Development of a novel passive sampling system for the time-averaged measurement of a range of organic pollutants in aquatic environments

Abstract

A new sampling system has been developed for the measurement of time-averaged concentrations of organic micropollutants in aquatic environments. The system is based on the diffusion of targeted organic compounds through a rate-limiting membrane and the subsequent accumulation of these species in a bound, hydrophobic, solid-phase material. It provides a novel and robust solution to the problem of monitoring in situations where large temporal fluctuations in pollutant levels may occur. Accumulation rates are regulated by choice of diffusion-limiting membrane and bound solid-phase material and have been found to be dependent on the physico-chemical properties of individual target analytes. Two separate prototype systems are described: one suitable for the sampling of non-polar organic species with log octanol/water partition coefficient (log P) values greater than 4, the other for more polar species with log P values between 2 and 4. Both systems use the same solid-phase material (47 mm C18 Empore disk) as a receiving phase but are fitted with different rate-limiting membrane materials (polysulfone for the polar and polyethylene for the non-polar analytes). The two systems complement each other and together can be used for sampling a wider range of organic analytes than generally possible using current passive sampling techniques. Calibration data are presented for both devices. In each case, linear uptake kinetics were sustained, under constant conditions, for deployment periods of between 1 and 9 days. The effects of water temperature and turbulence on sampling rates have been quantitatively assessed. The performance of the system was further investigated by means of field exposures for one and two weeks in marine environments where calibrated samplers were used to determine the time-averaged concentrations of the polar biocides diuron and irgarol 1051. The quantitative results obtained using the passive sampler were compared with those obtained using spot sampling.

Calibration and use of the Chemcatcher® passive sampler for monitoring organotin compounds in water

“…An increase in water temperature in the range of 4-11 • C increases the sampling rate, and this particularly marked at SL2. This is in general agreement with the temperature sensitive behaviour of non-polar organic compounds [15,24,25]. Other temperature dependent factors that can affect R s include changes in water viscosity affecting diffusion across bulk water and pore water in the diffusion membranes, and in the energy of interaction between the test compounds and the receiving phase.…”

“…At 11 • C and 18 • C the sampling rate increased with stirring speed. For non-polar organic compounds, similar effects have been reported for the SPMD [29] and Chemcatcher ® [24] passive samplers. These results suggest that accumulation was mainly affected by diffusion through an aqueous boundary layer, and to a lesser extent by diffusion across the CA membrane.…”

“…In more turbulent conditions the thickness of the boundary layer decreases (typically 1 mm in stagnant conditions and 0.001-0.1 mm in fast flowing waters). Hence, if the mass transfer is controlled by diffusion in the water boundary layer, the sampling rate increases with increasing water turbulence [24]. The rate of diffusion (and hence uptake) also increases with temperature [21,25].…”

“…The Chemcatcher ® passive sampler can be used to measure the TWA concentration of both organic [24,25] and heavy metal [26] pollutants in a range of aquatic environments. A common PTFE sampler body is used and selectivity and accumulation rates are regulated by the choice of the diffusion-limiting membrane and the receiving phase material employed in the different configurations of the device.…”

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

“…Currently, there are two main types of samplers for polar organic compounds: POCIS (polar organic chemical integrative sampler) [8] and Chemcatcher [9]. Both use adsorbent material such as Oasis HLB or styrenedivinylbenzene (SDB) polymers, which are well suited to undergo reversed phase and ion exchange interactions with polar substances.…”