酸性环境下嗜酸氧化亚铁硫杆菌对花岗岩风化作用的研究

Granite weathering caused by Acidithiobacillus ferrooxidans under acidic conditions

摘要:

目的 以嗜酸氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)为对象，探究其在酸性条件下(pH 2.0)对花岗岩的生物风化作用及机制。方法 通过36 d浸泡实验，对比微生物组、酸水组(pH 2.0，H₂SO₄)及纯培养基对照组，检测溶液理化参数(pH、Eh、EC)、花岗岩表面色度(CIE-Lab)及矿物溶解特征。结果 微生物组显著促进花岗岩风化，9 d后表面形成明显风化层；初期(0-3 d)斜长石溶解导致pH值升高后趋于稳定，Fe³⁺积累主导氧化还原电位(Eh)，电导率(electrical conductivity, EC)受初始离子背景与风化产物共同调控。生物风化后，花岗岩L*值下降11.6 (亮度降低)，a*值和b*值分别上升6.8 (红褐色增强)和9.6 (蓝色调增加)，表面红褐色区域与黄钾铁矾沉淀直接相关。结论 酸性环境下A. ferrooxidans通过Fe³⁺介导的氧化还原反应加速花岗岩风化，色度参数(ΔL*、Δa*、Δb*)及形貌特征可作为快速评估风化程度的指标，为矿山酸性废水引发的围岩风化风险评估及生态修复提供了新依据。

Abstract:

Objective To investigate the bio-weathering effects and mechanisms of Acidithiobacillus ferrooxidans on granite under acidic conditions (pH 2.0).Methods A 36-day immersion experiment was conducted, comparing the microbial group, acid solution group (pH 2.0, H₂SO₄), and pure culture medium (control) group. Physicochemical parameters [pH, redox potential (Eh), and electrical conductivity (EC)] of the soultion, surface chromaticity (CIE-Lab) of granite, and mineral dissolution characteristics were analyzed.Results The microbial group significantly accelerated granite weathering, forming a distinct weathered layer on the surface after 9 days. During the initial phase (0?3 days), plagioclase dissolution caused a pH increase followed by stabilization. Fe³⁺ accumulation-dominated Eh and EC were regulated by both the initial ion background and weathering products. After bio-weathering, the granite exhibited a decrease of 11.6 in L* (reduced brightness), an increase of 6.8 in a* value (enhanced reddish-brown tone), and an increase of 9.6 in b* value (increased bluish tone). Surface reddish-brown areas were directly correlated with jarosite deposition.Conclusion Under acidic conditions, A. ferrooxidans accelerate granite weathering via Fe³⁺-mediated redox reactions. The chromaticity parameters (ΔL*, Δa*, and Δb*) and morphological characteristics serve as indicators for rapidly assessing weathering intensity. These findings provide a novel basis for evaluating weathering risks caused by acid mine wastewater in surrounding rocks and guiding ecological remediation.