Characterization of urban aerosol sources in Debrecen, Hungary

Debrecen is an average middle European city from the point of view of aerosol pollution. Its locationmakes the city an ideal place for observing aerosol transport processes. Systematic investigation ofatmospheric aerosol of the east-Hungarian region has been performed in the Institute of NuclearResearch of the Hungarian Academy of Sciences for 20 years by accelerator based elementalanalytical technique. As a complementation of this research we observed the size distribution andshort-term time variation of the elemental component of fine (PM2.5) and coarse (PM10-PM2.5) urbanaerosol in the frame of sampling campaigns during 2007 and 2008 in a downtown site of Debrecen.Meteorological parameters were also recorded parallel to the aerosol sampling. Elementalconcentrations (Z ≥ 12) were determined by particle induced X-ray emission (PIXE) analyticaltechnique at the Laboratory of Ion Beam Applications (IBA) of the ATOMKI. On the obtaineddatabase six sources of the urban aerosol were identified: 2 types of soil, domestic heating, sulphateoriginating from long range transport processes, an unidentified source enriched with chlorine andtraffic. Emission episodes were also observed. The short-time variation of urban aerosol combinedwith meteorological data and with mass size distribution serves as a basis to reach a betterunderstanding of the aerosol sources in receptor areas, to select local emission and long rangetransport episodes, to follow the evolution of aerosol, and to make a better estimate on the healthimpact

Temporal variability of CO2 and N2O flux spatial patterns at a mowed and a grazed grassland

Spatial patterns of ecosystem processes constitute significant sources of uncertainty in greenhouse gas flux estimations partly because the patterns are temporally dynamic. The aim of this study was to describe temporal variability in the spatial patterns of grassland CO2 and N2O flux under varying environmental conditions and to assess effects of the grassland management (grazing and mowing) on flux patterns. We made spatially explicit measurements of variables including soil respiration, aboveground biomass, N2O flux, soil water content, and soil temperature during a four-year study in the vegetation periods at grazed and mowed grasslands. Sampling was conducted in 80×60 m grids of 10 m resolution with 78 sampling points in both study plots. Soil respiration was monitored nine times, and N2O flux was monitored twice during the study period. Altitude, soil organic carbon, and total soil nitrogen were used as background factors at each sampling position, while aboveground biomass, soil water content, and soil temperature were considered as covariates in the spatial analysis. Data were analyzed using variography and kriging. Altitude was autocorrelated over distances of 40–50 m in both plots and influenced spatial patterns of soil organic carbon, total soil nitrogen, and the covariates. Altitude was inversely related to soil water content and aboveground biomass and positively related to soil temperature. Autocorrelation lengths for soil respiration were similar on both plots (about 30 m), whereas autocorrelation lengths of N2O flux differed between plots (39 m in the grazed plot vs. 18 m in the mowed plot). Grazing appeared to increase heterogeneity and linkage of the spatial patterns, whereas mowing had a homogenizing effect. Spatial patterns of soil water content, soil respiration, and aboveground biomass were temporally variable especially in the first 2 years of the experiment, whereas spatial patterns were more persistent (mostly significant correlation at p<0.05 between location ranks) in the second 2 years, following a wet year. Increased persistence of spatial patterns after a wet year indicated the recovery potential of grasslands following drought and suggested that adequate water supply could have a homogenizing effect on CO2 and N2O fluxes