Airborne 210Pb, Si, Zn and Pb as tracers for atmospheric pollution in Helsinki metropolitan area

This study analyzed 16070 daily and 608 weekly air filter samples from the Helsinki metropolitan area collected between 1962 and 2005. The aim was to use the Potential Source Contribution Function (PSCF) to determine potential sources of silicon (Si), zinc (Zn), lead (Pb), and radioactive isotope 210Pb. The main sources for Si and Pb were industrial activities, particularly mining, metal industry, and traffic. Common source areas for Zn and 210Pb were identified in the eastern and southeastern parts of the measuring site.

Correlation between the latitudinal profile of the 7Be air concentration and the Hadley cell extent in the Southern Hemisphere

The cosmogenic radionuclide ⁷Be is one of the best tracers for aerosol transport since its half-life of 53 days is in the time scale of many atmospheric circulation phenomena. In this work, we analyze a 12-years-long daily time-series for the airborne ⁷Be concentration for nine air filtering stations in the Southern Hemisphere or close to it. The observed latitudinal distribution of ⁷Be concentration, with its maximum at the southern subtropical high-pressure belt, is similar to the one in the Northern Hemisphere. A good time correlation was found between the 7°-shift of the ⁷Be concentration latitudinal distribution and the seasonal displacement of the extent of the Hadley cell. This is consistent with tropopause folding events, mostly occurring in spring, being the main contribution for the injection of stratospheric ⁷Be into the descending branch of the Hadley cell.

Perfluorinated alkyl substances in snow as an atmospheric tracer for tracking the interactions between westerly winds and the Indian Monsoon over western China

Snow is an efficient scavenger for the deposition of contaminants. Atmospheric transport and snow deposition jointly control the distribution of pollutants in remote mountain/polar regions. But can the contaminants contained within snow be used to reflect the interactions of air circulation patterns? The physicochemical properties of perfluoroalkyl substances (PFASs) are unique because of their high water solubilities. Taking advantage of this, 15 surface-snow and 3 snow-pit samples were collected across a vast area of western China (spanning 20° of latitude and 25° of longitude), to investigate the concentrations, composition profiles (fingerprints), and deposition fluxes of PFASs. Both a high concentration (3974 pg/L) and deposition flux (4.0 μg/m²/yr) for a total of 16 PFASs were found in the snow at Yulong, the most southern sample site, possibly because of its close proximity to source regions of pollutants in South Asia and high rate of snow deposition. Perfluorobutanoic acid was the most commonly found chemical in snow, but in general the PFAS composition in the snow of western China showed large spatial differences, with long-chain (C > 10) PFASs being relatively dominant in the north and west of the region and short-chain (C < 6) PFASs in the south and east. On the basis of the different compositions of PFASs in the snow of western China and the previously reported features of pollutant sources in Europe and India, we found that PFASs in snow can be used as an atmospheric tracer for tracking the interactions between westerly winds and the Indian Monsoon. The belt along 33°N is a key location where both the Indian Monsoon and westerly winds can arrive/interact; however, the contribution of the monsoon was found to be above 70%, while that of the westerly winds can be lower than 30%. The western part of the 33°N belt was found to be more vulnerable to the Indian Monsoon, and could be grouped into the monsoon domain, while the influence of the westerly winds increased from west to east along the belt. This finding is opposite to previous results, which reported that the western part of the 33°N belt was mainly under the influence of the westerly winds, and for the first time quantifies the relative contribution of westerly winds and the Indian Monsoon to the atmospheric transport of chemicals.

Method for source localization proposed and applied to the October 2017 case of atmospheric dispersion of Ru-106

An efficient numerical method for the temporal and spatial localization of an unknown point source of an atmospheric tracer is proposed. The method, which is based on inverse modelling techniques, employs available data from a network of ground-level stations on the condition that the measurements represent the plume geographically and temporally. The method, which employs a level-of-agreement approach, is applied to the October 2017 air concentration measurements of Ru-106 in Europe.

Analysis of the vertical radon structure at the Spanish "El Arenosillo" tower station

This paper presents an analysis of one year of hourly radon and meteorological measurements at 10 m and 100 m a.g.l. at El Arenosillo tall-tower station, in the south-west of the Iberian Peninsula. Whole-year and seasonal composites of the diurnal radon cycle show the expected behaviour, with larger concentrations at 10 m than at 100 m during the night, due to poor vertical mixing, and similar concentrations at both heights during the daylight hours. Wind speed and wind direction analyses by sector show the prevailing contributions for each season. Sectors with air which has spent a longer period over the ocean and high wind speeds will lead to low concentrations at both levels, whereas inland sectors show a clear increase of the concentrations with similar overall averages for the two levels. The Sierra Morena, Guadalquivir and Bethics System sectors (continental pathways) are the sectors that show higher concentrations for mild to large wind speeds. The daily evolution of radon concentration differences at both heights has been grouped into four clusters by using a K-means algorithm method. The four clusters have been selected so that they sufficiently describe different characteristics in terms of stability. The temporal evolution of the mixing height (MH) and of the bulk diffusivity parameter (Kb) during the nocturnal period has been calculated by using the temporal variation of (222)Rn concentration at 10 m and the concentration gradient with height, respectively.