多因子影響下銅的水質(zhì)基準(zhǔn)及生態(tài)風(fēng)險(xiǎn)

劉 娜,李亞兵,劉紅玲,2*

多因子影響下銅的水質(zhì)基準(zhǔn)及生態(tài)風(fēng)險(xiǎn)

劉 娜1,李亞兵1,劉紅玲1,2*

(1.南京大學(xué)環(huán)境學(xué)院,污染控制與資源化研究國(guó)家重點(diǎn)實(shí)驗(yàn)室,江蘇 南京 210023；2.江蘇省生態(tài)環(huán)境保護(hù)化學(xué)品安全與健康風(fēng)險(xiǎn)研究重點(diǎn)實(shí)驗(yàn)室,江蘇 南京 210023)

為探究特定水環(huán)境中多因子影響下的銅水質(zhì)基準(zhǔn)及生態(tài)風(fēng)險(xiǎn),采用物種權(quán)重敏感度分布法、水效應(yīng)比法和生物配體模型推導(dǎo)保護(hù)太湖水生生物銅的水質(zhì)基準(zhǔn).根據(jù)推導(dǎo)結(jié)果,推薦采用最大濃度基準(zhǔn)值(CMC) 1.43 μg/L和持續(xù)濃度基準(zhǔn)值(CCC) 1.33 μg/L.結(jié)合水效應(yīng)比法和生物配體模型,采用聯(lián)合概率法評(píng)估太湖銅的生態(tài)風(fēng)險(xiǎn).結(jié)果表明,兩種方法下豐水期5%水生生物受到銅慢性毒性影響的概率分別為23.43%和39.43%,而未考慮多因子影響的風(fēng)險(xiǎn)概率為85.01%,高估了太湖銅生態(tài)風(fēng)險(xiǎn).可見(jiàn),水環(huán)境多因子對(duì)水質(zhì)基準(zhǔn)和生態(tài)風(fēng)險(xiǎn)的影響不容忽視,我國(guó)目前使用的銅標(biāo)準(zhǔn)可能無(wú)法保護(hù)特定區(qū)域的水生生物.考慮多因子影響可提高基準(zhǔn)值推導(dǎo)和風(fēng)險(xiǎn)評(píng)估的科學(xué)性,避免“過(guò)保護(hù)”和“欠保護(hù)”現(xiàn)象.

銅；多因子影響；水質(zhì)基準(zhǔn)；生態(tài)風(fēng)險(xiǎn)；物種權(quán)重敏感度分布法；水效應(yīng)比法；生物配體模型

銅是生物必需的微量元素,但攝入過(guò)量會(huì)危害生物體,尤其對(duì)水生生物會(huì)產(chǎn)生不同水平的毒性效應(yīng)[1-3].已有研究評(píng)估了多種金屬對(duì)水生生物的毒性,銅的潛在危害最大[4].最初研究關(guān)注銅本身給水生生物帶來(lái)的危害,近年來(lái)大量研究表明生物因素(不同物種、不同生命階段等)和區(qū)域水環(huán)境特征(溫度、硬度、溶解氧、pH值和有機(jī)質(zhì)等)能對(duì)銅的生物有效性及毒性產(chǎn)生影響[5-7],這也推動(dòng)了方法學(xué)的發(fā)展.其中,生物配體模型(BLM)考慮顆粒吸附、絡(luò)合作用、無(wú)機(jī)配體結(jié)合、競(jìng)爭(zhēng)活性位點(diǎn)等多個(gè)影響因素,能較好地預(yù)測(cè)重金屬對(duì)水生生物的毒性[8];物種權(quán)重敏感度分布法(WSSD)和水效應(yīng)比法(WER)則通過(guò)鏈接真實(shí)水環(huán)境,對(duì)毒性值進(jìn)行校正[9-10].三種方法也逐漸應(yīng)用于水質(zhì)基準(zhǔn)的研究中,但都集中于單一方法的應(yīng)用,缺乏對(duì)不同方法的適用性討論.如利用BLM對(duì)金屬水質(zhì)基準(zhǔn)進(jìn)行修訂[11];通過(guò)WSSD法得到校驗(yàn)后太湖鉛的水質(zhì)基準(zhǔn)[12];利用WER法所得銅水質(zhì)基準(zhǔn)值較U.S. EPA國(guó)家標(biāo)準(zhǔn)值更為嚴(yán)格[13].另一方面,我國(guó)現(xiàn)行水質(zhì)標(biāo)準(zhǔn)采用的是統(tǒng)一標(biāo)準(zhǔn)值,缺乏以保護(hù)水生生物為目標(biāo)的銅水質(zhì)標(biāo)準(zhǔn)[14].因此, 探討不同方法的適用性,研究多因子影響下銅的水質(zhì)基準(zhǔn)和生態(tài)風(fēng)險(xiǎn)十分必要.

太湖作為我國(guó)最大的淡水湖之一,也是受銅等重金屬污染最嚴(yán)重的水域之一[15].本文以太湖為例,在收集銅的急慢性毒性數(shù)據(jù)基礎(chǔ)上,補(bǔ)充了6種太湖本土生物急慢性毒性數(shù)據(jù),考慮生物類群和水化學(xué)等多因子對(duì)水質(zhì)基準(zhǔn)的影響,采用WSSD法、WER以及BLM模型法,得到基于多因子影響的保護(hù)太湖水生生物銅的水質(zhì)基準(zhǔn).進(jìn)一步基于WER法和BLM模型法,采用聯(lián)合概率法對(duì)太湖豐枯水期銅的生態(tài)風(fēng)險(xiǎn)進(jìn)行評(píng)價(jià),并對(duì)不同方法進(jìn)行討論.以期為太湖銅水質(zhì)基準(zhǔn)的制定提供參考,同時(shí)為多因子影響下我國(guó)保護(hù)水生生物重金屬類水質(zhì)標(biāo)準(zhǔn)的制定及生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)提供方法借鑒,支撐不同水域污染下“因地制宜”式的控制與管理.

1 材料與方法

1.1 水樣采集及參數(shù)測(cè)定

為推導(dǎo)太湖銅水質(zhì)基準(zhǔn),采集太湖重污染區(qū)陳東港、大浦港、分水大橋、分水橋和平臺(tái)山5 個(gè)代表點(diǎn)水樣,如圖1(a).溫度等參數(shù)及DOC分別采用YSI多參數(shù)水質(zhì)儀(6600V2-4, Ecosense, Ohio, USA)和島津TOC-5000A總有機(jī)碳測(cè)定儀(Shimadzu,京都,日本)進(jìn)行測(cè)定.為測(cè)定太湖Cu2+的環(huán)境濃度以評(píng)價(jià)太湖銅的水生生態(tài)風(fēng)險(xiǎn),考慮水生態(tài)功能區(qū),選擇太湖52個(gè)點(diǎn)位,分別于豐水期(2019年9月)和枯水期(2020年1月)依據(jù)HJ/T91相關(guān)規(guī)定[16]進(jìn)行采樣.采樣點(diǎn)位如圖1(b),其中湖體37個(gè)(綠色點(diǎn)為9個(gè)國(guó)控?cái)嗝?,湖口及周邊河流15個(gè)(紅色點(diǎn)).水樣采集后經(jīng)0.45μm水性微孔濾膜過(guò)濾,濾液中加入適量硝酸使其硝酸含量達(dá)1%作為測(cè)定樣品.銅的濃度利用電感耦合等離子體質(zhì)譜(ICP-MS (NexION 300X))測(cè)定.測(cè)定的標(biāo)準(zhǔn)曲線具有良好的線性(2=0.998),檢出限為0.18μg/L,重復(fù)樣品的標(biāo)準(zhǔn)偏差RSD<5.50%,回收率在90.5%～110.1%,本方法準(zhǔn)確性和穩(wěn)定性較好.

1.2 太湖銅的水質(zhì)基準(zhǔn)

1.2.1 毒性數(shù)據(jù)的收集 通過(guò)U.S.EPA的ECOTOX數(shù)據(jù)庫(kù)(http://cfpub.epa.gov/ecotox/)搜集太湖本土水生生物銅(Cu2+)的毒性數(shù)據(jù),數(shù)據(jù)篩選原則如下:

(1) 剔除非太湖本土生物毒性數(shù)據(jù).

(2) 生物毒性測(cè)試符合國(guó)標(biāo)[17]或OECD[18]及U.S. EPA的標(biāo)準(zhǔn)(包括受試生物年齡及健康狀態(tài)、空白對(duì)照的要求、測(cè)試時(shí)長(zhǎng)、生物培養(yǎng)、溫度、光照、喂食與否等).

(3) 測(cè)試暴露介質(zhì)為淡水,測(cè)試地點(diǎn)為實(shí)驗(yàn)室,毒性數(shù)據(jù)包含明確毒性終點(diǎn)、毒性單位、暴露時(shí)間及暴露方式.

(4) 對(duì)于急性毒性數(shù)據(jù),毒性終點(diǎn)選擇半數(shù)致死濃度(LC50)或半數(shù)有效應(yīng)濃度(EC50).優(yōu)先選擇暴露96h的魚類和兩棲類的LC50,水生無(wú)脊椎動(dòng)物96h(水溞類48h)的LC50,水生植物37d及水生藻類￡96h的EC50.對(duì)于慢性毒性數(shù)據(jù),選擇NOEC(無(wú)觀察效應(yīng)濃度)或LOEC(最低效應(yīng)濃度)為毒性終點(diǎn).毒性指標(biāo)選擇短生命周期生物>4d及長(zhǎng)生命周期生物>7d的亞致死效應(yīng),優(yōu)先選擇標(biāo)準(zhǔn)方法獲得的大型溞21d毒性數(shù)據(jù)[18].

1.2.2 急性毒性試驗(yàn) 對(duì)太湖6種本土水生生物(大型溞、青鳉魚、青魚、黃顙魚仔魚、林蛙蝌蚪、斜生柵藻)進(jìn)行急性毒性試驗(yàn)以補(bǔ)充毒性數(shù)據(jù),并利用二步外推法補(bǔ)充慢性毒性數(shù)據(jù)[19].對(duì)大型溞和青鳉進(jìn)行原水毒性試驗(yàn)以利用WER推導(dǎo)水質(zhì)基準(zhǔn).

(1)急性試驗(yàn)試劑及生物.金屬銅(CuCl2) 標(biāo)準(zhǔn)溶液購(gòu)自百靈威,曝氣時(shí)間>3d的曝氣水作為稀釋水.其水質(zhì)參數(shù)為pH值(8.00±0.14)、堿度(81.25±2.17) mg(CaCO3)/L、硬度(125.50±4.95) mg(CaCO3)/L、總有機(jī)碳TOC 2.55mg(C)/L.試驗(yàn)所用魚和蝌蚪購(gòu)自江蘇溧水淡水漁業(yè)研究所,斜生柵藻購(gòu)自中科院武漢水生所,大型溞為實(shí)驗(yàn)室馴養(yǎng)生物.受試生物于實(shí)驗(yàn)室馴養(yǎng)兩周以上,期間每日喂食并定時(shí)換水,斜生柵藻則定期接種更新培養(yǎng)基并保證生物死亡率￡10%.

(2)急性毒性試驗(yàn).急性毒性試驗(yàn)依據(jù)OECD和U.S.EPA技術(shù)指南進(jìn)行.選擇大小相近、健康的個(gè)體進(jìn)行隨機(jī)分組,將暴露液配置為5個(gè)濃度梯度并設(shè)置稀釋水空白對(duì)照,暴露液每天更新一次,每濃度4 組平行,每平行10個(gè)生物.除大型溞和斜生柵藻暴露48h外,其余受試生物暴露時(shí)長(zhǎng)均為96h.實(shí)驗(yàn)條件按照國(guó)標(biāo)或OECD標(biāo)準(zhǔn).每24h觀察記錄生物死亡及異常情況,并將死亡個(gè)體及時(shí)取出,實(shí)驗(yàn)過(guò)程中不喂食.對(duì)于藻類則取對(duì)數(shù)生長(zhǎng)期的斜生柵藻,每24h用分光光度法測(cè)定藻液濃度.

1.2.3 太湖銅的水質(zhì)基準(zhǔn)推導(dǎo) 利用WSSD、WER和BLM法推導(dǎo)太湖銅水質(zhì)基準(zhǔn).

傳統(tǒng)物種敏感度分布法(SSD),通常利用Weibull法(式(1))計(jì)算累積概率[20].本文在SSD基礎(chǔ)上,利用WSSD法推導(dǎo)太湖銅的水質(zhì)基準(zhǔn).考慮生物類群間的能量傳遞,將水生生物分為植物(P)、脊椎動(dòng)物(V)及無(wú)脊椎動(dòng)物(I).根據(jù)對(duì)太湖21世紀(jì)的水生生物的調(diào)查統(tǒng)計(jì),太湖水生生物共524 種,植物、脊椎和無(wú)脊椎動(dòng)物的物種數(shù)分別為353、60和111 種,占比分別為67.4%、11.4%和21.2%[21-25].根據(jù)式(2)～(5)賦予權(quán)重以計(jì)算累積概率P(式(1)～(5)中,P指累積概率,為排序,為樣本量,為太湖物種數(shù),p、v和i分別為太湖中植物、脊椎和無(wú)脊椎動(dòng)物數(shù)量,、和分別為可獲得的太湖植物、脊椎和無(wú)脊椎動(dòng)物相應(yīng)的毒性數(shù)據(jù)量,式(5)中的P或v或I取決于排序的物種類別,擬合WSSD曲線,得出急慢性HC5值(影響5%物種的危害濃度),最后除以評(píng)價(jià)因子(AF=2)[26],得到太湖銅的急慢性基準(zhǔn)值分別以最大濃度基準(zhǔn)值(CMC)和持續(xù)濃度基準(zhǔn)值(CCC)表示.

WER法基于經(jīng)驗(yàn)[27],推導(dǎo)因?qū)嶒?yàn)室與真實(shí)環(huán)境間的差異而導(dǎo)致的毒性比值WER,從而對(duì)實(shí)驗(yàn)數(shù)據(jù)推導(dǎo)的水質(zhì)基準(zhǔn)值進(jìn)行修正;BLM法則是從機(jī)制出發(fā)[28-29],反映多因子對(duì)生物有效性和毒性的影響.本文通過(guò)2 種本土生物(大型溞、青鳉)原位水和實(shí)驗(yàn)水的急性毒性試驗(yàn),利用WER方法獲得WER實(shí)際校正后的銅基準(zhǔn)值.測(cè)定陳東港等5個(gè)太湖代表性點(diǎn)位BLM模型所需參數(shù):pH值、溫度、溶解性有機(jī)碳(DOC)、主要陽(yáng)離子(Ca2+,Mg2+,Na+和K+)、陰離子(SO42-和Cl-)和堿度.以BLM模型中WQC計(jì)算模塊得到BLM法太湖銅的CMC及CCC值.

1.3 太湖銅的水生生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)

聯(lián)合概率法(JPC)能夠?qū)⒍拘詳?shù)據(jù)和化合物的環(huán)境濃度相結(jié)合[30-31],反映環(huán)境濃度超過(guò)影響一定百分比物種的概率.本文利用WER和BLM模型法得出兩種水效應(yīng)比WER實(shí)際和WERBLM,以校正毒性數(shù)據(jù),結(jié)合太湖不同水期52個(gè)點(diǎn)位Cu2+的暴露濃度,通過(guò)JPC反映太湖銅水生生態(tài)風(fēng)險(xiǎn).在水生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)中,通常以保護(hù)95%的水生生物作為保護(hù)目標(biāo)[30],故本文將太湖銅的水生生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)結(jié)果表征為“太湖銅濃度超過(guò)影響5%生物的概率”.

1.4 統(tǒng)計(jì)學(xué)分析

補(bǔ)充的急性毒性數(shù)據(jù)LC50及95%的置信區(qū)間以GraphPad Prism 8中的Sigmoidal dose-response模型獲得.慢性數(shù)據(jù)運(yùn)用Microsoft Office Excel 2019外推獲得,最終急慢性毒性數(shù)據(jù)采用Kolmogorov- Smirnov進(jìn)行正態(tài)性檢驗(yàn),SSD及WSSD曲線均采用GraphPad Prism 8中l(wèi)og-Normal方法擬合,以R2評(píng)價(jià)擬合優(yōu)度.聯(lián)合概率曲線由GraphPad Prism 8軟件繪制,BLM由Windward Environmental提供(http: //www.windwardenv.com/biotic-ligand-model).

2 結(jié)果與討論

2.1 急慢性數(shù)據(jù)補(bǔ)充結(jié)果

補(bǔ)充的急慢性毒性數(shù)據(jù)如表1.對(duì)銅最敏感的水生生物為斜生柵藻,最耐受物種為青鳉等脊椎動(dòng)物.結(jié)合搜集的毒性數(shù)據(jù),最終銅的急慢性毒性數(shù)據(jù)見(jiàn)表2.共獲得銅的22種太湖水生生物急性毒性數(shù)據(jù),包括5門14 科;16種太湖水生生物慢性毒性數(shù)據(jù),分屬于5門11科,滿足保護(hù)水生生物水質(zhì)基準(zhǔn)推導(dǎo)要求[32].

2.2 WSSD推導(dǎo)太湖銅水質(zhì)基準(zhǔn)結(jié)果

由銅對(duì)水生生物的急慢性毒性數(shù)據(jù),得到未考慮因子影響的太湖銅急慢性傳統(tǒng)SSD曲線如圖2所示.整體而言,對(duì)于銅的毒性,藻類是最敏感生物,其次是無(wú)脊椎動(dòng)物,最不敏感類群為魚類.根據(jù)傳統(tǒng)SSD,太湖銅的急慢性HC5值分別為5.70μg/L和3.44μg/L.考慮太湖水生生物組成,得到太湖銅急慢性物種權(quán)重敏感度分布曲線WSSD如圖3.WSSD與傳統(tǒng)SSD法識(shí)別出的太湖銅敏感物種與耐受物種一致,但閾值上有一定差異.

通過(guò)SSD和WSSD獲得的HC5值,推導(dǎo)出未考慮(SSD)和考慮生物影響(WSSD)的太湖銅水質(zhì)基準(zhǔn)(WQC)如表3.其中,WSSD推導(dǎo)的CMC和CCC分別為1.43μg/L和1.33μg/L,急性基準(zhǔn)值為傳統(tǒng)SSD推導(dǎo)值CMC 2.85μg/L的一半,慢性基準(zhǔn)值也較SSD的CCC 1.72μg/L低,可見(jiàn)考慮物種組成的WSSD比傳統(tǒng)SSD法對(duì)特定區(qū)域水生生物的保護(hù)更為嚴(yán)格.本文的基準(zhǔn)值與Shi等[33]利用WSSD推導(dǎo)的CMC 5.3μg/L和CCC 3.7μg/L略有差異,可能是由于補(bǔ)充了敏感物種藻類等生物的毒性數(shù)據(jù)以及在賦予權(quán)重時(shí)對(duì)太湖物種組成調(diào)研時(shí)間不同造成的.

表1 太湖6種本土水生生物的銅急性毒性數(shù)據(jù)及預(yù)測(cè)慢性毒性數(shù)據(jù)

表2 太湖水生生物銅的急慢性毒性數(shù)據(jù)

續(xù)表2

注:*為本研究補(bǔ)充的數(shù)據(jù).

我國(guó)目前的水質(zhì)標(biāo)準(zhǔn)主要參考美國(guó)等發(fā)達(dá)國(guó)家的水質(zhì)標(biāo)準(zhǔn)[34],使用最多的水質(zhì)基準(zhǔn)推導(dǎo)方法是SSD法,而我國(guó)水域眾多,與其他國(guó)家水生物種差異大,國(guó)內(nèi)不同水域中物種及生態(tài)狀況也有差異.相關(guān)研究表明不同物種對(duì)銅的敏感性存在顯著性差異,且相較而言無(wú)脊椎動(dòng)物對(duì)銅的敏感度更高[35],與本文的結(jié)論一致.此外,國(guó)內(nèi)不同水域的水質(zhì)基準(zhǔn)差異顯著,甚至可達(dá)6倍[36].由此可見(jiàn),在推導(dǎo)特定水域的水質(zhì)基準(zhǔn)時(shí),考慮物種的影響,結(jié)合研究區(qū)域特定的本土生物是非常必要的,WSSD法比傳統(tǒng)SSD更能真實(shí)地反映研究區(qū)域化合物對(duì)水生生物潛在的影響,體現(xiàn)同一化合物對(duì)不同區(qū)系水生生物的差異,從而針對(duì)性地支撐特定區(qū)域水生生物的保護(hù).

表3 未考慮和考慮太湖水生生物組成的銅基準(zhǔn)閾值

2.3 WER和BLM法推導(dǎo)太湖銅水質(zhì)基準(zhǔn)結(jié)果

2.3.1 WER法推導(dǎo)結(jié)果 根據(jù)太湖2種本土生物(大型溞、青鳉)的3個(gè)點(diǎn)位的原位水及實(shí)驗(yàn)水急性毒性試驗(yàn)結(jié)果,得出實(shí)際水效應(yīng)比WER實(shí)際為 2.55 (表4),最終推導(dǎo)出WER法的太湖銅水質(zhì)基準(zhǔn)CMC和CCC分別為7.27μg/L和4.39μg/L.

表4 WER實(shí)際的推導(dǎo)結(jié)果

2.3.2 BLM推導(dǎo)結(jié)果 BLM模型輸入?yún)?shù)如表5,包括點(diǎn)位(陳東港CD、大浦港DP、分水大橋FSD、分水橋FS和平臺(tái)山PT和實(shí)驗(yàn)室LAB)的水樣溫度、pH值、Cu2+濃度、有機(jī)物、主要陰陽(yáng)離子含量及堿度.其中,HA和缺省值2-分別采用推薦值10%和10-10mg/L[37-38],主要陰離子則采用2008～ 2014年報(bào)道的濃度均值[29,39],得到BLM模型法推導(dǎo)太湖銅的瞬時(shí)水質(zhì)基準(zhǔn)值及模型水效應(yīng)比見(jiàn)表6,CMC和CCC分別為42.57μg/L和26.44μg/L,結(jié)果與Zhang等[40]利用BLM模型得出的太湖水質(zhì)基準(zhǔn)CMC 32.2μg/L近似.BLM模型較為全面的考慮了影響生物有效性的因素(競(jìng)爭(zhēng)、吸附解析等)[41],能夠一定程度上反映不同區(qū)域的差異.Chen等利用BLM模型得到瀾滄江上中下游銅的急性水質(zhì)基準(zhǔn)CMC分別為22.39, 31.20和26.79μg/L[42].可見(jiàn),對(duì)于不同水環(huán)境的基準(zhǔn)值有所差異,BLM法應(yīng)用于水質(zhì)基準(zhǔn)中,能夠?qū)⑺h(huán)境因子對(duì)基準(zhǔn)的影響納入考慮,在結(jié)果中體現(xiàn)出時(shí)空差異性.

表5 BLM模型輸入?yún)?shù)

注:點(diǎn)位見(jiàn)2.3.2節(jié).

WER法和BLM模型法所得水效應(yīng)比WER實(shí)際2.55和WERBLM2.0值相近,急慢性基準(zhǔn)值相差6倍以內(nèi),此差異是由于兩種方法特點(diǎn)、內(nèi)在機(jī)制不同所造成的.兩種方法從不同層面鏈接了野外環(huán)境,在區(qū)域性水質(zhì)基準(zhǔn)的推導(dǎo)中,具有較強(qiáng)的針對(duì)性.

由于水域污染日益嚴(yán)重,水體富營(yíng)養(yǎng)化加劇,目前太湖生態(tài)狀況正在惡化.根據(jù)調(diào)查結(jié)果,太湖水生物種數(shù)大量減少,其中魚類和大型浮游動(dòng)物數(shù)量急劇下降,耐污物種也在增加[21,43].因此,基于WSSD、WER和BLM三種方法結(jié)果,為最大程度保護(hù)太湖水生生物的安全,本文推薦采用WSSD法推導(dǎo)的CMC 1.43μg/L和CCC 1.33μg/L作為保護(hù)太湖水生生物銅的水質(zhì)基準(zhǔn).WER和BLM法則可根據(jù)太湖污染及生態(tài)狀況的變化,進(jìn)行互補(bǔ)性應(yīng)用.

表6 BLM得出的水質(zhì)基準(zhǔn)及模型水效應(yīng)比結(jié)果

2.4 基于多因子的生態(tài)風(fēng)險(xiǎn)評(píng)價(jià)結(jié)果

利用WERBLM和WER實(shí)際校正后的銅慢性毒性數(shù)據(jù)及枯豐水期太湖銅的濃度分別見(jiàn)表7和表8.

表7 WER校正后的太湖銅慢性毒性

結(jié)合校正后的毒性數(shù)據(jù),得到JPC曲線如圖4.對(duì)于太湖豐水期(圖4,(a)),未考慮多因子影響的評(píng)估結(jié)果為“太湖銅對(duì)5%水生生物造成慢性危害的概率為85.01%”,而通過(guò)兩種WER校正后的評(píng)估風(fēng)險(xiǎn)概率分別為39.43%和23.43%,遠(yuǎn)低于傳統(tǒng)方法的評(píng)估結(jié)果,枯水期(圖4,(b))的結(jié)果類似.此外,相比傳統(tǒng)方法,考慮多因子的風(fēng)險(xiǎn)評(píng)估識(shí)別出銅在豐水期的風(fēng)險(xiǎn)明顯高于枯水期,體現(xiàn)了太湖銅生態(tài)風(fēng)險(xiǎn)的時(shí)間差異性.由此可見(jiàn),在評(píng)估太湖銅的水生生態(tài)風(fēng)險(xiǎn)時(shí),忽略水化學(xué)等多因子的影響,很可能會(huì)使得評(píng)估風(fēng)險(xiǎn)偏高,評(píng)估不確定性大,且“掩蓋”風(fēng)險(xiǎn)在特定區(qū)域的時(shí)間差異性,而鏈接研究區(qū)域的真實(shí)環(huán)境,能夠更為客觀地評(píng)估化合物風(fēng)險(xiǎn),指示不同時(shí)間特定區(qū)域的生態(tài)風(fēng)險(xiǎn)狀況,更好地支撐化合物的管控以及水生生態(tài)的保護(hù).

表8 太湖52 個(gè)點(diǎn)位枯豐水期銅離子濃度

3 結(jié)論

3.1 WSSD,WER和BLM模型3 種方法得出環(huán)境多因子影響下,保護(hù)太湖水生生物銅的CMC分別為1.43、7.27和42.57μg/L,CCC分別為1.33、4.39和26.44μg/L.根據(jù)太湖現(xiàn)狀,為最大程度保護(hù)太湖水生生物安全,本文推薦采用WSSD法推導(dǎo)的CMC 1.43μg/L和CCC 1.33μg/L作為保護(hù)太湖水生生物銅的水質(zhì)基準(zhǔn).

3.2 結(jié)合WER和BLM法,得出太湖豐水期銅的慢性生態(tài)風(fēng)險(xiǎn)分別為23.43%和39.43%,枯水期分別為0.64%和5.40%,傳統(tǒng)方法則高估了風(fēng)險(xiǎn)(85.01%和82.09%),太湖銅的水生生物風(fēng)險(xiǎn)不容忽視,尤其需要關(guān)注豐水季節(jié).

3.3 在水質(zhì)基準(zhǔn)和生態(tài)風(fēng)險(xiǎn)評(píng)估中,傳統(tǒng)方法會(huì)導(dǎo)致結(jié)果的偏高,考慮區(qū)域性生物組成和水環(huán)境因子的影響十分必要.

3.4 WSSD,WER和BLM法各有其應(yīng)用要求與特點(diǎn),對(duì)于我國(guó)重金屬類保護(hù)水生生物水質(zhì)基準(zhǔn)的制定及生態(tài)風(fēng)險(xiǎn)評(píng)價(jià),需根據(jù)實(shí)際情況進(jìn)行方法的擇優(yōu)或互補(bǔ)性應(yīng)用,達(dá)到“因地制宜”式保護(hù)水生生物的目標(biāo).

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致謝：本研究的采樣測(cè)定工作由王遵堯老師協(xié)助完成,在此表示感謝.

The water quality criteria and ecological risks of copper under the influence of multiple factors.

LIU Na1, LI Ya-bing1, LIU Hong-ling1,2*

(1.State Key Laborotory of Pollution Control & Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China；2.Jiangsu Province Ecology and Environment Protection Key Laboratory of Chemical Safety and Health Risk, Nanjing 210023, China)., 2022,42(7)：3353～3361

In order to explore the impact of multiple factors on water quality criteria and ecological risks, the weighted species sensitivity distribution (WSSD), water effect ratio (WER) and biological ligand model (BLM) were used to derive the water quality criteria of copper for protecting aquatic organisms in Tai Lake. The criterion maximum concentration (CMC) of 1.43μg/L and the criterion continuous concentration (CCC) of 1.33μg/L were recommended as the water quality criteria of copper in Tai Lake. Joint probability curve (JPC) combining WER and BLM were used to further assess the ecological risks. There were 23.43% (WER) and 39.43% (BLM) probability of affecting 5% aquatic organisms during wet season in Tai Lake, respectively, while the traditional method overestimated the risks of copper in Tai Lake with a probability of 85.01%. These findings clearly suggest that the influence of multiple factors in the aquatic environment on water quality criteria and ecological risks cannot be ignored, currently environmental quality standard of copper adopted in China may not be able to protect aquatic organisms in specific areas such as Tai Lake. Considering multiple factors will obtain more reasonable water quality criteria and ecological risks assessment results, and avoid the phenomenon of “over-protection” or “under-protection”.

copper；influence of multiple factors；water quality criteria；ecological risks；weighted species sensitivity distribution (WSSD)；water effect ratio(WER)；biological ligand model(BLM)

X524

A

1000-6923(2022)07-3353-09

劉 娜(1996-),女,江西吉安人,南京大學(xué)碩士研究生,研究方向?yàn)樗|(zhì)基準(zhǔn)及生態(tài)風(fēng)險(xiǎn)評(píng)價(jià).

2021-12-10

國(guó)家自然科學(xué)基金資助項(xiàng)目(22176095,21677073);國(guó)家科技重大專項(xiàng)(2018ZX07208001);國(guó)家重點(diǎn)研發(fā)項(xiàng)目(2018YFC1801505)

* 責(zé)任作者, 副教授,hlliu@nju.edu.cn