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961.
本文依据海岸动力地貌学理论与方法,研究了河北省王滩拟建港区的环境条件、泥沙来源、数量与运动特征、泥沙沉积速率及海岸演变趋势,为王滩建港作出了论证,并对港区工程布置提出了建议. 相似文献
962.
刘胤汉 《陕西师范大学学报(自然科学版)》1989,(4)
本文以南洛河上游土地类型与综合自然区划的实践为例,论证了两种自然区划步骤、土地类型是自然区划标形态单位、土地类型结构格局和由土地类型组合自然小区等主要的理论和方法问题. 相似文献
963.
利用历史地理资料和地貌、水文等方面的前人研究成果,针对长江口地区是中国经济最发达的地区之一,它的大部分地区尤其是长江北岸沿海平原的如皋、南通、上海的一部分成陆时间相对较晚,在它们的成陆过程中,河口沙洲起了重要作用,可是河口沙洲的成陆模式还是有许多未解决的、没有达成统一共识的问题做了初步研究.认为:河口地区在发育过程中不仅有河流径流及海洋的水动力因素,而且人类活动等在长江口成陆过程中也发挥了促进或减缓成陆速度的作用.其中人类活动在公元4世纪后的影响变得十分显著. 相似文献
964.
The hourly and daily air quality concentration in the total air pollutant emission amount control zone is not sure to be continuously up to national ambient air quality standard, even though the total annual air pollutant emission is permitted under the total air pollutant emission amount control (TAPEAC) on the basis of A-value method. So the concept of the environmental quality guarantee ratio (EQGR) for TAPEAC is advanced in this paper and its quantitative formula is figured out for both hourly and daily EQGR. It is concluded that the EQGR is related with the yearly arrangement of A-value besides the pollutant type. According to the meteorological data in a lower area along Yangtze River in 2000, the yearly A-value trend is analyzed. Based on the data, the hourly EQGR of SO2 and NO2 is respectively 97.4% and 90.2%, and daily EQGR respectively 90.2% and 79.5%. 相似文献
965.
我国四千多年来在治黄思想方面经历了以疏为主、堵疏并用、以堵为主和综合治理的阶段。在治河空间上,经历了由单一的下游防洪治理到上、中、下游通盘规划的全流域治理,特别是建国50多年来,在整个黄河流域的治理中体现了治理、开发、利用与保护相结合的系统论思想。 相似文献
966.
LU JianXia WANG YaWei ZHANG QingHua GAO ErLe JIANG GuiBint 《科学通报(英文版)》2007,52(10):1320-1326
Concentrations of polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs) and heavy metals in two sediment cores, taken from the Dagu Drainage River, were determined. The contamination trends of these three kinds of compounds were obtained. The results showed that concentrations of PBDEs increased in recent years; there were new contamination sources for OCPs in this area; contamination levels of heavy metals had no significant change in the last several years. Comparing the results of these two cores, erosion and dilution of seawater had different effects on the transportation of these compounds. 相似文献
967.
Daily variation of carbon flux in soils of Populus euphratica forests in the middle and lower reaches of the Tarim River 总被引:1,自引:0,他引:1
In order to lucubrate the daily variation of respiration in soils of Populus euphratica forests and analyze its relationship with environmental factors in the middle and lower reaches of the Tarim River, the LI-8100 instrument of soil CO2 flux system was used to measure the parameters of soil carbon flux and air temperature 10 cm above ground surface along the profiles of Usyman, Archy River, Yengisu and Karday, and the relationships between the soil carbon flux and the soil moisture content were analyzed. The nonlinear regression analysis was carried out with the software SPSS13.0. We observed that: (1) soil respiration began to be restrained when the air temperature was up to 30℃ 10 cm above the ground surface; (2) the rates of soil respiration under the forests of Populus euphratica were significantly different at various moisture contents, the soil carbon flux was high along the Usyman profile,which has a high soil moisture content, and it was low along the profiles of Archy River, Yengisu and Karday, which has a low soil moisture content; (3) the exponential model can be used to explain the relationship between soil respiration and air temperature 10 cm above the ground surface. The average Q10 values along the profiles of Usyman, Archy River, Yengisu and Karday are 0.61, 0.16, 0.22 and 0.35 respectively, much lower than the average of the world; (4) there is a positive correlation between the soil carbon flux and the soil moisture content 相似文献
968.
通过1996-2000年对辽河中下游流域地表水体25个断面的连续监测,采用“分布重心”模型,研究了地表水体中藻类、底栖动物和微生物分布的空间演化特征。结果表明,辽河中下游地表水体尤其是浑河河水的生物污染较为严重;藻类和细菌分布中心的位置均有向西北方向发生迁移的趋势,大肠杆菌分布中心的位置有向西南方向迁移的趋势,底栖动物的分布中心的位置有向东北发生迁移的趋势,同时,总体平均分布中心的位置有向西北方向迁移的趋势。以1999年为例,通过与林地、耕地、化肥、日照、气温、降雨、径流等生态水文因子的相关分析,结果表明,辽河中下游流域地表水体中藻类、底栖动物和微生物的空间分布特征与流域生态水文格局有较好的响应关系。 相似文献
969.
本文针对 90年代以来黄河断流的严重态势 ,具体分析了黄河断流的特点 ,对造成黄河断流的成因进行了分析 ,最后指出了如何缓解黄河断流的对策 相似文献
970.
Significant relationship between spring AO and the summer rainfall along the Yangtze River 总被引:7,自引:0,他引:7
The influence of spring AO on the summer rainfall along the Yangtze River is investigated. The long-term rainfall observations are filtered to remove the low-frequency variations longer than 10 years. The inter-annual components show a high correlation to AO in the last hundred years. The strongest correlation appears for May AO and summer rainfall with a value of -0.39, significant above the 99% confidence level. Associated with one standard deviation stronger May AO index, the rainfall over the Yangtze River to the southern Japan decreases by about 3%-9%, while, at the same time increases by about 3%-6% in the northern China and far-eastern Russia. The coherent changes in rainfall are significantly related to the East Asian summer jet stream in the upper troposphere. When there is stronger AO in spring, the jet stream tends to move polarward in summer, and leads the rainfall-belt to move northward too. That gives rise to a drier condition in the Yangtze River valley, wetter anomalies in northern China. This signal would be helpful for the summer rainfall prediction in China. 相似文献