Silicone–water partition coefficient
Dotaz
Zobrazit nápovědu
Total concentrations of hydrophobic organic contaminants (HOCs) in sediment present a poor quality assessment parameter for aquatic organism exposure and environmental risk because they do not reflect contaminant bioavailability. The bioavailability issue of HOCs in sediments can be addressed by application of multi-ratio equilibrium passive sampling (EPS). In this study, riverbed sediment samples were collected during the Joint Danube Survey at 9 locations along the Danube River in 2013. Samples were ex-situ equilibrated with silicone passive samplers. Desorption isotherms were constructed, yielding two endpoints: pore water (CW:0) and accessible (CAS:0) concentration of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers in sediment. CW:0 concentrations of DDT and its breakdown products exhibited elevated levels in the low Danube, with the maximum in the river delta. Other investigated HOCs did not show any clear spatial trends along the river, and only a moderate CW:0 variability. CAS:0 in sediment ranged from 10 to 90% of the total concentration in sediment. CW:0 was compared with freely dissolved concentration in the overlaying surface water, measured likewise by passive sampling. The comparison indicated potential compound release from sediment to the water phase for PAHs with less than four aromatic rings, and for remaining HOCs either equilibrium between sediment and water, or potential compound deposition in sediment. Sorption partition coefficients of HOC to organic carbon correlated well with octanol-water partition coefficients (KOW), showing stronger sorption of PAHs to sediment than that of PCBs and OCPs having equal logKOW. Comparison of CW:0 values with European environmental quality standards indicated potential exceedance for hexachlorobenzene, fluoranthene and benzo[a]pyrene at several sites. The study demonstrates the utility of passive sampling as an innovative approach for risk-oriented monitoring of HOCs in river catchments.
In recent years, organic ultraviolet filters (UVFs) received considerable attention as a group of emerging contaminants, including in Australia where the use of UVFs is particularly relevant. Passive sampling using polymers has become widely used for routine monitoring of chemicals in the aquatic environment. Application of passive samplers for monitoring chemicals in the water relies on calibration data such as chemical's polymer-water partition coefficient (Kpw) and diffusion coefficients in the sampling material (Dp), for understanding uptake and kinetic limitations. In the present study, Kpw and Dp for nine UVFs were estimated. Kpw values were determined in different water - polymer partition experiments where (1) a given mass of chemicals was dosed into the water and (2) into the polymer. Diffusion coefficients were determined using the stacking method. The estimated log Kpw and log Dp ranged from 2.9 to 6.4 L kg-1 and -11.1 to -10.5 m2s-1, respectively. The sufficient high Dp allows application of kinetic models that only consider water boundary-controlled uptake for converting silicone sampler uptake into an aqueous phase concentration using the presented Kpw.
- MeSH
- chemické látky znečišťující vodu analýza MeSH
- filtrace MeSH
- kalibrace * MeSH
- monitorování životního prostředí metody MeSH
- organické látky škodlivé účinky MeSH
- polymery chemie MeSH
- silikony * MeSH
- ultrafialové záření MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Austrálie MeSH
Passive sampling is increasingly applied for monitoring neutral hydrophobic compounds (HOC) in various environmental media like water, sediment, air and also soft biota tissue. Passive samplers for HOC are often constructed from permeable polymers like silicone and polyethylene (PE), while also SPMD are often applied. Their HOC uptake can be converted to freely dissolved or equivalent lipid-based concentrations using appropriate partition coefficients with or without the use of kinetic uptake models to adjust for non-equilibrium. To facilitate such conversions for seventy HOC partition coefficients are derived by combining polymer-water for Altesil™ silicone and PE, with new and earlier published polymer-polymer, polymer-lipid partition coefficients. Derived SSP silicone-water, lipid-water (Klip/w), and SPMD-water (Kspmd/w) partition coefficients demonstrate good agreement with literature data, except for Kspmd/w. For SPMD, this work demonstrates a linear Kspmd/w - Kow relationship (R2 = 0.99) in contrast to the parabolic Kspmd/w - Kow relationship utilized in the USGS "SPMD Water Concentrations Calculator". Following a thorough evaluation of this Calculator it is recommended that in combination with revised Kspmd/w, a radical different model approach should be used for obtaining accurate water concentrations from passive sampling with SPMD.
- MeSH
- chemické látky znečišťující vodu chemie MeSH
- hydrofobní a hydrofilní interakce MeSH
- lipidy chemie MeSH
- monitorování životního prostředí MeSH
- polycyklické aromatické uhlovodíky analýza MeSH
- polyethylen chemie MeSH
- polymery chemie MeSH
- silikony chemie MeSH
- voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
To further support implementation of monitoring by passive sampling, robust sampler-water partition coefficients (Kpw) are required to convert data from passive sampler into aqueous phase concentrations. In this work silicone-water partition coefficients were determined for ∼80 hydrophobic organic contaminants using the cosolvent method. Partition coefficients (Kpm) were measured in pure water and water-methanol mixtures up to a methanol mole fraction of 0.3 (50% v/v). Subsequently, logKpw in pure water was determined as the intercept of linear regression of the logKpm with the corresponding methanol mole fractions. LogKpw were determined for phthalates, musks, organo phosphorus flame-retardants, chlorobenzenes, pesticides, some PCBs and a number of miscellaneous compounds. The median standard error and 95% confidence interval of the measured logKpw was 0.06 and 0.13, respectively. The overall relationship between Kpw and Kow seems insufficient to predict Kpw for unknown compounds. Prediction may work within a group of compounds with similar nature, e.g. homologues but HCH isomers having the same Kow exhibit Kpw ranging over an order of magnitude. Long alkyl-chain phthalates and tris(2-ethylhexyl) phosphate; all having a molecular volume >400 Å3, deviated the most from the Kpw-Kow relationship.
- MeSH
- chemické látky znečišťující vodu chemie MeSH
- chlorbenzeny chemie MeSH
- fosfáty chemie MeSH
- kyseliny ftalové chemie MeSH
- kyseliny mastné mononenasycené MeSH
- pesticidy chemie MeSH
- polychlorované bifenyly chemie MeSH
- retardanty hoření MeSH
- silikony chemie MeSH
- voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
Polymers are increasingly used for passive sampling of neutral hydrophobic organic substances (HOC) in environmental media including water, air, soil, sediment and even biological tissue. The equilibrium concentration of HOC in the polymer can be measured and then converted into equilibrium concentrations in other (defined) media, which however requires appropriate polymer to media partition coefficients. We determined thus polymer-lipid partition coefficients (KPL) of various PCB, PAH and organochlorine pesticides by equilibration of two silicones and low density polyethylene (LDPE) with fish oil and Triolein at 4 °C and 20 °C. We observed (i) that KPLwas largely independent of lipid type and temperature, (ii) that lipid diffusion rates in the polymers were higher compared to predictions based on their molecular volume, (iii) that silicones showed higher lipid diffusion and lower lipid sorption compared to LDPE and (iv) that absorbed lipid behaved like a co-solute and did not affect the partitioning of HOC at least for the smaller molecular size HOC. The obtained KPLcan convert measured equilibrium concentrations in passive sampling polymers into equilibrium concentrations in lipid, which then can be used (1) for environmental quality monitoring and assessment, (2) for thermodynamic exposure assessment and (3) for assessing the linkage between passive sampling and the traditionally measured lipid-normalized concentrations in biota. LDPE-lipid partition coefficients may also be of use for a thermodynamically sound risk assessment of HOC contained in microplastics.
- MeSH
- chlorované uhlovodíky chemie izolace a purifikace MeSH
- fyzikální absorpce * MeSH
- hydrofobní a hydrofilní interakce MeSH
- látky znečišťující životní prostředí chemie izolace a purifikace MeSH
- lipidy chemie MeSH
- organické látky chemie izolace a purifikace MeSH
- polyethylen chemie MeSH
- regenerace a remediace životního prostředí metody MeSH
- silikony chemie MeSH
- vystavení vlivu životního prostředí prevence a kontrola MeSH
- Publikační typ
- časopisecké články MeSH
A passive sampler based on stir bars coated with polydimethylsiloxane (PDMS) was calibrated for the measurement of time-weighted average concentrations of hydrophobic micropollutants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls and organochlorine pesticides, in water. Stir bar/water partition coefficients were measured by equilibrating bars with sheets made of silicone rubber material for which partition coefficients had been reported previously. Kinetic parameters characterising the exchange of analytes between stir bars and water were determined under controlled exposure conditions using a passive dosing system. The dosing system consisted of silicone rubber sheets with a large surface area, spiked with analytes. During stir bar sampler exposure, analytes partitioned from dosing sheets to water in the exposure tank and maintained constant exposure concentrations. Reversible and isotropic exchange kinetics of analytes between sampler and water was confirmed by measuring the release of a range of performance reference compounds (PRCs) from stir bars. Application of a two-resistance model confirmed that, except for hexachlorocyclohexane isomers, uptake of the test compounds under the experimental conditions was controlled by diffusion in the water boundary layer. This permits the application of PRCs for in situ calibration of uptake kinetics of test compounds to stir bars.
- MeSH
- chemická frakcionace metody MeSH
- chemické látky znečišťující vodu analýza chemie izolace a purifikace MeSH
- hydrofobní a hydrofilní interakce * MeSH
- kalibrace MeSH
- kinetika MeSH
- organické látky analýza chemie izolace a purifikace MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Nowadays, passive sampling is a widely applied technique to determine freely dissolved aqueous concentrations of hydrophobic organic chemicals (HOCs), such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Crucial to the measurements are sampler-water partition coefficients, which are generally determined in the laboratory under "standard conditions" (in freshwater at 20 °C). Theoretically, however, the coefficients are dependent on environmental conditions, such as temperature and salinity. Yet, there are insufficient experimental data in the scientific literature to prove this for different polymers. Several polymers are already being applied during field monitoring, however, and neglecting any effects may lead to imprecise results. In the present study, we therefore quantified the effects of temperature and salinity on the sampler-water partition coefficients of PAHs and PCBs for silicone rubber, a material used in Dutch passive sampling monitoring campaigns. The results demonstrated a chemical-specific and hydrophobicity-dependent temperature effect, being independent of salinity, and a chemical- and temperature-independent salinity effect. Based on the obtained data, location-specific silicone rubber-water partition coefficients (Ksr-w; adjusted for temperature and salinity) can be calculated. The impact of applying such location-specific values was demonstrated using the Dutch passive sampling field monitoring database, covering ten years of PAH and PCB data for several locations. Adjusting the Ksr-w values resulted in aqueous concentrations that were lowered by a factor of 1.6 on average. The reduction was rather constant because of the manner of sampling (under nonequilibrium conditions and using performance reference compounds) and calculating. When sampling under equilibrium conditions in seawater at temperatures at about freezing, and/or applying different calculation approaches, the adjustment effect can potentially increase up to a factor of about 5-6 for the more hydrophobic PAHs and PCBs. Although this study exclusively focused on silicone rubber, qualitatively the results will also apply to other passive sampling materials.
- MeSH
- časové faktory MeSH
- hydrofobní a hydrofilní interakce * MeSH
- monitorování životního prostředí přístrojové vybavení metody MeSH
- organické látky analýza MeSH
- polychlorované bifenyly analýza MeSH
- polycyklické aromatické uhlovodíky analýza MeSH
- referenční standardy MeSH
- salinita * MeSH
- silikonové elastomery analýza MeSH
- teplota * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
This study aimed at evaluating and comparing five integrative samplers for the monitoring of indicator and dioxin-like polychlorinated biphenyls (PCBs) in water: semi-permeable membrane device (SPMD), silicone rubber, low-density polyethylene (LDPE) strip, Chemcatcher and a continuous-flow integrative sampler (CFIS). These samplers were spiked with performance reference compounds (PRCs) and then simultaneously exposed under constant agitation and temperature in a 200 L stainless steel tank for periods ranging from one day to three months. A constant PCB concentration of about 1 ng·L(-1) was achieved by immersing a large amount of silicone rubber sheets ("dosing sheets") spiked with the target PCBs. The uptake of PCBs in the five samplers showed overall good repeatability and their accumulation was linear with time. The samplers SPMD, silicone rubber and LDPE strip were the most promising in terms of achieving low limits of quantification. Time-weighted average (TWA) concentrations of PCBs in water were estimated from uptake of PCBs using the sampling rates calculated from the release of PRCs. Except for Chemcatcher, a good agreement was found between the different samplers and TWA concentrations ranged between 0.4 and 2.8 times the nominal water concentration. Finally, the influence of calculation methods (sampler-water partition coefficients, selected PRCs, models) on final TWA concentrations was studied.
- MeSH
- chemické látky znečišťující vodu analýza MeSH
- dioxiny analýza MeSH
- monitorování životního prostředí přístrojové vybavení metody MeSH
- polychlorované bifenyly analýza MeSH
- polychlorované dibenzodioxiny MeSH
- teplota MeSH
- voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
