Abstract:

Natural perchlorate (ClO₄⁻) is widespread in the natural environment. Its isotopic composition (e.g., ¹⁷O anomaly and/or positive ³⁶Cl value) indicates that it probably comes from the stratosphere, and ozone (O₃) is likely involved in its formation process. Polar ice sheets provide unique samples for the study of natural perchlorate. Snow and ice can provide chronological records indicating past perchlorate levels and spatial variability, and past and present primary perchlorate sources. This is important for understanding the influence of human activities on atmospheric perchlorate production and the relationships between atmospheric perchlorate production, atmospheric chemistry and environmental conditions. In this study, we reviewed the most recent findings in perchlorate research in polar snow, including findings on perchlorate sources, levels, trends, and production mechanism. We identified areas for future research. They include the dominant atmospheric (stratospheric or tropospheric) sources of perchlorate at different locations and the post-depositional processes of perchlorate in snow. Research results will contribute towards improving our understanding of the atmospheric chemistry of perchlorate and atmospheric perchlorate production and variability.

Key words: polar regions, snow and ice, perchlorate, source, formation mechanism