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Arsenic (As
III. EFFECTS ON PLANTS
Some heavy metals, such as arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), or selenium (Se), are not essential for the growth of plants as they have no established physiological role to function in plants. Other metals, such as cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn), are required considering its necessity as essential elements for the growth of metabolism of plants, but as their concentrations gets increased beyond the acceptable range can quickly lead to poisoning. The use of waste composts are most commonly used to improve the quality of soil used for production of crops, fruits, vegetables by the use of compost to boost agricultural productivity without regard for possible negative impacts may be an issue however the most vegetable species have edible parts, as concern for transfer of heavy metals from soil to human being. Many plant species have been successful in absorbing pollutants from soils, such as lead, cadmium, chromium, arsenic, and different radionuclides i.e., radioactive nuclide/isotope. Phytoextraction, one of the phytoremediation categories, can be used to remove heavy metals from soil by utilizing its ability to ingest ions that are required for plant growth such as Iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), magnesium (Mg), molybdenum (Mo), and nickel (Ni). Some metals with unknown biological function such as cadmium (Cd), chromium (Cr), lead (Pb), cobalt (Co), silver (Ag), selenium (Se), mercury (Hg) can also be accumulated. Soil can be polluted with lead from a variety of sources, including industrial sites, fuel wit lead content, ancient lead plumbing pipes, and even old orchard sites where lead arsenate is used in manufacture. Lead is very immobile and collects in the top layer of soil. Contamination lasts a long time. Lead content in high levels in soil will never return to normal without remediation.
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IV. VARIOUS EFFECTS ON AQUATIC ENVIRONMENT
Heavy metals have a long half-life and are hazardous in small concentrations as well, causing severe oxidative stress in aquatic organisms. As a result, these pollutants are extremely important in terms of ecotoxicology. Furthermore, metals are not degraded by microbes and hence persist in the marine environment indefinitely. Contamination/pollution of a river water with heavy metals can have disastrous consequences for the aquatic environment's biological balance, as the diversity of aquatic creatures decreases as contamination increases. Heavy metals are frequently associated to particulate matter in aquatic systems, which settles down and gets incorporated into sediments over time. As a result, surface sediment is the most important reservoir or sink of metals and other pollutants in aquatic environments. Sediment containing pollutants have the possibility to be absorbed by rooted aquatic macrophytes as well as with other aquatic organisms.
V. VARIOUS EFFECTS ON PROCESS OF COMPOSTING
The consequences of pollutants due to heavy metals are major to soil, plants, and human health and have an impact on the composting process by altering microbial diversity. Microorganisms aid in the decomposition of organic matter, the detoxification of some organic and inorganic contaminants, and the modification of heavy metal mobility and bioavailability in plants, because heavy metals can impair microbial reproduction and cause morphological and physiological abnormalities, they should be avoided. As a result, hazardous heavy metals in the environment may influence biodegradation processes. Heavy metals have the capacity to impede both enzymatic reactions and complex metabolic processes, which could impair microbial enzymes. During the composting process, heavy metals reduce phosphatase synthesis. Microorganisms must deal with hazardous lead (Pb) during their growth in lead (Pb)-contaminated substrates, as microbial growth and activity are always inhibited when they are exposed to metals.
VI. CONCLUSION
Heavy metal contamination is rapidly increasing as a result of industrialization and modern lifestyles. It travels from plant to person or animal through the soil, interfering with biological processes in the human body. The majority of remediation strategies lowered crop absorption by converting the toxic form of heavy metal to a nontoxic form; or by converting the available form of heavy metal to an unavailable form in soil. Segregation and safe disposal of heavy metal-containing waste should be the primary strategy. Heavy metal contaminated crops such as flowers, caster, and jatropha are used for non-edible food crops. Where contaminated water is used for agricultural production operations, regular monitoring of effluent, soil, and crop produce is required. The contaminated water discharge units, as well as their consumers, should be subjected to a strict policy. A large-scale public awareness campaign about heavy metal toxicity and its consequences, aided by government agencies or non-governmental organizations (NGOs) is required.
VII. ACKNOWLEDGEMENT
The author is thankful to all teaching and non-teaching staff.
