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This book provides a detailed examination of the concentration, form and cycling of trace metals and metalloids through the aquatic biosphere, and has sections dealing with the atmosphere, the ocean, lakes and rivers. It discusses exchanges at the water interface (air/water and sediment/water) and the major drivers of the cycling, concentration and form of trace metals in aquatic systems. The initial chapters focus on the fundamental principles and modelling approaches needed to understand metal concentration, speciation and fate in the aquatic environment, while the later chapters focus on specific environments, with case studies and research highlights. Specific examples deal with metals that are of particular scientific interest, such as mercury, iron, arsenic and zinc, and the book deals with both pollutant and required (nutrient) metals and metalloids. The underlying chemical principles controlling toxicity and bioavailability of these elements to microorganisms and to the aquatic food chain are also discussed. Readership: Graduate students studying environmental chemistry and related topics, as well as scientists and managers interested in the cycling of trace substances in aqueous systems Additional resources for this book can be found at: www.wiley.com/go/mason/tracemetals.
This book presents an intensive study on the biogeochemical cycle of mercury in a river-reservoir system in Wujiang River Basin, the upper branch of the Yangtze River. Six reservoirs located in the mainstream of the Wujiang River and their corresponding inflow/outflow rivers were selected for inclusion in this study, which was conducted by researchers from the Institute of Geochemistry, Chinese Academy of Sciences. The concentration and distribution of Hg in reservoirs (the water column, sediment, sediment pore water), inflow/outflow rivers of reservoirs, and wet deposition in Wujiang River Basin were systematically investigated, and measurements were taken of the water/air exchange flux of gaseous elemental mercury (GEM). On the basis of the data gathered, a detailed mass balance of total mercury (THg) and methylmercury (MeHg) in the six reservoirs was developed. In addition, the book identifies the primary factors controlling Hg methylation in the river-reservoir system in Wujiang River Basin. The accumulation and bio-magnification of Hg species within food chains in reservoirs and human health risk of MeHg exposure through fish consumption are also included in this book.
This book provides a detailed examination of the concentration, form and cycling of trace metals and metalloids through the aquatic biosphere, and has sections dealing with the atmosphere, the ocean, lakes and rivers. It discusses exchanges at the water interface (air/water and sediment/water) and the major drivers of the cycling, concentration and form of trace metals in aquatic systems. The initial chapters focus on the fundamental principles and modelling approaches needed to understand metal concentration, speciation and fate in the aquatic environment, while the later chapters focus on specific environments, with case studies and research highlights. Specific examples deal with metals that are of particular scientific interest, such as mercury, iron, arsenic and zinc, and the book deals with both pollutant and required (nutrient) metals and metalloids. The underlying chemical principles controlling toxicity and bioavailability of these elements to microorganisms and to the aquatic food chain are also discussed. Readership: Graduate students studying environmental chemistry and related topics, as well as scientists and managers interested in the cycling of trace substances in aqueous systems Additional resources for this book can be found at: www.wiley.com/go/mason/tracemetals.
Mercury pollution poses global human health and environmental risks. Although mercury is naturally present in the environment, human activities, such as coal burning, have increased the amount of mercury cycling among the land, atmosphere, and ocean by a factor of three to five. Emitted to the atmosphere in its elemental form, mercury travels worldwide before oxidizing to a form that deposits to ecosystems. In aquatic systems, mercury can convert into methylmercury, a potent neurotoxin. People and wildlife are exposed to methylmercury as it bioaccumulates up the food chain. Mercury continues to circulate in the atmosphere, oceans, and terrestrial system for centuries to millennia before it returns to deep-ocean sediments. Areas of uncertainty in the global biogeochemical cycle of mercury include oxidation processes in the atmosphere, land-atmosphere and ocean-atmosphere cycling, and methylation processes in the ocean. National and international policies have addressed direct mercury emissions, but further efforts to reduce risks face numerous political and technical challenges.
Nowadays, major environmental issues are the object of large public debates de spite the fact that scientific knowledge is often insufficient to draw unequivocal conclusions. Such is the case in the ongoing debate regarding the specific contri butions of anthropogenic greenhouse gas emissions and of natural climate changes to global warming. At least 10 to 20 years of additional observations will be re quired, before we will be able to conclude, with certainty, on this subject. In the mean time, and as directed by their immediate interests, people will continue to promote contradictory opinions. The media are, in part, responsible for perpetuat ing such debates in that they convey indiscriminately the opinion of highly credi ble scientists as that of dogmatic researchers, the latter, unfortunately too often expressing working hypotheses as established facts. Naturally, in a similarly mis informed manner, pressure groups tend to support the researcher whose opinions most closely represent either their particular ideological battles or their economic interests and, hence, in their own way, add further to the confusion and obscurity of the debate. Only a few years ago, mercury (Hg)contamination in hydroelectric reservoirs was the object of such media and social biases. At the time, analytical data used to support the discourse were themselves uncertain and numerous hypotheses, often times fanciful, were proposed and hastily "delivered" to the public.
Essential themes in the biochemical cycling of mercury are the relative importance of anthropogenic versus natural sources, transformation and migration processes at the local, regional and global scale, global emission inventories of different mercury sources (both point and diffuse) of both natural and anthropogenic origin. In this regard, Siberia, with its vast territory and variety of natural zones, is of special interest in the global mercury cycle and in terms of the influence of geographical zones on source and sink terms in regional budgets. Siberia contains large areas of mercuriferous belts; natural deposits that emit mercury into the atmosphere and water. Siberian gold has been mined with the use of mercury since the early 1800s. But there, too, huge forest zones and vast areas of tundra and wetland (bogs) can act as efficient sinks for atmospheric mercury. Audience: Environmental scientists, legislators, politicians and the interested citizen wishing to gain a clear picture of the biogeochemical cycling of mercury.