Sorption of nonionic organic chemicals to soil/sediment organic matter and black carbon.

摘要

The first portion of this dissertation describes the development of a new method for better estimating the equilibrium partitioning of nonionic organic compounds (NOCs) between water and the natural organic matter in soils and sediments based on polyparameter linear free energy relationships (pp-LFER).; The majority of this dissertation was devoted to developing precise and practical methods to measure NOC sorption from aqueous solution with selected soot black carbon (BC) reference materials, and to exploring the influence of various sorbent characteristics on the extent of organic contaminant sorption to BC over three orders of magnitude in concentration. Because of the popular use of diesel engines and numerous occurrences of forest and open-field fires, BC is ubiquitous in soils and sediments. BC materials have been identified as powerful sorbents for organic contaminants in the environment.; Carefully conducted sorption isotherm experiments and characterization of the studied BC reveal nonlinear sorption for all studied materials with sorption strongest at low contaminant concentrations. Behavior among materials is highly variable, however, and can depend on such characteristics as O/C ratio and amount of native organic phase. This organic phase comprises mainly polycyclic aromatic hydrocarbons (PAHs) and forms during the formation of black carbon. Comparison between pore size distribution-normalized and surface area-normalized uptakes for the studied sorbents and those for activated carbon was used to show the relative importance of surface adsorption to overall uptake. Experimental results showed that the presence of 20% extractable native organic phase in one type of diesel soot reduces adsorption at low contaminant concentrations but enhances absorption at high contaminant concentrations. For other types of soots that contain only 2% extractable organic phase, adsorption was shown to be the dominant sorption mechanism over all studied concentrations. In addition, sorption isotherms and high resolution nitrogen adsorption results were obtained for a natural char both before and after Sohxlet extraction for the removal of native organic phase. While phenanthrene sorption to the extracted char (extracted NCI) is higher than sorption to the original char (NCI), TCB sorption was the same for these two chars. (Abstract shortened by UMI.)