Long-term measurements (2011–2018) of ambient sulphur dioxide (SO₂) and meteorology were carried out at an urban site of Delhi, India, to study the seasonal and inter-annual variations of SO₂ over Delhi. The average mixing ratio of SO₂ was estimated as 2.26 ± 0.48 ppb for the entire study period. Mixing ratio of ambient SO₂ was estimated as 2.19 ± 0.64 ppb, 2.07 ± 0.89 ppb, 2.49 ± 1.05 ppb and 2.27 ± 0.71 ppb during winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. SO₂ mixing ratio was recorded maxima during monsoon (2.49 ± 1.05 ppb) season, whereas minima during pre-monsoon season (2.07 ± 0.89 ppb). The mixing ratio of SO₂ showed slightly increase in the trend during observational period. Surface wind speed and wind directions analysis indicates the influence of local sources on the mixing ratio of SO₂ at the study site. Backward trajectories and potential source contributing factor (PSCF) analysis also showed the local as well as the regional sources (industrial activities, coal burning and thermal power plants etc.,) influencing the mixing ratio of SO₂ over Delhi.

中文翻译：

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印度德里上空SO 2的长期测量

在印度德里的城市地区进行了环境二氧化硫（SO ₂）和气象学的长期测量（2011-2018年），以研究德里上空SO ₂的季节变化和年际变化。在整个研究期间，SO ₂的平均混合比估计为2.26±0.48 ppb。在冬季，季风前，季风和季风后季节，环境SO _2的混合比分别为2.19±0.64 ppb，2.07±0.89 ppb，2.49±1.05 ppb和2.27±0.71 ppb。在季风季节（2.49±1.05 ppb）期间记录到的SO ₂混合比最大值，而在季风季节之前（2.07±0.89 ppb）记录到最小。SO ₂的混合比例在观察期间显示趋势略有增加。地表风速和风向分析表明，在研究地点，局部来源对SO ₂的混合比有影响。向后的轨迹和潜在的源影响因素（PSCF）分析还显示，本地和区域源（工业活动，燃煤和热电厂等）都对SO ₂与德里的混合比产生影响。