Sambasiva R. Patchineelam

Sediment mixing and accumulation in a mangrove ecosystem: evidence from 210Pb, 234Th and 7Be

Abstract210Pb, 234Th and 7Be activities were measured to establish sediment accumulation rates, estimate sediment mixing rates, and determine the depth of the sediment mixed layer in the Sepetiba Bay mangrove ecosystem near Rio de Janeiro City, Brazil. Three sediment cores were collected from Enseada das Garças, a typical exposed tidal flat region with a sequence of sedimentary features. The seaward edge of this sequence is a mud flat with the landward portion covered with Spartina alterniflora followed by mangrove vegetation. An additional core was collected on an overwash island near Barra de Guaratiba, which is cover with mangroves without a mud flat or Spartina alterniflora sequence. Sediment accumulation rates were determined to range up to 1.8 cm/yr with the Spartina alterniflora having the maximum rate. Mixing rates were estimated for the Spartina alternifloracore at 40 cm2/yr based on 210Pb and 7Be from the upper mixed region of the core. The 234Th activity in this core suggested that either mixing or the input of 234Th were not in steady state. The sediment mixed region depth ranged from 4 cm to greater than 30 cm. At the Enseada das Garças site the mixing depth decreased in the landward direction (i.e. mud flats > 30 cm, Spartina alterniflora 11 cm, mangroves 4 cm). Along with this decrease in sediment mixing depth was a shift from physical to biological mixing. The Barra de Guaratiba core had a sediment mixed layer of 13 cm as a result of physical and intense biological activity.

Eutrophication history of Guanabara Bay (SE Brazil) recorded by phosphorus flux to sediments from a degraded mangrove area

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Organic matter content and particle size modifications in mangrove sediments as responses to sea level rise.

- see front matter 2009 Elsevier Ltd. All rights reserved.doi:10.1016/j.marpolbul.2009.08.005

Recent Sediment Accumulation in a Mangrove Forest and Its Relevance to Local Sea-Level Rise (Ilha Grande, Brazil)

Mangroves sediments contain large reservoirs of organic material (OM) as mangrove ecosystems produce large quantities and rapidly burial OM. Sediment accumulation rates of approximately 2.0 mm year(-1), based on (210)Pb(ex) dating, were estimated at the margin of two well-developed mangrove forest in southern Brazil. Regional data point to a relative sea level (RSL) rise of up to ∼4.0 mm year(-1). This RSL rise in turn, may directly influence the origin and quantity of organic matter (OM) deposited along mangrove sediments. Lithostratigraphic changes show that sand deposition is replacing the mud (<63 μm) fraction and OM content is decreasing in successively younger sediments. Sediment accumulation in coastal areas that are not keeping pace with sea level rise is potentially conducive to the observed shifts in particle size and OM content.

Heavy-metal pollution assessment in the coastal lagoons of Jacarepaguá, Rio de Janeiro, Brazil

Abstract An accumulation rate in a well-developed mangrove forest has been associated with relative sea-level rise on an island off the coast of Rio de Janeiro State. This rate was calculated by 210Pb dating models from a single sediment core. Results indicate an accumulation rate of approximately 1.7 mm/y for the past approximately 100 years. This rate is almost identical to the ongoing eustatic mean rise in global sea level, indicating a tectonically stable mangrove habitat. Organic C (OC), total N, δ13C(OC), and δ15N values from selected core intervals suggest a constant source of accumulating vegetal debris, dominated by C3-type vegetation with insignificant input of marine-derived organic matter, and a stable subaerial mangal habitat.

Nutrients, heavy metals and organic micropollutants in an eutrophic Brazilian lagoon☆

The Jacarepaguá lagoon receives the waste from 239 industries and domestic sewage. Bottom sediment analysis revealed that metal pollution is not spread over the lagoons but restricted to the discharge areas of the main metal-carrier rivers. Metal concentrations in superficial water showed the following concentrations values in ng/ml: Zn, 9.63+/-3.59; Pb, 0.61+/-0.43; Cu, 0.94+/-0.45; Mn, 12.7+/-8.0. Metal concentration in fish (average of seven different species) presented the following results, in mg/kg wet weight: Cr, 0.08+/-0.01; Cu, 0.4+/-0.15; Zn, 4.6+/-3.4; Fe, 2.4+/-1.3; Mn, 0.4+/-0.3. These results imply, considering fish consumption rate and the RfD (USEPA Reference Dose), that the local population is not exposed to undue health risks. Metal concentrations in the water may, however, increase due to their dissolution induced by pH and redox changes in the sediments.

Lead-210 and Beryllium-7 fallout rates on the southeastern coast of Brazil

Abstract This article documents the environmental quality with respect to nutrients, heavy metals, and organic micropollutants at Lagoa de Guarapina, a tropical eutrophic lagoon of Rio de Janeiro State, Brazil. Concentrations of nutrients and heavy metals in the lagoon and its tributaries were low, closely resembling natural conditions. However, Pb formed the exception, and its presence in conjunction with detectable concentrations of organic micropollutants suggest that minor pollution effects are occurring via atmospheric inputs.

An assessment of the pollution of heavy metals in Jacarepagua basin, rio de Janeiro, Brazil: A statistical approach

Total ²¹⁰Pb and ⁷Be fallout rates were measured on the coastal region of Niteroi, Brazil. The monthly depositional flux of ²¹⁰Pb and ⁷Be varied by a factor of 26, from 1.7 to 43.3 mBq cm⁻² year⁻¹ and ∼27, from 7.5 to 203.5 mBq cm⁻² year⁻¹, respectively. The relatively large oscillations in the depositional flux of ²¹⁰Pb at this study site were likely due to variations in air mass sources, while the ⁷Be fluctuations may be driven by a combination of weather conditions. Local geology could support the periodic high fluxes of ²¹⁰Pb from continental air masses, as shifting oceanic wind sources were affirmed by the uncorrelated ²¹⁰Pb and ⁷Be fallout activities and ⁷Be/²¹⁰Pb ratios. The ²¹⁰Pb atmospheric deposition was found to be in agreement with local sediment inventories, an important consideration in geochemical studies that estimate sedimentation processes.

Coupled anthropogenic anomalies of radionuclides and major elements in estuarine sediments.

Abstract The paper presents the metal pollution assessment of Jacarepagua basin rivers and lagoons based on statistical analysis of metal concentration in bottom sediments. It is demonstrated that Pavuna and Fundo Creeks are the main sources of anthropogenically introduced metals to the lagoons. Due to the weak process of water circulation in the lagoons the contamination is restricted to the discharge areas of both rivers. Metal concentration in river sediments appears to be highly dependent on rainfall events thus a seasonal (wet and dry seasons) variation in their concentration can be proposed. The examination of metal lognormal distribution plots indicates that concentration values, related to the curve inflexion(s), can be operationally used as thresholds between polluted and unpolluted areas. These values were; 0.92 μg g‐1 for Cd, 165 (μg g‐1 for Zn, 15 μg g‐1 for Cr and 26 μg g‐1 for Ni. Factor analysis was used to examine the main sources of metals to the aquatic environment. It can be suggested t...

Geochronology and heavy metal flux to Guanabara bay, Rio de Janeiro state: a preliminary study

Concentrations of fertilizer industry-derived P (up to 3.4%), Ca (up to 6.1%), (226)Ra (up to 744 Bq kg(-1)) and (210)Pb (up to 1317 Bq kg(-1)) at least one order of magnitude above natural levels were recorded in a sediment core from Morrão River estuary (SE Brazil). Unsupported (210)Pb (= total (210)Pb-(226)Ra) activities unexplained by atmospheric fallout and deviations from the radionuclides secular equilibrium also indicated strong anomalies. Anomalous constituents were positively correlated with each other and negatively correlated with clay mineral-bearing elements. These negative correlations were explained by a depletion of natural sediment constituents due to a dilution caused by elevated inputs of steel industry-derived elements (mainly by Fe levels up to 24%). Absolute data and normalizations by a proxy for clays (Al) and anthropogenic Fe evidenced variabilities in the quality of coastal and land-derived sediment inputs, mainly due to changes in the relative contributions from industrial sources.