Impact of the lavender rhizosphere on the mercury uptake in field conditions.

Lavender plants as well as their rhizosphere and bulk soil were sampled on a wide range of soils with different land use within the Almadén mercury mining district. The aim of this work is to evaluate the role of the rhizosphere on mercury behavior in soil-lavender plant system including chemometric analysis. The edaphic parameters that significantly differed between lavender rhizosphere and bulk soil were: total Hg; easily available Hg; electrical conductivity; organic matter; cation exchange capacity; soluble ions (Cl(-); SO(4)(2-); PO(4)(3-); NO(3)(-); Al(+); Mn(2+); Ca(2+) and Mg(2+)). The most important variable in the differentiation is electrical conductivity. Furthermore, both organic matter and Mn(2+) in rhizosphere soil seem to block Hg availability to plant. However, the presence of sulfates seems to favor it. Regarding other relationships, Hg seems to block Pb uptake by lavender plants and, on the other hand, the presence of Mn(2+) seems to favor it. Furthermore, Hg root uptake by lavender and its distribution throughout the plant have been studied. The more available Hg in rhizosphere soil, the more Hg is translocated to aerial part and less Hg is retained by root. In all cases, the Hg concentration in the root was higher than in the aerial part.