基于降水化学的渭南地区城乡大气污染差异探析

Difference of Atmospheric Pollution between Urban and Rural Areas in Weinan Based on Chemical Composition in Rainwater

摘要:根据渭南城区和乡村地区2013年6月至2014年9月采集的降水样品中主要离子浓度的测试结果,运用趋势分析法分析了两地降水中常量无机离子的化学特征,并结合富集因子法及端源贡献法探究其来源。结果表明:受人类活动影响,城区降水离子总浓度平均值(775.59μeq·L^(-1))远高于乡村(383.60μeq·L^(-1)),两地主要阳离子均为Ca^(2+)和NH_4^+,分别占阳离子总量的80.05%和89.82%;主要阴离子均为SO_4^(2-)和NO_3^-,分别占阴离子总量的93.54%和92.51%。城区降水中各离子浓度为:Ca^(2+)>NH_4^+>SO_4^(2-)>NO_3^->Na^+>K^+>Mg^(2+)>Cl^->F>NO^-_2,乡村为:NH_4^+>SO_4^(2-)>Ca^(2+)>NO_3^->Mg^(2+)>Cl^->Na^+>K^+>F^->NO^-_2。受排放源、降雨量和气象要素等影响,研究区降水总离子浓度表现出明显的季节差异,均为冬季>秋季>春季>夏季。经定量探源分析,城区和乡村降水中总离子浓度均受到人为源影响,其中两地降水中的NH^+_4和F^-均来自人为源,SO_4^(2-)和NO_3^-的95%以上由人为源贡献,Mg^(2+)和K^+均以非海盐源为主,且城区的非海盐源略大于乡村。城区Na^+主要由非海盐源贡献,而乡村的Na^+主要来自海盐源。

Abstract:The data of main ion concentrations in rainwater were collected from the urban and rural areas in Weinan City,China during the period from June 2013 to September 2014.The Trend Analysis and Enrichment Factor methods were used to analyze the chemical characteristics of constant ions.The Source Contribution method was used to explore the potential sources.The results showed that the average value of total concentration of ions in urban area(775.59μeq·L-1)was much higher than that in rural area(383.60μeq·L-1)due to the influence of human activities.The main cations in both areas were Ca2+and NH4+,accounting for 80.05%and 89.82%of the total cation concentration,respectively.The main anions in both areas were SO42-and NO3-,accounting for 93.54% and 92.51%of the total anion concentration,respectively.The concentration of ions in rainwater was in an order of Ca2+>NH4+>SO42->NO3->Na+>K>Mg2+>Cl->F->NO2-,and that in rural area was in an order of NH4+>SO42->Ca2+>NO3>Mg2+>Cl->Na+>K+>F->NO2-.Affected by the emission sources,rainfall and meteorological factors,the seasonal differences of total ion concentrations were significant,and they were in an order of winter>autumn>spring>summer.According to the quantitative source analysis,the ion concentrations in rainwater were affected by anthropogenic sources in both urban and rural areas.All sources of NH4+ and F- were anthropogenic,and>95%SO2-4and NO-3were also contributed by anthropogenic sources.Mg2+and K+ were mainly from non-seasalt sources,and the proportion of non-seasalt sources in urban area was slightly higher than that in rural area.Na+ in urban area was mainly contributed by non-seasalt sources,but it was mainly from the seasalt sources in rural area.