State Of Acre Research Articles

EVOLUÇÃO DE C-CO<sub>2</sub> EM SOLOS DE DIFERENTES ECOSSISTEMAS NA REGIÃO DO ALTO ACRE, ACRE, BRASIL

Different studies, developed over the years, have shown that the increase in human activities on the soil can influence the release of gases related to the increase in the greenhouse effect. In this sense, the use of methods that evaluate the evolution of C-CO2 has been considered as important indicators to detect changes in the environment, since they can be influenced by the crop and its cultivation system as a result of impacts on microbial activity. The objective of this work was to evaluate the release of C-CO2 from soils submitted to different ecosystems. Laboratory tests were carried out where soil samples, submitted to five different ecosystems, were collected in three different periods throughout the year in the municipalities of Brasiléia and Epitaciolândia, Alto Acre region, in the state of Acre, and were subsequently incubated. Subsequently, the evolution of C-CO2 was evaluated, and the readings were carried out periodically until the 500th day of incubation of the samples. The data were analyzed in order to evaluate the effect of different plant species on the evolution of C-CO2. Regarding the collection carried out in April, there was no difference in the evolution of C-CO2 between the areas. However, in the month of June, which comprises the period of the beginning of the transition between the rainy season and the dry season, and in the month of August, the dry season, it was observed that in the area of native forest occurred the highest values of C-CO2 flux, differing statistically from other areas within these months of collection. Between the collection times, only in the area of agroforestry system no significant differences were recorded in the evolution of C-CO2. The highest accumulated values of C-CO2 were recorded in the following sequence: native forest > agroforestry system > area with cassava > cultivated pasture > area with banana. It is concluded that the areas that present a greater contribution of plant material to the soil can serve as a stimulus to the development of microorganisms that, consequently, increase the flow of CO2, especially until the beginning of the dry season and that the absence of moisture negatively influences the emission of C-CO2, causing significant differences in the amount of release of C-CO2 between the study areas at the same time of evaluation.

Discovery of Buxaceae in Acre State, southwestern Amazon: First record of this ancient plant family in Brazil

The first record of Buxaceae for the flora of Brazil was made during fieldwork at the Rio Acre Ecological Station, Acre State, on the border between Brazil and Peru. This study describes the first record of Styloceras brokawii in the region and distinguishes it from other species within the genus based primarily on leaf and fruit morphology.

Three new species of Scottmoria (Lecythidaceae) from northwestern South America

Three new species of Neotropical Lecythidaceae are formally described: Scottmoria albomarginata from western Ecuador, S. decurrens from northwestern Ecuador to western Colombia, and S. spiralocucullata from western Amazonia in eastern Ecuador to the westernmost state of Acre in Brazil. The new species are illustrated and the relationships with related species are discussed.

Three new species of Demidospermus (Monopisthocotyla: Dactylogyridae) parasitizing Ageneiosus inermis (Siluriformes: Auchenipteridae) from western Amazon, Brazil.

During a study on the helminth fauna of fishes in the Juruá and Moa Rivers, State of Acre, north Brazil, three new species of Demidospermus Suriano, 1983 were found parasitizing Ageneiosus inermis (Auchenipteridae). Demidospermus juruaensis sp. nov. is characterized by its accessory piece, which is robust and straight, anchor-shaped distally, as well as by morphology of its hooks, which have a delicate and expanded shaft with a spear-shape ending. Demidospermus bifurcatus sp. nov. is characterized by a male copulatory organ (MCO) composed of a robust tube, with a bisected tip at the distal end and a robust accessory piece, that embraces the MCO along its entire length. Demidospermus takemotoi sp. nov. differs from its congeners by its long, tubular and slender accessory piece, which is almost the same length as the MCO. These findings bring the number of valid Demidospermus species to 36. The results of this research on the helminth parasites of fishes in Acre State underscore the importance of carrying similar studies on other fish species, thereby enhancing understanding of biodiversity in the Neotropical Region.

ATUAÇÃO DO ENFERMEIRO NA ASSISTÊNCIA AO PRÉ-NATAL DE ALTO RISCO NAS UNIDADES DE SAÚDE

The assistance provided by nurses to pregnant women, especially those at high risk, is crucial to guarantee maternal health and good fetal development. Prenatal care is an essential tool in the identification, treatment and control of possible pathologies during pregnancy and postpartum, aiming to reduce morbidity and mortality rates. Recent studies show that, in 2020, approximately 60% of pregnancy-related deaths could have been avoided with adequate prenatal care, especially in high-risk pregnancies. In the state of Acre, between 2016 and 2021, 89 deaths related to pregnancy, childbirth and the postpartum period were recorded, reinforcing the need for prevention policies and specialized care. This study focuses on the role of nurses in basic health units, addressing the complexities of monitoring high-risk pregnancies and presenting the role of this professional in interpreting events and managing frailties. The method applied was a literature review, based on articles and journals from databases such as Scielo, Google Scholar and LILACS. The results demonstrated the importance of prenatal care in UBS and highlighted the protocols followed by nurses to humanize care and improve the quality of care. It is concluded that the continuous training of nurses is vital to guarantee satisfactory results in prenatal care, promoting and preventing complications in the mother-baby binomial.

New Cernotina Ross 1938 (Trichoptera: Polycentropodidae) from Serra do Divisor, Acre, Brazil.

Two new species of the caddisfly genus Cernotina (Polycentropodidae) are described from the Parque Nacional da Serra do Divisor (PNSD), Acre, Brazil, Cernotina chicomendes sp. nov. and Cernotina divisor sp. nov. These two new species represent the first polycentropodids described from Acre State. Additionally, we update records for Cernotina hastilis Flint 1996 and Cernotina waorani Camargos, Ríos-Touma & Holzenthal 2017, including a distribution map for all the species mentioned here. We further emphasize the importance of protected areas for biodiversity conservation, especially the PNSD, which has recently faced threats due to a proposed road within its boundaries.

Acute kidney injury developed in the intensive care unit: a population-based prospective cohort study in the Brazilian Amazon

The Brazilian Amazon is a vast area with limited health care resources. To assess the epidemiology of critically ill acute kidney injury (AKI) patients in this area, a prospective cohort study of 1029 adult patients of the three intensive care units (ICUs) of Rio Branco city, the capital of Acre state, were evaluated from February 2014 to February 2016. The incidence of AKI was 53.3%. Risk factors for AKI included higher age, nonsurgical patients, admission to the ICU from the ward, higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores at ICU admission, and positive fluid balance > 1500 ml/24 hours in the days before AKI development in the ICU, with aOR of 1.3 (95% CI 1.03–1.23), 1.47 (95% CI 1.07–2.03), 1.96 (95% CI 1.40–2.74), 1.05 (95% CI 1.03–1.08) for each unit increase, and 1.62 (95% CI 1.16–2.26), respectively. AKI was associated with higher ICU mortality (aOR 2.03, 95% CI 1.29–3.18). AKI mortality was independently associated with higher age, nonsurgical patients, sepsis at ICU admission, presence of shock or use of vasoactive drugs, mechanical ventilation and mean positive fluid balance in the ICU > 1500 ml/24 hours, both during ICU follow-up, with aOR 1.27 (95% CI 1.14–1.43) for each 10-year increase, 1.64 (95% CI 1.07–2.52), 2.35 (95% CI 1.14–4.83), 1.88 (95% CI 1.03–3.44), 6.73 (95% CI 4.08–11.09), 2.31 (95% CI 1.52–3.53), respectively. Adjusted hazard ratios for AKI mortality 30 and 31–180 days after ICU discharge were 3.13 (95% CI 1.84–5.31) and 1.69 (95% CI 0.99–2.90), respectively. AKI incidence was strikingly high among critically ill patients in the Brazilian Amazon. The AKI etiology, risk factors and outcomes were similar to those described in high-income countries, but mortality rates were higher.

Regional development through innovation: a proposal for a technological hub framework

Brazil has made progress in innovation, although unevenly across its regions, with the state of Acre still facing challenges in this sector. The creation of an innovation and technology hub at Senai/AC aims to promote regional development by bringing together government, companies, and academia to stimulate local economic growth. This article proposes a strategic framework for the implementation of the Senai/AC Innovation and Technology Hub, with the goal of strengthening the regional economy and increasing industrial competitiveness. Based on a Systematic Literature Review, the best global and regional practices for the creation of innovation ecosystems were identified. The qualitative analysis of 40 articles resulted in strategic guidelines adapted to local needs, highlighting the importance of effective governance, resource mobilization, collaborative environments, human capital development, and a culture of innovation. The Senai/AC Hub has the potential to act as a catalyst for the state's socioeconomic development and strengthen local industries. Future studies can assess the effectiveness of the guidelines and the hub's impact on regional production chains, comparing it with other hubs to identify synergies and best practices.

Bartonella spp. in bats from the Brazilian Amazon Forest.

Despite the great diversity of bats (64 species) in the State of Acre, northwestern Brazil, there are no studies on occurrence and diversity of Bartonella spp. in bats in this region. The present study investigated the occurrence and molecular identity of Bartonella spp. in spleen samples (n = 271) from bats of 30 different species from this region, within the Amazon biome. Twenty-one out of 208 (10.1%) samples positive in the PCR for the mammalian gapdh endogenous genes were positive in the qPCR for Bartonella spp. based on the nuoG gene. The two gltA Bartonella genotypes detected grouped with those previously identified in bats from other locations, expanding the diversity of genotypes associated with bats. This study provided the first molecular evidence of the presence of Bartonella spp. in bats in the state of Acre and in bats of the species Lophostoma silvicolum, Vampyressa thyone, Tonatia saurophila and Phyllostomus elongatus.

Human outbreaks of a novel reassortant Oropouche virus in the Brazilian Amazon region.

The Brazilian western Amazon is experiencing its largest laboratory-confirmed Oropouche virus (OROV) outbreak, with more than 6,300 reported cases between 2022 and 2024. Here, we sequenced and analyzed 382 OROV genomes from human samples collected in Amazonas, Acre, Rondônia, and Roraima states, between August 2022 and February 2024, to uncover the origin and genetic evolution of OROV in the current outbreak. Genomic analyses revealed that the upsurge of OROV cases in the Brazilian Amazon coincides with spread of a novel reassortant lineage containing the M segment of viruses detected in the eastern Amazon region (2009-2018) and the L and S segments of viruses detected in Peru, Colombia, and Ecuador (2008-2021). The novel reassortant likely emerged in the Amazonas state between 2010 and 2014 and spread through long-range dispersion events during the second half of the 2010s. Phylodynamics reconstructions showed that the current OROV spread was mainly driven by short-range (< 2 km) movements consistent with the flight range of vectors. Nevertheless, a substantial proportion (22%) of long-range (> 10 km) OROV migrations were also detected, consistent with viral dispersion by humans. Our data provides a view of the unprecedented spread and evolution of OROV in Brazilian western Amazon region.

A multiproxy approach for the feeding ecology of Late Miocene ground sloths from the southwestern Amazonia, Upper Solimões Formation, Brazil

A rich assemblage of fossil sloths is recognized in the southwestern Brazilian Amazon, Upper Solimões Formation (Acre Basin), and represents some of the most diverse Folivora fauna from the Late Miocene of tropical South America. Here, we have used a multiproxy approach using carbon (δ13Csc) and oxygen (δ18Osc) isotope compositions of bioapatite structural carbonate, stereomicrowear, ecomorphological indices (relative muzzle width, RMW and occlusal surface area, OSA), and body mass estimates in order to suggest the habitats and diet of the mylodontids (Octodontobradys puruensis, Urumacotherium campbelli, Pseudoprepotherium venezuelanum and Mylodontinae gen. et. sp. nov.) and the nothrotheriid (cf. Mionothropus) ground sloths from localities along the banks at the Purus and Acre rivers in Amazonas and Acre states. The isotopic results (δ13Csc = −13.2 ± 1.2 ‰; δ18Osc = +24.7 ± 0.8 ‰) indicated a consistently C3 plant diet in open-canopy woodland and closed-canopy forest habitats during warm conditions across the Tortonian ages (∼10 and 8.5 Myr). U. campbelli (Urumacotherium sp., bm: 605 kg; Niterói Site) and cf. Mionothropus (bm: 163 kg; Acre 5 Site) possibly had specialized browsing habits (folivorous/frugivorous), due to the few coarse scars in relatively polished tooth surfaces and elongate skull with narrow muzzle, respectively. Both taxa, as also P. venezuelanum (bm: 733 kg; Niterói Site), showed a low OSA values suggesting limited oral food processing offset by higher fermentation capacity and/or lower metabolic requirements. Efficient capacity for oral food processing and a generalized browsing habit with consumption of high intrinsic toughness and abrasiveness items were inferred for O. puruensis (bm: 526 kg; Talismã Site), resembling the pattern observed for the Pleistocene megathere Eremotherium laurillardi from the southwestern Amazon (Acre State). A non-selective browser diet was also supported for the Mylodontinae gen. et. sp. nov. specimen from Cavalcante Site; its similar dentary morphology to the bulk-feeder taxa implies that this individual could occasionally eat C3 herbaceous/grasses.

A historical Llewellyn Ivor Price fossil fish collection from the Middle to Late Miocene of the Brazilian Amazon

Brazilian Miocene fluvial and lacustrine deposits are mainly found in the southwestern Amazon basin in the state of Acre, where fossiliferous sections from the Middle to Late Miocene of the Solimões Formation (Fm.) emerge in riverbanks during the dry season and low river-water level periods. The Solimões Fm. is notable for its high fossil vertebrate diversity (Myliobatiformes, Siluriformes, Ceratodontiformes, Osteoglossiformes, Characiformes, Acregoliathidae, Squamata, Crocodilia, Testudines, Suliformes, Rodentia, Notoungulata, Litopterna, Astrapotheria, Proboscidea, Didelphimorphia, Pilosa, Sirenia, Cetacea, Primates, Chiroptera, and Artiodactyla) deposited in the paleo-Amazon context. This fossiliferous faunal assemblage reflects the major geological and paleoclimatic Miocene/Pliocene transition events that triggered the greatest extinction of megafauna and other groups of animals in the Paleo-Amazon and, alongside the establishment of the largest Amazon transcontinental river in South America, led to species turnover and the diversity explosion to current levels. Paleontological expeditions carried out between 1950s and 1970s at Solimões Fm. outcrops along the Acre and Upper Juruá rivers allowed the recovery of an extraordinary vertebrate paleontological collection, albeit published in fragmentary contributions. Despite supporting the largest continental fish fauna, comprising ca. 2400 valid extant species, the Amazon hydrographic system harbors a still poorly known fossil ichthyofauna. This study describes a fossil fish assemblage from the Solimões Fm. for the first time based on high accuracy data acquired by improved microCT techniques, computerized systems, and examinations of the best recent and fossil fish collections. This fish assemblage is employed to elucidate ancestral Amazonian fauna paleodiversity and paleoenvironmental context interpretations and explore the elements that led to coeval paleo-ichthyofauna from the northwestern paleo-Amazon region. Miocene species Phractocephalus (†P. acreornatus and †P. nassi) are proposed as fossil guides.

Risk assessment of the laboratory host range and a molecular characterisation determining the field host range of Lixus aemulus, for the biological control of Chromolaena odorata in South Africa

Chromolaena odorata (Asteraceae: Eupatorieae) is a sprawling shrub native to the Americas, and a destructive invader of much of the humid tropics and subtropics of the Old World. Opportunistic native-range exploration in 1995 identified a stem-boring weevil, Lixus aemulus, as a promising biological control candidate agent. Host-specificity testing was conducted on L. aemulus in South Africa using laboratory no-choice and paired-choice tests. Three invasive alien plants closely related to C. odorata may be utilized by L. aemulus but no indigenous, ornamental or crop species in South Africa was or is expected to be attacked by the weevil. A native-range field survey was conducted in Brazil to determine the exact identity of the host plant L. aemulus had been collected in 1995, and to identify additional host-plant species. Genetic assessments of the Lixus sp.(p.). adults collected on the three host plants (C. odorata, Chromolaena laevigata and Heterocondylus vitalbae) reveal these individuals are L. aemulus and the weevil can be classed as an oligophage in its native range. Over 5,500 adults were released in South Africa, but overall establishment has been poor. The most likely explanation appears to be a climate mismatch between the region of South Africa invaded by C. odorata and the collection locality in Rio Branco, Acre state, Brazil. Additionally, because the full extent of the native range of L. aemulus is unknown, it is uncertain whether individuals can be sourced from an area whose climate resembles that of South Africa. Furthermore, despite being oligophagous, L. aemulus may perform sub-optimally on the southern African C. odorata biotype.

Characterization and economic losses caused by bruis in bovine carcasses in the state of Acre

The objective of this study was to characterize the injuries caused by bruises and evaluate the economic losses in carcasses of cattle slaughtered in a slaughterhouse, in the municipality of Rio Branco, Acre. The period from july 2020 to february 2021, two monthly visits were carried out, on random days, where 4,526 carcasses were analyzed. The presence of bruises was visually checked; the age, degree and size of the lesions, in addition, at the end of each slaughter, the distance between the municipality of origin of the animals and the slaughterhouse was verified. These lesions were later removed and weighed to quantify the damage caused. Among the carcasses analyzed, only 957 (21.12%) showed any lesion. The female category was the one that recorded the most injuries proportionally, with 172 (41%) of the 442 animals slaughtered, while 343 (25%) of the 1388 castrated males and 442 (16%) of the 2724 intact males had some injury. There was an average loss of 0.10443 kg per animal, extrapolating to the total number of cattle slaughtered in the state during the period, a loss of R$ 1.82 or U$ 0.33 per animal is estimated. Despite the low incidence, most bruises appear in the last 24 hours before slaughter, suggesting problems in pre-slaughter management. Therefore, improving animal welfare at this stage is essential to reduce these injuries and improve profitability in beef production.

New findings on the karyotype and distribution of two Rhipidomys Tschudi, 1845 species (Rodentia: Sigmodontinae) from Upper Purus River

Abstract Rhipidomys is a Sigmodontinae genus with a great diversity in western Amazonia, including Rhipidomys gardneri and Rhipidomys leucodactylus. These species shared the same diploid number of 44, however, two fundamental numbers were attributed to R. leucodactylus and one to R. gardneri. A new karyotype for R. leucodactylus is described, with a diploid and fundamental number shared by other Rhipidomys species. Data confirmed three karyotypes for R. leucodactylus, only one for R. gardneri, the presence of R. leucodactylus in the Brazilian state of Acre and extend the distribution of R. gardneri to Manoel Urbano, in Acre, showing both species occurring in the high Purus River basin.

Epidemiological Profile of COVID-19 in the State of Acre

Epidemiological Profile of COVID-19 in the State of Acre

CARACTERIZAÇÃO QUÍMICA E MINERALÓGICA DOS SUSPENSATOS DOS RIOS PURUS E JURUÁ NO ESTADO DO ACRE

The state of Acre, located in the southwest of the Brazilian Amazon, is drained by two large river basins, the Purus and Juruá rivers, which have their sources on the sub-Andean slopes of Peru and cross the state in a path almost parallel to each other and a southwest-northeast direction. They are meandering rivers, with a large amount of suspended sediment (suspended solids or load materials), which gives them their white or muddy color, in addition to transporting a lot of silty-sandy sediments by traction, forming significant beach bodies (pointed bars). The geological terrains drained by these rivers are made up of rocks from the Solimões Formation and sediments from the Alluvial Terraces. The present work sought to characterize the granulometry, mineralogy and chemical composition of suspensions from rivers in the State of Acre. These were subjected to granulometric analysis, mineral identification using X-ray diffraction (XRD) and scanning electron microscopy (SEM/SED) and total chemical analysis of trace elements. The highest concentration of suspended solids was found in the central part of the State both during the flood and dry periods, while the lowest are in the Moa and Paraná dos Mouras rivers. They are predominantly made up of silt with little fine sand and clay, averaging 12 microns. Mineralogically, they are made up of quartz, mica, smectite, illite, kaolinite, as well as albite and K-feldspar. These are sediments rich in SiO2 (55.69% +/- 3.89%), Al2O3 (18.68% +/- 1.76%), Fe2O3 (5.89% +/- 0.41%), with significant K2O values ​​(1, 93% +/- 0.07%), MgO (1.17% +/- 0.22%), Na2O (0.41% +/- 0.06%), in addition to TiO2 (0.85% +/- 0.10%). The values ​​of P2O5 (0.10% +/- 0.014%), CaO (0.14% +/- 0.17%) and MnO (0.10% +/- 0.021%) are at crustal levels. In terms of trace elements Rb, Sr, Cs, Ba, Th, U, Zr, Hf, Y, Nb, Cr, Co, Ni, Cu, Sc and V, are the elements that presented the highest concentrations. The average concentrations of these elements in the suspended materials when compared with beach sediments show enrichment in Al2O3, Fe2O3, MnO, MgO, Rb, Cs, Sc, and V. On the other hand, with the upper earth’s crust they show enrichment in Cs, Y, Cr, Co, Ni, Cu, Sc and V and with post-Archaean Australian shales only slightly enriched in Y. The presence of clay minerals (smectite, illite and kaolinite) and feldspars (albite and K-feldspars) are responsible for the high concentrations not only Al2O3 and Fe2O3, but also K2O, MgO and Na2O. The mineralogical and chemical composition shown by these suspensions, in addition to their granulometry, contribute to fertilizing both the floodplains (“varzeas”) as well as the beaches exposed by the rivers during the dry period, which are intensely cultivated with corn (Zea-mays) and beans (Vigna unguiculata (L) Walp) by riverside dwellers.

MINERALOGIA E GEOQUÍMICA DOS SEDIMENTOS DE PRAIAS (BARRAS EM PONTAL) E BARRANCOS DO RIO ACRE E SUA RELAÇÃO COM A FERTILIDADE AGRONÔMICA

The State of Acre is situated in the southwestern portion of the Amazon region and occupies 3.16% of its area. Two systems of drainage cross it: Juruá and Purus rivers. During the dry season, some beaches (point bars) are formed in the concave parts of the meanders. An example of this is observed on the Acre River, tributary of the Purus River. Incidentally, this area is of great historical importance for the region, as it was the site of a battle between Brazil and Bolivia for ownership of the State of Acre. Those beaches, which occur on the edges of the main rivers of the Acre, are intensely used for agriculture of subsistence of short cycle (beans (Vigna unguiculata (l) Walp), maize (Zea- Mays) and watermelon (Citrullus Lanatus) by the local peasants. These cultures occupy small areas, up to 2 hectares, on these beaches. Such situation is different from those on beaches from other regions of the Amazonia and Brazil. With the purpose of understanding the source of these sediments and the origin of this fertility, the present work was developed.The main unity of the State Acre is Solimões Formation, that occupies more than 80% of its surface (SEHA, 2000). It is formed mainly by argilites with carbonized organic matter (Radambrasil, 1976), and some fossils fragments of vertebrates and invertebrates. Locally, argillaceous siltites, calcareous rocks, ferruginous arenites and polimithics conglomerates are found (Radambrasil, 1976). On this Formation it was deposited holocenic sediments which constitute in part unstable abrupt declivities and, currently, beaches in both the edges of the rivers.The beach sediments, mainly in the cultivated areas, are predominantly siltics with unimodal distribution. The grains are angular to sub-angular and are constituted mainly of quartz, followed by smectite, illite, kaolinite and feldspar. The chemical composition shows high values of SiO2 (84,0 ± 4,7%, n = 10), and moderate to low values of the oxides (1 to 6%): Al2O3 (6,1 ± 1,7%, n = 10), Fe2O3 (2,7 ± 0,6%, n = 10), K2O (1,3 ± 0,2%, n = 10); Na2O (0,43 ± 0,12%, n = 10), CaO (0,28 ± 0,08%, n = 10) and MgO (0,4 ± 0,15%, n = 10), compatible with the mineralogical assembly identified, and therefore very different from those of other fluvial beaches, which are very poor in these components. Mineral constituents, such as feldspar and smectite and the angular form of the grains beach sediments, indicate immature evolution being Solimões Formation the source of these sediments.The fertility show that these sediments are comparable the eutrofic cambissols, with high capacity of exchange of cations (~ 11.01 Cmolc/Kg) and percentage of saturation of bases (v) above 90, indicating that they are in fact appropriate for agriculture. This fertility is related to clay minerals (smectite and illite) and its siltic and loosely bound grains.

GEOLOGIA, MINERALOGIA, GEOQUÍMICA, FERTILIDADE E POTENCIAIS IMPACTOS AMBIENTAIS EM PRAIAS, BARRANCOS E ÁGUAS FLUVIAIS E LACUSTRES (BACIAS DOS RIOS PURUS E JURUÁ) NO ESTADO DO ACRE: TEXTO DE APRESENTAÇÃO

This text explains why the results of research carried out in the State of Acre in the years 2002 to 2008 were released late, with financial support from two research projects financed by the CNPQ (SelenMerAs and Geosedintama) and a third (Ageopam) which also had a slight facet towards the region of this State. Although several works were published through communications at events and journals, much was restricted to dozens of dissertations, TCCs and reports from IC/PIBIC and others. It was concluded that even after almost 20 years, it was still opportune to disseminate these results and discussions, mainly because they are focused on the geological, mineralogical, multi-element chemical and fertility characterization of sediments on river cliffs, beach sands (bars in Pontal) and suspended sediments from rivers and lakes, in addition to environmental impacts, mainly on the wave of mercurial problem announced loudly in those years, which covered the entire Amazon. The BOMGEAM bulletin was chosen to disseminate unpublished results, due to its low cost, speed and accessibility. There will be two issues dedicated to the topic: BOMGEAM – ACRE 1 and BOMGEAM – ACRE 2. Issue 1 is dedicated more to the geology, mineralogy and geochemistry of sediments in ravines and bars; and number 2 to sediment fertility and potential environmental impacts. There are 13 contributions, involving dissertations, TCCs and monographs from IC/PIBIC and PDR.

MINERALOGIA, GEOQUÍMICA, FERTILIDADE E ORIGEM DOS SEDIMENTOS DE PRAIA (BARRA EM PONTAL) DAS BACIAS DOS RIOS PURUS E JURUÁ NOS TERRENOS DO ESTADO DO ACRE

The Acre state is in the southwestern part of the Brazilian Amazon region with an area of 164.123.738 km2 and a low population density (5.52 inhabitants/km2 for 2021). The geological context is mainly related to recent units that outcrop at the Acre basin and associated with the Solimões Formation, besides old alluvial terraces that follow main drainages. The Solimões Formation comprises fossil-bearing clayey siltstones intercalated to fine sandstones. The old alluvial terraces are composed by sand, silt, clay, and occasionally fossil fragments. The area of the Acre state is crossed by two main hydrographic basins: The Purus and Juruá rivers in the eastern and western part, respectively. Both rivers are the so-called “white-water rivers”. They exhibit a typical dendritic drainage pattern and are extremely meandering what give rise to lakes formed after abandoned meanders. During dry season, several beaches (point bars) are exposed on river‘s meanders, frequently used for swimming but also playing a very important role in the small-scale agriculture. These beaches are also used for planting corn (Zea-Mays) and beans (Vigna unguiculata (L) Walp). The main purpose of this work is to investigate the mineralogical and geochemical aspects of those beach sediments to understand their high fertility and to identify their primary source. Fourteen stations were selected for sampling purposes throughout the river valley close to BR-364 highway. Laboratory analyses were carried out as follow: grain sizes, x-ray diffraction, scanning electron microscopy and optical microscopy of heavy minerals concentrates; sediment whole chemistry (major and traces elements analyses including rare-earth elements) by means of ICP-MS; macronutrients (P, Mg, Ca, and K) besides available Na and Al and organic matter. The river sediments are mainly fine-grained, angular sub-angular and selected moderately. Mineralogical assemblage is represented by quartz, clay minerals (smectite, illite and kaolinite) and feldspars (K-feldspars and albite). The heavy minerals contents ranged from 0.5 to 4.6% and are mainly represented by zircon, epidote, kyanite, tourmaline, garnet, rutile, apatite, staurolite, ilmenite and hematite. Chemical results shown that the sediments are mainly composed by SiO2, besides minor amounts of Al2O3, Fe2O3, K2O, CaO and MgO, what is compatible with mineralogical composition. High SiO2 contents are mainly related to quartz and Al2O3 contents reflects the presence of clay minerals. Contents for alkaline and alkali-earths are relatively high for such beach environment related to feldspars and smectites. P2O5 is related to apatite and can also be adsorbed on smectite. Fe2O3 contents are mainly associated to smectite and a minor amount to ilmenite and hematite, the most common opaque minerals found in the beach sediments. Strong correlation coefficients were observed between Al2O3 and most major and trace elements, except for Zr, Hf, Ni and As. On the other hand, strong negative correlation was obtained between SiO2 and major and trace elements what points to the importance of smectites as scavenger of trace elements in such environment. The chemical results were compared with the mean of the Upper Crust and post-Archean Australian Shales (PAAS) and show that they are impoverished in MgO, CaO, Na2O and K2O in comparison with the former and MgO, in comparison with the latter. Such impoverishment is higher in samples enriched on sand fraction. The same comparison was carried out with the Chinese Changliang and Huanghe river sediments, showing impoverishment in CaO and MgO in comparison with the Changjiang River and MgO, CaO, Na2O and Sr, in comparison with the Huanghe River. The small value obtained for the Chemical Index of Alteration (CIA) shows that these sediments have experienced small degree of chemical weathering and consequently, physical weathering has prevailed in the source area. The beach sediments also exhibit high immature index as evidenced by the following very low rations: SiO2 / Al2O3 (11,64) and K2O/ Na2O (2,08). Rare-earth elements were normalized to the Upper Crust and to the PAAS patterns. They show similar patterns of LREE depletion and HREE enrichment. On the other hand, normalized to the chondrites present enrichment in LREE and horizontalization of the HREE, with similar standards of distribution between each other, presenting typical Eu negative anomalies of granitic and intermediary nature rocks. Analytical results for macronutrients exhibited high concentrations for P, Mg, Ca and K, and low contents of available Na and Al. Organic matter contents in below 1%. The sediments show high cation exchange capacity, base saturation over 70% and low Na and Al saturation. Accordingly, those sediments can be interpreted as representing a redistribution of the recent Miocene sediments (Solimões Formation) and the own sediments that were deposited in old alluviums. Chemical and mineralogical characteristics with a silty granulometry indicate that beach sediments are like the eutrophic cambisols.