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Comparison of methods used to calculate typical threshold values for potentially toxic elements in soil

机译：比较用于计算土壤中潜在毒性元素典型阈值的方法

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The environmental quality of land can be assessed by calculating relevant threshold values, which differentiate between concentrations of elements resulting from geogenic and diffuse anthropogenic sources and concentrations generated by point sources of elements. A simple process allowing the calculation of these typical threshold values (TTVs) was applied across a region of highly complex geology (Northern Ireland) to six elements of interest; arsenic, chromium, copper, lead, nickel and vanadium. Three methods for identifying domains (areas where a readily identifiable factor can be shown to control the concentration of an element) were used: k-means cluster analysis, boxplots and empirical cumulative distribution functions (ECDF). The ECDF method was most efficient at determining areas of both elevated and reduced concentrations and was used to identify domains in this investigation. Two statistical methods for calculating normal background concentrations (NBCs) and upper limits of geochemical baseline variation (ULBLs), currently used in conjunction with legislative regimes in the UK and Finland respectively, were applied within each domain. The NBC methodology was constructed to run within a specific legislative framework, and its use on this soil geochemical data set was influenced by the presence of skewed distributions and outliers. In contrast, the ULBL methodology was found to calculate more appropriate TTVs that were generally more conservative than the NBCs. TTVs indicate what a "typical" concentration of an element would be within a defined geographical area and should be considered alongside the risk that each of the elements pose in these areas to determine potential risk to receptors.
机译：可以通过计算相关的阈值来评估土地的环境质量，该阈值可以区分由人为地质源和散布人为源产生的元素浓度与由点源元素产生的浓度。在一个高度复杂的地质区域（北爱尔兰），对六个感兴趣的要素进行了一个简单的过程，就可以计算出这些典型的阈值（TTV）。砷，铬，铜，铅，镍和钒。使用了三种识别域的方法（可以显示易于识别的因子来控制元素的浓度的区域）：k均值聚类分析，箱线图和经验累积分布函数（ECDF）。 ECDF方法最有效地确定浓度升高和降低的区域，并在此研究中用于识别域。目前在英国和芬兰分别采用两种统计方法来计算正常背景浓度（NBCs）和地球化学基线变化上限（ULBLs），目前分别与英国和芬兰的立法制度结合使用。 NBC方法被构造为在特定的立法框架内运行，其在该土壤地球化学数据集上的使用受到偏斜分布和异常值的存在的影响。相反，发现ULBL方法可以计算出比NBC更保守的更合适的TTV。 TTV指示元素的“典型”浓度在定义的地理区域内，并且应与每种元素在这些区域中构成的风险一起考虑，以确定对受体的潜在风险。

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