2004/279/EC: Commission DecisionShow full title

1. U.K. FIELD EXPERIMENT: HEILBRONN/NECKARSULM (GERMANY)

The field experiment in the Heilbronn/Neckarsulm conurbation (approximately 200000 inhabitants) started with abatement actions on Thursday 23 June, 1994, and lasted until Sunday 26 June, 1994. It was accompanied by measurements at four fixed stations, with 15 mobile units, with an aircraft and balloons and included model calculations on the basis of a detailed emission inventory. The study was designed to answer the following question, taking a typical summer smog episode as an example.

• Can peak ozone concentrations during an episode be significantly reduced by local and temporary abatement actions, and how can reductions of NOx and VOC be achieved by realistic measures?

• Are local and temporary short term actions, such as traffic bans, feasible on the basis of a given infrastructure, and will they be accepted by the public?

Three zones were defined for the experiment. The total model area consisted of 910 km2. Within the inventory area (400 km2), comparably mild abatement actions were applied; a speed limit of 70 km/h or less was imposed on all roads including motorways, and industry and smaller enterprises promised emission reductions on a voluntary basis. In the downtown area of 45 km2, traffic bans were enforced; however cars equipped with controlled catalytic converters and low emitting diesel vehicles were exempted from this ban, as well as essential traffic, such as fire brigades, suppliers of fresh food, and medicines. Additional measures included a speed limit of 60 km/h or less and voluntary emission reductions by industry and smaller enterprises.

Fair weather, with maximum temperatures climbing from 25 °C to about 30 °C, prevailed during the experiment, with cloud cover on the afternoons of 25 and 27 June. Wind speeds were moderate (i.e. 2 to 4 m/s on 23 and 25 to 27) or elevated (i.e. 4 to 7 m/s on 24), the meteorological conditions thus being favourable, but not exceptionally good for ozone production.

As a result of the abatement actions the precursor emissions in the model area were reduced by 15 to 19 % for NOx and 18 to 20 % for VOC. In the downtown area the ambient concentrations were thus reduced by up to 30 % for NOxand up to 15 % for VOC.

However no significant changes of the ozone burden beyond measurement uncertainty could be detected. This result is in accordance with model calculations. A closer examination of the results revealed three main reasons for this lack of response in the ozone burden.

• The area with strict abatement actions was too small (45 km2).

• The voluntary reductions in the industrial sector (especially VOC) were not sufficient.

• Due to meteorological conditions during the experiment ozone concentrations were mainly influenced by regional ozone transport instead of local ozone production.

• Due to moderate wind speed any effects could only have been observed further downwind of the area where the field experiment took place.

References:

Umweltministerium Baden-Württemberg (Hrsg.):

Ozonversuch Neckarsulm/Heilbronn. Dokumentation über die Vorbereitung und Durchführung des Versuchs, Stuttgart, 1995

Umweltministerium Baden-Württemberg (Hrsg.):

Ozonversuch Neckarsulm/Heilbronn, Wissenschaftliche Auswertungen, Stuttgart, 1995

Bruckmann, P. and M. Wichmann-Fiebig: 1997. The efficiency of short-term actions to abate summer smog: Results from field studies and model calculations. EUROTRAC Newsletter, 19, 2 to 9.