N-Fertilizer (Urea) Enhances the Phytoextraction of Cadmium through Solanum nigrum L

Salt stress amelioration and nutrient strengthening in spinach (Spinacia oleracea L.) via biochar amendment and zinc fortification: seed priming versus foliar application

Soil salinity is a major nutritional challenge with poor agriculture production characterized by high sodium (Na+) ions in the soil. Zinc oxide nanoparticles (ZnO NPs) and biochar have received attention as a sustainable strategy to reduce biotic and abiotic stress. However, there is a lack of information regarding the incorporation of ZnO NPs with biochar to ameliorate the salinity stress (0, 50,100 mM). Therefore, the current study aimed to investigate the potentials of ZnO NPs application (priming and foliar) alone and with a combination of biochar on the growth and nutrient availability of spinach plants under salinity stress. Results demonstrated that salinity stress at a higher rate (100 mM) showed maximum growth retardation by inducing oxidative stress, resulted in reduced photosynthetic rate and nutrient availability. ZnO NPs (priming and foliar) alone enhanced growth, chlorophyll contents and gas exchange parameters by improving the antioxidant enzymes activity of spinach under salinity stress. While, a significant and more pronounced effect was observed at combined treatments of ZnO NPs with biochar amendment. More importantly, ZnO NPs foliar application with biochar significantly reduced the Na+ contents in root 57.69%, and leaves 61.27% of spinach as compared to the respective control. Furthermore, higher nutrient contents were also found at the combined treatment of ZnO NPs foliar application with biochar. Overall, ZnO NPs combined application with biochar proved to be an efficient and sustainable strategy to alleviate salinity stress and improve crop nutritional quality under salinity stress. We inferred that ZnO NPs foliar application with a combination of biochar is more effectual in improving crop nutritional status and salinity mitigation than priming treatments with a combination of biochar.

Unveiling the Rising Threat of Cadmium Pollution and Alarming Health Risks Associated with the Consumption of 15 Commercially Important Fish Species in the Middle Stretch of River Ganga, at Patna, India

Among environmental contaminants, the rising level of cadmium in freshwater ecosystems is one of the most significant global concerns. The study addresses the current pollution status of cadmium in the middle stretch of River Ganga and explores the potential hazard associated with the consumption of 15 commercially important fish species by the inhabitants. Together 72 water and sediment samples were analyzed from the four representative sampling sites of River Ganga after the surveillance of major anthropogenic stressors. The concentration of cadmium ranges from 0.003 to 0.011 mg/l and 0.2 to 3.48 mg/kg in water and sediment respectively in 2022. The average concentration of cadmium was recorded to be the highest in Channa punctatus (1.35 mg/kg), followed by Rita rita = Johnius coitor (1.15 mg/kg), and the lowest in Labeo bata (0.2 mg/kg). The finding highlights greater exposure duration and feeding preferences of fish species have played a significant role in the bioaccumulation of the metal in the riverine system. Notably, the domestic effluents, agricultural runoffs, and pollutants brought along by the tributaries of River Ganga are identified as the main anthropogenic stressors for the moderate to considerably polluted status of the River Ganga. The target hazard quotient (THQ) and target carcinogenic risk (TCR) have revealed a higher susceptibility to cadmium contamination in children followed by females, and males. In addition, hierarchical cluster analysis (HCA) has noted intake of Rita rita, Channa punctata, Puntius sophore, and Johnius coitor could be more detrimental to children's health than adults.

Enhancing Phytoextraction Potential of Brassica napus for Contaminated Dredged Sediment Using Nitrogen Fertilizers and Organic Acids

Dredged sediment contaminated with heavy metals can be remediated through phytoremediation. The main challenge in phytoremediation is the limited availability of heavy metals for plant uptake, particularly in multi-contaminated soil or sediment. This study aimed to assess the effect of the nitrogen fertilizers (ammonium nitrate (AN), ammonium sulfate (AS), and urea (UR)), organic acids (oxalic (OA) and malic (MA) acids), and their combined addition to sediment on enhancing the bioavailability and phytoremediation efficiency of heavy metals. The sediment dredged from Begej Canal (Serbia) had high levels of Cr, Cd, Cu, and Pb and was used in pot experiments to cultivate energy crop rapeseed (Brassica napus), which is known for its tolerance to heavy metals. The highest accumulation and translocation of Cu, Cd, and Pb were observed in the treatment with AN at a dose of 150 mg N/kg (AN150), in which shoot biomass was also the highest. The application of OA and MA increased heavy metal uptake but resulted in the lowest biomass production. A combination of MA with N fertilizers showed high uptake and accumulation of Cr and Cu.

Effects of willow and Sedum alfredii Hance planting patterns on phytoremediation efficiency under AC electric field

Heavy metal contamination to soil is tricky due to its difficult removal, long retention time, and biomagnified toxicity. The green and low-cost phytoremediation with electric field treatment and planting pattern selection is an emerging and more effective approach to remove heavy metals from soils. In this study, alternating current (AC) electric field-assisted phytoremediation was examined with different planting patterns, i.e., monoculture willow (Salix sp.), monoculture Sedum alfredii Hance, and interplanting of willow and S. alfredii. AC electric field greatly increased phytoremediation efficiency to soil cadmium (Cd) regardless of planting patterns, either single plant species of willow or S. alfredii. The Cd removal capacity of willow and S. alfredii raises apparently under 0.5 V cm-1 AC electric field. Under different planting patterns of AC electric field treatment, Cd accumulation in the whole plant by interplanting was 5.63 times higher than monoculture willow, but only 0.75 times as high as monoculture S. alfredii. The results showed that AC electric field-assisted interplanting of willow and S. alfredii is a promising remediation technique for efficiently clean-up Cd-contaminated soil.

Responses of the root morphology and photosynthetic pigments of ryegrass to fertilizer application under combined petroleum-heavy metal stress

With developments in industry, petroleum and heavy metal pollution are increasingly affecting soil, significantly harming the environment, biosecurity, and human health. Therefore, the remediation of contaminated soil is becoming increasingly important. In this study, ryegrass (Lolium perenne L.) was planted in petroleum-heavy metal co-contaminated soil with the application of nitrogen and phosphorus fertilizers. Three treatments were set up: uncontaminated soil + ryegrass (SH); petroleum-heavy metal co-contaminated soil + ryegrass (SPGH); and petroleum-heavy metal co-contaminated soil + ryegrass + nitrogen and phosphorus fertilizer (SPGH + NP). The results showed that the petroleum-heavy metal co-contamination promoted increases in the root length, surface area, volume, and diameter of ryegrass roots, increasing the below-ground biomass and decreasing the photosynthetic pigment content in the early stages of the experiment. The ratios of chlorophyll a/b and chlorophyll/carotenoid also increased. However, the application of fertilizer reduced the length, surface area, volume, and diameter of ryegrass roots in the co-contaminated soil, and the below-ground biomass decreased while the above-ground biomass increased. Furthermore, the photosynthetic pigment content was significantly higher than that in the unfertilized treatment and the chlorophyll a/b ratio decreased while the chlorophyll/carotenoid ratio increased. Therefore, fertilizers could alleviate the toxic effects of petroleum-heavy metal combined pollution on ryegrass roots and promote the synthesis of chlorophyll and other pigments, thus reducing the inhibitory effect of petroleum-heavy metal combined pollution on ryegrass growth and facilitating the remediation of the polluted soil.

Nitrogen and Phosphorus Fertilizer Increases the Uptake of Soil Heavy Metal Pollutants by Plant Community

Soil heavy metal pollution is widespread around the world. Compared with hyperaccumulation plants, non-hyperaccumulator plant communities have many advantages in the remediation of heavy metals pollution in soil. The application of nitrogen (N) and phosphorus (P) is inexpensive and convenient, which can promote the growth of plant. N and P fertilizer might increase plant community remediation of heavy metal polluted soils. In our study, the effects of N and P fertilizer on remediation of soil Cd, Cu, Pb pollution by plant community were studied through a greenhouse experiment. Our results indicated that addition of N, P and N + P fertilizer increased plant community aboveground biomass. Simultaneously, addition of N and P fertilizer increased the accumulation of heavy metals in aboveground of the plant community and accelerated plants absorption soil heavy metals. Among them, N fertilizer had the best effect. Our results provide an inexpensive method for remediation heavy metal pollution of contaminated farmland, abandoned land and mine tailings, etc.

Nitrogen and sulfur fertilizers promote the absorption of lead and cadmium with Salix integra Thunb. by increasing the bioavailability of heavy metals and regulating rhizosphere microbes

Fertilization is an effective agronomic strategy to improve the efficiency of phytoextraction by Salix integra Thunb. However, the specific effects of the simultaneous application of nitrogen (N) and sulfur (S) fertilizers in the rhizosphere remain unclear. We investigated the bioavailability of lead (Pb) and Cadmium (Cd) along with the microbial metabolic functions and community structure in the rhizosphere soil of S. integra after the application of N (0, 100, and 200 kg·ha⁻¹·year⁻¹) and S (0, 100, and 200 kg·ha⁻¹·year⁻¹) fertilizers for 180 days. The simultaneous application of N and S fertilizers significantly enhanced the absorption of Pb and Cd by S. integra, whereas this effect was not observed for the single application of N or S fertilizer. The contents of acid-soluble Pb and Cd in the rhizosphere soil significantly increased after either single or combined fertilize applications. The microbial metabolic activity was enhanced by the N and S fertilizers, whereas the microbial diversity markedly decreased. The metabolic patterns were mainly affected by the concentration of N fertilizer. The dominant fungi and bacteria were similar under each treatment, although the relative abundances of the dominant and special species differed. Compared to the N200S100 and N200S200 treatments, the N100S100 and N100S200 treatments resulted in fewer pathogenic fungi and more rhizosphere growth-promoting bacteria, which promoted phytoremediation by S. integra. Redundancy analysis indicated that the pH and nitrate content were the key factors affecting the structure of the microbial community. Collectively, the results suggest interactive effects between N and S fertilizers on the rhizosphere soil, providing a potential strategy for plant-microbial remediation by S. integra.

Biochar-based compost: a bibliometric and visualization analysis

The co-application of biochar compost as organic amendment for crop production and soil remediation has gained momentum due to their positive effect on plant growth and soil quality improvement. The application of biochar and compost which are green and cost-effective soil remediators would promote the availability and distribution of food, planetary conservation, alleviate poverty, and enhance the attainment of Sustainable Millennium Development Goals (SDGs). A bibliometric analysis was conducted to overview research on biochar compost from 2011 to 2021. Two hundred and fifty-four research papers were retrieved from the Scopus database and analyzed using VOS viewer. Analysis revealed that 217 (85.43%) were articles, 21 (8.27%) were conference papers, and 12 (4.72%) were review papers. The results showed an exponential increase in the number of publications. The most productive countries in the investigated subject were China (49), followed by USA (36), Australia (29), Italy (28), Germany (25), and Indonesia (20). After the search terms, 'soil,' which had links with keywords like 'soil fertility,' 'soil quality,' 'soil pollution,' 'phosphorus,' 'nitrogen,' 'maize,' 'greenhouse gas,' etc., had the highest occurrences (94). From the results of the current hotspot research in the field, the effect of biochar-compost mixture and co-composted biochar on soil remediation is currently being studied by several researchers. Biochar and compost incorporation in soil reduce the uptake of pollutants by plants which consequently increase essential nutrients for plant and soil productivity.

Phosphorus Fertilizers Enhance the Phytoextraction of Cadmium through Solanum nigrum L

Cadmium (Cd) toxicity strongly influences plants growth and seed germination in crop plants. This pot trial had aimed evaluate the benefits of two different kinds of phosphorus (P)-fertilizer in the phytoremediation of Cd by Solanum nigrum L. The current pot experiment was conducted to evaluate the role of P-fertilizers in phytoremediation of Cd by Solanum nigrum L. Single superphosphate (SSP) contain 7 to 9% P and Di-ammonium Phosphate (DAP) contain 46% P had been applied in single and combine form in soil with different ratios (0:0, 100:0, 0:100, 50:50%) accompanied by diverse Cd levels (0, 25, 50 mg kg⁻¹). Three weeks seeding were transferred into pots, and plants had been harvested afterward seventy days of growth in the pots. Significantly inhibited plant growth was observed in shoots and roots of Cd contaminated plants. Cadmium stress had stimulated oxidative stress in subjected plants. However, supplementation of P-fertilizers in an optimum manner significantly increased plant biomass along with enhancing antioxidants enzymatic activities and inhibiting oxidative stress. Maximum plant-growth had been noted in SSP + DAP supplemented plants in contrast to single SSP, DAP supplemented plants. Higher Cd concentrations observed in SSP + DAP supplemented plants over single treatment. It has been concluded that combination of SSP + DAP might be a better option to improve growth as well as uptake capacity of Solanum nigrum L. under Cd stress. However, a field study is recommended for detailed future investigations.

Effects of arbuscular mycorrhizal fungi on the growth and toxic element uptake of Phragmites australis (Cav.) Trin. ex Steud under zinc/cadmium stress

Arbuscular mycorrhizal fungi (AMF) play an important role in improving plant tolerance and accumulation of zinc (Zn) and cadmium (Cd). The growth, physiology and absorption of elements and transport in Phragmites australis (P. australis) were investigated under Zn and Cd stress to identify the transport mechanisms of toxic trace elements (TE) under the influence of AMF. Thus, AMF were observed to alleviate the toxic effects of Zn and Cd on P. australis by increasing plant biomass and through different regulatory patterns under different TE concentrations. The activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased under Zn stress, and the activities of SOD, catalase (CAT), peroxidase (POD), and APX significantly increased under high concentrations of Cd. AMF differ in their strategies of regulating the transport of different metals under TE stress. Under Zn stress, the concentration of Zn in P. australis decreased by 10-57%, and the effect on Zn translocation factor (TF_Zn) was concentration-dependent. AMF increased the TF_Zn under low concentration stress, but decreased under high concentration stress. Under Cd stress, the concentration of Cd increased by as much as 17-40%, and the TF_Cd decreased. AMF were also found to change the interaction of Zn×Cd. In the absence of AMF, Cd exposure decreased the Zn concentrations in P. australis at Zn_100 mg/L and Zn_300 mg/L, while it increased the contents of Zn at Zn_700 mg/L. The opposite trend was observed following treatment with AMF. However, regardless of the concentration of Cd, the addition of Zn decreased the concentration of Cd in both treatments in both the presence and absence of AMF. Under different TE stress conditions, the regulation of metal elements by AMF in host plants does not follow a single strategy but a trade-off between different trends of transportations. The findings of our study are important for applying AMF-P. australis systems in the phytoremediation of Zn-Cd co-contaminated ecosystems.

Organic nitrogen modulates not only cadmium toxicity but also microbial activity in plants

It is known that organic nitrogen may modify uptake and toxicity of metals but direct metabolic and microbial comparison of various organic N sources is not available. We therefore studied comparative impact of additional N sources (nitrate, urea or allantoin as 1 mM of N for each compound in addition to 15 mM of inorganic N in the Hoagland solution) on Cd toxicity and microbial activity in common crop cucumber. Organic N significantly elevated the growth, chlorophyll content and photosynthetic activity under Cd excess in comparison with inorganic N though the impact on Cd uptake was negligible. Both organic N compounds also affected accumulation of mineral nutrients, total N, amino acids, and protein content in Cd-stressed plants. Among organic acids, mainly allantoin and partially urea affected accumulation of citrate and tartrate. The most notably, we detected that allantoin was decomposed even within 24 h by microbes into the urea, but it significantly elevated rhizosphere microbial activity. All these data indicate that allantoin is metabolized by plants/microbes into the urea and that it affects microbes mainly in the rhizosphere, which could contribute to amelioration of Cd toxicity.

The predominant role of pectin in binding Cd in the root cell wall of a high Cd accumulating rice line (Oryza sativa L.)

Cell wall (CW) plays an important role in Cd accumulation in roots of metal-tolerant plants, including rice. The role of CW polysaccharides, especially pectin, in binding Cd in roots of a high Cd accumulating (HA) rice line of Lu527-8 and a non-high Cd accumulating (NHA) rice line of Lu527-4 was investigated in this study. About 59%-63% of Cd in roots of the two rice lines was bound to CWs, indicating that CW was the main site for Cd accumulation in roots of the two rice lines. Cd adsorbed on the root CWs of the HA was 1.1-1.2 times more than that of the NHA, demonstrating the root CWs of the HA showed greater Cd binding ability. Cd exposure induced more Cd accumulation in pectin and hemicellulose in the HA. In particular, up to 65% of Cd accumulation in root CWs of the HA was observed in pectin. The removal of pectin lead to a 50% decrease for the amounts of Cd adsorption on root CWs of the HA, indicating that pectin was the major binding site for Cd in root CWs of the HA. The HA showed greater pectin methylesterase activities, resulting in lower degree of pectin methylesterification along with more low-methylesterified pectins in root CWs than the NHA. The more accumulation of low-methylesterified pectins in CWs induced by Cd contributed greatly to the high Cd accumulation in roots of the HA rice line of Lu527-8.