Navegando por Assunto "Hidrogeologia"

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Aplicação dos métodos elétrico e eletricomagnético para o estudo hidrogeológico no município de Altamira-Pará
(Universidade Federal do Pará, 1998-11-20) BAPTISTA, João Júnior; RIJO, Luiz; http://lattes.cnpq.br/3148365912720676
This work due application of the electroresistivity and electromagnetic geophysical methods in the municipal district of Altamira, in the central area of the State of Pará, with the purpose of mapping the thickness of the aquifer layers and occurrence of diabase intrusions for finding a groundwater wells. In this area are many outcrops of basement crystalline rocks covered with sediments of ages from the Paleozioc to Quaternary. The objective is to obtain water from the sediments of Inferior Devonian, more exactly in the Maecuru Formation. There were made thirty four vertical electric soundings using the Shlumberger arrangement, the AB/2 distance varying from 100 to 500 meters. Also there were made 108 transient electromagnetic soundings with "coincident loop" arrangement, using an square loop of 50 meters. Due to electronic problems and supraparamagnetic noises, the results of this electromagnetic soundings became very distorted, impossible to get from them important geologic information. Then, electromagnetic synthetic models were created to represent the geology of the area. The data were obtained from the field were presented as apparent resistivity curves. They were plotted using a log-log scale and interpreted using the EGSLIB/SEV1D first and then with the EGSLIB/SEV1DIN program. The models used were horizontal, isotropic and homogeneous layers. The interpretation results allowed to determine approximate geoelectrical models which reflects the underground geological situation. The interpretation results from the electric surveys were confronted with the results of the qualitative interpretation from the isogams map of the total magnetic field, allowing to delimit with more precision the zone of incidence of diabase sills, located at the north of the area. From the four distinguished geoeletric horizons, the third is essentially constituted by sands, therefore it is best for groundwater storage.
Acesso aberto (Open Access)
Avaliação dos efeitos da mata ciliar sobres os fluxos hidrogeoquímicos em área de pastagem: caso das bacias hidrográficas dos igarapés do Sete e Pajeú - Paragominas (PA)
(Universidade Federal do Pará, 2006-09-22) SARDINHA, Aline Souza; SOUZA, Eliene Lopes de; http://lattes.cnpq.br/2060516413833723
It was studied the waters of uncofined aquifer and of portions of superficial drainage in the wartersheds of the Sete and the Pajeú rivers, in the municipal district of Paragominas, in the northeast of Pará. With total areas of around 150 and 45 Km2, respectively, those basins are mainly occupied by cattle areas. They are inserted in the sedimentary basin of Grajaú, occurring from the base to the top the Itapecuru formation, Ipixuna formation, Debris-Lateritic Paleogenic covering, Pleistocenic Sedimentary Covering and Alluvial Deposits. The chemistry of the water was evaluated in pasture areas, with and without preservation of the riparian forest that, although protected by law, is usually removed for several land uses. The waters of 9 monitoring wells were studied, installed in uncofined aquifer, and of 13 portions of superficial drainage placed in pasture areas and in riparian forest. The evaluated aquifer is constituted by sediments of the Ipixuna Formation, with kaolinite sandstones and mudstone kaulinic. Eight sampling campaigns were accomplished, during the dry and rainy periods in 2005. It was determined the contents of sodium, potassium, calcium, magnesium, nitrate, ammonium, sulfate, phosphate, bicarbonate and chloride, and in the Field pH, electrical conductivity, and temperature. In the waters of superficial drainage, the results indicate significant leaching of soils, evidenced by the higher the contents of nutrients. In the waters of superficial drainage concentrations of sulfate, potassium, magnesium and chloride were higher in the pasture areas. On the other hand, the contents of ammonium, nitrate, phosphate, calcium, sodium and bicarbonate were, in most case higher in an area of riparian forest, in which the main source of nutrients for the waters is the organic matter of the soil. I pastures these elements come from the either the limestone or the fertilizers used for pH correction and increasing of the soil fertility. Another source comes from the contribution of ashes, resulting from burning used to convert the original vegetation in pasture. In the freatic water, the contents of the cations and anions evaluated were, in general, higher in the pasture areas, except for the concentrations of sodium and chloride that were larger in the wells in riparian forest. Among the constituents analyzed, stood out, mainly, the concentrations of ammonium and bicarbonate, whose maximum values obtained in wells in riparian forest and pasture were, respectively, 0,81 and 17,6 mg.L-1 (ammonium) and 15,98 and 109,78 mg.L-1 (bicarbonate). When compared to the water of superficial drainage, it was verified that in the freatic waters most of the substances showed an increase in their contents in pasture areas. That 4 result is attributed to the fixation of nutrients by the riparian forest when the percolating water crosses the insaturated zone, while in the pastures the nutrients can reach the water table, once in those areas a significant retention of those substances does not happen. Most of the cations and anions analyzed showed higher concentrations in the wells of the point ST6, in the Sete river, where the area is of pasture and without riparian forest. The ions with higher contents were nitrate, ammonium and bicarbonate obtained in the dry period. For the alkalinity, pH and CE values were higher in pasture areas in the freatic waters. On the other hand, in the waters of superficial drainage, except for the pH, those parameters showed the highest values in the areas of riparian forest. Acid waters prevailed with pH between 5 and 6, although values close and even superior to 7 were obtained, attributed to the limestone used in the area and to the ashes, rich in bases, coming from the burning. In relation to the temperature, it was verified that it reflects the local average, 26,33oC. In the Pajeú watershed, the cation and anion contents were, in general, higher during the rainy period, while in the point ST6 in the basin of the Sete there was a relative increase in the contents of most of the ions analyzed during the dry period, due to the lowering of the water table and the low recharge of the aquifer. In the areas with riparian forest that effect was neglectable due to the small variations in the hydrological conditions along the year, resulting into a smaller annual variation in the depth of the water table.
Acesso aberto (Open Access)
Avaliação dos impactos da ocupação urbana sobre as águas da bacia hidrográfica do igarapé Mata Fome, Belém-PA
(Universidade Federal do Pará, 2001-05-17) GASPAR, Marcia Tereza Pantoja; SOUZA, Eliene Lopes de; http://lattes.cnpq.br/2060516413833723
The watershed of the Mata Fome stream, with 6 km2, is located to the north of the Metropolitan Region of Belém. It is the pilot area for the implementation of the UN's Urban Management Program (PGU), which has among its objectives the environmental recovery of this area. The present study, inserted in the above mentioned program, evaluates alterations related to the anthropic occupation of the basin, through hydrogeological and water quality data from the stream and the free aquifer. In the analyzes of the waters carried out in the dry (November) and rainy (April) periods of 2000, the nitrogen components (NH4+, NO2-, NO3-), dissolved oxygen (OD), total dissolved solids (STD), fecal coliforms and total values, pH and electrical conductivity (EC). The hydrological regime of the stream was evaluated through discharge measurements and readings of limnimetric rulers, which were installed in an intensely occupied area, at the mouth of the stream, under the influence of the tides (station 1), and at its source, relatively preserved and without tidal influence (station 2). The stream showed a regime characterized by 9 hours of low tide and 4 hours of high tide, reaching higher water level heights in the rainy season (January-June), in the high tide, with a maximum height of about 3 meters, and a minimum of 0.4 meters at low tide. In the dry season (July-December) the maximum height, 1.99 m, also occurred at high tide, while the minimum height, 0.40 m, occurred at low tide. the net discharge from the stream was measured only in the dry period and presented minimum and maximum values of 0.03 and 0.201 m3/s, respectively, with the minimum value occurring in the transition from the ebb to flood regime. Double cylinder infiltration tests, carried out in the occupied area and at the source, revealed a rapid stabilization of infiltration in the first area, in relation to the most preserved area. The water from the stream showed pH values close to or greater than 7, the highest being obtained in the dry period. The electrical conductivity was also higher in this period, with an average of 260 µS/cm. The DO contents, quite low, varied between 1.0 and 3.5 mg/L, with the highest values obtained in the rainy season, possibly resulting from a greater oxygenation of the water in this period. The presence of domestic waste and sewage in the stream is mainly portrayed by the high amount of fecal coliforms that, in station 1, during the rainy season, reach a maximum of 92,000 CF/100 mL, at high tide. In the spring area, although relatively preserved, the CF values were also high, reaching a maximum of 65,000 CF/100 mL in the dry period. Among the nitrogen components analyzed, the NH4+ contents stand out, reaching values above 3 mg/L, reaching 12 mg/L in station 2, during the dry period, reflecting a small "invasion" that was beginning to settle in that area. area. The load carried by the stream evaluated at station 1, only for the dry period, presented higher values in the ebb tide, due to higher discharges in this tidal regime. Nitrate discharge was the highest, reaching a maximum of 0.44 µg/sec in the ebb tide regime. The ionic balance (t+km-2+year-1) showed positive values for all analyzed parameters, indicating a greater outflow of substances to the Guajará Bay, in relation to the solutes brought from this bay, during the flood tide. According to CONAMA Resolution No. 20/86, the water in the creek is unsuitable for bathing (primary contact recreation). The free aquifer studied, the main source of supply for the residents of the area, has a static level with an average depth ranging from 2.26 m to 1.21 m, between the dry and rainy seasons, respectively. Hydraulic potential maps, prepared from static level measurements carried out in 30 excavated wells, in these two periods, indicate that the underground flow converges to the stream. The regulatory reserve, calculated from the natural flow rate (VEN), presented a value of 1,050,000 m3, with a restitution for the stream of 175,000 m3/Km2. Among the water quality indicators evaluated, the ammonium levels are worth mentioning, reaching 3.54 mg/L, well above the potability limit (0.06 mg/L) established by USEPA. The nitrate content reached 30 mg/L, still below the potability limit (45 mg/L), but already deserving attention, due to its conservative character. The presence of fecal coliforms in the water of some analyzed wells also indicates that their water is unfit for human consumption.
Acesso aberto (Open Access)
Avaliação experimental da mobilidade do dimetoato na zona não saturada, em áreas de agricultura intensiva na bacia hidrográfica do igarapé Cumaru, município de Igarapé-Açu (PA)
(Universidade Federal do Pará, 2003-10-21) LIMA, Lilianne Maia; SOUZA, Eliene Lopes de; http://lattes.cnpq.br/2060516413833723
Family farming in the eastern Amazon, and particularly in northeastern Pará, is characterized by the implementation of semi-perennial industrial crops with heavy application of pesticides. This study was carried out with the main objective of evaluating the mobility of pesticides, in particular dimeatoate, in the unsaturated zone of the Cumari creek watershed, in the municipality of Igarapé-Açu (PA). In the area, the aquifer is constituted by inconsolable sand-clay and sand-silt sediments belonging to the Post-Barreiras period. Specifically, the objective was to analyze the potential for contamination of groundwater by pesticides. The objective was also to quantify the geochemical process of sorption, relating it to the physical and chemical characteristics of the unsaturated zone. A mapping of the areas where passion fruit is cultivated was carried out, since a high volume of pesticides is used in this culture, together with a survey of the agricultural pesticides used in the area. Subsequently, the risk of groundwater contamination was assessed using the GUS index (Groundwater Ubiquity Score). This index has as parameters the half-life values of the compound in the soil (DT50) and the coefficient of adsorption to organic matter (Koc). In addition, manual auger drilling was carried out in order to collect sediment samples from the unsaturated zone for laboratory analysis. In the laboratory stage, the granulometry, mineralogy, natural pH and organic matter content of the different levels of the unsaturated zone were determined, aiming at its characterization. This step also included the sorption experiment and the determination of dimethoate. Based on the risk analysis, it was found that dimethoate has the greatest potential to contaminate groundwater, with a GUS index ranging from 2.36 to 3.36. The sorption experiment showed that, in percentage terms, the sorption of dimethoate by sediments in the unsaturated zone ranged from 2.5% to 3.2%. These data confirmed the high potential for groundwater contamination by this substance, which is mainly due to its mobility and low retention. It was also verified that the amount of organic matter and the pH exert a greater influence on the sorption of dimethoate.
Acesso aberto (Open Access)
Caracterização biogeoquímica de águas subterrâneas da zona urbana de Porto Velho-RO
(Universidade Federal do Pará, 1997-03-12) BAHIA, Maria Alves da Silva; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
The city of Porto Velho - RO has a population of 293,815 inhabitants (IBGE, 1996). Of these, 56% are supplied with treated water, collected from surface springs; the rest, with water from tubular wells of the "Amazon" type. Only 4.6% of the population has sewage collection services, so that wastewater is released into the open. These waters, when infiltrated, mix with those from pits, becoming potential sources of polluting the wells, drilled in a rudimentary way, without taking into account the geological and hydrogeological characteristics (lithology and structure of the land, level of the water table, etc. ), do not have a sanitary seal and the positioning of filters is done improperly. There is also the deficiency of regular household garbage collection services, especially in peripheral neighborhoods, most of them generated by "invasions". This garbage is thrown in areas close to the residences, which makes it possible to wash the mass of residues, with the consequent production of leachate, which can also constitute a potential source of pollution of groundwater. The present work evaluated the biogeochemical conditions of these waters and identified groundwater quality characteristics. In the periods from April/95 to October/95 and November/95 to February/96 (drought/95 and rainy/95), water analyzes were carried out from 86 wells in the study area, 43 of which were tubular wells and 43 excavated wells. “Amazon” type, with an average depth of 47 m and 12 m, respectively. Chemical analyzes were also carried out, in samples of gutters, of sediments from well logs drilled during the course of this research. The analytical results proved to be efficient in the assessment of the environmental impact caused by anthropogenic activities in groundwater, resulting from chemical and bacteriological contamination. Chemical contamination was manifested by the presence of nitrate and bacteria of the coliform group in the groundwater of most of the sampled wells. Bacteriological contamination results from the inappropriate use of sanitary disposal systems, domestic and livestock waste (mainly poultry and pigs) in the vicinity of wells, drilling and inappropriate location of these wells, among other causes. The results of the analyzed parameters also allowed the evaluation of the main characteristics of the water quality of the aquifers, and their probable interrelation with the local geology. There is groundwater poor in electrolytes, representative of heavily leached land, there is also groundwater richer in electrolytes. The physical-chemical composition of these waters results from the contact with the percolated rocks and the climatic conditions of the area, with a humid climate with high rainfall.
Acesso aberto (Open Access)
Caracterização geoquímica e avaliação da qualidade das águas subterrâneas do aqüífero freático da cidade de Bragança – Pará
(Universidade Federal do Pará, 2000-08-17) AMORIM, Hemert Santos; RAMOS, José Francisco da Fonseca; http://lattes.cnpq.br/8189651755374537
Acesso aberto (Open Access)
Caracterização hidrogeológica em área de agricultura intensiva, na microbacia do iguarapé Cumaru, nordeste do Pará
(Universidade Federal do Pará, 2003-06-30) CHAVES, Luciene Mota de Leão; TANCREDI, Antonio Carlos Felice Nicola Saverio; http://lattes.cnpq.br/3080055631075788
Acesso aberto (Open Access)
Caracterização hidroquímica dos aquíferos freáticos costeiros na cidade de Salinópolis-PA.
(Universidade Federal do Pará, 2016-06-08) RODRIGUES, Érika do Socorro Ferreira; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568
The city of Salinópolis is located in northeast Pará, Bragantina region, on Pará State. The geology of the area is characterized by a sedimentary cover Tertiary represented by Pirabas Formation , Barreiras Group and overlying these rocks may occur sandy-clay sediments to clay-sand the quaternary called Pós -Barreiras sediments. The main hydrogeological systems Salinópolis, in general, are: a) upper aquifer system developed in the Pós-Barreiras, unconfined aquifers; b) aquifer system Barreiras, unconfined aquifers and semi-confined; c) aquifer system Pirabas, deeper confined aquifers, which is an outcropping aquifer in the region. For the study were registered 22 wells of which 17 shallow wells with depths up to 30 m (PT), two dug wells (AM) and 3 sources (FT). The collection of samples was performed at intervals of two months for a full hydrological cycle, May 2014 to March 2015. The main quality parameters investigated were water temperature, pH, electrical conductivity, alkalinity, total dissolved solids and main ions : cations (Na+, K+, NH4+, Ca2+, Mg2+) and anions (F-, Cl-, NO3- and SO42-). Hydrochemical four groups were identified in the Piper diagram: group 1 (SO4-, Cl- and Na+) that resembles the aquifer Barreiras. In the waters of group 3 rich in calcium and bicarbonate is identified with the Pirabas water aquifer (HCO3- and Ca2+) since the water in groups 2 and 4 showed characteristics of group 1 and 3. From Piper diagrams, it was observed that with increasing water recharge the group 2 and 4 water had a water connection behavior, migrating to another group hydrochemical. In Scholler diagram, even identifying the main ions was possible to see that there are mixtures in water of the same hydrochemical group, visualized by the provision in fan. In Diagram Van Wirdum was identified climate and rocks actions on the aquifers hydrochemistry. Range distribution has been observed that with the beginning of the drought wells located in car washes and near gas stations as well as near the beach and estuarine rivers showed an increase of ions dissolved in the water. As well as in natural sources or springs there was a large increase in number of ions, especially the sulfate Climate Influence, rock, ocean waters, estuarine rivers, as well as the contribution of the aquifer Barreiras and Pirabas showed a peculiar hydrochemical composition in the waters of aquifers shallow coastal city in Salinópolis.
Acesso aberto (Open Access)
Contribuição ao conhecimento das formações Barreiras Pirabas utilizando-se ferramentas da análise estrutural com vistas à aplicação em hidrogeologia
(Universidade Federal do Pará, 2016-10-17) SILVA, Larissa Silva e; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626
The existence of hydraulic connection between Barreiras and Pirabas aquifers systems in the northeast area of the State of Pará, more specifically in the metropolitan region of Belém - RMB has been raised, a few years ago, by different authors from the application of various analytical techniques. This work presents further contribution to this theme, that has been aggregated to the data and to the information obtained from the use of structural analysis tools, to understand the groundwater flow mechanism and recharge conditions, which takes place in area under consideration. The work was performed from the databases on existing wells in private and public agencies. The performed structural analysis considered the geometric-kinematic elements present in the mentioned water systems and it advanced in the knowledge of the tectonic processes that have led to the conformation of the geometric arrangement present in the area, considered essentially as neotectonic. It was found that the development of brittle tectonic structures, especially holes, printed on regional rocks that enclose the water systems, leading to spatial composition of morpho-structural blocks arrangements horsts and grabens limited preferably by the NE and SW discontinuities resulting from the interaction of normal faults with strike-slip faults. The boundaries of these blocks, always marked by failures allow the interconnection of the movement of water from aquifers of different spatial positions systems, sustained by the principle of communicating vessels, the elapsing the mixture of water contained in each one of them individually. So it is impossible to keep the model advocated by several authors in the literature of regional aquifer confinement. On the other hand, the development of potentiometric maps and flow in regions of sedimentary rocks, where it is called homogeneous media, as this case is of the RMB cannot be done without considering the structural analysis, geometry and kinematics, otherwise it would be misunderstood in the preparation of such results and mistaken hydrogeological interpretation. Thus, it is necessary to review the methodologies for the preparation of these important instruments in order to obtain more precise results on the flow mechanisms, recharge and discharge of water systems which has been developed and answered in this work.
Acesso aberto (Open Access)
Estudo da hidrogeologia no município de Palestina do Pará usando o método de eletroresistividade
(Universidade Federal do Pará, 1998) MONTEIRO, Edson Cardoso; RIJO, Luiz; http://lattes.cnpq.br/3148365912720676
This work of geophysics applied to hydrogeology was carried out in the southeast of Pará in the Palestina district at the margin of Araguaia river. Ironically there exists problems of water supply for the city population. This is due to the fact that it is not economical to mantein a treatment station and to transport the water from the river to the city. Since is this case pumping groundwater wells are more economical than take water from the river, the Geophysics Department (UFPa) was asked to cooperate with the Health National Fundation (NSF) to carry out a electroresistivity survey to help the groundwater investigation of the area. There were made 21 vertical electrical soundings (SEV) with the Schlumberger array with 500 m and 50 m maximum AB and MN respectively. For the interpretation it was used the programs EGSLIB/SEV1D for forward modeling and EGSLIB/SEV1D1N for the inversion of homogeneous isotropic layered models. Based on the results of the interpretation of the 21 electrical soundings and the local geology, three contour maps and six geoelectrical sections were made. From the six horizons that are shown in these sections, the fourth one with thickness of 10 to 79 m at the depth of 50 m and resistivity of 150 — 850 ohm-m is the most suitable for groundwater exploration. The final analysis of the maps and geoelectrical sections show that the best place to locate the wells is near the area used today for capturing water.
Acesso aberto (Open Access)
Fatores controladores do quimismo de águas subterrâneas da região nordeste do Pará
(Universidade Federal do Pará, 1996-11-10) SOUZA, Eliene Lopes de; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
This work was carried out in the northeastern region of Pará State with the purpose of studying the factors that control the chemism of both spring and well waters. They are waters of aquifers constituted of alteration products of granites (Tracuateua), metassediments(Santa Luzia), metavolcano-sediments(serra do Piriá) and apatite-hornblendite (ilha de Itacupim). Waters in contact with limestones were also studied. Most of these waters purposes. The are used with local population supply waters were collected in restricted zones covered by Amazonian rainforest, in areas that support second growth vegetation(capoeira) and in jungle clearings. The collect period was 1992 dry season, 1993 dry and rainy seasons, 1994 rainy season and in 1995 dry and rainy season. Petrographic and mineralogical study of alteration products and in some cases of the bedrock, indicate the possible influente of these materials in the water composition. The pedogenetics processes taking place in the studied zones were characterized. The potential of these zones for occupation purposes were also evaluated. In Tracuateua, Santa Luzia and also in the Serra do Piriá saprolitic tone, the aquifers are formed by highly weathered products, constituted basically by quartz, kaolinite and iron oxi-hidroxides. In the metavolcano-sediments/lithomarge or apatite-hornblendite/lithomarge interface, minerals like biotite, albite or apatite are frequents. The upper layer (20 cm deep) of the soils in these areas is poor in bases and displays a pH value of about 5,0. The alteration products of calcareous are base saturated, presenting pH about 8,0 and are constituted of quartz and kaolinite, with calcite in small proportion. The content of organic material in soils, about 12% in preserved areas and less than 3% in degraded areas, reflects the nature of the vegetal coverage. Waters in contact with the most weathered products are chloride and sodium rich, acidic (average pH 4,4), poor in solutes(TDS < 30 ppm), mainly of pluvial origin. Waters in contact with less altered products, derived from metavolcano-sediments and apatite-hornblendite, raise the base, silica or phosphate content, which are derived principally from the hydrolysis of primary minerals. In waters from calcareous areas the relation HCO3:Ca+Mg1 indicates carbonates dissolution. They are calcium and bicarbonate rich, righ in solutes(average TDS 230 ppm), and presents pH value about 7,0. When in contact with clay layers that contains pyrite, waters becomes sodium and sulphate rich and acidic (pH 5,0). Marines aerosols, vegetal detritus and domestic waste waters are localized sources of solutes, while the organic acids, together with the scarcity of bases, are responsible for water acidity. The upper layer of the soils of the degraded areas shows intense eluviation with subsequent relative enrichment in quartz. The use of these lands for agricultural purposes requires nutrient reposition. Where sandy-clay sediments cover limestones, the pH value is about 5, what enables the plants to take more efficiently the marine nutrients which abound in the calcareous sediments.
Acesso aberto (Open Access)
Fundamentos hidrogeológicos para gestão integrada dos recursos hídricos da região de Belém/Ananindeua - Pará, Brasil
(Universidade Federal do Pará, 2002-12-20) MATTA, Milton Antonio da Silva; REBOUÇAS, Aldo da Cunha; http://lattes.cnpq.br/7322958772719317
The main goal of this study is to present the result of an investigation carried out in the region of Belém and Ananindeua. State of Pará — Brazil. The study comprised mainly hydrogeological aspects, together with hydrochemical, geological and socioeconomic data, in order to make it possible to determine the conditions to the wise use of groundwater. This work will also contribute to the municipal and state planners with a set of technical, legal and socioeconomic, data to be used toward the water resource management in the studied area. The activities and the methods applied permitted to achieve significant results which include the characterization of the physical environment, with geomorphology, soil and climate aspects, superficial water characteristics, hydrogeological systems properties, geometrical aspects of the main aquifer units. characteristics of the groundwater flow, hydrogeochemical and bacteriological qualities of the groundwater , the estimation of the groundwater reserves and an insight on its vulnerability. Ali those technical aspects were analyzed together with the legislation framework, from the federal to the municipal scales. in order to make it possible to define the fundamental aspects to the groundwater use and protection planning and its role in the general water management practices in the studied area. The main products include a data base, inserted in a Geographic Information System (GIS), based in the SPRING 3.5.1 program, a set of thematic maps (geological, geomorphologic, hydrogeological, soils, etc.), and a set of tables and graphics showing the physical, chemical and bacteriological aspects of groundwater quality. Technical, social and political propositions were made, including hidroambiental education, institutional projects against poverty, increase of the law enforcement to protect the water resources, water save actions by the government, and joint projects toward water management. The main conclusions of the study permit to demonstrate that the main goals have been achieved, with a significant contributions to the Hydrogeology of the Belém and Ananindeua area and to the future projects involved water resources management.
Acesso aberto (Open Access)
Impacto da urbanização na qualidade das águas subterrâneas nos bairros do Reduto, Nazaré e Umarizal - Belém/PA
(Universidade Federal do Pará, 2004-01-29) CABRAL, Natalina Maria Tinôco; MANOEL FILHO, João
The study evaluates the urban impacts in the groundwater quality of Barreiras aquifer, caused mainly by nitrogen compounds (nitrate and ammonium) from domestic sewage and aromatical composites (benzene, tolueno, ethylbenzeno and xylenes - BTEX), from underground fuel storage tanks of gasoline and diesel. The study was carried out on an area of 15 Km2, in the quarters of the Reduto, Nazaré and Umarizal in city of Belém/PA. The used methods incluided a cadastre of wells, analyses and stratigraphic well log correlations, execution of 9 periods of sampling, chemical analysis of water from and interpretation of results. The unsaturated zone, in the study area, has thickness varying of I to 9m, being conditional to the seasonals variability. Mineralogical studies of sediments collected in drill rig wells had defined a domain of quartz and, of a more subordinated form, caulinite. The grain sized analysis show a predominance of the fractions silte sand, silte arenaceous and silte clay. Test of infiltration indicated value corresponding to a material silte to silte arenaceous. Sediments with these textures, associates to the varied infiltration capacity, mineralogic composition, water levei flat and raised load of contaminants, of mainly septic and casspools, can lead to the contamination of the aquifers of the area. The aquifers ones identified are correlated to the aquifers of the Barreiras Group, having been defined two main ones. First, the most superficial one, was classified as unconfined-leaky, and as the second aquifer one was characterized as confined-leaky. The water level, by diverse reasons, had not been measured during the execution of this work. In this case, the presented measures correspond to those done ones during the time of drilling of the wells, in which had varied of less of lm, in the areas of lower topographical quotas, until 11m in the wells located in the more raised paris. Vulnerability data had established mainly that, to a large extent of the area, the Barreiras Aquifer presents contamination possibility, considering that the studied area is urban and, consequently, concentrate some potentially polluting activities. The interpretation of the directions of groundwater flows, of the studied area, shows that the main lines of preferential flow are guided for the center of the area, containning the quarter of the Reduto and part of the Nazaré. The global behavior of the variables shows that the hydrogeochemical characteristics of studied waters are differentiated, when compared with the regional standard. The main parameters that had marked this differentiation had been the electric conductivity, chloride, sodium, pH, ammonium and nitrate. It is standed out that the grades of ammonium and nitrate are above or very Glose to the limit to potability standards, and that such parameters are the main contamination indicators of waters by effluent domestic sewage. The global analysis showed for nitrate a positive correlations with electric conductivity and a weak correlation with chloride, sodium, calcium, sulphate and hardness. For ammonium one observes a positive correlation with chloride and negative correlation with calcium, sulphate, pH and hardness. This study it allowed to indicate the conductivity, chloride and calcium as good pointers of the contaminations. The effected factorial analyses had come to confirm the main comments gotten in the study of correlations. The statistical study by period of sampling, they indicate that the regional seasonality is influencing only in secondary way in the chemical behavior the studied waters. The slight enrichment, of some components, in the rainy period can be explained because, in this period, the groundwater level is raised until next to the ground , being next to the contamination sources. In the study of correlation by period of sampling, the results can be considered, without exception, similars to the gotten ones in the analysis of correlation made with the global data. The statistical analysis for a series of wells had indicated that the wells, when analyzed individually, they had shown a relatively homogeneous behavior along the periods, but when compared between itself, it was possible to distinguish wells with values always raised from those with the raised values less. In the study of the behaviors for nitrate and ammonium, it was observed that the wells, when analyzed individually, they had homogeneous behaviors. On the other hand, the joint study of the wells it allowed to the classification of 4 main styles of behavior for nitrate and ammonium. Style 1 would correspond the wells with high values of nitrate and low values of ammonium; style 2 would be characterized by high values to nitrate and ammonium; style 3 would correspond the wells with low to intermediate concentrations the nitrate and high the relatively high ammonium grades and, finally, style 4 would be translated by lower grades for ammonium, followed for intermediate nitrate grades. These styles can mean greater or minor distance of active sources of contamination, that would be, therefore, the preponderant factors in the hydrogeochemical characterization of the wells in an urban area as the studied one. In two wells a more detailed water sampling was effected. These samplings had evidenced, one more time, to little influence of the seasonality in the hydrochemical characterization of the studied wells. To identify the main types of waters, representative samples of the registered in cadastre wells had been located in the diagrams of Piper. The results had shown a trend, so that, the samples, independent of the period of sampling, to be concentrated in calcium chloride sulfate, cl sodium chloride and sodium nitrate cloride hydrochemical facies. These behaviors reflect that they are being strong affected for antropogenic factors, in detriment of natural processes. The analysis of the space distribution, of the main parameters, showed that, for nitrate, the more raised grades are located in the central and south portion of the area. The ammonium presented an inverse relation to the one of nitrate, with more raised grade the northwest and northeast of the area, diminishing for the center of the area. The map of electric conductivity coincides, in good part, with the one of nitrate, while that the chloride iso-grade map is, in a general, similar way to the one it ammonium. The iso-grade map of pH did not show any trend of correlation with nitrate. These correspondences had coincided with the comments of the studies of correlations. In the study of water contamination by gasoline/diesel, three critical areas were defined. The study finally sugests that, in regard to water samples with qualitative identification of diesel and or gasoline, the main biodegradation process, bisede the aerobic one, seems to be of nitrate one.
Acesso aberto (Open Access)
Influência da neotectônica sobre os arranjos geométricos dos aquíferos na Região Metropolitana de Belém – Estado do Pará
(Universidade Federal do Pará, 2004-08-31) COSTA, Francisco Ribeiro da; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626
The metropolitan area of Belém (RMB) is located in a distensive segment filled by sedimentary sequences of Pirabas and Barreiras Formations (COSTA et al., 1996) which constitute one of greater ground water reservoir of Brazil (Oliveira, 2003). The aim of this work is to offer information about these aquifers units thorough using data from geology, geometry and cinematic, hydrogeology and morph tectonic, to comprehend the evolution of these units in space and time. Databank used in this work was obtained from: (1) field data; (2) information of well drilling; (3) topographic maps in scal1 1:100,000; (4) Landsat 7 images; (5) SRTM – Shuttle Radar Topographic Mission; and (6) GIS – Geographic Information System of RMB, Guajará and Marajó Bay. Softwares SPRING, Arc View and Global Mapper were used to process and treatment of data and images. Two main scales were used in this study: (1) a regional scale 1:100,000 evolving maps of Belém, Acará and Abaetetuba giving a total of 10,635 km2; and (2) a semi detail scale 1:25,000 adjusted at RMB with total of 1, 929 km2. Morph tectonic analysis showed three geomorphologic domains: Fluvial Plain Terrain, Terrain of Hills and Terrain of Small Mountains. The directions of topographic elements of terrain are compatible with the directions of the drainage net. The analysis of drainage net gave five main basin domains: (1) Coastal; (2) Marapanim River; (3) Guamá River; (4) Acará-Moju River; and (5) Pará River. Thorough this analysis was identified and defined neotectonic elements represented for lineaments from each hydrographic basin, with general directions NE-SW, NW-SE and NNE-SSW in regional scale. The RMB shows main directions in NE-SW and NW-SE with secondary trends WNW-ESE. Using projection and extension of lineaments presents in RMB, was possible to draw a two-dimensional model, which form three-dimensional blocks. Were defined two kinds of sectors based on distinct aspects of blocks. Sector I is located in southeast and Sector II is in northeast portion of RMB. There are kinematics variations in these two sectors. Sector I has dextral moving with stretching direction NW-SE and normal faults NE-SW. In the Sector II the cinematic is sinistral with stretching direction NW-SE and normal faults NE-SW associated. 4 Correlation between water wells located in different blocks proved that geologic layers present in both blocks have distinct attitudes, probably influenced by neotectonic processes. In Sector I, the gradient is moderate 1/180 m/m in the other hand Sector II has gradient 5x bigger 1/30 m/m. The different values on gradient suggest that Sector I and II are distinct with regarding to the slope of layers. With treatment integrated of information obtained was possible to establish the stretching direction for Pirabas-Barreiras Basin in NW-SE. Normal faults related to the development of basin have trends NE-SW. These structures are potential surfaces of low pressure, being favorable places to recharging of aquifers intercepted by its. So it is necessary to be worried about the possibility of pollution in these aquifers by human activity in these places of recharge. Since the recharge areas are exposed to urban or agricultural purposes.
Acesso aberto (Open Access)
Neotectônica e estruturação dos sistemas hidrogeológicos da região de Castanhal/Pa
(Universidade Federal do Pará, 2008-05-13) BANDEIRA, Iris Celeste Nascimento; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626
The morphstructural and hydrogeological studies done in two distinct scales, 1:100,000 and 1:25,000, in Castanhal City (PA), the advance on the understanding of the relation between geometric elements of hydrogeological systems and structural elements related to neotectonic events as a base to determine, among other aspects, potential recharge areas of these systems, was allowed. The morphstructural study supported by collected geophysical data showed that the area has a structural control related to a neotectonic pulse responsible for the reactivation of NW-SE-, NE-SW, NS and EW direction failures, which caused anomalies and changes in drainage patterns, and conditioned the establishment of terrain units where river plains, pediplanizadas hills and top-flattened hills jut out. These failures can become compatible in a system of efforts, which generated a geometric formation characterized by tectonic blocks limited by such failures, as well as a kinematic framework of dextral configuration, where in an explicit way extension failures were formed in the NW-SE direction, consolidating important flumes for the recharge of hydrogeological systems. The area is composed of three hydrogeological systems: Superior, characterized as free and found at depths from 2 to 8m; Barreiras varying from free and semiconfined and found from 20m depth, and Pirabas characterized as confined and found at depths from 90 to 120m. These systems present variable depths related to the displacement caused by neotectonics failures. From the confined hydrogeologics systems (Pirabas) to the semi-confined ones (Barreiras) are being largely recharged in the area of Castanhal by natural flumes which are the areas of extension failures and fractures of NW – SE direction. The recharging of the free hydrogeological systems (Superior and Barreiras) occurs by direct precipitation from the rain water in the central-west portion of the study area, in other words, near Couro do Curió river and in the northeast portion near Defunto river.
Acesso aberto (Open Access)
Planos de sistemas aqüíferos como fundamento legal para a gestão de recursos hídricos
(Universidade Federal do Pará, 2010-07-14) GUTIERREZ, Lucy Anne Cardoso Lobão; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626; 9626349043103626
The evaluation of self supply conditions in RMB, especially in 25 districts, which present consolidated and available information, bespoke the need of improving the management of groundwater resources in the state. In order to achieve that, the elaboration of the Water Systems Plans as a legal fundament for the management of water resources in the State of Pará, especially in RMB. The information and data gathered showed that the public water supply system presents some deficit, mostly due to absence of the public water supply network in many areas; inefficiency or absence of plans to extend this network; need of improvement and adequacy for the existing network; low availability of goods acquisition to the general improvement of the system; the high index of loss verified; and so on. Because of this the number of users has increased, particularly in the residential sector, which uses the tubular wells for self supply, almost ever completed in the water systems Pós-Barreiras and Barreiras. This scenario is observed, mainly in the districts having the most of buildings, such as Nazaré, Reduto, Umarizal and São Braz, which respectively present (62,9%), (49,2%), (31,8%), and (33,3%) of the residential economies provided by private wells for self supply. These aquifers demonstrate moderate to high vulnerability, whereas the available data of their water quality reveal high nitrate indexes probably caused by almost entire absence of sewage collection and treatment systems. A survey and an analysis about federal and state laws which are relevant to the water resources were also made for planning the model, observing that this law is much more advanced for superficial water. The settlement of future scenarios, from the methodology described by Michel Goodet, brought the linkage between management and planning of superficial and ground water, in view of the fact that in the national model, the territory for the management of the water is the drainage basin. To allow that planning groundwater does not occur in a disintegrated way in the scope of drainage basins nor is totally attached to the start of superficial water management, a model of groundwater planning and management is proposed to the State of Pará. According to this model, the aquifer systems planning could be done through Aquifer Systems Plans, under the responsibility and coordination of the State. To the definition of elaboration and approval of these Plans, it is suggested the creation of Aquifer Systems Committees to be coordinated by the organ of the State for Water Resources, which will incorporate the imperative participation of users, representatives of the counties that are surrounded by overlying drainage basins to these aquifer systems, as well as the civil society organized, a new paradigm of operation for a contemporaneous society.
Acesso aberto (Open Access)
Síntese da hidrogeologia nas bacias sedimentares do Amazonas e do Solimões: Sistemas Aquíferos Içá-Solimões e Alter do Chão
(2013-03) SOUZA, Eliene Lopes de; GALVÃO, Paulo Henrique Ferreira; PINHEIRO, Cleane do Socorro da Silva; BAESSA, Marcus Paulus Martins; DEMÉTRIO, José Geilson Alves; BRITO, Wilker Roberto Rodrigues
Geological maps and stratigraphic charts of the Amazon and Solimões sedimentary basins were reviewed, emphasizing the formations Alter do Chão, Içá and Solimões, the largest reserves of fresh groundwater in these basins. The lack of information on these formations was minimized by sample probe and stratigraphic profiles of construction, lithological and geophysical water and oil wells, obtained in the Base Operacional Geólogo Pedro de Moura, Urucu region, about 650 km southwest of Manaus (AM). In the Amazon Basin, the Aquifer System Alter do Chão is characterized by unconfined and confined aquifers, with transmissivity between 1.5 and 9.1 x 10-3 m2/s, indicated for public supply. In the Solimões Basin, this system is confined by Aquiclude Solimões, recovered by the Içá-Solimões Aquifers. The reserve is estimated as 33,000 km3. The Aquifer System Içá-Solimões, in Urucu, is unconfined-confined, with two aquifers hydraulically connected: the superficial, with top and bottom at depths near 20 and 70 m, respectively; and the deeper, between 50 and 120 m. With an outcrop area of 948,600 km2 in the Solimões Basin, the reservation of this system was estimated as 7,200 km3, less expressive than the Aquifer System Alter do Chão. The average hydrodynamic parameters were: T = 3 x 10-3 m2/s, S = 5 x 10-4 and K = 1 x 10-4 m/s, orders of magnitudes similar to those found in the aquifer Alter do Chão. Assessing the interrelationships and potential of these two regional aquifers sought to contribute to the hydrogeological knowledge in the Amazon Basin region, where researches on groundwater are still incipient.
Acesso aberto (Open Access)
Uso de ferramentas multidisciplinares na avaliação de vulnerabilidade e risco a subsidência no meio cárstico na cidade de Castanhal, Nordeste do Pará – Brasil.
(Universidade Federal do Pará, 2009-11-06) PINHEIRO, Ana Valéria dos Reis; GOUVEIA, José Luiz; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626; 9626349043103626
Castanhal was chosen for this work for being one of the cities with the most demographic growth and also for having its public water supply taken from the Pirabas aquiferous system, whiose main characteristic as the fact that it is formed by carbonaceous rocks. The hypothesis suggested in this work is that this lithology explains the loss of drilling fluid that occurred during the drilling of the three wells in the Jaderlândia district, what can yield a subsurface collapse. The methodology applied in this work consisted of several techniques remote sensing, geomorphology, neotectonics, hydrogeology, geophysics and environmental analysis. The maps were prepared utilizing a Landasat -5/TM satellite images, SRTM images, aerial photos in 1: 70.000 scale and orthophotos mosaics in 1: 10.000 scale. To enhance the geological data, geophysical methods such as gravimetry, resistivity, and well logging: γ rays, spontaneous potential and resistance were applied. The hydrogeological study of Castanhal city was conducted mainly by using data from wells intended for public water supply and from private wells. Geologically, the northeast region of Pará state, where Castanhal city is located, is composed by Pós-Barreiras sediments and Barreiras Group rocks, that are underlied by Pirabas Formation, of calcareous constitution which is the focus of this work. The drainage system is structurally ordered and is represented by a stockwork pattern striking mainly NE-SW and NW-SE, withstrong asymmetry, which allowed to visualize a tectonic sectioning of the Sheet Castanhal SA.23-V-C-I including the Castanhal city, identifying in this way high and low blocks that where confirmed by lithostratigraphics profiles of the wells and by the geophysical survey. The tectonic structure is congruous with the dextral system transcorrent of Riedel, and still contains relaystructures found in all the Sheet of Castanhal, favoring to the recharge of the water-bearing systems; however, this increases its vulnerability to contamination. The hydraulical load and the underground flow present a zone of recharge in the center of the Castanhal city and another one in the Village of Apeú, and indicate effluent draining. The analysis of the quality of the waters showed high contents of total iron and turbidness in some wells and of calcium carbonate in the wells supplied by the Pirabas aquifer system. The gravity survey showed a positive anomaly inthe center of the city, indicating a less deep basement, what was corroborated by the resistivitysurvey. In Jaderlândia and Bom Jesus quarters in the city of Castanhal negative anomalies lined up, concordant with drainage alignments of NW direction indicating the construction of two4 karstics buildings between 60 m and 100 m of depth and 200 m and 400 m of extension representing a high risk of collapse in these quarters to occur. The interaction of the abovementioned information made possible the elaboration of geological sections, blocks diagrams and thematic maps that gave origin to the map of environmental risk for the city of Castanhal.
Acesso aberto (Open Access)
Variação sazonal isotópica de estrôncio e hidrogeoquímica dos sistemas aquíferos Barreiras e Marajó na borda leste da Bacia do Marajó.
(Universidade Federal do Pará, 2023-11-13) NORONHA FILHO, Francisco Áureo; GALARZA TORO, Marco Antonio; http://lattes.cnpq.br/8979250766799749; https://orcid.org/0000-0002-7271-4737
The two main aquifer systems used for consumption and supply in the metropolitan region of Belém-PA (RMB) are the Barreiras and Marajó aquifers, the latter was previously called Pirabas. Within the regional geological context, the interpretation of the existence of the Eastern Edge of the Marajó Basin and the Marajó Formation in the RMB brought interesting discussions that can contribute to greater detail and understanding of the local hydrogeology. As well as assisting in the interpretation and integration of similar works previously developed. Since previous work has demonstrated distinct behaviors of strontium isotopic geochemistry. In this way, this work addresses this topic by bringing together previous and current information and discussing new propositions. To this end, hydrogeochemical characterization and isotopic geochemical characterization of strontium were carried out in the Barreiras and Marajó aquifers in the municipalities of Benevides, Marituba and Santa Izabel. The main objective was to understand the seasonal dynamics of interaction between the Barreiras and Marajó aquifer systems, identifying the meteoric water recharge processes and the mixing proportions between the Barreiras and Marajó aquifers. Groundwater samples were collected in 15 wells, 09 from the Barreiras aquifer and 06 from the Marajó aquifer in the municipalities of Marituba, Benevides and Santa Izabel do Pará in the RMB. Sampling took place during 2013, bimonthly, covering the annual hydrological cycle and the seasonality of the rainiest (December-May) and least rainy (June-November) periods. The analyzes of the 87Sr/86Sr isotopic ratio in groundwater samples were carried out at the Isotopic Geology Laboratory of the Institute of Geosciences (PARÁ-ISO) using the High Resolution Multicollector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS, Neptune) according to the methodology proposed by Bordalo et al. in 2007. The hydrochemical analyzes were reproduced in accordance with the standard methodologies for water analysis of the American Public Health Association, APHA of 1995 and the National Water Agency of 2011 in the Hydrochemistry Laboratory of the Institute of Geosciences. For total iron, the determination was through spectrophotometry. The 1964 Grasshoff method was used for silica analysis. Using liquid chromatography, the main cations (Na+, K+, Mg2+ e Ca2+) and anions (Cl–,HCO3-, NO3–e SO4 2–) were determined using the DIONEX DX-120 ion chromatograph. The Barreiras aquifer presented high concentrations of nitrate associated with free aquifers, acidic pH and sodium chloride facies with an 87Sr/86Sr isotopic ratio that is more radiogenic in the less rainy period, similar to continental rocks and less radiogenic, similar to meteoric waters in the rainier period, suggesting the influence of the processes recharge. The Marajó aquifer presented confined behavior, neutral pH and calcium bicarbonate facies with some differences in the ion signature compared to the Pirabas aquifer. The 87Sr/86Sr ratios of the Marajó aquifer were less radiogenic and similar to macrofossils from the Pirabas Formation. It also showed small variations in isotopic ratios in both seasonal periods, which suggest a greater mixing ratio with the Barreiras aquifer in the rainiest period. The modeling results estimate that there is a greater contribution of meteoric water in the rainiest period in the Barreiras aquifer. Just as there is a greater proportion of mixing with the Barreiras aquifer in the Marajó aquifer in the rainiest period. The use of strontium isotopic geochemistry and the 87Sr/86Sr ratio associated with hydrogeochemistry for water mixing modeling proved to be an effective tool by presenting results that agree with each other.
Acesso aberto (Open Access)
Variações sazonais dos componentes nitrogenados, em aquífero livre na zona urbana de Santa Izabel do Pará, nordeste do estado do Pará
(Universidade Federal do Pará, 2001-08-28) ARAÚJO, Paulo Pontes; SOUZA, Eliene Lopes de; http://lattes.cnpq.br/2060516413833723
The work was carried out in the city of Santa Izabel do Pará, whose population is estimated at 45,000 inhabitants, supplied mainly by shallow hollowed and tubular wells, with depths between 1.50 and 20 m. It is estimated that about 15% of the total urban area is covered by sewage system. In the area, there are confined aquifers of the Pirabas Formation and free aquifers of the Post-Barreiras and Recent Sediments. The main objective of the study was to evaluate the variations of nitrogen components (NH4+ and NO3-) in the water of the Post-Barreiras free aquifer, considering the sanitary conditions of the area, as well as the effects of seasonality and local hydrogeological characteristics. The presence of fecal and total coliforms was also evaluated. Initially, pre-existing physical data and physical-chemical analysis, obtained by CPRM in 1994, in 33 registered wells (PIH Project) were used. The treatment of this information allowed the elaboration of maps: of natural vulnerability of free aquifers; of nitrate isotopes and potentiometric surface. Of these 33 wells, two sets were selected for this study: one located in the old area and the other in the expansion area of the city. Free aquifer water was collected in the dry (November 1999) and rainy (April 2000) periods. The analyzes for ammonium and nitrate, as well as bacteriological analyzes were carried out in the laboratory of the Instituto Evandro Chagas. The sediments of the unsaturated zone, classified as medium and coarse sand, have hydraulic conductivity between 10-3 and 10-4 cm/s, with flow velocity varying between 0.80 (old zone) and 5 m/day (old zone) expansion), indicating greater soil compaction in the old zone. Based on these velocities and on the depth of the water table close to the infiltration test sites, in the old 9.02 m and 3.70 m expansion zones, it appears that in the latter, conservative contaminants (such as nitrate) from pits and /or the ground surface would take about eighteen hours to reach the water table. On the other hand, in the old part of the city, the time required for these contaminants to reach the aquifer would be on the order of eleven days. Post-Barreiras free aquifers have hydraulic conductivity K = 8.30 x 10-4 cm/s, total porosity between 0.18 and 0.21 and flow velocity of 0.03 m/day. Considering the efficient transit times in the degradation of pathogens (210 days), the protection radius of the wells that capture the free aquifer must be at least 6.30 m. However, in the case of contaminants such as nitrate, dilution and denitrification factors must be analyzed in order to protect public health. With the exception of one well, it is observed that in the expansion zone, which is relatively new and with a lower population concentration, the wells in both samples (1994 and 1999) show significantly lower nitrate values, ranging from 4.5 to 13.5 mg /L, recorded in the rainy season. On the other hand, in the old zone, the levels are between 12.8 and 29.9 mg/L, referring to the same period, suggesting a tendency to increase the levels of nitrate in the waters over time. Ammonium levels were higher in the rainy season, with the highest levels reaching 0.710 and 1.520 mg/L obtained in the old zone. In some wells, the increase in nitrate during the dry period was accompanied by a reduction in the ammonium content, suggesting oxidation reactions of NH4+, giving rise to NO3- (nitrification). Based on the correction coefficient between the electrical conductivity parameters and the nitrate content, there was an increase in the area contaminated by nitrate between 1994 and 2001, mainly in the old zone. Most groundwater records the presence of coliforms with maximum and total fecal coliform values of 1,040 and 22,600 MPN/100 mL, respectively. It is observed that there is an increase in ammonium from the dry to the rainy season, at the same time that there is an increase in fecal and total coliforms. These data suggest that, during the rainy season, the transport of ammonium, fecal and total coliforms to groundwater is more efficient. Free aquifer vulnerability indices range from moderate to extreme. The presence of ammonium in water at values above 0.06 mg/L shows a strong indication of contamination by sewage, garbage, or other waste rich in organic matter. In some wells, nitrate concentrations are close to or above that established by potability standards, which is 45 mg/L. The correlation between electrical conductivity (E.C.) and nitrate levels in the water table suggests that about 45% of the city of Santa Izabel do Pará has free aquifer water that is unsuitable for human consumption. The Pirabas Formation aquifers are the best alternative for drinking water.