Aquatic systems estuaries

Changes in all downstream aquatic systems (incl. wetlands, lakes, estuaries, sea deltas)... 

We hypothesized that the input of terrestrial organic matter relative to the input of autochthonous carbon would be a good predictor of the relative importance of heterotrophic organic N formation in different aquatic systems. Following a flow path from streams to lakes to rivers to estuaries to oceans, this hypothesis would suggest that microbial organic N formation would be highest in wooded streams and rivers, moderate in lakes and estuaries, and lowest in open-water marine systems. 

Acyclic ketones, such as linear alkane-2-ones, are another class of lipids commonly found in aquatic systems (Volkman et al., 1983 Hernandez et al., 2001 Jaffe et al., 2001). Hernandez et al. (2001) found a shift in the alkane-2-one distribution from C27 to C31 in the upper estuary to C25 in the lower estuary and attributed these changes to tidal changes in the delivery of seagrass detritus. Another acyclic ketone recently found in estuarine sediments is 6,10,14-trimethylpentadecane-2-one, believed to be a decay product of phytol, which may be indicative of mangrove inputs (Jaffe et al., 2001). 

Phosphorus Cycling in Terrestrial Aquatic Systems Lakes, Rivers, and Estuaries... 

By no means is this book intended to provide a detailed account of all progress made in the past 25 years by aquatic chemists. Rather, chapters provide examples of recent developments in the field and contribute toward a better understanding of the mechanisms regulating the chemical composition of natural waters. Also, the transformation and transport of species (abiotic and biotic or soluble and insoluble) in aquatic systems (lakes, rivers, estuaries,... 

Several possible mechanisms are available for UV-induced photoreactions of iron complexes. First, direct photoreactions involving ligand-to-metal charge transfer are likely to be one of the most important mechanisms for photoreaction [117,198,224]. Second, iron complexes can be reduced by photochemically-produced superoxide [207-209]. Superoxide ions are formed via the photoreduction of molecular oxygen by CDOM and it is one of the most concentrated radicals in seawater and is the precursor to hydrogen peroxide [Chapter 8]. Superoxide-induced reduction of Fe(iii) is an important mechanism in certain lakes [207]. However, the fact that Fe(ii) photoproduction can be more rapid in oxygen-free water than in air-saturated water in acidic estuaries [59] or model systems with well-defined organic acid complexes of Fe(iii) [117] indicates that direct photolysis of Fe(iii) is likely to be a dominant mechanism for Fe(ii) photoproduction in many aquatic systems. 

There is extensive evidence from freshwaters, estuaries, and the oceans that the surface properties, colloidal stability, and the kinetics of aggregation reactions in natural waters are affected by naturally occurring organic substances dissolved in these waters. These effects of natural organic substances in establishing colloidal stability in aquatic systems are anticipated to occur in subsurface environments and to affect the kinetics of particle and pollutant passage and retention in subsurface systems. The kinetics, extent, and significance of... 

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