Transformation Of Particulate Matter Research Articles

Transformation of suspended particulate matter into sediment in the Kara Sea in September of 2011

The biogeochemical processes participating in the transformation of the particulate matter into sediment along the Yenisei River-St. Anna Trough (Kara Sea) meridional profile were studied using hydrochemical, geochemical, microbiological, radioisotope, and isotope methods. The water-sediment contact zone consists of three subzones: the suprabottom water, the fluffy layer, and the surface sediment. The total number, biomass, and integral activity of the microorganisms (dark 14CO2 assimilation) in the fluffy layer are usually higher than in the suprabottom water and sediment. The fluffy layer shows a decrease in the oxygen content and the growth of the dissolved biogenic elements. It was provided by the particulate organic matter supporting the vital activity of the heterotrophs from the overlying water column and by the flux of reduced compounds (NH4, H2S, CH4, Fe2+, Mn2+, and others) from the underlying sediments. The Corg isotopic composition of the fluffy layer and the sediments is 2–4 ‰ heavier than that of the particulate matter and sediment due to the presence of the isotopically heavy biomass of microorganisms. A change in the isotopic composition of the Corg in the fluffy layer and surface sediment as compared to the Corg of the particulate matter is a widespread phenomenon in the Arctic shelf seas and proves the leading role of microorganisms in the transformation of the particulate matter into sediment.

The Processes of Particulate Matter Transformation from Water Column to Sediment in the Kara Sea

The Processes of Particulate Matter Transformation from Water Column to Sediment in the Kara Sea

Transformation of size distributions of emitted particles in streets

Dispersion and transformation of particulate matter in streets are studied by using a combination of a street pollution dispersion model, the Operational Street Pollution Model (OSPM) and a particle transformation model. The particle model implements a very fast implicit method for solving the changes in particle size distribution due to coagulation, condensation and dilution processes. Using available measurements of emitted particle size distributions, impact analysis of the various transformation processes affecting the size distribution of particles was performed. For this purpose, a plume model simulating dilution of diesel exhaust has been developed and coupled with the particle coagulation model. The results show that due to the rapid dilution of the exhaust plume, the coagulation is not significant. Growth of the emitted particles due to condensation of water vapour appears also to be marginal, but this conclusion depends critically on the assumption of particle hygroscopicity. The freshly emitted diesel particles are believed to be less hygroscopic. Analysis of recent street measurements of particle size distributions in the range 0.2–20 μm reveals in general very poor correlation with the street traffic, but strong dependence on the relative humidity. This indicates that the particles measured are not freshly emitted and aged aerosols are dominant. Calculations with the street pollution dispersion model OSPM, using the diesel exhaust emissions as the only source, show that the mass concentrations of emitted particles in the street are predicted to be significantly lower than the measured concentrations.