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(C_org), 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 C_org, 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 C_org 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 C_org, 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 (¹³C_DOM) showed that in winter, most C_org 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.

中文翻译：

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在森林源头集水区，胶体集水区对融雪和降水事件的响应不同

气候变化影响集水流水中高排放 (HD) 事件的发生和相关的养分输出。基于胶体事件的重要营养物质（如有机 C(C _org )、N、P 和 S）的损失信息仍然相对稀缺。我们假设由于不同的水文机制，胶体输出的 N、S 和 P 的贡献在冬末和春季的 HD 事件之间有所不同。我们检查了一次融雪和降雨事件（2018 年 3 月）和一次降雨事件（2018 年 5 月）的时间 C _org、N、P 和 S 动态。通过不对称流场流分馏 (P) 和过滤级联 (N 和 S) 分析胶体及其子集纳米颗粒的集水出口。C_组织两个事件中的源是通过与土壤成分相关的河流水的 δ ¹³ C 组成来评估的。在冬季，<6% 的河流水 P 由胶体 (>0.1 μm) 运输，但在春季这一比例为 29-64%，并且与 C _org、Fe 和 Al 相关。在这两个事件中，胶体 N 和颗粒 S (>1 μm) 都较高，但大部分损失都被溶解了 (<0.1 μm)。溶解有机质 ( ¹³ C _DOM )的 δ ¹³ C 值表明，在冬季，大部分 C_组织由于融雪，流经矿层的水从水文相连的山坡输出。在降雨事件期间和之后，有机层的输出主要是作为颗粒物（包括胶体）的养分损失。这些事件突出表明需要更好地量化经常被低估的颗粒、胶体和纳米颗粒对集水区天气驱动的养分损失的贡献。