Ground And Surface Water Pollution: Causes And Effects

Groundwater accounts for around 30% of the world's freshwater, and over 50% of the United States population depends on it for drinking water. Groundwater pollution, or contamination, occurs when pollutants are released into the ground and make their way into groundwater. This can happen due to human activities such as industrial waste, oil, and sewage systems, or naturally from sources found in the soil like iron, arsenic, and fluoride. Similarly, surface water can be polluted by contaminants from the atmosphere or other parts of the water cycle.

Industrial waste, oil, and pharmaceuticals

Industrial waste is a major source of groundwater and surface water pollution. Many industries have dumped toxic substances, including ammonia and nitrates, into water sources. For example, the now-defunct Diamond Alkali Co. in New Jersey, which manufactured chemicals, including those used to make Agent Orange, polluted the Passaic River—a drinking water source for millions. Similarly, Anaconda Aluminum in Montana produced manufacturing wastes that contaminated local water sources with lead and chromium, and Gulf States Utilities in Louisiana discharged toxins, including benzene, into marshlands.

In addition to the direct dumping of industrial waste into water sources, pollutants can also enter water sources through industrial waste disposal in landfills. For example, in the Love Canal area of Buffalo, New York, chemical companies dumped industrial waste into landfills, leading to the contamination of both groundwater and surface water in the area.

Oil is another significant source of groundwater and surface water pollution. Leaks and flooding from oil tanks and depots can contaminate nearby soil and groundwater with petroleum products. Vehicle service stations and underground oil depots are among the main polluting sites due to the risk of oil leakage. A study in Yibin, China, found that tank leaks at a service station had resulted in the detection of petroleum product pollutants in several monitoring wells.

Oil pollution poses both non-carcinogenic and carcinogenic health risks. At the time of the investigation, non-carcinogenic health risks covered 25,462 m2, while carcinogenic health risks covered 21,390 m2. These risks are predicted to increase over time, highlighting the importance of addressing oil pollution in groundwater and soil.

Pharmaceuticals are also emerging as a growing source of water pollution. Pharmaceuticals are excreted in urine and feces and can enter water sources through urban wastewater and the inadequate disposal of expired or unused drugs. While pharmaceuticals are typically found in low concentrations, they are biologically active compounds that can have potential chronic toxicity, bioaccumulation, and biomagnification effects. Conventional wastewater treatment plants are often ineffective in removing these contaminants, leading to their presence in surface water, groundwater, and drinking water.

The massive increase in pharmaceutical consumption worldwide has led to a corresponding increase in their environmental impact. This has spurred the development of alternative treatment methods, such as advances in bioremediation technologies and mycoremediation, to address the presence of pharmaceuticals in water sources.

Sewage, septic tanks, and sanitation systems

Septic systems are commonly used for wastewater treatment, especially in areas not served by municipal sewers. They are designed to treat household wastewater before it filters into the soil. However, if a septic system is not properly maintained or becomes damaged, it can contaminate nearby water sources. This contamination occurs when untreated wastewater, containing pathogens, nutrients, and other harmful substances, is discharged directly into groundwater or surface waters. Failing septic systems can lead to public health hazards, causing illnesses and posing risks to anyone exposed, including children and pets.

Improperly maintained or failing septic systems can result in the spread of harmful bacteria, parasites, viruses, and other contaminants in groundwater, streams, and soil. Studies have linked septic tank issues to disease outbreaks, with data showing that a significant percentage of outbreaks were associated with contaminated drinking water from septic tanks or improperly designed wells. Regular maintenance, such as pumping and cleaning, is crucial to prevent septic system failures and reduce the risk of water pollution.

The placement of septic systems is also critical to preventing water contamination. If a septic system is located too close to a drinking water well, contaminants from the wastewater can infiltrate and contaminate the well water. Additionally, high-density placement of septic tanks in suburban areas can lead to high concentrations of wastewater, which may seep onto the land surface, run off into surface water, or flow directly into the water table. Proper separation distances between septic tanks and water sources are essential to mitigate this risk.

Furthermore, sewage leaks from sewer lines can contribute to water pollution. Leaking sewer lines can release untreated sewage, which may contain industrial waste chemicals, directly into groundwater. Sewer leaks can occur due to various factors, including tree root invasion, soil slippage, seismic activity, flooding, or sewage backup. Systematic inspection of sewer lines and adherence to modern construction and maintenance specifications are necessary to prevent sewage leaks and protect groundwater sources.

In summary, sewage, septic tanks, and sanitation systems play a crucial role in wastewater treatment. However, improper maintenance, system failures, and incorrect placement can lead to groundwater and surface water pollution. Regular maintenance, monitoring, and adherence to safety guidelines are essential to prevent water contamination and protect public health and the environment.

Natural sources: fluoride, arsenic, iron

Arsenic, fluoride, and iron are considered some of the most common toxic pollutants in water bodies. Natural sources of arsenic include rocks and sediments, and it can also be released into groundwater as a result of human activities such as mining, industry, animal feed, wood preservatives, and pesticides. Arsenic is a known carcinogen and can cause cancer in people with long-term exposure. It is tasteless and odourless, so groundwater sources must be sampled and analysed to determine their presence.

Fluoride, on the other hand, is added to toothpaste and drinking water in some countries for its positive effects on dental health and cavity prevention. However, too much fluoride can cause dental mottling and higher concentrations may lead to skeletal fluorosis, a debilitating stiffening of the joints. South Asian countries such as India, Pakistan, and Sri Lanka are considered the epicentre of fluoride-contaminated water.

Iron, in the form of solid-phase ferric iron (Fe(III)), is used in the monitored natural attenuation strategy at hydrocarbon spill sites. This strategy relies on the biodegradation of hydrocarbons and the reduction of electron acceptors.

The presence of these contaminants in groundwater poses a serious threat to human beings and aquatic life. In developing countries, in particular, where groundwater is the major source of drinking water, human health is under threat from polluted groundwater.

Pesticides, fertilisers, and other chemicals

Pesticides and fertilisers can contaminate groundwater and surface water through various means. Firstly, they can enter water bodies via point source and non-point source pathways. Point sources include chemical runoff during improper storage, loading, or disposal, as well as the misapplication of pesticides directly into water bodies. Non-point sources include runoff from agricultural and urban land, seepage into groundwater in areas where pesticides are used, and deposition of pesticides from the atmosphere.

The properties of the pesticide, the soil, and the site conditions influence the likelihood of groundwater or surface water contamination. For example, sandy soils with low organic matter content are more vulnerable to groundwater contamination due to their lower capacity to adsorb pesticides and higher infiltration rates. Similarly, soils with more clay and organic matter tend to retain water and dissolved chemicals for longer, increasing the potential for contamination. The time lag between applying pesticides and fertilisers and their arrival at a well is crucial to consider for groundwater quality management.

The solubility of pesticides also plays a role in water contamination. Highly water-soluble pesticides have a greater tendency to move by runoff or leaching from the application site. Pesticides with longer half-lives, or stability, take longer to break down and persist in the environment. Additionally, rainfall and irrigation increase the risk of pesticide contamination in water bodies by facilitating runoff and erosion.

The overuse and misuse of pesticides and fertilisers in homes, gardens, and agricultural settings can have detrimental effects on water quality. They can enter storm drains, indoor drains, and groundwater through improper disposal, spills, and runoff. These drainage points often flow into larger water bodies, contaminating them with chemicals. While wastewater treatment plants filter and disinfect water before release, they cannot remove all pesticide residues, leading to chemical discharge into waterways.

Saltwater intrusion and mining

Saltwater intrusion is a significant issue for coastal communities that rely on fresh groundwater supplies for their livelihood. Saltwater intrusion refers to the movement of seawater into freshwater systems, which can occur through various mechanisms. Firstly, excessive groundwater pumping can reduce the flow of freshwater towards coastal areas, causing a decrease in freshwater storage in the aquifers. This reduction in freshwater volume allows saltwater to migrate landward, contaminating the water supply. Climate change and rising sea levels also contribute to saltwater intrusion, as they can alter the balance between freshwater and saltwater in coastal aquifers.

Additionally, saltwater intrusion can occur through lateral encroachment from coastal waters and vertical movement near discharging wells. In some cases, leaking saltwater inland canals, leakage between aquifers, or upwelling of saltwater from depth can also impact freshwater aquifers. The intrusion of saltwater can render water unsuitable for drinking, irrigation, and agricultural purposes, posing significant challenges to communities dependent on freshwater resources.

The problem of saltwater intrusion has been observed in several regions, including the East Coast of the United States, where saltwater has intruded into drinking water wells in states like Maine, Georgia, and Florida. In Florida, saltwater has encroached into groundwater supplies due to decreasing freshwater levels relative to sea level, allowing saltwater to flow towards the freshwater sources. Water managers in Florida are working to prevent and reverse saltwater intrusion by utilizing information from monitoring networks, such as the USGS, to better manage their water resources.

Furthermore, saltwater intrusion has been a long-standing issue in Tripoli city at the Mediterranean coast of Jifarah Plain, North West Libya. Since the 1930s, Libya has experienced progressive seawater intrusion into its coastal aquifers due to increasing water demand from underground water resources. Groundwater samples from Tripoli city have shown high levels of electrical conductivity and increased concentrations of Na+, K+, Mg2+, Cl−, and SO42−, indicating significant seawater intrusion.

To address saltwater intrusion, it is essential to implement effective groundwater management plans that consider potential changes in water quality. Prevention methods include applying the precautionary principle, groundwater quality monitoring, land zoning for groundwater protection, and proper locating of on-site sanitation systems. By studying the "fingerprints" or "isotopes" of water, scientists can analyze the age and composition of groundwater to better understand and mitigate saltwater intrusion.

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