Atmospheric Inputs to the North Sea: Results for the Period 1986/1991
Report No FR/D0018

K PLayford, C L Rose, P J P Bonnett, T C Collier and P F Ambidge

Jan 1995

SUMMARY

Currently there is much concern regarding the possible adverse effects of heavy metals and certain organic compounds entering the North Sea. The Government is committed under the terms of the Hague Declaration to reduce the emissions of selected pollutants deemed to enter the North Sea (as defined in the declaration) from atmospheric deposition. The substances of particular interest are included in appendix 1A to the Final Declaration of the Third International Conference on the Protection of the North Sea held in the Hague on 7th and 8th March 1990. The sampling and analytical programme was funded by the Department of the Environment.

Estimates have previously been made and reported (Cambray et al., 1975) of trace element inputs via the atmosphere into the North Sea based on measurements of concentrations in rain at six coastal stations in the UK and Holland. This report provides details of a similar but smaller network operated between 1986 and 1991 as required under the Paris Commission's Comprehensive Atmospheric Monitoring Programme (CAMP).

Objectives

The principal objectives of the programme were: a) to repeat and extend the previous estimates of atmospheric inputs to the North Sea; b) to liaise with technical organisations associated with the Paris Commission to ensure standardisation of procedures and interpretation of results; c) to provide the Department of the Environment with an interpretation of the sampling and analytical results.

Monitoring Programme

Three sampling sites were established in the United Kingdom along the North Sea coast and one in Northern Ireland. They were chosen as representative of their respective geographic areas while being as far as practicable from local sources of pollution. Monthly samples of both bulk deposition and airborne particulate material were obtained at each of the east coast sites with only bulk deposition samples from Northern Ireland. All samples were analysed for aluminium, cadmium, chromium, copper, iron, lead, manganese, nickel, sodium and zinc. Bulk deposition samples were additionally analysed for arsenic, barium, boron, magnesium, mercury, phosphorus, potassium, silicon, strontium, sulphur, titanium and vanadium. At the three sampling sites on the east coast further samples were collected and analysed for a range of organochlorine compounds. Additional sampling and analysis was also undertaken to establish the variability of the sampling and analytical methods, and to provide comparison of the methods used in the UK with those used elsewhere.

Findings

Element to element correlations have been carried out of the concentrations in air and rain and also the calculated monthly deposition. These indicate that at some stations a number of elements probably result from emissions from a common source. In add ition to correlations between elements, temporal trends have also been considered. These show a gradual decrease in the concentrations in air of many of the elements considered. However, the much larger monthly variations observed in rain concentrations and total deposition make trends observed in these samples less certain. it is considered that the observation of concentrations over many more years may be required before significant trends can be confirmed. The chemical characteristics and possible sources of the various substances have been considered together with a discussion of deposition mechanisms.

Conclusions

From the results of the sampling and analytical programme it has been possible to show that:

• A significant decrease in the estimated deposition of lead is observed between 1972/3 and 1986/1991.
• In addition to lead, the air concentrations of a number of other heavy metals appear to have decreased during the period 1986/1991.
• Large monthly variations of the concentration of heavy metals in deposition samples make the observation of significant trends during the sampling period unreliable.
• The concentrations of organochlorine compounds in rainwater are generally low.
• The extrapolation of measurements carried out at coastal stations to areas such as the North Sea, although crude, allow deposition estimates to be made based on actual measured values.
• With the limited number of sampling stations, the results may not be fully representative of the whole of the UK. However, the relative concentrations measured at each station are consistent with their respective locations.
• A continuing sampling and analytical programme will be required to demonstrate any improvements resulting from pollution abatement strategies.

  Copies of the Report are available from FWR, price £25.00 less 20% to FWR Members