Bioaccumulation capacity of Chlorella vulgaris and Spirulina platensis exposed to silver nanoparticles and silver nitrate: Bio- and health risk assessment approach

Abstract

This study investigated the bioaccumulation capacity of Chlorella vulgaris and Spirulina platensis exposed to silver nanoparticles (AgNPs) and silver nitrate (AgNO3) affecting the cell growth, viability, pigment content, and health status. Toxicity experiment was conducted using concentrations of 0, 0.005, 0.001, 0.05, 0.01, 0.5, and 0.1 for AgNPs and AgNO3 during a 96-h exposure period. Results illuminated that S. platensis could largely bioaccumulate silver nanoparticles while C. vulgaris greatly absorbed ionic silver (AgNO3), and both microalgae showed a concentration-dependent manner in response to silver materials. AgNO3, compared to AgNPs, affected significantly the average specific growth and yield of algal populations. A concentration-dependent decrease was observed in the content of pigments in exposure to both forms of silver, albeit this biological factor showed the highest severity to AgNO3. Moreover, the content of chlorophyll a, b, and total chlorophyll in S. platensis decreased after 48 and 72 h. The pigment response of C. vulgaris to ionic silver was more severe than the respective nanoparticles. Bioconcentration factor in C. vulgaris populations exposed to 0.001 mg L−1 of AgNO3 and AgNPs (14,109.7 and 6819.7010, respectively) was in the highest level among other treatments, and the lowest BCF calculated for S. platensis at 86.6066 (0.05 mg L−1 AgNO3) and 170.2482 (0.5 mg L−1 AgNPs). Target hazard quotient ordered at THQY > THQM > THQTW > THQD for both microalgae, and maximum allowable limits (CR) reduced considerably with the increase of silver-based materials concentration in S. platensis and C. vulgaris. Taken together, C. vulgaris and S. platensis are strong bioaccumulators for AgNPs and AgNO3 and their biological properties and health status could be disturbed, which is dangerous for both aquatic ecosystem and human health.