Hydrogeochemical Investigation of Elevated Arsenic Based on Entropy Modeling, in the Aquifers of District Sanghar, Sindh, Pakistan

Zahid Ullah,Sami Bawazeer,Junaid Ghani,Yahia N Mabkhot,Abdur Rauf,Abdur Rashid,Muhammad Afnan Talib,Asfandyar Shahab,Muhammad Irfan,Zainab M Almarhoon

doi:10.3390/w13233477

Abstract

Arsenic (As) contamination in drinking groundwater is a common environmental problem in Pakistan. Therefore, sixty-one groundwater samples were collected from various groundwater sources in District Sanghar, Sindh province, Pakistan, to understand the geochemical behavior of elevated As in groundwater. Statistical summary showed the cations and anions abundance in decreasing order of Na+ > Ca2+ > Mg2+ > K+, and HCO3− > Cl− > SO42− > NO3−. Arsenic was found with low to high concentration levels ranging from 5 µg to 25 µg/L with a mean value of 12.9 µg/L. A major water type of groundwater samples was mixed with NaCl and CaHCO3 type, interpreting the hydrochemical behavior of rock–water interaction. Principal component analysis (PCA) showed the mixed anthropogenic and natural sources of contamination in the study area. Moreover, rock weathering and exchange of ions controlled the hydrochemistry. Chloro-alkaline indices revealed the dominance of the reverse ion exchange mechanism in the region. The entropy water quality index (EWQI) exposed that 17 samples represent poor water, and 11 samples are not suitable for drinking.

Highlights

Arsenic (As) is a toxic metalloid existing in groundwater from commonly anthropogenic and geogenic sources [1,2]
We studied groundwater contamination with As in Sanghar district, Sindh, Pakistan
The electrical conductivity value ranged from 305–5570 μs/cm, with a mean value of 1200 μs/cm, in all groundwater sources of district Sanghar

Summary

Introduction

Arsenic (As) is a toxic metalloid existing in groundwater from commonly anthropogenic and geogenic sources [1,2]. More than 150 million people are exposed to excessively high As contamination of drinking water sources [3,4]. The prevalent range of health hazards of As in groundwater is a serious threat to Pakistan [5]. Arsenic is commonly dispersed in Sindh province in different regions such as Manchar lake, Jamshoro, Hyderabad, Jaccobabad, and Nagar Parker [15,16,17,18]. The observation of arsenic in groundwater is used to indicate apparent health risks. As is contaminated in the food chain through drinking water, food, meat, milk, and eggs may cause several health disorders. The ingestion of bovine milk is one of the most important pathways of exposure to chemicals in the tissues in the agricultural food chain. [19,20]

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