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ARL Scientists Get Ready for Airborne Mercury Study
July, 2012
From August 3 to November 16, 2012, Air
Resources Laboratory scientists will participate in an airborne mercury
study with researchers from the University of Miami and the University of
Tennessee Space Institute (UTSI). The UTSI Piper Navajo aircraft (pictured
to the right) will be used to collect measurements of gaseous elemental
mercury (GEM) and gaseous oxidized mercury (GOM), as well as supporting
measurements of ozone (O
3), sulfur dioxide (SO
2),
condensation nuclei, and meteorological parameters at altitudes ranging
from the surface to 20,000 feet in the region near Tullahoma, TN. Mercury
speciation, including GEM, GOM, and particle bond mercury (PBM), will also
be measured at a ground site near the Tullahoma airport for comparison
with the aircraft measurements. The flights are scheduled to occur one
week out of each month to characterize seasonal variations in mercury
concentrations from summer to fall. ARL modelers will use a newly
developed version of the Hybrid Single-Particle Lagrangian Integrated
Trajectory (HYSPLIT)-based mercury model to simulate mercury
concentrations and use the data sets for an extensive
post hoc
model evaluation. The primary intentions of the study are to address the
importance of atmospheric mercury transport from the middle-to-upper
troposphere in influencing mercury concentrations at the surface and the
relative contributions of natural and anthropogenic
processes to local, regional, and global burdens of mercury.
Background: The research builds upon and extends similar flight
campaigns conducted by ARL and partners in 2010 and 2011 at the Grand Bay
National Estuarine Research Reserve (NERR) in Moss Point, MS. Flights
were conducted around the NERR, which also hosts an ARL ground-based
measurement site devoted to the long-term monitoring of mercury species in
the atmosphere. The NERR site also collects long-term and continuous
measurements of reactive nitrogen compounds, SO2, carbon monoxide, O3,
black carbon, and meteorological parameters, in order to better interpret
the measurements of atmospheric mercury. The earlier research found
periods of high GOM concentrations in the middle troposphere, which can be
easily scrubbed from the atmosphere by clouds and precipitation and
transferred to receiving landscapes, watersheds, and water bodies. While
the earlier flight campaigns were limited to altitudes of 15,000 feet, the
current study is intended to measure mercury at higher altitudes, where
GOM concentrations may be even larger.
Significance: Human exposure to mercury is primarily from the
consumption of contaminated fish and other aquatic organisms. The U.S.
Environmental Protection Agency has estimated that roughly 1 out of every
6 children born in the U.S. are exposed, in-utero, to levels of mercury at
concentrations sufficient to impair neurological development and motor and
cognitive skills. Nearly every state in the U.S. is home to at least one
water body affected by fish consumption advisories for mercury; in some
states these advisories apply to all water bodies within the state. The
release of mercury compounds to the atmosphere, followed by deposition,
often constitutes the dominant loading mechanism to water bodies and
watersheds. The upcoming study will allow scientists to address questions,
such as:
- Is there a persistent pool of reactive, oxidized mercury in the
middle troposphere which can be removed by convective activity and
rainfall and washed into local watersheds?
- How do concentrations of mercury species aloft vary with the seasons?
- To what extent can downward mixing from the middle troposphere
influence mercury concentrations at the surface?
- What role is played by local and regional anthropogenic sources of mercury?
For More Information, contact: Xinrong Ren
