Use of a 6-steps microcosm for studying a wastewater discharge in a freshwater ecosystem: a multidisciplinary study

An experimental microcosm has been designed for simulating and studying impacts of a wastewater treatment plant (WTP) discharge on a freshwater/sediment ecosystem. The study was focused on the changes in biodiversity of benthic populations, especially bacteria and oligochaetes. Effluents were discharged in the Saône river, near Lyon (France) from a small treatment plant which treated domestic raw water by an activated sludge process. Freshwater and sediments were sampled in the Saône river upstream of the discharge point and placed in microcosms. Following the WTP discharge, physicochemical parameters of the overlying water column and sediments exhibited only a slight change, as compared to a reference. Characterization of the sediment bacterial populations was conducted with the Biolog and API systems. Strain identification and interpretation of data was difficult using thesetwo systems. Bacterial taxa in the sediments increased slightly below the WTP discharge. Gram negative strains dominated in the effluents, but G+ and G- bacteria were balanced in the sediments. Pseudomonas sp. and Bacillus sp., were the dominant strains. Invertebrate populations indicated an effect of the WTP discharge, with increasing of pollution resistant strains (Tubificidae) and disappearance of pollution intolerant strains such as Limnodrilus udekemianus and Quistadrilus multicoetosus. Taken as a whole, biological parameters indicated an environmental changes despite only slight changes in the physicochemistry of water. This experimental microcosm has proven to be a useful tool for studying impact of wastewater discharge on benthic populations.     

Sediments in urban river basins: a review of sediment–contaminant dynamics in an environmental system conditioned by human activities

Background, aim and scope  Over 50% of the global population live in urban centres and, therefore, an understanding of the processes acting upon urban systems is a global issue. The nature of human-made, often impervious, land surfaces and heavily engineered waterways results in hydrological and sedimentological systems in urbanised basins which contrast significantly to those within more natural (i.e. pristine, forested, agricultural) aquatic systems. In addition, the abundance of contamination sources in urban systems results in chemical pressures often manifested as high pollution concentrations or loadings, which in turn have detrimental impacts on human and ecosystem health. These lead to management and sustainability issues not generally encountered in more natural environments. The purpose of this review is to provide a state-of-the-art assessment of sediment sources, pathways and storage within urban river systems, to consider sediment management within urban systems and river basins, and examine the role of local and global environmental changes on sediment processes and management. Inevitably, much of the sediment that is transported within urbanised basins is contaminated, so this review also considers sediment–contaminant sources and interactions. Conclusions and recommendations  We reach a number of conclusions and recommendations for future research. There is a need for better sampling and monitoring of sediment and sediment-associated contaminant fluxes and cycling in urban river channels and basins. This should include better techniques and studies to identify sources and transfers of road-deposited sediment (RDS), airborne particulate matter and sediments in the river system. Greater interdisciplinary research, combining sedimentologists, hydrologists, urban planners, urban archaeologists, chemists and biologists, is needed. More attention needs to focus on upscaling and connecting urban areas to the rest of the river basin, both upstream and downstream. Finally, there is a need to balance multiple needs (urban population, water resources) with likely trends in both urban development and global environmental change.     

流域土壤侵蚀测量系统研究

流域内降雨-径流-土壤侵蚀过程中不同时空点处流量、流速、泥沙含量的获取是土壤侵蚀机理研究中的难点,它们的实时、准确测量将为侵蚀模拟-预报模型的建立与检验提供必要的数据支持。针对这一问题,提出一套测量流域土壤侵蚀动态变化过程变量的自动化测量系统。该系统由四部分构成:量水堰和水位传感器实现径流流量的测量;薄层水流流速测量系统测量坡面流及其流域内沟道中水流速度;径流含沙量测量系统测量径流中的泥沙含量;数据采集控制以及存储系统,实现试验设计点处侵蚀量的动态变化过程测量及数据存储。这一系统的构建及应用必将推动侵蚀过程测量向着更自动化和可操作化方向发展。     

The Impact of Biochar Addition on Nutrient Leaching and Soil Properties from Tillage Soil Amended with Pig Manure

Poses dam in the Seine River estuary acts as receptacle of water drain-offs from highly urbanized and industrialized catchment area; therefore, this water is highly contaminated by trace metals. Most trace elements are mainly bound to particulate matter and are incorporated rapidly into the sediments. Scavenging of these metals in the sediments can be reversible due to several perturbations so as sediments also act as a source of pollutants for the overlying water. For instance, natural events (tide, flood, storm) and anthropogenic processes (water management actions) can cause disturbance of sediments and subsequent remobilization of pollutants to the water column, thereby posing a potential threat for aquatic organisms. The purpose of this study was to evaluate the mobility of trace metals by different methods in the Seine estuary sediments. The surface sediment sampled at Poses dam was characterized by high pollution level of Cd, Cu, Zn, and Pb. The estimation of metal bioavailability through ratio ΣSEM/AVS (simultaneously extracted metals/acid volatile sulfides) indicates a potential bioavailability of trace metals. The chemical partitioning using the European Community of Bureau of Reference sequential extraction method revealed that over 85, 82, and 80 % of the total Cd, Zn, and Pb, respectively, were found to be associated with the exchangeable and reducible fractions of the sediment. Another approach used consists in the quantification of dissolved metals released by sediment resuspension experiments in laboratory under controlled conditions. The results indicated that metals are released rapidly from sediment with a sharp peak at the beginning of the experiment, followed by a fast coprecipitation and/or adsorption processes on the suspended particles. Also, the Cd, Pb, and Ni mobility is higher compared to that of the other metals.     

Hazard identification of contaminated sites—ranking potential toxicity of organic sediment extracts in crustacean and fish

Background, aim, and scope  It is well known that contaminated sediments represent a potential long-term source of pollutants to the aquatic environment. To protect human and ecosystem health, it is becoming common to remediate contaminated sites. However, the great cost associated with, e.g., dredging in combination with the large numbers of contaminated sites makes it crucial to pinpoint those sites that are in greatest need of remediation. In most European countries, this prioritization process has almost exclusively been based on chemical analyses of known substances; only seldom toxicity data has been considered. The main objective of the current study was therefore to develop a tool for hazard identification of sediment by ranking potential toxicity of organic sediment extracts in a crustacean and a fish. A secondary objective was to investigate the difference in potential toxicity between compounds with different polarities. Materials and methods  Early life stages of the crustacean Nitocra spinipes and the fish Oncorhynchus mykiss, which represent organisms from different trophic levels (primary and secondary consumer) and with different routes of exposure (i.e., ingestion through food, diffusive uptake, and maternal transfer), were exposed to hexane and acetone fractions (semi-polar compounds) of sediment from five locations, ranging from heavily to low contaminated. Preliminary tests showed that the extracts were non-bioavailable to the crustacean when exposed via water, and the extracts were therefore loaded on silica gel. Rainbow trout embryos were exposed using nano-injection technique. Results and discussion  Clear concentration–response relationships of both mortality and larval development were observed in all tests with N. spinipes. Also for rainbow trout, the observed effects (e.g., abnormality, hemorrhage, asymmetric yolk sac) followed a dose-related pattern. Interestingly, our results indicate that some of the locations contained toxic semi-polar compounds, which are normally not considered in risk assessment of sediment since they are focused on compounds isolated in the hexane fraction. Conclusions  The ranking of the five sediments followed the expected pattern of potential toxicity in both organisms, i.e., sediments with known pollution history caused major effects while reference sediments caused minor effects in the two test systems. Silica gel turned out to be an excellent carrier for exposure of N. spinipes to very hydrophobic and otherwise non-bioavailable sediment extracts. Recommendations and perspectives  Since both test systems demonstrated that a substantial part of the potential toxicity was caused by semi-polar compounds in the acetone fractions, this study enlightens our poor understanding of which compounds are causing adverse effects in environmental samples. Therefore, by investigating potential toxicity (i.e., hazard identification) as a first screening step in prioritizing processes, these implications could be avoided. For proper sediment risk assessment, we however recommend whole sediment toxicity tests to be used for selected sites at following tiers.     

小流域土壤侵蚀及径流过程自动测量系统的实验应用

流域内降雨－径流－土壤侵蚀过程中不同时空点处流量、流速、泥沙含量的获取是土壤侵蚀机理研究中的难点,其实时、准确测量为侵蚀模拟－预报模型的建立与检验提供必要的数据支持。该文针对这一问题,将量水堰及水位传感器、薄层水流流速测量系统、γ射线泥沙含量测量仪有机组合,构成流域土壤侵蚀过程测量系统。将该系统测量仪器布设于室内小流域模型各沟道出口及沟道内典型点处,在降雨强度25 mm/h,降雨历时5 min条件下,系统测量的流域出口处流量及泥沙含量变化值与采用手工采样方法测量结果的决定系数R²分别为0.738,0.749,流速误差为8.7%,比较结果显示该系统具有较高的测量精度。在此测量精度范围内,同时测得各沟道口流量及泥沙含量动态变化过程及沟道中典型点处流速。流域内径流过程及径流含沙量的动态测量结果表明将该系统应用到土壤侵蚀动态过程的研究中是可行的。     

Modern eolian and fluvial processes and their interactions in an ephemeral desert stream in Inner Mongolia,China

Purpose

Floods and eolian activities are the dominant external agents to shape the topographic forms in ephemeral desert streams of drylands. So far, few studies have discussed the modern processes of eolian–fluvial interactions. To bridge this gap, we studied the modern interactions of eolian and fluvial process in a desert ephemeral river, the Maobula Gully in Inner Mongolia, which exhibits typical eolian–fluvial interactions.

Materials and methods

Multisource data such as integrated particle size data, hydrological data from the Tugerige Hydrological Station, high-spatial-resolution satellite images, and an eolian sediment saltation emission model were integrated to analyze the effects of eolian and fluvial delivery to the sediment on the riverbed, the eolian sediment feeding rate to the gully, the transport of sediment in flood events, and the interactions between eolian and fluvial processes.

Results and discussion

The desert reach of the Maobula Gully is a replacement reach between coarse sediment from the upper reaches and eolian sediment from the Kubuqi Desert. The annual eolian sediment feeding into the gully exhibited a significant decreasing trend. The eolian sediment into the gully increases the available sediment and the bed roughness, affecting the transport of sediment during floods. The sediment concentration and yields in flood events are mainly decided by the discharge and water yield, respectively. Through a comparison of the channel forms between 1970 and 2013, a recovery mechanism in the Maobula Gully was identified, which involves the equilibrium state between abrupt flood erosion and continuous dune migration.

Conclusions

This study analyzed the modern processes of eolian and fluvial processes and their interactions in a typical ephemeral desert stream named the Maobula Gully, and some interesting results were found. We believe that the methodology and results could provide references and evidence for understanding the mechanisms of fluvial and eolian interactions in other ephemeral desert streams around the world.

     

Assessment of soil microbial communities in surface applied mixtures of Illinois River sediments and biosolids

Restoration of the Illinois River and its backwater lakes involves the dredging of millions of cubic meters of sediment, and the relocation of this dredged sediment is a significant challenge. Beneficial use of sediment as landscaping soil on brownfields, strip mines, highway borders and other areas is a potential use for large quantities of this material, as sediments have desirable soil characteristics, including a favorable texture for plant growth and good water holding capacity. The addition of biosolids to Illinois River sediments has the potential to increase the organic and nutrient content of the sediments and thus to make these sediments more useful for the reclamation of damaged soils. The goal of the current study was to assess the impacts of biosolids additions on the physical/chemical characteristics and microbial communities of surface applied river sediments. Field plots containing various sediment/biosolids mixture were established and examined 1 year after application. Results indicated that biosolids addition had significant positive effects on soil organic carbon, total Kjeldahl nitrogen, total phosphorous, and microbial biomass and activity. In addition, the sediment/biosolids mixtures showed lower salinity and lower concentrations of copper, lead and zinc than the pure biosolids. PLFA analysis revealed that biosolids addition resulted in shifts in microbial community composition, with relative increases in Gram negative bacteria and relative decreases in Gram positive bacteria, fungi, and actinomycetes. These data suggest that a mixture of sediment and biosolids is preferable to either sediment or biosolids alone.     

Neutralization of acidic groundwater inputs and control of metal mobility by a near-shore adirondack lake sediment

Biogeochemical processes contributing to the neutralization of acidic groundwater passing through near-shore sediments of an acidified lake (Dart's Lake) were investigated in a controlled laboratory experiment. Three intact sediment cores collected from the near-shore region of the lake were connected to a system that simulated groundwater flow through lake sediments in a temperature controlled laboratory environment. The effect of sediment biogeochemical processes on groundwater chemistry was determined by evaluating changes in acid/base and metal chemistry for solutions entering and leaving the cores. Aluminum mobilization represented the most significant source of neutralization for each core and contributed up to 99% of H⁺ removal. Although the sediment cores were collected parallel to the shoreline and over a linear distance of only 0.3 m, significant differences in sediment chemistry were apparent and contributed to variations in the chemistry of water transported from the cores. For one core that exhibited retention of Al from the influent groundwater, retention of Pb by the sediment was similarly observed. Following acidification of this groundwater, Pb was readily remobilized. These results suggest that near-shore lake sediments may be effective at influencing seasonal variations in Al, Pb and base cations in lakes receiving groundwater inputs.     

Sediment remediation: U.S. focus on capping and monitored natural recovery

The Battelle Conferences series represent the state-of-the-art of emerging technologies, science and management issues for contaminated sediment remediation. In the 2007 Conference held in Savannah, GA, two in situ technologies for cleanup sites were at the centre of interest: Sediment capping, a form of in situ containment, which involves the placement of a subaqueous covering of clean sediment and/or other materials to isolate contaminated sediments, and monitored natural recovery (MNR), where natural processes are used to mitigate the transfer of particle-bound contaminants into the water phase and/or biota. A third priority technology in the Superfund program, recommended by the U.S. Environmental Protection Agency (EPA), is environmental dredging, i.e., removing the sediments from the aquatic environment. About 30 platform or poster presentations dealt with in situ capping as a technology, reflecting the rapid developments in this field, both in assessments and enhancements of ‘classic’ passive caps and the development and demonstration of active capping technologies. Issues relevant to monitored natural recovery were spread throughout many sessions; e.g., contaminant source identification, control, remediation strategies; innovative characterization and assessment, chemical/toxicological/biological measurements and characterization, bioavailability of contaminants, contaminant fate and transport and remediation effectiveness: defining, monitoring, and demonstrating success. Presentations addressing the role of science and stakeholder input were complemented by discussions on the importance of data quality considerations, uncertainty analysis, and careful selection of reference sites highlighted the complex nature of these multidisciplinary assessments. Case studies, in which site-specific information was linked to regional management objectives, various approaches to watershed-scale assessment and management, and the role of ecosystem considerations, were all discussed in these sessions, as well as in a complementary panel discussion. One compelling feature of the Savannah Conference 2007 (relative to the first couple of meetings) is that there were a much larger number of presentations that provided the tools, models, case studies, etc to fill in the lines of evidence that allow a fair comparison between removal and in situ management when appropriate, and evidence of a growing acceptance that the residuals and impacts of removal approaches can at times offset perceived benefits, so that in situ management can be considered if exposure risk can be properly assessed.     

Remobilization of trace elements from polluted anoxic sediments after resuspension in oxic water

Polluted sediments are periodically subjected to resuspension processes resulting from natural events (e.g. storms, strong waves) as well as from anthropogenically induced activities (e.g. dredging). The main part of the resuspended material is initially in an anoxic state and will be reoxidized more or less quickly in the oxic water column. In laboratory experiments reflecting, as far as possible, natural conditions (e.g. constant pH) the release of Cd, Cu and Zn during this reoxidation phase was investigated. Up to 2% of the particulate bound heavy metals were remobilized from the sediments. In addition the evolution of the concentrations of the anions PO₄, SO₄, NO₃ and NH₄ were measured to examine the influence of microbial processes on the release of trace elements. Cell counts and microbial activity of certain micro-organisms during the release processes were also investigated. The investigations illustrated that biological activity has a significant effect on release. In all sediment samples the release of cadmium was delayed in comparison with the other elements even in sediments from different river systems. The influence of different microbial processes on this divergent behavior was examined. The significance of dredging activities to the remobilization processes during reoxidation of anoxic sediments in the Elbe River is discussed.     

Manging contaminated sediments

Management of contaminated sediments, i.e. linking risk assessment and problem solutions, needs both quality criteria respecting recent findings on bioavailability of pollutants and in-depth knowledge on processes controlling their particular hydrological and biogeochemical dynamics. In thefirst part of our review, new insights into ‘diagenetic’ mechanisms on particles including ageing and their effects on biological interactions were presented. These findings clearly indicate the need to refine bioavailability models including equilibrium partitioning. A set of bioassays is a powerful supplement to assess sediment quality. In thesecond part, an interdisciplinary process approach relating to the release of DOC, nutrients and pollutants into the open water is described, which has been derived from the evaluation of the international state-of-the-technology with three major themes: ‘experimental techniques’, ‘processes and properties’ and ‘development and validation of models’. Special study targets are the formation of aggregates in turbulent water, flocs and biofilms from organic reactions, and formation of new surfaces for readsorption of dissolved pollutants. Of greatest importance is the degradation of organic matter, which affects both hydrodynamic processes and geochemical redox cycles, thus providing driving forces, e.g. for metal mobilization. Models for predicting pollutant transport in rivers are still dominated by hydromechanical parameters. A first step for extending these models could involve typical milieu factors such as competing ions, complexing agents, redox conditions and pH-values. The next steps would include binding constants and other factors describing solid/solution interactions of critical chemicals in a multicomponent system. In theforthcoming issues of JSS — J Soils and Sediments, two practical fields of application will be discussed: in-situ sediment treatment — natural attenuation approach (Part III) and subaquous storage/capping of dredged material (Part IV). The abstracts of both parts can be found in the appendix.     

Sublethal effects of contaminated sediment on Arenicola marina

Purpose

The highest concentrations of environmental contaminants are generally found in marine sediments, and there is a need for knowledge concerning how and whether they affect sediment-dwelling organisms. This study aimed to assess sublethal effects in Arenicola marina exposed to two sediments from a contaminated fjord and two reference locations with different sediment characteristics.

Materials and methods

Duplicate contaminated sediments were used to investigate the robustness of current protocols for sediment testing. The two reference sediments, with different grain sizes and total organic carbon, were collected from the outer Oslofjord and the two contaminated sediments from Frierfjord. Polychaetes were exposed in quadruplicate sediment microcosms and sampled after 1, 2, 4 and 8?weeks of exposure. Oxidative stress resistance (total oxyradical scavenging capacity, TOSC) and components comprising the energy budget (cellular energy allocation, CEA) were determined for individual polychaetes.

Results and discussion

Arenicola maintained and increased body weights over the initial 4?weeks of exposure in all groups, except in one reference sediment (Elle). There were no differences between treatments in the scavenging capacity (TOSC). The most striking difference in how polychaetes partitioned energy resources was a difference in lipid and carbohydrate allocations for Arenicola held in the contaminated sediments over the initial weeks. Cellular respiration appeared to increase in polychaetes held in the Elle sediment and decreased for polychaetes held in the two Frierfjord sediments by weeks?4 and 8. In the overall CEA, this was offset by increased energy per weight stored in the Elle group, which resulted in an overall positive CEA for polychaetes held in that sediment, whereas polychaetes in the other treatments were close to neutral. Although CEA would thus indicate that Elle polychaetes had good health status, their body weight also decreased significantly over the experimental period compared to other treatments, indicating an overall negative effect.

Conclusions

This study has shown the importance of sediment characteristics when evaluating toxicity and how resource allocation can differ dramatically over a short time span in polychaetes held in similarly contaminated sediments. There were no clear effects of sediment contamination on CEA or TOSC in the polychaete A. marina. The findings are relevant for the design of both short- and long-term sediment studies.     

Ripening of clayey dredged sediments during temporary upland disposal a bioremediation technique

Background and Goal  In the Netherlands about 40 million m³ of sediment has to be dredged annually for both maintenance and environmental reasons. Temporary upland disposal is the most widely adopted alternative for dredged sediments worldwide. For good management of temporary disposal sites, knowledge is needed on the processes controlling the behavior of the sediments during disposal. Therefore, a review of the literature was made to get an integrated overview about processes that take place during temporary disposal. Ripening  After disposal of clayey sediments, the following spontaneous dewatering processes can be distinguished: sedimentation, consolidation, and ripening. Sedimentation and consolidation are relatively fast processes, whereas ripening can take up to several years. In a remediation perspective, the ripening of sediments is the most important dewatering process. Ripening, which may be subdivided into physical, chemical, and biological ripening, transforms sediment into soil. Physical ripening is the irteversible toss of water and results in the formation of soil prisms separated by shrinkage cracks. Continuing water loss causes a breaking up of the prisms into aggregates. The aggregates produced by this ongoing desiccation process usually remain quite large (>50 mm) and can only be further broken down by weathering processes like wetting and drying or by tillage. As a result of the aeration caused by physical ripening, also chemical and biological ripening take place. Chemical ripening can be defined as the changes in chemical composition due to oxidation reactions and leaching of soluble substances. Biological ripening is the result of the activity of all kinds of soil fauna and flora that develop as a result of aeration, including both the larger and the microscopic forms of life. Decomposition and mineralization of soil organic matter caused by micro-organisms can be seen as the most important aspect of biological ripening. Many interactions exist between the different ripening processes. Conclusions and Outlook  Oxygenation of the dredged sediment is improved as a result of the natural ripening processes: the air-filled porosity increases, the aggregate size decreases, and the initially high respiration rates caused by chemical and biological ripening decreases. Therefore, conditions in the disposal site become more favorable for aerobic biodegradation of organic pollutants like Polycyclic Aromatic Hydrocarbons (PAH) and mineral oil. It is concluded that the naturally occurring process of ripening can be used as a bioremediation technique. Ripening in an upland disposal site is an off-site technique, and therefore, the process could be enhanced by means of technological interference. However, it is concluded that the knowledge currently available about upland disposal is not sufficient to distinguish critical process steps during the ripening and bioremediation of PAH and mineral oil polluted sediments because of the complex relationships between the different ripening processes and bioremediation.     

达里诺尔湖磷赋存特征及底泥释放影响因素

[目的]揭示封闭性内陆湖磷组成特点及底泥释放影响因素,为控制达里湖磷元素污染提供理论支持。[方法]对达里诺尔湖水体总磷(TP)、溶解性总磷(DTP)、溶解性无机磷(DIP),沉积物形态磷进行监测,并利用因子分析的方法对影响沉积物底泥释放的因素分类讨论。[结果]达里湖上覆水总磷(TP)均值2.00±0.02mg/L,间隙水TP均值2.50±0.02mg/L,沉积物TP在206.09~940.49mg/kg之间。沉积物中无机磷(IP)占TP的47.9%,是沉积物主要的磷形态之一。钙磷(Ca-P)是IP中含量最多的形态磷(217.76±47.01mg/kg),其次为铁铝结合态磷(Fe/Al-P,62.73±28.34mg/kg)和交换态磷(Ex-P,36.50±19.13mg/kg),有机磷(OP,200.28±135.13mg/kg)含量占TP的41.8%;通过因子分析法将影响底泥释放的因素分为三类:沉积物TP,Ca-P,Fe/Al-P和生物有效性磷含量归为沉积物磷因子;水体pH,DO,Eh值以及间隙水磷含量归为界面影响因子;湖水水深归为湖泊自身特征因子。[结论]达里湖存在沉积物磷底泥释放的风险,根据因子分析的结果可知,影响沉积物底泥释放的因素分为沉积物磷、水—沉积物界面理化指标和湖水水深3大类。     

湖泊沉积物内部因素对沉积物-水界面磷交换的影响

湖泊沉积物既可充当湖泊水体营养盐的汇也可转变为源,而磷则是富营养化的制约性因子。沉积物-水界面的磷交换过程与沉积物本身的物理化学特征直接相关。本文对沉积物-水界面磷交换动态的内部影响因子及其作用进行了综合分析,并分别论述了沉积物粒级分布、磷的存在形态、电子受体、有机物等对沉积物-水界面磷交换过程的影响与作用。     

Assessing the environment-benthic fauna coupling in protected and urban areas of southern Brazil

Growing urbanization adjacent to aquatic systems may alter water, sediment and benthic community interactions. The ecological effects of urbanization on regional, local and site-specific spatial variations of benthic macrofauna and of sediment and water properties were investigated in relatively pristine rivers and in urban rivers of southern Brazil. The benthic communities were found to be different in urbanized and protected areas. Their predominant responses to environmental conditions were characterized as either a: (i) sensitive species assemblage, formed by polychaetes Nephtys fluviatilis and Heteromastus similis and the crustacean Kalliapseudes schubarti; or a (ii) tolerant species assemblage, formed by the polychaete Laeonereis acuta and by an unidentified oligochaeta Tubificidae. The relationships between fauna and environment differed between protected and urban rivers. In protected areas the fauna distribution was directly related to grain sorting and phaeophytin a in sediments; and to chlorophyll a, dissolved oxygen and phosphorus in water. In urban sites the strongest determinants of fauna distribution were the presence of lead, copper, dissolved phosphorus, chlorophyll a and phaeophytin a in sediments, and suspended particulate matter, dissolved phosphorus, nitrogen, and silicate in water. The comparison of animal-sediment-water interaction in natural and urban areas can be useful in planning environmental impact mitigation strategies for conservation even in rivers and estuaries with non-point sources of pollution.     

copper,lead and zinc distribution in soils and sediments of the south-western coast of the río de la plata estuary

Background, Aim and Scope.  The compositional study of suspended matter in water from rivers of different latitudes and climates has revealed that the fine fraction reflects both substrate lithology from source areas or topsoil composition along the course. Metal distribution patterns are also strongly related to the clay mineral fate in fluvial aquatic systems. For the particular case of the coastal area of the Río de la Plata estuary in South America, previous studies have, on the one hand, focused on the analysis of distribution patterns of heavy metals in bottom river sediments and, on the other hand, on the assessment of metal contents in topsoils. The present study was conducted to evaluate the Cu, Pb and Zn distribution in soils and sediments from four drainage basins crossing two differentiated geomorphologic units composed of unconsolidated materials and to understand the metal behaviour. Methods  Data used included the existent, self-produced soil and sediment data sets (grain size, organic matter and Cu, Pb and Zn contents from 124 samples). Analyses were performed by using standardised methods: grain size analysis by sieving and settling; organic matter content based on the reduction of dichromate ion followed by titration; metal content by atomic absorption spectrophotometry following acid digestion. Results and Discussion. The average (% w/w) clay and organic matter content were 45.9 ± 17.1 and 1.5 ± 1.7 for sediments and 32.0 ± 19.8, and 7.5 ± 7.6 for soils, respectively. The raw mean metal concentrations (mg-kg^-1 dry weight) for sediments and soils were: Cu: 28.02 ± 27.28, 32.08 ± 21.64; Pb: 32.08 ± 46.94, 68.44 ± 69.25 and Zn: 83.09 ± 150.33, 118.22 ± 74.20, respectively. A good correlation for each clay-normalised metal concentration was found between soil and sediments using regression analysis considering average data for each basin sampling site (r > 0.89, p < 0.05). A comparison between metal concentration levels taking into account geomorphologic units by a t independent sample test showed significant differences for the normalised soil-sediment metal data (p < 0.001), responding to differences in grain size, clay mineralogy, organic matter and neoformed Fe-Mn oxide composition. Conclusion, Recommendation and Outlook  A clear parenthood between the topsoils and the bottom sediments in the study area was found. The Argiudolls from the inner zone are frequently affected by rainwater erosion, which washes the fine materials with sorbed metals and carries them to the streams. These watercourses reach the flat coastal plain, where soil flooding and bottom sediment depositional processes predominate. Here, both soils and bottom sediments are enriched in clay, organic matter and metals. The topography and lithology, under the environmental conditions of a temperate and humid climate control the fate of metals within these small basins. The influence of the physical media on the distribution and fate of pollutants should not be minimised in the understanding of the governing processes from natural systems.     

Sediment Yield Deduction from Check–dams Deposition in the Weathered Sandstone Watershed on the North Loess Plateau,China

As the basic unit of erosion and sediment yield, it was critical to determine the amount of soil erosion and sediment yield in the small watersheds for sustaining a reasonable water resource and sediment regulation system. In this study, we determined the sediment yield from the dams‐controlled watershed on the North Loess Plateau. Three check dams in the watershed were investigated by drilling ten‐hole sedimentation cores. The corresponding flood couplets were dated according to thickness of deposition layers, distribution of sediment particle size and historical erosive rainfall events. On the basis of the check dams capacity curve, the soil bulk density and the thickness of couplets, the deposit mass of check dams, and then the sediment yield of watershed at different temporal and spatial scale were deducted. In total of the 33, 60 and 55 couplets were corresponded to individual flood events in the dam MH1# from 1976 to 1984, the dam MH2# from 1985 to 2007, and the dam MH4# from 1981 to 2009, respectively. The specific sediment yield for flood events was 1,188.5–11,527.9 Mg km⁻², 1,278.6–17,136.7 Mg km⁻², and 3,395.9–33,698.5 Mg km⁻², and the annual average sediment yield was 10,728.6 Mg (km² · a)⁻¹, 12,662.9 Mg (km² · a)⁻¹, and 16,753.3 Mg (km² · a)⁻¹ in dam MH1#, MH2# and MH4# controlled watershed, respectively. The sediment yields were inversely proportional to the dams – controlled areas. For the whole watershed, the annual average sediment yield was 14,011.1 Mg (km² · a)⁻¹ from 1976 to 2009. There were large amounts of sediments (42.3–50.5%) were intercepted gradually along the way from small watersheds to the river channel. And the minimum rainfall for sediment deposited in the dams was greater than 20 mm in this watershed. The results of this study suggested that the sediments retained behind check dams were helpful to quantifying the amount of erosion sediment yield and understanding the soil erosion evolution in the small and ungauged watersheds. Copyright © 2016 John Wiley & Sons, Ltd.     

Speciation and Transformation of Sulfur in Freshwater Sediments: a Case Study in Southwest China

Sulfur (S) is one of the most redox-sensitive elements and has a marked impact on the geochemical cycling of biogenic elements in freshwater sediments. Current understanding of the speciation of sedimentary S, and of the processes regulating it, is insufficient. In this study, the speciation and spatial variations of S and iron (Fe) in sediments (soils) from Lake Hongfeng, one of the largest freshwater lakes in Southwest China, were investigated using X-ray absorption near-edge structure (XANES) spectroscopy and diffusive gradient in thin film technique (DGT). The results show that S in sediments and soils was composed of seven fractions in different electronic oxidation states (EOSs), including (i) reduced S (R-S, G1, EOS = ? 1), (ii) lowly oxidized S (LO-S, including G2-G5; EOS = 0, 0.5, 2, and 3.7), and (iii) highly oxidized S (HO-S, including G6 and G7; EOS = 5 and 6). Proportional differences of S speciation in sediments and soils indicated that HO-S is largely reduced to LO-S and R-S during depositional processes. The HO-S fraction decreased in the top surface sediments and then increased in the deeper layers, whereas the R-S fraction showed the opposite trend, suggesting that sulfate reduction and re-oxidation processes occurred in the sediments. High ratios of soluble Fe/S provided a favorable foundation for the reduction and burial of sedimentary S. The speciation and spatial variations of S in freshwater sediments are controlled by complex environmental factors, including terrigenous material discharges, water redox conditions, and porewater chemistry (such as for pH, Eh, and reactive Fe). Our study will help to deepen the understanding of the geochemical dynamics of S in the sediments of freshwater ecosystems.