Recent studies show that biodegradable microplastics (BMPs) could increase soil CO2 emission, but whether altered carbon emission results from modified soil organic matter (SOM) decomposition remains underexplored. In this study, the effect and mechanisms of BMPs on CO2 emission from soil were investigated, using poly(butylene adipate-co-terephthalate) (PBAT, the main component of agricultural film) as an example. Considering that straw returning is a common agronomic measure which may interact with microplastics through affecting microbial activity, both soils with and without wheat straw were included. After 120 d, 1 % (w/w) PBAT BMPs ificantly increased cumulative CO2 emission by 1605.6 and 1827.7 mg C kg−1 in soils without and with straw, respectively. Cracks occurred on the surface of microplastics, indicating that CO2 was partly originated from plastic degradation. Soil dissolved organic matter (DOM) content, carbon degradation gene abundance (such as abfA, xylA and manB for hemicellulose, mnp, glx and lig for lignin, and chiA for chitin) and enzyme activities increased, which significantly positively correlated with CO2 emission rate (p < 0.05), suggesting that PBAT enhanced carbon emission by stimulating the decomposition of SOM (and possibly the newly added straw) via co-metabolism and nitrogen mining. This is supported by DOM molecular composition analysis which also demonstrated stimulated turnover of carbohydrates, amino sugars and lignin following PBAT addition. The findings highlight the potential of BMPs to affect SOM stability and carbon emission.

中文翻译：

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PBAT 可生物降解微塑料增强了有机物分解能力和有和没有秸秆残留物的土壤中的 CO2 排放


最近的研究表明，可生物降解的微塑料 （BMP） 会增加土壤 CO2 排放，但改性土壤有机质 （SOM） 分解是否会导致碳排放改变仍未得到充分探索。本研究以聚己二酸丁二醇酯-对苯二甲酸丁二醇酯（PBAT，农用薄膜的主要成分）为例，研究了 BMP 对土壤 CO2 排放的影响和机制。考虑到秸秆还田是一种常见的农艺措施，它可能通过影响微生物活动与微塑料相互作用，因此包括有和没有小麦秸秆的土壤。120 d后，在无秸秆和有秸秆的土壤中，1 % （w/w） PBAT BMPs 的累积 CO2 排放量分别显著增加了 1605.6 和 1827.7 mg C kg-1。微塑料表面出现裂纹，表明 CO2 部分来源于塑料降解。土壤可溶性有机质 （DOM） 含量、碳降解基因丰度（如半纤维素的 abfA、xylA 和 manB，木质素的 mnp、glx 和 lig，几丁质的 chiA）和酶活性增加，与 CO2 排放速率呈显著正相关 （p < 0.05），表明 PBAT 通过共代谢和氮开采刺激 SOM（可能还有新添加的秸秆）的分解来增加碳排放。DOM 分子组成分析也支持这一点，该分析还表明添加 PBAT 后刺激碳水化合物、氨基糖和木质素的周转。研究结果强调了 BMP 影响 SOM 稳定性和碳排放的潜力。