Development of analytical methodologies for the monitoring of the atmospheric particulate matter

The present research project focused on the development of analytical methodologies for the monitoring of the atmospheric Particulate Matter. Particulate matter (PM) is one of the main pollutants exceeding the ambient standards for air quality in Europe. In Italy, the mass concentration standards are overcome many times per year, mainly due to the unfavourable meteorological conditions (especially in the Po Valley regions) and to the transportation of the air masses coming from the Sahara Desert (Southern and Central regions). The direct and indirect influence of the PM on human health, global climate change and reduced visibility have led to numerous studies in the last past decades, focusing upon its complex composition, toxicology and the source attribution. The particulate matter is constituted by an heterogeneous mix of components, characterized by a variable chemical composition and different chemical-physical properties that greatly influence its deposition and distribution. For these reasons nowadays it is still very difficult to develop efficient abatement strategies to protect both human health and environment. To achieve these specific objectives it is necessary to focus on some issues that are still not resolved, by taking advantage of both the analytical chemistry and the statistical methods. One of the “open” issues is the determination of water content in PM. Water plays an important role in the formation of the secondary species starting from gaseous precursors. It is well known that these species undergo gas-particle equilibria influencing the sampling phase and altering the results of the monitoring campaigns but, given the great variability of the measured concentrations, to date, a clear interpretation of these processes has still not been found. More information could be obtained by determining the water content in PM. Moreover, the knowledge of the water amount sampled together with the atmospheric particles on appropriate media could be very useful to establish the water influence on the PM mass concentration as well. Till now, the water determination has been carried out mostly by indirect methods estimating the water adsorbed on not-sampled particles. During the present project a simple method to determine water in PM samples has been optimized and validated, based on the Karl-Fisher theory. The potentialities of the thermal desorption were also explored to study the different types of water linked to the particles. After the validation, this methodology has been then applied to real PM samples collected in geographical areas characterized by several emission sources (traffic, industries, etc.), demonstrating that water is a relevant component of the PM and it influences in a significant way the PM mass concentration especially in samples very rich of secondary inorganic compounds or natural sand. Moreover the type of water present in the atmospheric particles is strictly dependent on the PM chemical composition. The second part of this project concerned the measurements of the PM at high temporal resolution. Sampling and analysis of PM in real time at high time resolution allow to have some precious information about the temporal variability of the atmospheric pollutants’ concentration, that usually are lost with the 24-hours sampling time. Our attention was focused on a new device able to sample and analyze in real time the atmospheric inorganic ions, the Particle Into Liquid Sampler coupled with the Ion Chromatography (PILS-IC). The instrument in its original configuration is affected by some limits, the high detection limit values that make difficult to apply it in low polluted areas and the low time resolution due to the analysis of the solution contained in the chromatographic loop only at the injection time into the column. These limits were solved modifying the original instrumental configuration, inserting a pre-concentration system. The new optimized system was then validated and applied to a monitoring campaign. The results have been compared with those obtained by other analytical techniques aimed to measure the same species, showing good performance of the new system. The data obtained by using this system were also useful to understand the chemical form in which the ions were present in the atmosphere at the sampling time and allowed to isolate some hot spot pollution events. The last part of the present project has been carried out at the University of Birmingham (United Kingdom) under the kindly supervision of Prof. Roy M.Harrison and focused on the traceability of the PM emission sources. The knowledge of the emission sources is one of the main objectives in the PM studies, as it is necessary for developing efficient abatement strategies. The Source Apportion techniques are very helpful to reach this objective. In particular, the Positive Matrix Factorization receptor model (PMF) was applied to identify and quantify the PM sources at an industrial area of the Po Valley. This model is very useful to manage large databases coming from the chemical analysis of PM collected during long monitoring campaigns and is able to determine the main PM sources by looking at the correlation of the variables (measured species) at the monitored receptor sites. The variables to process by the model have been chosen with the support of a detailed chemical characterization of PM using a fractionation methodology based on the elemental solubility. The main PM sources in the Po Valley have been identified with the secondary nitrate and the biomass burning, although the industrial nature of the monitored area. Because of the wideness of the topics they will be treated in separated chapters

Qualitative and quantitative determination of water in airborne particulate matter

Abstract. This paper describes the optimization and validation of a new simple method for the quantitative determination of water in atmospheric particulate matter (PM). The analyses are performed by using a coulometric Karl-Fisher system equipped with a controlled heating device; different water contributions are separated by the application of an optimized thermal ramp (three heating steps: 50–120 °C, 120–180 °C, 180–250 °C). The analytical performance of the method was verified by using standard materials containing 5.55% and 1% by weight of water. The recovery was greater than 95%; the detection limit was about 20 μg. The method was then applied to NIST Reference Materials (NIST1649a, urban particulate matter) and to real PM10 samples collected in different geographical areas. In all cases the repeatability was satisfactory (10–15%). When analyzing the Reference Material, the separation of four different types of water was obtained. In real PM10 samples the amount of water and its thermal profile differed as a function of the chemical composition of the dust. Mass percentages of 3–4% of water were obtained in most samples, but values up to about 15% were reached in areas where the chemical composition of PM is dominated by secondary inorganic ions and organic matter. High percentages of water were also observed in areas where PM is characterized by the presence of desert dust. A possible identification of the quality of water released from the samples was tried by applying the method to some hygroscopic compounds that are likely contained in PM (pure SiO2, Al2O3, ammonium salts, carbohydrates and dicarboxylic acids) and by comparing the results with those obtained from field samples

Improved time-resolved measurements of inorganic ions in particulate matter by PILS-IC integrated with a sample pre-concentration system

A particle-into-liquid sampler coupled with ion chromatograph (PILS-IC) for the on-line measurement of inorganic ions has been modified by the insertion of two ion-exchange pre-concentration cartridges that enrich the sample during the period of the IC analysis. The limits of detection of the modified instrument were 10-15 times lower and the time coverage 24 times higher (from 2 to 48 min per hour) than those of the original PILS-IC setup. The instrumental performance in terms of recovery and break-through volume from the cartridges was satisfactory. The modified PILS-IC was operated in comparison with a diffusion denuder line and with a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) during a short intensive measurement period organized in the framework of the European Monitoring and Evaluation Programme (EMEP), a co-operative program for monitoring and evaluation of the long-range transmission of the air pollutants in Europe. The instrument showed a quantitative response in agreement with the results of the diffusion lines, and an ability to trace fine concentration variations not so different from the performance of the much more complex HR-TOF-AMS. From the time patterns of the ion concentrations measured by the modified PILS-IC, it was possible to obtain useful information about the variations in the air quality and in the strength of the particulate matter sourc

sources of pm in an industrial area comparison between receptor model results and semiempirical calculations of source contributions

Source apportionment of PM_(10) and PM_(2.5) samples collected in an industrial area of the Po Valley was performed by using the Positive Matrix Factorization (PMF) model and a semiempirical calculation of five macro-source contributions. Samples were collected during four monitoring periods, January-February 2011, June 2012, January-February 2012, May-June 2012, resulting in a total of 720 samples (360 for PM_(10) and 360 for PM_(2.5)). PMF variables included major elements, ions, elemental carbon and organic compounds and minor and trace elements. In order to increase the selectivity of minor and trace elements as source tracers, a chemical fractionation methodology based on the elemental solubility was employed; it was thus possible to include the extractable, the residual or both thefractions of the minor and trace elements in the database. PMF resolved six factors for PM_(10) (crustal matter, marine aerosol, industry, secondary/oil combustion, secondary nitrate/biomass burning/exhaust particles, brake/tyre wear/re-suspended road dust) and seven factors for PM_(2.5) (crustal matter, marine aerosol, industry, secondary nitrate, biomass burning, other secondary components, secondary sulphate/oil combustion). Mixing properties of the lower atmosphere were monitored by using natural radioactivity. The lack in the separation of some sources was shown to be due to their co-variation during periods of high atmospheric stability in the cold months. Seasonal variations of the source contributions were evaluated and discussed. PMF results were compared with those obtained by a semiempirical calculation method in which analytical results are grouped into five macro-sources (crustal matter, marine aerosol, secondary inorganic compounds, combustion products from vehicular emissions and organics). Although similar trends in the temporal variation of the main PM sources were obtained, the absolute magnitude of the concentrations varied in some cases, especially for crustal matter and marine aerosol sources

Assessing the contribution of water to the mass closure of PM10

The data obtained during a number of field studies aimed at determining the chemical composition of atmospheric particulate matter (PM) have shown that the measurement of the main PM components (main elements, ions, elemental carbon, organic carbon) was generally sufficient to obtain a reasonable mass closure. Notwithstanding, a wide gap between PM mass concentration and reconstructed mass was observed in two peculiar environmental conditions: desert dust intrusion and severe atmospheric stability episodes characterized by very high ammonium nitrate concentration. In these two cases, the mass closure improved significantly by adding the concentration of PM-bound water. Water was determined by using a coulometric Karl-Fisher system equipped with a controlled heating device; the method was able to separate different water contributions released in different temperature ranges from 50 to 250 °C. In our field studies the amount of water associated to ammonium salts in winter stability conditions was mostly dependent on ammonium nitrate concentration and constituted up to 22% of the total PM10 mass; the specific water contribution linked to ammonium salts (released in the temperature range 180-250 °C) constituted up to 30% of the ammonium nitrate mass. It was confirmed that in these extreme conditions quartz and Teflon filters behave differently: when measured on quartz filters, PM concentration was lower than on Teflon, the mass closure was satisfactory and the concentration of water was presumably very low. In the case of desert dust episodes, water was up to 10% of total PM10 mass; the specific water contribution linked to desert dust (released in the temperature range 100-180 °C) constituted about 5% of the mass of soil components. In other environmental situations, such as urban environments, marine atmosphere and rural areas, the concentration of PM-bound water was below 2-3 μg/m3

Multi-elemental analysis of particulate matter samples collected by a particle-into-liquid sampler

Time-resolved elemental analysis of particulate matter (PM) helps in the reliable identification of specific source tracers and study of mixing dynamics in the lower atmosphere. In this study, a new flow system (FS) for the introduction of samples into the inductively coupled plasma mass spectrometry (ICP-MS) instrument, which consists of on-line filtration and acidification of samples collected by a particle-into-liquid sampler (PILS), was optimised. Through this system, the limits of detection and quantification were significantly reduced, compared to those of ICP-MS analysis of samples collected by a PILS after off-line filtration. This makes it possible to conduct multi-elemental analysis of the samples collected by the PILS without any pre-treatment. The optimised FS-ICP-MS system was directly coupled with a PILS in order to study the profiles of some selected indoor and outdoor sources of PM (cigarette smoking, incense burning, brushwood burning, pellet burning, and road dust resuspension). The application of the FS-ICP-MS system for off-line elemental analysis of samples collected by a PILS during spot events in indoor and outdoor environments allowed us to verify the suitability of this system for the time-resolved (10 min) analysis of PM. The results indicate a significant increase in the indoor concentrations of some toxic elements (such as, Cd, and Pb) during the cleaning operation of domestic biomass burning systems (pellet stoves and thermo-fireplaces). Similarly, increases in the concentration of these elements were also observed in the outdoor environment during spot events of agricultural waste combustion, an illegal activity frequently practiced in many rural areas

Determinazione qualitativa e quantitativa dell’acqua in campioni di particolato atmosferico

E‟ ben noto che l‟acqua interagisce con varie componenti igroscopiche del particolato atmosferico (PM), alterando una serie di caratteristiche chimico-fisiche delle particelle (massa e dimensione delle particelle, posizione degli equilibri solido-vapore dei sali di ammonio etc.). La determinazione quantitativa dell‟acqua contenuta nel PM è stata affrontata in diversi studi, la maggior parte dei quali ha riguardato la misura differenziale della massa delle particelle prima e dopo l‟esposizione ad atmosfere ad umidità controllata. Questi studi dimostrano che la quantità di acqua adsorbita dipende dalle dimensioni e dalla composizione chimica del PM, ma non sono ad oggi disponibili informazioni sulla tipologia e sulla forza delle interazioni. Questo lavoro ha riguardato l‟ottimizzazione e la validazione di un metodo per la determinazione qualitativa e quantitativa dell‟acqua, idoneo per la successiva applicazione a campagne di monitoraggio intensive. Il metodo si basa sull‟impiego di un sistema Karl-Fisher coulometrico dotato di un forno a temperatura programmabile e permette la separazione di differenti contributi di acqua [1] rilasciati in diversi intervalli di temperatura (figura 1). L‟applicazione del metodo ad una serie di campioni di PM10 collezionati in diverse aree geografiche ha permesso di evidenziare una notevole variabilità dei risultati in funzione della composizione chimica del PM. Nella maggior parte dei campioni, la quantità di acqua è risultata pari al 3-4% della massa totale, ma in campioni la cui composizione chimica è dominata dai sali secondari inorganici e dal carbonio organico o dalla presenza di polveri sahariane, tale valore sale fino a raggiungere valori superiori al 10%. E‟ stata inoltre evidenziata una notevole influenza della composizione chimica del campione sul profilo termico della curva. Allo scopo di tentare un‟identificazione del tipo di acqua rilasciata in ciascun intervallo di temperatura, i profili ottenuti sono stati confrontati con quelli di alcuni composti igroscopici possibilmente presenti nel PM, come SiO2, Al2O3, NaCl, sali di ammonio e carboidrati

Characterization of natural adsorbent material for heavy metal removal in a petrochemical site contamination

Despite of over 25 years of intensive technological efforts, sub-surface environment cleanup still remains a challenge, especially in case of highly contaminated sites. In this context, ion exchanger technologies could provide simple and effective solutions for heavy metal removal in water treatment. The challenge is finding exchanger able to operate in extreme natural environments or in situations involving natural interfering species such as inorganic ions. In this paper we exam the use of natural zeolites as versatile exchanger for environmental protection of coastal refinery's groundwater against pollution of Ni, Cd, Pb. The influence of particle diameter on clinoptilolite performances toward heavy metal removal is studied. Also, we evaluate the exchanger activities in condition of high ionic strength, commonly present in groundwater located under coastal petrol industries. The obtained results confirmed that ion exchangers could provide an effective solutions for remediation in c