Health risk assessment and quality reference values of potentially toxic elements in soils of the Southwestern Amazonas State - Brazil.

The geochemical processes involved in the Amazon soils formation are not totally understood because its geological and pedological features were formed during different geological events and different times. The Southwestern region of Amazonas State is an example of a region where the soils were developed from rocks formed by sedimentary processes and, nowadays, the soils continue receiving seasonal inputs from the Andes sediments. Data on geochemical patterns of this region are scarce, and there is no information about the possible effects of the natural or unnatural enrichment of potentially toxic elements (PTEs). Thus, this study represents the first research into the geochemical patterns of PTEs in soils of Southwestern Amazonas State. Further, we carried out a human health risk assessment and a proposal for Quality Reference Values (QRV) for thirteen PTEs (As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Ti, V, Zn and Zr). Our findings showed that the PTEs contents in soil samples collected in the lowland areas are strongly influenced by sediments inputs, while samples localized in the highland areas are weakly influenced by sediments inputs and present depletion of PTEs. Barium, Cr, Cu, Ni and Pb were the PTEs most influenced by sediment's deposition. The soil contamination assessment showed the existence of enrichment of the potentially toxic elements in soil samples, which may be a consequence of the natural inputs of the Andean sediments. Furthermore, Co and Cr exceed the safety zone for carcinogenic risk assessment, which indicates the need to monitor these elements and their possible effects on the health of the population in this region.

Human health risk assessment and geochemical mobility of rare earth elements in Amazon soils.

Rare earth elements (REEs) are a grouping of elements that encompasses lanthanides, yttrium and scandium due to their similar chemical properties and occurrence in ore deposits. Over the past few decades, economic interest in REEs has increased due to their use in several types of industries such as high-tech, medicine and agriculture. Extraction of REEs has been followed, in general, by incorrect disposal of tailing and waste, creating hazardous conditions in several countries. However, the magnitude of the possible impacts on ecosystem and human health are relatively unknown, especially in tropical systems. Thus, the objectives of this study were to assess the geochemical mobility and the bioaccessibility of REEs based on a series of chemical extractions and in vitro essay. We also tested two promising simple protocols (0.01 mol L-1 CaCl2 and 0.43 mol L-1 HNO3) for measuring REE bioaccessible fractions through a single extraction. Our findings show that the bioavailable fractions represent less than 20% of the ΣREEs fraction in all soil samples examine. Similarly, the oral bioaccessibility obtained by two in vitro methods (Gastric protocol and Gastric-Intestinal protocol) and by the single extraction tests represented less than 20% of the ΣREE contents. The non-carcinogenic risks and the carcinogenic risks associated to REEs oral exposure were low for children and adults. The extractions with 0.01 mol L-1 CaCl2 showed great potential as a method for measuring the REEs bioaccessible fraction.

Geochemical signatures and natural background values of rare earth elements in soils of Brazilian Amazon.

Rare earth elements (REEs) are generally defined as a homogenous group of elements with similar physical-chemical properties, encompassing Y and Sc and the lanthanides elements series. Natural REEs contents in soils depend on the parent material, the soil genesis processes and can be gradually added to the soil by anthropogenic activities. The REEs have been considered emerging pollutants in several countries, so the establishment of regulatory guidelines is necessary to avoid environmental contamination. In Brazil, REE soils data are restricted to some regions, and knowledge about them in the Amazon soils is scarce, although this biome covers more than 40% of the Brazilian territory. Thus, the objectives of this study were to determine the REE content in soils of two hydrographic basins (Solimões and Rio Negro) of the Amazon biome, establish their Quality Reference Values (QRV) and to investigate the existence of enrichment of REEs in urban soils. The ΣREE(Y + Sc) content of Solimões surface samples was 109.28 mg kg-1 and the ΣREE(Y + Sc) content in the subsurface samples was 94.11 mg kg-1. In soils of Rio Negro basin, the ΣREE(Y + Sc) was 43.95 15 mg kg-1 surface samples and 38.40 mg kg-1 in subsurface samples. The ΣREE(Y + Sc) in urban topsoils samples was 38.62 mg kg-1. The REEs contents pattern in three studied areas are influenced in different amplitude by natural soil properties. The REEs content in urban topsoils were slightly higher than the Rio Negro pristine soils, but the ecological risk was low. QRVs recommend for Solimões soils ranged from 0.01 (Lu) to 145.6 mg kg-1 (Ce) and for Rio Negro soils ranged from 0.05 (Lu) to 15.8 mg kg-1 (Ce).

Health risks of potentially toxic trace elements in urban soils of Manaus city, Amazon, Brazil.

The city of Manaus is the biggest industrial city of the north Brazilian region, and a haphazard urbanization process characterizes it. The continuous urbanization and industrialization processes have increased the levels of trace elements in the urban environment and have posed great threat on human health. It is, then, essential to assess the pollution levels and the potential risks of the trace elements presence in urban soils. Therefore, the purpose of this study was to investigate the status of trace elements soils pollution and their human health risks to the population of Manaus City. Twenty-two soil samples were collected from the surface layer (0-20 cm), and the contents of Ba, Cr, Mn, Zn, Co, Ni, Cu, Cd and Pb were analyzed. Results showed the predominance of kaolinite, gibbsite and goethite as the main minerals of the clay fraction. The trace elements contents were affected by both natural sources and anthropic activities such as industrial operations and vehicular emissions. The soil contamination assessment by Enrichment Factor showed the existence of eight samples classified as considerably contaminated and two samples classified as highly contaminated. Geoaccumulation index also showed the existence of eight samples exhibiting considerable contamination and one sample showing high contamination. The non-carcinogenic health risk was considered low (HI < 1) to both children and adults. However, the carcinogenic risk of Cd and Pb was higher than the safety limits (CRtotal > 1 × 10-6), indicating that the long exposure to contaminated soils increases the probability of children's cancer occurrence.

Risk assessment of trace elements pollution of Manaus urban rivers.

Manaus is the Capital City of Amazonas State, Brazil, in the heart of the Amazon rainforest. Its metropolitan area has a huge hydrographic basin where the disorganized urbanization has caused adverse effects in the urban rivers and creeks water quality. Thus, this study was conducted to evaluate the contents of Ba, Cr, Mn, Zn, Ni, Cu, the physicochemical parameters and their respective health risks in water samples from rivers and creeks located in urban areas with different degrees of urbanization in two different seasons. The determination of the physicochemical parameters showed the samples collected in areas with riparian vegetation presented mean values of temperature, pH, total dissolved solids and electrical conductivity lower than samples collected in urban environment. The hotspots of trace elements content were associated to the presence of industrial and domestic effluents as the main pollution source. The Water Quality Index results denoted a low water quality in four sampling sites, one during the rainy season and three others during the dry season. The overall non-carcinogenic health in the urban rivers was considered high in regions with huge population and intense anthropogenic activity. The results showed the potential risk of some of the trace elements on human beings, especially on children. The main element contributor to non-carcinogenic risk was Cr, although Mn and Ni also contributed to non-carcinogenic risk in a few areas, mainly for children during the dry season.

Efeitos de doses crescentes de calcário em solo Latossolo Amarelo na produção de mudas de pau-de-balsa (Ochroma lagopus sw, Bombacaceae) / Effects of the rising heat in Yellow Oxisoil in the production of silent wood rafts (Ochroma lagopus sw, Bombacaceae)

A produção de mudas de qualidade com adequado teor nutricional é fundamental para o desenvolvimento da planta e para a formação do sistema radicular, a qual apresentará melhor capacidade de adaptação ao novo local após o plantio. O objetivo deste trabalho foi avaliar o efeito de níveis crescentes de calcário na produção de mudas de pau-de-balsa. Os tratamentos foram constituídos de doses crescentes de corretivo e equivaleram a 0,0; 0,25; 0,5; 0,75; 1,0; 1,5 e 2,0 t ha-1 de calcário e o delineamento experimental utilizado foi o de blocos casualizados com cinco repetições. As características avaliadas foram: altura da planta; diâmetro do colo, matéria seca da parte aérea, matéria seca total, relação raiz/parte aérea, teores totais de macronutrientes nas plantas (N, P, K, Ca, Mg e S). Os resultados demonstraram que a prática de calagem como fator de correção do solo usado no substrato favoreceu todas as características de crescimento avaliadas na produção de mudas de pau-de-balsa. A correção do solo influenciou positivamente a absorção de Ca, Mg e S, por outro lado, não apresentou efeitos estatisticamente significativos para a absorção de N, P e K.

The production of quality rafts with appropriate nutritional tenor is fundamental for plant development and for forming of root systems, which present best ability to adapt to new locations after plantation. The goal of this work was to evaluate the effect of rising heat levels in the production of silent wood rafts. The treatment was constituted by rising doses of correction and was equal to 0.0; 0.25; 0.5; 0.75; 1.0; 1.5, and 2.0 t ha-1 of lime and the experimental detail used was of blocks, repeating five times. The characteristics evaluated were: plant height; diameter, dry material of the aerial part, root relation/aerial part, content of macronutrients in the plants (N, P, K, Ca, Mg and S). The results demonstrate that the practice of liming as a soil correction factor used in the soil substrate improved all the growth characteristics evaluated in seedling production of pau-de-balsa (Ochroma lagopus sw., bombacaceae). The soil correction positively influenced the absorption of Ca, Mg, and S, on the other hand, there weren't any statistically significant effects for absorption of N, P, and K resented.

Efeito da calagem e da correção dos teores de Ca e Mg do solo sobre o crescimento de mudas de angelim-pedra (Dinizia excelsa Ducke) / Liming effect and correction of the Ca and Mg contents of the soil on angelim-pedra (Dinizia excelsa Ducke) seedling growth

O conhecimento dos requerimentos nutricionais das espécies e de suas respostas à correção do substrato é fundamental para a produção de mudas de qualidade. O objetivo deste trabalho foi avaliar o efeito de diferentes tipos de calcário e da correção da deficiência de Ca e Mg sobre o desenvolvimento de mudas de angelim-pedra (D. excelsa) em casa de vegetação, utilizando-se como substrato Latossolo Amarelo. Foram testados três tipos de calcário e fornecimento de Ca e Mg por meio de fontes não-corretivas da acidez em três relações Ca:Mg. Os tratamentos consistiram de T0 & testemunha; T1 & calcário dolomítico; T2 & calcário magnesiano; T3 & calcário calcítico; T4 & Ca e Mg na relação 3:1; T5 & Ca e Mg na relação 9:1; e T6 & Ca e Mg na relação 15:1. O delineamento experimental foi de blocos ao acaso, com cinco repetições, totalizando 35 parcelas, cada uma delas com 3 mudas. O substrato foi adubado com doses equivalentes a 100-250-150 e 15 kg ha-1 de N, P2O5, K2O e S, respectivamente e com solução de micronutrientes (3 mL de Chelamix L-1 de água destilada). Foram avaliadas: a altura da planta, o diâmetro do colo, matéria seca da parte aérea, matéria seca da raiz, matéria seca total, relação raiz/parte aérea e conteúdos de nutrientes da parte aérea das plantas. De modo geral, a aplicação de calcário favoreceu o crescimento de D. excelsa, sendo os melhores resultados obtidos com a aplicação de calcário magnesiano na relação 9:1.

Knowledge of nutritional requirements of the species and their answers to correcting the substratum is fundamental for the production of quality seedlings. In this work, we aimed to evaluate the effect of different limestone types and the correction of Ca and Mg deficiency on the development of angelim-pedra (Dinizia excelsa) seedlings, under glasshouse conditions. We tested three types of limestone and three types of Ca:Mg provisioning on a Yellow Oxisol (with non-corrective acidity sources): T0 & control; T1 & soil limed with dolomitic lime (3:1); T2 & soil limed with magnesium lime (9:1); T3 & soil limed with calcitic lime (15:1); T4 & a mixture of calcium and magnesium, in the 3:1 proportion; T5 & calcium and magnesium, in the 9:1 proportion; and T6 & calcium and magnesium, in the 15:1 proportion. The experimental design was of random blocks, with 5 repetitions, totaling 35 parcels with 3 seedlings each. The substratum was fertilized with doses equivalent to 100-250-150 and 15 k ha-1 of N, P2O5, K2O and S respectively, and micronutrient solution (3 mL of Chelamix L-1 of distilled water). We evaluated the height, diameter of the stem, dry biomass of the aerial part, dry biomass of the root, dry biomass of the drought, aerial part/root relation and nutrient contents of the aerial part of the plants. The limestone application affected positively the height, the diameter, the matter total biomass and the absorption of Ca of the D. excelsa seedlings (p<0,05). The application of magnesium lime with Ca:Mg 9:1 proportion showed the best results.

Adubação nitrogenada na produção de mudas de mogno (Swietenia macrophylla King) / Nitrogen fertilization in the production of seedlings of mahogany (Swietenia macrophylla King)

Estudos sobre aspectos silviculturais de espécies florestais nativas da Amazônia são escassos, principalmente aqueles que visam a identificar técnicas de cultivo para a produção de mudas. O trabalho foi realizado objetivando avaliar efeitos de doses crescentes de N no desenvolvimento de mudas de mogno. O estudo consistiu de sete tratamentos, correspondentes à doses crescentes e equivalentes a 0, 20, 40, 60, 80, 100 e 120 g N ton-1 de substrato, utilizando-se uréia como fonte de N. Os tratamentos foram distribuídos em delineamento experimental de blocos casualizados, com oito repetições. Noventa dias após a repicagem foram avaliadas as seguintes características: altura de planta, diâmetro do caule, matéria seca das raízes, do caule, das folhas e total. Também se avaliou o conteúdo de N, P, K, Ca e Mg nas folhas. Os resultados mostraram que a dose de máxima eficiência física correspondeu a 61,5 g N ton-1 de substrato; o nível crítico de N para a parte aérea é de 27 g kg-1 e a dose para atingí-lo de 57,5 g N ton-1 de substrato. Observou-se também que na dose de 120 g N ton-1 houve efeito negativo da adubação nitrogenada sobre as características de crescimento avaliadas. Estes resultados indicam que as características de desenvolvimento e de acumulação de nutrientes pelas mudas de mogno foram influenciadas positivamente por doses crescentes de N, contudo na dose máxima utilizada neste estudo 120 g N ton-1, houve efeito negativo; a adubação nitrogenada resultou em aumento no conteúdo de N, P e Ca nas folhas; a dose de N recomendada para a produção de mudas de mogno, em substratos com características semelhantes ao empregado neste estudo, é de 57,5 g N ton-1 de substrato.

Studies on silvicultural aspects of native forest species of the Amazon Rainforest are scarce, mainly those that seek to establish cultivation techniques for production of seedlings. The current work had the objective of evaluating the effects of growing levels of N in the development of mahogany seedlings. The treatments were seven growing doses that were equivalent to the application of: 0; 20; 40; 80; 100 and 120 g N ton-1 of the substratum. The source of N was urea. The experimental design was randomized blocks with eight repetitions. Evaluations were accomplished after 90 days of transplanting where it was observed answers to the growing doses of N for the diameter of stem, dry matter of the leaves and for total content of N, P, K, Ca and Mg of the leaves. The recommendation of nitrogen fertilization for the production of mahogany seedlings is of 57,5 g N ton-1 of the substratum as a first approach.

Doses crescentes de corretivo na formação de mudas de mogno (Swietenia macrophylla King) / Growing doses of liming on mahogany (Swietenia macrophylla King) seedling formation

A produção de mudas é uma das fases mais importantes do cultivo de espécies arbóreas, sendo essa fase fundamental para o desenvolvimento adequado dessas espécies. O estudo teve como objetivo avaliar o crescimento e a absorção de nutrientes em mudas de mogno sob o efeito de doses crescentes de corretivo. O experimento foi conduzido no período de setembro de 2002 a agosto de 2003. Os tratamentos foram doses crescentes de uma mistura de carbonato de cálcio e carbonato de magnésio p.a., na proporção de 4:1, em doses equivalentes a 0; 0,5; 1,0; 2,0; 2,5; 3,0 e 5,0 t/ha. O delineamento experimental foi o de blocos ao acaso, com cinco repetições, num total de 35 parcelas, cada formada por 3 plantas. O substrato foi adubado com doses equivalentes a 200-500-300 kg.ha-1 de N, P2O5 e K2O, respectivamente e 15 kg.ha-1 de micronutrientes FTE-Br12. As características de crescimento avaliadas foram: altura, diâmetro do colo, matéria seca da parte aérea, raiz e total, relação parte aérea/raiz. Determinaram-se os teores de nutrientes da parte aérea, raiz e total, e em função desta última, estimaram-se os conteúdos. As médias foram comparadas pelo teste de Tukey a 5 por cento de probabilidade. A calagem afetou todas as características de crescimento, exceto a altura. O requerimento nutricional obedeceu à ordem decrescente de K>N>Ca>Mg>P>Fe>Mn>Zn>Cu. A dose de 0,5 t/ha mostrou-se mais vantajosa economicamente e pode ser recomendada quando se utiliza subsolo ácido e de baixa fertilidade natural como substrato.

Seedling production is one of the more important phases on the cultivation of trees, with this phase being essential for their appropriate development. The study had the objective of evaluating the growth and the absorption of nutrients in mahogany (Swietenia macrophylla King) seedling under the effect of corrective growing doses. The experiment was carried out from September 2002 to August 2003. The treatments were, 0; 0.5; 1.0; 2.0; 2.5; 3.0 and 5.0 t/ha, of a mixture of calcium carbonate and magnesium carbonate p.a., in the 4:1 proportion. The experimental design was randomized blocks with 5 repetitions, in a total of 35 parcels, each one with 3 plants. The substratum was fertilized with equivalents doses to 200-500-300 kg.ha-1 of N, P2O5 and K2O, respectively and 15 kg.ha-1 of micronutrients FTE-Br12. The growth characteristics evaluated were height, diameter of the stem, dry biomass of the aerial part, root and total, aerial part/root relation. It was determined the moisture contents of the aerial part, root and total and as a function of the last one it was estimated the contents. The averages were compared by the test of Tukey using 5 percent of probability. The liming affected all the growth characteristics, except the height. The nutritional necessity followed a decreasing order of K>N>Ca>Mg>P>Fe>Mn>Zn>Cu. The dose of 0.5 t.ha-1 was more advantageous from the economic point of view and can be recommended to acid subsoil of low natural fertility to compose substratum.

Dinâmica da mobilização de elementos em solos da Amazônia submetidos à inundação / Dinamics of elements in soils from Amazonia after controlled inundation

Parte significativa de solos da Amazônia permanece saturada ou inundada por períodos que podem variar de alguns dias a vários meses, em decorrência de enchentes ou deficiência de drenagem em algumas áreas, resultando em alterações químicas, físicas e biológicas nos solos. Este trabalho foi conduzido com o objetivo de avaliar a dinâmica da mobilização de Al, Ca, Fe, K, Mg, Mn, Na, Si e P em solos da Amazônia submetidos a inundação. Amostras de vários solos foram submetidas à inundação durante seis meses. Alíquotas da solução foram coletadas periodicamente durante o tempo de inundação e determinaram-se os teores dos diversos elementos em solução. A inundação influenciou a cinética dos elementos, com aumento da mobilização dos mesmos, principalmente, nas primeiras semanas. Os teores de Fe em solução foram mais elevados para os solos mais ricos em Fe amorfo. Em amostras com baixos teores de Fe amorfo e baixo conteúdo de matéria orgânica, os teores de Fe em solução foram muito reduzidos. O teor de P em solução foi influenciado por todas as formas de P. O P ligado ao Fe foi a forma que maior influência exerceu sobre o teor de P solúvel. Os teores dos cátions Ca, Mg, K e Na, em solução, foram diretamente influenciados por seus respectivos teores trocáveis, bem como pela cinética do Fe e do Mn.