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Resultados 4031-4040 de 4,309
Emission and distribution of PCDD/Fs, chlorobenzenes, chlorophenols, and PAHs from stack gas of a fluidized bed and a stoker waste incinerator in China Texto completo
2017
Wang, Tianjiao | Chen, Tong | Lin, Xiaoqing | Zhan, Mingxiu | Li, Xiaodong
The concentrations, homologue, and congener profiles, as well as the gas/particle distribution of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), chlorobenzenes (CBzs), chlorophenols (CPhs), and polyaromatic hydrocarbons (PAHs) from stack gas of two different municipal solid waste incinerators in China, were characterized. The incinerators were a stoker furnace incinerator equipped with the advanced air pollution control device (APCD) and a common circulating fluidized bed (CFB) furnace. The concentration of PCDD/Fs in the stack gas of the stoker incinerator ranged 0.011–0.109 ng international toxic equivalent factor (I-TEQ)/Nm³ and was below the current limit for PCDD/F emissions from the municipal solid waste incinerators (MSWIs) in China (0.1 ng I-TEQ/Nm³) in most of the cases. Moreover, the concentration of PCDD/Fs in the stack gas of the stoker incinerator was significantly lower than that of the CFB incinerator (0.734 to 24.6 ng I-TEQ/Nm³). In both incinerators, the majority of the total PCDD/F emissions (above 90%) ended up in the gas phase. 2,3,4,7,8-PeCDF, which occupied 24.3–43.6 and 32.5–75.6% of I-TEQ contribution in MSWIs A and B, respectively, was the most abundant congener. However, different types of incinerators and APCDs induced different congener and homologue distributions. The total concentration of CBzs from the stoker incinerator (0.05–3.2 μg/Nm³) was also much lower than that formed from the CFB incinerator (10.9–75.2 μg/Nm³). The phase distribution of CBzs followed the same pattern as with the PCDD/Fs. Moreover, the emission level of CBz was 100–1000 times higher than that of the PCDD/Fs, which determines the applicability of CBzs as indicators of PCDD/F emissions. High correlations between the emission concentrations of PCDD/Fs, TeCBz, and PCBz in specific ranges were revealed. Furthermore, high concentrations of CPhs (0.6–141.0 μg/Nm³) and PAHs (148.6–4986.5 μg/Nm³) were detected in the stack gases of MSWI B. In some cases, the concentrations were as high as the concentrations in the fumes exiting the boiler of one foreign stoker without flue gas purification indicating the abundance of CPh and PAH emissions in the stack gas of waste incinerators.
Mostrar más [+] Menos [-]Elemental content of mosses and lichens from Livingston Island (Antarctica) as determined by instrumental neutron activation analysis (INAA) Texto completo
2017
Culicov, Otilia A. | Yurukova, Liliana | Duliu, Octavian G. | Zinicovscaia, Inga
The total content of 8 major and 32 trace elements in four species of mosses and two of lichens as well as neighboring soil and rocks collected from different places of the Livingston Island Antarctica was determined by instrumental neutron activation analysis. The main goals of the project consisted of evidencing the possible trace of anthropogenic contamination as well as the influence of altitude on the distribution of considered elements. In the absence of a unanimously accepted descriptor, enrichment factor, geo-accumulation, and pollution load indices with respect to soil and rocks were used. The data, interpreted within the model of a reference plant, were compared with previous studies regarding the same organisms in similar geographic and climatological areas. The experimental results evidenced different capacity of mosses and lichens to retain the considered elements, but within experimental uncertainties, no traces of anthropogenic pollution were found. At the same time, it was found that the content of most of the elements decreased with the altitude.
Mostrar más [+] Menos [-]A review of AirQ Models and their applications for forecasting the air pollution health outcomes Texto completo
2017
Oliveri Conti, Gea | Heibati, Behzad | Kloog, Itai | Fiore, Maria | Ferrante, Margherita
Even though clean air is considered as a basic requirement for the maintenance of human health, air pollution continues to pose a significant health threat in developed and developing countries alike. Monitoring and modeling of classic and emerging pollutants is vital to our knowledge of health outcomes in exposed subjects and to our ability to predict them. The ability to anticipate and manage changes in atmospheric pollutant concentrations relies on an accurate representation of the chemical state of the atmosphere. The task of providing the best possible analysis of air pollution thus requires efficient computational tools enabling efficient integration of observational data into models. A number of air quality models have been developed and play an important role in air quality management. Even though a large number of air quality models have been discussed or applied, their heterogeneity makes it difficult to select one approach above the others. This paper provides a brief review on air quality models with respect to several aspects such as prediction of health effects.
Mostrar más [+] Menos [-]Biodegradability of fluoxetine, mefenamic acid, and metoprolol using different microbial consortiums Texto completo
2017
Velázquez, Yolanda Flores | Nacheva, Petia Mijaylova
The biodegradation of fluoxetine, mefenamic acid, and metoprolol using ammonium-nitrite-oxidizing consortium, nitrite-oxidizing consortium, and heterotrophic biomass was evaluated in batch tests applying different retention times. The ammonium-nitrite-oxidizing consortium presented the highest biodegradation percentages for mefenamic acid and metoprolol, of 85 and 64% respectively. This consortium was also capable to biodegrade 79% of fluoxetine. The heterotrophic consortium showed the highest ability to biodegrade fluoxetine reaching 85%, and it also had a high potential for biodegrading mefenamic acid and metoprolol, of 66 and 58% respectively. The nitrite-oxidizing consortium presented the lowest biodegradation of the three pharmaceuticals, of less than 48%. The determination of the selected pharmaceuticals in the dissolved phase and in the biomass indicated that biodegradation was the major removal mechanism of the three compounds. Based on the obtained results, the biodegradation kinetics was adjusted to pseudo-first-order for the three pharmaceuticals. The values of k bᵢₒₗ for fluoxetine, mefenamic acid, and metoprolol determined with the three consortiums indicated that ammonium-nitrite-oxidizing and heterotrophic biomass allow a partial biodegradation of the compounds, while no substantial biodegradation can be expected using nitrite-oxidizing consortium. Metoprolol was the less biodegradable compound. The sorption of fluoxetine and mefenamic acid onto biomass had a significant contribution for their removal (6–14%). The lowest sorption coefficients were obtained for metoprolol indicating that the sorption onto biomass is poor (3–4%), and the contribution of this process to the global removal can be neglected.
Mostrar más [+] Menos [-]Bioconcentration pattern and induced apoptosis of bisphenol A in zebrafish embryos at environmentally relevant concentrations Texto completo
2017
Wu, Minghong | Pan, Chenyuan | Chen, Zhong | Jiang, Lihui | Lei, Penghui | Yang, Ming
Bisphenol A (BPA) is a well-known endocrine-disrupting chemical that is ubiquitously present in the environment. In the present study, 4-h post-fertilization (hpf) zebrafish embryos were exposed to various environmentally relevant concentrations of BPA (0.1, 1, 10, 100, and 1000 μg/L) until 72 and 168 hpf, and the accumulation pattern of BPA and its potential to induce toxicity through apoptosis were determined. Compared to BPA concentrations in larvae at 168 hpf, BPA concentrations in embryos exposed until 72 hpf were at relatively higher levels (p < 0.05) with higher bioconcentration factor (BCF) values. The nonlinear fitting analysis indicated that the BCF values of BPA in fish embryos/larvae were significantly correlated to the log10-transformed BPA exposure concentrations in water in an inverse concentration-dependent manner. Fish accumulated more BPA as the exposure concentrations increased; however, their accumulation capacity of BPA declined and tended to be saturated in the high exposure groups of BPA. Moreover, caspase-3 activity was significantly induced upon BPA exposure at 0.1, 1, 10, and 100 μg/L BPA at 72 hpf, and also at 10 and 100 μg/L BPA at 168 hpf. Correspondingly, exposure to 10 and 100 μg/L of BPA significantly increased the DNA fragmentation in the extracted DNA at 168 hpf as determined by DNA ladder analysis. In addition, the expression patterns of four genes related to apoptosis including caspase-3, bax, p53, and c-jun were significantly up-regulated (p < 0.05) in fish embryos/larvae upon BPA exposure at 72 and 168 hpf. Our results revealed that low and environmentally relevant concentrations of BPA could be significantly accumulated in zebrafish and induced apoptosis with involvement of the regulation of caspase-3 and other apoptosis-related genes.
Mostrar más [+] Menos [-]Occurrence of 25 pharmaceuticals in Taihu Lake and their removal from two urban drinking water treatment plants and a constructed wetland Texto completo
2017
Hu, Xia-Lin | Bao, Yi-Fan | Hu, Jun-Jian | Liu, You-Yu | Yin, Da-Qiang
Pharmaceuticals in drinking water sources have raised significant concerns due to their persistent input and potential human health risks. The seasonal occurrence of 25 pharmaceuticals including 23 antibiotics, paracetamol (PAR), and carbamazepine (CMZ) in Taihu Lake was investigated; meanwhile, the distribution and removal of these pharmaceuticals in two drinking water treatment plants (DWTPs) and a constructed wetland were evaluated. A high detection frequency (>70%) in the Taihu Lake was observed for nearly all the 25 pharmaceutics. Chlortetracycline (234.7 ng L⁻¹), chloramphenicol (27.1 ng L⁻¹), erythromycin (72.6 ng L⁻¹), PAR (71.7 ng L⁻¹), and CMZP (23.6 ng L⁻¹) are compounds with both a high detection frequency (100%) and the highest concentrations, suggesting their wide use in the Taihu Basin. Higher concentrations of chloramphenicols, macrolides, PAR, and CMZP were observed in dry season than in wet season, probably due to the low flow conditions of the lake in winter and the properties of pharmaceuticals. The overall contamination levels of antibiotic pharmaceutics (0.2–74.9 ng L⁻¹) in the Taihu Lake were lower than or comparable to those reported worldwide. However, for nonantibiotic pharmaceutics, PAR (45.0 ng L⁻¹) and CMZP (14.5 ng L⁻¹), significantly higher concentrations were observed in the Taihu Lake than at a global scale. High detection frequencies of 25 pharmaceuticals were observed in both the two DWTPs (100%) and the wetland (>60%) except for florfenicol and sulfapyridine. The removal efficacies of the studied pharmaceuticals in DWTP B with advanced treatment processes including ozonation and granular activated carbon filtration (16.7–100%) were superior to DWTP A with conventional treatment processes (2.9–100%), except for sulfonamides. Wetland C with the constructed root channel technology was efficient (24.2–100%) for removing most pharmaceuticals. This work suggests that the application of cost-effective technologies such as constructed wetlands should be considered as an efficient alternative for removing pharmaceuticals from water supply sources.
Mostrar más [+] Menos [-]Variation in Cd accumulation among radish cultivars and identification of low-Cd cultivars Texto completo
2017
Dai, Hongwen | Yang, Zhongyi
Heavy metals have serious health consequences and ecosystem impacts. A pot experiment was conducted to investigate the variation of cadmium (Cd) uptake and accumulation among 40 cultivars of radish (Raphanus sativus L.) at three Cd levels, including 0.31 (T1), 0.83 (T2), and 1.13 (T3) mg kg⁻¹. Most of the tested cultivars had higher taproot biomass in the T3 treatment when compared to those in the T1 treatment, indicating a Cd stress-induced growth in radish. Taproot Cd concentrations in 95 and 5% of the tested cultivars were lower than 0.1 mg kg⁻¹ (fresh weight, FW) in the T1 and T2 treatments, respectively; however, there was no cultivar suitable for safe consumption in the T3 treatment. Radish production showed potential risk of Cd pollution as high as some leafy vegetables when grown in the soils where Cd concentration exceeded 0.8 mg kg⁻¹. When compared with Chinese heat-resisting or imported cultivars, Chinese common cultivars had significantly higher taproot Cd concentrations. Three low-Cd cultivars and five high-Cd cultivars were identified. Taproot Cd concentrations showed significant correlations between any two of the three treatments (p < 0.01), suggesting that Cd accumulation in taproot of radish was genotype-dependent.
Mostrar más [+] Menos [-]Molecularly imprinted membranes (MIMs) for selective removal of polychlorinated biphenyls (PCBs) in environmental waters: fabrication and characterization Texto completo
2017
Mkhize, Dennis S. | Nyoni, Hlengilizwe | Quinn, Laura P. | Mamba, Bhekie B. | Msagati, Titus A. M.
Molecularly imprinted membranes (MIMs) with selective removal properties for polychlorinated biphenyls (PCBs) were prepared through the phase inversion technique. The MIMs were obtained from casting the viscous solutions of molecularly imprinted polymers (MIPs), polysulfone (PSf), and N-methyl-2-pyrrolidone (NMP) as the casting solvent. Different membranes were prepared at different concentration of MIPs and PSf. The resulting MIMs were characterized by atomic force microscope (AFM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). Moreover, the performance of the membranes was evaluated by determining and interpreting the rejection (%), flux (F), permeability coefficient (P), permselectivity factor (α ′ PCB/DDT ₒᵣ ₐₙₜₕᵣₐcₑₙₑ), and enrichment factors of PCBs, dichlorodiphenyltrichloroethane (p,p′-DDT), and anthracene from model contaminated water using the dead-end filtration cell. Molecularly imprinted membrane prepared with 18 wt% PSf and 20 wt% MIP 4 exhibited a well-defined porous structure, which was accompanied by enhanced PCB enrichment. Furthermore, molecularly imprinted membrane showed good enrichment factors for PCBs even from spiked natural water samples of Hartbeespoort dam.
Mostrar más [+] Menos [-]A time series analysis of environmental and metrological factors impact on cutaneous leishmaniasis incidence in an endemic area of Dehloran, Iran Texto completo
2017
Nikonahad, Ali | Khorshidi, Ali | Ghaffari, Hamid Reza | Aval, Hamideh Ebrahimi | Miri, Mohammad | Amarloei, Ali | Nourmoradi, Heshmatollah | Mohammadi, Amir
The aim of this study was to investigate the relationship between the environmental and metrological variables and cutaneous leishmaniasis (CL) transmission and its prediction in a region susceptible to this disease prevalence using a time series model. The accurate locations of 4437 CL diagnosed from 2011 to 2015 were obtained to be used in the time series model. Temperature, number of days with temperature over 30 °C, and number of earthquake were related to CL incidence using the Seasonal Auto-correlated Integrated Moving Average (SARIMA) model according to the Box-Jenkins method. In addition, the relationship between land use and surface soil type in 500- and 1000-m radius around the CL patients were investigated. The SARIMA models showed significant associations between environmental and meteorological variables and CL incidence adjusted for seasonality and auto-correlation. The result indicated that there are need more robust preventive programs in earthquake-prone areas with high temperature and inceptisol soil type than other areas. In addition, the region with these characteristics should be considered as high-risk areas for CL prevalence.
Mostrar más [+] Menos [-]Phosphate and ammonium adsorption of the modified biochar based on Phragmites australis after phytoremediation Texto completo
2017
Gong, Yu-Peng | Ni, Zhi-Yi | Xiong, Zhao-Zhao | Cheng, Li-Hua | Xu, Xin-Hua
To effectively remove N and P from eutrophic water, the Phragmites australis after phytoremediation was harvested for preparation of modified biochar. The MgCl₂-modified biochar (MPB) was successfully synthesized at 600 °C under N₂ circumstance. The physiochemical characteristics, the adsorption capacity for N and P in the simulated solution, and their adsorption mechanism of MPB were then determined, followed by the treatment of eutrophic water of Tai lake and its inflow river from agricultural source. The results demonstrated that the MPB presented high adsorption capacity to both simulated NH₄-N and PO₄-P with the maximum adsorption capacity exceeding 30 and 100 mg g⁻¹, respectively. The entire ammonium adsorption process could be described by a pseudo-second-order kinetic model whereas the phosphate adsorption process could be divided into three phases, as described by both intra-particle diffusion model and the pseudo-first-order kinetic. It was further found that the dominant mechanism for ammonium adsorption was Mg²⁺ exchange instead of functional groups and surface areas and the Mg-P precipitation was the main mechanism for phosphate adsorption. The MPB also showed high removal ratio of practical TP which reached nearly 90% for both the water in Tai lake and its agricultural source. It suggested that MPB based on harvested P. australis was a promising composite for eutrophic water treatment and it could deliver multiple benefits. Graphic abstract
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