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Water Discharges measured by Biological Oxygen Demand Water Discharges measured by Biological Oxygen Demand
Illustration in a set of graphics prepared for a pilot assessment report on the Black Sea drainage basin, for the UNEP Global Impact on Waters Assessment (GIWA). All data and information were prepared in close collaboration with the GIWA Black Sea team and the GIWA secretariat. The graphics were never not used in this form in the final report on the Black Sea, published in 2005.
10 Mar 2006 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Regional trends in biological oxygen demand Regional trends in biological oxygen demand
The graphic is a global comparison of the biological oxygen demand measured in milligrams per litre. It covers the years from 1976 - 2000. The biological oxygen demand refers to the amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage.
28 Sep 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Sites with dead zones (oxygen depletion on the sea bottom) Sites with dead zones (oxygen depletion on the sea bottom)
Dead zones (hypoxic i.e. oxygen deficient water) in the coastal zones are increasing, typically surrounding major industrial and agricultural centers. This is commonly occuring due to nutrient pollution, in the form of nitrogen and phosphorous leading to algal blooms and eutrophication
01 Feb 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Industrial areas and seasonal zones of oxygen-depleted waters Industrial areas and seasonal zones of oxygen-depleted waters
This graphic illustrates that there is a strong correlation between the world's industrial areas and the areas in which seasonally oxygen-depleted waters occur. The accompanying text explains some of the effects of land-based activities on the marine environment.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Nitrate in major rivers Nitrate in major rivers
Considering the data for all the rivers at the continental level, there has been little change in nitrate (NO3-N) concentrations between the two decades under comparison. Changes in the median value were not statistically significant. European rivers showed the highest nitrate loads transported to the marine environment. Comparing data from the two decades, North American and European rivers have remained fairly stable, while major river basins i...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Regional trends in biochemical oxygen demand (BOD) Regional trends in biochemical oxygen demand (BOD)
Biochemical oxygen demand is an indicator of the organic pollution of freshwater. Alkalinity (concentration of calcium carbonate or CaCO3) is another indicator of freshwater quality. These graphics compare the concentrations of these two factors, in milligrams per litre, in the major regions of the world for the periods 1976 to 1990 and 1991 to 2000. The accompanying text explains the implications of the changes in BOD and alkalinity during these...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Discharge of selected pollutants Discharge of selected pollutants
Nitrogen and phosphorous represents nutrients that can be seen as pollutants, as large concentations of those increase eutrophication. Nutrients are present in primarily commercial fertilisers and in sewage. A measure of eutrophication is biochemical oxygen demand (BOD), which measures the activity in the water column. High BOD means that there is low water quality (in terms of eutrophication) and high activity of bacteria in the water. This grap...
29 Nov 2007 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Biological oxygen demand - BOD: 1976-2008 Biological oxygen demand - BOD: 1976-2008
The availability of oxygen is one of the most important indicators of the condition of a water body, because dissolved oxygen, or DO, (the amount of oxygen dissolved in water) is necessary for most aquatic organisms, including fish and invertebrates. Some species have very defined lower limits of DO that they can tolerate. Increases in DO can indicate improvements in water quality, such as has occurred in many parts of the world in the last 30 ye...
26 Jan 2009 - by Phillippe Rekacewicz, February 2006
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When the city harms its own water resources When the city harms its own water resources
In areas where surface water is not readily available (located far from areas of need), groundwater is the primary water source. Groundwater aquifers supply an estimated 20% of the global population living in arid and semi-arid regions. Despite their widespread presence, groundwater aquifers in arid areas receive only limited or seasonal recharge, making such aquifers susceptible to rapid depletion. The Northern Sahara Basin Aquifer, for example,...
01 Oct 2009 - by Philippe Rekacewicz
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Industrial areas and seasonal zones of oxygen depleted waters Industrial areas and seasonal zones of oxygen depleted waters
This graphic illustrates the strong link between areas with high densities of industrial activity and zones of seasonally oxygen-depleted waters. There is a strong link between areas with high densities of industrial activity and zones of seasonal oxygen-depleted waters. In recent years there has been an increasing focus on treating and reducing municipal and industrial waste, and on reducing nitrogen levels in agricultural runoff. However, less...
26 Jan 2009 - by Phillipe Rekacewicz, (Le Monde diplomatique) February 2008
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