How Pollution Impacts Water Ph Levels

The pH of water is a measure of how acidic or basic it is, with 7 considered neutral. pH levels outside of this range can have detrimental effects on the use of water, the health of waterways, and the organisms living within them. Pollution can cause changes in the pH of water, with the byproducts of air and water pollution often resulting in a more acidic environment. This can have a domino effect on the entire aquatic food chain, with fragile plants and animals becoming sick and dying.

Acid rain

Environmental Impact

Impact on Human Infrastructure

Human Health

While walking in acid rain is not considered dangerous, the pollutants that cause it can be harmful to human health. Sulfur dioxide (SO2) and nitrogen dioxide (NO2) can react in the atmosphere to form fine sulfate and nitrate particles, which can enter the lungs and cause respiratory issues, including lung disease and difficulties for people with asthma. Acid rain can also cause metals to leach from the soil into water sources, leading to serious illnesses.

Sources of Acid Rain

The main sources of the compounds that result in acid rain are anthropogenic, primarily from the combustion of fossil fuels such as coal, oil, natural gas, and wood. However, nitrogen oxides can also be produced naturally by lightning strikes, and sulfur dioxide is released during volcanic eruptions.

Effects on aquatic life

The pH of water is a logarithmic scale that measures how acidic or basic water is. The scale ranges from 1 to 14, with 7 being neutral, values below 7 being acidic, and above 7 being basic. The pH of water can be influenced by both natural and man-made factors, and even minor changes can have long-term effects on aquatic life.

Aquatic species, such as fish, are highly affected by changes in pH. The recommended pH range for most fish is between 6.0 and 9.0, with sensitive freshwater species like salmon preferring pH levels between 7.0 and 8.0. At pH levels below 6.0, sensitive species like salmon can suffer severe physiological damage due to absorbed metals. At pH levels below 4.5, most aquatic organisms will experience unfavorable conditions, and the fertilization of many fish species is unsuccessful at pH levels below 4.0. The hatching period and reproduction of several fish species, such as salmonids, carp, flag fish, and eastern catfish, are also influenced by pH levels.

Extreme pH levels, both high and low, can increase the solubility of toxic elements and compounds, making them more available for absorption by aquatic life. For example, at very high pH levels, metals tend to precipitate, and chemicals like ammonia become toxic to aquatic life. At low pH levels, the solubility of metals increases, and chemicals like cyanide and sulfide become more toxic. Additionally, at pH levels over 9, ammonium (NH4+) reverses and releases ammonia (NH3) into the water, which is extremely toxic to aquatic organisms.

Changes in pH can also affect aquatic life indirectly by altering other aspects of water chemistry. For example, a minor increase in pH levels can cause an oligotrophic lake, low in plant nutrients and high in dissolved oxygen, to become eutrophic, rich in nutrients and plant life but low in dissolved oxygen. This change in the lake's ecosystem can stress other organisms living in the water, even if pH levels remain within the optimum range.

Furthermore, pH levels can impact the early life stages of fishes, including their oogenesis, ion exchange with water, respiration, and fertilization. Chronic exposure to pH values above 10 is harmful to all species, causing severe physiological damage, and even death in adult fish and invertebrates. When the pH of freshwater becomes highly alkaline, fish may experience damage to their outer surfaces, such as gills, eyes, and skin, and may struggle to dispose of metabolic wastes.

Pollution sources

Human-induced sources of pollution that impact water pH include acid rain, which is caused by the reaction of water with nitrogen oxides, sulfur oxides, and other acidic compounds. These emissions often originate from mining, smelting, and fossil fuel combustion. Point source pollution, such as dumping industrial pollutants directly into water, can also affect pH levels. Mining activities can expose rocks to rainwater, producing acidic runoff, and if the resulting drainage is poorly buffered, the pH may reach toxic levels.

Other human activities that contribute to water pollution and pH changes include welding and mechanical servicing, which can introduce various chemicals and contaminants into water sources. High rainfall areas can experience heavy runoffs and leaching of surface soil chemicals, which can impact water pH and increase the solubility of certain pollutants.

Additionally, sewage outflow can decrease the alkalinity of water, making it more susceptible to pH changes. The presence of certain bacteria, such as total and faecal coliforms, can also be indicators of pollution and are associated with non-optimal water pH levels.

pH as an indicator of contamination

PH is a measure of how acidic or basic water is. The pH scale ranges from 0 to 14, with 7 being neutral. A pH of less than 7 indicates acidity, while a pH greater than 7 indicates a base. The pH of water is an important indicator of water quality and can be affected by both natural and human processes.

Water with a very high or very low pH can be unpleasant for certain purposes. For example, at a very high pH, metals tend to precipitate, and chemicals like ammonia become toxic to aquatic life. Water tends to have an unpleasant smell and taste in alkaline conditions. At a low pH, the solubility of metals is higher, and chemicals like cyanide and sulphide become more toxic. Acidic waters also corrode metal pipes. Therefore, heavy metals in water with a low pH tend to be more toxic as they become more soluble and bioavailable. Exposure to extreme water pH through ingestion or skin contact can cause irritation to the eyes, skin, and mucous membranes.

The pH of water can be affected by pollution in the air, soil, or directly in the water. Acid rain is a well-known example of human influence on water pH. Acid rain is caused by the reaction of water with nitrogen oxides, sulfur oxides, and other acidic compounds, resulting in precipitation with a pH lower than 5.0. These emissions typically come from mining, smelting, and fossil fuel combustion. In addition to acid rain, other forms of pollution, such as coal pile runoff, urban runoff, and improperly functioning septic systems, can also contribute to water acidification.

Changes in pH can have significant ecological impacts. Even minor changes in pH can affect the solubility of nutrients and heavy metals, influencing their availability to aquatic plants and organisms. For example, a slight increase in pH can increase the solubility of phosphorus, making it more accessible for plant growth. This can lead to a chain reaction, as more plants and algae thrive, increasing the demand for dissolved oxygen in the water. These changes can stress other organisms living in the water, even if pH levels remain within the optimum range.

Furthermore, certain biological indicators can suggest the presence of low pH conditions in water bodies. For instance, the presence of specific aquatic or semiaquatic plants, such as spike rushes, water lilies, and insectivorous marsh plants, may indicate low pH levels. Additionally, the presence of stream species that are particularly sensitive or tolerant of low pH can also provide clues about potential causes of impairment.

Human health implications

Water pollution has severe implications for human health. According to the UNESCO 2021 World Water Development Report, about 829,000 people die each year from diarrhea caused by unsafe drinking water, sanitation, and hand hygiene, including nearly 300,000 children under the age of five. This accounts for 5.3% of all deaths in this age group.

The pH of water is a critical factor in determining the health of a waterway. pH levels outside the range of 6.5 to 9.5 can damage and corrode pipes and other systems, increasing heavy metal toxicity. High pH levels can corrode or dissolve metals into the water, increasing toxicity levels and reducing water quality. Exposure to extreme water pH through ingestion and skin contact is associated with irritation to the eyes, skin, and mucous membranes. A pH value below 2.5 will cause irreversible damage to skin and organ linings.

Water with a pH greater than 8.5 can cause skin irritation and make the water taste more bitter. When the pH level rises, the effectiveness of chlorine as a disinfectant decreases, necessitating the use of more chlorine to improve water quality. A pH level below 6.5 is likely to be contaminated with pollutants, making it unsafe for human consumption.

Pollution can cause changes in the pH of water, which in turn can have serious implications for human health. Acid rain, caused by nitrogen oxides and sulfur dioxide in the air combining with water vapour, is a well-known example of how human activity can affect water pH. These pollutants are primarily emitted by automobiles and coal-fired power plants. Acid rain is responsible for the acidity of many first-order streams. In addition, coal mine drainage, which contains iron sulfide, combines with water to form sulfuric acid, further lowering the pH of stream waters.

To reduce the health risks associated with water pollution, it is crucial to strengthen the supervision of water quality, improve the treatment of drinking water, and enhance public health awareness through education.

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