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Update on Impact Categories, Normalisation and Weighting in LCA

8 Nutrient enrichment

• 8.1 Summary
• 8.2 Description of the impact category
• 8.3 Substances contributing to the impact category
• 8.4 Updating of the normalisation reference for Denmark
• 8.5 The normalisation reference for EU-15
• 8.6 The normalisation reference for selected European countries
• 8.7 Worldwide normalisation reference for nutrient enrichment
• 8.8 Evaluation of uncertainties
• 8.9 Recommendation for future updating
• 8.10 References
• Appendix A: Important parameters in relation to nutrient enrichment

Jørgen Larsen, Danish Technological Institute

8.1 Summary

The actual emissions for the same reference year, 1994, are inventoried for all environmental impact categories.

In addition to point source loading, nutrients are also input to inland and marine waters by diffuse loading and atmospheric deposition. The normalisation references are shown in Table 8-1.

Table 8-1
Normalisation references for nutrient enrichment for Denmark, EU-15, and worldwide.

The most significant diffuse sources of nutrient input to the aquatic environment are leaching of nitrogen from cultivated land and the deposition from the atmosphere of gaseous nitrogen compounds. Because of the ongoing reduction in direct point source discharges, diffuse loading and atmospheric deposition will eventually come to account for a relatively greater share of inputs to inland and marine waters, and hence be of correspondingly greater importance for the state of the environment.

8.2 Description of the impact category

The injurious effects of extensive quantities of nutrient salts have been observed regularly in lakes for many years. However, the discovery that the bottom of large bodies of water was practically oxygen-free and lifeless in some part of the year came as an unpleasant surprise to many people and triggered serious discussion of nutrient salt emissions and their potential impact on the environment. In connection with the 1987 Action Plan on the Aquatic Environment, a Danish nation-wide programme was established to monitor nutrient loading of aquatic areas from point sources, agriculture and the atmosphere to enable the expected reduction in loading to be followed. By point sources are understood discharges from sewage works, separate industrial discharges, storm water outfalls, freshwater, marine and terrestrial saltwater fish farms, and sparsely built-up areas.

8.2.1 Cause of oxygen depletion

The cause of oxygen depletion found in the bottom layers of lakes and coastal waters is nutrient enrichment. It can thus be defined as "an enrichment of the aquatic environment with nutrient salts leading to an increased production of planktonic algae and higher aquatic plants, which in time leads to a reduction in the water quality and in the value of the exploitation which occurs in the area" (Christensen et al. 1993). The algae sink to the bottom and are broken down consuming oxygen in the bottom layer. If fresh oxygen-rich water from the surface does not reach the bottom layers, the oxygen concentration near the bottom will gradually be reduced until the bottom-dwelling organisms move away or die.

The classification step defines nutrient enrichment as the man-made impact on aquatic or terrestrial systems of nitrogen, N, or phosphorus, P.

The total nutrient enrichment potential expresses the emissions as an equivalent emission of the reference substance NO₃^-.

The total impact potentials of the Danish emissions of nutrient salts in 1994 are used as reference for the normalisation of the potentials for nutrient enrichment. The normalisation references are presented as the average nutrient enrichment potential per Dane.

In a tripartite division of environmental impact categories into global, regional and local, nutrient enrichment is designated a local and a regional impact. For local and regional impact categories, the Danish or European emissions and populations are used to calculate normalisation references. To apply a comparable scale to impact potentials for the global impact categories (based on estimated global emissions) and the regional impact categories (based on Danish or European emissions), the environmental impact potentials found as the background impact are divided by the population of the region for which they were calculated. The environmental impact potential is thus expressed as the person-equivalent, i.e. the average contribution from each individual person in the area concerned.

8.3 Substances contributing to the impact category

8.3.1 Macro-nutrients

One of the two macro-nutrients nitrogen and phosphorus is usually the limiting element for the growth of primary producers, and it is therefore reasonable to consider only the elements nitrogen and phosphorus as contributors to nutrient enrichment. In Danish lakes, phosphorus deficiency, or a combination of nitrogen and phosphorus deficiencies, is typically limiting for growth, and their addition promotes algae growth. In Danish coastal waters and seas, nitrogen is often the limiting nutrient. Substances containing nitrogen or phosphorus in a biologically available form are therefore classified as potential contributors to nutrient enrichment.

Three equivalence factors are defined for use in the calculation of the potential contributions from a given substance:

• the N potential, which expresses the substance's nitrogen content,
• the P potential, which expresses the substance's phosphorus content, and
• the equivalence factor for the total nutrient enrichment potential, where the nitrogen and phosphorus contents are aggregated in a figure based on the assumption of an average ratio of 16:1 between the nitrogen and phosphorus contents in aquatic organisms.

8.3.2 Reference substance

The total nutrient enrichment potential expresses the emissions as an equivalent emission of the reference substance NO₃^-.

As it is evident from the formula on the average composition of aquatic organisms, the ratio of nitrogen to phosphorus is of the order of 16. If the concentration of bio-available nitrogen is significantly more than 16 times the concentration of bio-available phosphorus in an ecosystem, it is thus reasonable to assume that phosphorus is the limiting nutrient and vice versa. Since most of the atmosphere consists of free nitrogen, N₂, further addition of N₂ will not have any effect. N₂ is therefore not classified as contributor to nutrient enrichment. The most important airborne emissions include oxides of nitrogen, NO_x, which are predominantly emitted from incineration processes, and ammonia, NH₃, which is especially emitted from agricultural activities. Airborne emissions of phosphate are quite small and are therefore not included in the calculations.

Most of the nitrogen loading to the aquatic environment is mainly attributable to leaching from the root zone of agricultural land. An important part of the nitrogen loading is related to the use of nitrogen fertilisers and the number of livestock. Apart from the man-made emissions from agriculture an important loading of nitrogen comes from various point sources such as waste water treatment plants, industry, fish farming and from sparsely built-up areas.

Most of the phosphorus loading of surface water is attributable to discharges from point sources, especially municipal sewage and industrial effluent. Only a small part of the industrial sector is responsible for the majority of wastewater containing phosphorus. To name just a few important industries the fertiliser industry and other related chemical industries manufacturing products containing phosphorus (e.g. pesticides and detergents), as well as the pulp and paper industry and fish processing industry should be mentioned. However, leaching from agricultural land also plays a significant part.

8.4 Updating of the normalisation reference for Denmark

For nutrient enrichment, the Danish emissions of N and P are used as normalisation references. These are summarised, and their environmental impact potentials calculated in Table 8-2.

8.4.1 Nitrogen loading to the aquatic environment

The total loading of the Danish aquatic environment with nitrogen and phosphorus in 1994 is summarised by the Danish National Environmental Research Institute (Larsen et al. 1995).

Part of this loading is emitted via the fresh waters and some of the nitrogen is removed on the way to the marine systems by denitrification in watercourses and lakes. Loading of the fresh waters with nitrogen is thus greater than the quantity conveyed to the marine areas via the watercourses.

It has not been possible to find comprehensive accounts for losses on its way towards the sea and thus for the loading of fresh waters. However, it could easily be a third greater than the quantity of nitrogen added to the marine areas via watercourses (Kirkegaard 1995).

With this reservation, the normalisation reference for nitrogen loading is based on the figures for loading of the marine areas in 1994:

• 119.100 kt N/year from watercourses and
• 9.300 kt N/year from direct emissions (Larsen et al. 1995; Miljøstyrelsen 1995)

The direct emissions are man-made, but apart from the man-made emissions from agriculture and various point sources such as waste water treatment plants, industry and fish farming, the loading from watercourses also includes some natural leaching of nitrogen.

It is necessary for normalisation to know the anthropogenic loading. The natural background loading with nitrogen is estimated to be about 12% (Larsen et al. 1995). Thus, 88% of the waterborne emissions of nitrogen are man-made.

This gives a total man-made waterborne loading with nitrogen in 1994 of:

• 0.88 x 119.100 kt N/year + 9.300 kt N/year = 114.108 kt N/year

8.4.2 Diffuse nitrogen loading from cultivated land

Nitrogen loading of groundwater and surface water is mainly attributable to leaching from the root zone of agricultural land. An important step towards reducing nitrogen leaching is that storage capacity for animal fertiliser has been expanded considerably. Measurements and calculations of actual nitrogen leaching from the root zone have revealed considerable inter-annual variation. Measurements of nitrogen loss to watercourses reveal correspondingly large variation that is also attributable to climatic variation. Diffuse nitrogen loading is closely tied to the amount of precipitation that falls in the winter half year. As a consequence, the general decline in point source loading is blurred by the climatic variation in diffuse loading, especially that from cultivated land. It should be noted that the mean precipitation in Denmark was 880 mm in 1994, which is more than normal.

It is estimated that changes in agricultural practice (that the storage capacity for animal fertiliser has been expanded considerably) have led to a small reduction in nitrogen leaching from the root zone. However, it has not been possible to demonstrate this directly by means of measurements. In this connection, it should be noted that the majority of the measures decided in the "Action Plan on the Aquatic Environment" and the "Action Plan for Sustainable Agricultural Development" have now been implemented. Any further reduction in nitrogen loss as a result of these changes in agricultural practice is therefore likely to be limited (Miljøstyrelsen 1997).

8.4.3 Air emissions of nitrogen

A large part of nutrient input to Danish marine waters takes place via the atmosphere.

In the present study, the airborne emissions of nitrogen compounds are used for the normalisation references because it is assumed that the emissions have the potential to contribute to the nutrient enrichment. The airborne emissions of nitrogen compounds inventoried for Denmark in Table 8-2 include oxides of nitrogen, NO_x, which is emitted predominantly from incineration processes, and ammonia, NH₃, which is emitted especially from agricultural activities.

The goal, as stipulated in the EU declaration on the NO_x Protocol, is to reduce Danish emissions from the 1986 level of 312,000 tonnes to 218,000 in 1998, corresponding to a reduction of approx. 30%. International agreements to reduce NO_x emissions and national endeavours to reduce ammonia volatilisation will, in the long term, help reduce atmospheric deposition on Danish marine waters.

Danish emissions of nitrogen compounds to air in 1994 are estimated to 159.9 kt N/year. Airborne emissions of nitrogen and phosphate from "nature" are small and in the calculations we assume that 100% are man-made.

8.4.4 Phosphorus loading to the aquatic environment

The Aquatic Environment Plan's monitoring programme 1994 gives the total loading with phosphorus as

• 2.960 kt P/year from watercourses and
• 1.530 kt P/year from direct emissions (Larsen et al. 1995)

In contrast to nitrogen, there are no natural removal mechanisms for phosphorus. However, the emission of phosphorus in watercourses typically occurs in pulses, as phosphorus accumulates in the watercourses sediment during drier periods and is then completely washed out into marine environment when the water flow increases, e.g. after a thunderstorm. This type of pulse emission is difficult to include in a monitoring, and the emission of phosphorus in watercourses is therefore believed to have been underestimated (Kirkegaard 1995). It has not been possible to obtain any estimate of how large the emission of phosphorus to marine areas actually is. However, the composition of raw sewage has changed during the last 5 years. The change concerns the phosphorus content of the sewage, which has decreased significantly due to greater use of phosphate-free detergents.

It is estimated that 84% (Larsen et al. 1995) of the waterborne emissions of phosphorus are man-made. This gives a total man-made waterborne phosphorus loading in 1994 of:

• 0.84 x 2.960 kt P/year + 1.530 kt P/year = 4.016 kt P/year.

8.4.5 Airborne emissions of phosphate

Airborne emissions of phosphate are quite small and are therefore not included in the calculations.

8.4.6 Danish emissions of N and P

Total man-made riverine nutrient loading of marine waters in 1994 is estimated at approx. 104.808 kt nitrogen and 2.486 kt phosphorus. The overall trend in loading of inland waters is a decrease in both nitrogen and phosphorus loading from point sources.

Direct discharges to marine waters from point sources amounted in 1994 to 9.300 kt nitrogen and 1.530 kt/phosphorus. A decrease has also been seen in both nitrogen and phosphorus loading from point sources. Point source loading has decreased considerably since 1990. This is primarily attributable to the requirements stipulated in the Action Plan on the Aquatic Environment with regards to reducing discharges from municipal sewage works and industrial outfalls (Miljøstyrelsen 1994).

Nearly all emissions of nitrogen to the air are assumed to be man-made and are estimated to consist of 159.9 kt N/year.

Total loading of marine waters in 1994 from watercourses, direct point-source discharges and atmospheric deposition is calculated to be approx. 274 kt nitrogen and approx. 4 kt phosphorus.

Signs of reduced primary production of plankton and algae are seen in many areas, together with improved oxygen conditions. In general, however, no major changes have been detected in the level of nutrient enrichment in Danish marine waters relative to 1990 (Hauschild & Wenzel 1998).

Table 8-2
Danish emissions of nutrients in the form of nitrogen and phosphorus compounds to air and water. The unit is kt/year. Emissions to air from Ritter (1997); waterborne emissions from Larsen et al. (1995).

NO_x as NO₂

8.4.7 Normalisation references for 1994

Based on the total Danish emission (1994) of 274 kt N-equivalents, and 4 kt P-equivalents and a population (1994) of 5.2 million (Ritter 1997), the Danish normalisation references for nutrient enrichments are:

Person equivalents:

53 kg N-equivalents/capita/year
0.8 kg P-equivalents/capita/year

or aggregated as

260 kg NO₃- -equivalents/capita/year

8.5 The normalisation reference for EU-15

For the normalisation reference for EU-15, the emissions of nutrients are estimated from the EU-15 countries. These are summarised, and their environmental impact potentials calculated, in Table 8-9. In the following sections, the basic data are presented in some detail.

8.5.1 Air emissions of nitrogen and phosphorus compounds

A large part of the nutrient input to marine waters takes place via the atmosphere. Nutrient enrichment via the atmosphere primary depends on the emissions of NO_x and NH₃. The total emissions for the EU-15 countries in 1994 are shown in Table 8-3.

Table 8-3
National total1 emissions 1994 (Ritter 1997).

1 National total emissions follow the UN-ECE/EMEP guidelines.
However, emissions from sector "nature" are excluded to ensure
inter country comparison.

According to UN-ECE/EMEP requirements, sources of emissions to air have to be reported according to 11 main source sectors. The emissions in the EU-15 countries from these 11 main source sectors are given in Table 8-4.

Table 8-4
EU-15 main source sectors 1994 (Ritter 1997).

1 The EU-15 totally excludes emissions from sector "nature" (SNAP 11).

As shown in Table 8-4 the emission of nitrogen to the air from the sector "nature" constitutes less than 1% of the total emissions, therefore the exclusion of the emissions from "nature" is not assumed to course significant errors.

Airborne emissions of phosphate are quite small and are therefore not included in the calculations.

8.5.2 Direct discharges and riverine inputs of total nitrogen and phosphorus compounds

The direct discharges and riverine inputs of total nitrogen and phosphorus into the different sea areas surrounding Europe are depicted in the Table 8-5 and Table 8-6. All data are finally aggregated in Table 8-8, which illustrate the total direct discharges and riverine inputs to the sea of total nitrogen and phosphorus in the 15-EU countries.

Table 8-5
Direct discharges and riverine inputs of total nitrogen and total
phosphorus into the OSPAR area (kt/year)1 in 1994, Estimated from
EEA (1998a) and Excessive anthropogenic nutrients in European
ecosystems, EEA (in press).

1 High estimates used; some countries have given low and high estimates.

Table 8-6
Direct discharges and riverine inputs of total nitrogen and total
phosphorus into the Baltic Sea area (kt/year)1 in 1995, Estimated
from EEA (1998a) and Excessive anthropogenic nutrients in European
ecosystems, EEA (in press). These data are estimates from 1995 and
not from 1994; however, the error caused by this factor is expected to
be of minor importance.

1 High estimates used; some countries have given low and high estimates.

Table 8-7
Estimated direct discharges and riverine inputs of total nitrogen
and total phosphorus into the Mediterranean Sea from the
EU-15 countries (kt/year) (Kristensen 1999).

The Mediterranean Sea atmospheric inputs of nitrogen have been estimated to be about 1249 k tonnes/year, which are greater than those from direct discharges and riverine inputs.

Table 8-8
Direct discharges and riverine inputs to the sea of total nitrogen
and phosphorus in 15-EU countries (kt/year)1 in 1994. Estimated
from EEA (1998a) and Excessive anthropogenic nutrients in
European ecosystems, EEA (in press).

1 High estimates used; some countries have given low and high estimates.

8.5.3 EU-15 emissions of nutrients to air and water

It is necessary for normalisation to know the man-made loading, but the inventory published in "Excessive anthropogenic nutrients in European ecosystems" from the EEA (in press) does not admit the possibility of assessing the natural contribution. However based on Danish calculations, it is estimated that 85-90% (Tygesen 1998) of the waterborne emissions of nitrogen and phosphorus are man-made. In this calculation for the EU-15 emissions we assume that 88% are man-made as found for Denmark. However, it should be stressed that this is a rough estimate and that the actual amount differs significantly from country to country. This gives total man-made waterborne nitrogen and phosphorus loading in 1994 of:

• 0.88 x 2661.7 kt N/year = 2342.3 kt N-equivalents/year
• 0.88 x 171.4 kt P/year = 150.8 kt P-equivalents/year.

Airborne emissions of nitrogen and phosphate from "nature" are small and in the calculations we assume that 100% are man-made. Furthermore, airborne emissions of phosphate are quite small and are therefore not included in the calculations.

Table 8-9
EU-15 emissions of nutrients in the form of nitrogen and phosphorus compounds to air and water. The unit is kt/year. Emissions to air from Ritter (1997). Waterborne emissions from EEA (1998a).

1 NO_x as NO₂

8.5.4 Normalisation references for EU-15 in 1994

Based on a total EU-15 emission (1994) of 9004 kt N-equivalents and 151 kt P-equivalents and a population (1994) of 370 million (Ritter 1997), the EU-15 normalisation references for nutrient enrichment are:

Person equivalents:

24 kg N-equivalents/capita/year
0.4 kg P-equivalents/capita/year

or aggregated as

119 kg NO₃^- - equivalents /capita/year

8.6 The normalisation reference for selected European countries

For the purpose of calculating a normalisation reference for selected European countries, the emissions of nutrient are estimated from these countries. These are summarised, and their environmental impact potentials calculated in Table 8-14. The calculation has been made to establish whether a widening of the EU-15 area would change the normalisation reference.

8.6.1 Air emissions of nitrogen and phosphorus compounds

Table 8-10
National total 1 emissions 1994 (Ritter 1997; EEA 1998b).

1 Rough estimate of the population and emissions from the part of Russia that
has direct discharges and riverine inputs to the Baltic Sea. Air emissions and
populations are assumed to be comparable to that found in Latvia based on
the data of aquatic N inputs to the Baltic Sea.

8.6.2 Direct discharges and riverine inputs of total nitrogen and phosphorus compounds in selected countries in Europe

The direct discharges and riverine inputs of total nitrogen and phosphorus into the different sea areas surrounding Europe are depicted in the tables below. All data are finally aggregated in Table 8-13 illustrating the total direct discharges and riverine inputs to the sea of total nitrogen and phosphorus in the selected countries.

Table 8-11
Direct discharges and riverine inputs of total nitrogen and total
phosphorus into the OSPAR area (kt/year)1 in 1994 estimated from
EEA (1998a) and EEA (in press).

1 High estimates used; some countries have given low and high estimates.

Table 8-12
Direct discharges and riverine inputs of total nitrogen and total
phosphorus into the Baltic Sea area (kt/year)1 in 1995 Estimated
from EEA (1998a) and EEA (in press). This data are estimates from
1995 and not from 1994; however, the error caused by this factor is
expected to be of minor importance.

1 High estimates used; some countries have given low and high estimates.

The direct discharges and riverine inputs of total nitrogen and total phosphorus into the Mediterranean Sea from Europe are estimated to be about 823 kt N and 60 P kt/year (Kristensen, 1999). Discharges of nitrogen and phosphorus are of the order of 270 and 24 kt/year, respectively, in the Adriatic region including discharges from Italy, Croatia and Slovenia (UNEP 1996).

The annual total discharges in the Black Sea, mid 1990s are estimated to about 406 kt nitrogen and about 55 kt phosphorus (EEA 1998a). Of this amount, about 236 kt nitrogen and 43 kt phosphorus come from international rivers, thus, the total annual discharges for nitrogen and phosphorus from all the countries surrounding the Black Sea region are less than half of the total discharges from international rivers (EEA 1998a). The annual discharges of the Danube alone are estimated to be 230 kt total nitrogen and 40 kt total phosphorus (EEA, in press).

Table 8-13
Direct discharges and riverine inputs to the seas around Europe of
total nitrogen and phosphorus in (kt/year)1 in 1994, Estimated from
EEA (1998a) and EEA ( in press).

1 To the Baltic Sea area.

2 High estimates used; some countries have given low and high estimates.

8.6.3 Emissions of nutrients to air and water in selected European countries

It is estimated that 85-90% of the waterborne emissions of nitrogen and phosphorus is man-made. In this calculation, we assume that 88% (as the figure of Denmark) are man-made; however, it should be stressed that the actual amount differs significantly from country to country. This gives total man-made waterborne nitrogen and phosphorus loading in 1994 of:

1. 0.88 x 3308.6 kt N-eq./year = 2911.6 kt N-eq./year
2. 0.88 x 206.7 kt P-eq./year = 181.9 kt P-eq./year.

Airborne emissions of nitrogen and phosphate from "nature" are small and in the calculations we assume that 100% are man-made. Furthermore, airborne emissions of phosphate are quite small and are therefore not included.

Table 8-14
Emissions of nutrients in the form of nitrogen and phosphorus compounds to air
and water. The unit is kt/year. Emissions to air from Ritter (1997). Waterborne emissions from EEA (1998a).

1 NO_x as NO₂

8.6.4 Normalisation references for selected European countries in 1994

Based on the total emission (1994) of 10611.9 kt N-equivalents, and 181.9 kt P-equivalents and a population (1994) of 437 million, the normalisation references for nutrient enrichment in the selected European countries are:

Person equivalents:

24 kg N-equivalents/capita/year
0.4 kg P-equivalents/capita/year

or aggregated as

119 kg NO₃^- - equivalents/capita/year

8.7 Worldwide normalisation reference for nutrient enrichment

The worldwide for normalisation reference for nutrient enrichment is calculated by a simple extrapolation from the EU-15 data to a world basis by use of the GDP (Gross Domestic Product). A general extrapolation method is described in chapter 3, Development of normalisation references for different geographic areas. The general methodology is based on the following assumptions:

• linear relationship between normalisation factor and ln(GDP/capita)
• the normalisation factor is zero when the average income expressed as GDP/capita is zero.

Because of the lack of worldwide data the world-proxy presented in this report does not consider the differences between countries regarding degree of industrialisation, wastewater treatment, agricultural area, agricultural practice like livestock production etc.

The worldwide normalisation reference for nutrient enrichment can be calculated as:

0.8 x Normref_{Nutrient enrichment, EU-15}

i.e:

19 kg N-equivalents/capita/year

0.3 kg P-equivalents/capita/year

or aggregated as

95 NO₃^- - equivalents/capita/year.

8.8 Evaluation of uncertainties

The uncertainties are scored in three categories: "low", i.e. an uncertainty expected to be considerably lower than one order of magnitude, "medium", i.e. an uncertainty expected to be up to one order of magnitude, and "high", i.e. an uncertainty expected to be higher than one order of magnitude. The uncertainties are scored as "low" for the normalisation reference for Denmark, "medium" for EU-15, and "high" for the world-proxy. The uncertainties are due to the applied methodology and limitations of data. It should be stressed that these uncertainties are subjective and based on the authors experiences obtained during the project. Within the frame of this project it has not been possible to estimate the size of the uncertainties more precisely.

8.9 Recommendation for future updating

Most of the data sources used in the estimates are linked to international or national statistics, which are regularly updated. It should therefore be relatively simple to update the calculations for Denmark and the EU-15 countries.

Extrapolation from EU-15 to the world has been discussed in other LCA projects, and the conclusion is that all extrapolation methods will be based on general assumptions and generally they will therefore never be valid (see chapter 3, Development of normalisation references for different geographic areas). It is recommended to validate the estimated world-proxy for the normalisation reference for nutrient enrichment by comparison with an alternative method like the one described below. It was, however, not possible within the frame of the present project to perform this validation.

An alternative method is to calculate the nutrient enrichment potential for a few reference groups of countries or geographical areas that differ in the important parameters in relation to nutrient enrichment. When a normalisation reference for nutrient enrichment is calculated for a given country or region the selected factors of the specific country or region should be compared with the most comparable reference country or geographical area. After the comparison the nutrient enrichment potential (NO₃^- - equivalents/capita/year) can be estimated. Some of the important parameters, which should be considered when selecting the country reference groups or geographical areas, are listed in Appendix A.

8.10 References

Christensen, N., Paaby, H., and Holten-Andersen, J. 1993, Environment and society - the state of the environment in Denmark. Professional report no. 93, National Environmental Research Institute. In Danish ^[9]

EEA (European Environment Agency) (in press) Excessive anthropogenic nutrients in European ecosystems.

EEA 1998a, Europe's Environment: The Second Assessment. Eurostat, European Commission, European Environment Agency. Office for Official Publications of the European Commission, Luxembourg.

EEA 1998b,. Europe's Environment: statistical compendium for the Second Assessment. Eurostat, European Commission, European Environment Agency. Office for Official Publications of the European Commission, Luxembourg.

Hauschild, M. & Wenzel, H. 1998c, Nutrient enrichment as a criterion in the environmental assessment of products. In Hauschild M, Wenzel H (eds.). Environmental assessment of products. Volume 2: Scientific background. London: Chapman & Hall.

Kirkegaard, J. 1995, Personal communication, Danish Environmental Protection Agency.

Kristensen, P. 1999, Personal communications, DMU, Denmark.

Kristensen P. 1998, Nutrient discharges from point sources (industry and consumers) in the European Union. Contribution from the EEA ETC/IW as input to RIVM's DGXI study on priorities. DRAFT.

Larsen, S.E., Erfurt, J., Græsbøll, C., Kronvang, B., Mortensen, E., Nielsen, C.E., Ovesen, N.B., Paludan, C., Rebsdorf, Aa., Svendsen, L.M. & Nygaard, P. 1995, Ferske vandområder - vandløb og kilder. Vandmiljøplanens overvågningsprogram 1994. Danmarks Miljøundersøgelser. Faglig rapport fra DMU, nr. 140.

Miljøstyrelsen 1994, Punktkilder. Vandmiljø.planens overvågningsprogram 1993. Fagdatacenterrapport. Orientering fra Miljøstyrelsen No. 8. In Danish9.

Miljøstyrelsen 1995, Vandmiljø-95. Redegørelse fra Miljøstyrelsen Nr. 3. In Danish9.

Miljøstyrelsen 1997, Vandmiljø-97. Redegørelse fra Miljøstyrelsen Nr.4. In Danish9.

Ritter, M. 1997, CORINAIR 94 - Summary Report - European Emission Inventory for Air Pollutants. Copenhagen: European Environment Agency.

Skov, H., Ellermann, T., Hertel, O., Manscher, H., & Fohn, M. 1996, Atmosfærisk deposition af kvælstof. Vandmiljøplanens Overvågningsprogram 1995. Hovedrapport. Danmarks Miljøundersøgelser. Faglig rapport fra DMU nr. 173.

Tygesen Niels 1998, Personal communication. European Environment Agency.

Appendix A: Important parameters in relation to nutrient enrichment

• Emissions to air:
  • The main sources of emission to air in relation to nutrient enrichment are NO_x and NH₃. The main emissions of NO_x to air are from road transport, combustion in energy and transformation industries, and other mobile sources and machinery. These three main source sectors constituted more than 80% of the total emissions of NO_x in the EU-15 countries in 1994 and should therefore some how be included in the evaluation.
  • For NH₃ the main source sectors are agriculture and forestry, land use and wood stock change which constituted about 95% of the total NH₃ emission in the EU-15 countries in 1994.
    
  • Information on the activity in these sectors is not available in statistics covering the whole world; however, it should be available for different selected groups of countries or geographical areas that differ in industrial and agricultural activities.
• Airborne emissions of phosphate are quite small and are therefore not included.
• Waterborne emissions:
  • The main sources of emission of nitrogen to the aquatic environment are mainly due to leaching from agricultural land. An important parameter to estimate the emission of nitrogen is therefore to evaluate the agricultural land and compare it with the total area. Furthermore, the use of nitrogen fertiliser and the number of livestock should be included in the evaluation.
  • Most of the phosphorus loading of surface water is attributable to discharges from point sources, especially municipal sewage and industrial effluent cf. waste water below. However, leaching from agricultural land also plays a significant part and an estimation of the agricultural land and the use of phosphorus containing fertiliser should be made. Data might be available for different selected groups of countries or geographical areas that differ in industrial and agricultural activities.
• Wastewater:
  • Industrial production and household consumption result in wastewater containing nutrients. The nutrient content of wastewater from households is primarily determined by excreta from humans and phosphorus from detergents. Generally the amount of wastewater produced is proportional to the population and only to a little extent dependent on the economic development (Kristensen, 1998). The nutrient content of the wastewater from the industries is highly dependent on the type of industry. Only a small part of the industrial sector is responsible for the majority of wastewater containing phosphorus. To name just a few important industries the fertiliser industry and other related chemical industries manufacturing products containing phosphorus (e.g. pesticides and detergents), as well as the pulp and paper industry and fish processing industry should be mentioned. The extent to which the nutrients in wastewater are discharged into surface waters depends on the wastewater treatment facilities available. The majority of the households in the EU Member States are connected to sewers and municipal wastewater treatment plants (Kristensen 1998). However, in other parts of the world only a small part of the households may be connected to a wastewater treatment plant.
    
    For waste water from households it might be an idea to estimate the emission of the nutrient content to the aquatic environment by looking at the population density, the amount of phosphorus sold in detergents, and percent of people connected to a waste water treatment plant. For an evaluation of the emissions from industries it is important determine the industries that are present and the wastewater treatment facilities that are available.

Footnotes

[9] Most of the reports from Miljøstyrelsen (the Danish Environmental Protection Agency) contain English summaries.

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