Analysis of Indoor and Outdoor PM_2.5 Concentrations in a University of Nanjing

Objective To investigate the indoor and outdoor PM_2.5 concentrations and related impact factors in a university and provide valuable data for indoor air study or control.

Methods PM_2.5 concentrations in six environments in urban campus(Wutai) and suburban campus(Jiangning) of Nanjing Medical University were monitored using a portable particulate matter monitor. Meanwhile, temperature, humidity, ventilation, and carpet area were monitored. Differences in PM_2.5 concentrations among varied locations and functional indoor areas were also compared.

Results The highest indoor PM_2.5 levels were both found in the canteen areas(82.00 and 149.71 μg/m³) and the lowest in the library areas(31.20 μg/m³, 35.00 μg/m³) in Jiangning and Wutai campuses, respectively. The differences in indoor PM_2.5 concentrations were statistically significant between classroom, library, and canteen of Jiangning and Wutai(P < 0.001). In addition, the PM_2.5 concentrations of outside environments of classroom, laboratory, and canteen in Jiangning were higher than those in Wutai(P < 0.05). According to the results of multiple comparisons, the PM_2.5 indoor/outdoor concentrations(I/O) of laboratory(0.76) and canteen(1.09) were different from those of other areas in Jiangning campus(P < 0.001); the I/O values of library(0.8) and canteen(3.08) were different from those of other areas in Wutai campus(P < 0.001). According to the results of multivariate regression analysis, air conditioning and ventilation were negatively associated with indoor PM_2.5 concentration, but area was positively related with the PM_2.5 concentration. The regression equation was: ?=48.63-15.01X₁+0.022X₂-4.46X₃(Y denoted PM_2.5 concentration; X₁, X₂, and X₃ denoted air conditioning, area, and ventilation, respectively). When cooking activities were included, the regression equation was: ?=139.17-17.67X₁+0.025X₂-91.38X₄(Y denoted PM_2.5 concentration; X₁, X₂, and X₄ denoted air conditioning, area, and cooking activity, respectively).

Conclusion The PM_2.5 concentrations meet the standards of ambient air quality in all monitored places except canteen. Use of air conditioning or ventilation is beneficial to decrease indoor PM_2.5 concentration. Cooking activities significantly affect the quality of indoor PM_2.5.