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1.

Purpose

Traditionally, methods for sediment extractions are characterised using chemical analyses. However, in order to evaluate sediment extracts with regard to biological effects and, thus, bioaccessibility, extraction methods have to be compared to effect data obtained from experiments with in situ exposure scenarios, i.e., sediment contact tests. This study compares four extraction methods and sediment contact test data from a previous project with respect to predictive power in the fish embryo test with zebrafish (Danio rerio).

Materials and methods

A natural and an artificial sediment spiked with a mixture of six organic pollutants (2,4-dinitrophenol, diuron, fluoranthene, nonylphenol, parathion and pentachlorophenol) were extracted using (a) membrane dialysis extraction (MDE), (b) a Soxhlet procedure, (c) hydroxypropyl-??-cyclodextrin (HPCD) or (d) Tenax®-TA. Whereas the former two are regarded being exhaustive with respect to non-covalently bound contaminants, the latter two are considered to predict bioaccessibility. Resulting extracts were tested in the fish embryo assay with D. rerio for embryotoxic and teratogenic potential.

Results and discussion

Mortalities caused by organic extracts from Soxhlet extraction and MDE were high. However, HPCD extracts turned out to be at least as effective as extracts obtained with these two methods. One possible reason might be short ageing time of the spiked sediments. Only Tenax®-TA extracts gave results comparable to the sediment contact assay for natural sediment, but revealed low reproducibility. Significant differences between natural and artificial sediment were found for extracts obtained with techniques using native (i.e., non-freeze-dried) sediments, i.e., HPCD and Tenax®-TA. In contrast, MDE and Soxhlet extracts used freeze-dried sediment and did not differentiate between natural and artificial sediment. Therefore, freeze-drying has likely altered and equalised sediment properties that influence accessibility, such as composition of bacterial communities and organic matter quality.

Conclusions

Four extraction methods were successfully characterised with respect to their stringency and predictiveness for bioaccessibility. MDE was confirmed as an alternative to Soxhlet extraction. High mortalities induced by HPCD extracts underline the need to include ageing into consideration when assessing sediments. Although Tenax®-TA may basically be used to predict bioaccessibility in the fish embryo test, the high variability observed warrants further investigation of the relation between effect and extractability. Apparently, freeze-drying can severely affect sediment properties, potentially eliminating individual properties of natural sediments.  相似文献   

2.

Purpose

Obtaining a better understanding of the concentrations and origins of polycyclic aromatic hydrocarbons (PAHs) in the sediments Taihu Lake, China, is of paramount importance for the environmental protection and remediation of this lake. To investigate temporal and spatial variations in PAH concentrations, composition and possible source categories, 29 sediment samples were collected from Taihu Lake during both the flooding and dry seasons of the lake.

Materials and methods

Fifteen US Environmental Protection Agency priority PAHs were detected in 58 surface sediments (29 for each season) by gas chromatograph/mass selective detection, following extraction by accelerated solvent extraction.

Results and discussion

The concentrations of the total and individual PAHs in the flooding season were higher than those in the dry season, suggesting that high levels of fishing activity may be an important contributor to PAH pollution in the flooding season. The fractions of high molecular weight PAHs in the flooding season ranged from 63?% to 71?% and were higher than those in the dry season (which ranged from 52?% to 65?%). These results indicate that vehicle exhaust may be a more important pollutant source in the flooding season than in the dry season. Diagnostic ratios, principal component analysis and hierarchical cluster analysis were used to study possible source categories in the different seasons. Consistent results were obtained for all techniques. Seasonal and spatial variations were also investigated by the coefficient of divergence method. The results of previous studies support the conclusion of source identification.

Conclusions

Vehicle emissions were the dominant contributor to PAHs in the flooding season, while PAHs in the dry season sediments may have come from multiple sources. The findings of this study may provide a theoretical basis for seasonal PAH control strategies for Taihu Lake.  相似文献   

3.

Purpose

The assessing bias of rhizosphere effect on polycyclic aromatic hydrocarbons (PAHs) degradation in soils would come out from formation of nonextractable PAHs and extractability difference of various solvents. The aim of this study was to evaluate the role of rhizosphere effect in long-term PAHs polluted soils by using sequential extraction approach.

Material and methods

The scheme of sequential extraction included methanol/water extractable PAHs, butanol extractable PAHs, DCM extractable PAHs, humic acid-bound PAHs, crude humin-bound PAHs, and organic-C enriched humin-bound PAHs. PAHs in plant tissues were extracted by dichloromethane after saponifying. The correlations between PAHs in plant tissues and sequentially extracted fractions were generated by partial least squares regression.

Results and discussion

The profiles of sequentially extracted PAHs varied with plant species. The discrepancy of toxicity equivalency concentrations between rhizosphere and bulk soils was much more significant than that of total PAHs concentrations. In partial least squares regression models, the concentration of PAHs in plant tissues was correlated with fractions strongly associated with soil.

Conclusions

The novelty of this study is the evaluation of concentration and toxicity equivalency concentration of PAHs in rhizosphere of crops sampled in a field polluted with PAHs for long term. This study has highlighted more significant role of rhizosphere in cleanup of cancerogenic toxicity of soil than amount of PAHs in polluted soils.  相似文献   

4.

Purpose

The management of sediments from stormwater infiltration basins is nowadays a key issue for local authorities to ensure long-term performance. Speciation of pollutants is particularly required in view of reuse of these materials. If fractionation of trace metals in sediments is relatively well described, polycyclic aromatic hydrocarbons (PAHs) speciation was only studied using particle size distribution. Therefore, this study aims at the characterization of the PAHs-bearing fractions in sediments.

Materials and methods

Three sediments with various physicochemical properties were sampled in the west and north of France to characterize the distribution of PAHs among organic and inorganic components. Respective organic and inorganic matrixes were obtained by alkaline extraction and methyl isobutyl ketone (MIBK) fractionation procedure. The nature of the solid fractions was assessed through microanalyses: infrared spectroscopy (Fourier transform infrared spectroscopy), X-ray diffraction (XRD), and scanning electron microscopy with X-ray spectroscopy. Bulk sediments and extracted fractions were analyzed for organic matter parameters: elemental analysis (C, N, and H), total organic matter, total organic carbon, hydrocarbons (C10–C40), and PAHs.

Results and discussion

The characterization of bulk sediments highlighted that they were mainly composed of single particles, originating from the geological background, and aggregates (10 to 300 μm) composed of minerals and large organic matter content. The C/N ratio and PAH ratios were shown to be helpful for the determination of the natural or anthropogenic origin of organic matter or to evaluate additional contribution of industrial activities. The fractionation results underlined the role of the aggregates on the distribution of PAHs. Humin fraction and bound-humic acids were mainly composed of aggregates (10 to 150 μm) and accounted for 60 to 70 % of sample mass. The PAHs are mainly sequestrated in these fractions. Only up to 1 % of PAHs are adsorbed on the mineral fraction.

Conclusions

Both alkaline extraction and MIBK procedure demonstrated that PAH residues were readily sequestrated in humin and bound-humic acids fractions and that fulvic acids, humic acids, and mineral fractions contained poor concentrations of PAHs. Microanalyses underlined the high level of aggregation of particles in sediments and their mixed inorganic and organic nature. In case of stormwater sediments, the location of PAHs in highly organic aggregates is consistent with their sources, being both oil products and debris from vehicles and road.  相似文献   

5.

Purpose

The purpose of this study was to elucidate historical trends, spatial variations, and the sources of polycyclic aromatic hydrocarbons (PAHs) pollution in several Japanese lakes.

Materials and methods

The vertical distributions of PAHs in the core samples of sediments taken at several points in lakes Kasumigaura, Suwa, Kizaki, and Shinji were determined using a gas chromatograph equipped with a mass selective detector and combined with chronological information and the physical/elemental properties of the sediment.

Results and discussion

Seventeen related compounds (congeners) typically had concentration peaks at sediment depths corresponding to the 1960s to 1970s. In Lake Shinji and one bay of Lake Kasumigaura, there was a tendency for PAH concentrations to increase downstream; in contrast, another bay of Lake Kasumigaura showed the reverse trend. During big flood events, the fluxes of PAHs increased due to large inputs of particulate matter, although PAH concentrations were reduced. For the four study lakes and other similar lakes, PAH concentrations of surface sediments were approximately proportional to population densities in the respective watersheds, while the total input of PAHs to the lakes were correlated with their population and watershed area. The source apportionment analysis using isomer ratios for the congener profiles indicated that the principal sources of the PAHs in the lake sediments were gasoline and/or diesel engine exhausts and biomass burning.

Conclusions

The observed concentration peaks showed a deterioration of the chemical quality of atmospheric conditions around 1960?C1970 and a recent tendency for their amelioration. Between-lake differences suggest that the influence of human activity in the watersheds influences sediment PAH concentrations. The PAH sources were identified to be of pyrogenic origin.  相似文献   

6.

Purpose

One of the central issues related to global changes in weather is the increasing occurrence of flood events that can result in the re-suspension of contaminated sediments in rivers. Here, we report on a proof-of-concept study combining hydraulic engineering and ecotoxicology in a new interdisciplinary approach to assess the toxicity of re-suspended polluted sediments after a simulated flood event.

Materials and methods

Rainbow trout (Oncorhynchus mykiss) were exposed for 5 days under simulated flood conditions in an annular flume with artificial sediments that were spiked with a mixture of polycyclic aromatic hydrocarbons (PAH) at environmentally relevant concentrations. Specifically, the objective of this study was to bridge the gap between the physical re-suspension of pollutants and resulting toxicological impacts on aquatic organisms. A suite of different molecular, biochemical and histological markers was used to test the hypothesis that re-suspension of sediments can lead to re-mobilization of PAHs and subsequently to effects on aquatic organisms.

Results and discussion

The micronucleus frequency was significantly 4.3-fold elevated after exposure. There was no significant indication of Aryl hydrocarbon receptor signaling (no EROD induction or increased CYP1A protein content, only slight induction of CYP1A gene expression). Biliary metabolite concentration was the most sensitive marker of PAH exposure. Results for other biomarkers (glutathione-S-transferase, catalase and lipid peroxidation) were inconclusive.

Conclusions

In combination with chemical analyses of suspended matter, the presented approach will be used to improve understanding of the re-mobilization of pollutants from sediments in support of environmental risk assessment.  相似文献   

7.

Purpose

The single-step sodium hydroxide?Cethylenediaminetetraacetic acid (NaOH?CEDTA) extraction is currently the most common preparation technique for the measurement of organic phosphorus (P) composition in sediments using solution 31P nuclear magnetic resonance (NMR). In this study, detailed investigations were conducted to evaluate the performance of this technique, with an objective of finding an optimal procedure for the measurement of sediment organic P.

Materials and methods

A single-step extraction with NaOH?CEDTA was investigated on two types of sediment, i.e., Fe/Al-rich sediment and calcareous sediment. The influence of different sediment preparation methods, NaOH?CEDTA compositions, solid:solution ratios, extraction time, pre-concentration techniques, and NMR sample frozen storage time on P extraction and solution 31P NMR analysis were investigated.

Results and discussion

Both air- and freeze-drying increased organic P extraction for the calcareous sediment. An extraction time of 16?h was sufficient for quantitative recovery of extracted organic P for both Fe/Al-rich and calcareous sediments. The use of a 1:8 solid:solution ratio achieved stronger NMR signals and greater P diversity than the use of a 1:20 ratio. Extraction of the two sediments with 0.25 NaOH?C50?mM EDTA favored 31P NMR detection by reducing the relaxation times required and the risk of organic P degradation compared to the use of stronger NaOH?CEDTA solutions. Rotary evaporation was a better technique for pre-concentration of the NaOH?CEDTA extracts than freeze drying. The concentrated extracts could be preserved by freezing (?20?°C) for at least 2?months.

Conclusions

An optimized procedure was developed based on these investigations, including freeze-drying of fresh sediments, extraction with 0.25?M NaOH?C50?mM EDTA for 16?h using a solid:solution ratio of 1:8, pre-concentration of the extract to the level of ??10 times of its original concentration using rotary evaporation, and storage of the NMR sample at ?20?°C until 31P NMR analysis.  相似文献   

8.

Purpose

Polycyclic aromatic hydrocarbons (PAHs) are largely accumulated in soils in China. The immobilized-microorganism technique (IMT) is a potential approach for abating soil contamination with PAHs. However, few studies about the application of IMT to contaminated soil remediation were reported. Due to recalcitrance to decomposition, biochar application to soil may enhance soil carbon sequestration, but few studies on the application of biochars to remediation of contaminated soil were reported. In this study, we illustrated enhanced bioremediation of soil having a long history of PAH contamination by IMT using plant residues and biochars as carriers.

Materials and methods

Two PAH-degrading bacteria, Pseudomonas putida and an unidentified indigenous bacterium, were selected for IMT. The extractability and biodegradation of 15 PAHs in solution and an actual PAH-contaminated soil amended with immobilized-bacteria materials were investigated under different incubation periods. The effects of carriers and the molecular weight of PAHs on bioremediation efficiency were determined to illustrate their different bio-dissipation mechanisms of PAHs in soil.

Results and discussion

The IMT can considerably enhance the removal of PAHs. Carriers impose different effects on PAH bio-dissipation by amended soil with immobilized-bacteria, which can directly degrade the carrier-associated PAHs. The removal of PAHs from soil depended on PAH molecular weight and carrier types. Enhanced bio-dissipation by IMT was much stronger for 4- and 5-ring PAHs than for 3- and 6-ring ones in soil. Only P400 biochar-immobilized bacteria enhanced bio-dissipation of all PAHs in contaminated soil after a 90-day incubation.

Conclusions

Biochar can promote bioremediation of contaminated soil as microbial carriers of IMT. It is vital to select an appropriate biochar as an immobilized carrier to stimulate biodegradation. It is feasible to use adsorption carriers with high sorptive capabilities to concentrate PAHs as well as microorganisms and thereby enhance dissipation of PAHs and mitigate soil pollution.  相似文献   

9.

Purpose

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and persistent contaminants in aquatic bed sediments. A better understanding of their in-bed fate and transport is therefore key in minimising the risk to the environment over time through various remediation and monitoring strategies. Since ecological effects and risks are related to contaminant concentrations, this study developed CoReTranS, a predictive model that simulates one-dimensional organic contaminant reaction and transport in bed sediments.

Materials and methods

CoReTranS was benchmarked against analytical solutions of simplified reactive transport models and validated using a published study of marsh sediments contaminated with petroleum-derived hydrocarbons from Wild Harbour, West Falmouth, MA, USA.

Results and discussion

The CoReTranS model effectively predicted the vertical distribution of PAHs in the Wild Harbour sediments as confirmed by the modelling results from the published study. The CoReTranS model was also used to interpret results from a published study of PAH-contaminated fjord sediments from Kitimat Arm in British Columbia, Canada. Specific insights into the post-depositional fate and transport of selected PAHs in the Kitimat fjord sediments were obtained by comparing the measured concentration-depth profiles with the numerical results from the CoReTranS model. Key parameters such as effective diffusivity of contaminants and burial velocities of sediment particles were shown to possibly account for the predicted concentrations-depth profiles in the Kitimat fjord sediments.

Conclusions

As demonstrated, CoReTranS can simulate reactive transport models in order to predict PAH concentration profiles in porewater under site-specific conditions. The information derived from the use of the CoReTranS model highlighted practical application of such information by engineers to site-specific risk assessment and remediation.  相似文献   

10.

Purpose

This study addresses the feasibility of a flotation technique, using a lab-scale flotation cell, to simultaneously remove both metals and polyaromatic hydrocarbons (PAHs) from fine sediment fractions (<250 μm) that are potentially contaminated with copper (Cu).

Materials and methods

A multiple flotation process with three consecutive flotation stages was performed on three sediments (13S, 14B, and 24A) with different particle size distributions, Cu and PAH concentrations, and organic matter contents.

Results and discussion

Flotations performed under selected conditions allowed for significant removal of both Cu (61–70 %) and PAHs (75–83 %) with acceptable froth recoveries of approximately 23–29 %. Removal rates for arsenic, lead, and zinc were 48–61, 40–48, and 32–36 %, respectively. Flotation selectivity of Cu was greatly influenced by the contents of fine particles and organic matter of the sediments. The maximum flotation selectivity was obtained for the 53–125-μm size fraction. The high flotation selectivity of Cu (2.5–3.2) and PAHs (3.0–3.6) demonstrated the feasibility of flotation to treat soils or sediments containing both organic and inorganic pollutants.

Conclusions

Overall, the flotation results showed a high selectivity for both Cu and PAHs and demonstrated the feasibility of flotation to treat media contaminated with organic and inorganic contaminants.  相似文献   

11.

Purpose

Flood events are expected to increase both in intensity and frequency due to climate change in the near future. From an environmental toxicology perspective, there is concern that such flood events could lead to the remobilization of contaminated sediment layers in rivers. The aim of this pilot study was to establish a novel and interdisciplinary framework combining methods of hydrodynamic engineering and ecotoxicological assessment to enable investigation of the potential risks associated with such remobilization events.

Materials and methods

Formulated sediment was prepared according to OECD guideline 218 and spiked with a mixture of four polycyclic aromatic hydrocarbons (phenanthrene, chrysene, pyrene, benzo[a]pyrene) at concentrations of 3.3?C8.3?mg?kg?1 dry weight. Rainbow trout (Oncorhynchus mykiss) were exposed as test animals to re-suspended sediments in three out of five experiments. The experiments were carried out in an annular flume designed to investigate transport behaviour of fine-grained sediments. Several physicochemical (e.g. pH) and sedimentological (e.g. turbidity) parameters were measured to characterise environmental conditions and erosion behaviour of sediments. Furthermore, exposure concentrations were measured by means of an in vitro assay (7-ethoxyresorufin-o-deethylase (EROD), RTL-W1 cell assay) and chemical analysis.

Results and discussion

Preparation and spiking of large amounts of formulated sediments were feasible but not practical. Successful spiking could be confirmed by the bioanalytical methods with the spiked sediments showing significantly elevated EROD induction compared to control sediments. Conditions within the annular flume remained stable throughout all experiments and were adequate to support rainbow trout. Flood events were successfully simulated, resulting in re-suspension of formulated sediment. Different erosion behaviours of sediments during the simulated flood events were observed and could be associated with changes in microbial composition of sediments due to differences in storage conditions. Therefore, maintaining constant storage conditions of formulated sediments is crucial to enable consistency and comparability among erosion experiments.

Conclusions

This study clearly demonstrated the feasibility of a combined hydro-toxicological approach in support of the investigation of the potential ecotoxicological relevance of sediment re-suspension events. However, based on the results presented here, it is recommended to include additional physicochemical parameters, such as redox potential and conductivity, and to extend the experimental setup to natural sediments and different aquatic organisms. Future studies will use natural sediments containing representative microbial communities and extracellular polymeric substances to enable extrapolation from the annular flume to conditions in natural flowing waters.  相似文献   

12.

Purpose

Understanding the fate and behavior of polycyclic aromatic hydrocarbon (PAH) sources in aquatic systems is important for the efficiency of control policies. In this work, a new approach??organic carbon-normalized sediment?Cpore water partition coefficients of PAH source contributions (logK??Osource)??was developed to study the sediment?Cpore water partition of PAH source contributions. The focus of this study was the Yellow River, which is the second largest river in China and one of the largest rivers in the world.

Materials and methods

Sixteen priority US Environmental Protection Agency PAHs were analyzed in 14 surface sediments and 11 pore water samples. Principal component analysis?Cmultiple linear regression (PCA-MLR) and Unmix models were employed to estimate the source contributions of PAHs in sediments and pore water samples. Finally, logK??Osource values were calculated according to the modeled source contributions of PAHs.

Results and discussion

??PAHs (sum of the 16 PAH concentrations) in 14 sediment samples and 11 pore water samples from the Yellow River were 1,415?±?726?ng?g?1 dry weight (dw) and 123?±?57.4???g?l?1, respectively. The source apportionment results indicate the following: (1) for sediment samples, the contributions to ??PAHs from vehicular emissions, coal combustion, and petrogenic sources were 41.07?C61.05, 38.83?C45.56, and 11.18?C14.92?%, respectively, and (2) for pore water samples, vehicular emissions were the most significant contributor (45.51?C69.39?%), followed by petrogenic sources (29.80?C34.22?%) and coal combustion (7.35?C21.59?%). Coal combustion had the highest logK??Osource values (4.15?C4.26) among the three categories, followed by vehicular emissions (3.51?C3.57) and petrogenic sources (3.30?C3.43).

Conclusions

The possible categories of PAH sources identified by hierarchical cluster analysis, PCA-MLR, and Unmix models were consistent, indicating that vehicular emissions, coal combustion, and petrogenic sources were three important categories. The logK??Osource values indicate that contributions from coal combustion had a higher partition for the sediment phase compared with the other two source categories.  相似文献   

13.

Purpose

The aim of this study was to assess the applicability of ionic liquids (ILs) in the extraction of organic contaminants from sediments and in passive sampling as a receiving phase material.

Materials and methods

Solutions of two water-soluble ionic liquids (WSILs)—1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIm]BF4) and N-butyl-3-methyl pyridinium tetrafluoroborate ([BMPy]BF4)—were used for the extraction of endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA), 17β-estradiol (E2), and nonylphenol (NP), from different sediments. Furthermore, a hydrophobic IL (1-hexadecyl-3-methyl imidazolium hexafluorophosphate) was filled in a polyethylene (PE) membrane tubing to build an IL-PE passive sampler for sediment pore water. Uptake kinetics were studied by exposing samplers to sediments artificially contaminated by EDCs and identified by exposing samplers to field-contaminated sediments.

Results and discussion

EDCs were efficiently extracted by WSIL solutions from the two artificially contaminated sediments, with maximum extraction efficiencies of 84.2–104.6 % by the [BMIm]BF4 solution and 74.9–103.7 % by the [BMPy]BF4 solution. However, WSIL solutions are not suitable for EDC extraction from sediment with very low organic carbon contents. EDCs in sediment pore water can be efficiently taken up by the IL-PE sampler, with uptake rate constants of 2.08?×?10?2?l?g?1?day?1 (BPA), 5.74?×?10?2?l?g?1?day?1 (E2), and 2.10 l?g?1?day?1(NP).

Conclusion

BPA, E2, and NP can be extracted efficiently by IL water solution from most of the artificially and field-contaminated sediments used in this study. The IL ([HDMIm]PF6)-PE passive sampler can be used to monitor EDCs in the pore water of sediments. A good match between the calculated and measured concentrations of BPA and E2 in pore water of field-contaminated sediments was observed.  相似文献   

14.

Purpose

A multi-compartment monitoring study was performed to characterize the effect of environmental variables, such as temperature and water flow as well as sediment characteristics, on the distribution and transport of persistent organic pollutants (POPs) in a dynamic river system during 1 year in an industrial region in central Europe.

Materials and methods

Waterborne polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed over a period of 1 year at five sampling sites in the Morava River in the Czech Republic. Contaminants were measured monthly in riverbed sediments, freshly deposited sediments, water samples and passive samplers.

Results and discussion

Sediments are the main carrier of POPs in the river. Distinguishable patterns of PAHs, OCPs and PCBs in sediment indicate that their origin is from distinct sources and different transport pathways. The PAHs were identified as the dominant contaminant group of compounds with a mean concentration in sediment of 5,900 μg kg?1. Such concentrations are up to 10 times higher than in the Danube River, into which Morava drains. In contrast, mean concentrations of PCBs, hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane and its breakdown products (DDTs) and hexachlorobenzene (HCB) of 6.0, 0.4, 4.2 and 6.0 μg kg1, respectively, are similar to those in the Danube. With some exceptions, no significant difference in composition of surficial riverbed sediments and those collected using sediment traps was observed. Despite the presence of potential local pollutant sources, the differences in contaminant concentrations between sites in the region were in most cases not significant. Variations in POP concentrations in sediments are mainly induced by high flow events, whereas seasonal variability was not observed.

Conclusions

The changes in contaminant concentrations in Morava River sediments are induced by episodic high flow events that cause erosion of contaminant-containing particles and their deposition at suitable downstream sites.  相似文献   

15.

Purpose

The structure and properties of the soil organic matter and its interactions with solutes may be altered by changes in soil chemistry and by the aging of soil. The main objective of this study was to investigate the effect of long-term aging and cation saturation of soil on the extractability and degradability of two hydrophobic xenobiotics in soil. In addition, it was tested if drying or freezing of soils can accelerate the relevant aging processes.

Materials and methods

The sandy topsoil was treated by either 0.1?M NaCl, CaCl2, AlCl3 solutions or water and samples were sterilized by ??-radiation and spiked with 14C-labeled nonylphenol (NP) or phenanthrene (Phe) at 10???g?g?1 of soil. Samples were then used in four parallel experimental setups: (1) 9?months of aging under sterile conditions, (2) inoculation by native original soil with further 7?months of aging (bioaging), (3) drying and wetting or (4) freezing and thawing of soils. After different time intervals, the extractability of xenobiotics with water, cyclodextrin, and ethanol was investigated.

Results and discussion

During 9?months of aging under sterile conditions a continuous decrease of NP and Phe extractability and an increase of the non-extractable fraction occurred. During the 7?months of biologically active aging, the mineralization of NP was lower than of Phe while more NP remained extractable than Phe. In comparison to the sterile aging, the bioaging led to a less formation of non-extractable residues of NP and Phe. The long-term sterile aging effects on NP-extractability were also achieved by short-term freezing and thawing of the soils, while aging of Phe was better mimicked by drying?Cwetting cycles. The effects of cation saturation of soils on xenobiotics extractability were less pronounced.

Conclusions

Sterile aging, bioaging, freezing, and thawing facilitate the formation of the non-extractable fraction of NP and Phe in the soils. Different cation treatments alter soil properties, but the effects on aging of NP and Phe in soils were negligible.  相似文献   

16.
Specific stability of organic matter in a stormwater infiltration basin   总被引：1，自引：0，他引：1  

Purpose

In stormwater infiltration basins, sediments accumulate at the soil surface and cause a gradual filling up of soil pores. These sediments are composed of a mixture of natural and anthropogenic (as oil products) organic matters (OMs). The degradation kinetics of these sediment OMs and their biological stability has been neglected. This study aimed to characterize sediments OMs to assess their evolution and their capacity to degrade.

Materials and methods

To characterize OMs from the sediment layer, we measured at several places in the infiltration basin, total OM and carbon (C) contents, C distribution and biochemical fractions of the OM in the different size fractions, the sediment’s C mineralization potential, soil microbial biomass, and organic pollutants (polycyclic aromatic hydrocarbons (PAHs)) in the sediment layer.

Results and discussion

OM contents were high and varied from 66 to 193 g?kg?1 from the inlet to the outlet of basin. Depending on rainfall intensity and volume, organic particles were deposited at varying distances in the basin by decantation; this was confirmed by analysis of sediment C distribution in the different size fractions. Despite high amounts of OM, organic C had a low biodegradability. Mineralization potentials were low compared to natural soil (i.e., from 0.3 to 1.1 g CO2–C kg?1 total organic carbon). Biochemical fractionation of the organic fractions indicated that they were mainly composed of a soluble fraction, which contributed to reducing OM biodegradability. The activity of the sediment microbial biomass was low. PAH contents seemed to be partly responsible for the high biostability of OMs.

Conclusions

There was limited capacity for biodegradation of sediment OMs probably due to inhibitory effects of soluble PAHs and consequently low microbial activity.  相似文献   

17.

Purpose

Excess nutrients such as phosphorus (P) transported from the Everglades Agricultural Area (EAA) in South Florida, USA, to downstream water bodies have been identified as contributing to trophic imbalances within the Florida Everglades. Decades of farming drainage from the EAA has led to accumulation of sediments in regional canals which may be transported to downstream ecosystems and act as potential internal source of P.

Materials and methods

Intact sediment cores were collected from three main conveyance and three farm canals within the EAA. Physicochemical assessment, mineralogy, P speciation, and storage were determined for surface and subsurface layers.

Results and discussion

The main conveyance canal sediments had higher total P (TP) concentrations (1,280?±?360?mg?kg-1) than the farm canals (960?±?540?mg?kg-1), while farm canal sediments showed higher organic matter content (28?C53?%) compared to the main canal (24?C27?%) sediments. The minerals found in main conveyance canal sediments were similar to those found in Lake Okeechobee. The labile KCl?CP fraction comprised <2?% of TP from all canal sediments, while NaOH?CPi (i?=?inorganic) fraction consisted of 1?C14?% of TP. The majority of P in the canal sediments was contained in the HCl?CP fraction (Ca?CP and Mg?CP), comprising >50?% of TP in the main and farm canal sediments. An estimated 73 metric tons (mt) of P was stored in the 0?C10-cm layer of the three main conveyance canals within the EAA boundary of which 57-mt P is reactive and potentially available for release at different time scales.

Conclusions

The EAA canal sediments are highly organic with low bulk density and susceptible of being transported to downstream ecosystems. Many factors can impact the potential release of the reactive stored P, including redox potential of sediments as well as the overlying water column P concentration. Further investigation of potential P release from these sediments is warranted.  相似文献   

18.

Purpose

Many drainage basins are terminal recipients of hydrophobic contaminants such as pesticides. To minimize adverse effects of the contaminated sediments on wildlife, it is important to understand sediment contamination patterns. This study was conducted at the Salton Sea, which is a heavily polluted large lake in southern California, USA, with the purpose to identify areas with minimal contamination so as to support species conservation.

Materials and methods

We investigated the horizontal and vertical distribution of 14 organochlorine pesticides (OCPs) and 12 currently used pesticides (CUPs) in playas at locations near the drainage outfalls. The data were subjected to spatial analysis using Kriging interpolation and converted to contour maps. Statistical comparisons were made among different areas, between different sediment depths, and between air-exposed and submerged sediments.

Results and discussion

Various OCPs were found near two drainage inlets, with mean concentrations of 6?C30???g?kg?1 in air-exposed sediments and 3?C18???g?kg?1 in submerged sediments. Chlordane (detected frequency, DF?=?77?%) and DDT derivatives (DF?=?100?%) were among the most frequently detected OCP. Significantly higher concentrations were found in air-exposed sediments than in submerged sediments, and in subsurface sediments than in surface sediments (P?<?0.01), suggesting historical deposition and burial. Sediments at many locations exceeded the threshold levels for DDE. A total of seven CUPs were detected with the maximum ??CUPs concentration of up to 27???g?kg?1. Bifenthrin was the dominant CUP contaminant, representing more than 60?% of ??CUPs for most samples with the highest concentration of 26???g?kg?1.

Conclusions

Findings from this study provide a snapshot of the spatial distribution in both horizontal and vertical directions of hydrophobic pesticides in a drainage-dominated lake, and such information and the method of investigation may be used for identifying areas of minimal contamination as alternative habitats for this and other impacted lakes.  相似文献   

19.

Purpose

Wetlands are a popular tool to treat/polish wastewater by reducing nutrient loading into the environment. In addition to nutrients, organic contaminants, such as pharmaceuticals and personal care products (PPCPs), are commonly detected in treated wastewater. Treatment wetlands may reduce concentrations of PPCPs before the treated effluent enters rivers and streams. Oxygen status may greatly affect the attenuation of PPCPs in wetland sediments by influencing microbial makeup and activity. An understanding of the effect of redox conditions on the degradation of PPCPs and the factors influencing PPCP sorption to wetland sediments is needed to maximize PPCP removal in treatment wetlands.

Materials and methods

Three wetland sediments from the San Diego Creek and Newport Bay watershed in Southern California, USA, were incubated under aerobic and anaerobic conditions to assess the degradation of several regularly occurring PPCPs and their phase distribution as a function of time.

Results and discussion

Under aerobic conditions, ibuprofen, N,N-diethyl-meta-toluamide (DEET), and gemfibrozil generally had half-life values around 20?days, while the half-life of carbamazepine was substantially longer (between 165 and 264?days). The anaerobic half-lives of gemfibrozil and ibuprofen increased by factors of 11?C34 and carbamazepine increased by factors of 1.5?C2.5. There was no detectable anaerobic degradation of DEET. The apparent phase distribution coefficient increased over time for DEET, carbamazepine and gemfibrozil, indicating that sorption of PPCPs to wetland sediments may be more limited than that predicted using equilibrium sorption coefficient values.

Conclusions

Knowledge of the capacity of wetland sediments for degrading and sorbing PPCPs is vital to the design of treatment wetlands. Degradation of the selected PPCPs was enhanced under aerobic conditions as compared to anaerobic conditions. Sorption to sediments increased with contact time, indicating that longer hydraulic retention will increase wetland capabilities for removing PPCPs.  相似文献   

20.

Purpose

Rivers feeding into the Loskop Dam, South Africa, pass through coal mining and heavily industrialised areas. Previous studies investigating mass mortalities of crocodile and fish in the river system, revealed the presence of organic compounds, including polycyclic aromatic hydrocarbons (PAHs), in their tissues.

Materials and methods

Samples were collected from nine sites within the dam in winter and summer. Liquid-liquid and microwave-assisted extraction was used for preconcentrating PAHs from water and sediment samples, respectively. Extracts were analysed by gas chromatography-mass spectrometry in the selected ion monitoring mode to determine the presence and levels of the 16 United States Environmental Protection Agency (US EPA)-priority PAHs.

Results and discussion

Significant levels of PAHs were found in both water and sediment samples. Concentrations were higher in sediments than in water, as well as in samples collected in winter. Levels of PAHs in sediments were generally higher than those reported by many researchers for other water bodies in industrialised areas. Zebrafish embryos were used to assess potential risks associated with the water and sediment, and to determine the effects of PAHs on aquatic life. Embryos, exposed to intact water and sediment samples, as well as to diluted sediment extracts, were monitored for 120 h post fertilisation. Sediment proved more toxic to zebrafish embryos than water, causing delayed embryo development and malformations.

Conclusions

These findings are alarming as they indicate that this water system is under stress. These findings can be typical of any water system situated in a coal mining and industrial region.
  相似文献   

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