{"title":"Assessment of the Hydraulic Profiling Tool for Lower Permeability Characterization","authors":"Gaisheng Liu, Steven Knobbe","doi":"10.1111/gwmr.12685","DOIUrl":"https://doi.org/10.1111/gwmr.12685","url":null,"abstract":"The Hydraulic Profiling Tool (HPT) has become one of the most widely accepted approaches for obtaining vertical profiles of hydraulic conductivity (K) in environmental site investigations. The current tool, however, is limited to use in moderately permeable settings with a measurable K range of 0.03 to 25 m/d. In this work, we added a low‐flow injection system to standard HPT and modified the field profiling procedure so that it could be used more effectively in lower‐K settings. The modified lower‐K HPT was tested and evaluated against direct‐push slug tests at a field site in the Kansas River floodplain. Results indicated that when the injection rate was reduced, injection pressure decreased, which reduced the potential of injection‐induced formation alteration. A particular challenge of applying HPT in lower‐K zones is the large pressure generated by probe advancement; this can significantly affect the pressure signal measured at the injection screen. Our results showed that the impacts of advancement‐generated pressure could be mitigated by reducing the speed of probe advancement. Compared to K estimates by slug tests, the vertical variability in HPT K was much lower. The reduced variability in HPT K was likely due to formation alteration during probe advancement, as well as pressure interference from injections at previous depths and probe advancement at the bottom. Additional work, such as the use of a smaller‐diameter probe, is needed to further improve the performance of HPT in lower permeability zones.","PeriodicalId":501449,"journal":{"name":"Groundwater Monitoring & Remediation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Studies in Parameter Estimation for Analytical Transport Equations","authors":"Andrew Mills","doi":"10.1111/gwmr.12684","DOIUrl":"https://doi.org/10.1111/gwmr.12684","url":null,"abstract":"Three new programs have been developed to perform parameter estimation to assist in the calibration of analytical contaminant transport models. The Domenico equation was chosen as an example analytical model for each of the three programs rather than a model with the exact solution, because the former is a closed‐form expression involving significantly less processing time. One of the programs studied is a quasi‐exhaustive search method and the second is a successive parameter variation method. The third program is based on Box's Complex nonlinear, direct‐search optimization method. The three programs and an already available calibration tool (PEST) were compared in tests using data from two different sites in southeastern Pennsylvania. These tests demonstrated the validity of the three programs as examples to assist the calibration of groundwater analytical transport models. The final estimates for the parameter values for the three methods and PEST applied to the data from each of the two sites compared quite closely and, with two exceptions were well within an order of magnitude of each other. The three newly available programs individually should serve as calibrating tools indispensable for field hydrogeologists, environmental project managers, and others who have been asked to run analytical transport models. The results from the runs performed on the two sites indicate the Complex method to be the best option as a calibration tool, with the quasi‐exhaustive method and the successive parameter estimation method being acceptable alternatives.","PeriodicalId":501449,"journal":{"name":"Groundwater Monitoring & Remediation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Climatic Effects on Vapor Flow and Behavior in the Vadose Zone","authors":"Bart Eklund","doi":"10.1111/gwmr.12682","DOIUrl":"https://doi.org/10.1111/gwmr.12682","url":null,"abstract":"The concentrations and transport of volatile organic compounds (VOCs) and other vapors in the vadose zone may exhibit some degree of temporal variability due to the effect of various climatic factors, including (1) Air temperature; (2) Barometric pressure; (3) Surface winds; and (4) Soil moisture, including the effects of any water infiltration and/or changes in groundwater level. These variables may directly affect the rates of gas transport through the vadose zone or may indirectly affect transport by changing the soil‐gas concentrations at a given location and depth. To understand the potential effect of these factors due to climate change, it is first necessary to understand their effect over typical time periods of one to several days, seasonally, and annually. In this paper, the effects of the above variables over various time periods are presented and the long‐term effects due to climate change are discussed. Standard approaches for soil‐gas measurement attempt to account for these variables, either to negate their potential influence or to capture data under reasonably worst‐case conditions. The appropriateness and adequacy of typical soil vapor measurement approaches are discussed.","PeriodicalId":501449,"journal":{"name":"Groundwater Monitoring & Remediation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Henry C.G. Nicholls, H. Emma Mallinson, Steven F. Thornton, Markus Hjort, Stephen A. Rolfe
{"title":"Identification of Aerobic ETBE‐Degrading Microorganisms in Groundwater Using Stable Isotope Probing","authors":"Henry C.G. Nicholls, H. Emma Mallinson, Steven F. Thornton, Markus Hjort, Stephen A. Rolfe","doi":"10.1111/gwmr.12679","DOIUrl":"https://doi.org/10.1111/gwmr.12679","url":null,"abstract":"A limited number of microorganisms have been identified with the capability to degrade ethyl <jats:italic>tert</jats:italic>‐butyl ether (ETBE) in the environment. Knowledge of the identity and distribution of ETBE‐degrading microorganisms is important for the implementation of management measures such as natural attenuation and bioremediation at ETBE‐release sites. In this study, DNA‐stable isotope probing (SIP) was used to identify microorganisms able to aerobically degrade <jats:sup>13</jats:sup>C‐labeled ETBE in laboratory microcosms constructed with groundwater and aquifer material from an ETBE‐release site. Microorganisms in the Class γ‐proteobacteria, Order β‐proteobacteriales, Family Burkholderiaceae, and classified as <jats:italic>Methylibium</jats:italic> and <jats:italic>Leptothrix</jats:italic>, respectively, were identified as primary ETBE degraders. Comparisons with ETBE‐responsive microorganisms (those which increased in abundance after the addition of ETBE), identified by high‐throughput sequencing of microcosms established from the same site, showed that only a small proportion of the ETBE‐responsive organisms were primary degraders as determined by SIP. ETBE degraders were taxonomically related to microorganisms able to degrade other gasoline components, but not ETBE, implying that this functionality results from acquisition of the <jats:italic>eth</jats:italic> gene cluster by these organisms. These ETBE degraders could also be identified at ETBE‐release sites, but at low relative abundance and generally only in those locations from which the microcosms had been established. Therefore, we recommend that molecular investigations of ETBE‐contaminated sites focus on functional genes (i.e., the <jats:italic>eth</jats:italic> gene cluster) rather than specific taxa.","PeriodicalId":501449,"journal":{"name":"Groundwater Monitoring & Remediation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141745284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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