Diffusion Characteristics Of Indoor PM2.5 And Health Risk Assessment Of Rural Dwellings In Liaoning Province In Winter

In recent years,with the implementation of the rural revitalization strategy in China,the indoor environmental quality in rural areas has been concerned widely.Winter in Liaoning province of China is cold and long,and the heating period lasts for 150 days.The pollutants generated during cooking and heating processes,that are restricted by economic conditions,living habits,building structure and other factors,cannot be eliminated,or captured effectively in time.PM10 and PM2.5 are diffused into other functional rooms via doors and windows quickly,endangering residents’health directly.However,there are many studies on the influence of different stove structures,fuel forms,and heating methods on the indoor pollution degree of farm houses,lack of theoretical research and in-depth analysis on the changing rule and diffusion characteristics of indoor PM2.5 concentration.In addition,in the process of indoor PM2.5 diffusion in farm houses,there is a lack of exposure dose and health risk assessment for different age groups.Therefore,in order to clarify the indoor PM2.5 diffusion characteristics and residents’health risks of rural dwellings in Liaoning province,the main contents and results are as follows:Firstly,in order to clarify the PM2.5 changing rule of rural dwellings in Liaoning,the basic building information,space layout,heating method,fuel type,smoke exhaust method,daily behavior and work and rest time of 210 rural dwellings were counted in Liaoning Shenyang,Fushun,Yingkou,etc.by questionnaires and field surveys.The results showed that61.4%of the dwellings had an area of 60-100m~2,the dwellings were mainly three-bay and four-bay,the heating method were mainly kang and heating radiators.,and wood,straw and scattered coal were the main fuels.The three representative households were selected to conduct in-depth measurement and experimental research on the changing rule of PM2.5concentration in Liaoning.The results showed that the concentration of PM2.5 produced by cooking and heating in daily life was the highest,with a peak value of 1700μg/m~3,followed by smoking and cleaning.Due to the different pollution source intensities and diffusion paths of indoor PM2.5,the concentration of PM2.5 in each room during the cooking and heating stage is2-3 times higher than the standard.And with the gradual increase of PM2.5 concentration,the peak time lags behind the kitchen peak by 10-20min.At the same time,the concentration changes law of PM1,PM2.5,and PM10 was obtained.The factors affecting the indoor PM2.5concentration were clearly including the residents’daily behavior,indoor and outdoor PM2.5pollution sources,PM2.5 deposition characteristics,indoor airflows,indoor air temperature and relative humidity.Secondly,the multi-zone network model describing the characteristics and diffusion rules of PM2.5 in rural dwelling of Liaoning was established.The calculation results showed that the relative error is within±10%by theoretical calculation and experimental measurement.PM2.5diffusion in a rural dwelling could be predicted.Furthermore,the impacts of day life behavior on PM2.5 changing rule could be analyzed.Through experiments and simulation calculations,it was found that during the heating process,when the peak concentration of PM2.5 in the kitchen is 1559μg/m~3,the average diffusion rate to each room is 10.1μg/(m~3·min)-17.7μg/(m~3·min).During the cooking process,the peak concentration of PM2.5 in the kitchen was1059μg/m~3,and the average diffusion rate to each room at this time was 3.5μg/(m~3·min)-6.9μg/(m~3·min).Through comparative analysis,when the PM2.5 concentration of pollution source was decreased by 500μg/m~3,the diffusion rate from the source to each room could decrease by3 times.When cooking and heating are carried out together,the indoor PM2.5 concentration is about 1.5 times that of heating alone,and 2.0 times that of cooking alone.And the number of fuels,type of fuels,cooking methods and other energy consumption methods would have an impact on the indoor PM2.5 diffusion.In addition,the door opening behavior,the airtightness of the envelope structure and the layout of the building space could lead to different interzonal airflows and PM2.5 diffusion rates.Through simulation calculation and analysis,reducing the inner door opening time to less than 1min,PM2.5 could decrease to 300μg/m~3.Door closing behavior could decrease risk that PM2.5 diffuses to bedrooms by more than 50%.At the same time,the interzonal airflows were calculated via CONTAMW.The impact of the airtight structure and the spatial layout on PM2.5 diffusion process was discussed.Appropriate airtight structure and spatial layout form were proposed.Finally,the behavior activity characteristics of different age groups were clarified and the PM2.5 exposure levels of residents were obtained through the method of field test and tracking record of rural dwellings in Liaoning Province.The results showed that most of the farmers lived in 2-5 people,of which more than 40%were elderly people aged 60-79.86%of the time was spent indoors,and 71%of the activity time was in the bedroom.During the heating period,the highest comprehensive exposure and comprehensive potential dose of residents were 6419.1μg·h/m~3and 2270.9μg,respectively.By establishing an indoor PM2.5exposure model,the PM2.5 exposure levels of residents under different pollution source intensities,door opening times and spatial layouts were calculated.Based on the rural population in Liaoning in 2020,the health risks and economic losses of rural residents were assessed.The results showed that the PM2.5 generated by the indoor solid fuel combustion in rural houses had the greatest public health risk to internal medicine,about 44.1%.Among them,the patients with acute bronchitis were the most,about 948,000;the number of premature deaths was about 28,358.Among the corresponding additional health expenditures for illness,chronic bronchitis caused the largest economic loss,about 579 million yuan.Finally,the indoor pollution sources ventilation and smoke mode were analyzed by literature review and theoretical research during heating period.The wind pressure of the induced draft fan and the smoke exhaust volume of the range hood were determined respectively when the indoor air quality of the farm house meets the specification requirements,and a technical measure that could effectively solve the dual problems of exhausting oil fume and preventing the backflow of the flue gas in the stove was proposed.