Phytoremediation of Metal-Contaminated Soils Using Organic Amendments: Prospects and Challenges

With porous structures and large surface areas, activated carbons have been acclaimed as versatile materials. They have been used across different industrial sectors for food and beverage processing (Ioi et al., 2017), water purification (Ahmad and Azam, 2019), wastewater treatment (Boehler et al., 2012), remediation of contaminated soils (Sabir et al., 2015), retention of toxic gases, and solvent recovery (Rodríguez-Reinoso, 2001). Within healthcare, activated carbons have also been used for carbon filtering of exhaled and residue volatile anaesthetics in anaesthesia systems.

Soil microbes use the organic waste as a food source for energy, growth and multiplication. These findings confirm some earlier studies that stated that bacteria and fungi population structure could be altered by the application of organic materials (Wang et al., 2015; Sabir et al., 2015; Rashid et al., 2017a, b). Consequently, microbial activities have increased as evident from the higher CO2 emission or microbial respiration, which is considered as a direct indicator of higher microbial growth and activities.

Contaminant uptake rate was used to estimate phytoremediation potential (Meeinkuirt et al., 2012). Plant species may be categorized as excluders if they accumulate contaminants mainly in roots, even at low concentrations but produce substantial biomass (Sabir et al., 2015; Kaewtubtim et al., 2017b). Significant Mn uptake occurred in roots of A. marina in both greenhouse and field experiments (> 4000 μg plant− 1), with high BCF values (> 1) (Table 6).

A decrease in the mobile TE pool in soil, promoted by amendments through sorption or precipitation reactions, allows the settlement and the growth of vegetation as well as ecosystem restoration on highly contaminated sites (Ruttens et al., 2006). Moreover, some of these amendments can improve the agronomic quality of soils (Ram and Masto, 2014; Sabir et al., 2015). This phytomanagement has been assessed using various amendments (poultry manure, iron grit, steel shot, fly ash, red mud, etc) and plant genera (Agrostis, Populus, Miscanthus, Phaseolus, Panicum, Lolium, etc.) (Alvarenga et al., 2009a, 2009b; Lee et al., 2014; Lopareva et al., 2011a; Marchand et al., 2011; Ruttens et al., 2006).