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柴油污染土壤低温热处理及其对土壤理化性质的影响
任家强1, 宋 昕1, 何 跃2
1.中国科学院土壤环境与污染修复重点实验室(南京土壤研究所);2.生态环境部南京环境科学研究所
摘要:
石油化工厂加工、储藏、运输过程以及储油罐的泄露等易造成土壤柴油污染。热处理技术常用于修复各类挥发性和半挥发性污染土壤,但加热可能会改变土壤理化性质,因此本文综合评价了低温热处理对柴油污染土壤的修复效率及其对土壤理化性质的影响。对柴油污染土壤低温热处理进行参数优化,结果显示:在250 ℃ 加热10 min后,土壤总石油烃含量为358.7 mg/kg,总石油烃去除率为94%,低于土壤环境质量建设用地土壤污染风险管控标准中规定的一类用地总石油烃筛选值826 mg/kg。过高的温度和过长的加热时间反而会带来过多的能耗,并对土壤理化性质造成负面影响。低温热处理后土壤颜色由浊黄橙变为灰黄棕,土壤pH由7.39降为6.88,阳离子交换量由16.9 cmol/kg变为14.8 cmol/kg,田间持水量从0.32 g/g土变为0.29 g/g土,土壤有机碳降低约10%,硝态氮和铵态氮含量加热后增加分别超过5倍和15倍,土壤质地和全氮变化不显著。加热前后的土壤元素分析结果和土壤颜色变化说明加热过程中烃类炭化转化为“热解炭”,是污染土壤中柴油去除的主要反应机制。本研究表明低温热处理技术可以快速高效地修复柴油污染土壤,合理优化低温热处理的加热温度和加热时间是使低温热处理成为一种修复柴油污染土壤的绿色可持续性修复技术的关键。
关键词:  污染土壤  低温热处理  柴油  土壤性质
DOI:10.13758/j.cnki.tr.2020.05.012
分类号:X53
基金项目:中国科学院科技服务网络计划(STS计划)项目(KFJ-STS-ZDTP-039)和中国科学院重点部署项目(KFZD-SW-303)资助。
Low-Temperature Thermal Treatment of Diesel-Contaminated Soil and Its Effect on Soil Physicochemical Properties
REN Jiaqiang1, SONG Xin1, HE Yue2
1.Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences;2.Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment
Abstract:
The production, storage and transportation of diesel are likely to cause diesel contamination in soil. Thermal treatment is commonly used to remediate volatile and semi-volatile contaminated soils. However, heating can alter soil properties. This paper gives a comprehensive assessment on the removal efficiency of diesel-contaminated soil using low-temperature thermal treatment (LTTT) and the impact of LTTT on soil physicochemical properties. The optimization results of LTTT experiments showed that the total petroleum hydrocarbon (TPH) removal efficiency was 94% after LTTT at 250 ℃ for 10 min, resulting in a residual TPH concentration of 358.7 mg/kg, lower than the risk screening level of 826 mg/kg. Overheating and/or excessive heating duration can lead to excessive energy consumption and adversely affect the physicochemical properties of soil. The comparison on soil properties showed that soil color changed from yellowish orange to grayish brown, and the slight decreasing trends were observed as follows: soil pH from 7.39 to 6.88, CEC from 16.9 cmol/kg to 14.8 cmol/kg, and water holding capacity from 0.32 g/g soil to 0.29 g/g soil. In addition, soil organic carbon decreased by about 10%, while NO– 3-N and NH4+-N values increased by more than 14 and 4 times, respectively. No significant change was observed in soil texture and total nitrogen. It was inferred based on the elemental analysis and change in soil color that pyrolytic carbon was formed in LTTT process, which was the main removal mechanism of diesel by LTTT in contaminated soil. Therefore, it can be concluded that LTTT is a fast and efficient soil remediation technology, and the optimization of heating temperature and time is the key to make LTTT a green and sustainable remediation technology for applications on diesel-contaminated soil.
Key words:  Contaminated soil  Low temperature thermal treatment  Diesel  Soil properties

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