The wide range of sources and complex (trans)formation processes of aerosol particles lead to strong spatial and temporal variability in their physical, chemical and optical properties. Their accurate representation is essential to assess their impacts, notably on climate. Here, we investigate for the first time the aerosol optical properties and their relation to fine particle chemical composition in Northern France, based on a multi-annual in situ dataset. Real-time submicron aerosol measurements at the ATOLL (ATmospheric Observations in liLLe) site have shown that ammonium nitrate contributes about 36% of the total mass, being the predominant species regarding the extinction at 525 nm (35%). Yet, organics are responsible for 22% of the absorption in the UV range (370 nm), pointing at a significant contribution of Brown Carbon. Furthermore, our study highlights the need for site-specific values to correctly assess the impact of different aerosol species on extinction. It also sheds a light on the relevancy of widespread combined aerosol chemical and physical observations to better estimate their role on climate, particularly reducing uncertainties on future scenarios based on mitigation strategies.