The Monitoring and Remediation Optimization System (MAROS), a decision-support software, was developed to assist in formulating cost-effective ground water long-term monitoring plans. MAROS optimizes an existing ground water monitoring program using both temporal and spatial data analyses to determine the general monitoring system category and the locations and frequency of sampling for future compliance monitoring at the site. The objective of the MAROS optimization is to minimize monitoring locations in the sampling network and reduce sampling frequency without significant loss of information, ensuring adequate future characterization of the contaminant plume. The interpretive trend analysis approach recommends the general monitoring system category for a site based on plume stability and site-specific hydrogeologic information. Plume stability is characterized using primary lines of evidence (i.e., Mann-Kendall analysis and linear regression analysis) based on concentration trends, and secondary lines of evidence based on modeling results and empirical data. The sampling optimization approach, consisting of a two-dimensional spatial sampling reduction method (Delaunay method) and a temporal sampling analysis method (Modified CES method), provides detailed sampling location and frequency results. The Delaunay method is designed to identify and eliminate redundant sampling locations without causing significant information loss in characterizing the plume. The Modified CES method determines the optimal sampling frequency for a sampling location based on the direction, magnitude, and uncertainty in its concentration trend. MAROS addresses a variety of ground water contaminants (fuels, solvents, and metals), allows import of various data formats, and is designed for continual modification of long-term monitoring plans as the plume or site conditions change over time.

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A ground water flow and solute transport model was developed for a site contaminated with chlorinated solvents to simulate the site remediation activities that included natural attenuation and source control. MODFLOW was used to model the flow field, and RT3D was employed to simulate the sequential decay reactions involving perchloroethene, trichloroethene, dichloroethene, and vinyl chloride (VC). Predictive simulations were completed for two conditions: natural attenuation alone and source excavation followed by natural attenuation. Results demonstrated the feasibility of site remediation for both conditions with the latter one occurring in a shorter time frame. A detailed sensitivity analysis was performed to assess the uncertainty in model predictions. The most sensitive model parameters (i.e., initial contaminant concentrations, reaction rate constants, and source release rates) were perturbed and combined to form a number of parameter sets for use in the predictive simulations. The maximum plume length, the maximum plume concentration, and the persistence time for the noncompliance plume area were assessed to identify the possible failure scenarios and the most likely future plume configuration. Results indicated that further VC plume expansion or migration beyond site boundaries is unlikely.

BackgroundAlthough e-cigarette excise taxes have great potential to prevent the initiation and escalation of e-cigarette use, little information is available on pricing activities of online vape shops, and how well taxation is implemented during web-based sales remains unclear.ObjectivesWe examine e-liquid pricing activities in popular online vape shops that sell nationwide in the USA and present how those stores charge excise taxes based on shipping addresses in states and local jurisdictions that have e-cigarette taxation in place.MethodsWe collect e-liquid sales prices from five online vape shops using web data extraction, standardise prices for e-liquid products, and present e-liquid price distribution in the whole sample and in each store, as well as variations of excise taxes across states/local jurisdictions and between stores. The price data were scraped from the store websites from February to May in 2021.ResultsWe collected data on 14 477 e-liquid products from five stores. The average price of e-liquids is $0.25/mL, and the median price is $0.20/mL in our sample. E-liquid products sold online are very affordable and the average prices are lower compared with price estimates using other sources (eg, self-reports, sales data). In addition, online stores charge state excise taxes inconsistently and fail to comply with county-level or city-level excise taxes.ConclusionE-liquid products sold online are priced low, and stricter enforcement of e-cigarette excise tax is needed in online purchasing channels.

An innovative methodology for improving existing groundwater monitoring plans at small-scale sites is presented. The methodology consists of three stand-alone methods: a spatial redundancy reduction method, a well-siting method for adding new sampling locations, and a sampling frequency determination method. The spatial redundancy reduction method eliminates redundant wells through an optimization process that minimizes the errors in plume delineation and the average plume concentration estimation. The well-siting method locates possible new sampling points for an inadequately delineated plume via regression analysis of plume centerline concentrations and estimation of plume dispersivity values. The sampling frequency determination method recommends the future frequency of sampling for each sampling location based on the direction, magnitude, and uncertainty of the concentration trend derived from representative historical concentration data. Although the methodology is designed for small-scale sites, it can be easily adopted for large-scale site applications. The proposed methodology is applied to a small petroleum hydrocarbon-contaminated site with a network of 12 monitoring wells to demonstrate its effectiveness and validity.