Evaluation and application of diffusion-based passive samplers for polycyclic aromatic hydrocarbons (PAHs) in water

Identifying the sources of pollutants to water bodies and estimation of their concentration is integral to protection and remediation of the aquatic environment. Hydrophobic organic pollutants present a difficult analytical challenge because extremely low concentrations in water can magnify to ecologically significant concentrations in organisms. Passive In-Situ Concentration Extraction Sampler (PISCES) allows for the quantification of extremely low concentrations of hydrophobic organic compounds in water. Analytes diffuse from the water through a polymer membrane and into a receiving solvent. PISCES can be used to target sources of pollution to water bodies, because it effectively samples large volumes of water and produces extracts that are easy to analyze.; To accurately describe the uptake of analytes by the samplers, experiments were performed with polycylcic aromatic hydrocarbons (PAHs) to determine the rate-limiting step for uptake. The sampling rate was not dependent on the affinity of the PAHs for the membrane or on membrane thickness. Agitation of the water increased the sampling rate. Increasing the salinity reduced the sampling rate. The results show that transport through the water near the membrane controlled the uptake.; Two sampler designs were evaluated, a passive design, PISCES and a Stirring PISCES. The temperature dependence for the PISCES sampling rate (S, L/d cm 2) was evaluated. The data were fit to an exponential relationship (S = e[−2978.6 (1/T)] + 5.9861) and to a linear relationship (S = 0.00044 T − 0.211) equally well at environmentally relevant temperatures (4°–26°C). A stirring chamber was added to PISCES to improve the sampling rate. Stirring PISCES had a faster sampling rate, and was not affected by external agitation, as was noted in the non-stirring PISCES design. The temperature dependence of Stirring PISCES was best represented by an exponential relationship (S = e[−4456.3 (1/T)] + 14.721), but could also be described with a linear relationship (S = 0.0265 T − 7.101). Sampling rates of the two samplers were measured in Onondaga Lake, where PISCES sampled faster than in the laboratory and Stirring PISCES sampled at a comparable rate.