Combined toxicity of polycyclic aromatic hydrocarbons and heavy metals to biochemical and antioxidant responses of free and immobilized Selenastrum capricornutum

Abstract

Abstract-The aquatic environment often contains different groups of contaminants, but their combined toxicity on microalgae has seldom been reported. The present study compared the toxic effects of combined mixed polycyclic aromatic hydrocarbons (PAHs) and heavy metals on growth and antioxidant responses of free and immobilized microalga, Selenastrum capricornutum. Five PAHsphenanthrene, fluorene, fluoranthene, pyrene, and benzo[a]pyrene-and four heavy metals at different concentrations-0.05 to 0.1 mg Cd 2þ ml À1 , 0.05 to 1 mg Cu 2þ ml À1 , 0.05 to 1 mg Zn 2þ ml À1 , and 0.5 to 2.5 mg Ni 2þ ml À1 -were examined. Results showed that the chlorophyll a content of free and immobilized S. capricornutum was not affected by PAHs but was significantly inhibited by heavy metals. Conversely, the antioxidant parameters, including the content of reduced glutathione (GSH) and the activities of superoxide dismutase and peroxidase, were significantly induced by both PAHs and metals. For the combined toxic effects of PAHs and heavy metals, cell growth and antioxidant responses varied with exposure time and contaminants and differed between free and immobilized cells. The effects of cocontaminants on the GSH content in free cells were mainly synergistic but changed to antagonistic in immobilized cells. The toxic effects of cocontamination on free cells were also more obvious than those on immobilized cells. These findings suggest that immobilization offers some protection to microalgal cells against toxic contaminants causing differences in the interaction and responses to combined toxicants between free and immobilized cells. Immobilized cells might be more suitable for treating wastewater containing toxic contaminants than free cells. Environ. Toxicol. Chem. 2013;32:673-683. # 2012 SETAC

Effects of biochar and activated carbon amendment on maize growth and the uptake and measured availability of polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs)

“…Meanwhile, the capacity for AC to bind contaminants in soils reduced contaminant availability (as indicated by shoot uptake- Fig 2) in a way not accounted for by the POM extractions (Fig 1), thereby leading to improved shoot growth. Chlorophyll a has previously been used as a biomarker to assess photosynthesis ability in plants and the presence of both PAHs and PTEs has been shown to inhibit photosynthesis (Kummerová et al, 2006;Oleszczuk, 2008;Wang et al, 2013). Chlorophyll a content increased with PB and MB amendment (p<0.05) compared to the control, but not with AC amendment.…”

Immobilized microalgal system: An achievable idea for upgrading current microalgal wastewater treatment

“…Wang et al. [ 83 ] compared the growth and antioxidant responses of free and immobilized microalgae, Selenastrum capricornutum , under combined toxicity of polycyclic aromatic hydrocarbons and heavy metals. They found that immobilized systems can protect microalgal cells against the toxic contaminants and change the synergistic effect of co-contaminants on cells to antagonistic effects.…”

“…However, owing to heterogeneous cell distribution inside the immobilization carrier, the relatively low mass transfer of CO 2 or nutrients may limit the growth and cell division of the immobilized microalgae. Luckily, many researchers have reported that microalgae can overcome the imposed damage or space limitation caused by toxicity, high cell density, or uneven cell distribution after a long operation [ 73 , 83 , 84 ]. Besides, stock culture management of functional microalgae species is a vital part of microalgal wastewater treatment, which is also another embodiment of the application of microalgal immobilization technology.…”

“…During this process, polymers act as a buffer zone, which can alleviate the immediate effect of the sharp variance of pollutants concentration in bulk liquid media on microalgae cells. It explains the protective effects of the immobilized systems according to some studies [ 119 ]. This is also why some immobilization systems show less efficiency in removing pollutants [ 120 ].…”

Interactions between Microcystis aeruginosa and coexisting amoxicillin contaminant at different phosphorus levels

“…The total ATPase activity was analyzed according to a procedure described by Dehn et al [22]. Antioxidant responses including the activities of superoxide dismutase (SOD), peroxidase (POD) and glutathione S-transferase (GST) and the content of MDA were determined according to previous studies [18,23]. The activities of the enzymes and the content of MDA were expressed in units per mg of protein (U/mg protein) and g per mg protein, respectively, in order to eliminate the measurement deviation caused by varied extraction efficiency of protein.…”