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961.
962.
Feng XH Zhai LM Tan WF Liu F He JZ 《Environmental pollution (Barking, Essex : 1987)》2007,147(2):366-373
Several Mn oxide minerals commonly occurring in soils were synthesized by modified or optimized methods. The morphologies, structures, compositions and surface properties of the synthesized Mn oxide minerals were characterized. Adsorption and redox reactions of heavy metals on these minerals in relation to the mineral structures and surface properties were also investigated. The synthesized birnessite, todorokite, cryptomelane, and hausmannite were single-phased minerals and had the typical morphologies from analyses of XRD and TEM/ED. The PZCs of the synthesized birnessite, todorokite and cryptomelane were 1.75, 3.50 and 2.10, respectively. The magnitude order of their surface variable negative charge was: birnessite> or =cryptomelane>todorokite. The hausmannite had a much higher PZC than others with the least surface variable negative charge. Birnessite exhibited the largest adsorption capacity on heavy metals Pb(2+), Cu(2+), Co(2+), Cd(2+) and Zn(2+), while hausmannite the smallest one. Birnessite, cryptomelane and todorokite showed the greatest adsorption capacity on Pb(2+) among the tested heavy metals. Hydration tendency (pK(1)) of the heavy metals and the surface variable charge of the Mn minerals had significant impacts on the adsorption. The ability in Cr(III) oxidation and concomitant release of Mn(2+) varied greatly depending on the structure, composition, surface properties and crystallinity of the minerals. The maximum amounts of Cr(III) oxidized by the Mn oxide minerals in order were (mmol/kg): birnessite (1330.0)>cryptomelane (422.6)>todorokite (59.7)>hausmannite (36.6). 相似文献
963.
Modelling of the fate of selected endocrine disruptors in a municipal wastewater treatment plant in South East Queensland, Australia 总被引:3,自引:0,他引:3
The aim of this study was to develop a fugacity-based analysis of the fate of selected industrial compounds (alkylphenols and phthalates) with endocrine disrupting properties in a conventional activated sludge wastewater treatment plant (WWTP A) in South East Queensland, Australia. Using mass balance principles, a fugacity model was developed for correlating and predicting the steady-state-phase concentrations, the process stream fluxes, and the fate of four phthalates and four alkylphenols in WWTP A. Input data are the compound's physicochemical properties, measured concentrations and the plant's operating design and parameters. The relative amounts of chemicals that are likely to be volatilized, sorbed to sludge, biotransformed, and discharge in the effluent water was determined. Since it was difficult to predict biotransformation, measured concentrations were used to calibrate the model in terms of biotransformation rate constant. Results obtained by applying the model for the eight compounds showed <40% differences between most of the estimated and measured data from WWTP A. All eight compounds that were modelled in this study had high removal efficacy from WWTP A. Apart from benzyl butyl phthalate and bisphenol A, the majority is removed via biotransformation followed by a lesser proportion removed with the primary sludge. Fugacity analysis provides useful insight into compound fate in a WWTP and with further calibration and validation the model should be useful for correlative and predictive purposes. 相似文献
964.
965.
津河水系的修复对天津城市生态环境的影响 总被引:10,自引:1,他引:9
针对天津城市生态环境特点和背方城市大气污染现状,探讨了津河水系的修复对改善城市环境质量,丰富城市景观以及修复城市生态环境的重要意义。 相似文献
966.
Gangba sheep are known for having typical sensory characteristics attributed to free range conditions and grazing on wild plants. The genuine Gangba mutton was selected as the experimental group, and the commercial Tibetan mutton was selected as the control group, the nutritive composition of basic chemical components, amino acids and fatty acids in mutton were investigated to correlate its unique meat quality and eating satisfaction. The results showed that fatty acids were significantly higher (P<0.05) in Gangba mutton than in commercial mutton, and the higher content of flavoring amino acids (glutamic acid and aspartame) were primarily responsible for the taste attributes umami of meat juices. Moreover, the trace elements analysis in mutton and grazing factors (forage, water source and soil) were conducted, to explain the source of essential trace elements in mutton. The concentrations of essential trace elements show that the Gangba mutton was a valuable source for highly available Cu and Zn in human nutrition, and well managed with few detected of toxicity metal. The concentrations of essential trace elements in mutton are closely related to the trace elements in environmental grazing factors. In conclusion, the congenital grazing conditions (a highly mineralized water resource, natural forages and clean soils) were shown to contribute to the unique meat characteristics of Gangba sheep. 相似文献
967.
Characteristics of atmospheric non-methane hydrocarbons during haze episode in Beijing, China 总被引:1,自引:0,他引:1
Songjun Guo Jihua Tan Jingchun Duan Yongliang Ma Fumo Yang Kebin He Jimin Hao 《Environmental monitoring and assessment》2012,184(12):7235-7246
This study firstly focused on non-methane hydrocarbons (NMHCs) during three successive days with haze episode (16–18 August 2006) in Beijing. Concentrations of alkanes, alkenes, aromatic hydrocarbons, and ethyne all peaked at traffic rush hour, implying vehicular emission; and alkanes also peaked at non-traffic rush hour in the daytime, implying additional source. Especially, alkanes and aromatics clearly showed higher levels in the nighttime than that in the daytime, implying their active photochemical reactions in the daytime. Correlation coefficients (R 2) showed that propane, n-butane, i-butane, ethene, propene, and benzene correlated with ethyne (R 2?=?0.61–0.66), suggesting that their main source is vehicular emission; 2-methylpentane and n-hexane correlated with i-pentane (R 2?=?0.61–0.64), suggesting that gasoline evaporation is their main source; and ethylbezene, m-/p-xylene, and o-xylene correlated with toluene (R 2?=?0.60–0.79), suggesting that their main source is similar to that of toluene (e.g., solvent usage). The R 2 of ethyne, i-pentane, and toluene with total NMHCs were 0.58, 0.76, and 0.60, respectively, indicating that ambient hydrocarbons are associated with vehicular emission, gasoline evaporation, and solvent usage. The sources of other hydrocarbons (e.g., ethane) might be natural gas leakage, biogenic emission, or long-range transport of air pollutants. Measured higher mean B/T ratio (0.78?±?0.27) was caused by the more intensive photochemical activity of toluene than benzene, still indicating the dominant emission from vehicles. 相似文献
968.
A comparison of radiometric correction techniques in the evaluation of the relationship between LST and NDVI in Landsat imagery 总被引:1,自引:0,他引:1
Atmospheric corrections for multi-temporal optical satellite images are necessary, especially in change detection analyses,
such as normalized difference vegetation index (NDVI) rationing. Abrupt change detection analysis using remote-sensing techniques
requires radiometric congruity and atmospheric correction to monitor terrestrial surfaces over time. Two atmospheric correction
methods were used for this study: relative radiometric normalization and the simplified method for atmospheric correction
(SMAC) in the solar spectrum. A multi-temporal data set consisting of two sets of Landsat images from the period between 1991
and 2002 of Penang Island, Malaysia, was used to compare NDVI maps, which were generated using the proposed atmospheric correction
methods. Land surface temperature (LST) was retrieved using ATCOR3_T in PCI Geomatica 10.1 image processing software. Linear
regression analysis was utilized to analyze the relationship between NDVI and LST. This study reveals that both of the proposed
atmospheric correction methods yielded high accuracy through examination of the linear correlation coefficients. To check
for the accuracy of the equation obtained through linear regression analysis for every single satellite image, 20 points were
randomly chosen. The results showed that the SMAC method yielded a constant value (in terms of error) to predict the NDVI
value from linear regression analysis-derived equation. The errors (average) from both proposed atmospheric correction methods
were less than 10%. 相似文献
969.
G. H. Ong C. K. Yap M. Maziah H. Suhaimi S. G. Tan 《Environmental monitoring and assessment》2013,185(4):3243-3254
The first objective of this study was to provide data of arsenic (As) levels in Peninsular Malaysia based on soil samples and accumulation of As in Centella asiatica collected from 12 sampling sites in Peninsular Malaysia. The second objective was to assess the accumulation of As in transplanted C. asiatica between control and semi-polluted or polluted sites. Four sites were selected which were UPM (clean site), Balakong (semi-polluted site), Seri Kembangan (semi-polluted site) and Juru (polluted site). The As concentrations of plant and soil samples were determined by Instrumental Neutron Activation Analysis. The As levels ranged from 9.38 to 57.05 μg/g dw in soils, 0.21 to 4.33 μg/g dw in leaves, 0.18 to 1.83 μg/g dw in stems and 1.32–20.76 μg/g dw in roots. All sampling sites had As levels exceeding the CCME guideline (12 μg/g dw) except for Kelantan, P. Pauh, and Senawang with P. Klang having the highest As in soil (57.05 μg/g dw). In C. asiatica, As accumulation was highest in roots followed by leaves and stems. When the As level in soils were higher, the uptake of As in plants would also be increased. After the transplantation of plants to semi-polluted and polluted sites for 3 weeks, all concentration factors were greater than 50 % of the initial As level. The elimination factor was around 39 % when the plants were transplanted back to the clean sites for 3 weeks. The findings of the present study indicated that the leaves, stems and roots of C. asiatica are ideal biomonitors of As contamination. The present data results the most comprehensive data obtained on As levels in Malaysia. 相似文献
970.
污水生物除磷若干影响因素分析 总被引:23,自引:2,他引:21
在系统阐述污水生物除磷机理的基础上,深入分析了微生物群体平衡、城市污水水质、环境因子以及工艺运行参数和运行方式等方面对生物除磷效果的影响.分析结果表明:生物除磷系统的溶解氧浓度不宜太高,一般好氧区DO<2 mg/L,厌氧区DO<0.2 mg/L;厌氧段存在硝酸盐对生物释磷有负面影响,缺氧段存在一定浓度的硝酸盐有利于生物聚磷;碳源必须充分、易降解;TKN/COD<0.1的城市污水有利于生物除磷;pH偏碱性可提高生物除磷效率;低温对生物除磷效果影响不明显. 相似文献