Co-planting of Quercus nuttallii, Quercus pagoda with Solanum nigrum enhanced their phytoremediation potential to multi-metal contaminated soil.

To screen the efficient tree-herb co-planting patterns to remediate the heavy metal polluted soil, a greenhouse experiment was conducted for 150 days to examine the plant growth and metals accumulation across three co-planting patterns, including Solanum nigrum (S) co-planted with Quercus nuttallii (NS) or Quecrus pagoda (PS), and those three species are co-planted together (NPS). Results showed that the NPS pattern slightly decreased the tree biomass, while NS and PS treatments improved the plant growth (1.51-10.68%). It is worth noting that the NS treatment significantly (p < 0.05) increased photosynthetic pigment content (82.61-113.93%), net CO2 assimilation (21.44%), and the uptake of Cd (44.58%) in Q. nuttallii; the PS treatment significantly (p < 0.05) increased the net CO2 assimilation (8.61%) and the uptake of Cd (42.23%), Zn (31.18%) in Q. pagoda; and the uptake of Cd and Zn in the NPS co-planting treatment were only slightly increased. For S. nigrum, the photosynthetic pigment content was elevated and the metal accumulation in itself also maintained the relative stable in all the co-planting treatments. Thus, co-planting of Quercus with S. nigrum was a promising way to remediate heavily polluted soil by heavy metals. Novelty statement: Co-planting with multiple plant species, as a novel strategy, has great value for the remediation of heavy metal contaminated soil. The paper aimed to explore the suitable co-planting pattern of Quercus, arbor trees which showed phytoremediation potential, co-planted with Cd hyperaccumulator, Solanum nigrum. The result suggested the co-planting with S. nigrum enhanced the plant growth, photosynthesis, and metals extraction of Q. nuttallii and Q. pagoda. Co-planting also improved ecological adaptation of S. nigrum via elevating pigment content. Thus, co-planting of Quercus with S. nigrum was a promising way to remediate polluted soil.

Impacts of bamboo biochar on the phytoremediation potential of Salix psammophila grown in multi-metals contaminated soil.

We investigated the effects of bamboo biochar (BBC) as soil amendment on growth and phytoremediation potential of Salix psammophila in soil heavily polluted by Cd and Zn. Bamboo biochar was added to soil at ratios ranging from 1 to 7% (w/w), which significantly increased the organic matter, available potassium (K) content, while decreased the hydrolyzable nitrogen (N) content and the levels of total and bioavailable HMs in soil. The BBC amendment at ratios of 1% to 5% showed little effect on growth of plant, whereas at 7% ratio significantly decreased biomass compared to the control. BBC amendment stimulated the accumulation of Cu, Cd and Zn in plant tissues, meanwhile, Cd and Zn accumulation were more evident, especially in the BBC-3% treatment. BBC amendment improved the TF and BCF values of Cd, Zn and Cu compared to control. Higher BCF for Cd (BCF >1) and TF for Zn (TF >1) values indicate Salix psammophila have considerable potential for phytoremediation efficiency in BBC amended soil treatment. This study provides practical evidence of the efficient BBC-assisted phytoremediation capability of Salix psammophila and highlights its potential as a viable and inexpensive approach for in situ remediation.

The effect of particle size of bamboo biochar on the phytoremediation of Salix psammophila C. to multi-metal polluted soil.

Biochar shows great potential in soil remediation. The benefits of biochar on soil depend onits intrinsic properties and soil characteristics. However, the influence of particle sizes of biochar on soil remediation is not clear. In a pot experiment, we evaluated the effects of bamboo biochar (BBC) particle sizes (P1 < 0.15 mm, 0.15 mm < P2 < 0.25 mm, 0.25 mm < P3 < 0.50 mm) on phytoremediation efficiency of Salix psammophila C. cultivated in multi-metal polluted soil. We added the BBC at 3% (w/w) in tested soil. Next, the BBC was thoroughly mixed with soil and weighting to the pot, and S. psammophila cuttings were planted and grown for six months in the amended soil under model growth condition.Results revealed the addition of different sizes of BBC particles affected soil quality, plant growth, and HMs accumulation in plants. All sizes of BBC treatments improved Cd and Zn accumulation, whereas plants in P2 treatment showed the greatest accumulation, increased by 52.41 and 25.55% compared with the control (1,503 and 19,928 µg·plant-1). Overall, the results indicated BBC enhanced the phytoremediation efficiency of S. psammophila. Plants cultivated in P2 treatment showed the most significant effect on remediating contaminated soil.

Effects of exogenous 3-indoleacetic acid and cadmium stress on the physiological and biochemical characteristics of Cinnamomum camphora.

Indoleacetic acid (IAA) is a plant growth regulator that plays an important role in plant growth and development, and participates in the regulation of abiotic stress. To explore the effect of IAA on cadmium toxicity in Cinnamomum camphora, an indoor potted experiment was conducted with one-year-old C. camphora seedlings. The influence of IAA on cadmium accumulation, net photosynthetic rates, respiration, photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll and carotenoids), osmoregulatory substances (proline, soluble sugar and soluble protein) and the malondialdehyde content in C. camphora leaves treated with 30 mg kg-1 cadmium was analysed with or without the addition of 10 mg kg-1 IAA. Cadmium accumulation in the leaves of C. camphora with the addition of exogenous IAA was significantly higher than accumulation during cadmium stress without additional IAA (ca 69.10% after 60 days' incubation). During the culture period, the net photosynthetic rate in C. camphora leaves subjected to cadmium stress without the addition of IAA was up to 24.31% lower than that of control plants. The net photosynthetic rate in C. camphora leaves subjected to cadmium stress and addition of IAA was up to 30.31% higher than that of leaves subjected to cadmium stress without the addition of IAA. Chlorophyll a, total chlorophyll and carotenoid contents in the cadmium-stressed leaves without the addition of IAA were lower than those in the control treatment. The presence of IAA increased the chlorophyll a, total chlorophyll and carotenoid contents relative to the cadmium stress without the addition of IAA. The respiration rate and concentrations of proline, soluble sugar, soluble protein and malondialdehyde in C. camphora leaves subjected to cadmium stress without the addition of IAA were higher than those in the control. The addition of IAA reduced the respiration rate, and the concentrations of proline, soluble sugar, soluble protein and malondialdehyde in C. camphora leaves when compared with the cadmium stress without the addition of IAA. These results indicate that exogenous IAA improves photosynthetic performance and the growth environment of C. camphora by enhancing the net photosynthetic rate, increasing concentrations of osmoregulatory substances, removing reactive oxygen radicals and eliminating potential damage, thereby reducing the toxic effects of cadmium on C. camphora.

Terrestrial Trophic Transfer of Bulk and Nanoparticle La2O3 Does Not Depend on Particle Size.

The bioaccumulation and trophic transfer of bulk and nanoparticle (NP) La2O3 from soil through a terrestrial food chain was determined. To investigate the impact of growth conditions, lettuce (Lactuca sativa) was grown in 350 or 1200 g of bulk/NP amended soil. Leaf tissues were fed to crickets (Acheta domesticus) or darkling beetles (Tenebrionoidea); select crickets were fed to mantises. In the small pot (350 g), La2O3 exposure reduced plant biomass by 23-30% and La tissue content did not differ with particle size. In the large pot (1200 g), biomass was unaffected by exposure and La content in the tissues were significantly greater with bulk particle treatment. Darkling beetles exposed to bulk and NP La2O3-contaminated lettuce contained La at 0.18 and 0.08 mg/kg; respectively (significantly different, P < 0.05). Crickets fed bulk or NP La2O3-exposed lettuce contained 0.53 and 0.33 mg/kg, respectively (significantly different, P < 0.05) with 48 h of depuration. After 7 d of depuration, La content did not differ with particle size, indicating that 48 h may be insufficient to void the digestive system. Mantises that consumed crickets from bulk and NP-exposed treatments contained La at 0.05-0.060 mg/kg (statistically equivalent). These results demonstrate that although La does trophically transfer, biomagnification does not occur and NP levels are equivalent or less than the bulk metal.

Divergent responses of rhizosphere soil phosphorus fractions and biological features of Salix psammophila to fertilization strategies under cadmium contamination.

Soil oligotrophy in areas heavily contaminated with heavy metals poses a significant challenge to vegetation establishment and phytoremediation processes. Phosphorus (P) cycling plays a critical role in global biogeochemical cycles, but there is limited understanding of its response to varying fertilization strategies and its correlation with phytoremediation effectiveness. This study primarily investigated the effects of various fertilization strategies, including nitrogen (N, 300 mg·kg-1), P (100 mg·kg-1), NP (combined N and P at 300 mg·kg-1 and 100 mg·kg-1, respectively), and HP (high P, 300 mg·kg-1) application, on rhizosphere soil P fractions and P-solubilizing microbial community (harboring phoD and phoC genes, respectively) of Salix psammophila under cadmium contamination. Application of NP significantly enhanced plant growth and cadmium accumulation, whereas HP inhibited cadmium bioaccumulation but promoted its translocation. Compared to untreated soil, N application promoted P cycling, leading to increases of 141.9 %, 60.4 %, and 10.3 % in Resin-Pi, diluted HCl-Pi, and conc.HCl-Pi, respectively. P application decreased organic phosphorus (Po) fractions by 24.4 % - 225.8 %, but N incorporation mitigated the declining trend in Po and augmented alkaline phosphatase activity. Fertilization strategies significantly regulated phoC- or phoD-harboring bacterial community structure, but their differential nutrient demands resulted in distinct responses. The phoD-harboring bacteria exhibited higher diversity and network complexity, with numerous biomarkers and fertilizer-sensitive OTUs discovered across treatments. Structural equation modeling (SEM) analysis indicated that phytoremediation efficiency was directly affected by Pi fractions, and phoD-harboring bacteria exhibited stronger associations with Pi fractions than phoC-harboring bacteria. In conclusion, our results reveal potential pathways through which fertilization strategies influence phytoremediation by affecting the structure of P-solubilizing microbial community. Furthermore, our study emphasizes the importance of combined N and P application in promoting Cd accumulation in plants, with high P levels appearing as an ideal fertilization strategy for phytoremediation targeting the harvest of aboveground biomass.

Evaluating the role of rhizosphere microbial home-field advantage in Betula luminifera adaptation to antimony mining areas.

It has been established that the coevolution of plants and the rhizosphere microbiome in response to abiotic stress can result in the recruitment of specific functional microbiomes. However, the potential of inoculated rhizosphere microbiomes to enhance plant fitness and the inheritance of adaptive traits in subsequent generations remains unclear. In this study, cross-inoculation trials were conducted using seeds, rhizosphere microbiome, and in situ soil collected from areas of Betula luminifera grown in both antimony mining and control sites. Compared to the control site, plants originating from mining areas exhibited stronger adaptive traits, specifically manifested as significant increases in hundred-seed weight, specific surface area, and germination rate, as well as markedly enhanced seedling survival rate and biomass. Inoculation with mining microbiomes could enhance the fitness of plants in mining sites through a "home-field advantage" while also improving the fitness of plants originating from control sites. During the initial phase of seedling development, bacteria play a crucial role in promoting growth, primarily due to their mechanisms of metal resistance and nutrient cycling. This study provided evidence that the outcomes of long-term coevolution between plants and the rhizosphere microbiome in mining areas can be passed on to future generations. Moreover, it has been demonstrated that transgenerational inheritance and rhizosphere microbiome inoculation are important factors in improving the adaptability of plants in mining areas. The findings have important implications for vegetation restoration and ecological environment improvement in mining areas.

Modulating phyllosphere microbiome structure and function in Loropetalum chinense and Osmanthus fragrans: The impact of foliar dust and heavy metals.

Trees can effectively capture airborne particles and improve air quality. However, the specific response of phyllosphere microbiome (PMo) in different plant species to particulate matter (PM) and the heavy metals it contains are not yet fully understood. In this study, we investigated the impact of PM on the diversity and function of PMo in Loropetalum chinense and Osmanthus fragrans trees grown in industrial and clean zones with varying levels of PM pollution. Our findings revealed that leaf dust had a significant negative effect on microbial richness, with O. fragrans exhibiting higher microbial diversity than L. chinense. The dominant phylum of phyllosphere bacteria in all samples was Proteobacteria, and the dominant genera were Stenotrophomonas and Delftia. The relative abundance of these genera varied significantly among plant species and regions. Our results showed that PM had a significant impact on the community composition of PMo, with the presence of heavy metals exerting a greater effect than particle size. Moreover, the foliar microbial community of plants grown in industrial zones exhibited significantly higher metabolic functions related to stress resistance and disease resistance compared to plants in control zones. These findings highlight the structural and functional responses of PMo to PM and indicate their potential for enhancing plant adaptation to environmental stress.

CXCR4-Expressing Mesenchymal Stem Cells Derived Nanovesicles for Rheumatoid Arthritis Treatment.

Cell membrane camouflage technology, which a demonstrated value for the bionic replication of natural cell membrane properties, is an active area of ongoing research readily applicable to nanomedicine. How to realize immune evasion, slow down the clearance from the body, and improve targeting are still worth great efforts for this technology. Herein, novel cell membrane-mimicked nanovesicles from genetically engineered mesenchymal stem cells (MSCs) are presented as a potential anti-inflammatory platform for rheumatoid arthritis (RA) management. Utilizing the synthetic biology approach, the biomimetic nanoparticles are constructed by fusing C-X-C motif chemokine receptor4 (CXCR4)-anchored MSC membranes onto drug-loaded polymeric cores (MCPNs), which make them ideal decoys of stromal cell-derived factor-1 (SDF-1)-targeted arthritis. These resulting nanocomplexes function to escape from the immune system and enhance accumulation in the established inflamed joints via the CXCR4/SDF-1 chemotactic signal axis, thereby achieving an affinity to activated macrophages and synovial fibroblasts. It is further demonstrated that the MCPNs can significantly suppress synovial inflammation and relieve pathological conditions with favorable safety properties in collagen-induced arthritis mice. These findings indicate the clinical value of MCPNs as biomimetic nanodrugs for RA therapy and related diseases.

Enriched rhizospheric functional microbiome may enhance adaptability of Artemisia lavandulaefolia and Betula luminifera in antimony mining areas.

Dominant native plants are crucial for vegetation reconstruction and ecological restoration of mining areas, though their adaptation mechanisms in stressful environments are unclear. This study focuses on the interactions between dominant indigenous species in antimony (Sb) mining area, Artemisia lavandulaefolia and Betula luminifera, and the microbes in their rhizosphere. The rhizosphere microbial diversity and potential functions of both plants were analyzed through the utilization of 16S, ITS sequencing, and metabarcoding analysis. The results revealed that soil environmental factors, rather than plant species, had a more significant impact on the composition of the rhizosphere microbial community. Soil pH and moisture significantly affected microbial biomarkers and keystone species. Actinobacteria, Proteobacteria and Acidobacteriota, exhibited high resistance to Sb and As, and played a crucial role in the cycling of carbon, nitrogen (N), phosphorus (P), and sulfur (S). The genes participating in N, P, and S cycling exhibited metabolic coupling with those genes associated with Sb and As resistance, which might have enhanced the rhizosphere microbes' capacity to endure environmental stressors. The enrichment of these rhizosphere functional microbes is the combined result of dispersal limitations and deterministic assembly processes. Notably, the genes related to quorum sensing, the type III secretion system, and chemotaxis systems were significantly enriched in the rhizosphere of plants, especially in B. luminifera, in the mining area. The phylogenetic tree derived from the evolutionary relationships among rhizosphere microbial and chloroplast whole-genome resequencing results, infers both species especially B. luminifera, may have undergone co-evolution with rhizosphere microorganisms in mining areas. These findings offer valuable insights into the dominant native rhizosphere microorganisms that facilitate plant adaptation to environmental stress in mining areas, thereby shedding light on potential strategies for ecological restoration in such environments.

Contrasting effect of pristine, ball-milled and Fe-Mn modified bone biochars on dendroremediation potential of Salix jiangsuensis "172" for cadmium- and zinc-contaminated soil.

Bone biochar (BC) has a high capacity for the immobilization of potentially toxic elements (PTEs); however, its effect on dendroremediation efficiency remains unclear. Therefore, this study aimed to determine the effects of various concentrations (0, 0.5, 1, and 2 wt%) of BC, ball-milled BC (MBC), and Fe-Mn oxide-modified BC (FMBC) on soil properties, plant growth, and metal accumulation in Salix jiangsuensis "172" (SJ-172) grown in cadmium (Cd)- and zinc (Zn)-contaminated soil. BC and MBC promoted the photosynthetic rate, mineral element absorption, and plant growth of SJ-172, whereas FMBC inhibited the growth of SJ-172. Different biochars greatly influenced the concentrations of Cd and Zn in tissues of SJ-172. BC and MBC elevated the Cd levels, whereas FMBC decreased the Cd content in the leaves, stems, and cuttings of SJ-172. Unlikely, BC, MBC and FMBC show no evident change to the Zn concentration in the aboveground tissues of SJ-172, while decreased root Cd and Zn content compared with the control. MBC, at a 2.0% application rate, significantly increased the translocation factors of Cd (55.0%) and Zn (40.87%), whereas BC and FMBC demonstrated no significant effects compared with the control (P > 0.05). Moreover, 2.0% BC and MBC increased Cd and Zn accumulation in SJ-172 by 28.40 and 41.14, and 25.89 and 36.16%, respectively, whereas 2.0% FMBC reduced Cd and Zn accumulation by 53.20% and 13.18 %, respectively, compared with the control. The phytoremediation potential of SJ-172 for Cd- and Zn-contaminated soils was enhanced by MBC and BC, whereas it was lowered by FMBC compared to the control. These results provide novel insights for the application of fast-growing trees assisted by biochar amendments in the dendroremediation of severely PTEs-contaminated soil.

Microbial communities in tree root-compartment niches under Cd and Zn pollution: Structure, assembly process and co-occurrence relationship.

Woody plants have showed great potential in remediating severely contaminated soils by heavy metals (HMs) due to their cost-efficient and ecologically friendly trait. It is believed the root-associated microbiota plays a vital role in phytoremediation for HMs. However, the ecological process controlling the assembly and composition of tree root-associated microbial communities under HMs stress remains poorly understood. Herein, we profiled the bulk soil, rhizosphere and endosphere microbial communities of trees growing in heavily Cd and Zn polluted soil. The microbiota was gradually filtered from bulk soil to the tree roots and was selectively enriched in roots with specific taxa, such as Proteobacteria and Ascomycota. The microbial community assembly along the soil-root continuum was mainly controlled by deterministic processes from bulk soil to the endosphere, with the normalized stochasticity ratio (NST) indices of 67.16-31.05 % and 30.37-15.02 % for bacteria and fungi, respectively. Plant selection pressure sequentially increased from bulk soil to rhizosphere to endosphere, with the reduced bacterial alpha diversity accompanying the consequently reduced complexity of the co-occurrence network. Together, the findings provide new evidence for horizontal transmission of endophytic microbiome from soil to the host, which can shed light on the future screening and application of microbial-assisted phytoremediation.

Responses of soil seed banks to drought on a global scale.

The global increase in drought frequency and intensity in large areas has potentially important effects on soil seed banks (SSBs). However, a systematic evaluation of the impact of drought on SSBs at a global scale has not yet been well understood. We evaluated the effects of drought on SSBs and identified the association key drivers in the current meta-analysis. The overall effects of drought on soil seed density and richness were weak negative and positive, respectively. Drought significantly increased soil seed density by 11.94 % in forest ecosystem, whereas soil seed richness were significantly increased in vascular plants (7.39 %). Linear mixed-effect results showed that soil seed density and richness significantly reduced as increasing drought intensity. In addition, geography (altitude) has significance in controlling the lnRR of soil seed density by altering climate (mean annual precipitation, drought) and soil properties (pH, soil organic carbon, and clay content) in the structural equation model, whereas soil seed richness was controlled by geography (altitude, and latitude) via climate (mean annual precipitation). In summary, the results suggested the size of SSBs response to drought and its relationship with drought intensity in terrestrial ecosystems, it may shed light on ecosystem restoration, succession, and management using SSBs when estimating the future drought.

Facilitated remediation of heavy metals contaminated land using Quercus spp. with different strategies: Variations in amendments and experiment periods.

Phytoremediation using trees combined with soil amendments has gained much attention for its highly cost-effective trait. In natural field conditions, however, the results may not reflect the true performance of amendments based on short-term laboratory studies. In this three-year field trial, various soil amendments such as rice straw biochar, palygorskite, a combined biochar of rice straw biochar and palygorskite, and hydroxyapatite were used to systematically study the potential of the low-accumulator (Quercus fabri Hance) and high-accumulator (Quercus texana Buckley) for cadmium (Cd) and zinc (Zn) to remediate severely contaminated soils. Soil amendments enhanced the dendroremediation capacity of Quercus as the growth period prolonged. In 2021, the rice straw biochar treatment increased Cd and Zn accumulation by 1.76 and 2.09 times in Q. fabri, respectively, compared to the control. Cd and Zn accumulation increased to 1.78 and 2.10 times, respectively, under combined biochar treatment for Q. texana compared to the control. Metals accumulation was mainly enhanced by soil amendments through increasing the growth biomass of Q. fabri and improving the biomass and bioconcentration ability of Q. texana. Overall, soil amendments effectively improved the phytoremediation efficiency of Quercus in the long term, and selecting suitable amendments should be fully considered in phytoremediation.

Micro/nanoscale bone char alleviates cadmium toxicity and boosts rice growth via positively altering the rhizosphere and endophytic microbial community.

This present study investigated pork bone-derived biochar as a promising amendment to reduce Cd accumulation and alleviate Cd-induced oxidative stress in rice. Micro/nanoscale bone char (MNBC) pyrolyzed at 400 °C and 600 °C was synthesized and characterized before use. The application rates for MNBCs were set at 5 and 25 g·kg-1 and the Cd exposure concentration was 15 mg·kg-1. MNBCs increased rice biomass by 15.3-26.0% as compared to the Cd-alone treatment. Both types of MNBCs decreased the bioavailable Cd content by 27.4-54.8%; additionally, the acid-soluble Cd fraction decreased by 10.0-12.3% relative to the Cd alone treatment. MNBC significantly reduced the cell wall Cd content by 50.4-80.2% relative to the Cd-alone treatment. TEM images confirm the toxicity of Cd to rice cells and that MNBCs alleviated Cd-induced damage to the chloroplast ultrastructure. Importantly, the addition of MNBCs decreased the abundance of heavy metal tolerant bacteria, Acidobacteria and Chloroflexi, by 29.6-41.1% in the rhizosphere but had less impact on the endophytic microbial community. Overall, our findings demonstrate the significant potential of MNBC as both a soil amendment for heavy metal-contaminated soil remediation and for crop nutrition in sustainable agriculture.

Evaluation of dendroremediation potential of ten Quercus spp. for heavy metals contaminated soil: A three-year field trial.

Woody plants have gained considerable attention for remediating soils contaminated with heavy metals because of their cost-efficient and ecologically friendly nature. However, most studies on potential phytoremediation evaluation are limited to short-term experiments in greenhouse or field, meaning that differences may exist between laboratory results and application in natural environment. In this study, ten Quercus spp. were tested in a consecutive 3-year field trial (2018-2020) to assess their dendroremediation abilities for Cd and Zn contaminated soil. The results revealed that nine Quercus spp. demonstrated good survival ability without any stress, except for Quercus velutina Lam., in the 3-year growth period. In 2020, Quercus texana Buckley and Quercus fabri Hance plants produced the greatest biomass (2100 and 1880 g plant-1) among the nine Quercus spp. Quercus texana had the highest total Cd accumulation (39.3 mg plant-1) in 2020, which was 8.5 times higher than that in 2018, followed by Quercus pagoda Raf. (8.85 mg plant-1) and Q. fabri (8.07 mg plant-1) plants, respectively, whereas Cd accumulation increased by 7.4 times for Q. pagoda and 22 times for Q. fabri compared to 2018. The results from 2020 indicated that Q. fabri had the highest Zn accumulation (205 mg plant-1), followed by Quercus nigra L. (149 mg plant-1) and Q. texana (140 mg plant-1), respectively, and these values increased 14, 6.4, and 6.2 times in comparison to 2018. The comprehensive bioaccumulation index (CBAI) was proposed to evaluate the dendroremediation potential of Quercus spp., suggesting that Q. texana and Q. fabri had the most outstanding potential for remediation of Cd and Zn polluted soil, with the values of 0.82 and 0.60, respectively. In summary, Q. texana and Q. fabri are ideal for remediating Cd/Zn-contaminated soil, and long-term field trials and the CBAI method are helpful for comprehensively evaluating the remediation capacity of trees.

Foliar dust particle retention and metal accumulation of five garden tree species in Hangzhou: Seasonal changes.

As particulate matter and heavy metals in the atmosphere affect the atmospheric quality, they pose a threat to human health through the respiratory system. Vegetation can remove airborne particles and purify the atmosphere. Plant leaves are capable of effectively absorbing heavy metals contained by particulates. To evaluate the effects of different garden plants on the particulate matter retention and heavy metal accumulation, the seasonal changes of dust retention of five typical garden plants were compared in the industrial and non-industrial zones in Hangzhou. Results revealed that these species differed in dust retention with the descending order of Loropetalum chinense > Osmanthus fragrans > Pittosporum tobira > Photinia × fraseri > Cinnamomum camphora, which were related to the microstructure feature of the leaf. These species also showed seasonal variation in dust retention, with the highest in summer, followed by winter, autumn, and spring, respectively. The total suspended particle per unit leaf area was higher in the industrial site (80.54 g m-2) than in the non-industrial site (19.77 g m-2). Leaf particles in different size fractions differed among species, while coarse particles (d > ten µm) predominated in most cases. The L. chinense and C. camphora plants accumulated the greatest Pb and Ni compared to other plants. Overall, L. chinense was the best suitable plant species to improve the air quality.

Phytoremediation potential evaluation of multiple Salix clones for heavy metals (Cd, Zn and Pb) in flooded soils.

Climate-induced flooding makes soil more vulnerable to heavy metal contamination, posing challenges for soil remediation. Salix has the potential to cope with flooding stress and environmental contamination, but its effectiveness in flooded soils with multiple heavy metals has not yet been well assessed. Thus, the present work tested fifteen Salix clones grown in multimetal (Cd, Zn and Pb) contaminated soils under non-flooded versus flooded conditions. The results indicated that all tested Salix clones withstood long-term (90 d) flooding. Compared to the non-flooded condition, the flooded condition reduced the Cd (11.7-90.1%) contents in all organs but dramatically increased the Zn and Pb contents in the roots. The bioconcentration factor values of heavy metals in the aboveground organs were in the order of Cd > Zn > Pb. The tested Salix clones were characterized by high phytoextraction capacity for Cd and Zn under non-flooded condition and phytostabilization trait for Pb under flooded condition. To assess the overall performance of phytoremediation potentials, we attempted to use an analytic hierarchy process-entropy weight (AHP-EW) model, which considered the growth performance, photosynthetic parameters, accumulation, and mobility of toxic metals. Three Salix clones (J1010, P54 and P667) exhibited significant potential for multimetal remediation capacities. The current study provided valuable insights into the phytomanagement of woody plants, and the AHP-EW model is helpful for screening suitable trees for the phytoremediation of heavily multimetal contaminated wetlands.

Effects of copper oxide nanoparticles on Salix growth, soil enzyme activity and microbial community composition in a wetland mesocosm.

A model wetland with Salix was established to investigate the effects of CuO nanoparticles (NPs; the equivalent amount of Cu at 0, 100 and 500 mg/kg) on plant, soil enzyme activity and microbial community. Ionic Cu (100, 500 mg/kg) and bulk-sized CuO particles (BPs, 500 mg/kg) were included as controls. The results suggested the CuO NPs at 500 mg/kg and ionic Cu treatments inhibited the plant growth, while CuO NPs at 100 mg/kg and CuO BPs at 500 mg/kg played a facilitating role. CuO NPs significantly decreased the activities of peroxidase and polyphenol oxidase, while ionic Cu treatments increased peroxidase activity, BPs and ionic Cu (500 mg/kg) increased the polyphenol oxidase activity. Bacterial community richness and diversity were reduced in all Cu treatments; however, CuO NPs and BPs at 500 mg/kg significantly increased the richness and diversity of fungal community.Soil microbial community was significantly altered by Cu types and dose. In comparison with ionic Cu and CuO BPs, CuO NPs uniquely enriched the microbial community and the fungal families.Overall, it demonstrate that both particle size and dose regulate the impact of CuO on wetland ecology, which deepens our understanding on the ecological risks of CuO NPs in freshwater forested wetland.

Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash.

The mutual effects of metal cations (Cu2+, Pb2+, Zn2+, and Cd2+) and p-nitrophenol (NP) on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2+, Pb2+, and Zn2+ diminished the adsorption and increased the desorption of NP remarkably, while Cd2+ had no such effect. In contrast, NP diminished the adsorption of Cu2+, Pb2+, and Zn2+ onto ash, however, this suppression effect depended on the initial concentrations of metal cations. NP had no effect on Cd2+ adsorption on ash. Fourier transform infrared (FT-IR) and X-ray absorption spectroscopic (XAS) studies suggested the following mechanisms responsible for the metal suppression effect on NP adsorption: (1) large hydrated Cu2+, Pb2+, and Zn2+ shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; (2) Cu2+, Pb2+, and Zn2+ may block the micropores of ash, resulting in decreased adsorption of NP; (3) complexation of Cu2+, Pb2+, and Zn2+ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a "soft acid", Cd2+ is less efficient in the complexation of oxygen-containing acid groups than Cu2+, Pb2+, and Zn2+. Thus, Cd2+ had no effect on the adsorption of NP on wheat ash.