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近年来,工业用地土壤和地下水常受到持久性有机物的污染,已对人群健康及生态环境造成威胁[1-2]。其中,多环芳烃(Polycyclic aromatic hydrocarbons, PAHs)具有致癌变、致畸变及致突变的特点,成为一类备受关注的持久性有机污染物[3-4]。PAHs是含有2个以上苯环的碳氢化合物,属于疏水性有机污染物,在土壤环境中容易积累。有研究表明,环境中的PAHs可以通过土壤进入人体,危害人体健康[5]。目前,PAHs污染土壤是我国乃至全球亟待解决的环境问题之一。
国内外PAHs污染土壤修复技术主要包括热脱附技术、化学氧化修复技术、微生物修复技术和植物修复技术等[6-9]。近年来,化学氧化修复技术由于具有易操作、修复效果好和周期短的特点,已成为PAHs污染土壤修复领域的主流实用技术[2]。化学氧化修复技术是向污染土壤中添加氧化剂,利用氧化作用将土壤中有机污染物转化为毒性更小或无毒的物质。常用的氧化剂包括臭氧、双氧水、过硫酸钠和高锰酸钾[4, 10]。高锰酸钾由于具有氧化还原电位高、反应速率易控及反应过程易监测的特点而受到关注[11]。目前,国内外已有大量关于高锰酸钾氧化修复PAHs污染土壤的研究,诸多案例表明,高锰酸钾可有效去除土壤中PAHs[12-14]。LIAO等[13]研究并比较了不同化学氧化剂对煤气厂和焦化厂污染场地土壤中PAHs的去除效果,结果发现,高锰酸钾对土壤中PAHs的去除效率最高,达到90%以上。LEMAIRE等[14]的研究考察了不同土壤有机质类型、老化时间、PAHs有效性及碳酸盐质量分数等条件下,不同化学氧化剂对土壤中PAHs的去除效果,结果表明,在不同条件下高锰酸钾均是最有效的氧化剂。同时,高锰酸钾氧化修复技术运用过程中引发的环境问题也越来越受到国内外学者的关注[15-16]。例如,高锰酸钾氧化处理会降低土壤的渗透性,进而使土壤质量退化[16-17]。锰(Mn)虽然是一种土壤中常见的微量元素,但当质量分数过高时,也会对生态环境和人体健康造成危害。因此,针对高锰酸钾氧化修复技术应用过程中Mn元素迁移转化规律及其潜在的环境风险进行研究非常重要,但目前鲜见相关研究报道。
本研究通过室内模拟实验,采用某焦化厂PAHs污染土壤作为研究材料,系统研究高锰酸钾投加量对土壤Mn质量分数、赋存形态分布及有效态质量分数的影响,探讨高锰酸钾氧化修复PAHs污染土壤过程中Mn元素的迁移转化规律,旨在为高锰酸钾氧化修复技术应用工艺优化提供科学依据。
高锰酸钾修复PAHs污染土壤过程中Mn迁移转化规律
Migration and transformation of Mn during remediation process of soil contaminated with PAHs by potassium permanganate oxidation
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摘要: 为探究高锰酸钾氧化修复技术应用过程中Mn元素迁移转化规律及其潜在的环境风险,通过室内模拟实验,采用某焦化厂PAHs污染土壤作为研究材料,探究了高锰酸钾修复技术中不同药剂投加量对PAHs去除、高锰酸钾消耗量、土壤中Mn质量分数、Mn赋存形态分布及有效态Mn质量分数等的影响。结果表明,高锰酸钾氧化处理可有效去除土壤中PAHs;当高锰酸钾投加量为0.20 mmol·g−1、反应时间为1 d时,PAHs去除率最高,可达89.61%。氧化处理过程中,高锰酸钾消耗量和土壤Mn质量分数均与高锰酸钾的投加量有关,随投加量增加而升高。其中,土壤Mn的质量分数与高锰酸钾消耗量呈显著正相关关系。高锰酸钾氧化处理后土壤中Mn主要以铁锰氧化物结合态存在,所占比例为77.04%~92.17%。土壤经0.05 mmol·g−1高锰酸钾氧化处理后,土壤有效态Mn的质量分数比对照组增加了0.94倍;而在高锰酸钾投加量为0.10~0.40 mmol·g−1的处理条件下,土壤有效态Mn的质量分数下降了77.65%~99.09%。药剂投加量是影响高锰酸钾氧化修复PAHs污染土壤过程中Mn环境行为的关键因子。本研究结果可为高锰酸钾氧化修复技术应用工艺优化提供参考。Abstract: Potassium permanganate oxidation is an effective soil remediation technology being used widely for removing PAHs from soil. In order to investigate the migration and transformation of Mn, and its potential environmental risk during remediation process of soil contaminated with PAHs by potassium permanganate oxidation, a simulation experiment was carried out with PAHs contaminated soil from a coking site. The effects of different doses of potassium permanganate on amount of consumed potassium permanganate, content of manganese (Mn), speciation of Mn and extractable Mn content in soil were investigated. Then, the migration and transformation of Mn during the remediation process of PAHs contaminated soil by potassium permanganate oxidation was explored. The results showed that potassium permanganate may effectively remove PAHs from the soil of the coking plant. When the dosage of potassium permanganate was 0.20 mmol·g−1 and the reaction time was 1 d, the removal rate of PAHs was the highest, reaching 89.61%. In the remediation process, potassium permanganate consumption and contents of Mn in soil increased with the dose level of potassium permanganate. The result of correlation analysis demonstrated that there is a significant positive correlation between the content of Mn in soil and the amount of consumed potassium permanganate. Moreover, Mn in soil existed mainly in Fe-Mn oxides bound fraction, and its proportions were 77.04%~92.17%. Compared to the treatment without potassium permanganate, the content of extractable Mn in soil increased by 0.94 times after treatment with potassium permanganate at 0.05 mmol·g−1. However, extractable Mn content in soil declined by 77.65% to 99.09% after treatment with potassium permanganate oxidation at 0.10~0.40 mmol·g−1. In conclusion, the dose of oxidant is a key factor for the environmental behaviors of Mn in soil during the remediation process of PAHs contaminated soil by potassium permanganate oxidation. The results of this study can provide a reference for the process optimization of application of potassium permanganate oxidation.
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Key words:
- potassium permanganate oxidation /
- PAHs /
- remediation /
- manganese /
- migration /
- transformation
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表 1 实验处理
Table 1. List of treatments
处理组 高锰酸钾投加量/
(mmol·g−1)氧化剂溶液
浓度/(mol·L−1)加入氧化剂
溶液体积/mL去离子水
体积/mLCK 0 0 0 60.00 K1 0.05 0.20 7.50 52.50 K2 0.10 0.20 15.00 45.00 K3 0.20 0.20 30.00 30.00 K4 0.40 0.20 60.00 0 表 2 土壤中不同赋存形态Mn的质量分数
Table 2. Contents of Mn chemical forms in soil
mg·kg−1 处理组 可交换态 碳酸盐结合态 铁锰氧化物结合态 有机结合态 残渣态 CK 21.36±1.00 108.91±5.10 123.11±5.62 21.98±2.64 133.74±9.30 K1 2.00±0.24 295.60±18.15 2 138.21±246.13 181.84±38.68 157.86±5.34 K2 0.29±0.06 208.58±8.51 6 180.25±312.15 513.73±32.19 182.19±5.22 K3 ND 15.52±2.82 12 715.20±8.28 923.56±24.06 200.03±3.33 K4 ND 3.05±0.43 18 302.56±1208.37 1 238.72±99.39 205.65±9.91 注:ND表示未检出。 -
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