Aerosol acute events in Po valley, northern Italy: analysis of the chemical and numerical composition versus meteorological conditions conditions Vanes Poluzzi Arianna Trentini, Dimitri Bacco, Marco Deserti, Claudia Zigola, Giuseppe Mucci Arpae - Agency for Prevention, Environment and Energy of Emilia-Romagna Region 10th International Conference on Urban Climatology/14th Symposium of the Urban Environment 6-10 august 2018, New York, NY
Where… The Po valley City of City of Bologna Urban Background Measurement Station
Analysis 1. Period of study: 15 November 2011- 15 November 2017 2. Pollutants considered: Particulate matter: PM1, PM2.5, PM10 Particulate matter: PM1, PM2.5, PM10 PM2.5 Chemical analysis: EC/OC, main ions, BC, levoglucosan Particle number concentration and ASD (3nm-10µm) Gases: NO, NO X , NH 3 3. Meteorological analisys: Synoptic and local conditions
Defining the acute events: 1) 50 µgm -3 of PM2.5 ≥ 5 consecutive days 2) 50 µgm -3 of PM2.5 ≥ 3 consecutive days, in - at least - one of them with concentration ≥ 75 µgm -3 Results: 6 years of measurements � � 16 PM events; duration: from 3 to 9 days � � (all the events are in winter – December, January and February, only two in March and October) Following, two examples of event types are discussed…
Episode 1 28.1.2017 - 3.2.2017 Presence of a high on the south west… Wind speed Wind speed Temperature Temperature …then a mass of hot air climbing over the Apennines slips on the coldest underlying, causing a further crushing and compacting the layers of thermal inversion towards the ground. Moreover the presence of persistent cloud cover inhibits the thermal mixing of the atmosphere, further reducing the mixing height.
28.1.2017 – 3.2.2017 (m) H (m) …finally the transit of one series of weak depression waves allow a complete replacement of the mass of air, initially in the territory north of the Po river, and later in the whole basin.
PM10, PM2.5 e PM1 trends Bologna urban stations; 50 m. 1 - PM2.5 and PM10 increase, not PM1 2 - the increase of 2 - the increase of PM starts in the Apennine mountain Appennine mountain stations (PM10); 600-1200 m. stations, then in the Po valley
Chemical analysis PM2.5/PM10 PM1/PM2.5 - Increase of PM2.5 fraction, containing secondary species. - Decrease of combustion sources tracers (levoglucosan and black carbon). - Increase of ratio solid/gas of secondary inorganic species . + - - NH 4 (s) / NH 3(g) NO 3 (s) / NO (g) NO 3 (s) / NO 2(g)
Chemical analysis 16 th - 27 th Jan 28 th Jan - 2 nd Feb, 2017 25% 29% 1% 34% SIA* TC TC Other ions 55% Unknown 21% 3% 34% PM during NO event PM during event SIA*: Secondary Inorganic Aerosol
Particle Number Concentration PNC trend (0.28-10µm) During PM event: During PM event: Aerosol Size Distribution (3-600nm) - NoUFPs increase like part/cm3 Aerosol Size PM2.5 mass Distribution PM event - UFPs show a decrease PM no event due to the increase of dN/dLogDp 3-600 nm coarse particles (because of high values of condensation sinks) UFP (Ultra Fine Particles) < 100 nm Diameter (nm) NoUFP: > 100 nm
Episode 2: 16.2.2012 – 20.2.2012 From the beginning of february many inches of snow felt onto the southern Po • valley (in particular the east part of the south) and the Northern Apennines. The temperatures@850 hPa remain below 0°C until 16.2, then the polar vortex • recomposes and the Azorres high expand toward east entering in Europe. In this contest the simulatneous presence of the anticyclone and a new drop of cold air on the Balcans favoured phenomena of föhn from the Alps to the Po valley causing the snow melting starting from the western and northern part of the South Po valley. This complicated situation produced the effect to free a lot of nitrogen oxides • trapped into the snow [1,2,3] which are responsible of the formation of SIA and high peaks of PM . In the north part of the valley, with no snow • on the ground, spreading manure was permitted. This meant an increase of ammonia concentration in atmosphere. [1]: Bock J., Jacobi H.W., J. Phys. Chem. A , 114, 1790-1796, 2010; [2]: Helmig D., Seok B., Williams M.W., Hueber J., Sanford R., Biogeochemistry , 95, 115-130, 2009; [3]: Stanier C., Singh A., Adamski W., Baek J., Caughey M., Carmicheal G., Edgerton E., Kenski D., Koerber M., Oleson J., Rohlf T., Lee S.R., Riemer N., Shaw S., Sousan S., Spak S.N., Atmos. Chem. Phys., 12 11037-11056, 2012.
PM10, PM2.5, PM1 and Particle Number Concentration
%Unknown 26/02/2012 25/02/2012 24/02/2012 PM2.5 chemical composition % Unknown 23/02/2012 Rain %Sulphate PM max %TotalCarbon 22/02/2012 21/02/2012 20/02/2012 19/02/2012 18/02/2012 17/02/2012 %TotalCarbon %Other_Ions 16/02/2012 Föhn 15/02/2012 %Nitrate 14/02/2012 13/02/2012 12/02/2012 11/02/2012 %Sulphate 10/02/2012 %Ammonium 09/02/2012 %Other Ions 08/02/2012 07/02/2012 PM2.5 (BO) Chemical analysis %Nitrate 06/02/2012 PM2.5 (BO) 05/02/2012 04/02/2012 03/02/2012 %Ammonium 02/02/2012 01/02/2012 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 26/02/2012 Elemental Carbon 25/02/2012 Concentration change (C day(n) – C day(n-1) ) 24/02/2012 23/02/2012 Rain PM max 22/02/2012 21/02/2012 Nitrate Sulphate Elemental Carbon 20/02/2012 19/02/2012 Organic Carbon 18/02/2012 17/02/2012 16/02/2012 15/02/2012 Föhn 14/02/2012 13/02/2012 Sulphate Organic Carbon 12/02/2012 11/02/2012 10/02/2012 Ammonium 09/02/2012 08/02/2012 Nitrate 07/02/2012 06/02/2012 PM2.5 (BO) 05/02/2012 PM2.5 (BO) 04/02/2012 Ammonium 03/02/2012 02/02/2012 01/02/2012 50 40 30 20 10 0 -10 -20 -30 -40 µgm-3
Mass concentration average ‘PM’ events PM1-UB PM2.5-UB PM10-TR NO 3 - Other ions Levo** NO-UB OPC* Average Events 31 75 81 24.8 1.5 0.8 42 910 Winter 17 37 44 9.6 1 0.6 29 425 Winter without events events 15 15 32 32 39 39 7.8 7.8 0.9 0.9 0.5 0.5 27 27 366 366 (33% and % increasing due to 10% 14% 11% (=) (=) 7% 14% 26%) 1 the PM events % increasing during 50% 57% 51% 68% 37% 35% 37% 63% the PM events * 280nm-10µm 1 (% on PM2.5 during events and no events) **from October 2015
Conclusions - 16 events in 6 years - 15 similar to Episode 1 - in 3 or 4 of the 15 events there was a contribution of saharan dust to PM level - only 1 like Episode 2 - only 1 like Episode 2 In the future, due to the probable changes of the General Circulation, episodes like 1 could increase in number during wintertime in the Po valley, producing a general increase of aerosol acute events vpoluzzi@arpae.it
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