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Vital Water Graphics 2

Nitrate levels: concentrations at river mouths

Table of contents
Toward a world of thirst?ForewordExecutive summary Water and population

1. State of the world’s water

2. Freshwater resources3. Coastal and marine water4. Water and climate change

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Nutrients are essential to life. In aquatic systems, nitrogen and phosphorus are the two nutrients that most commonly control the growth of aquatic plants, algae and bacteria. Nitrogen and phosphorus are considered to be the primary drivers of eutrophication of aquatic ecosystems, where increased nutrient concentrations lead to increased primary productivity. Some systems are naturally eutrophic, whereas others have become eutrophic as a result of human activity, such as runoff from agricultural areas and the discharge of municipal waste into rivers and lakes.

Considering the data for all the rivers at a 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 in south-central and south-east Asia have recorded higher nitrate concentrations.