Nutrients in freshwater in Europe

Nutrient conditions in European surface waters have improved in recent decades. The average nitrate and phosphate concentrations in rivers and total phosphorus concentration in lakes have decreased. The decrease in nutrient concentrations is likely related to improvements in wastewater treatment, the reduction of phosphorus in detergents and measures reducing agricultural inputs. There is a tendency for concentrations to level off in recent years, especially for rivers. There has been no overall decrease in the nitrate concentration in groundwater.

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Nitrate in groundwater

The average nitrate concentration in European groundwater is similar in 1992 and in 2020, but the concentration increased from 1992 to 2008, and subsequently appears to decrease from 2008 to 2020. However, this is interrupted by a peak in 2018, largely caused by increased concentrations reported by France. The shorter, but more representative, time series from 2000 follows the longer one closely, but the concentration level is slightly lower. While the changes at European level are not large, this does not imply limited changes in groundwater nitrate concentrations overall, but rather that there are both groundwater bodies (GWBs) with increasing and decreasing trends.

Nitrate in rivers

The average river nitrate concentration in Europe decreased steadily over the period 1992-2009 but has levelled off since then. The shorter time series is parallel to the longer series, but the concentration level is lower. Agriculture remains the main contributor to nitrogen pollution, but the EU Nitrates Directive and national measures have contributed to lower concentrations. However, the apparent stabilisation in recent years may call for further measures to be taken.

See chart for nitrate in groundwater and rivers here.

Phosphate in rivers

The average phosphate concentration in European rivers more than halved over the period 1992-2012. The marked decline is also evident for the shorter time series, but the average concentration is somewhat higher when using this larger, more representative set of sites. Concentrations tend to level off and even increase slightly at the end of the period. The decrease in river phosphate can be related to measures introduced by national and European legislations, e.g. the Urban Waste Water Treatment Directive. Also, the change to phosphate-free detergents has contributed to lower phosphate concentrations.

Total phosphorus in lakes

There has been a gradual reduction in average total phosphorus concentrations in European lakes since 1992. The concentration level is higher for the shorter, more representative time series. As the treatment of urban wastewater has improved, the amount of phosphorus in detergents has been reduced, and many wastewater outlets have been diverted away from lakes, phosphorus from point sources has become less significant. However, diffuse runoff from agricultural land continues to be a major phosphorus source in European lakes. Moreover, phosphorus stored in sediment can keep lake concentrations high despite a reduction in inputs.

See chart for phosphorus in rivers and lakes here.

Rivers that drain land with intense agriculture or a high population density generally have the highest nitrate concentrations. In the period 2018-2020, Czechia and Lithuania had the largest proportion of river sites with average nitrate concentrations exceeding 5.6mg NO3-N/l (13% and 16%, respectively). Moreover, Belgium, Denmark, and Switzerland had a high proportion (more than 25%) of sites with concentrations exceeding 3.6mg NO3-N/l.

There has been a decrease in river nitrate concentrations at 47% of the monitoring sites since 1992, and an increase at 16% of the sites. Czechia, Denmark, Germany and Slovakia had the highest proportion of significantly decreasing trends (63-100%). France, Ireland, Spain and Switzerland had similar proportions of significantly increasing and decreasing trends, while Estonia had the highest proportion of significantly increasing trends (44%). An overall decline, although slowing in recent years, is observed for Austria, Belgium, Czechia, Denmark, Germany, Serbia and Sweden, contributing to the pattern seen in the European time series.

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