Measurements of gaseous HONO, HNO3, SO2, HCl, NH3, particulate sulfate and PM2.5 in New York, NY

Abstract

Simultaneous measurements of gaseous HONO, HNO3, HCl, SO2, and NH3 for a period of 1 year from July 1999 to June 2000 and fine-fraction particulate (<2.5 μm) sulfate (SO42−) from January 1999 to November 2000 were made at Bronx and Manhattan in New York City with an annular denuder system followed by ion chromatography. The hourly PM2.5 mass was measured with a Rupprecht and Patashnick TEOM Series 1400a real-time monitor for approximately 2 years (January 1999–November 2000) at the same sites. Concentrations at the two sites were highly correlated, with Manhattan being slightly higher than at the Bronx. The concentrations of HNO3, HCl, NH3 and SO42− were higher during summer than winter, the summer/winter ratios at Manhattan being 3.9, 3.1, 1.5, and 1.9, respectively. The concentrations of HONO and SO2 were lower during summer than winter, the summer/winter ratios at Manhattan being 0.48 and 0.44, respectively. Gaseous HONO concentrations were higher than that of HNO3 except in summer, when the HNO3 was higher. The annual mean concentration of PM2.5 was 15.2 μg/m3 at the Bronx, and 15.5 μg/m3 at Manhattan (based only on days when data were available from both sites). The monthly mean concentrations at Manhattan ranged from 13.2 to 21.7 μg/m3 and were highest in June and July 1999, and lowest in March and April. The monthly mean fraction of PM2.5 as SO42− ranged from 0.17 to 0.31, with the highest values observed during June–September. The hourly mean concentrations of PM2.5 showed a bimodal pattern, with peaks at around 7–8 AM and 8–9 PM. In general, the second maximum is lower than the morning one, but during summer this is reversed. The contributions from regional and local emissions and the influence of atmospheric transport and chemical reactions on the observed concentrations are discussed in a compendium paper.