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771.
Efficiency of surfactant-enhanced desorption for contaminated soils depending on the component characteristics of soil-surfactant--PAHs system 总被引:2,自引:0,他引:2
The sorption of surfactants onto soils has a significant effect on the performance of surfactant enhanced desorption. In this study, the efficiency of surfactants in enhancing desorption for polycyclic aromatic hydrocarbons (PAHs) contaminated soils relative to water was evaluated with a term of relative efficiency coefficient (REC). Since the sorption of surfactants onto soils, surfactants only enhanced PAH desorption when REC values were larger than 1 and the added surfactant concentration was greater than the corresponding critical enhance desorption concentration (CEDC), which was defined as the corresponding surfactant concentration with REC=1. A model was utilized to describe and predict the REC and CEDC values for PAH desorption. The model and experimental results indicated that the efficiency of surfactants in enhancing PAH desorption showed strong dependence on the soil composition, surfactant structure and PAH properties. These results are of practical interest for the selection of surfactant to optimize soil remediation technologies. 相似文献
772.
773.
Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event 总被引:3,自引:0,他引:3
To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60-70 and 200-300 nm, respectively. Aerosol concentration is 104 cm-3. nm-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03:00, 09:00 and 19:00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO2 concentration, followed by NO2, O3 is hardly affected. The impact of crop residual burning on fine particles (< 2.1 μm) is larger than on coarse particles (> 2.1 μm), thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K+, Cl-, Na+, and F- and has a weak impact on the size distributions of NH4+, Ca2+, NO3- and SO42-. 相似文献
774.
The optimal condition for a one-step process removing organic compounds from coking wastewater by simultaneously synthesized organobentonite as a pretreatment was investigated. Results showed that sorption of organic compounds by organobentonite was positively correlated to the cation surfactant exchange on the bentonite and the octanol-water partition coefficient (Kow) of the solutes. With 0.75 g/L bentonite and 180 mg/L (60% of bentonite cation exchange capacity) cetyltrimethylammonium bromide, the removal efficiencies of the 16 polycyclic aromatic hydrocarbon (PAHs) specified by the US Environmental Protection Agency in coking wastewater except naphthalene were more than 90%, and that of benzo(a)pyrene was 99.5%. At the same time, the removal efficiencies of CODCr, NH3-N, volatile phenols, colour and turbidity were 28.6%, 13.2%, 8.9%, 55% and 84.3%, respectively, and the ratio of BOD5/CODCr increased from 0.31 to 0.41. These results indicated that the one-step process had high removal efficiency for toxic and refractory hydrophobic organic compounds, and could improve the biodegradability of the coking wastewater. Therefore it could be a promising technology for the pretreatment of toxic and refractory organic wastewater. 相似文献
775.
膨润土对重金属铜的吸附随铜离子浓度的增加先快迭增长而后趋于缓慢最后达成平衡。饱和吸附量为34.10mg·g^-1。Langmuir方程、Freundlich方程和Temkin方程均能拟舍实验结果,但Temkin方程拟合为最佳。pH是影响膨润土对Cu^2+吸附的主要因素。低pH值不利于膨润土对Cu^2+的吸附。引入竞争离子,膨润土对Cu^2+的吸附量明显降低。Ph^2+、Cd^2+、Ni^2+对Cu^2+的吸附产生不同程度的竞争作用,其竞争力为Pb^2+〉Cd^2+〉Ni^2+。在竞争离子存在的情况下,Cu^2+的吸附依然遵守等温吸附模型。饱和吸附量从34.10mg·g^-1下降到16.93mg·g^-1(Pb^2+)、19.21mg·g^-1(Cd^2+)、26.08mg·g^-1(Ni^2+)。 相似文献
776.
催化湿式氧化处理H—酸溶液的反应动力学 总被引:5,自引:1,他引:5
两阶段一级反应动力学模型和广义动力学模型被用来描述湿式氧化(WAO)及催化湿式氧化(CWAO)反应过程,并确定了动力学参数。2个模型的计算值均与实验值相符,而广义动力学模型相对现准确些。2个确定均表明反尖分2个步骤:首先是H-酸被迅速氧化成小分子有机酸,后者再缓慢氧化,这2个步骤由模型参数加以表征,因而模型可被用来对CWAO催化剂进行评价。 相似文献
777.
Jinfei Feng Yinxi Wang Jian Zhao Liqun Zhu Xinmin Bian Weijian Zhang 《环境科学学报(英文版)》2011,23(7):1158-1164
Air and soil pollution from traffic has been considered as a critical issue to crop production and food safety, however, few efforts have
been paid on distinguish the source origin of traffic-related contaminants in rice plant along highway. Therefore, we investigated metals
(Pb, Cd, Cr, Zn and Cu) concentrations and stable Pb isotope ratios in rice plants exposed and unexposed to highway traffic pollution
in Eastern China in 2008. Significant differences in metals concentrations between the exposed and unexposed plants existed in leaf for
Pb, Cd and Zn, in stem only for Zn, and in grain for Pb and Cd. About 46% of Pb and 41% of Cd in the grain were attributed to the
foliar uptake from atmosphere, and there were no obvious contribution of atmosphere to the accumulations of Cr, Zn and Cu in grain.
Except for Zn, all of the heavy metals in stem were attributed to the root uptake from soil, although significant accumulations of Pb and
Cd from atmosphere existed in leaf. This indicated that different processes existed in the subsequent translocation of foliar-absorbed
heavy metals between rice organs. The distinct separation of stable Pb isotope ratios among rice grain, leaf, stem, soil and vehicle
exhaust further provided evidences on the different pathways of heavy metal accumulation in rice plant. These results suggested that
further more attentions should be paid to the atmospheric deposition of heavy metals from traffic emission when plan crop layout for
food safety along highway. 相似文献
778.
779.
Urban human thermal comfort (UHTC) is affected for interacting of weather condition and underlying surface framework of urban area. Urban underlying surface temperature value and Normalized Difference Vegetation Index(NDVI) were calculated using image interpreting and supervised classification technique by ERDAS IMAGE software using 1991 and 1999 Landsat TM images data. Reference to the relational standard of assessing human thermal comfort and other meteorology data of Hangzhou City in summer, air temperature and relative humidity variation of different land types of underlying surface were inversed. By choosing discomfort index as an indictor, the spatial distribution characteristic and the spatial variation degree of UHTC were estimated and mapped on a middle scale, that is, in six districts of Hangzhou. The main characteristics of UHTC spatial variation from 1991 to 1999 were revealed using a GIS-based calculation model. The variation mechanism were analyzed and discussed from the viewooint of citv olannino, construction and environmental orotection. 相似文献
780.