Effect of power plant emission reductions on a nearby wilderness area: a case study in northwestern Colorado

Abstract

This study evaluates the effect of emission reductions at two coal-fired power plants in northwestern Colorado on a nearby wilderness area. Control equipment was installed at both plants during [1999][2000][2001][2002][2003][2004] to reduce SO 2 and NOx emissions. One challenge was separating the effects of local from regional emissions, which also declined during the study period. The long-term datasets examined confirm that emission reductions had a beneficial effect on air and water quality in the wilderness. Despite a 75 % reduction in SO 2 emissions, sulfate aerosols measured in the wilderness decreased by only 20 %. Because the site is relatively close to the power plants (<75 km), the slow rate of conversion of SO 2 to sulfate, particularly under conditions of low relative humidity, might account for this less than one-to-one response. On the clearest days, emissions controls appeared to improve visibility by about 1 deciview, which is a small but perceptible improvement. On the haziest days, however, there was little improvement perhaps reflecting the dominance of regional haze and other components of visibility degradation particularly organic carbon and dust. Sulfate and acidity in atmospheric deposition decreased by 50 % near the southern end of the wilderness of which 60 % was attributed to power plant controls and the remainder to reductions in regional sources. Lake water sulfate responded rapidly to trends in deposition declining at 28 lakes monitored in and near the wilderness. Although no change in the acid-base status was observed, few of the lakes appear to be at risk from chronic or episodic acidification.

Links between N Deposition and Nitrate Export from a High-Elevation Watershed in the Colorado Front Range

“…Despite this complicating factor, lake concentration patterns were very similar to those of total inorganic N concentrations at high-elevation NADP sites (Figure B), supporting the conclusion that deposition is an important influence on nitrate export. This result is consistent with recent studies in eastern North America and Europe where declines in watershed N export appear to be have occurred in response to reductions in N deposition over the past decade. ,, We previously reported that streamwater sulfate in high-elevation watersheds has responded rapidly to reductions in sulfate deposition, , and herein we show the response to N deposition may be similar at least in areas with high rates of deposition where surface water nitrate concentrations are elevated.…”

“…This result is consistent with recent studies in eastern North America and Europe where declines in watershed N export appear to be have occurred in response to reductions in N deposition over the past decade. 15,16,18 We previously reported that streamwater sulfate in high-elevation watersheds has responded rapidly to reductions in sulfate deposition, 39,40 and herein we show the response to N deposition may be similar at least in areas with high rates of deposition where surface water nitrate concentrations are elevated.…”

Impacts of the Denver Cyclone on regional air quality and aerosol formation in the Colorado Front Range during FRAPPÉ 2014

“…Recent studies have shown O & G emissions of non-methane hydrocarbons (NMHC) such as short-chain alkanes (C 1 -C 4 ) and alkenes act as precursors to ozone (Pétron et al, 2012(Pétron et al, , 2014Edwards et al, 2013;Gilman et al, 2013;Karion et al, 2013), but the potential for these emissions to contribute to primary and secondary OA in the region has not been investigated. Additionally, agricultural practices and powerplant operations in the greater Colorado region contribute to visibility impairment and ecosystem degradation through formation of secondary nitrate and sulfate-containing compounds (Williams and Tonnessen, 2000;Nanus et al, 2003;Blett et al, 2004;Burns, 2004;Boy et al, 2008;Malm et al, 2013;Mast and Ely, 2013; T. M. Thompson et al, 2015).…”

Impacts of the Denver Cyclone on Regional Air Quality and Aerosol Formation in the Colorado Front Range during FRAPPÉ 2014

“…Recent studies have shown O & G emissions of non-methane hydrocarbons (NMHC) such as short-chain alkanes (C 1 -C 4 ) and alkenes act as precursors to ozone (Pétron et al, 2012(Pétron et al, , 2014Edwards et al, 2013;Gilman et al, 2013;Karion et al, 2013), but the potential for these emissions to contribute to primary and secondary OA in the region has not been investigated. Additionally, agricultural practices and powerplant operations in the greater Colorado region contribute to visibility impairment and ecosystem degradation through formation of secondary nitrate and sulfate-containing compounds (Williams and Tonnessen, 2000;Nanus et al, 2003;Blett et al, 2004;Burns, 2004;Boy et al, 2008;Malm et al, 2013;Mast and Ely, 2013; T. M. Thompson et al, 2015).…”