The changing face of lower tropospheric sulfur oxides in the United States

Abstract

Sulfur oxides, sulfur dioxide and airborne sulfate, SO x , are short-lived species in the troposphere whose concentrations in air and precipitation have changed dramatically in association with fossil fuel combustion. The historic rise in concentration is coincident with the era of the so-called "Anthropocene." Unlike concentrations of long-lived species such as carbon dioxide, atmospheric SO x in the United States (US) peaked between 1970 and 2005 then declined. The rise and fall of SO x is traced by comparing national data on emission changes, ambient concentrations, and precipitation sulfate from prior to World War II to the present. Surface SO x concentrations and precipitation sulfate have decreased with emissions in most parts of the US after the late 1970s. Continued reduction toward a natural "background" condition has depended on aggressive management of anthropogenic emission sources. Annual average ambient concentrations of SO 2 and SO 4 have become more uniform across the US at levels of 1-3 ppbv and 0.3-3 µg/m 3 , respectively. Precipitation SO 4 has a nominal concentration generally less than 0.5 mg/L. The effective lifetime of SO x in the troposphere is a few days. This duration limits the spatial extent of emission source influence of SO x to regional scales, wherein spatial gradients in species concentrations lead to variations in human exposure and impacts on vulnerable terrestrial and aquatic ecosystems. The effects of domestic emission reductions on SO x levels are moderated by intra-and intercontinental transport of SO x from Canada, Mexico, Asia and elsewhere. The trends in tropospheric SO x concentrations illustrate the results of more than a century of rising public awareness and action to progressively reduce a US environmental risk, accomplished with advances in energy production technology that have maintained economic well-being.

Greenwashing in the US Metal Industry? A Novel Approach Combining SO2 Concentrations From Satellite Data, a Plant-Level Firm Database and Web Text Mining

“…It has a seasonally varying but relatively short residence time (12-78 hours) in the lower troposphere, which can be further decreased by precipitation due to the solubility of SO 2 (Hidy & Blanchard, 2016;Lee et al, 2011). Consequently, SO 2 concentrations tend to be particularly high in the emission region (Lewinschal et al, 2019).…”

“…SO 2 is quite reactive in the atmosphere, resulting e.g. in the formation of sulfate (SO 4 2-) (Hidy & Blanchard, 2016;Lee et al, 2011), which is the main component of particulate matter with a diameter ≤ 2.5 µm (PM 2.5 ) (Zhang et al, 2007). PM 2.5 has a considerable effect on global and local climates (Smith et al, 2011), in addition to being the main cause of smog (Cheng et al, 2017).…”

“…Around the turn of the millennium, China became the largest emitter of SO 2 , but since 2016, the country has been overtaken by India (Li et al, 2017). As some researchers consider SO 2 pollution to be "well under control" in the US (Hidy & Blanchard, 2016), it would therefore be more sensible to conduct this research in Asia. However, the necessary business data was not available for this study, which consequently opens up the possibility of transferring the approach to another study area.…”

Detection of Sulfur Dioxide by Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS)

“…Sulfur dioxide (SO 2 ) is a precursor to the formation of atmospheric sulfate aerosol and acid rain [ 1 ]. SO 2 is emitted naturally through volcanic eruption [ 2 ], oxidation of other atmospheric sulfur species [ 3 ], and is emitted anthropogenically from the oxidation of sulfur from the combustion of coal and oil [ 4 , 5 ]. SO 2 directly affects health through the respiratory system with elevated risks for high-risk groups [ 6 ].…”

Detection of Sulfur Dioxide by Broadband Cavity Enhanced Absorption Spectroscopy (BBCEAS)

“…Sulfur dioxide (SO 2 ) is a precursor to formation of atmospheric sulfate aerosol and acid rain (Schwartz, 1987). SO 2 is emitted naturally through volcanic eruption (Holasek et al, 1996), oxidation of other atmospheric sulfur species (Logan et al, 1979), while it is emitted anthropogenically from the oxidation of sulfur in combustion from coal, oil, and other sources (Smith et al, 2011;Hidy and Blanchard, 2016). SO 2 has direct health effects through the respiratory system with elevated risks for high risk groups (EPA, 2017).…”