Modelling growth of, and removal of Zn and Hg by a wild microalgal consortium

Abstract

Microorganisms isolated from sites contaminated with heavy metals usually possess a higher removal capacity than strains from regular cultures. Heavy metal-containing soil samples from an industrial dumpsite in Northern Portugal were accordingly collected; following enrichment under metal stress, a consortium of wild microalgae was obtained. Their ability to grow in the presence of, and their capacity to recover heavy metals was comprehensively studied; the datasets thus generated were fitted to by a combined model of biomass growth and metal uptake, derived from first principles. After exposure to 15 and 25 mg/L Zn(2+) for 6 days, the microalgal consortium reached similar, or higher cell density than the control; however, under 50 and 65 mg/L Zn(2+), 71% to 84% inhibition was observed. Growth in the presence of Hg(2+) was significantly inhibited, even at a concentration as low as 25 μg/L, and 90% inhibition was observed above 100 μg/L. The maximum amount of Zn(2+) removed was 21.3 mg/L, upon exposure to 25 mg/L for 6 day, whereas the maximum removal of Hg(2+) was 335 μg/L, upon 6 day in the presence of 350 μg/L. The aforementioned mechanistic model was built upon Monod assumptions (including heavy metal inhibition), coupled with Leudeking-Piret relationships between the rates of biomass growth and metal removal. The overall fits were good under all experimental conditions tested, thus conveying a useful tool for rational optimisation of microalga-mediated bioremediation.

Desenvolvimento de métodos de análise por injeção sequencial com detecção eletroquímica para a aplicação em estudos de interação de Hg(II), As(III) e Se(IV) com ligantes heterogêneos de ocorrência natural

“…Como mencionado anteriormente, o efeito cooperativo observado em pH 5,0 e 6,0 e a baixa C Hg , T sugere que a exposição da microalga a Hg(II) desencadeia um mecanismo de defesa fisiológico que aumenta a adsorção de Hg(II). Por exemplo, a redução de Hg(II) e subsequente volatilização de Hg 0 tem sido considerada um mecanismo de resistência da Chlorella pyrenoidosato na presença de mercúrio inorgânico (Monteiro et al 2012). Para investigar o processo de interação, experimentos de adsorção foram realizados com 10 mL de Hg(II) 500 μmol L -1 (5,0 μmol).…”