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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

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SLIDE 1

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

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SLIDE 2

Where… City of

The Po valley

City of Bologna

Urban Background Measurement Station

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SLIDE 3

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, NOX, NH3

  • 3. Meteorological analisys:

Synoptic and local conditions

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SLIDE 4

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…

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SLIDE 5

Episode 1 28.1.2017 - 3.2.2017

Presence of a high on the south west…

Temperature Wind speed

…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.

Temperature Wind speed

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SLIDE 6

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.

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SLIDE 7

Bologna urban stations; 50 m.

PM10, PM2.5 e PM1 trends

1 - PM2.5 and PM10 increase, not PM1 2 - the increase of Appennine mountain stations (PM10); 600-1200 m. 2 - the increase of PM starts in the Apennine mountain stations, then in the Po valley

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SLIDE 8

PM2.5/PM10 PM1/PM2.5

Chemical analysis

  • 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.

NH4

+ (s) / NH3(g) NO3

  • (s) / NO(g) NO3
  • (s) / NO2(g)
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SLIDE 9

Chemical analysis

34% 29%

16th - 27th Jan

1% 25%

28th Jan - 2nd Feb, 2017

SIA* TC

34% 3% 55% 21%

PM during NO event PM during event

SIA*: Secondary Inorganic Aerosol TC Other ions Unknown

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SLIDE 10

During PM event:

Particle Number Concentration

PNC trend (0.28-10µm)

Aerosol Size Distribution 3-600 nm

During PM event:

  • NoUFPs increase like

PM2.5 mass

  • UFPs show a decrease

due to the increase of coarse particles (because of high values

  • f condensation sinks)

PM event PM no event

Diameter (nm) dN/dLogDp part/cm3

Aerosol Size Distribution (3-600nm)

UFP (Ultra Fine Particles) < 100 nm NoUFP: > 100 nm

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SLIDE 11
  • 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

  • n 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.

Episode 2: 16.2.2012 – 20.2.2012

  • 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
  • n 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.

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SLIDE 12

PM10, PM2.5, PM1 and Particle Number Concentration

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SLIDE 13

Chemical analysis

Concentration change (C day(n) – C day(n-1) ) PM2.5 chemical composition

70% 80% 90% 100% %Ammonium %Nitrate %Sulphate %Other_Ions %TotalCarbon %Unknown

PM2.5 (BO) PM2.5 (BO)

%Ammonium %Nitrate %Sulphate %Other Ions %TotalCarbon % Unknown

20 30 40 50

Ammonium Nitrate Sulphate Organic Carbon Elemental Carbon

PM2.5 (BO) PM2.5 (BO)

Ammonium Nitrate Sulphate Organic Carbon Elemental Carbon

Föhn PM max Rain

0% 10% 20% 30% 40% 50% 60%

01/02/2012 02/02/2012 03/02/2012 04/02/2012 05/02/2012 06/02/2012 07/02/2012 08/02/2012 09/02/2012 10/02/2012 11/02/2012 12/02/2012 13/02/2012 14/02/2012 15/02/2012 16/02/2012 17/02/2012 18/02/2012 19/02/2012 20/02/2012 21/02/2012 22/02/2012 23/02/2012 24/02/2012 25/02/2012 26/02/2012

Föhn PM max Rain

  • 40
  • 30
  • 20
  • 10

10 01/02/2012 02/02/2012 03/02/2012 04/02/2012 05/02/2012 06/02/2012 07/02/2012 08/02/2012 09/02/2012 10/02/2012 11/02/2012 12/02/2012 13/02/2012 14/02/2012 15/02/2012 16/02/2012 17/02/2012 18/02/2012 19/02/2012 20/02/2012 21/02/2012 22/02/2012 23/02/2012 24/02/2012 25/02/2012 26/02/2012

µgm-3

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SLIDE 14

Mass concentration average ‘PM’ events

Average

PM1-UB PM2.5-UB PM10-TR NO3

  • Other ions Levo** NO-UB OPC*

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 15 32 39 7.8 0.9 0.5 27 366 events 15 32 39 7.8 0.9 0.5 27 366 % increasing due to the PM events 10% 14% 11% (33% and 26%)1 (=) (=) 7% 14% % increasing during the PM events 50% 57% 51% 68% 37% 35% 37% 63%

* 280nm-10µm

**from October 2015

1(% on PM2.5 during events and no events)

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SLIDE 15
  • 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

Conclusions

  • 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