O presente trabalho teve como objetivo monitorar e avaliar a qualidade da água na microbacia hidrográfica do Córrego do Ipê, Município de Ilha Solteira, Estado de São Paulo, e o seu estado de degradação associado à utilização da área de entorno. Para isto, quinzenalmente, no período de março a dezembro de 2002, foram coletadas amostras de água em três pontos da microbacia hidrográfica e realizadas determinações de alguns parâmetros físico-químicos e biológicos que permitiram o cálculo do IQA. Mensalmente foram feitas análises da vazão em m3/s. Os resultados dos valores de IQA associados com observações feitas in loco, permitiram avaliar a qualidade da água e confirmar o atual estado de degradação desta bacia hidrográfica, manifestada pela inexistência de mata ciliar, assoreamento, elevação dos teores de elementos fertilizantes (fósforo e nitrogênio) e aumento dos níveis de concentrações de coliformes fecais e totais em alguns pontos analisados. Observou-se que a poluição do Córrego do Ipê manteve-se alta em escala temporal e espacial, levando-o a valores inferiores aos de um rio de Classe 2, com destaque para o Ponto “B”, situado no meio urbano com qualidade da água variando de ruim a péssima. Isto requer medidas urgentes de correção e mitigação nos locais mais afetados e um manejo sustentável que permita a conservação de toda a microbacia estudada.
Background, aim and scope Studies of particulateassociated pollutants, or PAPs, in urban areas have become necessary due to their potentially deleterious effects on the environment. However, it is not just the sediments themselves which are problematic but also their particle size composition, which has a great influence on their capacity to adsorb and transport pollutants. This paper presents the particle size distributions and concentrations of five metals (Cr, Cu, Ni, Pb and Zn) of urban sediments collected from paved streets and gully pots from 20 cities in southern Brazil. The cities have different characteristics and hence sources of PAPs associated with differing geologies, soil types and type of urbanisation. Studies of this nature enable elucidation of the relationship between diffuse sources such as streets and gully pots and the likelihood of PAPs to subsequently pollute the urban aquatic environment.Materials and methods Sediment samples were taken at random from paved streets and gully pots in 20 cities in Rio Grande do Sul state, southern Brazil by means of a portable vacuum cleaner to avoid loss of finer particles. The particle sizes of the samples were measured using a Cilas® 1180 laser particle analyzer, and the concentrations of five metals (Cr, Cu, Ni, Pb and Zn) were determined by wet acid digestion (HCl-HF-HClO 4 -HNO 3 ) followed by inductively coupled plasma atomic emission spectroscopy on the <63-µm fraction. Results It was found that in comparison to sediments collected from the streets, gully pot sediments were more heterogeneous in terms of particle size and also that sediment samples from the gully pots were predominantly coarser than those originating on the streets. From the gully pot results, analysis of the modal particle diameter enabled the cities to be divided into three categories. The concentrations of metals in the street sediments were similar across all 20 cities, with all concentrations above background values. Discussion The fact that concentrations of metals in the street sediments were above statutory guideline values and that the coarser material was deposited in the gully pots suggests that the finer, more polluted sediment is not retained in the gully pots but is transported to the nearest local receiving watercourse. This finding has implications for management strategies for reducing pollution in urban environments. Conclusions High concentrations of Cr, Cu, Ni, Pb and Zn in the <63-µm fraction of street sediments, in combination with coarse material retained in the gully pots, indicate that metals could be transferred quite rapidly from the diffuse source of pollutants, on impermeable street surfaces, to receiving watercourses.
Soil particles eroded from the land surface and transported into rivers by runoff are considered one of the main components of non-point source pollution in urban watersheds. These particles also serve as a vector for a wide variety of both organic and inorganic constituents. As a result, the identification of sediment sources in an urban watershed is necessary not only to understand erosion dynamics, but also to help implement more effective measures to control and/or remediate non-point source pollution. The present study employs sediment 'fingerprinting' to determine the main sediment sources in a small residential urban watershed (0.83 km2) on the outskirts of Porto Alegre in southern Brazil. Based on an evaluation spanning 12 rainfall events, the results show that paved and unpaved roads and the stream channel itself contribute, on average, 46%, 23%, and 31%, respectively, to the suspended sediment flux in the watershed. Furthermore, the source contributions varied both between events and over the course of a single event. This appears to imply that source contributions, at least to some extent, depend on local precipitation patterns. The results from this study indicate that the level of uncertainty in source ascription tends to decline with increasing numbers of tracers; hence, successful sediment fingerprinting and source ascription in complex hydrologic environments, such as urban watersheds, may require the use of a large number of chemical and/or physical tracers.
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