ABSTRACT

Introduction Environmental contamination is a serious issue originating from variable sources and applications, such as the use of agrochemical fertilizers, sewage sludge, and pesticides, or industrial activities, in particular metal mining, smelting, oil and gas operations, and other human uses [1, 2]. These applications release huge quantities of hazardous pollutants including organic and inorganic compounds into the air, water, and soil biospheres [3]. Inorganic contaminants involving heavy metals are natural components into the Earth’s crust [4, 5]. Heavy metals freeing from various sources represent approximately 22,000 t of Cd, 9,39,000 t of Cu, 7,83,000 t of Pb, and 13,50,000 t of Zn through the last decades [6]. Heavy metals are classified as a group of 53 elements having a specific density higher than 5 g/cm3 [7, 8]. Heavy metals can occur in soil for long periods of time, adhering to soil granules or polluting the underground water [9]. Among heavy metals, Cu, Fe, Mn, Ni, and Zn are essential elements required for normal plant growth [8], and these compounds have fundamental functions in nucleic acids metabolism; moreover, they are important for electron transfer, enzymatic catalyzation, as well as redox reactions [8]. On the contrary, other heavy metals like Cd, Pb, Hg, and As (as metalloids) are not required for living organisms [10].