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.

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.

Measurements of formaldehyde, acetaldehyde, acetone, propionaldehyde and butyraldehyde concentrations were made at five different forested regions in México. One set of two simultaneous samplings was performed at two sites located in the México State, one semi-rural area (Temascaltepec), and the other, a forested area (Rancho Viejo). A second set of two simultaneous samplings were made in southern Veracruz State, in one rural area (Monte Pío) and inside a tropical rainforest (at the Biology Station of the University of México). Finally, one sampling was performed in the Sierra of Puebla State (Cuetzalan). Propionaldehyde and butyraldehyde were not reported because their concentrations were always below or near the detection limit of the technique. The highest concentrations were found from 7:00 to 11:00 h and from 11:00 to 19:00 h in all the sampling sites. Arithmetic mean concentrations of acetone were the highest observed among the detected carbonyl compounds in almost all sites, ranging from 0.5 to 8.4 µgm-3. Arithmetic mean concentrations of formaldehyde and acetaldehyde ranged from 0.83 to 6 ugm3 and0.53 to 4.7 µgm-3, respectively. The Spearman's correlations between formaldehyde and acetone, and between acetaldehyde and acetone were statistically significant at p < 0.05 in almost all sites. A significant correlation (p < 0.05) between formaldehyde and acetaldehyde was observed in México State at Rancho Viejo and Temascaltepec. The mean ratio HCHO/ CH3CHO of concentrations was 1.83 and 1.31 in the forested area of Rancho Viejo, first and second sampling periods, respectively; 1.71 and 1.62 in the semi-rural area of Temascaltepec, first and second sampling periods respectively; 1.70 in Cuetzalan; 2.90 in the rural area of Monte Pío; and 1.61 in the Biology Station tropical rainforest. These values show a greater influence of atmospheric pollutants transported from sites with anthropogenic activities, because HCHO/CH3CHO concentration ratios between 1 and 2 are typical values of urban air. During the onset of strong winds from the south (locally known as "surada") a significant increase in carbonyl concentration was observed, in relation to the days before the "surada", as a result of a possible transport of pollutants emitted by distant anthropogenic sources such as the highway near Catemaco town and industrial complexes near Coatzacoalcos city. The air mass back trajectories were calculated for Rancho Viejo, Temascaltepec and Cuetzalan, and average carbonyl concentrations in air were discussed according to the air mass origin.

Se determinaron las concentraciones de formaldehído, acetaldehído, acetona, propionaldehído y butiraldehído en la atmósfera de cinco zonas boscosas de México. Se hicieron dos muestreos simultáneos en dos sitios localizados en el estado de México, el primero en Temascaltepec, un área semirural, y el otro en Rancho Viejo, un área boscosa. Se hizo otro muestreo simultáneo en el sur del estado de Veracruz en un área rural (Monte Pío) a la orilla del mar y en el interior de un bosque tropical en la Estación de Biología de la Universidad Nacional Autónoma de México y un muestreo en un sitio ubicado en la Sierra de Puebla (Cuetzalan). Los muestreos se realizaron entre el 12 de mayo de 2002 y el 8 de marzo de 2003. Las concentraciones de propionaldehído y butiraldehído no se reportaron porque siempre estuvieron abaj o o cerca del límite de detección del sensor de cromatografía líquida. Las concentraciones más altas de los otros compuestos se encontraron en los intervalos de muestreo de las 7:00 a las 11:00 y de las 11:00 a las 19:00 h en todos los sitios de muestreo. La media aritmética de las concentraciones de acetona fue la más alta en casi todos los sitios variando de 0.5 a 8.4 µgm-3. La media aritmética de las concentraciones de formaldehído y acetaldehído varió de 0.83 a 6 y de 0.53 a 4.7 µgm-3, respectivamente. La correlación de Spearman entre formaldehído y acetona y entre acetaldehído y acetona fue estadísticamente significativa en casi todos los sitios (p < 0.05). Se observó una correlación significativa (p < 0.05) entre formaldehído y acetaldehído en Rancho Viejo y Temascaltepec. La razón HCHO/ CH3CHO promedio de las concentraciones fue de 1.83 y 1.31 en Rancho Viejo, primer y segundo muestreo, respectivamente; 1.71 y 1.62 en Temascaltepec, primer y segundo muestreo, respectivamente; en Cuetzalan fue de 1.70, en Monte Pío de 2.90, y en La Estación de Biología fue de 1.61. Estos valores reflejan una mayor influencia de contaminantes atmosféricos transportados desde regiones con actividad antrópica, debido a que valores entre 1 y 2 de la razón de la concentración HCHO/CH3CHO son típicos del aire urbano. Durante el inicio de vientos fuertes del sur (localmente conocidos como "surada") se observó un incremento significativo en la concentración de carbonilos, con respecto a los días previos a la "surada", como resultado de un posible transporte de contaminantes emitidos por fuentes antrópicas distantes tales como la carretera cerca del poblado de Catemaco y los complejos industriales cercanos a Coatzacoalcos. Se calcularon las trayectorias 24 horas hacia atrás de las masas de aire para Rancho Viejo, Temascaltepec y Cuetzalan y las concentraciones de carbonilos en el aire se discutieron de acuerdo al origen de las masas de aire

Measurements of ambient carbonyls were carried out at one sampling site at the University of Mexico campus, Mexico City in dry season (November and December 1993, March 1994, and February and March 1996), and rainy season (June and September 1995, May, June, July, and September 1996). In general, formaldehyde had higher average hourly concentrations than those of the other sampled carbonyls, however, in May 1996, acetaldehyde concentrations were above 65 ppbv; much higher than the obtained for all the period of study. In June 1996, these levels decreased to 20 ppbv, even higher than the observed values in all the period of study, except February 1996 with 22.5 ppbv. It was not found a satisfactory explanation for the acetaldehyde levels observed in February, May and at the beginning of June 1996. Average hourly concentrations of acetone from 4 to 28 ppbv for all the period study were slightly higher or equal to formaldehyde and acetaldehyde concentrations at some days. Propionaldehyde (1 to 9 ppbv) and butyraldehyde (1 to 4 ppbv) levels were small but significant. In general, a decrease in carbonyl concentrations during the evening was observed. Comparison of carbonyl concentrations between March 1994 and 1995, June 1995 and June 1996 and September 1995 and 1996, indicated a significant difference (p ≤ 0.05) for acetaldehyde, acetone and propionaldehyde. On the other hand, formaldehyde concentration (14.9 ppbv) was higher in rainy season and acetaldehyde, acetone and butyraldehyde were higher in dry season (14.1, 12.4, 2.5 y 2.3 ppbv, respectively).

Se determinaron carbonilos ambientales en un sitio de la ciudad de México localizado en el campus de la Universidad Nacional Autónoma de México. Los muéstreos se realizaron en la temporada de secas (noviembre y diciembre de 1993, marzo de 1994 y 1995 y febrero de 1996) y en la temporada de lluvias (junio y septiembre de 1995 y mayo, junio, julio y septiembre de 1996). En general, el formaldehído fue el carbonilo que tuvo mayor concentración promedio horaria de 7 a 31 ppbv. Sin embargo, en mayo de 1996 la concentración promedio horaria de acetaldehído estuvo por arriba de 65 ppbv, concentración mucho más alta que la obtenida en todo el periodo de estudio. En junio de 1996, estos niveles disminuyeron a 20 ppbv, que es mayor que el nivel observado en todo el periodo de estudio, con excepción de febrero de 1996 con 22.5 ppbv. No se encontró una explicación satisfactoria sobre los altos niveles de acetaldehído observados en febrero, mayo y a principios de junio de 1996. La acetona, en todo el periodo de muestreo tuvo un promedio horario de 4 a 28 ppbv, siendo ligeramente más alta que o igual a la de formaldehído y acetaldehído en algunos días. Los niveles de propionaldehído (1 a 9 ppbv) y de butiraldehído (1 a 4 ppbv) fueron bajos pero significativos. En general, se observó una disminución de las concentraciones de carbonilos durante la tarde. La comparación de los niveles de carbonilos entre marzo de 1994 y 1995, junio de 1995 y 1996 y septiembre de 1995 y 1996, indicó diferencias significativas (p ≤ 0.05) sólo entre junio de 1995 y junio de 1996, para el acetaldehído, acetona y propionaldehído. Por otra parte, la concentración de formaldehído (14.9 ppbv) fue más alta en la temporada de lluvias. Las concentraciones de acetaldehído, acetona, propionaldehído y butiraldehído fueron más altas en la temporada de secas (14.1, 12.4, 2.5 y 2.3 ppbv, respectivamente).