Uptake and Accumulation of Heavy Metals of Pistia Stratiotes and Eicharnia Crassipes under Combinated Pollution Condition
|School||Kunming University of Science and Technology|
|Keywords||Heavy metals accumulative capacity cultivate content physiological and biochemical classification|
Contamination of the aquatic environment by the heavy metals has become a serious problem in the world. Phytoremediation is an emerging cost-effective and eco-friendly technology that widely utilized to remove the contaminants located in water. So exploring suitable hyperaccumulators is the key step for phytoremediating metal-contaminated aquatic environment.In present study, the concentration and growth status of 5 dominant plants grown in Datunhai arsenic contaminated area was evaluated and the contamination status was also assessed by field survey. Results indicated that E. crassipes and P. stratiotes were primarily defined as the As-accumulators. The accumulative capacities of these two floating-macrophytes were also demonstrated. From orthogonal combined, we screen out the best concentration combined way of heavy metals in water planting condition. Furthermore, we analyzed how major factors effect the accumulative capacities and the change of antioxidant enzyme activity under Cd、Pb、As、Cd-Pb-As stress. Field survey shows that:1 At the studied area, the average content of As, Zn, Pb, Cu and Cd in sediment were 142.62,417.91,373.25,123.21 and 6.26 mg·kg-1 respectively, and the content of As, Zn, Pb, Cu and Cd already exceeded the limits of Environmental Quality Standards for soils (GB 15618-1995, Grade II) that the pollution was serious.2 In study area, the average content of As, Zn, Pb, Cu and Cd in water were 0.14, 0.23,0.06,0.07and 0.007 mg/L respectively, and the content of As, Pb already exceeded the limits of Environmental Quality Standards for water (GB 3838-2002, Grade V) for 1.4, 2.3 folds.3 The roots of E. crassipes could accumulate more heavy metals including As, Pb, Cu, Zn and Cd, which average heavy metal concentrations are 61.39,110.13,183.97 and 12.88 mg·kg-1 DW. The roots of P. stratiotes also could show higher concentration of heavy metals which the average concentrations are 189.39,97.00,42.35,137.30 and 19.74 mg·kg-1DW.4 The bioaccumulation factors of Cd in shoots of E. crassipes and P. stratiotes were up to 719.37 and 944.71. And the bioaccumulation factors of As in roots of E. crassipes and P.stratiotes were up to 443.78 and 1255.39. The bioaccumulation factors of As in shoots of P. stratiotes were lowest and in roots it could reach1255.39. Indoor water planting experiment results showed that:1 The heavy metals stress significant reduced the biomass of macrophytes especially in high concentration. The growth rate of these two kinds of plants was positive in control and the average growth rate was 2.23,2.32 g·day-1.however, the growth rate was negative in heavy metal treantments that the growth rate of P. stratiotes and E. crassipes could reach-1.04 and-1.84 g·day-1 in As3+. At the same time, the growh rate could reach-0.97 g·day-1,-1.78 g·day-1;-0.64 g·day-1,-1.61 g·day-1;-0.4 g·day-1,-1.41 g·day-1；-0.55 g·day-1,-0.62 g·day-1 and 0.49 g·day-1,-0.45 g·day-1 seperately in As5+, Cd, Pb, Cu and Zn treatments.The root of E. crassipes could accumulate Cd 797.03, Pb 4647.10, Arsenite 909.58 and Arsenate 805.20 mg·kg-1W Meanwhile, the roots of P. stratiotes also could accumulate Cd 1150.47, Pb 2647.45, Arsenite 1451.25 and Arsenate 1274.75 mg·kg-1DW in single heavy metal condition.2 The E. crassipes and P. stratiotes could accumulated the highest concentration of As in combination of No 7. However, in combination of No 16 both of them could accumulated the highest concentration Cd and Pb.3 The highest concentration in shoots of P. stratiotes was As and it could reach 110.87 mg·kg-1DW, the highest concentration in roots was As and Pb that could separately reach 894.31 mg·kg-1DW and 208.94 mg·kg-1DW. The highest concentration in shoots of E.crassipes was Cd and Pb that could separately reach 18.50 and 5.81 mg·kg-1DW and in roots it also could separately reach 1315.71 and 115.64 mg·kg-1DW in No7 when pH was 5. The phosphate restricted the adsorption of As of P. stratioes. Especialy the Concentration of shoots and roots were only 21.91 and 266.64 mg·kg-1DW under metaphosphate condition (60 mg·L-1). The phosphate also restricted the adsorption of As of E.crassipes.The Concentration of shoots and roots were only 13.38 mg·kg-1DW and 152.05 mg·kg-1DW under pyrophosphate condition(60 mg·L-1).4 The heavy metal could negative effect the SOD, CAT, POD activity and the ability of generated and eliminate of active oxygen no matter in single or orthogonal combined conditions. Furthermore, the different conctent Cd, Pb, As greatly affect the tolerance of P. stratiotes than E. crassipes.