Evaluation of the Macroalga, Muskgrass, for the Phytoremediation of Selenium‐Contaminated Agricultural Drainage Water by Microcosms

Abstract

Previous field studies suggested that the macroalga, muskgrass (Chara canescens Desv. & Lois), plays an important role in the removal of selenium (Se) from agricultural drainage water. This study evaluated the efficiency of Se removal from drainage water by muskgrass-vegetated wetland microcosms, and determined the extent to which muskgrass removed Se through phytoextraction and biovolatilization. Six flow-through wetland microcosms were continuously supplied with drainage water containing an average Se concentration of 22 microg L(-1) over a 24-d experimental period. The Se mass input and outflow and the rate of Se volatilization were monitored daily for each microcosm. Three microcosms containing muskgrass reduced the daily mass Se input in the inflow drainage water by 72.1%; this compared with a reduction of 50.6% of the mass Se input for three unvegetated control microcosms. Selenium accumulated in muskgrass tissues accounted for 1.9% of the total mass Se input in the microcosm, followed by 0.5% via biological volatilization. The low rates of Se volatilization from selenate-supplied muskgrass, which were 10-fold less than from selenite, were probably due to a major rate limitation in the reduction of selenate to organic forms of Se in muskgrass. This conclusion was derived from X-ray absorption spectroscopy speciation analysis, which showed that muskgrass treated with selenite contained 91% of the total Se in organic forms (selenoethers and diselenides), compared with 47% in muskgrass treated with selenate.

Application of Aquatic Plants for the Treatment of Selenium-Rich Mining Wastewater and Production of Renewable Fuels and Petrochemicals

“…Previously, muskgrass (Chara canescens)-containing microcosms grown in Se-rich drainage water showed a similar efficiency of Se removal (39.8%) [37], which was lower than Se removal rates observed for other aquatic plants, such as cattail (up to 68%), duckweed (up to 99%), hydrilla (up to 100%), and swamp lily (up to 61%) [20]. This could be explained by the fact that sodium selenite solutions were used in these experiments as a source of Se, whereas the mining wastewater used in our experiments and Se-rich drainage water [37] contained a large amount of heavy metals and other microelements whose uptake by plants could compete with TSe bioremediation.…”

“…This could be explained by the fact that sodium selenite solutions were used in these experiments as a source of Se, whereas the mining wastewater used in our experiments and Se-rich drainage water [37] contained a large amount of heavy metals and other microelements whose uptake by plants could compete with TSe bioremediation. Table 2 shows the efficiency of uptake of different microelements including heavy metals from 100% SMW by the duckweed, elodea and water clover plants.…”

An Overview of Selenium Uptake, Metabolism, and Toxicity in Plants

“…Plants volatilize the accumulated Se as DMSe and DMDSe, which are almost 600 times less toxic than elemental Se (Dumont et al, 2006). Apart from terrestrial plants (Kahakachchi et al, 2004), macrophytes such as muskgrass, Phragmites australis (Shardendu et al, 2003), and Potamogeton crispus (Wu and Guo, 2002) had been used to clean Se present in agricultural drainage water (Lin et al, 2002). Brassica species have been known to accumulate and volatilize Se (Bañuelos et al, 2005, 2007).…”

Treatment of Wastewater With Slow Rate Systems: A Review of Treatment Processes and Plant Functions

“…Trace elements at concentrations potentially harmful to environment and public health are found in industrial effluents, agricultural drainage, landfill leachates, and in some cases in municipal wastewater, especially in developing countries where industrial discharges are not controlled efficiently (Lin et al, 2002;Tanji and Kielen, 2002;Mapanda et al, 2005;Scott et al, 2005). Vegetation can play an important role in the management of trace elements.…”