A nursery experiment was conducted to evaluate the potential role of arbuscular mycorrhizal (AM) fungi in encouraging the vegetation cover on bauxite residue (red mud) sites. An alkali tolerant bermudagrass (Cynodon dactylon) adapted to local conditions were grown in red mud with different amendments with and without AM fungi to assess mycorrhizal effects on plant growth, mineral nutrition, metal uptake and neutralization of bauxite residue. Inoculation of AM fungi significantly increased the plant growth, nutrient uptake and reduced Fe, Al accumulation in plant tissue and also improved the soil physico-chemical and biochemical properties. Gypsum and sludge amended treatments inoculated with AM fungi had maximum biomass, nutrient uptake and reduced accumulation of metals. The neutralization of red mud was significant in presence of AM fungi than control. The experiment provided evidence for the potential use of bermudagrass in combination with AM fungi for ecological restoration of bauxite residue sites.

The present study sought to evaluate the efficiency and kinetics of nitrogen removal in Horizontal Subsurface Flow Constructed Wetlands (HSSF-CWs) cultivated with different plant species used in the treatment of swine wastewater (SWW), under different nitrogen loading rates (LRTKN). For this purpose, nine tanks measuring 2.0 × 0.5 × 0.6 m were used, one maintained without plants (CW₁), while in the others two plant species were evaluated: CW₃, CW₅, CW₇, and CW₉ were planted with Tifton 85 grass (Cynodon spp.) and CW₂, CW₄, CW₆, and CW₈ were planted with cattail (Typha latifolia). The CWs received TKN application rates between 110 and 413 kg ha⁻¹ day⁻¹, and the removal efficiencies ranged from 27.6 to 44.9%. The average mass removal rates (MRR) for TKN and NH₄⁺ ranged from 45.3 to 115.9 kg ha⁻¹ day⁻¹ and 28.9 to 66.5 kg ha⁻¹ day⁻¹, respectively. Tifton 85 grass and cattail contributed, respectively, to 2.22 to 8.7% and 0.03 to 1.67% of the TKN mass removed by the CWs (MRR), equivalent to extraction rates of 2.72 to 4.94 kg ha⁻¹ day⁻¹ and 0.04 to 1.11 kg ha⁻¹ day⁻¹. Coefficients estimated by conventional, modified, and residual first-order models ranged from 0.017 to 0.0187 day⁻¹, 0.0691 to 0.1285 day⁻¹, and 0.0298 to 0.0715 day⁻¹, respectively. The modified first-order model and that with residual, due to their higher R² values (R² > 93%), indicated a good fit and considerable reliability of these equations to describe the processes of nitrogen removal from swine wastewater treated in HSSF-CW, and due to their mathematical simplicity and improvements in the representation of real behavior, they should be preferred for modeling of these systems.

The purpose of this study was to analyze the effects of the application of multivariate criteria of principal components and hierarchical clustering as a mechanism for monitoring the performance of Tifton 85 grass (Cynodon spp.) planted in horizontal subsurface flow constructed wetland reactor (HSSF-CW) under different organic (OLR), nutritional and sodium loads of swine wastewater (SW). The HSSF-CW planted with Tifton 85 grass was used as a swine wastewater after treatment applying organic loading rates between 26.1 (1st cut) and 360.6 kg ha⁻¹ day⁻¹ COD (8th cut). The maximum performances of HSSF-CW consisted of 52.0 t ha⁻¹ of productivity and 24.0% of crude protein, with the application of 59.7, 64.2, and 31.2 kg ha⁻¹ day⁻¹ of TKN, PT, and K⁺, respectively. The eleven original variables generated four new components, with PC₄ accounting for 94.0% of total variance, a condition strengthened with four data groupings greater than 48% similarity and three data groupings greater than 95% similarity between the variables. There was a strong association between of nitrogen, phosphorus, and potassium concentration by the hierarchical grouping and the intermediate cuts and lower temperatures.

Revegetation in the water-level-fluctuation zone (WLFZ) could stabilize riverbanks, maintain local biodiversity, and improve reservoir water quality in the Three Gorges Reservoir Region (TGRR). However, submergence and cadmium (Cd) may seriously affect the survival of transplantations. Bermuda grass (Cynodon dactylon) is a stoloniferous and rhizomatous prostrate weed displaying high growth rate. A previous study has demonstrated that Bermuda grass can tolerate deep submergence and Cd stress, respectively. In the present study, we further analyzed physiological responses of Bermuda grass induced by Cd-and-submergence stress. The ultimate goal was to explore the possibility of using Bermuda grass for revegetation in the WLFZ of China's TGRR and other riparian areas. The Cd-and-submergence-treated plants had higher malondialdehyde contents and peroxidase than control, and both increased with the Cd concentration increase. All treated plants catalase activity increased with the experimental duration increases, and their superoxide dismutase also gradually increased with the Cd concentration from 1 day to 15 days. Total biomass of the same Cd-and-submergence plants increased along the experimental duration as well. Plants exposed to Cd-and-submergence stress showed shoot elongation. The heights of all treated plants were taller than those of the control. Leaf chlorophyll contents, maximum leaf length, and soluble sugars contents of all the Cd-and-submergence-treated plants were more than those of the untreated control. Although Cd inhibits plants growth, decreases chlorophyll and biomass content, and with the submergence induced the leaf and shoot elongation, more part of the Cd-and-submergence stress plants appeared in the air, exhibited fast growth with maintenance of leaf color, which guaranteed the plants' photosynthesis, and ensured the total biomass and carbohydrate sustainability, further promoting Cd-and-submergence tolerance. The results imply that the negative effects of cadmium on Bermuda grass growth might be offset by submergence.

Introduction From the metallurgic industry zone of Dambovita County, we harvested and analyzed seven herbaceous plants species (Lolium perenne, Festuca pratensis, Stipa capillata, Agrostis alba, Cynodon dactylon, Luzula campestris, and Agrostis tenuis) to establish the heavy metal accumulation levels in these species. Materials and method The heavy metal contents (for Cr, Mn, Zn, Sr, Cu, Ba, and Sn) were determined by analyzing the dry matter with an inductively coupled plasma-atomic emission spectrometer. This method has detection limits of 0.4-0.6 mg/kg for the analyzed metals. The heavy metal concentrations in plants harvested from the industrial area are in milligram per kilogram of dry matter and ranged from 10.03 to 191.98 mg/kg of dry matter for Cr, 165.89 to 1,103.92 mg/kg of dry matter for Mn, 62.09 to 921.67 mg/kg of dry matter for Zn, 29.21 to 50.12 mg/kg of dry matter for Sr, 0.99 to 113.83 mg/kg of dry matter for Cu, 58.66 to 133.51 mg/kg of dry matter for Ba, and 8.38 to 276.44 mg/kg of dry matter for Sn. The heavy metal accumulation levels in the studied species of plants were calculated by the rapport between the concentration level of the metal in plant samples and the level of the same metal in the soil, near the radicular system for each species of plants. Results The highest accumulation levels were found in A. alba for Cr (267.69%); in L. perenne for Mn (51.45%), Sr (114.35%), and Ba (60.81%); and in C. dactylon for Zn (136.62%), Cu (97.65%), and F. pratensis for Sn (704.00%).