Natural attenuation, biostimulation and bioaugmentation on biodegradation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments

The biodegradability of a mixture of PAHs, namely fluorene (Fl), phenanthrene (Phe) and pyrene (Pyr), in mangrove sediment slurry was investigated. At the end of week 4, natural attenuation based on the presence of autochthonous microorganisms degraded more than 99% Fl and Phe but only around 30% of Pyr were degraded. Biostimulation with addition of mineral salt medium degraded over 97% of all three PAHs, showing that nutrient amendment could enhance Pyr degradation. Bioaugmentation with inoculation of a PAH-degrading bacterial consortium enriched from mangrove sediments did not show any promotion effect and the degradation percentages of three PAHs were similar to that by natural attenuation. Some inhibitory effect was observed in bioaugmentation treatment in week 1 with only 50% Fl and 70% Phe degraded. These results indicate that autochthonous microbes may interact and even compete with the enriched consortium during PAH biodegradation. Natural attenuation appeared to be the most appropriate way to remedy Fl- and Phe-contaminated mangrove sediments while biostimulation was more capable to degrade Pyr-contaminated sediments. The study also shows that although a large portion of the added PAHs (more than 95%) was adsorbed onto the sediments at the beginning of the experiment, most PAHs were degraded in 4 weeks, suggesting that the degraders could utilize the adsorbed PAHs efficiently.     

Inverse analysis of deformation mechanism by geodetic surveys−a case study

In 1988 two large earthquakes with magnitude of Ms 7.6 and Ms 7.2 occurred in Lancang-Genma area, Southwest China. This paper discusses the determination of the spatial distribution of fault slip caused by the earthquakes using geodetic surveys. The prior information obtained from geological surveys and seismological investigations was used to determine the geometry of the fault plane and the average fault slip. The smooth constraints on the fault slips have been described by a normal distribution with hyperparameters, which are incorporated in the inversion analysis with a Bayesian model. Akaike’s Bayesian Information Criterion (ABIC) is used to get the optimal values of hyperparameters. Once the hyperparameters are determined, the maximum likelihood method is employed to estimate the patterns of a fault slip. Based on the results of inverse analysis monitoring geodetic surveys can be properly designed and conducted to obtain crust deformations and predict potential earthquake sources.     

Characterization of Quaternary faults by electric resistivity tomography in the Andean Precordillera of Western Argentina

El río San Juan, situado en la Provincia de San Juan (Argentina) cruza la Precordillera y otras unidades geológicas incluyendo la Depresión de Ullum y la Zona de La Laja, entre las latitudes 31°S y 32°S. El curso del río tiene un cierto caracter antecedente como puede deducirse por sus dos trazas perpendiculares unidas por otra casi paralela a las alineaciones estructurales principales. En la zona de la Precordillera, el valle del río San Juan muestra numerosos abanicos aluviales, situados en las zonas de confluencia entre el río principal y sus tributarios. Las superficies de los abanicos aluviales cuaternarios estan cortadas por una serie de escalones que consideramos como terrazas aluviales generadas por episodios repetitivos de agradación y degradación. El sector estudiado incluye una zona con una importante actividad sísmica reciente(La Laja), otra sin una importante actividad sísmica reciente (Precordillera), y una zona subsidente (Ullum) donde se formó un gran lago natural hace unos 6500 años. El antiguo río San Juan fue capturado por el valle de la Quebrada de Ullum mediante una incisión del orden de 25 m, que implicó una nueva adecuación del gradiente del río mediante los efectos de la erosión remontante. El gradiente del río San Juan muestra algunas irregularidades que, aunque no se presenten relacionadas directamente con las estructuras principales, estan relacionadas con la propia dinámica fluvial que acentúa la diferenciación litológica. La anchura del valle del río principal, la geometria y el gradiente de cada tributario, junto a las litologias del basamento y a las dimensiones de cada area fuente local, son los factores principales que controlan los procesos de la generación de las terrazas aluviales. En la zona de La Laja, donde la terraza mas alta soporta un nivel de travertino, la datación de los depósitos travertínicos proporciona datos como para suponer una tasa de incisión del orden de 0,9–1 mm/año, asociada a la actuación periódica de la falla de La Laja.

Preliminary report on radionuclide concentrations in the bottom waters at the entrance of Wakasa Bay with special reference to the Japan Sea Proper Water

Marked fluctuation of concentrations of⁹⁰Sr and¹³⁷Cs was observed in the bottom waters at the entrance of Wakasa Bay during 1987–1992, and the cause was investigated. The concentrations of⁹⁰Sr and¹³⁷Cs in the bottom waters were significantly low when the upper level of the Japan Sea Proper Water (JSPW) was high and covered the sampling depth, but high when the upper level of the JSPW was low. The cause of the fluctuation observed in the bottom waters is, therefore, suggested to be the vertical fluctuation of the upper level of the JSPW on the shelf slope, which has been little described before.     

WORLD ATLAS OF THEMATIC MAPS OF DESERTIFICATION

The author describes the contents and participation of former Soviet republics in the compilation of a global atlas of desertification, published under the auspices of the United Nations. Translated by H. L. Haslett, Leamington Spa, UK, from: Izvestiya Akademii Nauk SSSR, seriya geograficheskaya, 1991, No. 6, p. 130.     

Bender Elements在测试土样剪切波速中的应用

本文以作者在香港理工大学土木与结构工程系设计制作的一套BenderElements为例,介绍了BenderElements的原理、发展历史、应用范围、使用方法和注意事项等。BenderElements是由压电陶瓷材料制成的,在拉伸、压缩作用下,会产生正、负电荷,反过来,给它施加正、负电荷后,它又可产生弯曲振动,正是利用它的这一特性,将其作成接收和发射装置,来测试土样的剪切波速Vs。BenderElements在安装使用时,防水和静电屏蔽十分关键。Vs可在场地地震反应、液化判别、动力基础设计、检测地基改良效果等方面获得应用。震相识别的原则是接收信号的第一个峰值为到时。     

Physical disturbance creates bacterial dominance of benthic biological communities in tropical deltaic environments of the Gulf of Papua

Unlike many reactive continental shelf mud deposits in temperate regions, bacteria and microfauna rather than macrofauna typically dominate benthic biomass and activities over large areas of the Gulf of Papua (GoP) deltaic complex, Papua New Guinea. During mid NW monsoon periods (Jan–Feb), macrofaunal densities at Gulf stations were relatively low (), large macroinfauna were absent (upper 25 cm), and small (), surface deposit-feeding polychaetes and tubiculous amphipods were dominant, reflecting a frequently destabilized seabed and high sedimentation/erosion rates. Although frequent physical disturbance generally inhibits development of macrobenthic communities, some regions of the Gulf deposits are periodically colonized and extensively bioturbated during quiescent periods, as shown by preserved biogenic sedimentary structures. Bacterial inventories integrated over the top 20 cm were extremely variable within each sub region of the clinoform complex. A possible bimodal pattern with bathymetric depth and distance offshore may occur: lowest-inventories within the sandy, proximal Fly River delta, an open Gulf inner topset zone (10–20 m) having sites of relatively high inventories, an open Gulf mid-topset region with intermediate values and less extreme variation, and the outer topset—upper foreset zone (40–50 m) where highest values are attained (). Various measures of microbial activity, including measures proportional to the cellular rRNA content and the proportion of dividing cells, indicate extremely productive populations over the upper 1-m of the seabed throughout the Gulf of Papua region. Bacterial biomass (0–20 cm) including data of Alongi et al. (1991, 1992, 1995) varied from a low of in intertidal mud banks to a high of in the topset—foreset zone. Macrofaunal biomass did not exceed in any sampled region, ranging from 0.009±0 to with no obvious correlation with bathymetric depth (1–63 m). Meiofaunal biomass was generally an order of magnitude lower than macrofaunal biomass. Relatively elevated bacterial biomass and high turnover rates are consistent with high measured rates of benthic remineralization, presumably reflecting the rapid response time of bacteria to physical reworking, the associated entrainment of organic substrate, and flushing of metabolites. Solute exchange is also enhanced below the directly mixed surface region, possibly producing ‘far field’ stimulation of microbes in underlying deposits. Physical reworking and reoxidation of sediments between 10 and 50 m water depth maintain suboxic, nonsulfidic conditions in the upper 0.5–1 m despite active microbial communities and high benthic remineralization rates.     

Random wave-current interactions in water of varying depth

Refraction of incoherent random gravity waves with currents and bottom topography results in spatial variations in the spectral characteristics of the free surface. Prediction of such variations based on the radiation transfer equation is in a simple analytic form for the case of one dimensional inhomogeneities in currents and topography. This analytic form is examined in terms of two-dimensional wave number- and polar frequency-direction spectra along the associated dynamic and kinematic constraints relevant to wave breaking and reflection. Results are specialized to the simplest case of horizontal shear currents in deep and shallow water with explicit examples to illustrate the relative and combined effects of currents and topography on free surface spectra.     

Evolution of sedimentary basins from the standpoint of petroleum origin and accumulation—an approach for a quantitative basin study

Generation, migration and accumulation of petroleum in a sedimentary basin is a function of geologic, hydrodynamic and thermodynamic development of the basin and the type and amount of organic matter. Temperature history not only determines rate of hydrocarbon generation, but also affects paleohydrodynamics and physical and thermal properties vs depth relationships. Therefore, paleotemperature is the most important parameter. Paleohydrodynamics together with geologic history of the basin is important in shaping secondary migration patterns and accumulation of hydrocarbons.Quantification of all the above processes is complicated. Steps in constructing a deterministic dynamic model for calculation of petroleum potential during a sedimentary basin development are stated and analyzed in this paper. The effect of paleotemperature variations on petroleum generation and on physical properties of sedimentary sequences are illustrated by numerical examples. Computer models will enable exploration geologists to make quantitative exploration predictions in sedimentary basins.     

Investigation on strength and stability of jointed rock mass using three‐dimensional numerical manifold method

This paper proposes a numerical model for jointed rock masses within the 3‐D numerical manifold method (NMM) framework equipped with a customized contact algorithm. The strength of rock sample containing a few sets of discontinuities is first investigated. The results of models with simple geometries are compared with the available analytical solutions to verify the developed computer code, whereas models with complex geometries are simulated to better understand the fundamental behavior and failure mechanism of jointed rock mass. Furthermore, the stability of jointed rock mass in an underground excavation is studied, where rock failure process is determined by the 3‐D NMM simulation. The simulation results provide valuable guidance on excavation process design and stabilization design in rock engineering practice. Copyright © 2012 John Wiley & Sons, Ltd.