| Burning traditional domestic solid fuels can cause severe household air pollution(HAP)and endanger human health.Biomass pellets together with improved stoves are promoted as an alternative measure to ensure clean heating during winter in households.However,to date,only a few studies have reported on HAP caused by biomass clean heating and have tried to classify fugitive stove emissions as a direct source of HAP.To fill the data gap,this study evaluated the household air pollution levels of biomass pellet stoves and biomass pellets on the field.In the laboratory,the fugitive emission levels of different types of biomass pellet stoves and biomass pellet fuels at different combustion stages were analyzed,and the household air pollution level was estimated based on the fugitive emissions,and compared with the measured values.The average indoor PM2.5 concentration found in rural areas of A county was 280.50±162.00 μg/m3,and the average concentration of CO also was 1.66±2.36 mg/m3.The daily average concentration of indoor PM2.5 in all rural households exceeded the World Health Organization(WHO)AQG recommended value of 25 μg/m3.Only 5%of households recorded daily average CO concentration which exceeded the WHO indoor air quality guideline value of 7 mg/m3.For the stove feeding methods,neither gravity feeding nor power feeding has a significant impact on household air pollution.For the heating type,the indoor pollutant concentration of RHS is higher than that of WHS,with significant differences(PM2.5:p=0.03,<0.05;CO:p=0.04,<0.05).Compared with raw coal and traditional biomass,there is no significant difference in the indoor PM2.5 of biomass clean heating,but there is a significant difference in the indoor CO.The laboratory test compared fugitive emission factors(EFs)of particulate matter with aerodynamic size less than 2.5 microns(PM2.5)and carbon monoxide(CO)of the power-feeding radiant heating stove(stove a)and gravity-feeding radiant heating stove(stove b).Fugitive emission factors of PM2.5 and CO of stove a were 2.7±1.1 mg/kg and 0.56±0.32 g/kg,respectively,and the corresponding EFs from stove b were 2.5±0.9 mg/kg and 0.33±0.08 g/kg.Generally,there is no significant difference in the fugitive emission factors of the two types of stoves.There is a significant difference between the high and low power of stove a(PM2.5:p=0.02,<0.05;CO:p=0.004,<0.05),the EF of high power is lower than that of low power;but there is no significant difference between high and low power of stove b.The EFPM2.5 and EFCO of humu wood pellets,mixed-wood pellets,cotton steam stalk pellets and mixed pellets were also compared.While the EFPM2.5 were 2.7±1.1,2.2±0.6,7.7±3.3,and 11.7±6.4 mg/kg,respectively,the corresponding EFco were 0.56±0.32,0.22±0.07,0.56±0.24,and 0.72±0.49g/kg.The lowest and highest EF was found for mixed-wood pellets and mixed pellets respectively,but there is no significant difference in the EFs of the fuels.All fuels in this study recorded lower EFs in the high-power combustion stage than in the low-power combustion stage,and there are significant differences(PM2.5:p=0.004,<0.05;CO:p=0.01,<0.05).Particle size distribution analysis showed that fugitive particulate matter is composed mainly of ultrafine particulate matter(PM0.1),accounting for 90%.And it is mainly concentrated around 0.01 μm.This study used a Monte Carlo single-area model to illustrate the impact of fugitive emissions on HAP.The indoor PM2.5 concentration estimated from different stove-fuel combinations was 165±59 μg/m3,and that of indoor CO concentration was 14±1 mg/m3.Comparing the results from both the field test and simulation,it was found that though the simulated PM2.5 emission concentration was consistent with the test results.The simulated CO value was higher than the test results. |
