Contaminated Saline Soils Research Articles

Arbuscular mycorrhizal fungi regulate amino acid metabolism, phytohormones and glycolysis pathway to promote the growth of Suaeda salsa under combined Cd and NaCl stresses

The use of halophytes in conjunction with arbuscular mycorrhizal (AM) fungi has been found to enhance the removal efficacy of heavy metals and salts in heavy metals contaminated saline soil. The mechanisms of AM fungi on promoting halophyte growth and regulating metabolism remain unclear. In this study, combinations of 0 g kg−1 NaCl and 3 mg kg−1 Cd (S0Cd3), 6 g kg−1 NaCl and 3 mg kg−1 Cd (S6Cd3), and 12 g kg−1 NaCl and 3 mg kg−1 Cd (S12Cd3) were employed to explore the impact of Funneliformis mosseae on the growth and metabolism of Suaeda salsa. The results showed that AM fungi increased the biomass and the P, K+, Ca2+, and Mg2+ accumulations, reduced the Cd and Na+ concentrations in S0Cd3 and S6Cd3, and increased the Cd concentrations in S12Cd3. AM fungi inoculation reduced the Cd and Na+ transfer factors and increased the Cd and Na+ accumulations in S6Cd3. The metabolomics of S6Cd3 showed that AM fungi upregulated the expression of 5-hydroxy-L-tryptophan and 3-indoleacid acid in tryptophan metabolism, potentially acting as crucial antioxidants enabling plants to actively cope with abiotic stresses. AM fungi upregulated the expression of arbutin in glycolysis process, enhancing the plants’ osmoregulation capacity. AM fungi upregulated the expression of 2-hydroxycinnamic acid in phenylalanine metabolism and dopaquinone in tyrosine metabolism. These two metabolites help effectively remove reactive oxygen species. Correspondingly, AM fungi decreased MDA content and increased soluble sugar content. These results indicate that AM fungi improve the stress resistance of S. salsa by increasing nutrient uptake and regulating physiological and metabolic changes.

Bioremediation of Crude Oil Contaminated Saline Soil Using a Bacterial Consortium and Different Carriers

AbstractBioremediation of crude‐oil‐contaminated soils is critical to supporting soil ecosystem health and functioning. Here, to explore the potential for different remediation strategies to restore soil microbial functioning and enhance remediation, three strains of bacteria, Bacillus toyonensis, Bacillus sp. and Bacillus cereus, were inoculated to saline, crude oil‐contaminated soil collected from Azadegan Oil Field, Iran. Bacteria were added using different carriers, including corn biochar, humic acid, chitosan and kaolin, and free bacteria as a control. Changes in soil metal concentrations and residual crude oil were determined after 60 days of incubation. Soil respiration, microbial biomass, and enzyme (dehydrogenase and catalase) activities were measured. The carriers accompanying a bacterial consortium were more efficient than free bacteria in removing crude oil and heavy metals from soil, and they performed better in removing n‐alkanes with carbon chains of C12–24. The oil removal rate and metal immobilization efficiencies were greatest in soils with chitosan‐bacteria treatment, with removal of crude oil, Al, Pb, Sr, and Cr (93%, 63%, 37%, 54%, and 15%, respectively) greater than for soils with free cells without treatment (61%, 54%, 9%, 50%, and 3%, respectively). Soil electrical conductivity decreased after application of bacterial mixtures with and without carriers. The inoculation of bacteria and application of soil amendments increased soil microbial biomass carbon and the activity of catalase and dehydrogenase. Overall, our results indicated the greatest potential remediation was achieved by applying immobilized microorganisms in chitosan to accelerate the biodegradation of crude oil and the removal of heavy metals.

Synergistic mechanisms of bioorganic fertilizer and AMF driving rhizosphere bacterial community to improve phytoremediation efficiency of multiple HMs-contaminated saline soil

The addition of Arbuscular mycorrhizal fungi (AMF) or bioorganic fertilizer (BOF) alone has been reported to enhance plant tolerance to heavy metals and salt stress and promote plant growth, while their synergistic effects on plant growth and rhizosphere microorganism are largely unknown. This study explored the effects of AMF (Rhizophagus intraradices), BOF and BOF + RI assisted phytoremediation on heavy metals contaminated saline soil improvement and revealed the microbial mechanism. For this purpose, a pot trial consisting of four treatments (CK, RI, BOF and BOF + RI) was carried out. The results showed that the biomass, nutrient element contents, the accumulation of heavy metals and Na of Astragalus adsurgens and soil properties were most significantly improved by BOF + RI. BOF + RI significantly impacted rhizosphere microbial diversity, abundance and community composition. Chloroflexi and Patescibacteria at the phylum level and Actinomadura, Iamia, and Desulfosporosinus at the genus level were significantly enriched in BOF + RI. Network analysis revealed that BOF + RI significantly changed the keystone and enhanced complexity and interaction. Most of the keystones had roles in promoting plant growth and stress resistance. This study suggested that phytoremediation assisted by BOF and AMF is an attractive approach to ameliorate heavy metals contaminated saline soil.

Bio-organic fertilizer promoted phytoremediation using native plant leymus chinensis in heavy Metal(loid)s contaminated saline soil

Heavy metal(loid)s (HMs) contaminated saline soil appeared around the world, however, remediation regarding these collected from field conditions remains unknown. Native plants cultivation and bio-organic fertilizer (BOF) application were two efficient tools for soil amelioration. Herein, a pot experiment was conducted to examine the feasibility of a native plant (Leymus chinensis) for phytoremediation, and investigate the impacts of lignite based bio-organic fertilizer (LBOF) and manure based bio-organic fertilizer (MBOF) on phytoremediation of the soil contaminated by Pb, Cd, As, Zn, Cu, Ca2+, and SO42−. The results demonstrated the effectiveness of L. chinensis and highlighted the positive impacts of BOF according to the improved plant growth, HMs phytostabilization, salt removal, and soil properties. LBOF and MBOF changed soil microbiome to assist phytoremediation in addition to physiological modulation. Having enhanced fungal and bacterial richness respectively, LBOF and MBOF recruited various plant growth promoting rhizobacteria with different functions, and shifted microbial co-occurrence networks and keystone taxa towards these different but beneficial forms. Structural equation models comprehensively reveled the strategy discrepancy of LBOF and MBOF to regulate the plant biomass, HMs uptake, and soil salt. In summary, L. chinensis coupled with BOF, especially LBOF, was a effective strategy to remediate HMs contaminated saline soil.

Перспективы применения дикорастущих растений Астраханской области при фитотестировании и фиторемедиации нефтезасоленных почв

The article highlights the problem of saline soils of the Astrakhan region which are contaminated with heavy metals due to oil spills. It has been found that the most promising plants in phytotesting and soil restoration are halophyte communities: Asteraceae, Poaceae, Chenopodiaceae, Fabaceae, Cyperaceae, Ranunculaceae, Brassicaceae, Lamiaceae, Apiaceae, Caryophyllaceae, Polygonaceae, Scrophulariaceae, Liliaceae, Rosaceae, Rubiaceae. Most of the families are typical for the flora of the Astrakhan region. The largest number of halophyte species is found in the Asteraceae family (15.10%). Halophytes are widespread in the Astrakhan region. Species of wormwood (Artemisia L.) are found on the soils with varying salinity. This fact allows to use them in environmental monitoring and to assess the content of heavy metals in saline soils. Accumulation of chromium, iron, copper, cadmium and zinc in the organs of Artemisia species in the Astrakhan region is considered. It has been stated that Artemisia is very important as a group of heavy metal accumulator plants. Artemisia species can be used in phytoremediation of contaminated saline soils, where these metals come with oil products. Besides, the wide distribution, resistance to high temperatures, and high xerophilicity make it possible to consider Artemisia species as objects for biomonitoring for assessing the degree of soil contamination with heavy metals with varying degrees of salinity. Artemisia species are widely represented in the Astrakhan region. A secondary effect of using some types of halophytes is their direct participation in combatting land desertification.

Arbuscular mycorrhizal fungi facilitate Astragalus adsurgens growth and stress tolerance in cadmium and lead contaminated saline soil by regulating rhizosphere bacterial community

Soil worldwide has been severely damaged by various stresses, particularly heavy metal pollution in natural saline soils. The rhizosphere microbial community and arbuscular mycorrhizal fungi (AMF) can effectively facilitate the phytoremediation of contaminated soil. However, the effects of heavy metals and AMF on plant growth and rhizosphere bacterial community in natural saline soils remain uncertain. Here, pot experiments (orthogonal experiments) were designed to investigate the effects of cadmium (Cd) and lead (Pb) on the rhizosphere bacterial community of Astragalus adsurgens with or without AMF, and the microbial regulation mechanism of AMF in promoting phytoremediation of Cd and Pb contaminated saline soil. The results showed that heavy metals inhibited plant growth with and without AMF, however, AMF significantly increased shoot biomass by 536 %–970 % and root biomass by 272 %–382 %. Heavy metals reduced the richness and diversity of the rhizosphere bacterial community without AMF, however, no significant reduction was observed with AMF. In all four treatments, AMF significantly enhanced the richness and diversity of the rhizosphere bacterial community. Linear discriminant analysis effect size revealed that heavy metals significantly enriched heavy metal-tolerant rhizosphere bacteria with and without AMF. AMF significantly enriched more beneficial rhizosphere bacteria (mainly Rhodobacter, Archangium, and Longimicrobium) that tolerated heavy metals and promoted plant growth. Network analysis showed that heavy metals weakened bacterial interactions without AMF, but did not influence it with AMF. AMF strengthened the interaction and enhanced negative correlation ratio between bacteria, suggesting less stress and a stable and healthy environment. Finally, the structural equation model confirmed that AMF could improve the phytoremediation efficiency by regulating the rhizosphere bacterial community. This study enables us to understand the influence of heavy metals and AMF on plants and rhizosphere bacterial community, providing a theoretical basis for further improving the phytoremediation of heavy metal-contaminated saline soils.

Newly isolated halotolerant Aspergillus sp. showed high diesel degradation efficiency under high salinity environment aided with hematite

The contamination of saline soil with hazardous petroleum hydrocarbons is a common problem across coastal areas globally. Bioaugmentation combined with chemical treatment is an emerging remediation technique, but it currently shows low efficiency under high saline environments. In this study, we screened and used a novel halotolerant lipolytic fungal consortium (HLFC) combined with hematite (Fe2O3) for the bioremediation of diesel contaminated saline soils. The changes in total petroleum hydrocarbons (TPH) concentrations, enzyme activity, and microbial diversity were compared among different treatments (HLFC, hematite, hematite-HLFC, and control). The results showed that TPH degradation was significantly (P<0.05) enhanced in hematite-HLFC (47.59-88.01%) and HLFC (24.26-72.04%) amended microcosms across all salinity levels, compared to the treatments of hematite (23.71-66.26%) and control (6.39-55.20%). TPH degradation was positively correlated with lipase and laccase enzyme activities, electrical conductivity, and the water holding capacity of the soil. Analyses of the microbial community structure showed that microbial richness decreased, while evenness increased in HLFC and hematite-HLFC treatments. The relative abundances of Alicyclobacillus, Sediminibacillus, Alcanivorax, Penicillium, Aspergillus, and Candida genera were significantly high in hematite-HLFC and HLFC amended microcosms. Our findings provide a promising new microbial-based technique, which can degrade TPH efficiently in saline soil.

Phytoremediation of Potentially Toxic Elements from Contaminated Saline Soils Using Salvadora persica L.: Seasonal Evaluation.

Plants in coastal ecosystems are primarily known as natural sinks of trace metals and their importance for phytoremediation is well established. Salvadora persica L., a medicinally important woody crop of marginal coasts, was evaluated for the accumulation of metal pollutants (viz. Fe, Mn, Cu, Pb, Zn, and Cr) from three coastal areas of Karachi on a seasonal basis. Korangi creek, being the most polluted site, had higher heavy metals (HM's) in soil (Fe up to 17,389, Mn: 268, Zn: 105, Cu: 23, Pb: 64.7 and Cr up to 35.9 mg kg-1) and S. persica accumulated most of the metals with >1 TF (translocation factor), yet none of them exceeded standard permissible ranges except for Pb (up to 3.1 in roots and 3.37 mg kg-1 in leaves with TF = 11.7). Seasonal data suggested that higher salinity in Clifton and Korangi creeks during pre- and post-monsoon summers resulted in lower leaf water (ΨWo) and osmotic potential at full turgor (ΨSo) and bulk elasticity (ε), higher leaf Na+ and Pb but lower extractable concentrations of other toxic metals (Cr, Cu, and Zn) in S. persica. Variation in metal accumulation may be linked to metal speciation via specific transporters and leaf water relation dynamics. Our results suggested that S. persica could be grown on Zn, Cr and Cu polluted soils but not on Pb affected soils as its leaves accumulated higher concentrations than the proposed limits.

Differential effects of arbuscular mycorrhizal fungi on three salt‐tolerant grasses under cadmium and salt stress

AbstractSalt‐tolerant plants generally grow in salty conditions, and some of them are also tolerant to heavy metal stress. Arbuscular mycorrhizal fungi (AMF) can help plants withstand abiotic stresses. However, few studies have focused on the effects of AMF on the growth of salt‐tolerant plants in cadmium (Cd)‐contaminated saline soils. In this study, a greenhouse pot experiment was conducted to investigate the effects of AMF (Funneliformis mosseae) on growth, ion uptake, and Na+ and Cd translocation in three salt‐tolerant grasses (Leymus chinensis, Puccinellia distans, and Astragalus adsurgens) in a Cd‐contaminated saline soil. The regulation of genes by AMF in A. adsurgens was also explored by transcriptome analysis. The results showed that AMF increased the biomass of A. adsurgens but not that of L. chinensis and P. distans. AMF promoted phosphorus (P) uptake from soil and improved shoot K+: Na+ ratio, but it decreased shoot Na+ and Cd concentrations and their translocation rates in A. adsurgens. Transcriptome analysis showed that AMF upregulated the differentially expressed genes (DEGs) encoding cytokinins, which may be linked to the increase in shoot biomass in inoculated A. adsurgens, but downregulated the DEGs related to light harvest, suggesting avoidance of photodamage. AMF downregulated the DEGs in the pathways of the cell wall and those associated with antioxidant enzymes. These results suggest that AMF symbiosis in A. adsurgens effectively alleviates the Na+ and Cd toxicity of shoots. This study implies the potential to use salt‐tolerant grasses in association with AMF to rehabilitate the heavy metal‐contaminated saline ecosystems.

Transcriptomic analysis reveals the molecular mechanisms of arbuscular mycorrhizal fungi and nitrilotriacetic acid on Suaeda salsa tolerance to combined stress of cadmium and salt

Halophytes are dominant plants in the phytoremediation of heavy metal contaminated saline soils. Arbuscular mycorrhizal (AM) fungi can improve plant abiotic stress tolerance and chelating agents nitrilotriacetic acid (NTA) can alleviate heavy metal stress. However, the combined effects and mechanisms of two amendments on halophytes grown in heavy metal contaminated saline soils are largely unknown. Pot experiment was conducted to explore the molecular mechanisms of Funneliformis mosseae (Fm) and NTA (10 mmol·kg−1) on Suaeda salsa tolerance to combined stress of Cd (5 mg·kg−1) and NaCl (2.5 g·kg−1). The results showed that AM fungi and NTA promoted growth of S. salsa, increased accumulations of Na+, Cd and mineral elements, but decreased Na+, Cd and malondialdehyde (MDA) concentrations in shoots under combined stress. Transcriptomic analysis presented various regulation pathways of the single or combined application of AM fungi and NTA on S. salsa. The identified differentially expressed genes (DEGs) in (Fm+NTA)/CK were mainly involved in antioxidant defense, osmoregulation, and photosynthesis; the DEGs in (Fm+NTA)/Fm were related to the maintenance of the cell membrane integrity and plant abiotic stress tolerance; and the DEGs in (Fm+NTA)/NTA were related to the enhancement ability of secondary cell wall synthesis and transcription factor. Our study provides new insights into the molecular mechanisms of AM fungi and NTA on halophytes tolerance to combined stress of heavy metal and salt.

A contrasting alteration of sulfamethoxazole bioaccessibility in two different soils amended with polyethylene microplastic: In-situ measurement using diffusive gradients in thin films

Microplastics and veterinary antibiotics are both emerging environmental contaminants that could be co-occurrence in agricultural soils. However, it's still unclear how the microplastics affect the bioaccessibility of antibiotics in a real soil environment. An in-situ measurement using diffusive gradients in thin-films devices suitable for polar organic compounds (o-DGT) coupled with soil moisture sampling were used to reveal such effects. Sulfamethoxazole (SMX) that was selected as a representative antibiotic and polyethylene (PE) microplastic with an average diameter of 35 μm were amended to the paddy soil and saline soil for the study. The result indicated that SMX degradation in the paddy soil was higher than that in the saline soil, meanwhile, PE microplastic addition promoted SMX degradation in both soils. In the paddy soil, PE microplastic addition enhanced release of SMX from soil solid to soil solution but no effects on the bioaccessibile SMX. However, in the saline soil, the PE microplastic addition reduced both SMX in soil solution and bioaccessibile SMX significantly (p < 0.05). The potential resupply ability of the labile SMX from soil solid to soil solution which was expressed as R value enhanced significantly in saline soil, while such a change was negligible in the paddy soil. This implied that long-term release risk of SMX in the PE microplastic contaminated saline soil could not be neglected. Therefore, co-occurrence of PE microplastic and SMX in the soils might increase uptake of SMX by biotas and such effects depended on soil properties.

Arbuscular mycorrhizal fungi and nitrilotriacetic acid regulated Suaeda salsa growth in Cd-contaminated saline soil by driving rhizosphere bacterial assemblages

Phytoremediation is an environmentally friendly method to remediate heavy metal contaminated saline soil. Arbuscular mycorrhizal fungi (AMF) and biodegradable chelators have potential roles in enhancing the phytoremediation efficiency, while their combined effects are largely unexplored. This study was objected to evaluate the effects of AMF and nitrilotriacetic acid (NTA) on phytoremediation using Suaeda salsa. A pot experiment consisting of four treatments (CK, AMF, NTA and AMF + NTA) was conducted for this purpose. The results showed that the shoot and root biomass of Suaeda salsa ranged from 1.84 to 5.86 mg kg−1 and 0.09 to 0.48 mg kg−1 respectively, and were the highest in the AMF + NTA treatment. The AMF + NTA treatment enhanced the Na accumulation by 116 % and 490 %, and enhanced Cd accumulation by 61 % and 33 %, respectively, in plant shoots and roots compared with the CK. The AMF treatment significantly promoted the dominance of Actinobacteria (mainly including Arenimonas, Gaiella, Nocardioides and Marmoricola), whereas the AMF + NTA treatment enhanced that of Proteobacteria (mainly including Aminobacter, Candidatus_Paracaedibacter, Longimicrobium and Flavitalea) in rhizosphere bacterial communities. Network analysis revealed that the bacteria related to Cd were independent from that related to Na in the AMF treatment, but they were consistent in the AMF + NTA treatment. Structural equation modeling further confirmed that single application of AMF or NTA affected plant growth both directly and indirectly, and their combined application could further promote phytoremediation efficiency by enhancing the interactions among bacteria, soil and plants. This study not only proved the benefit of the combined application of AMF and NTA to the improvement of phytoremediation efficiency, but also provided insights into the mechanisms for the improvement from the perspective of rhizosphere microbial community changes.

Phytoremediation with Augmentation of Oxalic Acid of Toxic Metals Contaminated Saline Soil by Suaeda salsa: Effects on Metal Translocation and Plant Physiology

Phytoremediation with augmentation of oxalic acid could improve the removal efficiencies of toxic metals in saline soil. Metal concentrations and species in saline soil, extraction of metals by Sua...

Biochar mitigates arsenic-induced human health risks and phytotoxicity in quinoa under saline conditions by modulating ionic and oxidative stress responses

Arsenic (As) is a toxic metalloid and its widespread contamination in agricultural soils along with soil salinization has become a serious concern for human health and food security. In the present study, the effect of cotton shell biochar (CSBC) in decreasing As-induced phytotoxicity and human health risks in quinoa (Chenopodium quinoa Willd.) grown on As-spiked saline and non-saline soils was evaluated. Quinoa plants were grown on As contaminated (0, 15 and 30 mg kg−1) saline and non-saline soils amended with 0, 1 and 2% CSBC. Results showed that plant growth, grain yield, stomatal conductance and chlorophyll contents of quinoa showed more decline on As contaminated saline soil than non-saline soil. The application of 2% CSBC particularly enhanced plant growth, leaf relative water contents, stomatal conductance, pigment contents and limited the uptake of As and Na as compared to soil without CSBC. Salinity in combination with As trigged the production of H2O2 and caused lipid peroxidation of cell membranes. Biochar ameliorated the oxidative stress by increasing the activities of antioxidant enzymes (SOD, POD, CAT). Carcinogenic and non-carcinogenic human health risks were greatly decreased in the presence of biochar. Application of 2% CSBC showed promising results in reducing human health risks and As toxicity in quinoa grown on As contaminated non-saline and saline soils. Further research is needed to evaluate the role of biochar in minimizing As accumulation in other crops on normal as well as salt affected soils under field conditions.

Effect of biochar-immobilized Sphingomonas sp. PJ2 on bioremediation of PAHs and bacterial community composition in saline soil

This study aimed to investigate the bioremediation efficiency and bacterial regulation mechanism of biochar-immobilized bacterium (BM) in polycyclic aromatic hydrocarbon (PAH)-contaminated saline soil by conducting pot experiments. In BM treatment, PAH-degrading strain Sphingomonas sp. PJ2 was inoculated into biochar produced at 400 °C and 600 °C using the pine needles (BM400 and BM600). The removal rates of PAHs, soil physicochemical properties, abundance of PAH-ring hydroxylating dioxygenase (PAH-RHD), and bacterial community composition were determined. After 60 days of bioremediation, BM treatment significantly (P < 0.05) increased the removal rate of PAHs compared with biochar and PJ2 alone (15.94% and 37.3%, respectively). BM treatment clearly improved the physicochemical properties of saline soil. Moreover, the amount of Gram-positive PAH degraders increased in BM-treated soils compared with other treatments, and their gene abundance had a strong positive correlation with the removal rates of PAHs in soils (r = 0.896; P < 0.01). Furthermore, BM treatment increased the abundance of Sphingomonas genus, indicating that the strain PJ2 could survive and colonize in PAH-contaminated saline soil under the protection of biochar. This study provided an effective and green approach for the remediation and improvement of the PAH-contaminated saline soil.

Biological silicon nanoparticles improve Phaseolus vulgaris L. yield and minimize its contaminant contents on a heavy metals-contaminated saline soil

The synthesis of biological silicon nano-particles (Bio-Si-NPs) is an eco-friendly and low-cost method. There is no study focusing on the effect of Bio-Si-NPs on the plants grown on saline soil contaminated with heavy metals. In this study, an attempt was made to synthesis Bio-Si-NPs using potassium silica florid substrate, and the identified Aspergillus tubingensis AM11 isolate that separated from distribution systems of the potable water. A two-year field trial was conducted to compare the protective effects of Bio-Si-NPs (2.5 and 5.0 mmol/L) and potassium silicate (10 mmol/L) as a foliar spray on the antioxidant defense system, physio-biochemical components, and the contaminants contents of Phaseolus vulgaris L. grown on saline soil contaminated with heavy metals. Our findings showed that all treatments of Bio-Si-NPs and potassium silicate significantly improved plant growth and production, chlorophylls, carotenoids, transpiration rate, net photosynthetic rate, stomatal conductance, membrane stability index, relative water content, free proline, total soluble sugars, N, P, K, Ca2+, K+/Na+, and the activities of peroxidase, catalase, ascorbic peroxidase and superoxide oxide dismutase. Application of Bio-Si-NPs and potassium silicate significantly decreased electrolyte leakage, malondialdehyde, H2O2, O2•−, Na+, Pb, Cd, and Ni in leaves and pods of Phaseolus vulgaris L. compared to control. Bio-Si-NPs were more effective compared to potassium silicate. Application of Bio-Si-NPs at the rate of 5 mmol/L was the recommended treatment to enhance the performance and reduce heavy metals content on plants grown on contaminated saline soils.

Application potential of Salicornia europaea in remediation of Cd, Pb and Li contaminated saline soil

Coastal and inland saline-alkali soil is important reserve land resources. However, some parts of saline land are now under the threat of heavy metals such as cadmium (Cd), lead (Pb) and the light metal lithium (Li). Phytoremediation with halophytes could be the most economical and effective way to restore the contaminated saline soil. In this study, the growth, physiological and biochemical indexes and ion contents of halophyte Salicornia europaea under different concentrations of Cd (0-50 mmol/L), Pb (0-50 mmol/L) and Li (0-400 mmol/L) were investigated to evaluate the tolerance and accumulation of the metal contaminations. The results showed that plant height, fresh weight and dry weight of S. europaea decreased significantly with the increase of Cd and Pb concentration. Low concentration of Li (< 20 mmol/L) promoted the growth of S. europaea, while the growth of plants was inhibited under higher concentration of Li (> 20 mmol/L). The tolerance order of S. europaea to Cd, Pb and Li was Li > Pb > Cd. Cd, Pb and Li stresses may negatively affected Na and K uptake and transport in S. europaea to affect plant growth. In addition, the antioxidant enzyme system synergistically responsed to resist the oxidative toxicity of different ions. The contents of Cd, Pb, Li in roots and shoots of S. europaea also increased with the increase of treatment concentration. Furthermore, Cd and Pb contents in roots were significantly higher than in shoots, while more Li accumulated in shoots than in roots. The aforementioned results showed that S. europaea had strong tolerance along with a high accumulate ability to Cd, Pb and Li, indicating its application potential in restoring Cd, Pb and Li contaminated saline soil. This study laid a basis for further exploration of the tolerance mechanism of S. europaea to Cd, Pb and Li stresses, and gave a new perspective for the usage of S. europaea to remediate Cd, Pb and Li pollutants in high-salinity alkali soils.

Change in soil ion content and soil water-holding capacity during electro-bioremediation of petroleum contaminated saline soil

This study investigated changes in soil ion content and soil water-holding capacity during electro-bioremediation (EK-Bio) of petroleum contaminated saline soil (ion content of 3.92 g/kg). The results indicated that the soil ions surrounded the electrodes with increasing time, thus changing the soil water-holding capacity. According to the Van Genuchten model fitting results, the soil residual water content (θr) increased with the soil ion content, which represented a capacity decrease of the soil water supply. At the end of the EK-Bio experiment, the θr values in the soil near (site A) and far from (site B) the electrodes were 19.1 % and 12.1 %, where the soil ion content was 7.92 g/kg and 0.55 g/kg, respectively. The ion aggregation process significantly impacted the growth of soil microbial. The bacteria numbers decreased when the soil ion content was high (7.41 g/kg, site A) and low (0.84 g/kg, site B) after 70 days of treatment. The applied electric field significantly enhanced the bioremediation efficiency. However, the biodegradation promotion effect was the weakest at site A. The synergistic effect between the applied electric field and degrading bacteria was delayed.

Effect of salinity on physiological, biochemical and photostabilizing attributes of two genotypes of quinoa (Chenopodium quinoa Willd.) exposed to arsenic stress

Soil salinity and arsenic (As) contamination are serious environmental problems. To investigate the effects of salinity on As uptake and physiological and biochemical attributes of quinoa (Chenopodiumquinoa Willd.), a hydroponic experiment was performed. One-month old healthy plants of two quinoa genotypes; Vikinga and A7 were transplanted in plastic tubs containing half strength Hoagland's nutrient solution. Plants were exposed to different levels of As (0, 150 and 300 μM), salinity (0, 150 and 300 mM) and their combinations (150 μM As + 300 mM NaCl; 300 μM As + 300 mM NaCl) for five weeks. Results revealed that combined application of salinity and As caused more pronounced reduction in growth, chlorophyll contents and caused more oxidative damage in both quinoa genotypes. Under combined application of salinity and As, Na+ concentration was increased whereas As content was decreased in plant tissues. Quinoa genotype A7 was more tolerant than Vikinga against salinity, As and their combination perhaps because of less uptake of toxic ions and higher activities of antioxidant enzymes (SOD, CAT, POD). Bioconcentration factor (BCF), translocation factor (TF) and tolerance index (TI) indicated that genotype A7 can be successfully employed for phytostabilization of As contaminated saline soils.

Phytoremediation and Accumulation of Cadmium from Contaminated Saline Soils by Vetiver Grass

Phytoremediation and Accumulation of Cadmium from Contaminated Saline Soils by Vetiver Grass