水溶性有机碳对菲吸附系数测定的影响

Influence of Water Soluble Organic Carbon on Determination of Adsorption Coefficient of Phenanthrene

以菲为代表性化合物,利用摇瓶吸附实验研究土壤水分配体系中溶解态有机碳(DOC)对有机碳归一化吸附系数测定结果的影响.研究结果表明,在吸附系数测定过程中土壤溶出的DOC会导致水相中菲的浓度显著增加,很大程度上改变了菲在土水两相中的分配平衡,从而导致吸附系数的测定误差.根据文献报道的菲与DOC相互作用常数(Kdoc)以及实测体系中DOC浓度可以对实验数据进行校正,以获得更为可靠的结果,本文对线性吸附系数和Freundlich吸附系数分别进行了校正,得到有机碳归一化的吸附系数lgKoc为4 . 35 ,lgKFoc为7. 0 1 .校正前后的lgKoc与文献数据的对比从侧面反映出在水土体系的吸附研究中可能普遍包含因不同浓度DOC影响所造成的偏差,考虑这种影响对于准确比较不同研究得到的吸附参数具有重要意义.

Organic carbon normalized sorption coefficient of phenanthrene in soils was determined in a batch experiment. The influence of the presence of dissolved organic carbon (DOC) on sorption coefficient was also investigated. The results demonstrated that, the DOC dissolved from the soil would enhance the water solubility of phenanthrene and change the sorption behavior of phenanthrene between soil and water, consequently leading to an underestimation of sorption coefficient. When the binding coefficient of DOC and phenanthrene (K_ doc) from the literatures was adopted for correction of measured data, a better estimation of sorption coefficient could be achieved. In this study, lgK_ oc and lgK_ Foc were 4.35 and 7.01, respectively. Comparison between the uncorrected/corrected lgK_ oc and the literature data could partially reflect the deviation caused by the influence from various concentrations of DOC may occur in many sorption studies in water-soil system. It was significant to compare the sorption coefficient derived from different studies considering this influence.