Environmental impact, degradation

Keywords Polyethylene Environmental degradation Environmental impact Degradation... 

Degradation or Transformation. Degradation or transformation of a herbicide by soil microbes or by abiotic means has a significant influence not only on the herbicide s fate in the environment but also on the compound s efficacy. Herbicides that are readily degraded by soil microbes or other means may have a reduced environmental impact but may not be efficacious. Consider the phenomenon of herbicide-resistant soils. In these cases, repeated application of a given herbicide has led to a microbial population with an enhanced ability to degrade that herbicide (252,253). This results in a decrease or total loss of the ability of the herbicide to control the weed species in question in a cost-effective manner. 

Environmental Impact of Ambient Ozone. Ozone can be toxic to plants, animals, and fish. The lethal dose, LD q, for albino mice is 3.8 ppmv for a 4-h exposure (156) the 96-h LC q for striped bass, channel catfish, and rainbow trout is 80, 30, and 9.3 ppb, respectively. Small, natural, and anthropogenic atmospheric ozone concentrations can increase the weathering and aging of materials such as plastics, paint, textiles, and mbber. For example, mbber is degraded by reaction of ozone with carbon—carbon double bonds of the mbber polymer, requiring the addition of aromatic amines as ozone scavengers (see Antioxidants Antiozonants). An ozone decomposing polymer (noXon) has been developed that destroys ozone in air or water (157). 

When antifreeze becomes unsuitable for use, either because of depletion of inhibitors, presence of corrosion products or corrosive ions, or degradation of the fluid, recycling and reuse of the antifreeze, rather than disposal, may be considered. Although ethylene glycol is readily biodegraded in typical municipal waste treatment faciHties, antifreeze disposal becomes problematic because the coolant may contain hazardous quantities of heavy metals picked up from the cooling system. Recycling may be economically preferred over coolant disposal and reduces the concern for environmental impact. 

Another method used at times is the Standard price method. This method presents environmental values as corresponding to the mitigation costs needed to avoid environmental degradation. The main disadvantage of this method is that the environmental value derived is poorly linked with the environmental impact. 

Methods are also available to measure degradation products of hexachloroethane in environmental samples, but these products (e.g., tetrachloroethylene) are released to the environment from many other sources and are therefore not useful determinants of the environmental impact of this chemical. 

As an industrial and commercial product, PVA is valued for its solubility and biodegradability, which contributes to its very low environmental impact. Several microorganisms ubiquitous in artificial and natural environments — such as septic systems, landfills, compost and soil — have been identified and they are able to degrade PVA through enzymatic processes. 

Librando, V. and Lane, D.A. Degradation of chemicals with significant environmental impact, in American Chemical Society-Division of Environmental Chemistry, Preprints of Extended Abstracts, 37(l) 283-284.1997. 

One important aspect of any cleanup technique, is the type of degradation products that are produced. These products must be known in order to assess their potential environmental impact and toxicological hazards. One of the major degradation products of diazinon, oxypyrimidine was measured in soil after treatment with parathion hydrolase. Figure 6 shows that oxypyrimidine increases in soil as the diazinon is degraded by the enzyme. 

Synthetic polymers obtained from sugar-based monomers are innocuous for human health. Their hydrophilic nature ensures a greater hydrolytic degradability [6], and reduces their environmental impact compared to classic polymers [3]. 

Illman, B. and Yang, V. (2004) Bioremediation and degradation of CCA-treated wood waste, Environmental Impacts of Preservative-Treated Wood, Florida Center for Environmental Solutions, Conference, February 8-11, Gainesville, Orlando, FL, pp. 259-69. 

Since the environmental degradation of polyethylene starts with abiotic oxidation, the determination of abiotic oxidation products is an important step towards establishing the environmental degradation mechanisms and environmental impact of the material. In a secondary process, microorganisms may utilise these abiotic degradation products and the low molecular weight... 

Barrett, M.R. (1996). The environmental impact of pesticide degradation in groundwater. In M.T. Meyer and E.M. Thurman, eds., Herbicide Metabolites in Surface Water and Groundwater. Washington, DC American Chemical Society, pp. 201-225. 

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