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81.
冰封期有机污染加重是松花江最重要的环境污染特征之一,加强松花江冰封期的有机污染防治,是解决松花江有机污染的关键.文章论述了松花江冰对期有机污染加重的原因和污染防治措施及重要意义. 相似文献
82.
Hongrui M Linke Ge Shengkai Cao Crispin Halsall Junfeng Niu Dongxiao Bai Guangkai He Peng Zhang 《环境科学学报(英文版)》2023,35(2):139-145
The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry.Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs,2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL),which are newly recognized contaminants in the wider environment including colder regions.Interestingly,their photodegradation kinetics were clearly influenced by whether they reside in ice or water.Under the same simulated s... 相似文献
83.
对溧水神仙洞的发掘和进行地质、地貌、孢粉、古脊椎动物与古人类、C14 年代及考古等多学科综合研究结果表明 :该洞是石炭系石灰岩沿层面裂隙经地下水溶蚀而成 ;洞穴堆积物的时代应属全新世早期 ,或新石器时代早期 ,绝对年代距今约为 1.1万年。其中发现的动物群为我国南方晚更新世动物群向现代动物群过渡的类型 ,而代表中 -晚更新世的最后鬣狗与代表新石器时代文化标志的陶片共生 ,为我国第四纪时代的划分 ,或新、旧石器时代文化的划分提供了重要依据。陶片则迄今为止是我国具有完整地层层位记录的最古陶片。它的发现 ,不仅将我国新石器时代文化大大推前 ,更为重写中华古史 ,校正“中华五千年文明”的提法 ,将中华文明追溯到一万年前并重排世界古文明位次增加了依据。同时 ,智人颞骨的发现 ,对长江中、下游古人类的研究 ,也提供了新的资料 相似文献
84.
黑龙江上游“冰坝”灾害分析及预报系统 总被引:1,自引:0,他引:1
黑龙江上游经常形成“冰坝”。本文分析了冰坝形成原因,建立了气象、水文、冰情等要素的数据库;通过对冰坝与各相关要素的关系分析,建立了冰坝中长期预报系统的数学模型,为“冰坝”中长期预报和减轻冰坝灾害提供了科学依据和有效方法。 相似文献
85.
Jan Weber Jana Klánová Crispin J. Halsall 《Environmental pollution (Barking, Essex : 1987)》2009,157(12):3308-3313
Here we investigate the photodegradation of structurally similar organophosphorus pesticides; methyl-parathion and fenitrothion in water (20 °C) and ice (−15 °C) under environmentally-relevant conditions with the aim of comparing these laboratory findings to limited field observations. Both compounds were found to be photolyzed more efficiently in ice than in aqueous solutions, with quantum yields of degradation being higher in ice than in water (fenitrothion > methyl-parathion). This rather surprising observation was attributed to the concentration effect caused by freezing the aqueous solutions. The major phototransformation products included the corresponding oxons (methyl-paraoxon and fenitroxon) and the nitrophenols (3-methyl-nitrophenol and nitrophenol) in both irradiated water and ice samples. The presence of oxons in ice following irradiation, demonstrates an additional formation mechanism of these toxicologically relevant compounds in cold environments, although further photodegradation of oxons in ice indicates that photochemistry of OPs might be an environmentally important sink in cold environments. 相似文献
86.
We summarize the latest results on the rapid changes that are occurring to Arctic sea ice thickness and extent, the reasons
for them, and the methods being used to monitor the changing ice thickness. Arctic sea ice extent had been shrinking at a
relatively modest rate of 3–4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer
2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million km2. Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially
rapid loss of mass from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat
and more rapid thinning rates. We review thickness monitoring techniques that show the greatest promise on different spatial
and temporal scales, and for different purposes. We show results from some recent work from submarines, and speculate that
the trends towards retreat and thinning will inevitably lead to an eventual loss of all ice in summer, which can be described
as a ‘tipping point’ in that the former situation, of an Arctic covered with mainly multi-year ice, cannot be retrieved. 相似文献
87.
Laila Ashrafun 《中国人口.资源与环境(英文版)》2016,14(1):53-57
The first birth marks a transition of a woman into motherhood. It contributes substantially to overall fertility of each individual woman. The age at which childbearing begins influences the number of children a woman bears throughout her whole reproductive life span. Thus, the mother’s age at first birth influences the total number of births that she might have in her life, which impacts the size, composition, and future growth of the population. Child-bearing at very young ages is common among the poor in Bangladesh. The objective of the present study is to examine the factors associated with age at first birth among slum dwellers of five selected slums (locally, colony) in Sylhet city corporation area, Bangladesh. The data of this study was collected from 520 women aged 14–50 years. The study found that almost 93% of women were married by the ages of 18 years and about 56% of the women have had their first child by the age of 18 years. The Ordinary Least Squares (OLS) regression model was used to analyze the factors correlated with women’s age at first birth. The regression model is significant with an F-value of 49.48 and can explain 40.4% of the variation in the dependent variable as it is indicated by the R-square. 相似文献
88.
《Environmental Forensics》2013,14(2):145-162
Investigators, regulators, and litigants having interest in gasoline hydrocarbon releases are almost always concerned with knowing when a release occurred. Gasoline releases to the subsurface have, historically, been the most difficult to age date because of their volatile nature and highly aromatic composition. Age dating of gasolines in the past has depended on the degree of weathering of the lower boiling hydrocarbons in gasoline, the use and disuse of lead, lead isotopes, the use of other additives such as methyl-tertiary-butyl ether, and major refining and formulation changes. However, these approaches are limited and many times difficult to demonstrate and apply. This paper describes a new age dating technique using gas chromatographic data. It is based on the progressive enhancement of the aromatics and the reduction of the normal alkanes (paraffins) in the manufacture of regular and mid-grade gasolines since the 1970s. The changing composition of gasoline was necessary to maintain octane ratings during the removal of lead from the gasoline and while meeting increasingly stringent air quality regulations over the past 30 years. This paper proposes the use of an index that reflects these changes in gasoline composition over time and can be correlated to when the gasoline was manufactured. The resulting curve can be used to estimate the age of release (manufacture) of gasolines. This forensic application can be successfully applied to liquid gasoline samples where the evaporation of the gasoline is less than 50%. Case histories and examples are presented to demonstrate application of the technique. 相似文献
89.
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