Environmental effects of China's coal ban policy: Results from in situ observations and model analysis in a typical rural area of the Beijing-Tianjin-Hebei region, China

Coal-to-clean energy programs (coal bans) can improve air quality and public health and welfare. However, the field measurements taken in rural areas are still insufficient to evaluate the efficacy of coal bans in China. In this study, more than three years of observations were made on organic carbon (OC), elemental carbon (EC, also called black carbon, BC) and PM_2.5 at a rural site (Xianghe) in the Beijing-Tianjin-Hebei region (BTH) of China in combination with auxiliary measurements in urban areas (Beijing, Tianjin, Langfang, Baoding and Shijiazhuang). As a result of the coal ban, the annual average PM_2.5 concentrations decreased in rural areas. Accordingly, the annual average concentrations of OC declined from 19.1 to 12.3 μg/m³, while those of EC declined from 4.7 to 3.0 μg/m³. The amplitudes of the decrease of total carbon (the sum of OC and EC) and PM_2.5 in the areas with implementation of coal ban were greater than those in the non-coal banned areas. Based on the simulation performed using the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), the quantitative contributions ascribed to coal ban policy and meteorology are discussed. In contrast to those observed in the winter of 2016/2017, the declines in the observed EC concentration could be attributed to meteorological impact (45% and 15%), changes in other emissions (29% and 40%) and coal bans (26% and 45%) for the winter of 2017/2018 and 2018/2019, respectively. Besides, in primary OC and PM_2.5 concentrations, 50% and 33% of fractional changes respectively were resulted from the reduced residential emissions associated with coal ban in the winter of 2017/2018; and more surprisingly, they rose to 66% and 57% in the winter of 2018/2019, respectively. In summary, coal ban policy had worked effectively in the BTH of China and should be widely implemented in this region if the supply of natural gas and electricity is sufficient and affordable to the local residents.