Oral communication: Plants, earthworms and bacteria: an integrated approach to assess and recover the health of soils contaminated with chromium (VI) and lindane

BECERRIL, JOSÉ MARÍA; MORENO, C.; APARICIO, JUAN DANIEL; GARBISU, CARLOS; ARTETXE, UNAI; SOTO LÓPEZ, MANUEL; URIONABARRENETXEA, ERIK; LACALLE, RAFAEL

Zurich

Conferencia; International Conference on the Biogeochemistry of Trace Elements ICOBTE 2017; 2017

Industrial activity is responsible for a great variety of contamination scenarios, often including the presence of more than one type of contaminant. Complex environmental problems can be generated when inorganic and organic compounds are simultaneously found in the same site. Tanning industries use compounds containing Cr(VI), an extremely toxic and carcinogenic element. The gamma isomer of hexachlorocyclohexane (lindane), used as insecticide, is an extremely hazardous contaminant. Rhizoremediation is a technology that combines phytoremediation and bioremediation strategies. This technology is most suitable to simultaneously remove organic and inorganic contaminants, while recovering the health of the soil. The aim of this work was to test an integrated methodological approach combining three taxa (plants, earthworms and bacteria), to assess and recover the health of soils contaminated with organic and inorganic compounds. A greenhouse experiment was carried out using soil, amended or not with organic matter. Both soils were artificially contaminated with lindane (15 mg kg-1) and two different concentrations of Cr(VI) (100 and 300 mg kg-1), keeping non polluted soils as control. The following treatments were applied: i) inoculation of a resistant actinobacteria consortium; ii) growth of Brassica napus; iii) application of Eisenia foetida earthworms; iv) combination of bacterial consortium and B. napus; v) combination of bacterial consortium and worms; vi) combination of bacteria, plant and worms; vii) no biological treatment. Pots were kept in the greenhouse for two months and then plants and soils were sampled. Chromium and lindane concentration in soils and plants was determined. Soil ecotoxicology was evaluated using three types of biological indicators: soil bacterial respiration, root elongation bioassay with Cucumis sativus, and Neutral Red Uptake assay in extruded coelomocytes of E. foetida.Organic matter amendment was the most effective treatment recovering soil health, due to a decrease of Cr(VI) bioavailability. Among the biological treatments, the inoculation of the actinobacteria consortium in the presence of plants and earthworms was most effective. When applied singly the inoculation of the consortium was more effective than the plants or earthworms alone. The inoculation of the consortium decreased lindane concentrations, especially in the presence of plants and/or earthworms. Although Cr phytoextraction was negligible, soil ecotoxicity was decreased in all treatments that included the actinobacteria consortium. No correlation was observed between lindane concentration and soil ecotoxicity. Even when contaminants are not fully removed, soil health can be improved by the combination of the three taxa. In conclusion, organic matter and the bacteria consortium are two effective factors on health recovery of soils polluted with Cr (VI) and lindane.Acknowledgements: This work was financially supported by project AGL 2015-64481-C2-1-R from MINECO and project IT018-16 from the Basque Government. R.G. Lacalle is the recipient of a predoctoral grant from the Basque Government.