Critical review of factors governing data quality of integrative samplers employed in environmental water monitoring

Abstract

Integrative sampling enables the collection of analyte mass from environmental liquids over extended timeframes from hours to months. While the incentives to complement or replace conventional, time-discrete sampling have been widely discussed, the data quality implications of employing alternative, integrative methods have not yet been systematically studied. A critical analysis of contemporary literature reports showed the data quality of integrative samplers, whether active-advection or passive-diffusion, to be governed by uncertainty in both sampling rate and analyte recovery. Derivation of two lumped parameters, representing the coefficient of accumulation (α) of a contaminant from an environmental fluid and the coefficient of subsequent recovery (ρ) of its mass from the sampler, produced a conceptual framework for quantifying error sources in concentration data derived from accumulative samplers. Whereas the precision associated with recovery was found to be fairly consistent across eight passive-diffusion and active-advection devices (averaging 5 – 16% relative standard deviation, RSD), active-advection samplers effectively improve precision in sampling rate (analyte uptake), as determined for two active-advection devices (2 – 7% average RSD) and five passive devices (12 – 42% average RSD). In summary, an approach is presented whereby the data quality implications of integrative sampler design can be compared, which can inform the selection, optimization, and development of sampling systems to complement the state of the art.

Calibration and application of the Chemcatcher® passive sampler for monitoring acidic herbicides in the River Exe, UK catchment

“…Key, however, is an improved understanding of the comparability of different sampling strategies (spot, event triggered or passive) particularly for pollutants (e.g. acidic herbicides, metaldehyde) that are present episodically in river catchments (Roll and Halden 2016 ).…”

Measuring metaldehyde in surface waters in the UK using two monitoring approaches

“…acidic herbicides, metaldehyde) that are present episodically in river catchments. 44 An additional use of passive samplers is to generate TWA concentrations that can be used in combination with in situ flow data to estimate monthly or annual fluxes of specific pollutants. 33 This information can be used to better inform environmental risk assessments at the catchment scale.…”

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

“…For passive samplers, R S is governed by a host of factors, including advective transport to and around the device and the diffusive transport of the contaminant to and into the sorbent material, the latter being a function of properties including the chemical species, ambient temperature, and length of the diffusive path. The RSD associated with R S has been variously reported for several passive and active samplers for a diversity of target species and ambient conditions, as reviewed recently (Roll and Halden, 2016). One study reported a range of RSD values for the Membrane-Enclosed Sorptive Coating (MESCO) of 4 to 49% (Vrana et al, 2001), whereas another employing the Polar Organic Chemical Integrative Sampler (POCIS) showed values varying from 9 to 95% (Jacquet et al, 2014), a third using the Semipermeable Polymeric Membrane Device (SPME) showed values of 1 to 33% (Huckins et al, 1999), and a final study employing Diffusive Gradient Thin Films showed values varying from 2–49% (Villanueva et al, 2013).…”

“…This suggests that variance associated with R S can be expected to be less than those associated with the extraction and quantification methods. Comparing the RSD for the sampling rate of the IS2 with that of several passive samplers, the results for the IS2 are particularly favorable, because the positive-displacement pumping system that governs R S for the IS2 is independent of the influences of temperature, mixing, and analyte-specific chemistry that cause significant variance in R S values of passive samplers (Roll and Halden, 2016). …”