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Diatomáceas epilíticas indicadoras da qualidade de água na bacia do Rio Gravataí, Rio Grande do Sul, Brasil.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Salomoni, Saionara Eliane |
| Copyright Year | 2004 |
| Abstract | Rivers are considered open ecosystems, strongly influenced by inputs and outputs of materials and energy from adjacent terrestrial systems, and therefore highly vulnerable to the nowadays accelerated changes in hydrographical basins. The present study aimed to analyse spatial and temporal variations in physical, chemical and microbiological variables in Gravataí River, RS (29° 45’ 30° 12’S and l50° 27’ 51° 12’W), aiming to understand its functioning considering the observable changes occurring in its basin. A set of climatological, hydrological, physical and chemical variables were monitored at three months intervals, in six selected localities along Gravataí River, during the period of September 2000 to August 2002. The variables analysed were: water temperature, pH, transparency, conductivity, OD, BOD-5, COD, total nitrogen, organic nitrogen, ortho-phosphate, total phosphorus, chloride and faecal coliforms. Also, air temperature, rainfall and river discharge data were obtained. Results have evidenced that from the headstream to the middle river course there is a continuum, characterized by gradual decrease in dissolved oxygen concentration, increases in turbidity, nutrients, conductivity, clorides and bochemical oxygen demand. It was also evidenced a descontinuity in the gradient, caused by the input of large amounts of organic materials where the parameters of many variables increased or decreased abruptly with changes of one order of magnitude or more. Two distinct portions of Gravataí River were characterized. The first corresponded to the upper-middle reach, more preserved, following the river continuum model, and the other in the lower reach, created by the discontinuity imposed by the input of organic waste. This study has also shown the existence of seasonal variations in the physical, chemical and microbiological characteristics, mainly influenced by climate (precipitation regime) and hydrology (water discharge) which determined changes in turbidity, ionic and nutrient concentrations. Spatial variation was much greater then seasonal variation. The comparison of present limnological characteristics of Gravataí River with information from previous years showed that significant changes have occurred in the last decade, characterizing an accelerated process of eutrophication. The differences found between the upper- |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://repositorio.ufscar.br/bitstream/handle/ufscar/1635/TeseSES.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
