Study On Passive Sampling And Influencing Factors Of Indoor Airborne PAEs

Phthalic acid esters（PAEs）are a typical type of semi-volatile organic compounds.PAEs gradually escape from materials into the gaseous environment,and then distribute to the particulate phase,settled dust,and surface phase.The gaseous phase is an important medium for the migration of PAEs in indoor media and is closely related to human exposure.However,due to limitations in sampling technology,reports on indoor air pollution by PAEs are limited.Active samplers cannot be widely used in indoor environments,and obtaining accurate gas-phase concentrations through passive samplers depends on calibrating the sampling rate.Currently,most studies on passive samplers focus on outdoor environments.Therefore,designing and developing a passive sampler for collecting PAEs in indoor air is an important prerequisite for studying indoor air pollution by PAEs and human exposure.This study conducted experiments on passive sampling in a relatively controllable test room and designed passive samplers suitable for collecting air-phase or both gas-phase and particle-phase in indoor environments.Parallel deployment of active and passive samplers in the test room was carried out to obtain the pollution status of PAEs in indoor and outdoor air and explore their possible sources,as well as calculate the sampling rates of each passive sampler under different working conditions.Changes in environmental parameters during passive sampling were monitored and the physical properties of the adsorbent material were measured.A multiple linear regression model was established to determine the correlation between various influencing factors and sampling rates.The research results are summarized below:（1）A total of 14 PAEs were detected in the active samples obtained in this study.The detection rate of DMEP in indoor gaseous media was less than 40%,while DPP,DNHP,and DNP in the particulate phase were also less than 40%.The distribution characteristics of PAEs in outdoor air were similar,with Di BP,Dn BP,and DBEP being the most prevalent PAEs in gaseous media,particularly with Dn BP accounting for 48.8%-83.7%ofΣ₁₀PAEs.Dn BP and DBEP had the highest proportion in the particulate phase.The concentration of PAEs in outdoor air was lower than that indoors.The median gas-phase concentrations of DMP,DEP,Di BP,Dn BP,DEEP,and BBz P were higher than those in the particulate phase,ranging from1.56 to 11.17 times higher,while DBEP,DCHP,DEHP,and Dn OP were the opposite,ranging from 0.54 to 0.74 times the median particulate phase concentration.The Mann-Whitney U test results showed that the concentration ofΣ₁₀PAEs indoors in summer was significantly higher than that in autumn.（2）The positive matrix factorization（PMF）results showed that DMP,Di BP,and Dn BP in the gas-phase media and DMP and DEP in the particle-phase media may originate from adhesives used in various indoor materials.DBEP,DCHP,DEHP,and Dn OP in both gas-phase and particle-phase media may originate from building decoration materials,while BBz P in the gas-phase media may originate from plastic packaging and paint.（3）PUF-PAS,SIP-PAS,PTFE-PAS,and ACF-PAS all showed linear adsorption of air-phase PAEs within 35 days,with average sampling rates of 3.36m³/day,4.78m³/day,0.09m³/day,and 4.81m³/day,respectively.SIP-PAS had a higher sampling rate for volatile organic compounds,but the impregnation of XAD-2 resin powder increased the resistance of the sampler and its manufacturing process was cumbersome,potentially introducing pollution.Moreover,XAD resin may decrease during sampling,making it unsuitable for indoor sampling.PTFE film is unsuitable for manufacturing passive samplers due to its smooth surface.ACF-PAS showed superior performance in sampling rate,manufacturing,and pre-treatment,and can be widely used.（4）Increasing the geometric area of activated carbon fiber felt significantly increased the sampling rate of ACF-PAS.When the longitudinal area of activated carbon fiber felt doubled,the sampling rate increased by 1.07-3.49 times.Similarly,when the horizontal area doubled,the adsorption rate increased by 1.06-1.48 times.（5）The filter cartridge-type passive sampler can collect compounds in both the gas and particulate phases,but the sampling rate of gas-phase is lower due to the complete blockage of the internal active carbon fiber felt by the filter cartridge.（6）The multiple linear regression results showed that the sampling rate of the air phase was related to temperature,particulate matter concentration,and gas-phase concentration.The temperature was linearly negatively correlated with the sampling rate,possibly because the increase in temperature decreased the sampler-air equilibrium coefficient K_SG,resulting in a negative impact on the sampling rate.There was a significant positive correlation between the particulate matter concentration and the sampling rate,as an increase in particulate matter concentration increased the probability of the sampler capturing particulate-phase compounds.The reason for the negative correlation between the gas-phase PAEs concentration and the sampling rate is still unclear and requires further research.（7）The multiple linear regression results showed that the pore size and specific surface area of the adsorbent were significantly positively correlated with the sampling rate.The theoretical model indicates that the sampling rate is a product of the specific surface area of the adsorbent and the gas-side mass transfer coefficient,and thus has a positive correlation with the sampling rate.In addition,the pore size of the adsorbent is related to the resistance on the sampler side,where larger pore sizes result in smaller resistance on the sampler side.Therefore,an increase in the specific surface area and pore size of the adsorbent promotes the sampling rate.However,due to the higher molecular weight of PAEs with larger K_oaand their presence in the particle phase,the K_oavalue of PAEs is significantly negatively correlated with the sampling rate.