Enzymatic Activity In Rhizosphere Soil Of Muddy Tidal Sediment And The Behaviors Of Heavy Metals In Yangze Estuary

Yangtze River estuary wetland formed with the interactions about continent and the ocean is a very important ecological system,which has unique water force,typical Biological community and the complicated environmental factors.Going with the quick development of estuary economy and the enhancement of people's living standard,the uncomparable function and value given by wetland in the human-land relationship have become more and more conspicuous in this region.Especially with the starting of the ecological project in Chongming Island,the wetland along Chongming Island as a very important wetland in this region has drawn more attentions than ever before.Material circulation and transportation is a basic function in wetland,which is not only important for maintenance of the well-going of wetland, but also very meaningful for the quality improvement for the whole regional ecological environment.Soil enzyme can hydrolyze complicated high polymer organic into the simple matter which can be easily absorbed by microorganism.Toxic substances in wetland also can be inactivated by soil enzyme.We can know the type and level of the organic transformation by the researching of the soil enzyme.Furthermore,we can choose the enzymatic criteria to show the matter circulation in wetland.Heavy metal can influence the soil enzyme's transformation ability for organic matters by activating the enzymatic activity or not,which will have effect on the wetland ability for storing or discharging some pollutants.All of which will be very meaningful for the wetland environmental functions.This paper under the project support(concentration and circulation of heavy metals in Chongming wetland)given by Shanghai Science Technology Commission takes the typical soil-plant system as researching aim,which will supply the heavy metals' circulation in wetland.It shows the changing regulation of soil enzyme and the heavy metals' influence on soil enzymes.Taking the influence on soil enzymatic activity given by heavy metals as a bridge,the heavy metals' environmental effect has been extended,based on which soil enzymatic criteria has been chosen for muddy tidal plant-absorbed metals,which will be helpful for wetland protecting and monitoring.1,Soil enzyme can hydrolyze complicated high polymer organic into the simple matter which can be easily absorbed by microorganism,which has the obvious effect on the soil development, formation of soil fertility,soil purification and the matters' cycles in ecological system..Through the systematical researching,the enzymatic activity in upper rhizophere sediments shows a little higher than that in the deeper sediment.For root soil in diffierent Biological community,the urease activity shows:Spartina alterniflora＞Scirpus mariqueter＞Phragmites australis,for different seasons the urease activity is little higher in spring and summer,a little lower in autumn and winter.Catalase activity and alkaline phosophatase acvity show the same regulation that Phragmites australis＞Scirpus mariqueter＞Spartina alterniflora.For acid phosophatase activity,the activity shows that Scirpus mariqueter＞Phragmites australis＞Spartina alterniflora.For season changes,Catalase activity,alkaline phosophatase activity and acid phosophatase acvity all show a little higher in summer and autumn and a little lower in spring and winter 2,According to national standard(GB 15618-1995),the contentment of Hg in root soil is still within the clear natural background.The average contentment of Hg in three plants is all within the 0.1μg/g.In three plants the contentment of Hg is all show a little higher in the segments on the ground and a little lower in the roots underground, for Spartina alterniflora and Phragmites australis,they all show:leaf＞stem＞root and leaf,stem＞root.However,in Scirpus mariqueter this kind of regulation is not so obvious.This phenomenon may be cause by the way about how the Hg is absorbed by plants.For the contentment of Hg in different plants,it shows that Scirpus mariqueter＞Phragmites australis＞Spartina alterniflora,this may have some relationship with the plant its own characteristics.3,The contentment of Mn Zn Cr which can be absorbed by plant all show a little higher in upper root soil layer than that in deeper root soil layer.However,the Cu show no obevious differemces in root soil,which may be influenced by the plant root and the soil biology.The contentment of Mn Cr which can be absorbed by plant show a little higher in summer and autumn,however,the peak of Zn Cu appear in winter.4,In the plant different segments,Mn shows a little higher in plant root segment when compared with that in the plant's leaf and stem.However,the contentment of Zn Cu Cr in different segments of plant show the opposite condition when compared Mn's distribution in plant body,which has convinced us that there are more Mn have been transported to the plants' stems and leaves in tidal flat environment.For different seasons,the containment of Zn in plant body shows highest in spring which may be caused by the new segments' growing which need a lot of Zn element in this process. Nevertheless,the other heavy metal's high contentment in plants' body all appear in summer and autumn which may have certain relationship with the strong Photosynthesis in these seasons.5,In the root soil environment of tidal flat in Chongming Island,plant-absorbed Zn Mn show the negative effect on the urease activity.Plant-absorbed Cr Mn show the positive effect on the acid phosophatase activity.Plant-absorbed Cr shows the negative effect on the catalase activity.The Hg shows the negative tendency for all the tested soil enzymatic activity.In the muddy tidal sediment-plant system,there also exist the relationship between the enzymatic activity and contentment of heavy metals in different segments of plants.Using the enzymatic activity can reflect the heavy metal available by plant.In muddy tidal environment,the alkaline phosophatase activity can represent the Cu Zn available by whole plant segments on the ground and the available Cr in the whole plant body.