Isolation as a restoration strategy for nutrient reduction in a small hypereutrophic lake

The restoration of a small hypereutrophic urban lake in Baton Rouge, Louisiana was accomplished by isolating the lake from its primary source of nutrient loading: a larger, connecting lake that was heavily contaminated by sewage. Restoration objectives were directed towards reducing phosphorus levels in the system to minimize chronic summer fish kills. Previous studies had identified a critical phosphorus level of 0.4 mg l⁻¹, below which no fish kills had been observed in this system. Above this level the kill frequency was a uniform 3.0%. Water quality data, consisting of 13 parameters, were collected over a four and one-quarter year period, representing conditions before, during and after the isolation. Evaluation of total phosphorus data indicated an approx. 90% reduction in estimated risk of summer fish kills as a result of the isolation. A general reduction in nutrient levels, as well as an increase in system stability, was also observed. Isolation of the lake proved to be a simple and economical means of attaining management objectives.     

A simple method to estimate lake phosphorus concentrations resulting from natural, background, loadings

The relation of mean total phosphorus concentrations to morphoedaphic index (calculated as the ratio between the mean depth and the alkalinity or the conductivity) has been examined for a large, diverse, widely distributed group of lakes.A highly significant correlation was found in lakes practically not affected by anthropogenic input of phosphorus. As a consequence the phosphorus concentration in a lake resulting from natural, background, loading could be calculated on the basis of the morphoedaphic index. The evaluation of natural phosphorus concentration allows the prediction of the maximum extent to which actual phosphorus concentrations could be reduced in culturally eutrophied lakes by eliminating the anthropogenic inputs and to calculate “permissible” loadings necessary to achieve natural trophic conditions that will not necessarily correspond to oligotrophy.     

浅议企业预算管理

介绍了企业实施预算管理的现状及存在的问题，从企业实施预算管理的意义、特征等方面进行了论述，指出了企业只有通过科学的预算管理，才能进行有效的决策控制。     

某会议中心人工湖水质生态修复

某会议中心人工湖富营养化问题严重,采用以人工湿地为主的工艺进行水质生态修复,工程运行至今,除总氮外,其余人工湖湖水水质指标均满足《地表水环境质量标准》(GB 3838—2002)中Ⅳ类水体要求,而且,人工湿地操作管理简单、运行费低、无二次污染。结果表明,人工湿地技术适宜于富营养化水体水质生态修复。     

Phosphorus partitioning in a shallow lake: implications for water quality management

This paper describes the seasonal partitioning of phosphorus (P) across the sediment–water interface in Loch Leven, Scotland, and discusses the implications for future lake management strategy with respect to recovery from eutrophication. In a 10‐month survey, surface water total phosphorus (TP) concentrations were highest in late summer and lowest in early spring. In contrast, sediment TP concentrations were highest in mid‐winter and lowest in late summer. Water discharge at the main outflow of the loch was highest when water‐column TP was low and sediment TP high, and vice versa. Monthly sediment P uptake/release values showed significant cycling between the water‐column and the sediment and showed seasonal variation in four release‐sensitive P pools. Regulating the water level to increase flushing during sediment release periods and decrease flushing during uptake periods has the potential to significantly enhance the recovery of shallow lakes and reservoirs following historic nutrient loading.     

如何提高工程概算准确性

通过对工程概算的重要性的认识,总结了建设项目进行工程概算时出现的问题,针对这些问题提出了应对措施,从而提高工程概算的准确性,确保项目投资的有效控制。     

工程预算管理与控制重点的探讨

工程预算作为建设项目的重要经济评价依据,其结果的准确性就更是重中之重,因此,对预算的管理控制就显得十分重要。本文阐述对工程预算进行管理控制应注意的方面。     

南湖的生态修复方案研究

结合南湖水质情况,探讨了南湖的生态修复方案,根据2008年南湖水水质分析报告,对比研究了南湖补水工程前后水质的变化情况,分析结果表明：生态浮岛和仿生植物净化技术是该湖生态修复的有效方法。     

不同底泥系统的湖泊内源释磷规律研究

综合运用了现场高频率水质和环境因子检测、底泥磷分级测定、实验室模拟这3种研究手段,对3个底泥生态系统各异（自然湖、存有底泥的人工湖、铺有防渗膜无底泥的人工湖）的典型湖泊进行了底泥磷释放和水体富营养化规律研究.结果表明：除掉底泥而铺设防渗膜无法改善湖泊的富营养化状况;夏季水华暴发会导致湖泊底层处于缺氧状态,最低DO浓度＜1 mg/L,同时pH值会升高,最高可达9.5,此状态可持续2个月以上;人工湖底泥中Fe-P和Al-P的成分均高于自然湖,在夏季高温、缺氧、碱性pH的典型环境条件下底泥磷的释放量要远大于自然湖,同时其富营养化程度也高于自然湖.     

工程预算管理中的常见问题与对策

以市政工程为例,针对目前工程预算管理中存在的专业化管理水平不高、缺乏高效预算管理方法等问题进行了分析,提出了相应的对策并作了具体阐述,以指导相关人员科学有效地进行工程预算管理。     

南方某水库秋季藻类监测调查研究

为了配合南方某水库水环境的调查,对库外、库首、库中、库尾等各监测点的浮游藻类群落结构和数量及藻毒素进行了为期三个月的监测和分析,并对藻类密度和环境因子做了相关性分析,评价了该水系的富营养化状态.结果表明,藻类密度与CODMn、DOC呈显著正相关,与水温、浊度、pH、TN、TP呈较小正相关性,与DO和TN/TP呈较小负相...     

The assessment of a water budget of North Cyprus

Water scarcity in North Cyprus (NC) began in the 1960s and is still tremendously increasing. Thus far no serious measurements have been taken to address this problem. Increased water demands led to extraction of water from unrestricted groundwater resources. Extreme water extractions caused the salinization of coastal aquifers up to brackish waters and the consequent depletion of interior aquifers. Such a situation requires precise control of water resources through an integrated water resources management (IWRM). Although the situation has reached an alarming state, no detailed research has been performed to establish the present demands of water in order to anticipate the future demands. Hence, this study, based on the IWRM approach, examines water budget of the country.     

基于物元可拓法的水库富营养化评价

以沈阳市中型水库富营养化评价为例,探讨了物元可拓法评价水体富营养化的可行性。通过建立水库富营养化评价标准以及选取评价因子,并利用关联度来确定水体富营养化等级。对沈阳市中型水库评价结果表明,丰水期40％的水库为中度富营养化,60％为重度富营养化;枯水期60％为中度富营养化,40％为重度富营养化。采用物元可拓法可以较精确地评价水体富营养化程度,还可以反映水体富营养化的趋势,该方法较其他方法更适用于水体富营养化评价。     

浅谈工程项目的预算(成本)管理

从施工单位管理的角度出发,在工程投标、施工前、施工中及完工等不同阶段对项目的预算管理重要性进行描述,充分表明了只有加强各个阶段的预算(成本)管理,才能真正提高经济效益。     

Delay in lake recovery caused by internal loading

A simplified model of the lake-sediment system is proposed, which aims to predict the long term evolution and the recovery time of eutrophied lakes.The model represents the state of lake and sediment each by means of a single variable. Having recourse to a well-defined set of assumptions as for sediment processes, and adopting time independent coefficients, the model balance equations can be solved analytically, and the evolution of the state variables towards steady state conditions, can be discussed in terms of characteristic times of the considered system. Particular attention is devoted to the consequences of P saturation of the solid phase in surface sediment layers, i.e. to a situation which is frequently present in eutrophied lakes.The model is applied to the case of the highly eutrophied Lake Varese (Northern Italy), in which internal P loadings from sediments appear to be substantial.Taking into account the coupling between lake and sediments, the time needed to attain the steady state P concentration compatible with the present P loadings is evaluated as 5 times the water renewal time of the lake.It is also shown to what extent the assumptions on sediment dynamics affect the model predictions.     

Nutrient Removal: Experiences in Johannesburg (Abridged)

The ability to remove nitrogen and phosphorus by biological means in the activated-sludge process represents the most significant refinement of the process since its discovery. This paper reviews the development of the activated-sludge process in Johannesburg. Emphasis is placed on the last twenty years'research into biological nutrient removal and the successful incorporation of research findings into the design and operation of full-scale plants of up to 200 Ml/d capacity.     

Phosphate exchange characteristics of wet and dried sediment samples from a hypertrophic reservoir: Implications for the measurements of sediment phosphorus status

This paper examines changes in the phosphate exchange characteristics induced in sediment samples by drying during preparation for analysis. Comparison of selected sediment parameters measured in wet and dried subsamples of a range of sediments from hypertrophic Hartbeespoort Dam showed that air drying resulted in major changes in their physical and chemical composition. Particle size distribution in the dried sediments showed a shift towards larger particles, particularly in samples in which smaller particles were abundant, indicative of irreversible aggregation of finer particles. Drying decreased the bioavailable phosphorus (NTA-extractable) content of sediments but reduced the phosphate buffering capacity and increased the phosphate equilibrium concentrations by a factor of 3, thereby increasing the phosphate release potential of dried sediments. Since sediment phosphorus status is often studied with a view to assessing the role of sediments in phosphorus cycling and eutrophication control, it is concluded that inappropriate decisions could result from the use of dried samples for analysis. The implications of these results in the marginal zones of lakes, which experience natural dehydration during periods of draw-down, are discussed.     

Phytoplankton in a polluted subarctic lake before and after nutrient reduction

Phytoplankton and water chemistry were studied in a eutrophic subarctic Swedish lake before and after nutrient reduction. Pollution started in 1964 and the lake had received about 4.5 tons of phosphorus by the time the treatment plant was built in 1974. After that only 18–20 kg P yr^?1 entered the lake. Before nutrient reduction the phytoplankton consisted principally of three species, Dictyosphaerium pulchellum var. minutum, Chromulina cv. darlecarlica and Cryptomonas cv. ovata. Two years after the P-load was reduced Chlamydomonas spp and Mallomonas akrokomos predominated in the plankton and their dominance has been maintained during the period of study. Seasonal average phytoplankton biomass decreased from 11.2 g m^?3 in 1973 to 2.9 g m^?3 in 1980. Average seasonal total phosphorus concentrations decreased from 168 μgl^?1 in 1973 to 74 μgl^?1 in 1980. Average Secchi depth readings increased from 1.3 m in 1973 to 2.1 m in 1980. Blue-green algae never had any quantitative importance in the lake and no blooms were observed.