Eriksson J, Skyllberg U
Dep. of Forest Ecology, Swedish Univ, of Agriculture, Umeå.
J Environ Qual. 2001 Nov-Dec;30(6):2053-61. doi: 10.2134/jeq2001.2053.
The widely used explosive 2,4,6-trinitrotoluene (TNT) and its degradation products are of large environmental concern because of their toxic properties and high concentrations encountered in contaminated soils. Batch experiments were used to study TNT* (the sum of TNT and its degradation products) bonding to dissolved (DOM) and particulate (POM) soil organic matter. Reversed-phase high performance liquid chromatography (RP-HPLC) was used as a separation technique in combination with 14C-labeled TNT to determine free TNT and TNT* bound to DOM. By use of dialysis we showed that DOM did not interfere with the HPLC analysis of free TNT. Depending on pH and total TNT concentration, the relative distribution of TNT* among water, POM, and DOM varied between 60 to 90, 10 to 30, and 0.5 to 6%, respectively, after 22 h of equilibration. The association of TNT* to DOM was strongly pH dependent and followed a nonlinear Langmuir isotherm. The association of TNT* to POM was less pH dependent and data were equally well fitted by linear and nonlinear isotherms. Particulate organic matter had 6.4 (pH 6.2) to 22 (pH 5.2) times greater capacity to bind TNT* than DOM, but the binding strength (the slope of the isotherm) was greater for DOM. The TNT degradation was enhanced with increasing concentration of soil organic matter, resulting in a stronger bonding of TNT* to DOM and POM. Based on our results, combined with other recent findings, we suggest that it is mainly the degradation products of TNT that associate with DOM and POM, and that the association with DOM is mainly of ionic character involving specific DOM sites. The greater binding capacity and a weaker, linear type of isotherm suggests a nonspecific type of partitioning in POM, possibly of hydrophobic character.
广泛使用的炸药2,4,6-三硝基甲苯（TNT）及其降解产物因其毒性以及在受污染土壤中出现的高浓度而备受环境关注。采用批次实验研究TNT*（TNT及其降解产物的总和）与溶解态（DOM）和颗粒态（POM）土壤有机质的结合情况。反相高效液相色谱法（RP-HPLC）作为一种分离技术，与14C标记的TNT相结合，用于测定游离TNT以及与DOM结合的TNT*。通过透析，我们表明DOM不会干扰游离TNT的HPLC分析。在平衡22小时后，根据pH值和总TNT浓度的不同，TNT在水、POM和DOM之间的相对分布分别在60%至90%、10%至30%和0.5%至6%之间变化。TNT与DOM的结合强烈依赖于pH值，并遵循非线性朗缪尔等温线。TNT与POM的结合对pH值的依赖性较小，线性和非线性等温线对数据的拟合效果相当。颗粒有机质结合TNT的能力比DOM大6.4倍（pH 6.2时）至22倍（pH 5.2时），但DOM的结合强度（等温线的斜率）更大。随着土壤有机质浓度的增加，TNT的降解增强，导致TNT*与DOM和POM的结合更强。基于我们的研究结果，并结合其他近期的发现，我们认为主要是TNT的降解产物与DOM和POM结合，并且与DOM的结合主要是离子性质，涉及特定的DOM位点。更大的结合能力和较弱的线性等温线类型表明在POM中存在非特异性的分配类型，可能具有疏水性。
