Leaching and fractionation of phosphorus in intensive greenhouse vegetable production soils.

Greenhouse vegetable production systems use excessive phosphorus (P) fertilizer. This study is set out to look into the P fractionation, mobility, and risk of P leaching in ten greenhouse soils. The mean P concentrations in leachates varied from 0.4 to 1.6 mg l-1 (mean of 30 days of soil leaching). Between 5.7 and 31.0 mg kg-1 of P was leached from soils during 30 days of column leaching. Organic matter (OM) and Olsen-extractable P (Olsen P) correlated strongly with cumulative P leached after 5, 10, 15, 20, 25, and 30 days of leaching. The high correlation between OM and Olsen P with cumulative P leached at 5 days of leaching suggests that in future leaching experiments, the leaching period should be extended to 5 days of leaching. The first two P fractions correlated significantly with the total P leached in the primary days of leaching. The pH had little effect on P leaching but had a significant impact on soluble and exchangeable P fraction, suggesting that P mobility would increase in these calcareous greenhouse vegetable soils as pH rose. The calculated change point (194 mg kg-1) was high, indicating that a high percentage (40%) of the studied greenhouse soils had exceeded the change point. In conclusion, due to the high degree of P saturation and change point in greenhouse vegetable soils, P mobilization is a significant risk, and the findings can be used to provide future direction for fertilizing greenhouse vegetable soils.

Leaching of Cr, Cu, Ni, and Zn from different solid wastes: Effects of adding adsorbents and using different leaching solutions.

The leaching of potentially toxic elements from different industrial solid wastes (ISWs) must be understood to manage the environmental concerns they pose. The objective of this research was to investigate the effect of clay mineral (bentonite) and nanoparticle (MgO) on potentially toxic elements (Cr, Cu, Ni, Zn) leaching in some ISWs, when they leached with different leaching solutions. The highest amount of Zn and Ni was leached from ceramic factory waste (CFW) and stone cutting wastes (SCW), respectively, while the highest amount of Cr was leached from leather factory waste (LFW). In ISWs, the leaching percentage of Cu, Ni, and Zn were up to 11.2%, whereas the greatest leaching percentage of Cr was 26.7% of the total content. The addition of bentonite and MgO decreased potentially toxic element leaching. The results of effluents speciation of SFW indicated that at the beginning of leaching with CaCl2, nitric acid, and citric acid, 75.1%, 84.1%, and 39.6% of Cr were in different forms of Cr (III), respectively, while at the end of leaching the percentage of Cr (III) species were decreased and Cr (VI) species were increased to 83.6%, 88.4%, and 93.4%, respectively. The addition of bentonite and especially MgO to the ISWs reduced the leaching of potentially toxic elements as well as reduced the percentage of Cr (VI) in the effluents of SFW. The findings suggested that bentonite has the potential to be a low-cost and environmentally acceptable adsorbent for minimizing the leaching of Cr and other potentially toxic elements from ISWs.

The release of Cd, Cu, Fe, Mn, Ni, Pb, and Zn from clay loam and sandy loam soils under the influence of various organic amendments and low-molecular-weight organic acids.

Low-molecular-weight organic acids (LMWOAs) interact with potentially toxic elements (PTEs) and affect their mobility; however, the effect of different amendments on PTEs release from soils when added along with LMWOAs is still unclear. In this study, two soils (a clay loam and a sandy loam) amended with sugar beet bagasse ash (SBBA), poultry manure (PM), sewage sludge (SS) from Kermanshah city (SSK), and SS from Toyserkan city (SST) at a rate of 5 %. In these treatments we studied release of Cd, Cu, Fe, Mn, Ni, Pb, and Zn with citric, oxalic, and malic acids added at 10 different rates each, i.e., 0.1, 1, 2.5, 5, 10, 30, 40, 50, 70, and 100 mmol L-1. We found that the percentage of PTEs release was higher for citric, followed by oxalic and malic acids. The highest amount of PTEs released in both soils decreased in the following order: SST > SBBA > SSK > PM. The percentage of PTEs complexed with LMWOAs and the log activity of PTEs species mostly increased with decreasing pH. It could be concluded that the application of PM is more environmentally friendly than that of the other amendments. Since Cd had the highest percentage of release in all treated soils and LMWOAs, more consideration should be given to Cd to prevent environmental pollution.

The status of phosphorus levels in Iranian agricultural soils - a systematic review and meta-analysis.

Phosphorus (P) inputs are essential for maximizing agronomic potential, yet high P inputs and subsequent P losses can cause eutrophication of water bodies. There is a need to evaluate P contents in agricultural soils globally both from an agronomic and environmental perspective. This systematic review and meta-analysis estimated the pooled mean levels of P contents of Iran. In this study, data on available and total P contents of Iran's calcareous soils was compiled (main focus on Olsen P) and compared to (i) estimated Iranian background and global agricultural soil P contents, and (ii) agronomic and (iii) environmentally critical Olsen P values. The pooled mean estimate from the meta-analysis indicates that the levels of Olsen P across 425 soil samples (27 studies) were 21.3 mg kg-1 and total P across 190 soil samples (12 studies) 805.5 mg kg-1. Using 26 mg kg-1 as the agronomic critical Olsen P value above which no increase in crop yield occurs, crops grown on 61% of the soil samples in the investigated region would respond to P fertilizer and 20% of soils are currently in the optimum category (26-45 mg kg-1 Olsen P). The environmentally critical Olsen P value (~ 63 mg kg-1), defined as the amount above which P leaches from soil rapidly, was exceeded by 11% of soils with a further 4% of soils with elevated eutrophication risk. To maximize crop yields while maintaining a minimal risk of P leaching in Iran's calcareous soils, we suggest an ideal Olsen P of 26 mg kg-1. The outcomes from this study inform about the P status of Iranian soils and could help update recommendations for P fertilizer applications in calcareous soils globally. The framework presented here could further be adopted to evaluate the P status in other soil types.

Empirical and Mechanistic Modeling of Release Kinetics of Heavy Metals and Their Chemical Distribution in the Rhizosphere and Non-rhizosphere Soils Under Vegetable Cultivation.

Biochemical processes in the rhizosphere affect the availability and distribution of heavy metals (HMs) in various forms. Rhizosphere soil (RS) and non-rhizosphere soil (NRS) samples were collected from 10 fields under tarragon (Artemisia dracunculus L.) cultivation to investigate the release kinetics and distribution of HMs including cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), and zinc (Zn) in five fractions. The cumulative amounts of Cu and Fe released after 88 h were in the following ranges, respectively: 1.31-2.76 and 3.24-6.35 mg kg-1 in RS and 1.41-2.72 and 3.15-5.27 mg kg-1 in NRS. The parabolic diffusion and pseudo-second-order equations provided the best fit to the release kinetics data of Cu and Fe, respectively. The cation exchange model (CEM) based on Gaines-Thomas selectivity coefficients implemented in the PHREEQC program could well simulate the release of Cu and Fe suggesting that cation exchange was the dominant mechanism in the release of Fe and Cu from soils by 0.01 M CaCl2. Cadmium was predominantly found in fraction F2, while other HMs were mainly present in fraction F5. According to the risk assessment code, there was a very high risk for Cd, a medium risk for Co and Cu, a very low risk for Fe, and a low risk for Zn. Correlation analysis showed that soil physicochemical properties were effective in the distribution and transformation of HMs. Significant positive correlations between five fractions indicated that different forms of HMs can potentially transform into each other.

Available and total phosphorus background levels in soils: a calcareous and semi-arid region.

It is critical to understand the risk of element pollution in soils by evaluating their background levels. Phosphorus (P) content in agricultural soils needs to be assessed from agronomic and environmental standpoints. The current study intended to calculate the background levels of available and total P in soils. To achieve this goal, 50 sites without human activities were selected. Soils were sampled from the surface and subsurface of each site (100 soil samples). The available P forms in soils were extracted using the water-extractable P (WEP), calcium chloride-extractable P (CCEP), and Olsen-extractable P (OEP) methods. The first two extractants are being used to evaluate P leaching from soils, while the last one is being used as an agronomic indicator. The methods used to calculate background levels were the iterative 2-δ technique (2-δ) and the calculated distribution function (CDF). Results showed that the upper limits of background levels using 2-δ method were 1.45, 0.92, 8.12, and 424.4 mg kg-1 for WEP, CCEP, OEP, and total P, respectively. Also, the upper limits of background levels using CDF method were 1.42, 1.15, 12.09, and 447.6 mg kg-1, for WEP, CCEP, OEP, and total P, respectively. It can be concluded that using these background levels, which for the first time were calculated for P, would enable us to have an accurate examination of P excess as a result of human activities.

Heavy metals accumulation in wheat (Triticum aestivum L.) roots and shoots grown in calcareous soils treated with non-spiked and spiked sewage sludge.

With growing urbanization and agriculture, the quantity of sewage sludge production increases every year. For the purpose of risk management, it is crucial to figure out how much heavy metals are transported to different parts of plants when sewage sludge is used. A greenhouse experiment was carried out to investigate the accumulation of heavy metals in wheat (Triticum aestivum L.) grown in 30 calcareous soils. The soils in this study were subjected to three different treatments: soils treated with sewage sludge at a rate of 2.5%, soils treated with sewage sludge at a rate of 2.5% and enriched with heavy metals, and control soils that received neither sewage sludge nor heavy metals. Wheat grown in sewage sludge-treated soils had the highest mean dry matter, and was 2.11 and 1.25 times greater than wheat grown in control and spiked-sewage sludge-treated soils, respectively. In all treatments, wheat roots had greater heavy metal levels than wheat shoots. Among all the heavy metals examined, Pb and Cu had the highest bioconcentration factors for roots and shoots (BCFRoots and BCFShoots) in control and sewage sludge-treated soils, followed by Cd in spiked-sewage sludge-treated soils, and Co and Ni had the lowest BCFRoots and BCFShoots across all treatments. In spiked-sewage sludge-treated soils, the root restriction for heavy metals translocation was more important for Co, Cu, and Ni than for Pb and Zn, indicating that wheat can be grown safely in a variety of calcareous soils amended with sewage sludge with high content of Cd, Co, Cu, and Ni. Reducing the transfer of Pb and Zn from soils to wheat in soils treated with sewage sludge yet having high concentrations of these heavy metals should be considered as a top priority strategy for preserving wheat products. Since a wide range of calcareous soils was used in this study and because calcareous soils make up the majority of soils in the Middle East, the findings are relevant for all of the countries in this region.

Minimizing phosphorus leaching from a sandy clay loam caused by phosphorus fertilizers.

At moderate to high fertilization rates, sandy-textured soils can leach much phosphorus (P) threatening surface water quality. High rates are used to compensate for P leaching, but there is also potential to reduce P leaching by using different P fertilizers. We examined the effect of poultry manure (PM), sheep manure (SM), triple superphosphate (TSP), sewage sludge of Sanandaj (SSS), sewage sludge of Toyserkan (SST), and biochars of Sanandaj and Toyserkan sewage sludges (BSSS and BSST, respectively) applied at a rate of 100 mg P kg-1 (equivalent to 220 kg P ha-1 yr-1, the current regional practice for capital applications designed to raise and maintain soil P in the region) on P leaching over 10 pore volumes (equivalent to 589 mm rainfall) through a sandy clay loam soil widespread in Iran (and the Middle East). Phosphorus leaching losses decreased in the following order: TSP > SM > PM > SST > BSSS > control > SSS > BSST. The leachability of fertilized soil was best estimated by measurement of the mobile KCl-P fraction. At the capital application rate used, SSs or their biochars represented the least risk of P leaching and could be used in place of highly soluble manures or TSP to either protect water quality or maintain more P in the soil. However, this should only occur after confirming that this substitution does not impair agronomic performance.

Simulating phosphorus leaching from two agricultural soils as affected by different rates of phosphorus application based on the geochemical model PHREEQC.

Phosphorus (P) leaching from agricultural soils, in consequence of long-term utilization of P fertilizers, decreases the water quality and leads to eutrophication. The effect of monopotassium phosphate (MKP) at the rates of 0, 50, 200, 400, and 800 mg P kg-1 on P and certain cations leaching from two agricultural soils (loam and sandy loam soils) was investigated in a laboratory study. Soil treatments were packed in columns with 5 cm in diameter, up to 10 cm. Soil columns were leached using distilled water solution for 20 pore volumes, and the leachates were analyzed for pH, electrical conductivity (EC), calcium (Ca), sodium (Na), potassium (K), and P. To simulate the concentrations of K and P in leachates, the PHREEQC model was utilized. In addition, the P vertical distribution in different depths of the soil columns after the leaching experiment was investigated using Olsen-extractable P (Olsen-P). Generally, as the MKP rates increased, the mean (mean of 20 pore volumes) value of pH and Ca concentration in leachates decreased, but the mean value of EC, Na, and K concentrations in leachates increased. In early pore volumes, the P concentration in all treatments begins to rise, then begins to fall. The application of different rates of MKP fertilizer increased the cumulative amount of P leached in both studied soils. Significant relations were obtained for the rates of MKP application and the cumulative amount of P leached. Overall, the model did a good job of simulating K and P concentrations in leachates, as well as the trend of K and P leaching. In both treated soils with increasing of fertilizer rates, the Olsen-P status in all depths increased, and the P content increased with depth. The Olsen-P contents before the leaching experiment for each treatment were predicted, and power equations significantly described its relation with mean P concentration in leachates. Higher application rates of MKP (400 and 800 mg P kg-1) resulted in much higher P concentrations in leachates than the threshold value (0.1 mg l-1), and these rates should not be used in agricultural soils, whereas applying 50 mg P kg-1 to agricultural soil could be a reasonable rate for preventing P losses.

Comparison of the effect of peritonsillar infiltration of tramadol vs dexmedetomidine on post-tonsillectomy pain.

INTRODUCTION: This study aimed to comparing the effect of peritonsillar infiltration of tramadol and dexmedetomidine in relieving post-tonsillectomy pain. METHODS: In this randomized double blinded clinical trial study, 90 children 5-12 years old undergoing tonsillectomy, involved. Induction of anesthesia was done by fentanyl 1 µg/kg, sodium thiopental 5 mg/kg and atracurium 0.5 mg/kg and intubation was done after 3 min. Anesthesia maintained by nitrous oxide 60% and oxygen 40% with isoflurane (1.2%). Tramadol 2 mg/kg in group A, dexmedetomidine 1 µg/kg in group B, and normal saline in group c were injected into the bed and anterior tonsillar pillar and surgery has begun after 3 min of injection. Time of surgery, all hemodynamic variables, pain intensity and degree of sedation were recorded and evaluated. RESULTS: The results showed that duration of the surgery (p value = 0.28) and duration of anesthesia (p value = 0.43) were not significantly different between the groups but pain score was significantly lower in dexmedetomidine group in comparison to tramadol and placebo group (p value = 0.001). The first time for analgesic request was longer in dexmedetomidine group (p value = 0.001) and Hemodynamic parameters were significantly lower in tramadol and dexmedetomidine group (p value = 0.001). Sedation level was not significantly different between tramadol and dexmedetomidine group (p value = 0.001). CONCLUSION: According to the results peritonsillar infiltration of dexmedetomidine is effective and safe in relieving post-tonsillectomy pain.

CFTR mutations causing congenital unilateral absence of the vas deferens (CUAVD) and congenital absence of the uterus (CAU) in a consanguineous family.

Cystic fibrosis (CF) is one of the most common recessive genetic diseases, with a wide spectrum of phenotypes, ranging from infertility to severe pulmonary disease. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are considered the main genetic cause for CF. In this study, we recruited a consanguineous Iranian pedigree with four male patients diagnosed with congenital unilateral absence of the vas deferens (CUAVD), and one female patient diagnosed with congenital absence of the uterus (CAU). Testicular biopsy of one patient was performed, and hematoxylin and eosin (H and E) staining of testis sections displayed the presence of germ cell types ranging from spermatogonia to mature spermatids, indicating obstructive azoospermia. To explore the underlying genetic factor in this familial disorder, we therefore performed whole-exome sequencing (WES) on all available family members. WES data filtration and CFTR haplotype analysis identified compound heterozygous mutations in CFTR among four patients (two CUAVD patients carried p.H949Y and p.L997F, and one CUAVD and the female CAU patient carried p.H949Y and p.I148T). All these mutations were predicted to be deleterious by at least half of the prediction software programs and were confirmed by Sanger sequencing. Our study reported that CFTR compound heterozygous mutations in a consanguineous Iranian family cause infertility in both sexes.

Assessment of trace element pollution in northern and western Iranian agricultural soils: a review.

The pollution of Iranian agricultural soils with trace elements (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) was assessed and compared with other agricultural soils around the world. Experimental data on trace element content in Iranian agricultural areas in the west and north were collected from the literature: 39 studies covered a total of 46 agricultural sites of 17 provinces in Iran, in order to characterize their patterns of accumulation of trace elements. Two pollution indices, namely, the pollution index (PI) and the integrated pollution index (IPI), were used to evaluate trace element accumulation. The data revealed a remarkable variation in trace element content among soils in different areas. Exploratory data analyses (EDAs) showed that a number of trace elements (Pb, Cu, and Zn) are asymmetrically distributed and scattered. Surveys indicated that 45.5% of the studied samples had elevated PI values for Cd, 13.0% for Cu, and 16.7% for Pb, clearly indicating an anthropogenic contribution of these three elements. The IPI of the agricultural soils also indicated that most areas are classified as having moderate and high pollution. Higher contents of trace elements (except for Mn) were found in some cities of the Isfahan, Hamadan, and Tehran provinces. Excessive application of conventional and organic fertilizers, pesticides, animal manure, and sewage sludge for enhancing crop production is responsible for high trace element content in Iran's agricultural soils. This in turn, through the food chain, is a threat to human health. Analysis of the correlation between trace elements exhibited that Cu, Pb, and Zn (Cd, Pb and Zn) were very closely associated with each other, showing that their prevalent sources are common and the efforts to regulate them linked in common actions. We consider this evaluation as a viable approach to other similar areas in the Middle East and beyond, which could be used by environmental scientists for risk assessment and decision making.

Availability of heavy metals to cabbage grown in sewage sludge amended calcareous soils under greenhouse conditions.

Compared to noncalcareous soils, data on the soil-to-plant transfer of heavy metals and their response to sewage sludge (SS) in calcareous soils with diverse properties are limited. Cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) transfer from soil to cabbage (Brassica oleracea L. var. capitata) under greenhouse conditions in 30 diverse soils amended with two types of sewage sludge (non-spiked and spiked with heavy metals) were investigated. Three transfer factors were calculated for heavy metals in three treated soils including control soils (CS), soils treated with non-spiked SS (NSS), and soils treated with spiked SS (PSS). The bio-concentration factor of heavy metals from soil to root (BCFRoots) in cabbage in three treatments was as follows: CS: Pb > Cu > Co > Zn > Ni; NSS: Pb > Co > Cu ≥ Zn > Ni; and PSS: Pb > Cd > Zn > Co > Cu > Ni. The same order was found for the bio-concentration factor of heavy metals from soil to shoots (BCFShoots) in PSS, and in CS and NSS treatments except that the position of Co, Cu, and Zn was changed. Based on the heavy metals translocation from plant roots to shoots, Cd, Cu, and Zn were the heavy metals that posed the highest risk due to the higher shoot content in all treatments, whereas Ni and Pb posed relatively lesser risk. Generally, the percentage of sand and silt in BCFRoots and BCFShoots was quite effective for Co, Ni, and Zn and it seems that soil texture is an important variable in heavy metals bioavailability. In conclusion, our findings highlight the significance of using SS to increase cabbage growth in soils contaminated with heavy metals. Furthermore, cabbage may be a good choice for phytoremediation of heavy metal-contaminated calcareous soils in terms of soil remediation. Novelty statement In recent years, sewage sludge production has increased as well as related waste disposal strategies because of the increasing population and growing demand for agricultural products. Sewage sludge utilization as a low-cost fertilizer has spread in some parts of Iran and the world. On the other hand, unnecessary and unproductive use of sewage sludge results in the accumulation of heavy metals in soils, adding them to food and the potential risk to human health. Currently, work on the transfer of heavy metals from soil to plant after soil treated with sewage sludge has focused on the bioavailability of heavy metals using specific extractants. The assessment of the transfer of heavy metals from soil to different parts of plants using sewage sludge has been less studied. In this study, the transfer of heavy metals (Cd, Co, Cu, Ni, Pb, and Zn) from several soils (30 soils samples) having diverse physical and chemical properties to the tissues of the cabbage plant in control soils, and two types of sewage sludge (nonspiked and spiked with heavy metals) were investigated. The novelty of this study is that the measured bio-concentration factor of heavy metals from soil to root and from soil to shoot and translocation of heavy metals from plant roots to shoots and correlations between these parameters and soil properties are reported for the first time in diverse calcareous soils.

Effect of organic and inorganic phosphorus fertilizers on phosphorus availability and its leaching over incubation time.

The use of organic and inorganic phosphorus (P) fertilizers in agricultural soils is very common, and few studies have been conducted to study the effect of different P sources on relative P extractability (RPE) and leaching using different P extractants and degree of P saturation (DPS), over a long period of time. Thus, this study was conducted to investigate the effect of incubation time and different P sources on RPE, DPS, and to predict the concentration of P leached from soil using different P extractants. In order to achieve these goals, nine sewage sludges (SSs), two biochars, animal manure (AM), poultry manure (PM), wheat residue (WR), diammonium phosphate (DAP), and triple superphosphate (TSP) were added to the soil as much as 100 mg P kg-1 in a 163 days incubation experiment. On average across all amendments and incubation periods, Mehlich-3 extractable P (M3EP) gave the highest mean RPE (42.9%, SE = 7.1%), with water-extractable P (WEP) the lowest (4.6%, SE = 0.93%), and Olsen-extractable P (OEP) (38.3%, SE = 6.3%) in between. Among SSs and based on average across of all incubation periods, soils treated with Shiraz and Takestan SSs were the least soluble source of P, while the highest soluble source of P were soils treated with Kermanshah and Tehran SSs. The results indicated that soil samples taken 16 days following the addition of amendments should reflect agronomic and environmental purposes aiming to assess available and the potential P loss from agricultural soils. The split line model perfectly fitted to the relation between OEP and M3EP (r = 0.93). The DPSs were calculated and the P leaching rate was estimated. Based on OEP, the soils treated with TSP and DAP were at high risk, the medium risk was for soils treated with Kermanshah, Saveh, Tehran, Rasht, Sanandaj, and Isfahan SSs, and PM. Control soil, and soils treated with WR were at no risk, and the soils treated with Arak, Shiraz, and Takestan SSs, ABC, WBC, and AM were classified as low risk.

Assessment of the health risks of heavy metals in soils and vegetables from greenhouse production systems in Iran.

Overuse of chemical and organic fertilizers in greenhouse (GH) crop production may cause the accumulation of heavy metals in soils and risks to human health. The aims of this study were to compare physical and chemical properties of GH with open-field (OF) soils, to clarify the buildup of heavy metals and phosphorus (P) in soils, and to assess the risks of selected heavy metals in soils and cucumber (Cucumis sativus L.) and tomato (Lycopersicon esculentum Mill.) from GH vegetables in Hamedan, western Iran. The average total and Olsen P of GH soils were significantly higher than the OF soils for both vegetables. The order of total and available heavy metal content in tomato GH soils has been set as zinc (Zn) > nickel (Ni) > chromium (Cr) > lead (Pb) > copper (Cu) > cadmium (Cd) and Zn > Cr > Cu > Pb > Ni > Cd, respectively. The same order was found for cucumber GH soils, except that the position of Pb and Cu was changed. The results indicated that in both GH cucumber and tomato soils, the mean content of total and available Zn, available Cu, Ni, and Pb, was extra than in OF soils. There were no significant differences between average total Cr, Cu, Ni, and Pb in GH and OF soils. Tomato vegetables had higher heavy metal content and transfer factors, particularly for Cr than cucumber vegetables. According to the health risk indices, Cr and Pb represented a high potential risk for health through cucumber and tomato consumption. There were limited Cd, Cu, Pb, and Zn inputs from the irrigation waters, while the input of Cr and Ni may be important. However, the amount of manure application and heavy metal content of the manures was significant.

Selectivity coefficients of K, Na, Ca, and Mg in binary exchange systems in some calcareous soils.

One of the major issues in surveying the sorption and mobility of elements is awareness of the behavior and reactions of elements in soils and their distribution coefficient (Kd) values. This study was conducted to investigate the adsorption of potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg) in six calcareous soils saturated with mentioned cations. The initial equivalent fraction of K, Na, Ca, and Mg in solutions increased from 0.1 to 1 at a total electrolyte of 30 meq L-1. The shape of isotherm curves and the amount of cations adsorbed varied in different binary exchange systems. The adsorption of cations increased gradually with increasing initial concentrations. The average values of Kd (L kg-1) in different binary systems were arranged in the following order: Ca-Mg (23.4) > Mg-Na (21.5) > Mg-K (20.7) > Mg-Ca (20.1) > Ca-Na (16.0) > Ca-K (15.4) > K-Mg (5.6) > K-Na (5.0) > K-Ca (4.6) > Na-Ca (2.7) > Na-Mg (1.9) > Na-K (1.7). The average values of Gaines-Thomas selectivity coefficients of cations in different binary exchange systems followed this order: K-Ca (16.5) > K-Mg (7.8) > Ca-Mg (4.1) > Mg-Ca (3.1) > Mg-Na (2.1) > K-Na (1.7) > Mg-K (1.0) > Ca-Na (0.8) > Ca-Na (0.6) > Na-Ca (0.5) > Na-Mg (0.1) = Na-K (0.1). So, the affinity of cations for adsorption by soils followed this order: K > Ca > Mg > Na which differed from the classical lyotropic series. The high affinity of K for adsorption by soils was attributed to the presence of illite. The free cations were the most abundant species (above 90%) in all soil solutions after reaching equilibrium with initial concentrations of 3 and 30 meq L-1. The saturation index (SI) values of minerals in all exchange systems were negative.

Almond and walnut shell-derived biochars affect sorption-desorption, fractionation, and release of phosphorus in two different soils.

Effective soil phosphorus (P) management requires higher level of knowledge concerning its sorption-desorption, fractionation, and release, as well as its interactions with soil amendments including biochar (BC). The purpose of this research was to investigate the influence of two different BCs, derived from almond and walnut shell, on P sorption-desorption and its redistribution among the geochemical fractions in two different soils. The BCs were applied to the soils in four doses (0, 2.5, 5, and 10% w/w) and the mixtures were incubated for one month. Phosphorus sorption increased due to the addition of BCs. Phosphorus sorption data fitted well the Freundlich isotherm and were simulated by the PHREEQC software. Biochar addition increased total P and the added P was mainly distributed in the exchangeable, Fe/Al-P and the residual fractions. Also, BC addition resulted in an increase in the water-soluble-, mobile-, and Olsen-P, making P more available for plant uptake. The kinetics data were well described by the simple Elovich, pseudo-second-order, and intra-particle diffusion equations. Walnut BC-added soils had higher P sorption capacity than those added with the almond BC. The results suggest that BC binds soil P and releases it gradually back into solution, making it thus available to plants; this renders the studied BCs promising materials for protecting P from being lost out of soil. Future research must be conducted over longer-term experiments that would study P dynamics in BC-added soils under real field conditions.

Synergistic immobilization of potentially toxic elements (PTEs) by biochar and nanoparticles in alkaline soil.

Biochar and nanoparticle (NP) have the ability to sorb potentially toxic elements (PTEs) from soil and reduce toxicity and leaching into water bodies. However, there is need to tailor biochar formulations to soil types. In this study, we investigate the mobility and chemical forms of Cd, Cr, Cu, Ni, and Zn in a spiked, alkaline soil after amendment with combination of NPs (nano-Fe (NF), nano-clay (NC)) and biochars (almond shell 500 °C, walnut shell 400 °C) in different doses (0, 2.5, 5, and 10%). Many previous studies concluded biochar immobilized PTEs due to an increase in soil pH, which can be disregarded here (soil pH 7.9). In a twenty-week column leaching experiment biochar addition significantly decreased PTE leaching and NP addition further immobilized PTEs in most cases. On average almond biochar more effectively reduced Zn leaching and walnut biochar was more effective in decreasing the leaching of Cd, Cr, and Ni (e.g. 5% biochar reduced Cr leaching by 68%). Copper was immobilized effectively by both biochars. Nano-clay combined with walnut biochar performed best in all treatments, in particular for Cd, Ni, and Zn (e.g. 10% walnut biochar only and in combination with NC reduced Zn leaching by 14.2% and 58.5%, respectively). After amendment, PTEs were present in the Fe-Mn oxides, organic and residual fractions and less in the exchangeable fraction, reducing PTE availability and leachability. The results demonstrate that even for cationic PTEs that behave similarly in the environment optimal biochar-mineral formulations can differ.

Effects of some industrial and organic wastes application on growth and heavy metal uptake by tomato (Lycopersicum esculentum) grown in a greenhouse condition.

In this study, pot experiments were conducted to determine the effects of industrial solid wastes (ISWs) (ceramic, stone, and sugar factory wastes) and organic wastes (rice husk and wheat straw) on growth and heavy metals uptake by tomato (Lycopersicum esculentum) plants. The soil was treated with 10% of ISWs and 5% of organic wastes. The fractionation of heavy metals also has been studied in all treated soils. It was observed that the addition of ISWs in soil increased heavy metal contents in all fractions. The addition of organic wastes to control and treated soils decreased exchangeable fraction and increased organic matter and residual fractions. Following the ceramic factory and stone cutting waste addition, tomato yield significantly decreased as compared to control soil. The application of ISWs caused an increase in heavy metal contents of tomato plants. In control and ISWs-treated soils, dry matter yield of tomato grown in the presence of wheat straw was significantly restricted, while the application of rice husk increased tomato shoot and root dry weight. Results of experiments indicated that the application of both organic wastes significantly decreased heavy metal uptake by tomato plants. The investigation of health risk index (HRI) values indicated that in these industrial areas, potential health risk by intake of heavy metals from tomato for both adults and children generally assumed to be safe. The values of HRI were lesser when rice husk was applied to the soil. In general, these results highlighted that the application of rice husk in soils contaminated with ISWs increased the growth and yield of tomato and reduced the heavy metal toxicity for tomato consumption in contaminated soils.