Heavy metals in soil ecosystems (Signal)

Key messages: A recent update on soil pollution shows that agricultural soils are exposed to high levels of some metals and excess nutrient inputs. In 2017, the EU area in which critical limits were exceeded amounted to 10% for copper and 2% for zinc, which is less than reported in the zero pollution monitoring assessment for 2022. This can be attributed to better quality soil data. If current agricultural inputs were to remain unchanged, 60% of agricultural soils would exceed their critical loads for copper and 46% for zinc, posing potential harm to the environment.

Soils can filter contaminants and immobilise them from being transported elsewhere (for example, to surface waters, towards plants and into groundwater). However, such accumulation of nutrients and potentially toxic metals including cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) can lead to adverse effects on ecosystem health and water quality.

Changes in agricultural inputs via manure and fertiliser between 2010 and 2017 were small, with inputs of Cu and Zn via manure increasing by 6% (Zn) and 7% (Cu), and in the case of inorganic fertilizer 12% (Cu), 10 % (Zn) and 2% (Romkens et al. 2024). Looking balances between inputs and outputs, in 2017, 45% of the agricultural area show increases for Cd , 81% for Zn, and 91% of the area have a net accumulation of Cu. Between 2010 and 2017, the area with an accumulation of Cd, Cu and Zn has slightly increased by 1-2%.

Despite the availability of gradually improving and available soil monitoring data, modelling and case-specific assumptions and predictions are still needed in order to assess the risk from soil pollution.Another study applying limit values under the Sewage Sludge Directive concluded that 10% (EU lower limit), 36% (EU upper limit) and 19% (national limit values) of a representative sample of monitored agricultural soils exceed the limit values for at least one metal (Yunta et al., 2024).

Another study applying limit values under the Sewage Sludge Directive concluded that 10% (EU lower limit), 36% (EU upper limit) and 19% (national limit values) of a representative sample of monitored agricultural soils exceed the limit values for at least one metal (Yunta et al., 2024).

An assumed infinite continuation of the current agricultural inputs would eventually eventually lead to Cu and Zn exceeding their critical loads for 60% and 46% of the soils, respectively (Romkens et al., 2023). This shows that soils have a limited capacity to filter metals before they impact ecosystems at harmful levels.

No such exceedances were found for Cd, so as far as that metal is concerned, the current quality of soils is sufficient to warrant quality crops. However, Cd is also accumulating in agricultural soils, so critical loads may be reached if inputs are not reduced.

Please consult the relevant indicators and signals below for a more comprehensive overview on the topic.

Zero Pollution Action Plan 2030 target or policy objectives

Reduce the impact of soil pollution to levels no longer considered harmful to health and ecosystems (EC, 2021).
Reduce nutrient losses to the environment from both organic and mineral fertilisers by at least 50% while maintaining soil fertility (EC, 2020).
Achieve healthy soils by 2025, which entails detecting soil pollution at unacceptable risk levels and restoring/remediating (EC, 2023).

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Ecosystems

Zero pollution monitoring assessment

Other relevant indicators and signals

Long-term impacts of sludge spreading on agricultural land (Signal)

Heavy metal emissions in Europe (Indicator)

Leachate pollution from landfills (Signal)

References and footnotes

Römkens, P.F.A.M. , H. Kros, J.C.H. Voogd, and L. Jeurissen, 2024, Balances and Critical Concentrations for nutrients and metals in Arable Soils in the EU. Wageningen Environmental Research (WENR). Report of the European Topic Centre Data Integration and Digitisation (ETC/DI).
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Yunta, F., et al., 2024, Quantitative analysis of the compliance of EU Sewage Sludge Directive by using the heavy metal concentrations from LUCAS topsoil database, Environmental Science & Pollution Research, https://doi.org/10.1007/s11356-024-31835-y.
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EC, 2021, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions ‘Pathway to a Healthy Planet for All’ (SWD (2021) 140 final).
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EC, 2020, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions, ‘A Farm to Fork Strategy for a fair, healthy and environmentally friendly food system’ (COM/2020/381).
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EC, 2023, ‘Proposal for a Directive on Soil Monitoring and Resilience’ (https://environment.ec.europa.eu/publications/proposal-directive-soil-monitoring-and-resilience_en) accessed 5 August 2024.
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