Environmental Science (2+1)

Soil Pollutants

Soil Pollutants

1. Acid rain : Oxides of sulphur and nitrogen
2. Heavy metals: Lead, Cadmium, Chromium, Copper, Nickel, Arsenic, Titanium, Mercury, Selenium etc.
3. Industrial wastes
4. Sewage
5. Agricultural wastes: Fertilizers, Pesticides, Herbicides, Other Chemicals
6. Volcanoes
7. Oil, grease and other petroleum products
8. Asbestos
9. Other solid wastes
Paper and paper products, Polythene bags and covers, Oil cans , Cloth wastes, Tires, Carcasses, Radioactive wastes, Municipal solid wastes, Hospital wastes, Animal wastes, Plastics, glass and other bio non degradable wastes, Crop residues

Plastics

• Plastics form a major part of global domestic and industrial waste. Not being biodegradable, waste plastic accumulates, adding to pollution. In USA plastic are 7% in weight of all solid waste but 30% of the volume. Standard plastic takes several hundreds of years to disintegrate, over 400 years for the plastic bottles used for mineral water.Using photodegradable plastic or biodegradable plastic can solve plastic pollution problem. Photodegradable plastic contains an element sensitive to UV rays. Under the effect of solar rays the element is activated and breaks the polymeric chain of the photodegradable plastic. It results in small fragments that are easily digested by microbes.


Biodegradable plastic

• Biodegradable plastic is made by adding at least 6% starch and an oxidizing agent (vegetable oil) to the polymers during manufacture. In the biologically active soil environment, the biodegradable plastic is decomposed easily. The metallic salts naturally present in soil interact with the oxidizing agent to form ferro oxides, which attack the polymer bonds and set the biodegradation of plastic in motion. Parallely, soil microbes break up the starch grains (amyloids), which results in an increased attack surface and accelerates the auto oxidation process.


• The presence of starch reduces the water resistance of plastic. Addition of a fine protective layer to the starch based plastic; make it possible to obtain high degree of water-resistance. In future, plastics with 50% starch will appear in the market. Biodegradable plastics may offer many solutions to the pollution problems.

Heavy metals



Lead

• Contamination of soils by lead is a major concern in many countries at the moment including the U.K. It is believed that the primary cause of the increased levels found in many soils is car exhaust emissions. Although unleaded petrol has been available for some time now the lead particles still remain from the time when lead was added to fuel as a thinner. In America, lead poisoning has been termed 'the silent epidemic'. 900,000 children under the age of 6 have a blood lead concentration of at least 10 nano grams / litre, this is the critical threshold, above this level lead is believed to have psychological effects on factors such as intelligence.


• The high concentrations of lead were also seen in hair and blood samples of local residents, although not to such an extent. This suggests that there is some kind of barrier which reduces the bioavailability of lead, within the body. In Derbyshire this is the process whereby the lead is slowly eroded into the secondary element of pyromorphite, which has a very low bioavailability is not easily put into solution.

Chromium

• As a trace element, chromium is essential for many organisms (just like iron), however an excess in chromium and many chromium compounds are poisonous. Chromium compounds are found in pigments and wastewater from tanneries. These materials can be cancerous, lead to eczema or impair the mucous membranes in the period 1985-1995.

Copper

• Copper is a toxic heavy metal. It ends up in the marine environment particularly through rivers and polluted dredged materials. Since the ban on using paint containing tin, copper is often used as an anti-foul material on ship hulls. In the vicinity of military training grounds, the bottom is locally polluted with copper from munition remnants. The Netherlands contributes around 25% to the total load of copper in the North Sea. With algae, a concentration of 0.5 microgametes of copper per litre seawater will decrease photosynthesis (and thereby growth decline). With higher concentrations (around 10 microgametes per litre), crustaceans will also be affected.

Nickel

• Nickel is found in nature. It is a heavy metal applied in producing steel and as a surface layer for metal products. In addition, nickel is used in a large number of alloys, batteries, the electrochemical industry and as catalyst, for example in congealing vegetable fats. It is in all probability an essential trace element. Some nickel compounds are cancerous. A concentration of 0.003 to 0.1 mg/l will lead to a decrease in bacteria growth

Arsenic

• Arsenic has been known to be poisonous for centuries. It is a heavy metal. The inorganic arsenic compounds are reputed to be extremely toxic, and are used in cases such as rat poison. Arsenic compounds are used in the production of copper, lead, zinc, steel and iron, as well as in agriculture. Arsenic affects fish and amphibians by increasing the chance in changes in hereditary material, and could cause an unnaturally high death rate among birds.

Cadmium

• Cadmium is a heavy metal. It is found throughout nature, especially as an impurity in zinc minerals. It is a white metal, fairly soft, easily flexible and non-corrosive. Due to dumping by human activities (especially the industry, and indirectly from dredging activities), the concentration of cadmium measured in the coastal waters is approximately 5 times higher than the natural concentration. Cadmium is poisonous for almost all organisms. That's why limiting the dumping of cadmium in the past decade has had a high priority, and with great success: the discharges have decreased by 81%.

Mercury

• Mercury is a heavy metal, originating from industry, most often from burning fossil fuels and from dumps. In addition, mercury is found in pesticides and fertilizers, is used in the production of chlorine and the removal of sulphur from natural gas. Actually, mercury is found naturally in low amounts in natural gas. Mercury poisoning damages the nerves, which can lead to deafness, blindness and paralysis. Less acute poisoning could lead to loss of concentration and memory and memorial disorders

Titanium

• In the 1980s, Greenpeace successfully conducted a campaign against the dumping of titanium dioxide wastes; for example, they prevented dumping ships from entering the harbours. In addition, Greenpeace gathered evidence concerning the effects dumping had on sea life. Scientists also discovered the consequences for those fish which had come into contact with the waste. With such evidence and facts on hand, pressure could be applied on the policy makers and the titanium dioxide dumpers themselves. Titanium dumping has deceased since 1989.

Agriculture

• Agriculture is an industry which works directly with the soil as a result it is bound to have some effects on the makeup of the soil. The uses of pesticides and fertilizers have come under scrutiny for many reasons. One of the most harmful ecotoxicological effects is that of the eutrophication of water bodies. This occurs due to over use and poor management of Phosphorous and Nitrogen fertilizers. It leads to over productivity in the water body and eventually to deoxygenating of the water, meaning that more fragile populations and communities cannot survive. This has many implications, not only for the environment and wildlife involved but it may also affect human activity such as drinking water, or leisure activities like swimming and fishing.


• Bioaccumulation and biomagnifications of these poisons as they move along the food chain is also a major problem which has influence on the whole ecosystem. One of the most famous incidents was that of the near extinction of the Peregrine Falcon in areas of North America during the late 1960's which lead to the den of the pesticide DDT.
  


• Persistent Organic Pollutants (POPs) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment. With the evidence of long-range transport of these substances to regions where they have never been used or produced and the consequent threats they pose to the environment of the whole globe, the international community has now, at several occasions called for urgent global actions to reduce and eliminate releases of these chemicals.

Industrial Effluents

• Contamination of drinking water supplies from industrial waste is a result of various types of industrial processes and disposal practices. Industries that use large amounts of water for processing have the potential to pollute waterways through the discharge of their waste into streams and rivers, or by run-off and seepage of stored wastes into nearby water sources. Other disposal practices which cause water contamination include deep well injection and improper disposal of wastes in surface impoundments.


• Industrial waste consists of both organic and inorganic substances. Organic wastes include pesticide residues, solvents and cleaning fluids, dissolved residue from fruit and vegetables, and lignin from pulp and paper to name a few. Effluents can also contain inorganic wastes such as brine salts and metals.