鼎湖山降水有机酸的变化特征及影响因素分析

VARIATION AND SOURCE ANALYSIS OF ATMOSPHERIC ORGANIC ACIDS FROM PRECIPITATION AT DINGHU MOUNTAIN

针对2009年3月至2010年2月于鼎湖山采集的大气湿沉降进行分析,旨在了解鼎湖山森林生态系统有机酸湿沉降变化特征及其影响因素.结果表明,研究期间鼎湖山甲酸、乙酸和乙二酸的当量平均浓度分别为4.12μeq.L-1、3.39μeq.L-1、2.51μeq.L-1,分别占已测定有机酸的41.1%、33.9%和25.0%;有机酸对降水酸度的总贡献为12.3%;有机酸湿沉降通量呈现湿季(4月—9月)高干季(10月—次年3月)低的季节性变化规律,湿季有机酸湿沉降通量占全年的70.8%.甲酸、乙酸和乙二酸的浓度呈显著正相关,而有机酸与无机离子的相关性不高.利用气团轨迹后推以及天气形势分析发现陆地性降水鼎湖山有机酸浓度略高于海洋性降水,陆地性降水中甲酸、乙酸和乙二酸的当量平均浓度分别为4.47μeq.L-1、3.44μeq.L-1、2.79μeq.L-1,分别是海洋性降水的1.2、1.0和1.2倍;海洋性降水中有机酸沉降负荷大,甲酸、乙酸和乙二酸沉降通量分别是陆地性降水的1.6、1.6和2.1倍.

Precipitation samples obtained from March 2009 to February 2010 at the Dinghu Mountain station,Guangdong Province,were analyzed to study wet deposition of organic acids and their origins.The results showed that the average concentrations of formic acid,acetic acid and oxalic acid were 4.12 μeq·L-1,3.39 μeq·L-1,and 2.51 μeq·L-1,respectively,which contributed to 41.1%,33.9% and 25.0% of total orgaic acids.The contribution of orgaic acids to the total free acidity of precipitation was 12.3%.Wet deposition flux of organic acids in wet seasons was higher than dry season,and contributed to 70.8% of total annual wet-deposition amount.Correlation coefficients among formic acid,acetic acid and oxalic acid were high,while the correlation coefficients with inorganic components were low.The results from back-trajectory analysis indicated that continental precipitation was the primary factor influencing organic acids in wet deposition at Dinghu Mountain.The average concentration of formic acid,acetic acid and oxalic acid from continental precipitation were 4.47 μeq·L-1,3.44 μeq·L-1,2.79 μeq·L-1,which were 1.2,1.0 and 1.2 times more than those in ocean precipitation,respectively.Deposition fluxes of formic acid,acetic acid and oxalic acid in ocean precipitation were 1.6,1.6 and 2.1 times higher than those in continental precipitation,respectively.