The Air Pollution at Rochester: Long-Term Trends

There have been a number of changes in the sources of air pollutant in the northeastern United States since 2001. Trend analyses of monthly averages were performed on PM 2.5, ionic species, elemental carbon (EC), organic carbon (OC) and gaseous pollutants collected between 2001 and 2015 for NYS Department of Environmental Conservation sites in Rochester. Non-parametric (Mann-Kendall regression with Sen’s slope) and parametric (weighted linear and non-linear regressions) approaches were applied to estimate the trends and seasonality. We fitted the different models to monthly averages of each species for each month over the 15 years of available data. Separating the data by month removes their seasonal dependence. The unequal number of attainable samples averaged to provide monthly asset value was accounted for by weighting each month proportional to its number of available daily concentration values. Sulfate and nitrate showed downward trends. For almost all of the species over the whole, the weighted linear parametric modeling yielded steeper slopes than the non-parametric Mann-Kendall approach. For sulfate, the slopes = -0.20 and -0.15 μg m -3 year -1, respectively. These trends will be compared to changes in emissions in the upwind source domain.