Study of Hg in soil cover of sealed urban landfills and its toxic impact in Lupinus albus L. grown in landfill soils with high levels of this trace element

M. J. Gutiérrez-Ginés,1* A. J. Hernández, 1 R. Millán, 2 J. Pastor, 3

1 Dpto. Ciencias de la Vida, Universidad de Alcalá, Alcalá de Henares, España 2 División de Suelos y Geología Ambiental, CIEMAT, Madrid, España 3 Dpto de Biología Ambiental, MNCN, CSIC, Madrid, España

*Presenting author contact: mjesus.gutierrezg@uah.es

The studies of heavy metal pollution of sealing soil cover of many urban landfills in Spain do not usually take into account mercury. This work presents the results of Hg analysis (Advanced Mercury Analyser, AMA-254, LECO Company, Czeck Republic) in sealing covers of four landfills, which were sealed some 20 years ago and are placed in the southeast of Community of Madrid. A total of 74 samples collected from the first 10 cm of the soil cover were analysed. 12 of them showed a Hg concentration higher than 1 mg·kg^-1 (reference level according to Spanish law, RD1310/1990). Maximum concentration was 10.5 mg·kg^-1.

Two of these soils with Hg concentration above reference limits were chosen for conducting a bioassay in 1 kg pots and in greenhouse. The aim was to evaluate the possible Hg toxic effects on Lupinus albus L. Results demonstrated a significant weight decrease of different plant parts (roots, stems and leaves) of plants grown on landfill soils compared with control ones. Difference between the two landfill soils was made by stem weight and flowering capacity of the plants. Potassium concentration was determined in the different plant parts. Bioaccumulation index ([K]_root·[K]_soil^-1) as well as transfer factor to stems ([K]_stem·[K]_root^-1) and leaves ([K]_leaf·[K]_stem^-1) were calculated. Potassium concentration in the plant parts was significantly different between treatments. However, it is those indices what indicates the effect of pollution on the uptake of this nutrient. Bioaccumulation index showed that K uptake is more important in soils with the highest Hg concentration. However, once K is in roots, the transfer to stems is more important in control plants than in landfill treatments. In the same way, transfer to leaves is greater in control plants.