The Harvard Forest research site located in central New England is influenced by numerous anthropogenic methane sources on a year-round basis. Methane is strongly correlated to other chemical species that have an anthropogenic component, including acetylene, propane, ethane, hexane, and additional short-lived nonmethane hydrocarbons. The correlation between methane and acetylene is due to the colocation of landfills and cities. The correlation between methane and other short-lived species implies that emissions from local and regional rather than distant sources are the primary cause of elevated events. Wind roses of chemical species are examined for annual and seasonal time periods with enhancements in anthropogenic species corresponding to the location of large cities and landfills. The southwest quadrant is subjected to the most severe pollution events and is impacted by outflow from nearby cities in that sector, including Northampton and Springfield, Massachusetts. Emissions from cities in other quadrants, including Boston and Worcester, Massachusetts, Providence, Rhode Island, and the close-by town of Petersham, Massachusetts, also affect the site, but to a lesser degree. Case studies are used to identify atmospheric conditions that lead to high concentrations of methane and other species. The co-occurrence of a persistent wind direction, light wind speed, and stable atmospheric conditions is the ideal scenario in which emission from nearby cities and landfills are advected to the site. Emissions from local and regional, rather than distant sources, are the primary cause of elevated events. ¿ 1998 American Geophysical Union