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Amino acids (AAs) are involved in the global nitrogen cycle and are important components of nitrogenous organic aerosols. Protein and free amino acid (FAA) concentrations in total suspended particulate (TSP) and their major emission sources were investigated in spring and autumn at Mount Tai (Mt. Tai) on the North China Plain and the nearby city named Liaocheng. There were significant spatial and seasonal differences in protein and FAA concentrations, with rainfall producing lower concentrations. For chiral isomers of AAs, there were significant diurnal differences in D/L-Methionine (Met), which was probably due to FAA source differences caused by regional valley winds and background winds. The high D/L-aspartic acid (Asp) and D/L-glutamine (Glu) concentrations may be indicative of the important contributions of chunk and honeycomb coal combustion. Stable nitrogen isotope analyses revealed that plant debris, soil dust, and biomass burning were important sources of glycine (Gly). Biomass burning, as well as chunk and honeycomb coal combustion, produced large amounts of L-arginine (Arg). Soil dust was the dominant source of FAAs for both Mt. Tai and Liaocheng, while biomass burning contributed more in autumn, and the proportional contribution of plant debris increased in spring. [Display omitted] • Molecular compositions and sources of atmospheric free amino acids in mountainous and urban aerosols were compared. • D/L ratio and stable nitrogen isotope analyses were used together to determine the source of particulate free amino acids. • Mechanism of regional transport of particulate free amino acids in mountainous area is proposed. [ABSTRACT FROM AUTHOR]