Dissolved aluminium (Al) and barium (Ba) are trace elements in the ocean thought to be derived from detrital minerals but both also to be involved in direct or indirect biogeochemical processes. Ocean-wide studies on such processes, budgets and balances for these elements are usually limited due to too many open-end boundaries and unknown fluxes.  However, for the Mediterranean fluxes for Al, Ba have recently been studied as well as several related biogeochemical processes. In addition, the Mediterranean is recognized as a restricted basin and considered to be a model-ocean for which sources and sinks of detrital and dissolved material can be effectively studied.
Dissolved Ba profiles for global ocean and Mediterranean show a so-called ‘nutrient-type behaviour’, i.e. low surface water and enhanced deep-water concentrations. Dissolved aluminium profiles for the global ocean often show elevated concentrations in surface waters thought to relate to fractional dissolution from (Saharan) dust deposition. Below the surface, its concentration usually first decreases due to scavenging/uptake, then increases with depth. In contrast and despite major Saharan dust fluxes and low primary productivity, dissolved Al in the Mediterranean shows the same ‘nutrient-type behaviour’ as Ba. The apparent behaviour of dissolved Al and Ba in the Mediterranean water column is related to Atlantic inflowing surface water with low concentrations of Al and Ba, whereas the outflowing intermediate/deep water has much higher concentrations. This results in a major net removal of dissolved Al, Ba from the Mediterranean. In steady state, the large net removal of dissolved Al, Ba must be compensated by external sources.
Fractional dissolution from dust for Al derived to be 2.2±0.2% appears to be the main source (92%) for dissolved Al but a minor source (0.5%) for dissolved Ba. For Ba it is not the fractional dissolution from Al-silicates but rather a small barite fraction in dust that contributes substantially (11.5%). In contrast, riverine fluxes appear to be a minor flux for dissolved Al but a pronounced or even dominant source for dissolved Ba (8 vs 40%). The large remaining imbalance for Ba can only be attributed to rivers/groundwater; hence the insufficiently known groundwater / river contributions are likely to contribute not 40 but rather a total of ~ 70±15% (De Lange et al., 2026). Minor contributions for both elements are related to bottom sediments (Al: 0%; Ba: 3%); mud volcanoes and Messinian evaporites (Al, Ba < 0.2%), and removal by biogenic carbonates (-0.04%). River- and groundwater- derived dissolved Ba are the major source but with the largest uncertainty, hence requiring additional studies.

(Cited Ref. : De Lange, Torres-Crespo N., Martinez-Ruiz F., Schnetger B., 2026. Contrasting provenance, fluxes and budgets for dissolved aluminium and barium in the Mediterranean; an integrating overview. QuaternaryScienceReviews381(2026); /10.1016/j.quascirev.2026.109888)

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