Multiproxy analysis in contaminated sediments from Niterói Harbour (Guanabara Bay), Brazil.

Harbours are located in major urban centres around the world and are of great economic importance to the cities in their surroundings. However, the intense traffic of boats and ships can generate environmental impacts that can directly affect the local biota as well as the population that lives in surrounding areas. Therefore, this work aimed to analyse the surface sediment of the Niterói Harbour using chemical, biological and micropalaeontological tools to investigate the environmental condition of this important harbour in Rio de Janeiro State. The pseudototal trace metal data analysed in the surface samples showed values far above those of the greater Guanabara Bay background. These data were corroborated by a high mortality rate of Artemia sp. and elevated presence of the bacterium Vibrio fischeri, indicating a high rate of local pollution. Dinoflagellate cysts also showed a direct response to high values of pseudototal trace metals. The data obtained in this study emphasize a need for greater monitoring of ports since the experience gained through this study in a Brazilian harbour can serve as an example for the management of other harbours located in large urban centres around the world.

Assessment of bottom sediment quality in Niterói harbor (Brazil, South America) through ecological indexes concerning nutrients and trace metals.

Bottom sediment quality from the Niterói harbor at Guanabara Bay (Rio de Janeiro, Brazil) was evaluated based on concentrations of organic phosphorus (OP) and inorganic phosphorus (IP) and bioavailability of trace metals through BCR fractionation analysis (Zn, Cu, Pb, Cr, Ni, Cd). The study area revealed elevated concentrations of fine sediments and organic matter (TOC: 2.26-7.31%). OP presented extremely elevated concentrations between 0.57 and 47.04 µmol/g, whereas IP reached a maximum concentration of 4.99 µmol/g. The anoxic bottom at the study area was confirmed by high TOC/OP values in most stations. Phosphorus enrichment index (PEI) varied between 0.07 and 2.57, pointing to ecological risk at some stations. Trace metals were mostly bonded to the bioavailable fractions (exchangeable, reducible, oxidizable), and decreasing order of mobility was Zn > Cu > Pb > Cr > Ni > Cd. The Risk Assessment Code (RAC) suggested a high risk of bioavailability for Zinc and a medium risk for the other metals. Overall, the Niterói harbor revealed poor sediment quality suggesting a strong anthropogenic pressure in the area.

Environmental assessment concerning trace metals and ecological risks at Guanabara Bay, RJ, Brazil.

Three-stage sequential extraction BCR was applied to surface sediments from the west part of Guanabara Bay to assess the mobility of Zn, Cu, Pb, Ni, Cr, and Mn. Results were satisfactory for the analysis of certificate standard material (BCR 701), with recoveries between 71 (Cu) and 123% (Cr). Evaluation of organic matter composition classified the area as eutrophic (CHO:PRT > 1), with aged organic detritus at some stations. Zn exhibited by far the greatest bioavailability, with 43.49% of its concentrations associated with the exchangeable fraction. Cu and Cr showed stronger affinity for organic matter, with 51.18 and 48.73% of their concentrations, respectively, bounded to the oxidizable fraction. Pb presented higher concentrations in the reducible fraction (45.41%). The strongest lithogenic contribution was shown by Ni (31.91%) and Mn (35.44%). PCA clearly showed the determinant role of organic matter and fine sediments in the distribution of metals in the study area and also a common source for these elements, with the exception of Cu. Risk Assessment Code (RAC) established Zn as the most concerning element in the study area. The decreasing mobility order, based on the sum of the three extractable fractions of BCR, was Pb > Cu > Cr > Zn > Ni > Mn. The comparison of the results with sediments quality guidelines (SQG) proved fractionation to be mandatory in the evaluation of effective ecological risk concerning trace elements in sediments.

Ecological risks of trace metals in Guanabara Bay, Rio de Janeiro, Brazil: An index analysis approach.

Total concentrations of Ni, Cr, Cu, Pb and Zn were determined in surface sediments from 30 stations in Guanabara Bay in 1999 and 2008. An approach using various environmental indices was used to assess contamination status of metals. This approach allowed the comparison with different coastal areas. Background Enrichment Index, Contamination index and Ecological Risk index (Pollution Load Index; Sediment Quality Guideline Quotient and Ecological Risk Index) were calculated for the metals. Results revealed a great load of organic matter and significant increases in Cu and Pb levels between 1999 and 2008. The concentrations of Cr and Zn were of great concern, surpassing the values of Probable Effect Level reference values. In spite of the differences of each index, results effectively revealed the striking contamination in Guanabara Bay concerning trace metals, and also suggested potential risk to local biota. The contamination of the northwest area was notably higher than the rest of the bay. In comparison with some other coastal bays around the world, Guanabara Bay stood out as a remarkably contaminated environment.

Eutrophication and hypoxia in four streams discharging in Guanabara Bay, RJ, Brazil, a case study.

Four streams in the city of São Gonçalo, were sampled to evaluate their potential as sources of nutrients to Guanabara Bay aiming to contribute with the government program to decrease the levels of pollution in this area. Imbuaçu, Guaxindiba, Marimbondo and Brandoas streams were sampled in 2007, 2008 and 2009. The streams revealed to be hipereutrophic with severe limitation of primary production by nitrogen, as shown by the N/P molar ratio. Phosphate levels were abnormally high varying between 4.35 and 130.82 µM, whereas nitrate and nitrite ranged from 0.06 to 54.05 µM and from 0.28 to 19.23 µM, respectively. The streams also presented severe hypoxia and anoxia, with oxygen values varying from non-detected to 3.72 ml l(-1). Heavy loads of particulate suspended material were recorded in the studied streams, ranging between 6.00 and 400.00 mg l(-1). The streams were considered inexorable sources of nutrients, enhancing the severe eutrophication process in Guanabara Bay.