Sampling techniques for the assessment of anthropogenic vapour and particulate mercury in the Brazilian Amazon atmosphere

A system, based on annular gold-coated denuders, was optimized and used in the atmospheric sampling of mercury in urban and rural sites of the Alta Fl oresta, a region in the Brazilian Amazon. Results showed that vapour phase mercury (Hg-v) is dominant in samples collected in both sites. However, par ticulate mercury (Hg) may sometimes be significant at the urban site, with values representing up to 77% of the total Hg collected during sampling, bu t may also be insignificant at the same site, depending on the gold commerc ialization activity and, probably, on the meteorological conditions during the sampling period. The presence of mercury in both the vapour and particu late phases in the atmosphere of the urban site can explain the high mercur y concentrations found in urban dust reported for some cities in the Amazon , and also the relatively high Hg concentrations found in soils adjacent to the urban centre of Alta Floresta. It appears that the urban dust of "gari mpo" areas in the Amazon can act as an efficient adsorber of Hg-v emitted b y gold dealer operations during the purification process. Mercury emissions from gold dealer shops in the Amazon have been considered as a human healt h risk through the inhalation of Hg vapour. However, although true for indo or sites, the significant contribution of particulate phase Hg shown in thi s study in outdoor urban sites calls for a re-evaluation of the risk assess ment estimates performed up to now in urban centres in the Amazon.