Lichen specie Canoparmelia texana as bioindicator of environmental impact from the phosphate fertilizer industry of Sao Paulo, Brazil

Abstract

The Brazilian phosphate industry is the sixth worldwide producer of phosphate rock concentrate generating phosphoric acid, fertilizers, intermediates for fertilizers and other products. Two of the most important of these industries are both located in the city of Cubata˜o— Sa˜o Paulo, Brazil, and they are responsible for the production of P2O5, generating a residue known as phosphogypsum. The raw material, phosphate rock and products are commonly transported to the industrial complex by a railroad line and present in their composition natural radionuclides from the U and Th series and rare earth elements. Lichens have been used for monitoring atmospheric pollution and radiological contamination for a long time and have proven to be an important tool. This paper aims to highlight the use of the lichen specie Canoparmelia texana (family Parmeliacea) as a bioindicator of atmospheric pollution by the natural radionuclides from the U and Th series and RREs due to the operation of these industries and the storage of their residue in the open air. Samples of these lichen specie were collected in the vicinity of the industries and the railroad. The radionuclides 226Ra, 228Ra and 210Pb were measured by alpha and beta counting, after radiochemical separation, and 238U, 232Th as well as REEs were determined by instrumental neutron activation analysis. The results showed that the lichens present the same fingerprint as the phosphate rock and phosphogypsum, furthermore the cluster analysis of the results showed that the lichen samples collected near to the railroad line presented the highest values for all the elements studied.