粵港細粒子(PM_2.5)污染導致能見度下降與灰霾天氣形成的研究

為了研究珠三角地區細粒子氣溶膠的環境效應,使用粵港地區長期氣象資料和珠三角大氣成分站網高分辨率資料,結合衛星遙感AOD結果,分析了珠三角地區由于細粒子(PM2.5)污染導致能見度下降與形成灰霾天氣的長期變化趨勢.結果表明,近年來珠江三角洲地區的氣溶膠污染日趨嚴重,氣溶膠云一年四季都可以出現,且長期穩定存在,重污染區位于珠江口以西的珠江三角洲西側.灰霾天氣主要出現在10月至次年4月.灰霾導致能見度惡化.自20世紀80年代初開始,該地區的能見度急劇惡化,灰霾天氣顯著增加,其中有3次大的波動,分別代表珠江三角洲經濟發展相伴隨的粗顆粒氣溶膠污染、硫酸鹽+粗顆粒氣溶膠污染、光化學過程的細粒子+硫酸鹽和粗顆粒氣溶膠的復合污染時期.霧和輕霧造成的低能見度的長期變化趨勢,沒有由于人類活動影響或經濟發展影響帶來趨勢性變化,其波動主要反映了氣候波動固有的年際和年代際變化.珠江三角洲能見度的惡化主要與細粒子關系比較大,PM10有一半年份的年均值超過國家二級標準的年均值限值(70μg·m-3),而PM2.5年均值全部年份都超過國家二級標準的年均值限值(35μg·m-3),尤其是有些年份的年均值濃度超過標準限值的2倍,細粒子濃度甚高.另外,近年PM2.5占PM10的比重非常高,可達51%～79%,黑碳氣溶膠濃度非常高,月均值達到5.0～9.1μg·m-3.和20余年前的資料相比較,細粒子在氣溶膠中的比重有明顯增加.因而在目前粵港地區的氣溶膠污染中,主要是細粒子的污染,尤其是黑碳氣溶膠污染嚴重. In order to investigate the environmental effects of fine particulate aerosols(PM2.5)in the Pearl River Delta (PRD), long-term meteorological data and high-resolution of atmospheric composition observations in the PRD and Hong Kong, as well as satellite-based Aerosol Optical Depth (AOD) data, were used to analyze the long-term variation trends of PM2.5-induced haze weather formation and visibility deterioration. The results indicated that the pollution of aerosols worsened over the PRD in recent years. The cloud of aerosol occurred all year round, with an area of heavy pollution located in the western side of the Pearl River Estuary. The haze weather mainly occurred from October to next April, resulting in visibility deterioration. Since the beginning of the 1980s, the frequency of hazy weather obviously increased and visibility dramatically deteriorated over the PRD. There were three major visibility deterioration fluctuations accompanied with the development of economy, arising from dust pollution, the sulphate and dust pollution, and the dust, sulphate, and automobile exhaust pollution caused by photochemical process, respectively. There was no indication that the long-term tendency of fog and light fog days was affected by human activities or economical development, and its fluctuation was governed by the intrinsically inter-annual and inter-decadal variations of climate. The deterioration of visibility was strongly associated with fine particle pollutions over the PRD. Half of monthly mean PM10 observations exceeded the mean critical value of national second graded standard (70 μg·m-3), and all of mean PM2.5 values exceeded the mean critical value of U.S. national standard (35 μg·m-3). Some mean values of PM2.5 almost reached twice the standard value, indicating high fine particle concentrations. The ratio of PM2.5 to PM10 was also very high about 51%~79%. Monthly mean black carbon aerosol concentration was up to 5.0~9.1 μg·m-3. Therefore, the current aerosol pollution over the Guangdong and Hong Kong is featured by significant fine particle pollution, in particular the black carbon pollution. Compared to observations data 20 years ago, the ratio of fine particles has obviously increased.