ATMOSPHERIC MERCURY CONTAMINATION BIOMONITORING USING EPIPHYTIC BROMELIADS (TILLANDSIA USNEOIDES). CASE STUDY: THE GOLD SHOPS IN PORTO VELHO, RONDONIA, BRAZIL.

 

Vergotti, M., Biogeochemical Laboratory, UNIR, vergotti@unir.br

Gali, P.A.S., Biogeochemical Laboratory, UNIR, priscilagali@zipmail.com.br

Bastos, W.R. , Biogeochemical Laboratory, UNIR, bastoswr@unir.br

Silveira, E.G., Biogeochemical Laboratory, UNIR, labmerc@unir.br

Malm, O., LREPF-IBCCF-UFRJ, olaf@biof.ufrj.br

Santos, S.S., Biogeochemical Laboratory, UNIR, labmerc@unir.br

Maniesi, V., Biogeochemical Laboratory, UNIR, maniesi@unir.br

Torres, J.P.M., LREPF-IBCCF-UFRJ, jptorres@biof.ufrj.br

 

ABSTRACT

 

            The Bromeliad Tillandsia usneoides is an epiphyte that captures all its nutrients from the atmosphere, and concomitantly accumulates heavy metals, among them mercury. Systems of two baskets each with T. usneoides were distributed in the gold shops and the ex-gold shops of the Porto Velho city and recovered after an exposure of 15, 30 and 60 days. Each compartment of basket contained 5g of plants previously collected in a clean area with known Hg concentrations.

 

INTRODUCTION

 

Goldmining in the Madeira river basin started around 1978 and grew up to 1985 producing something like 200 to 300 tons of Gold in the first 10 years. Today this activity is reduced by a factor of 10 times. During mining process small gold particles are concentrated and afterwards collected by amalgamation method. In the field amalgams are first time burnt releasing most of the Hg to atmosphere. At a later date in the goldshops in Gold trade centers cities a new burning for purification is releasing the remaining Hg through rudimentary exhaustion systems, but with indoor contamination also exposing workers as well as neighbourhood.

 

OBJECTIVES

 

·        Introduce the use of biomonitoring indoor air Hg with the bromeliad Tillandsia usneoides in Amazon region

·        Evaluate the Hg contamination in goldshops and ex-goldshops in Porto Velho city

·        Verify the Hg absorption by the bromeliad along time for optimising its use.

 

MATERIAL AND METHODS

 

Transplanting technique were applied systems containing two plastic baskets containing around 5g of the plant each. Those systems were exposed in goldshops and ex-goldshops for periods of 15, 30 and 60 days. Air temperature at the shops ranged from 33 ºC to 37 ºC. A waterfall distant 31km from the city was also investigated. After that the plants were  washed for particles removal and cut in very fine pieces for homogenising and making digestion easier. Mineralization were performed with strong acid solutions (H2SO4, H2O2 e KmnO4) and heating at water bath at 60 ºC. Hg determination was done by Atomic Absorption Spectrophotometry (Flow Injection Mercury System - FIMS-400, Perkin-Elmer). Samples were prepared and analysed in triplicates. Analytical Quality Control were performed by routine analysis of reference material IAEA-140/TM (Table 3). Results are presented in dry weight basis (mg de Hg.g-1d.w.).

 

RESULTS AND DISCUSSION

 

Hg concentrations in plants exposed in the all shops presented increasing values along exposing times (Tables 1 and 2 and figures of different active goldshops). Values obtained in plants after 30 days exposure in active goldshops showed the average of 1,24 mg.g-1 that is 16 times higher than the value observed in control plants and close to the waterfall. For ex-goldshops we found for the same exposure period the average value of 0,23 mg.g-1, that is only 3 times higher than control plants. Those values were much lower than the ones found by Malm (1998), in the same dry season in goldshops in Alta Floresta (MT), 4,25 mg.g-1 but with plants exposed for 45 days. This difference should be mainly explained by the reduced gold production nowadays compared with in 1995/6.

 

Table 1. Average Hg concentration in Tillandsia usneoides in the gold shops of the Porto Velho city.

Exposure time (days)

Sample

Average  (mg.g-1)

S.D.

15

3

0,80

0,29

30

3

1,24

0,28

60

3

2,84

0,31

 

Table 2. Average Hg concentration in Tillandsia usneoides in the ex-gold shops of the Porto Velho city.

Exposure time (days)

Sample

Average  (mg.g-1)

S.D.

15

2

0,20

0,03

30

2

0,23

0,01

60

2

0,21

0,04

 

Table 3. Average Hg concentration (mg.Kg-1) in reference sample.

Reference Sample

Average ± S.D. Our lab. value

Average ± S.D.   certificate value

Confidence Interval

IAEA-140/TM

30 ± 11

38

32 - 44

IAEA= International Agency of Energy Atomic

 

CONCLUSIONS

 

We conclude that the bromeliad Tillandsia usneoides  can be used for Hg atmospheric biomonitoring in both indoor as well as outdoor environments. This method allows long term exposure evaluations at extremely low cost and at an enormous number of places at the same time.


 

            REFERENCE

 

MALM, O.; Fonseca, M.F.; Hissnauer, P.M.; Bastos, W.R. and Pinto, F.N. 1998. Use of epiphyte plants as bomonitors to map atmospheric mercury in a gold trade center city, Amazon, Brazil. The Science of the Total Environment, 213/1-3 pp. 57-64.

 

 


 


 


Hg concentrations in Bromeliads from different goldshops along time.