The main objective of the ALPACA (ALaskan Pollution and Chemical Analysis) project is to gain new insights into the processes governing the formation and distribution of aerosols originating from local pollution sources in the Arctic during wintertime and early spring. For this purpose, this project makes a major contribution to, and benefits from, a major international field campaign being planned in Fairbanks, Alaska during winters 2019/20 and 2020/21 as part of the international programme ALPACA (supported by IGAC/IASC PACES). A combination of field data collection, chemical composition analysis in the laboratory, analysis of observations and atmospheric modelling will be used to better understand and simulate Arctic aerosol sources, interactions between chemical and dynamical (boundary layer) processes influencing aerosols, and the impacts of aerosols from local anthropogenic sources on climate relative to remote sources of pollutants transported from mid-latitudes (Arctic Haze). This project brings together 7 complementary French groups working on atmospheric chemistry and dynamics together with geochemists working on isotopes. This project requires support for the field campaigns in Alaska.