Adsorption of Pyrene and Arsenite by Micro/Nano Carbon Black and Iron Oxide.

Polycyclic aromatic hydrocarbons (PAHs) and arsenic (As) are common pollutants co-existing in the environment, causing potential hazards to the ecosystem and human health. How their behaviors are affected by micro/nano particles in the environment are still not very clear. Through a series of static adsorption experiments, this study investigated the adsorption of pyrene and arsenite (As (III)) using micro/nano carbon black and iron oxide under different conditions. The objectives were to determine the kinetics and isotherms of the adsorption of pyrene and As (III) using micro/nano carbon black and iron oxide and evaluate the impact of co-existing conditions on the adsorption. The microstructure of micro/nano carbon black (C 94.03%) is spherical-like, with a diameter of 100-200 nm. The micro/nano iron oxide (hematite) has irregular rod-shaped structures, mostly about 1 µm long and 100-200 nm wide. The results show that the micro/nano black carbon easily adsorbed the pyrene, with a pseudo-second-order rate constant of 0.016 mg/(g·h) and an adsorption capacity of 283.23 µg/g at 24 h. The micro/nano iron oxide easily adsorbed As (III), with a pseudo-second-order rate constant of 0.814 mg/(g·h) and an adsorption capacity of 3.45 mg/g at 24 h. The mechanisms of adsorption were mainly chemical reactions. Micro/nano carbon black hardly adsorbed As (III), but its adsorption capability for pyrene was reduced by the presence of As (III), and this effect increased with an increase in the As (III) concentration. The adsorbed pyrene on the micro/nano black carbon could hardly be desorbed. On the other hand, the micro/nano iron oxide could hardly adsorb the pyrene, but its adsorption capability for As (III) was increased by the presence of pyrene, and this effect increased with an increase in the pyrene concentration. The results of this study provide guidance for the risk management and remediation of the environment when there is combined pollution of PAHs and As.

Degradation of Benzo[a]pyrene and 2,2',4,4'-Tebrabrominated Diphenyl Ether in Cultures Originated from an Agricultural Soil.

Benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) are common contaminants in the environment, posing a threat to the ecosystems and human health. Currently, information on the microbial metabolism of BaP and BDE-47 as well as the correlated bacteria is still limited. This research aimed to study the degradation of BaP and BDE-47 by enriched cultures originated from an agricultural soil in Tianjin (North China) and characterize the bacteria involved in the degradation. Two sets of experiments were set up with BaP and BDE-47 (2 mg/L) as the sole carbon source, respectively. The degradation of BaP and BDE-47 occurred at rate constants of 0.030 /d and 0.026 /d, respectively. For BaP, the degradation products included benzo[a]pyrene-9,10-dihydrodiol or its isomers, ben-zo(a)pyrene-7,8-dihydrodiol-9,10-epoxide, and cis-4 (8-hydroxypyrenyl-7)-2-oxo-3-butenoic acid. For BDE-47, the degradation products included 2,2',4-tribrominated diphenyl ether (BDE-17), 2,4-dibrominated diphenyl ether (BDE-7), and hydroxylated dibromodiphenyl ether. The bacterial community structures in the original soil, the BaP culture, and the BDE-47 culture were quite different. The richness and diversity of bacteria in the two cultures were much lower than that in the original soil, and the BaP culture had higher richness and diversity than the BDE-47 culture. In the BaP culture, multiple species such as Niabella (23.4%), Burkholderia-Caballeronia-Paraburkholderia (13.7%), Cupriavidus (8.3%), and Allorhizobi-um-Neorhizobium-Pararhizobium-Rhizobium (8.0%) were dominant. In the BDE-47 culture, an unassigned species in the Rhizobiaceae was dominant (82.3%). The results from this study provide a scientific basis for the risk assessment and bioremediation of BaP and/or BDE-47 in a contaminated environment.

Bacterial response to the combined pollution of benzo[a]pyrene and decabromodiphenyl ether in soil under flooding anaerobic condition.

This study investigated the interaction between the co-pollutants of Benzo[a]pyrene (BaP) and decabromodiphenyl ether (BDE-209) and the bacterial community in soil under flooding anaerobic condition. Three levels of combined pollution (at nominal concentrations of 1, 5, and 25 mg/kg, respectively, for each pollutant), their corresponding sterilized controls, and a blank control (CK) were set up. During the incubation time of 270 days, BaP attenuated more easily than BDE-209. The second-order rate constant of BaP attenuation was negatively correlated with the Ln value of initial BaP concentration. Maximal difference in bacterial community occurred between the CK soil and the highly polluted soil. Desulfomonilaceae, Parcubacteria and Rhodanobacter were probably involved in BaP and BDE-209 degradation, while Nitrosomonadaceae, Phenylobacterium and Mitochondria were significantly suppressed by BaP and BDE-209 or their degrading products. Genes narI, bcrC, fadJ, had, dmpC, narG and CfrA were involved in the degradation of BaP and BDE-209. Impacts of BaP and BDE-209 on metabolisms of carbon, nitrogen and sulfur were not significant. The results provide guidance for the management and remediation of the contaminated soil.

Evaluation of the risk of human exposure to thiamethoxam by extrapolation from a toxicokinetic experiment in rats and literature data.

Previous studies suggest that exposure to thiamethoxam (TMX) may cause adverse effects to human. However, the distribution of TMX in various organs of human body and the associated risk are little-known. This study aimed to explore the distribution of TMX in human organs by extrapolation from a toxicokinetic experiment in rats and to assess the associated risk based on literature data. The rat exposure experiment was performed using 6-week female SD rats. Five groups of rats were oral-exposed to 1 mg/kg TMX (water as solvent) and executed at 1 h, 2 h, 4 h, 8 h and 24 h after treatment, respectively. The concentrations of TMX and its metabolites in rat liver, kidney, blood, brain, muscle, uterus and urine were measured in different time points using LC-MS. Data on concentrations of TMX in food, human urine and blood as well as human cell-based in vitro toxicity of TMX were collected from the literature. After oral exposure, TMX and its metabolite clothianidin (CLO) were detected in all organs of the rats. The steady-state tissue-plasma partition coefficients of TMX for liver, kidney, brain, uterus and muscle were 0.96, 1.53, 0.47, 0.60 and 1.10, respectively. Based on literature analysis, the concentration of TMX in human urine and blood for general population were 0.06-0.5 ng/mL and 0.04-0.6 ng/mL, respectively. For some people, the concentration of TMX in human urine reached 222 ng/mL. By extraplation from rat experiment, the estimated concentrations of TMX in human liver, kidney, brain, uterus and muscle for general population were 0.038-0.58, 0.061-0.92, 0.019-0.28, 0.024-0.36 and 0.044-0.66 ng/g, respectively, well below the relevant concentrations for cytotoxic endpoints (HQs ≤ 0.012); however, for some people they could be up to 253.44, 403.92, 124.08, 158.40 and 290.40 ng/g, respectively, with very high developmental toxicity (HQ = 5.4). Therefore, the risk for highly exposed people should not be neglected.

Evaluation of Biodegradation of BTEX in the Subsurface of a Petrochemical Site near the Yangtze River, China.

The contamination of soil and groundwater with BTEX (benzene, toluene, ethyl benzene, and xylenes) is a common issue at petrochemical sites, posing a threat to the ecosystems and human health. The goal of this study was to evaluate the biodegradation of BTEX in the subsurface of a petrochemical site near the Yangtze River, thus providing scientific basis for bioremediation of the contaminated site. Both molecular analysis of field samples and microcosm study in the laboratory were performed for the evaluation. Soil and groundwater samples were collected from the site. Microcosms were constructed with inoculum from the soil and incubated anaerobically in the presence of nitrate, ferric oxide, manganese oxide, sulfate, and sodium bicarbonate, respectively. The initial concentration of each component of BTEX (benzene, toluene, ethyl benzene, o-xylene) was 4-5 mg/L. Actinobacteria was dominant in the highly contaminated soil, while Proteobacteria was dominant in the slightly contaminated soil and the groundwater. The relative abundances of Firmicutes, Spirochaetes, and Caldiserica were higher in the highly contaminated soil and groundwater samples compared to those in the corresponding slightly contaminated samples. The relative abundances of predicted functions, such as carbohydrate transport and metabolism, nucleotide transport and metabolism, coenzyme transport and metabolism, amino acid transport and metabolism, etc., in the highly contaminated soil and groundwater samples were higher than those in the corresponding slightly contaminated samples. In microcosms, biodegradations of BTEX occurred, and the first-order rate constants in the presence of various electron acceptors had the following order: sulfate (0.08-0.10/d) > sodium bicarbonate (0.07-0.09/d) > ferric oxide (0.04-0.06/d) > nitrate (0.03-0.05/d) > manganese oxide (0.01-0.04/d).

Tranexamic acid for acute intracerebral haemorrhage growth based on imaging assessment (TRAIGE): a multicentre, randomised, placebo-controlled trial.

BACKGROUND: Studies show tranexamic acid can reduce the risk of death and early neurological deterioration after intracranial haemorrhage. We aimed to assess whether tranexamic acid reduces haematoma expansion and improves outcome in intracerebral haemorrhage patients susceptible to haemorrhage expansion. METHODS: We did a prospective, double-blind, randomised, placebo-controlled trial at 10 stroke centres in China. Acute supratentorial intracerebral haemorrhage patients were eligible if they had indication of haemorrhage expansion on admission imaging (eg, spot sign, black hole sign or blend sign), and were treatable within 8 hours of symptom onset. Patients were randomly assigned (1:1) to receive either tranexamic acid or a matching placebo. The primary outcome was intracerebral haematoma growth (>33% relative or >6 mL absolute) at 24 hours. Clinical outcomes were assessed at 90 days. RESULTS: Of the 171 included patients, 124 (72.5%) were male, and the mean age was 55.9±11.6 years. 89 patients received tranexamic acid and 82 received placebo. The primary outcome did not differ significantly between the groups: 36 (40.4%) patients in the tranexamic acid group and 34 (41.5%) patients in the placebo group had intracranial haemorrhage growth (OR 0.96, 95% CI 0.52 to 1.77, p=0.89). The proportion of death was lower in the tranexamic acid treatment group than placebo group (8.1% vs 10.0%), but there were no significant differences in secondary outcomes including absolute intracranial haemorrhage growth, death and dependency. CONCLUSIONS: Among patients susceptible to haemorrhage expansion treated within 8 hours of stroke onset, tranexamic acid did not significantly prevent intracerebral haemorrhage growth. Larger studies are needed to assess safety and efficacy of tranexamic acid in intracerebral haemorrhage patients.