Arsenic Polluted Soil Research Articles

Synchrotron tomography of magnetoprimed soybean plant root system architecture grown in arsenic-polluted soil.

The present study evaluated the repercussions of magnetopriming on the root system architecture of soybean plants subjected to arsenic toxicity using synchrotron radiation source based micro-computed tomography (SR-µCT). This will be used evey where as abbreviation for the technique for three-dimensional imaging. Seeds of soybean were exposed to the static magnetic field (SMF) of strength (200 mT) for 1h prior to sowing. Magnetoprimed and non-primed seeds were grown for 1 month in a soil-sand mixture containing four different levels of sodium arsenate (0, 5, 10, and 50 mg As kg-1 soil). The results showed that arsenic adversely affects the root growth in non-primed plants by reducing their root length, root biomass, root hair, size and number of root nodules, where the damaging effect of As was observed maximum at higher concentrations (10 and 50 mg As kg-1 soil). However, a significant improvement in root morphology was detected in magnetoprimed plants where SMF pretreatment enhanced the root length, root biomass, pore diameter of cortical cells, root hair formation, lateral roots branching, and size of root nodules and girth of primary roots. Qualitative analysis of x-ray micro-CT images showed that arsenic toxicity damaged the epidermal and cortical layers of the root as well as reduced the pore diameter of the cortical cells. However, the diameter of cortical cells pores in magnetoprimed plants was observed higher as compared to plants emerged from non-primed seeds at all level of As toxicity. Thus, the study suggested that magnetopriming has the potential to attenuate the toxic effect of As and could be employed as a pre-sowing treatment to reduce the phytotoxic effects of metal ions in plants by improving root architecture and root tolerance index. This study is the very first exploration of the potential benefits of magnetopriming in mitigating the toxicity of metals (As) in plant roots utilizing the micro-CT technique.

Complexation and immobilization of arsenic in maize using green synthesized silicon nanoparticles (SiNPs)

Arsenic (As) is a heavy metal that is toxic to both plants and animals. Silicon nanoparticles (SiNPs) can alleviate the detrimental effects of heavy metals on plants, but the underlying mechanisms remain unclear. The study aims to synthesize SiNPs and reveal how they promote plant health in Arsenic-polluted soil. 0 and 100% v/v SiNPs were applied to soil, and Arsenic 0 and 3.2 g/ml were applied twice. Maize growth was monitored until maturity. Small, irregular, spherical, smooth, and non-agglomerated SiNPs with a peak absorbance of 400 nm were synthesized from Pycreus polystachyos. The SiNPs (100%) assisted in the development of a deep, prolific root structure that aided hydraulic conductance and gave mechanical support to the maize plant under As stress. Thus, there was a 40–50% increase in growth, tripled yield weights, and accelerated flowering, fruiting, and senescence. SiNPs caused immobilization (As(III)=SiNPs) of As in the soil and induced root exudates Phytochelatins (PCs) (desGly-PC2 and Oxidized Glutathione) which may lead to formation of SiNPs=As(III)–PCs complexes and sequestration of As in the plant biomass. Moreover, SiNPs may alleviate Arsenic stress by serving as co-enzymes that activate the antioxidant-defensive mechanisms of the shoot and root. Thus, above 70%, most reactive ROS (OH) were scavenged, which was evident in the reduced MDA content that strengthened the plasma membrane to support selective ion absorption of SiNPs in place of Arsenic. We conclude that SiNPs can alleviate As stress through sequestration with PCs, improve root hydraulic conductance, antioxidant activity, and membrane stability in maize plants, and could be a potential tool to promote heavy metal stress resilience in the field.

Arsenic pollution and its impact on agricultural production, including the ecosystem services delivered by biodiversity

Arsenic (As), a noxious metal(loid) widely available in the biosphere, originates mainly from geogenic and anthropogenic origin. Massive global development and industrialization, using pesticides carrying arsenic, arsenical animal feeds, medicine, mining, aquifer sediments, coal burning, and microbial and natural processes continuously release this obnoxious bane to the natural environment and pollute soil and water. Inorganic (iAs) species, mainly arsenate and arsenite, are comparatively more lethal than methylated species. However, pentavalent [As (V)] organic species are nearly non-toxic. An elevated level of arsenic has been found in various crops and feeds consumed by humans and animals. This notable carcinogen threatens human health by drinking arsenic-polluted freshwater and/or ingesting arsenic-adulterated food like cereals, fruits and vegetables grown in arsenic-polluted soil or grown using arsenic-rich irrigation water. Arsenic pollution exerts an irreversible harmful effect on the aquatic and terrestrial ecosystem as well. Much research has been carried out in the last couple of centuries on arsenic pollution and reported its ability to influence the agro-ecosystem to a great extent, including plant accumulation, phytotoxicity, and land degradation. However, underground water is considered the principal source of arsenic pollution, Iron plaque, sulphur oxides, organic matter, microbiome activities and many other factors responsible for speciation, bioavailability and toxicity of As to the environment. This review attempts to comprehend the global arsenic pollution occurrence, its forms, bioavailability and toxicity to humans and microbiota, translocation and accumulation in plants and impact on crop yield. Besides providing the insights, the ultimate targets of this desktop study are to ascertain probable knowledge gaps linked to crop productivity and ecosystem benefit losses that need further investigation.

Isolation and characterization of PGPR obtained from different arsenic-contaminated soil samples and their effect on photosynthetic characters of maize grown under arsenic stress.

Contamination of the environment due to speedup of anthropogenic activities has become a serious threat to modern humanity. Among the contaminants, the new emerging concern is the heavy metal (HM) contamination in the environment. Because the persistence and harmfulness of heavy metals affect the ecosystem and the health of plants, animals, and humans, they are the most toxic substances in the environment. Among them, Arsenic (As) emerged as major environmental constraint leading to enormous negative effects on the plant, animal, and human health. Even in minute quantity, As is known to cause various critical diseases in humans and toxicity in plants. Research was performed to observe the capability of plant growth-promoting strains of bacteria in enhancing Zea mays (L.) growth in arsenic polluted soil. Total 30 bacterial strains were isolated from the polluted soils, screened for plant growth promotion potential and arsenic tolerance. Eighteen isolates showed resistance to different levels of sodium arsenate (ranging from 0 to 50 mM) in agar plate using LB media. Of 18 isolates, 83.3% produced IAA, methyl red, and hydrogen cyanide; 55.5% exhibited catalase activity; 61.1% showed siderophore production; 88.8% showed phosphate solubilization; and 44.4% showed oxidase, Voges proskauer activity, and KOH solubility. The most efficient isolates SR3, SD5, and MD3 with significant arsenic tolerance and plant growth-promoting (PGP) activity were examined via sequencing of amplified 16S rRNA gene. Isolates of bacteria, i.e., SR3, SD5, and MD3, showing multiple PGP-traits were identified as Bacillus pumilus (NCBI accession number: OR459628), Paenibacillus faecalis (NCBI accession number: OR461560), and Pseudochrobactrum asaccharolyticum (NCBI accession number: OR458922), respectively. Maize seeds treated with these PGPR strains were grown in pots contaminated with 50 ppm and 100 ppm sodium arsenate. Compared to untreated arsenic stressed plants, bacterial inoculation P. asaccharolyticum (MD3) resulted 20.54%, 18.55%, 33.45%, 45.08%, and 48.55% improvement of photosynthetic pigments (carotenoid content, chlorophyll content, stomatal conductance (gs), substomatal CO2, and photosynthetic rate), respectively. Principal component analysis explained that first two components were more than 96% of the variability for each tested parameter. The results indicate that in comparison to other isolates, P. asaccharolyticum isolate can be used as efficient agent for improving maize growth under arsenic polluted soil.

Remediation effect and mechanism of low-As-accumulating maize and peanut intercropping for safe-utilization of As-contaminated soil

Phytoremediation by intercropping is a potential method to realize both production and remediation. Maize and peanut are the main crops planted in arsenic(As) contaminated areas in south China and vulnerable to As pollution. Experiments were conducted on arsenic-polluted soil with low As-accumulating maize monoculture (M), peanut monoculture (P), and intercropping with different distances between the maize and peanut (0.2 m, 0.35 m, and 0.5 m, recorded as MP0.2, MP0.35, and MP0.5, respectively). The results indicated that the As content in the maize grains and peanut lipids in the intercropping system decreased significantly, meeting the food safety standard of China (GB 2762-2017). Moreover, the land equivalent ratio (LER) and heavy metal removal equivalence ratio (MRER) of all intercropping treatments were greater than 1, indicating that this intercropping agrosystem has the advantage of production and arsenic removal, among which the yield and LER of MP0.35 treatment were the highest. Additionally, the bioconcentration factors (BCF) and translocation factor (TF) of MP0.2 increased by 117.95% and 16.89%, respectively, indicating that the root interaction affected the absorption of As in soil by crops. This study preliminarily demonstrated the feasibility of this intercropping system to safely use and remedy arsenic-contaminated farmland during production.

Effects of Soil Amendments on Arsenic Uptake by Earthworms(Eisenia fetida) in Arsenic-Polluted Soil

This study was conducted to evaluate the effects of soil amendments on arsenic (As) bioavailability in As-polluted soils. We determined the subsequent changes in As toxicity toward earthworms (<i>Eisenia fetida</i>) and As uptake by earthworms. We also investigated whether As bioaccumulation could be used as an index to evaluate changes in quality of As-polluted soils. No significant changes in acute toxicity to earthworms were observed, and the observed increases (70-93 mg kg<sup>-1</sup>) or decreases (27-38 mg kg<sup>-1</sup>) in bioavailable As in soils at the end of test were not related to the As concentrations in earthworms. The As concentration in earthworms 14 days after exposure was significantly lower in calcium superphosphate (CSP)- and S-treated soils (101.4-112.8 mg kg<sup>-1</sup>) than in control soil (138.9 mg kg<sup>-1</sup>), probably owing to reduced earthworm growth due to lower pH in CSP- and S-treated soils (6.3-7.3) relative to control and steel slag-treated soils (7.5-8.4). Comparisons of As toxicity and the effects of soil properties on this toxicity toward various species of earthworms could facilitate the use of earthworms to produce biological indices for evaluating changes in quality of As-polluted soils following amendment treatments.

Effect of High-Power Ultrasound Washing on Arsenic-Polluted Soil

Effect of High-Power Ultrasound Washing on Arsenic-Polluted Soil

Microbial community composition in the rhizosphere of Pteris vittata and its effects on arsenic phytoremediation under a natural arsenic contamination gradient.

Arsenic contamination causes numerous health problems for humans and wildlife via bioaccumulation in the food chain. Phytoremediation of arsenic-contaminated soils with the model arsenic hyperaccumulator Pteris vittata provides a promising way to reduce the risk, in which the growth and arsenic absorption ability of plants and the biotransformation of soil arsenic may be greatly affected by rhizosphere microorganisms. However, the microbial community composition in the rhizosphere of P. vittata and its functional role in arsenic phytoremediation are still poorly understood. To bridge this knowledge gap, we carried out a field investigation and pot experiment to explore the composition and functional implications of microbial communities in the rhizosphere of four P. vittata populations with a natural arsenic contamination gradient. Arsenic pollution significantly reduced bacterial and fungal diversity in the rhizosphere of P. vittata (p < 0.05) and played an important role in shaping the microbial community structure. The suitability of soil microbes for the growth of P. vittata gradually decreased following increased soil arsenic levels, as indicated by the increased abundance of pathogenic fungi and parasitic bacteria and the decrease in symbiotic fungi. The analysis of arsenic-related functional gene abundance with AsChip revealed the gradual enrichment of the microbial genes involved in As(III) oxidation, As(V) reduction, and arsenic methylation and demethylation in the rhizosphere of P. vittata following increased arsenic levels (p < 0.05). The regulation of indigenous soil microbes through the field application of fungicide, but not bactericide, significantly reduced the remediation efficiency of P. vittata grown under an arsenic contamination gradient, indicating the important role of indigenous fungal groups in the remediation of arsenic-contaminated soil. This study has important implications for the functional role and application prospects of soil microorganisms in the phytoremediation of arsenic-polluted soil.

Loading ferric lignin on polyethylene film and its influence on arsenic-polluted soil and growth of romaine lettuce plant.

This work developed a composite (Pe-FeLs) which loaded ferric lignin on polyethylene film (PE film) by chemical modification and physico-chemically characterized by Microscope, FESEM with elemental mapping analysis, and XRD. Microscope pictures showed that chemical modification did not destroy the appearance of PE film. The FESEM images of Pe-FeLs showed the well-distributed clusters could be clearly seen and most of the particles were spherical morphology. Elemental mapping of individual element on Pe-FeLs clearly indicated the existing of iron. The XRD pattern showed the amorphous hydroxides of iron on Pe-FeLs. In arsenic solution, the total arsenic adsorption capacity of Pe-FeLs was much higher than that of ferric lignin and PE, which showed Pe-FeLs had the ability to adsorb arsenic. For making Pe-FeLs work well in the soil, a Pe-FeLs system was set up with plastic grid plate, PE film with holes, Pe-FeLs, PE film, and plastic grid plate from the upper to bottom in order. With applying Pe-FeLs system under the soil, arsenic was significantly reduced by 25.5 ~ 53.4% in heavily, moderately, and lower arsenic-polluted soils, the biomass of the romaine lettuce increased and arsenic accumulation in the romaine lettuce decreased.

Selenium alleviates arsenic induced stress by modulating growth, oxidative stress, antioxidant defense and thiol metabolism in rice seedlings

This study aims to investigate the potentiality of selenium in modulating arsenic stress in rice seedlings. Arsenate accumulation along with its transformation to arsenite was enhanced in arsenate exposed seedlings. Arsenite induced oxidative stress and severely affected the growth of the seedlings. Arsenate exposure caused an elevation in ascorbate and glutathione levels along with the activities of their metabolizing enzymes viz., ascorbate peroxidase, glutathione reductase, glutathione-S-transferase, and glutathione peroxidase. Phytochelatins content was increased under arsenic stress to subdue the toxic effects in the test seedlings. Co-application of arsenate and selenate in rice seedlings manifested pronounced alteration of oxidative stress, antioxidant defense, and thiol metabolism as compared to arsenate treatment only. ANOVA analysis (Tukey’s HSD test) demonstrated the relevance of using selenate along with arsenate to maintain the normal growth and development of rice seedlings. Thus, exogenous supplementation of selenium will be a beneficial approach to cultivate rice seedlings in arsenic polluted soil.

Transformation of Arsenic by Indigenous Soil Microbes as Affected by Phosphorus and Arsenic

Highly arsenic-polluted soil (16.5 mg kg –1 ) of West Bengal, India, was used for isolation, screening and identification of indigenous soil microbes. Citrobacter koseri significantly removed (7.6) and bioaccumulated (4.95) highest arsenic in P 15 As 15 treatment, while loss (2.9) was higher in P 10 As 15 . Similarly, Pseudomonas putida significantly removed (7.4) and bioaccumulate (4.8) highest as in P 15 As 15 and while loss (2.8) was higher in P 10 As 15 . Percentage removal of As was 47–59, bioaccumulation was 29–38 and loss 17–23 with Citrobacter sp . , while it was 47–58% (removal), 29–39% (bioaccumulation) and 17–21% (loss) with Pseudomonas putida . Maximum removal and bioaccumulation of phosphorus was 37.8% and 32.1% respectively, for P 10 As 15 in Citrobacter sp. In P. putida it was 33.1% and 27.2% respectively, for P 10 As 15 . At the same level of arsenic, increase in phosphorus significantly increased its removal and bioaccumulation, but the opposite was true during calculation in terms of percentage removal and percentage bioaccumulation.

Species and Distribution of Arsenic in Soil After Remediation by Electrokinetics Coupled with Permeable Reactive Barrier

Arsenic-polluted soil from a mining area in China was treated by electrokinetics coupled with permeable reaction barrier (EK/PRB). Batch tests with PRB media of zero valent iron (ZVI) under electric potential of 2 V cm−1 for 120 h were conducted. Species and distribution of arsenic in soil after remediation were investigated to evaluate the removal mechanisms of arsenic. Results showed that ZVI-PRB was the dominant role in the removal of arsenic in the EK/PRB systems. Arsenic transferring toward the anode was greater than cathode, due to the negatively charged arsenic anions which moved to the anode chamber by electromigration. Pentavalent arsenic (As(V)) in soil could not be reduced to more poisonous trivalent arsenic (As(III)), no matter if it were treated by EK alone or EK/ZVI-PRB. The surface characterization of ZVI, which was carried out using X-ray photoelectron spectrometry (XPS), showed that the ratio of As(V)/As(III) on the surface of PRB media was lower than that in the initial soil; no As(0) was detected on the surface of used ZVI, which indicates that arsenic was removed by surface adsorption/precipitation on ZVI-PRB, accompanied by As(V) partially reduced to As(III). The results reported in this study will be beneficial to optimizing the design of batch EK/PRB system and to enlarging the field-scale system.

Influence of phosphorus and organic matter on microbial transformation of arsenic

Abstract Experiment was conducted with an arsenic polluted soil (16.5 mg kg−1) to investigate different level of organic matter and phosphorus on microbial transformation of arsenic with two bacterial strain viz Citrobacter sp. and Pseudomonas sp.. Organic matter application as FYM @ 10 t ha−1 decreased the total (12.57 and 12.33 mg kg−1) and extractable soil arsenic (1.07 and 0.87 mg kg−1) significantly; and increased the bacterial population (144.33 and 200.83 CFU × 107), microbial biomass carbon (676.33 and 848.67 mg kg−1) and extractable soil phosphorus (14.43 and 14.80 mg kg−1) in arsenic polluted soil with Citrobacter sp. and Pseudomonas sp., respectively. Addition of phosphorus @ 15 mg kg−1 significantly reduced the total soil arsenic (8.77 and 8.60 mg kg−1) with Citrobacter sp. and Pseudomonas sp., respectively. The best result was obtained by Pseudomonas sp. than Citrobacter sp.. Thus organic matter and phosphorus along with bacterial strains have ability to mitigate the arsenic polluted soil and can be used for bio-remediation.

Rice-derived facultative endophytic Serratia liquefaciens F2 decreases rice grain arsenic accumulation in arsenic-polluted soil

In this study, an arsenic (As)-resistant facultative endophytic bacterial strain, F2, was isolated from the root of Oryza sativa Longliangyou Huazhan and identified as Serratia liquefaciens according to 16S rRNA gene sequence analysis. Strain F2 was characterized for i) its impacts on As immobilization in solution and rice tissue As accumulation, and ii) the mechanisms involved for different levels of As-pollution in soils. In strain F2-inoculated culture medium, the concentration of As decreased, while the pH, cell growth, and cell-immobilized As significantly increased over time. Grain As content reduced by between 23 and 36% in strain F2-inoculated rice plants in comparison to the control. Available As content decreased by between 28 and 52%, but unavailable As content increased by between 27 and 46% in the strain F2-inoculated soil when compared with the controls. Moreover, the strain decreased the As translocation factor by between 34 and 46%, but increased the As concentration by between 24 and 70% in Fe plaque on the rice root surfaces in comparison to the controls. These results suggested that strain F2 decreased the rice grain As uptake by i) decreasing available As in soil, ii) increasing rice root surface As adsorption, and iii) decreasing As translocation from the roots to grains. Our findings may provide a new rice-derived facultative endophytic bacteria-assisted approach for decreasing the As uptake to rice grains in As-polluted soils.

Remediation of contaminated soils: experience from two sites in Sweden

Experience from remediation of two old abandoned industrial sites is reviewed. One case is a tannery site where sludge lagoons and a solid waste dump have been covered by clay and turned into a park area. The other case is a wood preservation plant where arsenic polluted soil has been cleaned by washing before the site will be open to public for sport activities and recreation. The main contaminants, the reasons for chosen remediation measures and experience from the remediation works are presented.

Effects of arsenic toxicity on morphological characters in blackgram (Vigna mungo L.) during early growth stage.

Blackgram is an important pulse crop of the tropic and sub-tropic area and has been identified as a potential crop in many countries. In the south-East Asia arsenic toxicity in soil and water is one of the most environmental problems. Crop productivity is highly affected by cultivation in arsenic polluted soil or irrigation through arsenic polluted water. The present study was conducted to evaluate the effect of arsenic (As) on fresh shoot length, fresh shoot weight, fresh root length, fresh shoot weight and total fresh biomass, The results indicate that root length is more affected than shoot length due to arsenic toxicity. The fresh shoot weight observed was more affected than fresh root weight. This study indicates that arsenic toxicity causes the deleterious effect on blackgram growth. The toxic effect of blackgram depends on the genotypic variability. Some blackgram genotypes show very less toxic effect of arsenic due to its genetic makeup. Experimental findings of study indicate that longer root length and more shoot weight in arsenic stress condition may be tolerant blackgram genotype to arsenic toxicity.

In-situ Phytoremediation of Arsenic from Contaminated Soil

Arsenic contamination in the world is worrisome, excessive and increasing. In this study, the research was designed for the remediation of arsenic polluted soil site in Beijing China using in situ treatment method (phytoremediation). Chelating agents ethylenediaminedisuccinic (EDDS), and citric acid (CA) were used to aid the hyper accumulator to enhance quicker extraction rate. A hyper accumulator Chinese brake fern (Pteria vittata) was used with the additions of EDDS and CA at different ratios. The result obtained from the treated soil were analyzed and compared. It showed significant increase in the extraction of Arsenic (As). About 3.55 mg/kg of As was detected in the treated plant biomass whereas the control has 0.98 mg/kg. It was suggested that solubility in the soil after treatment readily for uptake was 3.9 mg/kg. The control plants and the Corn however, had little absorption. It will be more promising, to select hyper accumulator which naturally possess higher biomass and are plants of local and natural origin to peculiar location

Effects of Sulfate Application on Inhibiting Accumulation and Alleviating Toxicity of Arsenic in Panax notoginseng Grown in Arsenic-Polluted Soil

Panax notoginseng (P. notoginseng) is a well-known traditional Chinese medicinal herb. Due to elevated arsenic (As) levels in some planting area, P. notoginseng and its derivatives are contaminated, and the As concentration in these products exceeds the standard limit (As concentration < 2 mg/kg). In this study, the effects of sulfate (S) application on As uptake and the physicological response of P. notoginseng were investigated in a pot-culture experiment. The results showed that the As concentration in the roots was significantly decreased by a maximum of 64.9 % in response to the application of 75 mg/kg S. The proportion of methylated arsenic, which is less toxic, in the roots was increased by 263.4 %. Moreover, the application of S alleviated the oxidative damage due to As stress, and the activities of superoxide dismutase (SOD) and peroxidase (POD) were improved by 26.2 and 29.4 %, respectively. Finally, the total saponin content in the roots increased by 26.0 % in response to a supply of 50 mg/kg S. These findings implied that the application of S fertilizer could effectively reduce As accumulation in P. notoginseng and promote the formation of pharmaceutical components.

ACC Deaminase Producing Arsenic Tolerant Bacterial Effect on Mitigation of Stress Ethylene Emission in Maize Grown in an Arsenic Polluted Soil

Arsenic is a known hazardous metalloid not only to the animals but also to plants. With high concentrations, it can impede normal plant growth and cause even death of plants at extremely high levels. A known plant response to stress conditions such as toxic levels of metal (loids) is the production of stress ethylene, causing inhibitory effect on root growth in plants. When the effect of various arsenic concentrations was tested to maize plant, the stress ethylene emission proportionately increased with increasing concentration of As(V). The inoculation of two arsenic tolerant bacteria; Pseudomonas grimonti JS126 and Pseudomonas taiwanensis JS238 having respective high and low 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity reduced stress ethylene emission by 59% and 30% in maize grown in arsenic polluted soils. The result suggested the possible use of Pseudomonas grimonti JS126 for phytoremediation of arsenic polluted soils.

Effects of arbuscular mycorrhizal inoculation and phosphorus fertilization on the growth of escarole (Cichorium endivia L.) in an arsenic polluted soil

We have studied the effects of P fertilization and AMF inoculation on the growth of escarole (Chicorium endivia L.) plants ,grown in both As-non-contaminated (Padula) and As-contaminated (La Botte) soils and As and P uptake by these plants. Our study demonstrated that the combined use of AMF inoculation and P fertilization can significantly increase the production of biomass of escarole plants, even if grown in highly As-contaminated soils. In addition, this dual agricultural practice has also allowed to reduce the translocation of the harmful element from roots to leaves minimizing, hence, the accumulation of highly toxic levels of As in the edible part of the escarole. Therefore, the combined use of AMF inoculation and P fertilization may alleviate the As toxicity to sensitive plants as Cichorium endivia, by promoting their growth, limiting As assimilation and improving P nutrition.