2012 Progress Report: Investigating the Effects Of Atmospheric Aging on the Radiative Properties and Climate Impacts of Black Carbon Aerosol

EPA Grant Number: R835033
Title: Investigating the Effects Of Atmospheric Aging on the Radiative Properties and Climate Impacts of Black Carbon Aerosol
Investigators: Kroll, Jesse H. , Davidovits, Paul , Heald, Colette L.
Institution: Massachusetts Institute of Technology , Boston College
EPA Project Officer: Hunt, Sherri
Project Period: May 1, 2012 through April 30, 2015 (Extended to April 30, 2016)
Project Period Covered by this Report: May 1, 2012 through April 30,2013
Project Amount: $899,654
RFA: Black Carbon's Role In Global To Local Scale Climate And Air Quality (2010) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Climate Change , Air


Black carbon (BC) particles play a significant role in climate forcing, yet the effects of aging – atmospheric processes that affect the mass, size, shape, and chemical composition of aerosol particles – on their radiative properties are poorly constrained. This combined laboratory and modeling study will provide new insights into the detailed effects of atmospheric aging on the climate impacts of black carbon particles.

Progress Summary:

In Year 1 we made substantial progress towards meeting the goals of this project. Laboratory studies have focused on changes to the chemical composition of BC particles upon heterogeneous aging. A new technique for the sensitive characterization of BC coatings (SP-VUV-AMS) was demonstrated, and this technique was used to examine the chemical changes that organic species on the surface of BC particles undergo upon oxidation by O3 or OH. It also was shown that such heterogeneous oxidation reactions lead to significant changes in the CCN activity and shape of the BC particles, as does the condensation of secondary organic aerosol (SOA). Additional experiments included systematic studies of the mass spectra of different BC types, and a study of the light-absorbing properties of aged SOA (brown carbon, BrC).

Modeling efforts have focused on integrating a radiative transfer model (RRTMG) within the GEOS-Chem chemical transport model. This new combined model has been used to quantify and contrast the aerosol direct radiative forcing (DRF) with the aerosol direct radiative effect (DRE). The latter includes the contribution of all aerosol, including natural aerosol, on the radiative flux perturbation. In addition, the simulations of both BC and BrC within GEOS-Chem have been improved, using realistic aging timescales and optical properties based on literature studies, leading to improved agreement between model results and field measurements.

Future Activities:

A major focus of Year 2 is an experimental “intensive” (tentatively scheduled for November 2013) at MIT for the detailed examination of how optical and water-uptake properties of BC change with aging. The effects of heterogeneous aging and SOA condensation (as studied in Year 1) will be examined, though the focus will be on a wider range of atmospherically relevant aging processes. These include the secondary formation and condensation of sulfuric acid, ammonium sulfate, and ammonium nitrate, and mixtures of these different inorganic species with each other and with SOA. Additional efforts will go into construction of a multiplexed humidity control system, for the measurement of optical properties at multiple RH values; this will be used in a second intensive, to be carried out late in Year 2 or early in Year 3. For the modeling component of this work, we expect to complete our initial analysis of the impact of BC and BrC abundance, mixing state and optical properties on global radiative effects in the coming year. Next, we aim to develop an optical look-up table based on the observational constraints from the laboratory investigations and incorporate this into the global GEOS-Chem model carbonaceous aerosol scheme.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other project views: All 25 publications 9 publications in selected types All 9 journal articles
Type Citation Project Document Sources
Journal Article Lambe AT, Cappa CD, Massoli P, Onasch TB, Forestieri SD, Martin AT, Cummings MJ, Croasdale DR, Brune WH, Worsnop DR, Davidovits P. Relationship between oxidation level and optical properties of secondary organic aerosol. Environmental Science & Technology 2013;47(12):6349-6357. R835033 (2012)
R835033 (2013)
R835033 (2014)
R835033 (Final)
  • Abstract from PubMed
  • Full-text: ACPD-Full Text PDF
  • Abstract: ES&T-Abstract
  • Supplemental Keywords:

    black carbon, aerosol, light-absorbing carbon, brown carbon, direct radiative effects, climate, global modeling, optical properties, atmospheric aging

    Progress and Final Reports:

    Original Abstract
    2013 Progress Report
    2014 Progress Report
    Final Report