Title: Atmospheric Chemistry Division National Center for Atmospheric Research
1IMPACTS 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
2CLIMATE 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.
3NON-REFRACTORY AEROSOLS IN MÉXICO CITY MCMA2003
field campaign, Aerosol Mass Spectrometer (AMS)
courtesy Jose Jiménez, U. of Colorado
4ORIGIN 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)
5SOA 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
6stack
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
71st 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
8ATMOSPHERIC OXIDATION OF HYDROCARBONSFully
explicit gas phase chemistry
Aumont , Laval, and Madronich, accepted in ACPD,
2004
9CARBON BUDGET Fully explicit chemistry of
n-heptane
Aumont , Laval, and Madronich, accepted in ACPD,
2004
10Systematic Mechanism Reduction
Laval, Aumont , and Madronich, accepted in ACPD,
2004
11WORK 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.
12DELIVERABLES
- 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
13COLLABORATORS
- 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)
15REACTIVE NITROGEN BUDGET Fully explicit
n-heptane chemistry
Aumont , Laval, and Madronich, accepted in ACPD,
2004