The antarctic as sentinel of global pollution
- Autores: Gemma Casas Papell
- Directores de la Tesis: Begoña Jiménez Luque (dir. tes.), Jordi Dachs Marginet (dir. tes.), Francisco Javier Santos Vicente (tut. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Antonio Tovar Sánchez (presid.), Marta Llorca Casamayor (secret.), Alessandra Cincinelli (voc.)
- Programa de doctorado: Programa de Doctorado en Química Analítica y Medio Ambiente por la Universidad de Barcelona
- Materias:
- Texto completo no disponible (Saber más ...)
- Resumen
Over the past century, since the industrial revolution, the intensification of the industry, transport, agriculture and other anthropogenic activities have introduced thousands or tens of thousands of new synthetic compounds, originating a new environmental perturbation in the Earth’s system. Chemicals are the basis of life, but some of them pose inherent dangers to living beings, as are novel entities in the biosphere. Chemical pollution is one of the nine planetary boundaries that delimit a “safe operating space for humanity” in order to avoid an “unacceptable global change”. However, this planetary boundary, is not yet well defined and quantified. Among chemical synthetic compounds, there are the so-called persistent organic pollutants (POPs), which constitute a heterogenic group of chemical substances of environmental concern. POP’s intrinsic physicochemical properties, and biogeochemical cycling exert a strong influence on their environmental occurrence, behaviour and fate. Some of these properties are often used as criteria for their risk analysis and regulation, such as their persistence, bioaccumulation, long range transport potential and their toxic effects. As a consequence of the regulation of some POPs, there has been a decrease of the primary sources of some of these substances, notably for legacy POPs, even though chemicals that were banned decades ago, such as polychlorinated biphenyls, are still ubiquitous everywhere.
When we think of Antarctica, a pristine, wild, inaccessible and “pure” region comes to our mind. However, this remote ecosystem is polluted by POPs. Research at polar regions has been at the frontiers of knowledge in the environmental chemistry field for the last three decades. Polar areas have played an important role in the development of the environmental chemistry field, since these areas are especially susceptible to the harmful effects of pollution that originates thousands of kilometers away. In addition, polar regions are a ideal natural laboratory for the study of pollutants, their relevance and dynamics, as well their relevance at a global level. Studies in polar regions have played a key role in the development of important conceptual advances in our understanding of long range transport (LRT) such as the first reports of atmospheric deposition, cold trapping and the “Grasshopping” due to consecutive events of volatilization and deposition, as well as biogeochemical controls, such as changes in vegetation cover on land, or the biological and degradative pumps in the oceans.
Persistent and semi-volatile organic pollutants, have the potential for LRT, and through atmospheric deposition followed by partitioning and other biogeochemical processes accumulate in Antarctic soils, ice, snow, seawater and biota. Both climatic and biogeochemical factors influence the reservoir potential of the different Antarctic compartments, but there are a number of processes, especially those implying amplification, that have received little attention for all POPs, both legacy and emerging. For legacy POPs, such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), there has been a remarkable assessment of the cycling in the ocean, including polar regions. However, for emerging POPs, having different sources and properties, such as the organophosphate esters (OPEs) and perfluoroalkyl substances (PFAS); little is known about the processes that influence their occurrence, transport and fate in the global environment and particularly in remote areas, such as Antarctica.
The working hypothesis of this thesis is that the Antarctica, and especially the northern part of the Antarctic Peninsula (AP), is a sentinel region for the identification of legacy and emerging POPs, which have the potential to be globally distributed. The AP region is also very useful to understand the cycling of these pollutants in remote environments. This uniqueness of the AP is due to the abundant wet deposition events of rain and snow, the high primary productivity favouring the formation of the SML (sea-surface microlayer), the periods of high wind speed driving formation of SSA (sea-spray aerosols), and the dynamic climatic and biogeochemical controls on the fate and transport of organic pollutants in this coastal region. The overall goal of this thesis is to perform field and conceptual research in order to understand the cycling, accumulation and amplification processes of POPs with diverse physical-chemical properties and sources, such as OPEs and PFAS, in coastal Antarctica, and determine to which extend the AP can act as a sentinel of global pollution.
For this purpose, the largest known multi-compartment study was conducted during the austral summers from 2014 to 2018 in two Islands from the western AP, Livingston and Deception Island. Air (gas-and particle-phase), snow, rain, snowmelt, lake water, SML, seawater surface, deep water and plankton samples were sampled and analysed in this work. These sampling campaigns were designed for the study of different legacy and emerging POPs, with particular emphasis to PFAS and OPEs. Different sampling approaches and analytical methodologies were used depending on the matrix and the target compounds. Furthermore, two meta-analysis of previously published concentrations in rain and snow, covering different climate zones and a wide range of chemical classes, together with some concentrations of PFAS, OPEs and PAHs generated within this thesis, were performed, with the objective to assess the rain and snow deposition driven amplification of concentrations of POPs.
The results of this thesis contribute with the largest database of concentrations of PFAS and OPEs in the Antarctica, and shows the ubiquity of these pollutants in all the environmental compartments analysed. From meta-analysis studies, we observe that snow-melting amplification of concentrations and fugacities is relevant for most families of POPs, such as PCBs, PAHs, PFAS and OPEs. Such amplification is of larger magnitude for the more volatile compounds, such as neutral PFAS. Only, the polybrominated diphenyl ethers (PBDEs) showed no significant amplification in snow. Also, there is a generalized amplification of the fugacities and concentrations for most POPs in rain, being especially more relevant for the more volatile chemicals. The rain amplification can drive the occurrence of POPs not only in polar regions, but across different climatic regions. Results derived from this work show that snow and rain amplification of POPs are of comparable magnitude. Field evidences showed high concentrations of PFAS and OPEs in rain and snow samples and demonstrated that atmospheric wet deposition by snow and rain is a key input of these pollutants for the maritime Antarctica. Field evidences from the study of different sampling stations in Livingston Island suggest that penguin guano also act as an amplifier of PFAS concentrations in coastal Antarctic seawater.
SSA formation and their subsequent atmospheric transport and deposition have been suggested to play a prominent role in the occurrence of PFAS in the maritime Antarctica and other remote regions. However, field studies were lacking. Our field study allowed to prove that, in fact, there is an enrichment of PFAS in the SML, and a very large enrichment or amplification of PFAS in SSA, supporting the important role of SSA as a relevant vector for atmospheric LRT of PFAS. The potential impact of atmospheric pollution on aquatic ecosystems has been under-predicted by only considering air-water partitioning, as amplification processes have the potential to be controls of the POPs occurrence in cold environments.
Sampling on different Antarctic Islands showed that PFAS and OPEs concentrations were generally higher at Deception Island than at Livingston Island consistent with the semi enclosed nature of their waters, and the potential larger impact from tourism activities at Deception Island.
Concentrations of some PFAS, such as perfluorooctane sulfonate (PFOS) and perfluooctanoic acid (PFOA) have decreased in Antarctic coastal waters from 2015 to 2018, as previously reported for other oceans. This gives particular importance to the fact that the regulation of certain pollutants decreases their emissions and subsequent transport to remote regions such as Antarctica. This decrease, is also another field evidence of in-situ degradation of some PFAS, especially PFOS.
OPEs in different environmental compartments from Livingston and Deception Islands were assessed in order to study the occurrence and the transport of OPEs in Antarctica. Atmospheric inputs, as well, the microbial degradation and biological pump were identified as the main drivers of OPE’s occurrence in the maritime Antarctica. Additionally, it was found that there is a decoupling between the transport and fate of plastics and plasticizers, as leaching from plastics cannot explain the observed occurrence of OPE plasticizers in the maritime Antarctica.
The predominance of atmospheric inputs as a source of POPs, is not limited to legacy POPs characterized as semivolatile and highly hydrophobic, but also for emerging organic pollutants such as PFAS and OPEs, with a wide range of properties. In fact, some of these were previously thought to be “swimmers”. The multiple correlations between OPEs, PFAS and some bacterial taxa, concurrently with other geochemical evidences (fugacity ratios or relative occurrence), provide multiple field evidences of the important role that microbial degradation plays as a key environmental sink of POPs, even in cold environments. As chemicals previously thought to be “fliers” and “swimmers” can be atmospherically transported and deposited, as demonstrated in this thesis, it is derived that most synthetic chemicals may behave as “grasshoppers”. Their potential for being global pollutants and reach Antarctica may be a strong function of their persistence, which confirms this descriptor as key for prioritizing the risk of anthropogenic chemicals.
Overall, this thesis shows that South Shetland islands, and generally the northern sector of the AP, act as a key “environmental sentinel” of global pollution due to the abundant wet deposition events, as well as other amplification processes, facilitating the detection of synthetic chemicals emitted from remote sources.
