A bibliometric perspective on the occurrence and migration of microplastics in soils amended with sewage sludge.

The land application of sewage sludge from wastewater treatment plants has been recognized as a major source of microplastic contamination in soil. Nevertheless, the fate and behavior of microplastics in soil remain uncertain, particularly their distribution and transport, which are poorly understood. This study does a bibliometric analysis and visualization of relevant research publications using the CiteSpace software. It explores the limited research available on the topic, highlighting the potential for it to emerge as a research hotspot in the future. Chinese researchers and institutions are paying great attention to this field and are promoting close academic cooperation among international organizations. Current research hot topics mainly involve microplastic pollution caused by the land application of sewage sludge, as well as the detection, environmental fate, and removal of microplastics in soil. The presence of microplastics in sludge, typically ranging from tens of thousands to hundreds of thousands of particles (p)/kg, inevitably leads to their introduction into soil upon land application. In China, the estimated annual accumulation of microplastics in the soil due to sludge use is approximately 1.7 × 1013 p. In European countries, the accumulation ranges from 8.6 to 71 × 1013 p. Sludge application has significantly elevated soil microplastic concentrations, with higher application rates and frequencies resulting in up to several-fold increases. The primary forms of microplastics found in soils treated with sludge are fragments and fibers, primarily in white color. These microplastics consist primarily of components such as polyamide, polyethylene, and polypropylene. The vertical transport behavior of microplastics is influenced by factors such as tillage, wind, rainfall, bioturbation, microplastic characteristics (e.g., fraction, particle size, and shape), and soil physicochemical properties (e.g., organic matter, porosity, electrical conductivity, and pH). Research indicates that microplastics can penetrate up to 90 cm into the soil profile and persist for decades. Microplastics in sewage sludge-amended soils pose potential long-term threats to soil ecosystems and even human health. Future research should focus on expanding the theoretical understanding of microplastic behavior in these soils, enabling the development of comprehensive risk assessments and informed decision-making for sludge management practices. PRACTITIONER POINTS: Microplastics in sewage sludge range from tens to hundreds of thousands per kilogram. Sludge land application contributes significantly to soil microplastic pollution. The main forms of microplastics in sludge-amended soils are fragments and fibers. Microplastics are mainly composed of polyamide, polyethylene, and polypropylene. Microplastics can penetrate up to 90 cm into the soil profile and persist for decades.

Homology and heterogeneity of soil trace elements of coal power production bases in arid and semi-arid areas of Northwest China.

Coal power activities could cause regional fluctuations of trace elements, but the distribution information of these trace elements in arid and semi-arid areas is insufficient. In this study, the soil trace elements (As, B, Be, Cd, Co, Cr, Cu, Fe, Ga, Ge, Mn, Mo, Ni, Pb, Sb, Sn, Sr, Ti, Tl, and Zn) of Ningdong Coal Power Production Base in China were monitored. Results showed that the concentrations of B, Tl, Mn, Pb, Cr, K, Cu, and Co exceeded background values. The maximum risk index reached 265.66, while the trace elements posed a cancer risk to children. Combining correlation analyses (CA), principal component analysis (PCA), and positive matrix factorization (PMF) techniques, it indicated that trace elements were mainly coming from coal combustion (34.15%), livestock farming (17.44%), traffic emissions (12.42%), and natural factors (35.99%). This study reveals the sources and potential ecological risks of soil trace elements in the Ningdong Coal and Power Production Base. It provides a scientific basis for developing targeted environmental management measures and reducing human health risks.

Heavy metal spatial distribution, source analysis, and ecological risks in the central hilly area of Hainan Island, China: results from a high-density soil survey.

The presence of heavy metals in soil has gained considerable attention due to their potential risks to ecosystems and human health. In this study, a thorough soil investigation was performed in the hilly region of central Hainan, which was formerly regarded as an area with the highest ecological environmental quality. A total of 7094 soil samples were systematically collected with high density over a large area. Simultaneously, a detailed investigation was conducted on the surrounding environment of each sampling point, including environmental factors such as soil, land use and crop types. The soil samples were analysed for heavy metals, pH, organic matter, and other parameters. The soil heavy metal pollution level, ecological risk and health risk were evaluated using the geo-accumulation index and the potential ecological risk index. The findings showed that the average contents of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were 1.68, 0.042, 24.2, 6.49, 0.0319, 7.06, 29.6 and 49.8 mg·kg-1 respectively. Except for Hg, the mean values of the other heavy metals were either lower than or similar to the background values of Hainan. Also, only a few localised areas showed contamination by heavy metals. The primary sources of heavy metals, identified by a positive matrix factorisation model, could be categorised into four types: natural sources related to the soil formation process from acidic intrusive rocks (such as granite); natural sources primarily influenced by atmospheric deposition; anthropogenic sources associated with agricultural activities; and natural sources related to the soil formation process from middle-mafic intrusive rocks and black shales. The correlation analysis and variance analysis findings suggested that the content of heavy metals in the soil was primarily associated with the parent rock. The study area generally had low heavy metal levels and was not significantly polluted. However, agricultural activities still affected the enrichment of heavy metals. Therefore, it is imperative to remain vigilant about the ecological risks linked to soil heavy metals while continuing land development and expanding agricultural activities in the future. These findings indicate that conducting high-density soil surveys can enhance our understanding of regional soil heavy metals and enable reliable recommendations for agricultural planning. Whether in areas with low pollution risk or potential pollution risk, it is recommended that high-density soil surveys be conducted provide scientific guidance for further agricultural development.

Accumulation and translocation of lead in vegetables through intensive use of organic manure and mineral fertilizers with wastewater.

In many countries with wastewater irrigation and intensive use of fertilizers (minerals and organics), heavy metal deposition by crops is regarded as a major environmental concern. A study was conducted to determine the impact of mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse on soil's trace Pb content and edible parts of vegetables. It also evaluated the risk of lead (Pb) contamination in water, soil, and food crops. Six vegetables (Daucus carota, Brassica oleracea, Pisum sativum, Solanum tuberosum, Raphanus sativus, and Spinacia oleracea) were grown in the field under twelve treatments with different nutrient and water inputs. The lead concentrations in soil, vegetables for all treatments and water samples ranged from 1.038-10.478, 0.09346-9.0639 mg/kg and 0.036-0.26448 mg/L, The concentration of lead in soil treated with wastewater in treatment (T6) and vegetable samples was significantly higher, exceeding the WHO's permitted limit. Mineral and organic fertilizers combined with wastewater treatment reduced lead (Pb) concentrations in vegetables compared to wastewater application without organic fertilizers. Health risk indexes for all treatments except wastewater treatment (T6) were less than one. Pb concentrations in mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse treated were determined to pose no possible risk to consumers.

Engineering natural microbiomes toward enhanced bioremediation by microbiome modeling.

Engineering natural microbiomes for biotechnological applications remains challenging, as metabolic interactions within microbiomes are largely unknown, and practical principles and tools for microbiome engineering are still lacking. Here, we present a combinatory top-down and bottom-up framework to engineer natural microbiomes for the construction of function-enhanced synthetic microbiomes. We show that application of herbicide and herbicide-degrader inoculation drives a convergent succession of different natural microbiomes toward functional microbiomes (e.g., enhanced bioremediation of herbicide-contaminated soils). We develop a metabolic modeling pipeline, SuperCC, that can be used to document metabolic interactions within microbiomes and to simulate the performances of different microbiomes. Using SuperCC, we construct bioremediation-enhanced synthetic microbiomes based on 18 keystone species identified from natural microbiomes. Our results highlight the importance of metabolic interactions in shaping microbiome functions and provide practical guidance for engineering natural microbiomes.

The effect of thermal treatment on the transformation and transportation of arsenic and cadmium in soil.

Thermal treatment can effectively decontaminate soils but alter their properties. Previous research mainly focused on volatile organic compounds and metals, i.e. Hg, neglecting non-volatile metal(loid)s. This study aimed to investigate Cd and As transformation during aerobic and anaerobic calcination. The results showed that both aerobic and anaerobic calcination increased soil pH by reducing soil organic matter (SOM) content, which also influenced the cation exchange capacity (CEC) and the leaching behavior of Cd and As in the soil. The total concentrations of Cd and As in the calcined soils varied depending on the calcination temperature and atmosphere. When the aerobic calcination temperature exceeded 700 °C, Cd volatilized as CdCl2, while anaerobic calcination at relatively low temperatures (600 °C) involved reductive reactions, resulting in the formation of metallic Cd with a lower boiling point. Similarly, As volatilized at 800 °C aerobically and 600 °C anaerobically. The formation of As-based minerals, particularly Ca3(AsO4)2, hindered its gasification, whereas anaerobic calcination promoted volatilization efficiency through the generation of C-As(III) based gaseous components with lower boiling points. Contrasting trends were observed in the TCLP-extractable Cd and As contents of the calcined soils. Over 70% of TCLP-extractable Cd contents were suppressed after thermal treatment, attributed to the elevated pH and reduced CEC of the soil, as well as volatilization. However, TCLP-extractable As contents increased with elevated temperatures, likely due to the desorption of AsO43- and re-adsorption of gaseous As2O3 during cooling. These findings have implications for assessing the environmental impact of thermal treatment and provide insights for remediation strategies concerning Cd and As-contaminated soils.

Feasibility of using Vis-NIR spectroscopy and PXRF spectrometry to estimate regional soil cadmium concentration.

Conventionally, soil cadmium (Cd) measurements in the laboratory are expensive and time-consuming, involving complex processes of sample preparation and chemical analysis. This study aimed to identify the feasibility of using sensor data of visible near-infrared reflectance (Vis-NIR) spectroscopy and portable X-ray fluorescence spectrometry (PXRF) to estimate regional soil Cd concentration in a time- and cost-saving manner. The sensor data of Vis-NIR and PXRF, and Cd concentrations of 128 surface soils from Yunnan Province, China, were measured. Outer-product analysis (OPA) was used for synthesizing the sensor data and Granger-Ramanathan averaging (GRA) was applied to fuse the model results. Artificial neural network (ANN) models were built using Vis-NIR data, PXRF data, and OPA data, respectively. Results showed that: (1) ANN model based on PXRF data performed better than that based on Vis-NIR data for soil Cd estimation; (2) Fusion methods of both OPA and GRA had higher predictive power (R2) = 0.89, ratios of performance to interquartile range (RPIQ) = 4.14, and lower root mean squared error (RMSE) = 0.06, in ANN model based on OPA fusion; R2 = 0.88, RMSE = 0.06, and RPIQ = 3.53 in GRA model) than those based on either Vis-NIR data or PXRF data. In conclusion, there exists a great potential for the combination of OPA fusion and ANN to estimate soil Cd concentration rapidly and accurately.

The unexpected effect of the compound microbial agent NP-M2 on microbial community dynamics in a nonylphenol-contaminated soil: the self-stability of soil ecosystem.

Background: Nonylphenol (NP) is widely recognized as a crucial environmental endocrine-disrupting chemical and persistent toxic substance. The remediation of NP-contaminated sites primarily relies on biological degradation. Compound microbial products, as opposed to pure strains, possess a greater variety of metabolic pathways and can thrive in a wider range of environmental conditions. This characteristic is believed to facilitate the synergistic degradation of pollutants. Limited research has been conducted to thoroughly examine the potential compatibility of compound microbial agents with indigenous microflora, their ability to function effectively in practical environments, their capacity to enhance the dissipation of NP, and their potential to improve soil physicochemical and biological characteristics. Methods: In order to efficiently eliminate NP in contaminated soil in an eco-friendly manner, a simulation study was conducted to investigate the impact of bioaugmentation using the functional compound microbial agent NP-M2 at varying concentrations (50 and 200 mg/L) on the dynamics of the soil microbial community. The treatments were set as follows: sterilized soil with 50 mg/kg NP (CK50) or 200 mg/kg NP (CK200); non-sterilized soil with 50 mg/kg NP (TU50) or 200 mg/kg NP (TU200); non-sterilized soil with the compound microbial agent NP-M2 at 50 mg/kg NP (J50) or 200 mg/kg NP (J200). Full-length 16S rRNA analysis was performed using the PacBio Sequel II platform. Results: Both the indigenous microbes (TU50 and TU200 treatments) and the application of NP-M2 (J50 and J200 treatments) exhibited rapid NP removal, with removal rates ranging from 93% to 99%. The application of NP-M2 further accelerated the degradation rate of NP for a subtle lag period. Although the different treatments had minimal impacts on the soil bacterial α-diversity, they significantly altered the ß-diversity and composition of the bacterial community. The dominant phyla were Proteobacteria (35.54%-44.14%), Acidobacteria (13.55%-17.07%), Planctomycetes (10.78%-11.42%), Bacteroidetes (5.60%-10.74%), and Actinobacteria (6.44%-8.68%). The core species were Luteitalea_pratensis, Pyrinomonas_methylaliphatogenes, Fimbriiglobus_ruber, Longimicrobium_terrae, and Massilia_sp003590855. The bacterial community structure and taxon distribution in polluted soils were significantly influenced by the activities of soil catalase, sucrase, and polyphenol oxidase, which were identified as the major environmental factors. Notably, the concentration of NP and, to a lesser extent, the compound microbial agent NP-M2 were found to cause major shifts in the bacterial community. This study highlights the importance of conducting bioremediation experiments in conjunction with microbiome assessment to better understand the impact of bioaugmentation/biostimulation on the potential functions of complex microbial communities present in contaminated soils, which is essential for bioremediation success.

Heavy metals immobilization and bioavailability in multi-metal contaminated soil under ryegrass cultivation as affected by ZnO and MnO2 nanoparticle-modified biochar.

Pollution by heavy metals (HMs) has become a global problem for agriculture and the environment. In this study, the effects of pristine biochar and biochar modified with manganese dioxide (BC@MnO2) and zinc oxide (BC@ZnO) nanoparticles on the immobilization and bioavailability of Pb, Cd, Zn, and Ni in soil under ryegrass (Lolium perenne L.) cultivation were investigated. The results of SEM-EDX, FTIR, and XRD showed that ZnO and MnO2 nanoparticles were successfully loaded onto biochar. The results showed that BC, BC@MnO2 and BC@ZnO treatments significantly increased shoots and roots dry weight of ryegrass compared to the control. The maximum dry weight of root and shoot (1.365 g pot-1 and 4.163 g pot-1, respectively) was reached at 1% BC@MnO2. The HMs uptake by ryegrass roots and shoots decreased significantly after addition of amendments. The lowest Pb, Cd, Zn and Ni uptake in the plant shoot (13.176, 24.92, 32.407, and 53.88 µg pot-1, respectively) was obtained in the 1% BC@MnO2 treatment. Modified biochar was more successful in reducing HMs uptake by ryegrass and improving plant growth than pristine biochar and can therefore be used as an efficient and cost effective amendment for the remediation of HMs contaminated soils. The lowest HMs translocation (TF) and bioconcentration factors were related to the 1% BC@MnO2 treatment. Therefore, BC@MnO2 was the most successful treatment for HMs immobilization in soil. Also, a comparison of the TF values of plant showed that ryegrass had a good ability to accumulate all studied HMs in its roots, and it is a suitable plant for HMs phytostabilization.

Spatial variability and source analysis of soil heavy metals: A case study of the key planting area of special agricultural products in Cangxi County, China.

Heavy metal pollution in farmland soil represents a considerable risk to ecosystems and human health, constituting a global concern. Focusing on a key area for the cultivation of special agricultural products in Cangxi County, we collected 228 surface soil samples. We analyzed the concentration, spatial distribution, and pollution levels of six heavy metals (Cr, Cu, Pb, Ni, Zn, and Hg) in the soil. Moreover, we investigated the sources and contribution rates of these heavy metals using Principal Component Analysis/Absolute Principal Component Scores (PCA/APCS) and Positive Matrix Factorization (PMF) models. Our findings indicate that none of the six metals exceeded the pollution thresholds for farmland soils. However, the mean concentrations of Cr and Ni surpassed the background levels of Sichuan Province. A moderate spatial correlation existed between Pb and Ni, attributable to both natural and anthropogenic factors, whereas Zn, Cu, Hg, and Cr displayed a strong spatial correlation, mainly due to natural factors. The spatial patterns of Cr, Cu, Zn, Pb, and Ni were similar, with higher concentrations in the northern and eastern regions and lower concentrations centrally. Hg's spatial distribution differed, exhibiting a broader range of lower values. The single pollution index evaluation showed that Cr and Ni were low pollution, and the other elements were no pollution. The average value of comprehensive pollution index is 0.994, and the degree of pollution is close to light pollution. Predominantly, higher pollution levels in the northern and eastern regions, lower around reservoirs. The PCA/APCS model identified two main pollution sources: agricultural traffic mixed source (65.2%) and natural parent source (17.2%). The PMF model delineated three sources: agricultural activities (32.59%), transportation (30.64%), and natural parent sources (36.77%). Comparatively, the PMF model proved more accurate and reliable, yielding findings more aligned with the study area's actual conditions.

Effect of conventional and biodegradable microplastics on earthworms during vermicomposting process.

The potential effect of microplastics is an increasingly growing environmental issue. However, very little is known regarding the impact of microplastics on the vermicomposting process. The present study explored the effect of non-biodegradable (low density polyethylene; LDPE) and biodegradable (polybutylene succinate-co-adipate; PBSA) microplastics on earthworm Eisenia fetida during vermicomposting of cow dung. For this, earthworms were exposed to different concentrations (0, 0.5, 1 and 2%) of LDPE and PBSA of 2 mm size. The cow dung supported the growth and hatchlings of earthworms, and the toxicity effect of both LDPE and PBSA microplastics on Eisenia fetida was analyzed. Microplastics decreased the body weight of earthworms and there was no impact on hatchlings. The body weight of earthworm decreased from 0 to 60th day by 18.18% in 0.5% of LDPE treatment, 5.42% in 1% of LDPE, 20.58% in 2% of LDPE, 19.99% in 0.5% of PBSA, 15.09% in 1% of PBSA and 16.36% in 2% of PBSA. The physico-chemical parameters [pH (8.55-8.66), electrical conductivity (0.93-1.02 (S/m), organic matter (77.6-75.8%), total nitrogen (3.95-4.25 mg/kg) and total phosphorus (1.16-1.22 mg/kg)] do not show much significant changes with varying microplastics concentrations. Results of SEM and FTIR-ATR analysis observed the surface damage of earthworms, morphological and biochemical changes at higher concentrations of both LDPE and PBSA. The findings of the present study contribute to a better understanding of microplastics in vermicomposting system.

Chicken manure-derived biochar enhanced the potential of Comamonas testosteroni ZG2 to remediate Cd contaminated soil.

The combined remediation of Cd-contaminated soil using biochar and microorganisms has a good application value. In this study, the effect of chicken manure-derived biochar on CdCO3 precipitation induced by Comamonas testosteroni ZG2 was investigated. The results showed that biochar could be used as the carrier of strain ZG2, enhance the resistance of strain ZG2 to Cd, and reduce the toxicity of Cd to bacterial cells. Cd adsorbed by biochar could be induced by strain ZG2 to form CdCO3 precipitation. Strain ZG2 could also induce CdCO3 precipitation when biochar was added during precipitation formation and fermentation broth formation. The CdCO3 precipitation could enter the pores of the biochar and attach to the surface of the biochar. The single and combined effects of strain ZG2 and biochar could realize the remediation of Cd-contaminated soil to a certain extent. The overall effect was in the order of strain ZG2 with biochar > biochar > strain ZG2. The combination of strain ZG2 and biochar reduced soil available Cd by 48.2%, the aboveground biomass of pakchoi increased by 72.1%, and the aboveground Cd content decreased by 73.3%. At the same time, it promoted the growth and development of the root system and improved the microbial community structure of the rhizosphere soil. The results indicated that chicken manure-derived biochar could enhance the stability of CdCO3 precipitation induced by strain ZG2, and strain ZG2 combined with biochar could achieve a more stable remediation effect on Cd-contaminated soil.

Combined effects of micron-sized polyvinyl chloride particles and copper on seed germination of perilla.

Microplastics (MPs) and copper (Cu) pollution coexist widely in cultivation environment. In this paper, polyvinyl chloride (PVC) were used to simulate the MPs exposure environment, and the combined effects of MPs + Cu on the germination of perilla seeds were analyzed. The results showed that low concentrations of Cu promoted seed germination, while medium to high concentrations exhibited inhibition and deteriorated the morphology of germinated seeds. The germination potential, germination index and vitality index of 8 mg • L-1 Cu treatment group with were 23.08%, 76.32% and 65.65%, respectively, of the control group. The addition of low concentration PVC increased the above indicators by 1.27, 1.15, and 1.35 times, respectively, while high concentration addition led to a decrease of 65.38%, 82.5%, and 66.44%, respectively. The addition of low concentration PVC reduced the amount of PVC attached to radicle. There was no significant change in germination rate. PVC treatment alone had no significant effect on germination. MPs + Cu inhibited seed germination, which was mainly reflected in the deterioration of seed morphology. Cu significantly enhanced antioxidant enzyme activity, increased reactive oxygen species (ROS) and MDA content. The addition of low concentration PVC enhanced SOD activity, reduced MDA and H2O2 content. The SOD activity of the Cu2+8 + PVC10 group was 4.05 and 1.35 times higher than that of the control group and Cu treatment group at their peak, respectively. At this time, the CAT activity of the Cu2+8 + PVC5000 group increased by 2.66 and 1.42 times, and the H2O2 content was 2.02 times higher than the control. Most of the above indicators reached their peak at 24 h. The activity of α-amylase was inhibited by different treatments, but ß-amylase activity, starch and soluble sugar content did not change regularly. The research results can provide new ideas for evaluating the impact of MPs + Cu combined pollution on perilla and its potential ecological risk.

Compositional-geochemical characterization of lead (Pb) anomalies and Pb-induced human health risk in urban topsoil.

Urban areas are characterized by a constant anthropogenic input, which is manifested in the chemical composition of the surface layer of urban soil. The consequence is the formation of intense anomalies of chemical elements, including lead (Pb), that are atypical for this landscape. Therefore, this study aims to explore the compositional-geochemical characteristics of soil Pb anomalies in the urban areas of Yerevan, Gyumri, and Vanadzor, and to identify the geochemical associations of Pb that emerge under prevalent anthropogenic influences in these urban areas. The results obtained through the combined use of compositional data analysis and geospatial mapping showed that the investigated Pb anomalies in different cities form source-specific geochemical associations influenced by historical and ongoing activities, as well as the natural geochemical behavior of chemical elements occurring in these areas. Specifically, in Yerevan, Pb was closely linked with Cu and Zn, forming a group of persistent anthropogenic tracers of urban areas. In contrast, in Gyumri and Vanadzor, Pb was linked with Ca, suggesting that over decades, complexation of Pb by Ca carbonates occurred. These patterns of compositional-geochemical characteristics of Pb anomalies are directly linked to the socio-economic development of cities and the various emission sources present in their environments during different periods. The human health risk assessment showed that children are under the Pb-induced non-carcinogenic risk by a certainty of 63.59% in Yerevan and 50% both in Gyumri and Vanadzor.

Risk assessment of trace elements in vegetables grown in river Yamuna floodplain in Delhi.

Urban agriculture is common in fertile river floodplains of many developing countries. However, there is a risk of contamination in highly polluted regions. This study quantifies health risks associated with the consumption of vegetables grown in the floodplain of the urban river 'Yamuna' in the highly polluted yet data-scarce megacity Delhi, India. Six trace elements are analyzed in five kinds of vegetable samples. Soil samples from the cultivation area are also analyzed for elemental contamination. Ni, Mn, and Co are observed to be higher in leafy vegetables than others. Fruit and inflorescence vegetables are found to have higher concentrations of Cr, Pb, and Zn as compared to root vegetables. Transfer Factor indicates that Cr and Co have the highest and least mobility, respectively. Vegetable Pollution Index indicates that contamination levels follow as Cr > Ni > Pb > Zn. Higher Metal Pollution Index of leafy and inflorescence vegetables than root and fruit vegetables indicate that atmospheric deposition is the predominant source. Principal Component Analysis indicates that Pb and Cr have similar sources and patterns in accumulation. Among the analyzed vegetables, radish may pose a non-carcinogenic risk to the age group of 1-5 year. Carcinogenic risk is found to be potentially high due to Ni and Cr accumulation. Consumption of leafy vegetables was found to have relatively less risk than other vegetables due to lower Cr accumulation. Remediation of Cr and Ni in floodplain soil and regular monitoring of elemental contamination is a priority.

Combined application of arbuscular mycorrhizal fungi and selenium fertilizer increased wheat biomass under cadmium stress and shapes rhizosphere soil microbial communities.

BACKGROUND: Selenium (Se) fertilizer and arbuscular mycorrhizal fungi (AMF) are known to modulate cadmium (Cd) toxicity in plants. However, the effects of their co-application on wheat growth and soil microbial communities in Cd-contaminated soil are unclear. RESULTS: A pot experiment inoculation with two types of AMF and the application of Se fertilizer under Cd stress in wheat showed that inoculation AMF alone or combined with Se fertilizer significantly increased wheat biomass. Se and AMF alone or in combination significantly reduced available Cd concentration in wheat and soil, especially in the Se combined with Ri treatment. High throughput sequencing of soil samples indicated that Se and AMF application had stronger influence on bacterial community compared to fungal community and the bacterial network seemed to have more complex interconnections than the fungal network, and finally shaped the formation of specific microflora to affect Cd availability. CONCLUSION: These results indicate that the application of Se and AMF, particularly in combination, could successfully decrease soil Cd availability and relieve the harm of Cd in wheat by modifying rhizosphere soil microbial communities.

Modified diatomite for soil remediation and its implications for heavy metal absorption in Calendula officinalis.

BACKGROUND: Among different adsorbents, natural and inorganic compounds such as diatomite are important and advantageous in terms of high efficiency and cost-effectiveness, and function in stabilizing heavy metals in the environment. Calendula officinalis, a plant known as a high accumulator of heavy metals, was cultivated in soil treated with varying concentrations of modified diatomite to demonstrate the efficiency of modified diatomite in stabilizating of heavy metals in soils, RESULTS: The modification of diatomite aimed to enhance Calendula officinalis adsorptive properties, particularly towards heavy metals such as lead (Pb), Zinc (Zn), Chromium (Cr), Nickle (Ni), and Copper (Cu), common contaminants in industrial soils. The experimental design included both control and treated soil samples, with assessments at regular intervals. Modified diatomite significantly decreased the bioaccumulation of heavy metals in contaminated soils except Zn, evidenced by decreased DTPA extractable heavy metals in soil and also heavy metal concentrations in plant tissues. Using 10% modified diatomite decreased 91% Pb and Cu, 78% Cr, and 79% Ni concentration of plants compared to the control treatment. The highest concentration of Zn in plant tissue was observed in 2.5% modified diatomite treatment. Remarkably, the application of modified diatomite also appeared to improve the nutrient profile of the soil, leading to enhanced uptake of key nutrients like phosphorus (P) 1.18%, and potassium (K) 79.6% in shoots and 82.3% in roots in Calendula officinalis. Consequently, treated plants exhibited improved growth characteristics, including shoots and roots height of 16.98% and 12.8% respectively, and shoots fresh and dry weight of 48.5% and 50.2% respectively., compared to those in untreated, contaminated soil. CONCLUSION: The findings suggest promising implications for using such amendments in ecological restoration and sustainable agriculture, particularly in areas impacted by industrial pollution.

Improving plant adaptation to soil antimony contamination: the synergistic contribution of arbuscular mycorrhizal fungus and olive mill waste.

BACKGROUND: This study aimed to investigate the alterations in biochemical and physiological responses of oat plants exposed to antimony (Sb) contamination in soil. Specifically, we evaluated the effectiveness of an arbuscular mycorrhizal fungus (AMF) and olive mill waste (OMW) in mitigating the effects of Sb contamination. The soil was treated with a commercial strain of AMF (Rhizophagus irregularis) and OMW (4% w/w) under two different levels of Sb (0 and 1500 mg kg-1 soil). RESULTS: The combined treatment (OMW + AMF) enhanced the photosynthetic rate (+ 40%) and chlorophyll a (+ 91%) and chlorophyll b (+ 50%) content under Sb condition, which in turn induced more biomass production (+ 67-78%) compared to the contaminated control plants. More photosynthesis in OMW + AMF-treated plants gives a route for phenylalanine amino acid synthesis (+ 69%), which is used as a precursor for the biosynthesis of secondary metabolites, including flavonoids (+ 110%), polyphenols (+ 26%), and anthocyanins (+ 63%) compared to control plants. More activation of phenylalanine ammonia-lyase (+ 38%) and chalcone synthase (+ 26%) enzymes in OMW + AMF-treated plants under Sb stress indicated the activation of phenylpropanoid pathways in antioxidant metabolites biosynthesis. There was also improved shifting of antioxidant enzyme activities in the ASC/GSH and catalytic pathways in plants in response to OMW + AMF and Sb contamination, remarkably reducing oxidative damage markers. CONCLUSIONS: While individual applications of OMW and AMF also demonstrated some degree of plant tolerance induction, the combined presence of AMF with OMW supplementation significantly enhanced plant biomass production and adaptability to oxidative stress induced by soil Sb contamination.

Hazard estimation in urban home garden soils in an industrial area using microarthropods, soil properties and GIS modelling: an integrated approach.

The use of soil microarthropods as indicators of soil pollution in home gardens of an industrial area has been covered in this study. Soil samples were collected from 25 home gardens in three zones in Eloor during summer and North East monsoon from 2014 to 2018, for the study of soil microarthropods, soil properties, soil nutrients, and trace elements. The relationships among QBS-ar, microarthropod abundance, soil properties, and soil nutrients, were used to estimate the pollution hazard of the industrial area. The microarthropods present in the study area were Coleoptera, Hymenoptera, Diplopoda, and Araneae. A prominent study area feature was the absence of Collembola and Acari. The QBS-ar index score in these regions showed that the home gardens located adjacent to the industrial area showed low soil quality, with soil quality class values ranging from 1 to 2 throughout the study period. Discriminant analysis of soil nutrients with soil properties and microarthropod abundance showed that in Zone 1 and Zone 2, the data in 2018 was very well discriminated compared to other years. The hazard assessment in the Eloor region showed various levels of hazard zonation: Zone 1 with high-hazard and medium-hazard areas, Zone 2 with medium-hazard areas, and Zone 3 with low- and medium-hazard areas. The study is one of the first kinds that have used QBS-ar scores and soil properties along with soil nutrients and trace elements for estimating the level of hazard in home garden agroecosystems and thus points to an easy, simple, and practical approach in the monitoring and management of soil ecosystems.

Mechanism of clay mineral modified biochar simultaneously immobilizes heavy metals and reduces soil carbon emissions.

Heavy metal pollution in farmland soil has become increasingly severe, and multi-element composite pollution has brought enormous harm to human production and life. Environmental changes in cold regions (such as freeze-thaw cycles and dry-wet alternations) may increase the potential physiological toxicity of heavy metals and exacerbate pollution risks. In order to reveal the effectiveness of sepiolite modified biochar in the remediation of the soil contaminated with lead (Pb), cadmium (Cd), and chromium (Cr), the rice husk biochar pyrolyzed at 500 and 800 °C were selected for remediation treatment (denoted as BC500 and BC800). Meanwhile, different proportions of sepiolite were used for modification (biochar: sepiolite = 1: 0.5 and 1: 1), denoted as MBC500/MBC800 and HBC500/HBC800, respectively. The results showed that modified biochar with sepiolite can effectively improve the immobilization of heavy metals. Under natural conservation condition, the amount of diethylenetriaminepentaacetic acid (DTPA) extractable Pb in BC500, MBC500, and HBC500 decreased by 5.95, 12.39, and 13.55%, respectively, compared to CK. Freeze-thaw cycles and dry-wet alternations activated soil heavy metals, while modified biochar increased adsorption sites and oxygen-containing functional groups under aging conditions, inhibiting the fractions transformation of heavy metals. Furthermore, freeze-thaw cycles promoted the decomposition and mineralization of soil organic carbon (SOC), while sepiolite hindered the release of active carbon through ion exchange and adsorption complexation. Among them, and the soil dissolved organic carbon (DOC) content in HBC800 decreased by 49.39% compared to BC800. Additionally, the high-temperature pyrolyzed biochar (BC800) enhanced the porosity richness and alkalinity of material, which effectively inhibited the migration and transformation of heavy metals compared to BC500, and reduced the decomposition of soil DOC.