# Presentation: 077684

## VOC   SOA    o, S

**IMPACTS OF SECONDARY ORGANICS ON THE EVOLUTION OF CLIMATE-RELEVANT AEROSOL PROPERTIES DURING LAGRANGIAN PLUME EXPERIMENTS**

- Sasha Madronich
- ACD/NCAR, Boulder, Colorado USA

*PNNL, 20 October 2004*

**VOC ********  SOA  ********  ********o,**** S**

## 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.*

## NON-REFRACTORY AEROSOLS IN MÉXICO CITY MCMA2003 field campaign, Aerosol Mass Spectrometer (AMS) 

*courtesy Jose Jiménez, U. of Colorado*

## 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)*

## 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

## Radical ?

- VOC1
- VOC2
- .......
- VOCn

**stack**

- no

- CO(OONO2)?

- C-H ?

- C=C ?

- -C(O)H
- or
- C=C ?

- Chromophores ?

- yes

- RO ?

- RO2 ?

- RCO3 ?

**Notes:**
Ajout également de la chimie inorganique et cycliques et aromatiques

## 1st generation 

**products**

**VOC+oxidant **
**chemistry**

**Peroxy (RO****2****)**
**chemistry**

**Alkoxy (RO)**
**chemistry**

- NO3,
- (RO2)

- O2

- HO2, NO, (RO2)

**Parent (primary) **
**species**

- O3
-  h

- OH
- NO3

- NO

**VOC**

## ATMOSPHERIC OXIDATION OF HYDROCARBONSFully explicit gas phase chemistry

*Aumont , Laval, and Madronich, accepted in ACPD, 2004*

## CARBON BUDGET

**CARBON BUDGET**
- Fully explicit chemistry of n-heptane

*Aumont , Laval, and Madronich, accepted in ACPD, 2004*

## Systematic Mechanism Reduction

*Laval, Aumont , and Madronich, accepted in ACPD, 2004*

## 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.*

## 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

## 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

## Slide 14

## REACTIVE NITROGEN BUDGET Fully explicit n-heptane chemistry

*Aumont , Laval, and Madronich, accepted in ACPD, 2004*