Formation of the salinity minimum in the Mixed Water Region between the Oyashio and Kuroshio Fronts

The salinity minimum frequently occurring in the Mixed Water Region between the Oyashio and Kuroshio Fronts seems to originate from the salinity minimum at the density of 26.8σ_θ called the North Pacific Intermediate Water. We examined water exchange of this region with the Oyashio and the Kuroshio Extension using mixing ratio R_K defined as (θ - θ_OY)/(θ_K - θ_OY) × 100, where θ_OY, θ_K, and θ represent potential temperature of the Oyashio and Kuroshio Waters and their mixture on the isopycnal surfaces, respectively. CTD data were obtained by repeated observation from January 1990 to May 1991. R_K increases southward from the Oyashio Front to the Kuroshio Front with the range of −20 to 120%. The gradient of R_K on the isopycnal surfaces is large around the Oyashio Front above the 26.8σ_θ surface, while it is large around the Kuroshio Front below it. This agrees with the average R_K in the Mixed Water Region decreasing greatly with the increase of density at densities less dense than 26.8σ_θ. We calculated thickness and volume transport of the Oyashio between the isopycnal surfaces near the coast of Hokkaido. They increase largely with density at densities less dense than 26.8σ_θ. It is supposed that the salinity minimum in the Mixed Water Region is the upper limit of the water largely influenced by the Oyashio Water. Its density could depend only on the density structure of the Oyashio.     

土壤中可挥发性污染物清除的离心试验研究

土工离心模拟试验技术是研究环境岩土工程问题的有效手段。本文研究了非水相流体污染物在非饱和土中的迁移以及随后的抽气清除过程。 当离心机运行到要求的加速度时,汽油污染物从地下油罐中释放并在非饱和土中迁移一年,之后采用土壤通气法对污染土壤进行修复。对土壤取样分析,得到污染物在土体中的迁移规律和分布特征。试验结果表明,土壤通气法可以清除非饱和土体中的挥发性有机污染物,是一种有效的原位土壤修复技术。     

南沙海洋沉积物中生物标志化合物的组成及地化意义

对１９９０年取自南沙海域１０２站位岩芯柱样中饱和烃进行色谱－质谱分析，研究沉积物中生物标志化合物组成和地球化学意义，结果表明，正构烷烃，类异戊二烯烷烃，甾烷和藿烷组成特征指示了其先质主要为海洋浮游生物和细菌，部分为陆源高等植物，反映了南沙海洋沉积有机质起源于这些生物，较丰富的胡萝卜烷在和Ｐｒ／Ｐｈ比值低，说明沉积环境具强还原性，随沉积物理埋藏深度增加，藿烷和藿烷以及藿烷异体之间，均存在明显的成岩转     

The effects of dissolved organic matter on the aqueous partitioning of polynuclear aromatic hydrocarbons

The partitioning of six polynuclear aromatic hydrocarbons into aqueous solutions containing dissolved organic matter from various coastal environments was investigated by liquid chromatography. Specific hydrocarbon-organic matter interactions were observed. The greatest interactions occurred with the very low solubility hydrocarbons and with organic matter of terrestrial origin. Ultrafiltration experiments suggested that it was the relatively high (greater than approximately 500) molecular weight organic matter that was interacting with the hydrocarbons.     

Comparison of binding abilities of fulvic and humic acids extracted from recent marine sediments with UO2

Potentiometric titrations were used to measure conditional stability constants of UO₂²⁺-fulvic acid and UO₂²⁺-humic acid complexes. Both 2:1 and 1:1 COO^-:UO₂²⁺ binding were observed. With decreasing metal concentration (2.5·10⁻⁴-6.25·10⁻⁵ M) increasing amounts of UO₂²⁺ were in the form of 1:1 humate complexes and 2:1 fulvate complexes. Despite the high nitrogen content and the low acidic OH group content, the successive stability constant values were similar to those determined for divalent cations associated with fulvic and humic compounds isolated from soils. Stability constant values increase simultaneously with increasing ionization of the humic (or fulvic) acid polyelectrolytes and with decreasing metal concentration.     

Organic geochemical studies of a Messinian evaporitic basin, northern Apennines (Italy)—II Isoprenoid and n-alkyl thiophenes and thiolanes

Series of n-alkyl and isoprenoid thiophenes and thiolanes, most of which have not been previously reported, have been identified in an extract from a Messinian (Upper Miocene) marl layer deposited under hypersaline, euxinic conditions. The identifications were based on mass spectra and Chromatographic data of synthesized reference compounds and on comparison of mass spectra, relative retention times and response on the FPD. Their specific structures and their distribution patterns show similarities with those of the alkanes. Inorganic sulphur is therefore considered to be incorporated into specific lipid moieties from (archae)bacterial and/or algal input during diagenesis. A biosynthetic origin of these compounds is also possible, however. The organic sulphur compounds encountered are thought to be indicators of a hypersaline depositional environment.     

Variations in structures and distributions of C25 highly branched isoprenoid (HBI) alkenes in cultures of the diatom, Haslea ostrearia (Simonsen)

The highly branched isoprenoid (HBI) alkenes of three batch cultures of the diatom Haslea ostrearia have been examined and the occurrence of C₂₅ tri-, tetra- and pentaenes confirmed. Growth of cultures outside at ambient temperature, under natural sunlight, in May (6 days) and June (10 days) 1995 and monitoring of HBI concentrations in samples collected daily and stored frozen, revealed that in May greater concentrations of HBIs (ca 6500 fg cell⁻¹) were produced than in June and at a much earlier stage of growth. Furthermore, in May the HBIs were more unsaturated (predominantly a tetraene rather than a triene). The reasons for these differences are at present unknown and future investigations of the effect of irradiance, temperature, salinity and other environmental variables are required. Such experiments may allow the various HBI distributions in the alga and in sediments to be better understood and, like some other polyunsaturated lipids, HBI alkenes may become useful environmental and palaeoenvironmental indicators. Two previously unreported alkenes, 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)pentadec-2,5,9,13-ene (GC retention index, 2201_DB-1) and 2,6,10,14-tetramethyl-7-(3-methylene pent-4-enyl)pentadec-2,5,9,13-ene (GC RI, 2248_DB-1) from a batch culture of Haslea ostrearia grown in October/November 1993 and stored frozen for over a year, have also been isolated and characterised by ¹³C and ¹H NMR, epoxide derivatisation and mass spectrometry. Such structural characterisation studies of HBI alkenes should also aid our understanding of the geochemical fate of these widely distributed hydrocarbons.     

The Gas Phase Reaction of Unsaturated Oxygenates with Ozone: Carbonyl Products and Comparison with the Alkene-Ozone Reaction

Carbonyl products have been identified and their formation yields measured in the gas phase reaction of ozone with unsaturated oxygenates in experiments carried out at ambient T, p = 1 atm. of purified humid air (RH = 50%) and with sufficient cyclohexane added to scavenge the hydroxyl radical. The compounds studied are the esters methyl acrylate, vinyl acetate and cis-3-hexenyl acetate, the carbonyl crotonaldehyde, the hydroxy-substituted diene linalool, the ether ethylvinyl ether and the keto-ether trans-4-methoxy-3-buten-2-one. The alkene 1-pentene was included for comparison. The nature and formation yields of the carbonyl products from this study and those measured in earlier work under the same conditions are compared to those of alkenes and are supportive of a reaction mechanism that is similar to that for the reaction of ozone with alkenes, i.e. O₃ + R₁R₂C=CR₃X (R₁COR₂ + R₃XCOO) + (1 – )(R₃COX + R₁R₂COO), where R_i are the alkyl substituents, X is the oxygen-containing substituent (–CHO for aldehydes; –C(O)R for ketones; –C(O)OR and –OC(O)R for esters; –OH and hydroxyalkyl for alcohols; and –OR for ethers), R₁COR₂ is the primary carbonyl, R₃COX is the other primary product and R₁R₂COO and R₃XCOO are the carbonyl oxide biradicals. The biradicals lead to carbonyls in reactions that are also analogous to those involved in carbonyl formation from biradicals in the ozone-alkene reaction. These features make it possible to predict the nature and formation yields of the major carbonyl products of the reaction of ozone with unsaturated oxygenates that may be components of biogenic emissions.     

Toxic effects of decomposing red algae on littoral organisms

Large masses of filamentous red algae of the genera Polysiphonia, Rhodomela, and Ceramium are regularly washed up on beaches of the central Baltic Sea. As the algal masses start to decay, red coloured effluents leak into the water, and this tinge may be traced several hundred meters off shore. In this study, possible toxic effects of these effluents were tested on littoral organisms from different trophic levels. Effects on fertilisation, germination and juvenile survival of the brown seaweed Fucus vesiculosus were investigated, and mortality tests were performed on the crustaceans Artemia salina and Idotea baltica, as well as on larvae and adults of the fish Pomatoschistus microps. Fucus vesiculosus was the most sensitive species of the tested organisms to the red algal extract. The survival of F. vesiculosus recruits was reduced with 50% (LC50) when exposed to a concentration corresponding to 1.7 g l⁻¹ dw red algae. The lethal concentration for I. baltica, A. salina and P. microps were approximately ten times higher. The toxicity to A. salina was reduced if the algal extract was left to decompose during two weeks but the decline in toxicity was not affected by different light or temperature conditions. This study indicates that the filamentous red algae in the central Baltic Sea may produce and release compounds with negative effects on the littoral ecosystem. The effects may be particularly serious for the key species F. vesiculosus, which reproduce in autumn when filamentous red algal blooms are most severe.     

油藏色谱指纹非均质性形成机理及其稳定性实验模拟

从油田开发动态地球化学监测的基本地质概念模型出发，应用油藏流体非均质性理论，分析了不同地质时期原油色谱指纹变化的地质因素。通过指纹GC／MS鉴定和实验模拟地下不同温度和不同时间的开采条件，分析了油藏开采过程中色谱指纹的变化规律。结果表明：原油色谱指纹稳定性主要和化合物的性质、含量以及色谱柱分离度有关。油藏开采过程中，适当碳数范围内的原油色谱指纹在井底和井口的不同温度条件下以及同一单层在一定的观测时间范围内具有稳定性。研究结果对进一步开拓原油色谱指纹在油田开发管理中的应用具有重要的理论价值。