Manolis Mandalakis

Gas–particle concentrations and distribution of aliphatic hydrocarbons, PAHs, PCBs and PCDD/Fs in the atmosphere of Athens (Greece)

Abstract Air samples were collected at the urban center, a background site, and the adjacent coastal area of the metropolitan area of Athens during July 2000. Gas and particle phase concentrations of aliphatic hydrocarbons, α,β-hopanes, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were identified and measured. Total concentrations of aliphatic hydrocarbons, ranged between 943.0xa0ngxa0m−3 (urban site) and 947.1xa0ngxa0m−3 (coastal area) in the gas and from 141.8xa0ngxa0m−3 (coastal site) up to 469.0xa0ngxa0m−3 (urban center) in the particulate phase. The total concentration of α,β-hopanes (12 homologues) in the urban area was ca. 0.2xa0ngxa0m−3 in the gas and 1.0xa0ngxa0m−3 in the particulate phase. Total PAH concentrations (∑PAHs of 20 members) ranged from 3.5xa0ngxa0m−3 (background site) to 26.0xa0ngxa0m−3 (urban center) in the gas and from 1.3xa0ngxa0m−3 (coastal area) up to 5.0xa0ngxa0m−3 (urban center) in the particulate phase. The total concentration of PCBs (∑PCBs of 38 congeners) in the gas plus the particulate phase of the atmosphere ranged from 80.5xa0pgxa0m−3 (background site) up to 348.6xa0pgxa0m−3 (urban center) and the corresponding concentration of PCDD/Fs ranged from 166.6xa0fgxa0m−3 (background site) up to 701.5xa0fgxa0m−3 (urban center), respectively. Gas–particle partition coefficients Kp of n-alkanes, PAHs, PCBs and PCDD/Fs were well correlated (R2=0.50–0.99) with the sub-cooled liquid vapor pressure PLo. The average slopes mr of log K p versus log PLo for n-alkanes (−0.46) and PCBs (−0.44) were low compared to other urban areas. The corresponding mr values for PAHs (−0.57), PCDDs (−0.78) and PCDFs (−0.75) are comparable to those obtained in other urban areas.

Particle-size distribution and gas/particle partitioning of atmospheric polybrominated diphenyl ethers in urban areas of Greece

Ambient concentrations, gas/particle partitioning and particle-size distribution of polybrominated diphenyl ethers (PBDEs) were investigated in two urban areas (Athens and Heraklion) of Greece. Atmospheric (gas+particle) concentrations of summation operatorPBDE varied from 21 to 30 pg m(-3) in the center of Athens and from 4 to 44 pg m(-3) in the suburbs of Heraklion. A predominance of particulate PBDEs was observed in Athens (71-76% in particles), whereas the opposite was evident in Heraklion (69-92% in gas phase). In both urban areas, PBDE particle-size distribution featured a distinct enrichment in smaller particles. A similar trend was also observed in aerosols of a background marine site. For all sampling sites, more than 46% of summation operatorPBDE was associated with particles of <0.57 microm in diameter. Our results imply that particulate PBDEs may have long atmospheric residence time and they may be capable of reaching the deeper parts of the human respiratory system.

Phylogenetic diversity of sediment bacteria from the southern Cretan margin, Eastern Mediterranean Sea.

This study is the first culture-independent report on the regional variability of bacterial diversity in oxic sediments from the unexplored southern Cretan margin (SCM). Three main deep basins (water column depths: 2670-3603m), located at the mouth of two submarine canyons (Samaria Gorge and Paximades Channel) and an adjacent slope system, as well as two shallow upper-slope stations (water column depths: 215 and 520m), were sampled. A total of 454 clones were sequenced and the bacterial richness, estimated through five clone libraries using rarefaction analysis, ranged from 71 to 296 unique phylotypes. The average sequence identity of the retrieved Cretan margin sequences compared to the >1,000,000 known rRNA sequences was only 93.5%. A diverse range of prokaryotes was found in the sediments, which were represented by 15 different taxonomic groups at the phylum level. The phylogenetic analysis revealed that these new sequences grouped with the phyla Acidobacteria, Planctomycetes, Actinobacteria, Gamma-, Alpha- and Delta-proteobacteria. Only a few bacterial clones were affiliated with Chloroflexi, Bacteroidetes, Firmicutes, Gemmatimonadetes, Verrucomicrobia, Nitrospirae, Beta-proteobacteria, Lentisphaerae and Dictyoglomi. A large fraction of the retrieved sequences (12%) did not fall into any taxonomic division previously characterized by molecular criteria, whereas four novel division-level lineages, termed candidate division SCMs, were identified. Bacterial community composition demonstrated significant differences in comparison to previous phylogenetic studies. This divergence was mainly triggered by the dominance of Acidobacteria and Actinobacteria and reflected a bacterial community different from that currently known for oxic and pristine marine sediments.

Optimization and application of high-resolution gas chromatography with ion trap tandem mass spectrometry to the determination of polychlorinated biphenyls in atmospheric aerosols

Optimization of the Finnigan GCQ ion trap mass spectrometry (ITMS) system and a clean-up procedure were carried out in order to apply high-resolution gas chromatography-tandem mass spectrometry for the analysis of polychlorinated biphenyls (PCBs) in aerosols. Six ITMS operating parameters, including isolation time, excitation voltage, excitation time, q value, ion source temperature and electron energy were adjusted in order to optimize the instrument analytical performance. The adjustment of all parameters substantially increased the sensitivity of ITMS in the MS-MS mode. Changes in isolation time did not particularly affect ITMS sensitivity while ion source temperature had the strongest influence. After optimization, a limit of detection of 600 fg/microl with S/N varying from 8 up to 91 was achieved. The application of the optimized ITMS parameters conjointly with the developed clean-up procedure resulted in method detection limits of 10-20 fg/m3 for the determination of PCBs, in the particulate and gas phase of the atmospheric aerosol of background areas in the Eastern Mediterranean and Sweden.

Study of atmospheric PCB concentrations over the eastern Mediterranean Sea

[1]xa0Air samples were collected between April 1999 and March 2001 at a background marine site in the eastern Mediterranean Sea and analyzed for polychlorinated biphenyls (PCBs). The average concentrations of total PCB congeners (ΣPCBs) in the gas and particulate phases of the atmosphere were 68.1 ± 28.8 and 2.3 ± 1.8 pg/m3, respectively. The lack of seasonal variation for the atmospheric concentration of individual congeners and ΣPCBs and the shallow slopes obtained from the Clausius–Clapeyron (CC) plots for several PCB congeners indicated that long-range transport is the main factor controlling the atmospheric levels of PCBs in this area. Most of the episodes with elevated concentrations of ΣPCBs concurred with air transport from western and central Europe. This observation was mostly attributed to the predominance of N-NW winds in eastern Mediterranean. The wind speed apparently did not affect the atmospheric concentration of PCBs. Significant changes observed on the homologue group profile of PCBs were mostly related to the origin of air parcels sampled and during summer were most probably related to the reaction of the lighter congeners with OH radicals. Partitioning of PCBs between gas and particulate phases was well correlated with the subcooled liquid vapor pressure (PLo) for 11 of the 37 samples. The slopes of log Kp versus log PLo ranged between −0.233 and −0.445 and are among the shallowest measured worldwide. This fact may indicate absorption of PCBs in particles covered by a polar film.

Occurrence and diurnal variation of polychlorinated biphenyls and polybrominated diphenyl ethers in the background atmosphere of Eastern Mediterranean

During a two-week intensive field campaign conducted at a background location of the Eastern Mediterranean, consecutive 10-h air samples were collected under intense photochemical conditions and analyzed for polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). The average gas-phase concentration of total PCBs and PBDEs was 73+/-29 and 3.9+/-2.1 pg m(-3), respectively. The study of Clausius-Clapeyron plots and air mass back-trajectories assigned the origin of air masses as the factor largely controlling the variation of PCB and PBDE air concentrations in the study area. Using principal component analysis, discrete differences in PCBs homologue profiles were revealed between day and night samples and attributed to the daytime reaction with hydroxyl radicals. In contrast, PBDE homologue profiles did not show any characteristic day-to-night shifts that could be attributed to hydroxyl radical reaction or photolysis.

Trace analysis of free and combined amino acids in atmospheric aerosols by gas chromatography-mass spectrometry.

The analysis of amino acids by gas chromatography mass spectrometry (GC-MS) after their derivatization with N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide was investigated as an alternative approach for the determination of free (FAA) and combined amino acids (CAA) in aerosols. This technique showed excellent linearity with r(2) values ranging from 0.9029 to 0.9995 and instrumental limits of detection ranging from 0.3 to 46pg for the different amino acids. The quality of water used for sample extraction was found to be of utmost importance for achieving low blank levels of FAA and CAA. The addition of isopropanol during the extraction of aerosols was also shown to minimize the coextraction of inorganic salts that interfered with the analysis of FAA, Moreover, the ascorbic acid was found to be the most effective reagent for preventing the oxidative destruction of CAA during the hydrolysis process. By the analysis of spiked aerosol samples, the average recoveries determined for FAA and CAA were higher than 60% and the associated relative standard deviation was lower than 10% for the majority of amino acids. The application of the adopted method in background aerosols of the eastern Mediterranean enabled the unambiguous identification and quantification of 20 amino acids. The total concentration of FAA and CAA in aerosols ranged from 13 to 34ngm(-3) and from 29 to 79ngm(-3), respectively. The GC-MS based method is proposed to overcome several analytical difficulties usually encountered with the conventional HPLC-fluoresence technique.

Mass budget and dynamics of polychlorinated biphenyls in the eastern Mediterranean Sea

[1]xa0Polychlorinated biphenyls (PCBs) were measured in dry deposition and sediment trap samples from the eastern Mediterranean and the results of the present and previous studies were synthesized in order to construct a mass balance budget describing the status and dynamics of PCBs in this region. According to our calculations, the burden of total PCBs in the euphotic zone of the eastern Mediterranean should approach 84,000 kg, while the corresponding pool in the overlying atmosphere should be about 162 kg. The atmospheric input of PCBs in the respective water basin through dry and wet deposition should be 300 and 1300 kg yr−1, respectively. On the contrary, air-sea exchange should cause a net volatilization of PCBs from seawater to the atmosphere by 3150 kg yr−1. Moreover, PCBs are removed from the water column with a settling flux of 350 kg yr−1 and under steady state conditions, an additional input of these pollutants should be required to counterbalance the outflows from the water basin. The discharge of urban and industrial sewage, riverine input and transport of more polluted surface waters from western to eastern Mediterranean may account for most of this inflow. In the atmospheric compartment, the removal flux of PCBs due to their destruction by hydroxyl radicals (6650 kg yr−1) was approximately 4 times higher than their deposition flux (wet plus dry). On the basis of these data, 5100 kg of PCBs should enter into the atmosphere of eastern Mediterranean annually in order to achieve steady state conditions. This influx may result from long or short range transport of atmospheric PCBs emitted from contaminated terrestrial surfaces.

High-Resolution Gas Chromatography-Tandem Mass Spectrometry: A Sensitive Analytical Technique Suitable for the Study of Atmospheric Processes of Polychlorinated Biphenyls and Dibenzo-p-Dioxins/Furans

The trace-level environmental determination of polychlorinated biphenyls (PCBs) and 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) requires the use of delicate fractionation and analytical techniques such as high-resolution gas chromatography coupled with high-resolution mass spectrometry. The analytical requirements are even higher if atmospheric physicochemical processes of these persistent organic compounds (POPs) are to be studied in remote areas, where concentrations are very low. The optimization of a fractionation method, and of the high-resolution gas chromatography/ion trap tandem mass spectrometry system instrumental parameters enabled us to establish the optimum conditions for the determination of atmospheric PCBs and PCDD/Fs at the low pg or even fg m - 3 level. By using this analytical procedure, we accomplished the reliable determination of ca. 54 PCBs and 17 PCDD/Fs individual congeners, of different chlorination level, in the gas and particulate phase of atmospheric aerosol samples collected from the Eastern Mediterranean basin. Furthermore, we were also able to study the atmospheric physicochemical and loss processes of PCBs, such as gas-particle partitioning, wet and dry deposition, and PCBs reaction with hydroxyl radicals.