Elemental distributions in the marine sediments off Doha, Qatar: role of urbanisation and coastal dynamics

Abstract

This research investigates the present status and decadal variability of element distributions in the marine sediments off Doha, on the east coast of Qatar. Twenty elements were considered from 11 sediment sampling stations and 3 dust sampling stations by grouping them into major elements, toxic elements, and other trace elements. The results show elevated concentrations of certain toxic and trace elements, including Ba, Be, Co, Cr, Cu, Fe, Mg, V, Zn, Mg, and Ti, in the nearshore region, primarily influenced by the settling of dissolved elements under weak hydrodynamic circulations in the Doha Bay. The relatively higher currents in offshore enable quick advection and dispersion of the elements. On the other hand, the dust deposits have caused significant contributions to the Al, As, Mg, Ca, Sr, Fe, Zn, and Cd concentrations. Decadal variability is evident in element concentrations, which are linked to the urbanisation of the capital city in the State of Qatar. The Cu, Ni, V, Zn, and Cd concentrations indicate a notable increase in recent years compared to the last two decades, with values of about 20.7, 17.9, 25.0, 25.9, 0.66 ppm in 2022. In contrast, a few other elements fluctuate between the decades/years. The results pointed out the increased elemental concentrations in the bay due to the vast expansion of infrastructure facilities in the vicinity of Doha Bay in recent years. The Geoaccumulation Index resulted in a slight pollution of Cd, while other elements are unpolluted. The Degree of Contamination reveals low degree of contamination of sediments, and the Pollution Load Index illustrates no significant pollution in the sediments off Doha.