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DISSOLVED ORGANIC CARBON CHARACTERISTICS IN METAL-RICH WATERS AND THE IMPLICATIONS FOR COPPER AQUATIC TOXICITY
Impact/Purpose:
This research will test two main hypotheses. First, fractionation of DOC occurs when it is partially removed from stream water by adsorption to precipitated hydrous iron (HFO) and hydrous aluminum oxides (HAO). Secondly, the remaining DOC will have poorer metal binding properties than the fraction that sorbs to the HFO and HAO. An alternative hypothesis also will be examined, namely that variations in DOC characteristics will arise from differences in source (i.e., wetlands, streams, etc.), and this will be more significant than fractionation in defining DOC metal binding properties. The consequence of these processes is that the protective effects of DOC with respect to aquatic metal toxicity will be reduced.
Description:
This research will aim to quantify the effects of fractionation between DOC, HFO, HAO, free copper and the behavior of resultant free DOC in the water column on the toxicological effects of copper. Fractionation between DOC, free metals and iron (Fe) and aluminum (Al) hydroxides will be examined further in this research, particularly in AMD impacted aquatic systems that have variable Fe, Al and DOC chemistry. This variable chemistry likely will demonstrate differences in DOC fractionation with the free metal and HFO/HAO components. It is anticipated that the fraction of DOC remaining in the water will have lesser binding capacity than the fraction that has undergone adsorption or complexation with other ligands. The “depleted” DOC fraction will be characterized by specific UV absorbance and excitation-emission matrix (EEM) analyses. Moreover, the resultant DOC-Copper (Cu) species is especially important for aquatic toxicology applications. A better understanding of the DOC fractionation characteristics as related to bioavailability of free metal ions will provide significant acute and chronic LC50 data to more accurately represent metal-laden AMD impacted waters.
Potential to Further Environmental/Human Health
Protection
Results from this project potentially will have significant regulatory
impacts that will provide a continuum to improving water quality for
human health and aquatic ecosystems. This project likely may provide
some better insight to the effectiveness of DOC-rich effluent from
treatment systems in mitigating the toxicological effects of heavy metals.
As a result, this technology may aid efforts to improve the health
of numerous fisheries impacted by AMD originating from abandoned
mines and thus potentially lead to improved recreational opportunities
and tourism. Regulatory decisions based on utilizing the Biotic Ligand
Model for water quality certification standards likely will be enhanced
by this research.