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

Abstract

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

Climate reconstruction for the Entre‐Douro‐e‐Minho region (NWPortugal) betweenAD1626 andAD1820: synthesis of viticulture data and foraminiferal evidence

“…4A, C, D) throughout AD 1654-1725 (similar to the WP1 time frame), in which T. salsa/irregularis dominates (87-52%; mean 66%). This supports an increase in wetness in the studied area during the WP1 period, concomitant with higher contents of bromine and organic matter (OM) in the marsh's soils/sediments, both representative of rainy/colder conditions (Moreno et al 2015(Moreno et al , 2017b. Geochemical data from this marsh also revealed a maximum of terrestrial OM contribution at this time (de la Rosa et al 2012), moreover supporting increased continental runoff, and thus rainfall.…”

Towards integrating toxicity characterization into environmental studies: case study of bromine in soils

“…A comparison of several studies has shown that the wide variation of bromine contents in soils can be traced back to two main factors of influence. First, bromine concentration in soil mainly depends on the soil moisture content, and second, the bromine content of soil is positively correlated with the content of soil organic matter (Flury and Papritz 1993;Neal et al 2007;Moreno et al 2017). Since soil properties can influence related bioaccumulation and toxicity of bromine, it is important to determine soil parameters along with bromine concentrations in soils.…”

Using Principal Component Analysis (PCA) Combined with Multivariate Change-Point Analysis to Identify Brine Layers Based on the Geochemistry of the Core Sediment

“…In nature, Br is mainly concentrated in seawater in the form of ions, and the biggest natural reservoir is the ocean [44]. Br has historically been utilized in combination with Cl as a geochemical indicator for seawater intrusion in coastal regions and alone as a paleosalinity proxy and stratigraphic marker in cores [45].…”