DOWNWARD TRENDS OF SULFUR DIOXIDE (SO 2 ) EMISSIONS IN THE NORTHEAST DUE TO THE CLEAN AIR ACT: A CLIMATOLOGY OF THE REDUCTION OF ACID RAIN
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Authors
Connelly, Brittany
Date
2023-08
Type
Thesis
Language
en
Keywords
Alternative Title
Abstract
ABSTRACT
DOWNWARD TRENDS OF SULFUR DIOXIDE (SO2 ) EMISSIONS IN
THE NORTHEAST DUE TO THE CLEAN AIR ACT:
A CLIMATOLOGY OF THE REDUCTION OF ACID RAIN
by
Brittany C. Connelly
M.S. in Applied Meteorology, Plymouth State University, August 2023
Anthropogenic emissions of sulfur dioxide (SO2 ) are primarily caused the by burning of
sulfur containing fossil fuels at power plants for heat and power generation. Emitted SO2 reacts
with oxygen (O2 ) in the atmosphere to form the secondary pollutant sulfate (SO4 ). Acid rain
formation is the result of a change in atmospheric chemistry when SO4 combines with water
vapor (H2 O) in the air to form sulfuric acid (H2 SO4 ).
The Clean Air Act (CAA) was federally implemented by the United States
Environmental Protection Agency (EPA) to regulate hazardous air emissions which initiated the
creation of National Ambient Air Quality Standards (NAAQS) to protect public health and the
environment. Individual states are required to work with the Environmental Protection Agency
(EPA) to create state implementation plans (SIPs) in order to comply with NAAQS which, help
regulate and decrease air pollution.
This study contains a meteorological background of the transport of SO2 emissions from
power plants from the Midwest to the Northeast. There are three main components to this study:
a 10-year analysis of the trends in hourly SO2 concentrations in the Northeast compared to wind
direction, a case study comparing SO4 concentrations to two days that have different
meteorological conditions that impact winds, and a 35-year climatological analysis in acid rain
trends throughout the Northeast. Environmental and human health impacts of SO2 as a primary
air pollutant, in addition to the secondary air pollutants that result from SO2 emissions such as
SO4 and acid rain, are discussed, indicating the importance in SO2 emission regulations of the
CAA.
Annual hourly SO2 concentrations at two Interagency Monitoring of Protected Visual
Environments (IMPROVE) sites at Lawrenceville, PA and Londonderry, NH show a gradual
decrease from 2012 to 2021. Higher SO2 concentrations were measured when winds were from
the south or southwest with exception of Lawrenceville, PA site that had the greatest SO2
concentrations from the northwest which is influenced by surrounding topography. The case
study for this study analyzes daily SO4 concentrations from different wind directions on two days
in the summer of 2022 at the same two IMPROVE sites that were analyzed for SO2
concentrations. When winds were from the north on 1 July 2022, the measured SO4
concentrations were 1.838 μg/m 3 at the Lawrenceville, PA site and 1.508 μg/m 3 at the
Londonderry, NH site. When winds were from the southwest on 12 August 2022, the measured
SO4 concentrations were 0.188 μg/m 3 at the Lawrenceville, PA site and 0.315 μg/m 3 at the
Londonderry, NH site. Lastly, the acid rain climatological analysis of 19 National Trends
Network (NTN) sites throughout the Northeast show an increase in precipitation pH and a
decrease in SO4 concentrations between 1985 and 2020 at all 19 sites.