Leaching Of Sediments Research Articles

Nitrate attenuation potential of hypersaline lake sediments in central Spain: Flow-through and batch experiments

Complex lacustrine systems, such as hypersaline lakes located in endorheic basins, are exposed to nitrate (NO3−) pollution. An excellent example of these lakes is the hypersaline lake located in the Pétrola basin (central Spain), where the lake acts as a sink for NO3− from agricultural activities and from sewage from the surrounding area. To better understand the role of the organic carbon (Corg) deposited in the bottom sediment in promoting denitrification, a four-stage flow-through experiment (FTR) and batch experiments using lake bottom sediment were performed. The chemical, multi-isotopic and kinetic characterization of the outflow showed that the intrinsic NO3− attenuation potential of the lake bottom sediment was able to remove 95% of the NO3− input over 296days under different flow conditions. The NO3− attenuation was mainly linked with denitrification but some dissimilatory nitrate reduction to ammonium was observed at early days favored by the high C/N ratio and salinity. Sulfate reduction could be neither confirmed nor discarded during the experiments because the sediment leaching masked the chemical and isotopic signatures of this reaction. The average nitrogen reduction rate (NRR) obtained was 1.25mmold−1kg−1 and was independent of the flow rate employed. The amount of reactive Corg from the bottom sediment consumed during denitrification was 28.8mmol, representing approximately 10% of the total Corg of the sediment (1.2%). Denitrification was produced coupled with an increase in the isotopic composition of both δ15N and δ18O. The isotopic fractionations (ε of 15N-NO3− and 18O-NO3−) produced during denitrification were calculated using batch and vertical profile samples. The results were −14.7‰ for εN and −14.5‰ for εO.

Investigating uranium distribution in surface sediments and waters: a case study of contamination from the Juniper Uranium Mine, Stanislaus National Forest, CA

The uranium concentrations and isotopic compositions of waters, sediment leachates and sediments from Red Rock Creek in the Stanislaus National Forest of California were measured to investigate the transport of uranium from a point source (the Juniper Uranium Mine) to a natural surface stream environment. The (234U)/(238U) composition of Red Rock Creek is altered downstream of the Juniper Mine. As a result of mine-derived contamination, water (234U)/(238U) ratios are 67% lower than in water upstream of the mine (1.114–1.127 ± 0.009 in the contaminated waters versus 1.676 in the clean branch of the stream), and sediment samples have activity ratios in equilibrium in the clean creek and out of equilibrium in the contaminated creek (1.041–1.102 ± 0.007). Uranium concentrations in water, sediment and sediment leachates are highest downstream of the mine, but decrease rapidly after mixing with the clean branch of the stream. Uranium content and compositions of the contaminated creek headwaters relative to the mine tailings of the Juniper Mine suggest that uranium has been weathered from the mine and deposited in the creek. The distribution of uranium between sediment surfaces (leachable fraction) and bulk sediment suggests that adsorption is a key element of transfer along the creek. In clean creek samples, uranium is concentrated in the sediment residues, whereas in the contaminated creek, uranium is concentrated on the sediment surfaces (∼70–80% of uranium in leachable fraction). Contamination only exceeds the EPA maximum contaminant level (MCL) for drinking water in the sample with the closest proximity to the mine. Isotopic characterization of the uranium in this system coupled with concentration measurements suggest that the current state of contamination in Red Rock Creek is best described by mixing between the clean creek and contaminated upper branch of Red Rock Creek rather than mixing directly with mine sediment.

Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments

The radiogenic neodymium (Nd) isotope composition of foraminiferal shells provides a powerful archive to investigate past changes in sources and mixing of water masses. However, seawater Nd isotope ratios extracted from foraminiferal shells can be biased by contaminant phases such as organic matter, silicates, or ferromanganese coatings, the removal of which requires rigorous multiple step cleaning of the samples. Here we investigate the efficiency of Flow Through and batch cleaning methods to extract seawater Nd isotope compositions from planktonic foraminifera in a shelf setting in the Gulf of Guinea that is strongly influenced by riverine sediment inputs. Nd isotope analyses of reductively and oxidatively cleaned mono-specific planktonic foraminiferal samples and reductively cleaned mixed benthic foraminifera were complemented by analyses of non-reductively cleaned mono-specific planktonic foraminiferal samples, Fe–Mn coatings of de-carbonated bulk sediment leachates, and the residual detrital fraction of the same sediment.Al/Ca and Mn/Ca ratios of fully cleaned foraminiferal samples reveal indistinguishable levels of cleaning efficiency between the batch and the Flow Through methods and the Nd isotope compositions obtained from application of both methods are identical within error. Furthermore, non-reductively cleaned foraminiferal samples have the same Nd isotope composition as reductively cleaned foraminifera at our study sites. Close to the Niger River mouth the Nd isotope composition of the foraminifera agree with the seawater Nd isotope composition of nearby stations. Based on the combined extracted Nd isotope signatures and element to calcium ratios, as well as rare earth element distribution patterns, we infer that the planktonic foraminiferal Nd isotope signatures reflect bottom water/pore water signatures. The isotopic composition of the bulk de-carbonated sediment leachates (Fe–Mn coatings) differs significantly from the foraminiferal data at this site and probably reflects particles that acquired their ferromanganese/pre-formed pre-formed/ferromanganese coatings in nearby rivers. Therefore, in such river influenced shelf settings foraminiferal shells should be used to obtain unbiased bottom seawater signatures.

Dynamics of copper and zinc sedimentation in a lagooning system receiving landfill leachate

This study characterises the sediment dredged from a lagooning system composed of a settling pond and three lagoons that receive leachates from a municipal solid waste (MSW) landfill in France. Organic carbon, carbonate, iron oxyhydroxides, copper (Cu) and zinc (Zn) concentrations were measured in the sediment collected from upstream to downstream in the lagooning system. In order to complete our investigation of sedimentation mechanisms, leachates were sampled in both dry (spring) and wet (winter) seasonal conditions. Precipitation of calcite and amorphous Fe-oxyhydroxides and sedimentation of organic matter occurred in the settling pond. Since different distributions of Zn and Cu concentrations are measured in sediment samples collected downstream in the lagooning system, it is suggested that these elements were not distributed in a similar way in the leachate fractions during the first stage of treatment in the settling pond, so that their sedimentation dynamics in the lagooning system differ. In the lagoons, it was found that organic carbon plays a major role in Cu and Zn mobility and trapping. The presence of macrophytes along the edges provided an input of organic matter that enhanced Cu and Zn scavenging. This edge effect resulted in a two-fold increase in Cu and Zn concentrations in the sediment deposited near the banks of the lagoons, thus confirming the importance of vegetation for the retention of Cu and Zn in lagooning systems.

High-field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter

Abstract. High-performance, non-target, high-resolution organic structural spectroscopy was applied to solid phase extracted marine dissolved organic matter (SPE-DOM) isolated from four different depths in the open South Atlantic Ocean off the Angola coast (3° E, 18° S; Angola Basin) and provided molecular level information with extraordinary coverage and resolution. Sampling was performed at depths of 5 m (Angola Current; near-surface photic zone), 48 m (Angola Current; fluorescence maximum), 200 m (still above Antarctic Intermediate Water, AAIW; upper mesopelagic zone) and 5446 m (North Atlantic Deep Water, NADW; abyssopelagic, ~30 m above seafloor) and produced SPE-DOM with near 40% carbon yield and beneficial nuclear magnetic resonance (NMR) relaxation properties, a crucial prerequisite for the acquisition of NMR spectra with excellent resolution. 1H and 13C NMR spectra of all four marine SPE-DOM showed smooth bulk envelopes, reflecting intrinsic averaging from massive signal overlap, with a few percent of visibly resolved signatures and variable abundances for all major chemical environments. The abundance of singly oxygenated aliphatics and acetate derivatives in 1H NMR spectra declined from surface to deep marine SPE-DOM, whereas C-based aliphatics and carboxyl-rich alicyclic molecules (CRAM) increased in abundance. Surface SPE-DOM contained fewer methyl esters than all other samples, likely a consequence of direct exposure to sunlight. Integration of 13C NMR spectra revealed continual increase of carboxylic acids and ketones from surface to depth, reflecting a progressive oxygenation, with concomitant decline of carbohydrate-related substructures. Aliphatic branching increased with depth, whereas the fraction of oxygenated aliphatics declined for methine, methylene and methyl carbon. Lipids in the oldest SPE-DOM at 5446 m showed a larger share of ethyl groups and methylene carbon than observed in the other samples. Two-dimensional NMR spectra showed exceptional resolution and depicted resolved molecular signatures in excess of a certain minimum abundance. Classical methyl groups terminating aliphatic chains represented ~15% of total methyl in all samples investigated. A noticeable fraction of methyl (~2%) was bound to olefinic carbon. Methyl ethers were abundant in surface marine SPE-DOM, and the chemical diversity of carbohydrates was larger than that of freshwater and soil DOM. In all samples, we identified sp2-hybridized carbon chemical environments with discrimination of isolated and conjugated olefins and α,β-unsaturated double bonds. Olefinic proton and carbon atoms were more abundant than aromatic ones; olefinic unsaturation in marine SPE-DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation. The abundance of furan, pyrrol and thiophene derivatives was marginal, whereas benzene derivatives, phenols and six-membered nitrogen heterocycles were prominent; a yet unassigned set of six-membered N-heterocycles with likely more than one single nitrogen occurred in all samples. Various key polycyclic aromatic hydrocarbon substructures suggested the presence of thermogenic organic matter at all water depths. Progressive NMR cross-peak attenuation from surface to deep marine SPE-DOM was particularly strong in COSY NMR spectra and indicated a continual disappearance of biosignatures as well as entropy gain from an ever increased molecular diversity. Nevertheless, a specific near-seafloor SPE-DOM signature of unsaturated molecules recognized in both NMR and Fourier transform ion cyclotron mass spectrometry (FTICR/MS) possibly originated from sediment leaching. The conformity of key NMR and FTICR/MS signatures suggested the presence of a large set of identical molecules throughout the entire ocean column even though the investigated water masses belonged to different oceanic regimes and currents. FTICR/MS showed abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks and average mass from surface to bottom SPE-DOM. The proportion of CHO and CHNO negative ions increased from surface to depth, whereas CHOS and especially CHNOS molecular series markedly declined. While certain rather aliphatic CHOS and CHNOS ions were observed solely in the surface, deep marine SPE-DOM was enriched in unique unsaturated and rather oxygenated CHO and CHNO molecular series. With the exception of abyssopelagic SPE-DOM at 5446 m, which showed a peculiar CHOS chemistry of unsaturated carbon and reduced sulphur (black sulphur), CHO and CHNO molecular series contributed ~87% to total positive electrospray ionization FTICR mass peak integral, with a near constant ratio of CHNO / CHO molecular compositions near 1.13 ± 0.05. In case of all four marine SPE-DOM, remarkably disparate average elemental compositions as determined from either MS and NMR spectra were observed, caused by a pronounced ionization selectivity in electrospray ionization FTICR/MS. The study demonstrates that the exhaustive characterization of complex unknowns in marine DOM will enable a meaningful classification of individual marine biogeosignatures. Future in-depth functional biodiversity studies with a clear understanding of DOM structure and function might eventually lead to a novel, unified perception of biodiversity and biogeochemistry.

Influence of stream–floodplain biogeochemical linkages on aquatic foodweb structure along a gradient of stream size in a tropical catchment

We measured nutrients and dissolved organic matter (DOM) in surface water and floodplain sediments to evaluate biogeochemical linkages between streams and floodplains in 3 streams of increasing size in a tropical catchment in northwestern Australia. We hypothesized that stream–floodplain biogeochemical connectivity, measured as similar DOM concentrations and spectroscopic properties of streamwater and floodplain sediment leachate, would decrease with increasing stream size. We expected decreasing connectivity to shift support of aquatic foodweb structure from mainly allochthonous C in small streams to algal C in larger streams. Streamwater and sediment leachate concentrations of NH4-N, NO3-N, soluble reactive P, and DOM varied several-fold across the 3 sites but showed no strong pattern in stream–floodplain connectivity with increasing stream size. Fluorescence index, specific ultraviolet absorbance, and δ13C-dissolved organic C (DOC) for stream water and sediment leachate were most similar to each other at the mid-size Adcock River, indicating tight river–floodplain biogeochemical connectivity via input of allochthonous DOM and NH4-N to stream water. δ13C and δ15N signatures for key producers and consumers for all 3 streams showed that invertebrate consumers probably were supported by a range of in-stream (e.g., benthic and filamentous algae) and floodplain (allochthonous leaf litter) sources, whereas fish strongly reflected δ13C-enriched sources (e.g., benthic algae). Allochthonous C was probably only a minor energy source for metazoa, but we propose that river–floodplain biogeochemical linkages may be important for other aspects of ecosystem productivity, such as input of inorganic nutrients to support in-stream primary production. Terrestrial–aquatic biogeochemical linkages may be critical but poorly quantified components of river–floodplain ecosystems.

Reactivity of neodymium carriers in deep sea sediments: Implications for boundary exchange and paleoceanography

The dissolved neodymium (Nd) isotopic distribution in the deep oceans is determined by continental weathering inputs, water mass advection, and boundary exchange between particulate and dissolved fractions. Reconstructions of past Nd isotopic variability may therefore provide evidence on temporal changes in continental weathering inputs and/or ocean circulation patterns over a range of timescales. However, such an approach is limited by uncertainty in the mechanisms and importance of the boundary exchange process, and the challenge in reliably recovering past seawater Nd isotopic composition (εNd) from deep sea sediments. This study addresses these questions by investigating the processes involved in particulate–solution interactions and their impact on Nd isotopes. A better understanding of boundary exchange also has wider implications for the oceanic cycling and budgets of other particle-reactive elements.Sequential acid-reductive leaching experiments at pH ∼2–5 on deep sea sediments from the western Indian Ocean enable us to investigate natural boundary exchange processes over a timescale appropriate to laboratory experiments. We provide evidence that both the dissolution of solid phases and exchange processes influence the εNd of leachates, which suggests that both processes may contribute to boundary exchange. We use major element and rare earth element (REE) data to investigate the pools of Nd that are accessed and demonstrate that sediment leachate εNd values cannot always be explained by admixture between an authigenic component and the bulk detrital component. For example, in core WIND 24B, acid-reductive leaching generates εNd values between −11 and −6 as a function of solution/solid ratios and leaching times, whereas the authigenic components have εNd≈−11 and the bulk detrital component has εNd≈−15. We infer that leaching in the Mascarene Basin accesses authigenic components and a minor radiogenic volcanic component that is more reactive than Madagascan-derived clays. The preferential mobilisation of such a minor component demonstrates that the Nd released by boundary exchange could often have a significantly different εNd composition than the bulk detrital sediment.These experiments further demonstrate certain limitations on the use of acid-reductive leaching to extract the εNd composition of the authigenic fraction of bulk deep sea sediments. For example, the detrital component may contain a reactive fraction which is also acid-extractible, while the incongruent nature of this dissolution suggests that it is often inappropriate to use the bulk detrital sediment elemental chemistry and/or εNd composition when assessing possible detrital contamination of leachates. Based on the highly systematic controls observed, and evidence from REE patterns on the phases extracted, we suggest two approaches that lead to the most reliable extraction of the authigenic εNd component and good agreement with foraminiferal-based approaches; either (i) leaching of sediments without a prior decarbonation step, or (ii) the use of short leaching times and low solution/solid ratios throughout.

Heterogeneous seawater 187Os/188Os during the Late Pleistocene glaciations

We report high temporal resolution osmium isotopes records of bulk sediment and sediment leachates from DSDP Site 480 (Gulf of California) over the last 30ka; from ODP Site 849 (Eastern equatorial Pacific) from the last 200ka and from ODP Site 1002C (Cariaco Basin) across the 9–17ka time interval in order to critically evaluate claims of a global 10% shift in the 187Os/188Os of seawater from glacial to interglacial intervals. We use organic-rich continental margin sites and carbonate-rich pelagic sites to isolate the temporal variations of the osmium seawater isotopic composition. Our results reveal that variations in 187Os/188Os fail to correlate with global changes in temperature across glacials/interglacials cycles as previously claimed. Instead, these results indicate differences of a few percent in the measured 187Os/188Os between each oceanic basin. We argue that these differences strongly suggest that seawater is not well homogenized with respect to its Os isotope composition.

Hexavalent chromium reduction by whole cells and cell free extract of the moderate halophilic bacterial strain Halomonas sp. TA-04

The current study was aimed to characterize a bacterial strain isolated from Cr(VI)-polluted sediments for its role in Cr(VI)-reduction as whole cell and by cell free extract. A new moderately halophilic Cr (VI)-resistant bacterial strain TA-04 was isolated from polluted marine sediments near a stainless steel plant in Southern Italy, 16S rRNA analysis placed the isolate close to the species Halomonas aquamarina. Growth was inhibited at 4.0 mM Cr (VI), and reduction of Cr (VI) in the presence of 80 g l −1 NaCl was highlighted. Immobilized cells showed removal of Cr (VI) from sediment leachate. The cell free extract reduced Cr (VI) with a maximum of activity at pH 6.5 and at temperature of 28 °C, in the presence of NADH. Cr (VI) reduction activity was improved by Cu 2+ and Fe 2+ additions, whereas Hg 2+ depleted it. Free and immobilized cells of the isolate could be used for bioremediation of Cr (VI)-contaminated sites. Cell free extract could represents an alternative in conditions where the whole cells result difficult to apply. A bacterial strain of the genus Halomonas is characterized in term of whole cells and cell-free extract Cr(VI)-reduction. The results suggest a good potential for bioremediation processes, in particular concerning detoxification of saline polluted environments.

Prokaryotic diversity, composition structure, and phylogenetic analysis of microbial communities in leachate sediment ecosystems

In order to obtain insight into the prokaryotic diversity and community in leachate sediment, a culture-independent DNA-based molecular phylogenetic approach was performed with archaeal and bacterial 16S rRNA gene clone libraries derived from leachate sediment of an aged landfill. A total of 59 archaeal and 283 bacterial rDNA phylotypes were identified in 425 archaeal and 375 bacterial analyzed clones. All archaeal clones distributed within two archaeal phyla of the Euryarchaeota and Crenarchaeota, and well-defined methanogen lineages, especially Methanosaeta spp., are the most numerically dominant species of the archaeal community. Phylogenetic analysis of the bacterial library revealed a variety of pollutant-degrading and biotransforming microorganisms, including 18 distinct phyla. A substantial fraction of bacterial clones showed low levels of similarity with any previously documented sequences and thus might be taxonomically new. Chemical characteristics and phylogenetic inferences indicated that (1) ammonium-utilizing bacteria might form consortia to alleviate or avoid the negative influence of high ammonium concentration on other microorganisms, and (2) members of the Crenarchaeota found in the sediment might be involved in ammonium oxidation. This study is the first to report the composition of the microbial assemblages and phylogenetic characteristics of prokaryotic populations extant in leachate sediment. Additional work on microbial activity and contaminant biodegradation remains to be explored.

유지용수 공급형 인공저수지의 수질오염부하 특성 연구

Abstract : The first objective of this study was to investigate water pollution status of Meejae Reservoir, Kunsan, irregularly receiving river water for agricultural and recreational purposes. The second objective of the study was to compare nutrient pollutionloads of three nutrient sources: sediment leaching, non-point sources and the receiving water. Water analysis results showed that eutrophication was a concern especially in summer and the calculated TSI (secchi depth), TSI (chlorophyll-a), and TSI (TP) were 53.6, 57.7 and 56.7, respectively. Although there was no significant difference in seasonal mean values of sediment T-N, sediment T-P and sediment organic content, mean differences were found for sampling points. However, T-N and T-P sediment release flux showed seasonal mean differences, while showing no mean difference for sampling points. Water T-N data proportionally corre-lated with sediment T-N and sediment organic content data, while no statistical correlation was found for water T-P data. Com-parison of nutrient loads calculated from three sources showed that the highest T-N load was occurred from the receiving (pum-ped) water while T-P loads of the receiving water and sediment release flux were similar. The first solution would be considered for the receiving water to improve the water quality of Meejae Reservoir. Reduction of nutrient flux from the sediment would be then tried as the second alternative solution.

Mercury-resistant bacterial strains Pseudomonas and Psychrobacter spp. isolated from sediments of Orbetello Lagoon (Italy) and their possible use in bioremediation processes

This study was aimed to isolate Hg-resistant bacteria from contaminated sediments of the Orbetello Lagoon in Italy and to assess their possible use as biofilms in bioremediation processes. Enrichment cultures prepared from contaminated sediments in the presence of 0.05mM of mercury and under aerobic conditions allowed the isolation of five heterotrophic bacterial strains. 16S rDNA gene sequencing assigned the isolated strains to the genera Pseudomonas and Psychrobacter. For the first time mercury-resistant bacterial strains belonging to the genus Psychrobacter were evidenced. Minimum inhibitory concentrations in the presence of HgCl2 and of CH3HgCl showed high levels of resistance. EC50 values for the isolated bacterial strains in the presence of HgCl2 and of CH3HgCl confirmed the adaptation to the metal. Hg-resistant strains ORHg1, ORHg4 and ORHg5 showed the capacity to volatilize inorganic and organic mercury to elemental mercury, and formed biofilms on pumice particles, and were shown to play a role in the removal of mercury from sediment leachates. This study reports isolation and characterization of new Hg-resistant bacterial strains and provides novel insight into their possible use in bioremediation processes of mercury polluted sediments.

Ecotoxicological Assessment of Sediment Leachates of Small Watercourses in the Brno City Suburban Area (South Moravia, Czech Republic)

Sediments of two small watercourses Leskava and Troubsky Brook in the Brno city suburban area were examined for their ecotoxicity. Using a standard procedure, extracts of the sediments were prepared for diagnostic tests. These extracts were tested for acute toxicity to fresh-water organisms. The ecotoxicological tests were performed on the fresh-water algaPseudokirchneriella subcapitata, the vascular water plantLemna minor, on a representative of invertebrates – the water fleaDaphnia magnaand on theXenopus laevisfrog embryo and luminiscentVibrio fischeribacteria. Possible toxic effects were evaluated using the test determining the inhibition of the growth of white mustard rootSinapis alba. Results of ecotoxicological assessment of sediment leachates showed that their quality varied significantly during the year. Differences were found between results of sediment evaluations from different collection profiles, which may indicate effects of point source pollution. Of the ecotoxicological tests used, the most sensitive organisms included the green algaePseudokirchneriella subcapitata, bioluminiscent bacteriaVibrio fischeriand the African clawed frogXenopus laevis. The highest concentrations of arsenic were found by chemical analysis in both spring and autumn sediment leachate samples collected at Site L1 (Leskava). The highest organic pollutant concentrations were found in autumn sediment leachate samples from Site L1. In total PAH sums, phenanthrene was the dominant pollutant at all the sites investigated.

Mobility and potential bioavailability of traffic-derived trace metals in a ‘wet–dry’ tropical region, Northern Australia

The aqueous mobility and potential bioavailability of metals and metalloids in road runoff in a ‘wet–dry’ tropical location were assessed by analysing metal and metalloid concentrations in particulate, total dissolved and labile dissolved phases in runoff waters. Road-derived Al, Cu, Pb, Sb and Zn concentrations were substantially elevated in runoff when compared to receiving creek waters. Median dissolved concentrations in road runoff exceeded those in creek waters by up to an order of magnitude. Leaching experiments of road sediments confirmed that several metals and metalloids were released in high concentrations from road sediments. Labile Zn and Cu concentrations measured by diffusion gradients in thin films (DGT) showed that almost all dissolved Zn and up to half of dissolved Cu in runoff waters and in road sediment leachate were potentially bioavailable. Comparisons of dissolved metal concentrations in receiving waters affected by road runoff with ecosystem guideline levels, indicated a risk of reaching toxic levels of Cu and Zn in the receiving waters in the absence of adequate treatment or dilution. Low dilution rates of road runoff are likely to occur during late ‘dry’ season/early ‘wet’ season storms which have the potential to produce high metal concentrations derived from long periods of accumulation of road sediment at a time when creek flow rates are at their annual minimum.

Changes in the geochemistry and ecotoxicity of a Zn and Cd contaminated dredged sediment over time after land disposal

The management of dredged sediments is of environmental concern worldwide since they may be overloaded with myriads of pollutants. For inland waters' sediments, disposal on land is a common practice. For the long-term risks assessment of such a management, a better understanding of the fate of pollutants over time and an assessment of possible associated biological consequences are needed. Here, we studied the geochemical distribution of Fe, Mn, Zn and Cd in sediment dredged from the Scarpe canal (Nord-Pas-de-Calais Region, France). Analyses were carried out immediately after dredging and 12, 18 and 24 months after disposal in field conditions. In parallel, ecotoxicity of sediment leachates was assessed using standardized bioassays. The results reflected an initial oxidation of sulphides (first year) followed by changes explained by a reversible binding of metals to organic matter in winter and to Fe oxihydroxides in summer. The water-leachable fraction represented less than 2% of the total metal and its ecotoxicity was higher for deposited sediments than for the fresh one. After first year of disposal, sediment ecotoxicity remained stable. A long-term natural attenuation of metals within disposed sediment seemed unlikely since their speciation seemed to fluctuate seasonally without any time trend over years.

Analysis of Bio‐Obtainable Endocrine Disrupting Metals in River Water and Sediment, Sewage Influent/Effluent, Sludge, Leachate, and Concentrated Leachate, in the Irish Midlands Shannon Catchment

The application of an acid digestion and subsequent solid-phase extraction (SPE) procedure were implemented as preliminary treatments prior to quantifying the levels of potentially endocrine disrupting metals (EDMs) in a variety of solid and liquid matrices. These included (solid) river sediment, leachate sediment and sewage sludge and also (liquid) river water, landfill leachate, concentrated leachate, sewage influent, and sewage effluent, sampled in the Irish Midlands. The total concentrations of cobalt (Co), cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and manganese (Mn), after extraction and preconcentration, were determined by atomic absorption spectroscopy (AAS). Mercury (Hg) in sediment and sludge was determined using cold-vapour atomic fluorescence spectroscopy (AFS). For sewage sludge maximum values (mg/kgdw) of 4700 Ni, 1642 Mn, 100.0 Cd, 3400 Zn, 36.70 Co, 750.0 Pb, 485.8 Cr, and 1003 Cu were determined whilst in leachate sediment, maximum values (mg/kgdw) of 32.10 Ni, 815.0 Mn, 32.78 Cd, 230.3 Zn, 26.73 Co, 3525 Pb, 124.9 Cr, and 50.13 Cu were found. Over several months, the data showed elevated levels in sewage influents, effluents, and sludges compared to a battery of adjacent river water samples and corresponding sediments. There was a definite trend for target values for sediments to be exceeded, while intervention values were only exceeded for cadmium. Overall the pattern in terms of concentration was sewage > leachate > river matrices. A nonparametric assessment of the effect of sewage treatment method on median metal levels in sludge revealed statistically significant differences at the 95% level of confidence for Co, Cr, and Hg and at the 90% level of confidence for Cd.

Uranium in Municipal Solid Waste Landfill Leachate

Landfill leachates and leachate sediments were investigated in order to survey the discharge of uranium (U) from municipal solid waste (MSW) landfills and municipal solid waste incinerator (MSWI) bottom ash landfills. Concentrations of U in the leachates were as high as or higher than concentrations of Cd, a metal more often discussed when considering the environmental effects of landfill leachate. However, the U concentrations in leachate were no greater than levels occurring naturally in water. The U concentrations in leachate sediments were also the same as or lower than those reported in lake sediments around the world. Size charge fractionation of U in freshly sampled leachate showed that the metal was present mainly as either non-labile dissolved complexes or free anions, which have intermediate to high mobility and eco-toxicity. This is in contrast to other heavy metals, such as Cd, which are generally particulate bound in leachate. However, based on all the results of the investigations, it was concluded that leaching of U is not of major concern in MSW and MSWI bottom ash landfills.

Accelerated solvent-based extraction and enrichment of selected plasticisers and 4-nonylphenol, and extraction of tin from organotin sources in sediments, sludges and leachate soils

Enrichment techniques have become an important feature in the trace analysis of oestrogen mimicking chemicals in the environment. Recent developments such as accelerated solvent extraction (ASE) have improved extraction recoveries in a wide variety of solid matrices including sediments, sludges and leachate soils. Such samples taken from the Irish Midlands Shannon Catchment region during the winter of 2004/5 and suspected to contain certain xenooestrogens or hormonally active agents were extracted using this technique, which was then coupled with high performance liquid chromatography (HPLC) for quantification purposes. ASE was thus employed to both isolate and pre-concentrate targeted analytes using the minimum amount of solvent hence making extractions more conservational. Two simple, yet extremely sensitive liquid chromatographic methods were developed based on UV detection; one for phthalates and one for alkylphenols, with recoveries reaching up to 92.0%. Acid digestion was used for the extraction of the tin and organotin compounds with analysis by polarography. In river sediment, levels of up to 24.4 mg kg −1 phthalate, 1.14 mg kg −1 4-nonylphenol and 118 mg kg −1 tin were found. In leachate sediments, values up to 49.8 mg kg −1 phthalate, 1.57 mg kg −1 4-nonylphenol, and 36.0 mg kg −1 tin were determined. In sludge, values up to 174 mg kg −1 phthalate and 22.8 mg kg −1 4-nonylphenol were quantified. The highest value of tin (118 mg kg −1) was found present in an area of high leisure craft activity. Typical sediment levels of tin at other river locations ranged between 1.20 and 37.5 mg kg −1.

Sorption behavior of heavy metal species by soakaway sediment receiving urban road runoff from residential and heavily trafficked areas

Groundwater contamination by heavy metals from infiltration facilities receiving road runoff is of potential concern. In this study, sorption tests were conducted to evaluate the influence of the water quality of road runoff, especially dissolved organic matter (DOM), on the sorption of heavy metal species by soakaway sediment. Sequential batch tests were conducted to assess metal sorption by the soakaway sediment receiving road runoff from residential and heavily trafficked areas. Ni was adsorbed by the sediment, indicating that soakaway sediments function to prevent groundwater contamination by Ni. In contrast, Zn was released from the soakaway sediment in sorption tests using heavily trafficked road dust leachates. Ni, Cu, Zn, and dissolved organic carbon concentrations were higher in soakaway sediment leachates obtained by sorption tests using heavily trafficked road dust leachates than those using residential road dust leachates, suggesting traffic activities contaminate these pollutants. A large portion of Zn, released from the soakaway sediment, existed as stable complexes. DOM in road runoff possibly enhances the release of Zn from the sediments within infiltration facilities and might cause groundwater contamination.

Pesticides in Norwegian Landfill Leachates

Pesticides have been analyzed in 28 grab samples of untreated and 12 samples of treated leachate from eight Norwegian municipal solid waste (MSW) landfills, over a period of 10 years, with the purpose to screen for compounds and to evaluate the removal in different treatment systems. Also 1 grab samples of leachate sediments is included. A total of 12 compounds were detected. The most frequently detected group of compounds are the phenoxy acids, and they also occur in highest concentrations, up to 230 μg/l for mecoprop, in this study. Also three fungicides and one insecticide were detected, but in much lower concentrations. All samples exceeded the maximum limit value (MLV) for the sum concen- tration of pesticides in drinking water (0.5 μg/l), and six compounds exceeded the environmental toxicity limit (ETL). Re- verse osmosis showed good removal of phenoxy acids, while sequential batch reactor aerobic treatment, as well as aerated lagoons in combination with wetlands, groundwater infiltration and reactor treatment showed slightly lower removal.