The Enrichment Characteristics Of Cu,Cd In Plants Around Guiye And The Effects Of Plants On The Availability Of Heavy Metals In Soil

Phytoremediation has been widely used to remediate heavy metal contaminated soil,but there are few systematic studies on the investigation and screening of remediation plants and their effects on the bioavailability of heavy metals in soil after long-term phytoremediation.In this research,we selected eight areas Zhoujia(ZJ),Shenjia(SJ),Binjiangaxiaoqu(BJXQ),Wujia(WJ),Shuiquan(SQ),Jiuniugang(JNG),Yinshi(YS)and Shiwo(SW)around Guixi smelter as research objects.Through studying previous research data and doing field investigation,we collected the atmospheric deposition,soil and dominant plants samples to study the current situation of soil heavy metal pollution,and further screen potential Copper(Cu)and Cadmium(Cd)contaminated plants.Setaria pumila,Pennisetum sinese,Sedum plumbizincicola and Elsholtzia splendens continuous remediation soils were collected,and methods including soil physical and chemical properties,NH4OAc extraction,BCR classification,EDTA kinetic extraction,diffusive gradients in thin-films(DGT),germination rate,inhibition rate of root elongation and bud enzyme activity of wheat were used,to evaluate the changes of heavy metal availability after continuous phytoremediation of years and screen out remediation plants with good continuous remediation effect.The main findings are as follows:1.There are significant differences of the annual atmospheric deposition flux of Cu and Cd in the eight areas.JNG is located in the dominant downwind position of the smelter,and it had the highest deposition flux with 1340.16 mg/m2/a Cu and 123.29 mg/m2/a Cd,respectively.The minimum atmospheric deposition flux was found at ZJ,and the total annual atmospheric deposition flux of Cu and Cd were 12.19 and 2.85 mg/m2/a,respectively.The highest content of Cu and Cd in the eight regions were JNG(636.48 mg/kg)and WJ(1.2 mg/kg),while the lowest concentrations were SJ(49.48 mg/kg)and SW(0.06 mg/kg).The wind direction frequency in each station relative to the smelter are the main reasons for the significant differences in atmospheric deposition flux and soil Cu and Cd contents in the eight regions.2.The Cu content in different organs followed the order of root>stem>leaf.The highest contents of Cu in root,stem and leaf were found in Sedum plumbizincicola(180.3 mg/kg),Trogostolon(37.4 mg/kg),and Americana(176.1 mg/kg),respectively.There was no rule in the content distribution of Cd in different organs,the highest content of Cd in root,stem and leaf were found in Americana root(19.9 mg/kg),Sedum plumbizincicola stem(34.2 mg/kg)and Sedum plumbizincicola leaf(18.3 mg/kg),respectively.For Cu,the highest BCFabove for Phytolacca acinosa was 0.47,and the highest BCFroot for Pteris multifida was 2.04;For Cd,the highest BCFabove for Sedum plumbizincicola was 55.55,the highest BCFroot for Phytolacca acinosa was 36.67.The highest migration abilities(BTF)of Cu in Phytolacca acinosa and Cd in Cymbopogon were 45.75 and 6.32,respectively.3.The results of soil physical and chemical properties showed that Pennisetum sinese significantly increased the soil organic carbon content and reduced the exchangeable acid content compared with Setaria pumila,Sedum plumbizincicola and Elsholtzia splenden.The results of different methods for evaluating the bioavailability of heavy metals showed that the availability of Cu and Cd to total amount in each plant treated soils which compared with the blank as follows:The decrease extent of the NH4OAc extractable Cu followed the order of LP(44.3%)>LE(31.9%)>LW(27.2%)>LS(22.5%),and LE(51.1%)>LS(47.6%)>LP(40.1%)>LS(39.6%)for Cd;The decrease extent of the acid soluble Cu followed the order of LW(29.9%)>LP(23.5%)>LS(17.9%)>LE(16.6%),and LP(19.7%)>LW(13%)>LE(4.8%)>LS(1.2%)for Cd;The decrease extent of the EDTA-extractable Cu followed the order of LP(19.3%)>LW(13.5%)>LS(10.0%)>LE(4.1%),and LP(24.3%)>LW(13.4%)>LE(11.3%)>LS(-10.1%)for Cd;The decrease extent of the CDGT-Cu followed the order of LP(71.6%)>LW(40.6%)>LS(32.6%)>LE(24.6%),and LP(63.2%)>LE(44.2%)>LW(38.1%)>LS(31.5%)for CDGT-Cd.The bioavailability of Cu and Cd in soil was well reduced after years of continuous restoration of the four plants,and the results of correlation analysis showed that DGT can better evaluate the effects of different plants on the availability of Cu and Cd in soil than other methods.4.The results of phytotoxicity experiments showed that the biotoxicity of the plants treated soils was significantly reduced compared with blank.The increase extent of the germination rate of wheat followed the order of LP(53.6%)>LS(24.0%)>LE(3.7%)>LW(3.2%);The decrease extent of the inhibition rate of root growth followed the order of LP(53.6%)>LS(24.0%)>LE(3.7%)>LW(3.2%);The decrease extent of the CAT enzyme activity in wheat bud followed the order of LP(48.0%)>LE(45.9%)>LS(41.7%)>LW(36.8%),and LP(57.8%)>LE(48.7%)>LW(42.5%)>LS(32.2%)for SOD,and LP(60.4%)>LW(46.2%)>LE(44.4%)>LS(43.3%)for POD.In summary,Pennisetum sinese is more suitable as Cu and Cd remediation plants for years.Figure[21]table[11]reference[170]...