Recovery of interior brackish marshes seven years after the chalk point oil spill     

Jacqueline Michel  Zachary Nixon  David Betenbaugh  Dennis Burton 《Marine pollution bulletin》2009,58(7):995-1006

Seven years after the April 2000 spill of 140,000 gallons of a mixture of No. 6 and No. 2 fuel oils in the Patuxent River, Maryland, heavily oiled brackish marshes showed continuing effects. Stem density and stem height were significantly lower in oiled versus unoiled sites for Spartina alterniflora but not Spartina cynosuroides habitats. In contrast, belowground biomass was significantly lower in S. cynosuroides habitats but not S. alterniflora habitats. Total PAH concentrations were up to 453 mg/kg in surficial soils (0-10 cm) and 2921 mg/kg with depth (10-20 cm). The oil had lost 22-76% of its initial PAH content after seven years, although the oil in marsh soils has undergone little to no additional weathering since Fall 2000. Based on amphipod acute toxicity tests and sediment quality guidelines, 25% of the soils in the marsh are expected to be toxic (ESB-TU_FCV values > 3.0; P_Max > 0.65).  相似文献   

Distribution and seasonal fluctuations in the aquatic biodiversity of the southern Altiplano     

Marcela Mrquez-García  Irma Vila  Luis Felipe Hinojosa  Marco A. Mndez  Jos Luis Carvajal  María Catalina Sabando 《Limnologica》2009,39(4):314-318

We compared the distribution and seasonal fluctuations in the aquatic biota in relation to chemical and physical water variables in the Altiplano watersheds of the Ascotán, Carcote and Huasco salars; Chungará and Cotacotani lakes; Isluga and Lauca Rivers and the Parinacota wetland. We sampled during the austral autumn–winter of 2006 and in the spring–summer of 2006–2007, using three sampling stations for each system. We used canonical correspondence analysis to establish relations between frequency of taxa and environmental variables.We demonstrate that the structure and composition of the aquatic biota in humid areas of the Altiplano is determined by physical and chemical variables of the water. The most relevant one is total nitrogen, which is also the limiting nutrient for phytoplankton production in tropical systems.Benthos and zooplankton showed significant associations with the set of environmental variables (Monte Carlo test, p<0.05); however, the association was not significant for phytoplankton. Lake Chungará showed the greatest variation in composition and abundance of zooplankton between autumn-winter and spring-summer, while in the Huasco salar the physical and chemical characteristics were related to the composition and abundance of the benthonic fauna. Thus, changes in the water volume of these systems would have repercussions in chemical and physical variables, altering the species assemblage and possibly the efficiency and stability of ecosystem functions.  相似文献   

Shaping Sydney Harbour: Sedimentation,dredging and reclamation 1788-1990s     

Lynette C. McLoughlin 《The Australian geographer》2000,31(2):183-208

Described by Governor Phillip as 'the finest harbour in the world', Sydney Harbour was affected by accelerated sedimentation very soon after settlement in 1788. Dredging began in 1842 to deal with the problems caused by sedimentation and to enhance foreshore amenity. By the end of the nineteenth century, dredging was also excavating the bottom of the Harbour and its bays to accommodate larger ships with deeper draughts, and dredged sediment was increasingly used to reclaim mudflats or marshes deemed unhealthy or unsightly, thereby creating additional useful waterfront land. There was virtually continuous dredging in some part or other of the Harbour and its tributaries for almost 140 years. With increasing costs and mounting environmental concerns, dredging is now intermittent, and carried out largely to facilitate navigation for specific projects, despite continued sedimentation. While there was an early lack of understanding of the Australian environment and the impact of clearing on soils, the causes of increased sedimentation had been documented by the 1860s. However, measures to seriously address causes were not introduced until late in the twentieth century. This paper briefly outlines the development of the Sydney estuary to 1788, considers the impact of settlement in accelerating sedimentation, traces the development of dredging and reclamation, and discusses their significance for a number of areas of current research and environmental management, as well as to social and economic history. Within the limitations of the data available, annual sediment dredged, annual expenditure, cost per tonne, and areas reclaimed by dredging and filling are included.  相似文献   

基于越冬水鸟生境模拟的拟建鄱阳湖水利枢纽生态控制水位探讨   总被引：1，自引：0，他引：1  

陈炼钢  陈黎明  徐祎凡  贾建伟  栾震宇  施勇  金秋  胡腾飞 《湖泊科学》2020,32(5):1519-1528

长江及鄱阳湖水系上游水库群运用后鄱阳湖枯季水文节律出现新的变化,为应对新的枯水情势,鄱阳湖水利枢纽作为一个选项被提出,如何确定其适宜的调控水位才能维持鄱阳湖湿地生态系统健康是其中的重点与难点.本文选择鹤类、小天鹅、鸿雁等食植物块茎水鸟作为鄱阳湖湿地生态系统的指示物种,基于EFDC水动力学模型和生境适宜度曲线构建了鄱阳湖越冬水鸟生境数值模拟模型;从食物资源与取食可及性两个方面,分苦草(Vallisneria natans)生长期和水鸟越冬期两个时段,以水深作为关键生境因子,对近10年鄱阳湖苦草及水鸟取食潜在生境面积变化进行了连续模拟;揭示了鄱阳湖苦草及水鸟取食潜在生境面积随水位的变化规律并构建了定量响应函数:苦草潜在生境面积随水位呈单峰型变化,在星子站水位为14.8 m时达到最大,约为1703 km2;越冬水鸟取食潜在生境面积随水位呈三段式变化,最大和最小面积分别约为564和476 km2,相应星子站水位分别为11.73和9.56 m.在此基础上,针对拟建的鄱阳湖水利枢纽工程,基于不同调度分期内生境保护目标的差异确定了符合天然水位波动特征的生态水位动态调控方案:下闸蓄水期内水位宜控制在16 m以下,后续根据越冬水鸟迁入情况逐步下降以增加取食生境面积,在12月次年1月的越冬水鸟数量峰值期水位宜控制在12.5 m以下,后续根据来水情况逐步过渡至江湖连通期的自然状态.成果从保护越冬水鸟食物资源与取食可及性两个方面提出了鄱阳湖水利枢纽生态水位的动态调控阈值,为江湖新水沙条件下鄱阳湖湿地生态系统保育提供了量化依据.  相似文献   

Identifying environmental drivers of chlorophyll-a dynamics in Austral subtropical ephemeral ecosystems     

《Limnologica》2019

Environmental and biological features of Austral subtropical pan types were assessed, along with the drivers of chlorophyll-a (chl-a) concentrations. Chl-a biomass varied considerably across seasons and endorheic pans had elevated chl-a concentrations compared to floodplain pans. The major driver of chl-a concentration based on generalised linear/non-linear models (GLZ) was total phosphorous and total suspended solids for all pan types and seasons combined. These results are discussed within the context of secondary productivity, aquatic ecosystem heterogeneity and endorheic pan conservation.  相似文献   

Significance of enhanced infiltration due to groundwater extraction on the disappearance of a headwater lagoon system: Toluca Basin, Mexico   总被引：1，自引：0，他引：1  

D. L. Rudolph  R. Sultan  J. Garfias  R. G. McLaren 《Hydrogeology Journal》2006,14(1-2):115-130

Mexico City relies significantly on groundwater resources drawn from the Sistema Lerma well field located in the Toluca Basin, Mexico. Enhanced infiltration caused by groundwater extraction is suspected to be both a prime factor in the disappearance of a lagoon system at the Toluca Basin and a potential risk to long-term groundwater quality. A combined approach of field investigation and numerical modeling was adopted to assess the groundwater-surface water interactions within the lagoon system. Potentiometric data indicate that current downward vertical hydraulic gradients below the lagoon and surrounding wetland area are extremely low suggesting very slow infiltration rates. Geochemical and isotope data from surface water and groundwater sampling also indicate that very little surface water infiltration has occurred. Numerical simulations demonstrate that enhanced surface water infiltration is unlikely to be the primary cause in the significant reduction in size of the lagoon system. Other factors such as modifications to the surface water drainage system and capture of spring flow from the surrounding mountainous regions are likely more significant. Simulations also suggest that contaminants originating in the lagoon system are currently entering nearby production wells although the total contaminant mass flux to the wells is still very low and significantly diluted.

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Resumen La Ciudad de México depende significativamente de los recursos de aguas subterráneas obtenidos del campo de pozos Sistema Lerma ubicado en la Cuenca Toluca, oeste de la Cuenca de México. Se sospecha que la infiltración estimulada causada por extracción intensiva de aguas subterráneas es un factor principal en la desaparición de un sistema de lagunas en la cabeceras del Río Lerma en el centro de México y un riesgo potencial para la calidad de aguas subterráneas a largo plazo en la región. Se adoptó un enfoque combinado de investigación de campo y modelizado numérico para evaluar las interacciones de agua superficial-agua subterránea dentro del sistema de lagunas. Datos potenciométricos indican que los gradientes hidráulicos verticales descendentes actuales, ubicados por debajo de la laguna y vecina área de humedales, son extremadamente bajos sugiriendo ritmos de infiltración muy lentos. Datos geoquímicos e isotópicos provenientes del muestreo de agua superficial y subterránea también indican que ha ocurrido muy poca infiltración de agua superficial. Las simulaciones numéricas demuestran cuantitativamente que no es probable que la infiltración estimulada de agua superficial sea la causa principal en la reducción significativa del tamaño del sistema de lagunas en la cabecera. Otros factores tal como modificaciones al sistema superficial de drenaje de agua y captura de flujo de manantial en las regiones montañosas vecinas son probablemente más significativos. Las simulaciones también sugieren que los contaminantes que se originan en el sistema de lagunas están actualmente ingresando a pozos de producción cercanos aunque el flujo de masa contaminante total a los pozos es aún muy bajo y diluido significativamente en los volúmenes grandes de extracción. La magnitud de la amenaza a largo plazo a la calidad del agua subterránea en los pozos de producción Sistema Lerma proveniente de contaminantes infiltrados es una preocupación y amerita estudios futuros.

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Résumé La Cité de Mexico dépend significativement des ressources en eau souterraine pompées au site de captages de Sistema Lerma, dans le Bassin de Toluca, à lOuest du Bassin de Mexico. Laugmentation de linfiltration, causée par lextraction extensive des eaux souterraines, est suspectée dêtre à la fois un facteur primaire de la disparition dun système de lagons en amont de la rivière Lerma au centre de Mexico, et un risque potentiel à long-terme pour la qualité de leau souterraine dans la région. Uen approche combinée détudes de terrain et de modélisation numérique a été adoptée pour estimer les interactions entre les eaux de surface et les eaux souterraines, au sein du système de lagons. Les données potentiométriques indiquent que les gradients hydrauliques verticaux descendants sont très bas au niveau des lagons, ce qui suppose un taux dinfiltration faible. Les données géochimiques et isotopiques provenant des eaux de surface et souterraines, indiquent également que peu deau de surface sinfiltrent. La simulation numérique démontre quantitativement que laugmentation de linfiltration des eaux de surface nest probablement pas la première cause de réduction des lagons. Dautres facteurs, tels que les modifications du drainage des eaux de surface, laménagement en captage des sources situées aux pieds des montagnes environnantes, sont probablement plus importants. Les simulations suggèrent également que les contaminants provenant des lagons se retrouvent également dans les captages les plus proches, bien que le flux total de contaminants entrant dans les captages reste faible. Les volumes dextraction étant très important ils diluent effectivement les contaminants. Les effets à long-terme de lextraction critique au niveau des forages de Sistema Lerma et de la dégradation de la qualité des eaux souterraines par les contaminants, nécessite une grande attention pour le futur.

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大庆龙凤湿地须浮鸥巢址选择研究     

陈雪龙  杨焕民  齐艳萍  王晓龙 《湿地科学》2012,10(3):339-343

为了认知影响须浮鸥(Chlidonias hybridus)营巢的主要环境因素,于2011年6～7月,采用直接观察法和样方法在大庆龙凤湿地自然保护区内对须浮鸥的巢区进行了调查研究.在本次调查中共发现须浮鸥巢73个,逐巢进行了常规测量,并对须浮鸥巢址及附近无巢对照区域的生境进行了调查.主成分分析和独立样本t检验的结果表明,须浮鸥属于集群营巢,而影响须浮鸥巢址选择的主要因素依次为巢下水深、巢距植物距离、巢周明水面积、植物高度、植物密度和巢距干扰源距离.其中,前3个因素影响须浮鸥生境中食物的供给条件,后3个因素影响须浮鸥巢的隐蔽条件.须浮鸥选择巢址的条件是能提供丰富食物且具有较好隐蔽条件的生境.  相似文献   

中国湿地生态恢复评价标准制定探讨     

崔芳 《湿地科学与管理》2015,11(2):62-65

在概述国内外湿地生态恢复研究概况的基础上,探讨了湿地生态恢复标准的制定方法。在评价标准的制定上,试图综合考虑湿地恢复的生态结构和功能、生态环境、生物种群、景观恢复及资源稀缺性价值和基础设施建设、管理等方面的内容和关系,并尽可能选取一般性的评估指标来满足多数湿地的评价需要。在特定条件下的湿地恢复评价需要增加某些特殊性的评估指标,通过赋予不同限制性因子权重,在综合以上多方面评价结果的基础上,通过划分评价等级最终给出评价结果。对今后的研究方向进行了展望,并提出了研究重点。  相似文献   

Analysis of storm run-off sources using oxygen-18 in a headwater swamp     

A. R. Hill  J. M. Waddington 《水文研究》1993,7(3):305-316

A combination of hydrometric data and observations of natural isotope (oxygen-18) variations in saturation overland flow and stream discharge were used to investigate the sources of storm run-off in a headwater swamp located in a permanent groundwater discharge zone near Toronto, Canada. The results of a two-component hydrograph separation indicated that pre-event water formed 80–90% of the stream hydrograph volume for six of the seven storms analyzed in June–November 1990. However, the instantaneous event water contribution showed considerable variability, ranging from maximum values of 20–25% for four moderate intensity storms to 63% for a high intensity thunderstorm with a return period of two years. The relative contribution of event and pre-event water to storm run-off from saturated areas and small streamlets within the swamp was similar to the main outlet stream. The dominance of pre-event water during storms could be accounted for by the mixing of a small volume of event water with a large pool of pre-event water on the surface of permanently saturated areas within the swamp. Occasional storms of high intensity or long duration produced a greater shift towards an event water signature in the saturated areas and a larger event water contribution to the outlet stream hydrograph.  相似文献   

Dynamics of floodplain-island groundwater flow in the Okavango Delta, Botswana     

P. Wolski  H.H.G. Savenije   《Journal of Hydrology》2006,320(3-4):283-301

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