两种海源可溶性有机物对汞在沉积物中吸附特性的影响

Influence of two dissolved organic matters from marine products on mercury sorption in sediment samples

选取两种常见的近海滩涂养殖海产品菲律宾蛤仔和海带,分别制备了两种海源性生物的可溶性有机物(DOMc和DOMk),研究了海源性DOM影响下汞在胶州湾两种沉积物样品中的吸附解吸特征.结果表明,Elovich方程能够很好拟合不同DOM处理下汞在沉积物中的动力学过程,其次为双常数方程.添加两种海源性DOM均显著提高了汞在沉积物样品中的吸附速率,其中DOMc促进作用最为显著.Langmuir和Freundlich方程均能很好描述汞的等温吸附过程;与对照处理相比,DOMc使两个沉积物样品对汞的最大吸附量分别增加了70.1%和80.9%,DOMk则分别提高了12.4%和10.2%;海源性DOM抑制了沉积物中汞的释放,其中DOMc的抑制作用最强.添加DOM没有改变汞的吸附量随p H的变化趋势,但在相同p H条件下,DOM仍然明显促进了汞在沉积物中的吸附.研究结果显示,近海水产养殖产生的DOM可通过增加沉积物对汞的吸附而降低其生物有效性,而这却在一定程度上抑制了海湾水体中汞的对外交换,从而增加水体汞污染的风险.

To investigate the influence of dissolved organic matters （DOM） originating from marine products on adsorption and desorption of mercury （Hg） in sediments, two types of DOM, ie. DOMc and DOMk were obtained by incubating Ruditapes philippinarum and Thallus Laminariae, respectively, which were common marine products in Jiaozhou Bay. Elovich equation fitted well the adsorption kinetic process of Hg in sediments under various DOM treatments, followed by two-constant equation. The adsorption rates of Hg in sediments were enhanced significantly by adding two DOM, especially DOMc. Langmuir and Freundlich equation can well describe the isothermal adsorption of Hg. The maximum adsorption capacity in two samples was elevated by 70.1% and 80.9% in DOMc treatment, and 12.4% and 10.2% in DOMk treatment, respectively. DOM inhibited effectively the desorption of Hg adsorbed in sediments. Although the dependence of Hg adsorption on pH was not affected by adding DOM, the adsorption was elevated significantly in the presence of DOM at the same pH. The present results implicate that the DOM from offshore aquatic farm may reduce the bioavailability of Hg by increasing its adsorption in sediment, which to some extent restrains mercury exchange in bay water and increases the risk of mercury pollution of water body.