Small lakes of the boreal zone are highly sensitive indicators of both global environmental change and local anthropogenic pressure. This work presents the results of multidisciplinary study of three small, seasonally stratified lakes of NW Russia, conducted since 2002 to the present time. These lakes were subjected to various degree of impact by rural population and agricultural activity since the beginning of twentieth century but the population and anthropogenic pressure have decreased since 1990s. To monitor the recovering of these lakes from human impact and to relate the evolution of their hydrochemical parameters to short-term weather events and global climatic trend, we measured the lake water temperature and chemical composition (carbon, macro- and micronutrients, trace elements) in summer and winter over full depth of the water column. The pH and concentration of DIC, SO 4 and H 2 S decreased over past decade. Concentrations of Si and nitrite increased over past 15 years, probably linked to progressive replacement of diatoms by cyanobacteria. We also recorded an increase in concentration of Cl and major cations in all lakes, likely linked to increasing connection to groundwater reservoirs. Some trace elements (Fe, Mn, Al, Zn, As, Pb) can serve as suitable indicators of on-going natural processes controlling lake response to external factors. Unlike widely reported global trend of DOC and Fe concentration increase in boreal surface waters of Europe and Northern America, such trend was not discernable in studied Fe-rich humic lakes. We conclude on the necessity of complex, multidisciplinary studies of small humic lakes in the boreal zone, because these “model” lakes can serve as important proxies of on-going environmental changes in highly abundant aquatic ecosystems of poorly characterized regions of NW Russia.

中文翻译：

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自然和人为因素下北方小湖水化学参数的变化（以俄罗斯西北部为例）

北方地区的小湖泊是全球环境变化和当地人为压力的高度敏感指标。这项工作展示了自 2002 年至今对俄罗斯西北部三个季节性分层的小型湖泊进行多学科研究的结果。自 20 世纪初以来，这些湖泊受到农村人口和农业活动的不同程度的影响，但自 1990 年代以来人口和人为压力有所下降。为了监测这些湖泊从人类影响中的恢复情况，并将其水化学参数的演变与短期天气事件和全球气候趋势联系起来，我们测量了湖水温度和化学成分（碳、宏量和微量营养素、微量元素）在夏季和冬季超过整个水柱深度。DIC、SO 4 和H 2 S 的pH 值和浓度在过去十年中有所下降。在过去的 15 年中，Si 和亚硝酸盐的浓度有所增加，这可能与蓝藻逐渐取代硅藻有关。我们还记录到所有湖泊中 Cl 和主要阳离子的浓度增加，这可能与与地下水水库的连接增加有关。一些微量元素（Fe、Mn、Al、Zn、As、Pb）可以作为控制湖泊对外部因素响应的正在进行的自然过程的合适指标。与广泛报道的欧洲和北美北方地表水中 DOC 和 Fe 浓度增加的全球趋势不同，这种趋势在所研究的富铁腐殖质湖中是不可辨别的。我们得出结论，对北方地区的小型腐殖质湖进行复杂的多学科研究的必要性，