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

Most estuaries receive a high heavy-metal input from industries. This is reflected in the relatively high levels found in numerous estuarine organisms and in sediments. Many indicators have been suggested for facilitating the detection of heavy-metal pollution, but the problems in using these indicators to evaluate the metal loading of estuaries are considerable. Variations in species composition, and conditions at different sites, differences in season of sampling, and age of organism, as well as different metal levels in different parts of the organism, make the interpretation of results difficult. The levels reported here, similar to those in other unpolluted estuaries, have been used to suggest a baseline concentration for heavy metals in estuaries. The concept of a baseline is fundamental to the formation of a “Biological Quality Index” and “Pollution Load Index,” and a formula for such an index is suggested and tested at a preliminary level against published data for an English and a European estuary.

/pdf/problems-in-the-assessment-of-heavy-metal-levels-in-13u2wdhusu.pdf

Problems in the assessment of heavy-metal levels in estuaries and the formation of a pollution index

Bioavailability of trace metals to aquatic organisms — A review

The uptake of metals from food and water sources by insects is thought to be additive. For a given metal, the proportions taken up from water and food will depend both on the bioavailable concentration of the metal associated with each source and the mechanism and rate by which the metal enters the insect. Attempts to correlate insect trace metal concentrations with the trophic level of insects should be made with a knowledge of the feeding relationships of the individual taxa concerned. Pathways for the uptake of essential metals, such as copper and zinc, exist at the cellular level, and other nonessential metals, such as cadmium, also appear to enter via these routes. Within cells, trace metals can be bound to proteins or stored in granules. The internal distribution of metals among body tissues is very heterogeneous, and distribution patterns tend to be both metal and taxon specific. Trace metals associated with insects can be both bound on the surface of their chitinous exoskeleton and incorporated into body tissues. The quantities of trace meals accumulated by an individual reflect the net balance between the rate of metal influx from both dissolved and particulate sources and the rate of metal efflux from the organism. The toxicity of metals has been demonstrated at all levels of biological organization: cell, tissue, individual, population, and community. Much of the literature pertaining to the toxic effects of metals on aquatic insects is based on laboratory observations and, as such, it is difficult to extrapolate the data to insects in nature. The few experimental studies in nature suggest that trace metal contaminants can affect both the distribution and the abundance of aquatic insects. Insects have a largely unexploited potential as biomonitors of metal contamination in nature. A better understanding of the physicochemical and biological mechanisms mediating trace metal bioavailability and exchange will facilitate the development of general predictive models relating trace metal concentrations in insects to those in their environment. Such models will facilitate the use of insects as contaminant biomonitors.

Aquatic insects and trace metals: bioavailability, bioaccumulation, and toxicity.

646 . . . . . . VI . Variation in composition of metal-containing granules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI I. Formation of metal-containing granules ( I ) Intracellular metal-containing granules . . . . . . . . 650 (2) Extracellular metal-containing granules . . . . . . . . 655 . . . . . . . . . . . . . VIII. Granule function 656 659 . . . . . . . . . . IX. General discussion and summary X. Acknowledgements . . . . . . . . . . . . 661 XI. References . . . . . . . . . . . . . . 661

The form and function of metal-containing ‘granules’ in invertebrate tissues

Studies of tissue metal concentrations in shellfish have progressed along two major lines: first, to record the range of concentrations within commercial species, a response to the need to identify potentially hazardous levels from a human nutritional standpoint; and second, to compare concentrations within a single species on a geographical basis as a framework for an environmental monitoring programme. Body size is a parameter which can influence tissue metal concentrations, and if significant variations due to size do occur, then clearly it is a factor which should be taken into consideration within these contexts.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002531540002511X

C. R. Boyden

Papers

Effect of size upon metal content of shellfish