Dynamics of arsenic-containing compounds sorption on sediments

Background  River and lake sediments constitute complex and difficult analytical samples. On the other hand, sediments play a fundamental role in the distribution of toxic compounds in aquatic systems and in the evaluation of the current state and the course of changes taking place in the environment. Among elements present in the environment in trace concentrations, but having well-elaborated toxic properties, one of most dangerous is arsenic. The element occurs in the environment in several chemical forms, predominant are inorganic forms of As(V) and As(III), and methylated forms such as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). Objectives  Reported herein are experiments, which were undertaken with the aim of examining the dynamics of arsenic sorption in sediments and its dependence on speciation of the element and the pH in the environment. Simultaneously, influence of organic matter content and chemical composition of the sediments on As sorption, were investigated. Methods  Sediment samples (upper 10 cm layer) were collected from three sites located in the vicinity of Cracow:

Ornamental lakes — an overlooked conservation resource?

• 1. Shallow lakes excavated for ornamental purposes during the 18th and 19th centuries are abundant in lowland Europe. However, relative to older man‐made and/or natural lakes, these lakes may have been undervalued from the perspective of nature conservation.
• 2. To evaluate this idea a comparison was made between the aquatic macrophyte communities (submerged and floating‐leaved vegetation) of 66 shallow, English lakes including 34 ornamental lakes and 32 flooded medieval peat workings (the Norfolk and Suffolk Broads system), the latter being widely protected by conservation legislation.
• 3. Some 47%, 38% and 15% of the lakes studied were phytoplankton‐dominated, macrophyte‐dominated or deemed too shallow (<50 cm water depth), respectively, to support a macrophyte vegetation. A higher proportion of the ornamental lakes were macrophyte‐dominated (51%) by comparison with the broads (34%). In addition, many of the ornamental lakes contained diverse plant communities including abundant populations of Characeae, a common feature of lakes in the region before the major onset of eutrophication.
• 4. From the perspectives of macrophyte species richness, charophyte communities and indeed ‘reference condition macrophyte assemblages’, many of the studied ornamental lakes can be considered to be of high conservation value. Yet, in contrast to the broads, the vast majority of ornamental lakes have little conservation protection and are rarely subject to biological monitoring and/or surveying, thus leaving them vulnerable to eutrophication and inappropriate management. This study suggests that ornamental lakes are worthy of much greater attention from conservation organizations.

Copyright © 2008 John Wiley & Sons, Ltd.     

我国河湖管理存在的问题及解决途径

随着现代化、城市化步伐的加快,作为城市水资源、水环境重要载体的河道湖泊出现了一系列问题。加强河源管理与保护工作已经越来越显得重要和迫切。针对我国河湖管理的现状,分析了在河湖管理中存在的问题,对新时期的河湖管理提出具体的解决对策:抓好规划编制;理顺河湖管理与保护体制体制机制;建立长效管理机制,保障河湖功能的发挥;全面提高河湖管理信息化水平。     

乌梁素海和岱海上覆水中碳的形态分布及其制约机制

以乌梁素海和岱海2个不同类型湖泊上覆水中TIC、DIC、TOC、DOC的地球化学特征为基础,分析和探讨了2个湖泊上覆水的水化学特征和TIC、DIC、TOC、DOC的空间分布格局及其制约机制。结果表明,乌梁素海和岱海湖泊的水化学特征均属蒸发-浓缩类型,湖泊水体离子组分特征受控于流域的蒸发-浓缩作用及蒸发盐岩的风化作用;岱海TIC、DIC、TOC、DOC的含量范围分别为（0.93-1.16）×10^4、（0.78-0.90）×10^4、（0.07-0.63）×10^4、（0.07-0.48）×10^4 μmol·L^-1,乌梁素海TIC、DIC、TOC、DOC的含量范围分别为（0.18-1.00）×10^4、（0.03-0.81）×10^4、（0.10-0.51）×10^4、（0.04-0.32）×10^4 μmol·L^-1,2个湖泊上覆水中TIC和DIC含量的差异性是湖泊富营养化类型、自然地理区划、水文地质背景及水量收支方式等因素综合作用的结果;岱海上覆水中DIC、TIC、DOC、TOC受N、P、Si等3种营养盐的共同影响,乌梁素海上覆水中DIC、TIC、DOC、TOC主要受N的影响。     

Contamination history of suspended river sediments accumulated in oxbow lakes over the last 25 years

Background, aims, and scope  Embankment of meandering river systems in many industrial areas results in the formation of artificial oxbow lakes that may act as perennial or intermittent traps for river sediments. Their deposits can be dated using a combination of historical and stratigraphic data, providing a good means to study historical records of contamination transported by rivers. Contamination history over the last few decades is of special significance for Central and Eastern Europe as it can reflect high pollutant levels in the second half of the twentieth century and the subsequent improvement after the fall of the Iron Curtain. The purpose of this study was to investigate recent sediments of an oxbow lake of the Morava River, Czech Republic, their stratigraphic records, sediment architecture, and history of contamination. Materials and methods  Seven ground-penetrating radar (GPR) profiles and three sediment cores up to 4 m deep were studied. The stratigraphy of the cores was inferred from visible-light spectrophotometry, X-ray radiography, grain size analysis, and semiquantitative modal analysis of sandy fractions. The sediments were dated using the ¹³⁷Cs mass activity and combinations of stratigraphic and historical data. The cores were sampled for concentrations of heavy metals and persistent organic pollutants. Wet sampled, lyophilized, and sieved sediments were extracted and analyzed for heavy metals by inductively coupled plasma mass spectrometry (ICP-MS) of aqua regia leachate and for persistent organic pollutants by gas chromatography (GC-ECD and GC-MS). Results  Three distinct sedimentary sequences (S1, S2, and S3) were identified. The basal sequence S1 represents river channel sediments deposited before the formation of the oxbow lake, most likely before the 1930s. The boundary between the S1 and S2 sequence correlates with the level of sediment dredging from 1981 evidenced from historical data. The overlying sequences S2 and S3 represent a postdredging sediment wedge, which progrades into the lake. ¹³⁷Cs dating revealed a distinct Chernobyl 1986 peak at ∼150 cm depth inferring sedimentation rates up to 7.7 cm/year. Sediment contamination abruptly increased from the pre-1930s deposits to the post-1981 deposits. The concentration levels increased two to five times for Pb, As, Zn, and Cu, about 10 to 15 times for Cr, Sb, and Hg, up to 34 times for Cd, and 25 to 67 times for DDTs, PCBs, and PAHs. The concentrations of most contaminants remained approximately constant until the late 1980s when they started to decrease slowly. The decreasing trends were most prominent for heavy metals and anthracene, less prominent for DDTs, and almost absent for PCBs and most PAHs. Discussion  Different temporal and spatial patterns for various contaminants make it possible to distinguish between anthropogenic point sources from local industry (anthracene, Cr, Cd), possible diffuse sources (most PAHs), and geological background (V, Co, Ni, and Mo). The observed recent trends in heavy metal and persistent organic pollutant contamination are generally consistent with data from other Central European rivers. The roughly balanced contamination levels in sediments from the lake and the adjacent river channel suggest that the oxbow lake deposits reflect immediate levels of the contamination bound to suspended particulate matter passing through the river. Conclusions  The investigated oxbow lake accumulated suspended sediment from Morava River, developing a thick sedimentary body. The sediments offer a good time framework to study historical contamination of the river on a decade time scale. Continuous contamination trends can be traced back to the early 1980s. The results show that stratigraphic analysis of cores has a good potential for identification of uninterrupted historical trends and unconformities, e.g., due to dredging. Recommendations and perspectives  Oxbow lakes may provide an alternative to floodplains and reservoir deposits when studying river contamination history. High sedimentation rates of up to 7.7 cm/year offer a very good stratigraphic resolution, making it possible to study contamination patterns on annual or even seasonal time scales. On the other hand, oxbow lakes may represent long-term contamination stores, which are unlikely to be redistributed by river erosion and, hence, may possess significant environmental risks for the farther future.     

Evidence of cormorant‐induced mortality,disparate migration strategies and repeatable circadian rhythm in the endangered North Sea houting (Coregonus oxyrinchus): A telemetry study mapping the postspawning migration

Life history theory predicts a trade‐off between migration and residency where migration is favoured when it infers elevated fitness. Although migration to more favourable environments may offer higher growth rates, migrants often experience increased mortality due to predation. Here, we investigated mortality and migration behaviour of the North Sea houting (Coregonus oxyrinchus), an anadromous salmonid endemic to the Wadden Sea. We used acoustic telemetry to map the migration of the only remaining indigenous population by applying stationary hydrophones combined with manual tracking. Data suggested a total mortality of 26%, with 30% of the total mortality attributed to predation by great cormorants (Phalacrocorax carbo sinensis), highlighting that North Sea houting conservation could be jeopardised by increased cormorant predation. Risk of cormorant predation was size‐dependent, with smaller fish suffering higher risk of predation. The study found North Sea houting to exhibit disparate migration strategies and identified a lentic area in the estuary as an important habitat. Two newly established artificial lakes within the river system significantly reduced the migration speeds, possibly indicating constrained navigation through the lakes. The migration into the Wadden Sea correlated with temperature perhaps indicating osmoregulatory constraints of sea entry. Unlike many salmonid species, migration occurred both day and night. Moreover, fish exhibited repeatable individual differences in diel activity patterns, suggesting that individuals differ consistently in their migratory activity throughout the 24‐hr period. Our study provides novel information on salmonid migration, which is crucial for the development of science‐based conservation strategies.     

云南九大高原湖泊流域现行管理体制及其完善建议

云南省湖泊面积达到30 km2以上有9个,分别为滇池、阳宗海、抚仙湖、星云湖、杞麓湖、洱海、泸沽湖、程海和异龙湖,具有独特的自然地理条件和生态服务功能,在全省经济发展和生态文明建设中占有举足轻重的地位。近年来对9大高原湖泊的治理已取得一定成效,但水质日趋恶化仍是当前面临的突出问题,主要原因是现行的湖泊流域管理体制机制不够完善,未能适应流域经济的快速发展以及流域保护治理的需求。分析和总结了云南9个高原湖泊流域管理体制的现状及存在的问题,在国内外湖泊流域管理案例和成功经验的基础上,根据9大高原湖泊流域自身特点,提出了完善管理体制的建议。     

南昌市3个城中湖泊夏季轮虫和甲壳类群落特征及水质评价

为探究城市湖泊浮游动物群落结构特征和分布与水环境因子之间的关系,并评价南昌市典型城市湖泊夏季水质状况,运用多维尺度分析（MDS）和典范对应分析（CCA）方法,对南昌3个城市湖泊———东湖、青山湖、月亮湖的轮虫和甲壳类浮游动物群落进行了研究,分析了浮游动物的多样性指数。结果表明,轮虫是夏季城市湖泊中浮游动物的优势类群,优势度（Y）大于0．02的浮游动物分别为剪形臂尾轮虫（Brachionus forficula）、裂足臂尾轮虫（Brachionus diversicornis）、萼花臂尾轮虫（Brachionus calyciflorus）、桡足类无节幼体（Copepoda nauplii）和卜氏晶囊轮虫（Asplanchna brightwelli）;3个湖泊之间浮游动物的群落结构差异显著（P ＜0．05）,明显划分为东湖群落、青山湖群落和月亮湖群落。叶绿素 a 浓度、浊度和溶氧是浮游动物分布的显著影响因子（P ＜0．05）。多样性指数评价显示,东湖为清洁型水体,青山湖为清洁－中污型水体,月亮湖为轻污－中污型水体。综合评价表明,东湖和青山湖水体为寡营养水平,月亮湖为中富营养水平。     

Resource-use,body condition and parasite load metrics indicate contrasting health of stocked and native game fishes in Canadian prairie lakes

This study evaluated the status of native and stocked fish species in 13 prairie lakes in central Canada over eight years (2007–14) using three metrics: resource-use (benthic versus pelagic carbon via stable isotopes); body condition (relative weight index W_r); and parasite load (cestode gut enumerations). Analyses included game and non-game fishes, like naturally occurring northern pike, Esox lucius L., and yellow perch, Perca flavescens Mitchill, but focused on stocked walleye, Sander vitreus (Mitchill) because it supports a robust recreational fishery. Walleye and northern pike were significantly more reliant on benthic carbon than yellow perch or forage fishes (p < 0.05), but this reliance was not associated with any measured environmental variables for any species. In lakes with game fishes, forage fishes exhibited higher reliance on benthic energy, possibly due to predator avoidance strategy, particularly yellow perch. Walleye body condition index was consistently lower (<95–105) than values exhibited by the other two game fishes (81–139), and parasites were only common in walleye and associated with lake-water salinity (r² = 0.93, p < 0.05) and sex (p < 0.05). Based on the results, the most desirable game fish, walleye, appears less resilient to environmental variability than northern pike and yellow perch, making this species more susceptible to impacts of future climate change.     

Comparative assessment of food web structure and fisheries productivity of three reservoirs in Ghana

Three Ghanaian reservoirs (Tono, Bontanga and Golinga) were compared through a food web modelling approach (Ecopath with Ecosim) to assess production characteristics and food web structures. The lakes differ in size and morphology, generating specific conditions for fish growth and production. While the two top fishery target species were Sarotherodon galilaeus (L.) and Oreochromis niloticus (L.) in all reservoirs, the mean trophic level of the catch was lowest in the largest and deepest reservoir (Tono) due to higher trophic level species occupying less accessible deep “refuge” habitats. The smallest lake had the highest fish production under optimal conditions of water supply (17.1 compared with 15.5 and 10.1 t/km²/year for lakes Bontanga and Tono), but it appears to be most vulnerable under conditions of drought. For the planning and construction of adequately sized reservoirs used for fishery and irrigation purposes, the water budget (ratio of inflow and evaporation) needs to be estimated.