RESUMO
Pure biogenic new particle formation (NPF) induced by highly oxygenated organic molecules (HOMs) could be an important mechanism for pre-industrial aerosol formation. However, it has not been unambiguously confirmed in the ambient due to the scarcity of truly pristine continental locations in the present-day atmosphere or the lack of chemical characterization of NPF precursors. Here, we report ambient observations of pure biogenic HOM-driven NPF over a peatland in southern Finland. Meteorological decoupling processes formed an "air pocket" (i.e., a very shallow surface layer) at night and favored NPF initiated entirely by biogenic HOM from this peatland, whose atmospheric environment closely resembles that of the pre-industrial era. Our study sheds light on pre-industrial aerosol formation, which represents the baseline for estimating the impact of present and future aerosol on climate, as well as on future NPF, the features of which may revert toward pre-industrial-like conditions due to air pollution mitigation.
RESUMO
New particle formation (NPF) in the tropical free troposphere (FT) is a globally important source of cloud condensation nuclei, affecting cloud properties and climate. Oxidized organic molecules (OOMs) produced from biogenic volatile organic compounds are believed to contribute to aerosol formation in the tropical FT, but without direct chemical observations. We performed in situ molecular-level OOMs measurements at the Bolivian station Chacaltaya at 5240 m above sea level, on the western edge of Amazonia. For the first time, we demonstrate the presence of OOMs, mainly with 4-5 carbon atoms, in both gas-phase and particle-phase (in terms of mass contribution) measurements in tropical FT air from Amazonia. These observations, combined with air mass history analyses, indicate that the observed OOMs are linked to isoprene emitted from the rainforests hundreds of kilometers away. Based on particle-phase measurements, we find that these compounds can contribute to NPF, at least the growth of newly formed nanoparticles, in the tropical FT on a continental scale. Thus, our study is a fundamental and significant step in understanding the aerosol formation process in the tropical FT.
RESUMO
Objetivo: Conocer las características clínicas y epidemiológicas de los pacientes de menores de 05 años, que durante los años 2007 y 2008, hayan sido diagnosticados con diarrea aguda infecciosa y cuyo coprocultivo haya resultado positivo para algún enteropatógeno, en el Instituto Nacional de Salud del Niño. Metodología: Este es un estudio descriptivo retrospectivo. Luego de recolectar los resultados positivos obtenidos de todos los coprocultivos hechos a pacientes menores de 05 años en los años 2007 y 2008, se procedió a analizar las respectivas historias clínicas para hallar su relación con el resto de variables, que incluyen género, edad, hospitalización, antecedentes epidemiológicos (crianza de animales, servicios completos y lactancia materna exclusiva) y deshidratación. Los resultados fueron evaluados de acuerdo a medidas de resumen y variabilidad. Conclusiones: Campylobacter sp. fue el agente etiológico más prevalente para el total de la muestra, con el 41,5 por ciento de los casos. El 14,4 por ciento de pacientes criaban animales; 13,6 por ciento no tenía servicios completos (luz, agua, desagüe) y 19,1 por ciento no tuvo lactancia materna exclusiva. La deshidratación estuvo presente en 76 pacientes, lo que representa al 32,2 por ciento de la muestra. Un 28,4 por ciento de pacientes tuvo la necesidad de hospitalización