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INVESTIGATION ON PHYSICOCHEMICAL PROCESSES LEADING TO ACID PRODUCTION IN RADIATION FOG AND CAPTIVE CLOUDS

Objective

TO PROVIDE INFORMATION ON THE CONVERSION RATE OF SULPHUR AND NITROGEN OXIDES IN THE LIQUID PHASE.
An investigation was made of the interactions of cloud and fog droplets with atmospheric pollutants. It is now recognized that cloud water can contain high levels of acidity. The 2 different types of clouds investigated were ground fogs and captive frontal clouds.

Results from fog experiments support the idea of possible nonequilibrium conditions between gas and liquid phase in polluted fogs, caused by the presence of surface active substances on the surface of the droplets. If this effect is real, it will have to be taken into account in models describing cloud/fog evolution and chemistry. A sampling station has been designed and built in the Po Valley, Italy for automatic collection of samples during fog events. The automatic station has the capability to sample large numbers of fog events with a good reproducibility. The station comprises a fog detector, sampling unit and computer controller.
The sampling station was operated continuously from the beginning of November 1989 to the end of April 1990. During this period fog statistics, fog water chemical composition and deposition were investigated. Fog occurrence accounted for 23 % of the total time. The total ionic strength of fog water was mostly accounted for by ammonium, nitrate and sulphate ions observed from November to March. The notable increase of sulphate concentration over the period can be attributed to efficient sulphur dioxide to sulphate ion conversion due to an increased availability of oxidants. The data obtained so far with this automatic station gives information on the seasonal budget of chemical deposition due to fog in the Po Valley.
THE RESEARCH PROJECTS COMPLEMENTS, BY MEANS OF FIELD EXPERIMENTS, THE ALREADY PERFORMED LABORATORY STUDIES ON THE AQUEOUS PHASE CONVERSION OF SO2 AND NOX TO H2SO4 AND HNO3.
THE TWO LABORATORIES INVOLVED, UNIVERSITAT FRANKFURT AND CNR BOLOGNA, PROPOSAL 27, CONSIDER THREE DIFFERENT ENVIRONMENTAL AND CLIMATIC SITUATIONS:
- RADIATION FOG IN A RURAL AREA (PO VALLEY, ITALY)
- RADIATION FOG IN AN INDUSTRIALISED REGION (MAIN VALLEY, FRG)
- CAPTIVE CLOUDS IN AN INDUSTRIALISED REGION (KLEINER FELDBERG, FRG)
THE FORMATION OF SULPHATE AND NITRATE IN DROPLETS IS INVESTIGATED DURING THESE EXPERIMENTS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

JOHANN WOLFGANG GOETHE UNIVERSITAET FRANKFURT
Address
Seckenberg Anlage 31
60054 Frankfurt Am-main
Germany

Participants (1)

Consiglio Nazionale delle Ricerche (CNR)
Italy
Address
101,Via Gobetti 101
40129 Bologna