Types and sources of water pollution
Big idea: Water pollution comes from point sources (easy to identify, like a factory pipe) and non-point sources (spread across the landscape, like farm runoff). Non-point sources are harder to control!
Point vs non-point sources
Point sources
- Single, identifiable location
- Examples: factory discharge, sewage pipes, oil spills
- Easier to regulate and control
- Can be treated at source
Non-point sources
- Diffuse, spread across landscape
- Examples: agricultural runoff, urban stormwater, atmospheric deposition
- Very difficult to regulate
- Requires landscape-level management
Major types of water pollutants
- Nutrients - nitrates, phosphates from agriculture and sewage (cause eutrophication)
- Pathogens - bacteria, viruses from sewage (cause disease)
- Organic matter - reduces dissolved oxygen as it decomposes
- Heavy metals - mercury, lead, cadmium (toxic, bioaccumulate)
- Synthetic chemicals - pesticides, industrial chemicals, pharmaceuticals
- Thermal pollution - heated water from power plants (reduces oxygen)
- Plastics - especially microplastics (persist, enter food chains)
- Sediment - soil erosion clouds water, smothers habitats
Paper 1 tested this! Outline two reasons why nutrient pollution in the Gulf of Mexico is difficult to manage. Key: it is NON-POINT source (from huge drainage basin), agriculture is economically important, source is far from impact zone.