The distribution characteristics of pollutants released at different cross-sectional positions of a river

The distribution characteristics of heavier or lighter pollutants released at different cross-sectional positions of a wide river is investigated with a well-tested three-dimensional numerical model of gravity flows based on Reynolds-Averaged Navier-Stokes equations and turbulence k-? model. By focusing on investigating the influences of flow and buoyancy on pollutants, it is found that while carrying by the river flow downstream: i) a heavier pollutant released from the cross-sectional side position, forms transverse oscillation between two banks with decreased amplitude, i.e. forms kind of helical flow pattern along the straight part of channel bed; ii) a heavier pollutant released from the cross-sectional middle position, forms collapse oscillation in the middle of the straight channel part with reduced amplitude; iii) in the downstream sinuous channel, heavier pollutant is of higher concentration on the outer side of channel bends; iv) a light pollutant released from the cross-sectional side position, slips partly to the other side of the river, resulting in higher concentrations on two sides of the channel top; v) a light pollutant released from the cross-sectional middle position, splits into two parts symmetrically along two sides of the channel top; vi) in the downstream sinuous channel, light pollutant presents higher concentration on the inner side of channel bends. These findings may assist in cost-effective scientific countermeasures to be taken for accidental or planned pollutant releases into a river.     

Evaluation of the Trend of Air Quality in Taipei, Taiwan from 1994 to 2003

The data collected from the five air quality monitoring stations established by the Taiwan Environmental Protection Administration (TEPA) in Taipei City were analyzed to assess the changes in air quality. The analyses reveal that the air quality in Taipei City improved over the last decade from 1994 to 2003, as evidenced by the significant downward trends of the various primary air pollutant concentrations, such as CO, NO_X, SO₂, and PM₁₀. An air pollution fee was collected by TEPA in 1995, and several air pollution control measures were likewise taken to improve the air quality in Taiwan. However, although the extreme daily maximum O₃ concentrations occurred more frequently in earlier years and showed a downward trend, its moderately high concentrations increased annually in recent years. It implied that after the reduction of various primary pollutant concentrations, the effective reduction of O₃ pollution still remains an important issue.     

云微物理特性及云滴有效半径参数化:一次降水层状云的飞机观测资料结果

全球及区域气候模式中云滴有效半径的参数化对于理解云的辐射效应特别是气溶胶间接效应是非常重要的。本文利用延安地区(位于中国西北地区)一次降水层状云的飞机观测资料,首先给出该次过程的云微物理特性包括云滴数浓度(Nc),云水含量(Qc),云滴的半径(Rm),体积半径(Rv),以及有效半径(Re),云滴谱离散度(ε)以及Re/Rv比值因子β;并指出云滴谱离散度ε与云滴数浓度Nc有着很好的递减关系式,所对应的关系式可以表述为ε=0.579-7.42×10-4Nc+4.2×10-7Nc2。进一步,发现云滴尺度谱采用Lognormal分布函数,Gamma分布函数以及Weibull分布函数所参数化的云滴有效半径与观测结果较为一致。值得指出的是,基于Lognormal分布函数的参数化能够更好地描述云滴有效半径。该云滴有效半径的参数化结果将会加强对于气溶胶在中国西北地区间接辐射强迫的认识。     

上海市“十一五”COD总量控制核查方法探讨

通过对上海市水环境主要污染物总量的分析,从政府管理角度,探讨“十一五”上海市水环境主要污染物总量控制核查方法。主要从污水收集管网建设和污水处理厂建设及运行、重点污染源监管、水环境质量改善三方面入手,通过计划申报、日常监控、实时预警来保证总量控制目标完成,并探讨了核查职责体系和信息发布程序及内容。     

地形对日本福岛核事故放射性粒子扩散影响的敏感性研究

利用FLEXPART-WRF粒子扩散模式和Stohl等给出的福岛核事故137Cs排放数据,对日本福岛核事故放射性粒子扩散情况进行了数值模拟和有、无地形的敏感性试验;同时假定核污染物排放源位于日本高崎市的RN38站(36.3°N、139.1°E),对向东开口的V型特殊地形进行了敏感性试验. 福岛核事故数值模拟结果表明:放射性污染物的扩散路径、范围和强度既与天气形势有关,还与地形密切相关,不同天气或不同盛行风向条件下,地形的绕流和抬升作用对核污染物扩散输送态势的影响具有明显差异;在偏东气流影响下,由于地形作用,相比无地形时核污染物扩散偏西1个经度左右,偏高约0.5km. V型特殊地形敏感性试验结果表明:在合适的环流形势下(边界层为偏东风,中、高层为偏西风),由于V型地形的阻挡作用,可形成强烈上升运动区,核污染物主要向上、向东扩散输送,向上可扩散至3.0km以上,向东可扩散至145°E左右;而无地形时核污染物向上、向东影响范围减小,向东扩散至140°E,向上扩散至1.5km,但由于无地形阻挡和偏东风影响,向西扩散范围有所增加. 讨论了天气和地形条件对核电站选址的影响,不同天气形势下地形对核污染物扩散的影响并不相同,因此核电站选址应首先考虑选址地的大气环流背景和常见的天气系统,在此基础上再考虑地形的影响.      

河流污染物通量估算方法分析(Ⅰ)——时段通量估算方法比较分析

通过对河流时段通量所采用的估算方法的误差比较分析,说明了实测河流断面时段通量中时间平均离散通量的贡献;并讨论了污染源的点源、非点源类型的差别对选择年通量估算方法的影响.通过实例探讨了河流长时间通量估算方法的使用范围,对估算方法的取舍原则进行了分析.      

苏州河纵向离散系数的分析研究

通过对苏州河水文水质资料的分析，并进行了水槽因子影响试验、非定常潮汐水流的模拟试验以及环境水力学理论分析和相似律推算，得到了比较符合实际的纵向离散系数取值范围：苏州河为单向流时K≈（5－35）m^2/s；苏州河在潮流往复作用下，k=(2-12)m^2/s。运用水质数学模型和苏州河实测的水文水质同步资料对纵向离散系数进行了验证。     

西北某粘土矿水动力弥散系数的室内测定

使用室内水平土柱吸渗法测试了西北某粘土矿水动力弥散系数,根据测定的土壤中含水量动态数据,计算了非饱和粘土的水动力弥散系数,并建立了该土壤水动力弥散系数与质量含水率之间的关系。该方法物理概念清楚,计算公式简单实用。     

海岸线熏烟扩散模式中岸距与烟囱有效高度关系的研究

在海岸线熏烟扩散模式中,Lc、He与hf的值及其相互关系是决定海岸线熏烟是否发生及其严重程度的主要参数.任意处的hf是由自然状况决定的,而Le和He的值是由人为确定的.本文在深入分析海岸线熏烟的发生原理、过程及模式的基础上,确定了在其他条件相同时,不同Le处,Cfm所对应的He的值,以及Le与He之间的关系式及其危险值,为沿海或沿大型湖泊等水体附近的工业项目的Lc及He的选取及合理性检验提供了依据.     

三峡工程建筑废水排放对长江水质影响的模拟

对三峡工程建筑污水和受纳此污水的长江进行了水质监测 ,模拟计算了其浓度分布范围 ,对数值模型进行了校核 ,并在此基础上对最不利情况进行了预测。在长江划出了受纳其废水的混合区域 ,对混凝土骨料加工生产废水排放标准的制定具有参考价值。