Effect of Dissolved Matter on Fe (II) Transport in Groundwater

摘要

As the focus of ground water remediation efforts shifts increasingly towards natural attenuation as an alternative method for documenting and quantifying such intrinsic remediation. One indicator of natural attenuation under iron-reducing conditions is concentration of dissolved Fe(II). However, if Fe(II) is to be used to quantify the degradation of groundwater contaminants the process controlling Fe(II) transport in the subsurface must be better understood. Dissolved metals, such as Fe (II) can interact with dissolved organic matter (DOM) to produce both mobile and immobile complexes. These complexes may display sorptive characteristics different than those of the dissolved metal alone, thus potentially facilitating or retarding transport of the metal. Microcosm sorption studies were conducted to determine the effects of DOM on Fe (II) sorption to aquifer solids from 3 U.S. Air Force Bases as a functional of ionic strength (I). DOM at a concentration of 32 mg TOC/L resulted in a marked increase in the sorption of Fe(II) to each of the aquifer solids at I=0.01 M, as judged by Freundlich non-linear isotherm fits of the data. Sorption of Fe(II) in the presence of DOM at I=0.01 also increased over that of DOM-free systems but was less than that in the I=O.Ol 5 stems, indicating an inverse relationship between Fe(II) sorption and ionic strength.