Composition of Water
Water is a universal solvent which is composed of hydrogen and oxygen and is found in the earth in the form of seas, oceans, rivers, lakes, and even in the atmosphere. Water is a compound of hydrogen and oxygen, but depending on the dissolved substances and impurities, its composition may be different. Knowledge of the components of water assists in evaluating its quality and fitness for specific purposes.
The basic composition of pure water is that it is tasteless and odorless and is formed by the combination of hydrogen and oxygen in the proportion of two to one.
- Chemical Formula: Water, which is a chemical compound with the formula H₂O, meaning that it has two hydrogen atoms and one oxygen atom bonded together by covalent bonds.
- Physical Properties:
- State: It is present in the liquid state at room temperature and pressure but can also be in solid state (ice) and gaseous state (vapor).
- Density: Approximately 1 g/cm³ at 4°C.
- Boiling Point: 100°C (212°F) at sea level.
- Freezing Point: 0°C (32°F) at sea level.
Natural Composition of Water
In nature, water is not found in its pure form, but it is always mixed with some other substance. It often includes dissolved and suspended substances that are incorporated into its make-up. These include:
- Gases
- Oxygen (O₂): Dissolved oxygen is a crucial factor in the metabolism of aquatic life forms.
- Carbon Dioxide (CO₂): It is soluble in water and forms carbonic acid which affects the pH.
- Nitrogen (N₂): In most cases it is passive but can be a major contributor to the dissolved gases in water.
- Minerals and Salts
- Calcium (Ca²⁺): Often associated with water that passes through limestone regions, which causes water hardness.
- Magnesium (Mg²⁺): Sometimes associated with calcium, it also plays a role in the process of making the water hard.
- Sodium (Na⁺): May be present in different concentrations and can influence the taste and quality of water.
- Potassium (K⁺): Usually present in small amounts, required for various biochemical reactions in the body.
- Chloride (Cl⁻): Can be of biogenic or anthropogenic origin, for example, as a result of road salting.
- Sulfate (SO₄²⁻): It is naturally present in water from mineral springs and is also used in industrial applications.
- Organic Matter
- Natural Organic Matter (NOM): Comprises humic substances, plant residues, and microorganisms. Affects water color and can create disinfection byproducts.
- Anthropogenic Contaminants: This category comprises pesticides, pharmaceuticals, and industrial chemicals that may find their way into water through drainage and sewage.
- Nutrients
- Nitrate (NO₃⁻) and Nitrite (NO₂⁻): A nutrient that is necessary for plant growth but toxic when present in large amounts.
- Phosphate (PO₄³⁻): Causes eutrophication which results in the formation of algae.
- Metals and Metalloids
- Iron (Fe): Often found in water wells, it results in staining and changes the taste of water.
- Manganese (Mn): When found in association with iron, it has an impact on water quality and taste.
- Arsenic (As): A toxic metalloid associated with some geological structures, which is dangerous to human health.
- Microorganisms
- Bacteria: Such as coliforms and pathogens such as E. coli.
- Viruses: Can enter water through sewage and contaminated runoff.
- Protozoa: For example, Giardia and Cryptosporidium are parasites that are not easily killed by some forms of disinfection.
Some of the factors that determine the quality of water include the following:
- Geological Factors: The nature of rocks and soils that water passes through can determine its mineral content.
- Human Activities: Pollutants from agriculture, industries, and urbanization are some of the sources of pollutants that may find their way into water bodies.
- Atmospheric Conditions: Precipitation can also dissolve gases in the atmosphere and transport aerosols into water bodies.
Conclusion
The nature of water is diverse and depends on numerous factors of both geographical and anthropogenic nature. This is because the various elements and compounds present in water determine its quality and how it can be utilized. Testing and monitoring are crucial in making sure that water is safe for use in various ways including drinking.