• Vogel, C.; Helfenstein, J.; Massey, M.S.; Sekine, R.; Kretzschmar, R.; Beiping, L.; Peter, T.; Chadwick, O.A.; Tamburini, F.; Rivard, C.; Herzel, H.; Adam, C.; Pradas del Real, A.E.; Castillo-Michel, H.; Zuin, L.; Wang, D.; Félix, R.; Lassalle-Kaiser, B.; Frossard, E.: Microspectroscopy reveals dust-derived apatite grains in acidic, highly-weathered Hawaiian soils. Geoderma 381 (2021), p. 114681/1-11

Open Access Version

Dust deposition is an important source of phosphorus (P) to many ecosystems. However, there is little evidence of dust-derived P-containing minerals in soils. Here we studied P forms along a well-described climatic gradient on Hawaii, which is also a dust deposition gradient. Soil mineralogy and soil P forms from six sites along the climatic gradient were analyzed with bulk (X-ray diffraction and P K-edge X-ray absorption near edge structure) and microscale (X-ray fluorescence, P K-edge X-ray absorption near edge structure, and Raman) analysis methods. In the wettest soils, apatite grains ranging from 5 to 30 µm in size were co-located at the micro-scale with quartz, a known continental dust indicator suggesting recent atmospheric deposition. In addition to co-location with quartz, further evidence of dust-derived P included backward trajectory modeling indicating that dust particles could be brought to Hawaii from the major global dust-loading areas in central Asia and northern Africa. Although it is not certain whether the individual observed apatite grains were derived from long-distance transport of dust, or from local dust sources such as volcanic ash or windblown fertilizer, these observations offer direct evidence that P-containing minerals have reached surface layers of highly-weathered grassland soils through atmospheric deposition.