Bromine soil/sediment enrichment in tidal salt marshes as a potential indicator of climate changes driven by solar activity: New insights from W coast Portuguese estuaries

摘要: Abstract This paper aims at providing insight about bromine (Br) cycle in four Portuguese estuaries: Minho, Lima (in the NW coast) and Sado, Mira SW coast). The focus is on their tidal marsh environments, quite distinct with regard to key biophysicochemical attributes. Regardless of primary bromide (Br − ) common natural source, i.e., seawater, marshes present relatively higher surface soil/sediment Br concentrations than ones from coast. happens close connection organic matter (OM) content, controlled by main climatic contexts. Yet, anthropogenic impact cannot be discarded. Regarding [Br] spatial patterns across marshes, results show a general increase flat toward high marsh. Maxima occur upper driftline zone, transition highest low marsh, recognized as privileged setting for OM accumulation. Based discovery ubiquitous bromination marine transitional it assumed that this occurs mainly organobromine. Analysis two dated sediment cores indicates that, despite having same age (AD ~ 1300), Caminha salt (Minho estuary) evidences enrichment Casa Branca (Mira estuary). related greater storage ability, which linked build-up rate dynamics under different climate scenarios. Both evidence fairly similar temporal pattern, may interpreted light sun–climate coupling. Thereby, most well-known Grand Solar Minima during Little Ice Age appear have left an imprint these supported soils/sediments. Besides changes driven solar activity impacting biogeodynamics, those peaks might also reflect inputs enhanced volcanic covarying Minima.