The suspended loads at three stations in the middle estuary of the River Tay have been analysed monthly, at low and high water of the spring tides, over the period June 1983 to May 1984. Major mineral modal analyses were derived from bulk and mineral oxide analyses. The concentrations in the suspended loads of the trace metals Cr, Cu, Pb and Zn were determined. An efficient circulatory system operates within the middle estuary which largely retains the suspended loads acquired from the inner estuary, even at seasonal periods of high influx. The major mineral assemblage is quartz, chlorite, illite and kaolinite. There is some preferential landward return of quartz and chlorite. Chromium has an association with chlorite, while copper, lead and zinc seem linked with suspended particulate organic matter which, at least in part, is derived from sewage disposal into the estuary. Dissolved zinc is associated with dissolved organic matter.

The large hydro-electric schemes developed by the early 1960s now (1984/85) supply 12% of Scottish electricity demand. The pumped storage schemes contribute to the balance of production and demand but are not nett producers of electric power. Schemes remaining for development are numerous but small, in the range below 10 MW. Private development for local use is the best economic prospect for schemes below 500 kW. A rolling five-year programme of 10–15 MW per annum is suggested for the development of remaining resources. In Scottish conditions, peat does not appear to be a viable alternative to diesel power. Wave power is practicable, but probable costs are too high to justify investment at present. Wind power is promising, especially for island sites, but not as a complete replacement for diesel. Developments since 1980 include a successful small machine on Fair Isle and machines at 250 and 300 kW on Orkney where a 3 MW generator is being erected. A 750 kW machine has been ordered for Shetland.

The meaning to be assigned to “pollution” is discussed and an account given of the “natural” sources of radiation. The effects of radiation on human populations are described. The artificial sources of radiation in the environment associated with energy productions are reviewed. Particular attention is given to the effects of the discharge of radioactive waste on radiation exposures in the neighbourhood of nuclear establishments. This is followed by a consideration of nuclear accidents and the public reaction to them. Radioactive pollution and the necessary organisation for its control are discussed with particular attention being paid to the present position in the United Kingdom.

The River Tay and its estuary is one of Britain's largest and most important aquatic systems. Rising at 625 m and flowing for 148 km the River Tay is the largest by flow in Great Britain and has a catchment area of 5031 km2. There are considerable ecological changes from source to estuary. These take the form of transitions, but four main aquatic communities can be recognised: an upper, base-poor, swift-flowing alpine section, then an oligotrophic section with moderate flows at lower altitude, next a much richer, slower flowing, more lowland stretch and finally the upper estuary itself. The problems of classifying and conserving running water systems are discussed and the importance of the Tay system is emphasised. The linear form and catchment size of larger rivers makes it difficult to give them—particularly their lower reaches and estuaries—full conservation protection. The River Tay is sufficiently unique, both physically and biologically, to warrant further scientific investigation and nature conservation protection.

This paper discusses the four main invisible products of fossil fuel combustion: carbon dioxide, sulphur dioxide, nitric oxide and unburned hydrocarbons. If carbon exchanges between atmosphere, ocean and biosphere remain at their recent levels, the CO2 concentration in the atmosphere is likely to double later next century, with a possible rise in global mean temperatures of around 2°C resulting in significant changes in regional climates. The consequences are uncertain, but with adequate research, there should be time to develop the understanding necessary to guide future policies. Sulphur dioxide, acid rain and photochemical oxidants are a more pressing problem. Knowledge here is more complete, but still subject to considerable uncertainties that have an important bearing on the extent and rate of response of affected areas to reduction in acid deposition. However, from the year 2000 onwards, with the replacement of existing plant with nuclear power or new sulphur-free coal-burning technology, United Kingdom sulphur emissions will continue to decline at about twice the pace of their previous rise. Nitrogen oxides contribute to rain acidity, may have direct toxic effects on plants and, when accompanied by hydrocarbons, can generate ozone, itself a damaging pollutant. The chemistry of ozone production is, however, complex, such that intuitive control policies could be counter-productive.

Risk involves consideration both of the consequences of accidents and the frequency with which the accidents occur. Indeed formally risk is equal to the product of frequency and consequences. The important question of the perception of risk by the public and by the professional is first addressed. Two tenets are proposed as being a suitable summary of the public requirement:

1. If it can happen, then it must not matter.

2. If it matters, then it must not happen.

A mathematical interpretation is placed upon these tenets and is shown to be consistent with various professional safety targets. The tenets do not indicate what numerical values for risk would be acceptable to the public but they do show how the consequences of accidents should diminish as the frequency or likelihood of a particular accident increases. It is argued that the best way of determining what level of risk the public accepts is to be guided by statistics for man-caused accidents. These, it transpires, pose risks which are considerably greater than those implied, for example, by the professional targets for nuclear reactors. The risk posed to the public by two energy installations is summarised. The one installation, situated on Canvey Island, exports energy in the form of gas, some of which (methane) is pumped into a national gas grid. The other installation, the Sizewell “B” Pressurised Water Reactor nuclear power station has not yet been constructed, but a comprehensive risk assessment has been undertaken, the results of which are summarised. The two installations are comparable in the sense that each exports a power of the order of a million kilowatts (in the form of gas in the one case and electricity in the other). Both have been the subject of Public Inquiries. The risks posed by the Canvey installations are accepted, since they only constitute a small fraction of the risks which the public run in any case during the course of their everyday lives. The predicted risks for the PWR are smaller still. The form taken by the risks posed by both installations corresponds broadly with the two tenets. That is to say the greater the consequences the lower should be the frequency of a particular accident.

If technology aims to direct natural forces for the use and convenience of man, the inconvenience or worse arising from the concomitant hazards requires attention. The quantitative assessment of risk practised by the actuary and engineer differs substantially from the public perception of the same risks. In several longestablished activities there is a remarkably stable, and presumably socially tolerated, accident rate. In newer and more extensively hazardous activities political control, social toleration and public perception of risk interdepend in ways which require further exploration.

The collective expression of attitudes towards energy systems governs demand and hence cost, which combines with other factors to shape energy policy. For example, in the national debate over nuclear power, where decision makers either share the public's anxieties about costs and safety or are expediently responsive to them, there is a constant threat to political acceptance. The paper describes how perceived risks are one of the costs of all technologies and a brief summary is made of research on comparative risk perception. This confirms the wide disparities often observed between lay and expert risk assessments and provides some explanations. When attention is focussed on particular hazards, the concept of attitude becomes more appropriate than risk perception because choice behaviour is determined by overall evaluations and these are a trade off between perceived risks and benefits. Each of the latter is acquired from two overlapping classes of received knowledge, i.e. factual information (e.g. nuclear power comes from the fission of uranium atoms), and beliefs (e.g. nuclear power will create/reduce employment). In addition, the attitude acquires emotional associations and behavioural dispositions, forming an organised complex based on the environmental object. This structural approach facilities the “unpacking” of public attitudes towards energy systems into their constituents and this is essential for understanding, for consultation and for inducing attitude change.

Energy requirements in primitive societies in the past are estimated and compared with present energy requirements in the Third World. The interaction between the energy policy of the industrialised countries and fuel availability in the Third World is outlined. Conservation and substitution in industrialised countries are discussed. The different patterns observed in Sweden, France, Japan and the United Kingdom of the behaviour of the ratio of electricity consumption to fossil fuel consumption in recent years is detailed and interpreted. Attention is drawn to some very successful examples of electro-utilisation in Britain. Finally the question is raised of the Scottish economy's response to the opportunities presented by the combination of electro-utilisation and computerisation.

Heat pumps allow the reuse of what might otherwise be waste heat by upgrading such energy to useful temperature levels. Industrial applications to evaporation, distillation and drying are briefly described, together with heat pumps' place within process integration, using examples from the Scottish distilling industries. It is shown that heat pumps are another tool available for energy use optimisation.

Our President, Sir Alwyn Williams, asked me to act for him in this last element of our Symposium and he stressed that I should tell you how unhappy he was to be absent today.

I found myself reflecting on some possible reasons for the invitation to me to deputise. The most obvious is perhaps my seniority as a Fellow of the Royal Society of Edinburgh. I have been a Fellow for almost forty years. In addition, and more pertinent to my immediate task, for over fifty years I have been involved in research, or close to research, in nuclear science and particularly concerned with research on penetrating radiation. I trust this qualifies me to discuss some important trends.