Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime
<p>Atmospheric aqueous chemistry can have profound effects on our environment. The importance of chemistry within the atmospheric aqueous phase started gaining widespread attention in the 1970s as there was growing concern over the negative impacts on ecosystem health from acid deposition. Res...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/1619/2023/acp-23-1619-2023.pdf |
| _version_ | 1811176888502059008 |
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| author | C. E. Lawrence P. Casson R. Brandt J. J. Schwab J. E. Dukett P. Snyder E. Yerger D. Kelting T. C. VandenBoer S. Lance |
| author_facet | C. E. Lawrence P. Casson R. Brandt J. J. Schwab J. E. Dukett P. Snyder E. Yerger D. Kelting T. C. VandenBoer S. Lance |
| author_sort | C. E. Lawrence |
| collection | DOAJ |
| description | <p>Atmospheric aqueous chemistry can have profound effects on our environment. The importance of chemistry within the atmospheric aqueous phase started gaining widespread attention in the 1970s as there was growing concern over the negative impacts on ecosystem health from acid deposition. Research at mountaintop observatories including Whiteface Mountain (WFM) showed that gas phase sulfur dioxide emissions react in cloud droplets to form sulfuric acid, which also impacted air quality by increasing aerosol mass loadings. The current study updates the long-term trends in cloud water composition at WFM for the period 1994–2021, with special consideration given to samples that have traditionally been excluded from analysis due to inorganic charge imbalance. We emphasize three major findings: (1) a growing abundance of total organic carbon (TOC), with annual median concentrations more than doubling since measurements began in 2009, (2) a growing imbalance between the measured inorganic cations and anions, consistent with independent rain water observations, implying that a substantial fraction of anions are no longer being measured with the historical suite of measurements, and (3) a growing number of samples exhibiting greater ammonium concentrations than sulfate plus nitrate concentrations, which now routinely describes over one-third of samples. Organic acids are identified as the most likely candidates for the missing anions, since the measured inorganic ion imbalance correlates strongly with measured TOC concentrations. An “inferred cloud droplet pH” is introduced to estimate the pH of the vast majority of cloud droplets as they reside in the atmosphere using a simple method to account for the expected mixing state of calcium and magnesium containing particles. While the inferred cloud droplet pH closely matches the measured bulk cloud water pH during the early years of the cloud water monitoring program, a growing discrepancy is found over the latter half of the record. We interpret these observations as indicating a growing fraction of cloud droplet acidity that is no longer accounted for by the measured sulfate, nitrate and ammonium concentrations. Altogether, these observations indicate that the chemical system at WFM has shifted away from a system dominated by sulfate to a system controlled by base cations, reactive nitrogen species and organic compounds. Further research is required to understand the effects on air quality, climate and ecosystem health.</p> |
| first_indexed | 2024-04-10T19:59:09Z |
| format | Article |
| id | doaj.art-4ef4fb711d43471db6390f75844dafd8 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-10T19:59:09Z |
| publishDate | 2023-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-4ef4fb711d43471db6390f75844dafd82023-01-27T09:57:18ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242023-01-01231619163910.5194/acp-23-1619-2023Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regimeC. E. Lawrence0P. Casson1R. Brandt2J. J. Schwab3J. E. Dukett4P. Snyder5E. Yerger6D. Kelting7T. C. VandenBoer8S. Lance9Atmospheric Sciences Research Center (ASRC), University at Albany, SUNY ETEC building, 1220 Washington Ave, Albany NY 12226, USAAtmospheric Sciences Research Center (ASRC), University at Albany, SUNY ETEC building, 1220 Washington Ave, Albany NY 12226, USAAtmospheric Sciences Research Center (ASRC), University at Albany, SUNY ETEC building, 1220 Washington Ave, Albany NY 12226, USAAtmospheric Sciences Research Center (ASRC), University at Albany, SUNY ETEC building, 1220 Washington Ave, Albany NY 12226, USAAdirondack Lake Survey Corporation (ALSC), 1115 NYS Rt.86, P.O. Box 296, Ray Brook NY 12977, USAAdirondack Lake Survey Corporation (ALSC), 1115 NYS Rt.86, P.O. Box 296, Ray Brook NY 12977, USAPaul Smith's College Adirondack Watershed Institute (AWI), P.O. Box 265, Routes 86 and 30, Paul Smiths NY 12970, USAPaul Smith's College Adirondack Watershed Institute (AWI), P.O. Box 265, Routes 86 and 30, Paul Smiths NY 12970, USADepartment of Chemistry, York University, Toronto, Ontario, M3J 1P3, CanadaAtmospheric Sciences Research Center (ASRC), University at Albany, SUNY ETEC building, 1220 Washington Ave, Albany NY 12226, USA<p>Atmospheric aqueous chemistry can have profound effects on our environment. The importance of chemistry within the atmospheric aqueous phase started gaining widespread attention in the 1970s as there was growing concern over the negative impacts on ecosystem health from acid deposition. Research at mountaintop observatories including Whiteface Mountain (WFM) showed that gas phase sulfur dioxide emissions react in cloud droplets to form sulfuric acid, which also impacted air quality by increasing aerosol mass loadings. The current study updates the long-term trends in cloud water composition at WFM for the period 1994–2021, with special consideration given to samples that have traditionally been excluded from analysis due to inorganic charge imbalance. We emphasize three major findings: (1) a growing abundance of total organic carbon (TOC), with annual median concentrations more than doubling since measurements began in 2009, (2) a growing imbalance between the measured inorganic cations and anions, consistent with independent rain water observations, implying that a substantial fraction of anions are no longer being measured with the historical suite of measurements, and (3) a growing number of samples exhibiting greater ammonium concentrations than sulfate plus nitrate concentrations, which now routinely describes over one-third of samples. Organic acids are identified as the most likely candidates for the missing anions, since the measured inorganic ion imbalance correlates strongly with measured TOC concentrations. An “inferred cloud droplet pH” is introduced to estimate the pH of the vast majority of cloud droplets as they reside in the atmosphere using a simple method to account for the expected mixing state of calcium and magnesium containing particles. While the inferred cloud droplet pH closely matches the measured bulk cloud water pH during the early years of the cloud water monitoring program, a growing discrepancy is found over the latter half of the record. We interpret these observations as indicating a growing fraction of cloud droplet acidity that is no longer accounted for by the measured sulfate, nitrate and ammonium concentrations. Altogether, these observations indicate that the chemical system at WFM has shifted away from a system dominated by sulfate to a system controlled by base cations, reactive nitrogen species and organic compounds. Further research is required to understand the effects on air quality, climate and ecosystem health.</p>https://acp.copernicus.org/articles/23/1619/2023/acp-23-1619-2023.pdf |
| spellingShingle | C. E. Lawrence P. Casson R. Brandt J. J. Schwab J. E. Dukett P. Snyder E. Yerger D. Kelting T. C. VandenBoer S. Lance Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime Atmospheric Chemistry and Physics |
| title | Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime |
| title_full | Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime |
| title_fullStr | Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime |
| title_full_unstemmed | Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime |
| title_short | Long-term monitoring of cloud water chemistry at Whiteface Mountain: the emergence of a new chemical regime |
| title_sort | long term monitoring of cloud water chemistry at whiteface mountain the emergence of a new chemical regime |
| url | https://acp.copernicus.org/articles/23/1619/2023/acp-23-1619-2023.pdf |
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