Integrated Monitoring Program on Acidification of Chinese Terrestrial Systems (IMPACTS); Summary report 2003

Summary

Sulphur deposition is high at all IMPACTS sites and exceeds maximum levels observed in Europe and North-America. Total sulphur deposition at the IMPACTS sites in 2003 ranged from 1.8 to 16 g S m-2. The contribution from dry deposition is considerable; the dry deposition is often larger than the wet deposition. The IMPACTS data, in particular those from the remote Lei Gong Shan site clearly document long-range transport of air pollutants. Due to the actual and future energy consumption and emission strategy in China, the long-range transport of air pollutants may significantly increase with subsequent increased environmental damage in rural and remote areas in China. The deposition monitoring shows increased sulphur wet deposition at all sites from 2002 to 2003, corresponding with the increase reported for sulphur emissions. In addition to sulphur deposition, depositions of reactive nitrogen (nitrate and ammonia) and calcium are also important and clearly demonstrate that pH alone is not a good indicator for acid deposition. Total nitrogen deposition in 2003 ranged from 0.6 to 4.4 g N m-2. The calcium deposition ranged from 1.8 to 12 g m-2. High concentrations of ground level ozone, above critical levels for vegetation and forest, are observed at the Liu Xi He site in Guangdong province. Soil acidification gives rise to high concentrations of toxic aluminium in soil water at several sites. At the Tie Shan Ping site in Chongqing aluminium occurs at a level where long-term harmful effects on trees might be expected. Defoliation and mortality have been severe, however, fairly stable except for some variation probably related to weather conditions. Insect attacks are apparently a major cause of the damage, however, leaving the possibility of predisposing effects from air pollution as a key question for further studies. Defoliation has been considerable also in Liu Chong Guan in Guiyang, especially a considerable increase was observed in 2003. The three other catchments had minor defoliation only. High foliar nitrogen concentrations are seen in Cai Jia Tang in Hunan and, in particular in Lei Gong Shan in Guizhou. Although the phosphorous concentrations are not particularly low, the high N values result in low P/N-ratios. Possible effects of air pollution and soil acidification remain uncertain, and could include interactions with other stressors. The first reanalyses of ground vegetation in the LCG, TSP, LGS and CJT catchments were performed only two years after establishment analyses. Significant results for ground vegetation and plant biodiversity changes have been found. The results clearly show that bryophytes are good indicators of biotic effects of climatic fluctuations/climatic change. Experiences from other parts of the world, shows that vascular plants are good indicators for identifying long-term effects of acid rain and soil acidification. However, data from longer time periods are needed to identify vegetation changes that may be related to soil acidification or direct effects of air pollutants. Modelling results suggest that the currently planned 20% reduction in sulphur emissions is far from sufficient to avoid further acidification. This was shown for TSP in the 2002 report and calculations for LGS presented in this report give the same conclusion. As more data are generated, dose-response relationships, critical load estimates and model predictions will obviously be improved.