Spatial Variability and Health Implications of Heavy Metals in Wadi Al-Hamd’s Groundwater: A Multivariate and Risk-Based Approach
Spatial Variability and Health Implications of Heavy Metals in Wadi Al-Hamd’s Groundwater: A Multivariate and Risk-Based Approach
This study comprehensively evaluates heavy metal (HM) contamination and associated
health risks in 31 groundwater samples from Wadi Al-Hamd, northwest Saudi Arabia. Cd,
Pb, Zn, As, Cr, Cu, Ba, and Ni showed variable concentrations, some elements approaching
WHO guideline values in localized samples. The analyzed HMs showed variable concentrations,
with As reaching 5.02 μg/L (50% of WHO guideline) in sample M27. The heavy
metal pollution index (HPI) ranged from 0.15 (M29) to 10.07 (M27), with values below
15 indicating low pollution overall, while the metal index (MI) ranged from 0.022 (M29) to
0.621 (M27), all below the threshold of 1 for safe water, indicating geogenic enrichment,
particularly in arsenic and nickel. Principal component analysis identified three PCs explaining
73.58% of total variance, with PC1 (35.50%) dominated by Zn-Cu-Ni (geogenic
weathering) and PC2 (23.62%) by As-Cd (redox-driven dissolution). Health risk assessment
via chronic daily intake (CDI), hazard quotient (HQ), and hazard index (HI) models
confirmed negligible non-carcinogenic risks (HI < 1) for both adults and children, though
children exhibited 1.5–2 times higher exposure. The highest HQ values were observed for
As (HQoral-child: 0.365 in M27), approaching but not exceeding safety thresholds. Dermal
exposure contributed minimally (<1% of total risk). The average lifetime carcinogenic
risk (LCR) due to exposure to arsenic through drinking water aligns with the US EPA’s
acceptable risk range of 1 × 10−6 to 1 × 10−4 (average 1.18 × 10−5 for adults, 2.06 × 10−5
for children). These findings align with regional studies, but highlight localized As high
values for few samples. The study underscores the dominance of natural weathering in HM
release and provides a framework for targeted groundwater management in arid regions.
This study comprehensively evaluates heavy metal (HM) contamination and associated
health risks in 31 groundwater samples from Wadi Al-Hamd, northwest Saudi Arabia. Cd,
Pb, Zn, As, Cr, Cu,…
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