便携式X射线荧光光谱测定土壤中Cr,Cu,Zn,Pb和As的研究

应用便携式X射线荧光光谱对土壤中的重金属元素Cr,Cu,Zn,Pb和As进行测试,分析土壤粒径、含水量、土壤类型对检测结果的影响,并选用北京、新疆、黑龙江、云南和江苏的典型土壤研究重金属元素含量与X射线荧光光谱特征峰强的关系.实验表明,土壤粒径影响了测试的精密度,土壤粒径从40目降低到100目,检测的相对标准偏差从15.6%减少至6.9%;土壤含水量主要影响样品检测的特征峰强,土壤含水量从5%提高到25%,与无水样品相比的相对峰强从86%降低到69%,相对峰强与土壤含水量符合方程I=100e-0.015c,I为相对峰强,c为土壤含水量(R2=0.83,n=30).在0～1500 mg·kg-1区间,土壤中重金属元素含量与X射线荧光光谱特征峰强间有着良好的线性相关,但不同土壤类型间的线性方程有着较大的差异,云南土壤样品建立的线性方程有着较小的斜率.通过检测土壤标准样品,验证了便携式X射线荧光光谱检测土壤中重金属元素有着较好的准确度和精密度,适用于土壤中重金属的快速检测.

Determination of Cr, Cu, Zn, Pb and As in soil by field portable X-ray fluorescence spectrometry

Total concentrations of Cr, Cu, Zn, Pb and As were determined in soil samples from Beijing, Xinjiang, Heilongjiang, Yunnan, and Jiangsu provinces, using field portable X-ray fluorescence spectrometry (XRF). The relationship between XRF analysis results and the concentration of heavy metals in soils was established. The influence of soil particle size and humidity was also considered. Experiments showed that the particle size of soil affected XRF performance. While particle size decreased from 420 to 180 microm, the relative standard deviation (RSD) of XRF detect results reduced from 15.6% to 6.9%. Soil humidity mainly affected the counts of XRF measured. As the soil water content increased from 5% to 252, the analysis result's relative ratio of humid soil samples to oven dried soil samples decreased from 86% to 69%, according with the equation I = 100e(0.015c), where I means relative ratio, and c means water content (R2 = 0.83, n=30). A high degree of linearity was found for all the five heavy metals with the XRF measurement in the range of 0 to 1500 mg x kg(-1). But the linearity equation was not the same among these soils. The linearity equation established with Yunnan soil has a small slope because of higher Fe concentration in soil. The performance of instrument was assessed by comparing XRF analysis result with the standard sample reference, and the result showed that XRF is an effective tool for rapid, quantitative monitoring of soil metal contamination.