Freshwater synthetic

Pipes, valves, fittings, and almost all other components of small equipment are now available in plastic or ceramics, which do not corrode in salt water and are less expensive than the metals now used. Synthetic detergents are now available for use with seawater, although a final rinse with freshwater may be desired. Saltwater sewage can be treated successfully. Dual water systems using freshwater and seawater are already in use on ships and in many island resort hotels. Many of these also have seawater systems for fire fighting. This trend will grow. 

Synthetic pyrethroids now account for at least 30% of the world insecticide market and are rapidly replacing other agricultural chemicals for control of insect pests. Fenvalerate is one of the more widely used synthetic pyrethroid insecticides. It is derived from a combination of a-cyano-3-phenoxybenzyl alcohol and a-isopropyl phenylacetate ester. Technical fenvalerate is a mixture of four optical isomers, each occurring in equal amounts but with different efficacies against insect pests. Fenvalerate does not usually persist in the environment for >10 weeks, and it does not accumulate readily in the biosphere. Time for 50% loss (Tb 1/2) in fenvalerate-exposed amphibians, birds, and mammals was 6 to 14 h for reptiles, terrestrial insects, aquatic snails, and fish it was >14 h to <2 days and for various species of crop plants, it was 2 to 28 days. Fenvalerate degradation in water is due primarily to photoactivity, and in soils to microbial activity. Half-time persistence in nonbiological materials is variable, but may range up to 6 days in freshwater, 34 days in seawater, 6 weeks in estuarine sediments, and 9 weeks in soils. 

Anderson, R.L. 1989. Toxicity of synthetic pyrethroids to freshwater invertebrates. Environ. Toxicol. Chem. 8 403-410. 

Gatermann, R. Siselli, S. Huhnerfuss, H. Rimkus, G. G. Hecker, M. Karbe, L. 2002, Synthetic musks in the environment. Part 1 Species-dependent bioaccumulation of polycyclic and nitro musk fragrances in freshwater fish and mussels. Arch. Environ. Con. Tox. 42 437 46. 

Steroid hormones form a group of pollutants that includes natural hormones such as estradiol, testosterone, and their metabolites as well as several synthetic analogues. Steroid hormones used as growth promoters have already been found in water and sediments (Lai et al. 2000 Thorpe et al. 2003), and their adsorption properties on earth materials have been considered. Lee et al. (2003) report batch experiments where simultaneous sorption of three hormones (17- 3-estradiol, 17-a-ethyl estradiol, and testosterone) on four midwestem U.S. soils and a freshwater sediment were performed. Apparent sorption equilibria were reached within a few hours. Sorption isotherms generally were linear for the chemicals studied on one of these soils (Drummer soil), ranged from 23.4 to 83.2 L kg and log ranged... 

Although the term vitamin A has been used to denote specific chemical compounds, such as retinol or its esters, this term now is used more as a generic descriptor for compounds that exhibit the biological properties of retinol. Retinoid refers to the chemical entity retinol or other closely related naturally occurring derivatives. Retinoids also include structurally related synthetic analogues, which need not have retinol-like (vitamin A) activity. The structural formulas for the vitamin A family of retinoids are shown in Figure 66.3. Retinol (vitamin Aj), a primary alcohol, is present in esterihed form in the tissues of animals and saltwater fish, mainly in the liver. A closely related compound, 3-dehydroretinol (vitamin A2), is obtained from the tissues of freshwater fish and usually occurs mixed with retinol. 

Southworth, G.R., Beauchamp, J.J., Schmieder, P.K. (1978) Bioaccumulation potential and acute toxicity of synthetic fuels in freshwater biota azarenes. Environ. Sci. Technol. 12, 1062-1066. 

The chemistry of soap manufacturing stayed essentially unchanged until World War II, at which time synthetic detergents (syndets) became available. There had been a search for cleansing agents that would foam and clean when added to seawater in response to the need of sailors who spent months at sea under severe freshwater restrictions. 

The rotifer toxicity assay was performed with juveniles of B. calyciflorus hatched from cysts after 16-18 h of incubation at 25°C in synthetic freshwater (moderately hard U.S. Environmental Protection Agency medium)28 under continuous illumination (light source 3,000-4,000 lux). Test solutions were... 

The crustacean toxicity test to assess the mortality of T. platyurus was conducted by hatching these anostraca from cysts after 20-22 h of incubation at 25°C in the same synthetic freshwater used for rotifers and at the same illumination conditions. The test solutions in five concentrations (two-fold dilutions) with three replicates of 10 animals were poured in disposable multiwell test plates (1 mL per well). After 24 h in a 25 °C incubator in the dark, the number of dead crustaceans was recorded. 

Merlini, M., Pozzi, G., Brazzelli, A. and Berg, A. The transfer of Zn from natural and synthetic foods to a freshwater fish, p. 226-230, in Cushing, C. E., ed., "Radioecology and Energy Resources," Ecol. Soc. Amer. Publ. 1, Dowden, Hutchinson and Ross, Stroudsberg, Pennsylvania, 1976. 

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