Historical changes in trace metals and hydrocarbons in nearshore sediments, Alaskan Beaufort Sea, prior and subsequent to petroleum-related industrial development: part II. Hydrocarbons.

Composition and concentration of hydrocarbons (normal and isoprenoid alkanes, triterpenoids, steranes, and PAHs) in nearshore surface sediments from Elson Lagoon (EL), Colville Delta-Prudhoe Bay (CDPB) and Beaufort Lagoon (BL), Alaskan Beaufort Sea, were assessed for spatio-temporal variability. Principal component analysis of the molecules/biomarkers concentrations delineated CDPB and BL samples into two groups, and cluster analysis identified three station groups in CDPB. Overall there was no geographic distribution pattern in the groups. The diversities between groups and individual samples are attributed to differences in n-alkanes and PAHs contents, which are influenced predominantly by sediment granulometry and sitespecific fluvial input. The predominant hydrocarbon source is biogenic, mainly terrigenous, with hardly any contribution from natural oil seeps, oil drill effluents and/or refined crude. The terrigenous source is corroborated by δ(13)C, δ(15)N, and OC/N of sediment organic matter. Time interval (1976-1977, 1984 and 1997) changes in hydrocarbon compositions and concentrations in CDPB are not significant.

Historical changes in trace metals and hydrocarbons in nearshore sediments, Alaskan Beaufort Sea, prior and subsequent to petroleum-related industrial development: Part I. Trace metals.

Concentrations of Fe, As, Ba, Cd, Cu, Cr, Pb, Mn, Ni, Sn, V and Zn in mud (<63µm size), and total and methyl Hg in gross sediment are reported for Arctic Alaska nearshore. Multivariate-PCA analysis discriminated seven station clusters defined by differences in metal concentrations, attributed to regional variations in granulometry and, as in Elson Lagoon, to focused atmospheric fluxes of contaminants from Eurasia. In Colville Delta-Prudhoe Bay, V increase was noted in 1985 and 1997 compared to 1977, and Ba increase from 1985 to 1997. Presumably the source of increased V is the local gas flaring plant, and the elevated Ba is due to barite accumulation from oil drilling effluents. In Prudhoe Bay, concentration spikes of metals in ∼1988 presumably reflect enhanced metals deposition following maximum oil drilling in 1980s. In summary, the Alaskan Arctic nearshore has remained generally free of metal contamination despite petroleum-related activities in past 40 years.

Comparison of mercury and methylmercury in northern pike and Arctic grayling from western Alaska rivers.

In western Alaska, mercury (Hg) could be a potential health risk to people whose diet is primarily fish-based. In 2000, total Hg (THg) and methylmercury (MeHg) were examined in northern pike (Esox lucius) and Arctic grayling (Thymallus arcticus) from two watersheds in western Alaska, the Yukon and Kuskokwim rivers. Whitefish (Coregonus sp.) were also examined from the Kuskokwim River. Pike from the Yukon and Kuskokwim rivers had mean concentrations of THg in muscle of 1.506 and 0.628 mg/kg wet wt, respectively. The mean concentrations of THg in grayling muscle from these rivers were 0.264 and 0.078 mg/kg, respectfully. Whitefish had a mean THg concentration in muscle of 0.032 mg/kg. MeHg, in pike and grayling constituted nearly 100% of the THg concentrations; the proportion was less in whitefish. A significant positive correlation between Hg levels and fish length was also found. Generally, there were no changes in Hg concentrations in pike or grayling over the last several years. Only pike from theYukon River had THg concentrations that exceeded the USFDA action level for human consumption of edible fish (1 mg/kg). Human hazard index for pike was > or = 1 for both adults and children, indicating a potential for toxic concern, especially among children. Further studies are needed to determine the environmental and human health impacts associated with these Hg concentrations in western Alaska, especially in the context of potentially increased consumption of resident fishes when anadromous salmon catches are reduced.