Abstract Fertilizer-induced nitrogen oxides (NOx) emissions in sub-Saharan Africa are expected to increase substantially in the coming decades, driven by increasing application of fertilizers to increase crop yields in an effort to attain food security across the continent. In many parts of sub-Saharan Africa, surface ozone (O3) is sensitive to increasing atmospheric concentrations of NOx. In this study, we employ the GEOS-Chem chemical transport model to conduct a preliminary investigation of the impacts on O3 air quality and the consequential crop damage associated with increasing fertilizer-induced NOx emissions in sub-Saharan Africa. Our simulation results, constrained by field NO flux measurements for the years 2011 and 2012 in response to a variety of fertilizer application rates in western Kenya, show that the enhancements in NO flux with fertilizer application rate of 150 kg N ha−1 can increase surface NOx and O3 concentrations by up to 0.36 and 2.8 ppbv respectively during the growing season. At the same time, accumulated O3 exposure during the crop growing season (expressed as AOT40 values) could increase by up to 496 ppb h, leading to crop yield decline of about 0.8% for O3-sensitive crops. Our results suggest that, when accounting for the consequential impacts on surface O3 air quality and crop damage over sub-Saharan Africa, agricultural intensification is possible without substantial impacts on crop productivity because the relatively small decline of crop yield resulting from O3 damage appears unlikely to outweigh the gain in crop yield from fertilization.

中文翻译：

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加强施肥对撒哈拉以南非洲对流层臭氧和作物损害的影响

摘要 撒哈拉以南非洲的肥料引起的氮氧化物 (NOx) 排放量预计在未来几十年将大幅增加，这是由于为提高作物产量以增加作物产量以实现整个非洲大陆的粮食安全而增加施肥的推动下。在撒哈拉以南非洲的许多地方，地表臭氧 (O3) 对大气中 NOx 浓度的增加很敏感。在本研究中，我们采用 GEOS-Chem 化学传输模型对撒哈拉以南非洲地区因肥料引起的 NOx 排放量增加而对 O3 空气质量的影响以及随之而来的作物损害进行了初步调查。我们的模拟结果受 2011 年和 2012 年田间 NO 通量测量的限制，以响应肯尼亚西部的各种肥料施用率，表明，随着施肥量为 150 kg N ha-1，NO 通量的增加可以在生长季节分别使表面 NOx 和 O3 浓度增加高达 0.36 ppbv 和 2.8 ppbv。同时，作物生长季节累积的 O3 暴露量（表示为 AOT40 值）可能增加高达 496 ppb h，导致 O3 敏感作物的作物产量下降约 0.8%。我们的结果表明，当考虑到对撒哈拉以南非洲地表 O3 空气质量和作物损害的间接影响时，农业集约化是可能的，而不会对作物生产力产生重大影响，因为 O3 损害导致的作物产量下降相对较小似乎不太可能超过施肥带来的作物产量收益。