Atmospheric Chemistry Division National Center for Atmospheric Research

1
IMPACTS OF SECONDARY ORGANICS ON THE EVOLUTION OF
CLIMATE-RELEVANT AEROSOL PROPERTIES DURING
LAGRANGIAN PLUME EXPERIMENTS
VOC ? SOA ? wo, S
Sasha Madronich ACD/NCAR, Boulder, Colorado USA
PNNL, 20 October 2004
2
CLIMATE EFFECTS OF ORGANIC AEROSOLS

• Open circles new estimates based on measured
  aerosol ratios of carbonyl/carbon/total mass
• Solid symbols previously published estimates
• The gray region indicates the large uncertainty
  associated with the indirect effect of organic
  aerosol

Maria et al., Science, 306, 1921-1924, 10 Dec.
2004.
3
NON-REFRACTORY AEROSOLS IN MÉXICO CITY MCMA2003
field campaign, Aerosol Mass Spectrometer (AMS)
courtesy Jose Jiménez, U. of Colorado
4
ORIGIN OF SOA?Mexico City gas phase outlfow,
initial conditions 1.7 ppmC, 80 ppb NOx
S. Madronich, NCAR Master Mechanism, 2003
(http//mirage-mex.acd.ucar.edu)
5
SOA FORMATION ISSUES

• SOA formed by highly functionalized gas phase
  intermediates of VOC oxidation
• Current gas phase mechanisms (even master
  mechanisms) focus on oxidants, and do not
  represent accurately these VOC intermediates
• Empirical yields from smog chambers
• Little information about chemical identity
• Uncertain optical and physical properties

• Brute force approach Develop fully explicit
  mechanisms for VOC oxidation

6
stack
Radical ?
VOC1 VOC2 . VOCn
yes
no
C-H ?
RO2 ?
CC ?
RCO3 ?
-C(O)H or CC ?
RO ?
Chromophores ?
CO(OONO2)?
Treat next species in the stack
7
1st generation products
Parent (primary) species
VOCoxidant chemistry
VOC
OH NO3
O3 hn
HO2, NO, (RO2)
Peroxy (RO2) chemistry
NO3, (RO2)
NO
Alkoxy (RO) chemistry
O2
8
ATMOSPHERIC OXIDATION OF HYDROCARBONSFully
explicit gas phase chemistry
Aumont , Laval, and Madronich, accepted in ACPD,
2004
9
CARBON BUDGET Fully explicit chemistry of
n-heptane
Aumont , Laval, and Madronich, accepted in ACPD,
2004
10
Systematic Mechanism Reduction
Laval, Aumont , and Madronich, accepted in ACPD,
2004
11
WORK PLAN

• Objective 1 Development of an Explicit
  Secondary Organic Gas/Aerosol Model
• Task 1 Update the explicit mechanisms with
  available laboratory data, with special emphasis
  on aromatic oxidation.
• Task 2 Compute vapor pressures, solubility and
  activity coefficients for all species.
• Task 3 Couple the explicit MM organic gas
  mechanism chemistry into the MOSAIC aerosol
  module.
• Objective 2 Application of the explicit
  gas-aerosol model to the design and
  interpretation of field observations
• Task 4 Lagrangian simulations of the temporal
  evolution of gas and aerosol organic composition.
• Task 5 Lagrangian simulations the temporal
  evolution of climate-relevant aerosol properties
  such as soluble organic fraction, hygroscopicity,
  and absorption and scattering coefficients.
• Objective 3 Sensitivity studies and development
  of a simplified model for secondary organic
  gas/aerosols.
• Task 6 Sensitivity studies to identify key
  species and reactions over a wide range of
  realistic conditions.
• Task 7 Comparison with existing SOA models to
  identify key differences from the explicit model.
• Task 8 Development and evaluation of a
  semi-explicit chemical scheme for implementation
  in three-dimensional chemistry-transport models.

12
DELIVERABLES

• Fully explicit gas-phase hydrocarbon mechanism
• Repository of measured and estimated kinetic,
  mechanistic, thermodynamic, and spectroscopic
  data
• Benchmark for evaluating smaller mechanisms
• Fully explicit coupled gas-aerosol mechanism
• Predict chemical, physical, and optical
  properties
• Identification of key measurables (lab, field) in
  gas and aerosol phases
• Process hypothesis testing
• Emission source signatures
• Photochemical clocks
• Guidance to instrument development
• Systematic development and evaluation of
  gas-aerosol mechanisms for use in 3D models

13
COLLABORATORS

• Julia Lee-Taylor (NCAR/ACD), Project Scientist
• --------------------------------------------------
  -----------------
• Geoff Tyndall and John Orlando (NCAR/ACD)
  laboratory measurements
• Bernard Aumont (U. Paris) gas phase model
• Rahul Zaveri (DOE/PNNL) aerosol model

14
(No Transcript)
15
REACTIVE NITROGEN BUDGET Fully explicit
n-heptane chemistry
Aumont , Laval, and Madronich, accepted in ACPD,
2004