Green Remediation: Canna Indica for Sustainable Detoxification of Metals and Excess Nutrients

Abstract

Rivers are susceptible to metal pollution arising from anthropogenic activities such as mining, industrial processes, and urban runoff. Metals from both natural and man-made sources enter the river system and either settle in the riverbed sediments or are distributed in the aqueous, floating matter. Under some environmental conditions, the accumulation of metals in river systems disrupts biological processes. Apart from metal pollution, the escalating concentrations of nutrients, specifically nitrogen and phosphorus into aquatic ecosystems are of growing concern. The excess concentartions of metals and nutrients pose severe environmental challenges such as lake eutrophication and groundwater pollution. Therefore, the sustainable solution to mitigate their adverse environmental effects is need of the hour. Phytoremediation is a green remediation technology that employs plants to remove, detoxify, or immobilize toxins from soil, water, or air. The plants and their related microbial populations improve water quality by absorbing, adsorbing, and transforming contaminants like metals, nutrients, etc. In this research, a pot study was performed to investigate the efficacy of phytoremediation. In the controlled environment, small-scale tests were undertaken to examine the growth, pollutant removal capabilities, and effectiveness of using specific plants for larger-scale applications. The target pollutants were heavy metals (As, Al, Ca, Cd, Co, Cu, Fe, Pb, Mg, Hg, and Ni), macro-nutrients (Na, K, and Ca), and micro-nutrients (nitrates, ammonia nitrogen, and phosphates). Experimental setup included polyvinyl chloride containers (5 L capacity) as the vessel (pot) for growing Canna Indica plants. Water sample from Ratanpuri in Hindon river, one of the highly polluted rivers in north India, was used for the treatment. Initially, the containers were filled with 2.5 L of growing medium (soil, sand and gravels), arranged in a block design, and the experiment was performed for ten days (two runs), depending upon their treatment efficiency. Initial and final characterizations of water samples were performed as per standard methods. The phytoremediation efficiency of all considered metal parameters through Canna Indica was observed in the range of 52-60 % which prospectively got absorbed via phytoextraction. Moreover, the efficacy of nutrient removal, was also obtained satisfactorily ranging from 60-78%. Considering removal efficiencies, phytoremediation using Canna Indica could be economically and environmentally sustainable for countering nutrient and metal pollution at field scale, provided its controlled monitoring is performed effectively. Pot-scale study results could be baseline that support usage of Canna Indica at field scale in wetland systems for detoxifying ecosystems and assuring soil and water quality restoration in the face of increasing anthropogenic demands.