Plant metal accumulation in wetlands systems

Abstract

Several wastewaters, such as those from metallurgical industries, landfill leachate,and runoff waters contain metals (Arunbabu, Indu, & Ramasamy, 2017; Danet al., 2017; Luo, Sun, & Zhang, 2019; Maine et al., 2017). Phytoremediation is analternative eco-friendly technology applied for the treatment of contaminated watersand soils (Pilon-Smits, 2005; Vymazal, 2008). This technology uses aquatic orterrestrial plants to remove metals from water or soil. There are different phytoremediationmethods. One of them is phytostabilization, which consists of metal immobilizationand accumulation in the belowground plant tissues and the soil (Eid &Shaltout, 2014). Another method is phytoextraction using hyperaccumulator plants,which are capable of accumulate metals remarkably in their aboveground tissues fromsoil or sediment (Bose, Vedamati, Rai, & Ramanathan, 2008; Weis & Weis, 2004).Natural wetlands possess rich biodiversity. These ecosystems frequently showmetal contamination originated by industrial activities. Macrophytes accumulatemetals purifying the contaminated water bodies through mechanisms such as filtration,ion sorption, and influencing the redox conditions of the rhizosphere (Maine,Suñé, Hadad, Sánchez, & Bonetto, 2006; Wright & Otte, 1999). In comparison withthe surrounding water, metal concentrations in aquatic plant tissues are higher dueto the fibrous roots and other submerged organs present large surface area in contactwith water (Bragato et al., 2009). In natural wetlands, macrophytes were proposed asefficient biomonitors (Alonso et al., 2018; Bonanno, 2011, 2013; Bonanno & Lo Giudice,2010; Eid, Shaltout, El-Sheikh, & Asaeda, 2012). The metal uptake ability isdifferent among the wetland plant species (Deng, Yea, & Wong, 2004; Hadad, Maine,Natale, & Bonetto, 2007; Hadad, Mufarrege, Di Luca, & Maine, 2018). Plant speciesand their growth stage affect the metal uptake, accumulation, and translocation (Luoet al., 2019; Mufarrege, Hadad, Di Luca, & Maine, 2015; Yu, Gu, & Xing, 2008).Macrophytes can tolerate high metal concentrations, being key components inconstructed wetlands (Brix, 1994; Hegazy, Abdel-Ghani, & El-Chaghaby, 2011;Vymazal, 2008, 2011). Knowledge of the accumulation efficiency and tolerance ofdifferent wetland plants is necessary to choose the most convenient macrophytes tobe used in phytoremediation techniques, such as wetland systems (Duman, Cicek, &Sezen, 2007).Treatment wetlands can remediate efficiently several types of wastewaters (Hammer,1989; Kadlec & Knight, 1996; Kadlec & Wallace, 2009; Vymazal, 2011).These systems were widely used to remediate contaminants coming from sewage(Arden & Ma, 2018; Song et al., 2006), industrial effluents (Maine, Suñé, Hadad,Sánchez, & Bonetto, 2007; Maine, Suñé, Hadad, Sánchez, & Bonetto, 2009; Maineet al., 2013, 2017, 2019; Wu, Kuschk, Brix, Vymazal, & Dong, 2014), storm andmine waters (Di Luca, Mufarrege, Hadad, & Maine, 2019; Zhang et al., 2014),among others wastewaters (CamañoSilvestrini, Maine, Hadad, Nocetti, & Campagnoli,2019; Vymazal, 2008). The processes that occur among macrophytes andcontaminants are explained by chemical, biological, and physical approaches. Themain processes that could be mentioned are adsorption on plant tissues (roots andother plant organs in contact with the wastewater), root absorption and translocationto leaves, and precipitation enhanced by microorganisms and root secretions. Themechanisms operating in plant metal removal are different for each plant speciesand each metal (Maine, Hadad, Sánchez, & Caffaratti, 2016; Mufarrege et al., 2018).However, they are not sufficiently understood (Wu et al., 2015).This chapter describes macrophyte metal accumulation at different scales ofstudy, including natural wetlands that receive urban pollutants and wetlands constructedfor the treatment of several wastewaters. This information may contribute tothe design and management of wetland systems.