A 12‐month sediment and nutrient budget in a floodplain reach of the River Adour,southwest France

The sediment and nutrient budget in the floodplain reach of the River Adour in southwest France has been examined over a 1‐year period (1991–1992). Outputs of total suspended matter, dissolved inorganic nitrogen (i.e. nitrate+ammonium ions) and dissolved inorganic phosphorus (DIP) and particulate phosphorus (PP) have been compared with inputs. Alternating phases of mobilization and retention are observed for all the elements considered. Low water periods in summer allowed retention of both soluble material (24–26% for inorganic nitrogen) and suspended matter (9–19%). However, mobilization of PP associated with suspended matter transport during these periods. Elevated discharges associated with increased rainfall during the autumn period induced significant mobilization for all elements. In contrast, the winter flood event gave rise to a retention of particulate material (i.e. suspended matter and PP, 11% and 26%, respectively), but a loss of soluble materials (5% for inorganic nitrogen and 186% for DIP). The spring flood event produced retention for particulate materials (26%) while inducing losses of inorganic nitrogen (9%) and gains of DIP (7.4%). These results are related to riparian vegetation and the dynamics of nutrient cycling within the floodplain. Copyright © 2000 John Wiley & Sons, Ltd.     

Calibration of turbidity meter and acoustic doppler velocimetry (Triton‐ADV) for sediment types present in drained peatland headwaters: Focus on particulate organic peat

Suspended sediments have a clear impact on fluvial water quality and aquatic habitats. As the concentrations are highly variable, continuous measurement offers a good way to provide accurate and precise values of sediment concentration and yield. However, there is a lack of information regarding the effect of organic peat particles, which typically appear in boreal fluvial systems. In the present study, the effect of different types of suspended sediments on calibration of a turbidity meter and an acoustic Doppler velocimetry (Triton‐ADV) was studied in laboratory conditions. The measurements were performed using particulate organic peat, clay and silt with several concentrations ranging from clear water to 3500 mg L^?1. The present study primarily provides organic peat sediment calibration data for used sensors. Regression equations were developed for the different sediment. The results indicate that particle size, shape, concentration and sediment type have an effect on calibration. When the turbidity and the ADV calibration were performed for different particle size groups, sediment types and concentrations, the calibration and suspended solids calculation error was reduced. For the turbidity sensor used, the reliable upper continuous measurement limit for clay, peat and silt sediments was found to be at 1000, 2500 and 3500 mg L^?1, respectively. The ADV‐sensor was noticed to be reliable only with fine particles. The results enable easy and first step calibration and error assessment for automatic turbidity and acoustic monitoring of the suspended sediment quality typically present in headwater fluvial systems. This study can be used to evaluate the effect of different sediments on turbidity and ADV‐measuring error and reliability during changing particles size distributions, characteristics and concentrations. The laboratory‐based approach used in this study indicates that the shape of organic peat particles has an influence on sensor calibration, especially when suspended sediment concentrations are high. Copyright © 2009 John Wiley & Sons, Ltd.     

An algorithm to retrieve chlorophyll,dissolved organic carbon,and suspended minerals from Great Lakes satellite data

An algorithm that utilizes individual lake hydro-optical (HO) models has been developed for the Great Lakes that uses SeaWiFS, MODIS, or MERIS satellite data to estimate concentrations of chlorophyll, dissolved organic carbon, and suspended minerals. The Color Producing Agent Algorithm (CPA-A) uses a specific HO model for each lake. The HO models provide absorption functions for the Color Producing Agents (CPAs) (chlorophyll (chl), colored dissolved organic matter (as dissolved organic carbon, doc), and suspended minerals (sm)) as well as backscatter for the chlorophyll, and suspended mineral parameters. These models were generated using simultaneous optical data collected with in situ measurements of CPAs collected during research cruises in the Great Lakes using regression analysis as well as using specific absorption and backscatter coefficients at specific chl, doc, and sm concentrations. A single average HO model for the Great Lakes was found to generate insufficiently accurate concentrations for Lakes Michigan, Erie, Superior and Huron. These new individual lake retrievals were evaluated with respect to EPA in situ field observations, as well as compared to the widely used OC3 MODIS retrieval. The new algorithm retrievals provided slightly more accurate chl values for Lakes Michigan, Superior, Huron, and Ontario than those obtained using the OC3 approach as well as providing additional concentration information on doc and sm. The CPA-A chl retrieval for Lake Erie is quite robust, producing reliable chl values in the reported EPA concentration ranges. Atmospheric correction approaches were also evaluated in this study.     

水动力作用下太湖底泥的再悬浮通量

对太湖梅梁湾水体开展了两次野外实验,利用沉积物捕获器收集沉积物,研究了太湖悬浮物的沉降特征,计算了悬浮物的沉降通量和再悬浮通量,并建立了其与风速的关系。结果表明：太湖无机颗粒沉降是悬浮物沉降的主要形式。太湖平均风速在8m/s以内时,总悬浮物、有机物颗粒和无机物颗粒的沉降通量和再悬浮通量均呈现随风速增大而增大的特性,风速大小直接影响悬浮物在垂向的分布及垂向的沉降通量分布,并且相关性较好。该结论说明Gansith公式法适合于计算太湖再悬浮通量。     

非黏性沙级配对浊度法测量含沙量的影响

利用浊度仪测量水流含沙量时,泥沙颗粒级配和矿物成分是影响浊度仪标定结果的主要泥沙因素。采用黄河原型非黏性沙配制不同粒径、不同含沙量浑水水体,开展固定粒径、粗细沙、混合沙等多组次试验研究,对黄河天然沙粒径及级配对浊度仪输出浊度的影响进行定量分析和机制探讨。结果表明:固定含沙量条件下,非黏性泥沙粒径对水体浊度的影响特征符合Mie散射定律;含沙量变化对浊度仪输出浊度的影响数量级为10～10²,泥沙颗粒粒径变化对浊度仪输出浊度的影响数量级为10^-1～1;相同含沙量条件下,悬沙比表面积与浊度仪输出浊度符合线性分布。建立了考虑非黏性沙级配影响的含沙量与浊度关系模型,能够较准确地反映非黏性沙粒径及泥沙浓度对水体浊度的影响,可为浊度与含沙量关系的准确率定及测量结果的校准提供可靠依据。     

长江口枯水期最大浑浊带形成机制

用ADCP获得了长江口最大浑浊带内的高频率和高分辨率流速和悬沙浓度数据,对不同定点站位和走航断面的悬沙浓度、流速和盐度数据进行了分析,同时对不同站位的再悬浮通量以及悬沙输运机制也进行了计算,进而讨论了长江口枯水期最大浑浊带的形成机制。结果表明,枯水期的长江口处于淤积状态,再悬浮通量较小,其数量级介于10-4-10-7kg·m-2s-1之间;平均流输运在整个悬沙输送中占主导地位,斯托克斯漂移效应、垂向环流和潮振荡的垂向切变作用对悬沙输运也有着重要作用;通过分析走航断面的数据确定了枯水期中潮期内最大浑浊带的显著分布区域,“潮泵”作用和河口重力环流作用均在该地区最大浑浊带形成中都发挥着重要作用。     

Early Diagenesis of Mercury in the Laurentian Great Lakes

The early diagenesis of mercury in deep lake environments was investigated by examining the distribution of mercury among waters and sediments from several depositional basins in the Laurentian Great Lakes. Partitioning of mercury among different sediment phases was examined by sequential chemical extraction (using procedures specifically designed for mercury). Mercury in porewaters and sediment extracts was analyzed by flow-injection/hydride-generation atomic absorption spectroscopy.Results indicate that mercury is affected by early diagenesis at all of the sites studied. Much of the mercury is enriched in the surface layer of sediments, where it is primarily associated with organic matter and iron oxides. The redox cycling of iron and manganese influences the behavior of mercury; concentration profiles suggest that as oxides begin to dissolve in reduced sediments, nearly all of the adsorbed mercury is released. Organic matter decay also appears to release significant amounts of mercury. Porewater profiles suggest that most of the dissolved mercury released from decaying organic matter or from dissolving iron oxides may be taken up by freshly deposited organic matter and iron oxides in the near-surface layers. Much of the mercury that reaches the sediment column is thus recycled near the sediment-water interface, increasing both the residence time and the concentrations of mercury in surface sediments of these deep lake basins.     

Suspended solids transport in the regulated River Blithe,Staffordshire, U.K.

Suspended solids concentrations and turbidity were monitored on the regulated River Blithe at two sites downstream of the reservoir for a period of 18 months. Changes in the suspended solids loads transported and the nature of the material in suspension are related to dam overspill and tributary flood events. A hysteretic relationship between suspended solids concentrations and discharge is characteristic of both sites, sediment supply being limited within the regulated river. Downstream of the dam, rapid bank erosion occurred on meander bends but the suspended solids loads transported by the regulated river relate more to the resuspension and transport of tributary injected sediments and scouring of a dense periphyton. Close to the dam, fine biogenic matter dominated the seston, which scanning electron microscopy revealed to contain algal fragments and inorganic diatom frustules, but downstream, tributary-derived minerogenic particles were dominant.     

采用浊度监测实现悬移质泥沙监测自动化的探讨

介绍了南宁水文站通过对水体浊度参数测试,得到浊度与含沙量关系,研究新悬移质泥沙监测模式,实现悬移质泥沙监测自动化,推进水文信息化进程适应经济发展,为防灾减灾决策,及时、准确提供科学依据。     

OBS-3A在悬移质含沙量测验中的应用研究

传统悬移质含沙量主要采用烘干法测量,其操作繁琐、费时费力且无法实时连续施测,近年来越来越多地被光学仪器法（OBS-3A）替代。介绍了OBS-3A的测量原理、仪器结构,通过OBS-3A与传统方法测验悬沙浓度（SSC）比测试验,分析了传统方法测沙与OBS-3A测沙结果之间的关系。结果表明,只要样本覆盖一定范围且样本数达到一定数量,浊度和SSC之间能得到较好的相关关系。推荐采用0.6 H的水样率定工作曲线。OBS-3A的测量结果受泥沙粒径的影响较大,颗粒粒径越小,OBS-3A就越敏感,所测得结果也更为准确。     

Longitudinal spatial variation in ecological conditions in an in‐channel floodplain river system during flow pulses

A field survey was conducted during flow pulses to investigate the longitudinal spatial patterns in water quality, dissolved inorganic and organic matter, phytoplankton, planktonic bacteria, zooplankton, gross primary productivity (GPP) of phytoplankton and planktonic respiration (PR) in channels of the large floodplain system (～124 km in length) of the Macquarie Marshes, south‐eastern Australia. Four river reaches (areas) with distinct hydrogeomorphological characteristics within the distributary zone of the lower Macquarie River were chosen for analysis of abiotic and biotic variables in their in‐stream environments. The results showed marked longitudinal spatial variation in the values within and among the measured environmental variables including such functional aspects as primary productivity and PR. The variables that tended to have increasing values in a downstream direction were conductivity, total nitrogen (TN), total phosphorus (TP), dissolved reactive phosphorus (DRP), dissolved silica, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP), ratio of DOC/DON and counts of planktonic bacteria. Conversely, the values that tended to decrease downstream were the ratios of TN/TP, DIN/DRP, DOC/DOP, DON/DOP and GPP/PR. Variables that had a localized peak(s) were dissolved oxygen, turbidity, dissolved inorganic nitrogen, GPP, PR and counts of cyanobacteria, diatoms, green algae, cryptomonads, protozoans, rotifers, copepods and cladocerans. Overall, two distinct ecological zones were identified within the broader distributary functional process zone (FPZ): these being the upstream zone with relatively high levels of DO, turbidity, diatoms and GPP/PR ratio, and the downstream zone with relatively high levels of nutrients, dissolved organic matter, cyanobacteria, planktonic bacteria, protozoans and cladocerans. The results of this study describe the spatial connectivity of ecological processes related to hydrogeomorphological factors within a FPZ of a riverine ecosystem, and support the predictions of the riverine ecosystem synthesis framework that ecological patterns and processes can be discontinuous on a longitudinal spatial scale. Copyright © 2010 John Wiley & Sons, Ltd.     

Seasonal dynamics of light absorption by suspended particulate matter and CDOM in highly turbid inland rivers on the Loess Plateau,China

The spectral characteristics of optically active constituents in water are key parameters in bio‐optical modelling. Light absorption by phytoplankton [a_ph(λ)], nonalgal particles (NAPs) [a_NAP(λ)], and chromophoric dissolved organic matter (CDOM) [a_CDOM(λ)] was investigated at 28 sites in the Wuding River (WDR) during the abundant river flow period (AP) in July 2017 and the normal river flow period (NP) in May 2018. The water quality parameters in the WDR substantially differed between the AP and NP. The dissolved organic carbon and turbidity were high in the NP, and chlorophyll a (Chl‐a), total suspended matter (TSM), dissolved oxygen concentrations and electrical conductivity were low in the AP. a_p(675) and Chl‐a were more strongly correlated in the NP (r=0.96) than in the AP (r=0.41). a_NAP(440) and a_NAP(675) were strongly correlated with TSM (r=0.98 and 0.97) in the AP but weakly correlated in the NP. Moreover, a_ph(λ) was positively correlated with Chl‐a in both the AP and NP. In addition, a_CDOM(440) was significantly correlated with Chl‐a (r=0.62, p<.001) in the NP but not the AP. TSM was weakly correlated with a_CDOM(440) in both the AP and NP. The S_275‐295 values in the NP (0.0147‐0.020 nm^‐1) were lower than those in the AP, demonstrating that the molecular weights were higher in the AP than in the NP. The photosynthetically active radiation absorption of most samples was dominated by the NAPs and CDOM, implying a crucial role in light attenuation in highly turbid inland rivers on the Loess Plateau.     

Discriminating four temperate lakes using phytoplankton absorption spectra

Photosynthetic algal particles are integral to the ecology and optical quality of lake water. Their absorption properties (photopigments, often >20 per species) are modified in response to drivers that affect the intensity and spectral distribution of incident solar energy, including the plankton itself, water, and chromophoric dissolved and suspended particulate matter. The present study was based on the hypothesis that this complex interaction imparts a distinguishing optical signature in lakes. A multivariate discriminant model was applied to in situ phytoplankton spectra from four temperate lakes of different trophy to test this hypothesis. The analysis identified a small set of wavelengths with significant discriminatory power that permitted near‐perfect lake classification solely on the basis of the aggregate spectral features in the absorption coefficient of phytoplankton. Furthermore, weighting the sample spectra by the corresponding standard deviation increased model robustness considerably, as shown in both unsupervised and supervised classification. Also presented are additional multivariate techniques that allow for the visualization of the data structure to help explain contributing factors. The results support the possibility of utilizing the optical properties of the phytoplankton to monitor ecological change in lakes.     

Correlations between silt density index,turbidity and oxidation-reduction potential parameters in seawater reverse osmosis desalination

The reverse osmosis method is one of the most widely used methods of seawater desalination at present.Hydrophilic and desalting membranes in reverse osmosis systems are highly susceptible to the input pollutants.Various contaminants,including suspended organic and inorganic matter,result in membrane fouling and membrane degradation.Fundamental parameters such as the turbidity,the amount of chlorine injection,and silt density index(SDI)are the most predominant parameters of fouling control in the membranes.In this study,the operation system included a water intake unit,a pretreatment system,and an RO system.The pretreatment system encompassed a clarifier,a gravity sand filter,pressurized sand filters,and a cartridge filter.The correlation between the amount of chlorine injection in terms of the oxidation-reduction potential(ORP)and the SDI value of the input water was investigated at a specified site next to the Persian Gulf.The results showed that,at certain intervals of inlet turbidity,injection of a certain amount of chlorine into the raw water has a distinct effect on the decrease of SDI.     

河流底泥耗氧量测量方法及耗氧量影响因素

底泥耗氧量占据河流溶解氧消耗的一大部分，几十年来国内外学者对不同类型河流的底泥耗氧量展开大量试验研究.对国内外非悬浮底泥试验和悬浮底泥试验的主要试验方法进行总结，并阐述了不同方法各自的优缺点及相应的适用范围.底泥中生物系统的作用、水温、底泥的有机质含量影响河流底泥中生物和化学氧化过程，从而影响底泥耗氧量.另外，底泥的组成情况、上覆水体的流动速度和水深，以及上覆水体的水质等因素与底泥耗氧量也有一定相关性.最后，在总结前人研究工作的基础上，提出了对代表性的水域底泥耗氧量的试验方法、底泥耗氧量主导影响因素以及河流中的底泥耗氧量作进一步研究.     

Transport of Suspended Matter in the Hypolimnion of Lake Lugano: a Comparison of Field Observations and Model Predictions

An unusual feature was observed in the anoxic hypolimnion of the north basin of Lake Lugano during a campaign of regular measurements of turbidity profiles by forward light scattering nephelometry: turbidity increased with depth and decreased with time over the period of investigation (November 1992 to January 1994). Correlation of the chemical composition of the major elements present in lake particles with turbidity allowed the association of the measured turbidity with inorganic, mainly alumino-silicate particles. Particles in the turbidity structure probably originated from a gravity current triggered by a landslide that occurred in the port of Lugano in March 1992. Seasonal events such as fluxes of authochthonous calcite or diatom frustules had little influence on the observed hypolimnion turbidity. Allochthonous particles from flood events did not markedly affect the sedimentation structure either. Calculations showed that the evolution of the suspended particles cannot be explained by taking only particle sedimentation into account. To test whether particle aggregation could have been the dominating process leading to rapid settling, a simple coagulation-sedimentation model for hydrophobic particles was used to simulate the sedimentation event. The model provided clear evidence that particles involved in the sedimentation process were fine sized (1 to 2 μm mean diameter) and that coagulation played a major role in the sedimentation of mineral particles. Difficulties encountered in fitting the second phase of particle removal (after June 1993) have been tentatively explained by the increase in particle stability caused by the mineralization of the abundant organic matter generated during the lake productivity period.     

Tracking the Propagation of Solar Ultraviolet Radiation: Dispersal of Ultraviolet Photons in Inland Waters

Solar extraterrestrial ultraviolet radiation is tracked from its impingement upon the Earth's atmosphere to its dispersal in natural inland waters. This is accomplished through the use of a solar spectral irradiance model, a water column optical model, directly measured (AES monitoring network) values of ground-level ultraviolet radiation and stratospheric ozone, optical properties of aquatic matter indigenous to Lake Ontario and Waskesiu Lake, Setlow DNA damage action spectrum, and phyto-plankton photosynthesis inhibition spectrum. The conclusions from such a combined theoretical/experimental study include a) the presence of dissolved organic matter (DOM) provides an effective UV-B shield for aquatic organisms despite the absorption spectra of dissolved organic carbon (DOC) indigenous to North American waters displaying substantial variations, b) UV absorption for a given DOC concentration varies from water body to water body, c) when UV irradiance is weighted according to the Set-low DNA damage action spectrum, the physical depth of the 1% of surface irradiance level decreases, i.e., attenuation ofSetlow-weighted irradiance is greater than attenuation of actual UV-B irradiance, d) a single mathematical relationship can relate the change in Setlow-weighted daily irradiation at the surface of the Earth to ozone layer depletion while another single relationship can relate the change in depth-averaged Setlow-weighted daily irradiation to ozone layer depletion, these single relationships being applicable throughout the year for all mid-to-high latitudes, e) the increase in Setlow-weighted irradiation due to ozone layer depletion decreases with depth in the water column, f) phytoplankton photosynthesis inhibition by UV-A significantly exceeds inhibition by UV-B, g) inhibition of phytoplankton photosynthesis in many inland waters will not be significantly impacted by ozone layer thinning, h) modeling ground-level and subsurface values of ultraviolet radiation provides a suitable surrogate for the direct measurement of the minuscule and spectrally steep UV radiation, i) the highly diffusive character of the ground-level UV-B irradiance results in the reflectance of UV-B from the water being essentially constant (5% to 8%) throughout the year and the transmission of UV-B across the air-water interface being virtually unaffected by surface waves, j) in the absence of suspended sediments, the contribution of chlorophyll-bearing biota to the spectral UV photon budget is in anti-phase with the contribution of DOM, while the contributions of water and surface reflectance are comparable, small, and relatively constant, k)for the water bodies considered, dissolved organic matter accounts for the largest component of the UV photon budget.     

利用溶气气浮工艺强化处理低浊高色富含有机物地表水

低浊高色富含有机物地表水难于混凝,试验采用“混凝-溶气气浮”(“混凝-DAF”)工艺处理此类水,并与常规“混凝-沉淀”工艺进行了比较。结果表明,“混凝-DAF”工艺在较低投药量时能取得更好的处理效果;对于“混凝-DAF”工艺,增大混凝剂投量后出水浊度基本不变,但出水色度及CODMn可进一步降低;“混凝-DAF”工艺去除水中有机物的能力优于“混凝-沉淀”工艺。最后,对“混凝-DAF”工艺去除水中有机污染物的机理进行了探讨。     

城市小区雨水径流投加细砂强化混凝沉淀优化条件研究

城市小区雨水径流水质的污染主要为有机污染和悬浮固体污染,且污染物的可生化性差,采用投加混凝剂同时加细砂的强化混凝沉淀实验,确定了小区径流混凝沉淀处理最适宜的混凝剂种类、最佳的混凝反应运行条件及最优的药剂和细砂投加量.实验表明:在混凝沉淀过程中投加细砂,不仅能提高混凝沉淀效果,而且能提高沉淀速度.小区径流强化混凝沉淀的浊度去除率达99.7％,COD去除率达92.6％,处理水的浊度1.66 NTU,COD 35mg/L两主要指标均优于杂用水水质标准.因此,投加细料的混凝沉淀是小区雨水径流处理利用及污染控制最简便易行且有效的处理方法.     

Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

Characteristic dynamic features of sediment‐related processes in rivers include dramatic effects of stormwater events on particle transport, rapid and far‐reaching effects of sulphide oxidation during resuspension, and biological accumulation and potential release of toxic chemicals. Pollutant mobility is the net result of the stabilizing and mobilizing effects in both hydraulic and chemical fields. In practice, emphasis has to be given to fine‐grained sediments and suspended matter as these materials exhibit large surface areas and high sorption capacities. Organic materials are highly reactive. Degradation of organic matter will induce oxygen depletion and might enhance formation of flocs and biofilms. Study of variations of sediment and water chemistry should predominantly include changes of pH and redox conditions, competition of dissolved ions and processes such as complexation by organic substances. Major questions relate to the potential reduction of sorption sites on minerals and degradation of organic carrier materials. All these processes will influence solution/solid equilibrium conditions and have to be studied prior to modelling the overall effects of pollutants on the water body and aquatic ecosystems. With respect to handling and remediation of contaminated river sediments, either in‐place or excavated, a chemical and biological characterization of the material, of the (disposal) site and of the long‐term processes is crucial. Passive techniques (e.g. in situ stabilization, subaqueous capping) provide economic advantages as there are no operation costs following their installation. However, the success of these ecological and geochemical engineering approaches is mainly based on an in‐depth knowledge of the underlying processes.