Total HCHO Research Articles

Formaldehyde Exposure Racial Disparities in Southeast Texas.

Formaldehyde (HCHO) exposures during a full year were calculated for different race/ethnicity groups living in Southeast Texas using a chemical transport model tagged to track nine emission categories. Petroleum and industrial emissions were the largest anthropogenic sources of HCHO exposure in Southeast Texas, accounting for 44% of the total HCHO population exposure. Approximately 50% of the HCHO exposures associated with petroleum and industrial sources were directly emitted (primary), while the other 50% formed in the atmosphere (secondary) from precursor emissions of reactive compounds such as ethylene and propylene. Biogenic emissions also formed secondary HCHO that accounted for 11% of the total population-weighted exposure across the study domain. Off-road equipment contributed 3.7% to total population-weighted exposure in Houston, while natural gas combustion contributed 5% in Beaumont. Mobile sources accounted for 3.7% of the total HCHO population exposure, with less than 10% secondary contribution. Exposure disparity patterns changed with the location. Hispanic and Latino residents were exposed to HCHO concentrations +1.75% above average in Houston due to petroleum and industrial sources and natural gas sources. Black and African American residents in Beaumont were exposed to HCHO concentrations +7% above average due to petroleum and industrial sources, off-road equipment, and food cooking. Asian residents in Beaumont were exposed to HCHO concentrations that were +2.5% above average due to HCHO associated with petroleum and industrial sources, off-road vehicles, and food cooking. White residents were exposed to below average HCHO concentrations in all domains because their homes were located further from primary HCHO emission sources. Given the unique features of the exposure disparities in each region, tailored solutions should be developed by local stakeholders. Potential options to consider in the development of those solutions include modifying processes to reduce emissions, installing control equipment to capture emissions, or increasing the distance between industrial sources and residential neighborhoods.

Spatio-temporal distribution and source partitioning of formaldehyde over Ethiopia and Kenya

Abstract Understanding the local sources of atmospheric formaldehyde (HCHO) is a key step in accurately determining the inversion of biogenic volatile organic compounds (BVOCs). This study aims to clarify the main sources and emission patterns of local total HCHO column densities over Ethiopia and Kenya. Between 2005 and 2015, the total monthly HCHO varied from 3.7 × 1015 molecules/cm2 to 7.7 × 1015 molecules/cm2. Monthly HCHO showed a strong seasonal pattern with annual peaks on March, July (small peak) and October, which well matched with the rainy seasons in Ethiopia and Kenya. Natural sources contributed 36% to the total HCHO in the study area. Grassland and savannas showed high column densities in the long rainy season starting from March, with the monthly average emission value of 5.6 × 1015 molecules/cm2. Multiple regression result showed that vegetation contributed 3.5 × 1013 molecules/cm2 to monthly HCHO, with grassland and forest in eastern Kenya and the boundary of Ethiopia and Kenya were the main contributors in these regions. Biomass burning and methane contributed to HCHO emission in the western and northern Ethiopia with a magnitude of 1.4 × 1014 molecules/cm2 and 6.2 × 1016 molecules/cm2 per month, respectively. Economic activities showed negative response to HCHO columns, except over the two small-scale regions of Addis Ababa City and Nairobi City. This study quantified the HCHO from various sources and suggested that natural sources produce more HCHO than anthropogenic sources over Ethiopia and Kenya.

Primary and secondary sources of ambient formaldehyde in the Yangtze River Delta based on Ozone Mapping and Profiler Suite (OMPS) observations

Abstract. Formaldehyde (HCHO) in the ambient air not only causes cancer but is also an ideal indicator of volatile organic compounds (VOCs), which are major precursors of ozone (O3) and secondary organic aerosol (SOA) near the surface. It is meaningful to differentiate between the direct emission and the secondary formation of HCHO for HCHO pollution control and sensitivity studies of O3 production. However, understanding of the sources of HCHO is still poor in China, due to the scarcity of field measurements (both spatially and temporally). In this study, tropospheric HCHO vertical column densities (VCDs) in the Yangtze River Delta (YRD), East China, where HCHO pollution is serious, were retrieved from the Ozone Mapping and Profiler Suite (OMPS) onboard the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite from 2014 to 2017; these retrievals showed good agreement with the tropospheric HCHO columns measured using ground-based high-resolution Fourier transform infrared spectrometry (FTS) with a correlation coefficient (R) of 0.78. Based on these results, the cancer risk was estimated both nationwide and in the YRD region. It was calculated that at least 7840 people in the YRD region would develop cancer in their lives due to outdoor HCHO exposure, which comprised 23.4 % of total national cancer risk. Furthermore, the contributions of primary and secondary sources were apportioned, in addition to primary and secondary tracers from surface observations. Overall, the HCHO from secondary formation contributed most to ambient HCHO and can be regarded as the indicator of VOC reactivity in Hangzhou and in urban areas of Nanjing and Shanghai from 2015 to 2017, due to the strong correlation between total HCHO and secondary HCHO. At industrial sites in Nanjing, primary emissions more strongly influenced ambient HCHO concentrations in 2015 and showed an obvious decreasing trend. Seasonally, HCHO from secondary formation reached a maximum in summer and a minimum in winter. In the spring, summer, and autumn, secondary formation had a significant effect on the variation of ambient HCHO in urban regions of Nanjing, Hangzhou, and Shanghai, whereas in the winter the contribution from secondary formation became less significant. A more thorough understanding of the variation of the primary and secondary contributions of ambient HCHO is needed to develop a better knowledge regarding the role of HCHO in atmospheric chemistry and to formulate effective control measures to decrease HCHO pollution and the associated cancer risk.

Sources of formaldehyde and their contributions to photochemical O3 formation at an urban site in the Pearl River Delta, southern China

Two models (the Positive Matrix Factorization (PMF) model and a photochemical box model with Master Chemical Mechanism (PBM-MCM)) were applied to analyze the formaldehyde (HCHO) data collected in July 2006 at an urban site (GPEMC) in the Pearl River Delta (PRD), southern China. Three major HCHO sources (secondary formation, vehicular exhaust, and solvent usage) were identified and they were found to contribute in average 53%, 31% and 16% respectively to the total HCHO loading at GPEMC. Alkenes was the most important group contributing to the secondary formation of HCHO, followed by aromatics and alkanes. Among them, trans-2-butene had the largest contribution to secondary HCHO formation, with the average percentage of 16 ± 4%, followed by i-butene, cis-2-butene, propene, isoprene and m,p-xylene. Secondary HCHO and HCHO emitted from vehicular emissions contributed comparably to ground-based measured O3 and HOx radical at GPEMC, higher than that from solvent usage (1.3 ± 0.1 ppbv and (4.1 ± 0.3) × 106 molecule/cm3 for O3 and HOx radical). Our results highlight the importance of secondary HCHO formation for both photochemical formation of ozone and the oxidative capacity of the atmosphere in this region. It is hence critical for policy makers to propose strategies for controlling VOCs from vehicular emissions in order to reduce secondary HCHO formation. Our results also have important implication for improving the understanding of the source apportionments of HCHO and their contributions to photochemical pollution in the PRD region in China.

Impact of pollution controls in Beijing on atmospheric oxygenated volatile organic compounds (OVOCs) during the 2008 Olympic Games: observation and modeling implications

Abstract. Oxygenated volatile organic compounds (OVOCs) are important products of the photo-oxidation of hydrocarbons. They influence the oxidizing capacity and the ozone-forming potential of the atmosphere. In the summer of 2008, 2 months of emission restrictions were enforced in Beijing to improve air quality during the Olympic Games. Observational evidence reported in related studies that these control measures were efficient in reducing the concentrations of primary anthropogenic pollutants (CO, NOx and non-methane hydrocarbons, i.e., NMHCs) by 30–40%. In this study, the influence of the emission restrictions on ambient levels of OVOCs was explored using a neural network analysis with consideration of meteorological conditions. Statistically significant reductions in formaldehyde (HCHO), acetaldehyde (CH3CHO), methyl ethyl ketone (MEK) and methanol were found to be 12.9, 15.8, 17.1 and 19.6%, respectively, when the restrictions were in place. The effect of emission controls on acetone was not detected in neural network simulations, probably due to pollution transport from surrounding areas outside Beijing. Although the ambient levels of most NMHCs were reduced by ~35% during the full control period, the emission ratios of reactive alkenes and aromatics closely related to automobile sources did not present much difference (< 30%). A zero-dimensional box model based on the Master Chemical Mechanism version 3.2 (MCM3.2) was applied to evaluate how OVOC production responds to the reduced precursors during the emissions control period. On average, secondary HCHO was produced from the oxidation of anthropogenic alkenes (54%), isoprene (30%) and aromatics (15%). The importance of biogenic sources for the total HCHO formation was almost on par with that of anthropogenic alkenes during the daytime. Anthropogenic alkenes and alkanes dominated the photochemical production of other OVOCs such as acetaldehyde, acetone and MEK. The relative changes of modeled HCHO, CH3CHO, methyl vinyl ketone and methacrolein (MVK + MACR) before and during the pollution controlled period were comparable to the estimated reductions in the neural network, reflecting that current mechanisms can largely explain secondary production of those species under urban conditions. However, it is worth noting that the box model overestimated the measured concentrations of aldehydes by a factor of 1.4–1.7 without consideration of loss of aldehydes on aerosols, and simulated MEK was in good agreement with the measurements when primary sources were taken into consideration. These results suggest that the understanding of the OVOCs budget in the box model remains incomplete, and that there is still considerable uncertainty in particular missing sinks (unknown chemical and physical processes) for aldehydes and absence of direct emissions for ketones.

Formaldehyde content of atmospheric aerosol.

Formaldehyde (HCHO) is a highly soluble polar molecule with a large sticking coefficient and thus likely exists in both gaseous and particulate forms. Few studies, however, address particulate HCHO (HCHO(p)). Some report that HCHO(p) concentrations (obtained only with long duration sampling) are very low. The lack of data partly reflects the difficulty of specifically measuring HCHO(p). Long duration filter sampling may not produce meaningful results for a variety of reasons. In this work, gaseous HCHO (HCHO(g)) and (HCHO(p)) were, respectively, collected with a parallel plate wet denuder (PPWD) followed by a mist chamber/hydrophilic filter particle collector (PC). The PPWD quantitatively removed HCHO(g) and the PC then collected the transmitted aerosol. The collected HCHO from either device was alternately analyzed by Hantzsch reaction-based continuous flow fluorometry. Each gas and particle phase measurement took 5 min each, with a 10 min cycle. The limits of detection were 0.048 and 0.0033 μg m(-3), respectively, for HCHO(g) and HCHO(p). The instrument was deployed in three separate campaigns in a forest station in western Japan in March, May, and July of 2013. Based on 1296 data pairs, HCHO(p), was on the average, 5% of the total HCHO. Strong diurnal patterns were observed, with the HCHO(p) fraction peaking in the morning. The relative humidity dependence of the partition strongly suggests that it is driven by the liquid water content of the aerosol phase. However, HCHO(p) was 100× greater than that expected from Henry's law. We propose that the low water activity in the highly saline droplets lead to HCHO oligomerization.

Source apportionment of formaldehyde during TexAQS 2006 using a source‐oriented chemical transport model

In this study, a source‐oriented version of the Community Multiscale Air Quality (CMAQ) model was developed and used to quantify the contributions of five major local emission source types in Southeast Texas (vehicles, industry, natural gas combustion, wildfires, biogenic sources), as well as upwind sources, to regional primary and secondary formaldehyde (HCHO) concentrations. Predicted HCHO concentrations agree well with observations at two urban sites (the Moody Tower [MT] site at the University of Houston and the Haden Road #3 [HRM‐3] site operated by Texas Commission on Environmental Quality). However, the model underestimates concentrations at an industrial site (Lynchburg Ferry). Throughout most of Southeast Texas, primary HCHO accounts for approximately 20–30% of total HCHO, while the remaining portion is due to secondary HCHO (30–50%) and upwind sources (20–50%). Biogenic sources, natural gas combustion, and vehicles are important sources of primary HCHO in the urban Houston area, respectively, accounting for 10–20%, 10–30%, and 20–60% of total primary HCHO. Biogenic sources, industry, and vehicles are the top three sources of secondary HCHO, respectively, accounting for 30–50%, 10–30%, and 5–15% of overall secondary HCHO. It was also found that over 70% of PAN in the Houston area is due to upwind sources, and only 30% is formed locally. The model‐predicted source contributions to HCHO at the MT generally agree with source apportionment results obtained from the Positive Matrix Factorization (PMF) technique.

Estimating primary and secondary production of HCHO in eastern North America based on gas phase measurements and principal component analysis

Based on atmospheric measurements of multiple species at Egbert, a rural site in Ontario, Canada, during summer 1988, the emission ratios of HCHO/CO and HCHO/ΣNOy for area sources and secondary production of HCHO have been estimated using a modified principal component analysis technique. The technique yields three principal components that represent a photochemically aged air mass, a diurnal cycle, and fresh area emissions. The area emission component has an emission ratio CO/ΣNOy = 9±3 and SO2/CO = 0.005±0.003, in agreement with NAPAP area emission data for the eastern US [Buhr et al., 1992]. The emission ratios of HCHO/CO and HCHO/ΣNOy in this component are 0.0056±0.0022 and 0.05±0.007, respectively. If these ratios are typical of eastern North American area emissions, the total primary HCHO emission for this region will be 8×109 moles HCHO annually based on the NAPAP CO emission inventories. Evidence of secondary HCHO production can be found in the photochemically aged component which has considerably higher HCHO/CO (0.016±0.004) and HCHO/ΣNOy (0.29±0.03) ratios than the emission ratios. It is estimated that for every 1 ppb NOx converted to NOy, 0.4 ppb HCHO are produced for the ratio (1−NOx/NOy)<0.6; after which the relative HCHO production rate becomes smaller. Using this relative rate, the maximum total HCHO production over the eastern North America is estimated to be 1.3×1011 moles year−1, or approximately 16 times that from primary emission.

Chemistry of carbonyl compounds in Po Valley fog water

The importance of carbonyl compounds in Po Valley fog water chemistry is discussed. High concentrations of formaldehyde (HCHO) were detected in fog water (from 16 to 567 μM; average, 130 μM). The oxidant-limiting conditions during the fog season (fall-winter months) favour the presence of a large fraction of HCHO in the form of adducts with hydroxymethansulfonate: 85% of the total HCHO on average. Other carbonyl compounds were detected in the fog water: acetaldehyde, acrolein and acetone, but typically in much lower concentrations than formaldehyde. These other carbonyl compounds do not appear to be present in a bound form.

The use of temperature to simplify formose sugar composition

Form ose reaction, the Ca(OH)2 catalyzed condensation of HCHO to a complex mixture of sugars, does not lose its autocatalytic nature at 98°C. The induction period is 15 sec, and then, at 18% total HCHO conversion, there was a period of approximately 3 sec duration in which the reaction had produced C6 sugars at 84.3 wt.% selectivity. Glucose amounted to 90% of those sugars, and no branched sugars were detected. Conversion was complete within 3 min. The simple nature of the product was lost at lower temperatures or higher conversions.

Hygienic Study on Packaging and Vessel Made of Synthetic Resin (III)

The soluble components transferect from urea resin tablewares used for long period, were discussed in the previous paper.In this paper, the methods of separation and determination of free formaldehyde were studied by liquid chromatography with thermal detector, for a basic study on the toxicity of formaldehyde.The thermal detector was unsatisfactory for determination of formaldehyde in low concentration, because of poor sensitivity. Therefore, the determination were made on the combined use to liquid chromatography and colorimetry with acetylacetone.The chromatographic conditions used were as follows:Apparatus JLC A Type (Nihon Denshi)Fixed phase Dowex 50W-X8Eluent 0.1N HClFlow rate of eluent 0.6ml/minColumn: for separation 0.8×50cm (room temp.)for detection 0.8×8cm (35°C)Sensitivity ±1/100°C or 3/1000°C cfsChart speed 60mm/hrMain results of experiments are summarized as follows:(1) The recovery of free formaldehyde (Cf) was 90-100% in the case of addition of formaldehyde.(2) Total formaldehyde (Ct) was determined after steam distillation and combined form formaldehyde (Cc) was calculated from the following formula.Combined HCHO(Cc)ppm=Total HCHO(Ct)-Free HCHO(Cf)(3) Free formaldehyde was determined about 1-87ppm on 12 samples of urea and melamine resin tablewares, and combined formaldehyde was about 0-31ppm.