خيارات البحث
النتائج 3271 - 3280 من 4,033
Simultaneous GC-MS determination of seven phthalates in total and migrated portions of paper cups
2016
Park, Yu Na | Choi, Min Sun | Rehman, Shaheed Ur | Gye, Myung Chan | Yoo, Hye Hyun
Phthalate acid esters are widely used as plasticizers to impart plastic flexibility in various industrial applications. In this study, the content of seven phthalates, dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), di-(2-ethylhexyl) adipate (DEHA), di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DNOP), di-isononyl phthalate (DINP), and di-isodecyl phthalate (DIDP) were determined in paper cups using gas chromatography–mass spectrometry (GC-MS). In addition, the potential migration of these seven phthalates from paper cups into various food stimulants under different conditions was evaluated. The levels of DBP, DEHA, DEHP, and DNOP were in the ranges of 0.07–3.14, 0.16–42.69, 0.45–58.56, and 0.3–2.4 mg/kg, respectively. Meanwhile, BBP, DINP, and DIDP were not detected in most of the tested samples. In the migration test, DEHA was released to 50 % ethanol and n-heptane in a time-dependent manner and the maximum migration levels were 65.62 ± 3.61 and 95.56 ± 19.76 μg/L, respectively. The release of other phthalates was very low or negligible. These results demonstrated that paper cups are not a significant source of phthalate exposure; however, DEHA could be released from paper cups into alcoholic beverages or oily liquid beverages in the human diet.
اظهر المزيد [+] اقل [-]Comparison and mechanism of photocatalytic activities of N-ZnO and N-ZrO2 for the degradation of rhodamine 6G
2016
Sudrajat, Hanggara | Babel, Sandhya
N-doped ZnO (N-ZnO) and N-doped ZrO₂ (N-ZrO₂) are synthesized by novel, simple thermal decomposition methods. The catalysts are evaluated for the degradation of rhodamine 6G (R6G) under visible and UV light. N-ZnO exhibits higher dye degradation under both visible and UV light compared to N-ZrO₂ due to possessing higher specific surface area, lower crystalline size, and lower band gap. However, it is less reusable than N-ZrO₂ and its photocatalytic activity is also deteriorated at low pH. At the same intensity of 3.5 W/m², UVC light is shown to be a better UV source for N-ZnO, while UVA light is more suitable for N-ZrO₂. At pH 7 with initial dye concentration of 10 mg/L, catalyst concentration of 1 g/L, and UVC light, 94.3 % of R6G is degraded by N-ZnO within 2 h. Using UVA light under identical experimental conditions, 93.5 % degradation of R6G is obtained by N-ZrO₂. Moreover, the type of light source is found to determine the reactive species produced in the R6G degradation by N-ZnO and N-ZrO₂. Less oxidative reactive species such as superoxide radical and singlet oxygen play a major role in the degradation of R6G under visible light. On the contrary, highly oxidative hydroxyl radicals are predominant under UVC light. Based on the kinetic study, the adsorption of R6G on the catalyst surface is found to be the controlling step.
اظهر المزيد [+] اقل [-]Bioaccumulation of pathogenic bacteria and amoeba by zebra mussels and their presence in watercourses
2016
Mosteo, R. | Goñi, P. | Miguel, N. | Abadías, J. | Valero, P. | Ormad, M. P.
Dreissena polymorpha (the zebra mussel) has been invading freshwater bodies in Europe since the beginning of the nineteenth century. Filter-feeding organisms can accumulate and concentrate both chemical and biological contaminants in their tissues. Therefore, zebra mussels are recognized as indicators of freshwater quality. In this work, the capacity of the zebra mussel to accumulate human pathogenic bacteria and protozoa has been evaluated and the sanitary risk associated with their presence in surface water has also been assessed. The results show a good correlation between the pathogenic bacteria concentration in zebra mussels and in watercourses. Zebra mussels could therefore be used as an indicator of biological contamination. The bacteria (Escherichia coli, Enterococcus spp., Pseudomonas spp., and Salmonella spp.) and parasites (Cryptosporidium oocysts and free-living amoebae) detected in these mussels reflect a potential sanitary risk in water.
اظهر المزيد [+] اقل [-]Effects of gravel on infiltration, runoff, and sediment yield in landslide deposit slope in Wenchuan earthquake area, China
2016
Li, Tianyang | He, Binghui | Chen, Zhanpeng | Zhang, Yi | Liang, Chuan | Wang, Renxin
Amounts of landslide deposits were triggered by the Wenchuan earthquake with magnitude 8.0 on May 12, 2008. The landslide deposits were composed of soil and rock fragments, which play important roles in hydrological and erosion processes in the steep slope of landslide deposits. The mixtures of soil and gravels are common in the top layers of landslide deposits, and its processes are obviously different with the soil without gravels. Based on the data of field investigation, a series of simulated scouring flow experiments with four proportion of gravel (0, 25, 33.3, and 50 %) and three scouring flow rates (4, 8, 12 L/min) under two steep slopes (67.5, 72.7 %) were conducted sequentially to know the effects of proportion of gravel on infiltration capacity, runoff generation, and sediment production in the steep slope of landslide deposit. Results indicated that gravel had promoted or reduced effects on infiltration capacity which could affect further the cumulative runoff volume and cumulative sediment mass increase or decrease. The cumulative infiltration volume in 25 % proportion of gravel was less than those in 0, 33.3, and 50 % proportion of gravel. The cumulative runoff volume was in an order of 25 > 0 > 33.3 > 50 % while cumulative sediment mass ranked as 25 > 33.3 > 0 > 50 % with different proportions of gravel. A significant power relationship was found between scouring time and cumulative runoff volume as well as cumulative sediment mass. The relationship between average soil and water loss rate and proportion of gravel was able to express by quadratic function, with a high degree of reliability. The results have important implications for soil and water conservation and modeling in landslide deposit but also provide useful information for the similar conditions.
اظهر المزيد [+] اقل [-]Use of mixed solid waste as a soil amendment for saline-sodic soil remediation and oat seedling growth improvement
2016
Fan, Yuan | Ge, Tian | Zheng, Yanli | Li, Hua | Cheng, Fangqin
Soil salinization has become a worldwide problem that imposes restrictions on crop production and food quality. This study utilizes a soil column experiment to address the potential of using mixed solid waste (vinegar residue, fly ash, and sewage sludge) as soil amendment to ameliorate saline-sodic soil and enhance crop growth. Mixed solid waste with vinegar residue content ranging from 60-90 %, sewage sludge of 8.7–30 %, and fly ash of 1.3–10 % was added to saline-sodic soil (electrical conductivity (EC₁:₅) = 1.83 dS m⁻¹, sodium adsorption ratio (SAR₁:₅) = 129.3 (mmolc L⁻¹)¹/², pH = 9.73) at rates of 0 (control), 130, 260, and 650 kg ha⁻¹. Results showed that the application of waste amendment significantly reduced SAR, while increasing soil soluble K⁺, Ca²⁺, and Mg²⁺, at a dose of 650 kg ha⁻¹. The wet stability of macro-aggregates (>1 mm) was improved 90.7–133.7 % when the application rate of amendment was greater than 260 kg ha⁻¹. The application of this amendment significantly reduced soil pH. Germination rates and plant heights of oats were improved with the increasing rate of application. There was a positive correlation between the percentage of vinegar residue and the K/Na ratio in the soil solutions and roots. These findings suggest that applying a mixed waste amendment (vinegar residue, fly ash, and sewage sludge) could be a cost-effective method for the reclamation of saline-sodic soil and the improvement of the growth of salt-tolerant plants.
اظهر المزيد [+] اقل [-]Phosphorus characteristics, distribution, and relationship with environmental factors in surface sediments of river systems in Eastern China
2016
Zhang, Wenqiang | Jin, Xin | Zhu, Xiaolei | Shan, Baoqing | Zhao, Yu
Phosphorus (P) is an essential nutrient for aquatic organisms. However, too much P discharged into limnetic ecosystems can induce eutrophication. The concentration of P in freshwater ecosystems has escalated in Eastern China due to overuse of fertilizer and excess emission of sewage, which is the result of the development of industry and agriculture in this area. However, little is known about the P characteristics and its environmental factors in river systems. Here, we present the results of P characterization and its relationships with environmental factors in Eastern China by applying SMT and ³¹P-NMR methods. The results showed that the concentrations of P in surface sediments varied with the river system, and more than 50 % of the samples had P concentrations exceeding 500 mg kg⁻¹. HCl-Pi was the dominant Pi in surface sediments, with the highest percentage (96.5 %) in the Yellow River System. Mono-P was the dominant Po in river sediments, followed by DNA-P. The PCA approach indicated that NaOH-Pi and ortho-P clustered in one group, with a second group including mono-P, diesters-P, and HCl-Pi. Phon-P and pyro-P belonged to different groups. On a regional scale, NaOH-Pi and Po showed a negative relationship with pH in sediments. Continuous eutrophication was induced by the presence of dams, and oxygen-consuming pollutants, such as NH₃-N and CODcr, even when external P input was cut in heavily polluted rivers. The research revealed the characteristics of P in different river systems and proposed a conceptual model of P biogeochemical cycles in heavily polluted rivers. Results from this study may provide insight into P characteristics in Eastern China and would set a scientific basis for effective P management in developing countries.
اظهر المزيد [+] اقل [-]The occurrence and fate of siloxanes in wastewater treatment plant in Harbin, China
2016
Li, Bo | Li, Wen-Long | Sun, Shao-Jing | Qi, Hong | Ma, Wanli | Liu, Li-Yan | Zhang, Zi-Feng | Zhu, Ning-Zheng | Li, Yi-Fan
The occurrence and fate of four cyclic (D3 to D6) and 10 linear (L5 to L14) siloxanes were investigated in influent and effluent wastewater, sludge from a wastewater treatment plant (WWTP), and surrounding air and soil within the WWTP in Harbin, Northeast China. The mean concentrations of total siloxanes in influent and effluent were 4780 and 997 ng/L and in excess sludge and aerobic sludge were 25.1 and 32.3 μg/g dw, respectively. The concentrations in air and soil within the WWTP were 243 ng/m³ and 4960 ng/g dw, respectively. A similar composition profile of siloxanes in influent and sludge suggests their same source. Seasonal variation with concentration was comprehensively studied. It was found that temperature and rainfall are the two important factors for the seasonal variation of siloxanes. Adsorption with sewage sludge was the major way for the removal of siloxanes during the municipal wastewater treatment process. Overall, on a daily basis, the mass loading of the Σsiloxanes into the WWTP, out of the WWTP with the effluent and sludge, were estimated to be 3.0, 0.6 and 1.3 kg, respectively. In general, 21 % of siloxanes were discharged into the receiving body (Songhua River), 43 % of siloxanes were absorbed on sludge, and 36 % of siloxanes were lost during the whole process of WWTP.
اظهر المزيد [+] اقل [-]The environmental fate of polybrominated diphenyl ethers (PBDEs) in western Taiwan and coastal waters: evaluation with a fugacity-based model
2016
O’Driscoll, Kieran | Robinson, Jill | Chiang, Wen-Son | Chen, Yang-Yih | Kao, Ruey-Chy | Doherty, Rory
The environmental fate of polybrominated diphenyl ethers (PBDEs), a group of flame retardants that are considered to be persistent organic pollutants (POPs), around the Zhuoshui River and Changhua County regions of Taiwan was assessed. An investigation into emissions, partitioning, and fate of selected PBDEs was conducted based on the equilibrium constant (EQC) fugacity model developed at Trent University, Canada. Emissions for congeners PBDE 47, PBDE 99, and PBDE 209 to air (4.9–92 × 10⁻³ kg/h), soil (0.91–17.4 × 10⁻³ kg/h), and water (0.21–4.04 × 10⁻³ kg/h), were estimated by modifying previous models on PBDE emission rates by considering both industrial and domestic rates. It was found that fugacity modeling can give a reasonable estimation of the behavior, partitioning, and concentrations of PBDE congeners in and around Taiwan. Results indicate that PBDE congeners have a high affinity for partitioning into sediments then soils. As congener number decreases, the PBDEs then partition more readily into air. As the degree of bromination increases, congeners more readily partition to sediments. Sediments may then act as a long-term source of PBDEs which can be released back into the water column due to resuspension during storm events.
اظهر المزيد [+] اقل [-]Diversity, community structure, and bioremediation potential of mercury-resistant marine bacteria of estuarine and coastal environments of Odisha, India
2016
Dash, Hirak R. | Das, Surajit
Both point and non-point sources increase the pollution status of mercury and increase the population of mercury-resistant marine bacteria (MRMB). They can be targeted as the indicator organism to access marine mercury pollution, besides utilization in bioremediation. Thus, sediment and water samples were collected for 2 years (2010–2012) along Odisha coast of Bay of Bengal, India. Mercury content of the study sites varied from 0.47 to 0.99 ppb irrespective of the seasons of sampling. A strong positive correlation was observed between mercury content and MRMB population (P < 0.05) suggesting the utilization of these bacteria to assess the level of mercury pollution in the marine environment. Seventy-eight percent of the MRMB isolates were under the phylum Firmicutes, and 36 and 31 % of them could resist mercury by mer operon–mediated volatilization and mercury biosorption, respectively. In addition, most of the isolates could resist a number of antibiotics and toxic metals. All the MRMB isolates possess the potential of growth and survival at cardinal pH (4–8), temperature (25–37 °C), and salinity (5–35 psu). Enterobacteria repetitive intergenic consensus (ERIC) and repetitive element palindromic PCR (REP-PCR) produced fingerprints corroborating the results of 16S rRNA gene sequencing. Fourier transform infrared (FTIR) spectral analysis also revealed strain-level speciation and phylogenetic relationships.
اظهر المزيد [+] اقل [-]Enhanced degradation of benzene by percarbonate activated with Fe(II)-glutamate complex
2016
Fu, Xiaori | Gu, Xiaogang | Lu, Shuguang | Miao, Zhouwei | Xu, Minhui | Zhang, Xiang | Danish, Muhammad | Cui, Hang | Farooq, Usman | Qiu, Zhaofu | Sui, Qian
Effective degradation of benzene was achieved in sodium percarbonate (SPC)/Fe(II)-Glu system. The presence of glutamate (Glu) could enhance the regeneration of Fe(III) to Fe(II), which ensures the benzene degradation efficiency at wider pH range and eliminate the influence of HCO₃⁻ in low concentration. Meanwhile, the significant scavenging effects of high HCO₃⁻ concentration could also be overcome by increasing the Glu/SPC/Fe(II)/benzene molar ratio. Free radical probe compound tests, free radical scavenger tests, and electron paramagnetic resonance (EPR) analysis were conducted to explore the reaction mechanism for benzene degradation, in which hydroxyl radical (HO•) and superoxide anion radical (O₂•⁻) were confirmed as the predominant species responsible for benzene degradation. In addition, the results obtained in actual groundwater test strongly indicated that SPC/Fe(II)-Glu system is applicable for the remediation of benzene-contaminated groundwater in practice.
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