邻苯二甲酸酯在河流沉积物上的不可逆吸附行为

Irreversible Sorption of Phthalate Acid Esters to River Sediments

采用平衡吸附实验和循环吸附/解吸实验,研究了邻苯二甲酸二甲酯(DMP)和邻苯二甲酸双-(2-乙基-己基)酯(DEHP)在长江和黄河沉积物样品中的吸附特性和不可逆吸附作用.平衡吸附实验结果表明,DMP和DEHP在沉积物上的lgKoc均高于文献报道值,说明沉积物对PAEs的吸附不仅包括在有机质上的分配作用,而且还存在其他吸附过程.循环吸附/解吸实验结果表明,沉积物对DMP和DEHP的吸附包括可逆的线性吸附和不可逆的非线性吸附.DMP和DEHP在4种沉积物样品上的最大不可逆吸附量分别为125.19～337.37μg/g和515.89～591.41μg/g,且最大不可逆吸附量与沉积物的比表面积,阳离子交换量,黑炭含量等呈正相关.DMP可逆吸附部分的有机碳标化分配系数(lgkroecv)为3.69～4.98L/kg,该值仍大于文献报道的Koc值,说明除在有机碳上的分配作用外,DMP还存在其他的可逆吸附机制.DEHP的lgkorecv为4.12～5.31L/kg,与文献报道值接近,说明DEHP的主要可逆吸附机制为在有机碳上的分配作用.尽管DMP和DEHP的性质差异较大,但二者在4种沉积物上不可逆吸附部分的有机碳标化分配系数(lgkiorcr)接近常数(6.46±0.38)L/kg.由于PAEs在沉积物上存在不可逆吸附,在建立沉积物质量基准时需要考虑其最大不可逆吸附量.

Irreversible sorption behavior of two phthalate acid esters （ PAEs）,Dimethyl phthalate （ DMP） and Di-（2-ethyl-hexyl） phthalate （DEHP）,on four natural sediment samples from the Yangtze River and the Yellow River has been studied by equilibrium sorption and multiple cycles of adsorption /desorption experiments. The equilibrium sorption experiment results showed that the organic carbon-normalized partition coefficients （lgKoc） of DMP and DEHP were higher than those reported in references. This means that the sorption of DMP and DEHP on natural sediments include other sorption mechanisms besides the linear partition on organic carbon. The multiple cycles of adsorption /desorption experiment results showed that the sorption of PAEs included linear reversible sorption and irreversible sorption. For the four sediment samples,the maximum of irreversible sorption capacities were 125. 19-337. 37 μg /g and 515. 89-591. 41 μg /g for DMP and DEHP,respectively,which were positive correlated to the surface areas,cation exchange capacity and black carbon content of the sediments. The OC-normalized partition constants for the reversible compartment （ lgkorecv ） were 3. 69-4. 98 L /kg for DMP; they were higher than those （lgKoc） reported in references,suggesting other reversible sorption mechanisms exist besides the linear partition on organic carbon. The lgkorecv were 4. 12-5. 31 L /kg for DEHP; they were close to those （lgKoc） reported in references,suggesting the linear partition on organic carbon is the main reversible sorption mechanism. Although the physiochemical properties of DMP and DEHP are different,the OC-normalized partition constant for the irreversible compartment on the four sediments is essentially constant with lgkiorcr = （6. 46 ± 0. 38） L /kg. As irreversible sorption exists for PAEs,the maximum of irreversible sorption capacity should be considered when studying the sediment quality criteria.