Abstract
Algal blooms cause great damage to water quality and aquaculture. However, this study showed that dead algal cells and chlorophyll could accelerate the photo-transformation of benzo[a]pyrene (BaP), a ubiquitous and persistent pollutant with potently mutagenic and carcinogenic toxicities, under visible light irradiation. Chlorophyll was found to be the major active substance in dead algal cells, and generated a high level of singlet oxygen to catalyse the photo-transformation of BaP. According to various BaP metabolites formed, the degradation mechanism was proposed as that chlorophyll in dead algal cells photo-oxidized BaP to quinones via photocatalytic generation of singlet oxygen. The results provided a good insight into the role of chlorophyll in the photo-transformation of organic contaminants and could be a possible remediation strategy of organic pollutants in natural environment.
Highlights
Activity of intracellular enzymes[14]
Cellular contents releasing from dead algal cells, especially chlorophyll extracted from microalgae, were employed to test the photo-transformation rate of BaP under visible light irradiation
In order to confirm the efficiency of dead algal cells in BaP transformation, three different microalgal species, namely S. capricornutum, Chlorella vulgaris and Chlorella sp., were tested (Fig. 1a)
Summary
Dead cells with the unique enzyme systems being inactivated possibly acted as a photosensitizer to stimulate the photo-degradation of PAHs13. Some studies have reported that dead algal cells could accelerate the photolysis of contaminants under light irradiation, such as pesticides[15], aniline[16] and bisphenol A17. The mechanism responsible for accelerating PAH transformation by dead algal cells remains to be elucidated. The major objective of this study was to elucidate the mechanism of BaP photo-transformation induced by dead algal cells in the water. Dead algal cells were shown to be effective in BaP transformation under light irradiation[13,28]. Cellular contents releasing from dead algal cells, especially chlorophyll extracted from microalgae, were employed to test the photo-transformation rate of BaP under visible light irradiation. Effects of various ROS (OH and 1O2) on the photo-transformation of BaP were investigated
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