Multi-factors on biodegradation kinetics of polycyclic aromatic hydrocarbons (PAHs) by Sphingomonas sp. a bacterial strain isolated from mangrove sediment     

Jianlin Chen  M.H. Wong  Y.S. Wong  Nora F.Y. Tam   《Marine pollution bulletin》2008,57(6-12):695

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediment is an attractive remediation technique and its success depends on biodegradation kinetics, and the optimal condition for the PAH-degrading isolates; however, information on this aspect is still scarce. The effects of multi-factors on biodegradation of phenanthrene, a 3-ring model PAH, in contaminated sediment slurry by Sphingomonas sp. a bacterial strain isolated from surface mangrove sediment, were investigated using the orthogonal experimental design (form L₁₆(4⁵)). The most significant factors were salinity and inoculum size, while the effects of phenanthrene concentrations, nutrient addition and temperatures were insignificant. The optimal biodegradation condition in contaminated mangrove sediment slurry was 30 °C, 15 ppt salinity, a carbon/nitrogen ratio of 100:1 (the background ratio in sediment) and an inoculum size of 10⁶ most probable number g⁻¹ sediment. The phenanthrene biodegradation could be best described by the first order rate model, C = C₀e^−kt, where k (the rate constant) is equaled to 0.1185, under the optimal condition. The kinetic model was verified and its validity in predicting biodegradation by Sphingomonas sp. at various phenanthrene concentrations was proved by experimental data.  相似文献   

Study on the Historical Distribution of Metals in Aquatic Sediments     

Wagner José Barreto  Dílson Norio Ishikawa  Andressa Clara Nicolau  Evandro Domingues Magalhães  Fabiana Inoue  Paulo dos Santos Nora  Rodolfo Funfas  Sônia Regina Giancoli Barreto 《洁净——土壤、空气、水》2010,38(7):608-613

In this study, the historical distribution of metals, phosphorous, and sulfur at four different depths in the sediments of different lakes formed in the course of an urban river (in Londrina, Parana State, Brazil) were determined. The transport of metals along the course of the river was observed mainly for Mn, Cr, and Zn. High concentrations of Pb in the Capivara Bay and Cr in the river were attributed to contamination from a battery plant and a tannery, respectively. The concentrations of heavy metals in the deepest layers of the sediments remain high several years after deposition.  相似文献   

A case study on fuel oil contamination in a mangrove swamp in Hong Kong   总被引：5，自引：0，他引：5  

Tam NF  Wong TW  Wong YS 《Marine pollution bulletin》2005,51(8-12):1092-1100

Mangroves commonly found along tropical and subtropical coastlines are susceptible to oil pollution. In December 2000, around 500 1 m tall Kandelia candel saplings at the age of 3–5 years old located at the foreshore region of Sheung Pak Nai swamp, Hong Kong SAR, were found to be damaged by oil pollution. More than 80% of the saplings were either dead or washed away and leaving less than 5% healthy saplings with dense green leaves. Elevated concentrations of light n-alkanes (ranging from n-C₁₄ to n-C₂₀), pristane and phytane were recorded in surface sediments collected in December 2000. The ratio between light and total n-alkanes was 0.4. The total petroleum hydrocarbons (60–80 μg g⁻¹ TPH) and unresolved complex mixtures (60–70 μg g⁻¹ UCM) were higher than the background values of other mangrove sediments in Hong Kong, which were 40 and 20 μg g⁻¹, respectively. In certain root zone sediments, TPH concentrations were above 1000 μg g⁻¹. These results suggest that surface sediments in Sheung Pak Nai were contaminated by petroleum oil, most likely by illegal discharge of fuel oil which occurred between 1998 and 2002. One year later, in December 2001, unhealthy saplings had recovered and re-grown. The concentrations of TPH and UCM in sediments declined to around 40 μg g⁻¹, pristane and phytane dropped by 80%, and the ratio of light to total n-alkanes was 0.15, suggesting that residual oil in sediments was weathered leading to a remarkable recovery of the unhealthy saplings.  相似文献   

Locational Decisions and Residential Preferences of Taiwanese Immigrants in Australia     

Lan-Hung?Nora?ChiangEmail author  Jung-Chung?Richard?Hsu 《GeoJournal》2005,64(1):75-89

Since the 1980s, the increase of Asian migrants in large cities has contributed significantly to the cultural landscape of Australia, especially in the city suburbs. Based on the Census and in-depth interviews of 103 Taiwanese migrants, this research examines the location decisions and residential preferences of Taiwanese migrants in Sydney, Brisbane and Melbourne. The reasons for choosing the state, the particular city, and specific area of residence are probed into. The survey shows that migrants moved to Australia mainly for children’s education, lifestyle and political instability reasons. The main reasons for choosing to settle in Sydney were favourable business opportunities, and the northern part of Sydney was preferred. Those who chose Brisbane are attracted by the good climate there, and the residents preferred the Sunnybank area. Melbourne was chosen for the good education it offers, and areas on transportation lines near good schools are selected. Choice of residence was based mainly on their needs and their resources which may change over time. In general, they always choose to locate in close proximity to their family, friends and Taiwanese communities. Their locational choice depends on income and housing budget, proximity to good schools and shopping centers, and information from friends or earlier migrants. Based on such factors, this study clearly demonstrates that the Taiwanese immigrants are fundamentally different from early Chinese settlers who once aimed to settle at Chinatown locations.  相似文献   

Thermochemistry of strontium incorporation in aragonite from atomistic simulations     

Sergio E. Ruiz-Hernandez  Ricardo Grau-Crespo  A. Rabdel Ruiz-Salvador  Nora H. De Leeuw 《Geochimica et cosmochimica acta》2010,74(4):1320-13861

We have investigated the thermodynamics of mixing between aragonite (orthorhombic CaCO₃) and strontianite (SrCO₃). In agreement with experiment, our simulations predict that there is a miscibility gap between the two solids at ambient conditions. All Sr_xCa_1−xCO₃ solids with compositions 0.12 < x < 0.87 are metastable with respect to separation into a Ca-rich and a Sr-rich phase. The concentration of Sr in coral aragonites (x ∼ 0.01) lies in the miscibility region of the phase diagram, and therefore formation of separated Sr-rich phases in coral aragonites is not thermodynamically favorable. The miscibility gap disappears at around 380 K. The enthalpy of mixing, which is positive and nearly symmetric with respect to x = 0.5, is the dominant contribution to the excess free energy, while the vibrational and configurational entropic contributions are small and of opposite sign. We provide a detailed comparison of our simulation results with available experimental data.  相似文献