Comparison of the Heavy Metal Bioaccumulation Capacity of Epiphytic Moss and Lichen

Comparison of the Heavy Metal Bioaccumulation Capacity of Epiphytic Moss and Lichen

Biomonitors are organisms used in monitoring pollution and air quality in specific areas. Air pollution can cause bioaccumulation of elements, especially heavy metals, into these organisms. This makes them perfectly suited in studying several parameters that would give an idea about the degree of air pollution in that area. In this study, the heavy metal bioaccumulation capacity of two biomonitors, Scorpiurum Circinatum and Pseudevernia furfuracea (the former being a moss and the latter a lichen), were tested and compared.

The samples were first collected then washed and cleaned with distilled water. Then, 0.75g of each moss and lichen were placed in separate nylon mesh bags. Three bags each of the moss and lichen were stationed at the busiest urban streets of Acerra, Italy. Another set of samples were placed at sites located in Mount Faito to serve as controls. The bags were sprayed with distilled water to avoid dehydration.

Each month, a bag was retrieved from each sites and tested for results. The retrieved samples were then homogenized and subjected to a mixture of 6 mL of 65% HNO3, 2 mL of 39% H2O2 and 0.2 mL of HF. The resulting materials were tested for their As, Cd, Cr, Pb, V, Cu, Zn, Fe, Al and Mn content by inductively coupled plasma-mass spectrometry. The percentage of dead cells for each sample was also calculated by observing cells in the moss gametophytes and lichen thalli.

The results show a significant increase of metal content in both samples during the exposure. It is evident, however, that the moss is a better bioaccumlator than the lichen. Firstly, the element concentration of the moss is higher than the lichen, suggesting the moss’ better capability of collecting heavy metals. There is also a steady increase of accumulated particles in the moss as the months of exposure increases. This is in contrast with the lichen, where some elements show a discontinuous trend, like Cd, an element more likely to be leached from dead specimens. Furthermore, the moss has a higher surface/volume ratio, allowing a higher bioaccumulation capacity.