Aerosol Physicochemical Properties Breakout Group

Workshop SummaryMILAGRO science meeting

25 Oct. 2006

Part 1: Nuggets (i.e. preliminary findings)

Co-Chairs:Bety Cardenas, Tony Clarke, Jim Smith, Jose-Luis Jimenez

All C-130 Milagro Flight Tracks

Nuggets: Emissions/Sources• Lead a major component of PM2.5

– Pb, Zn, and Cl are high in PM2.5 particles at T0

– Pb is predominantly associated with SO42- particles at T0

– Plumes of almost 1 g m-3 of Pb at Tula

Nuggets: Evolution of Properties/Aging• While NOx/NOy going from 1 to 0.1 (aging), ratio of organics/CO

increases x10. Light absorption/CO increases x2. (G-1)• Increases continue for longer time scales (1-day, comparing to C-130). • Same effect comparing T0 and Tres Padres, but smaller presumably

because of shorter times.

Nuggets: Physical Properties• Internal mixing happens quickly (~ few hrs). • Fractal soot particles get coated and become spherical over the course

of the morning, J. Slowik, BC & ARI– Consistent observations with T0 and T1 (more fractal at T0 usually)

Nuggets: New Particle FormationRegarding measurements at T1 (McMurray et al.): - NPF occurred frequently, ion-induced nucleation not significant.

- Can infer particle sub 5-nm growth rates from charge distributions. - New particles varied proportionally to H2SO4.- Enhancement of both NH4+ and dimethylamine in new particles from

nucleation (10 nm). - NPF frequently evident at boundary between BL and free trop, also

boundaries of plumes.

C-130 - First airborne deployment of new FMPS (TSI) with 1Hz sizing from 7nm reveals details of nuclei distribution and evolution.

inversion

A. Clarke, V. Kapustin, S. Howell, J. Zhou, C. McNaughton, Y. Shinozuka University of Hawaii

Vertical profile

Aerosol Intercomparisons (AMS and light scattering)

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Fit to all: R2 = 0.85

(Fit to subset: R2 = 0.91)

Mass Scattering Efficiency = 3.5

• 3/10/06 MIRAGE Flight

•15 Second AMS PM1 mass compares well with PM1 Light Scattering

• Other flights show good

correlation as well

Outside City

DeCarlo, Dunlea, and Jimenez, CU

Clarke et al.-UH

Aerosol Chemistry 3/8/06

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HCN measured by Caltech

CO measured by NCAR For more see the Poster by

DeCarlo, Dunlea, and Jimenez, CU

Nuggets: Chemical Properties

• Most of (NH4)2SO4 particles are internally mixed with Si and K (TEM).

• Organics in particles at T0:– High proportion of oxygenated organics than primary– Oxygenated organics were less volatile than primary organics at T0

• Nitrate:– Rapid partitioning of NO3

- between gas and aerosol phase (from G-1). HNO3 equilibrium w/ particles changes w/ photochemical age.

– High nitrate in growing newly formed particles at T1.– Shift in NO3

- partitioning due to dilution between T0 and Pico Tres Padres

• Ca in coarse mode particles:– T1: Ca dominates PM2.5 – PM1 during dusty period up to March 21– PM coarse fraction at Tula is dominated by Ca. Many unidentified compounds

(60% of mass) in PM10.

– T0: Ca dust comes from Tula region.

• Higher concentrations of metals and Hg at T1 than T0. But total gaseous Hg higher at T0 than T1.

Nuggets: Hygroscopicity/CCN

• During new particle formation, particles activated at S=0.15 are smaller and less hygroscopic than at other times.

• S-classified particles are less hygroscopic than would be predicted.

• Hygroscopicity increases with age in Mexico City plume from C130 measurements.

• At T1 hygroscopicity increases at midday, coinciding with NPF events.

• CCN indicates high fraction of insoluble material in activated particles.

Effects of Ageing - Mexico City G-1 Obs. (L. Kleinman)Effects of Ageing - Mexico City G-1 Obs. (L. Kleinman)

Photochemical age = -Log(NOx/NOy)

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-100.0 -99.5 -99.0 -98.5Longitude

1.00.80.60.40.20.0Age = -Log ([NOx]/[NOy])

Fresh emissions over city. NOx/NOy near 1, "Age" = 0Aged pollutants over T1 and T2. NOx/NOy = 0.1, "Age" =1 (7h at OH = 107)

Ratio of Organic Aerosol (AMS) and Aerosol light absorption (PSAP) to CO will show effect of ageing on SOA and Specific Light Absorption

SOA, Light Absorption, ω0 & Composition

Kleinman, Springston, Senum, Lee, Wang, Nunnermacker, Daum, Weinstein-Lloyd, Hubbe, Ortega, Alexander, Jayne, Canagaratna

Dilution accompanies ageing

Ageing:Ageing:● Screen data to minimize non-urban sources● Screen data to minimize non-urban sources● Assume BC/CO emission ratio is constant● Assume BC/CO emission ratio is constant● Bin data by age, Calc. regression slopes vs. CO and 2 ● Bin data by age, Calc. regression slopes vs. CO and 2 σσ

For Age change from 0 to 1:

● Specific Light Absorption (absorption/BC) increases by 60% - lensing effect

● Organic Aerosol increases 8-fold – SOA production

As Age Increases:

● Aerosol mass and scattering (normalized to CO) increases ● Aerosol light absorption (normalized to CO) increases ● Light scattering wins, Single Scatter Albedo increases

Single Scatter AlbedoSingle Scatter Albedo

Age = 0.1 - 0.2

Nitrate

OrganicSulfateAmmonium

Age = 0.8 - 0.9

22.5 ug m-3 6.4 ug m-3

Aerosol CompositionAerosol Composition

● Organic and Sulfate fractions increase with Age

● Nitrate decreases as HNO3 evaporates

Part 2: Collaboration Ideas / Suggestions / Needs

Photo by C. McNaughton

Collaborations: General Issues• Need a data catalog for all measurements that exist (L. Kleinman).

• Important to compare the meteorological data at T1 between the different datasets available. (T. Castro).– There are some gaps, not clear yet whether there are

disagreements. Groups at T1 should be aware of this.

• How to merge the measurements of the aircraft and the surface sites? (G. Sosa)– Compare directly the aircraft measurements directly over the

urban area (R. Zaveri).– Use back-trajectories arising from MC and flag times the C-130

and DC-8 saw air from the city (T. Clarke).

• Jerome Fast & Ben de Foy have generated and will share many model products for meteorology. Some of them on the web (mce2.org),

Meteorological Overview of Meteorological Overview of MILAGROMILAGRO

Jerome D. Fast, Pacific Northwest National LaboratoryJerome D. Fast, Pacific Northwest National Laboratory

1)1)prior to Norte #1:prior to Norte #1: mostly sunny, dry mostly sunny, dry2)2)Norte #1 - #3:Norte #1 - #3: increased humidity, increased humidity,

cloudiness, and afternoon convectioncloudiness, and afternoon convection3)3)after Norte #3:after Norte #3: further increase in further increase in

humidity, cloudiness, afternoon humidity, cloudiness, afternoon convection, and showersconvection, and showers

Objective:Objective: Provide the meteorological context that affects the Provide the meteorological context that affects the transport, mixing, transformation, and fate of trace gases and transport, mixing, transformation, and fate of trace gases and particulates in the vicinity of Mexico.particulates in the vicinity of Mexico.

meteorological overview paper now on-line in MILAGRO special issue of ACPDmeteorological overview paper now on-line in MILAGRO special issue of ACPD

three cold surges affected local and regional meteorology (3rd three cold surges affected local and regional meteorology (3rd strongest) over the central Mexican plateaustrongest) over the central Mexican plateau

analyzed wide range of MILAGRO field measurements to divide field analyzed wide range of MILAGRO field measurements to divide field campaign into 3 meteorological regimescampaign into 3 meteorological regimes

Identified periods favorable for Identified periods favorable for pollutant transport from Mexico pollutant transport from Mexico City towards T1/T2 downwind City towards T1/T2 downwind sampling sites and the Gulf of sampling sites and the Gulf of Mexico (gray shading) - more Mexico (gray shading) - more detailed trajectory analyses to detailed trajectory analyses to

followfollow

GOES Aerosol and Smoke Product (GASP)

Predicted AOD Predicted Radiation & AOD

Observed AOD 21 UTC 19 March

cloud extent

aerosol transport

Grid 1: x=22.5 km

Grid 3: x=2.5 km

peak AOD ~ 1.4

T1

T2

0.1

peak AOD ~0.6

shortwave radiation reduced by as much as 100 W m-2

primarily from biomass burning plumes on this day

simulation without high-resolution domains (x=2.5 and x=7.5 km) results in AOD lower than observed over

both central Mexico and downwind over Gulf of Mexico

Local and Regional Modeling of Local and Regional Modeling of Particulates and Aerosol Radiative Particulates and Aerosol Radiative

ForcingForcingJerome D. Fast, Pacific Northwest National LaboratoryJerome D. Fast, Pacific Northwest National Laboratory

Objective:Objective: Use fully-coupled meteorological-chemical-aerosol model Use fully-coupled meteorological-chemical-aerosol model (WRF-chem) and measurements from a wide range of platforms (surface, (WRF-chem) and measurements from a wide range of platforms (surface, aircraft, satellite) to examine particulate evolution and aerosol radiative aircraft, satellite) to examine particulate evolution and aerosol radiative forcing over Mexico.forcing over Mexico.

Collab: Emissions / Sources• Need chemical characterization of various sources for CMB

analysis. Elizabeth Vega, IMP.

Collab: Evolution of Properties • Issue of “clocks” for evolution was discussed in detail in aerosol

optics & radiation session. It is important for that group, to correlate optical evolution with physico-chemical properties evolution.– Needs collaboration between these two groups

Collab: Physical Properties• Help on validating and interpreting RAMA network’s new PM2.5 measurements (TEOM, Beta,

etc.). B. Cardenas, CENICA.

• Need information relating to volatilization of aerosols entering aircraft. (eg. ammonium nitrate?) T. Clarke, Hawaii.

• Many groups performed various microscopy techniques, good opportunity to compare & collaborate. B. Cardenas, CENICA.

Collab: Chemical Properties• Interest in collaborations investigating:

– PAHs (G. Mejia / Marr / Gaffney / Jimenez)– Metals (Sosa / Onasch / Salcedo / Laskin) – Organic nitrates (Gaffney/Jimenez)– Organosulfates (Jimenez)– Amines (Moffet / Jimenez)– Oxalic acid (Moffet)– Nitrate in nanoparticles (J. Smith)– U, Th, and K in filters (E. Herrera)– Size-resolved composition (Mamani / Castro / Laskin / Sosa /

Onasch / Jimenez)• Multiple groups are going to investigate SOA formation rates and

yields, need to collaborate across time scales. (Kleinman, DeCarlo, Volkamer, Worsnop, Jimenez, etc.)

• Relative importance of burning in urban emissions and concentrations (POA and SOA) (many groups)

• Relative importance of dust vs. fine particles (J. Dibb)

Collab: New Particle Formation• Comparisons between ground and aircraft for NPF would be very

useful, not usually done. – P. McMurry & Tony Clarke will collaborate on this.

• Comparisons between ground sites on dynamics of NPF are possible– Most extensive data at T1 (McMurry / Smith), also at Pico Tres

Padres (Worsnop) and T0 (Jimenez)– Mexico City had “tomato events” instead of “banana events” (P.

McMurry)

Collaborations: Satellites

• Need aerosol data to study how well and how far can MC plume be detected from satellites, and on which conditions this depends. Also trying to classify particle types. Summary of morning discussion from S. Massie, NCAR.

Collaborations: Models

• Need gas and particle data to compare with model output (R. Zaveri)

List of topics and number of proposed papers

• Emissions / Sources (3)• Physical properties (12)• Chemical properties (23)• Hygroscopicity & CCN (6)• Evolution of properties (9)• New Particle Formation (5)• Models (2)• Satellites (0)• Health effects (6)