Post-monsoon air quality degradation across Northern India: assessing the impact of policy-related shifts in timing and amount of crop residue burnt
Post-monsoon air quality degradation across Northern India: assessing the impact of policy-related shifts in timing and amount of crop residue burnt
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DOI：
10.1088/1748-9326/aba714
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发表时间：
2020-10-01
影响因子：
6.7
通讯作者：
Khaiwal, R.
中科院分区：
文献类型：
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作者：
Sembhi, H.;Wooster, M.;Khaiwal, R.
在过去的十年中，在人口稠密的印度-恒河平原（IGP）的大部分地区，空气污染日益严重，特别是在后季风季节，作物残留物燃烧（CRB）最为普遍。最近的研究表明，造成这种空气质量下降的一个主要因素，可能是印度西北部（NW）的稻米残渣燃烧已经转移到后季风季节，这是2009年地下水保护政策的意外后果，该政策推迟了灌溉稻田的播种。在这里，我们结合联合收割机空气质量模型的细颗粒物（PM2.5）在IGP城市，气象，火灾和烟雾排放数据，直接测试这一假设。我们的分析卫星衍生的农业火灾表明，大约10天的转变，在印度西北部后季风残留物燃烧的时间发生自2009年地下水保护政策的出台。对于2016年的空气质量危机，我们发现西北印度CRB时间变化对后季风季节空气质量恶化（德里上空3%）的贡献很小。然而，如果同样的农业火灾进一步推迟，CRB源区（即卢迪亚纳）和德里的空气质量可能分别恶化30%和4.4%。对其他年份的模拟显示，这些时间变化的影响存在很强的年际变化，PM（2.5）浓度变化的幅度甚至方向都强烈依赖于特定的气象条件。总的来说，我们发现后季风IGP空气质量是更敏感的气象和残留物燃烧的数量在印度西北部的领域比残留物燃烧的时间变化。我们的研究呼吁立即采取行动，为农民提供负担得起的和可持续的替代残留物燃烧，以加快其有效的禁止，这是至关重要的，以减少后季风IGP空气污染事件的强度。
The past decade has seen episodes of increasingly severe air pollution across much of the highly populated Indo-Gangetic Plain (IGP), particularly during the post-monsoon season when crop residue burning (CRB) is most prevalent. Recent studies have suggested that a major, possibly dominant contributor to this air quality decline is that northwest (NW) Indian rice residue burning has shifted later into the post-monsoon season, as an unintended consequence of a 2009 groundwater preservation policy that delayed the sowing of irrigated rice paddy. Here we combine air quality modelling of fine particulate matter (PM2.5) over IGP cities, with meteorology, fire and smoke emissions data to directly test this hypothesis. Our analysis of satellite-derived agricultural fires shows that an approximate 10 d shift in the timing of NW India post-monsoon residue burning occurred since the introduction of the 2009 groundwater preservation policy. For the air quality crisis of 2016, we found that NW Indian CRB timing shifts made a small contribution to worsening air quality (3% over Delhi) during the post-monsoon season. However, if the same agricultural fires were further delayed, air quality in the CRB source region (i.e. Ludhiana) and for Delhi could have deteriorated by 30% and 4.4%, respectively. Simulations for other years highlight strong inter-annual variabilities in the impact of these timing shifts, with the magnitude and even direction of PM(2.5)concentration changes strongly dependent on specific meteorological conditions. Overall we find post-monsoon IGP air quality to be far more sensitive to meteorology and the amount of residue burned in the fields of NW India than to the timing shifts in residue burning. Our study calls for immediate actions to provide farmers affordable and sustainable alternatives to residue burning to hasten its effective prohibition, which is paramount to reducing the intensity of post-monsoon IGP air pollution episodes.