Monitoring of heavy metal contamination plume in soils can be helpful in establishing strategies to minimize its hazardous impacts to the environment. The objective of this study was to apply a new approach of visualization, based on tridimensional (3D) images, of pseudo-total (extracted with concentrated acids) and exchangeable (extracted with 0.5 mol L(-1) Ca(NO3)2) lead (Pb) concentrations in soils of a mining and metallurgy area to determine the spatial distribution of this pollutant and to estimate the most contaminated soil volumes. Tridimensional images were obtained after interpolation of Pb concentrations of 171 soil samples (57 points × 3 depths) with regularized spline with tension in a 3D function version. The tridimensional visualization showed great potential of use in environmental studies and allowed to determine the spatial 3D distribution of Pb contamination plume in the area and to establish relationships with soil characteristics, landscape, and pollution sources. The most contaminated soil volumes (10,001 to 52,000 mg Pb kg(-1)) occurred near the metallurgy factory. The main contamination sources were attributed to atmospheric emissions of particulate Pb through chimneys. The large soil volume estimated to be removed to industrial landfills or co-processing evidenced the difficulties related to this practice as a remediation strategy.

No abstract

Subtropical soils derived from basalt covers an area of 1.5 x 106 km2 intensively used for agriculture in South America. There is little information about such soils on a scale compatible with the planning of watersheds. This study has the aim to use topographic attributes to generate soil maps on a semi-detailed scale and elaborate land suitability maps. The study was carried out in a watershed in southern Brazil under a subtropical climate, and soils derived from basalt. A total of 129 points were morphologically described and 17 representative soil class profiles were sampled for laboratory analysis. Areas that should be destined for conservation had the lowest mean for AACN index indicating the proximity of the water table to the surface and the mean MrVBF value above 2. The TWI value higher than 10 was associated with Gleysol. The Regosol were situated in step relief, with the highest mean of LS Factor. Ferralsol and Nitisol were separated with 10 < AACN > 20 and MrRTF > 0.5, associated to flatter and higher areas. Nitisol was the predominant class, occupying 60.78% of the total area, while in previous maps it was identified in 14.94% of the watershed area. Land use beyond its capacity was identified in 31.15% of the Regosol while for the Gleysol this occurs in 38.10%. The farmers use areas of low suitability or with high potential for degradation for agricultural activities, being 2647.29 ha used above the land use capacity in the Lontra river watershed.