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<p>Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon (BrC) to the total particulate light absorption in the wavelength range of 370–950 nm (BrC<span class="inline-formula">_370–950</span>) and the particulate absorption Ångström exponents (AAE<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><mn mathvariant="normal">470</mn><mo>/</mo><mn mathvariant="normal">950</mn></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="00a71eee6b4eb5e19fb08c3fc9ca0516"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00001.svg" width="33pt" height="11pt" src="acp-24-3197-2024-ie00001.png"/></svg:svg></span></span>) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC<span class="inline-formula">_370–950</span> was estimated to be from 1 % to 21 % for wood log stoves and 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="57ee8123d9c9aefcf23d9c7f6463c158"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00002.svg" width="8pt" height="14pt" src="acp-24-3197-2024-ie00002.png"/></svg:svg></span></span> EC) and BrC<span class="inline-formula">_370–950</span> indicated that a one-unit increase in OC <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="073414a2b77546d8d5847ae97897d626"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00003.svg" width="8pt" height="14pt" src="acp-24-3197-2024-ie00003.png"/></svg:svg></span></span> EC corresponded to approximately a 14 % increase in BrC<span class="inline-formula">_370–950</span>. Additionally, BrC<span class="inline-formula">_370–950</span> was clearly influenced by the fuel moisture content and the combustion efficiency, while the effect of the combustion appliance type was less prominent. AAE<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><mn mathvariant="normal">470</mn><mo>/</mo><mn mathvariant="normal">950</mn></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="e245f1c8a93a39aef7656772febb694f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00004.svg" width="33pt" height="11pt" src="acp-24-3197-2024-ie00004.png"/></svg:svg></span></span> of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><mn mathvariant="normal">470</mn><mo>/</mo><mn mathvariant="normal">950</mn></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="d29c1db73a8715aeaf7da5df3330825a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00005.svg" width="33pt" height="11pt" src="acp-24-3197-2024-ie00005.png"/></svg:svg></span></span> and OC <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="165b352473919034209a9d51d0eaf41d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00006.svg" width="8pt" height="14pt" src="acp-24-3197-2024-ie00006.png"/></svg:svg></span></span> EC, an AAE<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><mn mathvariant="normal">470</mn><mo>/</mo><mn mathvariant="normal">950</mn></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="ee71790b6a619a268e962e93afb0b609"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00007.svg" width="33pt" height="11pt" src="acp-24-3197-2024-ie00007.png"/></svg:svg></span></span> close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><mn mathvariant="normal">470</mn><mo>/</mo><mn mathvariant="normal">950</mn></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="daffd81aab4af9cf74d3143c29df190c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00008.svg" width="33pt" height="11pt" src="acp-24-3197-2024-ie00008.png"/></svg:svg></span></span> of 1.02, with BrC contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC from residential wood combustion with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for northern European wood stove emissions with relatively high OC <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="539a58614ea8688159b8effbc6d3da8d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-3197-2024-ie00009.svg" width="8pt" height="14pt" src="acp-24-3197-2024-ie00009.png"/></svg:svg></span></span> EC ratios.</p>