PHYTOREMEDIATION POTENTIAL OF AQUATIC MACROPHYTE AZOLLA CAROLINIANA WITHREFERENCES TO ZINC PLATING EFFLUENT

Abstract

The effect of zinc plating industrial effluent on some biochemical parameters and the phytoremedial capacity of floating aquatic macrophyte Azolla caroliniana was assessed. The effects of increasing zinc concentrations on growth characteristics of A. caroliniana namely root length, leaf area and biomass production was studied. The root growth of A. caroliniana was severely affected at higher concentration of zinc effluent (especially at 3 and 4%). Overall slight fluctuations in the moisture content represent the favorable nature of this essential micronutrient especially at 1% and 2% concentration. Maximum chlorophyll contents were observed at 2% concentration of the effluent with an increase by 41.29% over the control. The least amount of carotenoid was observed at 4% concentration. Polyphenol content of the fronds of A. caroliniana was lowest at 4% while higher accumulation was observed at 2% effluent concentration. The level of proline in the leaves of A. caroliniana was considerably increased under the influence of zinc especially at 1, 2 and 3% of the effluent concentration. It was also seen that electrical conductivity (EC) and total dissolved solids (TDS), content of the various dilution were decreased remarkably after 10 days of treatment. pH of the solution tend to become neutral while increase in turbidity might be related with root exudates and dead organics by the plant growing in the tray. The decrease in hardness, acidity, sodium and potassium content of the effluent were observed with increase in concentration of the effluent. Values for biological oxygen demand (BOD) were decreased in the effluent concentration of 2% while the decrease in chemical oxygen demand (COD) was maximum in the same effluent concentration after 10 days treatment period. Zinc was accumulated in increasing order in the plants treated with increasing concentration of zinc. The bio concentration factor (BCF) values were increased serially as per increasing concentration of zinc plating effluent and all the plants growing in these concentrations showed higher accumulation capacities. 4% of the effluent recorded with higher BCF while minimum for control treated biomass was observed. In the present study increasing BCF shows that the A. caroliniana has capacity to accumulate the Zn++ through liquid medium after ten days of exposure period.