Water and Soil Pollutants
Simple Explanation
Water and soil pollutants include industrial chemicals and heavy metals, excess fertiliser runoff (nitrates and phosphates), untreated sewage, and pesticides — each disrupting the natural chemistry of water bodies and soil in different, specific ways.
Why Do We Need It?
These pollutants often enter the food chain — through crops grown in contaminated soil, or fish living in contaminated water — meaning environmental water and soil pollution frequently becomes a direct human health problem, not just an ecological one.
Why Does This Work?
Excess fertiliser runoff (nitrates, phosphates) causes eutrophication: it over-feeds algae, which grow explosively, then die and decompose, and that decomposition consumes the dissolved oxygen fish and other aquatic life need to survive — indirectly suffocating an ecosystem rather than poisoning it directly. Heavy metals and many pesticides, by contrast, are directly toxic and can accumulate up the food chain (bioaccumulation) as smaller organisms are eaten by larger ones.
Real-Life Example
Algal blooms from agricultural runoff
Lakes near farmland sometimes develop thick, green algal blooms after heavy rain washes fertiliser off nearby fields.
The excess nitrates and phosphates in the fertiliser runoff feed explosive algae growth (eutrophication); when the algae eventually die and decompose, the decomposition process consumes so much dissolved oxygen that fish and other aquatic organisms can suffocate.
Practice
Why does excess fertiliser runoff into a lake often lead to dead fish, even though fertiliser itself is not directly toxic to fish?
MediumCommon mistake
Assuming fertiliser pollution and heavy-metal pollution cause harm the same way — fertiliser runoff typically harms ecosystems indirectly through eutrophication (oxygen depletion), while heavy metals and many pesticides are directly toxic and can bioaccumulate up the food chain.
Quick Review
- Fertiliser runoff (nitrates/phosphates) causes eutrophication and oxygen depletion.
- Heavy metals and pesticides are directly toxic and can bioaccumulate.
- Water/soil pollutants often enter the human food chain.