Silver chloride nanoparticles and microplastics are polluting in surface waters, yet their interactions, associated toxicity and environmental risks are poorly known. Here we hypothesized that polystyrene microplastics could enhance the phototransformation of silver chloride nanoparticles and modify their toxicity. We conducted phototransformation of silver chloride nanoparticles with polystyrene microplastics under light irradiation. The photo-dissolution of silver chloride nanoparticles and photo-reduction of silver ions were determined in both double-distilled-water and environmental waters. We found that polystyrene microplastics highly enhanced the phototransformation of silver chloride nanoparticles by hydroxyl radicals, singlet oxygen, and triplet state microplastics, leading to the release of silver ions and chloride ions. Subsequently, the silver ions were reduced to silver nanoparticles by superoxide radicals. Consequently, the silver species transformation increased the toxicity of silver chloride nanoparticles even at environmental concentration, as evidenced by survival rate of zebrafish larvae reduced from 100% to 23.3%. This is the first study to show that polystyrene microplastics can enhance the phototransformation of silver chloride nanoparticles to silver nanoparticles, thereby increasing the environmental risks of silver chloride nanoparticles in environmental waters.

氯化银纳米颗粒和微塑料在地表水中造成污染，但它们的相互作用、相关毒性和环境风险知之甚少。在这里，我们假设聚苯乙烯微塑料可以增强氯化银纳米颗粒的光转化并改变其毒性。我们在光照射下用聚苯乙烯微塑料对氯化银纳米颗粒进行了光转化。在双蒸水和环境水中测定了氯化银纳米颗粒的光溶性和银离子的光还原性。我们发现聚苯乙烯微塑料高度增强了羟基自由基、单线态氧和三重态微塑料对氯化银纳米颗粒的光转化，导致银离子和氯离子的释放。随后，银离子被超氧自由基还原成银纳米颗粒。因此，即使在环境浓度下，银物种转化也增加了氯化银纳米颗粒的毒性，斑马鱼幼虫的存活率从 100% 降低到 23.3% 证明了这一点。这是首次表明聚苯乙烯微塑料可以增强氯化银纳米颗粒向银纳米颗粒的光转化，从而增加氯化银纳米颗粒在环境水域中的环境风险。