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4.4. WATER POLLUTION (Knowledge and Understanding (water pollution - both…
4.4. WATER POLLUTION
Knowledge and Understanding
water pollution - both ground water and surface water affects human and other biological systems
aquatic pollutants include - organic material, inorganic plant nutrients (nitrates and phosphates), toxic metals, synthetic compounds, suspended solids, hot water, oil, radioactive pollution, pathogens, light, noise and biological (invasive species)
testing the quality of aquatic systems - pH, temperature, turbidity (suspended solids), metals. nitrates and phosphates
biodegradation of organic material utilises oxygen which can lead to anoxic conditions and subsequent anaerobic decomposition - leads to formation of methane, hydrogen sulphide, and ammonia (toxic gases)
biochemical oxygen demand - measure of amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity - BOD used to indirectly measure amount of organic matter within a sample
Some species can be indicative of polluted waters and be used as indicator species
biotic index indirectly measures pollution by assaying the impact on species within the community according to their tolerance, diversity, and relative abundance
Eutrophication
when excess nutrients are added to an aquatic ecosystem - can be natural but anthropogenic eutrophication is more common
severe eutrophication leads to dead zones - not enough oxygen to support life
in less extreme cases - biodegradation of organic material uses up oxygen which can lead to anoxic (low oxygen) conditions and then anaerobic decomposition - can release methane, ammonia and hydrogen sulphide which are all toxic gases
Impacts of eutrophication
oxygen deficient water
loss of biodiversity and shortened food chains
death of higher plants (e.g. flowering plants)
death of aerobic organisms - invertebrates, fish, amphibians
increased turbidity of water
excess nutrients are nitrates and phosphates sources
detergent
fertilisers
drainage from intensive livestock rearing units
sewage
Process of eutrophication
fertilisers wash into river or lake
high levels of phossphates in particular allow algae to grow faster (phosphates are often limiting)
Algal blooms form that block out light to plants beneath them which die
more algae = more food for zoo plankton and small animals that feed on them - they are food to fish which multiple bc more food - then there are fewer zooplankton to eat the algae
Algae die and are decomposed by aerobic bacteria
not enough oxygen in water so soon everything dies as food chains collapse
ocygen levels fall lower - dead organic material forms sediments on lake or river bed and turbidity increases
eventually all life is gone and sediment settles leaving a clear blue lake
red tides
- in coastal water, algal blooms (large numbers of phytoplankton) are sometimes caused by excess nutrients - bloom looks red - dangerous as algae produces toxins which kill fish and accumulate in shellfish which can make humans sick too
Water pollution
kills over 14000 per day through waterborne diseases and poisoning
nearly half a billion people don't have access to clean, safe drinking water
types of water pollution
anthropogenic - created by human activities or natural - e.g. volcanic eruptions, algal blooms
point source or non point source
organic or inorganic
direct or indirect
direct or indirect
sources
fresh water pollution - agricultural run off, industrial discharge, wild domestic waste
marine - rivers, pipelines, atmosphere and human activities at sea - operational and accidental discharges
Measuring water pollution
can be measured directly or indirectly by sampling
biochemical oxygen demand
- measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity by microorganisms
biotic indices and indicator species
- indicator species are plants and animals that show something about the environment by their presence, absence, abundance or scarcity - biotic indices indirectly measure pollution by assaying the impact on species within the community according to their tolerance, diversity and relative abundance
indicator species are most sensitive tor change so they are early warning signs that something may have changed in the ecosystem
biotic index is a scale 1-10 that gives a measure of the quality of an ecosystem by the presence and abundance of the species living in it
Eutrophication management strategies
Altering the human activity producing the pollution
ban or limit detergents with phosphates
use ecodetergents with no phosphates or new technology in washing machines
plant buffer zones between the fields and water courses to absorb the excess nutrients
stop leaching of slurry (animal waste) or sewage from their sources
educate farmers about more effective timing for fertiliser application
Regulating and reducing pollutants at the point of emission
treat waste water before release to remove nitrates and phosphates
minimise fertiliser dosage on agricultural lands or use organic matter instead
divert or treat sewage waste effectively
Clean up and restoration
pumping air through the lakes
dredging sediments with high nutrient levels from river and lake beds
remove excess weeds physically or by herbicides and algicides
restock ponds or water bodies with appropriate organisms