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Electrokinetic remediation (EK) combined with a permeable reactive barrier (PRB) is a relatively new technique for efficiently remediating Cd-contaminated soil in situ. Eupatorium adenophorum, which is a malignant invasive plant, was used to synthesise biochar and a novel lanthanum-based biochar composite (LaC). The biochar and LaC were used as cheap and environmentally benign PRB filling materials to remediate simulated and real Cd-contaminated soils. The pH and residual Cd concentration in the simulated contaminated soil during remediation gradually increased from the anode to the cathode used to apply an electric field to the EK–PRB system. However, the soil conductivity changed in the opposite way, and the current density first increased and then decreased. For simulated contaminated soils with initial Cd concentrations of 34.9 and 100.6 mg kg−1, the mean Cd removal rates achieved using LaC were 90.6% and 89.3%, respectively, which were significantly higher than those of biochar (P < 0.05). Similar results were achieved using natural soils from mining area and polluted farmland, and the Cd removal rates were 66.9% and 72.0%, respectively. Fourier-transform infrared and X-ray photoelectron spectroscopy indicated that there were many functional groups on the LaC surfaces. The removal mechanism of EK-PRB for Cd in contaminated soil includes electromigration, electroosmotic flow, surface adsorption, and ion exchange. The results indicated that the LaC could be used in the EK–PRB technique as a cheap and ‘green’ material to efficiently decontaminate soil polluted with heavy metals.

The degradation of organic matter in soils plays an important role in the carbon cycle. Lignin is the main source of soil organics and it can be used to trace the source, distribution and turnover of organic matter. In this study the distribution and degradation of lignin were investigated to identify the source and degradation of soil organic matter during the succession of China's Zoige Plateau. Lignin monomers were determined by gas chromatography-mass spectrometry with alkaline CuO oxidation and the soils' δ

The impacts of different S/N molar ratios and fillers (polyurethane foam, multi-surface hollow spheres, and pall rings) on the process of simultaneous desulfurization and denitrification (SDD) were studied by using anaerobic biotrickling filer (BTF). Furthermore, the SDD mechanism was described by dividing the SDD process into three stages based on pH changes: (I) increase (II) decrease and (III) stable state. The maximum desulfurization and denitrification efficiency (13.5 g-S m−3 h−1 and 3.7 g-N m−3 h−1, respectively) was achieved by applying polyurethane foam as filler. When S2− and S0 coexist as electron donors in the SDD system, the functional microbes degrade S2− preferentially. The S/N molar ratios of the influent were higher, and the relative content of sulfate in the products was less. Considering the efficiency and economic benefits, polyurethane foam is suggested as fillers for practical implementations of SDD systems. The S/N molar ratios should be controlled in a 5/3 to 5/2 range and HS−/S2− concentration should be

Hippophae has been exploited as food, medicine as well as pioneer species for fixing nitrogen (N) and preventing desertification in Tibetan Plateau. In the paper, the eco-physiological responses and adaptive abilities of Hippophae rhamnoides and Hippophae thibetana seedlings under two levels of drought (50% and 30% field capacity) were investigated. The results indicated that two drought treatments differently affected biomass partition, water use efficiency, ammonia (NH4-N) and nitrate nitrogen (NO3-N) absorption, contents of hydrolysable amino acids (AA) and leaf ultrastructure of the two species of Hippophae. The two species had better resistance to moderate drought, while extreme drought showed more negative effects on biomass and ultrastructure of H. rhamnoides. Two drought treatments significantly increased water use efficiency of the two species. In H. rhamnoides, the two levels of drought stresses decreased the absorption of ammonia and nitrate nitrogen, whereas only inhibited NO3-N absorption of H. thibetana. The H. thibetana seedlings had more root nodules and higher R/S ratio than H. rhamnoides, while H. rhamnoides seedlings increased most individual and total AA in leaf and root organs under two drought treatments. The different growth, N-related absorption as well as metabolism responses of the two dominant species of Hippophae to drought stress may affect seedling colonization, the ecological function of N fixation and preventing desertification in Tibet Plateau in the future.

Lake eutrophication has become a serious environmental problem in China. Manipulations covering more elements of trophic pyramid are methods for lakes to obtain clear water state and should be studied in detail. In the present study, Meishan Dongpo Lake was divided into two parts, and a combined biomanipulation project was conducted in one part (RLake), and the other part was used as a control (CLake). Species of submerged-plant, fish, macrobenthos, and zooplankton were screened and a certain number of them were added to adjust the eco-chain in RLake. After restoration, the coverage of submerged macrophytes reached >85%; zooplankton greater than 0.6 mm in size increased in number, and the ratio of zooplankton biomass to chlorophyll-a (Chl-a) concentration increased. The dominant fish species changed, and disturbance of the sediment was reduced. The average density of mollusks in RLake was 111.5 ± 19.8 ind m−2, which was much higher than that in CLake (36.7 ± 2.1 ind m−2). Water quality and clarity were substantially improved, and nutrient concentrations, particularly total phosphorus, total nitrogen, and Chl-a were significantly reduced. The aquatic community parameters were negatively correlated with the nutrient parameters and Chl-a. The ecological restoration have adjusted the aquatic ecosystem in RLake, and many positive feedback effects among the aquatic communities made them remove internal nutrients and Chl-a more efficiently.

Mine tailings contain dangerously high levels of toxic metals which pose a constant threat to local ecosystems. Few naturally grown native plants can colonize tailings site and the existence of their root-associated microbial populations is poorly understood. The objective of this study was to give further insights into the interactions between native plants and their microbiota during natural attenuation of abandoned V–Ti magnetite mine tailings. In the present work, we first examined the native plants’ potential for phytoremediation using plant/soil analytical methods and then investigated the root microbial communities and their inferred functions using 16 S rRNA-based metagenomics. It was found that in V–Ti magnetite mine tailings the two dominant plants Bothriochloa ischaemum and Typha angustifolia were able to increase available nitrogen in the rhizosphere soil by 23.3% and 53.7% respectively. The translocation factors (TF) for both plants indicated that B. ischaemum was able to accumulate Pb (TF = 1.212), while T. angustifolia was an accumulator of Mn (TF = 2.502). The microbial community structure was more complex in the soil associated with T. angustifolia than with B. ischaemum. The presence of both plants significantly reduced the population of Acinetobacter. Specifically, B. ischaemum enriched Massilia, Opitutus and Hydrogenophaga species while T. angustifolia significantly increased rhizobia species. Multivariate analyses revealed that among all tested soil variables Fe and total organic carbon (TOC) could be the key factors in shaping the microbial structure. The putative functional analysis indicated that soil sample of B. ischaemum was abundant with nitrate/nitrite reduction-related functions while that of T. angustifolia was rich in nitrogen fixing functions. The results indicate that these native plants host a diverse range of soil microbes, whose community structure can be shaped by plant types and soil variables. It is also possible that these plants can be used to improve soil nitrogen content and serve as bioaccumulators for Pb or Mn for phytoremediation purposes.

Mine tailings contain toxic metals and can lead to serious pollution of soil environment. Phytoremediation using legumes has been regarded as an eco-friendly way for the rehabilitation of tailings-laden lands but little is known about the changes of microbial structure during the process. In the present study, we monitored the dynamic change of microbiota in the rhizosphere of Pongamia pinnata during a 2-year on-site remediation of vanadium-titanium magnetite tailings. After remediation, overall soil health conditions were significantly improved as increased available N and P contents and enzyme activities were discovered. There was also an increase of microbial carbon and nitrogen contents. The Illumina sequencing technique revealed that the abundance of taxa under Proteobacteria was increased and rhizobia-related OTUs were preferentially enriched. A significant difference was discovered for sample groups before and after remediation. Rhizobium and Nordella were identified as the keystone taxa at genus rank. The functional prediction indicated that nitrogen fixation was enhanced, corresponding well with qPCR results which showed a significant increase of nifH gene copy numbers by the 2nd year. Our findings for the first time elucidated that legume phytoremediation can effectively cause microbial communities to shift in favour of rhizobia in heavy metal contaminated soil.

Large-scale railway/highway construction in hilly areas in China has created a number of bare rock cut slopes. Artificial soil is often sprayed onto those slopes to promote revegetation. The artificial soil used is a mixture of backfill soil, humus, straws, soluble chemical fertilizer, composite material and plant seeds. The backfill soil is the most important component of the artificial soil. Knowledge of the changes in the artificial soil quality induced by backfill soil is important for the management of the revegetation of rock cut slopes. This study was conducted to assess the effects of different backfill soils on soil quality parameters and slope restoration parameters, including the particle size distribution, water-stable aggregates, soil organic carbon (SOC), organic carbon fractions, soil water characteristics (SWC), plant coverage, Margalef index and Shannon-Wiener diversity index. In experiment one, the treatments included slopes backfilled with rock fragment (RF), slopes backfilled with agricultural soil (AS) and a natural slope (NS). In experiment two, the treatments were experiment plots with different proportions of agricultural soil to rock fragments. Soils were sampled from the surface layer (0-5 cm) of the slopes. The results indicated that the backfill soil significantly affected the soil structure. RF increased the percentage of large particles (>0.25 mm) and decreased that of microparticles (

This study elucidated whether the adverse effect of soil salinity is different between Populus yunnanensis Dode males and females under climate change. We hypothesized that the magnitude and direction of sexual responses to elevated CO2and warming will be modified by soil salinity in dioecious plants. Populus yunnanensis was employed as a model species to study sexual responses in growth, photosynthesis, carbohydrate accumulation, and C and N allocation to elevated CO2and temperature under soil salinity. Cuttings were divided into control and salt groups and were exposed to two CO2regimes (ambient CO2and double ambient CO2) and two temperature regimes (ambient temperature and ambient temperature + 2.2 °C) in growth chambers. Males exhibited a greater down-regulation of the net photosynthesis rate (Anet) than did females at elevated CO2, primarily due to their poorer carbon sink–source balance and lower N availability. In the salt group, unlike in the control group, warming showed a positive effect on the growth of both females and males, and elevated CO2and temperature had a positive synergistic effect on the growth of both sexes. Sexual growth differences under soil salinity were reduced by elevated CO2, temperature, and a combination of both. These results provide evidence for sexually different responses to environmental changes in dioecious plants and support the idea that sex ratios will shift under climate change.