Effect of sulphur species on the hydrocarbon biodegradation of oil sludge generated by a gas processing facility

Oily sludge from gas processing facilities contains components that are major environmental pollutants. Biodegradation is an alternative treatment, but can be affected by other components of the sludge, such as sulphur compounds, so it is important to evaluate the effect of these on oil biodegradation in order to prevent negative impacts. This work studied the transformation of sulphur compounds in oily sludge biodegradation systems at the microcosm level. The predominant sulphur compounds in the original sludge were elemental sulphur and pyrite (9,776 and 28,705.4 mg kg^?1, respectively). In the biodegradability assays, hydrocarbon concentrations decreased from 312,705.6 to 186, 760.3 mg kg^?1 after 15 days of treatment. After this time, hydrocarbon degrading activity stopped, corresponding with a decrease in hydrocarbon degrading bacteria. These changes were related to a reduction in pH that inhibits biodegradation. During the assay, sulphur compounds were gradually oxidized and transformed. The concentration of sulphate increased from 5,096 to 64,868.3 mg kg^?1 after 30 days in the assay, although controls were unchanged. Therefore, it is important to determine changes to the main compounds of the waste in order to assess their impact.     

Petrography,geochemistry, and tectonics of a rifted fragment of Mainland Asia: evidence from the Lasala Formation,Mindoro Island,Philippines

Petrological and geochemical investigations of the sedimentary Lasala formation in northwest Mindoro, Philippines, offer new insights into the origin of this geologically contentious region. Mindoro island’s position at the boundary between Sundaland and the Philippine Mobile Belt has led to variable suggestions as to how much of it is continent derived or not. The Eocene Lasala formation overlies the Jurassic Halcon metamorphics, a regionally metamorphosed suite generally thought to have formed as a result of arc-continent collision processes. The sedimentary formation consists mainly of sandstones and shales interbedded with mudstones, basalt flows, and subordinate limestones and conglomerates. Petrographic information on the Lasala clastic rocks demonstrates a uniform framework composition that is predominantly quartzose. Major oxide, trace element abundances, and various elemental ratios similarly impart a strongly felsic signature. These characteristics are taken to indicate a chiefly continental, passive margin derivation and deposition of the Lasala sediments during the Eocene. The weak indication of active margin influence is suggested to be an inherited signature, supported by paleogeographic models of the southeastern Asian margin area during the pre-Cenozoic.     

Study of Seismic Clusters at Bahía de Banderas Region,Mexico

The coast in the state of Jalisco and south of Nayarit is located within a region of high seismic potential, increasing population, and tourism development. This motivated Civil Defense authorities of Jalisco and the Universidad de Guadalajara to launch in the year 2000 the assessment of the seismic risk of the region. This work focuses in the seismicity study of the area of Bahía de Banderas and northern coast of Jalisco, which is actually a seismic gap. We perform an analysis of available seismograms to characterize active crustal structures, their relationship to surface morphology, and possible extent of these structures into the bay shallow parts. The data consist of waveforms recorded during 2003 when the seismograph network spanned the region. Our method is based on the identification of seismic clusters or families using cross-correlation of waveforms, earthquake relocation and modeling of fault planes. From an initial data set of 404 located earthquakes, 96 earthquakes with M_L < 3.6 are related to 17 potentially active continental structures. We present fault plane model for 11 structures. A subgroup of 7 structures is aligned parallel to the Middle America Trench, as a possible consequence of oblique subduction. The foci of the earthquakes were grouped into clusters corresponding to fault dimensions of hundred of meters, may be considered as asperities or barriers in tectonic structures with lengths between 10 and 30 km. These structures could generate shallow earthquakes with magnitudes between 5.0 and 6.0 and represent an additional seismic threat to the region.     

Comparison of sparse‐grid geometric and random sampling methods in nonlinear inverse solution uncertainty estimation

A new uncertainty estimation method, which we recently introduced in the literature, allows for the comprehensive search of model posterior space while maintaining a high degree of computational efficiency. The method starts with an optimal solution to an inverse problem, performs a parameter reduction step and then searches the resulting feasible model space using prior parameter bounds and sparse‐grid polynomial interpolation methods. After misfit rejection, the resulting model ensemble represents the equivalent model space and can be used to estimate inverse solution uncertainty. While parameter reduction introduces a posterior bias, it also allows for scaling this method to higher dimensional problems. The use of Smolyak sparse‐grid interpolation also dramatically increases sampling efficiency for large stochastic dimensions. Unlike Bayesian inference, which treats the posterior sampling problem as a random process, this geometric sampling method exploits the structure and smoothness in posterior distributions by solving a polynomial interpolation problem and then resampling from the resulting interpolant. The two questions we address in this paper are 1) whether our results are generally compatible with established Bayesian inference methods and 2) how does our method compare in terms of posterior sampling efficiency. We accomplish this by comparing our method for two electromagnetic problems from the literature with two commonly used Bayesian sampling schemes: Gibbs’ and Metropolis‐Hastings. While both the sparse‐grid and Bayesian samplers produce compatible results, in both examples, the sparse‐grid approach has a much higher sampling efficiency, requiring an order of magnitude fewer samples, suggesting that sparse‐grid methods can significantly improve the tractability of inference solutions for problems in high dimensions or with more costly forward physics.     

Examining regulatory reform for bus operations in Latin America

Governments in Latin American cities are pursuing regulatory reforms to address the negative externalities of informal public transportation service providers. This is achieved by regulatory actions that work to consolidate many small operators competing “in the market” into fewer larger companies competing “for the market.” This reform addresses problems in the previous phase of the regulatory cycle, but requires a larger role for public authorities. The cities of Bogotá, Santiago and Mexico City took different approaches and have achieved different levels of formalization. Under these cities’ new regulatory regimes, bus companies have consolidated and public authorities now rely on renegotiation of contracts instead of open rebidding. However, industry formalization increases costs, requiring public subsidy or higher fares, and puts financial pressure on the public sector. These results imply a continued instability in the regulatory cycle; without increased public sector capacity, it is possible that large, entrenched operators and increasing costs will create a new market opening for informal service.     

LAND SUBSIDENCE IN THE LOS BANOS–KETTLEMAN CITY AREA,CALIFORNIA: PAST AND FUTURE OCCURRENCE

Land subsidence in the western San Joaquin Valley has been studied and monitored for almost six decades. Especially in the 1950s and 1960s, land subsidence had tremendous negative environmental and socioeconomic implications. The rate of land subsidence in the Los Banos–Kettleman City area, however, has decreased during the last three decades as a result of a decrease in groundwater withdrawal, following the importation of surface water to the Valley in late 1960s. The land subsidence in the Valley potentially could be a serious issue if the existing surface water supplies cannot meet increasing water demands during future critical drought periods. In this respect, this paper proposes a preliminary analysis to predict magnitudes of subsidence for the period 2000 to 2040, based on historical occurrences. In this study, extrapolation from earlier subsidence is based on: (1) knowledge of recent post-drought records at extensometers, (2) assumption of a single time porosity scenario, and (3) the premise that pumpage from the confined aquifer gradually will decrease as a result of progressive water quality degradation. Predicted magnitudes of land subsidence in the Los Banos–Kettleman City area are expected to be in the range 0.5 to 4.0 m for the next 4 to 5 decades under the scenario considered in this paper. [Key words: subsidence, groundwater extraction, aquitard, inelastic compaction, active porosity, Los Banos-Kettleman City, California.]     

Glacial and Fluvial Deposits in the Aragón Valley,Central‐Western Pyrenees: Chronology of the Pyrenean Late Pleistocene Glaciers

The Aragón Valley glacier (Central Western Pyrenees) has been studied since the late nineteenth century and has become one of the best areas in the Pyrenees to study the occurrence of Pleistocene glaciations and the relationships between moraines and fluvial terraces. New morphological studies and absolute ages for moraines and fluvial terraces in the Aragón Valley allow a correlation with other Pyrenean glaciers and provide solid chronologies about the asynchroneity between global last glacial maximum (LGM) and the maximum ice extent (MIE). Six frontal arcs and three lateral morainic ridges were identified in the Villanúa basin terminal glacial complex. The main moraines (M1 and M2) correspond to two glacial stages (oxygen isotopic stages MIS 6 and MIS 4), dated at 171 ± 22 ka and 68 ± 7 ka, respectively. From a topographical point of view, moraine M1 appears to be linked to the 60 m fluvioglacial terrace, dated in a tributary of the Aragón River at 263 ± 21 ka. The difference in age between M1 moraine and the 60 m fluvioglacial terrace suggests that the latter belongs to an earlier glacial stage (MIS 8). Moraine M2 was clearly linked to the fluvioglacial 20 m terrace. Other minor internal moraines were related to the 7–8 m terrace. The dates obtained for the last glacial cycle (20–18 ka) are similar to other chronologies for Mediterranean mountains, and confirm the occurrence of an early MIE in the Central Pyrenees that does not coincide with the global LGM.     

Is net ecosystem production higher in natural relative to constructed wetlands?

Ecosystem metabolism is an important measure of wetland restoration efficiency, and serves to indicate if the system is capable of processing energetic resources. Despite its value, ecosystem metabolism has rarely been included in monitoring programs. In this study, we aimed to achieve the following objectives: (i) compare net ecosystem production (NEP) rates of constructed vs. natural wetlands; (ii) identify the highest NEP rate habitats; and (iii) define the main environmental factors regulating NEP in different wetland types. Pelagic and benthic NEP rates and physicochemical features were measured in three natural and five constructed wetlands in the middle Ebro River floodplain (NE Spain). Statistical analyses showed pelagic NEP rates peaked in natural wetlands, which produced up to 187.5 mg C m^?3 h^?1 compared to lower rates in constructed wetlands (up to 46.2 mg C m^?3 h^?1). Pelagic NEP responded positively to temperature, total dissolved solids, and nutrients. Benthic NEP rates were 3 to 30-fold greater than pelagic in natural (up to 994.9 mg C m^?3 h^?1) and constructed (up to 1,551.5 mg C m^?3 h^?1) wetlands, and were heavily influenced by habitat type, with NEP peaking in areas dominated by submerged vegetation and fine organic sediment. Rapid recovery in aquatic communities (i.e. macroinvertebrate diversity) has been previously reported for the studied wetlands; however, our study suggests a slower recovery of functional processes (i.e. pelagic NEP) in constructed habitats. We therefore strongly advocate the inclusion of ecosystem function in the design and evaluation of restoration projects to optimise long-term wetland ecosystem sustainability.     

A Spectral Diagnostic for Density-Bounded HII Regions

Our spectral diagnostic based on the intensity of the [OI]λ6300Å line indicates that many observed HII regions are indeed density-bounded. The estimated fractions of escaping Lyman continuum photons range from 15 to even more than 50%.     

Temporal changes in Holocene δ18O records from the northwest and central North Iceland Shelf

The region of north Iceland is highly sensitive climatically owing to its location with respect to atmospheric and oceanographic fronts. In this study we present total carbonate and δ¹⁸O records of benthic and planktic Foraminifera from nine sediment cores from the North Iceland Shelf. The results of this work indicate that the deglaciation of the Vestfirdir Peninsula was completed by 10 200 cal. yr BP. The 8200 cal. yr BP cold event is present only as a minor isotopic event, and seems not to have had much of a cooling effect on the bottom waters of the northwest Iceland shelf. The Holocene maximum warmth, attributed to a stronger North Icelandic Irminger Current, occurred between ca. 7800 and 6200 cal. yr BP. Over the past 4500 cal. yr BP a general cooling trend has occurred on the North Iceland Shelf, and superimposed on this overall cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf. Relatively cooler waters were present at 4200–4000 cal. yr BP, 3200–2900 cal. yr BP, 2500–2350 cal. yr BP and 600–200 cal. yr BP, whereas relatively warmer waters were present on the shelf at 3750–3450 cal. yr BP, 2800–2600 cal. yr BP and 1700–1000 cal. yr BP. Copyright © 2004 John Wiley & Sons, Ltd.