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261.
262.
We estimate the response of chl-a (mg · m–3) to changes in concentrations of total phosphorus (TP) by calculating the slopeS = chl-a/TP in chl-a =f(TP) graphs. Results show that in years where algae are P-limited oligotrophic lakes respond less (median slope 0.21) to changes in nutrient concentrations than eutrophic lakes, (median slope 0.31) and these again less than hypereutrophic lakes, (median slope 1.02). We find no saturation value for the slope within the TP range considered (6–480 mg · m–3). Chl-a in eutrophic lakes responds more frequently to non-nutrient factors than oligotrophic and hypereutrophic lakes. Results obtained by replacing TP with a new nutrient parameter, TP = 0.056 · TP · IN0.226, in which inorganic nitrogen, IN, is factored in, suggest that nitrogen has an influence on chl-a in oligotrophic lakes. Blue-green algae respond less to changes in TP than other algal species, e.g., diatoms. 相似文献
263.
本文通过环境背景值、风化壳地球化学、对流层(大气气溶胶)地球化学和人为地球化学异常,初步探讨了南极长城站地区的现代环境地球化学特征。分析表明:环境要素固有的地球化学性质、区域环境条件和自然环境演变之间具有深刻的内在联系。 相似文献
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266.
采用SPSS软件,对2003年01月至2004年12月期间,倒天河水库和利民水库逐月水质监测数据进行数理统计分析,结果表明毕节市饮用水水质污染有较明显的季节变化和空间差异;且不同污染物对水体污染的贡献率各不相同,总磷和粪大肠菌群所占份额最大,方差累积贡献率达77%。在此基础上,利用加权综合污染指数对水体水质污染现状进行综合评价,结果显示倒天河水库和利民水库,水质污染总体较轻.饮用水水质符合《地表水环境质量标准(GB3838—2002)》中Ⅲ类水质标准;最后提出加大水环境保护的建议。 相似文献
267.
大气环境质量综合评价是一个城市环境质量考核的重要指标,改进的密切值法是其中一种切实可行的评价方法。通过对1991-2000年10年间广东省三大城市——广州、深圳和珠海的大气环境质量进行综合评价,发现20世纪末,大气环境质量最好的是珠海市,最差的是广州市。与广东省平均水平相比、三大城市中。广州市污染程度高于全省平均水平。从空气环境质量的变化趋势来看,自1997年开始,三大城市大气环境质量趋于好转,为新世纪城市空气环境质量改善提供了良好的基础。 相似文献
268.
This paper reviews the data concerning the fracture network and the hydraulic characteristics of faults in an active zone of the Gulf of Corinth. Pressure gap measured through fault planes shows that in this area the active normal faults (Aigion, Helike) act, at least temporarily and locally, as transversal seal. The analysis of the carbonate cements in the fractures on both the hangingwall and the footwall of the faults also suggests that they have acted as local seals during the whole fault zone evolution. However, the pressure and the characteristics of the water samples measured in the wells indicate that meteoric water circulates from the highest part of the relief to the coast, which means it goes through the fault zones. Field quantitative analysis and core studies from the AIG-10 well have been performed to define both regional and fault-related fracture networks. Then laboratory thin section observations have been done to recognize the different fault rocks characterizing the fault zone components. These two kinds of approach give information on the permeability characteristics of the fault zone. To synthesize the data, a schematic conceptual 3D fluid flow modeling has been performed taking into account fault zone permeability architecture, sedimentation, fluid flow, fault vertical offset and meteoric water influx, as well as compaction water flow. This modeling allows us to fit all the data with a model where the fault segments act as a seal whereas the relays between these segments allow for the regional flow from the Peloponnese topographic highs to the coast. 相似文献
269.
Shuyun XIE Zhengyu BAO Bing LI 《中国地球化学学报》2006,25(B08):7-8
Three kinds of spatial analysis methods (geostatistics, concentration-area fractal model and the multifractal analysis called the moment method) were used for almost 50 elements, including heavy metals, disperse elements, rare elements and even others, in 6586 top soil (0-20 cm) samples and 1833 deep soil (150-200 cm) samples from Chengdu metropolitan area of 12400 km^2, southwestern China. The ranges of spatial correlation revealed by variograms are quite different for different kinds of elements in the top and deep soils. The most interest is the fact that the multifractal spectra of environmentally important elements such as Pb, Cr, Cd and Ni in top soils in the metropolitan area show systematic change from those in the deep soils, revealing a strong anthropogenic addition, while Hg, Zn, As, Cu and all common elements show no such kind of addition. In terms of multifractal properties based on the multifractal spectrum curves, those disperse and rare elements show great deviation from other major and trace elements, which is also of great interest. 相似文献
270.
Norboo Tsering 《中国地球化学学报》2006,25(B08):69-69
Background: Radiographic signs of Pneumoconiosis found in farming Ladakhi despite absences of mines and industries were believed to be due to exposure to frequent dust storms and domestic fire pollutions. Seasonal Koilonychia (spoon nail) occurring predominantly in farming women in absences of iron deficiency anaemia was thought to arise from exposure to water made alkaline by weathering of hornblende minerals. The relation of these health conditions to environmental geohydrochemistry is postulated as the source of irrigation water in the affected population originates from glaciers in trans-Himalaya range of sedimentary geology and steep landscape favouring flushing of silica/silicate containing silts. Methods and results: Survey in two central Ladakh villages revealed radiographic evidence of silicosis in all middle aged women and half in middle aged men. In a large-scale study of 3105 subjects aged over 30 years from three villages; 101 (22.5%) of the 449 radiographed showed signs of pneumoconiosis (ILO 1980 criteria) including eggshell calcification of hilar gland and progressive massive fibrosis. Indoor dust analyzed using Philips 400T electron microscope with energy dispersive analysis system attached showed SiO2 levels upto 53.27% with particle size of 0.5 to 5.0 microns and the concentration during cooking period in the worst affected area was 7.495 mg/m^3. Microscopy and histopathology from the subject was characteristic of pneumoconiosis. Analysis of the inorganic dust in the lung showed 40.2% muscovite, 37.3% quartz with the extracted dust wt 147.9 mg/gm of dry tissue. Prevalence of chronic cough with chronic phlegm and percentage of villagers with FEV1/FVC ratio of less than 65% rose with age. Of 70 subjects studied 19 women and 2 men had Koilonychia with incidence being highest in summer. Absence of seasonal Koilonychia in villages fed by water derived from northern mountain range glaciers with mainly igneous geology supports our hypothesis. 相似文献