RESUMO
Litterfall is the main source of dry deposition of mercury (Hg) into the soil in forest ecosystems. The accumulation of Hg in soil and litter suggests the possibility of transfer to terrestrial invertebrates through environmental exposure or ingestion of plant tissues. We quantified total mercury (THg) concentrations in two soil layers (organic: 0-0.2 m; mineral: 0.8-1 m), litter, fresh leaves, and terrestrial invertebrates of the Araguaia River floodplain, aiming to evaluate the THg distribution among terrestrial compartments, bioaccumulation in invertebrates, and the factors influencing THg concentrations in soil and invertebrates. The mean THg concentrations were significantly different between the compartments evaluated, being higher in organic soil compared to mineral soil, and higher in litter compared to mineral soil and fresh leaves. Soil organic matter content was positively related to THg concentration in this compartment. The order Araneae showed significantly higher Hg concentrations among the most abundant invertebrate taxa. The higher Hg concentrations in Araneae were positively influenced by the concentrations determined in litter and individuals of the order Hymenoptera, confirming the process of biomagnification in the terrestrial trophic chain. In contrast, the THg concentrations in Coleoptera, Orthoptera and Hymenoptera were not significantly related to the concentrations determined in the soil, litter and fresh leaves. Our results showed the importance of organic matter for the immobilization of THg in the soil and indicated the process of biomagnification in the terrestrial food web, providing insights for future studies on the environmental distribution of Hg in floodplains.
Assuntos
Bioacumulação , Monitoramento Ambiental , Invertebrados , Mercúrio , Rios , Mercúrio/análise , Mercúrio/metabolismo , Brasil , Animais , Rios/química , Invertebrados/metabolismo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Pradaria , Cadeia Alimentar , Ecossistema , Solo/químicaRESUMO
Mercury (Hg) is a chemical element that, depending on its concentration, may become toxic to living organisms due to the ability of Hg to bioaccumulate in food chains. In this study, we collected samples of soil, litter, and organisms in the Middle Araguaia floodplain, Brazil. Total mercury (THg) concentrations in litter were significantly higher (p < 0.0001) than that in soil, ranging from 10.68 ± 0.55 to 48.94 ± 0.13 and 20.80 ± 1.07 to 55 .19 ± 1.59 ng g-1, respectively. Total mercury concentration levels in soil showed a linear, inversely proportional relationship with soil organic matter (SOM) contents and soil pH, consistent with the geochemical behavior of chemical elements in flooded environments. Ten orders of organisms were identified, and the average THg concentrations determined in their bodies were up to 20 times higher than those in soil and litter. We found a significant linear relationship between the levels of THg in litter and those found in soil organisms, thereby allowing the prediction of THg concentration levels in soil organisms through the analysis of litter at the sample units. The different dynamics and feeding habits of soil organisms and the concentration of THg in these organisms may be influenced by the river's course. This study provides evidence of the bioaccumulation of THg in soil organisms in the floodplain of the Middle Araguaia River, an important river basin in the Brazilian savanna.
Assuntos
Mercúrio , Poluentes Químicos da Água , Mercúrio/análise , Brasil , Solo , Poluentes Químicos da Água/análise , Cadeia Alimentar , Monitoramento AmbientalRESUMO
Freshwater ecosystems are essential to human and wildlife survival. They harbor a wide biodiversity that contributes to ecosystem services. In the ecosystem of the Brazilian Savanna, anthropic activities related to environmental pollution that includes mercury (Hg) is of concern. We studied total mercury concentrations ([THg]) in bottom sediments and macrophytes to assess its short-term (2012 and 2019) impact on a natural lake. Temporal changes in [Hg] were assessed with the geoaccumulation index (Igeo) and the sediment quality guidelines (SQG). The land use index (LUI) was used to assess differences in anthropogenic activities and the Normalized Difference Aquatic Vegetation Index (NDAVI) was used to assess macrophyte biomass density. The bioaccumulation factor (BAF) was used to assess Hg accumulation in macrophytes relative to sediments. The LUI showed an increase in the intensity of agricultural activities in the vicinities of the lake. The NDAVI indicated an increase in the density of macrophytes in the evaluated period. The Igeo indicated that in all sampling sites, pollution levels in sediments increased in 2019 (Igeo > 0), with concentrations exceeding the SQG in 2019. In 2012, [THg] in sediments ranged from 20.7 to 74.6 ng g-1, and in 2019 they ranged from 129.1 to 318.2 ng g-1. In macrophytes, [THg] ranged from 14.0 to 42.1 ng g-1 in 2012, to 53.0 and 175.3 ng g-1 in 2019. [THg] in bottom sediments and macrophytes were significantly higher in the second collection period (p < 0.05). There was no significant difference in BAF values between the periods and no significant bioaccumulation in macrophytes (BAF <1). Our results demonstrated that the macrophytes are not sensitive indicators of Hg pollution in lentic environments of the Brazilian Savanna; however, the increased land use intensity (agriculture, automotive traffic, and urban infrastructure) could increase Hg accumulation in sediments and macrophytes in a short time interval.
Assuntos
Mercúrio , Poluentes Químicos da Água , Humanos , Mercúrio/análise , Lagos/química , Ecossistema , Brasil , Pradaria , Monitoramento Ambiental , Poluentes Químicos da Água/análise , Sedimentos Geológicos/químicaRESUMO
Mercury (Hg) is a persistent environmental pollutant of global concern. Recognized anthropic contributions to environmental Hg pollution include fuel fossil emissions, soil erosion, and industrial and mining activities. Environmental Hg that enters water bodies can be methylated before entering the food chain and contaminating man and wildlife. We used a kriging approach for sampling and X-ray crystallography to study the pressure of road-traffic Hg emissions on soil Hg concentrations in an ecological reserve (ESECAE) in Central Brazil' savannah. We took samples of organic (n = 144) and mineral (n = 144) layers from the road-side and from the undisturbed soils at 0.1, 1, and 2 km from traffic, inside the ESECAE. Overall, total mercury (THg) concentrations determined by atomic absorption spectrophotometry were significantly higher in the organic layer than in the mineral layer. The mean soil THg in the organic and mineral layers was highest at the roadside (respectively 19.77 ± 12.01 and 16.18 ± 11.54 µg g-1), gradually decreasing with the distance from the road. At 2 km, the mean soil THg was 0.09 ± 0.30 and 0.029 ± 0.03 µg g-1, respectively, for the organic and mineral layers. X-ray crystallography showed mineralogical similarity of the sampled soils, indicating Hg externality, i.e, it did not originate from existing soil minerals. Co-kriging analysis (n = 288) confirmed Hg hotspots on the roadsides and a faster mobilization occurring up to a distance of 1 km for both layers. The soil reception and retention of traffic Hg emissions are mainly in the organic layer and can impact subsoil and adjacent areas. Thus, traffic soil-Hg pollution is limited to the road proximities; THg concentrations are high up to 100 m with an inflection point at 1 km.