Spatiotemporal Gradients of PAH Concentrations in Greek Cities and Associated Exposure Impacts.

To study the spatiotemporal variability of particle-bound polycyclic aromatic hydrocarbons (PAHs) and assess their carcinogenic potential in six contrasting urban environments in Greece, a total of 305 filter samples were collected and analyzed. Sampling sites included a variety of urban background, traffic (Athens, Ioannina and Heraklion), rural (Xanthi) and near-port locations (Piraeus and Volos). When considering the sum of 16 U.S. EPA priority PAHs, as well as that of the six EU-proposed members, average concentrations observed across locations during summer varied moderately (0.4-2.2 ng m-3) and independently of the population of each site, with the highest values observed in the areas of Piraeus and Volos that are affected by port and industrial activities. Winter levels were significantly higher and more spatially variable compared to summer, with the seasonal enhancement ranging from 7 times in Piraeus to 98 times in Ioannina, indicating the large impact of PAH emissions from residential wood burning. Regarding benzo(a)pyrene (BaP), an IARC Group 1 carcinogen and the only EU-regulated PAH, the winter/summer ratios were 24-33 in Athens, Volos, Heraklion and Xanthi; 60 in Piraeus; and 480 in Ioannina, which is afflicted by severe wood-burning pollution events. An excellent correlation was observed between organic carbon (OC) and benzo(a)pyrene (BaP) during the cold period at all urban sites (r2 > 0.8) with stable BaP/OC slopes (0.09-0.14 × 10-3), highlighting the potential use of OC as a proxy for the estimation of BaP in winter conditions. The identified spatiotemporal contrasts, which were explored for the first time for PAHs at such a scale in the Eastern Mediterranean, provide important insights into sources and controlling atmospheric conditions and reveal large deviations in exposure risks among cities that raise the issue of environmental injustice on a national level.

Seawater physics and chemistry along the Med-SHIP transects in the Mediterranean Sea in 2016.

The Mediterranean Sea has been sampled irregularly by research vessels in the past, mostly by national expeditions in regional waters. To monitor the hydrographic, biogeochemical and circulation changes in the Mediterranean Sea, a systematic repeat oceanographic survey programme called Med-SHIP was recommended by the Mediterranean Science Commission (CIESM) in 2011, as part of the Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP). Med-SHIP consists of zonal and meridional surveys with different frequencies, where comprehensive physical and biogeochemical properties are measured with the highest international standards. The first zonal survey was done in 2011 and repeated in 2018. In addition, a network of meridional (and other key) hydrographic sections were designed: the first cycle of these sections was completed in 2016, with three cruises funded by the EU project EUROFLEETS2. This paper presents the physical and chemical data of the meridional and key transects in the Western and Eastern Mediterranean Sea collected during those cruises.

Occurrence, sources and water column distribution trends of suspended particle-associated aliphatic and polycyclic aromatic hydrocarbons in the open northeastern Mediterranean Sea.

Herein, we study the occurrence and water column distribution trends of suspended particle-associated aliphatic (AHCs) and polycyclic aromatic hydrocarbons (PAHs) collected from 36 offshore/deep sea locations across the open northeastern Mediterranean Sea. Total concentrations of the determined compounds fall within the range previously reported for non-polluted coastal and open sea locations worldwide. Mixed natural and anthropogenic sources were evident for the studied compounds, based on their molecular profile and several diagnostic indices. In all cases, an enhanced fossil signal typifying chronic oil pollution was evident along the water column. AHCs and PAHs mixtures characteristics varied significantly within the studied sub-regions, highlighting the importance of inputs from various point sources and dispersion pathways. The circulation characteristics of water masses along with biogeochemical features impact on the water column distribution trends and overall fate of the determined compounds in the study area.

Dataset on the imprint of the Agia Zoni II tanker oil spill on the marine ecosystem of Saronikos Gulf.

These data relate to the research article entitled "Imprint and short-term fate of the Agia Zoni II tanker oil spill on the marine ecosystem of Saronikos Gulf" by Parinos et al., 2019 [1]. The dataset includes the concentrations of 32 individual compounds/groups of polycyclic aromatic hydrocarbons (PAHs) determined in 235 seawater samples and 55 sediment samples analyzed during the monitoring survey conducted by the Hellenic Centre for Marine Research (H.C.M.R.) following the September 2017 Agia Zoni II heavy fuel oil (HFO) spill incident in Saronikos Gulf, Greece. The survey effort included 69 seawater sampling sites, of which 55 coastal and 14 open sea areas, and 22 sediment sampling sites across the inner Saronikos Gulf, aiming to assess the spatial and temporal imprint of the spilled oil during the first six months from the incident. The data were acquired by means of gas chromatography - mass spectrometry, following proper pre-treatment of the collected samples. This dataset is, to the best of our knowledge, the very first PAHs record related to the Agia Zoni II oil spill incident, that should be of interest for future scientific research on this and HFO spills in general.

Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events.

The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales.

Influence of pollution history on the response of coastal bacterial and nanoeukaryote communities to crude oil and biostimulation assays.

Pollution history has often been proposed to explain site-dependent bioremediation efficiencies, but this hypothesis has been poorly explored. Here, bacteria and their heterotrophic nanoflagellates (HNF) predators originating from pristine and chronically oil-polluted coastal sites were subjected to crude oil ± nutrients or emulsifier amendments. The addition of crude oil had a more visible effect on bacteria originating from the pristine site with a higher increase in the activity of given OTU and inactivation of other petroleum-sensitive bacteria, as revealed by DNA and RNA-based comparison. Such changes resulted in a delay in microbial growth and in a lower bacterial degradation of the more complex hydrocarbons. Biostimulation provoked a selection of different bacterial community assemblages and stirred metabolically active bacteria. This resulted in a clear increase of the peak of bacteria and their HNF predators and higher oil degradation, irrespective of the pollution history of the site.