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Nitrogen (N) and phosphorus (P) deficiency in soils limit plant growth. Consequently, chemical fertilizers are applied to fulfill crop nutrient demands. However, low nutrient utilization can make these fertilizers unprofitable for low-income smallholding farmers. Therefore, we studied the influence of Bradyrhizobium sp. and phosphate-solubilizing bacteria (Pseudomonas) on N and P utilization by mungbean crop from fertilized nutrient-deficient soil. We inoculated novel Bradyrhizobium sp. TAL-377 and Pseudomonas sp. 54RB strains alone or their combination with seeds of mungbean varieties (C-MUNG, NM-06, and NM-11). A basal dose of chemical fertilizers was applied at the rate of 60 kg N and 90 kg P ha−1 in the form of urea and single super phosphate in all plots before crop sowing. All inocula increased soil mineral N and P compared to control (P < 0.05). Co-inoculation increased mineral N by 30%, 18%, and 18% than Bradyrhizobium sp. alone and increase in P was 22, 29 and 43% than Pseudomonas sp. in C-MUNG, NM-06, and NM-11, respectively. This resulted in 35%, 45%, and 36% higher shoot N uptakes than Bradyrhizobium sp., and 46%, 84%, and 62% higher shoot P uptake than Pseudomonas sp. in the varieties. Similarly, root nodulation, mungbean grains, and biological yields were higher in co-inoculation treatments than single strain (p < .05). Hence, co-inoculation of Bradyrhizobium sp. and phosphorus solubilizing bacteria (Pseudomonas sp.) is a vital strategy to increase mungbean growth, yield, N and P utilization from chemical fertilizers applied in nutrient-deficient soils.

Highlights • A high concentration BEP and DBP were detected from LDPE, HDPE and RP polymer films. • The impact salinity, temperature and UVR on leaching and re-adsorption of PaEs were investigated. • A mass balance approach was used to determine the adsorption loss of each target compounds during the leaching process. • Surface adsorption of PEs removed 40 to 80% of the leached PEs. Abstract In this study, the leaching of six phthalic acid esters (PAEs) from three common consumer plastics was investigated: low and high density polyethylene (LDPE, HDPE) and recycled polyethylene (RP). The effects of salinity, temperature, and ultraviolet irradiation (UVR) on leaching were investigated. The study of leaching of phthalates in aqueous environments in batch experiments is challenging due to their readsorption by the high hydrophobicity of PAEs, and there are no standard methods to study release processes. Here with the experiments, leaching (A) and spiking (B) using six PAEs to study the readsorption in the leaching process. PAEs were identified and quantified using GC–MS. Dibutyl phthalate (DBP) and benzyl butyl phthalate (DEHP) showed considerable leaching during the 5-day incubation: 14 ± 1 to 128 ± 14 and 25 ± 2 to 79 ± 5 ng/cm2, respectively, under UVR, corresponding approximately to (1.9–13%) and (12.4–22.4%) of the solvent extracted mass. The highest Kd values were measured for RP polymers (0.3–9.4), followed by LDPE (0.5–5.4) and HDPE (0.2–2.2) polymers. Thus, readsorption of PAEs at the surface removed 30–80% of the leached PAEs in the dissolved phase. For example in LDPE, the calculated total release of DBP was up to 54 ± 4 ng/cm2, while the dissolved amount was 8.5 ± 1 ng/cm2 during the 5-day incubation under freshwater conditions. Increasing salinity negatively affected the leaching rate, which decreased for DBP from 54 ± 4 ng/cm2 in freshwater to 44 ± 3 and 38 ± 3 ng/cm2 at salinity of 20 and 40 g/L, respectively, from LDPE during the 5-day incubation. Temperature and UVR had a positive effect on the leaching rate, with the release of DBP from LDPE increasing from 44 ± 3 ng/cm2 at room temperature (25 °C) to 60 ± 6 and 128 ± 14 ng/cm2 at high temperature (40 °C) and UVR, respectively. Overall, this study highlights the positive relationship between temperatures, UVR on the extent of leaching and surface adsorption on the leaching measurements. Graphical abstract Schematic of the leaching process in experiment (A: polymer) and in Experiment B (Polymer + spikes), shows that part of leachate were re-adsorbed on the surface of the polymer were may affect the dissolution concentration. The total leached mass (adsorbed and dissolved) were estimation by compared to a treatment containing both polymer and PAEs spike (P + S; Experiment B). The influence of salinities (0.1, 20 and 40 g/L), temperature (10, 25, and 40 °C), and ultraviolet radiation (UVR 350 nm) on the leaching and re-adsorption of PEs was investigated.

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.

In the present study, occurrence of arsenic (As) and lead (Pb) is reported in rural and urban household dust (floor and AC filter dust) of the Kingdom of Saudi Arabia (KSA). Several studies have found concerning concentrations of these toxic metals in indoor dust from different countries, but data from this region is missing. The association between studied toxic metals and different socioeconomic parameters was investigated. Furthermore, health risk associated with these toxic metals via dust exposure was evaluated for the Saudi population. Mean concentration of Pb was several times higher than As in both types of dust samples. AC filter dust was more contaminated with these metals than floor dust. Levels of Pb were up to 775 ppm in AC filter dust from urban areas, while 167 ppm in rural AC filter dust. Different socioeconomic parameters did not influence much on the presence of studied metals in both AC and floor dust. To estimate health risk from contaminated dust hazardous index (HI), hazardous quotient (HQ), and incremental lifetime cancer risk (ILCR) via dust ingestion, inhalation, and dermal contact was calculate using USEPA equations. The ILCR range for both toxic metals was within the tolerable range of reference values of USEPA (1 × 10−5 to 5 × 10−7). Nonetheless, HI was close to 1 for Pb via dust exposure for young urban children, which signifies the risk of non-carcinogenic health problems in studied area.

An increasing interest in biochar application has opened many multidisciplinary research areas in science. Biochar can be produced by thermochemical conversion of organic biomass in an oxygen-deficient condition. Extensive research has been conducted on the potential of biochar for agronomic applications, such as soil fertility improvement and carbon sequestration due to its specific mineralogical composition and long-term stability in the soil. Using biochar for environmental remediation has also been recognized recently as a promising area of research for its unique physicochemical characteristics, redox potential, and adsorption capacity. However, the published works are mostly focused only on the agronomic and environmental applications with little information presented to elucidate the different mechanisms involved. This study, therefore, aims to examine the influence of controlling parameters during biochar production, such as pyrolysis temperature, residence time, and types of feedstock on the characteristics of biochar. Various mechanisms explaining the potential of biochar for the environmental and agronomic applications are discussed in detail. The challenges faced in biochar development and its field applications for agronomic and environmental remediation purposes are also highlighted. Finally, recommendations for future research are given on the development of biochar with high redox functional groups and sorption potential as well as on understanding the behavior of biochar under the natural field conditions.

Quantification of phthalates or phthalic acid esters (PAEs) might be problematic due to matrix overlap, auto-self absorbance and background scattering noise by the plastic lab materials although plastics have been reported in the release of PAEs. These materials (ambient air, reagents bottles, sampling devices, and various analytical instruments), are ubiquitous in the laboratory environment, thereby making it more difficult to reliably analyze of trace concentration of PAEs. Thus, in the current study, a straight forward and reliable protocol has been established for the analysis of PAEs including control of blank contamination, and the experimental conditions such as extraction time and temperature were optimized. The mass of PAEs in blank tests of selected materials ranged from 3±0.7 to 35±6 ng for liquid-liquid extraction (LLE) and from 5±1.8 to 63±15 ng for solid-phase extraction (SPE). For both extraction methods, higher blank values were measured for dibutyl phthalate (DBP) (35±6 ng, 12±3 ng), and DEHP (63±12 ng, 23±5 ng) in LLE and SPE, respectively. Average recoveries of PAEs in LLE were 90-97% and obtained with successive aliquots of 2 mL, 1 mL, and 1 mL dichloromethane (DCM). For SPE, recoveries up to 86-90% were achieved with successive aliquots of 5, 3, and 2 mL DCM at a sample flow rate of 5 mL min -1 . Under the optimized conditions, the method quantification limits (MQL) for PAEs was 10-20 ng L -1 for LLE and 10-35 ng L -1 for SPE. Moreover, the dissolved concentrations of PAEs from LDPE measured by the LLE method ranged < 1.5 to 5.83 ng cm -2, and those measured by SPE ranged from 1.0to256ngL -1 , in seawater samples of Sharm Obhur. The method has lower MQL values for LLE and SPE than average reported values of 10-100 ng L -1 and 30-100 ng L -1 , respectively.

Highlights • This study examined MP concentrations and PAE distribution in a semi-enclosed Sharm Obhur leading to the Red Sea. • DEP, DBP and DEHP are the predominant PAEs. • A positive relationship was found between PAE concentration and PDs abundance. • The ecological risk of PAEs and PDs was found from low to moderate. The abundance of plastic debris (PDs) and its correlation with phthalic acid esters (PAEs), a class of pollutants associated with plastics, is not well understood, although PDs have been reported in relation to the release and distribution of aquatic pollutants such as PAEs. Few studies have linked the distribution of these pollutants in seawater. The current study examined the abundance and relationship of PDs and PAEs in seawater from Sharm Obhur and the Red Sea. Estimates were also made of their ecological impacts. Sharm Obhur is a semi-enclosed bay on the eastern shore of the Red Sea, near Jeddah, Saudi Arabia, and is heavily impacted by human activities. Contaminants from Sharm Obhur may be transported into the deep waters of the Red Sea by the subsurface outflow. The PAEs concentrations in the study area ranged from 0.8 to 1224 ng/L. Among the six PAEs studied, diethyl phthalate (DEP) (22–1124 ng/L), di-n-butyl phthalate (DBP) (9–346 ng/L) and di (2-ethylhexyl) phthalate (DEHP) (62–640 ng/L) were the predominant additives detected across all the sampling sits. Whereas the other PAEs, dimethyl phthalate (DMP) (5–76 ng/L), benzyl butyl phthalate (BBP) (4–25 ng/L) and di-n-octyl phthalate DnOp (0.5–80 ng/L) were generally lower in most samples. The sum of the six analyzed PAEs (∑6 PAEs) was lower at Sharm Obhur (587 ± 82 ng/L) and in the Red Sea shelf (677 ± 182 ng/L) compared to the Red Sea shelf break (1266 ± 354 ng/L). This suggests that degradation and adsorption of PAEs were higher in Sharm Obhur and on the shelf than on the shelf break. In contrast, there was no difference in the abundance of PDs between Sharm Obhur (0.04 ± 0.02 PDs/m3), Red Sea shelf (0.05 ± 0.02 PDs/m3) and in the Red Sea shelf break (0.03 ± 0.1 PDs/m3). Polyethylene (32%) and polypropylene (8%) were dominant, mostly smaller than 5 mm2 (78%), with the majority consisting of white (52%) and black (24%) fragments (39%), fibers (35%) and films (24%). A positive correlation between PAE concentration and abundance of PDs, suggests either a common source or a causal link through leaching. The ecological risk of ∑4PAEs (DMP, DEP, DBP and DEHP) ranged from (0.20–0.78), indicating a low to moderate risk for the Red Sea. The pollution index of PDs ranged from (0.14–0.36), showing that the Sharm Obhur and both sites of Red Sea suffered relatively low pollution.

The voltammetric (CV and DPV) behavior of multi-walled carbon nanotube/Nafion composite coupled with a glassy carbon electrode was investigated for the determination of 2,4-dichlorophenol. The structural and morphological evaluation by XRD and FESEM revealed that the acid treated MWCNT retained their morphology without any structural change. The existence of the possible functional groups was investigated by FTIR and Raman spectroscopy. Compared to bare GCE, a significantly reduced interfacial charge transfer resistance was noticed for MWCNT/Nafion/GCE by electrochemical impedance spectroscopy (EIS). The use of Nafion not only contributed to the non-covalent functionalization of MWCNT, but also protected the electrode surface against the polymerization of phenoxy radicals forming a passivating film. For MWCNT/Nafion/GCE, the combination of anti-passivating ability and excellent catalytic properties resulted in the rapid and direct electrochemical determination of 2,4-DCP. Under optimal experimental conditions, the DPV responses for MWCNT/Nafion/GCE is linear over the 1–150 μmol/L range with a detection limit (S/N = 3) of 0.01 μmol/L. The presence of many interfering species had no influence on the signals of 2,4-DCP. The proposed sensor was successfully tested for the determination of 2,4-DCP in tap water samples and the recovery was in the range of 99.0–102.5%. Keywords: 2,4-Dichlorophenol, Electrocatalytic oxidation, Multi-walled carbon nanotube/Nafion composite, Electrochemical sensor, Voltammetry

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 work is intended to biosynthesize zinc oxide nanoparticles (ZnO NPs) via facile and modern route using aqueous Ziziphus jujuba leaves extract assisted by microwave and explore their photocatalytic degradation of methyl orange anionic dye and methylene blue cationic dye under solar irradiation. The biosynthesized microwave assisted ZnO NPs were characterized and the results showed that ZnO NPs contain hexagonal wurtzite and characterized with a well-defined spherical-like shape with an outstanding band gap (2.70 eV), average particle size of 25 nm and specific surface area of 11.4 m2/g. The photocatalytic degradation of the MO and MB dyes by biosynthesized ZnO NPs under solar irradiation was studied and the results revealed the selective nature of the ZnO NPs for the adsorption and further photocatalytic degradation of the MO dye compared to the MB dye. In addition, the photocatalytic degradation of MO and MB dyes by the ZnO NPs under solar radiation was fitted by the first-order kinetics. Moreover, the photodegradation mechanism proposed that superoxide ions and hydroxyl radicals are the main reactive species.

In this research work, different ZnO NPs were prepared via eco-friendly green route using Ziziphus jujuba leaves extract assisted by microwave. Eco-friendly prepared ZnO NPs characterized by different techniques, and the results confirmed the preparation of hexagonal wurtzite ZnO nanoparticles with different particle sizes. The prepared ZnO NPs were then used for the adsorption and removal of two different azo dyes; methyl orange (MO), and methylene blue (MB), as well as toxic Pb(II) ions, from a model solution and real samples. Influence of experimental conditions was explored, and the results showed that most of the MB, MO and Pb(II) could be removed from the model solution within few minutes, at ambient conditions using 15 mg ZnO NPs. The removal of the MB, MO and Pb(II) using ZnO NPs was studied kinetically and thermodynamically, and the results showed that the experimental data were best fitted using the pseudo-second-order kinetic models. The thermodynamics study showed that the process was spontaneous, with exothermic nature. Finally, the prepared ZnO NPs were used for the removal of MB, MO and Pb(II) in real wastewater sample, and high removal efficiency was presented.

Aerogels are special class of porous gel materials in which the liquid part is replaced by gas without shriking the shape of it. Most of the aerogel are based on polysaccharide origins, for example, cellulose, chitosan, alginate, starch, agar aerogels. In terms of biomedical applications, aerogels can also be used for loading and diffusion of antimicrobial drugs and to further control the release of drugs. Silica and cellulose have been widely used in the biomedical field. The aerogels and its composite display controlled drug release behavior and efficient antibacterial performance, thus confirming their potential for biomedical applications. This chapter focuses on bio-aerogels from the viewpoints of loading of antimicrobial agent cellular uptake, toxicity, biodegradability, and the biomedical application perspectives.

In this study, we measured the occurrence of organophosphate esters (OPEs) and phthalates in the settled dust (floor and air conditioner filter dust) and in suspended particulate matter (PM10) from different microenvironments (households (n = 20), offices (n = 10) and hotels (n = 10)) of Jeddah, Saudi Arabia. Bis (2-Ethylhexyl) phthalate (DEHP) was the major pollutant (contributing &gt, 85% of total chemicals burden) in all types of indoor dust with a concentration up to 3,901,500 ng g−1. While dibutyl phthalate (DBP) and DEHP together contributed &gt, 70% in PM10 (1900 ng m−3), which indicate PM10 as a significant source of exposure for DBP and DEHP in different Saudi indoor settings. Tris (1-chloro-2-propyl) phosphate (TCPP) was the major OPE in PM10 with a concentration of up to 185 ng m−3 and the occurrence of OPEs in indoor dust varied in studied indoor settings. The estimated daily intake (EDI) of studied chemicals via dust ingestion and inhalation of PM10 was below the reference dose (RfD) of individual chemicals. However, estimated incremental lifetime cancer risk (ILCR) with moderate risk (1.5 × 10−5) for Saudi adults and calculated hazardous index (HI) of &gt, 1 for Saudi children from DEHP showed a cause of concern to the local public health.

The COVID-19 pandemic is responsible for an unprecedented disruption to the healthcare systems and economies of countries around the world. Developing novel therapeutics and a vaccine against SARS-CoV-2 requires an understanding of the similarities and differences between the various human coronaviruses with regards to their phylogenic relationships, transmission, and management. Phylogenetic analysis indicates that humans were first infected with SARS-CoV-2 in late 2019 and the virus rapidly spread from the outbreak epicenter in Wuhan, China to various parts of the world. Multiple variants of SARS-CoV-2 have now been identified in particular regions. It is apparent that MERS, SARS-CoV, and SARS-CoV-2 present with several common symptoms including fever, cough, and dyspnea in mild cases, but can also progress to pneumonia and acute respiratory distress syndrome. Understanding the molecular steps leading to SARS-CoV-2 entry into cells and the viral replication cycle can illuminate crucial targets for testing several potential therapeutics. Genomic and structural details of SARS-CoV-2 and previous attempts to generate vaccines against SARS-CoV and MERS have provided vaccine targets to manage future outbreaks more effectively. The coordinated global response against this emerging infectious disease is unique and has helped address the need for urgent therapeutics and vaccines in a remarkably short time.

Fungal Infection is a hidden enemy for mammals because it is inhibiting commonly in nasal and oral mucosa, where it colonizes and starts unwanted growth and form infection. The differentiation between pathogenicity with colonization and regular colonization in upper respiratory system infection is difficult initially. Sometimes fungal infection rate becomes high due to the immune system weakening by the immunosuppressive drugs and old age because of a weak immune system unable to fight opportunistic fungi. The most common fungal infection is an endemic mycosis caused by dimorphic fungal species that are ubiquitously present in the soil and environment of particular geographic regions. Few most common fungal infections are listed Athlete’s foot is caused by a number of different fungi, including species of Trichophyton, Epidermophyton, and Microsporum, Tinea Versicolor, Onychomycosis, Tinea Capitis and Ringworm caused by Dermatophytes, Candidiasis by Candida sp.. In general, fungal skin infection is a more frequent and more recurrent pathogen that often goes hidden by the physician and persistent body. Fungal Infection becomes more serious when it occurred as a secondary infection after bacterial Infection. Frequently simple measures can prevent the hidden fungal Infection and therefore reduce the possibility of complications. This chapter presents information on mysterious diseases caused by different fungi besides some possible ways of protection and treatments.

There is an increasing evidence that meteorological (temperature, relative humidity, dew) and air quality indicators (PM2.5, PM10, NO2, SO2, CO) are affecting the COVID-19 transmission rate and the number of deaths in many countries around the globe. However, there are contradictory results due to limited observations of these parameters and absence of conclusive evidence on such relationships in cold or hot arid tropical and subtropical desert climate of Gulf region. This is the first study exploring the relationships of the meteorological (temperature, relative humidity, and dew) and air quality indicators (PM10,CO, and SO2) with daily COVID-19 infections and death cases for a period of six months (1st March to August 31, 2020) in six selected cities of the Kingdom of Saudi Arabia by using generalized additive model. The Akaike information criterion (AIC) was used to assess factors affecting the infections rate and deaths through the selection of best model whereas overfitting of multivariate model was avoided by using cross-validation. Spearman correlation indicated that exponentially weighted moving average (EWMA) temperature and relative humidity (R > 0.5, P < 0.0001) are the main variables affecting the daily COVID-19 infections and deaths. EWMA temperature and relative humidity showed non linear relationships with the number of COVID-19 infections and deaths (DF > 1, P < 0.0001). Daily COVID-19 infections showed a positive relationship at temperature between 23 and 34.5 °C and relative humidity ranging from 30 to 60%; a negative relationship was found below and/or above these ranges. Similarly, the number of deaths had a positive relationship at temperature ˃28.7 °C and with relative humidity ˂40%, showing higher number of deaths above this temperature and below this relative humidity rate. All air quality indicators had linear relationships with the number of COVID-19 infections and deaths (P < 0.0001). Hence, variation in temperature, relative humidity and air pollution indicators could be important factors influencing the COVID-19 spread and mortality. Under the current scenario with rising temperature and relative humidity, the number of cases is increasing, hence it justifies an active government policy to lessen COVID-19 infection rate.

A highly conductive thin film composite based on silver nanoparticles (AgNPs) and malic acid (MA) was deposited on glassy carbon electrode (GCE) for the selective and sensitive electrochemical sensing of trichloroacetic acid (TCA). The casting solution containing MA functionalized AgNPs was employed as a precursor for the thermal deposition of the AgNPs integrated MA thin film composite onto the GCE surface. The uniform coverage of AgNPs within the thin film composite at GCE was obtained by field emission scanning electron microscopy (FESEM). A significantly high charge transfer resistance of the modified electrode (85.7 Ω for AgNPs-MA/GCE in 2 mM [Fe(CN)6]3-/4- at a bias of +0.235 V as compared to bare GCE (38.01 Ω) verified the optimum coating of AgNPs-MA composite at the surface of the electrode. The AgNPs-MA composite deposited GCE revealed substantial electrocatalytic activity toward TCA reduction with significantly enhanced reduction current. The novel electrode manifested a linear square wave voltammetric (SWV) response over the concentration ranges of 0.1–2 (R2 = 0.9953) and 4-100 μM (R2 = 0.9969) with a limit of detection (LOD) and limit of quantification (LOQ) of 30 nM and 92.5 nM, respectively. The modified electrode exhibited an excellent long-term stability (30 days) with the retention of >95% of initial current. The selectivity of the proposed electrode for the determination of TCA was examined in the presence of dichloroacetic acid (DCA) and monochloroacetic acid (MCA) with the retention of high recovery percentages.

This paper aims to examine the influence of biochar produced from lawn waste in accelerating the degradation and mineralization rates of food waste compost. Biochar produced at two different temperatures (350 and 450 °C) was applied at the rates 10 and 15% (w/w) of the total waste to an in-vessel compost bioreactor for evaluating its effects on food waste compost. The quality of compost was assessed against stabilization indices such as moisture contents (MC), electrical conductivity (EC), organic matters (OM) degradation, change in total carbon (TC) and mineral nitrogen contents such as ammonium (NH 4 + ) and nitrate (NO 3 − ). The use of biochar significantly improved the composting process and physiochemical properties of the final compost. Results showed that in comparison to control trial, biochar amended compost mixtures rapidly achieved the thermophilic temperature, increased the OM degradation by 14.4–15.3%, concentration of NH 4 + by 37.8–45.6% and NO 3 − by 50–62%. The most prominent effects in term of achieving rapid thermophilic temperature and a higher concentration of NH 4 + and NO 3 − were observed at 15% (w/w) biochar. According to compost quality standard of United States (US), California, Germany, and Austria, the compost stability as a result of biochar addition was achieved in 50–60 days. Nonetheless, the biochar produced at 450 °C had similar effects as to biochar produced at 350 °C for most of the compost parameters. Therefore, it is recommended to produce biochar at 350 °C to reduce the energy requirements for resource recovery of biomass and should be added at a concentration of 15% (w/w) to the compost bioreactor for achieving a stable compost.

This paper aims to (1) examine the challenges in the compost facilities of the Kingdom of Saudi Arabia (KSA), (2) optimize the composting techniques using indigenous natural zeolite and locally produced biochar from agricultural residues and (3) evaluate the environmental and economic benefits of optimized food waste composting. In KSA food waste is the most abundant stream of municipal solid waste that contribute up to 50% of the total waste. The landfill disposal of this waste results in several environmental and public health issues. Resource recovery through composting is one of the best approaches for treating such nutrient-rich organic waste. There exist several facilities in KSA for the conversion of food waste to compost using conventional methods of compost piles and trenches. However, none of the produced compost is capable of improving the quality and fertility of sandy soils and the growth of the crops due to limited values of organic matter, nutrients and water holding capacity along with high moisture contents, nitrification index, weed seed contents and ammonia emissions. In KSA, vast reservoirs of natural zeolite are available near to Jeddah city. Similarly, in KSA the most cultivated tree is date palm with more than 22 million date trees that would provide sufficient feedstock for biochar production. Therefore, diverting food waste from landfills to optimized composting facilities using natural zeolites and biochar could benefit the KSA economy with a total net savings of about US $70.72 million per year.

The recognition of the humans, vehicles or any other objects in the outdoor environment, such as roads, streets, pedestrian ways, car parking and public parks, is only possible with illumination after dark. The outdoor lighting consumes significant amounts of electricity. The best short-term payout period for reduction in energy consumption is implementation of energy efficiency solutions. A shift from traditional illumination technology to the advanced lighting solutions has the ability for significant energy savings. The main focus of this study is to find out the most suitable, environmentally friendly and “green” solution(s) to fulfill the outdoor lighting requirements. It includes ecological impact assessment of commonly available lighting technologies for outdoor illumination, such as high pressure sodium, compact fluorescent and light emitting diode, by using Sustainable Process Index methodology. The effects of different alternative energy resources and the impacts of geographical locations due to variations in energy provision system (i.e. energy mix) are also considered in this study. The obtained results show that Sustainable Process Index ranges from 258 km2 to 7760 km2 and carbon footprint from 930 t CO2 eq. to 48,496 t CO2 eq. to fulfill lighting requirement for 100,000 h of lighting. These results are compared with Sustainable Process Index and Carbon Footprint caused by high pressure sodium and light emitting diode luminaires providing electricity from Saudi Arabian electricity network.

This research reports, for the first time, the eco-friendly green synthesis of zinc oxide nanoparticles (ZnO NPs) using Ziziphus jujuba leaves extract assisted by microwave irradiation. Eco-friendly prepared ZnO NPs were characterized by different techniques, and the results confirmed the formation of hexagonal wurtzite ZnO nanoparticles with different particle sizes. The prepared ZnO NPs were then used for the adsorption and removal of two different azo dyes; methyl orange (MO), and methylene blue (MB), as well as toxic Pb(II) ions, from a model solution and real samples. The influence of experimental conditions was explored; ZnO NPs mass, contact time, solution pH, solution ionic strength, and solution temperature, and the results showed that most of the MB, MO, and Pb(II) could be removed from the model solution within a few minutes, at ambient conditions. The experimental removal capacities of 5.21, 2.57, and 596 mg of MO, MB, and Pb(II) per gram of microwave-assisted green ZnO NPs (MWG ZnO NPs), respectively, were obtained. The removal of the MB, MO, and Pb(II) using ZnO NPs was studied kinetically and thermodynamically, and the results showed that the experimental data were best fitted using the pseudo-second-order kinetic models, with rate constants of 0.165, 0.364, 247 × 10–6, for the MO, MB, and Pb(II), respectively. The thermodynamics study showed that the process was spontaneous, with an exothermic nature. Finally, the prepared ZnO NPs were used for the removal of MB, MO, and Pb(II) in real wastewater samples, and high removal efficiency was presented. The regeneration and reusability were explored, and the results revealed the applicability of using the MWG ZnO NPs for the removal of MB, MO, and Pb(II) for five consecutive cycles.

The MoO3 coated ZnO photocatalysts were synthesized for the optimum harvesting of the absorbed ultraviolet sunlight photons by initially permeating Mo6+ ions at the surface of pre-synthesized ZnO and finally transformed to MoO3 by thermal treatment in the air. The absorption spectra of the synthesized powders revealed the extension of the absorption edge in the visible region whereas, the photoluminescence spectroscopy established the supporting role of the MoO3 coating in gradually plummeting the excitons recombination. The growth of additional peaks in Raman as well as X-ray photoelectron spectra and the appearance of the corresponding low-intensity reflection substantiated the surface prevalence of MoO3. The absence of the individual particles of MoO3 in FESEM and the verification of coated layer by HRTEM images validated the authenticity of the adopted synthetic route. The electrochemical evaluation of the synthesized powders under illumination revealed the complete elimination of photocorrosion and the synergic role of the MoO3 layer for improved trap and transfer of charge carriers. The evaluation of the flat-band potentials of the coated powders by Mott-Schottky analysis revealed the suitability of the conduction band edges for the generation of superoxide anion radicals. The photocatalytic activity of the synthesized powders was assessed for the removal of chloro derivatives (mono-, di-, trichloroacetic acids) in comparison to pure acetic acid. A significant effect of the stability, polarity and stereochemical structure of the substrate on the photocatalytic removal process was observed and discussed. The experimental evidences from the time-scale chemical analysis were interpreted for the identification of the reactive oxygen species (ROS) involved in the degradation/mineralization process. The validation of the Langmuir-Hinshelwood kinetic model was also examined. Efforts were made to estimate the plausible route of the degradation/mineralization process.

This paper aims to examine the potential of waste biorefineries in developing countries as a solution to current waste disposal problems and as facilities to produce fuels, power, heat, and value-added products. The waste in developing countries represents a significant source of biomass, recycled materials, chemicals, energy, and revenue if wisely managed and used as a potential feedstock in various biorefinery technologies such as fermentation, anaerobic digestion (AD), pyrolysis, incineration, and gasification. However, the selection or integration of biorefinery technologies in any developing country should be based on its waste characterization. Waste biorefineries if developed in developing countries could provide energy generation, land savings, new businesses and consequent job creation, savings of landfills costs, GHG emissions reduction, and savings of natural resources of land, soil, and groundwater. The challenges in route to successful implementation of biorefinery concept in the developing countries are also presented using life cycle assessment (LCA) studies.

Ecological evaluation approaches assess different levels of comprehensiveness depending on anthropogenic ecological pressures on natural material and biogeochemical cycles. In this research potentials of biomass integration in agricultural processes were evaluated and all parts of their full life cycles were replaced with ecological processes of low impact. A method that covers global resource availabilities, life cycle chains and their emissions to final compartments on earth’ spheres in a detailed way is Sustainable Process Index. This footprint calculator accumulates the total resource use of a full life cycle of a process chain in one number of m2 area. Current typical conventional agricultural cropping processes shall be made comparable to a strongly sustainable ecological footprint which could be achieved if heavy footprint measures would be replaced by those with smaller impacts in natural cycles. The production of maize grain is evaluated to find out the ecological hotspots. A comparison of business as usual conventional farming practice and ecological/organic farming practice is carried out. The evaluation results confirmed that fossil fuel consumption and application of mineral fertilizers along with pesticides are the main ecological hotspots. The ecological footprint and carbon footprint showed a bandwidth of 24,731 to 10,690 m2/tonne and 88.5 and 22.6 kg carbon dioxide equivalent per tonne maize grain production respectively. The shift from conventional farming practice to organic farming and use of biogas as fuel showed an ecological footprint reduction potential ranging from 22% to 57% while the carbon footprint reduction potential ranges from 38% to 74%. It proves that SPI footprint methodology is quite effective in locating ecological hotspots and finding alternate environment friendly solution in the life cycle of a process. The assessment results are very promising and indicate that a shift from conventional farming practices towards organic farming and the use of renewable energy sources have a huge potential to achieve a more sustainable agriculture and strengthen a regionally based economy.

Professional driving is associated with high rates of occupational musculoskeletal disorders (OMSDs). The objective of this study was to assess the prevalence of OMSDs among drivers and office workers of taxi industry in Jeddah city. A detailed custom-made questionnaire was used that included socio-demographic and occupational characteristics of subjects together with OMSDs prevalence rates. In this research, 173 subjects participated of which 70.5% were drivers and 29.5% were office workers. Standard Nordic Questionnaire (SNQ) was used to assess 1-year and 1-week prevalence rates of OMSDs in nine body regions. 1-year and 1-week reported prevalence rates of OMSDs among taxi drivers were 85.3 and 51.6%, while among office workers were 52.9 and 31.4%, respectively. The highest self-reported prevalence rates of OMSDs for taxi drivers were found for the lower back (60.7%) and lowest rates for the elbow (14.8%). Whereas, among office workers, the highest prevalence rates were found for the lower back and knee (29.4%) and lowest rates for feet/ankle (2.0%). The chi-square test found significant correlation between being immigrant (p=0.038), hours of driving per day (p=0.002), number of working days per week (p=0.000) with 1-year prevalence of OMSDs, While job experience (p=0.006), hours of driving per day (p=0.004) and break during work (p=0.029) showed significant correlation with perceived 1-week prevalence of OMSDs among taxi drivers in Jeddah.

This review summarizes the environmental occurrence of new brominated flame retardants (NBFRs) and organophosphate compounds (OPs) in the environment of developing countries since 2000. The ban on the production and use of commercial formulations of polybrominated diphenyl ethers (PBDEs) have paved the way for the high use of NBFRs and OPs in consumer products to fulfill the fire safety regulations. Recent studies have shown that the ever increasing production volumes and extensive use of these chemicals as additive FRs and plasticizers have resulted into their ubiquitous occurrence in all environmental compartments. Although presumed to be safe for use and the environment, recent studies on their occurrence and persistence in the environment have raised questions. Due to the lack of awareness, research interest, and availability of technical facilities, limited scientific data is available on the occurrence of these chemicals in developing countries. In this study, we collected reported data and provide an overview of environmental occurrence of NBFRs and OPs in abiotic and biotic matrices of different developing countries. Finally, research gaps were identified with recommendations for future research work and would be useful towards the environmental management of these toxic chemicals.

We demonstrated one-step synthesis of silver nanoparticles (AgNPs) from Cassia fistula fruit extract and their antibacterial activity against E. coli and K. pneumoniae. Biogenic AgNPs were characterized by scanning electron microscopy, X-Ray diffraction and fourier transform infrared spectroscopy. Results confirmed spherical shaped AgNPs with an average crystallite size of ∼69 nm. Dose-dependent (0, 10, 20, 40 and 80 μg mL −1 ) growth kinetic studies showed 100% potency against E. coli (20 μg mL −1 ) and K. pneumoniae (80 μg mL −1 ) after 1 and 5 h, respectively. Surface morphology analysis revealed formation of groove/pits in the lysed cell membrane that eventually led to bacterial death.

This study reports levels and profiles of phthalates in dust samples collected from three different microenvironments (cars, air conditioner (AC) filters and household floor dust) of Saudi Arabia (KSA) and Kuwait. To the best of our knowledge, this is a very first study in the literature reporting phthalates in the indoor environments of KSA, which makes these findings very important. Our results showed that bis(2-ethylhexyl) phthalate (DEHP), di- n -butyl phthalate (DBP), di-isobutyl phthalate (DIBP), and di- n -octyl phthalate (DNOP) were the major chemicals in all dust samples. DEHP was the overwhelming compound in all microenvironments occurred at median concentrations (μg/g) of 1020, 1250, and 790 in Saudi household floor, car, and AC filter dust, respectively. The median levels (μg/g) of DEHP in Kuwaiti car (320) and household floor (240) dust samples were 3–4 times lower than respective Saudi dust. Phthalates were higher in car dust than household dust and Ac filter dust, suggesting people spending more time in vehicles are at higher risk of exposure to these chemicals. Different exposure scenarios, using 5th percentile, median, mean, and 95th percentile levels, were estimated for adults and toddlers. For Saudi and Kuwaiti toddlers worst exposure scenario for DEHP, a cardiotoxic and endocrine disruptor, was calculated at 37630 and 6722 ng/kg body weight/day (ng/kg bw/d), respectively. This preliminary study provided first-hand baseline data of Phthalates from Gulf countries and which necessitate more detailed future studies in this region. Practical implications The first study on the incidence of phthalates from different micro–environments of KSA. High levels of bis(2-ethylhexyl) phthalate (DEHP) were present in Kuwaiti and KSA indoor micro–environments suggesting a high use of DEHP in consumer products. Exposure to phthalates via dust ingestion is estimated high in Saudi toddlers, which is a cause of concern.

This paper aims to examine the effect of different plastic waste types such as polystyrene (PS), polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) on the yield and quality of produced liquid oil from the pyrolysis process. A small pilot scale pyrolysis reactor was commissioned for this purpose, and operated at optimum temperature and retention time of 450 °C and 75 min respectively. PS plastic waste showed maximum production of liquid oil (80.8%) along with least production of gases (13%) and char (6.2%) in comparison to other plastic types. Liquid oils from all plastic types contained mostly aromatic compounds with some alkanes and alkenes. Liquid oil from PS pyrolysis contained styrene (48.3%), ethylbenzene (21.2%) and toluene (25.6%). Pyrolysis liquid oils found to have ranges of dynamic viscosity (1.77–1.90 mPa s), kinematic viscosity (1.92–2.09 cSt), density (0.91–0.92 g/cm3), pour point (−11(-60 °C)), freezing point (−15-(-65 °C)), flash point (28.1–30.2 °C) and high heating value (HHV) (41.4–41.8 MJ/kg) similar to conventional diesel, thus have potential as an alternative energy source for electricity generation. Upgrading of liquid oil using different post-treatment methods such as distillation, refining and blending with conventional diesel is required to make it suitable as a transport fuel due to presence of high aromatic compounds. The recovery of aromatic compounds especially styrene from pyrolysis oil can be a potential source of precursor chemical in industries for polymerization of styrene monomers.

Nanolitre arrays of 4-(2-pyridylazo)resorcinol (PAR) reagent produced on polyethersulfone (PES) membrane surface has been utilized as a platform for rapid and precise determination of Cu2+ ions in water. The topography of the membrane surface was characterized by atomic force microscopy whereas internal morphology was revealed by scanning electron microscopy. The water contact angle (θ) corresponding to ~ 82° confirmed that the prepared PES membrane is a low-wetting substrate. The computed value of limit of detection (10− 3 μg mL− 1) achieved by the proposed membrane-based sensor was 4-order of magnitude lower than that obtained on the pristine filter-paper (10 μg mL− 1). The proposed method showed high robustness towards slight changes in pH, temperature and analyte volume. The interference of commonly occurring cations and anions in water was also evaluated. The analytical utility of the developed method was successfully demonstrated for determination of Cu2+ ions in spiked domestic tap water samples. The proposed method demonstrated excellent recovery of representative Cu2+ ions in real samples that was also validated by comparing the results with ICP-OES data. A good agreement between the two results was obtained at 95% confidence level. The analytical utility of the proposed method was also extended for the estimation Cu2+ ions in sewage and industrial wastewater samples and results were compared with ICP-OES analysis. The ease of usability/readability, low reagent/analyte volume requirement and superior robustness confirms the applicability of the developed low-cost method towards point-of-use applications.

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.

This paper reviews the status of microbial electrolysis cells (MEC) as a mean for hydrogen (H2) production and urban wastewater treatment method. A case study of the Kingdom of Saudi Arabia (KSA) under MEC concept was developed. KSA is the world’s third largest per capita water user country with no lakes and rivers. Every year, around 1.17 and 0.38 billion m3 of domestic and industrial wastewater is generated respectively. The KSA government is seeking sustainable solutions for wastewater treatment and waste-to-energy (WTE) production to bridge the ever increasing water and energy demand-supply gap. However, there is no WTE facility exists to convert the wastewater into energy. Moreover, the potential of wastewater is not examined as an energy recovery substrate. This study, for the first time, estimated that a total electricity of 434 MWe can be produced in 2015 from the KSA’s wastewater if MEC technology is employed. Similarly, an estimated total electricity of 612 and 767 MWe can be produced for the years 2025 and 2035 from the domestic and industrial wastewater by using MEC technology. A surplus electricity of 508 and 637 MWe for the years 2025 and 2035 respectively can be added to the national grid after fulfilling the energy requirement of MEC wastewater treatment plants. Collectively, MEC will contribute 20.4% and 25.6% share of the KSA government’s WTE target of 3G W in 2025 and 2035 respectively. A number of challenges in MEC such as ohmic and concentration losses, saturation kinetics and competing reactions that lower the H2 production are discussed with their potential solutions including, the improvements in MEC design and the use of appropriate electrolytes, antibiotics and air or oxygen.