劉合歡,李會茹,盛國
1,彭平安1
1. 中國科學(xué)院廣州地球化學(xué)研究所 有機(jī)地球化學(xué)國家重點實驗室和廣東省環(huán)境資源利用與保護(hù)重點實驗室,廣州 510640 2. 中國科學(xué)院大學(xué),北京 100049
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電子垃圾拆解區(qū)及其周邊大氣中得克隆的污染和呼吸暴露研究
1,彭平安1
1. 中國科學(xué)院廣州地球化學(xué)研究所 有機(jī)地球化學(xué)國家重點實驗室和廣東省環(huán)境資源利用與保護(hù)重點實驗室,廣州 510640 2. 中國科學(xué)院大學(xué),北京 100049
添加型高氯代阻燃劑得克隆(dechlorane plus, DP)因為在環(huán)境中表現(xiàn)出普遍存在性、持久性、生物富集性、長距離遷移性和毒性,近年來迅速引起各國環(huán)境科學(xué)家的關(guān)注和重視。DP廣泛應(yīng)用于電線電纜等電子產(chǎn)品塑料中,粗放式電子垃圾拆解活動已被證實是環(huán)境中DP的重要污染來源之一。為探討電子垃圾拆解區(qū)及其周邊地區(qū)大氣中DP的污染特征、呼吸暴露劑量和影響因素,對典型電子垃圾拆解區(qū)貴嶼(GY)及其周邊地區(qū)陳店(CD)和對照市區(qū)(廣州市天河區(qū),TH)進(jìn)行大氣采樣和DP分析,并運用Monte Carlo模擬計算其日呼吸攝入劑量,同時對暴露參數(shù)進(jìn)行了靈敏度分析。結(jié)果表明:受當(dāng)?shù)卮址攀诫娮永鸾饣顒拥挠绊懀珿Y大氣中的DP平均濃度(范圍)高達(dá)(1 119±1 021) pg·m-3(410~3 381 pg·m-3),遠(yuǎn)高于CD (52.2±30.2, 20.9~102 pg·m-3)和TH (5.04±2.73, 0.967~9.43 pg·m-3);受GY大氣污染擴(kuò)散遷移的影響,CD大氣中的DP濃度也顯著高于TH (t-test, P=0.006);GY大氣中反式DP的比例(fanti)與DP商業(yè)品(fanti=0.70)無顯著差異(t-test, P=0.08),這與其存在本地排放源一致,而TH大氣中的fanti顯著低于DP商業(yè)品(t-test, P=0.000);3個地區(qū)居民的DP日均呼吸攝入劑量(pg·kg-1·d-1)分別為:GY成人1 888,兒童1 912;CD成人60.9,兒童62.8;TH成人5.16,兒童5.25;呼吸速率是DP日呼吸攝入劑量的主要貢獻(xiàn)因子,其次為大氣中的DP濃度和體重,體重對于兒童的影響遠(yuǎn)高于成人。上述研究結(jié)果表明GY及其周邊地區(qū)居民均處于較高DP呼吸暴露風(fēng)險中。
氯代阻燃劑;得克??;電子垃圾;大氣氣溶膠;呼吸暴露
Received 24 November 2015 accepted 23 December 2015
得克隆(dechlorane plus, DP)即雙(六氯環(huán)戊二烯)環(huán)辛烷(C18H12Cl12),也叫敵可燃,是一類高度氯化的脂環(huán)族阻燃劑(Cl%=65%),由Hooker Chemical公司在19世紀(jì)60年代推出,用以取代與其結(jié)構(gòu)類似的持久性有機(jī)污染物(persistent organic pollutants, POPs)滅蟻靈(mirex)。DP具有良好的著色性、熱穩(wěn)定性、優(yōu)異的電學(xué)性能及低生煙量等一系列優(yōu)點,被廣泛用于紡織、電子電器和家具裝修材料中[1]。目前已知的DP生產(chǎn)廠家有北美OxyChem化學(xué)公司(1968年收購了Hooker Chemical公司)和我國安邦電化公司,其中OxyChem公司近50年來DP的年產(chǎn)量為450 t,被美國國家環(huán)境保護(hù)署(USEPA)列為高產(chǎn)量物質(zhì)(年產(chǎn)量>100萬磅);我國安邦電化公司自2003年起開始生產(chǎn)DP,年產(chǎn)量在300~3 000 t之間[2]。DP為添加型阻燃劑,與相應(yīng)的高分子聚合物之間無化學(xué)鍵作用,在其相關(guān)產(chǎn)品的生產(chǎn)、使用和回收過程中易釋放進(jìn)入環(huán)境[3],但環(huán)境中的DP自其被使用以來并未引起關(guān)注。2006年Hoh等[4]首次報道了五大湖地區(qū)環(huán)境中的DP,此后DP的污染來源、環(huán)境濃度、行為和毒性迅速引起人們的重視。迄今為止,DP已在世界各地的水體、土壤、大氣及生物體等多種環(huán)境介質(zhì)和人體樣品中被檢出[5-6],且在環(huán)境中表現(xiàn)出持久存在性、遠(yuǎn)距離遷移性、生物富集性、潛在的生物毒性等POPs特性,可能被加入POPs公約附件D的考察清單[5]。
研究表明,電子垃圾拆解活動、城市活動和DP相關(guān)產(chǎn)品的生產(chǎn)使用過程是環(huán)境中DP的重要污染來源[5-6]。為節(jié)省成本,我國一些地區(qū)采用手工拆解、烘烤、焚燒、酸洗等原始粗放式手段回收電子垃圾中的金屬、塑料等材料[7],對當(dāng)?shù)丨h(huán)境造成了嚴(yán)重污染。由于DP在電子產(chǎn)品中的廣泛應(yīng)用,電子垃圾拆解區(qū)各類環(huán)境介質(zhì)中都呈現(xiàn)出較高的DP濃度[8-24]。電子垃圾拆解作坊內(nèi)灰塵中DP的濃度均值(范圍)為1 515 (343~4 197) ng·g-1,比對照城市室內(nèi)灰塵濃度(18.9, 2.78~70.4 ng·g-1)高出兩個數(shù)量級[14];拆解區(qū)大氣中的DP濃度在13.1~1 794 pg·m-3之間,顯著高于對照區(qū)(0.47~35.7 pg·m-3)[15];拆解點表層土壤[16]中DP的濃度最高值(3 327 ng·g-1)與DP生產(chǎn)基地周圍土壤中[17]的DP濃度(1 490±3 580 ng·g-1干重)接近,遠(yuǎn)高于其周邊地區(qū)(n.d.~47.4 ng·g-1)和珠三角典型工業(yè)區(qū)(0.03~4.65 ng·g-1)[16];電子垃圾拆解區(qū)附近區(qū)域水和沉積物中的DP平均濃度分別達(dá)到(0.8±0.06) ng·L-1和7 590 ng·g-1dw[24]。與此同時,高濃度的DP也在電子垃圾拆解區(qū)各類生物樣品中被檢出,其中包括樹葉(0.45~51.9 ng·g-1dw)[15]、水稻(0.71~1.99 ng·g-1dw)[18]、陸生鳥類(n.d.~500 ng·g-1lw)[19]、水生鳥類(n.d.~2 200 ng·g-1lw )[20]、魚螺等水生生物(n.d. ~1 670 ng·g-1lw)[9, 21]、蚯蚓(3.43~89.2 ng·g-1lw)[22]、青蛙(2.01~291 ng·g-1lw)[23]等。
環(huán)境介質(zhì)中的DP可通過呼吸、飲食、皮膚接觸、灰塵吸入等多種暴露途徑進(jìn)入人體。研究表明,電子垃圾拆解區(qū)居民人體樣品中的DP濃度要顯著高于其他對照地區(qū)[14, 25-29],拆解區(qū)人體血清中的DP平均濃度達(dá)到42.6 ng·g-1,約為鄰近地區(qū)(13.7 ng·g-1)的3倍[25];母乳樣品中的DP濃度為2.19~4.46 ng·g-1lw,明顯高于城市地區(qū)(0.98 ng·g-1lw)[27];人體頭發(fā)中的DP濃度(0.19~35.7 ng·g-1)也遠(yuǎn)高于普通城市地區(qū)(0.02~4.97 ng·g-1)[14]。目前對于電子垃圾拆解區(qū)環(huán)境中的DP及其居民的DP內(nèi)外暴露水平都有一定研究,但對DP的具體暴露途徑、劑量和影響因素等討論較少,對典型電子垃圾拆解區(qū)貴嶼(Guiyu, GY)大氣中的DP污染尚未見報道。本文選取GY及其周邊地區(qū)和普通城市對照區(qū)進(jìn)行大氣采樣和DP分析,采用Monte Carlo模擬對研究區(qū)域居民的DP日呼吸暴露劑量進(jìn)行計算,并對計算結(jié)果的不確定性和影響因素進(jìn)行了分析。
1.1 采樣點及樣品采集
GY鎮(zhèn)地處廣東省汕頭市潮陽區(qū)西部,支柱產(chǎn)業(yè)是電子垃圾拆解業(yè)。GY早在19世紀(jì)80年代末期就開始涉及舊五金電器的拆解生意。由于獲利豐厚,整個行業(yè)規(guī)模逐漸擴(kuò)大,90年代初真正發(fā)展為GY主業(yè)。與此同時,國外電子垃圾通過轉(zhuǎn)運點開始大規(guī)模進(jìn)入GY。約80%的GY家庭參與該行業(yè),年拆解垃圾量超過100萬t[30]。陳店鎮(zhèn)(Chendian, CD)距離GY鎮(zhèn)9 km左右,支柱產(chǎn)業(yè)是商業(yè)貿(mào)易和內(nèi)衣家居服裝。廣州地處華南,為我國第三大城市和金融中心,城市對照采樣點位于廣州市天河區(qū)(Tianhe, TH)。
環(huán)境大氣樣品采集于2005-12-18至2006-1-3期間,采樣期間無降雨降雪天氣。大氣中的總懸浮顆粒物(total suspended particles, TSP)采用智能大流量空氣采樣器(武漢天虹智能儀表廠)和Whatman玻璃纖維膜(Glass fiber filters, GFFs, 20.3 cm×5.4 cm)收集,采樣設(shè)定流量1.05 m3·min-1。采樣前用無水乙醇或丙酮清洗采樣器內(nèi)壁及壓框,采樣結(jié)束后GFF用鋁箔包裹并裝入樣品袋密封,置于<-20 ℃冰箱中保存待用。樣品采集前后分別用流量校正器(武漢天虹智能儀表廠)進(jìn)行流量校正。每個樣品連續(xù)采樣8 h以上,采樣體積大于400 m3。本研究共采集到22個樣品,其中GY8個、CD7個、TH7個。
1.2 溶劑與試劑
順式(anti-)DP和反式(syn-)DP標(biāo)準(zhǔn)溶液(50 μg·mL-1,純度>95%)購自Wellington Laboratories (Guelph, ON, Canada)。分析過程中所使用的溶劑和試劑均為分析純或農(nóng)殘級。硅膠(70~230目)和氧化鋁(60~100目)分別購自美國Aldrich公司和德國Merck公司,使用前分別在180 ℃和250 ℃條件下活化24 h,冷卻后加3%(w:w)蒸餾水去活化,平衡12 h后加入正己烷并置于干燥器中備用。無水硫酸鈉在450 ℃下烘烤4 h后置于干燥器中保存待用。
1.3 樣品前處理
作為Festo首款獨家數(shù)字化產(chǎn)品,Smartenance是一款基于云端的APP,所有制造企業(yè)均可使用。該應(yīng)用程序引導(dǎo)清晰明確,因此設(shè)置更快捷。生產(chǎn)經(jīng)理用戶界面可便利地用瀏覽器打開。Smartenance讓終端用戶能計劃、監(jiān)控和評估系統(tǒng)維護(hù)。數(shù)字化的維護(hù)計劃讓維護(hù)更簡單、更快速、更可靠,為系統(tǒng)操作員與生產(chǎn)經(jīng)理的復(fù)查提高了可靠性,省卻了許多過程和協(xié)調(diào)工作。
樣品中加入13C標(biāo)記的PCB-141和PCB-209,用正己烷-丙酮(V:V=1:1)混合溶劑索氏抽提48 h。提取液經(jīng)無水硫酸鈉除水后旋轉(zhuǎn)蒸發(fā),轉(zhuǎn)換溶劑至正己烷并濃縮至1 mL左右。濃縮液采用多段氧化鋁/硅膠柱(1 cm i.d.)進(jìn)行凈化,濕法裝柱從下至上分別為6 cm氧化鋁、2 cm中性硅膠、5 cm堿性硅膠(1 mol·L-1NaOH, w:w, 33%)、2 cm中性硅膠、8 cm酸性硅膠(硅膠:硫酸= 2:1, w:w)和2 cm無水硫酸鈉,樣品上柱后分別用15 mL正己烷和70 mL正己烷-二氯甲烷(V:V=1:1)混合溶劑洗脫,收集后者并旋轉(zhuǎn)蒸發(fā)濃縮至100 μL,加入進(jìn)樣內(nèi)標(biāo)13C-PCB-208后進(jìn)行儀器分析。
1.4 儀器分析
負(fù)離子化學(xué)源氣相色譜-質(zhì)譜聯(lián)用儀(NCI-GC-MS, Agilent 7890A-5975C),選擇離子掃描模式,載氣為氦氣,無分流模式進(jìn)樣1 μL;15-m DB-5-HT MS毛細(xì)管柱(250 μm i.d. 0.10 μm, J&W Science, Folsom, CA, 美國),柱升溫程序:110 ℃保持5 min,20 ℃·min-1升溫至200 ℃,保持4.5 min,再以7.5 ℃·min-1升溫至300 ℃,保持16 min;進(jìn)樣口、傳輸線、離子源和四極桿的溫度分別為260 ℃、280 ℃、250 ℃和150 ℃;DP化合物監(jiān)測離子對(m/z)為651.7和653.7。
1.5 質(zhì)量控制與質(zhì)量保證(QA/QC)
GFF使用前于450 ℃馬弗爐中烘燒4 h以去除背景有機(jī)物干擾。所有樣品中均加入回收率指示物以衡量萃取凈化效率,每12個樣品包含一個野外采樣空白、一個實驗室空白、一個空白加標(biāo)和一個基質(zhì)加標(biāo)對分析流程進(jìn)行質(zhì)量控制,以確保分析結(jié)果的準(zhǔn)確性和可靠性。當(dāng)目標(biāo)物與標(biāo)準(zhǔn)物質(zhì)保留時間誤差在±0.1 min之內(nèi),信噪比(S/N)≥10,且監(jiān)測離子對同位素比值與理論值誤差在15%以內(nèi)才能對其進(jìn)行識別與定量。濃度計算采用8點標(biāo)準(zhǔn)曲線。所有樣品中13C-PCB-141和PCB-209的回收率分別在72%~125%和77%~132%之間,空白/基質(zhì)加標(biāo)樣品中DP化合物的回收率為80%~117%。樣品數(shù)據(jù)的統(tǒng)計分析均在SPSS v20軟件上運行,置信度P =0.05。
1.6 Monte Carlo模擬和靈敏度分析
為評價各研究區(qū)域居民對DP的呼吸暴露風(fēng)險,本研究根據(jù)美國EPA暴露因子手冊中推薦的評價方法和計算公式[31],對DP的日呼吸攝入劑量(daily inhalation intake dose, DID)進(jìn)行計算:
DID (pg·kg-1·d-1) = C × IR/BW
對相關(guān)參數(shù)進(jìn)行定義和計算,相關(guān)變量及分布模型參數(shù)見表1。Monte Carlo模擬在Oracle Crystal Ball(Release 11.1.2.500)軟件上運行,采樣次數(shù)為100 000次。
2.1 研究區(qū)域大氣中的DP濃度
DP化合物親脂性強(qiáng)(log Kow=9.3),正辛醇-空氣分配系數(shù)較高(log Koa=14),大氣中的DP約99%左右存在于顆粒相上,僅有約1%以氣態(tài)形式存在[4],因此可認(rèn)為顆粒相DP濃度近似等于DP的大氣濃度。順反式DP在本研究所有大氣樣品中被檢出,檢出率100%,說明DP在所研究區(qū)域大氣中普遍存在。各研究區(qū)域大氣中DP總濃度的平均值±標(biāo)準(zhǔn)偏差(范圍)分別為:(1 119±1 021) pg·m-3(410~3 381 pg·m-3)(GY)、(52.2±30.2) pg·m-3(20.9~102 pg·m-3) (CD)和(5.04±2.73) pg·m-3(0.967~9.43 pg·m-3) (TH),空間分布上呈現(xiàn)出電子垃圾拆解區(qū)GY > 電子垃圾拆解區(qū)周邊地區(qū)CD > 城市地區(qū)TH的變化規(guī)律(圖1)。
圖1 貴嶼(GY)、陳店(CD)和廣州市天河區(qū)(TH)大氣中的DP濃度Fig. 1 The concentrations of DP in air around Guiyu (GY), Chendian (CD) and Tianhe District of Guangzhou (TH)
表1 得克隆(DP)呼吸暴露劑量計算相關(guān)變量的分布模型及參數(shù)
注:* min表示最小值,max表示最大值,μ表示平均值,δ表示標(biāo)準(zhǔn)差;** BW符合正態(tài)分布規(guī)律,但實際體重需增加最大值和最小值限定以保證取值具有實際意義。
Note:*min, max, μ and δ represent minimum, maximum, mean and standard deviation, respectively;** BW is normally distributed, and the minimum and maximum were added to ensure all data are reasonable.
目前對世界不同地區(qū)大氣中的DP研究較多,表2列出了國內(nèi)外不同城市和地區(qū)大氣中的DP濃度,平均值在0.38[45]~44.8[46]pg·m-3之間。相比之下,TH大氣中的DP濃度與我國上海[42]和哈爾濱[43]相近,略低于Ren等[44]報道的我國21個城市地區(qū)的濃度,與世界其他國家和城市地區(qū)相比處于中等水平。GY地區(qū)以電子垃圾拆解為主業(yè),沒有其他工業(yè),也沒有涉及DP及相關(guān)產(chǎn)品的生產(chǎn)制造,但其大氣中的DP濃度約為城市對照區(qū)TH的200倍,顯著高于世界其他城市地區(qū)(表2),與我國江蘇淮安DP生產(chǎn)廠附近大氣中的DP濃度接近[47],說明該地區(qū)粗放式的電子垃圾拆解活動向環(huán)境中釋放了大量的DP,從而造成該地區(qū)嚴(yán)重的DP污染。CD是距離GY約9 km的一個小鎮(zhèn),以內(nèi)衣家居服制造為主業(yè),沒有電子垃圾拆解點,也沒有涉及DP及其相關(guān)產(chǎn)品的生產(chǎn)制造,但CD大氣中的DP濃度比典型城市地區(qū)TH高出一個數(shù)量級,也顯著高于我國其他城市地區(qū)(15.6±15.1 pg·m-3)[44](表2),由此可以推斷,GY大氣中嚴(yán)重的DP污染通過大氣遷移對CD產(chǎn)生了影響。
表2 世界不同城市和地區(qū)大氣中的DP濃度(pg·m-3)
圖2 DP的合成反應(yīng)Fig. 2 The synthesis reaction of DP
圖3 貴嶼(GY)、陳店(CD)和廣州天河區(qū)(TH)大氣中anti-DP的比例Fig. 3 The fractions of anti-DP in atmosphere from Guiyu (GY), Chendian (CD) and Tianhe District of Guangzhou (TH)
我國廣東浙江等地均存在與GY類似的電子垃圾拆解區(qū)。Chen等[15]報道了廣東清遠(yuǎn)電子垃圾拆解點大氣中的DP平均濃度(范圍)為363 (13.1~1 794) pg·m-3,顯著高于距離拆解點25 km的對照區(qū)(5.65, 0.47~35.7 pg·m-3)。浙江某電子垃圾拆解地大氣中的DP濃度[48]為11.6 pg·m-3。與上述電子垃圾拆解區(qū)相比,GY大氣中的DP濃度較高,這可能與GY地區(qū)前期主要拆解進(jìn)口電子垃圾的電線電纜和電腦組件有關(guān)。我國電子產(chǎn)品中添加的鹵系阻燃劑以溴代阻燃劑為主,尤其是十溴聯(lián)苯醚(Deca-BDEs, BDE-209),對DP的生產(chǎn)和使用量遠(yuǎn)小于歐美國家,因此,我國環(huán)境中的PBDEs濃度普遍比DP高兩到三個數(shù)量級[49-50]。但因為電子洋垃圾的輸入,我國電子垃圾拆解區(qū)環(huán)境中表現(xiàn)出較高的DP濃度:GY大氣中的DP濃度達(dá)到BDE-209濃度(2 164 pg·m-3)的一半[50];GY人體血清中的DP濃度(均值39.8 ng·g-1脂重)也約為BDE-209(均值70.6 ng·g-1脂重)的一半[25]。GY地區(qū)環(huán)境中DP與BDE-209濃度比例的升高證實了電子洋垃圾是該地區(qū)DP污染的主要來源。
2.2 DP異構(gòu)體組成
DP由1,5-環(huán)辛二烯和六氯環(huán)戊二烯以2:1的摩爾比通過Diels-Alder環(huán)化反應(yīng)合成,產(chǎn)物包括syn-DP和anti-DP兩種異構(gòu)體(見圖2)。不同DP商業(yè)品在顆粒尺寸上會存在差異,但其異構(gòu)體組成比例恒定,syn-DP:anti-DP近似等于1:3,即anti-DP的濃度比例(fanti)約為75%[4-5]。但因為生產(chǎn)廠家和生產(chǎn)批次之間的差異,目前文獻(xiàn)中報道的DP商業(yè)品fanti值稍有差別。Hoh等[4]和Qiu等[51]報道的DP商業(yè)品fanti值分別為0.75~0.80和0.75,Tomy等[44]報道美國Oxychem公司DP產(chǎn)品中的fanti值為0.65,Wu等[52]對我國生產(chǎn)的DP商業(yè)品分析后測得fanti值為0.70±0.003,此外0.59[53]、0.60[17]、0.68[3]等也都有報道,但總體來說DP商業(yè)品的fanti值基本在0.60~0.80范圍內(nèi)。
從結(jié)構(gòu)上看(圖2),anti-DP環(huán)辛烷結(jié)構(gòu)內(nèi)部的4個碳原子受氯原子和環(huán)戊二烯結(jié)構(gòu)的屏蔽程度低于syn-DP,理論上反應(yīng)活性比syn-DP強(qiáng),而syn-DP則相對穩(wěn)定[4]。實際研究中也發(fā)現(xiàn)anti-DP在大氣遷移過程中會發(fā)生選擇性降解或者可能向syn-DP轉(zhuǎn)化,從而導(dǎo)致fanti降低[4, 54-55],但Qiu等[51]對五大湖區(qū)沉積物柱狀樣的研究發(fā)現(xiàn)沉積年齡越長,樣品的fanti值越高,說明沉積物/土壤中的syn-DP容易在微生物作用下發(fā)生降解[6, 51]。2種異構(gòu)體在生物體中的情況更為復(fù)雜,已有研究表明syn-DP在水生生物體內(nèi)可發(fā)生選擇性富集,但2種異構(gòu)體在陸生生物和人體內(nèi)表現(xiàn)出的生物富集性沒有顯著差異[6]。鑒于2種異構(gòu)體不同的空間構(gòu)型、理化性質(zhì)和環(huán)境行為,實際研究中常通過考察anti-DP或syn-DP濃度比例與DP商業(yè)品之間的差異來探討2種異構(gòu)體在環(huán)境中的遷移行為和歸趨。
本文3個研究地區(qū)大氣中的fanti值如圖3所示。GY、CD和TH的fanti平均值(范圍)分別為0.68±0.02(0.65~0.71)、0.73±0.03(0.69~0.77)和0.54±0.05(0.48~0.62),其中GY的結(jié)果與Chen等[15]對清遠(yuǎn)電子垃圾區(qū)大氣的研究結(jié)果相同(fanti=0.726±0.037)。本研究采用0.70作為DP商業(yè)品的fanti值對樣本進(jìn)行了t檢驗,結(jié)果表明,GY大氣中DP的fanti值與DP商業(yè)品之間沒有顯著差異(P=0.08),再次說明了GY當(dāng)?shù)卮嬖贒P的污染排放源;CD地區(qū)的fanti值與商品級DP的fanti值接近(圖 3),結(jié)合CD距離GY較近且當(dāng)?shù)夭淮嬖贒P生產(chǎn)使用及電子垃圾拆解等污染源,這一結(jié)果進(jìn)一步證實了CD大氣中的DP主要來源于GY地區(qū)DP重污染的大氣遷移;TH大氣中DP的fanti值則顯著低于DP商業(yè)品(t-test, P=0.000),也低于我國其他城市和地區(qū)大氣的fanti值[42-44]。除DP生產(chǎn)和電子垃圾拆解活動外,含DP產(chǎn)品的使用[62]、城市活動[63]和點源污染的大氣遷移[51]也是環(huán)境中DP的重要來源。TH區(qū)是典型城市地區(qū),但其大氣中的DP濃度(5.04±2.73 pg·m-3)與我國郊區(qū)和鄉(xiāng)村地區(qū)的濃度(3.5±5.6 pg·m-3)接近[44],且其fanti值顯著偏低,由此推斷本地城市活動及含DP產(chǎn)品的生產(chǎn)使用對TH大氣中的DP貢獻(xiàn)較小,點源污染的大氣遷移是其主要來源,且anti-DP在遷移過程中發(fā)生了選擇性降解或轉(zhuǎn)化,從而使樣品中的fanti值低于商品級DP的fanti值[64]。
2.3 呼吸暴露
目前DP在各類環(huán)境介質(zhì)[62, 65]以及人體樣品中[3, 29]被廣泛檢出,盡管還沒有關(guān)于人體在DP暴露下急性中毒的案例,但對斑馬魚[66]、蚯蚓[67]和大型藻[68]等的研究表明,DP會對這些生物的生理機(jī)能造成傷害。環(huán)境中的DP能夠通過呼吸、皮膚接觸和飲食等途徑進(jìn)入人體并累積,可能會對人體造成不利的影響,因此有必要對不同暴露途徑DP的人體暴露劑量和影響因素進(jìn)行評價。
本研究根據(jù)美國EPA的呼吸暴露劑量計算公式及我國人群暴露參數(shù)對研究區(qū)域居民對DP的DIDs進(jìn)行了Monte Carlo模擬計算,同時采用參數(shù)平均值(最小值,最大值)和常規(guī)算法計算以進(jìn)行比較,結(jié)果如表3所示。根據(jù)Monte Carlo模擬計算結(jié)果,GY、CD和TH成人對DP的DID均值(范圍)分別為1 888 (39.6~8 153) pg·kg-1·d-1、60.9 (1.93~250) pg·kg-1·d-1和5.16 (0.101~23.6) pg·kg-1·d-1;GY、CD和TH兒童的DID均值(范圍)分別為1 912 (26.3~20 448) pg·kg-1·d-1、62.8 (1.22~587) pg·kg-1·d-1和5.25 (0.067~55.4) pg·kg-1·d-1,顯而易見,同地區(qū)兒童對DP的DIDs要略高于成人。相比之下,常規(guī)算法的計算結(jié)果均低于Monte Carlo模擬結(jié)果,且兩者差距隨大氣中DP濃度的增大而增大,此外,常規(guī)算法的計算結(jié)果表明同地區(qū)兒童對DP的DIDs約為成人的2倍左右(表 3),可見采用平均值常規(guī)計算的不確定性很大。而Monte Carlo模擬計算考慮了各暴露因素的實際變化情況和概率,能有效地減少這種不確實性,獲得較為準(zhǔn)確的結(jié)果。Wang等[69]對DP呼吸暴露劑量的計算表明,清遠(yuǎn)電子垃圾區(qū)居民的DP呼吸暴露劑量為2.1 pg·kg-1·d-1(成人)和3.2 pg·kg-1·d-1(兒童),該結(jié)果與本研究中城市對照區(qū)TH的數(shù)據(jù)接近,但遠(yuǎn)低于GY電子垃圾拆解區(qū)的計算結(jié)果。同為電子垃圾拆解區(qū),且均采用Monte Carlo模擬算法,但計算結(jié)果存在較大差異,主要原因可能為:(1)計算所采用大氣中DP的濃度存在較大差異。Wang等[69]分別采用Chen等[15]報道的清遠(yuǎn)電子垃圾拆解點和距離拆解點20 km對照區(qū)大氣中的DP濃度(分別為363 pg.m-3和5.65 pg.m-3)對拆解工人和居民的DP呼吸暴露劑量進(jìn)行計算,后者與本研究中TH的濃度接近,GY環(huán)境大氣中的DP濃度約為其200倍;(2) 計算選用的暴露參數(shù)存在較大差異。Wang等[69]采用美國EPA的暴露參數(shù)進(jìn)行計算,本研究依據(jù)侯捷等[41]報道的我國居民暴露數(shù)據(jù)對相關(guān)計算參數(shù)進(jìn)行定義和計算。
表3 不同算法下貴嶼(GY)、陳店(CD)和廣州天河區(qū)(TH)居民的DP日呼吸暴露劑量(DID, pg·kg-1·d-1)
圖4 不同暴露參數(shù)(C、IR和BW)對DP日呼吸暴露劑量(DID)的貢獻(xiàn)率 (GY、CD和TH分別為貴嶼、陳店和廣州市天河區(qū))Fig. 4 The contributions of C, IR and BW to the daily inhalation exposure dose (DID) of DP (GY, CD and TH stand for Guiyu, Chendian, and Tianhe District of Guangzhou, respectively)
此外,本研究對大氣中的DP濃度、呼吸速率、體重等參數(shù)對DP日呼吸暴露劑量的影響進(jìn)行了靈敏度分析,各參數(shù)的貢獻(xiàn)因子如圖4所示。由圖4可知,呼吸速率是各區(qū)域居民DP呼吸暴露劑量的主要貢獻(xiàn)因子(47.2%~67.9%),其次為大氣中的DP濃度(23.6%~42.8%)和體重(0.9%~23.1%)。體重對于成人的DP呼吸劑量貢獻(xiàn)較小,貢獻(xiàn)因子在0.9%~1.2%之間,但對兒童的DP呼吸劑量貢獻(xiàn)較大,貢獻(xiàn)因子達(dá)到19.0%~23.1%,表明體重對于兒童的DP呼吸暴露風(fēng)險更為重要,這也是Monte Carlo模擬和常規(guī)計算在兒童DIDs計算結(jié)果上存在差異的主要原因。與各地區(qū)大氣中DP的濃度變化趨勢一致,GY和CD居民對DP的DIDs顯著高于TH地區(qū),表明電子垃圾拆解及其周邊地區(qū)居民處于較高的DP呼吸暴露風(fēng)險中。Wang等[69]對DP生產(chǎn)地區(qū)及電子垃圾拆解區(qū)人體暴露風(fēng)險的研究表明,飲食暴露是人體DP暴露的主要方式,約占99%以上,因此未來應(yīng)對貴嶼及其周邊地區(qū)開展飲食、皮膚接觸等暴露途徑、劑量和影響因素的研究,以全面評估該地區(qū)居民的DP暴露風(fēng)險。
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Occurrence and Inhalation Exposure of Dechlorane Plus in the Atmosphere around E-waste Recycling Area and Its Surrounding Area
Liu Hehuan1,2, Li Huiru1,*, Sheng Guoying1, Fu Jiamo1, Peng Ping’an1
1. State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China 2. University of Chinese Academy of Sciences, Beijing 100049, China
Dechlorane plus (DP), a highly chlorinated additive flame-retardant used for about 50 years, recently attracted much attention from scientists worldwide due to its ubiquitousness, persistence, bioaccumulativity, long-range transportability and toxicity in environment. DP is mainly employed in commercial polymer products including coating electrical wires and cables, connectors in computer and televisions, and plastic roofing materials for building. Primitive electronic waste (e-waste) recycling activities have been proved as an important source of DP in environment. In this study, air samples were collected from Guiyu (GY), a typical e-waste recycling area, Chendian (CD), a neighboring town of GY, and Tianhe District (TH), a contrast urban area, and analyzed for DP with the aim to investigate the pollution, inhalation exposure dose and influential factors of DP in these areas. The results showed that the mean DP concentration±SD (range) in air of GY was up to 1 119±1 021 (410~3 381) pg.m-3, much higher than those of CD (52.2±30.2, 20.9~102 pg.m-3) and TH (5.04±2.73, 0.967~9.43 pg.m-3). This was attributed to the local e-waste recycling activities in GY, e.g. dismantling, burning, incineration, etc. Although there were neither e-waste recycling industry nor DP production or application in CD, the atmospheric DP levels in CD were significantly higher than in the contrast urban area TH (t-test, P=0.006). This was due to the long-rang transport of the heavily polluted air from GY. The fractions of anti-DP (fanti) in GY showed no significant difference from that of the commercial DP product (fanti=0.70, t-test, P=0.08), in accordance with its local e-waste recycling emission source. While significant difference was found between the fantis of TH and technical DP product (t-test, P=0.000). The daily inhalation dose (DID) of DP and its influential factors were estimated with Monte Carlo simulation for local residents. The average DIDs of DP were 1 888 and 1 912 pg·kg-1·d-1for adults and children in GY, 60.9 and 62.8 pg·kg-1·d-1for adults and children in CD, and 5.16 and 5.25 pg·kg-1·d-1for adults and children in TH, respectively. The sensitivity analysis results suggest that inhalation rate was the predominant contributor to the DID of DP, followed by the atmospheric concentration of DP and body weight (BW). Comparatively, the DIDs of children were more affected by BW than those of adults. On the whole, residents in GY and its surrounding areas were in high DP inhalation exposure risk.
chlorinated flame retardants; dechlorane plus; electronic waste; air aerosol; inhalation exposure
10.7524/AJE.1673-5897.20151124004
國家自然科學(xué)基金(NO. 41273002,41130752,40903043);有機(jī)地球化學(xué)國家重點實驗室專項基金(SKLOG2015A02)
劉合歡(1992-),男,碩士研究生,研究方向為新型污染物環(huán)境行為,E-mail: liuhehuan@gig.ac.cn
*通訊作者(Corresponding author), E-mail: huiruli@gig.ac.cn
2015-11-24 錄用日期:2015-12-23
1673-5897(2016)2-144-11
X171.5
A
簡介:李會茹(1981—),女,環(huán)境科學(xué)博士,副研究員,主要研究方向為新型/持久性有機(jī)污染物的分析方法和環(huán)境地球化學(xué)行為,發(fā)表學(xué)術(shù)論文20余篇。
劉合歡, 李會茹, 盛國英, 等. 電子垃圾拆解區(qū)及其周邊大氣中得克隆的污染和呼吸暴露研究[J]. 生態(tài)毒理學(xué)報,2016, 11(2): 144-154
Liu H H, Li H R, Sheng G Y, et al. Occurrence and inhalation exposure of dechlorane plus in the atmosphere around e-waste recycling area and its surrounding area [J]. Asian Journal of Ecotoxicology, 2016, 11(2): 144-154 (in Chinese)