Chemical Forms of Copper in Reeds under Papermaking Wastewater Irrigation
HUI Shu-rong;WANG Ping;LIU Hui;LI Li-feng;SONG Xiao-xing;College of Science,Shenyang Agricultural University;College of Biosciences and Biotechnology, Shenyang Agricultural University;Shanghai Environmental Sanitation Engineering Design Institute Co., Ltd;Shanghai Engineering Research Center of Contaminated Sites Remediation;
The experiments we re performed in one simulated wetland environment located at our laboratory. Multiple chemical forms of copper(extracted respectively by the order of ethanol, water, Na Cl, HAC and HCl) had been measured throughout the growth periods of reeds(including germination, leaf extension, rapid growth, heading and maturity) and in different tissues(including root, stem, leaf, panicle) to get the distribution characteristics and the evolution of copper speciation in reeds under the irrigation conditions with various wastewater concentrations. The results showed that the absorption of copper in reeds was influenced by both the wastewater concentration and growth periods. When the papermaking wastewater was 300 mg·L~(-1), the concentration of copper in the body of reeds was the highest 12.65 mg·kg~(-1), and roots absorbed the most abundant copper with10.67 mg·kg~(-1), while stem absorbed the least copper with 6.02 mg·kg~(-1). The highest concentration of copper occurred at leaf extension period with 14.52 mg·kg~(-1), and the case with the lowest concentration occurred at maturity with 5.57 mg·kg~(-1). The copper forms in reeds were greatly influenced by growth periods, and had a big difference between various parts of reeds. The extractable copper by ethanol and water was 3.43 mg·kg~(-1)and 3.00 mg·kg~(-1)respectively, which were the main contents of copper in reeds. Extractable copper by ethanol and water accounted for 32.02% and 24.77% respectively of the total copper in roots. At leaf extension period, the highest proportion of extractable copper by HAC was 30.83%, and extractable copper by ethanol and water took second place, which accounted for 18.97% and 21.54% respectively. However, in the other periods, themost abundant copper was extractable content by ethanol and water, and the sum accounted for 67.31%, 54.34%, 52.49% and49.23%, respectively. Copper absorbed in reeds was origined mostly from weak acid copper in soil. The increase of wastewater concentration improved absorption rate of copper in reed. When the papermaking wastewater was 300 mg·L~(-1), the highest absorption rate of copper in reeds was 9.62%, and the highest absorption rate of copper in reeds was 3.46% at leaf extension period, which was higher than weak acid copper in soil. Papermaking wastewater irrigation could promote the absorption of copper in reeds, and the percentage of various copper chemical forms in the body of reeds changed slightly under the experimental conditions of wastewater concentration.