Effect Of Sewage-sludge On Growth And Heavy Metal Absorption Character Of Pinus Sylvestris Seedings

During the course of sewage-sludge utilization, land-usage has become one of the important disposal ways, but the sewage-sludge contains variety of heavy metals, which become a main restriction to its usage. A lot of studies focu on the effect of plants applied the fertilizer to the soil with sewage-sludge both home and abroad, which show it can increase the fertility after applied the fertilizer to the poor soil and improve the growth of plants.There are few researches on heavy metal absorbtion instead, now.plants provide with the advantage of large biomass and Pinus sylvestris var. Mongolica has many fine characters, such as cold-resistant, drought-enduring, poorproof, fast-growing and great-biomass, etc. It has become the wind-break tree in desolate and boundless areas of northern China. Degeneration of Pinus appears in recent years due to the shortage of nutrients in soil. So the study was carried out by taking the sewage-sludge as a material to plant Pinus seedings. Through the experiment of cultivation of 2-year-old Pinus sylvestris seedlings in a pot, the effect of different sludge application on the growth and heavy metals absorbtion of seedlings was studied to provide a preliminary theoretical proof of feasibility and fertilizer in the sand. The main results were as follows:1. The Pinus sylvestris seedlings'biomass both above-ground and below-ground were significantly affected by sewage-sludge application. With the increasing of sewage-sludge,the biomass of Pinus increased firstly,then discreased.The increasment of biomass of S3,S4 treatment get the maximum. The increasment of biomass of treatment S5 began to decline, The increasment of biomass of treatment S6 was the smallest,which was lower than that of CK. The sewage-sludge at Medium or low level(S2,S3,S4) improved significantly the height,stem diameter, root length, leaf area and needle length of seedlings. Application of sewage-sludge at high level(S6) indicated obvious inhibition to the growth.2. Sludge application in appropriate level increased seedling'chlorophyll a and chlorophyll b contents.With the increasement of sewage-sludge, chlorophyll and chlorophyll b contents increased firstly,then decreased. chlorophyll a and chlorophyll b contents of S3 was the highest,CK'was lowest. The sewage-sludge had more effect on chlorophyll a than chlorophyll b. Chlorophyll a/b ratio declined in excessive application of sludge. Cu relieived the destroyment of chlorophyll,which made the ratio of chlorophyll a/b displayed the increasement-decreasement-increasement pattern. the seedlings'net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration and transpiration rate was correct with the amount and time of sewage-sludge which had been added. After applicated the sludge, the seedlings'net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration and transpiration rate of S3 treatment was significantly higher than those of CK.The values of the kind of S6 treatment was the lowest. Net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration and transpiration rate get to the top after the seedlingswere planted 80d～100d, then declined. S5, S6 declined faster than others'.The main reason is that the physiology action declined with the photosynthesis.Aother reason may be sewage-sludge at middle or high level poison the seedings with prolonging of time, which resulted in the dropment of physiology. It may be another reason to explain it.3. Sludge application improved the amount of heavy metal contents in organs of Pinus sylvestris.Thus improving the plants'accumulation of heavy metals. Under the conditions of application of sludge, the absorption rate of heavy metal of Pinus sylvestris seedlings is in order of Zn>Cu>Pb>Cd, while the migration coefficient order is Zn>Cd>Cu>Pb. Cu is the necessary element to the seedings, so it accumulated much in the bodies of seedings. S5 treatment accumulated heavy metals at the hightest level in bodies.After the application of sludge, the effective heavy metals in soil increasesd with the raising of sludge. After harvest, the heavy metals in effective state in each treatment declined less than the control. It indicated Cu,Cd,Pb,Zn could be accumulated efficiently by the seedings.To sum up, The increasement of S3 treatment reached maximum at biomass, as to the photosynthetic-physiological indicators; Heavy metals(Cu, Cd, Pb and Zn) accumulated in seedlings'bodies of S5 treatment is up to the most. The primary conclusion was drown that the volume ratio of sludge and sand is from 1:4 to 1:2 is the appropriate threshold.,which was good to the growth and heavy metals accumulation.