Assessment of Trace Element Contents in Soils and Water from Cerrado Wetlands, Triângulo Mineiro Region

Abstract

In the Brazilian Cerrado biome, there are wetlands locally known as "Veredas", which are swampy plains between hills and rivers. Since the 1970's, the Cerrado biome has been gradually converted to livestock, crop, or forestry production. Until now, very few studies were conducted to evaluate the baseline contents of trace elements in Cerrado wetland soils. Due to their position in the landscape (bottom lands), the wetlands are potentially susceptible to contamination by runoff and/or leaching from surrounding areas at higher altitudes. This work evaluated the As, Cd, Pb, Ni, Zn, Cu, Mn, and Fe contents in soils from six wetlands (undisturbed and disturbed) in the Minas Gerais Triangle region, Brazil. In each wetland, we collected topsoil samples (0.00-0.20 m layer) and subsurface samples (0.40-0.70 m layer) at different landscape positions in the wetlands (upper, middle, and bottom positions). The soil samples were air-dried, ground, and sieved through 2-mm mesh. Afterwards, the soil digestion was performed according to the USEPA 3051A protocol, and the trace elements were determined by atomic absorption spectrometry (flame or graphite furnace atomization). Water samples were also collected monthly from September 2014 to September 2015 to determine the elemental composition by inductively coupled plasma optical emission spectrometry. The contents of all soil trace elements studied were below the threshold values established by Brazilian guidelines. The soil trace element (cations and/or oxyanions) distributions varied according to soil depth and organic matter content. Our findings contribute to the sparse inventory of Brazilian Cerrado wetlands regarding trace-element contents.

The interactive pedological-hydrological processes and environmental sensitivity of a tropical isolated wetland in the Brazilian Cerrado

“…For example, Moraes and Horn [80] and Rosolen et al [81] have found high contents of As, Cd, Cr, Cu in five wetlands in the plateau, exceeding the threshold values established by Brazilian guidelines. At the same time, Ribeiro et al [82] did not determine soil trace elements in sufficient quantities to characterize pollution or contamination.…”

Qualidade dos sedimentos em áreas alagadas de veredas rurais e urbanas

“…No geral, a maioria das áreas apresentaram concentrações médias de Cu nos sedimentos inferiores ao estabelecido, sendo que na Vu1 o valor médio foi de 59,37mg Kg -1 . Ribeiro et al (2019) também encontrou valores de cobre abaixo da referência de qualidade.…”

“…Todas as áreas monitoradas apresentaram valores inferiores ao estabelecido como referência. Ribeiro et al (2019) observou que o Ni não é diretamente influenciado pelas condições alternantes de oxirredução, típicas de ambientes alagados e também encontraram valores abaixo da referência na maioria das veredas estudadas.…”

“…Dentre as médias dos sedimentos analisados nas áreas alagadas, não foram encontradas inconformidades. Ribeiro et al (2019) também encontrou valores inferiores ao limiar de prevenção nos solos de veredas na mesma região. Em outros solos do mesmo bioma de Cerrado, Rosolen et al (2015) observou variações nas concentrações de 12,1 a 81mg Kg -1 de Pb.…”

“…Os elementos em maior concentração nos sedimentos analisados foram o alumínio (Al) e o ferro (Fe), ambos abundantes no grupodos Latossolos. As concentrações de ferro (Fe) em solos de veredas são importantes por causa das reações de oxirredução que controlam a disponibilidade e mobilidade de outros elementos(RIBEIRO et al, 2019).…”