Human Activities


Human Activities Essay, Research Paper



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. EutrophicationPhosphates 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.


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.

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