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Characteristics and correlations of ions in wet and dry precipitations in a typical acid-rain city

摘要：对贵州省都匀市2013年3月—2014年2月降水和降尘样品的pH值及主要阴阳离子(NH₄⁺、K⁺、Ca²⁺、Na⁺、Mg²⁺、F^-、Cl^-、NO₃^-、SO₄^2-)进行测定,分析其分布规律及相应离子之间的相关性.结果表明,降水和降尘水溶液pH的加权平均值分别是5.47、5.06.Ca²⁺、SO₄^2-是降水和降尘的主要离子,均值分别是141.29 μeq·L^-1、191.67 μeq·L^-1,52022.33 mg·kg^-1、87590.52 mg·kg^-1.降水和降尘中的总离子浓度、[SO₄^2-]/[NO₃^-]、[SO₄^2-+NO₃^-]/[Ca²⁺+NH₄⁺]以及NH₄⁺、K⁺、Na⁺、F^-、NO₃^-、SO₄^2-浓度在冬季达到最大,且其[SO₄^2-]/[NO₃^-]均都大于3,表明都匀市酸雨类型仍为燃煤型.从季节的变化上看,降水和降尘中的NH₄⁺、K⁺、Na⁺、F^-、SO₄^2-、Ca²⁺、Mg²⁺存在明显的相关性,相关系数|r|>0.70.降水和降尘中[SO₄^2-+NO₃^-]/[Ca²⁺+NH₄⁺]表现出相似的季节变化规律,[SO₄^2-+NO₃^-]/[Ca²⁺+NH₄⁺]与pH相关系数|r|>0.80,与降雨量、污染物来源、能源使用等有关.

Abstract：A comprehensive study was performed to measure the pH and major ions (NH₄⁺, K⁺, Ca²⁺, Na⁺, Mg²⁺, F^-, Cl^-, NO₃^- and SO₄^2-) and their correlations in precipitation and dustfall in Duyun city of Guizhou Province from March 2013 to February 2014. The results indicated that the volume-weighted mean pH level of precipitation and dustfall water solution were 5.47 and 5.06, respectively. Ca²⁺ and SO₄^2- were the dominated ions in precipitation and dustfall, with the mean concentrations of 141.29 μeq·L^-1 and 191.67 μeq·L^-1 in precipitation and 52022.33 mg·kg^-1 and 87590.52 mg·kg^-1 in dustfall, respectively. The concentrations of total ions, NH₄⁺, K⁺, Na⁺, F^-, NO₃^-, SO₄^2- as well as the ratios of [SO₄^2-]/[NO₃^-] and [SO₄^2-+NO₃^-]/[Ca²⁺+NH₄⁺] were the highest in winter among the seasonal cycle. Both values of [SO₄^2-]/[NO₃^-] were more than 3, suggesting that Duyun was a typical coal-combustion acid-rain city. For seasonal variations, significant correlations were displayed among NH₄⁺, K⁺, F^-, SO₄^2-, Na⁺, Ca²⁺ and Mg²⁺ in precipitation and dustfall with the coefficients |r|> 0.70. A similar seasonal variation tendency of [SO₄^2-+NO₃^-]/[Ca²⁺+NH₄⁺] in precipitation and dustfall was observed, and the correlation coefficient between [SO₄^2-+NO₃^-]/[Ca²⁺+NH₄⁺] and pH was greater than 0.80, mainly as a result of rainfall amount, pollutant sources and energy use.