Water pollutants
Water pollutants are substances or forms of energy that alter the physical, chemical, or biological characteristics of water, making it harmful for organisms and ecosystems.
- Water pollution occurs when harmful substances enter water bodies, disrupting aquatic ecosystems and threatening human health.
- Pollutants can be organic (e.g., sewage), chemical (e.g., persistent organic pollutants), plastic-based, or thermal (heat pollution).
- These contaminants have varying effects, including eutrophication, endocrine disruption, biomagnification, and ecosystem degradation.
Types of Water Pollutants
- Water pollutants can be grouped into five main types:
- Organic matter (e.g., sewage)
- Dissolved substances (e.g., tributyltin)
- Persistent organic chemicals (e.g., PCBs)
- Plastics (macro and microplastics)
- Heat energy (thermal pollution)
- Each type affects ecosystems differently but often acts synergistically, compounding the overall environmental impact.
Organic Matter
- Organic pollutants include sewage, food waste, and agricultural effluents containing biological material.
- As decomposers (bacteria) break down the organic matter, they consume dissolved oxygen.
- This leads to oxygen depletion, fish kills, and ecosystem collapse.
- The process is closely linked to biochemical oxygen demand (BOD).
The Ganges River, India, suffers from severe organic pollution due to untreated sewage discharge, leading to high BOD levels and frequent fish kills.
TipHigh organic matter → High BOD → Low DO → Aquatic life death.
Dissolved Substances
- These are chemicals dissolved in water that may interfere with biological or physiological processes in organisms.
- A well-known example is tributyltin (TBT), a toxic organotin compound.
Tributyltin (TBT)
Endocrine disruptor
Endocrine disruptor is a chemical that interferes with the hormonal system, causing developmental, reproductive, or immune problems.
- Used as an antifouling agent in ship paints to prevent biofouling (growth of algae and barnacles).
- Slowly leaches into water, settling in sediments or entering aquatic food chains.
- Acts as an endocrine disruptor, altering hormonal balance in marine species.
- The effects are:
- Causes imposex (female mollusks developing male organs) in oysters and snails.
- Leads to immune suppression in dolphins and hearing loss in toothed whales.
- Humans exposed to TBT may experience fatigue, respiratory issues, and liver/kidney damage.
Due to its toxicity, TBT was banned internationally by the International Maritime Organization (IMO) in 2008.
Persistent Organic Pollutants (POPs)
- Persistent organic pollutants (POPs) resist degradation, remaining in the environment for decades.
- They accumulate in fatty tissues and increase in concentration up the food chain (biomagnification).
Biomagnification
Biomagnification refers to the process by which the concentration of non-biodegradable pollutants increases as you move up trophic levels in a food chain or food web.
