Green analytical strategies for monitoring atmospheric microplastics in mountain ecosystems: current advances and challenges

The ubiquity of air pollution, which is associated with microplastic pollution in high altitudes, has now become one of the most distressing aspects of the global plastic pollution problem, and of anthropogenic pressures on the most geographically remote mountain environments. This review critically reviews the state of the art of green analytical approaches used for the atmospheric monitoring of microplastics in mountain ecosystems, highlighting new developments in sampling design, spectroscopic characterisation and data harmonisation, and focussing on their ecological implications for cryospheric and terrestrial ecosystems. The review covers passive and active sampling platforms, comparative performance of µ-FTIR and µ-Raman techniques, and the emerging hyperspectral imaging techniques with increasing applications of machine learning for particle identification, mostly from peer-reviewed literature published after 2019. It also evaluates the drive towards greener analytical procedures, in the larger context of environmental monitoring efforts aimed at sustainability, which minimize the use of organic solvents, laboratory energy consumption and which are equipped with closed-loop management of chemicals. The key findings are: (1) standardization of sampling protocol remains the most important bottleneck, (2) current analytical detection limits systematically undercount sub 10 μm particles and (3) chemical weathering changes the spectral identity of the environmental microplastics which are not well captured by existing reference libraries. Finally, the review proposes a research agenda revolving around the concept of cross observatory networks, harmonized quality assurance procedures and the use of the principles of green chemistry as a non-negotiable condition to be included in the design of future monitoring programmes.