Chemical Property of Precipitation and Evaluation of Water Quality in Urban Forest of Changsha City
|School||Central South University of Forestry Science and Technology|
|Keywords||Changsha City Rainfall Stemflow Throughfall Variance analyse|
Urban forest play an important role on maintaining the global and region biogeochemical cycles and water cycle,conserving water and controlling water and soil erosion, cleaning environment, maintaining the atomosphere balance and the inhabitants’healthy in mind and body.So choose the urban forest ecosystem for the study.From February,2006 to January,2007, through the ways and means comprise survey of field investigative and interior experiment, and take the biogeochemical character of rainfall, throughfall, stemflow and undergroudfall as the contents for study, the elements of nonmetal like NH4+-N,NO3--N,P,SiO2, elements of metal like K, Ca, Mg, Cu, Fe, Zn, Mn and water enviroment parameter such as DO,pH,COND,TEMP,SAL was analysed.In order to understand the improvement of the forest ecosystem of Changsha City to water quality,evaluation methods included general index,blur-mathematics and grey incidence Conseque-ntly,which can offer theoretical sustain to the construction and management for Urban Forestry of Changsha City.Main research results:(1) Result indicated that the total rainfall was 1189.8mm in the research period,which reduce 12.63% compare with annual average rainfall of the latest 10 years.The maximum concetration of nonmetal of rainfall was NH4+-N,got 1.808 mg.L-1 the min was P,only 0.092mg.L-1,the order was NH4+-N>SiO2>NO3--N>P; The maximum concetration of metal was Ca,got 3,401mg.L-1,min was Mn,only 0.073mg.L-1,the order was Ca>K>Zn>Mg>Fe>Cu>Mn.The maximum concetration of nonmetal of throughfall was SiO2,got 5.214mg.L-1,the min was P,only 0.145mg.L-1,the order was SiO2>NH4+-N>NO3--N >P;The maximum concetration of metal was Ca,got 12.626mg.L-1,min was Fe,only 0.055mg.L-1,the order was Ca>K>Mg>Zn>Mn>Cu>Fe.Except for nutrient elements like pH,DO,Cu,Fe,the concentration of inside forest increase comparing with rain outside forest.Among of them,mostly increase was K,reached 742.7%, then was Mg,reached 606%,in the opposite,smally increase was TEMP,onlyl%,then was P, got 56.6%.At the aspect of water enviroment parament,pH,DO,performance rainfall> throughfall,COND,SAL was oppsite.Tendence of TEMP was not obvious.(2) In 4 tree species,besides the nutrient element Cu performanced that concentration was high in spring and winter,low in summer and autumn,the other nutrient elements content fluctuated,but all of them tent to consistently and all displayed for high in the fall and winter,low in spring and summer.pH was higgest in Mang lietia fordiana,was 6.15,lowest was Pinus ellotii,only 4.26;COND was highest in Pinus ellotii,reached 0.721ms/cm,lowest in Mang lietia fordiana,was 0.25ms/cm,thwas was oppsite on pH;DO maintained 6-7.5,change scope was small;their TEMP and SAL also changed small.(3) In all of the chemical element content,the highest concentration was Ca,reached 32.494mg.L-1;But in the aspect of the nutritive elements input character, Cu, P, Fe, Zn was a negative value,their migration amout was 0.037 mg.L-1,0.082mg.L-1, 0.088mg.L-1 respectively,its showed that the 4 kinds of nutrient elements name type of leaching migration,but in another way,other nutrient elements like NH4+-N,NO3--N, SiO2,K,Ca,Mg,Mn was a storing type.The max migration amout was K,got 29.64mg.L-1, then was Ca,got 27.566mg.L-1.The max migration coefficient was K and min migration coefficient was P,their value was 25.99 and 0.11 respectivly,the max had 236.27 times of the min.(4) The remarkable probability between throughfall,stemflow,underground runoff and rainfall respectively for 0.012,0.008,0.027,was smaller than 0.05,so throughfall was remarkable different from the 3 other kinds of water quality.’(5) Evaluation methods included general index, blur-mathematics and grey incidence to evaluate rainfall,stemflow,throughfall and underground fall.Because remarkable probability of stemflow of 4 tree species was bigger than 0.05,so their water quality was not obvious.we can use Cinnamomum camphora’s stemflow to evaluate.The results showed:the water quality of rainfall reachedⅢdegree,polluted lightly;stemflow reached IV degree;Both throughfall and the underground runoff reachedⅢdegree.The general result of three methods was consistant with general index, so advised the water quality of urban forest take the general index as the method for evaluate.