This book is a natural extension of the SCOPE (Scientific Committee of Problems on the Environment) volumes on the carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) biogeochemical cycles and their interactions (Likens, 1981; Bolin and Cook, 1983). Substantial progress in the knowledge of these cycles has been made since publication of those volumes. In particular, the nature and extent of biological and inorganic interactions between these cycles have been identified, positive and negative feedbacks recognized and the relationship between the cycles and global environmental change preliminarily elucidated. In March 1991, a NATO Advanced Research Workshop was held for one week in Melreux, Belgium to reexamine the biogeochemical cycles of C, N, P and S on a variety of time and space scales from a holistic point of view. This book is the result of that workshop. The biogeochemical cycles of C, N, P and S are intimately tied to each other through biological productivity and subsequently to problems of global environmental change. These problems may be the most challenging facing humanity in the 21 st century. In the broadest sense, "global change" encompasses both changes to the status of the large, globally connected atmospheric, oceanic and terrestrial environments (e. g. tropospheric temperature increase) and change occurring as the result of nearly simultaneous local changes in many regions of the world (e. g. eutrophication).

Understanding the ebb and flow of materials on the earth's surface is vital to comprehending environmental change. We need to differentiate between those that represent a progression of natural events from those that might be human induced. The latter can be managed by changing policies; the former probably cannot. This volume presents what researchers know and do not know about the base (or natural) level of surficial fluxes and their dynamics. Leading experts in the field offer a historical perspective on geofluxes and discuss the cycles of materials on the earth's surface, from weathering processes to the movement of material through the river system and oceans to their deposition. The committee sets research directions in five areas: shallow-water studies, mapping, rates of change, sample dating, andâ€"most criticalâ€"understanding whether human influence can exceed the natural variability in geoflux processes. This volume will be important reading for geophysical scientists, researchers, faculty, and students, as well as environmental policymakers.

The flux, preservation, and accumulation of organic carbon in marine systems are controlled by various mechanisms including primary p- duction of the surface water, supply of terrigenous organic matter from the surrounding continents, biogeochemical processes in the water column and at the seafloor, and sedimentation rate. For the world's oceans, phytoplankton productivity is by far the largest organic carbon 9 source, estimated to be about 30 to 50 Gt (10 tonnes) per year (Berger et al. 1989; Hedges and Keil 1995). By comparison, rivers contribute -1 about 0. 15 to 0. 23 Gt y of particulate organi.

A comprehensive account of the state of the science of environmental mass transportEdited by Louis J. Thibodeaux and Donald Mackay, renowned experts in this field, the Handbook of Chemical Mass Transport in the Environment covers those processes which are critically important for assessing chemical fate, exposure, and risk. In a comprehensive and a