Species and potential sources of phosphorus in groundwater in and around Mataram City, Lombok Island, Indonesia

Geochemical evaluation of the species and potential sources of P in groundwater in and around Mataram City, Lombok Island, Indonesia can aid in the initial research on evaluating the fate of P when detailed geological information is unavailable. The results of ion chromatography and inductively coupled plasma-optical emission spectroscopy show that the concentrations of PO43- and total dissolved P (TDP) in groundwater range from approximately 0.1 to 8.5 mg l(-1) and from 0.04 to 2.95 mg l(-1), respectively. Dissolved inorganic P accounted for 86%, on average, of the TDP concentration, and PO43- represented the predominant P species in this groundwater. The potential sources for most of this dissolved PO43-, according to indices developed based on the PHREEQC software and groundwater quality data, could be the dissolution of hydroxyapatite and/or vivianite minerals. However, the potential sources of dissolved PO43- in groundwater with a TDP concentration of >= 1 mg l(-1) is likely to be the reduction of Fe(III)-(hydro)oxides, the initial decomposition of organic matter, or the dissolution of carbonate-rich fluorapatite considering the Fe2+, dissolved organic carbon, Ca2+ and F- concentrations measured. In addition, as several groundwater samples had a TDP concentration of <= 1 mg l(-1) and comparatively high concentration of NO3-, other potential sources of dissolved PO43- in this groundwater could be anthropogenic.