Physicochemical or geochemical

• Heikens, A., Sumarti, S., Van Bergen, M., Widianarko, B., Fokkert, L., Van Leeuwen, K., Seinen, W., (2005), The impact of the hyperacid Ijen Crater Lake: risks of excess fluoride to human health, Science of the Total Environment, 346, 56-69, 10.1016/j.scitotenv.2004.12.007