Personal profile

Administrative Posts

  • Past editor of the School of Environmental Sciences Annual Report (4 years)
  • Science Faculty representative on the University IT Forum


After completing my Ph.D in 1986, I began my postdoctoral research in the Atmospheric and Oceanic Sciences group at Princeton University, working on the use of natural radionuclides and metals as tracers of the oceanic particle cycle. I continued this research as a Senior Scientific Officer at the Plymouth Marine Laboratory in the U.K. During my 3 years in Plymouth, I continued to work on the chemical thermodynamics of electrolytes, and in 1990 returned to the University of East Anglia to work on a new system of equations to model the chemical thermodynamics of aqueous solutions to the high concentrations found in atmospheric aerosols. I collaborated closely on this with the late Kenneth Pitzer of U.C. Berkeley. The first practical application of these equations was a demonstration that some types of polar stratospheric cloud (on which ozone depletion reactions occur) could be liquid rather than solid. This work was carried out in collaboration with the research group of Paul Crutzen at the Max Planck Institute in Mainz.

In 1993, I succeeded in winning the first of two consecutive 5 year Advanced Research Fellowships from the Natural Environment Research Council. These awards have allowed me to apply the chemical models I had developed to both stratospheric and tropospheric aerosols problems, to continue to advance understanding of the fundamental thermodynamics of the components of natural waters by measurement and in critical reviews of existing data, and to make available the chemical models I have developed for both research and teaching.

In 1998, I was appointed to the position of Reader in the School of Environmental Sciences. The following year I began a series of international collaborations in order to extend my research in atmospheric aerosol thermodynamics to include the organic components of aerosols. These began with projects at the Oak Ridge National Laboratory, and Electric Power Research Institute (Palo Alto), which have led to current studies with the U.S. Environmental Protection Agency and the California Institute of Technology aimed at improving regional scale air quality models. 

I became a Professor in 2007, and also have an appointment at the University of California at Davis, where I have a number of collaborative projects in the Air Quality Research Centre.

PhD Positions

Click here for current PhD opportunities in the School of Environmental Sciences. However, feel free to email me to discuss projects outside these areas and alternative sources of funding.


  • 1986-1987 Postdoctoral Researcher at Princeton University, USA.
  • 1987-1990 Senior Scientific Officer at the Plymouth Marine Laboratory, U.K.
  • 1990-1993 Leverhulme Trust Fellow, University of East Anglia
  • 1993-2003 NERC Advanced Research Fellow, University of East Anglia
  • 1998-2007 Reader, School of Environmental Sciences, Univesity of East Anglia
  • (2009-present Professional Researcher in the Air Quality Research Centre at the University of California, Davis)

Key Research Interests

Chemical thermodynamics of aqueous solutions; activity coefficient models and their application to problems in gas/aerosol partitioning in the atmosphere and air quality, brine chemistry, and solubility phenomena; predictive methods for physical properties of pure compounds (such as vapour pressures), and aqueous solutions; measurements of the properties of single aerosol particles using electrodynamic balances. 

Extended Aerosol Inorganics Model (E-AIM)

The thermodynamic and gas/aerosol partitioning models that are results of my work can be accessed and used interactively from the E-AIM site at Some of the data on which the models are based - for inorganic electrolyte mixtures, and for dicarboxylic acids - are tabulated on the site together with: (i) interactive vapour pressure and liquid density estimators for organic compounds, and (ii) a water activity calculator for aqueous dicarboxlylic acids.


Significant Publications

  • Clegg, S.L., Kleeman, M.J., Griffin, R.J. and Seinfeld, J.H. (2008) Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model - Part 2: Predictions of the vapour pressures of organic compounds. Atmospheric Chemistry and Physics, 8 (4), 1087-1103.
  • S. L. Clegg and J. H. Seinfeld (2006) Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. I. The acids as non-dissociating components. J. Phys. Chem. A 110, 5692-5717. DOI: 10.1021/jp056150j
  • S. L. Clegg and J. H. Seinfeld (2004) Improvement of the Zdanovskii-Stokes-Robinson model for mixtures containing solutes of different charge types. J. Phys. Chem. A 108, 1008-1017. DOI: 10.1021/jp030827q
  • A. S. Wexler and S. L. Clegg (2002) Atmospheric aerosol models for systems including the ions H+, NH4+, Na+, SO42-, NO3-, Cl-, Br-, and H2O. J. Geophys. Res.-Atmos. 107, D14, Art. No. 4207. DOI: 10.1029/2001JD000451
  • J. A. Rard, S. L. Clegg, and D. A. Palmer (2000) Isopiestic determination of the osmotic coefficients of Na2SO4(aq) at 25 and 50 degrees C, and representation with ion-interaction (Pitzer) and mole fraction thermodynamic models J. Solut. Chem. 29, 1-49.
  • D. R. Cocker, S. L. Clegg, R. C. Flagan and J. H. Seinfeld (2001) The effect of water on gas-particle partitioning of secondary organic aerosol. Part I: alpha-pinene/ozone system. Atmos. Environ. 35, 6049-6072. DOI:10.1016/S1352-2310(01)00404-6 
  • S. L. Clegg and J. M. Simonson (2001) A BET model of the thermodynamics of aqueous multicomponent solutions at extreme concentration. J. Chem. Thermodyn. 33, 1457-1472.

Publications: EPrints Digital Repository

Areas of Expertise

Atmospheric aerosol thermodynamics.

Teaching Interests

I teach postgraduate sessions on the preparation of tables and diagrams for scientific publications.

Expertise related to UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This person’s work contributes towards the following SDG(s):

  • SDG 12 - Responsible Consumption and Production

Collaborations and top research areas from the last five years

Recent external collaboration on country/territory level. Dive into details by clicking on the dots or