Lake eutrophication management modeling using dynamic programming

Lake eutrophication problems have received considerable attention in Taiwan, especially because they relate to the quality of drinking water. In this study, steady-state river water quality and lake eutrophication models are solved using dynamic programming algorithms to find the nutrient removal rates for eutrophication control during dry season. The kinetic cycle of chlorophyll-a, phosphorus and nitrogen for a complete-mixed lake is considered in the optimization framework. The Newton-iterative technique is adopted to solve the nonlinear equations for the steady-state lake eutrophication model. The optimization framework is applied to Cheng-Ching Lake in southern Taiwan. Several nutrient loading scenarios for eutrophication control are studied. Optimization results for nutrient removal rates and corresponding wastewater treatment capacities of each reach of the Kao-Ping River define the least cost approach to lake eutrophication control. A natural purification method, structural free water surface wetland, is also suggested to save more investment and improve river water quality at the same time.     

The dualistic approach of FCA: a further insight into Ontario Lake sediments

The investigation of object-by-attribute matrices is very common in statistics and data analysis with the aim of uncovering every possible relationship among objects and/or attributes. Formal Concept Analysis (FCA) is a method, which stems directly from partial order and lattice theory, which provides an efficient tool to symmetrically uncover linkages among objects and attributes whenever a relation stands among the two sets. It provides efficacious graphical representation and computes association rules between attributes, thus helping in the detection of possible synergism or antagonism of attributes. In this paper, FCA potentialities are discussed and described by means of a case study already investigated by other partial order techniques: the case of Lake Ontario sediment samples. Data derive from a ‘test battery’ for a simultaneous analysis of degradation of Lake Ontario samples, which are basically of two typologies: hygienic and toxicity tests. A multi-valued approach is adopted to cope with the ordinal feature of data. Results highlight interesting interaction among hygienic compounds and a synergism between the two toxicity tests.     

太湖零点行动前后水质状况对比分析

根据 1 998年 1 1月和 1 999年 1 0月的监测数据 ,对零点行动前后太湖各监测点位的水质状况及DO、CODMn、TP、TN、Chla等主要指标的空间分布进行了对比 ,发现污染状况并未得到明显改善 ,除了人为因素外 ,非点源污染的贡献和底泥营养物质的释放是影响水质改善的 2个重要因素     

Temporal Trends of Young-of-Year Fishes in Lake Erie and Comparison of Diel Sampling Periods

We explored temporal trends of young-of-year (YOY) fishes caught in bottom trawl hauls at an established offshore monitoring site in Lake Erie in fall during 1961–2001. Sampling was conducted during morning, afternoon, and night in each year. Catches per hour (CPH) of alewife (Alosa pseudoharengus) YOY were relatively low and exhibited no temporal trend. This result was consistent with the species’ intolerance to Lake Erie’s adverse winter water temperatures. Gizzard shad (Dorosoma cepedianum) YOY decreased sharply after 1991, which was consistent with recent oligotrophication of the lake. Following the establishment in 1979 and rapid increase of white perch (Morone americana) YOY, white bass (Morone chrysops) and freshwater drum (Aplodinotus grunniens) YOY decreased. Trout-perch (Percopsis omiscomaycus) YOY decreased during 1986–1991, but recovered to previous levels during 1991–2001. The recovery coincided with the resurgence of mayflies (Ephemoptera) in the lake. CPH of spottail shiner (Notropis hudsonius) and emerald shiner (N. atherinoides) YOY exhibited no temporal trend between 1961 and the late 1970s to early 1980s. CPH of yellow perch (Perca flavescens) YOY decreased during 1961–1988, and walleye (Sander vitreum) YOY increased overall during the time series. These observations were consistent with published studies of adults in the region. CPH of 4 of the 10 species of YOY considered were greatest during night. CPH for walleye YOY was higher in the morning than in the afternoon, but there was no significant difference between night and morning abundances. The results suggest that (1) CPH of YOY fishes may be a useful monitoring tool for Lake Erie, and (2) offshore monitoring programs that do not include night sampling periods may underestimate recruitment for several common species.     

Assessment of the Quality Characteristics of Two Lakes (Koronia and Volvi) of N. Greece

Quality parameters from 17 sampling stations from Lake Koronia and 18 from Lake Volvi were determined during sampling period of one year. Physicochemical parameters (pH, conductivity, DO) did not show remarkable differences neither between sampling sites nor between sampling periods. Nutrient concentrations (nitrogen and phosphorus compounds) were higher in lake Koronia than in Volvi showing relatively small temporal and spatial variations. As far as heavy metals in sediments, lake Koronia is considerably more polluted than Volvi lake especially with the metals Fe, Mn, Zn, Pb and Cd. The mean total concentrations of metals in lake Koronia decrease in the order Mn > Zn > Cr > Pb > Cu > Fe > Cd. The mean total concentrations of metals in lake Volvi decrease in the order Mn > Zn > Cr > Cu > Pb > Fe $>$ Cd.     

基于EOS/MODIS资料的太湖藻类动态模拟

建立了太湖藻类生长的动态模型,并将其与水动力模型和水质模型相耦合,利用2001年7～8月太湖的实测资料对模型进行了率定。借助该模型,对2004年8月太湖水体中TN、TP的变化以及藻类生长过程进行了模拟。利用中分辨率成像光谱仪EOS/MODIS的数据对太湖叶绿素a浓度进行遥感定量,将遥感监测数据和模型计算结果进行了比较。结果表明:该模型可进行风生湖流、TN、TP的模拟,以叶绿素a浓度描述的藻类浓度的模拟值能较好地拟合遥感监测值,且遥感监测图和模型模拟图所反映的全太湖叶绿素浓度分布基本一致。最后根据遥感和模拟对太湖全区的藻类分布作了具体的分析。     

太湖水源地水质净化的生态工程试验研究

基于生物净化技术与工程措施相结合的思想,在太湖北部的梅梁湾牵龙口水厂水源地实施了净化水质的生态工程试验.该水域位于太湖梅梁湾的东北岸.调查发现,由于这个地区夏季盛行偏南风,吹程长,风浪较大,导致沉积物易于悬浮,且蓝藻也易于在此堆积;同时该水域水较深、透明度较低.为了能够净化水质,在氮磷营养盐浓度依然很高、恢复沉水植物难以奏效的情况下,选择漂浮植物和浮叶植物为主要内容的水生植物恢复手段,结合消浪、挡藻和控藻等技术措施,使得示范区的环境条件得到改善,并达到了净化水源地水质的目的.同时,在试验区内布设大量用于附着生物富集的人工介质,如渔网.结果显示,试验区的水质得到了显著的改善.与示范区外的参照点相比,各项水质参数改善的程度达30%～60%.说明这种新的方法和思路是有效的.     

湖泊围栏养殖容量估算

随着中国水产养殖业的快速发展,水产养殖业对水环境的污染日益引起关注.确定合理的水产养殖容量是协调经济效益和环境保护的基础.分析、比较了目前关于养殖容量的主要观点,阐述了生态容纳量、环境容纳量和养殖容量等概念及其相互关系.从规划环境影响评价的角度,确定水产养殖容量的定义为:在自然条件、水环境及社会、经济和现有生产技术等因素的约束下,水产养殖活动所能获得的最大养殖产量.它由自然容纳量(Enp)、需求容量(Dp)和基于水环境容量的养殖容量(Ewp)3部分组成.据此,建立了养殖容量计算模型,并核算出东太湖围网养殖的最佳养殖模式为轮牧式养蟹600 kg/hm2,养殖容量为年河蟹养殖量1 685.0 t,年配套草食性鱼类5 015.6 t(散养,不围网),养殖面积为3 056.20 hm2(不使用外源性饲料).     

乌梁素海污染现状及驱动因子分析

乌梁素海湖泊位于我国北方半干旱地区的河套灌区内,属于典型的草型浅水湖泊。由于所处地区的特殊水文气象条件与灌区的影响,乌梁素海的水环境污染问题必定有其特殊性,文章将实测的湖泊水质监测数据与空间数据结合,采用基于因子分析的主成分方法将乌梁素海的水质参数概括为5个主成分,即:污染特征指标、湖泊形态特征指标、植物生长环境指标、水体酸碱指标、水体藻类生物量指标。进一步分析讨论各主成分的意义以及结合地区特征指出湖泊污染的驱动因子,为湖泊水体的合理利用与污染的治理提供科学依据。     

昆承湖水质参数空间分布特征研究

为了分析湖泊水质参数的空间分布特征,在面积为17.57km2的昆承湖布设水质监测点18个,运用基于Arc GIS的地统计学组件分析了湖区水质参数的空间分布特性.结果表明,昆承湖水质参数的空间结构变异性是客观存在的,各主要水质参数都具有块金效应;对昆承湖水质参数进行克立格插值,并绘制空间分布图,发现湖区各主要水质参数的空间异质性比较明显.其中,DO浓度呈西高东低之势;TN和NH4 -N的高浓度区主要集中在湖东北部和东部;TP的变化最为复杂,高浓度区主要分布在东北部和湖西的部分区域;Chla除在湖心较小区域出现低值,在整个湖区浓度均较高.