The uncertainty in emission estimation is strongly associated with the variation in emission factor （EF）,which could be influenced by a variety of factors such as fuel properties,stove type,fire management and even methods used in measurements.The impacts of these factors are complicated and often interact with each other.Controlled burning experiments were conducted to investigate the influences of fuel mass load,air supply and burning rate on the emissions and size distributions of carbonaceous particulate matter （PM） from indoor corn straw burning in a cooking stove.The results showed that the EFs of PM （EFPM）,organic carbon （EFOC） and elemental carbon （EFEC） were independent of the fuel mass load.The differences among them under different burning rates or air supply amounts were also found to be insignificant （p 〉 0.05） in the tested circumstances.PM from the indoor corn straw burning was dominated by fine PM with diameter less than 2.1 μm,contributing 86.4%±3.9% of the total.The size distribution of PM was influenced by the burning rate and air supply conditions.On average,EF PM,EF OC and EF EC for corn straw burned in a residential cooking stove were （3.84±1.02）,（0.846±0.895） and （0.391±0.350） g/kg,respectively.EF PM,EF OC and EF EC were found to be positively correlated with each other （p 〈 0.05）,but they were not significantly correlated with the EF of co-emitted CO,suggesting that special attention should be paid to the use of CO as a surrogate for other incomplete combustion pollutants.
Emission factors （EFs） of parent polycyclic aromatic hydrocarbons （pPAHs）, nitrated PAHs （nPAHs）, and oxygenated PAHs （oPAHs） were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were （7.9 ±3.4）, （6.5 ±1.6）×10^-3, and （6.1 ±1.4）×10^-1mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations.
Household air pollution is considered to be among the top environmental risks in China.To examine the performance of improved stoves for reduction of indoor particulate matter（PM） emission and exposure in rural households, individual inhalation exposure to size-resolved PM was investigated using personal portable samplers carried by residents using wood gasifier stoves or improved coal stoves in a rural county in Central China.Concentrations of PM with different sizes in stationary indoor and outdoor air were also monitored at paired sites. The stationary concentrations of size-resolved PM in indoor air were greater than those in outdoor air, especially finer particles PM0.25. The daily averaged exposure concentrations of PM0.25, PM1.0, PM2.5 and total suspended particle for all the surveyed residents were 74.4 ± 41.1, 159.3 ± 74.3, 176.7 ± 78.1 and 217.9 ± 78.1 μg/m3,respectively. Even using the improved stoves, the individual exposure to indoor PM far exceeded the air quality guideline by WHO at 25 μg/m3. Submicron particles PM1.0 were the dominant PM fraction for personal exposure and indoor and outdoor air. Personal exposure exhibited a closer correlation with indoor PM concentrations than that for outdoor concentrations. Both inhalation exposure and indoor air PM concentrations in the rural households with gasifier firewood stoves were evidently lower than the reported results using traditional firewood stoves. However, local governments in the studied rural areas should exercise caution when widely and hastily promoting gasifier firewood stoves in place of improved coal stoves, due to the higher PM levels in indoor and outdoor air and personal inhaled exposure.
Epidemiological studies have demonstrated the exacerbation of respiratory diseases following sandstorm-derived particulate matter（PM） exposure.The presence of anthropogenic and biological agents on the sandstorm PM and the escalation of PM 〈 2.5 μm（PM2.5）pollution in China have led to serious concerns regarding the health effects of PM2.5during Asian sandstorms.We investigated how changes in PM2.5composition,as the weather transitioned towards a sandstorm,affected human airway epithelial cells.Six PM2.5samples covering two sandstorm events and their respective background and transition periods were collected in Baotou,an industrial city near the Gobi Desert in China.PM samples from all three periods had mild cytotoxicity in human bronchial epithelial cell line BEAS-2B,which was positively correlated with the contents of polycyclic aromatic hydrocarbons and several metals.All PM samples potently increased the release of interleukin-6（IL-6） and interleukin-8（IL-8）.Endotoxin in all samples contributed significantly to the IL-6 response,with only a minor effect on IL-8.Cr was positively correlated with both IL-6 and IL-8 release,while Si was only associated with the increase of IL-6.Our study suggests that local agricultural and industrial surroundings in addition to the sandstorm play important roles in the respiratory effects of sandstorm-derived PM.
Controlled combustion experiments were conducted to investigate the influence of fuel charge size, moisture, air ventilation and feeding rate on the emission factors （EFs） of carbonaceous particulate matter, parent polycyclic aromatic hydrocarbons （pPAHs） and their derivatives from residential wood combustion in a typical brick cooking stove. Measured EFs were found to be independent of fuel charge size, but increased with increasing fuel moisture. Pollution emissions from the normal burning under an adequate air supply condition were the lowest for most pollutants, while more pollutants were emitted when an oxygen deficient atmosphere was formed in the stove chamber during fast burning. The impacts of these factors on the size distribution of emitted particles was also studied. Modified combustion efficiency and the four investigated factors explained 68%, 72%, and 64% of total variations in EFs of PM, organic carbon, and oxygenated PAHs, respectively, but only 36%, 38% and 42% of the total variations in EFs of elemental carbon, pPAHs and nitro-PAHs, respectively.
Guofeng ShenMiao XueSiye WeiYuanchen ChenQiuyue ZhaoBing LiHaisuo WuShu Tao
