Current Post: Professor of Environmental Sciences

Room Number: 2.37B

Telephone: 01603 593185 (+44 1603 593185)

Fax: 01603 591327 (+44 1603 591327)

Email: s.clegg@uea.ac.uk

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 http://www.aim.env.uea.ac.uk/aim/aim.php. 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.

 

Biography

After completing of 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.
 

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.

Click here for full list of publications since 2000