丁坝型挡板调控农田溪流暂态氮磷滞留能力的模拟研究

选择Na Cl作为保守性示踪剂、NH4Cl和KH2PO4为添加营养盐,在巢湖流域的二十埠河某一农田源头溪流段,采用恒定连续投加示踪剂的方式,开展野外示踪实验。通过对不同情景下暂态存储参数和营养螺旋指标模拟结果的比较,解析丁坝型挡板对于溪流暂态存储和氮磷滞留能力的调控效果。结果表明:丁坝型挡板使溪流交换系数α显著增大,其中间距为2.5 m的α值较无挡板情景高出132.36%,1.5 m和3.0 m间距则分别高出825.37%和641.29%;相对于无挡板情景,设置挡板的溪流交换长度Ls明显下降,水力持留因子Rh、行进时间中值F200med及过水断面面积和暂态存储区断面面积的比值As/A等出现不同程度的增大;设置挡板的氮磷吸收长度Sw较无挡板情景显著下降,吸收速度Vf则有不同程度的提高。丁坝型挡板对于农田溪流暂态存储和氮磷滞留能力具有很好的调控效果。     

芦苇占优势农田溪流营养盐滞留能力分析与评估

2014年9月—2015年4月,在合肥地区二十埠河流域的某一典型农田源头溪流段,选择以Na Cl为保守示踪剂,NH4Cl和KH2PO4为添加营养盐,采用恒速连续投加的方式,开展了7次野外现场示踪试验。在此基础上,利用OTIS模型和营养螺旋原理,从机制层面分析和评估芦苇占优势农田源头溪流氮磷营养盐滞留能力和滞留特征。结果表明,该芦苇占优势渠段的比值As/A明显超过一般源头溪流水体,暂态存储对于营养盐滞留有较大影响;NH4+和SRP的暂态存储区营养盐一阶吸收系数都较主流区高一个数量级,且所有吸收系数均为正值,表明芦苇占优势渠段具有氮、磷"汇"的功能;NH4+吸收长度明显低于SRP,特别是冬季和初春,意味着溪流对于NH4+的滞留能力超过SRP;NH4+和SRP的总滞留率分别为14.46%和10.73%,生物滞留率平均值分别为9.17%和3.67%;主流区流动水体和暂态存储区对于NH4+滞留的平均贡献率分别为43.12%、56.88%;对于SRP滞留的平均贡献率分别50.13%、49.87%。     

芦苇占优势农田溪流营养盐滞留的水文和生物贡献分析

为解析大型水生植物大量生长情形的源头溪流营养盐滞留的水文、生物作用贡献,于2014年9月—2015年6月在南淝河流域某一芦苇占显著优势的农田源头溪流段,开展8次野外示踪实验,计算渠段雷诺数Re、弗劳德数Fr、曼宁糙率系数n等水动力学参数,估算NH4+、PO43-的总滞留率以及水文、生物过程的实际滞留贡献率和相对滞留贡献率。结果表明,整个研究期间溪流水体表现出显著的紊流特征,水流流态属于缓流类型,渠道曼宁糙率系数n变化范围为0.066~0.112,平均值为0.089;NH4+总滞留损失率变化范围为9.17%~28.27%,平均值为14.68%,水文作用和生物过程对NH4+实际滞留贡献率平均值分别为10.12%和4.57%,相对贡献率平均值分别为72.51%和27.49%,表明NH4+滞留损失主要来自水文过程的影响;PO43-总滞留损失率变化范围为5.75%~17.79%,平均值为12.53%,水文作用和生物过程对PO43-实际滞留贡献率平均值分别为10.12%和2.41%,相对贡献率平均值分别为81.42%和18.58%,表明PO43-滞留损失也主要来自水文因素的影响;n与Re、Fr和Q均呈显著的幂函数关系,而实际滞留率ηNH4、ηPO4与n、Re之间均没有表现出明显的相关关系。     

光照对固定化菌藻反应器脱氮除磷效率的影响

采用气升式反应器对日光灯光暗比、日光灯光源和二极管光源在固定化菌藻共生系统去除氮磷的作用进行试验研究。结果表明:延长光照时间有利于该系统对NH4+-N、PO43--P的去除,采用日光灯光源去除效果优于采用二极管光源。     

五里湖水质现状与变化趋势

2007年8月—2008年7月对五里湖水体中的TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P等氮磷营养盐和pH、透明度、温度、CODMn、Chl-a等理化指标进行了为期1年的监测,并将监测结果与2004—2005年的同期结果进行了比较。结果表明:五里湖自2003年实施生态恢复工程以来,水体水质得到了一定改善,TN和TP负荷分别下降47.25%和10.06%,水体营养状况由中度富营养化变为轻度富营养化,但仍还没有完全从根本上解决水体的富营养化问题。     

菌藻混合固定化及其对污水的净化实验

对菌藻共固定化系统进行研究,初步确定菌藻共固定化中较佳的污泥包埋量。在同等条件下,固定化菌藻对氮磷的去除效果优于固定化细菌和固定化藻类的去除效果。对氨氮和磷酸盐磷去除能力的48 h实验结果表明,按去除率的大小排列为:固定化菌藻固定化小球藻固定化细菌,固定化菌藻对NH4+-N和PO43--P的去除率分别达到97.09%和88.69%,可见把细菌和藻类共同包埋于同一载体内,在同时去除污水中的氮磷和有机物方面有着更大的优势。     

浙江省古堰坝分布特征与历史价值研究

对浙江省灌溉面积千亩以上的古堰坝分布研究发现,堰坝平均灌溉面积约233.33 hm2（3500多亩）,金衢盆地堰坝数量最多,不同地区和不同朝代在堰坝数量、建设长度、灌溉面积上存在显著差异,而堰坝高度在各地区间无显著差异,但在各朝代间存在显著差异。浙江的古堰坝选址科学、堰形设计体现人与自然的和谐,是浙江农业文化形成和发展的根源,具有丰富的历史价值。     

不同流速下溢流堰对河道水质的影响

通过对不同流速条件下水体经过45°阶梯式溢流堰坝体后水体营养盐及有机污染物指标的定期监测和分析,探讨阶梯式溢流堰在何种水动力条件下对水体的改善作用最大。结果表明:水体经过溢流堰曝气作用后,不同流速条件下其复氧程度不同,中流速(125.00 cm/s)条件下效果最佳,DO增加率最大;水体经过45°阶梯式溢流堰曝气作用后,IMn、NH3-N、TN、TP含量均降低,其中IMn、NH3-N、TN在中流速条件下去除效果最佳,而TP去除率在低流速条件下最大;由于溢流堰距离较短,因此部分水质指标改善效果不显著。     

基于PFC3D的滑坡堰塞坝堆积过程与形态模拟

基于PFC3D离散元软件,开展雅砻江唐古栋滑坡1967年失稳堆积堰塞坝的反演模拟,并基于反演参数对强变形A区失稳堆积进行预测模拟。结果表明：① 通过开展唐古栋滑坡1967年失稳堆积堰塞坝的反演分析,校核得到一组合理的细观力学参数;② 强变形A区失稳并整体下滑约1 600 m后在河谷堆积形成堰塞坝,堰塞坝形态呈中部高两边低的梯形形态分布,坝顶宽437.91 m,坝底宽994.39 m,坝高92.65 m;③ 堰塞坝在3种不同来流量下发生溃坝,其洪峰流量均远大于楞古水电站拟选坝址校核洪水流量。通过模拟发现,PFC3D软件对于模拟滑坡堰塞坝堆积过程及堆积形态有较好的适用性,可以获取堰塞坝堆积的三维形态和较准确的坝高。     

磷素在河流生态系统中滞留的研究进展

氮磷等生源要素在河流生态系统中的滞留过程控制其输出形态和通量,进而影响河流生态系统结构和功能。流域面源、点源输出不同形态的磷素(溶解态、颗粒态,无机磷、有机磷等)在河流系统运移过程中,会发生复杂的物理、化学、生物过程,改变磷素形态、降低磷素运移通量。河道渠化、排污、修建水库等活动改变了河流系统中磷素循环过程和最终趋向,降低了源头溪流磷素滞留量,加剧下游河流、湖泊等水体富营养化进程。本文通过梳理国内外河流磷素滞留主要研究,系统总结物质平衡法、模型法、螺旋结构法等研究方法的优缺点,分析河流系统中磷素滞留机制和主要影响因素,认为流量、流速、藻类吸收、外源输入和暂时存储区域是磷素滞留最重要影响因子,可以通过恢复河流系统水文模式、恢复河道形态、维持河流生境多样化等措施促进河流磷素滞留,对于流域水污染控制和河流生态保护具有重要意义。     

IMPACT OF CHANGING HYDROLOGY ON NUTRIENT UPTAKE IN HIGH ARCTIC RIVERS

Despite the importance of river nutrient retention in regulating downstream water quality and the potential alterations to nutrient fluxes associated with climate‐induced changes in Arctic hydrology, current understanding of nutrient cycling in Arctic river systems is limited. This study adopted an experimental approach to quantify conceptual water source contributions (meltwater, groundwater), environmental conditions and uptake of NO₃^?, NH₄⁺, PO₄^3? and acetate at 12 headwater rivers in Svalbard and so determine the role of changing hydrology on nutrient uptake in these Arctic river systems. Most rivers exhibited low demand for NO₃^? and PO₄^3?, but demand for NH₄⁺ and acetate was more variable and in several rivers comparable with that measured in sub‐Arctic regions. The proportion of meltwater contributing to river flow was not significantly related to nutrient uptake. However, NH₄⁺ uptake was associated positively with algal biomass, water temperature and transient storage area, whereas acetate uptake was associated positively with more stable river channels. Mean demand for NH₄⁺ increased when added with acetate, suggesting NH₄⁺ retention may be facilitated by labile dissolved organic carbon availability in these rivers. Consequently, nutrient export from Arctic river systems could be influenced in future by changes in hydrological and environmental process interactions associated with forecasted climate warming. Copyright © 2013 John Wiley & Sons, Ltd.     

Discharge Coefficient for Trapezoidal Labyrinth Side Weir in Subcritical Flow

The discharge coefficient of a trapezoidal labyrinth side weir is a function of the Froude number F ₁, the dimensionless effective crest length L/ℓ, the dimensionless weir length L/B, the dimensionless weir height p/h ₁, and the sidewall angle α. A labyrinth weir is an overflow weir, folded in plan view to provide a longer total effective length for a given overall weir width. These weirs have advantages compared to the straight overflow weir and the standard ogee crest. Previous studies on the subject have generally focused on rectangular side weirs located on a straight channel. The present study investigates the hydraulic behavior of a trapezoidal labyrinth side weir. The results show that the discharge coefficient of labyrinth side weirs gives a significantly higher coefficient value compare to that of conventional straight side weirs. Discharge coefficient of the trapezoidal labyrinth side weir is 1.5 to 5.0 times higher than the conventional straight side weir. Consequently, an equation for the coefficient of discharge is introduced. The results predicted by the equation were shown to be very satisfactory using root mean square error (RMSE), mean absolute error (MAE) and correlation coefficient (R) statistics.     

Temperature,redox, and amendments alter wetland soil inorganic phosphorus retention dynamics in a Laurentian Great Lakes priority watershed

Surface water phosphorus loading must be reduced to improve water quality and decrease harmful algal blooms. Many wetlands have a natural capacity to retain inorganic reactive PO₄^3? via soil sorption. However, soil PO₄^3? retention capacity is finite and may be limited by soil legacy phosphorus effects in agricultural and urban areas. This study evaluated soil PO₄^3? retention in soils from a wetland constructed on former agricultural land in the Lake Erie, Maumee River watershed targeted for nutrient load reduction. Soil PO₄^3? sorption isotherms were evaluated under cool (10 °C), warm (22°), aerobic, and anaerobic treatments to determine changes in PO₄^3? retention due to environmental conditions and estimate seasonal changes in PO₄^3? sorption. The soils displayed a strong capacity for PO₄^3? retention by sorption. However, results indicate that cooler temperatures and anaerobic conditions decreased PO₄^3? sorption and lowered retention rates at PO₄^3? concentrations observed in the region. Soil amendment experiments investigated opportunities to increase PO₄^3? retention because many soils display elevated phosphorus concentrations due to historic land use, limiting their ability to adsorb additional PO₄^3?. Amendments increased PO₄^3? retention capacity compared to unamended soils in the presence of high PO₄^3? concentrations, suggesting soil PO₄^3? retention can be improved in areas where natural storage capacity has been exhausted. Results from this study can inform natural resources managers in the Laurentian Great Lakes and elsewhere when identifying potential nutrient reduction wetland locations and assist with developing operational guidelines to optimize PO₄^3? retention and water quality improvements using wetlands.     

Z形薄壁堰过流能力试验

鉴于Z形堰的水流特性及过流能力尚未见到相关报道,为研究Z形堰的过流能力,采用概化水工模型,进行了6个堰型方案、12组流量的水工模型试验。结果表明,Z形堰的过流能力大于直线堰,且Z形堰的展宽比越大,流量扩大倍数越大;Z形堰的流量计算可采用通用的堰流公式,其综合流量系数与堰上水深、堰高、展长、前堰宽、后堰宽等因素有关,展宽比、前后堰宽比越大,流量系数越大;堰上水深与堰高之比越大,流量系数越小。利用试验数据给出了考虑堰上水深与堰高之比、展宽比、前后堰宽比等因素的Z形堰流量系数估算公式。     

The influence of discharge and temperature on the ability of upstream migrant adult river lamprey (Lampetra fluviatilis) to pass experimental overshot and undershot weirs

The efficiencies of fish passes specifically designed and constructed to facilitate the movement of a limited number of species and life‐stages past structural barriers are likely to decline as site‐specific conditions shift with a changing climate. There is a need to develop realistic fish passage criteria based on understanding swimming capability and behaviour of multiple species in relation to temperature and flow. The influence of temperature and discharge on behaviour and ability of groups of migrating adult river lamprey (Lampetra fluviatilis), a threatened species, to pass a small overshot or undershot weir at night was investigated using a large experimental flume. Lamprey approached the weirs less, and more often maintained station by using the oral disk to attach to structure, under high flows. Oral disk attachment was more commonly observed during tests employing the undershot weir. Upstream movement tended to be in close proximity to the channel walls and floor where, compared to the mid‐channel, velocities were generally lower and velocity vectors more likely to be in a direction other than the bulk flow. Upstream movement was positively related to temperature, and was higher for the overshot weir. Weir passage rate was higher for undershot than overshot weirs, and negatively related to the maximum velocity at the weir. Passage rate was low when maximum velocities at the weir exceeded 1.5 m s^?1, although some fish passed at c. 1.7 m s^?1. Passage efficiency, the number of weir passes as a percentage of the number of approaches, was also higher for the undershot weir, but was not affected by discharge because lamprey approached less frequently at high flows. This study provides fish passage criteria under realistic conditions for an infrequently studied anguilliform species of conservation concern and provides a methodological perspective by which to improve fishway suitability for a wider range of species subject to changing climate. Copyright © 2010 John Wiley & Sons, Ltd. This article was published online on March 3, 2010. An error was subsequently identified in the Article title. This notice is included in the online and print versions to indicate that both have been corrected [April 12, 2010].     

Effect of Thermal Stratification on Phytoplankton and Nutrient Dynamics in a Regulated River (Saar,Germany)

The weir pool Serrig is the deepest one along the impounded river Saar. Damming caused massive changes in the river's hydrodynamics. We analyzed the spatio‐temporal variability of thermal density stratification in the weir pool and its effect on phytoplankton and nutrient dynamics. In the analysis, continuous measurements from the years 2014 and 2015 were combined with three two‐day sampling campaigns in spring 2015. Thermal stratification occurred regularly in the downstream section of the weir pool during spring and summer and showed a diurnal rhythm. Temperature differences >1 K between the 1 and 2 m water layer were observed during 34 out of 217 days (16%) in 2014, with maximum temperature gradients up to 3.71 K. Whereas the influence of thermal stratification on phytoplankton biomass and distribution was low during the algal bloom in early spring, stratification events between May and July promoted temporary algal blooms in the surface layer with chlorophyll a concentrations up to 98 µg Chla l^?1 and a maximum difference between the 1 and 2 m water layer of 36 µg Chla l^?1. Some of the stratification events resulted in reduced concentrations of dissolved nutrients in the surface layer as a result of increased uptake by algae, with maximum gradients between the surface and the 8 m water layer of 0.070 mg ortho‐PO₄^3‐‐P l^?1, 0.136 mg NH₄⁺?N l^?1 and 0.24 mg NO₃¯?N l^?1. These vertical gradients should be considered in sampling protocols for the assessment of the water quality of temporarily stratified river sections. Copyright © 2016 John Wiley & Sons, Ltd.     

Anthropogenic‐induced shifts in salinity and nutrient status of two freshwater tropical lakes in India

An understanding of ongoing changes in salinity and nutrient status, as influenced by anthropogenic forcing factors, is important for integrated lake basin management (ILBM) and conservation of water resources in dry tropical regions. This study analysed a range of water quality attributes, including salinity, nitrate (NO₃^?), ammonia (NH₄ ⁺ ), phosphate (PO₄ ^{3 ?}) and dissolved organic carbon (DOC) in two freshwater lakes in Rajasthan, India for three consecutive years (2000–2002). Between‐lake comparisons indicated marked differences in most of the water quality variables. The pH in both study lakes remained above neutral. Water hardness, salinity and concentrations of total dissolved salts (TDS), chlorides, NO₃^?, NH₄⁺, PO₃^3? and DOC were high in Lake Udaisagar, which received inputs from agricultural drainage and urban–industrial releases. The DOC in Lake Baghdara, which drains a woodland catchment, was similar to that for Lake Udaisagar, indicating the role of allochtonous inputs in the build‐up of DOC. The results of this study indicated that increasing human interferences have increased the nutrient concentrations in Lake Udaisagar. This factor, coupled with extended periods of dryness, drives these two freshwater lakes towards a high salinity. This study provides evidence of a human‐induced salinity increase and has relevance for ILBM and for the conservation of freshwater resources in dry regions.     

Numerical study of the effect of a V-shaped weir on turbulence characteristics and velocity in V-weir fishways

Fishways are used to allow fish to migrate around water infrastructure, whether movements are in the upstream or downstream direction. Hydrodynamic conditions within various fishways, including turbulence levels, are important for successful fish passage. A numerical hydrodynamic study was conducted for V-weir fishways, which assist species migrating upstream. The variables investigated included, fishway slopes of 4%, 7%, and 10%, relative spacing between weirs of 1.3, 2.6, and 4 (D/L, ratio of distance between weirs to pool width), and weir angles of 22.5°, 40°, and 60°. Turbulence characteristics, including turbulent kinetic energy (TKE), Reynolds shear stress (RSS), turbulent intensity (TI), turbulent dissipation (TD), as well as maximum water velocity, were examined by CFD (computational fluid dynamics) simulation using a re-normalized group or RNG turbulence model. The CFD was calibrated with flow measurements made in a physical model of the V-weir fishway in laboratory control experiments. Based on inferences from fish passage literature, the results showed that, in the range of parameters studied, a weir angle of 22.5^°, a slope of 10% and relative spacing between weirs of 1.3 and 2.6 were assessed as offering the best potential performance for several species and sizes of fish, while the latter has lower cost as it requires fewer weirs. The V-weir fishway may be adaptable for smaller fish.     

Predicting velocity in bendway weir eddy fields

Rehabilitation of the Middle Rio Grande (MRG) in central New Mexico has become necessary because of changes in morphology resulting from the installation of dams, and because of habitat restoration considerations for the endangered Rio Grande silvery minnow (Hybognathus amarus). Bendway weirs are erosion control and channel‐stabilization structures placed transverse to the channel flow that have been increasingly used to prevent river migration while simultaneously enhancing aquatic habitat. Plans for rehabilitation along the MRG include the use of bendway weirs; however, past projects using these structures have relied on field experience and engineering judgment rather than specific design guidelines. A physical model of a reach of the MRG was constructed to develop empirical design equations for eddy velocities in bendway weir fields. Data from physical model simulations were used to develop two empirical expressions for predicting eddy velocities behind bendway weirs, along with two expressions for predicting velocities at the toe of installed weirs. These equations relate the velocity found after bendway weir installation to weir design characteristics and pre‐weir channel conditions. A designer can use the described approach to predict velocities in eddies and velocities at the toe of bendway weirs using only weir design variables and pre‐weir channel conditions, and thus avoid some of the uncertainty with weir design that previously existed. Copyright © 2009 John Wiley & Sons, Ltd.