HR: 1340h
AN: A53C-0919    [Abstracts]
TI: Halocarbon Distributions at Appledore Island, ME and Thompson Farm, Durham, NH during ICARTT 2004
AU: * Varner, R K
EM: ruth.varner@unh.edu
AF: Climate Change Research Center, University of New Hampshire, Durham, NH 03824
AU: Sive, B C
EM: bcs@gust.sr.unh.edu
AF: Climate Change Research Center, University of New Hampshire, Durham, NH 03824
AU: Talbot, R W
EM: robert.talbot@unh.edu
AF: Climate Change Research Center, University of New Hampshire, Durham, NH 03824
AB: Halocarbons were measured during the ICARTT 2004 campaign at two AIRMAP monitoring sites, Appledore Island, 6 miles off the coast of NH and Thompson Farm, 10 miles inland in Durham, NH. An automated GC system using electron capture detectors (ECDs) was used at Thompson Farm for measurement of halocarbons every 40 minutes. The Thompson Farm GC system is a dual stage trapping system using liquid nitrogen. The measurement precision for each of the halocarbons ranged from 0.3-15 percent. Hourly canister samples were collected at Appledore Island from July 1 through August 13, 2004 for halocarbons. Canister samples were collected in 2-liter electropolished stainless steel canisters (UCI) and pressurized to 40 psig using a single head metal bellows pump. Canister samples were returned to the laboratory for analysis by gas chromatography using ECD in conjunction with mass spectrometry. Approximately 1032 samples were analyzed during the course of the campaign. Throughout the sampling period Appledore Island was largely influenced by marine air masses on a regular basis. The mixing ratios of bromoform, dibrmomethane and methyl iodide often track each other indicating that these gases have similar marine sources. There is a large variability of these gases on an hourly time scale in the marine environment, as compared to the anthropogenically produced halocarbon, C$_2$Cl$_4$. Overall, ratios of bromoform and dibromomethane were similar at both Appledore Island and Thompson Farm, except for the period from July 14-15. Back trajectory analysis of the air mass sampled during this period indicates that this air mass originated from out over the North Atlantic, was transported to the northwest then south along the coast of Maine and then out over Appledore Island. The increased mixing ratios of dibromomethane without a concurrent increase in bromoform could indicate that a coastal source of dibromomethane was encountered during the transport of this clean marine air mass. Coastal sources of halocarbons are not well understood and further analysis of the full suite of halocarbons measured during this study will provide much insight to coastal zone influences on atmospheric halocarbon concentrations.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0315 Biosphere/atmosphere interactions
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting