原子荧光光谱法测定成都市公共绿地土壤层中的镉

采用Tessier连续提取法对成都市公共绿地土壤层22个土壤样品中的Cd赋存化学形态进行了提取分离，并用原子荧光光谱法进行了测试。在仪器最佳工作条件下，通过条件实验确定在2%的盐酸介质中，在 30 g·L-1硼氢化钾的还原作用下，1 mg·L-1钴离子和10 g·L-1硫脲联合作用可提高Cd挥发性化合物的发生效率。加入一定浓度的焦磷酸钠、硫酸钾和氯化钡能降低土壤中共存元素对测定Cd的影响。该方法线性范围0～10 μg·L-1,相关系数r=0.999 1，检出限0.016 μg·L-1,相对标准偏差1.93%，回收率为97.80%～100.2%。土壤样品中Cd的五种赋存形态平均百分含量大小分布为：残留态(62.1%)＞离子交换态(11.7%)＞铁锰氧化物结合态(9.71%)＞碳酸盐结合态(4.17%)＞有机结合态(3.47%)；尽管残留态是Cd的主要赋存形态，但土壤样品中Cd的离子交换态含量较高，具有强的生物活性，应引起重视；成都市一环路、二环路和三环路绿化带土壤层存在不同程度的Cd污染，污染程度大小为：二环路＞一环路＞三环路。

Determination of Cadmium by HG-AFS in Soil of Virescent Zone in Chengdu City

The different speciations of cadmium in soil samples from Chengdu greenbelt were extracted by Tessier sequential extraction method. The contents of total cadmium and different speciation cadmium were determined using HG-AFS. Under optimization condition of HG-AFS and using 2% HCl as medium, and 30 g·L-1 KBH₄ as reductive reagent, 1 mg·L-1 Co2+ acting together with 10 g·L-1 CH₄N₂S can advance the generating efficiency of cadmium compound. The effects of the coexisting elements in soil on the determination of cadmium can be reduced if certain amount of Na₄P₂O₇, K₂SO₄ and BaCl₂ are added. The linear range is 0-10 mg·L-1 with r=0.999 1 and the detection limit is 0.016 mg·L-1. The recovery is 97.80%-100.2% with RSD of 1.93%. The analytical method is very sensitive and accurate. The distribution of average percentage of five speciations of cadmium in experimental soil samples is: residual fraction (62.1%)＞exchangeable fraction (11.7%)＞Fe-Mn oxide-bound (9.71%)＞carbonate-bound (4.17%)＞organic-bound (3.47%). Although residual fraction is the main speciation of cadmium in soil, the content of exchangeable fraction is relatively high. Thus the bioactivity of cadmium in the research area should be recognized. The concentration of cadmium exceeds the country standard in 19 soil sample, accounting for 86.4% of all soil samples. The soil from Chengdu greenbelt located in 1st ring road, 2nd ring road and 3rd ring road was polluted to different degree. The relative pollution magnitude of them is: 2nd ring road＞1st ring road＞3rd ring road.