相关分析和主成份分析在有机酸来源分析中的应用

Application of Correlation Analysis and Principal Component Analysis in the Study of Origin of Low-Weight-Molercular Carboxylic Acids in Rainwater

源解析是大气中低分子有机酸研究的重要内容。收集了贵阳市和尚重镇2006年5月至2007年4月降水样品,测定其中有机酸和主要的无机离子。结果表明,大气降水有机酸存在显著相关关系,说明两地区均存在有机酸的共同来源。运用不同来源示踪剂发现,尚重镇低分子有机酸来源比较单一,主要是受植物或土壤的直接和间接释放作用的影响;贵阳市低分子有机酸的来源相对复杂,尤其是人为活动和大气光化学反应都可能是大气有机酸的重要来源。主成分分析把贵阳市和尚重镇大气降水中主要离子大致分为3类,尚重镇SO42-、NO3-、HCOOH、CH3COOH和(COOH)2是第一主成份,反映了农业活动、土壤释放和生物质燃烧可能是这类污染物的重要来源,贵阳市降水中CH3COOH、HCOOH和(COOH)2具有较高的因子负荷,为第三主成份占方差总和的19.68%。

The sources of carboxylic acids in precipitation are scarely investigated. Rainwater in Guiyang and Shangzhong from May 2006 to April 2007 were collected, and low--molercular--weight carboxylie acids and major anions/cations were determined. A statistically significant （p=0. 001） correlation between CH3 COOH and HCOOH at both sites indicates that they either have common or different sources having fairly constant strengths or products of the same reaction. It was suggested that the LMW carboxylic acids in Shangzhong Town were mainly derived from direct emissions from vegetations or soils. However, human activities provided a large amount of unsaturated hydrocarbons, which could be the precursor of carboxylic acids through atmospheric oxidation in Guiyang. Principal component analysis indicated that the conducted principal components account for 82.3% and 75.5% of the total variability for Guiyang and Shangzhong, respectively. Principal component analysis was conducted to constrain the sources of carboxylic acids. The variables with higher loadings in the first eigenvector （representing 28.4M of total variability） were SO4^2-、NO3-、HCOOH、CH3COOH and （COOH）2 for Shangzhong, and this factor can be an indicator of bimass burning, soil emission or agricultural activity. CH3 COOH, HCOOH and （COOH）2 in rainwater of Guiyang are the chemical variables strongly associated with the principal component 3, which accounts for 19.7% of total variance. This factor can be related to organic compounds present in rainwater and their oxidation.