Assessing sediment and water quality issues in expanding African wetlands: the case of the Mara River,Tanzania

Climatological influences and catchment pressures have altered the natural energy regime in the lower Mara River in Tanzania, creating conditions favourable for sedimentation. Wetland growth in the lower Mara River is investigated through particle size analyses and high resolution micro-XRF screening of sediment cores from the area. Geochemical profiling indicates that the Mara wetlands serve as an important trap for contaminated sediments originating the North Mara Gold Mine complex. Heavy metals and arsenic (As) appear to be reasonably well bound in alluvial stores of the wetlands but selected elements (e.g. Cr) may become progressively mobile over time. Human activity in the catchment presents risks to the biodiversity of the wetland area, and also to its ability to buffer Lake Victoria by assimilating pollutants. Changes to the hydrological regime of the Mara wetlands could reverse the patterns of sedimentation and adversely affect water and sediment quality in Lake Victoria. Furthermore, the study highlights a deficit of data relating to sediment sources, deposition patterns and associated contamination, which must be understood before effective management strategies on sediment and contaminants can be applied.     

Treatment of chromium‐bearing wastewaters with constructed wetlands

Chromium can have detrimental effects on most organisms, including humans. The present study focused on the effect of treating chromium‐bearing, organic‐rich wastewater on constructed wetland performance. Eight laboratory‐scale systems were used to study organic matter and chromium removals, with three features tested in duplicate: media with proven chromium sorption capacity, vegetation presence and intermittent influent loading. A set of two wetlands acted as the base design. Average BOD₅ and chromium removal rates were 13.4 g/m² day and 135 mg Cr/m² day, respectively. From an influent chromium concentration of 5 mg/L, <0.5 mg/L could be detected at the outlet during the study in all systems. Chromium removal efficiencies were statistically different for all systems (P<0.01), except when comparing the base design against the intermittent feed systems (P>0.05). Overall treatment performance of all systems was remarkably good in spite of significant chromium content and salinity.     

Relationships between landforms,soils and vegetation in the River Plate coastal plain,Argentina

The River Plate coastal plain is a 160‐km‐long, 3–10‐km‐wide strip, located to <5 m a.s.l. on the right bank of the estuary. It is formed by sediments and landforms generated by the littoral transport and marine ingressions and regressions during the Holocene. The coastal plain faces heavy pressures from Buenos Aires Metropolitan Area, with about 13 million inhabitants, industrial, mining and rural activities. Here, we analyse the relations existing between landforms, soils and vegetation. Despite the anthropogenic influence, the natural landscape is more or less preserved in some areas, such as patches of the southernmost gallery forest in the world in natural levees, the xerophytic forests located in well‐drained soils of beach ridges and other units such as Inland and Coastal Mudflats with wetland soils and vegetation, Tidal Flats with contrasting soils and plant communities among others.     

Constructed wetlands: a review

The first aim of this invited literature review is critically to review and evaluate hydrological, physical and biochemical processes within natural and constructed wetlands. The second aim is to contribute the thoughts of the authors to the discussion with the help of a case study focusing on gully pot liquor treatment. The performances of constructed treatment wetlands with and without macrophytes, and aggregates of different adsorption capacities will be assessed, principle findings highlighted and conclusions, also relevant to the literature review, will be drawn. The relationships between aggregates, microbial and plant communities as well as the reduction of predominantly biochemical oxygen demand, suspended solids and heavy metals are investigated. After maturation of the biomass, which dominates the litter zone, organic and inorganic contaminants are usually reduced similarly for all wetland types. There appears to be no additional benefit in using macrophytes and expensive adsorption media in constructed wetlands.     

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。     

人工湿地修复富营养化景观水体的防堵塞研究

将微絮凝过滤前处理和人工湿地防堵塞结构构成的防堵塞体系应用于某会议中心富营养化景观水体水质生态修复工程,研究了其对人工湿地防堵塞性能的影响.结果表明:防堵塞体系对于预防湿地堵塞具有显著效果.经微絮凝过滤和配水渠过滤系统处理后,湿地进水端具有较低的SS和Chl-a浓度.基质的材料和构成对湿地水力坡度的影响较为明显,优化湿地基质的种类和级配对于预防湿地堵塞具有积极作用.     

不同人工湿地基质脱氮效果的小试

基质是人工湿地达成脱氮效果的重要部位,该试验研究了底泥（对照）、底泥砾石复合（砾石）、底泥沸石复合（沸石）3种基质条件下上覆水体中NH ＋4 N、NO -2 N、NO -3 N和TN的去除效果,以及底泥耦合水体混合（混合）对脱氮效果的影响。结果表明底泥耦合混合时TN和NO -3 N去除率最高,12 d达到85％和91％;单纯底泥条件次之,为69％和73％;底泥沸石复合和底泥砾石复合时对TN和NO -3 N的去除效果较差,为56％和61％。就NH ＋4 N而言,虽然沸石对NH ＋4 N有较好的吸附效果,但未能完全将NH ＋4 N从系统中去除,当水体中NH ＋4 N浓度较低时还会不断解吸出来。NO -2 N作为中间产物,均先升高后降低,但混合条件下峰值较早出现,且去除速率也较快。     

盐龙湖表面流人工湿地底泥氧化层对污染物释放的影响

为了解盐城市盐龙湖表面流人工湿地底泥氧化层理化性质,探讨其对底泥氮、磷及有机物释放过程的影响,在测定底泥理化性质的基础上进行了室内静态柱状试验。结果表明:盐龙湖表面流人工湿地长期运行后在底泥表层形成了厚度为1 cm、呈棕黄色、无明显臭味、含水率低、TP含量高、TOC和TN含量低的氧化层;氧化层对于底泥中污染物的释放特征影响显著(P0.05),对内源污染的控制具有一定的正面作用;无氧化层试验组上覆水中TN、NH_3-N和COD的平均质量浓度分别比有氧化层试验组高9.5%、30.8%和3.5%;在湿地的实际管理中,不宜对湿地进行疏浚,如疏浚则疏浚深度应达到健康层。     

Great Lakes coastal fish habitat classification and assessment

Basin-scale assessment of fish habitat in Great Lakes coastal ecosystems would increase our ability to prioritize fish habitat management and restoration actions. As a first step in this direction, we identified key habitat factors associated with highest probability of occurrence for several societally and ecologically important coastal fish species as well as community metrics, using data from the Great Lakes Aquatic Habitat Framework (GLAHF), Great Lakes Environmental Indicators (GLEI) and Coastal Wetland Monitoring Program (CWMP). Secondly, we assessed whether species-specific habitat was threatened by watershed-level anthropogenic stressors. In the southern Great Lakes, key habitat factors for determining presence/absence of several species of coastal fish were chlorophyll concentrations, turbidity, and wave height, whereas in the northern ecoprovince temperature was the major habitat driver for most of the species modeled. Habitat factors best explaining fish richness and diversity were bottom slope and chlorophyll a. These models could likely be further improved with addition of high-resolution submerged macrophyte complexity data which are currently unavailable at the basin-wide scale. Proportion of invasive species was correlated primarily with increasing maximum observed inorganic turbidity and chlorophyll a. We also demonstrate that preferred habitat for several coastal species and high-diversity areas overlap with areas of high watershed stress. Great Lakes coastal wetland fish are a large contributor to ecosystem services as well as commercial and recreational fishery harvest, and scalable basin-wide habitat models developed in this study may be useful for informing management actions targeting specific species or overall coastal fish biodiversity.     

西北地区潜流人工湿地冬季脱氮效果研究

对西安市皂河人工湿地示范工程中潜流人工湿地冬季脱氮效果、溶解氧和微生物的空间分布进行分析研究。结果表明,潜流湿地中总氮与氨氮的平均去除率分别为29.0%和35.1%,基质中氨化细菌、亚硝化菌和反硝化菌数量沿程都呈现递减的趋势,在深度上氨化和亚硝化菌数量都是随深度减少,而反硝化菌数量是随深度增加;溶解氧浓度与氨化细菌、亚硝化菌数量存在显著正相关性,而与反硝化菌存在显著负相关性,说明湿地中溶解氧的分布对脱氨效果有重要影响。