TITLE:
Assessment of Heavy Metals in Deep Groundwater Resources of the Kathmandu Valley, Nepal
AUTHORS:
Suman Man Shrestha, Kedar Rijal, Megh Raj Pokhrel
KEYWORDS:
Heavy Metals, Deep Groundwater, Principal Component Analysis, Cluster Analysis, Mineralization
JOURNAL NAME:
Journal of Environmental Protection,
Vol.7 No.4,
March
17,
2016
ABSTRACT:
A study was carried out to
address distribution of some heavy metals in deep groundwater resources of the
Kathmandu Valley. Groundwater samples were analyzed for pH, ORP, EC, iron,
manganese, zinc, and arsenic in 41 deep groundwater wells during pre monsoon
and post monsoon seasons for two consecutive years. The study showed elevated
concentrations of iron and manganese in the groundwater of the valley. The
occurrence of elevated concentrations of arsenic was also exhibited and
observed up to 0.160 mg/L. The spatial distribution patterns demonstrated
elevated levels of EC, iron, manganese, zinc, and arsenic in central
groundwater district (CGWD) of the valley. The monitored parameters except ORP
are not significantly correlated with studied time series, inferring similar
distribution of the metals. Correlation analysis and principal component
analysis (PCA) were performed to find out relationships among examined
parameters and metals. The ORP has strong negative correlations with iron,
manganese, and arsenic, suggesting reductive mobilization mechanism of the
metals in the groundwater. PCA results showed that iron and manganese with high
positive loading factors were due to common natural source of origin of these
metals in the groundwater, while negative loading factors of pH and ORP
indicated that iron and manganese mobilization was favorable in low pH and
reducing environment. Cluster analysis (CA) evidenced high mineralization in
most of the wells in the CGWD.