土壤溶液和水体中水溶性有机碳的比色测定

利用紫红色络合物Mn(Na₂HP₂O₇)3在浓H₂SO₄存在时可氧化有机质使络合物颜色变浅的基本原理,系统研究了不同种类、不同浓度的有机碳化合物(脂肪族与芳香族)、比色测定的条件(温度、显色时间和比色波长)与一些干扰离子对水溶性有机碳比色测定的影响.结果表明,所用的有机碳化合物的浓度与比色测定的吸光值之间有很好的相关性,比色波长为490～500nm.当溶液中Cl-浓度>80mg/L或Fe₂+>15mg/L,会使比色测定结果显著增大,测定前需要排除它们的干扰;在所建议的最佳比色条件下,天然水体中水溶性有机碳比色法测定结果相当于TOC仪测定结果的81%.当显色液中有机碳浓度为0～5mg/L时,土壤溶液水溶性有机碳比色法测定结果相当于TOC仪测定结果的76%.研究表明,采用该方法测定土壤溶液和水体环境中水溶性有机碳含量是可行的,最突出的优点是无需价格昂贵的TOC仪,而且测定速度要比仪器快得多.

Colorimetric determination of dissolved organic carbon in soil solution and water environment

Using the basic principle of the color fading of Mn(Na2HP2O7)3, due to oxidizing by oxidizable organic matter at concentrated H2SO4 the effects of different concentrations of organic carbon compounds (aliphatics and aromatics), colorimetric conditions (temperature, color developing time and colorimetric wave length) and some intervening ions on the colorimetric determination of dissolved organic carbon were systematically studied. The results show that there is quite linear correlation between the concentrations of the tested organic compounds and light absorption value of the determination with the wave length of 490~500nm. When the concentrations of Cl- and Fe2+ in solution are more than 80mg/L and 15mg/L respectively, there are significant increments of the determination results; so it is necessary to remove their interference. In the proposed optimal colorimetric conditions, the results of DOC colorimetric determination in natural water are equal to 81% of the results of TOC analyzer determination. When DOC concentration in colorimetric solution is 0~5mg/L, the results of colorimetric determination of DOC in soil solution are equal to 76% of the results of TOC analyzer determination. The studies show the feasibility of using this technique to determine the DOC content in soil solution and water environment, with outstanding merits of no necessity of the high price TOC analyzer and of much quicker determination than the analyzer.