Atmospheric partitioning and the air–water exchange of polycyclic aromatic hydrocarbons in a large shallow Chinese lake (Lake Chaohu)

The residual levels of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in dissolved phase from Lake Chaohu were measured by (GC–MS). The composition and seasonal variation were investigated. The diffusive air–water exchange flux was estimated by a two-film model, and the uncertainty in the flux calculations and the sensitivity of the parameters were evaluated. The following results were obtained: (1) the average residual levels of all PAHs (PAH16) in the atmosphere from Lake Chaohu were 60.85 ± 46.17 ng m⁻³ in the gaseous phase and 14.32 ± 23.82 ng m⁻³ in the particulate phase. The dissolved PAH16 level was 173.46 ± 132.89 ng L⁻¹. (2) The seasonal variation of average PAH16 contents ranged from 43.09 ± 33.20 ng m⁻³ (summer) to 137.47 ± 41.69 ng m⁻³ (winter) in gaseous phase, from 6.62 ± 2.72 ng m⁻³ (summer) to 56.13 ± 22.99 ng m⁻³ (winter) in particulate phase, and 142.68 ± 74.68 ng L⁻¹ (winter) to 360.00 ± 176.60 ng L⁻¹ (summer) in water samples. Obvious seasonal trends of PAH16 concentrations were found in the atmosphere and water. The values of PAH16 for both the atmosphere and the water were significantly correlated with temperature. (3) The monthly diffusive air–water exchange flux of total PAH16 ranged from −1.77 × 10⁴ ng m⁻² d⁻¹ to 1.11 × 10⁵ ng m⁻² d⁻¹, with an average value of 3.45 × 10⁴ ng m⁻² d⁻¹. (4) The results of a Monte Carlo simulation showed that the monthly average PAH fluxes ranged from −3.4 × 10³ ng m⁻² d⁻¹ to 1.6 × 10⁴ ng m⁻² d⁻¹ throughout the year, and the uncertainties for individual PAHs were compared. (5) According to the sensitivity analysis, the concentrations of dissolved and gaseous phase PAHs were the two most important factors affecting the results of the flux calculations.     

Assessment of denitrification process in lower Ishikari river system,Japan

Sediment denitrification rate and its role in removal of dissolved nitrate load in lower Ishikari river system were examined. Denitrification rate were measured using acetylene inhibition technique on the sediment samples collected during August 2009–July 2010. The denitrification rate varied from 0.001 to 1.9 μg N g⁻¹ DM h⁻¹ with an average value of 0.21 μg N g⁻¹ DM h⁻¹ in lower Ishikari river system. Denitrification rate showed positive correlation with dissolved nitrate concentration in the river basin, indicating overlying water column supplied nitrate for the sediment denitrification processes. Nutrient enrichment experiments result showed that denitrification rate increased significantly with addition of nitrate in case of samples collected from Barato Lake however no such increase was observed in the samples collected from Ishikari river main channel and its major tributaries indicating that factors other than substrate concentration such as population of denitrifier and hydrological properties of stream channel including channel depth and flow velocity may affects the denitrification rate in lower Ishikari river system. Denitrification rate showed no significant increase with the addition of labile carbon (glucose), indicating that sediment samples had sufficient organic matter to sustain denitrification activity. The result of nutrient spiraling model indicates that in- stream denitrification process removes on an average 5% d⁻¹ of dissolve nitrate load in Ishikari river. This study was carried out to fill the gap present in the availability of riverine denitrification rate measurement and its role in nitrogen budget from Japanese rivers characterize by small river length and high flow rate.     

Monitoring of environmental contaminants in raw bovine milk and estimates of dietary intakes of children in South Korea

Persistent organic pollutants (POPs) are ubiquitous residual contaminants in the environment and in the food chain. Milk is an important matrix for monitoring POP contamination. This study determined the concentrations of POPs including polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (DL-PCBs) in raw bovine milk, and the data was used to estimate dietary intakes in South Korea. The average concentrations of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw milk were 0.29 ng g⁻¹ fat, 0.50 ng g⁻¹ fat, 0.27 pg TEQ g⁻¹ fat, and 0.33 pg TEQ g⁻¹ fat, respectively. No significant relationship was found between the concentrations of analytes and the regions sampled. The dietary intakes of PBDEs from the consumption of milk was calculated to be 0.26, 0.10, and 0.05 ng kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. The dietary intakes of HCB was calculated to be 0.44, 0.16, and 0.09 ng kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. The dietary intakes of PCDD/Fs and DL-PCBs was calculated to be 0.78, 0.29, and 0.16 pg TEQ kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. These results indicated that the residual levels of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw bovine milk were within safe levels.     

Concentrations of cyclic volatile methylsiloxanes in biosolid amended soil,influent, effluent,receiving water,and sediment of wastewater treatment plants in Canada

A comprehensive surveillance program was conducted to determine the occurrence of three cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in environmental compartments impacted by wastewater effluent discharges. Eleven wastewater treatment plants (WWTPs), representative of those found in Southern Ontario and Southern Quebec, Canada, were investigated to determine levels of cVMS in their influents and effluents. In addition, receiving water and sediment impacted by WWTP effluents, and biosolid-amended soil from agricultural fields were also analyzed for a preliminary evaluation of the environmental exposure of cVMS in media impacted by wastewater effluent and solids. A newly-developed large volume injection (septumless head adapter and cooled injection system) gas chromatography – mass spectrometry method was used to avoid contamination originating from instrumental analysis. Concentrations of D4, D5, and D6 in influents to the 11 WWTPs were in the range 0.282–6.69 μg L⁻¹, 7.75–135 μg L⁻¹, and 1.53–26.9 μg L⁻¹, respectively. In general, wastewater treatment showed cVMS removal rates of greater than 92%, regardless of treatment type. The D4, D5, and D6 concentration ranges in effluent were <0.009–0.045 μg L⁻¹, <0.027–1.56 μg L⁻¹, and <0.022–0.093 μg L⁻¹, respectively. The concentrations in receiving water influenced by effluent, were lower compared to those in effluent in most cases, with the ranges <0.009–0.023 μg L⁻¹, <0.027–1.48 μg L⁻¹, and <0.022–0.151 μg L⁻¹ for D4, D5, and D6, respectively. Sediment concentrations ranged from <0.003–0.049 μg g⁻¹ dw, 0.011–5.84 μg g⁻¹ dw, and 0.004–0.371 μg g⁻¹ dw for D4, D5, and D6, respectively. The concentrations in biosolid-amended soil, having values of <0.008–0.017 μg g⁻¹ dw, <0.007–0.221 μg g⁻¹ dw, and <0.009–0.711 μg g⁻¹ dw for D4, D5, and D6, respectively, were lower than those in sediment impacted by wastewater effluent in most cases. In comparison with the no-observed-effected concentrations (NOEC) and IC50 (concentration that causes 50% inhibition of the response) values, the potential risks to aquatic, sediment-dwelling, and terrestrial organisms from these reported concentrations are low.     

Methyl-triclosan binding to human serum albumin: Multi-spectroscopic study and visualized molecular simulation

Methyl-triclosan (MTCS), a transformation product and metabolite of triclosan, has been widely spread in environment through the daily use of triclosan which is a commonly used anti-bacterial and anti-fungal substance in consumer products. Once entering human body, MTCS could affect the conformation of human serum albumin (HSA) by forming MTCS–HSA complex and alter function of protein and endocrine in human body. To evaluate the potential toxicity of MTCS, the binding mechanism of HSA with MTCS was investigated by UV–vis absorption, circular dichroism and Fourier transform infrared spectroscopy. Binding constants, thermodynamic parameters, the binding forces and the specific binding site were studied in detail. Binding constant at room tempreture (T = 298 K) is 6.32 × 10³ L mol⁻¹; ΔH⁰, ΔS⁰ and ΔG⁰ were 22.48 kJ mol⁻¹, 148.16 J mol⁻¹ K⁻¹ and −21.68 kJ mol⁻¹, respectively. The results showed that the interactions between MTCS and HSA are mainly hydrophobic forces. The effects of MTCS on HSA conformation were also discussed. The binding distance (r = 1.2 nm) for MTCS–HSA system was calculated by the efficiency of fluorescence resonance energy transfer. The visualized binding details were also exhibited by molecular modeling method and the results could agree well with that from the experimental study.     

Bioaccumulation and depuration of anthracene in Penaeus monodon (Fibricius) through food ingestion

Understanding on the bioaccumulation and depuration of PAHs (polycyclic aromatic hydrocarbons) in Penaeus monodon is important in seafood safety because it is one of the most popular seafood consumed worldwide. In this study, we used anthracene as the precursor compound for PAHs accumulation and depuration in the shrimp. Commercial feed pellets spiked with anthracene were fed to P. monodon. At 20 mg kg⁻¹ anthracene, P. monodon accumulated 0.1% of the anthracene from the feed. P. monodon deputed the PAH two times faster than its accumulation. The shrimp reduced its feed consumption when anthracene content in the feed exceeded 20 mg kg⁻¹. At 100 mg kg⁻¹ anthracene, P. monodon started to have necrosis tissues on the posterior end of their thorax. The bioaccumulation factor (BAF), uptake rate constant (k₁) and depuration rate constant (k₂) of anthracene in P. monodon were 1.15 × 10⁻³, 6.80 × 10⁻⁴ d⁻¹ and 6.28 × 10⁻¹ d⁻¹, respectively. The depuration rate constant is about thousand times higher than the uptake rate constant and this indicated that this crustacean is efficient in depurating hydrocarbons from their tissue.     

Historical trends in human dietary intakes of endosulfan and toxaphene in China, Korea and Japan

Recently, the Stockholm Convention prohibited the use of toxaphene and has been reviewing endosulfan. The historical use of these pesticides may contaminate food and tend to accumulate in the food chain. In this study, to evaluate the spatial and temporal trends of food contamination, the endosulfan and toxaphene levels were measured in pooled 24-h food composite samples from Chinese (n = 10), Korean (n = 10) and Japanese (n = 40) adults in the 1990s and 2007-2009. Endosulfan was detected in 32 of 40 samples from Japan, but its levels (sum of α- and β-isomers) were low in both the 1990s and 2009 (range as geometric mean (geometric standard deviation) [GM (GSD)]: 0.96 (1.6)-1.42 (1.4) ng kg⁻¹ d⁻¹). The dietary intakes of endosulfan in Seoul as GM (GSD) were 38.68 (1.3) ng kg bw⁻¹ d⁻¹ in 1994 and 92.17 (4.4) ng kg bw⁻¹ d⁻¹ in 2007, and significantly higher than those in Japan (p < 0.05). The samples from Beijing showed a 50-fold increase in the endosulfan levels from 1993 (GM: 0.58 ng kg⁻¹ d⁻¹) to 2009 (GM: 24.91 ng kg bw⁻¹ d⁻¹) (p < 0.05). Toxaphene was detected in 33 of 40 samples from Japan. The dietary intake of toxaphene in Japan (sum of Parlars #26, #50 and #62) was 0.32-1.21 ng kg bw⁻¹ d⁻¹ (range as geometric mean) and no temporal trend was observed. The dietary intake of toxaphene in Seoul increased significantly from 0.2 ng kg bw⁻¹ d⁻¹ (GM) in 1994 to 3.6 ng kg bw⁻¹ d⁻¹ (GM) in 2007 (p < 0.05). Only one of 10 pooled samples from Beijing contained a detectable level of toxaphene (0.3 ng kg bw⁻¹ d⁻¹). For the entire population, the risk of adverse health effects from dietary intakes of endosulfan and toxaphene is unlikely. However, the concentrations of endosulfan in several samples exceeded 10% of the acceptable daily intake limit value of 6 μg kg bw⁻¹ d⁻¹ set by the World Health Organization (WHO). It appears important to refine dietary intake estimates targeting food types and source identification to ensure safe food for consumers.     

Evaluation of food chain transfer of the antibiotic oxytetracycline and human risk assessment

There has been recent concern regarding the possibility of antibiotics entering the aquatic food chain and impacting human consumers. This work reports experimental results of the bioconcentration of the antibiotic oxytetracycline (OTC) by the Asian watermeal plant (Wolffia globosa Hartog & Plas) and bioaccumulation of OTC in watermeal and water by the seven-striped carp (Probarbus jullieni). They show, for the first time, the extent to which OTC is able to transfer from water to plant to fish and enter the food chain. The mean bioconcentration factor (dry weight basis) with watermeal was 1.28 × 10³ L kg⁻¹. Separate experiments were undertaken to characterize accumulation of OTC by carp from water and watermeal. These showed the latter pathway to be dominant under the conditions employed. The bioconcentration and biomagnification factors for these processes were 1.75 L kg⁻¹ and 2 × 10⁻⁴ kg g⁻¹ respectively. Using an aqueous concentration range of 0.34–3.0 μg L⁻¹, hazard quotients for human consumption of contaminated fish of 1.3 × 10⁻² to 1.15 × 10⁻¹ were derived.     

Copper and cadmium effects on growth and extracellular exudation of the marine toxic dinoflagellate Alexandrium catenella: 3D-fluorescence spectroscopy approach

In this study, metal contamination experiments were conducted to investigate the effects of copper and cadmium on the growth of the marine toxic dinoflagellate Alexandrium catenella and on the production of dissolved organic matter (Dissolved Organic Carbon: DOC; Fluorescent Dissolved Organic Matter: FDOM). This species was exposed to increasing concentrations of Cu²⁺ (9.93 × 10⁻¹⁰–1.00 × 10⁻⁷ M) or Cd²⁺ (1.30 × 10⁻⁸–4.38 × 10⁻⁷ M), to simulate polluted environments. The drastic effects were observed at pCu²⁺ = 7.96 (Cu²⁺: 1.08 × 10⁻⁸ M) and pCd²⁺ = 7.28 (Cd²⁺: 5.19 × 10⁻⁸ M), where cyst formation occurred. Lower levels of Cu²⁺ (pCu²⁺ > 9.00) and Cd²⁺ (pCd²⁺ > 7.28) had no effect on growth. However, when levels of Cu²⁺ and Cd²⁺ were beyond 10⁻⁷ M, the growth was totally inhibited. The DOC released per cell (DOC/Cell) was different depending on the exposure time and the metal contamination, with higher DOC/Cell values in response to Cu²⁺ and Cd²⁺, comparatively to the control. Samples were also analyzed by 3D-fluorescence spectroscopy, using the Parallel Factor Analysis (PARAFAC) algorithm to characterize the FDOM. The PARAFAC analytical treatment revealed four components (C1, C2, C3 and C4) that could be associated with two contributions: one, related to the biological activity; the other, linked to the decomposition of organic matter. The C1 component combined a tryptophan peak and a characteristic humic substances response, and the C2 component was considered as a tryptophan protein fluorophore. The C3 and C4 components were associated to marine organic matter production.     

Vertical fluxes of aromatic and aliphatic hydrocarbons in the Northwestern Mediterranean Sea

Aliphatic and aromatic hydrocarbon fluxes were measured in time series sediment trap samples at 200 m and at 1000 m depths in the open Northwestern Mediterranean Sea, from December 2000 to July 2002. Averaged fluxes of n-alkanes, UCM and T-PAH₃₅ were 2.96 ± 2.60 μg m⁻² d⁻¹, 64 ± 60 μg m⁻² d⁻¹ and 0.68 ± 0.59 μg m⁻² d⁻¹, respectively. Molecular compositions of both hydrocarbon classes showed a contamination in petrogenic hydrocarbons well above the background levels of such an open site, whereas pyrolytic hydrocarbons stand in the range of other open Mediterranean locations. Fluxes displayed ample interannual and seasonal variabilities, mainly related to mass flux variation while concentration evolutions trigger secondary changes in pollutant fluxes. High lithogenic flux events exported particles with a larger pollutant load than biogenic particles formed during the spring bloom and during the summer. Sinking hydrocarbons were efficiently transported from 200 m to 1000 m.     

Risk ranking of multiple-POPs in detritivorous fish from the Río de la Plata

To evaluate the bioaccumulation and the risk associated to consumption of lipid-rich detritivorous fish, a comprehensive set of organic pollutants (n = 213) including polychlorinated biphenyls (PCBs), dioxin like PCBs (dlPCBs), chlorinated pesticides (CHLPs), chlorobenzenes (CBzs), polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo dioxins and furans (PCDD/F), resolved (ALI) and unresolved aliphatic hydrocarbons (UCM) and linear alkyl benzenes (LABs) were analyzed in Sábalo fish (Prochilodus lineatus) collected in the polluted Metropolitan Buenos Aires coast and in migrating specimens. Fatty fish muscles (lipids: 74 ± 9.3% dry weight) contained homogeneous (24-51% variability) and very high-concentrations of organic pollutants ranging from 60 to 1300 μg g⁻¹ fresh weight (fw) ALI + UCM; 10-40 μg g⁻¹ fw LABs and PCBs; 0.1-1 μg g⁻¹ fw dlPCBs, DDTs, chlordanes, CBzs and PBDEs; 0.01-0.1 μg g⁻¹ fw mirex, endosulfans, aldrin, dieldrin, endrin and 0.07-0.2 ng g⁻¹ PCDD/F. Total toxicity equivalents (TEQs) ranged from 60 to 395 pg g⁻¹ fw (34 ± 17 and 213 ± 124 pg g⁻¹ TEQs for PCDD/F and dlPCBs respectively). These are among the highest concentrations reported for fish and point out the remarkable ability of Sábalo to feed on anthropogenic organic-enriched particles and tolerate a high pollutant load. Contaminant signatures show partial alteration with still abundant lower molecular weight components indicating that fish feeds directly in the outfalls. Consumption limits based on reference doses ranged from 0.1 (PCBs) to >12 000 g d⁻¹ (endosulfan) allowing a comprehensive risk-based ranking of contaminants in this long-range migrating, detritivorous fish.     

Effect of vegetation in pilot-scale horizontal subsurface flow constructed wetlands treating sulphate rich groundwater contaminated with a low and high chlorinated hydrocarbon

In order to characterize the effect of vegetation on performance of constructed wetlands (CWs) treating low and high chlorinated hydrocarbon, two pilot-scale horizontal subsurface flow (HSSF) CWs (planted with Phragmites australis and unplanted) treating sulphate rich groundwater contaminated with MCB (monochlorobenzene, as a low chlorinated hydrocarbon), (about 10 mg L⁻¹), and PCE (perchloroethylene, as a high chlorinated hydrocarbon), (about 2 mg L⁻¹), were examined. With mean MCB inflow load of 299 mg m⁻² d⁻¹, the removal rate was 58 and 208 mg m⁻² d⁻¹ in the unplanted and planted wetland, respectively, after 4 m from the inlet. PCE was almost completely removed in both wetlands with mean inflow load of 49 mg m⁻² d⁻¹. However, toxic metabolites cis-1,2-DCE (dichloroethene) and VC (vinyl chloride) accumulated in the unplanted wetland; up to 70% and 25% of PCE was dechlorinated to cis-1,2-DCE and VC after 4 m from the inlet, respectively. Because of high sulphate concentration (around 850 mg L⁻¹) in the groundwater, the plant derived organic carbon caused sulphide formation (up to 15 mg L⁻¹) in the planted wetland, which impaired the MCB removal but not statistically significant. The results showed significant enhancement of vegetation on the removal of the low chlorinated hydrocarbon MCB, which is probably due to the fact that aerobic MCB degraders are benefited from the oxygen released by plant roots. Vegetation also stimulated completely dechlorination of PCE due to plant derived organic carbon, which is potentially to provide electron donor for dechlorination process. The plant derived organic carbon also stimulated dissimilatory sulphate reduction, which subsequently have negative effect on MCB removal.     

Mobility of radionuclides in soil/groundwater system: Comparing the influence of EDTA and four of its degradation products

The adsorption behavior of ²⁴¹Am, ⁶⁰Co, ¹³⁷Cs and ⁸⁵Sr in the presence and absence of chelating ligands (ethylenediaminetetraacetic acid, ethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, iminodiaceiticacid and methyliminodiacetic acid) was investigated. Sorption affinity in the absence of chelating ligands followed: Am(III) > Co(II) > Cs(I) > Sr(II). The presence of chelating ligands generally had little effect on sorption of ⁸⁵Sr and ¹³⁷Cs with K_d values 110 and 690 mL g⁻¹, respectively. But at 0.02 M of ethylenediaminetetraacetic or hydroxyethyliminodiacetic, the K_d decreased to 5 or 63 mL g⁻¹, respectively, where thermochemical modeling indicated almost all ⁸⁵Sr is complexed with these ligands. The K_d values for ²⁴¹Am and ⁶⁰Co generally decreased with increasing chelating agent concentrations. In notable cases, the K_d values for Am increased at specific concentrations of 10⁻³ M for IDA, MIDA and 10⁻⁴ M for EDDA. This is proposed to be due to formation of a ternary surface complex.     

Influence of releases of I-129 from reprocessing plants on the marine environment of the North Adriatic Sea

Compared to the pre-nuclear era, large amounts of ¹²⁹I have been released to the marine environment, especially as liquid and gaseous discharges from two European reprocessing plants located at Sellafield and La Hague. Their liquid discharges influence Northern Europe and most research was conducted in the area of the North Atlantic Ocean and the Baltic Sea. In this article data on ¹²⁹I content and ¹²⁹I/¹²⁷I ratios observed in the North Adriatic Sea, which is a rather enclosed basin of the Mediterranean Sea, are presented. To the best of our knowledge no data on ¹²⁹I in the Mediterranean Sea have previously been reported. As this area is isolated from direct liquid discharges, the main transport pathway is probably gaseous releases from reprocessing plants. Surface sea water, the marine alga Fucus virsoides, an iodine accumulator, and the Mediterranean mussel Mytilus galloprovincialis collected in 2009 and 2010, and marine sediment collected in 2005 and 2009 were analysed. The ¹²⁹I/¹²⁷I isotopic ratios observed were in the range from 0.8 to 3.0 × 10⁻⁰⁸ for seawater, from 0.06 to 0.35 × 10⁻⁰⁸ for marine sediment, from 0.05 to 0.10 × 10⁻⁰⁸ for F. virsoides and from 0.3 to 0.9 × 10⁻⁰⁸ for M. galloprovincialis.     

Assessment of risk to humans of bisphenol A in marine and freshwater fish from Pearl River Delta, China

Bisphenol A (BPA) is a high production-volume chemical used in the manufacture of a wide variety of consumer products. However it is also a ubiquitous contaminant that can interfere with endocrine systems of wildlife and humans. China is the “world factory” and the Pearl River Delta is the major manufacturing center and is consequently polluted. Concentrations of BPA in meats of marketable fish had not been previously reported for this region. In the study upon which we report here concentrations of BPA were determined in 20 common species of freshwater and marine fish, collected from markets in Hong Kong, SAR, China. A comprehensive analytical method based on SPE extraction and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was developed, validated and applied. The method limit of detection (LOD) and limit of quantification (LOQ) were 0.5 and 1.25 ng g⁻¹ dw, respectively. BPA was detected in 19 species of fish at concentrations, ranging from 0.5 to 2.0 ng g⁻¹ ww. Average daily BPA intake per person ranged from 1.1 × 10² ng d⁻¹ for marine fish and 2.2 × 10² ng d⁻¹ for freshwater fish. Concentrations of BPA in fish from Hong Kong markets unlikely would be causing adverse population-level effects in humans.     

Production and sedimentation of peptide toxins nodularin-R and microcystin-LR in the northern Baltic Sea

This seven-year survey was primarily targeted to quantification of production of nodularin-R (NOD-R), a cyclic pentapeptide hepatotoxin, in Baltic Sea cyanobacteria waterblooms. Additionally, NOD-R and microcystin-LR (MC-LR; a cyclic heptapeptide toxin) sedimentation rates and NOD-R sediment storage were estimated. NOD-R production (70-2450 μg m⁻³; ∼1 kg km⁻² per season) and sedimentation rates (particles; 0.03-5.7 μg m⁻² d⁻¹; ∼0.3 kg km⁻² per season) were highly variable over space and time. Cell numbers of Nodularia spumigena did not correlate with NOD-R quantities. Dissolved NOD-R comprised 57-100% of total NOD-R in the predominantly senescent, low-intensity phytoplankton blooms and seston. Unprecedentedly intensive MC-LR sedimentation (0.56 μg m⁻² d⁻¹) occurred in 2004. Hepatotoxin sedimentation rates highly exceeded those of anthropogenic xenobiotics. NOD-R storage in surficial sediments was 0.4-20 μg kg⁻¹ (∼0.1 kg km⁻²). Loss of NOD-R within the chain consisting of phytoplankton, seston and soft sediments seemed very effective.     

Positive vs. false detection: A comparison of analytical methods and performance for analysis of cyclic volatile methylsiloxanes (cVMS) in environmental samples from remote regions

Contamination and analytical variation can significantly hinder trace analysis of cyclic methyl volatile siloxanes (cVMS); potentially resulting in the report of false positives at concentrations approaching detection limits. To assess detection and variation associated with trace cVMS analysis in environmental matrices, a co-operative laboratory comparison for the analysis of octametylcyclotetrasiloxane (D4), decamethylcylcopentasiloxane (D5), and dodecametylcyclohexasiloxane (D6) in sediment and biota from the Svalbard Archipelago was conducted. Two definitions of detection limits were evaluated in this study; method detection limits (MDL, matrix defined) and limits of detection (LOD, solvent defined). D5 was the only cVMS detected above both LOD (0.08–0.81 ng g⁻¹ ww) and MDL (0.47–2.36 ng g⁻¹ ww) within sediment by all laboratories where concentrations ranged from 0.55 to 3.91 ng g⁻¹ ww. The percentage of positive detects for D5 decreased by 80% when MDL was defined as the detection limit. D5 was also detected at the highest frequency among all laboratories in fish liver with concentrations ranging from 0.72 to 345 ng g⁻¹ ww. Similar to sediment, percentage of positive detects for D5 decreased by 60% across all laboratories for fish livers when using MDL (0.68–3.49 ng g⁻¹ ww). Similar observations were seen with both D4 and D6, indicating that sample matrix significantly contributes to analytical response variation. Despite differences in analytical methods used between laboratories, good agreement was obtained when using MDL to define detection limits. This study shows the importance of incorporating variation introduced by sample matrices into detection limit calculations to insure data accuracy of cVMS at low concentrations.     

Development of a combined isotopic and mass-balance approach to determine dissolved organic carbon sources in eutrophic reservoirs

A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9 mg L⁻¹) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ¹³C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ¹³C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ¹³C values of the DOC recovered in the reservoir (−28.5 ± 0.2‰; n = 22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ¹³C in algae = −30.1 ± 0.3‰; n = 2) being indistinguishable from the δ¹³C values of allochthonous DOC from inflowing rivers (−28.6 ± 0.1‰; n = 8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs.     

Contamination of nonylphenolic compounds in creek water, wastewater treatment plant effluents, and sediments from Lake Shihwa and vicinity, Korea: comparison with fecal pollution

Nonylphenolic compounds (NPs), coprostanol (COP), and cholestanol, major contaminants in industrial and domestic wastewaters, were analyzed in creek water, wastewater treatment plant (WWTP) effluent, and sediment samples from artificial Lake Shihwa and its vicinity, one of the most industrialized regions in Korea. We also determined mass discharge of NPs and COP, a fecal sterol, into the lake, to understand the linkage between discharge and sediment contamination. Total NP (the sum of nonylphenol, and nonylphenol mono- and di-ethoxylates) were 0.32-875 μg L⁻¹ in creeks, 0.61-87.0 μg L⁻¹ in WWTP effluents, and 29.3-230 μg g⁻¹ TOC in sediments. Concentrations of COP were 0.09-19.0 μg L⁻¹ in creeks, 0.11-44.0 μg L⁻¹ in WWTP effluents, and 2.51-438 μg g⁻¹ TOC in sediments. The spatial distributions of NPs in creeks and sediments from the inshore region were different from those of COP, suggesting that Lake Shihwa contamination patterns from industrial effluents differ from those from domestic effluents. The mass discharge from the combined outfall of the WWTPs, located in the offshore region, was 2.27 kg d⁻¹ for NPs and 1.00 kg d⁻¹ for COP, accounting for 91% and 95% of the total discharge into Lake Shihwa, respectively. The highest concentrations of NPs and COP in sediments were found in samples at sites near the submarine outfall of the WWTPs, indicating that the submarine outfall is an important point source of wastewater pollution in Lake Shihwa.     

Aerobic degradation of tetrabromobisphenol-A by microbes in river sediment

This study investigated the aerobic degradation of tetrabromobisphenol-A (TBBPA) and changes in the microbial community in river sediment from southern Taiwan. Aerobic degradation rate constants (k₁) and half-lives (t_1/2) for TBBPA (50 μg g⁻¹) ranged from 0.053 to 0.077 d⁻¹ and 9.0 to 13.1 d, respectively. The degradation of TBBPA (50 μg g⁻¹) was enhanced by adding yeast extract (5 mg L⁻¹), sodium chloride (10 ppt), cellulose (0.96 mg L⁻¹), humic acid (0.5 g L⁻¹), brij 30 (55 μM), brij 35 (91 μM), rhamnolipid (130 mg L⁻¹), or surfactin (43 mg L⁻¹), with rhamnolipid yielding a higher TBBPA degradation than the other additives. For different toxic chemicals in the sediment, the results showed the high-to-low order of degradation rates were bisphenol-A (BPA) (50 μg g⁻¹) > nonylphenol (NP) (50 μg g⁻¹) > 4,4′-dibrominated diphenyl ether (BDE-15) (50 μg g⁻¹) > TBBPA (50 μg g⁻¹) > 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209) (50 μg g⁻¹). The addition of various treatments changed the microbial community in river sediments. The results also showed that Bacillus pumilus and Rhodococcus ruber were the dominant bacteria in the process of TBBPA degradation in the river sediments.