Effects of dissolved organic matters on chemical transportation mechanisms of polycyclic aromatic hydrocarbons in marine environment

Abstract

The behavior and fate of pollutants in the marine environment depends on a series of processes such as physical dispersion, chemical and biological degradation. For hydrophobic, bioaccumulative and toxic pollutants (e.g. polycyclic aromatic hydrocarbons and polychlorinated biphenyls), their sorption characteristic of distribution between the particulate and dissolved phases is more important than other chemical or biological processes. Traditionally, the partition model is adopted in describing this phenomenon. Recently, many researchers have found that the existence of dissolved organic matter (DOM) tends to reduce the partition coefficients and enhance pollutant mobility. As such, this study elaborates an overall mechanistic sorption model (OMS model) to include this so-called 'third phase effect' in depicting this specific transportation mechanism. A series of batch experiments in obtaining several partition coefficients, K/sub p/, K/sub p(DOM)/, and K/sub p(fr)/ in this model were executed for the estimation of the partition coefficient between DOM and pollutants, K/sub dom/, K/sub p/ and K/sub p(fr)/, denote the partition coefficients of pollutant between the dissolved and particulate phase with and without DOM. K/sub p(DOM)/ denotes the partition coefficient of DOM between the dissolved and particulate phase. Furthermore, the K/sub dom/ was obtained directly by using the fluorescence quenching method. Effects of pH and ionic strength were studied by both methods. Results obtained from both methods present the same trends: the K/sub dom/ values reduced with increased pH or with decreased ionic strength. Similar trends were found in variations of K/sub p(DOM)/ regarding pH and ionic strength of pollutants in the system. Close results front these two independent experimental/model methods in estimation of K/sub dom/ indicates the feasibility of the OMS model in describing this process, which will be included as the source term in the numerical programming simulating the distribution of pollutants in the marine environment. The other significant contribution of this research is that the OMS model can be applied to non-fluorescent compounds like PCBs, CBzs etc. which cannot be estimated by the fluorescence quenching method.