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Here’s How Heavy Metals Cause Environmental Contamination

1. Overview about Heavy Metals

Heavy metals are naturally occurring, but it has been the human extraction and mass use of them that has introduced them in dangerous concentrations to our environment. The impact of heavy metals on environmental pollution has been a long-standing problem, has compromised human, animal, and plant health, and will continue to threaten us long into the future unless we make great strides in getting rid of all dangerous concentrations of these deadly contaminants.

The main issue is the bioaccumulation of heavy metals in the food chain because these metals are non-degradable and collect in plant and animal life. They continue passing through the food chain eventually collecting in humans and causing health problems, mental problems or death. Remediation of heavy metals is a vital process that is necessary for the protection of our soil, air, and water quality as well as animal and human health.

2. How Heavy Metals cause Environmental Contamination

Inorganic pollutants like metals, salts and minerals are found naturally but in the case of contamination their levels have been heightened by human production. These inorganic substances can enter the environment through human activities such as mine drainage, smelting, metallurgical and chemical processes. And they become toxic when their levels accumulate in natural food chains. Most environmental contamination by heavy metals occurs when elevated concentrations of these high atomic weight and high density elements collect in the environment at levels that far exceed the natural levels for the area and substance.

Of all the pollutants, heavy metals often receive special attention from environmentalists because of their toxic nature even at very low concentrations. Metals such as arsenic, lead, cadmium, nickel, mercury, chromium, cobalt, zinc and selenium are highly toxic even in extremely low concentrations. Which is why the impact of heavy metals on environmental pollution is such a major concern.

These toxic metals enter the human body through food and water consumption, breathing air or absorption through the skin. The toxicity of heavy metals is a result of animals inability to metabolize them leading to their accumulation in fish, bird and mammal soft tissues. Industrial processes, lead pipes, and food chain accumulations account for the most common human exposures.

The most significant environmental contamination by heavy metals is anthropogenic. Our human activities from the exhaust released when driving cars; metallurgical smelting in our industrial process; production and use of insecticides and burning of fossil fuels are the main sources of air contamination. The most common sources of heavy metals are waste products from mining, irresponsible disposal of heavy metal waste, leaded paints, application of fertilizers, sewage sludge, pesticides, wastewater irrigation, coal combustion residues and spillage of petrochemicals. The presence of heavy metals in soils only adds to the rising levels in food chains while also slowing the biodegradation rate of organic pollutants therefore doubling the overall impact of heavy metals on environmental pollution.

3. How do we solve these problems?

For the protection of plants, animals, air, water, soil (basically the overall environment for human health), we must get a handle on heavy metal contamination. Fortunately there are numerous remediation technologies available for removing heavy metals from the environment. Most of these heavy metal remediation technologies require cleaning large amounts of sludge, altering the existing ecosystems and are exceedingly expensive. Let’s look at several of the most common remediation techniques.


a- Precipitation

One method used for years to neutralize acid mine drainage (AMD) fis the introduction of a variety of alkaline chemical reagents resulting in an increase of the pH of the affluent and leads to the precipitation and recovery of metals. Some common alkaline reagents used for sequential recovery of heavy metals and other minerals from AMD are limestone (CaCO3), caustic soda (NaOH), soda ash (Na2CO3), quicklime (CaO), and magnesium hydroxide (Mg(OH)2) [21]. These precipitation processes have had some success at recovering metals and using them to create commercially valuable materials such as pigments and magnetite. Other minerals that are recovered can be sold to metallurgical industries to help pay for the treatment costs.


b- Adsorption

Adsorption is a chemical process that is most effective and an economically viable option for removing metals from water. In this process an adsorbate adheres to the surface of an adsorbent. Adsorption, though efficient, is best used with diluted concentrations of metals in the solution because otherwise the adsorbent gets quickly saturated with the adsorbate. This drawback makes the process very labour intensive, requiring frequent regeneration. It is also not selective in terms of metal attenuation making it difficult to use with large scale metal remediation.


c- Ion exchange

Ion exchange involves the exchange of ions between two or more electrolyte solutions. It can also involve the exchange of ions on a solid substrate to soil solution. Clays and resins with high ion exchange capacities are used to uptake the metals from aqueous solutions. Again the ion exchange method requires lots of labor and it is limited to specific concentrations of metals in the solution. The process must also occur at a very specific temperature and pH. Natural and synthetic clays, zeolites and synthetic resins are all being used to remove and attenuate metals from wastewater


d- Biosorption

Biosorption is a process for the removal of pollutants from water systems through the use of biological materials. Biosorption involves absorption, adsorption, ion exchange, surface complexation and precipitation procedures. Biosorption processes have the advantage of being readily and easily available. Regeneration is easy which makes this technology very favorable. However, at high concentrations the process will easily reach a saturation point which limits further pollutant removal.


e- Membrane technologies

The development and use of membrane technologies to recover metals from acid mine drainage has been shown to be highly effective for countering environmental contamination by heavy metals in water even when pollutants are high in concentration. These methods use the concentration gradients phenomenon or reverse osmosis. Multiple types of membranes are being used for mine water treatment including: ultrafiltration, nano-filtration, reverse osmosis, microfiltration and particle filtration.

4. Conclusion

When it comes to the impact of heavy metals on environmental pollution there is no doubt that discovery and remediation of these contaminants must be a high priority for human health and the long term health of the planet. Improving upon these technologies and continuing to develop new methods for remediation are essential steps to a healthier future.

For this reason Torrent offers testing to detect metals using ICP-MS (Inductively Coupled Plasma Mass Spectrometry). This method is effective when you need to detect low levels of trace metals in groundwater or drinking water, and when you need to confirm the presence of certain metals in a water or soil matrix.

Torrent Laboratories uses the latest technologies, employs the most highly qualified chemists and provides you with superb customer service. Discover why we are the premiere environmental testing laboratory for California and Hawaii.