Urbanization impact on metals mobility in riverine suspended sediment: Role of metal oxides

Spatial and temporal fractionation of trace metals and major elements in suspended particulate matter in the Seine River was investigated to study the impact of the increasing urbanization in the Greater Paris Region. Suspended sediments in the Seine River were collected between December 2008 to August 2009 upstream and downstream of Paris. They were subjected to total digestion and sequential extraction procedure certified by the Bureau Communautaire de Référence and trace metals along with major elements were analyzed with inductively coupled plasma mass spectroscopy. Metal enrichment factors increased up to eight folds after the Seine River downstream of the Greater Paris Region showing a significant contribution of urbanization. Enrichment of copper, lead and zinc downstream of Paris are followed by the increase of their reducible fraction of at least 10% implicating an increase in metals associated with iron oxides. The exchangeable fraction, which includes the carbonate-associated metals, is only significant for cadmium, nickel and zinc (more than 2 %) while the oxidisable fraction accounts for less than 20 % for the anthropogenic metals downstream except for copper. The metals can be divided to (a) “reducible” group including cadmium, lead, and zinc, associated with more than 60 % of the total Bureau Communautaire de Référence extractable metals to the reducible fraction containing mostly iron oxide phases for the downstream sites. (b) A “distributed” group including chromium, copper, and nickel that are associated to at least 3 different phase-groups: (1) oxides, (2) organic matter and sulphides and (3) mineral phases.     

Assessment of heavy metals in sediment and in suspended particles affected by multiple anthropogenic contributions in harbours

La Goulette, Rades and Sidi Bou Said harbours are considered as the most important commercial and tourist ports in the Gulf of Tunis. They are located on the northeast coast of Tunis and receive industrial and municipal wastewaters from Tunis city. The contamination level of copper, lead, zinc, cadmium, manganese, iron, total nitrogen and total organic carbon in the surface sediments was assessed on the basis of the enrichment index factors and corresponding to sediment quality guidelines. The results revealed moderate to highly elevated concentrations near to the sites of intense industrial, shipping and/or commercial activities suggesting a direct influence of these sources. In winter and summer, concentrations varied for cadmium, 0.28–1.40 mg kg^?1; lead, 18–217 mg kg^?1; zinc, 87–459 mg kg^?1; copper, 8–121 mg kg^?1; manganese, 208–254 mg kg^?1; and for iron, 24–40 g kg^?1. Furthermore, in summer the concentration of the total organic carbon and the total nitrogen contents range between 4.3–6.5 % and 0.06–0.49 % with an average value of 5.9 and 0.15 %, respectively. Whereas, in winter, total organic carbon and the total nitrogen concentrations varied between 2.3–9.6 % and 0.03–0.22 % with an average value of 6.1 and 0.14 %, respectively. The levels of lead, copper, zinc and iron in suspended particulate matter content range between 3.1–27.5 mg kg^?1; 0.4–11.7 mg kg^?1; 1–1.5 mg kg^?1; 1.2–1.7 g kg^?1, respectively. This study revealed that heavy metals pollution is mainly localized in the commercial (Rades) and fishing (La Goulette) harbours and not in the yachting (Sidi Bou Said) harbour.     

Top-down versus bottom-up limitation in benthic infaunal communities: Direct and indirect effects

Top-down effects of predators and bottom-up effects related to resource availability can be important in determining community structure and function through both direct and indirect processes. Their relative influence may vary among habitats. We examined the effects of nutrient enhancement and predation in southeastern North Carolina to determine relative effects on benthic macrofaunal communities. Short-term nutrient additions and predator exclusions were conducted in two estuaries to examine main and interactive effects on benthic microalgae and infauna. This experimental approach was complemented by comparisons of microalgal biomass, infaunal abundance and composition, predator abundance and predator exclusion among four estuarine systems that varied in background nutrient levels. In the short-term experiments, nutrient enhancement induced increased microalgal biomass but had limited effects on abundances or sizes of infauna. Predator exclusion increased the density of sedentary and near-surface dwelling fauna, but we did not observe interactions between predation and responses to nutrient additions as might be predicted from a simple cascade model. General patterns of abundance were explained to a larger extent by interannual and amongestuary pattems. These results indicate a lack of simple trophic cascade responses for this community over a short time scale and little evidence for local interactive effects. The lack of interactive effects may reflect the opportunistic nature of the dominant infaunal species and potentially different time and spatial scales for the effects of predation and resource controls.     

Dispersion of salt and suspended sediment in a partly mixed estuary

Observations are presented of the transverse and vertical structure of residual water, salt and sediment transport in the upper reaches of a partly mixed estuary. Measurements were made over spring and neap tidal cycles at three sections. The residual transport for each variable exhibited a characteristic transverse structure. This structure is interpreted in terms of fundamental physical processes. The results are used to estimate the relative importance of transverse shear, vertical shear and tidal pumping to the axial dispersion of salt and sediment.     

Mineralogy of suspended sediment in three karst springs

Springs in karstic carbonate rocks frequently carry a sediment load as well as a dissolved load. Analysis of morphology and mineralogy of suspended sediment from three contrasting karst springs reveals a suite of clastic particles that reflect both source areas and processes that take place within the aquifer. Nolte Spring in Lancaster County, Pennsylvania, USA, discharges sediment of apparently precipitated calcite, indicating that at some point in the aquifer or vadose zone, water exceeds saturation with respect to calcite. Sediment morphologies and chemical conditions in the aquifer point to two different scenarios for this precipitation. The other two springs, Arch Spring in Blair County, Pennsylvania and Bushkill Spring in Northampton County, Pennsylvania, show no evidence of calcite precipitation. Arch Spring discharges mainly layer silicates, while Bushkill Spring discharges mainly silica.

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Resumen Los manantiales en rocas carbonatadas karstficadas tienen frecuentemente una carga de sedimentos y de sólidos disueltos. Los análisis de la morfología y mineralogía de los sedimentos suspendidos de tres manantiales kársticos contrastados revela un conjunto de partículas clásticas que reflejan ambas áreas fuente y los procesos que tienen lugar dentro del acuífero. Nolte Spring en el Condado de Lancaster, Pennsylvania, USA, descarga sedimento de calcita aparentemente precipitada indicando que en cierto punto del acuífero o en la zona vadosa, el agua supera la saturación con respecto a la calcita. La morfología de los sedimentos y las condiciones químicas en el acuífero apuntan a dos escenarios diferentes para esta precipitación. Los otras dos manantiales, Arch Spring en el Condado de Blair, Pennsylvania y Bushkill Spring en el Condado de Norhtampton, Pennsylvania, no muestran evidencia de precitación de calcita. Arch Spring descarga principalmente filosilicatos mientras que Bushkill Spring descarga fundamentalmente Sílice.

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Résumé Les sources situées en contexte carbonaté karstique charrient fréquemment, outre les matières dissoutes, une charge solide. La morphologie et la minéralogie des sédiments en suspension issus de trois sources karstiques de caractéristiques distinctes ont été analysées : une série de particules clastiques, reflétant à la fois les secteurs des sources et les processus internes de l’aquifère, en ressort. Les sédiments issus de Nolte Spring (Comté de Lancaster, Pennsylvanie, Etats-Unis) sont constitués de calcite apparemment précipitée: ceci indique que l’eau atteint la sursaturation vis-à-vis de la calcite à un certain point de l’aquifère ou de la zone non-saturée. La morphologie des sédiments et les conditions chimiques au sein de l’aquifère mènent à deux scénarii différents pour expliquer cette précipitation. Les deux autres sources, Arch Spring (Comté de Blair, Pennsylvanie) et Bushkill Spring (Comté de Northampton, Pennsylvanie), ne présentent aucun indice de précipitation de calcite. Arch Spring exporte essentiellement des phyllosilicates, alors que la silice est majoritaire à Bushkill Spring.

     

Sunflower (Helianthus annuus): phytoextraction capacity for heavy metals on a mining-influenced area in Thuringia,Germany

On an uranium-mining-influenced area, sunflowers (Helianthus annuus) were grown on a small-scaled plot. Subsamples of sunflowers were harvested 34, 66, 96, 108, 140, and 170 days after sowing. Contents of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Th, U, Zn, and rare earth elements (REEs, La–Lu) were determined in the sunflower shoots, as well as total and bioavailable contents of these 25 elements in the soil taken on the day of sowing and after the last harvest. Shoot contents alone were not sufficient to evaluate the extraction capacity of the sunflowers. Instead total extracted masses (product of biomass and element content) had to be calculated. The total extracted mass increased for most of the elements until 140 days after sowing. Bioconcentration factors (BCFs) as ratio between element content in shoot and soil, were calculated for this time to evaluate the phytoextraction efficiency. BCFs ≥1 (relating total soil contents) and thus a very effective extraction was calculated for Cd. The BCFs, based on mobile soil contents, were ≥1 for all elements, except for U and REEs (La–Lu). Consequently, the sunflower is able to extract many elements effectively from the direct harmful soil fraction. To reduce the contents of Cd and Ni down to levels, where the mining-influenced area could be classified as arable land would require 55 and 207 sunflower growth cycles. Although this is quite a long time, the uranium-mining-influenced area could be successively remediated, while growing biofuel crops, without interfering with food production.     

Modeling diagnosis of suspended sediment transport in tidal estuarine system

A three-dimensional, time-dependent hydrodynamic and suspended sediment transport model was performed and applied to the Danshuei River estuarine system and adjacent coastal sea in northern Taiwan. The model was validated with observed time-series salinity in 2001, and with salinity and suspended sediment distributions in 2002. The predicted results quantitatively agreed with the measured data. A local turbidity maximum was found in the bottom water of the Kuan-Du station. The validated model then was conducted with no salinity gradient, no sediment supply from the sediment bed, wind stress, and different freshwater discharges from upstream boundaries to comprehend the influences on suspended sediment dynamics in the Danshuei River estuarine system. The results reveal that concentrations of the turbidity maximum simulated without salinity gradient are higher than those of the turbidity maximum simulated with salinity gradient at the Kuan-Du station. Without bottom resuspension process, the estuarine turbidity maximum zone at the Kuan-Du station vanishes. This suggests that bottom sediment resuspension is a very important sediment source to the formation of estuarine turbidity maximum. The wind stress with northeast and southwest directions may contribute to decrease the suspended sediment concentration. When the freshwater discharges increase at the upstream boundaries, the limits of salt intrusion pushes downriver toward river mouth. Suspended sediment concentrations increase at the upriver reaches in the Danshuei River to Tahan Stream, while decrease at Kuan-Du station.     

Shrimping as a source of suspended sediment in Corpus Christi Bay (Texas)

Our field study showed that the total amount of sediment disturbed in Corpus Christi Bay each year by shrimp trawling is 10-100 times greater than that dredged in an average year for maintenance of shipping channels. The maximum concentrations of suspended sediment measured in the trails of the shrimp boats were comparable of the dredge operating in the same area. of 3% is obtained.     

渭河源区典型小流域水沙演变规律分析

根据渭河源区清源河典型小流域实测水文资料,分析了流域水文要素的年内和年际变化规律,流域降水、径流和泥沙主要集中在汛期,5-9月降水量占全年的78.5%,5-10月径流占全年的78.7%,5-8月输沙量占全年的88.9%。受上游修建水库、水土保持等人类活动的影响,流域汛期径流和泥沙1997-2013年比1980-1996年均减少了5.9%。流域面平均降水量、平均流量、平均输沙量年际变化不稳定,总体呈减少趋势,序列最大可能变异点分别为1995年、1994年和1997年。建立了流域年降水量与年径流深、次降水量P+Pa与次径流深相关模型,相关系数达到0.902和0.860。以年最大洪峰流量为参数,分别建立了流域年径流量与年输沙量、次径流量与次输沙量关系模型,相关系数达到0.835和0.917,公式模拟值与实测值接近,误差较小,可以作为以径流推算泥沙的重要依据。通过定性定量分析人类活动对流域径流、泥沙的影响程度,对区域抗旱防洪减灾、水资源管理、小流域治理及生态环境保护具有重要意义。     

Regional rating curve models of suspended sediment transport for Turkey

Estimations of annual suspended sediment loads are required for various types of water resources studies. Often estimation of the sediment load is needed for ungauged watersheds. Regionalization methods provide a practical solution to solve such problems. The purpose of this study is to classify suspended sediment yields in watersheds into homogeneous regions in order to identify their regional sediment rating curves. This study has been carried out for suspended sediment stations on 26 main basins of Turkey. Long term-scale suspended sediment rating curves of 115 gauging stations in Turkey were classified using cluster analysis on the basis of hydrological homogeneity. An agglomerative hierarchical clustering algorithm is used so that stations from different geographical locations are considered in the same cluster independently of their geographical location. 115 gauging stations were clustered into 4 different homogenous regions and the regional suspended sediment rating curve was developed for each region. The performance efficiencies of the developed regional rating curves were evaluated for 8 test stations and compared to the performances of rating curves in test sites. A regionalization model is developed for estimating suspended sediment rating curves for ungauged sites in Turkey. The developed regional rating curve models result in very close performances to those of their corresponding site rating curves.     

应用MODIS影像估测太湖水体悬浮物浓度

以太湖为研究区域,同步获取悬浮物浓度实测数据、水体反射光谱数据和MODIS卫星影像数据,构建基于中分辨率成像光谱仪(MODIS)的悬浮物遥感估测模型.为了削弱大气效应,对MODIS影像了进行了粗略大气纠正.通过悬浮物特征光谱分析,将MODIS各敏感波段及波段组合与悬浮物浓度实测值进行相关分析,并应用实测光谱数据进行验证.在此基础上,运用回归分析建立半经验反演模型,并对模型进行了评价和应用.研究结果表明,MODIS影像可以很好地对大型内陆湖泊的悬浮物浓度进行遥感估测.250 m波段2 500 m波段4与1 000 m波段14是探测悬浮物的敏感波段.波段组合上,500 m组合因子r4/r3、r4-r3估测悬浮物含量的精度很高,适于构建反演模型;1 000 m波段8、11、131、4的多元组合也是构建模型的较好选择(R2均不低于0.85).     

Mn-oxides and sequestration of heavy metals in a suburban catchment basin of the Chesapeake Bay watershed

The Chesapeake Bay is greatly impacted by numerous pollutants including heavy metals and understanding the controls on the distribution of heavy metals in the watershed is critical to mitigation and remediation efforts in controlling this type of pollution. Clasts from a stormwater catchment basin draining a subdivision near George Mason University, Fairfax VA (38°50.090°N 78°19.204°W) were investigated using X-ray diffraction (XRD), Scanning electron microcopy (SEM) and energy dispersive spectroscopy (EDS) to determine the nature of Mn-oxide coatings and relationship to bound heavy metals. Mn-oxides are poorly crystalline and occur as subhedral to anhedral platy particles and more rarely as euhedral plates. Micronodules are a commonly observed texture. Chemical compositions of coatings are variable with average major constituent concentrations being Mn (33.38 wt%), Fe (11.88 wt%), Si (7.33 wt%), Al (5.03 wt%), and Ba (0.90 wt%). Heavy metals are found in the coatings with Zn being most prevalent, occurring in approximately 58% of analyses with an average concentration of (0.66 wt%). Minor amounts of Co, Ni, Pb, and Cl are observed. Heavy metals and Cl are interpreted as being derived from road pollution. Mn-oxides can serve as a sequestration mechanism for pollution but may also release heavy metals. Field and laboratory observations indicate Mn-oxides occurring on the surface of the clasts can be mechanically mobilized. This is a mechanism for transporting heavy metals into the Chesapeake Bay watershed. Deicing agents may serve as a mechanism to release heavy metals through cation exchange and increased ionic strength. This is the first detailed mineralogical investigation of Mn-oxides and the roles they may play in pollution in the Chesapeake Bay.     

Effects of concentration-dependent settling velocity on non-equilibrium transport of suspended sediment

In this study, non-equilibrium transport of suspended sediment from one equilibrium state to another is investigated. Based on a convective-diffusion equation, a numerical model for flow with suspended sediment is developed by considering the effect of concentration-dependent settling velocity. The numerical model is validated by comparing analytical solutions and experimental results. The concentration profiles, mean concentrations and distance necessary to reach a new equilibrium state are examined by comparing them with the results of constant settling velocity. For a high concentration flow, the results indicate that evident differences between the above three indicators can be determined with and without concentration-dependent settling velocity. Additionally, the effects of concentration-dependent settling velocity are sensitive to the sediment mobility parameter (or Rouse number), although they are nearly independent of the diffusion Reynolds number.     

Effect of placer mining on suspended sediment in reaches of sensitive fish habitat

 The McQuesten River system in central Yukon Territory, Canada, contains placer mines and reaches of sensitive fish habitat. Suspended sediment is supplied to the system by erosion of previously mined disturbed areas, bank erosion, resuspension of placer sediment deposited on bars, and active placer-mine discharges. Direct discharge from active placer mines did not have a large impact on suspended sediment in reaches of sensitive fish habitat in 1994–1995, although only two mines were active and concentrations did periodically exceed water quality objectives. Erosion of previously mined disturbed areas had a pronounced effect on suspended sediment during spring snowmelt and summer rainstorms in 1994–1995. Deposits in previously mined areas should be stabilized to reduce erosion and its downstream impact on fish habitat. Received: 10 November 1997 · Accepted: 30 March 1998     

Surface metal enrichment and partitioning of metals in a dated sediment core from a Norwegian fjord

A 24-cm long sediment core from an oxic fjord basin in Ranafjord, Northern Norway, was sliced in 2 cm sections and analysed for As, Co, Cu, Ni, Hg, Pb, Zn, Mn, Fe, ignition loss and Pb-210. Partitioning of metals between silicate, non-silicate and non-detrital phases was assessed by leaching experiments, in an attempt to understand the mechanisms of surface metal enrichment in sediments. Relative to metal concentrations in sediments deposited in the 19th century, metals in near surface sediments were enriched in the following order: Pb > Mn > Hg > Zn > Cu > As > Fe. Cobalt and Ni showed no enrichment. The non-detrital fraction of Cu, Pb, Mn and Zn was significantly higher in the upper 10 cm than at greater depth in the core. This corresponds to sediments deposited since 1900, when mining activities started in the area. The enrichment of Cu, Pb and Zn is assumed to be mainly a result of mining, while Mn is apparently enriched in the surface due to migration of dissolved Mn and precipitation in the oxic surface layer. Elevated concentrations of As and Fe in the upper 4 cm are presumably due to discharges from a coke plant and an iron works respectively. The excess Hg present in the near surface sediments is tightly bound, either in coal particles or ore dust introduced by local industry, or via long distance transport of atmospheric particles. Calculations of metal flux to the sediments indicate an anthropogenic flux of Zn equal to its natural flux, while the flux of Pb shows a threefold increase above natural input.     

Composition of water and suspended sediment in streams of urbanized subtropical watersheds in Hawaii

Urbanization on the small subtropical island of Oahu, Hawaii provides an opportunity to examine how anthropogenic activity affects the composition of material transferred from land to ocean by streams. This paper investigates the variability in concentrations of trace elements (Pb, Zn, Cu, Ba, Co, As, Ni, V and Cr) in streams of watersheds on Oahu, Hawaii. The focus is on water and suspended particulate matter collected from the Ala Wai Canal watershed in Honolulu and also the Kaneohe Stream watershed. As predicted, suspended particulate matter controls most trace element transport. Elements such as Pb, Zn, Cu, Ba and Co exhibit increased concentrations within urbanized portions of the watersheds. Particulate concentrations of these elements vary temporally during storms owing to input of road runoff containing elevated concentrations of elements associated with vehicular traffic and other anthropogenic activities. Enrichments of As in samples from predominantly conservation areas are interpreted as reflecting agricultural use of fertilizers at the boundaries of urban and conservation lands. Particulate Ni, V and Cr exhibit distributions during storm events that suggest a mineralogical control. Principal component analysis of particulate trace element concentrations establishes eigenvalues that account for nearly 80% of the total variance and separates trace elements into 3 factors. Factor 1 includes Pb, Zn, Cu, Ba and Co, interpreted to represent metals with an urban anthropogenic enrichment. Factor 2 includes Ni, V and Cr, elements whose concentrations do not appear to derive from anthropogenic activity and is interpreted to reflect mineralogical control. Another, albeit less significant, anthropogenic factor includes As, Cd and U and is thought to represent agricultural inputs. Samples collected during a storm derived from an offshore low-pressure system suggest that downstream transport of upper watershed material during tradewind-derived rains results in a 2-3-fold dilution of the particulate concentrations of Pb, Zn and Cu in the Ala Wai canal watershed.     

含沙量和悬沙粒径变化对长江宜昌-汉口河段年冲淤量的影响

依据三峡水库修建以前的资料,运用数理统计方法对含沙量和悬沙粒径变化对长江宜昌-汉口河段年冲淤量的影响进行研究,以期为三峡水库修建以后库下游河道冲淤特性的预测提供参考。建立了1980-1997年间宜昌-汉口#河段年冲淤量与宜昌站年均含沙量C宜昌之间的回归方程,据此估算出使宜昌-汉口#河段处于不冲不淤状态的宜昌站临界年均含沙量为0.734 kg/m3。以宜昌-汉口冲淤量作为因变量,以宜昌站的含沙量、悬沙中径D50、最大流量和三口分流比作为影响变量,建立了多元回归方程。基于1980-1997年资料的方程表明,宜昌站含沙量越高,悬沙中径越粗,宜昌站洪水流量越大,宜昌-汉口河段年淤积量越大;三口分流比越小,宜昌-汉口河段年淤积量越大。     

高坝工程总溶解气体过饱和与水体含沙量关系

为研究伴随高坝泄水产生的总溶解气体(TDG)过饱和现象与水体中含沙量关系的问题,提出切实可行的减缓TDG过饱和影响的措施,通过实验的方法,对含沙水体中TDG过饱和的生成和释放进行了研究分析。结果表明:同样初始条件下,在含沙水体与清水中的TDG过饱和生成过程中,TDG过饱和度没有明显变化。在TDG释放过程中,含沙水体中TDG释放速率明显快于清水中TDG释放速率,据此提出可通过开启排沙孔等泄洪调度方式使泄流中悬沙含量增加,促使TDG沿程释放加快,降低其对鱼类的影响。