Paula Godinho Ribeiro

The Amazon has undergone significant changes in the landscape with the expansion of human activities. The objective of this study was to characterize the relationship between soil temperature (ST) and moisture (SM) with meteorological data and soil attributes in pasture, forest, and transition areas in the Itacaiúnas River Watershed (IRW), Eastern Amazon. Soil samples were analyzed to determine chemical and granulometric attributes. SM and ST were measured up to 40 cm deep using sensors, and the meteorological variables were quantified by hydrometeorological stations. The chemical characteristics and granulometry indicated greater limitations in the Forest soil, with lower levels of organic carbon and higher contents of sand. In Pasture A, Pasture B, and Transition areas, with some exceptions, there was a progressive increase in ST from July to September. In general, SM was positively correlated with rainfall and negatively correlated with ST, air temperature, wind speed, and solar radiation. Linear models for ST (10–20 cm depth) in Pasture B and Forest areas indicate positive relationships with air temperature and wind speed and negative relationships with solar radiation. The findings of this study can be useful in decision-making regarding the management of ecosystems in the IRW.

One challenge of revegetating mined areas is establishing vegetation that quickly promotes soil cover and accumulates biomass. This work compared biomass production and vegetation cover between a Non‐native cocktail (8 noninvasive exotic species) and a Native cocktail (12 species native to the National Forest of Carajás, Brazil) to guide species selection for revegetation. Ex situ and in situ tests were conducted in the Carajás Mineral Province. During the ex situ phase, the growth of both cocktails was evaluated in four substrates from different waste piles. In the in situ phase, the Native, Non‐native, and Native + Non‐native cocktails were sown on the base of a cut slope, with soil vegetation cover evaluated every 2 months for 8 months. Non‐native cocktail produced more biomass (ex situ) and had greater growth and competitive vigor during the first 2 months of revegetation (in situ). Due to the delayed growth of some native species, the initial differences between cocktails disappear over time. Thus, combining native and non‐native species is recommended to achieve rapid biomass incorporation by non‐native species at the beginning of revegetation, followed by an enrichment or replacement by native species. This approach meets the legal requirements to reduce the application of non‐native species to the minimum while achieving quick soil coverage.

Biochar represents a promising alternative for enhancing substrates and remediating contaminants in mining areas. Given that arsenic (As) and phosphorus (P) share similar chemical forms, the combination of biochar and P fertilizers may reduce As uptake, thereby mitigating As-related impacts. This study aimed to evaluate the potential of biochar-based P fertilizers in improving soil fertility and mitigating human health risks from gold mining tailings in the eastern Brazilian Amazon. Biochar from açaí palm (Euterpe oleracea Mart.) seeds was produced through enrichment with single and triple superphosphate at a ratio of 1:4, at 400 °C, and applied to mining tailings at 0.5%, 1%, and 2%. After one year of incubation, lettuce plants were grown for 70 days. Biochar reduced As absorption by lettuce and improved biomass and nutrient accumulation, resulting in improved vegetation indices. Biochar was effective in reducing non-carcinogenic As risks via ingestion of soil and plants to acceptable levels. Regression equations explained the As absorption behavior as affected by the biochar and the importance of biochar-related nutrients in reducing As stress. This study demonstrates the potential of P-enriched biochar as an amendment for As-contaminated soils, reducing As absorption, increasing P availability, and improving plant growth.

Monitoring key soil and vegetation attributes in mining areas under environmental rehabilitation is essential to ensure that the intervention techniques are effective. There are several approaches to monitoring mining areas and their integration is necessary to process large amounts of information. Thus, this study aimed to (i) assess soil multi‐contamination with potentially toxic elements (PTE) and human health risks; (ii) obtain a soil quality index with soil fertility data; (iii) calculate spectral index; (iv) show rehabilitation status based on vegetation attributes, and (v) compile these indices in a single measure. Four tailings' ponds (TPs), two waste piles (WPs), and an area of native forest from a gold mine in the Carajás National Forest were evaluated. Soil quality and vegetation cover are good in forest areas, with no evidence of PTE contamination. On the other hand, the TPs have poor fertility and vegetation cover, as well as higher levels of PTE. Human health risk indices obtained for all PTE were lower than 1, indicating a low risk to human health. The results of integrating the different indices suggest that the environmental conditions of the WPs are better than those of the TPs, which are still far from the environmental conditions of native areas. Soil attributes and vegetation development in TPs areas could be enhanced by the incorporation of organic materials and fertilizers and by planting species with phytoremediation potential. Finally, the integrative approach of the different indices proved to be useful in assessing the rehabilitation progress of the areas.

Applications of metal-based nanomaterials for the remediation of heavy metal (HM) contaminated environments are of great importance. The ability of metal oxide-based carbon aerogel composite to immobilize HMs in multi-metal contaminated soils has not yet been investigated, particularly under acidic conditions. Herein, we investigate the performance of metal oxides (Sr_0.7 Mn_0.3 Co_0.5 Fe_0.5O_3−δ)-based carbon aerogel composite (MO-CAg) compared with coconut coil fiber biochar (CCFB) and carbon aerogel (CAg) for Cd and Pb immobilization in contaminated soil. The MO-CAg, applied at 2% (w/w), significantly decreased Pb leaching by 67–75% and Cd by 60–65%, CAg decreased Cd by 54% and Pb by 46%, while biochar decreased Cd by 40–44% and Pb by 43%. The addition of MO-CAg altered Cd and Pb geochemical fractions by increasing their residual fraction, i.e., stabilized both metals compared to the control. This presents a comprehensive elaboration on the probable reaction interactions between the MO-Cag and heavy metals, including a combination of (co)precipitation, and reduction-oxidation as the predominant mechanisms of metal stabilization with MO-CAg. Moreover, MO-CAg increased Pb and Cd stabilization in soils by strengthening the bonding between metal oxides and Cd/Pb. By imbedding MO into the CAg, in MO-CAg, the immobilization of Cd(II) and Pb(II) occurred through inner-sphere complexation, while with CCFB and CAg metals, immobilization occurred through outer-sphere complexation. MO-CAg is a promising and highly efficient material that could be recommended for the remediation of Cd- and Pb-contaminated soils in subsequent studies.