Colloidal catchment response to snowmelt and precipitation events differs in a forested headwater catchment

Abstract

Climate change affects the occurrence of high‐discharge (HD) events and associated nutrient exports in catchment stream water. Information on colloidal events‐based losses of important nutrients, such as organic C(Corg), N, P, and S, remain relatively scarce. We hypothesized that contributions of colloidal exported N, S, and P due to differing hydrological mechanisms vary between HD events in late winter and spring. We examined one combined snowmelt and rainfall event (March 2018) with one rainfall event (May 2018) for temporal Corg, N, P, and S dynamics. The catchment exports of colloids and their subset nanoparticles were analyzed by asymmetric‐flow field flow fractionation (P) and a filtration cascade (N and S). The Corg source in both events was assessed by δ13C composition of the stream water in relation to that of the soil. In winter, <6% of stream water P was transported by colloids (>0.1 μm), but this was 29–64% in spring and was associated with Corg, Fe, and Al. Colloidal N and particulate S (>1 μm) were higher during both events, but the majority of losses were dissolved (<0.1 μm). The δ13C values of dissolved organic matter (13CDOM) showed that in winter, most Corg was exported from the hydrologically connected hillslopes by water flowing through mineral horizons, due to snowmelt. During and after the rainfall events, export from organic horizons dominated the nutrient losses as particulates, including colloids. These events highlight the need for a better quantification of often underreported particulate, colloid, and nanoparticle contributions to weather‐driven nutrient losses from catchments.

Soil water status shapes nutrient cycling in agroecosystems from micrometer to landscape scales

“…Especially high discharge events can cause substantial particulate P exports (Burger et al, 2021;Jiang et al, 2021;Tiemeyer et al, 2009). Even though the export of dissolved nitrate and sulfate is exceeding colloidal N and S exports (Burger et al, 2021), there is evidence that colloidal export of S can be substantial. Mainly organic S in different oxidation states (e.g., reduced species in sulfides, thiols;…”

“…Especially high discharge events can cause substantial particulate P exports (Burger et al., 2021; Jiang et al., 2021; Tiemeyer et al., 2009). Even though the export of dissolved nitrate and sulfate is exceeding colloidal N and S exports (Burger et al., 2021), there is evidence that colloidal export of S can be substantial. Mainly organic S in different oxidation states (e.g., reduced species in sulfides, thiols; intermediately oxidized species in sulfoxides, sulfones, and sulfonates; and fully oxidized S in sulfate esters) are released and transported (Adediran et al., 2021; Fakhraee et al., 2017), with the redox state being dependent on the redox conditions of the soil (Adediran et al., 2021; Boye et al., 2011).…”

“…Colloids have a large specific surface area and consist of primary building blocks such as organic matter, Fe/Al-(hydr)oxides, clays, or calcium carbonates with potential adsorption sites for nutritional ions (Burger et al, 2021;Gottselig et al, 2017;Philippe & Schaumann, 2014). Phosphate has the highest potential for colloidal exports due to its high adsorption affinity compared with nitrate and sulfate (Johnson & Cole, 1980).…”

Deforestation alters dissolved organic carbon and sulfate dynamics in a mountainous headwater catchment—A wavelet analysis

“…They demonstrated that sub-and whole-catchment streams had differences in DOC, pH, and iron dynamics, and extremely dry weather had little effect on stream water catchment chemistry. Another study in this catchment quantified and highlighted the contributions of particulate, colloids, and nanoparticles to weather-driven organic carbon, nitrogen, phosphorus, and sulfur losses (Burger et al, 2021). Weigand et al (2017) examined the spatiotemporal relationships between DOC and nitrate before the clear-cut by using Wavelet analysis.…”

Effects of deforestation on dissolved organic carbon and nitrate in catchment stream water revealed by wavelet analysis

“…Such conditions stimulate microbial activity altering decomposition rates leading to C release in the form of dissolved C and CO 2 (Gandois et al, 2012). Dissolved organic matter is generally the primary form of labile C in temperate and boreal terrestrial ecosystems and it serves as an important transport vector for organically bound nutrients to microorganisms within water bodies (Mostovaya et al, 2017;Guo et al, 2020;Burger et al, 2021). Furthermore, studies suggest that deforestation may increase the runoff generation in a catchment, e.g., due to a decrease in rainfall interception, evapotranspiration and soil compaction (Gholami, 2013;Hlásny et al, 2015;Wiekenkamp et al, 2016Wiekenkamp et al, , 2019, and it can also reshape the land-surface energy-flux partitioning (Yuan et al, 2021).…”