Contaminated Soil Environment Research Articles

Prevention of Helminthiasis Through Increased Knowledge with Poster and Video Media: An Intervention Study

In 2016, the World Health Organization (WHO) stated that 24% of the world's population is infected with helminthiasis. In Indonesia, the highest prevalence at 30%-90% occurs at the age of 1-12 years, namely in preschool and elementary school children. Helminthiasis infection is transmitted through eggs in human feces. Contaminated soil environments occur in populations with poor sanitation. Helminthiasis can lead to nutritional, physical, intelligence, and productivity problems. Open defecation behavior in the environment makes the soil polluted with feces containing worm eggs. An unhealthy environment and behavior are risk factors for helminthiasis. Health efforts through health education need to always be carried out through the media to disseminate information to the public to prevent helminthiasis. This study aims to determine the effectiveness of video media compared to poster media in the prevention of helminthiasis in increasing the knowledge of mothers who have toddlers. The research method used was a quasi-experiment with a non-equivalent control group design. The population was mothers who have toddlers in the working area of the Ibrahim Adjie Community Health Center with a sample determination through a purposive sampling technique of 18 mothers of toddlers in both the video group and the poster group. The Data analysis used was a paired t-test and independent t-test. The results of the research that has been carried out found that there is a difference in the average knowledge of preventing helminthiasis in the video and poster groups with P-value = 0.000. There is effectiveness of intervention through video media and poster media on knowledge with P value=0.000. Video and poster media on the prevention of helminthiasis can increase the knowledge of mothers who have toddlers. This means that video and poster media on the prevention of helminthiasis can be used as intervention media in increasing the knowledge of mothers who have toddlers to prevent helminthiasis.

Treatment for heavy metal pollution: remediating soil environment by harnessing genetic and biochemical capabilities of bacteria

Pollution is the introduction of harmful substances, also known as pollutants, into the environment. As all living things depend on clean air, water, and land for survival, pollution is a significant problem on a worldwide scale. In addition, heavy metals are the most essential and common contaminants in soil environments. These pollutants are widely diffused, harmful to human health, and persistent in soil environments. Owing to the circumstances locally and worldwide, pollution assessment and bacterial remediation techniques for polluted soil have gained substantial attention and become essential. Here, this review covers four bacterial processes involved in bacterial remediation technology, including heavy metal adsorption and adhesion, redox transformation of heavy metals, and the function of mycorrhizal fungi. Also, a case study of a detailed experiment on pollution treatment is presented. This research aims to eliminate heavy metal pollution by using bacterial remediation technology in order to save human beings and the environment since long-term exposure to heavy metals can cause lung cancer and bone fractures in humans, thus posing a significant security threat and hidden danger to human society.

Toxicity of Nanoscale Zero-Valent Iron to Soil Microorganisms and Related Defense Mechanisms: A Review.

Soil pollution is a global environmental problem. Nanoscale zero-valent iron (nZVI) as a kind of emerging remedial material is used for contaminated soil, which can quickly and effectively degrade and remove pollutants such as organic halides, nitrates and heavy metals in soil, respectively. However, nZVI and its composites can enter the soil environment in the application process, affect the physical and chemical properties of the soil, be absorbed by microorganisms and affect the growth and metabolism of microorganisms, thus affecting the ecological environment of the entire soil. Because of the potential risks of nZVI to the environment and ecosystems, this paper summarizes the current application of nZVI in the remediation of contaminated soil environments, summarizes the various factors affecting the toxic effects of nZVI particles and comprehensively analyzes the toxic effects of nZVI on microorganisms, toxic mechanisms and cell defense behaviors to provide a theoretical reference for subsequent biosafety research on nZVI.

Signaling and Detoxification Strategies in Plant-Microbes Symbiosis under Heavy Metal Stress: A Mechanistic Understanding.

Plants typically interact with a variety of microorganisms, including bacteria, mycorrhizal fungi, and other organisms, in their above- and below-ground parts. In the biosphere, the interactions of plants with diverse microbes enable them to acquire a wide range of symbiotic advantages, resulting in enhanced plant growth and development and stress tolerance to toxic metals (TMs). Recent studies have shown that certain microorganisms can reduce the accumulation of TMs in plants through various mechanisms and can reduce the bioavailability of TMs in soil. However, relevant progress is lacking in summarization. This review mechanistically summarizes the common mediating pathways, detoxification strategies, and homeostatic mechanisms based on the research progress of the joint prevention and control of TMs by arbuscular mycorrhizal fungi (AMF)-plant and Rhizobium-plant interactions. Given the importance of tripartite mutualism in the plant-microbe system, it is necessary to further explore key signaling molecules to understand the role of plant-microbe mutualism in improving plant tolerance under heavy metal stress in the contaminated soil environments. It is hoped that our findings will be useful in studying plant stress tolerance under a broad range of environmental conditions and will help in developing new technologies for ensuring crop health and performance in future.

Evaluation of Diesel Degradation Potential of Klebsiellapneumoniae Strain VM18 Isolated from Petroleum Contaminated Soil of Mathura

The present investigation was conducted to isolate, characterize and identify one of the best bio degrader bacterial isolate and to measure its biodegradation capacity. strain VM18 was the isolated bacteria which showed the degradation efficacy of Klebsiella pneumoniae 62.84% after 35 day of incubation in Bushnell Hass medium. GC-MS analysis reveals that, strain VM18 degraded C -th Klebsiella pneumoniae 51C fraction from 2.54% to 1.49% and converted them into C -C after 21 days of incubation. This can be concluded that bacterial strains have 60 31 50 potential to degrade the petroleum hydrocarbons present in contaminated soil environment.

Coupled variations of dissolved organic matter distribution and iron (oxyhydr)oxides transformation: Effects on the kinetics of uranium adsorption and desorption

The interactions between dissolved organic matter (DOM) molecules and minerals play significant roles in affecting the fate of carbon and contaminants in soil environment. However, the mechanisms controlling the variations of DOM molecules distribution during the transformation of Fe (oxyhydr)oxides, and the effects of these variations on contaminant behaviors are still largely unknown. In this study, the dynamic variations of DOM properties and distributions, and the kinetics of uranium adsorption on and desorption from Fe (oxyhydr)oxides during the transformation were investigated, employing a combination of Orbitrap mass spectrometry (MS), high-resolution transmission electron microscopy (HR-TEM), and kinetic experiments. Orbitrap MS results indicated that aliphatic molecules and phenolic and polyphenolic molecules with lower O/C values were preferentially released to solution. HR-TEM results indicated that the coprecipitated DOM molecules by ferrihydrite were mainly released to solution rather than sorbed on the newly formed lepidocrocite or goethite during the transformation. Furthermore, the stirred-flow experiment results suggested that soil DOM significantly reduced the adsorption of uranium on, and accelerated the release of uranium from Fe (oxyhydr)oxides, which was ascribed to the changed distribution of DOM molecules and the structure and composition of Fe (oxyhydr)oxides. Our results contribute to predicting contaminant behaviors in soils.

Leaf Functional Traits of Invasive Grasses Conferring High-Cadmium Adaptation Over Natives

Heavy metal (HM) contamination resulting from industrialization and urbanization during the Anthropocene along with plant invasion can severely threaten the growth and adaptation of local flora. Invasive alien plant species generally exhibit a growth pattern consistent with their functional traits in non-contaminated environments in the introduced range. However, it remains unclear whether invasive alien plants have an advantage over native plants in contaminated environments and whether this growth pattern is dependent on the adaptation of their leaf functional traits. Here, we selected two congeneric pairs of invasive alien and native grasses that naturally co-exist in China and are commonly found growing in contaminated soil. To evaluate the effect of cadmium (Cd) on the structural and physiological leaf traits, we grew all four species in soil contaminated without or with 80 mg/kg Cd. Invasive plants contained significantly higher concentrations of Cd in all three organs (leaf, stem, and root). They displayed a higher transfer factor and bioconcentration factor (BCF) of shoot and root than natives, indicating that invasive species are potential Cd hyperaccumulators. Invasive plants accumulated polyphenol oxidase (PPO) to higher levels than natives and showed similar patterns of leaf structural and physiological traits in response to changes in Cd bioconcentration. The quantifiable leaf structural traits of invasive plants were significantly greater (except for stomatal density and number of dead leaves) than native plants. Leaf physiological traits, chlorophyll content, and flavonoid content were also significantly higher in invasive plants than in natives under Cd stress conditions after 4 weeks, although nitrogen balance index (NBI) showed no significant difference between the two species. Chlorophyll fluorescence parameters decreased, except for the quantum yield of photosystem II (ΦPSII) and the proportion of open photosystem II (qP), which increased under Cd stress conditions in both species. However, invasive plants exhibited higher fluorescence parameters than natives under Cd stress, and the decrement observed in invasive plants under Cd stress was greater than that in natives. High Cd adaptation of invasive grasses over natives suggests that invasive plants possess optimal leaf structural and physiological traits, which enable them to adapt to stressful conditions and capture resources more quickly than natives. This study further emphasizes the potential invasion of alien plants in contaminated soil environments within the introduced range. To a certain extent, some non-invasive alien plants might adapt to metalliferous environments and serve as hyperaccumulator candidates in phytoremediation projects in contaminated environments.

Pennisetum purpureum Improved Polycyclic Aromatic Hydrocarbons Removal in Weathered-Petroleum Contaminated Soil

Petroleum hydrocarbons are among the major driving forces of advancement in the last Century. Some of the hydrocarbons especially polycyclic aromatics are however of health and environmental significance, due to their recalcitrance and persistence leading to adverse effects on health and ecosystem stability. A number of treatment technologies have been used to cleanup hydrocarbon contaminants and the use of phytoremediation technology have recently been described as promising. In this study, phytoremediation of weathered crude oil contaminated soil was carried out in a microcosm using Pennisetumpurpureum for 60 days. Pristine soil samples were collected and mixed with weathered petroleum contaminated soil to achieve 5%, 25%, 35% and 50% w/w contamination levels. Bacterial species in the rhizosphere were isolated and identified and residual oil was extracted and analyzed using GC-MS. Results showed that there was high bacterial population in rhizosphere (5.0×105 cfu/g to 6.4×105 cfu/g) than non-rhizosphere soil (2.4 ×105 cfu/g to 4.0×105 cfu/g); and Bacillus spp. (64.71%) were observed to be predominant in the rhizosphere followed by Micrococcus spp. (17.65%), Pseudomonas aeruginosa (5.88%), Klebsiella pneumoniae (5.88%) and Flavobacterium sp. (5.88%). Hydrocarbon concentration in the rhizosphere was reduced by 82.5%, 60.5%, 58.0% and 48.8% respectively. Complex polycyclic aromatic hydrocarbon compounds detected in the control using GC-MS were significantly reduced or completely degraded. Polycyclic aromatic hydrocarbons such as anthracene, naphthalene, fluorene, benzo (a) anthracene, pyrene and chrysene were significantly reduced at a rate ranging between 13.33% and 97.54%. Based on the rate of PAHs reduction observed in this study, it was evident that P. purpureumsupports cleanup of persistent hydrocarbon contaminants in soil environment. The use of this plant in large scale petroleum hydrocarbon cleanup under field conditions should be investigated.

Biodegradation of di-(2-ethylhexyl) phthalate by novel Rhodococcus sp. PFS1 strain isolated from paddy field soil.

Di-(2-ethylhexyl)-phthalate (DEHP) is the phthalate ester frequently utilized as a plasticizer, commonly found in cosmetics, packaging materials; moreover, it has carcinogenic and mutagenic effects on humans. In the current study, we isolated the soil bacterium Rhodococcus sp. PFS1 and to assess its DEHP degradation ability in various environmental conditions. The strain PFS1 was isolated from paddy field soil and identified by the 16S rRNA sequencing analyses. The strain PFS1 was examined for its biodegradation ability of DEHP at various pH, temperature, salt concentration, glucose concentration, and high and low concentrations of DEHP. Moreover, the biodegradation of DEHP at a contaminated soil environment by strain PFS1 was assessed. Further, the metabolic pathway of DEHP degradation by PFS1 was analyzed by HPLC-MS analysis. The results showed that the strain PFS1 effectively degraded the DEHP at neutral pH and temperature 30°C; moreover, expressed excellent DEHP degradation at the high salt concentration (up to 50g/L). The strain PFS1 was efficiently degraded the different tested phthalate esters (PAEs) up to 90%, significantly removed the DEHP contamination in soil along with native organisms which are present in soil up to 94.66%; nevertheless, the PFS1 alone degraded the DEHP up to 87.665% in sterilized soil. According to HPLC-MS analysis, DEHP was degraded into phthalate (PA) by PFS1 strain via mono(2-ethylehxyl) phthalate (MEHP); then PA was utilized for cell growth. These results suggest that Rhodococcus sp. PFS1 has excellent potential to degrade DEHP at various environmental conditions especially in contaminated paddy field soil.

Characterization of biospheric bacterial community on reduction and removal of chromium from tannery contaminated soil using an integrated approach of bio-enhanced electrokinetic remediation

Intensive research efforts on different methods focus on reducing toxic Cr(VI) to less toxic Cr(III). However, most methods end up in improper removal, recurrence or subsequent pollutant generation. Therefore, our study focuses on the reduction and removal of Cr with no recurrence possibilities. So, the indigenous biospheric bacterial community is characterized by Metagenomics using EPI2ME 16S workflow Bioinformatics tool. The obtained metagenome raw data has been submitted in NCBI database with reference to the Bio Project ID PRJNA679434. Based on this data, the possible bio-mechanisms behind the reduction of Cr(VI) to Cr(III) by FeS particles generated by the biospheric microbes (4.5 × 103) was elucidated. Electrokinetic (EK) experiments further removed the reduced Cr(III) by Bio-enhanced electrokinetic remediation (BEER) approach. The presence of Mn (3.54%) in the soil was found to oxidize the reduced Cr(III) to Cr(IV), thus ruling out the Cr(VI) recurrence. The integrated approach of BEER showed an effective removal of Cr and Fe in the contaminated soil. Physico-chemical parameters such as chemical oxygen demand (COD) was assessed and found to show a drastic removal efficiency of 70% after the EK treatment. Thus, the presence of sulphide content (122 mg/L) generated by the biospheric microbial community was found to enhance the Cr(VI) reduction and Cr(III) removal significantly, thus proving the effectiveness of the BEER approach to overcome the drawback of Cr recurrence in heavy metal contaminated soil environments.

Evaluation of phytoremediation capability of French marigold (Tagetes patula) and African marigold (Tagetes erecta) under heavy metals contaminated soils

The pot experiment was conducted to explore the phytoremediation potential of two different marigold species grown in heavy metals contaminated red, black, alluvial, recent river clay, sewage irrigated, sewage sludge, and garden soil. Different soil types were treated uniformly with lead (20 mg Pb kg−1 soil), cadmium (5 mg Cd kg−1 soil), chromium (30 mg Cr kg−1 soil) and nickel (10 mg Ni kg−1 soil). Completely randomized design (CRD) was used with three replications. African marigold (Tagetes erecta) recorded ∼89.4% more dry matter yield over French marigold (Tagetes patula) when grown under metals treated soils. Both the marigold species were highly effective for removing Cd and Ni from contaminated soils (TF >1) however, Ni (TF ∼14.9) was more efficiently accumulated by T. patula and Cd (TF ∼12.1) by T. erecta. Higher biomass yield in T. erecta resulted higher accumulation of heavy metals (except Cr) compared to T. patula. Assessment of contamination factor (CF) and geo-accumulation index (Igeo) of heavy metals indicates that post-harvest soils had moderate to high degree of contamination by different metals, Cr being the highest. It may be concluded that T. erecta was more efficient in extracting heavy metals from different heavy metals contaminated soils. Novelty statement Contamination of land with heavy metals poses severe environmental threats. Physical and chemical remediation techniques are generally used for remediating metals contaminated sites. These methods are cost-intensive and therefore, commercially non-viable, besides being disruptive in nature and causing deterioration of soil. Alternatively, bio-remediation techniques are cost-effective and environment friendly. Among the various phytoremediation techniques, hyperaccumulator plants are most commonly used for the remediation of the contaminated sites. It has been found that different species of the same plant (marigold) differ in their ability to accumulate metals under various contaminated soils having different properties. Thus, this experiment provided an unique opportunity to investigate the effect of various soil properties on metal accumulation efficacy of marigold under metal-spiked soils. Marigold plants can grow rapidly by developing a robust root system which helps them to survive under contaminated soil environment. Thus, marigold being ornamental plant could be used to decontaminate polluted sites while providing ornamental value and may serve as a source of commercially valuable products extracting metals from biomass by way of incineration. However, meager information is available about the usage of various marigold species for phytoremediation of heavy metals under different metal-polluted soils. In the current experiment, we intend to evaluate the potential use of two different marigold species (Tagetes patula and Tagetes erecta) in remediating heavy metals under nine soils of different nature spiked with metals and assessing heavy metals pollution load indexes in these polluted soils.

Impact of elevated phosphogypsum on soil fertility and its aerobic biotransformation through indigenous microorganisms (IMO's) based technology

Phosphogypsum (PG) is a waste by-product of phosphate fertilizer industry, produced in huge amount during the manufacture of phosphoric acid by economic wet process. Assessment of PG toxicity on soil has been poorly emphasized, therefore an efficient methods needs to be adopted to assess its toxic effect on soil fertility. We also need an effective eco-technological strategies for better waste PG management in order to improve the environmental health. The present study aimed to investigate the impact of PG toxicity on fertile soil and utilization of indigenous microorganisms for aerobic detoxification of PG contaminated soil to evaluate the scope for biostimulation based in situ bioremediation. In this study it is evident that application of PG to fertile soil in certain concentration results highly acidic, sulfate rich, aerobic environment, thus severely weakens the metabolic activity of the indigenous microorganisms. This investigation via microcosm based study further evaluated the intrinsic biotransformation ability of these microorganisms and found that was enhanced significantly (>95% reduction in sulfate concentration in 180 days) with carbon, nitrogen and phosphate amendments. Community level physiological profiling analyses indicated distinct shift in metabolic abilities following carbon amendments. Our study for the first time may help to formulate a strategy in aerobic biotransformation of PG contaminated soil environment, yet appreciable rate by supplying adequate nutrients.

Soil Remediation Applications of Nanotechnology

With the growth of urbanization, the anthropogenic activities have increased and thus increase occurrence of soil contaminants. In order to eliminate the contaminants in soil environment, the application of nanotechnology for soil remediation has become a great concern in the world. This review will discuss about the fate of contaminants in soil environment; the mechanisms of nanotechnology with various types of nanomaterials for the soil remediation; the advantages and disadvantage of nanomaterials towards the terrestrial organisms, human health as well as the soil environment; and the challenges of using nanotechnology for soil remediation.

Mycorestoration of crude oil polluted soil using Pleurotus tuberregium

Crude oil contamination is known to cause unwholesome damage to man, his environment comprising of soil, air and water bodies as well as other forms of life. This study determined the effect of crude oil polluted soils on the composition of different microorganisms and plants and the growth of Pleurotus tuberregium. Oil polluted soils in bowls were amended with sawdust from Brachystegia nigerica as substrate. Fruiting bodies and the diameter of the mushroom cap were found to increase with increasing weeks of exposure to oil as against the control which had no fruiting bodies throughout the experiment. Pepperomia pellucida was found to be the predominant weed (n = 20), followed by Asystasia gangetica (n = 11). The bacterial and fungal counts were higher at the oil polluted soil attached to sclerotia than the control. The growth of Pleurotus tuberregium in the polluted soil samples showed its ability to degrade and utilize hydrocarbon as the source of carbon and energy, thereby remediating the contaminated soil environment. This work has shown that the fungus has bioremediation and pollution control capacity.

Efficacy of Vermiremediation to Remove Contaminants from Soil.

Background.In addition to improving soil fertility and crop production, earthworms have been found to be useful in the removal of contaminants from soil, known as vermiremediation. Previous studies on vermiremediation have focused primarily on organic wastes, with relatively less attention paid to inorganic contaminants. In addition, some basic terms used in environmental health studies have often not been properly clarified.Objectives.The present study is a review of the state of the literature on the effectiveness of using earthworms to remediate organic and inorganic (metal) soil contaminants. Earthworms’ actions in remediation of organic and inorganic contaminants are described. Some terms that are used interchangeably in environmental health are clarified. The challenges and limitations of vermiremediation are highlighted.Methods.A systematic literature search was conducted to access online academic publications indexed in Google Scholar, PubMed, Scopus, Clarivate Analytics (Web of Science), ScienceDirect, ResearchGate and Springer Link. A total of 165 publications on the subject matter were accessed, out of which 47 were used for the review.Discussion.Empirical and theoretical information from the literature showed evidence of the significant contributions of earthworms to the removal of soil organic contaminants and metals. Earthworms indirectly facilitate the conversion of organic contaminants by promoting microbial and enzyme activities. Some organic contaminants are directly taken up through dermal and intestinal absorption and accumulated by preferential sequestration in sub-organismic and tissue fractions of earthworms. Metals are directly removed and accumulated by the mechanism of detoxification and sequestration, via metallothioneins induction. The terms ‘contaminants’ and ‘pollutants’ have different meanings and should not be used interchangeably. Although vermiremediation presents an ideal clean-up technique, it is limited in application to only mildly contaminated soil environments. Ethical concerns should not pose a serious issue because vermiremediation simply takes advantage of earthworms’ natural soil-conditioning abilities. Many vermiremediation processes, especially of organic wastes, are harmless to earthworms, improving the soil for their growth and survival.Conclusions.Vermiremediation presents a good long-term biological option to clean up mildly contaminated soil. It may be deployed as a secondary measure to rid the soil of residual contaminants after applying physicochemical remediation techniques to an overtly polluted soil environment.Competing Interests.The authors declare no competing financial interests.

The Impact Assessment of Heavy Metal Contaminated Soil Environment and Exploration of Remediation Methods

The Impact Assessment of Heavy Metal Contaminated Soil Environment and Exploration of Remediation Methods

In silico analysis of the chemotactic system of Agrobacterium tumefaciens.

Agrobacterium tumefaciens is an efficient tool for creating transgenic host plants. The first step in the genetic transformation process involves A. tumefaciens chemotaxis, which is crucial to the survival of A. tumefaciens in changeable, harsh and even contaminated soil environments. However, a systematic study of its chemotactic signalling pathway is still lacking. In this study, the distribution and classification of chemotactic genes in the model A. tumefaciens C58 and 21 other strains were annotated. Local blast was used for comparative genomics, and hmmer was used for predicting protein domains. Chemotactic phenotypes for knockout mutants of ternary signalling complexes in A. tumefaciens C58 were evaluated using a swim agar plate. A major cluster, in which chemotaxis genes were consistently organized as MCP (methyl-accepting chemotaxis protein), CheS, CheY1, CheA, CheR, CheB, CheY2 and CheD, was found in A. tumefaciens , but two coupling CheW proteins were located outside the ‘che’ cluster. In the ternary signalling complexes, the absence of MCP atu0514 significantly impaired A. tumefaciens chemotaxis, and the absence of CheA (atu0517) or the deletion of both CheWs abolished chemotaxis. A total of 465 MCPs were found in the 22 strains, and the cytoplasmic domains of these MCPs were composed of 38 heptad repeats. A high homology was observed between the chemotactic systems of the 22 A. tumefaciens strains with individual differences in the gene and receptor protein distributions, possibly related to their ecological niches. This preliminary study demonstrates the chemotactic system of A. tumefaciens , and provides some reference for A. tumefaciens sensing and chemotaxis to exogenous signals.

Investigation of eluted characteristics of fulvic acids using differential spectroscopy combined with Gaussian deconvolution and spectral indices.

The characteristics of subfractions of soil fulvic acid (FA3, FA5, FA7, FA9, and FA13) using stepwise elution from XAD-8 resin with pyrophosphate buffers were investigated by differential absorption spectroscopy (DAS) and differential fluorescence spectroscopy (DFS) combined with mathematical deconvolution and spectral indices. The log-transformed absorbance spectra (LTAS) exhibited three regions for both acidic-buffer-eluted subfractions (AESF) and neutral-buffer-eluted subfraction (NESF) and four regions for basic-buffer-eluted subfractions (BESF) according to the differences in spectral slopes. The DAS spectra of FA subfractions were closely fitted with seven Gaussian bands with maxima location at 199.66, 216.18 ± 1.50, 246.20 ± 3.85, 285.22 ± 7.26, 345.64 ± 5.30, 389.27, and 307.37nm, respectively (R2 > 0.993). The content of salicylic-like and carboxyl groups in FA subfractions decreased, while the phenolic chromophore increased with elution sequence. From the 11 spectral indices, AESF had greater molecular weight, condensation, polymerization, hydroxyl radical production, humification degree, and terrigenous contribution, as well as contained more conjugated aromatic structures and less N-containing groups than NESF and BESF. The humification degree and humic characters of FA subfractions were closely associated to the aromaticity, molecular condensation, and DOM-metal-bound functional groups. The proper separation of FA into subfractions is beneficial for reducing its complexity and heterogeneity, which helps us to further explore its chemical properties and interactions with various contaminants in soil environments. Graphical abstract.

Arbuscular mycorrhizal fungi and exogenous glutathione mitigate coal fly ash (CFA)-induced phytotoxicity in CFA-contaminated soil

Coal fly ash (CFA) makes a bulk of the coal combustion wastes generated from coal-fired power plants. There are several environmental mishaps due to coal ash spills around the world and in the United States. Management of CFA-polluted sites has proven inefficient resulting in soil infiltration, leaching, and phytotoxicity. This study assessed the mitigation strategies for CFA-induced phytotoxicity using biological [arbuscular mycorrhizal fungi (AMF)] and chemical [exogenous glutathione (GSH)] agents. Indices of phytotoxicity include seed germination, plant morphometrics, lipid peroxidation and genomic double-stranded DNA (dsDNA) in switchgrass plant (Panicum virgatum). Experiments include laboratory screening (0, 5, 10, 15 and 20% w/w CFA/soil) and greenhouse pot study (0, 7.5 and 15% w/w CFA/soil) culturing switchgrass plant in Armour silt loam soil co-applied with AMF (Rhizophagus clarus) and GSH. Experiments showed that CFA exposure caused a concentration-dependent increase in seed germination. 10% CFA increased seedling growth while 15 and 20% CFA decreased seedling growth and induced leaf chlorosis. Furthermore, CFA (7.5 and 15%) in the 90-d pot study significantly (p < 0.05) impaired plant growth, induced lipid peroxidation and reduced genomic dsDNA. However, the incorporation of AMF or GSH enhanced seed germination, plant growth, and/or genomic dsDNA, reduced lipid peroxidation and prevented leaf chlorosis in CFA-exposed switchgrass plant. This study demonstrates that AMF and GSH have the potential to mitigate CFA-induced phytotoxicity. These biological and chemical strategies could be further harnessed for efficient utilization of switchgrass plant in the phytoremediation of CFA contaminated soil environment while simultaneously limiting CFA-induced phytotoxicity.

Effects of bacterial-feeding nematodes on soil microbial activity and the microbial community in oil-contaminated soil

Rapid economic development has caused an increase in serious pollution problems due to the ever-increasing use of oil and its products, thus making oil pollution control an urgent task. Studies have shown that large amounts of bacterial-feeding nematodes are present in oil-contaminated soil; their function is as yet unclear. In this experiment, different densities of Caenorhabditis elegans (C. elegans) were inoculated into artificially simulated oil-contaminated soil to examine their effects on microbial activity and the microbial community in oil-contaminated soil. Six treatments were investigated: sterilized oil-contaminated soil as control 1 (FSP), nematode-free soil as control 2 (S), oil-contaminated soil (SP), oil-contaminated soil + 5, 10 or 20 individual C. elegans per gram of dry soil (i.e., SPN5, SPN10, SPN20). Results showed that oil pollution significantly increased the soil basal respiration. However, C. elegans weakened the soil basal respiration to different degrees and soil microbial respiration entropy essentially changed in line with the soil basal respiration. Oil pollution and C. elegans boosted catalase activity in contaminated soil by approximately 64.2–145.1%. Soil urease activity of SPN5, SPN10 and SPN20 was 88.5%, 126.7% and 109.0% stronger, respectively, than that of SP. The inoculation of C. elegans changed the microbial phospholipid fatty acid content in the oil-contaminated soil, including soil bacteria, fungi, actinomycetes, Gram-positive bacteria (G+) and Gram-negative bacteria (G−). Therefore, this research demonstrates that C. elegans can stimulate microbial reproduction in oil-contaminated soil, enhance related soil enzyme activities and regulate soil microbial community structure and diversity, thereby improving the contaminated soil environment and promoting oil degradation.