基于MODIS影像估算中国大陆区域草地火污染物时空格局

草地火是草地生态系统重要干扰因子,对草地生态系统结构和功能有重要影响.草地火释放的大量烟气和颗粒物对大气环境、生态系统和人类健康有重要影响.本研究基于2001—2017年中国大陆区域MODIS-MCD64A1数据,结合生物质密度,估算各区域草地火燃烧生物量.并运用排放因子法,估算17年间中国大陆区域草地火排放污染物总量.研究结果表明,中国大陆地区草地生物质密度存在差异,由东向西逐渐递减.草地火时空分布不均衡且存在明显季节性差异,主要集中在3月和9月.中国大陆地区2001—2017年草地火次数、火面积和燃烧总量分别是1.63×10~5次、6.12×10~6 hm~2和23.86 Mt,排放CO_2、CO、CH_4、SO_2、NMVOC、NO_x、PM_(2.5)、BC、OC和TC总量分别为37.27 Mt、1.31 Mt、43.30 kt、11.05 kt、287.74 kt、79.60 kt、155.82 kt、9.25 kt、64.95 kt和75.54 kt.此外,各污染物在时间和空间上不均衡,在东北、华北、华中和西南区域呈增加趋势,华东和西北区域呈降低趋势,华南区域呈显著降低趋势.本研究揭示了中国大陆地区草地火释放污染物的时空变化,为深入揭示草地火对区域环境影响提供数据支持.

Temporal and spatial patterns of pollutants emitted from grassland fires based on MODIS images in Mainland China

Fire is an important disturbance factor in the grassland ecosystem and significantly impacts the structure and function of this ecosystem. The smoke and particulate matters released from grassland fires significantly influence the atmospheric air quality, ecosystem services and human health. Based on MODIS-MCD64A1 and data of grass biomass, the biomass consumption of grassland fire and an estimate of the total emission of pollutants released from grassland fire in mainland China from 2001 to 2017 were calculated using emission factor method. The results showed that there was a significant variation in spatial distribution of grass biomass, gradually decreasing from East to West of China. The ignitions of grass fire were unbalanced in space and time, mainly concentrating in March and September. The total ignition, burnt area and biomass consumption of grass fire in mainland China during 2001-2017 were 1.63×10⁵, 6.12×10⁶ hm² and 23.86 Mt. The total emission of CO₂, CO, CH₄, SO₂, NMVOC, NO_x, PM_2.5, BC, OC and TC was 37.27 Mt, 1.31 Mt, 43.30 kt, 11.05 kt, 287.74 kt, 79.60 kt, 155.82 kt, 9.25 kt, 64.95 kt and 75.54 kt, respectively. The spatial distribution of pollutants was unbalanced, showing an increasing trend in Northeast, North, Central and Southwest of China and a decreasing trend in East and Northeast of China, and significantly decreased in Southern China. The study reveals temporal and spatial variation in concentrations of pollutants released from grassland fires in mainland China and provides scientific evidence to support an understanding of the influence of grassland fire on the local environment.