III.  Emissions

National Trends

Since the implementation of the Clean Air Act in 1970, total U.S.  emissions of sulfur dioxide have declined 39% (USEPA 1996a, 1996b).   Recent trends reflect the implementation of the 1990 Clean Air Act Amendments (CAAA).

•  During 1995, the first year of Title IV implementation, Phase I units reduced their SO₂ emissions by 40%, from 7.4 million tons in 1994 to 4.5 millions tons in 1995. This contributed to a significant decline in total national emissions of 13% for that year.

•  However, between 1995 and 1996, total SO₂ emissions increased 3%, because of increased demand for electricity.

Regional Trends

Data from 12 states in the Chesapeake airshed were examined to evaluate changes in regional emissions before and after CAAA Title IV went into effect (Figure 2):

Figure 2: Comparison of Regional Emissions from 1993 to 1996.

•  The airshed experienced a 28% decrease in SO₂ emissions from all stationary sources between 1994 and 1995, similar to the national trend. 

•  Between 1995 and 1996, however, emissions from all stationary sources within the Chesapeake airshed increased 20%, significantly more than national emissions.

Of the 263 Phase I units nationwide, 169 are located within the airshed states and account for a significant amount of all stationary emissions in the eastern United States.

•  SO₂ emissions from Phase I  units within the airshed decreased 42% between 1994 and 1995. 

•  The Phase I units' emissions increased slightly (4%) between 1995 and 1996.  

Return to main page

Continue to Deposition

Search Maryland DNR

Rivers & Streams 101 | Monitoring & Research | Restoration & Protection
Want Data? | Meetings & Readings | Get Involved!

Return to the Maryland DNR Home Page.
Your opinion counts! Take a survey!
This page was updated on 4/7/2004