The composition of road dust is influenced by emissions from local industry as well as by traffic emissions. Thus, the composition of urban road dust can be used as an indicator for environmental pollution. Pollutants contained in road dust also are transferred into the atmosphere by resuspension and into the aquatic system by wash-off. In this transfer, the particle size of the road dust particles is of extreme importance. Therefore, information about the composition of road dust in dependence of the particle size is crucial. In this study, road dust samples were separated by air classification into size fractions down to 2 µm. The chemical analysis of the size fractions also revealed a significant size dependence of the metal concentrations in the finest size fractions. The least polluted size fraction was generally the fraction 200-500 µm, whereas the highest concentrations were measured in the finest size fraction < 2 µm. These results are important for the assessment of the mass fraction of the various pollutants in the mobile size fractions in re-entrainment as well as in runoff during rainfall.
In this study, a unicellular soil alga isolated from farmland in Germany was surveyed. The investigation of the hypervariable molecular markers ITS1 rDNA and ITS2 rDNA identified strain E71.10 as conspecific with Vischeria sp. SAG 51.91 (Eustigmatophyceae). The culture was tested for biomass generation and for the yield of fatty acids and amino acids. The survey included four different culture conditions (conventional, elevated CO 2 , nitrogen depletion, or sodium chloride stress) at room temperature. The best yield of dry biomass was achieved applying 1% CO 2 , whereas nitrogen-free medium resulted into least growth. The fatty acid content peaked in nitrogen-free medium at 59% per dry mass. Eicosapentaenoic acid was the most abundant fatty acid in all treatments (except for nitrogen free), accounting for 10.44 to 16.72 g/100 g dry mass. The highest content of amino acids (20%) was achieved under conventional conditions. The results show that abiotic factors strongly influence to which extent metabolites are intracellularly stored and they confirm also for this yet undescribed strain of Vischeria that Eustigmatophyceae are promising candidates for biotechnology.
Metals in road dust are increasingly investigated. The fine size fractions are of particular importance because of their higher mobility and the increased concentrations of pollutants. In this study, two average road dust samples from areas with highand low-traffic density were investigated. Prior to chemical analysis, a combined sieving and air classification procedure was applied where the road dust samples were split into seven size fractions. The metal concentrations in the road dust from the low-traffic area were only up to twice the background concentrations. An exception was Cu where the concentration was 15 time higher. In the sample from the high-traffic area, the respective concentrations of Zn, Mn, Fe, Pb, Ba, Sb and Cu were 5.4, 3.2, 3.0, 2.7, 2.7, 2.5 and 1.2 times higher compared to the low-traffic area. The ratio of the concentration in high-and low-traffic road dust was 0.8-2.0 for the fine size fractions and 2.0-6.0 for the coarse size fractions for several metals, including traffic-related metals like Fe and Ba. An explanation for this surprising result might be the atmospheric transport of re-suspended particles from high-traffic to low-traffic areas, which is feasible only for smaller particles because of their low sedimentation velocity. However, for the highly traffic-related metals Pb and Zn, the ratio was more size independent. For Cu, the concentration ratio was fluctuating. Some particles with a high Cu content in the analysed samples might be the reason.
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