State Key Laboratory of Urban Water Resource and Environment, School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen 518055, China.
State Environmental Protection Key Laboratory of Urban Ecological Environment Simulation and Protection, South China Institute of Environmental Sciences, Ministry of Ecology and Environment of China, Guangzhou 510535, China.
Sci Total Environ. 2022 Jul 15;830:154732. doi: 10.1016/j.scitotenv.2022.154732. Epub 2022 Mar 26.
The increasing contamination of heavy metals in agricultural soils and its impact on the nitrogen (N) cycle and N use efficiency have attracted considerable attention in recent years. In this study, agricultural soils neighboring the Dabaoshan copper mining area (DBS) and Qingyuan electronic-waste recycling area (QY), in Guangdong, China, were sampled to study the interaction between heavy metals and nitrification/denitrification processes, especially the related microbial functional profiles. Results showed that the contamination of heavy metals affected nitrifiers and denitrifiers differently. The potential nitrification activity was about four times lower in metal-polluted soils compared with the unpolluted ones, with a significant decrease in the abundance of amoA and nxrB (p < 0.05) in the polluted samples. On the other hand, the potential denitrification activity was more metal-resistant, which attributed to its complex species composition as shown by a slightly higher α-diversity index, and was slightly higher (p > 0.05) in the polluted samples. Among the five denitrifying genes tested, nosZ gene had the highest increase and the nirK gene the most decrease in numbers and in the polluted soils. The metal-polluted soils had fewer correlations among N functional genes based on the co-occurrence network analysis. In addition, the core taxa of the whole bacterial community changed from copiotrophic to oligotrophic bacteria in the presence of heavy metals. Mantel test indicated that heavy metals were the dominant factors determining N-related genes while the bacterial community composition was due to a combination of heavy metal presence and soil properties such as TOC, NO, and pH. It is concluded that long-term heavy metals pollution potentially affected nitrifiers and denitrifiers differently as indicated by the shift in N functional genes and the change in nitrification/denitrification processes.
近年来，农业土壤中重金属的不断污染及其对氮（N）循环和 N 利用效率的影响引起了广泛关注。本研究采集了中国广东大宝山矿区（DBS）和清远电子废物回收区（QY）周边的农业土壤，研究重金属与硝化/反硝化过程的相互作用，特别是相关微生物功能谱。结果表明，重金属污染对硝化菌和反硝化菌的影响不同。与未污染土壤相比，受重金属污染的土壤中潜在硝化活性约低 4 倍，受污染样品中 amoA 和 nxrB 的丰度（p<0.05）显著降低。另一方面，潜在的反硝化活性具有较强的耐金属性，这归因于其复杂的物种组成，表现在α多样性指数略高，且在受污染的样品中略高（p>0.05）。在所测试的五个反硝化基因中，nosZ 基因的增加最多，nirK 基因的数量和在受污染土壤中的减少最多。基于共现网络分析，受重金属污染的土壤中 N 功能基因之间的相关性较少。此外，重金属存在的情况下，整个细菌群落的核心分类群从富营养菌转变为寡营养菌。Mantel 检验表明，重金属是决定 N 相关基因的主导因素，而细菌群落组成则是由于重金属的存在和土壤特性（如 TOC、NO 和 pH）的综合作用。综上所述，长期重金属污染可能会通过改变 N 功能基因和硝化/反硝化过程的方式对硝化菌和反硝化菌产生不同的影响。
