RESUMO
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.
RESUMO
The association between plants and arbuscular mycorrhizal fungi (AMF) can be used to bioremediate areas contaminated by metals. The objectives of this work were to evaluate the lead (Pb2+) phytoaccumulation capacity, morpho-physiology and nutrition responses of Vernonia polyanthes exposed to a solution amended with concentrations of lead nitrate and arbuscular mycorrhizal fungi. The treatments consisted of increasing doses of Pb2+ as lead nitrate [Pb(NO3)2], two strains of AMF and an absolute control without lead and AMF. Lead negatively affected some morphophysiological variables, reduced 27.3, 25.63, 30.60, and 56.60% shoot length, root collar diameter, number of leaves and leaf area, respectively, besides reducing decreasing chlorophyll a. Lead accumulated in the shoot and roots, the latter at the highest concentrations. However, the translocation factor was above 1, indicating low efficiency. The bioaccumulation factor referring to the roots were above 1. The fungi colonization rate was low, 3.31% for Gigaspora margarita and 2.33% for Acaulospora morrowiae. However, the absorption of lead increased, reflecting in lower values of chlorophyll a, dry mass of root and diameter. Results indicated that the arboreal species V. polyanthes tolerate high concentrations of lead and can accumulate significant amounts in the roots. AMF increase the accumulation of lead in the shoot and can be used in projects aimed at the phytoextraction of metals.
