High time resolution mineral dust deposition characterization with respect to particle size, composition and atmospheric ageing at locations relevant for the atmospheric-oceanic dust budget

矿物粉尘是大气系统中主要的气溶胶类型之一，湿沉降和干沉降是去除矿物粉尘的主要过程。在条件适宜的情况下，每年可在洲际范围内输送数兆克的粉尘。当矿物粉尘到达远离其来源的地球表面时，可能会对生态系统产生重大影响。特别是海洋生态系统，由于缺乏可由灰尘提供的营养物质，其生产力受到限制。此外，地球工程的想法是通过人工海洋施肥。尽管有如此高的影响，但对尘埃沉积的测量很少，而且通过少数可用数据集验证的模型性能很差。目前，缺乏详细的数据限制了我们对全球尘埃循环的理解。此外，干沉积测量技术的缺陷阻碍了适当数据的获取。在该项目中，将开发一种新的干湿自动沉积采样系统，并对其进行全面表征。该系统将在气象相关的时间尺度（小时到天）上收集样本，克服了过去沉积测量的问题，过去的测量通常提供数周或数月的时间分辨率。通过使用自动扫描电子显微镜进行颗粒分析，该方法将提供前所未有的详细丰富的数据集。数据将包括粒径分布、元素组成和粒径范围在700 nm和100 μ m之间的颗粒混合状态。将特别注意潜在的营养物质，铁，磷，钾，镁和钙。将测量选定样品的颗粒吸湿性。在Frioul岛的测试阶段之后，采样器将用现有的时间序列进行验证，三个仪器将部署在与进入海洋的灰尘有关的地点：佛得角的圣维森特岛；巴巴多斯，捕捉撒哈拉外流；在冰岛的Heimaey岛捕捉北极尘埃。计划（在本项目之后）第二个项目阶段，其中网络将扩展到南美洲羽流的福克兰新岛；到在荒木，天草岛日本，亚洲的流出；以及位于南非东西流和澳大利亚东西流之间的阿姆斯特丹岛。该项目将首次提供矿物粉尘干湿沉积的连续系列，具有每日（干）或基于事件（湿）的时间分辨率和粒度分辨率。对导致沉积事件的大气关键因子进行了表征。我们将评估营养物质——特别是铁和磷——在湿沉积和干沉积之间的分配，并将确定相应的大小分布。通过混合模型和图像分析来评估颗粒混合状态和颗粒形状。将提供一个公共数据库用于模型验证。按照计划，这些监测站将在DFG筹资阶段结束后继续运作。

Wet and dry deposition are the major processes removing mineral dust, one of the major aerosol types, from the atmospheric system. Providing suitable conditions, teragrams of dust per year are transported on intercontinental scales. When mineral dust reaches the earth surface far away from its source, it may significantly influence ecosystems. In particular ocean ecosystems are limited in their productivity by lack of nutrients, which can be supplied by dust. Also, geo-engineering ideas exist by artificial ocean fertilization. Despite of this high impact, measurements of dust deposition are rare and model performance as validated by the few available data sets is poor. Mainly lack of detailed data is currently limiting our understanding of the global dust cycle. Moreover, deficits in dry deposition measurement techniques hamper acquisition of proper data.In the proposed project, a new automated wet and dry deposition sampling system will be developed and thoroughly characterized. The system will collect samples on meteorological relevant time scales (hours to days), overcoming the problem of past deposition measurements, which usually provided time resolution of weeks or months. By using automated scanning electron microscopy for particle analysis, the method will provide data sets of unprecedented detail richness. Data will include particle size distribution, elemental composition, and particle mixing state in the particle size range between 700 nm and 100 µm in diameter. Special attention will be given to the potential nutrients, iron, phosphorus, potassium, magnesium, and calcium. Particle hygroscopicity will be measured for selected samples.After the test phase on Frioul island, where the samplers will be validated with existing time series, three instruments will be deployed on locations relevant for dust input into the ocean: on the island of Sao Vicente, Cape Verde; Barbados, capturing Saharan outflow; and on Heimaey island, Iceland, capturing Arctic dust. A second project phase is planned (after present project), in which the network will be extended to New Island, Falkland, in the South American plume; to at Araoteke, Amakusa island Japan, Asian outflow; and to Amsterdam island, located between the South African west-east and Australian east-west outflow. The project will provide for the first time continuous series of mineral dust wet and dry deposition with daily (dry) or event-based (wet) time resolution and particle size resolution. Atmospheric key factors leading to deposition events will be characterized. We will assess the partitioning of nutrients - in particular of iron and phosphorus - between wet and dry deposition and will determine the according size distributions. Particle mixing state and particle shape will be assessed by mixing models and image analysis. A public database will be provided for model validation. It is planned that the stations will continue operation after the DFG funding phase.