Sand filtration systems (SF) are a well-established approach in ensuring the availability of clean water. Understanding the transport properties of colloidal particles within SF systems is of paramount importance for optimizing their performance. This study investigated the potential utilization of silica-encapsulated DNA particles, equipped with a magnetic core to enhance particle separation and quantification efficiency (SiDNAMag). These particles were evaluated as tracers for delineating complex pathways and conducting source tracking within sand filtration (SF) systems for particulate substances. The study focused on exploring the sensitivity of SiDNAMag to solution chemistry, while elucidating the underlying mechanisms governing their transport and retention in sand filtration systems. Laboratory columns and HYDRUS-1D modeling were employed to analyze a range of water chemistry solutions, encompassing NaCl, NaHCO₃, CaCl₂, and MgCl₂, with ionic strengths ranging from 0.1 mM to 20 mM. The results revealed that the transport of DNA-tagged silica particles could be described by a first-order kinetic attachment and detachment rate coefficient. Elevated ionic strengths consistently led to increased particle adhesion and decreased rates of detachment. The sticking efficiencies of SiDNAMag particles exhibited a range of 0.7 to 1. The remarkable adhesive effectiveness can be ascribed to the comparatively low negative charge exhibited by SiDNAMag particles. This leads to the creation of unstable colloids and encourages the aggregation of these colloidal particles, thereby limiting the potential application of these particles as a tracer. In conclusion, this work underlines the potential of SiDNAMag particles as a potential subsurface tracer. However, further research is warranted to investigate strategies for reducing the interaction between these particles and sand, particularly in response to the chemistry of the infiltrated water.

The present investigation involved the production of roof tile samples through the replacement of kaolin clay with varying proportions of Ferrosilicon slag (FS) (0%, 10%, 15%, 20%, and 25% by weight) at different firing temperatures (900 °C, 1000 °C, and 1100 °C). The present study investigated the impact of incorporating FS slag waste on durability, mechanical strength, thermal shock resistance, and thermal properties. Furthermore, an examination of the microstructure of the fired roof tiles was conducted through SEM analysis. The properties of the roof tiles exhibited enhancement as the percentage of FS slag increased, reaching a maximum of 15%, and the firing temperature increased up to 1000 °C. This can be attributed to the formation of significant amounts of corundum phase. Increased temperature and a higher percentage of FS slag are associated with the generation of a significant quantity of cristobalite phase, resulting in a reduction in the mechanical properties of roof tiles. The roof tile samples fabricated with up to 15% FS slag at 1000 °C exhibited low water absorption and porosity. Increases in temperature and FS slag, on the other hand, resulted in an increase in water absorption and porosity. There were no observable impacts on water absorption and apparent porosity at 900 °C. The firing temperature of 1000 °C and a slag percentage of 15% resulted in a minimum water absorption of 9.8%. This value meets the standard requirements for moderate weather resistance. Notwithstanding the increase in density of roof tiles containing elevated proportions of FS slag, they continue to fall within the limits of lightweight roof tiles as stipulated by determined standards. The experimental results indicate that the incorporation of 15% FS slag and firing at a temperature of 1000 °C resulted in a significant increase of 34.9% in the transverse breaking strength (TBS) of the clay roof tiles when compared to the conventional sample. This suggests that the structural properties of the clay roof tiles were improved through the addition of FS slag.

Recently, superparamagnetic silica encapsulated DNA microparticles (SiDNAFe) were designed and in various experiments used as a hydrological tracer. We investigated the effect of bed characteristics on the transport behaviour and especially the mass loss of SiDNAFe in open channel injection experiments. Hereto, a series of laboratory injection experiments were conducted with four channel bed conditions (no sediment, fine river sediment, coarse sand, and goethite-coated coarse sand) and two water qualities (tap water and Meuse water). Breakthrough curves (BTCs) were analysed and modelled. Mass loss of SiDNAFe was accounted for as a first-order decay process included in a 1-D advection and dispersion model with transient storage (OTIS). SiDNAFe BTCs could be adequately described by advection and dispersion with or without a first-order decay process. SiDNAFe mass recoveries exhibited a wide range, varying from 50% to 120% from sediment-free conditions to coarse (coated) sediment. In 6 out of 8 cases, SiDNAFe mass recovery was complete. Retention of SiDNAFe was 1–2 orders of magnitude greater than gravitational settling rates, as determined in Tang et al. (Hydrological Processes, e14801, 2023). We reason this was due to grain-scale hyporheic flows and coupled water-sediment-particle interactions. The dispersive behaviour of SiDNAFe generally mimicked that of NaCl tracer. We concluded that SiDNAFe can be used in tracing experiments. However, water quality and sediment characteristics may affect the fate of SiDNAFe in river environments. SiDNAFe is a promising tool for particulate multi-tracing in large rivers.

In the terrestrial environment, interactions between natural organic matter (NOM) and colloids can lead to the formation of an environmental corona around colloids, influencing their transport behaviour and, ultimately, their ecotoxicity. We used a synthetically designed colloid tagged with DNA (DNAcol) as a surrogate for natural colloids and investigated its transport in saturated sand columns. We varied the concentrations of NOM and ionic strength (CaCl₂), to better understand the transport and release of DNAcol in porous media under both steady and transient porewater chemistry conditions. In addition, we aimed to understand the main factors that control deposition and release of DNAcol under tested conditions. To induce transient chemistry, we replaced the injection solution containing NOM and/or CaCl₂ with Milli-Q water. The results showed that the deposition rate of DNAcol was inversely proportional to the concentration of NOM. The deposition rate increased significantly even under low ionic strength (CaCl₂) conditions of tested conditions. Notably, the influence of NOM on the transport of DNAcol was most pronounced at the lowest range of [Ca²⁺]/DOC ratios, and the attachment of DNAcol to the sand grains was negligible. Moreover, the results showed while the DLVO theory captured the general trend of experimental results, it significantly underestimated the deposition of DNAcol in the presence of CaCl₂. Under transient porewater chemistry conditions, colloid remobilization was observed upon flushing the column with Milli-Q water, leading to a secondary peak in the breakthrough curves. We observed that under transient porewater chemistry conditions, when the ionic strength of the solution was 10 mM, the magnitude of the remobilization peak was more significant compared to conditions with 1 mM ionic strength. Our work emphasized the complex interplay between water quality on the one hand and deposition and release of colloidal matter in saturated porous media on the other hand.

The numerous hydrothermal alteration zones and subsurface structures affecting the mineralized deposits of the Dungash region were identified using aeromagnetic data. The Center of Exploration Targeting (CET) approach and several filters, such as reduction-to-pole, Tilt derivative, First Vertical Derivative, Horizontal gradient map, Downward continuation, analytical signal methods, regional, and residual separation, were used to analyze the aeromagnetic data. The research region is impacted by several structural trends running in the N-S, E-W, NW-SE, and NE-SW directions, and these trends are strongly related to the gold mineralization and surrounding hydrothermal alteration zones. In the NW-SE direction, four alteration zones have been identified. The research region's northern and eastern regions have shallower basement relief, with depths of only approximately 100 m, and those depths show that the area is rootless. Conversely, the basement relief and surface depths are lower in the study region's western and southern regions. The routes taken by the ascending hydrothermal fluids can be seen as aeromagnetic lineaments at the hydrothermal alteration zones. Mineralization appears to be linked to structural lineaments, as evidenced by airborne magnetic data. For gold prospecting, the aeromagnetic technique seems to be the most effective and efficient geophysical method because gold is typically found in severely deformed shear zones and faults.

In order to cope with the rise in human-caused demands, Saudi Arabia is exploring new groundwater sources. The groundwater potential of Wadi Ranyah was studied using a multi-dataset-integrated approach that included time-variable gravity data from the Gravity Recovery and Climate Experiment (GRACE), vertical electrical sounding (VES), and time-domain-electromagnetic (TDEM) data with other related datasets to examine the variations and occurrence of groundwater storage and to define the controlling factors affecting the groundwater potential in Wadi Ranyah in southwestern Saudi Arabia. Between April 2002 and December 2021, the estimated variation in groundwater resources was −3.85 ± 0.15 mm/yr. From 2002 to 2019, the area observed an average yearly precipitation rate of 100 mm. The sedimentary succession and the underlying fractured basement rocks are influenced by the structural patterns that run mainly in three different trends (NW, NE, and NS). The sedimentary cover varies from 0 to 27 m in thickness. The outputs of the electrical sounding revealed four primary geoelectric units in the study area: on top, a highly resistant geoelectrical unit with a resistivity of 235–1020 Ω.m, composed of unsorted, loose, recent sediments; this is followed by a layer of gravel and coarse-grained sands with a resistivity of 225–980 Ω.m; then, a water-bearing unit of saturated sediments and weathered, fractured, basement crystalline rocks with a resistivity of 40–105 Ω.m, its depth varying from 4 to ~9 m; and then the lowest fourth unit composed of massive basement rocks with higher resistivity values varying from 4780 to 7850 Ω.m. The seven built dams store surface-water runoff in the southwestern part of the wadi, close to the upstream section, in addition to the Ranyah dam, as the eighth one is located in the middle of the wadi. The subsurface NW- and NS-trending fault lines impede the groundwater from flowing downstream of the wadi, forming isolated water-bearing grabens. Minimal surface runoff might occur in the northern part of the wadi. The combined findings are beneficial because they provide a complete picture of the groundwater potential of Wadi Ranyah and the controlling structural patterns. Using this integrated technique, the groundwater potential in arid and semiarid regions can now be accurately assessed.

The Nubian Sandstone Aquifer System (NSAS) is made up of three major sub-basins: Kufra, Dakhla, and the N. Sudan Platform. It is one of the world’s largest groundwater systems. The aquifer’s hydrologic setting, connectivity of its sub-basins, and groundwater flow across these sub-basins are currently unclear. To address these issues, we used a combined approach that included: (1) a regionally calibrated groundwater flow model that mimics early (>10,000 years) steady-state conditions under wet climatic periods and later (<10,000 years BP–1960; 1960–2010) transient conditions under arid climatic periods; and (2) groundwater ages (³⁶ Cl,⁸¹ Kr) and isotopic (¹⁸ O,² H) data. The NSAS was recharged on a regional scale in previous wet climatic periods; however, in dry periods, its outcrops are still receiving local modest recharge. A progressive increase in³⁶ Cl groundwater ages was found along groundwater flow directions and along structures that are sub-parallel to the flow direction. The NE–SW Pelusium mega shear zone is a preferential groundwater flow conduit from the Kufra to the Dakhla sub-basin. The south-to-north groundwater flow is hampered by the Uweinat–Aswan basement uplift. The findings provide useful information about the best ways to use the NSAS.

In the Middle East, water shortage is becoming more and more serious due to the development of agriculture and industry and the increase in population. Saudi Arabia is one of the most water-consuming countries in the Middle East, and urgent measures are needed. Therefore, we integrated data from Gravity Recovery and Climate Experiment (GRACE), and other relevant data to estimate changes in groundwater storage in Saudi Arabia. The findings are as follows: 1) Average annual precipitation (AAP) was calculated to be 76.4, 90, and 72 mm for the entire period, Period I (April 2002 to March 2006) and Period II (April 2006 to July 2016), respectively. 2) The average TWS variation was estimated to be −7.94 ± 0.22, −1.39 ± 1.35, and −8.38 ± 0.34 mm/yr for the entire period, Period I and Period II, respectively. 3) The average groundwater storage was estimated to be +1.56 ± 1.35 mm/yr during Period I. 4) The higher average groundwater depletion rate was calculated to be −6.05 ± 0.34 mm/yr during Period II. 5) Both soil texture and surface streams in the study area promote lateral flow and carry surface water to the Arabian Gulf and the Red Sea. 6) During Period II, average annual recharge rates were estimated to be +9.48 ± 2.37 and +4.20 ± 0.15 km³ for Saudi Arabia and the Saq aquifer, respectively. 7) This integrated approach is an informative and cost-effective technique to assess the variability of groundwater resources in large areas more efficiently.

This study used land gravity and airborne magnetic data to investigate the depth to the magmatic chamber and map the heat flow distribution beneath the active volcanoes of Hawaii Island using the Curie point depth (CPD) and gravity modeling. Obtaining some of the ground-based geophysical measurements was problematic due to accessibility limitations; therefore, this study used available data. The CPD and magnetic data were used to map the depth to the bottom of the magnetic layer by calculating the depth to the Curie isotherm (540°C) beneath Hawaii Island. The spectral peak method was used to calculate the depths to the shallow and deep magnetic sources for the entire island, and the CPD was calculated using the centroid method. A two-dimensional density model for two Earth layers was constructed using forward modeling of the gravity data. A large plume of dense intrusive material was observed beneath the three adjacent volcanoes of Mauna Loa, Mauna Kea, and Kilauea, and two small chambers were found to be located beneath the Kohala and Hualalai volcanoes. Based on the gravity modeling results, the depth to the magma layer varied from 0.5 to 10 km, and the heat flow was higher close to the volcanic eruption zones. The current study is informative and cost effective for the world’s most active volcanic areas.

Building insulation based on nanomaterials is considered one of the most effective means of reducing energy consumption in the hot desert climate. The application of an energy-efficient insulation system can significantly decrease the energy consumed via a building’s air-conditioning system during the summer. Hence, building insulation has become an interesting research topic, especially with regards to the use of insulation based on nanomaterials due to their low U-values. In the present study, the use of nano vacuum insulation panels (VIPs) or polystyrene foam in the walls enabled a significant reduction in the annual energy consumption, a savings of 23% compared to the uninsulated wall in a study in New Aswan City. The application of nanogel glazing to the windows (two layers of clear glass filled with the nanogel) achieved approximately 11% savings in annual energy. This savings, twice that obtained by using double-glazed windows, could be due to the low U-value of nanogel compared to the U-values of argon or air. The embedded nanogel layer between two layers of argon and two layers of single clear glass showed a significant reduction in annual energy consumption, saving 26% compared to the use of a single layer of glass. Moreover, the integration between this window and embedded walls with 50 mm of polystyrene foam exhibited a significant improvement of energy efficiency by 47.6% while presenting the lowest value of simple payback period (SPP). This research provides a way for buildings to be insulated to make them more energy efficient as well as attractive from the economic standpoint.