| Phthalates（PAEs）are a group of semi-volatile organic compounds that are widespread indoors.Due to their potential endocrine disrupting toxicity,relevant human exposure has become a major public health concern.In this thesis,the phthalates pollution in indoor environment was characterized using the raw concentration data of gas-,PM2.5-and dust-phase phthalates in Beijing urban residences,which was collected in both summer and winter.The partition coefficients of phthalates between air and PM2.5as well as between air and dust were calculated and analyzed,so as to decipher the mechanisms behind partition and transfer of phthalates among.The associations between phthalate concentrations and a wide array of built environmental conditions were examined with multivariate statistical analyses,and the underlying mechanisms were discussed.The results are as follows:（1）In the tested dwellings,the major phthalates（median concentration in the summer and winter,respectively,and thereafter）in indoor air were DMP（2442.3 and 2403.4 ng/m3）,DiBP（801.0 and 640.0 ng/m3）and DnBP（5173.2 and 1379.6 ng/m3）;whereas the major phthalates in PM2.5were DiBP（1055.1 and 585.9 ng/m3）and DnBP（1658.5 and 1517.0 ng/m3）and DEHP（215.1 and 344.9 ng/m3）;the major phthalates in house dust were DiBP（57.4 and39.5 ng/mg）、DnBP（104.1 and 41.0 ng/mg）and DEHP（871.7 and 398.7 ng/mg）.（2）The air-PM2.5partition coefficients（Kp）of DiBP,DnBP and DEHP were calculated:the summer and winter median values（m3/μg）were 0.053 and 0.011 for DiBP,0.010 and0.004 for DnBP,0.021 and 0.025 for DEHP,respectively.The air-PM2.5partition of DiBP and DnBP approached equilibrium,while that of DEHP did not reach equilibrium in either season.The air-dust partition coefficients（Kd）of DiBP,DnBP and DEHP were 0.13,0.02 and 5.62m3/mg in the summer and 0.06,0.018 and 0.76m3/mg in the winter,respectively.A comparison with Kd*at equilibrium state suggested that partition between air and dust deviated from equilibrium state in both seasons.The results also revealed that dust-phthalates may completely originate from source materials via direct transfer in the summer;while they came from both air（via partition）and source material（via direct transfer）in the winter.（3）The associations between built environmental conditions and indoor phthalate concentrations were examined.First,elevated temperature resulted in accumulation of airborne phthalates.The impacts of temperature on dust-phthalate concentrations differed by season,owing to different origin of dust-phthalates in two seasons.Second,the concentrations of ozone were higher in the summer.The reactions in which ozone are involved resulted in the higher fraction of polar organic matter in both air and dust;in the summertime humid conditions,these polar organic compounds in air and dust can absorb more water;absorbed water can increase the diffusion coefficient of organic layer,facilitate mass transfer of phthalates from air to PM2.5and from dust to air.Third,improved ventilation was not an effective measure to reduce indoor phthalate concentrations.Fourth,increasing indoor PM2.5concentrations resulted in significantly higher indoor phthalate concentrations.Fifth,airborne DnBP pollution was more serious in younger or bigger size dwellings;while dust-phase DnBP concentration in the residences that were renovated more than 10 years ago were higher.Further,more occupants resulted in higher fraction of unsaturated organics in house dust;these organics can react with ozone in the summer and generate polar organic compounds,which can absorb water in the summertime humid conditions and facilitate the mass transfer of phthalates from air to dust.In the end,frequent household cleaning can mitigate the concentrations of phthalates in house dust. |
PDF Full Text Request