Multi-year chemical composition of the fine-aerosol fraction in Athens, Greece, with emphasis on the contribution of residential heating in wintertime

Abstract

<p><strong>Abstract.</strong> In an attempt to take effective action towards mitigating pollution episodes in Athens, precise knowledge of PM<span class="inline-formula">_2.5</span> composition and its sources is a prerequisite. Thus, a 2-year chemical composition dataset from aerosol samples collected in an urban background site in central Athens from December 2013 to March 2016 has been obtained and a positive matrix factorization (PMF) was applied in order to identify and apportion fine aerosols to their sources. A total of 850 aerosol samples were collected on a 12 to 24<span class="thinspace"></span>h basis and analyzed for major ions, trace elements, and organic and elemental carbon, allowing us to further assess the impact of residential heating as a source of air pollution over Athens.</p> <p>The ionic and carbonaceous components were found to constitute the major fraction of the PM<span class="inline-formula">_2.5</span> aerosol mass. The annual contribution of the ion mass (IM), particulate organic mass (POM), dust, elemental carbon (EC), and sea salt (SS) was calculated at 31<span class="thinspace"></span>%, 38<span class="thinspace"></span>%, 18<span class="thinspace"></span>%, 8<span class="thinspace"></span>%, and 3<span class="thinspace"></span>%, respectively, and exhibited considerable seasonal variation. In winter, the share of IM was estimated down to 23<span class="thinspace"></span>%, with POM<span class="thinspace"></span><span class="inline-formula">+</span> EC being the dominant component accounting for 52<span class="thinspace"></span>% of the PM<span class="inline-formula">_2.5</span> mass, while in summer, IM (42<span class="thinspace"></span>%) and carbonaceous aerosols (41<span class="thinspace"></span>%) contributed almost equally.</p> <p>Results from samples collected on a 12<span class="thinspace"></span>h basis (day and night) during the three intensive winter campaigns indicated the impact of heating on the levels of a series of compounds. Indeed, PM<span class="inline-formula">_2.5</span>, EC, POM, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" 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="a33a7d42b70ca1fe513ac92c5832eec2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-14371-2018-ie00001.svg" width="25pt" height="16pt" src="acp-18-14371-2018-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">C</mi><mn mathvariant="normal">2</mn></msub><msubsup><mi mathvariant="normal">O</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="35pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="234a93f52b3dd967457cde266cf07d36"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-14371-2018-ie00002.svg" width="35pt" height="17pt" src="acp-18-14371-2018-ie00002.png"/></svg:svg></span></span>, non sea salt (nss) <span class="inline-formula">K⁺</span> and selected trace metals including Cd and Pb were increased by up to a factor of 4 in the night compared to the day, highlighting the importance of heating on air quality in Athens. Furthermore, in order to better characterize wintertime aerosol sources and quantify the impact of biomass burning on PM<span class="inline-formula">_2.5</span> levels, source apportionment was performed. The data can be interpreted on the basis of six sources, namely biomass burning (31<span class="thinspace"></span>%), vehicular emissions (19<span class="thinspace"></span>%), heavy oil combustion (7<span class="thinspace"></span>%), regional secondary (21<span class="thinspace"></span>%), marine aerosols (9<span class="thinspace"></span>%), and dust particles (8<span class="thinspace"></span>%). Regarding night-to-day patterns their contributions shifted from 19<span class="thinspace"></span>%, 19<span class="thinspace"></span>%, 8<span class="thinspace"></span>%, 31<span class="thinspace"></span>%, 12<span class="thinspace"></span>%, and 10<span class="thinspace"></span>% of the PM<span class="inline-formula">_2.5</span>mass during day to 39<span class="thinspace"></span>%, 19<span class="thinspace"></span>%, 6<span class="thinspace"></span>%, 14<span class="thinspace"></span>%, 7<span class="thinspace"></span>%, and 7<span class="thinspace"></span>% during the night, underlining the significance of biomass burning as the main contributor to fine particle levels during nighttime in winter.</p>