Predicting the Concentration of Total Mercury in Mineral Horizons of Forest Soils Varying in Organic Matter and Mineral Fine Fraction Content

anglais. The level of mercury (Hg) concentration in soils can be estimated using certain predictors such as the content of organic carbon (C org) or the fine fractions (FFs) such as silt and clay. This study was focused on the potential use of C org and FF contents as the predictors of Hg concentration at the spatial meso-scale in forest soils derived from Triassic sandstones and claystones, Quaternary sands derived from weathering sandstones and Quaternary sands of fluvioglacial origin. To understand the importance of C org and FF contents for Hg retention in mineral soil, the allocation of Hg in physically separated fractions of soil samples was also tested. The experiment was designed over a regular 200 × 200-m grid, where 275 plots were established. The results implied that the concentration of total Hg in mineral soil may vary by several orders of magnitude because of the natural variation in C org content. The model where the C org content was the only variable explained 44 % of Hg concentration variability in soil, and other significantly correlated variables were the FF content and the C/N ratio. Detailed analysis revealed that the particulate organic matter fraction accumulated more Hg per unit of C org than in the organic matter associated with FF. The content of C org, FF and C/N ratio allowed, for the local soils, a satisfactory prediction of the spatial distribution and the magnitude of total Hg concentration in soils.

anglais. Mercury, Forest soil, Organic matter, Particulate organic matter, Modelling

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1-9

1924