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首页> 外文期刊>Environmental Geology >Mineralogical and geochemical characterisation of alkaline lake sediments to trace origin, depositional processes, and anthropogenic impacts: Inle Lake (Southern Shan State, Myanmar)
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Mineralogical and geochemical characterisation of alkaline lake sediments to trace origin, depositional processes, and anthropogenic impacts: Inle Lake (Southern Shan State, Myanmar)

机译：碱性湖泊沉积物的矿物学和地球化学表征痕量，沉积过程和人为影响：Inle Lake（南山州，缅甸）

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摘要

Southeast Asia contains a major portion of wetland areas of international significance, but only 14% of these wetlands are under protection. Inle Lake is the second largest freshwater body in Myanmar and the most important for its environmental, economic, and agricultural values. However, the lake is seriously threatened by anthropic activities as they are dramatically decreasing its open water surface. While water-quality studies have assessed the presence of nutrients and contaminants, little is known about the sediment quality. Therefore, the overall objective of the present study was to analyse the natural sedimentation patterns and the anthropogenic disturbances in this lake. To this end, both grab and core sediments were investigated by combining mineralogical, morphological, and geochemical analyses, and their composition was compared to the composition of rocks and soil from the watershed. Mineralogical data indicate that sediment samples collected at or near the main inflow, and at the outflow show a lower abundance (about 43%) of calcite, which generally increases with depth in sediment cores, reaching more than 90% in the centre of the lake. Lower calcite contents correspond to higher percentages of other minerals. These findings allow us to clearly distinguish the allogenic (quartz, mica/illite, kaolinite, and detrital calcite) from the endogenic (mostly calcite) minerals, as confirmed by the soil and rock mineralogy. The origin of the mineral contents at the different sites is further supported by the observation of the grain morphology and composition. The most abundant metal in the lake sediments is Ca, in agreement with the high calcite content. Following in order of abundance are Al, Fe, and K, which are connected to the detrital input to the lake. In the rock and soil samples, the most abundant trace element is Mn, which is significantly correlated with many other trace elements (e.g., Co, Cr, Cu, Ni, V, Zn, and As), suggesting their common lithogenic origin. Similarly, in the lake sediments, the trace elements Co, Cr, Cu, Ni, Pb, V, Zn, and As display fairly homogenous concentration ranges, in the order of tens of ppm, and are strongly correlated with the detrital minerals (mica, kaolinite, and quartz) and negatively correlated with the calcite content. The mineralogical and elemental distribution in the lakebed area and with depth in the sediment cores allowed us to identify the increased soil and bedrock erosion as a major anthropogenic impact to the lake. The sedimentation disturbance is especially evident at the main inflow, the Nanlit stream, which has caused the development of a large alluvial fan, visible in satellite images. This large sediment input is likely to have accelerated the decrease in open water surface and in depth of this shallow lake. Additionally, when the measured concentrations of Potentially Toxic Elements were compared to consensus-based Sediment Quality Guidelines (SQGs), it was shown that As, Cr, Cu, Ni, Pb, and Zn often exceeded the threshold effect concentration (TEC), and that Cr, Ni, and Pb sometimes exceeded the probable effect concentration (PEC). On the other hand, Enrichment Factors (EFs), calculated with respect to soils of the watershed, showed minimal enrichment and indicated that the potential toxicity effect was primarily a result of detrital sedimentation outpacing carbonate sedimentation.Sediment characterisation allowed us to obtain a better understanding of lake dynamics and environmental impacts, which is fundamental in achieving effective management and maintenance of the ecological character of Inle Lake, in line with the objective set by the Ramsar Convention for wetlands of international relevance.
机译：东南亚包含湿地领域的主要部分国际意义，但只有14％的湿地受到保护。 Inle Lake是缅甸第二大淡水体，最重要的是其环境，经济和农业价值观。然而，湖泊受到人类活动的严重威胁，因为它们显着降低了其开阔的水面。虽然水质研究评估了营养和污染物的存在，但对于沉积物质量而言，毫无疑问。因此，本研究的总体目的是分析本湖泊的天然沉降模式和人为紊乱。为此，通过组合矿物学，形态学和地球化学分析来研究抢夺和核心沉积物，并将它们的组成与流域的岩石和土壤的组成进行比较。矿物学数据表明，在主要流入时或附近收集的沉积物样品，流出显示较低的丰度（约43％）方解石，这通常随着沉积物核心的深度增加，在湖中央达到90％以上。较低的方解石内容对应于较高百分比的其他矿物质。这些发现允许我们清楚地区分中生（石英，云母/伊雷耐力，高岭土和剥皮方解石）从内源性（主要是方解石）矿物质，如土壤和岩石矿物学所证实的那样。通过观察晶粒形态和组成，进一步支持不同部位的矿物质含量的来源。湖泊沉积物中最丰富的金属是CA，同时与高方解石含量一致。按照丰富的顺序是Al，Fe和K，它们与湖泊的脱歧投入连接。在岩石和土壤样品中，最丰富的痕量元素是Mn，其与许多其他微量元素显着相关（例如，CO，Cr，Cu，Ni，V，Zn和As），表明它们的常见型脑来源。类似地，在湖泊沉积物中，痕量元素CO，Cr，Cu，Ni，Pb，V，Zn，以及显示相当均匀的浓度范围，大量ppm，与碎屑矿物强烈相关（云母） ，高岭石和石英），与方解石含量负相关。湖边地区的矿物学和元素分布和沉积物核心深度允许我们鉴定较高的土壤和基岩侵蚀作为对湖泊的主要人为影响。在主要流入中，沉降扰动尤其明显，纳米杆流，这导致了大型冲积风扇的发展，在卫星图像中可见。这种大沉积物的投入可能加速了开放水表面的减少和这种浅湖的深度。另外，当比较潜在有毒元素的测量浓度与基于共有的沉积物质量指南（SQGS）进行比较时，结果表明，如，Cr，Cu，Ni，Pb和Zn经常超过阈值效果浓度（TEC），和CR，Ni和Pb有时超过可能的效果浓度（PEC）。另一方面，相对于流域的土壤计算的浓缩因子（EFS）表明富集的最小富集，并表明潜在的毒性效应主要是出现碳酸盐沉淀的滴乳沉降的结果。服务表征使我们能够获得更好的理解作者：王莹，湖泊动态与环境影响的影响是在实现INLE LAKE的生态特征的过程中，符合Ramsar湿地湿地的湿地公约的目标的有效管理和维护的基础。

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