posted on 2020-07-08, 18:12authored byRaegyn
B. Taylor, Valerie Toteu Djomte, Jonathan M. Bobbitt, Amanda S. Hering, Sunmao Chen, C. Kevin Chambliss
Polar organic chemical integrative
sampler (POCIS) is a passive
sampling device that offers many advantages over traditional discrete
sampling methods, but quantitative time-weighted average (TWA) concentrations
rely heavily on the robustness of sampling rates. The effects of changing
chemical concentration exposures on POCIS sampling rates and its ability
to operate in an integrative regime were investigated for 12 pesticides
across a range of environmentally relevant concentrations. In five
independent 21-day experiments, POCIS devices were exposed to these
compounds at constant concentrations ranging from 3 to 60 μg/L
and multiple pulsed concentrations with maximum peaks ranging from
5 to 150 μg/L (TWA concentrations = 3 to 92 μg/L). For
the 21-day exposures to constant and pulsed concentrations, there
were no significant differences in the POCIS sampling rates between
corresponding TWA concentrations. Similarly, there was no significant
effect on POCIS ability to operate in an integrative regime. However,
loss of linearity was visible for some replicates when exposed to
higher pulsed concentrations over an extended period. Modeling and
Freundlich isotherms did not predict sorbent saturation, but the extraction
and reconstitution protocol likely contributed to atrazine dissolution
and subsequent underestimation of sorbed chemical mass when HLB adsorption
exceeded 400 μg.