Atmospheric aerosols at a regional background Himalayan site--Mukteshwar, India.

Continuous aerosol measurements were made at a regional background station (Mukteshwar) located in a rural Himalayan mountain terrain from December 2005 to December 2008 for a period of 3 years. The average concentrations of particulate matter less than or equal to 10 μm (PM₁₀), particulate matter less than or equal to 2.5 μm (PM₂.₅) and black carbon (BC) are 46.0, 26.6 and 0.85 μg/m(3) during the study period. Majority of the PM₁₀ values lie below 100 μg/m(3) while majority of the PM₂.₅ values lie below 30 μg/m(3). It is further seen that during the monsoon months, especially July and August, the average values are comparatively low. It is also noted that the PM₂.₅/PM₁₀ ratios between 0.50 and 0.75 have the maximum frequency distribution in the data set. Furthermore, the monthly mean ratio of BC to PM₂.₅ mass lies between 3.0 and 7.5 % during the study period. Though the average PM₁₀ and PM₂.₅ concentrations during the study period are less than the respective Indian ambient air quality standards, however, they are still above the WHO guidelines and would have adverse health impacts. This shows that even in rural/background regions that are far away from major pollution sources or urban areas, the aerosol concentrations are significant and require long-term monitoring, source quantification and aerosol model simulations.