تخریب- PAH میکروبی در خاک و مسیرهای تخریب و عوامل موثر
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|10140||2006||11 صفحه PDF||سفارش دهید||3940 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Pedosphere, Volume 16, Issue 5, October 2006, Pages 555–565
Adverse effects on the environment and high persistence in the microbial degradation and environmental fate of polycyclic aromatic hydrocarbons (PAHs) are motivating interest. Many soil microorganisms can degrade PAHs and use various metabolic pathways to do so. However, both the physio-chemical characteristics of compounds as well as the physical, chemical, and biological properties of soils can drastically influence the degradation capacity of naturally occurring microorganisms for field bioremediation. Modern biological techniques have been widely used to promote the efficiency of microbial PAH-degradation and make the biodegradation metabolic pathways more clear. In this review microbial degradation of PAHs in soil is discussed, with emphasis placed on the main degradation pathways and the environmental factors affecting biodegradation.
Polycyclic aromatic hydrocarbons (PAHs), as a result of the incomplete combustion of organic matter, emission sources, automobile exhaust, coal-fired electricity generating power plants, domestic matter, and area source matter, are ubiquitous in the environment (Finlayson-Pitts and Pitts, 1997; Norse, 2005). PAHs in the air and water can also be brought into the soil and sediment through precipitation effects (Johnsen et al., 2005). Therefore, soil becomes the main environmental receptor of PAHs. Because of their carcinogenic, teratogenic, mutagenic, and other toxic properties, PAHs have been of great environmental interest (Bispo et al., 1999). Consequently, the US Environmental Protection Agency (EPA) has listed 17 PAHs (Table I) as priority pollutants for remediation (Liu, K. et al., 2001), among which 15 PAHs have carcinogenic risk to humans reported by the International Agency for Research on Cancer (IARC). PAHs are composed of fused, aromatic rings (Fig. 1) whose biochemical persistence arises from dense clouds of .rr-electrons on both sides of the ring structures making them resistant to nucleophilic attack (Johnsen et al., 2005). Besides this, they possess physical properties, such as low aqueous solubility and high solid-water distribution ratios (Table I). These properties stand against their ready microbial utilization and promote their accumulation in the solid phases of the terrestrial environment. Generally, the aqueous solubility and, as a consequence, the biodegradability of PAHs decreases almost logarithmically with an increase in molecular mass. However, there are reports of a variety of microorganisms, ranging from low molecular weight (naphthalene) to high molecular weight (coronene) that degrade various PAHs. More and more environmental concerns are turning to the biodegradation of PAHs. Therefore, this review will discuss microbial degradation of PAHs in soil with an emphasis on metabolic pathways and factors affecting biodegradation rates.