Seasonal characteristics of aerosol black carbon in relation to long range transport over Tripura in Northeast India

Abstract

This study presents the characteristics of aerosol black carbon (BC) from a rural continental site, Agartala, located in the North-Eastern part of India using two year measurements from September 2010 to September 2012. Diurnal and seasonal variations are examined in relation to the unique geographical location, changeable meteorological conditions and distinct source characteristics. Winter season is characterized by extremely high BC concentration (17.8 ± 9.2 µg/m³) comparable to those seen in urban environments of India, dropping off to much lower values during the monsoon (2.8 ± 1.7 µg/m³). Even this lowest seasonal mean is rather high, given the rural nature of Tripura. Examination of the spectral dependence of aerosol absorption coefficients indicates that the main source of aerosol to total BC burden at Agartala is the fossil fuel combustions. Concentration weighted trajectory (CWT) analysis indicate that the characteristic high BC during winter is mostly associated with the advection from the Indo-Gangetic Plains (IGP), while the air mass pattern is constricted to the oceanic region during monsoon making BC aloft due to local pollution only.