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Award: OCE-1434706
Award Title: Collaborative Research: GEOTRACES Arctic Section: Determination of atmospheric wet and dry deposition and air-sea exchange of mercury species from coastal to offshore waters
This project was a collaboration among the Universities of Connecticut, Nevada and Tennessee. As part of the GEOTRACES Arctic 2015 cruise on the Coast Guard Icebreaker Healy, we installed and operated a variety of mercury (Hg) sensors to determine the mercury contamination, and bio-chemical cycling, in the air, ice and water. This US Arctic Geotraces cruise took place between August and October 2015. Steve Brooks (PI – University of Tennessee) was on-board for the entire cruise and conducted all measurements. Also, samples were collected by Steve Brooks, or others on our behalf, from surface waters, ice cores, melt ponds and snow. Atmospheric samples of aerosols (Brooks and Landing) and precipitation (Landing) were also collected. The primary measurements made by our group on the cruise included baseline measurements of Hg species in the air, and gaseous elemental Hg (Hg0) in the open water from the ship, and under sea-ice environments of the Arctic Ocean. Mercury is a major contaminate in the Arctic environment where it bio-accumulates in top predators, causing foraging and reproductive problems. Results from this study confirm the theory that dissolved Hg0 builds up under uniform ice, and that these concentrations are higher than those found in open water. Also, the Hg0 concentrations in the ice-free waters were very low, suggesting the potential for Hg0 deposition to the ocean from the atmosphere. This has rarely been observed, and this finding suggests the air-sea exchange of Hg in the Arctic is unique compared to other ocean basins. Results were presented at the ASLO 2017 meeting, contributed to a PhD dissertation, and have been incorporated into three journal papers (in manuscript). Students at five Public Schools (3 Elementary and 2 Middle) produced ~250 student-made boats at part of the "Float Your Boat" outreach. We deposited these boats with tracking buoys on the sea ice close to the North Pole. The tracking of these "boats" is available to the public on the internet. Halogen-mercury chemistry was also investigated during this cruise. However, no significant halogen chemistry was detected during the time period (Aug-Oct) of the cruise. While halogen chemistry plays a substantial role in Arctic Hg cycling during the winter/spring (Feb-June), it was effectively absent during this cruise (Aug-Oct.). Also investigated were the ship-board Hg concentrations compared to our concurrent Hg measurement at the coastal site of Barrow, Alaska. Open (ice free) areas showed similar atmospheric Hg concentrations to Barrow, indicating that this ice-free coastal site (Barrow) was reflective of the regional ice-free marine environment. Last Modified: 06/21/2017 Submitted by: Steven B Brooks