Saharan dust is an important phosphorus (P) supply to remote and oligotrophic parts of the oceans and American lowland tropical rainforests. Phosphorus speciation in aeolian dust ultimately controls the release and bioavailability of P after dust deposition, but the speciation in Saharan dust and its change during the trans-Atlantic transport remains unclear. Using P K-edge X-ray absorption near edge structure (XANES) spectroscopy, we showed that with increasing dust traveling distance from the Sahara Desert to Cape Verde and to Puerto Rico, about 570 and 4000 km, respectively, the proportion of Ca-bound P (Ca-P), including both apatite and non-apatite forms, decreased from 68–73% to 50–71% and to 21–37%. The changes were accompanied by increased iron/aluminum-bound P proportion from 14–25% to 23–46% and to 44–73%, correspondingly. Laboratory simulation experiments suggest that the changes in P speciation can be ascribed to increasing degrees of particle sorting and atmospheric acidification during dust transport. The presence of relatively soluble non-apatite Ca-P in the Cape Verde dust but not in the Puerto Rico dust is consistent with the higher P water solubility of the former than the latter. Our findings provide insights into the controls of atmospheric processes on P speciation, solubility, and stability in Saharan dust.

中文翻译：

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跨大西洋尘埃运输过程中撒哈拉尘埃中磷转化的 X 射线光谱定量

撒哈拉尘埃是海洋和美国低地热带雨林的偏远和贫营养部分的重要磷 (P) 供应。风成尘中的磷形态最终控制着尘土沉积后磷的释放和生物利用度，但撒哈拉尘中的形态形成及其在跨大西洋运输过程中的变化尚不清楚。使用 P K 边缘 X 射线吸收近边缘结构 (XANES) 光谱，我们表明，随着从撒哈拉沙漠到佛得角和波多黎各的尘埃移动距离的增加，Ca-结合 P (Ca-P)，包括磷灰石和非磷灰石形式，从 68-73% 下降到 50-71% 和 21-37%。这些变化伴随着铁/铝结合的磷比例从 14-25% 增加到 23-46% 和 44-73%，相应地。实验室模拟实验表明，P 形态的变化可归因于粉尘运输过程中颗粒分选和大气酸化程度的增加。佛得角尘土中存在相对可溶的非磷灰石 Ca-P 而波多黎各尘土中不存在，这与前者的 P 水溶性高于后者是一致的。我们的研究结果提供了对大气过程对撒哈拉尘埃中 P 形态、溶解度和稳定性的控制的见解。佛得角尘土中存在相对可溶性的非磷灰石 Ca-P 而波多黎各尘土中不存在，这与前者的 P 水溶性高于后者是一致的。我们的研究结果提供了对大气过程对撒哈拉尘埃中 P 形态、溶解度和稳定性的控制的见解。佛得角尘土中存在相对可溶的非磷灰石 Ca-P 而波多黎各尘土中不存在，这与前者的 P 水溶性高于后者是一致的。我们的研究结果提供了对大气过程对撒哈拉尘埃中 P 形态、溶解度和稳定性的控制的见解。