Abstract: Dry deposition velocities have been calculated using three different approaches. Turbulent wind profile theory has been used to predict the drag coefficient, wind speed and friction velocity at 10 m height when the wind speed is measured at a higher altitude. The resulting parameters were introduced in a two-layer deposition model. The second approach was the well-known model of Slinn and Slinn (1980, Atmospheric Environment 14, 1013-1016), whereas the third corresponded to the model published by Williams (1982, Atmospheric Environment 16, 1933 1938). Results point to clear differences. However, in a field experiment carried out at the Southern Bight of the North Sea, all three approaches show relatively comparable results. The role played by the size distribution of atmospheric particulate matter is essential. In our case any of the three models could have given satisfactory outcomes taking into account the wide spread of the experimental results cited in the literature for the same airshed.

Abstract: Air particulate samples were collected at Chapiquiña near Arica (Chile) with a six-stage cascade impactor for about 17-day periods during a 31 month interval. Sixteen elements were determined by energy dispersive X-ray fluorescence analysis, and the elemental concentrations were subjected to principal factor analysis. The variability with time of the coarse particles was described by two factors both related to soil dispersion, whereas the fine particle variations could be explained by a third factor related to marine influence. Enrichment factors were compared with those obtained in other remote continental areas, in particular those of air particulate matter sampled at Chacaltaya, Bolivia. Results point to a negligible anthropogenic influence.

Abstract: The rate of iron(II) oxidation in North Sea water of pH 5.510 in the range 1025°C has been studied. The oxygenation rate depends linearly on the iron(II) and dissolved oxygen concentrations. The second-order dependence on [OH−], found by several investigators for synthetic solutions, was confirmed in seawater, but only for pOH > 6.9. For pOH < 5.9 the rate appeared to be independent of the pOH. In the intermediate range, pOH 5.96.9, corresponding to the natural pH of seawater, a first-order dependence on the pOH is obeyed. The important discrepancy in the literature between the second-order rate constant for NaCHO3 solutions and for seawater can be attributed predominantly to the incorrect assumption of a second-order pOH dependence in natural seawater. The results can be useful, for example, in predicting the effect of dumping acidic iron waste from the titanium-dioxide industry into the ocean.

Abstract: Two common procedures for wet destruction of biological materials for subsequent determination of selenium have been investigated. Rat organs and biological fluids were endogenously labelled with 75Se to monitor losses during the procedures. Addition of nitric and perchloric acids with gradual heating up to 210° seemed to be the best method: at this temperature the labelled selenium was still recovered quantitatively, and the destruction was fast and efficient.

Abstract: Elemental analysis for all of the light elements up through chlorine by elastic scattering of 16 MeV protons has been shown to be feasible. Basic problems associated with such measurements are discussed including kinematics, angular distribution, and sample backings. Spectra are presented for air particulate matter for both a total filter (Nuclepore) and a size fractionated air impactor (polystyrene backed) sample. The method is absolute, non destructive and can be used in conjunction with proton induced x-ray fluorescence to quantitatively analyze all elements in the same sample in minutes of time.

Abstract: A variety of samples, collected from different historical buildings and monuments throughout Belgium, were thoroughly studied, using several trace- and micro-analysis techniques. Thin sections of stones and mortar joints were characterized by means of electron probe X-ray microanalysis (EPXMA). The morphological appearance of the surface weathering crust and the possible presence of non-innate particles in the crust were elucidated using petrographical and electron microscopy. Quantitative characterization of the total chemical composition of the crust surface layer and underlying layer was performed by energy-dispersive X-ray fluorescence, and by ion chromatography and atomic absorption spectrometry for the leachable components. Special attention was also paid to the chemical composition of rain and air at the particular sampling sites. The element distribution in the transition zone between the weathering crust and the original stone material was found to vary greatly amongst the different samples analyzed. Detailed EPXMA measurements on pieces of the weathering crust showed remarkable differences in morphology and composition between the surface and the underlying layer, and provided information about the presence of fly-ash and soil dust particles in the crust. Except for crusts from the city of Brussels, which were all very high in sulphate, the samples appeared to contain very variable sulphate contents; very local micro-climate and environmental conditions at a particular site are more important in determining the weathering condition of the building stones than the local air pollution situation. Bulk analytical characterization further showed, in all the crust samples studied, a very small contribution of nitrogen- and chlorine-containing weathering products, in contrast to sulphur-containing weathering salts.