Are trace elements from iron-ore mining influencing fish health in a tropical coastal lagoon in Brazil?
In her PhD study Adriana Alves Pereira has performed integrated field studies on environmental levels, bioavailability, biological exposure, and effects of trace elements in lagoons near an iron-ore mine in Brazil. The study includes assessment of exposure, bioaccumulation, trophic transfer of trace elements in invertebrates and fish, biomarkers for oxidative stress, as well as public health risks due to fish consumption.
Iron-ore is the source of primary iron for the world's iron and steel industries. Almost all (98%) iron-ore is used in steelmaking. Australia and Brazil together dominate the world's iron-ore production, while China is the world’s largest iron-ore consumer. In Brazil, iron-ore mining is mainly located in the southeast. The area is also scattered with gold occurrence. In the past, artisanal small scale gold mining activities were frequent in this area.
This study deals with activities of the iron-ore mining, concentration plant, and pelletizing plant operated by Samarco Mineração S/A. A pipeline (396 km long), transports the ore from the mining and concentration site (mixed with water) to the pelletizing plant at the coast. In this plant, the ore is separated from the water and the effluent goes to an artificial lake (North Dam). Periodically, this artificial lake overflows into Mãe-Bá coastal lagoon.
The main objective of the work presented in this thesis was to investigate possible impacts of iron-ore mining and processing activities on local environmental levels of trace elements and possible consequences thereof for fish species of Mãe-Bá Lagoon, using a multidisciplinary approach. For comparisons we selected similar lagoons in the vicinity and not directly influenced by the iron-ore processing activities. Based on a series of field studies, the possible influence of iron-ore mining and processing activities on the release of metals and trace elements (Fe, Mn, Al, Zn, Cu, Cr, Ni, Pb, Cd, As, and Hg), speciation, and bioavailability was examined in different aquatic systems (rivers and coastal lagoons). Furthermore, trace element levels were measured in invertebrates and fish to assess potential trace element bioaccumulation and trophic transfer, biomarkers for effects of oxidative stress, as well as potential risks to human health due to consumption of fish. Moreover, possible changes in biochemical markers of exposure and effects of trace elements were investigated in fish species from the coastal lagoons.
The multidisciplinary approach revealed that the mining and processing operations constitute a potential source of Fe, Mn, Cr, Cu, Ni, Pb, As and Hg to the coastal lagoon. However, this appeared to have a limited influence on trace element accumulation in invertebrates and fish in Mãe-Bá Lagoon, which was attributed to a low bioavailability of the trace elements in this lagoon using speciation modelling. Studies on trace elemental accumulation in sediments, invertebrates and fish using stable isotopes (δ13C and δ15N) for trophic level characterisation revealed a significant negative association between trophic level (given by δ15N) and trace element concentrations in invertebrates and fish, confirming the absence of biomagnification at Mãe-Bá Lagoon. Based on national and international standards for human consumption, fish muscle of all species studied from Mãe-Bá Lagoon is suitable for human consumption. No straight forward associations were found between the levels of hepatic trace elements in the fish species and biomarkers for oxidative stress, such as lipid peroxidation (malondialdehyde) and antioxidant status parameters (catalase, superoxide dismutase, and glutathione S-transferase). Moreover, there was no evidence for a cause-effect linkage between exposure to iron-ore mining and processing effluents and effects on hepatic retinoid metabolism.
The overall conclusion from the data described in this thesis is that the data do not support the presence of adverse effects on health and condition of fish species due to exposure to trace elements in the lagoon directly influenced by periodical discharges from iron-ore mining and processing activities (Mãe-Bá Lagoon).
Adriana has defended her PhD thesis, entitled ‘Trace elements in a tropical coastal lagoon in Brazil, receiving effluents from iron-ore mining and processing. Integrated field studies on environmental levels, bioavailability, biological exposure, and effects’, on November 20th.