Abstract
Water quality has deteriorated in recent years as a result of rising population and unplanned development, impacting ecosystem health. The water quality parameters of Qaroun Lake are contaminated to varying degrees, particularly for aquatic life consumption. For that, the objective of this work is to improve the assessments of surface water quality and to determine the different geo-environmental parameters affecting the lake environmental system in Qaroun Lake utilizing the weighted arithmetic water quality index (WAWQI) and four pollution indices (heavy metal pollution index (HPI), metal index (MI), contamination index (Cd), and pollution index (PI), that are enhanced by multivariate analyses as cluster analysis (CA), principal component analysis (PCA), and support vector machine regression (SVMR). Surface water samples were collected at 16 different locations from the lake during years 2018 and 2019. Thirteen physiochemical parameters were measured and used to calculate water quality indices (WQIs). The WQIs of Qaroun Lake such WAWQI, HPI, MI, Cd, PI revealed a different degree of contamination, with respect to aquatic life utilization. The WQIs result revealed that surface water in the lake is unsuitable, high polluted, and seriously affected by pollution for an aquatic environment. The PI findings revealed that surface water samples of Qaroun Lake were significantly impacted by Al, moderately affected by Cd and Cu, and while slightly affected by Zn due to uncontrolled releases of domestic and industrial wastewater. Furthermore, increasing salinity accelerates the deterioration of the lake aquatic environment. Therefore, sewage and drainage wastewater should be treated before discharging into the lake. The SVMR models based on physiochemical parameters presented the highest performance as an alternative method to predict the WQIs. For example, the calibration (Val.) and the validation (Val.) models performed best in assessing the WQIs with R2 (0.99) and with R2 (0.97–0.99), respectively. Finally, a combination of WQIs, CA, PCA, and SVMR approaches could be employed to assess surface water quality in Qaroun Lake.
Highlights
The natural environment has been severely distorted by industrialization and uncontrolled urbanization
Because of the effect of evaporation associated with very high solute dissolution and continuous recharging from agricultural, domestic, sewage, and industrial wastes in the closed lake, the TDS values in the obtained samples revealed that the surface water at Qaroun Lake was semi-saline type (e.g., 10,000–100,000 mg/L)
Contamination Index (Cd) concentrations in the upper lake exhibited a temporal significant difference (p < 0.05), but Fe, Ni, Zn, and Cu values showed a highly spatial significant difference (p < 0.01). These findings revealed that the discharge of untreated effluents, sewage, and agricultural chemicals into the lakes via the El-Wadi drain and the increasing rate of water evaporation result in increased metal levels, potentially reversing the dramatic transformation story of Qaroun Lake and the deterioration of the aquatic environment
Summary
The natural environment has been severely distorted by industrialization and uncontrolled urbanization. The aquatic ecosystem is made up of the biological community, physiochemical elements, and their interactions. A complex interplay of physical and biological processes exists within the aquatic environment, and changes do not occur in isolation. Water quality indicators have received a lot of attention in recent years in water environment research because of the potential for toxic effects, persistence, and bioaccumulation issues that can harm aquatic ecosystems [3,4]. Agricultural activities, several industrial, and urbanization processes can pollute the environment and lead to water ecosystem contamination, endangering aquatic biota and humans [5,6]. Water quality is a crucial component of surface water management, evaluating surface water quality for aquatic environments in developing nations is a critical issue in recent times.
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