Time Integrative Passive Sampling: How Well Do Chemcatchers Integrate Fluctuating Pollutant Concentrations?

Abstract

Many environments are subject to periodic fluctuations in pollutant concentrations. Passive samplers, which can provide time weighted average concentrations integrated over the period of deployment, are ideally suited as monitoring tools for these environments. However, the potential for fluctuating concentrations to limit the integrative period of sampling needs to be investigated before sampling data from these environments can be interpreted with confidence. In this study, Chemcatchers using SDB-RPS Empore disks as the sorbent phase were exposed to herbicides for 28 days in a calibration chamber. A pulsed event of 10-fold greater concentrations was introduced on day 5 and returned to background concentrations over a period of 3 days. Observed uptake was compared with that predicted by a first order uptake model and by the reduced form of this model describing a strictly integrative response for samplers deployed with two surfaces exposed (two-sided naked), with one surface exposed (one-sided naked) and with a polyethersulfone membrane. Membrane covered samplers predicted time weighted average water concentrations within a factor 0.7-1.2 after 28 days exposure, while one- and two-sided naked samplers under predicted the average by a factor 1.9-2.2 and 2.4-3.2, respectively. First order modeling predicted uptake in membrane covered and one-sided naked samplers and was therefore applied to predict sampler response to several fluctuating concentration event scenarios.

Uptake and release kinetics of 22 polar organic chemicals in the Chemcatcher passive sampler

“…Understanding the desorption process is important when considering the behaviour of a sampler after a peak concentration event [15]. Understanding the desorption process is also important when considering the use of performance reference compounds (PRCs) in passive samplers [16].…”

Modeling the response of passive samplers to varying ambient fluid concentrations of organic contaminants

“…The sampler response is illustrated in Figure 4, and the time when it reaches a maximum (Equation 13) is a function of k e and k loss only. Employment of a PRC allows k e to be derived, so from Equation 13 k loss may be obtained.…”

“…Examples of other passive sampler configurations are solid-phase microextraction fibers [5], polymer-coated glass systems [6], polyurethane foam disks [7], and various single-phase polymeric materials, including those identified above [1,8,9]. A wide array of compounds may be accumulated, including hydrocarbons and halogenated hydrocarbons, such as polyaromatic hydrocarbons, polychlorinated biphenyls and polybrominated diphenyl ethers [3,10], and endocrine disruptors [11], together with various pesticides and herbicides [12,13].…”

“…Under such conditions, samplers operating in the linear or integrative mode are considered to afford a time-weighted average ambient fluid concentration [13,18,19]. Recently, the performance of passive samplers with a contamination pulse in the ambient fluid [13] has been scrutinized. It is uncertain how passive samplers react to contaminant concentrations varying in other ways.…”

Spatial and Temporal Variability in Pesticide Exposure Downstream of a Heavily Irrigated Cropping Area: Application of Different Monitoring Techniques

“…Previous studies show that PSDs 129 can under-or over-estimate the TWA concentrations of certain analytes when fluctuations 130 in both concentration and flow occur during the deployment period [35][36][37] . As such, each 131 deployment period during this study lasted for approximately four weeks except when a 132 runoff event occurred.…”