20 research outputs found
Disposal of dredged sediments in tropical soils: ecotoxicological effects on earthworms
The upper limit concentrations of metals
established by international legislations for dredged sediment
disposal and soil quality do not take into consideration
the properties of tropical soils (generally submitted
to more intense weathering processes) on metal
availability and ecotoxicity. Aiming to perform an evaluation
on the suitability of these threshold values in
tropical regions, the ecotoxicity of metal-contaminated
dredged sediment from the Guanabara Bay (Rio de
Janeiro, Brazil) was investigated. Acute and avoidance
tests with Eisenia andrei were performed with mixtures
of dredged sediment with a ferralsol (0.00, 6.66, 13.12,
19.98, and 33.30 %) and a chernosol (0.00, 6.58, 13.16,
19.74, and 32.90 %). Mercury, lead, nickel, chromium,
copper, and zinc concentrations were measured in test
mixtures and in tissues of surviving earthworms from
the acute tests. While ferralsol test mixtures provoked
significant earthworm avoidance response at concentrations
≥13.31 %, the chernosol mixtures showed significant
avoidance behavior only at the 19.74 % concentration.
The acute tests showed higher toxicity in
ferralsol mixtures (LC50=9.9 %) compared to
chernosol mixtures (LC50=16.5 %), and biomass increased
at the lowest sediment doses in treatments of
both test soils. Most probably, the expansive clay minerals
present in chernosol contributed to reduce metal
availability in chernosol mixtures, and consequently, the
ecotoxicity of these treatments. The bioconcentration
factors (BCF) for zinc and copper were lower with
increasing concentrations of the dredged sediment, indicating
the existence of internal regulating processes.
Although the BCF for mercury also decreased with the
increasing test concentrations, the known no biological
function of this metal in the earthworms metabolism
lead to suppose that Hg measured was not present in
bioaccumulable forms. BCFs estimated for the other
metals were generally higher in the highest dredged
sediment doses.Ricardo Cesar and Juan Colonese were
supported by grants from the National Brazilian Council for
Scientific and Technological Development (CNPq) and CAPES
(Coordination for the Improvement of Higher Level -or
Education- Personnel—Sandwich Doctorate)
Integrating ecosystem services and climate change responses in coastal wetlands development plans for Bangladesh
This study explores the integration of ecosystem services and climate change adaptation in development plans for coastal wetlands in Bangladesh. A new response framework for adaptation is proposed, based on an empirical analysis and consultations with stakeholders, using a modified version of the DPSIR (Driver-Pressure-State-Impact-Response) framework. The framework is tested in the Narail district of Bangladesh, where temperature has increased by about 1 0C in the summer in combination with an increase in rainfall of 0.70 mm day-1 yr-1 in the last decade. Calibrated model (MAGICC/SENGEN) projections forecast, on average, a temperature increase of up to 5 0C and an increase in rainfall of 25% by the end of this century. Water diversion in the upstream regions of the Ganges delta contributes to increase water scarcity in the dry season. Enhanced rainfall and the immense pressure of water discharges from upstream water sources are increasing the risk of floods and river erosion in the dry season. An increase in the water holding capacity of rivers, wetlands and canals by dredging is urgently required. The empirical model of this study is intended to support adaptation planning in Bangladesh and can be used in other data-poor areas which will suffer from climate change
Nutrient budgets (C, N and P) and trophic dynamicsof a Brazilian tropical estuary: Barra das Jangadas
This paper focuses on the nutrient dynamics of a tropical estuary on the northeastern Brazilian coast, studied using the LOICZ biogeochemical budgeting protocol. We describe the methodology and assumptions underlying this model. Input data (monthly for rainfall, evaporation, river discharge, and concentrations of salt, phosphorus and nitrogen) were obtained during field campaigns in the Barra das Jangadas Estuary (BJE) over a 5 years period (1999 to 2003). Mass balance results indicate large inputs of nutrients to the system. The model shows that the seasonal variation of the Net Ecosystem Metabolism (NEM) indicates that the system passes from a stage of organic matter liquid production and mineralization during the dry season (-0.5 mmoles C m-2 d-1) to liquid mineralization during the rainy season (-19 mmoles C m-2 d-1). We suggest that the system varies slightly between autotrophy and heterotrophy during the year due to the rainfall regime, human activities in the basin (density population and sugarcane plantations), and associated DIP riverine loads. High per capita loads of N and P indicate a high population density and high runoff. The application of flux balance modeling was useful to understand the nutrient dynamics of this typical small tropical estuary<br>Este trabalho se focalizou na dinâmica de nutrientes de um estuário tropical na costa nordeste brasileira, usando o protocolo LOICZ de balanços biogeoquímicos. Nós descrevemos a metodologia e os pressupostos subjacentes a este modelo. Os dados de entrada (precipitação e evaporação mensal, vazão do rio, e as concentrações de sal, fósforo e nitrogênio) foram obtidos durante as campanhas de campo no estuário de Barra das Jangadas - Brasil durante um período de 5 anos (1999 a 2003). Os resultados indicam grandes entradas de nutrientes ao sistema. O modelo mostrou que a variação sazonal do Metabolismo do Ecosistema (NEM) indica que o sistema passa de uma fase de produção de líquido da matéria orgânica, durante a estação seca (-0,5 mmoles C m-2 d-1) para uma mineralização líquida durante a estação chuvosa (-19 mmol m-2 C d-1). Sugerimos que o sistema varia ligeiramente entre autotrófica e heterotrófica durante o ano, devido ao regime de chuvas, as atividades antrópicas na bacia (densidade populacional e as plantações de cana de açúcar), e as cargas ribeirinhas de DIP associadas. A alta carga de N e P per capita, indica uma alta densidade populacional e um alto runoff. A aplicação da modelagem de balanço de fluxos foi útil para o entendimento da dinâmica de nutrientes em um pequeno estuário tipicamente tropica
Mercúrio total em músculo de cação Prionace glauca (Linnaeus, 1758) e de espadarte Xiphias gladius Linnaeus, 1758, na costa sul-sudeste do Brasil e suas implicações para a saúde pública Total mercury in muscle of the shark Prionace glauca (Linnaeus, 1758) and swordfish Xiphias gladius Linnaeus, 1758, from the South-Southeast coast of Brazil and the implications for public health
Foram analisadas as concentrações de mercúrio total (THg) em tecido muscular do tubarão azul Prionace glauca e do teleósteo Xiphias gladius, vulgarmente conhecido como espadarte, provenientes das regiões sul e sudeste da costa brasileira, para verificar se estas se encontram dentro dos padrões legais para consumo humano. As amostras foram obtidas utilizando-se o programa REVIZEE, de agosto a setembro de 2001, e por intermédio de uma empresa de pesca em Itajaí, Santa Catarina. Foi analisado um total de 95 espécimes, testando-se as correlações entre THg, comprimento (cm) e peso (kg). As concentrações de mercúrio total em todas as amostras variaram de 0,13 a 2,26µgg-1 (peso úmido). A média de mercúrio total em P. glauca foi de 0,76 ± 0,48µgg-1 (p.u.), e em X. gladius foi de 0,62 ± 0,31µgg-1 (p.u.) com diferença não significativa (teste Mann-Whitney, p < 0,05). Em cerca de 16% das amostras, o THg excedeu o limite de 1µgg-1 (Agência Nacional de Vigilância Sanitária) e em 62% excedeu o limite de 0,5µgg-1 (Organização Mundial da Saúde - OMS). O consumo regular (100 g.dia-1) de P. glauca e de X. gladius resultaria em uma ingestão diária de THg que excederia em mais de duas vezes o limite diário de ingestão recomendado pela OMS.<br>Total mercury (THg) was analyzed in muscle tissue from the blue shark Prionace glauca and the swordfish Xiphias gladius, obtained from the South and Southeast coast of Brazil, to verify compliance with current limits for human consumption. Samples were obtained through the REVIZEE Program and a commercial fishery in Itajaí, Santa Catarina State. A total of 95 specimens were analyzed (48 X. gladius and 47 P. glauca), and correlations were checked between THg and fish length and weight. THg ranged from 0.13 to 2.26µgg-1 (fresh weight), and there was no significant difference between the means for P. glauca, 0.76 ± 0.48µgg-1 (f.w.) and X. gladius, 0.62 ± 0.31 (Mann-Whitney test, p < 0.05). In 16% of samples, THg was above the limits set by the National Health Surveillance Agency (ANVISA), namely 1µgg-1, and 62% exceeded the World Health Organization (WHO) limit of 0.5µgg-1. The ingestion of 100g/ day-1 of P. glauca or X. gladius would result in a daily THg intake of more than twice the WHO (1990) suggested limit