The accurate measurement of pollutant baseline concentration is a crucial step for robust assessment, prediction and forecasting of air pollution in any region, especially in metro cities that witness extreme high level of pollution. The present study is an attempt to fill this gap and derive the baseline concentrations of two critical air pollutants, i.e., PM and NO in Delhi city. The study critically analyzes the data of winter period having consistent rainfall followed by complete weekend lockdown due to COVID-19. The findings indicate that the estimated baseline concentration is in the range of 20–36 μg/m and 12–63 μg/m for PM and NO (NO + NO), respectively during winter period of year 2022. The estimated baseline levels can be reasonably well compared with other reported values, both in the past studies as well as estimated using other referred methods. The baseline values are found higher in central areas of the city compared to outskirt located stations. The estimated baseline concentrations can be used in models for predicting the actual urban increment (actual increase in the source contribution with respect to the baseline), which will further help in decision making of target-oriented control actions.

中文翻译：

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德里市污染物基线浓度估算：降雨清除和封锁限制耦合效应的机遇

准确测量污染物基线浓度是对任何地区尤其是污染严重的大城市进行空气污染稳健评估、预测和预报的关键一步。本研究试图填补这一空白，并得出德里市两种关键空气污染物（即 PM 和 NO）的基线浓度。该研究批判性地分析了冬季持续降雨期间的数据，以及因 COVID-19 导致周末完全封锁的数据。研究结果表明，2022 年冬季 PM 和 NO (NO + NO) 的估计基线浓度分别在 20-36 μg/m 和 12-63 μg/m 范围内。估计的基线水平可表示为与过去的研究以及使用其他参考方法估计的其他报告值相比，效果相当好。与位于郊区的站点相比，城市中心区域的基线值较高。估计的基线浓度可用于预测实际城市增量（源贡献相对于基线的实际增加）的模型，这将进一步有助于目标导向控制行动的决策。