Copper is a toxic heavy metal regulated by the EPA and a common cause of water impairment across the US. One of the major contributors to copper in surface waters is wastewater. Copper complexation with dissolved organic matter (DOM) plays a key role in its toxicity in aquatic systems. Existing speciation models that serve as a basis for regulating copper assume DOM is dominated by humic substances. Meanwhile research suggests there are anthropogenic compounds in wastewater discharge that may be important copper binding ligands. However, their specific identities remain largely unknown.<br/>To address this knowledge gap, we developed a novel Liquid chromatography (LC) Inductively Coupled Plasma Mass Spectrometry (ICPMS) approach to separate and quantify distinct organic copper species across different stages of conventional wastewater treatment and compared them to those of a river water. Cu-DOM is first isolated using solid phase extraction (SPE), separated using a trace-metal free high-pressure LC and detected with an on-line quadrupole ICPMS. The results revealed differences in the copper species across treatment and in the river water. The LC-ICPMS chromatogram showed that ~92 % of the isolated Cu is bound to polydisperse organic matter that comprises an unresolved complex mixture while ~8 % exists as well-defined species that appear as resolved chromatographic peaks at distinct retention times. While the treatment process resulted in net removal of Cu, our results indicated that particular Cu-DOM species evaded removal, while some other species were generated by the treatment process. Ongoing work is focused on identifying these species by coupling the same chromatography with high resolution accurate mass Electrospray Ionization Mass Spectrometry (ESIMS) to detect the mass of the intact molecular ion and its isotopologues. Our findings demonstrate the utility of LCMS approaches for identifying and quantifying distinct organic-copper species that have different sources and behaviors in the environment.

Characterizing organic copper species in wastewater

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