Evaluation of Groundwater for Arsenic Contamination Using Hydrogeochemical Properties and Multivariate Statistical Methods in Saudi Arabia

The aim of this research is to evaluate arsenic distribution and associated hydrogeochemical parameters in 27 randomly selected boreholes representing aquifers in the Al-Kharj geothermal fields of Saudi Arabia. Arsenic was detected at all sites, with 92.5% of boreholes yielding concentrations above the WHO permissible limit of 10 μg/L. The maximum concentration recorded was 122 μg/L (SD = 29 μg/L skewness = 1.87). The groundwater types were mainly Ca+2-Mg+2-SO4-2-Cl− and Na+-Cl−-SO4-2, accounting for 67% of the total composition. Principal component analysis (PCA) showed that the main source of arsenic release was geothermal in nature and was linked to processes similar to those involved in the release of boron. The PCA yielded five components, which accounted for 44.1%, 17.0%, 10.1%, 08.4%, and 06.5% of the total variance. The first component had positive loadings for arsenic and boron along with other hydrogeochemical parameters, indicating the primary sources of As mobilization are derived from regional geothermal systems and weathering of minerals. The remaining principal components indicated reductive dissolution of iron oxyhydroxides as a possible mechanism. Spatial evaluation of the PCA results indicated that this secondary mechanism of arsenic mobilization may be active and correlates positively with total organic carbon. The aquifers were found to be contaminated to a high degree with organic carbon ranging from 0.57 mg/L to 21.42 mg/L and showed high concentrations of NO3- ranging from 8.05 mg/L to 248.2 mg/L

Pollution and health risk assessment of co-existing microplastics and heavy metals in urban dust of Riyadh city, Saudi Arabia

Microplastics (MPs) and heavy metals have recently attracted much attention due to their widespread distribution in the environment. Co-occurrence of MPs and heavy metals in dust poses potential health risks for humans. The objectives of this study were to investigate pollution and health risk factors associated with co-occurring MPs and heavy metals in urban dust. Here, 20 dust samples (both indoor and outdoor environments) were collected from different places in Riyadh, Saudi Arabia using sweeping method. The MPs were separated from dust samples via density separation using ZnCl2 Microscopic techniques were used to investigate MPs while inductively coupled plasma optical emission spectrometry was used heavy metals analyses in the collected samples. The results of the study showed that all the collected dust samples were contaminated with MPs of different shapes, sizes, and colors. Fragment-shaped MPs were the most dominant, followed by granules, fibers, and lines, while the majority of the MP particles were red and black. Furthermore, the size distribution analyses demonstrated that particles above 1,000 µm were abundant. Also, the number of MPs was in the range of 20 particles g-1 to 1,052 particles g-1. Human exposure estimations showed that toddlers could inhale more MPs (0.86 MPs particles kg-1 day-1 and 312.93 particles kg-1 year-1) than children, teenagers, and adults. In addition, the concentrations of heavy metals varied from one site to another, however, the average concentrations were lower than their corresponding values in the guidelines (except for Zn). The integrated potential ecological risk in dust samples was characterized as a low-risk criterion. The enrichment factor for Zn in dust samples at all sites was more than 2, indicating a major contamination concern and anthropogenic sources responsible for the existence of Zn. The estimated hazard quotient indicates that children and adults are saved from the adverse effects of dust inhalation in the studied area. These findings could serve as a preliminary step for efficient pollution management and environmental quality maintenance in Riyadh

Causes of Adverse Pregnancy Outcomes and the Role of Maternal Periodontal Status – A Review of the Literature

Preterm (PT) and Low birth weight (LBW) are considered to be the most relevant biological determinants of newborn infants survival, both in developed and in developing countries. Numerous risk factors for PT and LBW have been defined in the literature. Infections of the genitourinary tract infections along with various biological and genetic factors are considered to be the most common etiological factors for PT/LBW deliveries. However, evidence suggests that sub-clinical infection sites that are also distant from the genitor-urinary tract may be an important cause for PT/LBW deliveries. Maternal periodontal status has also been reported by many authors as a possible risk factor for PT and LBW, though not all of the actual data support such hypothesis. The aim of this paper is to review the evidence from various published literature on the association between the maternal periodontal status and adverse pregnancy outcomes. Although this review found a consistent association between periodontitis and PT/LBW, this finding should be treated with great caution until the sources of heterogeneity can be explained

Levels, solid-phase fractions and sources of heavy metals at site received industrial effluents: a case study

Heavy metals in the site received industrial effluents were investigated to assess the pollution levels, distribution of metal among solid-phase fractions and possible metal sources. The soil samples at different depths of 0–5, 5–25 and 25–50 cm were collected and analyzed for Fe, Mn, Cd, Zn, Cu, Ni and Pb. Among all metals, Cd content was not detected in all soil samples. The average contents of Pb and Zn are higher than the corresponding values of common range in earth crust. Meanwhile, the maximum contents of Cu and Zn are higher than those of Dutch optimum value but lower that the Dutch protection act target value. The maximum contents of Cu, Pb and Zn are higher than the average shale value. The most investigated heavy metals are mostly found in the potentially labile pool (>50.0%) including metal bound to carbonate, Fe/Mn oxides, or organically fractions. Enrichment factor (EF) in combination with multivariate analysis including principal component analysis (PCA) and hierarchical cluster analysis (HCA) suggest that Mn and Ni associated with Fe in the soil samples were primarily originated from lithogenic sources. Pb was largely derived only from anthropogenic source, while Cu and Zn in the soil samples were controlled by the mixed natural and anthropogenic sources. These results suggest that discharging the industrial effluents into dumping site increased pollution level of Pb, Zn and Cu as well as enhanced their potentially labile pool that may be responsible for occurring potential toxic impacts on environmental quality

Stability and Dynamic Aggregation of Bare and Stabilized Zero-Valent Iron Nanoparticles under Variable Solution Chemistry

Surface modification of nanoscale zero-valent iron (nZVI) using polymer stabilizers (e.g., sodium carboxymethyl cellulose, CMC) is usually used to minimize aggregation, increase stability, and enhance transport of nZVI. We investigated the stability and dynamic aggregation of bare and CMC–nZVI as affected by variations in pH, ionic strength (IS), and nZVI particle concentration. CMC coating of nZVI resulted in smaller hydrodynamic size and larger zeta potential. The largest hydrodynamic size of nZVI was associated with bare nZVI at high IS (100 mM), pH close to the point of zero charge (PZC, 7.3–7.6), and larger particle concentration (1.0 g L−1). The increase in the zeta potential of CMC–nZVI reached one- to four-fold of that for bare nZVI, and was greater at pH values close to PZC, high IS, and larger particle concentration. The stability of CMC–nZVI was increased by 61.8, 93.1, and 57.5% as compared to that of bare nZVI at IS of 1, 50 and 100 mM, respectively. Calculations of Derjaguin, Landau, Verwey and Overbeek (DLVO) interaction energy were in agreement with stability results, and showed the formation of substantial energy barriers at low IS indicating greater nZVI stability. Our results suggest that at IS above 50 mM and nZVI particle concentration larger than 0.1 g L−1, the likelihood of nZVI aggregation is high. Nevertheless, CMC polymer stabilizer would enhance the stability and transport of nZVI even under these unfavorable solution chemistry conditions

Assessment and heavy metal behaviors of industrial waste water: A case study of Riyadh city, Saudi Arabia

Abstract This study focuses on the temporal monitoring and chemical analysis of two pathways, unpadded and open drain canal, of the surface industrials effluent on industrial city of Riyadh city, Saudi Arabia. µg L -1 ), and then Cd (8.02 µg L -1 ). The monitoring of wastewater heavy metals concentrations (determined on filtrate for both pathway) recorded that the concentration of Fe, Mo, Zn, Cd, Pb, As, Ni, and Mn decreased from (60-100 µg L -1 ) at point sources to be (5-10 µg L -1 ) at 1000 m from point sources, however no clear behavior was recorded for Cu and Co. Moreover the concentrations of all heavy metals by the last sampling point on downstream were remained at 10 µg L -1 or less. The study emphasis that continuous application of industrial wastewater on Riyadh environment will lead to more accumulation of heavy metals in the soil and natural plants, and also high possibilities of groundwater contamination by nitrate

Soil Phosphorus Fractionation and Bio-Availability in a Calcareous Soil as Affected by Conocarpus Waste Biochar and Its Acidified Derivative

Biochar possesses more profound effects on the availability of soil P in acidic soil than in alkaline and/or calcareous soil, mainly due to P fixation. Therefore, biochar derived from Conocarpus waste (BC) was acidified with sulfuric acid to produce acidified biochar (ABC) and incorporated into a calcareous soil planted with alfalfa in order to investigate P availability and fractionation. Additionally, the changes in some other soil chemical properties were investigated. Both BC and ABC were applied at three rates (0%, 2.5%, and 5%) along with P fertilizer application at four rates (0, 75, 150 and 300 ppm). The results showed that acidification remarkably reduced the pH of ABC by 6.84 units. The application of ABC considerably lowered the soil pH; however, it did not significantly increase P availability in the studied soil. Furthermore, BC, especially at a higher application rate, increased the extractable soil K. Similarly, the amendments increased the soil cation exchangeable capacity (CEC) and soil organic matter (OM), where a profound increase was observed at a higher application rate in the case of soil OM. Similarly, soil-available micronutrients were increased over the control, where a more profound increase was observed in soils treated with ABC. The NaHCO3−P (exchangeable) fraction increased with increasing fertilizer application rate while the residual–P decreased. Therefore, BC and ABC could be used to improve soil quality and enhance soil nutrient availability. However, further studies are required on how to significantly improve soil available P in calcareous soil

Soil Phosphorus Fractionation and Bio-Availability in a Calcareous Soil as Affected by <i>Conocarpus</i> Waste Biochar and Its Acidified Derivative

Biochar possesses more profound effects on the availability of soil P in acidic soil than in alkaline and/or calcareous soil, mainly due to P fixation. Therefore, biochar derived from Conocarpus waste (BC) was acidified with sulfuric acid to produce acidified biochar (ABC) and incorporated into a calcareous soil planted with alfalfa in order to investigate P availability and fractionation. Additionally, the changes in some other soil chemical properties were investigated. Both BC and ABC were applied at three rates (0%, 2.5%, and 5%) along with P fertilizer application at four rates (0, 75, 150 and 300 ppm). The results showed that acidification remarkably reduced the pH of ABC by 6.84 units. The application of ABC considerably lowered the soil pH; however, it did not significantly increase P availability in the studied soil. Furthermore, BC, especially at a higher application rate, increased the extractable soil K. Similarly, the amendments increased the soil cation exchangeable capacity (CEC) and soil organic matter (OM), where a profound increase was observed at a higher application rate in the case of soil OM. Similarly, soil-available micronutrients were increased over the control, where a more profound increase was observed in soils treated with ABC. The NaHCO3−P (exchangeable) fraction increased with increasing fertilizer application rate while the residual–P decreased. Therefore, BC and ABC could be used to improve soil quality and enhance soil nutrient availability. However, further studies are required on how to significantly improve soil available P in calcareous soil

Mitigating the Toxic Effects of Chromium on Wheat (Triticum aestivum L.) Seed Germination and Seedling Growth by Using Biochar and Polymer-Modified Biochar in Contaminated Soil

The present study was conducted to investigate the potential influences of biochar in mitigating the phytotoxic effects of hexavalent chromium (CrVI) on the germination of wheat (Triticum aestivum L.). Biochar (JBC) was produced from Jujube (Ziziphus jujube L.) wood waste at three different pyrolysis temperatures (300 &deg;C, 500 &deg;C and 700 &deg;C), which was later polymerized (JPBC) via the solution-polymerization method. Phytotoxicity of CrVI was induced to wheat seeds at variable CrVI application rates (5, 10, 20, 40 mg L&minus;1). Applied CrVI concentrations confined the seed germination and seedling growth in order of: 5 &lt; 10 &lt; 20 &lt; 40 mg L&minus;1. The application of JBCs (0.2 g per petri plate) resulted in a 150% increase in shoot length, while dry biomass was increased by 250% with JPBCs application. Uptake of CrVI was significantly lower in JBC-300 (7.74 &mu;g/seedling) and JPBC-300 (1.13 &mu;g/seedling) treatments, as compared to control (13.24 &mu;g/seedling), at the highest stress level (40 mg L&minus;1). Therefore, the findings of the current study showed that JBCs and JPBCs performed excellently in improving seedling growth while JPBCs performed more efficiently than pristine JBCs in mitigating CrVI phytotoxicity and availability