In recent years, the number of cases of heavy metal contamination has increased worldwide, leading to reports on environmental pollution and human health problems. Phytoremediation can be potentially used to remove heavy metal from contaminated sites. This study determined heavy metal concentrations in the biomass of plant species growing on a multi-metal-contaminated site. Seven plant species and associated rhizospheric soil were collected and analyzed for heavy metal concentrations. While plant Cu, Zn, Cd, Ni, Pb, As, and Ba concentrations ranged from 8.8 to 21.1, 56.4 to 514.3, 0.24 to 2.14, 1.56 to 2.76, 67.8 to 188.2, 0.06 to 1.21, and 0.05 to 0.62 mg kg(-1), respectively, none of the plants was identified as hyperaccumulators. Those in the rhizospheric soil ranged from 10.5 to 49.1, 86.2 to 590.9, 0.32 to 2.0, 3.6 to 8.2, 19.1 to 232.5, 2.0 to 35.6, and 85.8 to 170.3 mg kg(-1), respectively. However, Zn, Cd, Pb, and As concentrations in the soil outside the rhizosphere zone were 499.0, 2.0, 631.0, and 48.0 mg kg(-1), respectively. Senecio brasiliensis was most effective in translocating Cu, Cd, and Ba. The most effective plant for translocating Zn and Pb was Baccharis trimera and, for element As, Dicranopteris nervosa and Hyptis brevipes. Heavy metal and metalloid levels in spontaneous plants greatly exceeded the upper limits for terrestrial plants growing in uncontaminated soil, demonstrating the higher uptake of heavy metal from soil by these plants. It is concluded that naturally occurring species have a potential for phytoremediation programs.
RESUMO O descarte de resíduos de lodo de curtume no solo tem sido um problema ambiental devido aos altos teores de cromo. O objetivo deste trabalho foi avaliar a dinâmica dos óxidos de ferro e os teores de cromo ligados a esses minerais em áreas de descarte de resíduos de curtume. Para isso, foram determinados os teores de ferro e cromo extraídos por oxalato de amônio dos óxidos de baixa cristalinidade e por ditionito-citrato-bicarbonato (DCB) dos óxidos cristalinos na fração argila do solo. Esses teores variaram entre 3,5 e 4,1 mg kg-1 nos tratamentos sem aplicação de lodo de curtume e entre 19,9 e 56,8 mg kg-1 nos com adição de lodo. Os teores de cromo extraídos dos óxidos cristalinos variaram entre 21,3 e 23,3 mg kg-1 nos tratamentos sem aplicação de lodo e entre 46,4 e 103,0 mg kg-1 nos com uso de lodo de curtume. A aplicação desse material proporcionou um aumento na relação do ferro extraído do óxido de ferro e o ferro extraído com o ditionito (Feo/Fed) dos óxidos da área de descarte, o que evidencia uma diminuição da cristalinidade dos óxidos. Foi encontrada uma redução na relação do ferro extraído com o ditionito e do cromo extraído com o ditionito (Fed/Crd), o que mostra a substituição do ferro pelo cromo nos óxidos, evidenciando uma troca isomórfica. Essa alteração pode ser uma alternativa para a retenção de cromo pelo solo com grande força.
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