RESUMO

This study is part of the limnological monitoring undertaken by the Energy Company of the State of São Paulo (CESP) during the filling up process of the Porto Primavera Reservoir (Hydroelectric Power Plant Engenheiro Sérgio Motta). This reservoir, located in the high Paraná River between the States of São Paulo and Mato Grosso do Sul, is the fourth largest in the country. The first filling up phase started in December 1998 and the second phase in March 2001. Samples for benthic community and sediment characteristics analysis were quarterly collected between August of 1999 and November 2001 and also in August of 2002 (11 sampling campaigns). Samplings were carried out at 13 stations distributed in the reservoir, and at one point located downstream of the dam. 128 invertebrate taxa were identified, being Mollusca, Annelida, Insecta and Nematoda the dominant groups during almost the whole study period. Insecta was the best represented class (9 different orders), and Diptera contributed with higher number of taxa, 63. The exotic species of bivalve Corbicula fluminea was recorded in all sampling stations showing its great capacity to colonize new habitats in the neotropical region. Noticeable variations in the fauna density were observed, considering both different periods and locations. The maximum density of organisms (mean value of 7812 ind.m-2) was recorded in the center of the reservoir, and the minimum (mean value 9 ind.m-2) in the more lacustrine area near the dam. The greatest species richness per sample (24 taxa) was observed in the reservoir upstream (fluvial zone). The maximum diversity (Shannon-Wiener Index) per station/period, 3.82 and 3.86 bits.ind-1, were calculated in the transitional river/reservoir zone during the beginning (August 1999) and in the reservoir central zones in the end (August 2002) of the filling up period, respectively. There was no clear relation between the distribution of the different faunistic groups and the sediment granulometric characteristics. However, the decrease or even total absence of organisms was observed at stations with high organic matter concentration (>40%) in a low degradation state (coarse detritus). This fact may be related to the lack of sediment deposits, which would cause difficulties to the fixation of the benthic fauna. Additionally, in those conditions more reduced chemical conditions are expected in function of the intense decomposition process of the flooded vegetation.

Assuntos

RESUMO

This study is part of the limnological monitoring undertaken by the Energy Company of the State of São Paulo (CESP) during the filling up process of the Porto Primavera Reservoir (Hydroelectric Power Plant Engenheiro Sérgio Motta). This reservoir, located in the high Paraná River between the States of São Paulo and Mato Grosso do Sul, is the fourth largest in the country. The first filling up phase started in December 1998 and the second phase in March 2001. Samples for benthic community and sediment characteristics analysis were quarterly collected between August of 1999 and November 2001 and also in August of 2002 (11 sampling campaigns). Samplings were carried out at 13 stations distributed in the reservoir, and at one point located downstream of the dam. 128 invertebrate taxa were identified, being Mollusca, Annelida, Insecta and Nematoda the dominant groups during almost the whole study period. Insecta was the best represented class (9 different orders), and Diptera contributed with higher number of taxa, 63. The exotic species of bivalve Corbicula fluminea was recorded in all sampling stations showing its great capacity to colonize new habitats in the neotropical region. Noticeable variations in the fauna density were observed, considering both different periods and locations. The maximum density of organisms (mean value of 7812 ind.m-2) was recorded in the center of the reservoir, and the minimum (mean value 9 ind.m-2) in the more lacustrine area near the dam. The greatest species richness per sample (24 taxa) was observed in the reservoir upstream (fluvial zone). The maximum diversity (Shannon-Wiener Index) per station/period, 3.82 and 3.86 bits.ind-1, were calculated in the transitional river/reservoir zone during the beginning (August 1999) and in the reservoir central zones in the end (August 2002) of the filling up period, respectively. There was no clear relation between the distribution of the different faunistic groups ...

Este estudo é parte do monitoramento limnológico empreendido pela Companhia Energética do Estado de São Paulo (CESP) durante o processo de enchimento do reservatório de Porto Primavera (Usina Hidrelétrica Engenheiro Sérgio Motta). Este reservatório, localizado no alto rio Paraná, entre os Estados de São Paulo e Mato Grosso, é o quarto maior do país. A primeira etapa de enchimento do lago começou em dezembro de 1998 e a segunda em março de 2001. Amostras para a análise da comunidade bentônica e das características sedimentológicas foram coletadas trimestralmente entre agosto de 1999 e novembro de 2001 e também em agosto de 2002 (11 campanhas). As coletas foram feitas em 13 estações de amostragem distribuídas no reservatório e em uma localizada a jusante da barragem. 128 táxons de invertebrados foram encontrados, sendo Mollusca, Annelida, Insecta e Nematoda os grupos dominantes durante praticamente todos os meses analisados. A classe Insecta foi a melhor representada, com 9 diferentes ordens, dentro das quais os Diptera contribuíram com a ocorrência de 63 táxons. A espécie exótica de bivalve Corbicula fluminea foi registrada em todas as estações de amostragem mostrando sua grande capacidade para colonizar novos habitats em regiões neotropicais. Variações consideráveis na densidade da fauna foram observadas para os diferentes períodos e locais analisados. A densidade máxima (média de 7812 ind.m-2) foi registrada no centro do reservatório enquanto que as densidades mínimas foram registradas na zona lacustre próxima à barragem (média de 9 ind.m-2). A maior riqueza de espécies por local/período (24 táxons) foi encontrada no trecho superior do reservatório (trecho fluvial). A diversidade máxima foi observada nas zonas superior e central do reservatório, com valores de 3.82 e 3.86 (bits.ind-1) no início (agosto/1999) e final (agosto/2002) do processo de enchimento, respectivamente. Não foi encontrado um padrão de distribuição dos grupos faunísticos ...

Assuntos

RESUMO

This study is part of the limnological monitoring undertaken by the Energy Company of the State of São Paulo (CESP) during the filling up process of the Porto Primavera Reservoir (Hydroelectric Power Plant Engenheiro Sérgio Motta). This reservoir, located in the high Paraná River between the States of São Paulo and Mato Grosso do Sul, is the fourth largest in the country. The first filling up phase started in December 1998 and the second phase in March 2001. Samples for benthic community and sediment characteristics analysis were quarterly collected between August of 1999 and November 2001 and also in August of 2002 (11 sampling campaigns). Samplings were carried out at 13 stations distributed in the reservoir, and at one point located downstream of the dam. 128 invertebrate taxa were identified, being Mollusca, Annelida, Insecta and Nematoda the dominant groups during almost the whole study period. Insecta was the best represented class (9 different orders), and Diptera contributed with higher number of taxa, 63. The exotic species of bivalve Corbicula fluminea was recorded in all sampling stations showing its great capacity to colonize new habitats in the neotropical region. Noticeable variations in the fauna density were observed, considering both different periods and locations. The maximum density of organisms (mean value of 7812 ind.m-2) was recorded in the center of the reservoir, and the minimum (mean value 9 ind.m-2) in the more lacustrine area near the dam. The greatest species richness per sample (24 taxa) was observed in the reservoir upstream (fluvial zone). The maximum diversity (Shannon-Wiener Index) per station/period, 3.82 and 3.86 bits.ind-1, were calculated in the transitional river/reservoir zone during the beginning (August 1999) and in the reservoir central zones in the end (August 2002) of the filling up period, respectively. There was no clear relation between the distribution of the different faunistic groups and the sediment granulometric characteristics. However, the decrease or even total absence of organisms was observed at stations with high organic matter concentration (>40%) in a low degradation state (coarse detritus). This fact may be related to the lack of sediment deposits, which would cause difficulties to the fixation of the benthic fauna. Additionally, in those conditions more reduced chemical conditions are expected in function of the intense decomposition process of the flooded vegetation.

Este estudo é parte do monitoramento limnológico empreendido pela Companhia Energética do Estado de São Paulo (CESP) durante o processo de enchimento do reservatório de Porto Primavera (Usina Hidrelétrica Engenheiro Sérgio Motta). Este reservatório, localizado no alto rio Paraná, entre os Estados de São Paulo e Mato Grosso, é o quarto maior do país. A primeira etapa de enchimento do lago começou em dezembro de 1998 e a segunda em março de 2001. Amostras para a análise da comunidade bentônica e das características sedimentológicas foram coletadas trimestralmente entre agosto de 1999 e novembro de 2001 e também em agosto de 2002 (11 campanhas). As coletas foram feitas em 13 estações de amostragem distribuídas no reservatório e em uma localizada a jusante da barragem. 128 táxons de invertebrados foram encontrados, sendo Mollusca, Annelida, Insecta e Nematoda os grupos dominantes durante praticamente todos os meses analisados. A classe Insecta foi a melhor representada, com 9 diferentes ordens, dentro das quais os Diptera contribuíram com a ocorrência de 63 táxons. A espécie exótica de bivalve Corbicula fluminea foi registrada em todas as estações de amostragem mostrando sua grande capacidade para colonizar novos habitats em regiões neotropicais. Variações consideráveis na densidade da fauna foram observadas para os diferentes períodos e locais analisados. A densidade máxima (média de 7812 ind.m-2) foi registrada no centro do reservatório enquanto que as densidades mínimas foram registradas na zona lacustre próxima à barragem (média de 9 ind.m-2). A maior riqueza de espécies por local/período (24 táxons) foi encontrada no trecho superior do reservatório (trecho fluvial). A diversidade máxima foi observada nas zonas superior e central do reservatório, com valores de 3.82 e 3.86 (bits.ind-1) no início (agosto/1999) e final (agosto/2002) do processo de enchimento, respectivamente. Não foi encontrado um padrão de distribuição dos grupos faunísticos que pudesse estar associado com a textura granulométrica dos diferentes locais amostrados. Por outro lado, constatou-se a diminuição, ou mesmo a não ocorrência de organismos, nas estações com elevada concentração de matéria orgânica (>40%) em baixo estado de degradação (grandes detritos vegetais). Tal fato pode estar relacionado com a falta de depósitos de sedimentos, dificultando a fixação de organismos da fauna bentônica, bem como com condições químicas mais redutoras em função da intensidade dos processos de decomposição da fitomassa inundada.

RESUMO

OBJECTIVE: The aim of this study was to discover the lead concentration in primary teeth extracted in the peripheral clinics of the Faculty of Dentistry, UNAM (Mexico City). DESIGN: One hundred healthy primary teeth were collected from 2 to 13-year-old children (52 girls and 48 boys). Sixty-six were maxillary teeth and 34 were mandibular teeth. Lead concentrations were measured by Graphite Furnace Atomic Absorption Spectrophotometry. RESULTS: Our results indicate that lead concentration in the 10-13-year-old group (7.7 micro g/g(-1)) was higher than in the other groups. Geometric mean lead concentration was higher in girls than in boys (7.3 micro g/g(-1) and 6.3 micro g/g(-1), respectively). Maxillary teeth had higher lead concentrations than mandibular teeth and primary canines showed the highest mean lead concentration followed by incisors and molars. Teeth from children living in the south-east area (which according to the Mexico City's Pollution Center data is the more polluted area), presented the highest lead concentration but no statistically significant difference was found among teeth from the different areas. CONCLUSIONS: Our results suggest that age, gender and place of residence are not related to the lead concentration in human primary teeth. This fact seems to indicate the ubiquitous presence of lead in the whole atmosphere of Mexico City and suggests that zones of residence do not appear to influence tooth lead concentration.

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It is difficult to develop control strategies for grain mold of sorghum because of the limited information on the epidemiology of grain mold in Mexico. The objectives of this study were to identify the fungi associated with grain mold in Morelos, Mexico, and to explore the relationship among planting dates, disease development, and relative humidity and temperature. Fusarium thapsinum was isolated from 97% of the grains from field samples of infested sorghum grains in Morelos, Mexico. The influence of planting dates on the development of sorghum grain mold was determined at Tlayca, Morelos, Mexico, during the rainy seasons of 1998, 1999, and 2000. Incidence of grain mold varied annually, but disease incidence and severity were highest in 1998. Planting dates from 1 June to 13 July had the highest incidence of grain mold during the 3 years. Throughout the study, disease severity was generally low, and yield was not affected. The late planting dates in 1999 and 2000 had reduced yields due to terminal drought of the crop. Increase of disease was predicted by mean temperature, but not by mean relative humidity.

RESUMO

OBJECTIVE: To determine the concentration of lead (Pb), cadmium (Cd), and chromium (Cr) and establish the possible association of these heavy metals with some sociodemographic factors. MATERIAL AND METHODS: A representative sample of one hundred dental students from the National Autonomous University of Mexico living in Mexico City participated in this study. Unstimulated human whole saliva samples were analyzed by Atomic Absorption Spectroscopy. RESULTS: Concentrations of Pb, Cd, and Cr were higher than those reported elsewhere: Pb (X = 3.10 micrograms/dL-1; Maximum: 16.8 micrograms/dL-1 and Minimum: 0.04 microgram/dL-1), Cd (X = 0.25 microgram/dL-1; Maximum: 2.04 micrograms/dL-1 and Minimum: 0.004 microgram/dL-1) and Cr (X = 1.43 micrograms/dL-1; Maximum: 4.82 micrograms/dL-1 and Minimum: 0.05 microgram/dL-1). No association was found between the variables studied (age, sex, geographic area and canned food consumption) with Pb and Cr. However, an inverse association was found between Cd and age (Chi 2 = 5.9012, p < or = 0.05); (gamma = -0.5224, p < or = 0.05). CONCLUSIONS: Salivary monitoring can be used for detection of environmental pollutants (atmospheric or occupational), in addition for detection of drugs, and local and systemic diseases. Heavy metal pollution continues to be a public health problem, and therefore the government should form a program for eliminating pollutants from the environment. Likewise, other studies should be carried out to verify the association between variables such as sex, age, use of glazed ceramics, nutrition, and home address with the concentrations of heavy metals in saliva.

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Mexico city has a very high pollution index. Based on the view 'that salivary monitoring can be extended to environmental pollutants', we performed this study in order to determine not only the concentrations of lead and cadmium in human saliva, but also to establish their possible association with some socio-demographic factors. One hundred dental students from the National Autonomous University of Mexico living in Mexico city participated in the study. Stimulated human whole saliva samples were analyzed by atomic absorption spectroscopy. The results show that Pb (x = 3.10 microg/dl(-1); maximum x = 16.8 microg/dl(-1) and minimum x = 0.04 microg/dl[-1]) and Cd (x = 0.25 microg/dl(-1); maximum x = 2.04 microg/dl(-1) and minimum x = 0.004 microg/dl[-1]) concentrations were higher than those reported elsewhere, and that there was no association between several variables studied (age, gender, geographic area and consumption of canned food) and salivary Pb. However, an inverse association was found between Cd and age (chi2 = 5.9012; P < or = 0.05; gamma = -0.5224, P < or = 0.05). From this study it can be concluded that saliva has potential as a technique for monitoring ambient pollutants recent exposure, since circulating levels of certain polluting chemicals can be transported into salivary glands and secretions.

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Ambient levels of carbonyls were measured at the University of Mexico campus, Mexico City. Only formaldehyde and acetaldehyde were measured, since aldehydes with higher molecular weight were not detected. The most abundant aldehyde was formaldehyde, with an overall ratio CH3CHO/H2CO of 0.43. Maximum concentrations occurred for formaldehyde at 10:00 h while for acetaldehyde at 8:00 h. Comparing the concentration measured in this work with those in urban areas it was found that the formaldehyde and acetaldehyde levels in Mexico City are among the highest reported in the literature.

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An evaluation of water quality and phytoplankton composition position was carried out in order to determine the trophic conditions of Lake Patzcuaro (2035 m above sea level), a high altitude tropical lake. Temperatures ranged from 15 to 23 degrees C. Total phosphorus and inorganic nitrogen showed a seasonal variation; highest values coincided with the rainy season (0.48 and 2.1 mg litre(-1), respectively). Dissolved oxygen ranged from 2 to 7.9 mg litre(-1) at the surface and from 0.6 to 7.3 mg litre(-1) on the bottom, the lowest values being found in shallow zones. Average transparency varied from 0.62 to 1.4 m Secchi depth. Rainfall was a primary factor in seasonal variability as it influenced both physical and biological conditions by contributing to the transport and deposition of silt, which mixed with sinking algal cells. The composition of the surface phytoplankton segregated along five major divisions comprising a total of 49 species. General seasonal patterns of dominance alternated in a sequence beginning with Bacillariophyta, through Chlorophyta to Cyanophyta. Diatoms, the dominant group from February to early June, included Melosira granulata, Stephanodiscus sp., Synedra sp. and Fragilaria sp. During the rainy season (late June to September), Microcystis aeruginosa, Oscillatoria sp., Anabaena sp., Merismopedia sp., Crucigenia cuadrata, Oocystis lacustris, Selenastrum gracile, Mallomonas sp. and Tetraediella sp. were important. Melosira granulata was present throughout the period of study. Spatial and temporal variability in both physical and biological conditions make it difficult to assign a specific trophic state to Lake Patzcuaro. Nevertheless, analysis of the algal community indicates a generally mesotrophic condition.

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Formaldehyde concentrations in ambient air and in rain water were measured at the University of Mexico, Mexico City. Air samples were taken twice a day, from 9:00 to 13:00 h and from 13:00 to 16:00 h local time from July to December 1985. Rain water was collected on daily bases from July to October, i.e. during the rainy season. The ambient air mean value was 24.4 x 10(-3) ppmv for morning hours, while the afternoon mean value was 18.5 x 10(-3) ppmv. The formaldehyde concentration in wet precipitation ranged from 0.10 to 0.80 mg liter(-1) (3.3 to 26.6 micromoles liter(-1)) 0.41 mg liter(-1) (13.7 microoles liter(-1)). A comparison of the results of this study with some measurements made at remote maritime sites, rural and urban areas, indicated that the formaldehyde levels in the atmosphere and rain water of Mexico City are among the highest reported in the literature, including the data reported by Grosjean (1982) for Los Angeles, California, during severe photochemical pollution conditions.

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Cadmium was bioassayed to observe cytogenetic effects in the water hyacinth (Eichhornia crassipes). Plants were exposed for 96 hr to freshwater containing 0.01, 0.05, 0.10, 1.5, and 10 mg/liter of cadmium. Metal concentrations in tissues were determined by atomic absorption spectrophotometry. The highest level was found in roots, thus root-tip cells were used for cytogenetic studies; after 24 hr of exposure, micronuclei, c-mitotic effects, and pycnosis were detected and after 48 hr polyploidy was observed. A linear relationship between frequencies of micronuclei and cadmium concentrations was found: at 1.5, and 10 mg/liter micronuclei numbers were always the lowest. The inhibition of cell proliferation. shown by the low mitotic index, was proportional to the concentration and time of exposure. From the results presented in this paper it may be concluded that water hyacinth is a good sensor, due to its fast rate of metal accumulation, which allows an easy way to determine the presence of potential mutagenic compounds in water.

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