4.8.3 The role of peat run-offs in pollution Peat extraction can cause water pollution if not properly managed. Associated disturbance of land releases substances which may reach watercourses, including iron - and even mercury (absorbed from the atmosphere). To avoid pollution, water discharged from significant turf cutting operations should be treated as industrial wastewater. The water table is also lowered by peat extraction, leading to higher concentrations of the polluting substances in the reduced water volume. Peat drainage releases the following pollutants: • Turbidity, suspended solids and phosphorous from erosion of the excavation areas and ditches. Cloudy water can lead to the death of some fish species and other aquatic life, including waterfowl and other fauna and flora. They can also reduce the availability of dissolved oxygen as they decompose. Phosphorous is a nutrient that leads to excessive algal growth, exacerbating the pollution problem. • Acidity (low pH): Drainage aerates the peat and releases acids (often nitric acid and sulphric acid). Acid waters can kill fish and aquatic life, and limit egg production and hatching. • Aluminum: Acid waters in peat drainage help to dissolve aluminum from the peat and carry it downstream. Aluminum can be highly toxic to fish and other aquatic life. • Ammonia: Peat drainage causes decomposition of much of the soil to release ammonia. Certain forms of ammonia are very toxic to fish and other aquatic life. • Iron: Acid waters in peat drainage also dissolve iron. Iron also can be released when attached to suspended solids. Iron deposits can clog fish gills and deposit harmful scums on stream, lake and wetland bottoms. • Mercury: Mercury can be released during peat drainage. It is very toxic to fish, and accumulates through the food chain. Mercury in watercourses, in particular, is classified as a Priority Hazardous Substance under the WFD. It is absorbed in peatlands from the atmosphere. Elemental mercury can be converted to methyl mercury, a toxic form, by aquatic bacteria in lake sediments and wetlands. Methyl mercury is concentrated as it moves up the aquatic food chain, with large game fish having the highest concentrations. There are several methods of water pollution control in peat extraction. One is peat runoff control. This collects suspended solids leaching from peat extraction areas in the bog’s ditch network. This can be done by constructing pipe dams in connection with the sedimentation basin or in main drains. The damming of water in the ditches reduces the flow velocity, and as a result, suspended solids deposit on ditch beds. Laboratory tests and theoretical simulations have shown that with peak runoff control, the suspended-solid loads deriving from peat mining areas can be reduced by 88%. A study conducted in the summer of 1996 on a peat mining area in Central Finland showed that the loss of suspended solids with peak runoff control was 53–88% - and up to 95% during peak flows caused by snow-melt. Reduced suspended-solid loads also decrease the loading of nutrients bound by suspended solids. WATER QUALITY – PRINCIPLES AND ACTIONS NPS P 29 Policies and decisions relating to the use of peatlands shall take full consideration of potential impacts on water quality and the attainment by the State of mandatory water quality standards. NPS A 26 An assessment shall be undertaken of the additional costs of treating drinking water arising from peatlands degradation and options proposed for reducing such costs through appropriate peatlands management. ahg.gov.ie/en/Publications/HeritagePublications/NatureConservationPublications/Final%20Draft%20National%20Peatlands%20Strategy.pdf
Posted on: Sat, 18 Jan 2014 23:14:37 +0000
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