The Diffusive Gradients In Thin Films Technique (DGT) For Researching The Determination Of The Active States Of Heavy Metals In Soils

Because of the severe pollution of heavy metal elements in soil and the lack of accurate and rapid method to evaluate the pollution degree of soil heavy metal elements in China.In this paper,a new DGT technology,the adsorption process and application were put as the background.The DGT was applied to measure the bioavailability of heavy metals in soils and the results showed:(1)The correlation between the effective content of Copper,cadmium,lead by DGT and the soil physical and chemical properties R2 is 0.25?0.35?0.24;the correlation between the effective content of Copper,cadmium,lead by chemical method and the soil physical and chemical properties R2 is 0.47?0.64?0.61.The R2 by DGT is lower than the R2 by chemical method,indicating that DGT is more suitable for the determination of the bioavailability of heavy metals in soil.(2)The correlation between DGT and heavy metal content in rice was higher than that in soil(R2 = 0.77,0.83,0.85,R2 = 0.67,0.65 and unrelated).The DTPA-LDH-DGT was more effective than the previous methods to determine the bioavailability of heavy metal elements in soils,and the results were more accurate.(3)The diffusion coefficients of copper,cadmium and lead by DTPA-LDH-DGT were 6.23×10-6cm2s-1,6.09×10-6cm2s-1 and 8.03×10-6cm2s-1,and the adsorption capacity of the elements can reach 90%of the total within 3 hours,and the elution efficiency is more than 95%,higher than the traditional Chelex-DGT elution efficiency of 80%,in the elution of the more advantages.(4)The adsorption capacity of Chelex-DGT to lead was higher than that of cadmium and cadmium was higher than copper.The adsorption capacity of DTPA-LDH-DGT to lead was higher than that of copper,and copper was higher than cadmium.Both of the two kinds of 'DGT were preferential adsorption of lead,but the adsorption sequence of copper and cadmium is different.The adsorption performance of DTPA-LDH-DGT to cadmium and lead was similar to that of Chelex 100,but the adsorption capacity of copper was 3 times higher than that of Chelex-DGT.(5)The effect of pH on the competitive adsorption of copper,cadmium and lead ions increased with the increase of pH,and tend to be stable at pH=7 and more.The effect of organic matter on the adsorption of copper,cadmium and lead ions was that the adsorption amount of organic heavy metals was lower than that of ionic heavy metals,and the adsorption order did not change.Both DGTs had the highest adsorption capacity for copper,Cadmium adsorption followed.