近20年来京津冀地区土壤风蚀扬尘颗粒物排放变化

京津冀地区是我国大气污染严重区域，土壤扬尘颗粒物排放变化研究对于改善京津冀地区空气质量具有重要意义。收集2000-2019年京津冀地区气候、土壤、植被覆盖数据，分析近20年来京津冀地区土壤扬尘颗粒物排放变化，揭示其变化的影响因素。结果显示2000-2019年京津冀地区土壤扬尘源总悬浮颗粒物（TSP）排放系数均值为1.79 t km^-2 a^-1，其中PM10占8.99%，PM2.5占0.25%。近20年土壤扬尘源TSP排放系数具有下降趋势，PM10和PM2.5排放系数变化过程与TSP一致。上述变化主要受气候因子变化影响，其次受植被覆盖度影响。分析发现近20年来京津冀地区土壤扬尘源TSP排放系数变化主要受年降水量影响。沧州市、天津市和石家庄市土壤扬尘源TSP、PM10和PM2.5排放系数均值较高，张家口市、保定市和沧州市土壤扬尘源TSP排放量占京津冀地区总量的19.18%、12.98%和11.63%。耕地土壤扬尘排放量最大占京津冀地区总量的59.83%，是抑制土壤扬尘源颗粒物排放的重点关注对象，其次为草地占15.66%。2019年邢台市土壤扬尘源PM10排放占观测值比例最高为12.66%，石家庄市和天津市占比也较高分别为11.09%和10.30%，沧州市和邯郸市占比分别为8.63%和8.02%。上述地区环境管理部门均应关注土壤扬尘源颗粒物排放对空气质量的影响。

Changes in the emission of dust particles from soil in the Beijing-Tianjin-Hebei region in the past 20 years

Soil wind erosion is the process by which the topsoil material departs from the original position due to wind action. The source of soil dust is formed by the particles on the bare ground under the action of nature or manpower. The source of dust caused by soil wind erosion is the main source of fine particles. Particulate matter from the uncovered ground enters the atmosphere and causes air pollution. At present, haze pollution has been the main factor affecting the air quality in cities of China and it has become one of the important factors affecting people''s happiness in life. Although the air quality is improving year by year, atmospheric particulate matter is still the primary pollutant that affects the air quality of many cities in China, and soil dust is one of the important factors that cause serious urban particulate pollution. The Beijing-Tianjin-Hebei region is an area with serious air pollution in China, and it is easily affected by sand and dust weather from the Inner Mongolia. According to the air quality status released by the Ministry of Ecology and Environment, only 53.1% of the days with good quality in Beijing-Tianjin-Hebei and surrounding areas are lower than the national average of 82.0%. Therefore, studying the changes in the emission of soil dust particles is of great significance for improving the air quality in the Beijing-Tianjin-Hebei region. In this study, we collected climate, soil, and vegetation coverage data in the Beijing-Tianjin-Hebei region, and analyzed the change of soil dust particulate emission in the region from 2000 to 2019. We also revealed the driving factors, with a view to provide scientific support for the Beijing-Tianjin-Hebei region to reduce the emission of soil dust particles and to improve the air quality together. The results show that from 2000 to 2019 the average total suspended particulate (TSP) emission coefficient of soil dust sources was 1.79 t km^-2 a^-1, of which PM10 accounted for 8.99% and PM2.5 accounted for 0.25% in the Beijing-Tianjin-Hebei region. The TSP emission coefficient of soil dust source had a downward trend in the past 20 years, and the change processes of PM10 and PM2.5 emission coefficients were consistent with TSP. The trend was firstly affected by changes in climatic factors, and secondly by vegetation coverage. Further analysis found that the changes in the TSP emission coefficient of soil dust sources in the Beijing-Tianjin-Hebei region were mainly affected by the annual precipitation. The Normalized Difference Vegetation Index of the vegetation showed a very significant upward trend, reflecting the overall improvement in vegetation growth in the Beijing-Tianjin-Hebei region from 2000 to 2019. The change of TSP emission coefficient showed a negative correlation with the Normalized Difference Vegetation Index, reaching some degree of significant level (P<0.1). Hence, vegetation coverage represented by the Normalized Difference Vegetation Index was the secondly factor of TSP emission coefficient change. The TSP, PM10 and PM2.5 emission coefficients of soil dust sources were relatively high in Cangzhou, Tianjin, and Shijiazhuang. The TSP emissions in Zhangjiakou, Baoding and Cangzhou accounted for 19.18%, 12.98% and 11.63% of that in the Beijing-Tianjin-Hebei region. The cultivated land accounted for 59.83% of soil dust emissions of the whole region, which is the focus of attention to suppress the emission of particulate matter from soil dust sources, followed by grassland 15.66%. In 2019, Xingtai had the highest proportion (12.66%) of PM10 emissions from soil dust sources, followed by Shijiazhuang (11.09%), Tianjin (10.30%), Cangzhou (8.63%) and Handan (8.02%). Managers of environment-related departments in those cities should pay attention to the impact of soil dust particulate emissions on air quality.