中国区域空气污染本底站的降水化学特征

CHEMICAL CHARACTERISTICS OF PRECIPITATION IN REGIONAL AIR POLLUTION BACKGROUND STATIONS OF CHINA

分析了 3个代表不同背景特征的WMO(世界气象组织 )区域本底空气污染站黑龙江五常县龙凤山本底站 ,北京密云县古北口上甸子本底站和浙江临安本底站的降水化学特征。分析内容为降水的pH值和SO2 -4 、NO-3 、Cl- 、F- 、NH+4、K+、Na+、Ca2 +、Mg2 +诸离子的浓度。结果表明 ,降水 pH值和SO2 -4 、NO-3 、NH+4、Ca2 +具有年际变化和年变化的特征 ,但其变化趋势各站及各要素不尽一致。离子Cl- 、F- 、K+、Na+、Mg2 +浓度偏低 ,变化不明显。就多年平均而言 ,临安站的 pH值为 3站最低 ,SO2 -4 为最高。上甸子除了SO2 -4 浓度次于临安外 ,其余所有离子浓度均为 3站之首 ,而且 pH值也为 3站最高。龙凤山除了降水中的Ca2 +、Mg2 +离子浓度略高于临安外 ,其它各离子的浓度是 3站中最低的 ,pH值在 3站中的位置居中。降水化学特征演变趋势为 :3个站的降水皆呈酸性 ,其中临安最严重 ,龙凤山其次 ,上甸子相对轻一些 ,但其酸化的速率为 3站之首。

Investigation was conducted on the chemical characteristics of precipitation in three WMO regional atmospheric background stations, the representatives of three different background features: Longfengshan (Wuchang County, Heilongjiang Province), Shangdianzi (Gubeikou village, Miyun county, Beijing) and Lin'an (Lin'an County, Zhejiang Province) background stations. The pH value and the contents of ions SO 2- 4,NO - 3,Cl -,F -,NO - 3,Cl -,F -,NH + 4, K +, Na +, Ca 2+ and Mg 2+ in the precipitation were analyzed. The results show that the pH values and concentrations of SO 4 2- ,NO 3- , NH 4 + and Ca 2+ have obvious annual and inter-annual variation features. The variation trends are different for the three stations and between various elements. However, the concentrations of ions Cl -,F - , K +, Na +, and Mg 2+ are quite low, and their variations are negligible. As for the multi-year average, the pH value for Lin'an is the lowest at the three stations, but the SO 4 2- concentration is the highest; while all values at Shangdianzi are the highest, except SO 4 2- concentration is in the middle; and all ion concentrations for Longfengshan are the lowest, except Ca 2+ and Mg 2+ concentrations are slightly higher than those for Lin'an, and the pH value is in the middle. The precipitation chemical features of these background stations show that the precipitation is acid at all the three stations. The worst is at Lin'an, better at Longfengshan and the slightest at Shangfianzi. It indicates that the air quality for all these three air pollution background stations is becoming worse.