4.4 Flashcards
Types of pollutants:
- Anthropogenic or natural
- point - source or nonpoint source
- Organic or inorganic
- Direct or indirect
sources of freshwater pollution
Sources of fresh-water pollution include agricultural run-off, sewage, industrial discharge and solid domestic waste.
sources of marine pollution
rivers, pipelines, the atmosphere and human activities at sea, both operational and accidental discharges.
two ways to measure water pollution
biochemical oxygen demand, biotic indices & indicator species
what is BOD
it is a measure of the amount of dissolved oxygen required to break down organic material in a given volume of water through aerobic biological activity by microorganisms
what are indicator species?
plants and animals that show something about the environment by their presence, absence, abundance or scarcity
for eg. invertebrates are used to estimate levels of pollution as they are sensitive to decreases in oxygen concentration in water, caused by the action of aerobic bacteria as they decompose organic matter. thus, the presence of certain indicator species that can tolerate various levels of oxygen is used to calculate a biotic index.
what is a biotic index?
it indirectly measures pollution by assessing the impact on species within the community according to their tolerance, diversity and relative abundance.
types of aquatic pollutants
Organic material
Inorganic plant nutrients (nitrates and phosphates)
Toxic metals
Synthetic compounds
Suspended solids
Hot water
Oil
Radioactive pollution
Pathogens
Light
Noise
Biological (invasive species)
process of eutrophication
- Fertilizers wash into the river or lake
- High levels of phosphate in particular, allow algae to grow faster
- Algal blooms form that block out light to plants beneath them, which die
- More algae means more food for the zooplankton and smaller animals that feed on them. They are food to fish which multiply as there is more food, so there are less zooplankton to eat the algae
- Algae die and are decomposed by aerobic bacteria
- But there is not enough oxygen in the water so, soon, everything dies as food chains collapse
- Oxygen levels fall lower. Death organic material forms sediments on the lake or river bed and turbidity increases
- Eventually, all life is gone and the sediment settles to leave a clear blue lake
impacts of eutrophication
Oxygen-deficient (anaerobic) water
Loss of biodiversity and shortened food chains
Death of higher plants
Death of aerobic organisms
Increased turbidity (cloudiness of water)
excess nutrients (nitrates and phosphates) come from:
Detergents
Fertilizers
Drainage from intensive livestock rearing units
Sewage
Increased erosion of topsoil into water
