[Characteristics of organic and elemental carbon in the indoor/outdoor air PM_(2. 5) in Beijing]. OBJECTIVE
 To study the characteristics of indoor/outdoor organic and elemental carbon in the PM_(2. 5).


 Seven type regions were selected in Beijing.  The samples of OC and EC in PM_(2. 5)were collected and were measured in the indoor /outdoor of seven type areas respectively from May 2013 to April 2014.


 The overall concentrations( median and P25-P75) of indoor OC and EC in PM_(2. 5)were 13.  79 μg /m~3( 2. 09-6. 98 μg /m~3), and the concentrations of outdoor OC and EC were 15.  96 μg/m~3( 2. 92-9. 39 μg/m~3), respectively.  Indoor and outdoor OC were the dominant species occupying78% and 73% of TC, respectively.  Outdoor carbonaceous matter was higher than indoor matter and the concentration of OC was higher than that of EC.  The outdoor OC concentration during heating period was the highest in all seasons and the concentrations ofother seasons found no difference.  The outdoor OC concentration in weekend was high, while was lower during the period of Monday to Wednesday.  The outdoor OC concentrations of seven type areas were different and the pollutants from dust area, aviation fuel emissions, industry and light industry were highest, followed by ones from vehicle emissions, coal-burning power plant, and one in clean district was the lowest.  There were high linear relationships between outdoor OC and outdoor EC( r = 0. 886), between indoor OC and outdoor OC( r = 0. 915), between indoor EC and outdoor EC( r =0. 894), between carbonaceous matter and PM_(2. 5)( rOC-PM_(2. 5)= 0.  785, rEC-PM 2.  775), respectively.  The indoor OC to outdoor OC ratio in summer was the highest in all seasons and the ratios of other seasons found no difference.  The outdoor OC to outdoor EC ratio in heating period was highest, and was lowest in summer.


 CONCLUSION
 We should pay attention to OC and EC pollution in Beijing air, should strengthen the protection to OC pollutants during the haze, and should take some measures to control the pollution of OC.
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