X射线荧光光谱法对于土壤中痕量汞的快速检测

土壤中的重金属污染会影响农产品品质，进而对人体的健康产生危害。土壤中多种重金属元素通常使用化学法进行检测，需要在实验室使用强氧化性物质对土壤样品进行消解处理，然后对消解液进行测试。而X射线荧光光谱法可以实现土壤中多种重金属元素的快速检测，相对化学法检测，X射线荧光光谱法检出限较高。对于汞元素来说，其在土壤中的限值相对其他元素较低，直接使用X射线荧光光谱法对于低含量的样品难以实现快速检测。通过设计一个富集装置对土壤中汞进行富集，并使用X射线荧光光谱仪进行测试，实现土壤中汞的快速检测，可以满足实际测试需求。该装置首先对已准确称量的土壤样品进行加热，其中的汞元素会发生解吸，并使用滤膜对解吸出来的汞进行吸附，从而实现汞元素的富集。汞发生器会产生特定含量的含汞空气，使用不同的滤膜进行吸附，研究发现碳纤维滤膜具有很好的吸附作用，可以对空气中的汞进行有效富集。称取相同质量的土壤样品，在解吸温度为800 ℃的条件下，使用不同的抽气速率，并叠加两层膜进行吸附测试。研究发现随着通过滤膜气流速率的增加，第一层滤膜的谱峰强度随之降低，第二层滤膜的谱峰强度随之增加，结果表明较低的气流流速更有利于滤膜的吸附，并且使用1 L·min-1的气流流速时，解吸出来的汞基本全部富集到第一层滤膜上。通过滴加不同量的含汞溶液到高纯二氧化硅中，并通过此体系进行富集和测试，绘制汞的工作曲线，线性相关系数为0.998 5。通过对高纯二氧化硅进行多次测量，可计算检出限和定量限分别为7.52和25.06 ng，如果此时称样量为0.3 g, 计算可得土壤样品的定量限为0.083 mg·kg-1。对国家标准土壤样品进行测试，除低于定量限的一个样品之外，其余样品的相对偏差不大于11.1%，表明该方法可以实现农业用地土壤中重金属汞的快速检测。

The Rapid Detection of Trace Mercury in Soil With EDXRF

The pollution of heavy metals in the soil will affect the quality of agricultural products,which could further influence human health.Multiple heavy metals are us ually detected with chemical methods in soil,during the process,strong oxidizing materials would be used to digest the samples in the laboratory,and finally,the dissolved solutions are tested.X-ray fluorescence spectrometry could realize the rapid detection of multiple heavy metals in soil,but compared with chemical methods,which has a higher detection limit.For mercury,the national pollution limit is lower than other metals,which makes it difficult to detect rapidly with X-ray fluorescence spectrometry in low-content samples.In this paper,an enrichment device was designed to realize the enrichment of mercury in soil,after testing with the X-ray spectrometer,the rapid detection of mercury in soil could be realized,which met the requirement of the actual test.The soil samples that had been weighed accurately would be heated first,and in this process,the mercury would be desorbed,and at the same time,the filter membrane was used to adsorb it,so as to realize the enrichment of mercury.A mercury generator was used to provide the air with a certain amount of mercury,and different kinds of membranes would be used to study the effects of adsorption.The result found that carbon fiber filter membranes have a good effect on adsorption and could enrich mercury in the air.When different flow velocity was adopted with the same weight of the samples,and the desorption temperature was set up at 800℃,the adsorption behavior of two membranes was studied.The results showed that,with the increase of the flow velocity,the intensity of the first membrane decreased,but the intensity of the second membrane increased,which meant that lower flow velocity was a benefit for the adsorption of membranes.when the different amount of mercury contained in solution was added in high-purity silicon dioxide,after enriching and testing by the designed device,the working curve could be obtained with the linear correlation coefficient to be 0.9985.And the detection limit and quantification limit could be calculated as 7.52 and 25.06 ng respectively when multiple high-purity silicon samples were tested.It meant that if the weight of the sample was 0.3 g,the quantification limit would be 0.083 mg·kg^-1 in the soil.The relative deviations were no more than 11.1% for the national standard samples except one sample that was below the quantitative limit,which indicates that this method could realize the rapid detection of mercury in the soil for agricultural land.