The leading cause of soil contamination is industrial wastes from iron, power, chemicals, and steel manufacturing plants. Most of these industries use the earth as their main disposal area. As a result, they leave toxic materials whose effects can last for years
Hyderabad: Soil contamination is the improper disposal of chemicals such as artificial hydrocarbons, toxic waste, heavy metals, and agro-chemicals among other deadly substances into the natural soil environment due to human activities and industrialization. It is commonly associated with improper disposal of wastes, non-organic farming practices, and industrial activities
What is it?
Soil contamination is any substance in the soil that exceeds naturally-occurring levels and poses human health. For example arsenic naturally occurs in some soils. But if a person sprays certain pesticides on their yard, that could cause soil contamination. Lead is also very dangerous but occurs naturally in some soils. The biggest risks for soil contamination are in urban areas and former industrial sites.
Examples of soil contaminants
Examples of soil contaminants include lead, petroleum, pesticides, mercury, hydrocarbons, and polynuclear aromatic hydrocarbons. As such, concerns have been growing over soil contamination and the harmful consequences associated with it including increased health risks, secondary water contamination, and harmful vapors. Despite the institutionalization of legal frameworks in most western countries to identify and solve the issues affecting the environment, remedy measures such as mapping, treatment, and cleanups still prove to be quite expensive thereby augmenting the risks and impacts.
Inorganic farming practices
In non-organic farming, pesticides, fungicides, and herbicides are used to control pests, diseases, and weeds respectively. They are heavily used by farmers to increase productivity but the problem is that they are synthetic substances created through the combination of several artificial chemicals. Improper and continuous use of these chemicals leads to alteration of the basic composition of the soil. They also make the soil toxic for crop growth.
For example, some pesticides containing organophosphates such as methyl parathion and Malathion are still acceptable in most countries in the world regardless of the fact that they also contaminate the soil because of their high levels of toxic substances. The chemicals accumulate in the soil over time due to their slow degradation by both soil and water bacteria. In the soil, they are known for their harmful effects which result in stunted growth in plants, reduced size of fruits, and low yield.
Mining activities
Mining activities result in the production of radioactive wastes and heavy metals. Radioactive wastes from nuclear processes and mining activities may then find their way into the soil through run-off water. Anthropogenic activities such as smelting and mining of metal ores also release high levels of heavy metals in the soil.
An example is the Perlis city, northwest Malaysia around Chuping industrial area where high levels of copper, lead, chromium, nickel, and cadmium have been recorded, as a result of the cement mining activities around the same location. Coal mining activities are known to produce coal ash which has high amounts of lead and zinc which concentrate during its formation.
Nitrification
Nitrification is the process of converting atmospheric nitrogen, harmless organic matter, and insoluble nitrites to soluble nitrates. This process, which is very vital for crop growth, also contributes to soil contamination when the nitrates are in high amounts. The nitrates may also leach and find its way into water supply where they accumulate to toxic levels.
Landfills and poor disposal of e-waste
Substances in poorly maintained landfills and electronic wastes contain toxic chemicals such as lead, mercury, arsenic, cadmium, chromium, copper, and selenium among other heavy metals. Improper disposal of such waste would lead to a gradual degradation of these substances, which eventually lead to toxicity of the soil.
Fuel leakages from automobiles
Fossil fuel powered engines in automobiles usually leak petroleum products and this often ends up contaminating the soil with hydrocarbon chemicals like lubricants, petroleum oil, grease, and other chemicals used for the engines and moving parts.
Harmful effects
Contaminated soil found in parks or neighborhoods is a major health concern. When humans come into direct contact, inhale, or use water which has been affected by contaminated soil, they tend to develop pollution-related diseases. The health effect depends on the type of contaminant in the soil, the pathway, and the vulnerability of an individual.
Examples of long term health effects include developmental problems resulting from children being exposed to heavy metals such as lead. Contaminant such as chromium, PAH and lead from organic farm inputs, petroleum products wastes, coal mines and solvents are carcinogenic in nature and chronic exposure can cause congenital diseases and cancer.
Poor crop production
In the ecosystem, the soil contaminants pose a great threat to crop growth and production. High levels of contaminants in the soil can render the soil unfit for crop production. The plants grown in a field that contains contaminants are equally unhealthy for human consumption. Ingestion of such plants can hence lead to the accumulation of the harmful chemicals in larger organisms up in the food chain.
The contaminants in the soil also change the composition of soil and its microorganisms. When plants are grown in such areas, they tend to have lower yields compared to those grown in areas with no contamination. The low yields can also be attributed to the changes in metabolism caused by the contaminants.
Groundwater contamination
Chemical soil contaminants from the land’s surface can leach and end up in the groundwater. Pesticides and chemical fertilizer components have been reported in groundwater supplies over time in areas adjacent to agricultural sites. As a result, they leaky chemicals contaminate groundwater. Consumption of contaminated groundwatercan adversely affect one’s health as it is associated with certain types of cancer and hepatitis.
Effects on aquaculture, aquatic animals
Some non-organic herbicides and pesticides are made up of benzene hex chloride, arsenic acid, aldrin, atrazine, and DDT among other chemicals. They are preferred because they are very effective and cheap to manufacture. Since the 1930s, they have been manufactured in huge quantities and were in use until the 1970s.
Recently, usage of those with significant impacts have been dropped but their effects are widespread while some are still in use. Pesticides containing organophosphates such as methyl parathion and Malathion are still acceptable and their traces have been found in aquatic mammals and fishes because it is highly absorbed in blood than in water and soil. Once the chemicals are absorbed, they move up the food chain to humans through a process known as bio-accumulation.