Esther Lasheras

Use of native mosses as biomonitors of heavy metals and nitrogen deposition in the surroundings of two steel works.

A biomonitoring survey using the moss species Hypnum cupressiforme Hedw. was conducted in the surroundings of two steel plants located in the North of Spain. Levels of V, Cr, Ni, Cu, Zn, As, Cd, Hg, Pb and N were determined. Very high concentrations in the areas of study were detected when compared to nearby unaffected regions. Similar trends were observed for all the elements in the differently orientated transects, showing an appreciable influence of the NW prevailing winds of the region in the dispersion of pollutants, as well as a clear decreasing gradient in the concentrations of metals in mosses within a distance of 1500 meters from the facilities. A differentiation between the elements emitted by the chimney as result of the industrial activity (V, Cr, Ni, Cu and As) and those with a high presence in steel slag deposits (Zn, Cd, Hg and Pb) was observed. The range of contamination was also established by means of the Contamination Factor, indicating a category 4 out of 6 categories, which shows the high levels reported in the areas of study. A different dynamic was registered for nitrogen regarding the rest of the heavy metals analysed except for Hg, probably due to the elevated volatility and mobility of both elements, as well as their high persistence in the atmosphere.

Application of microwave digestion and ICP-MS to simultaneous analysis of major and trace elements in aerosol samples collected on quartz filters

A microwave digestion method in a closed vessel was developed for the simultaneous determination of trace and major elements, with the highest possible recoveries, in atmospheric aerosols using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method was developed to quantify the concentration of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Cd, Sb, Cs, Ba, La, Ce and Pb present in quartz filters containing particulate matter (PM10). The performance of the procedure was evaluated by analysis of the standard reference material NIST 1633b and CTA-FFA-1. Different combinations of nitric acid (HNO3), hydrogen peroxide (H2O2), hydrofluoric acid (HF) and hydrochloric acid (HCl) were tested to improve the recovery factors for the studied elements. The addition of a large amount (3 mL) of HF was required to fully dissolve the quartz filters. This fact made difficult the obtention of high recoveries for alkali (Rb, Cs), alkaline earth (Mg, Ca, Ba), and rare earth (La, Ce) elements, which showed the lowest recoveries. In this study three different digestion methods were assessed using a closed evaporation system, the addition of boric acid and a mixture of both procedures to minimize the effects of residual fluoride.

Assessment of Indexes for Heavy Metal Contamination in Remote Areas: A Case Study in a Pyrenean Forest, Navarra, Spain

The objective of the present work was to verify and compare the performance of different geochemical indices employed to identify the anthropogenic origin of selected heavy metals and other trace elements in soils. To that end, two background values, the upper continental crust and the metal content in the bed rock, were used and obtained from a forested basin of the western Pyrenees. The enrichment factor (EF), geo-accumulation index (Igeo), and contamination factor (Cif) were finally evaluated for their ability to determine anthropogenic contamination: Results indicate that an in-depth knowledge of the bed rock geochemistry and the geological background content is essential to distinguish between the natural variability of soils and any anthropogenic contribution of heavy metals. Although both EF and Cif show a similar ability to detect soil contamination, the latter is proposed as a more appropriate and sensitive marker given its ability for finding episodically elevated contamination levels.