Lichen parmotrema austrosinense as a biomonitor of air pollution by heavy metals in Nairobi

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dc.contributor.authorMathenge, Samuel Ndiritu
dc.date.accessioned2012-01-30T12:19:21Z
dc.date.available2012-01-30T12:19:21Z
dc.date.issued2012-01-30
dc.descriptionThe QK 581.M3en_US
dc.description.abstractA total of 80 samples of lichen Parmotrema austrosinense were collected from industrial area, Central Business District (CBD) and two residential areas (lavington/Kileleshwa and Eastlands) in Nairobi. Twenty seven samples of the same lichen species were also collected from Aberdares and were exposed for 21, 34, and 56 days in three high volume traffic sites in Nairobi CBD area. Heavy metals Fe, Mn, Zn, Pb, Cu, and Cd in lichen samples were analyzed using atomic absorption spectrometer. The level of heavy abundance in indigenous lichens showed that there was a contribution from the soils as well as anthropogenic sources. The heavy metals detected in P. austrosinense cannot be removed by washing the samples with water. In addition, the detected heavy metals in P. austrosinense originate primarily from atmospheric deposition and not from the supporting tree bark. For Mn and Zn, substantial uptake from the supporting tree may take place. The highest values of heavy metals were noted in industrial and CBD areas while the lowest values were observed in residential areas, probably because of low industrial, commercial and transportation activities. The contents of Mn in lichens were not significantly (p>0.05) different between the various locations in Nairobi indicating that concentrations of Mn in lichen are probably biochemically regulated. Regression and correlation analysis (r=0.40 to 0.77, p<0.10) revealed that concentrations of Fe and Mn in the indigenous lichens in Nairobi could have common sources and probably some contamination with soil dust. The contents of Pb, Cu and partly Zn originate primarily from anthropogenic activities. The correlation coefficients between the contents of Cu and Pb were also significant (P<0.10) and ranged from 0.49 to 0.79. Transplanted lichen P. austrosinense was shown to accumulate heavy metals in relation to environmental abundance and with increasing duration of exposure. The heavy metal uptake by P. austrasinense followed the order: Cu>Mn=Fe>Zn=Pb>Cd. The high uptake of Cu, Fe and Zn made it possible to detect short-term level changes of these metals between various sites. The concentrations of heavy metals in transplanted lichens showed strong positive correlation coefficients (r=0.48 to 1.00) indicating common sources of these metals. The sources of these heavy metals may be atmospheric deposition from the vehicular activities in Nairobi CBD area. There was a negative correlation (r=0.12 to 0.99) between Cu and other metals indicating that Cu has a high affinity to lichen exchange sites.en_US
dc.description.sponsorshipKenyatta Universityen_US
dc.identifier.urihttp://ir-library.ku.ac.ke/handle/123456789/2508
dc.language.isoenen_US
dc.subjectLichens--Kenya//Pollution--Environment aspect//Pollutants--Kenyaen_US
dc.titleLichen parmotrema austrosinense as a biomonitor of air pollution by heavy metals in Nairobien_US
dc.typeThesisen_US
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