Armstrong Grace J, Janssen Sarah E, Lepak Ryan F, Rosera Tylor J, Peterson Benjamin D, Cushing Samia T, Tate Michael T, Hurley James P
U.S. Geological Survey, Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States.
Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
ACS ES T Water. 2025 Apr 10;5(5):2444-2454. doi: 10.1021/acsestwater.5c00028. eCollection 2025 May 9.
Increased lake eutrophication, influenced by changing climate and land use, alters aquatic cycling and bioaccumulation of mercury (Hg). Additionally, seasonally dynamic lake circulation and plankton community composition can confound our ability to predict changes in biological Hg concentrations and sources. To assess temporal variation, we examined seasonal total Hg (THg) and methylmercury (MeHg) concentrations and stable isotope values in seston, waters, sediments, and fish from two adjacent urban eutrophic lakes in Madison, Wisconsin. In Lake Monona, surface sediment THg concentrations were elevated due to comparably higher urbanization and historical industrial inputs, whereas Lake Mendota sediments had lower concentrations corresponding with largely agricultural and suburban surrounding watershed. Surface water THg and MeHg were similar between lakes and seasonally dynamic, but water profiles exhibited elevated concentrations in the meta- and hypolimnia, highlighting water column MeHg production. Seston MeHg concentrations were often highest at shoulder seasons, possibly owing to metalimnetic MeHg delivery, but also differences in biomass and water clarity. The ΔHg and δHg values in seston were similar between lakes, despite differing sediment THg concentrations and isotope values, suggesting a shared bioaccumulated source of MeHg. Measurement of MeHg stable isotopes further elucidated that seston and fish predominantly bioaccumulated pelagic-sourced MeHg.
受气候变化和土地利用变化的影响，湖泊富营养化加剧，改变了汞（Hg）的水生循环和生物累积。此外，湖泊季节性动态环流和浮游生物群落组成可能会干扰我们预测生物汞浓度和来源变化的能力。为了评估时间变化，我们检测了威斯康星州麦迪逊市两个相邻的城市富营养化湖泊中，悬浮物、水体、沉积物和鱼类的季节性总汞（THg）、甲基汞（MeHg）浓度以及稳定同位素值。在莫诺纳湖，由于城市化程度较高和历史工业投入较多，表层沉积物中的THg浓度升高，而门多塔湖沉积物中的浓度较低，这与周边流域主要为农业和郊区的情况相对应。两个湖泊的地表水THg和MeHg相似且具有季节性动态变化，但水体剖面显示，温跃层和湖下层的浓度升高，突出了水柱中MeHg的产生。悬浮物中的MeHg浓度通常在过渡季节最高，这可能是由于温跃层中MeHg的输送，也可能是由于生物量和水体透明度的差异。尽管沉积物THg浓度和同位素值不同，但两个湖泊悬浮物中的ΔHg和δHg值相似，这表明MeHg存在共同的生物累积来源。对MeHg稳定同位素的测量进一步表明，悬浮物和鱼类主要生物累积来自远洋的MeHg。
