Origin of high fluoride contents in groundwater of the Santa Maria Formation, Guarany Aquifer System, southern Brazil

Abstract

A comprehensive assessment of man-made impact on the environment is much kept behind because of missing unified systems of environmental monitoring. They represent sources of reliable information on the current status of the environment, as well as the absence of approaches to assess the impact of chemical pollution by different anthropogenic sources. Vegetation, being the component of environmental systems, is very sensitive to atmospheric man-made load. However, permissible concentrations of elements in plants, causing deflection in their development are differently estimated in different regions and vegetation species. As to the Baikal region, it is commonly the sanitary state of woods, that is primarily assessed. Coniferous trees, in particular pine, represent the main tree species in the region. In the Olkhon region we investigated the trace element compositions in pine needles to obtain the background contents of toxic metals. This region of the National park lies 300 km away from the industrial sources of pollutants, beyond the zone of wind effect, and has no industry. The research was made on the healthy (green) and dried up (red) pine needles. The elements like Zn, A1, Mn, Fe, Cr, Cu, Co, Ni, Sr, Cd, Pb, Li, Rb, Sb and As were measured by atomic absorption and flame emission photometry. The samples were decomposed in autoclaves with the mixture of nitric acid and hydrogen peroxide. Distinct differences were found in a series of elements contained in the green and dried needles. The red needles are characterized by higher contents of Zn, A1, Cu and low Mn, Fe, Pb with similar contents of other elements. It is proposed to use the ratio Fe/Mn for evaluating the ecological status and characterization of the damage to trees. In the study region in the green needles Fe/Mn=0.5, in red ones it is 0.7 (for comparison the ratio Fe/Mn in the zone of industry influence the ratio is 1.1-2.0). The obtained values of metal concentrations in the green pine needles can be accepted as background in the assessment of the sanitary state of the Prebaikalian woods, and reddening of the needles most likely reflects the natural serial level of tree stands.