Research On The Characteristics Of Anion And Nitrogen Under Acid Deposition In Shaoshan Forest

Acid rain problem becomes more and more serious in China since 1990s', especially in Hunan province situated in Central-south China. This article have studied on the following subject:(1)The leaching law of major ions in forested acid precipitation in a subtropical forest was examined based on the experiment in 4 fields sampling sites in Shaoshan forest from January 2001 to June 2002.(2) The input-output fluxes of nitrogen in Shaoshan forest ecosystem under acid deposition were examined in Caijiatang station in Shaoshan forest during the year of 2001.(3)The net retention of nitrogen in Shaoshan forest ecosystem were examined in Caijiatang station in Shaoshan forest during the year of 2001.(4)Take Changsha city for example, the atmospheric pollution and acid rain pollution are also researched. The time and spatial variation law of main air pollutants such as SO₂, NO_X(NO₂), TSP, and the characteristics of the representative chemical compositions of rainwater are analyzed and discussed based on the three monitoring stations in Changsha in the period of 2000²001. And the influence of air pollutants on the formation of acid rain is analyzed.Results showed that:(1)The pH value obviously increased and the ionic uptake evidences were proved by SO₄^2-, NO₃^-, Mg²⁺ and NH₄⁺, especially for NH₄⁺ and NO₃^-, when rain water passing through the canopies. The dissolved percentage of SO₄^2-, Ca²⁺ and Mg²⁺ had the tendency to reduce with increase of the rainfall. Dissolved percentage of Ca²⁺, K⁺ and Cl^- showed a tendency to increase along with increase of pH. Shaoshan forest canopies has the strongest effects on the uptake of SO₄^2-,NO₃^- under acid rain. Ionic leaching order in Shaoshan forest based on the average ionic concentrations of 18 months monitoring was: K⁺>Ca²⁺>Cl^->Mg²⁺>SO₄^2->NO₃^->NH₄⁺>Na⁺.(2)N-input flux was 53.80 kgN·ha^-1 in 2001, and the flux of NH₄⁺ accounted for 64% of total N-input flux. The N-output flux was 3.56 kgN·ha^-1 in 2001, and the flux of NO₃^- accounted for 64% of total N-output, which suggested a net retention of 50.24 kgN ha^-1 in Shaoshan forest. The flux in May, June and July accounted for 72% of the total annual N-output, and most of them exported out Shaoshan forest ecosystem as NO₃^-, indicating that the large amount of precipitation was the main cause for the loss of N in Shaoshan(.3)N-input flux was 53.80 kgN·ha^-1 in 2001, and the N-output flux was 3.56 kgN·ha^-1 in 2001, and the N-retention flux...