DSS
Federal Office for the Environment FOEN
Copper and zinc are essential nutrients for plants. They are also essential trace elements for both humans and animals. However, one characteristic feature of trace elements is that both deficiency and excess can cause problems. Excessively high concentrations of copper and zinc can therefore also be harmful.
This type of pollution is mainly caused by direct inputs from agriculture, as copper and zinc are found in both farm manure and plant protection products. Farm manure such as cattle or pig slurry contains large amounts of zinc and copper. These nutrients originate from animal feed additives that are used for health reasons or to improve animal performance.
Since farm manure is mainly spread on arable land or intensively used grassland, these types of land pose the greatest risk of pollution. Copper is also a component of fungicides. These are often used on specialised crops such as vegetables, fruit and vines, which is why the soil in these areas sometimes contains very high concentrations of copper and occasionally exceeds the guidance values.
medium
negative
On average, soils used for intensive agriculture are considered unpolluted, but the concentration of copper in particular is very close to the guidance value (guidance value in accordance with Annex 1, SoilPO: Cu 40mg·kg-1 DM; Zn 150mg·kg-1 DM).
Compared to the last survey period, both zinc and copper levels have increased in 2023. For this reason, the condition is assessed as medium. The concentrations are therefore not a cause for concern. However, as the average content of both copper and zinc has increased slightly but continuously over the entire measurement period, the trend can be classified as negative.
The trend nevertheless varies depending on the crop, which is largely due to crop-related differences in fertiliser and pesticide use. Soils that are used less intensively and extensively show significantly lower concentrations of both heavy metals. More detailed information can be found in the publication 'Results of the National Soil Observation 1985–2019' (available in german and french).
Since 1985, composite samples have been taken every five years from the top 20cm of soil at all 114 permanent plots of the Swiss Soil Monitoring Network (NABO).
The indicator was calculated based on data from intensively farmed monitoring plots. Arable land, intensively farmed grassland and specialised crops (vegetables, fruit, vines) were taken into account.
Zinc and copper pollution is assessed in the topsoil because pollutants from substances applied to the surface of agricultural soils accumulate there.
The zinc and copper content is analysed using the method specified in the Soil Protection Ordinance (SoilPO) (solvent: 2M nitric acid (HNO3)). The results (in mg·kg-1 of dry soil) are presented in the form of average content per survey cycle.
| Targeted trend | Initial value | Final value | Variation in % | Observed trend | Assessment |
|---|---|---|---|---|---|
| Decrease | Average 1985/89-1995/99 | Average 2005/09-2015/19 | (1) 1.31%, (2) 6.34% | (1) Stabilisation, (2) Growth | negative |
| (1) Average copper content, (2) Average zinc content | |||||