中国东北与西北地区季节冻土中水溶性离子质量分数及土壤盐渍化特征

Characteristics of mass fractions of water-soluble ions and salinization in seasonally frozen soil of Northeast and Northwest China

采集季节冻土样品90份,利用离子色谱量化分析其中水溶性离子的质量分数,阐明中国东北及西北地区季节冻土中水溶性离子的分布特征及潜在来源.结果表明,中国季节冻土中离子组分具有较强的空间差异性,表现出“东北低、西北高”的特征.主要阳离子平均质量分数w(Na^(+))、w(Ca^(2+))、w(K^(+))、w(Mg^(2+))东北地区分别为(5.10、5.60、1.25、0.94)×10^(-6),西北地区分别为(104.0、57.1、11.3、7.67)×10^(-6);主要阴离子平均质量分数w(SO_(4)^(2-))、w(Cl^(-))、w(NO_(3)^(-))东北地区分别为(4.10、1.41、2.87)×10^(-6),西北地区分别为(222.0、71.2、14.2)×10^(-6).聚类分析与相关性分析结果表明,东北地区季节冻土中离子的主要来源为燃煤排放、农业施肥及植物残体,其主要盐类化合物可能为NaCl、Na_(2)SO_(4)及Mg(NO_(3))_(2);西北地区离子主要源于工业生产、农业灌溉及大气沉降,盐类组成以硫酸盐与氯盐化合物为主.西北地区季节冻土盐渍化程度高于东北地区,氯化物-硫酸盐盐土是研究区域季节冻土的主要类型.

A total of 90 seasonally frozen soil samples were collected,and the mass fractions of watersoluble ions in seasonally frozen soil were quantitatively analyzed by ion chromatography.The spatial distribution and potential sources of water-soluble ions in seasonally frozen soil in this study were also clarified.The results showed that the ion composition in seasonally frozen soil in China had a strong spatial difference.The average mass fractions of major cations w(Na+),w(Ca^(2+)),w(K^(+)),w(Mg^(2+))in the Northeast China were(5.10,5.60,1.25,0.94)×10^(-6),and the average mass fractions of major cations in the Northwest were(104.0,57.1,11.3,7.67)×10^(-6),respectively.The average mass fractions of main anions w(SO_(4)^(2-)),w(Cl^(-)),w(NO_(3)^(-))in the Northeast China were(4.10,1.41,2.87)×10^(-6),which were significantly lower than the average mass fractions of main anions in the Northwest,i.e.(222.0,71.2,14.2)×10^(-6).The results of the cluster and correlation analysis showed that the main sources of water-soluble ions in seasonally frozen soil of Northeast China were coal combustion,agricultural fertilization and the return of plant residues,and the main salt compounds might be NaCl,Na2SO4 and Mg(NO3)2,whereas the main sources in Northwest China were industrial production,agricultural irrigation and atmospheric deposition.The degree of salinization of seasonally frozen soil in Northwest China was higher than that in the Northeast,with chloride-sulfate saline soil being the main type of seasonally frozen soil in Northeast and Northwest China.