University of Maryland, College Park, MD, USA.
NASA Marshall Space Flight Center, Huntsville, AL, USA.
Environ Pollut. 2018 May;236:795-806. doi: 10.1016/j.envpol.2018.01.098.
In Southeast Asia and Vietnam, rice residues are routinely burned after the harvest to prepare fields for the next season. Specific to Vietnam, the two prevalent burning practices include: a). piling the residues after hand harvesting; b). burning the residues without piling, after machine harvesting. In this study, we synthesized field and laboratory studies from the literature on rice residue burning emission factors for PM. We found significant differences in the resulting burning-practice specific emission factors, with 16.9 g kg(±6.9) for pile burning and 8.8 g kg(±3.5) for non-pile burning. We calculated burning-practice specific emissions based on rice area data, region-specific fuel-loading factors, combined emission factors, and estimates of burning from the literature. Our results for year 2015 estimate 180 Gg of PM result from the pile burning method and 130 Gg result from non-pile burning method, with the most-likely current emission scenario of 150 Gg PM emissions for Vietnam. For comparison purposes, we calculated emissions using generalized agricultural emission factors employed in global biomass burning studies. These results estimate 80 Gg PM, which is only 44% of the pile burning-based estimates, suggesting underestimation in previous studies. We compare our emissions to an existing all-combustion sources inventory, results show emissions account for 14-18% of Vietnam's total PM depending on burning practice. Within the highly-urbanized and cloud-covered Hanoi Capital region (HCR), we use rice area from Sentinel-1A to derive spatially-explicit emissions and indirectly estimate residue burning dates. Results from HYSPLIT back-trajectory analysis stratified by season show autumn has most emission trajectories originating in the North, while spring has most originating in the South, suggesting the latter may have bigger impact on air quality. From these results, we highlight locations where emission mitigation efforts could be focused and suggest measures for pollutant mitigation. Our study demonstrates the need to account for emissions variation due to different burning practices.
在东南亚和越南，水稻收获后通常会将稻茬焚烧，为下一季做准备。具体到越南，有两种常见的焚烧方式：a）人工收割后堆积稻茬；b）机器收割后不堆积直接焚烧稻茬。在本研究中，我们综合了文献中关于水稻残茬燃烧产生颗粒物排放因子的田间和实验室研究。我们发现，由于焚烧方式的不同，排放因子有显著差异，堆积焚烧的排放因子为 16.9 g kg（±6.9），不堆积焚烧的排放因子为 8.8 g kg（±3.5）。我们根据水稻种植面积数据、区域燃料加载因子、综合排放因子以及文献中的燃烧估计值，计算了焚烧方式特异性排放量。2015 年的研究结果表明，堆积焚烧方式会产生 180 万吨 PM，不堆积焚烧方式会产生 130 万吨 PM，而目前越南最有可能的排放情景是 150 万吨 PM 排放。为了进行比较，我们使用了全球生物质燃烧研究中使用的通用农业排放因子来计算排放量。这些结果估计会产生 80 万吨 PM，仅为堆积焚烧方式估计值的 44%，表明之前的研究存在低估。我们将排放量与现有的所有燃烧源清单进行了比较，结果表明，根据焚烧方式的不同，排放量占越南总 PM 的 14-18%。在高度城市化和云层覆盖的越南首都河内地区（HCR），我们利用 Sentinel-1A 提供的水稻种植面积来获得空间上明确的排放量，并间接估算稻茬燃烧日期。根据季节划分的 HYSPLIT 轨迹分析结果表明，秋季来自北方的排放轨迹最多，而春季来自南方的排放轨迹最多，这表明后者可能对空气质量的影响更大。根据这些结果，我们突出了可以集中进行减排努力的地点，并提出了污染物减排措施。本研究强调了需要考虑不同焚烧方式造成的排放变化。
