Identification

Title

The relative importance of chlorine and bromine radicals in the oxidation of atmospheric mercury at Barrow, Alaska

Abstract

Mercury is a toxic environmental contaminant originating from both natural and anthropogenic sources. Gaseous elemental mercury (GEM) is relatively long lived in the midlatitudes and can be transported long distances in the atmosphere. In the Polar Regions, mercury can have a much shorter lifetime and is known to experience episodic depletions following polar sunrise in concert with ozone depletion events. A series of photochemically initiated reactions involving halogen radicals is believed to be the primary pathway responsible for converting elemental mercury to oxidized forms of reactive gaseous mercury (RGM) that are subsequently deposited to snow and ice surfaces. Using field measurements from the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) 2009 field campaign of GEM, RGM, ozone, and a large suite of both inorganic halogen and volatile organic compounds, we calculated steady state Br and Cl atom concentrations and investigated the contribution of Br, BrO, Cl, ClO, O₃, and OH to the observed decay of GEM for five cases of apparent first-order decay. The results of this study indicate that Br and BrO are the dominant oxidizers for Arctic mercury depletion events, with Br having the greatest overall contribution to GEM decay. Ozone is likely the primary factor controlling the relative contribution of Br and BrO, as BrO is a product of the reaction of Br with ozone, and reaction with O₃ can be the largest Br atom sink. Cl was not found to be significant in any of the studied events; however, this result is highly dependent on the rate constant, for which there is a large range in the literature. Modeled 48 h back trajectories of the mercury depletion events studied here indicate significant time spent over sea ice-covered regions, where the concentration of halogen radicals is likely higher than those estimated using local-scale chemical mole fractions.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7qz2bkt

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2012-03-03T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

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version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact