A new method for trend analyses in PM10 and impact of crop residue burning in Delhi, Kanpur and Jaipur, India

Crop residue burning (CRB) is a widespread practice in the Indian States. Emission from CRB is transported from west to east in the Ganga Basin (GB). Long-term (5 to 9 years) patterns of PM10 were studied in three cities in GB: Delhi, Kanpur and Jaipur, with an emphasis on assessing the impact of CRB. Mean half-monthly PM10 concentrations were plotted over the years and a fifth degree polynomial was fitted. These plots logically explained PM10 pattern in different seasons. It was concluded that the episodic CRB in the States of Punjab, Haryana and Uttar Pradesh during post-monsoon (October-November) has altered the air quality of Delhi and Kanpur for the worse. Impact of CRB is least in Jaipur. A new quantitative method is developed to detect the trend in a time series by fitting a polynomial to the data and examining the rate of change of slope of fitted polynomial over the years in statistical sense. Detection of trend from the proposed method and that from Mann-Kendall test showed a match of 80%. It is concluded that the proposed method provides a quantitative assessment of trend. These cities did not show any particular trend in 45-day slots over the years.