Humic substances: remediation option for anthropogenically acidified waterways

The acidification of waterways through anthropogenic means is a global problem. Treatment options for anthropogenically acidified waterways are currently limited. This review proposes the use of humic substance (HS) to treat waterways acidified via anthropogenic means such as those affected by acid rain, acid mine drainage and acid sulphate soils. In laboratory settings, HS have been shown to successfully remove metals from solutions. HS also have the added benefit of being present in all natural waters and have been shown to positively influence aquatic organism's survival to acidification, metals and the combined stressors of low pH and metal mixtures commonly associated with anthropogenically acidified waters. Comparative food webs of waterways affected by natural and anthropogenic acidification are provided along with a third conceptual food web showing the potential benefits of adding HS to an affected system. HS may represent a sustainable remediation option as it may be locally sourced from environmentally friendly options such as green waste. However, if such options are to be fully developed and utilised, the specific requirements for treating anthropogenically acidified waters with different HS sources (e.g. treatment volumes and efficacy) will require further study.