成都市土壤天然放射性核素的外照射水平估算研究

利用IED22000A便携式微机多道能谱仪对成都市区土壤的天然放射性核素进行了直接就地测量,估算出天然环境放射性核素^238U、^232Th、^40K的比活度范围分别为10.37～77．19Bq／kg、17,85～225．74Bq／kg、284．83～892．67Bq／kg;外照射指数范围为0．16—0．8;离地面1m高的空气吸收剂量率均值为83．23nGy／h;1外照射年有效剂量当量为0．34～0．70mSv;等效镭浓度的变化范围是59．06-386．45Bq／kg,均值为164．15Bq／kg。各项指标均在容许范围之内,因而成都市属于外照射水平的安全区域,人居环境不受影响。     

建设项目竣工环境保护验收监测应注意的问题

针对建设项目竣工环境保护验收监测中存在的问题,阐述了工况控制、总量监测、环境相容性等环节的技术要求和注意事项,并就与之相关的公众参与、监测人员的素质等问题展开了讨论。     

Experimental Study of the Criteria of Flow Laminarization in Two-Dimensional Dense Gas Plumes

Laminarization of flow in a two-dimensional dense gas plume was experimentally investigated in this study. The plume was created by releasing CO₂ through a ground-level line source into a simulated turbulent boundary layer over an aerodynamically rough surface in a meteorological wind tunnel. The bulk Richardson number (Ri_*), based on negative plume buoyancy, plume thickness, and friction velocity, was varied over a wide range so that the effects of stable stratification on plume laminarization could be observed. A variety of ambient wind speeds as well as three different sizes of roughness arrays were used so that possible effects of roughness Reynolds number (Re_*) on plume laminarization could also be identified. Both flow visualization methods and quantitative measurements of velocity and intermittency of turbulence were used to provide quantitative assessments of plume laminarization.Flow visualization provided an overall picture of how the plume was affected by the negative buoyancy. With increasing Ri_*, both the plume depth and the vertical mixing were significantly suppressed, while upstream propagation of the plume from the source was enhanced. The most important feature of the flow revealed by visualization was the laminarization of flow in the lower part of the plume, which appeared to be closely related to both Ri_* and Re_*.Measurements within the simulated dense gas plumes revealed the influence of the stable stratification on mean velocity and turbulence intensity profiles. Both the mean velocity and turbulence intensity were significantly reduced near the surface; and these reductions systematically depended on Ri_*. The roughness Reynolds number also had considerable influence on the mean flow and turbulence structure of the dense gas plumes.An intermittency analysis technique was developed and applied to the digitized instantaneous velocity signals. It not only confirmed the general flow picture within the dense plume indicated by the flow visualization, but also clearly demonstrated the changes of flow regime with variations in Ri_* and Re_*. Most importantly, based on this intermittency analysis, simple criteria for characterizing different flow regimes are formulated; these may be useful in predicting when plume laminarization might occur.     

湖南林业科技成果市场化的思考

林业科技成果转化为现实生产力,须通过一系列的中介才能发挥作用,尤其是在社会主义市场经济条件下,其中介更主要地表现为市场.如何使湖南林业科技成果市场化,作者认为:加强湖南林业科技推广是实现湖南林业科技成果市场化的重要环节.     

新世纪如何加强思想道德建设的几点思考

如何加强思想道德建设,文章认为应确立新的道德价值观、继承发扬传统道德精华,准确把握新时期的道德原则、道德建设的基本结构与目标,同时切实抓好思想道德教育,实行综合治理.     

江西农田鼠害及其防治措施

农田鼠害是江西农业生物灾害中的主要灾种之一,它具有发生面积之、造成损失重、灾情越来越严重的特点,本文在回顾了江西农田鼠发生概况的基础上,简述了农田害鼠的种类、分布、主要特征及其发生发展规律,并从自然因素和人为因素等方面分析了鼠害成灾的主要原因,最后,提出了农田鼠害的防治措施。     

废旧电池资源化、无害化

对当前国内外在废旧电池的处理处置方面进行了综合性论述,对废旧电池的危害及当前应采取的对策进行分析。     

垂直面绿化植物遮阳系数与叶面积指数研究

比较、分析了农业研究中提出的叶面积指数LAI与用于建筑节能领域的垂直面绿化植物叶片遮阳系数SCPVW两个概念的异同和各自的应用范围。指出城市绿化采用水平或垂直绿化方式时,由于下垫面差异,植物叶片的遮阳系数应当分别采用LAI和SCPVW进行计算。     

中国自然保护区可持续管理模式探讨——伦敦自然保护区管理模式借鉴

近年来,世界各地自然保护区迅速发展,如何有效持续地管理这些自然保护区成为一个重要的问题。文章分析了我国自然保护区现有管理模式的特点与存在的问题,简要介绍了伦敦自然保护区的管理模式现状,根据我国的实际情况,笔者认为中国的自然保护区应采用强制式和完全参与合作式相结合的管理模式,并提出了几点管理模式的改革建议。     

城郊土壤共存元素对土壤作物系统Cd、Pb迁移的影响分析——以白银市城郊区为例

通过共存元素对土壤小麦系统Cd、Pb行为影响的调查研究发现：大田条件下共存元素以正对数模式与根系Cd、Pb密切相关,同种元素间相关程度最高;根系Cd、Pb积累主要取决于土壤环境Cd、Pb的含量,共存元素也产生一定的影响,认为要防止重金属通过食物链对人类的危害,就必须降低土壤环境中重金属的总量。