Plant Soil Environment Research Articles

Predictive Machine Learning Model to Assess the Adsorption Efficiency of Biochar-Heavy Metals for Effective Remediation of Soil-Plant Environment.

Biochar is crucial for agricultural output and plays a significant role in effectively eliminating heavy metals (HMs) from the soil, which is essential for maintaining a soil-plant environment. This work aimed to assess machine learning models to analyze the impact of soil parameters on the transformation of HMs in biochar-soil-plant environments, considering the intricate non-linear relationships involved. A total of 211 datasets from pot or field experiments were evaluated. Fourteen factors were taken into account to assess the efficiency and bioavailability of HM-biochar amendment immobilization. Four predictive models, namely linear regression (LR), partial least squares (PLS), support vector regression (SVR), and random forest (RF), were compared to predict the immobilization efficiency of biochar-HM. The findings revealed that the RF model was created using 5-fold cross-validation, which exhibited a more reliable prediction performance. The results indicated that soil features accounted for 79.7% of the absorption of HM by crops, followed by biochar properties at 17.1% and crop properties at 3.2%. The main elements that influenced the result have been determined as the characteristics of the soil (including the presence of different HM species and the amount of clay) and the quantity and attributes of the biochar (such as the temperature at which it was produced by pyrolysis). Furthermore, the RF model was further developed to predict bioaccumulation factors (BAF) and variations in crop uptake (CCU). The R2 values were found to be 0.7338 and 0.6997, respectively. Thus, machine learning (ML) models could be useful in understanding the behavior of HMs in soil-plant ecosystems by employing biochar additions.

Ecological Stoichiometry of Multiple Nutrients in Leymus chinensis and Soils Subjected to Long-Term Saline-Sodic Stress in Western Jilin Province, China

L. chinensis is considered an important plant for saline-sodic soil restoration. Ecological stoichiometry of multiple nutrient elements in Leymus chinensis (L. chinensis) and soils subjected to long-term saline-sodic stress remains unclear, which hinders our understanding of the mechanisms regulating nutrient cycling in the plant-soil environment. We examined nutrient element levels in saline-sodic soil and L. chinensis in western Jilin Province. Soil analysis revealed medium to high levels of available N, K, P, Mo, Mn, Fe, Cu, and Zn. The Mn/Fe and N/P ratios exceeded the national soil average of China, while those of Fe/Cu, Fe/Zn, and P/K were comparatively lower. Furthermore, L. chinensis exhibited deficiencies in the Mn, Zn, and P. Mo/Mn, Mo/Zn, and Fe/Zn ratios, which were significantly higher compared to healthy plants, while Mn/Fe and P/K showed the opposite trend. Soil pH had the most significant effect on element stoichiometry in both the soil and in L. chinensis. Particularly, the soil available Mn, Zn, K, along with L. chinensis Mn, Fe, Cu, and P levels exhibited sensitivity to pH fluctuations. Additionally, we observed significant synergistic or antagonistic effects between the soil available element concentration and stoichiometry ratios. Among these, only Mn, Fe, Fe/Zn, Mo/Zn, N/K, and Mo/Fe in L. chinensis were significantly modeled (P < 0.05). The Mo/Fe homeostasis index was the lowest at 0.97, followed by Fe (1.16), N/K (2.28), Mo/Zn (2.59), Fe/Zn (3.38), and Mn (4.92), while other elements and their stoichiometric ratios remained stable. Overall, L. chinensis, as the dominant species in saline-sodic soil, demonstrated high homeostasis.

Effects of microplastics and cadmium co-contamination on soil properties, maize (Zea mays L.) growth characteristics, and cadmium accumulation in maize in loessial soil-maize systems

Microplastics (MPs) are pervasive pollutants found in agricultural soils, yet research on the combined impacts of MPs and heavy metals on soil-plant systems remains limited. This study investigates the combined impact of low-density polyethylene (LDPE) microplastics (L: 1 mm, S: 100 μm, 0.1%, 1%) and Cd on soil properties, available Cd content, maize growth, and Cd accumulation by mazie through pot experiments. The findings unveiled notable impacts of the treatment groups, namely MP-L0.1%, MP-S0.1%, MP-L1%, and MP-S1%, on soil organic carbon (SOC), maize height, and catalase (CAT) activity (P < 0.05). The dosage of MPs significantly influenced maize height, MP-S0.1% treatment resulted in a 5.6% reduction, while the other groups had insignificant effects. Particle size and dosage significantly affected SOC and CAT (P < 0.01). The MP-L1% and MP-S1% groups resulted in increases of SOC by 121.5% and 281.0%, respectively. CAT reductions were 32.6%, 62.8%, 41.9%, and 34.9% in MP-L0.1%, MP-S0.1%, MP-L1%, and MP-S1% groups, individually. The Cd treatment induced a significant decrease in soil cation exchange capacity (CEC), maize stem diameter, and root length, accompanied by significant increases in maize plant height, malondialdehyde (MDA), CAT, and superoxide dismutase (SOD) activities. Combined LDPE and Cd contamination had significant effects on maize height and Cd content in leaves. Specifically, MP-L0.1%+Cd, MP-S0.1%+Cd, MP-L1%+Cd, and MP-S1%+Cd reduced maize height by 4.1%, 4.5%, 8.7%, and 13.8%, respectively. The co-presence of LDPE and Cd increased available Cd content in soil while elevating Cd concentration in maize shoots and roots, with a notable 25.5% increase in Cd concentration in maize leaves in the MP-L1%+Cd group compared to the Cd group. Furthermore, LDPE effects on soil-plant systems varied depending on particle size and dosage. This research provides important perspectives on evaluating the concurrent contamination and potential dangers of MPs and toxic metals in soil-plant environments.

Strategy matters: Phytoremediation potential of native halophytes is jointly associated with their distinct salt tolerances

Halophytes are effective candidates for phytoremediation of heavy metal-contaminated saline soils. Still, little is known about the relationships between their potential for metal enrichment and salt-tolerance strategies. This study comprehensively investigated the plant community and concentrations and accumulation characteristics of heavy metals (As, Cd, Cr, Cu, Pb, and Zn) in the soil and dominant native plants with different salt-tolerance strategy groups, namely salt-dilution (SD), salt-excretion (SE), salt-exclusion (SC), and non-halophyte, in a semiarid region of Northwest China. The results showed that the soil in this area was primarily polluted by As and Cd, which were 5.80 and 21.18 times higher than the corresponding background values, respectively. The primary vegetation was desert steppe, and 95 species of 34 families were investigated, most of which were herbaceous (64.2%) with the Asteraceae dominating. Eleven of the thirteen dominant plants, except Zea mays and Helianthus annuus, were halophytes with distinct salt tolerances, exhibiting differing metal accumulation and transport capacities. All the bioconcentration factors of the selected species for six metals were lower than 1, and their accumulation ability decreased in the order of Cu (0.466) > Cr (0.315) ≈ Cd (0.093) ≈ Zn (0.082) ≈ As (0.076) > Pb (0.049). Salt-tolerance strategies were significantly correlated with As and Cd accumulations in the soil-plant environment, but in diametrically opposite directions. Also, metal accumulations and translocations partly depended on plant salt resistance strategies. Salt-diluting halophytes such as Suaeda glauca and Kochia scoparia seem applicable for phytoextraction of single or mixed metal pollution, particularly Cd. In comparison, salt-excreting halophytes such as Chenopodium glaucum and Salsola collina would be more suited to As phytostabilization due to the potential for second pollution. In conclusion, SD halophytes could be used in various metal-contaminated soils in salt-affected regions, while SE halophytes would be well suited for phytostabilization. This study would enhance the exploitation advantages of halophyte germplasms with different salt tolerances in multiple-stressed environments.

Interplay between nano zinc oxide-coated urea and summer green manuring in basmati rice under basmati rice-wheat cropping system: implications on yield response, nutrient acquisition and grain fortification

Identifying appropriate nutrient management options is crucial for reversing the yield plateau and enhancing the nutritional status of basmati rice under the basmati rice-wheat cropping system of the Indo Gangetic Plain (IGP). Alternative to the conventional chemical fertilizer, ZnO nanoparticles as carrier material for the micronutrient Zn has shown promise in reducing the bulkiness of fertilizer use in the soil–plant environment. But whether its integration and interaction with an organic source such as green manuring could enrich basmati rice grain with micronutrients and promote protein nutrition is not well investigated. Therefore, we conducted a field experiment during the summer and rainy seasons (April–October) of 2020 and 2021 at the research farm of the ICAR-Indian Agricultural Research Institute, New Delhi in a split-plot design with two summer green manuring (SGM) options (Sesbania and cowpea, along with fallow) as main plots and six fertilization strategies as subplots: 5 kg Zn ha−1 as bulk ZnO, N at 120 kg N ha−1 as prilled urea (PU), N at 120 kg N ha−1 as PU + 5 kg Zn ha−1 as bulk ZnO, 1% bulk ZnO-coated PU, 0.1% nano ZnO coated PU and 0.2% nano ZnO coated PU replicated thrice. On average, SGM increased basmati rice grain yield by 13.2 and 12.3% during 2020 and 2021, respectively compared to fallow. Integrated application of zinc with urea significantly (p &amp;lt; 0.05) increased the grain yield of basmati rice by 9.56% and by 10.5% relative to urea without zinc and by 33.7 and 33.8% than the sole application of 5 kg Zn ha−1 through ZnO, respectively during 2020 and 2021. On average, SGM boosted Zn, Cu, Mn, and Fe content in milled rice by 25, 22.38, 20.0, and 18.85% during 2020 and 23.75, 21.4, 19.6, and 13.3% during 2021, respectively compared to fallow. Relative to sole urea application, zinc, and urea together improved the Zn and Fe content in milled rice by 2.99 mg kg−1 and 2.62 mg kg–1, respectively during the first year and by 2.83 mg kg−1 and 2.6 mg kg−1, respectively during the second year of study. The highest protein content in basmati rice grain was observed when it was grown after Sesbania aculeata residue incorporated plot during both the years and it decreased in the order: Sesbania aculeata &amp;gt; Vigna unguiculata &amp;gt; summer fallow. Our findings revealed that with the application of 1% bulk ZnO coated PU with Sesbania; the yield response, micronutrient acquisition, and protein accumulation in milled rice was higher than in other plant fertilization methods. However, in plots treated with Sesbania, along with 0.2% nano ZnO-coated PU exhibited statistically equivalent yield and micronutrient loading in edible tissues. Hence, this study unveils the critical role of nano ZnO-coated urea and summer green manuring in elevating micronutrient and protein bioavailability in basmati rice and concurrently reducing Zn dose by 20%, making it a profitable option for farmers.

Diversity and assembly of root-associated microbiomes of rubber trees.

Understanding the diversity and assembly of the microbiomes of plant roots is crucial to manipulate them for sustainable ecosystem functioning. However, there are few reports about microbial communities at a continuous fine-scale of roots for rubber trees. We investigate the structure, diversity, and assembly of bacterial and fungal communities for the soil (non-rhizosphere), rhizosphere, and rhizoplane as well as root endosphere of rubber trees using the amplicon sequencing of 16S ribosomal ribonucleic acid (rRNA) and Internally Transcribed Spacer (ITS) genes. We show that 18.69% of bacterial and 20.20% of fungal operational taxonomic units (OTUs) in the rhizoplane derived from the endosphere and 20.64% of bacterial and 20.60% of fungal OTUs from the soil. This suggests that the rhizoplane microbial community was a mixed community of soil and endosphere microbial communities and that microorganisms can disperse bidirectionally across different compartments of the plant root. On the other hand, in the absence of an enrichment or depletion of core bacterial and fungal OTUs in the rhizosphere, little differences in microbial composition as well as a more shared microbial network structure between the soil and the rhizosphere support the theory that the rhizosphere microbial community is a subset of the soil community. A large number of functional genes (such as nitrogen fixation and nitrite reduction) and more enriched core OTUs as well as a less stable but more complex network structure were observed in the rhizoplane of rubber tree roots. This demonstrated that the rhizoplane is the most active root compartment and a hotspot for plant-soil-environment interactions. In addition, bacterial and fungal communities in the rhizoplane were more stochastic compared to the rhizosphere and soil. Our study expands our understanding of root-associated microbial community structure and function, which may provide the scientific basis for sustainable agriculture through biological process management.

A Review of Sustainable Use of Biogenic Nanoscale Agro-Materials to Enhance Stress Tolerance and Nutritional Value of Plants.

Climate change is more likely to have a detrimental effect on the world's productive assets. Several undesirable conditions and practices, including extreme temperature, drought, and uncontrolled use of agrochemicals, result in stresses that strain agriculture. In addition, nutritional inadequacies in food crops are wreaking havoc on human health, especially in rural regions of less developed countries. This could be because plants are unable to absorb the nutrients in conventional fertilizers, or these fertilizers have an inappropriate or unbalanced nutrient composition. Chemical fertilizers have been used for centuries and have considerably increased crop yields. However, they also disrupt soil quality and structure, eventually impacting the entire ecosystem. To address the situation, it is necessary to develop advanced materials that can release nutrients to targeted points in the plant-soil environment or appropriate receptors on the leaf in the case of foliar applications. Recently, nanotechnology-based interventions have been strongly encouraged to meet the world's growing food demand and to promote food security in an environmentally friendly manner. Biological approaches for the synthesis of nanoscale agro-materials have become a promising area of research, with a wide range of product types such as nanopesticides, nanoinsecticides, nanoherbicides, nanobactericides/fungicides, bio-conjugated nanocomplexes, and nanoemulsions emerging therefrom. These materials are more sustainable and target-oriented than conventional agrochemicals. In this paper, we reviewed the literature on major abiotic and biotic stresses that are detrimental to plant growth and productivity. We comprehensively discussed the different forms of nanoscale agro-materials and provided an overview of biological approaches in nano-enabled strategies that can efficiently alleviate plant biotic and abiotic stresses while potentially enhancing the nutritional values of plants.

Role of biochar-based free radicals in immobilization and speciation of metals in the contaminated soil-plant environment

The structure of biochar produced at various pyrolysis temperatures influences metal geochemical behavior. Here, the impact of wheat straw-derived biochar (300, 500, and 700 °C) on the immobilization and transformation of metals in the contaminated soil-plant system was assessed. The findings of the sequential extraction revealed that biochar additives had a substantial influence on the speciation of Cr, Ni, Pb, and Zn in the contaminated soil. The lowest F1 (exchangeable and soluble fraction) + F2 (carbonate fraction) accounted for Cr (44%) in WB-300, Ni (43.87%) in WB-500, Pb (43.79%), and Zn (49.78%) in WB-700 with applied amendments of their total amounts. The characterization results indicated that high pyrolysis temperatures (300–700 °C) increased the carbon-containing groups with the potential to adsorb metals from the soil-plant environment. The bioconcentration and translocation factors (BCF and TF) were less than 1, indicating that metal concentration was restricted to maize roots and translocation to shoots. Reactive oxygen species (ROS) intracellularly influence metal interactions with plants. Electron paramagnetic resonance (EPR) was performed to determine hydroxyl radical generation (•OH) in plant segments to assess the dominance of free radicals (FRs). Consequently, the formation of •OH significantly depends on the pyrolysis temperature and the interaction with a contaminated soil-plant environment. Thus, metal transformation can be effectively decreased in the soil-plant environment by applying WB amendments.

Phosphorus Mobilization in Plant–Soil Environments and Inspired Strategies for Managing Phosphorus: A Review

Crop productivity and yield are adversely affected by the deficiency of P in agricultural soil. Phosphate fertilizers are used at a large scale to improve crop yields globally. With the rapid increase in human population, food demands are also increasing. To see that crop yields meet demands, farmers have continuously added phosphate fertilizers to their arable fields. As the primary source of inorganic phosphorous, rock phosphate is finite and the risk of its being jeopardized in the foreseeable future is high. Therefore, there is a dire need to improve plant-available P in soil, using feasible, environmentally friendly technologies developed on the basis of further understanding of P dynamics between soil and plants. This study systemically reviews the mechanism of P uptake and P-use efficiency by plants under starvation conditions. The recent advances in various strategies, especially imaging techniques, over the period 2012–2021 for the measurement of plant-available P are identified. The study then examines how plants fulfill P requirements from tissue-stored P during P starvation. Following this understanding, various strategies for increasing plant-available P in agricultural soil are evaluated. Finally, an update on novel carriers used to improve the P content of agricultural soil is provided.

Impact of buried debris from agricultural biodegradable plastic mulches on two horticultural crop plants: Tomato and lettuce

Biodegradable mulches (BDM) are increasingly valued and used for substituting non-biodegradable plastic mulches polluting agricultural soils. They are tilled into soil, where they fragment and release compounds throughout their biodegradation. The consequences of BDM use on the plant-soil environment have been partially studied with pristine and with artificially-weathered BDM fragments. However, to guarantee safety use of BDM, studies on the BDM debris effects are required. For this, to determine potential effects of the field-weathering BDM on plants, a mesocosm experiment was performed by sowing seeds from two major plant species commonly cultivated with BDM, tomato (Lycopersicon esculentum) and lettuce (Lactuca sativa), in plant pots containing pristine and field-weathered pieces from seven different BDM formulations, one paper mulch, a polyethylene (PE) mulch, and no-mulch control pots.Germination of both plant species was unaffected by any of the mulch treatments; however, PHB (polyhydroxybutyrate)-based BDM fragments severely inhibited tomato and lettuce plant growth, 90 and 95 %, respectively. Moreover, all pristine and field-weathered BDM significantly delayed lettuce plant development. Tomato plant growth progressed better, but growth retardation was also evidenced with most field-weathered BDM treatments. Overall, field-weathered fragments caused stronger effects on plants than the pristine unused ones. No effects were found for PE mulch, either pristine or field-weathered. The obtained results highlight that BDM debris may alter plant development depending on their nature and on their weathering, rather than on their physical presence, and evidence the need to conduct further experiments on the impact of field-weathered BDM on the plant-soil environment.

Analysis of the contribution of Lotus corniculatus to soil carbon content in a rice-pasture rotation system

Productivity in continuous rice cropping agroecosystems (RR) is lower than in rice-pasture rotation agroecosystems with pastures based on legumes (RP). This may be attributed to changes in soil carbon (C) and nitrogen (N) levels. However, there is a lack of quantitative information about the contribution of the legume crop in RP agroecosystems in terms of soil quality indicators. The current study analyzed an RR and an RP in order to contribute to the understanding of the underlying processes involved in C and N dynamics in the soil-plant environment, finding better soil quality indexes in RP than in RR, and an interaction between N and C parameters. The percentage of total N explained 90 % of the C pool index (CPI) variability, and 72 % of the percentage of particulate organic C (%POC) variability. Furthermore, a biological N fixation (BNF) study performed in RP showed that almost 80 % of the N content in the aerial biomass of Lotus corniculatus plants originated from the legume–rhizobia symbiosis. Taken together, our results suggest that the soil N derived from the BNF associated with L. corniculatus plants could be a key factor for increasing soil C content, thereby improving soil structure.

Immobilization of hexavalent chromium in soil-plant environment using calcium silicate hydrate synthesized from coal gangue

The presence of excessive hexavalent chromium (Cr(VI)) in the contaminated soils and plants has become a global environmental issue due to its toxicity and carcinogenicity. This work investigated the feasibility of immobilizing Cr(VI) in the soil-plant environment using calcium silicate hydrate (C–S–H) synthesized from coal gangue. The results revealed that the C–S–H amendment increased soil pH and organic matter (OM), which further promoted Cr(VI) immobilization. Results also revealed that exchangeable and carbonate bound fractions of Cr were either converted into Fe/Mn oxide and OM bound fractions of Cr or hardly released residual fraction of Cr due to C–S–H treatment. The C–S–H accelerated conversion of Cr(VI) into Cr(III) promoting plant growth and alleviating the toxic effect of Cr(VI). Cr(VI) was mainly immobilized and accumulated in the plant roots which resulted in comparatively lower Cr(VI) content in the edible part of plants. The exchangeable fraction of Cr in soil could be used as a bioavailability evaluation index of Cr(VI) in plants. In short, C–S–H was proved to be a practical and environmentally friendly amendment for in-situ immobilization of Cr(VI) contaminated soil.

Characteristics and Applications of Biochar in Soil–Plant Systems: A Short Review of Benefits and Potential Drawbacks

The available literary data suggest the general applicability and benefits of different biochar products in various soil–plant–environment systems. Due to its high porosity, biochar might generally improve the physicochemical and biological properties of supplemented soils. Among the direct and indirect effects are (i) improved water-retention capacity, (ii) enhanced soil organic matter content, (iii) pH increase, (iv) better N and P availability, and (v) greater potential uptake of meso- and micronutrients. These are connected to the advantage of an enhanced soil oxygen content. The large porous surface area of biochar might indirectly protect the survival of microorganisms, while the adsorbed organic materials may improve the growth of both bacteria and fungi. On the other hand, N2-fixing Rhizobium bacteria and P-mobilizing mycorrhiza fungi might respond negatively to biochar’s application. In arid circumstances with limited water and nutrient availability, a synergistic positive effect was found in biochar–microbial combined applications. Biochar seems to be a valuable soil supplement if its application is connected with optimized soil–plant–environment conditions. This work aims to give a general review of the potential benefits and drawbacks of biochar application to soil, highlighting its impacts on the soil–plant–microbe system.

Effects of diverse irrigation with wastewater in soil and plants: assessing the risk of metal to the animal food chain

In District Jhang, farmers use municipal wastewater to irrigate fodder crops as an alternative source to the deficient availability of fresh water. Therefore, the present study selected the three irrigation sources in District Jhang (canal water, ground water and municipal wastewater) to study the iron (Fe) concentration in the soil, fodder crops and ultimately their transfer into the animal body. Analysed Fe concentration varied as 16.40-27.53mg/kg in soil samples, 19.72-30.34mg/kg in fodder crops and 2.49-5.11mg/kg in animals. Analysed Fe concentration in soil was higher on the wastewater irrigation site while canal water-irrigated fodder crop Zea mays exhibit the higher Fe concentration. In animal samples, higher Fe concentration was observed in the cow blood (4.09mg/l), cow hairs (3.39mg/kg) and cow faeces (5.11mg/kg). Results of pollution load index (0.288-0.484mg/kg) and enrichment factor (0.112-0.197mg/kg) indicated that Fe concentration was minimally dispersed and enriched in these sites. Health risk and daily intake values were observed between the 0.029-0.059 and 0.042-0.084mg/kg/day. Bio-concentration factor (0.834-1.47mg/kg) for Fe which was greater than 1 explains that Fe contamination was transferred from the soil to fodder tissues and may raise health issues in the grazing animals if they are continuously exposed to these contaminated forages. Wastewater irrigation in study area has increased the Fe content in soil-plant environment that is a risking factor for animal and human health. Hence, this study recommended that wastewater should be treated prior to their irrigation on agricultural lands.

Spatial Distribution and Influencing Factors of Soil Fungi in a Degraded Alpine Meadow Invaded by Stellera chamaejasme

Alpine meadow degradation causes a notable decrease in palatable grasses and an increase in forbs and toxic plants in recent decades. Stellera chamaejasme is one of the most serious toxic weeds, which exerts an increasing threat on alpine meadow in Qinghai–Tibetan Plateau. Combined DNA sequencing with geostatistics was applied to analyze a typical degraded meadow invaded by S. chamaejasme in Qinghai Province, China. The study aimed to determine the spatial variation of soil fungi and its interrelationship with the plant–soil environment. Alpha diversity and relative abundance of fungal phyla and classes showed moderate or strong spatial dependency and were structured in patches of 19–318 m, and taxonomic composition exhibited much higher spatial variability than alpha diversity. Compared to plant cover, the matching of patch size showed a closer spatial link between soil properties and fungal community. Community coverage, SOM, TN, TP, and TK positively correlated to fungal diversity and taxonomic composition; no direct correlation was found between S. chamaejasme coverage and fungal community. The result suggested significant but weak association between plant–soil properties and soil fungal community at local scale. Patchy pattern of S. chamaejasme may disturb spatial variations of soil properties and fungal community, since S. chamaejasme in higher coverage corresponded to lower TK content, which contributed to a decrease in fungal diversity indirectly.

Phosphorus Dynamics in the Soil–Plant–Environment Relationship in Cropping Systems: A Review

This work performs a review of the relevant aspects of agronomic dynamics of phosphorus (P) in the soil–plant relationship as a community (crop ecophysiology), the effect of environmental conditions and global warming on the redistribution and translocation of P in some crop, and the use of good agricultural practices with the aim of improving the efficiency of the element. The research focuses on Northern Europe, North-Eastern Asia, Oceania, North America, and the tropical area of Latin America. This review covers general research and specific works on P found in the literature, 70% of which date from the last 10 years, as well as some older studies that have been of great relevance as references and starting points for more recent investigations. The dynamics of P in a system implies taking into account genetic aspects of the plant, component of the soil–plant–fertilizer–environment relationship, and use of technologies at the molecular level. In addition, in a climate change scenario, the availability of this element can significantly change depending on whether it is labile or non-labile.

Strategies to Control Human Health Risks Arising from Antibiotics in the Environment: Molecular Modification of QNs for Enhanced Plant-Microbial Synergistic Degradation.

In the present work, a comprehensive screening and evaluation system was established to improve the plant–microbial synergistic degradation effects of QNs. The study included the construction of a 3D-QSAR model, the molecular modification, environmental friendliness and functional evaluation of drugs, degradation pathway simulation, and human health risk assessment. Molecular dynamics was applied to quantify the binding capacity of QNs toward the plant degradation enzyme (peroxidase) and microbial degradation enzymes (manganese peroxidase, lignin peroxidase, and laccase). The fuzzy comprehensive evaluation method was used in combination with the weighted average method for normalization and assigning equal weights to the plant and microbial degradation effect values of the QNs. Considering the synergistic degradation effect value as the dependent variable and the molecular information of the QNs as the independent variable, a 3D-QSAR model was constructed for the plant–microbial synergistic degradation effect of QNs. The constructed model was then employed to conduct the molecular modification, environmental friendliness and functional evaluation, degradation pathway simulation, and human health risk assessment of transformation products using pharmacokinetics and toxicokinetics. The results revealed that the synergistic degradation effect 3D-QSAR (CoMSIA) model exhibited good internal and external prediction ability, fitting ability, stability, and no overfitting phenomenon. Norfloxacin (NOR) was used as the target molecule in the molecular modification. A total of 35 NOR derivatives with enhanced plant–microbial synergistic degradation effect (1.32–21.51%) were designed by introducing small-volume, strongly electronegative, and hydrophobic hydrogen bond receptor groups into the active group of the norfloxacin structure. The environment-friendliness and the functionality of NOR were evaluated prior to and after the modification, which revealed seven environment-friendly FQs derivatives exhibiting moderate improvement in stability and bactericidal efficacy. The simulation of the NOR plant and microbial degradation pathways prior to and after the modification and the calculation of the reaction energy barrier revealed Pathway A (D-17 to D-17-2) and Pathway B (D-17 to D-17-4) as the most prone degradation pathways in plants and Pathway A (D-17 to D-17-1) and Pathway B (D-17 to D-17-4) as the most prone degradation pathways in microorganisms. This demonstrated that the degradation of the modified NOR derivatives was significantly enhanced, with the hydroxylation and piperazine ring substitution reaction playing an important role in the degradation process. Finally, the parameters, including hepatotoxicity, mutagenicity, and rodent carcinogenicity, among others, predicted using the pharmacokinetics and toxicokinetics analyses revealed a significant reduction in the human health risk associated with the modified NOR, along with a considerable reduction in the toxicity of its transformation products, implying that the human health risk associated with the transformation products was reduced remarkably. The present study provides a theoretical basis for novel ideas and evaluation programs for improving the plant–microbial synergistic degradation of the QNs antibiotics for source control and drug design, thereby reducing the residues of these antibiotics and the associated hazard in the complex plant–soil environment, ultimately decreasing the potential risks to human health.

Blood, Hair and Feces as an Indicator of Environmental Exposure of Sheep, Cow and Buffalo to Cobalt: A Health Risk Perspectives

Exposure to toxic metals (TMs) such as cobalt (Co) can cause lifelong carcinogenic disorders and mutagenic outcomes. TMs enter ground water and rivers from human activity, anthropogenic contamination, and the ecological environment. The present study was conducted to evaluate the influence of sewage water irrigation on cobalt (Co) toxicity and bioaccumulation in a soil-plant environment and to assess the health risk of grazing livestock via forage consumption. Cobalt is a very necessary element for the growth of plants and animals; however, higher concentrations have toxic impacts. Measurement of Co in plant, soil and water samples was conducted via wet digestion method using an atomic absorption spectrophotometer. The Co pollution severity was examined in soil, forage crops (Sorghum bicolor Kuntze, Sesbania bispinosa (Jacq.) W. Wight, Cynodon dactylon (L.) Pers., Suaeda fruticosa (L.) Forssk. and Tribulus terrestris L.) in blood, hair and feces of sheep, cow and buffalo from district Toba-Tek-Singh, Punjab, Pakistan. Three sites were selected for investigation of Co level in soil and forage samples. Highest concentration of Co was 0.65 and 0.35 mg/kg occurring in S. bicolor at site I. The sheep blood, cow hair and sheep feces samples showed highest concentrations of 0.545, 0.549 and 0.548 mg/kg, respectively at site I and site II. Bioconcentration factor, pollution load index, enrichment factor and daily intake were found to be higher (0.667, 0.124, 0.12 and 0.0007 mg/kg) in soil, S. bicolor, S. fruticosa and in buffalo, respectively, at site I. It was concluded that forage species irrigated with wastewater are safe for consumption of livestock. However, though the general values were lower than the permissible maximum limit, it was observed that the bioaccumulation in the forage species was higher. Therefore, soil and food chain components should be avoided from trace metal contamination, and other means of nonconventional water resources should be employed for forages irrigation.

Uptake, translocation, weathering and speciation of gold nanoparticles in potato, radish, carrot and lettuce crops

Extensive use of nanomaterials in agriculture will inevitably lead to their release to the environment in significant loads. Thus, understanding the fate of nanoparticles in the soil-plant environment, and potential presence and consequent implication of nanoparticles in food and feed products, is required. We study plant uptake of gold nanoparticles from soil, and their distribution, translocation and speciation (in terms of particle size change and release of ionic Au) in the different plant tissues of four important crops (potato, radish, carrot and lettuce). Our new analytical protocol and experiments show the feasibility of determining the presence, concentration and distribution of nanoparticles in different plant parts, which differ from plant to plant. Critically, we identify the evident capacity of plants to break down (or substantially change the properties of) nanoparticles in the rhizosphere prior to uptake, as well as the evident capacity of plants to reorganize ionic metals as nanoparticles in their tissues. This could lead to nanoparticle exposure through consumption of crops.

Isotope fractionation of zinc in the paddy rice soil-water environment and the role of 2’deoxymugineic acid (DMA) as zincophore under Zn limiting conditions

Non-traditional stable isotope systems are increasingly used to study micronutrient cycling and acquisition in terrestrial ecosystems. We previously proposed for zinc (Zn) a conceptual model linking observed isotope signatures and fractionations to biogeochemical processes occurring in the rice soil environment and we suggested that 2’deoxymugineic acid (DMA) could play an important role for rice during the acquisition of Zn when grown under Zn limiting conditions. This proposition was sustained by the extent and direction of isotope fractionation observed during the complexation of Zn with DMA synthesised in our laboratory. Here we report a new set of experimental data from field and laboratory studies designed to further elucidate the mechanisms controlling Zn isotope fractionation in the rice rhizosphere and the role of DMA. First, we present acidity (pKa) and complexation (logK) constants for DMA with H+ and Zn2+, respectively, using synthetic 2’deoxymugineic acid and show that they are significantly different from previously published data using isolates from plants. Our new set of thermodynamic data allows for a more accurate calculation of the formation of ZnDMA complexes over pH ranges typically found in the rhizosphere of flooded lowland rice soils and in rice plant compartments (xylem, phloem). We show that at pH > 6.5, Zn is fully complexed by DMA and at pH <4.5 fully dissociated. This has important implications, i.e. that in alkaline paddy soils, DMA can strip Zn from soil solids (organic and inorganic) and that ZnDMA complexes are stable at the root interface if the pH is alkaline and in the phloem and xylem of the rice shoot. Second, we present a new set of Zn isotope data in rice grown in alkaline soils with low Zn availability with and without Zn addition. We used two genotypes not tested to date, i.e. A69–1, tolerant to low Zn supply, and IR26, sensitive to low Zn supply. We confirm previous findings that, in contrast to observations with rice grown in hydroponic studies, no isotopically light Zn is taken up into the shoot irrespective of Zn fertilization and that isotopically heavier Zn is taken up by rice grown in soils with low Zn supply. Third, we determined the isotope fractionation isotherm for Zn during absorption on goethite, representing the iron phase (plaque) typically forming on rice roots, in acidic solution. The negative Zn isotope fractionation observed (i.e., Δ66Zngoethite-solution < 0, where Δ66Zngoethite-solution = (δ66Zn of goethite) – (δ66Zn of solution)) is in contrast to the positive isotope fractionation (Δ66Zngoethite-solution > 0) detected during adsorption of Zn on goethite in alkaline solutions or between root and soil solution in rice grown in alkaline soils. We show that removal of different Zn species from solution and changes in the Zn coordination control extent and direction of isotope fraction during adsorption. Using the new set of results and combining it with recent findings from the literature, we present a refined conceptual model linking biogeochemical processes to Zn isotope fractionation in the rice soil system. Our results confirm the importance of root induced chemical changes in the rhizosphere of rice growing in soils with low Zn availability, demonstrate the unique ability of isotope signatures to deconvolve geochemical processes and conditions in the plant-soil environment and support the hypothesis of an important role of DMA in Zn acquisition under Zn limiting conditions.