Abstract: Lead nanoparticles are major pollutants adsorbed to atmospheric fine particles. The phytotoxicity of lead nanoparticles is largely unknown. Here, the toxicity of lead nanoparticles to Chlorella vulgaris was investigated by taking lead sulfate nanoparticles (nano-PbSO₄) as a model. The morphology and growth inhibition of C. vulgaris exposed to nano-PbSO₄ or lead ion (Pb²⁺) were examined to elucidate the toxic effects. The concentration of Pb²⁺ in the culture medium containing nano-PbSO₄ was analyzed to probe the toxicity mechanism. The results showed that C. vulgaris cells were sunken and shrunken after being exposed to nano-PbSO₄, with visible nanoparticle aggregation on the surface. The inhibition on the growth of C. vulgaris increased with the increases of nano-PbSO₄ concentration and followed the nonlinear Logit model. The inhibition of nano-PbSO₄ to the growth of C. vulgaris was significantly lower than that of corresponding concentration of Pb²⁺, with the median effective concentration being 4.2 times of that of Pb²⁺. Only 0.31%-0.81% of the nano-PbSO₄ (0.01-1 mmol·L^-1) was dissolved into Pb²⁺ in the culture medium, indicating that the toxicity of nano-PbSO₄ was mainly attributed to the nano-effects with minor contribution of dissolved Pb²⁺. Our results provide reference for ecological risk assessment of lead nanoparticles.

Key words: sap flow velocity, environmental factors, soil moisture, Quercus liaotungensis, Populus davidiana.