Occurrence and air-water diffusive exchange legacy persistent organic pollutants in an oligotrophic north Patagonian lake

Occurrence and diffusive air-seawater exchanges of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in Fildes Bay, King George Island, Antarctica

We report the levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in seawater and air, and the air-sea dynamics through diffusive exchange analysis in Fildes Bay, King George Island, Antarctica, between November 2019 and January 30, 2020. Hexachlorobenzene (HCB) was the most abundant compound in both air and seawater with concentrations around 39 ± 2.1 pg m-3 and 3.2 ± 2.4 pg L-1 respectively. The most abundant PCB congener was PCB 11, with a mean of 3.16 ± 3.7 pg m-3 in air and 2.0 ± 1.1 pg L-1 in seawater. The fugacity gradient estimated for the OCP compounds indicate a predominance of net atmospheric deposition for HCB, α-HCH, γ-HCH, 4,4'-DDT, 4,4'-DDE and close to equilibrium for the PeCB compound. The observed deposition of some OCs may be driven by high biodegradation rates and/or settling fluxes decreasing the concentration of these compounds in surface waters, which is supported by the capacity of microbial consortium to degrade some of these compounds. The estimated fugacity gradients for PCBs showed differences between congeners, with net volatilization predominating for PCB-9, a trend close to equilibrium for PCB congeners 11, 28, 52, 101, 118, 138, and 153, and deposition for PCB 180. Snow amplification may play an important role for less hydrophobic PCBs, with volatilization predominating after snow/glacier melting. As hydrophobicity increases, the biological pump decreases the concentration of PCBs in seawater, reversing the fugacity gradient to atmospheric deposition. This study highlights the potential impacts of climate change, through glacier retreat, on the biogeochemistry of POPs, remobilizing those compounds previously trapped within the cryosphere which in turn will transform the Antarctic cryosphere into a secondary source of the more volatile POPs in coastal areas, influenced by snow and ice melting.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.

Metal(loid)s in organic-matter-polluted urban rivers in China: Spatial pattern, ecological risk and reciprocal interactions with aquatic microbiome

Black-odorous urban rivers can serve as reservoirs for heavy metals and other pollutants, in which sewage-derived labile organic matter triggering the water blackening and odorization largely determine the fate and ecological impact of the heavy metals. Nonetheless, information on the pollution and ecological risk of heavy metals and their reciprocal impact on microbiome in organic matter-polluted urban rivers remain unknown. In this study, sediment samples were collected and analyzed from 173 typical black-odorous urban rivers in 74 cities across China, providing a comprehensive nationwide assessment of heavy metal contamination. The results revealed substantial contamination levels of 6 heavy metals (i.e., Cu, Zn, Pb, Cr, Cd, and Li), with average concentrations ranging from 1.85 to 6.90 times higher than their respective background values in soil. Notably, the southern, eastern, and central regions of China exhibited particularly elevated contamination levels. In comparison to oligotrophic and eutrophic waters, the black-odorous urban rivers triggered by organic matter exhibited significantly higher proportions of the unstable form of these heavy metals, indicating elevated ecological risks. Further analyses suggested the critical roles of organic matter in shaping the form and bioavailability of heavy metals through fueling microbial processes. In addition, most heavy metals had significantly higher but varied impact on the prokaryotic populations relative to eukaryotes.

Concentration levels, spatial variations and exchanges of polychlorinated biphenyls (PCBs) in ambient air, surface water and sediment in Bursa, Türkiye

In this study, ambient air, surface water and sediment samples were simultaneously collected and analyzed for PCBs to investigate their levels, spatial variations and exchanges between these three compartments at different sampling sites for 12 months in Bursa, Türkiye. During the sampling period, a total of 41 PCB concentrations were determined in the ambient air, surface water (dissolved and particle phase) and sediment. Thus, 945.9 ± 491.6 pg/m³ (average ± STD), 53.8 ± 54.7 ng/L, 92.8 ± 59.3 ng/L and 71.4 ± 38.7 ng/g, respectively. The highest concentrations of PCBs in the ambient air and in water particulate phase were measured at the industrial/agricultural sampling site (1308.6 ± 252.1 pg/m³ and 168.7 ± 21.2 ng/L, respectively), ∼ 4-10 times higher than background sites; while the highest concentrations in the sediment and dissolved phase were measured at the urban/agricultural sampling sites (163.8 ± 27.0 ng/L and 145.7 ± 15.3 ng/g, respectively), ∼ 5-20 times higher than background sites. PCB transitions between ambient air-surface water (f_A/f_W) and surface water-sediment (f_W/f_S) were investigated by fugacity ratio calculations. According to the fugacity ratios obtained, volatilization from the surface water to the ambient air was observed at all sampling sites (98.7 % of f_A/f_W ratios are <1.0). Additionally, it has been determined that there is a transport from the surface water to the sediment (100.0 % of f_W/f_S ratios are higher than 1.0). The flux values in ambient air-surface water and surface water-sediment environments ranged from -1.2 to 1770.6 pg/m²-day and from -225.9 to 0.001 pg/m²-day, respectively. The highest flux values were measured for PCBs with low chlorine content (Mono-, Di-Cl PCBs), while the lowest flux values were measured for the high chlorine content PCBs (Octa-, Nona- and Deca-Cl PCBs). As it was determined in this study that surface waters contaminated by PCBs have the potential to pollute both air and sediments, it will be important to take measures to protect surface waters.

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. ƩPAHs (35-920 pg L^-1) were around half of those observed in the past, which agrees with reductions in European atmospheric emissions. ƩPCB 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. ƩOPEs (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.

Surface hydrochemical dynamic in an artificial lake with anthropic impact: La Purísima reservoir, Central Mexico

In the present study, the hydrochemical dynamic and the water quality of La Purísima reservoir, Central Mexico, have been determined. The reservoir presents total dissolved solids (TDSs) between 146 and 328 mg L^-1 and water quality neutral to slightly alkaline (pH 7.0 to 8.7) during the dry season, whereas it becomes clearly alkaline (pH 8.1-9.9) in the rainy-warm season. Through its main tributaries, La Purísima reservoir has been receiving water affected by anthropic activities, such as mining, urbanization, and agriculture. La Purísima reservoir indicates water quality suitable for irrigation and aquatic lives, but unsuitable for drinking purposes. A geochemical evolution from the riverine to the lacustrine zone is evidenced by the complexation of several free ions: the higher saturation indexes; the lower toxic metal concentrations; and the lower trophic status, which ameliorate the water quality in the lacustrine zone. Trace elements co-precipitate and are adsorbed onto bottom sediments. During summer, high evaporation rates and atmospheric precipitation are found to decline the water quality. Cluster analyses reflect the geo-setting and different pollution levels: urban impact from the north coast, and agricultural activities from the east coast. The sensitivity of the lake to geochemical behavior can be used to understand the complex dissolved geochemical dynamics in a lake and the potential effects from long-term anthropic impact variability. The information about water quality of La Purísima reservoir may be useful to preserve the ecosystem and its biodiversity.