Laberge-Carignan Audrey, Mercier Florence, Larivière Dominic, Couture Raoul-Marie
Department of Chemistry, Centre for Northern Studies (CEN) and Interuniversity Research Group in Limnology (GRIL), Université Laval, 1045 Avenue de La Médecine, Québec, QC G1V 0A6 Canada.
Department of Chemistry and Centre for Northern Studies (CEN), Université Laval, 1045 Avenue de La Médecine, Québec, QC G1V 0A6 Canada.
Biogeochemistry. 2025;168(4):65. doi: 10.1007/s10533-025-01256-1. Epub 2025 Aug 1.
Selenium (Se) biogeochemistry in boreal and permafrost-rich soils and sediments remains poorly constrained, despite its importance as both an essential micronutrient and potential contaminant. As climate change accelerates warming in northern ecosystems, the mobilization of vast carbon pools may significantly alter Se cycling and bioavailability, with cascading effects on aquatic food webs. In this context, we aim to investigate how temperature and organic matter (OM) lability influence Se redox dynamics in lake sediments, providing insights for predicting its behavior as these northern ecosystems continue to warm. We studied Se sequestration as a function of OM lability, temperature (4 and 23 °C) and Se speciation in minimally disturbed lacustrine sediments using flow-through reactors (FTRs). Initial sediments contained OM characterized as either labile (fresh) or recalcitrant (aged), and were fed with environmentally relevant, low Se concentrations and filtered lake water. We monitored Se concentration as well as speciation along with pH and the concentrations of dissolved OM, NO , NO , Fe(II), SO and HS in the outflow of FTRs during 8 experimental phases. All sediments sequestered a large proportion of Se, with FTRs containing fresh OM removing 50% more Se than those containing aged OM. Along with a higher production of reduced species, such as ferrous Fe and sulfides, in the reactors with fresh OM, this result is consistent with reducing conditions promoting Se sequestration. Inflowing selenite was sequestered to a larger extent than inflowing selenate. Lastly, only selenate removal responded strongly to temperature. With an inflow concentration of 100 nM, selenate was sequestered at a rate of 92 pmol cm d at 23 °C, which decreased to 80 pmol cm d at 4 °C. In selenate removal experiments, outflow Se speciation consisted mostly of organic Se species at 23 °C and, in contrast, entirely of selenate at 4 °C. We hypothesize that selenate removal proceeded via microbial processes, consistent with temperature-dependent reactions catalyzed by enzymes. Overall, our findings suggest that the mobilization and warming of the boreal and permafrost carbon pools may increase the capacity of aquatic environments to sequester Se, lowering its bioavailability.
The online version contains supplementary material available at 10.1007/s10533-025-01256-1.
尽管作为一种必需的微量营养素和潜在污染物，硒（Se）在北方和富含永久冻土的土壤及沉积物中的生物地球化学过程仍未得到充分的限制。随着气候变化加速北方生态系统的变暖，大量碳库的活化可能会显著改变硒的循环和生物有效性，并对水生食物网产生连锁反应。在此背景下，我们旨在研究温度和有机物质（OM）的易分解性如何影响湖泊沉积物中硒的氧化还原动态，为预测这些北方生态系统持续变暖时硒的行为提供见解。我们使用流通式反应器（FTR）研究了在最小程度扰动的湖相沉积物中，硒的固存作为OM易分解性、温度（4和23°C）以及硒形态的函数。初始沉积物中的OM被表征为易分解的（新鲜的）或难分解的（老化的），并以与环境相关的低硒浓度和经过过滤的湖水为食。在8个实验阶段中，我们监测了FTR流出物中的硒浓度、形态以及pH值，同时监测了溶解有机物质、NO 、NO 、Fe(II)、SO 和HS的浓度。所有沉积物都固存了很大比例的硒，含有新鲜OM的FTR比含有老化OM的FTR多去除50%的硒。随着新鲜OM的反应器中产生更多的还原态物质，如亚铁和硫化物，这一结果与促进硒固存的还原条件一致。流入的亚硒酸盐比流入的硒酸盐被固存的程度更大。最后，只有硒酸盐的去除对温度有强烈响应。当流入浓度为100 nM时，23°C下硒酸盐的固存速率为92 pmol cm d，4°C时降至80 pmol cm d。在硒酸盐去除实验中，23°C时流出物中的硒形态主要由有机硒物种组成，相反，4°C时完全由硒酸盐组成。我们假设硒酸盐的去除是通过微生物过程进行的，这与酶催化的温度依赖性反应一致。总体而言，我们的研究结果表明，北方和永久冻土碳库的活化和变暖可能会增加水生环境固存硒的能力，降低其生物有效性。
在线版本包含可在10.1007/s10533-025-01256-1获取的补充材料。
