Groundwater Contamination, Subsurface Processes, and Remediation Methods: Overview of the Special Issue of Water on Groundwater Contamination and Remediation

GIS-Based Spatiotemporal Mapping of Groundwater Potability and Palatability Indices in Arid and Semi-Arid Areas

This paper aims to assess groundwater potability and palatability in the West Bank, Palestine. It combines the adjusted weighted arithmetic water quality index method (AWAWQIM), a close-ended questionnaire, and step-wise assessment ratio analysis (SWARA) to develop groundwater potability (PoGWQI) and palatability (PaGWQI) indices. Both a geographic information system (GIS) and the kriging interpolation method (KIM) are employed to create spatiotemporal mapping of PoGWQI and PaGWQI. The research is based on data from 79 wells, which were provided by the Palestinian Water Authority (PWA). Data include fecal coliform (FC), nitrate (NO3), pH, chloride (Cl), sulfate (SO4), bicarbonate (HCO3), total dissolved solids (TDS), turbidity, and hardness. Results indicate that 2% and 5% of water samples were unpotable and unpalatable, respectively. Unpotable samples were found in areas with poor sewer networks and intensive use of agrochemicals. All groundwater samples (100%) in the eastern part of the West Bank were unpalatable because of seawater intrusion. Unconfined aquifers were more vulnerable to potability and palatability contamination. It was noticed that PoGWQI is sensitive to FC and NO3, while PaGWQI is sensitive to HCO3, TDS, and Cl. Consequently, these quality parameters should be monitored well. The proposed method is of great interest to water decision-makers in Palestine for establishing strategies to protect water resources.

Comparative Study of Mercury(II) Removal from Aqueous Solutions onto Natural and Iron-Modified Clinoptilolite Rich Zeolite

The contamination of soil and water bodies with mercury from anthropogenic sources such as mining and industry activities causes negative effect for living organisms due to the process of bioaccumulation and biomagnification through the food chain. Therefore, the need for remediation of contaminated areas is extremely necessary and very desirable when it is cost-effective by using low-cost sorbents. This paper compares the sorption abilities of natural and iron-modified zeolite towards Hg(II) ions from aqueous solutions. The influence of pH, solid/liquid ratio (S/L), contact time, and initial concentration on the sorption efficiency onto both zeolites was investigated. At the optimal pH = 2 and S/L = 10, the maximum amount of sorbed Hg(II) is 0.28 mmol/g on the natural zeolite and 0.54 mmol/g on the iron-modified zeolite. It was found that rate-controlling step in mass transfer is intraparticle diffusion accompanied by film diffusion. Ion exchange as a main mechanism, accompanied with surface complexation and co-precipitation were included in the Hg(II) sorption onto both zeolite samples. This is confirmed by the determination of the amount of sorbed Hg(II) and the amount of released exchangeable cations from the zeolite structure as well as by the scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS) of saturated zeolite samples. In a wide pH range, 4.01 ≤ pH ≤ 11.08, the leaching of Hg(II) was observed in the amount of only 0.28–0.78% from natural zeolite and 0.07–0.51% from iron-modified zeolite indicating that both zeolites could be used for remediation purposes while the results suggest that modification significantly improves the sorption properties of zeolite.