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  • 1
    Electronic Resource
    Electronic Resource
    Variation of heavy metals in recent sediments from Piratininga Lagoon (Brazil): interpretation of geochemical data with the aid of multivariate analysis (1994)
    Springer
    Environmental geology 23 (1994), S. 241-247 
    Details
    ISSN: 1432-0495
    Keywords: Coastal lagoon ; Metallic concentration ; Multivariate analysis ; Depositional environment ; Anthropogenic discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In the last decade, the Atlantic coast of south-eastern Brazil has been affected by increasing deforestation and anthropogenic effluents. Sediments in the coastal lagoons have recorded the process of such environmental change. Thirty-seven sediment samples from three cores in Piratininga Lagoon, Rio de Janeiro, were analyzed for their major components and minor element concentrations in order to examine geochemical characteristics and the depositional environment and to investigate the variation of heavy metals of environmental concern. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed on the analytical data set to help visualize the sample clusters and the element associations. On the whole, the sediment samples from each core are similar and the sample clusters corresponding to the three cores are clearly separated, as a result of the different conditions of sedimentation. Some changes in the depositional environment are recognized using the results of multivariate analysis. The enrichment of Pb, Cu, and Zn in the upper parts of cores is in agreement with increasing anthropogenic influx (pollution).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00766738
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  • 2
    Electronic Resource
    Electronic Resource
    Ammonification rates and 210Pb in sediments from a lagoon under a wet tropical climate: Marica, Rio de Janeiro state, Brazil (1992)
    Springer
    Hydrobiologia 242 (1992), S. 69-76 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ammonification rates in surficial sediments of the Marica lagoon (Rio de Janeiro, Brazil) were estimated using two methods: (1) A direct evaluation of the ammonia productivity in sediments by means of an incubation procedure: the ammonia production rate is deduced from the difference in the ammonia concentrations in interstitial waters which were extracted directly after sampling and after incubation from two samples collected at the same point. (2) Since ammonia results essentially from the destruction of organic nitrogen, the ammonia productivity will be obtained by evaluating the nitrogen destruction rate: the amount of organic N mineralized is assumed to correspond to NH inf4 sup+ produced. The organic N destruction rate can be calculated by means of the matter balance equation provided the organic nitrogen profile and the sediment accumulation rate are known. The sedimentation rate, evaluated by means of the 210Pb method, differed in various areas of the lagoon. It was 0.35 cm y−1 in the open area of the lagoon (at 1.6 m in water depth), near the mouth of the Mombuca river (site M2); and 0.27 to 0.28 cm y−1 at 1.6 to 1.7 m at a greater distance of the river mouth (site M4). In a confined part of the lagoon (Z1), surrounded by reeds (Typha dominguensis), the rate is lower: 1 to 1.4 mm y−1 in the upper level (from 0 to 4 cm) where the organic matter amount reaches 60 to 80% (dry w.), and 1.1 to 1.2 mm y−1 deeper (below 5 cm) where organic matter corresponds to less than 40% of the sediment. The organic nitrogen destruction rate was calculated to be 0.8 · 10−6 µmol cm−3 s−1 (= 0.07 µmol cm−3 d−1) for the upper sediment level (0–2 cm) of site M4. This computed rate is slightly less than the value 1.1 · 10−6 µmol NH inf4 sup+ cm−3 s−1 obtained by means of the incubation experiment. For the upper level of the site close to the reeds (Z1), the calculated nitrogen destruction rate was 1.7 · 10−6 µmol cm−3 s−1 (0.15 µmol cm−3 d−1), the ammonification rate obtained by the incubation method 1.4 · 10−6 µmol cm−3 s−1. It appears that the two methods provided similar results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018062
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    Paper (German National Licenses)
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