Elemental Analysis of Mosses and Lichens from the Western Cape (South Africa) using INAA and ICP-MS

Ndlovu, Ntombizikhona Beaulah (2016-12)

Thesis (MPhil)--Stellenbosch University, 2016

Thesis

ENGLISH ABSTRACT : Mosses and lichens, analyzed by nuclear and related techniques, have been extensively used as biomonitors in the European countries to provide information about air quality, but not in South Africa. The aim of this project was to infer air pollution levels in the Western Cape, South Africa by collecting and analysing mosses and lichens for chemical content using nuclear and related techniques. Since they lack a root system, which causes them to trap chemicals from air only through wet and dry deposition, mosses and lichens serve as good biomonitors of air pollution. These plants possess efficient accumulation capacity for many air pollutants (heavy metals and other trace elements). Three major causes of atmospheric pollution are industrialisation, urban growth and the wide-spread use of vehicles. Studying air pollution with plants, instead of the commercial air filters is a simple but effective method to estimate levels of air pollutants. Biomonitoring can be performed using naturally growing (indigenous) biomonitors collected in the area under investigation. This is known as passive biomonitoring. The steady global increase in the use of active biomonitoring, whereby biomonitors are collected from relatively pristine habitats and transplanted to different environments, is due to the scarcity or total absence of native biomonitors in certain environments e.g. large cities with heavy technogenic load and industrial regions as well as in arid areas. Hence active biomonitoring was also used in this study to assess elemental content of atmospheric pollution due to urbanisation, industrialisation and vehicle use, in selected areas of the Western Cape, South Africa. In this study, the collected samples were analysed by the multi-elemental nondestructive technique called instrumental neutron activation analysis (INAA) as well as the ion-coupled mass spectrometry (ICP-MS), thus facilitating an intercomparison of the results obtained by both techniques. From both passive and active biomonitoring techniques, the intercomparison of INAA and ICPMS results showed major and essential elements (i.e. Na, Ca, Mg, K, Mn, Sr, Al, V, Ba, Zn) to have good linear correlations, R ≥ 80%. In order to facilitate the identification and characterization of different pollution sources from the collected sample element content, descriptive statistics were generated and correlation analyses were done using the StatisticaTM package. Our passive biomonitoring results showed the concentration levels for halogens (Cl, I, Br) to be elevated in areas closest to the ocean. The moss-sampling areas closest to the ocean, in relation to Stellenbosch, were False Bay and Betty’s Bay. Signal Hill was the lichen-sampling area closest to the ocean, in relation to Stellenbosch, Coetzenburg Mountain and Franschoek. High concentrations of elements associated with vehicular emission (i.e. Pb, V, Zn, Cd, Cr, Cu, Ni, As, Ba, Sn) were observed for Stellenbosch samples that were collected adjacent to roads (Marais Road and Victoria Street). The active biomonitoring results showed Stellenbosch to have higher concentration levels of Al, V, Ba, Cr, Cu, Ti and Zn. These indicate emissions from soil and vehicles. The fingerprints for a combination of potential air pollution sources (oil rig facility, steel plant, heavy mineral plant, galvanising plant and the oil storage facility as well as sea-salt emissions) were identified in the Vredenburg results. The elements associated with these fingerprints are Fe, Al, Hg, As, Cd, Pb, Ba and Na. The Huguenot tunnel results revealed high concentrations of elements associated with the fingerprints for vehicle emissions. These are Zn, V, Ba, Cr, Pb, Ni, Cu, Al and Sb. In general, mosses showed the highest bioaccumulation capacity for metals and presented a more linear element accumulation trend than lichens. Due to their differences in metal uptake and retention, it is advisable to use mosses and lichens concurrently, since the respective results will be complementary.

AFRIKAANSE OPSOMMING : Die analise van die chemiese samestelling van mos en ligene deur middel van onder andere tegnieke in kernfisika kan gebruik word om lugkwaliteit te moniteer. Hierdie gebruik van mos en ligene as biomonitors word wyd toegepas in Europa, maar is tot op hede nog nie wyd in Suid-Afrika in gebruik nie. Hierdie studie het ten doel om biomonitering te gebruik om die vlakke van lugbesoedeling in die Wes-Kaap, Suid Afrika, te bepaal. Die gebrek aan ’n wortelstelsel verseker dat mos en ligene as ideale lugbesoedeling biomonitors optree aangesien slegs chemikalieë uit die atmosfeer versamel kan word. Swaar metale en spoor elemente in die atmosfeer word effektief versamel deur nat en droë neerslag prosesse. Drie belangrike oorsake van lugbesoedeling sluit in industrialisasie, verstedeliking en wydverspreide voertuig gebruik. Die gebruik van biologiese materiaal in plaas van kommersiële lug filters word beskou as ’n eenvoudige en koste effektiewe metode om die vlakke van lugbesoedeling te bepaal. Passiewe biomonitering verwys na die gebruik van mos en ligeen wat natuurlik voorkom in die omgewing wat bestudeer word. In teenstelling hiermee behels aktiewe biomonitering die verplasing van biomateriaal vanaf ongerepte habitat na die omgewing wat bestudeer word. Aktiewe biomonitering is aan die toeneem wêreldwyd as gevolg van die afwesigheid van mos en ligene in streke wat gebuk gaan onder menslike impak, omgewings met swaar industrië asook droë gebiede. Daar is in hierdie studie van beide aktiewe en passiewe biomonitering gebruik gemaak om vas te stel watter elemente deel uitmaak van atmosferiese besoedeling in die Wes-Kaap, Suid Afrika, spesifiek as gevolg van verstedeliking, industrialisering en voertuig gebruik. Verskeie monsters is versamel en die resultate van twee verskillende analitiese metodes, naamlik die nie-vernietigende instrumentele neutron aktivering (INA) en ioon- gekoppelde massa spektromtrie (IGMS), is gebruik om die verskillende biomonitering resultate te vergelyk. Beide analitiese metodes toon ’n sterk linieêre korrelasie (R≥80%) tussen die teenwoordigheid van die algemene elemente (Na, Ca, Mg, K, Mn, Sr, Al, V, Ba, Zn) in aktiewe en passiewe biomonitering monsters. Beskrywende statistiese en korrelasie data is met behulp van die StatisticaTM pakket gegeneer ten einde verskillende besoedelingsbronne te kan indentifiseer en karakteriseer. In kusgebiede, soos Valsbaai en Bettiesbaai is bevind dat passiewe biomonitering met behulp van mos monsters ’n verhoogde konsentrasie van halogene (Cl, I, Br) aandui. Dit is in teenstelling met gebiede soos Stellenbosch (Victoria straat) en Coetzenburg (berg). Soortgelyke resultate is verkry deur ligeen monsters te analiseer wat versamel is op Seinheuwel (kusgebied), in teenstelling met binnelandse monsters versamel by Franschoek en Stellenbosch . Hoë konsentrasies van elemente wat gepaard gaan met voertuig uitlaatgasse (soos bv. Pb, V, Zn, Cd, Cr, Cu, Ni, As, Ba, Sn) is waargeneem in passiewe monitering monsters afkomstig van gebiede langs paaie in Stellenbosch (Victoria en Marais Strate). Die resultate verkry deur aktiewe biomonitering toon daarteenoor hoër vlakke van Al, V, Ba, Cr, Cu, Ti en Zn.Beide resultate dui op ’n mengsel van voertuig uitlaatgasse en gesuspendeerde grond partikels. Die karakter eienskappe van industriële lugbesoedeling afkomstig van bronne soos olietorings, staal industrië, galvaniserings-en oliebergingsfasiliteite, vermeng met elemente geassosieer met die nabyheid van die see, is waargeneem in die Vredenburg resultate. Dit sluit elemente in soos Fe, Al, Hg, As, Cd, Pb, Ba en Na. Daarteenoor is die elemente waargeneem in die resultate van die Hugenote tonnel, naamlik Zn, V, Ba, Cr, Pb, Ni, Cu, Al en Sb, tipies geassosieer met voertuig uitlaatgasse. Dit blyk uit hierdie studie dat mos ’n beter vermoë het om as bio- akkumulator op te tree as ligene aangesien die opname van elemente teen ’n meer konstante tempo geskied. Ten spyte hiervan is dit steeds belangrik om van beide mos en ligeen gebruik te maak aangesien die opname en behoud van metale verskillend is, en die resultate dus as aanvullend beskou kan word.

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