The Mystery Of Polluted Surface Water: What's The Cause?

Surface water pollution is a pressing issue that poses significant risks to both human health and the environment. It refers to the contamination of oceans, lakes, rivers, and streams—water sources that are essential for human consumption, agriculture, industry, and recreation. Surface water is highly susceptible to pollution due to its extensive presence on Earth's surface, and human activities play a pivotal role in its degradation. A multitude of contaminants, including agricultural runoff, sewage, wastewater, oil pollution, and chemical dumping, contribute to the deterioration of these vital water sources. The consequences of surface water pollution are far-reaching, impacting aquatic ecosystems, drinking water supplies, and the overall health and well-being of human populations and the planet alike.

Industrial waste and sewage

Industrial Waste

Industrial waste encompasses a range of toxic substances, including heavy metals, petroleum products, hazardous wastes, and sediments. These contaminants originate from various industries, such as metal processing, manufacturing, construction, mining, and petroleum production. For instance, the metal processing industry releases lubricants, primarily mineral oils, which increase the chemical oxygen demand (COD) value of water. Electroplating processes contaminate water with heavy metals like zinc, nickel, copper, or cadmium.

Improperly treated or untreated industrial wastewater is a primary concern. In emerging countries with rapidly growing industrial sectors, such as China, India, Africa, and South America, the illegal discharge of untreated wastewater into rivers and lakes is a common occurrence due to inadequate environmental regulations and enforcement. This results in the accumulation of non-biodegradable toxins in water sediments, which eventually seep into groundwater, affecting drinking water sources.

Sewage

Sewage, or domestic wastewater, is another major source of surface water pollution. It contains pathogens, bacteria, and viruses that carry waterborne diseases. These include harmful microorganisms, such as cholera, typhoid, and giardia, which can cause severe illnesses in humans and animals. Sewage can also promote the growth of algae, leading to eutrophic "dead zones" where aquatic life cannot survive due to oxygen depletion.

The direct release of sewage into water bodies, open excretion, farm runoffs with synthetic fertilizers and pesticides, and liquid waste from agricultural production are significant contributors to water pollution, especially in rural areas. Additionally, sewage treatment facilities in developed nations occasionally experience accidental or illegal releases, further contaminating waterways.

Agricultural activities

Agriculture is a leading cause of surface water pollution. Farms discharge large quantities of agrochemicals, organic matter, drug residues, sediments, and saline drainage into water bodies. The use of pesticides and fertilisers is a significant contributor to water pollution, as these chemicals can contaminate water sources and harm aquatic life. For example, phosphorus (P) fertiliser has contributed to the eutrophication of freshwater ecosystems, and pesticides can pose risks to aquatic life and drinking water supplies.

Soil erosion and nutrient loss are also significant issues, as they can lead to increased levels of nitrogen and phosphorus in water bodies, stimulating algal blooms that create hypoxic (low oxygen) conditions harmful to aquatic life. Excessive sedimentation from erosion can overwhelm aquatic ecosystems, smother breeding areas, and degrade coastal and marine ecosystems, including coral reefs.

Livestock production accounts for 70% of all agricultural land and 30% of the planet's land surface. It is a significant contributor to water pollution, as bacteria and nutrients from livestock manure can contaminate water sources, affect drinking water supplies, and cause beach and shellfish bed closures. Poorly managed livestock operations can also contribute to water pollution through cattle loafing in stream corridors and stream channel erosion.

Aquaculture, particularly in Asia, has grown more than 20-fold since the 1980s and is now recognised as a major problem in freshwater, estuarine, and coastal environments, leading to eutrophication and ecosystem damage. Fish excreta and uneaten feeds from fed aquaculture diminish water quality. Increased production has combined with the greater use of antibiotics, fungicides, and anti-fouling agents, which may contribute to polluting downstream ecosystems.

Agricultural conservation practices can help mitigate these issues. For example, buffer strips of vegetation at the margins of farms and along rivers can effectively decrease concentrations of pollutants entering waterways. Integrated farming systems, where crops, vegetables, livestock, trees, and fish are managed collectively, can increase production stability, resource use efficiency, and environmental sustainability.

Oil spills

The impact of oil spills on near-surface creatures depends on the timing and location of the spill. Seabird populations, for instance, may vary with reproductive cycles and seasonal changes. Some animals, like fish, can swim away from the spill, while others, such as plankton, may be unable to escape and suffer harm or mortality. Oil spills can also have economic consequences, affecting activities like fishing and hunting, which are crucial for many rural communities.

Cleaning up oil spills is a challenging task, and no entirely satisfactory method has been developed to date. Common approaches include using floating booms to contain the spill, skimming to separate oil from the water, and applying sorbents like natural or synthetic organic materials to absorb the oil. In situ burning of oil slicks is another method, but it can lead to additional pollution due to the release of nitrogen and sulphur, causing acid rain. While cleanup efforts can mitigate the impact of oil spills, they cannot completely eliminate the oil, and care must be taken to minimise further harm to sensitive habitats.

Radioactive substances

Radioactive radium and uranium are found in small amounts in almost all rock and soil and can dissolve in water. Radon, a radioactive gas created through the decay of radium, can also naturally occur in groundwater. If it is not removed, radon in water can be released into the air during activities like showering or washing dishes. Radium-226 and its derivatives, as well as the derivatives of radium-228, likely have the greatest potential for producing radiation doses that are harmful to humans. The radium-226 content of fresh surface water varies, ranging from 0.01 to about 0.1 pCi/liter. Some groundwater may contain up to 100 pCi/liter. Drinking water obtained from surface supplies generally does not contain significant amounts of radium, and treatment processes can remove most of the radium from the water.

Radioactive contamination is more prevalent in groundwater than surface water due to its proximity to radioactive elements in the rocks. However, surface water is still vulnerable to radioactive pollution. Nuclear weapons testing, nuclear power plants, and the dumping of radioactive waste are significant anthropogenic sources of radioactive surface water pollution. Nuclear calamities, such as the Fukushima Daiichi nuclear power plant disaster, have resulted in the release of thousands of tons of radioactively contaminated water into the ocean. Atmospheric deposition, both dry and wet, of cosmogenic radionuclides also contributes to radioactive contamination in surface water.

Mining activities for radioactive elements like uranium and thorium pollute surface and groundwater. Oceans and seas naturally contain uranium, and significant concentrations are expected in areas of greater salinity. Nuclear power plants located in coastal regions release atomic waste, adding to the radiological contaminants in marine water. Water is also used as a coolant in these power plants, which can become contaminated.

Pharmaceuticals

Surface water can become contaminated with pharmaceuticals through various pathways, posing significant ecological and health risks. One significant source of pharmaceutical pollution in surface water is manufacturing facilities. Studies have found that pharmaceutical manufacturing plants can discharge substantial amounts of pharmaceutical waste into wastewater, which then makes its way into rivers and streams. For example, a U.S. Geological Survey (USGS) study revealed that contamination levels downstream from two drug plants in New York were 10 to 1,000 times higher than at comparable facilities.

Another critical source of pharmaceutical pollution in surface water is human activity. Drugs that people take internally are only partially metabolized by the body, and the unmetabolized portion is excreted in urine and feces, entering civil sewage treatment systems. From there, they can gradually disperse into surface water bodies. Additionally, the use of medications applied topically, such as creams or lotions, can contribute to water pollution when the unabsorbed portions are washed off and enter the wastewater stream.

The use of antibiotics and drugs in agriculture also contributes to pharmaceutical pollution in surface water. Runoff from animal-feeding operations, laced with hormones and antibiotics, can find its way into nearby streams and rivers. A USGS study found pharmaceuticals such as acetaminophen, caffeine, cotinine, diphenhydramine, and carbamazepine in streams receiving runoff from these operations.

The presence of pharmaceuticals in surface water has been linked to adverse effects on both aquatic life and humans. They can affect the health and behavior of wildlife, including insects, fish, and birds. In humans, exposure to pharmaceutical pollutants has been associated with reproductive issues and neurotoxic effects. Additionally, the presence of antibiotics in the environment contributes to the development of antibiotic-resistant bacteria, which is a significant global health concern.

While water treatment facilities play a crucial role in ensuring safe drinking water, they are not always equipped to effectively remove pharmaceutical contaminants. Many plants do not routinely remove pharmaceuticals from treated water, allowing these chemicals to remain in the water that reaches our taps. This highlights the need for improved wastewater treatment processes and the development of more effective methods for removing pharmaceuticals from water.

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