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(38-63) Experimental studies to increase the mercury bioavailability and transfer in the soil-plant system. Millan, Rocio*,1, Vera, Ricardo1, Schmid, Thomas1, Tallos, Alberto1, Recreo, Fernando1, 1 CIEMAT (Research Centre for Energy, Environment and Technology), Av. Complutense 22, Madrid, Spain ABSTRACT- The experimental work is focused on the recovery of a soil containing mercury applying a phytoremediation technique. This remedial action is based on the use of plants with the capacity to absorb and accumulate contaminants from the soil. In order to improve the mercury uptake by vegetation, specific solutions have been implemented to increase the bioavailable mercury fraction in the soil solution. Furthermore, a set of crops has been selected to test their absorption capacity of this element. The soil used in the experimental work proceeds from the surroundings of a mercury mine (Almaden, Spain). The soil sample has been divided in two fractions respecting the soil horizons. The first one corresponds to an organic top layer, where Hg content is about 30 ppm. The second fraction is a clayey horizon immediately below, and presents a mercury concentration of about 15 ppm. In addition, a mixture of both fractions has been considered in order to simulate a ploughed horizon. Mercury content is determined in the three fractions. The experimental work has been performed using columns, where selected extractant solutions have been added. After a period of contact, mercury concentration has been analysed in the following phases: soil at field capacity, leachate, soil at wilting point and total available water to plant. In order to evaluate the capacity of vegetation to absorb mercury from soil, typical crops grown in the study area have been tested. This experimental work has been made under controlled conditions using the same Almaden soil sample. The optimum extractant-crop combination obtained, will be tested in lysimeters and in experimental plots under real conditions in the Almaden area. Key words: Mercury, Soil contamination, Bioavailability, Phytoremediation |
