Monthly physicochemical variation of tropical island groundwater of Pulau Bidong, south China sea

Abstract

The groundwater of Pulau Bidong, Terengganu, Malaysia was investigated to monitor the quality of freshwater source. Groundwater samples were collected from five sampling stations from June 2016 to October 2016. Physical parameters such as temperature, specific conductivity, dissolved oxygen (DO), pH, salinity, and DO saturation were measured in-situ by using handheld device. Meanwhile, total suspended solid (TSS), total dissolved solid (TDS), nitrate (NO3−), nitrite (NO2−), ammonium (NH4+) and phosphate (PO43−) were also analysed. The inorganic nutrients of NO3−, NO2−, NH4+, and PO43− were ranged from 0.000 to 4.310 mg/L, 0.000–0.190 mg/L, 0.000–0.807 mg/L and 0.003–0.028 mg/L, respectively. The monthly trends of specific conductivity, DO, salinity, DO saturation, NH4, NO3 and NO2 demonstrated significant variation in June (the lowest rainfall) compared to other months. Correlation matrix revealed that temperature was associated with the specific conductivity, and NH4+ strongly correlated with DO, NO3− and NO2−. Nevertheless, there is a strong negative correlation between physicochemical parameters and monthly rainfall distribution. The physicochemical parameters were within the recommended safe limits suggested by the World Health Organization (WHO) and National Drinking Water Quality Standard (NDWQS) except for pH. Nevertheless, pH of water does not directly impact on the human health. Environmetrics analysis demonstrated that NO3− and PO43− significantly influenced the groundwater quality spatially. Furthermore, the temporal variation of groundwater quality was affected by pH and salinity. Overall, the groundwater sources from Pulau Bidong are considered safe to be used as drinking water. Notably, future studies are required for long-term monitoring to ensure the good quality of groundwaters from Pulau Bidong.