Contamination Of Agricultural Soils Research Articles

PFAS, PCBs, PCDD/Fs, PAHs and extractable organic fluorine in bio-based fertilizers, amended soils and plants: Exposure assessment and temporal trends

Bio-based fertilizers (BBFs) produced from organic waste contribute to closed-loop nutrient cycles and circular agriculture. However, persistent organic contaminants, such as per- and poly-fluoroalkyl substances (PFAS), polychlorobiphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as well as polyaromatic hydrocarbons (PAHs) can be present in organic waste or be formed during valorization processes. Consequently, these hazardous substances may be introduced into agricultural soils and the food chain via BBFs. This study assessed the exposure of 84 target substances and extractable organic fluorine (EOF) in 19 BBFs produced from different types of waste, including agricultural and food industrial waste, sewage sludge, and biowaste, and through various types of valorization methods, including hygienization at low temperatures (<150 °C) as well as pyrolysis and incineration at elevated temperatures (150–900 °C). The concentrations in BBFs (ΣPFOS & PFOA: <30 μg kg−1, Σ6PCBs: <15 μg kg−1, Σ11PAHs: <3 mg kg−1, Σ17PCDD/Fs: <4 ng TEQ kg−1) were found to be below the strictest thresholds used in individual EU countries, with only one exception (pyrolyzed sewage sludge, Σ11PAHs: 5.9 mg kg−1). Five BBFs produced from sewage sludge or chicken manure contained high concentrations of EOF (>140 μg kg−1), so monitoring of more PFAS is recommended. The calculated expected concentrations in soils after one BBF application (e.g. PFOS: <0.05 μg kg−1) fell below background contamination levels (PFOS: 2.7 μg kg−1) elsewhere in the literature. This was confirmed by the analysis of BBF-amended soils from field experiments (Finland and Austria). Studies on target legacy contaminants in sewage sludge were reviewed, indicating a general decreasing trend in concentration with an apparent half-life ranging from 4 (PFOS) to 9 (PCDD/Fs) years. Modelled cumulative concentrations of the target contaminants in agricultural soils indicated low long-term risks. Concentrations estimated and analyzed in edible plant part were low, indicating that exposure by plant consumption is well below tolerable daily intakes.

Biochar and nanoscale silicon synergistically alleviate arsenic toxicity and enhance productivity in chili peppers (Capsicum annuum L.)

Arsenic (As) contamination in agricultural soils threatens crop productivity and food safety. In this study, we examined the efficacy of biochar (BC) and silicon nanoparticles (SiNPs) as environmentally sustainable soil amendments to alleviate As toxicity in chili (Capsicum annuum L.) plants. Our findings revealed that As stress severely inhibited the growth parameters of Capsicum annuum L., and subsequently reduced yield. However, the application of BC and SiNPs into the contaminated soil significantly reversed these negative effects, promoting plant length and biomass, particularly when applied together in a synergistic manner. Arsenic stress led to increased oxidative damage, as evidenced by a 29% increase in leaf malondialdehyde content as compared to the healthy plants. Nevertheless, the synergistic (BC + SiNPs) application effectively modulated antioxidant enzyme activity, resulting in a remarkable 55% and 66% enhancement in the superoxide dismutase and catalase levels, respectively, boosting chili's resistance against oxidative stress. Similarly, BC + SiNPs amendments improved photosynthesis by 52%, stomatal conductance by 39%, soluble sugars by 42%, and proteins by 30% as compared with those of control treatment. Additionally, the combined BC + SiNPs application significantly reduced root As content by 61% and straw As by 37% as compared with the control one. Transmission electron microscopy confirmed that the synergistic use of BC and SiNPs preserved chili leaf ultrastructure, shielding against As-induced damage. Overall, the supplementation of contaminated soil with BC and SiNPs was proved to be a sustainable strategy for mitigating As toxicity in chili peppers, enhancing plant growth, physiology, and yield, and thereby food safety.

De-Methyl Esterification Modification of Root Pectin Mediates Cd Accumulation of Lactuca sativa.

Cadmium (Cd) contamination in agricultural soil brings severe health risks through the dietary intake of Cd-polluted crops. The comprehensive role of pectin in lowering Cd accumulation is investigated through low Cd accumulated (L) and high Cd accumulated (H) cultivars of L. sativa. The significantly different Cd contents in the edible parts of two L. sativa cultivars are accomplished by different Cd transportations. The pectin is the dominant responsive cell wall component according to significantly increased uronic acid contents and the differential Cd absorption between unmodified and modified cell wall. The chemical structure characterization revealed the decreased methyl esterification in pectin under Cd treatment compared with control. Significantly brighter LM19 relative fluorescence density and 40.82% decreased methanol in the root pectin of L cultivar under Cd treatment (p < 0.05) supported that the de-methyl esterification of root pectin is more significant in L cultivar than in H cultivar. The pectin de-methyl esterification of L cultivar is achieved by the upregulation of pectin esterases and the downregulation of pectin esterase inhibitors under Cd treatments, which has facilitated the higher Cd-binding of pectin. Our findings provide deep insight into the differential Cd accumulation of L. sativa cultivars and contribute to the understanding the pollutant behaviors in plants.

Decreased Sulfamethoxazole Uptake in Lettuce (Lactuca sativa L.) due to Transpiration Inhibition by Polypropylene Microplastics

Microplastics and antibiotics are emerging contaminants in agricultural soil that can have negative effects on crops. However, limited research has been conducted on the effects of the polypropylene (PP) microplastic and sulfamethoxazole (SMX) co-exposure on crops, specifically regarding the impact of PP microplastics on SMX uptake and transport in crops. In this study, hydroponic experiments were carried out using lettuce (Lactuca sativa L.), PP microplastics (1.0 g L-1), and SMX (0.5 mg L-1 or 2.5 mg L-1) to investigate the individual and co-exposure effects of PP microplastics and SMX on Lettuce growth, explore the uptake and translocation of SMX in lettuce and elucidate the underlying mechanism of PP microplastic impact on SMX uptake. Results demonstrated that co-exposure to 1.0 g L-1 of PP microplastics and 0.5 mg L-1 of SMX resulted in an enhanced toxic effect. However, no intensified toxic effect on the lettuce was observed when 1.0 g L-1 PP microplastics were added in the presence of 2.5 mg L-1 SMX, indicating that the SMX dominated the toxic effect on lettuce at high concentrations. Additionally, the study found that the water absorption process controlled by the aquaporin and transpiration contributed to the uptake and translocation of SMX in lettuce. When exposed to PP microplastics, no impact was observed on the aquaporin contents of the lettuce while the transpiration rate was significantly decreased by 31.6 % - 44.2 % resulting from microplastics adhered to the root surface. Therefore, in the presence of 2.5 mg L-1 SMX, the SMX uptake in the lettuce root was inhibited by 35.9 % (P < 0.05) when exposed to 1.0 g L-1 PP microplastic. This work deepens our understanding of the behaviour of microplastics and antibiotics in the terrestrial environment.

Inoculation with multifunctional Bacillus sp. NEAU-DCB1-2 mitigates chromium toxicity in pakchoi (Brassica rapa ssp. chinensis) through a multi-level mechanism

Soil chromium (Cr) accumulation is escalating, severely hindering plant growth and development. Plant growth-promoting bacteria (PGPB) have shown potential in enhancing plant tolerance to heavy metals. However, the role and mechanisms of Cr(VI)-reducing PGPB strains in improving the growth of pakchoi under Cr toxicity remain unclear. This study aimed to isolate a Cr(VI)-reducing PGPB strain from Cr-contaminated soil, evaluate its effect on pakchoi growth under Cr(VI) stress, and investigate the mechanisms involved. Our findings showed that Bacillus sp. NEAU-DCB1-2 effectively reduce Cr(VI) to Cr(III) and produced indole-3-acetic acid and siderophores. Under Cr(VI) stress, inoculation with NEAU-DC1-2 significantly promoted seed germination and early growth of pakchoi. In pot experiments, NEAU-DCB1-2 significantly increased biomass accumulation, plant height, and root length of Cr(VI)-treated pakchoi seedlings, while reducing the Cr(VI) content in root, shoot and soil. Moreover, NEAU-DCB1-2 greatly increased catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase activities in seedlings under Cr(VI) stress, thereby reducing malondialdehyde content. Transcriptome analysis indicated substantial alterations in gene expression patterns after inoculation with NEAU-DCB1-2 under Cr(VI) stress. Further analyses revealed that NEAU-DCB1-2 mainly affected the responses of antioxidant system, metal chelation and transport, together with auxin, abscisic acid, and jasmonic acid signaling to Cr(VI) stress. Conclusively, the Cr(VI)-reducing PGPB strain NEAU-DCB1-2 significantly enhances the growth and Cr tolerance of pakchoi through multiple mechanisms, offering a valuable microbial resource for mitigating the adverse effects of heavy metal contamination in agricultural soils on the yield and safety of vegetable crops.

Homocysteine S-Methyltransferase 3 Positively Regulates Cadmium Tolerance in Maize.

The increasing contamination of agricultural soils with cadmium (Cd) poses a significant threat to human health and global food security. Plants initiate a series of mechanisms to reduce Cd toxicity. However, the response of maize to Cd toxicity remains poorly understood. In this study, we identified that ZmHMT3, which encodes a homocysteine S-methyltransferases family protein, acted as a regulator of Cd tolerance in maize. Subcellular localization and in situ PCR exhibited that ZmHMT3 was localized in the cytoplasm and predominantly expressed in the phloem. Overexpression of ZmHMT3 enhanced Cd tolerance and reduced Cd concentration in both shoots and roots. In contrast, ZmHMT3 mutants attenuated Cd tolerance but did not change shoot Cd concentration. Heterologous overexpression of ZmHMT3 in rice enhanced Cd tolerance and reduced grain Cd concentration. Transcriptome analysis revealed that ZmHMT3 upregulated the expression of stress-responsive genes, especially glutathione S-transferases (GSTs) and transcription factors, including MYBs, NACs and WRKYs, and modulates the expression of different ATP-binding cassette (ABC) transporters, thereby enhancing Cd tolerance. Collectively, these findings highlight the pivotal role of ZmHMT3 in Cd tolerance and as a candidate gene for improving Cd tolerance in elite maize varieties.

Ameliorating arsenic and PVC microplastic stress in barley (Hordeum vulgare L.) using copper oxide nanoparticles: an environmental bioremediation approach

The present study investigates the impact of varying concentrations of PVC microplastics (PVC–MPs) – specifically 0 (no PVC–MPs), 2, and 4 mg L− 1 –alongside different arsenic (As) levels of 0 (no As), 150, and 300 mg kg− 1 in the soil, with the concurrent application of copper oxide–nanoparticles (CuO–NPs) at 0 (no CuO –NPs), 25 and 50 µg mL− 1 to barley (Hordeum vulgare L.) plants. This research primarily aims to assess plant growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress indicators, as well as the response of various antioxidants (both enzymatic and non-enzymatic) and their relevant genes expression, proline metabolism, the AsA–GSH cycle, and cellular fractionation within the plants. The findings showed that increased levels of PVC–MPs and As stress in the soil significantly reduced plant growth and biomass, photosynthetic pigments, and gas exchange characteristics. Additionally, PVC–MPs and As stress increased oxidative stress in the roots and shoots, as evidenced by elevated levels of malondialdehyde (MDA), hydrogen peroxide (H2O2), and electrolyte leakage (EL), which in turn stimulated the production of various enzymatic and non-enzymatic antioxidants, gene expression, and sugar content. Furthermore, a notable increase in proline metabolism, the AsA–GSH cycle, and cellular pigmentation was observed. Conversely, the application of CuO–NPs resulted in a substantial improvement in plant growth and biomass, gas exchange characteristics, and the activity of enzymatic and non-enzymatic antioxidants, along with a reduction in oxidative stress. Additionally, CuO–NPs enhanced cellular fractionation while decreasing proline metabolism and the AsA-GSH cycle in H. vulgare plants. These outcomes provide new insights into sustainable agricultural practices and offer significant potential in addressing the critical challenges of heavy metal contamination in agricultural soils.

Spatial and Bioaccumulation of Heavy Metals in a Sheep-Based Food System: Implications for Human Health.

Heavy metal contamination in agricultural soils presents serious environmental and health risks. This study assessed the bioaccumulation and spatial distribution of nickel, cadmium, zinc, lead, and copper within a sheep-based food chain in the Baia Mare region, Romania, which includes soil, green grass, sheep serum, and dairy products. Using inductively coupled plasma mass spectrometry (ICP-MS), we analyzed the concentrations of these metals and calculated bioconcentration factors (BCFs) to evaluate their transfer through trophic levels. Spatial analysis revealed that copper (up to 2528.20 mg/kg) and zinc (up to 1821.40 mg/kg) exceeded permissible limits, particularly near former mining sites. Elevated lead (807.59 mg/kg) and cadmium (2.94 mg/kg) were observed in industrial areas, while nickel and cobalt showed lower concentrations, but with localized peaks. Zinc was the most abundant metal in grass, while cadmium transferred efficiently to milk and cheese, raising potential health concerns. The results underscore the complex interplay between soil properties, contamination sources, and biological processes in heavy metal accumulation. These findings highlight the importance of continuous monitoring, risk assessment, and mitigation strategies to protect public health from potential exposure through contaminated dairy products.

Transect approach for assessing major and trace elemental contamination in agricultural soils of the palamaner division, chittoor district, andhra pradesh, india.

Three soil transects located in the granitic regions of Palamaner mandal, Andhra Pradesh, India, were examined to assess the pollution levels of both primary and secondary metals (Si, Al, Fe, Ca, Mg, Na, K, Cu, Mn, P, and Zn) and to ascertain the degree of soil pollution in agricultural areas. The soils along these transects are slightly acid to neutral, with dark brown to red rubified argillic clay-rich B horizons alongside a moderate cation exchange capacity. The A horizon soils display low organic carbon levels with a moderate variability and contain over 70% SiO2, exhibiting low variability due to limited leaching in a semiarid climate. The findings suggest that iron (Fe) and manganese (Mn) oxides play a role in reducing contamination levels through oxidation and precipitation processes. Furthermore, the soils show low to moderate cation exchange capacity, which restricts the retention of absorbed heavy metals, thus lessening their negative impacts. A two-way ANOVA revealed significant differences in CEC, organic carbon, and total zinc content across different horizons and landscape positions. Si, Al, and Cu had small increases and negative geoaccumulation indices in all soil profiles, suggesting no pollution. However, the Nemerow and mean contamination degree over 6 point to slight to moderate pollution. The analysis identified three distinct clusters with significant variations in contamination factors for SiO2 and Cu. Five principal components were determined, explaining 76% of the total variance, primarily derived from geogenic sources and remaining within acceptable limits. This research on soil transects in granitic regions contributes to a better understanding of the distribution, movement, and concentration of elemental oxides based on slope position, which is essential for pollution assessment and soil quality enhancement.

Nanopriming with phytofabricated selenium nanoparticles alleviates arsenite-induced oxidative stress in Spinacia oleracea L.

Arsenic (As) contamination of agricultural soil has become a major concern due to its adverse effects on plant growth and human health. Selenium nanoparticles (SeNPs), a novel selenium (Se) source, are characterised by their exceptional biocompatibility, degradability, and bioactivities. In the present study, SeNPs were biogenically synthesised and further characterised using UV-visible spectroscopy, XRD, FTIR, and TEM analysis. Different concentrations of the synthesised SeNPs were used to treat Spinacia oleracea L. (spinach) seeds to determine their impact on growth profile, gas exchange, photosynthetic pigments, oxidative stress, and antioxidant enzyme status upon arsenite (AsIII) treatment. The findings revealed that SeNP supplementation at a concentration of 100µM (SeNPs100) led to a significant reduction in As accumulation by twofold in roots and 1.5-fold in leaves when compared to plants exposed to AsIII100 (µM) alone. Interestingly, the photosynthetic efficiency was also remarkably enhanced upon SeNPs100 treatment, associated with increased activities of the defence enzymes (ascorbate peroxidase, catalase, and glutathione peroxidase) in the AsIII + SeNP-exposed spinach plants as compared to AsIII treatment alone. Overall, the present study highlights the potential of biogenic SeNP supplementation in promoting plant growth and mitigating As toxicity in spinach under AsIII stress. This study could have significant implications for the use of SeNPs as a nanofertiliser in regions grappling with As-contaminated soils for sustainable agriculture and human health.

Engineered biochars for simultaneous immobilization of as and Cd in soil: Field evidence

Agricultural soil contamination by potentially toxic elements (PTEs) such as arsenic (As) and cadmium (Cd) poses a serious threat to food security. Immobilization serves as a widely used approach for the remediation of PTEs contaminated soils, nevertheless, the long-term effectiveness for the simultaneous immobilization of both cations and oxyanions remains a challenge. In order to effectively enhance the synergistic immobilization effect of soil As and Cd contaminated by multiple elements and improve the ecological environment of farmland. In this study, a typical polluted tailings area farmland was selected for situ immobilization experiments, and biochar was prepared from cow manure (CMB), rice straw (RSB), and pine wood (PWB) as raw materials. On this basis, the pristine biochar was modified with ferric chloride (F), potassium permanganate (K), magnesium chloride (M), and aluminum chloride (A), respectively. Furthermore, the immobilization effect of modified biochar on As-Cd and the stress effect on soil respiration were investigated. The results showed that CMB and RSB reduced the bioavailability of heavy metals, potassium permanganate has strong oxidizing properties, and the strong oxidability of potassium permanganate stimulated the generation of more oxygen-containing functional groups on the surface of biochar, thereby enhancing the adsorption and complexation effect of modified materials on As and Cd. Among them, the extracted Cd concentration of Diethylenetriamine pentaacetic acid (DTPA) in KCMB and KRSB in 2020 decreased by 8.23–43.12% and 9.67–35.29% compared to other treatments, respectively. Meanwhile, the KCMB and KRSB treatments also reduced the enrichment of As and Cd in plant tissues. In addition, the dissolved organic carbon (DOC) content in KCMB treatment was relatively high, and the carbon stability of the material was weakened. Simultaneously, the soil respiration emission of KCMB treatment was increased by 5.63% and 11.93% compared to KRSB and KPWB treatments, respectively. In addition, the structural equation also shows that DOC has a large positive effect on soil respiration. In summary, the KRSB treatment effectively achieve synergistic immobilization of As-Cd and provide important guiding significance for green and low-carbon remediation of polluted farmland.

Biochar solutions: Slow and fast pyrolysis effects on chromium stress in rapeseed roots

Chromium (Cr) contamination in agricultural soils, largely due to industrial activities, poses a significant threat to plant growth and productivity. This study examines the effects of Cr stress at concentrations of 100 and 200 mg of K2Cr2O7 per kg soil on rapeseed (Brassica napus) roots and evaluates the mitigating potential of biochar. Biochar, produced through both slow and fast pyrolysis and applied at 30 g per kg soil, was investigated for its ability to neutralize Cr toxicity. Our findings indicate that Cr stress significantly decreased the growth and physiological functions of rapeseed roots. However, biochar application improved soil pH, cation exchange capacity, and the uptake of essential nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium. Additionally, biochar enhanced the production of osmotic regulators like glycine betaine and soluble proteins, as well as indole acetic acid, promoting better root growth and water uptake under Cr stress. Notably, biochar reduced Cr availability and absorption in rapeseed roots, leading to lower levels of stress-related hormones such as abscisic acid, salicylic acid, and jasmonic acid. Among the biochars tested, slow pyrolysis biochar was more effective than fast pyrolysis biochar in mitigating Cr toxicity. These results highlight the potential of slow pyrolysis biochar as a sustainable strategy to alleviate Cr pollution and enhance plant resilience in contaminated soils.

Evaluation of the growth, enzymatic activity, electrolyte leakage, and phytoremediation efficiency of Conocarpus erectus under cadmium and lead stress.

Contamination of agricultural soil by heavy metals poses a significant threat to soil quality and crop yields. Using plants as a natural remediation approach attracts researchers' attention around the world. A 16-month pot experiment was conducted using Conocarpus erectus in a randomized complete block design. The growth, enzymatic activity, electrolyte leakage, and remediation potential were estimated under Cd nitrate]40 low (L), 60 medium (M), 80 high (H) mg/kg soil [and Pb nitrate]400 (L), 700 (M), 1,000 (H) mg/kg soil [applied individually and in combination. Conocarpus erectus demonstrated a good tolerance (over 70%) against lower and medium cadmium (Cd) and lead (Pb) levels and a medium resistance against high Cd and Pb levels, with a survival rate of 100% under all the treatments used. The most negative treatment on the growth traits and tolerance of C. erectus was (H) Cd and (H) Pb, which reduced plant height; chlorophyll index; dry weights of the leaves, stems, and roots; root length; and tolerance index of biomass and roots by 25.87%, 48.97%, 50.56%, 47.25%, 58.67%, 50.18%, 51.00%, and 50% in comparison to the respective control, consecutively. Relative to the control, all Cd and Pb applications increased polyphenol oxidase (PPO), peroxidase (POD), and catalase (CAT) activities, and the increment was parallel up to medium Cd and Pb levels and then decreased with their high levels but still higher than the control. Electrolyte leakage (EL) was upheaved by raising the levels of Cd and Pb, and it reached the maximum (52.79%) at the (H) Cd (H) Pb treatment. Cd and Pb in the leaves, stems, and roots were boosted by raising their levels in the treatments. Conocarpus erectus is considered a phytoextractor for the Cd levels used because the bioconcentration factor of the stem (BCFs) and the translocation factor (TF) of Cd were >1, and it is a suitable plant for Pb phytoextraction at (L) Pb, (M) Pb, and (M) Cd (M) Pb levels because its Pb BCFs and bioconcentration factor of the root (BCFr) were <1 and its Pb TF was >1. On the other hand, C. erectus is considered a phytostabilizator for Pb at (H) Pb, (L) Cd, (L) Pb, and (H) Cd (H) Pb levels because its Pb BCFs, BCFr, and TF were <1.

Phosphate Fertilizers’ Dual Role in Cadmium-Polluted Acidic Agricultural Soils: Dosage Dependency and Passivation Potential

Cadmium (Cd) contamination in agricultural soils is a common issue, posing health risks as it enters the human body through the food chain. Commonly used phosphate fertilizers (PFs) not only provide essential phosphorus (P) nutrients to crops but also serve as P-containing materials for immobilizing heavy metals (HMs) like Cd in soils. Therefore, understanding the passivation effects of PFs on soil Cd and their potential influencing factors is crucial for mitigating soil Cd pollution. In this study, the impact of multi-crop applications (75 mg P kg−1, 150 mg P kg−1) of four kinds of PFs on reducing soil Cd toxicity and decreasing Cd accumulation in spinach was investigated. The results indicated that under the low application rate (75.0 mg P kg−1), all PFs could passivate Cd, and CMP demonstrated the most effective passivation of Cd. However, under the high application rate (150 mg P kg−1), the immobilization effect diminished or even activated Cd. Among the different types of PFs, CMP application alleviated soil acidification and significantly reduced soil-available Cd, showing the best performance in promoting spinach growth and Cd inhibition. These results suggest that PF application in Cd-contaminated soils affects spinach growth and Cd accumulation, with soil pH, available phosphorus (AP), and Cd dynamics being crucial; moreover, low-P, micronutrient-rich, alkaline PFs like CMP optimize spinach yields and minimize Cd uptake, and excessive application of soluble PFs decreases pH, increases Cd mobility, and poses health risks, suggesting a need for balanced fertilizer use.

Wood- and Manure-Derived Biochars Reduce Antibiotic Residues and Shift Antibiotic Resistance Genes and Microbial Communities in Manure Applied Forage–Soil Systems

The increasing use of antibiotics in livestock poses environmental risks, leading to contamination of agricultural soils and propagation of microbial antibiotic-resistant genes (ARGs). This study examined the impacts of wood- and manure-derived biochar (BC) on antibiotic residues, ARGs, and microbial communities in sandy loam and clay loam soils amended with manure in Cynodon dactylon pastures. We hypothesized that BC amendments would influence the degradation of antibiotics and the structure of microbial communities based on their physicochemical properties and soil types. Our results demonstrated that wood BC reduced the concentrations of tetracycline and sulfonamides, particularly in sandy loam soil, due to its larger surface area and hydrophobic properties. In contrast, manure BC provided additional nutrients and supported atmospheric nitrogen-fixing microbial groups, especially in clay loam soil, while exhibiting variable efficiency in reducing antibiotic residues due to its lower surface area and higher ash content. These findings underscore the differential impacts of each BC type, emphasizing the need for tailored BC applications based on soil type to effectively mitigate antibiotic contamination and promote sustainable agricultural practices. In conclusion, wood BC was more effective in enhancing soil health by reducing antibiotic residues and improving microbial diversity, particularly in sandy loam soils, while manure BC was beneficial for nutrient cycling in clay loam soils.

Manganese enhances cadmium tolerance in barley through mediating chloroplast integrity, antioxidant system, and HvNRAMP expression

Cadmium (Cd) is a toxic heavy metal that poses risks to crop production and food safety worldwide. This study evaluated whether manganese (Mn) addition could mitigate Cd toxicity and reduce Cd accumulation in barley seedlings. Hydroponically grown seedlings of Cd-tolerant (WSBZ) and Cd-sensitive (Dong17) barley cultivars were treated with 0.1 μM and 1 μM Cd as well as 0.2 mM Mn alone and in a combination with 0.1 or 1.0 μM Cd for 21 days. Cd exposure caused the dramatic alteration of growth and physiological parameters by disrupting chloroplast, and increased Cd accumulation in both genotypes. However, Mn addition markedly alleviated the negative impacts of all examined parameters caused by Cd stress. Cd addition enhanced expression of anti-oxidative enzyme related genes, including HvSOD, HvCAT, HvAPX, HvPOD in the two barley genotypes exposed to Cd stress. The expression analysis showed nearly all HvNRAMPs genes are dramatically up regulated by both Mn and Cd, with WSBZ having higher expression than Dong 17. Notably, HvNRAMP1 showed the highest expression due to Mn addition, highlighting its crucial role in Mn uptake and transportation in barley. Moreover, Cd stress and Mn addition increased and suppressed the expression of HvYSL5, HvHMA2 and HvHMA3, respectively. Conversely, the expression of HvYSL2, HvIRT1 and HvMTP8 was upregulated by both Mn and Cd treatments, with a further increase observed in the combined Cd and Mn treatments. It may be concluded that sufficient Mn supply is quite important for reducing Cd uptake and accumulation in plants.

Biodegradation of PAEs in contaminated soil by immobilized bacterial agent and the response of indigenous bacterial community

Phthalic acid esters (PAEs) are common hazardous organic contaminants in agricultural soil. Microbial remediation is an effective and eco-friendly method for eliminating PAEs. Nevertheless, the operational mode and potential application of immobilized microorganisms in PAEs-contaminated soil are poorly understood. In this study, we prepared an immobilized bacterial agent (IBA) using a cedar biochar carrier to investigate the removal efficiency of PAEs by IBA in the soil. We found that IBA degraded 88.35% of six optimal-control PAEs, with 99.62% biodegradation of low-molecular-weight PAEs (DMP, DEP, and DBP). The findings demonstrated that the IBA achieved high efficiency and a broad-spectrum in degrading PAEs. High-throughput sequencing revealed that IBA application altered the composition of the soil bacterial community, leading to an increase in the relative abundance of PAEs-degrading bacteria (Rhodococcus). Furthermore, co-occurrence network analysis indicated that IBA promoted microbial interactions within the soil community. This study introduces an efficient method for the sustainable remediation of PAEs-contaminated soil.

Application of soil amendments to reduce the transfer of trace metal elements from contaminated soils of Lubumbashi (Democratic Republic of the Congo) to vegetables

The extraction of copper and cobalt from mines has led to the contamination of agricultural soils by trace metal elements (TMEs) (e.g. Cu: 204 to 1355 mg/kg). The mining industry is one of the sources of metal discharges into the environment, contributing to water, soil, and air contamination and causing metabolic disorders in the inhabitants of the city of Lubumbashi (R.D. Congo). This study assessed the effectiveness of organocalcareous soil improvers applied to TME-contaminated soils to reduce their transfer to plants. Following a factorial design, increasing doses of organic soil improvers (chicken droppings and sawdust) and agricultural lime were applied to the soils of three market gardens (high, medium, and low Cu contamination). The experiment was monitored for 60 days. Soil physicochemical properties (pH, TOC, and total and available copper, cobalt, lead, cadmium, and zinc (mg/kg)) were determined for the three gardens and in the vegetable biomass. The daily consumption index of the vegetables was determined based on total TME content. The results show that organocalcareous soil improvers did not promote plant growth and survival on soils with high and medium levels of copper contamination. However, on soils with low copper content, organocalcareous soil improvers improved germination and plant survival and reduced the transfer of metals from the soil to the plants. The best germination and plant survival rates were obtained with the lightly contaminated market garden. In addition, the organo-limestone amendments applied to the soils slightly increased the soil pH from acidic to slightly acidic, with pH values ranging from (5.43 ± 0.07 to 7.26 ± 0.33). The daily vegetable consumption index obtained for cobalt in the low-contaminated garden ranged from (0.029 to 0.465 mg/60 kg/day), i.e. from 0.5 to 8.45 times higher than the FAO/WHO limit, unlike the other trace metals (Cd, Cu and Pb) for which the daily consumption index found was lower than the FAO/WHO limit. Organocalcareous soil improvers can only be applied to soils with low levels of TME contamination, but for soils with medium to high levels of metal contamination, new soilless production techniques such as hydroponics or bioponics are needed.

Stability and heavy metals accumulation of soil aggregates under different land uses in the southwest coastal Bangladesh

Agricultural soil contamination is increasing day-by-day and becoming a major problem over the globe. Trace elements accumulation in the bulk soil is frequently documented, however, there is no precise mechanism of their distribution in the different soil aggregates level. We collected twelve composite soil samples from banana fields, fallow land, rice cultivated with pond water (rice field-I), and rice cultivated with rain water (rice field-II). We separated soil samples into four different size of aggregates (4-2, 2–0.25, 0.25–0.053, <0.053-mm) and then, aggregate stability (MWD), soil organic carbon (SOC), and heavy metals content (Pb, Cd, Cr, As, Fe, Mn, Zn, Ni, Co, Cu) in the soil samples were measured with different techniques. Results showed that MWD was higher in the rice-based land use, which was significantly contributed by SOC (p < 0.001). The concentration of Pb, As, Cd, Fe, and Mn were increased, while Cu and Zn concentration were reduced with increasing aggregate size (p < 0.05). In contrast, aggregate size did not influence on Ni and Co accumulation (p > 0.05). Moreover, macroaggregate acted as an accumulator for Fe, Mn, and As, while all the aggregate fractions acted as accumulators for Cu and Zn. Our study indicated that MWD, SOC, aggregate size and composition, and metal species were the controlling factors of trace elements accumulation and distribution in the various sizes of soil aggregates.

Unraveling the characteristics of microplastics in agricultural soils upon long-term organic fertilizer application: A comprehensive study using diversity indices

Microplastics negatively impact soil health and productivity. Organic fertilizers constitute significant contributors of microplastics in agricultural soils. Nevertheless, comprehensive data on the diversity of microplastics in long-term fertilized soils remain unavailable. In this study, we assessed the presence of microplastics in soils subjected to application of three different organic fertilizers (pig manure, chicken manure, and sludge composts) over 12 years, and evaluated the potential ecological risks posed by microplastic accumulation. The average microplastic abundance in soil was 368.88 ± 207.97 (range: 90–910) items/kg. Microplastic abundance differed among fertilization treatments, with substantial increases of 16.67%, 71.67%, and 61.43% upon low to high application of the three treatments, respectively. Overall, the microplastics predominantly comprised fibers (70.94%) and fragments (25.25%), of which a substantial proportion constituted light-colored microplastics (transparent and white). The size of microplastics was mainly concentrated in the 1–2 mm range (39.96%), with rayon, polypropylene, polyester, and polyethylene being identified as the major types. The risk assessment indices of the three treatments were 229.38, 257.64, and 175.89, respectively, and were all classified as level 4 (high risk). The microplastic diversity integrated index and principal component analysis revealed that microplastics were uniformly distributed throughout the 0–20 cm soil depth consequent to tillage activity. Together, these findings provide a comprehensive assessment of microplastic pollution in long-term fertilized soils and serve as a scientific basis for reducing microplastic contamination in agricultural soils.