No abstract

No abstract

A detailed view of particulate air pollution in Mexico City resulting from several analyses of data collected during four field campaigns is given. The resulting database from the March 1997 campaign was used to identify and quantify the contribution of particles to the atmosphere from different emission sources, to estimate transport and dispersion of pollutants and to estimate the amount of secondary organic carbon. Emission inventories of PM 10 , PM 2.5 and ammonia were also calculated. Data from March 1997 and March 2002 campaigns were used to estimate aerosol optical properties and its impact on visibility, and measurements during March and November 2001 and March 2002 were used to obtain particle mass size distributions. Results showed that major contribution of PM 2.5 were the mobile source emissions with 45%. Computer simulations were run for a wind blown dust episode and results agreed with observations. Particle concentrations were found to be inversely related to transport wind speed, and the highest pollutant dispersion was in the afternoon as calculated with the ventilation index. An average of 25% of the total organic carbon in the PM 2.5 was associated to secondary organic aerosol estimated with an empirical model. Particles of sizes between 0.1 and 1.0 μm accounted for the highest mass concentrations and were associated mainly to primary emissions. The earlier visible light absorption peaks that appeared in the diurnal patterns were attributed to the elevated elemental carbon vehicular emissions during the heavy traffic hours while the later light scattering peaks were attributed to secondary aerosol formed photochemically in the atmosphere. Dairy and non-dairy cattle were the dominant sources according to the calculated emission inventory (EI) for ammonia. PM 2.5 mobile sources derived from the EI were 11% whereas those estimated with the receptor model were 45%.

No abstract

PM2.5 monitoring campaigns were conducted in 2006, 2010, and 2011 in Tula de Hidalgo, Mexico, a highly industrialized area which includes a refinery, a thermoelectric power plant, five cement plants, limestone mining, and industrial waste combustion. These data establish baselines and trends against which later concentrations can be compared as emission reduction plans are implemented. PM 2.5 mass, chemical composition, and 15 particle-bound polycyclic aromatic hydrocarbons (PAHs) were measured at two sites. PM2.5 masses ranged from 26 to 31 µg m −3 . Carbonaceous aerosols were the largest PM2.5 component, accounting for 47-57% of the mass. Approximately 40-51% of the carbonaceous aerosol was attributed to secondary organic carbon. Ionic species accounted for 40-44% of PM2.5, with sulfate being the dominant ion. The sum of particle-bound PAH concentrations ranged from 14−31 ng m −3 . Six factors derived from Principal Component Analysis (PCA) explained ~ 85% of the PM2.5 variance. The derived factors were associated with sources based on marker species resulting in heavy-oil combustion (22% of variance), vehicle engine exhaust (13-19% of variance), fugitive dust (18% of variance), biomass burning (9-13% of variance), secondary aerosols (14% of variance), and industrial emissions (6-10% of variance). Combustion of solid waste (e.g., tires and industrial waste) of the recycling cement kilns and incinerators resulted in elevated toxic species such as, Cd, and Sb in the range of 0.02-0.3 µg m −3 .A health risk assessment of carcinogenic trace elements was performed showing that the total cancer risk decreased for both children and adults in 2010/2011 (ranging from 3.5×10 −6 to 6.0×10 −5 ) as compared to 2006 (ranging from 8.6×10 −7 to 5.7×10 −6 ). The inhalation life-time cancer risk (ILCR) for particle-bound PAHs ranged from 8.6×10 −5 to 1.2×10 −4 .Air quality can be improved by switching to cleaner fuels and benefit from the use of natural gas instead of fuel oil in the power plant.