The indoor and outdoor carbonaceous pollution during winter and summer in rural areas of Shaanxi, China

Indoor and outdoor concentrations of PM_2.5, OC, EC and BC were investigated at three rural sites during the winter of 2007 and the summer of 2008 in Shaanxi, China. The average indoor concentrations of PM_2.5, OC, EC and BC were found to be higher in winter (237.2 μg/m3, 61.1 μg/m3, 6.2 μg/m3, and 14.3 μg/m³, respectively) than in summer (99.0 μg/m³, 18.0 μg/m³, 2.8 μg/m³, and 7.4 μg/m³, respectively). The average indoor/outdoor (I/O) ratios for PM_2.5 and EC were close to or less than 1.0 and those for OC and BC were above 1.0. The correlation coefficients of PM_2.5 and carbon species also indicated that the indoor concentrations of PM_2.5 and carbonaceous aerosol were correlated with the corresponding outdoor concentrations. Average OC/EC ratios ranged from 4.6 to 23.6 with an average of 9.1 during winter and from 4.2 to 12.0 with an average of 6.3 during summer. The results of this study showed that the OC and EC concentrations and OC/EC ratios in rural areas were higher than those of an urban area in Xi'an. These findings showed that improving energy efficiency and structure will be very important in reducing emissions in rural areas of Shaanxi.