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The goal of EUROTRAC-2
EUROTRAC-2 was the second phase of the project on the Transport and
Chemical Transformation of Environmentally Relevant Trace Constituents in the
Troposphere over Europe. It was accepted as a project within the EUREKA
initiative (No. 1489) in February 1996 to run until the end of December 2002.
The project followed on from the first phase of EUROTRAC (EUREKA project
No. 7) which was carried out from 1988 - 1995. The goal of EUROTRAC-2 has
been to improve the quantitative understanding of the factors determining the
formation, transport, chemical transformation, deposition and impact of photo-
oxidants, aerosols, acidifying substances, mercury and persistent organic
pollutants (POPs) in the troposphere, and in this way to contribute directly to the
further development of strategies for reducing the ambient concentrations and
deposition fluxes of these species. EUROTRAC-2 has assisted in alleviating the
growing environmental problems which stem from these species by integrating
scientific results with policy needs.
Although EUROTRAC has not funded research directly, it has been a platform
for the exchange of information, knowledge and experience and co-operation in
joint projects. The results obtained have provided a common scientific
understanding upon which effective environmental abatement and control
strategies throughout Europe have been and will be based. A European network
of scientists has been formed, qualified to advise their own governments and the
international bodies on environmental issues connected with the atmosphere. In
both phases of EUROTRAC, the research resources of the participating countries
and the European Union have been brought together to create viable active
research groups to address interdisciplinary and international, transboundary
problems. EUROTRAC has contributed strongly to building European capacity
for scientific research in air pollution. As well as being a platform covering all
Europe, EUROTRAC has also facilitated the training of young scientists. The
active involvement in EUROTRAC of many groups in Central and Eastern
Europe has also been of great importance. This has helped to transfer knowledge
to countries with lower economic activity, less scientific facilities, and often
more severe environmental problems.

The reasons for EUROTRAC-2 to exist
The air quality in large areas of Europe at the beginning of EUROTRAC-2, and
also today, is still far from acceptable and often above limit values, despite
international agreements and the efforts made in various countries to reduce the
emissions of major pollutants. The atmospheric changes being brought about by
human activities can have serious effects on air quality, human health, the
ecosystem, materials, acidification and eutrophication, and on climate change.
2                                                                    Introduction

There was, and still is, much public concern over the high concentrations of fine
particles and ozone over large parts of Europe. To meet the obvious challenges in
abating these environmental problems, also in a cost-effective way, requires an
in-depth understanding of atmospheric chemistry and its interaction with the
biosphere. EUROTRAC was set up to create this understanding and to provide a
scientific basis for abatement strategies. EUROTRAC-2 has built on the success
of the first phase to intensify and extend this work. An essential feature of the
problems mentioned is the complexity and intertwining of processes contributing
to the cycle of pollutants between their emission and deposition. This includes
the physical and chemical transformation of primary pollutants into secondary
products, the interrelation between primary and secondary pollutants, transport
and deposition, and the impact on the biosphere. Some compounds contribute to
a number of environmental problems; for example, the nitrogen oxides emitted
by traffic and industry affect the formation of photo-oxidants and aerosols and
also the deposition of nutrients.
The investigation, interpretation and understanding of such a complex field are
beyond the capacity of single groups, institutes or disciplines; these problems
require a thorough, interdisciplinary approach on a European scale. They are also
facilitated by coordinated planning and pooling of resources. Furthermore, the
atmospheric transport of pollutants does not recognise international boundaries.
With the small geographical size of Europe, pollutants produced in one country
are frequently exported to neighbouring countries where environmental damage
is produced by the primary and secondary pollutants. Thus the environmental
problems in Europe are literally transboundary and require effective,
internationally coordinated action in research as well as in abatement and
reduction measures. These elements together were the reasons for the creation of
EUROTRAC and, subsequently, EUROTRAC-2.
The objectives of EUROTRAC-2 were specified as:
· 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, aerosols, acidifying substances, mercury and
  POPs in the troposphere.
· Evaluation of feedback mechanisms
  To evaluate the consequences of feedback mechanisms, for example, the
  feedback between the concentrations of tropospheric photo-oxidants and
  biogenic emissions, the feedback between the concentrations of photo-
  oxidants and those of climatically relevant atmospheric constituents, and the
  feedback between the changing intensity of ultraviolet radiation and photo-
  oxidant production.
· Contribution to the formulation of abatement strategies and prediction
  of future air quality
   To contribute to the formulation and improvement of strategies for reducing
   the anthropogenic contribution to the abundance of photo-oxidants, aerosols,
Introduction                                                                       3

    acidifying substances, mercury and POPs and to the prediction of future air
    quality on shorter and longer time scales.
For a more detailed description, see the EUROTRAC-2 Project Description and
Handbook (1998).
A number of scientific tasks were defined to achieve these objectives. In broad
terms these aimed to improve the scientific understanding of the emission rates,
to improve the monitoring capacity and strategy, to improve the chemistry
transport models currently used in the policy work on abatement, to improve the
understanding of how air pollutants affect the air quality in cities and, finally, to
improve the understanding of the deposition mechanisms and their rates. The
formulation of these tasks was based on the current understanding of what was
required in order to support policy development in these fields at the initiation of
the project. Obviously, modifications and changes have been made in the focus
of the research in the six years of EUROTRAC-2, to reflect changing priorities.
The principal policy drivers have been the Convention on Long-range
Transboundary Air Pollution under the aegis of the United Nations Economic
Commission for Europe (UNECE) and the air quality legislation of the European

The strategy of EUROTRAC-2
By its nature EUROTRAC-2 was to a large extent a scientific project and not, in
the first place, a policy and assessment project. All research projects in
EUROTRAC-2 were funded by national bodies, or by international
organisations, such as the EC research directorate. The subproject coordinators
and the members of the various committees were all active on a voluntary basis.
Because the intention was to address environmentally relevant issues, the
strategy of EUROTRAC-2 has been to integrate with environmental policy issues
as far as possible, whilst keeping its scientific character. To intensify the support
for policy making compared to the first phase, an Environmental Assessment
Group (EAG) was established in EUROTRAC-2 including representatives from
the technical centres of UNECE/EMEP, the EEA Topic Centre for Air and
Climate Change and the EC Environment Directorate. The main task of the EAG
was to ensure that the environmental issues of current concern to the
participating countries were addressed in the scientific programme and to present
the scientific findings to those responsible for policy management in Europe.

The structure of EUROTRAC-2
EUROTRAC-2, as a follow-up of the first phase of EUROTRAC, was set up as a
project lasting for a period of six years. The analysis made at the end of the first
phase in the report Photo-oxidants, Acidification and Tools: Policy Applications
of EUROTRAC Results (Borrell et al., 1997) defined the uncertainties still
existing upon which EUROTRAC-2 was then focussed.
EUROTRAC-2 was basically a “bottom-up” project, with only limited central
funding for coordination activities including the maintenance of a small
4                                                                                                                                                         Introduction

secretariat. It was organised around a number of scientific subprojects and
administered by three committees and the international scientific secretariat (see
Figure 1).

                                                           International Executive

                                Scientific Steering                                                  Environmental
                                   Committee                                                       Assessment Group
                                      (SSC)                                                             (EAG)

                                                                   Internat. Scientific


Figure 1. Organisation scheme of EUROTRAC-2.

·   Organisation of scientific work
    The research within EUROTRAC-2 was organised among 14 subprojects,
    each with clearly formulated goals. The scientific programme of each
    subproject was suggested by the subproject group itself and was finally
    agreed after consultation with the SSC, EAG and IEC. The work of the
    subprojects was fostered through joint workshops, meetings and, where
    appropriate, field campaigns.
·   Project management
    The International Executive Committee (IEC) held the overall responsibility
    for the project. Members were appointed by the funding or environmental
    agencies of the participating countries together with a representative from the
    European Commission (EC).
·   Scientific steering
    The Scientific Steering Committee (SSC) was responsible for the scientific
    programme, setting the scientific direction and focus, approving proposals
    for subprojects and conducting reviews of scientific progress. It consisted of
    15 leading scientists.
· Environmental assessment
  The Environmental Assessment Group (EAG) ensured that relevant
  environmental issues were addressed within the scientific programme. It was
Introduction                                                                      5

    also responsible for the exchange of scientific information between
    EUROTRAC-2 and the agencies responsible for environmental policy
    development. The members belonged to environmental agencies and
    programmes, or were experts in the application of environmental policy.
· Administrative coordination
  The International Scientific Secretariat (ISS) was responsible for the
  administrative coordination of EUROTRAC-2. It maintained contacts with
  the committees, subproject coordinators and principal investigators.

The strengths of EUROTRAC-2
EUROTRAC-2 has achieved the harnessing of a variety of resources in over 30
participating countries to support European projects with pan-European goals.
The number of groups active in EUROTRAC-2 over the course of the project has
been more than 300. This has enabled active, interdisciplinary research groups to
be created of a viable size in areas of importance and the close coordination at
each level has ensured that most goals specifically set by the different
subprojects within EUROTRAC-2 have been achieved.
Its strength has also been the bottom-up structure and the scientific network
established which was essential in generating and promoting new ideas.
Networking has been facilitated by annual subproject workshops and a biennial
Symposium which has regularly attracted 400 or more participants. Many young
scientists have given their first talk at a EUROTRAC workshop and have made
many contacts and friends at the EUROTRAC Symposia. The outcome of
EUROTRAC-2 has included almost 900 scientific papers published in the peer-
reviewed literature to date as well as more than 100 PhD theses. In addition,
EUROTRAC-2 has produced a wealth of other activity such as contributions to
scientific assessments and conferences, book chapters and review articles.
EUROTRAC-2 has shown a successful collaboration between basic and more
applied research. The continuous dialogue between basic and applied science is a
long-term, powerful tool to promote new scientific findings into application and
policy development. EUROTRAC-2 also provided a trans-national platform that
helped coordinate national research programmes within Europe in close
cooperation with the European Commission, contributing to a European
consensus on environmental strategies (see also EUROTRAC-2 Mid-term
Review, 2001).

The successes of EUROTRAC-2
First, an overwhelming amount of top-quality science has been created better to
quantify the anthropogenic and natural contributions of relevant emissions and
atmospheric processes to the abundance and the long term changes of photo-
oxidants, aerosols, acidifying substances, mercury and POPs in the troposphere.
Special attention has been given to the development of instruments and chemical
transport models for aerosols. Furthermore, research has started into the use and
usability of satellite data for tropospheric research and into the quantification of
6                                                                        Introduction

the global impact on the concentration levels in the European troposphere as well
as the export of pollutants from European regions.
EUROTRAC-2 has stimulated a wealth of scientific activities, bringing together
funding from national and international programmes. Its approach, combining a
basically bottom-up structure with oversight by the respective committees,
served to create a new European dimension in atmospheric research. In its second
phase, the work of EUROTRAC has been extended and deepened to become a
very successful platform in Europe for the study of the troposphere in all its
environmental aspects. It has helped to forge the scientific consensus which is
essential to underpin environmental policy development in Europe.
EUROTRAC-2 has also served as an environment in which young scientists can
become familiar with the current state of knowledge and with colleagues from
other countries. Its outreach to involve research groups within Central Europe
and in Eastern Europe formerly not active in European research programmes has
been especially valuable.

About the Synthesis and Integration Project
To assess the success of EUROTRAC-2 in supporting policy development, a
Synthesis and Integration Project was set up. The aim was to address specific
cross-cutting themes, covering results from the different subprojects. Viewing the
final reports of the subprojects as “horizontal” reporting, the themes addressed in
synthesis and integration were vertical cross-sections.
Five themes were selected:
·   Emissions of gases and particles
·   Deposition fluxes of air pollutants
·   Tropospheric ozone and its control
·   Urban and local scale air pollution
·   Tropospheric aerosols and clouds

These themes were not intended to cover all the results of EUROTRAC-2, but to
give specific examples, to tell specific stories, and to answer specific, policy-
relevant questions. The full scientific results of EUROTRAC-2 are presented in
detail in the final reports of the subprojects which are published separately. Thus,
in this Synthesis and Integration report, ample attention is given to certain topics,
ozone and aerosols for example, while other topics such as wet deposition and
POPs receive less attention. This does not reflect any strict priority with respect
to environmental issues, but rather illustrates for some selected topics how
scientific results can be integrated to support policy development. Results on
these aspects for the remaining topics can be found in the subproject final
reports. There is also an overview of the work of each of the 14 subprojects in the
companion volume to this book: Towards Cleaner Air for Europe - Science,
Tools and Applications Part 2 (Midgley and Reuther, eds., 2003).
Introduction                                                                           7

Ideally, the process of developing sound environmental policy should be a serial
one. The first step is to develop an understanding - ideally as complete as
possible - of the scientific nature of the system in question. Once this
understanding has been achieved, tools such as mathematical models of the
system can be developed. These tools can be used iteratively to increase our
understanding of the system and for the purposes of assessment and policy
development. In EUROTRAC-2, much effort has been devoted to following this
path from science via tools to policy. However, it should be made clear that the
progress from science to policy is, in reality, not that straightforward. Policies
have to be developed based necessarily upon an incomplete knowledge of the
system in question. The precautionary principle is often invoked, i.e., that if the
consequences of a potential environmental problem are sufficiently grave, then
regulations should be put into effect even though the scientific basis is not yet
complete. While this approach may be entirely justified, or even necessary in
some cases, it should be noted that truly sound policy cannot be developed if the
science aspect is ignored. Policy should be refined and re-evaluated as new
information becomes available and investigations into specific environmental
issues need not necessarily stop because a first strategy for policy has been
For each theme chapter in this book, an attempt has been made to follow the path
described above, which means addressing science, tools, and policy (Figure 2).

                                                  Tools               Assessment of
      Scientific                                                      Usefulness for
    Understanding                                                     Policy-making
                                         Quality Assessment
Figure 2. Schematic diagram of the S&I chapter structure.

It will be clear to the reader that the style of each chapter reflects the approach of
the individual authors who were given overall guidelines but were not
constrained into a meaningless consistency in presentation of the five themes.
The general outline of each chapter (explicitly or implicitly) is an overview of the
current policy-related questions and issues, followed by:
·      What have we learned about...?
·      What new tools do we have?
·      What can we contribute to policy development? (in which the policy-related
       questions are answered as far as possible), and
·      What are the most pressing needs?
The first chapter Emissions of Gases and Particles to the Atmosphere in
Europe addresses the progress made with respect to the emissions of
anthropogenic and biogenic volatile organic compounds (VOC), the biogenic
emissions of nitrogen oxides, and, as a relatively new subject, the emissions of
particles: anthropogenic, biogenic and natural. Also current knowledge
8                                                                     Introduction

concerning the emissions of POPs and mercury is presented. Special attention is
given to the assessment of the accuracy of the emission data..
The following chapter considers Deposition Fluxes of Air Pollutants to
Terrestrial Surfaces in Europe. Both emissions and deposition of ammonia are
treated here because of the close and complicated emission/deposition/re-
emission cycle of ammonia. New findings concerning the fluxes of sulphur
dioxide and its interaction with ammonia are presented. Deposition of nitrogen
oxides, ozone and particles are also discussed.
Tropospheric Ozone and its Control is discussed in the third chapter. The key
question addressed here is: which scientific findings are available to determine
the impact of the global and hemispheric background to the concentrations in the
troposphere over Europe. The chapter describes that, notwithstanding the clear
impact that the hemispherical background has on ozone over Europe, the amount
of controllable European ozone is large enough to require specific European
abatement strategies. The impact on episodic peak ozone concentrations across
Europe of the VOC Protocol to the UNECE Convention on Long-range
Transboundary Air Pollution is also analysed.
Urban and Local Scale Air Pollution is the subject of the next chapter. Various
aspects are addressed associated with urban and local scale air quality
assessments and their uncertainty. The chapter discusses in detail scientific
improvements in estimating urban emissions and describing urban aerosols.
Improvements of air pollution models, new approaches towards their validation
and methods for multi-scale analyses are also presented. Better scientific insight
and the availability of refined practical tools resulted in the formulation of
improved urban air quality management systems. Such systems are very useful
for addressing various important policy issues related to urban air quality.
The last thematic chapter discusses the subject of Tropospheric Aerosols and
Clouds, showing the progress made in this rapidly developing new area and the
first steps made towards the development of tools/models which enable the
analysis of abatement strategies.
These thematic chapters are followed by a Summary and Conclusions chapter in
which selected, significant scientific results from the work within the
EUROTRAC-2 project are linked to their relevance to policy application and
future needs. Finally some reflections on EUROTRAC-2 and the future are