[Characterization of carbon and oxygen isotopes of plant on climate and plant physiology at the southeastern margin of Qinghai-Tibet Plateau, China]. / é’è—é«˜åŽŸä¸œå—ç¼˜æ¤ç‰©ç¢³æ°§åŒä½ç´ å¯¹æ°”å€™åŠæ¤ç‰©ç”Ÿç†çš„è¡¨å¾.

To investigate the correlation between carbon and oxygen isotope compositions of plant cellulose and climatic factors as well as plant physiological indices on the southeastern margin of the Qinghai-Tibet Plateau, we examined plant species in eight sampling sites with similar latitudes and different longitudes in this region. Through the characteristics of δ13C and δ18O values, fractionation values (Δ13C and Δ18O) in leaf cellulose, we discussed water use efficiency (WUE) and the environmental factors, the variation of carbon and oxygen isotopes in the southeastern margin of the Qinghai-Tibet Plateau with elevation and longitude, and revealed the indication degrees of isotopic signals to different environments and vegetation physiology. By using the semi-quantitative model of carbon and oxygen dual isotopes, we investigated the physiological adaptation mechanisms of plants to varying environmental conditions. The results demonstrated that both Δ13C and Δ18O of cellulose decreased with increasing elevation and longitude, and Δ13C was more influenced by longitude, while Δ18O was more susceptible to elevation variation. Additionally, Δ13C and Δ18O were significantly and positively correlated with temperature (TEM), precipitation (PRE), potential evapotranspiration (PET), and relative humidity (RH). PRE was the dominant meteorological factor driving the variation of Δ13C, while RH was the dominant meteorological factor influencing Δ18O variation. In contrast to Δ13C, WUE showed a stronger correlation with elevation than with longitude, which increased as elevation and longitude increased. According to the carbon-oxygen model, plant stomatal conductance (gs) and photosynthetic capacity (Amax) decreased with increasing precipitation and relative humidity, while the values increased with increasing elevation and longitude. The combined analysis of carbon and oxygen isotopes of organic matters would yield additional environmental and gas exchange information for studies on climate tracing and vegetation physiology studies on the southeastern margin of the Qinghai-Tibet Plateau.

Effects of warming on soil organic carbon pools mediated by mycorrhizae and hyphae on the Eastern Tibetan Plateau, China.

Mycorrhizae and their hyphae play critical roles in soil organic carbon (SOC) accumulation. However, their individual contributions to SOC components and stability under climate warming conditions remain unclear. This study investigated the effects of warming on the SOC pools of Picea asperata (an ectomycorrhizal plant) and Fargesia nitida (an arbuscular mycorrhizal plant) mycorrhizae/hyphae on the eastern Tibetan Plateau. The results indicated that mycorrhizae made greater contributions to SOC accumulation than hyphae did by increasing labile organic carbon (LOC) components, such as particle organic carbon (POC), easily oxidizable organic carbon, and microbial biomass carbon, especially under warming conditions. Plant species also had different effects on SOC composition, resulting in higher mineral-associated organic carbon (MAOC) contents in F. nitida plots than in P. asperata plots; consequently, the former favored SOC stability more than the latter, with a lower POC/MAOC. Partial least-squares path modelling further indicated that mycorrhizae/hyphae indirectly affected LOC pools, mainly by changing soil pH and enzyme activities. Warming had no significant effect on SOC content but did change SOC composition by reducing LOC through affecting soil pH and iron oxides and ultimately increasing SOC stability in the presence of mycorrhizae for both plants. Therefore, the mycorrhizae of both plants are major contributors to the variation of SOC components and stability under warming conditions.

Clonal integration of stress signal induces morphological and physiological response of root within clonal network.

Clonal integration of defense or stress signal induced systemic resistance in leaf of interconnected ramets. However, similar effects of stress signal in root are poorly understood within clonal network. Clonal fragments of Centella asiaticas with first-young, second-mature, third-old and fourth-oldest ramets were used to investigate transportation or sharing of stress signal among interconnected ramets suffering from low water availability. Compared with control, oxidative stress in root of the first-young, second-mature and third-old ramets was significantly alleviated by exogenous ABA application to the fourth-oldest ramets as well as enhancement of antioxidant enzyme (SOD, POD, CAT and APX) activities and osmoregulation ability. Surface area and volume in root of the first-young ramets were significantly increased and total length in root of the third-old ramets was significantly decreased. POD activity in root of the fourth-oldest and third-old ramets was significantly enhanced by exogenous ABA application to the first-young ramets. Meanwhile, total length and surface area in root of the fourth-oldest and third-old ramets were significantly decreased. Ratio of belowground to aboveground biomass in the whole clonal fragments was significantly increased by exogenous ABA application to the fourth-oldest or first-young ramets. It is suggested that transportation or sharing of stress signal may induce systemic resistance in root of interconnected ramets. Specially, transportation or sharing of stress signal against phloem flow was observed in the experiment. Possible explanation is that rapid recovery of foliar photosynthesis in first-young ramets subjected to exogenous ABA application can partially reverse phloem flow within clonal network. Thus, our experiment provides insight into ecological implication on clonal integration of stress signal.

Enhanced removal of phosphate from aqueous solutions by oxygen vacancy-rich MgO microspheres: Performance and mechanism.

The efficient removal of phosphate from water environments was extremely significant to control eutrophication of water bodies and prevent further deterioration of water quality. In this study, oxygen vacancy-rich magnesium oxide (OV-MgO) microspheres were synthesized by a simple solvothermal method coupling high-temperature calcination. The effects of adsorbent dosage, contact time, initial pH and coexisting components on phosphate adsorption performance were examined. The physicochemical properties of OV-MgO microspheres and the phosphate removal mechanisms were analyzed by various characterization techniques. The maximum adsorption capacity predicted by the Sips isotherm model was 379.7 mg P/g for OV-MgO microspheres. The phosphate adsorption in this study had a fast adsorption kinetics and a high selectivity. OV-MgO microspheres had a good acid resistance for phosphate adsorption, but their adsorption capacity decreased under alkaline conditions. The electrostatic attraction, ligand exchange, surface precipitation, inner-sphere surface complexation and oxygen vacancy capture were mainly responsible for efficient removal of phosphate from aqueous solutions. This study probably promoted the development of oxygen vacancy-rich metal (hydr)oxides with potential application prospects.

Image-based vegetation analysis of desertified area by using a combination of ImageJ and Photoshop software.

Fractional vegetation cover (FVC) is a crucial indicator to estimate degradation and desertification for grasslands. However, traditional small-scale FVC analysis methods, such as visual estimation and point-sampling, are cumbersome and imprecise. Innovative methods like image-based FVC analysis methods, while accurate, face challenges such as complex analytical procedures and the necessary training for operations. Therefore, in this study, a combined application of ImageJ and Photoshop was employed to achieve a more effective analysis of FVC values in desertification areas. Our results showed that the FVC results obtained by combination of Photoshop and ImageJ were dependable and precise (R2 > 0.98), demonstrating equivalency to results obtained through either visual estimation or Photoshop-based methods. Furthermore, even in the face of background interference and varied shooting angles, the combination of ImageJ and Photoshop software was still able to maintain a low error rate when analyzing FVC values (average error rate = - 2.6%). In conclusion, the imaged-based combined FVC analysis method employed in our research was an effective, precise, and efficient technique for analyzing small-scale FVC, promising substantial improvement over conventional methods.

Simplification of the pretreatment method for phosphate oxygen isotope measurement in phosphogypsum leachate.

The stacking of phosphogypsum has caused considerable phosphorus pollution in water bodies near phosphogypsum yards through surface runoff and underground infiltration. The phosphate oxygen isotope (δ18Op) tracing method has served as a valuable tool for tracing phosphorus pollution in water. However, the existing δ18Op enrichment and purification methods are complex, costly, and inefficient for phosphate recovery, particularly for phosphogypsum leachate with complex compositions. Herein, a simplified and optimized pretreatment method for δ18Op measurement in phosphogypsum leachate was developed. Zirconium/polyvinyl alcohol (Zr/PVA) gel beads showed good selectivity for phosphate enrichment from water at different initial phosphate concentrations with appropriate Zr/PVA dosage. The optimal enrichment pH value was <7, and the concentrated phosphate on the Zr/PVA gel beads could be effectively eluted in an alkaline environment. Compared with the traditional Fe or Mg coprecipitation enrichment methods, impurities in the solution showed no obvious adverse effects on the phosphate enrichment process. Further, the phosphate solution eluted from the Zr/PVA gel beads was purified by a simple adjustment of the pH instead of cation exchange in the traditional purification process. Magnesium ions in the solution could be completely removed when the pH ranged from 3.17 to 6.15, and the phosphate recovery rate could reach 98.66% when the eluent pH was 5.02. Fourier-transform infrared spectroscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy revealed that similar to traditional pretreatment method, the proposed method can obtain high-purity Ag3PO4 solids for δ18OP measurement and no isotope fractionation of δ18OP was observed. Therefore, this study provides a promising and reliable pretreatment method for δ18OP measurement, especially in complex phosphogypsum leachate.

Decoupling the response of vegetation dynamics to asymmetric warming over the Qinghai-Tibet plateau from 2001 to 2020.

Global land surface air temperature data show that in the past 50 years, the rate of nighttime warming has been much faster than that of daytime, with the minimum daily temperature (Tmin) increasing about 40% faster than the maximum daily temperature (Tmax), resulting in a decreased diurnal temperature difference. The Qinghai-Tibet Plateau (QTP) is known as the "roof of the world", where temperatures have risen twice as fast as the global average warming rate in the last few decades. The factors affecting vegetation growth on the QTP are complex and still not fully understood to some extent. Previous studies paid less attention to the explanations of the complicated interactions and pathways between elements that influence vegetation growth, such as climate (especially asymmetric warming) and topography. In this study, we characterized the spatial and temporal trends of vegetation coverage and investigated the response of vegetation dynamics to asymmetric warming and topography in the QTP during 2001-2020 using trend analysis, partial correlation analysis, and partial least squares structural equation model (PLS-SEM) analysis. We found that from 2001 to 2020, the entire QTP demonstrated a greening trend in the growing season (April to October) at a rate of 0.0006/a (p < 0.05). The spatial distribution pattern of partial correlation between NDVI and Tmax differed from that of NDVI and Tmin. PLS-SEM results indicated that asymmetric warming (both Tmax and Tmin) had a consistent effect on vegetation development by directly promoting greening in the QTP, with NDVI values being more sensitive to Tmin, while topographic factors, especially elevation, mainly played an indirect role in influencing vegetation growth by affecting climate change. This study offers new insights into how vegetation responds to asymmetric warming and references for local ecological preservation.

Effects of several polymeric materials on the improvement of the sandy soil under rainfall simulation.

Poor cementation between soil particles is a fundamental cause of soil erosion and desertification. In recent decades, many polymers have been used to cement soil particles and improve the physical and chemical properties of soils. The contributions of polymers with different structures and functional groups to soil improvement vary considerably. In this study, a mixture comprising polyacrylamide (PAM), sodium polyacrylate (PAAS), hydroxypropyl methylcellulose (HPMC), and polyvinyl alcohol (PVA) was investigated to meet the requirements of soil water retention, erosion resistance, and plant growth. The results showed that the time required for the modified soil to reach drought conditions was extended by 4-7 days. The PAM/HPMC, PAM/PVA and PAM/PAAS experimental groups reduced the erosion rate by 99.57%, 98.3% and 96.38%, respectively, compared to that of the control group. The belowground plant biomass was significantly increased by PAM/HPMC, PAM/PAAS, and PAM/PVA, with increases of 115.92%, 145.23%, and 205.67%, respectively. HPMC contributed more to the soil erosion resistance and water-holding capacity, PAAS improved the soil porosity substantially, and PVA significantly increased the plant biomass. The rigid structures of the polymer chains enhanced the structural stability of the soil, and the hydrophilic functional groups increased the hydrophilicity of the amended soil. This study indicates different polymers that may be used to improve soil properties.

Application of Cu isotopes to identify Cu sources in soils impacted by multiple anthropogenic activities.

Copper (Cu) is an important micronutrient for animals and plants, but it is toxic at high concentrations in soil. Soils adjacent to industrial areas would be subjected to severe Cu pollution. Identifying Cu sources in the surface environment is crucial for understanding their pollution level and fate. This study investigated Cu content, isotope composition of topsoils, and two soil profiles with varying levels of Cu contamination and related potential Cu sources in southwest China. The difference in Cu isotope compositions of tailing (1.29 ± 0.08 ‰), smelting fly ash (0.04 ± 0.03 ‰), coal (2.44 ± 0.09 ‰), coal-burning fly ash (0.34 ± 0.03 ‰), and geogenic soil (0.10 ± 0.03 ‰) enabled us to distinguish anthropogenic Cu from geogenic Cu. The plot of δ65Cu and 1/Cu demonstrates that Cu of the polluted soils was from three end-members: the smelting fly ash, the vehicle exhaust, and the background soils. Based on the mass balance model, we calculated that the fly ash from smelting was the major anthropogenic source, contributing approximately 29 % of Cu contamination in soils, and the diesel exhaust was another important source, with a contribution rate of approximately 25 %. Additionally, soil profile results suggest that anthropogenic Cu could transport through soil profiles and influence Cu content and isotope signatures of subsurface soils, at least to a depth of ∼60 cm. Finally, our research indicates that Cu isotopes could be a promising tool for tracing industrial pollution, as significant Cu isotope fractionation would occur during the smelting process. Our research highlights the contribution of smelting and diesel exhaust to Cu contamination in the soils in a representative mining area. These findings serve as a scientific foundation for the development of policy for pollution control in industrial-affected regions.

A critical review of adsorption isotherm models for aqueous contaminants: Curve characteristics, site energy distribution and common controversies.

The quantitative description of the equilibrium data by the isotherm models is an indispensable link in adsorption studies. The previous review papers focus on the underlying assumptions, fitting methods, error functions and practical applications of the isotherm models, usually ignoring their curve characteristics, selection criteria and common controversies. The main contents of this review include: (i) effect of the model parameters on the isotherm curves; (ii) determination of the site energy distribution; (iii) selection criteria of the isotherm models; and (iv) elimination of some common controversies. It is of great significance to reveal the curve characteristics for selecting a proper isotherm model. The site energy distribution is conducive to understanding the physicochemical properties of the adsorbent surface. The complete isotherm is recommended to be correlated with the experimental data. The model parameter qmax should be cautiously adopted for comparison of the adsorbent performance. The residual plot can be used to diagnose the fitting quality of the isotherm models further. This review also addresses some common mistakes and controversies and thereby avoids their propagation in future publications.

Shear behavior of bedding fault material on the basal layer of DGB landslide.

Daguangbao (DGB) Landslide (12 × 108 m3) is the largest landslide triggered by the 2008 Ms8.0 Wenchuan Earthquake, in which basal shear failure develops on an interlayer fault at 400 m deep under the ground. After the landslide, a 1.8 km long (in the sliding direction) oblique shear face is exposed. Different kinds of materials in the interlayer fault of DGB landslide are taken for direct shear test, medium scale shear test, in-situ shear test and ring shear test. The test results show that fault material cohesion ranges from 20 to 320 kPa and internal friction angle from 15° to 41°. Shearing strength of interlayer fault materials is related to fragmentation degree of structure. The lower fragmentation degree the more obvious strain softening characteristics of materials, the higher fragmentation degree the poorer shearing resistance of materials. Compared with argillaceous materials in the same fault, the mylonitic materials are of higher shear strength and internal friction angle. Both mylonitic materials and breccia materials are strong in liquefying. In saturated undrained cases, shear strength of fault materials could drop to 9.7°, with S3 down to 0. In saturated undrained dynamic shear conditions, fault internal friction angle could be reduced to 23.1° and 4.2°. It is concluded that low friction feature of fault materials caused by the influence of groundwater is the main reason for destabilization of DGB landslide.

127I and 129I species in the English Channel and its adjacent areas: Uncovering impact on the isotopes marine pathways.

Radioactive iodine-129 has been released from the La Hague nuclear fuel reprocessing facility (NRF) into the English Channel, but the distribution and transformation of the isotope species, and environmental consequences have not been fully characterized in the Channel. Here we present data on iodine isotopes (129I and 127I) species in surface water of the English Channel and the southern Celtic Sea. Compared to 127I species, the concentrations of 129I- and 129IO3- show more variations, but iodate is the major species for both 129I and 127I. Our data provide new information regarding iodide-iodate inter-conversion showing that water dilution and mixing are the main factors affecting the 127I and 129I species distribution in the Channel. Some reduction of iodate occurs within the English Channel and mainly in the west part because of biotic processes. The 129I species transformation is overall insignificant, especially in the eastern Channel, where a constant value of 129IO3-/129I is observed, which might characterize the La Hague wastewater signal. In the Celtic Sea, oxidation of iodide can be traced by 127I and 129I species. On a larger scale, 129I generally experienced an oxidation process in the Atlantic Ocean, while in the coast of shallow shelf seas, new produced 129I- can be identified, especially in the German Bight and the Baltic Sea. The data of 129I species in the English Channel can provide estimate of redox rates in a much broader marine areas if the transit time of 129I from La Hague is well-defined. Furthermore, estimate of inventories for 129I and its species in the Channel, and fluxes of 129I species from the English Channel to the North Sea add important information to the geochemical cycle of 129I.

Hydrogeochemical controls on As and B enrichment in the aqueous environment from the Western Tibetan Plateau: A case study from the Singe Tsangpo River Basin.

Although enrichment of As and B has been extensively observed in major rivers within the Tibetan Plateau, the mechanisms regulating natural enrichment of As and B in the river basins remain poorly understood. To evaluate the hydrogeochemical controls on the As and B enrichment in the aqueous environment in the western Tibetan Plateau, samples of river waters, river sediments, and groundwater were collected within the Singe Tsangpo River basin. The results revealed significant enrichment of As and B in river water (up to 104 µg L-1 for As and 3.2 mg/L for B), river sediment (up to 141 mg/kg for As and 79.4 mg/kg for B), and groundwater (up to 73 µg /L for As and 2.5 mg/L for B). Moreover, the decreases in the molar ratios from the Ca2+ /(Na++K+) in river water and the chemical index of alteration (CIA) in the sediments accompanied with the enrichment of heavier δ18O values along the river flow path suggested that, carbonate and silicate weathering were more substantial at the upper reaches, and the dissolution of evaporites was enhanced at the lower reaches. The As and B enrichment in the river waters primarily resulted from the discharge of geothermal springs, while the carbonate weathering has facilitated the B enrichment through providing HCO3- for the competitive adsorption with H3BO3 or B(OH)4- . In addition, the recharge of surface water into groundwater resulted in elevated As and B concentrations in the alluvial aquifers at the lower reaches of the Singe Tsangpo River. The present study highlighted that variations in the weathering processes within the river basin could significantly contribute to the enrichment of As and B, which can improve our understanding of hydrogeochemical controls on the transport and enrichment of trace elements at the catchment scale worldwide.

A data-driven estimate of litterfall and forest carbon turnover and the drivers of their inter-annual variabilities in forest ecosystems across China.

Strong influences of climate and land-cover changes on terrestrial ecosystems urgently need to re-estimate forest carbon turnover time (τforest), i.e., the residence time of carbon (C) in the living forest carbon reservoir in China, to reduce uncertainties in ecosystem carbon sinks under ongoing climate change. However, in absence of accurate carbon loss (e.g., forest litterfall), τforest estimate based on the non-steady-state assumption (NSSA) in forest ecosystems across China is still unclear. In this study, thus, we first compiled a litterfall dataset with 1025 field observations, and applied a Random Forest (RF) algorithm with the linkage of gridded environmental variables to predict litterfall from 2000 to 2019 with a fine spatial resolution of 1 km and a temporal resolution of one year. Finally, τforest was also estimated with the data-driven litterfall product. Results showed that RF algorithm could well predict the spatial and temporal patterns of forest litterfall with a model efficiency of 0.58 and root mean square error of 78.7 g C m-2 year-1. Mean litterfall was 205.4 ± 1.1 Tg C year-1 (mean ± standard error) with a significant increasing trend of 0.65 ± 0.14 Tg C year-2 from 2000 to 2019 (p < 0.01), indicating an increasing carbon loss from litterfall. Mean τforest was 26.2 ± 0.1 years with a significant decreasing trend of -0.11 ± 0.02 years (p < 0.01) from 2000 to 2019. Climate change dominated the inter-annual variability of τforest in high latitude areas, and land-cover change dominated the regions with intensive human activities. These findings suggested that carbon loss from vegetation to the atmosphere becomes more quickly in recent decades, with significant implication for vegetation carbon cycling-climate feedbacks. Meanwhile, the developed litterfall and τforest datasets can serve as a benchmark for biogeochemical models to accurately estimate global carbon cycling.

An efficient manganese-oxidizing fungus Cladosporium halotolerans strain XM01: Mn(II) oxidization and Cd adsorption behavior.

The applications of biogenic Mn oxides (BMOs) formed by Mn-oxidizing fungus in decontaminating heavy metals have attracted increasing attention. In this study, an efficient Mn-oxidizing fungus was isolated from soil and identified as Cladosporium halotolerans strain XM01. The Mn(II) adsorption and oxidation activities of this strain were investigated, showing significantly high removal and oxidation rates of soluble Mn(II) of 99.9% and 88.2%, respectively. Dynamic analysis of the Mn(II) removal process demonstrated the oxidation process of Mn(II) to Mn(III) was the rate-limiting step in the Mn(II) metabolic process. The XRD and SAED characterization showed that more layers were orderly accumulated along the c-axis with the formation of fungal BMOs, which might lead to the decrease in its specific surface area. The adsorption of Cd(II) by the formed BMOs was investigated and compared with two typical abiotic Mn oxides, indicating that the adsorption capacity decreased with the following order: immature BMO, mature BMO, δ-MnO2, acid birnessite, while the fixation capacity decreased in the order of acid birnessite, mature BMO, δ-MnO2, immature BMO. The inverse correlation between the capacity of Cd(II) adsorption and fixation of immature and mature BMOs was probably attributed to the increase in the layer stacking of BMOs. This result indicates an interesting phenomenon of high reservation of Cd(II) resulting from sequential transformation from strong adsorption to strong fixation with the formation of BMOs. This study offers considerable insights into fungal Mn oxidation mechanisms and provides theoretical guidance for fungal BMOs in heavy metals bioremediation.

Enhanced photodegradation of doxycycline (DOX) in the sustainable NiFe2O4/MWCNTs/BiOI system under UV light irradiation.

In this study, a magnetic NiFe2O4/MWCNTs/BiOI composite were fabricated and applied for enhanced and sustainable photocatalytic degradation of doxycycline (DOX) under UV light irradiation. The as-synthesized material was characterized by a series of techniques and its photocatalytic property was assessed via a couple of batch tests. With the pH at 3.0 and NiFe2O4/MWCNTs/BiOI loading of 1.5 g L-1, the DOX degradation (at 45 mg L-1) efficiency could achieve 92.18% with the reaction rate constant k of 0.0072 min-1. The high mineralization of DOX suggests the strong oxidation of both the parent pollutant and the intermediary products in the ternary catalyst system. DRS spectra indicated that compared with BiOI, the introduction of NiFe2O4 and MWCNTs reduces the band gap energy of the NiFe2O4/MWCNTs/BiOI. The quenching test illustrates that h+, OH and O2- all functioned in the developed photocatalytic system, where O2- and h+ play the dominant roles in DOX degradation. The more efficient electron-h+ separation and more oxidizing species induced by UV light resulted in the significant improvement of DOX abatement in the developed coupling system compared with that on either BiOI or NiFe2O4/MWCNTs. The magnetic property of NiFe2O4/MWCNTs/BiOI enables its easy separation of the solid catalyst from the reaction solution and the sustainable application in the photocatalysis. Based on the intermediates of DOX decomposition identified by UPLC-MS, the possible degradation routes were proposed accordingly.

Responses of fungal communities along a chronosequence succession in soils of a tailing dam with reclamation by Heteropogon contortus.

Phytoremediation can obviously change the fungal communities in the soils, which will significantly impact carbon (C) and nitrogen (N) cycling in ecological system. So far, the relationship between soil fungal communities and environmental factors is still poorly understood along a long chronosequence. In this study, fungal communities in the surface and rhizosphere soils of a tailing dam with Heteropogon contortus phytoremediation were investigated to explore the evolution of fungal community in a span of 50 years. The results showed that microbial community diversity increases along with time series of Heteropogon contortus phytoremediation. The dominant Dothideomycetes (20.86%), Agaricomycetes (18.09%), and Arthoniomycetes (1.69%) in rhizosphere soils were relatively higher than those in topsoil (13.9%, 2.65%, and 0.20%) at class level. Spearman correction analysis by phylum level was conducted to detect whether microflora was related to soil Physico-chemical properties, which affecting the composition of fungal communities along with the Heteropogon contortus phytoremediation. The nitrogen cycle indicators represented good linear correlations as chronosequence goes on, the indexes in the rhizosphere soil were much higher than those in the surface soils and the highest level has occurred in the 47-year-old Heteropogon contortus phytoremediation. The relative abundance of plant pathogen, wood saprotroph, dung saprotroph, and Arbuscular Mycorrhizal showed an upward tendency in rhizosphere soils along with the Heteropogon contortus phytoremediation. The highest soil fungal communities abundance and diversity were possibly attributed to the high-quality Heteropogon contortus litter returning to the ground and artificial disturbance treatments. Such changes in soil fungal communities might demonstrate a significant step forward and provided theoretical support for the biological governance of Heteropogon contortus phytoremediation in 50 years. Our study provides an insight on microbial communities connecting with soil C, N, P and S cycles and community functions in a complex plant-fungal-soil system along a long chronosequence in mine micro-ecology.

Study on detoxification and removal mechanisms of hexavalent chromium by microorganisms.

Extensive industrial activities have led to an increase of the content of chromium in the environment, which causes serious pollution to the surrounding water, soil and atmosphere. The enrichment of chromium in the environment through the food chain ultimately affects human health. Therefore, the remediation of chromium pollution is crucial to development of human society. A lot of scholars have paid attention to bioremediation technology owing to its environmentally friendly and low-cost. Previous reviews mostly involved pure culture of microorganisms and rarely discussed the optimization of bioreduction conditions. To make up for these shortcomings, we not only introduced in detail the conditions that affect microbial reduction but also innovatively introduced consortium which may be the cornerstone for future treatment of complex field environments. The aim of this study is to summary chromium toxicity, factors affecting microbial remediation, and methods for enhancing bioremediation. However, the actual application of bioremediation technology is still facing a major challenge. This study also put forward the current research problems and proposed future research directions, providing theoretical guidance and scientific basis for the application of bioremediation technology.

The combined effects of Cu and Pb on the sex-specific growth and physiology of the dioecious Populus yunnanensis.

In recent years, pollution by heavy metals (HM) has become an increasingly serious problem in forest ecosystems, making their remediation a primary research focus in China. Poplars are ideal candidates for phytoremediation because of their great commercial value, ability to produce large biomass, and high capacity for HM uptake. The individual and combined effects of copper (Cu) and lead (Pb) on Populus yunnanensis growth and physiology were tested for both male and female potted plants in four treatment groups: control, Pb only (1,000 mg kg-1 PbAc dry soil), Cu only (400 mg kg-1 CuSO4·5H2O dry soil), and combined Pb and Cu. Each treatment group contained 25 male and 25 female individuals. The experimental duration was 3 months. Compared with the control plants, the Cu and Pb treatment groups experienced reduced leaf, stem, root, and total biomass for both sexes, but the impact on growth rate was more severe in females than in males. The cellular ultrastructure of leaves was extensively damaged in both male and female trees but was more severely damaged in females. Male trees demonstrated a stronger Cu absorption ability with a bioconcentration factor 2.30 times that of females. Significant changes in pigment content, membrane lipid peroxidation, and protein oxidation (carbonyl) also indicated that females were more sensitive than males to Cu- and Pb-induced stress. The higher Cu and Pb tolerance in males correlated with better H2O2 scavenging ability and proline accumulation. Nevertheless, the combined stress from both Cu and Pb yielded greater negative effect on the growth and physiology of P. yunnanensis for both sexes.

Laboratory experiments on HMC coupling mechanisms in innovative clean foundation treatments for Zn-contaminated dredger fills.

Large-scale contaminated dredger fills have comprehensively resulted from human activities and geological deposition processes, and their disposal is a worldwide challenge. Innovative soil remediation coupling foundation treatment methods, namely, clean foundation treatment methods (CFTMs), were proposed and verified using a hydraulic-mechanical-chemical coupling triaxial testing system. The CFTM exploration triaxial tests on undisturbed clayey, silty, and sandy dredger fills showed that the critical injection significantly dilated soil volume even after the soil was vacuum pumped. Critical injection-vacuum soil flushing (CIVF), critical injection soil flushing (CIF), and vacuum soil flushing (VF) were proposed to perform clean foundation treatment for clayey silt, sandy silt, and silty sand of 1900-2300 ppm Zn. EDDS, HCl + CaCl2, and HCl were selected as the three chelating agents. Orthogonal tests on three factors (CFTM, soil type, and eluent) showed that CIF with 5:1 EDDS aq. of pH 3.8 was the best CFTM scheme for the three soil types at a depth of 2.5-10 m. CIF with HCl aq. of pH 3.8 also reached a high comprehensive clean foundation treatment efficiency for silty sand at a depth of 2.5 m. The deep depth and heterogeneous texture resulted in low Zn contamination extraction efficiency.