天津农田土壤镉和汞污染及有效态提取剂筛选

采集天津3条排污河污灌区重金属污染农田的22个土壤及油麦菜样品,测定镉（Cd）和汞（Hg）的浓度,筛选两种重金属生物有效性的最佳提取剂,并分析了混合提取剂（M3）及DTPA对两种重金属生物有效性的预测能力。结果表明,22个土壤采样点中有9个样点Cd超标,7个样点Hg超标,60%以上的油麦菜受到Cd的污染,但大部分处于轻污染级别,且M3、DTPA都能够很好地表征油麦菜中Cd的生物有效性,相关系数分别为：RM3=0.92（P〈0.0001）,RDTPA=0.88（P〈0.0001）,其中M3预测能力强,提取用时短,可推广应用;100%的油麦菜都受到Hg污染,且都处于重污染级别,油麦菜中Hg与M3、DTPA提取结果具有显著负相关,相关系数分别为：RM3=-0.82（P〈0.0001）,RDTPA=-0.47（P〈0.05）,这可能是因为可提取态Hg的增加对植物吸收产生负面影响。

Comtamination of Cadmium and Mercury in Farmland of Tianjin and Extration Methods for Predicting Their Bioavailability

Irrigation of sewage water has been applied for agriculture production in Tianjin for over 50 years,since Tianjin is a city lacking water resource seriously.Heavy metals in soils could not be degraded,but accumulated,causing hazards to human beings though food-chain.Twenty-two sites of samples（including pairing soil and lettuce） were collected from seriously polluted areas along the three sewage rivers in Tianjin,and the contents of cadmium（Cd） and mercury（Hg） were measured.Moreover,different extraction methods were studied to check their applicability for predicting bioavailability of the two metals.Nine of the 22 soils exceeded the National Soil Quality Standard Ⅱ for Cd（0.6 mg·kg-1） and 7 exceeded the standard for Hg（1.0 mg·kg-1）.Over 60% percent of Cd concentration in lettuce exceeded the National Food Quality and Safety Standard for Cd（0.2 mg·kg-1）,while the Hg concentrations of all the samples exceeded the standard for Hg（0.01 mg·kg-1）.Hence,the heavy metal pollution has threatened the safty of vegetable.The metal contents in lettuce did not correlate with those in soils,wich were influenced by soil physico-chemical properties.Of five extraction solvents tested（HCl,CaCl2,NH4AC,diethylene-triaminepentaacetic acid（DTPA） and M3）,M3 and DTPA showed good capacity for predicting the bioavailability of Cd,with the correlative coefficients（R） being 0.92 and 0.88 respectively.M3 showed better correlation,moreover,it cost shorter time for extraction.Hence,M3 was a promising method for Cd bioavailability prediction.However,both M3 and DTPA failed for the prediction of Hg bioavailability,showing a negative correlation for Hg（R=-0.82 and-0.47,respectively）.This might be because Hg has caused adverse effects on lettuce,hindering the transfer of Hg from root to the edible part of lettuce.