The Antarctic as Sentinel of Global Pollution

Abstract

Since the industrial revolution, we have introduced thousands or tens of thousands of new synthetic compounds, originating a new environmental perturbation in the Earth’s system. Among these, there are the so-called persistent organic pollutants (POPs), which constitute a heterogenic group of chemical substances of environmental concern. POPs are persistent, can bioaccumulate and biomagnificate, have toxic effects and have 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, there has been a remarkable assessment of the cycling in the ocean, including polar regions. However, for other 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 overall goal of this thesis was 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. 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. The potential impact of atmospheric pollution on aquatic ecosystems has been under-predicted by only considering air-water partitioning, as amplification processes, such as snow and rain deposition or the sea-spray aerosols formatted from the sea-surface microlayer, have the potential to be controls of the POPs occurrence in cold environments. 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. As Antarctica is distant from primary sources of POPs, it is especially suited as a sentinel of persistent anthropogenic chemicals.

Des de la revolució industrial, hem introduït milers de nous compostos sintètics, originant una nova pertorbació ambiental en el sistema terra. Entre els compostos químics sintètics, hi ha els anomenats contaminants orgànics persistents (COPs). Els COPs són persistents, es bioacumulen i es biomagnifiquen, son tòxics i es poden transportar a llargues distància fins a zones remotes, com ara l'Antàrtida. Tant els factors climàtics com els biogeoquímics influeixen en el potencial de reservori dels diferents compartiments antàrtics, però hi ha una sèrie de processos, especialment els que impliquen amplificació, que han rebut poca atenció per a tots els COP, tant els "històrics" com els emergents. Per als COPs "històrics,hi ha hagut una avaluació notable del coneixement dels seus cicles a l'oceà ia les regions polars. Tanmateix, per a altres COPs, amb diferents fonts i propietats, com els compostos organofosforats (OPEs) i les sustancias perfluoroalquiladas (PFAS), es coneix poc sobre els processos que influeixen en la seva aparició, transport i destí al medi ambient global i especialment a zones remotes com l'Antàrtida. L'objectiu general d'aquesta tesi era realitzar investigacions de camp i conceptuals per entendre els processos dels cicles, acumulació i amplificació de COPs amb propietats i fonts fisicoquímiques diverses, com ara OPEs i PFAS, a la costa de l'Antàrtida, i determinar fins a quin punt l'AP pot actuar com a sentinella de la contaminació global. Amb aquesta finalitat, s'ha dut a terme l'estudi multicompartiment més gran conegut a l'Antàrtida. Els resultats d'aquesta tesi aporten la base de dades més gran de concentracions de PFAS i OPEs a l'Antàrtida, i mostren la ubiqüitat d'aquests contaminants en tots els compartiments ambientals analitzats. En general, aquesta tesi mostra que les illes Shetland del Sud, i en general el sector nord de l'AP, actuen com a "sentinella ambiental" clau de la contaminació global a causa dels abundants esdeveniments de deposició humida, així com altres processos d'amplificació, facilitant la detecció de contaminants sintètics emesos des de fonts remotes. Com que l'Antàrtida està lluny de les fonts primàries de COP, és especialment susceptible de ser una sentinella de la contaminació de compostos persistents antropogènics.