AQUA-GAPS/MONET-Derived Concentrations and Trends of PAHs and Polycyclic Musks across Global Waters.

Polycyclic aromatic hydrocarbons (PAHs), released from petrogenic, pyrogenic or diagenetic sources (degradation of wood materials), are of global concern due to their adverse effects, and potential for long-range transport. While dissolved PAHs have been frequently reported in the literature, there has been no consistent approach of sampling across water bodies. Passive samplers from the AQUA/GAPS-MONET initiative were deployed at 46 sites (28 marine and 18 freshwater), and analyzed for 28 PAHs and six polycyclic musks (PCMs) centrally. Freely dissolved PAH concentrations were dominated by phenanthrene (mean concentration 1500 pg L-1; median 530 pg L-1) and other low molecular weight compounds. Greatest concentrations of phenanthrene, fluoranthene, and pyrene were typically from the same sites, mostly in Europe and North America. Of the PCMs, only galaxolide (72% of samples) and tonalide (61%) were regularly detected, and were significantly cross-correlated. Benchmarking of PAHs relative to penta- and hexachlorobenzene confirmed that the most remote sites (Arctic, Antarctic, and mountain lakes) displayed below average PAH concentrations. Concentrations of 11 of 28 PAHs, galaxolide and tonalide were positively correlated (P < 0.05) with population density within a radius of 5 km of the sampling site. Characteristic PAH ratios gave conflicting results, likely reflecting multiple PAH sources and postemission changes.

Passive-Sampler-Derived PCB and OCP Concentrations in the Waters of the World─First Results from the AQUA-GAPS/MONET Network.

Persistent organic pollutants (POPs) are recognized as pollutants of global concern, but so far, information on the trends of legacy POPs in the waters of the world has been missing due to logistical, analytical, and financial reasons. Passive samplers have emerged as an attractive alternative to active water sampling methods as they accumulate POPs, represent time-weighted average concentrations, and can easily be shipped and deployed. As part of the AQUA-GAPS/MONET, passive samplers were deployed at 40 globally distributed sites between 2016 and 2020, for a total of 21 freshwater and 40 marine deployments. Results from silicone passive samplers showed α-hexachlorocyclohexane (HCH) and γ-HCH displaying the greatest concentrations in the northern latitudes/Arctic Ocean, in stark contrast to the more persistent penta (PeCB)- and hexachlorobenzene (HCB), which approached equilibrium across sampling sites. Geospatial patterns of polychlorinated biphenyl (PCB) aqueous concentrations closely matched original estimates of production and use, implying limited global transport. Positive correlations between log-transformed concentrations of Σ7PCB, ΣDDTs, Σendosulfan, and Σchlordane, but not ΣHCH, and the log of population density (p < 0.05) within 5 and 10 km of the sampling sites also supported limited transport from used sites. These results help to understand the extent of global distribution, and eventually time-trends, of organic pollutants in aquatic systems, such as across freshwaters and oceans. Future deployments will aim to establish time-trends at selected sites while adding to the geographical coverage.

Accessibility investigation of semi-volatile organic compounds in indoor dust estimated by multi-ratio equilibrium passive sampling.

Many semi-volatile organic compounds (SVOCs) accumulate in indoor dust, which serves as a repository for those compounds. The presence of SVOCs in indoor environments is of concern because many of them are suspected to have toxic effects. Total SVOC concentrations in the dust are generally used for exposure assessment to indoor contaminants, assuming that 100% of the SVOCs is accessible for human uptake. However, such an assumption may potentially lead to an overestimated risk related to dust exposure. We applied a multi-ratio equilibrium passive sampling (MR-EPS) for estimation of SVOC accessibility in indoor settled dust using silicone passive samplers and three particle size dust fractions, <0.25 mm, 0.25-0.5 mm, and 1-2 mm in dry and wet conditions. Equilibrations were performed at various sampler-dust mass ratios to achieve different degrees of SVOC depletion, allowing the construction of a desorption isotherm. The desorption isotherms provided accessible fractions (FAS), equivalent air concentrations (CAIR), dust-air partition coefficients (KDUST-AIR) and organic carbon-air partition coefficients (KOC-AIR). The highest FAS were observed in the <0.25 mm dust fraction in wet conditions which is relevant for exposure assessment via oral ingestion. The highest CAIR were estimated for several organophosphorus flame retardants (OPFRs), polycyclic aromatic hydrocarbons (PAHs) and synthetic musks. The logKOC-AIR did not differ between dust particle sizes in dry and wet conditions but within compound groups, different relationships with hydrophobicity were observed. Equivalent lipid-based concentrations (CL⇌DUST) calculated using available lipid-silicone partition coefficients (KLIP-SIL) were compared with lipid-based concentrations (CL) measured in human-related samples collected from Europeans. For hexachlorobenzene (HCB), CL⇌DUST, and CL were similar, indicating equilibrium attainment between environment and human samples. Lipid-based concentrations for persistent legacy contaminants were also similar but lower for PBDEs in human samples. Overall, accessibility estimation using MR-EPS in dust further contributes to human risk assessment.

Performance comparison of silicone and low-density polyethylene as passive samplers in a global monitoring network for aquatic organic contaminants.

Contamination with hydrophobic organic compounds (HOCs) such as persistent organic pollutants negatively affects global water quality. Accurate and globally comparable monitoring data are required to understand better the HOCs distribution and environmental fate. We present the first results of a proof-of-concept global monitoring campaign, the Aquatic Global Passive Sampling initiative (AQUA-GAPS), performed between 2016 and 2020, for assessing trends of freely dissolved HOC concentrations in global surface waters. One of the pilot campaign aims was to compare performance characteristics of silicone (SSP) and low-density polyethylene (PE) sheets co-deployed in parallel under identical conditions, i.e. at the same site, using the same deployment design, and for an equal period. Individual exposures lasted between 36 and 400 days, and samples were collected from 22 freshwater and 40 marine locations. The sampler inter-comparability is based on a rationale of common underlying principles, i.e. HOC diffusion through a water boundary layer (WBL) and absorption by the polymer. In the integrative uptake phase, equal surface-specific uptake in both samplers was observed for HOCs with a molecular volume less than 300 Å3. For those HOCs, transport in the WBL controls the uptake as mass transfer in the polymer is over 20-times faster. In such a case, sampled HOC mass can be converted into aqueous concentrations using available models derived for WBL-controlled sampling using performance reference compounds. In contrast, for larger molecules, surface-specific uptake to PE was lower than to SSP. Diffusion in PE is slower than in SSP, and it is likely that for large molecules, diffusion in PE limits the transport from water to the sampler, complicating the interpretation. Although both samplers provided mostly well comparable results, we recommend, based on simpler practical handling, simpler data interpretation, and better availability of reliable polymer-water partition coefficients, silicone-based samplers for future operation in the worldwide monitoring programme.

A Simple Teabag Equilibrium Passive Sampler using hydrophilic divinylbenzene sorbent for contaminants of emerging concern in the marine environment.

A promising concept for sampling contaminants of emerging concern (CECs) using a home-made Simple Teabag Equilibrium Passive Sampler (STEPS) containing hydrophilic divinylbenzene (h-DVB) sorbent is presented and evaluated for application in estuarine systems. The uptake of a multi-class mixture of CECs with a broad polarity range (Log P ranging from -0.1 to 9.9) was investigated in static exposure batch experiments. Sampling rates (Rs) and equilibrium partitioning coefficients (Ksw) were determined for up to 74 CECs. Fast uptake (Rs = 0.3-12 L d-1) was noticed and the STEPS attained equilibrium partitioning after 1 to 2 weeks of exposure, with Log Ksw ranging from 4.1 to 6.5 L kg-1. Field application of this novel h-DVB containing STEPS, followed by ultra-high performance liquid chromatography coupled to high-resolution Orbitrap mass spectrometry, revealed the presence of up to 40 steroidal hormones, (alkyl)phenols, phthalates, pharmaceuticals, personal care products, and pesticides in the Belgian Part of the North Sea. The measured trace concentrations (from 0.003 ng L-1 to 1.9 µg L-1) and good precision (average RSD < 30%, n = 3) demonstrate the STEPS as fit-for-purpose for micropollutant analysis in the marine environment.

Application of equilibrium passive sampling to profile pore water and accessible concentrations of hydrophobic organic contaminants in Danube sediments.

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.

Unraveling the Relationship between the Concentrations of Hydrophobic Organic Contaminants in Freshwater Fish of Different Trophic Levels and Water Using Passive Sampling.

The concentrations of hydrophobic organic compounds (HOCs) in aquatic biota are used for compliance, as well as time and spatial trend monitoring in the aqueous environment (European Union water framework directive, OSPAR). Because of trophic magnification in the food chain, the thermodynamic levels of HOCs, for example, polychlorinated biphenyl congeners, dichlorodiphenyltrichloroethane, and brominated diphenyl ether congeners, in higher trophic level (TL) organisms are expected to be strongly elevated above those in water. This work compares lipid-based concentrations at equilibrium with the water phase derived from aqueous passive sampling (CL⇌water) with the lipid-based concentrations in fillet and liver of fish (CL) at different TLs for three water bodies in the Czech Republic and Slovakia. The CL values of HOCs in fish were near CL⇌water, only after trophic magnification up to TL = 4. For fish at lower TL, CL progressively decreased relative to CL⇌water as KOW of HOCs increased above 106. The CL value decreasing toward the bottom of the food chain suggests nonequilibrium for primary producers (algae), which is in agreement with modeling passive HOC uptake by algae. Because trophic magnification and the resulting CL in fish exhibit large natural variability, CL⇌water is a viable alternative for monitoring HOCs using fish, showing a twofold lower confidence range and requiring less samples.

Ex situ determination of freely dissolved concentrations of hydrophobic organic chemicals in sediments and soils: basis for interpreting toxicity and assessing bioavailability, risks and remediation necessity.

The freely dissolved concentration (Cfree) of hydrophobic organic chemicals in sediments and soils is considered the driver behind chemical bioavailability and, ultimately, toxic effects in benthic organisms. Therefore, quantifying Cfree, although challenging, is critical when assessing risks of contamination in field and spiked sediments and soils (e.g., when judging remediation necessity or interpreting results of toxicity assays performed for chemical safety assessments). Here, we provide a state-of-the-art passive sampling protocol for determining Cfree in sediment and soil samples. It represents an international consensus procedure, developed during a recent interlaboratory comparison study. The protocol describes the selection and preconditioning of the passive sampling polymer, critical incubation system component dimensions, equilibration and equilibrium condition confirmation, quantitative sampler extraction, quality assurance/control issues and final calculations of Cfree. The full procedure requires several weeks (depending on the sampler used) because of prolonged equilibration times. However, hands-on time, excluding chemical analysis, is approximately 3 d for a set of about 15 replicated samples.

Investigating levels of organic contaminants in Danube River sediments in Serbia by multi-ratio equilibrium passive sampling.

The Danube River is a large transboundary river with many tributaries. Pollution from industries, municipal wastewater and navigation is discharged into the river directly or via its tributaries. These discharges can adversely contribute to the water and sediment quality, posing a risk to aquatic life. Contaminants with low water solubility tend to accumulate in suspended solids, which deposit in riverbed sediments. Subsequently, their levels in sediment represent a time integrated sample indicating the pollution in the watercourse. However, total concentrations in sediment do not directly represent the exposure risk to aquatic life as accumulation in sediment heavily depends on its properties, i.e. the amount of organic material and its composition, which is difficult to characterize as any natural material. To provide contaminant concentrations on a defined basis, surface layer riverbed sediment samples collected at eleven locations along the Danube stretch in the territory of Serbia in 2012, were ex-situ (in the laboratory) equilibrated with silicone passive samplers of constant accumulative properties, using the multi-ratio equilibrium passive sampling approach. Contaminant's equilibrium concentrations in passive samplers are mutually comparable in time and space and are better measure for bioavailability than total sediment concentrations. Uptake in the passive sampler converted to equivalent freely dissolved (pore-) water concentrations agreed well with those obtained from surface water passive sampling carried out within the Joint Danube Survey 3 in 2013. Furthermore, equilibrium passive sampler PCB concentrations, converted to lipid-based concentrations, agreed well with concentrations measured in fish sampled in the Danube several years earlier. Out of eleven priority substances, only fluoranthene exceeded the EU EQS in water, while the EQS for biota was exceeded or approached for fluoranthene and benz[a]pyrene, and hexachlorobenzene.

Hydrophilic Divinylbenzene for Equilibrium Sorption of Emerging Organic Contaminants in Aquatic Matrices.

Hydrophilic divinylbenzene (DVB) (Bakerbond) has surfaced as a promising sorbent for active sampling of analytes from aqueous matrices over a very broad polarity range. Given this, hydrophilic DVB may likewise offer potential for passive sampling, if sorbent/water partitioning coefficients (Ksw) were to be available. In this work, static exposure batch experiments were performed to quantitatively study the equilibrium sorption of 131 environmentally relevant organic contaminants (P values ranging from -1.30 to 9.85) on hydrophilic DVB. The superior affinity of hydrophilic DVB, as compared to Oasis HLB, for compounds with a broad polarity range was confirmed by functional Fourier-transform infrared spectroscopy and Raman characterization, demonstrating the presence of carboxyl moieties. Concentration effects were studied by increasing compound concentrations in mixture experiments and resulted in the steroidal endocrine disrupting compounds in higher Ksw, while lower Ksw were obtained for the (alkyl)phenols, personal care products, pesticides, pharmaceuticals, and phthalates. Nevertheless, Ksw remained constant in the said design for equilibrium water concentrations at environmentally relevant seawater levels. An independent analysis of thermodynamic parameters (change in enthalpy, entropy, and Gibbs free energy) revealed the nature of the main partitioning processes. While polar (log P < 4) compounds were mainly served by physisorption, nonpolar (log P > 4) compounds also exhibited binding by multiple hydrogen bonding. In conclusion, this research facilitates the future application of hydrophilic DVB for active as well as passive sampling in the analysis of organic contaminants for monitoring purposes and for toxicity testing.

SSP silicone-, lipid- and SPMD-water partition coefficients of seventy hydrophobic organic contaminants and evaluation of the water concentration calculator for SPMD.

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.

Calibration parameters for the passive sampling of organic UV filters by silicone; diffusion coefficients and silicone-water partition coefficients.

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.

Chasing equilibrium passive sampling of hydrophobic organic compounds in water.

We investigated a combination of approaches to extend the attainment of partition equilibria between silicone passive samplers (samplers) and surface or treated waste water towards more hydrophobic organic compounds (HOC). The aim was to identify the HOC hydrophobicity range for which silicone sampler equilibration in water is feasible within a reasonable sampler deployment period. Equilibrium partitioning of HOC between sampler and water is desirable for a simpler application as a "chemometer", aiming to compare chemical activity gradients across environmental media (e.g. water, sediment, biota). The tested approaches included a) long sampler exposure periods and high water flow to maximize mass transfer from water to sampler; b) the use of samplers with reduced sheet thicknesses; and c) pre-equilibration of samplers with local bottom sediment, followed by their exposure in surface water at the same sampling site. These approaches were tested at three sites including a fish pond with a low level of pollution, a river impacted by an urban agglomeration and an effluent of municipal wastewater treatment plant. Tested compounds included polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), DDT, its metabolites and their isomers, hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDE). The study shows that samplers with a surface area of 400-800 cm2 consisting of thin (100-500 µm) silicone sheets exposed at sampling rates of 10-40 L d-1 for a time period of up to four months reach partition equilibrium with water for compounds with log Kow ≤ 5.5. Nevertheless, for compounds beyond this limit it is challenging, within a reasonable time period, to reach equilibrium between sampler and water in an open system where water boundary layer resistance controls the mass transfer. For more hydrophobic HOC (log Kow > 6), the kinetic method using performance reference compounds is recommended instead.

Partitioning and Bioaccumulation of Legacy and Emerging Hydrophobic Organic Chemicals in Mangrove Ecosystems.

Knowledge regarding partitioning behavior and bioaccumulation potential of environmental contaminants is important for ecological and human health risk assessment. While a range of models are available to describe bioaccumulation potential of hydrophobic organic chemicals (HOCs) in temperate aquatic food webs, their applicability to tropical systems still needs to be validated. The present study involved field investigations to assess the occurrence, partitioning, and bioaccumulation behavior of several legacy and emerging HOCs in mangrove ecosystems in Singapore. Concentrations of synthetic musk fragrance compounds, methyl triclosan (MTCS), polychlorinated biphenyls, organochlorine pesticides, and polycyclic aromatic hydrocarbons were measured in mangrove sediments, clams, and caged mussels. Freely dissolved concentrations of the HOCs in water were determined using silicone rubber passive samplers. Results showed that polycyclic musks and MTCS are present in mangrove ecosystems and can accumulate in the tissues of mollusks. The generated HOC concentration data for mangrove water, sediments, and biota samples was further utilized to evaluate water-sediment partitioning (e.g., Koc values) and bioaccumulation behavior (e.g., BAF and BSAF values). Overall, the empirical models fit reasonably well with the data obtained for this ecosystem, supporting the concept that general models are applicable to predict the behavior of legacy and emerging HOCs in mangrove ecosystems.

Passive sampling of pesticides and polychlorinated biphenyls along the Quequén Grande River watershed, Argentina.

Water monitoring is of great importance, especially for water bodies in agricultural or industrial areas. Grab sampling is a widely used technique for aquatic monitoring but represents only a snapshot of the contaminant levels at a specific point in time. Passive sampling, on the other hand, is an integrative technique that provides an average concentration of contaminants representative of its deployment period. Thus, the current contamination by organochlorine pesticides, polychlorinated biphenyls (PCBs), and some currently used pesticides was assessed along the Quequén Grande River watershed (Argentina) using the integrative silicone rubber passive sampling technique in a year-long study. Silicone rubber samplers were deployed at 6 sampling sites selected according to different land uses (agricultural-livestock production, agricultural and urban activities) during 3 periods in 2014 and 2015. The organochlorine pesticides were dominated by endosulfan (sum of α-, ß-endosulfan, endosulfan sulfate = 0.15-23.4 ng/L). The highest endosulfan levels were registered during the pesticide application period (December-March), exceeding the international water quality guidelines for protecting freshwater biota (3 ng/L). Compared with previous reports, no reductions in endosulfan levels were observed at the Quequén Grande River watershed. These results would suggest the illegal use of remaining stocks because water sampling was carried out after endosulfan was banned in Argentina. Chlorpyrifos was the second major pesticide found in water (0.02-4.3 ng/L), associated with its widespread usage on soybean crops. A reduction in levels of legacy pesticides (heptachlors, DDTs, dieldrin, and chlordanes) was evident compared with previous reports from 2007. Levels of PCBs were very low, indicating that probably only minor diffuse sources were still available along the Quequén Grande River watershed. Environ Toxicol Chem 2019;38:340-349. © 2018 SETAC.

Time-Integrative Passive sampling combined with TOxicity Profiling (TIPTOP): an effect-based strategy for cost-effective chemical water quality assessment.

This study aimed at demonstrating that effect-based monitoring with passive sampling followed by toxicity profiling is more protective and cost-effective than the current chemical water quality assessment strategy consisting of compound-by-compound chemical analysis of selected substances in grab samples. Passive samplers were deployed in the Dutch river delta and in WWTP effluents. Their extracts were tested in a battery of bioassays and chemically analyzed to obtain toxicity and chemical profiles, respectively. Chemical concentrations in water were retrieved from publicly available databases. Seven different strategies were used to interpret the chemical and toxicity profiles in terms of ecological risk. They all indicated that the river sampling locations were relatively clean. Chemical-based monitoring resulted for many substances in measurements below detection limit and could only explain <20% of the observed in vitro toxicity. Effect-based monitoring yielded more informative conclusions as it allowed for ranking the sampling sites and for estimating a margin-of-exposure towards chronic effect ranges. Effect-based monitoring was also cheaper and more cost-effective (i.e. yielding more information per euro spent). Based on its identified strengths, weaknesses, opportunities, and threats (SWOT), a future strategy for effect-based monitoring has been proposed.

Silicone-water partition coefficients determined by cosolvent method for chlorinated pesticides, musks, organo phosphates, phthalates and more.

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.

Mobile dynamic passive sampling of trace organic compounds: Evaluation of sampler performance in the Danube River.

A "dynamic" passive sampling (DPS) device, consisting of an electrically driven large volume water pumping device coupled to a passive sampler exposure cell, was designed to enhance the sampling rate of trace organic compounds. The purpose of enhancing the sampling rate was to achieve sufficient method sensitivity, when the period available for sampling is limited to a few days. Because the uptake principle in the DPS remains the same as for conventionally-deployed passive samplers, free dissolved concentrations can be derived from the compound uptake using available passive sampler calibration parameters. This was confirmed by good agreement between aqueous concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) derived from DPS and conventional caged passive sampler. The DPS device enhanced sampling rates of compounds that are accumulated in samplers under water boundary layer control (WBL) more than five times compared with the conventionally deployed samplers. The DPS device was deployed from a ship cruising downstream the Danube River to provide temporally and spatially integrated concentrations. A DPS-deployed sampler with surface area of 400cm2 can reach sampling rates up to 83Ld-1. The comparison of three passive samplers made of different sorbents and co-deployed in the DPS device, namely silicone rubber (SR), low density polyethylene (LDPE) and SDB-RPS Empore™ disks showed a good correlation of surface specific uptake for compounds that were sampled integratively during the entire exposure period. This provided a good basis for a cross-calibration between the samplers. The good correlation of free dissolved PAHs, PCBs and HCB concentration estimates obtained using SR and LDPE confirmed that both samplers are suitable for the identification of concentration gradients and trends in the water column. We showed that the differences in calculated aqueous concentrations between sampler types are mainly associated with different applied uptake models.

Advancing the Use of Passive Sampling in Risk Assessment and Management of Sediments Contaminated with Hydrophobic Organic Chemicals: Results of an International Ex Situ Passive Sampling Interlaboratory Comparison.

This work presents the results of an international interlaboratory comparison on ex situ passive sampling in sediments. The main objectives were to map the state of the science in passively sampling sediments, identify sources of variability, provide recommendations and practical guidance for standardized passive sampling, and advance the use of passive sampling in regulatory decision making by increasing confidence in the use of the technique. The study was performed by a consortium of 11 laboratories and included experiments with 14 passive sampling formats on 3 sediments for 25 target chemicals (PAHs and PCBs). The resulting overall interlaboratory variability was large (a factor of ∼10), but standardization of methods halved this variability. The remaining variability was primarily due to factors not related to passive sampling itself, i.e., sediment heterogeneity and analytical chemistry. Excluding the latter source of variability, by performing all analyses in one laboratory, showed that passive sampling results can have a high precision and a very low intermethod variability (