Polyethylene Passive Samplers Research Articles

Challenges of Using Polyethylene Passive Samplers to Determine Dissolved Concentrations of Parent and Alkylated PAHs under Cold and Saline Conditions

Passive samplers can be useful tools for determining truly dissolved concentrations of organic contaminants in the water. Polyethylene (PE) samplers were validated for measuring polycyclic aromatic hydrocarbons (PAHs), with a focus on alkylated PAHs that can dominate in an oil spill. Equilibrium partition coefficients between water and PE passive samplers (KPEw) were measured for 41 PAHs both at ambient conditions (20 °C, no salt) and down to -15 °C with up to 245 psu present in ice brine. For each additional alkylated carbon, logKPEw increased by an average of 0.40 (±0.20) log units, close to predictions. The increase per aromatic carbon was only 0.33 (±0.02) log units. Apparent PE-water distributions of pyrene and deuterated pyrene (performance reference compound) were within 0.1 log unit for all experiments at 20 and 2 °C but started to diverge by 0.8 log units at -4 °C (100 psu) and by 3.1 log units at -15 °C (245 psu). The delay in equilibrating PAHs in these experiments was dominated by increases in the water viscosity, which, in turn, affected both the aqueous diffusivities of the PAHs and the thickness of the water boundary layer. In a simulated marine oil spill in the laboratory, PE-based results were within a factor of 2 of conventional sampling results for the most abundant PAHs.

Feasibility of using low density polyethylene sheets to detect atmospheric organochlorine pesticides in Alexandria, Egypt

Egypt is a major agricultural country in Africa with a known past of organochlorine pesticides (OCPs) application, yet data on atmospheric levels of OCPs in Egypt is sparse. Low density polyethylene (LDPE) passive samplers were therefore deployed for 3 weeks each at 11 locations in July, 2010 and January, 2011 in Alexandria to screen for gas-phase OCPs. Performance reference compounds were used to investigate the uptake kinetics. Field-derived sampler-air partitioning coefficients (KPE-As) for OCPs were significantly correlated against the compounds' subcooled liquid vapor pressure (log PL): [log KPE-A = −0.77 ± 0.07*log PL + 6.35 ± 0.13 (R2 = 0.90; n = 17; SE = 0.19; p < 0.001)]. Estimated and measured OCP concentrations in Alexandria agreed well (factor difference ≤ 2) indicating the feasibility of monitoring OCPs using LDPEs. OCP concentrations ranged from <LOD to 168 pg/m3. Calculated isomeric ratios indicated recent usage of chlordanes and endosulfans.

Field Validation of Polyethylene Passive Air Samplers for Parent and Alkylated PAHs in Alexandria, Egypt

Polyethylene samplers (PEs) were deployed at 11 locations in Alexandria, Egypt during summer and winter to test and characterize them as passive samplers for concentrations, sources, and seasonal variations of atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs). PE-air equilibrium was attained faster for a wider range of PAHs during the winter season possibly due to increased wind speeds. Calculated PE-air partitioning constants, K(PE-A), in our study [Log K(PE-A) = 0.9426 × Log K(OA) - 0.022 (n = 12, R(2) = 0.99, Std error = 0.053)] agreed with literature values within <46%. For parent (except naphthalene), mono- and dialkylated PAHs, active sampling based concentrations of PAHs were within an average factor of 1.4 (1.0-5.6) compared to the PE based values. For C(3-4) alkylated PAHs, K(PE-A) values were lower than predicted, on average by ~0.8 log units per carbon in the alkylation. Enthalpies of vaporization (ΔH(vap)) accurately corrected K(PE-A)s for temperature differences between winter and summer sampling. PAH profiles were dominated by naphthalene, phenanthrene, and alkylated phenanthrenes. Calculated diagnostic ratios indicated that PAHs originated mainly from vehicle emissions.

Measuring nonpolar organic contaminant partitioning in three Norwegian sediments using polyethylene passive samplers

Freely dissolved pore water concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), penta- and hexachlorobenzene (PeCB and HCB), octachlorostyrene (OCS), p,p′-DDE and p,p′-DDD were measured in bottom sediments from three sites in Norway. Sediments were from Aker Brygge, site of a former shipyard in the inner part of Oslofjord, Frierfjord in the Grenlandsfjord area, impacted during the 50year-long activity of a magnesium smelter plant, and from Kristiansand harbour, site with high industrial activity. Low density polyethylene (LDPE) membrane samplers were exposed to these sediments in laboratory incubation under constant and low-level agitation for periods of 1, 2, 6, 13, 23 and 50days. Freely dissolved pore water concentrations were estimated from contaminant masses accumulated and sampling rates obtained from the measurement of kinetics of dissipation of performance reference compounds (PRCs). Marked differences in freely dissolved PAH concentrations and resulting organic carbon-normalised sediment-pore water partition coefficients, logKTOC, between these three sediments could be observed despite the generally similar total sediment concentrations. In contrast with the PAH data, partitioning of PCBs and other organochlorine compounds (OCs) was relatively similar in all three sediments. For sediments from Frierfjord and Kristiansand, logKTOC values were lower for PCBs/OCs than for PAHs, indicating higher availability. Similar partitioning of PAHs and PCBs/OCs was found for sediments from Aker Brygge. No simple logKoc–logKow relationships could model these data successfully. These results support the notion that the assessment of the risk posed by these compounds present in sediments in most cases requires actual measurement of contaminant availability.

Freely dissolved PBDEs in water and porewater of an urban estuary

Polyethylene passive samplers (PE) were deployed in Narragansett Bay, RI, to examine freely dissolved concentrations of polybrominated diphenyl ethers (PBDEs) in surface, bottom, and sediment porewater. PBDE congeners in the water column and porewater were below 3 pg L −1. In the surface water, only PBDE congeners containing up to 5 bromines were detected, while in the deeper water congeners 153 and 154 (6 bromines) were also detected. Activity ratios of surface-bottom water and porewater-bottom water suggested that lower brominated (di-tetra) congeners reached Narragansett Bay from surface waters and sediments. PBDEs in the surface water probably originated from a combination of air–water exchange, freshwater runoff, rivers, and wastewater treatment plants. It is suggested that deep water was the source of higher brominated PBDEs to the Bay implying that the more hydrophobic PBDEs reached depth on particles and/or that these congeners were degraded in sediments. On-going sources supply PBDEs to Narragansett Bay.

Passive sampling provides evidence for Newark Bay as a source of polychlorinated dibenzo‐p‐dioxins and furans to the New York/New Jersey, USA, atmosphere

Freely dissolved and gas phase polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in the water column and atmosphere at five locations within Newark Bay (New Jersey, USA) from May 2008 to August 2009 with polyethylene (PE) passive samplers. Mono- to octa-CDDs and mono- to hepta-CDFs were detected in bottom and surface waters at ≤ 20 pg/L with no clear gradient between sampling locations, suggesting freely dissolved PCDD/Fs are well mixed in Newark Bay. The most concentrated, freely dissolved gas phase congener was 2,7/2,8-dichlorodibenzo-p-dioxin (2,7/2,8-DiCDD), likely originating from photochemical conversion of triclosan in Newark Bay. Air-surface water gradients strongly favored net volatilization of PCDD/PCDFs from Newark Bay. Water-to-air fluxes of 2,7/2,8-DiCDD and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most concentrated and the most toxic PCDD/PCDFs, respectively, were approximately 60 ng/m(2) per month and 14 to 51 pg/m(2) per month. Significant decreases in freely dissolved 2,3,7,8-TCDD concentrations with increasing freshwater near the Passaic River and conservative behavior during the summer of 2009 suggested Passaic sediments as a likely source of 2,3,7,8-TCDD to Newark Bay. Mass balance calculations implied that almost 50% of freely dissolved 2,3,7,8-TCDD delivered to Newark Bay from the Hackensack and Passaic Rivers was lost to volatilization in the summer of 2009.

Sorption of polycyclic aromatic hydrocarbons (PAHs) to low and high density polyethylene (PE)

According to their high sorption capacity polyethylene (PE) passive samplers are often used for the analysis of polycyclic aromatic hydrocarbons (PAHs) in the aquatic environment. PE is also one of the primary synthetic polymers found in oceans, and sorption of PAHs to marine PE debris may determine PAH exposure and therefore hazards in marine ecosystems. Thus, an understanding of the sorption process is of great importance. In the present study, the sorption of several PAHs with different polarities to low density polyethylene (LDPE) and high density polyethylene (HDPE) was studied in order to improve our understanding of the influence of material properties on the Fickian diffusion of PAHs into PE. Batch sorption experiments were performed with aqueous solutions containing acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, and LPDE or HDPE pellets. Samples were shaken in the dark at 20 ± 1°C for 16 time intervals within one week. Concentrations of PAHs were determined in the aqueous samples using solid-phase microextraction coupled with gas chromatography-mass spectrometry. The distribution coefficients (K (PE)) between PE and water were estimated from different models reported in the literature. Kinetic sorption of the PAHs into the plastic pellets was described by a diffusion model based on Fick's second law in spherical coordinates. A comparison between different models describing the equilibrium distribution of PAHs between PE and water revealed that the sorption equilibrium seemed to be driven by parameters other than, or in addition to, organic carbon. For both plastic types, diffusion coefficients decreased while the molecular weight of the PAHs increased which indicates a hindered diffusion through the matrix as a result of a larger molecule size. Higher diffusion coefficients were derived for LPDE than for HDPE indicating a greater sorption velocity for LPDE according to the lower polymer density. Our results revealed that equilibrium time could be shortened during passive sampling as polymer membranes of lower density are used. In some areas, marine ecosystems may not be in equilibrium with respect to concentrations of organic contaminants and abundance of marine plastic debris. In such cases, different polymer densities should be taken into account in risk assessments.

Development and Use of Polyethylene Passive Samplers To Detect Triclosans and Alkylphenols in an Urban Estuary

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.

Changes in polycyclic aromatic hydrocarbon availability in River Tyne sediment following bioremediation treatments or activated carbon amendment

Bioremediation and activated carbon (AC) amendment were compared as remediation strategies for sediment from the River Tyne containing 16.4 ± 7.3 μg/g polycyclic aromatic hydrocarbons (PAHs) and approximately 5% coal particles by total dry sediment weight. Unamended, nutrient amended (biostimulated) and nutrient and Pseudomonas putida amended (bioaugmented) sediment microcosms failed to show a significant decrease in total sediment PAH concentrations over a one month period. Polyethylene passive (PE) samplers were embedded for 21 days in these sediment microcosms in order to measure the available portion of PAHs and accumulated 4.70 ± 0.25, 12.43 ± 1.78, and 23.49 ± 2.73 μg PAHs/g PE from the unamended, biostimulated, and bioaugmented microcosms, respectively. Higher PAH uptake by PE samplers in biostimulated and bioaugmented microcosms coincided with slower degradation of spiked phenanthrene in sediment-free filtrate from these microcosms compared to filtrate from the unamended microcosms. Microbial community analysis revealed changes in the bacterial community directly following the addition of nutrients, but the added P. putida community failed to establish itself. Addition of 2% by dry sediment weight activated carbon reduced PAH uptake by PE samplers to 0.28 ± 0.01 μg PAHs/g PE, a greater than 90% reduction compared to the unamended microcosms.

Partitioning of organochlorine pesticides from water to polyethylene passive samplers

The mass transfer rates and equilibrium partitioning behaviour of 14 diverse organochlorine pesticides (OCP) between water and polyethylene (PE) passive samplers, cut from custom made PE sheets and commercial polyethylene plastic bags, were quantified. Overall mass transfer coefficients, k O, estimated PE membrane diffusion coefficients, D PE, and PE-water partitioning coefficients, K PE-water, are reported. In addition, the partitioning of three polycyclic aromatic hydrocarbons (PAHs) from water to PE is quantified and compared with literature values. K PE-water values agreed mostly within a factor of two for both passive samplers and also with literature values for the reference PAHs. As PE is expected to exhibit similar sorption behaviour to long-chain alkanes, PE-water partitioning coefficients were compared to hexadecane-water partitioning coefficients estimated with the SPARC online calculator, COSMO therm and a polyparameter linear free energy relationship based on the Abraham approach. The best correlation for all compounds tested was with COSMO therm estimated hexadecane-water partitioning coefficients.

Modeling the Mass Transfer of Hydrophobic Organic Pollutants in Briefly and Continuously Mixed Sediment after Amendment with Activated Carbon

Activated carbon (AC) amendment is currently being investigated as an in situ remediation technique for sediments contaminated by persistent organic pollutants. Understanding the mass transfer of pollutants from weaker binding sites on sediment particles, to stronger binding sites inside AC particles, is important for the evaluation of this strategy. Here we study the mass transfer of polycyclic aromatic hydrocarbons (PAHs) from River Tyne sediment to polyethylene (PE) passive samplers in the presence and absence of AC under two mixing regimes. Continuously mixing and a brief initial mixing period to incorporate AC to the system, followed by unmixed conditions in settled sediments, were compared. The reduction in total PAH concentration in the PE sampler was greater than 99% after 12 months AC contact for both conditions. A numerical model based on concepts used to simulate well-mixed AC-sediment slurries was further developed to describe the briefly mixed system. These models could predict upper and lower limits for the expected remediation effectiveness for variable AC-sediment mixing regimes. It appears that mixing mode has a small impact on the treatment effectiveness for River Tyne sediment which has a strongly bound, slowly released pollutant source. However, a greater impact is anticipated for contaminated sediments containing more available pollutants.

Using Performance Reference Compounds in Polyethylene Passive Samplers to Deduce Sediment Porewater Concentrations for Numerous Target Chemicals

Polymeric passive samplers are useful for assessing hydrophobic organic chemical contamination in sediment beds. Here, an improved method is described for measuring concentrations of contaminants in porewater by using performance reference compounds (deuterated phenanthrene, pyrene, and chrysene) to calibrate sampler/site-specific mass transfer behavior. The method employs a one-dimensional diffusion model of chemical exchange between a polymer sheet of finite thickness and an unmixed sediment bed. The model is parametrized by diffusivities and partition coefficients for both the sampler and sediment. This method was applied to estimate porewater concentrations for seventeen PAHs from polymeric samplers deployed for 3-10 days in homogenized sediment from a coal-tar contaminated site. The accuracy of the method was verified by comparing the passive sampler results to concentrations measured through liquid-liquid extraction of physically separated porewaters, with corrections for sorption to colloidal organic carbon. The measurements made using the two methods matched within about a factor of 2.0 (+/-0.9) for the 17 target PAHs.

Comparing Polychaete and Polyethylene Uptake to Assess Sediment Resuspension Effects on PCB Bioavailability

Polyethylene sampler uptake was compared to polychaete uptake to assess bioavailability of polychlorinated biphenyls (PCBs) from resuspended sediments. New Bedford Harbor (MA, U.S.) sediment contaminated with PCBs, was resuspended under four different water column oxidation conditions: resuspension alone, resuspension under aeration, resuspension under helium, and no resuspension (control). Residuals were tested for differences in PCB availability to the marine polychaete Nereis virens and to polyethylene (PE) passive samplers. Few significant differences between the four resuspension treatments were observed: under aeration, three of 23 PCBs analyzed showed significant increases in polychaete accumulation, while resuspension alone showed increased concentrations in PE samplers for nine of 23 PCBs. Otherwise, no differences were observed and overall we concluded that resuspension had no effect on residual PCB availability. The relationship between disequilibrium-corrected PE and lipid-normalized polychaete PCB concentrations was nearly 1:1 with a strong linear correlation (r2 = 0.877), demonstrating PCBs are taken up similarly into PE and lipid. On average, PE samplers suggested dissolved PCB concentrations 3.6 times greater than those calculated with lipid-water partitioning, though on a congener-specific basis this was only observed for lower chlorinated PCBs; for higher chlorinated PCBs, PE-water partitioning suggested lower dissolved concentrations than those based on lipid. Organic carbon (OC)-water and OC and black carbon combined (OC+BC)-water partitioning suggested average dissolved concentrations 29 and 10 times greater, respectively, than those estimated with lipid-water partitioning. This demonstrates that PE-measured porewater concentrations can provide a more reliable estimate of bioavailability than sediment geochemistry.

Measurement of Freely Dissolved PAH Concentrations in Sediment Beds Using Passive Sampling with Low-Density Polyethylene Strips

To assess hydrophobic organic chemical (HOC) contamination in sediments, a method was developed using polyethylene (PE) passive samplers inserted directly in the intact sediment beds to measure freely dissolved HOC concentrations. Performance reference compounds (PRCs: d10-phenanthrene, d10-pyrene, and d12-chrysene), impregnated into the PE before use, allowed porewater concentrations to be deduced after exposure times much shorter than would be required for sampler equilibration (days instead of months). Three diverse sediments were used in the laboratory, and PE-deduced porewater concentrations of six native PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, and chrysene) matched results from air-bridge testing and from direct porewater extractions after correcting for colloid effects. PE strips, deployed from a boat in Boston Harbor, yielded concentrations that were like those measured in porewaters from a sediment core collected nearby. Notably, equilibrium partitioning (EqP) estimates were always much higher (up to 100x) than those measured using the other methods, suggesting the large inaccuracy of that approach. Hence, PE passive sampling appears to greatly improve the accuracy of assessing the hazards posed by compounds like PAHs in sediment beds.

Detecting Air−Water and Surface−Deep Water Gradients of PCBs Using Polyethylene Passive Samplers

Polyethylene passive samplers (PEs) were deployed in a vertical array (bottom water, surface water, near-surface air) to study the cycling of active polychlorinated biphenyls (PCBs) between reservoirs in an urban estuary (Narragansett Bay, RI), from May to November 2006. Performance reference compounds were used to account for nonequilibrium of PCBs in PEs. Activity gradients were established from direct comparisons of temperature, salt, and nonequilibrium corrected PE concentrations. The uncertainty of determining air-water gradients was < 70%, and < 50% within the water column. Except during the height of summer, PCB activities were up to 30 times higher in the air than in the surface water, but closer to equilibrium in the water column. Surface waters became depleted in PCBs during periods of highest temperature and stratification, leading to the uptake of gaseous PCBs. Our results demonstrate that passive samplers are powerful tools to determine the flux directions of organic contaminants in the environment.

Characterizing uptake kinetics of PAHs from the air using polyethylene-based passive air samplers of multiple surface area-to-volume ratios.

Polyethylene passive sampling devices (PSDs) were deployed to investigate how passive samplers of multiple surface area-to-volume ratios could be used to characterize uptake kinetics for polyaromatic hydrocarbons (PAHs). Theoretically, uptake profiles for different thickness PSDs of the same surface area should show the following: where uptake is linear, the amount of compound accumulated in the different PSDs will be the same and where equilibrium is approached, the amount accumulated by the different PSDs will be proportional to sampler thickness. Polyethylene sheets of the same surface area and approximately 100 and 200 microm thickness were collected after 30, 60, and 90 days of exposure along with samples from a codeployed high volume sampler. Twelve priority pollutant PAHs could be routinely quantified in replicate PSDs. Overall, reproducibility between replicate PSDs was satisfactory, with normalized differences rarely exceeding 25%. The smallest analytes quantified, fluorene, phenanthrene, and anthracene, were shown to approach equilibrium during the deployment period, whereas uptake for fluoranthene and pyrene moved into the curvilinear stage. For most of the larger molecular weight PAHs such as indeno[1,2,3-cd]pyrene, uptake could be described using a linear uptake model. Preliminary sampling rates for the compounds which remained in the linear stage of uptake ranged between 0.5 and 1.5 m3 d(-1) dm(-2). Sampler to air partition coefficients were estimated for PAHs which approached equilibrium and predicted for some of the other compounds. Results suggest that a single deployment of PSDs with multiple surface area-to-volume ratios can be sufficient to determine whether uptake was linear or approaching equilibrium for a range of PAHs.

Statistics and Data Analysis in GeologyJ.C. Davis, 1973. Wiley, Chichester, 550 pp., U.S. $18.50

Superfund sites with sediments contaminated by hydrophobic organic compounds (HOCs) can be difficult to characterize because of the complex nature of sorption to sediments. Porewater concentrations, which are often used to model transport of HOCs from the sediment bed into overlying water, benthic organisms, and the larger food web, are traditionally estimated using sediment concentrations and sorption coefficients estimated using equilibrium partitioning (EqP) theory. However, researchers have begun using polymeric samplers to determine porewater concentrations since this method does not require knowledge of the sediment's sorption properties. In this work, polyethylene passive samplers were deployed into sediments in the field (in situ passive sampling) and mixed with sediments in the laboratory (ex situ active sampling) that were contaminated with polychlorinated biphenyls (PCBs). The results show that porewater concentrations based on in situ and ex situ sampling generally agreed within a factor of two, but in situ concentrations were consistently lower than ex situ porewater concentrations. Imprecision arising from in situ passive sampling procedures does not explain this bias suggesting that field processes like bioirrigation may cause the differences observed between in situ and ex situ polymeric samplers.