Pollution will reduce the biodiversity potential of a ...



Potential causes of river water pollution

Nutrient enrichment leads to eutrophication of soil water

Eutrophication describes the biological effects of an increase in the concentration of nutrients. The collective term ‘nutrients’ refers to those elements that are essential for primary production by plants or other photosynthetic organisms. Eutrophication is most often caused by increases in the availability of nitrogen and phosphorus, commonly present in soil and water in the form of nitrate and phosphate, respectively. However, altered concentrations of any plant nutrient may have a recognizable biological effect. Eutrophication can occur in any aquatic system (freshwater or marine), and the term is also used to describe the process whereby terrestrial vegetation is affected by nutrient-enriched soil water.

Fertilisers

Man made agricultural fertilisers typically contain nitrates and phosphates and are frequently used in farming.

Nitrate & phosphate pollution problems occur when too much chemical fertiliser is applied to the land. The excess runs off can find its way into drinking water sources, or can trickle into rivers and lakes.

This causes phytoplankton to grow and reproduce more rapidly, resulting in algal blooms creating a 'pea soup' effect. The water becomes clogged with fast-growing plant life like algae and weeds. The algal blooms disrupts normal ecosystem functioning and causes many problems as the algae uses up much of the oxygen in the water, leaving little for other organisms. This may result in the death of many aquatic organisms such as fish, which need the oxygen in the water to live. The algal bloom may also block sunlight from photosynthetic marine plants under the water surface that help maintain the level of oxygen compounding the problem. Some algae even produce toxins that are harmful to higher forms of life which can then cause problems along the food chain and affect any animal that feeds on them.

Nitrates used in agriculture can also arise from organic sources like silage or liquid manure derived from animal dung (slurry). When organic farm wastes like silage or liquid manure (slurry) escape into rivers these too can cause algal blooms and unsightly excessive higher plant growth within the channel. The amount of oxygen in the water is again reduced and this can kill thousands of fish as was the case in 1985 when pig slurry escaped into a tributary of the River Severn.

Some experts believe that high levels of nitrate in drinking water may pose a threat to health. A European directive states that drinking water should not contain more than 50 milligrammes of nitrates per litre of water.

Phosphate fertilisers –used in agriculture and forestry can also pose a problem if used excessively but these are also extensively used in domestic washing powders and if discharged into sewers and water courses can also cause excess growth of bottom living algae and higher plants, leading to severely reduced oxygen levels.

Untreated and/or diluted sewage

Untreated and/or diluted sewage can enter the watercourse from combined sewage overflows and via wrong household connections into surface water drainage systems. The combination of toxic effects, nutrient enrichment and reduced oxygen levels in the watercourse may severely impact water quality and kill wildlife.

Oils and Solvents

Oils and solvents are occasionally accidentally and sometimes deliberately disposed of down drains which discharge into watercourses. These may be toxic to aquatic life, and can also build up in time in sediments on the river bottom, and have a long term impact.

If oil enters a slow-moving river it forms a rainbow-coloured film over the entire surface preventing oxygen from entering the water. On larger stretches of water the oil contaminates the feathers of water birds and when they preen the oil enters their gut and kills them.

Industrial Waste

Chemical waste products from industry are sometimes accidentally discharged into rivers. Examples of such pollutants include cyanide, zinc, lead, copper, cadmium and mercury. These substances may enter the water in such high concentrations that fish and other animals are killed immediately. Sometimes the pollutants enter a food chain and accumulate. Heavy metals - include lead and vanadium, can originate from road run-off from cars and lorries and these heavy metals can accumulate in river sediment and slowly build up until they reach toxic levels, eventually killing birds, fish and mammals.

Warm Water

Industry often uses water for cooling processes, sometimes discharging large quantities of warm water back into rivers. Raising the temperature of water lowers the level of dissolved oxygen and upsets the balance of life in the water.

Other road debris

Other typical pollutants that enters watercourses from road and urban hard surfaces include dog faeces, tyre debris, grit, de-icing road grit/salt and effluent from wheelie bin cleaners and people washing their cars.

Heavy sediment loads

Heavy sediment loads normally caused by interference with a watercourse, such as building works near a river or changes in catchment land-use can lead to excess erosion and heavy sediment loads becoming mobile. Excessive sediment moving through the ecosystem can smother and kill vegetation and invertebrates, as well as suffocating fish by blocking their gills and preventing them from taking in oxygen from the water.

Acid rain

Rain falling through polluted air absorbs some of the pollutants as it falls. The main pollutant gases are sulphur dioxide and nitrogen oxides, which form when fuels are burned. They react with rainwater to form sulphuric and nitric acids.

Other Sources

Abandoned mines produce a large quantity of polluting chemicals. Many dangerous metals including iron, aluminium, tin, lead, mercury and cadmium come out of old mine workings. Mines in Wales and Cornwall are causing serious water pollution problems.

Phosphorus accumulating in sewage treatment facilities is another powerful pollutant. It comes from detergents and stays in rivers for a long time, taking up valuable oxygen. Few sewage works are equipped to remove phosphates.

Careless people can also pollute rivers and harm wildlife by pouring things like used car oil and paint into drains.

Rubbish dumps create a strong chemical cocktail called leachate. This can be deadly to fish, small water creatures and plants. In modern waste sites great care is taken to ensure that none escapes, but leachate from older rubbish dumps has been know to seep into rivers and pollute drinking water causing health issues.

Impacts of Pollution on Rivers

Between 1985 and 1990 there was a decrease in the total length of rivers and canals in England and Wales having top quality water. Meanwhile the total length of 'poor' quality waterways increased.

Since 1990 the situation in England and Wales has improved. The Environment Agency reports an increase in length in the best quality grades of waterway and a reduction in the poorest. Indeed there has been significant improvement in 10.7% of the total length of rivers and canals in England and Wales.

Serious incidents resulting from spillages or discharges of toxic chemicals are the pollution events that make the news. For example, just one litre of insecticide killed over 1,000 fish in the River Glaven in Norfolk. The impact of a slow build-up of pollution over a long time and in a wide area can be even more serious. During the 1950s, otters in many parts of the country were nearly wiped out by the accumulation of pesticides in our rivers

Protecting rivers and streams

Both the European Union and the British government are concerned about water pollution. Water quality is protected by many different laws. England's first water pollution act of 1388 made it illegal to dump animal remains, dung or garbage into rivers. Anyone breaking that particular law in those days could be hanged.

The most important modern legislation is the Water Resources Act of 1991. It instructs the Environment Agency to police the use of water in England and Wales. The Environment Agency manages fisheries, flood defence, navigation, recreation and nature conservation. In Scotland, The Scottish Environment Protection Agency (SEPA) is Scotland’s environmental regulator.

The Environment Agency protects water resources by issuing licences for drawing off large volumes of water (abstraction) from watercourses, and for the discharge of pollutants.

News articles from around the World on river pollution incidents

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River pollution 'wipes out' fish

Fish stocks on a stretch of the River Trent in Staffordshire that was polluted with cyanide appear to have been wiped out, experts have said.

Investigations are continuing into the source of last week's chemical leak near Stoke-on-Trent.

The Environment Agency said a survey along a 700m section near Stone on Wednesday had found almost no evidence of living fish. Stocks several miles further downstream appear relatively unaffected, it added. The agency said further tests were being carried out on river life and later this week sediment samples would be taken for more detailed analysis.

Sewage released

The pollution, which affected the river between Stoke-on-Trent and Yoxall, was discovered on 6 October.

Environment officers were able to greatly reduce pollution levels on the 30-mile (48 km) stretch by pumping oxygen into the water.

The public, farmers, anglers and boaters were warned to stay away from the water as a precaution and keep animals away.

Severn Trent Water, which was not linked in any way to the chemical, said the cyanide had been released into the sewers upstream from the company's Strongford sewage treatment works in Stoke.

That caused problems at the works and resulted in partially-treated sewage also being released into the river.

The Environment Agency said it would prosecute those responsible under the Water Resources Act which makes it an offence to allow poisonous or polluting matter to enter rivers.

There is no limit on the fines which can be imposed if the case leads to a conviction at crown court.

Story from BBC NEWS:



Published: 2009/10/14 23:02:51 GMT

© BBC MMX

Investigation underway after River Trent cyanide pollution

The Environment Agency will seek to prosecute those responsible for polluting the River Trent with cyanide – killing thousands of fish.

Environment Officers spent Tuesday night and Wednesday morning pumping oxygen into the river between Stoke-on-Trent and Yoxall – pollution levels in the river have been greatly reduced.

Environment Manager David Lowe said: “This incident is under control - river water quality is improving.  Levels of pollutant in the river have fallen significantly, but we continue to monitor the situation closely.

“As a precaution – people and animals should stay out of the water until further notice.

“There are no drinking water abstraction points on the affected stretch of river and the Drinking Water Inspectorate have confirmed that public drinking supplies have not been affected.

“But thousands of fish have been killed and the Environment Agency considers this to be a serious pollution incident.

“We will thoroughly investigate and seek to prosecute those responsible.”

Severn Trent Water has confirmed that cyanide entered the Strongford Sewage Treatment Works in Stoke-on-Trent.

This disrupted the treatment process, allowing partially treated sewage to be released into the River Trent.

Under the Water Resources Act it is an offence to cause poisonous, noxious or polluting matter to enter rivers. Should a prosecution reach the Crown Court, fines are unlimited.

The largest fine for a similar offence occurred in 2004, with an Avonmouth-based chemical company Sevalco fined £240,000 for deliberating discharging cyanide into controlled water.

[pic]Europe

[pic]Hungary battles to stem torrent of toxic sludge

[pic][pic]Emergency services in Hungary are trying to stop a torrent of toxic red sludge flowing into major waterways, including the River Danube.

A state of emergency has been declared in three western counties after the chemical waste burst from a reservoir at an alumina plant.

Four people are known to have died, with 120 injured. Six more are missing. At least seven villages and towns are affected including Devecser, where the torrent was 2m (6.5ft) deep.

The flood swept cars from roads and damaged bridges and houses, forcing the evacuation of hundreds of residents.

The sludge - a mixture of water and mining waste containing heavy metals - is considered hazardous, according to Hungary's National Directorate General for Disaster Management (NDGDM).

While the cause of the deaths has not been established officially, it is believed the victims probably drowned. Some 600,000-700,000 cubic metres (21m-24m cubic feet) of sludge escaped from the plant, 160km (100 miles) from the capital, Budapest.

Nearly 500 police officers and soldiers, including six emergency detection teams, have been deployed. Plaster has been poured into the Marcal river in a bid to bind the sludge and stop further flooding.

Dr Attila Nyikos, of the NDGDM, told the BBC News website that a police investigation had been opened and tests were still being carried out to determine the environmental impact of the leak.

An alert has been declared on both the Marcal and Torna rivers, and Mr Illes said workers were "desperately" trying to stop contamination of the Raba and Danube rivers.

Alumina, a synthetically produced aluminium oxide, is a white or nearly colourless crystalline substance that is used as a starting material for the smelting of aluminium metal.

It also serves as the raw material for a broad range of advanced ceramic products and as an active agent in chemical processing.

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