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Contribution to the Workshop on
Photochemical Oxidants and Aerosols in Lombardia, 21st - 22nd June 1999

 

Some current problems in the atmospheric environment; the potential contribution of EUROTRAC-2

Peter Borrell
(formerly Executive Secretary of EUROTRAC-2)
P&PMB Consultants, Ehrwalder Straße 9, D-82467 Garmisch-Partenkirchen

1. Abstract

Current environmental concerns include the increase in free-tropospheric ozone levels over the past 50 years, the difficulties caused by non-linearity in devising strategies to ameliorate ozone concentrations under NOx controlled conditions, the health effects of particulates and the possible synergism between pollutants. The environmental issues are paralleled by scientific problems, particularly those of the description and analysis of heterogeneous atmospheric components, the adequacy and representativeness of measurements, the difficulties of modelling complex heterogeneous chemistry in turbulent situations and the validation of the current models.

The EUREKA environmental project, EUROTRAC-2, was established in 1996 to provide some solutions to the scientific problems. Particularly appropriate to the Lombardy region is the work of the "urban" subprojects, LOOP and SATURN, as well as in the modelling subproject, GLOREAM, and the emission subproject, GENEMIS.

2. Introduction: the environmental problem

Despite the measures taken under the Convention on the Long Range Transport of Air Pollutants (ECE, 1994) and by the European Commission (Lutz, 1999) there is continuing public concern about the concentrations of ozone and other photo-oxidants throughout Europe. In addition there are worries about the health effects of emissions within urban areas, particularly aromatic hydrocarbons and particulate matter of all types. The environmental problems are closely inter-related because photo-oxidant precursors are emitted by road traffic and by industrial and domestic activities which occur mainly within urban areas. Ozone increase diagram

A complication for the policy maker is the variety of effects that have to be taken into account in formulating appropriate measures (Borrell et al., 1996). On a regional scale, the background concentration of ozone throughout the region has apparently increased, from the turn of the century until the nineteen eighties, to a level which is now close to concentrations which are believed to inhibit crop growth. Some indication of the changes that took place in Europe between 1950 and the 1980 can be seen in figure 1 which shows that at all altitudes, there has been an appreciable increase in average ozone concentrations (Staehelin et al., 1994). The increase appears to have levelled off at the moment but the general levels of ozone and photo-oxidants are still too high.

Under sunny stagnant atmospheric conditions, ozone episodes occur which produce over the course of several days concentrations which lead to ozone exposures well in excess of the WHO health guidelines. In the centre of many conurbations, the production of ozone is limited by the concentrations of volatile organic compounds (VOC) in the air while in the hinterland of cities and throughout most of the region the production is limited by concentrations of nitrogen oxides, NOx. However the non-linearity in the ozone chemistry can actually, under appropriate conditions, lead to increasing ozone concentrations if the NOx is reduced. This is demonstrated by the anomalous "weekend" effect observed in Belgium for example where, although the emissions decrease over the weekend, ozone concentrations actually increase (Dumollin et al., 1999). In Vienna on the other hand ozone decreases slightly (Schneider, 1998).

The progress in legislation has gone hand in hand with progress in the science of the troposphere. The realisation that international policy development requires an international scientific consensus led to the formation in 1986 of the EUREKA project, EUROTRAC. It came to an end in 1995 with the publication of a final report which contained not only a plethora of scientific results (Borrell et al., 1999) but also an assessment of the environmental situation in the troposphere (Borrell et al., 1996).

However, despite the scientific progress, a number of substantial problems remained, leading to the formation in 1996 of a new project, EUROTRAC-2, which is tackling these problems on a broad front (EUROTRAC-2, 1999). The purpose of the present paper is to outline some of the problems and to indicate how the project is attempting to solve them.

3. Scientific uncertainties

To support cost-effective measures to reduce concentrations of harmful pollutants, a suite of reliable validated models is required that encompass the scientific understanding of the problem. These can then be used to create regional and local scenarios and subsequently, when used with the monitored concentrations, to ensure legal compliance with the agreed emission reduction targets.

Much scientific progress has been made over the last twenty five years in building, from countless experiments, a general understanding the processes leading to photo-oxidant formation. The major chemical processes have been characterised in laboratory work; the processes by which pollutants reach their sink in the biosphere have been studied; emissions both anthropogenic and biogenic have been estimated, models for all scales have been developed and many field campaigns have been used both to validate particular models and to provide indications of unexpected processes occurring in the atmosphere (Borrell, 1999). However, despite the progress, substantial uncertainties still remain in the components required for reliable modelling.

There are uncertainties:

Some of the general questions to which answers should be sought in an urban context are as follows.

4. The role of EUROTRAC-2

EUROTRAC-2 is a co-ordinated research project within the EUREKA initiative, studying the transport and chemical transformation of pollutants and trace substances in the troposphere over Europe. Since the inception of the first phase some thirteen years ago the project achieved a remarkable success in bringing together groups of European scientists to study scientific problems related to the development of environmental policy in Europe. The project now entirely reconstituted, began a second phase, EUROTRAC-2 in 1996. The project started again from scratch: new committees were appointed and groups of scientists were encouraged to propose the formation of new subprojects.

The overall objective of EUROTRAC-2 (The Transport and Chemical Transformation of Environmentally Relevant Trace Constituents in the Troposphere over Europe; Second Phase) is to support the further development of abatement strategies within Europe by providing an improved scientific basis for the quantification of source-receptor relationships for photo-oxidants and acidifying substances. In 1997 the IEC decided to extend the project to include mercury and persistent organic pollutants (POPs), since it recognised the increasing concern over these pollutants in Europe and was persuaded that EUROTRAC could contribute scientifically to understanding the problems associated with their transport and distribution.

The specific objectives of the project are

  1. Quantification of atmospheric interactions . To quantify the anthropogenic and natural contributions of relevant emissions and atmospheric processes to the abundance and the long term changes of photo-oxidants and acidifying substances in the planetary boundary layer and free troposphere.
  2. Evaluation of feedback mechanisms . To evaluate the consequences of feed-back mechanisms, for example: the feed-back between the concentrations of tropospheric photo-oxidants and biogenic emissions; the feed-back between the concentrations of photo-oxidants and those of climatically relevant atmospheric constituents; and the feed-back between the changing intensity of ultraviolet radiation and photo-oxidant production.
  3. Contribution to the formulation of abatement strategies and future air quality . To contribute to the formulation and improvement of strategies for reducing the anthropogenic contribution to the abundance of photo-oxidants and acidifying substances and to the prediction of future air quality on shorter and longer time scales.
In these objectives there is the recognition that, although much was achieved in the first phase, there is still much to do before the scientific understanding is good enough for modern policy development. The authorities responsible for implementing environmental policy must have confidence in the predictions of the models before they will be prepared to enact the necessary but expensive abatement measures that are likely to be needed to deal with the present environmental situation.

5. The new subprojects

Fourteen subprojects shown in Table 1 have been approved for inclusion in EUROTRAC-2 by the Scientific Steering Committee (SSC). Most started work in 1997 and the current annual reports suggest that much scientific work has already been done.

Table 1: EUROTRAC-2 Subprojects

 
AEROSOL Aerosol balance in Europe Harry ten Brink ECN, Petten
BIATEX-2 Biosphere/Atmosphere exchange of pollutants David Fowler ITE, Edinburgh
CAPP Coastal air pollution processes Gary Geernaert DEAP, Roskilde
CMD Chemical mechanism development Ulrich Schurath FZK, Karlsruhe
GENEMIS Generation and evaluation of emission data Rainer Friedrich IER, Stuttgart
GLOREAM Global and Regional Atmospheric Modelling Peter Builtjes TNO, Apeldoorn
LOOP Limitation of oxidant production Albrecht Neftel FAL, Berne
MEPOP Research on mercury and POPs John Munthe IVL, Göteborg
PROCLOUD Processing of trace constituents in clouds over Europe Sandro Fuzzi CNR, Bologna
SATURN Studying atmospheric pollution in urban areas N. Moussiopoulos U. of Thessaloniki
TOR-2 Tropospheric Ozone Research Anne Lindskog IVL, Göteborg
TRAP45 Trends in air pollution since 1945 P. Brimblecombe UEA, Norwich
Of particular interest in the context of the urban environment are the two "urban" subprojects, LOOP and SATURN, the aims of which are given in Table 2

LOOP carried out an extensive field campaign in 1998 to study the plume from Milan. The results are presently being evaluated and the first publications will appear in the near future. SATURN is an ambitious project involving a host of modelling activities to try to take advantage of the field measurements being made at all scales in cities throughout Europe.

Table 2: The aims of the EUROTRAC-2 "urban" subprojects

LOOP: Limitation of oxidant production (Neftel, 1999). SATURN: A study of atmospheric pollution in urban areas (Moussiopoulos, 1999) Two other subprojects of interest in the urban field are GENEMIS and GLOREAM. Emissions are the principal uncertainty in models at almost all scales and the methods for obtaining spatial and temporal resolution and the validation of emissions, started by GENEMIS in the first phase and being continued today, are essential for the success of nearly all the subprojects in EUROTRAC-2, (Friedrich, 1999). Similarly the model development work being undertaken in GLOREAM should assist all modellers in dealing with problems of the scale interactions which abound in urban situations (Builtjes, 1999).

6. Conclusions

The work being undertaken in EUROTRAC-2 should go some way to providing some solutions to the problems and questions outlined in section 2. However the environmental problems remain with those actually responsible for developing policy for the atmospheric environment but, from past experience, but we can be sure that the measures proposed will have a good scientific foundation.

However one problem remains which is neither scientific nor legislative but concerns our society as a whole: Are we as a developed society prepared to pay for and if necessary be limited by the measures necessary to ameliorate the problems in the atmospheric environment? The major cause of our present troubles is the expanding industrialisation and the ever-increasing amounts of road traffic. At the moment we are engaged in doing the easier and cheaper things to improve matters. But in the future, draconian reductions in pollutants may be necessary in many places, and technical "fixes" may not be enough. Then the crunch may come not only in terms of cost but also in limitations on our freedom to travel wherever and whenever we want. The new millennium certainly promises to be an "interesting" century!

7. Acknowledgements

It is a pleasure to thank the organisers of the meeting for inviting me to give this paper and for their support to enable me to attend. I would also like to thank Dr. Pauline Midgley, the Executive Secretary of EUROTRAC-2, for her encouragement.

8. References

 
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