Aqueous phase sulfate production in clouds at Mt. Tai in eastern China
| dc.contributor.author | Shen, Xinhua, author | |
| dc.contributor.author | Collett, Jeffrey L., advisor | |
| dc.contributor.author | Kreidenweis, Sonia M., committee member | |
| dc.contributor.author | Rutledge, Steven A., committee member | |
| dc.contributor.author | Reynolds, Stephen J., committee member | |
| dc.date.accessioned | 2007-01-03T05:44:17Z | |
| dc.date.available | 2007-01-03T05:44:17Z | |
| dc.date.issued | 2011 | |
| dc.description.abstract | Clouds play an important role in the oxidation of sulfur dioxide to sulfate, since aqueous phase sulfur dioxide oxidation is typically much faster than oxidation in the gas phase. Important aqueous phase oxidants include hydrogen peroxide, ozone and oxygen (catalyzed by trace metals). Because quantities of emitted sulfur dioxide in China are so large, however, it is possible that they exceed the capacity of regional clouds for sulfate production, leading to enhanced long-range transport of emitted SO2 and its oxidation product, sulfate. In order to assess the ability of regional clouds to support aqueous sulfur oxidation, four field campaigns were conducted in 2007 and 2008 at Mt. Tai in eastern China. Single and 2-stage Caltech Active Strand Cloudwater Collectors were used to collect bulk and drop size-resolved cloudwater samples, respectively. Key species that determine aqueous phase sulfur oxidation were analyzed, including cloudwater pH, S(IV), H2O2, Fe, and Mn. Gas phase SO2, O3, and H2O2 were also measured continuously during the campaigns. Other species in cloudwater, including inorganic ions, total organic carbon (TOC), formaldehyde, and organic acids were also analyzed to provide a fuller view of cloud chemistry in the region. Numerous periods of cloud interception/fog occurred during the four Mt. Tai field campaigns; more than 500 cloudwater samples were collected in total. A wide range of cloud pH values was observed, from 2.6 to 7.6. SO42-, NO3-, and NH4+ were the major inorganic species for all four campaigns. TOC concentrations were also very high in some samples (up to 200 ppmC), especially when clouds were impacted by emissions from agricultural biomass burning. Back-trajectory analysis also indicated influence by dust transport from northern China in a few spring cloud events. Differences between the compositions of small and large cloud droplets were observed, but generally found to be modest for major solute species and pH. Mt. Tai clouds were found to interact strongly with PM2.5 sulfate, nitrate, and ammonium with average scavenging efficiencies of 80%, 75%, and 78%, respectively, across 7 events studied. Scavenging efficiencies for total sulfur (PM2.5 sulfate plus gaseous sulfur dioxide), however, averaged only 43%, indicating the majority of gaseous sulfur dioxide remained unprocessed in these cloud events. H2O2 was found to be the most important oxidant for aqueous sulfate production 68% of the time. High concentrations of residual H2O2 were measured in some samples, especially during summertime, implying a substantial capacity for additional sulfur oxidation. The importance of ozone as a S(IV) oxidant increased substantially as cloud pH climbed above pH 5 to 5.3. Overall, ozone was found to be the most important aqueous S(IV) oxidant in 21% of the sampling periods. Trace metal-catalyzed S(IV) autooxidation was determined to be the fastest aqueous sulfate production pathway in the remaining 11% of the cases. Complexation with formaldehyde was also found to be a potentially important fate for aqueous S(IV) and should be examined in more detail in future studies. Observed chemical heterogeneity among cloud drop populations was predicted to enhance rates of S(IV) oxidation by ozone and enhance or slow metal-catalyzed S(IV) autooxidation rates in some periods. These effects were found to be only of minor importance, however, as H2O2 was the dominant S(IV) oxidant most of the time. | |
| dc.format.medium | born digital | |
| dc.format.medium | doctoral dissertations | |
| dc.identifier | SHEN_colostate_0053A_10291.pdf | |
| dc.identifier.uri | http://hdl.handle.net/10217/50158 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2000-2019 | |
| dc.rights | Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. | |
| dc.subject | aqueous phase oxidation | |
| dc.subject | China | |
| dc.subject | clouds | |
| dc.subject | Mt. Tai | |
| dc.subject | sulfate | |
| dc.subject | sulfur dioxide | |
| dc.title | Aqueous phase sulfate production in clouds at Mt. Tai in eastern China | |
| dc.type | Text | |
| dcterms.rights.dpla | This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). | |
| thesis.degree.discipline | Atmospheric Science | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) |
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