•MFe2O4/CNTs (M: Fe, Mn) were used as cathodic catalysts for electro-peroxone treatment of DTZ.•Electro-peroxone was efficient for DTZ degradation, and MFe2O4/CNTs exhibited some catalytic features.•Process conditions that favor HO production have a pronounced positive effect on DTZ degradation.•MFe2O4 might enhance O3/H2O2 decomposition and improve electron transfer during reaction, thereby promoting HO generation.In this study, ferrite modified carbon nanotubes (MFe2O4/CNTs, M: Fe, Mn) were prepared and employed as cathodic catalysts to assist electro-peroxone (i.e., combined ozonation with electrolysis process using a carbon-polytetrafluoroethylene cathode) treatment of emerging pollutant diatrizoate (DTZ) in aqueous solution. The structural and surface property of synthesized catalysts was studied, and the performance of electro-peroxone process using MFe2O4/CNTs based gas diffusion cathode (GDC) was systematically investigated from the kinetic and mechanistic viewpoints. Results show that the combination of ozonation and electrolysis exhibited synergistic degradation of DTZ. Approximately 71.9% DTZ had been degraded with MFe2O4/CNTs based GDC after 10 min, 13.2% higher than with bare CNTs based GDC, implying that the combined treatment efficiency could be enhanced by the presence of MFe2O4. The performance of MFe2O4/CNTs catalytic electro-peroxone process was positively correlated with inlet ozone concentration (10–30 mg/L), and an increase in applied current stimulated DTZ degradation at a low cathodic current density (5–40 mA/cm2) but inhibited the degradation at a high cathodic current density (40–60 mA/cm2). The MFe2O4/CNTs catalytic electro-peroxone treatment also showed a significant dependence on initial pH and reaction temperature, but was little affected by supporting electrolyte concentration. Higher removal efficiency was obtained at a lower initial DTZ concentration. The comparison tests reveal that peroxone reaction was the main pathway of hydroxyl radicals (HO) production in the present system, and the presence of MFe2O4 at the cathode could promote HO generation. These observations suggest that electro-peroxone is efficient for DTZ degradation in aqueous solution, and MFe2O4/CNTs are good and promising cathodic materials and catalysts for this process.Download high-res image (137KB)Download full-size image

Little is known about the potential toxicity of Cu nanoparticles (nCu), Cr nanoparticles (nCr), and their mixtures to aquatic organisms. To fill this gap, a comprehensive toxicity assessment was conducted using Daphnia magna as a test organism, including a 48-h acute toxicity test, a 21-day chronic test, and a feeding experiment. Four biomarkers were estimated after exposure to nCu, nCr, and their mixtures for 7 days, including acetylcholinesterase (AChE), catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST). The results at all endpoints showed that nCu was more toxic than nCr. The 48-h median lethal concentration values of nCu and nCr were 0.63 and 1.57 mg/L, respectively. Significant inhibition of reproduction and growth of D. magna was found, and the intrinsic rate of natural increase was a sensitive parameter for nCu and nCr during the 21-day exposure. A concentration-dependent decrease in filtration and ingestion was observed which was consistent with inhibition of reproduction and growth of D. magna. The biochemical responses revealed an increase in GST activity and decrease in AChE activity, while SOD and CAT activities were increased at low concentrations and decreased at high concentrations for all exposures. Collectively, our results confirmed that nanoscale Cu and Cr can exert negative effects at different levels on D. magna.

•Crucian carp bioaccumulated erythromycin and ketoconazole in the brain.•Addition of ketoconazole increased erythromycin accumulation in the brain of fish.•Erythromycin and ketoconazole induced biochemical and behavioral alterations in fish.•Behaviour was a sensitive marker to assess exposure of ketoconazole.The presence of pharmaceuticals in the aquatic environment has received great attention due to their potential impacts on public health. The single, as well as the combined toxicities of erythromycin (ERY) and ketoconazole (KCZ) on the bioaccumulation, biochemical and behavioral responses, were examined in crucian carp. This study focused on the uptake of contaminants, acetylcholinesterase (AChE) activity in the brain, swimming and shoaling behavior of fish. After 14 days of binary exposure, the addition of KCZ at nominal concentrations of 0.2, 2 and 20 μg/L significantly increased the accumulation of ERY in the brain of the fish and the bioconcentration factor of 2.08 was 2.6-fold higher than that calculated from the ERY-alone exposure. The brain AChE activity was significantly inhibited by ERY and KCZ with a significant correlation with respect to the accumulative concentration of the contaminants. The inhibition rates of swimming activity to KCZ were increased with a corresponding increase in the exposure concentration of KCZ in the single exposure. However, this manner was altered by the combined exposure. In addition, shoaling was significantly enhanced by KCZ-alone exposure, which was significantly correlated with the swimming activity. This study indicates that the mixture of the contaminants may cause endocrine disrupting effects and behavior modification especially in fish with known ecological and evolutionary consequences.Download high-res image (203KB)Download full-size image

•Multi-walled carbon nanotubes accelerated the roxithromycin accumulation in fish.•Metabolism and oxidative stress were also enhanced by multi-walled carbon nanotubes.•Multi-walled carbon nanotubes alter the bioavailability of roxithromycin in fish.•Biofluid accelerate the release of roxithromycin from multi-walled carbon nanotubes.Carbon nanotubes are increasingly entering the aquatic environment and may interact with other co-existing contaminants, such as antibiotics. However, whether these interactions may affect their bioavailability in aquatic organisms is the subject of considerable debate. The primary objective of this study was to assess the risks arising from the coexistence of roxithromycin (ROX) and multi-walled carbon nanotubes (MWCNTs) in waters containing natural organic matter (NOM), focusing on the distribution and bioaccumulation of ROX in crucian carp (Carassius auratus), and the related biochemical status. There were no significant differences in ROX bioaccumulation in fish following exposure to ROX with and without NOM. However, the further addition of MWCNTs significantly facilitated the bioaccumulation of ROX in the liver (32–80%), gill (15–74%), intestine (51–113%), and bile (15–67%) in different exposure periods. Meanwhile, a 0.3-fold increase in the metabolic enzyme activity and oxidative stress in the liver were markedly accelerated by the co-exposed MWCNTs compared to ROX alone. The findings imply that the ROX adsorbed on MWCNTs may be a higher threat to fish than ROX alone. The high and fast release of ROX from MWCNTs in bile salts and serum albumin may contribute to the enhancement in bioaccumulation and bioactivity of ROX in fish with MWCNTs.

In this work, magnetic ferrite modified carbon nanotubes (MFe2O4/CNTs, M: Mn or Co) were synthesized and employed as adsorbents to remove emerging pollutant bezafibrate (BZF) from aqueous solution. The structural and surface properties of the prepared adsorbents were characterized, and the performances of the MFe2O4/CNTs were systematically investigated from adsorption kinetics and mechanistic points of view. Results showed that the fabricated MFe2O4/CNTs could integrate the advantages of CNTs and ferrite, thereby exhibiting an excellent adsorption performance and recyclability. The MnFe2O4/CNTs were more effective than CoFe2O4/CNTs for BZF adsorption. When the initial concentration of BZF was varied from 5 to 40 mg L−1, the maximum adsorption capacity of MnFe2O4/CNTs and CoFe2O4/CNTs increased from 14.8 to 33.4 mg g−1 and 8.1 to 27.8 mg g−1, respectively. Moreover, the Langmuir isotherm model and pseudo-second-order equation could elaborate well the adsorption of BZF on MFe2O4/CNTs. The thermodynamic analysis further revealed that the adsorptions were spontaneous processes. Based on measurements of surface and pore diffusion and the results of adsorption reactions, possible mechanisms were proposed to explain the adsorption process. This research indicates that the MFe2O4/CNTs are potentially applicable for the removal of BZF from aqueous solution.

The individual and combined biochemical responses of erythromycin and ketoconazole have been examined in an organism representative of the aquatic environment, crucian carp (Carassius auratus). The possible interactions between erythromycin and ketoconazole were investigated on the bioaccumulation and the expression of biotransformation enzymes 7-ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST), and an antioxidant defense enzyme superoxide dismutase (SOD) in fish tissues. After 14 days of combined exposure (erythromycin + ketoconazole), the addition of ketoconazole at nominal concentrations of 0.2, 2, and 20 μg/L significantly increased the accumulation of erythromycin in fish bile; however, elevated erythromycin accumulation levels were not observed in the other test tissues. The inductions of EROD and SOD activity to erythromycin were inhibited by the combined exposure of ketoconazole in most cases; however, the GST activity returned to normal with exposure time and concentration of combined administration. From the tested pharmaceutical mixtures, it indicated that certain specific combinations may pose some perturbations in biochemical responses in fish and also provide a better understanding of the effects of toxic mixtures.

Suspended sediment (SPS) plays an important role in the aquatic ecosystems. Selective serotonin uptake inhibitors (SSRIs) are commonly used antidepressants and are frequently detected in aquatic environments. However, the biological effects of SSRIs in the presence of SPS are not well understood. To fill this gap, an SPS-water system was constructed to investigate the effects of citalopram (CIT) on Daphnia magna in the presence of SPS with different concentrations (0.1, 0.5, 1 g l−1) and organic carbon contents (0.5, 1, 1.5, 2%). A dialysis bag was applied in the exposure system to control the same dissolved concentration of CIT and prevent SPS from entering into the bag. The dissolved CIT concentration obviously decreased in the SPS-water system during the exposure period. The presence of SPS significantly increased the immobilization of D. magna, and the immobilization rates were positively correlated with the SPS concentration and negatively correlated with the organic carbon content in SPS. For a single exposure, CIT significantly increased superoxide dismutase (SOD) activity and inhibited acetylcholinesterase (AChE) activity in D. magna, while SPS itself did not change the SOD and AChE activities. In the SPS-water system, SOD activity was significantly suppressed, indicating that the SPS-CIT combination could result in oxidative damage. However, SPS did not enhance the neurotoxicity of D. magna that was induced by CIT. These results suggest that SPS exerts a vital role on the biological effects of CIT and the contaminants sorbed on SPS should be taken into consideration.

Organic UV filters (OUV-Fs) are increasingly used for protection against UV irradiation. The widespread occurrence of OUV-Fs residues in aquatic systems has been reported, but little is known regarding their distribution and potential impact to the surface water in China. This study reports the occurrence, distribution and risk assessment of eight widely used OUV-Fs in the surface water of Nanjing. The results indicated butyl-methoxydibenzoylmethane, octyl-dimethyl-PABA and benzophenone-types (BP3, BP4 and BP1) were the most frequently detected compounds at concentrations of 3.63–104 ng/L. In general, the concentrations of OUV-Fs were decreased along the rivers; however, due to a substantial pollution load from the tributaries, higher concentrations of OUV-Fs were observed near the tributary inlet, compared to the other study areas. The risk assessment based on the calculated risk quotients (RQs) demonstrated that all OUV-Fs posed at least low risks to certain sensitive aquatic organisms, and BP3 posed high risk with RQ values of 1.64. It should be noted that the exclusion of adsorbed OUV-Fs might have contributed to an underestimation of the risk, therefore, it’s necessary to assess both adsorbed and dissolved OUV-Fs in further studies.

Pharmaceutically active compounds (PhACs) have been universally detected in rivers, lakes and coastal waters that are affected by effluents from sewage treatment plants (STPs). In this study, the biological effects and bioaccumulation of PhACs were assessed in crucian carp (Carassius auratus) caged in an effluent-receiving river for 21 days. Compared with control fish in the laboratory and at a reference site, a significant reduction in hepatosomatic index (HSI) and increase in the biotransformation enzymes ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities were observed in the fish that was caged downstream from the STP outfall. In general, the total concentrations of PhACs detected in fish tissues were in the order as follows: liver > brain > gill > muscle > bile. The bioaccumulation factors (BAFs) for PhACs were between 195 and 2782 in the major storage tissue liver. The corresponding results for both risk quotient (RQ) and enhanced integrated biomarker response (EIBR) based on laboratory and field studies, respectively, indicated that environmental risk for adverse effects to aquatic organisms were clearly higher at the downstream of the STP outfall than at the upstream.

The aim of this study was to evaluate the interactive effects of the metals lead (Pb) and zinc (Zn) and the polycyclic aromatic hydrocarbon benzo(k)fluoranthene (BkF) on crucian carp (Carassius carassius). To this end, various biomarkers in the fish [7-ethoxyresorufin-O-deethylase (EROD); superoxide dismutase (SOD); malondialdehyde (MDA) and metallothioneins (MT)] were measured after 96 h of exposure. When compared to either treatment with Pb and Zn mixtures or BkF-only treatment, the treatment with BkF combined with Pb and Zn resulted in lower responses of EROD and MT synthesis activity, and higher SOD and MDA increases. These results indicated that the co-exposure of metals and polycyclic aromatic hydrocarbons may cause more severe oxidative stress on fish. However, the effect of these interactions on EROD and MT may lead to an underestimation of the actual exposure in the field and thereby should be carefully considered.

•Zeolitic imidazolate framework-8 was applied as sorbent of μ-SPE.•The μ-SPE device was firstly established to determine estrogens in water.•Important extraction parameters were optimized.•The proposed method can successfully determine the estrogens in real water.A novel micro-solid-phase extraction (μ-SPE) device coupled with ultra-high performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS) was established to determine five typical estrogens in aqueous samples. Zeolitic imidazolate framework-8 (ZIF-8) as sorbent was packed in polypropylene membrane to construct the μ-SPE device. Important extraction parameters including extraction time, extraction temperature, desorption solvent, desorption time and sample pH were carefully optimized to improve the extraction efficiency of the μ-SPE device. ZIF-8 sorbent showed an exceptional chemical stability and extraction efficiency for estrogens. In theory, the high extraction efficiencies may be due to the coordination bonding, intermolecular π–π interactions and hydrophobic interactions between ZIF-8 and the estrogens. Under the most favorable extraction conditions, for estrogens in aqueous samples, the proposed method provided low limits of detection (0.05–0.1 μg/L), wide linearity range (three orders), excellent correlation coefficients (0.959–0.999) and satisfactory measurement precision (4.9–9.2%). which can meet the demand of determining estrogens at the trace level. Finally, the proposed method was successfully applied to determine the estrogens in real sewage water samples.

Taihu Lake is the largest shallow freshwater lake in eastern China and is suffering not only from an increasingly serious threat of eutrophication but also potential ecological risk due to the input of emerging contaminants. Active biomonitoring was conducted in Taihu Lake using transplanted goldfish (Carassius auratus) to determine the contamination by pharmaceuticals and metals and to assess the potential ecological risk. A suite of biomarkers including acetylcholinesterase, ethoxyresorufin O-deethylase, glutathione S-transferase, glutathione peroxidase and superoxide dismutase activities in fish after 7, 14, 21 and 28 days of exposure in situ, as well as pharmaceuticals and metals in water, were determined during the field exposure period. The results indicate that pharmaceuticals exist mainly in Zhushan Bay and Meiliang Bay, while metals are present mainly in Gong Bay. An integrated biomarker response (IBR) was calculated and used to evaluate the ecological risk of the polluted area of Taihu Lake. It was found that Zhushan Bay might present higher risk to fish, followed by Meiliang Bay. IBR values were in good agreement with copper and caffeine concentrations.

In this study, the sublethal effects of caffeine, sulfamethoxazole and their mixture on goldfish (Carassius auratus) were investigated, the biomarkers including acetylcholinesterase (AChE) in brain, 7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST) and superoxide dismutase (SOD) in liver and vitellogenin (VTG) in serum were determined after 1, 2, 4, and 7 days of exposure. AChE activity was significantly inhibited by caffeine (≥0.4 mg/l), sulfamethoxazole (≥0.4 mg/l) and their mixtures (≥0.048 mg/l) during all exposure periods, and obvious concentration-response and time-response relationships were obtained. EROD, GST and SOD activities were significantly increased by individual compounds and mixtures in most cases. GST induction exhibited bell-shaped concentration-response curves. Serum VTG was significantly induced by 2 mg/l of caffeine, 10 mg/l of sulfamethoxazole and the mixtures at concentrations ≥1.2 mg/l. In general, the two pharmaceuticals induced similar biological responses. The joint effect of caffeine/sulfamethoxazole was additive with regard to AChE and GST activity variation and was antagonistic with regard to EROD and SOD induction. The results indicated that multiple biomarker response method might be a useful tool for describing an integrated toxicological effect of chemicals. VTG induction suggested that caffeine and sulfamethoxazole may cause a slightly feminization effect.

Goldfish (Carassius auratus) bred in clean water were transferred into different stations in Taihu Lake for active biomonitoring exposures. The biotransformation enzymes 7-ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST), the antioxidant defense enzymes catalase (CAT), reduced glutathione content (GSH), and lipoperoxidation (TBARS) and metallothionein (MT) in liver were determined as biomarkers during the field exposure period. At the same time, the contents of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and heavy metals in the surface sediments of biomonitoring sites were measured. The total concentrations of PAHs ranged 378.6−1047.8 μg kg−1 dry weight, PCBs ranged 0.76−3.27 μg kg−1, OCPs ranged 1.12−3.08 μg kg−1, and heavy metal Zn ranged 31.82−85.04 mg kg−1, Cu ranged 13.04−91.02 mg kg−1, Ni ranged 4.96−28.66 mg kg−1, and Pb ranged 9.33−22.44 mg kg−1. The results indicate that persistent organic pollutants exist mainly in Meiliang Bay, while heavy metals are present mainly in Gong Bay. The integrated biomarker response (IBR) was calculated by combining multiple biomarkers to a single value and used to evaluate the toxically induced stress level of populations in different areas. The results demonstrate that Tuoshan and Mashan in Meiliang Bay as well as Dagongshan in Gong Bay showed higher IBR values compared to the other sites. IBR values were in good agreement with OCP concentrations.

Our study investigated multiple biomarker responses of goldfish exposed to sediments collected from northern Taihu Lake. The activities of acetylcholinesterase, 7-ethoxyresorufin-O-deethylase, glutathione-S-transferase and superoxide dismutase did not differ significantly from controls following exposure to sediment from the center of the lake. However, sediment collected from the northern bays did significantly alter enzymatic activities. An integrated biomarker response (IBR) was calculated and used to evaluate the impact of pollutants from different stations. The results indicated that Mashan in Meiliang Bay and Xiaogongshan in Gong Bay were the most stressful places for fish. Sediment polychlorinated biphenyl and polybrominated diphenyl ether concentrations were associated with IBR variation.

Estrogenic activities and main causative fractions in three representative sections of Yangtze River (Nanjing section) were determined. The results showed that significant vitellogenin (VTG) and 17β-estradiol (E2) induction and gonad atrophy were observed. Estradiol equivalents of actual water samples from Jiangxinzhou section, Sanchahe section and Daqiao section were 0.3651, 0.1301 and 0.5060 ng L−1, respectively. Polar contaminants were responsible for the estrogenic activities in Jiangxinzhou section and Daqiao section while mid-polar and nonpolar contaminants resulted in majority of the estrogenic activity in Sanchahe section. To Jiangxinzhou section, Sanchahe section and Daqiao section, good positive correlations between VTG and E2 (the correlation coefficients were 0.737, 0.690 and 0.817, respectively) and good inverse correlations between VTG and gonado-somatic index (GSI; the correlation coefficients were −0.838, −0.540 and −0.794, respectively) were obtained, whereas the correlations between E2 and GSI were relatively poor (the correlation coefficients were only −0.557, −0.620 and −0.509, respectively).

ObjectiveTo study the biological effects of nanoscale copper oxide (nCuO), zinc oxide (nZnO), cerium dioxide (nCeO2) and their mixtures on Carassius auratus.MethodsJuvenile fish (Carassius auratus) were exposed to aqueous suspensions of nCuO, nZnO, and nCeO2 (alone and in mixtures) at concentrations of 20, 40, 80, 160, and 320 mg/L. The biomarkers-acetylcholinesterase (AChE) in brain, sodium/potassium-activated ATPase (Na+/K+-ATPase) in gill, and superoxide dismutase (SOD) and catalase (CAT) in liver-were determined after 4 days of exposure. Integrated biomarker response (IBR) was calculated by combining multiple biomarkers into a single value.ResultsAChE and SOD activities were significantly inhibited by all test metal oxide nanoparticles (NPs) at high concentrations (≥160 mg/L) with the exception of nCeO2. Na+/K+-ATPase induction exhibited bell-shaped concentration-response curves. CAT activity was significantly inhibited at concentrations equal to or higher than 160 mg/L. The order of IBR values was nCeO2 ≈ nZnO/nCeO2 ≈ nCuO/nCeO2 < nCuO/nZnO/nCeO2 < nZnO < nCuO < nCuO/nZnO. The joint effect seemed to be synergistic for nCuO/nZnO mixtures, additive for the ternary mixture and less than additive or antagonistic for the binary mixtures containing nCeO2.ConclusionConcentration-dependent changes of enzymatic activities (AChE, Na+/K+-ATPase, SOD, and CAT) were observed in fish exposed to nanoscale metal oxides. IBR analysis allowed good discrimination between the different exposures and might be a useful tool for the quantification of integrated negative effects induced by NPs toward fish.

•Bioaccumulation and tropic transfer of pharmaceuticals in aquatic food webs were studied.•Pharmaceuticals displayed high bioaccumulation potential in zoobenthos.•Tissue-specific bioaccumulation of pharmaceuticals was observed in wild fish.•The trophic magnification factors of pharmaceuticals were consistent across two food webs in Taihu Lake.Pharmaceuticals are increasingly detected in environmental matrices, but information on their trophic transfer in aquatic food webs is insufficient. This study investigated the bioaccumulation and trophic transfer of 23 pharmaceuticals in Taihu Lake, China. Pharmaceutical concentrations were analyzed in surface water, sediments and 14 aquatic species, including plankton, invertebrates and fish collected from the lake. The median concentrations of the detected pharmaceuticals ranged from not detected (ND) to 49 ng/L in water, ND to 49 ng/g dry weight (dw) in sediments, and from ND to 130 ng/g dw in biota. Higher concentrations of pharmaceuticals were found in zoobenthos relative to plankton, shrimp and fish muscle. In fish tissues, the observed pharmaceutical contents in the liver and brain were generally higher than those in the gills and muscle. Both bioaccumulation factors (median BAFs: 19–2008 L/kg) and biota−sediment accumulation factors (median BSAFs: 0.0010–0.037) indicated a low bioaccumulation potential for the target pharmaceuticals. For eight of the most frequently detected pharmaceuticals in food webs, the trophic magnification factors (TMFs) were analyzed from two different regions of Taihu Lake. The TMFs for roxithromycin, propranolol, diclofenac, ibuprofen, ofloxacin, norfloxacin, ciprofloxacin and tetracycline in the two food webs ranged from 0.28 to 1.25, suggesting that none of these pharmaceuticals experienced trophic magnification. In addition, the pharmaceutical TMFs did not differ significantly between the two regions in Taihu Lake.Download high-res image (154KB)Download full-size image

•BM-DBM and OD-PABA can be accumulated in different organs of crucian carp.•BCF values are 0.163 – 17.0 for BM-DBM and 0.369 – 101 for OD-PABA, respectively.•BM-DBM and OD-PABA can induce the change of biomarkers in crucian carp.Organic UV filters (OUV-Fs) are increasingly used in sunscreens and personal care products. In the present work, the bioconcentration and multi-biomarker effects of butyl methoxydibenzoylmethane (BM-DBM) and ethylhexyl dimethyl p-aminobenzoate (OD-PABA) were investigated in crucian carp (Carassius auratus). The fish were exposed to various concentrations of BM-DBM (3.88, 35.61, 181.85 and 337.15 μg/L), OD-PABA (4.66, 53.83, 264.22 and 459.32 μg/L) and their mixture (2.31+2.79, 23.69+26.18, 97.37+134.81 and 193.93+246.08 μg/L) for 28 days. The maximal concentrations of two OUV-Fs were detected in the fish liver, followed by the brain, kidney, gill and muscle in most cases. The maximal BCF values of OD-PABA calculated in various exposure concentrations were 0.37 – 101.21 in single exposure groups and 0.11 – 31.09 in mixed exposure groups. Acetylcholinesterase (AChE) activity was significantly inhibited by BM-DBM as well as the mixtures at all of the exposure concentrations and by OD-PABA at higher concentrations (≥264.22 μg/L) during 28 days of exposure. The maximal inhibition rates of AChE activity reached 64.04% for BM-DBM, 41.05% for OD-PABA and 61.50% for the mixtures at the highest concentration, which indicated that these two OUV-Fs might damage the central nervous system. Concerning oxidative stress status, BM-DBM and the mixtures significantly increased superoxide dismutase (SOD) and glutathione reductase (GR) activities and inhibited catalase (CAT) activity, while OD-PABA caused a significant increase of GR and CAT activities. AChE and GR activities seemed to be more sensitive biomarkers for BM-DBM and OD-PABA.

In order to study toxicological effects of perfluorononanoic acid (PFNA), perfluorooctane sulfonate (PFOS), and their mixtures (PFNA/PFOS) on Daphnia magna (D. magna), a suite of comprehensive toxicity tests were conducted, including a 48-h acute toxicity test, a 21-day chronic test, a feeding experiment, and a biomarker assay. D. magna were exposed to aqueous solutions of PFNA and PFOS (alone and in combination) at concentrations ranging from 0.008 to 5 mg/L. The survival, growth, and reproduction of D. magna were monitored over a 21-day life cycle. The biomarkers, including acetylcholinesterase (AChE), superoxide dismutase (SOD), and catalase (CAT) activities, were determined after seven days of exposure. PFOS was more toxic than PFNA based on the results of the acute toxicity test. Perfluorinated compounds (PFCs) inhibited both growth and reproduction of D. magna during the testing period. The ingestion rates and the biomarkers, including AChE, SOD, and CAT activities, were significantly inhibited by PFCs in most cases. Moreover, the combined effects related to the growth and reproduction showed the antagonistic effects of PFCs.

The bacterial growth inhibition test was used to determine toxicity of the halogenated aromatics on the mixed bacteria from the Yangtze River. The concentration values causing 50% reduction of bacteria growth for 24 hr (IC50) and the maximum tolerance concentration for 7 d (MATC) were gained according to the concentration-response curves. An obvious linear relationship was found between the two toxicity descriptors. The following quantitative structure- activity relationships were developed by using the valence molecular connectivity index method: -lgIC50 = 0.8266Xpcv- 0.2363Xpv + 3.811 (R2 = 0.833) and -lgMATC = 1.2016Xpcv-0.3783Xpv + 4.614 (R2 = 0.900). The two equations were found to fit well. It suggested that the models derived from the molecular connectivity index could be used successfully to predict the toxicity of halogenated aromatic compounds.

There are often many chemicals coexisting in aquatic ecosystems, and few information on the joint toxicity of a mixture of organic pollutants is available at present. The 48-h toxicity of substituted phenols and anilines and their binary mixtures to Scenedesmus obliquus was determined by the algae inhibition test. The median effective inhibition concentration EC50 values for single compounds and EC50mix values for coexistent compounds were obtained. The n-octanol/water partition coefficient (logPmix) and the frontier orbital energy gap (ΔEmix) for mixtures were calculated. The following two-descriptor quantitative structure-activity relationships (QSARs) models were developed to predict single toxicity and joint toxicity respectively: log(1/EC50) = 0.445logP – 0.801ΔE + 9.501 (r2 = 0.876) and log (1/EC50mix) = 0.338logPmix – 0.492ΔEmix + 6.928 (r2 = 0.831). The two equations were found to fit well. In addition, the model derived from the structural parameters of single components in binary mixtures log(1/EC50mix) = 0.222logP – 0.277ΔE + 5.250 (r2 = 0.879) can be used successfully to predict the toxicity of a mixture.

Pharmaceutically active compounds (PhACs) have been universally detected in rivers, lakes and coastal waters that are affected by effluents from sewage treatment plants (STPs). In this study, the biological effects and bioaccumulation of PhACs were assessed in crucian carp (Carassius auratus) caged in an effluent-receiving river for 21 days. Compared with control fish in the laboratory and at a reference site, a significant reduction in hepatosomatic index (HSI) and increase in the biotransformation enzymes ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities were observed in the fish that was caged downstream from the STP outfall. In general, the total concentrations of PhACs detected in fish tissues were in the order as follows: liver > brain > gill > muscle > bile. The bioaccumulation factors (BAFs) for PhACs were between 195 and 2782 in the major storage tissue liver. The corresponding results for both risk quotient (RQ) and enhanced integrated biomarker response (EIBR) based on laboratory and field studies, respectively, indicated that environmental risk for adverse effects to aquatic organisms were clearly higher at the downstream of the STP outfall than at the upstream.