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121.
All JD 《Environmental management》2006,37(1):111-125
Accurate procedures that measure hydrologic variability would have great value for evaluating ecosystem impacts of upstream
water use in the Colorado River Basin. Many local extractive income-based stakeholders rely directly or indirectly on ecosystem
health and are adversely affected when the river does not flow. This study focuses on the impact of little or no Colorado
River flow on the Mexican shrimp industry. Although there have been complaints that U.S. diversions of Colorado River flow
have greatly impaired the shrimp fishery, this research demonstrates that freshwater rarely reaches the Gulf even during times
of flooding, and that other factors such as overfishing may influence the instability of shrimp populations. Advanced very-high-resolution
radiometer (AVHRR) satellite imagery was used to assess water volumes diverted away from the channel of the Colorado River
and ultimately the Gulf of California during flooding periods. Analysis of data demonstrated that little freshwater actually
reaches the Gulf even during floods because of its diversion into a large dry lake bed basin known as Laguna Salada. Fuller
use of the Colorado River throughout its entire course to the sea is possible and could benefit a large cohort of users without
catastrophic habitat destruction in delta ecosystems. Reconstruction of a natural earthen berm, as proposed by Ducks Unlimited,
would maximize the use of floodwaters for ecosystem benefits. These findings have profound implications for local economic
activities dependent on hydrologic resources in the Colorado River Delta and Upper Gulf. 相似文献
122.
根据2014年全年实时在线观测数据,分析了徐州睢宁地区大气细颗粒物(PM_(2.5))和气态污染物(包括SO_2、CO、NO_x、O_3)质量浓度的季节性变化特征。结合后向轨迹模型,分析不同气团对该地区大气污染浓度的影响。PM_(2.5)与O_3值在夏季最低,呈显著相关,表明夏季PM_(2.5)主要受控于本地大气光化学活性。在冬季,除O_3外,PM_(2.5)、SO_2、CO、NO_x值最高,且大气颗粒物主要以细粒子为主。O_3在春季最高,并与远程传输的气团且经过我国东部污染源密集地区相对应。高浓度的PM_(2.5)主要与冬季缓慢移动的气团相对应,这可能将PM_(2.5)及其气态前体物传输至该地区进而加重大气污染程度。 相似文献
123.
Pu R Gong P Tian Y Miao X Carruthers RI Anderson GL 《Environmental monitoring and assessment》2008,140(1-3):15-32
For monitoring and controlling the extent and intensity of an invasive species, a direct multi-date image classification method
was applied in invasive species (salt cedar) change detection in the study area of Lovelock, Nevada. With multidate Compact
Airborne Spectrographic Imager (CASI) hyperspectral data sets, two types of hyperspectral CASI input data and two classifiers
have been examined and compared for mapping and monitoring the salt cedar change. The two types of input data are all two-date
original CASI bands and 12 principal component images (PCs) derived from the two-date CASI images. The two classifiers are
an artificial neural network (ANN) and linear discriminant analysis (LDA). The experimental results indicate that (1) the
direct multitemporal image classification method applied in land cover change detection is feasible either with original CASI
bands or PCs, but a better accuracy was obtained from the CASI PCA transformed data; (2) with the same inputs of 12 PCs, the
ANN outperforms the LDA due to the ANN’s non-linear property and ability of handling data without a prerequisite of a certain
distribution of the analysis data. 相似文献
124.
Land use/land cover (LULC) has a profound impact on economy, society and environment, especially in rapid developing areas.
Rapid and prompt monitoring and predicting of LULC’s change are crucial and significant. Currently, integration of Geographical
Information System (GIS) and Remote Sensing (RS) methods is one of the most important methods for detecting LULC’s change,
which includes image processing (such as geometrical-rectifying, supervised-classification, etc.), change detection (post-classification),
GIS-based spatial analysis, Markov chain and a Cellular Automata (CA) models, etc. The core corridor of Pearl River Delta
was selected for studying LULC’s change in this paper by using the above methods for the reason that the area contributed
78.31% (1998)–81.4% (2003) of Gross Domestic Product (GDP) to the whole Pearl River Delta (PRD). The temporal and spatial
LULC’s changes from 1998 to 2003 were detected by RS data. At the same time, urban expansion levels in the next 5 and 10 years
were predicted temporally and spatially by using Markov chain and a simple Cellular Automata model respectively. Finally,
urban expansion and farmland loss were discussed against the background of China’s urban expansion and cropland loss during
1990–2000. The result showed: (1) the rate of urban expansion was up to 8.91% during 1998–2003 from 169,078.32 to 184,146.48 ha;
(2) the rate of farmland loss was 5.94% from 312,069.06 to 293,539.95 ha; (3) a lot of farmland converted to urban or development
area, and more forest and grass field converted to farmland accordingly; (4) the spatial predicting result of urban expansion
showed that urban area was enlarged ulteriorly compared with the previous results, and the directions of expansion is along
the existing urban area and transportation lines. 相似文献
125.
成都市河流水质变化趋势及污染控制措施 总被引:1,自引:0,他引:1
研究了2001—2012年成都市河流水质类别变化趋势,结果表明:该市河流Ⅰ类~Ⅲ类水质类别占比从"十五"期间的35.5%上升后,能多年稳定在61.5%~71.8%之间;岷江内江劣Ⅴ类水质占比从"十一五"的4.5%飙升至2012年的33.3%,水质恶化情势令人担忧;集中式饮用水源地都江堰水文站2011—2012年连续2 a水质由Ⅱ类降为Ⅲ类;岷江出境断面黄龙溪、岳店子水质多年不达标,形势堪忧。为此,提出有效划定全市人口、经济生态红线,建立入境断面水质监测管理与启用应急备用水源联动机制,发掘和推广水质持续改善区域先进管理经验,着力Ⅳ类水域治理,是实现成都市河流水质污染控制目标的关键措施。 相似文献
126.
S. P. Henzi D. Lusseau T. Weingrill C. P. van Schaik L. Barrett 《Behavioral ecology and sociobiology》2009,63(7):1015-1021
There is an established and very influential view that primate societies have identifiable, persistent social organizations.
It assumes that association patterns reflect long-term strategic interests that are not qualitatively perturbed by short-term
environmental variability. We used data from two baboon troops in markedly different habitats over three consecutive seasons
to test this assumption. Our results demonstrate pronounced cyclicity in the extent to which females maintained differentiated
relationships. When food was plentiful, the companionships identified by social network analysis in the food-scarce season
disappeared and were replaced by casual acquaintanceships more representative of mere gregariousness. Data from the fourth,
food-scarce, season at one site indicated that few companions were re-united. It is likely that this reflected stochastic
variation in individual circumstances. These results suggest that attention could profitably be paid to the effects of short-term
local contingencies on social dynamics, and has implications for current theories of primate cognitive evolution.
This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and
R. James). 相似文献
127.
The United Nations Framework Convention on Climate Change (UNFCCC), which was signed by some 153 countries at the Earth Summit in Rio de Janeiro, Brazil in 1992, represented a singular triumph for the geographically dispersed group of island states and low-lying coastal developing countries, located in the Pacific, Atlantic and Indian Oceans, as well as in the Caribbean, South China and Mediterranean Seas, and known as the Alliance of Small Island States (AOSIS). This article focuses on the goals of AOSIS during the negotiations leading up to the adoption of the UNFCCC. For the first time in the history of the United Nations, a group of small states, hitherto relegated to the sidelines, was able to develop a specific negotiating agenda addressing areas which are of overriding concern to them and succeeded in having those concerns incorporated in a legally binding Convention of historic importance. As this article reveals, AOSIS set itself 12 negotiating goals during the negotiating rounds leading up to the UNFCCC, and 10 of these 12 goals were realized. Nevertheless, AOSIS, whose member states are most vulnerable to the possible adverse effects of climate change, was particularly concerned about those provisions of the UNFCCC that were either watered-down significantly, made largely meaningless or excluded altogether. These include: the absence of definite targets or specific timetables for the significant reduction of carbon dioxide by the industrialized countries of the North; the lack of permanent and clear financing arrangements in particular the lack of definitive financial provisions for adaptive response measures to the adverse impacts of climate change such as sea-level rise; and the absence of a specific provision for the implementation of coastal zone management schemes for those countries most vulnerable to sea-level rise. As the UNFCCC moves into the implementation phase, AOSIS should and must build on its past success. To do so, it will need to develop clearly defined initiatives aimed at strengthening the commitments for financing and insurance, and to seek inclusion of a provision to develop and finance coastal zone management schemes for the most vulnerable small states. While the article covers the AOSIS negotiating period up to and including the Earth Summit in June 1992, we nevertheless postulate some possible objectives which the AOSIS group might wish to consider in what is sure to be an intensive post-Earth Summit phase of the UNFCCC, leading up to the first Conference of the Parties of that Convention. 相似文献
128.
This study investigates environmental change over a 30-year period and attempts to gain a better understanding of human impacts
on an arid environment and their consequences for regional development. Multi-temporal remotely sensed imagery was acquired
and integrated to establish the basis for change detection and process analysis. Land cover changes were investigated in two
categories, namely categorical change using image classification and quantitative change using a vegetation index. The results
show that human-induced land cover changes have been minor in this remote area. However, the pace of growth of human-induced
change has been accelerating since the early 1990s. The analysis of the multi-temporal vegetation index also shows no overall
trend of rangeland deterioration, although local change of vegetation cover caused by human activities was noticeable. The
results suggest that the current trend of rapid growth may not be sustainable and that the implementation of effective counter-measures
for environmentally sound development is a rather urgent matter. 相似文献
129.
Tato L Tremolada P Ballabio C Guazzoni N Parolini M Caccianiga M Binelli A 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2656-2664
The seasonal and spatial variability of polychlorinated biphenyls (PCBs) in vegetation and cow milk was studied in a high altitude pasture in the Alps (1900 m a.s.l.). PCB contamination in vegetation shows a concentration peak in June, which is mainly interpreted as the consequence of a temporary PCB enrichment of the air layer above the ground due to net emission fluxes from the soil. A three compartment dynamic model was developed to test this hypothesis. The North/South enrichment factor in the vegetation was 1.5-1.6 for penta- and hexa-substituted congeners and 1.7 for hepta- and octa-PCBs, according to the effect of temperature on compounds having higher Koa values. Milk concentrations followed the vegetation seasonal trend. The congener abundance in milk is in agreement with the biotransformation susceptibility, absorption efficiency and residence time of the different congeners in dairy cows. 相似文献
130.
Wang R Cao H Li W Wang W Wang W Zhang L Liu J Ouyang H Tao S 《Environmental pollution (Barking, Essex : 1987)》2011,159(5):1413-1418
A dynamic fugacity model was developed to simulate the spatial and seasonal variations of PAHs in Haihe Plain, China. The calculated and measured concentrations exhibited good consistency in magnitude with deviations within a factor of 4 in air and 2 in soil. The spatial distributions of PAHs in air were mainly controlled by emission while the seasonal variations were dominated by emission and gas-particle partition. In soil, the spatial distributions of PAHs were controlled by the soil organic carbon content while the seasonal variations were insignificant. The severest soil contamination was observed in Shanxi and followed by the southwest of Hebei province. Transfer fluxes of total PAHs between air and soil were calculated. The spatial distribution of air-to-soil flux was closely related to the landcover while the soil-to-air flux changed with soil organic matter content. Monte Carlo simulation was done to evaluate the uncertainty of the estimated results in air. 相似文献