LAND POLLUTION

Land pollution

 Land pollution is the demolition of Earth's land surfaces often caused by human activities and their misuse of land resources. It occurs when waste is not disposed properly. Health hazard disposal of urban and industrial wastes, exploitation of minerals, and improper use of soil by inadequate agricultural practices are a few factors. Urbanization and industrialization are major causes of land pollution. The Industrial Revolution set a series of events into motion which destroyed natural habitats and polluted the environment, causing diseases in both humans and many other species of animals.

Increased mechanization

The major increase in the concentration of population in cities, along with the internal combustion engine, led to the increased number of roads and all the infrastructure that goes with them.

As the demand for food has grown exponentially with the increase of the human population, there is an increase in field size and mechanization. The increase in field size makes it economically viable for the farmer but results in loss of person and shelter for wildlife, as hedgerows and copses disappear. When crops are harvested, the naked soil is left open to wind after it has been compacted by heavy machinery. Another consequence of more intensive agriculture is the move to monoculture. This is unnatural, will deplete the soil of nutrients, allows diseases and pests to spread and, as it happens, it quickly exhausts all the natural resources in an area, causing the introduction of chemical fertilizers and foreign substances to the soil that poisons it. The chemical fertilizers in the soil cause its infertility. The farmer put artificial manure to the plants to grow faster but it indirectly infertility occurs to soil.

Pesticides and herbicides

A pesticide is a substance or mixture of substances used to kill a pest. A pesticide may be a chemical substance, biological agent (such as a virus or bacteria), antimicrobial, disinfectant or device used against any pest. Pests include insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms) and microbes that compete with humans for food, destroy property, spread or are a vector for disease or cause a nuisance. Although there are benefits to the use of pesticides, there are also drawbacks, such as potential toxicity to humans and other organisms.

Herbicides are used to kill weeds, especially on pavements and railways. They are similar to auxins and most are biodegrale by soil bacteria. However, one group derived from trinitrotoluene (2:4 D and 2:4:5 T) have the impurity dioxin, which is very toxic and causes fatality even in low concentrations. Another herbicide is Paraquat. It is highly toxic but it rapidly degrades in soil due to the action of bacteria and does not kill soil fauna.

Insecticides are used to rid farms of pests which damage crops. The insects damage not only standing crops but also stored ones and in the tropics it is reckoned that one third of the total production is lost during food storage. As with fungicides, the first insecticides used in the nineteenth century were inorganic e.g.Paris Green and other compounds of arsenic. Nicotine has also been used since the late eighteenth century.

There are now two main groups of synthetic insecticides - Organochlorines include DDT, Aldrin, Dieldrin and BHC. They are cheap to produce, potent and persistent. DDT was used on a massive scale from the 1930s, with a peak of 72,000 tonnes used 1970. Then usage fell as the harmful environmental effects were realized. It was found worldwide in fish and birds and was even discovered in the snow in the Antarctic. It is only slightly soluble in water but is very soluble in the bloodstream. It affects the nervous and endocrine systems and causes the eggshells of birds to lack calcium causing them to be easily breakable. It is thought to be responsible for the decline of the numbers of birds of prey like ospreys and peregrine falcons in the 1950s - they are now recovering. As well as increased concentration via the food chain, it is known to enter via permeable membranes, so fish get it through their gills. As it has low water solubility, it tends to stay at the water surface, so organisms that live there are most affected. DDT found in fish that formed part of the human food chain caused concern, but the levels found in the liver, kidney and brain tissues was less than 1 ppm and in fat was 10 ppm which was below the level likely to cause harm. However, DDT was banned in Britain and America to stop the further build up of it in the food chain. The USA exploited this ban and sold DDT to developing countries, who could not afford the expensive replacement chemicals and who did not have such stringent regulations governing the use of pesticides.

Organophosphates, e.g. parathion, methyl parathion and about 40 other insecticides are available nationally. Parathion is highly toxic, methyl-parathion is less so and Malathion is generally considered safe as it has low toxicity and is rapidly broken down in the mammalian liver. This group works by preventing normal nerve transmission as cholinesterase is prevented from breaking down the transmitter substance acetylcholine, resulting in uncontrolled muscle movements.

Mining

• Modern mining projects leave behind disrupted communities, damaged landscapes, and polluted water.
• Mining also affects ground and surface waters, the aquatic life, vegetation, soils, animals, and the human health.
• Acid mine drainage can cause damage to streams which in return can kill aquatic life.
• The vast variety of toxic chemicals released by mining activities can harm animals and aquatic life as well as their habitat.

Mining gas and petroleum also pollutes the land. Petroleum extraction and manufacturing contaminates the soil with bitumen, gasoline, kerosene and mining brine solutions.

Opencast mining, which is a process where the surface of the earth is dug open to bring out the underground mineral deposits, destroys the topsoil and contaminates the area with toxic metals and chemicals.

Increased waste disposal

In Scotland in 1993, 14 million tons of waste was produced. 100,000 tons was toxic waste and 260,000 tons was controlled waste from other parts of Britain and abroad. 45% of the special waste was in liquid form and 18% was asbestos - radioactive waste was not included. Of the controlled waste, 48% came from the demolition of buildings, 22% from industry, 17% from households and 13% from business - only 3% were recycled. 90% of controlled waste was buried in landfill sites and produced 2 million tons of methane gas. 1.5% was burned in incinerators and 1.5% were exported to be disposed of or recycled. There are 900 disposal sites in Scotland. There are very few vacant or derelict land sites in the north east of Scotland, as there are few traditional heavy industries or coal/mineral extraction sites. However some areas are contaminated by 'aromatic hydrocarbons' (500.25 cubic meters).

The Urban Waste Water Treatment Directive allows sewage sludge to be sprayed onto land. The volume is expected to double to 185,000 tons of dry solids in 2005. This has good agricultural properties due to the high nitrogen and phosphate content. In 1990/1991, 13% wet weight was sprayed onto 0.13% of the land; however, this is expected to rise 15 fold by 2005. There is a need to control this so that pathogenic microorganisms do not get into water courses and to ensure that there is no accumulation of heavy metals in the top soil.

Causes of soil pollution

Soil is polluted in many ways:

1. When pollutants spill dimentionally 2. Garbage dumping, especially plastics, degrades the soil fertility as they are non biodegradable therefore making the soil infertile and uncapable to be irrigated.

3. Chemical fertilizers and pesticides, when over used, pollute the soil and also penetrate into ground water and make it non potable.