Small but different effect of fouling on the uptake rates of semipermeable membrane devices and polar organic chemical integrative samplers.
ABSTRACT Semipermeable membrane devices (SPMD) and polar organic chemical integrative samplers (POCIS) were exposed to a cocktail of organic chemicals using a flow-through system. Samplers were removed and analyzed every 7 d over a four-week period in order to determine sampling rates (Rs) for individual compounds. Prior to laboratory exposure, half of the samplers were allowed to foul naturally for six weeks, in order to examine differences in uptake due to fouling. The amount of fouling ranged from 0.2 to 2.8 g dry weight/dm2 for POCIS and 0.1 to 1.4 g dry weight/dm2 for SPMDs, and the pattern of accumulation was also different between them. The Rs values were determined by fitting curves to time course uptake data and also by using performance reference compounds (PRCs) for SPMDs. Sampling rates ranged from 2.7 to 14.2 L/d for SPMDs and 0.01 to 0.27 L/d for POCIS. Fouled SPMDs showed a reduction in Rs (<20%) for all but one compound, and there was a similar reduction in the release of PRCs. However, PRC-predicted R, values were overall somewhat higher than those from fitted curves. Uptake of alkylated phenols in POCIS was generally higher (up to 55%) in fouled samplers. The reason for this is not known, but is possibly due to some reduction in interactions with the membrane in fouled samplers. There was no overall pattern in the relationship of sampling rate differences with log Kow or over time for either sampler. Release of compounds from POCIS after a drop in exposure water concentrations provides some encouragement for the application of a PRC approach to polar passive samplers.
Article: Development and use of polyethylene passive samplers to detect triclosans and alkylphenols in an urban estuary.[show abstract] [hide abstract]
ABSTRACT: To be able to use polyethylene passive samplers (PE) in the field, the partitioning constants between PE and water (K(PEw)) of the compounds examined must be known. The K(PEw)s of triclosan (TCS), methyl-triclosan (MTCS), n-nonylphenol (n-NP), nonylphenol-technical mix (NP-tech), n-octylphenol (n-OP), and t-octylphenol (t-OP) were measured as a function of pH, temperature, and salinity, and a salt effect was calculated for TCS, n-OP, and t-OP. Log K(PEw)s used for calculating dissolved concentrations were taken from 20 °C studies taking salt into account: 3.42 (TCS), 4.53 (MTCS), 4.20 (n-NP), 3.69 (n-OP), and 2.87 (t-OP). The K(PEw) of hydroxyl-group containing compounds were strongly affected by pH, whereas MTCS with its methoxy-group was not. Measured K(PEw)s could not be estimated from octanol-water partitioning constants due to the semipolar makeup of the compounds investigated. Instead, a good correlation (K(PEw) = 0.679 × K(hdw) + 1.033, r(2) = 0.984, p = 0.001) was obtained with hexadecane-water partitioning constants (K(hdw)) predicted from COSMOtherm. During deployments in Narragansett Bay (RI) in the fall of 2009, concentrations of MTCS and t-OP in surface and bottom waters ranged from 40-225 pg L(-1) and 3.5-11 ng L(-1), respectively. These concentrations are far below EC(50) values for rainbow trout. Surface/bottom and bottom/porewater activity ratios were calculated. These indicated surface waters as the main source of MTCS, while surface water as well as sediments were sources of t-OP.Environmental Science & Technology 02/2011; 45(6):2270-7. · 4.80 Impact Factor