Need suggestion

Hi, I'm working on a project that requires to measure SO2(Sulphur-dioxide) and NO2 (Nitrogen-dioxide) in the atmosphere. I've searched on the web and found many sensors such as MQ136 and other MQ series sensors but couldn't get any conclusive results for the same. What particular sensor I should use to measure the gases ??
Any suggestion will be helpful

Edit1: The sensors must be low-cost so the overall cost of the project remains low

If you want accurate results, buy a certified, industrial quality sensor. There are many, and they are all expensive.