Heavy metals are described as metallic elements with a density more significant than that of water. Heavy metals also include metalloids, such as arsenic, that can cause toxicity at low levels of exposure, based on the assumption that heaviness and toxicity are linked. Understanding their effects is necessary for environmental protection. In recent years, environmental contamination by these metals has been a growing problem for the environment and global public health.
Furthermore, human exposure has increased considerably due to an exponential expansion in their use in various industrial, agricultural, residential, and technical applications. Geogenic, industrial, agricultural, pharmaceutical, home effluents, and atmospheric sources have all been reported as heavy metals in the environment. Point sources of pollution, such as mining, foundries and smelters, and other metal-based industrial operations, are particularly polluted.
Heavy metals are naturally occurring elements found throughout the Earth’s crust. However, anthropogenic activities such as mining and smelting, industrial production and use, and domestic and agricultural use of metals and metal-containing compounds cause most environmental contamination and human activities exposure, this is everything against environmental protection.
Metal corrosion, air deposition, soil erosion of metal ions and leaching of heavy metals, sediment resuspension, and metal evaporation from water supplies to soil and groundwater can all cause environmental pollution. In addition, natural occurrences such as weathering and volcanic eruptions have also been documented to contribute significantly to heavy metal contamination. Metal processing in refineries, coal combustion in power plants, petroleum combustion, nuclear power plants and high-tension lines, plastics, textiles, microelectronics, wood preservation and paper processing factories are industrial sources.
Metals including cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), and zinc (Zn) are vital nutrients that are needed for a variety of biochemical and physiological activities, according to research. A lack of certain micronutrients leads to several deficiency illnesses and syndromes.
Sources of heavy metal pollution causing lack of environmental protection
Since the Earth’s origin, these heavy metals have been found naturally on the Earth’s crust, however they are not for environmental protection. The incredible increase in the use of heavy metals has resulted in an impending influx of metallic compounds in both the terrestrial and aquatic environments which is against environmental protection. Heavy metal pollution has emerged as a result of anthropogenic activity, primarily due to metal mining, smelting, foundries, and other metal-based industries, as well as metal leaching from various sources such as landfills, waste dumps, excretion, livestock and chicken manure, runoffs, automobiles, and roadworks.
In agriculture, pesticides, insecticides, fertilizers, and other heavy metals have been a secondary source of heavy metal contamination. Volcanic activity, metal corrosion, metal evaporation from soil and water, sediment re-suspension, soil erosion, and geological weathering are natural causes of heavy metal contamination.
Pollutant entry, impacts, and transport into the ecosystem
Pollutants can enter the environment through various routes, including the hydrosphere, lithosphere, and atmosphere destroying environmental protection. Apart from entering through natural routes like volcanic activity and rock weathering, anthropogenic activity is a significant source of contaminants entering the environment. They can occur as a result of an unexpected release, such as in shipwrecks, oil spills, mines, and fires; in the intended application of biocides, such as vector control; and in waste disposal, such as industrial effluents and sewage disposal. Temperature, movement and direction of surface waters, circulation of air masses, and wind speed all influence the migration of heavy metals and other contaminants.
Water pollution
Water contamination is caused by two key factors: urbanization and industrialization, destroying environmental protection. Runoff from villages, towns, cities and factories convey the metals, which accumulate in the sediments of water bodies. Even if traces make their way into bodies of water, they might be extremely harmful to humans and other organisms. Heavy metal toxicity is determined by various factors, including the type of metal present, the nature of the metal, the biological role of the metal, the organism exposed, and the period during which the organism is exposed.
If one organism is harmed, it will have an impact on the entire food chain. Because humans are generally at the end of the food chain, this will have a more significant impact on us because we will have absorbed more heavy metals as the concentration rises the food chain. In most cases, both industrial and home wastes are discharged into the sewer system. Pollutants can exist in a variety of states, including surface waters, solutions, and suspensions.
They can be transported by water over a long distance, with particle materials sinking to the bottom. Droplets of liquid can either fall into the sediment or float to the surface. The length of time a pollutant travels in a river is determined by the pollutant’s currants, stability, and physical state. Wind and currents convey the contaminant further once it reaches the sea and seas. Another aspect in transit to a higher concentration of salt or a drop in temperature is the difference in density of the saltwater.
Persistent pollutants, such as heavy metals, can enter the food chain via marine life, affecting predators such as larger fish, birds, and mammals, including humans, who migrate and transmit the pollutant to various environments destroying environmental protection.
The fate of heavy metals in the ecosystem
The localization of a large amount of heavy metal causes an increase in toxicity and destroys environmental protection. Chimneys have been erected taller in some regions to dilute metal emissions, distributed more, and not fall in a concentrated area. However, this can have additional consequences, such as making it more susceptible to acid rain because it is emitted higher. Even though the Earth is viewed as a single compartment, it can be divided into more organisms or individual cells.
Potential toxins on organisms can be compartmentalized into insoluble deposits, which prevents them from interfering with cytoplasmic metabolic reactions. Metals cannot be broken down since they are non-biodegradable and exist in the environment for a long time. Heavy metals in soils and sediments stay in the environment for a long time before being eluted to other compartments. They can also form or degrade in the presence of other elements in the soil or sediment, making them more poisonous and destroying environmental protection.
Anthropogenic activity has resulted in high metal concentrations in contaminated locations such as abandoned mines or herbicides containing metals. Only metal-tolerant strains grow in these locations, which have limited vegetation. In certain zones, capping may be used, which entails placing an impermeable layer on top of the polluted site and covering it with new soil. Capping will prevent heavy metals from being absorbed by the flora and prevent heavy metals from entering the groundwater. However, arsenic, copper, lead, and chromium were detected in metal-containing pesticides, and these metals may still be present in some locations where it was used.
Farmers sometimes combine sewage sludge with soil. However, this can contain heavy metals, especially if industries generated the sludge. Heavy metals like copper, zinc, lead, cadmium, and chromium have been identified in significant concentrations in the soil of these agricultural lands.
Smelting pollutes the air, which then settles on the ground, causing localized pollution. Some sites where smelting takes place have dead vegetation and a lack of life, such as earthworms and woodlice, which aid in the decomposition of flora. Lead shotgun pellets, lead fishing weights, and lead-contaminated gasoline with a high percentage of lead all contributed to the presence of lead in our surroundings. Some have been outlawed in some parts of the globe. Birds have eaten shotgun pellets, which then migrate up the food chain; the weights have also caused lead to be detected in wetlands.