Sources and transport of surface sediment and metals in B.C. fjord, Tahsis and Zeballos Inlets
Purdy, Shon; and Sachs, Julian
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[author abstract] Metal contaminants in marine sediments can pose a threat to marine biota and can bio-accumulate in the higher trophic levels of fjord communities (Bryan 1992, Buggy 2008). Mining activity on land can be a source of metal-contaminated dissolved and suspended sediments to estuaries and fjords where they can accumulate on the seafloor. Nootka Sound, western Vancouver Island, British Columbia, Canada, is an area of known metal mining activity adjacent to marine estuarine systems. In this two-year study in December 2014 and 2015, 40 surface marine sediment samples were collected in the coastal fjord region of Nootka Sound, including Tahsis and Zeballos Inlets. Each sample was analyzed for grain size, loss on ignition (LOI), and concentrations of 22 different metals. Principal Components Analysis (PCA) revealed distinct patterns of co-variation between metals. Two major groupings of variables were created by the first two principal component axes, and they were deemed Type I (D50, OC%, Ca, B, Si, S, Na, and K) and Type II (Cu, Cr, Ni, Pb, Mo, Mg, Cd, Se, Al, and Fe) variables. The Type I variables were concluded to be marine derived elements, while Type II showed an anthropogenic and terrigenous influence. Higher heavy metal concentrations were observed in marine sediments close to river mouths in Zeballos and Tahsis Inlets. These enrichments are attributed to local mining activities, physical transport via currents and landslide deposition.