Eutrophication

Eutrophication is an unwanted explosion of living aquatic-based organisms in lakes and estuaries which results in oxygen depletion that can destroy an aquatic ecosystem. It has been regarded as the most important environmental problem caused by phosphorus losses. Significant eutrophication took place in the 1950s in the Great Lakes of North America and has been prevalent in many lakes and estuaries around the world. Phosphorus is often the limiting factor responsible for eutrophication, since nitrogen fluxes to water bodies are relative large.

Phosphorus losses from industries, croplands, animal farms, and households constitute the main sources. Figure 4 illustrates a cross-country comparison of the phosphorus loads in European countries and in China to their domestic aquatic environments.

The results show that the phosphorus loads range from 0.2 kgP ha-1 in Sweden to 2.5 kgP ha-1 in Belgium at the national level. China lies between Germany and Northern Ireland in turns of the load per unit land area. At the basin level, the comparison of phosphorus loads shows a similar figure. These results suggest that the Chinese economy is in general processing phosphorus 'wastes' less efficiently than developed countries. However, regarding phosphorus control strategy, it is nearly impossible to determine a common benchmark (of a desired phosphorus load) to prevent water bodies

Belgium Northern Ireland Germany Denmark Estonia Latvia Lithuania

Netherlands China Poland Austria Norway Finland Sweden

Figure 4 Comparison of phosphorus loads to aquatic environments by country (unit: kg P ha-1). Based on EEA (2005) Source Apportionment of Nitrogen and Phosphorus Inputs into the Aquatic Environment, No.7/2005. Copenhagen: European Environment Agency; Liu Y (2005) Phosphorus Flows in China: Physical Profiles and Environmental Regulation. PhD Thesis, Environmental Policy Group, Wageningen University, Wageningen, The Netherlands.

Belgium Northern Ireland Germany Denmark Estonia Latvia Lithuania

Netherlands China Poland Austria Norway Finland Sweden

Figure 4 Comparison of phosphorus loads to aquatic environments by country (unit: kg P ha-1). Based on EEA (2005) Source Apportionment of Nitrogen and Phosphorus Inputs into the Aquatic Environment, No.7/2005. Copenhagen: European Environment Agency; Liu Y (2005) Phosphorus Flows in China: Physical Profiles and Environmental Regulation. PhD Thesis, Environmental Policy Group, Wageningen University, Wageningen, The Netherlands.

from eutrophication. This is because the complex interrelations between the amount of aquatic biomass and the phosphorus load are affected by a number of hydrological, meteorological, and biochemical factors that remain unclear under current knowledge. Further improvement of our current understanding of phosphorus movement and transformation within aquatic and territorial ecology, across socioeconomic and ecological boundaries, is desired.

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