Effect-directed analysis of toxic organics in PM2.5 exposure to the cellular bioassays in vitro: Application in Shanxi of China.

To optimize the effect-directed analysis (EDA) approach to identify the fine particulate matter (PM2.5) bound organic toxicants, Jinzhong city, in the Shanxi Province of China, was selected as the object of our study. First, PM2.5 samples were collected and their organic extracts were separated out in 9 fractions (F1-F9) using reversed-phase high performance liquid chromatography after purification using gel permeation chromatography. Second, the toxicity effects of each fraction were measured by human bronchial epithelial cells (BEAS-2B) in vitro. And toxicity effects included antioxidant stress (ROS, LDH, and CAT) and an inflammatory response (IL-6, IL-1ß, and TNF-α). The results showed that the scores of the toxicity effects on multiple lines of evidence were the highest in the F3 and F4 fractions compared with those of the control. Subsequently, the main poisons, o-cymene, p-cymene, benzene, ethylbenzene, xylene, and styrene, were identified using GC×GC-TOF/MS. Finally, to confirm the above possible candidates, (1) the levels of o-cymene, p-cymene and BTEXS in daily PM2.5 were measured using GC-MS in November 2020, and the rates of detection of these pollutants were 100% in PM2.5. Among them, o-cymene and p-cymene were first reported as the key toxic substances of PM2.5, and their average concentration values were 0.16 ± 0.11 and 0.18 ± 0.15 ng‧m-3, respectively. (2) the toxicity of p-cymene may be no less than that of other benzene derivatives according to their LC50 in Daphnia magna. (3) based on canonical correlation analysis, the exposure to p-cymene, benzene, and styrene in PM2.5 was most likely associated with the toxicity effects (CAT, IL-6, and TNF-α), which in turn caused the observed toxicity. In conclusion, p-cymene, benzene, and styrene were found to be the key toxic organics in PM2.5 for cells in vitro. EDA technology avoids the limitations of chemical analysis and uncertainty of the biological testing and adds new toxicants to the control list of PM2.5, contributing to this study field. However, the application of EDA to PM2.5 still faces challenges such as the selection of biological effects, loss of toxicity with the separation process, influence of the dosing method, and identification of the unknown effects of pollutants.

Sulfur dioxide improves drought tolerance through activating Ca2+ signaling pathways in wheat seedlings.

Sulfur dioxide (SO2) and drought are two important co-occurring abiotic stresses affecting the growth and productivity of plants. Here, we will investigate the role of Ca2+ in regulating antioxidant defense during drought or SO2/drought stress, and the effect of SO2 pretreatment on the physiological response of wheat seedlings to drought stress. The results showed that exogenous Ca2+ increased the activities of SOD, CAT and POD, and reduced the contents of H2O2 and MDA in drought-treated wheat seedlings, suggesting Ca2+ could improve drought tolerance by promoting antioxidant defense in plants. Moreover, exogenous Ca2+ up-regulated the expression of two stress-responsive transcription factor (TF) genes, ERF1 and MYB30, to cope with drought stress. Exposure of wheat seedlings to 10 mg m-3 SO2 significantly enhanced the activities of SOD, CAT and POD. The contents of H2O2 and MDA remained at control levels, showing that SO2 at this concentration led to an activation of the antioxidant defense system and did not cause oxidative damage to the seedlings. Furthermore, 10 mg m-3 SO2 pretreatment increased the expression of CCaMK and CPK10, enhanced the activities of SOD and POD, and reduced the accumulation of H2O2 and MDA in drought-treated wheat seedlings, showing a role of SO2 in protection of plants against drought stress. However, with removal of Ca2+ by spraying EGTA on the SO2-pretreated wheat seedlings, the expression of transcription factor genes and activities of antioxidant enzymes were decreased, and the contents of H2O2 and MDA enhanced to the level of drought treatment alone, suggesting a role of Ca2+ in the SO2-induced alleviation of drought stress. Together, these results indicated that exogenous Ca2+ increased defense-related gene expression and enzyme activity in response to drought stress, and that pre-exposure to appropriate levels of SO2 could improve drought tolerance through activation of Ca2+ signaling pathways in plants. This study would provide new strategy for enhancing plant resistance to environmental stress.

Sulfur dioxide enhance drought tolerance of wheat seedlings through H2S signaling.

Drought is one of the most common factors that limit plant growth and productivity. Sulfur dioxide (SO2) has recently been found to play a benefical role in protection of plants against environmental stress. In this study, we investigated the effect of SO2 on the physiological and molecular response of wheat seedlings to drought stress. Pretreatment with 10 mg/m3 SO2 significantly increased the survival rate and relative water content (RWC) of wheat seedlings under drought stress, indicating that pre-exposure to appropriate level of SO2 could enhance drought tolerance of plants. These responses were related to the enhanced proline accumulation in the drought-treated wheat seedlings that induced by SO2 pretreatment. Meanwhile, SO2 pretreatment increased the activities of superoxide dismutase (SOD) and peroxidase (POD), and effectively reduced the content of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in drought-treated wheat seedlings, suggesting SO2 could alleviate drought-induced oxidative damage by enhancing antioxidant defense system in plants. Expression analysis of transcription factor genes also showed that SO2 pretreatment decreased the expression of TaNAC69, but the expression of TaERF1 and TaMYB30 changed slightly and maintained at higher levels in wheat seedlings in response to drought stress. Furthermore, SO2 pretreatment triggered marked accumulation of hydrogen sulfide (H2S) in wheat seedlings under drought stress. When scavenged H2S by spraying Hypotaurine (HT), the activities of antioxidant enzymes and the expression of transcription factor genes were decreased, and the content of H2O2 and MDA increased to the level of drought treatment alone, suggesting a regulatory role of SO2-induced H2S in plant adaptation to drought stress. Together, this study indicated that SO2 enhanced drought tolerance of wheat seedlings through H2S signaling, and provided new strategy for enhancing plant tolerance to drought stress.

Cancer risk assessment of soils contaminated by polycyclic aromatic hydrocarbons in Shanxi, China.

To assess the human cancer risk exposed to soil contaminated by polycyclic aromatic hydrocarbons (PAHs) in Shanxi province, China, the total 33 samples in the surface soil were collected from 11 cities, and the priority 15 PAHs were analyzed using gas chromatography-mass spectrometry after the soxhlet extraction and silica-alumina column purification. As a result, the levels of ∑15PAH in soil varied from 66.2 to 2633 ng/g dry weight (dw) with a mean of 732 ng/g dw, and seven carcinogenic PAHs made up 42-69% of the total priority PAHs and had an average value of 367 (in the range of 33.2 to 1181) ng/g dw. Accordingly, the total concentrations of benzo[a]pyrene equivalents (BaPeq) for 15 PAHs ranged from 10.3 to 358 (average 98.3) ng/g dw, and the seven carcinogenic BaPeq accounted for above 90%. Subsequently, the possible sources of PAHs in soil were identified by isomer ratios, demonstrating that the combustion contributed to the main source. Finally, the incremental lifetime cancer risks (ILCR) of soil contaminated by 15 priority PAHs were estimated using the targeted chemical-specific approach. ILCR values were considered to be greater than 1 × 10-6 in 16 of 33 sites and followed a decreasing trend of adulthood > childhood > adolescence. Subsequently, the analysis of variance was performed by average ILCR value among the 11 cities (n = 3, p < 0.01), which indicated that the potential low cancer risk significantly increased for nearby residents in two areas, including Datong and Xinzhou, with the ILCR values of 4.61 ±â€¯1.93 and 3.92 ±â€¯2.54 per million, respectively. Therefore, the consumption of traditional coal should be controlled and partially replaced with the alternative energy sources. And the rigorous monitoring should be termly warranted to avoid the cancer risk for human being in agricultural area of Shanxi, China.

Effect-Directed Analysis of Toxicants in Sediment with Combined Passive Dosing and in Vivo Toxicity Testing.

Identifying key toxicants in sediment is a great challenge, particularly if nontarget toxicants are involved. To identify the contaminants responsible for sediment toxicity to Chironomus dilutus in Guangzhou reach of the Pearl River in South China, passive dosing and in vivo toxicity testing were incorporated into effect-directed analysis (EDA) to account for bioavailability. Fractionation of sediment extracts was performed with gel permeation chromatography and reverse phase liquid chromatography sequentially. Polydimethylsiloxane served as passive dosing matrix for midge bioassays. The fractions showing abnormal enzymatic response were subject to a nontarget analysis, which screened out 15 candidate toxicants. The concentrations of the screened contaminants (log-based organic carbon normalized) in sediments of 10 sites were compared to sediment toxicity (10 and 20 day mortality and 10 day enzymatic response) to C. dilutus using correlation analyses. The results suggested that oxidative stress induced by cypermethrin, dimethomorph, pebulate and thenylchlor may have in part caused the observed toxicity to C. dilutus. The present study shows that EDA procedures coupled with passive dosing and in vivo toxicity testing can be effective in identifying sediment-bound toxicants, which may pose high risk to benthic organisms but are not routinely monitored and/or regulated. The findings of the present study highlight the importance of incorporating environmentally relevant approaches in assessing sediment heavily impacted by a multitude of contaminants, which is often the case in many developing countries.

A novel dithiocarbamate derivative induces cell apoptosis through p53-dependent intrinsic pathway and suppresses the expression of the E6 oncogene of human papillomavirus 18 in HeLa cells.

Dithiocarbamates (DTCs) exhibit a broad spectrum of antitumor activities, however, their molecular mechanisms of antitumor have not yet been elucidated. Previously, we have synthesized a series of novel dithiocarbamate derivatives. These DTCs were examined for cytotoxic activities against five human cancer cell lines. In this study, one of dithiocarbamate (DTC1) with higher potential for HeLa cells was chosen to investigate molecular mechanisms for its anti-tumor activities. DTC1 could inhibit proliferation, and highly induce apoptosis in HeLa cells by activating caspase-3, -6 and -9; moreover, activities of caspase-3, -6 and -9 were inhibited by pan-caspase inhibitor, Z-VAD-FMK. Furthermore, DTC1 decreased the levels of Bcl-2 and Bcl-xL, and increased expression of cytosol cytochrome c, Bak, Bax and p53 in a time-dependent manner but had no effect on the level of Rb. It was shown that DTC1 induced HeLa cells apoptosis through a p53-dependent pathway as tested by the wild type p53 inhibitor, pifithrin-α. Additionally, the relative expression of E6 and E7 were evaluated in HPV18-positive (HeLa cells) by real-time PCR and western blotting. The results firstly demonstrated that DTC1 suppressed both expression of E6 mRNA and E6 oncoprotein, but had no effect on the expression of E7 mRNA and protein in HPV18. Our results suggested that DTC1 may serve as novel chemotherapeutic agents in the treatment of cervical cancer and potential anti-HPV virus candidates that merit further studies.

Integrated sediment quality assessment through biomarker responses and bioavailability measurements: Application in Tai Lake, China.

A weight of evidence (WoE) framework has been applied to assess sediment quality of a typical freshwater lake, Tai Lake in China, where the sediments were contaminated by various chemicals but showed no acute lethality to the benthic invertebrate, Chironomus dilutus. A quantitative scoring method was employed to integrate three lines of evidence (LoE), including adverse effects in life cycle bioassays, biomarker responses, and bioavailability-based chemical analysis. Six biomarkers were determined in C. dilutus after the exposure to the sediments from Tai Lake and provided sensitive indication of sublethal effects at the molecular level. The biomarkers included cytochrome P450, glutathione S-transferase, carboxylesterase, acetylcholinesterase, catalase, and lipid peroxidation. The changes of the biomarkers were summarized for individual sampling sites by computing the integrated biomarker response (IBR) indices. Complementary information was also confirmed by the interrelationship of the LoEs. The IBR indices gained before pupation correlated well with the impairments of emergence of the midges, and altered acetylcholinesterase was corroborated by the detection of chlorpyrifos, an organophosphate pesticide. The relationship between bioavailable toxic units estimated by Tenax extractable concentrations of chemicals in sediment and the observed toxicity in the midges helped to identify the putative toxicity contributors to C. dilutus. Overall, the WoE method clearly distinguished the contaminated sites and ranked them by the level of contamination. Sediment-associated pesticides, particularly γ-hexachlorocyclohexane and chlorpyrifos, were the possible contributors to chronic toxicity to the midges.

Joint toxicity of sediment-associated DDT and copper to a polychaete, Nereis succinea.

As major components in antifouling paints, both dichlorodiphenyltrichloroethane (DDT) and copper are ubiquitous in estuarine sediment and have been detected at high concentrations in the harbors in South China. In the present study joint toxicity between DDT and copper to an estuarine polychaete, Nereis succinea, was examined using bioaccumulation potential, growth impairment and change in lipid peroxidation contents as sub-lethal endpoints. In general, the toxicity of DDXs (DDT and its metabolites) and copper acted independently and copper was more toxic to the lugworms at environmentally relevant concentrations. Nevertheless, co-exposure to copper led to a significant reduction in the bioaccumulation of DDXs when the concentrations of DDXs in sediment were high. The inhibition of DDX bioaccumulation by copper may be partially explained by the decrease in the bioavailability of sediment-associated DDXs which were estimated by biomimetic gut fluid extraction. The saturation of the solubilization agents or the inhibition of protease activity in gut fluid of N. succinea by copper limited the DDX bioavailability and the subsequent bioaccumulation.

Assessment of Sediment Risk in the North End of Tai Lake, China: Integrating Chemical Analysis and Chronic Toxicity Testing with Chironomus dilutus.

Whole life-cycle bioassays with Chironomus dilutus were performed to evaluate sediment toxicity in Tai Lake, a typical freshwater lake in China. Meanwhile, contaminants of concern were analyzed in sediment. The sediments in Tai Lake showed no acute mortality in 10-day testing to C. dilutus. After chronic exposure to the sediments, however, adverse effects-including decreased survival and sublethal impairments of growth, emergence, and fecundity-were observed at most sites in Tai Lake. A variety of contaminants were detected in sediment with the total concentrations in the range of 504-889 ng/g dry weight (dw) for polycyclic aromatic hydrocarbons, 0.56-1.81 ng/g dw for polychlorinated biphenyls, 38.6-87.8 ng/g dw for polybrominated diphenyl ethers, 8.34-14.2 ng/g dw for organochlorine pesticides, 1.27-2.95 ng/g dw for organophosphate pesticides, 0.11-0.21 ng/g dw for pyrethroid pesticides, and 332-609 µg/g dw for metals. Finally, a canonical correlation analysis was applied to link chronic sediment toxicity to the toxic units of individual contaminants. Results suggested that two pesticides (hexachlorocyclohexane and chlorpyrifos) and two metals (chromium and nickel) in sediments from Tai Lake were the potential contributors to the noted toxicity in C. dilutus in the life-cycle toxicity testing. In conclusion, acute bioassays with the benthos were not sensitive enough to assess sediment toxicity in freshwater lakes in China, and it is desirable to integrate chronic toxicity testing with chemical analysis to better understand sediment risk.

Ursolic acid induces apoptosis through mitochondrial intrinsic pathway and suppression of ERK1/2 MAPK in HeLa cells.

Ursolic acid (UA), a natural pentacyclic triterpenoid compound, has been demonstrated to induce apoptosis in various tumors. The aim of the present study was to elucidate the molecular mechanisms of UA-induced apoptosis in HeLa cells. Here, we reported that UA induced apoptosis through the mitochondrial intrinsic pathway in HeLa cells, as shown by release of cytosol cytochrome c, activation of caspase-9 and -3, reduction of Bcl-2 and Bcl-xL, and increase of Bax and Bak. UA down-regulated the phosphorylation of ERK1/2 and p38, whereas phosphorylation of JNK was unchanged. The roles of ERK1/2 and p38 were further confirmed using the ERK1/2 inhibitor (U0126) and p38 inhibitor (SB203580). U0126 markedly increased UA-induced the Bax/Bcl-2 ratio, the increase of cytosol cytochrome c, and the levels of cleaved caspase-3, but SB203580 had little effects on the above characters, suggesting the ERK1/2 signaling pathway is required for apoptosis. Furthermore, UA up-regulated DUSP 1, 2, 4, 5, 6, 7, 9, and 10 mRNA expressions, which may be a clue for the role of dephosphorylation of ERK1/2 and p38. These data suggested that the apoptotic mechanism of UA treatment in HeLa cells was through the mitochondrial intrinsic pathway and closely associated with the suppression of the ERK1/2 signaling pathway.

Assessment of the estrogenic activities of chickpea (Cicer arietinum L) sprout isoflavone extract in ovariectomized rats.

AIM: Chickpea (Cicer arietinum L) is a traditional Uighur herb. In this study we investigated the estrogenic activities of the isoflavones extracted from chickpea sprouts (ICS) in ovariectomized rats. METHODS: Ten-week-old virgin Sprague-Dawley female rats were ovariectomized (OVX). The rats were administered via intragastric gavage 3 different doses of ICS (20, 50, or 100 mg·kg(-1)·d(-1)) for 5 weeks. Their uterine weight and serum levels of 17ß-estradiol (E2), follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured. The epithelial height, number of glands in the uterus, and number of osteoclasts in the femur were histologically quantified, and the expression of proliferating cell nuclear antigen (PCNA) was assessed immunohistochemically. Bone structural parameters, including bone mineral density (BMD), bone volume/tissue volume (BV/TV), trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp) were measured using Micro-CT scanning. RESULTS: Treatments of OVX rats with ICS (50 or 100 mg·kg(-1)·d(-1)) produced significant estrogenic effects on the uteruses, including the increases in uterine weight, epithelial height and gland number, as well as in the expression of the cell proliferation marker PCNA. The treatments changed the secretory profile of ovarian hormones and pituitary gonadotropins: serum E2 level was significantly increased, while serum LH and FSH levels were decreased compared with the vehicle-treated OVX rats. Furthermore, the treatments significantly attenuated the bone loss, increased BMD, BV/TV and Tb.Th and decreased Tb.Sp and the number of osteoclasts. Treatment of OVX rats with the positive control drug E2 (0.25 mg·kg(-1)·d(-1)) produced similar, but more prominent effects. CONCLUSION: ICS exhibits moderate estrogenic activities as compared to E2 in ovariectomized rats, suggesting the potential use of ICS for the treatment of menopausal symptoms and osteoporosis caused by estrogen deficiency.

Optimization of Cancer Risk Assessment Models for PM2.5-Bound PAHs: Application in Jingzhong, Shanxi, China.

The accurate evaluation of the carcinogenic risk of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) is crucial because of the teratogenic, carcinogenic, and mutagenic effects of PAHs. The best model out of six models was selected across three highly used categories in recent years, including the USEPA-recommended inhalation risk (Model I), inhalation carcinogen unit risk (Models IIA-IID), and three exposure pathways (inhalation, dermal, and oral) (Model III). Model I was found to be superior to the other models, and its predicted risk values were in accordance with the thresholds of PM2.5 and benzo[a]pyrene in ambient-air-quality standards. Models IIA and III overestimated the risk of cancer compared to the actual cancer incidence in the local population. Model IID can replace Models IIB and IIC as these models exhibited no statistically significant differences between each other. Furthermore, the exposure parameters were optimized for Model I and significant differences were observed with respect to country and age. However, the gender difference was not statistically significant. In conclusion, Model I is recommended as the more suitable model, but in assessing cancer risk in the future, the exposure parameters must be appropriate for each country.

Composition, Source Apportionment, and Health Risk of PM2.5-Bound Metals during Winter Haze in Yuci College Town, Shanxi, China.

The composition, source, and health risks of PM2.5-bound metals were investigated during winter haze in Yuci College Town, Shanxi, China. The 24-h PM2.5 levels of 34 samples ranged from 17 to 174 µg·m−3, with a mean of 81 ± 35 µg·m−3. PM2.5-bound metals ranked in the following order: Zn > Cu > Pb > As > Ni > Cr (VI) > Cd > Co. The concentrations of 18% As and 100% Cr (VI) exceeded the corresponding standards of the Ambient Air Quality Standards set by China and the WHO. Subsequently, positive matrix factorization analyses revealed that the three major sources of metals were combustion (37.91%), traffic emissions (32.19%), and industry sources (29.9%). Finally, the non-carcinogenic risks for eight metals indicated that only 2.9% of the samples exceeded a threshold value of one, and As accounted for 45.31%. The total carcinogenic risk values for six metals (As, Cd, Co, Cr (VI), Ni, and Pb) were in the range from 10−6 to 10−4, with Cr (VI) and As accounting for 80.92% and 15.52%, respectively. In conclusion, winter haze in Yuci College Town was characterized by higher metal levels and health risks; among the metals, As and Cr (VI) were probably the main contributors.

Size controllable synthesis of ZSM-5 zeolite and its catalytic performance in the reaction of methanol conversion to aromatics.

ZSM-5 zeolites were hydrothermally synthesized with commercial silica sol, and the crystal size was controlled by adding silicalite-1 seed in the synthetic system. The crystal size of ZSM-5 was affected by the crystallization time of seed, seed content and seed size. ZSM-5 zeolites with controllable particle size in the range of 200-2200 nm could be obtained. The prepared samples with different particle sizes were used for the reaction of methanol conversion to aromatics (MTA). The results suggested that the HZSM-5 catalyst with small crystal size showed much longer catalyst lifetime and higher selectivity for C5 + hydrocarbons and aromatics, especially C9 + aromatics in the MTA reaction. Moreover, the introduction of zinc (Zn) into the HZSM-5 zeolites can considerably promote the selectivity to aromatics in the products. Zn modified HZSM-5 zeolites with different Zn loading amounts were prepared by the incipient wetness impregnation method, and the highest aromatics selectivity was obtained when the Zn loading was 1.0%. The improvement of methanol aromatization was ascribed to the synergistic effect of Brønsted acid sites and the newly formed Zn-Lewis acid sites.

Heavy metal contamination and ecological risk assessment of the agricultural soil in Shanxi Province, China.

To assess contamination levels and ecological risks of heavy metals in agricultural soil from Shanxi Province of China, a total of 33 samples in the surface soil were collected from 11 cities in Shanxi. The soil samples were digested by a mixed acid of nitric acid and hydrofluoric acid on a microwave digestion system, then the levels of eight heavy metals were analysed using an inductively coupled plasma mass spectrometer. The pollution levels of soil heavy metals were evaluated using a geo-accumulation index and their ecological risks were assessed using risk index calculated by Hakanson's method. As a result, the average concentrations of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were 12.9 ± 4.8, 0.35 ± 0.23, 43 ± 14, 27 ± 19, 0.25 ± 0.14, 21.7 ± 5.7, 17 ± 13 and 89 ± 53 mg kg-1, respectively. By comparison to the Chinese soil environmental quality (GB15618-2018), only 9% of Cd samples and 3% of Cu samples exceeded their corresponding screening criteria. Subsequently, the results of geo-accumulation indices suggested that Shanxi's soil suffered from moderate to heavy contamination posed by Cd and Hg, and risk indices exhibited a similar trend that Cd and Hg were the main contributors for considerable to very high ecological risk. Finally, the analysis of variance indicated that the mean levels of Cd significantly occurred at Yuncheng areas among the 11 cities (n = 3, p < 0.05), but Hg concentrations did not have significantly statistical differences. This study demonstrated that metals Cd and Hg had higher levels and ecological risks for agricultural soil in Shanxi, especially, Yuncheng City suffered from heavy Cd contamination. The findings of the present study will provide basic information on management and control of the agricultural soil contamination in Shanxi Province, China.

Effect of acute ammonia exposure on the glutathione redox system in FFRC strain common carp (Cyprinus carpio L.).

Ammonia is one of the most common aquatic pollutants. To analyze the effect of ammonia exposure on the glutathione redox system, we investigated the levels of hydrogen peroxide (H2O2) and glutathione, and transcription and activities of glutathione-related enzymes in liver and gills of FFRC strain common carp (Cyprinus carpio L.) exposed to 0, 10, 20, and 30 mg/L of ammonia. The results showed that H2O2 content reached a maximum level at 48 h of exposure in the liver of fish. In gills, H2O2 increased rapidly at 6 h and reached to maximum levels at 24 h of exposure, indicating that gills experienced oxidative stress earlier than the liver of fish exposed to ammonia. Reduced glutathione (GSH) content and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio increased significantly within 24 h of exposure. Meanwhile, the transcription and activities of glutathione S-transferase (GST) and glutathione reductase (GR) increased significantly in the liver, and glutathione peroxidase (GSH-Px) and GST increased in the gills of fish exposed to ammonia. Malondialdehyde (MDA) content kept at a low level after exposure to low concentration of ammonia, but increased significantly after exposure to 30 mg/L ammonia for 48 h along with a decrease in GSH content and GSH/GSSG ratio. These data showed that the glutathione redox system played an important role in protection against ammonia-induced oxidative stress in the liver and gills of FFRC strain common carp, though the defense capacity was not able to completely prevent oxidative damage occurring after exposure to higher concentration of ammonia. This research systematically studied the response of the glutathione redox system to ammonia stress and would provide novel information for a better understanding of the adaptive mechanisms of fish to environmental stress.

NiFe2O4 nanoparticles supported on cotton-based carbon fibers and their application as a novel broadband microwave absorbent.

In this work, NiFe2O4 nanoparticles were successfully supported on cotton-based carbon fibers through a flexible two-step approach consisting of calcination of cotton in a N2 atmosphere and subsequent hydrothermal reaction. The incorporation of the NiFe2O4 nanoparticles into cotton-based carbon fibers resulted in better impedance matching, leading to better microwave absorption performance than cotton-based carbon fibers and NiFe2O4 nanoparticles. For NiFe2O4/carbon fibers, reflection loss (RL) values less than -10 dB were obtained in the frequency range of 11.5-18 GHz with 2.4 mm thickness, which covered the entire Ku-band (from 12 to 18 GHz). Meanwhile, when the matching thickness was 3.2 mm, the RL values less than -10 dB were in the range of 8.0-12.7 GHz, which covered the entire X-band (from 8 to 12 GHz). This excellent and interesting microwave absorption performance can satisfy multiple applications. Owing to the characteristics of a cost-effective synthetic route, low density and excellent microwave absorption, the NiFe2O4/carbon fibers have a promising future in X-band and Ku-band absorption.

Contribution of pyrethroids in large urban rivers to sediment toxicity assessed with benthic invertebrates Chironomus dilutus: A case study in South China.

The importance of pyrethroids as potential stressors to benthic organisms has gradually become evident in urban creeks; however, the occurrence and toxicity of sediment-associated pyrethroids are rarely studied in large rivers. In this context, 10 sediments from a large urban river (Guangzhou reach of the Pearl River in China) were assessed for pyrethroid occurrence and sediment toxicity to the benthic invertebrate Chironomus dilutus. One half of the sediments exhibited lethality to C. dilutus in a 10-d exposure and all surviving midges showed significant change of enzymatic activity. Moreover, mortality occurred during a 20-d exposure for all the sediments, in accordance with the high hazard quotients to benthic species estimated from pyrethroid residues in sediment. Pyrethroids were detectable in all sediments with the concentrations ranging from 2.43 to 61.2 ng/g dry weight, and permethrin and cypermethrin dominated pyrethroid composition. Acute toxic units for pyrethroids ranged from 0.03 to 0.56 (cypermethrin accounted for 13-81%) and showed a direct relationship with sediment mortality among the midges. This is consistent with the studies on small creeks in Guangzhou in which sediment-bound cypermethrin was found as a main stressor to benthic invertebrates. Comparatively, sediment toxicity and pyrethroid residues in large rivers were significantly lower than those in nearby creeks (urban tributaries). The difference may be partially explained by differing flow rates and water-carrying capacity among waterbodies at different scales; further validation is required. Overall, extensive use of pyrethroids has caused a threat to benthic species not only in small creeks but also in large rivers. Environ Toxicol Chem 2017;36:3367-3375. © 2017 SETAC.