The role of dissolved organic matter in atmosphere-land-river interactions

Since 2017, we investigated iDOM in tropical and temperate rivers across Amazonia and Scotland using the next-generation liquid chromatography organic carbon detection – organic nitrogen detection system utilised by Pereira et al. (2014). Monthly sampling of rivers including the Cree, the Clyde and the Forth show evidence for iDOM mobilisation, but no clear quantitative relationship between DOC and iDOM. Humic compounds are the dominant DOC fraction (40 to 80%), contrasting with observations from tropical rivers. In order to get a better understanding of short-term temporal changes of iDOM and its mobilisation in headwaters we studied the DOM composition and changes in a small headwater stream of the River Forth in Scotland, the Menstrie Burn.

We investigated the riverine carbon exports from a two headwater peatland environments in the UK, and examined the potential uncertainty of quantification due to the role of optically “invisible” dissolved organic matter (iDOM). Importantly, our work captured compositional changes of riverine DOM in during an exceptionally dry period and compared these with rain events during a generally wetter cooler period in 2018, perhaps an analogue of future climate and weather scenarios. A novel size exclusion chromatography technique allowed elucidation of five different DOM pools including Humics to Biopolymers, Building Blocks, lower molecular weight (LMW) Acids, and LMW Neutrals, without isolating or modifying the original sample.