| Soil mercury pollution poses a significant threat to ecosystem.It is important to assess the soil bioavailable mercury.The diffusive gradient in thinfilms(DGT)technique is popular because of its ease of operation,low disturbance,and ability to provide information about the flux of a specific substance over time.It has successfully simulated the process of plant absorption of other heavy metals in many cases,which provides a new idea for the determination of bioavailable mercury.Water spinach was cultured in aged soil with pH gradient(8.34±0.08,7.50±0.09,7.17±0.14)and total Hg content of 3.16～27.30 mg/kg.The concentration of total mercury accumulated by water spinach cultivated on the aging soil was 16.83-66.55 mg/kg.The bioconcentration factor(1.93～6.44)showed a decreasing trend with the increase of total Hg concentration and pH.Correlation analysis results showed that the mercury forms significantly related to the mercury extracted by DGT were:"exchangeable+bound to carbonate+bound to organic matter" extracted by modified Tessier,and "labile+bound to humic and fulvic complexes+elemental and bound to crystalline oxides" extracted by CIEMAT.The two form combinations with the highest correlation with the absorption of mercury by water spinach were"exchangeable+ bound to carbonate+ bound to organic matter" extracted by modified Tessier,and the same CIEMAT species group mentioned above.The extraction of mercury by DGT technique was highly consistent with that by water spinach.The linear fitting correlation coefficient between Hg extracted by the four methods and Hg absorbed by water cabbage was HgT1+2+4(0.826)>HgC1+2+3(0.815)>CDGT-Hg(0.773)>HgPK(0.678).The fitting correlation coefficient of HgT1+2+4 is the highest,and the fitting stability of HgC1+2+3 is the best with pH fluctuation.However,the operation of these two chemical methods is complicated and time-consuming..By contrast,the correlation of DGT method was higher than that of protease K method,and the stability was second only to CIEMAT method,and the operation was simple.In conclusion,DGT technique has a good application potential in predicting soil bioavailable mercury. |
