Emerging mercury and methylmercury contamination from new artisanal and small-scale gold mining along the Nile Valley, Egypt.

The past decade witnessed the initiation and boom of the Artisanal and Small-scale Gold Mining (ASGM) activities in the hyper-arid southern Egypt. The ores are mined in the Eastern Desert and then transported to the densely populated farming communities in the Nile Valley, where the river provides the water resources needed for ore processing. In search for economic benefits, the poorly educated farmers with limited technical resources transformed their cultivated lands into ASGM operations, exposing themselves, their families, the residents, and the Nile ecosystems to several environmental and occupational health problems. Using integrated remote sensing, field, geochemical, and isotopic analyses, we report the first inventory of ASGM-related total mercury (THg) and methylmercury (MeHg) levels in tailings, amalgamation-tailing ponds, and surface and groundwater with emphasis on the Edfu city and its surroundings. The field and remote sensing-based mapping of ASGM activities reveals clustering around the Nile waterways and suggests interaction of Hg contamination sources with their surrounding receptors. Common ASGM practices include release of contaminated water from unlined amalgamation-tailing ponds into irrigation and drainage canals, and spreading of tailings over cultivated soils. In a short period (10 years), the released Hg contaminated multiple media, including the surface water, the shallow and deep aquifers, and possibly the soil, crops, and livestock. THg levels in amalgamation-tailing ponds (1200-8470 ng/L) are fourfold higher than US EPA and eightfold the WHO thresholds. The contaminated waters released from amalgamation-tailing ponds raised THg levels in surface water (irrigation canals: 50-100 ng/L; drainage canals: THg: > 200 ng/L) and groundwater (shallow and deep aquifers: 80-500 ng/L). Our findings highlight the need to extend the adopted approach to cover the entire length of the Nile River and its valley and the importance of conducting awareness campaigns to educate residents and health care providers about potential ASGM-related environmental and health hazards.

Advances on concrete strength properties after adding polypropylene fibers from health personal protective equipment (PPE) of COVID-19: Implication on waste management and sustainable environment.

Using Health personal protective equipment (PPE) such as face masks, safety foot shoes and protective suits has expanded dramatically due to COVID-19 pandemic leading to a widespread distribution of the PPE, particularly the face masks, in the environments including streets, dump sites, seashores and other risky locations. The environmental degradation of polypropylene, the essential plastic component in single-use face masks (SUM), takes between 20 and 30 years and thus it is essential to develop experimental approaches to recycle the polypropylene or to reuse it in different ways. This paper explores the integration of SUM into concrete structures to improve its mechanical properties. We first to cut the inner nose wire and ear loops, then distribute the PPE material among five different mixed styles. The PPE were applied by volume at 0%, 1%, 1.5%, 2.0%, and 2.5%, with tests focusing on UCS, STS, FS, and PV to determine the concrete's overall consistency and assess the improvement in its mechanical properties. The results showed that adding PPE improves the strength properties and general performance of the concrete specimens. The pattern of rising intensity started to fade after 2%. The findings demonstrated that adding PPE fibers enhanced the UCS by 9.4% at the optimum 2% PPE. The PPE fibers, on the other side, are crucial in calculating the STS and FS of the reinforcement concrete.

Assessment of supplied water quality during mass gatherings in arid environments.

Mass gathering events commonly encounter environmental challenges that necessitate assurance of water quality and food security. The current outbreak of the coronavirus disease 2019 (COVID-19) call for maintaining safe drinking water supply and providing assessment tools of drinking water quality to avoid contamination in water sources or distribution networks. Arid environmental conditions also add more stress on supplied water to mass gathering events. Herein, we assess the quality of the water supply (desalinated 95% and groundwater 5%) in Makkah city, Saudi Arabia during a mass gathering event in 2019 (9.6 million people) for religious purposes. Fifty five samples were randomly collected from nine different districts of Makkah city, analyzed for TDS, turbidity, pH, EC, free Cl2, Al, Cd, Pb, Cr, F, major ions, coliform and E.coli bacteria and were finally used to estimate the water quality index (WQI). Major ions, trace elements and heavy metals analyses show values below permissible limits in most of the samples, while a few samples show slightly higher values. No bacterial count found in any sample. WQI values of all fifty-five samples were below 50 and were identified as "excellent water". The WQI variations could be attributed to the distribution network conditions rather than a direct impact of adding groundwater with uncontrolled chemical composition. The use of WQI to report the quality of water during mass gathering events to governmental authorities has been proved to be beneficial and should be applied for further mass gathering events worldwide.

Buffering the impacts of extreme climate variability in the highly engineered Tigris Euphrates river system.

More extreme and prolonged floods and droughts, commonly attributed to global warming, are affecting the livelihood of major sectors of the world's population in many basins worldwide. While these events could introduce devastating socioeconomic impacts, highly engineered systems are better prepared for modulating these extreme climatic variabilities. Herein, we provide methodologies to assess the effectiveness of reservoirs in managing extreme floods and droughts and modulating their impacts in data-scarce river basins. Our analysis of multiple satellite missions and global land surface models over the Tigris-Euphrates Watershed (TEW; 30 dams; storage capacity: 250 km3), showed a prolonged (2007-2018) and intense drought (Average Annual Precipitation [AAP]: < 400 km3) with no parallels in the past 100 years (AAP during 1920-2020: 538 km3) followed by 1-in-100-year extensive precipitation event (726 km3) and an impressive recovery (113 ± 11 km3) in 2019 amounting to 50% of losses endured during drought years. Dam reservoirs captured water equivalent to 40% of those losses in that year. Additional studies are required to investigate whether similar highly engineered watersheds with multi-year, high storage capacity can potentially modulate the impact of projected global warming-related increases in the frequency and intensity of extreme rainfall and drought events in the twenty-first century.

Groundwater mounding: A diagnostic feature for mapping aquifer connectivity in hyper-arid deserts.

Shallow aquifer mapping and large-scale characterization of groundwater dynamics in the Saharan-Arabian Desert is largely impeded by the limited hydrological datasets from sparse and unevenly distributed well logs. Today, as these aquifers are depleting at alarming rates in response to climatic and anthropogenic stresses, accurate knowledge of their dynamical characteristics is not only essential for understanding the water deficit in these increasingly populated areas but also to understand the regional and global environmental impacts of such changes. Herein, we suggest that groundwater mounding can be used for assessing aquifer connectivity in hyper-arid deserts. Using the shallow Post Nubian Aquifer System (PNAS) in Egypt as a test site, we integrate remote sensing, isotopic, hydrochemical and geoelectrical methods to characterize the Saharan groundwater mounds, examine the structural control on groundwater dynamics and discuss the potential of future satellite missions to characterize aquifer connectivity. The results suggest that groundwater mounding in the PNAS is attributed to artesian discharge of the deep Nubian Aquifer System (NAS) along the intersection of WNW and E-W major faults. This is evident by the dominant isotopic signature (δ18O: -9.93‰; δ2H: -79.05) of the deep NAS in the shallow PNAS with a percentage of up to 85% in the faulted zone. The 2D-Electrical Restively Imaging (ERI) delineate multiple small-scale mounds, atop of faults, that can attain 37 m height above average water table creating a relatively steep hydraulic gradient and deviating the groundwater flow direction. Future orbital radar sounding missions can benefit from characterizing the geometry of these mounds to define the measurement requirements of such hydrological features. The large-scale time-coherent subsurface mapping of the Saharan-Arabian aquifers can provide unique insights to examine the aquifer connectivity and the response of aquifers to climatic and anthropogenic stresses in desert areas that otherwise cannot be addressed using existing sporadic well-logs.

The respective roles of modern and paleo recharge to alluvium aquifers in continental rift basins: A case study from El Qaa plain, Sinai, Egypt.

Even though assessment of aquifer characterization and recharge mechanisms in rift-related basins, especially in arid environments, is essential for developing sustainable management strategies and food security assurance, a little attention has been paid to understand these parameters. In this manuscript, we utilize an integrated remote sensing, hydrological and isotopic approach together with previously published data to better understand the aquifer characteristics and the respective roles of modern and paleo recharge to the post-Miocene alluvium aquifer in El Qaa plain, which represents the eastern margin of the Gulf of Suez continental rift basin. Our findings indicate that: (1) the alluvium aquifer is largely formed of sand and gravels intercalated with silt and clay lenses and exceeds 500 m thick, (2) the groundwater salinity gradually increases towards the Gulf of Suez (from 402 to 5613 mg/l) with increasing the distance from the crystalline rocks bounding the alluvium-dominated plain, (3) isotopic analysis reveals that all of the groundwater samples show mixed isotopic signature between modern and paleo waters (δ18O: -6.79 to -4.433‰, and δ2H: -46.36 to -21.99‰). Basin-scale hydrological parameters show that the aquifer receives an annual modern recharge of 39 × 106 m3 and isotopic mass balance calculations indicate that the modern water ranges between 20 and 70% of the total volume of water in the aquifer. We suggest three dam locations along the southernmost basins in El Qaa plain to enhance the modern recharge to the aquifer and to harvest surface runoff of an annual volume of 737 × 103 m3 sufficient to supply freshwater to 13 thousands of the residents of south Sinai. The present study suggests that topographically-driven modern recharge to rift-related basins is taking place with significant amounts even under hyper-arid conditions and calls for paying special attention to investigate the response of these aquifers to climate variability.

Inferencing the land subsidence in the Nile Delta using Sentinel-1 satellites and GPS between 2015 and 2019.

The Nile Delta is home to half of Egypt's population and has ample agricultural, industrial, and cultural resources, yet the land subsides in response to many natural and anthropogenic impacts. We report the recent subsidence rate and patterns in the Nile Delta using the synthetic aperture radar Sentinel-1 data of 144 images obtained between 2015 and 2019, based on coherence small baseline subset interferometry of ~2900 interferograms. We distinguished three patterns of deformation due to three different physical mechanisms: 1) The land subsides with rates ranging from -12 to -20 mm/year in major cities (such as Zagazig, Mit Ghamr, Tanta, Mansoura and Mahla) due to urban-induced loading; 2) A subsidence rate ranges between -3 and -8 mm/year along the coastal margins due to natural sediment dewatering and compaction. This rate is consistent with the global positioning system rate of -3.5 mm/year and 3) A subsidence rate ranges from -20 to -16 mm/year and -6 to -12 mm/year in newly reclaimed lands on the west and east of the delta's flood plains, respectively, due to groundwater overexploitation. Our findings, in contrast with results from previous studies of regional deformation mainly felt to be controlled by natural processes, demonstrate a localized subsidence and predominant anthropogenic control on the land deformation and call for revisiting sea level rise-related flooding models in the Nile Delta. In light of the new findings, the authorities should take necessary measures to reduce the ongoing land subsidence through enforcement of urban planning policies in the delta's flood plain and development of a sustainable management strategy for groundwater extraction.

Response of deep aquifers to climate variability.

There is a general agreement that deep aquifers experience significant lag time in their response to climatic variations. Analysis of Temporal Gravity Recovery and Climate Experiment (GRACE), Soil Moisture and Ocean Salinity mission (SMOS), satellite altimetry, stable isotopic composition of groundwater, and precipitation and static global geopotential models over the Nubian Sandstone Aquifer System (NSAS) revealed rapid aquifer response to climate variability. Findings include: (1) The recharge areas of the NSAS (Northern Sudan Platform subbasin) witnessed a dry period (2002-2012), where average annual precipitation (AAP) was modest (85 mm) followed by a wet period (2013-2016; AAP: 107 mm), and during both periods the AAP remained negligible (<10 mm) over the northern parts of the NSAS (Dakhla subbasin); (2) the secular trends in terrestrial water storage (TWS) over the Dakhla subbasin were estimated at -3.8 ±â€¯1.3 mm/yr and + 7.8 ±â€¯1 mm/yr for the dry and wet periods, respectively; (3) spatial variations in TWS values and phase are consistent with rapid groundwater flow from the Northern Sudan Platform subbasin and Lake Nasser towards the Dakhla subbasin during the wet period and from the lake during the dry period; and (4) networks of densely fractured and karstified bedrocks provide preferential pathways for groundwater flow. The proposed model is supported by (1) rapid response in groundwater levels in distant wells (>280 km from source areas) and in soil moisture content in areas with shallow (<2 m) groundwater levels to fluctuations in Lake Nasser surface water, and (2) the isotopic composition (O, H) of groundwater along the preferred pathways, consistent with mixing of enriched (Lake Nasser water or precipitation over Sudan) and depleted (NSAS fossil water) endmembers. Findings provide new insights into the response of large, deep aquifers to climate variability and address the sustainability of the NSAS and similar fossil aquifers worldwide.