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501.
Simultaneous removal of ammonium and phosphate by zeolite synthesized
from coal fly ash as influenced by acid treatment 总被引:5,自引:0,他引:5
ZHANG Bao-hu WU De-yi WANG Chong HE Sheng-bing ZHANG Zhen-ji KONG Hai-nan 《环境科学学报(英文版)》2007,19(5):540-545
Zeolite synthesized from fly ash (ZFA) without modification is not efficient for the purification of NH4+ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 (≥0.9 mol/L) resulted in a limited maximum phosphate immobilization capacity (PIC). It was concluded that through a previous mild acid treatment (e.g. 0.01 mol/L of H2SO4), ZFA can be used in the simultaneous removal of NH4+ and P at low concentrations simulating real effluent. 相似文献
502.
根据环境在线监控的数据特征和普遍存在的问题,提出了针对环境在线监控数据交换的系统设计方案,包含数据交换中心、前置系统、发布过程安全的设计。该系统可实现污染源(固定源、移动源)、水环境、大气环境、生态环境、辐射环境等各类在线监控数据的自动归集、交换和集成。为各级环保部门同时、准确地掌握各种在线监控数据,提高监管能力提供技术支撑。 相似文献
503.
The effluents and sludge from municipal sewage treatment plants (MSTPs) are considered as potential sources of many contaminants to the ambient environments. In the present work, the air-water exchange of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) was studied using passive air samplers at an urban lake, which receives the effluents from a MSTP in Beijing, China. The concentrations of PCBs and PBDEs in atmosphere were in the range 15.5-108 ng sample−1 and 2.37-27.8 ng sample−1, respectively, during the sampling period (August, 2007-July, 2008). The predominant PCBs and PBDEs were lowly halogenated congeners. The calculation for the exchange fluxes of PCBs and PBDEs using fugacity model showed that, the net exchange fluxes in different seasons were closely related to the halogen number of different congeners. Except for CBs-28 and 52, the net exchange fluxes was mainly directed from air to water for most of predominant congeners, which implied that the lower chlorinated CBs were dominated by volatilization process rather than the dry/wet depositions and diffusion between air-water interface, additionally, for heavy congeners, the dry/wet deposition process was an important source of PCBs and PBDEs in this lake. 相似文献
504.
Fate of radium (Ra) in liquid regeneration brine wastes from water softeners disposed to septic tanks in the New Jersey Coastal Plain was studied. Before treatment, combined Ra (226Ra plus 228Ra) concentrations (maximum, 1.54 Bq L−1) exceeded the 0.185 Bq L−1 Maximum Contaminant Level in 4 of 10 studied domestic-well waters (median pH, 4.90). At the water table downgradient from leachfields, combined Ra concentrations were low (commonly ≤0.019 Bq L−1) when pH was >5.3, indicating sequestration; when pH was ≤5.3 (acidic), concentrations were elevated (maximum, 0.985 Bq L−1 - greater than concentrations in corresponding discharged septic-tank effluents (maximum, 0.243 Bq L−1)), indicating Ra mobilization from leachfield sediments. Confidence in quantification of Ra mass balance was reduced by study design limitations, including synoptic sampling of effluents and ground waters, and large uncertainties associated with analytical methods. The trend of Ra mobilization in acidic environments does match observations from regional water-quality assessments. 相似文献
505.
Best estimates for the solid-liquid distribution coefficients (Kd) of radiostrontium and radiocaesium for various soil types, were derived from geometric means (GM) calculated from grouping soils by texture and organic matter content, and also using soil cofactors governing soil–radionuclide interaction. The Kd (Sr) GM for Sand, Loam, Clay and Organic groups were similar, although the value for the Sand group was significantly lower. The Sr cofactor approach, based on the ratios of cation exchange capacity (CEC) to Ca and Mg concentrations in the soil solution, leads to Kd (Sr) GM with a lower variability, from which best estimates could be proposed. The Kd (Cs) GM for Sand and Organic groups differed, although similar values were obtained for Loam and Clay groups. Grouping the Kd (Cs) according to the Radiocaesium Interception Potential (RIP) and the RIP divided by the K concentration in the soil solution also allows to suggest Kd (Cs) best estimates with a lower variability. 相似文献
506.
Review of fluoride removal from drinking water 总被引:9,自引:0,他引:9
M. Mohapatra S. Anand B.K. Mishra Dion E. Giles P. Singh 《Journal of environmental management》2009,91(1):67-77
Fluoride in drinking water has a profound effect on teeth and bones. Up to a small level (1–1.5 mg/L) this strengthens the enamel. Concentrations in the range of 1.5–4 mg/L result in dental fluorosis whereas with prolonged exposure at still higher fluoride concentrations (4–10 mg/L) dental fluorosis progresses to skeletal fluorosis. High fluoride concentrations in groundwater, up to more than 30 mg/L, occur widely, in many parts of the world. This review article is aimed at providing precise information on efforts made by various researchers in the field of fluoride removal for drinking water. The fluoride removal has been broadly divided in two sections dealing with membrane and adsorption techniques. Under the membrane techniques reverse osmosis, nanofiltration, dialysis and electro-dialysis have been discussed. Adsorption, which is a conventional technique, deals with adsorbents such as: alumina/aluminium based materials, clays and soils, calcium based minerals, synthetic compounds and carbon based materials. Studies on fluoride removal from aqueous solutions using various reversed zeolites, modified zeolites and ion exchange resins based on cross-linked polystyrene are reviewed. During the last few years, layered double oxides have been of interest as adsorbents for fluoride removal. Such recent developments have been briefly discussed. 相似文献
507.
Sebastiaan J.H. Rietjens Kirsten Verlaan Thijs W. Brocades Zaalberg Sirp J. De Boer 《Disasters》2009,33(3):412-435
This paper seeks to contribute to an improved information management and exchange between humanitarian organisations and military agents in complex emergencies. To do so, a theoretical information management process model was developed and applied to the case of information management between International Security Assistance Force troops and humanitarian organisations such as Cordaid, DACAAR and the International Office for Migration in Kabul, Afghanistan. Based on this analysis the main shortcomings and problems in each stage of the information management process were identified. These include a lack of structured information databases, the absence of identification of information needs, and an over‐classification of documents by the military. Using a logical framework analysis, six major improvement tactics were developed, including the creation of more overlap in rotations of personnel, the specification of aims and tasks regarding information management, the improvement of skills and competences of personnel involved, and the introduction of regular joint civil–military evaluations. 相似文献
508.
Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area 总被引:3,自引:0,他引:3
Bozlaker A Odabasi M Muezzinoglu A 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):784-793
Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle + gas) ∑41-PCB concentrations were higher in summer (3370 ± 1617 pg m−3, average + SD) than in winter (1164 ± 618 pg m−3), probably due to increased volatilization with temperature. Average particulate ∑41-PCBs dry deposition fluxes were 349 ± 183 and 469 ± 328 ng m−2 day−1 in summer and winter, respectively. Overall average particulate deposition velocity was 5.5 ± 3.5 cm s−1. The spatial distribution of ∑41-PCB soil concentrations (n = 48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga. 相似文献
509.
510.