资源环境科技发展态势分析平台

Concentration and chemical composition of dissolved organic carbon (DOC) influence several lake functions; greenhouse gas exchange, nutrient cycling, food webs and water treatability. To assess spatial and inter-annual controls on DOC characteristics, 34 lakes were sampled annually for eight years on the Boreal Plains, Western Canada – a region with heterogeneous surficial geology, and a sub-humid climate with pronounced inter-annual wet-dry periods. Large spatial variability in long-term average DOC concentration (10 to 49 mg C L^-1) and aromaticity (SUVA₂₅₄: 1.2 to 3.9 L mg^-1 C m^-1) among lakes was found. Higher DOC concentrations and aromaticity were associated with lakes in watersheds with fine-textured surficial geology and with relatively large contributions through shallow, organic-rich flow paths. Lake DOC aromaticity was also higher in lakes with lower evaporative enrichment, regardless of surficial geology, indicating shorter lake water residence times and less within-lake degradation of allochthonous DOC. High inter-annual variability for both DOC and aromaticity was observed, with coefficients of variation at 10.9 ±4.6% and 11.1 ±2.5% among lakes, respectively. Inter-annual variability in DOC concentrations had low synchronicity among lakes, with patterns of variability linked to surficial geology and primarily responsive to short-term cumulative precipitation. Conversely, inter-annual variability in aromaticity had high synchronicity among lakes, driven by longer-term cumulative precipitation and shifts in lake water residence times. Our study shows it is necessary to consider lake hydrogeomorphic setting and climate to understand spatial and inter-annual variability in lake DOC characteristics and associated lake functions, and that Boreal Plains lakes have high climate sensitivity.

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