Simultaneous influence of light and CO2 on phytoremediation performance and physiological response of plants to formaldehyde.

Phytoremediation technology is an effective method to remove formaldehyde indoors, but the purification capacity and physiological response of plants to formaldehyde under the simultaneous influence of light and CO2 have not been examined in previous studies. In this study, formaldehyde fumigation experiments were conducted on the C3 plants Epipremnum aureum A. and Chlorophytum comosum L., and the crassulacean acid metabolism (CAM) plant Dieffenbachia maculate A. The phytoremediation performance and physiological response of plants were studied. The initial concentration of formaldehyde was established at 11.950 ± 1.442 [Formula: see text]; the light intensities were 448 ± 7 [Formula: see text], 1628 ± 22 [Formula: see text], and 3259 ± 22 [Formula: see text], respectively; and the concentrations of CO2 were 455 ± 29 [Formula: see text], 978 ± 50 [Formula: see text], 2020 ± 66 [Formula: see text], and 3006 ± 95 [Formula: see text], respectively. The results indicated that the highest purification rates of formaldehyde by E. aureum, D. maculata, and C. comosum were 55.8%, 43.7%, and 53.2%, respectively. The light intensity had a positive effect on the formaldehyde purification rates of all three plants and positively stimulated peroxidase (POD) activity, while the CO2 concentration had no significant impact on the formaldehyde purification capacity and plants' physiological characteristics. Exposure to formaldehyde inhibited formaldehyde dehydrogenase (FADH) activity and positively stimulated catalase (CAT) activity. The superoxide dismutase (SOD) activity positively correlated with the formaldehyde purification capacity of plants.

Measurement of Personal Experienced Temperature Variations in Rural Households Using Wearable Monitors: A Pilot Study.

The time-varying data of air temperatures experienced by people in their daily lives is an important basis for studying human thermal sensation, adaptation, comfort, and health. It is also very important for designing targeted strategies to help people reduce uncomfortable experience. In this study, a small (98 mm × 49 mm × 25 mm), lightweight (~100 g), and portable temperature logger with a wide measurement range (-40 to 100 °C) and appropriate accuracy (±0.3 °C precision) was combined with a phone holder that was adapted as an armband sleeve to constitute a wearable monitor. Fourteen monitors were worn by 14 residents in 6 different households in rural Beijing, China, to monitor their personal thermal environment. In the context of having very similar living habits in winter and coping strategies for thermal discomfort, the temperatures that 14 residents experienced exhibited wide ranges and large variations during the two-day test period. The highest and lowest temperatures experienced by residents reached 30.6 and -16.6 °C, respectively. This paper provided new data and evidences about various temperatures experienced by residents, even though they were from the same family and lived together for decades. In terms of methodology, as an exploration, the present study indicated that using personal wearable monitors is a viable method to capture the real experienced thermal environment, which extended the method for collecting data regarding complex experiences in different environments to aid the study of human responses to the real-world thermal environment.

Air pollutant emission factors of solid fuel stoves and estimated emission amounts in rural Beijing.

Solid fuels used for heating and cooking in rural households cause a large amount of pollutant emissions. Actions are being taken to replace these solid fuels with cleaner energy carriers. However, the pollutant emission amounts from solid fuels over large areas have rarely been evaluated. In this study, we tested eight common heating stoves consuming bituminous coal chunk, anthracite coal chunk, and anthracite coal briquette; three honeycomb briquette stoves; and three traditional cookstoves consuming corn straw and wood in rural Beijing. Emission factors of particulate matter with aerodynamic diameters ≤2.5 µm (PM2.5), carbon monoxide (CO), nitrogen oxide (NOx), and sulfur dioxide (SO2), were measured as 0.08-13.74 g/kg, 10.80-148.5 g/kg, 0.52-8.44 g/kg, and 0-0.85 g/kg, respectively, for coal heating stoves; 0.35-1.11 g/kg, 16.10-109.43 g/kg, 0.51-0.75 g/kg, and 0-1.98 g/kg, respectively, for honeycomb briquette cookstoves; and 5.90-11.79 g/kg, 28.96-50.23 g/kg, 1.52-2.46 g/kg, and 0-0.05 g/kg, respectively, for traditional biomass cookstoves. Combining emission performance and solid fuel consumption, the estimated annual PM2.5, CO, NOx, and SO2 emission amounts were 26.18 Gg, 394.07 Gg, 14.56 Gg, and 1.53 Gg, respectively. The results present useful information regarding the emission inventory of common solid fuels in rural Beijing on a city-scale. This study provides an example for future intervention projects and environment evaluation in the rural areas of other cities.

Optimizing supply airflow and its distribution between primary and secondary air in a forced-draft biomass pellet stove.

Forced-draft biomass stoves improve the pollutant emission performance of biomass combustion. The parameters of supply airflow and its distribution between primary air (PA) and secondary air (SA) have a significant effect on the performance of this stove type. In this study, we designed an air supply control system to accurately quantify the airflow rates, and monitored the dynamic emissions of focused pollutant species including carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM2.5), and the fuel burning rate. The tested stove had a combustion structure typical of many popular stoves, and wood pellets were the burning fuel. Three total airflow rates (92 L/min, 184 L/min, and 276 L/min) were selected, and six distributions between PA and SA (PA:SA) for each airflow rate were tested, which included 10:0 (full PA), 8:2, 6:4, 5:5, 4:6, and 2:8. The results showed that the test duration, burning rate, and pollutant (CO, NOx, and PM2.5) emission performances of different airflows or distributions varied. Overall, when the PA and SA distribution mode was determined, the total airflow rate of 184 L/min was the optimal supply airflow rate. Under the same total airflow rate, the burning and emission performances were better when the primary and secondary airflows were similar, namely from 4:6 to 6:4. This study provided core information about stove air supply and distribution, which is essential to quantitatively determine the stove air supply mode to significantly improve stove performances.

Characterizing dynamic relationships between burning rate and pollutant emission rates in a forced-draft gasifier stove consuming biomass pellet fuels.

Biomass is a dominant solid fuel type worldwide. Traditional biomass combustion leads to severe indoor and ambient environmental problems. Biomass pellet utilization in forced-draft gasifier stoves is regarded as an improved approach to these problems. Previous studies on forced-draft biomass stoves mainly considered average emission amounts and lacked details of the combustion properties and dynamic correlations between emissions and combustion. This study used a dynamic measurement system to test a typical forced-draft gasifier stove consuming wood pellets and maize straw pellets. Real-time fuel burning rate, that partly reflects the combustion performance, and CO, NOx and PM2.5 emission rates, over a whole combustion course, were monitored. In all tests, the burning rate rose to a high and stable level, and then sharply subsided. CO, NOx and PM2.5 emission rates varied across the combustion course. CO (NOx) emissions have a negative (positive) logarithmic linear relationship with burning rate, while no consistent relationship was observed for PM2.5 emission rate. The identified relationships between burning rate and pollutant emission rates suggest the possibility of estimating emission performance of forced-draft biomass pellet stoves based on combustion indicators, or vice versa.

Differences in chemical composition of PM2.5 emissions from traditional versus advanced combustion (semi-gasifier) solid fuel stoves.

A common strategy to improve indoor air quality in households burning coal and biomass is the introduction of advanced combustion solid fuel stoves, which can use existing fuels yet emit fewer pollutants. Chemical composition of PM is affected by numerous combustion parameters, but is often not considered in energy transitions, despite varying toxicity among chemical components. We analyzed PM2.5 emissions from combustion of solid fuels (coal, wood, and straw; whole and pelletized) in a variety of stoves (cookstoves and heating stoves; traditional and semi-gasifier, including forced versus natural draft and fixed versus reciprocating grate). To assess the effects of fuel and stove type on PM2.5 composition, we measured elemental carbon (EC), organic carbon (OC), water-soluble OC, water-soluble inorganic ions (e.g. SO42-, Cl-, K+), and organic molecular markers. PM2.5 emissions from traditional stoves were mostly carbonaceous: 76-90% organic matter (OM), 5-6% EC, and less than 2% inorganic ions. In contrast, semi-gasifier stoves emitted more inorganic PM2.5: on average, ions comprised 65%, 9% was OM, and 4% was EC. Within the semi-gasifier cookstoves, forced-draft cookstove emissions had lower OM (1-3%) and higher ion concentrations (84-88%) than the natural-draft cookstove (5-14% OM, 30-83% ions). Levoglucosan was detected in PM2.5 from combustion of wood in the traditional cookstove and biomass pellets in the natural-draft semi-gasifier cookstove, but not from wood pellets in the forced-draft semi-gasifier cookstove. Across a range of different fuels and stoves, stove type influenced emitted PM composition more than fuel type, underscoring the impact of combustion conditions on PM chemical composition.

Real-time combustion rate of wood charcoal in the heating fire basin: Direct measurement and its correlation to CO emissions.

Previous studies of solid fuel emissions in household stoves focused more on emission measurements of the overall combustion process instead of the dynamic burning rate and its connection to the emissions. This study put forward a measurement system to monitor the dynamic fuel burning rate and emission rate directly, and explored their relationships during different combustion phases. Experiments were conducted using two types of wood charcoal consumed in a small open pan (i.e. fire basin) used commonly for space heating in rural China. The measured real-time CO emission rate (ERCO), fuel burning rate (BRF), and calculated carbon burning rate (BRC) all rose and then subsided as the combustion progressed. The relationships between ERCO and BRF and between ERCO and BRC were different for the two charcoals during a phase with rising carbon content in the combusted fuel (Phase I), likely because moisture evaporation and volatile matter release were the dominant processes and the reaction was complex during this phase. ERCO and BRF or BRC had linear relationships during a phase with stable carbon content in the combusted fuel (Phase II) for the two charcoals, which may be generalized to other solid fuels, because this phase is associated to fixed carbon dominating phase which usually exist during solid fuel combustion. The study presented a novel measurement approach to the combustion properties of solid fuels. The results implied that a complex relationship between the combustion and pollutant emissions existed in Phase I, and presented the possibility of estimating the fuel burning rate based on emission measurements in Phase II, or vice versa.

The impact of cookstove operation on PM2.5 and CO emissions: A comparison of laboratory and field measurements.

Inefficient biomass combustion in traditional cookstoves generates high levels of household air pollution (HAP) that is associated with numerous adverse environmental and human health conditions. Many cookstoves have been evaluated using laboratory tests, but past studies revealed discrepancies between laboratory and field measurements. Fuel re-loading, a common operation in actual use but not required in the laboratory test, might be a contributing factor to this laboratory-field gap. In this study, we evaluated the pollutant emissions performance of a semi-gasifier cooking stove using both laboratory and field measurements. Emission factors and real-time properties of CO and PM2.5 were separately measured during the following 4 phases of a typical cooking event: lighting, stable combustion, fuel re-loading and post fuel re-loading. We quantified the CO and PM2.5 contributions to total cooking event emissions in each phase. We found over 70% lower PM2.5 emissions and 60% lower CO emissions during 3 no re-loading laboratory tests compared with all 16 field tests. Lighting generated 83.8% ±â€¯15.6% of the total PM2.5 and 39.1% ±â€¯7.8% of the total CO in laboratory tests without fuel re-loading, and 57.8% ±â€¯33.5% and 37.9% ±â€¯21.2% of the total PM2.5 and CO in field tests, respectively. On average, fuel re-loading led to 29.1% ±â€¯30.8% of PM2.5 emissions and 24.9% ±â€¯22.6% of CO emissions in 16 field tests, which also contributed to significant discrepancies between laboratory and field-based emissions. According to the ISO IWA tiered stove ratings for emissions, fuel re-loading led to at least one tier lower ranking in both laboratory and field cookstove tests. Fuel re-loading could be an important factor causing laboratory-field discrepancy of emissions, thus it could be considered in future cookstove selection and intervention projects.

Cytotoxicity analysis of indoor air pollution from biomass combustion in human keratinocytes on a multilayered dynamic cell culture platform.

Skin tissue is the first barrier against ambient harmful matter and has direct contact with indoor air pollutants. Nevertheless, a comprehensive understanding of cytotoxicity of indoor air pollution on skin cells is insufficiently clear. Herein, for the first time a multilayered dynamic cell culture platform was established to study the cytotoxicity of indoor air pollutant from biomass combustion in human skin keratinocytes. The platform consisted of seven repetitive polydimethylsiloxane modules carrying six pieces of polycarbonate membrane between them as substrate for cell growth to realize the simultaneous dynamic culture of 12 layers of keratinocytes. After exposure to biomass combustion soluble constituents (BCSCs), cell viability under microfluidic platform conditions declined more significantly, and apoptosis rates increased more obviously compared with well plate conditions. Transmission electron microscope showed that keratinocyte microstructures displayed obvious signs of cellular damage. Our study confirmed that the nuclear factor of kappa B (NF-κB) signaling pathway was activated, which significantly increased the Bax/Bcl-2 ratio and tumor necrosis factor-alpha and interleukin 6 expression, indicating that NF-κB signaling pathway was the major factor in BCSCs-induced cytotoxicity. These findings offer an insight into the mechanism of BCSCs-induced cytotoxicity in keratinocytes and provide a theoretical basis for future studies on skin cells.

A field experimental study on non-methane hydrocarbon (NMHC) emissions from a straw-returned maize cropping system.

Non-methane hydrocarbons (NMHCs) play an important role in the atmospheric environment. However, NMHC emissions from agricultural fields, especially their variations with straw return, are poorly understood. Therefore, a field study comprising two treatments, i.e., (1) S0 (straw removal) and (2) S1 (incorporation of maize straw at a rate of 9000 kg ha-1), was conducted in a straw-returned maize cropping system to characterize NMHC emissions as well as to estimate the effect of straw return on those emissions. Using a Gas Chromatography-Mass Spectrometer (GC-MS) method, 28 types of NMHCs were identified. The total NMHC emission from S0 was 2018 g ha-1, where 1-methyl-3-propyl-benzene, (1-methylethyl)-benzene, and toluene were obviously predominant, whereas the total NMHC emission from S1 was 1903 g ha-1, where 1-methyl-3-propyl-benzene, 2-methyl-pentane, and (1-methylethyl)-benzene were the main species. The results showed that straw return had opposing effects on NMHC emissions, ranging from -55.4% to 478.6%. Overall, the total NMHC emission with returned straw alone decreased by 2963 ng kg straw-1 h-1. Furthermore, NMHC fluxes had higher correlations with soil temperature than with soil moisture or pH. Notably, the higher correlations of NMHC fluxes with 10 cm soil temperature than with 5 cm soil temperature indicate that soil in the deeper layer might play a more important role in NMHC fluxes. The results also suggest that more field study is needed to accurately estimate the effect of straw return on NMHC emissions from agroecosystems and fully understand its underlying mechanism.

A user-centered, iterative engineering approach for advanced biomass cookstove design and development.

Unclean combustion of solid fuel for cooking and other household energy needs leads to severe household air pollution (HAP) and adverse health impacts in adults and children. Replacing traditional solid fuel stoves with high efficiency, low-polluting semi-gasifier stoves can potentially contribute to addressing this global problem. The success of semi-gasifier cookstove implementation initiatives depends not only on the technical performance and safety of the stove, but also the compatibility of the stove design with local cooking practices, the needs and preferences of stove users, and community economic structures. Many past stove design initiatives have failed to address one or more of these dimensions during the design process, resulting in failure of stoves to achieve long-term, exclusive use and market penetration. This study presents a user-centered, iterative engineering design approach to developing a semi-gasifier biomass cookstove for rural Chinese homes. Our approach places equal emphasis on stove performance and meeting the preferences of individuals most likely to adopt the clean stove technology. Five stove prototypes were iteratively developed following energy market and policy evaluation, laboratory and field evaluations of stove performance and user experience, and direct incorporation of stove user input. The most current stove prototype achieved high performance in the field on thermal efficiency (ISO Tier 3) and pollutant emissions (ISO Tier 4), and was received favorably by rural households in Sichuan province of Southwest China. Among household cooks receiving the final prototype of the intervention stove, 88% reported lighting and using it at least once. At five-months post-intervention, the semi-gasifier stoves were used at least once on an average of 68% [95% CI: 43, 93] of days. Our proposed design strategy can be applied to other stove development initiatives in China and other countries.