Comparative assessment of Azolla pinnata and Vallisneria spiralis in Hg removal from G.B. Pant Sagar of Singrauli Industrial region, India

Abstract

The aim of the present work was to monitor the Hg pollution in water and sediments of G.B. Pant Sagar located in Singrauli Industrial Region, India and to suggest the efficient aquatic plants for its phytoremediation. The study assessed the comparative potential of a free floating water fern Azolla pinnata and submerged aquatic macrophyte Vallisneria spiralis to purify waters polluted by Hg. Six days laboratory experiments have been conducted to mark the percentage removal of Hg at initial concentration of 0.1, 0.5, 1.0 and 3.0 mg L(-1). The percentage removal of Hg was higher for A. pinnata (80-94%) than V. spiralis (70-84%). Likewise, the Hg accumulated in dry mass was much higher for A. pinnata and a high correlation (R(2) = 0.91 for A. pinnata and 0.99 for V. spiralis) was obtained between applied Hg doses and accumulated amounts in biomass. A concentration dependent decrease in chlorophyll a, protein, RNA, DNA and nutrients (NO(3-) and PO(4)(3-)) uptake was detected in A. pinnata and V. spiralis due to Hg toxicity. The decrease was more prominent in Azolla than Vallisneria. The results recommended the use of A. pinnata and V. spiralis to ameliorate the industrial effluents (thermal power, chlor-alkali and coal mine effluent) contaminated with Hg.

Phytoremediation Potential of Aquatic Macrophyte, Azolla

“…This suggested that the Cd-induced change in color of fronds might be due to the decrease in chlorophyll and carotenoids while the increase in total phenolics and their biosynthesis-related PAL play a role in detoxification of Cd in A. imbricata. Rai and Tripathi (2009) found a concentration-dependent decrease in the content of chlorophyll a, protein, RNA, and DNA, and nutrient (nitrate and phosphate) uptake was detected in A. pinnata because of Hg toxicity. Sánchez-Viveros et al (2010) reported that heavy metal copper disrupted photosystem II resulting in drop in potential phytochemical yield at higher concentrations in A. filiculoides and A. caroliniana.…”

“…Increasing environmental awareness and concern has attracted scientific community to extend its exploitation more vigorously in the area of phytoremediation because the fern can hyperaccumulate variety of pollutants such as heavy metals, radionuclides, dyes, and pesticides etc. from aquatic ecosystems along with other macrophytes (Padmesh et al 2006;Rai and Tripathi 2009;Mashkani and Ghazvini 2009;Sood et al 2011). This fern has many features that prove it as a better plant system than many other macrophytes, which include:…”

“…They concluded that P. stratiotes was a better accumulator of mercury, with higher removal efficiencies than A. pinnata. However, Rai and Tripathi (2009) A direct comparison of findings of other macrophytes with Azolla species (as given in Table 4) is not possible due to difference in initial concentration of heavy metal and biomass of Azolla employed for particular investigation along with duration of the experiment, details of experimental design. Table 4 reveals the tremendous phytoaccumulation potential existing within and among Azolla spp.…”

“…The bioaccumulation of heavy metals by Azolla spp. is known to exhibit a concentration-dependent relationship (Stepniewska et al 2005;Arora et al 2006;Dai et al 2006;Rai and Tripathi 2009). Duncan (1997, 1998a, b) investigated the removal of sexivalent Cr, Ni, and Zn by A. filiculoides from aqueous solution and from electroplating rinse effluent.…”

Influence of humic acids on the accumulation of copper and cadmium in Vallisneria spiralis L. from sediment

“…(family Hydrocharitaceae; common name: 'flat grass', 'noodle grass' and 'channel grass') is widely distributed in shallowwater lakes in Asia and growing well in good transparence, deep-thick silt and slow-flow water areas (Sun 1992). V. spiralis plays a significant role in decreasing eutrophication of water body for its productivity and disposing industrial wastewater for its adaptability and well potential pollutant absorption (Xian et al 2006), and it has also been shown to accumulate significantly high amount of heavy metals from water bodies, including copper and cadmium (Sinha et al 1994;Gupta and Chandra 1998;Sinha et al 2002), and its phytoremediation effect of heavy metals from water is well documented (Rai and Tripathi 2009). However, little is known about the ability of this plant to accumulate toxic metals from sediments, especially when heavy metals are applied in moderately high concentration.…”