Find in Library

<p>2-Methoxyphenol (guaiacol) is derived from the lignin pyrolysis and taken as a potential tracer for wood smoke emissions. In this work, the effect of <span class="inline-formula">SO₂</span> at atmospheric levels (0–56&thinsp;ppbv) on secondary organic aerosol (SOA) formation and its oxidation state during guaiacol photooxidation was investigated in the presence of various inorganic seed particles (i.e., NaCl and <span class="inline-formula">(NH₄)₂SO₄</span>). Without <span class="inline-formula">SO₂</span> and seed particles, SOA yields ranged from (<span class="inline-formula">9.46±1.71</span>)&thinsp;% to (<span class="inline-formula">26.37±2.83</span>)&thinsp;% and could be well expressed by a one-product model. According to the ratio of the average gas-particle partitioning timescale (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mover accent="true"><mi mathvariant="italic">τ</mi><mo mathvariant="normal">‾</mo></mover><mrow><mi mathvariant="normal">g</mi><mo>-</mo><mi mathvariant="normal">p</mi></mrow></msub><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="27pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="c1f0715597d045e637f429235d9eea86"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-2687-2019-ie00001.svg" width="27pt" height="15pt" src="acp-19-2687-2019-ie00001.png"/></svg:svg></span></span> over the course of the experiment to the vapor wall deposition timescale (<span class="inline-formula"><i>τ</i>_g−w</span>), the determined SOA yields were underestimated by a factor of <span class="inline-formula">∼2</span>. The presence of <span class="inline-formula">SO₂</span> resulted in enhancing SOA yield by 14.04&thinsp;%–23.65&thinsp;%. With <span class="inline-formula">(NH₄)₂SO₄</span> and NaCl seed particles, SOA yield was enhanced by 23.07&thinsp;% and 29.57&thinsp;%, respectively, which further increased significantly to 29.78&thinsp;%–53.43&thinsp;% in the presence of <span class="inline-formula">SO₂</span>, suggesting that <span class="inline-formula">SO₂</span> and seed particles have a synergetic contribution to SOA formation. The decreasing trend of the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mover accent="true"><mi mathvariant="italic">τ</mi><mo mathvariant="normal">‾</mo></mover><mrow><mi mathvariant="normal">g</mi><mo>-</mo><mi mathvariant="normal">p</mi></mrow></msub><mo>/</mo><msub><mi mathvariant="italic">τ</mi><mrow><mi mathvariant="normal">g</mi><mo>-</mo><mi mathvariant="normal">w</mi></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="50pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="55a0081107ab58d88238bd5131f13a29"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-2687-2019-ie00002.svg" width="50pt" height="16pt" src="acp-19-2687-2019-ie00002.png"/></svg:svg></span></span> ratio in the presence of seed particles and <span class="inline-formula">SO₂</span> suggested that more SOA-forming vapors partitioned into the particle phase, consequently increasing SOA yields. It should be noted that <span class="inline-formula">SO₂</span> was found to be in favor of increasing the carbon oxidation state (OS<span class="inline-formula">_C</span>) of SOA, indicating that the functionalization or the partitioning of highly oxidized products into particles should be more dominant than the oligomerization. In addition, the average <span class="inline-formula">N∕C</span> ratio of SOA was 0.037, which revealed that <span class="inline-formula">NO_<i>x</i></span> participated in the photooxidation process, consequently leading to the formation of organic N-containing compounds. The experimental results demonstrate the importance of <span class="inline-formula">SO₂</span> on the formation processes of SOA and organic S-containing compounds and are also helpful to further understand SOA formation from the atmospheric photooxidation of guaiacol and its subsequent impacts on air quality and climate.</p>