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Agricultural production systems are recognised as a major source of atmospheric ammonia. Deposition of ammonia and ammonium may contribute to undesired changes in oligotrophic ecosystems. The continuous measurement of atmospheric ammonia requires expensive and sophisticated techniques and is performed only in a very restrict number of ambient air stations in Europe. Therefore, the application of passive samplers, which have the advantage of being easy to handle and cost-efficient, is useful. In the past the comparability of different passive samplers must be considered as rather scarce. In a joint European project under the leadership of the GSF-Forschungszentrum für Umwelt und Gesundheit, Neuherberg, in 1997 a comparison of different passive ammonia monitoring methods was carried out in a prealpine rural site near Garmisch-Partenkirchen. It was considered valuable to include not only well established systems but also methods still being developed. For the comparative test ten working groups with different methods took part. A wet annular denuder system, which has been developed by the Netherlands Energy Research Foundation for on-line measurement of atmospheric ammonia, served as reference of passive methods. The experiment, which started in June and finished in December, showed that most of the passive samplers fulfil the requirements and can be recommended for further measurements. Additional measurements of meteorological parameters were performed to check the influences of different weather conditions on passive sampling.

Passive samplers provide an excellent opportunity to perform indicative measurements or establish a dense network of measuring sites. A drawback compared with conventional active measuring methods is the larger spread of results. This variation can, to a large extent, be attributed to the influence of temperature, sampler geometry and wind on sampling results. A proper design of sampler geometry and optimum choice of draught shield can reduce the influence of wind velocity on a badge type sampler to less than 10%. Wire mesh screens prove to be inadequate in damping turbulence. Filters give good results. Attention should be paid to the size and isolation value of the walls of the sampler to prevent thermal updrafts occurring within the sampler. Tube type samplers are less influenced by wind, provided that turbulence is prevented from influencing diffusion within the sampler.

In the spring and summer of 1989 an epidemiologic study was conducted to evaluate the acute effects of photochemical air pollution episodes on pulmonary function of children living in three nonindustrial towns in the Netherlands. Spirometry was performed repeatedly in the schools of the children, mostly during the morning hours. Data from 533 children having more than four valid pulmonary function tests were included in the analyses. The association between previous-day ambient ozone concentration and pulmonary function was evaluated, using individual linear regression analysis and subsequent evaluation of the distribution of individual regression coefficients. One hour maximum ambient ozone concentrations frequently exceeded 160 micrograms/m3 but were all lower than the Dutch Air Quality Guideline of 240 micrograms/m3 for all three populations. Significant negative associations of previous-day ambient ozone with FVC, FEV1, peak expiratory flow (PEF), and maximal midexpiratory flow (MMEF) were observed. There were indications of systematic differences in responses among the children. Children with chronic respiratory symptoms did not have a stronger response than children without these symptoms.

In January 1985, a decline of primary school children's pulmonary function was observed during an air pollution episode. Ambient 24 hour average levels of SO2, TSP and RSP were in the range of 200-250 micrograms/m3. The response persisted for at least two weeks. In January 1987, again a decline of school children's pulmonary function was observed associated with an air pollution episode. Levels of TSP were about as elevated as in the 1985 episode. Two weeks after the episode, lung function levels were even lower than during the episode. In June 1987 a long term study was started to investigate potential effects of winter and summer air pollution episodes on pulmonary function and occurrence of acute respiratory symptoms of primary school children. An important issue for this study is the characterization of short term variation of lung function in absence of air pollution. Exposure is characterized by ambient levels of several gases (SO2, NO2, O3, HNO3), PM10, TSP and components of particulate matter (SO4(2-), NO3-, H-, NH4+). Sampling is being conducted on a daily basis to obtain a continuous exposure estimate. In the winter of 1987/1988, no air pollution episodes were observed. The study will continue through the winters of 1988/1989, and 1989/1990.

In January 1987, an air pollution episode occurred in central and western Europe. Levels of SO2, NO2, black smoke, sulphates and other components were elevated, with 24 hour average concentrations of SO2 reaching a maximum of close to 300 micrograms/m3 in an area in the southeast of the Netherlands. Pulmonary function was measured in a group of children of 6-12 years old at the end of the episode, and also two and three and a half weeks after the episode. A baseline lung function value was obtained about three months before the episode. Pulmonary function growth between baseline and retest dates was estimated from a simple growth model which was validated using measured pulmonary function growth data from a longitudinal study. A decline of pulmonary function (FVC, FEV1 and PEF) from predicted baseline levels was observed, starting on the last day of the episode. Two weeks after the episode, FVC, FEV1, PEF and MMEF were all decreased, and three and a half weeks after the episode, there was still a deficit compared to predicted baseline levels for FVC and FEV1.

Within the Dutch National Research Programme on Climate Change, the emission of methane from urban areas was considered to be one of the uncertain sources in the national methane budget. Amsterdam was chosen to be a representative urban area for methane emission assessment. An emission inventory was made and concentration fields were calculated using the Danish OML model. Calculated concentration values were compared to concentrations measured continuously at a site near Amsterdam and corrected for background concentrations, The methane emissionof the Amsterdam area is low. Main sources are traffic emissions (1.3 ktons y-1) and the gas distribution network (0.44 ktons y-1). The background corrected outdoor concentrations are a factor of twenty higher than the calculated outdoor concentrations.The most probable sources for this discrepancy are uncertainty in background concentration and the choice of the roughness length in modelling. [ABSTRACT FROM AUTHOR]