Photolysis, oxidation and subsequent toxicity of a mixture of polycyclic aromatic hydrocarbons in natural waters

Abstract

Photodegradation of a mixture of three polycyclic aromatic hydrocarbons fluorene (FLU), dibenzofuran (DBF), and dibenzothiophene (DBT) using UV and UV/H 2 O 2 processes was studied. Treating a mixture of the PAHs stimulated a more realistic contamination composition present in polluted water. Effects of pH, PAH concentration, and water matrix composition on removal rates and efficiencies of these compounds are discussed. Batch experiments were conducted using both monochromatic low pressure (LP, 253.7 nm) and polychromatic medium pressure (MP, 200-400 nm) UV sources, in a quasi-collimated beam setup. A synergistic effect was observed during direct photolysis and LP-UV/H 2 O 2 of the mixture as compared to photodegradation as a single component in an aqueous solution. Similar results were obtained for FLU using MP-UV/H 2 O 2 whereas, degradation of DBF and DBT was inhibited in a mixture. Natural water enhanced the direct photolysis compared to laboratory buffered water, whereas, degradation of the PAHs in the natural water was inhibited using UV/H 2 O 2 process. Toxicity testing using a luminescent inhibition bioassay was correlated to intermediates generated during UV-based oxidation reactions.

The abundant occurrence of hydrocarbon-utilizing bacteria in the phyllospheres of cultivated and wild plants in Kuwait

“…There is currently extensive information about hydrocarbonutilizing microorganisms in aquatic habitats (Adebusoye et al, 2007;Shemer and Linden, 2007;Radwan, 2008;Das and Chandran, 2011), terrestrial habitats (Radwan, 2008;Chikere et al, 2011;Erdogan and Karaca, 2011), plant leaves (Ilori et al, 2006), and rhizospheres (Barea et al, 2005;Radwan, 2009;Yateema and Al-Sharrahb, 2011), and their role in the bioremediation of oil-polluted environments (Leahy and Colwell, 1990;Radwan, 2008Radwan, , 2009Kumar et al, 2011). The unique property of these microorganisms, which makes them capable of degrading hydrocarbons, is their possession of oxygenase (also called hydroxylase) systems that catalyze the splitting of O 2 molecules into oxygen atoms, introducing the latter into aliphatic and aromatic hydrocarbons yielding the corresponding hydroxylated compounds.…”

Removal of organic matter from a variety of water matrices by UV photolysis and UV/H2O2 method

“…Besides organic constituent, natural waters and especially industrial waters contain many inorganic anions, such as phosphate, sulfate and chlorine, which may inhibit the oxidation reaction of UV/H 2 O 2 process by reacting with HO • and producing less reactive radicals. However, only alkalinity, originating from bicarbonate ions, was found to decrease the decomposition rate of PAHs [31]. Bicarbonate/carbonate species compete with organic matter for reaction with HO • and hence lower the concentration of those [30].…”

“…Shemer and Linden [31] discovered that the degradation of the PAHs by UV/H 2 O 2 in the natural waters was less efficient compared to laboratory buffered water. Direct oxidation, on the other hand, was found to be enhanced in the natural water probably through reactions with photo-oxidants.…”

Photodecomposition of 4-chlorophenol by reactive oxygen species in UV/air system

“…Among AOPs, the photo-degradation processes such as UV/Fe 3+ , UV/H 2 O 2 and UV/O 3 have shown great potential for the destruction of persistent organic contaminants including chlorophenols [5][6][7][8][9]. During these photodegradation processes, the contaminants are degraded mainly by the attack of • OH radical produced via photoreaction of H 2 O 2 , Fe 3+ or O 3 .…”