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Background Meadows and shrublands are two major vegetation types on the Qinghai-Tibetan Plateau, but little is known about biochemical characteristics and its relation to decomposability of soil organic carbon (OC) under these two vegetation types. The present study was designed to evaluate effects of aspectvegetation complex on biochemical characteristics and decomposability of soil OC. Methods Two hills were randomly selected; both with vegetation being naturally divided into southward meadows and northward shrublands by a ridge, and soils were sampled at depths of 0-15 and 15-30 cm, along contours traversing the meadow and shrubland sites. Particulate (particle size 2-0.05 mm) OC and nitrogen (N), microbial biomass C and N, non-cellulosic sugars, and CuO lignin were analyzed, and OC mineralization was measured for 49 days at 18 and 25°C under laboratory incubation, respectively. Results More than half of soil OC was present as particulate fraction across all samples, indicating the coarse nature of soil organic matter in the region. Averaging over depths, shrublands contained 87.7−114.1 g OC and 7.7−9.3 g N per kg soil, which were 63−78 and 26−31 % higher than those in meadows, respectively. Meanwhile the C/N ratio of soil organic matter was 11.4 −12.3 under shrublands, being 29−40 % higher than that under meadows. Soil OC under meadows was richer in noncellulosic carbohydrates and microbial biomass in the 0-15 and 15-30 cm depths but contained less lignin in the 15-30 cm depth. Ratios of microbiallyto plant-derived monosaccharides and between acid and aldehyde of the vanillyl units were greater in soils under shrublands, showing more abundant microbiallyderived sugars and microbially-transformed ligneous substances in OC as compared to meadow soils. By the end of 49 days' incubation, total CO 2 -C evolution from soils under meadows was 15.0-16.2 mg g −1 OC averaging over incubation temperatures and soil depths, being 27-55 % greater than that under shrublands.

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A novel material named Fe/Mn-C layered double hydroxide composite (Fe/Mn-C-LDH) was synthesized to remove arsenic from an aqueous solution. The removal performance of the composite toward arsenic ions was studied through the batch experiments. The experiment results showed that Fe/Mn-C-LDH exhibited a high adsorption capacity of 46.47 mg/g for As(III) and 37.84 mg/g for As(V) at 318 K, respectively. In addition, the investigation of the release of Fe3+ and Mn2+ in the process of arsenic adsorption revealed that the Fe/Mn-C-LDH exhibited better stability than Fe/Mn-layer double hydroxide (Fe/Mn-LDH) with fewer Mn2+ and Fe3+ releasing under the same condition. The BET results showed that the specific surface area of Fe/Mn-C-LDH decreased after adsorption of As (III) and As (V). Furthermore, the Density Functional Theory (DFT) calculation results proved that the adsorbent combining arsenic by T-site to produce a better adsorption effect for arsenic. Possessing better stability and adsorption capacity, Fe/Mn-C-LDH could potentially serve as a perfect adsorbent for arsenic removal from an aqueous environment. It would provide a promising approach for removing heavy metal from the aquatic environment in the future.

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As an innovative and economical material, hydroxyapatite does little harm to the environment. In this study, a magnesium hydroxyapatite (Mg-HAP) adsorbent was prepared by doping magnesium. Magnesium doping can increase the hydroxyl groups on the surface of Mg-HAP to form more adsorption sites and improve the removal effect of the heavy metal Zn(II) in water. This study was implemented to survey the effect of different sorption elements, including the liquor initial pH, initial concentration, dose of adsorbents, and other factors, on the adsorption effect. The outcomes show that the sorption effect was best at the time that the liquor was weakly acidic (pH = 6); At a pH of 6, the temperature of 25 °C when the optimal dosage of adsorbent is 0.25 g, the maximum adsorption amount is 62.11 mg/g. Through data fitting, the adsorption process can be accurately described as a pseudo-second-order dynamics model and the Langmuir isotherm equation. According to the thermodynamic analysis, the sorption of zinc ions by Mg-HAP belongs to the process of spontaneous endothermic and entropy increase, and the increase of temperature was conducive to adsorption. Material characterization and analysis indicate that surface complexation and dissolution-precipitation was the main mechanism for adsorption of Zn(II).

A novel adsorbent Mn-Fe layered double hydroxides intercalated with ethylenediaminete-traacetic (EDTA@MF-LDHs) was synthesized by a low saturation coprecipitation method. The behavior and mechanism of As(III) removed by EDTA@MF-LDHs were investigated in detail in comparison with the carbonate intercalated Mn-Fe layered double hydroxides (CO3@MF-LDHs). The results showed that EDTA@MF-LDHs had a higher removal efficiency for As(III) than As(V) with a broader pH range than CO3@MF-LDH. The large adsorption capacity of EDTA@MF-LDHs is related to its large interlayer spacing and the high affinity of its surface hydroxyl groups. The maximum adsorption capacity for As(III) is 66.76 mg/g at pH 7. The FT-IR and XPS characterization indicated that the removal mechanism of the As(III) on EDTA@MF-LDHs include surface complexation, redox, and ion exchange.

Reseeding with native plants to rebuild alpine meadow has become a popular way of ecological restoration. However, the harsh environment poses a great challenge to the establishment of native plants due to poor management of water and nutrients. How water–fertilizer interaction influences dominant grass species is still unclear, and reasonable water and fertilizer conditions are still not determined. Our results showed that addition of nitrogen could mitigate the photosynthetic and water-use traits caused by water stress, i.e., a reduction in Pn and water use results from fewer and thinner leaves, weak stomatal traits, etc. Compared to the control, the peak Pn values of Poa crymophila, Festuca coelestis, and Stipa purpurea increased significantly (71.2%, 108.4%, and 25.4%, respectively). Under drought stress, Pn tended to decrease due to reduced stomatal conductance (Gs). However, appropriate fertilization buffered against Pn decreases by altering the stomatal size and regulating the Gs. Based on reduced water consumption, the water-use efficiency of P. crymophila and F. coelestis decreased whereas that of S. purpurea increased. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea growth were suitable for the alpine region. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea were suitable for their establishment in the alpine region. A reasonable water–fertilizer combination could effectively reduce the risk of establishment failure in ecological restoration.