Human Activities Essay, Research Paper
1.
Organic
effluent from discharge of sewage works and farms. Main pollutants are a.
Nitrates -
often a limiting factor, vital for plant growth. Highly soluble and leached
from the soil. Sources – sewage /
manure / inorganic fertiliser. b.
Phosphates -
Often limit plant growth. Fairly
insoluble. Main source – detergents in
sewage. Eutrophication – Phosphates and nitrates are often limiting so
cause increased growth of water plants such as algae. Once nutrients are used up and light becomes limiting due to
competition the plants die. This
increases the detritus which will be
decomposed by decomposing bacteria in
the water. Increases BOD ( biochemical oxygen demand) due to
bacteria respiring and using up any available oxygen in the water. Animals that need large amounts of oxygen
will die eg. Trout, mayfly nymph. This
leaves only animals that can cope in
conditions with little oxygen eg sludge worms and bloodworms ( indicator
species). 2.
Heavy metal ions Mercury, lead, copper, aluminium. Sources – Industrial run off from mining, exhaust fumes, run off
from agriculture (pesticides). All Are
highly toxic, act as enzyme inhibitors also
act on the nervous system ( mercury). 3.
Sulphur
dioxide From combustion of
fossil fuels. Combines with water to
form acid rain. Influence due to wind
direction , amount of rainfall and type of soil. Affect on organisms :- a.
Increased solubility of aluminium ions from soil
results in increased mucus in fish gills and reduced haemoglobin efficiency b.
Increased acidity reduces activity of decomposers reducing availability of phosphates and
nitrates leading to oligotrophic
conditions, clear nutrient lacking lakes and streams. Reduced plant and animal diversity. Diversity index – need to know numbers of species and total number
of individuals. c.
Reduced calcium ions results in reduced mollusc nos (
calcium needed for shells ). d.
Effect on enzymes needed for dissolving fish egg coats
leads to reduced fish. e.
Loss of leaves in trees and decreased resistance to
disease. Lichens -are indicator species.
Reduced numbers where significant pollution. 4.
Crude oil From oil spills, washing tanks and
accidents. ·
Reduced light penetration – reduced photosynthesis. ·
Reduced surface tension ·
Oil film prevents oxygen entering water. ·
Oil is toxic, absorbed via digestive system and
lungs. Can accumulate through food
chains. ·
Coating feathers and fur results in reduced insulation
/ flight/ buoyancy. ·
Coating gills prevents oxygen absorption. Solutions – Booms to reduce spread. Detergents ( are also toxic ). Conservation Active process that aims to keep
ecosystems stable as environmental conditions change. Methods ·
Set aside -
provides a wider range of habitats- food plants and breeding sites for animal
species. ·
SSSI?s and nature reserves- havens for
threatened species. ·
Captive breeding
programmes – to allow release into wild. ·
Changes in agricultural
practice – reduced use of herbicides, pesticides and fertilisers. Reduced drainage of wetlands. Reduced grazing pressure.