Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes
<p>Depolarization ratio (<span class="inline-formula"><i>δ</i></span>) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by ground-based lidar observation systems. In th...
| Main Authors: | , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-01-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/219/2019/acp-19-219-2019.pdf |
| _version_ | 1818943552447578112 |
|---|---|
| author | X. Pan B. Ge Z. Wang Z. Wang Y. Tian Y. Tian H. Liu H. Liu L. Wei S. Yue S. Yue I. Uno H. Kobayashi T. Nishizawa A. Shimizu P. Fu P. Fu P. Fu Z. Wang Z. Wang Z. Wang |
| author_facet | X. Pan B. Ge Z. Wang Z. Wang Y. Tian Y. Tian H. Liu H. Liu L. Wei S. Yue S. Yue I. Uno H. Kobayashi T. Nishizawa A. Shimizu P. Fu P. Fu P. Fu Z. Wang Z. Wang Z. Wang |
| author_sort | X. Pan |
| collection | DOAJ |
| description | <p>Depolarization ratio (<span class="inline-formula"><i>δ</i></span>) of backscattered light is an
applicable parameter for distinguishing the sphericity of particles in real time, which
has been widely adopted by ground-based lidar observation systems. In this study, <span class="inline-formula"><i>δ</i></span> values of particles and chemical compositions in both PM<span class="inline-formula"><sub>2.5</sub></span> (aerodynamic diameter
less than 2.5 <span class="inline-formula">µ</span>m) and PM<span class="inline-formula"><sub>10</sub></span> (aerodynamic diameter less than
10 <span class="inline-formula">µ</span>m) were concurrently measured on the basis of a bench-top optical particle
counter with a polarization detection module (POPC) and a continuous dichotomous aerosol
chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban
site in Beijing megacity. In general, measured <span class="inline-formula"><i>δ</i></span> values depended on both size and
sphericity of the particles. During the observation period, mass concentrations of
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="8a872e45f44a0fc3c08e466e371cfb3a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-219-2019-ie00001.svg" width="25pt" height="16pt" src="acp-19-219-2019-ie00001.png"/></svg:svg></span></span> in PM<span class="inline-formula"><sub>2.5</sub></span> (<span class="inline-formula"><i>f</i>NO<sub>3</sub></span>) were about an order of
magnitude higher than that in PM<span class="inline-formula"><sub>2.5−10</sub></span> (<span class="inline-formula"><i>c</i>NO<sub>3</sub></span>) with a mean
<span class="inline-formula"><i>f</i>NO<sub>3</sub>∕<i>c</i>NO<sub>3</sub></span> ratio of <span class="inline-formula">14±10</span>. A relatively low
<span class="inline-formula"><i>f</i>NO<sub>3</sub>∕<i>c</i>NO<sub>3</sub></span> ratio (<span class="inline-formula">∼5</span>) was also observed under higher
relative humidity conditions, mostly due to heterogeneous processes and particles in the
coarse mode. We found that <span class="inline-formula"><i>δ</i></span> values of ambient particles in both PM<span class="inline-formula"><sub>2.5</sub></span> and
PM<span class="inline-formula"><sub>2.5−10</sub></span> obviously decreased as mass concentration of water-soluble species
increased at unfavorable meteorological conditions. This indicated that the morphology of
particles was changed as a result of water-absorbing processes. The particles
with optical size (Dp) of Dp <span class="inline-formula">=</span> 5 <span class="inline-formula">µ</span>m were used to represent mineral dust
particles, and its <span class="inline-formula"><i>δ</i></span> values (<span class="inline-formula"><i>δ</i><sub>Dp=5</sub></span>) decreased by 50 % as
the mass fraction of <span class="inline-formula"><i>c</i>NO<sub>3</sub></span> increased from 2 % to 8 % and
ambient relative humidity increased up to 80 %, suggesting that mineral dust
particles were likely to be spherical during humid pollution episodes. During the
observation, relative humidity inside the POPC measuring chamber was stable at <span class="inline-formula">34±2</span> %, lower than the ambient condition. Its influence on the morphology was estimated
to be limited and did not change our major conclusion. This study highlights the evident
alteration of non-sphericity of mineral dust particles during their transport owing to a
synergistic effect of both pollutant coatings and hygroscopic processes, which plays an
important role in the evaluation of its environmental effect.</p> |
| first_indexed | 2024-12-20T07:29:08Z |
| format | Article |
| id | doaj.art-b8a2b5b60d7e4d3e9604d79ed5606a62 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-20T07:29:08Z |
| publishDate | 2019-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-b8a2b5b60d7e4d3e9604d79ed5606a622022-12-21T19:48:28ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-01-011921923210.5194/acp-19-219-2019Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodesX. Pan0B. Ge1Z. Wang2Z. Wang3Y. Tian4Y. Tian5H. Liu6H. Liu7L. Wei8S. Yue9S. Yue10I. Uno11H. Kobayashi12T. Nishizawa13A. Shimizu14P. Fu15P. Fu16P. Fu17Z. Wang18Z. Wang19Z. Wang20State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaResearch Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, JapanState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaUniversity of Chinese Academy of Sciences, Beijing, 100049, ChinaState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaUniversity of Chinese Academy of Sciences, Beijing, 100049, ChinaState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaUniversity of Chinese Academy of Sciences, Beijing, 100049, ChinaResearch Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, JapanUniversity of Yamanashi, Yamanashi, 400–0016, JapanNational Institute for Environmental Studies, Ibaraki, 305-8506, JapanNational Institute for Environmental Studies, Ibaraki, 305-8506, JapanState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaUniversity of Chinese Academy of Sciences, Beijing, 100049, ChinaInstitute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, ChinaState Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, ChinaUniversity of Chinese Academy of Sciences, Beijing, 100049, ChinaCenter for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China<p>Depolarization ratio (<span class="inline-formula"><i>δ</i></span>) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by ground-based lidar observation systems. In this study, <span class="inline-formula"><i>δ</i></span> values of particles and chemical compositions in both PM<span class="inline-formula"><sub>2.5</sub></span> (aerodynamic diameter less than 2.5 <span class="inline-formula">µ</span>m) and PM<span class="inline-formula"><sub>10</sub></span> (aerodynamic diameter less than 10 <span class="inline-formula">µ</span>m) were concurrently measured on the basis of a bench-top optical particle counter with a polarization detection module (POPC) and a continuous dichotomous aerosol chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban site in Beijing megacity. In general, measured <span class="inline-formula"><i>δ</i></span> values depended on both size and sphericity of the particles. During the observation period, mass concentrations of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="8a872e45f44a0fc3c08e466e371cfb3a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-219-2019-ie00001.svg" width="25pt" height="16pt" src="acp-19-219-2019-ie00001.png"/></svg:svg></span></span> in PM<span class="inline-formula"><sub>2.5</sub></span> (<span class="inline-formula"><i>f</i>NO<sub>3</sub></span>) were about an order of magnitude higher than that in PM<span class="inline-formula"><sub>2.5−10</sub></span> (<span class="inline-formula"><i>c</i>NO<sub>3</sub></span>) with a mean <span class="inline-formula"><i>f</i>NO<sub>3</sub>∕<i>c</i>NO<sub>3</sub></span> ratio of <span class="inline-formula">14±10</span>. A relatively low <span class="inline-formula"><i>f</i>NO<sub>3</sub>∕<i>c</i>NO<sub>3</sub></span> ratio (<span class="inline-formula">∼5</span>) was also observed under higher relative humidity conditions, mostly due to heterogeneous processes and particles in the coarse mode. We found that <span class="inline-formula"><i>δ</i></span> values of ambient particles in both PM<span class="inline-formula"><sub>2.5</sub></span> and PM<span class="inline-formula"><sub>2.5−10</sub></span> obviously decreased as mass concentration of water-soluble species increased at unfavorable meteorological conditions. This indicated that the morphology of particles was changed as a result of water-absorbing processes. The particles with optical size (Dp) of Dp <span class="inline-formula">=</span> 5 <span class="inline-formula">µ</span>m were used to represent mineral dust particles, and its <span class="inline-formula"><i>δ</i></span> values (<span class="inline-formula"><i>δ</i><sub>Dp=5</sub></span>) decreased by 50 % as the mass fraction of <span class="inline-formula"><i>c</i>NO<sub>3</sub></span> increased from 2 % to 8 % and ambient relative humidity increased up to 80 %, suggesting that mineral dust particles were likely to be spherical during humid pollution episodes. During the observation, relative humidity inside the POPC measuring chamber was stable at <span class="inline-formula">34±2</span> %, lower than the ambient condition. Its influence on the morphology was estimated to be limited and did not change our major conclusion. This study highlights the evident alteration of non-sphericity of mineral dust particles during their transport owing to a synergistic effect of both pollutant coatings and hygroscopic processes, which plays an important role in the evaluation of its environmental effect.</p>https://www.atmos-chem-phys.net/19/219/2019/acp-19-219-2019.pdf |
| spellingShingle | X. Pan B. Ge Z. Wang Z. Wang Y. Tian Y. Tian H. Liu H. Liu L. Wei S. Yue S. Yue I. Uno H. Kobayashi T. Nishizawa A. Shimizu P. Fu P. Fu P. Fu Z. Wang Z. Wang Z. Wang Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes Atmospheric Chemistry and Physics |
| title | Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes |
| title_full | Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes |
| title_fullStr | Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes |
| title_full_unstemmed | Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes |
| title_short | Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes |
| title_sort | synergistic effect of water soluble species and relative humidity on morphological changes in aerosol particles in the beijing megacity during severe pollution episodes |
| url | https://www.atmos-chem-phys.net/19/219/2019/acp-19-219-2019.pdf |
| work_keys_str_mv | AT xpan synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT bge synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT zwang synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT zwang synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT ytian synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT ytian synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT hliu synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT hliu synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT lwei synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT syue synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT syue synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT iuno synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT hkobayashi synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT tnishizawa synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT ashimizu synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT pfu synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT pfu synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT pfu synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT zwang synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT zwang synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes AT zwang synergisticeffectofwatersolublespeciesandrelativehumidityonmorphologicalchangesinaerosolparticlesinthebeijingmegacityduringseverepollutionepisodes |