Comparison on the chemical composition of PM2.5 in the urban and rural regions of Guanzhong plain, China
LI Jin1,2, LI Jian-jun1, WU Can1,2, CAO Cong1,2, WU Yu-hang1, LIU Lang1,2, HAN Jing4, WANG Ge-hui1,2,3
1. State Key Laboratory of Loess and Quaternary Geology, Key Lab of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China;
3. Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China;
4. College of Public Health, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China
PM2.5 samples were collected on a day/night basis at an urban site in Xi'an in July 2016 and at Lin Village, a rural site 80km northeast to Xi'an, in August 2016. The samples were determined for organic carbon (OC), elemental carbon (EC), and inorganic ions to investigate the differences in chemical compositions and sources of PM2.5 between the urban and rural areas of Guanzhong Plain. The results showed that PM2.5 in Xi'an and Lin Village during the sampling period were (49.7±22.8)μg/m3 and (62.6±14.2)μg/m3, respectively. Concentrations of OC and EC in PM2.5 were similar between Xi'an[(6.5±2.5)μg/m3 and (3.2±1.8)μg/m3] and Lin Village[(6.8±1.8)μg/m3 and (3.8±2.3)μg/m3]. The OC/EC mass ratios in Xi'an were higher in the daytime (2.6) than in the nighttime (1.9), in contrast to those in Lin Village, which were lower in the daytime (1.6) and higher in the nighttime (2.7). Such diurnal differences can be explained by an enhanced emission of EC due to the nighttime occurrence of heavy-duty trucks in the urban area and a decreased emission of EC due to the nighttime absence of anthropogenic activities (e.g., biomass burning and coal combustion) in the rural area. Inorganic ions of PM2.5 were (20.2±14.6)μg/m3 and (30.1±10.5)μg/m3 in Xi'an and Lin Village and accounted for 40.6% and 47.6% of PM2.5 in the two regions, respectively. SO42- of PM2.5 in the rural area was 19.0μg/m3 and accounted for one-third of the fine particle mass, which was much higher than that in Xi'an (9.4μg/m3 and 18.9%). Concentrations of NO3- and Ca2+ in Xi'an, their masses relative to PM2.5 and NO3-/SO42- mass ratio were significantly higher than those in Lin Village, suggesting that the urban atmosphere was more affected by motor vehicle exhausts and emissions from road-dust and construction activities. K+ in the samples showed stronger correlations with Ca2+ and Mg2+ in Xi'an due to the dominant source of dust. In contrast, K+ was correlated with EC in the rural area, mainly due to the dominance of biomass burning emissions.
李瑾, 李建军, 吴灿, 曹聪, 吴宇航, 刘浪, 韩晶, 王格慧. 关中典型城市及农村夏季PM2.5的化学组成对比[J]. 中国环境科学, 2018, 38(12): 4415-4425.
LI Jin, LI Jian-jun, WU Can, CAO Cong, WU Yu-hang, LIU Lang, HAN Jing, WANG Ge-hui. Comparison on the chemical composition of PM2.5 in the urban and rural regions of Guanzhong plain, China. CHINA ENVIRONMENTAL SCIENCECE, 2018, 38(12): 4415-4425.
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