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Human remains and corpses' cremation is an increasing practice worldwide alternative to burials, which have increased their cost and reduced spaces in cemeteries. Alike to other combustion processes, cremation produces pollutant emissions that contribute to worsen air quality in modern cities. A 6-month sampling campaign was performed in order to characterize emissions from corpse cremation in three different crematorium ovens and develop emission factors which were used to determine the population exposure to those pollutants during cremation activities applying a dispersion model. The main difference among crematoria was the inclusion or non-inclusion of controlled air supply devices. Using isokinetic samplings in the chimneys crematoria, emissions were measured and characterized with different chemical analyses. No significant differences were found in arsenic and metal concentrations among different crematories, although carbon monoxide, particles, elemental carbon, organic carbon, and polycyclic aromatic hydrocarbon concentrations in facilities without controlled air supply were up to seven times higher than those with controlled air supply. Nevertheless, these pollutants exceeded standards in all crematoria. Except for elemental and organic carbon concentration that correlated with corpse weight, other recorded cadaver characteristics bear no relation with pollutant emissions. Emission factors among different ovens did not present significant differences; then, they were used for dispersion modeling of particles and mercury emissions over Mexico City when 35 crematoria operate simultaneously through an hour showing that PM2.5 and Hg increase 0.01-1 µg m-3 and 0.01-0.1 ng m-3, respectively, in that scenario.

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Biomass burning is a common agricultural practice, because it allows elimination of postharvesting residues; nevertheless, it involves an inefficient combustion process that generates atmospheric pollutants emission, which has implications on health and climate change. This work focuses on the estimation of emission factors (EFs) of PM2.5, PM10, organic carbon (OC), elemental carbon (EC), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) of residues from burning alfalfa, barley, beans, cotton, maize, rice, sorghum, and wheat in Mexico. Chemical characteristics of the residues were determined to establish their relationship with EFs, as well as with the modified combustion efficiency (MCE). Essays were carried out in an open combustion chamber with isokinetic sampling, following modified EPA 201-A method. EFs did not present statistical differences among different varieties of the same crop, but were statistically different among different crops, showing that generic values of EFs for all the agricultural residues can introduce significant uncertainties when used for climatic and atmospheric pollutant inventories. EFs of PM2.5 ranged from 1.19 to 11.30 g kg-1, and of PM10 from 1.77 to 21.56 g kg-1. EFs of EC correlated with lignin content, whereas EFs of OC correlated inversely with carbon content. EFs of EC and OC in PM2.5 ranged from 0.15 to 0.41 g kg-1 and from 0.33 to 5.29 g kg-1, respectively, and in PM10, from 0.17 to 0.43 g kg-1 and from 0.54 to 11.06 g kg-1. CO2 represented the largest gaseous emissions volume with 1053.35-1850.82 g kg-1, whereas the lowest was CH4 with 1.61-5.59 g kg-1. CO ranged from 28.85 to 155.71 g kg-1, correlating inversely with carbon content and MCE. EFs were used to calculate emissions from eight agricultural residues burning in the country during 2016, to know the potential mitigation of climatic and atmospheric pollutants, provided this practice was banned. IMPLICATIONS: The emission factors of particles, short-lived climatic pollutants, and atmospheric pollutants from the crop residues burning of eight agricultural wastes crops, determined in this study using a standardized method, provides better knowledge of the emissions of those species in Latin America and other developing countries, and can be used as inputs in air quality models and climatic studies. The EFs will allow the development of more accurate inventories of aerosols and gaseous pollutants, which will lead to the design of effective mitigation strategies and planning processes for sustainable agriculture.

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Open-air burning of agricultural wastes from crops like corn, rice, sorghum, sugar cane, and wheat is common practice in Mexico, which in spite limiting regulations, is the method to eliminate such wastes, to clear the land for further harvesting, to control grasses, weeds, insects, and pests, and to facilitate nutrient absorption. However, this practice generates air pollution and contributes to the greenhouse effect. Burning of straws derived from the said crops was emulated in a controlled combustion chamber, hence determining emission factors for particles, black carbon, carbon dioxide, carbon monoxide, and nitric oxide throughout the process, which comprised three apparent stages: pre-ignition, flaming, and smoldering. In all cases, maximum particle concentrations were observed during the flaming stage, although the maximum final contributions to the particle emission factors corresponded to the smoldering stage. The comparison between particle size distributions (from laser spectrometer) and black carbon (from an aethalometer) confirmed that finest particles were emitted mainly during the flaming stage. Carbon dioxide emissions were also highest during the flaming stage whereas those of carbon monoxide were highest during the smoldering stage. Comparing the emission factors for each straw type with their chemical analyses (elemental, proximate, and biochemical), some correlations were found between lignin content and particle emissions and either particle emissions or duration of the pre-ignition stage. High ash or lignin containing-straw slowed down the pre-ignition and flaming stages, thus favoring CO oxidation to CO2.

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We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce-Co/Al2O3 membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce-Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns.

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Sugarcane burning is an agricultural practice implemented to ease farm worker duties; nevertheless, as a consequence, tons of particles are emitted to the atmosphere. Additionally, during harvesting the sugar-mills operate the whole day emitting hundreds of tons of pollutants. Therefore, health risks to neighboring population should be a major governmental concern, leading first to identification and quantification of toxic compounds, such as polycyclic aromatic hydrocarbons (PAHs). In order to establish the magnitude of the problem, four sampling campaigns of PM10 and PM2.5 were carried out in this study, during harvesting and no-harvesting seasons in two municipalities of México, with different climatic and social conditions. Concentrations of PM10, PM2.5, and organic compounds were determined daily, followed by extraction, identification and quantification of the 17 EPA-established PAHs from all samples. The results showed that during harvest, the PM10 mass increased lightly in Chiapas, but approximately twice in Morelos, whereas total PAH concentrations increased twice and six times, respectively. The most abundant PAHs, namely: indene [1,2,3cd] pyrene, benzo[b]fluoranthene, benzo[a]pyrene and dibenzo [a,h] anthracene are composed of 5 or more aromatic rings. Of the total PAHs quantified, 44% to 52% corresponded to carcinogenic compounds, consequently, the overall carcinogenic potential increased twice or three times. Principal component analysis with varimax rotation was applied to source apportionment at each site, suggesting three different sources during harvesting: the combustion process in the sugar mill, sugarcane burning and vehicular emissions. The combustion markers for sugar mill are, BAA, BBF, BKF, BAP, IND and BGP, whereas for sugarcane burning were ANT, PHE, FLT and PYR. The results obtained indicate that processing and burning sugarcane are the main sources of the PAH levels measured, proving that the health risks are boosted during harvesting due to increases of PM and PAHs.

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Benzene alkylation with propylene was studied in the gas phase using a catalytic membrane reactor and a fixed-bed reactor in the temperature range of 200-300 °C and with a weight hourly space velocity (WHSV) of 51 h-1. ß-zeolite was prepared by hydrothermal synthesis using silica, aluminum metal and TEAOH as precursors. The membrane's XRD patterns showed good crystallinity for the ß-zeolite film, while scanning electron microscopy SEM results indicated that its random polycrystalline film was approximately 1 µm thick. The powders' specific area was determined to be 400 m²×g-1 by N2 adsorption/desorption, and the TPD results indicated an overall acidity of 3.4 mmol NH3×g-1. Relative to the powdered catalyst, the catalytic membrane showed good activity and product selectivity for cumene.