淀山湖沉積物PAHs季節(jié)分布與風(fēng)險(xiǎn)度指數(shù)評(píng)價(jià)

杜威寧,劉 敏,朱俊敏,楊 靜,魏昕怡

淀山湖沉積物PAHs季節(jié)分布與風(fēng)險(xiǎn)度指數(shù)評(píng)價(jià)

杜威寧,劉 敏*,朱俊敏,楊 靜,魏昕怡

(華東師范大學(xué)地理科學(xué)學(xué)院,地理信息科學(xué)教育部重點(diǎn)實(shí)驗(yàn)室,上海 200062)

對(duì)淀山湖湖體6個(gè)站位表層沉積物中多環(huán)芳烴(PAHs)進(jìn)行了季節(jié)測(cè)定,結(jié)果表明,16種美國(guó)EPA優(yōu)先控制的PAHs均有檢出,PAHs總含量(干重)波動(dòng)范圍54.6~1331.2ng/g,均值373.4ng/g.與國(guó)內(nèi)外大多數(shù)湖泊相比,淀山湖沉積物中PAHs含量水平屬中等偏下.總含量季節(jié)變化大體為冬季>春季>秋季>夏季.另對(duì)出入湖口河流6個(gè)站位表層沉積物中PAHs含量測(cè)定,表現(xiàn)為入湖口>出湖口>湖體,季節(jié)變化特征與湖體相一致.PAHs環(huán)數(shù)所占比重為4環(huán)>5~6環(huán)>2~3環(huán),采用特征比值法進(jìn)行源解析,其主要來(lái)源是煤炭和生物質(zhì)的不完全燃燒,主因子分析顯示貢獻(xiàn)率為80.22%.基于沉積物質(zhì)量基準(zhǔn)法(SQGs),提出一種PAHs風(fēng)險(xiǎn)量化評(píng)價(jià)新方法——風(fēng)險(xiǎn)度指數(shù)法(RIM),用此方法風(fēng)險(xiǎn)評(píng)價(jià)表明,部分單體(Acy、Ace、Ant和BaA)風(fēng)險(xiǎn)度指數(shù)RI為3.09~3.29,屬中等風(fēng)險(xiǎn)水平,大多數(shù)PAHs單體風(fēng)險(xiǎn)度指數(shù)RI為0.79~2.73,相對(duì)處于中低風(fēng)險(xiǎn)水平,總體PAHs風(fēng)險(xiǎn)度指數(shù)TRI為2.64,污染狀況處于中低風(fēng)險(xiǎn)水平.淀山湖作為上海市一個(gè)重要水源地,PAHs污染的潛在風(fēng)險(xiǎn)仍不可忽視.

淀山湖；表層沉積物；多環(huán)芳烴；季節(jié)分布；風(fēng)險(xiǎn)度指數(shù)

多環(huán)芳烴(PAHs)是一類(lèi)極具生態(tài)和健康風(fēng)險(xiǎn)的持久性有機(jī)污染物,有較強(qiáng)的毒性(致癌性、致畸和致突變),主要來(lái)源于有機(jī)物質(zhì)的不完全燃燒或高溫?zé)峤鈁1].PAHs可通過(guò)多種途徑進(jìn)入湖泊水環(huán)境中,由于本身的低溶解性和疏水性,極易吸附在顆粒物或轉(zhuǎn)移至生物有機(jī)體內(nèi),并最終進(jìn)入沉積物中[2].通過(guò)再懸浮使PAHs成倍的增加[3].因此沉積物成為水環(huán)境中一個(gè)重要的PAHs源.通過(guò)沉積物中PAHs含量與分布可以考察一定時(shí)期內(nèi)水體環(huán)境的污染情況[4].

淀山湖(30°59′~30°16′N(xiāo),120°53′~121°17′E),位于上海市青浦區(qū)西部,水域面積62km2.是全市最大的天然淡水湖泊和重要的水源地[5].隨著湖區(qū)社會(huì)經(jīng)濟(jì)的發(fā)展,污染物排放總量和種類(lèi)趨于上升,其中持久性有機(jī)污染物的排放和進(jìn)入是主要原因之一[6].目前國(guó)內(nèi)有關(guān)該地區(qū)重金屬和各類(lèi)POPs污染研究已有報(bào)道[7-9].但多是針對(duì)某一時(shí)間點(diǎn)取樣的離散分析.缺乏長(zhǎng)周期變化的認(rèn)識(shí).在關(guān)于該地區(qū)PAHs時(shí)空分布特征、尤其是季節(jié)變化方面的研究?jī)?nèi)容還鮮見(jiàn)報(bào)道.為了更清楚地了解PAHs在湖區(qū)表層沉積物中較長(zhǎng)周期的污染程度,本研究對(duì)該區(qū)域PAHs污染物季節(jié)分布、來(lái)源進(jìn)行分析,并對(duì)其生態(tài)風(fēng)險(xiǎn)進(jìn)行了評(píng)價(jià),為該區(qū)域PAHs污染防控與治理提供了依據(jù).

1 材料與方法

1.1 樣品采集

于2015年12月~2016年12月,1a內(nèi)按季進(jìn)行沉積物采樣,在湖區(qū)設(shè)置12個(gè)采樣點(diǎn)位,包括6個(gè)湖體采樣點(diǎn)(H1、H2、H3、H4、H5、H6)和3個(gè)入湖口采樣點(diǎn)(大朱砂港DZS、急水港JSG、白石磯港BSJ)、3個(gè)出湖口采樣點(diǎn)(石塘港ST、攔路港LLG、淀浦河DPH),具體采樣點(diǎn)分布狀況,見(jiàn)圖1.

采用多用途沉積物采樣器采集表層沉積物樣品,然后將樣品用密封袋包好置于不銹鋼盒中,- 20℃冷凍保存.

圖1 淀山湖采樣點(diǎn)分布圖

1.2 樣品預(yù)處理

預(yù)處理使用試劑:正己烷(HPLC色譜級(jí)),二氯甲烷(HPLC色譜級(jí)),丙酮(HPLC色譜級(jí)),硅膠(優(yōu)級(jí)純)等,所有試劑均購(gòu)置于上海安普科學(xué)儀器有限公司.

樣品冷凍干燥后過(guò)篩,稱(chēng)取10g樣品加入回收率指示物標(biāo)樣,200mL正己烷和丙酮的混合溶劑(V:V=1:1)索氏抽提48h.提取液濃縮并置換后,進(jìn)行層析柱分離純化.分別用15mL正己烷、70mL二氯甲烷和正己烷混合溶劑(:=3:7)淋洗烷烴和PAHs組分.PAHs組分濃縮定容至200μL,按照GC-MSD方法(美國(guó)HP Agilent6890-5973),采用內(nèi)標(biāo)法和多點(diǎn)校正曲線進(jìn)行PAHs的定量分析[10].

1.3 儀器分析

1.4 質(zhì)量控制

按樣品空白、方法空白、空白加標(biāo)、基質(zhì)加標(biāo)、樣品平行樣等方法進(jìn)行質(zhì)量控制,配備濃度梯度標(biāo)準(zhǔn)溶液計(jì)算標(biāo)準(zhǔn)曲線,內(nèi)標(biāo)法計(jì)算目標(biāo)物質(zhì)含量,氘代三聯(lián)苯指示實(shí)驗(yàn)樣品回收率.空白樣品中僅有低環(huán)Nap、Acy、Ace、Flu、Phe、Ant微量檢出,未檢測(cè)出中高環(huán)目標(biāo)PAHs.在分析測(cè)試中,每10個(gè)樣品中加入2個(gè)標(biāo)樣保證準(zhǔn)確度,每10個(gè)樣品中加入2個(gè)平行樣控制精密度.實(shí)驗(yàn)空白加標(biāo)回收率為62.0%~110.8%;基質(zhì)加標(biāo)回收率為62.8%~111.2%;實(shí)際樣品回收率為65.6%~111.5%.樣品平行樣的相對(duì)標(biāo)準(zhǔn)偏差均在20%以下,所有樣品數(shù)據(jù)均是在扣除空白樣品PAHs,經(jīng)回收率校正得到.

2 結(jié)果與討論

2.1 淀山湖湖體沉積物中PAHs含量季節(jié)分布特征

湖體水環(huán)境中PAHs往往會(huì)隨著顆粒物的沉降和水體-沉積物界面的遷移、擴(kuò)散過(guò)程進(jìn)入到沉積物中累積下來(lái),僅少部分隨沉積物再懸浮作用重新回到水體中[12],沉積物是水環(huán)境中主要的PAHs源.實(shí)測(cè)結(jié)果,淀山湖體(樣點(diǎn)H1~H6)沉積物中16種PAHs平均檢出率為98%,絕大部分單體檢出率接近100%.見(jiàn)表1.

表1 湖體沉積物PAHs質(zhì)量濃度季節(jié)變化(干重, ng/g)

注:n.d.表示未檢出.

各季度PAHs總含量(干重)的變化范圍:冬季217.9~1331.2ng/g、春季164.6~622.9ng/g、夏季84.8~500.7ng/g、秋季54.6~548.1ng/g,年度變化范圍54.6~1331.2ng/g,均值373.4ng/g.

表2為國(guó)內(nèi)外11個(gè)湖泊PAHs含量對(duì)比情況,淀山湖沉積物中PAHs含量雖然均值較低,低于絕大多數(shù)的10個(gè)湖泊,但極差、方差偏大,高值區(qū)潛在風(fēng)險(xiǎn)比均值較高.其中均值和最大、最小值整體均低于烏梁素海、Baikal湖、微山湖、巢湖和Florida湖,最大值卻高于紅楓湖、天目湖、南四湖、太湖,均值上與這4個(gè)湖泊又較為接近,可以認(rèn)為基本與其處于同一水平.由此可見(jiàn),淀山湖表層沉積物中PAHs濃度均值雖然極低,但總體濃度范圍處于與4個(gè)湖泊相近的中等偏下水平.

表2 國(guó)內(nèi)外湖泊沉積物PAHs含量對(duì)比(干重, ng/g)

淀山湖表層沉積物從均值和最大、最小值看,PAHs總量的季節(jié)變化大體為:冬季(546.1、1331.2、217.9ng/g)>春季(393.9、633.9、164.6ng/g)>秋季(301.3、548.1、54.6ng/g)>夏季(249.4、500.7、84.8ng/g),僅有秋季最小值略低于夏季.從季節(jié)差異性看,冬季與其他三季差異明顯,秋、夏季差異不顯著.分析原因主要是冬、春季工業(yè)生產(chǎn)煤炭和石油燃燒源較多, PAHs輸入量較大,加之此季水體和懸浮顆粒相中PAHs向沉積物累積過(guò)程較顯著,且不易降解,所以總量高于其他季節(jié).而夏秋季各種燃燒源大為減少,沉積物中微生物又相當(dāng)活躍,起一定的降解作用, 因此呈現(xiàn)出低量特征[24].

運(yùn)用單因素方差分析(<0.05),結(jié)果表明,除6環(huán)PAHs季節(jié)差異性不顯著外(=0.32),3~5環(huán)PAHs均存在顯著季節(jié)差異(<0.05),2環(huán)PAHs因夏季檢出率較低不再分析(圖3).

各環(huán)數(shù)PAHs所占比重變化的季度特征:4環(huán)(Fla、Pyr、Chr、BaA)>5~6環(huán)(BbF、BkF、BaP、DBA、Ipy、Bpe)>2~3環(huán)(Nap、Acy、Ace、Flu、Phe、Ant),總之中高環(huán)占比重較高.原因主要是中高環(huán)PAHs相對(duì)低環(huán)PAHs在結(jié)構(gòu)和性質(zhì)上更趨穩(wěn)定,受季節(jié)變化影響較小,極易吸附和富集在顆粒物上,沉降在沉積物中長(zhǎng)時(shí)間賦存.這與韓景超[25]的研究結(jié)果相一致.

圖2 湖體沉積物中PAHs的組分特征及季節(jié)變化

2.2 淀山湖入出湖口沉積物中 PAHs 含量分布特征.

入湖口河流沉積物中PAHs季度變化范圍為2187.5~2509.3ng/g,出湖口河流沉積物中PAHs的季度變化為1376.5~1580.9ng/g.受人類(lèi)活動(dòng)影響,河流沉積物中PAHs含量:入湖口>出湖口>湖體,季節(jié)變化均呈現(xiàn)出冬、春濃度高,夏、秋濃度低的特征,但季度波動(dòng)范圍較窄.季節(jié)變化與湖體一致的原因同上.空間分布上,表現(xiàn)為湖口含量與湖體差異較大,主要是由于入湖水流造成PAHs在湖口沉積,使該處含量增高,隨湖水流動(dòng),湖體水中含量迅速下降,而出湖湖水帶來(lái)的泥沙顆粒沉降,使出湖口PAHs含量又有所升高.另外受湖濱工業(yè)化進(jìn)程影響,由于入湖口樣點(diǎn)地處交通繁雜區(qū)段,伴隨大量油氣和污水排放,污染物來(lái)源較多而造成含量較高, 出湖口樣點(diǎn)則接近保護(hù)區(qū),強(qiáng)化了環(huán)境監(jiān)管減少了污染,使得含量有所下降[26].

2.3 沉積物中PAHs含量與TOC關(guān)系

淀山湖沉積物中總有機(jī)碳(TOC)含量各季度分別為:冬季0.04~10.78mg/g、春季0.04~11.79mg/ g、夏季4.22~8.65mg/g、秋季0.28~8.81mg/g,分季度進(jìn)行spearman相關(guān)性分析,如圖3所示,淀山湖沉積物中PAHs含量與TOC的相關(guān)性在冬季和夏季較大,相關(guān)系數(shù)分別為=0.77、=0.80>0.75,對(duì)應(yīng)顯著性指數(shù)分別為=0.076、=0.054?(0.05,0.1),表現(xiàn)為一定的正相關(guān)性,而春季和秋季均未表現(xiàn)出顯著相關(guān)性.

圖3 湖體沉積物PAHs濃度與TOC濃度相關(guān)性分析

這與陳衛(wèi)鋒等[27](冬季取樣)、童寶鋒等[28](豐、枯水季取樣)的研究結(jié)果相似.主要原因是沉積物中的有機(jī)碳在PAHs的吸附和遷移過(guò)程中起作用[29],使得PAHs容易在有機(jī)顆粒上積聚,與TOC具有一定的相關(guān)性[30].至于春季和秋季均未表現(xiàn)出顯著相關(guān)性,可能是因?yàn)樵摷綪AHs含量本身變化幅度較小,沉積物中的PAHs主要為自然沉降吸附,受TOC的影響較小.二者相關(guān)性表現(xiàn)較為復(fù)雜,深層次原因尚待進(jìn)一步探究.

2.4 沉積物中PAHs來(lái)源分析

低分子量的 PAHs(2環(huán)和3環(huán))一般來(lái)源于石油污染,而高分子量的PAHs(4環(huán)及以上)主要來(lái)源于各種燃燒過(guò)程,因此它們的比例可以在一定程度上反映PAHs的來(lái)源和存在環(huán)境.對(duì)此采用Yunker等[31]總結(jié)提出的特征比值法(CRM)進(jìn)行源解析(表3).

表3 PAHs同分異構(gòu)體特征比值與對(duì)應(yīng)來(lái)源

來(lái)源初判采用Phe/Ant(菲/蒽)、Pla/Pyr(熒蒽/芘)的比值,實(shí)測(cè)he/Ant=0.89<10,Pla/Pyr=1.57>1,據(jù)此初判來(lái)源主要是化石燃料的不完全燃燒.繼續(xù)分析淀山湖沉積物中4項(xiàng)特征比值:(1)各季度Ant/ (Ant+Phe)比值為0.17~0.88>0.1,來(lái)源對(duì)應(yīng)煤、油和生物質(zhì)的不完全燃燒.(2)各季度Fla/(Fla+Pyr)比值為0.51~0.89>0.5,對(duì)應(yīng)煤、生物質(zhì)的不完全燃燒.(3)夏季BaA/(BaA+Chr)比值為0.2~0.35,對(duì)應(yīng)混合源.其余3個(gè)季度BaA/(BaA+Chr)比值>0.35,指示為煤、油和生物質(zhì)的不完全燃燒. (4)各季度Ipy/(Ipy+Bpe)比值為0.02~0.65,其中秋季比值<0.2,指示石油泄露污染,夏季比值?(02,0.5),指示石油不完全燃燒,冬、春季比值>0.5,對(duì)應(yīng)煤、生物質(zhì)不完全燃燒(圖4).

圖4 同分異構(gòu)體沉積物特征比值來(lái)源判斷

綜上可知,沉積物中PAHs的主要污染來(lái)源是煤炭、生物質(zhì)的不完全燃燒,但秋、夏季來(lái)源類(lèi)別更加多樣,表現(xiàn)出混合源特征.交通燃油排放、石油泄漏和揮發(fā)、焦炭燃燒都可能產(chǎn)生影響.來(lái)源比重采用SPSS11.5主因子分析(表4).

表4 PAHs來(lái)源主因子分析

其中F1主要由中高環(huán)構(gòu)成,按載荷得分大小為BkF、Fla、BbF、Pyr、Ant和Phe,可認(rèn)為代表燃煤排放;F2主要由高環(huán)Ipy構(gòu)成,代表車(chē)船燃油天然氣燃燒排放; F3主要由低環(huán)Acy構(gòu)成,代表木材生物燃燒排放,將主因子分析結(jié)果進(jìn)行多元線性回歸得:∑PAHs=0.961F1+0.273F2+0.149F3(=0.997),由此得到3個(gè)主因子貢獻(xiàn)率: F1(煤炭燃燒源)為69.27%, F2(交通油氣燃燒源)為19.78%, F3(木材生物質(zhì)燃燒源)為10.95%.煤炭和生物質(zhì)的不完全燃燒貢獻(xiàn)率為80.22%.

最后對(duì)來(lái)源遠(yuǎn)近進(jìn)行分析,因?yàn)镃hr比其同分異構(gòu)體BaA更易揮發(fā)和長(zhǎng)距離遷移,所以BaA/Chr比值可作為研判污染源距離指標(biāo),比值小趨于外地源,比值大則趨于本地源[32],實(shí)測(cè)BaA/Chr比值為0.78(較小),表明遷移距離較遠(yuǎn),市區(qū)工業(yè)生產(chǎn)的煤、油燃燒排放是PAHs主要輸入源.從源頭上減少沉積物中PAHs的輸入,尤其是在冬、春季節(jié),應(yīng)當(dāng)提倡工業(yè)清潔生產(chǎn),逐步降低煤炭、石油燃燒源,推廣光伏、核電等新能源,減少農(nóng)田草、木等生物質(zhì)燃燒,控制交通油氣排放.

2.5 沉積物中PAHs 風(fēng)險(xiǎn)評(píng)價(jià)

低環(huán)數(shù)的 PAHs通?？沙尸F(xiàn)顯著的急性毒性,一些高環(huán)數(shù)的PAHs則具有潛在的致癌性[33],對(duì)單體和總體PAHs的風(fēng)險(xiǎn)評(píng)價(jià)方法和標(biāo)準(zhǔn)目前并未統(tǒng)一,列出質(zhì)量標(biāo)準(zhǔn)的現(xiàn)有12種PAHs.沉積物質(zhì)量基準(zhǔn)法(SQGs)是評(píng)估淡水、港灣和海洋沉積物質(zhì)量的常用工具. Long等[34]提出,當(dāng)沉積物中某種PAHs的濃度低于效應(yīng)范圍低值(ERL),表明生物毒性效應(yīng)很少發(fā)生;當(dāng)污染物濃度高于效應(yīng)范圍中值(ERM)時(shí),表明生物毒性效應(yīng)將頻繁發(fā)生;如果介于兩者之間, 生物毒性效應(yīng)會(huì)偶爾發(fā)生(表5).

表5 湖體沉積物中PAHs的毒性評(píng)價(jià)(ng/g)

其中僅有Acy(苊)、Ant(蒽)2種介于ERL和ERM之間,其余均低于ERL,定性評(píng)價(jià)認(rèn)為生態(tài)風(fēng)險(xiǎn)處于較低水平.

為了能夠較為準(zhǔn)確地量化評(píng)判,本研究提出一種新方法——風(fēng)險(xiǎn)度指數(shù)法,該方法以風(fēng)險(xiǎn)指數(shù)值(RI)做為定量判斷風(fēng)險(xiǎn)大小依據(jù),數(shù)值落入?yún)^(qū)間[0,2],認(rèn)為處于較低風(fēng)險(xiǎn)水平;落入?yún)^(qū)間[2,3],認(rèn)為處于中低風(fēng)險(xiǎn)水平;落入?yún)^(qū)間[3,4],認(rèn)為處于中高風(fēng)險(xiǎn)水平;落入?yún)^(qū)間[4,5],認(rèn)為處于較高風(fēng)險(xiǎn)水平,若>5則處于極高風(fēng)險(xiǎn)水平.該方法基于加拿大魁北克省沉積物質(zhì)量標(biāo)準(zhǔn)的5個(gè)細(xì)分閾值,1-5個(gè)指數(shù)級(jí)別分別對(duì)應(yīng)于生物毒性影響5種的罕見(jiàn)效應(yīng)濃度值(REL)、臨界效應(yīng)濃度值(TEL)、偶然效應(yīng)濃度值(OEL)、可能效應(yīng)濃度值(PEL)和頻繁效應(yīng)濃度值(FEL).單體PAHs的風(fēng)險(xiǎn)度指數(shù)值(RI),依據(jù)質(zhì)量濃度值所落入的閾值區(qū)間[12]由內(nèi)插法得出,計(jì)算公式為: RI=RI1+ (1)/(21),其中RI1為1對(duì)應(yīng)的風(fēng)險(xiǎn)度指數(shù)值,指數(shù)值的小數(shù)部分實(shí)際上也是超出所對(duì)應(yīng)閾值的概率大小.如本研究中Ant質(zhì)量濃度值為0.84~ 130.72(均值20.08),最高值落入閾值區(qū)間[110,240],對(duì)應(yīng)于風(fēng)險(xiǎn)度指數(shù)區(qū)間[3,4],按公式得RI=3+ (130.72-110)/(240-110)=3.16,其中0.16實(shí)際也是風(fēng)險(xiǎn)超出閾值110的概率.同理可得均值的RI=1.15.

考慮到單體PAHs之間的相互作用影響,引入朱潔羽等[35]S-T模型中的單體PAHs權(quán)重系數(shù)進(jìn)行修正,權(quán)重系數(shù)值大小與推導(dǎo)方法詳見(jiàn)文獻(xiàn),風(fēng)險(xiǎn)度指數(shù)值與權(quán)重系數(shù)相乘,所得積稱(chēng)為風(fēng)險(xiǎn)度指數(shù)分布量(RI′),即RI′=RI×μ,對(duì)所有單體PAHs風(fēng)險(xiǎn)度指數(shù)分布量求和即得到總體PAHs風(fēng)險(xiǎn)度指數(shù)TRI,即TRI=∑RI′,用于總體風(fēng)險(xiǎn)定量評(píng)價(jià)(表6).

表6 湖體沉積物中PAHs的風(fēng)險(xiǎn)度指數(shù)值

由表6可知,淀山湖沉積物中PAHs中單體Acy(苊)、Ace(二氫苊)、Ant(蒽)、BaA(苯并[a]蒽)風(fēng)險(xiǎn)度指數(shù)RI為3.09~3.29?[3,4],超出第三閾值概率為0.29,屬于中度風(fēng)險(xiǎn),其余單體風(fēng)險(xiǎn)度指數(shù)RI為0.79~2.73?[0,3],屬于中低度風(fēng)險(xiǎn),但是BaP(苯并[a]芘)、DBA(二苯并[a,h]蒽)的RI分別為2.73和2.39接近于3,超出第二閾值概率為0.39~0.73,這些高分子量PAHs組分在環(huán)境產(chǎn)生負(fù)面生態(tài)效應(yīng)更明顯,潛在風(fēng)險(xiǎn)應(yīng)給予足夠重視;而總體PAHs的風(fēng)險(xiǎn)度指數(shù)TRI=2.64,超出第二閾值概率為0.64.總體PAHs的均值TRI=1.59,分別對(duì)應(yīng)于中低風(fēng)險(xiǎn)水平和低風(fēng)險(xiǎn)水平.結(jié)論與文獻(xiàn)[7,26]相近,由于引入相互作用權(quán)重系數(shù),多考慮了PAHs的不同毒性和單體之間相互影響的模糊性, 所以評(píng)價(jià)結(jié)果更為準(zhǔn)確、更具實(shí)際意義.

3 結(jié)論

3.1 淀山湖表層沉積物中16種PAHs含量年度變化范圍54.6~1331.2ng/g,均值373.4ng/g,與其他地區(qū)湖泊相比處于中等偏下水平.季節(jié)變化特征為冬季顯著最高,春季次之,夏、秋季差異不明顯.主要受輸入源和氣溫的影響.PAHs含量與TOC的相關(guān)性在冬夏季有一定的正相關(guān)性(0.05<<0.1),春秋季均未表現(xiàn)出顯著相關(guān)性.

3.2 沉積物中PAHs組分中高環(huán)比例較高,低環(huán)比例較低,主要是高環(huán)具有較高的吸附平衡系數(shù),易被顆粒物吸附并沉降在沉積物中累積.特征比值分析,PAHs主要來(lái)源是煤炭和生物質(zhì)的不完全燃燒,主因子分析貢獻(xiàn)率為80.22%.但秋季和夏季來(lái)源類(lèi)別更加多樣.

3.3 淀山湖表層沉積物中總體PAHs風(fēng)險(xiǎn)度指數(shù)TRI為2.64,介于區(qū)間[2,3],污染處于中低風(fēng)險(xiǎn)水平,對(duì)周?chē)鷳B(tài)環(huán)境影響較低.但4種單體Acy、Ace、Ant、BaA風(fēng)險(xiǎn)度指數(shù)RI為3.09~3.29,介于[3,4],處于中度風(fēng)險(xiǎn)區(qū),而2種高環(huán)單體BaP、DBA的RI接近于3,潛在風(fēng)險(xiǎn)不容忽視,尤其是在冬春季,應(yīng)當(dāng)引起重視并加強(qiáng)監(jiān)測(cè).

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Season distribution characteristics and the risk index assessment of PAHs in surface sediments of Dianshan Lake.

DU Wei-ning, LIU Min*, ZHU Jun-min, YANG Jing, WEI Xin-yi

(School of Geographical Science, East China Normal University, Key Laboratory of Geographic Information Science, Ministry of Education, Shanghai 200062, China)., 2019,39(9)：3999~4006

PAHs contents of surface sediments were tested with seasons from 6sampling sites of the Dianshan Lake body, The results showed that: 16kinds of PAHs, which are listed as priority pollutants by EPA, were found in all the samples. The total PAHs concentration (dry weight) reached 54.6~1331.2ng/g, and the average amount was 373.4ng/g.Compared with other most areas, the total PAHs concentration of surface sediments of Dianshan Lake, were below the middle level. Seasonal fluctuation of the total PAHs concentration on the average and at the minimum and the maximum was essentially that: winter >spring>autumn>summer. In addition, PAHs contents of surface sediments were tested from other 6sampling sites of the lake out-inlet, the results were shown as: inlet>outlet>the lake body, and the seasonal characteristics were consistent with the lake body. Ring contents of PAHs share quantity: tetracyclic>pentacyclic to hexacyclic>bicyclo to tricyclic, by characteristic ratio method, source analysis showed that most of PAHs were originated from incomplete combustion of coal and biomass, which contributed 80.22% by Princical factor analysis. Based on Sediment Quality Guidelines (SQGs), this paper proposes a new method of PAHs risk quantitative evaluation——the Risk Index Method (RIM), the assessment result by it showed that the monomers of PAHs(Acy?Ace?Ant and BaA)were at medium level of ecological risk (RI reached 3.09~3.29), While most of the rest monomers of PAHs were at a relatively low to middle risk level (RI reached 0.79~2.73), Pollution status of the total PAHs was at low to middle risk level (TRI was 2.64). Dianshan Lake serves as the mein water source of Shanghai city, the potential risk of PAHs pollution of which should not be ignored.

Dianshan Lake；surface sediments；PAHs；season distribution；risk index assessment

X524

A

1000-6923(2019)09-3999-08

杜威寧(1994-),男,黑龍江齊齊哈爾人,華東師范大學(xué)博士研究生, 主要研究方向?yàn)榈厍颦h(huán)境化學(xué).發(fā)表論文2篇.

2019-01-22

國(guó)家自然科學(xué)資助基金項(xiàng)目(41730646,41601526)

* 責(zé)任作者, 教授, mliu@geo.ecnu.edu.cn