Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an, China.
PLoS One. 2013 Jul 18;8(7):e68894. doi: 10.1371/journal.pone.0068894. Print 2013.
Long-term (1973 to 2010) trends in visibility at Chengdu, China were investigated using meteorological data from the U.S. National Climatic Data Center. The visual range exhibited a declining trend before 1982, a slight increase between 1983 and 1995, a sharp decrease between 1996 and 2005, and some improvements after 2006. The trends in visibility were generally consistent with the economic development and implementation of pollution controls in China. Intensive PM2.5 measurements were conducted from 2009 to 2010 to determine the causes of visibility degradation. An analysis based on a modification of the IMPROVE approach indicated that PM2.5 ammonium bisulfate contributed 27.7% to the light extinction coefficient (bext ); this was followed by organic mass (21.7%), moisture (20.6%), and ammonium nitrate (16.3%). Contributions from elemental carbon (9.4%) and soil dust (4.3%) were relatively minor. Anthropogenic aerosol components (sulfate, nitrate, and elemental carbon) and moisture at the surface also were important determinants of the aerosol optical depth (AOD) at 550 nm, and the spatial distributions of both bext and AOD were strongly affected by regional topography. A Positive Matrix Factorization receptor model suggested that coal combustion was the largest contributor to PM2.5 mass (42.3%) and the dry-air light-scattering coefficient (47.7%); this was followed by vehicular emissions (23.4% and 20.5%, respectively), industrial emissions (14.9% and 18.8%), biomass burning (12.8% and 11.9%), and fugitive dust (6.6% and 1.1%). Our observations provide a scientific basis for improving visibility in this area.
利用美国国家气候数据中心的气象数据，研究了中国成都的长期（1973 年至 2010 年）能见度趋势。在 1982 年之前，视程呈下降趋势，在 1983 年至 1995 年之间略有增加，在 1996 年至 2005 年之间急剧下降，在 2006 年之后有所改善。能见度趋势与中国的经济发展和污染控制实施基本一致。2009 年至 2010 年进行了密集的 PM2.5 测量，以确定能见度下降的原因。基于 IMPROVE 方法的改进分析表明，PM2.5 硫酸铵对消光系数（bext）的贡献为 27.7%；其次是有机物质（21.7%）、水分（20.6%）和硝酸铵（16.3%）。元素碳（9.4%）和土壤尘埃（4.3%）的贡献相对较小。人为气溶胶成分（硫酸盐、硝酸盐和元素碳）和地表水分也是 550nm 处气溶胶光学深度（AOD）的重要决定因素，bext 和 AOD 的空间分布均受到区域地形的强烈影响。正矩阵因子化受体模型表明，煤炭燃烧是 PM2.5 质量（42.3%）和干燥空气光散射系数（47.7%）的最大贡献者；其次是机动车排放（分别为 23.4%和 20.5%）、工业排放（14.9%和 18.8%）、生物质燃烧（12.8%和 11.9%）和扬尘（分别为 6.6%和 1.1%）。我们的观测结果为改善该地区的能见度提供了科学依据。
