Equilibration time scales of organic aerosol inside thermodenuders: Evaporation kinetics versus thermodynamics

The interpretation of thermodenuder (TD) data often relies on the assumption that thermodynamic equilibrium is reached inside the instrument. We modeled the evaporation of three organic aerosol types (adipic acid, α-pinene SOA and aged OA) inside a thermodenuder with a mass transfer model, and calculated equilibration time scales for these systems at realistic conditions. The equilibrium times varied from less than a second to several hours, decreasing with increasing aerosol concentrations, decreasing particle sizes, decreasing volatilities and increasing mass accommodation coefficients. The results indicate that generally TDs measure particle evaporation rates rather than equilibria, and time-dependent modeling of the evaporation is usually needed to interpret the data. Measurements at varying residence times and temperatures, on the other hand, are desirable to investigate the equilibration of the studied aerosol and decouple the kinetic effects from the effects caused by the thermodynamic properties of the aerosol. Organic aerosol is likely to be further from equilibrium under typical field conditions compared with laboratory data. When determining the aerosol properties from TD data, assuming incorrectly equilibrium results in under-prediction of the vaporization enthalpy of the evaporating species. Similar under-estimation is predicted if multicomponent aerosols are approximated with single-component properties.     

Simulating the fine and coarse inorganic particulate matter concentrations in a polluted megacity

A three dimensional chemical transport model (PMCAMx) is applied to the Mexico City Metropolitan Area (MCMA) in order to simulate the chemical composition and mass of the major PM₁ (fine) and PM_1–10 (coarse) inorganic components and determine the effect of mineral dust on their formation. The aerosol thermodynamic model ISORROPIA-II is used to explicitly simulate the effect of Ca, Mg, and K from dust on semi-volatile partitioning and water uptake. The hybrid approach is applied to simulate the inorganic components, assuming that the smallest particles are in thermodynamic equilibrium, while describing the mass transfer to and from the larger ones. The official MCMA 2004 emissions inventory with improved dust and NaCl emissions is used. The comparison between the model predictions and measurements during a week of April of 2003 at Centro Nacional de Investigacion y Capacitacion Ambiental (CENICA) “Supersite” shows that the model reproduces reasonably well the fine mode composition and its diurnal variation. Sulfate predicted levels are relatively uniform in the area (approximately 3 μg m^?3), while ammonium nitrate peaks in Mexico City (approximately 7 μg m^?3) and its concentration rapidly decreases due to dilution and evaporation away from the urban area. In areas of high dust concentrations, the associated alkalinity is predicted to increase the concentration of nitrate, chloride and ammonium in the coarse mode by up to 2 μg m^?3 (a factor of 10), 0.4 μg m^?3, and 0.6 μg m^?3 (75%), respectively. The predicted ammonium nitrate levels inside Mexico City for this period are sensitive to the physical state (solid versus liquid) of the particles during periods with RH less than 50%.     

Volatile halogenated organics in swimming pools

This survey undertaken in Greece (Mytilene town) has shown that Volatile halogenated organics (VHO) are present in swimming pool water. Analysis was performed by purge‐and‐trap (PAT) gas chromatographic (GC) technique and samples from two public indoor swimming pools in Mytilene were analyzed for VHO. Water samples were collected every week for a period of three months, and have shown the occurrence of chloroform, dichlorobromomethane, chlorodi‐bromomethane, bromoform (all four are trihalomethanes [THMs]), as a result of the chlorination and the occurrence of tetrachloroethylene and 1,1,1,2‐tetrachloroethane is assigned to their introduction as impurities during the process treatment of water. The levels of concentrations ranged from 4.0 to 26.0 μg/1 for chloroform, from 0.26 to 7.0 μg/1 for dichlorobromomethane, from 0.5 to 3.0 μg/1 for chlorodibromomethane, from 0.07 to 0.9 μg/1 for bromoform, from no detectable levels to 0.07 μg/1 for tetrachloroethylene and from no detectable levels to 0.2 μg/1 for 1,1,1,2‐tetrachloroethane.     

Formation of organic by-products during chlorination of natural waters

Natural water from six sources in Mytilene, Greece, was chlorinated in order to identify and quantify some of the organic by-products formed. The compounds examined were trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, chloral hydrate and chloropicrin. The factors tested were time and chlorine dose. The presence of bromide ion in some of the waters studied resulted in significant changes in the by-product speciation, with enhanced brominated species formation. In addition, UV absorbance, measured at three wavelengths, led to correlation of organic matter content with the concentrations of by-products produced. The species formed, varying among different water sources, increased with increasing chlorine dose. Most of the species also increased with increasing contact time, although there were some exceptions due to hydrolysis reactions.     

Advanced multi-perspective computer simulation as a tool for reliable consequence analysis

Major accidents involving hazardous materials are a crucial issue for the chemical and process industries. Many accidental events taken place in the past showed that dangerous substances may pose a severe threat for people and property. Aiming at loss prevention, a series of actions have been instituted through international regulations concerning hazardous installations safety preparedness. These actions involve efficient land-use planning, safety studies execution, as well as emergency response planning drawing up. A key factor for the substantial consideration of the above is the effective prediction of possible accident forms and their consequences, for the estimation of which, a number of empirical models have been developed so far. However, (semi-)empirical models present certain deficiencies and obey to certain assumptions, thus leading to results of reduced accuracy. Another approach that could be used for this purpose and it is discussed in this work, is the utilization of advanced computational fluid dynamics (CFD) techniques in certain accident forms modeling. In particular, composite CFD-based models were developed for the simulation of several characteristic accident forms involving isothermal and non-isothermal heavy gas dispersion, confined and unconfined explosion in environment of complex geometry, as well as flammable cloud fire. The simulation cases were referred to real-scale trials allowing us to conclude about the validity of the quantitative results. Comparisons of the computational predictions with the experimental observations showed that obtained results were in good agreement with the experimental ones, whereas the evaluation of statistical performance measures proved the simulations to be statistically valid.     

Life Cycle Assessment for biodiesel production under Greek climate conditions

The aim of this paper is to understand and to model the environmental performance of biodiesel produced by various Greek raw materials under current conditions. Three energy crops (rapeseed, sunflower and soybean) have been studied, with regard to their levels of biodiesel productivity. Throughout the entire process, current Greek climatic conditions and cultivation parameters have been taken into account. At the stage of assessment, we conclude that the environmental impacts per crop area indicate that soybean has the lowest environmental impacts. However, by assessing the results per quantity of produced biodiesel, the crop with the minimum environmental impacts is sunflower. This paper shows that environmental benefits from biodiesel have better results, compared to conventional diesel, thus leading to the conclusion that it is feasible to succeed improved environmental performance.     

Multiple regression models: a methodology for evaluating trihalomethane concentrations in drinking water from raw water characteristics

The presence of trihalomethanes (THMs) in drinking water has attracted the attention of both researchers and professionals, because of the harmful effects of these substances on human health. A multiple regression model was developed to estimate THM concentrations in finished drinking water, using data from the Menidi Treatment Plant of Athens. A number of routinely measured characteristics--including chlorine dose, chlorophyll a, temperature, pH and bromide--of raw water, were used to generate a reliable methodology for predicting both total THM and individual species concentrations. Seasonality effects were also considered during the analysis. In general, these models were found to give acceptable fits, estimating accurately lows and highs over the annual cycle.     

Assessment of the Virological Quality of Marine and Running Surface Waters in NW Greece: A Case Study

The virological quality of surface marine and running water samples collected from Igoumenitsa gulf and Kalamas river (NW Greece) was assessed from October 2012 to September 2013. Sampling sites were exposed to different land and/or anthropogenic effects. Seawater samples were collected monthly from five sampling stations (new harbor, old harbor, wastewater treatment plant outlet, protected Natura area, Drepano beach). Viral targets included human adenoviruses (hAdVs), as index human viruses, while noroviruses (NoVs) and hepatitis A virus (HAV) were also studied. Kalamas river samples were collected seasonally, from three sampling stations (Soulopoulo, Dam, Sagiada-estuaries), while viral targets included also porcine adenoviruses (pAdVs) and bovine polyoma viruses (bPyVs), as additional index viruses. All water samples were analyzed for standard bacterial indicators, as well. Physicochemical and meteorological data were also collected. Based on the standard bacterial indices, both sea and river water samples did not exceed the limits set according to Directive 2006/7/EU. However, positive samples for hAdVs were found occasionally in all sampling sites in Igoumenitsa gulf (23.3%, 14/60) showing fecal contamination of human origin. Moreover, HAV was detected once, in the sampling site of the old port (at 510 GC/L). Most of the Kalamas water samples were found positive for hAdVs (58.3%, 7/12), while human noroviruses GI (NoVGI) (8.3%, 1/12) and GII (NoVGII) (16.7%, 2/12) were also detected. HAV, pAdVs, and bovine polyomaviruses (bPyVs) were not detected in any of the analyzed samples. No statistically significant correlations were found between classic bacterial indicators and viral targets, nor between viruses and meteorological data. Overall, the present study contributed to the collection of useful data for the biomonitoring of the region, and the assessment of the overall impact of anthropogenic activities. It provided also valuable information for the evaluation of the risk of waterborne viral infections and the protection of public health. It was the first virological study in the area and one of the few in Greece.     

The war in Kosovo

During the operation “Allied Force” in the spring of 1999, the burning or damaging of industrial and military targets in the Former Republic of Yugoslavia resulted in the release of a large number of chemicals into the atmosphere. The releases contained not only conventional air pollutants, but also Semi-Volatile Organic compounds (SVOs) which are known to be hazardous to health. Under suitable meteorological conditions, these chemicals can be transported across borders over large distances. In this paper, an analysis of measurements and dispersion calculations is presented which provides evidence of pollutant transport from the conflict area to Greece. The measuring program was carried out in Xanthi, Greece and included aerosol sampling and subsequent analysis for the determination of the concentration of SVOs including dioxins, furans, PCBs (PolyChlorinated Biphenyls), PAHs (Polycyclic Aromatic Hydrocarbons) and organic phthalates. This paper focuses on two episodes of organic phthalates that were observed during the conflict period. Pollution measurements are interpreted by means of air trajectories and dispersion calculations. For this purpose, the HYSPLIT_4 (HYbrid Single-Particle Langrangian Integrated Trajectory) modeling system is used to calculate the dispersion of toxic substances.     

Biodecolorization of the azo dye Reactive Red 2 by a halotolerant enrichment culture.

The decolorization of the azo dye Reactive Red 2 (RR2) under anoxic conditions was investigated using a mesophilic (35 degrees C) halotolerant enrichment culture capable of growth at 100 g/L sodium chloride (NaCl). Batch decolorization assays were conducted with the unacclimated halotolerant culture, and dye decolorization kinetics were determined as a function of the initial dye, biomass, carbon source, and an externally added oxidation-reduction mediator (anthraquinone-2,6-disulphonic acid) concentrations. The maximum biomass-normalized RR2 decolorization rate by the halotolerant enrichment culture under batch, anoxic incubation conditions was 26.8 mg dye/mg VSSxd. Although RR2 decolorization was inhibited at RR2 concentrations equal to and higher than 300 mg/L, the halotolerant culture achieved a 156-fold higher RR2 decolorization rate compared with a previously reported, biomass-normalized RR2 decolorization rate by a mixed mesophilic (35 degrees C) methanogenic culture in the absence of NaCl. Decolorization kinetics at inhibitory RR2 levels were described based on the Haldane model (Haldane, 1965). Five repetitive dyeing/decolorization cycles performed using the halotolerant culture and the same RR2 dyebath solution demonstrated the feasibility of biological renovation and reuse of commercial-strength spent reactive azo dyebaths.