Occurence Of Heavy Metals In Gills,Muscles, And Liver Of Chrysichthys Nigrodigitatus
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Occurence Of Heavy Metals In Gills,Muscles, And Liver Of Chrysichthys Nigrodigitatus
Chapter one
1.1 Introduction.
Heavy metals are metallic elements with an atomic or specific gravity that is at least five times that of water. This group has several elements listed. Heavy metals in trace amounts in the aquatic environment are necessary for the organism’s regular development.
They could be detected in the aqueous medium and at the bottom; however, some are completely deleterious and must be monitored continuously in the bodies of organisms because they are capable of bioaccumulation, resulting in morbidity and, in some cases, mortality (Ayotunde et al., 2011, 2012; Ada et al., 2012). Heavy metal human health concerns have spurred a lot of research in this field, including the efforts of Muchuweti.
et al. (2006); Satarug et al. (2000); and Adefemi et al. (2012).
When metals enter the aquatic environment, a large fraction settles and is absorbed by bottom mud (Ayotunde, 2012). They can be recycled by chemical, physical, and biological processes, with some remaining dissolved in the water column and some absorbed by the occupants (Rayms- Keller et al., 1998; Kori- Siakpere and Ubogu, 2008). Fish are at the top of the food chain and can bioaccumulate some of these chemicals in their tissues (Olaifa et al., 2004).
Kori-Siakpere and Ubogu (2008) discovered lower haematological parameter values and heamodilution in fish subjected to sublethal zinc doses for 15 days. They explained that zinc accumulates in fish gills, which indicates a negative influence on respiration in tissues.
It can cause death owing to hypoxia, impaired egg hatchability, changes in ventilator heart physiology, and overall changes in fish behaviour such as lack of balance, frantic swimming, air gulping, and death.
Some heavy metals are not biodegradable and can accumulate in organisms’ tissues until they reach toxic levels that cause sickness or death (Offem and Ayotunde, 2008). Man’s increased position in the food chain increases the risk of bioaccumulation.
The risks of heavy metals have long been recognised, but symptoms are rarely detected, and patients may be treated for various illnesses, exacerbating man’s heavy metal pollution concerns (Kaye et al., 2002 and Nolan, 2003).
There is growing concern about the roles and outcomes of trace metals in Nigerian environments. Much of this concern stems from the lack of available information on the amounts of these metals in the environment.
Trace metal contamination of sea seafood poses a potential human health risk. Metals are accumulated by aquatic species at far higher quantities than those found in water.
Lead, zinc, nickel, chromium, arsenic, selenium, vanadium, beryllium, and barium are examples of potentially harmful metals. Natural and man-made activities emit gases and discharge waste water into the air, water, and land.
Contaminants are compounds found in emissions and effluent discharges in the environment that are in trace levels or concentrations, are not hazardous to plants or animals, and have a limited residence time in the environment (Odiete, 1999).
Bioconcentration is the net buildup of a drug in water that results from the substance’s simultaneous uptake and removal by an aquatic creature. Fish and bivalve molluscs are used in bioaccumulation studies because they are higher tropic level species that are commonly consumed by humans. Metal concentrations are determined by analysing tissues such as liver, kidney, muscle, viscera, and whole organisms (Dublin-Green, 1994).
Heavy metals are widely found in natural streams, and while some are essential to living creatures, they can become extremely poisonous when present in large concentrations. These metals enter the ecosystem from anthropogenic sources and are then distributed in water bodies, suspended solids, and sediments as they move around.
The rate of heavy metal bioaccumulation in aquatic animals is determined by the organisms’ ability to digest the metals as well as the concentration of the metal in the river. (Kukusetging, Ochiai & Cornel 2006). Aquatic creatures (including fish) bioaccumulate trace metals in large quantities and retain them for extended periods of time.
Fish have been identified as effective accumulators of organic and inorganic pollutants. The age of the fish, liquid content in the tissue, and style of feeding all have a substantial impact on heavy metal accumulation in fish.
They are eventually passed to other animals, including humans, via the food chain. Odoemelam et al. (1989) found high quantities of heavy metals such as Cd, Pb, Cu, Ni, Zn, Mn, Mg, and Co in rivers around Nigerian industrial centres.
The discharge of industrial wastes containing toxic heavy metals into water bodies may have significant effects on fish and other aquatic organisms, putting public health at risk through consumption of contaminated sea food and irrigated food crops. According to Nwaedozie (2000), zinc contamination affects the hepatic distribution of other trace metals in fish.
Environmental contamination is a global issue, with heavy metals accounting for the majority of contaminants. Industrial growth has resulted in increased pollutant emissions into the environment.
The southern Caspian sea coast is one of the most important aquatic systems, as is the eastern south of the Caspian, which receives effluent discharge from extensively industrialised and densely populated settlements. Heavy metals can also occur naturally in the ecosystem, albeit their concentrations vary greatly.
In modern times, manmade sources of heavy metals, or “that is” pollution, have been introduced into the ecosystem. Heavy metals are particularly prevalent in waste-derived fuels, hence heavy metals are a worry when considering water as a fuel (Cheng, 2003).
Heavy metal contamination can come from a variety of sources, the most prevalent of which being metal purification processes, such as copper melting and nuclear fuel preparation.
Electroplating is the principal source of chromium, either by precipitation of their compound or ion exchange into soil and mud; heavy metal contaminants can localise and remain latent. Heavy metals, unlike biological pollutants, do not degrade and so present a unique cleanup difficulty (Dufuss 2002).
1.1 Aim and Objectives
This research effort aims to:
1. Determine whether fish in this river possess heavy metal concentrations in their tissues that could make them unsafe for human consumption.
2. Determine the level of heavy metal contamination in the gills, muscle, and liver of Chrysichthys nigrodigitatus.
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