Zhang Yanxia, Li Xing, Xiao Mao, Feng Ziyi, Yu Yongxiang, Yao Huaiying
Research Center for Environmental Ecology and Engineering, School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, 206 Guanggu 1st road, Wuhan 430205, China.
Research Center for Environmental Ecology and Engineering, School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, 206 Guanggu 1st road, Wuhan 430205, China; Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China; Zhejiang Key Laboratory of Urban Environmental Processes and Pollution Control, Ningbo Urban Environment Observation and Research Station, Chinese Academy of Sciences, 88 Zhongke Road, Ningbo 315800, China.
Sci Total Environ. 2022 Feb 1;806(Pt 3):150714. doi: 10.1016/j.scitotenv.2021.150714. Epub 2021 Oct 1.
The accumulation of microplastics (MPs) in agricultural fields can not only disguise soil organic carbon (SOC) storage but also affect the production of carbon dioxide (CO) by microbial decomposition. However, little is known about the impact of this emerging pollutant on soil CO emissions and the functional genes related to SOC degradation. In the present study, a short-term (30-day) microcosm experiment was performed to investigate the effects of virgin and aged low-density polyethylene (LDPE) MPs on soil CO emissions. We also measured functional gene abundances related to starch (sga), hemicellulose (abfA, manB and xylA), cellulose (cex) and lignin (lig and mnp) degradation through a high-throughput quantitative-PCR-based chip. Compared with the soils without MPs, low doses (0.01% and 0.1%) of both virgin and aged MPs had negligible effects on SOC decomposition, whereas a high dose (1.0%) of these two MPs significantly (p < 0.05) accelerated the production of CO in soils by 15-17%, showing a dose-dependent effect. The presence of MPs did not significantly affect soil dissolved organic carbon or microbial biomass carbon. A higher metabolic quotient at 1.0% MP concentration indicated that the microbes were stressed and needed more substrates and energy during their metabolic process, which could likely explain the increase in CO emission induced by this dose of MPs. Exposure to virgin MPs significantly reduced the functional genes related to hemicellulose (abfA and manB) degradation, whereas increasing the aged MPs concentrations significantly decreased the abundances of functional genes encoding starch (sga), hemicellulose (abfA, manB and xylA), and cellulose (cex) hydrolysis. Overall, we conclude that the low dose (<0.1%) of MPs in the soils has a negligible effect on the production of CO, but this factor should be considered in evaluating the global C budget in future research as this contaminant reaches a certain threshold (1.0%).
微塑料（MPs）在农田中的积累不仅会掩盖土壤有机碳（SOC）储量，还会影响微生物分解产生二氧化碳（CO₂）。然而，对于这种新兴污染物对土壤CO₂排放以及与SOC降解相关的功能基因的影响，人们知之甚少。在本研究中，进行了一项短期（30天）的微观实验，以研究原始和老化的低密度聚乙烯（LDPE）微塑料对土壤CO₂排放的影响。我们还通过基于高通量定量PCR的芯片测量了与淀粉（sga）、半纤维素（abfA、manB和xylA）、纤维素（cex）和木质素（lig和mnp）降解相关的功能基因丰度。与无微塑料的土壤相比，低剂量（0.01%和0.1%）的原始和老化微塑料对SOC分解的影响可忽略不计，而高剂量（1.0%）的这两种微塑料显著（p < 0.05）加速了土壤中CO₂的产生，增幅为15 - 17%，呈现剂量依赖性效应。微塑料的存在并未显著影响土壤溶解有机碳或微生物生物量碳。在1.0%微塑料浓度下较高的代谢商表明，微生物受到压力，在其代谢过程中需要更多底物和能量，这可能解释了该剂量微塑料诱导的CO₂排放增加。暴露于原始微塑料显著降低了与半纤维素（abfA和manB）降解相关的功能基因，而增加老化微塑料浓度则显著降低了编码淀粉（sga）、半纤维素（abfA、manB和xylA）和纤维素（cex）水解的功能基因丰度。总体而言，我们得出结论，土壤中低剂量（<0.1%）的微塑料对CO₂产生的影响可忽略不计，但在未来研究评估全球碳预算时应考虑这一因素，因为这种污染物达到一定阈值（1.0%）。
