Simple on-site extraction and GC-MS analysis of rotenone and degradation products for monitoring invasive fish eradication treatments in fresh and brackish waters.

The introduction of invasive fish species to aquatic ecosystems has been demonstrated to cause disastrous ecological effects. Current conservation strategies regard rotenone-containing piscicide formulations, such as commercial product CFT Legumine, as a potentially viable alternative to the cumbersome traditional approaches to fish eradication. This consideration relies on the fast degradation of rotenone and its relatively rapid dissipation from the environment. Piscicide treatments in fragile aquatic ecosystems should thus monitor not only rotenone concentrations following application, but also other byproducts and degradation products. We present a methodology for the analysis of rotenoids in fresh and brackish waters that addresses two main challenges: the accurate determination of applied concentrations in different salinity concentrations by performing a simplified on-site solid-phase extraction, overcoming the fast degradation of rotenone in sample storage conditions, and the selective analysis of rotenoid byproducts and degradation products by gas chromatography coupled to mass spectrometry. Limits of quantification were below the ecological no-effect concentration of rotenone (2 µg/L) and average recoveries exceeded 80%. Accuracy (compared to expected values) and precision (deviation of replicates) ranged from 78 to 103% and 3 to 14%, respectively, across various rotenoid concentrations. These metrics are more than satisfactory for the intended application of this simplified procedure. The method was applied to piscicide-treated samples, revealing significant and fast degradation of parent rotenoids in storage conditions, as well as a non-negligible accumulation of rotenone in the particulate fraction of water that could impact the effectivity of eradication efforts.

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.

Determination of subpicogram levels of airborne polycyclic aromatic hydrocarbons for personal exposure monitoring assessment.

A method based on the use of GC coupled to Q-exactive Orbitrap mass spectrometry (GC-Orbitrap-MS) has been developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) at sub-picogram levels. Outdoor ambient air particulate matter (PM2.5) and standard reference materials (SRM2260a) were analyzed in full scan mode showing low instrumental uncertainties (1-22%) and high linearity over a wide concentration range (0.5 pg and 500 pg/µL). Good reproducibility was obtained compared to the use of conventional single quadrupole GC-MS of PM samples. The quantification limit of the GC-Orbitrap-MS method for full scan analysis of PAHs in outdoor ambient air PM samples was 0.5 pg/µL. This low limit allowed the analysis of PAHs in samples collected with low volumes (< 0.5 m3), such as punch samples from whole filters or filter strips from personal exposure monitoring equipment. PAHs were successfully analyzed in filter strips from real-time Aethalometer AE51 equivalent black carbon (eBC) analyzers used in urban and rural sites, and in personal exposure monitors of firefighters during prescribed burns. The correlations between PAHs and eBC in these analyses were very strong (r2 ≥ 0.93). However, the equations obtained reflected the dominance of different emission sources, such as traffic in urban areas, wood burning for domestic heating, or wildfires. The method reported here affords the analyses of PAHs in high precision studies of atmospheric PM samples, e.g., high frequency sampling of low volumes, affording personal exposure monitoring assessments.

Passive water sampling and air-water diffusive exchange of long-range transported semi-volatile organic pollutants in high-mountain lakes.

The concentrations of legacy and currently emitted organic pollutants were determined in the freely dissolved phase of water from six high-mountain lakes in the Pyrenees (1619-2453 m) by passive water sampling. Low-density polyethylene (LDPE) and silicone rubber (SR) sheets were exposed for three consecutive periods lasting each one year between 2017 and 2020 for the study of polychlorinated biphenyls (PCBs), organophosphate esters (OPEs), polycyclic aromatic hydrocarbons (PAHs), and other organochlorine compounds (e.g., hexachlorobenzene, HCB). HCB concentrations (1.0-14 pg L-1) remained essentially the same as those measured with pumping systems over two decades ago in the same area. Æ©PAHs (35-920 pg L-1) were around half of those observed in the past, which agrees with reductions in European atmospheric emissions. Æ©PCB concentrations (1.2-2.2 pg L-1) were substantially lower, although unexpectedly large differences could be due to comparing yearly averages from the present study to seasonally variable (i.e., affected by snowmelt, stratification, and colloidal organic matter) episodic pumping measurements from previous studies. Æ©OPEs (139-2849 pg L-1) were measured for the first time in this area and were found at high concentrations in some sites. Concentrations of most compounds obtained with LDPE and SR samplers agreed with each other by ratios generally lower than three or four times, except for a few PAHs and OPEs. Diffusive exchange flux calculations between the atmospheric gas phase and the freely dissolved water phase revealed net deposition of pollutants from air to water, except for some OPEs and PCBs presenting equilibrium conditions, and HCB with volatilization fluxes. Atmospheric degradation fluxes of PAHs and OPEs pointed at competing removal mechanisms that support the air-to-water direction of their diffusive exchange, while PCBs and organochlorines were not affected by photodegradation. In their current state, these remote lakes accumulate many emerging and legacy pollutants subject to long-range atmospheric transport.

Changes and distribution of gas-phase polycyclic aromatic hydrocarbons and organochlorine compounds in a high-mountain gradient over a three-year period (Pyrenees, 2017-2020).

The atmospheric gas-phase concentrations of several polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), hexachlorobenzene (HCB), and pentachlorobenzene (PeCB) were measured in six high-mountain sites in the Pyrenees (1619-2453 m). Polyurethane foam passive air samplers were used for this purpose, providing continuous records spanning over three years (2017-2020). The mean concentrations of ∑PCBs, HCB, and PeCB, 13 ± 4 pg m-3, 44 ± 18 pg m-3, and 23 ± 20 pg m-3, respectively, were of the order of those reported in other mountain sites and similar to those measured 20 years ago in the same area, evidencing the persistence of these compounds despite the international regulatory actions. The mean concentration of ∑PAHs was 631 ± 238 pg m-3, representing between two- and three-times lower values than 20 years ago in the same area, but still in the range of other mountain regions. Statistically significant increases in gas-phase concentrations at higher temperatures were observed for most compounds. The experimental phase-change pseudo-enthalpies calculated from the slopes of the regressions between the natural logarithm of the concentrations and the reciprocal of temperature were lower than the reference values for nearly all compounds. This difference suggested a main contribution of long-range atmospheric transport of the gas-phase PAH and organochlorine concentrations in this mountain area. However, the less volatile compounds such as benz[a]anthracene, PCB138, and PCB180 showed a closer similarity between experimental and laboratory enthalpies, indicating that a significant portion of the variations in concentration of these compounds originated from temperature-dependent diffusive exchange by re-volatilization from local surfaces. The concentrations found in these sentinel ecosystems demonstrate that long-range transport of organic pollutants remains a risk in remote continental environments.

Occurrence and temperature dependence of atmospheric gas-phase organophosphate esters in high-mountain areas (Pyrenees).

The air concentrations of organophosphate esters (OPEs) were studied in a network of six remote high-mountain areas of the Pyrenees located along an altitudinal profile between 1619 m and 2453 m above sea level on a restricted planar surface to assess their vertical distribution based on long-range atmospheric transport and temperature gradients. Polyurethane foam passive samplers were used in five periods spanning over three years (September 2017-October 2020). The sum of concentrations of five OPEs were between 5.3 and 100 pg m-3, averaging 16-53 pg m-3 across campaigns at the different locations. These concentrations were much lower than those observed in areas under anthropogenic influence but also than those found in low altitude remote continental sites. A significant progressive change in predominant compounds was observed along the altitudinal gradient, with prevalence of tris(1-chloro-2-propyl) phosphate (TCIPP) or tris(2-chloroethyl) phosphate (TCEP) below or above 2300 m above sea level, respectively. This trend was consistent with the higher volatility of TCEP, which was retained at greater extent at lower environmental temperatures (higher altitude). A significant temperature dependence of the gas phase concentrations was observed for TCEP, TCIPP and triphenyl phosphate (TPHP), which could be explained by retention in the cold periods, predominantly adsorbed in snow, and their release to the atmosphere during snowmelt. This mechanism was consistent with the good agreement found between the vaporization enthalpies measured under laboratory conditions and the experimental values obtained from the slopes of the significant linear regressions when representing the vertical gradients.

Field comparison of passive polyurethane foam and active air sampling techniques for analysis of gas-phase semi-volatile organic compounds at a remote high-mountain site.

Polyurethane foam passive air samplers (PUF-PAS) are good candidates for the determination of gas-phase semi-volatile organic compound (SVOC) air concentrations in high-mountain areas over long periods because they do not require an energy supply. However, the harsh meteorological conditions present in such locations can increase the uncertainties inherently associated to PAS sampling rates due to the many variables involved in their calculation and to the assumptions made regarding PUF diffusive uptake mechanics, which can considerably bias the resulting concentrations. Therefore, we studied the performance of PUF-PASs in a remote location in the Pyrenees mountain range for the analysis of several SVOCs in air, including polychlorobiphenyls (PCBs), hexachlorobenzene, pentachlorobenzene, polycyclic aromatic hydrocarbons (PAHs), and the less studied emerging organophosphate flame retardants (OPFRs). An in-situ PUF-PAS calibration using Performance Reference Compounds (PRCs) provided compound- and sampler-specific sampling rates, showing mean experimental errors (12%) that adequately conformed to an estimate of their expanded theoretical uncertainties (15%). This showcases the suitability of this calibration strategy in an area with conditions beyond those typically considered in calibration efforts available to date. Moreover, gas-phase concentrations of the studied pollutants from PUF-PAS samples showed very good agreement (R2 up to 0.91, p < 0.01) when compared to those obtained using a conventional high-volume active air sampler (PUF-AAS), with some minor deviations observed for PAHs caused by the seasonality in their atmospheric concentrations. No relevant levels of pollutants preferentially bound to the particle phase were detected in the PUF-PASs, the particle infiltration efficiency of the sampler configuration used was found to be low, and compounds typically distributed between the gas and particle phases of AAS samples revealed profiles consistent with their vapor pressures, except for some OPFRs.

Origin of polycyclic aromatic hydrocarbons and other organic pollutants in the air particles of subway stations in Barcelona.

Underground subways transport large numbers of citizens in big cities, which must breathe air with limited ventilation. These atmospheric conditions may enhance the concentration of air pollutants from both outdoor and indoor air. The influence of ventilation conditions and maintenance activities on the concentrations of air pollutants have been studied. Particulate matter with aerodynamic diameter smaller than 2.5 µm (PM2.5) in indoor air was sampled in ten platforms of nine subway stations of the metropolitan area of Barcelona in 2015 and 2016. These particles were analyzed for polycyclic aromatic hydrocarbons (PAH) and organic tracer compounds. The concentrations of PAH were in the range of the street air levels with higher PAH values in the colder period. No influence of nighttime maintenance activities was observed on the platform air quality during daytime. Source apportionment analysis using the concentrations of hopanes, nicotine and levoglucosan as molecular tracer compounds showed that 75% of the detected PAH at the platforms have an outdoor PM origin. The modern subway stations, with advanced ventilation and platform screen doors that separate the subway system from the platform, showed lowest PAH and PM concentrations.