Six common tree species were used to check their suitability to use as magnetic biomonitors for particulate air pollution. The morphology and chemical composition of their leaf dust were identified using SEM/EDX. The results showed that the shape of particles are sphers, ovoid, irregular or grouped into aggregates; they were well within the size range of urban dust, especially hazardous for public health (PM 2.5 and PM10). These particles enriched by Fe (iron oxides), Al and silicates, with varying concentrations of minor elements, including Mg, K, Ca, Na, Ti, V, Au and Zn, Pb, Cd besides C and O2.
The tree leaf deposit samples gave rise to 2.46 folds higher magnetic values than the active filter, reflecting the advancing use of the tree leaves as air pollutant collectors than the industralized chemical filters. Except Cd, all tested parameters have significant correlation (p<0.01) with each other as well as with the recorded remanent magnetization values, suggestive an anthropogenic nature of the magnetic carrier, and indicating that magnetic particles and heavy metals coexist in the city dust. Both IRM and SIRM show highly signifcant (P<0.01) variations between the diffrent studied species. Their maximum values were recorded in Bougainvilla glabra and Bauhinia variegate. Bougainvilla glabra showed a higher value of (ε) as compared to other tested species, reflecting its ability for using as magnetic biomonitor for PM.