RESUMEN
The concentrations of heavy metals (HMs) can be increased by various anthropogenic activities such as mining, fuel combustion, pesticide use, and urban development, which can alter the mechanisms determining their spatial variability in the environment. Determining natural concentrations, monitoring, and assessing potential ecological risks are essential in the management of pollution prevention policies and soil conservation in watersheds. The aim of this study was to determine HMs natural concentrations, establish quality reference values (QRVs), and evaluate pollution indices in a watershed-scale. Composite surface soil samples (n = 115) were collected from areas: native vegetation, pasture, perennial crops, urbanization, planted forest, annual crops, and desertification. The soil samples digestion followed the EPA 3051A, and metals determination in ICP-OES. The data were subjected to the Kruskal-Wallis test, Spearman's correlation, multivariate clustering analysis and. geostatistics. The QRVs established (75th) for the Gurgueia River watershed in descending order were (mg kg-1): V (26.16) > Cr (18.06) > Pb (6.24) > Zn (3.86) > Cu (2.66) > Ni (1.45) > Co (0.57) > Mo (0.46) > Cd (0.07). The concentrations of Cd, Co, Cr, Mo, Ni, V, and Zn in types of land and management practices were significantly increased compared to those in natural vegetation. Overall, the watershed falls into the categories of minimal to moderate enrichment, moderate to considerable contamination, and low to moderate potential ecological risk, with Cd presenting elevated values. The percentages of polluted samples ranged from 14.3 to 82.5%, indicating the need for monitoring these areas to ensure environmental quality and food safety.
Asunto(s)
Monitoreo del Ambiente , Sedimentos Geológicos , Metales Pesados , Ríos , Contaminantes del Suelo , Metales Pesados/análisis , Brasil , Medición de Riesgo , Contaminantes del Suelo/análisis , Sedimentos Geológicos/química , Ríos/química , Suelo/química , Contaminantes Químicos del Agua/análisisRESUMEN
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.