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981.
基于工程实例和数值模拟,分析了高速公路加宽工程中,原有路基荷载作用引起的软基性质改善对路基沉降变形的影响机理。研究表明:新、老路基的沉降变形均受软基性质改善的影响;软基性质改善改变了新路基荷载在老路地基中引起的附加应力分布,这种附加应力的改变也对老路基的沉降产生影响,而传统的计算方法不能考虑附加应力的变化对沉降的影响;对比考虑与不考虑老路基荷载作用的影响,新路基的沉降量会不同,这种沉降差异随路基高度、新路基宽度以及软基厚度的增加而逐渐增大,但老路基的沉降差异只受软基深度的影响。 相似文献
982.
本文依据湖泊、水库的箱式模型理论,建立了简阳三岔湖水库网箱养鱼总磷模型和容解氧模型。并利用这一模型对不同网养面积下三岔湖水库总磷浓度和溶解氧进行了模拟实验。结果指出:按照三岔湖1991年养鱼特征和水文特征,网养面积最好不超过4.4×104m2,绝对不能超过6×104m2。 相似文献
983.
Electromagnetic field sources used for communication always have been subject of serious interest. There are many publications
concerning exposure and risk assessment of the working in such environment. Results of epidemiological study performed in
Bulgaria in the 1990's show exceeding of the maximal permissible values especially in radio stations for the personnel in
24 h working shift [Israel et al. (1992). Study of the electromagnetic in its influence on personnel working in radio and
TV stations, Report, National Centre of Hygiene, Medical Ecology and Nutrition; Israel and Tomov (2001). Epidemiological study
of the effects of radiofrequency radiation on operators in radio, TV and relay stations, Proceeding of the Eastern European
Regional Meeting and Workshop “Measurements and Criteria for Standard Harmonization in the field of EMF Exposure” and WHO
EMF Standards Harmonization Meeting, Varna, Bulgaria, 28 April—3 May, 2001, pp.145–153]. In the last years the situation is
strongly influenced by the development of the technology which leads to changes in equipment in radio and TV stations, using
lower power, facilitate the working regime. The paper presents data of exposure assessment of different professional groups
in selected radio and TV stations. Assessment is being performed on basis of EMF parameters values and energetic load calculations
according to the national legislation. Data are compared with the results of previous investigation to evaluate the new situation
in this branch. Exposure levels are much lower than those in the previous study, and lower compared to the exposure limits,
as well [Israel et al. (1992). Study of the electromagnetic in its influence on personnel working in radio and TV stations,
Report, National Centre of Hygiene, Medical Ecology and Nutrition; Israel and Tomov (2001). Epidemiological study of the effects
of radiofrequency radiation on operators in radio, TV and relay stations, Proceeding of the Eastern European Regional Meeting
and␣Workshop “Measurements and Criteria for Standard Harmonization in the field of EMF Exposure” and WHO EMF Standards Harmonization
Meeting, Varna, Bulgaria, 28 April—3 May, 2001, pp.145–153]. 相似文献
984.
NONROAD非道路移动源排放量计算模式研究 总被引:3,自引:0,他引:3
研究和分析了影响非道路移动源污染物排放的各种因素,系统地剖析了美国环保署推荐的NONROAD非道路移动源污染物排放量的计算模式。给出了模式中关于排放因子的工况、使用水平、燃料中氧和硫含量以及环境温度修正的方法,并提供了非道路机械的活动因子和负载水平的调查结果,为模式及其参数的正确应用和修正提供了理论指导,探讨了中国非道路移动源排放应该考虑的主要因素。 相似文献
985.
986.
ABSTRACT: Several factors affect the occurrence and transport of pesticides in surface waters of the 29,400 km2 White River Basin in Indiana. A relationship was found between pesticide use and the average annual concentration of that pesticide in the White River, although this relationship varies for different classes of pesticides. About one percent of the mass applied of each of the commonly used agricultural herbicides was transported from the basin via the White River. Peak pesticide concentrations were typically highest in late spring or early summer and were associated with periods of runoff following application. Concentrations of diazinon were higher in an urban basin than in two agricultural basins, corresponding to the common use of this insecticide on lawns and gardens in urban areas. Concentrations of atrazine, a corn herbicide widely used in the White River Basin, were higher in an agricultural basin with permeable, well‐drained soils, than in an agricultural basin with less permeable, more poorly drained soils. Although use of butylate and cyanazine was comparable in the White River Basin between 1992 and 1994, concentrations in the White River of butylate, which is incorporated into soil, were substantially less than for cyanazine, which is typically applied to the soil surface. 相似文献
987.
以控制渤海富营养化、减少TN排放量为目的,对渤海TN总量分配进行了研究. 综合考虑污染物总量分配的公平性和效率,采用环境容量、水资源量、人口、耕地面积、GDP和现状排放量6个因子建立了渤海污染物总量分配指数,构建了基于线性响应场的污染物总量分配模型. 考虑到权重系数的影响,分别按全指标、强调水资源利用和强调非点源3类,构建了7种权重系数方案(F11、F12、F13、F14、F21、F31、F32). 结果表明,渤海2010年TN入海量(16.4×104 t/a)是其环境容量(4.7×104 t/a)的3.5倍,同时受污染源位置和分配公平性的影响,接近或超过一半以上的环境容量实际上并不能被充分利用. 采用总体削减率和削减率≥95%的污染源所占比例2个指标,对7种权重方案下的总量分配结果进行了比较. 方案中凡是过分强调单项因子(如环境容量、水资源量、耕地面积等)的TN分配结果均具有明显的不足,只有F13方案兼顾了公平和效率. 综合考虑TN总体削减率和削减率≥95%的污染源所占比例2个指标,建议方案F13为推荐方案,其TN总体削减率为85%,其中前10位的污染源削减量之和可占总削减量的79%. 相似文献
988.
Xiaolu ZHANG Hongwei YANG Xiaofeng WANG Yu ZHAO Xiaomao WANG Yuefeng XIE 《Frontiers of Environmental Science & Engineering》2015,9(6):995-1003
Swimming has become a popular exercising and recreational activity in China but little is known about the disinfection by-products (DBPs) concentration levels in the pools. This study was conducted as a survey of the DBPs in China swimming pools, and to establish the correlations between the DBP concentrations and the pool water quality parameters. A total of 14 public indoor and outdoor pools in Beijing were included in the survey. Results showed that the median concentrations for total trihalomethanes (TTHM), nine haloacetic acids (HAA9), chloral hydrate (CH), four haloacetonitriles (HAN4), 1,1-dichloropropanone, 1,1,1-trichloropropanone and trichloronitromethane were 33.8, 109.1, 30.1, 3.2, 0.3, 0.6 µg∙L−1 and below detection limit, respectively. The TTHM and HAA9 levels were in the same magnitude of that in many regions of the world. The levels of CH and nitrogenous DBPs were greatly higher than and were comparable to that in typical drinking water, respectively. Disinfection by chlorine dioxide or trichloroisocyanuric acid could substantially lower the DBP levels. The outdoor pools had higher TTHM and HAA9 levels, but lower trihaloacetic acids (THAA) levels than the indoor pools. The TTHM and HAA9 concentrations could be moderately correlated with the free chlorine and total chlorine residuals but not with the total organic carbon (TOC) contents. When the DBP concentration levels from other survey studies were also included for statistical analysis, a good correlation could be established between the TTHM levels and the TOC concentration. The influence of chlorine residual on DBP levels could also be significant. 相似文献
989.
通过连续3年对武汉市汉阳城区降雨径流污染的监测研究,考察了降雨径流污染对受纳水体的贡献.结果表明,城市降雨径流向受纳水体输入的污染负荷占有很大的比例,是引起城市水环境质量恶化的主要原因之一.在城市集水区尺度上,3个没有实施截污工程的雨、污合流制集水区降雨径流输出的TSS、COD、TN和TP分别占集水区总污染负荷的59.4%、26.3%、11.2%和10.1%.采取截流措施,控制初期径流污染是合流制城区降雨径流污染控制的关键. 相似文献
990.
SBR法处理垃圾填埋场新鲜渗滤液的实验研究 总被引:1,自引:0,他引:1
采用SBR渐减曝气工艺处理模拟城市生活垃圾填埋场新鲜渗滤液,实验研究了反应器运行条件与出水水质的关系及有机碳的转移规律。研究结果表明新鲜渗滤液经24h曝气处理后,出水COD浓度约为500mg/L,BOD5/COD降为014左右;出水COD浓度与容积负荷无明显相关性;COD去除率与容积负荷呈正比,并在容积负荷为50kgCOD/m3·d时达到最高,约95%;去除的有机碳气相转化率与容积负荷呈正比,在容积负荷为50kgCOD/m3·d时,有机碳气相转化率接近100%;该系统最高容积负荷为50kgCOD/m3·d,相应的污泥浓度(以混合液悬浮性挥发固体(MLVSS)计)为712g/L。 相似文献