Research On Heavy Metal Contamination In Urban Industrial Area And Metal Tolerances Of Garden Plants

With fast urbanization,some factories located in the city were moved to the suburbs,so there left large industrial areas with serious heavy metal contamination, which will threaten urban ecosystem and citizen health.So it has become more and more necessary and important to evaluate and remedy it.So far,using hyperaccumulators on phytoremediation of the soil contaminated by heavy metal has not been applied in urban in large scales because of its own shortages.In another hand, garden plants are the main compositions in city greenings,which can not only be used to reduce and clean the heavy metal in urban contaminated soils,but also beautify the urban environment.This research took a certain industrial area in Shanghai as an example,sampling and analyzing the concentration of Zn,Cu,Pb and Cd in soil and plants,then compared the plants capacity on heavy metal absorption and accumulation.In order to explore the potential of garden plants on phytoremediation of urban contaminated soil, some lawn plants and flower plants were selected.The tolerance and accumulation capacity of heavy metal on garden plants through seed germination and seeding growth under stress of Zn,Pb,Cu and Cd were mianly studied.The major results were as follows:1.The soils in industrial area were polluted by different types and degrees,such as single contamination(extremely high Zn,Pb,Cu contamination),two or several elements compound contamination(middle Pb/Cu/Cd contamination,extremely high Zn/Cu,Pb/Zn/Cu/Cd contamination and high Pb/Cu,Pb/Zn/Cu/Cd contamination).The content of NH₄NO₃ extractable has been over the value of plant normal growth.2.The concentration of heavy metal in plants in industrial area was higher than in contrasting area.Meanwhile,some plants were found with a certain heavy metal tolerance and accumulation capacity.3.In order to research the effect of heavy metal stress on seed germination,the index such as germination rate,germination power,germination index,shoot and root length were used.The result showed that on seed germination,Zn,Pb promoted or affected not significantly,while Cu,Cd inhibited.On initial growth, Zn,Pb promoted while Cu inhibited and Cd took both effects.Root growth was inhibited of all species.So take the tolerant index of root length to compare the tolerance of plants selected in the study.The result showed that the resistance of Lolium perenne,Festuca arundinacea and Poa pratensis to Zn(Pb),Coreopsis lanceolata to Cu and Cynodon Dactylon to Cd were strongest.4.The result of hydroponic experiment showed that there was a positive correlation between concentration in solution and plants absorbing and the main content absorbed was deposited in the root.Under Zn single contamination both of two plants Zn accumulation in shoot was largest.Cu inhibited Zn transport to shoot; For Coreopsis lanceolata and Festuca arundinacea,the capacity of root with Zn accumulation was strongest under Zn/Cu compound contamination and Zn single contamination,respectively.On root Zn(Cu)absorption,the interraction between them showed "cooperation" and "antagonism" respectively.Under Zn,Cu alternate contamination,Zn took a promotion on Cu absorbing and transporting, while Cu took the opposite effect.5.The result of short-term(0-72h)stressed by Zn,Cu showed that there was a fast absorption process on them by two plants.Under various types contamination,the concentration of Zn,Cu in Coreopsis lanceolata root highest reached 16076,2036 mg/kg respectively while Festuca arundinacea reached 94389,5466 mg/kg respectively.The accumulation coefficient of Zn,Cu with Coreopsis lanceolata shoot highest reached 26,10 respectively and for Festuca arundinacea reached 23, 113 respectively.The results also show that both two plants had a strong absorbing and accumulation capacity on Zn,Cu and Zn absorbing was larger than Cu.So both plants had a widely application prospects for phytoremediation on urban soil with Zn,Cu pollution.Through planting,Zn,Cu in the soil not only could be stabilized by root with strong absorption capacity and but also could be declined and cleaned through harvesting aboveground biomass,meanwhile it also could improve urban ecological environment.