Raquel Franco de Souza

Composição florística de uma comunidade savânica no Rio Grande do Norte, Nordeste do Brasil

In the municipality of Rio do Fogo (in 1976) a savanna community was registered by radar that, until now, has not been studied in loco. Some questions were asked about this community: Is this area Cerrado, floristically? What is the phytogeography of plant species in this community? Do rare, endemic or endangered species occur in this community? To answer these questions a floristic inventory, from August 2007 to September 2009, was performed in 400 ha of this region. The data indicated that of the 94 species recorded, 73 are associated with Cerrado, 69 also with Caatinga, 60 with Atlantic Forest, 47 with Amazonian forest, 14 with the Pantanal and 11 with the Pampa flora. Thirty-nine species are first listed for Rio Grande do Norte (RN); Stylosanthes gracilis Kunth (Fabaceae) and Aristida laevis (Nees) Kunth (Poaceae) are first records for the Northeast of Brazil. Aspilia procumbens Baker (Asteraceae) showed a restricted distribution in the state and is listed as critically endangered. Stilpnopappus cearensis Hobber is listed as vulnerable to extinction. It was concluded that this area can be floristically classified as Cerrado, which points to a key area for conservation.

Ecotoxicological evaluation of water and sediment of an urban and coastal water reservoir in northeastern Brazil

A Lagoa de Extremoz, localizada na zona metropolitana de Natal, Nordeste do Brasil, e um importante reservatorio urbano que contribui para abastecimento de aproximadamente 300 mil pessoas. Devido a importância desse corpo hidrico para manutencao e desenvolvimento das atividades humanas, e importante conhecer como a qualidade da agua e sedimento deste ambiente varia ao longo do tempo e do espaco. Em 2013 foram realizadas quatro coletas, duas quando o nivel de agua da lagoa era inferior a 45% de sua capacidade (abril e maio) e, depois, quando o nivel de agua da lagoa estava no maximo de sua capacidade (julho e agosto), sempre em dois pontos na Lagoa de Extremoz e um no Rio Guajiru. Essas amostragens foram necessarias para avaliar as concentracoes de metais (Zn, Cu, Pb, Cd, Cr, Fe, Ni) no sedimento superficial, e sua relacao aos resultados de testes ecotoxicologicos realizados em agua e sedimentos. A extracao dos metais foi realizada por solucao mista (HCl 0,5 mol.L-1 + H2 SO4 0,012 mol.L-1) e analisada por Espectrometria de Absorcao Atomica (EAA). Os ensaios ecotoxicologicos cronicos usaram Ceriodaphnia dubia e C. silvestrii para analise da toxicidade da agua e Hyalella azteca para sedimento. Foram realizadas analises no sedimento para determinar os teores de materia orgânica - MO (incineracao em mufla a 600 oC), de carbonato (solubilizacao com acido acetico a 4%) e a granulometria (peneiramento simples). Os resultados sugerem riscos as comunidades de crustaceos bentonicos e, consequentemente, a todo o ecossistema da lagoa, atribuidos principalmente ao aporte antropogenico de Zn, Cu, Pb e Cd, a correlacao positiva de MO, CaCO3 e porcao siltico-argilosa, bem como a frequencia de amostras com efeito toxico cronica ao Hyalella azteca. Abstract The Extremoz Lagoon located in the metropolitan area of Natal, Northeast Brazil, is an important reservoir that helps to supply approximately 300,000 people. Due to the importance of this water body for maintenance and development of human activities, it is important to know how the quality of the water and sediment of this environment varies over time and space. Four samples were taken in 2013, two when the level of the water was less than 45% of capacity (april and may) and then when it reached the full capacity (july and august), always two points in Extremoz Lagoon and one in Guajiru River. These samplings were needed to evaluate the concentrations of metals (Zn, Cu, Pb, Cd, Cr, Fe, Ni) in the surface sediment, and its relationship to the results of ecotoxicological tests on water and sediment. The metals extraction was performed by mixed solution (0.5 mol L-1 HCl + H2 SO4 0.012 mol L-1) and analyzed by Atomic Absorption Spectrometry (AAS). The chronic ecotoxicological tests used Ceriodaphnia dubia and C. silvestrii to analyze the toxicity of the water and Hyalella Azteca for sediment. Analyses were performed in the sediment to determine the levels of organic matter (incineration in mufle furnace at 600 °C), carbonate (solubilization with acetic acid 4%) and particle size (single screening). The results suggest risks to the benthic crustaceans communities and consequently to the entire ecosystem of the lagoon, attributed mainly to anthropogenic contribution of Zn, Cu, Pb and Cd, to the positive correlation of MO, CaCO3 and siltic-clay portion, as well as the frequency of samples with chronic toxic effect to Hyalella azteca.

ANÁLISE COMPARATIVA DE METODOLOGIAS APLICADAS À DELIMITAÇÃO DA BACIA HIDROGRÁFICA DO RIO DOCE – RN

A bacia hidrografica e considerada um recorte geografico importante para o planejamento ambiental. A sua precisa delimitacao permite realizar um planejamento adequado para ocupacao e uso correto pela sociedade. Nesse sentido, o presente trabalho tem como objetivo realizar uma analise comparativa visual das delimitacoes automaticas realizadas com os programas TauDEM, SAGA e TERRAHIDRO, bem como da delimitacao por analise visual, com as delimitacoes oficiais do SEMARH - RN e da ANA (ottobacia nivel 05), visando redefinir e atualizar os limites da bacia hidrografica do Rio Doce/RN. Para fazer a delimitacao utilizaram-se os dados de elevacao do terreno do banco de dados geomorfometricos do Brasil, TOPODATA, hidrografia das cartas topograficas da SUDENE, na escala 1:100.000 e imagens do Google Earth. Os dados foram trabalhados nos SIGs QGIS 2.14 Essen e Terraview hidro 0.4.1. Os resultados mostraram que a delimitacao por analise visual e automatica utilizando a plataforma TERRAHIDRO possibilitou identificar os limites da bacia em suas areas aplainadas. Ja o TauDEM e o SAGA identificaram um paleocanal do rio Doce, direcionando assim o ponto exutorio da bacia. Entende-se que o TERRAHIDRO apresentou o melhor resultado para a delimitacao da bacia, propondo-se seu uso em bacias hidrograficas com escalas media e grande.

Influence of mining activity on the downstream sediments of scheelite mines in Currais Novos (NE Brazil)

The study area is one of the most important mineral provinces of the Rio Grande do Norte State (NE Brazil), which has been extensively exploited since 1940. This article presents a geochemical investigation of stream sediments taken in the drainage system between the Brejuí and Barra Verde scheelite mines, and the Gargalheiras municipal reservoir, in Acari city. In addition to the major elements, the trace elements V, Cr, Co, Ni, Cu, Zn, As, Rb, Sr, Zr, Mo, Sn, Ba, W were analyzed and compared to metal levels reported in the literature for the same area. The elements W, Mo, Cu, Sn and in part Zn are enriched in sediments of rivulets forming the drainage system close to the mining district. This is due to emission from uncovered mine waste dumps. Dispersion of elements is controlled by both, aeolian as well as fluvial transport. The concentration of Cu in stream sediments close to the mines reaches toxic levels. At the mouth of the drainage system to the reservoir, the elements W and Mo are still enriched in the stream sediments relative to the geogenic background by factors of 15 and 11, respectively. This indicates the probable influence of mining activity to the reservoir sediments, and mobilization of W and Mo in the reservoir water cannot be ruled out.