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Abstract: With compiled and analyzed information about recent advances in passive sampling techniques for sediment porewater, we discuss common quantitation methods (equilibrium and kinetic diffusion-controlled sampling), effects of temperature and salinity on passive sampling, and benefits and drawbacks of currently available passive samplers based on the principles of solid-phase microextraction. The results show that the in-fiber standardization technique, which is kinetic diffusion-controlled, could shorten sampling time and obtain accurate results using isotopically-labeled reference compounds. Another quantitative method, time-weighted average sampling, may be viable for simultaneously measuring all analytes in sediment porewater, as it is more effective with respect to cost and time. In addition, the effects of temperature and salinity on passive sampling should be quantified in field applications. Currently available passive samplers (e.g., employing polymer-coated fibers and low-density polyethylene sheets) can sense hydrophobic organic chemicals (HOCs) in sediment porewater, but the small capacity and the inflexibility of polymer-coated fibers need to be further improved, while better physical protection of polyethylene devices, particularly when they are deployed under rough conditions, should be carefully considered. In conclusion, passive samplers for in-situ measurement of dissolved HOCs in sediment porewater should be combined with a suitable quantitative method and calibration for the effects of temperature and salinity. [Copyright &y& Elsevier]

Abstract: A conventional solid-phase microextraction (SPME) method combined with liquid–liquid extraction was applied under equilibrium and nonequilibrium conditions to determine the partition coefficients (K doc) of 25 polychlorinated biphenyl congeners (PCBs) between Sigma–Aldrich humic acid (HA) and water. The values of log K doc determined with equilibrium SPME were linearly correlated with the logarithm of the octanol–water partition coefficients (K ow) for PCB congeners at log K ow <∼7.2, but the trends were disrupted for log K ow from ∼7.2 to 8.18. In addition, short-term (5min to 4 days) and long-term (5–44 days) uptake profiles of PCBs were established, from which a pseudo-equilibrium for sorption of PCBs was revealed at ∼4 days of extraction. To understand this phenomenon, the uptake profiles were fitted with two equations (one equation is often used for pure water samples and the other one is applicable for samples containing complex matrices) derived from a first-order kinetics model. Subsequently, K doc values obtained through kinetic approaches were compared with those acquired from equilibrium SPME. The comparison of K doc values indicated that the pseudo-equilibrium was caused by the slow desorption of PCBs from HA rather than the biphasic desorption mechanism. [Copyright &y& Elsevier]