On the horizontal homogeneity of mass-related aerosol properties

We studied the mass-related aerosol properties, simultaneously at two sites at the urban roof top level in the same city. No systematic influence of the wind vector on the difference in the aerosol concentrations between the two locations could be found. These results are compared with results from a second, similar experiment over a larger distance including one urban and one rural site. Surprisingly, we could not detect a tendency which would indicate that sampling air at distance in the order of 1 km would be less affected by the heterogeneity than sampling distanced in the order of 10 km apart. On the contrary, the results suggest that mass-related properties at two sites in the same city are not necessarily more similar than at an urban and a rural site outside the city. These results stress the limited horizontal homogeneity of urban atmospheric aerosol. As a conclusion it is suggested that single-site measurements of mass-related aerosol properties should be considered to be representative for an area smaller than 1 km2 on size.

Low-molecular weight dicarboxylic acids and glyoxylic acid: seasonal and air mass characteristics

Low-molecular weight dicarboxylic acids are important constituents ofthe organic fraction of atmospheric particulate matter in remote and polluted regions. The knowledge on their sources is sparse, however, and organic aerosols in general need to be better characterized. Observations of C2-C5 alpha,omega-dicarboxylic acids (DCAs oxalic, malonic, succinic, and glutaric acid) and C2 oxomonocarboxylic acid (glyoxylic acid) from rural and urban sites in different seasons in Germany are reported using filter sampling and ion chromatography. The C2-C5 DCAs accounted for (by average) 0.07-0.51 microg m(-3) at the various sites corresponding to 3.4-23 mg g(-1) of total suspended particulate matter and glyoxylic acid for < 0.18-0.28 mg g(-1). Both, the transport of air masses over the continent and the summer season favored the occurrence of the acids. Secondary photochemical formation dominated the sources. It was found that for central Europe the anthropogenic emissions are more important than the biogenic emissions for all the acids determined and most important for oxalic acid. The biogenic precursors play a signifcant role for malonic acid. The influence of the marine sources was detectable for malonic and glutaric acid.

[Tuberculous encephalitis--a complication of lung tuberculosis]

On the basis of a number of cases, the symptomatology and the diagnostic work-up of encephalitis tuberculosa are presented. All the patients had neurological findings, which in some cases were masked. Although computed tomography of the head and CSF examination provide sensitive, but nonspecific findings, the diagnosis would not have been established without a detailed knowledge of the clinical picture. A greater incidence of complications than has previously been assumed, is postulated.