Deciphering challenges in the marble dust dominated ecosystem of Kishangarh through atmospheric composition measurements

The town of Kishangarh is located between two major tourist destinations (Jaipur and Ajmer/Pushkar) in the desert state of Rajasthan in western India. Apart from being impacted by desert dust and mining activities, the town bears repercussions of marble cutting and processing industries and is aptly known as the marble capital of India. The combined impacts of desert dust and marble dust pose a number of challenges in the urban and peri-urban regions of the semi-arid landscape of Kishangarh district. These include many cases of silicosis in the region and extremely scant greenery in the marble cutting industrial area of Kishangarh. Despite close proximity to Ajmer, Kishangarh exhibits significantly lower rainfall compared to Ajmer. In summer, the temperature in the district can reach upto 49^◦C, exacerbating the heat island effect. Further, the region sees high night-time values of surface ozone (O₃) in contrast to many other observations over western India indicating low net photochemical O₃ formation during the day. O₃ values reach above the threshold of 50 ppbv nearly 43% of the time despite the high dust content favoring dry-deposition of O₃. Almost during the entire rabi cropping season, the monthly AOT40 values are above threshold; potentially detrimental to agriculture. Considering the top 10 contributing non-methane hydrocarbons, surprisingly a biogenic fingerprint, Isoprene, is the major contributor to propylene-equivalent concentration in post-monsoon (27%), winter (25%) and pre-monsoon (33%), indicating the major role to be leveraged from biogenics in maintaining atmospheric oxidation and hence air quality to satisfactory levels. Comparison of butane isomeric ratios to butane-propane ratios indicates impact of chlorine chemistry competing with daytime OH chemistry, and points to growing instances of haze impacting traffic, which also needs to be addressed for maintaining better civic infrastructure.