定常风场下的太湖风生流水动力特征研究

太湖的主要流动类型为风生流,本文采用数学模型模拟了四种定常风场作用下的太湖风生流水动力特征,总结了风向对太湖风生流分布的影响。研究结果指出：东南风与西北风作用下太湖主湖区存在西部环流、中部环流和北部环流三个大尺度环流,北风与南风作用下太湖主湖区仅存在西部环流和中部环流两个大尺度环流。东南风和西北风作用下,太湖北部竺山湾东北部、梅梁湾东南部和西北部及贡湖湾东北部存在大尺度环流。东风与南风作用下,竺山湾西部、梅梁湾东南部和中部南北两岸及贡湖湾东部存在大尺度环流。定常东南风作用下,太湖表面流向与风向相同,底层流向与风向相反,流向拐点一般出现在相对水深hc=0.8 处。     

浅析太湖梅梁湾的生态修复与重建

太湖位于长江三角洲地区。是我国第三大淡水湖泊．湖泊面积2338km^2，平均深度1．89m，湖容量44亿m^3，具有饮用水源、排洪蓄洪、工农业用水、旅游、航运、养殖等功能，是该地区社会经济发展的基础。梅梁湾作为太湖北部的一个较大湖湾，是无锡市著名的风景旅游区和水源地，又是主要航运通道．汛期还担负着泄洪排涝。随着其周围地区的经济发展．无锡、宜兴、常州、武进等地的工农业及生活污水不断排入湾内，梅梁湾水质受到严重污染．水体富营养化以蓝藻的大量繁殖而引起水华暴发为主要表象，严重影响周围地区的供水．破坏水体景观．从而制约周围地区的经济发展。为此．国家将太湖水污染控制与水体修复技术及工程示范项目列为“十五”重大科技专项水污染控制技术与治理工程的首要专项，并把太湖梅梁湾水源地水质改善技术列为此专项的第一子课题。近三年来，课题组对太湖梅梁湾的生态进行了一系列的修复与重建工作。     

铜绿微囊藻对Cd~(2+)胁迫的生理生化响应

为探讨重金属离子Cd~(2+)对铜绿微囊藻的毒性效应,通过室内实验,研究了铜绿微囊藻在不同Cd~(2+)浓度胁迫下的生理生化变化。结果表明:1 Cd~(2+)对铜绿微囊藻具有明显的毒害作用,Cd~(2+)对铜绿微囊藻的24hEC_(50)、48h-EC_(50)、72h-EC_(50)、96h-EC_(50)分别为0.978,0.863,0.646,0.302 mg/L,随着作用时间的延长,EC_(50)显著降低(P0.05);2在Cd~(2+)胁迫下,铜绿微囊藻的光合生理特性受到不同程度的影响,叶绿素荧光特性Fv/Fm、Y[Ⅱ]、ETR、q P变化趋势基本一致,且与叶绿素a都表现出剂量-效应关系;3 Cd~(2+)诱导藻细胞产生氧化应激反映,其中丙二醛(MDA)和超氧化物歧化酶(SOD)活性均显著升高(P0.05),且随暴露时间延长,氧化应激强度增大。综上,重金属离子Cd~(2+)能够抑制铜绿微囊藻的生长,阻碍其光合作用,同时造成氧化应激效应。     

基于马尔科夫模型的太湖水质综合评价

对2000—2005年太湖整个湖区水质监测资料进行分析,得出不同湖区水质浓度均值,采用灰色聚类法对各湖区水质进行评价,并根据马尔科夫模型计算各湖区水质季节变化的相对进步度。结果表明:太湖水质的时空差异性较大,竺山湖和梅梁湾的水质最差,为Ⅴ类,而东太湖和东部湖区水质相对较好,为Ⅱ类;不同的水质指标中,NH3-N的空间差异性最大,TN、TP,CODMn的空间差异性相对较小,表明城镇污水是太湖的主要外源污染;竺山湖和梅梁湾的水质季节性变化最大,在夏秋季水质相对较好,冬春季水质相对较差,其他湖区的水质季节性变化很小。     

近30年太湖沉水植物优势种遥感监测及变化分析

利用1985—1986年、1995—1996年、2004—2006年和2014—2015年多时相遥感影像数据,构建了水生植物分类决策树模型,结合沉水植物的生活史差异,研究太湖近30年沉水植物优势种的演替模式。4个时期的沉水植物遥感分类总体精度与Kappa系数依次为64.86%和0.59,70.83%和0.65,63.93%和0.50,64.94%和0.60。研究表明:1985—2015年马来眼子菜由东山湾向西山岛、东太湖向南太湖扩张,竺山湾、梅梁湾的苦草呈锐减的趋势,近年来梅梁湾的沉水植物只有菹草1种,湖心区一直未监测到沉水植物,东太湖沉水植物分布面积最广、种类最多。近30年太湖沉水植物演替主要经历4个阶段,依次为苦草-眼子菜型、小眼子菜型、金鱼藻-伊乐藻型和眼子菜-伊乐藻型阶段。水体富营养化和围网养殖是沉水植物演替的主要原因。     

太湖风生流垂向切变规律的原位观测

浅水湖泊垂向环流存在着上下层反向现象,为了探究太湖湖流垂向切变规律,用声学高频流速仪ADV、ADP及风向风速仪在梅梁湾进行了9 d的连续观测;基于获取的高频同步数据,利用概率统计方法,对各层流场在不同风向、不同风速以及持续同向风场影响下的切变率进行了统计分析,并研究了流场垂向分布特征。结果表明:5月太湖梅梁湾在风向为ESE、ES、E,风速2~5 m/s,同向风场持续作用10~11h时,流场基本达到稳定且切变率最大;表层流场(水下50cm)处,切变率最小,为20%,底层流场(距水-土界面7 cm)处,切变率最大达到60%;流向改变的拐点出现在表层至中层,即水下50~100 cm;风速、风向的出现频率,以及同向风场的持续时间决定了流场反向率大小,流场反向率决定了拐点的位置。     

方形混凝土桩列消浪效果试验研究

结合太湖梅梁湾水源地水质改善示范试验区的消浪工程,通过方形混凝土桩列的波浪模型试验,比较了5种桩列平面布置形式的消浪效果后,推荐了方案2的桩列布置形式.并按线性小振幅波理论,导出了改进的透射系数计算式,其计算结果与试验值符合良好.     

城市地表径流胶体对重金属下渗迁移行为的影响

为了解城市地表径流胶体对重金属在下渗设施中迁移行为的影响,提取道路雨水径流中的胶体,采用下渗柱试验研究了存在径流胶体时Cu~(2+)、Pb~(2+)和Cd~(2+)的下渗迁移出流质量浓度变化,分析进水流速、pH值、Na~+浓度、重金属离子共存和胶体粒径对胶体携带重金属迁移行为的影响。结果表明:径流胶体能够促进重金属离子的下渗迁移;进水流速越高,径流胶体对重金属离子的携带迁移作用越明显;弱酸性条件更有利于径流胶体对重金属离子的携带迁移;雨水径流中存在Na~+或多种重金属离子共存时,胶体携带重金属离子的下渗迁移过程会受到抑制,且离子浓度越大,其受抑制作用越明显;胶体粒径会显著影响径流胶体对重金属离子的携带迁移能力,胶体粒径越小,越容易携带重金属离子下渗迁移。     

Cu2+对凤眼莲根系吸附四环素的影响及机理

以凤眼莲根系为生物吸附材料,通过批吸附平衡实验,考察Cu~(2+)共存条件下凤眼莲根系吸附四环素(tetracycline,TC)的动力学特性和吸附等温线,并结合傅里叶红外光谱(Fourier infrared spectroscopy,FTIR)和基团屏蔽技术分析Cu~(2+)对凤眼莲根系吸附TC特征的影响及机理。结果表明:共吸附动力学和吸附热力学分别符合准二级动力学模型和Freundlich等温吸附模型。随着共存Cu~(2+)浓度的增加,凤眼莲根系对TC的吸附量和去除率也逐渐增大。凤眼莲根系表面羧基、氨基经化学屏蔽后,对TC的吸附量均降低了20%~30%;结合FTIR技术确定Cu~(2+)通过与凤眼莲根系表面的活性官能团(羟基、羧基和氨基以及芳环结构等)发生相互作用,在根系与TC之间形成架桥,从而促进了根系对TC的吸附。     

围隔导流对太湖蓬坑湾藻类富集效能的影响

针对围隔可改变水体流场、影响藻类漂移聚集,通过改变围隔布设角度和长度,探究不同围隔导流方案下藻类的富集效果。选取梅梁湾内的打捞点蓬坑湾作为研究对象,在建立太湖水量水质模型基础上,进一步建立太湖蓬坑湾套网模型,根据角度、长度两个因素,模拟6种布设方案下藻类富集效果,分析得到最佳角度、长度组合布设方案,并进一步考虑蓬坑湾地形和经济效益,提出适宜于蓬坑湾地形的优化方案。结果表明:围隔布设角度与水流方向呈120°时,湾内富集效果最佳;围隔布设长度越长,蓝藻收集区域越大,湾内富集效果越好;综合考虑地形特点和经济效益,最终确定围隔布设最佳方案为在上下湾口处分别布设一段围隔,布设角度与水流方向呈120°,上下湾口处围隔布设长度分别为100、30 m。研究成果对于改善湖泊水环境具有较好的应用前景。     

太湖梅梁湾、贡湖套网格风生流数值模拟

对太湖梅梁湖、贡湖湖流进行套网格数值模拟。根据1998年8月太湖富营养化水质监测水文物理资料,绘制出梅梁湖、贡湖各站点位置分布图和其流速大小和方向。模拟计算与实测结果吻合较好,证明其套网格数值模型的建立是合理和有效的。分析结果表明,太湖各水域流速相差很大,近岸区域流速高于远岸区域,存在明显的近岸流。但流速值不大,即梅梁湖、贡湖和大太湖的水体交换量不大,通过流场分布可初步判断污染物质在水体中的扩散与迁移情况。     

Contrasting zooplankton communities of two bays of the large,shallow, eutrophic Lake Taihu,China: Their relationship to environmental factors

Zooplankton are an important link in aquatic food webs of lakes serving as consumers of algae, bacteria, and other microorganisms and as prey for fish and invertebrates. Despite their importance, little is known about the structure of the zooplankton communities of subtropic, large, shallow, eutrophic freshwater lakes. Our investigation of zooplankton communities in Lake Taihu, a subtropic, shallow, eutrophic lake and the third largest lake in China provides new information on this subject. Zooplankton, phytoplankton, and water chemistry samples were collected monthly from July 2006 to June 2007 in Meiliang and Gonghu Bays of Lake Taihu. Thirty zooplankton species were identified in Meiliang Bay with small-bodied cladocerans Bosmina coregoni and Ceriodaphnia cornuta contributing 21% and 11%, respectively to total zooplankton abundance which averaged 459 ind/L. Thirty-five species were identified in Gonghu Bay with the rotifers Polyarthra trigla and Brachionus calyciflorus the dominant species, contributing 21% and 11% respectively to total zooplankton abundance which averaged 467 ind/L. Predation by lake anchovy (Coilia ectenes taihuensis) and ice fish (Neosalanx tangkahkeii taihuensis) likely accounted for the dominance of both bays by small-bodied species. Community structure and community patterns were correlated with differences in Microcystis blooms and organic matter levels (chemical oxygen demand) in the two bays. Based on canonical correspondence analyses dissolved total nitrogen, orthophosphate, Cyclotella and Pinnularia also contributed to variability in zooplankton community composition.     

Effects of temperature and nutrients on phytoplankton biomass during bloom seasons in Taihu Lake

Long-term variations of phytoplankton chlorophyll-a (Chl-a), nutrients,and suspended solids (SS) in Taihu Lake, a large shallow freshwater lake in China, during algal bloom seasons from May to August were analyzed using the monthly investigated data from 1999 to 2007. The effective accumulated water temperature (EAWT) in months from March to June was calculated with daily monitoring data from the Taihu Laboratory for Lake Ecosystem Research (TLLER).The concentrations of Chl-a and nutrients significantly decreased from Meiliang Bay to Central Lake. Annual averages of the total nitrogen (TN), total phosphorus (TP), and Chl-a concentrations, and EAWT generally increased in the nine years. In Meiliang Bay, the concentration of Chl-a was significantly correlated with EAWT, ammonia nitrogen (NH4+-N ), TN, the soluble reactive phosphorus (SRP),TP, and SS. In Central Lake, however, the concentration of Chl-a was only correlated with EAWT, TP, and SS. Multiple stepwise linear regression revealed that EAWT, dissolved total phosphorus (DTP), and TP explained 99.2% of the variation of Chl-a in Meiliang Bay, and that EAWT, NH4+-N, and TP explained 98.7% of the variation of Chl-a in Central Lake. Thus EAWT is an important factor influencing the annual change of phytoplankton biomass. Extreme climate change, such as extremely hot springs or cold springs, could cause very different bloom intensities in different years. It is also suggested that both nutrients and EAWT played important roles in the growth of phytoplankton in Taihu Lake. The climate factors and nutrients dually controlled the risk of harmful algal blooms in Taihu Lake. Cutting down phosphorus and nitrogen loadings from catchments should be a fundamental strategy to reduce the risk of blooms in Taihu Lake.     

太湖底泥的生态疏浚工程

指出:①太湖底泥是湖体水生态系统的基本要素,也是重要的内污染源.②在湖泊外源污染得到一定控制后,以减少内源污染负荷为目的的生态疏浚是控制内源污染效果较为明显的工程措施.③太湖底泥疏浚属水生态整治工程,以最大可能取走污染物、改善水生态环境为控制目标,生态疏浚是局部的薄层精确疏浚.经采用生态调查方法,查明太湖底泥总蓄积量为19亿m3.主要疏浚范围是底泥厚且污染重的重点功能湖区,如梅梁湖、贡湖等.依据太湖底泥的污染特性,疏浚深度以40～50cm为宜,并应为后续生物修复技术介入创造必要的生态环境条件.密闭无扰动抽吸式头部掘进是关键,冬初至春末为最佳施工期.排泥场防渗、尾水处理达标后排放、淤泥安全处置和资源化利用是生态疏浚的环保要求.     

Benthic macroinvertebrate community structure in Lake Taihu,China: Effects of trophic status,wind-induced disturbance and habitat complexity

Lake Taihu, the third largest lake in China, is subjected to severe eutrophication and cyanobacterial blooms as a result of development and urbanization. However, little is known about the macroinvertebrate assemblages and their relationship with eutrophication and other environmental factors in this lake. To characterize the community structure of macroinvertebrates and to examine the benthos-environmental relationships in Lake Taihu, a quarterly investigation was conducted from February 2007 to November 2008. A total of 42 taxa was recorded; Limnodrilus hoffmeisteri, Rhyacodrilus sinicus, Corbicula fluminea, Bellamya aeruginosa, Tanypus chinensis and Gammarus sp. dominated the community in abundance and biomass. Cluster analysis and one-way analysis of similarity (ANOSIM) identified three groups of stations that had significantly different macroinvertebrate communities. Stations in the north bays and three river mouths had the lowest diversity and were dominated by pollution-tolerant species such as L. hoffmeisteri and R. sinicus while Gonghu Bay, the Central Region and the Western Region contained intermediately diverse communities mainly dominated by C. fluminea. Diversity and evenness were highest in the East Bays where aquatic macrophytes were abundant; the zoobenthos were characterized by gastropods. One-way ANOVAs revealed that environmental characteristics differed significantly among the three groups of stations. Canonical correspondence analyses showed that community structure and spatial patterns of macroinvertebrates in Lake Taihu were strongly correlated to three ecological factors—trophic status, wind-induced disturbance and habitat complexity. Our results could provide valuable information that could be used by managers and policy makers to evaluate and modify restoration practices.     

太湖波浪特征参数反演计算

为研究声学多普勒流速仪(acoustic doppler velocimetry,ADV)测量的流速与水压数据在湖泊波浪特征参数反演中的适用性,在太湖梅梁湖和湖心区两个区域进行野外观测,利用预处理后的水压和流速数据进行傅里叶变换和转换获得表面波浪谱,取截断频率为0.03~0.5 Hz对表面波浪谱进行反演计算。结果表明,梅梁湾5月和湖心7月使用水压数据反演得到的有效波高分别为0.454 m、0.187 m,有效波周期分别为2.82 s、2.56 s;使用ADV流速数据反演计算得到的有效波高分别为0.451 m、0.181 m,有效波周期分别为2.82 s、2.62 s;与使用压力式方向波潮仪测得的有效波高(0.461 m,0.180 m)和有效波周期(2.77 s,2.60 s)非常接近且变化趋势基本相同,可见ADV的水压和流速数据可用来进行湖泊的波浪的计算。     

Seasonal variations of phytoplankton species in Lake Victoria and the influence of iron and zinc ions on the dominant species identified during 2006–2007 studies

The current study was conducted for 2 years (2006 and 2007) during January, April and September to investigate seasonal variations in biological parameters and planktonic biodiversity observed at four sampling sites (MRM, M500, SRM and S500) in Lake Victoria. Blue‐green algae (Cyanophyta) dominated the lakeshore waters of Lake Victoria, comprising 54.1% of the total algal content, compared to 24.4% for diatoms and 14.7% for green algae (Chlorophyta). Euglenophytes and dinoflagellates both constitute <10% of the algal biomass. The algal distribution at the Sango Bay sampling sites, however, is different in that it is dominated by diatoms, in contrast to Murchison Bay, which was dominated by blue‐green algae. This study also investigated the influence of iron (Fe²⁺and Fe³⁺) and zinc (Zn²⁺) ions on four strains of microcystis (CYN 464, CYN 465, CYN 478 and CYN 522) isolated from Murchison Bay in Lake Victoria. The suggestion that iron species and zinc ions might limit phytoplankton growth in Lake Victoria was tested by enriching algal culture media with different metal concentrations. Based on measurements of the algal biomass of four species of Lake Victoria, the algal biomass of the four microcystis strains generally decreased with increased zinc and Fe²⁺ concentrations. The algal biomass of the four strains, however, increased with increased Fe³⁺ concentrations. This response to different metal concentrations provides evidence that high Zn²⁺ and Fe²⁺ ion concentrations limit phytoplankton growth and species distribution. The availability of Fe³⁺ ions is an important selective force on Lake Victoria phytoplankton communities.     

引江济太对不同水域氮磷浓度的影响

在国内外调水实践的基础上,运用现状监测资料,具体分析流经望虞河、望亭立交水利枢纽调入太湖的长江水质和太湖不同湖区的水质,研究在调水初期及其后的过程中,氮磷浓度影响水质的变化规律。结果表明:长江水源中总磷、总氮浓度总体上低于贡湖、梅梁湖;长江水在流经望虞河进入太湖的过程中,太湖地区水质随着进水时间的延长而好转,水质浓度与进水流量的大小成反比;"引江济太"调水对迅速抑制太湖蓝藻暴发起到了重要作用。     

Variations in water level,area and volume of Hongze Lake,China from 2003 to 2018

Lake changes have great impacts on local and regional ecosystems and socioeconomic activities. To determine the recent changes in Hongze Lake, radar altimeter and Landsat data were used to examine the water level and area and estimate the water volume changes from 2003 to 2018. Generally, the annual water level results from radar altimeter data showed good agreement with in situ measurements (r² = 0.62, bias = −0.02 m, mean absolute error = 0.10 m and root mean square error = 0.12 m). Although the results show that the water level and water volume of Hongze Lake had no trends during the 16 years, the water area decreased significantly at a rate of 19.76 km² per year. Despite great fluctuations throughout 16 years, two shifts occurred in approximately 2007 and 2013. The water level, area and volume of Hongze Lake decreased from 2007 to 2012, but they all showed increasing trends after 2013. The interannual changes in the water level and volume of Hongze Lake were consistent with the changes in annual precipitation, while the change in area was mainly affected by human activities, especially land reclamation and aquaculture activities along the lakeshore. In addition, the intra-annual change in the water level was greatly affected by artificial activities such as irrigation and flood prevention.