Inputs of mercury, cadmium and lead via water and air
Total inputs of cadmium, mercury and lead to the Greater North Sea have decreased considerably since 1990, although further improvements, since 2012, are not evident. Atmospheric sources make up a considerable proportion of the total inputs. The major sources are now re-suspended material from exposed terrestrial soils and from long-range transport.
Background
UK target on inputs of metals
The UK has no formal Marine Strategy Framework Directive (European Commission, 2008) target relating to the inputs of metals from water and the atmosphere to the marine environment, but it supports the OSPAR strategic objective to prevent pollution of the North East Atlantic by continuously reducing discharges, emissions and losses of hazardous substances.
Key pressures and impacts
In the UK Initial Assessment (HM Government, 2012) the key pressures associated with this indicator were the atmospheric deposition and riverine and direct inputs of cadmium, mercury and lead, from various industrial and diffuse sources. These are still relevant.
Measures taken to address the impacts
The UK Marine Strategy Part Three (HM Government, 2015) describes the robust UK legislative framework for controlling and reducing pollution from cadmium, mercury and lead including appropriate consenting and source control regimes and river basin management plans. However, much of the cadmium, mercury and lead entered the environment before many of the controls were put in place and due to their persistence, are still present.
Monitoring, assessment and regional co-operation
Areas that have been assessed
For waterborne loads of mercury, cadmium and lead the assessment scale is the UK portion of the Greater North Sea and the Celtic Seas. For atmospheric loads, the deposition to the whole of the Greater North Sea has been used because the modelling reports from the European Monitoring and Evaluation Programme used by OSPAR could not provide estimates just for the UK portions of this sub-region. A breakdown into Greater North Sea and Celtic Seas for waterborne loads is included in the extended results section.
Monitoring and assessment methods
Risk-based monitoring and assessment of the inputs of metals from rivers and direct discharges was conducted according to methods and procedures set out in the OSPAR Riverine Inputs and Direct Discharges programme (OSPAR Commission, 2014) and the related annual national reports. Atmospheric load data were produced by OSPAR using information from the European Monitoring and Evaluation Programme – Meteorological Synthesising Centre East based on national reporting of emissions to the air under the UN Economic Commission for Europe Convention on Long-range Transboundary Air Pollution (UNECE, 1983). For operational reasons, the OSPAR assessment focussed on the Greater North Sea.
Assessment thresholds
Assessment thresholds are not available for this indicator. Trends of inputs were used to assess progress towards the OSPAR reduction objective, which is supported by the UK.
Regional co-operation
The UK has regularly reported information on inputs of metals to OSPAR, held in the associated OSPAR database, and the UK has participated in the monitoring and assessment of the OSPAR “metals inputs” common indicator. The UK results have been used in the OSPAR Intermediate Assessment (OSPAR Commission, 2017).
Further information
The metals mercury, cadmium and lead are known to have significant effects on the health of humans, fish, shellfish and ecosystems as a whole. They are emitted through a range of natural, agricultural and industrial processes and have long been used by humans. These metals are most often transported as, or tightly bound to, fine particles. Mercury can also evaporate and be transported as a gas. Metals can be lifted into the air from exposed soils and earth, and from the surface of the sea. Metals are then transported via the atmosphere.
Mercury, cadmium and lead are highly toxic and can accumulate in the food chain. Mercury accumulates into top predators (Figure 1). Cadmium can also accumulate in algae and animals. Lead is mainly attached to particles and does not generally accumulate in the food chain. Although other metals can cause environmental problems and are carefully monitored, cadmium, mercury and lead cause the most harm and are on the OSPAR list of chemicals for priority action and are Water Framework Directive priority hazardous substances (European Commission, 2001).
Figure 1. Mercury from coal fired power plants and other sources travels through the atmosphere and water. Some is changed to methylmercury, which can enter the food chain to be concentrated at each step on that chain (Figure source: OSPAR Commission, 2017).
OSPAR has an objective to steadily reduce metal inputs, including those of cadmium, mercury and lead. Waterborne inputs of cadmium, mercury and lead, are monitored in the OSPAR riverine and atmospheric monitoring programmes. Atmospheric inputs are calculated based on annual emissions reported under European Union emissions directives and the United Nations Convention on Long-range Transboundary Air Pollution (UNECE, 1983) activities. As the majority of atmospheric inputs to the Greater North Sea now come from non-OSPAR countries, the implementation of Heavy Metals Protocol to the UN Economic Commission for Europe Convention on Long-range Transboundary Air Pollution (UNECE, 1983; 1998) by non-OSPAR countries is seen as an important vehicle to further reduce atmospheric inputs.
This assessment presents results from analyses of riverine data and atmospheric deposition modelling data to describe progress in meeting OSPAR’s environmental objectives.
OSPAR’s Co-ordinated Environmental Monitoring Programme requires OSPAR countries to monitor metals, including cadmium, mercury and lead. OSPAR has also produced guidelines for monitoring in air, precipitation and rivers (OSPAR Commission, 1997).
Assessment method
Metals concentrations are measured in the OSPAR Riverine Inputs and Direct Discharges monitoring programme. These measurements are combined with river flow measurements to give the total riverine load. These inputs are then supplemented by national reports of waterborne discharges from industry, which EU Member States also report under the Industrial Emissions Directive (European Commission, 2010).
Atmospheric load data have been produced by the European Monitoring and Evaluation Programme – Meteorological Synthesising Centre East based on national reporting of emissions to the air under the UN Economic Commission for Europe Convention on Long-range Transboundary Air Pollution (UNECE, 1983). Emissions data are reported to the European Monitoring and Evaluation Programme, then the resulting transport and deposition is modelled using atmospheric chemistry and meteorological models, together with estimates of ‘background’ metal emissions due to re-suspension from exposed soils and earth or in the case of mercury, emission from the surface of the sea. Source apportionment allows the relative contributions of OSPAR countries and ‘natural’ sources, as well as sources outside the OSPAR Maritime Area, to be assessed. Model results from the European Monitoring and Evaluation Programme are validated against observations of metal deposition from the same programme (often including the OSPAR Comprehensive Atmospheric Monitoring Programme).
Results
Findings in the 2012 UK Initial Assessment
The Initial Assessment, done in 2012, indicated there were downward trends in the waterborne and atmospheric inputs of cadmium, mercury and lead between 1990 and 2007 (HM Government, 2012).
Latest findings
Status assessment
A status assessment was not possible for this indicator.
Trend assessment
Although there are insufficient data for a robust trend analysis, the data since 2007 indicates that the UK waterborne inputs have stabilised, with annual increases and decreases largely reflecting rainfall patterns. The downward trend observed in the UK Initial Assessment does not appear to have been maintained.
The method for calculating atmospheric inputs used by OSPAR for atmospheric loads has changed, so direct comparison with the UK Initial Assessment findings (HM Government, 2012) is not possible. However, the results for atmospheric inputs originating from OSPAR countries show a similar picture, indicating that the reductions observed in the 1990s and early 2000s are have now stabilized.
Total inputs to the Greater North Sea for cadmium, mercury and lead are shown in Figures 2, 3 and 4. The largest inputs to the Greater North Sea are now coming from non-OSPAR countries via atmospheric transport. For mercury, this source appears to have shown little decrease since the 1990s.
There are a number of uncertainties associated with both the riverine and atmospheric load estimates, which gives them a medium confidence rating. There is moderate confidence in the methods and low confidence in the data used for this assessment.
Figure 2. Total cadmium inputs to the Greater North Sea (GNS), tonnes per year.
Figure 3. Total mercury inputs to the Greater North Sea (GNS), tonnes per year.
Figure 4. Total lead inputs to the Greater North Sea (GNS), tonnes per year.
Further information
The UK Rivers and catchment areas that are used for the UK reporting to the OSPAR Riverine Inputs and Direct Discharges programme (OSPAR Commission, 2014) are shown in Figure 5. The Celtic Seas assessment scale used for this assessment is comprised of the aggregated information for the OSPAR Sea Areas: Celtic Sea, Irish Sea and Atlantic. The Greater North Sea assessment scale is comprised of the aggregated information for OSPAR Sea Areas: the Channel, the North Sea South and the North Sea North areas.
Figure 5. Sampling areas and associated rivers used in the UK Riverine and Direct Discharges Programme.
The OSPAR Riverine Inputs and Direct Discharges programme (OSPAR Commission, 2014) requires the reporting of loads from rivers and sewage treatment works and industrial installations that discharge directly to the sea (that is, they are closer to the sea than the sampling point where the concentrations of the rivers are measured). The riverine inputs loads shown in Figures 2, 3 and 4 include the discharges from sewage treatment works and industrial installations. Figures 6 and 7 show the relative contributions of loads from the riverine, sewage and industrial inputs for cadmium for the Celtic Seas and the Greater North Sea. Mercury and lead have similar profiles to cadmium, with the riverine sources providing the majority of the load.
Figure 6. Annual mean Loads of Cadmium (tonnes per year) for riverine (RI) sewage (SE) and industrial (IN) inputs to the Celtic Seas.
Figure 7. Annual mean Loads of Cadmium (tonnes per year) for riverine (RI) sewage (SE) and industrial (IN) inputs to the Greater North Sea.
Annual loads for riverine inputs are calculated by using the concentrations of the metals and the annual river flows (cubic metres). Most major rivers have automated continuous flow meters, and the load estimation is of high confidence, but the flow of a number of the smaller rivers included in the survey is measured only periodically. The flow patterns vary considerably from year to year due to the rainfall patterns in the various regions, which explains some of the variation in the load figures. In a wet year, more metals are washed into the rivers through run-off and the results tend to be higher than in a dry year. Figure 8 shows how the flows vary from year to year since the OSPAR Riverine Inputs and Direct Discharges programme survey began in 1990. In the driest year, the loads are around 40 % lower than in the wettest year.
Figure 8. Annual variation of total flow from UK rivers (Celtic Seas and Greater North Sea) from 1990 to 2014.
Conclusions
Since the UK Initial Assessment (HM Government, 2012) loads of cadmium, mercury and lead in waterborne inputs from the UK have remained stable for both the Greater North Sea and the Celtic Seas. Atmospheric deposition to the Greater North Sea has also remained stable. Re-suspended material and that from sources outside the OSPAR Maritime Area are now the major sources of airborne inputs to the Greater North Sea.
Knowledge gaps
There are no major knowledge gaps, but there is moderate confidence in the methods used and low confidence in the data used for this assessment.
References
European Commission (2001) ‘Decision No 2455/2001/EC of the European Parliament and of the Council of 20 November 2001 establishing the list of priority substances in the field of water policy and amending Directive 2000/60/EC (Text with EEA relevance)’ Official Journal of the European Union L331, 5.12.2001, pages 1–5 (viewed on 16 November 2018)
European Commission (2008) ‘Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive)’ Official Journal of the European Union L 164, 25.6.2008, pages 19-40 (viewed on 16 November 2018)
European Commission (2010) Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control) Official Journal of the European Union L334 17.12.2010, p. 17–119 (viewed on 16 November 2018)
HM Government (2012) ‘Marine Strategy Part One: UK Initial Assessment and Good Environmental Status’ (viewed on 16 November 2018)
HM Government (2015) ‘Marine Strategy Part Three: UK Programme of Measures’ December 2015 (viewed on 16 November 2018)
OSPAR Commission (1997) ‘Guidelines for the sampling and analysis of mercury in air and precipitation’ Agreement 1997-08
OSPAR Commission (2014) ‘Riverine Inputs and Direct Discharges Monitoring Programme (RID)’ Agreement 2014-04, applicable from 1 January 2015 (viewed 8 January 2019)
OSPAR Commission (2017) ‘Intermediate Assessment 2017’ (viewed on 16 November 2018)
United Nations Economic Commission for Europe (UNECE) (1983) Convention on Long-Range Transboundary Air Pollution, CLRTAP.
United Nations Economic Commission for Europe (UNECE) (1998) ‘Protocol on Heavy Metals’ CLRTAP
Acknowledgements
Assessment metadata
| Assessment Type | UK Marine Strategy Framework Directive Indicator Assessment |
|---|---|
D8 Contaminants | |
D8.1 Metal inputs | |
| Point of contact email | marinestrategy@defra.gov.uk |
| Metadata date | Sunday, September 1, 2019 |
| Title | Inputs of mercury, cadmium and lead via water and air |
| Resource abstract | The data shows the input loads of mercury, cadmium and lead via water and air to the Greater North Sea between 1990 and 2014. |
| Linkage | Data shows input loads of the three contaminants, mercury, cadmium and lead from the UK rivers, the atmospheric deposition from OSPAR and non-OSPAR countries. It also provides a break down the UK specific riverine input loads including the flow rates. Atmospheric inputs are calculated based on annual emissions reported under European Union (EU) emissions directives and the United Nations (UN) Convention on Long-range Transboundary Air Pollution activities. |
| Conditions applying to access and use | © Crown copyright, licenced under the Open Government Licence (OGL). |
| Assessment Lineage | |
| Dataset metadata | |
| Links to datasets identifiers | Please, see below |
| Dataset DOI | Moxon (2019). Inputs of mercury, cadmium and lead via water and air to the Greater North Sea between 1990 and 2014. doi: https://doi.org/10.14466/CefasDataHub.90 |
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Recommended reference for this indicator assessment
Richard Moxon1 2018. Inputs of Mercury, Cadmium, lead via water and air. UK Marine Online Assessment Tool, available at: https://moat.cefas.co.uk/pressures-from-human-activities/contaminants/metal-inputs/
1Department for Environment, Food and Rural Affairs