In situ immobilization is a potential approach that can be used to remediate low-to-medium levels of heavy-metal in contaminated-soil. There is little known about how modifications to soil characteristics may affect Pb\'s release from soil. The four different amendments, triple-superphosphate and attapulgite were combined in Ad-1; zeolite and triple-superphosphate were in Ad-2; hydroxyapatite and humus were in Ad-3; and nano-carbon. These amendments are mostly made of phyllosilicate minerals, humus, base minerals, and nano-carbon, respectively. Results revealed that the test amendments\' maximal Pb-adsorption capacity varied from 7.47 to 17.67 mg g-1. Surface precipitation and ion-exchange were found to be the main mechanisms for Pb-adsorption by Ad-1 and Ad-2, while Ad-3 and Ad-4 were promising among the all, according to analysis of the modifications both before and after Pb loading. When the pH dropped (7-1) or the ion-strength rose (0-0.2 M), there was a discernible rise in the Pb-desorption percentages from the amendments. It was determined that Ad-3 and Ad-4 were more effective in situ immobilizing lead in contaminated-soils because of their high adsorption capacities (12.82 and 17.67 mg g-1) and low-desorption percentages (4.46-6.23%) at ion-strengths of 0.01-0.1 mol L-1 and pH levels ranging from 5 to 7.
This study pioneers a comprehensive exploration into the efficacy of novel soil amendments, Ad-3 and Ad-4 crafted from phyllosilicate minerals, humus, base minerals, and nano-carbon, showcasing their unprecedented potential in mitigating lead pollution. By delving into the intricate mechanisms of lead adsorption and desorption within treated soils, this research fills a critical gap in understanding how modifications to soil characteristics can influence the secondary release of lead, thus providing essential insights for tailored in situ remediation strategies to safeguard both plant and human health in lead-endangered environments.

A novel adsorbent, calcium alginate-modified HAP (Hydroxyapatite)-wood ear mushroom sticks biochar (CA-HAPMB), was synthesized to enhance the immobilization of Cd and Pb in soil. Over 150 days, applying CA-HAPMB at concentrations of 0%-3% in contaminated soils from Chenzhou City in Hunan Province (CZ) and Shenyang City in Liaoning Province (SY) resulted in decreased effective concentrations of Cd and Pb. Specifically, in CZ soil, Cd and Pb decreased by 30.9%-69.3% and 31.9%-78.6%, respectively, while in SY soil, they decreased by 27.5%-53.7% and 26.4%-62.3%, respectively. Characterization results, obtained after separating CA-HAPMB from the soil, indicate that complexation, co-precipitation, and ion exchange play crucial roles in the efficient immobilization of Cd and Pb by CA-HAPMB. Additionally, adjusting the amount of CA-HAPMB added allows modulation of soil pH, leading to increased soil organic matter and nutrient content. Following treatment with CA-HAPMB for immobilizing Cd and Pb, soil bacteria abundance and diversity increased, further promoting heavy-metal immobilization.

Veterinary antibiotics have become an emerging pollutant in water and wastewater sources due to excess usage, toxicity and resistance to traditional water and wastewater treatment. The present study explored the degradation of a model antibiotic- Florfenicol (FF) using electrochemical oxidation (EO) with Ti-RuO2/IrO2 anode. The anode material was characterized using SEM-EDS studies expressing stable structure and optimal interaction of the neighboring metal oxides with each other. The EDS results showed the presence of Ru, Ir, Ti, O and C elements with 6.44%, 2.57%, 9.61%, 52.74% and 28.64% atomic weight percentages, respectively. Optimization studies revealed pH 5, 30 mA cm-2 current density and 0.05 M Na2SO4 for 5 mg L-1 FF achieved 90% TOC removal within 360 min treatment time. The degradation followed pseudo-first order kinetics. LC-Q-TOF-MS studies revealed six predominant byproducts illustrating hydroxylation, deflourination, and dechlorination to be the major degradation mechanisms during the electrochemical oxidation of FF. Ion chromatography studies revealed an increase in Cl-, F- and NO3- ions as treatment time progressed with Cl- decreasing after the initial phase of the treatment. Toxicity studies using Zebrafish (Danio rerio) embryo showed the treated sample to be toxic inducing developmental disorders such as pericardial edema, yolk sac edema, spinal curvature and tail malformation at 96 h post fertilization (hpf). Compared to control, delayed hatching and coagulation were observed in treated embryos. Overall, this study sets the stage for understanding the effect of mixed metal oxide (MMO) anodes on the degradation of veterinary antibiotic-polluted water and wastewater sources using electrochemical oxidation.

Under the dual constraints of economic development and ecological carrying capacity, it is necessary to explore more technical means to achieve carbon neutrality and peak in China. Plants are important carriers of terrestrial and marine carbon sink systems, whereas phytoremediation is also a scientific method to remedy environmental pollution. However, the current studies mostly focus on the single aspect of plant carbon sequestration (including both the reduction of pollutant concentrations in environmental media and degradation of pollutants) or plant pollution reduction, without considering the dual benefits of plant pollution reduction and carbon sequestration. In order to explore the carbon neutral effect of plants, we focused on the pollution reduction and carbon sequestration effect of carbon neutral plants and its progress and evaluated the pollution reduction and carbon sequestration potential of carbon neutral plants and other organisms (such as animals and soil microorganisms) and environmental functional materials. The mechanisms underlying the synergistic coupling of carbon neutral plants and animals, microorganisms, and environmental functional materials and ecosystems in reducing pollution and carbon sequestration were also explored. Finally, we proposed constructive prospects for future research on the effects of carbon neutral plants on pollution reduction and carbon sink.

Chemical stabilization is frequently used to stabilize lead (Pb) or arsenate (As), but faces challenges in Pb-As co-contaminated soils because of the antagonistic reactions between chemical stabilizers and contaminants. In this work, we innovated an effective and cost-efficient stepwise steam flash heating (SSFH) strategy to simultaneously immobilize Pb and As, and unraveled the underlying mechanisms. The combination of 1.5% Ca(H2PO4)2 and 2% Fe2(SO4)3 only decreased 1.99% Pb by toxicity characteristic leaching procedure (TCLP-Pb) but increased 17.8% of TCLP-As due to the antagonistic effects. SSFH with Ca(H2PO4)2 in the first step and Fe2(SO4)3 in the second step achieved the minimal TCLP-Pb and TCLP-As of 0.778 and 0.327 mg/L, respectively. It also reduced 69.8% of leachable As in 100-year acid rain simulation, indicating a favorable long-term stabilization performance. Additionally, SSFH approach reduced 43.2% stabilizer dosage and 14.9% cost. X-ray absorption near edge structure (XANES) documented that the stepwise SFH promoted the transformation of Pb(NO3)2 and NaAsO2/NaAsO3/As2O3/As2O5 into stable Pb3(PO4)2 and FeAsO4, preventing the formation of AsO43- and FePO4. Our findings proved the state-of-the-art SSFH approach and unraveled its mechanisms to stabilize Pb and As co-contamination in soils, offering a green and sustainable remediation alternative for the management of heavy metal contaminated sites. ENVIRONMENTAL IMPLICATION: A novel stepwise SFH approach can be applied to overcome the stabilizer antagonist effects by separately immobilizing Pb and As in two sequential steps. It also decreased 43.2% of stabilizer dosage and 14.9% of cost comparing to conventional chemical stabilization. This approach can be used for other metal co-contaminated soils facing similar antagonistic challenges, and our work raises a state-of-the-art solution for cost-effective, green and sustainable remediation practices.

This study explored the redox-mediated changes in a lead (Pb) contaminated soil (900 mg/kg) due to the addition of solar cell powder (SC) and investigated the impact of biochar derived from soft wood pellet (SWP) and oil seed rape straw (OSR) (5% w/w) on Pb immobilization using an automated biogeochemical microcosm system. The redox potential (Eh) of the untreated (control; SC) and biochar treated soils (SC + SWP and SC + OSR) ranged from -151 mV to +493 mV. In SC, the dissolved Pb concentrations were higher under oxic (up to 2.29 mg L-1) conditions than reducing (0.13 mg L-1) conditions. The addition of SWP and OSR to soil immobilized Pb, decreased dissolved concentration, which could be possibly due to the increase of pH, co-precipitation of Pb with FeMn (hydro)oxides and pyromorphite, and complexation with biochar surface functional groups. The ability and efficiency of OSR for Pb immobilization were higher than SWP, owing to the higher pH and density of surface functional groups of OSR than SWP. Biochar enhanced the relative abundance of Proteobacteria irrespective of Eh changes, while the relative abundance of Bacteroidota increased under oxidizing conditions. Overall, we found that both OSR and SWP immobilized Pb in solar panel waste contaminated soil under both oxidizing and reducing redox conditions which may mitigate the potential risk of Pb contamination.

Cadmium (Cd) is a heavy metal that significantly impacts human health and the environment. Microorganisms play a crucial role in reducing heavy metal stress in plants; however, the mechanisms by which microorganisms enhance plant tolerance to Cd stress and the interplay between plants and microorganisms under such stress remain unclear. In this study, Oceanobacillus picturae (O. picturae) was isolated for interaction with soybean seedlings under Cd stress. Results indicated that Cd treatment alone markedly inhibited soybean seedling growth. Conversely, inoculation with O. picturae significantly improved growth indices such as plant height, root length, and fresh weight, while also promoting recovery in soil physiological indicators and pH. Metabolomic and transcriptomic analyses identified 157 genes related to aspartic acid, cysteine, and flavonoid biosynthesis pathways. Sixty-three microbial species were significantly associated with metabolites in these pathways, including pathogenic, adversity-resistant, and bioconductive bacteria. This research experimentally demonstrates, for the first time, the growth-promoting effect of the O. picturae strain on soybean seedlings under non-stress conditions. It also highlights its role in enhancing root growth and reducing Cd accumulation in the roots under Cd stress. Additionally, through the utilization of untargeted metabolomics, metagenomics, and transcriptomics for a multi-omics analysis, we investigated the impact of O. picturae on the soil microbiome and its correlation with differential gene expression in plants. This innovative approach unveils the molecular mechanisms underlying O. picturae\'s promotion of root growth and adaptation to Cd stress.

Phosphogypsum (PG) is the produced solid waste during phosphorus (P) extraction from phosphate rocks. PG is featured by its abundant PO43- and SO42-. This study investigated the utilization of PG as a material for lead (Pb) remediation, with the assistance of functional fungus. Aspergillus niger (A. niger) is a typical phosphate-solubilizing fungi (PSF), which has high ability to secret organic acids. Oxalic acid is its major secreted organic acid, which is often applied to enhance the P release from phosphate minerals. In this study, synthetic oxalic acid increased the immobilization rate of Pb2+ up to >99 % with the addition of PG. Then, it was observed that biogenic oxalic acid from A. niger can achieve comparable remediation effects. This was due to that PG could provide sufficient P for fungal growth, which allowed sustainable remediation. Subsequently, oxalic acid secreted by A. niger significantly increased the release of active P from PG, and then induced the formation of PPb minerals. In addition, other metabolites of A. niger (such as tyrosine-like substance) can also be complexed with Pb2+. Simultaneously, A. niger did not induce evidently elevation water-soluble fluorine (F) as PG contained abundant Ca2+. Moreover, this study elucidated that oversupply of PG promoted the formation of anglesite (Ksp = 1.6 × 10-8, relatively unstable), whereas the formation of lead oxalate (Ksp = 4.8 × 10-10, relatively stable) was reduced. This study hence shed a bright light on the sustainable utilization of PG for fungus-assisted remediation of heavy metals.

As of now, submerged plants and biochar have demonstrated significant benefits in aquaculture pond sediment remediation. However, there is limited research on the synergistic effects of biochar and submerged plants in mitigating hydrophobic organic contaminant (HOC) accumulation in aquaculture benthic organisms and in controlling the nutrient (nitrogen and phosphorus) levels in aquaculture water. This study assesses a submerged plant-biochar system\'s efficacy in removing HOCs from simulated freshwater aquaculture ponds. Vallisneria natans was planted in sediment with varying levels of wheat straw biochar, while Corbicula fluminea served as the targeted benthic organism. The bioaccumulation experiment identified the optimal biochar ratio for the Vallisneria natans-biochar system in controlling HOCs in aquaculture products. Analyses included final accumulation concentrations in benthic organisms, changes in freely-dissolved concentrations in aquaculture sediment, and a mass balance calculation to explore key factors in their removal from the system. Results indicated that the Vallisneria natans-1.5% biochar composite system achieved optimal control of HOCs in sediment and aquaculture products. Biochar addition to the sediment in the composite system demonstrated a \"promotion with low addition, inhibition with high addition\" effect on Vallisneria natans growth. Notably, the addition of 1.5% biochar (VN1.5 group) significantly promoted the growth of Vallisneria natans leaves and roots. Comparing the final pollutant proportions in different environmental media, concentrations in water (0.20%-1.8%), clam accumulation (0.032%-0.11%), and plant absorption (0.10%-0.44%) constituted a minimal portion of the overall pollutant load in the system. The majority of pollutants (24%-65%) were degraded in the aquaculture environment, with microbial degradation likely playing a predominant role. Bacterial phyla, particularly Proteobacteria and Firmicutes, were identified as potential direct contributors to pollutant degradation in the Vallisneria natans-biochar system.

Although oilseed rape is frequently used as an alternative planting crop in the phytoremediation of cadmium (Cd)-contaminated agricultural land, methods for screening excellent oilseed rape varieties in this regard are inadequate. Herein, we developed a screening method that incorporates Cd accumulation, distribution, and removal, economic output, adaptability to Cd-contaminated agricultural land, and trace element variation. A Cd-adaptability index (Cd-AI) based on 10 agronomic traits was used to measure the adaptability of varieties to Cd-contaminated agricultural land. Moreover, to simplify the evaluation of adaptability, yield, biomass, and pod number with high weightings were selected to construct a discriminant function for Cd-contaminated agricultural land adaptability (correctly classified 94.20%). In a 2 year field trial, we evaluated 225 oilseed rape varieties, among which we identified two promising low-Cd-accumulating and two Cd-remediating varieties. For the low-Cd-accumulating varieties (HuYou17 and DeXingYou558), we obtained grain bioaccumulation factor (BAF) values of 0.07 and 0.08, BAFsoil-stalk values of <1, and economic outputs of RMB 25,054 and 32,292 yuan hm-2, respectively. Similarly, the Cd-remediating varieties (ZaoZa8 and YuYou61) were characterized by BAFsoil-stalk values of 4.65 and 3.61, BAFsoil-grain values of 0.16 and 0.16, Cd removals of 69.02 and 58.25 g hm-2, and economic outputs of RMB 31,189 and 24,962 yuan hm-2, respectively. Compared with the control variety, we detected lower uptakes of multiple trace elements (3-43%) in the low-Cd-accumulating varieties, whereas the Cd-remediating varieties were characterized by 15.40% and 8.30% increases in the accumulation of magnesium and zinc, respectively. Our findings augment the evaluation indices used for evaluating oilseed rape varieties and provide valuable insights from the perspectives of varietal screening and promotional application. The effective varieties identified have application potential for safe production and the remediation of agricultural land without interrupting annual agricultural production, and provide an economically sustainable approach for the utilization of Cd-contaminated agricultural land.