Bougiatioti A.,Georgia Institute of Technology |
Bougiatioti A.,National Technical University of Athens |
Bougiatioti A.,University of Crete |
Bezantakos S.,University of Aegean |
And 11 more authors.
Atmospheric Chemistry and Physics | Year: 2016
This study investigates the concentration, cloud condensation nuclei (CCN) activity and hygroscopic properties of particles influenced by biomass burning in the eastern Mediterranean and their impacts on cloud droplet formation. Air masses sampled were subject to a range of atmospheric processing (several hours up to 3 days). Values of the hygroscopicity parameter, κ, were derived from CCN measurements and a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA). An Aerosol Chemical Speciation Monitor (ACSM) was also used to determine the chemical composition and mass concentration of non-refractory components of the submicron aerosol fraction. During fire events, the increased organic content (and lower inorganic fraction) of the aerosol decreases the values of κ, for all particle sizes. Particle sizes smaller than 80 nm exhibited considerable chemical dispersion (where hygroscopicity varied up to 100% for particles of same size); larger particles, however, exhibited considerably less dispersion owing to the effects of condensational growth and cloud processing. ACSM measurements indicate that the bulk composition reflects the hygroscopicity and chemical nature of the largest particles (having a diameter of ∼ 100 nm at dry conditions) sampled. Based on positive matrix factorization (PMF) analysis of the organic ACSM spectra, CCN concentrations follow a similar trend as the biomass-burning organic aerosol (BBOA) component, with the former being enhanced between 65 and 150% (for supersaturations ranging between 0.2 and 0.7%) with the arrival of the smoke plumes. Using multilinear regression of the PMF factors (BBOA, OOA-BB and OOA) and the observed hygroscopicity parameter, the inferred hygroscopicity of the oxygenated organic aerosol components is determined. We find that the transformation of freshly emitted biomass burning (BBOA) to more oxidized organic aerosol (OOA-BB) can result in a 2-fold increase of the inferred organic hygroscopicity; about 10% of the total aerosol hygroscopicity is related to the two biomass-burning components (BBOA and OOA-BB), which in turn contribute almost 35% to the fine-particle organic water of the aerosol. Observation-derived calculations of the cloud droplet concentrations that develop for typical boundary layer cloud conditions suggest that biomass burning increases droplet number, on average by 8.5%. The strongly sublinear response of clouds to biomass-burning (BB) influences is a result of strong competition of CCN for water vapor, which results in very low maximum supersaturation (0.08% on average). Attributing droplet number variations to the total aerosol number and the chemical composition variations shows that the importance of chemical composition increases with distance, contributing up to 25% of the total droplet variability. Therefore, although BB may strongly elevate CCN numbers, the impact on droplet number is limited by water vapor availability and depends on the aerosol particle concentration levels associated with the background. © 2016 Author(s).
Moschou D.,Greek National Center For Scientific Research |
Vourdas N.,Greek National Center For Scientific Research |
Kokkoris G.,Greek National Center For Scientific Research |
Papadakis G.,Greek National Center For Scientific Research |
And 3 more authors.
Sensors and Actuators, B: Chemical | Year: 2014
The design, fabrication and evaluation of a low-cost and low-power, continuous-flow microfluidic device for DNA amplification by polymerase chain reaction (PCR) with integrated heating elements, on a commercially available thin polymeric substrate (Pyralux® Polyimide), is presented. The small thermal mass of the chip, in combination with the low thermal diffusivity of the polymeric substrate on which the heating elements reside, yields a low power consumption PCR chip with fast amplification rates. A flow-through μPCR device is designed and fabricated using flexible printed circuit (FPC) technology on a foot-print area of 8 cm × 6 cm with a meandering microchannel realized at a very small distance (50 μm) above 3 independently operating resistive (copper) serpentine microheaters, each one defining one of the three PCR temperature zones. The 145 cm-long microchannel is appropriately designed to cross the alternating temperature zones as many times as necessary for the DNA sample to perform 30 PCR cycles. Numerical computations lead the design so that there is no thermal crosstalk between the 3 zones of our chip and indicate excellent temperature uniformity in each zone. In addition, the total power consumption during the chip operation is calculated to be in the order of a few Watts, verified experimentally by means of thermal characterization of our heaters. Thermal camera measurements also verified the excellent temperature uniformity in the three thermal zones. An external, home-made temperature control system was utilized to maintain the heater temperatures in the designated values (±0.2 °C). The PCR chip was validated by a successful amplification of a 90 base-pairs DNA template of the mouse GAPDH housekeeping gene within 5 min. © 2014 Elsevier B.V.
Myriokefalitakis S.,University of Crete |
Daskalakis N.,University of Crete |
Daskalakis N.,Institute of Chemical Engineering science ICE HT |
Mihalopoulos N.,University of Crete |
And 5 more authors.
Biogeosciences | Year: 2015
The global atmospheric iron (Fe) cycle is parameterized in the global 3-D chemical transport model TM4-ECPL to simulate the proton- and the organic ligand-promoted mineral-Fe dissolution as well as the aqueous-phase photochemical reactions between the oxidative states of Fe (III/II). Primary emissions of total (TFe) and dissolved (DFe) Fe associated with dust and combustion processes are also taken into account, with TFe mineral emissions calculated to amount to ∼ 35 Tg-Fe yr-1 and TFe emissions from combustion sources of ∼ 2 Tg-Fe yr-1. The model reasonably simulates the available Fe observations, supporting the reliability of the results of this study. Proton- and organic ligand-promoted Fe dissolution in present-day TM4-ECPL simulations is calculated to be ∼ 0.175 Tg-Fe yr-1, approximately half of the calculated total primary DFe emissions from mineral and combustion sources in the model (∼ 0.322 Tg-Fe yr-1). The atmospheric burden of DFe is calculated to be ∼ 0.024 Tg-Fe. DFe deposition presents strong spatial and temporal variability with an annual flux of ∼ 0.496 Tg-Fe yr-1, from which about 40 % (∼ 0.191 Tg-Fe yr-1) is deposited over the ocean. The impact of air quality on Fe deposition is studied by performing sensitivity simulations using preindustrial (year 1850), present (year 2008) and future (year 2100) emission scenarios. These simulations indicate that about a 3 times increase in Fe dissolution may have occurred in the past 150 years due to increasing anthropogenic emissions and thus atmospheric acidity. Air-quality regulations of anthropogenic emissions are projected to decrease atmospheric acidity in the near future, reducing to about half the dust-Fe dissolution relative to the present day. The organic ligand contribution to Fe dissolution shows an inverse relationship to the atmospheric acidity, thus its importance has decreased since the preindustrial period but is projected to increase in the future. The calculated changes also show that the atmospheric DFe supply to the globe has more than doubled since the preindustrial period due to 8-fold increases in the primary non-dust emissions and about a 3-fold increase in the dust-Fe dissolution flux. However, in the future the DFe deposition flux is expected to decrease (by about 25 %) due to reductions in the primary non-dust emissions (about 15 %) and in the dust-Fe dissolution flux (about 55 %). The present level of atmospheric deposition of DFe over the global ocean is calculated to be about 3 times higher than for 1850 emissions, and about a 30 % decrease is projected for 2100 emissions. These changes are expected to impact most on the high-nutrient-low-chlorophyll oceanic regions. © Author(s) 2015.
Bougiatioti A.,Georgia Institute of Technology |
Bougiatioti A.,National Technical University of Athens |
Stavroulas I.,University of Crete |
Kostenidou E.,Institute of Chemical Engineering science ICE HT |
And 12 more authors.
Atmospheric Chemistry and Physics | Year: 2014
The aerosol chemical composition in air masses affected by wildfires from the Greek islands of Chios, Euboea and Andros, the Dalmatian Coast and Sicily, during late summer of 2012 was characterized at the remote background site of Finokalia, Crete. Air masses were transported several hundreds of kilometers, arriving at the measurement station after approximately half a day of transport, mostly during nighttime. The chemical composition of the particulate matter was studied by different high-temporal-resolution instruments, including an aerosol chemical speciation monitor (ACSM) and a seven-wavelength aethalometer. Despite the large distance from emission and long atmospheric processing, a clear biomass-burning organic aerosol (BBOA) profile containing characteristic markers is derived from BC (black carbon) measurements and positive matrix factorization (PMF) analysis of the ACSM organic mass spectra. The ratio of fresh to aged BBOA decreases with increasing atmospheric processing time and BBOA components appear to be converted to oxygenated organic aerosol (OOA). Given that the smoke was mainly transported overnight, it appears that the processing can take place in the dark. These results show that a significant fraction of the BBOA loses its characteristic AMS (aerosol mass spectrometry) signature and is transformed to OOA in less than a day. This implies that biomass burning can contribute almost half of the organic aerosol mass in the area during periods with significant fire influence. © 2014 Author(s).
Tatoulis T.I.,University of Patras |
Zapantiotis S.,University of Patras |
Frontistis Z.,University of Patras |
Akratos C.S.,University of Patras |
And 6 more authors.
International Biodeterioration and Biodegradation | Year: 2016
In this work table olive processing wastewaters (TOPW) were treated by aerobic biological processes using indigenous microorganisms originating from TOPW, as well as the combination of two successive steps, i.e. aerobic biological treatment followed by electrochemical oxidation over a boron-doped diamond anode.In the single aerobic biological processes, experiments in suspended and attached growth reactors (trickling filters) were carried out using different TOPW feed concentrations of 5500 ± 350, 7500 ± 650 and 15,000 ± 1050 mg dissolved COD L-1. Two different operating modes were used to investigate the optimum performance of the filter, i.e. batch and SBR with recirculation. The latter mode with recirculation of 0.5 L min-1 led to high removal rates of dissolved COD and total phenolic compounds, up to 96.5% and 64.5%, respectively, for the initial COD concentration of 7500 mg dissolved COD L-1.Depending on the type and operating conditions of the bioreactors, residual COD ranged between a few hundred and a few thousand mg L-1, while decolorization could not be achieved even under the most favorable conditions. A biologically treated effluent with residual dissolved COD of 5100 mg L-1 was completely mineralized and decolorized at 187.5 mA cm-2 applied current density; complete removal of COD, color and total phenolic compounds was achieved in 180-240 min, 30-60 min and 30 min of electrochemical oxidation, respectively. Lower treatment times and current densities were needed to polish effluents with lower organic loads. © 2016 Elsevier Ltd.