The stability of carbonate products resulting from microbially induced carbonate precipitation (MICP) under acid rain is under question. The present study investigated the stability of CaCO3 precipitated by MICP in soil under simulated acid rain (SAR). Soils were treated continuously for two months with four SAR pH levels: 3.5, 4.5, 5.5, and 7.0. During SAR, biostimulation using nutrient broth containing urea and calcium chloride was adopted to ensure CaCO3 precipitation. At the end of treatments, soil samples from top and bottom layers were analyzed for bacterial diversity by Illumina MiSeq sequencing, Fourier transform infrared (FTIR) spectroscopy for identification of chemical functional groups related to calcite precipitation, and X-ray diffraction (XRD) for identification of the main crystalline phases. The analysis identified several ureolytic bacteria mainly from Arthrobacter and Sporosarcina genera in SAR-treated soils accelerated with biostimulation, and urease quantities of greater than 300 mg NH4+ per kg soil at all pH levels. The precipitation of CaCO3 was pronounced and its stability was maintained even when the pH was as low as 3.5. The results obtained in this study are helpful to the scientific community to ensure the immobilization of heavy metals with microbial carbonate precipitation in soil under acid rain.

中文翻译：

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模拟酸雨对微生物碳酸盐沉淀固定化碳酸钙稳定性的影响。

在酸雨下由微生物引起的碳酸盐沉淀（MICP）产生的碳酸盐产品的稳定性受到质疑。本研究调查了在模拟酸雨（SAR）下土壤中MICP沉淀的CaCO3的稳定性。用四个SAR pH值（3.5、4.5、5.5和7.0）连续处理土壤两个月。在SAR期间，采用含有尿素和氯化钙的营养肉汤进行生物刺激以确保CaCO 3沉淀。处理结束时，通过Illumina MiSeq测序，傅立叶变换红外（FTIR）光谱法（用于鉴定与方解石沉淀有关的化学官能团）和X射线衍射（XRD），分析了顶层和底层的土壤样品中细菌的多样性。鉴定主要结晶相。分析确定了几种脲酶解细菌，这些细菌主要来自节杆菌属和孢子菌属，在经过SAR处理的土壤中随着生物刺激而加速，并且在所有pH值下，每千克土壤中尿素酶的含量超过300 mg NH4 +。CaCO3沉淀明显，即使在pH值低至3.5时也能保持其稳定性。这项研究获得的结果有助于科学界确保酸雨条件下土壤微生物碳酸盐沉淀对重金属的固定。