Aquatic chemistry is becoming both a rewarding and substantial area of inquiry and is drawing many prominent scientists to its fold. Its literature has changed from a compilation of compositional tables to studies of the chemical reactions occurring within the aquatic environments. But more than this is the recognition that human society in part is determining the nature of aquatic systems. Since rivers deliver to the world ocean most of its dissolved and particulate components, the interactions of these two sets of waters determine the vitality of our coastal waters. This significant vol ume provides not only an introduction to the dynamics of aquatic chem istries but also identifies those materials that jeopardize the resources of both the marine and fluvial domains. Its very title provides its emphasis but clearly not its breadth in considering natural processes. The book will be of great value to those environmental scientists who are dedicated to keeping the resources of the hydrosphere renewable. As the size of the world population becomes larger in the near future and as the uses of materials and energy show parallel increases, the rivers and oceans must be considered as a resource to accept some of the wastes of society. The ability of these waters and the sediments below them to accommodate wastes must be assessed continually. The key questions relate to the capacities of aqueous systems to carry one or more pollutants."

Metal pollution in the aquatic environment

During the last decade a new pattern of Hg pollution has been discerned, mostly in Scandinavia and North America. Fish from low productive lakes, even in remote areas, have been found to have a high Hg content. This pollution problem cannot be connected to single Hg discharges but is due to more widespread air pollution and long-range transport of pollutants. A large number of waters are affected and the problem is of a regional character. The national limits for Hg in fish are exceeded in a large number of lakes. In Sweden alone, it has been estimated that the total number of lakes exceeding the blacklisting limit of 1 mg Hg kg-1 in 1-kg pike is about 10 000.

Mercury in the Swedish environment — Recent research on causes, consequences and corrective methods

The use of biological indicator organisms to monitor trace metal pollution in marine and estuarine environments—a review

THERE have been incidences of extensive alkyl-mercury poisoning in Japan and Sweden. In Japan a large number of people belonging to the fishing population around Minamata Bay were seriously affected by what is now called Minamata disease. This incident was traced back to pollution of the bay with the mercury containing effluent of a large chemical plant. When methyl thiomethyl-mercury was isolated from shellfish in the area of the bay it was suggested that mercury could be alkylated by “plankton and other marine life”2. It was discovered later that the spent catalyst of an acetaldehyde reactor, which caused the pollution, contained approximately 1 per cent methyl mercury; and the biological methylation of mercury was thought to be insignificant.

Synthesis of methyl-mercury compounds by extracts of a methanogenic bacterium.

The net uptake of zinc, cadmium, lead and copper by the common mussel Mytilus edulis (L.) exposed to different conditions was investigated with a view to using this species as an indicator of contamination of the marine environment by these metals. The variables studied were season, position of the mussel in the water column, water salinity, water temperature, and the simultaneous presence of all four metals. Each of these 5 variables affected the net uptake of some or all of the metals studied under some conditions. Seasonal variation in concentrations of zinc, cadmium and copper was found in samples collected at three separate locations. The relationship of seasonal variation to tissue weight and absorption route of the metals is discussed. Near to freshwater inputs of trace metals, the concentrations of zinc, cadmium and lead in mussels were found to vary according to the depth at which the mussels were collected; in summer when freshwater run-off is less, this effect was absent. Low salinities did not affect the net uptake of zinc by mussels, but increased the net uptake of cadmium and decreased that of lead. Low temperatures had no effect on the net uptake of zinc or lead; the net uptake of cadmium was unaffected by low temperatures at high salinities but was decreased by low temperatures at low salinities. The presence of the other metals had no effect on the individual net uptake of either zinc, cadmium or lead. A sampling programme was devised to eliminate the effects of these environmental variables and to allow the use of M. edulis as an indicator of zinc, cadmium and lead in marine and estuarine environments. In contrast to the other metals, the net uptake of copper by the mussel was extremely erratic, and was affected by salinity and temperature changes and by the presence of the other metals and changes in their relative concentrations. The effects of other metals on the net uptake of copper cannot be easily eliminated or allowed for; it is, therefore, suggested that the mussel should not be used as an indicator of copper in the marine environment.

The common mussel Mytilus edulis as an indicator of pollution by zinc, cadmium, lead and copper. I. Effects of environmental variables on uptake of metals

Activation analysis of mercury content in axial musculature of pike (Esox lucius) has been used in the present study as a means of estimating the level of mercury present in the water environment. The concentration factor from water to pike is of the order 3000 or more. The relation between mercury content and weight and age of fish specimens is discussed. By a graphical method the values for mercury content for specimens representing 1 kilogram of weight have been calculated for a number of localities and used for geographical comparison. The effect of industrial contamination is demonstrated by a comparison of mercury content of samples of pike from above and below localities, where emission of waste water containing mercury takes place. There are strong indications that mercury appears also as an airborne pollution affecting the water environment. A number of sources of mercury contamination are discussed. It is concluded that in many areas human activities has raised the mercury content of the environment far above the natural levels. Pe3loMe

A. G. Johnels

Papers

Pike (Esox lucius L.) and some other aquatic organisms in Sweden as indicators of mercury contamination in the environment