Natural variations in pH and oxygen status are also important and are not restricted to deep environments. Many groundwaters in tropical regions in weathered basement aquifers and alluvial sequences have low pH, and the reducing conditions which prevail can promote the mobilisation of metals and other parameters of health significance such as arsenic. Thus prevailing hydrochemical conditions of the groundwater that are naturally present and develop need to be taken into account when: (i) developing schemes for groundwater abstraction for various uses and in protecting groundwater; and (ii) considering the transport and attenuation of additional chemicals entering groundwaters due.
