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Abstract The objective of this study was to discuss the phytoremediation potential of Leersia hexandra Swartz in Cu contaminated soil and its enhancement by agronomic management practices. The results showed that L. hexandra had a high extraction capacity for copper (Cu), and Cu concentration was found maximum in shoots (755.4 mg/kg), which is very close to the Cu-hyperaccumulators. Three successive harvests did not reduce the biomass and Cu level in shoots of L. hexandra (p > 0.05), indicating that sequential harvest was feasible for the increase of total biomass and Cu extraction amount. Fertilization could obviously increase the tissue dry weight, resulting in the total amount of extracted-Cu up to 52.3%. 3-Indole acetic acid (IAA) also significantly increased biomass, causing the efficiency of Cu phytoextraction up to 204.6%. These suggested that fertilization and IAA were effective for enhancing Cu phytoextraction by L. hexandra. [ABSTRACT FROM AUTHOR]

This study used hydroponics with different copper (Cu) concentrations to assess metal accumulation and growth in two different populations ofLeersia hexandraSwartz, one obtained from a contaminated area (CP) and the other from a non-contaminated area (NCP). Data demonstrated that Cu exerted a lesser effect on the biomass of CP than NCP. The root and shoot biomass measurements of CP were significantly higher than those noted at NCP. Copper concentration in the tissues ofL. hexandrafrom CP increased markedly correlated with the concentration of metal in the culture solution, and this trend was stronger than that in NCP. Copper concentrations in roots and shoots were significantly higher in CP than NCP. As Cu stress levels in the culture solution rose, the transport coefficient of both populations decreased. Furthermore, the coefficient of CP was significantly higher than NCP. At a Cu concentration of 38.4 mg/L, the transfer factor value of CP is 40% higher than NCP. In summary, CP showed higher accumulation and resistance to Cu compared with NCP. [ABSTRACT FROM PUBLISHER]

Constructed wetlands planted with Leersia hexandra Swartz can effectively remove Cr(VI) from water. This work aims to assess the function of L. hexandra in constructed wetlands that treat Cr(VI)-contaminated water. Cr(VI) removal performance of planted and unplanted mesocosms were compared under two different temperatures (25 °C and 5 °C). Results indicated that the Cr(VI) removal performance of the planted mesocosm was more efficient and stable than that of the unplanted mesocosm. The planted mesocosm showed enhanced Cr(VI) removal even in cold season (5 °C) when the shoots were wilted. Therefore, L. hexandra played important roles in enhancing Cr(VI) removal. However, direct Cr uptake by plants only accounted for 9.3% of the total amount of Cr loading in the wetlands. This finding suggested that L. hexandra indirectly improved Cr(VI) removal by influencing other removal processes. Organic content and microbial abundance in the sediments of the planted mesocosm were significantly higher than those in the sediments of the unplanted mesocosm ( p < 0.05). The major functions of L. hexandra as an ecosystem engineer include producing organic matter and facilitating microbial growth, which are the key factors that influence Cr(VI) reduction and sequestration. A small proportion of Cr accumulated in biomass (4.7–8.6%) was released during plant litter decomposition, indicating that the effect of litter decomposition on water quality was negligible. [ABSTRACT FROM AUTHOR]

Hexavalent chromium [Cr(VI)] is considered a hazardous water pollutant. Thus, the removal of Cr(VI) is necessary for the protection of the environment. In this study, two lab-scale constructed wetlands vegetated with Leersia hexandra Swartz (CWL) were set up to purify Cr(VI)-contaminated water. X-ray absorption near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) were employed to determine the speciation of chromium (Cr) in plant tissues and substrates, respectively. Results showed that the CWL efficiently removed Cr(VI) from water. XANES analysis revealed that Cr was predominantly trivalent in plant tissues, although minimal Cr(VI) was observed in roots. In substrates, the majority of chromium existed as trivalent chromium [Cr(III)], whereas only 5.9% of chromium existed as Cr(VI). Therefore, CWL is capable of detoxifying through the reduction of Cr(VI) to Cr(III). We propose that CWL has a great potential for decontaminating and detoxifying water contaminated with Cr(VI). [ABSTRACT FROM AUTHOR]

As a low-cost treatment technology for effluent, the constructed wetlands can be applied to remove the heavy metals from wastewater.Leersia hexandraSwartz is a metal-accumulating hygrophyte with great potential to remove heavy metal from water. In this study, two pilot-scale constructed wetlands planted withL. hexandra(CWL) were set up in greenhouse to treat electroplating wastewater containing Cr, Cu and Ni. The treatment performance of CWL under different hydraulic loading rates (HLR) and initial metal concentrations were also evaluated. The results showed that CWL significantly reduced the concentrations of Cr, Cu and Ni in wastewater by 84.4%, 97.1% and 94.3%, respectively. High HLR decreased the removal efficiencies of Cr, Cu and Ni; however, the heavy metal concentrations in effluent met Emission Standard of Pollutants for Electroplating in China (ESPE) at HLR less than 0.3 m3/m2d. For the influent of 5 mg/L Cr, 10 mg/L Cu and 8 mg/L Ni, effluent concentrations were below maximum allowable concentrations in ESPE, indicating that the removal of Cr, Cu and Ni by CWL was feasible at considerably high influent metal concentrations. Mass balance showed that the primary sink for the retention of contaminants within the constructed wetland system was the sediment, which accounted for 59.5%, 83.5%, and 73.9% of the Cr, Cu and Ni, respectively. The data from the pilot wetlands support the view that CWL could be used to successfully remove Cr, Cu and Ni from electroplating wastewater. [ABSTRACT FROM PUBLISHER]