The Toxicity Of Binary Mixtures Of Cetyltrimethyl Ammonium Chloride And Aromatic Hydrocarbon On Chlorella Vulgaris

When two or more different properties or different sources of contaminations existedin the same environment medium, there were reciprocal interactions among them. Thesephenomena, which are ubiquitous in actual aquatic environment, have been calledcombined pollution. Therefore, it can provide theoretical basis for evaluating theinfluence of combined pollution by understanding the joint toxicity of multi-pollutantsand its mechanism. Furthermore, it is crucial for the ecological risk assessment ofcontaminants in aquatic systems.Based on the effects of binary mixtures of cetyltrimethylammonium chloride(CTAC) and six aromatic hydrocarbons (AHs) on Chlorella vulgaris, a unicellulargreen alga which is sensitive to contaminants, this paper concentrated on thecombined pollution system of CTAC and fluoranthene (Flu) on C. vulgaris. Weinvestigated the residual CTAC and Flu in the medium, the accumulation anddegradation of Flu in algal cells, the intracellular Flu concentration in algal cells and thesubcellular distribution of Flu in different organelles. The results could be listed asfollows:(1)96h-EC50of CTAC on the biomass of C. vulgaris was0.18mg/L, however, theinhibition of single AHs on algal biomass was very low. The joint action of CTAC andthe six AHs mixtures on C. vulgaris changed from synergetic effect to antagonisticeffect with the incease of AHs, and the synergism initially increased and then decreased.In particular, the maximum inhibition was achieved in the binary mixtures when theconcentrations of benzene, toluene, aniline, phenol, nitrobenzene, benzaldehyde,naphthalene, phenanthrene, fluoranthene were4,4,10,8,4,8,4,5and2.5μg/L,respectively. The percent inhibition were1.59,1.42,1.37,1.65,1.60,1.55,1.26,1.34、and2.06times than that of control treatment which containing100μg/L CTAC alone.(2) The residual concentration of CTAC in medium initially decreased and thenincreased with the increasing initial concentration of Flu. But the percentage of Fluremaining in the medium gradually decreased in relation to incubation time. Whenthe initial concentration of Flu was2.5μg/L, the percentage of Flu accumulated inalgal cells firstly increased and then decreased, and the percentage of Flu degraded byalgae totally increased in individual system. However, the percentage of Fluaccumulated in algal cells increased as time changes, and the percentage of Flu degraded by algae totally decreased in binary system. When the initial concentrationof Flu was200μg/L, the percentage of Flu accumulated in algal cells graduallyincreased with time increasing in both individual and binary systems.(3) The dynamic subcellular distribution of Flu in C. vulgaris was changed in thepresence of CTAC compared with the individual Flu system. It was clear that thelargest fraction of Flu was detected in cellular debris at24h, which decreasedgradually during96h exposure. The percentage of Flu in cytosol general increased. Atthe end of96h exposure, the lowest percentage of Flu was detected in the cellulardebris and the highest percentage was detected in the cytosol in the binary mixtureswith2.5μg/L of Flu when synergism was observed. Nevertheless, a reversed trendwas exhibited in individual Flu system. The highest percentage of Flu in the cellulardebris and the lowest in the organelles were observed in binary mixtures with200μg/L of Flu when antagonism displayed. However, the largest subcellular pool for Fluwas cytosol in C. vulgaris, and the least in cellular debris in individual Flu system.