Abstract— The Jose Antonio Alzate dam is the main man-made reservoir along the Lerma River in central Mexico. The water in this dam is heavily contaminated with organic and inorganic residues including copper and other heavy metals. For many years, people living in the vicinity of the dam use sediments as fertilizers, resulting in heavy soil contamination. This study focuses on the use of native Leucadena leucocephala, a small, fast-growing mimosid tree cultivated under greenhouse conditions in an attempt to reduce the levels of copper. The plant was inoculated with a fungus of the Glomus sp. Zac-19 species that in a symbiotic manner increases the decontaminating properties of L. leucocephala. The study was carried out in three stages, starting with sequential extractions to assess the geochemical distribution of copper. Next, L. leucocephala was grown under controlled conditions using a factorial statistical model adding two known doses of Cu2+ and a third plantlet grown under normal conditions to be used as control. The plant growth was followed at random during 30, 60, 90 and 180 days to assess the level of copper bioaccumulation in leaves, stem and in the whole plant. The bioaccumulation index was evaluated using the initial six fractions, with fraction five revealing a direct relationship between the levels of copper in plant and sediment. Due to the relation of fraction V with humic material, it was finally considered for the calculation of the bioaccumulation index. Copper accumulation in stems was greater than in leaves and the metal concentration decreased with time. The percentage of arbuscules, vesicles and complete colonization was affected by high doses of Cu2+,inhibiting the growth of stem and leaves of L. leucocephala. These results suggest that the plant can be useful for the biological removal of copper in contaminated sediments or soils.
Keywords— copper speciation, polluted soil, phytoremediation, Glomus sp.,Rhizobium, Leucaena.
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