This study assesses the effect of lockdown, due to the coronavirus disease (COVID-19) pandemic, on the concentration of different air pollutants and overall air quality of a less industrialized region (Kerala) of India. We analysed data from four ambient air quality stations over three years (January to May, 2018–2020) with pairwise comparisons, trend analysis, etc. Results indicated unprecedented reduction in the concentration of the air pollutants: nitrogen dioxide, NO₂ (-48 %), oxides of nitrogen, NO_x (-53 % to -90 %), carbon monoxide, CO (-24 % to -67 %) and the particulate matter (-24 % to -47 % for particulate matter with a diameter of less than 2.5 μm, PM_2.5; -17 % to -20 % for particulate matter with a diameter of less than 10 μm, PM₁₀), as well as the reduction of the National Air Quality Index (NAQI). These reductions indicate an overall improvement of the ambient air quality due to restrictions on transportation, construction, and the industrial sectors during lockdown, even in an area considered less industrial. Despite the general decreasing trend of the concentration of various air pollutants from January to May, suggesting seasonal influences, the trend was intensified in the year 2020 due to the added effect of the lockdown measures. Comparison of the results with those from larger and more industrialized cities suggests that the effects of lockdown are more variable, and focused on the levels of gaseous pollutants. Findings from this study demonstrate the far-reaching effects and implications of the COVID-19 lockdown on ambient air quality, even on less industrialized and less urbanized regions.

这项研究评估了由于冠状病毒病（COVID-19）大流行而导致的封锁对印度工业化程度较低的地区（喀拉拉邦）不同空气污染物浓度和整体空气质量的影响。我们通过成对比较，趋势分析等方法分析了三年内（2018年1月至5月至2018年2020年5月）四个空气质量监测站的数据。结果表明，空气污染物的浓度空前降低：二氧化氮，NO ₂（-48 ％），氮氧化物，NO _x（-53％至-90％），一氧化碳，CO（-24％至-67％）和颗粒物（对于直径较大的颗粒物为-24％至-47％小于2.5μm，PM _2.5 ;直径小于10μm，PM _10的颗粒物的-17％至-20％），以及降低国家空气质量指数（NAQI）。这些减少表明由于锁定期间运输，建筑和工业部门的限制，即使在被认为工业程度较低的地区，环境空气质量也得到了整体改善。尽管从一月到五月各种空气污染物的浓度总体呈下降趋势，这表明受到季节的影响，但由于封锁措施的附加作用，这一趋势在2020年得到了加强。将结果与较大的和工业化程度更高的城市的结果进行比较表明，锁定的影响变化更大，并且集中在气态污染物的水平上。这项研究的结果证明了COVID-19锁定对周围空气质量的深远影响和影响，