Environmental interfaces

From this general description of the Earth s solid-fluid-gaseous envelope, it is apparent that reactions governing the chemistry of the environment are dominated by those at environmental interfaces. The importance of such reactions is well summarized in a 1987 quotation from the late Werner Stumm [3] Almost all of the problems associated with understanding the processes that control the composition of our environment concern interfaces, above all the interfaces of water with naturally occurring solids. ... 

This example illustrates the qualitative nature of information that can be gleaned from macroscopic uptake studies. Consideration of adsorption isotherms alone cannot provide mechanistic information about sorption reactions because such isotherms can be fit equally well with a variety of surface complexation models assuming different reaction stoichiometries. More quantitative, molecular-scale information about such reactions is needed if we are to develop a fundamental understanding of molecular processes at environmental interfaces. Over the past 20 years in situ XAFS spectroscopy studies have provided quantitative information on the products of sorption reactions at metal oxide-aqueous solution interfaces (e.g., [39,40,129-138]. One... 

Cu(0H)°), (Cu0H , Cu (OH) " ), (Cu(OH)", Cu(OH) ") and a detennin-ation of the relative toxicity of these species. Underlying these statements is the assumption that the mechanism of interaction of copper at the environmental interface remains the same over this pH range. 

Al-Abadleh HA, Grassian VH (2003). Oxide surfaces as environmental interfaces. Surf Sci Rep, 52, 63... 

Below, we discuss examples of chemical reactions at environmental interfaces studied by SR methods. We start with a brief discussion of SR studies of relatively simple model systems, such as MgO-H20 and AI2O3-H2O, continue with a brief discussion of the structure and properties of water at solid/water interfaces, and progress to more complex interfacial systems, including those with microbial biofilms present. 

Satish . B. Myneni (PhD, Ohio State University) is an Assistant Professor in the Department of Geosciences at Princeton University and is also affiliated with the Departments of Chemistry and Civil and Environmental Engineering. He conducts his research activities at the Lawrence Berkeley National Laboratory where he is a Faculty Scientist. He earlier worked in the Berkeley Lab as a post-doctoral researcher and as Geological Scientist and developed soft X-ray spectroscopy and spectromicroscopy methods for examining light elements in aqueous solutions and on surfaces. His research interests are to explore ion solvation and complexation, and the chemistry of natural organic molecules at environmental interfaces. 

FIGURE 75.2 A summary of the major constructs of the Elemental Resource Model, emphasizing the categorization of performance resources at the basic element level into four life-sustaining, environmental interface, central processing, and information domains. 

Performance resource (PR) One of a pool of elemental resources, from which the entire human is modelled (Kondraske, 1995b), and which is available for performing tasks. These resources can be subdivided into life sustaining, environmental interface, central processing, and skills domains, and have a parallel with basic elements of performances. 

X-ray absorption fine structure spectroscopy has become one of the key molecular-scale methods in studies of reactions mechanisms of aqueous cations and anions at environmental interfaces. 

The focus in designing a fuel-cell power system is to develop and optimize the system configuration to meet the specifications of its intended appHcation. These specifications could include the following fuel specification, duty cycle, cost (purchase and installation), cycle efficiency, reliability, maintenance, size and weight, environmental interfaces, cogeneration, acoustic noise, power quaUty, and safety. 

The reaction mechanism of aluminum oxidation is summarized by Macdonald [50] as a reasonable model. The oxides grow as bilayer structures with an inner layer due to movement of oxygen vacancies from metal/ film interface and an outer layer due to the movement of cations outward from the film/environmental interface. The vacancy concentrations vary exponentially with distance. The cathode consumes electrons by evoloving hydrogen and reducing oxygen. Barrier layer grows into metal phase via reaction... 

HA is the systematic examination of a system, item, or product within its life cycle, to identify hazardous conditions including those associated with human, product, and environmental interfaces, and to assess their consequences to the functional and safety characteristics of the system or product. In order to design-in safety, hazards must be designed-out (eliminated) or mitigated (reduced in risk), which can only be accomplished through HA. Hazard identification is a critical system safety function and is one of the basic required elements of an SSP. 

F. M. Geiger, A . Rev. Phys. Chem., 60,61 (2009). Second Harmonic Generation, Sum Frequency Generation, and Dissecting Environmental Interfaces with a Nonlinear Optical Swiss Army Knife. 

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