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951.
Transport and Diffusion of Ozone in the Nocturnal and Morning Planetary Boundary Layer of the Phoenix Valley 总被引:2,自引:0,他引:2
Lee Sang-Mi Fernando Harindra J.S. Princevac Marko Zajic Dragan Sinesi Michela McCulley Jennifer L. Anderson James 《Environmental Fluid Mechanics》2003,3(4):331-362
The evolution of ozone (O
3) in the nocturnal and morning-transitional planetary boundary layer (PBL) of the Phoenix valley was measured as a part of the `Phoenix Sunrise Experiment 2001' of the U.S. Department of Energy conducted in June 2001. The goal of the field program was to study the transport, distribution and storage of ozone and its precursors in the urban boundary layer over a diurnal cycle. The ground level O
3 as well as mean meteorological variables and turbulence were measured over the entire period, and vertical profiling (using a tethered balloon) was made during the morning transition period. Approximately half of the observational days showed the usual diurnal cycle of high O
3 during the day and low O
3 at night, with nitrogen oxides (NO
x = NO
2 + NO) showing an out of phase relationship with O
3. The rest of the days were signified by an anomalous increase of O
3 in the late evening ( 2200 LST), concomitant with a sudden drop of temperature, an enhancement of wind speed and Reynolds stresses, a positive heat flux and a change of wind direction. NO
x measurements indicated the simultaneous arrival of an `aged' air mass, which was corroborated by the wind predictions of a mesoscale numerical model. In all, the results indicate that the recirculation of O
3 rich air masses is responsible for the said high-O
3 events. Such air masses are produced during the transport of O
3 precursors by the upslope flow toward mountainous suburbs during the day, and they return back to the city at night via downslope winds (i.e. mountain breeze). The corresponding flow patterns, and hence the high-O
3 events, are determined by background meteorological conditions. The vertical profiling of O
3 and flow variables during the morning transition points to a myriad of transport, mixing and chemical processes that determine the fate of tropospheric O
3. How well such processes are incorporated and resolved in predictive O
3 models should determine the accuracy of their predictions. 相似文献
952.
Kenneth H. Pollock William S. Hearn Thomas Polacheck 《Environmental and Ecological Statistics》2002,9(1):57-69
A major objective of analyzing multiple year tag return data in fisheries is to estimate fishing and natural mortality rates which may vary by age class and calendar year. To do this one needs to be able to estimate the reporting rates for the tags recovered. Some fisheries such as that for Southern Bluefin Tuna (Thunnus maccoyii) have multiple components with potentially different reporting rates for the tag returns. In this paper we develop a general model for multi-cohort, multi-year tag return analyses where there are multiple components to the fishery with potentially different reporting rates. We require the assumption that one component has a reporting rate of 100% (i.e., this could be the component of a boat based fishery where scientific observers are present). We show further how it is possible to partition the overall likelihood developed into two conditionally independent components. The first component of the likelihood is the standard multinomial likelihood that allows estimation of fishing and natural mortality rates. It uses the tag return matrix summed over all the components of the fishery. It requires an average reporting rate for the tag returns (where the average reporting rate is a weighted average of the individual reporting rates of the different components). The second component is also multinomial for the individual component tag returns and allows us to estimate individual component reporting rates. However, this requires that we augment our second component tag return likelihood with a catch data likelihood for the corresponding components. The methodology is illustrated on some Southern Bluefin Tuna tagging and catch data. We also discuss important model assumptions and give suggestions for future research including the integration of tag-return and catch at age data analyses. 相似文献
953.
改性天然沸石去除水中氨氮的研究 总被引:22,自引:0,他引:22
分别采用NaCl、KCl和CaCl2对黑龙江省某市天然沸石进行改性,考察了pH值、氨氮初始浓度以及温度对改性沸石交换性能的影响,并对改性沸石的交换动力学进行了研究。结果表明,NaCl和KCl改性对沸石原矿交换容量有不同程度提高,而KCl改性后容量有所降低。pH、NH4初始浓度以及温度对交换性能有明显影响,pH6.0附近沸石交换容量最大;NH4初始浓度越高,反应速度越快,相同初始浓度下,钾型沸石交换速度较快,而沸石原矿交换速度最慢。采用Langmuir型离子交换等温线进行非线性回归的结果显示,低温有利于交换反应的进行。溶液中NH4^+在改性沸石上的离子交换反应可采用Vermeulen模型描述,沸石原矿拟合相关系数较差。改性沸石多次再生后,其交换容量均有所降低。 相似文献
954.
955.
文章从系统论的科学原理出发,分析和探讨内蒙古工业经济发展模式,即线性经济模式和循环经济模式的不同点。同时指出,走循环经济的道路更符合系统科学的原理,是内蒙古地区参与西部大开发建设的需要,也是实现可持续发展的一个非常重要的途径。 相似文献
956.
文章根据石油天然气勘探开发的实际情况,对石油天然气生产、储存、集输过程中的污染防治和生态环境保护进行了深入的研究,提出了相应的法律措施和手段. 相似文献
957.
958.
959.
我国农业自然资源法的问题与改善途径初探 总被引:6,自引:0,他引:6
在介绍我国农业自然资源基本法律体系的基础上,分析了现行法律存在的主要问题,提出了强化农业资源管理的若干建议:①制定农业自然资源综合法律,完善农业自然资源法律体系;②更新充实现行农业自然资源法,以适应社会主义市场经济的要求;③从机制和手段两方面革新管理体制,强化农业自然资源相对统一的综合管理。 相似文献
960.
区域农业可持续发展的生态安全及其评价研究 总被引:91,自引:3,他引:91
资源、生态环境是区域农业可持续发展的核心和基础。农业可持续发展的生态安全是指农业赖以发展的自然资源、生态环境处于一种不受威胁、没有危险的健康、平衡的状态 ,具有战略性、整体性、区域性、层次性和阶段性等特点。文章以浙江省嘉兴市为例 ,讨论了区域农业可持续发展的生态安全评价的基本过程和方法 ,提出了包括资源生态环境压力、质量和保护整治能力三方面23项指标在内的生态安全评价的指标体系 ,以及不安全指标阈值的确定和不安全指数的计算方法 ,提出了区域农业可持续发展的生态安全建设的途径和对策。 相似文献