Objective To analyze the pollution characteristics of PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) during the non-heating period, heating period, and haze period in Harbin, and infer their possible sources, and to evaluate their impact on population carcinogenesis. Methods From 2020 to 2022, sampling points were set up in different districts of Harbin. PM_2.5 samples were regularly collected every month to analyze the contents of 10 types of PM_2.5-bound 4-6 rings PAHs. The pollution characteristics of PAHs were analyzed during different monitoring periods (non-heating period, heating period, and haze period). The excess carcinogenesis risks of PM_2.5-bound PAHs were assessed according to the Technical Specifications for Health Risk Assessment of Ambient Air Pollution and the U. S. Environmental Protection Agency (US EPA) risk assessment method. The characteristic ratio method and the positive matrix factorization (PMF) model were used to infer the sources of PAHs. Results The median mass concentrations of ambient PM_2.5-bound 4-6 rings PAHs (ΣPAHs) during the non-heating period, heating period, and haze period were 6.44 ng/m³, 37.85 ng/m³, and 106.79 ng/m³, respectively. During the heating season and haze period, the concentrations of benzo[a]anthracene, benzo[k]fluoranthene, pyrene and fluoranthene were relatively high. The excess carcinogenic risks for ASF_>16, ASF_2-16 and ASF_<2 caused by exposure to PM_2.5-bound 4-6rings PAHs during the heating season were 2.34×10^-6, 1.82×10^-6, and 0.88×10^-6, respectively, while the excess carcinogenic risks for the whole population during the heating season and haze period were 5.05×10^-6 and 1.75×10^-6, respectively. The results of the two source methods showed that the main characteristic elements during the heating season were fluoranthene, pyrene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]pyrene. According to the emission source standards, it was determined that the sources were mainly coal and biomass combustion, accompanied by traffic source emissions. Conclusion In Harbin, the PM_2.5-bound 4-6 rings PAHs during the haze period is significantly higher than that during the heating period. The pollution is mainly from coal combustion emissions, accompanied by continuous traffic source pollution. The exposure to PAHs during the heating period poses a potential carcinogenic risk to the population.

Objective: To explore the indoor air quality of Harbin and its suburbs, and analyze the influence of indoor air quality on the pulmonary function indexes of schoolchildren, and to provide a reference for preventing the related respiratory diseases. Methods: The concentration of CO 2, formaldehyde, benzene, PM 10 and total bacterial count in indoor of 80 residents in Harbin and its suburb were monitored. The IAAH model was used to evaluate the indoor air quality, and the correlation between the indoor air quality and the pulmonary function indexes of schoolchildren was analyzed. Results: The levels of indoor air pollutant in suburb was higher than that in the urban of Harbin, and the concentration of CO 2, PM 10 and total bacteria count in the suburb of Harbin increase significantly during the heating season(t=5.86，4.92，21.16, P<0.05). Among the 40 households monitored by IAAH model in suburb during heating season, 37.5% had moderate air pollution, and 20.0% had severe air pollution. The IAAH was correlated with FVC, FEF75% and FEF25% after excluding the confounding factors by multiple linear regression(β=-0.17, -0.34, -0.43, P<0.05). Conclusion Indoor air pollution is very serious in the suburb of Harbin during heating season, which should be paid attention to by parents to prevent related respiratory diseases of schoolchildren.

Objective: To understand the drinking water quality of rural schools in Harbin in the past five years. Methods: According to the requirements of Harbin municipal drinking water sanitation monitoring program, rural schools were monitored for drinking water in dry and wet periods, water quality was tested according to the standard test method for drinking water (GB/T 5750—2006), and water quality was evaluated according to the standard for drinking water (GB 5749—2006). Results: A total of 320 water samples were tested from 2014 to 2018, and the qualified rate was 75.63% in 5 years, which showed an increasing trend( χ 2=10.81, P <0.05). The qualified rate of drinking water in treated rural schools (79.41%) was higher than that in untreated rural schools(68.97%)( χ 2=4.38, P <0.05). Conclusion The drinking water sanitation of rural schools in Harbin is not optimistic. Supervision and monitoring of drinking water in rural schools, construction and management of treatment and disinfection facilities should be strengthened to ensure the safety of drinking water for teachers and students.