J.M. López

Spatial and temporal PAH concentrations in Zaragoza, Spain

The concentration of seven polycyclic aromatic hydrocarbons (PAH) associated with the atmospheric solid phase was measured in the Zaragoza (North-East of Spain) atmosphere using fluorescence spectroscopy in the synchronous mode (FS). The PAH results were reported for four different urban and suburban places, located within the city and during the period October 1999-September 2001. The PAH data obtained indicated the importance of local sources generated from urban/industrial areas. Although the PAH total concentration was quite similar in all the sampling sites, the main differences were due to Benzo[a]pyrene (BaP) and Coronene (Cor) concentrations, reaching the highest values in the sites associated with heavy traffic (trucks, lorries, etc.). The temporal evolution of atmospheric solid phase PAH concentrations indicated a seasonal trend. Higher PAH concentrations were found during colder seasons for the four sampling sites. The influence of environmental parameters such as temperature, rain, relative humidity, wind speed and direction on the PAH emissions was analyzed observing a positive correlation between the total PAH concentration and the relative humidity and a negative one with the temperature. With regard to the wind direction, higher PAH emissions were detected when wind was coming from an east and north-east direction. Wind from a north-westerly direction showed lower PAH emissions associated with the cierzo wind which provided cleaner air.

Comparison of receptor models for source apportionment of the PM10 in Zaragoza (Spain)

Receptor models are useful to understand the chemical and physical characteristics of air pollutants by identifying their sources and by estimating contributions of each source to receptor concentrations. In this work, three receptor models based on principal component analysis with absolute principal component scores (PCA-APCS), Unmix and positive matrix factorization (PMF) were applied to study for the first time the apportionment of the airborne particulate matter less or equal than 10microm (PM10) in Zaragoza, Spain, during 1year sampling campaign (2003-2004). The PM10 samples were characterized regarding their concentrations in inorganic components: trace elements and ions and also organic components: polycyclic aromatic hydrocarbons (PAH) not only in the solid phase but also in the gas phase. A comparison of the three receptor models was carried out in order to do a more robust characterization of the PM10. The three models predicted that the major sources of PM10 in Zaragoza were related to natural sources (60%, 75% and 47%, respectively, for PCA-APCS, Unmix and PMF) although anthropogenic sources also contributed to PM10 (28%, 25% and 39%). With regard to the anthropogenic sources, while PCA and PMF allowed high discrimination in the sources identification associated with different combustion sources such as traffic and industry, fossil fuel, biomass and fuel-oil combustion, heavy traffic and evaporative emissions, the Unmix model only allowed the identification of industry and traffic emissions, evaporative emissions and heavy-duty vehicles. The three models provided good correlations between the experimental and modelled PM10 concentrations with major precision and the closest agreement between the PMF and PCA models.

Source apportionment of atmospheric PM2.5-bound polycyclic aromatic hydrocarbons by a PMF receptor model. Assessment of potential risk for human health

One year sampling (2011-2012) campaign of airborne PM2.5-bound PAH was performed in Zaragoza, Spain. A source apportionment of total PAH by Positive Matrix Factorization (PMF) was applied in order to quantify potential PAH pollution sources. Four sources were apportioned: coal combustion, vehicular emissions, stationary emissions and unburned/evaporative emissions. Although Directive 2004/107/EC was fulfilled regarding benzo(a)pyrene (BaP), episodes exceeding the limit value of PM2.5 according to Directive 2008/50/EC were found. These episodes of high negative potential for human health were studied, obtaining a different pattern for the exceedances of PM2.5 and the lower assessment threshold of BaP (LATBaP). In both cases, stationary emissions contributed majority to total PAH. Lifetime cancer risk exceeded the unit risk recommended by the World Health Organization for those episodes exceeding the LATBaP and the PM2.5 exceedances for the warm season. For the cold season, the risk was higher for the LATBaP than for the PM2.5 exceedances.

Catalytic pyrolysis of wood biomass in an auger reactor using calcium-based catalysts

Wood catalytic pyrolysis using calcium-based materials was studied in an auger reactor at 450°C. Two different catalysts, CaO and CaO·MgO were evaluated and upgraded bio-oils were obtained in both cases. Whilst acidity and oxygen content remarkable decrease, both pH and calorific value increase with respect to the non-catalytic test. Upgrading process was linked to the fact that calcium-based materials could not only fix the CO2-like compounds but also promoted the dehydration reactions. In addition, process simulation demonstrated that the addition of these catalysts, especially CaO, could favour the energetic integration since a lowest circulation of heat carrier between combustor and auger reactor should be needed. An energy self-sustained system was obtained where thermal energy required for biomass drying and for pyrolysis reaction was supplied by non-condensable gas and char combustion, respectively.

Some inferences on the mechanism of atmospheric gas/particle partitioning of polycyclic aromatic hydrocarbons (PAH) at Zaragoza (Spain)

Gas/particle partitioning of pollutants is an important mechanism determining atmospheric processing and its impact to environmental and human health. In this paper, the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAH) has been studied with the aim of determining the main mechanism of PAH partitioning in Zaragoza (Spain) aerosols. To reach this goal, the ambient concentrations of PAH (gas and particle phase) collected in this city for one year period (2003-2004) have been analyzed. The partitioning between the particle and gas phases was studied according to three different models: the Junge adsorption model, the absorption into the organic matter model using the octanol-air (K(OA)) partition coefficient and the absorption into the organic matter plus the adsorption onto the soot carbon model using the soot-air (K(SA)) partition coefficients. Experimental gas/particle partition coefficients (K(P)) correlated well with the subcooled liquid vapour pressures (P(L)(0)) of PAH but with slopes higher than the expected value of -1. Experimental K(p) values were well fit to the modelled ones when, in addition to absorption into organic matter, adsorption onto the soot carbon was considered. It could be concluded that the main partition mechanism in Zaragoza aerosols was explained by adsorption onto the soot carbon. However, K(p) modelled values were affected by the different thermodynamic parameters related to soot types. The influence of the organic matter and elemental carbon fractions on the K(p) modelling was also studied. The different particle characteristics, local factors, the presence of non-exchangeable fraction and non-equilibrium were considered like main keys to explain deviations of the experimental K(p) values from predictions according to models.

Valorisation of forestry waste by pyrolysis in an auger reactor.

Pyrolysis of forestry waste has been carried out in an auger reactor to study the influence of operational variables on the reactor performance and the properties of the related products. Pine woodchips were used for the first time as raw material and fed continuously into the reactor. Ten experiments were carried out under inert atmosphere at: (i) different reaction temperature (1073, 973, 873, 823 and 773 K); (ii) different solid residence time (5, 3, 2 and 1.5 min); and (iii) different biomass flow rate (3.9, 4.8 and 6.9 kg/h). Results show that the greatest yields for liquid production (59%) and optimum product characterisation were obtained at the lowest temperature studied (773 K) and applying solid residence times longer than 2 min. Regarding bio-oil properties, GC/MS qualitative identification show that the most abundant compounds are volatile polar compounds, phenols and benzenediols; and very few differences can be observed among the samples regardless of the pyrolysis operating conditions. On the whole, experimental results demonstrate that complete reaction of forest woodchips can be achieved in an auger reactor in most of the experimental conditions tested. Moreover, this study presents the initial steps for the future scaling up of the auger reactor with the aim of converting it into a mobile plant which will be able to remotely process biomass such as energy crops, forestry and agricultural wastes to obtain bio-oil that, in turn, can be used as energy vector to avoid high transport costs.

Critical review on atmospheric PAH. Assessment of reported data in the Mediterranean basin

Polycyclic aromatic hydrocarbons (PAH) are a special group of atmospheric contaminants included in the persistent toxic substances (PTS) and also in the volatile organic compounds (VOC) groups. PAH are present in the atmosphere and its origin can be due to anthropogenic and/or biogenic activities. Their specific characteristics, high volatility, mutagenic and/or carcinogenic power, easily transportable for long distances with the wind undergoing photodecomposition processes, which imply reactions with solar light, NOx and O3, make them important contaminants despite of the fact that they are present at very low concentrations. These characteristics make some of the PAH to be listed by the Environmental Protection Agency (EPA) as priority pollutants with negative environmental impact due to their toxicity and they can affect very negatively the living being due to their carcinogenic/mutagenic character. Because of atmospheric PAH properties, it is not worth to study them in small areas because they do not know about natural or political borders and they can affect to a huge population. The growing use of transport and energy consumption, PAH have mainly anthropogenic origin, joined the growing cancer incident, must be the alarm to take these toxic organic contaminants into account and under control. This paper is a revision on the reported data on atmospheric PAH in the Mediterranean basin and was shown at the Workshop of the United Nations Environmental Protection (UNEP), meeting held in Athens, February 2002.

Study of the viability of the process for hydrogen recovery from old tyre oils

In this paper, an approach to the production of hydrogen from waste rubber is proposed. The process consists in performing the pyrolysis of waste rubber to produce the raw material (oils) that will be used in a gasification process with oxygen to obtain hydrogen. Tyre pyrolysis runs were experimentally performed to study the influence of temperature and reaction time on oils production, concluding that tyre pyrolysis requires low-severity process variables because at severe conditions, no improvements in conversion are obtained and a slight decrease in oils production is observed. In addition, thermodynamic calculations were performed to know the energy requirements for the oils gasification process. The equilibrium constants in terms of process pressure and temperature were calculated observing that all the processes are spontaneous and clearly lead to conversion products. The hydrogen recovery is calculated and from overall data, it is concluded that the production of hydrogen from old tyre seems to be a feasible process and a way of obtaining a clean energy for the future from a non-biodegradable waste material.

Sorbent characteristics influence on the adsorption of PAC: I. PAH adsorption with the same number of rings

Abstract The aim of this paper is to study the abatement of three-ring polycyclic aromatic hydrocarbons (PAHs) from hot gas emissions during energy generation in coal combustion. The three-ring PAHs are one of the most abundant PAH groups emitted during coal combustion. Four of them—Acenaphthene (Ac), Phenanthrene (Phe), Fluorene (Fu) and Anthracene (An)—have been listed by US EPA as priority pollutants. The three-ring PAH adsorption capacities are related to the textural properties of the 16 sorbents used in this work. Single and multiple linear regressions —principal component regression (PCR)—were applied in this study. The main conclusions reached are two: (1) the micropore volume is the most determinant parameter for these PAH removal; (2) the adsorption of three-ring PAH by sorbents from waste hot gas emissions is inversely proportional to their volatility: the lower the PAH volatility, the higher the adsorbent adsorption capacity. The adsorption isotherms show that Phe and An, both examples of PAHs with three aromatic rings, behave similarly. However, their behaviour differs from that of Ac and Fu, compounds where only two of their three rings exhibit an aromatic nature.

Seasonal variation of benzo(a)pyrene in the Spanish airborne PM10. Multivariate linear regression model applied to estimate BaP concentrations

The estimation of benzo(a)pyrene (BaP) concentrations in ambient air is very important from an environmental point of view especially with the introduction of the Directive 2004/107/EC and due to the carcinogenic character of this pollutant. A sampling campaign of particulate matter less or equal than 10 microns (PM10) carried out during 2008-2009 in four locations of Spain was collected to determine experimentally BaP concentrations by gas chromatography mass-spectrometry mass-spectrometry (GC-MS-MS). Multivariate linear regression models (MLRM) were used to predict BaP air concentrations in two sampling places, taking PM10 and meteorological variables as possible predictors. The model obtained with data from two sampling sites (all sites model) (R(2)=0.817, PRESS/SSY=0.183) included the significant variables like PM10, temperature, solar radiation and wind speed and was internally and externally validated. The first validation was performed by cross validation and the last one by BaP concentrations from previous campaigns carried out in Zaragoza from 2001-2004. The proposed model constitutes a first approximation to estimate BaP concentrations in urban atmospheres with very good internal prediction (Q(CV)(2)=0.813, PRESS/SSY=0.187) and with the maximal external prediction for the 2001-2002 campaign (Q(ext)(2)=0.679 and PRESS/SSY=0.321) versus the 2001-2004 campaign (Q(ext)(2)=0.551, PRESS/SSY=0.449).