Conclusions

A long-term programme of measurements of trace and major elements, in air particulate and rainwater at ground level at three rural locations in England, has been maintained over the period 1996-1998. Concentrations of 35 elements in air and 25 elements in rainwater (plus nitrate and sulphate) have been measured on a quarterly basis during this three-year period.

These measurements have also been compared with earlier data from the 1990s along with corresponding historical data, compiled since the early 1970s, to investigate any long-term changes in relation to changes in methods of energy production, energy consumption and emissions control policy.

The main conclusions are:

Air (ng m-3)

As (0.3 - 0.9); ~3 at Styrrup.

Cd (0.1 - 0.4).

Cr (0.4 - 0.9); ~5 at Styrrup.

Cu (2 - 4); ~8 at Styrrup.

Ni (0.8 - 2); ~4 at Styrrup.

Pb (4 - 20); ~40 at Styrrup.

Zn (16 - 32);~60 at Styrrup.

Rainwater (m g l-1)

As (0.1 - 0.3); ~0.5 at Styrrup.

Cd (0.1 - 0.2); ~0.3 at Styrrup.

Cr (0.1 - 0.5).

Cu (1 - 2); 6 - 9 at Chilton, Styrrup and Wraymires.

Ni (0.4 - 1); ~2 at Styrrup.

Pb (2 - 5).

Zn (10 - 21);~40 at Styrrup.
 
 

Recommendations

The following recommendations are:

The Rural Trace Elements network is the longest running network, for the measurement of metals, in the UK. Since the early 1970s this monitoring network has produced a unique time-series dataset for concentrations of 35 elements in air particulate and some 25 elements in rainwater. The continued operation of this small network is recommended to allow further data to be collected. This would allow any further changes in concentrations of airborne trace and major elements at rural UK locations to be quantified. Therefore, any such changes may then be examined and related to changes in methods of energy production, energy consumption and industrial emissions which may be brought about by future changes in relevant UK Government or EC policy and legislation, e.g. the future EC daughter Directives that will set limit values for As, Cd, Hg and Ni concentrations in air.

In view of the future EC daughter Directive on Hg concentrations in air, consideration should be given to more detailed measurements of airborne mercury. Information is only available on particulate-bound mercury from the current network. AEA Technology made measurements of both particulate and total gaseous mercury (TGM) at Chilton over a period of a year in 1995/1996. This work could be re-started, either at Chilton or at another appropriate location(s), so that improved data on airborne Hg levels at UK rural locations can be obtained.

The dataset could be subjected to a more thorough and rigorous statistical examination. This may allow a more detailed investigation of the long-term trends, or a more accurate identification of the source or sources of potentially toxic heavy metals at rural locations in the UK.

An archive of samples, including both air filters and rainwater, has been assembled over the years. Retrospective analysis of those that have produced anomalous results is possible for confirmation. Also many historical measurements, particularly Cd in air particulate and other heavy metals, e.g. As in rainwater, were below the prevailing analytical limits of detection. Appropriate samples could be re-analysed using more appropriate and improved analytical techniques to further improve the quality of the dataset.

Expansion of the current suite of analytes to include the measurement of other metals should be considered. For example, concentrations of platinum, palladium and rhodium could be measured in both current and historical samples, to assess the impact of the introduction of catalytic converters to vehicle exhausts on levels of these metals on the UK rural environment.
 
 
 
 

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