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 (

Depth Profiles of Persistent Organic Pollutants in the North and Tropical Atlantic Ocean.

Little is known of the distribution of persistent organic pollutants (POPs) in the deep ocean. Polyethylene passive samplers were used to detect the vertical distribution of truly dissolved POPs at two sites in the Atlantic Ocean. Samplers were deployed at five depths covering 26-2535 m in the northern Atlantic and Tropical Atlantic, in approximately one year deployments. Samplers of different thickness were used to determine the state of equilibrium POPs reached in the passive samplers. Concentrations of POPs detected in the North Atlantic near the surface (e.g., sum of 14 polychlorinated biphenyls, PCBs: 0.84 pg L(-1)) were similar to previous measurements. At both sites, PCB concentrations showed subsurface maxima (tropical Atlantic Ocean -800 m, North Atlantic -500 m). Currents seemed more important in moving POPs to deeper water masses than the biological pump. The ratio of PCB concentrations in near surface waters (excluding PCB-28) between the two sites was inversely correlated with congeners' subcooled liquid vapor pressure, in support of the latitudinal fractionation. The results presented here implied a significant amount of HCB is stored in the Atlantic Ocean (4.8-26% of the global HCB environmental burdens), contrasting traditional beliefs that POPs do not reach the deep ocean.

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, log KPEw 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.

Transects of polycyclic aromatic hydrocarbons and organochlorine pesticides in an urban estuary using passive samplers.

Hydrophobic organic contaminants (HOCs) are tracers of anthropogenic impacts, which can negatively affect water quality. The relative importance of new emissions versus the remobilization of HOCs from legacy reservoirs is not well constrained. Polyethylene passive samplers were deployed in vertical profiles at four sites to determine the concentrations and gradients of atmospheric and freely dissolved polycyclic aromatic hydrocarbons (PAHs) and freely dissolved organochlorinated pesticides (OCPs) in Narragansett Bay, an urban estuary. The concentrations of the sum of 20 PAHs ranged from 4.3 to 240 ng/m3 in the air and 3.2-21 ng/L in the water column, dominated by phenanthrene and pyrene. OCP concentrations varied from below the detection limit to 150 ng/L in the water column. Common OCPs included α-hexachlorocyclohexane, hexachlorobenzene, and aldrin. Gradients displayed net deposition for PAHs, but equilibrium through the water column. Results from this study provided evidence that key OCPs displayed mostly similar concentrations (at or near equilibrium) in the water at both Conimicut Point and Block Island.

Gaseous and soil OCPs and PCBs along the Indus River, Pakistan: spatial patterns and air-soil gradients.

This study presents first-hand information on the occurrence of persistent organic pollutants (POPs) in the ambient air and surface soil along the Indus flood-plain, Pakistan. The sampling campaign was conducted at 15 site locations during 2014-15, along the Indus River (approximately 1300 km). Composite surface soil samples (N = 15) and passive air samples (N = 15) were collected for the estimation of gaseous POPs as well as air-soil exchange to evaluate the POP emission and distribution or dispersion patterns, source tracking, and contribution of the local and regional sources towards POP accumulation in the Indus River system. Among the studied POPs, levels of DDTs and PCBs were noticeably higher in ambient air (50-560 and 10-1100 pg m-3) and in soil (0.20-350 and 1.40-20 ng g-1), respectively. Regarding the spatial patterns, higher DDT concentrations (ng g-1) were detected in the air and soil samples collected from the wet mountain zone (WMZ) (p < 0.05), followed by the alluvial riverine zone (ARZ), low-lying mountain zone (LLZ), and frozen mountain zone (FMZ). The PCB data did not exhibit significant differences (p > 0.05) for the air samples, while PCB concentrations were significantly higher (p < 0.05) in soil from the LLZ, which may be associated with rapid urbanization and industrial activities in this area. The air-soil exchange of DDTs and PCBs showed net volatilization at most of the studied sites except for a few samples from the FMZ and WMZ. Results of this study about air-soil exchange gradients indicate the long range regional atmospheric transport (LRAT) of POPs to the colder areas (FMZ) of Pakistan, where these act as a secondary source of POPs in these areas.

Freely dissolved organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Indus River Pakistan: spatial pattern and risk assessment.

Freely dissolved OCPs and PCBs were measured by using polyethylene passive samplers at 15 sites during 2014 throughout the stretch of the Indus River to investigate the spatial pattern and risk assess. Levels (pg/L) of dissolved ∑OCPs and ∑PCBs ranged from 34 to 1600 and from 3 to 230. Among the detected OCPs, dissolved DDTs (p,p'-DDE, followed by p,p'-DDT) predominated with levels of 0.48 to 220 pg/L. The order of occurrence for other studied OCPs was as follows: HCB, endosulfans, chlordanes, and HCHs. Spatially, dissolved (pg/L) ∑OCPs varied (p < 0.05) as the following: surface water of the alluvial riverine zone (ARZ) showed the highest levels (114) followed by the frozen mountain zone (FMZ) (52.9), low-lying zone (LLZ) (28.73), and wet mountain zone (WMZ) (14.43), respectively. However, our zone-wise PCB data did not exhibit significant differences (p > 0.05). Principal component analysis/multilinear regression results showed pesticide usage in the crop/orchard fields and health sector, electric and electronic materials, and widespread industrial activities as the main source of OCPs and PCBs along the Indus River. Our results showed that OCPs and PCBs contaminated water intake, playing an important role towards the considerable cancer/non-cancer risk (HI and CR values) along the Indus River Flood-Plain.

Spatial distribution and air-water exchange of organophosphate esters in the lower Great Lakes.

Organophosphate esters (OPEs) have been detected at elevated concentrations in the Great Lakes region, dwarfing other flame retardants, such as polybrominated diphenylethers (PBDEs), as chemicals of emerging concern (CECs). This prompted us to deploy polyethylene (PE) passive samplers in air and water column of the lower Great Lake region (Lake Erie and Lake Ontario) to detect gaseous and dissolved OPEs, evaluate their occurrence and spatial distribution, and estimate their air-water gas exchange fluxes. The median concentration of the total dissolved and gaseous phase OPEs detected (Σ9OPEs) were 95 ng L-1 and 404 pg m-3, respectively, during April-November 2014. Gaseous and dissolved concentrations were dominated by chlorinated compounds, in particular (tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloroisopropyl) phosphate (TCPP), while tri-n-butyl phosphate (TnBP) was the dominant non-chlorinated OPEs in both media. Decreasing concentration gradients from shoreline/nearshore to offshore sites for both gaseous and aqueous OPEs reflect anthropogenic influence from the adjacent rural and urban regions. The partial dependence of gaseous OPEs on temperature indicate the importance of volatilization from local sources, fresh emissions as well as advection from distant sources to air. Almost all OPEs underwent net gas-phase deposition to the lakes, dominated by TCEP and TCPPs with median fluxes of -3980 ng/m2/day and -1320 ng/m2/day; the exception was TnBP, which underwent volatilization with the median fluxes of 1980 ng/m2/day. For all air-water pairs, the gaseous diffusive fluxes were 2-4 orders of magnitude greater than the estimated particle dry deposition fluxes.