SAQs
Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.
Why is a point source of pollution easier to identify than a non-point source of pollution?
Point sources of pollution are easier to identify because they come from points or places that you can easily locate, such as a pipe discharging waste into a river. A non-point source is more difficult to identify because it does not come from just one place, but can come from a wide area, for example fertiliser washing off a number of fields or floodwater that washes waste from latrines.
Rewrite the sentences below using terms from the list provided to fill the gaps:
concentration, heavy metals, organic matter, persistent pollutant, sewage.
……………… consists of human excreta and wastewater. It has a high ……………… of ………………
Some pollutants, called ………………, do not break down naturally in the environment. Examples are mercury, cadmium and other ………………
Sewage consists of human excreta and wastewater. It has a high concentration of organic matter.
Some pollutants, called persistent pollutants, do not break down naturally in the environment. Examples are mercury, cadmium and other heavy metals.
Describe what is meant by the terms liquid waste and solid waste, using examples from your own experience to illustrate your answer.
Liquid waste is liquid material that is thrown away, or discharged into the environment. From the household you might include human excreta (both faeces and urine) and other wastewaters. In your area you might also see urban run-off when rain washes waste from the land surface. You might also see liquid waste discharged from factories through a pipe into a river.
Solid waste is any solid material that is assumed not to be useful and is therefore thrown away; examples that you might use include food waste, cloth, paper and plastic that are thrown out from your own household or that you see in the area where you live.
For the scenarios (a) to (d), fill in the table below to show the pollutant, the source of pollution, the possible pathways and the recipients:
- A farmer washes an empty pesticide sack in a river; the river flows into a lake which is used for drinking water by people from a local town.
- Rain falls on a waste dump used to collect household waste; the waste dump isn’t properly sealed and liquid percolates down into the soil and into groundwater that is extracted from a nearby well for domestic use.
- A tannery based in a town produces liquid waste that contains organic matter and chemicals used in the tanning process; this effluent is discharged into the local river which flows out of the town and through a nature park.
- A bus driving through a busy town emits black smoke from its tailpipe.
| Pollutant | Source | Pathway | Recipient | |
| (a) | ||||
| (b) | ||||
| (c) | ||||
| (d) |
| Pollutant | Source | Pathway | Recipient | |
| (a) | pesticide | agriculture | through the river | lake, humans |
| (b) | leachate | domestic / household | through soil and groundwater | soil, groundwater, humans |
| (c) | liquid effluent (organic matter and tannery chemicals) | industry | through the river | river, humans, wildlife |
| (d) | black smoke | transport | through the air | humans |
Describe how water pollution can change the characteristics of water.
Natural or unpolluted water is colourless, odourless and transparent. Water pollution changes the characteristics of water by the presence of excess physical, chemical or biological substances that change the qualities of the water and are capable of causing harm to living organisms.
Polluted water can taste or smell bad or be cloudy. Polluted water can contain suspended solids that make the water look brown in colour; most of the solids are fine particles of soil that have been washed into the river by rain from surrounding land. Large quantities of solids in the water can reduce light penetration into the water which can affect the growth of plants.
Water pollution changes more than just the appearance of the water. Polluted water can also contain chemicals, such as pesticides, fertilisers and heavy metals that are toxic. Polluted water also can contain biological substances such as organic matter and micro-organisms that cause waterborne diseases.