Natural or Manmade Sources of Heavy Metals in Water Resource
Among all the natural resources, water is one of those that man has fully exploited for the sustainability of life (Goel, 2006, p.1). Because of the fact that only 2.5% of the earth’s water is fresh, many people have relied on the rain in order to meet their daily water demands. However, water pollution has become a major issue in the recent times owing to the diminishing water supply and it is clear that no organism can survive without water. Heavy metals occur naturally in the environment and include the elements with an atomic number that is greater than 20 (Agarwal, 2009, p.1). Besides, other heavy metals like zinc, iron and copper are useful in our bodies. Lead, arsenic or mercury which can be manufactured in the fish we eat can be harmful to our health if consumed in large quantities (Goel, 2006, p.1). If these metal contaminants are released into the environment, they cause water pollution.
The commonly known source of heavy metals is volcanic activities, which after being released find their way into many water bodies (Agarwal, 2009, p.8). The main sources of heavy metals are magmatic rocks that are formed from magma that has cooled down. Ore minerals that are hidden in the crust also release a few metals into the environment. Such metals include iron ores, argite, and apatite among others. Such produce mild levels of toxic effect (Agarwal, 2009, p.9). Heavy metals like copper occur naturally and are found in the crust of the earth, at low levels that are less toxic. Copper is released to the water bodies through decaying vegetation, mining activities or agricultural activities like the application of fertilizers.
One of the human activities, mining produces lots of toxic heavy metals into the environment. According to a study on Zawar mines, Udaipur effluents had higher levels of lead and zinc (Agarwal, 2009, p.10). The mines release waste through the effluents, thereby causing toxic materials. Mining of gold is yet another example whereby a mixture of Hg is released. This is released into the river streams through draining them away in a process known as flushing, especially in the Amazon where the release is not restricted (Bradl, 2005, p.23) which causes water pollution. The Acidic sulphur that is found in wastewater that is obtained from the acidic mine drainage is the water that flows from most mine drainages (Hardy, 2008, p.1). It is usually acidic and contains high concentrations of sulphate, iron and other heavy metals (Hardy, 2008, p.1). If the levels of acidic concentration are so high, heavy metals become more toxic.
Bradl (2005, p.20) say that agricultural activities are also a significant source of heavy metals in water bodies resulting into water pollution. The increasing population needs more food production, thereby pushing farmers to using fertilizers and pesticides in order to ensure enhanced production and fast harvesting. Fertilizers are added onto the soil for additional nutrients while pesticides are used for the protection of crops (Bradl, 2005, p.20). Heavy metals that originate from the soil sediments are oxidized, therefore, enhancing the movement of heavy metals (Bradl, 2005, p.20). Owing to the interconnection between soil and ground water, metals that are produced in the soil affect those that are found in the water through infiltration (Bradl, 2005, p.21) hence causing water pollution.
Bio solids, which are also known as sewage sludge, animal wastes and certain industrial wastes (Bradl, 2005, p.22) are at times released into the water bodies. Sewage sludge contains low levels of zinc and copper (Bradl, 2005, p.22). According to an observation made in the Ganga Basin from Bandtrinth to Narora, which are 480 kilometers apart, the upper zone has only a few industries (Agarwal, 2009, p.43). High levels of iron, nickel, lead, cadmium, cobalt and zinc concentrations were found underneath as a result of the high number of industries. This explains that countries that are more industrialized are often faced with the impacts of toxic heavy metals.
Quite a number of avenues have been created to help in controlling the high concentration of heavy metal in bio solids. One of them is the use of alkaline materials in neutralizing acidic mine waters (Hardy, 2008, p.66). The process increases the PH of the acidic mine drainage, and also stirs up the rate of oxidation causing the precipitation of heavy metals from solution in the form of hydroxides or carbonates (Hardy, 2008, p.6). Absorbents can be useful in the removal of metals from the contaminated water but is a bit costly.
An estimated 10% of farms in China had recently experienced excessive levels of heavy metals as a result of contamination of water. This form of soil pollution is caused by the water used for irrigating the farms that contain high levels of lead, mercury and cadmium, which are renowned for causing cancer. The increased use of wells containing pyrite has also contributed to oxidation (Bradl, 2008, p.21).
The recommended limit for mercury in drinking water has been identified as 0.001 because a recent research revealed that we have been drinking water with quite higher limits. According to the observation, the trace elements originate from both natural and manmade sources. Therefore, it is important that we protect our health by setting standards for drinking water through the identification of toxicity levels of every metal (Agarwal, 57). It is clear that if caution is not taken, the heavy metals will continue to cause harm to human health. Thus, it is high time we began protecting our limited sources.
Agarwal, S. K. (2009). Heavy metal pollution. New Delhi: A.P.H. Pub. Corp.
Bradl, H. B. (2005). Heavy metals in the environment: [origin, interaction and remediation]. Amsterdam: Elsevier Academic Press.
Goel, P. K. (2006). Water pollution: Causes, effects and control. New Delhi: New Age International.
Hardy, M. A. (2008). Retention of heavy metals from acidic sulfur-rich waste water by water treatment residuals: A reconaissance study.