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This paper aimed to evaluate the ecological and health risks for some potentially toxic trace elements (PTEs) in agricultural soils irrigated with sewage wastewater for more than 50 years. Therefore, soil and plant samples were collected from 21 sites at sewage wastewater irrigated area and these samples were analyzed for their contents of PTEs i.e. Cd, Cr, Cu, Ni, and Pb. The risks of PTEs pollution in the study area were analyzed using indices such as the individual and comprehensive potential ecological risk indices (E r and RI, respectively), hazard quotient (HQ), hazard index (HI), and carcinogenic risk (CR) model. The results showed that the PTEs in soil samples ranged from 1.70 to 9.90 mg/kg for Cd, from 39.9 to 183.4 mg/kg for Cr, from 31.5 to 655.1 mg/kg for Cu, from 18.8 to 113.1 mg/kg for Ni and from 5.4 to 65.4 mg/kg for Pb. The results also demonstrated that the soil samples were characterized by high to very high ecological risk for Cd. According to the health risk assessment, the mean HQ and HI of the PTEs in soil for adults and children were below the risk threshold of 1, indicating no risk for non-carcinogenic health effects. However, the HI of PTEs via plant consumption was > 1, suggesting a non-carcinogenic health risk. The CR for most plant samples was above the acceptable range. These findings may offer helpful information regarding the ecological and human risks related to PTEs exposure in soil and plants irrigated with wastewater under arid conditions.i and RI, respectively), hazard quotient (HQ), hazard index (HI), and carcinogenic risk (CR) model. The results showed that the PTEs in soil samples ranged from 1.70 to 9.90 mg/kg for Cd, from 39.9 to 183.4 mg/kg for Cr, from 31.5 to 655.1 mg/kg for Cu, from 18.8 to 113.1 mg/kg for Ni and from 5.4 to 65.4 mg/kg for Pb. The results also demonstrated that the soil samples were characterized by high to very high ecological risk for Cd. According to the health risk assessment, the mean HQ and HI of the PTEs in soil for adults and children were below the risk threshold of 1, indicating no risk for non-carcinogenic health effects. However, the HI of PTEs via plant consumption was > 1, suggesting a non-carcinogenic health risk. The CR for most plant samples was above the acceptable range. These findings may offer helpful information regarding the ecological and human risks related to PTEs exposure in soil and plants irrigated with wastewater under arid conditions., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

In the present work, the olive mill solid waste (OMSW)-derived biochar (BC) was produced at various pyrolytic temperatures (300-700°C) and characterized to investigate its potential negative versus positive application effects on pH, electrical conductivity (EC), and nutrients (P, K, Na, Ca, Mg, Fe, Mn, Zn, and Cu) availability in a calcareous loamy sand soil. Therefore, a greenhouse pot experiment with maize (Zea mays L.) was conducted using treatments consisting of a control (CK), inorganic fertilizer of NPK (INF), and 1% and 3% (w/w) of OMSW-derived BCs. The results showed that BC yield, volatile matter, functional groups, and zeta potential decreased with pyrolytic temperature, whereas BC pH, EC, and its contents of ash and fixed carbon increased with pyrolytic temperature. The changes in the BC properties with increasing pyrolytic temperatures reflected on soil pH, EC and the performance of soil nutrients availability. The BC application, especially with increasing pyrolytic temperature and/or application rate, significantly increased soil pH, EC, NH4OAc-extractable K, Na, Ca, and Mg, and ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable Fe and Zn, while AB-DTPA-extractable Mn decreased. The application of 1% and 3% BC, respectively, increased the NH4OAc-extractable K by 2.5 and 5.2-fold for BC300, by 3.2 and 8.0-fold for BC500, and by 3.3 and 8.9-fold for BC700 compared with that of untreated soil. The results also showed significant increase in shoot content of K, Na, and Zn, while there was significant decrease in shoot content of P, Ca, Mg, and Mn. Furthermore, no significant effects were observed for maize growth as a result of BC addition. In conclusion, OMSW-derived BC can potentially have positive effects on the enhancement of soil K availability and its plant content but it reduced shoot nutrients, especially for P, Ca, Mg, and Mn; therefore, application of OMSW-derived BC to calcareous soil might be restricted., Competing Interests: The authors have declared that no competing interests exist.

Biochar (BC) was produced by pyrolyzing the date palm leaf waste at 600 °C and then loaded with phosphorus (P) via sorption process. Greenhouse pot experiment was conducted to investigate the application effects of BC and P-loaded biochar (BCP) on growth and availability of P and heavy metals to maize (Zea mays L.) plants grown in contaminated mining soil. The treatments consisted of BC and BCP (at application rates of 5, 10, 20, and 30 g kg -1 of soil), recommended NK and NPK, and a control (no amendment). Sorption experiment showed that Langmuir predicted maximum P sorption capacity of BC was 13.71 mg g -1 . Applying BCP increased the soil available P, while BC and BCP significantly decreased the soil labile heavy metals compared to control. Likewise, heavy metals in exchangeable and reducible fractions were transformed to more stable fraction with BC and BCP applications. The highest application rate of BCP (3%) was most effective treatment in enhancing plant growth parameters (shoot and root lengths and dry matter) and uptake of P and heavy metals by 2-3 folds. However, based on metal uptake and phytoextraction indices, total heavy metals extraction by maize plants was very small for practical application. It could be concluded that using P-loaded biochar as a soil additive may be considered a promising tool to immobilize heavy metals in contaminated mining areas, while positive effects on the biomass growth of plants may assist the stabilization of contaminated areas affected by wind and water erosion., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This study was conducted to identify and quantify polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in soil samples collected from selected industrial areas in the central and eastern regions of Saudi Arabia. All the investigated compounds of PCDDs/PCDFs were identified in the studied locations. The average concentrations of PCDDs (sum of seven congeners measured) ranged from 11.5 to 59.6 pg g(-1), with a maximum concentration of 125.7 pg g(-1) at an oil refinery station followed by 100.9 pg g(-1) at a cement factory. The average concentrations of PCDFs (sum of 10 congeners measured) accounted for 11.68-19.35 pg g(-1), with a maximum concentration of 38.67 pg g(-1) at the cement factory. It was generally observed that the soil samples collected from industrial areas have substantially high toxicity equivalence (TEQ) values of PCDDs/PCDFs compared to soils of remote areas. Principal component analysis revealed that the cement factories and oil refineries were the primary sources of PCDDs and PCDFs.

Many studies have reported the positive effect of biochar on soil carbon sequestration and soil fertility improvement in acidic soils. However, biochar may have different impacts on calcareous sandy soils. A 90-day incubation experiment was conducted to quantify the effects of woody waste biochar (10 g kg(-1)) on CO2-C emissions, K2SO4-extractable C and macro-(N, P and K) and micro-(Fe, Mn, Zn and Cu) nutrient availability in the presence or absence of poultry manure (5 g kg(-1) soil). The following six treatments were applied: (1) conocarpus (Conocarpus erectus L.) waste (CW), (2) conocarpus biochar (BC), (3) poultry manure (PM), (4) PM+CW, (5) PM+BC and (6) untreated soil (CK). Poultry manure increased CO2-C emissions and K2SO4-extractable C, and the highest increases in CO2-C emission rate and cumulative CO2-C and K2SO4-extractable C were observed for the PM+CW treatment. On the contrary, treatments with BC halted the CO2-C emission rate, indicating that the contribution of BC to CO2-C emissions is negligible compared with the soils amended with CW and PM. Furthermore, the combined addition of PM+BC increased available N, P and K compared with the PM or BC treatments. Overall, the incorporation of biochar into calcareous soils might have benefits in carbon sequestration and soil fertility improvement., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Kinetic aspects of metal release were investigated to understand the effects of synthetic chelating agents (EDTA, EDDS and NTA) and low molecular weight (LMW) organic acids (oxalic and citric acids) on the release kinetics of Cr, Cu and As in chromated copper arsenate (CCA)-contaminated soil, as well as their uptake by maize (Zea mays L.). The results showed that the release of metals from soil was better described by parabolic diffusion, power function or simple Elovich model than by the first- and second-order models, indicating a heterogeneous diffusion of metals. Synthetic chelating agents afforded a higher release of Cu than that of LMW organic acids, whereas citric acid was the most effective chelating agent for Cr and As release. The most effective treatments for stimulating metal uptake in plant shoots were EDDS for Cu, EDTA for Cr, and citric acid for As, as indicated by the removal efficiencies of 0.046%, 0.036%, and 0.004%, respectively. However, Zea mays is not an attractive species for chelate-enhanced phytoremediation of CCA-contaminated soils due to its low phytoextraction rate, even in the presence of chelating agents and ligands.

In recent decades, heavy metal contamination in soil adjacent to chromated copper arsenate (CCA) treated wood has received increasing attention. This study was conducted to determine the pollution level (PL) based on the concentrations of Cr, Cu and As in soils and to evaluate the remediative capacity of native plant species grown in the CCA contaminated site, Gangwon Province, Korea. The pollution index (PI), integrated pollution index (IPI), bioaccumulation factors (BAF(shoots) and BAF(roots)) and translocation factor (TF) were determined to ensure soil contamination and phytoremediation availability. The 19 soil samples from 10 locations possibly contaminated with Cr, Cu and As were collected. The concentrations of Cr, Cu and As in the soil samples ranged from 50.56-94.13 mg kg(-1), 27.78-120.83 mg kg(-1), and 0.13-9.43 mg kg(-1), respectively. Generally, the metal concentrations decreased as the distance between the CCA-treated wood structure and sampling point increased. For investigating phytoremediative capacity, the 19 native plant species were also collected in the same area with soil samples. Our results showed that only one plant species of Iris ensata, which presented the highest accumulations of Cr (1120 mg kg(-1)) in its shoot, was identified as a hyperaccumulator. Moreover, the relatively higher values of BAF(shoot) (3.23-22.10) were observed for Typha orientalis, Iris ensata and Scirpus radicans Schk, suggesting that these plant species might be applicable for selective metal extraction from the soils. For phytostabilization, the 15 plant species with BAF(root) values>1 and TF values<1 were suitable; however, Typha orientalis was the best for Cr., (Copyright © 2012 Elsevier Ltd. All rights reserved.)