Lead (Pb) leaching in sludge-amended soils is a prominent issue. While amide-functionalized covalent organic framework (COF-PA) has shown good Pb adsorption performance, its applicability potential, remediation mechanisms in heavy metal-contaminated soils remain unclear. Herein, we optimized the preparation process of COF-PA via a nano-silicon templating method. COF-PA showed exceptional Pb-selective adsorption, with a 223 mg/g capacity (59 % higher than the non-template approach), 67-fold faster adsorption rate, and a high selectivity coefficient (756) in mixed metal systems. Spectral analysis and theoretical studies have shown that the affinity of COF-PA for lead is the result of the coordination between lead and the amide. DFT calculations indicate that the selectivity of COF-PA for Pb stems from the electronic-geometric synergistic mechanism. In this case, COF-PA exhibits good adsorption performance for Pb in complex environments. The 60-day pot experiment showed 0.25-3 mg/g COF-PA reduced Pb leaching by 69 %-87 % (0.5 mg/g dose met Class IV groundwater standards), lowered Pb plant accumulation by only 15-26 %, and exhibited excellent soil microecosystem compatibility. This study demonstrates the high efficacy of COF-PA for Pb immobilization in contaminated soils, revealing the multi-dimensional synergy mechanism among the electrons, geometries, functional groups and pore structures. The results provide a precise, selective method for soil heavy metal control (especially single-metal contamination) and insights for targeted remediation strategies.

Sludge land application is limited by heavy metal leaching, particularly Pb and Cu. Conventional stabilization techniques often lack the precision and efficiency needed for precise metal immobilization. This study developed a novel polysaccharide-based stabilizer, Azyl@SA-CCS, which demonstrated exceptional adsorption capacities of 333 mg g- 1 for Pb2+ and 69.0 mg g- 1 for Cu2+. The selectivity coefficients (Kd) for Pb2+ and Cu2+ were 20-65 times and 5.9-18.8 times higher than for competing ions (Zn2+, Cd2+, Ni2+), respectively. FTIR spectroscopy and DFT calculations revealed that abundant oxygen-containing functional groups generate negatively charged binding domains, enabling strong coordination with target ions. Structural reconstruction after ion re-adsorption further confirmed the material's intrinsic preference for Pb2+ and Cu2+. Pot experiments and leaching tests verified its high immobilization efficiency, while high-throughput sequencing confirmed minimal disturbance to soil microbial diversity, highlighting its environmental compatibility. This work establishes both a theoretical framework and a scalable technology for precise, eco-friendly heavy-metal stabilization in soils, suggesting a promising strategy for sustainable sludge management.

Copper (Cu) contamination in soils, especially sludge-made nutrient soils, poses environmental and agricultural risks due to its high bioavailability and toxicity. Current stabilization methods often lack efficiency and selectivity. Here, we developed a cysteine-modified chitosan composite (Cys-CS) as an eco-friendly stabilizer for targeted Cu remediation. In the single-metal system, Cys-CS's adsorption capacity for Cu gradually increases as solution pH rises from 3.5 to 6.5, reaching the maximum at pH near 6.5, with a Langmuir maximum adsorption capacity of 97.8 mg/g (1.54 mmol/g). In mixed-metal systems, Cu adsorption (0.687-1.718 mmol/g) greatly exceeded that for Pb, Zn, Cd, and Ni (0.003-0.120 mmol/g), giving KCu/Kother ratios 11.09-118 and demonstrating strong selectivity. Soil incubation with only 0.5wt parts per thousand Cys-CS transformed Cu from bioavailable fractions (BCR1/BCR2) into stable forms (BCR3/BCR4), while preserving soil pH, soil organic matter, cation exchange capacity, and microbial community structure, and minimally affecting non-target metals. Field-relevant trials in Cu-polluted sludge-made nutrient soils confirmed its high stabilization efficiency and negligible ecological disturbance. FTIR spectroscopy reveals that functional groups of L-cysteine, including-SH, -NH-, and CONH2, form coordination bonds with Cu2+. Density functional theory (DFT) calculations further confirm Cu-selective binding: the interaction energy of Cys-CS with Cu2+ is significantly lower than with coexisting metals (Pb, Zn, Cd, Ni), and-CONH2 coordination with Cu exhibits a lower band gap energy (Egap) than other Cys-CS functional groups, indicating higher binding affinity. This work demonstrates that functional group regulation of biopolymer-based adsorbents enables precise, low-dose, and environmentally safe remediation of Cu-contaminated soils, offering a practical pathway toward selective in situ stabilization in complex multi-metal environments.

Denitrification plays a critical role in controlling the fate of nitrate (NO3-) in groundwater. The nitrogen isotope enrichment factor (εN) during denitrification is essential for quantifying the role of denitrification in nitrate reduction in groundwater. Experimental columns containing groundwater and sediment were established to simulate aquifer conditions. Denitrification rates and the N and O isotope fractionation effects of NO3- in both groundwater and sediment during dentrification were measured in experimental columns using four organic substances as electron donors (ethanol, acetate, glucose and brown sugar) under two different dissolved oxygen (DO) concentrations of 1 and 2 mg·L-1, respectively. Significant variations in denitrification rates and stable isotope enrichment factors were observed in both overlying groundwater (εNo and εOo) and sediment pore water (εNp and εOp), depending on the carbon source and DO concentration. At DO =2 mg·L-1, acetate (εNo, -9.2 ‰; εNp, -7.4 ‰), glucose (εNo, -7.4 ‰; εNp, -4.3 ‰), brown sugar (εNo, -2.6 ‰; εNp, -2.4 ‰) exhibited less negative isotope enrichment factors compared to ethanol (εNo, -11.7 ‰; εNp, -10.0 ‰). For brown sugar, more negative isotope enrichment factors was observed at DO =1 (εNo, -5.0 ‰; εNp, -3.5 ‰) than at DO = 2 mg·L-1. Higher denitrification rates correlated with more negative εNo and εNp values, reflecting stronger nitrogen fractionation. Due to the O-exchange fraction and NO3- reduction processes, positive εOo and εOp values were observed in the denitrification columns, ranging from 5.0 ‰ to 29.2 ‰ for εOo and from 3.9 ‰ to 22.8 ‰ for εOp. Fractionation by diffusive transport of NO3- resulted in higher absolute values of εNo (εOo) compared to those of εNp (εOp). The calculated isotope enrichment factors (εNo and εNp) may be applied to quantify denitrification linked to C sources application under in situ conditions.

Quantifying NO3- sources by the combination of dual nitrate isotopes (δ15N-NO3- and δ18O-NO3-) with Stable Isotope Analysis in R (SIAR) models is crucial for mitigating NO3- pollution in groundwater. However, isotope fractionation effects during denitrification lead to significant uncertainties when quantifying groundwater NO3- sources using the SIAR model. In this study, hydrochemical data, water isotopes (δD-H2O and δ18O-H2O), and dual nitrate isotopes of groundwater at the West Lake watershed, East China were measured to estimate the isotope fractionation effect of denitrification in groundwater and assess its impact on quantifying NO3- source contributions using the SIAR model. The significant spatial (εN: -6.9 ‰ and εO: -3.1 ‰ in G1; εN: -15.1 ‰ and εO: -10.0 ‰ in G2) and temporal (εN: -17.0 ‰ and εO: -4.1 ‰ in spring; εN: -4.9 ‰ and εO: -2.5 ‰ in summer; εN: -7.2 ‰ and εO: -6.0 ‰ in autumn) variations in isotope fractionation effects of denitrification in groundwater at the West Lake watershed were observed. By incorporating these respective isotope fractionation enrichment factors into the SIAR model, more accurate NO3- source apportionments for G1 and G2 were obtained, confirming that the isotope fractionation effect of denitrification is an important parameter for quantifying NO3- sources in groundwater using the SIAR model. Furthermore, the national δ15N-NO3- and δ18O-NO3- observations of groundwater were compiled and the SIAR model integrated with isotope fractionation effect of denitrification were used to quantify NO3- sources in groundwater of China. It was found that regional differences in human activities directly influenced spatial variations of δ15N-NO3- and δ18O-NO3- values. The SIAR model outputs on a national scale revealed that sewage/manure (22.9-42.1 %) and chemical fertilizers (23.0-42.7 %) were the main NO3- sources in groundwater of China, attributable to large populations and extensive agricultural cultivation areas. These results provide direct evidence for formulating suitable policies and measures to control and reduce groundwater NO3- in China.

Co-occurring algal blooms and lead (Pb) pollution pose severe threts to freshwater ecosystems. In this study, Aspergillus oryzae (A. oryzae) 3.042 fungal pellets (FPs) were produced to harvest Chlorella pyrenoidosa, creating fungal-algal pellets (FAPs), which were used as heavy-metal capture materials. Under optimized conditions (2 mm diameter, 180 rpm, 3 g·50 mL-1, pH 3-7), FPs achieved 95 %-99 % algae removal efficiency, with these factors significantly influencing removal efficiency. Under complex water conditions, including microalgae concentration, Pb concentration and N:P ratio, FPs achieved satisfactory microalgae removal efficiency, demonstrating its advantages in water body restoration. Multiscale characterization revealed that FAPs formation relies primarily on electrostatic attraction complemented by functional-group interactions. Furthermore, FAPs structure facilitates Pb immobilization via chemisorption (94 mg·g-1), mediated by surface amide, carboxyl, and phosphate groups, forming {FAPs-tyrosine-Pb} complexes. A. oryzae 3.042, utilizing FPs technology, is biosafe, high-efficient, and sustainable solution for microalgae harvesting and Pb remediation in water.

Heavy metals in soil exhibit variable forms and characteristics, with certain elements displaying high mobility, posing a risk of leaching during land application. The selection of soil stabilizers is vital for the targeted removal of metals during soil remediation. While covalent organic frameworks (COFs) have shown potential in water- based heavy metal treatment, their role and mechanisms in soil remediation are yet to be fully understood. The study has explored the effects of amide COF (AmCOF) on the bioavailability and migration activity of target element lead (Pb) and non-target heavy metal elements through pot experiments and leaching tests. The findings demonstrate that AmCOF effectively reduced the leaching amount of Pb by preferentially adsorbing the acid extractable fraction (BCR1). Compared to the control group, the leaching Pb significantly decreased by 49.9-65.0 %. AmCOF selectively reduced the bioavailability of the target metal Pb without significantly affecting the bioavailability of other target metals. This selectivity is attributed to the multi-coordinate interactions between the amide groups on its surface and Pb. After the application of AmCOF, the physicochemical properties of the soil remain unaffected. Festuca arundinacea growth promoted and soil microbial indicators remained unchanged, demonstrating its environmentally friendly side. This study provides a solution to the problem of easy leaching of certain elements during the soil remediation of heavy metals in soil, and innovates the concept of precise soil remediation.

Severe ground-level ozone (O3) pollution over major Chinese cities has become one of the most challenging problems, which have deleterious effects on human health and the sustainability of society. This study explored the spatiotemporal distribution characteristics of ground-level O3 and its precursors based on conventional pollutant and meteorological monitoring data in Zhejiang Province from 2016 to 2021. Then, a high-performance convolutional neural network (CNN) model was established by expanding the moment and the concentration variations to general factors. Finally, the response mechanism of O3 to the variation with crucial influencing factors is explored by controlling variables and interpolating target variables. The results indicated that the annual average MDA8-90th concentrations in Zhejiang Province are higher in the northern and lower in the southern. When the wind direction (WD) ranges from east to southwest and the wind speed (WS) ranges between 2 and 3 m/sec, higher O3 concentration prone to occur. At different temperatures (T), the O3 concentration showed a trend of first increasing and subsequently decreasing with increasing NO2 concentration, peaks at the NO2 concentration around 0.02 mg/m3. The sensitivity of NO2 to O3 formation is not easily affected by temperature, barometric pressure and dew point temperature. Additionally, there is a minimum IRNO2 at each temperature when the NO2 concentration is 0.03 mg/m3, and this minimum IRNO2 decreases with increasing temperature. The study explores the response mechanism of O3 with the change of driving variables, which can provide a scientific foundation and methodological support for the targeted management of O3 pollution.

The application of municipal sewage sludge compost (MSSC) in landscaping contributes to sustainable material recycling, the use of soil stabilizers to stabilize heavy metals and reduce associated risks. Nevertheless, a comprehensive understanding of the complex interplay between metal immobilization effects and factors such as soil stabilizer dosage, site-specific soil physicochemical properties, and plant growth is essential for practical application. The influence of varying rice husk biochar (RHB) additions on heavy metal bioavailability in MSSC-amended soil using a ryegrass pot experiment were investigated, followed by a thorough analysis of soil and plant physicochemical properties and correlation assessments. In the RHB treatment groups, most heavy - metal concentrations in ryegrass shoots were lower than those in the control group (CK), with maximum decreases from 71.3 to 13.6

Microalgae exhibit remarkable capacity for heavy metal (HM) accumulation, which can be enhanced by natural organic matter (NOM) in aquatic systems. This synergy often leads to deviations in HM bioaccumulation assessments. This study investigated the effects of NOM on lead (Pb) bioaccumulation by Chlorella sp., focusing on Pb concentration, functional group concentration, and stability constants of polymeric complexes. Results showed a remarkable Pb adsorption capacity of 2.438 mmol g-1 (513 mg g-1) at pH 6.5, primarily attributed to the formation of ternary complexes {alga-Pb-(NOM-Pb)}. A surface multilayer adsorption mechanism was identified, driven by the deprotonation of functional groups, with carboxyl groups preferentially adsorbing over amino groups. Notably, the ratio of algae-Pb to Pb-NOM stability constants is critical in ternary complex formation, surpassing the traditional emphasis on NOM functional groups. Advanced modeling approaches, including response surface methodology and random forest analysis, confirmed the paramount importance of stability constant ratios in predicting complex formation. These findings provide crucial implications for assessing and controlling ecological risks associated with ternary complexes in algal bloom waters, offering new perspectives on the biotransformation process of HMs. This study contributes to a more comprehensive understanding of HM-microalgae interactions and their environmental impacts.

As a key contributor to atmospheric pollution, the petrochemical industry emits substantial quantities of volatile organic compounds (VOCs), nitrogen oxides (NOx), and carbon dioxide (CO2) emissions. This study develops a novel multi-objective optimization model for a local petrochemical facility (based on 2022 operational data), simultaneously addressing VOCs and NOx emissions, carbon intensity, and economic expenditures. By quantifying the cost-carbon nexus,it enables policy-relevant, priority-specific reduction pathways. Employing the weighted sum method under carbon emission constraints, this approach achieves >10 % reduction in individual emission (VOCs and NOx), with an overall emission decrease exceeding 30 % compared to baseline levels. Through the multi-objective optimization, we determine technologically optimal portfolios corresponding to three strategic scenarios: multi-pollutant control prioritization (VOCs-NOx co-reduction), cost-minimization orientation, and carbon-constrained operation. The optimized results demonstrate: (i) Annual emissions are minimized at 2,112.94 tons, representing a 66.52 % reduction versus baseline; (ii) Total costs are reduced to 1.549 billion CNY (16.45 % decrease compared to reference levels); (iii) Carbon emissions achieve a 9.83 % reduction, reaching 653,200 tons annually. Key sector-specific reduction potentials are quantified as: 9.99 % from VOCs emissions in circulating water systems, 4.53 % from equipment sealing point VOCs, and 88.9 % of total NOx treatment attributable to organized emission sources. These findings demonstrate that the proposed model offers considerable practical value in supporting the development of coordinated VOCs and NOx treatment strategies for carbon-regulated industrial facilities.

The extraordinary Super Typhoon (STY) Muifa (2022) made landfall four times and had a significant impact on the coastal regions from south to north of China. Although previous studies have demonstrated the 'pumping effect' of typhoons on the enhancement of reactive nitrogen (Nr) wet deposition over the ocean, it is uncertain how Nr deposition is influenced by typhoons that make prolonged mechanism due to multiple landfalls. In this study, the Nr wet deposition induced by STY Muifa was investigated from the perspective of in- and below-cloud processes based on the Nested Air Quality Prediction Modeling System with an online tracer-tagging module. High volume of Nr wet deposition caused by Muifa migrated from south to north, passing over half of China's coastal cities. Compared to the typhoon generated vicinity, both mean values of the oxidized and reduced nitrogen wet deposition over the Typhoon affected regions were increased about 20.4 and 66.1 times after landfall even with the similar rainfall. Emissions from the four landfall areas of China contributed to the majority of Nr wet deposition with significantly enhanced proportion of in-cloud deposition. The strong pumping effect of typhoon to the Nr deposition along the coastal areas and the risk of ecosystem effects requires further researches and higher demands on the control of nitrogen emissions of National Industrial Park, which usually located in China's coastal cities.

Cultivating algae in swine wastewater (SWW) leverages the nutrients in the wastewater. However, the role of suspended solids (SS) in algae growth and nitrogen removal remains unclear. Here, we report a 14-day batch trial that employs correlation and structural equation model (SEM) analyses to assess the effects of SS removal treatments. The untreated SWW group achieved the highest ammonium nitrogen (NH4+-N) and total nitrogen (TN) removal efficiencies at 79.7 % and 80.9 %, respectively, whereas the ultrafiltration-treated group produced the maximum algal biomass (404 mg/L). On day 2, NH4+-N and TN removal correlated positively and significantly with wastewater transmittance (p < 0.05), highlighting the inhibition of SS-induced shading. On day 8, these removals were associated with TN, phosphate phosphorus (PO43--P), and total phosphorus (TP) concentrations, suggesting the onset of nutrient release from SS. On day 14, nitrogen assimilation and uptake had nearly ceased, with chl-a and chl-b synthesis correlating with PO43--P (R = 0.93-0.94) and TP concentrations (R = 0.77), respectively (p < 0.01). Furthermore, SEM revealed that, on day 2, the shading effect of SS indirectly inhibited NH4+-N removal by reducing photosynthetic pigment synthesis (standardized coefficient: 0.88). Conversely, on day 8, NH4+-N removal was directly driven by phosphorus availability from SS (standardized coefficient: 0.95). These findings demonstrated that SS plays a dual role in algae growth and nitrogen removal from SWW; this role closely tied to the reciprocal regulation of NH4+-N assimilation and photosynthetic pigment synthesis. Overall, this study offers critical theoretical and technical support for optimizing algal cultivation in SWW.

The deployment of element-specific stabilizers is pivotal for the precision remediation of contaminated soils. A novel amide-containing porous polymer (APOP) has been designed based on coordination chemistry theories. An impressive adsorption capacity of 92.8 mg g-1 (1.461 mmol g-1) at pH 6 has been achieved, showcasing APOP's exceptional performance. Notably, APOP exhibits a pronounced selectivity for Cu ions, boasting a remarkable Kd of 883 mL g-1 in a 50 mg L-1 multi-metal ion matrix. This selectivity markedly surpasses its affinity for any other metals, highlighting APOP's superior targeting ability for Cu ions. Density functional theory calculations reveal an innovative adsorption mechanism grounded in frontier orbital theory, suggesting that the close alignment of frontier orbital energy levels between Cu ions and APOP significantly contributes to APOP's high selectivity, a finding that warrants further investigation. Pot-and-elution experiments showed that APOP effectively reduced the leaching risk of Cu in an eco-friendly manner. This study provides fresh perspectives and strategic guidance for the molecular-level design of selective adsorbents, which aims to effectively mitigate the leaching risk of heavy metals and preventing groundwater contamination.

Quantifying and comparing nitrate (NO3-) sources in typhoons and non-typhoons is important for controlling and reducing their emissions. In this study, the chemical compositions and stable isotopes (delta N-15-NO3- and delta O-18-NO3-) of non-typhoon and Typhoon Lekima precipitation in Hangzhou (from May-August during 2019 and 2020) were determined. The results revealed that severe acid rain occurred in Hangzhou, except during Typhoon Lekima. According to the positive matrix factorization (PMF) model results, the ion contributions of sources in non-typhoons were as follows: secondary inorganic aerosols + biomass burning > sea salt aerosols > agricultural sources > terrestrial sources, whereas sea salt aerosols + biomass burning were the primary contributors of ions in Typhoon Lekima. The delta N-15-NO3- values of non-typhoon and Typhoon Lekima ranged from -4.0 to -1.3 parts per thousand and -2.7 to 5.8 parts per thousand, respectively. The delta O-18-NO3- values of non-typhoon and Typhoon Lekima ranged from 56.3 parts per thousand to 74.7 parts per thousand and 32.2-55.3 parts per thousand, respectively. The calculated contribution of N2O5 pathway in NOx oxidation to NO3- during non-typhoon precipitation was 64.7 +/- 12.2%. If the contribution of OH pathway during Typhoon Lekima precipitation was 87%, the Monte Carlo simulation results demonstrated that the estimated oxidation proportions of NO via O-3 and RO2 (or HO2) ranged from 48.8 to 100% and 0-51.2%, respectively. Based on the improved Bayesian model combined with nitrogen isotope fractionation, the NOx contributions from four sources (biomass burning > coal combustion > mobile sources > microbial N cycle) in non-typhoon precipitation ranged from 21 to 30% (epsilon = 3.6). In Typhoon Lekima (epsilon = 5.2), lightning (23.6 +/- 11.2%) was one of the primary NOx contributors and a lower contribution from microbial N cycle (17.9 +/- 5.4%) compared with the PMF model (22.8%). Moreover, for Typhoon Lekima, the sum of biomass burning, coal combustion, and mobile sources in the improved Bayesian model (58.5%) was slightly lower than that of secondary inorganic aerosols in the PMF model (62.4%). Therefore, the coupled PMF-improved Bayesian model is a feasible and reliable method for source identification and apportionment of NO3- in precipitation.

In aquatic ecosystems, dissolved organic matter (DOM) enhances the adsorption of heavy metals onto microalgae by participating in the formation of algae-heavy metal-DOM ternary complexes, thereby increasing environmental risks. The functional groups in the DOM play a crucial role. However, a quantitative description based on these groups is lacking. This study investigates the effects of amino acids (AAs) with varying functional group ratios on the accumulation of lead (Pb) in Chlorella pyrenoidosa (C. C. pyrenoidosa) ) using batch experiments. Isotherm model fitting, and Fourier transform infrared spectroscopy (FTIR) are employed for characterisation. Results indicate that the addition of AAs facilitated Pb enrichment in microalgae. In particular, incorporating lysine (Lys) led to maximum accumulation, reaching 1.45 mmol g- 1 . The adsorption rate decreased after AA addition, particularly with Lys, dropping form 0.0032 g mg-- 1 min-- 1 to 0.0009 g mg-1 min-- 1 . The reaction sequence showed carboxyl groups taking precedence over amino groups. The model developed from the data on Pb adsorption by C. pyrenoidosa following AA addition, demonstrated reliability with an R2 2 of 0.91 and an Fvalue of 157.6. Notably this study employed two-dimensional correlation spectroscopy (2D-COS), offering novel insights into the key roles of functional groups and their distinct contributions. These valuable insights contribute to intensive research on the ternary complex of algae- heavy metal- DOM and elucidating their ecological risks.

The widespread discharge of halogenated organic pollutants (HOPs) in wastewater brings significant risks to the environment and human health due to potent high toxicity, antibacterial activity, and strong biodegradation resistance. Adsorbed atomic hydrogen (H-ads*)-mediated electrocatalytic hydrodehalogenation (EHDH) has been recognized as an efficient strategy for HOPs removal through selectively breaking carbon-halogen bonds. In this work atomic Pd uniformly anchored on molybdenum disulfide (denoted as Pd-MoS2) was synthesized through a facile hydrothermal method and found with state-of-the-art specific activity in florfenicol (FLO) removal via the H-ads*-mediated EHDH process. Pd-MoS2 completely dehalogenated (similar to 100 %) FLO within 30 min at a rate constant of 0.15 min(-1), which was 6.0, 6.5 and 33.1 times the value of MoS2, Pd/C and carbon paper samples, respectively. Notably, the toxicity of the wastewater was reduced to 1/6 of its original value after the treatment. Moreover, Pd-MoS2 presented superior catalytic stability in five successive cycles. Furthermore, Pd-MoS2 was also robust in complex water environment with practical applicability for industrial wastewater treatment. A dual-active-center mechanism with enhanced H-ads* production capacity and the improved H-ads* utilization efficiency was contributed to the increased EHDH activity on Pd-MoS2.

Biomass burning is a primary source of atmospheric nitrogen oxide (NOx), x ), however, the lack of isotopic fingerprints from biomass burning limits their use in tracing atmospheric nitrate (NO3-) 3- ) and NOx. x . A total of 25 biomass fuels from 10 provinces and regions in China were collected, and the S15N 15 N values of biomass fuels (S15N- 15 N- biomass) and S15N-NOx 15 N-NO x values of biomass burning (S15N-NOx 15 N-NO x values of BB, open burning, and rural cooking stove burning) were determined. The S15N-NOx 15 N-NO x values of open burning and rural cooking stove burning ranged from-0.8 %o to 11.6 %o and 0.8 %o to 9.5 %o, respectively, indicating a significant linear relation with S15N-biomass. 15 N-biomass. Based on the measured S15N-NOx 15 N-NO x values of BB and biomass burning emission inventory data, the S15N-NOx 15 N-NO x values of BB in different provinces and regions of China were calculated using the S15N-NOx 15 N-NO x model, with a mean value of 5.0 f 1.8 %o . The spatial variations in the estimated S15N-NOx 15 N-NO x values of BB in China were mainly controlled by the differences in the S15N-NOx 15 N-NO x values and the proportions of NOx x emissions from various straw burning activities in provinces and regions of China. Furthermore, by using the combined local emissions of biomass burning with regional transportations of NOx x based on air-mass backward trajectories, we established an improved S15N-NOx 15 N-NO x model and obtained more accurate S15N-NOx 15 N-NO x values of BB in regions (2.3 %o to 8.4 %o ). By utilising the reported S15N-NOx 15 N-NO x values of precipitation and particulate matter from 21 cities in China and the more accurate S15N-NOx 15 N-NO x values of BB, the NOx x contributions from four sources (mobile sources, coal combustion, biomass burning, and microbial N cycle) at the national scale were estimated using a Bayesian model. The significant contributions of biomass burning (20.9 % to 44.3 %) to NOx x emissions were revealed, which is vital for controlling NOx x emissions in China.

Megacities face significant pollution challenges, particularly the elevated levels of heavy metals (HMs) in particulate matter (PM). Despite the advent of interdisciplinary and advanced methods for HM source analysis, integrating and applying these approaches to identify HM sources in PM remains a hurdle. This study employs a year-long daily sampling dataset for PM1 and PM1-10 to examine the patterns of HM concentrations under hazy, clean, and rainy conditions in Hangzhou City, aiming to pinpoint the primary sources of HMs in PM. Contrary to other HMs that remained within acceptable limits, the annual average concentrations of Cd and Ni were found to be 20.6 ± 13.6 and 46.9 ± 34.8 ng/m³, respectively, surpassing the World Health Organization's limits by 4.1 and 1.9 times. Remarkably, Cd levels decreased on hazy days, whereas Ni levels were observed to rise on rainy days. Using principal component analysis (PCA), enrichment factor (EF), and backward trajectory analysis, Fe, Mn, Cu, and Zn were determined to be primarily derived from traffic emissions, and there was an interaction between remote migration and local emissions in haze weather. Isotope analysis reveals that Pb concentrations in the Hangzhou region were primarily influenced by emissions from unleaded gasoline, coal combustion, and municipal solid waste incineration, with additional impact from long-range transport; it also highlights nuanced differences between PM1 and PM1-10. Pb isotope and PCA analyses indicate that Ni primarily stemmed from waste incineration emissions. This explanation accounts for the observed higher Ni concentrations on rainy days. Backward trajectory cluster analysis revealed that southern airflows were the primary source of high Cd concentrations on clean days in Hangzhou City. This study employs a multifaceted approach and cross-validation to successfully delineate the sources of HMs in Hangzhou's PM. It offers a methodology for the precise and reliable analysis of complex HM sources in megacity PM.

Landscape utilization is a green and environment-friendly way of disposing of compost sludge. Garden plants can extract heavy metals from the sludge of land use, but the effect is not enough to be widely used. Chelating agents have been found to facilitate the extraction of heavy metals from plants and are expected to be popularized if they are also environmentally friendly. In this study, the effects of methylglycinediacetic acid trisodium salt (MGDA), tetrasodium glutamate diacetate (GLDA), and ethylene diamine tetraacetate (EDTA) on the extraction of Ni and Cd from compost sludge by Symphytum officinale L. were studied through the pot experiment. Compared with the control group, the application of 5–10 mmol kg−1 MGDA and 1–9 mmol kg−1 GLDA promoted plant growth, while the application of 3–4 mmol kg−1 EDTA inhibited plant growth. The highest Ni content in shoots appeared in 4 mmol kg−1 GLDA treatment, which was 4.2 times that of the CK group. The highest shoot Cd concentration appeared in 4 mmol kg−1 EDTA treatment, 6.5 times that of CK. The promotion effects of the three reagents on the acid-extractable state of Cd were similar, while that of GLDA on the acid-extractable state of Ni was outstanding. The results of this study suggested that S. officinale could be a potential phytoextraction plant for Cd and Ni, and GLDA could friendly promote the Ni phytoextraction ability of the plant. The study provides a new and efficient method for phytoremediation of heavy metals in soil.