Biophysical measurements lead in some biosensors

ABSTRACT

Heavy metal [lead] concentrations in two marsh plants [Phragmites australis and Cyperus rotundus] and one free floating hydrophyte [Eichhornia crassipes] growing near metal smelters [lead pollutant area] were investigated. The shoots of the investigated plants were analyzed for lead content by flame atomic absorption spectrometry. Data indicated high lead levels due to the influence of urban and industrial effluents. This showed that the target plants could be considered as lead pollution biosensors. Scanning electron microscopy [SEM] and positron annihilation lifetimes [PAL] technique were used to ascertain the localization of lead in the living tissues. Cross sections of the plant organs were examined using SEM attached with an energy dispersed X-ray [EDX] unit for elemental analysis of the formed crystals that appeared abundant in the aerenchyma tissues of the polluted plants. PAL data reflected the correlation between the fraction of free volume hole and lead concentration, the higher lead accumulation gives a lower fraction of free volume hole. The results demonstrated the extreme sensitivity of the PAL technique towards the structural changes occurring in polluted plants