The concentrations and sources of PM_(2.5) in metropolitan New York City

摘要

The concentration time series of chemical species measured in PM_(2.5) samples from four speciation trend network (STN) sites in the New York City metropolitan area and a upwind background site were explored. PM_(2.5) concentrations and chemical compositions measured in metropolitan area of New York City are uniform. About 69-82% of PM_(2.5) mass derives from transport. The most important constituents of the PM_(2.5) were SO_4~(2-), NH~4 and NO_3~- and account 54-67% of PM_(2.5) mass. More than 93% of SO_4~(2-) and about 54-65% of NO_3~- are likely to have been transported into the NYC area based on the concentrations observed at the background site. Backward air parcel trajectories indicate that coal-fired power plants in the border area among West Virginia, Ohio and Pennsylvania are related to typical high PM_(2.5) events having peak secondary pollutant concentrations in New York City. Positive matrix factorization (PMF) was applied to identify the PM_(2.5) sources and estimate the source contributions. Sources common to all five sites included secondary sulfate, secondary nitrate, soil and aged sea salt. Oil combustion was identified at four of the sites. At the Elizabeth site, the oil combustion source appears to show an influence from ship emissions. Motor vehicles were apportioned into two sources (gasoline and diesel) at three site and three sources at the Elizabeth site, probably because of its proximity to a major interstate highway. At the Queens College site, only a combined motor vehicle factor could be resolved. The source profiles, source contributions and seasonal or weekday variations derived by PMF are compared to source inventories for the area. It appears that there were more vehicle exhausts and less dust and wood smoke than are indicated by the source inventories.