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771.
Farideh Golbabaei Maryam Mamdouh Keramat Nouri Jelyani Seyed Jamaleddin Shahtaheri 《International journal of occupational safety and ergonomics》2013,19(3):283-289
Exposure to methyl methacrylate (MMA), total dust and health symptoms were investigated in 20 dental laboratories located in Tehran, Iran. Time-weighted average (TWA) of MMA and peak concentrations were determined, using XAD-2 tubes followed by GC-ID analysis. Total dusts were evaluated gravimetrically. Health symptoms were asked using a questionnaire. TWA for technicians with direct and indirect exposure to MMA were 327.28 ± 79.42 and 282.9 ± 41.84 mg/m3 , respectively. Peak concentration of MMA for those technicians were 337.0 ± 36.81 and 328.88 ± 45.40 mg/m3, respectively.There were no significant differences between TWA of MMA and peak concentration in different weekly workdays; however, within-day variations were observed (P < .05).TWA of MMA and peak concentration correlation with the laboratory volume were 0.61-0.65. Dust exposure of technicians was 2.35 ± 2.70 mg/m3. Cough and skin dryness were the common health symptoms. Smoking and asbestos exposure history were factors influencing cough prevalence (p < .05).It is concluded that the current Short-Term Exposure Limit (STEL) is not low enough to protect technicians against the adverse effects caused by MMA. 相似文献
772.
测定自来水中铀浓度及其变化规律,对评估饮用水质量及公众接受的铀放射水平有较大意义。该文介绍了经过一年连续监测所获得的上海市自来水中铀浓度及其变化。结果表明,上海市自来水中铀浓度在0.025 ̄0.28μg/L之间,年均值为0.112μg/L;一年中的12月-15月浓度较高,6-11月浓度略低,其中3月份浓度最高,8月份深度最低,上海市自来水中铀浓度较低,比全国平均浓度低一个数量级。 相似文献
773.
从灾害史料中,可以看出河南灾害的严重性,进而论述了河南省灾害区域成灾背景,最后针对河南省灾害现状,提出了减灾对策建议。 相似文献
774.
E. L. Genikhovich I. G. Gracheva R. I. Onikul E. N. Filatova 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):501-512
Urban concentration fields are extremely inhomogeneous andtheir gradients are very high. It results in specificproblems when modelling air pollution at the urban scalethat are analysed in this paper. Some examples ofmisrepresentation of the urban concentration field,computed with the use of the source-receptor type models,are given here. They can help in understanding the natureof the problems we face and reveal deficiencies of thecomputational technologies in use. Filtering of thecomputed fields is suggested as an instrument for improvingtheir quality. Its efficiency is proved on the test runs.An algorithm for refinement of the filtered fields isintroduced in this paper. 相似文献
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This article presents an evaluation of the performance of the urban atmospheric dispersion model (DAUMOD) in estimating nitrogen oxides (NOx) background concentrations in Copenhagen. Estimations of hourly average (averaged over a year), mean daily and mean monthly concentrations of NOx are compared with observed values for two years of data. The model slightly underestimates low hourly average values and overestimates high values. The cumulative frequency distribution of mean daily concentration obtained from model estimations is in good agreement with the obtained from observed data. We performed a statistical analysis to determine the agreement between estimated and observed concentration values. The results show that 95.8% of hourly average estimations, 86.8% of mean daily and 100% of monthly average concentrations are within a factor of two of the observed values. The normalised mean square error of predictions is +0.13 for hourly average estimations, +0.22 for mean daily values and +0.02 for monthly mean concentrations. The fractional bias values are: –0.049 for hourly mean estimations, –0.047 for mean daily values and –0.053 for monthly average estimations. The values of the statistical parameters allow us to consider that though estimations are lightly larger than the observed values, the model performance is acceptable. 相似文献
777.
Zhang Tongsheng & Gan Guohui Institute of Geographical Sciences Natural Resources Research Chinese Academy of Sciences Beijing China Graduate School Chinese Academy of Sciences Beijing China 《中国人口.资源与环境(英文版)》2006,4(1)
This paper empirically examines variations and changes in manufacturing concentration and their determinants in China over the 1980-2003 period with a sample of 26 industries. The analysis indicates that average industrial concentration has increased during the 1990s. Studies show that scale economies and industry policies are important determinants for industries geographical concentration; factor endowments and the location of foreign direct investment are also found to have a positive effect on concentration. 相似文献
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利用甘蔗渣生产纸浆厂堆垛蔗渣产生的渗出液CODCr,浓度高达8000~13000mg/L,属于较难处理的高浓度有机废水。将UASB废水处理技术应用于处理清洁堆垛蔗渣产生的渗出液,不仅能够获得良好的处理效果,而且能降低废水处理成本,从而实现经济效益、环境效益和社会效益三赢。 相似文献