From iPhone to Soil, Analysis of Trace Element in Soil of Southern Québec

Forest soils represent an important stock of nutrients available to sustain forest productivity. They also contain an amount, still unknown, of trace elements inherited from natural or anthropogical sources. Many of these trace elements can be toxic to living organisms. Thereby, quantification of the concentration and the total content of trace elements in forest soils is necessary to assess the impact of these elements on soil quality. The objectives of this project were: 1) to measure the total content of trace elements in solid phase (Ag, As, Ba, Cd, Ce, Co, Cr, Cu, Mn, Ni, Pb, Rb, Se, Sr, Tl, V, Y, Zn) of various soil horizons in two forest ecosystems of southern Quebec, 2) to establish significant correlations between the bioavailable fraction (water-soluble) of trace elements and soil horizons properties and 3) to compare the trace element stock of two Canadian Shield’s forest soil with those of similar soils situated in the Montreal area. To achieve these goals four soil profiles situated in the pristine region of St-Hippolyte and two in the urban area of Montréal, were excavated and analyzed down to the parent material. The results of this research have established that the trace element’s total stock is mainly concentrated in coarse fragments of the soil. Multivariate statistical analyses revealed significant links between organic carbon, organometallic complexes, Fe-Al oxides as well as amorphous forms of Si and the distribution of trace element in soil profiles. Finally, it was proved that Montreal’s soil contained more trace element (Ag, As, Ba, Cu, Mn, Pb, Rb, Se, Sr, Tl et Zn) than Canadian Shield’s soils. This project constituted a fundamental contribution to soil science in Québec and increased our comprehension of spatial variation of trace element in southern Quebec. Specifically, the identification of coarse fragments as a major source of trace element as well as the quantification of the trace element total content in organic horizons represent original discovery. Moreover, the use of multivariate statistic to identified significant variables explaining the distribution of trace element is innovative and allows a better understanding of trace element biogeochemical cycle in natural ecosystem.