The Tolerance And Enrichment Effects Of Soil Mercury Pollution On Three Kinds Of Turfgrass

The experiments have conducted to study the effects of adding different Hg²⁺concentrations on the seeds germination, roots configuration, and leaves photosynthetic,physiological and biochemical characteristics of three turfgrass（Axonopus compressus（Sw.） Beauv., Eremochloa ophiuroides（Munro） Hack. and Lolium perenne L.）, which were widely planted in Suzhou, and then made a comprehensive evalution of them. In addition, the eliminating efficiency on Hg²⁺ by these three turfgrass have also been investigated in this research. Furthermore, the enrichment effects and parts of three kinds of turfgrass on the soil mercury have been studied preliminarily in this research.The results obtained are listed as follows:1 Compared with the control, there were promoting effects on embryo lengths and radicel lengths of three kinds of turfgrass as mercury concentrations less than 1μmol?L-1. With the increases of mercury concentrations, the effects of inhibition on embryo lengths and radicel lengths has gradually become apparent. The seed germination rate of Axonopus compressus（Sw.） Beauv., Eremochloa ophiuroides（Munro） Hack. and Lolium perenne L. began to decline compared with the control treatment at 1.0 μmol?L-1, 5.0 μmol?L-1 and 200.0 μmol?L-1, respectively.2 Lower Hg²⁺ concentrations（0.5 and 1.0 mg?kg-1） could promote the growth of the roots of three kinds of turfgrass in the seedling stage, showing the increase of total lengths, total volumes, total surface areas, average diameters and tips of roots, in contrast to higher Hg²⁺ concentrations treatments（3.0, 5.0, 10.0, 30.0, 60.0 and 120mg?kg-1）, inhibited roots growths with mainly to the produces of root tips and the vertical elongation of roots. With the Hg²⁺ concentrations increased and time prolonged,the Pn, Gs, Tr and chlorophyll contents decreased continuously while Ci continued to rise of Axonopus compressus（Sw.） Beauv. and Eremochloa ophiuroides（Munro） Hack.,and the Pn, Gs, Tr and chlorophyll contents of Lolium perenne L. increased and then decreased, while Ci of Lolium perenne L. decreased and then increased. The lower Hg²⁺concentrations（0.5 mg?kg-1） had a promoting effects on the photosynthesis of plants, in contrast to higher Hg²⁺ concentrations（1.0, 3.0, 5.0, 10.0, 30.0, 60.0, and 120 mg?kg-1）had inhibition effects on the photosynthesis of three kinds of plants. With the increase of Hg²⁺ concentrations from 0.5 mg?kg-1 to 5.0 mg?kg-1, the expressions of SOD and POD of the leaves of turfgrass could induced, and the synthesises of SP and the accumulations of Pro could promoted. With the Hg²⁺ concentrations increased and time prolonged, the degrees of oxidation of membrane lipid had aggravated which led to the increase of the contents of MDA and Pro, and the decrease of the contents of SP and the activities of SOD.3 By using the method of principal component analysis, found that the rank of mercury tolerance strength of three kinds of turfgrass: Lolium perenne L.> Axonopus compressus（Sw.） Beauv.> Eremochloa ophiuroides（Munro） Hack.. The stepwise regression analysis showed that there were six indices which has significant effects on the mercury resistance of turfgrass, including total surface area of roots, average diameter of roots, fresh weights of aerial part, chlorophyll b contents, GS in leaves and POD activities in leaves. In addition, the prediction model of mercury resistance of turfgrass was established.4 The removal rate of mercury from high to low of each treatment were showed as follows: Lolium perenne L. > Axonopus compressus（Sw.） Beauv. > Eremochloa ophiuroides（Munro） Hack.. The repair effect of three kinds of turfgrass varies from the different levels of Hg²⁺ concentrations in soil. The best treatments of soil mercury remediation effect of Axonopus compressus（Sw.） Beauv., Eremochloa ophiuroides（Munro） Hack. and Lolium perenne L. were 5 mg?kg-1, 0.5 mg?kg-1 and 10 mg?kg-1,respectively. The removal rates were 48.33%, 39.43% and 59.27%, respectively.Mercury accumulation in turfgrass were all showed as follows: underground part >overground part. But the proportion of mercury in the overground part of Lolium perenne L. was augmented with the increase of the Hg²⁺ concentrations in the soil.5 Application of chemical regulation agents could improve the aboveground andunderground biomass and accumulation of Hg²⁺ concentrations in a certain extent, thus improving the enrichment of total mercury accumulation amounts in Lolium perenne L..The enhancement effects of three chemical control agents on the overground biomass of Lolium perenne L. were showed as follows: DTPA>EDTA>SLS. The enhancement effects of three chemical control agents on the underground biomass, overground Hg²⁺enrichment concentrations, underground Hg²⁺ enrichment concentrations, overground mercury accumulation amounts, underground mercury accumulation amounts and total mercury accumulation amounts from high to low were all showed as follows:SLS>DTPA>EDTA. Take the overground mercury accumulation amounts as the evaluation criteria, it was concluded that The best three kinds of chemical control agents and concentration combinations from high to low were showed as follows: 6 mmol?kg-1SLS>2 mmol?kg-1 EDTA>4 mmol?kg-1 SLS. The overground mercury accumulation amounts in Lolium perenne L. were increased 4.44 times, 2.79 times and 2.78 times,respectively.