(212)Pb as tracer for PM deposition on urban vegetation.

(212)Pb concentration in outdoor air is closely correlated with fine suspended particulate matter in the atmosphere. Thanks to this association, this isotope can be used to trace the sinking processes of particulate matter due to the vegetation, also providing accurate estimations of the deposition velocity on foliar surfaces. This approach is particularly effective in areas with high thoron fluxes and, consequently, high (212)Pb fluxes from soil. The contribution of vegetation to the improvement of air quality (AQImp) in the municipality area (MA) of Rome (Latium, Italy), almost entirely located on Th-enriched volcanic soils, was estimated by studying (212)Pb deposition velocity on the grasses (0.9-2.5mm·s(-1)) and on the most common tree classes, namely conifers (1.5-15mm·s(-1)), evergreen (1-4mm·s(-1)) and deciduous (0.2-1.5mm·s(-1)). (212)Pb activity in outdoor air was determined by gamma spectrometry after air pumping with accumulation on cellulose filters and after collection on artificial electrostatically charged surfaces (ECS). The high (212)Pb activity values obtained from this analysis (0.90±0.6Bqm(-3) and 0.58±0.15Bqm(-3), respectively near and far from the soil) are consistent both with the average regional thoron flux from volcanic soils (2.9·10(4)Bqm(-2)·h(-1)) and with the thoron flux measured in the volcanic soils of the study area. Thoron and (212)Pb fluxes were also measured both in laboratory and in the field under different soil moisture conditions. The total AQImp for the period from September 2014 to September 2015, calculated after the classification of the MA of Rome into six classes of vegetation, provided a value of 0.20 corresponding to 2.3 Tons per day of removed PM10. The role of grasslands in the PM10 removal, the contribution of the vegetation to the improvement of AQImp and the possibility of improving the sinking efficiency of green areas by increasing conifer trees coverage were also highlighted.

Bioaccessible selenium in Italian agricultural soils: Comparison of the biogeochemical approach with a regression model based on geochemical and pedoclimatic variables.

Biogeochemical mapping of selenium in Italian agricultural soils was accomplished by measuring the Se concentration of representative samples of wheat grains from 71 provinces. The range of the concentration values averaged on a provincial basis was 7-245 ng Se g(-1). A multiple regression model based on six geochemical and pedoclimatic variables was developed to interpret the observed data and to predict Se concentration of wheat in areas where analytical data were missing and in the different Italian soil regions. The statistical model explained only part of the observed variance, but succeeded in identifying Se-enriched as well as Se-depleted areas with an acceptable level of agreement with the biogeochemical map based on measured Se in wheat. Furthermore, the model showed that within the range of concentrations measured in Italian soils, Se-bioaccessibility is controlled not only by the Se content of the soil parent rocks, but also by their overall geochemical nature (carbonatic vs. silicatic) and by pedoclimatic variables (temperature and rain intensity excursions) related to fluctuations of soil moisture and pH. Overall, several Se-marginal and Se-deficient areas were identified on the Italian territory. The implications of these findings for public health are discussed briefly.

A methodology for assessing the maximum expected radon flux from soils in northern Latium (central Italy).

Northern Latium (Italy) is an area where the Rn risk rate is potentially high because of the extensive outcropping of Neogene U-rich volcanics and the presence of major active tectonic lineaments. The lack of data on Rn risk rates in that area, which is undergoing major urban and industrial development, has prompted this study. It proposes a methodology to evaluate the maximum potential diffusive Rn flux from soils based on the measurement of (226)Ra, (232)Th and (40)K activities by gamma-ray spectrometry, and the measurement of main soil parameters influencing the Rn emanation. This methodology provides a simple, reliable and low-cost tool for drawing up radon flux maps useful to both public planners and private individuals, who want to operate safely in the study area. The proposed methodology may also be applied to other geographic areas outside the prescribed study area.