Immobilization of Cr3+, Cd2+, and Pb2+ added to calcareous soils amended with composted agro-industrial residues

Sub Levels

Experimental plan

Field experiments were conducted during the 2021/2022 season in the city of Newborg El Arab, Alexandria Governorate, Egypt (30°53´33.17″N, 29°22´46.43″E). We ensure that laboratory and field research on cultivated wheat plants, including the collection of plant material, complies with relevant institutional, national and international guidelines and laws. Fieldwork was conducted at his SRTA city experimental farm, and permission was granted by the farm’s scientific advisor as our study complies with local and national regulations. wheat seedswheat L. (GIZA 171 cultivar) was purchased from the Accredited National Seed Center, Agricultural Research Center, Ministry of Agriculture, Giza, Egypt. All agricultural practices for wheat crop production, including organic and mineral fertilizers, were carried out in accordance with the 2013 recommendations of the Egyptian Ministry of Agriculture and Land Reclamation.37. Soil carbonate content was detected by over-addition of 4 M HCl and released CO.2 was quantified using a developed Soil Royal Eikelkamp Calcimeter (Eichelkamp Soil & Water, Giessbeek, The Netherlands, Scheibler Apparatus) that meets the accreditation standard NEN-ISO 10693. Accurate measurements were made according to the Scheibler method, which involves determination of carbonate content in soil. Soil volumetrically (measurement range: 0 to > 200 g kg)-1 Reading accuracy 1 g kg-1).

Plot experiments were divided into two regions.Non-contaminated soil with no added metals and contaminated soil treated with high concentration CrCl3 (SIGMA-Aldrich Labrochemikalien GmbH, Riedstr.2, D-89555 Steinheim, Germany, 98.5%) (100 mg Cr/kg soil), PbCl2 (SIGMA-Aldrich Labrochemikalien GmbH, Riedstr.2, D-89555 Steinheim, Germany, 99.0%) (100 mg Pb/kg soil), and CdCl2 (SIGMA-Aldrich Labrochemikalien GmbH, Riedstr.2, D-89555 Steinheim, Germany, 99.0%) (3 mg Cd/kg soil), reaching the critical soil limit proposed by Alloway38Exceeding limits encountered in areas with alkaline soils39. In addition, each soil was treated with either compost (Cp) or vermicompost (Vp) at a rate reaching 2% of soil organic matter, but was the control. In both soils, compost and vermicompost, known as organic treatments, were subtreated with NPK at different percentages of 0% (control), 50% (NPK50), and 100% (NPK100).37. A 100% NPK dose contains 118 kg N, 33.5% N (NH) per fedan.Fourno3), 29kgP2Five 15.5% P per fedan2Five59 kg K2O 48% K per Phedane2O. Phosphorus was added before cultivation, and nitrogen and potassium were added in three doses after germination, at the beginning of the vegetative stage, and at the tiller stage.Surface irrigation was applied at 4000m3 haha-1 It provides the wheat crop with the water it needs and prevents the stress of metal transfer from the soil to the plant.

A randomized complete block design (RCBD) was used for contamination (uncontaminated versus contaminated soil), organic treatment (control, compost, and vermicompost), mineral fertilizer levels (0, 50, and 100%). It was used for an experimental design based on three factors. NPK) is run 3 times for each subprocess, for a total of 54 subprocesses. A total of 18 subtreatments were obtained, 9 on uncontaminated soil (n = 27 = 9 × 3 replicates) and 9 on contaminated soil (n = 27 = 9 × 3 replicates) (Supplementary Table S1). The term “control sub-treatment” refers to the control, NPK50, and NPK100 sub-treatments. Therefore, the term “compost subtreatment” refers to Cp, Cp+NPK50, and Cp+NPK100 subtreatments, and the term “worm compost subtreatment” refers to Vp, Vp+NPK50, and Vp+NPK100 subtreatments. increase. . Each subtreatment was run three times on square (3 × 3 m) plots.

soil analysis

After the experiment, soil samples of uncontaminated and contaminated soil were collected in triplicate from each subtreatment (3 × 9 × 2 = 54 samples), air-dried, ground, and subjected to subsequent soil analysis according to the manual. A 2 mm sieve was used to perform proposed by Ryan et al.40. Soil particle analysis was performed using the Robinson pipette method (Eijkelkamp Agriresearch Equipment, Giesbeek, The Netherlands). Soil pH and electrical conductivity (EC) were measured in 1:2.5 w/v and 1:1 w/v soil aqueous suspensions, respectively. Wet oxidation method was used to oxidize soil organic carbon (SOC). Total nitrogen (TN) was measured using the Kjeldahl method.40. Soluble cation (Na+K+Ca2+Mg2+) and anions (SOFour2−ClHCOs3) was determined from saturated soil paste extracts40. Soluble Na+ and K.+ It was measured by a flame photometer (PG Instruments Ltd, Almapark, Wibtoft, Leicestershire, England: FP902). Sodium adsorption rate (SAR) was calculated as suggested by Robbins.41.

$$SAR = \frac{{\text{Na }}}{{\sqrt {\frac{1}{2}\left( {{\text{Ca }} + {\text{Mg }}} \right )} }}$$


Soluble SOFour2− Measured by barium sulfate precipitation.soluble chlorine and HCO3 titrated with AgNO3 (SIGMA-Aldrich CHEMIE GmbH, PO1120–89555 Steinheim, Germany) and 0.01 NH2SoFour (SIGMA-Aldrich Laborechemikalien GmbH, D 30926 Seelze, Germany). Soluble Ca was assessed using the EDTA (SIGMA-Aldrich CHEMIE GmbH, Riedstr 2–89555 Steinheim, Germany) titration method.2+ and magnesium2+. Available phosphorus (PAV) was extracted with 0.5 M NaHCO3 (SIGMA-Aldrich CHEMIE GmbH, PO1120–89555 Steinheim, Germany) pH 8.5, measured with a PG Instruments Ltd T80 UV/VIS spectrophotometer, Alma Park, Woodway Lane, Wibtoft, England42. Available Potassium (KAV) was extracted with 1 N NHFourOAc (PANREAC QUIMICA SA, E-08211 Castellar del valles, Barcelona, ​​Spain) was used with a flame photometer (PG Instruments Ltd, Alma Park, Wibtoft, Leicestershire, England: FP902).

Sequential extraction of transition metal fractions43,44. Five fractions were determined for Cr.3+CDs2+Pb2+ As follows: commutative fractions (Yuan) was extracted with 1 M MgCl2 (SIGMA-Aldrich CHEMIE GmbH, PO1120–89555 Steinheim, Germany) pH 7, 25 °C for 1 hour. The portion bound to the carbonate (car) was extracted with 1 M CH3COONa (SIGMA-Aldrich CHEMIE GmbH, Riedstr 2 -89555 Steinheim, Germany), pH 5, 25 °C for 5 hours. The portion bound to the Fe-Mn oxide (OXD) was extracted with 0.04 M NH2OH·HCl (SIGMA-Aldrich CHEMIE GmbH, D-30926 Seelze, Germany) in 25% acetic acid (SIGMA-Aldrich CHEMIE GmbH, PO1120 -89555 Steinheim, Germany) at 96°C for 5 hours. The portion bound to the organic matter (organization) was extracted with 30% H22 (PANREAC QUIMICA SA, E-08211 Castellar del valles, Barcelona, ​​Spain) 0.02 M HNO3 (SIGMA-Aldrich Laborchemikalien GmbH, D-30926 Seelze, Germany) pH 2 at 85 °C for 5 h followed by 3.2 M NHFourOAc (SIGMA-Aldrich CHEMIE GmbH, Riedstr2, D-89555 Steinheim, Germany) 20% HNO3(SIGMA-Aldrich Laborchemikalien GmbH, D-30926 Seelze, Germany); and the remainder (response) extracted with concentrated nitric acid3(SIGMA-Aldrich Laborchemikalien GmbH, D-30926 Seelze, Germany) 2 hours at 100°C. All fractions were filtered using Whatman No.1 filter paper (Whatman paper, Z240079) and then quantified on an Agilent 4100 Microwave Plasma Atomic Emission Spectrometer (MP-AES) (Agilent Technologies, G8000A, Australia). bottom. The available fraction for each metal was evaluated as the sum of exchangeable and carbonate-bound fractions.34.

Mobility assessment in soil

Cr mobility coefficient3+CDs2+Pb2+ It was evaluated to detect the relative abundance of readily mobile and available fractions in soil.34 as follows:

$$Mobility\,factor\,\left( {\text{\% }} \right) = \frac{EX + CAR}{{EX + CAR + OXD + ORG + RES}}{ } \times 100$$


where Yuan is a commute fraction, car is the carbonate-related fraction, OXD is the bonding part of Fe-Mn oxide, organization is the organically bound part, and response is the remainder.

Chemical characterization of organic modifiers

Recycled agroindustrial residues, by-products from the food industry, were analyzed before being added to the soil.40. pH, EC, organic carbon, total nitrogen, organic matter, C/N ratio were 7.50, 2.16 dS m.-1were 25.93%, 1.57%, 44.59%, 16.51, 7.98 and 3.01 dS m for compost.-1For earthworm compost, they were 36.41%, 1.89%, 62.63%, and 19.26, respectively. Their NPK contents were 1.57%, 0.52% and 1.02% in compost and 1.89%, 0.23% and 0.41% in vermicompost, respectively. The Fe, Zn, Mn and Cu contents were 4870.00, 35.40, 315.00 and 11.30 mg kg.-1 Compost and 2081.00, 28.11, 127.00, and 7.22 mg kg-1 Each for earthworm compost. The Cr, Cd and Pb contents were 0.54, 0.23 and 5.93 mg kg.-1 For compost and 0.32, 0.10, and 2.25 mg kg−1 Each for earthworm compost.

Pre-experiment soil chemical characterization

Moderate soil alkalinity (pH 8.39, 1:2.5 w/v) and salinity (EC 2.69 dS m-1, 1:1 w/v) are observed. Content of soluble cations such as Na+K+Ca2+Mg+2 were 7.97, 0.80, 7.15 and 0.82 meq L.−1respectively, soluble anions such as ClHCOs3SuchFour2− was 6.12, 4.52, and 7.12 meq L-1, Each. Total nitrogen (TN) and organic matter were 0.09% and 0.98%, respectively. Available soil phosphorus and potassium were 5.00 mg kg and 105.22 mg kg.−1, Each. Soil micronutrients such as Fe, Zn, Mn and Cu were 4.81, 0.65, 7.74 and 0.85 mg kg.-1, Each. The contents of the three investigated metals such as Cr, Cd and Pb were 0.02, 0.01 and 0.66 mg kg.−1Each.

plant analysis

After harvesting (155 days), wheat plants (n = 9) were randomly selected from each sub-treatment (9 × 9 × 2 = 162 plant samples) by measuring plant height (cm), weight 1000 Wheat yield was evaluated. -Grain (g), wheat straw (t ha-1), grain yield (t ha−1). Biological yield (t ha−1) was calculated as the sum of wheat straw and grain yields. Harvest index was expressed as the ratio of grain yield to biological yield.

Wheat grain washed with DH2Oven dry at 65 °C for 48 h. Grains were wet-digested using H.2SoFour/H22 (SIGMA-Aldrich Laborechemikalien GmbH, D 30926 Seelze, Germany), mixture of NPK and transition metal (Cr)3+CDs2+Pb2+) Determined according to the manual proposed by Ryan et al.40.

Grain bioaccumulation factor (BAF)

BAF is the accumulation efficiency of each metal accumulated in plant grains.45 It can be calculated using the following formula:

$$BAF = \frac{{total\,metal\,content{ }_{grain} }}{{total\,metal\,content_{{{ }soil}} }}$$


statistical analysis

Statistical analysis was performed using STATISTICA 10 from StatSoft, Inc. (Tulsa, OK, USA).46. All studied soils and plants, using minerals and organic amendments as two categorical factors, to confirm a significant variance in each dataset obtained from uncontaminated and contaminated soils. A two-way ANOVA was tested to analyze the variation of variables. Principal component analysis was performed twice for each dataset obtained from uncontaminated and contaminated soils. The contribution of each subtreatment (mineral × organic) to the associated factor structure was calculated by the factor score.

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