Influence of Iron on Physiological Parameters and Intracellular Microcystin in Microcystis Panniformis Strain Isolated from a Reservoir in the Amazon.

In the Amazon, the leaching from soil left unprotected by deforestation increases the entry of iron, among other elements, in aquatic ecosystems, which can cause cyanobacterial blooms. This study aimed to investigate the physiological response of a strain of Microcystis panniformis to iron variation. The strain was isolated from a reservoir located in the Western Amazon and produces microcystin-LR. After a period of iron deprivation, the cultures were submitted to three conditions: control (223 µgFe.L-1), treatment with 23 µgFe.L-1, and absence of iron. At regular intervals for eight days, the cell density, levels of chlorophyll a and microcystins were determined. On the second and fourth day, transcription of genes responsive to iron limitation was quantified. Starting on the fourth day of the experiment, the different iron concentrations affected growth, and on the eighth day in the iron-free condition cell density was 90% lower than in control. Chlorophyll cell quota in 23 µgFe.L-1 and control presented similar values, while without iron the cells became chlorotic as of the fourth day Toxin concentration in cells grow in 0 µgFe.L-1 in relation to the control. Higher transcription levels of the feo and fut genes were observed in the 0 µgFe.L-1 and 23 µgFe.L-1 treatments, indicating that the cells were activating high-affinity capture systems to reestablish an adequate concentration of intracellular iron. The increasing deforestation in the Jamari River Basin (Amazon region), can contribute to the occurrence of toxic cyanobacterial blooms due to the greater entrance of iron in water bodies.

Arsenic in the lower drainage basin of the Paraíba do Sul River (Southeast Brazil): dynamics between the water column and sediment.

The presence of arsenic (As) in the sediment and the particulate and dissolved fractions of the water column determines its behavior and bioavailability. The main geochemical parameters responsible for As mobility are organic matter and oxide-forming metals such as Fe. The As distribution and its concentration were evaluated in the dissolved fraction, suspended particulate matter (SPM) and sediment of the lower Paraíba do Sul River (PSR), its main tributaries (Muriaé, Pomba, and Dois Rios rivers), and flooded and estuarine areas. As was not detected in the dissolved fraction. The river flow influenced the As concentration in the SPM, which was higher in the dry season than in the rainy season (2.6 ± 0.69 and 1.98 ± 0.29 mg kg-1, respectively). The Fe oxyhydroxides, organic carbon, and surface area measured in the sediment were positively related with As concentration (R2 = 0.11, 0.34, and 0.30; p < 0.05). The highest As concentrations in the sediment occurred in the secondary estuary and flooded areas (5.16 ± 4.78 and 1.23 ± 0.44 mg kg-1, respectively), in which finer granulometric fractions (silt and clay) predominated (64% and 71%, respectively), in addition to greater surface area. The measurement of stable carbon and nitrogen isotopes (δ13C and δ15N) and atomic ratio (C:N)a indicated the existence of a combination of autochthonous and allochthonous sources of organic matter composing the SPM. In general, the As concentrations in the sediment and SPM were low, with values below that permitted by Brazilian regulations (5.9 mg kg-1), which suggests that the As sources in the lower basin of the PSR are diffuse and natural.

Arsenic Exposure and Effects in Humans: A Mini-Review in Brazil.

Arsenic (As) is widely studied in several countries due to its toxicity to biota in the environment. Arsenic sources may be natural or anthropogenic, and the mobility of the element is ruled by physicochemical conditions that also define the dominant As species in the environment. Arsenic levels are evaluated in various abiotic and biotic environmental samples. The highest As levels are observed in sediment, from where it may be mobilized into the aquifers. This article reviews studies about As in the world but with emphasis on studies performed in Brazil, a country where continental water bodies are a common geographic feature. We reviewed 64 studies published between 1985 and 2016. The results indicate that in recent years more studies have been conducted to determine As levels in foods and human samples as a tool to evaluate the exposure of populations and identify potential sources. In Brazil, the main problems associated with contamination with As are the use of wood preservatives and herbicides as well as the impact caused by mining. Also, the precarious character of sewage treatment systems contributes to the contamination of water bodies.

Exposure to toxic and essential trace elements through the intake of processed and meat cuts (beef and chicken) in southeastern Brazil.

The present study evaluated the concentration of six trace elements in processed meat products and in meat cuts. We also assessed the risk associated with the consumption of these foods based on the estimated daily intake (EDI) of these elements. Fifty-eight processed meat and 148 meat cuts samples were analyzed using ICP-OES. As and Cd were not detected in any sample of processed meat. The highest mean level of lead was observed in frankfurters (0.056 µg g-1), which is half the maximum permissible level. For Cr, the highest mean concentrations were detected in chicken nuggets and beef hamburger (0.121 and 0.105 µg g-1, respectively), which are above the allowed limit. The comparison between the impact of a diet restricted to processed meats with a diet restricted to meats cuts showed that the individuals following the latter are exposed to higher amounts of the trace elements analyzed.

Impact of Land Use on the Mobility of Hg Species in Different Compartments of a Tropical Watershed in Brazil.

This study evaluated the levels of total Hg and CH3Hg+ from a comprehensive perspective, considering the retention, leaching, and deposition of these contaminants in the main compartments (soil, plant litter, and sediment) of three landscapes (Atlantic Forest, pasture, and agricultural area) in a watershed in northern Rio de Janeiro State, Brazil. Variables analyzed were total Hg, CH3Hg+, organic carbon, total nitrogen, grain size, and surface area. In soil samples, total Hg levels were the highest in agricultural soil followed by forest soil and pasture (97.3, 87.6, and 77.1 ng g-1, respectively), and CH3Hg+ was lower than 1.7%. Total Hg levels in leaf litter varied between 22.6 and 34.2 ng g-1, and CH3Hg+ was 4.37%. In sediment, Hg (60-180 ng g-1) and CH3Hg+ (<1%) indicate the transport of these contaminants from soils to this compartment and may be associated with soil use and cover. Multiple regressions were used to understand the dispersion of Hg species, and the effect of each variable varied with the landscape, showing that plant cover should not be ignored in investigations related to Hg species retention in a watershed. The landscapes surveyed in the present study clearly influence the quantitative and qualitative distribution of Hg species. On the other hand, anthropic processes associated with changes in soil use did not have any critical effects on the absolute levels of total Hg and CH3Hg+, meaning that the landscapes evaluated seem to represent the background concentration of these chemical species for the evaluated watershed.

Effects of dams on As and Hg concentrations in three southeastern Brazil fluvial systems: Ocean inputs, sources and seasonal dynamics among environmental compartments.

Damming rivers for hydropower generation interferes in the flow of water bodies and, consequently, in trace element biogeochemistry and transport. This study focused on the effects of dams on the seasonal dynamics of arsenic (As) and mercury (Hg) in three fluvial systems (Itabapoana River, Flechas Channel and Paraíba do Sul River) and on the input of these elements to the ocean. The elements were evaluated in suspended particulate matter (SPM), surface sediments, and the roots of the aquatic macrophyte Eichhornia crassipes. Our results showed that the proximity of the dams in the Flechas Channel and Rio Itabapoana in relation to their mouth (distances of 4 km and 58 km, respectively) changed As and Hg seasonal dynamics in the environmental compartments analyzed, with the Flechas Channel being the most impacted area. In contrast, the lower part of the Paraíba do Sul River that has more distant dams to its mouth (distance of 184 km) did not show such marked changes, suggesting that most of the inputs are coming from the long river reach. The isotopic and elemental composition of organic matter indicated the soils of native forests as the main source of trace elements to the water bodies. Flow rate was the main driver controlling As and Hg ocean inputs, with higher inputs observed in the Paraíba do Sul River (9.69 and 0.59 t∙year-1, respectively) compared to the other assessed fluvial systems. Also, this study demonstrated that, if a dam is closer to the mouth of a river, less contaminants will be input.

Risk of exposure to total and inorganic arsenic by meat intake among different age groups from Brazil: a probabilistic assessment.

Beef and poultry as well as cattle and chicken livers are staple food items for Brazilian population, and previous studies had detected arsenic levels in these foods. This study aims to evaluate the risk of exposure to total and inorganic arsenic by meat intake in three age groups from Brazil (11-16, 16-21, and > 21 years). Our hypotheses are (i) that there is differences in the risk of exposure between age groups and (ii) the older individuals (> 21 years) are under higher risk. To test these hypotheses, we calculated the probabilistic estimated daily intake of total As (TAsEDI) from poultry, beef, cattle liver, and chicken liver, and the probabilistic estimated incremental lifetime skin, bladder, and lung cancer risk (ILCR) associated with inorganic As ingestion from poultry only. TAsEDI and ILCR from poultry differed among groups which confirm the first hypothesis. However, TAsEDI and ILCR results cannot support the second hypothesis. Even though the age groups are under a low risk of exposure to As by meat intake, the results indicate that bladder/lung cancer risk (from poultry intake) slightly exceeds the safe limits in the older population.