Major Components:
* Water (H₂O): The primary component, usually making up over 99% of rainwater.
* Dissolved Gases:
* Carbon dioxide (CO₂): Forms carbonic acid (H₂CO₃), contributing to the rainwater's slight acidity.
* Oxygen (O₂): Present in small amounts.
* Nitrogen (N₂): Also present in small amounts.
Minor Components (Vary Significantly):
* Acids:
* Sulfuric acid (H₂SO₄): From sulfur dioxide (SO₂) emissions, mainly from burning fossil fuels.
* Nitric acid (HNO₃): From nitrogen oxides (NOx) emissions, primarily from vehicle exhaust.
* Ions:
* Sodium (Na+): From sea spray and dust.
* Chloride (Cl-): From sea spray and industrial emissions.
* Calcium (Ca²⁺): From dust and rock weathering.
* Magnesium (Mg²⁺): From dust and rock weathering.
* Potassium (K+): From dust and rock weathering.
* Ammonium (NH₄⁺): From decomposition of organic matter and industrial processes.
* Organic Compounds:
* Humic substances: From decaying plant matter.
* Pesticides: From agricultural runoff.
* Heavy metals: From industrial pollution.
pH of Rainwater:
* Unpolluted Rainwater: Slightly acidic, with a pH around 5.6. This is due to the formation of carbonic acid from dissolved CO₂.
* Acid Rain: Has a pH lower than 5.6, due to the presence of sulfuric and nitric acids.
Factors Affecting Rainwater Composition:
* Location: Coastal areas have higher salt content, while industrial areas have higher acid and heavy metal levels.
* Time of Year: Precipitation patterns and seasonal changes influence the composition.
* Pollution Levels: Industrial emissions, vehicle exhaust, and agricultural practices significantly impact rainwater chemistry.
Understanding rainwater composition is crucial for environmental monitoring, water resource management, and human health.
