Relevant aspects on biomonitoring of heavy metal concentration in environmental air in Asunción city

Aspectos relevantes del Biomonitoreo de la concentración de metales pesados en el aire ambiental de la ciudad de Asunción

Resumen

Introduction. Bryophytes (mosses) have long been used to determine the concentration of heavy metals as an alternative to the collection of atmospheric aerosols. Objective. To evaluate the environmental concentration of lead, cadmium, mercury and arsenic in autochthonous species of moss and to analyze some methodological aspects of biomonitoringin Paraguay. Methodology. In an observational study moss samples were obtained from sub rural zone to be transplanted in 5 sites of high vehicular traffic in Asunción city. The samples were left outdoors for 58 days and then collected and subjected to study using the inductive coupling plasma source mass spectrometry technique. The bryophytes were characterized and all the climatological variables during the study period were consigned.  Results. Lead concentrations detected in moss explants exposed to the urban environment were higher than mosses from natural forest, while arsenic levels in the latter were higher than those found in bryophytes transferred to the city. No conspicuous levels of cadmium and mercury were found. The bryophytes used belonged to two families: Hypnaceae and Pilotrichaceae. The range of temperature, relative humidity, wind and precipitation did not reach extreme levels during the studied period. Conclusion. The different lead levels measured here, could be surrogates of urban pollution while the notorious arsenic level in natural forest moss points to other sources like wildfires. Several aspects of the biomonitoring methodology are discussed.