| Because of serious pollution of the environment caused by human factors of acid rain, had become a global hot topic. Brought great harm to ecological environment and human health, were also restricts the development of global economy, acid rain had become one of the world’s three major public hazard. Forest ecological system would enhance the acidity of rainfall, thus effectively alleviate the harm of acid rain, is the human one of the most powerful green barriers in the process of economic development.With camphor tree plantations in changsha city as the research object in the study,which was made of the changes and variation in7water-soluble ions including SO42-、NO3-、Cl-、NO2-、F-、Br-、PO43-of rainwater passing through the different strata of Camphor forest ecosystems,Water samples were taken as rainfall, throughfall, stemflow and surface runoff.The result showed that:(1)Br-and PO43-were failed to be detected in waters. Both SO42-(Accounted for36.07%to62.05%of the total anion) and NO3-(Accounted for28.13%to45.51%of the total anion) were the major inorganic anions in waters under Camphor forests, which accounted for79.17%-90.18%of total anion contents in the forest ecosystems.㏄recipitation and total anion, SO42-and NO3-all cash for logarithmic function relation, and NO2-、F-were all characterized by power function relation, and the regression equation coefficient R2of these functions changed within the scope of0.41to0.56.(3)Each hydrological component SO42-, NO3-, Cl-and NO2-, F" content cha nged greatly:Both atmospheric precipitation and trunk stem flow were in an or der SO42-(58.24μeq/L、423.64μeq/L)>NO3-(50.59μeq/L、192.10μeq/L)>Cl-(12.55μe q/L、47.93μeq/L)>F-(5.06μeq/L、14.11μeq/L)>NO2-(2.66μeq/L、5.01μeq/L),and fo r throughfall water was SO42-(259.71μeq/L)>NO3-(159.89μeq/L)>Cl-(55.00μeq/L)> NO2-(31.48μeq/L)>F-(23.92μeq/L)、surface runoff was NO3-(209.42μeq/L)>SO42-(165.95μeq/L)>Cl"(58.38μeq/L)>F-(17.01μeq/L)>NO2-(9.38μeq/L); SO42-,NO3-, Cl", F" content size according to the trunk diameter class were in an order:dl>d2>d3 >d4, but the content of NO2-level according to the diameter class, respectively dl>d4>d2>d3.(4)The leaching coefficients were4.13、2.90、3.96、4.50and10.46;7.27、3.80、3.82、2.40and1.88, and2.85、4.14、4.65、2.89and3.53for SO42-、NO3-、Cl-、 F-、NO2-in throughfall, stemflow and surface runoff, respectively.Leaching coefficients is greater than1, which indicated that anion in the hydrology process of camphor tree all showed different degree of enrichment effect.(5)The pH value averaged4.86in rainwater and the ratio of SO42-/NO3-was1.15in the study area, which indicated that the rainwater was a sulfuric-nitric mixed acid rain.A significant positive correlation(P<0.01) was found between rainfall and throughfall for all anions, except for NO2-,but not found between rainfall and throughfall, surface runoff.(6)Cl-、NO2-in throughfall water were significantly positive(P<0.05) related to that in stemflow. SO42-、Cl-、F-in surface runoff were positive(P<0.05) related to that in throughfall, and Cl、NO2in surface runoff were positive(P<0.05) related to that in stemflow, but for NO3was negative relationship.(7)SO42-、NO3-、Cl-、F-、NO2-in forest hydrological component had no significant correlation with precipitation.(8)NO3-and NO2-between throughfall water PH and surface runoff had a significant negative correlation(P<0.01), and surface runoff SO42-show significant positive correlation(P<0.05), which indicated that the NO3-and NO2-helps promote surface water acidification, and SO42-can reduce surface water acidification.(9)Through water PH average5.95, to neutralize the acid rain, trunk stem flow average PH4.83, slightly by acidification trend, surface runoff PH average7.03, closed to neutral.Suggesting that Camphor tree could absorb acid material,and let the acid nutrient in water soluble ionic form to its own system internal migration, transformation, Our results demonstrated that Camphor forest ecosystems had a relative high ability to purify acid rainfall through adsorbing, uptaking, leaching and neutralizing processes. |
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