ARL News

Mercury Speciation And Deposition In The Arctic


June 26, 2001

Most of the mercury in the atmosphere is as elemental mercury, in gaseous form. It is only a small part of the total mercury burden of the air that is chemically reactive. This reactive gaseous murcury (RGM) deposits to the surface, enabling transfer of mercury to the terrestrial and aquatic environments, where it bioaccumulates. (A further small part of the mercury burden is associated with particles. This deposits very slowly whereas the RGM is thought to deposit very efficiently.) In the first airborne measurement of mercury speciation in the Arctic, it has been found that RGM is largely confined to the lowest part of the atmosphere, strongly suggesting that its production is quite local. These results were obtained using a small aircraft flown from Point Barrow, Alaska, by scientists from the Atmospheric Turbulence and Diffusion Division of ARL. RGM concentrations averaged 1.5 pg m-3 at 1000m and 18.3 pg m-3 at 100m, independently verifying for the first time the restriction of both production and significant concentration of RGM to the atmospheric boundary layer. In the same experiment, the world’s first Relaxed Eddy Accumulation (REA) flux measurements for dry deposition of RGM were conducted at Barrow in late March and early April, using techniques also developed at ATDD. Relatively strong RGM fluxes were measured, largely in accord with expectations. Mercury instrumentation will be transported to Lavrentiya, Russia on the US Coast Guard Polar Sea icebreaker in the period August 10 to 19. Set-up in Lavrentiya will occur from August 14-16.

Contact information: Steven B Brooks
Phone: (865) 576-9148