Apparatus and method for time-integrated, active sampling of contaminants in fluids demonstrated by monitoring of hexavalent chromium in groundwater

Abstract

Annual U.S. expenditures of $2B for site characterization invite the development of new technologies to improve data quality while reducing costs and minimizing uncertainty in groundwater monitoring. This work presents a new instrument for time-integrated sampling of environmental fluids using in situ solid-phase extraction (SPE). The In Situ Sampler (IS2) is an automated submersible device capable of extracting dissolved contaminants from water (100s – 1000s mL) over extended periods (hours to weeks), retaining the analytes, and rejecting the processed fluid. A field demonstration of the IS2 revealed 28-day average concentration of hexavalent chromium in a shallow aquifer affected by tidal stresses via sampling of groundwater as both liquid and sorbed composite samples, each obtained in triplicate. In situ SPE exhibited 75 ± 6% recovery and an 8-fold improvement in reporting limit. Relative to use of conventional methods (100%), beneficial characteristics of the device and method included minimal hazardous material generation (2%), transportation cost (10%), and associated carbon footprint (2%). The IS2 is compatible with commercial SPE resins and standard extraction methods, and has been certified for more general use (i.e., inorganics and organics) by the Environmental Security Technology Certification Program (ESTCP) of the U.S. Department of Defense.

TIMFIE Sampler–A New Time-Integrating, Active, Low-Tech Sampling Device for Quantitative Monitoring of Pesticides in Whole Water

“…However, grab samples do not give a fair estimate of chronic exposure and are only inadvertently collected at time points representing acute exposure from e.g., fast water flows following heavy rain. For estimating chronic exposure, a more appropriate approach than grab sampling would be to collect time-averaged water samples over a longer period. − This can be done with an electric pump and in situ SPE , or, more commonly, by collecting many small sample aliquots, evenly distributed over the study period, into one or several bottles using automatic field samplers . To minimize degradation of compounds during sampling, the pooled water must be stored in a refrigerator, and to protect this electrical equipment a small hut may be needed.…”