ALBERT

Description / Table of Contents: INTRODUCTION Sediments are increasingly recognized as both a carrier and a possible source of contaminants in aquatic systems, and these materials may also affect groundwater quality and agricultural products when disposed on land. Contaminants are not necessarily fixed permanently by the sediment, but may be recycled via biological and chemical agents both within the sedimentary compartment and the water column. Bioaccumulation and food chain transfer may be strongly affected by sediment-associated proportions of pollutants. Benthic organisms, in particular, have direct contact with sediment, and the contaminant level in the sediment may have greater impact on their survival than do aqueous concentrations. Following the findings of positive correlations between liver lesions in English Sole and concentrations of certain aromatic hydrocarbons in Puget Sound (Washington) sediment, it can be suspected that such substrates may also be responsible for a host of other serious and presently unrecognized changes at both the organismal and ecosystem levels (Malins et al., 1984). Modern research on particle-bound contaminants probably originated with the idea that sediments reflect the biological, chemical and physical conditions in a water body (Züllig, 1956). Based on this concept the historical evolution of limnological parameters could be traced back from the study of vertical sediment profiles. In fact, already early in this century Nipkow (1920) suggested that the alternative sequence of layers in a sediment core from Lake Zürich might be related to variations in the trophic status of the lake system. During the following decades of limnological research on eutrophication problems sediment aspects were playing only a marginal role, until it was recognized that recycling from bottom deposits can be a significant factor in the nutrient budget of an aquatic system. Similarly, in the next global environmental issue, the acidification of inland waters sediment-related research only became gradually involved. Here too, it is now accepted that particle-interactions can affect aquatic ecosystems, e.g. by enhancing the mobility of toxic metals. In contrast to the eutrophication and acidification problems, research on toxic chemicals has included sediments aspects from its beginning: Artificial radionuclides in the Columbia and Clinch Rivers in the early sixties (Sayre et al., 1963); in the late sixties heavy metals in the Rhine River system (De Groot, 1966) and methyl mercury (Jensen & Jerne- 16v, 1967) at Minamata Bay in Japan, in Swedish lakes, in Alpine Lakes, Laurentian Great Lakes and in the Wabigoon River system in Canada; organochlorine insecticides and PCBs in Lakes St. Clair and Erie during the seventies (Frank et al., 1977); chlorobenzenes and TCDDs in the Niagara River system and Lake Ontario in the early eighties (Oliver & Nicol, 1982; Smith et al., 1983). In the present lecture notes, following the description of priority pollutants related to sedimentary phases (Chapter 2), four aspects will be covered, which in an overlapping succession also reflect the development of knowledge in particle-associated pollutants during the past twenty-five years: - the identification, surveillance, monitoring and control of sources and distribution of pollutants (Chapter 3); - the evaluation of solid/solution relations of contaminants in surface waters (Chapter 4); - the study of in-situ processes and mechanisms in pollutant transfer in various compartments of the aquatic ecosystems (Chapter 5);- The assessment of the envlroD-mental impact of particle-bound contaminants, i.e. the development of sediment quality criteria (Chapter 6). A final chapter will focus on practical aspects with contaminated sediments. Available technologies will be described as well as future perspectives for the management of dredged materials. Here too, validity of remedial measures can only be assessed by integrated, multidisciplinary research. In the view of the growing information on the present subject and owing to the limitations in the framework of this monography, the reader is referred to additional selected bibliography, which is attached at the end of this Chapter i. Additional information on the more recent publications on contaminated sediments is given in the annual review volume of the Journal of the Water Pollution Control Federation, June edition.

Description / Table of Contents: Abstract 500 samples of water and suspended load were taken at different water levels from the Alpenrhein at Lustenau, a few kilometers' distance from its Lake Constance-delta. Conductibility and hardness of the water decrease with increasing water discharge (100–1000 m3/sec) corresponding to the dilution, the pH-values (8.0 to 8.8) weakly increase. The redox-potentials are always positive. With increasing water discharge, the suspended load concentration increases strongly (50 to 5000 mg/l). At the same water levels, the suspended load concentration during early-summer high-water is greater during rising than during falling water level. This may be caused by the loose material (accumulated during winter and spring low waters) being washed out of the river channel. On a double logarithmic scale the relation between flow velocity (V=1–3 m3/sec) and suspended load concentration (Cs in mg/l) can be expressed by a straight line. Its equation is Cs (Alpenrhein at Lustenau)=5· V6 In a general equation Cs=x· Vy, for various rivers (data taken from literature), the exponent y seems to be a measure of the erosional forces (depending on cross-section and slope of the river channel); the factor x seems to express outer influences as climate, vegetation, rock erodibility, stability of the channel geometry. A similar relationship exists between the suspended load concentration and the water discharge. Grain-size distribution and carbonate content are almost independent of water discharge and flow velocity respectively. They are, however, clearly related to distinct supply areas. A pronounced frequency minimum exists at about 0.04 mm between the mean sizes of river sands (Hahn, 1967) and that of suspended load (this paper). This value may be used to distinguish suspended load from bedload at Lustenau sampling station. The values for sorting, skewness and kurtosis amplify the results ofFolk &Ward (1957) concerning finer grain sizes. On an average, the suspended load consists of 10% clay (〈0.002 mm), 70% silt (0.002–0.063 mm) and 20% sand (〉0.063 mm). The mean carbonate content is 37% (26% calcite, 11% dolomite). The clay minerals are mainly illite and chlorite.

Description / Table of Contents: Abstract Lake Shala, the deepest lake in the internal Galla lakes basin of the Ethiopian Rift, fills a depression in Pleistocene volcanic rocks. Its sodium-bicarbonate (-chloride) water (salinity 16 g/l) is remarkably low in earth alkalines and sulphate. Stratification is indicated by different ion concentrations in the surface and bottom waters and by a thermocline in a water depth of 50–70 m. Hot soda springs emerging on the shores of Lakes Shala and Langano are believed to be derived from a hot saline underground reservoir recharged by meteoric waters. The ion composition of the hot spring waters is uniform and matches that in the Galla Lakes except for total salinities. Anomalous heavy metal concentrations are lacking in lake and hot spring waters. Sediments of Lake Shala belong to an extremely fine-grained group of deposits. They are poorly sorted and the lateral distribution of the grain sizes does not follow the normal scheme for aquatic depositional environments. A belt, 50–100 m below lake level containing the finest-grained sediments, separates the shallow periphery of the lake bottom from the deep center, both characterized by coarser-grained deposits. The sediments consist of a large portion of glassy components. A poorly cristallized smectite is most abundant in the clay mineral group. The components of the sand fraction are quartz, feldspar, glass particles and occasionally calcite. Nickel, cobalt and lead are depleted in the Lake Shala sediments compared with the averages of shales. Iron, manganese and zinc are relatively high. Silver, cadmium and some of the rare earth elements are enriched by factors of 〉 5.

Description / Table of Contents: Abstract Arid lakes of South, Central and Western Australia generally fill local depressions in Pre-Cambrian rocks. Their hydrochemical evolution represents a special type within the system of inland waters and is characterized by the lack of carbonate sedimentation. The mineralogical and chemical composition of the fine-grained lake deposits is mainly influenced by mechanical weathering products, indicating a distinct “detrital heritage” from the lithology of the lake basins and of the surrounding areas. Thus, sediments from arid lakes provide simplified conditions to evaluate both (1) economic metal accumulations and (2) baseline data for environmental geochemistry. The former is shown by the concentrations of nickel, chromium and cobalt in lakes of the Western Australian greenstone area. The latter is demonstrated by the concendations of zinc and copper, which are particularly uniform and similar to average shale composition; elevated contents of lead in sediments in some of the lakes studied might indicate an increase of atmospheric lead pollution.