Publicações 2026

DOI: https://doi.org/10.1016/j.envres.2025.123621

Abstract:

Mercury (Hg) contamination is a serious environmental problem due to its toxicity and bioaccumulation in aquatic communities. In the Amazon, hydrological fluctuations influence plankton structure and abundance, while gold mining constitutes an important anthropogenic source of Hg, releasing the metal into the water column and facilitating its incorporation by biota. In this study, we assessed total Hg (THg), methylmercury (MeHg), and the MeHg:THg ratio in the planktonic community of the upper Madeira River basin (Brazil) over a 10-year period. Mean concentrations of THg, MeHg, and MeHg:THg were 0.144 ± 0.138 mg kg⁻¹, 0.035 ± 0.049 mg kg⁻¹, and 0.283 ± 0.245, respectively. THg concentrations were higher during the rising-water period, particularly in larger zooplankton, reflecting seasonal hydrological inputs and changes in plankton composition. MeHg concentrations in total plankton were lower during the rising-water period, likely due to dilution effects and reduced bioavailability. When stratified by mesh size, MeHg concentrations were primarily determined by organism size, with larger zooplankton exhibiting higher levels than phytoplankton. The highest MeHg:THg ratios in total plankton and zooplankton were observed during low-water periods, likely driven by lower THg concentrations rather than by increased MeHg production alone. Across all seasons, larger zooplankton consistently exhibited higher MeHg:THg ratios than phytoplankton, indicating size-dependent bioaccumulation patterns. Our results demonstrate that Hg dynamics in plankton are strongly modulated by the hydrological cycle and exacerbated by anthropogenic inputs, emphasizing the importance of long-term monitoring to assess ecological risks in tropical river systems.

Graphical Abstract:

Effect of seasonality and organism size on mercury (MeHg) bioaccumulation in plankton of the Madeira River Basin, Western Amazon

Iuri Aparecida da Silva Oliveira, Lucas Cabrera Monteiro, Izidro Ferreira de Sousa-Filho, Elisabete Lourdes do Nascimento, Ronaldo de Almeida, Cássio da Silva Cabral, Wanderley Rodrigues Bastos

DOI: https://doi.org/10.1016/j.marpolbul.2025.118654

Abstract:

Mercury (Hg) emissions from both natural and anthropogenic sources influence Hg levels in the biota of a given region. Tropical regions, such as those in the Southwestern Atlantic (SWA) and the Eastern Pacific (EP) are particularly interesting due to differences in natural Hg sources, which may impact Hg levels in marine organisms, including sea turtles. In the EP, the Circum-Pacific Belt is a significant natural source of Hg, while natural Hg sources in the SWA are negligible. Moreover, anthropogenic sources are similar in both regions. We analyzed Hg concentrations and stable isotopes (δ13C and δ15N) in scutes, a non-invasive sampling procedure, of two populations of sea turtle's (Lepidochelys olivacea and Eretmochelys imbricata), found on the Pacific coast of Panama and the Northeastern coast of Brazil. The main objective of this study was to compare Hg concentrations between these populations and relate them to the environmental characteristics and feeding behaviors. The results revealed significantly higher Hg concentrations in L. olivacea and E. imbricata from the EP compared to those from the SWA, likely linked to higher environmental Hg levels from natural sources, as well as dietary habits, which were observed through the analysis of their trophic niches. Additionally, the results confirm the effectiveness of sea turtles' scutes as an interoceanic monitoring tool.

Graphical Abstract:

Assessment of mercury (Hg) contamination in tropical areas of the Eastern Pacific and Southwestern Atlantic oceans using two species of sea turtles

César Augusto Barrios-Rodriguez, Moisés F. Bezerra, Eric Enrique Flores, Carlos Antonio Vigil-González, Wilfredo Poveda-Pineda, Joelbin de la Cruz, Carlos Eduardo de Rezende, Marcelo Gomes de Almeida, Wanderley Rodrigues Bastos, Luiz Drude de Lacerda

Linking remote sensing and soil properties to model mercury spatial patterns in a natural reserve in the Amazon rainforest

Ygor Oliveira Sarmento Rodrigues, Lucas Cabrera Monteiro, Ronaldo de Almeida, Ângelo Gilberto Manzatto, Wanderley Rodrigues Bastos, Carlos Tadeu Carvalho do Nascimento & José Vicente Elias Bernardi

DOI: https://doi.org/10.1007/s10661-025-14941-3

Abstract:

Mercury (Hg) accumulation in Amazonian soils is influenced (governed) by atmospheric deposition, hydrological processes, and the rapid turnover of organic matter. Understanding its spatial distribution is critical for assessing ecosystem vulnerability and informing conservation strategies in tropical forests. We collected thirty surface soil samples within a 5 × 5 km grid in a protected area of the Amazon rainforest to investigate spatial relationships of total mercury (THg) concentrations. Variogram analysis and geostatistical interpolation—Ordinary Kriging (OK) and Co-Kriging (CK)—were applied to characterize spatial autocorrelation. Remotely sensed variables, including Gross Primary Productivity (GPP) and Height Above Nearest Drainage (HAND), were integrated alongside soil classification and soil organic matter (SOM) to improve predictive accuracy. THg concentrations, determined by cold vapor generation atomic absorption spectrophotometry, averaged 60.51 ± 18.16 μg kg⁻¹, with Oxisols and Ultisols showing comparable means (~ 62 μg kg⁻¹). CK models incorporating GPP and HAND achieved the lowest mean absolute error (MAE = 0.027), with similar spatial ranges for THg, GPP, and HAND supporting their joint predictive capability. GPP alone was a significant predictor (MAE = 0.04), consistent with links to atmospheric Hg deposition, terrain morphology, and sediment redistribution. Spatial patterns revealed Hg hotspots in intermediate topographic zones where organic and inorganic leaching (podzolization) and high humic activity occur, while Hg losses were associated with transport from upland plateaus and seasonally flooded areas. These results demonstrate that coupling geostatistical modeling with remote sensing products provides a robust approach for predicting Hg distribution in Amazonian soils and can inform environmental monitoring and management efforts in sensitive tropical ecosystems.