Multi-year urban and rural semi-continuous PM2.5 sulfate and nitrate measurements in New York state: Evaluation and comparison with filter based measurements

Measurements of PM2.5 sulfate and nitrate were carried out over a period of 3 years with a 10-min time resolution, using Rupprecht and Patashnick Co., Inc., (R&P) Ambient Particulate Sulfate and Nitrate Monitors, models 8400S and 8400N, respectively. The instruments were deployed at an urban site in the South Bronx, NY, and at Whiteface Mountain, a rural field monitoring location in upstate New York. At both sites collocated 24-h integrated filter measurements are compared to the semi-continuous sulfate and nitrate data. The sites are also equipped with a suite of gas phase (NOx, SO2, and O3) and other particulate-based instrumentation. The semi-continuous data is used to examine the diurnal, seasonal and yearly variability of PM2.5 sulfate and nitrate at both locations. Clear seasonal trends were observed for both sulfate and nitrate with maximum sulfate concentrations in the warmer months and highest nitrate in the winter–spring periods at both locations. PM2.5 nitrate showed a clear diurnal pattern with peak concentrations in the early morning hours at the South Bronx site. Results of the comparisons between the semi-continuous measurements and 24-h filter data are presented. The potential use of the R&P sulfate and nitrate instruments for routine monitoring is evaluated based on these results, and our operational experiences with the instruments.