高硫高铁土壤全硫提取和测定方法的改进

Determination of total sulfur in high-sulfur and high-iron soil samples by spectroscopic barium turbidity method

硫酸钡分光光度比浊法是大批量测定土壤环境样品硫含量的常用方法，但影响测定结果的因素较多，如稳定剂的选择、酸度的控制、BaCl：的形态和用量等均可对测定结果产生影响。在多金属硫化物矿区，由于长期的采矿冶炼活动，造成周边土壤中硫、铁含量增加，用比浊法测定硫含量时，铁的含量也对测定结果产生显著影响。针对这些影响因素，本研究在用硝酸．高氯酸湿法对土壤进行消解后，优化了硫酸钡分光光度比浊法测定高硫高铁样品的实验条件和实验步骤，并对多金属硫化物矿区的土壤样品进行了测定，得到了较好的结果。实验证明，称取0．50g土壤样品，消解后过滤，取滤液7mL，加入1mL研（1＋2）甘油．乙醇]=6％的甘油．乙醇为稳定剂，1mL浓磷酸掩蔽Fe3＋与cl-反应所显的黄色，定容到10mL，加入w（BaCl2）=10％的氯化钡溶液10mL，电磁搅拌1min，静置20-40min，在波长440nm处，比浊法测定土壤全硫含量，相对误差〈10％，取得良好的测定结果。此方法简单、快捷、方便，适合大批量环境样品的测定。

Spectroscopic barium turbidimetry （SBT） is commonly used in determining the content of sulfur in the soil samples, which was influenced by the stabilizers, acidity, and the forms of adding BaC12, etc. The long-term mining and metallurgical activities have resulted in the generation of huge amounts of mine wastes including acid-generating sulfuric tailings and acid mine drainage （AMD）. They lead to the increase of the concentration of sulfur and iron in the surrounding environment. And the higher concentration of Fe3＋ will disturb the determination of sulfur for the formation of color. The aim of this study was to improve conditions and procedures of operation for sulfur determination with SBT method, so that this method could be used in the high-sulfur and high-iron soil samples. At first, 0.50 g of soil samples were digested using HNOa-HC104 and made up to 25 mL. 7 mL of the digestion solution was added 1 mL of （1＋2） glycerol-ethanol solution （q7=6%） as stabilizer and 1 mL concentrated phosphoric acid as masking agent which masked yellow colour caused by Fe3＋ and CI reaction. The mixture was made up to 10 mL and then transferred into a 50 mL beaker. After adding 10 mL of BaC12 solution （w=10%） and electromagnetic stirring for 1 min, total sulfur in the soil was determined between 20 minutes and 40 minutes at 440 nm wavelength. The result showed that the relative error was less than 10%, which suggested that the modified turbidimetry could be applied to determine the sulfur content in high-sulfur and high-iron soil samples.