Erich S. Hinlein

Soil gas transport above a jet fuel/solvent spill at Plattsburgh Air Force Base

We calibrate a stoichiometrically coupled soil gas diffusion model with spatially resolved observations of oxygen, carbon dioxide, total hydrocarbon, and trichloroethylene vapor concentrations in the unsaturated zone above a weathered jet fuel/solvent spill at Plattsburgh Air Force Base in upstate New York. The calibration suggests that aerobic microorganisms in the capillary fringe degrade jet fuel vapor at a steady rate of 9.5 μg hydrocarbons (m−2 s−1). The solvent does not degrade in the fringe, however, and the model and data estimate a steady evaporation rate of 1.2×10−2 μg TCE (m−2 s−1). Barometric pumping slightly alters the steady concentration profile at Plattsburgh, although the transient advective flux is the same order of magnitude as the steady diffusive flux. We derive a simple perturbation theory for the second-order transient concentration corrections and include it in the calibration. The perturbation theory is valid at Plattsburgh because the soil is uniform and permeable with a relatively deep capillary fringe.

Near Surface Soil Vapor Clusters for Monitoring Emissions of Volatile Organic Compounds from Soils

ABSTRACT The overall objective of this research was to develop and test a method of determining emission rates of volatile organic compounds (VOCs) and other gases from soil surfaces. Soil vapor clusters (SVCs) were designed as a low dead volume, robust sampling system to obtain vertically resolved profiles of soil gas contaminant concentrations in the near surface zone. The concentration profiles, when combined with a mathematical model of porous media mass transport, were used to calculate the contaminant flux from the soil surface. Initial experiments were conducted using a mesoscale soil remediation system under a range of experimental conditions. Helium was used as a tracer and trichloroethene was used as a model VOC. Flux estimations using the SVCs were within 25% of independent surface flux estimates and were comparable to measurements made using a surface isolation flux chamber (SIFC). In addition, method detection limits for the SVC were an order of magnitude lower than detection limits with the SIFC. Field trials, conducted with the SVCs at a bioventing site, indicated that the SVC method could be easily used in the field to estimate fugitive VOC emission rates. Major advantages of the SVC method were its low detection limits, lack of required auxiliary equipment, and ability to obtain realtime estimates of fugitive VOC emission rates.

Reduced Road Salt Spillage Owing to Indoor Delivery and Loading

The authors analyze runoff and road salt delivery and loading data from an indoor salt storage facility in eastern Massachusetts over multiple deicing seasons. The facility converted its delivery/loading from outdoors to indoors. Data and simple theory document a fivefold decrease in spillage as a result of the conversion. A seasonally varying balance of first order dissolution and a spill fraction is used to quantify the improvement; the data and model suggest that 0.3% of the outdoor delivered/loaded road salt spilled onto the pavement. The conversion to indoor delivery/loading reduced the spillage fraction to 0.06%.

Groundwater Plume from an Infiltration Basin

We model and measure the groundwater plume from an infiltration basin in the Plymouth-Carver Aquifer near State Route 25 in southeastern Massachusetts. The advective transport model superimposes axisymmetric basin hydraulics and two dimensional ambient flow. The basin component incorporates a surface source of finite radius into a Hankel transform model for unconfined aquifers, while the ambient component varies linearly in the horizontal and vertical directions. Contaminant streamlines describe the resulting groundwater plume. Deicing agent constituent data confirm the plume boundaries, and calibrate plausible source concentrations and spread rates.

Groundwater Dispersivity Induced by Stormwater Runoff

Stormwater infiltration basins change groundwater transport processes. The focused infiltration of the basin depresses streamlines below their ambient locations as an steady expression of altered advection. Stormwater infiltration is aperiodic, and creates unsteady seepage velocity fluctuations as a consequence. The vertical fluctuations can materially increase vertical dispersion-a stormwater infiltration basin in the Plymouth-Carver Aquifer adds a 25 cm vertical excursion amplitude to the mechanical and hydrodynamic dispersion of the ambient flow field. Contaminant concentration profiles suggest a 39 cm vertical dispersivity value far exceeding the 1.5 mm value exhibited by a wastewater effluent plume in a similar aquifer.