The present study was conducted in one of the most densely cultivated area of Al-Qassim region in Kingdom of Saudi Arabia to (i) monitor trace metal (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) contents in surface and subsurface soils, (ii) assess the pollution and potential ecological risk levels of trace metals, and (iii) identify trace metal sources using enrichment factor (EF), correlation matrix, and principal component analysis (PCA). The pollution levels of the analyzed trace metals calculated by the geoaccumulation index (I ) and contamination factor (C) suggested that the soils were highly contaminated with Cd and moderately contaminated with Pb. Based on the average values of EF, soil samples were found to present extremely high enrichment for Cd, significant enrichment for Pb, moderate enrichment for Zn, and deficient to minimal enrichment for other trace metals. Among the analyzed trace metals, a very high ecological risk was observed only in the case of Cd at some sampling sites. Meanwhile, other investigated trace metals had a low ecological risk. The results of PCA combined with correlation matrix suggested that Fe, Mn, Zn, Cu, Cr Ni, Cu, and Co represent natural abundance in soil, but Cd, Pb, and Cu are of anthropogenic inputs, mainly due to agrochemical and fertilizer applications. It could be generally concluded that the obtained results can be useful for assessing and conducting a future program for trace metal monitoring in agricultural areas of Saudi Arabia.

Polymer-clay composites were prepared by natural zeolite (clinoptilolite) or naturally local clay deposits in an N,N-methylene-bis-acrylamide as cross-linked. The resultant composites were used for the removal of Cr(VI) from an aqueous solution. Additionally, their effects on soluble ions of tannery wastewater were investigated. The produced composites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The results showed that Cr(VI) removal is dependent upon initial concentrations and pH. The adsorption quantity of Cr(VI) onto the polymerized clay deposit followed by polymerized zeolite exhibited higher values than their original samples. The polymer-clay composite of clay deposit showed the highest removal of 76.3-100% overall initial concentrations of 10-50 mg L −1 and at initial pH of 2. Kinetics of Cr(VI) removal by various sorbents was predicted using a pseudo-second order model. Our findings showed that the levels of salinity and various soluble ions (Cr 2+ , Na + , Cl − and SO 4 2− ) in tannery wastewater are very high, and their levels were reduced after treatment, especially by polymerized sorbents. It could be concluded that the polymer-clay composites may be employed as a highly efficient sorbent for the removal of Cr(VI) and toxic ions from the wastewater.

Until now, there is no method can be used to accurately assess the particles size distribution as well as textural classes of gypsiferous soils for proper interpretation of physical behavior of these soils, and most laboratory methods involve pretreatment to remove gypsum from the samples. Therefore, the results of the particle size distribution do not reflect the size distribution of the whole soil. This study aimed to develop an alternative method to determine particle size distribution for some gypsiferous soils selected from Al-Ahsa governorate, Saudi Arabia. Five samples from different profiles with different gypsum content were selected to evaluate the modified method. Sand fractions were separated with three disaggregation methods: 1) drying sieving, 2) shaking for 5 hours in a 7:3 ethanol: water solution, and 3) sonication for 3 minutes in a 7:3 ethanol: water solution. The statistical analysis results revealed that the sonication for 3 minutes in a 7:3 ethanol: water solution was the most effective method for separating sand fractions as compared to dry sieving and shaking. Meanwhile, there was slight difference in separating sand fractions between sonication for 3 minutes and shaking for 5 hours. The particle size distribution by the developed method showed increasing in total sand content as compared to standard particle size method. Likewise, comparison of the CEC/clay ratio between the two methods also indicated that the developed method yielded clay contents more consistent with other property data for the same horizons. Consequently, the textural classes obtained from the two methods were different. Therefore; we concluded that the determination of particle size distribution for gypsiferous soils (≤ 40% gypsum) using this developed method will improve the understanding and ability to proper interpret of physical behavior of these unique soils. We highly recommended using this developed method to separate soil particles from the gypsiferous soils.