Destino ambiental de los Contaminantes Orgánicos Persistentes (COP) durante el verano austral en la Antártica
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2023
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en
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Universidad Andrés Bello
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Licencia CC
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This study investigated the environmental fate of Antarctica's persistent organic pollutants
(POPs). These anthropogenic compounds are stable, resistant to degradation, and can bioaccumulate
in organisms and biomagnify through the food chain. The fate of persistent organic pollutants (POPs)
in the environment depends on their chemical properties and the exchange processes between
different compartments. In particular, the air-water exchange is important in aquatic systems,
affecting POP levels through atmospheric volatilization and deposition. Once POPs reach the water,
they may remain dissolved, volatilize again, or bind to particles such as phytoplankton. These
contaminants can follow different environmental pathways, including transfer to higher trophic
levels, resulting in biomagnification, export to deep water, and subsequent inclusion in the biological
pump. In Antarctica, there needs to be more information on these processes, although the polar
regions act as ultimate sinks for POPs. It has been observed that during periods of high productivity,
POPs are transferred to sediments due to high biological pump fluxes and accumulation in living
organisms. However, previous studies in Antarctica have had limitations in accurately quantifying
POP levels due to samples taken at different locations. In addition, the assessment of POP cycling in
aquatic systems has been conducted regarding organic carbon, which has left uncertainty about the
fate of POPs in the Southern Ocean. Therefore, the main objective of this study was to assess the
environmental fate of POPs, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides
(OCPs), during periods of blooms in Antarctica. Simultaneous air, water, phytoplankton, and
zooplankton sampling was conducted in Fildes Bay, King George Island, Antarctica, from December
2019 to January 2020. Several factors were calculated, such as air-water exchange and
bioaccumulation, bioconcentration, and biomagnification factors. In addition, the atmospheric halflife was estimated using characteristic decay times (TD), where we observed that HCB levels in the
Antarctic atmosphere were higher than those of the other target OCs. However, HCB also showed
greater fluctuations and did not significantly decrease over time.
In contrast, atmospheric levels of HCH and some DDT and PCBs have decreased
significantly. The estimated atmospheric half-lives of persistent organic pollutants (POPs) vary by
compound. For DDT compounds, the half-lives are 4.4' DDE (13.5 years), 4.4' DDD (12.8 years),
and 4.4' DDT (7.4 years). For HCH compounds, the half-lives are 2.4' DDE (6.4 years), 2.4' DDT
(6.3 years), α-HCH (6 years), HCB (6 years), and γ-HCH (4.2 years). For PCB congeners, half-lives
decrease in the following order: PCB 153 (7.6 years), PCB 138 (6.5 years), PCB 101 (4.7 years), PCB
180 (4.6 years), PCB 28 (4 years), PCB 52 (3.7 years) and PCB 118 (3.6 years). These estimates show
the persistence of POPs in the atmosphere and their ability to remain in the environment for long
periods. In the case of HCH isomers and PCBs, the ban on POPs imposed by the Stockholm
Convention has reduced their levels in recent decades. However, their ubiquity in the Antarctic
atmosphere shows the problems associated with highly persistent synthetic chemicals. The results
showed that hexachlorobenzene (HCB) was the most abundant compound in air and water. Significant
concentrations of PCB 11 were also found in air and seawater. The estimated fugacity gradient for
PCB compounds indicates a predominance of net atmospheric deposition for HCB, α-HCH, γ-HCH,
4,4'-DDDT, 4,4'-DDE, and close to equilibrium for the compound PeCB. The observed deposition of
some OCs may be due to high biodegradation rates and sedimentation fluxes contributing to the
decrease of these compounds in surface waters, supported by the measured ability of the microbial
consortium to degrade some of these compounds. 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 essential role in decreasing PCBs in surface waters. Snow amplification
may play an important role in 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 toward atmospheric deposition.
Finally, regarding the levels detected in plankton, we recorded high concentrations of HCB
in phytoplankton and of the congener PCB 11 in zooplankton, elucidating for the first time the
presence of this congener in Antarctic biota high concentrations. On the other hand, BCF and BAF
estimates of OCP and PCB show a direct and significant linear relationship with Log KOW,
evidencing a trend of equilibrium or near equilibrium between water and phytoplankton and between
water and zooplankton, respectively. BAF and BCF values were in a similar range, indicating that, in
this study, zooplankton did not accumulate POPs from phytoplankton grazing, in agreement with the
BMF values obtained, where most of the analyzed compounds show values lower than 1, indicating
no or low biomagnification. According to the results, an effective and significant transfer of OCPs
and PCBs from water to phytoplankton and from water to zooplankton was obtained. However, there
was no effective and significant transfer between phytoplankton and zooplankton.
Overall, the study highlights the importance of continued monitoring, regulating atmospheric
sources, and understanding the environmental fate of POPs in Antarctica. Coordinated efforts are
needed among countries with an Antarctic presence to establish monitoring networks similar to those
in the Arctic to ensure comprehensive assessment and protection of the region's ecosystem.
Notas
Tesis (Doctora en Medicina de la Conservación)
Palabras clave
Contaminantes Orgánicos del Agua, Chile, Antártica