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Nitrogen Loadings from Land to the Marine Environment: 1990-2004
Nitrogen Loadings (ktonnes)
Source | 1990 | 1995 | 2000 | 2002 | 2003 | 2004 |
|---|
Industrial | 6.5 | 5.1 | 4.6 | 3.5 | 5.2 | 4.4 |
|---|
Riverine | 46.5 | 59.8 | 62.7 | 50.2 | 47.5 | 55.5 |
|---|
Waste water treatment works | 15.6 | 16.0 | 11.6 | 16.1 | 14.9 | 15.0 |
|---|
Total | 68.6 | 80.8 | 78.9 | 69.9 | 67.6 | 74.9 |
|---|
Enhanced levels of nitrogen inputs in the marine environment may lead to eutrophication. Although most estuaries and coastal waters are not significantly affected by inputs of nutrients, localised impacts can occur, and in certain areas Nitrate Vulnerable Zones have been established to reduce diffuse contributions of nitrogen.
Riverine inputs make up the greater part of nitrogen loads from land to Scotland's marine waters contributing 74% of the total. These inputs are dominated by contributions from diffuse sources such as agriculture and atmospheric deposition, and vary in size in response to the prevailing weather conditions.
In addition to the 74.9 ktonnes of nitrogen inputs from land, it is estimated that a further 8.2 ktonnes of nitrogen is unloaded into the marine environment from fish farming. Although locally aquaculture may be an important contributor of nitrogen, SEPA's routine surveys indicate that direct anthropogenic inputs of nutrients to west coast marine waters are insignificant in comparison to those resulting from the oceanic and coastal currents which occur around the coasts of Scotland.
SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY
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