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Resultados 5761-5770 de 6,498
Adsorption of dichromate ions from aqueous solution onto magnetic graphene oxide modified by β-cyclodextrin Texto completo
2020
Wang, Guanghui | Luo, Qiuyan | Dai, Jialing | Deng, Nansheng
In this work, the β-cyclodextrin modified magnetic graphene oxide (β-CD/MGO) composite was fabricated by the in situ co-precipitation method and characterized by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and particle size analysis. The adsorption behavior of dichromate ions on the β-CD/MGO was investigated, and the mechanism of adsorption was also studied using FT-IR and XPS. The results from SEM and TEM showed that the graphene oxide (GO) layer became rough, and many fine particles were attached after compounding with ferroferric oxide and β-cyclodextrin. The characterization results of FT-IR and XPS show that that β-cyclodextrin and ferroferric oxide have been perfectly compounded to the graphene oxide layer and β-CD/MGO has a particle size of about 460 nm, a specific surface area of 252.3 m²g⁻¹, and a saturation magnetization of 73.5 emu g⁻¹. The adsorption amount of dichromate ions on the β-CD/MGO is affected by pH, adsorbent dosage, and adsorption time. Kinetic studies showed that the adsorption process followed a pseudo-second-order kinetic model. Equilibrium data agreed very well with the Langmuir model, the maximum adsorption amount of dichromate ions on the β-CD/MGO was 49.95 mg g⁻¹. After five successive adsorbent reuses, the reuse rate is still 73%, indicating the excellent potential reusability of β-CD/MGO adsorbent. β-CD/MGO exhibits excellent adsorption performance for dichromate ions. As an environmentally friendly magnetic adsorbent, β-CD/MGO is suitable for the treatment of dichromate-containing wastewater.
Mostrar más [+] Menos [-]The efficacy of smoking ban policy at the workplace on secondhand smoking: systematic review and meta-analysis Texto completo
2020
Rashiden, Ikmal | Ahmad Tajuddin, Nur Amani @ Natasha bt | Yee, Anne | Zhen, Stephen Tan Eyu | bin Amir Nordin, Amer Siddiq
Exposure to secondhand smoke (SHS) in the workplace has led many workplaces to set up smoke-free policies to protect non-smoking employees. Although smoke-free workplaces are pervasive, the intensity of the practice is questionable. The purpose of this review is to identify the pooled prevalence estimate of secondhand smoke at smoke-free workplaces and the factors associated with SHS exposure at the workplace despite existing smoke-free policies. Fourteen studies (total 7458 employees) were identified from Pubmed, ScienceDirect, Cinahl, Scopus, and Web of Science from inception to December 2017. Results indicate that despite the existence of smoke-free policies at the workplace, 14 studies reported exposure to secondhand smoke. The pooled prevalence of the SHS exposure was 0.29 (95% CI = 0.23 to 0.36) (P < 0.001). Male young adults working in the hospitality industry are likely to report exposure to secondhand smoke at the smoke-free workplace. While most of the selected studies show the exposure of SHS within the smoking ban workplace, only two studies reported no exposure to secondhand smoke after implementation of smoke-free policies. Although the smoking ban policy at the workplace has been introduced, there are still a number of employees being affected by secondhand smoke. This indicates that there is still a gap of knowledge, attitude, and practice of non-smokers in strengthening the smoke-free policy at the workplace.
Mostrar más [+] Menos [-]Mutual interactions of E. andrei earthworm and pathogens during the process of vermicomposting Texto completo
2020
Roubalová, Radka | Procházková, Petra | Hanč, Aleš | Dvořák, Jiří | Bilej, M.
Vermicomposting is a process by which earthworms together with microorganisms degrade organic wastes into a humus-like material called vermicompost. This process does not include a thermophilic stage, and therefore, the possible presence of pathogens represents a potential health hazard. To elucidate the effect of earthworms in the selective reduction of pathogens, grape marc substrate was artificially inoculated with Escherichia coli, Enterococcus spp., thermotolerant coliform bacteria (TCB), and Salmonella spp., and their reduction during vermicomposting was monitored. Various defense mechanisms eliminating microorganisms in the earthworm gut were assumed to be involved in the process of pathogen reduction. Therefore, we followed the expression of three pattern recognition receptors (coelomic cytolytic factor (CCF), lipopolysaccharide-binding protein (LBP), and Toll-like receptor (v-TLR)), two antimicrobial molecules (fetidin/lysenins and lysozyme), and heat shock protein HSP70. We detected the significant decrease of some defense molecules (fetidin/lysenins and LBP) in all pathogen-inoculated substrates, and the increase of CCF and LBP in the Salmonella spp.-inoculated substrate. At the same time, the reduction of pathogens during vermicomposting was assessed. We observed the accelerated reduction of E. coli, Enterococcus spp., and TCB in pathogen-inoculated substrates with earthworms compared to that without earthworms. Moreover, the differences between the microbiome of grape marc substrate and earthworm intestines were determined by high throughput sequencing. This analysis revealed that the bacterial composition of grape marc substrate differed from the composition of the content of earthworm intestines, suggesting the elimination of specific bacterial species during food passage through the gut.
Mostrar más [+] Menos [-]Lanthanum hydroxide: a highly efficient and selective adsorbent for arsenate removal from aqueous solution Texto completo
2020
Wang, Yulong | Liu, Yanhong | Guo, Tianqi | Liu, Hupeng | Li, Jiale | Wang, Shaofeng | Li, Xuhui | Wang, Xin | Jia, Yongfeng
In the present work, a lanthanum hydroxide adsorbent was prepared by a simple precipitation process, and its arsenic removal performances and adsorption mechanisms were investigated by batch experiments and various techniques including field emission scanning electron microscopy with energy-dispersive X-ray spectrophotometry (FESEM–EDX), Brunauer–Emmett–Teller (BET) analysis, powder X-ray diffraction (p-XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The influence of pH on arsenic removal showed that the lanthanum hydroxide adsorbent can effectively remove As(V) from solution, whereas the As(III) removal was very low, indicating that the lanthanum hydroxide adsorbent can selectively remove As(V) but not As(III). The isotherm study showed that the maximum adsorption capacities of As(V) at pH 5.0 and 9.0 were 299.4 and 192.3 mg/g, respectively, much higher than those of the widely used ferrihydrite. Significant interference on As(V) removal was caused by the presence of phosphate and natural organic acids (NOAs), such as citric acid. Powder XRD, FTIR, and XPS analysis showed that the lanthanum hydroxide was almost transformed into lanthanum arsenate after As(V) adsorption at pH 4.0, while a portion of lanthanum hydroxide remained after As(V) adsorption at pH 6.0 and 9.0. Furthermore, ligand exchange between the hydroxyl groups of the adsorbent and As(V) and the formation of inner-sphere surface complexes could play a central role in arsenic removal which needs further investigation.
Mostrar más [+] Menos [-]Chemical content and source apportionment of 36 heavy metal analysis and health risk assessment in aerosol of Beijing Texto completo
2020
Cui, Limeng | Wu, Zhuona | Han, Peng | Taira, Yasuyuki | Wang, Huan | Meng, Qinghua | Feng, Zechen | Zhai, Shuguang | Yu, Jun | Zhu, Weijie | Kong, Yuxia | Wang, Hongfang | Zhang, Hong | Bai, Bin | Lou, Yun | Ma, Yongzhong
The concentration levels of 36 airborne heavy metals and atmospheric radioactivity in total suspended particulate (TSP) samples were measured to investigate the chemical characteristics, potential sources of aerosols, and health risk in Beijing, China, from September 2016 to September 2017. The TSP concentrations varied from 6.93 to 469.18 μg/m³, with a median of 133.97 μg/m³. The order for the mean concentrations of heavy metals, known as hazardous air pollutants (HAPs), was as follows: Mn > Pb > As > Cr > Ni > Se > Cd > Co > Sb > Hg > Be; Non-Designated HAPs Metals: Ca > Fe > Mg > Al > K > Na > Zn > P > Ba > Ti > Cu > Sr > B > Sn > I > V > Rb > Ce > Mo > Cs > Th > Ag > U > Pt. The median concentration of As was higher than China air quality standard (6 ng/m³). The gross α and β concentration levels in aerosols were (1.84 ± 1.59) mBg/m³ and (1.15 ± 0.85) mBg/m³, respectively. The enrichment factor values of Cu, Ba, B, Ce, Tl, Cs, Pb, As, Cd, Sb, Hg, Fe, Zn, Sn, I, Mo, and Ag were higher than 10, which indicated enriched results from anthropogenic sources. Pb, As, and Cd are considered to originate from multiple sources; fireworks released Ba during China spring festival; Fe, Ce, and Cs may come from stable emissions such as industrial gases. The health risks from anthropogenic metals via inhalation, ingestion, and dermal pathway were estimated on the basis of health quotient as well as the results indicated that children faced the higher risk than adults during the research period. For adults, the health risk posed by heavy metals in atmospheric particles was below the acceptable level.
Mostrar más [+] Menos [-]Positive impact of improved cookstove usage on respiratory health in Congolese refugees: a prospective cohort study Texto completo
2020
Wolff, Fernando | Kothe, Henning | Mubiru, Allan | Gashirabake, Joseph | Uwimana, Immaculée | Dalhoff, Klaus
Around 3 billion people worldwide use solid biomass fuels for cooking. Exposure to indoor biomass smoke is an important cause of COPD and therefore a target of many public health interventions, such as usage of improved cookstoves. The aim of our study was to show whether usage of improved cookstoves can lead to relevant improvement in lung function and CAT-score in a well characterized population including a subgroup of this population with preexisting airway obstruction. Interviews and spirometry were performed in Congolese women living in an UNHCR (United Nations High Commissioner for Refugees) refugee camp in Rwanda before (baseline, BL) and 9 months after (follow-up, F9) they received an energy-efficient cookstove (Save80) and were trained how to use it. Two hundred sixty-two women completed both spirometry and interview appropriately at BL and F9 and were included in per protocol (pp) analysis, which showed no change in mean FEV1. The predefined subgroup of this population with airway obstruction at baseline (N = 31) showed a significant FEV1 increase (FEV1F₉ = 1.70 L; p < 0.01 vs FEV1BL = 1.58 L, p < 0.01). Median CAT-scores were significantly lower in the F9 assessment. Our data indicate that usage of improved cookstoves has a positive impact on respiratory health especially in individuals with preexisting airway obstruction. Further studies to investigate long-term outcome are warranted.
Mostrar más [+] Menos [-]Effects of fuel types and fuel sulfur content on the characteristics of particulate emissions in marine low-speed diesel engine Texto completo
2020
Shen, Feixiang | Li, Xiaobo
The emission of particulate matter from ships does great harm to human health and atmospheric environment. Sulfur emission regulations also affect particulate matter emissions due to fuel change. Particulate matter (PM) emitted from low-speed, two-stroke, large-power diesel engine were studied in test-bed experiments. Experiments were conducted at 25%, 50%, 75%, and 100% load with heavy fuel oil (HFO, 3.36%m/m S) and a lighter marine diesel oil (MDO, 0.1%m/m S). The experiments revealed that using MDO could decrease the mass emission factors (EFs) of PM compared to HFO due to the fuel quality and content; however, there was no obvious difference for the number EFs of PM. The main particle when using HFO consists sulfates and bound water, and the hydrate sulfur increased with the increased engine loads. Then, another 21% is organic carbon (OC). Emission factors for inorganic elements were also studied in particles from combustion of HFO and MDO. The EFs of OC and elemental carbon (EC) were affected by engine loads, fuel type, fuel sulfur content (FSC), and combustion conditions. The size distribution of OC was similar to EC, and there were two clearly peaks for every particulate matter sample. The key effect factor for EFs of PM with marine fossil fuels was FSC.
Mostrar más [+] Menos [-]Structural path analysis of China’s coal consumption using input–output frameworks Texto completo
2020
Yang, Ligao | Li, Lulu | Zhu, Kunfu | Xie, Rui | Wang, Zhenguo
In-depth study of the key sectors and supply chain paths driving coal consumption in China is valuable for effectively formulating coal reduction and replacement policies to achieve sustainable development. This study conducted a structural path analysis, based on the latest publicly available input–output tables and energy use data provided by the World Input–Output Database, to trace China’s coal consumption transmission throughout its entire supply chain. The results indicate that investment, exports, and household consumption are important factors in coal consumption. “Electricity, Gas and Water Supply” is a critical sector for, largely indirect, coal consumption. The path of “Electricity, Gas and Water Supply→ intermediate sectors→ Construction→ Investment” accounts for the bulk of coal consumption in China. The node path analysis shows that the 2-node transmission paths, starting from Construction and ending with “Other Non-Metallic Mineral” and “Basic Metals and Fabricated Metal” are important sources of coal consumption induced by investment demand. The 1-node path of “Basic Metals and Fabricated Metal” is an important path for coal consumption induced by export demand. The 1-node path of “Electricity, Gas and Water Supply” is an important path for coal consumption caused by household consumption demand. In order to effectively implement coal reduction and replacement policies, China should control coal consumption in these key sectors and channels and optimize intermediate input and energy use structures.
Mostrar más [+] Menos [-]Health risk assessment of heavy metals in cosmetic products sold in Iran: the Monte Carlo simulation Texto completo
2020
Ghaderpoori, Mansour | Kamarehie, Bahram | Jafari, Ali | Alinejad, Abdol Azim | Hashempour, Yalda | Saghi, Mohammad Hossein | Yousefi, Mahmood | Oliveri Conti, Gea | Mohammadi, Ali Akbar | Ghaderpoury, Afshin | Ferrante, Margherita
Cosmetics can contain harmful compounds such as heavy metals. Several metals have a cumulative effect on the body, especially fatty tissues, and may have different health effects on the human body over the long term. Therefore, the main objective of this study was to assess the health risks of heavy metals in cosmetics in Iran. Also, in this study, Monte Carlo simulation was used to investigate uncertainties. In this study, heavy metals data of cosmetics were extracted from studies carried out at intervals 2010–2018. International and Iranian databases such as Google Scholar, Web of Science, Springer, Science Direct, PubMed, Scopus, Irandoc, Magiran, Scientific Information Database (SID), and Information Institute for Scientific (ISC) were searched for this purpose. In this study, the index of the Margin of Safety was calculated to determine the risk of human contact with metallic impurities in cosmetic products used by humans. In the selected period, 11 studies were conducted on the measurement of heavy metals in cosmetics in Iran. In these studies, cosmetics such as eye shadow, eye pencil, powder, cream, and lipstick were studied. The Margin of Safety (MoS) values calculated for different metals were higher than the established safe standard by WHO. The highest and lowest amount of systemic exposure dosage in all types of cosmetic investigated (lipstick, cream, eye pencil, face powder, and eye shadow) was related to Fe and Hg. The mean hazardous quotient (HQ) for Cd, Cr, Ni, Cu, Mn, Zn, Pb, and Hg was 1.05E-03, 1.03E-01, 7.95E-03, 2.59E-03, 1.05E-03, 4.98E-03, 7.22E-04, 1.85E-01, and 1.35E-05, respectively. The highest HQ (6.10E-01) was found for Pb, which was observed in the cream.
Mostrar más [+] Menos [-]Valuing urban air quality: a hedonic price analysis in Beijing, China Texto completo
2020
Mei, Yingdan | Gao, Li | Zhang, Jiawei | Wang, Jiahao
Although Chinese government has implemented a series of laws, regulations, and policies to deal with air pollutants, air pollution is still one of the biggest concerns in China. Most of the cities in China suffered from extremely high air pollution levels and cannot meet the national air quality standards. In this study, we attempt to measure individuals’ average marginal willingness to pay (MWTP) in Beijing with the hedonic price model. We combine an extensive housing transaction dataset with emission data of six air pollutants from 2013 to 2016 in Beijing, China. When estimating the hedonic price function, we apply both ordinary least squares (OLS) and panel model with various fixed effects to better control for unobservables. The empirical results reveal that the concentrations of CO, NO₂, PM₂.₅, and PM₁₀ are significantly negatively correlated with housing prices. However, we found an insignificant relationship with the concentration of SO₂ and the concentration of O₃ appears to positively increase the housing values. Policy implications based on these results were also discussed.
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