This study examined dissolved redox sensitive elements（Mo，U and V, refers as RSMs）and sedimentary RSMs along with hydrochemical parameters during estuarine mixing between river water and seawater  end members in the upper Gulf of Thailand in May and November 2023. Mo and U behaved conservatively during estuarine mixing in May 2023, but showed removal in the low to mid-salinity range (e.g. Tha Chin River) in November 2023. The mild negative correlation between Chl-a and dissolved Mo and U suggests the possible involvement of high algal productivity in removing them out of the water column. Vanadium shows a general conservative mixing and potential removal at low to mid-salinities in November 2023, but has higher concentrations than that can be achieved from mixing of river water and average seawater at salinity <30 in May 2023. The observed excess V close to the estuary which may be due to the desorption from river-borne and estuarine sedimentary particles.
 

redox sensitive elements,,Upper Gulf of Thailand