Green synthesis of ZnO, MgO and SiO2 nanoparticles and its effect on irrigation water, soil properties, and Origanum majorana productivity

The synthesis of different metal oxide nanoparticles (NPs) (e.g., ZnO, MgO and SiO2) using green methods is a promising alternative to traditional chemical methods. In this work, ZnO, MgO, and SiO2 NPs were prepared using lemon peel extract. The synthesized NPs were characterized using Fourier transform infrared spectroscopy, UV–Visible spectroscopy, X-ray diffraction, and transmission electron microscopy. Also, the effects of the green synthesis of different NPs on the irrigation water quality, the availability of some heavy metals in soil and plants, and the productivity of Origanum majorana (marjoram) were studied in detail. The obtained results showed that the addition of the NPs resulted in noticeable variations in the removal percentages of Cu2+ and Fe3+ from aqueous solutions. The maximum values obtained for the adsorption of Cu(II) on ZnO, MgO, and SiO2 NPs within the pH values of 3–5 were 89.9%, 83.3%, and 68.36%, respectively. Meanwhile, the maximum adsorption values of Fe(III) at pH 3.3 were 82%, 80%, and 65% for ZnO, MgO, and SiO2 NPs, respectively. Clearly, the application of the NPs effectively reduced the available Cu2+ in the studied soil samples in the following order: Zn2 > Zn1 > Mg2 > Si2 > Mg1 > Si1 > C (control). The highest values of available Cu2+ were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added. The same tendencies were observed with substantial concentrations of Fe. The addition of NPs to the soil samples positively affected the plants' Cu2+ uptake. The effects of NPs and the additions of Cu2+ and Fe3+ on the availability of nitrogen, phosphorus, and potassium (NPK) in the soil system were very completed and osculated from one treatment to another. The same tendencies were observed with the total concentration of NPK in plants.

www.nature.com/scientificreports/ Synthesis of MgO, SiO 2 , and ZnO NPs. For preparing MgO, SiO 2 , and ZnO NPs, we added 0.5 mol L −1 of magnesium nitrate, sodium metasilicate, and zinc sulfate aqueous solution to the lemon peel that was separated previously from the extraction solution. The solution was then boiled to 70 °C for 1 h until it was reduced into a white-colored solution. This color change is considered a mark of the formation of soluble fractions from the peel extract. It was demonstrated that the ethanol lemon peel extract contained hesperidin flavanol, which discharges aglycone that may be used as a reducing agent 24,25 . The pH of each NP mixture was adjusted through the addition of ammonium hydroxide solution (0.1 mol L −1 to maintain the pH values of 9.7, 11.58, and 6.95 for MgO, SiO 2 , and ZnO NPs, respectively. Afterward, the precipitates were washed several times with deionized water, centrifuged and collected in a clayey crucible, and heated in a muffle at 500 °C for 3 h for both MgO and ZnO NPs and at 700 °C for SiO 2 NPs. Elevating the temperature in the muffle was mandatory to remove any organic residuals. Finally, a white precipitate for each NP was obtained and packed carefully for further characterization. The probable mechanisms for the production of MgO, ZnO, and SiO 2 NPs are defined below: Characterization of the prepared nanoparticles. The MgO, SiO 2 , and ZnO NPs were characterized using the following procedures. Powdered NPs were analyzed using X-ray diffraction (XRD) (PAN Analytical X'Pert TopScore Plus Diffractometer) operated at 40 kV with a current of 30 mA under Cu-Kα radiation of a 2θ range of 10°-80°. The surface morphologies of the NPs were observed using transmission electron microscopy (TEM) with an elevated-resolution (JEOL JEM-1400 UHR, operated at 80 kV). The chemical structures of the prepared NPs were investigated using Fourier transform infrared spectroscopy (FTIR) infrared spectra (using a Nicolet Avatar 230 spectrometer. UV-Vis spectrophotometer between 200 and 800 nm wavelength range (Elico EI 301E, India) was used for scanning different prepared nanoparticles.
Soil sampling and analysis. Soil samples were collected from a constant depth of 0-30 cm from the El-Gabal El-Asfar area, Egypt. Some soil and water properties are listed in Table 1. The soil samples were air-dried, crushed, and sieved through a 2-mm sieve to ensure the removal of gravel and organic waste. The soil texture was determined following the international pipette method. The other properties of the soil samples, including organic matter content, pH, and electrical conductivity, were determined according to published literature [25][26][27] . The heavy metal contents were determined using inductively coupled argon plasma optical emission spectrometry (ICAP 6500 Duo, Thermo Scientific, England). N, P, and K were determined in an acid digested solution, which was prepared according to Dahnke and Johnson 28 . The available nitrogen in the soil samples was extracted using a 2M potassium chloride solution and determined according to 29 . The available potassium and phosphorous were extracted using a DTPA + ammonium bicarbonate solution and measured following the method described by Soltanpour 30 . Adsorption experiments. Series of experiments was conducted to investigate the effects of different pH levels on the removal of Cu 2+ and Fe 3+ ions using MgO, SiO 2 , and ZnO NPs as adsorbent materials with an initial concentration of 50 mg L −1 for both Cu 2+ and Fe 3+ . The solid to liquid ratio was 10 g L −1 the shaking rate was 175 rpm, and the temperature was adjusted to 25 °C. Solutions with different pH values were prepared, and the pH was adjusted by adding nitric acid (0.1 M mol). After the prevailing 24 h of adsorption, the concentrations of the remaining Cu 2+ and Fe 3+ ions in each solution were detected using inductively coupled argon plasma optical emission spectrometry (ICAP 6500 Duo, Thermo Scientific, England). The adsorption isotherm of Cu 2+ and Fe 3+ was obtained using the prepared NPs as adsorbents, in which a series of concentrations of Cu 2+ and Fe 3+ was prepared by dissolving copper sulfate and iron chloride with an initial concentration of copper and iron ranging from 20 to 500 mg L −1 . The initial pH values for the Cu 2+ and Fe 3+ solutions were 5.2 and 3.2, respectively. Generally, 50 ml of each solution and 0.5 g of the adsorbent were mixed in a 100-ml sealed conical flask shaken at a constant speed of 175 rpm in a thermostatic water bath at 25 °C. After 24 h of adsorption, the concentrations of the remaining Cu 2+ and Fe 3+ in each solution were determined.

Pot experiments.
Pot experiment was carried out in green house of Desert Research Center, Egypt. located at 30° 7.29′ N, 31° 18.93′ E. Pot experiments were conducted during the cropping season of 2020-2021 to investigate the effects of MgO, SiO 2 , and ZnO NPs on plant yield and the availability of some heavy metals in both the soil and marjoram hat were polluted at three levels with either Fe 3+ or Cu 2+ . Marjoram was planted in pots containing 18 kg of soil after approximately 30 days from seed germination. Fertilizer doses were added to all treatments (as ammonium sulfate, calcium superphosphate, potassium sulfate, and biofertilizers) 31 . The experimental . The heavy metal contents were detected using ICAP. Statistical analysis. The data obtained in the present work were statistically analyzed, and the differences between the means of the different treatments were considered significant when they were greater than the values of the least significant difference at the 5% level using the Statistic program version No. 9. Alltreatments were used in a factorial design.
Statement. The collection of lemon peel and the cultivated Origanum majorana samples was done by getting the permission from the local suppliers. Te authors confirm that all methods were performed in accordance with the relevant guidelines and regulations.

Results and discussion
Characterizations of the NPs. XRD is a widely used method for determining particle size and NP structure. The XRD of the different NPs produced with the lemon peel extract is shown in Fig. 1. The following is how the Debye-Scherrer equation was used to determine the dimensions of the MgO, SiO 2 , and ZnO NPs: where D is the crystal volume, λ is the wavelength of the X-ray radiation (λ = 0.15406 nm) for Cu-Kα,K is frequently taken as 0.9, and β is the line width at half-maximum height. The peaks of the MgO NPs matched with the plane (JCPDS card No. 89-7102) and were found at 2θ = 36.72° (111), 2θ = 42.80° (200), 2θ = 62.38° (202), 2θ = 74.5° (311), 2θ = 78.5° (312), (222). The MgO NPs produced with lemon peel extract had a crystallized face-centered cubic (fcc) phase of magnesium oxide, according to the XRD spectrum 33 . Using Scherrer's formula, the crystal size was predicted to be around 16.77 nm. The SiO 2 NPs had peaks that correspond to the planes 2θ = 28.4° (040), 2θ = 31.5° (200), 2θ = 36.06° (130), 2θ = 48.4° (330), and 2θ = 56.9° (330) 34 . The XRD spectra indicate that the SiO 2 NPs made from the lemon peels were crystalline. Using Scherrer's formula, the calculated crystal diameters were around 42.6 nm. In addition, the ZnO NP patterns also suggest that the planes were approximately 2θ = 31.   www.nature.com/scientificreports/ diffraction peaks were identified. These findings revealed that the produced ZnO was extremely pure. No usual graphitic carbon diffraction peaks were found. Because graphitic carbon is naturally amorphous, its existence cannot be ruled out. The sample's highly crystalline nature is indicated by the crisp and high diffraction peaks 36 . High heat treatment is likely to provide sufficient kinetic energy for rearranging atomic groupings and hence the development of NP crystal structures 37 . ZnO was synthesized in this process at a sufficiently high temperature of around 500 °C, resulting in a product with a crystalline structure. Using Scherrer's formula, the crystallite size of the ZnO nanocrystallite was around 60.5 nm. TEM images provide a more detailed insight into the interior structure of NPs. Figure 2 shows a TEM image of the MgO, SiO 2 , and ZnO NPs produced with lemon peel extract. The circular structures are built of unique individuals of the distinct manufactured NPs, according to the increased two-dimensional picture of the NPs. Each produced NP has a size of about less than 100 nm, as measured by the TEM imaging. This size corresponds to that calculated from the XRD pattern. The FTIR technique was used to determine the probable chemical bonds in the lemon peel extract and the produced NPs. The FTIR spectra of the MgO, SiO 2 , and ZnO NPs, as well as that of the lemon peel extract, are shown in Fig. 3. The spectrum of the lemon peel extract had a strong peak at around 3200-3700 cm −1 , which may be attributed to the stretching mode of the hydroxyl of the phenols, which also coincide with the N-H of the amines, which could be attributable to the various bioactive chemicals found in lemon 38,39 . The symmetrical and asymmetrical C-H of the aliphatic groups has been assigned to two minor intensity peaks at about 2925 cm −1 . The bending vibration of the OH group was attributed to a wide broad peak at about 1717 cm −1 , which could be due to chemisorbed and/or physisorbed moisture on the surface of the NPs 40 .
The occurrence of C-O symmetric stretching of alcohol and vibrating C-H of the -CH=CH of the ethylene structure can be seen in the bands at 1019 and 616 cm −1 , respectively. When these peaks are compared with the spectra of the MgO NPs, a decrease in the peak position of the MgO NPs is observed. The MgO NPs had an absorption band at 450-850 cm −1 in the FTIR spectrum. The O-H stretch manifested as a very broad band in the spectra, spanning 3700 cm −141,42 . The saturated main peak between 1092 and 1456 cm −1 indicate significant concentrations of carbon and are also characteristic of the ligand 40 . Glycone steroids may have played a key role in the stabilization and capping of MgO NPs in our research 25,38,39 . When these peaks are compared with the spectra of the ZnO NPs, the peak broadening of the ZnO NPs is reduced. The typical Zn-O stretching vibration of the ZnO NPs caused a significant peak at about 450 cm −143, 44 . Before the calcination of the intermediate product to ZnO NPs, biomolecules were responsible for the conversion of ZnSO 4 to Zn(OH) 2 .  47 . The peaks at 354 nm indicate the presence of organic chromophores within the lemon peel extract. The peak located between 320 and 360 nm should be ascribable to the existence of phenolic mixtures 1 . Similarly, the band between 280 and 315 nm signposts to the presence of flavonoids and aloin 1 . Nevertheless, Jain et al. 47 , stated that, the use of UV-visible spectrophotometery in the studding of complex extract is limited by the essential difficulties in assigning the absorption peaks to any certain components in the structure. Hence, UV-VIS outcomes must be accompanied with GC/MS, to assist appropriate extract characterization and component identification 47       In general, adsorption percentages are reduced with lower pH levels. This is may be because of the reduced number of negative sites and the competition between the positive copper, iron, and hydrogen ions on these negative adsorption sites 50 . By increasing the pH of media, more adsorptive sites are created, and the adsorption capacity is increased. However, with continued increases in pH values, the formation of precipitates of Cu 2+ and Fe 3+ hydroxide is increased. Accordingly, adsorption experiments at pH values of 5.2 and 3.3 were preferable for Cu 2+ and Fe 3+ , respectively.
Adsorption isotherm models. Adsorption isotherms were used to easily describe the adsorption of different fractions of sorbet molecules that are partitioned between liquid and solid phases at equilibrium. Generally, the adsorption of Cu 2+ and Fe 3+ ions on the ZnO, MgO, and SiO 2 NPs was modeled using two adsorption isotherms.
Freundlich isotherm. The Freundlich isotherm is a model used to represent monolayer (chemisorption) and multilayer (physisorption) adsorption. It is founded on the supposition that molecules adsorb onto the uneven surface of an adsorbent 51  www.nature.com/scientificreports/ The Freundlich isotherm coefficients K F and n are calculated first from the intercept and slope of a chart of logq e vs. logC e , as shown in Fig. 6. In this investigation, n values greater than unity were discovered, indicating chemisorptions (Table 2) 52 . L-type isotherms with n > 1 suggest a high affinity between the adsorbate and the adsorbent and are suggestive of chemisorption 53 . With increasing temperature, the Freundlich constant (K F ) shows that the adsorption mechanism is endothermic.
Langmuir isotherm. The Langmuir isotherm assumes the adsorption of a monolayer on a uniform surface with a finite number of adsorption sites. Once a site is filled, no further sorption can take place at that site as the surface will eventually reach a saturation point where the maximum adsorption of the surface will be achieved. The linear form of the Langmuir isotherm model is described as follows: where K L is the Langmuir constant related to the energy of adsorption, and q max is the maximum adsorption capacity (mg g −1 ) 54 . The slope and intercept of plots of C e /q e versus C e at different temperatures were used to calculate q max and K L , as is shown in Fig. 7. The Langmuir isotherm parameter was appropriate for Cu 2+ and Fe 3+ adsorption on the ZnO, MgO, and SiO 2 NPs and yielded isotherms that were in good agreement with the observed behaviors, as presented in Table 3. The Cu 2+ and Fe 3+ adsorption capacities on the ZnO, MgO, and SiO 2 NPs at room temperature (297 K) were respectively 135, 66, and 58 mg g −1 for Cu 2+ and 104, 100, and 94 mg g −1 for Fe 3+ , as shown in Table 3. These are much higher than the adsorption capacities of other adsorbents reported in other relevant literature:that of activated carbon reached 3.37 mg g −155 , whereas the adsorption of hematite reached 4.94 mg g −156 . Table 4 show the effects of adding Cu 2+ at concentrations of 5 and 10 mg kg −1 together with different treatments of NPs. It can be clearly seen that the NP application without the addition of any pollutant reduced the available Cu 2+ in the studied soil samples. The order of the effects of the NP application was as follows: Zn2 > Zn1 > Mg2 > Si2 > Mg 1 > Si1 > C (control).

Effects of ZnO, MgO, and SiO 2 NPs and polluted irrigated water containing Cu 2+ and Fe 3+ on the soil and plants. Effects of ZnO, MgO, and SiO 2 NPs and polluted irrigated water containing Cu 2+ on the available concentrations of Cu 2+ in the soil and plants. The data listed in
The highest values of the available Cu 2+ were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added 57 .
There was a significant difference between all treatments except for Si2/Mg2 and Si1/Mg1. When Cu 2+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of the NP application on the availability of Cu 2+ extracted using DTPA took the following order: Zn2 > Zn1 > Si2 > Mg2 > Si1 > Mg1 > C (control). The highest value of the effects of NP addition on artificially polluted soils with Cu 2+ (5 mg kg −1 ) was found when Zn2 was added to the soil, whereas the lowest effect was found when Mg1 was added 58 . There was a significant difference between all treatments except for Si2/Mg2 and Si1/Mg1, similar to what was observed in the control experiments. Increasing the original values of Cu 2+ by 10 mg kg −1 changed the order of effects of the NPs to the following: Zn2 > Zn1 > Mg2 > Si2 > Mg1 > Si1 > C (control).
There was a significant difference between all treatments except for Si2 and Mg1. It can beclearly seen that the highest reduction effect on the available Cu 2+ in the three trials studied (thecontrol, 5 mg kg −1 , and 10 mg kg −1 ) was related to the addition of Zn2. The mean values for the three NPs presented significant differences except for Si1 and Mg1. The data presented in Table 4 explore the effects of NPs on Cu 2+ uptake through plants that were osculated among the higher and lower values compared with the control experiments. The order for increasing Cu 2+ uptake through plants without the addition of Cu 2+ was as follows: There was a significant difference between all treatments except for Si2/Zn2 and C(control)/Mg1. When Cu 2+ was added to the soil at a constant concentration of 5 mg kg −1 , the order of effects of the NP application was as follows: C (control) > Si1 > Si2 > Mg1 > Zn1 > Zn2 > Mg2. This indicates that the addition of NPs to the soil system decreased Cu 2+ uptake through plants.
There was a significant difference between all treatments except for Zn1, Si2, and Mg1. Increasing the addition of Cu 2+ pollutants to the soil to 10 mg kg −1 changed the sequence of effects of NP addition to the following order: There was a significant difference between all treatments except for Zn1 and Mg2. The application of NPs minimized the Cu 2+ levels in marjoram because of the antagonistic impacts of metals. The trend of these results agrees with those reported by Saifullah et al. 59 , Hussain et al. 60 , and Wang et al. 61 .
Effects of ZnO, MgO, and SiO 2 NPs and polluted irrigated water containing Fe 3+ on the available concentrations of Fe 3+ in soil and plant. The effects of adding Fe at concentrations of 5 and 10 mg kg −1 with different NP treatments are listed in Table 4. It can be clearly seen that the NP application without the addition of any pollutants reduced the available Fe 3+ in the soil samples. The order of the effects of the NP application on the reduction of available Fe was found as follows: Zn2 > Zn1 > Mg2 > Mg1 > Si1 > Si2 > C (control) 57 . The highest values of the available Fe 3+ were observed in the control, whereas the lowest values were obtained when Zn2 was added.
There was a significant difference between all treatments except for Si1 and Mg1. When Fe 3+ was added to the soil as an external pollutant source to increase the original exit values by 5 mg kg −1 , the effects of the NPs addition on the availability of Fe 3+ extracted using DTPA took the following order: Zn2 > Zn1 > Si2 > Mg2 > Si1 > Mg1 > C (control).This is considered similar to what was observed with the same treatment of Cu 2+ . The highest values   There was a significant difference between all treatments. Clearly, the highest effect in the three trials studied in this work (control, 5 mg kg −1 , and 10 mg kg −1 ) was related to the addition of Zn2 58,62 . The data presented in Table 4 also explore the effects of NPs on Fe 3+ uptake through plants that were osculated among the higher and lower values compared with the control experiments. The order of the effects of NP addition on increasing Fe 3+ uptake through plants was as follows: There was a significant difference between all treatments except for the control and Si1. When Fe 3+ was added to the soil at a constant concentration of 5 mg kg −1 , the order of the effects of NP application was as follows: Thisindicates that the addition of NPs to the soil system had positive effects on the Cu 2+ uptake through plants.
There was a significant difference between all treatments except for Mg2 and Zn1. Increasing the addition of Fe 3+ pollutants to the soil to 10 mg kg −1 changed the sequence of the effects of NP addition on increasing Fe 3+ concentrations inside the plant tissue to the following order: There was a significant difference between all treatments. At the root surface, NPs can compete with Fe 3+ as these metals are being transported by common transporters in the roots 63 . Higher Zn concentrations in the roots may inhibit Fe 3+ uptake by marjoram plants. The trend of these results agrees with those reported by Ali et al. 60 , who suggested that the improved Zn nutritional status with foliar-applied ZnO NPs may suppress the expression of Zn 2+ transporters in roots, decreasing the Cd 2+ accumulation by roots. This variation in metal accumulation by plants under NP treatments might be due to the variation in the sizes and shapes of NPs as well as the crop species and NP application modes.
Effect of Cu 2+ and Fe 3+ additives and ZnO, MgO, and SiO 2 NPs treatment on the availability of N, P, and K in soils. Effect of Cu 2+ additives and ZnO, MgO, and SiO 2 NPs treatment on the availability of N, P, and K in soils. The effects of Cu 2+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs are listed in Table 5. It was clearly seen that the effects of NPs application on the availability of substantial concentrations of N without any pollutants additives resulted in an osculating in the reduction or increment of the available N in the soil system. The order of sequence for the effects of NPs application on reducing available N was found to take the following sequence Mg2 > Mg1 > C (control) > Si2 > Zn2 > Zn1 > Si1. he highest values that were affected the reduction of the available N were observed with Mg2, whereas the lowest values were obtained when Si1 was added. There was a significant difference between all treatments except for the treatments of (control and Mg1) 58,62 . When Cu 2+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the availability of N were found to take the following order Mg2 > Zn2 > Si2 > Si1 > Mg2 > Si2 > C (control) > Zn1. The highest value of the effects of adding NPs on the artificially polluted soils with Cu 2+ (5 mg kg −1 ) to reduce the availability of N was found when Mg2 was added to the soil, whereas the lowest effect was found when Zn1 was added. There was a significant difference between all treatments except for the treatments of (control and Si2) and (Z2 and Si1). Increasing the values of polluted Cu 2+ to 10 mg kg −1 resulted in changing the order of effects of NPs on the availability of N to the following order Si2 > Mg1 = Mg2 = Si1 = Zn2 > C (control) > Zn1. There was a significant difference between all treatments except for the following treatments Mg1, Mg2, Si1, and Zn2. It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Mg2 and Si2. The effects of Cu 2+ additives as two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on available phosphorous (P) are listed in Table 5. It was clearly seen that the effect of NPs application on the availability of substantial concentrations of P without any pollutants additives resulted in an osculating of the reduction or increment of the available P in the soil system. The order of sequence for the effects of NPs application on reducing available P was found to take the following sequence Zn2 > C (control) > Mg2 > Mg1 > Zn1 > Si1 > Si2. The highest values that affected the reduction of the available P were observed with Zn2, whereas the lowest values were obtained when Si2 was added. There was a significant difference between all treatments except for the treatments of (control and Zn2). When Cu 2+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on reducing the availability of P was found to take the following  www.nature.com/scientificreports/ to the soil, whereas the lowest effect was found when Zn2 was added. There was a significant difference between all treatments except for the treatments of (Si2 and Mg2). Increasing the values of an external pollution of Cu 2+ to 10 mg kg −1 resulted in changing the order of effects of NPs on the availability of P to the following order C (control) > Zn1 > Mg2 > Si1 = Si2 > Mg1 > Zn2. There was a significant difference between all treatments except for the following treatments (Si1 and Si2). It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Zn2, Mg2, and control. The effects of Cu 2+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on the availability of K are also listed in Table 5. It was clearly seen that the effect of NPs application on the availability of substantial concentrations of K without any pollutants additives resulted in an osculation in the reduction or increment of the available concentrations of available K in the soil system. The order of sequence for the effects of NPs application on reducing the available concentrations of K was found to take the following sequence Mg2 > Si2 > Mg1 > C (control) > Si1 > Zn1 > Zn2. The highest values affected the reduction of the available K were observed with Mg2, whereas the lowest value was obtained when Zn2 was added. There was a significant difference between all treatments except for the treatments of (Si2 and Mg1). When Cu 2+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the availability of K were found to take the following order Si1 > Mg1 > Zn2 > C (control) > Mg2 > Zn1 > Si2. The highest value of the effect of adding NPs on the artificially polluted soils with www.nature.com/scientificreports/ Cu 2+ (5 mg kg −1 ) to reduce the availability of K was found when Si1 was added to the soil, whereas the lowest effect was found when Si2 was added. Generally, there was a significant difference between all treatments. Increasing the values of an external polluted Cu 2+ to 10 mg kg −1 resulted in changing the order of effects of NPs on the availability of K to the following order Si2 > Si1 > Mg2 > Zn2 > Mg1 = Zn1 > C (control). There was a significant difference between all treatments. It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 on K availability were osculated among Mg2, Si1, and Si2. On the other hand, the lowest effects were attributed to the Zn2 in the control experiment, whereas in the experiments that have been carried out with the addition of Cu 2+ (5 mg kg −1 and 10 mg kg −1 ), the effects of Si2 and control were more dominant. The highest values of available K were found with the control experiment followed by the experiments that were carried out with the addition of an external Cu 2+ with concentrations of 5 mg kg −1 and 10 mg kg −1 , respectively.

Effect of Fe 3+ additives and ZnO, MgO, and SiO 2 NPs treatment on the availability of N, P, and K in the treated soils.
The effects of Fe additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs are listed in Table 6. It was clearly seen that the effect of NPs application on the availability of substantial concentrations of N without any an external Fe additives resulted in an osculating in the reduction or increment of the available N in the soil system. The order of sequence for the effects of NPs application on reducing the available N was found to take the following sequence C (control) = Mg1 > Si1 > Mg2 > Zn2 > Zn1 > Si1.
The highest values that affected the reduction of the available N were observed with both control and Mg1, whereas the lowest values were obtained when Si1 was added. There was a significant difference between all treatments except for the treatments of (control and Mg1). When Fe was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the reduction of available N were found to take the following order Zn2 > Si2 > Mg2 = C (control) > Si1 = Mg1 > Zn1. The highest value of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) to reduce the availability of N was found when Zn2 was added to the soil, whereas the lowest effect was found when Zn1 was added. There was a significant difference between all treatments except for the treatments of (control, Si1, Mg1, and Mg2) 58,62 .
Increasing the values of an external addition of Fe 3+ to 10 mg kg −1 resulted in changing the order of effects of NPs on reducing the availability of N to the following order Si1 > Zn1 = Si2 = Zn2 > C (control) > Mg1 > Mg2. There was a significant difference between all treatments except for the following treatments (control and Zn2), (Zn2 and Mg1), and (Zn1 and Si12). It was clearly seen that the highest effect in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 was osculated among Mg1, control, Zn2, and Si1. On the other hand, the lowest effects were attributed to the Si1 in the control experiment, whereas in the experiments that have been carried out with the addition of Fe 3+ with concentrations of 5 mg kg −1 10 mg kg −1 , www.nature.com/scientificreports/ the effects of Zn1 and Mg2 were more dominant. The highest values of available N were found with the control experiment followed by experiments that were carried out with the addition of Fe 3+ at concentrations of 5 mg kg −1 and 10 mg kg −1 . The effects of Fe 3+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 with different treatment of NPs on the reduction of available P are listed in Table 6. It was clearly seen that the effect of NPs application on the availability of substantial concentrations of P in soil without any pollutants additives resulted in an osculating in the reduction or increment values of the available P in the soil system. The order of sequence for the effects of NPs application on reducing the available P was found to take the following sequence Zn2 > C (control) > Mg2 > Mg1 > Zn1 > Si1 > Si2. The highest values affected the reduction of the available P were observed with Zn2, whereas the lowest values were obtained when Si2 was added. There was a significant difference between all treatments 62 . When Fe 3+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the availability of P were found to take the following order Mg2 > Si2 > Mg1 > Si2 > Zn2 > Zn1 > C (control). The highest value of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) to reduce the availability of P was found when Mg2 was added to the soil, whereas the lowest effect was found when Zn1 was added. There was a significant difference between all treatments except for the treatments of (Si1 and Mg2). Increasing the values of an external addition of Fe 3+ to 10 mg kg −1 resulted in changing the order of effects of NPs on the availability of P to the following order Si1 > M g1 > Mg2 > Si2 > Zn2 > Zn1 > C (control). There was a significant difference between all treatments except for the following treatments (Zn1, Zn2, Si2, and Mg2). It was clearly seen that the highest effect in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 was osculated among Zn2, Mg2, and Si1. The effects of Fe 3+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on the reduction of available K are listed in Table 6. It was clearly seen that the effect of NPs application on the availability of substantial concentrations of K in soil without any pollutants additives resulted in an osculating in the reduction or increment of the available concentrations of K in the soil system. The order of sequence for the effects of NPs application on reducing the available concentrations of K was found to take the following sequence Mg2 > Si2 > Mg1 > C (control) > Zn1 > Si1 > Zn2. The highest values affected the reduction of available K were observed with Mg2, whereas the lowest values were obtained when Zn2 was added 58,62 . There was a significant difference between all treatments. When Fe 3+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the availability of K was found to take the following order Zn2 > Si2 > C (control) > Mg2 > Zn1 > Mg1 > Si1. The highest value of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) to reduce the availability of K was found when Zn2 was added to the soil, whereas the lowest effect was found when Si1 was added. There was a significant difference between all treatments except for (Mg1 and Mg2). Increasing the values of an external addition of Fe 3+ to 10 mg kg −1 resulted in changing the order of effects of NPs on the availability of K to the following order C www.nature.com/scientificreports/ (control) > Zn2 > Mg2 > Zn1 > Mg1 > Si2 > Si1. There was a significant difference between all treatments except for (Z1 and Mg1) 62 . It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 on K availability were osculated among Mg2, Zn2, and control.

Effect of Cu 2+ and Fe 3+ additives and ZnO, MgO, and SiO 2 NPs treatment on the accumulation of N, P, and K in the plant. Effect of Cu 2+ additives and ZnO, MgO, and SiO 2 NPs treatment on the ac-
cumulation of N, P, and K in the plant. The effects of Cu 2+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on increasing the total amounts of N in the plant are listed in Table 6. It was clearly seen that the effect of NPs application on increasing the total concentrations of N without any Cu 2+ additives resulted in an osculation in the reduction or increment of N in the plant 62 . The order of sequence for the effects of NPs application on the increasing the total N was found to take the following sequence Mg2 > Zn2 > Si2 > Si1 > C (control) > Zn2 > Zn1 > Si1. The highest values affected the increases of the available N in the plant were observed with Mg2, whereas the lowest values were obtained when Si1 was added. There was a significant difference between all treatments except for the treatments of (control and Si2) and (Si1 and Mg1). When Cu 2+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the increment of total N were found to take the following order Si2 > C (control) > Mg1 > Zn1 = Mg2 > Zn2 > Si1. The highest value of the effects of adding NPs on the artificially polluted soils with Cu 2+ (5 mg kg −1 ) to increase the total concentrations of N in the plant was found when Si2 was added to the soil, whereas the lowest effect was found when Si1 was added 62 . There was a significant difference between all treatments except for the treatments of (control and Si2) and (Z1 and Mg2). Increasing the values of an external addition of Cu2 + to 10 mg kg −1 resulted in changing the order of effects of NPs on increase the total concentrations of N in the plant to the following order Si2 > Si1 > C (control) > Zn2 = Mg1 > Zn1 > Mg2.
There was a significant difference between all treatments except for the following treatments (control and Si1) and (Zn1, Zn2, and Mg1). It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Mg2, Si2, and Si2, respectively. The effects of Cu 2+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on increasing the total amounts of P in the plant are listed in Table 6. It was clearly seen that the effect of NPs application on increasing the total concentrations of P without any pollutants additives resulted in an osculating in the reduction or increment of P in the plant. The order of sequence for the effects of NPs application on the increasing the total P was found to take the following sequence Si1 > Si2 > Mg1 > C (control) > Zn1 > Zn2 > Mg2. The highest values affected the increases of the available P were observed with Si1, whereas the lowest values were obtained when Mg2 was added. There was a significant difference between all treatment except for the treatments of (Si2 and Mg1). When Cu 2+ was added to the soil as a pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the increment of total P were found to take the following order Zn1 > Si2 > C (control) > Si1 > Zn2 > Mg2 > Mg1 62 . The highest value of the effects of adding NPs on the artificially polluted soils with Cu 2+ (5 mg kg −1 ) to increase the total concentrations of P in the plant was found when Zn1 was added to the soil, whereas the lowest effect was found when Mg1 was added. There was a significant difference between all treatments. Increasing the values of an external addition of Cu 2+ to 10 mg kg −1 resulted in changing the order of effects of NPs on increase the total concentrations of P in the plant to the following order Si1 > Zn1 > C (control) > Si2 > Mg1 > Mg2 > Zn2. There was a significant difference between all treatments. It was clearly seen that the highest effects in the three trials that were studied in the present work including the control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Si1, Zn1, and Si1, respectively. The effects of Cu 2+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneous with different treatments of NPs on increasing the total amounts of K in the plant are listed in Table 6. It was clearly seen that the effect of NPs applications on increasing the total concentrations of K without any Cu 2+ additives were resulted in an osculating in the reduction or increment of total K in the plant. The order of sequence for the effects of NPs application on increasing the total K was found to take the following sequence Zn2 > C (control) > Mg1 > Mg2 > Si2 > Si1 > Zn1. The highest values affected the increases of the total N were observed with Zn2, whereas the lowest values were obtained when Zn1 was added. There was a significant difference between all treatments. When Cu 2+ was added to the soil as an external pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the increment of total K were found to take the following order Si2 > Zn1 > Zn2 > Mg2 > Si1 > C (control) > Mg1. The highest values of the effects of adding NPs on the artificially polluted soils with Cu 2+ (5 mg kg −1 ) to increase the total concentrations of K in the plant were found when Si2 was added to the soil, whereas the lowest effect was found when Mg1 was added. There was a significant difference between all treatments except for the treatments of (Z1 and Zn2). Increasing the values of Cu 2+ to 10 mg kg −1 resulted in changing the order of effects of NPs on increase the total concentrations of K in the plant to the following order C (control) > Zn1 > Zn2 > Si2 > Mg1 > Si1 > Mg2 58,62 . There was a significant difference between all treatments except for the following treatments (control and Zn1). It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Zn2, Si2, and control, respectively.
Effect of Fe 3+ additives and ZnO, MgO, and SiO 2 NPs treatment on the accumulation of N, P, and K in the plant. The effects of Fe 3+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on increasing the total amounts of N in the plant are listed in Table 6. It was clearly seen that the effect of NPs application on increasing the total concentrations of N without any pollutants additives resulted in an osculating in the reduction or increment of N in the plant. The order of sequence for the effects of NPs application on the increasing the total N was found to take the following sequence Mg2 > Zn2 > Si2 > C (control) > Mg1 > Si1 > Zn1. The highest values affected the increases of the total N were observed with Mg2, whereas www.nature.com/scientificreports/ the lowest values were obtained when Zn1 was added. There was a significant difference between all treatment except for the treatments of (Si1 and Mg1). When Fe 3+ was added to the soil as an external addition to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the increment of total N were found to take the following order Si1 > C (control) > Mg1 > Si1 > Zn1 > Zn2 = Mg2. The highest value of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) to increase the total concentrations of N in the plant was found when Si1 was added to the soil, whereas the lowest effect was found when Mg2 was added.
There was a significant difference between all treatments except for the treatments of (Zn2 and Mg2). Increasing the values of polluted Fe 3+ to 10 mg kg −1 resulted in changing the order of effects of NPs on increase the total concentrations of N in the plant to the following order C (control) > Mg1 > Zn1 > Si2 > Zn2 > Si1 > Mg2. There was a significant difference between all treatments. It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Mg2, Si1, and control, respectively. The effects of Fe 3+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on increasing the total amounts of P in the plant are listed in Table 6. It was clearly seen that the effect of NPs application on increasing the total concentrations of P without any pollutants additives resulted in an osculating in the reduction or increment of P in the plant 58 . The order of sequence for the effects of NPs application on the increasing the total P was found to take the following sequence Si1 > Si2 > Mg1 > C (control) > Zn1 > Zn2 > Mg2 which is similar to what was observed with Cu 2+ additives at the same concentrations. The highest values affected the increases of the total P were observed with Si1, whereas the lowest values were obtained when Mg2 was added. There was a significant difference between all treatments except for the treatments of (Si2 and Mg1). When Fe 3+ was added to the soil as pollutant to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the increment of total P were found to take the following order Si2 > Si1 > Mg2 > Mg1 > Zn2 > C (control) > Si1 = Mg2. The highest values of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) to increase the total concentrations of P in the plant were found when Si2 was added to the soil, whereas the lowest effects were found when Mg2 were added. There was a significant difference between all treatments except for (control and Zn1) and (Zn2 and Mg1). Increasing the values of an external addition of Fe 3+ to 10 mg kg −1 resulted in changing the order of effects of NPs on increasing the total concentrations of P in the plant to the following order Zn1 > Mg1 > Zn2 > Si2 > C (control) > Si1 = Mg2 62 .
There was a significant difference between all treatments. It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Si1, Si2, and Zn1, respectively. The effects of Fe 3+ additives with two concentrations of 5 mg kg −1 and 10 mg kg −1 simultaneously with different treatment of NPs on increasing the total amounts of K in the plant are listed in Table 6. It was clearly seen that the effect of NPs application on increasing the total concentrations of K without any pollutants additives resulted in an osculating in the reduction or increment of K in the plant. The order of sequence for the effects of NPs application on increasing the total K was found to take the following sequence Zn2 > C (control) > Mg1 > Mg2 > Si2 > Si1 > Zn1 which is similar to what was observed during Cu 2+ additives at the same concentrations. The highest values affected the increases of the total K were observed with Zn2, whereas the lowest values were obtained when Zn1 was added. There was a significant difference between all treatments except for (control and Mg1). When Fe 3+ was added to the soil as an external addition to increase the original exit values by 5 mg kg −1 , the effects of NPs application on the increment of total K were found to take the following order Zn1 Mg2 > Si1 > Zn2 > C (control) > Mg1 > Si2. The highest value of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) to increase the total concentrations of K in the plant was found when Zn1 was added to the soil, whereas the lowest effect was found when Si2 was added. There was a significant difference between all treatments except for the treatments of (control and Mg1) 58 . Increasing the values of an external addition of Fe 3+ to 10 mg kg −1 resulted in changing the order of effects of NPs on increase the total concentrations of K in the plant to the following order Si2 > Zn2 > C (control) > Zn1 > Si1 > Mg1 > Mg2. There was a significant difference between all treatments. It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were osculated among Zn2, Zn1, and Si2, respectively. The trend of these results agreed with those reported by Hegab et al. 63 Table 7. The effects of two concentrations (5 mg kg −1 and 10 mg kg −1 ) of Cu 2+ additives have been investigated. It was clearly seen that the effect of NPs application presented a negative effect on Marjoram dry weight in the experiments that have been carried out without Cu 2+ additives. The order of sequence for the effects of NPs application on increasing the dry weight was found to take the following order control > Si2 = Mg1 > Si1 > Zn1 > Mg2 > Zn2. The highest values of means for dry weight were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added. There was a significant difference between all treatments except for the treatments of (Si2 and Mg2) 62 . When Cu 2+ was added to the soil as an external addition to increase the original exit values by 5 mg kg −1 , the effects of NPs application on Marjoram dry weight took the following order Zn2 > Mg2 > Si2 > C (control) > Zn1 > Si1 > Mg1. The highest value of the effects of adding NPs on the artificially polluted soils with Cu 2+ (5 mg kg −1 ) was found when Zn2 was added to the soil, whereas the lowest effect was found when Mg1 was added. There was a significant difference between all treatments except for the treatments of (control, Zn1, and Si2) and (Si1 and Mg1). Increasing the values of original exist values of Cu 2+ by 10 mg kg −1 resulted in changing the order of effects of NPs on Marjoram dry weight to the following order Zn1 > Zn2 > Mg2 > Si2 > C (control) > Si1 Mg1. There was a significant difference between all treatments except for the treatments of (control, Si1, Si2 and Mg1) and (Zn2, Mg2). It was clearly seen that the highest effect in the three trials that were www.nature.com/scientificreports/ studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 was relevant to the additives of control, Zn2, and Zn1, respectively. It was clearly seen that the effect of NPs application presented a negative effect on Marjoram wet weight in the experiments that have been carried out without Cu 2+ additives. The order of sequence for the effects of NPs application on increasing the wet weight was found to take the following order control > Si2 = Mg1 > Si1 > Mg2 > Zn1 > Zn2. The highest values of means for wet weight were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added which is similar to data that has been observed in dry weight. There was a significant difference between all treatments except for the treatments of Si2 and Mg1. When Cu 2+ was added to the soil as an external pollutant to increase the original exiting values by 5 mg kg −1 , the effects of NPs application on Marjoram wet weight took the following order Zn2 > Si1 = Mg2 > Zn1 = Mg1 > C (control) > Si2. The highest value of the effects of adding NPs on the artificially polluted soils with Cu 2+ (5 mg kg −1 ) was found when Zn2 was added to the soil, whereas the lowest effect was found when Si2 was added. There was a significant difference between all treatments except for the treatments of control, Zn1, Si1, Mg1, and Mg2. Increasing the values of original exist values of Cu 2+ addition by 10 mg kg −1 resulted in changing the order of effects of NPs on Marjoram wet weight to the following order Zn1 > Zn2 > C (control) > Mg1 > Si2 = Mg2 > Si1. There was a significant difference between all treatments except for the treatments of (control and Zn2) and (Si2, Mg1, and Mg2). It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were relevant to the additives of control, Zn2, and Zn1, respectively similar to what was observed in dry weight. The fresh and dry weights were affected by the use of Zn, Si, Mg NPs and may be the lower biomass in the control plants might be due to the higher Fe 3+ and Cu 2+ levels in these plants. These elements mediated reduction in plant growth might be associated with the disturbance of several mechanisms in plants such as chlorophyll biosynthesis, water deficit, and ultra-structural alteration in plant 65 . These results are in close conformity with Venkatachalam et al. 66 .
Effect of ZnO, MgO, and SiO 2 NPs and polluted water containing Fe 3+ on dry and wet weights of Marjoram plant. The effects of Fe 3+ additives with different NPs treatments on dry and wet weights of Marjoram are presented in Table 7. The effects of two concentrations of 5 mg kg −1 and 10 mg kg −1 of Feon dry and wet weights of Marjoram plant have been investigated. It was clearly seen that the effect of NPs application presented a negative effect on Marjoram dry weight in the experiments that have been carried out without Fe 3+ additives. The order of sequence for the effects of NPs application was found to take the following order C (control) > Si2 = Mg1 > Si1 > Zn1 > Mg2 > Zn2. The highest values of means for dry weight were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added. There was a significant difference between all treatments except for the treatments of Si2 and Mg1. When Fe 3+ was added to the soil as an external addition to increase the original exit values by 5 mg kg −1 , the effects of NPs application on Marjoram dry weight took the following order Mg1 > Si1 > C (control) = Zn2 > Zn1 > Mg2 > Si2. The highest value of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) was found when Mg1 was added to www.nature.com/scientificreports/ the soil, whereas the lowest effect was found when Si2 was added. There was a significant difference between all treatments except for the treatments of (control and Zn2) and (Zn1, Si2, and Mg2) 54,58 . Increasing the values of original exist values of Fe 3+ by 10 mg kg −1 resulted in changing the order of effects of NPs on Marjoram dry weight to the following order Mg1 > Si2 > C (control) = Zn2 = Mg2 > Zn1 > Si1. There was a significant difference between all treatment except for the treatments of (control, Zn2, and Mg2) and (Zn1 and Si1). It was clearly seen that the highest effects in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 were relevant to the additives of control, Mg1, and Mg1, respectively. It was clearly seen that the effect of NPs application presented a negative effect on Marjoram wet weight in the experiments that have been carried out without Fe 3+ additives. The order of sequence for the effects of NPs application was found to take the following order C (control) > Si2 = Mg1 > Si1 > Mg2 > Zn1 > Zn2. The highest values of means for wet weight were observed in the control treatment, whereas the lowest values were obtained when Zn2 was added. There was a significant difference between all treatments except for the treatments of (Si2 and Mg1). When Fe 3+ was added to the soil as an external addition to increase the original exit values by 5 mg kg −1 , the effects of NPs application on Marjoram wet weight took the following order Mg1 > Si1 > control = Zn2 > Si2 > Zn1 > Mg2. The highest values of the effects of adding NPs on the artificially polluted soils with Fe 3+ (5 mg kg −1 ) were found when Mg1 was added to the soil, whereas the lowest effect was found when Mg2 was added. There was a significant difference between all treatments except for the treatments of control and Zn2. Increasing the values of original exist values of Fe 3+ by 10 mg kg −1 resulted in changing the order of effects of NPs on Marjoram wet weight to the following order Mg1 > Si2 > C (control) > Zn2 > Mg2 > Zn1 > Si1. There was a significant difference between all treatment except for the treatments of (Zn2 and Mg2). It was clearly seen that the highest effect in the three trials that were studied in the present work including control, 5 mg kg −1 , and 10 mg kg −1 was relevant to the additives of control, Mg1, and Si2, respectively. These results are in close conformity with Tripathi et al. 67 who reported that Supply of SiO 2 NPs enhanced the photosynthetic pigments in Cr-stressed pea leaves.

Conclusion
In this study, we conducted a green synthesis of ZnO, MgO, and SiO 2 NPs to investigate their effects on the quality of irrigation water, the availability of some heavy metals in soil and plants, and the productivity of marjoram. The results obtained from our experiments explored that the addition of NPs resulted in noticeable variations in the removal percentages of both Cu 2+ and Fe 3+ . The maximum values obtained for the adsorption of Cu 2+ on ZnO, MgO, and SiO 2 NPs within the pH values of 3-5 were 89.9%, 83.3%, and 68.36%, respectively. In contrast, the maximum adsorption values of Fe 3+ at pH 3.3 were 82%, 80%, and 65% for the ZnO, MgO, and SiO 2 NPs, respectively. Whereas, the maximum adsorption values of Fe 3+ at pH 3.3 were 82%, 80%, and 65% for ZnO, MgO, and SiO 2 NPs, respectively. Whereas, the maximum adsorption values of Fe 3+ at pH 3.3 were 82%, 80%, and 65% for ZnO, MgO, and SiO 2 NPs, respectively. It was clearly seen that the effect of NPs application on the availability of substantial concentrations of Cu 2+ without any pollutants additives resulted in the reduction of the available Cu 2+ in the soil samples, and that same tendency was observed with the substantial concentrations of Fe exist in the soil. Adding NPs to the soil system had positive effects on Cu 2+ uptake via the plant. The effect of NPs and the addition of Cu 2+ and Fe 3+ on the availability of NPK in the soil system were very completed and osculated from one treatment to another. The same tendency was observed with the total concentration of NPK in the plant. It was clearly seen that the effects of NPs application have presented a negative effect on Marjoram dry and wet weight in the experiments that have been carried out without the additions of either Cu 2+ or Fe 3+ .