Bioaccumulation of isocarbophos enantiomers from laboratory-contaminated aquatic environment by tubificid worms

Enantiomerization and enantioselective bioaccumulation of diclofop-methyl in tubifex worms

In this study, the hydrolysis of diclofop-methyl (DM) in aqueous system and the bioaccumulation of its main metabolite, Diclofop (DA), in the tubifex worms were investigated using enantioselective high-performance liquid chromatography. With the addition of tubifex, rapid hydrolysis was observed for DM. It is revealed that the hydrolysis of DM in the water and the accumulation of DA in the worms were both enantioselective. Meanwhile, either the hydrolysis amount or the levels of enantioselectivity were influenced by the tubifex. After incubated for 24 h, about 94.6% of the DM was hydrolyzed and the enantiomer fraction of metabolite (DA) deviated from 0.5 with R-DA significantly higher than S-DA. The enantiopure S-DM and R-DM and S-DA and R-DA were incubated, and enantiomerizations were detected between the two DM enantiomers with S-form inversing into R-form and vice versa. It was found that the S-DM exhibited a higher tendency to invert than the R-DM.

Effect of fertilization on the degradation and enantioselectivity of fipronil in soil

BACKGROUND

Fertilizers and pesticides are commonly used simultaneously in agriculture. However, the effects of common fertilizers on the dissipation, enantioselectivity, and metabolites of the chiral insecticide fipronil in soil are yet to be reported.

RESULT

An enantioselective method for detecting fipronil enantiomers and their metabolites in different soil matrices was developed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that organic and compound fertilizers significantly decreased the degradation of S- and R-fipronil, whereas phosphate and microbial fertilizers slightly reduced fipronil dissipation. The half-life values for S- and R-fipronil were 43.3 and 28.9 days, 99.0 and 63.0 days, 69.3 and 43.3 days, 46.2 and 30.1 days, and 43.3 and 31.5 days, respectively, in the control and the four fertilizer treatments, respectively. The enantioselectivity of fipronil enantiomers occurred and R-fipronil exhibited preferential degradation with an enantiomeric fraction (EF) of 0.4900-0.6238 in all treatments; but the four tested fertilizers decreased enantioselectivity with EF values changed from 0.4970 to 0.6238 in the control to 0.4900-0.6171 in fertilizer treatments. Two metabolites, fipronil sulfone and sulfide, were produced, and their amounts increased with culture time in all treatments. Fertilization reduced the content of fipronil sulfide and sulfone but hardly reduced the total amount of fipronil and its metabolites.

CONCLUSION

Fertilizers affect the environmental behavior of fipronil in the soil. Fertilization alters the soil bacterial community, which may be an important factor. This influence is relatively complicated and should be comprehensively considered in the environmental risk assessment of pesticides. © 2023 Society of Chemical Industry.

Dissecting the Enantioselective Neurotoxicity of Isocarbophos: Chiral Insight from Cellular, Molecular, and Computational Investigations

Chiral organophosphorus pollutants are found abundantly in the environment, but the neurotoxicity risks of these asymmetric chemicals to human health have not been fully assessed. Using cellular, molecular, and computational toxicology methods, this story is to explore the static and dynamic toxic actions and its stereoselective differences of chiral isocarbophos toward SH-SY5Y nerve cells mediated by acetylcholinesterase (AChE) and further dissect the microscopic basis of enantioselective neurotoxicity. Cell-based assays indicate that chiral isocarbophos exhibits strong enantioselectivity in the inhibition of the survival rates of SH-SY5Y cells and the intracellular AChE activity, and the cytotoxicity of (S)-isocarbophos is significantly greater than that of (R)-isocarbophos. The inhibitory effects of isocarbophos enantiomers on the intracellular AChE activity are dose-dependent, and the half-maximal inhibitory concentrations (IC₅₀) of (R)-/(S)-isocarbophos are 6.179/1.753 μM, respectively. Molecular experiments explain the results of cellular assays, namely, the stereoselective toxic actions of isocarbophos enantiomers on SH-SY5Y cells are stemmed from the differences in bioaffinities between isocarbophos enantiomers and neuronal AChE. In the meantime, the modes of neurotoxic actions display that the key amino acid residues formed strong noncovalent interactions are obviously different, which are related closely to the molecular structural rigidity of chiral isocarbophos and the conformational dynamics and flexibility of the substrate binding domain in neuronal AChE. Still, we observed that the stable "sandwich-type π-π stacking" fashioned between isocarbophos enantiomers and aromatic Trp-86 and Tyr-337 residues is crucial, which notably reduces the van der Waals' contribution (ΔG_vdW) in the AChE-(S)-isocarbophos complexes and induces the disparities in free energies during the enantioselective neurotoxic conjugations and thus elucidating that (S)-isocarbophos mediated by synaptic AChE has a strong toxic effect on SH-SY5Y neuronal cells. Clearly, this effort can provide experimental insights for evaluating the neurotoxicity risks of human exposure to chiral organophosphates from macroscopic to microscopic levels.

Enantioselective degradation of prothioconazole in soil and the impacts on the enzymes and microbial community

In this work, the stereoselective degradation of prothioconazole in five soils was investigated and the metabolite prothioconazole-desthio was determined. The effects of prothioconazole on soil enzymes activities and microbial community were also studied. The dissipation of prothioconazole fitted with a first-order kinetic equation with half-lives ranging from 3.45 to 9.90 days. In addition, R-prothioconazole degraded preferentially than S-prothioconazole in all soils with EF values >0.5. Prothioconazole-desthio formed rapidly with preference in R-enantiomer, and the concentration kept at a considerable level even at the end of the incubation, indicating it was relatively persistent in soil. Prothioconazole and its metabolite inhibited the activity of dehydrogenase, catalase and urease in soils, and could affect the diversity of the soil microbiota as well. Redundancy analysis (RDA) and Spearman analysis showed the abundance of Proteobacteria, Fusobacteria, Firmicutes, Thaumarchaeota, Saccharibacteria, Chloroflexi, Chlorobi, Actinobacteria and Nitrospirae might be related to the enantioselective degradation. The work was helpful for understanding the environmental behavior of the fungicide prothioconazole and its primary metabolite on an enantiomeric level.

Spiking organic chemicals onto sediments for ecotoxicological analyses: an overview of methods and procedures

Laboratory testing with spiked sediments with organic contaminants is a valuable tool for ecotoxicologists to study specific processes such as effects of known concentrations of toxicants, interactions of the toxicants with sediment and biota, and uptake kinetics. Since spiking of the sediment may be performed by using different strategies, a plethora of procedures was proposed in the literature for spiking organic chemicals onto sediments to perform ecotoxicological analyses. In this paper, we reviewed the scientific literature intending to characterise the kind of substrates that were used for spiking (i.e. artificial or field-collected sediment), how the substrates were handled before spiking and amended with the organic chemical, how the spiked sediment was mixed to allow the homogenisation of the chemical on the substrate and finally how long the spiked sediment was allowed to equilibrate before testing. What emerged from this review is that the choice of the test species, the testing procedures and the physicochemical properties of the organic contaminant are the primary driving factors affecting the selection of substrate type, sediment handling procedures, solvent carrier and mixing method. Finally, we provide recommendations concerning storage and characterization of the substrate, equilibrium times and verification of both equilibration and homogeneity.

Enantioselective separation, analysis and stereoselective dissipation of the chiral pesticide cloquintocet-mexyl using a modified QuEChERS method by high-performance liquid chromatography tandem mass spectrometry

An efficient and novel enantioseparation method was successfully developed and validated to quantify the enantiomers of cloquintocet-mexyl in soil, millet, enoki mushroom, oilseed rape, and watermelon using a modified QuEChERS technique combined with HPLC-MS/MS. This method showed reliable performances for determining both enantiomers of cloquintocet-mexyl in all five matrices. The limits of detection and limits of quantification were in the range of 0.06-0.15 μg kg^-1 and 0.2-0.5 μg kg^-1, respectively. Good linearities were obtained with correlation coefficients ≥0.9954. The mean recoveries were between 84.1% and 111.5%, with relative standard deviations ranging from 1.2% to 9.8% at three spiked levels. Additionally, the study of stereoselective dissipation of cloquintocet-mexyl in soil indicated that (R)-cloquintocet-mexyl was preferentially degraded. This work is the first to describe a chiral analytical method and enantioselective behavior of cloquintocet-mexyl and provide basic data for the risk evaluation of cloquintocet-mexyl in food and environmental safety.

Old pesticide, new use: Smart and safe enantiomer of isocarbophos in locust control

Locust plagues are still worldwide problems. Selecting active enantiomers from current chiral insecticides is necessary for controlling locusts and mitigating the pesticide pollution in agricultural lands. Herein, two enantiomers of isocarbophos (ICP) were separated and the enantioselectivity in insecticidal activity against the pest Locusta migratoria manilensis (L. migratoria) and mechanisms were investigated. The significant difference of LD₅₀ between (+)-ICP (0.609 mg/kg bw) and (-)-ICP (79.412 mg/kg bw) demonstrated that (+)-ICP was a more effective enantiomer. The enantioselectivity in insecticidal activity of ICP enantiomers could be attributed to the selective affinity to acetylcholinesterase (AChE). Results of in vivo and in vitro assays suggested that AChE was more sensitive to (+)-ICP. In addition, molecular docking showed that the -CDOKER energies of (+)-ICP and (-)-ICP were 25.6652 and 24.4169, respectively, which suggested a stronger affinity between (+)-ICP and AChE. Significant selectivity also occurred in detoxifying enzymes activities (carboxylesterases (CarEs) and glutathione S-transferases (GSTs)) and related gene expressions. Suppression of detoxifying enzymes activities with (+)-ICP treatment suggested that (-)-ICP may induce the detoxifying enzyme-mediated ICP resistance. A more comprehensive understanding of the enantioselectivity of ICP is necessary for improving regulation and risk assessment of ICP.

Influence of Tubificidae Limnodrilus and electron acceptors on the environmental fate of BDE-47 in sediments by (14)C-labelling

2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was difficult to degrade in sediments. In this study, the environmental behavior of BDE-47 with/without the effect of benthos (Tubificidae Limnodrilus) and electron acceptors in sediments was investigated using C-14 tracer. Generally, extractable residues of BDE-47 were dominant in sediment and posed high environment risk. The amount of non-extractable residues (NERs) accounted for 39.0% of initial radioactivity in oxic sediments was significantly higher than those in anoxic sediments (17.6%). Most of NERs were localized in the humin fraction and presented as sequestrated forms. Under oxic conditions, the present of Limnodrilus significantly increased the proportion of NERs in sediment. Limnodrilus accumulated 34.2% of initial radioactivity. Under anoxic conditions, the addition of iron (Ⅲ) [Fe(III)], sulfate and nitrate reduced the environmental risk of BDE-47 with the increase of NERs formation, while manganese (IV) [Mn(IV)] addition had no effect on the formation of NERs. The present of Limnodrilus and electron acceptors promoted the production of metabolites. Meanwhile, BDE-47 changed the microbial community structure of sediments. These findings indicated that the environmental behavior and risk of BDE-47 was affected by benthos and electron acceptors, and the high proportion of sequestrated NERs posed high bioactivity and toxic threat to ecological environment.

Enantioselective degradation of the organophosphorus insecticide isocarbophos in Cupriavidus nantongensis X1T: Characteristics, enantioselective regulation, degradation pathways, and toxicity assessment

The chiral pesticide enantiomers often show selective efficacy and non-target toxicity. In this study, the enantioselective degradation characteristics of the chiral organophosphorus insecticide isocarbophos (ICP) by Cupriavidus nantongensis X1^T were investigated systematically. Strain X1^T preferentially degraded the ICP R isomer (R-ICP) over the S isomer (S-ICP). The degradation rate constant of R-ICP was 42-fold greater than S-ICP, while the former is less bioactive against pest insects but more toxic to humans than the latter. The concentration ratio of S-ICP to R-ICP determines whether S-ICP can be degraded by strain X1^T. S-ICP started to degrade only when the ratio (C_S-ICP/C_R-ICP) was greater than 62. Divalent metal cations could improve the degradation ability of strain X1^T. The detected metabolites that were identified suggested a novel hydrolysis pathway, while the hydrolytic metabolites were less toxic to fish and green algae than those from P-O bond breakage. The crude enzyme degraded both R-ICP and S-ICP in a similar rate, indicating that enantioselective degradation was due to the transportation of strain X1^T. The strain X1^T also enantioselectively degraded the chiral organophosphorus insecticides isofenphos-methyl and profenofos. The enantioselective degradation characteristics of strain X1^T make it suitable for remediation of chiral organophosphorus insecticide contaminated soil and water.

Effects of tubificid bioturbation on bioaccumulation of Cu and Zn released from sediment by aquatic organisms

To investigate the effects of bioturbation on absorption and enrichment of pollutants from sediments by aquatic organisms, microcosm systems similar to natural aquatic environment were established, and the release of Cu and Zn from the sediment, and their accumulation in some typical aquatic organisms, including submerged plants, floating plants and fish, with the presence of tubificids of different densities were measured. The results of this pilot study showed that the presence of tubificids promoted the migration of the trace metals from sediment to overlying water, especially when there were more worms and especially for Cu which is not easily released from the sediment. During the experiment, Cu in overlying water was mainly in particulate fraction. While for Zn, it was mainly in dissolved form in the early stage of the experiment, and then the dominant fraction gradually changed to particulate fraction. The bioturbation of tubificids also promoted the accumulation of both Cu and Zn in the aquatic organisms. In one system, different types of aquatic organisms showed different features for the accumulation of Cu and Zn. Meanwhile, with the presence of different intensity of bioturbation, the concentration of Cu or Zn in the same kind of organism was different. After a 30-day experiment, trace metal concentration in the aquatic organisms generally decreased in the order of floating plants (lesser duckweed) > submerged plants (Amazon sword) > small fish (zebrafish), and the concentration of Zn in the organisms was usually significantly higher than that of Cu in the same organism, especially in duckweed and zebrafish. However, the presence of tubificids and the density of them had more considerable effects on the uptake of Cu by the organisms, than on the uptake of Zn.

Microplastics Exposure Causes Negligible Effects on the Oxidative Response Enzymes Glutathione Reductase and Peroxidase in the Oligochaete Tubifex tubifex

Microplastics (MPs) are emerging pollutants, which are considered ubiquitous in aquatic ecosystems. The effects of MPs on aquatic biota are still poorly understood, and consequently, there is a need to understand the impacts that MPs may pose to organisms. In the present study, Tubifex tubifex, a freshwater oligochaete commonly used as a bioindicator of the aquatic environment, was exposed to fluorescent polyethylene microspheres (up to 10 µm in size) to test whether the oxidative stress status was affected. The mortality rate of T. tubifex, as well as the activities of the oxidative stress status biomarker enzymes glutathione reductase and peroxidase, were assessed. In terms of oxidative stress, no significant differences between the exposure organisms and the corresponding controls were detected. Even though the data suggest that polyethylene MPs and the selected concentrations did not pose a critical risk to T. tubifex, the previously reported tolerance of T. tubifex to environmental pollution should be taken into account and thus MPs as aquatic pollutants could still represent a threat to more sensitive oligochetes.

Comprehensive Study of Isocarbophos to Various Terrestrial Organisms: Enantioselective Bioactivity, Acute Toxicity, and Environmental Behaviors

The enantioselective bioactivity, toxicity, and environmental behaviors of isocarbophos (ICP) were investigated. The order of the bioactivity and toxicity was S-(+) ≥ rac > R-(-), and the difference of R-(-) and S-(+) was up to 232 times. The usage of S-(+)-ICP may efficiently reduce the usage amount of rac-ICP by 35% under the same effect, and the toxicity was not increased. Based on the toxic unit analysis, the additive effect and synergistic effect of ICP enantiomers were found in the four nontarget organisms, and R-(-)-ICP might cooperate the side-effects of S-(+)-ICP. The accumulation of rac-ICP in earthworms was enantioselective with an enantioenrichment of R-(-)-ICP, so the usage of racemic ICP might increase the exposure risk of R-(-)-ICP to earthworms. From the comprehensive results, the production of enantiomer enriched S-(+)-ICP might increase bioactivity and reduce environmental pollution, while the toxicity of S-(+)-ICP to other nontarget organisms needs to be further assessed.

A systemic study of enantioselectivity of isocarbophos in rice cultivation: Enantioselective bioactivity, toxicity, and environmental fate

The enantioselective bioactivity and acute toxicity to target and non-target model species, and environmental fate of isocarbophos (ICP) in rice cultivation were investigated systematically. Bioactivity and toxicity of S-(+)-ICP was significantly greater than R-(-)-ICP, and the difference was 2.9-101 times. Based on the toxic unit analysis, the toxic interaction of ICP enantiomers for target pests was synergistic effect, while for non-target fish was concentration addition or antagonistic effect. Rac-ICP displayed equivalent bioactivity to S-(+)-ICP under the equal dosage, but the toxicity of rac-ICP to the tested fishes reduced at least 2 times. Rac-ICP is more suitable than optically pure S-(+)-ICP for rice cultivation based on the toxicity and bioactivity results. In environmental behavior experiments, the main metabolite of ICP, isocarbophos oxon (ICPO) was detected in rice plants, water, rice and rice hull samples. S-(+)-ICP and S-(+)-ICPO were more persistent than the R-form in these matrices. The comprehensive data of ICP enantiomers in rice cultivation will improve environmental and ecological risk assessment, and using racemate may be more safe and reasonable in rice cultivation system.

Bioaccumulation of dichlorodiphenyltrichloroethanes (DDTs) in carp in a water/sediment microcosm: important role of sediment particulate matter and bioturbation

Sediments are reservoirs and sources of DDTs to the aquatic ecosystem. However, the role of sediment particulate matter and benthic organisms in transferring DDTs remains unclear. In this study, microcosms were built up with different groups to simulate a freshwater system with DDT-contaminated sediment and organisms. The impacts of different exposure routes (water and sediment) on the changes of DDT and its metabolites (DDD and DDE) in carp (Cyprinus carpio) were investigated. The bioturbation of Tubifex tubifex (Oligochaeta, Tubificidae) was investigated to understand the fate and transfer of DDTs in aquatic environment. For the sediment treatment, the concentrations of o,p'-DDT in carp were significantly higher than those of p,p'-DDT, and the metallothionein (MT) content decreased. The bioaccumulation of DDTs in carp via sediment particulate matter was significantly higher/faster than that via overlying water. T. tubifex and sediment particulate matter accelerate DDT bioaccumulation in carp. Selective enrichment of the (+)-o,p'-DDT and (+)-o,p'-DDD was found in carp. These results help to reduce uncertainty in ecological and health risk assessments and to better understand the risk of DDTs in the environment.

The role of the home environment in neurocognitive development of children living in extreme poverty and with frequent illnesses: a cross-sectional study

Background: The home environment is reported to contribute significantly to children’s developing cognitive skills. However, it is not yet evident whether this role prevails in the context of extreme poverty and frequent ill-health. We therefore investigated the role of the home environment in Ugandan children taking into account the frequent infections and extreme poverty in which they lived.

Methods: Cognitive abilities of 163 5-year-old children were assessed. Home environments of these children, their health status and family socioeconomic status (SES) were assessed respectively using the EC-HOME, anthropometry and illnesses, and traditional SES measures. Structural equation analyses compared five models on the influence of the home environment, SES, and child health on the cognitive scores.

Results: The model in which the home environment mediates the combined influence of SES and child health on cognitive performance showed a particularly good fit to the data compared with the four alternative models, i.e. those in which the HOME, SES and health independently influence cognitive performance.

Conclusions: Home environments providing cognitive stimulation can enable children to overcome effects of major adverse life experiences on cognitive development.

Assessment of tissue-specific accumulation, elimination and toxic effects of dichlorodiphenyltrichloroethanes (DDTs) in carp through aquatic food web

Microcosms containing DDT spiked-sediment, Tubifex tubifex and carp (Cyprinus carpio) were constructed to simulate a freshwater system. The accumulation, elimination and toxic effects of DDT (p,p'-DDT, o,p'-DDT), and its metabolites DDD (p,p'-DDD, o,p'-DDD) and DDE (p,p'-DDE, o,p'-DDE) were studied in T. tubifex and carp. Tissue/organ distributions of DDTs were also investigated in carp. The bioaccumulation and elimination of DDT differed in T. tubifex, carp and its tissues/organs. Unimodal or bimodal distributions were observed, and the concentrations of DDT metabolites (DDD and p,p'-DDE) increased over time. The carp organ with the highest concentrations of DDTs (DDT, DDD and DDE) was the gill. The largest mass distribution of DDTs was also in gill, followed by muscle and gastrointestinal tract. Maximum levels of DDTs in whole carp and carp muscle were 161 and 87 ng/g, respectively; therefore, the levels of DDTs observed in carp in this study were insufficient to constitute a health concern if present in fish for human consumption. Significant changes were observed in some biomarkers, including superoxide dismutase, catalase, glutathione-S-transferase, glutathione, and carboxylesterase, in T. tubifex and carp tissues during DDT exposure. Tissue-specific accumulation of DDTs in carp can be a key indicator of exposure to environmentally relevant concentrations.

Enantioselective oxidative stress and oxidative damage caused by Rac- and S-metolachlor to Scenedesmus obliquus

The rational use and environmental security of chiral pesticides has gained the interest of many researchers. The enantioselective effects of Rac- and S-metolachlor on oxidative stress in Scenedesmus obliquus were determined in this study. Stronger green fluorescence was observed in response to S-metolachlor treatment than to Rac-metolachlor treatment, suggesting that more reactive oxygen species (ROS) were stimulated by S-metolachlor. ROS levels following S-metolachlor treatment were 1.92-, 8.31-, and 1.08-times higher than those observed following Rac-metolachlor treatment at 0.1, 0.2, and 0.3 mg/L, respectively. Superoxide dismutase (SOD) and catalase (CAT) were stimulated with increasing herbicide concentrations, with S-metolachlor exhibiting a greater effect. Oxidative damage in terms of chlorophyll (Chl) content, cellular membrane permeability, and cellular ultrastructures of S. obliquus were investigated. Chla and Chlb contents in algae treated with Rac-metolachlor were 2-6-fold higher than those in algae treated with S-metolachlor at 0.1, 0.2, and 0.3 mg/L. The cellular membrane permeability of algae exposed to 0.3 mg/L Rac- and S-metolachlor was 6.19- and 42.5-times that of the control. Correlation analysis implied that ROS are the major factor responsible for the oxidative damage caused by Rac- and S-metolachlor. Damage to the chloroplasts and cell membrane of S. obliquus, low production of starch granules, and an increased number of vacuoles were observed upon ultrastructural morphology analysis by transmission electron microscope. These results indicate that S-metolachlor has a greater effect on S. obliquus than Rac-metolachlor.

Selective bioaccumulation and elimination of hexachlorocyclohexane isomers in Tubifex tubifex (Oligochaeta, Tubificidae)

In this study, Tubifex tubifex worms were exposed to sediment-associated hexachlorocyclohexane (HCH) isomers to study the bioaccumulation and elimination behaviors of HCH isomers in T. tubifex. During a 10-day bioaccumulation experiment, bioaccumulation curves of HCHs were approximate to M-type in T. tubifex. The enantioselective behaviors of α-HCH enantiomers were observed in T. tubifex, with concentrations of (+)-α-HCH higher than that of (-)-α-HCH. The concentration of γ-HCH in T. tubifex was higher than that of β-HCH and α-HCH. The existence of worms can accelerate the dissipation of HCHs in sediment, and the dissipation half-lives of α-HCH, β-HCH, and γ-HCH were 8.39, 23.90, and 3.10 days, respectively. In the elimination experiment, approximately 0.053 (37.1%), 0.074 (45.9%), and 0.042 mg/kgwwt (38.4%) α-HCH, β-HCH, and γ-HCH were depleted or excreted in T. tubifex on the first day, respectively. The body residues in T. tubifex were 0.084 (α-HCH), 0.082 (β-HCH), and 0.061 mg/kgwwt (γ-HCH) at the end of elimination experiment. Furthermore, the existence of T. tubifex could affect the overlying water quality parameters.

Effects of benthic organism Tubifex tubifex on hexachlorocyclohexane isomers transfer and distribution into freshwater sediment

In this study, bioaccumulation and elimination of HCHs in tubifex, and the distribution of HCHs in overlying water and sediment, were studied during a 10-d experiment. A sensitive method was developed for the determination of HCHs in samples based on gas chromatograph (GC) equipped with a nickel-63 electron capture detector (μECD). The limit of detection (LOD) was 0.35 µg/kg for α-HCH and 0.82 µg/kg for β-HCH. Tubifex accumulated HCHs rapidly, and the curves were approximately M-type. The highest level was reached on the 7th day, with 0.34 mg/kg(wwt) for α-HCH and 0.87 mg/kg(wwt) for β-HCH in worms. The AFs of β-HCH in tubifex were higher than those of α-HCH. Moreover, the existence of tubifex significantly reduced β-HCH fluxes from the overlying water to sediment by uptake or degradation and decreased the concentrations of β-HCH in the sediment, but it had little influence on α-HCH fluxes. Moreover, enantioselectivity of α-HCH enantiomers was not observed in tubifex, whether in the bioaccumulation or elimination experiments. At the end of the elimination experiment, approximately 80% and 70% of α-HCH and β-HCH were eliminated, and the depuration half-lives were 4.43 and 5.39 days, respectively.

Enantioselective Determination of Polycyclic Musks in River and Wastewater by GC/MS/MS

The separation of chiral compounds is an interesting and challenging topic in analytical chemistry, especially in environmental fields. Enantioselective degradation or bioaccumulation has been observed for several chiral pollutants. Polycyclic musks are chiral and are widely used as fragrances in a variety of personal care products such as soaps, shampoos, cosmetics and perfumes. In this study, the gas chromatographic separation of chiral polycyclic musks, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclo-penta-γ-2-benzopyrane (HHCB), 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetra-hydronaphthalene (AHTN), 6-acetyl-1,1,2,3,3,5-hexamethylindane (AHDI), 5-acetyl-1,1,2,6-tetramethyl-3-iso-propylindane (ATII), and 6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)-indanone (DPMI) was achieved on modified cyclodextrin stationary phase (heptakis (2,3-di-O-methyl-6-O-tert-butyl-dimethylsilyl-β-CD in DV-1701)). Separation techniques are coupled to tandem mass spectrometry (MS-MS), as it provides the sensitivity and selectivity needed. River and wastewaters (influents and effluents of wastewater treatment plants (WWTPs)) in the Nakdong River were investigated with regard to the concentrations and the enantiomeric ratios of polycyclic musks. HHCB was most frequently detected in river and wastewaters, and an enantiomeric enrichment was observed in the effluents of one of the investigated wastewater treatment plants (WWTPs). We reported the contamination of river and wastewaters in Korea by chiral polycyclic musks. The results of this investigation suggest that enantioselective transformation may occur during wastewater treatment.

Enantioselective degradation and chiral stability of the herbicide fluazifop-butyl in soil and water

The stereoselective degradation and transformation of the enantiomers of the herbicide fluazifop-butyl in soil and water were studied to investigate the environmental behavior and chiral stability of the optical pure product. Its main chiral metabolite fluazifop was also monitored. LC/MS/MS with Chiralpak IC chiral column was used to separate the enantiomers of fluazifop-butyl and fluazifop. Validated enantioselective residue analysis methods were established with recoveries ranging from 77.1 to 115.4% and RSDs from 0.85 to 8.9% for the enantiomers. It was found the dissipation of fluazifop-butyl was rapid in the three studied soils (Beijing, Harbin and Anhui soil), and the degradation half-lives of the enantiomers ranged from 0.136 to 2.7 d. Enantioselective degradations were found in two soils. In Beijing soil, R-fluazifop-butyl was preferentially degraded leading to relative enrichment of S-enantiomer, but in Anhui soil, S-fluazifop-butyl dissipated faster. There was no conversion of the R-fluazifop-butyl into S-fluazifop-butyl or vice versa in the soils. The formation of fluazifop in the soils was rapidly accompanied with the fast degradation of fluazifop-butyl, and the enantioselectivity and the transformation of S-fluazifop to R-fluazifop were found. The degradation of fluazifop-butyl in water was also quick, with half-lives of the enantiomers ranging from 0.34 to 2.52 d, and there was no significant enantioselectivity of the degradation of fluazifop-butyl and the formation of fluazifop. The effects of pH on the degradation showed fluazifop-butyl enantiomers degraded faster in alkaline conditions. This study showed an evidence of enantioselective behavior and enantiomerization of the chiral herbicide fluazifop-butyl.

Evaluation of single and joint toxicity of perfluorooctane sulfonate and zinc to Limnodrilus hoffmeisteri: Acute toxicity, bioaccumulation and oxidative stress

Perfluorooctane sulfonate (PFOS) and zinc have been detected in aquatic environment widely. In order to study the combined effects of PFOS and Zn, a series of experiments was conducted to explore the acute mortality, bioaccumulation and antioxidant status of Limnodrilus hoffmeisteri. The acute toxicity was evaluated by calculating 24h-EC50 values, and it was observed that 24h-EC50 values in single and joint treatments decreased with decreasing pH value or increasing exposure concentration. Toxic unit analysis suggested that the combined effects of the PFOS+Zn binary mixture were mostly simple addition, with 8 groups showing synergism and only one group showing antagonism. The analysis of internal Zn and PFOS concentration showed that the possible interaction between Zn and PFOS can affect the bioaccumulation of the two chemicals in L. hoffmeisteri. In addition, oxidative stress status was assessed by measuring oxidation-related biochemical parameters such as superoxide dismutase, glutathione peroxidase and malondialdehyde, and the integrated biomarker response index was estimated to rank the toxicity order. Exposures to Zn and PFOS were found to evoke some changes in the antioxidant defense system, and a strong self-adaptive ability was noticed for L. hoffmeisteri after 10 d exposure.

Toxicokinetics and oxidative stress in Tubifex tubifex exposed to hexachlorocyclohexane isomers

In this study, Tubifex tubifex (Oligochaeta, Tubificida) was exposed to hexachlorocyclohexane isomers in an aquatic environment to study the bioaccumulation and elimination of these chemicals, and oxidative stress in this organism.