We investigated the sources and processes affecting the vertical distribution of tropical PM_x aerosols (particulate matter -PM- smaller than 10, 2.5 and 1 μm, PM₁₀, PM_2.5 and PM₁, respectively) in the low troposphere of Santo Antão and São Vicente islands, in Cape Verde archipelago, a region where a better understanding of aerosols is needed due to their involvement in tropical meteorology and their impact on air quality, ocean and climate. We found that local sources had a low-scale impact. From transect measurements at ground level, we found that PM_x levels were predominantly low, except near to PM_x sources, where distinctive PM₁ / PM_2.5 ratios were measured, linked to vehicle exhaust (0.96), biomass burning (0.67) and Cape Verdean dust (0.36) emissions. The depth of the marine boundary layer (MBL) and the vertical distributions of PM_x showed wide variability prompted by meteorological conditions. The trade winds prevailed in the MBL, whereas other airflows were situated above it: North-Atlantic, African easterly airflow and Saharan Air Layer. Under North-Atlantic airflow conditions, the MBL extended to 1400 m above sea level (m.a.s.l.). Above this altitude, PM_x concentrations decreased quickly (< 3 μg/m³) due to the free troposphere conditions. Under Saharan dust conditions, the MBL was confined to just 70 m.a.s.l., whereas a complex dust stratification was observed above, characterized by alternating dry air layers with high dust loads (PM₁₀ ~ 100 μg/m³) and more humid air layers with lower aerosol loads (PM₁₀ ~ 40 μg/m³). Within the dry easterly African airflow occurring above the marine stratocumulus typical of the MBL top (placed at 500 m.a.s.l.), we detected layers enriched in hydrophilic aerosols (PM₁₀: ~ 8 μg/m³). These were imbedded in relatively humid air (RH ~48%), probably linked to secondary aerosol formation by in-cloud processes in the marine stratocumulus situated below. We found that PM_x transport from North Africa, both under dust and dust-free conditions, is associated with complex vertical stratifications, even within the dusty Saharan Air Layer.

我们调查了影响Santo Antão 和 São 低对流层中热带 PM _x气溶胶（颗粒物质 -PM- 分别小于 10、2.5 和 1 μm，PM ₁₀、PM _2.5和 PM ₁）垂直分布的来源和过程佛得角群岛的维森特群岛，该地区需要更好地了解气溶胶，因为它们涉及热带气象学及其对空气质量、海洋和气候的影响。我们发现本地来源的影响很小。从地面横断面测量中，我们发现 PM _x水平主要较低，但靠近 PM _x源的地方除外，其中独特的 PM ₁ / PM _2.5测量了与汽车尾气 (0.96)、生物质燃烧 (0.67) 和佛得角粉尘 (0.36) 排放相关的比率。海洋边界层 (MBL) 的深度和 PM _x的垂直分布显示出受气象条件影响的广泛可变性。信风在 MBL 盛行，而其他气流则位于其上方：北大西洋、非洲东风气流和撒哈拉空气层。在北大西洋气流条件下，MBL 延伸至海拔 1400 m (masl)。在这个高度以上，PM _x浓度迅速下降（< 3 μg/m ³) 由于自由对流层条件。在撒哈拉沙尘条件下，MBL 仅限于 70 masl，而在上面观察到复杂的灰尘分层，其特征是具有高灰尘负载（PM ₁₀  ~ 100 μg/m ³）的干燥空气层和具有较低灰尘负载的更多潮湿空气层交替出现。气溶胶负荷（PM ₁₀  ~ 40 μg/m ³）。在 MBL 顶部典型的海洋层积云（位于 500 masl）上方发生的干燥的东风非洲气流中，我们检测到富含亲水性气溶胶的层（PM ₁₀：~8 μg/m ³）。它们嵌入在相对潮湿的空气中（相对湿度~48%），可能与位于下方的海洋层积云中的云中过程形成的二次气溶胶有关。我们发现，即使在尘土飞扬的撒哈拉空气层内，在有尘和无尘条件下，来自北非的PM _x传输都与复杂的垂直分层有关。