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STUDY TITLE: Evaluating Chukchi Sea trace metals and hydrocarbons in the 

Yukon River Delta, Alaska

REPORT TITLE: Evaluating Chukchi Sea trace metals and hydrocarbons in the Yukon 

River delta, Alaska 

CONTRACT NUMBER: M12AC00001

SPONSORING OCS REGION: Alaska 

APPLICABLE PLANNING AREA(S): Chukchi Sea 

FISCAL YEAR(S) OF PROJECT FUNDING:2012-2015

COMPLETION DATE OF REPORT: 12/20/16 

COSTS: $232,760 

PROJECT MANAGER(S): Paul McCarthy 

AFFILIATION: University of Alaska Fairbanks 

ADDRESS: Department of Geology and Geophysics, PO Box 755780, Fairbanks, AK, 99775 

PRINCIPAL INVESTIGATOR(S): Paul McCarthy, John Perreault 

KEY WORDS: Chukchi Sea, Yukon River, Polycyclic Aromatic Hydrocarbons, Trace Metal, 

sediment 

BACKGROUND: Yukon River sediments may comprise the majority of the deposits currently 

present in the Chukchi Sea. Currently, one-third of the Yukon River’s sediment load may be 

carried to the Chukchi Sea, but sediment transport was greater in the past, with as much as 

81% of Yukon sediments possibly reaching the Chukchi Sea during the Holocene. This 

suggests that the majority of sediment currently present in the Chukchi Sea is likely derived 

from the Yukon River. Evaluating the trace metal and hydrocarbon concentrations of the Yukon 

River system and temporal trends in fluxes of these constituents to the Chukchi Sea will 

contribute additional baseline data in the Chukchi Sea. This work focuses on evaluating the 

trace metal concentrations and polycyclic aromatic hydrocarbons (PAHs) of the Yukon basin, 

the largest contributor to the overall sediment budget of the eastern Chukchi Sea. 

OBJECTIVES: To develop an inventory of trace metals and PAHs to the Chukchi Sea, derived 

from the Yukon Basin and to explore whether sediment cores taken from high-sedimentationrate Yukon delta deposits provide a complete historic (~150 years) record of metal and 

hydrocarbon delivery to the Chukchi Sea. 

DESCRIPTION: Active river channel bedload and suspended-load sediments were collected for 

trace metal and PAH analyses from the Yukon River at five points (Figure 1). Bedload samples 

were collected from riverbanks or midstream sandbars. Suspended load samples were collected 

from water pumped at 1m below the river surface. Sites were selected in the active delta lobe of 

the river and are permafrost-free. Cores were taken from the active channel and from 

abandoned channels upstream. Radiocarbon dating and Lead-210 (Pb210), Lead-214 (Pb214), 

and Cesium-137 (Cs137) radioisotopes were determined at Woods Hole Oceanographic Institute, 

where the cores are archived. Suspended load and water samples were collected in the 

summers of 2012 and 2013, and in early spring of 2013 before break-up. PAH samples were 

analyzed at the Water and Environmental Research Center at UAF using a gas chromatograph 

mass spectrometer. Trace metal analysis was done at the Advanced Instrumentation Laboratory 

at UAF with an Induction Coupled Plasma Mass Spectrometer.

STUDY RESULTS: This report provides a snapshot of the active water and bed load and allows 

for future construction of a historical data set, through cored material, for both a suite of trace 

metals and polycyclic aromatic hydrocarbons. Seventeen PAH targets were sought in bed load 

sediments, water samples with suspended and dissolved material, and cores up to three meters 

in depth. No PAHs were detected at a concentration above 4ppb. The USGS, in 2002-2003, 
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sampled as far down river as Pilot Station, which is the furthest upriver sampling station in this 

study. This study complements the USGS data to complete a full survey of the Yukon River 

trace metal content from Eagle, AK to the opening of the delta at the river mouth. This project 

provided the first published trace metal values for the part of the Yukon River sampled. 

SIGNIFICANT CONCLUSIONS: The data presented shows the current state of the lower, nontidally influenced stretch of the Yukon River. Data from this project provide a baseline for 

comparison for future studies. These data may be of particular use as climate conditions in the 

Yukon River basin evolve, potentially altering the contributions of trace metals and 

hydrocarbons from the many tributaries and drainage areas. 

STUDY PRODUCT(S): 

a. Quarterly and annual project reports since 2012.

b. Perreault, John M., McCarthy, P., Baseline values of Polycyclic Aromatic

Hydrocarbons and Trace Metals in the Yukon River sediments, Alaska. Abstract

accepted, American Geophysical Union, 2015 Fall Meeting.

c. Perreault, John M., and P. McCarthy. 2016. Evaluating Chukchi Sea trace metals and

hydrocarbons in the Yukon River delta, Alaska. Final Report, OCS study BOEM 2016-

078. Coastal Marine Institute, University of Alaska, Fairbanks, AK, 23 p.

Figure 1: Map of study area. Location of core samples (red dots) and suspended sediment 

and water samples (blue dots) along the Yukon River delta.