Atmospheric Environment 36 (2002) 881–887 Hg localisation in Tillandsia usneoides L. (Bromeliaceae), an atmospheric biomonitor G.M. Amado Filho a, *, L.R. Andrade b , M. Farina b , O. Malm c a Programa Zona Costeira, Instituto de Pesquisas Jardim Bot # anico do Rio de Janeiro, Rua Pacheco Le * ao 915, Jardim Bot # anico, 22460-030 Rio de Janeiro (RJ), Brazil b Laborat ! orio de Biomineraliza - c * ao, Departamento de Anatomia, Instituto de Ci # encias Biom ! edicas, CCS/UFRJ, Cidade Universit ! aria, 21941-590 Rio de Janeiro (RJ), Brazil c Laborat ! orio de Radiois ! otopos Eduardo Penna Franca, Instituto de Biof ! ısica Carlos Chagas Filho, CCS/UFRJ, Cidade Universit ! aria, 21941-590 Rio de Janeiro RJ, Brazil Received 21 March 2001; received in revised form 4 September 2001; accepted 17 September 2001 Abstract The Spanish moss, Tillandsia usneoides, has been applied as an atmospheric biomonitor of Hg contamina- tion, although the mechanism of metal plant accumulation has not been understood until now. In the present work, analytical scanning electron microscopy (SEM) was used to localize Hg in T. usneoides exposed to a Hg–air-contaminated area during 15 days. After this period, Hg was determined by the flow injection mercury system, and plants were prepared for SEM observation and energy-dispersive X-ray analysis. A concentration of 27027318 mg Hgg À1 was determined in exposed plants. The presented microanalytical results demonstrated that Hg was partly associated with atmospheric particles deposited upon the plant surface, but it was highly absorbed by the scales, stem and leaves surfaces and less absorbed by epidermal cells of T. usneoides. No Hg was detected in mesophyll parenchyma or in vascular system cells. The great surface adsorption area provided by the scales, in addition to the characteristics of T. usneoides morphology, especially of the node region, are suggested to confer the great capability of T. usneoides in Hg holding. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Spanish moss; Atmospheric contamination; Hg; Scanning electron microscopy; EDXA 1. Introduction The increase of mercury transport by the atmosphere has been associated with gold/silver mine activities, burning of fossil fuels, volcanic emissions, geochemical processes, wastes of mercury content of batteries, residues of pesticides, wiring production and chlor- alkali plant processes (Barghigiani et al., 1991; Bacci et al., 1994; Artaxo et al., 1996; Guimar * aes et al., 1998). Elemental gaseous mercury (Hg 0 ) is the principal form of mercury in the atmosphere. Hg 0 is extremely volatile, and can bind to water vapour or airborne particulates. Also it can be oxidized to mercuric ion (Hg +2 ) photochemically, and methylated by microorganisms (Bacci et al., 1994; Guimar * aes et al., 1998). The atmospheric mercury contamination in a chlor- alkali plant and surrounding area situated at Rio de Janeiro City (Brazil), has been monitored through transplants of non-contaminated Spanish moss Tilland- sia usneoides (Calasans and Malm, 1997). After 15 days of exposition, total Hg concentrations in transplanted T. usneoides reached a maximum of 10,400 mgg À1 dry wt. (Calasans and Malm, 1997). *Corresponding author. Tel./fax: +55-21-2947526. E-mail address: gfilho@jbrj.gov.br (G.M. Amado Filho). 1352-2310/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S1352-2310(01)00496-4