Expanded application of the Passive Flux Meter: in-situ measurements of 1,4-dioxane, sulfate, Cr(VI), and RDX

Abstract

Passive flux meters (PFMs) have become invaluable tools for site characterization and evaluation of remediation performance at groundwater contaminated sites. To date, PFMs technology has been demonstrated in the field to measure low - to midrange hydrophobic contaminants (e.g., chlorinated ethenes, fuel hydrocarbons, perchlorate) and inorganic ions (e.g., uranium and nitrate). However, flux measurements of a low partitioning contaminant (e.g., 1,4-dioxane, hexahydro-1,3,5-trinitro-s-triazine (RDX)) and reactive ions-species (e.g., sulfate (SO42-), Chromium(VI) (Cr(VI)) are still challenging because of their low retardation during transport and quick transformation under highly reducing conditions, respectively. This study comprises the first application of PFMs for the in-situ mass flux measurements of 1,4-Dioxane, RDX, Cr(VI) and SO42- reduction rates. Laboratory experiments were performed to model kinetic uptake rates and extraction efficiency for sorbent selections. Silver impregnated granular activated carbon (GAC) was selected for capture of 1,4-Dioxane and RDX, whereas Purolite 300A was selected for chromium and SO42-. PFM field demonstrations measured 1,4-Dioxane fluxes ranging from 13.3 to 55.9 mg/m2/day, an RDX flux of 4.9 mg/m2/day, Cr(VI) fluxes ranging from 2.3 to 2.8 mg/m2/day, and SO42- consumption rates ranging from 20 to 100 mg/L/day. These data suggest other low-partitioning contaminates and reactive ion-species could be monitored using the PFM.

Subsurface flow measurements using passive flux meters in variably‐saturated cold‐regions landscapes

“…Subsurface flow through the meter causes the de‐soprtion of multiple tracers at (different) known rates, allowing the user to determine the flux of water through the cartridge over the period of observation (Hatfield, Annable, Cho, Rao, & Klammler, 2004; Hatfield, Rao, Annable, & Campbell, 2002). These PFMs have predominantly been used in contaminant monitoring in which contaminants are sorbed while the known tracers are de‐sorbed (Desormeaux, Annable, Dobberfuhl, & Jawitz, 2019; Haluska, Thiemann, Evans, Cho, & Annable, 2018; Hatfield et al, 2004; Klammler, Hatfield, & Annable, 2007; Kunz et al, 2017; Lee et al, 2007) but they also provide reliable time‐integrated subsurface flux measurements.…”