土壤金属元素测量结果的不确定性与其关键影响因素

Uncertainty in soil metal element measurements and its key influencing factors

土壤检测是第三次全国土壤普查数据的核心来源,而由于测量误差的存在,导致测量结果具有不确定性,并影响结果的可靠性。为提高检测结果的质量水平,选取普查中的总铬、全锰、全铜、全锌、全镍、全钼、总镉和总铅指标开展不确定度评定,研究影响不确定度大小的关键因素。结果表明,土壤金属元素测量的关键不确定度分量来源于消解液的质量浓度ρ和测量重复性R。减小ρ引入的不确定度可通过设置合理的标准曲线线性范围,使ρ尽可能接近曲线最高点;使用相关系数r值高的标准曲线;使用更多的质量浓度点建立标准曲线和增加仪器信号采集次数等方法。减小R引入的不确定度可通过提高测量精密度。通过优化,土壤总镉的不确定度范围由(0.365±0.126)mg·kg^(−1)(k=2)降低至(0.365±0.030)mg·kg^(−1)(k=2),对于0.4 mg·kg^(−1)的筛选值,不确定度的减小使土壤总镉在进行合格评价时得到更准确可靠的结果。该研究结果阐明了影响土壤金属元素测量的关键不确定度分量,为实验室有效控制土壤金属元素的测量不确定度,减小检测结果的分散性,提高检测结果的质量水平提供了理论参考。

Soil testing is the cornerstone of data for the Third National Soil Condition Census.However,the presence of measurement errors introduces uncertainty and affects the reliability of the results.To enhance the quality of testing outcomes,an evaluation of uncertainty was conducted for total chromium,manganese,copper,zinc,nickel,molybdenum,cadmium and lead in the survey,focusing on the factors that influence the magnitude of uncertainty.The findings indicated that the key components of uncertainty in soil metals measurements stem from the mass concentration of the digestion solution(ρ),and the measurement repeatability(R).The uncertainty introduced byρcould be reduced by appropriate establishing a linear range for the standard curve to ensure thatρwas as close as possible to the highest point of the curve;using a standard curve with a higher Pearson correlation coefficient(r);employing more mass concentration points to establish standard curves and increasing the number of instrument signal acquisitions.The uncertainty introduced by R could be reduced by improving measurement precision.Through optimization,the uncertainty range for total cadmium was reduced from(0.365±0.126)mg·kg^(−1)(k=2)to(0.365±0.030)mg·kg^(−1)(k=2).For the screening value of 0.4 mg·kg^(−1),the reducing uncertainty led to more accurate and reliable results in the conformity assessment of total cadmium in soils.This study clarified the key components of uncertainty affecting the measurement of soil metals,providing a theoretical reference for laboratories to effectively control the measurement uncertainty of soil metals,reduce the dispersion of test results,and enhance the quality level of the outcomes.