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1.
Springs are the point of origin for most headwater streams and are important regulators of their chemical composition. We analysed solute concentrations of water emerging from 57 springs within the 3 km2 Fool Creek catchment at the Fraser Experimental Forest and considered sources of spatial variation among them and their influence on the chemical composition of downstream water. On average, calcium and acid neutralizing capacity (bicarbonate-ANC) comprised 50 and 90% of the cation and anion charge respectively, in both spring and stream water. Variation in inorganic chemical composition among springs reflected distinct groundwater sources and catchment geology. Springs emerging through glacial deposits in the upper portion of the catchment were the most dilute and similar to snowmelt, whereas lower elevation springs were more concentrated in cations and ANC. Water emerging from a handful of springs in a geologically faulted portion of the catchment were more concentrated than all others and had a predominant effect on downstream ion concentrations. Chemical similarity indicated that these springs were linked along surface and subsurface flowpaths. This survey shows that springwater chemistry is influenced at nested spatial scales including broad geologic conditions, elevational and spatial attributes and isolated local features. Our results highlight the role of overlapping factors on solute export from headwater catchments.  相似文献   
2.
遥感技术已被广泛应用于生态环境调查与研究。为获取西昌市近30 a生态环境演化趋势,利用1989年、2000年、2010年的专题绘图仪(Thematic Mapper,TM)遥感影像和2018年的陆地成像仪(Operational Land Imager,OLI)遥感影像,通过图像处理、目视解译和野外验证等方法,获得了西昌市1989—2018年的土地利用/覆盖数据,并对林地、草地和湿地的动态变化特征进行了研究。结果表明: 1989—2018年,西昌市林地、湿地和草地面积持续增加,生态环境持续向好; 林地主要分布于安宁河谷和邛海盆地四周山地,在牦牛山、螺髻山一带形成主要林区; 草地主要呈星岛状分布于牦牛山、螺髻山一带林地之间; 湿地以河流湿地与湖泊湿地为主,主要沿安宁河及邛海分布。但仍存在一些问题: 森林存在针叶化现象较普遍、树种单一等问题,需要重点加强林区火灾防范; 草地多数呈零星片状分布,不具有完整的系统结构和良好的功能,多数草地承载力和生产力较低,不宜大规模开发利用,应通过封山育林促使其向森林转化; 湿地分布也比较局限,需要着力予以保护。研究成果可为西昌市生态保护修复措施的制定及经济社会可持续发展提供科学依据。  相似文献   
3.
Current efforts to assess changes to the wetland hydrology caused by growing anthropogenic pressures in the Athabasca Oil Sands Region (AOSR) require well-founded spatial and temporal estimates of actual evapotranspiration (ET), which is the dominant component of the water budget in this region. This study assessed growing season (May–September) and peak growing season (July) ET variability at a treed moderate-rich fen and treed poor fen (in 2013–2018), open poor fen (in 2011–2014), and saline fen (in 2015–2018) using eddy covariance technique and a set of complementary environmental data. Seasonal fluctuations in ET were positively related to net radiation, air temperature and vapour pressure deficit and followed trends typical for the Boreal Plains (BP) and AOSR with highest rates in June–July. However, no strong effect of water table position on ET was found. Strong surface control on ET is evident from lower ET values than potential evapotranspiration (PET); the lowest ET/PET was observed at saline fen, followed by open fen, moderately treed fen, and heavily treed fen, suggesting a strong influence of vegetation on water loss. In most years PET exceeded precipitation (P), and positive relations between P/PET and ET were observed with the highest July ET rates occurring under P/PET ~1. However, during months with P/PET > 1, increased P/PET was associated with decreased July ET. With respect to 30-year mean values of air temperature and P in the area, both dry and wet, cool and warm growing seasons (GS) were observed. No clear trends between ET values and GS wetness/coldness were found, but all wet GS were characterized by peak growing seasons with high daily ET variability.  相似文献   
4.
随着现代工业的发展,城市黑臭河道问题日趋严重,严重影响了城市形象、生态环境和居民身心健康。利用多水塘活水链人工湿地技术净化江苏常州永胜河河水水质。监测结果显示:该技术使水体总氮浓度削减了92.0%、总磷浓度削减了82.9%,处理后的水体总氮、总磷含量达到地表IV类水标准。项目年处理水量约30万t,每年以较低的成本(平均水处理费用约为0.03元/t),削减总氮、总磷和氨氮量分别为1496.6 kg、176.0 kg和1408.6 kg。通过引植多种浮叶植物、挺水植物、沉水植物,该湿地修复工程为当地营造了优美的湿地景观。多水塘活水链人工湿地是集经济效益、生态效益、环境效益于一体的新型水体生态治理技术,为我国城镇黑臭河道治理提供了一条新的途径。  相似文献   
5.
Peatland restoration practitioners are keen to understand the role of drainage via natural soil pipes, especially where erosion has released large quantities of fluvial carbon in stream waters. However, little is known about pipe-to-stream connectivity and whether blocking methods used to impede flow in open ditch networks and gullies also work on pipe networks. Two streams in a heavily degraded blanket bog (southern Pennines, UK) were used to assess whether impeding drainage from pipe networks alters the streamflow responses to storm events, and how such intervention affects the hydrological functioning of the pipe network and the surrounding peat. Pipeflow was impeded in half of the pipe outlets in one stream, either by inserting a plug-like structure in the pipe-end or by the insertion of a vertical screen at the pipe outlet perpendicular to the direction of the predicted pipe course. Statistical response variable η2 showed the overall effects of pipe outlet blocking on stream responses were small with η2 = 0.022 for total storm runoff, η2 = 0.097 for peak discharge, η2 = 0.014 for peak lag, and η2 = 0.207 for response index. Both trialled blocking methods either led to new pipe outlets appearing or seepage occurring around blocks within 90 days of blocking. Discharge from four individual pipe outlets was monitored for 17 months before blocking and contributed 11.3% of streamflow. Pipe outlets on streambanks with headward retreat produced significantly larger peak flows and storm contributions to streamflow compared to pipe outlets that issued onto straight streambank sections. We found a distinctive distance-decay effect of the water table around pipe outlets, with deeper water tables around pipe outlets that issued onto straight streambanks sections. We suggest that impeding pipeflow at pipe outlets would exacerbate pipe development in the gully edge zone, and propose that future pipe blocking efforts in peatlands prioritize increasing the residence time of pipe water by forming surface storage higher up the pipe network.  相似文献   
6.
The water level of marsh wetlands is a dominant force controlling the wetland ecosystem function, especially for aquatic habitat. For different species, water level requirements vary in time and space, and therefore ensuring suitable water levels in different periods is crucial for the maintenance of biodiversity in marsh wetlands. Based on hydrodynamic modelling and habitat suitability assessment, we determined suitable dynamic water levels considering aquatic habitat service at different periods in marsh wetlands. The two-dimensional hydrodynamic model was used to simulate the temporal and spatial variation of water level. The habitat suitability for target species at various water levels was evaluated to obtain the fitting curves between Weighted Usable Area (WUA) and water levels. And then suitable water levels throughout the year were proposed according to the fitting curves. Using the Zhalong Wetland (located in northeastern China) as a case study, we confirmed that the proposed MIKE 21 model can successfully be used to simulate the water level process in the wetland. Suitable water levels were identified as being from 143.9–144.2 m for April to May, 144.1–144.3 m for June to September, and 144.3–144.4 m for October to November (before the freezing season). Furthermore, proposed water diversion schemes have been identified which can effectively sustain the proposed dynamic water levels. This study is expected to provide appropriate guidance for the determination of environmental flows and water management strategies in marsh wetlands.  相似文献   
7.
Dissolved organic matter (DOM) is integral to fluvial biogeochemical functions, and wetlands are broadly recognized as substantial sources of aromatic DOM to fluvial networks. Yet how land use change alters biogeochemical connectivity of upland wetlands to streams remains unclear. We studied depressional geographically isolated wetlands on the Delmarva Peninsula (USA) that are seasonally connected to downstream perennial waters via temporary channels. Composition and quantity of DOM from 4 forested, 4 agricultural, and 4 restored wetlands were assessed. Twenty perennial streams with watersheds containing wetlands were also sampled for DOM during times when surface connections were present versus absent. Perennial watersheds had varying amounts of forested wetland (0.4–82%) and agricultural (1–89%) cover. DOM was analysed with ultraviolet–visible spectroscopy, fluorescence spectroscopy, dissolved organic carbon (DOC) concentration, and bioassays. Forested wetlands exported more DOM that was more aromatic‐rich compared with agricultural and restored wetlands. DOM from the latter two could not be distinguished suggesting limited recovery of restored wetlands; DOM from both was more protein‐like than forested wetland DOM. Perennial streams with the highest wetland watershed cover had the highest DOC levels during all seasons; however, in fall and winter when temporary streams connect forested wetlands to perennial channels, perennial DOC concentrations peaked, and composition was linked to forested wetlands. In summer, when temporary stream connections were dry, perennial DOC concentrations were the lowest and protein‐like DOM levels the highest. Overall, DOC levels in perennial streams were linked to total wetland land cover, but the timing of peak fluxes of DOM was driven by wetland connectivity to perennial streams. Bioassays showed that DOM linked to wetlands was less available for microbial use than protein‐like DOM linked to agricultural land use. Together, this evidence indicates that geographically isolated wetlands have a significant impact on downstream water quality and ecosystem function mediated by temporary stream surface connections.  相似文献   
8.
A suite of instruments was deployed in a coastal wetland ecosystem in the Albemarle estuarine system, North Carolina (USA), to characterize wind‐driven transport of saltwater through a constructed (man‐made) channel. Flow velocity, electrical conductivity, and stage were measured in a representative channel over a 2‐month period from May to July 2014, during which 4 wind tides were observed. Collected data show that thousands of metric tons of salt were advected through the channel into coastal wetlands during each event, which lasted up to 4 days. The results reveal that as much as 36% of advected salts accumulated in the wetlands, suggesting that the cumulative effects of these events on the health of coastal wetlands in the Albemarle system may be substantial due to the abundance of constructed channels and the frequency of wind‐driven tidal events. This study is the first to quantify wind‐driven salt fluxes through constructed channels in coastal wetland settings.  相似文献   
9.
异化铁还原是湿地土壤和沉积物中重要的生物地球化学过程,也是有机质矿化的主要途径之一。湿地干湿交替等过程会使土壤的氧化还原状态发生改变,影响铁元素及与其相关的元素的迁移和转化。总结了湿地土壤和沉积物中异化铁还原过程及其与碳、磷、硫等元素在生物地球化学循环关键过程中的相互作用,阐述了湿地土壤和沉积物中异化铁还原过程对微量金属元素迁移和转化的影响,分析了影响湿地土壤和沉积物异化铁还原过程的主要环境因子。未来相关研究应集中于湿地土壤和沉积物中异化铁还原微生物分析和纯化、不同有机质形式对异化铁还原过程的影响以及异化铁还原对土壤有机质矿化的贡献。  相似文献   
10.
叶翔  李靖  王爱军 《海洋学报》2018,40(7):79-89
滨海湿地作为人类活动和全球变化反应最为敏感的区域,其沉积记录可以反映出周边地区环境变化及人类活动信息。珠江口淇澳岛滨海湿地钻孔分析结果表明,在中全新世期间淇澳岛附近海域为河口湾环境,在风化层以上开始出现淤积,但在4 200 a BP前后受极冷气候的影响,沉积物粗化;自2 500 a BP以来,沉积环境相对稳定,在小冰期期间略有变化。沉积速率计算结果显示:淇澳岛附近海域自中全新世高海面以来的平均沉积速率为0.29 cm/a,4 160~2 500 a BP、2 500 a BP-1488年、1488-1893年、1893-1986年、1990-2007年期间的平均沉积速率分别为:0.17 cm/a、0.23 cm/a、0.35 cm/a、1.37 cm/a和5.94 cm/a,沉积速率逐渐增大,反映了珠江三角洲演化过程中沉积相与沉积环境的变化;1986-1990年期间的海堤建造极大地扰动了该钻孔上部的沉积过程,在工程施工期间共沉积了厚度约112 cm的沉积层,而在海堤建成后,沉积速率也显著增大。沉积物总有机碳、总氮和C/N值的垂向分布表明,在4 160~2 500 a BP期间受海洋环境影响较大,沉积物中有机碳以海源为主,2 500 a BP以来沉积物中碳、氮含量明显增大,C/N也相应变大,有机碳主要来源于陆源输入,但在小冰期期间海源有机碳贡献略有所增大;近百年来由于受人类活动影响显著,陆源有机碳的贡献快速增加。  相似文献   
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