Department of Environmental & Safety Engineering, Ajou University, Suwon, South Korea.
Georgia Environmental Protection Division, Atlanta, GA, 30354, USA.
Environ Pollut. 2021 Jan 1;268(Pt A):115794. doi: 10.1016/j.envpol.2020.115794. Epub 2020 Oct 12.
Emissions reductions in upwind areas can influence the PM concentrations in downwind areas via long-range transport. However, few studies have assessed the impact of upwind PM precursor controls on changes in downwind PM concentrations. In this study, we analyzed the overall impact of PM precursor emission controls in upwind areas on PM in downwind areas with two types of impacts: "direct impact" and "cross impact." The former refers to PM changes in downwind areas due to the transported PM itself, whereas the latter represents PM changes due to reactions between the transported gaseous precursors and intermediates (i.e., HNO) originating from upwind areas and locally emitted precursors (i.e. NH) in the downwind areas. As a case study, we performed air quality modeling for Northeast Asia for January 15-17, 2016 by setting China and South Korea as the upwind and downwind areas, respectively. To account for potential spatiotemporal variations in NH emissions in downwind areas, we considered two NH conditions. When NOx emissions in China were reduced by 35%, in downwind areas the PM concentrations decreased by 2.2 μg/m under NH-rich conditions, while PM concentrations increased by 2.3 μg/m under NH-poor conditions. The direct impact increased by 4.0 μg/m in both cases due to upwind NO disbenefit effects. However, the cross impacts led to a PM decrease of 6.2 μg/m under NH-rich conditions versus a PM increase of 1.7 μg/m under NH-poor conditions. We noted that PM concentrations in the downwind areas may not improve unless a cross impact outweighs a direct impact. This may be one of the reasons why South Korea PM concentrations have not declined despite efforts by China to reduce their PM precursor emissions.
上风地区的排放减少可以通过远距离输送影响下风地区的 PM 浓度。然而，很少有研究评估上风地区 PM 前体排放控制对下风地区 PM 浓度变化的影响。在这项研究中，我们分析了 PM 前体排放控制在整个上风地区对下风地区 PM 的影响，包括两种影响类型：“直接影响”和“交叉影响”。前者是指下风地区由于输送而来的 PM 本身而发生的 PM 变化，而后者则代表由于来自上风地区的输送气体前体和中间产物（即 HNO）与下风地区本地排放的前体（即 NH）之间的反应而导致的 PM 变化。作为案例研究，我们分别将中国和韩国设为上风区和下风区，针对 2016 年 1 月 15 日至 17 日的东北亚空气质量进行了建模。为了考虑下风地区 NH 排放的潜在时空变化，我们考虑了两种 NH 条件。当中国的 NOx 排放量减少 35%时，在 NH 充足的条件下，下风地区的 PM 浓度降低了 2.2μg/m，而在 NH 缺乏的条件下，PM 浓度增加了 2.3μg/m。由于上风地区 NO 的不利影响，两种情况下的直接影响都增加了 4.0μg/m。然而，交叉影响导致 NH 充足条件下的 PM 减少了 6.2μg/m，而 NH 缺乏条件下的 PM 增加了 1.7μg/m。我们注意到，除非交叉影响超过直接影响，否则下风地区的 PM 浓度可能不会改善。这可能是尽管中国努力减少 PM 前体排放，但韩国 PM 浓度没有下降的原因之一。
