Water pollution aquatic systems

This book covers the basics of bioremediation. Topics Include treatment of soil, ground water, and aquatic systems design and use of bioreactors adapted cultures and genetically-engineered microbes major classes of chemical pollutants and detailed analysis of the Exxon-Valdez cleanup. 

Counterexamples teach a lesson that these exaggerations of aquatic biological activity are highly idiosyncratic and depend on the fluxes of nutrients, the types of phytoplankton ecosystems that are involved, and - most importantly - the local and regional circulations of the aquatic system. For example, the Mediterranean Sea is landlocked and has many large pollution sources, but the large flux of nutrient-poor ("impoverished") water from the Atlantic... 

Kelly CA, Rudd JWM, St. Louis VL, Heyes A. 1995. Is total mercury concentration a good predictor of methylmercury concentration in aquatic systems Water Air Soil Pollut 80 715-724. 

Allard, B. and I. Arsenie. 1991. Abiotic reduction of mercury by humic substances in aquatic system — an important process for the mercury cycle. Water Air Soil Pollut. 56 457-464. 

The adsorption of ions on iron oxides regulates the mobility of species in various parts of the ecosystem (biota, soils, rivers, lakes, oceans) and thereby their transport betv een these parts. Examples are the uptake of plant nutrients from soil and the movement of pesticides and other pollutants from soils into aquatic systems. In such environments various ions often compete with each other for adsorption sites. Adsorption is the essential precursor of metal substitution (see Chap. 3), dissolution reactions (see Chap. 12) and many interconversions (see Chap. 14). It also has a role in the synthesis of iron oxides and in crystal growth. In industry, adsorption on iron oxides is of relevance to flotation processes, water pollution control and waste and anticorrosion treatments. 

The problem of toxic pollutants is difficult to handle because of the great variety of chemicals involved. They represent a hazard not only to aquatic life, but also to human health, either through direct exposure or indirectly through consumption of contaminated fish or waterfowl. The degree of hazard depends on the pollutanf s toxicity, rate of discharge, persistence and distribution in the aquatic system, and bioaccumulation potential. Some highly volatile compounds, when discharged into water, evaporate and become air pollutants. 

Other plants such as potatoes, cauliflower, cherries, and soybeans and several fungi may also be used as sources of peroxidase enzymes. Soybeans, in particular, may represent a valuable source of peroxidase because the enzyme is found in the seed coat, which is a waste product from soybean-based industries [90]. In this case, it may be possible to use the solid waste from the soybean industry to treat the wastewaters of various chemical industries. In fact, the direct use of raw soybean hulls to accomplish the removal of phenol and 2-chlorophenol has been demonstrated [105]. However, it should be noted that this type of approach would result in an increase in the amount of solid residues that must be disposed following treatment. Peroxidases extracted from tomato and water hyacinth plants were also used to polymerize phenolic substrates [106], Actual plant roots were also used for in vivo experiments of pollutant removal. The peroxidases studied accomplished good removal of the test substrate guaiacol and the plant roots precipitated the phenolic pollutants at the roots surface. It was suggested that plant roots be used as natural immobilized enzyme systems to remove phenolic compounds from aquatic systems and soils. The direct use of plant material as an enzyme source represents a very interesting alternative to the use of purified enzymes due to its potentially lower cost. However, further studies are needed to confirm the feasibility of such a process. 

As sediments act as pollutant sinks in aquatic systems, they can be important sources of exposure, and so of the entry of chemicals into aquatic food chains. Sediments are the ultimate residence location for many pollutants released to water. The widespread presence of complex mixtures of contaminants in sediment is thus likely to occur in any location where multiple localized and diffuse contaminant sources contribute to the overall chemical load within natural waters. The role of sediment in the receipt and resupply of the chemical to the water phase means that there is interest in monitoring sediment chemical pollutant load over both different spatial and temporal scales. Because the process of sediment deposition and chemical adsorption on the one hand and solubilization and resuspension on the other link the pollutant loads of the sediment and water column, many of the species that can be used to sample the environment for waterborne pollutants (e.g., filter feeders such as mussels) can also describe the pollutant load present in sediments (Baumard et al. 1998). 

The chlorophenoxy groups of herbicides includes 2,4-D, 2,4,5-T, and many other chemically related compounds. The chlorophenoxy compounds are primarily selective herbicides and comprise approximately half the total domestic herbicide market. Although 2,4-D is essentially insoluble in water, its esters are slightly water-soluble, and salts of 2,4-D are completely water-soluble. Several of these compounds are used not only for application to plant foliage and soil but also as aquatic herbicides (8). Each year hundreds of tons of these compounds are applied directly to lakes, rivers, and other surface waters for weed control. Approximately 100,000 pounds of 2,4-D granules are applied annually to the lakes in the TVA system alone (7). The herbicide 2,4-D may persist for several months in lake water whereas the esters of 2,4-D are usually broken down in a few days (I). When applied to watershed areas, the phenoxy herbicides are not likely to constitute a major water pollution hazard since the rate of bacterial degradation is sufficiently rapid to destroy them within a few days (26). However, a few of these compounds can remain in the environment for a year or more. 

Suspended and bottom sediments are widely regarded as a sink for PCBs released into aquatic systems [108], Sorption of non-ortho CBs is stronger than other CBs with the same degree of chlorination [132]. Sediments fairly reflect water pollution in a region from the past. Trends in assessment of PCBs in lake sediments of the Grofier Arbersee (Germany) over the past 130 years (1860-1990) showed that levels of non- and mono-ortho CBs were found to be highest in around 1968-1972. The di-ortho CBs reached their maxima earlier in 1968-1972 [133]. 

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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