Abstract:

In order to evaluate the feasibility of high-definition X-ray fluorescence spectrometry （HDXRF） in the rapid analysis and investigation of excessive Cd in paddy fields， the national standard soil materials and Cd-exceeding paddy fields in central Guizhou was used as the research objects. The relative error （RE） and relative standard deviation （RSD） were used to evaluate the accuracy of HDXRF method for the determination of Cd content in soil. The difference between HDXRF method and （inductively coupled plasma source mass spectrometer ICP-MS）method for the determination of Cd content in paddy soil was studied， and the effects of sample preparation and test conditions such as soil moisture， sieve particle size and detection time on the determination of Cd content in paddy soil by HDXRF method were analyzed. The results showed that the lower limit of determination of Cd in soil by HDXRF method was 0.254 mg·kg^-1， which was lower than the minimum screening value （0.3 mg·kg^-1） of Cd in Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard （Trial） （GB 15618—2018）. When the soil Cd content was higher than the lower limit of determination （0.254 mg·kg^-1）， the accuracy and precision of HDXRF method for the determination of soil Cd content were higher （<10%）. There was no significant difference in Cd content in paddy soil by HDXRF method and ICP-MS method. The fitting equation of soil Cd content determined by these 2 methods was y=0.981x+0.006 （R²=0.998）. With the increase of soil moisture content， the RE and RSD of Cd content in paddy soil by HDXRF method showed an increasing trend. There was no significant difference in Cd content between 2.5% （air-dried） soil moisture content and 0% （oven-dried） soil moisture content. With the decrease of soil sieve particle size， the RE and RSD of Cd content in paddy soil by HDXRF method decreased. When the sieve particle size was 0.15 mm， the variation range of Cd content in paddy soil by HDXRF method was the smallest， and both RE and RSD were less than 10%. With the increase of detection time， the RE and RSD of Cd content in paddy soil by HDXRF method showed a decreasing trend. When the detection time was 10 min， theRE and RSD of Cd content in paddy soil by HDXRF method were less than 10%. In summary， HDXRF method was suitable for rapid analysis and investigation of Cd exceeding standard in paddy fields. The suitable sample preparation and test conditions were soil moisture content of 2.5%， sieve particle size of 0.15 mm and detection time of 10 min.

Key words: soil Cd, rapid detection, accuracy, precision, influencing factors

摘要：

为评价高精度便携式X射线荧光光谱（high-definition X-ray fluorescence spectrometry，HDXRF）法运用于稻田Cd超标快速分析与调查评估的可行性，以国家标准土壤物质和黔中Cd超标稻田为研究对象，采用相对误差（relative error，RE） ）与相对标准偏差（related standard deviation，RSD）评价HDXRF法测定土壤Cd含量的精准度，研究HDXRF法与电感耦合等离子体质谱仪（inductively coupled plasma source mass spectrometer，ICP-MS）法测定水稻土Cd含量的差异，并分析土壤水分、过筛粒径及检测时长等样品制备与测试条件对HDXRF法测定水稻土Cd含量的影响。结果表明，HDXRF法测定土壤Cd含量的测定下限为0.254 mg·kg^-1，低于《土壤环境质量 农用地土壤污染风险管控标准（试行）》（GB 15618—2018）中Cd的最低筛选值（0.3 mg·kg^-1）。当土壤Cd含量高于测定下限（λ=0.254 mg·kg^-1）时，HDXRF法测定土壤Cd含量的准确度和精密度较高（<10%）。HDXRF法与ICP-MS法测定水稻土Cd含量差异不显著，2种方法测定土壤Cd含量的拟合方程为：y=0.981x+0.006（R²=0.998）。随着土壤水分含量的增加，HDXRF法测定水稻土Cd含量的RE与RSD呈升高趋势，2.5%（风干）的土壤水分含量与0%（烘干）的土壤水分含量的水稻土Cd含量检测结果差异不显著；随土壤过筛粒径的降低，HDXRF法测定水稻土Cd含量的RE与RSD降低，过筛粒径为0.15 mm时，HDXRF法测定水稻土Cd含量变幅最小，RE与RSD均<10%；随着检测时长的增加，HDXRF法测定水稻土Cd含量的RE与RSD均呈降低趋势，当检测时长为10 min时，HDXRF法测定土壤Cd含量的RE与RSD均小于10%。综上，HDXRF法适用于稻田Cd超标快速分析与调查评估，适宜的样品制备与测试条件为土壤含水率2.5%、过筛粒径0.15 mm、检测时长10 min。

关键词: 土壤Cd, 快速检测, 准确度, 精密度, 影响因素