The source and diagenesis of sediment organic matter in the upper Pearl River Estuary as indicated by amino sugars

Purpose

The source and diagenesis of sediment organic matter (OM) based on amino sugar yields and compositions were investigated in sediment samples collected along a reach of the upper Pearl River Estuary in south China.

Materials and methods

Sediment samples were collected from the estuary. Three sediment size fractions—coarse particulate OM (CPOM), fine particulate OM (FPOM), and ultrafiltered dissolved OM (UDOM)—were analyzed for total hydrolysable amino sugars (THAS), total organic carbon (TOC), and total nitrogen (N).

Results and discussion

THAS contributed much more to sediment TOC and total N in UDOM than in CPOM and FPOM. Percentages of TOC as THAS increased with increasing sediment size. The low glucosamine/galactosamine ratios indicated a relatively large bacterial contribution to the sediment OM size fractions and the less reactive nature of sediment OM in the upper Pearl River Estuary. However, the depletion in muramic acid in the three sediment fractions, especially in UDOM, suggested that living bacteria or intact peptidoglycan units were not a major contributor to sediment OM.

Conclusions

The increases of TOC as THAS and C-normalized yields of THAS with the different sediment size fractions demonstrated that they could be used as diagenetic indicators.     

The German Environmental Specimen Bank

Goal, Scope and Background  

The European Water Framework Directive implies a risk based sediment management. In this approach, sediments are recognised as secondary sources of contaminants, and suspended particulate matter (SPM) as the carrier. For that reason, the concept of the German Environmental Specimen Bank (ESB) includes the establishment of these specimens. The ESB is characterised by a high quality assurance system of standard operation procedures (SOP) to preserve the integrity of the specimens under cryogenic conditions for transportation, storage and handling. The aim of this study was (1) the development and validation of SOPs for the collection of sediment and SPM, and (2) the adaptation and standardisation of sampling techniques for the ESB. This paper provides information about sediment and SPM as new specimens in the ESB.     

Widespread endocrine activity in river sediments in Hesse, Germany, assessed by a combination of in vitro and in vivo bioassays

Purpose  

There is a growing concern regarding the effects of endocrine disrupting compounds on humans and wildlife. Since some of them have the ability to bind to particulate matter, high concentrations can be reached in sediments of surface waters. The objective of this study was an assessment of 50 sediment samples from predominantly small rivers in the German federal state of Hesse with emphasis on endocrine activity.     

Characterization and spatial distribution of particulate and soluble carbon and nitrogen from wildfire-impacted sediments

Purpose

The heavily forested Cache la Poudre (CLP) watershed in northern Colorado, USA, was impacted by the High Park wildfire in 2012. The wildfire burned land and vegetation immediately adjacent to the CLP River where blackened, ashy sediment samples were collected from five sites upstream of the City of Fort Collins drinking water intake to evaluate the spatial distribution and characteristics of burned sediments, along with quantifying and characterizing soluble compounds following a leaching experiment.

Materials and methods

At each site, samples were collected from three locations: (1) the edge of the bank adjacent to the water edge (downbank), (2) 1 m upslope of location 1 (midbank), and (3) 2 m upslope of location 1 (upperbank). All solid sediment samples were analyzed for elemental composition, and a subset of solid sediment samples were analyzed with ¹³C solid-state nuclear magnetic resonance spectroscopy. Sediments were mixed with the background CLP River water collected from upstream of the wildfire and allowed to leach for 6 and 24 h to determine the quantity and quality of water-soluble constituents. Filtered samples were analyzed for dissolved organic carbon (DOC), iron, manganese, and inorganic nutrient concentrations, by optical properties, and for disinfection byproduct (DBP) formation.

Results and discussion

Percent carbon and nitrogen content of the solid sediments were good predictors of leachate DOC concentration. The mean fluorescence index was higher for wildfire-impacted sediment leachates (1.50) compared to the background CLP River water (1.37), which may be due to changes in DOM molecular weight and oxidation of organic matter. All sediment leachates showed consistently higher haloacetonitrile and chloropicrin yields (DBP concentration/DOC concentration) compared to background CLP River water, whereas carbonaceous DBPs did not.

Conclusions

The collected sediments showed that burned material accumulated downstream near the river and was composed of inputs from burned soil and biomass along with the mobilization of unburned terrestrial material. The leachates of these sediments have different characteristics compared to the background CLP River water, indicating that DOM leached from sediments following a wildfire may increase aquatic DOC concentrations and N-DBP formation.

     

Phosphorus fractions and release potential of ditch sediments from different land uses in a small catchment of the upper Yangtze River

Purpose  

Drainage ditches act as a major conduit of phosphorus (P) from contributing land to receiving waters. The aims of this study were to characterize the phosphorus fractions of ditch sediments from different land uses and to evaluate their potential for P release to provide management strategies for ditch sediment.     

Seasonal delivery of organic matter and metals to farm canals: effect on sediment phosphorus storage capacity

Purpose

The Everglades Agricultural Area (EAA), USA, comprises nearly 280,000 ha of organic soil farmlands that are drained by a network of farm canals. During the wet summer season, the water-table in the farmlands is maintained by moving water from farm canals via low-fit, high-volume drainage pumps. The drainage pumping creates a hydraulic pressure gradient, which has the potential to deliver particulate and dissolved substrates from surrounding farmlands into farm canals. This study investigated the role that seasonal drainage plays on the fate and transport of farm canal water including nutrients and metals, plants, and sediments.

Materials and methods

Intact sediment cores were collected from eight farm canals during the months of November and June, sectioned into two depth intervals (0–2.5 and 2.5–5 cm), and tested for organic matter (OM), phosphorus (P), iron (Fe), and aluminum (Al). In addition, water from the canal (core-water) was also collected and tested for total P, total dissolved P, soluble reactive P, particulate P, dissolved organic carbon, and calcium (Ca). Oxalate extractable Fe, Al, and P were used to estimate sediment P storage capacity. In order to evaluate the seasonal variability in aquatic vegetation coverage in the farm canals, spatial assessment of coverage was conducted every 2 months over a 2-year period.

Results and discussion

Significant increases in Fe and Al concentrations were observed in the sediment in November compared with June, possibly derived from surrounding soils. The source of OM to the sediments was directly associated with aquatic plants, following a seasonal trend. Total P and Ca were significantly higher in the water during June compared with November. The seasonal trends in sediment and core-water concentrations can be explained by groundwater inputs, surface runoff, and plant coverage within farm canals. High concentrations of Fe and Al in the sediments did not reflect a high P storage capacity, due to the presence of high OM content and seasonal fluctuations in redox potential.

Conclusions

The discharge of groundwater from surrounding farmlands is seasonal and has the potential to deliver nutrients, OM, and metals into adjacent farm canals. During summer, primary productivity is at its peak, and this has a direct effect on the percent aquatic plant coverage, nutrient cycling, and P storage capacity within the farm canals. Within the EAA farm canals, the presence of Ca-carbonate may have a greater influence on P storage capacity of the sediments than Fe and Al.     

Phosphorus transfer across boundaries: from basin soils to river bed sediments

Purpose  

The study of phosphorus (P) transfer from soils to rivers is a subject of interest as there is a clear relation between land use and water quality. P transfer in the soil/sediment system was evaluated by comparing the concentrations of total (P_T) and bioavailable P (P_A).     

A new sediment contact assay to assess particle-bound pollutants using zebrafish (<Emphasis Type="Italic">danio rerio</Emphasis>) embryos

Goal, Scope and Background  

Based on a bioassay battery covering only primary producers and consumers as well as degraders, the potential ecological hazard of sediments to vertebrates cannot be estimated comprehensively. Therefore, there is an urgent need to develop and standardize integrated vertebrate-based test systems for sediment investigation strategies. Whereas vertebrate-based in vitro systems have frequently been used for the investigation of aqueous samples, there is a significant lack of whole sediment assays. Thus, the purpose of the present study was: (1) to develop a rapid and reliable, but comprehensive method to investigate native sediments and particulate matters without preceding extraction procedures; (2) to compare the hazard potential of solid phase sediments to the effects of corresponding pore waters and organic extracts in order to characterize the bioavailability of the particle-bound pollutants; and (3) to relatively evaluate the embryotoxic effects of sediments from the catchment areas of the rivers Rhine, Neckar and Danube.     

Applicability of a sequential P fractionation procedure to Si in sediment

Purpose  

A sequential phosphorus (P) fractionation procedure for sediments was applied to silicon (Si) to test its applicability. We wanted to know (1) whether it would be used in a cost-efficient way to study the finding of both elements, defining Si pools corresponding to the respective P pools, and in particular, (2) whether it could be shown that redox-sensitive processes affect Si mobility in sediment.     

Erodibility and transport behavior of dreissenid mussel deposits in an annular flume

Purpose

Zebra mussels (Dreissena polymorpha) alter the transport dynamics and fate of particulate matter in aquatic systems by intercepting, retaining, and recycling suspended materials. This study examines the effect of particle processing by dressenids on the nature (grain size distribution, settling velocity, porosity  and density) and transport properties (critical shear stress for erosion, erosion rates, and bed stability) of suspended particulate matter in lakes.

Materials and methods

The bed stability, erosion rate, and critical shear stress for erosion of dreissenid biodeposits were measured in an annular flume. The particle size distribution, settling rate, density, and porosity were measured to characterize the physical nature of the biodeposits. Materials studied in the flume include (1) a combination of biodeposits and surface sediments collected from dreissenid beds and (2) biodeposits harvested in a weir box populated with dreissenids.

Results and discussion

The settling rates of both biodeposit/sediment mixtures and pure biodeposits were lower than natural sediment in lacustrine environments. Erosion characteristics and transport properties of biodeposits were strongly influenced by bed age and the presence of mussels. Bed stability increased after 7 days, with a τ_crit of 0.26 Pa compared to the 2- and 14-day consolidation periods (τ_crit?=?0.13 and 0.15 Pa), respectively. The observed changes in bed stability with bed age will modify the transfer of particulate materials to the offshore profundal zone as well as the rates and magnitudes of sediment-associated nutrients in the near shore zone.

Conclusions

Biostabilization of surficial lake-bottom sediments impacted by mussel biodeposits may increase bed stability and reduce the export of particulate matter to the offshore environment. Further, well-developed communities of dreissedid mussels have an armoring effect on deposited sediment, which reduces remobilization of sediment and biodeposits. However, once eroded, the dreissedid modified deposits will likely be transported further due to their low-settling velocity.

     

Factors controlling sediment yield at the catchment scale in NW Mediterranean geoecosystems

Purpose  

This study aimed to (1) increase understanding of the relation between sediment yield and environmental variables at the catchment scale; (2) test and validate existing and newly developed regression equations for prediction of sediment yield; and (3) identify how better predictions may be obtained.     

A 50-year record of quinolone and sulphonamide antimicrobial agents in Seine River sediments

Purpose  

Even though sediments may represent a reservoir for antimicrobial agents, little is known about the persistence of these molecules over time or their accumulation. In this study, six antimicrobial agents, oxolinic acid, flumequine, nalidixic acid, norfloxacin, sulphamethoxazole and trimethoprim, were investigated in a sediment core from the Seine River. This work aimed to (1) measure antimicrobial agent contamination levels in the sediment and identify their origins, (2) obtain information on the persistence of these compounds in sediment over long periods (>4 years) and (3) show the existence of a historical record in sediment of river contamination by antimicrobial agents.     

Link between black carbon and resistant desorption of PAHs on soil and sediment

Purpose  

The effects of black carbon (BC) on resistant desorption of organic pollutants in soil and sediment were evaluated to further understand the mechanisms for the resistant desorption and to find a more accurate desorption model which can improve risk assessment and management of ubiquitous soil/sediment contamination.     

Application of an incomplete factorial design for the formation of an autotrophic biofilm on river bed sediments at a microcosms scale

Purpose  

River bed sediments are often colonized by microorganisms which can produce large amounts of extracellular polymeric substances (EPS) forming biofilms that may increase the resistance of the bed sediment towards erosion and affect the nutrient and pollutant exchange between water and sediments. The objective of this work was to study the influence of organic carbon, ionic concentration (NaCl) and N/P ratio on the growth of autochthonous biomass and the production of EPS in autotrophic biofilms by measuring the extracellular carbohydrates produced, a specific component of the EPS.     

Waterjet injection of powdered activated carbon for sediment remediation

Purpose  

In situ contaminated sediment remediation through the addition of activated carbon has been proven to be an effective remediation technique. An amendment delivery system was developed to accurately place and inject a powdered activated carbon slurry. The system was set up to deliver a series of discrete injections over a rectangular grid with the objective to deliver 3% carbon (C) by dry weight to an inundated saturated sediment at a maximum sediment depth of 30 cm.     

PCB partitioning during sediment remobilization—a 1D column experiment

Purpose

Remobilization of polychlorobiphenyl (PCB)-contaminated sediments by anthropogenic activities (e.g. dredging) or natural flow conditions could lead to the release of PCBs into the water column and consequently increase the availability of PCBs to benthic organisms. The fate of the released PCBs following such events is not well understood and such knowledge is necessary for the management of contaminated sediments. The objective of this study was to understand the processes that control the fate of PCBs following remobilization of field-aged contaminated sediments.

Materials and methods

Sediments contaminated with PCBs collected from Lake Bourget (Savoie, France) were resuspended in a column experiment. The relationships between physical–chemical parameters—i.e. suspended particulate matter, pH, inorganic and organic carbon content, redox-sensitive species and the concentrations of dissolved PCBs both in the water column and in the interstitial water of the sediment—were investigated so as to determine the key processes controlling PCB fate.

Results and discussion

Following the simulated resuspension event (SRE), dissolved PCBs were found in much higher concentrations in the water column than under stationary conditions. Desorption of PCBs from the sediment depended on the degree of the hydrophobicity of the PCBs and the initial PCB content in the sediment. Principal component analysis showed that the variations in the concentrations of released PCBs over time and space closely followed those of suspended particulate matter (SPM) and not those of redox conditions. The partitioning behaviour of PCBs on SPM showed that equilibrium state was not attained within 40 days following the SRE. A particle size fractionation study, before and after remobilization of the sediment, showed the presence of PCBs in every fraction of the sediment, but with higher amounts in large particles with high organic matter content and in the finest fractions. Remobilization of contaminated sediment did not affect this distribution profoundly but a significant enrichment in PCBs of the clay-sized fraction was observed in the re-settled sediment.

Conclusions

Sediment resuspension induced non-equilibrium conditions in the water column for more than 5 weeks and led to the enrichment with PCBs of the newly formed surface bed sediment. This enrichment was due to the preferential re-sorption of PCBs on clay-sized particles during the SRE and to the physical segregation and accumulation of the less dense particles at the surface of the sediment column; such particles thought to be the principal carriers of contaminants. These changes concerned <0.05 % of the total PCB content.     

Speciation and potential long-term behaviour of chromium in urban sediment particulates

Purpose

Chromium, a potentially harmful element, occurs commonly within the urban sediment cascade as a result of abundant industrial and transport-related sources. The risks that Cr-bearing particles pose to ecosystems and humans depend on the solid-phase chemical speciation of Cr and its environmental mobility. In this study, we adopt an integrated geochemical approach to investigate and determine the long-term fate of Cr in the urban sediment cascade.

Materials and methods

We use bulk chemical digests, sequential chemical extraction analysis, electron microscopy, electron microprobe and microfocus XANES analysis to describe the solid-phase speciation, geochemical characteristics and potential long-term behaviour of Cr in urban particulate matter from both aquatic sediment and road dust sediment (RDS) in Manchester, UK.

Results and discussion

Cr-bearing grains within RDS and aquatic sediment are predominantly iron oxides and alumino-silicate glass grains. Electron microprobe analysis indicates Cr concentrations up to 3300 and 133,400 μg g^?1 in the RDS and aquatic grains, respectively. XANES analysis indicates that Cr(III) is the dominant oxidation state, with only trace amounts of Cr(VI). Importantly, Cr speciation does not appear to have changed between sedimentary environments and the dominance of Cr(III) suggests limited bioavailability or toxicity under predominant environmental (anoxic and neutral pH) conditions in the aquatic sediment sink. Furthermore, geochemical analyses suggest the environmental mobility of Cr in the aquatic sediment sink is low (compared to other toxic metals) due to its association mainly with alumino-silicate glass grains and its inclusion as an integral part of the glass structure.

Conclusions

Industrial glass grains are a major component of urban sediment worldwide. The speciation and geochemical investigations performed in this study suggest most Cr within the urban sediment cascade may be resistant to environmental processes that could mobilise other toxic metals.

     

How effectively does a single or continuous iron supply affect the phosphorus budget of aerated lakes?

Purpose

In lake restoration, the redox sensitivity of iron (Fe)?Cphosphorus (P) compounds has been regarded as detrimental for a sustainable increase in sedimentary P retention since developing low redox potentials release Fe-bound P. Thus, Fe salts alone have rarely been used successfully to inactivate sediment P, and there are no studies on the long-term effects of in-lake Fe applications on P retention. Here, we analyzed for how long, and how efficiently, a single and continuous Fe application can affect the P budget of lakes.

Materials and methods

Two aerated lakes in Berlin, Germany were compared: Lake Tegel (TEG) experienced a continuous Fe supply via its tributaries, while Lake Gro?-Glienicke (GGS) was treated once with Fe in the winter of 1992/1993. By controlling the operation of aerators, their effectiveness on P exchange at the sediment?Cwater interface (non-aerated vs. aerated) was directly compared in spring and autumn between 2008 and 2010. The amount of P controllable by aeration (P _control) was experimentally determined by non-aerated vs. aerated sediment cores (at 10 and 16?°C). Core stratigraphy of Fe was observed by high-resolution ??X-ray fluorescence analysis.

Results and discussion

In TEG, the mobility of Fe was limited due to its sulfidic fixation, and thus Fe only accumulated slightly at the sediment surface (Fe/P ratio, ??3). P _control corresponded to only 4?% of the P content of the lake and 18?% of P loading. Hence, aeration only slightly influenced trophy-relevant epilimnetic P. In GGS, the single Fe application still ensures a high P binding ability of sediment since Fe relocated towards the surface (Fe/P ratio, ??7). P _control corresponded to 38?% of the P content of the lake and 74?% of annual P loading. Thus, the P release is not relevant for the P supply to the epilimnion since with the lake??s overturn P is co-precipitated by the hypolimnetically accumulated Fe.

Conclusions

When external P loading is sufficiently reduced, as in GGS, amendments to Fe precipitants can increase sediment P retention in a redox-dependent manner over the long term. Thus, the redox-dependent mobility of Fe should no longer be regarded as a disadvantage of Fe-containing precipitants. To compensate for co-precipitation and complexation of Fe with sediment organic matter, a high Fe dosage (??200?g?m^?2) is needed.     

Evaluation of the mayfly <Emphasis Type="Italic">Ephoron virgo</Emphasis> for European sediment toxicity assessment

Purpose  

The mayfly Ephoron virgo plays a key role in the ecological recovery in large European rivers. The larvae spend their life in the sediment and are therefore exposed to contaminants in various ways. In this study, the use of E. virgo as a test species for whole sediment bioassays was evaluated. The sensitivity was compared with Hexagenia limbata (a North American mayfly recommended for standard sediment testing). Lead (Pb) was used as a model contaminant.