驻马店市区采暖季PM2.5时间和空间来源解析研究

Temporal and Spatial Source Apportionment During the Heating Period in Zhumadian

为了明确驻马店市区PM2.5污染特征及贡献源类,2019年1—3月在驻马店市区2个采样点采集PM2.5样品,分析了其化学组分特征;结合PMF和后向轨迹模型构建了PM2.5的时间和空间来源解析方法,并对该解析方法进行应用.结果表明:①采暖季,驻马店市区环境空气中ρ(PM2.5)平均值为117μg m 3,NO 3-和OC是其主导组分;ρ(OC)和ρ(EC)分别达18.2和5.2μg m 3,且ρ(OC)ρ(EC)平均值为3.5,说明机动车源和燃煤源的影响较明显.②ρ(SO 4^2-)与ρ(NO 3^-)相关性显著(R=0.80,P<0.01),表明SO 42-和NO 3-具有较高的同源性.③重污染过程中ρ(SNA)(SNA为SO 4^2-、NO 3^-和NH 4+三者统称)平均值为61.5μg m 3,显著高于清洁期;重污染过程中硫氧化率(SOR)和氮氧化率(NOR)分别达0.42和0.39,说明存在明显的二次离子生成过程.④重污染过程中Si、Al、Mg等地壳类元素的浓度和占比均高于清洁期,说明重污染过程中扬尘源的贡献可能较高.⑤来源解析结果表明,二次源是采暖季PM2.5的最大贡献源,贡献率为32.6%,其次为扬尘和生物质燃烧混合源(26.4%)、机动车源(21.4%)、燃煤源(13.2%)和工业源(6.3%);两次重污染过程中的最大贡献源分别为二次源(54.5%)和机动车源(46.2%),清洁期的主要贡献源主要为二次源(45.2%)和燃煤源(29.8%).从空间变化来看,扬尘和生物质燃烧混合源对天方二分厂的贡献率(29.3%)明显高于对彩印厂的贡献率(23.3%),而燃煤源对彩印厂的贡献率(16.5%)高于对天方二分厂的贡献率(10.1%),其他源类的贡献率相差不大.正东、东南以及西北方向是彩印厂和天方二分厂各类源的主要贡献方向.研究显示:二次源是采暖季、重污染期间和清洁期最大的贡献源;相比于清洁期,重污染期间扬尘和生物质燃烧混合源贡献增加.源类贡献存在空间差异,正东、东南及西北方向是采样点各类源主要贡献方向.

The source apportionment of PM2.5 is extremely important for effective control of emission sources,which has become an urgent need for air pollution control at present.In order to clarify the PM2.5 pollution characteristics and sources in Zhumadian,the ambient PM2.5 samples were collected at two sampling sites in Zhumadian from January to March 2019,and the chemical characteristics of PM2.5 species were analyzed.A temporal and spatial source apportionment method was developed and applied by combining the Positive Matrix Factorization(PMF)and the backward trajectory model.The results indicated that the annual mean concentration of ambient PM2.5 was 117μg m 3,of which NO 3-and organic carbon(OC)were the main species.During the sampling period,the average concentrations of OC and EC were 18.2 and 5.2μg/m^3,respectively,and the meanρ(OC)ρ(EC)ratio was 3.5,indicating the significant effect of vehicle exhaust and coal combustion.Theρ(SO 4^2-)andρ(NO 3^-)showed a significant correlation(R=0.80,P<0.01),implying a high degree of homology.In the haze episodes,the average concentration of SNA(Sulfate,Nitrate and Ammonium)was 61.5μg/m^3,which was significantly higher than the clean-air period.During the haze episodes,SOR and NOR values were 0.42 and 0.39,respectively,suggesting an obvious formation process of secondary particles.The concentration and proportion of crustal elements such as Si,Al,Mg during the haze episodes were higher than in the clean-air period,likely indicating an important influence of dust sources.The results of source apportionment indicated secondary sources were the primary contributor(32.6%)during the heating period,followed by the mixed source of dust and biomass burning(26.4%),vehicles exhaust(21.4%),coal combustion(13.2%),and industrial sources(6.3%).The primary sources during the two haze episodes were vehicle sources(46.2%)and secondary sources(54.5%).Secondary sources(45.2%)and coal combustion(29.8%)were the major contribution sources during the clean-air period.The contribution of the mixed source of dust and biomass burning at Tianfang site(29.3%)was significantly higher than that of Caiyinchang site(23.3%),while that of coal combustion at Caiyinchang site(16.5%)was significantly higher than at Tianfang site(10.1%).There was no significant difference in the contributions of other sources.The east,southeast and northwest were the major contribution directions of sources of the two sampling sites.This research showed that secondary source was the largest contribution source during the heating season,haze episodes and the clean-air period.Compared with the clean-air period,the contribution of the mixed source of dust and biomass burning increased apparently during the haze episodes.There was a spatial difference between source contributions,and the main contribution directions of emission sources were in the east,southeast and northwest.