Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station
<p>A study of the stable carbon isotope ratios (<span class="inline-formula"><i>δ</i><sup>13</sup>C</span>) of total carbon (TC) and the nitrogen isotope ratios (<span class="inline-formula"><i>δ</i><sup>15</sup...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/3463/2019/acp-19-3463-2019.pdf |
| Summary: | <p>A study of the stable carbon isotope ratios (<span class="inline-formula"><i>δ</i><sup>13</sup>C</span>) of total carbon (TC) and the nitrogen isotope ratios (<span class="inline-formula"><i>δ</i><sup>15</sup>N</span>) of total
nitrogen (TN) was carried out for fine aerosol particles
(PM<span class="inline-formula"><sub>1</sub></span>) and was undertaken every 2 days with a 24 h sampling period at a rural
background site in Košetice (Central Europe) from 27 September 2013 to
9 August 2014 (<span class="inline-formula"><i>n</i>=146</span>). We found a seasonal pattern for both <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> and <span class="inline-formula"><i>δ</i><sup>15</sup>N</span>. The seasonal variation in <span class="inline-formula"><i>δ</i><sup>15</sup>N</span>
was characterized by lower values (average of <span class="inline-formula">13.1±4.5</span> ‰) in winter and higher values (<span class="inline-formula">25.0±1.6</span> ‰) in
summer. Autumn and spring were transition periods when the isotopic
composition gradually changed due to the changing sources and ambient
temperature. The seasonal variation in <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> was less pronounced
but more depleted in <span class="inline-formula"><sup>13</sup>C</span> in summer (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">27.8</mn><mo>±</mo><mn mathvariant="normal">0.4</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="e3b07b92bcdb01cfe5a8c2c470d9babd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00001.svg" width="58pt" height="10pt" src="acp-19-3463-2019-ie00001.png"/></svg:svg></span></span> ‰) as compared to winter (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">26.7</mn><mo>±</mo><mn mathvariant="normal">0.5</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="2025e72aedee8470a65076b55beca847"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00002.svg" width="58pt" height="10pt" src="acp-19-3463-2019-ie00002.png"/></svg:svg></span></span> ‰).</p>
<p>A comparative analysis with water-soluble ions, organic carbon, elemental
carbon, trace gases and meteorological parameters (mainly ambient
temperature) has shown major associations with the isotopic compositions,
which has provided greater knowledge and understanding of the corresponding processes. A comparison of <span class="inline-formula"><i>δ</i><sup>15</sup>N</span> with <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" 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="ecc3e6dd5af0ffb1da8bfbfcb16b8e8b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00003.svg" width="25pt" height="16pt" src="acp-19-3463-2019-ie00003.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="97c709e7ff43e05afce356dc3f53b497"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00004.svg" width="24pt" height="15pt" src="acp-19-3463-2019-ie00004.png"/></svg:svg></span></span> and organic nitrogen (OrgN)
revealed that although a higher content of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" 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="822fcc3376206f5298bc14405cca7022"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00005.svg" width="25pt" height="16pt" src="acp-19-3463-2019-ie00005.png"/></svg:svg></span></span> was associated
with a decrease in the <span class="inline-formula"><i>δ</i><sup>15</sup>N</span> of TN, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M19" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="b054521cc8a5d2267742c16e315b1d01"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00006.svg" width="24pt" height="15pt" src="acp-19-3463-2019-ie00006.png"/></svg:svg></span></span> and OrgN
caused increases. The highest concentrations of nitrate, mainly represented
by <span class="inline-formula">NH<sub>4</sub>NO<sub>3</sub></span> related to the emissions from biomass burning leading
to an average <span class="inline-formula"><i>δ</i><sup>15</sup>N</span> of TN (13.3 ‰) in
winter. During spring, the percentage of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" 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="23164037a5a41a281ec2bd2a6e11aeb2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00007.svg" width="25pt" height="16pt" src="acp-19-3463-2019-ie00007.png"/></svg:svg></span></span> in PM<span class="inline-formula"><sub>1</sub></span> decreased. An
enrichment of <span class="inline-formula"><sup>15</sup>N</span> was probably driven by the equilibrium exchange
between the gas and aerosol phases (<span class="inline-formula">NH<sub>3</sub></span>(g) <span class="inline-formula">↔</span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="0ee21626c7ea7176080e9ce12af1c86d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00008.svg" width="24pt" height="15pt" src="acp-19-3463-2019-ie00008.png"/></svg:svg></span></span>(p)), which is supported by the increased ambient temperature.
This equilibrium was suppressed in early summer when the molar ratios of
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup><mo>/</mo><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="ae696540f6947feedb28dca18d4713d1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-3463-2019-ie00009.svg" width="57pt" height="17pt" src="acp-19-3463-2019-ie00009.png"/></svg:svg></span></span> reached 2, and the nitrate partitioning in
aerosol was negligible due to the increased ambient temperature. Summertime
<span class="inline-formula"><i>δ</i><sup>15</sup>N</span> values were among the highest, suggesting the aging of
ammonium sulfate and OrgN aerosols. Such aged aerosols can be coated by
organics in which <span class="inline-formula"><sup>13</sup>C</span> enrichment takes place by the photooxidation
process. This result was supported by a positive correlation of <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> with ambient temperature and ozone, as observed in the summer
season.</p>
<p>During winter, we observed an event with the lowest <span class="inline-formula"><i>δ</i><sup>15</sup>N</span> and
highest <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> values. The winter event occurred in prevailing
southeast air masses. Although the higher <span class="inline-formula"><i>δ</i><sup>13</sup>C</span> values probably
originated from biomass-burning particles, the lowest <span class="inline-formula"><i>δ</i><sup>15</sup>N</span>
values were probably associated with agriculture emissions of <span class="inline-formula">NH<sub>3</sub></span> under
low-temperature conditions (< 0 <span class="inline-formula"><sup>∘</sup></span>C).</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |