Modelling the release, dispersion and fate of nanoparticulate titanium dioxide from sunscreen products in recreational lakes

二氧化钛纳米颗粒（n-TiO 2）代表了一个日益增长的威胁，由于其持久性和直接释放的防晒霜在娱乐沃茨在沐浴季节的水生生态系统。然而，它们的影响仍然难以评估，一方面是因为监测其在环境介质中浓度的分析方法只是最近才开发出来。另一方面，它们在水生系统中的命运仍然没有得到充分的了解。特别是，表面微层（SML），散装水，沉积物，植物和浮游生物之间的分布取决于在实验室实验中单独研究的各种机制，但很少在环境条件下进行评估。此外，风在SML中存在的纳米粒子的分散中的作用迄今尚未研究，尽管预计它将显著有助于疏水性n-TiO 2的空间分散。在这个项目中，我们建议调查的n-TiO 2在一个典型的休闲湖泊中的分布，并根据详细的经验数据，评估反应运输模型描述他们的命运。我们将量化和表征防晒霜的输入使用的调查和样本之间的沐浴，并确定防晒霜的洗掉率从皮肤在现场条件下使用专门的实验。将使用一种新开发的方法测定水相、表面水（疏水膜）和水生生物中n-TiO 2的含量，该方法依赖于痕量元素，以校正天然TiO 2背景。将进行高测量频率的采样活动，以获得关于由于对流和风在SML上漂移引起的扩散率的经验数据。沉积物中人为n-TiO 2的积累将通过监测沐浴季节前后的浓度来确定。所获得的数据将用于开发，测试和优化命运分布模型，同时考虑到由于对流和风以及纳米颗粒的性质和水化学引起的空间分散。将进行功能试验，以确定命运模型所需的参数。将使用从防晒霜中提取并在湖水中自然涂覆的n-TiO 2确定附着效率。天然胶体的替代物将根据对研究湖泊中胶体的详细调查进行选择，并在功能测定中用作异源聚集伴侣。为了参数化风对SML的影响，将进行水槽围隔实验，以在受控的空气动力和水动力条件下产生和测试防晒SML的稳定性。结果将使我们能够确定最相关的过程中涉及的n-TiO 2的命运从防晒霜在娱乐沃茨，此后，打开了大门，更准确的生态风险评估无机紫外线过滤器的防晒霜。

Titanium dioxide nanoparticles (n-TiO2) represent an increasing threat for aquatic ecosystems due to their persistence and the direct release from sunscreens in recreational waters during the bathing season. However, their impact is still difficult to evaluate because, on one side, analytical methods for monitoring their concentration in environmental media have been developed only recently. On the other side, their fate in aquatic systems is still insufficiently understood. In particular, the distribution between the surface microlayer (SML), bulk water, sediments, plants, and plankton depends on various mechanisms that were investigated individually in laboratory experiments, but were rarely assessed under environmental conditions. Furthermore, the role of wind in the dispersion of nanoparticles present in the SML has not been investigated so far, although it is expected to contribute significantly to the spatial dispersion of hydrophobic n-TiO2. In this project, we propose to investigate the distribution of n-TiO2 in a typical recreational lake and, based on detailed empirical data, assess a reactive transport model describing their fate. We will quantify and characterize the input of sunscreens using surveys and samples among bathers and determine the wash-off rate of sunscreen from the skin under field conditions using dedicated experiments. The amount of n-TiO2 in the water phase, in the surficial water (hydrophobic films), and in aquatic organisms will be determined using a newly developed method relying on trace elements to correct for the natural TiO2-background. A sampling campaign at a high measurement frequency will be conducted to obtain empirical data on the dispersion rate due to convection and wind drift on the SML. The accumulation of anthropogenic n-TiO2 in the sediment will be determined by monitoring the concentration before and after the bathing season. The obtained data will be used to develop, test, and optimize fate distribution models taking into account spatial dispersion due to convection and wind together with the nanoparticles’ properties and the water chemistry. Functional assays will be carried out for determining the parameters required for the fate model. Attachment efficiencies will be determined using n-TiO2 extracted from sunscreen and coated naturally in lake water. Surrogate for natural colloids will be selected based on a detailed investigation of the colloids in the study lake and used as heteroaggregation partners in the functional assays. To parametrize the effect of wind on the SML, flume mesocosm experiments will be conducted to produce and test the stability of sunscreen SML under controlled aero- and hydrodynamic conditions. The results will enable us to determine the most relevant processes involved in the fate of n-TiO2 from sunscreens in recreational waters and, thereafter, open the door to more accurate ecological risk assessment of inorganic UV-filter in sunscreens.