摘要
为揭示桂林市大气降水的组成成分变化特征和来源,于2015年1—12月期间采集了桂林市大气降水样品,分析其中pH、电导率、主要阴阳离子(K^+、Na^+、Ca^2+、Mg^2+、NH^+4、SO^2-4、NO^-3、F^-、Cl^-)及重金属元素(As、Cr、Hg、Zn、Cu、Pb)浓度的季节变化特征及湿沉降通量.研究结果显示,桂林市大气降水pH值分布范围介于4.13—7.37之间,其中pH值小于酸雨临界值5.6的占48.0%,表明桂林市降雨存在一定的酸化现象.电导率(EC)变化介于4.53—128.10μS·cm^-1之间,雨量加权平均值为16.44μS·cm^-1.阴离子以SO^2-4和NO^-3为主,雨量加权平均含量分别为94.50μeq·L^-1、30.48μeq·L^-1,占阴离子总量的65.28%和21.06%,其次为Cl^-,阳离子以Ca^2+为主,雨量加权平均含量为97.67μeq·L^-1,占阳离子总量的58.76%,其次为NH^+4,占阳离子总量的/NO^-3平均值为2.45,大气降水属于硫酸-硝酸混合型,具有逐步向硝酸型转变的趋势.阴阳离子三角图和pearson相关性分析表明,Ca^2+和Mg^2+主要来自地壳源和人为源,Ca^2+对致酸阴离子NO^-3、SO^2-4的中和作用大于NH^+4,桂林降水中可能存在以CaSO4和Ca(NO3)2为主的化学物质,Na^+主要来源于海洋输送,K^+则来源于人类活动.溶解态重金属元素的平均浓度为127.4μg·L^-1(0.349—443.8μg·L^-1),重金属湿沉降通量平均值为12.193 mg·(m^2·a)^-1,其中Zn、Cu的年沉降通量较高,分别占总沉降通量的59.72%和28.80%.
This study aimed to identify the sources and the variation of chemical composition of atmospheric precipitation in Guilin City.Rainwater samples were collected from January 2015 to December 2015.We then analyzed their pH,electrical conductivity,seasonal variation of concentrations and wet deposition fluxes of major ions(SO^2-4,NO^-3,F^-,Cl^-,NH^+4,Ca^2+,Mg^2+,Na^+,K^+)and metal elements(As,Cr,Hg,Zn,Cu,Pb).Results showed that the pH values of all samples ranged from 4.13 to 7.37,in which the samples with pH below 5.6 accounted for 48%.This indicates that the precipitation of Guilin City has been acidified to some extent.The electrical conductivity ranged from 4.53μS·cm^-1 to 128.10μS·cm^-1 with the volume weighted mean of 16.44μS·cm^-1.SO^2-4 and NO^-3 were the dominant anions in the precipitation with concentrations(volume weighted mean)of 94.50μeq·L^-1 and 30.48μeq·L^-1,which account for 65.28%and 21.06%of the anions,respectively,followed by Cl^-.Meanwhile,Ca^2+was the dominant cation with concentration of 97.67μeq·L^-1,which account for 58.76%of the cations.NH^+4 was the next one accounting for 19.10%.The mean of the SO^2-4/NO^-3 ratio was 2.45,suggesting that the precipitation of Guilin City belongs to both sulfuric and nitric acid,and may gradually evolve from a mixed type acid to nitric acid type.Cation and anion triangle analysis and pearson correlation analysis suggest that Ca^2+and Mg^2+mainly originated from both crustal and anthropogenic sources.Comparing to NH^+4,Ca^2+is the main neutralization component of rain,indicating that CaSO4 and Ca(NO3)2 might be the main chemical compositions in the precipitation.Furthermore,Na+is derived from ocean transportation,while K+is mainly derived from anthropogenic sources.The average concentration of the dissolved heavy metals was 127.40μg·L^-1(ranging from 0.349 to 443.8μg·L^-1),Furthermore,the average wet deposition flux was 12.193 mg·(m^2·a)^-1.Specifically,the annual wet deposition fluxes of Zn and Cu are higher than other heavy metals,which account for 59.72%and 28.80%,respectively.These results confirm the sources and chemical composition of the atmospheric precipitation in Guilin City.
作者
张清华
黎永珊
于奭
罗专溪
ZHANG Qinghua;LI Yongshan;YU Shi;LUO Zhuanxi(Key Laboratory of Karst Dynamics,Ministry of Natural Resources&Guangxi,Institute of Karst Geology,Chinese Academy of Geological Sciences,Guilin,541004,China;Institute of Urban Environment,Chinese Academy of Sciences,Xiamen,361021,China;Guilin Environment Monitoring Center,Guilin,541000,China)
出处
《环境化学》
CAS
CSCD
北大核心
2020年第1期229-239,共11页
Environmental Chemistry
基金
国家重点研发计划(2016YFC0502302)
水体污染控制与治理科技重大专项(2017ZX07101001-02)
地质调查项目(DD20160305)国家自然科学基金(41402324)
广西自然科学基金(2014GXNSFBA118228)资助.
关键词
桂林市
大气降水
酸雨
离子来源
重金属
Guilin City
atmospheric precipitation
acid rain
ions source
heavy metal
