Upwelling and river runoff as sources of dissolved nitrous oxide to the Alsea estuary,Oregon     

Marie A. de Angelis  Louis I. Gordon 《Estuarine, Coastal and Shelf Science》1985,20(4):375-386

Surface waters of Alsea Bay, an unpolluted estuary on the Oregon coast, were analysed for nitrous oxide, nitrate and nitrite on a weekly or biweekly basis during the summer of 1979. The estuary was found to be a variable source of N₂O to the atmosphere. Large and rapid increases in the concentrations of N₂O, NO₃^?, and NO₂^? occurred at the beginning of the sampling period and are attributed to the influx of nutrient-rich upwelling water into the estuary with the tide. The subsequent decline in concentrations of nitrate, nitrite and nitrous oxide over the remainder of the summer is attributed to a decrease in upwelling intensity, a decline in nitrification rates and to assimilatory nitrate reduction. Measurements of nitrous oxide at six stations along the Alsea River were also made in September and October before and after the onset of the rainy season. Samples taken after flood conditions were established were systematically 50% higher than pre-flood samples. The data suggest that soil runoff results in elevated concentrations of N₂O in rivers.  相似文献   

基于Windows消息机制的人机交互的研究与应用   总被引：1，自引：0，他引：1  

廖俊平  马永强  段国兵 《成都信息工程学院学报》2004,19(1):36-39

结合实例着重介绍了如何通过串行通讯利用Windows的消息机制来解决目前工业设备控制中人机交互的模拟问题,并对这两种技术进行了详细的论述.  相似文献   

Statistical analysis of surface hydrography and circulation variations in northern South China Sea     

吴玲娟  崔茂常 《中国海洋湖沼学报》2005,23(4):383-392

1 INTRODUCTIONThe South China Sea (SCS) is a semi-enclosedmarginal sea in western North Pacific Ocean withvery complex topography and is the important pas-sage connecting the Pacific and Indian Oceans. Ithas great impact to the global climate and a greatinterest of many oceanography researchers. Twodominant surface hydrographic and circulation fea-tures in the northern SCS are a strong fresh waterexpansion and a warm and high-salinity seawaterintrusion such as the SCS Diluted Water…  相似文献   

Study on numerical simulation to water lowering in an open coal mine digging     

Yanjun ZHANG Fenglong ZHANG Full QI Fuquan NI 《东北亚地学研究》2006,9(2):199-203

In view of the situation of excavation of open coal mine for the underground water disaster,we should carry out simulation studies for the numerical value of the water lowering project and improve the accuracy and the level of the water lowering project.On the basis of the hydrological geological conditions of certain open mine digging,a more reasonable seepage numerical model was built according to MODFLOW.It was simulated in advance that the process of the confined water level descending with the time,and combining with the actual observations to test the correctness of the model.The calculation showed that the results coincided well with the results of actual measurement.Based on this,different water lowering numerical simulations were built for the open coal mine digging.It could be simulated and forecast that the changes of the groundwater level in drainage process within and outside the mine pit,and it was quantitatively assessed that the possible water lowering result of the opencast water drainage process,which provide an important basis for the actual water lowering project and the possible project disposal.  相似文献   

On salinity regimes and the vertical structure of residual flows in narrow tidal estuaries     

D. Prandle 《Estuarine, Coastal and Shelf Science》1985,20(5):615-635

An examination is made of the circulation in narrow estuaries subject to a predominant tidal forcing. Velocity structures are derived separately for residual flow components associated with (a) river flow, (b) wind stress, (c) a well-mixed longitudinal density gradient and (d) a fully stratified saline wedge. Dimensionless parameters are introduced to indicate the magnitude of each component and these parameters are evaluated for 9 major estuaries, thereby revealing their sensitivity to each component.For a channel of constant breadth and depth, formulae are deduced for the length of saline intrusion, L. Comparisons with observed data show that such formulae may be used with confidence to predict changes in L arising from variations in river flow, tidal range or channel depths.The level of stratification is shown to be related to a product of two parameters, one associated with velocity structure and a second involving the square of the ‘flow ratio’ $\text{u}\text{u}\text{?}$ (i.e. residual velocity/amplitude of the tidal velocity). This relationship provides a simple classification system for estuarine stratification which can be used to indicate the sensitivity of any particular estuary to changing conditions.  相似文献   

Simulating methane emission from a Chinese rice field as influenced by fertilizer and water level     

Z. Yu  X. Shangguan  D. Pollard  E. J. Barron 《水文研究》2003,17(17):3485-3501

Natural and agricultural wetlands are considered to be the major sources of global atmospheric methane (CH₄). A one‐dimensional model was developed to simulate methane emission and used to examine the influence of various physical processes on the rate of methane emission. Three processes involved in the methane emission are implemented in the model: production, reoxidation and transport. Three transport pathways were considered: diffusion across water–air or soil–air interfaces, ebullition and diffusion through plants. These pathways are influenced by soil properties, plant growth, water‐table conditions, temperature and external inputs (e.g. fertilizer). The model was used to examine the seasonal variation of the methane emission at a rice field in Hunan, China, which was observed during a field experiment for consecutive (early and late) rice seasons in 1992. The observed seasonal variations of methane emission, and role of plants in transporting methane to the atmosphere, are captured by the model simulation. Further model applications were conducted to simulate effects of fertilizer and water‐level condition on the methane emission. The results indicate that unfermented organic fertilizer produces a higher methane emission rate than mineral fertilizer. The simulations with treatments of a deep‐water covering and constant moisture reduced the methane emission. The rice field study provides a framework for further development of the model towards simulations based on spatially distributed variables (e.g. water table, soil temperature and vegetation) at a regional scale. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

美国的地下空间开发和利用     

康宁 《浙江国土资源》2001,17(1):67-72

通过对美国地下空间开发利用的考察,认为有如下特点,第一,结合城市建设,构筑地下铁道,第二立足于战略,建立水下通路,第三,地下空间的开发利用平战结合.这些方法对我国的地下空间开发利用值得借鉴.  相似文献   

济南市地下水资源现状分析及开发利用建议          下载免费PDF全文

段秀铭  林常平  靳丰山 《山东国土资源》2001,17(1):40-45

本文采用较新的统计资料,对济南市地下水资源的开发利用现状及开采潜力,以行政区划为单元进行了分析论证.针对地下水资源开发利用中存在的环境水文地质问题,提出了开发利用规划和建议.  相似文献   

IMPACTS OF FUTURE SEA LEVEL RISE ON SALT WATER INTRUSION IN THE CHANGJIANG RIVER ESTUARY   总被引：1，自引：0，他引：1  

杨桂山 《中国地理科学(英文版)》1992,2(1):30-41

Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water. The implications of sea level rise for increasing salinity have been examined in the Changjiang (Yangtze) River estuary. By correlative analysis of chlorinity, discharge and tidal level and calculation of two-dimensional chlorinity, distribution of the Changjiang River estuary, the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50-100 cm. The intensity of salt water intrusion in the future will be far more serious than current trend.  相似文献   

A laboratory test of the soil chemical submodels of two models of catchment acidification     

Ian C. Grieve 《水文研究》1989,3(4):339-346

Parameters for ion exchange selectivity and aluminium hydroxide dissolution in the soil chemical submodels used in applications of the Birkenes model and of MAGIC are compared and several discrepancies identified for organic soils. A laboratory column simulation of the soil chemical submodels is proposed and applied to soils from the Loch Dee area in Galloway. Experimental results were well predicted by a simplified version of MAGIC, with ion exchange selectivity parameters similar to those used in a previous simulation of one subcatchment of Loch Dee. The aluminium hydroxide dissolution parameter used previously was found to be too low for the organic soil materials, where a value of 106 predicted the experimental results more closely. The model developed also included a simple silicate weathering reaction to release base cations into the system. It is concluded that such simple laboratory simulations are useful for independent calibration of the soil chemical submodel of catchment models.  相似文献