Water Pollutants and Dangers of Polluted Water

Formal Definition: Water pollution is defined as the occurrence of any artificial products within a body of water.
Pollutants and Contaminants: In the context of environmental science, these artificial products are categorized as pollutants or contaminants. They include the following classes of materials:
- Organics: Organic chemical compounds.
- Inorganic Chemicals: Various chemical substances not based on carbon-hydrogen bonds.
- Pathogens: These are defined as infectious microorganisms.
- Macroscopic Objects: Visible physical debris including, but not limited to, trash, shipwrecks, and plastics.

Freshwater Vulnerability: Water pollution is a global crisis that affects freshwater sources across the entire world.
Economic Disparity in Management:
- Developing Countries: Often struggle with the fundamental means and infrastructure required to control acute water pollution.
- Developed Countries: Despite advanced infrastructure, developed nations still struggle significantly with water quality issues.
United States Water Quality Statistics:
- According to documented classifications, $44\%$ of streams in the United States are classified as polluted.
- $64\%$ of lakes in the United States are classified as polluted.
- $30\%$ of bays in the United States are classified as polluted.
Oceanic Pollution vs. Freshwater: Generally, the vast oceans are not as acutely polluted as freshwater sources. This is attributed to the fact that they are extremely deep and vast. While surface pollution exists, most of the ocean's volume remains unpolluted.

Industrialization Impact: While chemical contamination in the ocean may be less acute than in freshwater, industrialization over the last $200$ years has significantly impacted the ocean's pH levels.
Carbon Dioxide ( $CO_2$ ) Absorption: Total industrialization has increased the release of the greenhouse gas $CO_2$ into the atmosphere. The world's oceans absorb approximately $30\%$ of this atmospheric $CO_2$ .
Chemical Mechanism of Acidification: When carbon dioxide dissolves in water, it undergoes a chemical reaction to form carbonic acid. This process releases hydrogen ions ( $H^+$ ), which lowers the pH and increases the acidity of the water.
Chemical Equation:

$CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$

Marine Life Disruption: Acidification serves as a major threat to various types of marine organisms.
Impact on Shelled Mollusks:
- Mollusks that rely on shells are unable to properly deposit calcium into their shell structures because carbonate ions interfere with the process.
- A lower pH environment leads to the development of thinner shells, making the organisms more vulnerable.

Definition: Point sources of pollution are those that release contaminants into a body of water through a single, identifiable source.
Primary Examples:
- Factories.
- Sewage treatment plants.
- Storm drains.
Urban Runoff: Water that runs over streets and pavement collects specific pollutants, including chemicals from automobile exhausts and various oils. This contaminated water is gathered by storm drains, which are frequently directed straight into larger bodies of water.

Definition: Non-point sources of pollution are contaminants that cannot be attributed to a single, localized source. Instead, this type of pollution originates from contaminants spread over a large geographic area.
Agricultural Runoff: A primary example is the leaching of nitrogen-containing compounds from fertilized farming fields.
Residential and Cleaning Products:
- Phosphates: These are commonly found in fertilizers but are also prevalent in dishwasher detergents, laundry detergents, and other household cleaning products.
- Accumulation: Phosphates collect from residential areas through the use of these cleaning products and eventually find their way into streams and lakes.