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Concentrations of black carbon (BC), organic carbon (OC), and total suspended particulate matter (TSP) were simultaneously assessed in urban, rural and residential areas in Jeddah city for one year from January to December 2017. It was aimed in the present study to provide information about the spatial and seasonal variability of these aerosol species in Jeddah, and insight into sources, processes and effects of meteorological conditions. To the best of our knowledge, this is the first study investigating the variability of carbonaceous aerosols (OC and BC) in Saudi Arabia. The average concentrations of OC, BC, and TSP varied spatially and temporally. The annual average concentrations of OC, BC, and TSP were 134.05, 7.16, and 569.41 μg m-3 and 34.32, 5.14, and 240.64 μg m-3 and 10.67, 4.39 and 101.31 μg m-3 in the urban, residential and rural areas, respectively. Moreover, there was a clear seasonal variation in the concentration of carbonaceous aerosols; the highest concentrations were recorded in February and September, while the lowest concentrations of OC were recorded during April, May and August in the urban, residential and rural sites, respectively. Nevertheless, the lowest concentrations of BC were recorded during March in the urban and residential sites and during November in the rural site. The relative concentrations of OC and BC to the TSP were relatively high, and they have a significant correlation with prevalent wind speed (-0.636, and -0.581 in the urban area), (-0.539 and -0.511 in the residential area), and (-0.508 and -0.501 in the rural area), respectively. The marked differences in the concentrations of BC and OC were reflected on OC/BC ratio, which is a good representative of different source types. This preliminary study showed that the potential local sources were emissions from traffic (fossil fuel), biomass burning, anthropogenic activities (e.g. car drifting and outdoor cooking), and industrial activities. The present study suggest the presence of highly inefficient combustion sources and highlight the need for the regulation of such emissions.

A systematic study was performed in the arid coastal aquifer to evaluate groundwater quality using drinking water quality indices (DWQI) and health risk assessment models in southern Saudi Arabia. Groundwater samples were collected (n = 80) and analysed for major and minor ions. Results suggest that 85% of wells are unsuitable for drinking due to high salinity and hardness. Likewise, high NO

Gravity Recovery and Climate Experiment (GRACE) data, along with readily available remote sensing datasets and the outputs of land-surface and climate models, are used to monitor spatiotemporal variabilities in the groundwater resources of the Red Sea Coastal Aquifer (RSCA) system in Saudi Arabia; to investigate their responses to climate projections; and to provide sustainable and resilient management scenarios for these resources. Our results indicate that, during the investigated period (April 2002–June 2017), the RSCA received an average annual recharge of 3.16 ± 0.52 km3. Recharge events (~16% of rainfall) are related to the observed increase in rainfall rates. Analysis of climate models' outputs over the RSCA indicates an increase in the median annual rainfall (17–31%) and recharge rates (2.7–4.9%) by the end of the 21st century. To ensure sustainable management and utilization of RSCA's water resources, groundwater extraction should be located in the southern and central parts of the aquifer, and groundwater extraction rates should be kept lower than 2.0 km3/yr. Findings highlight the importance of GRACE data as a unique, cost-effective, and decisive tool in monitoring the health of coastal and inland aquifer systems across the globe.

PAHs were extracted and quantified in meat and chicken grilled with wood charcoal at two levels (medium- and well-done) by GC–MS and estimated the dietary exposure of Egyptian population for first ...

The present study focused on developing the predominant relationships between morphological and morphological-hydrological parameters of watersheds in the Makkah Al-Mukarramah region, Kingdom of Saudi Arabia (KSA). These relationships are essential for flood mitigation studies in the region. The relationships developed in this study are averaged over 43 watersheds (varying in size from 42.2 to 6081.4 km2) to provide a theoretical basis for regional morphological and hydrological analyses. In addition, the similarity of the hydrologic response of these watersheds is studied via the theory of geomorphological instantaneous unit hydrograph (GIUH). The results show that there is a relatively high similarity among the 43 basins (the average similarity parameter is 0.61, and the values vary from 0.57 to 0.68 at 95% confidence). Comparisons of the peaking factor between the Soil Conservation Service (SCS) and the Arid-Zone, Ari-Zo, (Albishi et al., Arabian Journal of Geosciences 10:1–13, 2017) models show that the common SCS model underestimates the peak discharge. The time of concentration is overpredicted by the Kirpich (Civil Engineering 10:362, 1940) equation (up to 17 times) compared to the Ari-Zo model. The GIUH and SCS models overestimate the time to peak when compared with the Ari-Zo model. These results are crucial for flood estimation and mitigation in the region.

Plastic pollution and its impact on marine ecosystems are major concerns globally, and the situation was exacerbated after the outbreak of COVID-19. Clean-up campaigns took place during the summer season (June–August 2020) in two coastal cities in Egypt (Alexandria and Hurghada) and Jeddah, Saudi Arabia to document the abundance of beach debris through public involvement, and then remove it. A total of 3673, 255, and 848 items were collected from Alexandria, Hurghada, and Jeddah daily, respectively. Gloves and face masks (personal protective equipment “PPE”) represent represented 40–60% of the total plastic items collected from each of the three cities, while plastic bags represented 7–20% of the total plastics litter collected from the same cities. The results indicated the presence of 2.79, 0.29, and 0.86 PPE item m−2 in Alexandria, Hurghada and Jeddah, respectively. This short focus provides an assessment of the environmental impacts of single-use gloves and masks used for COVID-19 protection from June to August 2020. To the best of our knowledge, this study presents the first such information from the Middle East, specifically Egypt and Saudi Arabia. It highlights the need for further knowledge and action, such as safe, sustainable, and transparent waste management processes related to COVID-19 to reduce the negative impacts now, as well as in future events. Furthermore, this study helps in achieving key components of the United Nation's Sustainable Development Goals (SDGs). This short focus can serve as a multipurpose document, not only for scientists of different disciplines but for social media and citizens in general.

A unified and systematic approach for hydrological modeling is presented for assessing flood hazards in arid and semi-arid regions with wadi Itwad as a case study. The approach consists of the following steps: (1) estimation of the design storm duration, (2) estimation of the design rainfall depth, (3) development of the design storm hyetograph, (4) setup of the watershed hydrological system, (5) infiltration tests for estimate of soil characteristics, (6) land use and land cover analysis for curve number estimation, (7) how to incorporate dams (if any) and their reservoir characteristics for reservoir routing analysis, and (8) performing hydrological modeling under different scenarios, namely: lumped with and without the effect of dams and routed scenarios. An emphasis is made on the comparison between the SCS unit hydrograph and the unit hydrograph (UH) estimated for stream flow data. The UH method produces hydrographs that are typical of arid regions. It is characterized by a steep rising limb with a short time to peak, a rapid recession to zero base flow, and less flood volume due to transmission losses. The scenarios show that the lumped case overdesigns the protection schemes, while the lumped central basin with detention dams storing the flood water completely leads to underdesign in the downstream area. The routed scenario is more realistic, since it considers the detention dams with an overflow. The runoff volume (66.6 MCM) of the 10-year return period of the routed scenario is in the order of magnitude within the observed historical data (50 to 100 MCM) reported in the literature. The study concludes that the proposed approach is robust and takes into account the Saudi arid environment while performing flood risk assessment in KSA.

This study focused on the impact of flash flood (FF) on trace metal pollution in the groundwater, Wadi Baysh Basin, Western Saudi Arabia using spatial interpolations, integrating pollution indices and statistical analysis. Groundwater (n = 182) is neutral to alkaline in nature and the order of mean metals before and after FF are Sr > Ba > B > Fe > Al > V > Mn > Cr > Cu=Pb > Mo > Zn and Sr > Al > B > Fe > V > Ba > Cr > Cu > Pb > Mn > Mo > Zn > Ni > Cd, respectively. Enhancement (Al, Cr, Cu, Mn, Mo, Pb and V) and depletion (B, Ba, Fe, Sr) of trace metals are noticed in the groundwater after FF, which is due to dilution, dissolution/desorption, flushing of weathered layer, saline sources and surface input. Before and after FF, 57–63%(Pb), 55–56%(V), 43-16%(B), 27-0%(Ba), 15-5%(Sr), 6-3%(Fe), 0–16%(Al), 0–9%(Cr) and 1–2%(Mn) of groundwater samples, respectively, exceeded the drinking water standards. Coastal wells have elevated B, Sr and Mn concentration due to saline water intrusion. Integrated pollution evaluation indices (Heavy metal pollution index (HPI), Contamination index (Cd) and Heavy metal evaluation index (HEI)) reveal that number of samples in the unsuitable classes are increased after FF event (HPI: 13%–55%; Cd : 11%–38%; HEI: 5%–19%) and groundwater quality is degraded due to the trace metals enhancement after FF especially in the downstream wells. Wells in the upstream is flushed by FF recharge and groundwater flow accumulated the metals in the downstream and coastal region. This study demonstrates that metal accumulation and mobility are regulated by the groundwater flow in the study region. Pearson correlation analysis and Principle component analysis also justify that water chemistry is influenced by the saline sources, flushing of weathered layer, natural processes and anthropogenic inputs. Continuous groundwater monitoring is an important task to protect and manage valuable groundwater resources in the arid region.

Petroleum hydrocarbons are major pollutants in marine environments. The present study describes the potential of a halothermophilic bacterial consortium capable of degrading polycyclic aromatic hydrocarbons (PAHs) in petroleum wastewater under extreme conditions. The consortium was enriched from brine originating from a desalination plant. The consortium efficiently degraded both the low molecular weight (LMW) PAHs-naphthalene (NAP), phenanthrene (PHN), anthracene (AN) and fluorene (FLU) as well as the high molecular weight (HMW) PAHs-pyrene (PY), benzo(e)pyrene (B(e)P) and benzo(k)fluoranthene (B(k)F), respectively. A nearly quantitative release of carbon dioxide (85 ± 1.2%) in conjunction with significant reduction of PAH concentration and an increase in bacterial cell count (from 10 4 to 10 9 cfu/mL) pointed at mineralization of PHN. The consortium was able degrade 86± 2.7% and 58± 4.1% of PHN (200 ppm) at 20% and 30% NaCl concentration respectively. Co-metabolism with PHN thereby enhanced the degradation of HMW PAHs. In petroleum refinery wastewater the PAHs were potently degraded by the bacterial consortium with 94 ± 3.8% COD removal in a continuous stirred tank reactor. Ochrobactrum halosaudia strain AJH1, Ochrobactrum halosaudia strain AJH2 and Pseudomonas aeruginosa strain AJH3 were present in the PAH-degrading halothermophilic consortium.

An optical assay for the rapid determination and chemical speciation of Fe2+/Fe3+ species has been proposed for the first time on a polyether sulfone (PES) membrane platform. The small pore size and low wettability (θ ∼82°) of the membrane disallowed the dissipation of analyte droplets on the surface, thus localizing it onto nanoliter arrayed 1,10-phenanthroline spots. Under optimized conditions and within ∼5 min, an acceptable limit of detection (0.1 μg mL-1) and linear dynamic range (1 - 100 μg mL-1) were achieved. The proposed method was also successfully applied for indirect determination of Fe3+ ions in synthetic samples after reduction to Fe2+ using SO2. The performance of the proposed sensor was validated for its robustness and stability. Due to high selectivity and accuracy, the method was satisfactorily applied for the analysis of Fe2+/Fe3+ species in marine water samples. The proposed method is an easy and low-cost system coupled with good reproducibility and ruggedness, applicable for point-of-use testing.

The issues of low photocatalytic activity and dissolution of ZnO in natural sunlight exposure were addressed by implanting p-type Mn3O4 on its surface. The optical analysis revealed the composite nature and suppression of exciton excitons recombination whereas the cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and chronopotentiometry substantiated the elimination of photocorrosion respectively, low charge transfer resistance and better charge retention ability for the as-synthesized composites. The Mott-Schottky analysis by staircase potential impedance spectroscopy (SPIES) verified the p-n nature while the measurement of flat band potential (Vfb) predicted the suitability of the band potentials for the enhanced generation of reactive oxygen species (ROS). The structure and morphology of the Mn3O4-ZnO composites were evaluated by x-ray diffraction (XRD) and field emission electron microscopy (FESEM) whereas the fine structure analysis was performed by high-resolution transmission electron microscopy (HRTEM) analysis that revealed the discrete fringe patterns of p-type Mn3O4 and ZnO in composites. The x-ray photoelectron spectroscopy (XPS) verified the simultaneous existence of Mn2+ and Mn3+ in Mn3O4 nanoparticles. Compared to pure ZnO, due to the existence of charge transfer synergy between the p-type Mn3O4 and n-type ZnO, the composites with moderate Mn3O4 loadings exhibited marked activity for the removal of stable pollutants like 4-bromo and 4-chlorophenol in natural sunlight exposure. The correlation of the findings from various analytic tools of chemical analysis such as high-performance liquid chromatography (HPLC), ion chromatography (IC), total organic carbon (TOC) measurements and GC–MS analysis revealed the persuasive role of Cl and Br groups in regulating the degradation process. The composite catalyst exhibited excellent stability and reproducible activity in the repeated scans.

The use of inexpensive semiconducting materials and abundant natural sunlight can deliver the sustainable as well as cost-effective cleaning of contaminated water. In the current effort, the low photocatalytic activity of ZnO in sunlight exposure has been addressed by the slow deposition and after calcination, the deposition pattern of Fe 3+ ions was investigated. The appearance of distinct multiple absorption edges in the optical spectra verified the composite nature of the synthesized materials whereas the absorption edge at ∼2.5 eV indicated the formation of visible light responsive structures other than Fe 2 O 3 . The additional reflections, besides the characteristic reflections of ZnO and Fe 2 O 3 , in the X-ray diffraction patterns and the appearance of discrete assortments in HRTEM analysis exposed the formation of surface ZnFe 2 O 4 in the interfacial region between the ZnO and Fe 2 O 3 . The X-ray photoelectron analysis revealed the minor transitions in the oxidation state, more pronounced at higher Fe 3+ loadings, during the synthetic route. The electrochemical characterization revealed the p-type nature of the oxides of Fe 3+ whereas the flat-band potentials of the composites were assessed by Mott-Schottky analysis. As compared to pure ZnO, the composites loaded with lower concentrations (0.5% and 1%) of Fe 3+ showed substantially high activity for the removal of 2,4-dichlorophenoxy acetic acid (2,4-D) in the complete spectrum whereas 3% Fe 3+ loading exhibited optimum activity in the exposure of the visible region of natural sunlight. The higher Fe 3+ loadings revealed the detrimental effect on the photocatalytic removal process. The variations in the photocatalytic activity with the increasing Fe 3+ were discussed in correlation with electrochemical properties. The key intermediates were identified and the plausible mechanisms of the removal of 2,4-D were proposed by correlating the evidence from various experimental tools such as HPLC, IC, and TOC. The probable contribution of the reactive oxygen species (ROS) involved in the degradation process was estimated and discussed. The validity of the Langmuir-Hinshelwood kinetic model was also examined for the degradation as well as mineralization process.

The city of Makkah in the Kingdom of Saudi Arabia (KSA) hosts millions of Muslim worshippers every year. As a consequence, the municipal solid waste (MSW) quantities become enormous. City landfills receive about 2.4 thousand tons of MSW every day, whilst during the months of fasting (Ramadan) and Pilgrimage (Hajj), these quantities become 3.1 and 4.6 thousand tons per day respectively. Currently, there is no waste-based biorefinery or waste-to-energy (WTE) facility existing in KSA to treat different fractions of MSW as a source of renewable energy production and a solution to landfill waste problems. Therefore, the waste-based biorefinery, if developed in Makkah city, including WTE technologies such as anaerobic digestion (AD), transesterification, pyrolysis and refuse derived fuel (RDF) can be able to treat around 87.8% of the total MSW. The remaining 12.2% of MSW fraction can be recycled. The waste-based biorefinery, along with the recycling approach, can generate savings of about 87.6 million Saudi Arabian Riyal (SAR) from carbon credits. Similarly, a total net revenue of 758 million SAR can be generated from landfill diversion (530.4 million SAR) and electricity generation (288.5 million SAR). Moreover, 1.95 million barrels of oil and 11.2 million MCF of natural gas can be saved with a cost savings of 485.5 million SAR. Collectively, the waste-based biorefinery and recycling can reduce the global warming potential (GWP) of 1.15 million Mt.CO2 eq.

Airborne concentrations of Polycyclic Aromatic Hydrocarbons (PAH), quinone and nitro derivatives have been measured at three sites on the coast of Saudi Arabia to the north of the city of Jeddah. The PAH show a general reduction in concentrations from northwest to southeast, consistent with a source from a petrochemical works to the northwest of the sampling sites. In comparison, the concentrations of quinones show little variation between the sampling sites consistent with these being predominantly longer lived secondary pollutants formed from PAH oxidation. The nitro-PAH show a gradient in concentrations similar to but smaller than that for the PAH suggesting a balance between atmospheric formation and removal by photolysis. The 2-nitrofluoranthene:1-nitropyrene ratio increases from north to south, consistent with atmospheric chemical formation of the former compound, while the ratio of 2-nitrofluoranthene:2-nitropyrene is consistent with hydroxyl radical as the dominant reactant. An investigation of the changes in PAH congener ratios during air mass transport along the Red Sea coast shows consistency with reaction with a relatively low concentration of hydroxyl radical only for the day with the highest concentrations. It is concluded that while PAH degradation is occurring by chemical reaction, emissions from other locations along the air mass trajectory are most probably also leading to changes in congener ratios.

Regional groundwater modeling is a valuable tool for ensuring the sustainable development and management of groundwater resources as it allows the assessment of the aquifer behavior under different types of hydrological stresses. The objective of this study was to use 3D flow modeling to assess the best options for managing groundwater in the Wadi Baysh basin in Saudi Arabia. The model for the Wadi Baysh aquifer system was based on groundwater monitoring data for 10-year period from 2007 to 2016. The model was tested with different hydrological stresses until the year 2050. The model behavior shows that groundwater levels in Wadi Baysh aquifer show no signs of depletion at the current pumping rates. The impact of the water stored in the dam reservoir is clearly seen and the zone of influence is very well demarcated. At this stage, groundwater use in the Wadi Baysh aquifer system is sustainable and no decline in groundwater levels is observed.

Scarcity of measured hydrologic data is the main cause for difficulty in demonstrating the assessment of groundwater recharge. The aim of this study is to provide a new scope to assess the runoff and groundwater recharge in ungauged basins based on paleo-flood and morphometric features in arid environment in spite of limited hydrological data. This study is based on rainfall-runoff modeling through the integration between paleo-flood mark measurement, basin physiographic features, and geographic information system (GIS) techniques. Four models of ArcHydro, Grinne (channel) model, Watershed Modeling System (WMS), and HEC-HMS were integrated together and used to assess flood risk and the relationship between rainfall and runoff in the study basin. Al Dawasir basin was selected to demonstrate this study, because it is the biggest basin in the Kingdom of Saudi Arabia with an area of 257,689 km2 and extends for about 700 km from Makkah al-Mukarramah region in the west side of Saudi Arabia to Riyadh region and the Rub` Al Khali in the middle of Saudi Arabia. Al Dawasir basin which has stream order reaches to 8th order, composed of 2 sub-basins of 7th order, 12 sub-basins of 6th order, and 44 basins of 5th order. This study deals with the hydrological study of large sub-basins of highest order (7th and 6th) such as Al Fushsh, Turbah, Al Khurmah, Ranyah, Bishah, Shiab Yafikh, Tathlith, Al Hinu, Al Maqran, Himam, and Uyaynah sub-basins. Wadi Al Dawasir Basin is usually subjected to sporadic storm events, which vary spatially and temporally in intensity. Based on the paleo-flood measurement of Wadi Ranyah sub-basin, calibrated scenarios have been done and the resulted hydrograph is matching with rainfall event of 10-year return period with and without routing scenarios. Some scenarios have been done to calculate the surface runoff volume of the whole Wadi Al Dawasir basin and calibrated the results based upon the paleo-flood measurement of Wadi Ranyah sub-basin. The calculated volume of Wadi Al Dawasir basin ranges from 4.8 BCM to 27.4 BCM for 2- and 100-year return periods, respectively.

Twenty infiltration tests and 12 pumping tests were carried out in Wadi Baysh in southwestern Saudi Arabia. The objective of the study was to assess the soil and aquifer permeability from the point of view of artificial groundwater recharge. Infiltration tests showed that the soil permeability values ranged from 0.58 to 37.15 m/day and showed good recharge potential. The analysis of the pumping tests showed that the aquifer permeability values ranged from 2.6 to 57.4 m/day and were approximately within the same range as those obtained from infiltration tests. Monitoring of groundwater levels in a few wells before and 1 month after a heavy rainfall event in August 2016 shows an average increase of 2.25 m in the groundwater levels which substantiates the recharge rates obtained from infiltration and pumping tests. Average annual groundwater recharge for the area calculated from water table fluctuation method is 72.08 mm/year indicating that the lower reaches of Wadi Baysh catchment has good potential for groundwater recharge and if managed properly can help in tackling the problem of groundwater depletion due to excessive pumping.

Assessment of the flash flood hazard in arid regions is a serious challenge, especially as the climate changes. The Kingdom of Saudi Arabia lies in one of the most arid regions of the world and is known for recurring flash floods in many basins, particularly in the southwest. Many dams have been constructed in some basins; however, flash floods sometimes cause catastrophic damage for mankind and infrastructure when the floods’ intensity and capacity are higher than those the dams and reservoirs were intended to contain. This study aims to assess runoff and reservoir capacity of the Jazan Basin in different return periods of rainfall events based on integrations between two models deals with morphometric parameters and hydrologic characteristics. These models are, Watershed Modeling System (WMS) and the Hydrological Modeling System (HEC HMS) in addition to Geographic Information Systems (GIS). Our results show that the dam peak storage in the condition of zero and full reservoir storage ranges from 55 × 106 to 98 × 106 m3 and from 84 × 106 to 124 × 106 m3, respectively. The corresponding area of the dam reservoir (lake) in all scenarios ranges from 9 to 11.3 km2, respectively, for 5 and 100 year return periods. Sub-basins 2 and 3 contribute about 56% of the total runoff volume of Jazan Basin, while Sub-basins 1, 4, and 5 contribute about 44%. These results highlight the value of using an integrated modeling approach to assess and mitigate flash flood hazards in arid environments worldwide.

Measurements of 16 polycyclic aromatic hydrocarbon (PAH) congeners (particles and vapour) have been made at three sites over a distance of 230 km on the Red Sea coast of Saudi Arabia. The data have been pooled with an earlier dataset from three sites in the city of Jeddah, with one urban site common to both studies. The concentrations and congener profiles are broadly similar for the two measurement campaigns at the common site. Coefficients of Divergence have been calculated and show more substantial differences between the sites within the city of Jeddah than are found between the sites to the north of the city which emphasises the strong concentration gradients within Jeddah in comparison to those found in the atmosphere of the coastal sites to the north of the city. A sub-set of data corresponding to days on which the air mass travelled from the northwest parallel with the Red Sea coast, hence linking the three sites, showed a progressive reduction in concentrations as the air mass travelled towards the southeast, which is attributed to emissions from a large source area to the northwest of the sampling sites and either atmospheric dilution or chemical reaction accounting for a progressive reduction in concentrations with advection of the air mass. The congener profile is very similar to that identified in earlier work relating to oil refinery emissions and is consistent with the major petrochemical installation at Yanbu contributing substantial emissions to the atmosphere which are advected to downwind sites.

The photophysical properties of the 2,6-bis((E)-2-(benzoxazol-2-yl)vinyl)naphthalene (BBVN) laser dye have been investigated by time-dependent density functional theory (TDDFT) using the BMK functional in the gas phase and solvents. Upon photon absorption, the dye undergoes an intense ππ* transition polarized along the long molecular axis. The natural transition orbital (NTO) representation of excitation indicates that the benzoxazole nucleus provides a room for a larger charge displacement in absorption/emission. The calculated small value of Stokes shift together with the root-mean-square distance demonstrates that the excited state (S1) geometry is not significantly displaced from that of the ground state (S0). Using a panel of solvation models (LR-PCM, cLR-PCM, and SS-PCM) we have shown that the solvent hardly has an impact on absorption but has a slight positive solvatochromic effect on fluorescence. The calculated E0–0 energy agrees with the experimental absorption-fluorescence crossing point (AFCP). The vibronic band simulation supports the vibronic origin of the measured spectra. Owing to its large oscillator strength, short fluorescence lifetime, high photo-stability and increased rigidity in the excited state, the BBVN dye meets the necessary requirements for being a good laser dye.

Statistical analyses are performed on the geomorphological characteristics of Makkah Al-Mukaramah basins. The purpose of these analyses is to study the variability of the geomorphological characteristics (13 parameters) and their effects on the variability of the hydrological and kinematic response (6 variables). Different probability density functions (PDF) of the prevailing morphometric variables are tested. The Kolmogorov–Smirnov test is utilized for the goodness of fit test to find the best PDF together with Akaike Information Criterion to assess various best fits. The statistical analyses revealed that the highest coefficient of variation (CV = 1.43) is for peak discharge of the geomorphological instantaneous unit hydrograph (GIUH). Apparently, this is due to the high CV (1.14) for the length of the highest order stream. The lowest CV(0.07) is observed for the similarity parameter of basins. This indicates a high similarity between the basins from the geomorphological point of view. The PDF analyses show that the morphological and hydrological variables display different probability distribution patterns. Based on the geomorphoclimatic instantaneous unit hydrograph GCIUH, it has been shown that there is a high variability in the basin response as a result of an exponential distribution of rainfall intensity and duration. Peak discharge and time to peak have a practical truncations of the distribution tail at 0.5 h−1and 10 h, respectively. The quartile classification of the basins shows that some variables have distinct clusters, while others show almost no clustering at all. The study provides assessment of the potential flood risk and the potential recharge basins in the study area.

The availability and the future of freshwater resources are major challenges in the Middle East, and a vital issue for the Kingdom of Saudi Arabia. Temporal Gravity Recovery and Climate Experiment (GRACE) data along with other datasets are employed to monitor the spatiotemporal trends in freshwater availability over the Red Sea Hills, and to examine natural and anthropogenic factors controlling these trends. Results indicate that the Red Sea Hills are witnessing GRACE-derived terrestrial water storage (TWS) depletion of − 3.92 ± 0.09 km3. TWS depletions are attributed mainly to decline in annual rainfall amounts during the investigated period (April 2002 to December 2016; 70 mm) compared to that of the previous two decades (1979–2001; 115 mm). Higher TWS depletion rates (− 6.31 ± 0.10 km3/year) are observed over the central and northern parts of the Red Sea Hills compared to those observed over the southern parts (− 1.89 ± 0.30 km3/year). The Red Sea Hills witness lower TWS depletion rates (− 1.22 ± 0.51 km3/year) during the first 4 years of the investigation (April 2002 to August 2006; Period I); higher TWS depletion rates (− 4.31 ± 0.15 km3/year) are observed during the remaining part of the investigation (September 2006 to January 2017; Period II) due to the temporal variability in annual rainfall amounts (Period I 85 mm; Period II 65 mm). Findings demonstrate the successful use of GRACE data for monitoring freshwater availability in the Red Sea Hills and potential for use in studying freshwater resource availability in other hydrologic systems around the globe.

An integrated approach was used to evaluate the impact of flash flood recharge on groundwater quality and its suitability for drinking, irrigation, livestock and poultry uses in the Wadi Baysh Basin, Western Saudi Arabia. Analyses of 182 groundwater samples, collected from the study area before and after a flash flood (FF) event, show that the average concentrations of TDS, Mg, Na, Cl, NO3 and EC decreased significantly after the event. The major water types (mixed CaMgCl, NaCl and CaCl) indicate that the infiltration of surface water from FF recharge has a great influence on groundwater chemistry. Drinking water suitability maps, created using WHO standards, indicate that wells located in the upstream region are suitable for drinking despite their high TDS and total hardness (TH) values. Groundwater in the coastal region is unsuitable due to its high salinity, high TH and high concentrations of major ions. The suitability of groundwater for irrigational use was assessed using salinity, sodium adsorption ratio, bicarbonate hazard, residual sodium carbonate, Kelly’s ratio, magnesium hazard, sodium percentage and permeability index values, which indicated that groundwater in the study region is suitable for most soils and crops. After FF, groundwater quality is improved by dilution, especially in the downstream region. USSL classification shows that the majority of the water samples are in the C3S1, C4S2, and C3S2 classes and are therefore suitable for the irrigation of salt-tolerant crops. Irrigational suitability maps suggest that wells in the upstream region are suitable for irrigation, whereas wells located near to the coast are unfit for irrigation. This study implies that construction of check dams in the dry valleys (wadies) may improve the groundwater quality in the area.

This research was conducted during 2014/2015 and 2015/2016 seasonsin the Agricultural Research Station, King Abdulaziz University at Hada Al-Sham region, Saudi Arabia to produce mungbean as a new legume crop in Saudi Arabia using low water consumption through maximizing crop yield with optimizing irrigation water use efficiency under drought stress during vegetative and flowering growth stages.No significant differences were found between the yield and yield components when practicing water stress during vegetative stage compared with full irrigation treatment in the two seasons. MN96 cv. was significantly dominated over NMf cv. in all studied traits except flowering date.The highest IWUE and seed yield/ha were obtained from the MN96 cv. under full irrigation and water stress during vegetative stage without significantly differences between them in the two seasons.

We examined time-dependent effect of iron oxide nanoparticles (IONPs) at a rate of 2000 mg kg−1 soil on Cynodon dactylon litter (3 g kg−1) decomposition in an arid sandy soil. Overall, heterotrophic cultivable bacterial and fungal colonies, and microbial biomass carbon were significantly decreased in litter-amended soil by the application of nanoparticles after 90 and 180 days of incubation. Time dependent effect of nanoparticles was significant for microbial biomass in litter-amended soil where nanoparticles decreased this variable from 27% after 90 days to 49% after 180 days. IONPs decreased CO2 emission by 28 and 30% from litter-amended soil after 90 and 180 days, respectively. These observations indicated that time-dependent effect was not significant on grass-litter carbon mineralization efficiency. Alternatively, nanoparticles application significantly reduced mineral nitrogen content in litter-amended soil in both time intervals. Therefore, nitrogen mineralization efficiency was decreased to 60% after 180 days compared to that after 90 days in nanoparticles grass-litter amended soil. These effects can be explained by the presence of labile Fe in microbial biomass after 180 days in nanoparticles amendment. Hence, our results suggest that toxicity of IONPs to soil functioning should consider before recommending their use in agro-ecosystems.

International audience; Clean-up of contaminated wastewater remains to be a major challenge in petroleum refinery. Here, we describe the capacity of a bacterial consortium enriched from crude oil drilling site in Al-Khobar, Saudi Arabia, to utilize polycyclic aromatic hydrocarbons (PAHs) as sole carbon source at 60 degrees C. The consortium reduced low molecular weight (LMW; naphthalene, phenanthrene, fluorene and anthracene) and high molecular weight (HMW; pyrene, benzo(e)pyrene and benzo (k)fluoranthene) PAH loads of up to 1.5 g/L with removal efficiencies of 90% and 80% within 10 days. PAH biodegradation was verified by the presence of PAH metabolites and evolution of carbon dioxide (90 +/- 3%). Biodegradation led to a reduction of the surface tension to 34 +/- 1 mN/m thus suggesting biosurfactant production by the consortium. Phylogenetic analysis of the consortium revealed the presence of the thermophilic PAH degrader Pseudomonas aeruginosa strain CEES1 (KU664514) and Bacillus thermosaudia (KU664515) strain CEES2. The consortium was further found to treat petroleum wastewater in continuous stirred tank reactor with 96 +/- 2% chemical oxygen demand removal and complete PAH degradation in 24 days.

Egyptian pea cultivars (Pisum sativum L. cultivars Little Marvel, Perfection and Victory) grown in open-top chambers were exposed to either charcoal-filtered (FA) or non-filtered air (NF) for five consecutive years (2009-2013) at a rural site in northern Egypt. Net photosynthetic rates (PN), stomatal conductance (gs), intercellular CO2 (Ci) and chlorophyll fluorescence were measured. Ozone (O3) was found to be the most prevalent pollutant common at the rural site and is suspected to be involved in the alteration of the physiological parameters measured in the present investigation. PN of different cultivars were found to respond similarly; decreases of 23, 29 and 39% were observed in the cultivars Perfection, Little Marvel and Victory, respectively (averaged over the five years) due to ambient O3. The maximum impairment in PN was recorded in the cultivar Victory (46%) in 2013 when the highest O3 levels were recorded (90 nL L(-1)). The average stomatal conductance decreased by 20 and 18% in the cultivars Little Marvel and Perfection, respectively, while the average stomatal conductance increased on average by 27% in the cultivar Victory. A significant correlation was found between PN and Ci, indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The PN vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (ΦPSII) and photochemical quenching coefficient (qP) were significantly decreased in the leaves of plants exposed to NF air. Non-photochemical quenching (NPQ) was increased in all cultivars. Exposure to NF air caused reductions in chlorophyll (Chl a) of 19, 16 and 30% in the Little Marvel, Perfection and Victory cultivars, respectively.

Aims: The aim of the present study was to investigate some biochemical changes in field grown lettuce (Lactuca sativa L. cv Romaine) plants in terms of importance of the accumulation of anthocyanins, flavonoids and photosynthetic pigments as well as photosynthetic limitations which changed during exposure of plants to drought stress and UV-B radiation in order to circumvent the deleterious effects of these Stresses. Place and Duration of Study: The experiment was conducted under filed conditions from November 2012 to January 2013, at the Agricultural Research Center, KAU. Methodology: The experimental design was a factorial arrangement in randomized complete blocks with four replicates. The first factor was UV-B (300 nm). The second factor was irrigation regime (complete irrigation to field capacity and limited irrigation. Gas exchange measurements were carried out using a LI-6200 portable IRGA. Chlorophyll fluorescence of Fv/Fm was measured by PAM 2000 fluorometer. Biochemical analyses and antioxidant enzymes assays were performed according to the appropriate methods. Results: Exposure of lettuce plants to enhanced UV-B radiation and drought stresses (DS) negatively and significantly affected the process of photosynthesis including CO2 assimilation (PN), stomatal conductance to water vapour (gs) and transpiration rate (E). However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercellular CO2 (Ci) concentration was only reduced due to water stress compared to control plants. The maximum efficiency of photosystem II (Fv/Fm) was not affected by UV-B radiation stress but reduced by drought. There was an increase in the activities of some antioxidant due to both stresses when applied singly and in combination UV-B irradiation increased the contents of the UV-B absorbing compounds (carotenoids, soluble phenols, anthocyanins), while drought stress caused a notable increase in free proline content. Increase in content of Proline may be the drought-induced factor which plays a protective role in response to UV-B. Conclusion: UV-B radiation provoked in general more severe damage, evaluated as changes in the amounts of stress markers, than DS, when applied separately. Under multiple stress conditions, each of the stress factors seems to bring out some adaptive effects to reduce the damage experienced by plants caused by the other one. DS can induce accumulation of UV-B absorbing compounds (flavonoids, carotenoids and soluble phenols), which is likely to offer some increased protection from UV-B.

Lettuce (Lactuca sativa L. cv. Romaine) plants were exposed to different levels of urbanization in Jeddah city, Saudi Arabia. They showed different degrees of visible injury symptoms and dramatic changes in enzymatic activities as well as net photosynthetic rates (P N ), variable to maximum chlorophyll fluorescence (Fv /Fm) and stomatal conductance (gs). Visual symptoms of phytotoxicity of heavy metals were observed on plants grown at industrial and urban areas, where the concentrations of metals was about 36 times higher than in other sites. The decrease in chlorophyll reached 70 and 64% in plants cultivated in the industrial and urban regions, while lengths of shoots reduced by 50 and 41% in plants collected from the same locations, respectively. The reduction in chlorophyll and other physiological and biochemical parameters were correlated with the concentrations of airborne pollutants measured in the atmosphere of the locations examined. Moreover, lettuce plants cultivated in the industrial region accumulated more heavy metals than others, which can pass into the human food chain. Photosynthetic efficiency was significantly decreased and lipid peroxidation was enhanced. Antioxidant enzymes were significantly altered during exposure. The biochemical and physiological parameters measured in the present study clearly showed that they could form the basis of a plant biomarkers battery for monitoring and predicting early effects of exposure to airborne heavy metals.

Concentrations of ambient ozone (O3) and nitrogen oxides (NOx) were measured continuously for a period of 12 months in the city of Jeddah from December 2011 to December 2012. Meteorological parameters, wind speed, temperature, and relative humidity were also monitored. Concentrations of ground O3 were found to be highly dependent on the NOx diurnal cycle and wind speed. Nitrogen oxides were found to exceed air quality standards, especially in industrial sites, while O3 concentrations were found to exceed 40 ppb, averaged over 1 h, on more than 24% of the measured days in the rural sites. Furthermore, they exceeded 30% in all other areas (i.e., the urban ones). O3 and NOx were inversely related. The highest average NOx concentration (96 ppb) occurred in a rural area downwind of a desalination plant, while the average O3 concentration peaked in a rural area upwind of a desalination plant, reaching 63.5 ppb, although it also reached 72.6 in another rural area, and we consider this latter result as the background figure in the present study. The seasonal variations of O3 were more distinct than those of NOx. To the best of our knowledge, this is the first report providing comprehensive background information on air quality in an arid area of the developing world.

In arid and semiarid areas, the only surface and groundwater recharge source is the runoff generated through flash floods. Lack of hydrological data in such areas makes runoff estimation extremely complicated. Flash floods are considered catastrophic phenomena posing a major hazardous threat to cities, villages, and their infrastructures. The objective of this study is to assess the flash flood hazard and runoff in Wadi Halyah and its sub-basins. Integration of morphometric parameters, geo-informatics, and hydrological models has been done to overcome the challenge of scarcity of data. Advanced Spaceborne Thermal Emission and Reflection (ASTER) data was used to prepare a digital elevation model (DEM) with 30-m resolution, and geographical information system (GIS) was used in the evaluation of network, geometry, texture, and relief features of the morphometric parameters. Thirty-eight morphometric parameters were estimated and have been linked together for producing nine effective parameters for evaluation of the flash flood hazard in the study basin. Flash flood hazard in Wadi Halyah and its sub-basins was identified and grouped into three classes depending on nine effective parameters directly influencing the flood prone areas. Calculated runoff volume of Wadi Halyah ranges from 26.7 × 106 to 111.4 × 106 m3 with an inundation area of 15 and 27 km2 at return periods of 5 and 100 years, respectively. Mathematical relationships among rainfall depth, runoff volume, infiltration losses, and rainfall excess demonstrate a strong directly proportional relationships with correlation coefficient of about 0.99.

The antiozonant chemical, ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N'-phenylurea, abbreviated as EDU), was applied as stem injections or soil drenches to 5-year-old containerized plants of olive (Olea europaea L. cultivar Kalamata) in growth chambers in order to assess its ameliorative effects against realistic ozone (O3) stress. Visible injury symptoms were reduced greatly in individuals treated with EDU, with injection applications having greater protection than soil drenches. EDU application caused increases in the measured ecophysiological parameters compared to untreated individuals. In particular, the stem injection protected plants against photosynthetic impairment (unchanged net photosynthetic rates and intercellular CO2 concentration, in comparison to plants grown in filtered air). EDU application increased the protection of PSII from ambient O3 oxidative stress, although it did not retain the proportion of redox state of QA, pigment composition of photosynthetic apparatus and size of light-harvesting complex of PSII. However, the stem injection of plants with EDU induced lower non-photochemical quenching (NPQ) values in comparison to ambient air (-2 %), indicating a better photoprotection of PSII in comparison to soil drench application. EDU application caused increases in the morphological and biometric parameters compared to individuals exposed to ambient air. To the best of our knowledge, this is the first study highlighting the protection of Kalamata olive trees due to EDU in terms of growth, yield, visible injury, and photosynthetic performance. Furthermore, this study proved that EDU could be a low-cost and a low-technology efficient tool for assessing O3 effects on plant performances in the field in Saudi Arabia.

The excited state hydrogen bonding dynamics of BBVN in hydrogen donating methanol solvent was explored at the TD-BMK/cc-pVDZ level of theory with accounting for the bulk environment effects at the polarizable continuum model (PCM). The heteroatoms of the BBVN laser dye form hydrogen bonds with four methanol molecules. In the formed BBVN-(MeOH)4 complex, the A-type hydrogen bond (N…HO), of an average strength of 25 kJ mol− 1, is twofold stronger than the B-type (O…HO) one. Upon photon absorption, the total HB binding energy increases from 78.5 kJ mol− 1 in the ground state to 82.6 kJ mol− 1 in the first singlet (S1) excited state. In consequence of the hydrogen bonding interaction, the absorption band maximum of the BBVN-(MeOH)4 complex, which was anticipated at 398 nm (exp. 397), is redshifted by 5 nm relative to that of the free dye in methanol. The spectral shift of the stretching vibrational mode for the hydrogen bonded hydroxyl groups (with a maximum shift of 285 cm− 1) from that of the free methanol indicated the elevated strengthening of hydrogen bonds in the excited state. The vibrational modes associated with hydrogen bonding provide effective accepting modes for the dissipation of the excitation energy, thus, decreasing the fluorescence quantum yield of BBVN in alcohols as compared to that in the polar aprotic solvents. Since there is no sign of photochemistry or phosphorescence, it seems reasonable in view of the outcomes of this study to assign the major decay process of the excited singlet (S1) of BBVN in alcohols to vibronically induced internal conversion (IC) facilitated by hydrogen bonding.