خيارات البحث
النتائج 3851 - 3860 من 4,033
Levels and patterns of organochlorine pesticides in agricultural soils in an area of extensive historical cotton cultivation in Henan province, China النص الكامل
2016
Wang, Beibei | Wu, Chunfa | Liu, Wuxing | Teng, Ying | Luo, Yongming | Christie, Peter | Guo, Dong
Organochlorine pesticides (OCPs) have attracted widespread concern because of their environmental persistence and toxicity. The historical influence of different agricultural land use types on soil concentrations of OCP residues was investigated by collecting a total of 52 surface soil samples from long-term cotton fields and fields with other crops in Lvdian township, Henan province, eastern central China. The concentration, composition, and possible sources of 16 OCPs were determined and a health risk assessment of these soils was conducted. Hexachlorocyclohexane (HCH), heptachlor, chlordane, and dichloro diphenyl trichloroethane plus its main metabolites (DDTs) were the most frequently detected OCPs with concentrations of 2.9–56.4 ng g⁻¹, 4.3–14.0 ng g⁻¹, 18.0–1254.4 ng g⁻¹, and below detection limit (BDL) −206.1 ng g⁻¹, respectively. Analysis of variance of p,p-DDE shows significant (P < 0.05) differences while other OCPs show no significant differences between historical cotton fields and fields containing other crops. Compositional analysis suggests that the HCH is derived mainly from the use of lindane and that there are recent inputs. Analysis of variance and compositional analysis indicate that the p,p-DDE in surface soil from long-term cotton fields is derived mainly from the aerobic biodegradation of historical residues. The sum of carcinogenic risk values of OCPs for soil samples were found to be 1.58 × 10⁻⁶, posing a low cancer risk to the inhabitants of the region studied.
اظهر المزيد [+] اقل [-]Phosphorus speciation of sediments from lakes of different tropic status in Eastern China النص الكامل
2016
Zhang, Wenqiang | Rong, Nan | Jin, Xin | Li, Jie | Ding, Yuekui | Zhu, Xiaolei | Shan, Baoqing
Information about the chemical composition of phosphorus (P) in sediment is critical for understanding P dynamics and eutrophication in lake ecosystems. Eutrophication as a result of P pollution still persists so we chose to determine the P characteristics of sediments from ten lakes of different trophic status and the relationships between P fractions and environmental factors. The results show that the Standards, Measurements and Testing (SMT) method combined with ³¹P-nuclear magnetic resonance (³¹P-NMR) can efficiently show the P characteristics of sediment. Phosphorus concentrations in sediments decreased as the trophic status of the lake improved. Inorganic P (Pi) was the dominant form of total P (TP) in most of the lake sediments and was mainly comprised of HCl-Pi, a stable Pi fraction. Results of ³¹P-NMR analysis show that the extracts were dominated by ortho-P (36.4–94.8 %) and mono-P (4.0–36.2 %), with smaller amounts of diester-P (.6–23.1 %), pyro-P (.2–4.4 %), and phon-P (.3–.7 %). Analysis of the relationships between the P composition and the trophic status of the lakes indicated that the bioavailability of P forms has an influence on the surface water trophic conditions and the health of aquatic ecosystems.
اظهر المزيد [+] اقل [-]Improvement of the environmental and operational characteristics of vehicles through decreasing the motor fuel density النص الكامل
2016
Magaril, Elena
The environmental and operational characteristics of motor transport, one of the main consumers of motor fuel and source of toxic emissions, soot, and greenhouse gases, are determined to a large extent by the fuel quality which is characterized by many parameters. Fuel density is one of these parameters and it can serve as an indicator of fuel quality. It has been theoretically substantiated that an increased density of motor fuel has a negative impact both on the environmental and operational characteristics of motor transport. The use of fuels with a high density leads to an increase in carbonization within the engine, adversely affecting the vehicle performance and increasing environmental pollution. A program of technological measures targeted at reducing the density of the fuel used was offered. It includes a solution to the problem posed by changes in the refining capacities ratio and the temperature range of gasoline and diesel fuel boiling, by introducing fuel additives and adding butanes to the gasoline. An environmental tax has been developed which allows oil refineries to have a direct impact on the production of fuels with improved environmental performance, taking into account the need to minimize the density of the fuel within a given category of quality.
اظهر المزيد [+] اقل [-]Urinary 1-hydroxypyrene concentration as an exposure biomarker to polycyclic aromatic hydrocarbons (PAHs) in Mexican women from different hot spot scenarios and health risk assessment النص الكامل
2016
Pruneda-Álvarez, Lucia G. | Pérez-Vázquez, Francisco J. | Ruíz-Vera, Tania | Ochoa-Martínez, Ángeles C. | Orta-García, Sandra T. | Jiménez-Avalos, Jorge A. | Pérez-Maldonado, Iván N.
Recently, in developing countries, polycyclic aromatic hydrocarbons (PAHs) have been considered contaminants of grave concern for women and children. Therefore, the aim of this study was twofold: (1) evaluate exposure assessment to PAHs using urinary 1-hydroxypyrene (1-OHP) as an exposure biomarker and (2) perform a health risk assessment in women from four different high risk scenarios in Mexico. From 2012 to 2013, in a cross-sectional study, we evaluated a total of 184 healthy women from the following scenarios: (A) indoor biomass combustion site (n = 50); (B) brick manufacturing site using different materials such as fuel sources (n = 70); (C) industrial site (n = 44); and (D) high vehicular traffic site (n = 20). 1-hydroxypyrene (1-OHP) was quantified using a high-performance liquid chromatography (HPLC) technique. Afterward, a probabilistic health risk assessment was performed (Monte Carlo analysis). Mean urinary 1-OHP levels found were 0.92 ± 0.92; 0.91 ± 0.83; 0.22 ± 0.19; and 0.14 ± 0.17 μg/L for scenario A, B, C, and D, respectively. Then, based on the measured urinary 1-OHP levels, the estimated median daily intake doses of pyrene were calculated: 659, 623, 162, and 77.4 ng/kg/day for the women participating in the study living in areas A, B, C, and D, respectively, and finally, the hazard quotient (HQ) was calculated (22 ± 21, 21 ± 20, 5.5 ± 5.5, and 2.6 ± 3.5; for areas A, B, C, and D, respectively), high health risk was noted for the women living in the studied communities. The data shown in this study (exposure levels to PAHs and health risk assessment) made it reasonable to conclude that the exposure levels found have a significant potential for generating adverse effects on human health in the studied scenarios.
اظهر المزيد [+] اقل [-]Characteristics of uranium biosorption from aqueous solutions on fungus Pleurotus ostreatus النص الكامل
2016
Zhao, Changsong | Liu, Jun | Tu, Hong | Li, Feize | Li, Xiyang | Yang, Jijun | Liao, Jiali | Yang, Yuanyou | Liu, Ning | Sun, Qun
Uranium(VI) biosorption from aqueous solutions was investigated in batch studies by using fungus Pleurotus ostreatus biomass. The optimal biosorption conditions were examined by investigating the reaction time, biomass dosage, pH, temperature, and uranium initial concentration. The interaction between fungus biomass and uranium was confirmed using Fourier transformed infrared (FT-IR), scanning electronic microscopy energy dispersive X-ray (SEM-EDX), and X-ray photoelectron spectroscopy (XPS) analysis. Results exhibited that the maximum biosorption capacity of uranium on P. ostreatus was 19.95 ± 1.17 mg/g at pH 4.0. Carboxylic, amine, as well as hydroxyl groups were involved in uranium biosorption according to FT-IR analysis. The pseudo-second-order model properly evaluated the U(VI) biosorption on fungus P. ostreatus biomass. The Langmuir equation provided better fitting in comparison with Freundlich isotherm models. The obtained thermodynamic parameters suggested that biosorption is feasible, endothermic, and spontaneous. SEM-EDX and XPS were additionally conducted to comprehend the biosorption process that could be described as a complex process involving several mechanisms of physical adsorption, chemisorptions, and ion exchange. Results obtained from this work indicated that fungus P. ostreatus biomass can be used as potential biosorbent to eliminate uranium or other radionuclides from aqueous solutions.
اظهر المزيد [+] اقل [-]Atmospheric deposition of organochlorine pesticides by precipitation in a coastal area النص الكامل
2016
Cindoruk, S Sıddık | Ozturk, Erman
Wet deposition fluxes of organochlorine pesticides (OCPs) were determined for rain samples collected in a coastal area of Turkey. Seventeen precipitation samples were collected over a 1-year period from 2008 to 2009. Rainwater was accumulated at the beginning of rain events using real time monitoring. Atmospheric concentrations were also measured in parallel with deposition samples. Both atmospheric concentrations and deposition fluxes were determined as particle and gas phases. The particle phase and dissolved phase deposition fluxes were 794.26 ± 756.70 ngm⁻² day⁻¹ and 800.77 ± 672.63 ngm⁻² day⁻¹, respectively. The washout ratios for OCP compounds were calculated separately for the particle and dissolved phases using the atmospheric concentrations and rain concentrations. The minimum washout ratio for the particle phase was 2339.47 for Endrin aldehyde, whereas the maximum washout ratio was 497593.34 for Methoxychlor. The maximum washout ratio for the dissolved phase was 247523.89 for Endosulfan beta, whereas the minimum washout ratio was 10169.69 for p,p′-DDT. The dry deposition velocities ranged from 0.01 to 1.67 cms⁻¹. The partitioning of wet deposition between the particle and dissolved phases was 50 % in terms of total OCP deposition.
اظهر المزيد [+] اقل [-]Natural radioactivity and radiological hazard assessment of Egyptian oil ashes النص الكامل
2016
Mohammed, Hesham | Sadeek, Sadeek | Mahmoud, Abu Rehab | Diab, Hanan | Zaky, Doaa
Oil fly and boiler ash samples were collected from the four major Egyptian power plants in order to determine their natural radioactivity. Secular equilibrium between ²³⁸U and ²³²Th and their decay products is significantly disturbed in oil ash samples. The ²²⁶Ra/²³⁸U ratios were between 440 and 1993 with an average value of 801, indicating that the concentrations of daughters ²²⁶Ra were very high compared to the parent ²³⁸U in the oil ash samples. While, the average ratios for ²¹⁰Pb/²²⁶Ra in most samples were 1.19 ± 0.05, indicating a secular equilibrium in the ²²⁶Ra–²¹⁰Pb sub series. The natural radioactivity due to ²³⁸U and ²³²Th was found to be negligible. While the activity concentrations of ²²⁶Ra ranged from 3205 to 12,320 Bq kg⁻¹ with an average value of 9284 Bq kg⁻¹, ²¹⁰Pb ranged from 5960 to 13,930 Bq kg⁻¹ with an average value of 11,513 Bq kg⁻¹. The results are compared with the reported data from other countries. The average value of radium equivalent activity was 9308 ± 2729 Bq kg⁻¹, while the external and internal hazard indexes were found to be 25 ± 7 and 50 ± 15, respectively. All the studied radiological parameters were higher than the recommended limit by the IAEA in all ash samples.
اظهر المزيد [+] اقل [-]Root morphological responses of five soybean [Glycine max (L.) Merr] cultivars to cadmium stress at young seedlings النص الكامل
2016
Wang, Peng | Deng, Xiaojuan | Huang, Yian | Fang, Xiaolong | Zhang, Jie | Wan, Haibo | Yang, Cunyi
To examine the differences in root morphological responses of soybean cultivars with different cadmium (Cd) tolerance and accumulation to Cd stress, the biomass, Cd concentration, and root morphological features of five soybean cultivars were determined under 0, 9, 23, 45, and 90 μM Cd stress via hydroponic experiments. Significantly genotypic differences in Cd tolerance and Cd concentration were observed between five soybean cultivars at four Cd levels. For Cd tolerance, HX3 showed a strong Cd tolerance with tolerance indexes of shoot biomass at 92.49, 76.44, 60.21, and 46.45 % after 18 days at four Cd levels, and others had similar weak tolerance at young seedling. For Cd accumulation, Cd concentration in roots showed far higher than that in shoots. The different accumulation features in roots and shoots among five cultivars were found at four Cd levels. Comparing with the control, the total root length (RL), root surface area (SA), and root volume (RV) of all cultivars were decreased significantly at four Cd levels. Tolerant cultivar HX3 had the largest root system and sensitive cultivar BX10 had the smallest root system at young seedling stage. Correlation analysis indicated that RL, SA, and RV were positively correlated with root biomass and shoot biomass under 9 and 23 μM Cd treatments, but root average diameter (RD) was negatively correlated with shoot biomass and root biomass only under 9 μM Cd treatments, while RL and SA were negatively correlated with root Cd concentration under 23 and 45 μM Cd treatments. The results suggested that root morphological traits were closely related to Cd tolerance at young seedlings under Cd treatments.
اظهر المزيد [+] اقل [-]Occurrence and fate of PBDEs and novel brominated flame retardants in a wastewater treatment plant in Harbin, China النص الكامل
2016
Li, Bo | Sun, Shao-Jing | Huo, Chun-Yan | Li, Wen-Long | Zhu, Ning-Zheng | Qi, Hong | Kong, Ling-Jun | Li, Yi-Fan | Ma, Wanli
Wastewater treatment plant (WWTP) is considered to be an important medium for the transport and transformation of organic pollutants. This study attempted to comprehensively investigate polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in a WWTP in Harbin, one of the main “Old Industrial Base” in China. The mean concentrations of the total PBDEs in the influent, effluent, and sludge were 152 ng/L, 16.2 ng/L, and 503 g/g dw, respectively, which were at the low end of the global range. BDE-209 was the most abundant congener, with contributions to the total PBDE ranging from 90.5 to 98.5 %. The level of the total NBFRs ranged from 24.5 to 107 ng/L, 0.95 to 20.3 ng/L, and 305 to 1202 ng/g dw in the influent, effluent, and sludge, respectively. For NBFRs, DBDPE was the most abundant congener (38.8–50.5 %), followed by BEHTBP (11.0–35.0 %). The ratio for DBDPE/BDE-209 (0.62 ± 0.42) was found less than 1 in sludge, which indicated that Deca-BDE is still the major BFR product in this city. Source identification suggested that indoor dust should be an important source of BFRs in the WWTP. Approximately 20.8 and 7.79 kg of PBDEs and NBFRs on annual basis were removed with the sludge. Biodegradation could play an important role on the fate of BFRs in the WWTP, which is required for future research.
اظهر المزيد [+] اقل [-]An analysis of the impact on land use and ecological vulnerability of the policy of returning farmland to forest in Yan’an, China النص الكامل
2016
Hou, Gang | Li, Xuxiang | Wang, Jing jing | Zhang, Jing
During the past decades, land use change has taken place around the Loess Plateau at unprecedented rates. Due to the impact of existing land use policy, great changes have taken place in the land use types in this ecologically vulnerable area. Taking eight counties in Yan’an, Shaanxi province, China, as the study area, this study analyzed the long-term (from 1997 to 2011) changes in land use and ecological vulnerability. Based on thematic mapper (TM) images of Yan’an in 1997, 2004, and 2011, the dynamic changes in land use are analyzed with the application software for remote sensing (RS) and geographic information system (GIS) since the implementation of the policy of returning farmland to forest. Combined with the land use data, the local socio-economic data, and natural resources condition, ecological vulnerability is evaluated using the spatial principal component analysis (SPCA) model in Yan’an region. Using the natural breaks classification (NBC), the evaluation results are divided into five categories: potential, slight, light, medium, and heavy. The results show that although the regional land use types changed markedly, the ecological vulnerability in the study shows greater than average optimism, and the ecological vulnerability index of the southern four counties is lower than that of the northern four counties. In 1997–2011, the eco-environmental quality gradually improved in most areas. However, it gradually deteriorated in some regions.
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