Profile

Biography

I was appointed as a Lecturer in the Environment Department in November 2000 and promoted to senior lecturer in 2008. My research interests are in the general fields of atmospheric and indoor air chemistry. My work focuses on using detailed chemical models to try and understand the chemical processing that occurs both indoors and outdoors. Through gaining an understanding of such processes, abatement policies can be based on sound scientific principles. I am a member of the editorial board of Atmospheric Environment, as well as of the UK Indoor Environment Group Committee and an EU working Group on Reactive Indoor Air Chemistry.

Career

Research

Current projects

My major research activity is in the numerical modelling of atmospheric chemistry, both outdoors in the boundary layer, but also in the indoor environment. The outdoor modelling work is often in support of highly instrumented field campaigns, which have taken place in urban areas such as Birmingham and downwind of London in the UK, as well as more remote areas such as Cape Grim, Tasmania and Mace Head on the west coast of Eire. More recently, we have been involved in the OP3 project in Malaysia. During such field campaigns, the atmosphere is sampled by a number of ground-based and sometimes aircraft-based instruments, to determine the concentrations of many important atmospheric species.

The field measurements, carried out in conjunction with both national and international partners, provide a wide range of input data for the models. The models can then be used to gain insight into atmospheric chemistry processes and once validated, used to predict future events.

We currently work on a number of projects related to field campaigns, such as the NERC-funded TORCH (Tropospheric ORganic CHemistry Experiment) programme, which took place in July and August of 2003 at Writtle in Essex. Coincidentally, the south of England was subjected to an intense heat-wave during this period, with record temperatures of 38°C. The heat-wave was associated with high concentrations of atmospheric pollutants and it has been estimated that around 800 excess deaths were caused by the high concentrations of ozone and particulate matter (Stedman, J.R., Atmospheric Environment, 38, 1087-1090, 2004). The heat wave received much publicity at the time.

The TORCH campaign enabled us to model the complex chemistry that occurs in the atmosphere downwind of urban areas. In particular, we are interested in the key reactions driving the radical chemistry as an urban plume ages. Using our detailed chemical model, we have been able to reproduce the OH concentrations made by a dedicated instrument over most days of the campaign (Emmerson et al., 2007).

Further analysis has enabled us to learn much about chemical processing during such conditions and work in this area is still ongoing.

Using data from the NERC SOAPEX II (Southern Ocean Atmospheric Photochemistry EXperiment II) and NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) programmes, we have been able to investigate the chemistry of clean air in the marine boundary layer (see Sommariva et al., 2004, 2006; Haggerstone et al., 2005). Again, the emphasis is on understanding radical chemistry. In particular, we are investigating new ways to represent the heterogeneous loss of HO_X radicals in a chemical model. For instance, the figure below shows various model predictions of HO₂ and the measurements. With subsequently more detailed treatments of HO₂ loss onto aerosol surfaces in the model (from T1 to T4), the model predictions become much closer to the measured values (Haggerstone et al., 2005).

The project "Oxidant and particle photochemical processes above a South-East Asian tropical rain forest" (OP3) is a three year scientific research project funded by the Natural Environment Research Council, for the period from 1 October 2007 to 30 September 2010. The overall goal of the project is to provide a better understanding of the interactions that exist between natural forests and the Earth's climate system. It has the following specific objectives:

i. to understand how emissions of reactive trace gases from a tropical rain forest mediate the regional scale production and processing of oxidants and particles, and

ii. to better understand the impact of these processes on local, regional and global scale atmospheric composition, chemistry and climate.

The field elements of the project were based at the Bukit Atur Global Atmospheric Watch research station in Sabah, Malaysia and at the nearby Danum Valley Field Centre (the latter seen below from the research aircraft).

Measurements were made of emission rates of compounds from the forest canopy and of atmospheric chemical composition, both ground based and from the aircraft. Simon Malpass is a NERC-funded PhD student in my group, using these data in models that simulate the local chemistry to try and understand the atmospheric processing in this part of the world. As much of the region is currently being converted from native rainforest to palm oil plantations, it is essential that we try and understand what human perturbations can do to a natural environment such as this one.

My other research focus is on indoor air chemistry. Despite the fact that people in the developed world spend around 90% of their time indoors, there are no regulations for indoor air quality and relatively little is known about it. Most of the work in this area is driven by model predictions as there are relatively few indoor air measurements when compared to outdoors. My main contribution to this field to date has been to develop a new detailed chemical model for indoor air, using the expertise I have gained through my modelling work in the outdoor atmosphere (Carslaw, 2007). Unlike previous models for indoor air, it considers the chemical breakdown of each indoor species explicitly, rather than lumping species together, or working on a subset of the chemistry as has been the tendency in the past. More latterly, I have been adding the reactions that form particles in indoor environments.

The new model has produced some surprising results. The first is that despite the absence of sunlight indoors, there are still appreciable quantities of the OH radical indoors - comparable to outdoors at night-time or in winter, but about a factor of ten lower than summer outdoor concentrations.

The OH found indoors is produced largely through reactions of ozone with terpenes (found commonly in paints, fragrances, cleaning products and furnishing to name but a few). These reactions also produce fine particles indoors, which are a major concern for health. The particles indoors are predicted to contain nitrated and organic material and may adversely change the toxicological properties of the particles (e.g. see Oberdorster, G., Phil. Trans. R. Soc. Lond. A., 2000, 358, 2719-2740. Kavouras et al., EST, 1999, 33, 1028-1037).

In the coming months, the model will be used to elucidate further features of the chemical processing indoors.

Grants

Supervision

Current students

Recent students

Publications

Full publications list

Carslaw, N., S. Langer, P. Wolkoff, (2009), Where is the link between reactive indoor air chemistry and health effects?, in press in Atmospheric Environment.

Emmerson, K.M. and N. Carslaw, (2009), Night Time Radical Chemistry during the TORCH campaign, in press in Atmospheric Environment.

Jackson, L. S., N. Carslaw, D.C. Carslaw, and K.M. Emmerson, (2009), Modelling trends in OH radical concentrations using generalized additive models, Atmos. Chem. Phys., 9, 2021-2033.

Westmoreland, E.J., N. Carslaw, D.C. Carslaw, A. Gillah, and E. Bates, (2007), Analysis of air quality within a street canyon using statistical and dispersion modelling techniques, Atmospheric Environment, 41, 9195-9205.

Carslaw, D.C. and N. Carslaw, (2007), Detecting and characterising small changes in urban nitrogen dioxide concentrations, Atmospheric Environment, 41, 4723-4733.

Emmerson, K.M., N. Carslaw, D.C. Carslaw, J.D. Lee, G.McFiggans, W.J. Bloss, T. Gravestock, D.E. Heard, J. Hopkins, T. Ingham, M.J. Pilling, S.C. Smith, M. Jacobs, and P.S. Monks, (2007), Free Radical Modelling Studies during the UK TORCH Campaign in Summer 2003, Atmospheric Chemistry and Physics, 7, 167-181.

Carslaw, N. (2007), A new detailed chemical model for indoor air pollution, Atmospheric Environment, 41, 1164-1179.

Lee et al. (26 authors) (2006), Ozone photochemistry and elevated isoprene during the U.K. heat wave of August 2003, Atmospheric Environment, 40, 7598-7613.

Heard et al. (63 authors) (2006), The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002, Atmospheric Chemistry and Physics, 6, 2241-2272.

Harrison, R.M., J. Yin, R.M. Tilling, X. Cai, P.W. Seakins, J.R. Hopkins, D.L. Lansley, A.C. Lewis, M.C. Hunter, D.E. Heard, L. J. Carpenter, D.J. Creasey, J.D. Lee, M.J. Pilling, N. Carslaw, K.M. Emmerson, A. Redington, R.G. Derwent, D. Ryall, G. Mills and S.A. Penkett (2006), Measurement and modelling of air pollution and atmospheric chemistry in the U.K. west midlands conurbation: overview of the puma consortium project, Science of the Total Environment, 360, 5-25.

Sommariva, R., W.J. Bloss, N. Brough, N. Carslaw, M. Flynn, A.-L. Haggerstone, D.E. Heard, J.R. Hopkins, J.D. Lee, A.C. Lewis, G. McFiggins, P.S. Monks, S.A. Penkett, M.J. Pilling, J.M.C. Plane, K.A. Read, A. Saiz-Lopez, A.R. Rickard and P.I. Williams (2006), OH and HO₂ chemistry during NAMBLEX: roles of oxygenates, halogen oxides and heterogeneous uptake, Atmospheric Chemistry and Physics, 6, 1135-1153.

Carslaw, N. and P. Wolkoff, (2006) A new European initiative for indoor air pollution research, Indoor Air, 16, 4-6.

Emmerson, K.M., Carslaw, N., Carpenter, L.J., Heard, D.E., Lee, J.D., and Pilling, M.J., (2005): Urban Atmospheric Chemistry during the PUMA Campaign. 1: Comparison of Modelled OH and HO₂ Concentrations with Measurements, Journal of Atmospheric Chemistry, 52, 143-164

Emmerson, K.M., Carslaw, N., and Pilling, M.J., (2005): Urban Atmospheric Chemistry during the PUMA Campaign. 2. Radical budgets for OH, HO₂ and RO₂. Journal of Atmospheric Chemistry, 52, 165-183.

Haggerstone, A.-L., L.J. Carpenter, N. Carslaw and G. McFiggans (2005), Improved model predictions of HO2 with gas to particle mass transfer rates calculated using aerosol number size distributions, J. Geophys. Res., 110, D04303, doi:10.1029/2004JD005282.

Heard, D.E., L.J. Carpenter, D.J. Creasey, J.R. Hopkins, J.D. Lee, A.C. Lewis, M.J. Pilling, P.W. Seakins, N. Carslaw, and K.M. Emmerson (2004), Unexpectedly high levels of the hydroxyl radical in the winter urban troposphere, in press in Geophysical Research Letters , 31 (18): art. no. L18112.

Sommariva, R., A.-L. Haggerstone, L. J. Carpenter, N. Carslaw, D. J. Creasey, D. E. Heard, J. D. Lee, A. C. Lewis, M. J. Pilling, J. Zádor (2004), OH and HO₂ chemistry in clean marine air during SOAPEX-2, Atmos. Chem. Phys., 4, 839-856.

Carslaw N. (2003), Where next with indoor air measurements? Atmospheric Environment, 37, 5645-5646.

Carslaw N., Creasey D.J., D.E. Heard, P.J. Jacobs, J.D. Lee, A.C. Lewis, J.B. McQuaid, M.J. Pilling, P.S. Monks, and S.A. Penkett (2002), Modelling the concentrations of OH, HO₂ and RO₂ during the EASE97 campaign: 2. Comparison with measurements, J. Geophys. Res., 107, 10.1029/2001JD001568.

Ryall, D.B., R.G Derwent, A.J. Manning, A.L. Redington, J. Corden, W. Millington, P.G. Simmonds, S. O’Doherty, N. Carslaw and G.W. Fuller (2002), The origin of high particulate concentrations over the United Kingdom, March 2000, Atmos. Environ. 36, 1363-1378.

Salisbury G., A.R. Rickard, P.S. Monks, B.J. Allan, S. Bauguitte, S.A. Penkett, N. Carslaw, A.C. Lewis, D.J. Creasey, D.E. Heard, P.J. Jacobs, J.D. Lee and M.J. Pilling (2001), The production of peroxy radicals at night via reactions of ozone and the nitrate radical in the marine boundary layer, J. Geophys. Res., 106, 12669-12687.

Carslaw N., D.J. Creasey, D. Harrison, D.E. Heard, M.C. Hunter, P.J. Jacobs, M.E. Jenkin, J.D. Lee, A.C. Lewis, M.J. Pilling, S.M. Saunders, P.W. Seakins (2001), Modelling OH and HO₂ radicals in a forested region of north-western Greece, Atmos. Environ., 35, 4725-4737.

Carslaw N. and D.C. Carslaw (2001), The chemistry of urban areas, Surveys in Geophysics, 22, 31-53.

Lewis A.C., N. Carslaw, P.J. Marriott, R.M. Kinghorn, P. Morrison, A.L. Lee, K.D. Bartle and M.J. Pilling (2000), A larger pool of ozone-forming carbon compounds in urban atmospheres, Nature, 405, 778-781.

Carslaw N., N. Bell, A.C. Lewis, J.B. McQuaid and M.J. Pilling (2000), A detailed case study of isoprene chemistry during the EASE96 campaign, Atmos. Environ., 34, 2827-2836.

Carslaw N., P.J. Jacobs and M.J. Pilling (2000), Understanding radical chemistry in the marine boundary layer, Physics and Chemistry of the Earth, 25, 235-243.

Carslaw N., D.J. Creasey, D.E. Heard, A.C. Lewis, J.B. McQuaid, M.J. Pilling, P.S. Monks, B.J. Bandy and S.A. Penkett (1999), Modelling OH, HO₂ and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with measurements, J. Geophys. Res., 104, 30241-30255.

Carslaw N., P.J. Jacobs, and M.J. Pilling (1999), Modelling OH, HO₂ and RO₂ radicals in the marine boundary layer: 2. Mechanism reduction and uncertainty analysis, J. Geophys. Res., 104, 30257-30273.

R.G. Derwent, N. Carslaw, P.G. Simmonds, M. Bassford, S. O'Doherty, D. Ryall, M.J. Pilling, A.C. Lewis and J.B. McQuaid (1999), Hydroxyl radical concentrations estimated from measurements of trichloroethylene during the EASE/ACSOE campaign at Mace Head, Ireland during July 1996, J. Atmos. Chem., 34, 185-205.

Allan B.J., N. Carslaw, H. Coe, R.A. Burgess, and J.M.C. Plane (1999), Observations of the nitrate radical in the marine boundary layer, J. Atmos. Chem., 33, 129-154.

Lewis A.C., J.B. McQuaid, N. Carslaw and M.J. Pilling (1999), Observations of diurnal cycles in short-lived tropospheric alkenes at a North Atlantic coastal site, Atmos. Environ., 33, 2417-2422.

Carslaw N., H. Coe, J.M.C. Plane and E.C. Cuevas (1997) Observations of the Nitrate Radical in the Free Troposphere at Izaña de Tenerife.  J.Geophys.Res., 102, 10613-10622.

Carslaw N., B.J. Allan, L.J. Carpenter, R.A. Burgess, K.C. Clemitshaw, S.A. Penkett and J.M.C. Plane (1997) The Simultaneous Observation of Nitrate and Peroxy Radicals in the Marine Boundary Layer at Night.  J.Geophys.Res., 102, 18917-18933.  

Camy-Peyret C., B. Bergqvisk, B. Galle, M. Carleer, C. Clerbaux, R. Colin, C. Fayt, F. Goutail, M. Nunes-Pirharanda, J.P. Pommereau, M. Hausmann, F. Heintz, U. Platt, I. Pundt, T. Rudolph, C. Hermans, P.C. Simon, A.C. Vandaele, J.M.C. Plane and N. Smith, (1996) Intercomparison of Instruments for Tropospheric Measurements using Differential Optical Absorption Spectroscopy, J. Atmos. Chem., 23, 51-80.

Smith N., H. Coe and J.M.C Plane (1995), Comment on U.Platt and C.Janssen, 'Observation and role of the free radicals NO₃, ClO, BrO and IO in the troposphere, Faraday Discussion, 1995, 100, 175-198', on p208-210, same volume.

Smith N., J.M.C.Plane, C.-F. Nien and P. Solomon (1995) Nighttime Radical Chemistry in the San Joaquin Valley, Atmos. Environ., 29, 2887-2897.

Published abstracts and conference proceedings

Carslaw N., P.J. Jacobs and M.J. Pilling, (1999) Understanding radical chemistry in the marine boundary layer, Geophysical Research Abstracts, 1, (3), p695.

Carslaw N., P.J. Jacobs and M.J. Pilling, Applications of the Master Chemical Mechanism in the analysis of field measurements of OH, HO₂ and RO₂ radicals, Proceedings of the third German-Italian workshop on tropospheric chemistry, October 1998.

Carslaw N., P.J. Jacobs and M.J. Pilling (1998), Modelling radical chemistry in the marine boundary layer, Annales Geophysicae, 16, Part II, Oceans, Atmosphere, Hydrology and Nonlinear Geophysics, pC724.

Smith N., B.J. Allan, H. Coe and J.M.C. Plane (1995), Studies of the Reaction of the Nitrate Radical with Dimethylsulphide in the Marine Boundary Layer, Annales Geophysicae, 13, Part II, Oceans, Atmosphere, Hydrology and Nonlinear Geophysics, pC394.

Books/Chapters in books

Carslaw, N. (2009) Chemistry of Indoor Air in Indoor Air Pollution, P.Harrison and R. Maynard (Eds.), Imperial College Press Series, Volume V. In press.

Penkett, S.A., et al. (39 authors) (2003) Atmospheric photooxidants in Atmospheric chemistry in a changing world: an integration and synthesis of a decade of tropospheric chemistry research (The International Global Atmospheric Chemistry Project of the International Geosphere-Biosphere Programme), G.P Brasseur, R.G Prinn and A.A.P. Pszenny (Eds.), Springer, Berlin.

Plane J.M.C. and N. Smith (1995) Atmospheric Monitoring by Differential Optical Absorption Spectroscopy in Spectroscopy in Environmental Science, R.E. Hester and R.J.H. Clark (Eds), J. Wiley, London.

Teaching

Undergraduate

• Current Topics in Environmental Science (year 1)
• Climate Change: Science, Observations and Impacts (year 2)
• Current Issues in Atmospheric Science (year 3)