Log BCF Research Articles

Interpretable attention-based multi-encoder transformer based QSPR model for assessing toxicity and environmental impact of chemicals

The rising demand from consumer goods and pharmaceutical industry is driving a fast expansion of newly developed chemicals. The conventional toxicity testing of unknown chemicals is expensive, time-consuming, and raises ethical concerns. The quantitative structure–property relationship (QSPR) is an efficient computational method because it saves time, resources, and animal experimentation. Advances in machine learning have improved chemical analysis in QSPR studies, but the real-world application of machine learning-based QSPR studies was limited by the unexplainable ‘black box’ feature of the machine learnings. In this study, multi-encoder structure-to-toxicity (S2T)-transformer based QSPR model was developed to estimate the properties of polychlorinated biphenyls (PCBs) and endocrine disrupting chemicals (EDCs). Simplified molecular input line entry systems (SMILES) and molecular descriptors calculated by the Dragon 6 software, were simultaneously considered as input of QSPR model. Furthermore, an attention-based framework is proposed to describe the relationship between the molecular structure and toxicity of hazardous chemicals. The S2T-transformer model achieved the highest R2 scores of 0.918, 0.856, and 0.907 for logarithm of octanol-water partition coefficient (Log KOW), octanol-air partition coefficient (Log KOA), and bioconcentration factor (Log BCF) estimation of PCBs, respectively. Moreover, the attention weights were able to properly interpret the lateral (meta, para) chlorination associated with PCBs toxicity and environmental impact.

Sorption in soils and bioaccumulation potential of 2,2′-DiBBPA

2,2′-Dibromobisphenol A (2,2′-DiBBPA) is frequently detected in the environment. However, the mobility of 2,2′-DiBBPA in the soil environment is poorly understood. The present study examined the effects of soil components such as the NaClO-resistant fraction, dithionite-citrate-bicarbonate -demineralized fraction, humin fraction, black carbon, DOC-removed fraction, exogenous dissolved organic carbon and heavy metal cations on the adsorption of 2,2′-DiBBPA on several types of agricultural soils. The adsorption isotherms on soils and soil components were well fitted to the linear isotherm equation. 2,2′-DiBBPA sorption onto soils was dominated by soil organic matter content (SOM) and affected by exogenous dissolved organic carbon. Linear regression relationships between adsorption capacity (Kd) and soil characteristics were evaluated to predict partitioning of 2,2′-DiBBPA. Black carbon played a predominant role in the adsorption of 2,2′-DiBBPA. Heavy metal ions significantly inhibited the adsorptive behavior of 2,2′-DiBBPA under alkaline conditions. Semiempirical linear relationships were observed between biota-sediment accumulation factors (1.18–2.47)/logarithm of bioconcentration factors (BCFs, 2.49–2.52) of 2,2′-DiBBPA in lugworms and Kd. These results allow for the prediction of the bioaccumulation of 2,2′-DiBBPA in other soils. Furthermore, values of log BCF > 1.0 indicate the preferential bioaccumulation of 2,2′-DiBBPA in biota. These data are of significance for understanding the migration of 2,2′-DiBBPA in agricultural soils and bioaccumulation in organisms.

Immobilized Keratin HPLC Stationary Phase-A Forgotten Model of Transdermal Absorption: To What Molecular and Biological Properties Is It Relevant?

Chromatographic retention data collected on immobilized keratin (KER) or immobilized artificial membrane (IAM) stationary phases were used to predict skin permeability coefficient (log Kp) and bioconcentration factor (log BCF) of structurally unrelated compounds. Models of both properties contained, apart from chromatographic descriptors, calculated physico-chemical parameters. The log Kp model, containing keratin-based retention factor, has slightly better statistical parameters and is in a better agreement with experimental log Kp data than the model derived from IAM chromatography; both models are applicable primarily to non-ionized compounds.Based on the multiple linear regression (MLR) analyses conducted in this study, it was concluded that immobilized keratin chromatographic support is a moderately useful tool for skin permeability assessment.However, chromatography on immobilized keratin may also be of use for a different purpose-in studies of compounds' bioconcentration in aquatic organisms.

Modeling plant uptake of organic contaminants by root vegetables: The role of diffusion, xylem, and phloem uptake routes

The uptake of organic contaminants by root vegetables involves diffusion, transport by xylem and phloem saps, degradation, and volatilization. To understand the role of uptake and elimination routes in the bioconcentration modeling of organic contaminants, a two-compartment uptake model (root and leaf compartments) was proposed. The results showed that for the root compartment, logarithm values of bioconcentration factors (log BCF, the concentration ratio between plant tissues and soil) of chemicals fell within a narrow range when the logarithm of octanol-water partition coefficient (log KOW) was less than 3.0, whereas log BCF values decreased rapidly with increasing log KOW values when log KOW was greater than 3.0. This is because the diffusion route had a significant impact on the root uptake of chemicals, wherein the first-order rate constant dropped rapidly for high-lipophilicity chemicals, resulting in very low log BCF values. For the leaf compartment, chemicals with moderate lipophilicity (log KOW of 3.0–4.0) had the highest simulated log BCF values. This is because moderate log KOW values generated the highest transpiration stream concentration factors (TSCFs, the concentration ratio between xylem or phloem saps and water), resulting in high uptake efficiency of chemicals by leaves. Furthermore, we improved the uptake model by considering the surface-deposition route for pesticides (foliar spray), and the simulation results indicated that this uptake route cannot be neglected for lipophilic compounds. Although the simulations agreed with an experimental study and some reported data, future studies should focus on factors, such as plant physiology (plant varieties, periderm effects and compositions of xylem and phloem saps) and environmental conditions (soil properties and weather conditions), to improve the plant uptake model.

Kinetics and mechanisms of flumequine degradation by sulfate radical based AOP in different water samples containing inorganic anions.

Many studies have reported that hydroxyl radical (HO˙) driven advanced oxidation processes (AOPs) could degrade fluoroquinolones (FQs) antibiotics effectively. Compared with HO˙, sulfate radical (SO4˙−) shows a similar oxidation capacity but a longer half-life. SO4˙− could cause chain reactions and resulted in the generation of halogen radicals and carbonate radicals from the main anions in sea water including Cl−, Br− and HCO3−. However, few studies were focused on the degradation of FQs in marine aquaculture water and seawater, as well as the bioaccumulation of transformation products. As a typical member of FQs, flumequine (FLU) was degraded by UV/peroxodisulfate (PDS) AOPs in synthetic fresh water, marine aquaculture water and seawater. The reaction rate constants in the three water samples were 0.0348 min−1, 0.0179 min−1 and 0.0098 min−1, respectively. The reason was attributed to the inhibition of the anions as they could consume SO4˙− and initiate the quenching reaction of free radicals. When the pH value increased from 5 to 9, the reaction rate decreased from 0.0197 min−1 to 0.0066 min−1. The energy difference between HOMO and LUMO of FLU was calculated to be 8.07 eV indicating that FLU was a stable compound. The atoms on quinolone ring of FLU with high negative charge would be more vulnerable to attack by free radicals through electrophilic reactions. Two possible degradation pathways of FLU were inferred according to the degradation products. Preliminary bioaccumulation analysis of transformation products by the EPI suite software proved that the values of log Kow and log BCF of the final product P100 were less than those of FLU and the intermediates.

A 3D-QSAR model for the comprehensive bioenrichment and biodegradation effect of benzotriazole ultraviolet stabilisers and application of the model in molecular modification.

Ultraviolet (UV) absorber, a type of light stabiliser, has received considerable attention because of its high bioenrichment ability and low biodegradability. In this study, benzotriazole ultraviolet stabilisers (BUVSs) were used as the research object, and the bioenrichment and biodegradation data of 13 types of BUVS molecules were subjected to dimensionless processing through quartile data transformation. Additionally, a three-dimensional quantitative structure-activity relationship (3D-QSAR) model was constructed for the investigation of the comprehensive effect of molecular bioenrichment and biodegradation of BUVSs, and improved derivative molecules were designed. Furthermore, the validity of the model was predicted using EPI simulation software, and finally, the biodegradability of BUVSs and their bioenrichment and biological effect before and after modification in the food chain and in the aerobic and anaerobic bacteria in sewage were analysed through the molecular docking technology. A total of 10 derivatives with reduced enrichment ability and enhanced degradability were designed using the CoMFA model analysis (reduction: combined effect value, 0.32-20.55%; log BCF, 2.37-17.59%; and log HL, 0.47-16.94%). Molecular docking showed that the bioenrichment ability of two derivative molecules in the four organisms was decreased by 1.87-27.67%, and the biodegradation ability of four derivative molecules in the three sewage bacteria was enhanced by 1.60-33.38% compared with those before modification. The molecular modification method of UV absorbent developed in this study provides a new perspective for further studies on environment-friendly UV absorbent and helps reduce the risks of these emerging pollutants on the environment and human body.

RP-18 TLC retention data and calculated physico-chemical parameters as predictors of soil-water partition and bioconcentration of organic sunscreens

RP-18 TLC chromatography was used to evaluate the impact on the environment (mobility in soil expressed as soil-water partition coefficient, log Koc; bioconcentration factor in aquatic organisms, log BCF) of several cosmetic raw materials - sunscreens, preservatives and vitamins. The retention parameters RM0 (RM extrapolated to zero concentration of an organic modifier in a mobile phase), S (slope), PC1 (1st principal component) and RM75% (single TLC run parameter for mobile phases containing 75% (v/v) of an organic modifier) obtained for six organic modifiers (methanol, acetonitrile, THF, acetone, dioxane, DMF) were used as the sole descriptors or combined with calculated physico-chemical properties (PSA – polar surface area; MW – molecular weight; VM – molar volume) of studied compounds.The chromatographic parameters considered in this study are, generally speaking, good predictors of the compounds’ mobility in soil or the affinity for aquatic organisms. The parameters RM0, S and RM75% obtained for THF, dioxane and acetone may be used to investigate even very lipophilic compounds. RM75% is of a little bit limited use but it should be considered a time- and cost-effective alternative to the chromatographic parameters obtained by extrapolation or interpolation methods. In the case of some environmental parameters investigated in this study additional descriptors (PSA) have a significant influence on the quality of correlations.

Bioconcentration potential and microbial toxicity of onium cations in photoacid generators.

Despite the widespread utilization of onium salts as photoacid generators (PAGs) in semiconductor photolithography, their environmental, health, and safety (EHS) properties remain poorly understood. The present work reports the bioconcentration potential of five representative onium species (four sulfonium and one iodonium compound) by determining the octanol-water partition coefficient (POW) and lipid membrane affinity coefficient (KMA); microbial toxicity was evaluated using the bioluminescent bacterium Aliivibrio fischeri (Microtox bioassay). Four of the oniums exhibited varying degrees of hydrophobic (lipophilic) partitioning (log POW: 0.08-4.12; KMA: 1.70-5.62). A strong positive linear correlation was observed between log POW and KMA (KMA = log POW + 1.76, R2 = 0.99). The bioconcentration factors (log BCF) estimated from POW and KMA for the four oniums ranged from 0.13 to 3.67Lkg-1. Bis-(4-tert-butyl phenyl)-iodonium and triphenylsulfonium had 50% inhibitory concentrations (IC50) of 4.8 and 84.6μM, whereas the IC50 values of the other three oniums were not determined because these values were higher than their aqueous solubility. Given the increased regulatory scrutiny regarding the use and potential health impacts from onium PAGs, this study fulfills critical knowledge gaps concerning the EHS properties of PAG oniums, enabling more comprehensive evaluation of their environmental impacts and potential risk management strategies.

Phytoremediation uptake model of heavy metals (Pb, Cd and Zn) in soil using Nerium oleander

Phytoremediation is an important and effective tool to remove different contaminations in the soil, water and air. The main objective of this research was to evaluate the effect of phytoremediation using one species of shrubs, Nerium oleander plants, on reducing the heavy metals (HMs) contamination in the soil. The present study was carried out during 2015 in El-Dakhyla (industrial zone), Alexandria Egypt. A simple Uptake Plant Model (UPM) was used to estimate the contribution of various pathways in remediating ((Lead (Pb), Cadmium (Cd) and Zinc (Zn)) through different parts, in one of the evergreen shrubs (leaves, stem and root). These include soil-root-leaf pathway, soil-air-leaf pathway, and its deposition. The model calculations revealed that the (Root concentration Factor) log RCF of the root equals 0.5, 0.41, and 0.45, respectively. The Translocation Stem Concentration Factor (TSCF) of the upward in the xylem equals 0.85, 0.98 and 0.99. Moreover, the Bioaccumulation Factors (log BCF) of the soil is 1.32, 0.014 and 0.061. In addition, the partition coefficient of Octanol-Water (log Kow) is 4.67, 2.75, and 3.35, respectively. Therefore, one may conclude that Pb was accumulated in the root, while Cd and Zn were concentrated in the aerial parts of the Nerium oleander plant. On the other hand, Pb considered one of the heavy metals where it's movement in the plants is slower than Cd and Zn due to its molecular weight is bigger than the latter HMs.

Seasonal variation and the distribution of endocrine-disrupting chemicals in various matrices affected by algae in the eutrophic water environment of the pearl river delta, China

The seasonal variation and distribution among different matrices of endocrine-disrupting chemicals (EDCs) were investigated in the eutrophic water ecosystem of the Pearl River Delta, Guangdong, China. The chlorophyll a (Chl a) levels were generally higher in summer than in spring; however, the concentrations of 4-tert-octylphenol (OP), 4-nonylphenol (NP), and bisphenol A (BPA) in surface water were generally higher in spring (oligotrophic) than in summer (eutrophic). The levels of EDCs in SPM were lower in spring than in summer, a pattern seen in the seasonal variation of Chl a and particulate organic carbon (POC). The seasonal variations of EDCs in water bodies with different levels of eutrophication were analyzed in several dimensions including sediment, POC, algae and fish bile. The log Koc for SPM/water was higher in summer than in spring. The log Koc values for NP, OP, and BPA exhibited the following trends between matrices: colloid/water > sediment/water > SPM/water > algae/water, colloid/water > sediment/water > algae/water > SPM/water, and colloid/water > algae/water > sediment/water > SPM/water. The EDCs levels were different in fish tissues with the order bile > liver > muscle, with the concentrations being an order of magnitude higher in bile than in liver and an order of magnitude higher in liver than in muscle. The sequence of the bioconcentration factor (log BCF) for bile/water and liver/water was NP < OP < BPA in eutrophic conditions, but NP > OP > BPA in oligotrophic conditions. The order in eutrophic conditions was the same as the log BCF and log Koc for algae/water, indicating that the accumulation of EDCs in water bodies could be affected by algae, which could be one of the reasons of the seasonal variation of EDCs in water.

Assessing bioaccumulation potential of personal care, household and industrial products in a marine echinoderm (Holothuria tubulosa)

A bioaccumulation study of 16 emerging contaminants including preservatives, UV-filters, biocides, alkylphenols, anionic surfactants and plasticizers, in Holothuria tubulosa Gmelin, 1791 specimens was developed. Water and sediments from their coastal habitat were also analyzed. Sediment-water distribution coefficients (log Kd) were in the range 0.78 to 2.95. A rapid uptake and bioaccumulation of pollutants was found. Compounds were detected in intestine and gonads of H. tubulosa after only eight days of exposure. Field-based bioconcentration (BCF) and biota-sediment accumulation factors (BSAF) were calculated. Log BCF > 1 were obtained for most of the compounds studied, indicating their tendency to accumulate in tissue of H. Tubulosa. BCF values decrease as follow: Triclocarban > anionic surfactants > benzophenone 3 > non-ionic surfactants > bisphenol A > parabens. These data provide a detailed accounting of the distribution patterns of some emerging contaminants in organisms at the lower trophic level, representing a potential source of contaminants for organisms in higher levels of the food chain.

Bioaccumulation Potential of CPs in Aquatic Organisms: Uptake and Depuration in Daphnia magna.

Chlorinated paraffins (CPs) are industrial chemicals, subdivided into three categories: short chain (SCCPs), medium chain (MCCPs), and long chain (LCCPs) chlorinated paraffins. SCCPs are currently restricted in Europe and North America. MC and LCCPs are being used as substitution products, but there is a knowledge gap concerning their bioaccumulation potential in aquatic organisms. In this work, we performed laboratory bioconcentration (passive uptake) and bioaccumulation (including dietary uptake) experiments with Daphnia magna using five different CP technical substances. All tested CP technical substances were bioaccumulative in D. magna, with log BCF and log BAF values ranging between 6.7-7.0 and 6.5-7.0 (L kg lipid-1), respectively. An increase in carbon chain length and an increase in chlorine content (% w/w) of the CP technical substances had significant positive effects on the log BCF and log BAF values. For the different CP technical substances, 50% depuration was achieved after 2 to 10 h when D. magna were transferred to clean media. Our results show that SC, MC, and LCCPs are (very)bioaccumulative in aquatic organisms. We believe these data can aid the ongoing policy discussion concerning the environmental risk posed by CPs.

Toxicokinetics and toxic effects of a Chinese PFOS alternative F-53B in adult zebrafish

6:2 chlorinated polyfluorinated ether sulfonate (F-53B), a Chinese PFOS alternative, has recently been identified in river water, sewage sludge, wildlife and humans, causing great concerns about its potential toxic effects. Here, we report the first investigation of the toxicokinetics and oxidative stress of F-53B in adult zebrafish. Adult male and female zebrafish were exposed to 10 and 100 μg/L of F-53B for 7 days followed by a 5-d depuration period to examine bioaccumulation, distribution, and depuration of F-53B in fish. The results showed that F-53B was readily accumulated in fish tissues with log BCF values of 2.36–3.65, but was eliminated slowly (t1/2 = 152.4–358.5 h). F-53B accumulation was greater in males than in females and the concentration in tissues decreased in the following order: gonad ≈ liver ≫ gill ≫ brain in females and liver ≈ gill ≫ gonad ≫ brain in males, showing sex- and tissue- specific accumulation of F-53B in fish. After chronic exposure to F-53B for 28 days, a significant dose-dependent increase in histopathological changes in the liver were mainly manifested by vacuolation. Furthermore, F-53B also significantly reduced the enzyme activity (or content) of most of the measured oxidative stress-related markers (e.g., SOD, CAT and MDA) except for an increase in GSH-Px activity, indicating that oxidative stress was induced in zebrafish after treatment with F-53B. The results of this study provide important information on the toxicokinetics and toxic effects of F-53B, which will contribute to the ecological risk assessments of F-53B released into surface waters.

Quantitative structure-property relationship (QSPR) models for predicting the physicochemical properties of polychlorinated biphenyls (PCBs) using deep belief network

Octanol/water partition coefficient (log P), octanol/air partition coefficient (log KOA) and bioconcentration factor (log BCF) are important physiochemical properties of organic substances. Quantitative structure-property relationship (QSPR) models are a promising alternative method of reducing and replacing experimental steps in determination of log P, log KOA and log BCF. In the current study, we propose a new QSPR model based on a deep belief network (DBN) to predict the physicochemical properties of polychlorinated biphenyls (PCBs). The prediction accuracy of the proposed model was compared to the results of previous reported models. The predictive ability of the DBN model, validated with a test set, is clearly superior to the other models. All results showed that the proposed model is robust and satisfactory, and can effectively predict the physiochemical properties of PCBs without highly reliable experimental values.

Determination of endocrine disrupting compounds and their metabolites in fish bile

This work describes a new methodology for the simultaneous determination of a large variety of emerging and persistent organic compounds and some of their metabolites in fish bile samples. The target compounds were musk fragrances, alkyl phenols, hormones, pesticides, phthalate esters and bisphenol-A, all of them with a known endocrine disrupting effect. To achieve the determination these three steps were optimized: i) an enzymatic hydrolysis of the metabolites to render the unconjugated compounds; ii) the solid phase extraction of the target analytes (Plexa cartridges 200-mg); and, iii) a clean-up of the extracts (Florisil cartridges 1-g). The samples were analyzed by gas-chromatography–mass spectrometry (GC–MS), though the polar fraction required a previous derivatization with O-bis (trimethylsilyl) trifluoroacetamide. Good apparent recoveries (63–122%), repeatability (<20%) and limits of detection (LODs) ranging between 0.04 and 459ng/mL were obtained. This method was applied to the analysis of the target analytes in bile samples of thicklip grey mullets (Chelon labrosus) from five different populations of the Basque Coast (South East Bay of Biscay) during the period of May–June 2012. The target analytes were found at concentrations ranging from <LOD to 19,226ng/mL and the most polluted site was Gernika. Bioconcentration factors (log BCF) were estimated (range of 1.69–5.55) and BBP and NP mix showed the highest values. A deep discussion has been carried out in order to explain the different concentration levels of the different sampling sites.

Critical body residue to fish of organic pollutants

The internal concentration represented by critical body residue(CBR) is an ideal indicator of the intrinsic toxicity of a chemical that can be used to assess toxicity to aquatic organisms. In this study, we systematically summarized the method for calculation of CBR in fish, CBR values with different modes of toxic action, the relationship between CBR and BCF, and the factors influencing the CBR based on the progress in this field as a result of studies conducted worldwide and our own investigations. The CBRs could be calculated by the LC50 and BCF based on the toxicokinetic model. The modes of toxic action of fish are usually recognized based on classification of organic compounds as acting by non-polar narcosis(baseline compounds), polar narcosis(less inert compounds), or reactive and specific acting mechanisms. Baseline toxicity is associated with chemicals acting narcosis mechanism, which is the reversible suppression of physiological function brought about by hydrophobic binding of chemicals to cell membranes and proteins. The CBRs to fish for narcotic chemicals vary in a narrow range and are close to constant. The CBRs for non-polar narcotic chemicals are higher than those for polar narcotic chemicals. Moreover, non-polar and polar narcotic compounds have different underlying mechanisms. Polar compounds intercalate less deeply into membranes, leading to lower CBR values than non-polar narcotic compounds. Reactive compounds interact and/or react with biological molecules, leading to enhanced toxicity relative to that associated with narcosis, and their CBRs are lower than those of narcotic compounds. Because the CBRs of narcotic compounds are close to constant, their toxicities are mainly affected by bioconcentration and linearly related to hydrophobicity. Conversely, the CBRs of reactive compounds are closely related to the reactivity of chemicals with biomolecules at the target site, with different values being observed for different reactive compounds. Their toxicities are not only related to the bioconcentration factor, but also to the descriptors used to describe the reactivity of chemicals with biomolecules(CBRs). Many factors can affect the CBRs of chemicals. For example, linear models of the relationship between log BCF and log Kow can underestimate the log BCF for compounds with log Kow 0.5 and overestimate the log BCF for compounds with log Kow 7, resulting in larger errors for CBRs calculated from the BCF and LC50 of highly hydrophilic and hydrophobic compounds. Organism size, lipid content, exposure time, metabolism and transformation, and uncertainty of toxic data can also affect the calculation or determination of CBRs.

Bioconcentration and trophic transfer of polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins and dibenzofurans in aquatic animals from an e-waste dismantling area in East China.

Eight aquatic biota species were collected from an e-waste dismantling area in East China to investigate bioconcentration and trophic transfer of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The mean concentrations of PCBs varied widely from 6.01 × 10(4) to 2.27 × 10(6) pg per g dry weight (dw). The ∑25PCB concentrations in eels were significantly higher than those in other species. The levels of PCDD/Fs changed from 8.13 pg per g dw in toads to 617 pg per g dw in stone snails. World Health Organization-toxic equivalents (WHO2005-TEQs) ranged from 2.57 to 2352 pg WHO-TEQ per g dw with a geometric mean value of 64.7 pg WHO-TEQ per g dw, which greatly exceeded the maximum levels of 4 pg per g ww set by the European Commission. The log-transferred bioconcentration factors (BCFs) of 25 PCB congeners ranged from 1.0 to 6.6, with the highest value for CB-205 in crucian carp and the lowest value for CB-11 in frog. A parabolic correlation was observed between log BCF and log Kow (R(2) = 0.53, p < 0.001), where the maximum value occurred at a log Kow of approximately 7. A similar correlation was also found in the plot of log BCF against the number of chlorine atoms of PCBs (R(2) = 0.57, p < 0.001), indicating that medium-halogenated congeners of PCBs are more easily accumulated by aquatic biota species. There were no significant correlations between the log-transferred concentrations and trophic levels of aquatic species, suggesting that trophic magnification for PCBs and PCDD/Fs was not observed in this study.

Bioconcentration of Organic Contaminants in Daphnia Resting Eggs

Organic contaminants detected in sediments from Lake Greifensee and other compounds falling in the log Dow range from 1 to 7 were selected to study the bioconcentration of organic contaminants in sediments in Daphnia resting eggs (ephippia). Our results show that octocrylene, tonalide, triclocarban, and other personal care products, along with pesticides and biocides can accumulate in ephippia with log BCF values up to 3. Data on the uptake and depuration kinetics show a better fit toward a two compartment organism model over a single compartment model due to the differences in ephippial egg content in the environment. The obtained BCFs correlate with hydrophobicity for neutral compounds. Independence between BCF and hydrophobicity was observed for partially ionized compounds with log Dow values around 1. Internal concentrations in ephippia in the environment were predicted based on sediment concentrations using the equilibrium partitioning model and calculated BCFs. Estimated internal concentration values ranged between 1 and 68,000 μg/kglip with triclocarban having the highest internal concentrations followed by tonalide and triclosan. The outcomes indicate that contaminants can be taken up by ephippia from the water column or the pore water in the sediment and might influence fitness and sexual reproduction in the aquatic key species of the genus Daphnia.

Bioconcentration of triclosan and methyl-triclosan in marine mussels (Mytilus galloprovincialis) under laboratory conditions and in metropolitan waters of Gulf St Vincent, South Australia

The anti-microbial agent triclosan (TCS), and its derivative methyl-triclosan (Me-TCS), are discharged with treated effluents from wastewater treatment plants to receiving environments. We investigated the bioconcentration of TCS and Me-TCS in mussels (Mytilus galloprovincialis) exposed to TCS (100ngL−1) for 30days in seawater aquaria (19±2°C) with fresh phytoplankton as a food source. Bioconcentration increased with time reaching a steady-state around 24–30days. The bioconcentration factor (log BCF) for TCS were 2.81Lkg−1 (dry weight) and 4.13Lkg−1, when lipid normalised concentrations were used. Mussels were also deployed in cages at four marine locations receiving effluents from WWTPs. The mean (±SD) TCS and Me-TCS concentrations for mussels from these sites were 9.87 (±1.34) and 6.99 (±2.44)μgkg−1. The study showed that mussels can be a useful tool for monitoring pollution of TCS and Me-TCS in marine and estuarine environments.

Distribution and bioconcentration of polycyclic aromatic hydrocarbons in surface water and fishes.

To examine spatial distribution and bioconcentration of PAHs, water and fish samples were collected from Pearl River Delta in summer and spring, respectively. Particulate organic carbon, dissolved organic carbon, biodegradable DOC (BDOC), and chlorophyll a were measured. PAHs were dominated by 2- and 3-ring compounds in the water and SPM samples. Aqueous and solid-phase PAHs, respectively, showed significant correlations with total organic matter (TOC) in SPM or dissolved organic matter (DOC) in the water. The in-situ partitioning coefficients (logK oc, mL/g) for the samples were observed to be related to logK ow, implying that the hydrophobicity of PAHs is a critical factor in their distribution. It was also observed that BCF increased with the increasing K ow in the viscera of tilapia (logBCF = 0.507logK ow − 1.368, r = 0.883). However, most of the observed log BCF values in other different fish tissues at first increased with the increasing of log K ow, then reached a maximum value when logK ow is between 5 and 7, and then decreased when logK ow is higher than 7, indicating that the value of BCF may vary due to the diversity of fish species.