A new configuration of polar organic chemical integrative sampler with nylon membranes to monitor emerging organophosphate ester contaminants in urban surface water

Systematic evaluation of sampling rate influences and variability in POCIS using meta-analysis and quantitative structure property relationship (QSPR)

Despite the significant benefits of aquatic passive sampling (low detection limits and time-weighted average concentrations), the use of passive samplers is impeded by uncertainties, particularly concerning the accuracy of sampling rates. This study employed a systematic evaluation approach based on the combination of meta-analysis and quantitative structure-property relationships (QSPR) models to address these issues. A comprehensive meta-analysis based on extensive data from 298 studies on the Polar Organic Chemical Integrative Sampler (POCIS) identified essential configuration parameters, including the receiving phase (type, mass) and the diffusion-limiting membrane (type, thickness, pore size), as key factors influencing uptake kinetic parameters. The incomplete availability of these details across studies potentially impacts data reproducibility and comparability. The subsequent meta-regression and subgroup analysis were performed to reveal the most significant factors contributing to sampling rate variability and inter-study heterogeneity. The flow rate and octanol-water partitioning (Kow or pH-dependent Dow) were identified from all environmental factors and chemical properties. Furthermore, the impact of chemical properties on the sampling rates of POCIS was predicted by Quantitative Structure-Property Relationship (QSPR) models using 2D descriptors and random forest regression. The analysis highlighted that the electrotopological state and molecular mass are the most important chemical properties influencing the sampling rate. This study systematically unraveled the most important impact factors on reliable estimates of passive sampling rates, and these causes of uncertainty should be further considered in aquatic monitoring and assessment with passive samplers.

Distribution Characteristics and Ecological Risk Assessment of Organophosphate Esters in Surface Soils of China

The chemical flame retardants represented by organophosphate esters (OPEs) are widely used and have a serious impact on the environment. In this study, we collected data on the exposure levels of ten OPEs in Chinese soils in recent years and performed an ecological risk assessment. The results showed that the levels of OPEs varied considerably throughout different regions of China, with high exposure levels in highly urbanized or industrialized areas such as Guangdong Province and Northeast China, where the mean value was >200 ng/g. The content of OPEs in the soil in industrial and commercial areas was significantly higher than in other regions, indicating that the concentration of OPEs in the soil is closely related to local economic development and the degree of industrialization. Meanwhile, the number of studies reporting on OPEs and their exposure concentrations have increased significantly since 2018. Through the ecological risk assessment, it was found that TCP, EHDPP and TEHP pose high ecological risks. Although some OPEs, such as TCIPP, have low ecological risk levels overall, their high exposure concentrations are still worthy of attention. This study details the general status of OPE contamination in Chinese soils, which can serve as a reference for ecological environmental supervision.

Tracing the attenuation of fipronil and its transformation products from a rice paddy field to receiving rivers using polar organic chemical integrative samplers

Irrational use of fipronil for rice pest control often occurred, resulting in high concentrations of fipronil and its transformation products (TPs) (collectively termed fiproles) in aquatic sediment, calling for a better understanding of the migration and transformation of fipronil in surface water as well as efficient methods for source identification. Herein, the fate and transport of fiproles from a paddy field to receiving rivers were assessed in Poyang Lake basin, Jiangxi, China using polar organic chemical integrative samplers with mixed-mode adsorbents (POCIS-MMA). Average concentrations of fiproles in water were 6.16 ± 6.32 ng/L, with median, minimum, and maximum values being 2.99 ± 0.67, 0.40 ± 0.08, and 18.6 ± 3.1 ng/L, respectively. In all samples, over half of fiproles (55.9 %-90.8 %) presented in the form of TPs and fipronil desulfinyl was the dominant TP. Two approaches were applied for source identification, including the change of molar concentration ratios of fipronil to its TPs and the relative attenuation values of fiproles normalized to a reference compound (acetamiprid) that was stable in aquatic environment. While the paddy field upstream was the main source of waterborne fiproles, additional input sources in the downstream region were identified. The present study indicated that the combination of attenuation of molar concentration ratios of micro-pollutants to their respective TPs and relative attenuation values of micro-pollutants' concentrations normalized to a reference compound measured by POCIS is an effective means to study the migration and transformation of micro-pollutants in field.

The coupling between biological pump export and air-water exchange of organophosphate esters in a subtropical water environment

Organophosphate esters (OPEs) are well-known persistent organic pollutants with their ubiquitous environmental presence and adverse ecological and human health impacts. To study the transport and fate of OPEs in a subtropical environment, nine OPE compounds were analyzed in the gas phase (air samples), dissolved phase (water samples), and plankton samples collected over one year from or in the vicinity of an urban lake in Guangzhou, South China. The mean concentrations of ∑₉OPEs were 2.93 ± 1.68 ng/m³ in the air, 455 ± 236 ng/L in the dissolved phase, 81.3 ± 41.2 ng/L in phytoplankton, and 4.79 ± 1.94 ng/L in zooplankton. Although the compositional profiles of OPEs varied among different media, tris (1-chloro-2-propyl) phosphate (TCPP) was the predominant OPE in most samples. Less hydrophobic OPEs such as TCPP and tris (2-chloroethyl) phosphate (TCEP) had lower bioaccumulation potential in the lake. The biological pump export played an important role in eliminating OPEs from the surface water, with fluxes ranging from 30.5 to 361 ng/m²/d. The more phytoplankton biomass in surface water, the greater the role of the biological pump. The fugacity fractions and air-water exchange fluxes suggested that TCPP and tris (1,3-dichloro-2-propyl) phosphate (TDCP) would enter the urban lake by gaseous deposition. Nevertheless, the lake acted as an important "secondary source" for TCEP and triphenyl phosphate (TPhP). The bio-pump might influence the air-water exchange processes of OPEs.

A Review on Polyethersulfone Membranes in Polar Organic Chemical Integrative Samplers: Preparation, Characterization and Innovation

The membranes in polar organic chemical integrative samplers (POCIS) enclose the receiving sorbent and protect it from coming into direct contact with the environmental matrix. They have a crucial role in extending the kinetic regime of contaminant uptake, by slowing down their diffusion between the water phase and the receiving phase. The drive to improve passive sampling requires membranes with better design and enhanced performances. In this review, the preparation of standard polyethersulfone (PES) membranes for POCIS is presented, as well as methods to evaluate their composition, morphology, structure, and performance. Generally, only supplier-related morphological and structural data are provided, such as membrane type, thickness, surface area, and pore diameter. The issues related to the use of PES membranes in POCIS applications are exposed. Finally, alternative membranes to PES in POCIS are also discussed, although no better membrane has yet been developed. This review highlights the urge for more membrane characterization details and a better comprehension of the mechanisms which underlay their behavior and performance, to improve membrane selection and optimize passive sampler development.

Point or non-point source: Toxicity evaluation using m-POCIS and zebrafish embryos in municipal sewage treatment plants and urban waterways

Municipal sewage treatment plants (STPs) have been regarded as an important source of organic contaminants in aquatic environment. To assess the impact of STPs on occurrence and toxicity of STP-associated contaminants in receiving waterways, a novel passive sampler modified from polar organic chemical integrative sampler (m-POCIS) was deployed at the inlet and outlet of a STP and several upstream and downstream sites along a river receiving STP effluent in Guangzhou, China. Eighty-seven contaminants were analyzed in m-POCIS extracts, along with toxicity evaluation using zebrafish embryos. Polycyclic musks were the predominant contaminants in both STP and urban waterways, and antibiotics and current-use pesticides (e.g., neonicotinoids, fiproles) were also ubiquitous. The m-POCIS extracts from downstream sites caused significant deformity in embryos, yet the toxicity could not be explained by the measured contaminants, implying the presence of nontarget stressors. Sewage treatment process substantially reduced embryo deformity, chemical oxygen demand, and contamination levels of some contaminants; however, concentrations of neonicotinoids and fiproles increased after STP treatment, possibly due to the release of chemicals from perturbed sludge. Source identification showed that most of the contaminants found in urban waterways were originated from nonpoint runoff, while cosmetics factories and hospitals were likely point sources for musks and antibiotics, respectively. Although the observed embryo toxicity could not be well explained by target contaminants, the present study showed a promising future of using passive samplers to evaluate chemical occurrence and aquatic toxicity concurrently. Zebrafish embryo toxicity significantly decreased after sewage treatment, but higher toxicity was observed for downstream samples, demonstrating that urban runoff may produce detrimental effects to aquatic life, particularly in rainy season. These results highlight the relevance of monitoring nonpoint source pollution along with boosting municipal sewage treatment infrastructure.

Tracing neonicotinoid insecticides and their transformation products from paddy field to receiving waters using polar organic chemical integrative samplers

Neonicotinoid insecticides are ubiquitous in surface water worldwide, yet the transportation and transformation of these compounds in aquatic environment remain unclear. In the present study, polar organic chemical integrative sampler with mixed-mode adsorbents (POCIS-MMA) was developed for simultaneously tracing environmental fate of seven neonicotinoids and 10 transformation products (TPs) from a paddy field to receiving waters in Poyang Lake basin, Jiangxi, China. All neonicotinoids (5.20 ± 0.75‒866 ± 143 ng/L) and seven TPs (116 ± 4‒334 ± 78 ng/L) were detected, demonstrating widespread occurrence of these insecticides in aquatic environment. Dinotefuran (up to 802 ± 139 ng/L) and its TP, 1-methyl-3- (tetrahydro-3-furylmethyl) guanidium dihydrogen (DN) (103 ± 4‒320 ± 76 ng/L) were the dominant neonicotinoids and TPs with mean concentrations of 200 ± 296 and 208 ± 58 ng/L, respectively. Spatial attenuation of neonicotinoids stretched downstream along the rivers, while TP concentrations firstly increased (D1‒S6) and then kept constant (S7‒S16) from upstream to downstream. Though paddy field was the main source of neonicotinoids, additional input sources downstream were identified by analyzing the composition of neonicotinoids and their TPs. Our study highlighted the applicability of POCIS-MMA passive sampling to investigate the transportation and transformation of neonicotinoids in agricultural waterways.