Influence of Hydrophilic Organic Matter on Copper and Mercury Speciation and Bioavailability in Urbanized River

摘要

n aquatic systems, dissolved organic matter (DOM) constitutes a key component of the carbon cycle controlling the speciation, bioavailability and toxicity of trace metals [1,2]. Over the past few decades, many studies have been published regarding the capacity of DOM to complex copper. It is interesting to note however that the published data pertain mainly to the so called ‘‘humic substances” (HS) and demonstrate the ability of these substances to complex metals. HS are derived from oxidative and hydrolytic biodegradation of plants and animals [3] and they make up 40–60% of DOC in natural surface water [4]. In urbanized aquatic system, the hydrophobic characteristic of DOM is weaker as a result of various urban DOM discharges and the strong primary productivity induced by these discharges [5,6]. Because of the difficulty in isolating the hydrophilic fraction of DOM, very little information is available in the literature regarding hydrophilic DOM and their influence on metal complexation. The primary objective of this study is to exhaustively extract DOM from water samples then to fractionate it according to polarity criteria [7] and to further characterize the obtained fractions by means of various physico-chemical analyses. The second objective is to study binding affinity of each isolated fraction with copper and mercury. The third goal is to study the influence of every isolated fraction on copper bioavailability and toxicity.