Air pollution at Rochester, NY: Long-term trends and multivariate analysis of upwind SO2 source impacts

Highlights: • PM2.5, major species and gaseous pollutants are analyzed over 15 years (2001–2015). • Trends are estimated trough Mann-Kendall tau-Sen's slope and piecewise regression. • Impacts of changes in fuel sulfur content and power plant emissions are pointed out. • Regional sources of sulfate are related to state-wide changes in SO2 emissions. • The feedback of past mitigation strategies and action plans in U.S. is discussed. There have been many changes in the air pollutant sources in the northeastern United States since 2001. To assess the effect of these changes, trend analyses of the monthly average values were performed on PM_2.5 and its components including major ions, elemental carbon (EC), organic carbon (OC), and gaseous pollutant concentrations measured between 2001 (in some cases 1999) and 2015 at the NYS Department of Environmental Conservation sites in Rochester, NY. Mann-Kendall regression with Sen's slope was applied to estimate the trends and seasonality. Using piecewise regression, significant reductions in the air pollution of Rochester area were observed between 2008 and 2010 when a 260 MW coal-fired power plant was decommissioned, new heavy-duty diesel trucks had to be equipped with catalytic regenerator traps, and the economic recession that began in 2008 reduced traffic and other activities. The monthly average PM_2.5 mass showed a downward trend (− 5 μg/m³; − 41%) in Rochester between 2001 and 2015. This change is largely due to reductions in particulate sulfate that showed a 65% decrease. The sulfate concentrations were compared to changes in SO₂ emissions in seventeen upwind source domains, and other systematic changes by multivariate linear regression. Selectivity ratio obtained from target projection discriminated the most important source domains that are SO₂ emissions from Georgia for winter, North Carolina for transition (spring and fall) and Ohio along with other influences for summer. North Carolina and Michigan were identified as the main sources for entire period. These observations suggest that any further reductions in the specified regional SO₂ emissions would result in a proportional decrease in sulfate in Rochester.