Prioritization of pollution potential zones for conservation activities of a lake system

Many coastal lakes are under serious threats due to increased pressures associated with population growth, accelerated eutrophication, invasive species and toxic contamination. The extent of the pollution depends almost entirely on the characteristics and processes taking place in the lake basin. The objective of this study was to identify the pollution potential zones (very high, high, medium and low) in the Akkulam–Veli (A–V) Lake Basin (Thiruvananthapuram, Kerala) using GIS‐enabled, multithematic overlay analysis. The primary characteristics considered were geomorphology, lithology, land use, soil, slope and population density. The results of this study indicated the major portion of the lake basin exhibits very high or high pollution potential zones, with the drains passing through the very high pollution potential zone being mainly responsible for the contamination of the lake water. High population density, predominant commercial use and settlement with mixed tree crop, level and gentle slope (low slope) are the factors responsible for the very high pollution potential. The organic pollutants in the lake system increase with the increased extent of the very high pollution potential area. This analysis approach will help authorities to identify the underlying causes of lake water quality degradation and plan and implement effective measures for protecting the lake. This process can also be utilized by scientists elsewhere to facilitate lake protection.     

鄱阳湖流域入湖径流时空变化预测

对鄱阳湖未来入湖径流变化的准确预测可为"后三峡"时期水资源调度决策提供理论依据。基于实测资料发现,三峡水库蓄水后,鄱阳湖入湖年径流及各调度期径流均不同程度减少。通过ASD(Automated Statistical Downscaling)统计降尺度方法将GCM(General Circulation Model)输出数据与新安江水文模型耦合,得到未来鄱阳湖流域"五河七口"的入湖径流过程。结果表明,未来年径流相比实测变化幅度更小,偏多和偏少交替出现;集水面积较大的赣江、抚河和信江对鄱阳湖径流变化的贡献最大;无论A2还是B2情景下,均是蓄水期变化幅度最大、枯水期最小,且各调度期的入湖径流变化程度比年径流更大。     

An analysis of satellite-derived chlorophyll and algal bloom indices on Lake Winnipeg

Lake Winnipeg has experienced dramatic increases in nutrient loading and phytoplankton biomass over the last few decades, accompanied by a marked shift in community composition towards the dominance of cyanobacteria. Comprehensive lake-wide observations of algal blooms are critical to assessing the lake's health status, its response to nutrient management practices, and an improved understanding of the processes driving blooms. We present an analysis of the spatial and temporal variability of algal blooms on Lake Winnipeg using satellite-derived chlorophyll and indices for algal bloom intensity, spatial extent, severity, and duration over the period of ESA's MERIS mission (2002–2011). Imagery documented extensive blooms covering as much as 93% of the lake surface. Bloom conditions were analysed in the context of in-lake and watershed processes to gain further insight on the drivers of bloom events. Day to day bloom variability was driven primarily by intermittent wind mixing events, with quiescent periods leading to the formation of dense surface blooms. Seasonal bloom distribution was consistent with light limitation in the south basin and lake circulation transporting bloom material towards the north-east shore. Inter-annual variability in average bloom severity was related to both total phosphorus (TP) loadings and summer lake surface temperatures. Results provide a valuable historical time series of bloom conditions to which ongoing observations from Sentinel-3's OLCI sensor can be added for longer term monitoring and change detection.     

Fossil diatoms,geochemistry, and the Anthropocene paleolimnology of Lake Huron

Sediment cores from northern (NL) and southern (SL) Lake Huron were analyzed for diatom fossils and sediment geochemistry to investigate human effects on the lake over the last two centuries. Anthropogenic activities drove two major transformations in diatom indicators of lake ecology for the NL around 1972 and 1991 and three transformations for the SL around 1921, 1964, and 1998. The synergistic effects of increased agriculture and decreased forest land coincided with a shift in the SL to a more mesotrophic condition after 1921. Population increase and attendant industry and mining pollution were apparent in sediment contaminants that increased rapidly in the 1930s. Diatom indicators of climate change appeared as early as the 1970s. Mitigation efforts resulted in water quality improvements as indicated by geochemical indicators of contamination and diatom species shifts, but these changes were concurrent with the negative impacts of invasive mussels and climate warming since the 1990s. Until these stressors are alleviated phytoplankton abundance will likely remain at the current low levels. The composition of the diatom flora will continue toward dominance by Cyclotellasensulato, which may have implications on food web characteristics such as feeding strategies of zooplankton. Overall, these paleo-records provide evidence of human impacts, remediation, and future trajectories for lake condition, all of which are important factors for consideration by lake managers.     

Distribution and geochemical processes of boron in the multimedia of Lake Qinghai,China

Lake Qinghai on the Qinghai-Tibet plateau is the largest lake in China. This study investigated the concentration and geochemical processes of boron (B) in lake water, lake sediment and river samples collected from Lake Qinghai and the Buha River. In addition, lake sediment pore water samples were analyzed. The concentrations of B and major ions, including K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^? and SO₄^2?, were analyzed in all the water samples. The average concentration of B was 0.07?mg?L^?1, 6.37?mg?L^?1, 12.79) mg?L^?1 and 59.42?mg?kg^?1 for river water, lake water, pore water, and sediment, respectively. There were significant (p?<?0.05) and positive (r?=?0.70) relationships between the B concentrations in bottom water of the lake and in lake sediment, indicating that B diffusion from the sediment plays an important role in the concentration of B in bottom lake water. The differences in B concentrations and B/major ion molar ratios of the river water, lake water, and pore water indicated the following geochemical processes: 1) B is enriched in the lake water through evaporative concentration; 2) B is removed from the lake water through mineral precipitation as well as sorption onto colloids; 3) Solid-phase B in sediments was released through dissolution driven by organic matter mineralization. B/Cl and Na/Cl molar ratios alone are not enough to identify the sources of B in the water of inland closed-basin saline lakes because of these processes.     

变化环境下七里山水域高洪水位研究

七里山水域是洞庭湖汇入长江的江湖交汇区,受三峡工程及上游溪洛渡、向家坝水库运用清水下泄影响,江湖水沙输运、河道冲淤及河势演变、河段蓄泄关系、洪水位和泄流能力等出现诸多新变化,对长江中游特别是洞庭湖区的防洪蓄洪格局产生影响。在长江中下游水沙整体宏观数学模型的基础上建立了七里山水域二维水沙局部细致模拟数值模型,模拟研究了水库群运用后,在不同控制水位、不同蓄滞洪区启用条件下,针对各种典型洪水的防洪蓄洪问题。对于1998年型洪水,通过三峡等上游水库调节并抬高七里山控制水位0.5 m时,可不分蓄洪;对于1954年目标洪水,则需利用洞庭湖区24蓄洪垸和洪湖对等承担分蓄洪任务。     

洞庭湖区水环境现状调查与分析

为摸清洞庭湖区水体污染现状,揭示各区域水体营养化水平及营养盐的空间分布特征,利用长江水利委员会水文局在湖区的水文-水质综合站网,于2017年8月在全湖24个代表性断面开展了水文-水质同步监测,分析了洞庭湖各区域营养水平和水环境质量状况,计算了出入湖的污染物通量。结果表明,全湖除汨罗江和六门闸为中度富营养化外,其他区域为轻度富营养化,洞庭湖总体营养水平呈恶化趋势;藕池河北支(东洞庭湖入口之一)总氮含量显著高于其他区域,其次是东洞庭湖出口处;沅水总磷含量显著高于其他区域,其次是大通湖、东洞庭湖出口处和藕池河;六门闸(东洞庭入口之一)高锰酸盐指数含量显著高于其他区域,其次是大通湖、沅水;汨罗江叶绿素a含量显著高于其他区域,其次是东洞庭湖出口处和六门闸。根据地表水环境质量标准进行单因子数据分析及评价,总氮总磷两项营养指标的污染比较严重,使得全湖水质类别为Ⅳ类或者Ⅴ类,甚至为劣Ⅴ类。空间分布上,入湖污染负荷主要来源是沅水,其次是长江三口之一的松滋河;长江干流监利至螺山段污染负荷的主要来源为洞庭湖。经综合考虑,对洞庭湖实施水资源保护和综合治理已刻不容缓。     

童家湖蓄滞洪区洪水演进数值模型研究

为更加科学、有效地运用童家湖蓄滞洪区,降低洪涝灾害损失,以二维非恒定流基本控制方程为理论基础,根据童家湖蓄滞洪区1:5000实测地形资料,基于非结构三角形网格,采用有限体积算法建立了蓄滞洪区洪水演进数学模型。依据所建立的模型,模拟分析了设计分洪条件下分蓄洪区内洪水演进过程,还选取了蓄滞洪区内若干有重要代表意义部位,在其模拟计算的水位增长及流速变化过程基础上,进一步分析了分洪不同时段蓄洪区各区域的洪水淹没趋势。模拟结果显示:童家湖分洪开始约2 h,分洪洪量主要在分洪口附近填洼;分洪前20 h洪量主要集中在蓄滞洪区南部;20 h后,北部洼地填满后蓄滞洪区内联通,各处水位同步涨落。模型可以较完整地反映童家湖蓄滞洪区内洪水演进过程,研究成果可为童家湖蓄滞洪区分洪准备、撤离转移等工作提供决策参考。     

2008~2014年滇池水质时空变化特征分析

滇池位于昆明市南部,是该市重要的水源地,支持着昆明市现代工业、农业、旅游业等的发展,分析其水质的时空变化十分重要。利用2008~2014年水质监测数据,分析了滇池主要污染物、富营养化指数和浮游植物丰度的时空变化特征。结果发现：滇池总磷、总氮、氨氮、高锰酸盐指数年尺度上整体呈减小的趋势,不同监测点的变化趋势存在一定的差异;富营养化指数年尺度上表现为减小的趋势,年内变化差异较大,6~8月富营养化指数较高,其他月份富营养化指数较低;浮游植物丰度年尺度上呈下降趋势,年内变化表现为6~8月浮游植物丰度较大,其他月份丰度较小。滇池的草海及邻近区域主要污染物、富营养化指数和浮游植物丰度大于外海部分。得益于滇池治理力度的加强,近年来滇池水质得到较大改善。     

洞庭湖区重金属分布特征及潜在生态风险评价

为研究和评价洞庭湖重金属污染现状,选取洞庭湖区及不同入湖水系共24个采样点分别研究表层水及底泥中重金属的浓度水平,采样点的布设覆盖了整个湖区及湖区的入水、出水水系,在空间上保证了监测数据的代表性和完整性。采用地累积指数法和潜在生态风险指数法对底泥中的重金属污染现状进行评价,同时对湖区重金属进行了Pearson相关关系分析,能较全面客观地反映洞庭湖区的重金属污染现状。结果表明:湖区内监测点位Cr,Cd,Pb,Cu,As,Hg的平均值分别为地球化学背景值的2. 0,10,2. 2,2. 3,6. 6倍;洞庭湖底泥中不同种类的重金属Igeo表现为Cd Hg Pb Cu Cr As,湖区内Itot(综合地累积指数)值表现为东洞庭(君山)南洞庭(万子湖)西洞庭(目平湖);各重金属潜在风险程度表现为Cd Hg As Cu Pb Cr,Cd和Hg的生态风险贡献率之和为87. 78%;湖区内的RI值在25. 32～222. 40之间,平均值128. 49,与2013年相比RI值显著降低,处于低生态风险水平。