Incremental effect of festive biomass burning on wintertime PM10 in Brahmaputra Valley of Northeast India

•PM10 during festive meji burning was monitored and characterised.•PM10 was highly carbonaceous, enriched with Br and metals.•Enrichment factors suggest strong anthropogenic influence and long-range transport.•Thermal inversion and lowering of mixing height — vital functions of PM10 levels•Incremental effect of meji burning was evident from the calculated MBIEs.

PM10 concentration was monitored at a receptor site in the Brahmaputra Valley during a unique, local, episodic festive biomass burning called meji burning. Mean mass concentration of PM10 during monitoring was found to be 149 ± 45 μg m− 3 with maximum and minimum concentrations of 293 μg m− 3 and 93 μg m− 3 respectively. Elemental analysis by Energy Dispersive X-ray Spectrometer (EDX) revealed high carbonaceous and Br content in PM10 samples. Particulate carbon showed high significant correlation with PM10 and dominance in samples taken during night time. Back trajectory analysis supported long range transport of carbonaceous aerosol from the Indo-Gangetic Plain (IGP) to the region under study. Prevailing meteorology – thermal inversion and low mixing heights – was found to have a strong influence on PM10 levels in the post festive burning period. Enrichment factors of several elements ranged above thousand which indicated a strong influence of anthropogenic activities and input of aged particulates driven from long distance. Incremental effect of meji burning, which we coined as Meji Burning Induced Enrichments (MBIEs), was calculated. MBIE values supported incremental effects explicitly.