Aarhus University Seal / Aarhus Universitets segl

No. 263: Zinc and copper in the aquatic environment

Jensen, J. & Bak, J.L. 2018. Zink og kobber i vandmiljøet. Kilder, forekomst og den miljømæssige betydning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 44 s. - Videnskabelig rapport fra DCE - Nationalt Center for Miljø og Energi nr. 263. http://dce2.au.dk/pub/SR263.pdf

Summary 

Previous investigations have shown agricultural soils in Denmark having markedly increased concentrations of zinc and copper, i.e. a 19 and 24% increase in the period 1998-2014. At the same time, two-third of Danish fresh water recipients had average concentrations of zinc above the environmental quality criteria. This project aims to evaluate the major sources of zinc and copper to fresh water recipient with special focus on the use in pig farming.  Furthermore, it aims to re-evaluate the measured metal concentrations after correcting for bioavailability, which recently has been included in the Danish regulation.   

Data does not permit a full evaluation of the various zinc and copper sources to fresh water systems. However, they show that besides effluent from wastewater treatment plants, which locally may be a dominant source, leaching and run-off from agricultural soils are likely to be a very important source, especially in catchment areas where soils are amended with manure from intensive piglet production. 

Corrected for bioavailability, approximately 25 % of the streams, where sufficient data for such correction was available, had zinc concentrations above the environmental quality standard. For copper almost no exceedance of the environmental quality standard was observed. Unfortunately, such bioavailability correction was not possible for all recipients, as it needs data on calcium, dissolved organic matter and pH besides measurement of dissolved metal concentration. The analysis are furthermore troubled by the fact that the required data did not represent annual averages since monitoring was not necessarily covering several time-periods over the year. Finally, data indicates that the limited number of streams included in the current analysis may have lower zinc concentration than the average scenario for Danish streams. Overall, even when corrected for bioavailability, a relative large part of Danish streams, i.e. approximately one-quarter, is likely to have zinc concentration close to or above the Danish environmental quality standard. It is, however, uncertain how the trend will be if based upon annual averages rather than a relative few sampling occasions. It is hence recommended to repeat the analysis with a data set after 2017 where all relevant parameters are sampled simultaneously within the national monitoring program