Organic copper and chromium complexes in the interstitial waters of Narragansett Bay sediments

Dissolved organic copper and chromium complexes were measured in both overlying and interstitial waters of Narragansett Bay and mesocosm sediments using C 18 reverse-phase liquid chromatography and atomic absorption spectroscopy. In the interstitial and overlying waters, the isolation procedure recovered 22–67% of the total dissolved copper, 23–55% of the total dissolved chromium and 14–40% of the dissolved organic carbon. The distribution of both total and organic copper decreased with depth in the cores and exhibited a subsurface maximum near the zero Eh level ( z = 2–4 cm). Below that depth, both forms of copper continued to decrease until an apparent equilibrium with sulfide minerals was established (7–8 cm). Dissolved chromium exhibited a different geochemistry, with both total and organic chromium increasing in concentration with depth in the cores, possibly due to remobilization from some mineral phase such as chromic hydroxide or chromite.