Hydrochemistry of Three Dystrophic Lakes in Northeastern Poland

A hydrochemical investigation was carried out in spring, summer, and autumn, in the years 1991–1994, in three dystrophic lakes of the Wigry National Park (NE Poland). In spite of the fertile catchment basin, the developing ombrofile peat bogs of lake environment results in the acidification of lakes, the presence of small concentrations of dissolved mineral substances (below 50 mg L^–1), and exceptionally high DOC concentrations, exceeding 10 mg L^–1 C. During summer, a strong thermic stratification develops in the lakes, with constant conditions of oxygen deficiency prevailing below 3 m. In the course of the spring and autumn mixing of dystrophic lakes, the deterioration of oxygen conditions occurs in the epilimnion. In spite of high TP and NH₄⁺ concentrations, which increase from spring to autumn, the conditions developing in the lakes are unfavourable, for the functioning of aquatic organisms, on account of the strong shading. The increased direct irradiation of water bodies caused by deforestation or favourable atmospheric conditions results in an increased trophy of lakes.     

湖、库水体N2O排放研究进展

湖、库水体是重要的N₂O排放源,在全球氮素循环及全球气候变化中具有重要作用.本文综述了目前有关湖、库水体N₂O排放研究进展,重点介绍湖、库水体N₂O产生和排放的过程、不同时空尺度的排放特征、N₂O排放的影响因子框架及监测方法.湖、库水体N₂O不仅源于内部微生物硝化作用、反硝化作用、硝化-反硝化耦合作用、脱氮作用以及极少数底栖无脊椎动物代谢过程,同时流域上游河流汇入、地表径流输入、污水排放以及地下水排泄等构成湖、库水体N₂O的重要外源,但目前对内源/外源的相对贡献的定量化研究不足;湖、库水体N₂O排放方式包括扩散、植物传输及少量气泡排放,对水库而言,大坝下游水电涡轮机形成的脱气作用可能是N₂O排放的潜在途径.对文献综合分析表明,湖、库水体N₂O排放通常呈现明显的季节变化（夏季>冬季）和日变化,同时在全球（一般低纬度>高纬度）、区域及水体内部等不同尺度上表现出显著的空间变异性;这种时空变异特征主要受到湖、库自身理化因子（温度、营养盐、溶解氧、C/N、水文）、生物因子（水生植物、藻华）以及陆域人类活动（污水排放、农业活动以及城市化等）的影响;湖、库N₂O排放不同监测方法的差异也是潜在的影响因素,传统的漂浮箱法和薄边界层法均可能低估水体N₂O排放通量,未来需将传统的监测方法与新型的涡度相关法相结合,减小监测方法的不确定性.结合当前湖、库水体N₂O排放的研究不足,建议未来可以从湖、库N₂O产生的微生物机制,区域尺度上人类活动与湖、库群N₂O排放的耦合关系,水陆交错带的产、排过程,变化环境下的湖、库N₂O排放以及监测方法等方面深入研究.     

Stratigraphy of the mid-Holocene black bands in Lakes Michigan and Huron: Evidence for possible basin-wide anoxia

The post-glacial history of the Great Lakes has involved several changes in lake levels throughout the latest Pleistocene and Holocene, resulting from the changing position of the retreating Laurentide ice sheet, outlet incision and isostatic rebound. The final lowering of lake levels occurred at approximately 7600 ¹⁴C yr BP, after which lake levels began to rise again to the Nipissing highstand at approximately 4700 ¹⁴C yr BP. During this time of rising lake levels, black bands of iron sulfide were being formed in the sediments of all five of the Great Lakes. These bands signify suboxic to anoxic conditions, at least within the sediments and possibly at the sediment-water interface, during the middle Holocene warm interval. During this interval, the climate was warmer and drier than present, possibly resulting in the occasional absence of seasonal turnover in the lakes. We examined a series of piston cores from northern Lakes Michigan and Huron and found that the black bands are correlatable among cores taken from within the same basin. The observation that the banding can be correlated suggests a basin-wide cause, near-bottom or sub-bottom anoxia in the northern Michigan and northern Huron sediments during the mid-Holocene warm period. The sedimentary and geochemical processes in the Great Lakes during the middle Holocene warm interval are good indicators of possible future scenarios for the lakes as a result of global warming, as 21^st-century temperatures are predicted to reach similar levels due to increased concentrations of greenhouse gases.     

Paleoshoreline geomorphology of Böön Tsagaan Nuur, Tsagaan Nuur and Orog Nuur: the Valley of Lakes, Mongolia

We conducted a preliminary study of paleoshoreline features associated with Böön Tsagaan Nuur, Tsagaan Nuur, and Orog Nuur, lakes located in the Gobi–Altai transition zone of the Valley of Lakes (Dolina Ozor) which stretches from central to western Mongolia. The paleoshoreline features were first identified on RADARSAT satellite SAR imagery. We investigated the features during the 1998 field season of the Joint Mongolian–Russian–American Archaeological Expedition to the Gobi–Altai region. We identified paleoshorelines of multiple elevations in the field, which are considered to be relict beach ridges and wave-cut terraces. Other paleolake landforms include spits and Gilbert-type deltas. These landforms are complex, large and well established, implying that the paleolakes were stable for extended periods. The reconstructed paleolakes cover extensive areas of the valley floor, implying that hydrological and climatic conditions were very different in the past. Paleolake expansions may have occurred under a variety of circumstances. One hypothesis is that the high lake stands occurred during the wetter period corresponding to the Oxygen Isotope Stage 3 prior to the Last Glacial Maximum (LGM), during the warmest early Holocene and the late Holocene, or during all these periods. If low evaporation rates due to lower temperatures, glacier meltwater and possibly increased precipitation are important factors, then the expansions may have occurred during the terminal Late Glacial period after the Last Glacial Maximum. The greatly expanded lakes in the Gobi–Altai could have significantly affected the Quaternary human demography and migration in the region.     

Quantifying climatic change through the last glacial–interglacial transition based on lake isotope palaeohydrology from central Turkey

Questions remain as to the nature of climatic change through the last glacial–interglacial transition in the eastern Mediterranean region, particularly the relative contribution of evaporation and precipitation to regional water balance. Here changes in oxygen isotope values through this time period from Eski Acıgöl, a crater lake in central Turkey, are investigated using hydrological and isotope mass balance models. These allow changes in evaporation and precipitation to be quantified and their relative importance evaluated. We show that it is the volumetric flux rate of water passing through the lake system and not the precipitation-to-evaporation ratio per se which controlled the stable isotope record in Eski Acıgöl. Early Holocene precipitation is shown to be much greater than that during both the latter part of the last glaciation and the present day. We test these calculated values against other records in the same region, firstly with other lake records in Anatolia, the Konya basin and Lake Van, and secondly with isotope-inferred palaeo-precipitation data from Soreq cave in Israel. This reveals a contrast between pre- and post-LGM precipitation values in Turkey (wetter and drier, respectively) and also suggests that during the last glacial–interglacial transition there was a more marked precipitation gradient than at present between northern/interior and southern/coastal parts of the eastern Mediterranean region.     

南四湖沼泽化现状及其驱动因素分析

为了解南四湖近几年沼泽化加剧的现状及其根源,2008年8月,2009年6月,2009年8月,2010年6月和2010年8月先后多次对南四湖全湖,及21条主要入湖河道河口区进行调查和采样分析.结果表明:调查的25个样点中除微山岛保护区附近和船舶密集的界河口附近4个样点无沼泽化表征,运输繁忙的老万福河人湖口和南阳湖敞水区2...     

Inter-annual Arcellinida (testate lobose amoebae) assemblage dynamics within lacustrine environments

Arcellinida (testate lobose amoebae) were examined from 22 surface-sediment samples collected from homogenous environments in eastern Canadian lakes (Lac du Castor Blanc, SW Quebec; Oromocto Lake, SW New Brunswick) to: 1) evaluate the faunal consistency of assemblages within the targeted environments; and, 2) assess the Arcellinida assemblage response evident in samples collected from Oromocto Lake in 2010 CE (n = 10) and 2012 CE (n = 6) to inter-annual changes in environmental conditions. Cluster analysis and detrended correspondence analysis (DCA), redundancy analysis (RDA), and Bray-Curtis Dissimilarity Matrix (BCDM) were used to identify the dominant arcellinidan assemblages, determine physicochemical controls over the Arcellinida distribution, and assess the assemblages’ faunal homogeneity, respectively. Cluster analysis, DCA, and BCDM results revealed two distinct and relatively homogenous arcellinidan assemblages: 1) Lac du Castor Blanc Assemblage; and 2) Oromocto Lake Assemblage, which could further be subdivided into Oromocto Lake 2010 CE (OL10), and 2012 CE (OL12) sub-assemblages. RDA results showed that 65.6% of the variance in the arcellinidan distribution could be attributed to four significant parameters; sand size fraction (32.1%), calcium (29.2%), manganese (2.7%), and organic content (1.5%). The OL10 and OL12 sub-assemblages aligned well with the respective sample collection dates of 2010 CE and 2012 CE, with proportions of the healthy-lake-indicating Diffluggiid taxa being higher in OL12, likely due to a concurrent slight increase in substrate organic content in the 2012 CE sediments. Our results confirm the faunal homogeneity of assemblages in limnologically similar environments, and demonstrate the rapid response of Arcellinida assemblages to changes in lake conditions at inter-annual time scales.     

北美五大湖水环境保护经验分析

介绍了位于美国和加拿大边界的世界上最大的淡水水体--北美五大湖的基本情况及水环境污染和治理历程,讨论美加两国政府在水环境保护方面合作的经验,概括了五大湖环境保护工作所取得的成就.实践证明,五大湖水资源综合管理体制、水环境保护策略是行之有效的.经过几十年的努力,五大湖的水质状况已有明显改善,尤其是在人群健康保障、富营养化治理和有毒物质消减方面取得了长足的进步.     

广州市湖泊水体中防腐剂浓度及其潜在毒性风险

为研究广州市湖泊水体中的防腐剂及其毒性,在广州市选择15个湖泊采集水样,采用液液萃取-气质联用法对湖泊水体中的对羟基苯甲酸甲酯、对羟基苯甲酸乙酯等5种防腐剂进行浓度检测和毒性分析.结果表明:广州市区内15个湖泊水体中均检出防腐剂,但其浓度略低于国外天然水体中的浓度,溶解相的防腐剂平均浓度为5.06 ng/L,颗粒相的平均浓度为0.78 ng/L;广州市区的湖泊水体中溶解相浓度最高的防腐剂为对羟基苯甲酸丁酯,占总量的30.45%,对羟基苯甲酸苯甲酯所占比例最小,占6.71%;以防腐剂对发光细菌光强的抑制强弱来表征其毒性的大小,对羟基苯甲酸苯甲酯的毒性最强,对广州市湖泊水体环境的影响最大.     

南四湖演变过程及其背景分析

建立在前人研究的基础上,对南四湖演变过程及其背景进行了分析,指出四湖成因及演变过程有所不同。昭阳湖演变由大到小而微山湖则相反,独山湖应运而生,南阳湖因下游淤塞而成,它们的演变与黄河泛滥、运河的改道及人工对运河的运作关系密切。