Abstract
This study evaluated water parameters in ponds affected by coal extraction. Allium cepa assay was used to measure genotoxicity/mutagenicity of the sediment. Samples were collected from four ponds in the southern state of Santa Catarina. Water temperature, pH, dissolved oxygen, conductivity and turbidity were measured. Sediments were analyzed for heavy metals. Elutriate samples were prepared at a ratio of 1:4 sediment:water. Allium cepa bulbs were placed in samples prepared from each pond, with ultrapure water used as negative control and methyl methane sulfonate as positive control. Root length, mitotic index, chromosomal aberrations, micronuclei, and nuclear abnormalities were measured. The pH of two ponds, as well as electrical conductivity and dissolved oxygen of all ponds were below the minimum limits set by Brazilian regulation. All heavy metals analyzed were found in all sediment samples, but only Cd concentration was above the legal limit set by Brazilian law. Allium cepa root growth for samples from Ponds 1, 2, and 4 was significantly lower than the negative control. Meristematic cells exposed to elutriate samples showed no significant changes in cell division. There was a significant increase in total chromosomal aberrations in all treated samples in comparison with the negative control. This study demonstrates that even low concentrations of heavy metals can damage exposed biota, possibly due to synergistic effects. We also found the A. cepa bioassay to be a simple and useful tool for genotoxicity/mutagenicity analyses, and recommend its use for environmental monitoring and management in areas influenced by mining activities.
Highlights
The extraction and processing of coal has been among the principle economic activities in the southern state of Santa Catarina for over 100 years (Silva et al 2011)
The lowest values (3.86 and 5.81) are below the limits established by CONAMA Resolution 357/05 (CONAMA, 2005), which considers 6 to 9 normal for Class 2 rivers
Dissolved oxygen values from all samples were below the limit of 5 mg/L (Table 1; CONAMA, 2005)
Summary
The extraction and processing of coal has been among the principle economic activities in the southern state of Santa Catarina for over 100 years (Silva et al 2011). The improper disposal of coal extraction waste results in sulfide-rich effluent combining with oxygen and water to form an abundance of sulfuric acid (H2SO4) and iron compounds, generating contaminants with potential toxicity for soil, air, groundwater, surface water, and local biota (Ribeiro et al, 2013). Coal mining and combustion produces abundant waste rich in heavy metals such as lead, iron, copper, zinc, chromium, cadmium, manganese and arsenic, all of which are deposited in the soil and sediment. These compounds can cause metabolic changes in local biota, and may cause harmful DNA modifications that lead to irreversible mutagenic damage (Leonard et al, 2004; Alimba et al, 2016). Fertility disorders and cellular/metabolic abnormalities are among the potential lethal and sub-lethal effects resulting from the presence of complex mixtures in water (Villela et al, 2007; Alimba et al, 2016)
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