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No. 309: Aquatic environment and Nature 2017

Jensen, P.N., Boutrup, S., Jung-Madsen, S., Hansen, A.S., Fredshavn, J.R., Nielsen, V.V., Svendsen, L.M., Blicher-Mathiesen, G., Thodsen, H., Hansen, J.W., Ellermann, T., Thorling, L. & Skovmark, B. 2019. Vandmiljø og Natur 2017. NOVANA. Tilstand og udvikling - faglig sammenfatning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 48 s. - Videnskabelig rapport nr. 309
http://dce2.au.dk/pub/SR309.pdf

Summary

This report summarizes the results from the National Danish Monitoring program NOVANA for the year 2017 and the development in a number of parameters for the period 1990-2017. The basis for data, reservations, e.g. in relation to uncertainties on results, or specific conditions in a single year are not included in this report, but can be found in the scientific background reports.

Reporting of data from 2017 is still characterised by the error analyses of total nitrogen and total phosphorus that were made in surface water in 2016 and parts of 2017 (see Larsen et al., 2018). This means that results for total nitrogen (TN) and total phosphorus (TP) in streams are only reported (including nutrient transport) for 2017, where it has been possible to restore data. For all other types of water (marine, lakes, etc.), it has not been possible to report the TN and TP. However, there is no error in the analyses of nitrate and phosphate, which is why these data are included in this year's report, where appropriate.

The same type of error is seen in the analyses of TN and TP from the period 2007-14. Preliminary restoring of these data has been done, which constitutes the basis for calculating nutrient transport of nitrogen and phosphorus in this report. It is expected that in 2019 restoring of data from the period 2007-14 will be completed.

Nutrients

Since 1990, there has been a general reduction of almost 50% in the content of nitrogen in the surface water. This generally correlates well with reduction in sources, listed here as the development in fertiliser use and in emissions from wastewater treatment plants. Nitrogen surplus (added minus harvested) increased from 2015 to 2016, but fell again in 2017. A possible effect of changes in nitrogen surplus on the leaching of nitrogen depends on a number of factors, including catch crops.

In 2017, the total load of nitrogen to marine areas was approximately 64,000 tonnes of N – compared with 62,000 tonnes N in 2016. When taking precipitation etc.  into account (normalised),  the load in 2017 was approx. 60,000 tonnes of N, which is largely the same as in 2016, when it was 59,000 tonnes N.

It is still too early to assess the overall effect of the increased use of nitrogen fertilizer and the compensatory catch crops, which were made possible by the Food and Agriculture package in 2015.

Nitrogen supply from precipitation has been included in the total load of nitrogen and has been at the same level over the past nearly ten years.

For phosphorus, the relationship is somewhat different. Since 1990, there has been a marked 50-60% reduction in the phosphorus content in the surface water, which is only supported by improved waste water treatment - primarily at the large wastewater treatment plants - until about year 2000. The total load of phosphorus to marine areas was approx. 2,500 tonnes in 2017 - about the same as in 2016, when it was approx. 2,300 tonnes P.

Metals and organic environmentally hazardous substances

Through precipitation, surface water and soil are supplied much more zinc than any of the other metals. Over the past three years, copper has been supplied in the second largest quantity.

Pesticides are among the organic environmentally hazardous substances included in the monitoring. As in previous years, the pesticide prosulfocarb was found in the greatest amount among the 19 substances measured in precipitation. The deposition was greatest in the autumn, i.e. just after the spraying season. In 2017, for the first time continuous measurements of pesticides in the air, including prosulfocarb, were conducted. As for precipitation, the highest concentrations in ambient air were found in the autumn.

Air

In 2017, limit values for nitrogen dioxide and particulate matter were not exceeded. The AEI-value (Average Exposure Indicator) is determined as a three-year average mark of PM2.5  concentration in the urban background. This value has dropped approximately 30% since 2010. The target value (15% reduction from 2010 to 2020) has, thus, been achieved.

Ozone concentrations were in 2017 at the same level as previous years. The threshold for information to the public about high ozone levels (180 µg/m3 as the hourly average value) was not exceeded in 2017.

Groundwater

Aquatic environment action plans have impacted the nitrate content in groundwater. This is reflected in a clear correlation between the nitrate content in the oxygen-containing groundwater and the excess nitrogen in agricultural production in a given year. During the past 10 sampling years, nitrate levels in the oxygen-containing groundwater have, on average, varied around the limit value.

In 2017, one or more pesticides or degradation products from pesticides were found in 32.5% of the intake in the groundwater monitoring program. The quality standard of 0.1 µg/l was exceeded in 10.5% of intakes. Most cases involved pesticides or degradation products that are no longer permitted. The results in 2017 differ from previous results, as in 2017 degradation products from the herbicide chloridazon which have been prohibited in Denmark since 1996 were analysed. The decomposition product 1,2,4-triazole, which derives from triazole fungicides, was also studied. Both groups of substances were found more frequently than previously observed for other substances.

Marine areas

The extent of oxygen depletion in September 2017 was significantly less than in 2016. The extent of oxygen depletion in the month of September has varied somewhat in the past ten years, with least in 2010-2012 and most in 2008 and 2016. Wind and temperature significantly influence the variation in the prevalence of oxygen depletion, but the supply of nutrients is a fundamental factor for widespread oxygen depletion.

The amount of planktonic algae in coastal waters, measured as chlorophyll a, was nearly at the same level as in 2016 and, thus, higher than the previous years. The level corresponded to the levels in the 1990s and 2000s.  The prevalence of higher plants in the ocean (eelgrass and seaweed) has increased considerably over the past 10 years in most areas, but the positive development has stagnated in several areas in recent years. Benthic invertebrates in the coastal waters has increased in the number of species since a low point in 2008, while 2017 still indicated poor conditions for the benthic fauna in the North Sea and Skagerrak and several coastal areas. Thus, there are mixed signals in the marine parameters over the past 10 years.

Habitats and species

The description of and data from monitoring of terrestrial habitats and species can be found on the website http://novana.au.dk/. In 2017, the website was supplemented by a description of the monitoring results for 10 forest habitat types and their monitoring parameters.

In general, the Danish forest habitat types are characterised by forest management with few large trees, few trees with cavities and decay and a small amount of dead wood. There are indications that forest types are getting darker in general, and that especially the beech forest types are becoming more impoverished. Geographically, there are only minor regional differences in the condition of the forests, and there are no significant differences in conditions within and outside the habitat areas.