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

矿物粉尘是大气中主要的气溶胶类型之一，其主要的沉降过程是干湿沉降。如果条件合适，每年有太克的尘埃在洲际范围内传播。当矿物粉尘到达远离其来源的地球表面时，它可能会对生态系统产生重大影响。特别是，海洋生态系统的生产力因缺乏营养而受到限制，而这些营养可以由灰尘提供。此外，地球工程的想法存在的人工海洋施肥。尽管影响很大，但对灰尘沉积的测量很少，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了解。此外，干沉积测量技术的缺陷妨碍了获得适当的数据。在拟议的项目中，将开发一种新的自动化湿和干沉积取样系统，并对其进行彻底的表征。该系统将收集气象相关时间尺度（小时至天）的样本，克服过去沉积测量的问题，过去的沉积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细节丰富的数据集。数据将包括粒径分布、元素组成和粒径范围在700 nm至100 µm之间的颗粒混合状态。特别注意潜在的营养素，铁，磷，钾，镁和钙。在Frioul岛的测试阶段之后，将利用现有的时间序列对采样器进行验证，之后将在与灰尘进入海洋有关的地点部署三台仪器：佛得角的Sao Vicente岛;巴巴多斯，捕获撒哈拉外流;冰岛的Heimaey岛，捕获北极灰尘。计划进行第二个项目阶段（在本项目之后），其中网络将扩展到南美洲羽流中的福克兰群岛新岛;亚洲外流中的日本阿马库萨岛Araoteke;以及位于南非东西外流和澳大利亚东西外流之间的阿姆斯特丹岛。该项目将首次提供矿物粉尘湿和干沉积的连续系列，具有每日（干）或基于事件的（湿）时间分辨率和粒度分辨率。将描述导致沉积事件的大气关键因素。我们将评估营养物质的分配-特别是铁和磷-在湿和干沉积之间，并将确定相应的粒度分布。通过混合模型和图像分析评估颗粒混合状态和颗粒形状。将为模型验证提供一个公共数据库。计划在DFG供资阶段之后，这些台站将继续运行。

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.