Potential of macrophyte for removing arsenic from aqueous solution

Abstract

-The potential of three aquatic macrophytes, Azoll caroliniana, Salvinia minima and Lemna gibba, was evaluated in this work aimed at selection of plants to be used in remediation of environments contaminated by arsenic (As). The experiments were carried out in a greenhouse during six days in pots containing Hoagland solution (¼ ionic strength) at As concentrations of 0.5; 2.5 and 5.0 mg L -1 . The three species showed greater As accumulation as the concentration of the metalloid in solution increased. However, a reduction was detected in fresh and dry mass gain when the plants were exposed to high As concentrations. The macrophytes showed differences in efficiency of removal of As in solution. A. caroliniana, S. minima and L. gibba accumulated, on average, 0.130; 0.200; and 1.397 mg mDM -1 , respectively, when exposed to 5.0 mg L -1 of As. The macrophytes absorbed a greater quantity of As in solution with low phosphate content. The greater As concentration in L. gibba tissues lowered the chlorophyll and carotenoid contents as shown by the high chlorosis incidence. Lemna gibba also exhibited a decrease in leaf size, with the total chlorophyll and carotenoid synthesis not being affected by As in A. caroliniana. This species exhibited purplish leaves with high concentration of anthocyanin, whose presence suggested association to phosphate deficiency. Marginal necrosis occurred on S. minima floating leaves, with the released daughter-plants not showing any visual symptoms during the treatment. The percentage of As removed from the solution decreased when the plants were exposed to high concentrations of the pollutant. Among the three species studied, only L. gibba could be considered an As hyper-accumulator. The use of this plant species for remediation of aquatic environments was shown to be limited and requires further investigation.Keywords: bio-remediation, phyto-remediation, aquatic plants, pollutant. RESUMO -O potencial de três macrófitas aquáticas -Azolla caroliniana, Salvinia mínima e Lemna gibba -foi avaliado neste estudo, com vistas à seleção de plantas para remediação de ambientes contaminados com arsênio (As). Os experimentos foram conduzidos em casa de vegetação durante seis dias, em vasos contendo solução Hoagland (¼ força iônica) e As nas concentrações de

Accumulation of copper by the aquatic macrophyte Salvinia biloba Raddi (Salviniaceae)

“…Symptoms like these are typical of the toxicity of metals to macrophytes, some however, may be specific to each species (Guimarães et al, 2012). These authors observed in the Azolla caroliniana Willd.…”

“…In general, the roots of macrophytes play a key role in the accumulation of substances. For Barros and Henares (2015), this is assertive for floating aquatic weeds, which absorb most of the nutrients through this compartment, with the area and the length of the root being factors which influence the absorption of metal ions. In studies with macrophytes coming from contaminated water systems, the floating species S. auriculata and E. crassipes were highlighted by the high levels of mercury (Hg) present in their biomass, mainly in the roots (Molisani et al, 2006).…”

“…Studies on S. biloba are scarce, however, results obtained with other species of the same genus report the effectiveness of these macrophytes as regards to the removal of toxic metals from aquatic biota (Dhir et al, 2008;Guimarães et al, 2012;Wolff et al, 2009Wolff et al, , 2012. These elements resulting from industrial, agricultural, mining and domestic sewage activities directly impact the water bodies when they do not receive appropriate treatment and are inadequately disposed of in the environment.…”

Anthocyanins, thiols, and antioxidant scavenging enzymes are involved in Lemna gibba tolerance to arsenic

“…Lemna gibba (duckweed) is an aquatic plant that has been reported to uptake large quantities of arsenic and is considered a hyperaccumulator of this element (Mkandawire et al 2004;Guimaraes et al 2012). Almost all studies that correlate L. gibba with arsenic are based on the capacity of this plant to accumulate metals and mineral nutrients (Mkandawire & Dudel 2005;Mkandawire et al 2006;Sasmaz & Obek 2009;Guimaraes et al 2012).…”

“…Almost all studies that correlate L. gibba with arsenic are based on the capacity of this plant to accumulate metals and mineral nutrients (Mkandawire & Dudel 2005;Mkandawire et al 2006;Sasmaz & Obek 2009;Guimaraes et al 2012). Based on the fact that the comprehension of the physiological aspects involved in arsenic tolerance mechanisms is essential to the application of phytoremediation, and considering that oxidative stress is one of the main causes of damage to plants caused by heavy metals, the aim of this work was to study the effects of arsenic on the enzymatic and nonenzymatic antioxidant mechanisms that are ordinarily involved in defense mechanisms.…”