This review draws on knowledge for the treatment of heavy‐metal leachate in contaminated mine sites. Mine waste rock dumps and tailings generate a continuous stream of metalliferous and saline leachate over the long term. The mining industry has many legacy sites, which have compromised aquatic ecosystems and groundwater because of heavy‐metal contamination. Chemical and engineering methods are available and have been extensively utilised. However, these methods require intensive energy and often produce substantial volumes of secondary waste. We therefore argue in favour of phytoremediation as a sustainable remediation strategy leading towards efficient and sustainable metal removal and immobilisation through constructed wetlands.

No abstract

A glasshouse–pot trial using four levels of soil moisture (>100%, 90%, 75%, and 60% field capacity) and three levels of salinity (1.0 dSm–1, 3.5 dSm–1, and 6.0 dSm–1) was done to evaluate Na+, K+, and Cl− accumulation capacity and the physiological responses (net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, quantum efficiency of PSII, and non‐photochemical quenching) in Melilotus siculus, Tecticornia pergranulata, Cynodon dactylon , and Thinopyrum ponticum. Results reveal that the combined effects of soil water and salinity had a significant effect on Na+ and Cl− accumulation and not on that of K+. Concentrations of Na+ and Cl− and non‐photochemical quenching increased significantly whereas, the net photosynthetic rate (Pn), stomatal conductance (gs), and intercellular CO2 concentration decreased significantly in the tested plants, because of salinity. Salinity had no significant effect on the maximum quantum yield and relative water contents in shoots. Soil moisture had a significant effect on Na+, K+, and Cl− accumulation and the physiological responses in tested plants. T. pregranulata accumulated the highest concentrations of Na+ and Cl− and had the lowest Pn. C. dactylon accumulated the lowest concentrations of Na+ and Cl−, whereas Pn was the highest. No strong positive correlation between Pn and gs was evident in tested plants. We indicate that the reduced physiological performance was because of non‐stomatal activities. Na+ and Cl− accumulation capacity in the tested plants was in the following order: T. pergranulata>M. siculus>T. ponticum>C. dactylon. C. dactylon, a C4 plant, accumulated lower salt ions than the other three C3 plants. Copyright © 2015 John Wiley & Sons, Ltd.

No abstract

We measured proline and glycine betaine levels and photosynthetic performance (net-photosynthetic rate (Pn), stomatal conductance (gs), maximum quantum yield of PSII (Fv/Fm) and non-photochemical quenching (NPQ)) in relation to Na+ and Cl– accumulation in Melilotus siculus (Turra) B.D.Jacks. (Fabaceae), Tecticornia pergranulata (J.M.Black) K.A.Sheph. & Paul G.Wilson (Amaranthaceae: Salicornioideae) and Thinopyrum ponticum (Podp.) Z.-W.Liu & R.-C.Wang (Poaceae) grown under saline conditions in the greenhouse. These plants were selected in this study because of their known salt-tolerance capacity and value as forage plants. Moreover, the pasture legume M. siculus is considered to have particular potential for saline land remediation because of its salinity and waterlogging tolerance. Maximum Na+ and Cl– accumulation occurred in Te. pergranulata shoots. Minimum was in Th. ponticum shoots. Maximum Na+ accumulation occurred in the roots of Te. pergranulata, whereas that of Cl– occurred in the roots of Th. ponticum. Accumulation of both Na+ and Cl– was the least in M. siculus roots. Te. pergranulata metabolized high levels of glycine betaine (110 µmol g–1 DW). M. siculus metabolized high levels of proline (6 µmol g–1 DW). Th. ponticum accumulated intermediate levels of these organic osmolytes. No significant change occurred in Fv/Fm values. Pn value increased and NPQ value decreased in Te. pergranulata with increasing salinity and the reverse occurred in both M. siculus and Th. ponticum. A negative significant correlation occurred between Pn and glycine betaine in M. siculus and Th. ponticum. A positive significant correlation occurred between NPQ and glycine betaine in M. siculus. No correlation occurred between proline and Pn, proline and NPQ in the tested three plants. Te. pergranulata could maintain cell-osmotic balance by synthesising high levels of organic osmolytes especially glycine betaine and concurrently showing the most efficient photosynthetic performance. Compared with the levels of osmolytes in Te. pergranulata, the levels of osmolytes that occur in M. siculus and Th. ponticum were insufficient to maintain cell-osmotic balance and also that M. siculus and Th. ponticum showed a lower level of photosynthetic performance. We conclude that glycine betaine is potentially the vital organic osmolyte for Te. pergranulata and Th. ponticum enabling salinity stress tolerance. However, in M. siculus, proline appears to be the potential organic osmolyte in salinity stress tolerance. In terms of the potential of these species for stabilising saline soils in central-western New South Wales, Te. pergranulata would be the candidate of choice; however, for greater pasture value Th. ponticum would be the next.