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661.
Kristina L. Sundqvist Mats Tysklind Ingemar Cato Anders Bignert Karin Wiberg 《Environmental science and pollution research international》2009,16(4):396-409
Background, aim, and scope The primary aim of this study was to explore the variations in PCDD/F levels and homologue profiles of Baltic surface sediments
by comprehensively analyzing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in samples from a large number of sites, encompassing not only previously
known hotspot areas, but also sites near other potential PCDD/F sources, in pristine reference areas (in which there was no
industrial activity) and offshore sites.
Materials and methods Surface sediment samples (146 in total) were collected at various points along the Swedish coast and offshore areas. In addition,
bulk deposition was sampled, monthly, at a single site in northern Sweden during 1 year. The concentrations of tetra- through octa-substituted CDD/Fs were determined in both matrices.
Results Highly elevated concentrations of PCDD/Fs were found at many sites in coastal areas and concentrations were also slightly
elevated in some offshore areas. Homologue profiles varied substantially amongst samples from coastal sites, while those from
offshore and other pristine sediments were relatively similar. The offshore sediments showed different profiles from those
observed in the deposition samples. Sediment levels of PCDD/Fs were not generally significantly correlated to organic carbon
levels, except in some pristine areas. Comparison of data obtained in this and previous studies suggest that both their levels
and profiles are similar today to those observed 20 years ago in coastal and offshore areas. The only detected trend is that
their levels appear to have decreased slightly in the offshore area of the Bothnian Sea.
Discussion The localization of hotspot areas along the coast, the lack of consensus between PCDD/F profiles of sediments and general
background, and their weak correlations with organic carbon suggest that PCDD/Fs in the study area largely originate from
local/regional emissions. However, due to complicating factors such as sediment dynamics and land upheaval, it is not possible
to conclude whether these pollutants derive from recent emissions or from a combination of recent emissions and re-distribution
of previous inputs.
Conclusions The results show that: elevated levels of PCDD/Fs are present in both coastal and offshore areas of the Baltic Sea, the major
hotspots are close to the shore, and there are large variations in profiles, indicating that local emissions are (or have
been) the major causes of pollution.
Recommendations and perspectives In order to identify other hotspot areas and trace sources, comprehensive analysis of PCDD/Fs in surface sediments is needed
in all areas of the Baltic Sea that have not been previously investigated. The high levels of PCDD/Fs observed in surface
sediments also indicate a need to elucidate whether they are due mainly to current emissions or a combination of recent pollution
and re-distribution of historically deposited pollutants. To do so, better understanding of sediment dynamics and present-day
inputs, such as riverine inputs, industrial effluents, and leakage from contaminated soil is required. There are indications
that contaminated sediments have a regional impact on fish contamination levels. However, as yet there is no statistically
robust evidence linking contaminated sediments with elevated levels in Baltic biota. It should also be noted that the Baltic
Sea is being massively invaded by the deep-burrowing polychaete Marenzielleria ssp., whose presence in sediments has been shown to increase water concentrations of hydrophobic pollutants. In awareness
of this, it is clear that high levels in sediments cannot be ignored in risk assessments. In order to investigate the emission
trends more thoroughly, analysis of PCDD/Fs in offshore sediment cores throughout the Baltic Sea is also recommended.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
662.
This study examines the impact of flooding on land of high conservation value located along part of the southern shoreline
of the River Clyde Estuary in western Scotland. This paper hypothesizes that, over the next 50 years, the frequency and extent
of coastal flooding will increase due to the gradual effect of global warming and the consequent rise in sea-level and increase
in storminess. It is argued that because of the great cost of constructing new flood defence systems it will not be possible
to protect all land areas to an equal extent from flooding. A means of ranking different land use will be necessary so that
society can make a rational judgement concerning which sections of coastline will be worth protecting. This study provides
a methodology that combines an objective ranking of conservation areas using non-economic indicators with a GIS model of flood
potential, and permits accurate forecasts of flood losses to conservation areas of different ecological value. The conservation
case study used in this paper proposes the use of an ecological weighting value based on five ecological variables each of
10 categories. Tables and maps identify the sites that have been highlighted as consisting of the most ‘valuable’ conservation
sites. The methodology makes extensive use of geographical information systems (GIS) to model the predicted areas of flooding
and to calculate conservation weighting values of the land areas. 相似文献
663.
流域环境系统演化概念模型:山-河-湖-海互动及对全球变化的敏感响应--以长江为例 总被引:1,自引:0,他引:1
流域是一个复杂的环境系统。长江流域环境研究表明,山-河-湖-海互动是流域环境系统变化的实质,同时也是流域对全球变化响应最敏感、最直接的体现。地貌过程变化,水、沙等物理通量变化,C、P、N等化学通量变化是系统内各子系统之间联系的纽带,也是流域环境系统中最活跃的因子。以山-河-湖-海互动为核心的流域环境系统模型,主要包括:山、河、湖、海各系统之间的能量流与物质流的输入、迁移和输出理论,系统演化平衡理论和系统自组织、自反馈理论。 相似文献
664.
665.
根据数理统计的原理,将环境质量标准,平均值,标准偏差以及样本容量综合进行考虑,提出了污染分界线的计算公式,并以表格形式给出了不同显著性水平下,不同的相对标准偏差和样本容量所对应的污染分界线,对污染分界线与样本容量及相对标准的偏差的关系进行了讨论,指出提高监测精度和适当增加监测数据个数,可以使污染分界线接近评价标准。 相似文献
666.
三峡水库水位涨落带土地资源的初步研究 总被引:88,自引:8,他引:88
三峡大坝建成后,将在库区两岸形成永久性的水位涨落带。涨落带冬半年为水域,丰半年出露水面成陆,是一种具有多功能的土地资源类型,在夏半年,涨落带成陆面积大,成陆期较长,与同期丰富的光热水资源构成优势组合,使涨落带土地具有较高的生产潜力。对三峡库区水位落带土地资源的质量、数量和分布特点进行分析,在此基础上提出了合理利用的设想。 相似文献
667.
Australian approaches to coastal vulnerability assessment 总被引:2,自引:1,他引:1
The Australian coastline is one of the longest and most diverse of any in the world, and Australian researchers have developed
preliminary models of the behaviour of major coastal systems such as beaches and reefs. The Australian population is particularly
focused along the coastline, especially in metropolitan centres; however, the population of regional centres along the coast
is increasing steadily in response to a phenomenon termed seachange. Coastal systems are increasingly threatened by potential
impacts as a result of climate change, as indicated by the successive assessments by the Intergovernmental Panel on Climate
Change (IPCC). Although Australia played a central role in applying a common methodology (CM), developed from IPCC guidelines
in the 1990s, and in devising alternative approaches, which were initially trialled at nine sites on the Australian coast,
there has not been a nationally co-ordinated approach to assessing the coastal vulnerability of Australia, and such an approach
is only emerging now. Instead, there have been a series of different approaches adopted to look at the different parts of
the Australian coast, including wetland mapping in northern Australia; geomorphic unit mapping in South Australia; storm surge
vulnerability modelling in Queensland; probabilistic approaches to beach erosion in New South Wales; indicative mapping of
potential coastal retreat in Tasmania. Additionally, there have been methods proposed by insurers and coastal engineers to
meet their requirements. Since 2005, the Australian government has once again seen the need for a national coastal vulnerability
assessment, and a series of studies are planned or under way to achieve the aims of a National Climate Change Adaptation Framework. 相似文献
668.
大型通江湖泊鄱阳湖水文节律独特,水位和流速是其生态系统功能维持的关键因子。为探究其水位和流速时空特征,基于EFDC(Environmental Fluid Dynamics Code)模型,利用五河及湖口水文数据、气象数据及湖底高程作为输入条件,模拟出鄱阳湖的枯水水文统计年(2010-07-01~2011-06-30)水位和流速时空变化过程。模拟结果表明:(1)星子等4个站点拟合程度较好(r20.85),达到了复杂湖库水动力模拟的精度。(2)高水位期,湖区水位空间分布无明显差异,水深直接受湖底高程影响,自上游至下游呈逐级递增;低水位期,鄱阳湖水位在空间上出现明显差异,湖区外缘水位至入江水道逐级递减,水深分布空间差异不大,仅入江水道处水深明显高于其他水域。(3)流速也包括一系列时空变化特征,如高水位时期流速小于低水位时期;除大水面时期外,深水道流速大于主湖区;高水位时期上游流速略高于下游,但其他月份,北部入江水道流速均大于南部湖区等。(4)流速与水位关系密切,且不同水位对应流速大小及分布有所差异。鄱阳湖枯水水位和流速模拟分析可为大型湖库枯水水情管理提供科学参考和辅助决策支持。 相似文献
669.
人类活动对浙江近海赤潮发生频率的影响分析 总被引:1,自引:0,他引:1
根据1933年到2004年间的统计资料,以10 a为周期分析了浙江沿岸赤潮的发展变化历程,并进一步以1997~2004年的统计资料为基础,采用灰色系统关联分析法研究了的浙江近海赤潮的发生频率和人类活动引起的营养物质输入的关系.结果表明,各相关因子对赤潮发生频率影响的关联序为:海水养殖产量(0.03)>海水养殖面积(0.99)>工业废水(0.89)>生活污水(0.88)>生活COD(0.79)>总悬浮颗粒物(0.75)>工业COD(0.72)>降雨量(0.71)>粉尘(0.69)>烟尘(0.68).可见,赤潮发生与人类活动关系密切,其中海洋养殖自身污染是赤潮发生频率的主要诱因,陆源污染和大气湿沉降起着重要作用. 相似文献
670.