An empirical regression model of soluble phosphorus retention for small pristine streams evaluating tracer experiments     

Marcus Schulz  Maik Bischoff  Jörg Klasmeier  Jürgen Berlekamp  Michael Matthies 《Aquatic Sciences - Research Across Boundaries》2008,70(2):115-122

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Nutrient flux, uptake, and transformation in a spring-fed stream in the Missouri Ozarks, USA     

Dev K. Niyogi  Janet M. Bandeff  Cem Selman  Drew E. Menke 《Aquatic Sciences - Research Across Boundaries》2010,72(2):203-212

We examined nutrient flux, uptake, and transformation along a spring-fed stream in the Ozark region of Missouri, USA, over the year 2006. Water in Mill Creek originates from several springs, with a single spring contributing over 90% of the stream discharge during much of the year of study. Soluble reactive phosphate concentrations were usually low (<10 μg L⁻¹) along Mill Creek, but peaked during high discharge. Concentrations of dissolved inorganic nitrogen (DIN) were relatively high in the spring water, mainly as nitrate, but usually declined across a small pond and the 10-km length of Mill Creek. During low flows in summer and early autumn, the stream removed over 300 μg L⁻¹ of DIN over its 10-km length, or about 80% of the initial amount. DIN retention along the stream, as a percentage of the DIN upstream, was related mainly to discharge, with higher flows having much higher DIN concentrations. The net uptake rate of DIN uptake was 0.91 μg m⁻² s⁻¹ in the stream during summer baseflow. The uptake rate declined downstream for different reaches and was closely related to DIN concentration. In experimental channels, uptake by epilithic algae was one significant sink for nitrate-N in Mill Creek. In 2006, inorganic nutrient export during a single day after a spring storm was similar to export during 40–100 days of low flow conditions in summer and early autumn. Our results suggest that significant nutrient retention can occur during baseflow periods via biological uptake, whereas substantial export occurs during high flow conditions.  相似文献   

Contrasts among macrophyte riparian species in their use of stream water nitrate and ammonium: insights from 15N natural abundance     

Marc Peipoch  Esperança Gacia  Alba Blesa  Miquel Ribot  Joan L. Riera  Eugènia Martí 《Aquatic Sciences - Research Across Boundaries》2014,76(2):203-215

We examined the relevance of dissolved inorganic nitrogen (DIN) forms (nitrate and ammonium) in stream water as N sources for different macrophyte species. To do this, we investigated the variability and relationships between ¹⁵N natural abundance of DIN forms and of four different macrophyte species in five different streams influenced by inputs from wastewater treatment plants and over time within one of these streams. Results showed that ¹⁵N signatures were similar in species of submersed and amphibious macrophytes and in stream water DIN, whereas ¹⁵N signatures of the riparian species were not. ¹⁵N signatures of macrophytes were generally closer to ¹⁵N signatures of nitrate, regardless of the species considered. Our results showed significant relationships between ¹⁵N signatures of DIN and those of submersed Callitriche stagnalis and amphibious Veronica beccabunga and Apium nodiflorum, suggesting stream water DIN as a relevant N source for these two functional groups. Moreover, results from a mixing model suggested that stream water DIN taken up by the submersed and amphibious species was mostly in the form of nitrate. Together, these results suggest different contribution to in-stream N uptake among the spatially-segregated species of macrophytes. While submersed and amphibious species can contribute to in-stream N uptake by assimilation of DIN, macrophyte species located at stream channel edges do not seem to rely on stream water DIN as an N source. Ultimately, these results add a functional dimension to the current use of macrophytes for the restoration of stream channel morphology, indicating that they can also contribute to reduce excess DIN in streams.  相似文献   

Fine particulate organic matter transport dynamics in a small Coastal Plain stream: influence of hydrology and channel morphology     

Hwaseong Jin  G. M. Ward 《Aquatic Sciences - Research Across Boundaries》2013,75(4):483-492

Fine particulate organic matter (FPOM) represents a major component of stream organic matter budgets, and its dynamics greatly affect the productivity and metabolism of a stream community. FPOM transport dynamics has been well documented in high-gradient streams with rocky substrates, but information from low-gradient, sandy-bottom streams has been lacking. We estimated FPOM retention patterns in Payne Creek, a 2nd order Coastal Plain stream (USA), under naturally varying hydraulic conditions (discharge and velocity). Corn pollen, as an FPOM analogue, was released along with a conservative solute tracer and the particle retention coefficient (k _p) was calculated by fitting the ratio of total pollen remaining in the water column against the longitudinal transport distance to an exponential decay model. Pollen k _p (n = 4) ranged from 0.034 to 0.214 /m, and particle transport distance (S _p) ranged from 4.7 to 29.7 m. The S _p measured in Payne Creek was in the lowest range of previously reported values, and such rapid particle retention was attributed to the low channel slope and slow current velocity. S _p was significantly correlated to water velocity and the channel friction factor, but not to discharge (Q). Two summer experiments conducted in contiguous stream segments resulted in the shortest (4.7 m) and longest (29.7 m) S _p, despite the similar Q. This was attributed to the segment-scale channel alterations that occurred during the previous winter, which led to very different hydraulic conditions in the two stream segments. In Payne Creek, seasonal changes in hydrology and segment-scale variation in channel morphology were the main factors controlling FPOM transport and retention.  相似文献   

引水工程絮凝剂余铝对杭州西湖水体、底泥铝盐分布的影响   总被引：1，自引：1，他引：0  

张玥  徐栋  张义  刘碧云  肖恩荣  周巧红  贺锋  吴振斌 《湖泊科学》2017,29(4):796-803

通过对杭州西湖综合保护工程钱塘江引水范围内多个湖区水体和底泥中铝盐含量的调查分析,研究了工程絮凝剂余铝对西湖水体、底泥铝盐及沉水植物附着物的影响.结果表明:(1)引水工程输入的絮凝剂残余铝盐导致各湖区入水口水中铝离子含量普遍高于湖心,高出7.86%~288.55%不等,但底泥中Al_2O_3含量在整个湖区分布较为均匀;(2)约0.04~0.20 m/s流速下,沉水植物很容易成为残余铝盐絮凝物的附着受体;(3)秋、冬季水体中铝离子浓度较高,对西湖水生生物存在更大的生物潜在危害,有必要重视秋、冬季的沉水植物恢复工作.引水工程对西湖水体的影响是长久且难以预见的,在引水的同时应尽量减少其负面影响,可减少絮凝剂的使用或选择环保型絮凝剂,并选择合适的水生植物.  相似文献   

Macrophyte‐driven transient storage and phosphorus uptake in a western Wisconsin stream          下载免费PDF全文

Katherine J. Bohrman  Eric A. Strauss 《水文研究》2018,32(2):253-263

Investigations of phosphorus cycling and transport in streams lend insight into potential mechanisms of nutrient sequestration and can help mitigate human impacts. In this study, we examined the relationship between transient storage and phosphorus uptake in a cold‐water stream in western Wisconsin. Hydrological characteristics, nutrient spiralling metrics, macrophyte biomass, and geomorphological properties were quantified in 7 reaches of Spring Coulee Creek using injections of a conservative tracer alone or with added PO₄^3?. Fraction of median travel time due to transient storage (F_med²⁰⁰) was correlated with macrophyte biomass (r = .794, p = .033), and PO₄^3? uptake velocity was correlated with F_med²⁰⁰ (r = .756, p = .049). Stepwise linear regression was used to build models for transient storage and uptake velocity. Macrophyte biomass, stream bed slope, and riffle to pool ratio accounted for 99.6% of the variation in transient storage (p < .001). Transient storage, canopy cover, and slope accounted for 98.0% of the variation in uptake velocity (p = .002). This study shows that transient storage, primarily resulting from macrophyte beds, can be a significant factor regulating phosphorus uptake in stream ecosystems.  相似文献   

呼伦湖浮游植物群落季节动态及其与环境因子的关系     

钱玺亦  李金彪  敖文  庞博  包萨茹  王琪  刘波  王增龙 《湖泊科学》2022,34(6):1814-1827

为探究呼伦湖浮游植物群落的季节变化特征及其与环境因子的关系,本研究分别于2019年3、5 10月对呼伦湖浮游植物的种类、细胞密度和生物量及湖水水质进行调查.结果显示,共鉴定出120种浮游植物,隶属于7门72属.从浮游植物群落季节组成差异上来看,春季绿藻门种类数最多,其次是硅藻门、蓝藻门;夏秋季绿藻门种类数最多,蓝藻门次之;冬季硅藻门种类数最多,绿藻门次之.呼伦湖浮游植物优势种主要为硅藻门的梅尼小环藻(Cyclotella meneghiniana)、蓝藻门的卷曲长孢藻(Anabaena circinalis)和细小平裂藻(Merismopedia minima),种类数在春季最多,秋冬季最少.浮游植物细胞密度在春季(123.52×10⁴cells/L)和冬季(16.41×10⁴cells/L)较夏季(280.80×10⁴cells/L)和秋季(380.63×10⁴cells/L)低,春冬季绿藻门细胞密度最高,夏秋季蓝藻门细胞密度最高.就浮游植物生物量而言,夏季(0.38mg/L)最大,其次是秋季(0...  相似文献   

湖北金沙河水库浮游植物群落结构及其与水环境因子的关系   总被引：8，自引：3，他引：5  

张云  马徐发  郭飞飞  李建柱  熊邦喜 《湖泊科学》2015,27(5):902-910

为探明长江中游大型水库水质状况,并为饮用水源安全保障提供科学依据,于2013 2014年按季节对湖北红安金沙河水库浮游植物群落结构及其多样性进行调查,并运用多元统计定量分析浮游植物群落结构与环境因子之间的关系.共鉴定出浮游植物8门94属216种,其中绿藻门为优势种群,其种类数占总物种数的51.39%,其次是硅藻门和蓝藻门.金沙河水库优势种随季节变化而变化,夏季以尖针杆藻(Synedra acus)的优势度最大(0.195),秋季以小胶鞘藻(Phormidium tenus)(0.180)和中华尖头藻(Raphidiopsis sinensia)(0.171)的优势度最大,冬季以具星小环藻(Cyclotella stelligera)(0.220)和圆筒锥囊藻(Dinobryon cylindricum)(0.234)的优势度最大,春季则是链状曲壳藻(Achanthidum catenatum)成为绝对优势种(0.910);金沙河水库浮游植物群落总的变化规律为夏季的硅藻门、蓝藻门和绿藻门,秋季的蓝藻门、绿藻门、硅藻门和隐藻门,向冬季的硅藻门和金藻门转变,春季则是硅藻门为绝对优势类群.Shannon-Wiener多样性指数和Pielou均匀度指数显示,浮游植物在秋季的多样性和均匀度较高,春季的多样性指数和均匀度指数显著低于其它季节,这是因为春季有绝对单一的优势物种,而秋季没有,且秋季的物种数最多,因此其Margalef丰富度指数也最高.将各季节优势种和经Pearson相关性分析筛选出的环境因子进行冗余分析,结果表明筛选的环境因子中磷酸盐、总磷和溶解氧浓度是影响金沙河水库浮游植物群落结构的主要环境因子.从藻类季节变化规律来看,金沙河水库夏、秋季水质污染程度较春、冬季严重;但从藻类丰度和多样性指数来看,春、夏季水质较秋、冬季污染严重.  相似文献   

滆湖水体光学性质初步研究   总被引：3，自引：1，他引：2  

何尚卫  李勇  赵海光  潘继征 《湖泊科学》2014,26(5):707-712

基于2009年7月至2010年6月滆湖全湖15个采样点的水体光学参数及相关水质理化因子数据,分析滆湖水体周年光合有效辐射(PAR)衰减特性,以期为滆湖沉水植物生态修复提供相关水体光学资料.结果表明,滆湖水体PAR衰减系数(Kd)周年变化范围为1.32～17.42 m-1.秋季Kd相对最小,平均值为2.35 m-1,变化范围为1.32 ～3.70 m-1;夏季Kd相对最大,平均值为6.23 m-1,变化范围为3.68～17.42 m-1.春、秋、冬季,滆湖水体真光层平均深度均满足沉水植物的生长需求,而在夏季滆湖水体真光层平均深度仅为0.84m,小于全湖平均水深(1.20 m),因此夏季PAR是限制沉水植物恢复的因子之一.滆湖水体Kd与透明度(SD)在秋、冬季的关系为:Kd =2.089 +0.705/SD.叶绿素a浓度和悬浮物浓度是影响滆湖水体Kd的重要因子之一.  相似文献   

Temporal cycles of karst denudation in northwest Georgia,U.S.A.     

Rudi H. Kiefer 《地球表面变化过程与地形》1994,19(3):213-232

Time patterns of karst denudation in northwest Georgia (U.S.A.) were investigated at three spring sites for 12 months and at five stream sites for 10 years. Rainfall was evenly distributed and showed no significant seasonality. At the springs, as well as the streams, water hardness was largely controlled by discharge. At the springs, soil pCO₂ and water pH were strongly correlated (r + -0·69 to -0·83). Solute transport in spring waters was highly seasonal, with two conduit flow springs removing more limestone in the winter, and the diffuse flow spring removing more during the growing season. At the stream sites, most denudation occurred during the winter and spring seasons, and least during the summer. Fourier analysis showed that variations in denudation occur on deterministic (long-wave) as well as stochastic (shortwave) time scales. As contributing variables, discharge varied in short-wave and long-wave cycles, whereas soil pCO₂ showed only a long-wave cycle. The 12 month deterministic cycles were the most important, with changes in discharge taking precedence over soil pCO₂. Time series regression explains up to 69 per cent of changes in denudation through rain and soil pCO₂. Time cycles in available water are the key controlling factor of denudation, and amounts of available soil CO₂ may not be as important in the temporal patterns of karst downwearing as has been believed previously.  相似文献   

Abundance distribution and seasonal variations of Calanus sinicus (Copepoda: Calanoida) in the northwest continental shelf of South China Sea   总被引：2，自引：0，他引：2  

Jianqiang Yin  Liangmin HuangKaizhi Li  Shumin LianChaolun Li  Qiang Lin 《Continental Shelf Research》2011,31(14):1447-1456

The effect of monsoon, coastal current and temperature on the distribution and seasonal variations of Calanus sinicus abundance were studied. The samples from the northwest continental shelf of South China Sea were collected with 505 μm planktonic nets from July 2006 to October 2007. The abundance of C. sinicus made up 34.28% and 12.34% of all copepods in spring and summer, respectively. The distribution of C. sinicus varied seasonally and regionally. The distribution of C. sinicus ranged between east inshore and offshore waters from the Leizhou Peninsula to Hainan Island, with a mean of 23.00 (±77.78) ind. m⁻³ in spring. In summer it had a mean of 13.74 (±45.10) ind. m⁻³ occurring only in the east inshore waters from Leizhou Peninsula to Hainan Island. C. sinicus was not abundant during autumn and winter seasons. The surveyed area was divided into three sub-regions based on topographical analysis and water mass, region I (included the east inshore waters of Leizhou Peninsula), region II (included the east inshore waters of Hainan Island) and region III (included the offshore waters from Leizhou Peninsula to Hainan Island). The average abundance of C. sinicus within region I was determined to be 115.63 (±145.93) and 68.12 (±84.00) ind. m⁻³ in spring and summer, respectively, values higher than those of regions II and III. Our findings suggested that C. sinicus was transported from the East China Sea to the northwest continental shelf of South China Sea by the Guangdong Coastal Current, which was driven by the northeast monsoon in spring. The presence of a cold eddy, in addition to coastal upwelling driven by the southwest monsoon, provided suitable survival conditions for C. sinicus in summer. This species disappeared in autumn due to high temperatures (>27 °C) and did not begin to enter into the northwest continental shelf of South China Sea from the East China Sea during the period of investigation in winter. The frequency of C. sinicus was low in region III during the year as a result of the South China Sea Warm Current and pelagic waters with high temperature during the spring and summer months.  相似文献   

Measurement of soluble reactive phosphorus concentration profiles and fluxes in river-bed sediments using DET gel probes   总被引：3，自引：0，他引：3  

Helen P. Jarvie  Robert J.G. Mortimer  Elizabeth J. Palmer-Felgate  Katherine St. Quinton  Sarah A. Harman  Patricia Carbo 《Journal of Hydrology》2008,350(3-4):261-273

DET (diffusive equilibrium in thin films) gel probes were used for sampling river-bed sediment porewaters, to characterise in situ soluble reactive phosphorus (SRP) concentration profiles and fluxes. DET probes were deployed in three contrasting rural streams: (1) a headwater ‘pristine’ stream, with minimal P inputs from low intensity grassland and no point sources, (2) an intensively cultivated arable catchment, and (3) a stream subject to high P loadings from sewage effluent and intensive arable farming. The DET results showed highly enriched porewater SRP concentrations of between ca. 400 and 5000 μg-P l⁻¹ in the sewage-impacted stream. In contrast, the arable and pristine streams had porewater SRP concentrations <70 μg-P l⁻¹ and <20 μg-P l⁻¹, respectively. Porewater SRP concentration profiles in both the sewage-impacted and arable-impacted streams showed well-defined vertical structure, indicating internal sources and sinks of SRP within the sediment. However, there was little variability in porewater SRP concentrations in the pristine stream. The DET porewater profiles indicated net diffusion of SRP (a) from the overlying river water into the surface sediment and (b) from subsurface sediment upwards towards the sediment–water interface. A mass balance for the sewage-impacted site showed that the influx of SRP into the surface sediments from the overlying river water was small (ca. 1% of the daily river SRP load). The DET results indicated that, in the arable and sewage-impacted streams, the surface ‘cap’ of fine sediment may play an important role in inhibiting upward movement of SRP from subsurface porewaters into the overlying river water, under steady-state, low-flow conditions.  相似文献   

太湖贡湖湾虾类种类组成与时空分布特征   总被引：3，自引：1，他引：2  

温周瑞  谢平  徐军 《湖泊科学》2011,23(6):961-966

分别于2005年4月、7月、10月利用蹦网对贡湖湾虾类种类组成和时空分布进行调查.共采集到虾类9605尾,属于2科3属5种,分别是秀丽白虾(Exopalaemon modestus)、日本沼虾(Macrobrachium nipponense)、锯齿新米虾中华亚种(Neocaridina denticulata sin...  相似文献   

Influence of rural land use on streamwater nutrients and their ecological significance   总被引：1，自引：0，他引：1  

Helen P. Jarvie  Paul J.A. Withers  Robin Hodgkinson  Adam Bates  Margaret Neal  Heather D. Wickham  Sarah A. Harman  Linda Armstrong 《Journal of Hydrology》2008,350(3-4):166-186

Concentrations and loads of N and P fractions were examined for lowland rivers, the Wye and Avon, draining a range of representative agricultural land-use types in two major UK river basins. Data collected over a 2-year period demonstrated important diffuse agricultural source contributions to N and P loads in these rivers. Ground water provided a major source of total dissolved nitrogen (TDN) loads, whereas near-surface sources provided a major contribution to total phosphorus (TP) loads. In terms of aquatic ecology, concentrations of nutrients, at times of eutrophication risk (spring and summer low flows) were of key environmental and management significance. Agricultural diffuse sources provided the major source of long-term P loads across the two basins. However, the results demonstrated the dominance of point-source contributions to TP and SRP concentrations at times of ecological risk. Point sources typically ‘tip the balance’ of dissolved inorganic P (soluble reactive P, SRP) above the 100 μg l⁻¹ guideline value indicative of eutrophication risk. The significance of point sources for TP and SRP concentrations was shown by (a) the strong correlations between TP, SRP and B concentrations, using B as a tracer of sewage effluent, (b) the dominant contribution of SRP to TP concentrations and (c) the predominant pattern of dilution of SRP and B with flow. The clean Chalk streams draining low intensity grassland in areas of the Avon with sparse human settlement were oligotrophic and P limited with low SRP concentrations under spring and summer baseflows attributable to groundwater sources. The data provide important insights into the ecological functioning of different lowland stream systems. There was evidence of greater SRP losses and N-limitation in a stream which drains a pond system, demonstrating the importance of longer water residence times for biological nutrient uptake.  相似文献   

Seasonality of epCO2 at different scales along an integrated river continuum within the Dee basin,NE Scotland     

Dr Julian J.C. Dawson  Chris Soulsby  Markus Hrachowitz  Mark Speed  Doerthe Tetzlaff 《水文研究》2009,23(20):2929-2942

Spatial and temporal variations of free CO₂ concentrations in surface waters are mainly controlled by dynamic processes encompassing terrestrial inputs and in‐stream biotic cycling. Free CO₂ can be expressed as ‘excess partial pressure of CO₂’ (epCO₂), indicating supersaturation or under‐saturation with respect to atmospheric CO₂. Seasonal patterns of epCO₂ at sites draining nested upland catchments between 3·40 and 1837 km² were assessed within the River Dee basin in NE Scotland. EpCO₂ values ranged from 0·14 at the lowermost site on the mainstem in autumn to 12·7 on a major tributary during spring. A seasonality index was derived to describe contrasting winter/spring maxima and summer/autumn minima as annual mean epCO₂ values could not clearly distinguish between different sites. Seasonal differences tended to increase downstream as progressive changes in physicochemical conditions enhanced the influence of autotrophic communities. However, perturbations to this continuum occurred as CO₂ inputs from high DOC, heterotrophic tributaries and land‐use changes between open moorland and forest affected downstream continuity. Major tributaries showed reduced differences between seasons compared to the mainstem. Smaller headwaters indicated a lack of seasonality as high connectivity of responsive, peaty soils enabled continual inputs of terrestrially derived free CO₂ to streams concomitant with limited autotrophic CO₂ removal, maintaining epCO₂ > 1 throughout. Seasonality of epCO₂ was mainly driven by the ability of in‐stream biota to consume CO₂ during optimal conditions in summer/autumn. This was confirmed by multiple linear regression analysis, which indicated that, apart from catchment area, baseflow and biotic activity indicators were the best predictors of epCO₂ seasonality characteristics at any particular stage of the river system. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

基于15N稳定同位素示踪技术的太湖梅梁湾浮游植物群落氮吸收动力学研究     

杨柳  刘正文 《湖泊科学》2019,31(2):449-457

浮游植物对氮的吸收与其生长繁殖密切相关,太湖梅梁湾湖区蓝藻水华频频暴发,对该水域浮游植物氮吸收进行研究具有重要意义.本文分别在冬、春、夏、秋4个季节于梅梁湾采样,对水体常规理化指标和浮游植物群落结构进行分析,并利用¹⁵N稳定同位素示踪技术研究了浮游植物对铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）和尿素态氮（Urea-N）吸收的动力学特征.结果表明,太湖梅梁湾浮游植物群落除了秋季对NH₄⁺-N的吸收不符合米氏方程外,其余均符合.冬季和春季3种形态氮最大吸收速率（V_max）的大小依次为：NH₄⁺-N > NO₃^--N > Urea-N,而夏季为：NH₄⁺-N > Urea-N > NO₃^--N.3种形态氮V_max的季节变化规律为夏季 > 秋季 > 春季 > 冬季.V_max在不同季节以及不同形态氮之间的差异性可能与浮游植物群落组成以及水体中NH₄⁺-N浓度不同有关.浮游植物对NH₄⁺-N吸收的K_S值在冬、春季高于夏季,对Urea-N吸收的K_s值则在夏、秋季高于冬、春季,而对NO₃^--N吸收的K_s值则在夏季显著高于其他3个季节.冬季和春季梅梁湾浮游植物群落最容易受到NO₃^--N限制,而最不容易受到Urea-N的限制;而夏季,则最容易受到NO₃^--N限制,而最不容易受到NH₄⁺-N的限制,且浮游植物群落对NH₄⁺-N的亲和力最高.与NO₃^--N相比,秋季浮游植物更容易受到Urea-N的限制.不同季节,容易对浮游植物产生限制作用的氮的形态不同.  相似文献   

太湖草/藻型湖区沉积物-水界面环境特征差异   总被引：3，自引：0，他引：3  

王永平  朱广伟  洪大林  秦伯强 《湖泊科学》2013,25(2):199-208

在太湖草、藻型湖区进行冬、夏两季多点采样,分别对采样点的水环境特征、泥面以上5 cm上覆水中营养盐以及沉积物的含水量、中值粒径、有机碳、氮、磷、金属元素和溶解氧进行测定.结果表明:夏季藻型湖区表层水体pH高于中、底层,冬季草型湖区各层水体pH高于藻型;草型湖区水体浊度夏季低于藻型,冬季反之;藻型湖区上覆水中的硝态氮和磷酸根浓度显著高于草型;草型湖区沉积物中含水量冬季显著高于夏季;草型湖区沉积物中总有机碳显著高于藻型;Fe、Zn、Ca、Pb、Na和K等元素在草、藻型湖区间差异显著;沉积物中溶解氧表现为冬季深于夏季,藻型深于草型的规律.  相似文献   

The effect of transient storage on nitrate uptake lengths in streams: an inter‐site comparison     

Laura K. Lautz  Donald I. Siegel 《水文研究》2007,21(26):3533-3548

Surface water–groundwater interaction in the hyporheic zone may enhance biogeochemical cycling in streams, and it has been hypothesized that streams exchanging more water with the hyporheic zone should have more rapid nitrate utilization. We used simultaneous conservative solute and nitrate addition tracer tests to measure transient storage (which includes hyporheic exchange and in‐stream storage) and the rate of nitrate uptake along three reaches within the Red Canyon Creek watershed, Wyoming. We calibrated a one‐dimensional transport model, incorporating transient storage (OTIS‐P), to the conservative solute breakthrough curves and used the results to determine the degree of transient storage in each reach. The nitrate uptake length was quantified from the exponential decrease in nitrate concentration with distance during the tracer tests. Nitrate uptake along the most downstream reach of Red Canyon Creek was rapid (turnover time K^?1_c = 32 min), compared with nitrate uptake reported in other studies (K^?1_c = 12 to 551 min), but other sites within the watershed showed little nitrate retention or loss. The uptake length S_w‐NO^?₃ for the most downstream reach was 500 m and the mass transfer coefficient V_f‐NO^?₃ was 6·3 m min^?1. Results from 15 other nitrate‐addition tracer tests were used to create a regression model relating transient storage and measures of stream flow to nitrate uptake length. The model, which includes specific discharge and transient storage area, explains almost half the variability in nitrate uptake length (adjusted R² = 0·44) and is most effective for comparing sites with very different stream characteristics. Although large differences in specific discharge and storage zone area explain inter‐site differences in nitrate uptake, other unmeasured variables, such as available organic carbon and microbial community composition, are likely important for predicting differences in nitrate uptake between sites with similar specific discharge rates and storage zone areas, such as when making intra‐site comparisons. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Modelling climate change impacts on hydropower lake inflows and braided rivers in a mountain basin     

Brian Caruso  Simon Newton  Regan King  Christian Zammit 《水文科学杂志》2017,62(6):928-946

This study models climate change impacts on the natural flow regime of braided rivers and inflows to hydropower lakes in a New Zealand mountain basin. Flow metrics include the magnitude, frequency, timing and duration of unaltered flows. The TopNet hydrological model was used to simulate impacts in the Upper Waitaki Basin of the South Island for the 1990s, 2040s and 2090s. An average emissions scenario and results from 12 global circulation models were used as input. Indicators of hydrological alteration and Kruskal-Wallis tests were used to evaluate flow differences. Modelled total inflows increase over time for all lakes, with most increases in winter/early spring and small decreases in summer/autumn. High flows generally increase, while low flows decrease. Although these changes may benefit hydropower and floodplain ecology, they may increase flood risk in winter and spring and drought risk in summer and autumn, causing additional challenges managing hydropower operations.