酸性土壤有效汞提取方法研究

Extraction Method for Available Mercury in Acid Soils

为了更好地评价酸性土壤中汞的生物有效性和生态风险,以酸性土壤为供试土壤,通过比较国内外几种常用的土壤有效汞的浸提剂的提取效果,筛选适合于酸性土壤的有效汞浸提剂并优化相应的提取条件,从而建立酸性土壤有效汞的提取方法。结果表明,在0.1 mol·L-1HCl、1 mol·L-1NH4OAc、0.005 mol·L-1DTPA、0.03%TGA-1/15 mol·L-1Na2HPO4这4种常用浸提剂中,0.03%TGA-1/15 mol·L-1Na2HPO4是最佳的浸提剂,因为它具有最高的提取率,且其所提取的有效汞与相应稻米中Hg含量的相关性最好。0.03%TGA-1/15 mol·L-1Na2HPO4的最佳浸提条件为土液比1∶10、振荡时间120 min、振荡速度250 r.min-1,浸提出的有效汞量与油菜的相关性达到极显著相关,能较好地指示田间条件下土壤汞对作物的可给性。

The available fractions of heavy metals in soils are considered to be better than their total amounts in indicating their bioavailabili- ty and ecological risks. Chemical extraction is widely used for extracting the available fractions of heavy metals in soils. However, there are always several cxtractants for one metal so that the determination results are incomparable. It is necessary to specify a suitable method for extracting the available metal for one given group of soils for evaluating better their bioavailability and ecological risks. Based on this considera- tion, the extraction results of 4 extractants commonly used for extracting soil available Hg, 0.1 mol· L-1 HC1, 1 mol. L-1 NH4OAc, 0.005 mol· L-1 DTPA, and 0.03%TGA-1/15 mo· L-1 Na2HPO4, were compared in order to choose a best extractant for extraction available Hg of acid soils. The extraction conditions of the chosen extractant were also optimized. The results showed that 0.03%TGA-1/15 mol· L-1 Na2HPO＋ was the best extractant because it had the highest Hg extraction efficiency, and the amount of the extracted Hg showed the best correlation with the Hg concentration in brown rice harvested from the soils among the 4 extractants. The optimized extraction conditions for 0.03%TGA-1/15 mol-L-1Na2HPO4 extraction were as follows：ratio of soil to liquid=1：1 O, shaking time= 120 rain, and shaking speed=250 r· min-t. The method was examined by determining the amounts of the available Hg in some field soils and the Hg in the corresponding pakehoi samples. The available Hg of the soils extracted by 0.03%TGA-1/15 mol· L-1 Na2HPO4 significantly correlated with the Hg concentrations in the pakchoi samples（r=-0.7432＊＊, n=15 ）, showing that this extractant can indicate well the bioavailability of Hg in acid soils.