污染场地调查中离散采样的局限性分析

采样误差是污染场地调查不确定性的主要来源.对污染场地调查采样方法进行研究，是提升调查数据精度和风险管控决策水平的重要手段.该研究结合污染场地的调查目标、污染物在土壤中分布的空间异质性特征，重点对离散采样方法和增量采样方法的应用现状及局限性进行了分析阐述.结果表明:①采样目标的设定取决于决策尺度.基于地块尺度决策的采样目标是表征污染物的空间分布，基于网格尺度决策的采样目标是获取更小尺度决策单元内污染物的平均浓度水平；②利用离散点表征污染物空间分布时，由于本身空间自相关性不强，表征结果不确定性大；③通过采用大样本量、高覆盖率的增量采样方法，能增强样本的代表性，更加精确地表征污染物在决策单元内的平均浓度，弥补离散采样的不足.但增量采样在挥发性有机物场地、深层土壤调查等情景下存在局限性.因此，污染场地调查应充分考虑污染物分布的空间异质性特征、采样方法应用条件、决策尺度等因素，选择合适的采样方法才能有效提升污染场地风险管控决策的科学性. 

Limitation Analysis of Discrete Sampling of Contaminated Site Investigations

Sampling error is the main source of uncertainty in contaminated site investigations, which affects the accuracy of investigation data and risk control decision-making. This study combines the investigation objectives and spatial heterogeneity of soil pollutants, and focuses on the application status and limitations of discrete and incremental sampling methods. A sampling target based on site-scale decisions characterizes the spatial distribution of pollutants, while the target based on grid-scale decisions measures the average concentration of pollutants in smaller units. Discrete sampling to characterize pollutant distribution produces results with large uncertainties due to the low spatial autocorrelation. Incremental sampling of large sample sizes with high coverage improves representativeness and the accuracy of pollutant concentrations in decision-making units, but it has limitations for sub-surface soil investigation and volatile organic compounds. The investigation of contaminated sites should fully consider the spatial heterogeneity of pollutants, application conditions of sampling methods, decision-making scale, and the selection of sampling methods to optimize risk management and control decisions.