Field Investigation of Nutrient Pulse Mixing in an in Situ Biostimulation Experiment

A permeable wall was installed in a shallow,uncontaminated portion of the Borden aquifer,and periodically flushed with a solution of potassium acetate.The acetate pulses were injected at intervals of 5-7 weeks and were observed to merge within 5-10 m of the injection wall. The chief mechanism for the merging of these pulses was longitudinal dispersion. Geochemical changes in the aquifer, manifested as the development of a sustained reducing environment, indicated that the dispersive mixing occurred at the scale of the microorganisms and was not merely an artifact of the sampling method.This work indicates that large-period pulsed injections of a substrate solution might be useful in bioremediation programs where the promotion of injected and ambient water mixing is desirable. It is also advantageous, from the stand point of biofouling prevention, that this mixing occur at some distance from the injection wells.This research was funded by the Ontario Ministry of Environment and Energy. Additional support from the University Consortium Solvents-in-Groundwater Research Program is also gratefully acknowledged. Sponsors of the program have included The Boeing Company, Ciba-Geigy, Dow Chemical, Eastman Kodak, General Electric, Mitretek Systems, Motorola, PPG Industries, United Technologies Corporation, the Natural Sciences and Engineering Research Council of Canada, and the Ontario Research University Fund

HydrogeoSieveXL: an Excel-based tool to estimate hydraulic conductivity from grain-size analysis

Please note: The HydroSieveXL file is in XLSM format. If it is clicked to view/open, some web browsers will open the file as an XLSX format. If that is the case with your browser, please Save the file and rename the file so that the extension is XLSM.For over a century, hydrogeologists have estimated hydraulic conductivity (K) from grain-size distribution curves. The benefits of the practice are simplicity, cost, and a means of identifying spatial variations in K. Many techniques have been developed over the years, but all suffer from similar shortcomings: no accounting of heterogeneity within samples (i.e., aquifer structure is lost), loss of grain packing characteristics, and failure to account for the effects of overburden pressure on K. In addition, K estimates can vary by an order of magnitude between the various methods, and it is not generally possible to identify the best method for a given sample. The drawbacks are serious, but the advantages have seen the use of grain-size distribution curves for K estimation continue, often using a single selected method to estimate K in a given project. In most cases, this restriction results from convenience. It is proposed here that extending the analysis to include several methods would be beneficial since it would provide a better indication of the range of K that might apply. To overcome the convenience limitation, an Excel-based spreadsheet program, HydrogeoSieveXL, is introduced here. HydrogeoSieveXL is a freely available program that calculates K from grain-size distribution curves using 15 different methods. HydrogeoSieveXL was found to calculate K values essentially identical to those reported in the literature, using the published grain-size distribution curves

HydrogeoEstimatorXL: an Excel-based tool for estimating hydraulic gradient magnitude and direction

HydrogeoEstimatorXL is a free software tool for the interpretation of flow systems based on spatial hydrogeological field data from multi-well networks. It runs on the familiar Excel spreadsheet platform. The program accepts well location coordinates and hydraulic head data, and returns an analysis of the area flow system in twodimensions based on a) a single best fit plane of the potentiometric surface and b) three-point estimators, i.e., well triplets assumed to bound planar sections of the potentiometric surface. The software produces graphical outputs including histograms of hydraulic gradient magnitude and direction, groundwater velocity (based on a site average hydraulic properties), as well as mapped renditions of the estimator triangles and the velocity vectors associated with them. Within the software, a transect can be defined and the mass discharge of a groundwater contaminant crossing the transect can be estimated. This kind of analysis is helpful in gaining an overview of a site’s hydrogeology, for problem definition, and as a review tool to check the reasonableness of other, independent calculations

Hydrogeologic assessment of in situ natural attenuation in a controlled field experiment

An experiment to investigate the natural attenuation of three volatile organic compounds, toluene, carbon tetrachloride, and tetrachloroethene (∼1–10 mg L−1) was performed in a 3 m deep, sandy aquifer isolated within a 24 m long, 2 m wide, three-sided sheet pile alleyway (hereafter referred to as the gate). A constant flow was maintained in the test volume by pumping a well at the closed end of the gate at 130 mL min−1. The test compounds were introduced to the aquifer using diffusive emitters installed inside 25 cm diameter wells located at the open end of the gate. Monitoring was performed by sampling along six multilevel fences (consisting of 12 sampling points each) ranging in distance from 1 to 22 m from the source wells. A bromide tracer experiment established that there were no significant hydraulic leaks, nor was there any continuous channeling through the gate. Degradation of the test compounds was assessed by mass balance calculations between fences located 1 and 7 m from the source, and the results were compared with degradation rate estimates from snapshot analyses and the analysis of fluxes. There was reasonably good agreement between rates estimated by these different methods. Toluene degraded with a half-life of 58–62 days, carbon tetrachloride degraded with a half-life of ∼11–13 days, and tetrachloroethene degraded too slowly for a reliable estimate of rate to be made. Transformation products identified in the gate included acetate, possibly from toluene degradation, chloroform, trichloroethene, and cis-1,2, dichloroethene. The latter two compounds only appeared in trace quantities and could not be assessed for continuing degradation. However, chloroform degradation was assessed with the snapshot data and using the flux estimates and was found to degrade with a half-life in the range of 10–34 days. No additional chlorinated methanes were detected in the gate, suggesting that the carbon tetrachloride was completely dechlorinated by natural processes within 10 m of the source wells. This experiment demonstrated that degradation of chlorinated solvents occurs naturally at the Borden site but that the ethenes are more resistant to biodegradation than the methanes. In addition, the flux calculations were found to be the most robust in terms of estimating degradation rates.Financial support for this research was provided by the Advanced Alternative Technology Demonstration Facility, funded by the Department of Defense and administered by Rice University. Additional support was provided by the NSERC/Motorolla/ETI Industrial Research Chair in Groundwater Remediation and the Solvents in Groundwater Consortium, University of Waterloo. T. Anderson of the University of Massachusetts assisted with hydrogen measurements, while Susan Froud and Dennis Katic assisted with all other aspects of the fieldwork and participated in discussions of the data. Mike Brown is acknowledged for his contribution to the installation of the gate, and Stephanie Fiorenza is acknowledged for her comments and assistance liaising with AATDF

Field comparison of the point velocity probe with other groundwater velocity measurement methods

Field testing of a new tool for measuring groundwater velocities at the centimeter scale, the point velocity probe (PVP), was undertaken at Canadian Forces Base, Borden, Ontario, Canada. The measurements were performed in a sheet pile-bounded alleyway in which bulk flow rate and direction could be controlled. PVP velocities were compared with those estimated from bulk flow, a Geoflo® instrument, borehole dilution, colloidal borescope measurements, and a forced gradient tracer test. In addition, the velocity profiles were compared with vertical variations in hydraulic conductivity (K) measured by permeameter testing of core samples and in situ high-resolution slug tests. There was qualitative agreement between the trends in velocity and K among all the various methods. The PVP and Geoflo® meter tests returned average velocity magnitudes of 30.2 ± 7.7 to 34.7 ± 13.1 cm/d (depending on prior knowledge of flow direction in PVP tests) and 36.5 ± 10.6, respectively, which were near the estimated bulk velocity (20 cm/d). The other direct velocity measurement techniques yielded velocity estimates 5 to 12 times the bulk velocity. Best results with the PVP instrument were obtained by jetting the instrument into place, though this method may have introduced a slight positive bias to the measured velocities. The individual estimates of point velocity direction varied, but the average of the point velocity directions agreed quite well with the expected bulk flow direction. It was concluded that the PVP method is a viable technique for use in the field, where high-resolution velocity data are required.The NSERC/Motorola/ETI Industrial Research Chair in Groundwater Remediation, NSERC, CRESTech, the National Council for Scientific Research of Lebanon (NCSR), OGSST, and NSF under grant 0134545 are acknowledged for funding this work. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Carl McElwee performed the high-definition slug tests; Peter Kearl performed the colloidal borescope measurements; and Bob Ingleton, Paul Johnson, and Greg Friday assisted with probe construction and field installatio

Ground-penetrating radar observations of enhanced biological activity in a sandbox reactor

In this study, we evaluate the use of ground-penetrating radar (GPR) to investigate the effects of bacterial activity in water saturated sand. A 90-day laboratory-scale controlled experiment was conducted in a flow-through polycarbonate sandbox using groundwater from the Kansas River alluvial aquifer as inoculum. After 40 days of collecting baseline data, bacterial growth was stimulated in the sandbox by the addition of a carbon and nutrient solution on a weekly basis. Radar signal travel time and attenuation were shown to increase downgradient of the nutrient release wells relative to upgradient locations. After 60 days, the frequency of nutrient injections was increased to twice per week, after which gaseous bubbles were visually observed downgradient of the nutrient release wells. Visual observation of active gas production correlated spatially and temporally with a rapid decrease in radar signal travel time, confirming that GPR can monitor the generation of biogenic gases in this system. Analysis of the sediments indicated microbial lipid biomass increased by approximately one order of magnitude and there were no changes in the inorganic carbon content of bulk sediment mineralogy. These findings suggest that the increase in biomass and gas production may be responsible for the observed changes in radar signal travel time reported in this study. Therefore, this study provides evidence that GPR can be used to monitor biological activity in water saturated sand.Funding for this project was through the National Science Foundation CAREER grant 0134545 awarded to J.F. Devlin and NSF EAR/IF-0345445 for acquisition of GPR instrumentation awarded to G. Tsoflias. The opinions, findings, and recommendations of this study are the views the author(s) and do not necessarily reflect the views and opinions of the National Science Foundation. We would like to thank Mike McGlashan, Kwan Yee Cheng, Kelly Peterson, Lindsay Mayer, and Breanna Huff for assistance with this project. We also thank two anonymous reviewers for their helpful comments that led to the improvement of this manuscript

First complete genome sequence of infectious laryngotracheitis virus

BACKGROUND: Infectious laryngotracheitis virus (ILTV) is an alphaherpesvirus that causes acute respiratory disease in chickens worldwide. To date, only one complete genomic sequence of ILTV has been reported. This sequence was generated by concatenating partial sequences from six different ILTV strains. Thus, the full genomic sequence of a single (individual) strain of ILTV has not been determined previously. This study aimed to use high throughput sequencing technology to determine the complete genomic sequence of a live attenuated vaccine strain of ILTV. RESULTS: The complete genomic sequence of the Serva vaccine strain of ILTV was determined, annotated and compared to the concatenated ILTV reference sequence. The genome size of the Serva strain was 152,628 bp, with a G + C content of 48%. A total of 80 predicted open reading frames were identified. The Serva strain had 96.5% DNA sequence identity with the concatenated ILTV sequence. Notably, the concatenated ILTV sequence was found to lack four large regions of sequence, including 528 bp and 594 bp of sequence in the UL29 and UL36 genes, respectively, and two copies of a 1,563 bp sequence in the repeat regions. Considerable differences in the size of the predicted translation products of 4 other genes (UL54, UL30, UL37 and UL38) were also identified. More than 530 single-nucleotide polymorphisms (SNPs) were identified. Most SNPs were located within three genomic regions, corresponding to sequence from the SA-2 ILTV vaccine strain in the concatenated ILTV sequence. CONCLUSIONS: This is the first complete genomic sequence of an individual ILTV strain. This sequence will facilitate future comparative genomic studies of ILTV by providing an appropriate reference sequence for the sequence analysis of other ILTV strains

Herschel and ALMA observations of the ISM in massive high-redshift galaxy clusters

The Sunyaev-Zel'dovich effect (SZE) can be used to select samples of galaxy clusters that are essentially mass-limited out to arbitrarily high redshifts. I will present results from an investigation of the star formation properties of galaxies in four massive clusters, extending to z~1, which were selected on the basis of their SZE decrements in the Atacama Cosmology Telescope (ACT) survey. All four clusters have been imaged with Herschel/PACS (tracing star formation rate) and two with ALMA (tracing dust and cold gas mass); newly discovered ALMA CO(4-3) and [CI] line detections expand an already large sample of spectroscopically confirmed cluster members. Star formation rate appears to anti-correlate with environmental density, but this trend vanishes after controlling for stellar mass. Elevated star formation and higher CO excitation are seen in "El Gordo," a violent cluster merger, relative to a virialized cluster at a similar high (z~1) redshift. Also exploiting ATCA 2.1 GHz observations to identify radio-loud active galactic nuclei (AGN) in our sample, I will use these data to develop a coherent picture of how environment influences galaxies' ISM properties and evolution in the most massive clusters at early cosmic times