Heavy Metals Contamination in Environment

Heavy metals can be defined as per their physical properties, toxicity to living organisms, and chemical reactivity. Heavy metals are an important group of environmental contaminants because they are toxic to living beings, bioaccumulate, and also persist in the environment. Heavy metals can originate from geogenic and anthropogenic sources. The geogenic sources of metals include weathering of parent rock material and volcanic emissions. The anthropogenic sources of metals include agricultural activities, industrial emissions, solid waste disposal, and urban activities. Heavy metals are present in all components of the environment and can be transferred from one medium to another. Heavy metals are present in the air in the form of aerosol. These aerosols are then deposited in soil, water, and biota through natural sedimentation and precipitation processes. Atmospheric deposition is a significant path by which metals enter other components of the environment. The heavy metal's behavior during atmospheric transport depends on their particle size-distribution and meteorological conditions. Heavy metal contamination in aquatic environments is a serious problem because of potential toxicity of metals and their accumulation in aquatic habitats. Once heavy metals are released into waterbodies, they are adsorbed into sediments. After metal adsorption on the sediments, the organisms living in these habitats start accumulating the metals at erratic rate. Heavy metals in soil get adsorbed to soil particles and then get accumulated in crops grown in the contaminated soil. Hence, heavy metals from the soil affect humans through food chain transfer. Biota accumulates the metals via two pathways, namely root and foliar uptake. Heavy metals contaminate all components of environment like soil, water, air, and biota, and they affect the human health as metals reach humans from the contaminated media via various pathways such as food chain transfer, drinking, and dermal contact.