Microplastics (MPs) and nanoplastics (NPs) are ubiquitous and contaminate soil, surface waters, atmospheric aerosol, precipitations, indoor and outdoor environments. However, the occurrence, transformation and fate of NPs in the environment are still unclear. In this work, polystyrene nanoparticles (PS-NPs) are used as a proxy of NPs to study their reactivity and potential impact on atmospheric and surface waters. In particular, the reactivity with hydroxyl radicals (OH) in the aqueous phase is investigated. For the first time, a reactivity constant for the reaction of NPs with OH is measured, strongly dependent on the exposed particle surface area of NPs. Degradation products (short chain carboxylic acids and aromatic compounds), obtained by direct and OH-mediated photolysis of PS-NPs suspensions, are identified by mass spectrometry. Irradiation of a PS-NPs suspension under natural sunlight for 1 year has shown the formation of formic acid and organic compounds similar to those found in riverine and cloud dissolved organic matter, which could contribute significantly to the dissolved organic matter in the aqueous phase.

微塑料（MPs）和纳米塑料（NPs）无处不在，并污染土壤，地表水，大气气溶胶，降水，室内和室外环境。然而，环境中NP的发生，转化和命运仍不清楚。在这项工作中，聚苯乙烯纳米颗粒（PS-NPs）被用作NPs的代用品，以研究其反应性以及对大气和地表水的潜在影响。特别地，研究了与水相中的羟基自由基（OH）的反应性。首次测量了NP与OH反应的反应常数，这在很大程度上取决于NP的暴露颗粒表面积。通过直接和间接获得的降解产物（短链羧酸和芳族化合物）通过质谱鉴定OH-介导的PS-NPs悬浮液的光解。在自然阳光下照射PS-NPs悬浮液1年已表明，形成了甲酸和有机化合物，类似于在河流和云层中溶解的有机物中发现的那些，这可能对水相中的溶解有机物有很大贡献。