广州地区酸雨长期变化趋势分析

Trends of Precipitation Acidity at Guangzhou from 1992 to 2012

根据1992—2012年的酸雨观测记录,对广州地区的酸雨变化特征及其长期趋势进行了统计分析。结果表明,近21年,广州地区酸雨年、季、月变化明显,降水年均pH最低出现在1998年,其年均pH为3.43,最高出现在2012年,其年均pH为4.65。降水pH大体经历了两个阶段,1998年以前降水pH呈现波动式下降,平均变化率约为-0.14a-1,1999年后降水pH逐年增大,特别是2009年后降水pH稳步增长,平均变化率约为0.03a-1;春季酸雨污染严重,夏、秋季次之,而冬季酸雨污染相对较轻;各月降水pH均较低,pH最高月出现在12月,平均值为4.36,2月pH最低,为3.95。在污染源稳定的情况下,降水强度影响pH,降水量增大时,降水pH越高,降水电导率K也越低;风速越大,降水pH则越高,降水电导率K则越小,酸雨发生频率也越小;风向影响降水pH,出现偏西风时,酸雨污染相对严重。

The long-term trends of precipitation acidity at Guangzhou are analyzed, based on the monitoring data from 1992 to 2012. The results indicate that there was obvious inter-annual variation in precipitation pH from 1992 to 2012, the lowest in 1998 with the annual mean pH being 3.43, the highest in 2012 with the annual mean pH being 4.65. The variation of annual precipitation pH values can be divided into two stages： before 1998, precipitation pH decreased fluctuatingly, with an annual mean rate of about --0114 a^ -1; after 1999, precipitation pH increased gradually, especially after 2009 increasing steadily, with an annual mean rate about 0.03 a ^-1. The seasonal distribution of acid rains was uneven, lower in winter and spring and higher in summer and autumn. The annual variation of acid rains was also obvious, the heaviest in February with the average pH being 3.95, the lightest in December with the average pH being 4.36. When the sources of air pollution were stable, the greater the wind speed was, the higher the pH value and the lower the K （precipitation conductivity） was, consequently the smaller the occurrence frequency of acid rains. Wind direction also affects precipitation pH values. The average pH was generally lower when west winds blow in Guangzhou. When precipitation increased, the higher the pH value was, the lower the K.