TO DEVELOP AUTOMATED DENUDER TECHNIQUES FOR DRY DEPOSITION MEASUREMENTS OF ACIDIC SUBSTANCES
Research has been carried out into the development of new and/or the improvement of already existing denuder based chemical sensors for dry deposition measurements in the field by a micrometerorological (gradient) technique. The development or improvement was limited to:
the automated rotating wet denuder;
the continuous flow rotating denuder technique;
to the automated thermodenuder technique, the nonautomated annular (differential) denuder technique.
Improvement of denuder and micrometerorological systems involved:
using a set up consisting of 1 sodium chloride and 2 sodium carbonate glycerol coated annular denuders fitted in series;
the completion of the wet denuder technique by a portable ion chromatography system for online analysis of sulphate, nitrate, nitrite and chlorine ions in samples of the wet denuder system (this further automation is the final improvement step for the application of the wet denuder technique in long term studies of dry deposition of sulphur dioxide, nitric acid, ammonia and hydrochloric acid);
improvement of an existing multilevel dry and wet bulb temperature measurement system.
As far as the nonautomated (differential) annular denuder technique is concerned, two new methods were developed.
The general conclusion from intercomparisions is that the results of the determined gaseous pollutants (by denuder and filter pack techniques) agree sufficiently good. For the filter pack technique, which was not specifically addressed in this research, the agreement for particulate matter determination was not satisfactory. Corresponding improvement is definitely needed, since vertical fluxes of gaseous and particulate nitrate and ammonia could be strongly interrelated.
Field experiments were then carried out on dry deposition fluxes. In conclusion, the precision of the denuder systems for the acidifying compounds such as ammonia, nitric acid, nitrous acid, ammonium nitrate and sulphur dioxide was 5% or better, which allows the mea surement of atmosphere surface exchange fluxes by the gradient method.
TWO DIFFERENT TYPES OF DENUDER ARE DEVELOPED TO MEASURE DRY DEPOSITION OF SO2, HNO3, HNO2, NH3, H2SO4 AND HCL : THERMODENUDER AND WET DENUDER SYSTEM.
BOTH DENUDER SYSTEMS ARE TESTED AGAINST OTHER METHODS AT DIFFERENT LOCATIONS IN SOUTHERN BAVARIA, WHICH ARE REPRESENTATIVE OF MANY OTHER LOCATIONS WITH EXTENSIVE FOREST DAMAGE.
THE PROJECT INCLUDES PROPOSAL 275 OF FRAUNHOFER INSTITUTE, GARMISCH-PARTENKIRCHEN, ENTRUSTED WITH THE OVERALL COORDINATION, PROPOSAL 418 OF ECN PETTEN AND PROPOSAL 354 OF CNR ROME.
THE DEVELOPMENT OF THESE TECHNIQUES MAY BE THE FUTURE BASIS TO PERFORM SPATIALLY WIDE SPREAD DRY DEPOSITION MEASUREMENTS DURING LONG TIME PERIODS.
Funding SchemeCSC - Cost-sharing contracts