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191.
Little is known about the concentrations, deposition rates, and effects of nitrogenous and sulfurous compounds in photochemical smog in the San Bernardino National Forest (SBNF) in southern California. Dry deposition of NO(3)(-) and NH(4)(+) to foliage of ponderosa pine (Pinus ponderosa Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf.) was correlated (R = 0.83-0.88) with historical average hourly O(3) concentations at 10 sites across an O(3) gradient in the SBNF. Mean deposition fluxes of NO(3)(-) to ponderosa and Jeffrey pine branches were 0.82 nmol M(-2)s(-1) at Camp Paivika (CP), a high-pollution site, and 0.19 nmol m(-2) s(-1) at Camp Osceola (CAO), a low-pollution site. Deposition fluxes of NH(4)(+) were 0.32 nmol m(-2) s(-1) at CP and 0.17 nmol m(-2) s(-1) at CAO, while mean values for SO(4)(2-) were 0.03 at CP and 0.02 nmol m(-2) s(-1) at CAO. Deposition fluxes to paper and nylon filters were higher in most cases than fluxes to pine branches at the same site. The results of this study suggest that an atmospheric concentration and deposition gradient of N and S compounds occurs along with the west-east O(3) gradient in the SBNF. Annual stand-level dry deposition rates for S and N at CP and CAO were estimated. Further studies are needed to determine if high N deposition loads in the SBNF significantly affect plant/soil nutrient relations, tree health, and the response of ponderosa pine to ozone. 相似文献
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The exploration of offshore areas for hydrocarbons has involved new technical and economic considerations and has posed new problems, not the least of which has been the changing relationship between companies and governments. In this article, the authors present an analysis of the different perspectives and policies which emanate from national governments on the one hand and from transnational oil companies on the other. The issues examined include the considerations involved in establishing exploration legislation, post-discovery problems, the impact on revenues of increased production, the interests of companies in developing fields and the overall economic environment within which decisions have to be agreed. 相似文献
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Various suggested definitions of the term “traceability” are discussed from the standpoint of proposed adoption and use of the concept by the International Organization of Legal Metrology. 相似文献
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Deposition velocities have been determined for corn and soybeans in the first 4–6 weeks of growth in a full-scale study of canopy flow in a wind tunnel. Particles of 1, 5, 10 and 15 μm aerodynamic diameter made of sodium florescein were injected into the Environmental Wind Tunnel Facility at Colorado State University. Deposition velocities were determined as a function of free stream velocity (183, 305 and 610 cm/s) and approach flow turbulence intensity (~1% and 8%). Plants were arranged in realistic field configurations. Hot-wire anemometer studies confirmed that the fluid velocity profiles developed in the wind tunnel were similar to the flow realized in canopies in natural fields. An increase in velocity and turbulence intensity was found to decrease the deposition velocities. A minimum deposition velocity was observed at a particle diameter of 5 μm. 相似文献
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To some degree it is unfair to evaluate a post-disaster housing program as to its effectiveness in decreasing vulnerability and preventing future disasters. As Burton states, "With rare exceptions, administrators and techniques have been trained to cope with disaster rather than to prevent it" [reference (2), p.197]. These were certainly not goals articulated by the agency responsible for constructing housing after Fifi. However, the authors feel that failure to evaluate specific projects by persons knowledgeable of the projects functioning, will only forestall the shift which Cuny calls for, "… from disaster response to disaster mitigation and prevention" [reference (4), p.123). In doing this we hope to add some specific case study data to the growing literature on disaster mitigation and prevention. Disaster vulnerability in Honduras is overwhelmingly related to flooding. More crucial than the materials and construction of housing is the issue of siting. If appropriately sited, houses made of bajarique, wood, or concrete block are able to withstand the heavy rains associated with a hurricane. Regarding the siting of the projects, the Honduras Project clearly has one positive and one negative accomplishment in the cases of Santa Rica and Flores, respectively. San Jose is less clear but is certainly a much safer site than those formerly occupied by the residents, in that there is no danger of flooding. The present site was not flooded during Fifi nor did it experience mudslides. However, the future is not so clear regarding the latter. Within the village proper a large amount of vegetation has been added which will tend to stabilise the soil on the steeper slopes. The streets, however, are seriously eroded and probably can not be maintained for vehicle usage, which does not pose a serious problem to the residents as none possess automobiles or trucks. One large gully bisects the village and receives run-off from the adjacent hills. It has been expanding, which would suggest that the slopes above the village could prove problematic in case of a Fifi-sized storm. Flores is located on a very poor site in reference to prevention and mitigation. It is located in a portion of the Sula Valley which is prone to flooding and, as mentioned before, was inundated by over 2m of water during hurricane Fifi. No prevention techniques were possible by NAEA/HEA and the houses were built on earthen mounds barely adequate to keep water out during the rainy season. The nearby dike which could possibly provide protection is non-functional due to poor maintainance. Given a storm of Fifi's magnitude, or possibly smaller, this site will again be flooded. Santa Rica is clearly well sited concerning flooding: it did not experience flooding during Fifi and is not flood prone. However, houses did experience some wall damage due to earthquakes following and associated with the Guatemalan quake of 1976. Due to the size and nature of the latter much "re-adjustment" occurred in the neighbouring fault system; however, damage to the houses was all superficial. We feel the residents were vocal about their concern due to the severity of the Guatemalan disaster and their lack of experience with concrete block houses. That the two sites (particularly Flores and partially San Jose) are vulnerable to future disasters cannot be considered solely the fault of an outside agency without local knowledge and understanding. In the engineering report issued during the construction it was explicitly stated that in Flores, "Future flooding remains a danger," [reference (6), p.49]. The future residents of Flores had gained access to the land from the National Agrarian Institute and were anxious to receive assistance in building homes. In fact, CARE, which had previously given these people tin roofing for houses, was threatening to take it back since the people had not yet started building. NAEA/HEA were responding to people in a rather desperate situation. But, on the other hand, they were responding to people who had been promised (not given) land by an agency of the Honduran national government which would be cognizant of the potential flooding at this site. Likewise, in San Jose, where mudslides and erosion remain a threat, the land was provided by a local government agency, the municipality. Although our goal in this discussion has not been to establish blame, we feel it imperative to mention the sequence of events that resulted in the questionable siting of Flores and San Jose. It is very easy and often accurate to place blame on outsiders who lack sophistication and knowledge about such matters. In this case local input did not result in post-disaster planning that is actually precautionary. This, we feel, illustrates the extreme complexity of cross-cultural aid, especially in the post-disaster period. It also points to the need for precautionary planning with reference to permanent post-disaster reconstruction. 相似文献
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说明:本次排名是综合美国的100家安防界企业而制作的,这些企业中的多数都是从事产品销售、安装及监控服务的,也有少数企业仅仅提供监控服务。由于篇幅有限,仅选取其中前25名的排名公司列表。 总体来说2002年是风平浪静的一年,各大企业的收入状况并没有大起大落的现象,对应的企业排名也没有太大的变化。今年排行榜的特点可以概括为一个字,那就是“稳”。从文中所附的图表可以看出,2002年排名Top 10的公司本年度都在前11名之内。 相似文献