Microbial metabolic limitation and carbon use feedback in lead contaminated agricultural soils

• Published in: Chemosphere (Oxford) 2022-12, Vol.308, p.136311-136311, Article 136311
• Main Authors: Wang, Xiangxiang, Cui, Yongxing, Chen, Li, Tang, Kun, Wang, Dawei, Zhang, Zhigang, Yu, Jialuo, Fang, Linchuan
• Format: Article
• Language: English
• Subjects: Carbon use efficiency (CUE); Ecoenzymatic stoichiometry; Heavy metal pollution; Microbial metabolic quotients (qCO2)
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.136311

Potentially toxic elements (PTEs) pollution causes a great threat to microbial metabolism, which plays a vital role in studying soil nutrient cycling and predicting carbon (C) storage in agroecosystems. However, the responses of microbial metabolism characteristic to heavy metal contamination and the mechanisms through which microbial metabolism mediate nutrient cycling and C dynamics in contaminated soil remain elusive. Here, we performed an incubation experiment over 80 days to investigate the variations in microbial metabolic limitation under various Pb levels (0, 100, 500, 800, 1500, 2000, and 3000 mg Pb kg−1 dry soil) in cropland soil using extracellular enzymatic stoichiometry, and to reveal the impact of Pb stress on soil C storage by associating with microbial metabolic quotients (qCO2) and C use efficiency (CUE). The results showed microbial relative C limitation and phosphorus (P) limitation were observed in Pb-contaminated soils. Pb addition enhanced the microbial relative C limitation by approximately 7.3%, while decreasing the P limitation by approximately 12.3%. Furthermore, Pb addition led to higher qCO2 (from 8.75 to 108 μg C kg−1 MBC−1 d−1) duo to the increase of microbial relative C limitation, suggesting that the more CO2 was released of per unit of microbial biomass C. The increase of microbial relative C limitation reduced CUE (from 0.35 to 0.10) because of the change in microbial metabolism from growth to respiration maintenance under Pb stress. Consequently, the CUE and qCO2 together determined the loss of soil C. Our study reveals that microbial relative C limitation is the dominant driver of soil C loss and provides important knowledge of microbial metabolic limitation regulating soil C turnover in PTEs-contaminated agricultural soils. [Display omitted] •Pb pollution increased microbial C limitation while decreasing P limitation.•Pb pollution increased soil C loss by increasing qCO2 and decreasing CUE.•Microbial C limitation is the dominant driver of qCO2 increase and CUE decrease.•Microbial C limitation is more sensitive than microbial P limitation to Pb stress.•Ecoenzymatic stoichiometry is promising for evaluating heavy metal pollution.