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Interactions between sediments and water: summary of the Eighth International Symposium
The Science of the Total Environment 266 Ž2001. 1᎐5
Introduction
Interactions between sediments and water: summary of the Eighth International SymposiumR.D. Evans En¨ ironmental Sciences Centre, Trent Uni¨ ersity, Peterborough, ON Canada K9J 7B8
As the use of water resources becomes more intense, the need to have a better understanding of the factors that control water quality grows as well. Within any water system, the particulate phase, i.e. suspended particles and bottom deposits, plays a key role in geochemical and biological cycles. The interaction between sediments and water is one of the key determinants of water quality in a wide range of aquatic systems including rivers, lakes, estuaries and coastal areas. Recognition of the importance of sediment᎐water interactions has led to a greater understanding of the many physical, chemical and biological processes that ultimately limit our use of water resources. Because of this new understanding, there has been an increased number of sedimentrwater related research and assessment projects, as well as a renewed awareness in the regulatoryrpolicy arena. Furthermore, this interest has led to a series of international symposiums that are used as a platform for the international community to present and publish their latest findings and results. The international symposium on ‘The Interactions Between Sediments and Water’, held in Beijing, China during the 13᎐17 September 1999,
was the eighth in a series held since 1976, all focusing on issues related to processes occurring at the sediment᎐water interface and responses to interactions between sediments and water. Previous symposiums were held in Amsterdam in 1976, Kingston in 1982, Geneva in 1984, Melbourne in 1986, Uppsala in 1990, Santa Barbara in 1993, Baveno in 1996 and the current one in Beijing. The next symposium will be held in Banff, Canada in the spring of 2002. Interest in the role of sediments in freshwater and marine ecosystems is evidenced by the number of participants worldwide attending each symposium; Six plenary presentations, approximately 135 oral presentations and approximately 35 poster presentations were made by attendees representing 27 nations. Particularly gratifying at this conference was the presence of many participants from Asian countries. The scientific sessions in Beijing were organized around the following themes: physical dynamics of sediment, nutrients and biota in sediments, chemical processes in sediments, and management, assessment and remediation. The sediment᎐water symposia bring together scientists and regulators with a diversity of back-
0048-9697r01r$ - see front matter 䊚 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 0 . 0 0 8 3 7 - 8
2
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
grounds. The focus on ‘interactions’ demands a level of interdisciplinarity not found in many other fields. Sediment models require field studies for validation. Particle dynamics affect chemical partitioning between pollutants and particles. As a result, the eighth symposium presented a spectrum of work covering many fields of study that impact on sediment᎐water interactions. Marine, estuarine and freshwater studies were all well represented. Both pristine and highly impacted systems were discussed. The scale of study ranged from massive river systems like the Yellow and Yangtze Rivers to small, man-made shallow lakes like Agmon in Israel. It was apparent from many of the presentations that the observations, models and conclusions from one type of system often inform the work of others in different media. Sediments are a link between our present and the past. Much of our understanding about past conditions in aquatic systems, including nutrient status, climatic conditions and contaminant history comes from our study of sediment cores. The accumulated knowledge of many disciplines is thus necessary to understand and manage aquatic systems. The sediment᎐water symposia are about interactions. While the interactions occurring in aquatic systems are the primary focus of these meetings, interactions among the participants are equally important. The opportunity for researchers and regulators from various disciplines and from different countries to come together and discuss new ideas is invaluable. Many of the most exciting presentations at future meetings will have started as a discussion among participants at this meeting. With the meeting being held in China, it was possible for many scientists from Asia to attend. This provided many of the attendees with their first opportunity to get a comprehensive view of science in China, Japan, Korea and Malaysia. The type and scale of issues concerning sediment᎐water interactions in these countries tends to be different than in Europe or the Americas. For example, the Three Gorges Project on the Yangtze River is the largest diversion project in the world. Erosion is a major problem in China.
A plenary presentation by Professor Lin highlighted the issues with respect to sediment movement and accumulation in the Yangtze and other major Chinese rivers. His presentation helped to focus the scientific community on the real issues of the Three Gorges Project, dispelling many of the myths about it presented in the popular press. The presence of the symposium in China was, therefore, particularly relevant at this important time. This symposium summary statement provides a brief summary of the key ideas and issues that arose during the symposium. Sediments are a driving force for many elemental cycles in aquatic systems and are recognized as one of the largest sources of in-place pollutants. It is hoped that the results of this symposium will offer new insights into the behavior and role of sediments in aquatic systems and will help to guide those with an interest in reducing sediment toxicity levels on local, regional or global scales, and will assist those concerned with the development of management strategies, policy and legislation that will enable this objective to be reached. Until these goals are reached, impacts from sediment contamination will continue to be a growing concern to the international environmental community, experts in science and industry, and government and private organizations. The presentations were organized into several theme areas, including the physical dynamics of sediment, nutrients and biota in sediments, chemical processes in sediments, and management, assessment and remediation. Within each general category, sub-themes were explored. Given the interdisciplinary nature of the field, the categorization of many presentations is difficult. For example, physical distribution models often find their relevance in prediction of changes in sediment chemistry. An understanding of sediment nutrient chemistry is indivisible from the management of sediments as sources of in-place nutrients. Thus, the work presented during the symposium should be viewed as a continuum, rather than several discrete areas of focus. A few of the highlights and significant developments presented in Beijing are discussed below.
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
1. Theme areas 1.1. Physical dynamics of sediment There were 38 platform talks and three posters presented as part of 12 separate sessions that dealt with sedimentrwater dynamics. The conference began with the plenary session on sediment dynamics in large Chinese rivers presented by Professor Lin mentioned above. The issues of erosion, transport of particles, deposition in lakes, bays and estuaries and the resuspension of deposited material were examined in several sessions. It is clear from several of the presentations that our ability to predict the movement and fate of particles is improving rapidly. However, many models remain sitespecific. Evidence suggests that factors such as age, organic content, and chemical composition affect the transportability of particles. Several authors have examined the transport of contaminated sediments. Sediment-bound contaminants clearly affect the behavior of particles. Thus, the development of a general-purpose model, applicable to a wide range of systems, still seems elusive. The deposition and resuspension of sediments remain key issues for both regulators and scientists. Several papers explored the use of natural or anthropogenic radionuclides as tracers of sediment particle movement. New techniques for measuring sediment accumulation, both locally via collectors and on a larger scale using mapping and remote measurement, were presented. Case studies from Denmark, Sweden, Brazil, China and Myanmar reminded us of the complexity of systems for which good predictive tools are required. The implications of sediment transport and resuspension for contaminant dispersion and release into the water column were the focus of several papers in both this theme and theme 3. This latter problem remains one of the most important issues concerning the role of sediments as in-place pollutants. 1.2. Nutrients and biota in sediments Thirty-six platform presentations and 9 posters dealt with aspects of nutrient cycles in lakes and
3
the role of biota in sediments. The role of sediments in nutrient cycles has been a recurrent theme in each of the past symposia. However, our predictive capabilities with respect to nutrient fluxes into and out of sediments remains poor. Several presentations reminded us of the importance of sediments as an internal source of nutrients in aquatic systems. In some lakes, sediments can be the major source of nutrients. The role of sediments as a source of nutrients in streams, rivers and coastal zones was the focus of several presentations. While we often think of these high-energy systems as relatively unaffected by nutrients from sediments, the evidence presented would argue otherwise. The roles of other chemicals, such as Si, organic carbon or sulfate in nutrient cycles were discussed in several papers. We were reminded that nutrient cycles are intimately interwoven with other biological and geochemical cycles. Processes such as diatom blooms, the reduction and release of soluble iron and the breakdown of organic matter all drive sediment᎐nutrient interactions. Several presentations dealt with the role of macrophytes in sediment and nutrient dynamics. Macrophytes can act as traps for fine particles, allowing deposition in areas that otherwise would be erosion zones. This changes the sediment distribution patterns and, ultimately, the nutrient dynamics. From a management perspective, it is critical that we develop models that allow us to predict the impact of sediment-bound nutrients. Plenary presentations by Drs Kumagai from Japan and Hakanson from Sweden illustrated this need ˚ nicely. Experiments to control cyanobacteria in Lake Biwa, Japan are likely to serve as a model for many lakes around the globe. Several papers discussed remediation techniques for sediments that contain high levels of nutrients. There appear to be clear limits to the usefulness of dredging techniques, and other control systems, like the capping or prevention of algal breakdown, appear more promising. The cycling of many substances in sediments is largely determined by the activity of organisms living in sediments. Microbiological processes are particularly important to nutrient cycles. Bacte-
4
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
rial activity affects sediment structure, mineralization and diagenesis. The subject area of bacterial activity has been under-represented in past symposia and it was gratifying to see the increased interest in this important area. 1.3. Chemical processes in sediments Thirty-two platform presentations and 9 posters examined the chemistry of sediments, issues of contaminants on particles and the role of sediments in the fate of anthropogenic substances. Two plenary presentations set the stage for this theme. Dr Bill Davison, from the UK, discussed problems in defining pore᎐water chemistry and some novel approaches to the solution of the problems, while Dr Graeme Batley, from Australia, talked about the issues of bioavailability of metals in sediments and the development of sediment quality guidelines. The use of tracers to follow geochemical cycles in sediments was demonstrated in several papers. Using 14 C as a tracer for carbon processing in sediments, one author showed that diffusion of inorganic carbon into the sediments seems to be quantitatively more important than breakdown of organic C in the sediments. This could have implications for global ocean bottom water 14 C budgets. Sediment deposits build through time incorporating materials from the water column and the atmosphere. At every symposium, several studies have examined the use of sediment core profiles of contaminants and other elements as recorders of change in atmospheric or catchment processes. Several presentations at this symposium examined the potential use of radiotracers such as 7 Be, 137 Cs and 226 Ra to measure sediment dynamics and accumulation in many systems. The use of stable C and N isotopes to measure benthic activity was the subject of several other papers. Sediments are a significant source of in-place pollutants and the potential remobilization of those pollutants was the theme of several studies. Several papers used partitioning studies to examine different fractions of pollutants, with the aim of predicting potential remobilization. It is clear from the range of systems discussed that
dynamics in sediment-laden and highly polluted rivers such as those found in China are very different than in the relatively particle-poor systems of Europe and North America. Several papers dealt with metal speciation changes or changes in redox chemistry. The extent to which these changes control contaminant cycling is at present unclear, but several papers highlighted the significant changes which can occur in the speciation of sediment-bound metals under changing conditions of redox. As noted after our previous meeting in Baveno, several methodological issues concerning metal speciation in sediments remain unresolved. The development of new analytical and experimental procedures should remain a priority for the sediment research community. 1.4. Management, assessment and remediation Given the problems of erosion and pollutants associated with sediments, it is not surprising that a significant part of the Beijing meeting was devoted to the discussion of means of assessment and remediation of impacted systems. Several of the 30 platform presentations and 12 posters given in this theme area were descriptions of models that could be used for management purposes. In general, these talks generated significant debate. In part, the debates centered on the issues of realism vs. predictability. It is clear that the management community is in need of good working tools immediately. The challenge is to ensure that the preliminary models presented are used in the full understanding of their limitations. Despite current limitations, the quality and number of efforts in this area was encouraging. The final area of discussion was that of remediation. Once we have a full understanding of the scope of sedimentary problems in a particular area, remediation is the final step. Several novel approaches to the remediation of sediments containing substances as diverse as petroleum product, butyltins, and nutrients were presented. While symposium attendees were pleased to see the work ongoing in this area, clearly we have need of much more research into remediation methods for in-place pollutants. It is to be hoped
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
that future symposium organizers make a special effort to encourage presentations in this area. There are still many parts of the globe for which we lack any basic information about aquatic systems. Sediments can be used as a means of obtaining information from remote regions quickly. Remote regions, apart from their intrinsic interest as unknowns, have a value as endmembers of geographical and concentration gradients. This symposium had several presentations on regions for which relatively little literature exists, particularly Asian sites. The benefits of studying these regions were apparent to all that attended the conference. In summary, there were many presentations, both poster and platform, which could be identified as highlights of the Seventh SedimentrWater
5
Interactions Symposium. There were many more papers submitted than it was possible to publish in this volume. However, those papers which are included provide a good representation of the complexity of issues confronting the sediment᎐water interactions community. The multidisciplinarity of the field is apparent, as is the numerous novel approaches that groups around the world are bringing to bear on the issues. From this brief review of the proceedings of the symposium, and the papers that follow, it should be apparent that the study of sedimentrwater interactions has many important insights to offer society for the management of aquatic resources. We look forward with anticipation to the next symposium in Canada in 2002.
Introduction
Interactions between sediments and water: summary of the Eighth International SymposiumR.D. Evans En¨ ironmental Sciences Centre, Trent Uni¨ ersity, Peterborough, ON Canada K9J 7B8
As the use of water resources becomes more intense, the need to have a better understanding of the factors that control water quality grows as well. Within any water system, the particulate phase, i.e. suspended particles and bottom deposits, plays a key role in geochemical and biological cycles. The interaction between sediments and water is one of the key determinants of water quality in a wide range of aquatic systems including rivers, lakes, estuaries and coastal areas. Recognition of the importance of sediment᎐water interactions has led to a greater understanding of the many physical, chemical and biological processes that ultimately limit our use of water resources. Because of this new understanding, there has been an increased number of sedimentrwater related research and assessment projects, as well as a renewed awareness in the regulatoryrpolicy arena. Furthermore, this interest has led to a series of international symposiums that are used as a platform for the international community to present and publish their latest findings and results. The international symposium on ‘The Interactions Between Sediments and Water’, held in Beijing, China during the 13᎐17 September 1999,
was the eighth in a series held since 1976, all focusing on issues related to processes occurring at the sediment᎐water interface and responses to interactions between sediments and water. Previous symposiums were held in Amsterdam in 1976, Kingston in 1982, Geneva in 1984, Melbourne in 1986, Uppsala in 1990, Santa Barbara in 1993, Baveno in 1996 and the current one in Beijing. The next symposium will be held in Banff, Canada in the spring of 2002. Interest in the role of sediments in freshwater and marine ecosystems is evidenced by the number of participants worldwide attending each symposium; Six plenary presentations, approximately 135 oral presentations and approximately 35 poster presentations were made by attendees representing 27 nations. Particularly gratifying at this conference was the presence of many participants from Asian countries. The scientific sessions in Beijing were organized around the following themes: physical dynamics of sediment, nutrients and biota in sediments, chemical processes in sediments, and management, assessment and remediation. The sediment᎐water symposia bring together scientists and regulators with a diversity of back-
0048-9697r01r$ - see front matter 䊚 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 0 . 0 0 8 3 7 - 8
2
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
grounds. The focus on ‘interactions’ demands a level of interdisciplinarity not found in many other fields. Sediment models require field studies for validation. Particle dynamics affect chemical partitioning between pollutants and particles. As a result, the eighth symposium presented a spectrum of work covering many fields of study that impact on sediment᎐water interactions. Marine, estuarine and freshwater studies were all well represented. Both pristine and highly impacted systems were discussed. The scale of study ranged from massive river systems like the Yellow and Yangtze Rivers to small, man-made shallow lakes like Agmon in Israel. It was apparent from many of the presentations that the observations, models and conclusions from one type of system often inform the work of others in different media. Sediments are a link between our present and the past. Much of our understanding about past conditions in aquatic systems, including nutrient status, climatic conditions and contaminant history comes from our study of sediment cores. The accumulated knowledge of many disciplines is thus necessary to understand and manage aquatic systems. The sediment᎐water symposia are about interactions. While the interactions occurring in aquatic systems are the primary focus of these meetings, interactions among the participants are equally important. The opportunity for researchers and regulators from various disciplines and from different countries to come together and discuss new ideas is invaluable. Many of the most exciting presentations at future meetings will have started as a discussion among participants at this meeting. With the meeting being held in China, it was possible for many scientists from Asia to attend. This provided many of the attendees with their first opportunity to get a comprehensive view of science in China, Japan, Korea and Malaysia. The type and scale of issues concerning sediment᎐water interactions in these countries tends to be different than in Europe or the Americas. For example, the Three Gorges Project on the Yangtze River is the largest diversion project in the world. Erosion is a major problem in China.
A plenary presentation by Professor Lin highlighted the issues with respect to sediment movement and accumulation in the Yangtze and other major Chinese rivers. His presentation helped to focus the scientific community on the real issues of the Three Gorges Project, dispelling many of the myths about it presented in the popular press. The presence of the symposium in China was, therefore, particularly relevant at this important time. This symposium summary statement provides a brief summary of the key ideas and issues that arose during the symposium. Sediments are a driving force for many elemental cycles in aquatic systems and are recognized as one of the largest sources of in-place pollutants. It is hoped that the results of this symposium will offer new insights into the behavior and role of sediments in aquatic systems and will help to guide those with an interest in reducing sediment toxicity levels on local, regional or global scales, and will assist those concerned with the development of management strategies, policy and legislation that will enable this objective to be reached. Until these goals are reached, impacts from sediment contamination will continue to be a growing concern to the international environmental community, experts in science and industry, and government and private organizations. The presentations were organized into several theme areas, including the physical dynamics of sediment, nutrients and biota in sediments, chemical processes in sediments, and management, assessment and remediation. Within each general category, sub-themes were explored. Given the interdisciplinary nature of the field, the categorization of many presentations is difficult. For example, physical distribution models often find their relevance in prediction of changes in sediment chemistry. An understanding of sediment nutrient chemistry is indivisible from the management of sediments as sources of in-place nutrients. Thus, the work presented during the symposium should be viewed as a continuum, rather than several discrete areas of focus. A few of the highlights and significant developments presented in Beijing are discussed below.
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
1. Theme areas 1.1. Physical dynamics of sediment There were 38 platform talks and three posters presented as part of 12 separate sessions that dealt with sedimentrwater dynamics. The conference began with the plenary session on sediment dynamics in large Chinese rivers presented by Professor Lin mentioned above. The issues of erosion, transport of particles, deposition in lakes, bays and estuaries and the resuspension of deposited material were examined in several sessions. It is clear from several of the presentations that our ability to predict the movement and fate of particles is improving rapidly. However, many models remain sitespecific. Evidence suggests that factors such as age, organic content, and chemical composition affect the transportability of particles. Several authors have examined the transport of contaminated sediments. Sediment-bound contaminants clearly affect the behavior of particles. Thus, the development of a general-purpose model, applicable to a wide range of systems, still seems elusive. The deposition and resuspension of sediments remain key issues for both regulators and scientists. Several papers explored the use of natural or anthropogenic radionuclides as tracers of sediment particle movement. New techniques for measuring sediment accumulation, both locally via collectors and on a larger scale using mapping and remote measurement, were presented. Case studies from Denmark, Sweden, Brazil, China and Myanmar reminded us of the complexity of systems for which good predictive tools are required. The implications of sediment transport and resuspension for contaminant dispersion and release into the water column were the focus of several papers in both this theme and theme 3. This latter problem remains one of the most important issues concerning the role of sediments as in-place pollutants. 1.2. Nutrients and biota in sediments Thirty-six platform presentations and 9 posters dealt with aspects of nutrient cycles in lakes and
3
the role of biota in sediments. The role of sediments in nutrient cycles has been a recurrent theme in each of the past symposia. However, our predictive capabilities with respect to nutrient fluxes into and out of sediments remains poor. Several presentations reminded us of the importance of sediments as an internal source of nutrients in aquatic systems. In some lakes, sediments can be the major source of nutrients. The role of sediments as a source of nutrients in streams, rivers and coastal zones was the focus of several presentations. While we often think of these high-energy systems as relatively unaffected by nutrients from sediments, the evidence presented would argue otherwise. The roles of other chemicals, such as Si, organic carbon or sulfate in nutrient cycles were discussed in several papers. We were reminded that nutrient cycles are intimately interwoven with other biological and geochemical cycles. Processes such as diatom blooms, the reduction and release of soluble iron and the breakdown of organic matter all drive sediment᎐nutrient interactions. Several presentations dealt with the role of macrophytes in sediment and nutrient dynamics. Macrophytes can act as traps for fine particles, allowing deposition in areas that otherwise would be erosion zones. This changes the sediment distribution patterns and, ultimately, the nutrient dynamics. From a management perspective, it is critical that we develop models that allow us to predict the impact of sediment-bound nutrients. Plenary presentations by Drs Kumagai from Japan and Hakanson from Sweden illustrated this need ˚ nicely. Experiments to control cyanobacteria in Lake Biwa, Japan are likely to serve as a model for many lakes around the globe. Several papers discussed remediation techniques for sediments that contain high levels of nutrients. There appear to be clear limits to the usefulness of dredging techniques, and other control systems, like the capping or prevention of algal breakdown, appear more promising. The cycling of many substances in sediments is largely determined by the activity of organisms living in sediments. Microbiological processes are particularly important to nutrient cycles. Bacte-
4
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
rial activity affects sediment structure, mineralization and diagenesis. The subject area of bacterial activity has been under-represented in past symposia and it was gratifying to see the increased interest in this important area. 1.3. Chemical processes in sediments Thirty-two platform presentations and 9 posters examined the chemistry of sediments, issues of contaminants on particles and the role of sediments in the fate of anthropogenic substances. Two plenary presentations set the stage for this theme. Dr Bill Davison, from the UK, discussed problems in defining pore᎐water chemistry and some novel approaches to the solution of the problems, while Dr Graeme Batley, from Australia, talked about the issues of bioavailability of metals in sediments and the development of sediment quality guidelines. The use of tracers to follow geochemical cycles in sediments was demonstrated in several papers. Using 14 C as a tracer for carbon processing in sediments, one author showed that diffusion of inorganic carbon into the sediments seems to be quantitatively more important than breakdown of organic C in the sediments. This could have implications for global ocean bottom water 14 C budgets. Sediment deposits build through time incorporating materials from the water column and the atmosphere. At every symposium, several studies have examined the use of sediment core profiles of contaminants and other elements as recorders of change in atmospheric or catchment processes. Several presentations at this symposium examined the potential use of radiotracers such as 7 Be, 137 Cs and 226 Ra to measure sediment dynamics and accumulation in many systems. The use of stable C and N isotopes to measure benthic activity was the subject of several other papers. Sediments are a significant source of in-place pollutants and the potential remobilization of those pollutants was the theme of several studies. Several papers used partitioning studies to examine different fractions of pollutants, with the aim of predicting potential remobilization. It is clear from the range of systems discussed that
dynamics in sediment-laden and highly polluted rivers such as those found in China are very different than in the relatively particle-poor systems of Europe and North America. Several papers dealt with metal speciation changes or changes in redox chemistry. The extent to which these changes control contaminant cycling is at present unclear, but several papers highlighted the significant changes which can occur in the speciation of sediment-bound metals under changing conditions of redox. As noted after our previous meeting in Baveno, several methodological issues concerning metal speciation in sediments remain unresolved. The development of new analytical and experimental procedures should remain a priority for the sediment research community. 1.4. Management, assessment and remediation Given the problems of erosion and pollutants associated with sediments, it is not surprising that a significant part of the Beijing meeting was devoted to the discussion of means of assessment and remediation of impacted systems. Several of the 30 platform presentations and 12 posters given in this theme area were descriptions of models that could be used for management purposes. In general, these talks generated significant debate. In part, the debates centered on the issues of realism vs. predictability. It is clear that the management community is in need of good working tools immediately. The challenge is to ensure that the preliminary models presented are used in the full understanding of their limitations. Despite current limitations, the quality and number of efforts in this area was encouraging. The final area of discussion was that of remediation. Once we have a full understanding of the scope of sedimentary problems in a particular area, remediation is the final step. Several novel approaches to the remediation of sediments containing substances as diverse as petroleum product, butyltins, and nutrients were presented. While symposium attendees were pleased to see the work ongoing in this area, clearly we have need of much more research into remediation methods for in-place pollutants. It is to be hoped
R.D. E¨ ans r The Science of the Total En¨ ironment 266 (2001) 1᎐5
that future symposium organizers make a special effort to encourage presentations in this area. There are still many parts of the globe for which we lack any basic information about aquatic systems. Sediments can be used as a means of obtaining information from remote regions quickly. Remote regions, apart from their intrinsic interest as unknowns, have a value as endmembers of geographical and concentration gradients. This symposium had several presentations on regions for which relatively little literature exists, particularly Asian sites. The benefits of studying these regions were apparent to all that attended the conference. In summary, there were many presentations, both poster and platform, which could be identified as highlights of the Seventh SedimentrWater
5
Interactions Symposium. There were many more papers submitted than it was possible to publish in this volume. However, those papers which are included provide a good representation of the complexity of issues confronting the sediment᎐water interactions community. The multidisciplinarity of the field is apparent, as is the numerous novel approaches that groups around the world are bringing to bear on the issues. From this brief review of the proceedings of the symposium, and the papers that follow, it should be apparent that the study of sedimentrwater interactions has many important insights to offer society for the management of aquatic resources. We look forward with anticipation to the next symposium in Canada in 2002.