Avaliação do incremento nos teores de arsênio (AS) em solos com histórico de uso de ulexita

Abstract

The present study aimed to determine the pseudototal content of arsenic (As) in agricultural soils with a history of ulexite use in the region of Triangulo Mineiro, State of Minas Gerais, Brazil. The history of application of ulexite, fertilizer used to supply boron to plants, was fundamental for the choice of areas, as well as the class of soil (Oxisol) was the same. For all uses a reference area with native vegetation was selected to obtain the background values of As from the selected sites. Soil samples were collected at depths of 0 - 20 and 20 - 40 cm, considering the uses as follows: i. Grain cultivation (areas with irrigated corn, soybean in dry land and native vegetation); ii. Coffee cultivation (an area cultivated for 10 years, an area currently under reform for grain, in addition to native vegetation); iii. Eucalyptus cultivation (samples collected in the line and interlace of two distinct plots, as well as in an area of native vegetation). The interaction between different land uses within the same area, as well as the interaction between depths within each area were statistically evaluated. The pseudototal arsenic contents were determined by US-EPA 3051, and the analyses were carried out at the ABC Foundation in the state of Paraná. The data were submitted to analysis of variance (ANOVA) to verify the effect of different land uses (p 0.05), and the averages are grouped by the Scott-Knott test (p 0.05). The soil quality reference values considered were the limits established by COPAM resolution 166 of 2011 that establishes the pseudo-total value of As of 8 mg/dm3 for the state of Minas Gerais. The coffee growing area and most of the eucalyptus plots presented quality reference values higher than the limit established by state legislation. However, despite these high values, not all cultivated areas showed significant difference in relation to native vegetation. In addition, one of the eucalyptus stands was the only cultivated area that did not exceed the Quality Reference Value (QRV), recording a lower value than the native area, possibly due to the slope of the terrain or other pedological factors. When the depths were compared, there was a difference in the samples of the eucalyptus cultivation area. The results indicate that the use of land for agricultural crops can promote increase in As, however, it was not possible to prove the influence of ulexite as responsible for these increases.