Application of in-situ horizontal barrier risk control technology in the treatment of a decommissioned industrial contaminated site
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摘要:
为满足人体健康风险管控目标,结合某退役工业污染场地后期开发工作情景,分别针对室内外区域设计了针对性的风险管控方案。室内区域建筑物地基下方−2 m污染土采用土壤气阻隔控制工程,在建筑物地基底板与导气层之间喷涂隔气膜对土壤气进行阻隔,控制建筑物下方导气层负压为−5~−2 Pa,利用抽提系统对土壤气进行集中收集,经尾气处理系统处理达标排放;室外区域原始地面标高−3 m以下污染土采用HDPE膜(两布一膜)进行水平阻隔,阻隔层上方采用清洁黏土覆盖压实。工程设施完工1年内开展的风险管控效果评估结果表明,室内外区域风险管控工程的工程性能指标及污染物指标均符合评估标准要求,达到预期效果,工程已于2021年12月通过生态环境主管部门验收,进入后期环境监管。
Abstract:In order to meet the goal of human health risk control, targeted risk control schemes were designed for indoor and outdoor areas in combination with the working situation of later site development scenarios of a decommissioned industrial contaminated site. For the −2 m contaminated soil under the foundation of indoor regional buildings, the soil gas barrier control project was adopted. The soil gas was blocked by spraying a film between the foundation and the air guide layer of the building, and the negative pressure of the air guide layer below the building was controlled to be −5-−2 Pa. The soil gas was collected by the extraction system, which was treated by the tail gas treatment system to reach the standard before discharge. HDPE film (two cloth and one film) was used as a horizontal barrier for contaminated soil with an original ground elevation below −3 m in outdoor areas, and clean clay was used for cover and compaction above the barrier layer. The results of the risk control effectiveness evaluation carried out within one year after project completion showed that the engineering performance indicators and pollutant indicators of the indoor and outdoor areas met the evaluation standards and achieved the expected effect. The project passed the acceptance of the ecological environment department in December 2021 and entered the later stage of environmental supervision.
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Key words:
- industrial contaminated site /
- in-situ horizontal barrier /
- air barrier /
- risk control
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表 1 场地地层分布
Table 1. Site stratigraphic distribution
地层 层厚/m 岩性描述 第四系人工填土层(Q4ml) 0.3~6.5 颜色为褐红、褐黄、杂色,土质松散,稍湿;该层主要由混凝土、黏土夹碎石组成 第四系残坡积层(Q4el+dl) 0.4~24.5 颜色为红色、褐黄色,土质从稍密至中密,稍湿,可塑至硬塑状;该层主要由
原生红黏土组成二叠系下统倒石头组(P1d) 顶板埋深2.4~11.5 颜色为灰白色,岩层全风化、层状构造;
该层主要由白云岩组成二叠系下统栖霞茅口组(P1q+m) 顶板埋深2.1~18.2,
未揭穿颜色为灰、灰白色,岩层中风化、节理裂隙发育;该层主要由石灰岩组成 表 2 室内区域概化分层暴露浓度及风险计算结果
Table 2. Exposure concentration and risk calculation results of generalized stratification (indoor areas)
分层/m 暴露浓度
取值方法暴露浓度/
(mg/kg)风险水平 3~8 不符合正态分布,
采用最大值70.1 1.63×10−6 8以下 伽马分布拟合参数法计算95%置信上限 6.4 1.82×10−7 注:土层概化为2层,3~8 m为包气带层,8 m以下为饱和层。全文同。 表 3 室内区域增加底板负压环境后风险计算结果
Table 3. Risk calculation results after adding negative pressure environment of floor indoors
分层/m 增加负压/Pa 暴露浓度/(mg/kg) 风险水平 3~8 −2 70.1 6.06×10−12 表 4 室外区域概化分层暴露浓度及风险计算结果
Table 4. Exposure concentration and risk calculation results of generalized stratification (outdoor areas)
分层/m 暴露浓度取值方法 暴露浓度/
(mg/kg)风险水平 3~8 最小方差无偏估计方法计算95%置信上限 52.9 1.14×10−6 8以下 最小方差无偏估计方法计算95%置信上限 46.4 2.33×10−7 表 5 室外区域高浓度点位削减至管制值后的风险计算结果
Table 5. Risk calculation results after reducing outdoor high concentration point to the control value
分层/m 浓度削减 暴露浓度取值方法 暴露浓度/
(mg/kg)风险
水平3~8 JXS19-2点位3~4 m土壤(苯浓度696 mg/kg)及JXS19点位4~6 m土壤(苯浓度713 mg/kg)苯浓度削减至低于40 mg/kg 最小方差无偏估计方法计算95%置信上限 10.6 2.3×10−7 表 6 阻隔工程分区统计
Table 6. Partition statistics of barrier engineering
m2 区域 阻隔工艺 污染区域
面积阻隔工程
面积室内区域 土壤气阻隔 3 059.2 8 158.4 室外区域 HDPE膜阻隔 5 778.4 6 771.3 合计 8837.6 14 929.7 表 7 室内土壤气阻隔层材料性能要求
Table 7. Material performance requirements for indoor soil gas barrier layer
喷涂型隔气膜 复合底衬及保护层 检测性能 指标
要求检测性能 复合底衬
指标要求保护层
指标要求厚度/mm ≥1.5 厚度/mm ≥0.5 ≥2.5 断裂延展性% ≥1 000 纵横向标准强度
对应伸长率/%40~80 40~80 与混凝土的剥离
强度/(kN/m2)≥100 纵横向断裂
强度/(kN/m)≥30 ≥30 拉伸断裂强
度/(N/mm)≥30 CBR顶破强
力/kN≥6.4 ≥6.4 水蒸气渗透系数/
〔g·cm/(cm2·s·Pa)〕1.0×10−12 纵横向撕破强
力/kN≥0.82 ≥0.82 直角撕裂强度/N ≥250 抗穿刺强度/N ≥535 注:隔气膜、复合底衬及保护层的化学稳定性、耐腐蚀性、抗老化性(满足设计使用期50年)、水的溶解性及有机物挥发性能等检测参考ASTM检测方法。 表 8 隔气膜铺设位置及工程量参数
Table 8. Laying position and engineering quantity parameters of gas barrier film
项目 参数 项目 参数 底部铺设内容 复合衬底、喷涂型隔气膜
及保护层侧壁铺设
厚度/mm3 200 底部铺设
标高/m−2.60 高于室内
地面/mm1 500 底部铺设内容 复合衬底、喷涂型
隔气膜阻隔面积/m2 约8 158.4 侧壁铺设
标高/m−2.60~0.6 喷涂型
隔气膜面积/m2约8 974.25 表 9 土壤气收集穿孔管施工参数
Table 9. Construction parameters of perforated pipe for soil gas collection
项目 参数 项目 参数 平行管路间距/m 12 材质 316L不锈钢 管路直径/mm 100 单管长度/mm 5 970 壁厚/mm 2.5 穿孔管数量 90 管路连接方式 法兰连接 孔布置/mm 穿孔管环向开孔,孔径5;
环向数量6个,轴向距离100表 10 土壤气处理设备参数
Table 10. Parameters of soil gas treatment equipment
项目 参数 土壤气处理
装置数量3套 材质 304不锈钢 轴流风机 直径420 mm,风机运行功率1.1 kW,风量大于
800 Nm3/h,全压大于400 Pa活性炭吸附罐 处理能力大于500 Nm3/h。使用后的活性炭需按照
危险废物进行管理,运送至有资质的危险废物
处置单位进行处置,并根据相关规定办理
危险废物转移联单表 11 普通HDPE土工膜性能指标
Table 11. Performance indexes of ordinary HDPE geomembrane
项目 参数 项目 参数 厚度/mm 1.5 纵横向断裂
伸长率/%≥600 密度/(g/cm3) ≥0.94 纵横向直角撕裂
负荷/N≥170 纵横向拉伸屈服
强度/(N/mm)≥20 抗穿刺强度/N ≥360 纵横向拉伸断裂
强度/(N/mm)≥30 水蒸气渗透系数/
〔g·cm/(cm2·s·Pa)〕≤1.0×10−13 纵横向屈服
伸长率/%≥11 常压氧化诱导时间(OIT)/min ≥60 表 12 复合土工膜外观瑕疵评定
Table 12. Evaluation of appearance defects of composite geomembrane
疵点 轻缺陷 重缺陷 备注 布面不匀、折痕 轻微 严重 杂物、僵丝 软质,粗≤5 mm 硬质;软质,
粗>5 mm边不良 ≤300 cm时,
每50 cm计1处>300 cm 破损 ≤0.5 cm >0.5 cm,破洞 以疵点最
大长度计其他 参照相似疵点评定 参照相似疵点评定 表 13 环境空气监测结果
Table 13. Monitoring results of ambient air
污染物 监测浓度/
(μg/m3)标准浓度/
(μg/m3)标准来源 苯 ND 110 HJ 2.2—2018《环境影响评价
技术导则 大气环境》甲苯 ND~73 200 苯并(a)芘 ND~0.001 9 0.002 5 GB 3095—2012
《环境空气质量标准》非甲烷总烃 70~1 240 10 000 GB 37822—2019《挥发性
有机物无组织排放控制标准》 -
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