羅 瑩,劉 娜,孫善偉,侯 嵩,郭昌勝*,徐 建

我國(guó)地表水中典型DBPs的暴露水平及生態(tài)風(fēng)險(xiǎn)

羅 瑩1,2,3,劉 娜3,孫善偉1,侯 嵩1,郭昌勝1,3*,徐 建1,3

(1.中國(guó)環(huán)境科學(xué)研究院,國(guó)家環(huán)境保護(hù)化學(xué)品生態(tài)效應(yīng)與風(fēng)險(xiǎn)評(píng)估重點(diǎn)實(shí)驗(yàn)室,北京 100012；2.北京師范大學(xué)水科學(xué)研究院,北京 100875；3.中國(guó)環(huán)境科學(xué)研究院,環(huán)境基準(zhǔn)與風(fēng)險(xiǎn)評(píng)估國(guó)家重點(diǎn)實(shí)驗(yàn)室,北京 100012)

氯消毒過(guò)程中可能生成有毒有害的副產(chǎn)物,會(huì)對(duì)水生態(tài)系統(tǒng)和環(huán)境健康產(chǎn)生直接和間接的次生危害.三鹵甲烷(THMs)和鹵乙酸(HAAs)是地表水中檢出率最高的消毒副產(chǎn)物(DBPs),其毒性效應(yīng)受到廣泛關(guān)注.本文檢索整理了三氯甲烷(TCM)、三溴甲烷(TBM)、二氯乙酸(DCAA)和三氯乙酸(TCAA)在我國(guó)地表水暴露濃度和對(duì)水生生物的毒性效應(yīng)濃度,了解我國(guó)重點(diǎn)流域地表水環(huán)境中TCM、TBM、DCAA和TCAA的濃度水平,分別利用急、慢性毒性數(shù)據(jù)推導(dǎo)預(yù)測(cè)無(wú)效應(yīng)濃度(PNEC),并使用風(fēng)險(xiǎn)商(RQ)和概率生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)法(PERA)對(duì)我國(guó)重點(diǎn)流域水環(huán)境中TCM、TBM、DCAA和TCAA進(jìn)行多層次生態(tài)風(fēng)險(xiǎn)評(píng)估.結(jié)果表明,我國(guó)地表水環(huán)境中TCM、TBM、DCAA和TCAA暴露濃度范圍為n.d.~51μg/L.以致死和生長(zhǎng)、繁殖等為測(cè)試終點(diǎn)的急、慢性毒性數(shù)據(jù),構(gòu)建物種敏感度分布(SSD)曲線,推導(dǎo)出TCM、TBM、DCAA和TCAA的PNEC值分別為0.586,0.857,0和44.880mg/L; 0.006,0.064,0.956和0.012mg/L.基于急、慢性毒性數(shù)據(jù)計(jì)算出的RQ小于1.我國(guó)重點(diǎn)流域中TCM和TCAA對(duì)1%的水生生物造成生長(zhǎng)、繁殖等慢性毒性影響的概率分別為78.86%和20.61%,存在潛在的生態(tài)風(fēng)險(xiǎn).

消毒副產(chǎn)物；地表水；生態(tài)風(fēng)險(xiǎn)評(píng)估

目前我國(guó)新冠肺炎疫情形勢(shì)依然嚴(yán)峻,為防止傳染病毒快速傳播,含氯消毒劑大量使用,消毒劑在阻隔緩解病毒擴(kuò)散的同時(shí),也產(chǎn)生大量含氯消毒副產(chǎn)物,通過(guò)醫(yī)療廢水和生活污水等途徑由城鎮(zhèn)排水系統(tǒng)進(jìn)入河流水體.同時(shí),為保證公眾飲用水安全,氯化消毒通常也是國(guó)內(nèi)外集中式供水最主要的消毒方式.但氯消毒劑會(huì)與水中的天然有機(jī)物反應(yīng),生成對(duì)人體和水生生物有害的消毒副產(chǎn)物(DBPs)[1],對(duì)人體健康和水生態(tài)系統(tǒng)產(chǎn)生直接和間接的次生危害.DBPs種類(lèi)繁多[2],主要包括三鹵甲烷(THMs)、鹵乙酸(HAAs)、鹵乙腈、鹵代酚、鹵代酮等物質(zhì)[3],其中THMs和HAAs含量較高,并且已納入飲用水監(jiān)管體系[2].近年來(lái),THMs和HAAs在地表水中均有檢出,其濃度達(dá)到μg/L的水平[3-13].

20世紀(jì)70年代,國(guó)內(nèi)外陸續(xù)對(duì)THMs和HAAs展開(kāi)毒性研究,結(jié)果表明,兩者具有“三致效應(yīng)”[14-17].同時(shí),相關(guān)研究證實(shí),THMs和HAAs對(duì)水生生物具有死亡[18-40]、發(fā)育[18,32,41-43]和繁殖效應(yīng)[27,44],評(píng)估THMs和HAAs存在的潛在生態(tài)風(fēng)險(xiǎn)對(duì)保護(hù)水生生物至關(guān)重要.

生態(tài)風(fēng)險(xiǎn)評(píng)估是預(yù)測(cè)環(huán)境中污染物對(duì)生態(tài)系統(tǒng)或其中一部分產(chǎn)生有害影響可能性的過(guò)程[45],主要將污染物暴露濃度與效應(yīng)濃度進(jìn)行比較.暴露濃度通常指實(shí)測(cè)或預(yù)測(cè)的環(huán)境中化合物的濃度,效應(yīng)濃度指化合物對(duì)生物造成不良效應(yīng)的濃度,通常由預(yù)測(cè)無(wú)效應(yīng)濃度(PNEC)來(lái)表示.風(fēng)險(xiǎn)商(RQ)和概率生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)法(PERAs)是風(fēng)險(xiǎn)評(píng)估中常用的方法. RQ是污染物暴露濃度與預(yù)測(cè)無(wú)效應(yīng)濃度PNEC的比值[46].但RQ的不確定性較大,因而適用于低水平或多層次中較低層次的風(fēng)險(xiǎn)評(píng)估.為了得到更確切的風(fēng)險(xiǎn)概率,一般采用PERAs作為多層次風(fēng)險(xiǎn)評(píng)估中較高層次的評(píng)估方法[47].為了獲得更準(zhǔn)確的風(fēng)險(xiǎn)結(jié)果,一些學(xué)者和研究機(jī)構(gòu)提出連續(xù)應(yīng)用低層次到高層次的風(fēng)險(xiǎn)評(píng)價(jià)方法,即將RQ和PERAs進(jìn)行綜合,充分利用各種方法進(jìn)行從簡(jiǎn)單到復(fù)雜的風(fēng)險(xiǎn)評(píng)價(jià)[47].本文通過(guò)文獻(xiàn)檢索和資料收集,獲取THMs和HAAs在我國(guó)地表水環(huán)境中的暴露濃度和毒性效應(yīng)濃度,對(duì)我國(guó)地表水中THMs和HAAs進(jìn)行全面的多層次生態(tài)風(fēng)險(xiǎn)評(píng)估,為T(mén)HMs和HAAs的環(huán)境管理提供理論依據(jù)和科學(xué)支撐.

1 材料與方法

1.1 THMs和HAAs環(huán)境暴露濃度

THMs和HAAs是水環(huán)境中最主要的DBPs[8]. THMs包括三氯甲烷(TCM)、一溴二氯甲烷(BDCM)、一氯二溴甲烷(DBCM)和三溴甲烷(TBM)[48];HAAs包括一氯乙酸(MCAA)、二氯乙酸(DCAA)、三氯乙酸(TCAA)、一溴乙酸(MBAA)和二溴乙酸(DBAA)[48].通過(guò)檢索國(guó)內(nèi)外期刊文獻(xiàn)、碩博學(xué)位論文等,獲取我國(guó)重點(diǎn)流域及其水源地THMs和HAAs的暴露濃度數(shù)據(jù),以全面評(píng)估THMs和HAAs在我國(guó)地表水環(huán)境中的暴露水平.結(jié)果表明,THMs和HAAs在水源水[3,6-8,10-12]和地表水[4-5,9,13]中均有檢出.低于方法檢出限的同一流域中不同檢測(cè)點(diǎn)位的濃度數(shù)據(jù)按最低檢出限的50%計(jì)算.使用IBM SPSS Statistics 24的Kolmogorov-Smirnov檢驗(yàn)對(duì)THMs和HAAs在我國(guó)地表水中的濃度分布數(shù)據(jù)進(jìn)行正態(tài)分布檢驗(yàn).

1.2 THMs和HAAs毒性效應(yīng)評(píng)估

THMs和HAAs的水生生物毒性數(shù)據(jù)來(lái)自毒理數(shù)據(jù)庫(kù)(如美國(guó)的ECOTOX數(shù)據(jù)庫(kù),http://cfpub.epa. gov/ecotox/)、已發(fā)表論文及期刊文獻(xiàn)[47,49].數(shù)據(jù)篩選遵循相關(guān)性、可靠性、精確性的原則[50].根據(jù)暴露時(shí)間和測(cè)試終點(diǎn)將THMs和HAAs水生生物毒性數(shù)據(jù)分為:急性毒性(測(cè)試終點(diǎn)為致死)和慢性毒性,由于現(xiàn)有研究中THMs和HAAs的慢性毒性數(shù)據(jù)較少,因而將生長(zhǎng)、繁殖、生物化學(xué)與分子生物學(xué)及其他行為學(xué)等慢性毒性測(cè)試終點(diǎn)合并分析.根據(jù)水生生物的測(cè)試終點(diǎn),以半致死濃度(LC50)或半效應(yīng)濃度(EC50)為測(cè)試終點(diǎn)的毒性數(shù)值作為急性毒性數(shù)據(jù),以無(wú)觀察效應(yīng)濃度(NOEC)為測(cè)試終點(diǎn)的毒性數(shù)值作為慢性毒性數(shù)據(jù).當(dāng)NOEC數(shù)據(jù)不足時(shí),采用最大可接受濃度、最低可觀察效應(yīng)濃度或EC50替代[47].當(dāng)一個(gè)物種同一測(cè)試終點(diǎn)具有多個(gè)數(shù)值時(shí),使用幾何平均值;同一個(gè)生物有不同測(cè)試終點(diǎn)時(shí),選擇最敏感測(cè)試終點(diǎn)的毒性數(shù)據(jù)[51].

通過(guò)查閱文獻(xiàn)和毒理數(shù)據(jù)庫(kù)收集到THMs和HAAs的水生生物毒性數(shù)據(jù),滿足使用物種敏感度分布曲線(SSD)推導(dǎo)5%物種受到危害時(shí)的濃度(HC5)的要求,采用SSD推導(dǎo)HC5,以不同生物毒性數(shù)據(jù)的對(duì)數(shù)濃度值為橫坐標(biāo),以累計(jì)概率為縱坐標(biāo)作圖.其中累計(jì)概率是將所有已篩選物種的最終毒性值按從小到大的順序進(jìn)行排列,并且給其分配等級(jí),最小的最終毒性值等級(jí)為1,最大的最終毒性值等級(jí)為,依次排列,計(jì)算公式為[52]:

/1(1)

式中:為累計(jì)概率,%;為物種排序的等級(jí);為物種的個(gè)數(shù).

如果有2個(gè)或者2個(gè)以上物種的毒性值是相等的,則將其任意排成連續(xù)的等級(jí),計(jì)算每個(gè)物種的最終毒性值的累計(jì)概率.該研究采用荷蘭國(guó)家公共衛(wèi)生與環(huán)境研究院(RIVM)開(kāi)發(fā)的ETX 2.0推導(dǎo)基于50%置信度的HC5[47].

由于非本地物種數(shù)據(jù)、物種種類(lèi)以及野外實(shí)際暴露等會(huì)對(duì)PNEC產(chǎn)生影響,最終PNEC值為:

PNEC=HC5/AF(2)

式中:HC5為5%物種受到危害時(shí)的化合物濃度, mg/L;AF取5[53].

1.3 消毒副產(chǎn)物的生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)

本文采用多層次生態(tài)風(fēng)險(xiǎn)評(píng)估法對(duì)我國(guó)包括水源在內(nèi)的地表水中的THMs和HAAs進(jìn)行生態(tài)風(fēng)險(xiǎn)評(píng)估.首先,采用風(fēng)險(xiǎn)商進(jìn)行評(píng)估,見(jiàn)下式:

RQ=MEC/PENC(3)

式中:MEC為實(shí)測(cè)環(huán)境濃度, μg/L;PNEC為預(yù)測(cè)無(wú)效應(yīng)濃度,μg/L.

當(dāng)RQ<0.1,該化合物對(duì)水生生物的風(fēng)險(xiǎn)可忽略;當(dāng)0.1￡RQ<1,該化合物對(duì)水生生物的風(fēng)險(xiǎn)較低;當(dāng)1￡RQ<10,該化合物對(duì)水生生物為中等風(fēng)險(xiǎn);當(dāng)RQ310,該化合物對(duì)水生生物的風(fēng)險(xiǎn)高[47].

其次,采用聯(lián)合概率分布曲線法(JPCs)作為概率生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)對(duì)THMs和HAAs進(jìn)行高層次風(fēng)險(xiǎn)評(píng)價(jià).聯(lián)合概率分布曲線法(JPCs)可以計(jì)算出某一特定百分比物種引起不利影響的濃度在地表水中出現(xiàn)的概率,反映各毒性損傷水平下暴露濃度超出相應(yīng)臨界濃度值的概率,體現(xiàn)暴露情況和暴露風(fēng)險(xiǎn)之間的關(guān)系[46-47].

2 結(jié)果與討論

2.1 暴露水平

我國(guó)地表水中THMs的濃度范圍為0~51μg/L; HAAs的濃度范圍為n.d~12.61μg/L(表1),其中, TCM、TBM、DCAA和TCAA分別是THMs和HAAs中檢出率較高化合物,濃度范圍分別為0~51,0.22~ 1.46,0.01~2.56和n.d.~12.61μg/L.從THMs和HAAs來(lái)看,除大連市地表水中DCAA和TCAA的平均濃度(6μg/L)外,水體中THMs的平均濃度(0.14~2.8μg/ L)高于HAAs的平均濃度(0.01~3.37μg/L),其中,THMs中TCM的最高濃度(51μg/L)高于HAAs中DCAA的最高濃度(12.61μg/L).同區(qū)域不同種類(lèi)的消毒副產(chǎn)物,TCM的平均濃度高于DCAA和TCAA的平均濃度水平.由表1可知,THMs中主要的消毒副產(chǎn)物為T(mén)CM,其平均濃度的范圍為0.33~ 2.80μg/L,遠(yuǎn)高于其余3種化合物;HAAs中, DCAA (0.01~6μg/L)和TCAA(0.12~1.30μg/L)是主要的化合物.

表1 我國(guó)地表水中THMs和HAAs污染水平

注:“-”表示數(shù)據(jù)不可獲得.

2.2 不同測(cè)試終點(diǎn)PNEC值的推導(dǎo)

本文通過(guò)文獻(xiàn)和毒理數(shù)據(jù)庫(kù)收集TCM、TBM、DCAA和TCAA的急性和慢性毒性數(shù)據(jù)(表2). 基于致死為測(cè)試終點(diǎn),本文收集了大量脊椎和無(wú)脊椎水生動(dòng)物以及藻類(lèi)的急性毒性數(shù)據(jù), TCM,TBM, DCAA和TCAA的急性毒性數(shù)值范圍分別為2~7771.18, 2.90~75, 23~4060和1.2~9300mg/L,均值分別為341.77,29.10,1468.20和3576.45mg/L.從THMs和HAAs兩類(lèi)主要DBPs來(lái)看,THMs對(duì)水生生物的急性毒性遠(yuǎn)高于HAAs,因而THMs水生生物的生命具有較高的威脅.從不同化合物來(lái)看,TBM對(duì)水生生物的致死效應(yīng)濃度最高,TCAA水生生物的致死效應(yīng)濃度最低,TBM對(duì)水生生物的生存影響可能高于其他3種DBPs,地表水環(huán)境中TBM對(duì)水生生物的生存存在一定影響.基于生長(zhǎng)、繁殖和分子生物學(xué)等為測(cè)試終點(diǎn),本文收集了脊椎和無(wú)脊椎水生動(dòng)物以及藻類(lèi)的慢性毒性數(shù)據(jù),TCM,TBM,DCAA和TCAA的毒性濃度范圍分別為0.1~185, 0.24~38.6, 0.0002~1485和0.01~1740mg/L,均值分別為36.07, 13.45, 235.24和512.39mg/L.從THMs和HAAs 2類(lèi)主要DBPs來(lái)看,THMs對(duì)水生生物的慢性毒性高于HAAs,地表水環(huán)境中THMs對(duì)水生生物的慢性毒性影響大于HAAs.從不同化合物來(lái)看,TBM對(duì)水生生物的生長(zhǎng)、繁殖和分子生物學(xué)等慢性毒性效應(yīng)濃度最高,TBM對(duì)水生生物的生長(zhǎng)和繁殖等毒性影響可能高于其他3種DBPs.

表2 THMs和HAAs對(duì)水生生物的毒性數(shù)值

續(xù)表2

續(xù)表2

注:“-”表示信息不可獲得.

基于對(duì)TCM、TBM、DCAA和TCAA各類(lèi)水生生物急慢性毒性數(shù)據(jù)進(jìn)行統(tǒng)計(jì)分析,獲得相關(guān)參數(shù)(表3).通過(guò)Kolmogorov-Smirnov檢驗(yàn),數(shù)據(jù)均符合對(duì)數(shù)正態(tài)分布(>0.05).采用SSD曲線推導(dǎo)TCM、TBM、DCAA和TCAA的HC5.基于TCM的急性和慢性毒性數(shù)據(jù)推導(dǎo)的HC5分別是2.932和0.029mg/L,推導(dǎo)出的PNEC值分別為0.586和0.006mg/L;基于TBM的急性和慢性毒性數(shù)據(jù)推導(dǎo)的HC5分別是4.286和0.320mg/L,推導(dǎo)出的PNEC值分別為0.857mg/L和0.064mg/L;基于DCAA以生長(zhǎng)、繁殖等為測(cè)試終點(diǎn)的慢性毒性數(shù)據(jù)推導(dǎo)的HC5是1.912mg/L,推導(dǎo)出的PNEC值為0.956mg/L,由于DCAA的急性毒性數(shù)據(jù)不滿足構(gòu)建SSD曲線最低條件,因此選擇最敏感物種的急性毒性數(shù)據(jù)與AF(AF=1000)[59]相比,計(jì)算得到DCAA基于急性毒性數(shù)據(jù)的PNEC值為23mg/L;基于TCAA的急性和慢性毒性數(shù)據(jù)推導(dǎo)的HC5分別是224.40和0.061mg/L,推導(dǎo)出的PNEC值分別為44.880和0.012mg/L.綜上所述,TCM、TBM、DCAA和TCAA對(duì)水生生物的生長(zhǎng)、繁殖等慢性毒性更敏感,其中TCM對(duì)水生生物的慢性毒性高于其他化合物,DCAA對(duì)水生物的生長(zhǎng)、繁殖、生物化學(xué)和分子生物學(xué)等慢性毒性相對(duì)較不敏感.從2類(lèi)不同DBPs來(lái)看,THMs基于急性毒性數(shù)據(jù)推導(dǎo)出的PNEC值遠(yuǎn)低于HAAs,水生生物的生存對(duì)水環(huán)境中THMs更加敏感,尤其是TCM,這一結(jié)果與毒性數(shù)據(jù)進(jìn)行均值比較的結(jié)果存在一些差異,為獲得更準(zhǔn)確的結(jié)果,不能僅僅進(jìn)行簡(jiǎn)單的分析,應(yīng)該使用更科學(xué)的統(tǒng)計(jì)分析方法,例如SSD[47].從不同化合物來(lái)看, TCM對(duì)水生生物的生長(zhǎng)、繁殖和分子生物學(xué)等毒性更加敏感,TCAA次之,同樣的,與利用毒性均值比較時(shí)存在一些差異,根據(jù)國(guó)內(nèi)外研究人員的結(jié)果表明[47,51-52,63-64,66],采用SSD曲線進(jìn)行毒性效應(yīng)分析更加科學(xué),準(zhǔn)確.

表3 基于不同測(cè)試終點(diǎn)構(gòu)建THMs和HAAs的SSD曲線相關(guān)參數(shù)

注:“-”表示數(shù)據(jù)不可獲得.

2.3 我國(guó)地表水中THMs和HAAs生態(tài)風(fēng)險(xiǎn)評(píng)估

該研究采用RQ對(duì)我國(guó)地表水中的THMs(TCM和TBM)和HAAs(DCAA和TCAA)平均濃度進(jìn)行風(fēng)險(xiǎn)評(píng)估,我國(guó)地表水中TCM、TBM、DCAA和TCAA的平均濃度分別與急性毒性數(shù)據(jù)推導(dǎo)出的PNEC相比,求出RQ值(圖1).

圖1 基于急性毒性計(jì)算TCM、TBM、DCAA和TCAA的RQ

由圖1可知,基于TCM、TBM、DCAA和TCAA急性毒性數(shù)據(jù)計(jì)算出的RQ均小于1.從不同流域來(lái)看,除中山市河流中TCM的RQ超過(guò)0.1,其他流域中基于TCM、TBM、DCAA和TCAA的平均濃度與急性毒性數(shù)值計(jì)算得出的RQ均小于0.1,表明TCM、TBM、DCAA和TCAA在我國(guó)地表水中的生態(tài)風(fēng)險(xiǎn)較小,可以忽略.從不同消毒劑副產(chǎn)物的種類(lèi)來(lái)看,我國(guó)地表水中THMs基于急性毒性數(shù)據(jù)計(jì)算出的RQ高于HAAs基于急性毒性數(shù)據(jù)計(jì)算出的風(fēng)險(xiǎn)商,中山市河流中TCM的RQ最高(RQ=0.11).此外,DCAA和TCAA在大連市地表水中的RQ最高,分別為0.026和0.00013,表明THMs對(duì)我國(guó)地表水中水生生物的致死風(fēng)險(xiǎn)高于HAAs.此外,我國(guó)地表水中TCM 基于急性毒性數(shù)據(jù)計(jì)算出的RQ高于TBM基于急性毒性數(shù)據(jù)計(jì)算出的RQ;DCAA基于急性毒性數(shù)據(jù)計(jì)算出的RQ高于TCAA的RQ.

基于我國(guó)水源中TCM、TBM、DCAA和TCAA的平均濃度與慢性毒性數(shù)據(jù)推導(dǎo)出的PNEC相比,求出RQ,如圖2所示.

圖2 基于慢性毒性計(jì)算TCM、TBM、DCAA和TCAA的RQ

圖2表明,基于TCM、TBM、DCAA和TCAA慢性毒性數(shù)據(jù)計(jì)算出RQ,除中山市河流中TCM的RQ,其余均小于1.從不同化合物來(lái)看,我國(guó)地表水中THMs(TCM和TBM)和HAAs(DCAA和TCAA)基于慢性毒性數(shù)據(jù)計(jì)算出的RQ排序依次為T(mén)CM、TCAA、DCAA和TBM.從THMs和HAAs的空間分布來(lái)看,除常州市河流中TCM的RQ外(RQ= 0.056),其余流域中TCM基于慢性毒性數(shù)據(jù)計(jì)算出的RQ均高于0.1,中山市河流中TCM的RQ最高(RQ=1.12).其次,我國(guó)地表水中TCAA的RQ較高,范圍為0.002~0.099. TCM基于慢性毒性數(shù)據(jù)計(jì)算出的RQ值高于TBM基于慢性毒性數(shù)據(jù)計(jì)算出的RQ值,TCAA和DCAA基于慢性毒性數(shù)據(jù)計(jì)算出的RQ值呈現(xiàn)相同的規(guī)律.綜上,TCM對(duì)地表水中的水生生物具有一定的生態(tài)風(fēng)險(xiǎn),且對(duì)我國(guó)地表水中水生生物的繁殖、生長(zhǎng)及生物化學(xué)及分子生物學(xué)的毒性影響高于TBM、TCAA和DCAA.

TCM和TCAA對(duì)我國(guó)地表水中的水生生物具有一定的慢性毒性生態(tài)風(fēng)險(xiǎn),因而選擇JPC進(jìn)行較高層次的生態(tài)風(fēng)險(xiǎn)評(píng)估.JPC是以所有生物毒性數(shù)據(jù)的累積函數(shù)和污染物暴露濃度的反累積函數(shù)作圖,將風(fēng)險(xiǎn)評(píng)價(jià)的結(jié)論通過(guò)連續(xù)分布曲線的形式表現(xiàn).聯(lián)合概率曲線的軸表示不良效應(yīng)產(chǎn)生的強(qiáng)度,即水生生物受到影響的百分比;軸表示事件發(fā)生的概率;聯(lián)合概率曲線上的每一個(gè)點(diǎn)表示在目標(biāo)水體(評(píng)價(jià)對(duì)象)中,一定百分比的生物受到影響(事件)的概率.聯(lián)合概率曲線越靠近軸,生物受到影響的可能性越小,則目標(biāo)水體越安全[63-65].

根據(jù)地表水中TCM和TCAA濃度分別與慢性毒性數(shù)據(jù)建立聯(lián)合概率曲線(圖3).結(jié)果表明,我國(guó)地表水中TCM對(duì)1%、5%和10%的水生生物造成繁殖、生長(zhǎng)及其他行為學(xué)等慢性毒性影響的概率分別為78.86%、3.6%和0.07%;我國(guó)地表水中TCAA對(duì)1%和5%的水生生物的繁殖、生長(zhǎng)及其他行為學(xué)等造成慢性毒性影響的概率分別為20.61%和0.01%.綜上所述,我國(guó)地表水中TCM濃度對(duì)水生生物的風(fēng)險(xiǎn)高于地表水中TCAA濃度對(duì)水生生物的風(fēng)險(xiǎn),TCM對(duì)我國(guó)地表水中水生生物存在一定的生態(tài)風(fēng)險(xiǎn), TCAA對(duì)我國(guó)地表水具有潛在生態(tài)風(fēng)險(xiǎn).

圖3 TCM和TCAA水生態(tài)風(fēng)險(xiǎn)聯(lián)合概率曲線

2.4 不確定性分析

不確定性在生態(tài)風(fēng)險(xiǎn)評(píng)估過(guò)程中是不可避免的,無(wú)論是低層次的生態(tài)風(fēng)險(xiǎn)評(píng)估還是較高層次的生態(tài)風(fēng)險(xiǎn)評(píng)估.水體中THMs和HAAs濃度的實(shí)際變化,毒性數(shù)據(jù)與生態(tài)的關(guān)聯(lián)性以及風(fēng)險(xiǎn)表征模型的選擇是生態(tài)風(fēng)險(xiǎn)評(píng)估過(guò)程中產(chǎn)生不確定性的主要因素.

首先,THMs和HAAs在地表水中的暴露濃度數(shù)據(jù)有限,為了更全面精確地了解THMs和HAAs的暴露情況,需要進(jìn)一步搜集整理并開(kāi)展全國(guó)范圍地表水中THMs和HAAs暴露濃度的時(shí)空變化數(shù)據(jù)監(jiān)測(cè).其次,研究表明THMs和HAAs對(duì)水生生物的繁殖、生長(zhǎng)等慢性毒性更為敏感,該研究中THMs和HAAs的毒性數(shù)據(jù)均以致死為測(cè)試終點(diǎn)的急性毒性數(shù)據(jù)為主,不能充分反映THMs和HAAs對(duì)水生生物的慢性毒性的影響.若考慮對(duì)水環(huán)境中THMs和HAAs開(kāi)展更加全面的毒性評(píng)估,則需要更多魚(yú)類(lèi)、無(wú)脊椎動(dòng)物等水生生物慢性毒性相關(guān)試驗(yàn).此外,由于生物具有地域性的特點(diǎn),收集的所有毒性數(shù)據(jù)是否具有代表性仍存在爭(zhēng)論[45].Jin等[64]的研究表明當(dāng)本地物種毒性數(shù)據(jù)不足時(shí),使用一定的安全系數(shù)(AF=2~10)即可將非本土物種的毒性數(shù)據(jù)納入風(fēng)險(xiǎn)評(píng)估的研究.生態(tài)風(fēng)險(xiǎn)評(píng)估過(guò)程中,數(shù)據(jù)分析模型的選擇影響SSD曲線的構(gòu)建[66],例如對(duì)數(shù)正態(tài)分布、對(duì)數(shù)邏輯斯蒂、波爾III模型等.因而,通過(guò)數(shù)據(jù)的隨機(jī)性、評(píng)估過(guò)程和數(shù)據(jù)分析模型的選擇所產(chǎn)生的誤差,導(dǎo)致風(fēng)險(xiǎn)評(píng)估結(jié)果具有一定的不確定性.

3 結(jié)論

3.1 通過(guò)文獻(xiàn)檢索和資料收集,我國(guó)地表水中TCM、TBM、DCAA和TCAA的濃度范圍分別為0~51,0.22~1.46,0.01~2.56和n.d.~12.61μg/L.

3.2 根據(jù)RQ的評(píng)價(jià)結(jié)果,TCM基于急性和慢性毒性數(shù)據(jù)計(jì)算得出的RQ值大于1,其余THMs和HAAs的RQ值均小于1.利用JPCs得到TCM和TCAA對(duì)1%的水生生物產(chǎn)生慢性毒性影響的概率分別為78.86%和20.61%,TCM對(duì)我國(guó)地表水中水生生物具有一定的生態(tài)風(fēng)險(xiǎn).

3.3 地表水中TCM和TCAA對(duì)水生生物的繁殖、發(fā)育等具有較低影響,毒性影響不可忽略,其余化合物對(duì)地表水中的水生生物具有潛在的影響.

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Occurrence and ecological risk of typical DBPs in Chinese surface water.

LUO Ying1,2,3, LIU Na3,SUN Shan-wei1, HOU Song1, GUO Chang-sheng1,3*, XU Jian1,3

(1.State Environmental Protection Key Laboratory of Ecological Effect and Risk Assessment of Chemicals, Chinese Research Academy of Environmental Sciences, Beijing 100012, China；2.College of Water Sciences, Beijing Normal University, Beijing 100875, China；3.State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China)., 2021,41(4)：1806~1814

Trihalomethanes (THMs) and haloacetic acids (HAAs), the disinfection by-products (DBPs) in surface water, have given rise to major concern in recent years. In this study, exposure and ecotoxicity data of 4 DBPs (trichloromethane, tribromomethane, dichloroacetic acid and trichloroacetic acid) were collected from literature published in China and abroad, and a multiple-level environmental risk assessment was performed. THMs and HAAs were collected from previous studies, with concentrations range from n.d. to 51μg/L. Predicted no effect concentration (PNEC) for trichloromethane (TCM), tribromomethane (TBM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) was based on acute and chronic toxicity data. The PNEC of TCM, TBM, DCAA and TCAA derived from acute and chronic toxicity data which based on endpoints of survival, reproduction and development, with concentrations range from 0mg/L to 44.88mg/L, 0.006mg/L to 0.956mg/L, respectively. Besides, risk quotient (RQ) and probabilistic ecological risk assessments (PERA) were calculated by exposure data, and PNEC of acute and chronic toxicity data. The results showed that RQ were less than 1. TCM of probabilities of exceeding NOEC based on chronic toxicity for 1% of the species were 78.86%. And TCAA of probabilities of exceeding NOEC based on chronic toxicity for 1% of the species were 20.61%. Based on these results, the ecological risks of TCM and TCAA in Chinese surface water were low.

disinfection by-products；surface water；ecological risk assessment

X171.5;X824

A

1000-6923(2021)04-1806-09

羅 瑩(1992-),女,新疆奎屯人,北京師范大學(xué)博士研究生,主要研究方向?yàn)樯鷳B(tài)毒理及風(fēng)險(xiǎn)評(píng)價(jià).發(fā)表論文4篇.

2020-08-04

中央級(jí)公益性科研院所基本科研業(yè)務(wù)專(zhuān)項(xiàng)(2020-JY-003; 2019YSKY-022)

* 責(zé)任作者, 副研究員, guocs@craes.org.cn