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1.
A mass-balance model was developed for the prediction of the biomass and annual production of phytoplankton, macrophytes, epiphytes, and phytobenthos (primary producers), bacterioplankton and bacteriobenthos (reducers), herbivorous and predator zooplankton, zoobenthos, planktivorous fish, benthivorous fish, and predatory fish (consumers). The model is controlled by a small number of parameters.__________Translated from Vodnye Resursy, Vol. 32, No. 3, 2005, pp. 361–370.Original Russian Text Copyright © 2005 by Boulion.  相似文献   

2.
Water Resources - The study considers the factors that had an effect on water quality in the Bureiskoe Reservoir (Far East) after a large landslide event in December 2018 (with a volume of 24.5...  相似文献   

3.
Relationships between the North Pacific Oscillation (NPO) and the typhoon as well as hurricane fre-quencies are documented. The correlation between NPO index in June-July-August-September and the annual typhoon number in the western North Pacific is 0.37 for the period of 1949―1998. The NPO is correlated with the annual hurricane number in the tropical Atlantic at -0.28 for the same period. The variability of NPO is found to be concurrent with the changes of the magnitude of vertical zonal wind shear, sea-level pressure patterns, as well as the sea surface temperature, which are physically asso- ciated with the typhoons and hurricanes genesis. The NPO associated atmospheric circulation vari- ability is analyzed to explain how NPO is linked with variability of the tropical atmospheric circulation in the western Pacific and the tropical Atlantic, via the atmospheric teleconnection.  相似文献   

4.
The sciaenid Protonibea diacanthus is a large, long-lived predatory fish of inshore northern Australian waters, which forms annual aggregations that are fished extensively by traditional (subsistence) and recreational fishers. There are now widespread concerns that the resource is being overexploited.  相似文献   

5.
The parameters commonly considered to define climate are the mean annual precipitation and mean annual potential evapotranspiration. In this study an attempt has been made to develop a relationship between average drought frequency and the evapotranspiration/precipitation ratio for the arid, semi‐arid and subhumid climatic regions of India. The climatic regions are delineated using two climatic indices: namely (i) the ratio of mean annual precipitation (Pa) to global terrestrial mean annual precipitation (Pg), and (ii) the ratio of mean annual potential evapotranspiration (Ep) to mean annual precipitation (Pa). It was noted that the average drought frequency (i e., year?1.) decreases gradually from dry to wet regions. The return period varies from 2 to 3 years in the arid regions (12>Ep/Pa≥5), 3 to 5 years in semi‐arid regions (5>Ep/Pa≥2), and 5 to 8 years in sub‐humid regions (2>Ep/Pa≥3/4). Another relationship was developed between the average frequency of drought occurrence and the ratio of mean annual deficit to mean annual precipitation, (Ep?Pa)/Pa. The results have been compared with the drought experiences documented for other regions of the world. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

6.
Multi-regression, hydrologic sensitivity and hydrologic model simulations were applied to quantify the climate change and anthropogenic intervention impacts on the Lower Zab River basin (LZRB). The Pettitt, precipitation-runoff double cumulative curve (PR-DCC) and Mann–Kendall methods were used for the change points and significant trend analyses in the annual streamflow. The long-term runoff series from 1979 to 2013 was first divided into two main periods: a baseline (1979–1997) and an anthropogenic intervention period (1998–2013). The findings show that the mean annual streamflow changes were consistent using the three methods. In addition, climate variability was the main driver, which led to streamflow reduction with contributions of 66–97% during 2003–2013, whereas anthropogenic interventions caused reductions of 4–34%. Moreover, to enhance the multi-model combination concept and explore the simple average method (SAM), Hydrologiska Byrans Vattenbalansavdelning (HBV), Génie Rural a Daily 4 parameters (GR4J) and Medbasin models have been successfully applied.  相似文献   

7.
亚热带地区典型水库流域氮、磷湿沉降及入湖贡献率估算   总被引：1，自引：0，他引：1  
为了探究汤浦水库流域氮、磷湿沉降对水库水体营养的贡献率,本研究对2014 2015年的汤浦水库流域4个采样点的雨水及3条溪流进行样品收集,测定其中磷和不同形态氮的质量浓度,分析汤浦水库流域大气湿沉降中氮、磷营养盐的分布特征,并估算氮、磷营养盐湿沉降对汤浦水库入库负荷的贡献率.结果表明:湿沉降中总氮(TN)平均浓度为1.02±0.58 mg/L,氨氮、硝态氮和有机氮浓度占TN浓度的比例分别为60.65%、34.07%和5.28%;总磷(TP)平均浓度为0.033±0.028 mg/L.4个采样点湿沉降中氮、磷浓度均表现为冬春季(少雨季)高、夏秋季(多雨季)低.空间上,王化点位的各形态氮和总磷浓度显著高于其他3个采样点.TN和TP年均湿沉降通量约为18.15和0.62 kg/(hm~2·a),年均沉降总量为834.94和28.39 t;库区TN和TP水面湿沉降量为24.14和0.82 t,直接贡献率占河流输入的1.77%和3.07%.湿沉降来源的氮、磷营养盐随河流输入的间接贡献率为8.3%和4.6%.综上所述,氮、磷湿沉降是水库外源营养的重要输入部分,深入掌握其时空分布特征及入库贡献率是进一步加强流域管理和减轻水库外源营养输入的重要前提.  相似文献   

8.
Fieldwork, radiometric (40Ar/39Ar and 14C) ages and whole-rock geochemistry allow a reconstruction of eruptive stages at the active, mainly dacitic, Pichincha Volcanic Complex (PVC), whose eruptions have repeatedly threatened Quito, most recently from 1999 to 2001. After the emplacement of basal lavas dated at ∼1100 to 900 ka, the eruptive activity of the old Rucu Pichincha volcano lasted from ∼850 ka to ∼150 ka before present (BP) and resulted in a 15 × 20 km-wide edifice, which comprises three main building stages: (1) A lower stratocone (Lower Rucu, ∼160 km3 in volume) developed from ∼850 to 600 ka; (2) This edifice was capped by a steeper-sided and less voluminous cone (the Upper Rucu, 40–50 km3), the history of which started 450–430 ka ago and ended around 250 ka with a sector collapse; (3) A smaller (8–10 km3) but more explosive edifice grew in the avalanche amphitheatre and ended Rucu Pichincha's history about 150 ka ago. The Guagua Pichincha volcano (GGP) was developed from 60 ka on the western flank of Rucu with four growth stages separated by major catastrophic events. (1) From ∼60 to 47 ka, a basal effusive stratocone developed, terminating with a large ash-and-pumice flow event. (2) This basal volcano was followed by a long-lasting dome building stage and related explosive episodes, the latter occurring between 28–30 and 22–23 ka. These first two stages formed the main GGP (∼30 km3), a large part of which was removed by a major collapse 11 ka BP. (3) Sustained explosive activity and viscous lava extrusions gave rise to a new edifice, Toaza (4–5 km3 in volume), which in turn collapsed around 4 ka BP. (4) The ensuing amphitheatre was partly filled by the ∼1-km3 Cristal dome, which is the historically active centre of the Pichincha complex. The average output rate for the whole PVC is 0.29 km3/ka. Nevertheless, the chronostratigraphic resolution we obtained for Lower Rucu Pichincha and for the two main edifices of Guagua Pichincha (main GGP and Toaza), leads to eruptive rates of 0.60–0.65 km3/ka during these construction stages. These output rates are compared to those of other mainly dacitic volcanoes from continental arcs. Our study also supports an overall SiO2 and large-ion lithophile elements enrichment as the PVC develops. In particular, distinctive geochemical signatures indicate the involvement of a new magma batch at the transition between Rucu and Guagua. At the GGP, the same phenomenon occurs at each major collapse event marking the onset of the ensuing magmatic stage. Since the 11-ka-BP collapse event, this magmatic behaviour has led to increasingly explosive activity. Four explosive cycles of between 100 and 200 years long have taken place at the Cristal dome in the past 3.7 ka, and repose intervals between these cycles have tended to decrease with time. As a consequence, we suggest that the 1999–2001 eruptive period may have initiated a new eruptive cycle that might pose a future hazard to Quito (∼2 million inhabitants).  相似文献   

9.
The climatic and environmental effects of atmospheric aerosols are a hot topic in global science community, and radiative properties of the aerosols are one of the important parameters in assessing climatic change. Here we studied the black carbon concentration and absorption coefficient measured with aethalometers, scattering coefficient measured with nephelometers, and single scattering albedo derived at an atmospheric composition watch station in Guangzhou from 2004 to 2007. Our main results are as follows. The data of black carbon concentration and absorption coefficients measured with instruments cannot be directly used until they are measured in parallel with internationally accepted instruments for comparison, calibration, and reduction. After evaluation of the data, the result shows that the monthly mean of BC concentration varies 3.1–14.8 μg·m−3 and the concentration decreases by about 1 μg·m−3 in average over the four years; It is higher in the dry season with a multi-year mean of 8.9 μg/m3 and lower in the rainy season with a multi-year mean of 8.0 μg·m−3; The extreme maximum of monthly mean concentration occurred in December 2004 and extreme minimum in July 2007, and a 4-year mean is 8.4 μg·m−3. It is also shown that monthly mean scattering coefficient derived varies 129 −565 Mm−1, monthly mean absorption coefficient 32–139 Mm−1, and monthly mean single scattering albedo 0.71–0.91, with annual mean values of 0.80, 0.82, 0.79 and 0.84 for 2004, 2005, 2006 and 2007, respectively. Three instruments were used to take simultaneous measurements of BC in PM10, PM2.5, and PM1 and the results showed that PM2.5 took up about 90% of PM10 and PM1 accounted for about 68% of PM2.5, and BC aerosols are mainly present in fine particulates. The variability of BC concentrations is quite consistent between the Nancun station (141 m above sea level) and the Panyu station (13 m above sea level), which are 8 km apart from each other. The concentration in higher altitude station (Panyu) is consistently lower than the lower altitude station (Nancun), and the difference of annual mean is about 4 μg·m−3. Supported by Natural Science Foundation of China (Grant Nos. U0733004, 40375002, 40418008, 40775011), National High Technology R & D Program of China (Grant Nos. 2006AA06A306 and 2006AA06A308) and National Basic Research Program of China (Grant No. 2005CB422207)  相似文献   

10.
江汉平原湖群藻相特征及其环境状况评价   总被引：1，自引：1，他引：0  
于2011年4月—2012年5月丰、平、枯3个水期对江汉平原水面面积为10 km2以上的22个湖泊进行了水质和藻类同步监测.结果显示:江汉平原主要湖泊中鉴定出藻类7门100属191种(亚种、变种),其中蓝藻门17属29种,绿藻门45属99种,硅藻门26属40种,隐藻门2属5种,裸藻门4属9种,甲藻门3属5种,金藻门3属4种;全年平均藻细胞丰度为0.93×106~84.18×106cells/L,细胞丰度以蓝藻门最高(50.65%),其次是绿藻门(29.56%),再次是硅藻门(12.30%)、隐藻门(6.19%)、裸藻门(0.56%)、甲藻门(0.39%)和金藻门(0.35%);丰水期生物量显著高于平水期和枯水期,Shannon-Wiener多样性指数年均值在1.44~2.10之间,丰水期的多样性指数略高于其他水期;藻类种类组成及优势种有明显的季节变化和空间差异.依据藻相特征的PCA分析将22个湖泊分为4个类群,不同类群具有显著不同的环境状况,氮磷营养负荷、水质状况和开发利用程度的不同是导致湖泊分化的内在原因;研究结果显示,江汉平原湖群总体上属于轻度污染状况,水体主要是中营养状态,丰水期与枯水期的湖泊生态环境状况具有显著差异;以藻相特征判断22个湖泊存在明显的时空异质性,部分湖泊因过度开发利用存在严重的富营养化风险;基于湖泊生态状况的显著时空异质性,对江汉平原湖群的管理应"因湖而异"制订科学合理的方法.  相似文献   

11.
Introduction In the last 20 years, with observation technique development in space monitoring to Earth, a large progress has been made in monitoring crustal movement. This makes it possible for us to study crustal movement and the present geodynamic. Continuous GPS observation conducted in Chinese mainland and its neighboring region provides us for studying the present strain field of crustal micro-behavior tectonic. Crustal micro-behavior tectonic means that we can study the dif-ference bet…  相似文献   

12.
A suite of event deposits, isochronous and interrelated in origin, occurs widely near the Frasnian- Famennian boundary in Guangxi, South China. It is mainly distributed in the facies areas of the platform-margin slope and inter-platform rift-trough. The rudstone or calcirudite occur in the Liujing section of Hengxian and Luoxiu and Baqi sections of Xiangzhou in the facies area of platform-margin slope. The turbidites are observed in the sections of Yangdi and Baisha of Guilin, Du'an of Debao, Nandong and Sanli of Wuxuan, Xiangtian, Ma'anshan of Xiangzhou, Nayi of Chongzuo, Yunpan of Shanglin in the facies area of inter-platform rift-trough. The massive homogenites occur in sections of Mangchang, Luofu and Road from Nandan to Tian'e and Ma'anshan etc in the facies area of inter-platform rift-trough. Herein event deposits can be correlated in stratohorizon to the turbidite in the bottom of the Lower triangularis Zone in Hony railroad cut of Belgium, Devils Gate of Nevada, USA, Atrous of Morocco, South Urals and Fore-Kolyma of northeastern Siberia of Russia, and erosional discontinuities and brecciation in the Frasnian-Famennian boundary in South Polish-Moravian shelf. The event deposits could be caused by a violent tsunami related to bolide impacts into ocean.  相似文献   

13.
In this paper,finite element method (FEM) of axisymmetric linear elastic model has been used to calculate the tilt and strain induced by small annual temperature variations in a deep tunnel. The results show that even if the am-plitude of the annual variation meets the construction standard of seismic station issued by China Earthquake Ad-ministration (the annual temperature variation amplitude in the tunnel is no more than 0.5 °C),a small annual tem-perature variation of amplitude just 0.2 °C in the tunnel would produce 10?7 rad changes in tilt and 10?7 changes in strain. Especially,at the end and the corner of the tunnel,changes of tilt and strain can be even larger. Therefore,in the future,it is an important task to reduce the annual temperature variation in the tunnel as far as possible. Within the tunnel,for both baseline instrument and pendulum instrument,the modeling suggests ways of construction of the tunnel and installation of the instrument to decrease the influence of the annual temperature variation.  相似文献   

14.
The Early Triassic is a critical period in earth his- tory. A series of events such as volcano eruptions[1,2], sea-level fluctuations, changes in environmental con- ditions[3], mass extinctions[4,5] as well as global negative carbon isotope excursions[6-9] have been discovered in the uppermost Permian or across the Permian-Triassic boundary. Large scale sea-level rise[10-12], restoration of environment conditions, re- covery of ecosystem[13], including gradual carbon iso- tope rise[14] occur…  相似文献   

15.
Based on observations of mesopause emissions, namely, emissions of hydroxyl (band (6-2)) and molecular oxygen (band (0-1) of the atmospheric system), their systematic nighttime and seasonal variations are determined at Zvenigorod Observatory in 2000–2008. It is shown that the intensity of hydroxyl emission decreases during the entire night or first half-night, probably due to the influence of the chemical sink of atomic oxygen on the nighttime behavior of hydroxyl emission. The nighttime behavior of the intensity of molecular oxygen emission is explained by the action of atmospheric tides. The seasonal behavior of emissions is characterized by two minima, in April–May and December; it is caused by the annual behavior of the atomic oxygen content, temperature, and atmospheric density in the emitting layer. Based on the emission data, we determined the seasonal variations of atomic oxygen at heights of ∼87 km (maximum of hydroxyl emission) and ∼95 km (maximum of molecular oxygen emission).  相似文献   

16.
采集柱状芯样,室内静态模拟不同温度下太湖沉积物铵态氮释放.结果表明,经面积加权,5℃、15℃和25℃下氮的交换速率分别为-16.0±17.6mg/穴m2·d雪、12.6±6.9mg/穴m2·d雪和34.1±20.8mg/穴m2·d雪,不同湖区其释放速率差异极大.受外源污染影响较大的水域,氮释放量随温度的升高而增加;受死亡残体沉降和分解影响明显的草藻型湖区,氮的年释放通量较大.全太湖沉积物-水界面NH4 -N的年净通量为9960.3±4960.0t,其中成汇的通量值约为-911±637.9t/a,大部分泥区在一年中至少经过了一次的源-汇转换过程.  相似文献   

17.
ABSTRACT

The hydrological data available for the Lower Mekong River are presented in directly usable form for design purposes by means of a regional frequency study of the annual maximum daily mean flows (floods) and by means of the annual mean minimum flows for various durations (droughts). In addition, a regional analysis is given of the annual dry season recession hydrograph. The only information required to apply these results is the size of the drainage area or the distance along the river upstream from Phnom-Penh.  相似文献   

18.
邓山  邱爽  王利肖  闫云君 《湖泊科学》2014,26(2):297-304
为了加强长江中游地区大型无脊椎底栖动物的研究工作,2009年3月至2010年3月,对长江中游巴河支流的胜利河毛翅目优势种的生产力和营养基础进行了为期一年的调查研究.结果表明,胜利河中主要毛翅目优势种纹石蛾的生活史为一年3代.一至四级河流中,其生物量周年平均值分别为1.77、7.80、44.82、51.55 mg/m2.采用体长频率法测算的年均生产量为7.72 mg/m2,P/B系数为13.21.利用肠内含物分析法研究了胜利河中纹石蛾的营养结构.比较一至四级河流的营养基础发现,无形态碎屑为纹石蛾最常见的食物,占肠内含物的45.22%~62.92%;而对生产量贡献率最高的多是动物组织,达52.86%~68.58%.各季节的营养基础状况也有差异,春季无形态碎屑所占比例和对生产量的贡献率较高,而夏、秋和冬季动物组织则有更高的生产量贡献率.一至四级河流的年均物质通量分别为11.83、34.76、237.52和273.17g/(m2·a).由此可见,该优势种在河流生态系统中发挥着重要作用.  相似文献   

19.
Coarse fragmental rocks, previously interpreted as primary pyroclastic accumulations infilling flared vents (Richey JE 1938) “The rhythmic eruptions of Ben Hiant, Ardnamurchan, a tertiary volcano. Bull Volcanol” 2(3):1–21), are re-interpreted as predominantly debris flow deposits, with minor hyperconcentrated and stream-flow deposits, temporally and spatially associated with the Palaeogene Ardnamurchan Central Complex (ACC), NW Scotland. These volcaniclastic rocks are conglomerates and breccias, interbedded with siltstones and sandstones, which formed by surface processes on a dissected landscape, developed in response to shallow emplacement of the ACC. Clast-matrix and photo-statistical analyses allow the palaeo-topography and drainage system to be reconstructed and the development of a palaeo-geographic model for the volcanic landscape. Slabs of basalt, dolerite and sandstone were transported as megablocks during catastrophic, gravity-driven events. Lower energy intervals during volcanic hiatuses are marked by lacustrine-fluvial volcaniclastic siltstones and sandstones preserving palynomorph assemblages. We suggest that shallow intrusion is a plausible initiation mechanism for mass wasting in other large igneous provinces. Historically, deposits of the type described here may have been misidentified as vent facies pyroclastic materials.  相似文献   

20.
To understand regional status and differences is groundwork for researching environmental change, such as regional response to global change, land use/land-cover change, land desertification, and sand/dust storms. At present, geographers are search- ing for driving forces of environmental change and making efforts to reflect human actions on these changes[1―4]. To recognize regional difference, most researches focus on single factor, such as temperature, precipitation, soil and vegetation. Ho…  相似文献   

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