摘要：Graphical abstractDisplay OmittedAbstractWe developed the effect of titanium dioxide nanoparticles (nano-TiO2) on the bioaccumulation and biotransformation of arsenic (As), which remain largely unknown. We thus exposed two freshwater algae (Microcystis aeruginosaandScenedesmus obliquus) to inorganicAswith the aim of increasing our understanding onAsbioaccumulation and methylation in the presence of nano-TiO2. Direct evidence of TEM and EDX image showed that nano-TiO2(anatase) entered the exposed algae. Thus, nano-TiO2as carriers boosted arsenic accumulation and methylation in these two algae species, which varied with both inorganicAsspeciation and algae species. Specifically, nano-TiO2could enhance markedly arsenate accumulation inM. aerugginosaand arsenite accumulation inS. obliquus. Similarly, we found higher content ofAsmethylation inM. aeruginosaof arsenite with 2 mg L−1of nano-TiO2treatment and inS. obliquusof arsenate treatment. Additionally,S. obliquusexhibited higherAsmethylation compared toM. aeruginosa, being more sensitive toAsassociated with nano-TiO2thanM. aeruginosa. Due to changes in pH levels inside these exposed algae, theAsdissociation from nano-TiO2inside algal cell enhancedAsmethylation. Accordingly, the potential influence of nanoparticles on the bioaccumulation and biotransformation of their co-contaminants deserves more attention.•Nano-TiO2entry is assumed to promoteAsaccumulation into exposed algae.•Nano-TiO2had different carrying capacities for different forms ofAsand algae.•Asdissociation from nano-TiO2is assumed to enhanceAsmethylation in algae.
