Heavy metals are well-known environmental contaminants because of their toxicity, endurance in the environment, and bioaccumulative nature. Weathering of metal-bearing rocks and volcanic eruptions are natural sources, whereas mining and different industrial and agricultural operations are artificial sources.
Mining and industrial processing for mineral resource extraction and their subsequent applications for industrial, agricultural, and economic development have resulted in an increase in the mobilization of these elements in the environment and disruption of their biogeochemical cycles. Toxic heavy metal contamination of aquatic and terrestrial ecosystems is a serious environmental problem.
This article examines the various elements of heavy metals as hazardous compounds in-depth, with a particular focus on their environmental durability, toxicity for living beings, and bioaccumulative potential. Bioaccumulation of these elements and their consequences for human health are examined, with a focus on fish, rice, and cigarettes. The publication will be a significant instructional resource for environmental science undergraduate and graduate students, as well as researchers.
Importance of Metals
Metals are “elements that conduct electricity, exhibit a metallic sheen, are malleable and ductile, form cations, and have basic oxides,” according to chemistry. Metal, metalloid, semimetal, light metal, heavy metal, an essential metal, helpful metal, hazardous metal, great metal, accessible metal, trace metal, and micronutrient are terms commonly used in biological and environmental studies in relation to metals.
Metals have a wide range of applications and play an essential part in today’s industrialized society. Various materials are also used in packaging bottled and jarred packaged goods.
Some metals play critical physiological and biochemical roles in biological systems, and their deficiency or excess can cause metabolic disturbances and, as a result, a variety of diseases. Metals and metalloids are required for (biological) life to exist. They may be found in biomolecules like enzymes, which catalyze biochemical reactions in the body and play crucial physiological and biochemical roles in the body.
Heavy Metals Overview
Heavy metal is described as “a metal with a density larger than 5 g/cm3 (i.e., specific gravity greater than 5)” by Csuros. “The phrase “heavy metals” is typically used as a group name for metals and semimetals (metalloids) that have been linked to contamination and possible toxicity or ecotoxicity,” according to Duffus. We recently proposed a more significant definition for heavy metals, including naturally occurring metals with an atomic number greater than 20 and an elemental density greater than five gcm3.
Heavy Metal Contamination of Natural Waters, Sediments, and Soils
Both aquatic and terrestrial ecosystems are threatened by toxic trace metals . Heavy metals pollute natural water bodies, sediments, and soils once released from natural and anthropogenic sources. Heavy metals released into the atmosphere due to volcanic eruptions and various industrial emissions eventually fall to the ground, contaminating water and soils. Heavy metals accumulate in biota or leach into groundwater because they are persistent in the environment.
1. Water Contamination
Water is referred to as the “life-blood of the biosphere.” Because water is a universal solvent, it dissolves a wide range of organic and inorganic substances and contaminants in the environment. Pollution threatens both freshwater and marine aquatic environments. Heavy metal contamination of water supplies is a severe environmental problem that negatively impacts plants, animals, and human health.
Even at relatively low concentrations, heavy metals are exceedingly harmful to aquatic creatures. These components have been shown to produce severe histopathological changes in aquatic creatures like fish. Heavy metals contaminate aquatic habitats from a variety of sources.
Effluents from mining operations are one source of heavy metals in aquatic ecosystems. Different industrial effluents, home sewage, and agricultural run-off are all sources of heavy metal contamination in water.
The untreated discharge of industrial effluents into aquatic bodies is a major source of surface and groundwater pollution. Heavy metal pollution of water bodies is a global issue due to their environmental persistence, bioaccumulation, and biomagnification in food chains and their toxicity.
Heavy metal contamination of sediments is a severe environmental problem that impacts aquatic creatures and human health. In the marine environment, deposits serve as the primary source of metals. Their quality might indicate the level of pollution in the water. Heavy metals are released into the water column by sediments, which act as both a sink and a source of heavy metals. Continued deposition of heavy metals in sediments can lead to pollutant contamination of groundwater.
Many physicochemical factors influence the adsorption, desorption, and subsequent concentrations of heavy metals in sediments, including temperature, redox state, hydrodynamic conditions, organic matter, and microbe content, as well as particle size.
Heavy metal distribution in sediments is influenced by the chemical composition of the sediments, grain size, and total organic matter content. It will be beneficial if the companies start using lighter materials such as glass for their packaging purposes. You might contact a reliable glass packaging manufacturer who can provide you with bulks of glass bottling available at reasonable prices.
3. Soil Contamination
Heavy metals and metalloids are introduced into soils by both lithogenic and anthropogenic causes. The composition of parent rock, physical, degree of weathering, chemical as well as biological features of earth, and climatic circumstances are all factors that influence the presence and distribution of heavy metals in soils. In comparison to virgin soils and soils with modest inputs, significant enrichment of heavy metals has been recorded in soils receiving greater fertilizer and Cu fungicide.
Extensive metal contamination of soils can occur in metropolitan areas due to heavy motor activity on roads. Pb concentrations in urban soil samples are high, with 45–85 percent of it being bioaccessible. Heavy metal bioavailability in soils is critical for their destiny in the environment and plant uptake. Varying heavy metals have different bioavailabilities in soils, which are influenced by metal speciation as well as soil physicochemical features.
4. Heavy Metal Trophic Transfer
Heavy metals accumulate in living creatures and are transported from one trophic level to another in food chains because they are persistent in the environment. The amount of heavy metals accumulated in biota is determined by their rate of accumulation and elimination from the body. As a result, the half-lives of various heavy metals vary depending on the species.
Heavy metals can enter an organism’s body directly through the abiotic environment, such as water, sediments, and soil, or indirectly from its food/prey.
Heavy metals are also transferred from soil to plants, a crucial stage in the trophic transmission of these metals in food chains. These metals are absorbed by plants from polluted soil and then passed along the food chain to herbivorous animals. Pollution of crops such as cereals and vegetables is a severe concern regarding human food chain contamination.
Human health may be jeopardized if harmful heavy metals are present in cereals. Vegetables planted with wastewaters have been found to contain greater concentrations of heavy metals than those produced with groundwater.