泄漏条件下影响土壤介质中非水相液体残留量的敏感孔隙特征因子识别

Amount of pore and property of its structure in soil are considered as an important index in evaluating the characteristics of non-aqueous phase liquid (NAPL) migration, distribution and residual formation in the subsurface environment. However, there have been few quantitative investigation in the statistics correlation of the residual NAPL and soil pore characteristics of different soils. NAPL is one of the chemicals with high frequency of leaking. In this study, the residual concentration (determined through gas chromatography analysis) and vertical distribution of NAPL (diesel is taken as a NAPL probe) were investigated in 13 typical real soils of China with simulative leakage experiments. Combination with determination methods for pore distribution,specific surface area, mineral composition，morphology of residual contaminants, the pore characteristics，residual NAPL and their differences in the various types of soils are identified quantitatively and systematically. Based upon different geographical features of soil types in China, the multivariate linear relation of diesel residual amount and the pore characteristics (soil porosity, pore size distribution, average equivalent diameter, specific surface area and uniformity coefficient, etc.) are established through SPSS statistical analysis, and the sensitive pore factors which affect the residual amount of diesel are identified as well. The research will be benefit to further comprehend the discipline and mechanic underlying the formation of residual NAPL in soil pore space.

土壤孔隙数量与结构特征是影响非水相液体（NAPL）在土壤中运移、分布和残留的重要因素。但是目前关于不同类型土壤孔隙特征与NAPL残留量的统计学关系还没有进行深入的定量研究。本项目针对我国发生频率较高的NAPL（以柴油为例）泄漏问题，采用实际土壤物理实验模拟和气相色谱定量分析等方法，研究柴油在我国13种典型类型土壤中的稳定残留量及其垂向分布规律。结合土壤的不同尺寸孔径分布、比表面积、矿物组成和污染物残留态形貌等表征手段，系统地定量研究不同类型土壤的孔隙特征、污染物残留量及其差异性原因分析。最后，基于我国土壤类型的分布特征，采用SPSS统计软件建立柴油在土壤中残留量与孔隙特征（孔隙率、孔径分布特征、平均当量孔径、比表面积与不均匀系数等特征因子）的多元线性关系，识别出影响柴油残留量的敏感孔隙特征因子。希望本研究有助于进一步理解NAPL污染物在土壤孔隙空间中形成稳定残留态的规律与机制。

非水相液体在土壤中的残留量是决定污染土壤修复费用及修复时间长短的关键因素之一。土壤结构特征及基本理化性质是影响土壤中污染物环境行为的重要因素，其中孔隙数量决定了可被污染物占据的土壤空间大小及污染物的残留形态。本项目选择我国14种典型类型土壤为代表性供试土壤，采用土工试验方法、激光衍射法、压汞法、氮吸附法分别系统表征了这14种典型类型土壤的理化性质及粒径、孔隙特征。利用一维土柱装置模拟柴油泄漏过程，以柴油为例研究了非水相液体在不同类型土壤中的迁移和残留规律。结果表明柴油在不同类型土壤中垂向迁移的平衡迁移距离差异较大，平衡迁移距离随土壤质地不同表现为：砂土>砂质壤土>砂质粘壤土>壤质粘土>砂质粘土。分析发现平衡迁移距离与分形维数呈极显著负相关，与土壤巨孔的体积呈正相关，但与大孔、中孔体积呈负相关关系。在不同类型土壤中，柴油的残留量随着土层深度增加总体呈降低趋势，但最大残留量不在土壤表层。柴油在不同类型土壤中的残留量具有显著差异，在海南土壤中残留量最小，在贵州、江苏和浙江等地区土壤中残留量较大。利用SPSS软件进行相关性分析及多元逐步回归分析，建立了柴油在土壤运移过程中的迁移距离和残留量与土壤结构特征量之间的定量关系，鉴别出影响柴油在土壤中迁移及残留的主控结构特征因子为孔隙体积，其中孔径为0.05-0.5 μm的大孔隙体积是影响柴油纵向迁移距离的关键因素，孔径为0.5-7.5 μm的大孔隙体积是柴油在土壤表层残留量的最关键的影响因素，而<0.05 μm的中孔体积是影响柴油在表层以下残留的主控因子。本研究还分析了非水相液体在我国不同类型土壤中形成残留态的过程和机理，为我国土壤环境事故应急响应、泄漏场地环境风险评估和修复工作提供基础信息和技术支持。