Long Term Black Carbon Measurements at Two Urban Locations in New York

Abstract

Measurements of PM 2.5 black carbon (BC) over an 8-9 year period are used to characterize temporal patterns at sites in New York City (NYC) and Rochester, NY. Annual mean BC at the NYC location ranges from 1.4 to 2.0 μg/m 3 , whereas mean concentrations at Rochester are approximately a factor of 2-3 lower. BC amounts to 15-20% of PM 2.5 mass in NYC compared to 7-10% at Rochester. Seasonal patterns reveal the highest BC concentrations in NYC from November to February versus June to November at Rochester. At both locations, mean weekday (Monday-Friday) BC concentrations are statistically higher compared to weekends (Saturday and Sunday). Weekday BC diurnal profiles exhibit a morning peak between 6-10 AM EST followed by an afternoon minimum, with a secondary peak in the late evening. Sunday BC diurnal profiles show highest concentrations at night, from 8 PM to 2 AM. These patterns are consistent with vehicle counts on nearby roadways and boundary layer dynamics at both locations. Simultaneous measurements of BC at 370 and 880 nm show an enhancement in BC 370 relative to the BC 880 from October to March. This enhanced signal is most evident at Rochester during late evening and early morning hours (8 PM to 4 AM) on weekends, and is attributed to UV absorbing species (such as wood smoke markers) in the ambient particle mixture. At the NYC site, the levels of Nickel (Ni) and Cobalt (Co) in PM 10 are elevated during the heating season due to residual oil combustion. The long term datasets are used to explore the seasonal relationship between BC 880 and EC at both sites.

Long Term Trends in New York: PM2.5 Mass and Particle Components

“…S10, with higher concentrations (more than a factor of 2 between winter and summer) during colder months consistent with the major sources being residential heating oil combustion used for space and water heating (Lippmann, 2009). In addition the ratio of Ni to Co of around 12-14 (Rattigan et al, 2013) is typical of fuel oils used in the Northeastern states (Graham, 2010). The very low Ni concentrations observed at sites outside NYC is due to the predominant use of natural gas and wood rather than oil for domestic heating in these areas.…”

Mercury Wet Deposition and Speciated Air Concentrations from Two Urban Sites in New York State: Temporal Patterns and Regional Context

“…10(a). Rattigan et al (2013) showed that residential wood smoke events can be observed at Rochester, especially on cold weekend nights. During this period nighttime wind speeds were generally low, and overnight minimum temperatures were near or below 0°C.…”

“…In general, elevated RGM and PBM at Rochester are associated with north/northwest winds, which may be indicative of nearby sources in those directions. The area in the immediate vicinity of the Rochester site is generally residential, and emissions from wood combustion for recreational use occasionally impact the monitoring site (e.g., Rattigan et al, 2013). …”

Chemical Characterization and Source Apportionment of PM2.5 in Rabigh, Saudi Arabia

“…In addition the daily estimates of Delta-C were very low with an overall mean of-0.16 ± 0.17 (Table 2). C 2 O 4 2-and Delta-C are strong markers for bio-mass burning as the major source of air particulate emissions Wang et al, 2012;Rattigan et al, 2013). Thus, bio-mass burning was ruled out as a possible source of PM 2.5 in Rabigh during our study period since the estimates on C 2 O 4 2-and Delta-C were very low.…”

“…As shown in Eq. (1), the difference between the BC measurement at λ = 370 nm and λ = 880 nm gives the estimate for Delta-C which is a strong marker for organic matter combustion as a source of PM 2.5 Wang et al, 2012;Rattigan et al, 2013).…”