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61.
四川省卧龙地区土壤中二噁英类化合物和多氯萘的海拔梯度分布及对牦牛的毒性风险评价 总被引:2,自引:1,他引:2
初步研究了四川省卧龙地区5个不同海拔高度的表层土壤和2个牦牛样品中二噁英/呋喃(PCDD/Fs)、共平面多氯联苯(co-PCBs)和多氯萘(PCNs)的分布特征、来源、毒性当量以及生态风险状况.土壤样品中总2,3,7,8-PCDD/Fs的含量范围为2.48-4.30 pg·g-1dw,平均3.50 pg·g-1dw,最高含量在海拔3927 m的塘房.co-PCBs的总含量平均为9.14 pg·g-1dw,最高值在海拔4487 m的垭口.总2,3,7,8-PC-DD/Fs和总co-PCBs含量随海拔高度的变化表现出正相关关系.不同海拔高度土壤中的PCDD/Fs和co-PCBs异构体的分布相似,表明具有相同的来源.总PCNs与海拔梯度呈负相关关系,最高含量出现在海拔3345 m的贝母坪,平均21.4 pg·g-1dw,主要以3.氯为主.土壤中PcDD/Fs毒性当量浓度范围为0.29-0.43pg TEQ·g-1dw.牦牛肉和牦牛组织中PcDD,/Fs总浓度分别为27.5和23.6 pg·g-1脂肪,毒性当量浓度为4.04和4.07 pg TEQ·g-1脂肪.结果表明,牦牛中的PCDD/Fg,co-PcBs和PCNs不大可能对卧龙地区人群导致严重的负面效应. 相似文献
62.
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64.
1994年江淮伏旱及其影响研究 总被引:1,自引:0,他引:1
利用江谁地区18个站点1951~1995年6~8月降水量资料,用Z指数建立了历年夏季旱涝序列,着重对1994年江淮伏旱及其对农业、水资源的影响进行了分析评述,获得了一些有意义的结论。 相似文献
65.
区域分工对区域经济发展具有重要作用。山东地处我国东部沿海,是全国人口大省、经济大省,在全国经济发展格局中占有举足轻重的地位。根据区域分工理论,对山东省在全国和区域内部分工进行了分析,揭示了山东省在全国的区际地位以及所辖17个市之间的区域分工与合作格局,为山东省强化区域分工和联系,提高区域竞争力提供决策依据。 相似文献
66.
Windblown dust is known to impede visibility, deteriorate air quality and modify the radiation budget. Arid and semiarid areas with unpaved and unvegetated land cover are particularly prone to windblown dust, which is often attributed to high particulate matter (PM) pollution in such areas. Yet, windblown dust is poorly represented in existing regulatory air quality models. In a study by the authors on modeling episodic high PM events along the US/Mexico border using the state-of-the-art CMAQ/MM5/SMOKE air quality modeling system [Choi, Y.-J., Hyde, P., Fernando, H.J.S., 2006. Modeling of episodic particulate matter events using a 3D air quality model with fine grid: applications to a pair of cities in the US/Mexico border. Atmospheric Environment 40, 5181–5201], some of the observed PM10 NAAQS exceedances were inferred as due to windblown dust, but the modeling system was incapable of dealing with time-dependent episodic dust entrainment during high wind periods. In this paper, a time-dependent entrainment parameterization for windblown dust is implemented in the CMAQ/MM5/SMOKE modeling system with the hope of improving PM predictions. An approach for realizing windblown dust emission flux for each grid cell over the study domain on an hourly basis, which accounts for the influence of factors such as soil moisture content, atmospheric stability and wind speed, is presented in detail. Comparison of model predictions with observational data taken at a pair of US/Mexico border towns shows a clear improvement of model performance upon implementation of the dust emission flux parameterization. 相似文献
67.
Bolca M Turkyilmaz B Kurucu Y Altinbas U Esetlili MT Gulgun B 《Environmental monitoring and assessment》2007,131(1-3):409-419
Because of their intense vegetation and the fact that they include areas of coastline, deltas situated in the vicinity of big cities are areas of greet attraction for people who wish to get away from in a crowded city. However, deltas, with their fertile soil and unique flora and fauna, need to be protected. In order for the use of such areas to be planned in a sustainable way by local authorities, there is a need for detailed data about these regions. In this study, the changes in land use of the Balçova Delta, which is to the immediate west of Turkey’s third largest city Izmir, from 1957 up to the present day, were investigated. In the study, using aerial photographs taken in 1957, 1976 and 1995 and an IKONOS satellite image from the year 2005, the natural and cultural characteristics of the region and changes in the coastline were determined spatially. Through this study, which aimed to reveal the characteristics of the areas of land already lost as well as the types of land use in the Balçova delta and to determine geographically the remaining areas in need of protection, local authorities were provided with the required data support. Balçova consists of flat and fertile wetland with mainly citrus-fruit orchards and flower-producing green houses. The marsh and lagoon system situated in the coastal areas of the delta provides a habitat for wild life, in particular birds. In the Balçova Delta, which provides feeding and resting for migratory birds, freshwater sources are of vital importance for fauna and flora. The settlement area, which in 1957 was 182 ha, increased 11-fold up to the year 2005 when it reached 2,141 ha. On the other hand, great losses were determined in farming land, olive groves, forest and in the marsh and lagoon system. This unsystematic and rapid urbanization occurring in the study region is not only causing the loss of important agricultural land and wetland, but also lasting water and soil pollution. 相似文献
68.
The need for accurate carbon budgeting, climate change modelling, and sustainable resource management has lead to an increase
in the number of large area forest monitoring programs. Large area forest monitoring programs often utilize field and remotely
sensed data sources. Sampling, via field or photo plots, enables the collection of data with the desired level of categorical
detail in a timely and efficient manner. When sampling, the aim is to collect representative detailed data enabling the statistical
reporting upon the characteristics of larger areas. As a consequence, approaches for investigating how well sample data represent
larger areas (i.e., the sample neighbourhood and the population) are desired. Presented in this communication is a quantitative
approach for assessing the nature of sampled areas in relation to surrounding areas and the overall population of interest.
Classified Landsat data is converted to forest/non-forest categories to provide a consistent and uniform data set over a 130,000 km2 study region in central British Columbia, Canada. From this larger study area 322 2 × 2 km photo plots on a 20 × 20 km systematic
grid are populated with composition and configuration information for comparison to non-sampled areas. Results indicate that
typically, within the study area, the spatial pattern of forest within a photo plot is representative of the forest patterns
found within primary and secondary neighbourhoods and over the entire population of the study. These methods have implications
for understanding the nature of data used in monitoring programs worldwide. The ability to audit photo and field plot information
promotes an increased understanding of the results developed from sampling and provides tools identifying locations of possible
bias. 相似文献
69.
70.
Nutrient transfer functions: the site of integration between feeding behaviour and nutritional physiology 总被引:6,自引:0,他引:6
Summary. We describe and extend a graphical approach to quantitative nutrition that focuses on the interplay between behavioural and
physiological components of nutritional regulation. The site of integration is the nutrient transfer function, which is the
function describing the time course of nutrient transfer between serially connected nutritional compartments (e.g., from the gut to the blood). The relationship between the shape of the nutrient transfer function and the temporal patterns
of feeding determines the values of two key quantitative parameters of nutrition: the rate ('power') and the efficiency of nutrient acquisition. The approach can be extended to consider, in addition to the short-term behavioural and physiological
decisions made by animals, some ecological determinants and longer-term, life history consequences of such decisions. Most
importantly, this category of models can provide insights into the interplay among the various nutrients in an animal's diet.
We illustrate this using hypothetical examples, and also present preliminary data for the power-efficiency relationships of
protein and digestible carbohydrates in locusts. Finally, we consider existing evidence for the various means available to
these and other insects for regulating such relationships.
Received 24 September 1997; accepted 9 December 1997. 相似文献