Arain et al. 2026 — Groundwater arsenic and hydrochemistry in flood-prone Dadu district, Sindh, Pakistan
This study characterized the hydrochemistry of 159 groundwater samples from District Dadu, Sindh, one of Pakistan’s most flood-prone agricultural districts, assessing fitness for drinking and irrigation. Arsenic concentrations ranged up to 500 µg/L, exceeding WHO and Pakistan National Standards for Drinking Water Quality limits (10 µg/L) at a substantial fraction of sampling sites. Fluoride co-contamination was also widespread. Total dissolved solids reached up to 22,900 mg/L, and Escherichia coli was detected in 59.7% of samples, indicating concurrent microbiological hazard. Hazard quotient analysis showed elevated non-carcinogenic health risks for arsenic and fluoride, with infants and children identified as the highest-risk subpopulations due to their lower body weight relative to intake. The sodium adsorption ratio and residual sodium carbonate indices indicated that a majority of groundwater samples are unsuitable for irrigation without treatment, raising concerns for arsenic transfer to crops grown in the district.
Key numbers
- Sample count: n = 159 groundwater samples
- Maximum As: 500 µg/L (50× WHO guideline of 10 µg/L)
- Maximum TDS: 22,900 mg/L
- E. coli detection rate: 59.7% of samples
- Analytes assessed: As, F⁻, pH, EC, TDS, major cations/anions, SAR, RSC
- Health risk subpopulations ranked highest: infants, children
- Analytical methods: ICP-MS for As; ion chromatography for fluoride; standard methods for physicochemical parameters
Methods (brief)
Cross-sectional groundwater sampling in Dadu district, 2023–2024. ICP-MS for trace elements including arsenic. Hazard quotients calculated per US EPA risk assessment methodology using body-weight-adjusted daily intake. Irrigation suitability assessed via Wilcox diagram, SAR, RSC, and Piper diagram for hydrochemical facies classification.
Implications
Certification: Not directly applicable to product concentration thresholds, but relevant to supply-chain water sourcing in regions where groundwater is used for irrigation or food processing; arsenic at 500 µg/L irrigation water transfers to crops, particularly rice in flood-irrigated paddy agriculture.
Courses: Good case study for supply-chain contamination pathways — flood-driven arsenic mobilization from alluvial geology, compounded by microbiological hazard, illustrates the multi-hazard character of water quality in South Asian agricultural districts.
App: Supports geographic risk weighting for ingredients sourced from Sindh province of Pakistan, particularly rice and wheat grown under flood irrigation.
Microbiome: Not directly addressed.