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You are here: Home / Data and maps / Indicators / Oxygen consuming substances in rivers / Oxygen consuming substances in rivers (CSI 019) - Assessment published Oct 2012

Oxygen consuming substances in rivers (CSI 019) - Assessment published Oct 2012

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Generic metadata

Topics:

Water Water (Primary topic)

Tags:
soer2010 | csi | freshwater quality | bod5 | ammonium | water | rivers | thematic assessments | freshwater
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 019
Dynamic
Temporal coverage:
1992-2010
Geographic coverage:
Albania Austria Belgium Bulgaria Cyprus Czech Republic Denmark Estonia Finland France Germany Greece Hungary Iceland Ireland Italy Latvia Liechtenstein Lithuania Luxembourg Macedonia (FYR) Malta Netherlands Norway Poland Portugal Romania Slovakia Slovenia Spain Sweden Switzerland United Kingdom
 
Contents
 

Key policy question: Is organic matter and ammonium pollution of rivers decreasing?

Key messages

Concentrations of BOD and total ammonium have decreased in European rivers in the period 1992 to 2010 (Fig. 1), mainly due to general improvement in wastewater treatment.

See also WISE interactive maps: Mean annual BOD in rivers and Mean annual Total Ammonium in rivers

Biochemical Oxygen Demand (BOD5) and total ammonium concentrations in rivers between 1992 and 2010

Note: Concentrations are expressed as annual mean concentrations. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per country is given in metadata (see downloads and more info). BOD7 data has been recalculated into BOD5 data.

Data source:
Downloads and more info

BOD5 concentrations in rivers between 1992 and 2010 in different geographical regions of Europe

Note: The data series per region are calculated as the average of the annual mean for river monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per geographical region is given in parentheses. BOD7 data has been recalculated into BOD5 data.

Data source:
Downloads and more info

Total ammonium concentrations in rivers between 1992 and 2010 in different geographical regions of Europe

Note: The data series per region are calculated as the average of the annual mean for river monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per geographical region is given in parentheses.

Data source:
Downloads and more info

BOD5 concentrations in rivers between 1992 and 2010 draining to different sea regions of Europe

Note: The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per sea region is given in parentheses. There were no stations with consistent data series on BOD7 in rivers draining to the Arctic Ocean. BOD7 data has been recalculated into BOD5 data.

Data source:
Downloads and more info

Total ammonium concentrations in rivers between 1992 and 2010 draining to different sea regions of Europe

Note: The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per sea region is given in parentheses.

Data source:
Downloads and more info

Key assessment

Introduction
Organic matter, measured as Biochemical Oxygen Demand (BOD) and total ammonium, are key indicators of the oxygen content of water bodies. Concentrations of these parameters normally increase as a result of organic pollution caused by discharges from waste water treatment plants, industrial effluents and agricultural run-off. Severe organic pollution may lead to rapid de-oxygenation of river water, a high concentration of ammonia and the disappearance of fish and aquatic invertebrates.

The most important sources of organic waste load are: household wastewater; industries such as paper industries or food processing industries; and silage effluents and manure from agriculture. Increased industrial and agricultural production, coupled with a greater percentage of the population being connected to sewerage systems, initially resulted in increases in the discharge of organic waste into surface water in most European countries after the 1940s. Over the past 15 to 30 years, however, the biological treatment (secondary treatment) of waste water has increased, and organic discharges have consequently decreased throughout Europe. See also CSI 024: Urban waste water treatment.

Overall trend in BOD and total ammonium (Fig. 1)

In European rivers, the oxygen demanding substances measured as BOD and total ammonium have decreased by 55 % (from 4.9 mg/l to 2.2 mg O2/l) and 73 % (from 587 to 159 µg N/l), respectively, from 1992 to 2010 (Fig. 1). The decrease is due mainly to improved sewage treatment resulting from the implementation of the Urban Wastewater Treatment Directive and national legislations. The economic downturn of the 1990s in central and eastern European countries also contributed to this fall, as there was a decline in heavily polluting manufacturing industries. In recent years, however, the downward trends in BOD across Europe have generally levelled. This suggests that either further improvement in wastewater treatment is required or that other sources of organic pollution, for example from agriculture, require greater attention, or both.

Overall there has been a significant decrease in BOD concentrations at 56.8 % of the stations (an additional 6.1 % marginally significant) on the European rivers between 1992 and 2010, while there has been a significant increase at only 3.1 % of the stations (an additional 0.9 % marginally significant). Similarly, there has been a significant decrease in total ammonium concentrations at 56.4 % of the stations (an additional 7.0 % marginally significant), while there has been a significant increase at only 3.2 % of the stations (an additional 1.2 % marginally significant).

BOD and total ammonium time series and trends per geographical regions (Fig. 2 and Fig. 3)

The largest decrease of BOD from 1992 to 2010 has occurred in the southern and southeastern European rivers (63 % and 57 %, respectively) (Fig. 2). The concentrations in the southeastern European rivers are still the highest in Europe, but with a fall below 4 mg O2/l in 2010, which is the lowest level to date. The concentrations of the southern European rivers (represented by the Spanish rivers only) reached the lowest level in 2003. They increased afterwards to about 2.9 mg O2/l. The concentrations in the western European rivers decreased by 50 %. Their concentrations are the lowest in Europe (about 1.5 mg O2/l). The concentrations in the northern European rivers (represented by the Finnish rivers only) are the most stable (less than 2 mg O2/l) with a decrease of 22 %.

The largest proportion of monitoring stations with significant or marginally significant negative trend in BOD is found for the western and the southern European rivers, while the lowest proportion is found for the northern European rivers. Based on the sum of significant and marginally significant trends the trends for the rivers in different geographic regions are: West: 72.5 % negative, 0.6 % positive; South: 62.7 % negative, 2.8 % positive; East: 56.5 % negative, 9.0 % positive; Southeast: 50.0 % negative, 6.9 % positive; North: 33.3 % negative, 6.7 % positive. Countries with more than 60 % of the stations with negative trend in BOD are the United Kingdom, Spain, Luxembourg, the Czech Republic, Austria, Denmark, Slovakia, France, Slovenia and Ireland.

The decrease of total ammonium from 1992 to 2010 is the largest in the southeastern (77 %) and eastern European rivers (76 %), closely followed by the decrease in the western European rivers (74 %) (Fig. 3). The concentrations in the eastern European rivers (about 200 µg N/l) have approached the concentrations in the western European rivers (about 150 µg N/l). The lowest decrease has occurred in the southern European rivers (represented by Spanish rivers only) (20 %) and the northern European rivers (14 %). The concentrations in the first ones are very fluctuating and among the highest in Europe (above 400 µg N/l). The same is true for the southeastern European rivers that faced a significant fall in 2010 (from above 400 µg N/l to less than 300 µg N/l). On the contrary, concentrations in the northern European rivers are stable and the lowest in Europe (about 40 µg N/l).

The largest proportion of monitoring stations with significant or marginally significant negative trend in total ammonium is found for the western and eastern European rivers, while the lowest proportion is found for the northern European rivers as follows: West: 74.6 % negative, 2.9 % positive; East: 73.5 % negative, 1.9 % positive; Southeast: 70.5 % negative, 3.2 % positive; South: 64.0 % negative, 8.0 % positive; North: 27.0 % negative, 9.8 % positive (sum of significant and marginally significant trends). Countries with more than 60 % of the stations with negative trend in total ammonium are Spain, Latvia, Austria, France, Belgium, Bulgaria, Ireland, Poland, the former Yugoslav Republic of Macedonia, Germany, the United Kingdom, Lithuania and Slovenia.

BOD and total ammonium time series and trends per sea regions (Fig. 4 and Fig. 5)

The largest decrease of BOD from 1992 to 2010 has occurred in the rivers draining to the Mediterranean Sea (78 %), resulting in the lowest concentrations in Europe (about 1.5 mg O2/l) (Fig. 4). Their concentrations fall below stable concentrations in the rivers draining to the Baltic Sea (about 1.8 mg O2/l) with a decrease of 26 %. The second highest decrease of BOD has occurred in the rivers draining to the Black Sea (59 %). Their concentrations (about 2.5 mg O2/l) have approached the concentrations in the rivers draining to the Greater North Sea (about 2.2 mg O2/l) that correspond to the European average. The decrease of BOD is 39 % for the rivers draining to the Greater North Sea and 30 % for the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast. The concentrations of the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast have increased compared to 2003 (the lowest level), resulting in the highest concentrations in Europe (about 3.2 mg O2/l).

The trend analysis also shows that the largest proportion of monitoring stations with significant or marginally significant negative trend in BOD is found for the rivers draining to the Mediterranean Sea and the Black Sea, while the lowest proportion is found for the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast, and the Baltic Sea (Mediterranean Sea: 81.7 % negative, 2.5 % positive; Black Sea: 75.0 % negative, 0.8 % positive; Greater North Sea: 64.2 % negative, 2.9 % positive; Celtic Seas, Bay of Biscay, Iberian Coast: 46.1 % negative, 2.9 % positive; Baltic Sea: 42.8 % negative, 12.3 % positive; sum of significant and marginally significant trends).

The largest decrease of total ammonium from 1992 to 2010 has occurred in the rivers draining to the Mediterranean Sea (78 %) (Fig. 5). The decrease is somewhat lower in the rivers draining to the Black Sea (75 %), the Baltic Sea (74 %) and the Greater North Sea (72 %). The concentrations in the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast decreased by 60 %. Concentrations in rivers draining to different sea regions have become similar (less than 150 µg N/l for the Mediterranean Sea and the Baltic Sea; less than 200 µg N/l for the Celtic Seas, the Bay of Biscay and the Iberian Coast, and the Black Sea; about 200 µg N/l for the Greater North Sea). The lowest decrease has occurred in the rivers draining to the Arctic Ocean (35 %) with very low concentrations (about 5 µg N/l). 

The largest proportion of monitoring stations with significant or marginally significant negative trend in total ammonium is found for the rivers draining to the Celtic Seas, the Bay of Biscay and the Iberian Coast, and the Black Sea, while the lowest proportion is found for the rivers draining to the Arctic Ocean (Celtic Seas, Bay of Biscay, Iberian Coast: 82.6 % negative, 2.8 % positive; Black Sea: 75.5 % negative, 0.9 % positive; Greater North Sea: 67.7 % negative, 3.2 % positive; Mediterranean Sea: 55.2 % negative, 6.9 % positive; Baltic Sea: 55.1 % negative, 5.3 % positive; Arctic Ocean: 23.1 % negative, 15.4 % positive; sum of significant and marginally significant trends).

BOD and total ammonium present concentrations by countries
See WISE interactive maps for information displayed for countries, for river basin districts (BOD) and for individual stations: Mean annual BOD in rivers and Mean annual Total Ammonium in rivers

Countries with more than 50 % of all river stations within the category of the lowest BOD concentrations (class 1: < 1.4 mg O2/l) for 2010 or the latest reported year are France, Latvia, Denmark, Spain, Cyprus and Slovenia. Countries with more than 20 % of the stations within the category of the highest BOD concentrations (class 5: >= 4 mg O2/l) are Romania, Belgium, Hungary, Greece, Albania, Kosovo under UNSCR 1244/99 and Turkey.

Countries with more than 50 % of all river stations within the category of the lowest total ammonium concentrations (class 1: < 0.04 mg N/l) for 2010 or the latest reported year are Croatia, Spain, France, Bosnia and Herzegovina, Liechtenstein, Sweden, Austria, Finland, Norway and Iceland. Countries with more than 20 % of the stations within the category of the highest total ammonium concentrations (class 5: >= 0.4 mg N/l) are Romania, Greece, Luxembourg, Albania, Belgium and Kosovo under UNSCR 1244/99.

Data sources

More information about this indicator

See this indicator specification for more details.

Contacts and ownership

EEA Contact Info

Peter Kristensen

Ownership

EEA Management Plan

2012 1.4.2 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled every 1 year in July-September (Q3)
European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100