厦门酸雨与气象要素的关系及污染源的分析   总被引：1，自引：0，他引：1  

俞绍才  蔡小平  陈小江  陈泽面 《气象》1994,20(5):20-23

根据厦门市１９８３－１９９１年９年春雨，梅雨及台风雨酸度的观测结果，结合各场雨水同步观测的气象要素资料，分析各类型雨水酸度与气象要素的关系。同时依降水的酸化原理估计了外来源及局的地源对厦门酸雨形成的贡献。  相似文献   

Karst terranes and environmental aspects     

F. A. Assaad  H. Jordan 《Environmental Geology》1994,23(3):228-237

Karst is a complex geological phenomenon that relates to terranes composed of limestone, dolomites, gypsum, halite, or other soluble rocks. Protection of groundwater in karst against pollution is needed because of the high velocity of its flow (several hundreds of thousands of meters per day) and where polluted materials are carried without being filtered. Protection of karstic aquifers against pathogens and rapidly degradable chemicals is carried out for the catchment areas with an estimated delay time of 60 days and for a distance of more than 30 m. Tracer methods have recently become quite useful in karst regions; a tracer may respond as a multiimpulse because of different flow lines, flow velocities, and water aquifers. Therefore, if a total water balance has to be established, nearly all answer-back impulses should be considered.  相似文献   

降雨及地下水对边坡稳定性动态影响的初步研究   总被引：8，自引：0，他引：8  

罗文强  晏同珍 《地质科技情报》1995,14(4):77-81

论述了降雨及地下水对边坡稳定性的动态影响及作用特征。这种影响特征具有典型的周期性和滞后性，通过对坡体地下水位的动态模拟，取得了边坡稳定性随时间而变化的规律认识。  相似文献   

台风影响期间珠江三角洲局地强风暴和大暴雨发生的环境条件   总被引：4，自引：0，他引：4  

王沛霖 《热带气象学报》1995,11(4):375-378

采用１９７６－１９８３年６－８月珠江三角洲地区受台风影响期间区内各站逐日的强风暴和降水资料以及广泛站的探空资料，用相关对比度分析方法，对台风环流中的珠江三角洲局地强风暴和大暴雨发生的环境条件进行统计诊断，得出台风影响珠江三角洲时这两种强天气发生的有利的环境条件，并发现二者在气压、风速、层结稳定度和中下层位势不稳定等方面显著不同。  相似文献   

一个三重嵌套的中尺度模式及暴雨模拟试验          下载免费PDF全文

郑国安  郭肖容 《应用气象学报》1995,6(2):129-137

该文介绍了新近发展的一个高分辨率有限区模式(HLAM)。它是通过三重嵌套在现有计算机(CYBER-992)条件下实现的，其范围、地理位置及侧边界宽度均设计为灵活可变，尤其水平分辨率可按任意倍数提高。利用水平分辨率为50km左右的模式版本进行了实际资料的降水个例实验。结果是令人鼓舞的:(1)与嵌套的低分辨率(格距增大4倍)模式预报比较，不论低压中心位置、强降水落区、雨带走向及降水中心位置的预报都更接近实况;(2)高分辨率模式积分区域虽然缩小，但并未影响预报效果，其48小时预报仍有较高精度。初步试验表明，进一步完善和改进后的HLAM完全可以发展为一个用于中尺度研究及业务使用的高分辨率区域模式。  相似文献   

Statistics on the sizes and internal structures of rainshowers     

R. R. Rogers  K. J. Keen  A. P. Schwartz 《Pure and Applied Geophysics》1983,121(1):133-166

A large sample of radar reflectivity data from essentially a full summer of operation was analyzed to determine the horizontal extents and internal structure of rain areas observed at altitude levels from 2 to 10 km. Results are given on the size distributions of individual cells or patches defined by reflectivity thresholds approximately 4 dBz apart, on the dependence of mean size on altitude and reflectivity threshold, and on the interior structure of the patches as characterized by the number and sizes of higher-threshold patches contained in each echo. In a more detailed analysis of internal structure, the data were restricted to convective echoes in which certain prescribed reflectivities, ranging from about 30 to 50 dBz, were exceeded. It was found that the dependence of mean quantities, such as patch area, on reflectivity and altitude could be approximately described by simple functions, but that the scatter of observations about the mean was usually large.  相似文献   

Improving the accuracy of tipping-bucket rain records using disaggregation techniques   总被引：1，自引：0，他引：1  

A. Molini  L.G. Lanza  P. La Barbera 《Atmospheric Research》2005,77(1-4):203

We present a methodology able to infer the influence of rainfall measurement errors on the reliability of extreme rainfall statistics. We especially focus on systematic mechanical errors affecting the most popular rain intensity measurement instrument, namely the tipping-bucket rain-gauge (TBR). Such uncertainty strongly depends on the measured rainfall intensity (RI) with systematic underestimation of high RIs, leading to a biased estimation of extreme rain rates statistics. Furthermore, since intense rain-rates are usually recorded over short intervals in time, any possible correction strongly depends on the time resolution of the recorded data sets. We propose a simple procedure for the correction of low resolution data series after disaggregation at a suitable scale, so that the assessment of the influence of systematic errors on rainfall statistics become possible. The disaggregation procedure is applied to a 40-year long rain-depth dataset recorded at hourly resolution by using the IRP (Iterated Random Pulse) algorithm. A set of extreme statistics, commonly used in urban hydrology practice, have been extracted from simulated data and compared with the ones obtained after direct correction of a 12-year high resolution (1 min) RI series. In particular, the depth–duration–frequency curves derived from the original and corrected data sets have been compared in order to quantify the impact of non-corrected rain intensity measurements on design rainfall and the related statistical parameters. Preliminary results suggest that the IRP model, due to its skill in reproducing extreme rainfall intensities at fine resolution in time, is well suited in supporting rainfall intensity correction techniques.  相似文献   

Calibration of tipping bucket rain gauges in the Graz urban research area   总被引：2，自引：0，他引：2  

Vilmos Vasvri 《Atmospheric Research》2005,77(1-4):18

The Institute of Urban Water Management and Landscape Water Engineering of the Graz University of Technology (Austria) operates a hydrological research area in the City of Graz. In this urban research area precipitation and runoff data are collected by order of the municipality of Graz. At present precipitation data are measured by seven tipping bucket rain gauges. Comparative measurements have shown a deviation between the recorded and the actual precipitation intensity. This made the institute calibrate the rain gauges periodically. In the middle of the 1990s, the development of a field calibration kit was started. Based on the experiences with the first field calibration kit, a microprocessor controlled device was developed. With this calibration device, the tipping bucket rain gauges are calibrated at regular intervals. In this paper the calibration process and the current results for seven rain gauges are discussed. The calibration process is dynamic calibration and uses a peristaltic pump. Not all of the tipping buckets investigated underestimate the rain intensity in the whole measuring range. Several rain gauges have a positive relative deviation, not exceeding 22%, in the low intensity range up to 0.5 mm/min. Positive deviation can be explained by retention of water in the buckets between tips. The reason for the negative deviation is the loss of water during the tips. It leads to the underestimate of the actual intensity. The largest relative deviation in the range of underestimate exceeds 30%. In the range of extreme intensities, the larger buckets (5 cm³) show a lower relative deviation than the smaller (2 cm³) buckets. The gauge characteristic can change in favourable or unfavourable directions after several years. Therefore, the calibration of tipping buckets is recommended at least every 2 to 3 years.  相似文献   

Factors Controlling Sulfide Geochemistry in Sub-tropical Estuarine and Bay Sediments     

John W. Morse  Heather Thomson  David W. Finneran 《Aquatic Geochemistry》2007,13(2):143-156

The primary factors that control the concentration of total reduced (inorganic) sulfide in coastal sediments are believed to be the availability of reactive iron, dissolved sulfate and metabolizable organic carbon. We selected nine sites in shallow (<3 m), close to sub-tropical, estuaries and bays along the central Texas coast that represented a range in sediment grain size (a proxy for reactive iron), salinity (a proxy for dissolved sulfate), and total organic carbon (a proxy for metabolizable organic carbon). Based on these parameters a prediction was made of which factor was likely to control total reduced sulfide at each site and what the relative total reduced sulfide concentration was likely to be. To test the prediction, the sediments were analyzed for total reduced sulfide, acid volatile sulfide, and citrate dithionate-extractable, HCl-extractable and total Fe in the solid phase. Using solid-state gold–mercury amalgam microelectrodes and voltammetry, we determined pore water depth profiles of Fe(II) and ΣH₂S and presence or absence of FeS_(aq). At five of the nine sites the calculated degree of sufildization of citrate dithionite-reactive-iron was close to or greater than 1 indicating that rapidly reactive iron was probably the limiting factor for iron sulfide mineral formation. At one site (salinity = 0.9) dissolved Fe(II) was high, ΣH₂S was undetectable and the total reduced sulfide concentration was low indicating sulfate limitation. At the last three sites a low degree of sulfidization and modest total reduced (inorganic) sulfide concentrations appeared to be the result of a limited supply of metabolizable organic carbon. Fe(II)–S(-II) clusters (FeS_(aq)) were undetectable in 10 out of 12 bay sediment profiles where ΣH₂S was close to or below detection limits, but was observed in all other porewater profiles. Acid volatile sulfide, but not total reduced sulfide, was well correlated with total organic carbon and ranged from being undetectable in some cores to representing a major portion of total reduced sulfide in other cores. Although predicted controls on total reduced sulfide were good for very low salinity water or sandy sediments, they were only right about half the time for the other sediments. The likely reasons for the wrong predictions are the poor correlation of total organic carbon with grain size and differing fractions of metabolizable organic carbon in different sedimentary environments. Differences in sediment accumulation rates may also play a role, but these are difficult to determine in this region where hurricanes often resuspend and move sediments. This study demonstrates the need to examine more complex and often difficult to determine parameters in anoxic “normal marine” sediments if we are to understand what controls the concentration and distribution of sulfides.  相似文献   

Bio‐based Ester Oils for Use as Lubricants in Metal Working     

Hubertus Wichmann  Muefit Bahadir 《洁净——土壤、空气、水》2007,35(1):49-51

The potential application of bio‐based ester oils for use as lubricants in metal working has been investigated for sustainable production processes in the future. When waste edible and animal fats came into focus as starting materials, it was already proven, that ester oils produced from plant fats performed very well as cooling lubricants. Waste fats were first characterized by analyzing and monitoring samples for one complete year. Inorganic and organic contaminations were found to be low and without seasonal variations. Fatty acid methyl esters (FAME) were produced by transesterification of the waste fats and they were separated into fractions with saturated FAME or unsaturated FAME by fractional crystallisation (winterisation). Further transesterification with 2‐ethylhexanol led to products that could be successfully tested as lubricants. The development of an extraction process aimed at the recycling of oil containing grinding mud by enabling the recirculation of lubricating oil and reutilization of oil‐free metal chips.  相似文献