浙北地區(qū)PM2.5中多環(huán)芳烴特征

徐宏輝,徐婧莎,何 俊*,浦靜姣,俞科愛(ài)

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浙北地區(qū)PM2.5中多環(huán)芳烴特征

徐宏輝1,徐婧莎2,何 俊2*,浦靜姣1,俞科愛(ài)3

(1.浙江省氣象科學(xué)研究所,浙江 杭州 310008；2.寧波諾丁漢大學(xué)化學(xué)環(huán)境工程系,浙江 寧波 315100；3.寧波市北侖區(qū)氣象局,浙江 寧波 315826)

為了研究浙北地區(qū)PM2.5中多環(huán)芳烴(PAHs)的季節(jié)性變化和它們的來(lái)源,于2014年11月~2015年11月收集了杭州和寧波2個(gè)城市中4個(gè)采樣點(diǎn)的PM2.5樣品,利用氣-質(zhì)聯(lián)用儀測(cè)定了17種PAHs濃度.結(jié)果表明,∑PAHs年平均濃度范圍為24.1~51.9ng/m3,平均值為(35.5 ± 12.3) ng/m3.2~3環(huán)PAHs在PM2.5中的濃度較低(<1ng/m3),而4~6環(huán)PAHs占總PAHs的77.0%.∑PAHs的濃度與PM2.5呈相似的季節(jié)性變化特征,冬季濃度最高而夏季最低.惹烯作為軟木燃燒的示蹤物,冬季的濃度是夏季的4倍,表明在冬季軟木燃燒的排放和對(duì)PM2.5的貢獻(xiàn)都有所增加.除了夏季的2個(gè)城區(qū)站點(diǎn),其它季節(jié)和站點(diǎn)∑PAHs濃度和PM2.5呈現(xiàn)一定的正相關(guān)性.特征PAHs比值顯示,浙北地區(qū)氣溶膠相關(guān)的多環(huán)芳烴主要來(lái)自燃燒和熱解排放,如生物質(zhì)燃燒和煤燃燒,而交通排放和石油揮發(fā)源的影響不大.

多環(huán)芳烴；PM2.5；浙北地區(qū)；季節(jié)性變化；來(lái)源

多環(huán)芳烴 (PAHs)在大氣中普遍存在,具有高親油性,低生物降解性和高持久性[1].其中一些PAHs對(duì)人類和動(dòng)物有致癌風(fēng)險(xiǎn),例如苯并蒽類化合物,苯并芘和二苯并萘[2-3].這些有致癌性的PAHs大多與大氣顆粒物相關(guān)[3]. PAHs主要來(lái)自不完全燃燒或者有機(jī)物的高溫裂解,特別是化石燃料和生物質(zhì)的燃燒[4].由于PAHs在大氣中十分穩(wěn)定,能夠廣泛的傳輸和擴(kuò)散進(jìn)而影響較大區(qū)域內(nèi)的環(huán)境和公眾健康.因此研究大氣中PAHs的豐度、分布和來(lái)源十分重要.

目前,我國(guó)氣溶膠中PAHs的研究主要集中在京津冀、珠三角等地區(qū)[5-8].長(zhǎng)三角地區(qū)對(duì)PAHs的觀測(cè)研究通常關(guān)注上海、南京等單個(gè)城市[9-10],在浙江地區(qū)的研究相對(duì)比較缺乏.本文分析了浙江省北部城區(qū)、城郊和偏遠(yuǎn)地區(qū)典型站點(diǎn)PM2.5中PAHs的季節(jié)變化規(guī)律,包括惹烯和16種被美國(guó)環(huán)境保護(hù)署(EPA)列入188種有害空氣污染物的PAHs[11],其中惹烯可以作為軟木燃燒的示蹤物質(zhì)[12-14],并利用特征比值估計(jì)PAHs的可能來(lái)源.

1 研究方法

1.1 觀測(cè)站點(diǎn)

選取浙江省北部4個(gè)站點(diǎn)(圖1).

圖1 采樣點(diǎn)位置

杭州氣象局國(guó)家基準(zhǔn)氣候站(HMB):北緯30.22°,東經(jīng)120.17°,為城區(qū)觀測(cè)點(diǎn),位于杭州市區(qū)中心,周圍200m區(qū)域內(nèi)有交通密集的道路.

寧波氣象局觀測(cè)站(NMB):北緯29.86°,東經(jīng)121.52°,為城區(qū)觀測(cè)點(diǎn),位于寧波市區(qū)中心,和居民住宅區(qū)毗鄰,距離省際高速約500m,機(jī)場(chǎng)高架橋約1km.

寧波鄞州高教園區(qū)觀測(cè)站(UNNC):北緯29.80°,東經(jīng)121.56°,為城郊觀測(cè)點(diǎn),位于寧波諾丁漢大學(xué)內(nèi),距離中心商業(yè)區(qū)約10km.

臨安區(qū)域大氣本底站(LRABS):北緯30.30°,東經(jīng)119.73°,為偏遠(yuǎn)地區(qū)觀測(cè)點(diǎn),處于杭州市所轄臨安市郊區(qū),監(jiān)測(cè)站周圍是農(nóng)田和森林,是隸屬于世界氣象組織全球大氣觀測(cè)網(wǎng)絡(luò)的本底監(jiān)測(cè)站.

1.2 觀測(cè)方法

每個(gè)站點(diǎn)從2014年12月~2015年11月每6d一次同步進(jìn)行PM2.5采樣,每次采樣24h.所用儀器為武漢天虹中流量采樣器(型號(hào)為TH-150CIII),使用90mm石英膜采樣,采樣流速為80L/min;每月在這4個(gè)采樣點(diǎn)取1次空白樣本.所有的濾膜使用前在550℃的馬弗爐內(nèi)預(yù)烘烤5h以去除殘留的有機(jī)雜質(zhì).濾膜在采樣前后皆在恒溫(22±1)℃恒濕(30±5)%下平衡24h并通過(guò)微量天平(型號(hào):SE2-F ,賽多利斯,精確度0.1μg)進(jìn)行稱重.然后將所有的濾膜包裹在預(yù)烘烤過(guò)的鋁箔中并存儲(chǔ)在-20℃以下直至進(jìn)行樣品提取和分析.研究中使用的氣象數(shù)據(jù)(風(fēng)速,降水,溫度以及相對(duì)濕度)從距離每個(gè)采樣點(diǎn)最近氣象站獲取.

1.3 實(shí)驗(yàn)方法

17種PAHs的簡(jiǎn)稱見(jiàn)表1.PAHs用快速萃取儀(型號(hào)為ASE350,Thermo,美國(guó))和純二氯甲烷進(jìn)行萃取,并通過(guò)氣相色譜-質(zhì)譜聯(lián)用儀(型號(hào)為7890B, 5977A, Agilent,美國(guó))進(jìn)行分析檢測(cè).17種多環(huán)芳烴的線性回歸系數(shù)在0.99(Ind)和1.00(BaA)之間.單個(gè)PAH的LOD (LODext,17種PAHs的10ng/mL標(biāo)準(zhǔn)混合物的標(biāo)準(zhǔn)差的3倍)列于表1中,其范圍從0.148ng/ m3(Ret)~0.001ng/m3(BkF).PAHs的LOD轉(zhuǎn)化為它們?cè)诖髿庵邢鄳?yīng)的濃度(LODair),由于用于GC-MS分析的1mL有機(jī)溶液濃縮樣品是提取自中容量采樣器(80L/min, 24h采樣, 90mm膜直徑)所采集的?的90mm石英纖維膜(相當(dāng)于收集的28.8m3空氣),因此,LODair= LODext×1mL/28.8m3.加標(biāo)樣品中17種多環(huán)芳烴的回收率為85.9%(Ret)~109.3%(BaA).所有分析結(jié)果都經(jīng)過(guò)空白值校正.

表1 17種PAHs的簡(jiǎn)稱,苯環(huán)數(shù)和檢測(cè)限

鉀離子(K+)和鈉離子(Na+)濃度由離子色譜儀(型號(hào)為ICS-1600, Dionex,美國(guó))檢測(cè),詳細(xì)實(shí)驗(yàn)步驟見(jiàn)文獻(xiàn)[15].由于采樣點(diǎn)位于我國(guó)東部沿海,海洋的影響不可忽視,非海鹽成分對(duì)氣溶膠的貢獻(xiàn)需要進(jìn)行量化[16].Na+被假定為僅來(lái)自海洋,

K+的非海鹽(nss)部分可以由以下公式進(jìn)行計(jì)算[17]:

nss-K+= K+– Na+′(K+/Na+)sea(1)

式中:K+和 Na+分別代表K+和Na+在氣溶膠樣本中的濃度.(K+/Na+)sea是海水中該離子和Na+濃度的比值,根據(jù)海水成分,比值分別為0.037[18-19].

有機(jī)碳(OC)和元素碳(EC)濃度由碳熱光學(xué)分析儀(型號(hào)為2001A, DRI,美國(guó))檢測(cè),應(yīng)用了熱光學(xué)反射法(TOR),詳細(xì)實(shí)驗(yàn)步驟見(jiàn)文獻(xiàn)[20].

1.4 氣團(tuán)后向軌跡分析

使用美國(guó)國(guó)家海洋和大氣管理局(NOAA)發(fā)布的最新混合單粒子拉格朗日積分軌跡模型(HYSPLIT 4.9)模擬氣團(tuán)的后向軌跡.其中氣象數(shù)據(jù)來(lái)源于美國(guó)國(guó)家環(huán)境預(yù)報(bào)中心(NCEP)全球數(shù)據(jù)同化系統(tǒng)(GDAS1, 2006).后向氣團(tuán)軌跡起始時(shí)間為采樣當(dāng)日的9:00(當(dāng)?shù)貢r(shí)間),向后追蹤96h,軌跡起始高度選取距地面500m.所有獲取的軌跡根據(jù)不同季節(jié)進(jìn)行聚類分析.由于4個(gè)站點(diǎn)的地理位置接近,氣團(tuán)后向軌跡相似,因此本文以臨安本底站點(diǎn)為代表分析遠(yuǎn)距離輸送氣團(tuán)與PAHs濃度的關(guān)系.

2 結(jié)果與討論

2.1 PAHs的濃度水平和季節(jié)變化

浙北地區(qū)4個(gè)采樣點(diǎn)的PM2.5中總多環(huán)芳烴(∑PAHs)的季節(jié)平均濃度如圖2所示.4個(gè)采樣點(diǎn)∑PAHs的年平均值濃度范圍為24.1~51.9ng/m3,平均值為(35.5±12.3)ng/m3.該結(jié)果遠(yuǎn)高于巴西∑PAHs濃度(3.80±2.88) ng/m3[21],低于長(zhǎng)三角地區(qū)南通、無(wú)錫、蘇州2009年7月~2010年4月觀測(cè)濃度(范圍: 13.9~229ng/m3,平均值為88.2ng/m3)[22],與廣州總顆粒∑PAHs濃度相當(dāng)(范圍為4.7~98.7ng/m3,年均值為(23.7±18.4)ng/m3[23].以年均值來(lái)看,浙北地區(qū)各種PAHs中含量最多的是Ret, BkF, BbF, Ind, Bpe, Flt和Chr (>2ng/m3), Ret在所有已測(cè)的PAHs中濃度最高,年均值為(4.75±1.70)ng/m3.有高致癌性的BaP在浙北地區(qū)的年均濃度為(1.54±0.46)ng/m3,比華北地區(qū)測(cè)得的年均BaP濃度要低(4.2ng/m3)[24],但是超過(guò)了國(guó)家規(guī)定的濃度標(biāo)準(zhǔn)(1ng/m3)[25].總的來(lái)說(shuō),分子質(zhì)量相對(duì)較低的2~3環(huán)PAHs—Nap, Ace, Acy, Flu和Ant在顆粒物上的濃度較低(<1ng/m3),而分子質(zhì)量較高的4~6環(huán)PAHs在顆粒物上的濃度較高,占∑PAHs的77.0%.這個(gè)結(jié)果與在南京地區(qū)相近,該地區(qū)含4~6環(huán)的PAHs約占∑PAHs的80%[26].通常,2~3環(huán)PAHs由于其較高的揮發(fā)性而主要以氣態(tài)形式存在,而且它們?cè)诖髿庵械纳芷趦H有幾個(gè)小時(shí)或更短[21],這是2~3環(huán)PAHs濃度較低的主要原因.

圖2 4個(gè)采樣點(diǎn)PM2.5及其∑PAHs季平均濃度

如圖2所示,從季節(jié)來(lái)看,∑PAHs的濃度變化趨勢(shì)和PM2.5相似.冬季的∑PAHs濃度最高,而夏季最低.這個(gè)季節(jié)性特征與廣州和美國(guó)亞特蘭大的觀測(cè)結(jié)果一致[3,23].冬季∑PAHs的濃度范圍為(48.8± 50.7)~(85.9±32.0)ng/m3,其均值為(65.7±15.5) ng/m3.夏季∑PAHs的濃度范圍為(6.4±2.2)~(15.8±7.2)ng/ m3,均值為(10.3±4.0)ng/m3.值得注意的是,處在農(nóng)村地區(qū)的臨安本底站的∑PAHs濃度與寧波城區(qū)站點(diǎn)相當(dāng),特別是秋季,不僅高于寧波城區(qū)站點(diǎn),而且已經(jīng)接近杭州城區(qū)站點(diǎn)的濃度.臨安本底站中生物質(zhì)燃燒示蹤物非海鹽鉀離子(nss-K+)的年平均濃度為0.74μg/m3,高于NMB(0.60μg/m3).該地區(qū)生物質(zhì)燃燒活動(dòng)較多是臨安本底站高∑PAHs濃度水平原因之一,特別是秋收季節(jié)通過(guò)焚燒秸稈來(lái)清理田地會(huì)導(dǎo)致排放大量PAHs.

與夏季相比,冬季浙北地區(qū)所有采樣點(diǎn)的Flt和BaA含量均明顯增多,冬季濃度比夏季高出約12~13倍.Chr, BbF, BkF和Ind在冬季比夏季高出8~9倍,冬季Phe, Ant, Pyr, BaP和Bpe比夏季高5~6倍.Ret已被確定為軟木特別是針葉樹燃燒的示蹤物質(zhì)[12],冬季與夏季相比,其濃度增加了4倍;在冬季和夏季,Ret質(zhì)量濃度分別占PM2.5的0.0086%和0.0053%,表明在冬季軟木燃燒的排放和對(duì)PM2.5的貢獻(xiàn)都有所增加.冬季其他的PAHs濃度也較高,與夏季相比增加1~3倍.

冬季多環(huán)芳烴濃度最高的現(xiàn)象可歸因于許多因素.一方面,冬季較低的混合邊界層高度導(dǎo)致了當(dāng)?shù)貧馊苣z的大量積累[3];另一方面,由于冬季相對(duì)較低的溫度,通過(guò)氣-固分配更多的PAHs可分配附著在顆粒物上[27].而在夏季高溫度下,較大部分的PAHs往往處于氣態(tài)[21],因此導(dǎo)致夏季顆粒態(tài)PAHs濃度相對(duì)較低.此外,輸入性污染源的貢獻(xiàn)也不可忽略,北方地區(qū)冬季供暖需求增大,生物燃料和煤炭燃燒的排放量大大提高.如圖3氣團(tuán)后向軌跡,從西北和華北平原的地區(qū)跨界輸送的氣溶膠也可導(dǎo)致冬季PAHs含量增高.

圖3 臨安站各個(gè)季節(jié)中氣團(tuán)后向軌跡群組分布

此外,4個(gè)采樣點(diǎn)均發(fā)現(xiàn)冬季PAHs占PM2.5濃度的比例最高(范圍0.060%~0.082%;平均值為0.069%),夏季占比最低(范圍:0.024%~0.032%;平均值為0.028%),除了夏季高溫使更多的PAHs以氣態(tài)形式存在, PM2.5中其他污染物的相對(duì)濃度增加較多也是原因之一.硫酸鹽作為PM2.5的重要成分,夏季高溫等促進(jìn)硫酸鹽的形成[3],其在PM2.5的相對(duì)豐度在22.3%~25.4%之間,而在冬季僅為11.4%~14.8%.

2.2 相關(guān)性分析

為了探究∑PAHs、有機(jī)碳(OC)、元素碳(EC)和PM2.5之間的關(guān)系,本研究對(duì)其進(jìn)行了相關(guān)性分析.除了夏季的2個(gè)城區(qū)站點(diǎn),其它季節(jié)和站點(diǎn)∑PAHs濃度和PM2.5呈現(xiàn)一定的正相關(guān)性(30.66);如表2,∑PAHs和EC的相關(guān)性比OC強(qiáng),特別是夏季,∑PAHs和OC的相關(guān)性很弱,這可能是因?yàn)榇髿庵蠵AHs主要來(lái)自一次污染源,而夏季城區(qū)OC主要來(lái)自大氣中揮發(fā)性有機(jī)物(VOCs)從氣態(tài)到顆粒態(tài)的反應(yīng)轉(zhuǎn)變生成[28-29].冬季在2個(gè)寧波采樣點(diǎn),OC和∑PAHs相關(guān)性良好(30.80);秋季在UNNC、LRABS和HMB相關(guān)性良好(30.66),這說(shuō)明冬季寧波地區(qū)和秋季UNNC, LRABS 和HMB的PAHs和OC的主要來(lái)源較一致.

此外,生物質(zhì)燃燒示蹤物nss-K+和軟木燃燒示蹤物-惹烯也作為變量進(jìn)行了相關(guān)性分析.秋季,所有采樣點(diǎn)nss-K+都與∑PAHs有一定的相關(guān)性(:0.69~0.86),說(shuō)明在秋季生物質(zhì)燃燒對(duì)顆粒態(tài)PAHs的貢獻(xiàn)顯著.冬季,所有采樣點(diǎn)惹烯和∑PAHs有一定的相關(guān)性(:0.60~0.94),表明冬季長(zhǎng)三角地區(qū)的PAHs部分來(lái)自軟木燃燒.如圖3所示,冬季,浙北地區(qū)約有75%~97%的氣團(tuán)來(lái)自我國(guó)西北和北部地區(qū),部分氣團(tuán)源于俄羅斯和哈薩克斯坦.可見(jiàn)北方地區(qū)軟木,特別是針葉樹的燃燒產(chǎn)生的污染氣團(tuán)對(duì)浙北地區(qū)有一定的影響.

表2 夏季∑PAHs, PM2.5, OC, EC,惹烯和nss-K+的相關(guān)性

2.3 PAHs的特征比值

顆粒態(tài)PAHs的比值通常被用于指示PAHs的來(lái)源分布[30-33].參考文獻(xiàn)中PAHs的特征比值列于表3中.

表3 區(qū)分可能來(lái)源的PAH比值

Flt/(Flt+Pyr)比值可用于區(qū)分交通(0.26~0.34)、垃圾焚燒(0.37)、不完全燃燒的石油(<0.40)、原油燃燒(0.40~0.50)、木材燃燒(>0.50)、生物質(zhì)燃燒(0.50)和煤炭燃燒(0.58)多種污染源.如表4,冬季Flt/(Flt+ Pyr)的季平均值范圍為NMB的(0.55±0.15)~HMB的(0.60±0.17),均值為(0.58±0.02),該值在木材燃燒的范圍之內(nèi)(>0.50),接近煤炭燃燒的比值0.58,說(shuō)明冬季PAHs的可能來(lái)源為煤炭燃燒和木材燃燒.春秋季,長(zhǎng)三角大多數(shù)樣品的Flt/(Flt+Pyr)>0.50,表明大氣中的PAHs來(lái)自木材燃燒.秋季臨安本底站采樣點(diǎn),季平均Flt/(Flt+Pyr)比值為(0.51±0.07),接近生物質(zhì)燃燒的比值(0.50),說(shuō)明秋季農(nóng)村地區(qū)生物質(zhì)燃燒活動(dòng)頻繁,這可能是該地秋季PAHs含量高于寧波市區(qū)的原因之一.在夏季,Flt/(Flt+Pyr)比值落在0.40~0.50的范圍之內(nèi),說(shuō)明PM2.5中的PAHs可能的來(lái)源為原油燃燒(0.40~0.50).

表4 浙北地區(qū)4個(gè)采樣點(diǎn)PAHs的季節(jié)平均比值

Ind/(Ind+Bpe)比值可用于區(qū)分機(jī)動(dòng)車燃料排放(汽油車:0.18~0.20;柴油車:0.37~0.45)、生物質(zhì)燃燒 (0.44)、草-木材-煤炭燃燒(>0.50)以及垃圾焚燒(0.55).浙北冬春秋季季節(jié)平均Ind/(Ind+Bpe)比值30.50,落在草-木材-煤炭燃燒的范圍內(nèi).然而,該比值在臨安本底站春季為(0.46±0.14),比其他3個(gè)采樣點(diǎn)稍低(30.50), 接近于生物質(zhì)燃燒比值(0.44),柴油車排放(0.37~0.45),臨安本底站位于偏遠(yuǎn)地區(qū),交通源的影響相對(duì)較小,說(shuō)明該站春季可能的污染源為生物質(zhì)燃燒.浙北地區(qū)夏季Ind/(Ind+Bpe)比值為0.46±0.07,接近生物質(zhì)燃燒和柴油車排放的比值,說(shuō)明浙北夏季空氣中PAHs的可能來(lái)源為生物質(zhì)燃燒排放和機(jī)動(dòng)車排放.

BaA/(BaA+Chr)的比值可以用于區(qū)分石油來(lái)源(<0.20),燃燒排放(0.20~0.35)和熱解排放(>0.35),其中熱解排放指在缺氧或者無(wú)氧條件下,通過(guò)高溫使有機(jī)物發(fā)生裂解,從而排放出PAHs.該比值在浙北采樣期間在0.20(夏)~0.27(秋冬)之間,說(shuō)明采樣期間大部分污染源為燃燒排放,同時(shí)可能夏季石油揮發(fā)排放偏多,秋冬季熱解排放偏多.為了進(jìn)一步探究石油和熱解排放所占比例,這里引入了Ant/(Ant+Phe)的比值.Ant/(Ant+Phe)可被用于區(qū)分石油揮發(fā)源(<0.1)和熱解來(lái)源(>0.1).在采樣期間所有采樣點(diǎn)的比值均高于0.1,說(shuō)明該區(qū)域大部分顆粒態(tài)PAHs受石油揮發(fā)源影響不大.

BaP/Bpe的比值可用來(lái)探究交通源的排放,在浙北地區(qū)比值在0.39(夏)~0.57(秋)之間,和非交通排放相關(guān)(<0.6),說(shuō)明交通排放對(duì)PAHs濃度影響不大.

總的來(lái)說(shuō),顆粒態(tài)PAHs受交通排放和石油揮發(fā)源影響不大,主要污染源為燃燒和熱解排放,包括生物質(zhì)燃燒和煤炭燃燒等.

3 結(jié)論

3.1 浙北地區(qū)PM2.5中∑PAHs平均值為35.5ng/m3,以4~6環(huán)PAHs為主,高致癌性的BaP年均濃度為(1.54±0.46)ng/m3,超過(guò)了國(guó)家標(biāo)準(zhǔn).

3.2 ∑PAHs的濃度與PM2.5呈相似的季節(jié)性變化特征,冬季濃度最高而夏季最低.惹烯作為軟木燃燒的示蹤物,冬季的濃度是夏季的4倍,表明北方地區(qū)軟木,特別是針葉樹的燃燒產(chǎn)生的污染氣團(tuán)對(duì)浙北地區(qū)有一定的影響.秋季生物質(zhì)燃燒對(duì)顆粒態(tài)PAHs的貢獻(xiàn)顯著.

3.3 特征PAHs比值顯示,浙北地區(qū)顆粒態(tài)多環(huán)芳烴主要來(lái)自燃燒和熱解排放,如生物質(zhì)燃燒和煤燃燒,而交通排放和石油揮發(fā)造成的影響不大.

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致謝：本實(shí)驗(yàn)的現(xiàn)場(chǎng)采樣工作由杭州市氣象局齊冰、杜榮光、馬千里等協(xié)助完成,在此表示感謝.

Characteristics analyses of PAHs in PM2.5in the northern Zhejiang province.

XU Hong-hui1, XU Jing-sha2, HE Jun2*, PU Jing-jiao1, YU Ke-ai3

(1.Zhejiang Institute of Meteorological Sciences, Hangzhou 310008, China；2.Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China；3.Ningbo Beilun Meteorological Bureau, Ningbo 315826, China)., 2018,38(9)：3247~3253

To investigate the seasonal variations and sources of polycyclic aromatic hydrocarbons (PAHs) in fine particles (PM2.5) in the northern Zhejiang province (NZP), one year-long field PM2.5sampling was conducted at four representative sites in both cities of Hangzhou and Ningbo from December 2014 to November 2015 and in total 17 PAHs were analyzed by GC-MS. The results showed that the total annual averaged concentration of all these 17 PAHs ranged from 24.1 to 51.9ng/m3with an average of (35.5±12.3) ng/m3. Basically, 2~3 rings PAHs were observed in low abundance in particle phases (<1ng/m3), while 4~6rings PAHs accounted for 77.0% of total particulate PAHs. The total concentration of 17 PAHs followed a similar seasonal trend to that of PM2.5, showing the highest total PAHs concentration in winter while lowest in summer among four seasons. As a tracer for soft wood burning, the concentration of retene was quadruple in winter compared to that in summer, indicating the increased contribution from soft wood burning in NZP. Except at two urban sites during summer, moderate positive correlations were found between OC and PAHs. The PAHs diagnostic ratios implied that aerosols related PAHs in NZP were not significantly contributed by traffic emissions and petrogenic sources, but mainly originated from pyrogenic sources, such as biomass burning and coal combustion.

PAHs；PM2.5；the northern Zhejiang province；seasonal variations；sources

X513

A

1000-6923(2018)09-3247-07

徐宏輝(1978-),男,浙江龍游人,高級(jí)工程師,博士,主要從事大氣化學(xué)研究.發(fā)表論文30余篇.

2018-01-18

國(guó)家重點(diǎn)研發(fā)計(jì)劃(2016YFC0201900);國(guó)家自然科學(xué)基金資助項(xiàng)目(91544229,41303091);寧波市室內(nèi)空氣污染凈化技術(shù)創(chuàng)新團(tuán)隊(duì)資助項(xiàng)目(2017C510001)

* 責(zé)任作者, 副教授, Jun.He@nottingham.edu.cn