High Variability in Sediment Characteristics of a Neotropical Stream Impacted by Surface Mining and Gully Erosion |
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Authors: | Francisco L Nascimento Iola G Boëchat Alexandre O Teixeira Björn Gücker |
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Institution: | 1. Department of Biosystems Engineering, Federal University of S?o Jo?o del-Rei, Campus Tancredo Neves, Av. Visconde do Rio Preto, 36301-160, S?o Jo?o del-Rei, MG, Brazil
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Abstract: | This study examined patterns of stream sediment granulometry, organic matter (OM) and metal concentration, and surface water
characteristics in a catchment in the Brazilian Iron Quadrangle that is highly impacted by surface iron mining and gully erosion.
Sediment granulometry indicated fine sediment deposition at impacted stream sites, i.e., tendencies towards bimodal particle
size distributions with an additional peak in the sand fraction at impacted stream sites that did not occur at pristine reference
sites, as well as towards smaller mean sediment particle sizes at impacted sites than at reference sites. Impacted sites also
had significantly lower sediment OM contents than reference sites. Sediment heavy metal and arsenic concentrations did not
differ between impacted and reference sites and were generally below published target or threshold effect concentrations.
Impacts on surface water characteristics occurred only locally at a site that received tailings pond effluent from an iron
mine and had very low pH and conductivity values. Sediment characteristics exhibited substantial spatial variability in the
studied tropical catchment, showing that land use impacts can hardly be detected in routine monitoring and impact assessment
studies that adopt a before–after control-impact approach and do not consider pristine reference streams. These results underline
the importance of high-resolution and long-term sediment monitoring as well as integrated basin-scale sediment management
programs. |
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