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1.
珠江流域东江干流浮游植物叶绿素a时空分布及与环境因子的关系 总被引：7，自引：2，他引：5
为了解珠江流域东江干流水体叶绿素a的时空分布及与环境因子的关系,于2012年6月(丰水期)和12月(枯水期)对东江干流进行采样调查分析.结果表明,东江水体叶绿素a含量具有明显的时空分布特征,其全年变化范围为0.84~14.93μg/L,整体均值为3.60±2.45μg/L,丰水期叶绿素a含量显著高于枯水期;而丰、枯水期叶绿素a含量空间分布特征相似,上游河段显著低于下游河段.相关性与主成分分析结果显示,水体中总氮浓度、总磷浓度、有机物含量、水温和水流流速等都是影响东江浮游植物生长的重要因素,其中以总磷的影响最为显著,表明磷可能是东江浮游植物生长的限制因子. 相似文献
2.
2022年我国长江流域经历了长期的高温干旱,对湖泊水生态环境和湖内藻情态势产生了深远影响。但目前关于干旱环境下湖泊水华的响应特征研究较少。以太湖为例,基于2005—2022年湖体营养盐与叶绿素a浓度的长期监测数据,结合卫星遥感影像反演的蓝藻水华面积变化,探讨了2022年高温干旱对太湖蓝藻的影响特征及驱动机制。结果表明,2022年蓝藻水华高发季节(5—9月),太湖蓝藻水华的平均面积和最大面积均明显下降,其中5月的水华面积仅为近5年同期平均面积的20%;水样采集分析获得的水体叶绿素a浓度和微囊藻生物量在春季也明显下降。营养盐方面,2022年太湖的总氮和总磷均值分别为1.41和0.084 mg/L,较近5年均值分别下降了30.6%和27.3%,均为2005年以来的最低值。氮磷浓度空间分布的克里金插值显示,除西北湖区(竺山湾)受河流入湖影响外,大部分湖区的溶解态氮磷也都处于较低状态,冬季溶解性总磷浓度小于0.02 mg/L的水域面积占全湖面积的79%。随机森林分析表明,总磷、水温和风速是影响春季微囊藻和藻类生物量的关键因子。冬季湖体磷水平低,加上春季外源负荷较少,致使2022年春季太湖大范围湖... 相似文献
3.
本文研究2018—2020年鄱阳湖水质及营养水平关键指标——叶绿素a、总磷、总氮浓度时空特征,采用分位值法与压力-响应关系法等研究氮磷基准和适宜的控制标准。结果表明,2018—2020年鄱阳湖水质以Ⅳ类为主,超标污染物为总磷和总氮。近3年鄱阳湖处于“中偏富”营养水平,叶绿素a浓度均值为7.6μg/L,总磷浓度均值为0.070 mg/L,总氮浓度均值为1.30 mg/L。所有水域在年内皆会出现富营养时段;年内各月份皆有水域处于富营养水平。总磷、总氮浓度枯水期高于丰水期;8月总磷浓度最低,8—9月总氮浓度最低。叶绿素a浓度较高的季节为秋季,尤以9月最高,9月全湖叶绿素a浓度均值和中位值分别为16和12μg/L,皆超中-富营养界限值10μg/L,原因在于9月“五河”退水与仍处汛期的长江干流顶托导致流速减缓。叶绿素a浓度较高的水域为入湖河流尾闾水域、浅水湖湾、碟形湖(如南湖村、金溪咀、南矶山、蚌湖等)。鄱阳湖平均N/P比为52,相对于藻类繁殖需求而言,氮、磷皆处于过量状态,总磷宜作为首要控制因子,总氮控制亦应考虑。鄱阳湖总磷基准范围为0.029～0.054 mg/L,总氮基准范围为0.50～0... 相似文献
4.
基于富营养化阈值的松花湖水环境容量分析 总被引：4，自引：0，他引：4
通过对松花湖水体中浮游植物的绝对优势种——铜绿微囊藻(Microcystis aeruginosa)单藻株生长与磷、氮定量关系的室内模拟研究,得出松花湖富营养化发生的阈值为：总磷浓度0．065 mg/L,总氮浓度0．843 mg/L．利用风险分析理论和蒙特卡罗随机模拟方法,在分析2002-2004年松花湖水体中总磷和总氮浓度实际分布规律的基础上,提出了计算湖、库总磷和总氮水环境容量的不确定性方法．通过对松花湖磷、氮水环境容量的计算,得出松花湖流域总磷和总氮的最大允许排放量为2123．78 t/a和7018．82 t/a,为了使松花湖富营养化发生的概率在0．001以下,总磷和总氮需要分别削减3208．34 t/a和18648．91 t/a． 相似文献
5.
水体营养物及其响应指标基准制定过程中建立参照状态的方法—以典型浅水湖泊太湖为例 总被引：14，自引：2，他引：12
建立参照状态是水体营养物及其响应指标基准制订的关键性工作,建立参照状态的方法主要有时间参考状态法、空间参考状态法、频率法、沉积物历史反演法和预测或外推模型法等,以我国东部湖区典型水体太湖为例,主要应用频率分析法建立了太湖营养物总氮、总磷及响应指标叶绿素a、塞氏深度基准的参照状态,并用时间参考状态法和沉积物历史反演法进行了总氮和总磷参照状态值的验证,综合研究分析显示太湖营养物总磷、总氮的参照状态值应为0.03mg/L、0.6mg/L;响应指标叶绿素a、塞氏深度的参照状态值应为0.004mg/L、0.70m.研究结果旨在为我国水体营养物及其响应指标基准、标准的研究与制订以及我国水体富营养化的控制提供理论和方法借鉴. 相似文献
6.
三峡工程运行前后洞庭湖水质变化分析 总被引：2，自引：1，他引：1
为了解三峡工程运行前后洞庭湖水质变化,基于1996 2013年洞庭湖水质监测数据,采用内梅罗污染指数(IP)法对三峡工程运行前后洞庭湖水质进行评价,并对洞庭湖水质与主要污染物的时空变化特征进行分析.结果表明,1996 2013年洞庭湖IP值在1.10~2.20之间,平均值为1.63,水质属轻污染~污染,总体变化平稳,但从2010年起,洞庭湖IP值连续低于其多年平均值,总体水质趋好;主要污染物为总磷和总氮,总磷浓度变化平稳,总氮浓度则呈显著上升趋势.与三峡工程运行前相比,三峡工程运行后洞庭湖全年和汛期总氮浓度以及南洞庭湖IP值和总氮浓度显著升高,南洞庭湖水质显著恶化.洞庭湖IP值和总磷浓度的水期分布格局均由三峡工程运行前的汛期非汛期变化为三峡工程运行后的非汛期汛期,其空间分布格局均由三峡工程运行前的西洞庭湖东洞庭湖南洞庭湖变化为三峡工程运行后的西洞庭湖南洞庭湖东洞庭湖;从2010年起,洞庭湖IP值的空间分布格局发生新的变化,其大小顺序变化为东洞庭湖南洞庭湖西洞庭湖.三峡工程运行前后洞庭湖IP值与总磷浓度的时空变化与其水沙条件变化有关,总氮浓度的空间分布受三峡工程运行影响较小,主要受湘江、资水等"四水"流域氮污染的影响. 相似文献
7.
系统解析长江中游河湖交汇区域航道水深资源的变化,可支撑“黄金航道”的可持续发展。本研究以洞庭湖-荆江交汇段为对象,研究洞庭湖分汇区域水沙条件、荆江河段滩槽演变与河湖交汇段航道水深资源的关系。研究表明:三峡工程运行以来,洞庭湖三口分流量和分沙量延续了三峡工程运行前的减少态势,伴随洞庭湖分流量减少,相对增加的长江干流径流量增强了河床冲刷强度,反馈使得洞庭湖三口分流量和分沙量均处于较低值;荆江河段河床冲刷给航道尺度提升奠定了有利基础,河湖分汇区域不满足4.5 m×200 m(水深×宽度)的长度为12.6 km,占荆江河段碍航总长度的68.35%。碍航驱动机制上:松滋口分流区段(枝城-昌门溪)的4.5 m水槽贯通但宽度不足200 m,汊道分流关系不稳定及洲滩萎缩制约航道条件稳定,枯水位下降及“坡陡流急”现象仍然严峻,不利于航道条件保障及船舶安全航行;太平口分流区段水位下降、洲滩萎缩、汊道交替发展使得枯水航路不稳定或水深不足4.5 m;藕池口分流区域的洲滩崩退、洲滩冲刷引起的向下游泥沙输移,碍航表现为航宽不足200 m或出现水深不足4.5 m的浅滩;洞庭湖入汇影响区段(熊家洲-城陵矶)受弯道冲淤... 相似文献
8.
典型富营养化城市河流——浙江温瑞塘河的浮游植物群落类型与季节变化 总被引：2，自引：0，他引：2
为评估温瑞塘河水环境状况及水华风险,于2015年每月15日7:00-18:00对其下游滞流河段进行高频监测分析,考察了水体叶绿素a浓度、浮游植物群落类型和光合活性等的季节变化及日变化情况,并分析了其与温度、营养盐等环境因子的关系.结果表明:温瑞塘河表层水体中的叶绿素a浓度表现为春季(3-5月)夏季(6-8月)秋季(9-11月)冬季(12-2月),分别为39.98、37.62、21.59和10.74μg/L;4个季节的平均水温则是夏季秋季春季冬季,分别为30.91、25.34、20.72和13.80℃.全年总氮浓度为5.33±0.81~9.40±1.25 mg/L,总磷浓度为0.32±0.18~0.95±0.25mg/L,营养程度属于超富营养.温瑞塘河的浮游植物群落类型为硅藻-绿藻型,全年以绿藻和硅藻种群为主,蓝藻种群只在春末夏初出现,并且所占比例很小.绿藻种群在夏季占绝对优势,而硅藻种群在冬季占优势.绿藻种群的相对丰度与水温呈正相关,而硅藻种群的相对丰度与水温呈负相关.水体的叶绿素a浓度与水温呈正相关,而与总氮、总磷浓度没有相关性.叶绿素a在不同季节呈现出不同的日变化模式,而浮游植物的有效光合量子产率在四季均呈现类似的日变化模式:都是先降后升,与晴天时的日照强度变化趋势相反.绿藻的有效光合量子产率高于硅藻,且除春季外皆存在显著差异.以上结果表明温瑞塘河具备发生各类水华的营养条件,但是由于蓝藻在全年所占的比例都很低,因此发生蓝藻水华的可能性很小;同时由于日照变化会对表层水体中叶绿素a浓度及浮游植物生理活动产生影响,因此在对小型湖泊或者水流滞缓的河道进行浮游植物群落结构调查时还应考虑时间和天气因素. 相似文献
9.
水华的频发已成为当前三峡水库最为突出的生态环境问题之一。尽管水动力调控叠加上温度变暖和营养负荷增加会诱导水华暴发强度和频率增加,但仍缺乏有效的方法框架去利用野外观测数据评估环境因子与浮游植物间的因果关联。本研究以三峡水库澎溪河监测数据为例,采用非线性时序分析的建模框架来量化浮游植物的因果响应规律。数据来自于2007年6月至2018年9月澎溪河流域的高阳平湖和汉丰湖两个观测点,其中包含了水文、气象和水质及叶绿素a等11种变量。首先,利用奇异谱分析(SSA)分离了叶绿素a和环境因子的低维确定性动力学信号;其次,采用收敛交叉映射(CCM)方法检验了叶绿素a与环境因子间的因果关联。结果显示:(1)气象因子、支流流量、水温、三峡大坝水位和上游调节坝水位是影响高阳平湖叶绿素a时序变化的重要因素;(2)总氮、总磷为代表的营养盐只在汉丰湖观测点中表现出与叶绿素a的因果关系,且总氮较之于总磷对叶绿素a变化影响更为显著;(3)CCM结果与传统的皮尔森相关性分析及格兰杰因果检验比较,证实非线性时序分析方法在分析浮游植物的因果响应上更具优势。本研究为水生态系统的因果建模提供了研究范例,也为推动利用长期观测数据... 相似文献
10.
云南省高原深水湖泊程海磷形态分布和变化 总被引：1，自引：1，他引：0
采用GPS定位,在程海设置了3个断面9个采样点,对各种形态磷进行了为期1 a的研究,分析了高原深水湖泊程海磷形态分布和变化.结果表明:程海中总磷含量范围为0.008～0.155 mg/L,年平均值为0.046 mg/L,含量水平已经较高.存在形态是颗粒态总磷占54.35%;溶解态有机磷占19.56%;溶解态无机磷占26.09%.各形态磷时间分布和变化与水生生物特别是浮游植物生命活动和周期变化密切相关;水平分布格局受浮游生物活动、湖流风动等综合影响;由水表层-亚底层垂直分布比较均匀,湖底层含量不同程度升高. 相似文献
11.
D. M. Pechersky A. A. Lyubushin Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2010,46(7):613-623
The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The
times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized
by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and
the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between
the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic
world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by
the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle
of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes
in the organic world. 相似文献
12.
In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January. 相似文献
13.
The developed dynamic model of the main geomagnetic field (MGF) includes the sources of three levels, which have existed and continuously changed during the 100-year period. The spatial-temporal dynamics of the secular variations in MGF has been considered based on this model. It has been indicated that, at different times, the formation of anomalies (located in similar regions) depended on the total dynamics of different combinations of sources, including a change in the parameters of the dipoles of the secondorder smallness. Anomalies generated by the dynamics of the dipoles of the third-order smallness do not evidently manifest themselves in the total secular variations but are responsible for the specific shapes of isodynamic lines. Based on the stability and continuity of the constructed model, the conclusion is made that long-living turbulent flows of different scales can exist in the liquid core. 相似文献
14.
Site response in the Qionghai Basin in the Wenchuan earthquake 总被引：2，自引：1，他引：1
Amplification effects of soil site response can significantly impact ground motions, and must be considered in the seismic fortification of buildings/structures to prevent or mitigate this potential seismic hazard. Utilizing acceleration time histories from the main shock of the Wenchuan earthquake recorded at four stations (i.e., one on bedrock and three on soil) in the Qionghai Basin, the site responses from three soil sites are studied by using the traditional spectral ratio method. The bedrock site is selected as a reference site. This study found that peak ground accelerations (PGAs) on the soil sites are much larger than on bedrock, with EW, NS and UD components of 3.96–6.58, 6.27–10.98, and 3.17–6.66 times those of the bedrock site, respectively. The amplification effects of the soil sites on ground motions in the frequency range of 0.1 Hz to 10 Hz are significant, depending on the thickness of the soil layer and the frequency content of the site. A significant amplification occurs with high frequency components of ground motion at shallow soil sites, and low and high frequency components of ground motion at intermediate soil sites. 相似文献
15.
浙江省北部及邻区中强地震前地倾斜异常特征及其预测意义 总被引：1，自引：1，他引：0
钟羽云 《地震地磁观测与研究》1998,(3)
解释并讨论了湖州和宁波台１９９３年以来的地倾斜资料,总结了震前有异常显示的６次地震。发现：①异常在现场记录资料中均有显示,异常形态的识别对预报地震有重要的意义;②能观测到异常全过程的倾斜仪与震中的距离基本符合式ｌｇＤｊ＝０．３０３（ＭＳ＋１．６）给出的监测能力半径,大于这个半径的台有时也能观测到异常,但多为短临异常。如果震前记录到异常的全过程,则利用单台资料可能对地震三要素进行预测。 相似文献
16.
Yu. F. Moroz T. A. Moroz V. A. Loginov A. G. Nurmukhamedov D. A. Alekseev 《Izvestiya Physics of the Solid Earth》2016,52(1):29-44
The results of the magnetotelluric (MT) soundings before and after an earthquake are analyzed. The interpretation is based on the longitudinal and transverse MT curves (along and across the strike of the main tectonic elements, respectively). The MT curves are distorted by the ρ- and coast effect. The distortions due to the coast effect are estimated by the testing three-dimensional (3D) model. It is established that the coast effect distortion at the periods up to 1000 s is small and can be disregarded. The divergence of the longitudinal and transverse MT curves, which points to the presence of the deep faults, is thoroughly studied. The inversion of the MTsounding curves is carried out by the REBOCC program of the numerical two-dimensional modeling. This program implements the procedures of elimination of the ρ-effect and the joint inversion of the longitudinal and transverse MT sounding curves. The obtained geoelectrical cross sections provide an insight into the structure of electrical conductivity of the lithosphere before and after the earthquake. The more intense variations in the electric conductivity are observed in the zone of the deep faults. These variations are related to the changes in the porosity and saturation of the rocks by the highly mineralized fluids. 相似文献
17.
The continuous increase in concentration of greenhouse gases in the atmosphere is expected to cool higher levels of the atmosphere. There is some direct and indirect experimental evidence of long-term trends in temperature and other parameters in the mesosphere and lower thermosphere (MLT). Here we look for long-term trends in the annual and semiannual variations of the radio wave absorption in the lower ionosphere, which corresponds to the MLT region heights. Data from central and southeastern Europe are used. A consistent tendency to a positive trend in the amplitude of the semiannual wave appears to be observed. The reality of a similar tendency in the amplitude of the annual wave is questionable in the sense that the trend in the amplitude of the annual wave is probably induced by the trend in the yearly average values of absorption. The phases of both the annual and semiannual waves display a forward tendency, i.e. shift to an earlier time in the year. A tentative interpretation of these results in terms of changes of the seasonal variation of temperature and wind at MLT heights does not contradict the trends observed in those parameters. 相似文献
18.
M. MONIRUL QADER MIRZA 《水文科学杂志》2013,58(5):613-631
Abstract The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly. 相似文献
19.
George E. Backus 《Physics of the Earth and Planetary Interiors》1982,28(3):191-214
A rigorous singular perturbation theory is developed to estimate the electric field E produced in the mantle M by the core dynamo when the electrical conductivity σ in M depends only on radius r, and when |r?rln σ| ? 1 in most of M. It is assumed that σ has only one local minimum in M, either (a) at the Earth's surface ?V, or (b) at a radius b inside the mantle, or (c) at the core-mantle boundary ?K. In all three cases, the region where σ is no more than e times its minimum value constitutes a thin critical layer; in case (a), the radial electric field Er ≈ 0 there, while in cases (b) and (c), Er is very large there. Outside the critical layer, Er ≈ 0 in all three cases. In no case is the tangential electric field ES small, nearly toroidal, or nearly calculable from the magnetic vector potential A as ??tAS. The defects in Muth's (1979) argument which led him to contrary conclusions are identified. Benton (1979) cited Muth's work to argue that the core-fluid velocity u just below ?K can be estimated from measurements on ?V of the magnetic field B and its time derivative . A simple model for westward drift is discussed which shows that Benton's conclusion is also wrong.In case (a), it is shown that knowledge of σ in M is unnecessary for estimating ES on ?K with a relative error |r?r 1nσ|?1from measurements of ES on ?V and knowledge of ?tB in M (calculable from ?tB on ?V if σ is small). Then, in case (a), u just below ?K can be estimated as . The method is impractical unless the contribution to ES on ?V from ocean currents can be removed.The perturbation theory appropriate when σ in M is small is considered briefly; smallness of σ and of |r?r ln σ|?1 a independent questions. It is found that as σ → 0, B approaches the vacuum field in M but E does not; the explanation lies in the hydromagnetic approximation, which is certainly valid in M but fails as σ → 0. It is also found that the singular perturbation theory for |r?r ln σ|?1 is a useful tool in the perturbation calculations for σ when both σ and |r?r ln σ|?1 are small. 相似文献
20.
Matthias Koschorreck Katrin Wendt-Potthoff Burkhard Scharf Hans H. Richnow 《Journal of Volcanology and Geothermal Research》2008
The biogeochemistry of methane in the sediments of Lake Caviahue was examined by geochemical analysis, microbial activity assays and isotopic analysis. The pH in the water column was 2.6 and increased up to a pH of 6 in the deeper sediment pore waters. The carbon isotope composition of CH4 was between − 65 and − 70‰ which is indicative for the biological origin of the methane. The enrichment factor ε increased from − 46‰ in the upper sediment column to more than − 80 in the deeper sediment section suggesting a transition from acetoclastic methanogenesis to CO2 reduction with depth. In the most acidic surface layer of the sediment (pH < 4) methanogenesis is inhibited as suggested by a linear CH4 concentration profile, activity assays and MPN analysis. The CH4 activity assays and the CH4 profile indicate that methanogenesis in the sediment of Lake Caviahue was active below 40 cm depth. At that depth the pH was above 4 and sulfate reduction was sulfate limited. Methane was diffusing with a flux of 0.9 mmol m− 2 d− 1 to the sediment surface where it was probably oxidized. Methanogenesis contributed little to the sediments carbon budget and had no significant impact on lake water quality. The high biomass content of the sediment, which was probably caused by the last eruption of Copahue Volcano, supported high rates of sulfate reduction which probably raised the pH and created favorable conditions for methanogens in deeper sediment layers. 相似文献