Chapter 9

General Aspects/Case Studies

on Sources and Bioremediation

Mechanisms of Metal(loid)s

Manoj Kumar, Sushma K. Varma, Renju,

Neeraj Kumar Singh and Rajesh Singh*

9.1 Introduction

With the growing world population, the consequential demand for industrial establishments to

suit human requirements has caused a rise in pollution in air, land and aquatic ecosystems due to

an overuse of accessible resources (Tarekegn et al. 2020). Environmental pollution by inorganic

pollutants like heavy metal(loid)s is the main problem (Kumar and Singh 2017). Apart from Arsenic

(As), Boron (B), and Selenium (Se), ‘heavy metal(loid)s’ refers to elements (metalloids and metals)

having atomic densities larger than 6 g cm^–3 in general. In this category, there are both biologically

necessary (viz. Zn, Co, Mn, Cu and Cr) and non-essential components (viz. Hg, Cd and Pb). The

necessary components with nutritional value for plants and animals. As these are required only

in small quantities, are referred to as micronutrients. In the chemical industry, because they are

phytotoxins and zootoxins, non-essential metal(loid)s are referred to as “toxic elements. Higher

amounts of these non-essential metal(loids) are harmful to both plants and animals (Adriano 2001).

Heavy metal(loid)s contamination through natural and anthropogenic activities may deteriorate

the environment and cause adverse effects on humans and animals (Douay et al. 2008, Shen

et al. 2017, Liu et al. 2021, Adlane et al. 2020). Heavy metal(loid)s have become increasingly

controversial due to their possible harmful health and environmental consequences, as well as their

effects on international trade in a number of locations throughout the world. The increase of Cd in

grazing animals’ (mainly kidneys and liver) renders it unfit for human consumption; however, it

also poses a threat to the export of offal products. The Cd bioaccumulation in potatoes, wheat and

rice crops has significant consequences for the marketing of these crops on a local and international

basis (Roberts et al. 1994, Mclaughlin et al. 1996, Kirkham, 2006, Makino et al. 2006, Mavropoulos

et al. 2002, Pérez and Anderson 2009). Therefore, there is a worldwide alarm in ensuring that the

heavy metal(loid)s content of food fulfills regulatory criteria and compares well to those of other

countries. An organic amendment to soil can enhance the process of bioremediation, which is a

School of Environment and Sustainable Development, Central University of Gujarat, Gandhinagar, 382030, Gujarat, India.

* Corresponding author: rajeshsnain@gmail.com