Comparative Study Of 3 Instruments And 15 Digestion Systems For Soil Mercury Analysis

Mercury(Hg),as a highly toxic substance,has been concerned and has been listed as a priority pollutant for soil control.The analysis of total mercury in soil has become an important subject in the field of environmental monitoring.There are many analytical methods for the monitoring of total mercury in soil,and each method has different characteristics.Based on the previous research on analysis methods of soil mercury,this paper studied combined analysis methods of soil mercury of three kinds of instruments(including cold atomic absorption method,CVAAS:atomic fluorescence method,AFS;catalytic pyrolysis-cold atomic absorption method,CP-CVAAS)and 15 kinds of pre-treatment digestion system(traditional pretreatment methods including water bath extraction,acid soluble electric hot plate digestion,microwave digestion of different acid system,etc.,and labeled from A to O,respectively).Hg contents in 4 typical soil standard samples and 4 real soil samples were determined for testing the accuracy and precision of those combinations.The main results are given as follows:(1)CVAAS is used to analyze soil mercury,it is difficult to obtain satisfactory accuracy and precision by using the 15 pretreatment digestion systems commonly used at present.The relative error of all test results exceeds 20%,and the relative standard deviation is only within 20%for a few data.Therefore,CVAAS is not suitable for the analysis of mercury in soil samples with the current 15 pretreatment digestion systems.(2)AFS is used to analyze soil mercury,in the current consideration of 15 kinds of pre-treatment digestion system,only aqua regia water bath digestion system(system D)shows better accuracy and precision.The relative error of the determination results are within 20%(12.5%?5.1%),respectively,and the scope of relative standard deviation is 3.8%?21.5%.However,the relative standard deviation of two samples with low Hg concentration is greater than 20%(21.4%and 21.5%respectively).Thus,AFS with aqua regia bath pre-treatment digestion(system D)is more appropriate.(3)Using CP-CVAAS to determine the mercury content of 4 representative soil standard samples and 4 typical soil actual samples,the relative error range of the test results was-4.1%?6.3%,and the relative standard deviation range was 1.8%?5.7%,showing good precision and accuracy.This method has the advantages of simple operation,small environmental pollution,and high efficiency,and does not need the pre-treatment digestion process.It is the preferred method for the determination of mercury in soil.(4)The results showed that the relative error range of the results obtained by using CP-CVAAS in the determination of mercury:in soil,including standard soil samples and actual soil samples,was small,and the precision of repeated tests was also very high,and satisfactory analysis results could be obtained.This technique requires no pretreatment,causes little pollution and causes little error,so it is recommended as the best method to determine mercury in soil.