Abstract
Aim: The aim of present study was to evaluate the Hg concentration in two species of fish (Astyanax sp and Corydoras paleatus) and its potential use as a biomonitor, in order to know if the use of pesticides and fertilizers in paddy can enhance the Hg contamination to adjacent aquatic environment.MethodsSoil, suspended particulate matter and fish samples were sampled in a paddy field in South Brazil. A cold vapor system, coupled with a GBC 932 atomic absorption spectrophotometer was used for total Hg determinations in samples.ResultsThe paddy soil shows Hg concentration 2-fold higher (mean 31 ng g-1) in comparison to background areas (not cultivated). Suspended particle matter Hg concentration in paddy channels (mean 232.5 ± 44.2 ng g–1) are 1.5 times higher than the regional background. The analyzed fish specimens Astyanax sp in paddy showed Hg concentration 4-fold higher and significant different to background area. The mean Hg concentration in fish was: 51.7 ± 19.5 ng g–1 in Astyanax sp and 156.8 ± 44.0 ng g–1 in Corydoras paleatus.ConclusionsConsidering the linear regression and Man whitney test hypothesis to Hg concentration in fish tissue from paddy suggests that Astyanax sp. can be a good biomonitor of Hg contamination, whereas Corydoras paleatus is a potential biomonitor. However, more studies with Corydoras are necessary in order to aggregate consistency to this hypothesis.
Highlights
Mercury (Hg) is considered a highly toxic metal and has been used in the composition of pesticides utilized in rice fields (Smart & Hill, 1968)
The aim of present study was to evaluate the Hg concentration in two species of fish (Astyanax sp and Corydoras paleatus) and its potential use as a biomonitor, in order to know if the use of pesticides and fertilizers in paddy can enhance the Hg contamination to adjacent aquatic environment
The mercury concentration in the soil was around 2 times higher than found in the total fraction (Table 1). This result agrees with that found by Conceição (2005) for the regional background. It was not found any considerable variability in the Hg concentration in the different soil depths evaluated
Summary
Mercury (Hg) is considered a highly toxic metal and has been used in the composition of pesticides utilized in rice fields (Smart & Hill, 1968). In Brazil, the use of pesticides containing Hg was banned in the 70’s. More recent studies in paddies reported high concentration of methylmercury (MeHg) in rice grains (Zhang et al, 2010a,b; Zhao et al, 2010; Zhu et al, 2011; Peng et al, 2012; Rothenberg et al, 2012; Li et al, 2013). In Brazil, the study developed by Silva et al (2010) found Hg concentrations ranging from 2.2 to 4.4 ng g-1 in rice grains. The large use of fertilizers in the rice production can intensify the methylation process in paddy fields due to bacteria growth stimulation
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