Kinetics of Disproportionation of Inorganic Polysulfides in Undersaturated Aqueous Solutions at Environmentally Relevant Conditions

The rate of the reversible homogeneous disproportionation of polysulfides was studied by following the optical absorbance of polysulfide solutions in a continuous plug flow reactor equipped with an on-line photometric detector. In order to avoid heterogeneous slow reactions involving sulfur colloids or precipitate, the reaction was initiated by an abrupt pH change from an undersaturated solution containing predominantly tetrasulfide species to a pH where pentasulfide is the dominant species. The disproportionation was found to follow first order reversible reaction dynamics. At environmentally relevant conditions the characteristic time of the disproportionation reaction is of the order of 10 s. This characteristic time implies that necessary conditions for speciation of the different polysulfide species by chromatography or another separation and subsequent quantification scheme should be of the order of 1 s.     

An invariance in the carbazoles of petroleum

A remarkable invariance in the ratio of 1,3-dimethylcarbazole （DMC） to 1,6-DMC was discovered in crude oils from the Pearl River Mouth Basin, South China Sea. The remarkably invariant ratio is kept at a constant of about unity regardless of their concentrations, sources or maturities for the sampies. In combination with the molecular structures of 1,3- and 1,6-DMCs, the invariance might indicate that the nitrogen compounds share a common precursor with a skeleton of 1-methylcarbazole and are formed through methylation at C3 and C6 with an essentially identical rate.     

The wreck of the MV Rena: spatio-temporal analysis of ship-derived contaminants in the sediments and fauna of Astrolabe Reef

ABSTRACT

The October 2011 sinking of the container ship MV Rena on Astrolabe Reef, New Zealand, provided a rare opportunity to examine the fate of shipwreck-derived contaminants on an offshore rocky reef and food chain. Analyses of trace metals, polycyclic aromatic hydrocarbons (PAHs) and organotins indicated significant but localised contamination of Astrolabe Reef but not of nearby Mōtītī Island. Three years after the grounding, PAH concentrations were greater in sediments at Astrolabe (up to 131?mg kg^?1) than at control locations, while organotins from the ship's antifouling hull paint were found exclusively in Astrolabe Reef sediments and biota. Over 80% of Astrolabe sediment samples contained tributyltin at concentrations above guideline sediment levels (>0.07?mg kg^?1). Tributyltin and its decomposition products were also recorded in sea urchins, gastropods, lobster and fishes at concentrations up to 0.2?mg kg^?1. Wreck and cargo-derived metals, particularly copper, tin and zinc, were present in some Astrolabe sediment samples above Australia and New Zealand Environment and Conservation Council guideline concentrations. However, there appeared to be only limited transmission of metals through the food chain. Copper, tin and zinc were recorded at greater concentrations in Astrolabe sea urchins and gastropods compared to control specimens, while metal concentrations in other biota were comparable across impact and control sites. Despite over 3 years having passed since the Rena grounding, the data series does not show any upward or downward trends in contaminant concentrations on Astrolabe Reef. Consequently, there is uncertainty about the long-term implications of the Rena grounding for the ecology of Astrolabe Reef.     

双酚A及其类似物对哺乳动物和鱼类神经毒性效应及机制研究进展

双酚A及其类似物双酚S、双酚F、双酚AF和卤代双酚A等双酚类化合物广泛用于生产聚碳酸酯塑料和环氧树脂,生产量大且目前在各种环境介质、食品及人体内均有检出。近年来,研究发现很多神经疾病的发生与双酚类化合物的暴露密切相关,有关双酚A及其类似物的神经毒性日益受到国内外研究者关注。本研究从对动物行为、神经发育、神经递质含量及神经递质代谢等方面综述了双酚类化合物的神经毒性效应及作用机制,为今后进一步探究双酚A类似物的神经毒性作用及其安全性评价提供更多的理论参考。     

加氯水体有机浓集物对团头鲂血液指标的影响

本文对团头鲂 2项血液学指标 (红细胞数 RBC和血红蛋白量 Hb)的正常值进行了研究 ,同时检测了加氯水体中有机浓集物对这 2项指标的影响。结果表明 ,团头鲂血液中 RBC和 Hb的正常值受生长和水温等因素影响 ;在相同的试验条件下 ,加氯水体中的有机浓集物对团头鲂血液 RBC和 Hb有抑制作用 ,抑制率分别为 4 .3 %～ 2 6.0 %和 5.0 %～ 2 2 .5% ,表明此类物质对鱼类正常的生长代谢有一定的危害。     

Interaction of glucose and cellulose with hydrogen sulphide and polysulphides

This paper describes simulation experiments in which glucose and cellulose were reacted with polysulphide and hydrogen sulphide at ambient temperatures in an aqueous environment. Organic sulphur containing compounds were formed that yield several thiophenes upon pyrolysis/evaporation. The experiments show that interaction of carbohydrates with hydrogen sulphide or polysulphides is a possible way for carbohydrates to react in very recent sediments. From the results of this study it can be concluded that carbohydrate carbon can be preserved in sediments in a form that is resistant to microbial attack and that will have a greater potential for survival during diagenesis than the carbohydrate precursor.     

Identification and occurrence of novel C36–C54 3,4-dialkylthiophenes with an unusual carbon skeleton in immature sediments

A series of novel long-chain 3,4-dialkylthiophenes (C₃₆–C₅₄) was identified in a number of sediments ranging from Pleistocene to Cretaceous. The identifications were based on mass spectral characterisation, desulphurisation and mass spectral data of synthesised model compounds. These organic sulphur compounds are probably formed by sulphur incorporation into mid-chain dimethylalkadienes with two methylenic double bonds. These putative precursor lipids are unprecedented and may be considered rather unusual. The distribution of 3,4-dialkylthiophenes in sediments varies considerably with the depositional palaeoenvironment, indicating that these compounds have a potential as molecular markers reflecting changes in palaeoenvironment.     

Prediction of the abiotic degradability of organic compounds in the troposphere

A statistically relevant correlation between the reaction rate coefficient, k _OH, for the OH radical reaction with 161 organic compounds in the gas phase at 300 K, and the corresponding vertical ionisation energies E _i,v, reveals two classes of compounds: aromatics where –log(k _OH/cm³s^-1)3/2E _i,v(eV)–2 and aliphatics where –log(k _OH/cm³s^-1)4/5E _i,v(eV)+3. The prediction of the rate coefficient, k _OH, for the reaction of OH with organic molecules from the above equations has a probability of about 90%. Assuming a global diurnal mean of the OH radical concentration of 5×10⁵ cm³, the upper limit of the tropospheric half-life of organic compounds and their persistence can be estimated.     

Effect of system variables and particle size on physical characteristics of air sparging plumes

Air was injected through a well in a thin transparent tank filled with saturated glass beads to study how the size and air saturation of air sparging plumes are affected by particle size and gradation; operational parameters such as injection pressure, well depth, injection pressure pulsing; and well outlet configuration. V-shaped air plumes with an apex between 40° and 60° were obtained for all tests. The air pressure required to initiate sparging agreed closely with the sum of the air entry pressure and the hydrostatic pressure, with higher initiation pressures required in the fine and well-graded beads. Higher air flow rates and air saturations were obtained in coarser beads at a given pressure, and the variation in flow rate was consistent with estimated air permeabilities. Peak average air saturations were 28–56% for the coarse-medium beads, 10% for the well-graded beads, and 8% for the fine beads. Air saturation and the radius of influence increased modestly (<40%) as the normalized injection pressure exceeded 0.1. Radius of influence increased by approximately a factor of two as the well depth increased, but leveled off once the ratio of radius of influence to well depth reached 0.60–1.05. Pulsing of injection pressure had no effect on the initiation pressure, air flow rate, or air saturation, but increased the size of the air plume and the radius of influence slightly (<15%). Well outlet configuration had only a slight affect the radius of influence (<10%), air saturation (<10%), or air flow rate (<12%). Dye testing showed that water surrounding the air plume circulated during continuous and pulsed sparging. However, pulsed sparging resulted in greater and more defined circulation of water within and adjacent to the air plume, which should reduce mass transfer limitations during sparging.     

水资源中氯代烃污染物的去除方法

随着工业化的发展。氯代有机溶剂使用越来越广泛。并且难于去除。在20世纪90年代初期，人们就已认识到用Fe^0恢复污染的地下水的潜力。国外正在研究帮使用扔几种还原挥发性氯代烃的还原反应介质，尤其要提高的是双金属反应系统，反应速度快，而且脱Cl中国难解产物少，目前国也只停留在实验室研究阶段，个别做了地上反应器的验证实验，它的脱Cl机理、介质钝化和完全脱Cl问题还有待于进一步研究。