共查询到20条相似文献，搜索用时 46 毫秒
1.
浮游植物动力学模型及其在海域富营养化研究中的应用 总被引：10，自引：2，他引：10
浮游植物动力学模型用来研究特定海域浮游植物生物量的时空分布规律，定量确定各种物理，生物过程的贡献，对解决浮游植物生物量异常增加导致的富营养化问题具有至关重要的作用，综述了国内外海洋浮游植物动力学模型研究的发展过程和现状，介绍了几种不同时空尺度浮游植物动力学模型的特点和性能，此类模型在发达国家的海域富营养化研究和环境管理中已取得了相当的进展，而我国目前虽已开展了海洋生态模型的初步研究，但面临一些困难，其中不仅需要获取特定海域的过程参数，而且急需对海域的强迫过程和边界过程加强认识。 相似文献
2.
Estuarine turbidity maxima (ETM) play an important role in zooplankton and larval fish productivity in many estuaries. Yet in many of these systems, little is known about the food web that supports this secondary production. To see if phytoplankton have the potential to be a component of the ETM food web in the Chesapeake Bay estuary a series of cruises were carried out to determine the biomass distribution and floral composition of phytoplankton in and around the ETM during the winter and spring using fluorometry, high-performance liquid chromatography (HPLC), and microscopy. Two distinct phytoplankton communities were observed along the salinity gradient. In lower salinity waters, biomass was low and the community was composed mostly of diatoms, while in more saline waters biomass was high and the community was composed mostly of mixotrophic dinoflagellates, which were often concentrated in a thin layer below the pycnocline. Phytoplankton biomass was always low in the ETM, but high concentrations of phytoplankton pigment degradation products and cellular remains were often observed suggesting that this was an area of high phytoplankton mortality and/or an area where phytoplankton derived particulate organic matter was being trapped. These results, along with a box model analysis, suggest that under certain hydrodynamic conditions phytoplankton derived organic matter can be trapped in ETM and potentially play a role in fueling secondary production. 相似文献
3.
Edward J. Phlips Susan Badylak Jane Hart Daniel Haunert Jean Lockwood Kathyrn O’Donnell Detong Sun Paula Viveros Mete Yilmaz 《Estuaries and Coasts》2012,35(1):335-352
The St. Lucie Estuary, located on the southeast coast of Florida, provides an example of a subtropical ecosystem where seasonal
changes in temperature are modest, but summer storms alter rainfall regimes and external inputs to the estuary from the watershed
and Atlantic Ocean. The focus of this study was the response of the phytoplankton community to spatial and temporal shifts
in salinity, nutrient concentration, watershed discharges, and water residence times, within the context of temporal patterns
in rainfall. From a temporal perspective, both drought and flood conditions negatively impacted phytoplankton biomass potential.
Prolonged drought periods were associated with reduced nutrient loads and phytoplankton inputs from the watershed and increased
influence of water exchange with the Atlantic Ocean, all of which restrict biomass potential. Conversely, under flood conditions,
nutrient loads were elevated, but high freshwater flushing rates in the estuary diminished water residence times and increase
salinity variation, thereby restricting the buildup of phytoplankton biomass. An exception to the latter pattern was a large
incursion of a cyanobacteria bloom from Lake Okeechobee via the St. Lucie Canal observed in the summer of 2005. From a spatial
perspective, regional differences in water residence times, sources of watershed inputs, and the proximity to the Atlantic
Ocean influenced the composition and biomass of the phytoplankton community. Long water residence times in the North Fork
region of the St. Lucie Estuary provided an environment conducive to the development of blooms of autochthonous origin. Conversely,
shorter residence times in the mid-estuary limit autochthonous increases in biomass, but allochthonous sources of biomass
can result in bloom concentrations of phytoplankton. 相似文献
4.
遥感技术在泸定县地质灾害调查中的应用 总被引：1，自引：0，他引：1
泸定县地质灾害频繁发生,严重威胁人民生命财产安全。遥感技术具有时效性好、宏观性强、信息丰富等特点,可以真实地反映地质灾害发生时的具体情况,已经成为地质灾害调查的一种重要技术方法手段。运用SPOT5图像和ETM融合SPOT5-PAN图像,通过一定的图像处理手段,获得地质灾害遥感解译底图,采用机助目视解译方法结合地面调查,可以快速、全面地查明泸定县地质灾害分布、规模和危害,提高地质灾害调查的效率和精度,取得较好的应用效果。 相似文献
5.
Hans W. Paerl Karen L. Rossignol S. Nathan Hall Benjamin L. Peierls Michael S. Wetz 《Estuaries and Coasts》2010,33(2):485-497
Estuarine and coastal systems represent a challenge when it comes to determining the causes of ecological change because human
and natural perturbations often interact. Phytoplankton biomass (chlorophyll a) and group-specific photopigment indicators were examined from 1994 to 2007 to assess community responses to nutrient and
climatic perturbations in the Neuse River Estuary, NC. This system experienced nutrient enrichment and hydrologic variability,
including droughts, and an increase in hurricanes. Freshwater input strongly interacted with supplies of the limiting nutrient
nitrogen (N) and temperature to determine the location, magnitude, and composition of phytoplankton biomass. Multi-annual,
seasonal, and episodic hydrologic perturbations, including changes in the frequency and intensity of tropical storms, hurricanes
and droughts, caused significant shifts in phytoplankton community structure. Climatic oscillations can at times overwhelm
anthropogenic nutrient inputs in terms of controlling algal bloom thresholds, duration, and spatial extent. Eutrophication
models should incorporate climatically driven changes to better predict phytoplankton community responses to nutrient inputs
and other anthropogenic perturbations. 相似文献
6.
遥感图像中地表水体同山体、建筑物等地物产生的阴影在光谱特征上存在较高的类间相似性,导致提取过程中容易出现混淆和错分的情况。针对此问题,提出一种基于面向对象和人工蜂群的地表水体提取方法。该方法首先对遥感图像进行分割以获取分割对象的光谱、比率、几何形状等统计特征,以弥补高分遥感图像波段数目少,信息量不足的缺陷;并借助人工蜂群算法在解决复杂问题最优化方面的优势,选取水体同阴影二值分类的几何平均正确率作为算法的适应度函数,最终获取地表水体的最优化提取规则。选取厦门市大嶝岛和湖南省资兴市部分区域,基于国产高分一号、二号遥感数据进行水体提取,并与传统SVM分类结果进行比较。实验结果表明本算法提取水体的总体精度和Kappa系数均优于传统SVM分类器,表明该方法可应用于高分遥感图像的地表水体提取。 相似文献
7.
Thomas C. Malone Daniel J. Conley Thomas R. Fisher Patricia M. Glibert Lawrence W. Harding Kevin G. Sellner 《Estuaries and Coasts》1996,19(2):371-385
The scales on which phytoplankton biomass vary in response to variable nutrient inputs depend on the nutrient status of the plankton community and on the capacity of consumers to respond to increases in phytoplankton productivity. Overenrichment and associated declines in water quality occur when phytoplankton growth rate becomes nutrient-saturated, the production and consumption of phytoplankton biomass become uncoupled in time and space, and phytoplankton biomass becomes high and varies on scales longer than phytoplankton generation times. In Chesapeake Bay, phytoplankton growth rates appear to be limited by dissolved inorganic phosphorus (DIP) during spring when biomass reaches its annual maximum and by dissolved inorganic nitrogen (DIN) during summer when phytoplankton growth rates are highest. However, despite high inputs of DIN and dissolved silicate (DSi) relative to DIP (molar ratios of N∶P and Si∶P>100), seasonal accumulations of phytoplankton biomass within the salt-intruded-reach of the bay appear to be limited by riverine DIN supply while the magnitude of the spring diatom bloom is governed by DSi supply. Seasonal imbalances between biomass production and consumption lead to massive accumulations of phytoplankton biomass (often>1,000 mg Chl-a m?2) during spring, to spring-summer oxygen depletion (summer bottom water <20% saturation), and to exceptionally high levels of annual phytoplankton production (>400 g m?2 yr?1). Nitrogen-dependent seasonal accumulations of phytoplankton biomass and annual production occur as a consequence of differences in the rates and pathways of nitrogen and phosphorus cycling within the bay and underscore the importance of controlling nitrogen inputs to the mesohaline and lower reaches of the bay. 相似文献
8.
Remote sensing has been widely used to map geological structure, regolith materials and hydrothermal alteration minerals in different regions of the world, based largely on the spectral characteristics of clay/carbonate and iron oxide minerals. Given that features related to minerals may form very subtle patterns in Landsat imagery, finding suitable methods for enhancing the spectral information due to alteration minerals has been the subject of much research since the satellites were launched. Although multispectral sensors such as Landsat do not have enough spectral resolution to distinguish between specific minerals, effective processing of the data does yield useful images for regional exploration and targeting when combined with a good understanding of the associated landforms. ASTER and various airborne systems can now provide useful, high-resolution mineral information. However, the cost and time taken to acquire and process good resolution spectral data should now be balanced against the enhanced spectral discrimination possible using temporal merging, or data stacking, from the existing Landsat data archive dating back to 1972. One critical characteristic of the spectra related to surface mineral composition is its persistence over time. This study proposes a further enhancement to the data using temporal merging to create images that are both easier to interpret, and more reliable indicators of lithology and alteration. The new approach is to select a large number of scenes, typically separated by two or more years, and to merge the data for each band to give a cumulative spectral signature. The technique of stacking Landsat data to create a new dataset with much greater spectral depth is termed Landsat TM3, or Landsat TM Temporal Merge for Terrain Mapping. This emphasises not only the process used to create the dataset, but also the dominant use to which these data are ideally suited, namely mapping geological and mineral-related terrains. 相似文献
9.
遥感的科学推动作用与重点应用领域 总被引：1，自引：0，他引：1
在调研国内外遥感案例的基础上,论述了遥感在推动地球系统科学发展方面的作用,及在我国的重点应用领域。遥感催生了全球变化研究,使得人类得以从新的视角来探索地球上的生命未来;遥感推动了地球科学从定性到定量、从描述到分析、从单站点到多时空尺度的变革,诸多新兴交叉学科应运而生。遥感是应用驱动的,一致性及可对比性是定量遥感的核心,也是遥感深化应用的基础。遥感应用于众多领域,但不同的国家基于各自的国情有不同的侧重点,其中,维护国家全球利益、灾害快速响应与灾后评估、第三方独立监督、保障国防安全是我国的应用重点。 相似文献
10.
笔者在新疆吉木萨尔地区开展航空高光谱遥感油气探测示范研究的过程中,发现油气渗漏地区往往有盐碱化现象。据此,利用航空高光谱成像系统在该区取得的可见光-近红外和短波红外遥感数据,采用自主开发的波段分类填图方法,对吉木萨尔农田、荒地和戈壁地区的油气渗漏异常信息进行了提取,经野外验证和化学分析,圈定了7处油气渗漏异常区。同时,构建了盐碱化的高光谱识别模型,利用该模型进行了盐碱化信息填图,并对吉木萨尔同一覆盖区的盐碱化异常进行了提取,圈定了盐碱化异常区。通过对油气渗漏异常区与盐碱化异常区的叠置聚焦分析,发现二者空间位置有高度的重合性。笔者认为这一高光谱遥感探测发现,不仅具有探索的理论意义,而且具有实用价值。其实用价值主要体现在高光谱遥感油气探测中,通过烃碱信息的相互印证,可以减少油气信息的漏判,提高油气渗漏信息识别的准确性。同时,在缺少航空高光谱遥感数据的情况下,还可以利用卫星多光谱遥感数据源,通过提取盐碱化异常和圈定盐碱化异常区的途径,帮助缩小找油气的目标区,为油气资源的调查、评价和选区提供新的信息和依据。上述研究同时表明,自然界的盐碱化可能并非全是由"干旱蒸发"形成,很可能还存在与油气有关的盐碱化,在油气勘查中如何区分这两种类型的盐碱化,特别是应用高光谱遥感技术将二者区分开来,是值得深入探讨的科学问题。 相似文献
11.
震害遥感快速提取研究——以2003年2月24日巴楚—伽师6.8级地震为例 总被引：14，自引：0，他引：14
论述了遥感影像提取震害的研究进展 ,提出了基于GIS和数字图像处理技术的震害遥感快速提取与损失评估的技术途径。在此基础上 ,介绍了巴楚—伽师地震的航空与卫星遥感资料的获取、图像数字处理与震害提取过程 ;描述了地震造成的建筑物震害与地质灾害的遥感图像特征 ;根据以往震害遥感影像统计经验与本次地震震害遥感特征 ,提出了遥感震害分级分类标准和地震烈度划分标准 ,进而得到基于震害遥感影像的伽师地震等震线图。文中对所得到的地震烈度与地面实际调查结果进行了比较。通过遥感信息源空间分辨率要求与信息获取与处理的时效性分析 ,认为我国利用航空遥感与卫星遥感资料获取地震灾情信息已进入实用阶段 相似文献
12.
遥感岩石学的研究及其进展 总被引：10，自引：1，他引：10
结合近几年来的研究实践以及国内外大量研究成果的分析，提出了遥感地质学中的一个重要分支科学－－“遥感岩石学”的概念及定义，介绍了遥感岩石学的三个重要研究内容：（１）岩石，矿物的光谱特征研究；（２）机载遥感数据的岩石信息提取与识别；（３）星载遥感数据的岩石信息提取与识别，并对遥感岩石学的未来发展作了展望。 相似文献
13.
The potential risk from cyanobacteria blooms is the basis for predicting, preventing, and managing eutrophication. Poyang Lake lies on the southern bank of the middle and lower reaches of the Yangtze River. This lake is a large shallow lake connected to the Yangtze River and is affected by monsoon. The comprehensive evaluation index system, evaluation model, and method of the potential risk from cyanobacteria blooms were constructed based on the nutrient zoning in Poyang Lake, and the potential risk from cyanobacteria blooms was evaluated in 2013. (1) The evaluation index system comprises physical, chemical, and biological indicators. The physical indicators consist of blocking degree, lake region location, transparency (Secchi disk depth, SD), and temperature; the chemical indicators consist of total nitrogen (TN) and total phosphorus (TP); and the biological indicators consist of chlorophyll a (Chla) and phytoplankton biomass. Among the indicators, blocking degree and lake region location along with the prevailing wind direction were selected to represent the indicators affected by water retention time and wind direction. (2) We established a comprehensive evaluation method for assessing the potential risk from cyanobacteria blooms by adopting both analytic hierarchy process weighting and a comprehensive evaluation method. (3) Results show that the high-risk periods for cyanobacteria blooms were August, July, and December, and the high-risk regions were in the Northeastern Lake Region, Western Lake Region and Northern Lake Region. The Northeastern Lake Region is particularly in high risk in August and July. These cyanobacteria blooms presented heavy risk or close to heavy risk. Based on the risk evaluation indicators, outbreaks of cyanobacteria blooms are limited by temperature and location. Chla and phytoplankton biomass were the key indices affecting the level of potential risk from cyanobacteria blooms during the high-water-level period (July and August). In contrast, TN and TP are the key indices affecting the level of harm during the low-water-level period. Within a year, Chla, phytoplankton biomass, and TP are key indicators for the prediction of cyanobacteria blooms in Poyang Lake. 相似文献
14.
Increased frequency and severity of droughts, as well as growing human freshwater demands, in the Apalachicola-Chattahoochee-Flint River Basin are expected to lead to a long-term decrease in freshwater discharge to Apalachicola Bay (Florida). To date, no long-term studies have assessed how river discharge variability affects the Bay’s phytoplankton community. Here a 14-year time series was used to assess the influence of hydrologic variability on the biogeochemistry and phytoplankton biomass in Apalachicola Bay. Data were collected at 10 sites in the bay along the salinity gradient and include drought and storm periods. Riverine dissolved inorganic nitrogen and phosphate inputs were correlated to river discharge, but chlorophyll a (Chl a) was similar between periods of drought and average/above-average river discharge in most of the Bay. Results suggest that the potentially negative impact of decreased riverine nutrient input on Bay phytoplankton biomass is mitigated by the nutrient buffering capacity of the estuary. Additionally, increased light availability, longer residence time, and decreased grazing pressures may allow more Chl a biomass to accumulate during drought. In contrast to droughts, tropical cyclones and subsequent increases in river discharge increased flushing and reduced light penetration, leading to reduced Chl a in the Bay. Analysis of the time series revealed that Chl a concentrations in the Bay do not directly mirror the effect of riverine nutrient input, which is masked by multiple interacting mechanisms (i.e., nutrient loading and retention, grazing, flushing, light penetration) that need to be considered when projecting the response of Bay Chl a to changes in freshwater input. 相似文献
15.
基于多时相Landsat遥感影像,利用适合白洋淀湿地信息提取的综合提取方法提取湿地范围。将湿地范围视为水体淹没区,淹没区的边界线视为对应地表水位高程的等高线,并根据遥感影像、高程控制点等对淀区内受人为影响的局部区域进行校正,插值生成白洋淀湿地底部的数字高程模型(DEM)。选用遥感影像和地面高程控制点对构建的数字高程模型进行验证,遥感影像验证精度在80%以上,地面控制点验证误差在±0.5 m以内的点达到80%。这种由一系列遥感影像提取等高线生成数字高程模型的方法可以弥补白洋淀湿地内数字高程信息不足的缺陷,对于提高白洋淀湿地的水均衡计算和构建湖泊与地下水耦合模型的精度有着重要意义。 相似文献
16.
Karol Przeździecki Jarosław Zawadzki Zygmunt Miatkowski 《Environmental Earth Sciences》2018,77(17):623
Anthropogenic activities, especially resulting in changes in the water conditions, usually disturb biological and agricultural functions of grasslands, leading to their degradation, often on large areas. Remote sensing observations of such changes in grassland ecosystems evoke a great interest, but they are still a difficult task, especially when performed on industrial and mining areas. This paper presents a new effective method of remote sensing of grassland moisture conditions based on temperature–vegetation dryness index (TVDI) calculated from free Landsat imagery, and employing the TVDI spatial variability estimated from a semivariance analysis. The practical applicability of the method is demonstrated on the example of monitoring of the extensive neighborhood of lignite open-cast mine within a period of a few years. Besides, the developed method was validated at the studied area, using in situ information. Thus, we demonstrated that TVDI may serve as an effective indicator of grassland moisture conditions, even in problematic areas. 相似文献
17.
Thomas J. Jackson 《Hydrogeology Journal》2002,10(1):40-51
Remote sensing provides information on the land surface. Therefore, linkages must be established if these data are to be
used in groundwater and recharge analyses. Keys to this process are the use of remote sensing techniques that provide information
on soil moisture and water-balance models that tie these observations to the recharge. Microwave remote sensing techniques
are used to map the spatial domain of surface soil moisture and to monitor its temporal dynamics, information that cannot
be measured using other techniques. The physical basis of this approach is presented with examples of how microwave remote
sensing is utilized in groundwater recharge and related studies.
Electronic Publication 相似文献
18.
Understanding land-use/cover change process for land and environmental resources use management policy in Ghana 总被引：2，自引：0，他引：2
Opoku Pabi 《GeoJournal》2007,68(4):369-383
Accurate information on land-use/cover change is a critical input for natural resource use management policy decisions. In
Ghana, however, land-use/cover change is premised on the assumption that there has been a historically simple, linear, and
uniform degradation of vegetation across all landscapes. The Kintampo and neighboring districts have become a subject of intense
debate as to the real nature of prevailing land cover changes .It is commonly assumed that there is ubiquitously progressive
irreversible woody vegetation loss across the area. The paper reports on the process and amount of land-use/cover changes
that have prevailed in specific localities across the area within a 10-year period. It is hoped this will improve understanding
and management of land-use/cover change in Ghana. Remote sensing and Geographic information systems technologies were used
for the investigation. A multi-site satellite imagery approach was adopted to ensure that inductive inferences could be made.
The outcome of the study indicated that, in space and time, there have been significant land-use/cover changes. Variability
in change was a constant, rather than occasional feature across these human dominated landscapes. The conversion and transformation
processes indicated that the traditional land-use strategies are self-sustaining. Any effective land-use/cover management
strategy should be built upon the existing traditional farming system knowledge and practices. 相似文献
19.
S. A. Rizvi M. Latif S. Ahmad 《International Journal of Environmental Science and Technology》2012,9(3):441-452
In this study, a great variation in crop yield, which affects the socio-economic and physical environment of the area, is observed along the irrigation channels in Pakistan. This is mainly due to inequitable distribution of canal water causing spatial variations along the system. Assessing the performance of irrigation system can help to find any disparity which should be rectified to achieve the desired objectives of irrigation. Due to lack of real-time data, performance of an irrigation system cannot be readily determined particularly in developing countries. Remote sensing and geographic information system are the best tools to overcome this difficulty. Normalized difference vegetation index indirectly indicates the presence of water in plants. Biomass production and evapotranspiration are crucial indicators for describing the spatial variation of irrigation water. In this study, infrared bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer sensor were used to determine surface temperatures and various components of the energy balance equation. The spatial disparity in evapotranspiration was found from head to tail of the system. Classification of evapotranspiration into different groups revealed that the area under higher evapotranspiration range is more at the head of the system than its tail, which indicates that more canal water is supplied at the head of the system. These results clearly testify the disparity of canal water distribution along the system leading to reduced income and environmental degradation of the downstream water users. 相似文献
20.
Iveta Jurgensone Jacob Carstensen Anda Ikauniece Baiba Kalveka 《Estuaries and Coasts》2011,34(6):1205-1219
Trends in phytoplankton monitoring data (1976–2008) from the Gulf of Riga were investigated and linked to environmental factors.
Annual means of spring phytoplankton biomass correlated to phosphorus input from land and shifts between diatoms and dinoflagellates
were attributed to potential Si limitation and time of sampling relative to the spring phytoplankton succession. The summer
phytoplankton biomass, which more than doubled over the study period, was related to the abundance of summer copepods that
similarly declined. Cyanobacterial blooms proliferated in summer and the proportion of diatoms similarly declined when the
winter–spring inorganic N/P ratio was low. The chlorophyte proportion in summer increased over the study period, and this
was linked to increasing temperatures favoring their higher growth rates. The dinoflagellate proportion appeared to decrease
with temperatures above a threshold of 15.5°C. Although nutrient inputs and their ratios are important factors for the phytoplankton
community, this study suggests that climate change and overfishing could be equally important. 相似文献