Air sampling on a series of 10 cruises, spanning the whole area of the North Sea, yielded detailed spatial distributions of atmospheric concentrations of Al, Si, S, Cl, P, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb determined by EDXRF. A strong influence of the air mass history on the heavy metal concentrations was demonstrated for the whole sampling period of 5 years. Factor analysis performed on all samples collected with a stack filter unit resulted in the identification of three factors for the coarse particle fraction (sulphate particles with trace metals, sea salt particles and soil dust or metallurgic particles containing Fe) and four factors for the fine particle fraction (sea salt, sulphate with Pb and Zn), trace metal particles with Cu, Ni, Zn and fly-ash particles. The same statistics performed on all samples collected above the Southern Bight of the North Sea yielded three factors, namely: sea salt particles, particles enriched in Ni and V, originating from natural oil combustion and particles containing a variety of elements such as S, K, Ca, Fe, Pb, Cu and Zn. Compared with relevant measurements of trace elements in this area, a relatively good agreement can be found.

Vertical profiles of SO2 and O-3 concentrations were measured continuously within the lower atmosphere during 18 flights over the Southern Eight of the North Sea. The average SO2 concentration below the temperature inversion layer ranged from 1.9 to 19.5 ppb. The highest levels were observed when the air masses came from the southeast-east and under variable wind sector conditions: 15.2 and 12.0 ppb, respectively. The highest SO2 concentrations were found at altitudes between 100 and 200 m. The overall average O-3 concentration was 46 ppb, with values of 30-40 ppb at sea level to 60-70 ppb at altitudes above 100 m. Low O-3 concentrations reflect O-3 depletion through reaction with freshly emitted pollutants, while high O-3 concentrations are an indication of photochemical activity. O-3 concentrations are primarily dependent on seasonal influences, while SO2 levels are dictated more by the history of the sampled air mass. The results are discussed in relation to the heavy metal concentrations, measured within the same experiment. In spite of some differences, SO2 and trace metals showed similar trends. The individual SO2 and O-3 profiles clearly illustrated the high variability in vertical concentration distributions.

Chemicals, both natural and man-made, reach the North Sea through a number of different routes. For many years, research on pollution of the marine environment has focused on the most obvious inputs: those borne by rivers and direct discharges of waste. However, a number of studies conducted at the end of the 1970’s and at the beginning of the 1980’s revealed that a substantial fraction of the contamination entering the ocean, the North Sea and Baltic Sea, derives from sources located on land via atmospheric input. Gradually more importance has been given to the atmospheric route relative to the other pathways. The aim of this study was to estimate from field measurements the atmospheric input of some heavy metals into the Southern Bight of the North Sea, namely between the Dutch and English coast, for comparison with the input by other pathways, and to serve as a calibration reference for model calculations.

In an effort to assess the atmospheric input of heavy metals to the Southern Bight of the North Sea, aircraft-based aerosol samplings in the lower troposphere were performed between September 1988 and October 1989. Total atmospheric particulate and size-differentiated concentrations of Cd, Cu, Pb and Zn were determined as a function of altitude, wind direction, air-mass history and season. The obtained data are compared with results of ship-based measurements carried out previously and with literature values of Cu, Pb and Zn, for the marine troposphere of the southern North Sea. The results point out the high variability of the concentrations with the meterological conditions, as well as with time and location. The experimentally found particle size distribution are bimodal with a significant difference in fractions of small and large particles. These large aerosol particles have a direct and essential impact on the air-to-sea transfer of anthropogenic trace metals, in spite of their low numerical abundance and relatively low heavy metal content.

Sixty-six 24-hour precipitation samples were collected in Antwerp, Belgium and analyzed for pH and major ions. The samples were strongly acidic with a volume weighted average pH of 4.07. The results of stoichiometric ratios and regressive analysis indicate that the free acidity is mostly due to sulfuric and nitric acid. The observed neutralization of strong acids can mainly be attributed to ammonia. The chloride ion is one of the major ions in precipitation; it originates largely from marine aerosols and does not influence significantly the acidity.

Various micro-analysis techniques have been developed recently. They can advantageously be applied to particulate environmental samples to complement measurements made by traditional bulk analysis methods. Their characteristics are compared.In automated EPXMA, several hundreds of individual particles on a loaded filter can be located, sized and analysed in a few hours. The observed X-ray intensities for every particle which are related to the weight concentrations of the elements present are processed by a hierarchical cluster analysis. Different specific groups of particles with similar chemical composition are thus obtained and their abundance can be followed as a function of time and location. Although trace elements cannot be detected, the automated EPXMA method is essentially fast and reliable.In LAMMA, one single micrometer-size particle is evaporated by a powerful laser pulse and the generated ions are measured in a time-of-flight mass spectrometer. The laser beam can be attenuated to yield information about the particle surface only. LAMMA is a very sensitive and multi-element technique, it gives inorganic speciation and organic fingerprinting but its quantitative character is still limited for particles.Several examples of successful environmental applications of these techniques are discussed, namely: the composition and behaviour of atmospheric aerosols in remote areas and polluted marine environments, of suspended particles in the sea surface microlayer, in seawater and in rainwater and runoff water from an historical building.

Individual micrometer-size particles of inorganic nitrogen salts, such as NaNO3, NaNO2, (NH4)2SO4, NH4Cl, NH4NO3 and their mixtures, were analysed in the laser microprobe mass analyser. The cluster-ion distributions of the salts are systematically described and can be used to gain speciation information. The results can be used to study the distribution of the atmospheric aerosol inorganic nitrogen compounds and to investigate their chemical transformations under ambient conditions.

Ammonia is important in the atmosphere because it neutralizes acidic species. The relative importance of different inorganic ammonium compounds (chloride, nitrate and sulfate) in marine air chemistry was studied by single-particle characterization with the laser microprobe mass analyser. Standard aerosols were generated as a reference for compound identification, based on the fingerprint spectra obtained, and calculation of the relative sensitivity achieved for different ions in a marine aerosol matrix. The relative sensitivity for ammonium was low. Aerosol samples were collected in the Southern Bight of the North Sea under different meteorological conditions and examined for their ammonium compounds. Samples collected during an inversion period with continental influences showed a much higher content in all particles than samples collected under different meteorological conditions, where ammonium was mostly detected in the submicrometer particle-size range.

Observed enrichments of NaNO3 in marine aerosols have been attributed to NaNO3-formation during the sampling procedure in the case of filter sampling. This artifact was investigated for cascade impactor sampling. Experiments were carried out in which an air stream containing 1 μg HNO3 per m3 was led over 1-2 μm NaCl-particles deposited in an impactor. The morphology of the particles and the chemical composition of their core and surface layer was then investigated using laser microprobe mass analysis (LAMMA) and electron microprobe measurements. A definite NaNO3 formation was observed. It can, however, be avoided completely by placing a suitable denuder or pre-stage in front of the impactor. Even with such a precaution, NaNO3 was still found in ambient marine aerosols over the North Sea. This can thus be attributed now with certainty to a previous atmospheric interaction of NaCl with HNO3.