1.1 Introduction
Heavy metals are natural elements with atomic number greater than 20, characterized by a relatively high density (at least 5 g cm−3), and are toxic even at low concentrations (Koller et al. 2018). They are characteristically existing components found in changing variation in the environments and are part of human daily activities, they are also found in important structures and in a range of other artificial mixes (Govind et al., 2014). The activities of human have greatly impacted on some heavy metal biochemical cycles and equalization of which a great number of heavy metals have found its use in various items such as cars and batteries (Oyeleke et al., 2016).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Biosorption is a biological remediation technology that involves the removal of metal species from a solution by inexpensive biomaterials, and it has been reported that most biological materials can be useful as biosorbents for heavy metals sequestration and can be a vital passive procedure in organisms, but the exceptions are mobile alkali metal cations like Na+ and K+ (Mustapha et al., 2015). Most biosorbent materials have good biosorption capacities toward all types of metal ions, so many affordable and easily available biosorbents used for the elimination of heavy metals in the environment are mainly derived from bacteria, fungi, algae, plants and some polysaccharide materials. Many researches involving biosorption of heavy metals from the environment have been carried out in vitro and in vivo (Mustapha et al., 2015). Karthik et al. (2017) and Karthik et al. (2017) reported the biosorption and bioaccumulation of high chromium by Cellulosimicrobium funkei AR8 and AR6, respectively, under batch conditions. Dhanarani et al. (2016) reported the biosorption of aluminum by Bacillus safensis. Live and dead biomass of Aspergillus niger have been used to biosorb fluoride in aqueous solution under batch and continuous condition (Annadurai et al., 2019).
The materials used for biosorption include a solid stage biomaterial (sorbent) and a solvent stage containing disintegrated species like metal particles to be sorbed (sorbate). Similar to each sorption procedure, binding of sorbate species to biosorbent proceeds until it reaches a balance between the sorbate species in fluid and solid stages. Biosorbents contain some atomic groups that have tendency to sorbates, for example, metal ions. This innovation utilizes different sorts of biomass to expel heavy metals from contaminated environment (Abioye et al., 2018).
Biosorbents of biological origin particularly various microorganisms have received growing interest for the removal of heavy metal and recovery owing to their greater performance (Kumar et al., 2014). Although biosorption is influenced by many factors such as pH, temperature and contact time (Shanmugaprakash et al., 2018), the use of microorganisms as biosorbent materials offers a selective removal of heavy metals under varied physicochemical properties, adsorption and desorption and another advantage of microorganisms is their high surface-to-volume ratio (Munees et al., 2013). Several microorganisms have been used for biosorption, examples include Bacillus cereus used in Cd (Arivalagan et al., 2014) and Cu (Pugazhendhi et al., 2018) removal, Cellulosimicrobium funkei AR6 and Cellulosimicrobium funkei AR8 used in biosorption of Cr (Karthik et al., 2017), Bacillus safensis used to biosorb aluminum (Dhanarani et al., 2016), Aspergillus niger used for fluoride biosorption (Annadurai et al., 2019), and Pugazhendhi et al. (2018) reported lead biosorption using Ralstonia solanacearum. Therefore, this study is aimed at determining the biosorption rate of cadmium, nickel, chromium and copper by fungi and bacteria isolated from soil.
Heavy metals are generated from both anthropogenic and natural sources and are eventually discharged into the environment (Masindi et al., 2018). The main natural discharge of heavy metals is during volcanic eruptions and weathering of metal-bearing rocks (Ali et al. 2019). The discharge of heavy metals through various man-made activities, for example excessive application of chemical fertilizers, wood burning, coal combustion, vehicle exhaust, mining, smelting and incineration (Ali et al. 2019), has caused a wide spread disruption of the normal biogeochemical cycles of metals causing a larger accumulation of heavy metals in the environment, especially the soil (Pugazhendhi et al., 2018). The major heavy metals of concern include lead, cadmium, arsenic, mercury, copper and chromium because of their toxic impact on human health; for instance, environmental exposure to high concentrations of heavy metals has been linked with various cancers and kidney issues (García et al., 2016). Heavy metals have also greatly affected soil microorganisms and plants growth and development (Sharma et al., 2018). The presence of heavy metals in the environment has been a source of concern over the past few decades due to their persistence, potential harm and toxicological hazards (Ali et al., 2019). Besides the fact that they are non-biodegradable, they may also undergo microbial or chemical transformation (Das et al., 2019). Recently, Hasani et al. (2019) and Nath et al. (2019) reported that heavy metal polluted environments activate co-selection process and cause a decrease in microbial tolerance to antibiotics due to their ability to co-regulate genes responsible for antibiotic resistance.
The soil is a reservoir for some essential trace elements such as zinc and copper, which are necessary for the growth of plants and animals, but external influence can increase their concentration and consequently reduce the overall soil fertility and agricultural productivity. Therefore at soil concentration above normal level, if permitted to accumulate in the food chain, heavy metals such as lead and cadmium can have adverse effects on human and animal health (Thompson et al., 2019). There is also the risk of leaching of heavy metals, and this may contaminate underground water and in turn affect human health, especially those that consume underground water through boreholes and well water (Koller et al., 2019). The increase in industrialization and urbanization offers ascend to heavy metal pollution of the environment, which might have resulted from the discharge of effluents containing metals such as lead, cadmium, chromium, nickel and mercury (Dhanarani et al., 2016).
According to Thompson and Darwish (2019), heavy metals are of genuine environmental concern because of their potential toxicity, reactivity and soil mobility. The emissions of these metal pollutants have become a severe threat to mankind. The routes of exposure of human to heavy metals include inhalation, dermal absorption and ingestion (WHO, 2018). In order to alleviate the environmental impacts of heavy metal, several efforts are currently being adopted. Such methods include thermal, chelating, precipitation, adsorption, ion exchange, membrane technologies and biosorption strategies. Biosorption has several advantages over other conventional methods of heavy metal remediation because of its accessibility and efficiency (Dhanarani et al., 2016). One important economic aspect of biosorption technology is that the biomass used for decontamination of heavy metal pollutants is natural, easily available and affordable, and also it provides a better performance compared to conventional methods of decontamination (Abioye et al., 2017). Thus, there is the need to apply affordable metal remediation technology like biological method so as to reduce the toxic effect of these heavy metals in the environment.
Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Biosorption of Heavy Metals by Microorganism Isolated from Marina Soil.
1.3 Statement of Problems
The concentration of heavy metals may very well be too low to be of significant concern, but it’s definitely a legitimate reason to avoid eating sizable portions of chocolate on a regular basis. Furthermore, because the cacao beans used to make chocolate come from all over the world, the amounts of heavy metals that they contain can vary widely. Although there’s no guarantee, certified organic chocolate is less likely to be produced from cacao beans that have been grown in a contaminated environment or exposed to contaminants during processing (Carter-Pokras et al., 2007).
The major heavy metals of concern include lead, cadmium, arsenic, mercury, copper and chromium because of their toxic impact on human health; for instance, environmental exposure to high concentrations of heavy metals has been linked with various cancers and kidney issues (García et al., 2016). Heavy metals have also greatly affected soil microorganisms and plants growth and development (Sharma et al., 2018). The presence of heavy metals in the environment has been a source of concern over the past few decades due to their persistence, potential harm and toxicological hazards (Ali et al., 2019). Besides the fact that they are non-biodegradable, they may also undergo microbial or chemical transformation (Nwidi et al., 2015). Recently, Hasani et al. (2019) and Nath et al. (2019) reported that heavy metal polluted environments activate co-selection process and cause a decrease in microbial tolerance to antibiotics due to their ability to co-regulate genes responsible for antibiotic resistance.
1.4 Aim and Objectives of Study
The aim of the study is to scrutinize the Biosorption of Heavy Metals by Microorganism Isolated from Marina Soil. In achieving this aim, the following specific objectives were laid out as follows:
- To identify the Microorganism Isolated from Marina Soil
- To determine the biosorption rate of cadmium, nickel, chromium and copper by fungi and bacteria isolated from marina soil.
1.5 Significance of Study
This study will be of immense benefit to soil science researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.6 Scope of Study
The study focuses on the Biosorption of Heavy Metals by Microorganism Isolated from Marina Soil in Nigeria.
1.7 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
