Publication Details

Category Text Publication
Reference Category Journals
DOI 10.1016/j.chemgeo.2023.121621
Title (Primary) Chemical composition of monsoon bulk precipitation in the Salalah area, Oman
Author Michelsen, N.; Friesen, J. ORCID logo ; Strauch, G.; Al-Balushi, Z.M.; Bait Said, A.B.A.; Al Balushi, H.; Schmidt, M.; Müller, T.
Source Titel Chemical Geology
Year 2023
Department ISOBIO; HDG; UBZ
Volume 635
Page From art. 121621
Language englisch
Topic T5 Future Landscapes
T7 Bioeconomy
Keywords Rain; Precipitation chemistry; Dry deposition; Indian Ocean; Monsoon; Khareef; Dhofar

Precipitation chemistry data provide important information for environmental studies on large-scale element cycling and anthropogenic impacts on our atmosphere, but also for hydrochemical models and groundwater recharge estimations via the Chloride Mass Balance method. Such recharge data play a crucial role in groundwater management, particularly in (semi-)arid areas. Unfortunately, precipitation analyses are often scarce in such regions. This also applies to the Arabian Peninsula, including southern Oman. To overcome this lack of rain chemistry data, we developed a strategy for automatic weekly bulk precipitation sampling, using recently designed automatic rainwater samplers. The integral samples were gathered along an elevation gradient from the Salalah coast to the Dhofar mountains during the Indian Ocean Monsoon seasons 2017 and 2018.

Our major ion analyses of the rainwater samples revealed considerable temporal and spatial heterogeneity, in terms of ion proportions and absolute concentrations. Samples from the coast were relatively salty (EC mostly >3000 μS cm−1) and rich in Na+ and Cl, reflecting small rain amounts and a sea spray effect. Further inland, solute concentrations were lower, partly due to more precipitation, and ions such as Ca2+ and SO42− gained importance, probably due to calcite and gypsum dust. This pattern reflects the interplay between solute availability (influenced by regional geology, wind direction at different altitudes, and wind speed) and precipitation amounts. Cl/Br ratios were fairly uniform and scattered around the seawater value. Combining ion concentrations and rain amounts yielded bulk depositions that showed an erratic pattern along the elevation gradient, i.e., depositions did not decrease steadily in inland direction, as one may assume. This suggests that the occasionally reported approach of collecting a few opportunistic grab samples at a single site is unlikely to yield data that are representative for a larger coastal study area.


Persistent UFZ Identifier
Michelsen, N., Friesen, J., Strauch, G., Al-Balushi, Z.M., Bait Said, A.B.A., Al Balushi, H., Schmidt, M., Müller, T. (2023):
Chemical composition of monsoon bulk precipitation in the Salalah area, Oman
Chem. Geol. 635 , art. 121621 10.1016/j.chemgeo.2023.121621