生态环境学报 ›› 2023, Vol. 32 ›› Issue (4): 776-783.DOI: 10.16258/j.cnki.1674-5906.2023.04.015

• 研究论文 • 上一篇    下一篇

KI淋洗对黄绵土汞污染的去除效果及土壤理化性状的影响

冯树娜(), 吕家珑, 何海龙()   

  1. 西北农林科技大学资源环境学院,陕西 杨陵 712100
  • 收稿日期:2023-02-07 出版日期:2023-04-18 发布日期:2023-07-12
  • 通讯作者: *何海龙(1985年生),男,教授,主要研究方向土壤物理与水土保持。E-mail: hailong.he@hotmail.com
  • 作者简介:冯树娜(1998年生),女,硕士研究生,主要研究方向土壤修复。E-mail: fsn2945074751@nwafu.edu.cn
  • 基金资助:
    国家自然科学基金项目(42077135)

Effect of KI Leaching on the Hg (Ⅱ) Removal of Loess Soil and the Physicochemical Properties of the Soil

FENG Shuna(), LÜ Jialong, HE Hailong()   

  1. College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, P. R. China
  • Received:2023-02-07 Online:2023-04-18 Published:2023-07-12

摘要:

土壤中重金属污染严重威胁人类健康和生态环境安全,而化学淋洗是重要的重金属污染修复措施之一且取得了较大进展,但目前针对汞污染土壤修复的淋洗研究不足,严重制约其机理解析和应用。采用室内土柱试验和HYDRUS-1D数值模拟,探究不同化学淋洗剂EDTA、柠檬酸(CA)、Na2S2O3和KI对黄绵土中重金属汞的去除效果,并筛选出最优的淋洗剂种类和配比。同时研究了土壤理化性状对重金属迁移过程和淋洗的响应,并建立溶质运移模型明确土壤中汞的迁移过程。结果表明:(1)KI对黄棉土中汞的去除效果较好,优化配比后土壤汞去除率达46.4%。KI溶液对土壤汞解吸过程符合准一级动力学模型(r2=0.96),最大解吸量为4.09 mg?kg?1;(2)KI溶液淋洗后土柱中残留的汞含量随土柱深度增加而增加,平均质量分数为1.34 mg?kg?1,去除率为82.9%;KI对土柱中重金属汞的去除效果较振荡试验好,且淋洗过程有利于土壤中半移动性汞向移动性汞的转化;(3)HYDRUS-1D对土柱中汞穿透曲线拟合较好,拟合系数r2>0.95;拟合参数和误差评价值均在置信区间范围之内,可根据拟合预测出土柱中淋出液汞质量浓度达到安全排放标准所需的时间为87.7 h;(4)淋洗后土壤pH值和电导率较淋洗前增加显著,分别增加了0.67、1.15 mS?cm?1,而阳离子交换量则显著减少,平均减少量为1.64 cmol?kg?1;土壤阳离子交换量和pH值对土壤汞含量和形态影响显著。综上,KI淋洗能较好的修复汞污染土壤,淋洗后显著降低了土壤中汞的毒性和生物利用度,且满足高效、经济的修复目标,为汞污染土壤的淋洗修复提供了理论依据和技术思路。

关键词: 重金属污染, 化学淋洗, 土壤修复, 理化性状

Abstract:

Serious threats to human health and ecological safety have been caused by soil heavy metal contamination. Chemical leaching is one of the most effective and important remediation measures for heavy metal contamination with great progress. However, few studies were conducted on chemical leaching of the Hg (Ⅱ) contaminated soil, which severely limits the mechanism analysis and applications. In this study, indoor soil column tests and HYDRUS-1D numerical simulations were used to investigate the effects of different eluents, including EDTA, citric acid (CA), Na2S2O3 and KI on the removal of Hg (Ⅱ) from loess soil, and the optimal drencher types and ratios were selected. In addition, it is critical to investigate the response of physical and chemical soil properties to the migration process and leaching of heavy metals, and establish a solute transport model to better describe the migration process of Hg (Ⅱ) in soil for more efficient remediation of Hg-contaminated soil. The results showed that (1) KI was effective in removing Hg (Ⅱ) from loess soil, with a removal rate of 46.4% after the optimized ratio. The desorption of Hg (Ⅱ) from the KI solution followed the quasi-first-order kinetic model (r2=0.96), and the maximum desorption amount was 4.09 mg?kg?1. (2) The residual mercury content in the soil column increased with the depth of the column after KI leaching, with an average mass fraction of 1.34 mg?kg?1 and a removal rate of 82.9%. KI performed better in the removal of mercury from the soil column than the oscillation test, and the leaching process was conducive to the conversion of semi-mobile mercury to mobile mercury in the soil. (3) HYDRUS-1D could well simulate Hg (Ⅱ) penetration curve in the soil column with the fitting coefficient r2>0.95. The fitting parameters and error evaluation values were within the confidence interval. According to the fitted inversed parameters, it was predicted that 87.7 hours would be required for the mercury concentration in the leached liquid to reach the safe emission standard. (4) Soil pH and conductivity increased significantly by 0.67 and 1.15 mS?cm?1, respectively, after KI leaching. The cation exchange capacity decreased significantly, with an average reduction of 1.64 cmol?kg?1. Soil cation exchange capacity and pH had significant effects on Hg (Ⅱ) content and morphology. In conclusion, KI leaching could better remediate mercury-contaminated soil, and the toxicity and bioavailability of mercury in soil were significantly reduced after leaching. The remediated soil meets the efficient and cost-effective remediation objectives, which also provides a theoretical basis and technical guidance for the remediation of mercury-contaminated soil.

Key words: heavy metal pollution, chemical leaching, soil remediation, physical and chemical properties

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