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Atmospheric Mercury Measurements
In conjunction with the National Atmospheric Deposition Program's (NADP) Atmospheric Mercury Initiative, ARL operates three stations for the long-term, research-grade monitoring of concentrations of mercury species and other trace pollutants in the atmosphere:
Location of ARL's three long-term speciated atmospheric mercury measurement sites (Mauna Loa, Beltsville, Grand Bay), overlain on a map of large mercury point sources (for 2002) based on data from the U.S. EPA and Environment Canada.
Goals and Objectives:
(a) Measurement tower at Grand Bay NERR, showing two sets of Tekran reactive gaseous mercury and fine particulate mercury collection units; (b) Mercury measurement equipment in climate-controlled trailer adjacent to tower.
At each site, ambient air concentrations of gaseous elemental mercury, reactive gaseous mercury, and fine particulate mercury are measured. In addition, ambient air concentrations of trace gases (e.g., sulfur dioxide, nitrogen oxides, carbon monoxide, ozone) are measured. Meteorological parameters such as temperature, humidity, precipitation, wind speed and direction are also measured. Wet deposition measurements are being made following Mercury Deposition Network (MDN) protocols at the Beltsville site by collaborators (Univ. of MD, State of MD) and MDN sites are planned to be implemented at the Grand Bay and CVI sites as resources permit. Deposition in precipitation is quantified through chemical analysis of collected rain and snow samples.
In addition to the three long-term sites noted above, a number of short-term mercury measurement campaigns have been carried out, including the following: Cove Mtn, TN (Summer 2002); Gulf of Mexico (Ship) (Summer 2003); Oxford and Wye, MD (Summer 2004); Harcum, VA (Summer 2005); Houston, TX (Summer 2006).
Grand Bay NERR, MS:
View from Grand Bay NERR atmospheric mercury measurement tower.
Speciated ambient mercury measurements began at the Grand Bay NERR in September 2006. Mercury measurements at this time were made with a single Tekran instrument suite at a temporary location (30.4294o N, -88.4277o W). In 2007, a second Tekran instrument suite was added and the site location was moved to its permament location on FWS Grand Bay National Wildlife Refuge property adjacent to the Grand Bay NERR (30.412o N, - 88.404o W). In January 2010, an aerosol soot carbon monitor was added as a tracer for combustion processes. In March 2010, a National Atmospheric Deposition Program (NADP) Mercury Deposition Monitoring site was established and includes measurements for total mercury, trace metals, and monthly composite for methyl mercury in precipitation. An NADP National Trend Network site was also established at that time to measure major ions in preciptation.
ARL is grateful to NOAA National Ocean Service's National Centers for Coastal Ocean Science for assistance in purchasing measurement equipment for the site. Summaries of activities and measurements at the Grand Bay NERR site are available , , , , .
The two co-located mercury measurement systems at the site are particularly useful in that they:
Atmospheric measurement monitoring tower at Beltsville MD.
In November 2006, the U.S. EPA Clean Air Markets Division (CAMD) and ARL established a comprehensive atmospheric mercury monitoring site (39.0284o N, -76.8172o W) near Beltsville, Maryland, on the campus of the USDA Beltsville Agricultural Research Center, and bordering the U.S Fish and Wildlife Service's Patuxent National Wildlife Refuge (NWR). The site is located on parkland embedded within a suburban portion of the Washington, DC metropolitan area, and is representative of much of the semi-urban nature of the Chesapeake Bay watershed. Other collaborating organizations at the site include the State of Maryland Department of Natural Resources and the University of Maryland. The Howard University Atmospheric Observatory, a multi-agency research facility for the study of atmospheric physics and chemistry, lies approximately 5 km to the northwest.
The Beltsville site includes two Tekran speciation systems measuring Hg0, RGM, and Hg(p), like the Grand Bay NERR site, providing comparable quality assurance, continuity and other benefits. Mercury compounds, ancillary trace gases (SO2, O3, CO, NO, NOy), and meteorological parameters are measured at a height of 10 meters to minimize local surface effects. The site also hosts measurements under the EPA CASTNet, NADP/NTN (major ions in precipitation) and MDN (mercury wet deposition) programs. These existing co-located measurements were an important factor in choosing the Beltsville location for enhanced mercury monitoring. Summaries of activities and measurements at the Beltsville site are available ,,.
Mauna Loa Observatory:
Atmospheric mercury measurement equipment at Mauna Loa Observatory.
In January, 2011, ARL partnered with NOAA's Earth System Research Laboratory and EPA's Clean Air Markets Division (CAMD) to continue speciated mercury measurements at the Mauna Loa Observatory (MLO) near Hilo, Hawaii. EPA's Office of Research and Development established mercury measurements at MLO in 2001 (date approximate), but in 2011 funding for the site was transferred to CAMD.
MLO is located on the Island of Hawaii at an elevation of 3397 m on the northern flank of Mauna Loa volcano. The observatory was established in 1957, and is one of six global baseline monitoring stations for the study of the background global atmosphere. The first long-term carbon dioxide (CO2) measurements illustrating the seasonal and inter-annual variations in carbon dioxide (the so-called "Keeling curve") were made at MLO. Now, up to 250 different atmospheric parameters are measured there by a complement of 12 NOAA/ESRL and other agency scientists and engineers.
Species and parameters measured include carbon cycle flask sampling (for greenhouse gases, hydrocarbons, and measurements of carbon and oxygen isotopes); in situ carbon cycle and halocarbon measurements; aerosol measurements; continuous radiation measurements; surface and column ozone; lidar observations; and meteorological parameters. See the MLO web site for more information.
A single Tekran speciation system measures elemental mercury (Hg0. 5-minute measurements), reactive gaseous mercury (RGM, 1-hr measurements) and fine-particulate bound mercury (FPM. 1-hr measurements).
Winds are typically from the east and northeast (trade wind circulation), with local upslope (daytime) and downslope (nighttime) circulations superimposed on the mesoscale and synoptic flows.
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