Assessing the Effect of Intensive Agriculture and Sandy Soil Properties on Groundwater Contamination by Nitrate and Potential Improvement Using Olive Pomace Biomass Slag (OPBS)

Abstract

The relationship between agricultural activities, soil characteristics, and groundwater quality is critical, particularly in rural areas where groundwater directly supplies local people. In this paper, three agricultural sandy soils were sampled and analyzed for physicochemical parameters such as pH, water content, bulk density, electrical conductivity (EC), organic matter (OM), cation exchange capacity (CEC), and soil grain size distribution. Major and trace elements were analyzed by inductively coupled plasma-optical emission spectrometry (ICP/OES) to determine their concentrations in the fine fraction (FF) of the soils. Afterward, the elemental composition of the soils was identified by X-ray powder diffraction (XRD) and quantified by X-ray fluorescence (XRF). The surface soil characteristics were determined by the Brunauer–Emmett–Teller (BET) method, whereas the thermal decomposition of the soils was carried out using thermogravimetric analysis and differential scanning calorimetric (TGA-DSC) measurements. The morphological characteristics were obtained by scanning electron microscopy (SEM). Afterward, column-leaching experiments were conducted to investigate the soil’s retention capacity of nitrate (NO−3). Parallelly, a chemical and physical study of olive pomace biomass slag (OPBS) residue was carried out in order to explore its potential use as a soil additive and improver in the R’mel area. The OPBS was characterized by physicochemical analysis, assessed for heavy metals toxicity, and characterized using (XRD, XRF, SEM, and BET) techniques. The results show that the R’mel soils were slightly acidic to alkaline in nature. The soils had a sandy texture with low clay and silt percentage (<5% of the total fraction), low OM content, and weak CEC. The column experiments demonstrated that the R’mel irrigated soils have a higher tendency to release large amounts of nitrate due to their texture and a higher degree of mineralization which allows water to drain quickly. The OPBS chemical characterization indicates a higher alkaline pH (12.1), higher water content (7.18%), and higher unburned carbon portion (19.97%). The trace elements were present in low concentrations in OPBS. Macronutrients in OPBS showed composition rich in Ca, K, and Mg which represent 10.59, 8.24, and 1.56%, respectively. Those nutrients were quite low in soil samples. Both XRD and XRF characterization have shown a quasi-dominance of SiO2 in soil samples revealing that quartz was the main crystalline phase dominating the R’mel soils. Oppositely, OPBS showed a reduced SiO2 percentage of 26,29% while K, Ca, and P were present in significant amounts. These results were confirmed by XRF analysis of OPBS reporting the presence of dolomite (CaMg, (CO3)2), fairchildite (K2Ca (CO3)2), and free lime (CaO). Finally, the comparison between the surface characteristic of OPBS and soils by BET and SEM indicated that OPBS has a higher surface area and pore volume compared to soils. In this context, this study suggests a potential utilization of OPBS in order to (1) increase soil fertility by the input of organic carbon and macronutrients in soil; (2) increase the water-holding capacity of soil; (3) increase soil CEC; (4) stabilize trace elements; (5) enhance the soil adsorption capacity and porosity.

Spatial distribution and quantification of plant-available nutrients and soil properties in Punjab, Pakistan

“…For sandy soil, both locations have sufficient saturation concentrations. Due to the higher particle size of sandy soil, which enables water to swiftly drain through the soil profile (Sarti et al, 2022), minimizing waterlogging, and maintaining adequate saturation, sandy soil has a high saturation level (El-Naggar et al, 2021;Ibrahim and Alghamdi, 2021). Electrical conductivity was mainly within acceptable ranges, with one sodic soil sample in Sahiwal being the outlier.…”

Efficient Removal of Tannic Acid from Olive Mill Wastewater Using Carbon Steel Slag

“…Accordingly, SS could be considered a liming agent given its high content of dolomite (CaMg(CO 3 ) 2 ) and portlandite (Ca(OH) 2 ). Similarly, Sarti et al demonstrated the potential use of olive pomace biomass slag, which contains a similar composition as SS, to neutralize acidic agricultural sandy soils [68]. Therefore, regardless of the potential unexplored effects of OMWW treatment by SS.…”

Biochar Enhanced Chemical and Biological Properties of Contaminated Soils with Lead

“…While, the highest value was nearby 30.977 g kg -1 at the clay loam texture with treatment WSB3%. Sandy soil treatment have lower organic matter content than clay loam soils, due to the low organic matter content of sandy soils and the increase in the rate of oxidation [23]. An increase in the organic matter was observed when sandy loam soils to which biochar has been added, as it was about (16.327 g kg -1 ) at the WSB1% treatment, which is a significant increase compared to the sample control treatment (1.453 g kg -1 ).…”