Are acid volatile sulfides (AVS) important trace metals sinks in semi-arid mangroves?

Highlights: • AVS formation and trace metals retention were studied in semiarid mangroves. • The semiarid climatic conditions limited the AVS formation. • The AVS contents were strongly correlated with reactive iron and organic. • AVS fraction is a minor sink for toxic metals in semiarid mangroves. - Abstract: Acid-volatile sulfides (AVS) formation and its role on trace metals bioavailability were studied in semi-arid mangroves. The semi-arid climatic conditions at the studied sites, marked by low rainfall and high evapotranspiration rates, clearly limited the AVS formation (AVS contents varied from 0.10 to 2.34 μmol g^{− 1}) by favoring oxic conditions (Eh > + 350 mV). The AVS contents were strongly correlated with reactive iron and organic carbon (r = 0.84; r = 0.83 respectively), evidencing their dominant role for AVS formation under semi-arid conditions. On the other hand, the recorded ΣSEM/AVS values remained > 1 evidencing a little control of AVS over the bioavailability of trace metals and, thus, its minor role as a sink for toxic metals.