurements demonstrated that chain scission ultimately yields CO, a newly identified abiotic loss term of CDA in the environment. Measurements of fabric mass loss and enzymatic activities in seawater implied that photodegradation enhanced biodegradation by performing steps typically facilitated by cellulase. TiO accelerated CDA photodegradation, expediting biodegradation. Collectively, these findings (i) underline the importance of formulation in plastic's environmental fate and (ii) suggest that overlooking synergy between photochemical and biological degradation may lead to overestimates of marine plastic persistence.
阳光会将海洋塑料化学转化为一系列产物，配方（即聚合物和添加剂的特定混合物）会影响转化速度和产物。然而，光驱动转化对随后微生物的不稳定性的影响还不太清楚。在这里，我们研究了由纤维素二醋酸酯（CDA）制成的织物的光化学和生物降解之间的相互作用，CDA 是一种常用于消费品的生物基聚合物。我们还研究了约 1%的二氧化钛（TiO）的影响，TiO 是一种常见的颜料和光催化剂。我们依次将 CDA 暴露于模拟阳光和天然海洋微生物中，以了解光降解如何影响代谢速率和途径。核磁共振波谱表明，阳光引发了链断裂反应，降低了 CDA 的平均分子量。自然丰度碳同位素测量表明，链断裂最终产生 CO，这是环境中 CDA 的一个新发现的非生物损失项。在海水中测量织物的质量损失和酶活性表明，光降解通过执行通常由纤维素酶促进的步骤来增强生物降解。TiO 加速了 CDA 的光降解，从而加速了生物降解。总的来说，这些发现（i）强调了配方在塑料环境命运中的重要性，（ii）表明忽视光化学和生物降解之间的协同作用可能导致对海洋塑料持久性的高估。
