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Ozonolysis of monoterpenes is an important source of atmospheric biogenic secondary organic aerosol (BSOA). While enhanced BSOA formation has been associated with sulfate-rich conditions, the underlying mechanisms remain poorly understood. In this work, the interactions between SO₂ and reactive intermediates from monoterpene ozonolysis were investigated under different humidity conditions (10 % vs. 50 %). Chamber experiments were conducted with ozonolysis of <i>α</i>-pinene or limonene in the presence of SO₂. Limonene SOA formation was enhanced in the presence of SO₂, while no significant changes in SOA yields were observed during <i>α</i>-pinene ozonolysis. Under dry conditions, SO₂ primarily reacted with stabilized Criegee intermediates (sCIs) produced from ozonolysis, but at 50 % RH heterogeneous uptake of SO₂ onto organic aerosol was found to be the dominant sink of SO₂, likely owing to reactions between SO₂ and organic peroxides. This SO₂ loss mechanism to organic peroxides in SOA has not previously been identified in experimental chamber studies. Organosulfates were detected and identified using an electrospray ionization–ion mobility spectrometry–high-resolution time-of-flight mass spectrometer (ESI-IMS-TOF) when SO₂ was present in the experiments. Our results demonstrate the synergistic effects between BSOA formation and SO₂ oxidation through sCI chemistry and SO₂ uptake onto organic aerosol and illustrate the importance of considering the chemistry of organic and sulfur-containing compounds holistically to properly account for their reactive sinks.