Seasonal dynamics of particulate matter pollution and its dispersion in the city of Delhi, India

Particulate pollution of any area is not only influenced by its local sources, but meteorological parameters too govern its dispersion in the atmosphere, its concentration and deposition. The present study evaluates the role of seasonal meteorological factors in governing the concentration of particulate pollution in one of the most polluted cities in the world, Delhi, India. The work analyzed the particulate matter (PM) concentration at four selected sites of Delhi covering North, South, East and West Delhi. The influence of meteorological factors such as temperature, relative humidity and wind speed on the concentration of PM was evaluated using Pearson correlation statistics. Also, the effect of long-range dispersion on the PM concentration was studied by computing the backward HYSPLIT particle trajectory model. The outcome of the study depicted that North and East Delhi are the most polluted areas of Delhi and seasonal meteorology has a complex role in the PM concentration of the selected areas. Majorly in the summer and monsoon season, where dispersion and washing out effect prevails, temperature showed significant positive and relative humidity with a significant negative impact on PM concentration at all the selected sites. The long-range dispersion pattern too was influenced by season, as during the monsoon season wind coming to Delhi were southeasterly and in other seasons (summer, post-monsoon and winter) winds were predominantly from the northwestern part of India, which bring a lot of dust and smoke from the neighboring states that increase the PM concentration of Delhi. The study showed that it is not only the local sources within Delhi that make it the most polluted city in the world, but the climatic profile of this city also puts it in a vulnerable state by increasing its particulate matter concentration that comes from nearby areas.