Aquatic organisms, degradation

In a battery of tests, which determine the tendency of chemicals to inhibit aquatic organisms, accumulate in such organisms, and degrade in the environment, 2-hydroxy-2-nitro-l,3-propanediol was found to have low potential for harm in the environment (7). 

Food Chain Bioaccumulation. There are a few studies to determine residues of methyl parathion in organisms in the environment. These have consistently shown low methyl parathion residues, indicating that methyl parathion does not bioconcentrate to a significant extent in aquatic organisms, plants, or animals (Crossland and Bennett 1984 Sabharwal and Belsare 1986). The methyl parathion that does get into organisms is rapidly degraded (Sabharwal and Belsare 1986). Some recent analyses of fish in a... 

Degradation and evaporation seem to be the major pathways for acrolein loss in water smaller amounts are lost through absorption and uptake by aquatic organisms and sediments (USEPA 1980 Reinert and Rodgers 1987). The half-time persistence of acrolein in freshwater is 38 h at pH 8.6 and 50 h at pH 6.6 degradation is more rapid when initial acrolein concentrations are less than 3000 pg/L (Bowmer and Higgins 1976). Nordone et al. (1998) show a half-time persistence of 2.9 to 11.3 h at initial nominal concentrations of 20 pg/L, and 27.1 to 27.8 h at 101 pg/L. At pH 5, acrolein reacts by reversible hydrolysis to produce an equilibrium mixture with 92% beta-hydroxy-... 

Paraquat is used to control aquatic weeds. It also passes into aquatic environments through rain, where it is rapidly accumulated by aquatic organisms, especially fish (Gabryelak and Klekot 1985). Paraquat applied to control aquatic weeds is accumulated by aquatic macrophytes and algae, and it is adsorbed to sediments and suspended materials. Initial applications of 1 to 5 mg/L in the water column are usually not detectable under field conditions after 8 to 27 days (Summers 1980). The half-time persistence of paraquat in water column at normal doses for weed control (i.e., 0.5 to 1.0 mg/L) was 36 h less than 0.01 mg/L was detectable in 2 weeks (Calderbank 1975). In solution, paraquat was subject to photodecomposition and microbial metabolism, degrading to methylamine... 

The second difference between the laboratory tests and exposure under realistic environmental conditions is that in the laboratory exposure concentrations are maintained, or the ecotoxicological endpoints are adjusted to account for any decline. Under natural conditions a combination of the pyrethroids tendency to partition rapidly and extensively to organic matter, coupled with their susceptibility to degradation in aquatic systems where algae and macrophytes are present [13,14], means their overall dissipation rate from the water phase is generally relatively rapid. Water column dissipation half-lives tend to be around 1 day (see Sect. 5). This behavior means that it is unlikely that aquatic organisms will be exposed to pyrethroids in the water phase for prolonged periods in natural water bodies. 

Smital T, Luckenbach T, Sauerborn R, Hamdoun AM, Vega RL, Epel D (2004) Emerging contaminants - pesticides, PPCPs, microbial degradation products and natural substances as inhibitors of multixenobiotic defense in aquatic organisms. Mutat Res 552 101-117 Snyder MJ (2000) Cytochrome P450 enzymes in aquatic invertebrates recent advances and future directions. Aquat Toxicol 48 529-547... 

In addition, bioaccumulation in aquatic organisms has been studied, again mainly for LAS [62], the non-ionic surfactants and their degradation products (see Chapter 7.2). A close relation with hydrophobicity can be drawn from studies performed with pure homologues of LAS. 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

It soon became obvious, however, that these "wonder chemicals" pose some serious environmental hazards. Because they are synthetic products, the microorganisms that normally degrade natural products do not affect them. Therefore, they tend to persist in the soil on which they are sprayed for long periods. They eventually become part of groundwater or are washed into lakes and rivers by rain. In the water, they are toxins that threaten aquatic organisms. 

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