The PhD student Nupur Nagar, from the Geochemistry & Pollution research group, will defend her thesis on 2nd May at 11h in Universitat de Vic.
The PhD student Nupur Nagar, from the Geochemistry & Pollution research group, will defend her thesis on 2nd May at 11h in Universitat de Vic. The PhD defence will be streamed at this link.
Title: Source assessment of the organochlorine pollutants in sediment and fish from Greenland lakes
Directors: Joan O. Grimalt and Mireia Bartrons
Thesis Committee: David Huertas, Pilar Fernández and Àngels Leiva
Abstract:
In the thesis, three studies were conducted across temporal and spatial gradients to deepen our understanding of OHCs accumulation in the fish and sediments from Greenlandic freshwater lakes. The first chapter aimed to understand the levels of POPs arriving to the high Arctic freshwater lakes in Greenland and how the presence of the living organisms affects their depositional patterns. The role of sea birds as carriers of pollutants over long distances was evaluated. One of the three lakes selected for this purpose had a little auk (Alle alle) bird colony, and the other two were devoid of these seabirds. We found a strong influence of these seabirds in the transport and deposition of these hydrophobic compounds to remote sites. However, not all compounds showed the same relative increases. We found a discriminating effect in the seabird accumulation and transport of organohalogen to remote sites.
The second chapter aimed to establish a record of OHCs contamination in Greenlandic freshwater lakes sediments. Airports, military bases, and research stations were important local sources for DDTs, HCB, OCS, Methoxychlor, Mirex, Chlordanes, and Heptachlors in Greenland freshwater lakes. Populated areas were essential sources for PCBs. The effect of LRAT was evident for HCHs, HCB, Chlordanes, and Heptachlors. Positive longitudinal gradients explained the arrival of HCHs and PBDEs from the Eurasian and Northeastern American continents. The concentrations of most compounds showed a decrease through the years due to the past restrictions. This study is the first to analyse a broad spectrum of OHCs, including Endosulfans, Drins, OCS, Mirex, and Methoxychlor, which were never studied in freshwater lake sediments of Greenland.
The third chapter study aimed to determine the range of concentrations of PCBs, DDTs and PBDEs in the top predator Arctic charr across Greenland freshwater lakes and understand OHCs accumulation and distribution patterns. We found that PCBs and DDTs concentrations in some Arctic charr crossed the toxicity thresholds, which may be of concern since it is an important component in the local population’s diet. The most critical factors determining PCBs, PBDEs, and DDTs accumulation in Arctic charr were mean annual air temperature (indicating LRAT) and anthropogenic impact. The Arctic charr from lakes with higher anthropogenic impact also accumulated higher levels of heavier molecular weight PCBs. Total nitrogen in the lake was also an important factor determining PBDEs bioaccumulation, indicating a dilution factor of PBDEs in Arctic charr when nitrogen concentrations in the lake were higher. Some Layman metrics were significant predictors for DDTs and PBDEs bioaccumulation, providing insight into the relevance of biomagnification, trophic diversity and niche overlap effects for the cycling of these organic compounds across the freshwater food webs.
