Potentially Harmful Elements Associated with Dust of Mosques: Pollution Status, Sources, and Human Health Risks.

Potentially harmful elements (PHEs) associated with dust generated from anthropogenic sources can be transported into mosques and deposited on the filters of the air-conditioners (AC); thereby, children and adults are exposed to such PHEs while visiting mosques. Data dealing with the assessment of PHEs pollution and its human health risk in mosques dust in Saudi Arabia are scarce. Therefore, this work aims to examine the levels and pollution status of PHEs in AC filter dust (ACFD) of mosques and their associated human health risk in three Saudi cities: Jubail, Jeddah, and Dammam metropolitan. A similar concentration pattern of PHEs is observed in three cities' mosques with noticeably higher concentrations than both global crustal and local background values for Zn, Cu, Pb, As, and Cd only. Except for Fe, Al, and Mn, the highest PHEs concentrations were found in Jeddah (1407 mg/kg), followed by Dammam (1239 mg/kg) and Jubail (1103 mg/kg). High PHEs' concentrations were also recorded in mosques located near workshops and suburban areas compared to urban areas. Based on the spatial pattern, enrichment factor, geo-accumulation index, pollution load index, and ecological risk values, Jubail, Jeddah, and Dammam have shown moderate pollution levels of Cd, As, Pb, and Zn. On the other hand, Cu. Zn, Cu, Cr, Pb, Ni, As, and Cd had degrees of enrichment levels that varied from significantly enriched to extremely highly enriched in the ACFD of the three cities. Heavy pollution is found in Jubail, which posed a higher potential ecological risk than in Jeddah and Dammam. Cd presents the highest ecological risk factors (ER) in the three cities. Carcinogenic and non-carcinogenic risks for children and adults follow the order: Jeddah > Dammam > Jubail, and the ingestion pathway was the main route for exposure. Carcinogenic and con-carcinogenic risks in the mosques of the various studied cities were generally within the acceptable range.

Air Quality Over Major Cities of Saudi Arabia During Hajj Periods of 2019 and 2020.

Mecca and Madinah are two holy cities where millions of people in general, visit throughout the years, during Hajj (Muslim's pilgrimage) time number of people visit these holy cities from different parts of the world is very high. However, the Government of Saudi Arabia only allowed 1000 pilgrims during the 2020 Hajj especially when the world is suffering from COVID-19. In the present paper, a detailed analysis of air quality parameters available from ground measurements have been carried over major cities of Saudi Arabia, Mecca, Madinah, and Jeddah from June to September 2019 and 2020. At Mecca and Jeddah, PM10, NO2 and CO concentrations are found to be higher in comparison to stations located close to Madinah. In addition, meteorological parameters, temperature, relative humidity, and wind directions are also analysed to understand changes associated with the meteorological parameters. Our detailed analysis shows a reduction in concentrations of pollutants during the 2020 Hajj, when the lockdown was observed in Saudi Arabia due to COVID-19. During June-August 2020 lockdown period, no major changes in PM10 concentration was observed since there were frequent dust events were observed. In contrast, our results show 44% reduction in NO2 (8.77 ppbv in 2019 to 4.97 ppbv in 2020) and 16% reduction in CO (0.85 ppm in 2019 to 0.72 ppm in 2020) concentrations during COVID-19 restrictions. The concentrations of NO2 and CO do not cause any issue for the air quality as NO2 and CO Indices lie within the green band (Air quality index 0-50). In Mecca, Madinah and Jeddah, the air quality is generally affected during Hajj, but during 2020, the concentration of particulate matter was influenced by local weather conditions.

Risk-based framework for optimizing residual chlorine in large water distribution systems.

Managing residual chlorine in large water distribution systems (WDS) to minimize human health risk is a daunting task. In this research, a novel risk-based framework is developed and implemented in a distribution network spanning over 64 km2 for supplying water to the city of Al-Khobar (Saudi Arabia) through 473-km-long water mains. The framework integrates the planning of linear assets (i.e., pipes) and placement of booster stations to optimize residual chlorine in the WDS. Failure mode and effect analysis are integrated with the fuzzy set theory to perform risk analysis. A vulnerability regarding the probability of failure of pipes is estimated from historical records of water main breaks. The consequence regarding residual chlorine availability has been associated with the exposed population depending on the land use characteristics (i.e., defined through zoning). EPANET simulations have been conducted to predict residual chlorine at each node of the network. A water quality index is used to assess the effectiveness of chlorine practice. Scenario analysis is also performed to evaluate the impact of changing locations and number of booster stations, and rehabilitation and/or replacement of vulnerable water mains. The results revealed that the proposed methodology could facilitate the utility managers to optimize residual chlorine effectively in large WDS.