Using pollen samples as bioindicators for atmospheric heavy metal content

Abstract

In this dissertation pollen, soil and air samples were collected in order to determine the presence of heavy metals in them. The samples were acquired from two distinct types of locations; rural and urban in order to identify the difference between highly polluted areas and lesser polluted areas in heavy metal contamination. The pollen species made use of throughout this research were from the Ceratonia siliqua and from the Oxalis pes-caprae. These plant species are both highly abundant across the Maltese islands, making them ideal for the role of bioindicators. Two sets of results were gathered from the pollen samples, one with regards to the superficial aspect of the pollen grain, and the other for the internal structure itself. All samples were analysed by an Microwave Atomic Plasma Emissions Spectrometry (MP-AES) in order to detect the presence of ten metals, Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sn and Zn. In order to prepare samples which could be effectively analysed for their heavy metal content, all samples underwent a series of procedures. The air samples were simply filtered of any organic matter, the soil samples were both filtered and dried in a furnace to remove any unnecessary compounds, and the pollen samples were digested using a combination of 2ml of 5% nitric acid and 1ml of 30% hydrogen peroxide. The results proved the effectiveness of the use of pollen as a bioindicator of heavy metals, and a distinction was made between the two species with regards to which one is better suited for such practices. The highest recorded measurements were seen in the case of Arsenic with the highest concentrations being found in the air samples.