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| Author(s): |
Bolivar Antunes Matos
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Geociências (IG/BT) |
| Defense date: | 2001-05-30 |
| Examining board members: |
Alberto Pacheco;
Samuel Murgel Branco;
José Eloi Guimarães Campos;
Luiz Roberto Cottas;
Vivian Helena Pellizari
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| Advisor: | Alberto Pacheco |
| Abstract | |
This work assessed occurrence and transport of microorganisms in the unconfined aquifer of Vila Nova Cachoeirinha cemetery, located on pre-cambrian terrains at the northern zone of the city of São Paulo The applied methodology was divided in laboratory and field stages. In the lab, cemetery soil columns were designed; chemical and biological tracers were injected in the columns and the effluent was monitored. A numerical model was used to simulate the tracers transport through the columns. In the field, several investigations were done to characterize the unconfined aquifer; water quality was monitored to study occurrence and transport of chemicals, bacteria and viruses in groundwater. In Vila Nova Cachoeirinha cemetery, the depth to the bedrock is about 9.0 m at small elevation areas and 20.5 m at the top of the hill. The depth to the water table varies from 4 to over 16 m. The soil is formed by the weathered material of the granite rocks, clay content of 43%, pH = 5,0, cation exchange capacity between 10.2 and 109.0 mmolc/kg. The hydraulic conductivity of the aquifer varies from 2.90 x 10-8 to 8.41 x 10-5 m/s. The hydraulic gradient at the western part of the study area is about 0.07 m/m; considering a homogeneous and isotropic medium and an effective porosity of 2%, the average linear velocity was estimated in 8 cm/day. The water samples of the unconfined aquifer of Vila Nova Cachoeirinha cemetery presented, mainly, heterotrophic bacteria (53 x 103 UFC/mL), proteolitic bacteria (31 NMP/100 mL) and clostridium perfringes (45 NMP/100 mL). We have also found enterovirus and adenovirus in groundwater. The main sources of contamination are the within-a-year-graves located at the low elevation areas, close to the water table. At these sites, the occurrence of bacteria is greater and there is a greater consumption of oxygen in the water due to oxidation of organic matter. Moreover, the graves cause an increase in salts and electrical conductivity of the groundwater. There seems to be an increase in major ions: hydrogen carbonate, chloride, sodium, calcium; and metals: iron, aluminium, lead and zinc, next to the graves. The bacteria traveled a distance of a few meters, decreasing in concentration with increasing distance to the graves. The viruses seem to be more mobile than bacteria, they traveled distances of tens of meters at the Vila Nova Cachoeirinha cemetery. The viruses were transported at least 3.2 m through the unsaturated zone before reaching the unconfined aquifer. (AU) | |