Delineating Source Contributions to Stream Dissolved Organic Matter Composition Under Baseflow Conditions in Forested Headwater Catchments

Abstract

 High-frequency monitoring of water absorbance and high-resolution chemical analysis are highly complementary in the study of DOM dynamic. Ultrahigh-resolution mass spectrometry revealed linkage between dissolved organic matter molecular composition in-stream and soil. At comparatively higher DOC concentration at baseflow, DOM composition reflects the contribution of more superficial layers of the soil.

Riparian Microtopography Affects Event‐Driven Stream DOC Concentrations and DOM Quality in a Forested Headwater Catchment

“…The additional information on molecular DOC composition provided by FT‐ICR‐MS data showed that H/C wa , O/C wa , and AI mod wa during the precipitation event deviated from the values found in the shallow groundwater below the forest soil. All pre‐event molecular signatures (H/C wa = 1.19, O/C wa = 0.41, AI mod wa = 0.33) were similar to values found in water of a spring close to the stream in an earlier study (H/C wa = 1.18, O/C wa = 0.43, AI mod wa = 0.31; Da Silva et al., 2021). This DOC pool was characterized by aliphatic‐like, saturated compounds.…”

“…Pronounced spatial differences in DOC concentrations, DOM quality, and geochemistry were observed between the shallow groundwaters of sites FS and P despite the sampling locations being in close proximity to each other relative to catchment size. DOC concentrations in the shallow groundwater exceeded the concentrations found in the stream during baseflow and precipitation events investigated in previous studies (Blaurock et al, 2021;Da Silva et al, 2021). The convergence of DOC-rich subsurface flow pathways (Ploum et al, 2021) or the accumulation of DOC-rich surface water (Scheliga et al, 2019) could have led to the higher DOC concentrations in the topographic depressions at site P. Moreover, the large oscillations of the water table at site P could indicate a larger dominant carbon source layer and a more frequent activation of it (Ledesma et al, 2015;.…”

Swabian MOSES 2021: An interdisciplinary field campaign for investigating convective storms and their event chains

“…Grab samples were collected from various tributaries to identify potential water and pollution sources that may have contributed to both high discharge and contamination in the river. Analyses in the laboratory included water isotopes, greenhouse gases (Mwanake et al, 2022), total suspended solids, total organic carbon, dissolved organic matter composition (da Silva et al, 2021), nutrients, trace elements (Baborowski et al, 2004) organic contaminants and associated mixture toxicity (Neale et al, 2020).…”

Seasonal and spatial variation of stream macroinvertebrate taxonomic and functional diversity across three boreal regions

“…Boreal freshwaters experience particularly high seasonal variation in temperature and resource quality and quantity (Frainer et al, 2014). Accordingly, boreal freshwaters in forested regions (i.e., headwaters) are particularly dependent on allochthonous energy inputs (but see Brett et al, 2017), predominantly in the form of organic matter from runoff and seasonal leaf fall (da Silva et al, 2021), which are key factors responsible for shaping biological communities and food webs further down the stream continuum (Vannote et al, 1980; Woodward et al, 2010). By contrast, as global environmental change alters the seasonal variation of temperature regimes and allochthonous inputs (Woods et al, 2022), macroinvertebrate communities in headwaters, which are evolutionarily adapted to predictable seasonal conditions, are increasingly more at risk of alteration (Floury et al, 2018; Frainer et al, 2014; Tonkin et al, 2017).…”