Geochemical tracing of synoptic scale modern dust transport over the Northeast Arabian Sea during the southwest monsoon

Udisha Singh; K Suresh; Priyesh Prabhat; Waliur Rahaman; Ashwini Kumar

doi:10.1016/j.scitotenv.2023.164438

Geochemical tracing of synoptic scale modern dust transport over the Northeast Arabian Sea during the southwest monsoon

Sci Total Environ. 2023 Oct 1:893:164438. doi: 10.1016/j.scitotenv.2023.164438. Epub 2023 May 27.

Authors

Udisha Singh¹, K Suresh², Priyesh Prabhat³, Waliur Rahaman³, Ashwini Kumar⁴

Affiliations

¹ Geological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa-403004, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India.
² Geosciences Division, Physical Research Laboratory, Ahmedabad-380009, India.
³ National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Goa-403804, India.
⁴ Geological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa-403004, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India. Electronic address: ashwinik@nio.org.

PMID: 37247736
DOI: 10.1016/j.scitotenv.2023.164438

Abstract

During the Southwest monsoon (SWM), aeolian dust is mainly supplied via wet deposition over the northeast Arabian Sea (NEAS). To understand their impact on the biogeochemistry of the Arabian Sea, it is important to identify their sources and characteristics. In this context, wet deposit particulate (WDP) samples were collected at a coastal station (Goa; 15.4° N, 73.8° E) in the NEAS during the SWM for three years. These samples were used to characterize and identify mineral dust sources using mineralogical, elemental, and isotopic (Sr and Nd) signatures. The WDP samples were classified as Beginning of Monsoon (BM, June samples), Mid Monsoon (MM, July-August samples) and End of Monsoon (EM, September samples). Clay mineralogical composition indicate high palygorskite content during BM, which subsequently found to decrease in MM, and almost negligible in EM. However, smectite is highest during MM, with moderate presence of palygorskite during this period. The considerable variation in the relative percentages of clay minerals suggests significant temporal variability in dust sources which is further corroborated by the radiogenic isotopic composition. A strong seasonality in the isotopic composition is observed with ⁸⁷Sr/⁸⁶Sr ratio being relatively less radiogenic during MM than the BM and highly radiogenic at the EM. Whereas Ɛ_Nd values show an opposite trend to ⁸⁷Sr/⁸⁶Sr ratios throughout the monsoon, with more radiogenic Ɛ_Nd in the MM, and less radiogenic at the EM. End member mixing plot indicate dominant contribution of dust from the Arabian Peninsula (ARB) and Northeast African (NEA) sources during BM and MM, while a shift towards the Thar desert and Southwest Asian (SWA) sources at the EM. Trace elements associated with different sources were quantified and suggest high Fe concentration is associated with NEA dust sources, despite ARB being major supplier of aeolian dust to the Arabian Sea.

Keywords: Arabian Sea; Clay mineralogy; Mineral dust; Sr-Nd isotopes; Trace elements.