RESUMEN
Gypsum plays a prominent role in agriculture, being considered an effective alternative to alleviate subsurface acidity due to its higher solubility and containing sulfur. However, another significant aspect is which pose long-term risks of groundwater contamination due to excessive applications of salts, pesticides, and other chemicals that will be leached, or even soil chemical depletion. So far, no study has focused on understanding the impacts of the atmospheric gypsum plume originating from gibbsite mining and processing on the leaching of soil bases and chemical degradation surrounding these sites. In this study, we evaluated the behavior of chemical characteristics in soil profiles distributed along the dispersion of the atmospheric plume and in areas without interference from the industrial sector in the state of Maranhão, Northeast Brazil. Fifty-three sampling points were collected at 7 locations based on the dispersion of the dust plume through wind drift. Each sampling point was represented by three composite soil samples at depths of 0.0-0.20, 0.40-0.60, and 1.00-1.20 m, where the chemical soil characteristics were evaluated. The average levels of Ca, Mg, and K in the studied layers are classified as low, with minimum values below the method's detection limit, and they also show imbalance due to higher concentrations of Ca in the surface layer in areas affected by atmospheric dispersion. The sum and saturation of bases at all depths are classified as low. Higher aluminum saturation values were observed in the deeper soil layers. The gypsum dust altered the soil's chemical characteristics at the evaluated depths; therefore, it is necessary to seek means to mitigate gypsum dust release during gibbsite extraction and processing and ensure that the soils in areas near these enterprises maintain their natural characteristics.
RESUMEN
Understanding the processes of mobility and availability of potentially toxic elements in soil is crucial for informed decision-making in the development of public policies aimed at minimizing environmental impacts. Monitoring, in combination with the determination of natural concentrations, can provide effective tools for controlling pollution sources. In this study, enrichment, pollution, and ecological risk indices were used for some potentially toxic elements in an anthropogenically influenced watershed in southwestern Bahia, Brazil. The study involved 63 composite surface soil samples collected from areas with natural forest, crops, pastures, and urbanization. The samples were analyzed for fertility and particle size. Metal extraction followed the EPA 3051A method, and element determination was carried out via ICP-OES. The soils in the Verruga River watershed exhibit a high variability in fertility and granulometric attributes. The Kruskal-Wallis test at a 5% significance level was employed to assess the impact of land management on the availability of elements (As, Co and Pb), while Spearman's correlation, along with hierarchical clustering analysis, was used to comprehend element dynamics. Geostatistics were applied to identify pollution hotspots. Consequently, it became evident that potentially toxic elements can accumulate in the soil depending on land use and management practices (As, Co, and Pb), as well as the weathering process linked to the type of source material, such as diamictite deposits (Ni and Co). Soils in the Verruga River watershed qualify as having minimal enrichment, low pollution levels, and individual ecological risk concerning Cd. The percentage of samples enriched with Cu, As, Zn, and Cd exceeded 67%, with agricultural activities being the primary source of pollution. Meanwhile, in pasture and urban areas, Co and Pb were notably prominent, respectively.
Asunto(s)
Monitoreo del Ambiente , Contaminantes del Suelo , Brasil , Contaminantes del Suelo/análisis , Medición de Riesgo , Suelo/química , Bosques , Metales Pesados/análisis , Ríos/químicaRESUMEN
The evaluation of the concentration of a potentially toxic element (PTE) in soils under native vegetation is the base study to obtain the quality reference values (QRVs), and the watershed is the strategic planning unit for decision making. The objective of this study was to determine the natural concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn and to establish QRVs for the Verruga river basin. Soils with no or minimal anthropic intervention from the surface layer (0.0-0.2 m) were collected and processed, and PTEs were extracted according to the USEPA 3051A method and determined by ICPâOES. The quality of the analyses was checked by blank tests and soil samples certified SRM 2709 - San Joaquin Soil. The data set was subjected to exploratory analysis and multivariate statistics. The mean background concentrations of PTEs in soils showed high variability compared to other locations in Brazil and in the world and were (mg kg-1) Fe (24,300) > Mn (211.10) > Cr (40.98) > Zn (28.28) > Cu (10.68) > Ni (9.44) > Pb (4.95) > Co (4.08) > As (3.48) > Cd (0.09). The QRVs for the PTEs were established based on the 75th percentile, where (mg kg-1) Mn (124.59) > Cr (54.51) > Zn (31.66) > Cu (7.89) > Ni (7.20) > Pb (5.98) > As (4.05) > Co (3.40) > Cd (0.10). The chemical attributes and topography variation along the watershed are very heterogeneous and influence the dynamics of the PTEs. This survey will support future research on the impact of human activities on soil contamination in the watershed. This survey will support future research on environmental monitoring and the impacts caused by increased human activities on soil contamination in the Verruga river watershed, in the state of Bahia, Brazil.