Titan haze: structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers     

Clarke DW  Ferris JP 《Icarus》1997,127(1):158-172

The structure and morphological properties of polymers produced photochemically from the UV irradiation of cyanoacetylene and cyanoacetylene mixtures have been examined to evaluate their possible contribution to the haze layers found on Titan. A structural analysis of these polymers may contribute to our understanding of the data returned from the Huygens probe of the Cassini mission that will pass through the atmosphere of Titan in the year 2004. Infrared analysis, elemental analysis, and thermal methods (thermogravimetric analysis, thermolysis, pyrolysis) were used to examine structures of polycyanoacetylenes produced by irradiation of the gas phase HC3N at 185 and 254 nm. The resulting brown to black polymer, which exists as small particles, is believed to be a branched chain of conjugated carbon-carbon double bonds, which, on exposure to heat, cyclizes to form a graphitic structure. Similar methods of analysis were used to show that when HC3N is photolyzed in the presence of Titan's other atmospheric constituents (CH4, C2H6, C2H2, and CO), a copolymer is formed in which the added gases are incorporated as substituents on the polymer chain. Of special significance is the copolymer of HC3N and acetylene (C2H2). Even in experiments where C2H2 was absorbing nearly all of the incident photons, the ratio of C2H2 to HC3N found in the resulting polymer was only 2:1. Scanning electron microscopy was used to visually examine the polymer particles. While pure polyacetylene particles are amorphous spheres roughly 1 micrometer in diameter, polycyanoacetylenes appear to be strands of rough, solid particles slightly smaller in size. The copolymer of HC3N and C2H2 exhibits characteristics of both pure polymers. This is particularly important as pure polyacetylenes do not match the optical constants measured for Titan's atmospheric hazes. The copolymers produced by the incorporation of other minor atmospheric constituents, like HC3N, into the polyacetylenes are expected to have optical constants more comparable to those of the Titan haze.  相似文献   

Photochemistry of the atmosphere of Titan: comparison between model and observations     

Yung YL  Allen M  Pinto JP 《The Astrophysical journal. Supplement series》1984,55(3):465-506

The photochemistry of simple molecules containing carbon, hydrogen, nitrogen, and oxygen atoms in the atmosphere of Titan has been investigated using updated chemical schemes and our own estimates of a number of key rate coefficients. Proper exospheric boundary conditions, vertical transport, and condensation processes at the tropopause have been incorporated into the model. It is argued that he composition, climatology, and evolution of Titan's atmosphere are controlled by five major processes: (a) photolysis and photosensitized dissociation of CH4; (b) conversion of H to H2 and escape of hydrogen; (c) synthesis of higher hydrocarbons; (d) coupling between nitrogen and hydrocarbons; (e) coupling between oxygen and hydrocarbons. Starting with N2, CH4, and H2O, and invoking interactions with ultraviolet sunlight, energetic electrons, and cosmic rays, the model satisfactorily accounts for the concentrations of minor species observed by the Voyager IRIS and UVS instruments. Photochemistry is responsible for converting the simpler atmospheric species into more complex organic compounds, which are subsequently condensed at the tropopause and deposited on the surface. Titan might have lost 5.6 x 10(4), 1.8 x 10(3), and 4.0 g cm-2, or the equivalent of 8, 0.25, and 5 x 10(-4) bars of CH4, N2, and CO, respectively, over geologic time. Implications of abiotic organic synthesis on Titan for the origin of life on Earth are briefly discussed.  相似文献   

The concept of biotope in marine ecology and coastal management   总被引：3，自引：0，他引：3  

Olenin S  Ducrotoy JP 《Marine pollution bulletin》2006,53(1-4):20-29

The term "biotope" was introduced by a German scientist, Dahl in 1908 as an addition to the concept of "biocenosis" earlier formulated by M?bius (1877). Initially it determined the physical-chemical conditions of existence of a biocenosis ("the biotope of a biocenosis"). Further, both biotope and biocenosis were respectively considered as abiotic and biotic parts of an ecosystem. This notion ("ecosystem = biotope + biocenosis") became accepted in German, French, Russian and other European "continental" ecological literature. The new interpretation of the term ("biotope = habitat + community") appeared in the United Kingdom in the early 1990s while classifying "marine habitats" of the coastal zone. Since then, this meaning was also used in international European environmental documents. This paper examines the evolution of the biotope notion. It is concluded that the contemporary concept is robust and may be used not only for the classification and mapping but also for functional marine ecology and coastal zone management.  相似文献   

The impact of legislation on the usage and environmental concentrations of Irgarol 1051 in UK coastal waters     

Cresswell T  Richards JP  Glegg GA  Readman JW 《Marine pollution bulletin》2006,52(10):1169-1175

In 2001, legislative measures were introduced in the UK to restrict usage of antifouling agents in small (<25 m) vessel paints to dichlofluanid, zinc pyrithione and zineb. This removed the previously popular booster biocides diuron and Irgarol 1051 from the market. To investigate the impact of this legislation, water samples were taken from locations where previous biocide levels were well documented. Results from analyses demonstrate a clear reduction in water concentrations of Irgarol 1051 (between 10% and 55% of that found during pre-restriction studies), indicating that legislation appears to have been effective. Although other booster biocides were screened for (chlorothalonil, dichlofluanid and Sea-Nine 211), they were below the limits of detection (<1 ng/l) in all samples. A survey of chandlers and discussions with legislative authorities supports these results and concurs the removal of Irgarol 1051 based paints from the market using simple regulations at a manufacturer level with little regulation at a retailer level.  相似文献   

Prevalence of microplastics in Singapore's coastal marine environment     

Ng KL  Obbard JP 《Marine pollution bulletin》2006,52(7):761-767

Microplastics have been recently identified as marine pollutants of significant concern due to their persistence, ubiquity and potential to act as vectors for the transfer and exposure of persistent organic pollutants to marine organisms. This study documents, for the first time, the presence and abundance of microplastics (>1.6 microm) in Singapore's coastal environment. An optimized sampling protocol for the collection and analysis of microplastics was developed, and beach sediments and seawater (surface microlayer and subsurface layer) samples were collected from nine different locations around the coastline. Low density microplastics were separated from sediments by flotation and polymer types were identified using Fourier transform infrared (FTIR) spectrometry. Synthetic polymer microplastics identified in beach sediments included polyethylene, polypropylene, polystyrene, nylon, polyvinyl alcohol and acrylonitrile butadiene styrene. Microplastics were detected in samples from four out of seven beach environments, with the greatest quantity found in sediments from two popular beaches in the eastern part of Singapore. Polyethylene, polypropylene and polystyrene microplastics were also found in the surface microlayer (50-60 microm) and subsurface layer (1m) of coastal waters. The presence of microplastics in sediments and seawater is likely due to on-going waste disposal practices from industries and recreational activities, and discharge from shipping.  相似文献   

Quantitative interpretation of specific conductance frequency distributions in karst   总被引：3，自引：0，他引：3  

Massei N  Mahler BJ  Bakalowicz M  Fournier M  Dupont JP 《Ground water》2007,45(3):288-293

Use of the coefficient of variation (CV) of specific conductance has been a simple and popular approach to classifying karst aquifers; however, problems with this approach arise because specific conductance frequency distributions (CFDs) are usually multimodal and the use of the CV sometimes erroneously classifies aquifers in terms of their dominant flow type or recharge type. Here, we demonstrate a more rigorous analysis of the CFD, which gives insight into the water types contributing to spring flow. The CFD for a water year is separated into an additive series of normal distributions, each related to a hydrogeochemical population. For each water type, its mean, variance, and contribution to the overall CFD can be quantified and compared between water types and water years. We applied this method to 4 years of data collected at Barton Springs, Austin, Texas. Although the overall shape of the CFD changed from year to year, it could consistently be separated into the same set of normally distributed populations. We suggest that each population represents a water type resulting from a particular mode of aquifer functioning. Changes in the parameters describing the curves reflect aquifer response to climatic variations. The results suggest that no single parameter of specific conductance can be used to describe the degree of karst behavior of an aquifer but that the degree of karst behavior itself varies from year to year depending on hydrologic conditions.  相似文献   

Biological and ecological factors related to trace element levels in harbour porpoises (Phocoena phocoena) from European waters     

Lahaye V  Bustamante P  Law RJ  Learmonth JA  Santos MB  Boon JP  Rogan E  Dabin W  Addink MJ  López A  Zuur AF  Pierce GJ  Caurant F 《Marine environmental research》2007,64(3):247-266

Selected trace elements (Cd, Cu, Hg, Se, Zn) were measured in the kidneys and the liver of 104 harbour porpoises (Phocoena phocoena) stranded along the coasts of France, Galicia (Spain), Ireland, Scotland (UK), and the Netherlands. Generally, relatively low concentrations of toxic elements were encountered in the tissues of European porpoises, except for two individuals, which displayed high hepatic Hg concentrations. Also, elevated Cd levels obtained in Scottish porpoises could be related to their feeding preferences and this result suggests an increase of the proportion of cephalopods in their diet with latitude. Moreover, significant geographical differences were seen in hepatic Zn concentrations; the elevated Zn concentrations displayed by porpoises from the Netherlands may relate their poor health status. Variation in metal concentrations within porpoises from the North Sea is likely to reflect a long-term segregation between animals from northern (Scotland) and southern areas (the Netherlands), making trace elements powerful ecological tracers.  相似文献   

An easy, non-destructive, probabilistic method to evaluate the imposex response of gastropod populations     

Fernandez MA  Pinheiro FM  de Quadros JP  Camillo E 《Marine environmental research》2007,63(1):41-54

Endocrine disruption in marine populations is a growing concern. One of the best documented examples is imposex, the development of male characteristics in female gastropods, including the development of a penis and/or vas deferens, by exposure to organotins, mainly tributyltin. This syndrome has been an effective and widely used biomarker of organic tin contamination for almost 20 years. However, established imposex evaluation protocols sacrifice all the animals and repeated assessments can result in depletion of populations. To preserve animal lives as much as possible and to have a fast screening of areas subjected to organotin impacts, a non-destructive approach was tested. This approach uses reversible narcotization and a statistical criterion to evaluate the extent of imposex in the populations, instead of imposex indexes, which are based on evaluation of sacrificed, fixed animals. The data consist of two categories: males plus masculinized females in one category and normal females in another. The probability is then calculated that this sample could have been drawn from a normal population. This new method was tested in two contrasting areas of Brazil and with two different species, and the results compared to the conventional evaluation. Narcotization was completely reversed with a survival rate of 98%. Impacted sites could be identified with this technique in the same way as with the conventional one. The only limitation was that female sterility could not be verified. This disadvantage could well be compensated by the minimal mortality in the studied populations.  相似文献   

Mercury contamination in invertebrate biota in a temperate coastal lagoon (Ria de Aveiro, Portugal)     

Coelho JP  Policarpo E  Pardal MA  Millward GE  Pereira ME  Duarte AC 《Marine pollution bulletin》2007,54(4):475-480

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Histopathology of mussels (Mytilus sp.) from the Tamar estuary, UK     

Bignell JP  Stentiford GD  Taylor NG  Lyons BP 《Marine environmental research》2011,72(1-2):25-32

This study assessed numerous histological parameters as markers of health status in mussels (Mytilus spp.) collected from several locations along a contamination gradient on the River Tamar and two coastal sites on the north and south coast of Cornwall, UK. Twenty-seven health parameters were assessed including the presence of pathogens, inflammatory lesions, non-specific pathologies and reproductive condition. Logistic regression showed that reproductive condition and inflammatory lesions showed changes indicative of a contamination gradient response. Mussel populations further upstream within the Tamar were relatively less developed compared to mussels situated downstream in the estuary. Compared to coastal locations, mussels sampled within the Tamar also exhibited a higher prevalence of inflammatory lesions that increased at locations situated furthest upstream. Similarly, levels of lipofuscin within the kidney epithelium were highest in mussels sampled within the estuary and Whitsand Bay compared to Trebarwith Strand. The most prevalent pathogens observed during this survey included Rickettsia/Chlamydia-like organisms (R/CLO), gill ciliates including Ancistrum mytili, the copepod Mytilicola intestinalis, Ciliophora-like organisms and Marteilia sp. Marteilia sp. was observed in 31% of the mussels sampled from the Cremyll Ferry site. Generally, the range and prevalence of pathogens was highest from the two estuarine locations at Cremyll Ferry and Wilcove. No significant differences were observed between estuarine sampling sites and Whitsand Bay with respect to median epithelial cell height of digestive tubules, however mussels from Trebarwith Strand did exhibit a reduced median epithelial cell height compared to mussels sampled from other sampling sites. Species genotyping was also undertaken during this study in order to consider any histological differences in relation to species. Results are discussed in relation to histopathology health parameters and biological effects monitoring.  相似文献