Browsing by Author "Hopkins, Loren Palmer"

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    A hydrogeologic database for stochastic groundwater modeling with hydrogeologic environment-specific applications
    (1989) Hopkins, Loren Palmer; Bedient, Philip B.
    The development of a method to restrict the land disposal of hazardous waste is an area of great concern for the United States Environmental Protection Agency. A proposed method is to determine allowable concentrations, below cancer limits, of specific chemical contaminants slated for land disposal based on the results of a Monte Carlo type contaminant groundwater transport model. The proposed regulatory model does not account for site specific conditions because the hydrogeologic environment specific data required has not previously been available. A hydrogeologic database is developed and analyzed for specific environments. The behavior of the proposed regulatory model is examined using the hydrogeologic environment specific information as input.
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    A statistical investigation of ozone exposure assessment by direct and indirect measurement
    (1998) Hopkins, Loren Palmer; Bedient, Philip B.
    Recent studies have proposed the application of exposure-based criteria in developing alternative primary ambient ozone standards. Historically, epidemiological studies of ozone have approached exposure assessment in a simplistic fashion with simplistic methods used to estimate ambient ozone concentrations in exposure assessment. A new method for assessing human exposure to ozone has been developed. The research uses a spatial temporal statistical method, kriging, in conjunction with subject activity logs to estimate personal exposure to ozone. The personal ozone exposure to human subjects was monitored using Harvard passive samplers during August and September of 1997. Each subject logged their location and activity during the exposure period. A three-dimensional kriging model of ozone was developed to estimate the ozone exposure for each subject from ambient fixed site monitoring data. The ozone predications from the model were combined with the activity and location information, adjusted for indoor environment when applicable, to estimate personal exposure concentrations for each subject. Using two independent approaches, the kriging model was proven to provide accurate spatial and temporal estimates of ozone at subject exposure points. The results from this work show that the method developed to estimate exposure through kriging over (x,y,t) to predict ozone concentrations at exposure points combined with subject activity and location logs produces exposure estimates within the error bounds of the analytical methods for personal monitoring.