Find in Library

<p>SO<span class="inline-formula">₂</span> and NO<span class="inline-formula">₂</span> are the critical precursors in forming sulfate and nitrate in ambient particles. We studied the mechanism of sulfate and nitrate formation during the co-uptake of NO<span class="inline-formula">₂</span> and SO<span class="inline-formula">₂</span> into NaCl droplets at different RHs under irradiation and dark conditions. A significant formation of nitrate attributable to NO<span class="inline-formula">₂</span> hydrolysis was observed during the NO<span class="inline-formula">₂</span> uptake under all conditions, and its formation rate increases with decreasing RH. The averaged NO<span class="inline-formula">₂</span> uptake coefficient, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="italic">γ</mi><mrow class="chem"><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="9994a0145bf18567b5d51cd11b781e64"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00001.svg" width="24pt" height="12pt" src="acp-23-6113-2023-ie00001.png"/></svg:svg></span></span>, from the unary uptake of NO<span class="inline-formula">₂</span> into NaCl droplets under dark conditions is 1.6 <span class="inline-formula">×</span> 10<span class="inline-formula">⁻⁵</span>, 1.9 <span class="inline-formula">×</span> 10<span class="inline-formula">⁻⁵</span>, and 3.0 <span class="inline-formula">×</span> 10<span class="inline-formula">⁻⁵</span> at 80 %, 70 %, and 60 % RH, respectively. Chloride photolysis and nitrate photolysis play a crucial role in sulfate formation during the co-uptake. Nitrate photolysis generates reactive species (e.g., OH radicals, NO<span class="inline-formula">₂</span>, and N(III)) that directly react with S(IV) to produce sulfate. The OH radicals generated from nitrate photolysis can also react with chloride ions to form reactive chlorine species and then sulfate. To parameterize the role of nitrate photolysis and chloride photolysis in forming sulfate, the SO<span class="inline-formula">₂</span> uptake coefficient, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="italic">γ</mi><mrow class="chem"><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="7b9410df74d6fda480a64fc8606aaf92"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00002.svg" width="23pt" height="12pt" src="acp-23-6113-2023-ie00002.png"/></svg:svg></span></span>, as a function of the nitrate photolysis rate, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="da19ac2768e7dcd8b97125e02ffb8017"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00003.svg" width="25pt" height="16pt" src="acp-23-6113-2023-ie00003.png"/></svg:svg></span></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>j</mi><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="a1ec66b903008f20411aa0f52124fb6e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00004.svg" width="23pt" height="16pt" src="acp-23-6113-2023-ie00004.png"/></svg:svg></span></span> <span class="inline-formula">×</span> [NO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M26" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="d96e0e0e6a6172a7d34ac185b1d0a8a7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00005.svg" width="9pt" height="16pt" src="acp-23-6113-2023-ie00005.png"/></svg:svg></span></span>]), and chloride photolysis rate, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mrow class="chem"><msup><mi mathvariant="normal">Cl</mi><mo>-</mo></msup></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="c20a22d03150bc6a02a165a42d80bf4f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00006.svg" width="21pt" height="12pt" src="acp-23-6113-2023-ie00006.png"/></svg:svg></span></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>j</mi><mrow class="chem"><msup><mi mathvariant="normal">Cl</mi><mo>-</mo></msup></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="19pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="5a5e5821e30a4aa083481a712d7b2f61"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00007.svg" width="19pt" height="12pt" src="acp-23-6113-2023-ie00007.png"/></svg:svg></span></span> <span class="inline-formula">×</span> [Cl<span class="inline-formula">⁻</span>]), was derived as <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M31" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="italic">γ</mi><mrow class="chem"><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="80233142351d2e72f6461524fc3ad109"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00008.svg" width="23pt" height="12pt" src="acp-23-6113-2023-ie00008.png"/></svg:svg></span></span> <span class="inline-formula">=</span> 0.41 <span class="inline-formula">×</span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M34" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="b0783186d815e9fba508cdfddc2f7861"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00009.svg" width="25pt" height="16pt" src="acp-23-6113-2023-ie00009.png"/></svg:svg></span></span> <span class="inline-formula">+</span> 0.34 <span class="inline-formula">×</span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M37" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>P</mi><mrow class="chem"><msup><mi mathvariant="normal">Cl</mi><mo>-</mo></msup></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="6c8feedebb5852880e99969496449ecd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-6113-2023-ie00010.svg" width="21pt" height="12pt" src="acp-23-6113-2023-ie00010.png"/></svg:svg></span></span>. Our findings open up new perspectives on the formation of secondary aerosol from the combined effect of nitrate photolysis and chlorine chemistry.</p>