CONCURRENT SORPTION OF HEAVY METAL POLLUTANTS OF SEDIMENT OF DIFFERENT GRAIN SIZES

Generally, sediment in natural rivers is non-uniform, and sorption capacities of different grain sizes vary greatly. In order to quantitatively describe sorption of heavy metal pollutant by sediment in natural rivers, the concurrent sorption by sediment of different grain sizes should be studied. By combining systematic laboratory experiments and theoretical analysis the concurrent equilibrium sorption model and the concurrent sorption dynamic model by sediment of different grain sizes have been set up. Both of them indicate that there is no competition or interference among different grain sizes, its sorption content of unit weight of sediment is the sum of the sorption contents of each grain sizes , and the content of each grain size in non-uniform sediment. Furthermore, formulas for determining characteristic parameters ( b and k) in the Langmuir sorption isotherm for non-uniform sediment are deduced as follows: These can be used as a tool for predicting the sorption content of non-uniform sediment     

不同粒径泥沙解吸重金属污染物静态试验研究

从吸附反应动力学方程和质量守恒方程出发，导得静态解吸试验中泥沙剩余吸附量和水相重金属浓度随时间变化的计算公式，并导得泥沙剩余平衡吸附量和水相平衡浓度随泥沙吸附－解吸的特性、泥沙初始重金属吸附量和泥沙浓度变化的计算公式。在此基础上，结合试验进一步研究了不同粒径泥沙解吸重金属污染物的能力。     

Two Dimensional Heavy Metal Transport Model for Natural Watercourses

This work presents the development and calibration of a two‐dimensional (depth‐averaged) river flow, sediment transport and heavy metal transport model in natural watercourses. Because heavy metals occur in dissolved and adsorbed phases, implementing the active‐layer concept for sediment transport computation enabled the development of a heavy metal transport model that accounts for pollutant moving in dissolved phase, adsorbed on suspended sediment, adsorbed on bed‐load, deposited in the active‐layer of the river bed or adsorbed on sediment in deeper strata. The proposed concept also enables the modelling of pollutant exchange processes using accessible sediment particle surface area for suspended and bed sediment separately. The presented heavy metal transport model is able to manage sediment mixtures found in natural watercourses using an arbitrary number of sediment size‐classes, distinguishing in this way smaller size‐classes that engage in interaction with the pollutant. Using field measurements for a reach of the Danube River, simulations were conducted for water flow, sediment transport and heavy metal transport. While some discrepancies between measured and computed values for pollutant concentrations were observed, the model reproduced the water and sediment contamination quite reasonably with acceptable mass conservation errors. The simulations also gave an insight in the general behaviour of the monitored heavy metals in the considered river reach. Therefore, it can be concluded that the developed model is suitable for simulating complex flow, sediment transport and heavy metal transport conditions in natural watercourses. Copyright © 2015 John Wiley & Sons, Ltd.     

海河流域主要河口水沙污染现状分析

2005年底,对海河流域海河口、独流减、子牙新河和北排河4个入海河口6处水域实地考察并取水沙样,进行重金属、砷、总氮和总磷含量分析。采用了《地表水环境质量标准》和水体综合污染指数法等对水域单个污染物污染、水体综合污染、水体富营养化现状及变化进行分析,采用《海洋沉积物质量》等对底泥污染进行分析,并与2001年实测数据进行比较。水质分析结果表明,海河流域4个河口的水污染严重,主要重金属污染物为汞(Hg)。子牙新河和北排河河口的氮磷污染严重,水体呈严重的富营养状态。与2001年水质相比,4个河口的重金属浓度几乎全部大幅度下降,海河口和独流减河口水质情况有很大改观,但子牙新河河口水污染加重,北排河河口水质状况则与2001年相近。从底质分析来看,4个河口的底质重金属污染尚不严重,但底泥均存在严重的氮磷污染。与2001年相比,底泥中污染物含量大多变化不大,略有下降。这些数据反映出近年来海河流域在水污染治理、工业废水排放控制等方面的成效,但远离城市局部水域的水污染和富营养化加剧的趋势值得关注。     

明渠挟沙水流的两相流模式

本文从两相流基本方程出发对明渠挟水流含沙量、流速垂线分布及近底层平均流动特性进行了理论研究，建立了一个新的泥沙扩散方程，并用大量资料进行了验证。结果表明：现有含沙量公式和流速垂线分布公式只是本文理论模式在低含沙量条件下的简化形式。当含沙量增加时，固相泥沙对流动结构的影响亦趋显著而不可忽略。精确模拟水沙流动，需要发展高级的两相湍流模式。     

EXPERIMENTS ON SELF-PURIFICATION OF HEAVY METALPOLLUTANTS IN NATURAL RIVERS

1.INTRODUCTIONThemovementofwater,sedimentandpollutantsandtheinteractionamongtheminnaturalriversareverycomplicated.Movementofwater,sedimentandPOllutantsarerandom.ButfromastatisticalviewPOint,theirmovementfollowssomerules.Twokindsoftypicalcases,thatis,atributarywithheavymetalpollutantsjoiningamainstream,andanunPOllutedtributarywithmuchsedimententeringamainstreamcontaminatedbyheavymetals,arestudiedinthispaper.Besides,flowscenesinnaturalriversaredifferentindifferentseasons.InthenabPeriod,g…     

颗粒态和溶解态磷浓度计算公式的推导与验证

河流水体中的含磷营养物质与较细颗粒的悬移质泥沙发生吸附作用,将对水质循环过程产生影响。基于拟合磷与泥沙颗粒吸附过程的Langmuir方程和修正Langmuir方程分别推导了计算颗粒态磷(PP)和溶解态磷(DP)的计算公式。并采用香溪河泥沙样品的磷吸附实验数据和野外观测数据验证了推导公式,计算结果与实测值符合良好。研究结果表明:当悬移质泥沙浓度较低时,可采用线性吸附方程近似计算颗粒态和溶解态磷浓度,但当悬移质泥沙浓度较高时,需要采用本研究推导的计算公式,特别是解吸和吸附现象并存时,需要使用基于修正的Langmuir模型推导的计算式。研究成果可用于水质或水生态模型建模。     

Pollutant removal efficiency of alternative filtration media in stormwater treatment.

Sorption experiments were used to assess the ability of various materials (sand, compost, packing wood, ash, zeolite, recycled glass and Enviro-media) to remove heavy metal contaminants typically found in stormwater. Compost was found to have the best physicochemical properties for sorption of metal ions (Cu, Zn and Pb) compared with sand, packing wood, ash, zeolite and Enviro-media. The compost sorption of these metal ions conformed to the linear form of the Langmuir adsorption equation with the Langmuir constants (q,) for Zn(ll) being 11.2 mg/g at pH 5. However, compost was also found to leach a high concentration of dissolved organic carbon (DOC, 4.31 mg/g), compared with the other tested materials. Various combinations of sand, compost and other materials were observed to have excellent heavy metal removal (75-96% of Zn and 90-93% of Cu), with minimal DOC leaching (0.0013-2.43 mg/g). The sorption efficiency of the different Enviro-media mixes showed that a combination of traditional (sand) and alternative materials can be used as an effective medium for the treatment of dissolved metal contaminants commonly found in stormwater. The application of using recycled organic materials and other waste materials (such as recycled glass) also provides added value to the products life cycle.     

潮汐作用对河网区重金属输移的影响

根据相关文献,推导了只考虑溶解态和悬浮态输移过程的一维河流重金属输移模型的表达式。根据2005年12月北江镉污染事故背景资料,对该模型的参数进行率定,以分析珠江流域西、北江河网区潮汐对重金属输移的影响。设定北江上游突发污染事故与下游大、中、小潮相遭遇的情景,将情景资料代入重金属输移模型进行模拟,根据模拟结果评价了事故对佛山市水厂供水带来的影响。分析结果发现,潮汐作用造成河流内水流往复震荡,对污染物的迁移过程影响较大;不同的潮汐作用导致西江、北江的水流补给形式发生变化,进而影响污染物的传播途径;污染事故与大潮相遭遇时,对供水造成的危害要远大于与中、小潮相遭遇时。     

Modeling of sediment and heavy metal transport in Taihu Lake, China

With the current rapid economic growth, heavy metal pollution has become one of the key issues in the Taihu Lake. Although heavy metal pollution levels and distributions of the Taihu Lake have previously been described, an effective model to describe the transport process of heavy metals between the water column and sediment bed for this lake is not available. It is known that heavy metals in the water column can be related to the resuspension of sediment in the lake bed. In this study, we set up a coupled model of relating hydrodynamics, sediment and heavy metals based on Environmental Fluid Dynamics Code (EFDC), and applied it to Taihu Lake, China. For calibration and validation of the model, we employed two series of field sampling data taken all over Taihu Lake during April and July of 2009. The results show that the hydrodynamics simulations of the coupled model agree with the observations reasonably well and the sediment and heavy metal model shows similar variation trends during the simulation. Our results indicate that the model can be used for simulating the sediment and heavy metal transport process in the Taihu Lake and here we provide an effective tool for water quality management at small time scales.     

Influence of compost characteristics on heavy metal sorption from synthetic stormwater.

This paper has the aim to assess the ability of garden derived compost to remove dissolved heavy metal contaminants typically found in stormwater. Compost was found to have excellent chemical and physical properties for the sorption of dissolved metal ions (Cu2+, Pb2+ and Zn2+). Batch sorption data were used to determine the sorption efficiency of Cu (93%), Zn (88%) and Pb (97%) by compost. The relative sorption affinity of these metals by compost is found to be in the order of Pb2+ > Cu2+ Zn2+. The effect of different particle size fractions of compost upon the sorption of Cu was also investigated. Sorption conformed to the linear form of the Freundlich isotherm and can be considered favourable because the sorption intensity values obtained in this study are between 0.1 and 1. Compost with a smaller particle size fraction has larger surface areas and greater sorption than the larger particle size fraction. Compost derived from garden waste is efficient for removal of heavy metals from wastewater or treating water for industries.     

An assessment of sediment reuse for sediment management of Gallito Ciego Reservoir,Peru

Gallito Ciego Reservoir, with a surface area of 14.2 km² and mean depth of 40.3 m, is located in the Jequetepeque River basin in north‐western Peru. It is rapidly filling with sediments, endangering its main purpose of supplying agricultural irrigation water. A sediment volume corresponding to 70% of the dead water volume has accumulated in the reservoir up to 2007, with reservoir bottom outlet becoming blocked. Below the dam, 35 000 ha of irrigated cropland, supporting 115 000 habitants, are endangered. This study was conducted to evaluate the possibilities of sediment management, especially the use of the sediment for agricultural purposes in the Jequetepeque River basin. Sediment samples were collected from littoral and profound sites in the reservoir. Suspended sediments also were collected. Physical parameters were investigated, and the nutrient and heavy metal concentrations were determined. By comparing grain‐size distribution and nutrient content, as well as pollutant concentration of the sediments, to those of terrestrial soils near the reservoir, an assessment of the potential for applying the sediments on the cropland was undertaken. Texture investigations of profound sediments revealed a strong grain‐size classification within the reservoir. Because the heavy metal concentrations in the sediments were below toxic thresholds, and the concentrations of nutrients also were low, using the sediments for agricultural purposes would not constitute risks, although they cannot replace fertilizer. As a soil amendment and building material, the sediments do have an economical value. Its dredging and use, however, must be seen as only one component of more holistic sediment management of the Jequetepeque Watershed.     

Cd, Cu and Zn mobility in contaminated sediments from an infiltration basin colonized by wild plants: the case of Phalaris arundinacea and Typha latifolia

Infiltration basins are shallow reservoirs in which stormwater is temporarily collected in order to reduce water volume in downstream networks. The settling of stormwater particles leads to a contaminated sediment layer. Wild plants can colonize these basins and can also play a role on the fate of heavy metals either directly by their uptake or indirectly by modification of physico-chemical characteristics of the sediment and therefore by modification of the mobility of heavy metals. The aim of this study, carried out in a vegetated infiltration basin, is to assess Cd, Cu and Zn mobility in two zones colonized by different species, Phalaris arundinacea and Typha latifolia. The study was carried out using three single chemical extractions: CaCl2 for the exchangeable phase, acetate buffer for the acido-soluble fraction and diethylenetriamine-pentaacetic acid (DTPA) for the fraction associated to the organic matter. Zn and Cd are mainly associated to carbonated and organic matter phases of the sediment. Moreover, acetate buffer-extractable Zn contents are strongly correlated to carbonates content in the sediment. DTPA-extractable Cu contents are strongly correlated with organic carbon sediment contents. We have also noted that extractable contents were significantly different between both zones whatever the metal.     

浅水湖泊含泥沙影响的水质模型研究

以水体中的污染物浓度(包括液相和固相)为对象,根据对流扩散过程和紊动力学原理,从理论上导出了三维水流、泥沙和污染物耦合作用的方程;方程的底边界条件采用泥沙动力学理论进行分析和处理,同时给出了含有泥沙通量形式的二维水质方程。以江苏省苏州市澄湖为例,对澄湖有底泥、无底泥时水质进行了计算。结果表明,含内源污染的水质方程的计算结果与实测值吻合更好,这也证实了含底泥影响的浅水湖泊二维水质模型的有效性和实用性。     

倾斜岸坡深度平均浓度分布及污染混合区解析计算

倾斜岸坡深度平均理论对其水质模型的构建、验证和参数率定具有十分重要的指导作用。在等强度连续点源岸边排放条件下,对倾斜岸坡深度平均浓度分布及污染混合区的几何特征参数进行了理论求解和曲线拟合。分别给出了深度平均浓度分布方程、深度平均污染混合区最大长度、最大宽度和相应纵向坐标、面积和面积系数的计算公式以及外边界标准曲线方程。分析表明,倾斜岸坡水体中污染物扩散宽度远大于扩散深度,对同一岸坡倾角的深度平均污染混合区形状具有相似性。提出了岸坡倾角分区的简化条件和相应污染混合区几何特征参数的计算公式,可为倾斜岸坡河流和水库深度平均浓度分布、污染混合区几何尺度和控制排污量的计算,提供科学依据。     

重金属污染物动态吸附试验及数学模拟

本文采用泥沙动力学中Ｒｏｕｓｅ等人用来研究泥沙浓度沿垂线分布的装置。对泥沙吸附重金属污染物进行了动态模拟。试验分有底泥和无底泥两种情况。研究中发现在Ｒｏｕｓｅ装置的水力、泥沙条件下泥沙吸附重金属污染物达到平衡状态需要６小时以上，由极坐标下的重金属迁移转化数学模型方程，在本文具体试验条件下进行数值求解，计算结果和试验结果合良好，说明数学模型是正确合理的试验是可靠的。计算时依据室内静态试验结果，对动态     

河流泥沙吸附磷的研究现状与展望

输送水流泥沙和营养物质是河流的主要功能之一。大坝等水利工程拦截泥沙的同时,改变了河流营养物质的迁移和转化。从国内外近20 a泥沙吸附磷的相关研究文献可以看出:泥沙对磷的吸附与泥沙颗粒的理化性质、水体初始磷浓度、含沙量以及环境因子等相关,即颗粒越细,表面吸附位越多,更有利于磷的吸附;水体初始磷浓度越高,吸附量越多;含沙量越大,总吸附量越大,单位质量泥沙吸附量越少;泥沙吸附磷的机理模型主要有热力学模型和动力学模型两类,Langmuir模型和Freundlich模型在等温吸附中应用较广;二级动力学模型对泥沙吸附磷的全过程拟合程度更高;在河流生态系统中,泥沙吸附的磷以颗粒态磷的形式作为生物可利用磷的储备,间接影响水生生物的生长。颗粒态磷与水生生物的生长关系、吸附量与含沙量等多因子的动力学模型在今后有待进一步研究。     

重金属污染物在土壤中的扩散规律及埋置策略研究

为了探索重金属污染物在土壤中的扩散规律,本文基于三维扩散方程,推导出了空间、时间和扩散系数等因素对埋置点周围重金属污染物浓度的影响规律。在此基础上,分析比较了集中埋置和分散埋置方法对重金属污染物浓度分布影响的异同。结果表明:在其他条件相同时,某一空间位置的浓度随扩散时间和扩散系数的增大先增大后逐渐减小,最后曲线趋于平缓;相同扩散时间情况下,浓度随着扩散半径的增大而减小,当扩散半径大于一定值时,浓度趋于零。对同量的污染物的三种不同的埋置方案进行分析发现:埋置点越少,其附近的浓度越高,而埋置点越多,远处的浓度越低。