Kinetics of arsenic absorption by the species Eichhornia crassipes and Lemna valdiviana under optimized conditions

• Published in: Chemosphere (Oxford) 2018-10, Vol.209, p.866-874
• Main Authors: Souza, Tamara Daiane de, Borges, Alisson Carraro, Matos, Antonio Teixeira de, Veloso, Renato Welmer, Braga, Amanda Fernandes
• Format: Article
• Language: English
• Subjects: Arsenate; Arsenic - analysis; Arsenic - metabolism; Arsenite; Decay coefficient; Duckweed; Eichhornia - growth & development; Kinetics; Plants - chemistry; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water-hyacinth
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.06.132

This work aimed to study the kinetics of arsenic absorption by Eichhornia crassipes and Lemna valdiviana under pre-established conditions of pH phosphate and nitrate in the nutrient solution. Additional aims were to evaluate the conversion kinetics between As(III) and As(V), and the effect of arsenic concentrations on development of the species. The plants were cultivated in nutrient solutions containing different arsenic concentrations: 0, 0.56, 0.89 and 1.38 mg L−1 for the water-hyacinth, and 0, 0.13, 0.48, 0.99 and 1.4 mg L−1 for Lemna. Monitoring of arsenic removal by the plants was performed by sampling at intervals of 0, 4, 8, 16, 24, 48, 96, 144, 192 and 240 h for the water hyacinth, and 0, 4, 8, 16, 24, 48, 96, 144 and 168 h for Lemna. The samples were submitted to analysis of total arsenic, As(III), As(V) and phosphorus. The first-order kinetics was fit to the arsenic removal kinetics by the plants, and it was observed that the decay coefficient (k) decreased with the increase of its initial concentration in the nutrient solution. For the, absorption was observed after 96 h of culture, the time coinciding with the greatest As(V) concentrations. For Lemna, the metal was only absorbed by the plant after decay of the phosphate levels of the medium, which occurred at 48 h. Concentrations above 1 mg L−1 implied deleterious effects in both plant species and in the phytoremediation process, and the bioaccumulation factor decreased for concentration above this for both E. crassipes and L. valdiviana. •Arsenic speciation was studied on phytoremediation with 2 macrophytes.•As decreased exponentially over the time allowing fit of 1st order kinetic equation.•Dynamics of As(III) and As(V) influenced the absorption of As by water-hyacinth.•The absorption of As by lemna showed minor relation to the oxidation dynamics.•[As] greater than 1 mg L−1 implied deleterious effects in both macrophytes.