Research Center for Environmental Ecology and Engineering, Key Laboratory of Green Chemical Engineering Process of Ministry of Education, School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, 206 Guanggu 1st road, Wuhan 430205, China.
Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
J Hazard Mater. 2024 Sep 5;476:135080. doi: 10.1016/j.jhazmat.2024.135080. Epub 2024 Jul 2.
The current carbon dioxide (CO) evolution-based standard method for determining biodegradable microplastics (MPs) degradation neglects its priming effect on soil organic matter decomposition, which misestimates their biodegradability. Here, a C natural abundance method was used to estimate the mineralization of poly(lactic acid) (PLA) MP in various agricultural soils, and to trace its utilization in different microbial groups. In alkaline soils, the PLA-derived CO emissions increased with increasing soil carbon/nitrogen (C/N) ratios, and the mineralization of PLA MP concentrations ranged from 3-33 %, whereas the CO evolution method probably over- or under-estimated the mineralization of PLA in alkaline soils with different soil C/N ratios. Low PLA mineralization (1-5 %) were found in the acidic soil, and the standard method largely overestimated the mineralization of PLA MP by 1.3- to 3.3-fold. Moreover, the hydrolysate of PLA MP was preferentially assimilated by Gram-negative bacteria, but Gram-positive bacterial decomposition mainly contributed to the release of PLA-derived CO at low MP concentrations (≤ 1 %). Overall, the C natural abundance method appears to be suitable for tracking the mineralization and microbial utilization of biodegradable PLA in soils, and the PLA-derived C is mainly assimilated and decomposed by bacterial groups.
目前基于二氧化碳（CO）释放的测定方法来评估可生物降解微塑料（MPs）的降解忽略了其对土壤有机质分解的激发作用，从而错误地估计了它们的生物降解性。在这里，采用 C 自然丰度法来估算不同农业土壤中聚乳酸（PLA）MP 的矿化作用，并追踪其在不同微生物群体中的利用情况。在碱性土壤中，PLA 衍生的 CO 排放量随土壤碳氮比（C/N）的增加而增加，PLA MP 浓度的矿化率范围为 3-33%，而 CO 释放法可能高估或低估了不同 C/N 比的碱性土壤中 PLA 的矿化作用。在酸性土壤中，PLA 的矿化率较低（1-5%），标准方法大大高估了 PLA MP 的矿化率，倍数为 1.3-3.3 倍。此外，PLA MP 的水解产物优先被革兰氏阴性菌同化，但在低 MP 浓度（≤1%）下，革兰氏阳性菌的分解主要有助于 PLA 衍生 CO 的释放。总的来说，C 自然丰度法似乎适用于追踪土壤中可生物降解 PLA 的矿化和微生物利用情况，PLA 衍生的 C 主要被细菌群体同化和分解。
