Phytoremediation of Pb and Cd by Alfalfa (Medicago sativa L.): An Applied Study in the Presence of Lettuce Plants (Lactuca sativa L.)

Abstract

A pot study was conducted to investigate the potential of alfalfa for phytoremediation of soil artificially contaminated with different concentrations of Pb and Cd and their combinations. Harvested plants were divided and used for two purposes: (1) separation into roots and shoots, which were digested to determine N, P, K, Pb, and Cd concentrations, and (2) the use of fresh shoots to make an alfalfa extract representing each treatment. Subsequently, lettuce seedlings were grown in the same pots with the same soil and without adding fertilizers; however, the alfalfa shoot extract prepared from each treatment was added to the treatment itself. Lettuce crops harvested after 67 days from transplanting were divided into roots and shoots, and these were digested to determine the previous studied elements. In addition, soil samples were collected after harvesting alfalfa and lettuce plants and prepared for chemical analyses. Results showed that alfalfa is an effective accumulator plant for the phytoremediation of Pb- and Cd-contaminated soils. In addition, using the alfalfa shoot extract to fertilize lettuce crops was beneficial to their growth without any risk of translocation of heavy metals. Thus, we recommend adding alfalfa to crop rotations, especially where soils are contaminated with heavy metals.