Civil and Environmental Engineering

For performance-based design, non-linear dynamic structural analysis for various types of input ground motions is required. Stochastic (simulated) ground motions are sometimes useful as input motions, because unlike recorded motions they are not limited in number and because their properties can be varied systematically to understand the impact of ground motion properties on structural response. Here a stochastic ground motion model with time and frequency nonstationarity is developed using wavelet packets. Wavelet transform is a tool for analyzing time-series data with time and frequency nonstationarity, as well as simulating such data. Wavelet packet transform is an operation that decomposes time-series data into wavelet packets in the time and frequency domain, and its inverse transform reconstructs a time-series from wavelet packets. The characteristics of a nonstationary ground motion therefore can be modeled intuitively by specifying the amplitudes of wavelet packets at each time and frequency. In the proposed model, 13 parameters are sufficient to completely describe the time and frequency characteristics of a ground motion. These parameters can be computed from a specific target ground motion recording or by regression analysis based on a large database of recordings. The simulated ground motions produced by the proposed model reasonably match the target ground motion recordings in several respects including the spectral acceleration, inelastic response spectra, duration, bandwidth, and time and frequency nonstationarity. In addition, the median and logarithmic standard deviation of the spectral acceleration of the simulated ground motions match those of the published empirical ground motion prediction. These results suggest that the synthetic ground motions generated by the proposed model can be used for the non-linear dynamic structural analysis as the input ground motions.

Earthquake ground motion has non-stationary characteristics. It affects responses and damages of structures, so we should design input motion with non-stationary characteristics in mind. In order to evaluate non-stationary characteristics quantitatively, we define a parameter that reflects strength of non-stationary characteristics based on group delay time. The parameter is a relevant measure for evaluation of non-stationary characteristics. In this paper, we examine the fundamental characteristics of the parameter using idealized waveforms, focusing on how it controls the non-stationary characteristics. Then non-stationary characteristics of ground motion using observed records are dealt with.

An analytical framework to model the recovery and reconstruction of buildings in the regions impacted by the 2011 Tohoku Earthquake and Tsunami is presented in this paper and a series of reconstruction models for 39 selected cities are developed. As of March 2013, it is estimated that the 2011 Tohoku Earthquake and Tsunami resulted in 12.5% reduction in the total building exposure of those 39 cities. This reduction in pre-event building exposure decreases over time and those cities eventually recover to their pre-event states, however in meanwhile recovery and reconstruction models presented in this paper can be used for estimating the exposure at risk at any given time in order to ensure more realistic earthquake risk and loss estimations.

The response of a glucose-fed anaerobic community to a long-term (>400 days) periodic substrate perturbation was examined. A completely mixed "mother" reactor operated at steady state with a 10-day hydraulic retention time (HRT) and constant 8 g/liter glucose feed served as the source of organisms for a "daughter" reactor. The daughter reactor was initially operated in the same manner as the mother reactor, i.e. at a 10-day HRT and a constant 8 g/liter glucose feed. After reaching steady state, the daughter reactor was subjected to a periodic organic loading pattern in which the influent glucose concentration was alternately varied from 16 to 0 g/liter (mineral media only) on a 6-day cycle. A rapid accumulation in glucose fermentation intermediates occurred immediately after initiating the perturbation. Effluent chemical oxygen demand (COD) increased from ca 400 to a peak level of 6000 mg/liter, methane content of the biogas decreased from 50 to less than 20% and the pH decreased from 7.0 to 6.2. This was followed by a 230-day metastable "steady state" during which the effluent COD concentration fluctuated about a new median value of 5000 rag/liter and the acetate and butyrate concentrations varied in a cyclic, inverse pattern. At the end of the metastable period, volatile fatty acid concentrations decreased rapidly. Within ca 40 days, a new steady state was established. These observations indicate that the anaerobic system was able to adapt to the periodic substrate perturbation through a long-term change in microbial community. © 1997 Elsevier Science Ltd A~ = physiological concentration of the component i in the reaction (mol) [H+]=molar concentration of protons in the reactor solution re=net number of protons in the reaction (m is negative when more protons are consumed than formed) R=gas constant, 8.3143 (J/K per mole) T= temperature (308 K under operation conditions) V, = stoichiometrical coefficients for component Ai in a biological reaction (i = 1, 2, 3 .... ) AG'=free-energy change under operation conditions (35°C, measured pH, measured concentrations for products and reactants) (k J/tool) AG O' =free-energy change under standard physiological conditions (25°C, 1 atm and pH 7) (k J/tool) WR 319 C 2195

flushing, the pH of the extracted water gradually increased to 5.5-6.0, and nitrate concentrations fell to 0.5-1.0 mM. These conditions were judged suitable for biostimulation. In a companion paper (Wu et al., Environ. Sci. Technol. 2006, 40, 3978-3987), we describe the effects of ethanol addition on in situ denitrification and U(VI) reduction and immobilization.

The microbial community dynamics of a functionally stable, well-mixed, methanogenic reactor fed with glucose were analyzed over a 605-day period. The reactor maintained constant pH and chemical oxygen demand removal during this period. Thirty-six rrn clones from each of seven sampling events were analyzed by amplified ribosomal DNA restriction analysis (ARDRA) for the Bacteria and Archaea domains and by sequence analysis of dominant members of the community. Operational taxonomic units (OTUs), distinguished as unique ARDRA patterns, showed reproducible distribution for three sample replicates. The highest diversity was observed in the Bacteria domain. The 16S ribosomal DNA Bacteria clone library contained 75 OTUs, with the dominant OTU accounting for 13% of the total clones, but just 21 Archaea OTUs were found, and the most prominent OTU represented 50% of the clones from the respective library. Succession in methanogenic populations was observed, and two periods were distinguished: in the first, Methanobacterium formicicum was dominant, and in the second, Methanosarcina mazei and a Methanobacterium bryantii-related organism were dominant. Higher variability in Bacteria populations was detected, and the temporal OTU distribution suggested a chaotic pattern. Although dominant OTUs were constantly replaced from one sampling point to the next, phylogenetic analysis indicated that inferred physiologic changes in the community were not as dramatic as were genetic changes. Seven of eight dominant OTUs during the first period clustered with the spirochete group, although a cyclic pattern of substitution occurred among members within this order. A more flexible community structure characterized the second period, since a sequential replacement of a Eubacterium-related organism by an unrelated deep-branched organism and finally by a Propionibacterium-like species was observed. Metabolic differences among the dominant fermenters detected suggest that changes in carbon and electron flow occurred during the stable performance and indicate that an extremely dynamic community can maintain a stable ecosystem function.

Owing to their vast diversity and as-yet uncultivated status, detection, characterization and quantification of microorganisms in natural settings are very challenging, and linking microbial diversity to ecosystem processes and functions is even more difficult. Microarray-based genomic technology for detecting functional genes and processes has a great promise of overcoming such obstacles. Here, a novel comprehensive microarray, termed GeoChip, has been developed, containing 24 243 oligonucleotide (50 mer) probes and covering 410 000 genes in 4150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance, and organic contaminant degradation. The developed GeoChip was successfully used for tracking the dynamics of metal-reducing bacteria and associated communities for an in situ bioremediation study. This is the first comprehensive microarray currently available for studying biogeochemical processes and functional activities of microbial communities important to human health, agriculture, energy, global climate change, ecosystem management, and environmental cleanup and restoration. It is particularly useful for providing direct linkages of microbial genes/populations to ecosystem processes and functions.

We characterize the hydraulics of an extraction-injection well pair in arbitrarily oriented regional flow by the recirculation ratio, area, and average residence time in the recirculation zone. Erratic regional flow conditions may compromise the performance of the reactor between a single well pair. We propose an alternative four-well system: two downgradient extraction and two upgradient injection wells creating an inner cell nested within an outer cell. The outer cell protects the inner cell from the influence of regional flow. Compared to a two-well system, the proposed four-well system has several advantages: (1) the recirculation ratio within the nested inner cell is less sensitive to the regional flow direction; (2) a transitional recirculation zone between the inner and outer cells can capture flow leakage from the inner cell, minimizing the release of untreated contaminants; and (3) the size of the recirculation zone and residence times can be better controlled within the inner cell by changing the pumping rates. The system is applied at the Field Research Center in Oak Ridge, Tennessee, where experiments on microbial in situ reduction of uranium (VI) are under way.

1] This paper evaluates the microbial transport and degradation processes associated with carbon tetrachloride (CT) biodegradation in laboratory aquifer columns operated with a pulsed microbial feeding strategy. A seven component reactive transport model based on modified saturation kinetics and on a two-site sorption model was developed to describe the linked physical, chemical, and biological processes involved in CT degradation by Pseudomonas stutzeri KC, a denitrifying bacterium that cometabolically converts CT to harmless end products. After evaluating several expressions for attachment and detachment, we selected a dynamic partitioning model in which strain KC detachment decreases at low substrate concentrations. The resulting model enabled improved understanding of the complex coupled processes operative within our system and enabled us to test a model for field-scale design and transport studies. Batch studies were used to identify initial degradation and microbial transport processes, and constrained optimization methods were used to estimate a set of reaction rates that best describe the column experiment data. The optimal set of parameters for one column provided a reasonable prediction of solute and microbial concentrations in a second column operated under different conditions, providing an initial test of the model. This modeling strategy improved our understanding of biodegradation processes and rates. The CT degradation rate in the columns was lower than values obtained from batch studies, and processes in addition to the growth and decay of strain KC cells (due to native flora) are necessary to describe the observed nitrate consumption.

Pseudomonas sp. strain KG is a denitrifying bacterium that, under iron-limited conditions and in the presence of sufficient quantities of growth substrate, rapidly transforms carbon tetrachloride (CCl4) to carbon dioxide and nonvolatile products without production of chloroform. Bench-scale laboratory methods were used to evaluate the feasibility of bioaugmentation with strain KC to remediate aquifer materials from an aquifer of documented CCl4 contamination at Schoolcraft, Michigan. Nine glass columns packed with uncontaminated aquifer materials from the site were used to simulate aquifer conditions. Columns were alternately exchanged with ground water from the site in a rapid (20–30 minute) displacement of the pore fluid, then incubated under static conditions for a period of days to weeks. The exchange and incubation procedure continued until CCl4 removal began to plateau, indicating equilibration of the sorbed CCl4 with CCl4 in the pore fluid. Information obtained during this period was used to evaluate porosity (total and effective) and CCU sorption. In subsequent exchanges, base, acetate, and phosphorus were added to the exchange fluids to create conditions favorable for growth of strain KC and expression of its CCU transformation activity (niche adjustment). Three columns were inoculated with strain KC; three were not inoculated; and three were chemically disinfected with thimersol. Strain KC was transported more rapidly than the average linear velocity of the exchange fluids in the inoculated columns. Protein levels measured in the effluent of the inoculated columns during subsequent exchanges indicated that niche adjustment enabled rapid growth and colonization of the aquifer solids by strain KC. Little or no protein was detected in the effluent of uninoculated columns. CCl4 mass balances on the inoculated, noninoculated, and chemically disinfected columns indicated that niche adjustment and inoculation with strain KC created conditions favorable for CCl4 removal from the aquifer solids. Up to 70% removal of soluble CCl4 (30–50 μg/l) occurred in inoculated columns over a period of seven to nine days.

Whole-genome DNA microarrays were used to examine the gene expression profile of Shewanella oneidensis MR-1 during U(VI) and Cr(VI) reduction. The same control, cells pregrown with nitrate and incubated with no electron acceptor, was used for the two time points considered and for both metals. U(VI)-reducing conditions resulted in the upregulation (>3-fold) of 121 genes, while 83 genes were upregulated under Cr(VI)-reducing conditions. A large fraction of the genes upregulated [34% for U(VI) and 29% for Cr(VI)] encode hypothetical proteins of unknown function. Genes encoding proteins known to reduce alternative electron acceptors [fumarate, dimethyl sulfoxide, Mn(IV), or soluble Fe(III)] were upregulated under both U(VI)-and Cr(VI)-reducing conditions. The involvement of these upregulated genes in the reduction of U(VI) and Cr(VI) was tested using mutants lacking one or several of the gene products. Mutant testing confirmed the involvement of several genes in the reduction of both metals: mtrA, mtrB, mtrC, and menC, all of which are involved in Fe(III) citrate reduction by MR-1. Genes encoding efflux pumps were upregulated under Cr(VI)but not under U(VI)-reducing conditions. Genes encoding proteins associated with general (e.g., groL and dnaJ) and membrane (e.g., pspBC) stress were also upregulated, particularly under U(VI)-reducing conditions, pointing to membrane damage by the solid-phase reduced U(IV) and Cr(III) and/or the direct effect of the oxidized forms of the metals. This study sheds light on the multifaceted response of MR-1 to U(VI) and Cr(VI) under anaerobic conditions and suggests that the same electron transport pathway can be used for more than one electron acceptor.