خيارات البحث
النتائج 4311 - 4320 من 4,924
Formation, extracellular polymeric substances, and structural stability of aerobic granules enhanced by granular activated carbon
2019
Liang, Zixuan | Tu, Qianqian | Su, Xiaoxuan | Yang, Xiangyu | Chen, Junyu | Chen, Yi | Li, Hong | Liu, Caihong | He, Qiang
Granular activated carbon (GAC) has been proved to accelerate the formation of aerobic granules during wastewater treatment. However, there has never been a study on the extracellular polymeric substances (EPS) or structural stability of the GAC aerobic granules. Thus, this study evaluated the impact of GAC on these characteristics. With GAC addition, granules matured 12 days earlier than those of the control group. Scanning electron microscopy showed the surface of aerobic granules enhanced by GAC to be denser and smoother than the surface of control granules, which could be the first line of defense against external selection pressure. After granules matured, there was no difference in contamination removal between the two types of granules. The protein content in EPS of GAC aerobic granules was higher than that of the control group; however, there was no difference in the polysaccharide content. EPS fluorescence in situ staining demonstrated that inside the aerobic granules, a high concentration of protein encapsulated the GAC. In addition, integrity coefficients indicated that GAC significantly improved the ability of aerobic granules to resist hydraulic shear. The result of hydrolase treatment proved that the outer layer structure of the GAC aerobic granules was maintained by β-polysaccharide, and the inner layer structure was maintained by protein. The ability of GAC-enhanced aerobic granules to resist single hydrolase was stronger than that of the control group.
اظهر المزيد [+] اقل [-]A photosynthetic algal microbial fuel cell for treating swine wastewater
2019
Zhang, Ying | Zhao, Yingying | Zhou, Minghua
A photosynthetic algal (Chlorella vulgaris) microbial fuel cell (PAMFC) with double chambers was adopted for power production and removal of carbon and nitrogen in swine sewerage that could provide nutrients for the growth of C. vulgaris. C. vulgaris was expected to utilize carbon dioxide (CO₂) delivered from the anode chamber and generate oxygen as an electron acceptor by photosynthesis. PAMFC presented a maximum voltage output of 0.747 V and a maximum power density of 3720 mW/m³ at 240 h, much higher than that of the standalone MFC. 85.6%, 70.2%, and 93.9% removal of ammonia nitrogen, total nitrogen (TN), and total organic carbon (TOC), respectively, were obtained in the anode chamber of the PAMFC system, while the corresponding removal in MFC was 83.1%, 56.0%, and 87.2%, respectively. PAMFC also presented a much higher removal of ammonia nitrogen (68.7%) in the cathode chamber than MFC (47.5%). The results indicated the superiority of the PAMFC device for carbon and nitrogen removal.
اظهر المزيد [+] اقل [-]Effects of dietary fluoranthene on nymphs of Blaptica dubia S. (Blattodea: Blaberidae)
2019
Mrdaković, Marija | Ilijin, Larisa | Vlahović, Milena | Filipović, Aleksandra | Grčić, Anja | Todorović, Dajana | Perić-Mataruga, Vesna
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants which exert detrimental effects on living beings. Considering the health risk associated with exposure to these pollutants, their presence in food increases efforts to establish early-warning indicators of pollution. We aimed to examine the effects of environmentally relevant concentrations of fluoranthene (0.2 ng and 18 ng/g dry weight of diet) on the activities of midgut antioxidant and detoxification enzymes in Blaptica dubia. Significant changes of superoxide dismutase and catalase activities, recorded at the higher fluoranthene concentration regardless of the exposure time, suggest that they may be used as biomarkers of PAH pollution. Increased GST activity and decreased total GSH content, detected upon acute exposure to the lower concentration, indicate processes of detoxification. Reorganization of B. dubia mechanisms of defense in response to oxidative stress caused by exposure to dietary PAH point to the necessity for further examination of fluoranthene actions.
اظهر المزيد [+] اقل [-]The enhancement roles of sulfate on the adsorption of sodium dodecylsulfate by calcium-based layered double hydroxide: microstructure and thermal behaviors
2019
Zhang, Ping | Xiang, Mingxue | Li, Peng | Ouyang, Sida | He, Tao | Deng, Qiang
As a commonly used surfactant, sodium dodecyl sulfate (SDS) usually coexists with inorganic anions in the industrial wastewater. These anions have a significant influence on SDS removal, indirectly threatening the environment. It is important to understand the relationship between the adsorption of SDS and inorganic anions. In this study, calcium-based layered double hydroxide (CaAl-LDH-Cl) as an efficient adsorbent was synthesized for investigating the effect of SO₄²⁻ on SDS removal. The SDS adsorption capacities were enhanced to 3.21 and 4.21 mmol g⁻¹ in the presence of SO₄²⁻ with low/high SDS concentration, respectively. The phenomenon and mechanism were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM). Anionic exchange played a dominant role in the adsorption of SDS onto CaAl-LDH-Cl at DS⁻/SO₄²⁻ < 2, while both anion exchange and precipitation occurred when DS⁻/SO₄²⁻ exceeded 2. Moreover, the thermal analysis (TG–DTA) was employed to further reveal the interaction mechanism. The results showed the highest total mass loss and the lowest loss temperature of interlayer water in the sulfate coexist system, confirming the enhancement of SDS adsorption amount in the presence of SO₄²⁻.
اظهر المزيد [+] اقل [-]Effect of induction hydroxy and hydrogen along with algal biodiesel blend in a CI engine: a comparison of performance and emission characteristics
2019
Atiqur Rahman, Md.
Gaseous fuel as a combustion enhancer with a pilot fuel offers significant benefits in improving engine efficiency. Hydrogen and hydroxy are the two most common gaseous fuels that have been widely investigated in the CI engine but which one performs best is still inconvenient. In this study, hydrogen and hydroxy were injected with BD40 (v/v) separately in a common diesel engine to compare the performance and emission characteristics of these fuels. Engine performance parameters include brake thermal efficiency (BTE) and brake-specific energy consumption (BSEC), and exhaust emissions include hydrocarbon (HC), CO, CO₂, NOx, and smoke opacity. The induction of both hydroxy and hydrogen with BD40 has a positive effect on engine performance and emissions except NOx when compared to neat diesel fuel and BD40. The BTE of hydroxy-rich BD40 increased by 7.2% while BSEC reduced by 7.6% as compared to BD40 with hydrogen. The CO, HC, and smoke opacity of hydroxy-operated engine was found to be better than hydrogen-inducted engine. The NOx emission increased with the induction of both gaseous fuels and hydroxy-enriched BD40 produced 12.5% more emission than hydrogen-operated BD40 engine. Thus, more concisely, hydroxy-operated biodiesel engine performed better than hydrogen engine in terms of BTE, BSEC, CO, HC, and smoke opacity.
اظهر المزيد [+] اقل [-]Effects of Rhizophagus clarus and biochar on growth, photosynthesis, nutrients, and cadmium (Cd) concentration of maize (Zea mays) grown in Cd-spiked soil
2019
Rafique, Mazhar | Ortas, Ibrahim | Rizwan, Muhammad | Sultan, Tariq | Chaudhary, Hassan Javed | Işık, Mehmet | Aydin, Oğuzhan
Cadmium (Cd) toxicity in agricultural crops is a widespread problem. Little is known about biochar and arbuscular mycorrhizal fungi (AMF) effect on Cd concentration in maize plant either applied separately or in combination. Current study was performed to demonstrate effects of biochar and Rhizophagus clarus on plant growth, photosynthesis activity, nutrients (P, Ca, Mg, Fe, Cu, and Mn), and Cd concentration in maize grown in Cd-spiked soil. The alkaline soil was spiked by Cd factor at three levels: 0 (Cd 0), 5 (Cd 5), and 10 (Cd 10) mg/kg; biochar factor at two levels: 0 and 1%; and mycorrhizal inoculum factor at two levels: MF0 and MF1 (R. clraus). Plants were harvested after 70 days of seed germination, and various morphological and physiological parameters, as well as elemental concentration and root colonization, were recorded. Addition of biochar increased plant biomass by 21% (Cd 5) and 93% (Cd 10), MF1 enhanced by 53% (Cd 0) and 69% (Cd 10), while biochar + MF1 enhanced dry plant biomass by 70% (Cd 0) and 94% (Cd 10). Results showed maximum increase of 94% (Cd 10) in plant biomass was observed in Cd-spiked soil. Root colonization decreased proportionally by increasing Cd concentration and at Cd 10, colonization was 36.7% and 31.7% for MF1 and biochar + MF1 treatments, respectively. Besides that, addition of biochar enhanced root attributes (root length, volume, and surface area) by 34–58% compared to control in Cd 10. The MF1 increased these attributes by 11–78% while biochar + MF1 enhanced by 32–61% in Cd-spiked soil. However, biochar + MF1 neutralized Cd stress in maize plant for gaseous attributes (assimilation rate, transpiration rate, intercellular CO₂, and stomatal conductance). The MF1 enhanced Cd concentration in plant as it was 3.32 mg/kg in Cd 5 and 6.73 mg/kg in Cd 10 treatments while addition of biochar phytostabilized Cd and reduced its concentration in plants by 2.0 mg/kg in Cd 5 and 4.27 mg/kg in Cd 10. The biochar + MF1 had 2.9 mg/kg and 4.8 mg/kg Cd concentration in Cd 5 and Cd 10 plants, respectively. Phosphorus concentration was augmented in shoots (up to 26%) and roots (up to 20%) of maize plant in biochar-amended soil than control plants. In biochar + MF1, concentration of P was 1.01% and 0.73% in Cd 5 and Cd 10, respectively. It is concluded that biochar + MF1 treatment enhances plant biomass while addition of sole biochar reduced Cd uptake, slightly indifferent to earlier treatment.
اظهر المزيد [+] اقل [-]Identification and analysis of odor-active substances from PVC-overlaid MDF
2019
Dong, Huajun | Jiang, Liqun | Shen, Jun | Zhao, Zheng | Wang, Qifan | Shen, Xiwei
This study sought to identify volatile organic compounds (VOCs) and examine the characteristics of odor-active substances from polyvinyl chloride (PVC)-overlaid medium density fiberboard (MDF). A microchamber thermal extractor was used for sampling, gas chromatography–mass spectrometry was used to identify VOCs, and gas chromatography–olfactometry–mass spectrometry was used to analyze odor-active substances from PVC-overlaid MDF over 28 days. The results showed that 38 VOCs were identified from PVC-overlaid MDF, while only 23 odor-active substances were detected by gas chromatography–olfactometry, which indicated that some VOCs did not generate odor. The main VOCs released by PVC-overlaid MDF were aromatic hydrocarbons, ketones, and esters. There was a strong correlation between concentration and odor intensity of the main VOCs. When the total amount of odor-active substances was not significantly different, the overall odor intensity was determined by the intensity of the key odorants. The greater the intensity of the key odorants, the greater the overall odor intensity. There were eight main classes of odors from PVC-overlaid MDF: aromatic, fresh scent, fruity, sour, sweet, grassy, pungent, and special scent. Among them, the main odor characteristics were aromatic, sour, and fresh scent, which were primarily generated by toluene, ethylbenzene, phenanthrene, and dibutyl phthalate.
اظهر المزيد [+] اقل [-]Increased DMT-1 expression in placentas of women living in high-Cd-contaminated areas of Thailand
2019
Somsuan, Keerakarn | Phuapittayalert, Laorrat | Srithongchai, Yupa | Sonthi, Pattaraporn | Supanpaiboon, Wisa | Hipkaeo, Wiphawi | Sakulsak, Natthiya
Cadmium (Cd) is a toxic heavy metal and contamination was reported in soil and rice in several areas of Thailand. Humans are normally exposed to environmental Cd, leading to gradual Cd accumulation in their bodies, including the placenta. DMT-1 is a divalent metal transporter which is found in placental tissue and plays a vital role in the transportation of Fe²⁺ and Cd²⁺. This study investigated DMT-1 protein and mRNA expressions in full term human placentas comparing those from high-Cd-contaminated areas (high-Cd group) and low-Cd-contaminated areas (low-Cd group), n = 6 per group. The maternal blood Cd (B-Cd) and placental Cd (P-Cd) of the high-Cd group was significantly raised in comparison with those in the low-Cd group. DMT-1 in the fetal portion of the placentas was localized in the apical and basal portions of the cytoplasm of the syncytiotrophoblastic cells, the endothelium of fetal capillaries which is functional structure of the placental barrier, and was also found in the cytoplasm of Hofbauer cells. Moreover, DMT-1 localization in the maternal portion was also detected in most decidual cells. In addition, the DMT-1 protein and mRNA expressions in the high-Cd group were significantly higher than those in the low-Cd group. Therefore, we suggest that pregnant women, who are exposed to environmental Cd, show an increased level of Cd in their maternal blood and this Cd can accumulate in the placenta. Intracellular Cd may induce DMT-1 mRNA transcription which further translates into DMT-1 protein, which can then function as a reciprocal Cd transporter in placental tissue.
اظهر المزيد [+] اقل [-]The associations of air pollution exposure during pregnancy with fetal growth and anthropometric measurements at birth: a systematic review and meta-analysis
2019
Fu, Li | Chen, Yi | Yang, Xinyi | Yang, Zuyao | Liu, Sha | Pei, Lei | Feng, Baixiang | Cao, Ganxiang | Liu, Xin | Lin, Hualiang | Li, Xing | Ye, Yufeng | Zhang, Bo | Sun, Jiufeng | Xu, Xiaojun | Liu, Tao | Ma, Wenjun
Fetal growth has been demonstrated to be an important predictor of perinatal and postnatal health. Although the effects of maternal exposure to air pollution during pregnancy on fetal growth have been investigated using ultrasound in many previous studies, the results were inconsistent and disputable. We aimed to qualitatively and quantitatively investigate the associations of air pollution exposure during different periods of pregnancy with fetal growth and anthropometric measurements at birth. We searched for all studies investigating the associations of air pollution exposure during pregnancy with fetal growth and birth anthropometric measurements in English and Chinese databases published before July 31, 2017. A random-effects model was employed in the meta-analysis to estimate the pooled effects of each 10 μg/m³ increment in air pollutant exposure. The ACROBAT-NRSI tool was applied to assess the quality of each included study, and the GRADE tool was employed to assess the overall quality of the meta-analysis. Maternal PM₂.₅ exposure (10 μg/m³) during the entire pregnancy was negatively associated with head circumference at birth (β = − 0.30 cm, 95% CI − 0.49, − 0.10), and NO₂ exposure during the entire pregnancy was significantly linked to shorter length at birth (β = − 0.03 cm, 95% CI − 0.05, − 0.02). Maternal exposure to higher NO₂ and PM₂.₅ during pregnancy may impair neonatal head circumference and length development, respectively. More studies are needed to confirm the effects of NO₂ and PM₂.₅ and to identify the sources and major toxic components of PMs.
اظهر المزيد [+] اقل [-]Comparison of Prioritisation Schemes for Human Pharmaceuticals in the Aquatic Environment
2019
Letsinger, Sarah | Kay, Paul
Only a small proportion of pharmaceuticals available for commercial use have been monitored in the aquatic environment, and even less is known about the effects on organisms. With thousands of pharmaceuticals in use, it is not feasible to monitor or assess the effects of all of these compounds. Prioritisation schemes allow the ranking of pharmaceuticals based on their potential as environmental contaminants, allowing resources to be appropriately used on those which are most likely to enter the environment and cause greatest harm. Many different types of prioritisation schemes exist in the literature and those utilising predicted environmental concentrations (PECs), the fish plasma model (FPM), critical environmental concentrations (CECs) and acute ecotoxicological data were assessed in the current study using the 50 most prescribed drugs in the UK. PECs were found to be overestimates of mean measured environmental concentrations but mainly underestimations of maximum concentrations. Acute ecological data identified different compounds of concern to the other effects assessments although the FPM and CECs methods were more conservative. These schemes highlighted antidepressants, lipid regulators, antibiotics, antihypertensive compounds and ibuprofen as priority compounds for further study and regulation.
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