Characterization of Dust Fallout with a Microscan Analyzer and SEM – EDX.

1. Characterization of Dust Fallout with a Microscan Analyzer and SEM – EDX. Shadung Moja : Pr.Sci.Nat. (Environmental Science) (University of South Africa) Earth Science & Climate Change Conference, Alicante, Spain, 16 – 18 June 2015

2. University of South Africa

3. Outline • Poor Air Quality (AQ) • Dispersion & Dilution of Air Pollutants • Evolution - AQ Legislations & Man. Plans in S.A. • Dust Fallout Sampling and Analyses • Results and Discussion • Future Plans

4. Poor Air Quality Fig. 1: Built up of biological, chemical or geological material in the lowest part of the atmosphere  troposphere. • Air pollutants – particulate matter (PM) & gases; haze • Troposphere – very unstable & turbulent layer of air • Composition is influenced mainly by ground based activities • PM – small particles (nm - m or liquid droplets) • PM Differ in size, shape and composition • PM pollution is a concern in Gauteng Province (mining; coal)

5. Interested in Particulate Matter? • They contribute to: • Health related problems • Visibility impairment • Soiling of buildings • Damaging effects on crops – food production • Contribute to climate variability • - some PM absorb heat from sun readily & lead to • localize warming – BC / soot • - other PM reflect sunlight & lead to localized cooling – • SO4-2, NO3-1]

6. Dispersion & Dilution of Air Pollutants - Horizontal Air Movement : wind (F fric. , FP , Facc.rot.) [irregular ground surfaces compress wind and generate mechanical turbulence; mixing and dilution are enhanced due to  wind speed; but, high building & valleys reduce these effects and give rise to enhanced localized pollution] - Vertically Air Movement : FH , F gr [compressibility of gases, cools upon expansion and heat upon compression. During the day, differential heating of the earth’s surface by the sun generate thermal turbulence. Warm air rises and is replaced by cold air, in this way vertical air currents are created and pollutants are dispersed. In winter and at night, atmospheric pressure drops, which give rise to little wind, less mixing, less dilution, enhanced localized pollution and impacts inversion effects]

7. Residence Time and Diffusion of Particles Coarse particles (PM10): • settle out readily under gravity within seconds / minutes / hours / days. Fine particles (PM2.5): • spread like a gas • can not be washed out by rain • settle latter (days / weeks / months / years) • through processes : enrichment / g-p conversion / coagulation.

8. Evolution - AQ Legislations & Man. Plans in S.A. • Atmospheric Pollution Prevention Act (APPA) Act 45 (RSA, 1965): controlled AP at sources, smoke free residential zones were declared, BC & SO2 ; limitations- fragmented source control, focuses on listed point sources, could not to link sources with impacts; lacked public involvement, poor access to information, etc. • Section 103 (Act No. 108) of the Constitution Republic of South Africa (CRSA, 1996): adopted,  our mindset; advocates for the environment that is not harmful to the health & wellbeing of residents; etc • National Environmental Management Act 107 (NEMA, 1998): encouraged prevention, minimisation and remediation of environmental pollution and degradation, advocated for a polluter pays principle, etc. • Air Quality Act 39 (AQA, 2004): shift AQ Man. responsibilities from national to provincial and local government; focused on receiving environment; involves the identification of priority areas, pollutants and sources; all point sources are addressed & not only scheduled / listed ones; encourages public participation; easy access to information. • Under AQA, South African National Standards (SANS-1929) were published by South African Bureau of Standards (SABS) Standards Division which specifies limit values for common air pollutants; EI (SANS-1929, 2011; DEAT, 2005).

9. Objectives To study the: • Mineral • Chemical and • Morphological characteristics of the fallout dust samples.

10. Study Area – City of Tshwane / Pretoria Fig. 2: Location of sampling sites (Modified - Tshwane, 2013)

11. Capital city & 2nd largest city, after Johannesburg, in Gauteng Province • Initially, we had 7 sampling sites, two were interfered with and we have no results (sites in North and West of City centres). • Site A (UNISA – Main Campus): South, near a paved parking lot, vegetation and a few meters from the R21 national road to OR Tambo International airport & N1 national road to Jo’burg. • Site B (UNISA – Main Campus): ~ 25 m from site A, near a bus stop, paved parking area and a beautiful garden. • Site C (UNISA): Background; up on the hill surrounded by natural vegetation; no or minimal input from anthropogenic sources. • Site D (Primary School premises – Sunnyside Suburb) within residential flats, ~ 1.5 km SE of city centre; near a shopping centre. • Site E (UNISA – City Centre Campus); within Pretoria CBD; near busy streets.

12. Methods: Sampling and Analytical • Passive sampling method used : mass concentration data • Micro particle analyzers : mineral content • SEM–EDX : image of particle (size, shape) and elemental distribution

13. Fig. 3: Passive sampling method and period • South African National Standard & American Standard for Testing Methods (SANS-1929, 2005; ASTM-1982) . • Crude open single buckets containing ¾ of DH2O and 10.0 ml NaClO, hoisted at a height of ~ 2.5 m. • Collection period: March – June 2013. (Kuhn and Loans, 2012)

14. Analytical Methods • Microscan Particle Analyzer - instrument settings: • Microscope UOP UB 100j • Most images captured with eye piece 10x and objective 10x. • Camera DCM310 5 megapixel CMOS chip • Programme ScopeTek 3.0 • Micrometer – Optical 5-50 µm. • Analyses done by DustWatch (Kuhn and Loans, 2013) • Mineral content • SEM-EDS Sample Prep. and instrument setting • Munktell filter papers with settled dust were mounted on the Al stubs. • Samples were coated with a thin layer (10 nm) of Iridium (Ir) using a vacuum-coating Quorum Q150T-ES unit (conductive layer eliminate the charging artifacts and increase the contrast and conductivity of the sample). • Focused electrons beam of 30 kV, a beam current of 1–20 Amps, X-ray detection limit of ~0.1% and an 8.5mm working distance of samples away from Si (Li) detector. • Images and elemental content

15. Mass Concentration Data Dust Fallout (mg/m2/day) Fig. 4: Monthly dust fallout distribution per site. (lowest standard levels in residential area 300 mg/m2/day)

16. Mineralogical Data Common minerals detected within the crustal material at all sites: • Quartz: sand, SiO2 (dominant mineral) • Haematite: oxides of Al, Fe; Fe2O3; Al2O3 • Feldspar: alumino-silicates, with Ca, Mg, Na and K as the balancing cations; (Na, K, Mg, Ca) AI2Si2O8 • Garnet: SiO4 • Aluminium silicates: AI2Si2O8 • Calcium hydroxide : Ca(OH)2

17. Site A • Particle size and shape: • Particle of interest  7 m triangular • Irregular edges • Smaller :  2 m • Elemental composition on • particle of interest: • Si, Ca, P, Al, S, Fe

18. Particle size & shape: • Particle of interest • ~ 5 m in length • Irregular shaped • Smaller : < 1.0 m • Round shaped group of particles • Elemental composition on particle of interest: • Ca, Ti, Si, S, Al, Fe, Cu

19. Particle size and shape: • Many large particles of variable shapes • Particle of interest ~ 5 m • Almost rectangular in shape • Elemental composition on particle of interest: • S, Cu, Fe, Si, Al, P

20. Site B • Particle size and shape: • Mixture of large, multi shaped particles • Particle of interest is long tubular in shape • > 10 m in length • Main chemical element on • surface of particle of • interest : • Si

21. Particle size and shape: • Many multi shaped • Particle of interest is diamond shaped • ~ 10 m in size • Main chemical element on • particle of interest : • Si

22. Site C • Particle size and shape: • Many large particles or irregular shapes • Particle of interest ~ 3 m long & ~ 1m wide • Rectangular shaped • Elemental composition on • particle of interest: • Si, Al, K, Mg, Cu, Fe, Ti

23. Particle size and shape: • Many large samples of variable shape • Particle of interest is almost spherically shaped • Diameter ~ 1.5 m size • Elemental composition on particle of interest: • Fe, K, Cu, Al, Si

24. Site D • Particle size and shape: • Several large particles • Particle of interest is oval to round shaped • ~ 1.0 m diameter size • Elemental composition on particle of interest: • Si, Al, Fe, P

25. Particle size and shape: • One long material, could be from plant • White coloured particle of interest  7 m • Almost triangular in shape • Elemental composition of particle of interest: • Si, Fe, Al, Cu

26. Site E • Particle size and shape: • Several shaped particles • Particle of interest ~ 5 m in size • Oval to round shaped • A smaller ( 1.0 m) round shaped particle is attached on top right side of large particle • Elemental composition on particle of interest: • Si, Al, Ti,Ca, K, Mg, Fe

27. Particle size and shape: • Particle of interest is almost triangular in shape • Each side ~ 5 m long. • Large material running across filter could be filter or plant material • Elemental composition on particle of interest: • Si, Al, K, Ca, Fe, Na, Mg, K

28. Conclusions • Minerals detected : SiO2 ; Fe2O3; Al2O3; (Na, K, Ca) AI2Si2O8; SiO4; AI2Si2O8 ; Ca(OH)2 • Dominant mineral: quartz or sand stones, SiO2 • Dominant elements: Si, Ca, P, Al, K, S, Fe, Cu, Ti, Mg, • Coarse particle size range: 2.5 – 10 m • Fine particle sizes ranges: < 1.0 to 2.5 m • Large irregular shaped: linked to crustal material • Small, round – oval shaped: linked to combustion sources • Probable contributors: • Main source: - crustal material – minerals, mining activities • Diesel burning emissions – S (vehicle, industries) • Industrial activities – Al, P, Fe, Cu, Ti (steel, alloys) • Coal burning activities – Cu, S

29. Next Phase • Include time resolved measurement for particulate matter on filter paper: . Active samplers: continuous, real-time . Physical, chemical, microbiological .pinpoint activities at particular times . source apportionment • BC, Hg • SO4-2, NO3-1 • Started to monitor O3 precursors: CH4, BTEX (benzene, toluene, ethylbenzene and xylene); NOX (NO2 + NO.) + CO • Gas anayses: GC, HPLC, GC-MS, HPLC-MS

30. Thanks for Listening • Acknowledgements • Mr Marks Sebaiwa – MSc student, data presented. • University of South Africa – sponsoring this trip. • Earth Science-2015 Conference Organizers – allowing me to • participate. mojasj@unisa.ac.za