METHANE MEASUREMENTS IN CENTRAL NEW-ENGLAND - AN ASSESSMENT OF REGIONAL TRANSPORT FROM SURROUNDING SOURCES

The Harvard Forest research site located in central New England is inf luenced by numerous anthropogenic methane sources on a year-round basi s. Methane is strongly correlated to other chemical species that have an anthropogenic component, including acetylene, propane, ethane, hexa ne, and additional short-lived nonmethane hydrocarbons. The correlatio n between methane and acetylene is due to the colocation of landfills and cities. The correlation between methane and other short-lived spec ies implies that emissions from local and regional rather than distant sources are the primary cause of elevated events. Wind roses of chemi cal species are examined for annual and seasonal time periods with enh ancements in anthropogenic species corresponding to the location of la rge cities and landfills. The southwest quadrant is subjected to the m ost severe pollution events and is impacted by outflow from nearby cit ies in that sector, including Northampton and Springfield, Massachuset ts. Emissions from cities in other quadrants, including Boston and Wor cester, Massachusetts, Providence, Rhode Island, and the close-by town of Petersham, Massachusetts, also affect the site, but to a lesser de gree. Case studies are used to identify atmospheric conditions that le ad to high concentrations of methane and other species. The co-occurre nce of a persistent wind direction, light wind speed, and stable atmos pheric conditions is the ideal scenario in which emissions from nearby cities and landfills are advected to the site. Emissions from local a nd regional, rather than distant sources, are the primary cause of ele vated events.