Chemical composition and mass closure for PM10 aerosols during the 2005 dry season at a rural site in Morogoro,Tanzania

An intensive aerosol field campaign was carried out from 11 July to 11 August 2005 (dry season) at a rural site in Morogoro, Tanzania. The objectives were to determine the chemical composition of the atmospheric particulate matter (PM) and to examine to which extent the gravimetric PM mass can be explained by the measured aerosol components. Two low‐volume filter samplers were deployed, a PM₁₀ filter holder with two Whatman QM‐A quartz fibre filters in series and a Gent PM₁₀ stacked filter unit (SFU) sampler with coarse and fine Nuclepore polycarbonate filters. The samplers operated in parallel and a total of 51 parallel collections were made. All samples were analysed for the PM mass by weighing. Depending on the sampler type and/or collection substrate, further analyses were performed for 25 elements by particle‐induced x‐ray emission spectrometry, for major water‐soluble inorganic ions by ion chromatography, and for organic carbon and elemental carbon by a thermal—optical transmission technique. The PM₁₀ mass, as derived from the SFU samples, was, on an average, 46 ± 12 µg/m³. Aerosol chemical mass closure calculations were made for this PM₁₀ mass; eight aerosol components were considered and they explained 93% of the average PM₁₀ mass. Organic matter (OM) and crustal matter were the dominant aerosol components; they accounted for, on an average, 44% and 33%, respectively, of the PM₁₀ aerosol. The large contribution from OM is thought to originate mainly from the burning of biomass, especially of charcoal and agricultural residues. Copyright © 2009 John Wiley & Sons, Ltd.     

Elemental content of aerosol particles in an underground tram station

Particulate matter is an important air pollutant, especially in closed environments like a tunnel. The aim of this study was to determine the mass, black carbon, and elemental concentrations of particulate matter of two size fractions at an underground tram station in Hammarkullen, Gothenburg, Sweden. Samples were collected during June 2007 using a dichotomous virtual impactor separating the sampled aerosol particles into coarse (PM_(2.5–10)) and fine (PM_2.5) fractions. To minimize the possible influence of waiting passengers, the platform for trams going towards the suburb Angered was chosen. The elemental analysis of the samples, collected on Teflon filters, was carried out using energy dispersive x‐ray fluorescence (EDXRF) spectrometry, resulting in concentrations of 14 elements in most of the samples. Principal component analysis (PCA) was applied to identify possible sources for the elements in the particles. Owing to the tunnel environment, the elemental difference between the fine and coarse particle fractions was not as large as that in similar particles collected under normal outdoor ambient conditions. Likewise, the influence of the local weather situation was not significant. Particle content from the tram traffic was identified by PCA, with Fe being the major element in both coarse and fine particles. The particle mass concentration was higher in the tunnel compared to the ambient concentration at the monitoring station Femman in downtown Gothenburg. In some days, the mass concentration exceeded the Swedish daily ambient air quality standard of 50 µg m^?3, but it was lower than the limits in the environmental work act, 5 mg m^?3. Copyright © 2009 John Wiley & Sons, Ltd.     

Elemental composition of fine particulate matter (PM2.5) in Skopje,FYR of Macedonia

Aerosol samples were collected at an urban background site in Skopje, Former Yugoslavic Republic of Macedonia, during four measurement campaigns from December 2006 to October 2007. An impactor was used to collect particulate matter (PM_2.5) aerosol particles and the samples were analyzed for the concentrations of particulate mass, black carbon (BC), and 17 elements. The 12‐h average PM_2.5 concentrations varied in the range 10–140 µg m^?3 with the highest concentrations measured during wintertime pollution episodes and during the summer period. Pair‐wise correlations and crustal enrichment were studied and the data set was analyzed by factor analysis and positive matrix factorization. Major aerosol components were identified as mineral dust (main observed tracers Si, K, Ca, Ti, Fe, Sr, and Rb), combustion (BC, S, K, V, and Ni), traffic‐related aerosol (Pb and Zn), and secondary sulfate combined with mineral dust. Combustion sources dominated during wintertime and were likely due to heavy oil combustion, biomass burning, and other industrial activities within the city area. Mineral dust was observed throughout the year, but the concentrations peaked during the unusually hot and dry summer of 2007. It is concluded that Skopje suffers from serious air pollution due to central and residential heating, the transport sector, and industrial activities within the city, and contributions from mineral dust increase the PM_2.5 concentrations under dry periods. Topography and meteorological conditions aggravate the problems and make the air quality comparable with the conditions in other highly polluted cities in Southern Europe and worldwide. Copyright © 2011 John Wiley & Sons, Ltd.     

Concentrations and sources of trace elements in particulate air pollution,Dar es Salaam,Tanzania, studied by EDXRF

Trace elements in near‐ground atmospheric aerosols were investigated in Dar es Salaam, Tanzania. Particles were collected at two sites, one urban and one rural, during two months with different meteorological conditions. The samplers, dichotomous impactors, segregate the particles into two size fractions, fine (PM_2.5, d_a < 2.5 µ m) and coarse (2.5 < d_a < 10 µ m). A sharp cyclone was used to sample finer particles (PM₁, d_a < 1 µ m). Meteorological parameters were also examined at both sites. An EDXRF spectrometer, based on three‐axial geometry, was used for quantitative elemental analysis. Concentrations of elements heavier than phosphorus were determined. Also, the content of black carbon on the filters was measured with a reflectometer. The elemental concentrations were compared with respect to season and geographical location in the city. The levels of different species in Dar es Salaam were also compared with similar data from other African and European countries. This showed low values of Pb with respect to the size of the city and no legislation on the use of leaded petrol, that often is the main source of lead. High values of Cl were also found, as would be expected in a coastal city. The coarse particles in the air, originating from soil, had a different composition in Dar es Salaam than in Gaborone, Botswana, and the concentration of black carbon was higher than in other cities. On the basis of the data collected, source assignments were made and the following sources found; sea‐spray, soil, city road dust, biomass burning, industries and traffic. Comparing the concentrations of different elements in PM_2.5 and PM₁ revealed that black carbon, Zn, Pb, K and Br are present only in the smallest particles. Copyright © 2004 John Wiley & Sons, Ltd.     

Importance of flue gas cooling conditions in particulate matter formation during biomass combustion under conditions pertinent to pulverized fuel applications

Laboratory-scale experiments pertinent to pulverised fuel (PF) combustion are often carried out in drop-tube furnaces (DTFs) at air-fuel equivalence ratios and cooling rate for quenching flue gas that are much higher than those in PF boilers. This paper reports the effect of flue gas cooling conditions on the properties of PM with aerodynamic diameter of <10 µm (PM₁₀) from biomass combustion. This study considers four cooling rates (1000, 2000, 6000 and 20,000 °C/s) and two biomass feeding rates (0.05 and 0.25 g/min) that represents flue gases with significantly-different concentrations of inorganic vapours. The PSDs of PM₁₀ have a bimodal distribution with a fine mode within PM with aerodynamic diameter of <1 µm (PM₁) and a coarse mode within PM with aerodynamic diameter of 1–10 µm (PM_1–10). All experimental conditions produce PM₁₀ with similar PM₁ and PM_1–10 yields (～0.8 and ～1.6 mg/g_biomass, respectively) and similar coarse mode diameters (i.e. 6.863 µm). However, at a biomass feeding rate of 0.05 g/min, the fine mode diameter shifts from 0.022 to 0.077 µm when the cooling rate decreases from 20,000 to 1000 °C/s, indicating more profound heterogeneous condensation at a lower cooling rate. As the biomass feeding rate increases to 0.25 g/min, the fine mode diameter further shifts to 0.043 µm and at 20,000 °C/s but remained at 0.077 µm at 1000 °C/s though a clear shift of PSD to larger diameters is evident. These are attributed to enhanced heterogeneous condensation and coagulation of small particulates resulting from increased particle population density in hot flue gas. Chemical analyses show PM₁ contains dominantly volatile elements (i.e. Na, K and Cl) while PM_1–10 consists of mainly Ca. Similar trends are also observed for elemental PSDs and yields. It is also observed that slow cooling of hot flue gas leads to an increased yield of Cl in PM_1–10 due to enhanced chlorination of Ca species.     

Identification of elemental composition of PM2.5 collected in Makkah,Saudi Arabia,using EDXRF

Makkah city, Saudi Arabia, represents the most attractive place for religious tourism for Muslims all over the world. More than 15 million visitors come to the city per year, especially during Hajj (pilgrimage) and Ramadan seasons. Due to the lack of air quality assessment data for Makkah, measurement of different pollutants in Makkah is of great interest. In the present work, airborne particulate matter with aerodynamic diameter equal to or less than 2.5 µm (PM_2.5) has been collected from two different sites in the city, namely the Grand mosque and Al‐Shraie, from December 2012 to January 2014 covering the different seasons of the year. The average mass concentrations at the sites are comparable, 48 ± 28 µg/m³ and 53 ± 27 µg/m³ for the Grand mosque and Al‐Shraie sites, respectively. For quantitative elemental analysis, energy dispersive X‐ray fluorescence (EDXRF) spectrometry was used. Twenty elements (Si, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Se, Br, Rb, Sr and Pb) were quantified in the PM_2.5 samples. Fortunately, the obtained results of Pb and S are below the maximum allowance level of European commission for air quality. However, the average concentration of Ni in both sites is close to the maximum allowance level 20 ng/m³ and the Ni concentration reaches 25 ng/m³ at Grand mosque site during August 2013. Based on the Positive Matrix Factorization (PMF) analysis, four source factors were found, some signalling mixed sources, showing the main influence from mineral dust, anthropogenic/industrial sources and a marine source. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of the torrefaction on the emission of PM10 from combustion of rice husk and its blends with a lignite

Torrefaction is a competitive biomass pretreatment technology. However, its impacts on particulate matter (PM) formation during biomass combustion and co-combustion with coal have little been investigated. This work provides new data on the formation of PM₁₀ (particulate matter with aerodynamic diameters less than or equal to 10 µm) from combustion of raw (RH), torrefied rice husk (TRH) and their blends with a lignite (SZ). All combustion experiments were carried out on a drop-tube furnace at 1300 °C and in air. The combustion-generated PM₁₀ was collected by a Dekati low pressure impactor and classified into 14 size fractions for further quantification and characterization. The results indicate that, compared with the RH, the TRH-derived PM₁₀₊ (particle size above 10?µm) contains more alkalis, leading to a decrease in the production of PM₁ (particle size below 1?µm). During co-combustion, fuel interactions promote the transformation of alkali chlorides to aluminosilicates. A considerable amount of water-soluble Ca and P in PM₁ transforms to PM_1–10 (particle size between 1–10?µm). As a result, the production of PM₁ (on an ash basis) decreases while that of PM_1–10 increases. Co-combustion of coal with torrefied rice husk is found to generate less PM₁ but more PM_1–10 than that with raw rice husk.     

Mechanism on the contribution of coal/char fragmentation to fly ash formation during pulverized coal combustion

In this paper, the correlations between coal/char fragmentation and fly ash formation during pulverized coal combustion are investigated. We observed an explosion-like fragmentation of Zhundong coal in the early devolatilization stage by means of high-speed photography in the Hencken flat-flame burner. While high ash-fusion (HAF) bituminous and coal-derived char samples only undergo gentle perimeter fragmentation in the char burning stage. Simultaneously, combustion experiments of two kinds of coals were conducted in a 25?kW down-fired combustor. The particle size distributions (PSDs) of both fine particulates (PM_1-10) and bulk fly ash (PM₁₀₊) were measured by Electrical Low Pressure Impactor (ELPI) and Malvern Mastersizer 2000, respectively. The results show that the mass PSD of residual fly ash (PM₁₊) from Zhundong coal exhibits a bi-modal shape with two peaks located at 14?µm and 102?µm, whereas that from HAF coal only possesses a single peak at 74?µm. A hybrid model accounting for multiple-route ash formation processes is developed to predict the PSD of fly ash during coal combustion. By incorporating coal/char fragmentation sub-models, the simulation can quantitatively reproduce the measured PM₁₊ PSDs for different kinds of coals. The sensitivity analysis further reveals that the bi-modal mass distribution of PM₁₊ intrinsically results from the coal fragmentation during devolatilization.     

Ash cenosphere fragmentation during pulverised pyrite combustion: Importance of cooling

This paper as the first time in the field reports the direct experimental evidence for demonstrating the important role of cooling in ash cenosphere fragmentation using a simple but unique combustion system. The combustion system used pulverised pyrite (38–45 µm) for combustion in drop-tube furnace under designed conditions (gas temperature: 1000 °C; residence time: 1.2 s), which produced dominantly ash cenosphere particles or fragments. The combustion products were quenched under various cooling conditions (represented by nominal cooling rates of 6400–11,800 °C/s) for sampling. The results show that increasing cooling rate from 6400 to 11,800 °C/s substantially intensifies ash cenosphere fragmentation. Such enhanced ash cenosphere fragmentation leads to a significant shift in the particle size distribution of ash collected in the cyclone (>10 µm) to much smaller sizes. It also produces considerably more particulate matter (PM) with aerodynamic sizes less than 10 µm (i.e., PM₁₀) that consists of dominantly PM with aerodynamic sizes between 1 and 10 µm (i.e., PM_1–10) and some PM with aerodynamic sizes less than 1 µm (i.e., PM₁). It is further noted that the PM₁ is mainly PM with aerodynamic sizes between 0.1 and 1 µm (i.e., PM_0.1–1) and to a considerably lesser extent PM with aerodynamic sizes less than 0.1 µm (i.e., PM_0.1). Chemical analyses further show that both ash and PM samples contain only Fe₂O₃, indicating that complete consumption of sulphur and full oxidation of iron have been achieved during pulverised pyrite combustion under the conditions.     

Fundamental investigation into characteristics of particulate matter produced from rapid pyrolysis of biochar in a drop-tube furnace at 1300 °C

This paper reports the emission characteristics of leaf and wood biochar (LC500 and WC500) pyrolysis in a drop tube furnace at 1300 °C in argon atmosphere. The char yields at 1300 °C are ～ 65% and ～ 73% respectively for LC500 and WC500. Over 60% Mg, Ca, S, Al, Fe and Si are retained in char after pyrolysis at 1300 °C. The retentions of Na and K in the char from LC500 pyrolysis are lower than those in the char from WC500 pyrolysis due to release via enhanced chlorination as a result of much higher Cl content in LC500. Particulate matter (PM) with aerodynamic diameter of < 10 µm (i.e. PM₁₀) from LC500 and WC500 pyrolysis exhibits a bimodal distribution with a fine mode diameter of 0.011 µm and a coarse mode diameter of 4.087 µm. The PM₁₀ yield for LC500 pyrolysis is ～ 8.2 mg/g, higher than that of WC500 pyrolysis (～2.1 mg/g). Samples in PM_1-10 (i.e. PM with aerodynamic diameter 1 µm – 10 µm) are char fragments that have irregular shapes and similar molar ratio of (Na+K + 2Mg+2Ca)/(Cl+2S+3P) as the char collected in the cyclone. In PM₁ (i.e. PM with aerodynamic diameter < 1 µm), the main components in sample are inorganic species, and carbon only contributes to ～5% and ～8% the PM₁ produced from rapid pyrolysis of LC500 and WC500, respectively. Na, K and Cl are main inorganic species in PM₁, contributing ～ 98.8% and ～ 97.5% to all inorganic species. Na, K and Cl from rapid pyrolysis of biochar have a unimodal distribution with a mode diameter of 0.011 µm. In PM_1–10, Ca is the main inorganic specie, contributing to ～71.2% and ～65.3% to all inorganic species in PM_1–10 from pyrolysis of LC500 and WC500, respectively.     

Mechanistic investigation into particulate matter formation during air and oxyfuel combustion of formulated water-soluble fractions of bio-oil

This paper reports a systematic study on the formation of particulate matter with diameter of <10 µm (i.e., PM₁₀) during the combustion of two formulated water-soluble fractions (FWSFs) of bio-oil in a drop-tube-furnace (DTF) at 1400 °C under air or oxyfuel (30%O₂/70%CO₂) conditions. FWSF-1 was an organic-free calcium chloride solution with a calcium concentration similar to that in the bio-oil. FWSF-2 was formulated from the compositions of major organics in bio-oil WSF, doped with calcium chloride at the same concentration. The results suggest that similar to bio-oil combustion, the FWSF combustion produces mainly particulate matter with diameter of between 0.1 and 10 µm (i.e., PM_0.1–10). Since there are no combustibles in the organic-free FWSF-1, the PM is produced via droplet evaporation followed by crystallization, fusion and further reactions to form CaO (in air or argon) or partially CaCO₃ (under oxyfuel condition). With the addition of organics, FWSF-2 combustion produces PM₁₀ shifting to smaller sizes due to extensive break up of droplets via microexplosion. Sprays with larger droplet size produce PM₁₀ with increased sizes. The results show that upon cooling CaO produced during combustion in air can react with HCl gas to form CaCl₂ in PM_0.1. The predicted PSDs of PM₁₀ based on the assumption that one droplet produces one PM particle is considerably larger than experimentally-measured PSDs of PM₁₀ during the combustion of FWSFs, confirming that breakup of spray droplets takes place and such breakup is extensive for FWSF-2 when organics are present in the fuel.     

Effect of water vapour on particulate matter emission during oxyfuel combustion of char and in situ volatiles generated from rapid pyrolysis of chromated-copper-arsenate-treated wood

This paper reports the effect of water vapour on particulate matter (PM) during the separate combustion of in situ volatiles and char generated from chromated-copper-arsenate-treated (CCAT) wood at 1300 °C. Combustion of in situ volatiles produces only PM with aerodynamic diameter?<1?µm (i.e., PM₁), dominantly PM with aerodynamic diameter?<0.1?µm (i.e., PM_0.1). Water vapour could significantly enhance the nucleation, coagulation and condensation of fine particles and reduce the capture of Na and K by the alumina reactor tube via reduced formation of alkali aluminates, leading to increases in both yield and modal diameter of PM_0.1. Water vapour could also enhance char fragmentation hence increase the yield of PM with aerodynamic diameter between 1 and 10?µm (i.e., PM_1–10) during char combustion. For trace elements, during in situ volatiles combustion, volatile elements (As, Cr, Ni, Cu and Pb) are only presented in PM₁ and water vapour alters the particle size distributions (PSDs) but has little effect on the yields of these trace elements. During char combustion, As, Cr, Cu and Ni are present in both PM₁ and PM_1–10 while the non-volatile Mn and Ti are only present in PM_1–10. Increasing water vapour content increases the yields of As, Cr, Cu, Ni, Mn and Ti in PM_1-10 due to enhanced char fragmentation. During char combustion, water vapour also originates less oxidising conditions locally for enhancing As release, promotes the generation of gaseous chromium oxyhydroxides and inhabits the production of NiCl₂ (g), leading to increased yields of As and Cr and decreased yield of Ni in PM_0.1.     

Elemental characterization and source identification of the near-road PM2.5 using EDXRF in Chengdu,China

To characterize the elemental composition and source apportionment of aerosols in roadside area, particulate matters with aerodynamic diameter less than 2.5 μm (PM_2.5) were collected in close proximity to a road from September 2017 to February 2018 in downtown Chengdu, China. An energy-dispersive X-ray fluorescence spectrometer was used to quantify elemental constituents (Al, Si, S, K, Mn, Fe, Ni, Cu, Zn, As, and Pb) of PM_2.5 and was calibrated by in-house standards instead of commercial standards. The constructed calibration curves exhibited good linearity with all correlation coefficients greater than 0.98. The proposed calibration method proved to be reliable for the subsequent elemental analyses due to the satisfactory performance of u-score and precision that were validated by the certified reference materials (#2783). The results revealed that average PM_2.5 concentrations of 92.2 ± 45.6 and 113.2 ± 60.3 μg/m³ were respectively observed in autumn and in winter. The major trace elements identified were K, S, and Fe and the minor contributions were from Cu and As. Most crustal elements showed decline in winter except for K, and most anthropogenic elements showed increase in winter except for Ni. Using rotation factor analysis and cluster analysis based on the elemental dataset, four potential sources were identified: road dust, vehicular emissions, coal and biomass burning, and industrial emissions. This research will provide a better understanding of traffic-related PM_2.5 composition, and this can be used in the mitigation and prevention programs.     

Evaluation of the concentration of chemical elements in suspended particulate matter inside a small bronze and iron foundry industry,using a streaker sampler and EDXRF

The aim of this study was to determine and evaluate the temporal profiles of the concentration of chemical elements in the suspended particulate matter present inside a small bronze and an iron foundry industry. To collect the samples, we used a streaker sampler that separates particles with aerodynamic diameters smaller than 10 µm (PM₁₀) in two fractions: fine (particles with aerodynamic diameters less than 2.5 µm; PM_2.5) and coarse (between 2.5 µm and less than 10 µm; PM_10–2.5). The collection of samples was taken every 20 min during a total time of 8 and 5 h of molding and casting of bronze and iron, respectively. The samples collected in the form of strips on a filter (fine fraction) and an impactor (coarse fraction) were analyzed by the energy dispersive X‐ray fluorescence technique. In the excitation, an X‐ray tube with Mo target and Zr filter was used, operated at 30 mA/30 kV. For detecting the characteristic of X‐rays, a semiconductor Si(Li) detector was used, coupled to a multi‐channel spectrometer, with a 300 s excitation/detection time. The results of the temporal profiles of chemical element concentrations in coarse and fine fractions were discussed and compared with the maximum levels set by the Brazilian and international environmental agencies. Copyright © 2013 John Wiley & Sons, Ltd.     

Aerosol source (biomass,traffic and coal emission) apportionment in Lithuania using stable carbon and radiocarbon analysis*

In the present study, a combination of the stable carbon isotope ratio (¹³C/¹²C) with radiocarbon data (¹⁴C) allowed us to perform the aerosol source apportionment. Filter samples of PM₁ were collected during the warm and cold periods in rural and urban sites in Lithuania. The ¹⁴C/¹²C ratio of total carbon (TC) was measured using the single stage accelerator mass spectrometer quantifying of fossil and non-fossil derived aerosol emissions. The δ¹³C value was measured using an elemental analyser interfaced with an isotope ratio mass spectrometer. We have found that the highest fraction of contemporary carbon (f_c?=?0.82) was measured during a warm period in a rural location. A higher fraction of fossil fuel-derived carbon was observed for air masses transported from highly industrialized Western European regions during both seasons. Isotope mass balance calculations revealed that the traffic emissions composed 15 and 25?% in rural and urban sites, respectively, and did not change during either season. Input from coal-derived aerosol particles was estimated to be 15?% at an urban site during the cold period. The combination of the stable carbon isotope ratio with the radiocarbon data allowed us to distinguish coal, liquid fossil fuel combustion, and non-fossil derived aerosol particle emissions.     

Elemental analysis of particulate matter in a metal workshop and of biological samples from exposed workers

During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM_2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m³, respectively, whereas in the nearby city, daily PM_2.5 concentrations are on average 11 μg/m³. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded.     

Reduction effect of co-firing of torrefied straw and bituminous coal on PM1 emission under both air and oxyfuel atmosphere

Straw sample was torrefied at 260 °C and 300 °C in N₂, respectively, to prepare torrefied straw named as T-260 and T-300, and the reduction effect of co-firing straw or torrefied straw and steam coal on PM₁ is investigated. The combustion experiments were conducted in a high temperature drop tube furnace (DTF) at 1400 °C to collect the inorganic PM₁₀ for further analysis. Combustion atmosphere was air for all cases and 50% O₂/50% CO₂ (OXY50) for coal, T-260 and their blends of 1:1 and 4:1. The results show that all three biomass fuels show obvious emission reduction of PM with aerodynamic diameters of ≤?0.3?µm (PM_0.3) under both mix ratios. Reduction ratios of co-firing are overall higher at mix ratio of 1:1 than 4:1, and co-firing of T-260 or T-300 with coal shows higher reduction ratio than co-firing of straw. The higher ash content in torrefied straw leads to higher contents of alkali and alkaline earth metals (AAEM), which will further react with both Si and S during co-firing and coagulate into particles of larger sizes, leading to higher reduction ratios of PM_0.3 and unconspicuous reduction effects in PM_0.3–1 emitted from co-firing. During co-firing in oxyfuel atmosphere, a higher combustion temperature compared to air leads to an intensitive gasification, may resulting in effective and even higher reduction ratio in PM_0.3.     

Morphology and elemental behaviour in the alteration layer of borosilicate glass in simulated groundwater

To understand the behaviour of nuclear waste glass in groundwater, borosilicate glasses were placed in simulated groundwater for more than 200 days. The composition of the simulated groundwater was similar to that of the groundwater in Beishan (a potential nuclear waste site). The pH value of groundwater was adjusted to 7.5, and the ratio of the surface area of glass to the volume of the solution (SA/V) was set to 10?m^?1. Solutions and bulk glasses were characterised to obtain the elemental behaviour and surface morphology of the glass/solution interface, which was named the alteration layer. The mean thicknesses of the alteration layer were 5.16?±?0.11?µm and 11.67?±?0.28?µm at 70°C and 90°C, respectively. A thicker alteration layer was attributed to the lower surface activation energy of the glass and a high ion exchange between K⁺ and Na⁺ in the interface between the glass surface and the solution. For the elemental behaviour, mobile species B and Na were depleted, while K and Ca from the solution were enriched in the alteration layer due to ion exchange. Network species Si decreased in the layer, leading to the corrosion of the backbone of the glass; however, species Al increased, which implied that some [SiO₄] units were partially replaced by [AlO₄] units. In this work, glass in groundwater suffered much more intense corrosion than that in de-ionised water.     

Cosmogenic beryllium-7 in soil,rainwater and selected plant species to evaluate the vegetal interception of atmospheric fine particulate matter

Beryllium-7 is a radionuclide produced in the upper atmosphere by cosmic-ray spallation with ions of carbon, oxygen and nitrogen. It is one of radionuclides that can be used to trace the fine particulate matter of 2.5-µm diameter (PM_2.5) and smaller. In this work, ⁷Be was determined in leaves of 10 plant species collected from streets, parks and open land and in 5 consecutive rains over Alexandria, Egypt. ⁷Be levels were also measured in soil covered by each type of plant as well as in the nearest uncovered soil to be reference values to determine its intercepted amount and consequently PM_2.5. The lowest interception, 17.7?%, was by Ficus elastica L., while Ficus retusa L. intercepted about 45?%. Radiologically, the annual effective dose due to the usage of Thymelea hirsute plant leaves as a medicine and Nicotiana glauca Graham for smoking were 0.013 and 0.66 µSv, respectively. The observed levels in rainwater indicated that ⁷Be decreased consecutively from 3.1 Bq kg^–1 in the first rain to 0.71 Bq kg^–1 in the last one during the 2016/2017 rain season. The wet deposition of ⁷Be is less than 1?% of its total deposition on the ground.     

Determination of the concentration of aerosol particles in a vertical atmospheric column from satellite measurements of the spectral optical depth

We propose a method for fast retrieval of the inhalable particle concentration (PM_2.5 and PM₁₀) in a vertical atmospheric column from satellite measurements of the aerosol optical depth (AOD) without using a priori assumptions concerning the refractive index and the aerosol particle size distribution function. The method is based on a polynomial regression between PM_2.5, PM₁₀, and AOD at the wavelengths 466 nm and 644 nm, established from AERONET data. We have studied the sensitivity of the method to errors in the optical measurements and have estimated the errors in retrieval of PM_2.5 and PM₁₀ for different atmospheric situations. We carry out parametrization of the regressions on the value of the integrated air moisture content.