摘要
动态模型可以弥补已有的观测的时间序列资料的不足,以及用模拟森林及湖泊生态系统过去和未来化学变化的静态临界负荷计算的缺陷。他们用于生态系统酸化的动态评价,制定目标负荷函数来描述在给定的目标年份,系统要达到的化学或生物学标准所需要硫和氮的减排量的共同影响作用。在瑞典,利用动态酸化模型MAGIC应用到不受农业活动影响的133个湖泊,同时利用SAFE模型应用到645个森林站点。在哥德堡协议(Gothenburg protocol)的实施下,从长期来看可以使瑞典大约75%的森林土壤得到保护,但瑞典的最终目标是要达到95%。2030年以后,酸化生态系统的恢复速度将十分缓慢,并且也只能涉及到有限的地区。如果1980年以来没有实施减排措施,长期来看将有87%的林区土壤会变成人们不愿看到的境况。1990年,大约有17%的未受农业活动影响的瑞典湖泊的酸性沉降物超过临界负荷。在哥德堡协议的实施下,2010年这个比例将会缩小到10%。酸化湖泊的恢复速度要比土壤的恢复速度快的多。根据MAGIC模型的模拟结果,在工业革命以前,酸敏感湖泊的酸中和容量(ANC)中间值为107 μeq/L,到酸化高峰时(1975～1990年)降至60 μeq/L,预计到2010年又会增加到80μeq/L。估计进一步增加是非常小的,2010～2040年只有2μeq/L。保护瑞典95%的湖泊的目标需要在哥德堡协议水平上进一步实施减排措施。瑞典有7000多个湖泊人工定期施加石灰,进行人工酸化恢复,如果不想对湖泊水体化学和生物产生负面作用,在短暂的未来,人工施加石灰的措施是不可能被废止的。
Dynamic models complement existing time series of observations and static critical load calculations by simulating past and future development of chemistry in forest and lake ecosystems.They are used for dynamic assessment of the acidification and to produce target load functions,that describe what combinations of nitrogen and sulfur emission reductions are needed to achieve a chemical or biological criterion in a given target year. The Swedish approach has been to apply the dynamic acidification models MAGIC,to 133 lakes unaffected by agriculture and SAFE,to 645 productive forest sites.While the long-term goal is to protect 95% of the area,implementation of the Gothenburg protocol will protect approximately 75% of forest soils in the long term.After 2030,recovery will be very slow and involve only a limited geographical area.If there had been no emission reductions after 1980,87% of the forest area would have unwanted soil status in the long term.In 1990,approximately 17% of all Swedish lakes unaffected by agriculture received an acidifying deposition above critical load.This fraction will decrease to 10% in 2010 after implementation of the Gothenburg protocol.The acidified lakes of Sweden will recover faster than the soils.According to the MAGIC model the median pre-industrial ANC of 107μeqL^(-1) in acid sensitive lakes decreased to about 60 μeq L ^(-1) at the peak of the acidification (1975-1990) and increases to 80 μeq L ^(-1) by 2010.Further increases were small,only 2 μeq L ^(-1) between 2010 and 2040.Protecting 95% of the lakes will require further emission reductions below the Gothenburg protocol levels.More than 7000 lakes are limed regularly in Sweden and it is unlikely that this practice can be discontinued in the near future without adverse effects on lake chemistry and biology.
