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排序方式: 共有302条查询结果,搜索用时 15 毫秒
261.
Yang L Xiaoye Z Sunling G Huizheng C Dan W Wenjun Q Junying S 《Environmental monitoring and assessment》2006,120(1-3):301-312
The concentrations of EC, BC and dust aerosols were determined for atmospheric samples collected from an observation station in Xi'an, China. The results show that the averaged correlation coefficient between EC and BC was founded to be 0.72 with 0.81 (n = 49) in autumn, 0.70 (n = 112) in winter and 0.69 (n = 57) in spring, respectively. Absorption coefficients of dust aerosol were estimated to be 2.7 m2 g−1 in autumn and 4.4 m2 g−1 in winter. The comparison of absorption coefficients of dust aerosol with those of BC implies that BC is the principal light-absorbing aerosol over Xi'an atmosphere. By combining thermal analysis of elemental carbon and dust contents in the aerosol samples, however, the fraction of dust absorption to total light absorption is estimated to be 19% in autumn and 31% in winter, respectively. 相似文献
262.
为了解北京市公共场所室内甲醛污染水平及影响因素,在工作日和周末上下午对北京市内家具市场、综合商场和服装批发市场3类公共场所不同功能区的室内甲醛浓度进行监测和分析。结果表明:家具市场中包含木质家具的功能区甲醛浓度最高;服装批发市场中包含外贸针织功能区的甲醛浓度最高;综合商场中包含化妆品功能区的甲醛浓度最高;服装批发市场和家具市场整体的甲醛浓度已超过《商场(店)、书店卫生标准》(GB 9670—1996)规定的限值0.12mg/m3。3类公共场所甲醛点位超标率服从显著性水平p0.05的χ2双侧检验,具有统计学意义。长期暴露在服装批发市场和家具市场内的工作人员和顾客,可能存在健康风险,应对家具市场、服装批发市场的甲醛污染进行控制。 相似文献
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利用2016—2020年近地面臭氧和气象逐时数据,基于相关性分析和概率统计方法,在分析臭氧敏感气象要素特征基础上,综合各气象因子对臭氧生成贡献大小,建立了广州逐时臭氧污染气象条件指数模型及等级标准,并进行了预报及检验.结果表明:(1)高浓度臭氧主要发生在高温低湿情况下,臭氧浓度及臭氧超标率均随着气温的升高而增加,当气温高于30℃时,臭氧浓度随温度的变化升高更为明显;臭氧浓度和超标率随着相对湿度的升高而逐渐降低,其中,当40%≤RH<50%时,臭氧浓度及超标率最高;当风速在1~2 m·s-1时,臭氧超标率最大.(2)对所建立的广州本地化的逐时臭氧污染气象条件指数模型和分级标准进行了检验评估,结果显示,臭氧污染气象条件指数等级越高,臭氧浓度和超标率也越大,说明该指数能够较好地表征臭氧污染天气的强弱.(3)基于欧洲中心高分辨率数值预报产品,根据污染气象条件指数模型,对广州3种不同天气类型下的指数预报进行对比验证,预报效果较好,说明该指数对臭氧污染天气预报有较好的指导意义. 相似文献
265.
为探究金属长滤芯的脉冲喷吹性能,运用ANSYS Fluent软件开展脉喷流场的数值模拟,考察滤芯长度和金属网目数对喷吹强度和均匀性的影响。研究结果表明:脉冲喷吹过程中金属滤芯内存在4类压力峰,分别为静压波峰、气团膨胀峰、蓄积反弹峰、余压波动峰;不同长度滤芯内的静压力分布不同,金属短滤芯(1 m)的底部喷吹气流蓄积最为剧烈,形成的压力最大,中等长度滤芯(2~4 m)底部压力蓄积减弱,低于上部区域,长滤芯(5~10 m)内喷吹气流沿途先膨胀后持续减弱,侧壁压力整体表现为上部>中部>底部;1~5 m金属滤芯的喷吹强度及均匀性随着滤芯长度增加而变差,6~10 m金属滤芯的喷吹强度及均匀性随着滤芯长度增加而得到改善,且都随金属网目数的增加而改进。研究结果对金属滤芯的设计与优化具有指导意义。 相似文献
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268.
Xiaowei Wang Beidou Xi Shouliang Huo Wenjun Sun Hongwei Pan Jingtian Zhang Yuqing Ren Hongliang Liu 《环境科学学报(英文版)》2013,25(7):1281-1290
Characterization, treatment and releases of eight polybrominated diphenyl ethers (PBDEs) congeners and sixteen polycyclic aromatic hydrocarbons (PAHs) in wastewater were evaluated along the treatment processes of a typical secondary treatment municipal sewage treatment plant (STP) (in Hefei City) situated the beside Nanfei River, East China. The findings showed that the average concentrations of the total PBDEs in raw wastewater and treated effluent were 188.578 and 36.884 ng/L respectively. Brominated diphenyl ether (BDE) 209 congener, the predominant PBDE in the STP and Nanfei River, could be related to the discharge of car-industry-derived wastes. For PAHs, the average concentrations in raw wastewater and treated effluent were 5758.8 and 2240.4 ng/L respectively, with naphthalene, benzo[a]pyrene and indeno[1,2,3-c,d]pyrene being detected at the highest concentrations. PAHs mainly originate from the combustion of biomass/coal and petroleum. The STP reduced about 80% of the PBDEs and 61% of the PAHs, which were eliminated mainly by sedimentation processes. The removal rates of PBDEs/PAHs increased with the increase of their solid-water partitioning coefficients. Accordingly, the STP's effluent, containing some PBDE congeners (e.g., BDE 47, 99 and 209, etc.) and low-molecular-weight PAHs, could be an important contributor of these contaminants' input to Nanfei River. It resulted in a significant increase of PBDE/PAH concentrations and PAH toxicological risk in the river water downstream. About 4.040 kg/yr of PBDEs and 245.324 kg/yr of PAHs could be released into the Nanfei River. The current conventional wastewater treatment processes should be improved to remove the relatively low-molecular-weight PBDEs/PAHs more effectively. 相似文献
269.
Zhengzheng Zhang Hong Li Hongyan Liu Yingchen Bai Jinjuan Li Guorui Zhi Yanting Yu Wenjun Li Hao Zhang Fan Meng 《环境科学学报(英文版)》2021,33(4):363-372
The pollution characteristics of surfactant substances in fine particles (PM2.5) in spring were studied in the Beibu Gulf Region of China, 68 samples of PM2.5 were collected at Weizhou Island in Beihai City from March 12 to April 17, 2015. The Anionic Surfactant Substances (ASS) and Cationic Surfactant Substances (CSS) in the samples were analyzed using Byethyl Violet Spectrophotometry and Disulfide Blue Spectrophotometry, respectively. Combined with the data from backward trajectory simulation, the effects of air pollutants from remote transport on the pollution characteristics of surfactant substances in PM2.5 in the Beibu Gulf Region were analyzed and discussed. The results showed that the daily mean concentrations of ASS and CSS in spring in the Beibu Gulf Region were 165.20 pmol/m3 and 8.05pmol/m3, and the variation ranges were 23.21–452.55 pmol/m3 and 0.65–31.31 pmol/m3, accounting for 1.82‰ ± 1.65‰ and 0.12‰ ± 0.11‰ of the mass concentration of PM2.5, respectively. These concentrations were lower than those in comparable regions around the world. There was no clear correlation between the concentrations of ASS and CSS in PM2.5 and the mass concentrations of PM2.5. Tourism and air transport had a positive contribution on the concentrations of ASS. The concentration of surfactant substances in PM2.5 was significantly impacted by wind speed and wind direction. Atmospheric temperature, air pressure and precipitation had little effect on the concentrations of surfactant substances. Surfactant substances in PM2.5 significantly impacted visibility. Results also showed that the main sources of surfactant substances were from the southern China and Southeast Asia. 相似文献
270.
Abstract The issue of agricultural insurance subsidy is discussed in this paper aiming to make it provided more rationally and scientifically. It is started with the connection between agricultural insurance and financial subsidy. It is really necessary and crucial to implement the financial insurance due to the bad operational performance, especially in the developing countries. But the subsidy should be provided more rationally because financial subsidy has lots of negative effects. A model in competitive insurance markets developed by Ahsan et al (1982) and a farmers' decision model are developed to solve the optimal subsidized rate. Finally, the equation is got to calculate it. But a quantitative subsidized rate is not made here because the calculation should be under some restricted conditions, which are always absent in the developing countries. So the government should provide some subsidy for the ex ante research and preparation to get the scientific probability and premium rate. 相似文献