Aquatic sinks

Kinetics Considerations. Kinetics concepts and data concerning halocarbon sources and sinks can be used for a variety of purposes. For example, such information is required in mathematical models to evaluate the fate and exposure concentrations of low-volatility toxic organohalogens in water (18, 19). Moreover, kinetics relationships and data concerning physical, chemical, and biological processes are needed to predictively model aquatic sinks of volatile halocarbons (11). 

Aquatic Sinks for Methylchloroform. Methylchloroform distributions in the troposphere have been used to estimate the concentrations of tropospheric hydroxyl radicals (65). The estimates assume that reaction with tropospheric OH radicals is the dominant sink. Aquatic sinks have been ignored. Wine and Chameides (66), however, presented model computations that indicated that hydrolysis and reaction with solvated electrons may be a significant sink for methylchloroform and other halocarbons in the open ocean. 

There is a further complication in shallow lakes containing macrophytes (aquatic flowering plants, pteridophytes, and macroalgae). These take up and accumulate nutrients from the water and from the aquatic soil in which they are rooted (sediment). Although these plants are sometimes classed as nuisance weeds, they nevertheless act as an important alternative sink for nutrients which are denied to the plankton. In recent times, a key role of macrophytes in the successful and sustained management of water quality has been identified and explained. ... 

Sediment Analysis. Sediment is the most chemically and biologically active component of the aquatic environment. Benthic invertebrate and microbial life concentrate in the sediment, a natural sink for precipitated metal forms, and an excellent sorbent for many metal species. TTie extent to which potentially toxic trace element forms bind to sediment is determined by the sediment s binding intensity and capacity and various solution parameters, as well as the concentration and nature of the metal forms of interest. Under some conditions sediment analyses can readily indicate sources of discharged trace elements. 

Sediments are important compartments for many organic contaminants in the aquatic environment, in particular for hydrophobic POPs such as PAHs and PCBs. Sediments have been recognised as important sinks for these compounds but with the reduction in levels of them in water, the question arises of whether the older highly contaminated sediments will function in the future as secondary sources of the compounds or whether burial by recent, cleaner sediment will prevent exchange with the water phase. This will depend on the strength of turbulence/bioturbation and on anthropogenic influences such as dredging. 

A new direction in searching for the atmospheric CO2 sink considering the joint action of carbonate dissolution, global water cycle and the photosynthetic uptake of die by aquatic organisms... 

ABSTRACT The locations, magnitudes, variations and mechanisms responsible for the atmospheric C02 sink are uncertain and under debate. Previous studies concentrated mainly on oceans, and soil and terrestrial vegetation as sinks. Here, we show that there is an important C02 sink in carbonate dissolution, the global water cycle and photosynthetic uptake of DIC by aquatic ecosystems. The sink constitutes up to 0.82 Pg C/a 0.24 Pg C/a is delivered to oceans via rivers and 0.22 Pg C/a by meteoric precipitation, 0.12 Pg C/a is returned to the atmosphere, and 0.23 Pg C/a is stored in the continental aquatic ecosystem. The net sink could be as much as 0.70 Pg C/a, may increase with intensification of the global water cycle, increase in C02 and carbonate dust in atmosphere, reforestation/afforestation, and with fertilization of aquatic ecosystems. Under the projection of global warming for the year 2100, it is estimated that this C02 sink may increase by 22%, or about 0.18 Pg c/a. 

KEYWORDS atmospheric CO2 Sink, carbonate dissolution, global water cycle, aquatic photosynthesis, organic matter storage/burial... 

Previous studies addressed oceans and terrestrial vegetation as C02 sinks. Here, we describe an important C02 sink in carbonate dissolution, the global water cycle (GWC), and uptake of dissolved inorganic carbon (DIC) by aquatic. The sink is larger than previous estimates (Meybeck 1993 Gombert 2002). 

This sink, a negative climate feedback mechanism, may increase with the global-warming-intensified GWC, the increase in C02 and carbonate dust in atmosphere, reforestation/afforestation, and fertilization of the aquatic ecosystems. Using the global warming projection for the year 2100 by IPCC, it is estimated that the C02 sink by the GWC will increase by 22%, or 0.18 Pg c/a. 

This paper presents an estimate of the C02 sink by carbonate dissolution, GWC and photosynthetic uptake of DIC by aquatic ecosystems, and suggests a new direction in balancing the global C budget. 

Liu et al. (2008) for the current global flux of 0.13 Pg C yr1 to the continental aquatic ecosystem. In effect, based on the above estimates, the flux of C to groundwater could account for 2% to 12% of the missing carbon sink in the global carbon budget. 

Mirex has been detected in air, surface water, soil and sediment, aquatic organisms, and foodstuffs. Historically, mirex was released to the environment primarily during its production or formulation for use as a fire retardant and as a pesticide. There are no known natural sources of mirex and production of the compound was terminated in 1976. Currently, hazardous waste disposal sites and contaminated sediment sinks in Lake Ontario are the major sources for mirex releases to the environment (Brower and Ramkrishnadas 1982 Comba et al. 1993). 

Philpot, R.M. et al. in "Sources, Effects and Sinks of Hydrocarbons in the Aquatic Environment" American Institute of Biological Sciences, 576 p., Washington, D.C., 1976. 

Our questions broadened to consider how the transport and metabolic capabilities of these aquatic species compare with those of mammalian species. One reason for asking such a question is to assess whether the presence or absence of these capabilities alters the ability of fish to survive in toxic environments. Survival mechanisms fall into two catagories - behavioral and physiologic. An example of a behavioral mechanism could be as simple as a fish avoiding that area of a stream which contains toxic quantitites of phenol. When external perturbations caused by pollutants are small, homeostatic mechanisms such as those of the liver and kidney, allow fish to adapt to the body of water in which they exist. The problem then is related to defining the limits to which homeostatic phenomena can be stressed in aquatic species. An important reason to establish such information in fish is that bodies of water are the "ultimate sink" for a number of pollutants (12). Thus, while a behavioral response such as removing itself from a toxic environment is invariably available to a mammalian species, this type of response is impossible for a fish if a toxic xenobiotic occurs uniformly throughout an entire body of water. 

The marine environment acts as a sink for a large proportion of polyaromatic hydrocarbons (PAH) and these compounds have become a major area of interest in aquatic toxicology. Mixed function oxidases (MFO) are a class of microsomal enzymes involved in oxidative transformation, the primary biochemical process in hydrocarbon detoxification as well as mutagen-carcinogen activation (1,2). The reactions carried out by these enzymes are mediated by multiple forms of cytochrome P-450 which controls the substrate specificity of the system (3). One class of MFO, the aromatic hydrocarbon hydroxylases (AHH), has received considerable attention in relation to their role in hydrocarbon hydroxylation. AHH are found in various species of fish (4) and although limited data is available it appears that these enzymes may be present in a variety of aquatic animals (5,6,7,8). 

The anomalous density behavior of water has important consequences for the survival of aquatic organisms at mid-latitudes. As winter approaches, the surface waters of ponds and lakes cool. The ensuing increase in density causes this water to sink to the bottom of the water body. This process continues until water temperatures drop... 

Wetlands are intermediate between upland systems and true aquatic systems, both in terms of their hydrologies, being intermittently to permanently flooded, and in terms of their biogeochemistries, being sources, sinks and transformers of... 

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