Re-acidification refers to the process by which previously neutralized or mitigated acidic environments, such as lakes or rivers, experience a resurgence in acidity levels. This can occur due to factors such as continued emissions of acidifying pollutants, changes in land use practices, or natural processes such as volcanic eruptions. Research in re-acidification focuses on understanding the underlying causes of this phenomenon, its impact on ecosystems and human health, and developing strategies to prevent or mitigate its effects. This area of research is particularly important in regions where acid rain or acid mine drainage has led to widespread environmental degradation.