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Aquatic Geochemistry (v.18, #5)
Evaluating Copper Behavior in Urban Surface Waters Under Anthropic Influence. A Case Study from the Iguaçu River, Brazil by Fernando F. Sodré; Danielle C. Schnitzler; Elizabeth W. O. Scheffer; Marco T. Grassi (pp. 389-405).
The goal of this work was to investigate the changes in copper behavior in Iguaçu River, a body of water strongly affected by urban inputs. This work was carried out in a subtropical Brazilian watershed suffering with high loads of raw sewage discharges from the Metropolitan Region of Curitiba. A comparison between sampling sites located upstream and downstream from the urban region revealed that human inputs are able to modify the water chemistry of the river in a short distance basis, that is, approximately nine miles. Probably, the most important alterations were the creation of an anaerobic environment as well as the enhancement of humic-coated suspended solids. These two aspects were determinant to explain the high concentrations observed for particulate copper (57% of total recoverable copper) and dissolved copper sulfide species (13%) in the water column. Copper in the sediment was also higher in the downstream site, probably due to the sedimentation of the Cu-enriched particles. However, copper sulfides at the bottom sediment may also be a potential source for the metal in the water column due to the creation of anaerobic conditions in both compartments. Labile copper concentration was not affected by the changes in water chemistry. Despite the fact that sewage discharges motivate the enhancement of organic matter, but not the increase in potential complexing agents, additional ligands such as chloride, carbonates, and anthropogenic dissolved organic ligands can be now computed as a part of the labile fraction.
Keywords: Copper speciation; Raw sewage discharges; Dissolved sulfides; Urban waters
Biogeochemical Behavior of Arsenic Species at Paranaguá Estuarine Complex, Southern Brazil by Vanessa E. dos Anjos; Eunice da C. Machado; Marco T. Grassi (pp. 407-420).
The behavior and dynamics of arsenic at Ilha do Mel, Guaraqueçaba, and Paranaguá, located in the Paranaguá Estuarine Complex, Brazil, were investigated in this work. Samples were collected in March, September, and December of 2005. With respect to arsenic behavior, the total concentrations were higher for Paranaguá (22.5 ± 2.5 μg L−1) on average, followed by the samples of Guaraqueçaba (14.4 ± 3.2 μg L−1) and Ilha do Mel (8.7 ± 1.1 μg L−1). The concentrations found in this work were consistently greater when compared to other estuaries. The results can be attributed to geological factors. Nevertheless, it was also possible to realize that higher concentrations were found in Paranaguá, the more impacted environment. These results represent a strong indication that human activities in the area contribute to the enrichment of the estuary with this metalloid. Arsenic was mainly present in the dissolved phase, which corresponded to more than 70% of the total concentration. This behavior can represent a greater residence time of this metalloid in the water column. The marine phytoplankton presence was decisive in dictating the distribution of As in the waters of Paranaguá estuary. Organic species, which are considered the less toxic, were found in higher concentrations in the eutrophic areas such as Guaraqueçaba and Paranaguá. This was a typical behavior during the summer probably due to higher biological activity.
Keywords: Arsenic; Speciation; Bioavailability; Marine phytoplankton
Total Mercury Distribution and Volatilization in Microcosms with and Without the Aquatic Macrophyte Eichhornia Crassipes by Raquel Rose Silva Correia; Diana Ciannella Martins de Oliveira; Jean Remy Davée Guimarães (pp. 421-432).
Mercury (Hg) is one of the most toxic pollutants and spreads in the environment according to its affinity to several compartments. Aquatic macrophytes, such as Eichhornia crassipes, are known as sites for accumulation of Hg and methylmercury formation. The objective of this research was to observe Hg distribution among air, water and whole plants of the macrophyte E. crassipes for 17 days. The distribution of a single 203Hg spike was evaluated by gamma spectrometry. Two experiments, with and without macrophytes, were made, and the compartments analyzed for the presence of Hg were air, 0.2-μm filtered water, suspended and settled particles, roots, leafs, petioles and adsorption on the desiccators walls. 203Hg was detected in all analyzed compartments, and the highest total Hg concentrations were found in the roots and particles of the incubations with and without macrophytes that retained in average 68 and 34 % of added Hg, respectively. On the other hand, the lowest concentrations were found in air for both incubations, with higher volatilization (up to 2.5 % of added Hg) in the absence of macrophytes. The lower Hg values in leafs and petioles suggest this plant has mechanisms of Hg retention in the roots. Results suggest this macrophyte promotes changes in the Hg cycle since it attracts most Hg present in water and particulate to its roots and settled particles underneath and also reduces Hg volatilization.
Keywords: Mass balance; Freshwater lake; Aquatic macrophyte; Gamma spectrometry
Fecal Sterols in Estuarine Sediments as Markers of Sewage Contamination in the Cubatão Area, São Paulo, Brazil by Valquíria Campos; Renata Fracácio; Leonardo F. Fraceto; André H. Rosa (pp. 433-443).
Sterol biomarkers serve as an alternative method for detecting sewage pollution. Sterols were extracted from samples of surface sediment collected in Cubatão (the Vila dos Pescadores and Vila Esperança communities) and quantified using GC–MS after Soxhlet extraction, cleanup, and derivatization. Fecal contamination was evaluated based on the concentration of coprostanol and the ratio of the selected sterols. The most abundant sterol was cholestanol, followed by coprostanol. The concentrations of coprostanol in surface sediments ranged from a minimum of 4.21 μg g−1 dry sediment (Vila dos Pescadores station) to a maximum of 8.32 μg g−1 dry sediment (Vila Esperança station). A coprostanol concentration of about 10 μg g−1 was found, indicating areas of high sewage contamination. Coprostanol levels at sewage stations were higher than in other Brazilian coastal areas, which may be attributed to the fraction of the population without sanitation services.
Keywords: Mangrove swamps; Fecal sterols; Sewage pollution; Cubatão, São Paulo
Mercury in the Waters of the Jundiaí River, SP, Brazil: The Role of Dissolved Organic Matter by Enelton Fagnani; José Roberto Guimarães; Pedro Sérgio Fadini (pp. 445-456).
Many developing countries have regions of high demographic density, where untreated residuary waters from different sources are often discharged into rivers, streams and other water bodies. This paper discusses the reducing action of organic matter of anthropic origin on the mercury redox cycle in the Jundiaí River impacted by discharged wastes, and on the Piraí River, a non-impacted water body. The total mercury concentrations in these locations vary from 1.7 to 32 ng L−1 in the former and from 0.6 to 10.6 ng L−1 in the latter. Dissolved organic carbon concentrations of up to 68.3 and 6.5 mg L−1 were observed, confirming the higher impact on the Jundiaí River. It was found that an inverse correlation between the concentration of dissolved organic carbon and total mercury was stronger in the Jundiaí River, given that it receives higher organic loads, suggesting that organic matter exerts a reducing action on mercury, which is released as gas into the atmosphere. This correlation was not observed in the Piraí River, where the organic matter of natural origin is probably not sufficiently labile to act intensely upon the Hg redox cycle, favoring the metal transport.
Keywords: Mercury redox cycle; Jundiaí River