4:00 PM - 4:15 PM
[AHW22-02] The Use of Ammonium and Trace Metals in Identifying Low Redox Environment Zone at Indonesian Coastal Alluvial Groundwater
Keywords:Ammonium, Manganese, Ferrous, Reduction, Coastal Groundwater, Indramayu
In this research, we used combined chemical parameters: ammonium (NH4+-N), dissolve manganese (Mn2+) and ferrous (Fe2+), to trace reduction condition in the groundwater. NH4+-N is one form of nitrogen compound that usually arise under reduction condition. Other parameters that arise with the reduction process are Mn2+ and Fe2+. Therefore, in this investigation, we assumed the use of NH4+-N, combined with the concentrations of Mn2+ and Fe2+ elements, are able to identify groundwater reduction environment.
Totally, there was ten soil taken from 2 boreholes located at the south and north of the research site and 20 water samples collected from groundwater (18) and river (2). The soil samples were analyzed for NH4+-N and C/N ratio parameters. These data were used to explain further about NH4+-N presence in groundwater. Additionally, the water samples were analyzed for NH4+-N, Mn2+, and Fe2+ concentrations. The aquifer materials consist of sandstone, claystone, and sandy claystone. The NH4+-N concentrations were ranged from 0.82 until 3.37 mg / L. However; there was no clear relationship between the soil’s depth and compositions with NH4+-N concentrations. The soil samples had low C/N ratios, with values of 8.00 to 12.19. This is indicating that N-organic in the soil potentially experiences mineralization, one that produces NH4+-N. Furthermore, NH4+-N in water samples were detected as the dominant nitrogen form at most sites. Similarly, Mn2+ was detected at almost all locations. Moreover, the concentrations of Mn2+ were high (> 0.05 mg / L), around 0.07 - 12.8 mg / L, at 16 locations. High concentrations of Fe2+ (> 0.3 mg/L), were found in groundwater at 6 locations. The concentrations were ranged from 1.39 to 9.91 mg/L. The presence of NH4+-N along with high Mn2+ contents indicated that almost all locations experienced reduction condition at a zone of manganese reduction. Moreover, at 6 locations, the reduction process was stronger and lead to becoming ferrous zone. This was shown by NH4+-N existence as dominant nitrogen form and high concentrations of Fe2+ as well as Mn2+.