首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
大通湖及东洞庭湖区生物体重金属的水平及其生态评价   总被引:4,自引:0,他引:4  
于2005年11月采集了大通湖及东洞庭湖区湖水和水生生物样品,并测定了水和水生生物样品中重金属(Cd、Pb、Hg、As)的含量,并对湖区生物体重金属进行了污染评价.研究结果表明,大通湖及东洞庭湖区湖水中重金属含量较小,绝大部分采样点水质都属于国家Ⅰ类水标准;水生生物体内CD、Pb含量为虾>螺>鱼,Hg的含量为鱼>螺>虾,As的含量为螺>虾>鱼;而鱼类重金属含量则为底栖鱼类>中上层鱼类,肉食性鱼类>植食性鱼类.大通湖及东洞庭湖区生物体中CD、Pb的污染指数为虾>螺>鱼,Hg的污染指数则为鱼>螺>虾,As的污染指数则为螺>虾>鱼.  相似文献   

2.
淮河流域焦岗湖水质参数时空变化及影响因素   总被引:3,自引:1,他引:2  
焦岗湖是淮河左岸一个天然湖泊,集防洪、灌溉、养殖、旅游等多种功能于一体.利用焦岗湖4个季节水质监测数据,运用Kriging方法,分析焦岗湖水质参数的时空变化及影响因素.结果表明:由于受水文季节变化过程及人类活动等综合影响,焦岗湖水质参数在时间及空间上均存在一定差异.从时间变化来看,夏季透明度较低、秋季较高;溶解氧浓度在春、冬季显著高于夏、秋季;总氮、总磷浓度与高锰酸盐指数均表现为夏季最高、秋季最低.从空间变化来看,4个季节的透明度空间差异较为显著;溶解氧浓度在春、冬季空间分布较为均匀,夏季呈现中心高周围低的变化趋势,秋季则表现为西高东低;总磷浓度春季分布较为均匀,夏、秋及冬季则呈西高东低之势;高锰酸盐指数在春、秋季节呈现东高西低之势,夏季高浓度主要集中在湖区北部,冬季浓度变化不大.  相似文献   

3.
滇西怒江断裂带新构造特征   总被引:9,自引:0,他引:9       下载免费PDF全文
李京昌 《地震地质》1998,20(4):25-320
怒江断裂带从走向上可以分为南北走向段和北东走向段,其喜马拉雅期的构造变形以右行剪切为主导。右行剪切的变形历史可以分为早期压剪变形和晚期张剪变形两个大的阶段。这两期变形各自在南北走向段和北东走向段表现出不同的特点。总之,怒江断裂带喜马拉雅期构造变形具有时空不均一性的特点  相似文献   

4.
1990s长江流域降水趋势分析   总被引:2,自引:0,他引:2  
依据国家气象局提供的实测月降水和日降水资料,运用Mann-Kendall(M-K)非参数检验法验证了降水趋势,并通过空间插补法,由点扩展到面,分析了1990s长江流域降水变化特征,发现1990s长江流域降水变化以降水在时间和空间分布上的集中度的增加为主要特点:时间上,年降水的增加趋势以冬季1月和夏季6月降水的集中增加为主;一日降水量大于等于50mm的暴雨日数和暴雨量在1990s也有了较明显的增加.空间上,年降水、夏季降水、冬季降水的增加都以中下游区的增加为主,尤其以鄱阳湖水系、洞庭湖水系的降水增加为主.1990s长江流域春季和秋季降水的减少以5月和9月两个汛期月份的降水减少为主,除金沙江水系和洞庭湖水系等少数地区外,流域大部分地区降水呈减少趋势.上述1990s出现的降水趋势明显与近年来全球变暖背景下长江流域各地区不同的温度及水循环变异有关.  相似文献   

5.
Spatial and temporal distributions of the trends of extreme precipitation indices were analysed between 1986 and 2005, over the Iberian Peninsula (IP). The knowledge of the patterns of extreme precipitation is important for impacts assessment, development of adaptation and mitigation strategies. As such, there is a growing need for a more detailed knowledge of precipitation climate change.This analysis was performed for Portuguese and Spanish observational datasets and results performed by the Weather Research and Forecast (WRF) model forced by the ERA-Interim reanalysis. Extreme precipitation indices recommended by the Expert Team for Climate Change Detection Monitoring and Indices were computed, by year and season. Then, annual and seasonal trends of the indices were estimated by Theil-Sen method and their significance was tested by the Mann-Kendal test. Additionally, a second simulation forced by the Max Planck Institute Earth System Model (MPI-ESM), was considered. This second modelling configuration was created in order to assess its performance when simulating extremes of precipitation.The annual trends estimated for the 1986–2005, from the observational datasets and from the ERA-driven simulation reveal: 1) negative statistically significant trends of the CWD index in the Galicia and in the centre of the IP; 2) positive statistically significant trends of the CDD index over the south of the IP and negative statistically significant trends in Galicia, north and centre of Portugal; 3) positive statistically significant trends of the R75p index in some regions of the north of the IP; 4) positive statistically significant trends in the R95pTOT index in the Central Mountains Chain, Leon Mountains and in the north of Portugal.Seasonally, negative statistically significant trends of the CWD index were found in Galicia, in winter and in the south of the IP, in summer. Positive statistically significant trends of the CWD index were identified in the Leon Mountains, in spring, and in Galicia, in autumn. For the CDD index, negative statistically significant trends were seen in Valencia, in the spring, and, in Galicia and Portugal (north and centre), in summer. Positive statistically significant trends of the CDD index were found: in the east of the IP, in the winter; in the Cantabrian Mountain, in the spring; and, in the south of the IP, in summer. Regarding to the R75p index, negative statistically significant trends were found in Galicia, in winter and positive statistically significant trends in the north of Portugal, in spring and in the Central Mountains Chain and north of Portugal, in autumn. For the R95pTOT index, negative statistically significant trends were found over the Sierra Cuenca and Sierra Cazorla, in winter and positive statistically significant trends were found over the Sierra Cebollera, in winter and in Castile-la Mancha region, in spring.The results of the annual and seasonal trends of the extreme precipitation indices performed for observational datasets and the simulation forced by ERA-Interim, are similar. The results obtained for the simulation forced by MPI-ESM are not satisfactory, and can be a source of criticism for the use of simulation forced by MPI-ESM in this type of climate change studies. Even for the relatively short period used, the WRF model, when properly forced is a useful tool due to the similar results of Portuguese and Spanish observational datasets and the simulation forced by ERA-Interim.  相似文献   

6.
Changes in potential evapotranspiration and surface runoff can have profound implications for hydrological processes in arid and semiarid regions. In this study, we investigated the response of hydrological processes to climate change in Upper Heihe River Basin in Northwest China for the period from 1981 to 2010. We used agronomic, climatic and hydrological data to drive the Soil and Water Assessment Tool model for changes in potential evapotranspiration (ET0) and surface runoff and the driving factors in the study area. The results showed that increasing autumn temperature increased snow melt, resulting in increased surface runoff, especially in September and October. The spatial distribution of annual runoff was different from that of seasonal runoff, with the highest runoff in Yeniugou River, followed by Babaohe River and then the tributaries in the northern of the basin. There was no evaporation paradox at annual and seasonal time scales, and annual ET0 was driven mainly by wind speed. ET0 was driven by relative humidity in spring, sunshine hour duration in autumn and both sunshine hour duration and relative humility in summer. Surface runoff was controlled by temperature in spring and winter and by precipitation in summer (flood season). Although surface runoff increased in autumn with increasing temperature, it depended on rainfall in September and on temperature in October and November. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

7.
8.
张贵刚  韩博平 《湖泊科学》2010,22(3):445-450
舌状叶镖水蚤(Phyllodiaptomus tunguidus)是我国特有的大型哲水蚤,主要分布在我国华南地区.根据2000年对广东省19座典型大中型水库的2次采样和2002年对流溪河水库和新丰江水库的5次采样,重点测定了流溪河水库、新丰江水库和鹤地水库等3座大型水库中舌状叶镖水蚤个体体长及形态参数,分析了广东省大中型水库中舌状叶镖水蚤的种群与个体大小的分布特征.在对19座水库的2次采样中,11座水库发现该种成体,其中5座水库在丰水期没有出现该种的成体,6座水库在丰水期和枯水期都有该种类成体的出现.丰水期与枯水期舌状叶镖水蚤的平均丰度分别为0.465ind./L和0.996ind./L.舌状叶镖水蚤主要出现在大型水库中,特别是贫营养的大型水库,其丰度主要由食物数量、质量与捕食压力所决定.2002年,流溪河水库丰度和新丰江水库舌状叶镖水蚤全年的平均值为1.308ind./L和0.294ind./L,丰水期高于枯水期.在个体大小和形态特征上,2座贫营养水体——流溪河水库、新丰江水库的舌状叶镖水蚤的体长与第一触角长度均大于中营养水体——鹤地水库,这种形态上的差异是由鱼类捕食方式(滤食或选择性捕食)所决定.  相似文献   

9.
A close negative correlation was found to exist between oxygen concentration in winter and the latitude in rivers in the basins of the Ob and Volga. This can be explained by an increase in the duration of the freeze-up period (during which oxygen is consumed for oxidation of organic matter (OM) in water and bottom sediments) in the direction from the south to the north, while the input from oxygen from the atmosphere and photosynthesis is practically zero. No inverse relationship was found to exist between dissolved oxygen and the latitude, because in rivers of mountain and semimountain types, typical of this basin, organic matter (OM) does not accumulate in bottom sediments and the conditions of atmospheric circulation are better than in lowland rivers. The magnitude of seasonal variations in oxygen in lowland rivers is greater than in mountain ones because of an abrupt drop in oxygen concentration in slowly flowing rivers in winter and the saturation of their water by oxygen from photosynthesis in summer.  相似文献   

10.
Spatial and seasonal patterns of flood change across Brazil   总被引:1,自引:1,他引:0  
Brazil has some of the largest rivers in the world and has the second greatest flood loss potential among the emergent countries. Despite that, flood studies in this area are still scarce. In this paper, we used flood seasonality and trend analysis at the annual and seasonal scales in order to describe flood regimes and changes across the whole of Brazil in the period 1976–2015. We identified a strong seasonality of floods and a well-defined spatio-temporal pattern for flood occurrence. There are positive trends in the frequency and magnitude of floods in the North, South and parts of Southeast Brazil; and negative trends in the North-east and the remainder of Southeast Brazil. Trends in the magnitude (frequency) were predominant in the winter (summer). Overall, floods are becoming more frequent and intense in Brazilian regions characterized by wet conditions, and less frequent and intense in drier regions.  相似文献   

11.
大姚地热动态特征分析   总被引:3,自引:1,他引:3  
通过大姚高精度水温观测井水地质、井孔条件的分析,震例观测资料、实验观测数据的处理,以及井水水质分析结果,表明大姚水温周期性变化的突出位置是井深75m左右,根本原因是该地层石膏脉稳定释热,含水层热水与井内冷水混合过程中,在通道内形成钙盐类沉淀物(如CaSO4CaCO3),堵塞对流通道,含水层内外压差突破被阻塞通道,热水反复侵入井内,便形成水温周期性变化。地震的孕育、发生和调整过程,由于应力场作用,产生附加地热场,水温基值发生变化,周期畸变或消失,这种附加地热动态是可以恢复的。所以认为大姚地热动态是井区特殊地层地热信息的反映。  相似文献   

12.
Levels and trends of persistent organic pollutants and trace elements in seabirds breeding in the vast Canadian Arctic have been monitored since 1975. Data from this monitoring have indicated both spatial and temporal variation across the region, attributable in part to differences in species' diets, differences in regional deposition patterns, and unidirectional trends in contaminants reaching this area from emissions in temperate and tropical areas to the south. Seabird tissues have served as effective biomonitors to examine this variation, and national and international collaboration in this monitoring effort has promoted valuable synthetic assessments of spatial and temporal patterns in Arctic contaminants. Here we review the history of the monitoring program, the critical role played by Environment Canada's National Wildlife Specimen Bank, and we summarize important spatial and temporal trends in various contaminants in Canadian Arctic seabirds.  相似文献   

13.
Seventy-four samples of adipose fat of 10 species of fisheating birds commonly wintering in Gdańsk Bay and one of little auk, a rare species in this area, have been analysed for residues of HCB, ΣBHC, ΣDDT and PCBs. Auks (guillemot, black guillemot and razorbill), which probably stay a whole year in the Baltic area, contained in their fat twice the level of PCBs as mergansers, and 5–6 times as much as in divers and grebes—birds which stay in the sea mainly after the breeding season. ΣDDT levels were somewhat higher but comparable in auks and grebes, and lower in mergansers and divers. ΣBHC and HCB levels were 3–4 times and 5–10 times higher, respectively, in auks than in birds from other families studied. When comparing residue levels found in adipose fat of birds taken during the wintering seasons of 1981–1982 and 1982–1983 with those taken in 1975–1976 or 1980–1981, an initially rapid, but in recent years a rather slow decline in ΣDDT level is detectable for grebes, mergansers and divers, and in the case of PCBs the residue levels fell slightly. In auks, the ΣDDT residue level fell by half, but remains rather stable in recent years, while there are only minor fluctuations in the residue level of PCBs.  相似文献   

14.
研究丹江口水库在完成高水位蓄水期间浮游植物群落的时空动态特征可为丹江口水库的水质保护与生态系统结构优化及健康管理提供一定科学依据。本研究基于2018—2020年的水库浮游植物监测数据,结合同期水库水体的理化参数,分析了丹江口水库浮游植物在不同年度、季度及空间的变化特征,以及影响浮游植物群落结构变化的主要环境因子。结果显示该区域共检测出浮游植物7个门类,其中蓝藻门、硅藻门、绿藻门、隐藻门为优势类群。2018—2020年浮游植物年均密度分别为1.96×106、2.55×106和5.07×106 cells/L,呈现出逐年增高趋势。浮游植物季度密度表现为秋季>夏季>春季>冬季,在夏秋季节蓝藻门和绿藻门占优势,春冬季节硅藻门和隐藻门占优势,同时硅藻门在四季中均占据生长优势。空间上库区浮游植物密度明显高于支流,且汉江库区浮游植物密度高于丹江库区,其中蓝藻门和绿藻门主要在库区大量出现,而支流则以硅藻门和隐藻门为主。RDA分析显示,影响丹江口水库浮游植物的主要环境因子是水温,其次为化学需氧量、氨氮和总磷。在不同季节和...  相似文献   

15.
This study investigated the subcellular distribution of Cu, Zn, Cd and Ag in liver of mallard (Anas platyrhynchos), spot-billed duck (A. poecilorhyncha) and great cormorant (Phalacrocorax carbo) to better understand metal fractionation and dynamics in avian liver. Most of the total Cu, Zn, Cd and Ag were present in hepatocytosol, and their concentrations increased with total hepatic levels in all the three avian species. Copper, Zn and Cd in hepatocytosol were present mostly in metallothionein fractions (MTs), and Cu and Cd contents in this fraction were positively correlated with hepatocytosol levels in all the species. Silver was observed mostly in both high-molecular weight and MT fractions in hepatocytosol in mallard and great cormorant, whereas it was present in both low-molecular weight and MT fractions in spot-billed duck, suggesting that distribution of Ag in the hepatocytosol was species-specific. The elution profile of metals in MT fractions revealed six metallic peaks in mallard and spot-billed duck, and three peaks in great cormorant, implying the presence of multiple MT isoforms in the liver of these avian species. The present study demonstrated that MTs are closely associated with metal regulation, especially Cu and Cd, in these three aquatic birds.  相似文献   

16.
分析了1995年日本阪神地震(M7.2)近场强地面运动特征.结果表明,震中附近地区水平加速度峰值达600~800gal,竖向加速度峰值达300gal,强地面运动持续时间为10~15s,加速度时程的卓越周期为0.2~2s.谱分析的结果还表明,在较宽的频带范围内该次地震的近场地震动的强度都比较大.  相似文献   

17.
强地震附近视电阻率各向异性变化的原因   总被引:23,自引:2,他引:21       下载免费PDF全文
讨论了强地震、孕震晚期阶段、震源区及附近介质的物理变化过程,证明了视电阻率变化最显著的方向与最大加载方向之间的正交关系,建立了真、视电阻率各向异性变化与裂隙率ν、骨架电阻率ρo、饱水裂隙电阻率ρf的本构关系,解释了视电阻率各向异性变化的原因.研究认为:在强地震孕震晚期阶段,在震源区及附近地壳近地表的较深部,介质微裂隙发育,其走向沿最大主压应力方位优势取向,低阻水充填微裂隙,导电通道连通,引起最大主压应力方向真电阻率变化最显著的真各向异性变化,从而产生垂直主压应力方向视电阻率变化最显著的视各向异性变化,低阻水在其物理过程中起了显著作用.  相似文献   

18.
鄂尔多斯盆地油气资源丰富,盆地构造平缓,以岩性、岩性-地层和古地貌油气藏为主,储层厚度薄。本文详细分析了鄂尔多斯盆地油气地质、油气资源的形成与分布,指出了鄂尔多斯盆地油气勘探方向及地震勘探技术系列在该盆地大油气田的发现中的不可替代的重要作用。  相似文献   

19.
1951~2002年中国东、西部地区地面气温变化对比   总被引:27,自引:1,他引:26       下载免费PDF全文
利用1951~2002年全国733个测站经过非均一性检验的月平均气温资料,在剔除50万以上人口大城市测站后,分析了52年来中国东、西部及青藏高原地区的气温变化趋势的一致性和差异性,并讨论了其可能原因.结果表明我国东、西部地区年、季平均气温变化有着较好的一致性;近52年来,我国东、西部和青藏高原地区年平均气温均呈升温趋势,年平均气温的增温速率东部为026℃/10a,西部018℃/10a,东部比西部高008℃/10a;季平均气温东部地区冬、春季的增暖趋势大于西部和青藏高原,而其夏、秋季的增暖趋势小于西部和青藏高原.我国东、西部地区年、季平均气温变化关系密切,说明其主要是受全球气候变化的影响而变化,但东部年平均气温的增暖总趋势大于西部,又说明地域差异在气温变化中也有重要作用.  相似文献   

20.
太湖底泥及其间隙水中氮磷垂直分布及相互关系分析   总被引:97,自引:16,他引:81  
范成新  杨龙元  张路 《湖泊科学》2000,12(4):359-366
对太湖主要湖区柱状样底泥的总氮、总磷含量及其间隙水铵态氮(NH^+4-N)、磷酸根磷(PO^3-4-P)和二价铁Fe(II)含量进行了分析,并对底泥和间隙水中相应物质含量进行了比较,结果表明:太湖近表层10cm内底泥TN、TP赋存含量较之下层高12%-20%左右,间隙水中PO^3+4-P和NH^+4-N含量随浓度增加而大致呈上升趋势,表层未见高浓度层存在,各湖区底泥间隙水中PO^3+4-P和NH^  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号