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.     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

Sorption of polycyclic aromatic hydrocarbons to soils enhanced by heavy metals: perspective of molecular interactions

Purpose

Combined pollution by polycyclic aromatic hydrocarbons (PAHs) and heavy metals are commonly found in industrial soils. This study aims to investigate the effect of the coexistence of heavy metals on the sorption of PAHs to soils. We focused specifically on the relationship of the sorption capacity with the estimation of the binding energy between PAHs and heavy metals.

Materials and methods

The sorption of typical PAHs (naphthalene, phenanthrene, and pyrene) to soils coexisting with heavy metals (Cu(II), Pb(II), and Cr(III)) was characterized in batch sorption experiments. The binding energy between PAHs and heavy metals in aqueous solution was estimated by quantum mechanical (QM) method using density functional theory (DFT) at the M06-2x/def2svp level of theory.

Results and discussion

Sorption capacity and nonlinearity of the PAHs to the soils were enhanced by the coexisting heavy metals. The extent of increment was positively associated with the hydrophobicity of the PAHs and the electronegativity and radius of the metal cations: Cr(III)?>?Pb(II)?>?Cu(II). The cation-π interaction was revealed as an important noncovalent binding force. There was a high correlation between the binding energies of the PAHs and K _f ′ (K _f adjusted after normalizing the equilibrium concentration (C _e) by the aqueous solubility (C _s)) (R ²?>?0.906), indicating the significant role of the cation-π interactions to the improved PAH sorption to soils.

Conclusions

In the presence of heavy metals, the sorption capacities of naphthalene, phenanthrene, and pyrene to soils were enhanced by 21.1–107 %. The improved sorption capacity was largely contributed from the potent interactions between PAHs and heavy metals.

     

Adsorption of Dimethyl Phthalate on Marine Sediments

Experiments were performed to investigate the sorption behaviors of dimethyl phthalate on marine sediments. The sorption of dimethyl phthalate on marine sediments reached equilibrium within 10 h. The sorption behavior of dimethyl phthalate on HCl-treated and untreated sediments accorded well with the linear sorption isotherm. The sorption occurred primarily via partition function of organic carbon of marine sediments. The sorption behavior of dimethyl phthalate on H₂O₂-treated sediment was nonlinear and conformed to Freundlich isotherm. Sorption of dimethyl phthalate on H₂O₂-treated sediment was chiefly through surface function of clay in marine sediments. Salinity of seawater had an important effect on the sorption of dimethyl phthalate. As the salinity of seawater increased, both the partitioning coefficients K _d and empirical constant K would increase.     

Sediment Quality in Burlington Harbor,Lake Champlain,U.S.A.

Surface samples and cores were collected in 1993 fromthe Burlington Harbor region of Lake Champlain. Sediment samples were analyzed for trace metals(cadmium, copper, lead, nickel, silver and zinc),simultaneously extracted metal/acid volatile sulfide(SEM-AVS), grain size, nutrients (carbon and nitrogen)and organic contaminants (polycyclic aromatichydrocarbons (PAHs) and polychlorinated biphenyls(PCBs)). The concentrations of cadmium, copper,silver and zinc from the partial sediment digestion ofthe surface samples correlated well with each other(r ²>0.60) indicating that either a commonprocess, or group of processes determined the sedimentconcentrations of these metals. In an analysis of thespatial distribution of the trace metals and PAHs,high surficial concentrations were present in thesouthern portion of the Harbor. The trace metal trendwas strengthened when the concentrations werenormalized by grain size. A sewage treatment plantoutfall discharge was present in the southeasternportion of the Harbor at the time of this study and isthe major source of trace metal and PAH contamination. Evaluation of sediment cores provides a proxy recordof historical trace metal and organic inputs. Thepeak accumulation rate for copper, cadmium, lead, andzinc was in the late 1960s and the peak silveraccumulation rate was later. The greatestaccumulation of trace metals occurred in the late1960s after discharges from the STP began. Subsequentdeclines in trace metal concentrations may beattributed to increased water and air regulations. The potential toxicity of trace metals and organiccontaminants was predicted by comparing contaminantconcentrations to benchmark concentrations andpotential trace metal bioavailability was predictedwith SEM-AVS results. Surface sample results indicate lead,silver, ΣPAHs and ΣPCBs are potentially toxicand/or bioavailable. These predictions were supportedby studies of biota in the Burlington Harborwatershed. There is a clear trend of decreasing PAHand trace metal contaminant concentrations withdistance from the STP outfall.     

Effects of pH,solid/solution ratio,ionic strength,and organic acids on Pb and Cd sorption on kaolinite

Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal concentration, kaolinite concentration and time. The organic acids used were p-hydroxybenzoic acid, o-toluic acid, and 2,4-dinitrophenol. Titrations were used to derive previously unavailable aqueous conditional stability constants for the organometallic complexes. Batch results showed that aqueous lead-organic complexation reduced sorption of Pb by kaolinite. Cadmium behavior was similar, except for 2,4-dinitrophenol, where Cd sorption was increased. Metal sorption increased with increasing pH and decreasing ionic strength. Distribution ratios (K _d 's) decreased with increasing solid/solution ratio. The subsurface transport of lead and cadmium may be enhanced via complex interactions with organic wastes or their degradation products and sorbent mineral surfaces.

     

Investigating particle concentration effects of polycyclic aromatic hydrocarbon (PAH) sorption on sediment considering the freely dissolved concentrations of PAHs

Purpose

Suspended particulate sediment (SPS) concentration has a great impact on the sediment to water partitioning coefficients (K _p) of hydrophobic organic compounds (HOCs), which is called the particle concentration effect (PCE). However, the mechanisms regarding the PCE are not yet well understood, and there is little direct experimental evidence for these mechanisms. The aim of this study was to investigate the PCE of polycyclic aromatic hydrocarbon (PAH) sorption on sediment by analyzing the freely dissolved concentrations of PAHs.

Materials and methods

Sediments were collected from the Yellow River and the Haihe River in China. Pyrene was selected as a model PAH to investigate the sorption of PAH on sediments. In addition to the total dissolved concentration (C _TW) of pyrene, the freely dissolved concentration (C _FW) measured by polyethylene devices was used to investigate the PCE of pyrene in the presence and absence of phenanthrene and chrysene.

Results and discussion

For both the Haihe River and Yellow River sediments, in the presence and absence of other PAHs, the K _p value of pyrene with C _FW as the equilibrium concentration in the water phase was approximately two times higher than that with C _TW as the equilibrium concentration. With either C _TW or C _FW as the equilibrium concentration in the water phase, the K _p value of pyrene decreased with increasing SPS concentration as a power function. In addition, the K _p value with C _TW as the equilibrium concentration decreased faster than that with C _FW. This inferred that, apart from a third phase including dissolved organic carbon (DOC) and colloids, particle–particle, or particle–DOC interactions were important for the PCE. The contribution of the third phase to the PCE for the Haihe River sediment (72.5?±?26.4 %) was greater than the contribution for the Yellow River sediment (48.4?±?16.2 %), which had a larger particle size and lower total organic carbon and black carbon contents.

Conclusions

The PCE of PAH sorption onto sediments was attributed to both the third phase and to particle–particle or particle–DOC interactions. The contribution of the third phase to the PCE depended on both the TOC content and the particle size of sediment. As high SPS and DOC concentrations exist in many rivers, their effects on the sorption of HOCs should be considered when conducting bioavailability and ecological risk assessment.     

Sediment–pore water partition of PAH source contributions to the Yellow River using two receptor models

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.     

Effect of soil pH on the sorption capacity of soil organic matter for polycyclic aromatic hydrocarbons in unsaturated soils

Sorption by soil organic matter (SOM) is considered the most important process affecting the bioavailability of hydrophobic organic chemicals (HOCs)in soil.The sorption capacity of SOM for HOCs is affected by many environmental factors.In this study,we investigated the effects of soil pH and water saturation level on HOC sorption capacity of SOM using batch sorption experiments.Values of soil organic carbon-water partition coefficient (K_OC) of six selected polycyclic aromatic hydrocar...     

The use of a microbial contact toxicity test for evaluating cadmium bioavailability in soil

Background, Aims and Scope

Bioavailability of toxic compounds in soil can be defined as the fraction able to come into contact with biota and to cause toxic effects. The contact toxicity tests may detect the total toxic response of all bioavailable contaminants present in a sample. The objectives of this study were to evaluate the use of microbial contact toxicity tests for cadmium bioavailability assessment and to evaluate the relationship between sorption, soil characteristics and cadmium bioavailability.

Methods

A test soil bacterium,Bacillus cereus, was put in direct contact with the solid sample. Four unpolluted soils were selected to provide solid samples with a variety of physicochemical characteristics. The toxicity and sorption behaviour of cadmium spiked to the soil samples were determined.

Results, Discussion and Conclusions

A significant correlation between contact toxicity test results and partitioning of cadmium in the soil samples (r²= 0.79, p <0.05; n = 26) was found. The results confirm that the bioavailability of cadmium in soil depends on its sorption behaviour. Cadmium sorbed to the cation exchange sites associated with fulvic acids is non-bioavailable in the toxicity test employed in this study. It is concluded that the microbial contact toxicity test is a suitable tool for detecting cadmium bioavailablity in the soils used in this study.

Outlook

The application of microbial contact toxicity tests for bioavailability assessment can be very useful for the risk identification and remediation of soil-associated contaminants.     

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

Goal, Scope and Background. Based on a bioassay battery covering only primary producers and consumers as well as degraders, the potential ecological hazard of sediments to vertebrates cannot be estimated comprehensively. Therefore, there is an urgent need to develop and standardize integrated vertebrate-based test systems for sediment investigation strategies. Whereas vertebratebased in vitro systems have frequently been used for the investigation of aqueous samples, there is a significant lack of whole sediment assays. Thus, the purpose of the present study was: (1) to develop a rapid and reliable, but comprehensive method to investigate native sediments and particulate matters without preceding extraction procedures; (2) to compare the hazard potential of solid phase sediments to the effects of corresponding pore waters and organic extracts in order to characterize the bioavailability of the particle-bound pollutants; and (3) to relatively evaluate the embryotoxic effects of sediments from the catchment areas of the rivers Rhine, Neckar and Danube. Methods (or Main Features).  To investigate the toxicity of sediment samples on vertebrates, the standard embryo toxicity test with the zebrafish (Danio rerio; Hamilton-Buchanan 1922) according to DIN 38415-6 was modified with respect to exposure scheme and toxicological endpoints. Sediments from the catchment area of the Neckar River were assessed using pore waters, acetonic extracts and native sediments in order to get inside into the potential bioavailability of particle-bound pollutants. A comprehensive test protocol for the investigation of native sediments in the embryo toxicity test with the zebrafish is presented. Results and Discussion.  The fish embryo assay with Danio rerio can be carried out with both aqueous and organic sediment extracts as well as native (whole, solid phase) sediment samples. Elongation of exposure time from 48 to up to 196 h significantly increased the mortality. Using the fish egg assay with native sediments, a broad range of embryotoxic effects could be elucidated, including clear-cut dose-response curves for the embryotoxic effects of contaminated sediments; in contrast, absence of embryotoxic effects could be demonstrated even for the highest test concentrations of unpolluted sediments. With native sediments, embryotoxicity was clearly higher than with corresponding pore waters, thus corroborating the view that — at least for fish eggs — the bioavailability of particle-bound lipophilic substances in native sediments is higher than generally assumed. The relative ranking of sediment toxicity was identical using both native sediments and sediment extracts, EC₂₀ values of the latter, however, being eight time lower higher than with the native sediments. A comparison of the embryo toxic effects of samples from the Neckar area with locations along the Rhine and Danube rivers elucidated a broad range of results, thus indicating different levels of contamination. Conclusions.  A modified protocol of the zebrafish embryo test allows the assessment of sediment toxicity in both aqueous extracts and native sediments. The isolated investigation of pore waters may result in a clear-cut underestimation of the bioavailability of lipophilic particle-bound substances (as determined by native sediments). Recommendations and Perspectives.  The zebrafish embryo test with native (whole, solid phase) sediments appears very promising for the evaluation of the bioavailable fraction of lipophilic particle-bound substances and can therefore be recommended for the evaluation of vertebrate toxicity in tiered sediment test strategies and dredging directives such as the HABAB-WSV. Whereas acetone extracts may be tested as a rough estimation of embryotoxicity, native sediment samples will provide a more comprehensive and realistic insight into the bioavailable hazard potential     

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.     

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.     

Biodegradation of PAHs and PCBs in Soils and Sludges

Results from a multi-year, pilot-scale land treatment project for PAHs and PCBs biodegradation were evaluated. A mathematical model, capable of describing sorption, sequestration, and biodegradation in soil/water systems, is applied to interpret the efficacy of a sequential active–passive biotreatment process of organic chemicals on remediation sites. To account for the recalcitrance of PAHs and PCBs in soils and sludges during long-term biotreatment, this model comprises a kinetic equation for organic chemical intraparticle sequestration process. Model responses were verified by comparison to measurements of biodegradation of PAHs and PCBs in land treatment units; a favorable match was found between them. Model simulations were performed to predict on-going biodegradation behavior of PAHs and PCBs in land treatment units. Simulation results indicate that complete biostabilization will be achieved when the concentration of reversibly sorbed chemical (S _RA) reduces to undetectable levels, with a certain amount of irreversibly sequestrated residual chemical (S _IA) remaining within the soil particle solid phase. The residual fraction (S _IA) tends to lose its original chemical and biological activity, and hence, is much less available, toxic, and mobile than the “free” compounds. Therefore, little or no PAHs and PCBs will leach from the treatment site and constitutes no threat to human health or the environment. Biotreatment of PAHs and PCBs can be terminated accordingly. Results from the pilot-scale testing data and model calculations also suggest that a significant fraction (10–30%) of high-molecular-weight PAHs and PCBs could be sequestrated and become unavailable for biodegradation. Bioavailability (large K _d , i.e., slow desorption rate) is the key factor limiting the PAHs degradation. However, both bioavailability and bioactivity (K in Monod kinetics, i.e., number of microbes, nutrients, and electron acceptor, etc.) regulate PCBs biodegradation. The sequential active–passive biotreatment can be a cost-effective approach for remediation of highly hydrophobic organic contaminants. The mathematical model proposed here would be useful in the design and operation of such organic chemical biodegradation processes on remediation sites.     

Partition of Nonylphenol and Related Compounds Among Different Aquatic Compartments in Tiber River (Central Italy)

Nonylphenol (NP), nonylphenol mono- and di-ethoxylate (NP1EO, NP2EO) and bisphenol A (BPA) were determined in water, suspended particulate matter (s.p.m.) and bed sediment collected from the most polluted stretch of Tiber river (Italy) in the neighbourhood of Rome. Analytes were recovered from water samples by solid-phase extraction (SPE) on Si–C₁₈ cartridges and analysed by HPLC with fluorescence detection. Solid samples were extracted by using an aqueous solution of the non-ionic surfactant Tween 80. Results indicated that 2–42% of NP, 9–45% of NP1EO, 11–18% of NP2EO and 4–62% of BPA respectively occurred in the suspended phase. In general, for all compounds a higher affinity for s.p.m. than for bed sediments was observed, reflecting differences in the nature of particles and in their sorption capacity for organic micro-pollutants. The partition of target compounds in river compartments was affected by differences in hydrological conditions between the two sampling campaigns. Run-off from the basin or resuspension/redissolution from sediments was an important source of nonylphenol and bisphenol A during high discharge regimes. Partition coefficients of compounds (log K _oc ) between water and s.p.m. were calculated under stable flow condition. K _oc values, experimentally measured in the river, were higher than those predicted by K _ow , implying that specific chemical interaction could occur in the sorption mechanisms for these group of compounds.     

Using solid-phase microextraction to evaluate the role of different carbon matrices in the distribution of PAHs in sediment-porewater systems of the Baltic Sea

Purpose  

The speciation of polycyclic aromatic hydrocarbons (PAHs) in sediment-porewater systems affects both the chemical fate and bioavailability of these compounds. PAHs may be dissolved or sorbed to sediment particles or dissolved organic carbon (DOC). Furthermore, soot carbon has been shown to control the sorption of PAHs onto particles in natural waters. The present study investigates the distribution of individual PAHs among these three phases by examining sediments from the western Baltic Sea, focusing on a highly contaminated former dumping area and evaluating the importance of soot-carbon partitioning.     

有机质对多环芳烃环境行为影响的研究进展

多环芳烃(PAHs)的归宿和毒性受其环境行为的影响,主要取决于环境中各个因素的交互作用,而有机质是相当重要的因素,有机质对环境中PAHs的物理化学行为、生物过程均有一定的影响。本文着重介绍了有机质对水体、土壤和沉积物中PAHs的吸附、溶解和迁移以及生物可利用性和毒性等方面的影响,总结了离子强度、pH、表面活性剂、时间等影响有机质与PAHs作用的因素,同时简要介绍了土壤和沉积物中结合残留态PAHs的研究情况,指出结合残留态PAHs现有的研究方法有热解法和同位素标记法,最后提出系统地研究内源有机质(尤其碳黑和腐殖酸)的组成、性质与土壤PAHs的锁定与降解的关系和利用外源有机物强化修复污染的环境是今后研究的重点。     

Influence of Increasing Soil Copper Concentration on the Susceptibility of Phosphomonoesterase and Urease to Heat Disturbance

The sorption of chromium (Cr) species to soil has become the focus of research as it dictates the bioavailability and also the magnitude of toxicity of Cr. The sorption of two environmentally important Cr species [Cr(III) and Cr(VI)] was examined using batch sorption, and the data were fitted to Langmuir and Freundlich adsorption isotherms. The effects of soil properties such as pH, CEC, organic matter (OM), clay, water-extractable SO₄ ^2– and PO₄ ^3–, surface charge, and different iron (Fe) fractions of 12 different Australian representative soils on the sorption, and mobility of Cr(III) and Cr(VI) were examined. The amount of sorption as shown by K _f was higher for Cr(III) than Cr(VI) in all tested soils. Further, the amount of Cr(III) sorbed increased with an increase in pH, CEC, clay, and OM of soils. Conversely, the chemical properties of soil such as positive charge and Fe (crystalline) had a noticeable influence on the sorption of Cr(VI). Desorption of Cr(VI) occurred rapidly and was greater than desorption of Cr(III) in soils. The mobility of Cr species as estimated by the retardation factor was higher for Cr(VI) than for Cr(III) in all tested soils. These results concurred with the results from leaching experiments which showed higher leaching of Cr(VI) than Cr(III) in both acidic and alkaline soils indicating the higher mobility of Cr(VI) in a wide range of soils. This study demonstrated that Cr(VI) is more mobile and will be bioavailable in soils regardless of soil properties and if not remediated may eventually pose a severe threat to biota.     

A Hybrid Approach for PAHs and Metals Removal from Field-Contaminated Sediment Using Activated Persulfate Oxidation Coupled with Chemical-Enhanced Washing

The aim of this study was to investigate the removal of both polycyclic aromatic hydrocarbons (PAHs) and heavy metals from field-contaminated sediments by activated persulfate oxidation. Various chemicals, including hydroxypropyl-??-cyclodextrin (HPCD), S,S-ethylenediaminedisuccinic acid (EDDS), tetrasodium pyrophosphate (Na₄P₂O₇), and hydrochloric acid (HCl), were applied individually before or after activated persulfate oxidation to enhance the co-removal of both types of pollutants. It was found that the organic removal efficiency was not significantly enhanced by increasing the concentration of HPCD from 2.5 to 5.0?mM. The removal efficiency of heavy metals was not improved even at an excess amount of EDDS after activated persulfate oxidation. However, the addition of EDDS acted as the Fe²⁺ carrier for activated persulfate oxidation. In addition, no significant enhancement of heavy metal removal was observed by increasing the concentrations of Na₄P₂O₇ and HCl from 0.01 to 0.1?M after activated persulfate oxidation. However, comparing 0.1?M HCl with 0.1?M Na₄P₂O₇, HCl was shown to be more effective in promoting the removal of organic pollutants. With further adjustments on the experimental conditions, the highest removal amount of metals and PAHs was achieved by adding 2?M of HCl with 3?days mixing, followed by Fe²⁺-activated persulfate oxidation (PS/Fe²⁺ molar ratio at 4:1) for further 6?h mixing. The removal efficiency of low and high molecular weight PAHs was about 70 and 20?%, respectively, while the removal efficiency of metals was 70, 100, 40, 65, 65, 80, and 100?% for Cr, Cu, Hg, Mn, Ni, Pb, and Zn, respectively.     

Impact of low-molecular-weight organic acids on the availability of phenanthrene and pyrene in soil

The impact of low-molecular-weight organic acids (LMWOAs) on the availability of phenanthrene and pyrene was investigated using laboratory batch assays. Experiments were conducted with two types of soil with different organic contents. The LMWOAs used were citric and oxalic acid. A mild solvent extraction procedure and a sorption-desorption experiment were used to predict the availability of phenanthrene and pyrene. Results showed that the extractable amounts of phenanthrene and pyrene in both soil types increased with increased citric or oxalic acid concentration. Citric acid addition promoted phenanthrene and pyrene extraction to a greater degree than oxalic acid. Compared with freshly spiked soils, the extractable amounts of phenanthrene and pyrene with the addition of LMWOAs decreased significantly after 60 days of cultivation. Soils with higher values of soil organic carbon content (f_oc) showed decreased phenanthrene and pyrene availability after the addition of LMWOAs. The sorption and desorption results also demonstrated the enhanced availability of PAHs with LMWOA addition. Phenanthrene sorption could be described using a linear model, regardless of the addition of LMWOAs. The simulated distribution constants (K_d) for phenanthrene sorption decreased significantly with the addition of LMWOAs. In contrast, phenanthrene desorption clearly increased with the addition of LMWOAs. These results suggest that the availabilities of phenanthrene and pyrene can be increased with the addition of suitable LMWOAs.