Characteristics of precipitation chemistry at Lushan Mountain, East China: 1992–2009

Abstract

Trends in precipitation pH and conductivity during 1992-2009, and in ionic compositions from January 2007 to June 2009, are reported from Lushan Mountain, one of the highest mountains in mid-east China. Annual mean pH was in the range of 4.35-5.01 and showed a statistically very significant (P < 0.01) decreasing trend with time. Annual mean conductivity showed a statistically significant (P < 0.05) increasing trend, although this was not the case for non-H conductivity. Increasing rainwater acidity was mainly caused by increasing amounts of acid substances entering the rain. The trends in precipitation pH and conductivity were directly associated with energy consumption. Over the period of study, Lushan Mountain received more rainfall in spring and summer. The pH values varied seasonally with winter minima. The winter multiyear seasonal mean pH was 4.35. The corresponding summer value was 4.88. SO (4) (2-) and NO (3) (-) were the main anions, and NH (4) (+) and Ca(2+) the main cations. The anion to cation ratio was 0.8-1.0, and that of [SO (4) (2-) ] to [NO (3) (-) ] was 2.4-3.0, much lower than that of the 1980s. However, sulfuric acid was still the main acid present. The ratio of [NH (4) (+) ] to [Ca(2+)] was about 1.0, suggesting that these two alkaline substances provided close acid neutralizing capacity. The ratio of [Cl(-)] to [Na(+)] was about 0.67, somewhat lower than that of natural precipitation. Ionic composition varied seasonally and was closely correlated to the amounts of rainfall and pollution. Trajectory analyses showed that the trajectories to Lushan Mountain could be classified in six clusters and trajectories originating from the South Sea and the areas surrounding Lushan Mountain had the greatest impacts on precipitation chemistry.