State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation CAS and MWR, Yangling, 712100, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
College of Natural Resources and Environment, Northwest A&F University, Yangling, 712100, China.
Environ Pollut. 2022 May 1;300:118978. doi: 10.1016/j.envpol.2022.118978. Epub 2022 Feb 9.
Slow nutrient turnover and destructed soil function were the main factors causing low efficiency in phytoremediation of heavy metal (HM)-contaminated soil. Soil ecoenzymatic stoichiometry can reflect the ability of soil microorganisms to acquire energy and nutrients, and drive nutrient cycling and carbon (C) decomposition in HM-contaminated soil. Therefore, for the first time, we used the enzymatic stoichiometry modeling to examine the microbial nutrient limitation in rhizospheric and bulk soil of different plants (Medicago sativa, Halogeton arachnoideus and Agropyron cristatum) near the Baiyin Copper Mine. Results showed that the main pollutants in this area were Cu, Zn, Cd, and Pb, while Cd and Zn have the greatest contribution according to the analysis of pollution load index (PLI). The activities of soil C-, nitrogen (N)-, and phosphorus (P)-acquiring enzymes in the rhizosphere of plants were significantly greater than that in bulk soil. Moreover, microbial C and P limitations were observed in all plant treatments, while the lower limitation was generally in the rhizosphere compared to bulk soil. The HM stress significantly increased microbial C limitation and decreased microbial P limitation, especially in the rhizospheric soil. The partial least squares path modeling (PLS-PM) further indicated that HM concentration has the greatest effects on microbial P limitation (-0.64). In addition, the highest enzyme activities and the lowest P limitation were observed in the rhizospheric and bulk soil of M. sativa, thereby implying that soil microbial communities under the remediation of M. sativa were steadier and more efficient in terms of their metabolism. These findings are important for the elucidation of the nutrient cycling and microbial metabolism of rhizosphere under phytoremediation, and provide guidance for the restoration of HM-contaminated soil.
养分缓慢转化和土壤功能破坏是导致重金属（HM）污染土壤植物修复效率低下的主要因素。土壤生态酶化学计量可以反映土壤微生物获取能量和养分的能力，并驱动 HM 污染土壤中的养分循环和碳（C）分解。因此，我们首次利用酶化学计量模型来检验不同植物（紫花苜蓿、白刺和冰草）根际和非根际土壤中微生物的养分限制。结果表明，该地区的主要污染物是 Cu、Zn、Cd 和 Pb，而根据污染负荷指数（PLI）分析，Cd 和 Zn 的贡献最大。植物根际土壤中 C、N 和 P 获取酶的活性明显大于非根际土壤。此外，所有植物处理均观察到微生物 C 和 P 的限制，而根际土壤中的限制通常低于非根际土壤。HM 胁迫显著增加了微生物 C 的限制，降低了微生物 P 的限制，特别是在根际土壤中。偏最小二乘路径模型（PLS-PM）进一步表明，HM 浓度对微生物 P 限制的影响最大（-0.64）。此外，在紫花苜蓿的根际和非根际土壤中观察到最高的酶活性和最低的 P 限制，这意味着在紫花苜蓿修复下，土壤微生物群落在新陈代谢方面更加稳定和高效。这些发现对于阐明植物修复下根际的养分循环和微生物代谢具有重要意义，并为 HM 污染土壤的修复提供了指导。
