Rocío García

Carbonyl levels in indoor and outdoor air in Mexico City and Xalapa, Mexico.

Carbonyl compounds in air were measured at two houses, three museums, and two offices. All sites lacked air-conditioning systems. Although indoor and outdoor air was measured simultaneously at each site, the sites themselves were sampled in different dates. Mean concentrations were higher in indoor air. Outdoor means concentrations of acetone were the highest in all sites, ranging from 12 to 60 microg m(-3). In general, formaldehyde and acetaldehyde had similar mean concentrations, ranging from 4 to 32 and 6 to 28 microg m(-3), respectively. Formaldehyde and acetone mean indoor concentrations were the highest, ranging from 11 to 97 and 17 to 89 microg m(-3), respectively, followed by acetaldehyde with 5 to 47 microg m(-3). Formaldehyde and acetaldehyde had the highest mean concentration in the offices where there were smokers. Propionaldehyde and butyraldehyde concentrations did not show definite differences between indoor and outdoor air. In general, the highest outdoor and indoor hourly concentrations were observed from 10:00 to 15:00 h. Mean indoor/outdoor ratios of carbonyls exceeded 1. Formaldehyde and acetaldehyde risks were higher in smoking environments.

Trace metals and inorganic ion measurements in rain from Mexico City and a nearby rural area

Rain is a main source of water for the ecosystem in Mexico. Emitted particulate matter and gases enter the ecosystem by rain scavenging. Although the chemistry of rainwater has been the subject of a number of studies, the insoluble fraction has been virtually ignored. This fraction is made up of particulate material, and can be significant, particularly in rural forest regions. Average aluminium weights were the highest of all elements, in both the soluble and insoluble fractions. Ions with the highest concentrations were and , followed by , Na+, Cl−, Ca2+, Mg2+ and K+. The Spearman rho correlation showed that the acidity was caused by and , and the most important neutralising ion was . High crustal enrichment factors (EFcrusts) suggested that Mexico City in general was richer in Cd, Cr, Mn, Pb, and V than Rancho Viejo. The enrichment factors support the idea that the metals observed in rainwater have an anthropogenic origin. Air mass back trajectories were associated with the concentrations of trace metals and of , Ca2+, Mg2+, and observed during each rainy day.

Determination of trace elements in total suspended particles at the Southwest of Mexico City from 2003 to 2004

The purpose of the present study is to describe the relationships of eight elements analysed in total suspended particles collected in Mexico City, during 2003 and 2004. Al, Cd, Cr, Fe, Mn, Ni, Pb and V were analysed in to the atmospheric samples and the results were treated by Principal Components Analysis and Cluster Analysis trying to identify the possible sources of aerosols in the sampling site. Factor analysis calculations allowed the elements classification, related to their source on oil combustion, crustal and urban dust, smelting industries and motor vehicle emissions. A further statistical analysis of chemical results from the atmospheric samples was also performed, in order to see what environmental concentrations of those elements have been affected by industrial and mining activities. The eight elements analysed were arranged into two groups that presents high and positive Pearson r values suggesting common emission sources.

Measurements of carbonyls in a 13-story building

Background, Aim and ScopeFormaldehyde and acetaldehyde are emitted by many mobile and stationary sources and secondary aldehydes are intermediates in the photo-oxidation of organic compounds in the atmosphere. These aldehydes are emitted indoors by many materials such as furniture, carpets, heating and cooling systems, and by smoking. Carbonyls, mainly formaldehyde and acetaldehyde, have been studied because of their adverse health effects. In addition, formaldehyde is a suspected carcinogen. Therefore, the concentrations of formaldehyde and acetaldehyde were determined to assess the inhalation exposure doses to carbonyls for people who work in a 13-story building and in order to evaluate the cancer hazard.MethodsCarbonyl compounds in indoor and outdoor air were measured at a 13-story building located in Mexico City. The mezzanine, fifth and tenth floors, and the third level-parking garage were selected for sampling. Samples were collected in two sampling periods, the first from April 20 to 29, 1998 and the second from December 1 to 20, 1998. Carbonyls were sampled by means of DNHP-coated cartridges at a flow rate of 1 1 min-1 from 9:00 to 19:00 hours, during 2-hour time intervals and analyzed by HPLC with UV/VIS detection.ResultsMean carbonyl concentrations were highest in the 3rd level-parking garage, with the formaldehyde concentration being the highest ranging from 108 to 418 ug m-3. In working areas, the highest carbonyl arithmetic mean concentrations (AM) were observed on the 5th floor. Acetone and formaldehyde concentrations were highest in April ranging from 161 to 348 µg m5 (AM = 226) and from 157 to 270 µg m-3 (AM= 221), respectively. Propionaldehyde and butyraldehyde were present in smaller concentrations ranging from 2 to 25 and 1 to 28 µg m-3, respectively, considering all the samples. Mean indoor/outdoor ratios of carbonyls ranged from 1.8 to 9.6. A reduction of inhalation exposure doses of 41% and 45% was observed in the fifth floor air after the air conditioning systems had been repaired. Formaldehyde and acetaldehyde concentrations were higher in smoking environments.ConclusionIndoor carbonyl concentrations were significantly greater than outdoor concentrations. Tobacco smoke seems to be the main indoor source of formaldehyde. After the air conditioning system was maintained and repaired (as was recommended), an important reduction in the emission of formaldehyde and acetaldehyde was achieved on all floors, except for the 3rd level parking garage, thereby reducing the inhalation exposure doses.RecommendationThe results obtained in this research demonstrated that maintenance of air conditioning systems must be carried out regularly in order to avoid possible adverse effects on health. Additionally, it is mandatory that isolated smoking areas, with air extraction systems, be installed in every public building.

Measurement of indoor-outdoor carbonyls at four residential homes in Mexico city metropolitan area

Formaldehyde, acetaldehyde, acetone, propionaldehyde and butyraldehyde were measured in indoor and outdoor air at three houses and one apartment in the Mexico city metropolitan area (MCMA). Formaldehyde presented the highest concentration in indoor and outdoor air, followed by acetone and acetaldehyde. Indoor carbonyl concentrations were higher than outdoor concentrations at all sampling sites. Indoor exposure factors were estimated for formaldehyde and acetaldehyde, ranging from 202 µg day–1 to 554 µg day–1 for formaldehyde and from 82 µg day–1 to 202 µg day–1 for acetaldehyde. Indoor-outdoor correlations were significant at all sites. However, these correlations were the highest in the Miguel Hidalgo house, which was naturally well ventilated, and where very few activities like cooking, were done. Concerning the Tlalnepantla house, although it was also well ventilated, the correlations were not as high as those observed at the Miguel Hidalgo house, possibly because its inhabitants cook a lot more and throughout the whole day.

Carbonyls in the metropolitan area of Mexico City

A great number of studies on the ambient levels of formaldehyde and other carbonyls in the urban rural and maritime atmospheres have been published because of their chemical and toxicological characteristics, and adverse health effects. Due to their toxicological effects, it was considered necessary to measure these compounds at different sites in the metropolitan area of Mexico City, and to calculate the total rate of photolytic constants and the photolytic lifetime of formaldehyde and acetaldehyde. Four sites were chosen. Sampling was carried out at different seasons and atmospheric conditions.The results indicated that formaldehyde was the most abundant carbonyl, followed by acetone and acetaldehyde. Data sets obtained from the 4 sites were chosen to calculate the total rate of photolysis and the photolytic lifetime for formaldehyde and acetaldehyde. Maximum photolytic rate values were obtained at the maximum actinic fluxes, as was to be expected.

BIOSORPTION OF CD, CR, MN, AND PB FROM AQUEOUS SOLUTIONS BY Bacillus SP STRAINS ISOLATED FROM INDUSTRIAL WASTE ACTIVATE SLUDGE

The microorganisms are capable of accumulating heavy metal ions from water as biosorbent agents, offering a potential alternative for the detoxification and recovery of toxic/precious metals in industrial wastewater. In the present work, metal-resistant bacterial strains were isolated and identified from activated sludge of a waste treatment plant in the Municipality of Santa Rosa Jauregui, Queretaro. To obtain bacteria tolerant to metals, 37 bacterial strains and two isolates were selected based on their ability to show high tolerance (strains C-13 and C-16), maximum adsorption capacity for the studied metals. In this article, the term biosorption is used to encompass uptake by whole (dead) biomass via physicochemical mechanisms such as adsorption or ion exchange. The adsorption capacity was measured with alkaline and acid treatments to determine the conditions for maximum adsorption. The adsorption capacity with acid treatment was lower than biosorbent with alkaline treatment. A second part of the study was the biosorption of heavy metals (Cd, Cr, Mn, and Pb) from aqueous dead biomass of Bacillus sp (strain C13 and C16) isolated from the activated sludge in the first stage.

Performance of the SciBar cosmic ray telescope (SciCRT) toward the detection of high-energy solar neutrons in solar cycle 24

We plan to observe solar neutrons at Mt. Sierra Negra (4,600 m above sea level) in Mexico using the SciBar detector. This project is named the SciBar Cosmic Ray Telescope (SciCRT). The main aims of the SciCRT project are to observe solar neutrons to study the mechanism of ion acceleration on the surface of the sun and to monitor the anisotropy of galactic cosmic-ray muons. The SciBar detector, a fully active tracker, is composed of 14,848 scintillator bars, whose dimension is 300 cm × 2.5 cm × 1.3 cm. The structure of the detector enables us to obtain the particle trajectory and its total deposited energy. This information is useful for the energy reconstruction of primary neutrons and particle identification. The total volume of the detector is 3.0 m × 3.0 m × 1.7 m. Since this volume is much larger than the solar neutron telescope (SNT) in Mexico, the detection efficiency of the SciCRT for neutrons is highly enhanced. We performed the calibration of the SciCRT at Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) located at 2,150 m above sea level in Mexico in 2012. We installed the SciCRT at Mt. Sierra Negra in April 2013 and calibrated this detector in May and August 2013. We started continuous observation in March 2014. In this paper, we report the detector performance as a solar neutron telescope and the current status of the SciCRT.

Trends in Chemical Composition of Wet Precipitation in Mexico City, Mexico: 1992-2007

This paper presents the results of a study of variation in the chemical composition of wet precipitation over a 16-year period. The ions SO4 2- , NO3 - , Cl - , Ca 2+ , Mg 2+ K + , Na + , NH4 + and H + were analyzed. The correlation analysis showed a high positive correlation among these ions, indicating that anthropogenic emissions were the most important source. Trends in annual concentrations of SO4 2- , NO3 - , Cl - , NH4 + , Mg 2+ , Ca 2+ , K + , H + and alkalinity as function of time were calculated using a linear least-square regression of the volume weighted mean concentrations of these ions in rainwater collected over a 16-year period. Sulfate (SO4 2- ) in wet precipitation showed a significant decreasing trend, corresponding to the reduction in SO2 emissions in the Mexico City valley due to the change from oil to gas fuel in thermoelectric power plants and heavy and medium sized industries. In spite of the fact that the number of motor vehicles has risen considerably in Mexico City, NO3 - did not show a significant increasing trend. The NH4 + /Ca 2+ ratio showed a nearly significant increasing trend, due mainly to the significant decrease in Ca 2+ concentration. This decreasing trend was not as marked as that of SO4 2- . The contribution of NH4 + to neutralization was relatively small, showing only a non significant increase in NH4 + over the study period, while a considerable decreasing SO4 2- trend occurred, which could mean that part of the NH4 + ions reacted with other ions, forming ammonium compounds.

Total peroxides in rainwater at two mountainous sites and in Mexico City, Mexico

Rainwater samples were collected in the western sector of Mexico City (MC) and at Rancho Viejo (RV), 80 km west-south-west of MC, from 2001 to 2005, and Orizaba City (OC), about 90 km from the Gulf of Mexico, where rainwater collections were only possible on some weekends in 2001. Rainwater samples were treated in the field, and analysed by fluorescence at the laboratory. The volume-weighted mean concentration (VWMC) of H2O2 was 13.2 μM at RV, and 11.2 μM in MC, for the period 2001–2005. The highest VWMC was observed in OC (21.6 μM). The VWMCs for each year were 9.5, 14.4, 11.5, 16.7, and 14.3 μM at RV, and 12.2, 12.2, 14.3, 11.8, and 9.9 μM in MC, for 2001–2005, respectively. Hydrogen peroxide in rainwater correlated significantly and negatively with sulfate in both MC and RV, but not, however, in OC. This study confirmed that H2O2 concentration in rainwater is controlled by a complex combination of rain intensity, washout processes and in-cloud formation of H2O2, acting simultaneously. This was suggested by the fact that rain intensity seemed to predominate in certain rain fractions of a rain event, while washout processes seemed to predominate in other fractions of the same rain event.