Distribution of PAH residues in humic and mineral fractions of sediments from stormwater infiltration basins

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.     

Using in situ solid phase microextraction (SPME) for depth profiling in sediments treated with activated carbon

Purpose

Sediment contamination in US waterways is an expensive and complicated issue, and as acceptance of nontraditional sediment remediation strategies broadens, novel and efficient methods to assess and monitor the bioavailability of hydrophobic organic contaminants (HOCs) in contaminated sediments will play an important role.

Materials and methods

In this project, solid phase microextraction (SPME) fibers inside perforated steel tubes were used as in situ passive samplers to measure polycyclic aromatic hydrocarbon (PAH) concentrations in sediment before and after treatment with activated carbon (AC). Two modes of waterjet amendment injection were used to apply the AC. In the first treatment, a single 2-min injection was shot into the center of a test vessel, and in the second treatment, multiple 7-s injections in a grid were placed in sediment.

Results and discussion

In the single injection, no treatment was observed 5 cm away from the injection, while at 2.5 cm, >90 % decrease of PAH pore water concentration was observed, indicating a similar bioavailability decrease. In the multiple injection experiment, >90 % PAH pore water level reductions were observed throughout the test vessel. Highly contaminated and less contaminated sediments were mixed with 0–5 % AC by weight to develop AC treatment curves. Over 99 % reduction in PAH pore water concentrations and bioavailability was observed in the less contaminated sediment at 3 % AC, while 99 % reduction was never reached even at 5 % AC addition in the highly contaminated sediment. Different treatment curves were observed for the different contaminated sediments. In situ equilibration times were 120, 215, and 250 h for phenanthrene, pyrene, and benzo(a)anthracene, respectively.

Conclusions

The results show that in situ SPME is a viable method to observe AC treatment and evaluate reductions in pore water concentrations and bioavailability.     

Specific stability of organic matter in a stormwater infiltration basin

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.     

Annual dynamics of persistent organic pollutants in various aquatic matrices: a case study in the Morava River in Zlín district,Czech Republic

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.     

Effect of SDBS–Tween 80 mixed surfactants on the distribution of polycyclic aromatic hydrocarbons in soil–water system

Purpose

Enhancing desorption of hydrophobic organic contaminants from soils is a promising approach for the effective remediation of soils contaminated with organic compounds. The desorption efficiency of chemical reagent, such as surfactant, should be evaluated. In this study, the effect of mixed anionic–nonionic surfactants sodium dodecylbenzene sulfonate (SDBS)–Tween 80 on the distribution of polycyclic aromatic hydrocarbons in soil–water system was evaluated.

Materials and methods

Batch desorption experiments were employed to evaluate the distribution of polycyclic aromatic hydrocarbons (PAHs) and surfactants in soil–water system. PAHs and SDBS were determined by high-performance liquid chromatography, Tween 80 by spectrophotometry, and total organic carbon with a carbon analyzer.

Results and discussion

Sorption of PAHs to soil was increased at low surfactant concentration due to the effective partition phase on soil formed by sorbed surfactants. The mixture of anionic and nonionic surfactants decreased the sorption of surfactants to soil, increasing the effective surfactant concentration in solution and thus decreasing the sorption of PAHs on soil. Anionic–nonionic mixed surfactant showed better performance on desorption of PAHs from soil than single surfactant. The greatest desorption efficiency was achieved with low proportions of SDBS (SDBS/Tween80?=?1:9).

Conclusions

SDBS–Tween 80 mixed surfactant showed the highest desorption rate with low proportion of SDBS, which indicated that the addition of relative low amount of anionic surfactant could significantly promote the desorption efficiency of PAHs by nonionic surfactants. Results obtained from this study did provide useful information in surfactant-enhanced remediation of soil and subsurface contaminated by hydrophobic organic compounds.     

Evaluation of sugar beet pulp efficiency for improving the retention of copper in stormwater basin

Purpose

Sugar beet pulp (SBP) has been shown to be a promising low-cost sorbent for the removal of metals from contaminated waters. The objective of this study was to investigate the impact of SBP addition to horizontal-flow gravel filters in increasing the copper (Cu) retention ability of stormwater basins.

Material and methods

Small-scale gravel filters filled with 6 kg of a sand–sediment mix (SS) were used to experimentally treat Cu-contaminated water under conditions that represented an intense storm event. Sugar beet pulp efficiency was assessed by adding 100 g of raw SBP. Two ways of applying SBP were tested: (1) mixed with SS into the gravel filter or (2) packed at the outlet in a PVC column. Eluates were characterized by their volume, pH, Cu and dissolved organic carbon (DOC) concentrations.

Results and discussion

When placed at the outlet, SBP fixed 73 % of the Cu remaining in solution and increased the overall retention capacity of the gravel filter to 99.4 %. Conversely, when SBP was mixed with SS, the outflowing water carried higher concentrations of Cu and DOC. Complementary batch experiments underlined the crucial role of DOC in the decline of Cu sorption ability observed when SS and SBP were mixed. Geochemical calculations suggested that DOC (assumed to be pectins) promotes the mobilisation of Cu from SS by complexing it in porewater.

Conclusions

Accompanied with careful guidance, SBP has the potential of removing dissolved Cu from contaminated water in gravel filters. Protocols for SBP preparation and conditions of use should be established so as to promote its sorption efficiency and decrease its release of Cu-complexing compounds like pectins.     

Multiproxy investigation of a Holocene sedimentary sequence near Ferrara (Italy): clues on the physiographic evolution of the eastern Padanian Plain

Purpose

This paper investigates soils and sediments from the eastern Padanian Plain (northern Italy) in order to delineate the physiographic evolution of the area.

Materials and methods

We present new geochemical, mineralogical and textural analyses of alluvial sediments collected from a 13-m-deep section located a few kilometres south of Ferrara. The chronology of the related depositional events is provided from ¹⁴C dating of tree trunks buried at depths of ca. 9 m and organic matter from the underlying horizons.

Results and discussion

The data indicate that (1) the upper part of the sequence (down to depths of 9 m) includes sediments characterized by low nickel–chromium (Ni–Cr) concentrations ascribed to the alluvial deposits of the river Reno, deposited in the last 400 years; (2) buried soils (depths of 9–10.5 m) developed on Ni–Cr-rich sediments related to the river Po; and (3) the deeper facies (depths of 10.5–13 m) are CaCO₃-free and characterized by higher amounts of organic carbon, sulphur and arsenic, reflecting episodic lacustrine/marsh environments. These wetlands probably developed in the area during the Iron and Roman ages, persisting up to the Middle Ages.

Conclusions

The data provide a contribution to the understanding of the evolution of the river network during the last 3,000 years and provide insights on the related paleohydrological framework that can be useful for geographical and historical reconstructions of the area. Results highlight the importance of investigating alluvial sediments to elucidate (1) fluctuations of environmental conditions and (2) anthropogenic impacts on the natural landscape.     

Eisenia fetida growth inhibition by amended activated carbon causes less bioaccumulation of heavy metals

Purpose

Activated carbons (ACs) were applied to evaluate the effects of surface oxidation on bioavailability and bioaccumulation of cadmium (Cd) and copper (Cu) in freshwater sediment along with Eisenia fetida biomass change.

Materials and methods

A modified sequential extraction procedure was conducted to measure the changes in bioavailable fractions of heavy metals 6 weeks after the addition of nitric acid-oxidized AC. Bioaccumulation of heavy metals in E. fetida was analyzed after 2 weeks of exposure to AC-amended contaminated sediments. Changes in biomass of earthworms caused by AC amendments were observed over 2 weeks of exposure to clean sand.

Results and discussion

Surface oxidation of AC caused little impact on AC surface properties except for oxygen contents leading to enhanced sorption capacity for heavy metals. Bioavailable fractions of the heavy metals increased after 6 weeks, and less was bioavailable with various ACs than without AC. The earthworms were exposed to the sediments mixed with ACs for 6 weeks. After 2 weeks of exposure, bioaccumulation of Cd and Cu decreased drastically. More than 76 % of Cd and 80 % of Cu reductions were observed with each type and dose of AC. Weight loss of E. fetida incubated in clean sand for 13 days after AC amendments was observed, but was not affected by surface oxidation.

Conclusions

Inhibited growth of E. fetida due to AC could be responsible for the reduced bioaccumulation of Cd and Cu in the earthworms as AC inhibited the movement of earthworms, leading to less bioturbation and decreased consumption of nutrients.     

Inorganic and organic pollution in agricultural soil from an emerging e-waste recycling town in Taizhou area, China

Purpose

The emerging recycling of electronic and electric waste (e-waste) is causing critical levels of soil pollution in those relatively poor towns surrounding the central cities, which have been involved in recycling activities for quite some time. Agricultural soil is of great importance due to its direct impact on food and human health. The objective of this study was to provide a systematic investigation of the contamination in agricultural soil for a range of inorganic compounds (Cr, Cd, Pb, Zn, Cu, and Ni) and organic compounds (PAHs and PCBs) in town A, an emerging e-waste recycling town in China.

Materials and methods

A total of 20 agricultural soil samples were collected from three sampling locations throughout town A. Levels of inorganic compounds (Cr, Cd, Pb, Zn, Cu, and Ni) and organic compounds (PAHs and PCBs) were determined by AAS, GC/MS, and GC/electron capture detector, respectively. Data was processed with SPSS 13 and Arcview 3.3 GIS software.

Results and discussion

The findings demonstrate that agricultural soil was contaminated to various extents by inorganic and/or organic pollutants. Comparison among the three sampling areas indicated that the soil was highly contaminated in the agricultural area near e-waste recycling workshops. Moreover, the contaminants (Cu, Pb, PAHs, and PCBs) may be connected through a common source as found in the Pearson correlations and cluster analysis.

Conclusions

There exists a heightened sense of awareness concerning the hazardous implications of current emerging e-waste recycling issues in the agricultural soil of those areas close to the central city in Taizhou.     

Immobilization of Cu and Cd in a contaminated soil: one- and four-year field effects

Purpose

Many amendments have been applied to immobilize heavy metals in soil. However, little information is available on the changes of immobilization efficiencies of heavy metals in contaminated soils over time. This work investigated the immobilization efficiencies of copper (Cu) and cadmium (Cd) in contaminated soils in situ remediated with one-time application of three amendments for 1 year and 4 years.

Materials and methods

Apatite, lime, and charcoal were mixed with the topsoil of each plot with the amounts of 22.3, 4.45, and 66.8 t/ha, respectively. Soil chemical properties and fractions of Cu and Cd were examined after in situ remediation for 1 year and 4 years. Soil sorption and retention capacities and desorption proportions for Cu and Cd were investigated by batch experiments.

Results and discussion

The addition of amendments significantly increased soil pH, but decreased exchange acid and aluminum (Al). The amendments significantly decreased the CaCl₂ extractable Cu and Cd and transformed them from active to inactive fractions. After the application of amendments for 1 year, the maximum sorption capacities ranged from 35.6 to 38.8 mmol/kg for Cu and from 14.4 to 17.0 mmol/kg for Cd, which were markedly higher than those of the application of amendments for 4 years (Cu, 29.6–34.7 mmol/kg; Cd, 10.9–16.4 mmol/kg). Desorption proportions (D) of Cu and Cd using three extractants followed the order of \( {D}_{{\mathrm{NaNO}}_3}<{D}_{{\mathrm{CaCI}}_2}<{D}_{{\mathrm{MgCI}}_2} \) . Moreover, the retention capacities (R) of Cu and Cd both increased and followed the order of R _apatite?>?R _lime?>?R _charcoal, resulting in higher Cu and Cd in the amended soils than the untreated soil.

Conclusions

Apatite, lime, and charcoal increased the soil sorption and retention capacities of Cu and Cd and resulted in higher immobilization efficiencies in the amended soils than the untreated soil. However, the immobilization efficiencies of Cu and Cd decreased with the decrease of sorption capacities after 4 years. It was concluded that apatite had the best effect on the long-term stability of immobilized Cu and Cd and can be applied to immobilize heavy metals in contaminated soils.     

Modelling post-depositional transport of PAHs in aquatic bed sediments using CoReTranS

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.     

Desorption behaviour of polycyclic aromatic hydrocarbons after long-term storage of two harbour sludges from the port of Rotterdam, The Netherlands

Purpose

The desorption behaviour of 16 polycyclic aromatic hydrocarbons (PAHs) in sludges from two sites of the port of Rotterdam, The Netherlands, which are designated to be stored in a subaqueous sludge depository, was investigated after a storage time of 14 years at 4 °C under anaerobic conditions in the dark, mimicking depository conditions. Such long-term storage is believed to effect the desorption of the PAHs.

Materials and methods

Batch desorption experiments over a time period of 130 days were performed with the brackish Beerkanaal (BK) sludge and the freshwater Beneden Merwede River (BMR) sludge. The organic carbon–water partitioning coefficient (K _OC) values were calculated and compared to values of a previous study on the same sludges after a storage time of 3 years and to values obtained from calculations based on octanol–water partitioning coefficient (K _OW) values. Additionally, the organic matter of the sludges was characterised by C and N elemental analysis and solid-state ¹³C nuclear magnetic resonance spectroscopy.

Results and discussion

Only desorption of low molecular weight PAHs up to pyrene was detected. Several K _OC values were higher compared to the values from the previous study, and all were increased compared to values based on K _OW values. It is assumed that the increase in K _OC was an effect of the prolonged contact time, causing slow intradomain diffusion of PAHs into the condensed carbon domains. Desorption was higher in BK than in BMR, which is explained by differences in organic matter composition because BMR (containing predominantly aromatic carbon) and BK (which was dominated by lipids) contained the same amount of organic carbon. It is inferred that lipids compete with PAHs for sorption sites on the aromatic carbon, so that lipids block these sorption sites, and the PAHs are adsorbed to the lipids.

Conclusions

Since the amounts of PAHs desorbed from both sludges in this study were so low, it is supposed that long-term storage of these sludges in subaqueous depositories will likely result in increased sorption and thus a reduced release of these contaminants into the environment over time.     

Geochemical monitoring of organic and inorganic pollutants in the sediment of the Eastern Posavina (Serbia)

Purpose

The aim of this study was to obtain a complete picture of the geochemical character of the sediment in the eastern Posavina region, Serbia, an area which has thus far not been systematically investigated. Geological mapping and impact assessment were thus carried out for this area.

Materials and methods

Sediments were sampled (from 0 to 0.5 m depth) in four locations in eastern Posavina between 2002 and 2014. Eight heavy metals (Ni, Zn, Cd, Cr, Cu, Pb, As and Hg) and a wide variety of organic parameters (16 EPA polycyclic aromatic hydrocarbons (PAHs), mineral oils, selected pesticides and polychlorinated biphenyls (PCBs)) were monitored. Metals were analysed by flame and graphite atomic absorption spectrometry, and gas chromatography with mass detection was used for the PAH analyses. The origins of the monitored substances were classified using geoaccumulation index (I _geo), ecological risk index (RI) and principal component analysis (PCA/FA).

Results and discussion

The sediments all contained higher heavy metals concentrations than the upper continental crust (UCC), suggesting dynamic natural and anthropogenic processes in this unique region. Significant variations (RSD values from 13 to 190) were observed for Cd (0.001–80.00 mg kg^?1), Hg (0.01–5.40 mg kg^?1), mineral oil (2.00–1851 mg kg^?1) and the sum of 16 EPA PAHs (0.003–5.57 mg kg^?1). The I _geo index classified the pollution risk due to Cr as strong, Cd, Zn and Hg as moderate to strong and Ni as moderate. Based on PCA/FA analysis, the parameters were grouped somewhat differently, with anthropogenic activity found to be responsible for much of the Hg, Cd and Cr pollution present in the sediments.

Conclusions

The analysis revealed eight heavy metals (Ni, Zn, Cd, Cr, Cu, Pb, As and Hg), the sum of 16 EPA PAHs and mineral oil as parameters of great interest for this unique region. These parameters must be the focus of future monitoring programs, in support of appropriate remediation techniques and/or dredging activities, which are required in order to comply with the new Serbian regulations and the relevant EU recommendations.

     

Influence of mixtures of acenaphthylene and benzo[a]anthracene on their degradation by Pleurotus ostreatus in sandy soil

Purpose

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds commonly found as soil contaminants. Fungal degradation is considered as an environmentally friendly and cost-effective approach to remove PAHs from soil. Acenaphthylene (Ace) and Benzo[a]anthracene (BaA) are two PAHs that can coexist in soils; however, the influence of the presence of each other on their biodegradation has not been studied. The biodegradation of Ace and BaA, alone and in mixtures, by the white rot fungus Pleurotus ostreatus was studied in a sandy soil.

Materials and methods

Experimental microcosms containing soil spiked with different concentrations of Ace and BaA were inoculated with P. ostreatus. Initial (t ₀) and final (after 15 days of incubation) soil concentrations of Ace and BaA were determined after extraction of the PAHs.

Results and discussion

P. ostreatus was able to degrade 57.7% of the Ace in soil spiked at 30 mg kg^?1 dry soil and 65.8% of Ace in soil spiked at 60 mg kg^?1 dry soil. The degradation efficiency of BaA by P. ostreatus was 86.7 and 77.4% in soil spiked with Ace at 30 and 60 mg kg^?1 dry soil, respectively. After 15 days of incubation, there were no significant differences in Ace concentration between soil spiked with Ace and soil spiked with Ace + BaA, irrespective of the initial soil concentration of both PAHs. There were also no differences in BaA concentration between soil spiked with BaA and soil spiked with BaA + Ace.

Conclusions

The results indicate that the fungal degradation of Ace and BaA was not influenced by the presence of each other’s PAH in sandy soil. Bioremediation of soils contaminated with Ace and BaA using P. ostreatus is a promising approach to eliminate these PAHs from the environment.     

Application of ionic liquids for the extraction and passive sampling of endocrine-disrupting chemicals from sediments

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.     

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 of 90Sr and other metal cations in artificially contaminated soils: the influence of bone sorbent addition

Purpose

The influence of bone sorbent addition onto distribution of ⁹⁰Sr in artificially contaminated soil was preliminary studied to assess the possibility of biogenic apatite utilization for reduction of ⁹⁰Sr mobility and availability. Simultaneously, the disruption of soil micro- (Cd, Zn, Co, Cu, Cr, and Ni,) and macroelements (Al, Fe, Mn, K, Mg, and Ca) upon Sr contamination and sorbent addition was monitored.

Materials and methods

The model soil was contaminated by inactive Sr, in the form of Sr(NO₃)₂ solution. As a soil additive, sorbent obtained by annealing bovine bones at 400 °C (B400) was applied. Both the uncontaminated and Sr-contaminated soils were mixed with 1, 3, 5, and 10 % of sorbent, suspended in distilled water (initial pH?5; solid/solution ratio, 1:2), and equilibrated for 15 days on a rotary shaker. Solid residues were subjected to modified Tessier five-step sequential extraction analysis, and the amounts of chosen metals in each fraction were determined by inductively coupled plasma–optical emission spectroscopy.

Results and discussion

In the original soil, Sr was mainly found in exchangeable (61 %) and carbonate phase (16 %), whereas after contamination, the content of Sr in exchangeable phase raised to 94 %. With the addition of B400, the decrease in Sr amounts in exchangeable fraction was detected, whereas increase occurred mainly in operationally defined carbonate phase and in the residual. High level of Sr contamination caused the increase in Zn, Ni, Co, Cu, Cd, and Mn and decrease in Ca content in exchangeable phase. Sorbent addition resulted in a migration of these cations to less soluble fractions. This effect was observed even for major soil elements such as Fe, Al, and Mn, regardless of the excessive amounts of Sr in the soil.

Conclusions

Mixing the soil with B400 resulted in reduced Sr mobility and bioavailability. B400 acted as a stabilizing agent for heavy metals, as well. Apatite distinguished selectivity towards heavy metals may interfere with the Sr immobilization and disrupt original cation distribution. Further studies should include more realistic (lower) Sr concentrations in the soil, different soil types, pH, and longer incubation times.     

Ecotoxicological characterization of sediment cores from the western Baltic Sea (Mecklenburg Bight) using GC–MS and in vitro biotests

Background, aim, and scope

The Mecklenburg Bight (Western Baltic Sea) near Luebeck, Germany was historically used to dump industrial waste at sea and, thus, sediments in some regions are highly polluted at present. While earlier studies identified hot spots of chemical pollution, little is known about biological activities and impacts on exposed marine organisms. This study aimed to assess the pollution in the Mecklenburg Bight to determine the degree of contamination with sediment-bound polycyclic aromatic hydrocarbons (PAHs) as well as biological activities.

Materials and methods

Sediment cores with a depth of 30 cm were sampled at a dumping site and at a reference site, sliced in distinct layers, freeze-dried, and processed using the accelerated solvent extraction method. Sediment was characterized measuring total organic carbon (TOC) and soot contents. Concentrations of the 16 EPA-PAHs were determined with chemical analysis (gas chromatography–mass spectroscopy) in each sediment slice and referred to the determined TOC content. Further on, in vitro biotests were applied to determine toxic effects of contaminants in the sediment. The acute neutral red retention assay indicated no specific cytotoxic effects. Arylhydrocarbon receptor (AhR)-mediated activities were measured using the mechanism-specific 7-ethoxyresorufin-O-deethylase induction assay. Both biotests were performed with rainbow trout (Oncorhynchus mykiss) liver cells (RTL-W1). Analyzed compound concentrations and biological activities were given in toxicological equivalent concentrations (chem- and bio-TEQs) to determine shares of analyzed EPA-PAHs to the overall activity.

Results

TOC and soot contents indicated a significant alteration through the sediment core at the dumping site. EPA-PAH concentrations were referred to TOC and indicated elevated concentrations at the dumping site. Maximum PAH concentrations (14 to 16 cm depth; 5.44 µg/g TOC) were 300-fold increased at the dumping site, compared to the reference site (4 to 6 cm depth; 0.017 µg/g TOC). Cytotoxicity as determined in the neutral red retention assay was elevated in some layers at the dumping site (maximum in 4 to 6 cm depth; NR₅₀?=?14 mg/ml), but not correlated with TOC or soot contents. Ah receptor agonist activities were clearly elevated in highly PAH-loaded layers at both sites. At the dumping site, maximum activities were determined reflected by a bio-TEQ of 223,000 pg/g (19 to 22 cm), in contrast to a bio-TEQ of 41,000 pg/g (6 to 8 cm) at the reference site. Further on, shares of EPA-PAHs to the overall activity were determined and contributed >40% at the dumping site and between 4% and 17% at the reference site. Chem-TEQs were found to exceed bio-TEQs in a depth of 11 to 22 cm, indicating the presence of Ah receptor antagonistic or inhibitive compounds.

Discussion

Sediments from the dumping site were determined to be highly contaminated and caused toxic effects in depths that are known to be influenced by dumping activities. In contrast, the reference sediment indicated only near to surface layers to be minor contaminated. In comparison with highly polluted sediments from other marine sites, the contamination of the dumping site could be ranked as elevated. Chem-TEQs exceeding bio-TEQs in a depth of 11 to 22 cm seem to be caused by AhR antagonistic compounds in the dumped material. Furthermore, particle-bound PAH concentrations assessed in this study were discussed against freely dissolved concentrations in interstitial water, as determined in a different study with the same sediment core.

Conclusions

Sediments in the inner Mecklenburg Bight could be shown to be highly contaminated, at least with PAHs, causing articulate increased Ah receptor-mediated activities. Marine organisms may be exposed to these contaminants, in particular when inhabiting the sediment.

Recommendations and perspectives

Further research activities should extend the range of chemically analyzed pollutants and applied biotests and endpoints. Monitoring should close the gap between analytical methods in the laboratory and the field to determine possible impacts on organisms at site.     

Polycyclic aromatic hydrocarbons (PAHs) in rural soils of Dongjiang River Basin: occurrence,source apportionment,and potential human health risk

Purpose

A comprehensive study was conducted to investigate the presence of polycyclic aromatic hydrocarbons (PAHs) in Dongjiang River Basin (DRB) soils and to evaluate their sources and ecological and health risk. In addition, factors affecting the distribution and fate of PAHs in the soils such as emission density, soil organic matter, degradation, etc. were studied.

Materials and methods

Surface soil (0–20 cm) samples from 30 sampling sites in the rural areas of DRB were collected and analyzed for 17 polycyclic aromatic hydrocarbons (16 EPA priority PAHs and perylene). Positive matrix factorization model was used to investigate the source apportionment of these PAHs, and an incremental lifetime cancer risk (ILCR) was used to estimate the integrated lifetime risks of exposure to soil-borne PAHs through direct ingestion, dermal contact, and inhalation collectively.

Results and discussion

The total PAH concentrations in the rural soils in DRB range from 23.5 to 231 μg/kg with a mean concentration of 116 μg/kg. The predominant PAHs in the rural soils were naphthalene, fluoranthene, phenanthrene, and benzo(b)fluoranthene. Cluster analysis was performed to classify the soil PAHs into three clusters, which could be indicative of the soil PAHs with different origins and different properties. Source apportionment results showed that coal, biomass, oil, commercial creosotes, and vehicle contributed 24 %, 24 %, 17 %, 17 %, and 18 % of the total soil PAH burden, respectively. The ILCR results indicated that exposure to these soil-borne PAHs through direct ingestion, dermal contact, and inhalation collectively produces some risk.

Conclusions

PAHs in the soils of the DRB will produce long-term influences on rivers and oceans via soil erosion and river transport. Therefore, PAHs in rural soils of DRB have potential impacts on the water supply and human health risk.     

Effect of soil pollution with polycyclic aromatic hydrocarbons on the properties of humic acids

Purpose

Interestingly, soil is the component of the natural environment in which most hydrophobic organic pollution including polycyclic aromatic hydrocarbons (PAHs) gets accumulated. The aim of the present paper was to determine the effect of soil pollution with PAHs on the elemental composition, spectral properties, and hydrophobic and hydrophilic properties of humic acids. The research was performed on different types of soil samples that were artificially polluted with selected PAHs (anthracene, pyrene, fluorene and chrysene).

Materials and methods

The soil samples were polluted with selected PAHs in an amount corresponding to 10 mg PAHs kg^?1. The PAHs-polluted soil samples were incubated for 180 and 360 days at a temperature of 20–25 °C and fixed moisture (50 % of field water capacity). Humic acids (HAs) were extracted from the soil samples prior to the incubation (additionally, soils not polluted with PAHs) and after 180 and 360 days of incubation. For isolated HAs, the following analyses were performed: elemental composition, UV–Vis and IR spectra, susceptibility to oxidation, and hydrophilic (HIL) and hydrophobic (HOB) properties were determined using high-performance liquid chromatography.

Results and discussion

The research demonstrated that introducing anthracene, fluorene, pyrene and chrysene to soil samples resulted in a change in some of the quality parameters of humic acids. However, the intensity and the direction of those changes were determined by soil properties. The changes of the parameters, once PAHs were introduced, that did not depend on the soil properties were ΔA _665u and ΔA _465u (susceptibility to oxidation at wavelengths of 465 and 665 nm) as well as HIL/ΣHOB. The same tendency in changes in the structure of humic acids, once PAHs were introduced, was also observed based on the Fourier transform infrared spectra pattern.

Conclusions

A single pollution of soils with PAHs that leads to changes in the quality parameters of humic acids shows that, as for the soils permanently exposed to pollution with those compounds, significant changes can occur in the properties of humic acids. As a result, it can lead to a change in the functions played by humic acids in the environment.